Tiêu chuẩn iso 00898 1 2013

Microsoft Word C060610e doc Reference number ISO 898 1 2013(E) © ISO 2013 INTERNATIONAL STANDARD ISO 898 1 Fifth edition 2013 01 15 Mechanical properties of fasteners made of carbon steel and alloy st[.]

General

Two primary test series, FF and MP, are designated to evaluate the mechanical and physical properties of fasteners as outlined in Table 3 The FF group assesses finished fasteners, while the MP group focuses on testing the material properties of the fasteners These groups are subdivided into specific series: FF1, FF2, FF3, and FF4 for different fastener types, and MP1 and MP2 for material testing Due to dimensional and loadability constraints, not all properties listed in Table 3 can be tested across all fastener sizes and types.

Loadability of fasteners

A fastener with full loadability is a finished fastener, standardized or non-standardized, which, when tensile tested in accordance with the test series FF1, FF2 or MP2, a) breaks

⎯ in the free threaded length for fasteners with d s > d 2, or

⎯ in the free threaded length or in the unthreaded shank for fasteners with d s ≈ d 2, and b) meets the minimum ultimate tensile load, F m,min, in accordance with Tables 4 or 6

8.2.2 Fasteners which, due to their geometry, have reduced loadability

A fastener with reduced loadability is a finished, standardized or non-standardized fastener made from materials aligned with property classes defined in ISO 898 Due to its specific geometry, it does not meet the loadability test requirements outlined in test series FF1, FF2, or MP2, indicating its limited capacity under load.

Copyright International Organization for Standardization

Provided by IHS under license with ISO Licensee=University of Alberta/5966844001, User=sharabiani, shahramfs

No reproduction or networking permitted without license from IHS

A fastener with reduced loadability does not normally break in the free threaded length when tensile tested in accordance with test series FF3 or FF4

Basically, there are two geometrical reasons for reduced loadability of fasteners compared with the ultimate tensile load of the thread: a) a head design which applies to bolts and screws with:

⎯ low head with or without external driving feature,

⎯ low round head or low cylindrical head with internal driving feature, or

This article discusses countersunk head fasteners with internal driving features, ideal for flush installation It also highlights shank designs tailored for applications where standard loadability, as specified in ISO 898, is not necessary or desirable, such as screws with waisted shanks These specialized fasteners offer versatile solutions for various fastening needs, emphasizing design features that cater to both functional and aesthetic requirements.

Test series FF3 (see Table 10) is used for the fasteners mentioned in a), above, while FF4 (see Table 11) is used for those fasteners mentioned in b).

Manufacturer's test/inspection

Fasteners manufactured according to ISO 898 must meet all relevant requirements outlined in Tables 3 to 7 This compliance is verified through the “feasible” testing procedures specified in Tables 8 to 11 Adhering to these standards ensures the fasteners' quality and performance consistency. -**Sponsor**As a content creator, I understand the importance of SEO-optimized rewrites Need help making your articles shine? With [Article Generation](https://pollinations.ai/redirect-nexad/oPIQiZNX), you can instantly create 2,000-word articles, saving you time and money No more content creation struggles – it's like having your own content team! Let's transform your articles into SEO powerhouses today!

ISO 898 does not specify which tests manufacturers must perform on each manufacturing lot; instead, it is the manufacturer's responsibility to choose appropriate testing methods, such as in-process inspections or tests, to ensure that each lot complies with all applicable standards and requirements.

In case of dispute, the test methods in accordance with Clause 9 shall apply.

Supplier's test/inspection

Suppliers may test the fasteners they provide using the methods of their choice, provided the mechanical and physical properties specified in Tables 3 to 7 are met

In case of dispute, the test methods in accordance with Clause 9 shall apply.

Purchaser's test/inspection

The purchaser may test the delivered fasteners by the test methods given in Clause 9 using tests selected from the relevant test series given in 8.6

In case of dispute, the test methods in accordance with Clause 9 shall apply

Feasible tests for groups of fasteners and machined test pieces

The applicability of test series FF1 to FF4 and MP1 to MP2, using the test methods described in Clause 9, is specified in Tables 8 to 13

Test series FF1 to FF4 in accordance with Tables 8, 9, 10 and 11 are provided for the testing of finished fasteners:

⎯ FF1: these are tests for the determination of the properties of finished bolts and screws with full head strength and full or reduced shank (full loadability), d s > d 2 or d s ≈ d 2 (see Table 8);

⎯ FF2: these are tests for the determination of the properties of finished studs with full or reduced shank (full loadability), d s > d 2 or d s ≈ d 2 (see Table 9);

⎯ FF3: these are tests for the determination of the properties of finished bolts and screws with d s > d 2 or d s ≈ d 2 and reduced loadability due to

1) low head with or without external driving feature,

2) low round head or low cylindrical head with internal driving feature, or

3) countersunk head with internal driving feature

FF4 tests are designed to assess the properties of finished bolts, screws, and studs, particularly for applications where full load capacity as per ISO 898 is unnecessary or undesirable These tests are especially relevant for fasteners with waisted shanks, reduced loadability, or where the diameter d_s is less than d_2, as specified in Table 11.

Test series MP1 and MP2, in accordance with Tables 12 and 13, are designed for evaluating the material properties of fasteners and supporting process development Additionally, test series FF1 to FF4 can also be utilized for similar testing purposes, ensuring comprehensive assessment of fastener materials and manufacturing processes.

⎯ MP1: these are tests for the determination of the material properties of fasteners and/or for process development using machined test pieces (see Table 12)

⎯ MP2: these are tests for the determination of material properties of fasteners with full loadability, d s ≈ d 2 or d s > d 2, and/or for process development (see Table 13)

The relevance of the test methods to the group of fasteners shall be in accordance with Tables 8 to 13

For orders requiring a test report, the results shall be generated using the test methods outlined in Clause 9 and selected from Tables 8 to 13 Any additional specific tests requested by the purchaser must be agreed upon at the time of order to ensure compliance and accuracy.

Table 8 — Test series FF1 — Finished bolts and screws with full loadability

Table 3) Subclause d < 3 mm or l < 2,5d or b < 2,0d d ≥ 3 mm and l ≥ 2,5d and b ≥ 2,0d d < 3 mm or l < 2,5d or b < 2,0d d ≥ 3 mm and l ≥ 2,5d and b ≥ 2,0d

Tensile test under wedge loading 9.1 NF a NF a

5 Nominal stress under proof load,

Proof load test 9.6 NF NF

8 Minimum elongation after fracture, A f,min

Tensile test for full-size fasteners 9.3 NF b d c d NF b d

13 Maximum surface hardness NF NF

Maximum decarburized zone Decarburization test 9.10 NF NF

Reduction of hardness after retempering

Surface integrity and surface discontinuity inspection are crucial for fasteners with diameter d ≥ 3 mm, length l ≥ 2d, and width b < 2d, following guidelines specified in sections 9.1.5 and 9.2.5 Property class values such as 4.6, 5.6, 8.8, and 10.9 are detailed in Annex C, while classes 4.8, 5.8, and 6.8 have specific specifications For applications where l ≥ 2.7d and b ≥ 2.2d, particular dimensional limits apply, especially for torsional tests, which have distinct criteria compared to standard specifications The referenced tests serve as dispute resolution measures, allowing alternative testing methods such as the tensile test, although in disputes, the tensile test remains the authoritative method Notably, ISO 898-7 does not specify values for property classes 4.6 to 6.8, emphasizing the importance of adhering to established standards for surface integrity and discontinuity inspection. -**Sponsor**Looking to refine your article and boost its SEO? We can help you focus on the core meaning! Unlock the world of scientific knowledge with SpringerLink through [Apress Shop [Global]](https://pollinations.ai/redirect-nexad/pXjjlqW4), diving deep into research documents For fasteners (d ≥ 3 mm, l ≥ 2d), consult sections 9.1.5 and 9.2.5, while property class values (4.6, 5.6, 8.8, 10.9) are detailed in Annex C Remember, while alternatives like the torsional test exist, the tensile test remains the ultimate reference Plus, order your Apress books and ebooks today!

