Tiêu chuẩn iso tr 17844 2004

CTS, y-groove, etc;  Parent metal composition and range of applicability;  Material thickness and range of applicability;  Hydrogen level and welding processes;  Heat input;  Other

Cracking test method

This method utilizes a unique concept of critical hardness to prevent hydrogen cracking in the heat affected zone (HAZ) It has been empirically developed through extensive research on HAZ hardenability and cracking tests, particularly the CTS test Initially published in 1973, this scheme has undergone modifications and has been consistently included in British Standards for nearly 25 years Its application in the UK and internationally has yielded highly satisfactory results.

Parent metal composition range

The parent metals covered are carbon, carbon manganese, fine grained and low alloyed steels (groups 1 to 3 of

The steels that were used over many years to develop the method have covered a wide range of compositions and it is believed that they are adequately represented by Table 1

Table 1 — Range of chemical composition of the main constituents for parent metal for CE -method

Carbon equivalent values (in %) for parent metals are calculated using the following equation (1):

CE IIW = + + + + + + (1) and are applicable to steels with carbon equivalents in the range CE = 0,30 % to 0,70 %

When only carbon and manganese are specified on the mill sheet for carbon and carbon-manganese steels, an additional 0.03% should be included in the calculated value to account for residual elements and impurities In cases where steels with varying carbon equivalents or grades are being joined, the higher carbon equivalent value must be utilized.

This carbon equivalent formula may not be suitable for boron containing steels.

Plate thickness and joint geometry

The combined thickness, which influences the plate thickness and joint geometry, is calculated by averaging the parent metal thickness over a distance of 75 mm from the weld center line.

Combined thickness is used to assess the heat sink of a joint for the purpose of determining the cooling rate

If the thickness increases greatly beyond 75 mm from the weld centre line, it may be necessary to use a higher combined thickness value

Steels with thicknesses, t, in the range 6 mm ≤ t ≥ 100 mm were used in the tests to develop the scheme.

Hydrogen level and welding process

Hydrogen scales

The hydrogen levels suitable for various arc welding processes are primarily determined by the diffusible hydrogen content in the weld, as specified by EN ISO 3690, and are outlined in Table 2.

Diffusible hydrogen content (ml/100 g deposited material) Hydrogen scale

The development of the scheme is based on data from various arc welding processes, including manual metal arc (111), gas metal arc with solid wire (131, 135) and tubular wire (136, 137) in both gas shielded and self shielded types, as well as submerged arc welding (121).

NOTE The numbers in brackets are process numbers according to EN ISO 4063.

Selection of hydrogen scales

The following is general guidance on the selection of the appropriate hydrogen scale for various welding processes

Manual metal arc welding utilizing basic covered electrodes is applicable within scales B to D, as determined by the classification provided by the electrode manufacturer or supplier In contrast, rutile or cellulosic electrodes should be employed with scale A for optimal results.

Flux cored or metal cored consumables are classified by manufacturers as scales B to D, depending on the wire electrodes used Submerged arc welding with a single wire electrode (121) and flux consumables can achieve hydrogen levels that typically fall within scale C, although assessments are necessary for each specific product combination and condition While submerged arc fluxes are classified by suppliers, this classification does not guarantee that a practical flux wire combination will meet the same standards.

Solid wire electrodes for gas-shielded arc welding (131, 135) and TIG welding (141) can be utilized with scale D, provided they are specifically evaluated to meet scale E requirements Additionally, scale E may be suitable for certain cored wires (136, 137) and manual metal arc covered electrodes, contingent upon thorough assessment To achieve low hydrogen levels, it is essential to consider the hydrogen contribution from the shielding gas composition and atmospheric humidity.

For plasma arc welding (15), specific assessment should be made

Heat input

Heat input values (in kJ/mm) for use with Figure 2 a) to m) should be calculated in accordance with EN 1011-1/ ISO/TR 17671-1 and EN 1011-2/ISO/TR 17671-2

For manual metal-arc welding, heat input values are expressed in Tables 3 to 6 in terms of electrode size and weld run lengths

The details given in Tables 3 to 6 relate to electrodes having an original length of 450 mm For other electrode lengths the following equation (2) may be used:

Run length m m Electrode diam eter L F

L is the consumed length of the electrode (in mm) (normally the original length of 450 mm less 40 mm for stub end);