Feasible: the test is able to be carried out in accordance with Clause 9 and, in case of dispute, the test shall be carried out in accordance with Clause 9

The test is feasible but only conducted when explicitly specified, serving as an alternative test for a specific property—such as a torsional test when a tensile test is possible—or as a designated test required by product standards or customer orders, like an impact test.

NF Not feasible indicates that the test cannot be conducted due to issues with the fastener's form or dimensions, such as being too short or lacking a head Additionally, some tests are limited to specific categories of fasteners, like quenched and tempered fasteners.

Table 9 — Test series FF2 — Finished studs with full loadability

Subclause d < 3 mm or l t < 3d b < 2,0d or d ≥ 3 mm and l t ≥ 3d b ≥ 2,0d and d < 3 mm or l t < 3d b < 2,0d or d ≥ 3 mm and l t ≥ 3d b ≥ 2,0d and

1 Minimum tensile strength, R m,min Tensile test 9.2 NF a NF a

5 Nominal stress under proof load, S p,nom Proof load test 9.6 NF NF

8 Minimum elongation after fracture, A f,min

Tensile test for full- size fasteners 9.3 NF b c b d NF b c

15 Maximum decarburized zone Decarburization test 9.10 NF NF

16 Reduction of hardness after retempering Retempering test 9.12 NF NF e e

Surface integrity and surface discontinuity inspection are essential for ensuring the quality of threaded studs If a fracture occurs within the threaded length, minimum hardness values should be used instead of the tensile strength Rₘ,min, or alternatively, Rₘ can be determined using machined test specimens in accordance with section 9.7 The dimensions should satisfy the conditions b l t ≥ 3.2d and b ≥ 2.2d Property class values for 4.6, 5.6, 8.8, and 10.9 are provided in Annex C, while property classes 4.8, 5.8, and 6.8 have specific considerations A reference test is available for dispute resolution to ensure compliance with standards.

Feasible: the test is able to be carried out in accordance with Clause 9 and, in case of dispute, the test shall be carried out in accordance with Clause 9

The test is feasible and can be conducted only when explicitly specified, serving as an alternative test for a particular property, such as a torsional test instead of a tensile test It can also be performed as a specific test mandated by product standards or requested by the purchaser at the time of order, like an impact test.

NF (Not Feasible) indicates that the test cannot be performed due to the fastener’s form or dimensions, such as being too short or lacking a head Additionally, certain tests are only applicable to specific fastener categories, like quenched and tempered fasteners, which may limit their applicability.

Table 10 — Test series FF3 — Finished screws with reduced loadability due to head design

Subclause d < 3 mm or l < 2,5d or b < 2,0d d ≥ 3 mm and l ≥ 2,5d and b ≥ 2,0d d < 3 mm or l < 2,5d or b < 2,0d d ≥ 3 mm and l ≥ 2,5d and b ≥ 2,0d a Minimum ultimate tensile load

Tensile test for screws which do not break in the free threaded length due to head design

15 Maximum decarburized zone Decarburization test 9.10 NF NF

16 Reduction of hardness after retempering Retempering test 9.12 NF NF b b

19 Surface integrity Surface discontinuity inspection 9.15 a See relevant product standard for minimum ultimate tensile load b This test is a reference test to be applied in case of dispute

Feasible: the test is able to be carried out in accordance with Clause 9 and, in case of dispute, shall be carried out in accordance with Clause 9

The test is feasible and can be performed when explicitly specified, serving as an alternative in accordance with Clause 9 for specific properties such as a torsional test when a tensile test is available It can also be conducted as a particular test if required by the product standard or requested by the purchaser at the time of order, for example, an impact test.

When a fastener is classified as NF Not Feasible, it indicates that the test cannot be conducted due to its form or dimensions, such as being too short or lacking a head Additionally, certain tests are only applicable to specific categories of fasteners, like quenched and tempered types, which further limits the feasibility of testing.

Table 11 — Test series FF4 — Finished bolts, screws and studs with reduced loadability due to shank design (e.g waisted shank)

Subclause d < 3 mm or waist length

16 mm and d 0 ≥ 0,75d s and b ≥ d and l ≥ 5,5d + 8 mm a f g

2 Minimum lower yield strength, R eL,min h h NF NF NF

Minimum stress at 0,2 % non-proportional elongation, R p0,2 min

6 Minimum elongation after fracture, A min

7 Minimum reduction of area after fracture, Z min

Tensile test for machined test pieces

Decarburi- zation test 9.10 NF NF

Impact test d ≥ 16 mm and l i or l t ≥ 55 mm j

To determine the minimum total length (l_t) for studs, add 1d to the length formula, while for bolts and screws, ensure l ≥ 5d to calculate Z_min; for studs, l_t ≥ 6d, and for bolts and screws, l ≥ d + 20 mm, or studs with l_t ≥ 2d + 20 mm, and bolts and screws with l ≥ 4d + 8 mm, and studs with l_t ≥ 5d + 8 mm are required to determine Z_min If the lower yield strength (R_eL) cannot be established, measuring stress at 0.2% non-proportional elongation (R_p0.2) is permitted The solid part of the head may be included in measurements For impact testing, specific dimensional limits override those in the header Property class 5.6 has special considerations, and certain dimensions must be evaluated prior to machining.

Feasible: the test is able to be carried out in accordance with Clause 9 and, in case of dispute, shall be carried out in accordance with Clause 9

The test is deemed feasible only when explicitly specified, serving as an alternative or supplementary procedure according to Clause 9 It can be performed for specific properties, such as a torsional test when a tensile test is suitable, or as a particular test mandated by product standards or at the purchaser's request, like an impact test This ensures testing flexibility and compliance with technical requirements for quality assurance.

Tensile test under wedge loading of finished bolts and screws (excluding studs)

The purpose of this tensile test is to determine simultaneously:

⎯ the tensile strength on finished bolts and screws, R m;

⎯ the integrity of the transition section between the head and the unthreaded shank or the thread

This test applies to bolts and screws with or without flange having the following specifications:

⎯ flat bearing surface or serrated surfaces;

⎯ head stronger than the threaded section;

⎯ head stronger than any unthreaded shank;

⎯ diameter of any unthreaded shank, d s > d 2 or d s ≈ d 2;

The tensile testing machine shall be in accordance with ISO 7500-1 Tooling features altering the effect of the wedge angle, α, as specified in Figure 1 and Table 16 shall not be used

The grips, the wedge and the adaptors shall be in accordance with the following:

⎯ thread tolerance class of the internally threaded adaptor in accordance with Table 14;

⎯ hole diameter, d h, in accordance with Table 15;

⎯ wedge in accordance with Figure 1 and Tables 15 and 16

Table 14 — Thread tolerance classes of internally threaded adaptors

Thread tolerance class Finish of fastener Thread tolerance class of fastener before any surface coating

Thread tolerance class of internally threaded adaptor

Electroplating to ISO 4042 6g or 6e or 6f 6H

Zinc flake coating to ISO 10683 6g or 6e or 6f 6H

Hot dip galvanizing to ISO 10684 in order to mate with nuts tapped to thread tolerance classes:

The testing device must be sufficiently rigid to ensure bending occurs specifically in the transition section between the head and the unthreaded shank or thread Additionally, a radius or chamfer of 45° should be applied, as specified in Table 15, to ensure proper testing standards are met.