F is a factor (in kJ/mm 3 ) having a value depending on the electrode efficiency, as follows: efficiency approximately 95 % F = 0,0368

Table 3 — Run length for manual metal-arc welding – 95 % electrode efficiency, approximately

Run length from 410 mm of a 450 mm electrode of diameter 2,5 3,2 4,0 5,0 6,0 6,3

Heat input kJ/mm mm mm mm mm mm mm

Table 4 — Run length for manual metal-arc welding – 95% < electrode efficiency ≤ 110%

Run length from 410 mm of a 450 mm electrode of diameter

Table 5 — Run length for manual metal-arc welding – 110 %< electrode efficiency ≤ 130 %

Run length from 410 mm of a 450 mm electrode of diameter

Table 6 — Run length for manual metal-arc welding – electrode efficiency > 130%

Run length from 410 mm of a 450 mm electrode of diameter 3,2 4,0 5,0 6,0 6,3

Heat input kJ/mm mm mm mm mm mm

Special considerations

Conditions which might require more stringent procedures

The preheating conditions illustrated in Figure 2 a) to m) serve as a reliable foundation for establishing safe welding procedures for various fabrications However, the risk of hydrogen cracking is affected by multiple factors, which may have a more significant impact than indicated in Figure 2 This article discusses several elements that could elevate the risk of cracking beyond the anticipated levels Currently, precise quantification of these factors' effects on the necessity for stricter procedures and modifications to the welding process to prevent cracking is not feasible Therefore, the following information should be regarded as guidelines only.

Joint restraint is influenced by various factors, including section thickness, weld preparation, joint geometry, and structural stiffness For welds in sections thicker than approximately 50 mm, particularly in double bevel butt joints, more rigorous procedures may be necessary.

Welding processes may be insufficient to prevent hydrogen cracking in weld metal when working with low carbon equivalent steels, particularly in thicker sections exceeding 50 mm and with elevated heat inputs.

Using higher strength alloyed or carbon manganese weld metal with over 1.5% manganese can result in elevated operational stresses This may increase the risk of heat-affected zone (HAZ) cracking, as the weld deposit tends to be harder and more prone to cracking Therefore, it is recommended to take additional precautions to prevent hydrogen cracking in these conditions.

Research suggests that reducing the inclusion content in steel, particularly by decreasing sulfur and oxygen levels, can enhance the hardness of the heat-affected zone However, this may also slightly elevate the risk of hydrogen cracking in the HAZ Currently, precise quantification of this effect is not feasible.

To effectively reduce weld hydrogen levels, modifications can be made by either lowering the hydrogen input through the use of low-hydrogen welding processes or consumables, or by enhancing hydrogen loss via post-heat treatment Post-heat should typically last between 2 to 3 hours, depending on various factors, to achieve optimal results It is advisable to determine the necessary procedural modifications through comprehensive joint simulation weld testing.

Relaxations

Relaxations of the welding procedures may be possible under the following conditions:

 General preheating If the whole component or a width more than twice that stated in Clause 12 of EN 1011-2 :

2001 (ISO/TR 17671-2:2002) is preheated, it is generally possible to reduce the preheating temperature by a limited amount;

When a heat sink is restricted in one or more directions, particularly when the shortest heat path is less than ten times the fillet leg length, it may be feasible to lower preheating levels This situation often arises in thicker plates, such as in lap joints where the outstand is only slightly greater than the fillet weld leg length.

In situations where adequate preheating to prevent cracks in welds is not feasible, utilizing austenitic or high nickel alloyed consumables can be beneficial These consumables may eliminate the need for preheating, particularly when they are designed to deposit weld metal with minimal hydrogen content.

 Joint fit up Close fillet welds (where the gap is 0,5 mm or less) may justify relaxation in the welding procedure.

Simplified conditions for manual metal-arc welding

For designs specifying single run minimum leg length fillet welds, Table 7 can be utilized to obtain approximate heat input values, which are essential for determining the welding procedure as illustrated in Figure 2.

Table 7 — Values for heat input for manual metal-arc welding of single run fillet welds

Heat input for electrodes with covering types a and electrodes efficiencies

Minimum leg length mm R and RR < 110 % kJ/mm

8 2,2 2,7 1,3 a Covering types (R, RR, B) see EN 499/ISO 2560

In practical applications, contractors often need to create single run fillet welds that meet specific dimensions tied to the minimum leg length Typically, one leg of the fillet weld will exceed this minimum requirement, particularly in cases such as horizontal-vertical fillet welds (position PB).