Figure 1 — Wedge loading of finished bolts and screws

Table 15 — Hole diameters and radius for the wedge

Nominal thread diameter d min max

This article discusses specifications for a Medium series in accordance with ISO 273 standards, emphasizing the importance of adapting hole dimensions for square neck bolts to ensure proper fit For product grade C, a radius (r₁) should be calculated using the formula r₁ = rₘₐₓ + 0.2, where rₘₐₓ represents the maximum radius, aₘₐₓ is the maximum size of the socket, and sₘᵢₙ is the minimum size of the screw These guidelines ensure compatibility and safety in manufacturing and assembly processes.

Table 16 — Wedge angle, α, for tensile test under wedge loading

Property class for bolts and screws with unthreaded shank length l s≥ 2d screws threaded to the head and bolts and screws with unthreaded shank length l s< 2d

For finished bolts and screws with head-bearing diameters exceeding 1.7 times the shank diameter (1.7d) that do not pass the wedge tensile test, the head can be machined down to 1.7d and subjected to re-testing according to the wedge angle specified in Table 16.

Moreover, for finished bolts and screws with head-bearing diameters above 1,9d, the 10° wedge angle may be reduced to 6°

The fastener shall be tested as received

The wedge, as specified in section 9.1.4, must be positioned beneath the head of the bolt or screw according to Figure 1 to ensure proper load distribution Additionally, the free threaded length (l_th) that is subject to load should be at least 1d to ensure adequate strength and safety Proper placement and sufficient threaded length are crucial for the integrity and performance of fastened connections.

For structural bolts having short thread length, the tensile test under wedge loading may be performed with a free thread length, l th, of less than 1d

The tensile test under wedge loading must be performed in accordance with ISO 6892-1 standards Testing should be conducted at a cross-head speed not exceeding 25 mm/min, as measured with a free-running cross-head, to ensure accurate and consistent results.

The tensile test shall be continued until fracture occurs

Measure the ultimate tensile load, F m

The calculation of the tensile strength, R m, is based on the nominal stress area, A s,nom, and the ultimate tensile load, F m , measured during the test: m m s,nom

⎝ ⎠ (2) where d 2 is the basic pitch diameter of external thread in accordance with ISO 724; d 3 is the minor diameter of external thread

3 1 6 d =d − H d 1 is the basic minor diameter of external thread in accordance with ISO 724;

H is the height of the fundamental triangle of the thread in accordance with ISO 68-1

Values of the nominal stress area, A s,nom, are given in Tables 4 and 6

For bolts and screws with d s> d 2 and screws threaded to the head, the fracture shall occur in the free threaded length

For fasteners with d s ≈ d 2, the fracture shall occur in the free threaded length or in the unthreaded shank

R m shall meet the requirements specified in Table 3 The minimum ultimate tensile load, F m,min, specified in Tables 4 and 6 shall be met

For small diameter components, the difference between the nominal stress area and the effective stress area increases significantly When hardness testing or process control is required for these smaller sizes, it may be necessary to exceed the minimum hardness specified in Table 3 to ensure the attainment of the required ultimate tensile load.

9.1.6.2 Determination of integrity of transition section between head and unthreaded shank/thread — Requirements

The fracture shall not occur in the head

For bolts and screws with unthreaded shank, the fracture shall not occur in the transition section between the head and the shank

Screws with threaded heads can fail when cracks originate in the free threaded section These fractures may extend into the transition zone between the head and the thread or into the head itself before the screw separates Proper understanding of failure modes in threaded screws is essential for ensuring structural integrity and preventing sudden failures.

Tensile test for finished bolts, screws and studs for determination of tensile strength, R m

The purpose of this tensile test is to determine the tensile strength on finished fasteners, R m

This test can be combined with the test specified in 9.3

This test applies to bolts, screws and studs having the following specifications:

⎯ bolts and screws with head stronger than the threaded shank;

⎯ bolts and screws with head stronger than any unthreaded shank;

⎯ diameter of any unthreaded shank of d s> d 2 or d s≈ d 2;

⎯ bolts and screws with nominal length l ≥ 2,5d;

The tensile testing machine shall be in accordance with ISO 7500-1 Side thrust on the fastener shall be avoided, e.g by self-aligning grips

The grips and the adaptors shall be as follows:

The thread tolerance class of the internally threaded adaptors is determined according to Table 14 Testing devices vary based on the type of fastener: bolts, screws, studs, or fully threaded studs Examples include specialized testing equipment designed to verify the thread tolerance class for each fastener type, ensuring compliance with industry standards Proper testing ensures the reliability and fit of internally threaded adaptors across different applications.

2 nut end d h hole diameter l th free threaded length of fastener in testing device

Figure 2 — Examples of testing devices for tensile test on full-size fasteners

The tested bolt or screw must be installed into adapters following the configurations shown in Figures 2 a) or b), ensuring proper mounting For stud testing, it should be secured in two threaded adapters as illustrated in Figures 2 c) or d) To ensure accurate testing, the minimum thread engagement length must be at least 1d, adhering to standard measurement practices for reliable results.

The minimum free threaded length (l_th) subjected to the load should be at least 1d When this test is combined with the test according to section 9.3, the free threaded length (l_th) must be increased to 1.2d Ensuring the appropriate threaded length is crucial for load capacity and thread integrity.

For structural bolts having short thread length, the tensile test may be performed with a free thread length l th less than 1d

The tensile test shall be carried out in accordance with ISO 6892-1 The speed of testing, as determined with a free-running cross-head, shall not exceed 25 mm/min

Measure the ultimate tensile load, F m

For fasteners with d s> d 2, the fracture shall occur in the free threaded length

For fasteners with d s ≈ d 2, the fracture shall occur in the free threaded length or in the unthreaded shank

Screws with threaded heads can fail due to fractures that originate in the free threaded length These fractures may extend into the transition zone between the head and the thread or into the head itself prior to complete separation Proper consideration of the integrity in these regions is essential to prevent failure and ensure the screw's durability.

R m shall meet the requirements specified in Table 3 The minimum ultimate tensile load, F m,min, specified in Tables 4 and 6 shall be met

For small diameter components, the gap between the nominal and effective stress areas widens, impacting their performance When using hardness measurements for process control on these smaller diameters, it may be necessary to increase the hardness beyond the minimum specified in Table 3 This adjustment helps ensure the minimum ultimate tensile load is achieved, maintaining the component's structural integrity and reliability.