EN ISO 6947) and the data is therefore not appropriate for direct conversion to welds of specified throat dimension

In other cases heat input should be controlled by control of electrode runout (see Table 6) or directly through welding parameters

Determination of preheat 1 0

Table 8 — Steps for the determination of preheat

Step Terms Clause/Figure/ equation

1 Determine the carbon equivalent of the steel This may be assessed by reference to mill certificates or the maximum carbon equivalent in the steel standard

2 Determine the hydrogen scale of the welding process and consumable as hydrogen scale A, B, C, D or E

2.4 and Table 2 Manual metal-arc welding and that the weld hydrogen level is appropriate to scale

3 Determine whether the joint is a fillet or butt weld – Butt weld

To determine the appropriate graph for scale B with a carbon equivalent of 0.45, refer to Figure 2 e) If a graph corresponding to the selected hydrogen scale and carbon equivalent is unavailable, utilize the graph for the next highest carbon equivalent value.

5 Determine the heat input to be used This can be done either by reference to 2.5 or by using the minimum run dimensions for the butt weld

Table 5 Assume this will be deposited with a 4 mm electrode to be run out in about 260 mm of run length 1,2 kJ/mm

6 Determine the combined thickness of the butt joint, referring to 2.3

– Assume calcuated combined thickness of 50 mm

To plot the coordinates for a heat input of 1.2 kJ/mm and a combined thickness of 50 mm, refer to Figure 2 e) The preheating temperature should be determined by locating the preheat line that is immediately above or to the left of the specified coordinates for heat input and combined thickness.

Read off minimum preheating and interpass temperature required Variation at step 7 In the event that the preheat is undesirable, proceed as follows

8 Re-examine Figure 2 e) to determine the minimum heat input for no preheat (20 ºC line, normally)

If the heat input is deemed feasible based on Table 5 and the welding position, continue with the selected electrode diameter and run length from the table If it is not feasible, move on to step 10.

Examining Figure 2 a) and d), we assess the feasibility of utilizing lower hydrogen levels through methods such as increasing electrode drying temperatures, altering consumables, or modifying the welding process This approach aims to eliminate the necessity for preheating while maintaining acceptable heat input levels.

ISO/TR 17844:2004(E) d 1 = average thickness over a length of 75 mm

Combined thickness = ẵ (D 1 + D 2 ) to take account of heat sink

Maximum diameter 40 mm for bar

Figure 1 — Examples for determination of combined thickness

5 To be used for carbon equivalent not exceeding

Figure 2 — Conditions for welding with defined carbon equivalents

The calculation of the minimum preheat temperature for arc welding primarily relies on the y-joint (Tekken) weld cracking test and butt welds, with additional data from CTS-test type fillet welds It is important to note that single run fillet welds exhibit lower restraint compared to critical root runs in butt welds, leading to a difference in preheat temperature of approximately 60 °C Consequently, the calculated preheat temperature for fillet welds may be overly stringent, allowing fabricators to leverage their experience When determining the preheat temperature for fillet and butt welds with varying plate thicknesses, the thicker parent metal should serve as the calculation basis Multi run fillet welds demonstrate restraint comparable to butt welds, making it advisable to apply the same preheat temperature as that used for butt welds.

The investigations were carried out in the early 1980s and published as IIW-Documents IX-1630-91 and IX-1631-

91 After successful application especially in welding high-strength low-alloyed steels with yield strengths up to

The method introduced in the German national guideline Stahl Eisen Werkstoffblatt SEW 088 effectively predicts conditions for welded joints, ensuring they do not experience cold cracking, with a strength of 960 N/mm².

Cold cracking behavior is significantly affected by several factors, including the chemical composition of both the parent and weld metals, plate thickness, hydrogen content in the weld metal, heat input, and residual stress A detailed examination of these factors can be found in sections 3.2 to 3.5.

The parent metals discussed are fine-grained low-alloyed steels and unalloyed steels from groups 1 to 4 and 11, as specified by CR ISO 15608:2000 Detailed composition ranges can be found in Table 9.

Table 9 — Range of chemical composition of the main constituents for parent metal for the CET -method

Silicon ≤ 0,8 Manganese 0,5 to 1,9 Chromium ≤ 1,5 Copper ≤ 0,7 Molybdenum ≤ 0,75 Niobium ≤ 0,06 Nickel ≤ 2,5 Titanium ≤ 0,12 Vanadium ≤ 0,18 Boron ≤ 0,005

The effect of the chemical composition on the cold cracking susceptibility is characterised by the carbon equivalent,

CET, which is defined (in %) as:

Within the range of the chemical composition detailed in Table 9 usual CET values are between 0,2 % and 0,5 %

Normally, the higher value either of the parent metal or the weld metal increased by 0,03 % is to be used

Abbreviation Term Dimension Range of validity d Thickness mm 10 ≤ d ≤ 90

HD Hydrogen content ml/100 g 1 ≤ HD ≤ 20

YS Yield strength N/mm 2 YS ≤ 1 000

A linear relationship exists between the carbon equivalent CET and the preheat temperature T p

Figure 3 — Preheat temperature in relation to CET

Figure 3 shows that an increase of about 0,01 % in the carbon equivalent, CET, leads to an increase of about 7,5 °C in the preheat temperature.

Plate thickness 2 0

The relationship between plate thickness (\$d\$) and preheat temperature (\$T_p\$) is illustrated in equation (5) and Figure 4 When considering varying parent metal thicknesses, the thickness of the thicker metal is the most significant factor.

Figure 4 — Preheat temperature in relation to the plate thickness

A change in plate thickness significantly affects performance when the thickness is less than 40 mm, but this influence decreases as the thickness increases, becoming minimal for thicknesses greater than 60 mm.

Hydrogen level and welding process 2 1

The effect of hydrogen content, HD, of the weld metal according to EN ISO 3690 on preheat temperature level is given in equation (6) and Figure 5

2 Hydrogen content HD in ml/100g

Figure 5 — Preheat temperature in relation to hydrogen content, HD

An increase in hydrogen content (HD) necessitates a rise in preheat temperature, as illustrated in Figure 5 Notably, the impact of hydrogen content on preheat temperature is more pronounced at lower concentrations compared to higher ones.

Reducing the hydrogen content in weld metal through the use of properly dried and baked consumables, or those with low hydrogen levels, significantly decreases the necessary preheat temperature for manual metal arc welding (111) and submerged arc welding (121).

However, the most favourable welding process in this context is gas shielded arc welding with solid wire (131, 135) resulting in a hydrogen content of about 2,0 ml/100g deposit weld metal

Heat input

Values of the heat input, Q, (in kJ/mm) for use with Figure 6 should be calculated in accordance with EN 1011-1 and EN 1011-2

The influence of the heat input, Q, on the preheat temperature is given in equation (7) and Figure 6

2 Heat input Q in kJ/mm

Figure 6 — Preheat temperature in relation to heat input, Q

An increase in heat input during welding allows for a reduction in preheat temperature, with the effect being more significant for alloys with a low carbon equivalent compared to those with a higher carbon equivalent If different carbon equivalent values are needed, they should be interpolated from the plotted curves However, it is important to note that the maximum heat input may be limited due to its impact on the toughness of the heat-affected zone (HAZ) and weld metal.

Influence of residual stress 2 2

The connection between residual stress levels and preheat temperature is understood primarily in qualitative terms Higher residual stresses and constraints necessitate a greater preheat temperature The equation for determining preheat temperature is based on the assumption that the residual stresses in the weld area align with the yield strength of either the parent metal or the weld metal.

Determination of preheat 2 2

Calculation of the minimum preheat temperature 2 2

The impact of the influencing factors is encapsulated in a formula, highlighting that when varying parent metal thicknesses are present, the thicker metal is the primary consideration Additionally, the chemical composition is defined by the carbon equivalent.

CET, the heat input Q, the plate thickness d, and the hydrogen content of the weld metal HD are combined in equation (8) pQ pHD pd pCET p T T T T

This results to the following equation to calculate the preheat temperature T p

According to experience, welding is safe when using the preheat temperatures calculated with the aid of equation

(9) provided the following conditions are fulfilled

Tack and root welds, along with single run fillet welds, must have a minimum length of 50 mm For plates thicker than 25 mm, a minimum of two layers should be applied It is advisable to use consumables that produce a mild ductile weld metal for tack and root welds.

For butt welds, it is crucial to avoid any intermediate cooling until the weld thickness reaches one-third of the thickness of the thicker parent metal If this threshold is exceeded, it is advisable to reduce hydrogen content through post-heating (soaking).