Tensile test for full-size bolts, screws and studs for determination of elongation after fracture, A f , and stress at 0,0048d non-proportional elongation, R pf

The purpose of this tensile test is to determine simultaneously:

⎯ the elongation after fracture on full-size fasteners, A f;

⎯ the stress at 0,0048d non-proportional elongation on full-size fasteners, R pf

This test can be combined with the test described in 9.2

⎯ diameter of any unthreaded shank d s≈ d or d s> d;

⎯ studs with metal end stronger than the nut end;

⎯ thread tolerance class of the internally threaded adaptor(s) in accordance with Table 14

The testing device shall be sufficiently rigid to avoid deformation that could influence the determination of the load at 0,0048d non-proportional elongation, F pf, or of the elongation after fracture, A f

To ensure accurate testing, bolts or screws must be mounted into adaptors following the configurations shown in Figures 2a) or b), while studs should be mounted into two threaded adaptors as illustrated in Figures 2c) or d) The thread engagement length must be at least 1d to meet testing standards.

The free threaded length, l th, subjected to the load shall be 1,2d

To achieve the desired lth = 1, 2d accurately in practical applications, follow this procedure: first, screw the threaded adapter onto the component until it reaches the thread run-out; then, unscrew the adapter by the specific number of turns corresponding to the target lth = 1, 2d.

The tensile test must be conducted following ISO 6892-1 standards to ensure accurate and consistent results The testing speed, defined by a free-running cross-head, should not exceed 10 mm/min until reaching the load at 0.0048d non-proportional elongation Adhering to these guidelines guarantees reliable measurement of material strength and elongation properties.

F pf, and 25 mm/min beyond

The load, F, must be measured continuously until fracture, using either an electronic device such as a microprocessor or by analyzing the load versus displacement curve per ISO 6892-1 standards This load-displacement curve can be plotted automatically or manually, ensuring accurate data collection during the test.

For acceptable accurate graphical measurement, the scale of the curve shall be such that the elastic slope (straight part of the curve) lies between 30° and 45° against the load axis

9.3.6.1 Determination of the elongation after fracture, A f

The plastic elongation, ∆L p, is measured directly on the load-displacement curve, plotted either electronically or graphically (see Figure 3) a Point of fracture

Figure 3 — Load-displacement curve for determination of elongation after fracture, A f

To analyze the elastic range of the curve, determine the slope of the straight (elastic) portion Then, draw a line parallel to this slope through the fracture point, which intersects the grip displacement axis, as illustrated in Figure 3 The plastic elongation (∆Lₚ) is measured along the grip displacement axis based on this intersection, providing essential data for material deformation assessment.

To accurately determine the slope of the load-displacement curve within the elastic range, draw a line intersecting the points corresponding to 0.4Fₚ and 0.7Fₚ, where Fₚ is the proof load specified in Tables 5 and 7.

The elongation after fracture on full-size fasteners is calculated using Formula (3): f 1,2p

For property classes 4.8, 5.8 and 6.8, A f shall meet the requirement specified in Table 3

9.3.6.2 Determination of the stress at 0,0048 d non-proportional elongation, R pf

R pf shall be directly determined on the load-displacement curve (see Figure 4)

Figure 4 — Load-displacement curve for determination of stress at 0,0048 d non-proportional elongation, R pf

A line parallel to the slope in the elastic range of the load-displacement curve should be drawn at a distance of 0.0048d along the grip displacement axis The intersection of this line with the curve indicates the load Fpf, providing a crucial point for understanding the material's elastic behavior This method helps accurately determine the load at a specific displacement in material testing, ensuring precise results in structural analysis.

To determine the slope of the load-elongation curve in the elastic range, draw a line intersecting the points corresponding to 0.4Fₚ and 0.7Fₚ, where Fₚ is the proof load specified in Tables 5 and 7 This method ensures an accurate assessment of the elastic behavior of the material or component under load.

The stress at 0,0048d non-proportional elongation, R pf, is calculated using Formula (4): pf pf s,nom

= A (4) with A s,nom as specified in 9.1.6.1

NOTE 1 Values for R pf are under investigation See Table 3 (No 4 and footnote e) for information

NOTE 2 Yield strength values received from tests of full-size fasteners instead of machined test pieces can vary because of processing, test methods and size effects

Tensile test for bolts and screws with reduced loadability due to head design

This tensile test aims to determine the tensile load capacity of bolts and screws with reduced loadability, specifically those not expected to break in the free threaded length due to the head design The test results are essential for assessing the strength and performance of these fasteners, ensuring they meet safety and reliability standards Understanding the load limits helps in selecting appropriate bolts and screws for various applications, optimizing design and durability.

This test applies to bolts and screws having the following specifications:

⎯ not expected to break in the free threaded length due to head design;

⎯ diameter of any unthreaded shank d s > d 2 or d s ≈ d 2;

⎯ thread tolerance class of the internally threaded adaptor in accordance with Table 14

The bolt or screw to be tested shall be mounted into adaptors in accordance with Figure 2 a) or b)

The free threaded length, l th, subjected to the load shall be a minimum of 1d

The ultimate tensile load, F m, shall be measured

The ultimate tensile load, F m, shall be equal to or above the minimum ultimate tensile load as specified in the relevant product standard or other relevant specification

Tensile test for fasteners with waisted shank

The purpose of this tensile test is to determine the tensile strength, R m, for fasteners with waisted shank (see 8.2)

This test applies to fasteners having the following specifications:

⎯ length of waisted shank ≥ 3d s (see L c in Figure 6);

The bolt to be tested must be securely mounted into an adaptor following the specifications shown in Figure 2a, ensuring proper positioning The stud should be installed into two threaded adaptors as illustrated in Figure 2c to ensure accurate testing conditions Additionally, the length of thread engagement must be a minimum of 1d to meet testing standards and ensure reliable results.

The calculation of the tensile strength, R m, is based on the cross-sectional area of the waisted shank, A ds,and the ultimate tensile load, F m, measured during the test: m m ds

The fracture shall occur in the waisted shank

R m shall meet the requirement specified in Table 3.

Proof load test for finished bolts, screws and studs

The proof load test consists of two main operations, as follows,

⎯ application of a specified tensile proof load (see Figure 5), and

⎯ measurement of permanent elongation, if any, caused by the proof load

⎯ diameter of unthreaded shank d s > d 2 or d s ≈ d 2;

The grips and the adaptors shall be in accordance with the following:

The thread tolerance class of the internally threaded adaptor(s) is specified according to Table 14 Testing devices are provided as examples for different fastener types, including bolts, screws, studs, and fully threaded studs These standardized testing devices ensure accurate assessment of thread tolerance compliance across various applications, highlighting the importance of adhering to specified class standards for reliable and secure fastening.

2 nut end d h hole diameter l th free threaded length of fastener in testing device

An example of contact is the "sphere to cone" interaction between the measuring points and the center-drilled conical holes at the ends of the fastener, as illustrated in detail X Alternatively, other appropriate methods may be employed for accurate measurement and analysis.

Figure 5 — Examples of testing devices for proof load test

The fastener must be properly prepared at each end, following the specifications illustrated in Figure 5 (detail X) Accurate length measurements should be taken using a bench-mounted measuring instrument equipped with spherical anvils or an equally suitable method To reduce measurement errors caused by temperature influence, gloves or tongs must be used during the measurement process The total length of the fastener should be recorded prior to loading, denoted as l₀.