 The welding sequence should be selected in such a way that the plastic deformations of partly filled welds are reduced

Single run fillet welds exhibit less restraint compared to the critical root runs in butt welds, which may lead to a calculated preheat temperature that is overly conservative, around 60 °C It is essential for the fabricator to leverage this advantage based on their experience In the case of multi run fillet welds, it is recommended to apply the same preheat temperature as that used for butt welds.

Example for determination : numerical determination of the preheat temperature .2 3

The following example shows how to calculate the minimum preheat temperature for a butt joint according to the equations or figures

Table 11 — Steel with the following chemical composition in % by weight

C Mn Cu Ni Cr Mo

Carbon equivalent according to equation (3) CET = 0,33 %

The required preheat temperature is calculated according to equation (9):

Example for determination : graphical determination of the preheat temperature 2 3

The preheat temperature T p and the minimum interpass temperature T i can also be determined graphically using Figure 7

 CET is known or can be calculated by using equation (3)

 Hydrogen content is known depending on the welding process and applied consumables

 Heat input, Q (in kJ/mm), is known or should be calculated by using the following equation:

24 where k is the heat transfer efficiency (0,9 for SAW(121), 0,8 for MMA(111), MIG(131) and MAG (135), 0,6 for

U is the voltage (V); v is the travel speed (mm/s)

6 Hydrogen content HD in ml/100g

8 Heat input Q in kJ/mm

Figure 7 — Graphical method for the determination of minimum preheat temperature

Step Terms Figure/equation Example

1 Determine the preheat temperature depending on the influencing factor CET Figure 3 T CET = 98 °C

2 Determine the preheat temperature depending on the influencing factor d Figure 4 T d = 32 °C

3 Determine the preheat temperature depending on the influencing factor HD Figure 5 T HD = 22 °C

4 Determine the preheat temperature depending on the influencing factor Q Figure 6 T Q = - 14 °C

5 Add up the single values of the temperature T p 8 °C

Reduction of hydrogen content by post heating (soaking)

To mitigate the risk of cold cracking in multilayer submerged arc welded joints, particularly with steels having a yield strength of ≥ 460 N/mm² and thicknesses ≥ 30 mm, it is recommended to lower hydrogen content through heat treatment immediately post-welding This involves maintaining the weld region at a temperature between 200 °C and 300 °C for a duration that varies based on the plate thickness.

Welding with reduced preheating

The experience of the fabricator in multi-run welding can allow for a reduction in preheating by maintaining a sufficiently high interpass temperature, $ T_i $, through an appropriate welding sequence and short interpass times This reduction is influenced not only by the fabrication conditions but also by the steel's chemical composition, specifically the Carbon Equivalent Temperature (CET) and the corresponding value for $ T_i $ The interpass temperature $ T_i $ should be calculated using the same equation as for the preheat temperature $ T_p $.

Welding with austenitic consumables

When adequate preheating is not feasible, utilizing austenitic or high nickel alloy consumables can provide significant benefits This approach allows for a notable reduction in the required preheat temperature due to improved strain conditions and hydrogen distribution It is advisable to prioritize basic consumables, but this method must be implemented in compliance with the applicable design codes or application standards.

This method utilizes y-groove tests, a long-established practice in Japan among steel manufacturers, to assess the weldability performance of newly developed steels These tests serve as welding procedure specification evaluations for fabricators Originally published in 1989, the scheme was later modified and detailed in the 1995 issue of Welding in the World, Vol 35, No 5, pp 327-334.

The parent metals covered are ferritic carbon, carbon manganese, and low carbon low alloy steels

The range of chemical compositions applicable for this method is shown in Table 13

Table 13 — Range of chemical composition of main constitutents for parent metal for CE N method

Manganese ≤ 2,0 Chromium ≤ 2,5 Copper ≤ 1,0 Nickel ≤ 3,75 Molybdenum ≤ 0,75 Vanadium ≤ 0,10 Niobium ≤ 0,10 Boron ≤ 0,0003 (3ppm)

This method uses two types of carbon equivalents

The carbon equivalent (CE N) is a key index used to assess the susceptibility of steels to hydrogen cracking This value is determined using a specific equation.

= ( ) 24 Si Mn 6 Cu 15 20 Ni Cr Mo 5 V

CE N (11) where, f(C)= 0,75 + 0,25 tanh{ 20 (C-0,12) } f(C) is a coefficient which decreases with a decreasing carbon content and values of f(C) are given in Table 14

Figure 8 illustrates the master curves that indicate the essential minimum preheat required to prevent root cracks in y-groove testing, depending on the CE N and material thickness, while considering the hydrogen content in the weld metal.

5ml/100g and a heat input of l,36 kJ/mm (arc energy of 1,7 kJ/mm and arc heat transfer efficiency of 0,80)

The IIW type carbon equivalent serves as an indicator of the durability of high hardness levels during high heat input welding conditions (refer to Figure 9) This carbon equivalent is determined using the equation provided in (11).

Material thickness

This method is applicable for the material thickness in the range 10 ≥ t ≤ 200 mm The effect of the material thickness on hydrogen cracking is indicated in Figure 8.

Weld metal hydrogen content and welding process

This method can be applied to all arc welding processes, measuring the weld metal hydrogen content as the volume of diffusible hydrogen (ml) per 100 g of deposited metal This measurement can be determined using either the mercury displacement method (IIW-method) or the gas-chromatographic method (JIS Z 3118) The relationship between weld metal hydrogen content and hydrogen cracking is illustrated in Figure 10.

Heat input

This method is suitable for heat input values between 0.4 and 5.0 kJ/mm Typically, preheating is unnecessary for welding most steels when the heat input is 4.0 kJ/mm or higher The relationship between heat input and hydrogen cracking is illustrated in Figure 9 The heat input can be determined using equations (13) and (14).

Heat input (kJ/mm) = k ⋅ Arc energy (kJ/mm) (13)

Arc energy (kJ/mm) = I⋅U/v (14) where k is the heat transfer efficiency (0,9 for SAW (121), 0,8 for MMA (111), MIG (131) and MAG (135), 0,6 for

NOTE The numbers in brackets are process numbers according to EN ISO 4063

U is the voltage (V); v is the travel speed (mm/s)

Graduation for heat input in Figure 9 is prepared for the case of k = 0,8.

Weld metal yield strength

This method is suitable for weld metal yield strength levels between 300 MPa and 800 MPa The influence of weld metal yield strength on hydrogen cracking is illustrated in Figure 11, while Table 15 presents the yield strength levels of all-weld-metal for various steel grades.

Table 15 — Yield strength levels for all-weld-metal

HT 780 (Tensile strength 780 MPa) 700 1,25%Cr-0,5Mo 570 2,25%Cr-1%Mo 600 2,5%Ni 520 3,5%Ni 500

Determination of preheat

Table 16 — Steps for the determination of preheat

1 Determine the carbon CE N and equivalents, CE IIW of the steel This may be assumed by reference to mill certificates

Assume 0,40 CE N and 0,45 CE IIW

2 Determine the hydrogen content of weld metal and find

3 Determine the heat input value of the welding process and find ∆CE N (heat input) from heat input and CE IIW from Figure 9

4 Calculate the relevant CE N as follows:

CE N (relevant) CE N + ∆CE N hydrogen + ∆CE N heat input

5 Determine the material thickness, which is that of the thicker plate or pipe in both a butt and fillet geometry Assume 50 mm

6 Find the necessary preheat temperature to avoid root cracking in the y-groove test from CE N (relevant) and the plate thickness from Figure 8

Preheat for y-groove test, PHT(y-groove) is 142 °C

7 Determine the yield strength of the weld metal This may be assumed by reference to manufacturer's catalogue of the all-weld-metal or to Table 15

8 Find the preheat temperature correction for the welding practice from the weld metal strength from Figure 11

In case of repair welding or short-single- run welding, select slit welding Otherwise, select ordinary welding

∆PHT is -70°C for ordinary welding

9 Calculate the necessary preheat temperature from the following relation:

10 Round the preheat value established in step 9 upwards to the nearest 5°C Preheat is 75 °C.

Weld metal hydrogen content

A reduction of the weld metal hydrogen content is very beneficial in avoiding hydrogen cracking as shown in Figure

10 Therefore, the use of a low hydrogen welding process or welding consumable is recommended However, it should be noted that the weld metal hydrogen content increases by 1 ml/100 g to 3 m1/100 g in the following cases: a) welding is performed on grooves with rust or grease present; b) welding is performed using moist welding materials or rusted welding electrodes due to inappropriate storage;

30 c) welding is performed under hot and humid conditions

The cases a) and b) apply to all the welding processes and the case c) applies only to manual metal arc welding

Number of the weld layers and weld metal strength

The y-groove test evaluates root cracks that develop at the acute notch of a y-groove in a short single-run weld subjected to high restraint In typical welding practices, longer weld runs lead to slower cooling rates, and multi-run welding, along with post-heating from subsequent layers, helps facilitate the escape of hydrogen from the weld root Consequently, the likelihood of root cracking is significantly lower in standard multi-run welding compared to the y-groove test.