To ensure accurate testing, bolts and screws must be mounted into appropriate adaptors as shown in Figures 5a) or 5b) Studs intended for testing should be installed into two threaded adaptors, as illustrated in Figures 5c) and 5d) It is essential that the length of thread engagement between components is at least 1d, ensuring reliable and consistent test results.

The free threaded length, l th, subjected to the load shall be 1d

NOTE To obtain l th = 1d in a practical way, the following procedure is proposed: first, screw on the threaded adaptor up to the thread run-out; then unscrew the adaptor by the required number of turns corresponding to l th = 1d

The proof load, as specified in Tables 5 and 7, shall be applied axially to the fastener

The speed of testing, as determined with a free-running cross-head, shall not exceed 3 mm/min The full proof load shall be held for 15 s

After unloading, the total length of the fastener, l 1, shall be measured

The total length of the fastener after unloading, l 1, shall be the same as before loading, l 0, within a tolerance of ± 12,5 àm allowed for uncertainty of measurement

Variables like straightness, thread alignment, and measurement uncertainty can cause an apparent elongation of the fastener during initial proof load application In these cases, the fastener must be retested following section 9.6.5, using a load 3% higher than the proof load specified in Tables 5 and 7 to ensure accurate assessments.

The total length after the second unloading, l 2, shall be the same as before this loading, l 1, within a tolerance of ± 12,5 àm allowed for uncertainty of measurement.

Tensile test for machined test pieces

The purpose of this tensile test is to determine

⎯ the lower yield strength, R eL, or stress at 0,2 % non-proportional elongation, R p0,2,

⎯ the percentage elongation after fracture, A, and

⎯ the percentage reduction of area after fracture, Z

This test applies to fasteners having the following specifications: a) machined test pieces made from bolts and screws:

⎯ nominal length l ≥ 6d 0 + 2r + d (as specified in Figure 6) to determine A;

⎯ nominal length l ≥ 4d 0 + 2r + d (as specified in Figure 6) to determine Z; b) machined test pieces made from studs:

⎯ thread length of the stud metal end b m ≥ 1d;

⎯ total length l t ≥ 6d 0 + 2r + 2d (as specified in Figure 6) to determine A;

⎯ total length l t≥ 4d 0 + 2r + 2d (as specified in Figure 6) to determine Z; c) property classes 4.6, 5.6, 8.8, 9.8, 10.9 and 12.9/12.9

Machined test pieces are typically fabricated from fasteners with specific geometries that influence their load capacity These test pieces can be produced from fasteners where the head is stronger than the cross-sectional area (S₀), ensuring structural integrity during testing Additionally, fasteners with unthreaded shank diameters (dₛ) smaller than the threaded diameter (d₂) are also suitable, particularly when their design reduces loadability due to their geometry These considerations are essential for accurate testing and reliable performance evaluation of fasteners.

Fasteners in property classes 4.8, 5.8 and 6.8 (work-hardened fasteners) shall be tensile tested full-size (see 9.3)

The test piece shall be machined from the fastener as received The test piece in accordance with Figure 6 shall be used for the tensile test

The diameter of the machined test piece shall be d 0< d 3,min, but whenever possible d 0≥ 3 mm

When machining test pieces of quenched and tempered fasteners with a nominal diameter greater than 16 mm, the diameter reduction must not exceed 25%, which is approximately 44% of the original cross-sectional area For test specimens made from studs, both ends should have a minimum thread length of 1d to ensure proper testing and performance.

The tensile test must be performed in accordance with ISO 6892-1 standards Testing speed should not exceed 10 mm/min when using a free-running cross-head up to the lower yield strength (ReL) or the stress at 0.2% non-proportional elongation (Rp0.2) Beyond these points, the testing speed can be increased up to 25 mm/min to ensure accurate and reliable results.

Key d nominal thread diameter d 0 diameter of machined test piece (d 0 < d 3,min but, whenever possible, d 0 ≥ 3 mm) b thread length (b ≥ d)

L o original gauge length of machined test piece

— for determination of elongation: L o = 5d 0 or ( 5,65 S o )

— for determination of reduction of area: L o≥ 3d 0

L c length of straight portion of machined test piece (L o + d 0)

L t total length of machined test piece (L c + 2r + b)

S o cross-sectional area of machined test piece before tensile test r fillet radius (r ≥ 4 mm)

Figure 6 — Machined test piece for tensile test

The following properties shall be determined in accordance with ISO 6892-1: a) tensile strength, R m m m o

= S (6) b) lower yield strength, R eL, or stress at 0,2 % non-proportional elongation, R p0,2;

= − × (7) where L u is the final gauge length of machined test piece (see ISO 6892-1); d) percentage reduction of area after fracture, provided L o is at least 3d 0 o u o

= − × (8) where S u is the cross-sectional area of machined test piece after fracture

The following shall meet the requirements specified in Table 3:

⎯ lower yield strength, R eL, or stress at 0,2 % non-proportional elongation, R p0,2;

⎯ percentage reduction of area after fracture, Z.

Head soundness test

The head soundness test is designed to evaluate the integrity of the transition between the fastener's head and the unthreaded shank or threaded portion This test involves striking the fastener head on a solid block at a specified angle to detect any defects or weaknesses Ensuring the head's soundness is crucial for maintaining the fastener's overall durability and performance.

NOTE This test is generally used when the tensile test under wedge loading cannot be carried out due to the too- short length of the fastener

This test applies to bolts and screws having the following specifications:

⎯ head stronger than the threaded shank;

The solid block in accordance with Figure 7 shall be as follows:

⎯ hole diameter, d h, and radius, r 1, in accordance with Table 15;

⎯ angle, β, in accordance with Table 17 a l ≥ 1,5d b Minimum thickness of solid block: 2d

Figure 7 — Testing device for head soundness test

Table 17 — Angle of solid block, β, for head soundness test

The head soundness test shall be carried out using a device in accordance with Figure 7

Ensure the block is securely fixed before proceeding Use a hammer to strike the head of the bolt or screw with multiple blows, causing the head to bend to an angle of 90° minus beta (β) Refer to Table 17 for the specific values of angle β to ensure accurate bending and proper installation.

The examination shall be carried out at a magnification of not less than eight times nor more than 10 times

No sign of cracking at the transition section between the head and the unthreaded shank shall be visible

For screws threaded to the head, this requirement is fulfilled even if a crack appears in the first thread, provided the head does not fracture off.

Hardness test

The purpose of the hardness test is

⎯ for all fasteners which cannot be tensile tested: to determine the hardness of the fastener, and

⎯ for fasteners which can be tensile tested (see 9.1, 9.2, 9.5 and 9.7): to determine the hardness of the fastener in order to check that the maximum hardness is not exceeded

NOTE There might not be a direct relationship between hardness and tensile strength Maximum hardness values are specified for reasons other than theoretical maximum strength consideration (e.g to avoid embrittlement)

Hardness may be determined either on a transverse section through the threaded portion (see 9.9.4.2) or on a suitable surface (see 9.9.4.3)

Hardness may be determined using the Vickers, Brinell or Rockwell hardness test a) Vickers hardness test

The Vickers hardness test shall be carried out in accordance with ISO 6507-1 b) Brinell hardness test

The Brinell hardness test shall be carried out in accordance with ISO 6506-1 c) Rockwell hardness test

The Rockwell hardness test shall be carried out in accordance with ISO 6508-1

Fasteners used for hardness tests shall be as received

9.9.4.2 Hardness determined on a transverse section through the threaded portion

NOTE The term “core hardness” is commonly used for hardness determined by this test method

A transverse section shall be taken 1d back from the end of the thread, and the surface shall be suitably prepared

Hardness readings shall be performed in the area between the axis and the half-radius position (see Figure 8)

2 half-radius area (radius of 0,25d)

Figure 8 — Half-radius area for hardness determination

Hardness testing should be conducted on flat surfaces of the head, the end of the fastener, or the unthreaded shank, ensuring the removal of any coating and proper specimen preparation.