Welding fabrication experience shows that y-groove testing yields conservative results, allowing for a preheat temperature range of 50 ºC to 75 °C when welding 360 MPa yield strength grade steel As illustrated in Figure 11, a preheat relaxation of 75 °C is applicable for this steel grade; however, it is not advisable for short single-run welds, such as those in jig or tack welding In such cases, the slit welding method depicted in Figure 11 should be utilized.

Hydrogen cracking is significantly affected by the level of weld residual stress As the yield strength of the weld metal rises, the associated residual stress also increases, leading to a higher likelihood of root, toe, and under layer cracks However, y-groove testing is unable to assess toe and under layer cracking Consequently, it is essential to minimize the relaxation of preheat from the critical preheat determined in y-groove testing as the yield strength of the weld metal increases, as illustrated in Figure 11.

Restraint .3 0

Joint restraint plays a crucial role in hydrogen cracking during single-run welding, with high restraint increasing the likelihood of such cracking Interestingly, in fillet geometry, low restraint can lead to root cracking due to elevated bending stress at the weld root In multi-run welding, the impact of joint restraint diminishes since the weld joint is secured after the root weld is finished Consequently, joint restraint is not a key factor in determining preheat for this method, except in repair welding, which typically occurs under high restraint It is important to note that relaxing preheat is not advisable in repair welding, as illustrated in Figure 11.

Weld metal hydrogen cracking 3 0

The relative behavior of hydrogen cracking in the heat-affected zone (HAZ) of the parent metal compared to the weld metal remains unclear Hydrogen cracking in weld metal is particularly concerning when welding carbon-reduced higher strength steels When the carbon equivalent (CE N) of the steel is lower than that of the weld metal, it is advisable to use the CE N of the weld metal or the all-weld-metal for now, until further clarification on this issue is achieved.

1 Critical preheat temperature in ºC

Figure 8 — Master curves for minimum preheat for y-groove cracking test

2 Heat input in kJ/mm

Figure 9 — CE N correction with respect to weld heat input and CE IIW

2 Weld metal hydrogen, HD IIW in ml/100g DM

Figure 10 — CE N correction with respect to weld metal hydrogen content (DM is deposited metal)

1 Correction preheat temperature in ºC

Figure 11 — Correction of necessary preheat of welding practice

General

Two methods are used as the basis for estimating welding conditions to avoid cold cracking:

 heat-affected zone (HAZ) hardness control;

HAZ hardness control method

HAZ hardness control aims to prevent cracking by maintaining the hardness of the heat-affected zone (HAZ) below critical values, which is influenced by the steel's hardenability and cooling rate The critical hardness threshold varies based on factors like steel type, hydrogen levels, restraint, and service conditions Laboratory tests indicate that HAZ cracking is unlikely if the hardness remains below 350 HV, even when using high-hydrogen electrodes, while low-hydrogen electrodes can tolerate hardness levels up to 400 HV without cracking.

ISO/TR 17844:2004(E) tolerable in service where there is an increased risk of stress corrosion cracking, brittle fracture initiation, or other risks for the safety or serviceability of the structure

The critical cooling rate necessary for achieving a specific hardness in steel is approximately linked to its carbon equivalent This relationship, while not exact, suggests that the curve depicted may be conservative for unalloyed carbon and carbon-manganese steels, enabling the application of the high hardness curve with reduced risk.

Some low-alloy steels, particularly those containing niobium, may be more hardenable than Figure 12 indicates, and the use of the lower hardness curve is recommended

The method is primarily valuable for identifying the minimum heat input required to avoid excessive hardening, which in turn helps determine the smallest weld size It is especially effective for establishing the minimum dimensions of single-run fillet welds that can be applied without the need for preheating.