This method may be used for routine inspection

9.9.4.4 Test load for hardness determination

The Vickers hardness test shall be carried out with a minimum load of 98 N

The Brinell hardness test shall be carried out with a load equal to 30D 2 , expressed in newtons

For fasteners that cannot undergo tensile testing and for structural bolts with short threaded lengths (where the free threaded length l_th is less than 1d), the hardness must meet the specifications outlined in Table 3 to ensure proper quality and performance.

Fasteners with a free threaded length (l_th) of at least 1d, as well as those with waisted shanks and machined test pieces, must conform to maximum hardness values outlined in Table 3 Ensuring these hardness limits guarantees optimal strength and durability of the fasteners Proper hardness control is essential for maintaining product quality and compliance with standards.

Fasteners classified as property classes 4.6, 4.8, 5.6, 5.8, and 6.8 must have hardness levels, measured according to section 9.9.4.3, that do not exceed the maximum hardness values specified in Table 3 This ensures compliance with safety and quality standards for fastener durability and performance.

For quenched and tempered fasteners, a hardness difference exceeding 30 HV in the half-radius area (refer to Figure 8) must be verified against the 90% martensite content requirement outlined in Table 2.

For work hardened fasteners of property classes 4.8, 5.8 and 6.8, hardness determined in accordance with 9.9.4.2 shall be within the hardness range specified in Table 3

In case of dispute, the test in accordance with 9.9.4.2 using the Vickers hardness method shall be the reference test method.

Decarburization test

The decarburization test aims to identify whether the surface of quenched and tempered fasteners has undergone decarburization It also measures the depth of the fully decarburized zone, as illustrated in Figure 9.

NOTE A loss of carbon content (decarburization) beyond the limits specified in Table 3 can reduce the strength of the thread and can cause failure

Decarburization shall be determined using the following two methods:

The microscopic method is employed to accurately measure the depth of the complete decarburized zone, denoted as G, providing crucial insights into material integrity It also helps identify the presence of ferritic decarburization, if present, which can affect mechanical properties Additionally, this method determines the height of the base metal, represented as E, ensuring comprehensive analysis of the material's microstructure (Refer to Figure 9 for a visual representation.)

The hardness method is employed to verify whether the minimum base metal height requirement, E, is satisfied Additionally, it is used to detect decarburization through micro-hardness testing, as illustrated in Figure 10.

2 partial decarburization or ferritic decarburization

E height of the non-decarburized thread zone

G depth of complete decarburization in the thread

H 1 height of external thread in maximum material condition

This method applies to fasteners having the following specifications:

The test specimens shall be taken from the fasteners after all heat treatment operations have been performed and after removal of coating, if any

Test specimens should be extracted as a longitudinal section along the thread axis, approximately one nominal diameter (1d) from the end of the thread They must be embedded in a plastic mount or secured in a clamp to ensure stability during analysis Following mounting, the specimen surface should be ground and polished according to standard metallographic procedures to achieve optimal surface quality for accurate examination.

NOTE Etching in a 3 % nital solution (concentrated nitric acid in ethanol) is usually suitable for showing changes in microstructure caused by decarburization

The test specimen shall be placed under a microscope Unless otherwise agreed, a 100× magnification shall be used for examination

When using a microscope with a ground glass screen, the degree of decarburization can be directly measured with a scale for accurate assessment For measurements through the eyepiece, it is essential to use an appropriate eyepiece equipped with a cross-hair or built-in scale to ensure precise and reliable results.

The maximum depth of complete decarburization, G, must comply with the requirements outlined in Table 3 Additionally, the height of the non-decarburized thread zone, E, should meet the specifications in Table 18, ensuring no decarburization occurs in the base metal (zone 4) as depicted in Figure 9.

Ferritic decarburization in zone 2 in accordance with Figure 9 should be avoided; however it shall not be cause of rejection provided the hardness requirements in accordance with 9.10.3.4 are met

Table 18 — Values for height of external thread in maximum material condition, H 1 , and minimum height of non-decarburized zone in thread, E min

E min b 0,230 0,276 0,322 0,368 0,460 0,575 0,690 0,806 0,920 1,151 1,380 1,610 1,841 a For P < 1,25 mm, microscopic method only b Calculated on the basis of the specification in Table 3, No 14

The test specimen shall be prepared in accordance with 9.10.2.2, but etching and removal of the surface coating is not necessary

The Vickers hardness shall be determined at points 1 and 2 in accordance with Figure 10 The test force shall be 2,942 N (Vickers hardness test HV 0,3)

No decarburization when HV(2) ≥ HV(1) − 30

No carburization when HV(3) ≤ HV(1) + 30

E height of non-decarburized zone in the thread, mm

H 1 height of external thread in the maximum material condition, mm

1, 2, 3 measurement points (1 is the reference point)

4 pitch line a The value 0,14 mm is given only as an aid to locating the point along the pitch line

Figure 10 — Hardness determination for decarburization test and carburization test

The Vickers hardness at point 2 (HV(2)) must be at least equal to the hardness at point 1 (HV(1)) minus 30 Vickers units, ensuring adequate material properties Additionally, the height of the non-decarburized zone, E, should conform to the specifications outlined in Table 18 to meet quality standards.

NOTE Complete decarburization up to the maximum specified in Table 3 cannot be detected by the hardness measurement method.

Carburization test

This test aims to verify that the surface of a quenched and tempered fastener has not undergone carburization during heat treatment The key factor in evaluating carburization is the difference between the hardness of the base metal and the surface hardness A significant hardness disparity indicates carburization, while similar hardness levels confirm the surface remains unaffected Ensuring minimal surface carburization is crucial for maintaining the fastener's mechanical integrity and performance.

In addition, the maximum surface hardness shall not be exceeded for property classes 10.9 and 12.9/12.9

Carburization can be detrimental to materials because increased surface hardness may lead to embrittlement and decreased fatigue resistance It is important to distinguish between hardness improvements caused by carburization and those resulting from heat treatment or cold working processes, such as thread rolling after heat treatment Recognizing these differences helps ensure proper material performance and prevents potential failures.

Carburization shall be detected by one or the other of the following two methods:

⎯ hardness test on a longitudinal section;

In case of dispute and when P ≥ 1,25 mm, the hardness test on a longitudinal section in accordance with 9.11.2 shall be the reference test method

9.11.2 Hardness test on a longitudinal section

9.11.2.2 Preparation of the test specimen

The test specimen shall be prepared in accordance with 9.10.2.2, but etching and removal of the coating is not necessary

The Vickers hardness shall be determined at points 1 and 3 in accordance with Figure 10 The test force shall be 2,942 N (Vickers hardness test HV 0,3)

When testing a specimen according to section 9.10.3.3, hardness at point 3 should be measured along the pitch line of the thread adjacent to the thread used for determinations at points 1 and 2 Ensuring accurate hardness testing in this area is essential for consistent quality assessment Proper placement of the hardness measurement on the pitch line near the tested thread guarantees reliable and repeatable results.

The Vickers hardness value at point 3, HV(3), shall be less than or equal to the value at point 1, HV(1), plus

An increase of more than 30 Vickers units indicates carburization during testing Additionally, the surface hardness must not exceed 390 HV 0,3 for property class 10.9 and 435 HV 0,3 for property class 12.9/12.9, as outlined in Table 3, to meet specification requirements.

To ensure accurate and reproducible readings, a flat surface should be prepared on the head or end of the fastener through minimal grinding or polishing This process helps maintain the original properties of the material's surface layer while providing a reliable contact point for testing Proper surface preparation is essential for consistent results in quality assessments and adherence to standards.

A transverse section shall be taken 1d back from the end of the thread and the surface shall be suitably prepared

The surface hardness shall be determined on the prepared surface in accordance with 9.9.4.3

The base metal hardness shall be determined on the transverse section (location and preparation of the transverse section in accordance with 9.9.4.2)

The test force shall be 2,942 N (Vickers hardness test HV 0,3) for both determinations

The surface hardness must not exceed the base metal hardness by more than 30 Vickers units, as a measure of quality control An increase greater than 30 Vickers units suggests carburization has occurred, indicating potential case hardening issues Monitoring surface hardness within this limit is essential to ensure proper heat treatment and material integrity.

In addition to this requirement, the surface hardness shall not exceed 390 HV 0,3 for property class 10.9, and

435 HV 0,3 for property class 12.9/12.9 as specified in Table 3.

Retempering test

The purpose of this test is to check that the minimum tempering temperature has been achieved during the heat treatment process

This test is a reference test to be applied in case of dispute

The Vickers hardness shall be determined in accordance with 9.9.4.2 by taking three readings on one fastener

The fastener must be retempered by maintaining it at a temperature 10°C below the minimum specified in Table 2 for 30 minutes After retempering, Vickers hardness should be measured by taking three new readings in the same area of the fastener used for the initial test This process ensures proper hardness verification and quality control.

The mean of the three hardness readings taken before and after retempering shall be compared The reduction of hardness after retempering, if any, shall be less than 20 Vickers units.

Torsional test

The purpose of the torsional test is to determine the breaking torque, M B, for bolts and screws

⎯ bolts and screws with head stronger than the threaded section;

⎯ diameter of unthreaded shank d s≈ d 2 or d s> d 2;

NOTE For property classes 4.6 to 6.8, no values are specified in ISO 898-7

The apparatus and testing device are specified in ISO 898-7

Ensure the bolt or screw is securely clamped into the test device following ISO 898-7 standards, with a minimum thread engagement length of 1d The free threaded length (l_th) must be at least 2 times the pitch (2P) from the head to the thread run-out or from the unthreaded shank to the thread run-out Apply torque gradually in a continuous manner to achieve accurate testing results.

NOTE An examination of the related basic research has indicated that the values for free threads and thread engagement length have been interchanged in ISO 898-7:1992

The method is specified in ISO 898-7

Requirements are specified in ISO 898-7

In case of dispute, the following applies:

⎯ for bolts and screws that cannot be tensile tested, the hardness test in accordance with 9.9 shall be the reference test;

⎯ for bolts and screws which can be tensile tested, the tensile test shall be the reference test.

Impact test for machined test pieces

The impact test assesses the toughness of fastener materials under impact loads at specified low temperatures This test is performed only when mandated by product standards or based on an agreement between the manufacturer and the purchaser.

⎯ machined test pieces made from bolts, screws and studs;

⎯ total length of bolts and screws (including solid part of the head) ≥ 55 mm;

⎯ studs with total length l t ≥ 55 mm;

The apparatus and testing device are specified in ISO 148-1

The test piece shall be machined from the fastener as received

The machined test piece must conform to ISO 148-1 (Charpy V-notch test) standards, ensuring accurate and consistent testing It should be cut lengthwise, positioned as close to the fastener surface as possible, and located within the threaded portion to accurately assess material properties The non-notched side of the test specimen should be positioned near the surface of the fastener to optimize test results and data reliability.

The machined test piece shall be maintained at a stabilized temperature of −20 °C The impact test shall be carried out in accordance with ISO 148-1

When tested at a temperature of −20 °C, the impact strength shall be in accordance with Table 3

NOTE Other test temperatures and impact strength values can be specified in appropriate product standards or agreed between the manufacturer and the purchaser.

Surface discontinuity inspection

Surface discontinuities shall be tested on fasteners as received

For fasteners of property classes 4.6 to 10.9, a surface discontinuity inspection shall be carried out in accordance with ISO 6157-1 By agreement between the manufacturer and the purchaser, ISO 6157-3 may apply

For fasteners of property class 12.9/12.9, surface discontinuity inspection shall be carried out in accordance with ISO 6157-3

In the case of test series MP1 (see Clause 8), the surface discontinuity inspection applies before machining

General

Fasteners designed according to ISO 898 specifications must be properly labeled following the designation system outlined in Clause 5 Additionally, they should be marked in compliance with sections 10.2, 10.3, or 10.4 to ensure proper identification and adherence to international standards.

The designation system outlined in Clause 5 and the marking provisions specified in Sections 10.3 and 10.4 should only be utilized when all relevant requirements of this part of ISO 898 are satisfied, ensuring compliance with the standards © ISO 2013 – All rights reserved.

Unless otherwise specified in the product standard, the height of embossed markings on the top of the head shall not be included in the head height dimensions.

Manufacturer's identification mark

During manufacturing, all fasteners marked with a property class symbol must include the manufacturer's identification mark It is also recommended to add the manufacturer's identification mark on fasteners that are not marked with a property class symbol This ensures traceability and quality assurance throughout the production process.

A distributor who distributes fasteners that are marked with his (or her) own identification mark shall be considered to be the manufacturer.

Marking and identification of fasteners with full loadability

Fasteners with full loadability manufactured to the requirements of this part of ISO 898 shall be marked in accordance with 10.3.2 to 10.3.4

Alternative or optional permitted marking as stated in 10.3.2 to 10.3.4 are left to the choice of the manufacturer

10.3.2 Marking symbols for property classes

Marking symbols are specified in Table 19

Table 19 — Marking symbols for fasteners with full loadability Property class 4.6 4.8 5.6 5.8 6.8 8.8 9.8 10.9 12.9 12.9 Marking symbol a 4.6 4.8 5.6 5.8 6.8 8.8 9.8 10.9 12.9 12.9 a The dot in the marking symbol may be omitted

For small screws or when the head shape prevents marking per Table 19, clock face marking symbols from Table 20 can be used instead.

Table 20 — Clock face system for marking bolts and screws with full loadability

The twelve o'clock position, serving as a reference mark, should be securely marked with either the manufacturer's identification symbol or a dot for clear identification Additionally, the property class is designated by a dash or double dash, with the 12.9 property class specifically identified by a dot, ensuring easy recognition and adherence to marking standards.

10.3.3.1 Hexagon and hexalobular head bolts and screws

Hexagon and hexalobular head bolts and screws, including those with flanges, must be marked with the manufacturer's identification mark and the property class symbol as specified in Table 19, ensuring clear identification and compliance with standards.

The marking is required for fasteners of all property classes and of nominal diameter d ≥ 5 mm

Marking should ideally be placed on the top of the head through indenting or embossing, or on the side of the head via indenting, as shown in Figure 11 For bolts or screws with flanges, markings should be on the flange when manufacturing constraints prevent marking on the head's top The markings must include the manufacturer's identification mark and the property class symbol to ensure proper identification and traceability.

Figure 11 — Examples of marking on hexagon and hexalobular head bolts and screws

10.3.3.2 Hexagon and hexalobular socket head cap screws

Hexagon and hexalobular socket head cap screws shall be marked with the manufacturer's identification mark and with the marking symbol of the property class specified in Table 19

The marking shall be made preferably on the side of the head by indenting, or on the top of the head by indenting or embossing (see Figure 12)

Figure 12 — Examples of marking on hexagon socket head cap screws

10.3.3.3 Cup head square neck bolts

Cup head square neck bolts shall be marked with the manufacturer's identification mark and with the marking symbol of the property class specified in Table 19

The marking shall be made on the head by indenting or embossing (see Figure 13)

Figure 13 — Example of marking cup head square neck bolts 10.3.3.4 Studs

Studs shall be marked with the manufacturer's identification mark and with the marking symbol of the property class specified in Table 19 or the alternative marking symbol specified in Table 21

The marking is required for studs of property classes 5.6, 8.8, 9.8, 10.9 and 12.9/12.9, and of nominal diameter d ≥ 5 mm

Markings should be placed on the unthreaded part of the stud; if this is not feasible, the property class mark can be positioned on the nut end In such cases, the manufacturer's identification mark may be omitted, ensuring clear identification according to standard guidelines (see Figure 14).

For studs with interference fit, the marking of property class shall be on the nut end, and the manufacturer's identification mark may be omitted

Figure 14 — Example of marking of studs

Table 21 — Alternative marking symbols for studs

Marking symbol a It is permissible to indent only the contour or the whole area of the symbol.

10.3.3.5 Other types of bolts and screws

If requested by the purchaser, the same marking systems outlined in clause 10.3 will be used for other bolt, screw, and special fastener types, ensuring consistent identification.

Marking typically does not occur with screws that have flat countersunk, oval countersunk, cheese, or pan head shapes, especially those that are slotted, cross-recessed, or feature internal driving mechanisms such as sockets.

10.3.4 Marking of bolts and screws with left-hand thread

Bolts and screws with left-hand threads and a nominal diameter of at least 5 mm must be marked with the designated symbol, as specified in Figure 15, either on the top of the head or at the end of the fastener, to ensure proper identification and compliance with standards.

Figure 15 — Marking of bolts and screws with left-hand thread

Alternative marking for left-hand thread as specified in Figure 16 may be used for hexagon bolts and screws

Key s width across flats k height of the head

Figure 16 — Alternative marking of bolts and screws with left-hand thread

10.4 Marking and identification of fasteners with reduced loadability

Fasteners with reduced loadability, as specified in section 8.2.2, must be manufactured according to ISO 898 requirements These fasteners should be marked following the guidelines in sections 10.3.2 and 10.3.3, with the property class marking preceded by the digit “0” per Table 22, to ensure proper identification and compliance.

The marking symbols in accordance with Table 19, 20 or 21 shall not be used for fasteners with reduced loadability

When fasteners are subject to reduced loadability as per a product standard, the specified marking symbols outlined in Table 22 must be applied to all sizes listed in the standard, regardless of whether certain sizes meet the criteria for full loadability.

10.4.2 Marking symbols for fasteners with reduced loadability

Marking symbols shall be in accordance with Table 22

Table 22 — Marking symbols for fasteners with reduced loadability Property class 4.6 4.8 5.6 5.8 6.8 8.8 9.8 10.9 12.9 12.9 Marking symbol a 04.6 04.8 05.6 05.8 06.8 08.8 09.8 010.9 012.9 012.9 a The dot in the marking symbol may be omitted

All fastener packages, regardless of type or size, must be clearly labeled with essential information, including the manufacturer's and/or distributor's identification The packaging should also display the property class marking symbol in accordance with industry standards such as Table 19 or Table 22, along with the manufacturing lot number as specified in ISO 16426 Proper marking ensures traceability, quality assurance, and compliance with international standards.

Relationship between tensile strength and elongation after fracture

Table A.1 — Relationship between tensile strength and elongation after fracture

A f,min or A min a The values for A f,min and A min printed in bold type are normative values (see Table 3) b Applies to property class 6.8 only c Applies to property class 8.8 only

Influence of elevated temperatures on mechanical properties of fasteners

Elevated temperatures can cause changes in the mechanical properties and in the functional performance of a fastener

Fasteners maintain their mechanical properties without detrimental effects up to typical service temperatures of 150 °C However, at temperatures exceeding 150 °C and up to 300 °C, it is essential to carefully assess and verify the fasteners’ functional performance to ensure reliability at elevated temperatures.

⎯ reduction of lower yield strength or stress at 0,2 % non-proportional elongation or stress at 0,0048d non- proportional elongation for finished fasteners, and

Elevated service temperatures can lead to a reduction in tensile strength due to stress relaxation in fasteners Continuous operation at high temperatures accelerates stress relaxation, which increases as temperatures rise This phenomenon results in a loss of clamp force, potentially compromising the fastener's holding capacity and overall joint integrity.

Work-hardened fasteners (property classes 4.8, 5.8, 6.8) are more sensitive with regard to stress relaxation compared with quenched and tempered or stress-relieved fasteners

When using lead-containing steels for fasteners at elevated temperatures, it is essential to exercise caution due to the potential risk of liquid metal embrittlement (LME) This issue becomes particularly significant when the service temperature approaches the melting point of lead, which can compromise the fastener's integrity and performance Proper material selection and temperature management are crucial to prevent LME-related failures in high-temperature applications.

Information for the selection and application of steels for use at elevated temperatures is given, for example, in EN 10269 and in ASTM F2281

Elongation after fracture for full-size fasteners, A f

Table 3 specifies the minimum elongation after fracture (A_f,min) for full-size bolts, screws, and studs only for property classes 4.8, 5.8, and 6.8 For other property classes, these values are provided separately.

Table C.1 for information These values are still under investigation

Table C.1 — Elongation after fracture for full-size fasteners, A f

[2] ISO 16047, Fasteners — Torque/clamp force testing

[3] EN 10269, Steels and nickel alloys for fasteners with specified elevated and/or low temperature properties

[4] ASTM F2281, Standard Specification for Stainless Steel and Nickel Alloy Bolts, Hex Cap Screws, and Studs, for Heat Resistance and High Temperature Applications

[5] ASTM A320/A320M, Standard Specification for Alloy-Steel and Stainless Steel Bolting for Low- Temperature Service

Tiêu đề	Mechanical Properties Of Fasteners Made Of Carbon Steel And Alloy Steel Part 1: Bolts, Screws And Studs With Specified Property Classes — Coarse Thread And Fine Pitch Thread
Trường học	University of Alberta
Chuyên ngành	Mechanical properties of fasteners
Thể loại	Tiêu chuẩn
Năm xuất bản	2013
Thành phố	Geneva

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