The hardness approach overlooks the potential for weld metal cracking; however, practical experience indicates that the heat input calculated by this method is typically sufficient to prevent such cracking in most cases of fillet welds This is particularly true when using low-hydrogen electrodes, such as low-hydrogen (MMA) electrodes, gas shielded metal arc, flux cored arc, or submerged arc, rather than high-strength filler metals.

Because the method depends solely on controlling the HAZ hardness, the hydrogen level and restraint are not explicitly considered.

Hydrogen controlled method

The hydrogen control method operates on the principle that cracking is unlikely if the average hydrogen content in the joint, after cooling to about 50 °C (120 °F), remains below a critical threshold determined by the steel's composition and restraint This approach also helps estimate the required preheat to facilitate sufficient hydrogen diffusion from the joint.

This method primarily relies on the outcomes of restrained partial penetration butt weld tests, utilizing weld metal that corresponds with the parent metal Although extensive testing on fillet welds is limited, the method has been effectively modified to accommodate these types of welds by considering restraint.

A determination of the restraint level and the original hydrogen level in the weld deposit is required for the hydrogen method

The hydrogen control method utilizes a single low-heat input weld run to create a root layer, assuming that the heat-affected zone (HAZ) will harden This approach is especially beneficial for high strength, low-alloy steels with significant hardenability, where controlling hardness can be challenging However, since it presumes complete hardening of the HAZ, the suggested preheat may be overly cautious for carbon steels.

Hardness controlled method

The parent metals covered are carbon, carbon manganese and low-alloy steels

This method is not applicable to quenched and tempered steels.

This method is particularly useful for high strength, low-alloy steels having quite high hardenability where hardness control is not always feasible.

Selection of method

The following procedure is suggested as a guide for selection of either the hardness control or hydrogen control method

Determine carbon and carbon equivalent (in %) from the following equation (15):

( Mn Si Cr Mo V Ni Cu C

CE = + + + + + + + (15) to locate the zone position of the steel in Figure 13

The chemical analysis may be obtained from:

 typical production chemistry (from the mill);

 specification chemistry (using maximum values);

The performance characteristics of each zone and the suggested action are as follows:

 Zone I Cracking is unlikely, but may occur with high hydrogen content or high restraint Use the hydrogen control method to determine preheat for steels in this zone

In Zone II, the hardness control method and selected hardness are essential for determining the minimum energy input for single-run fillet welds without preheat If the energy input is impractical, the hydrogen method should be employed to establish preheat requirements For butt welds, particularly in high carbon content steels, the hydrogen control method is crucial for determining preheat Both fillet and butt welds may necessitate a minimum energy input to manage hardness and preheat to control hydrogen levels effectively.

 Zone III The hydrogen control method is used, where heat input is restricted to preserve the HAZ properties

(e.g some quenched and tempered steels), the hydrogen control method should be used to determine preheat.

The values of the composition parameters P CM (in %) is calculated from the following equation (16):

Mo Cr Ni Cu Mn

The chemical analysis is obtained as in 5.2.3

HAZ hardness controlled method

The provisions included in this document for use of this method are restricted to fillet welds

The range of applicability for flange thickness is 6 mm (approximately ẳ in) up to 100 mm (approximately 4 in).

This method primarily relies on the outcomes of restrained partial joint penetration groove weld tests Although extensive testing on fillet welds is limited, the method has been effectively adapted for these welds by incorporating restraint.

Hydrogen levels and welding process

The low hydrogen consumables give a diffusible hydrogen content of less than 10 ml/100g deposited metal when measured using EN ISO 3690

This method is valid for the following welding processes shown in Table 17

Table 17 — Welding process designations and terminology Terminology of welding process EN ISO 4063 previous US abbreviation

Submerged arc welding (SAW) 121 SAW

Manual metal arc welding (MMA) 111 SMAW Metal active gas welding (MAG) 135 GMAW Fluxed cored welding (FCAW) 136/137 FCAW

The hydrogen level is determined and defined as follows

Extra-low hydrogen content consumables ensure a diffusible hydrogen content of ≤ 5 ml/100g of deposited metal, as per EN ISO 3690 standards This measurement can be verified by testing each type and brand of consumable or wire/flux combination after it has been removed from its packaging and exposed to the intended storage conditions before use It is assumed that the following consumables meet this requirement.

 Low-hydrogen electrodes taken from hermetically sealed containers, dried at 370 °C ≤ Τ ≤ 430 °C

(700 °F ≤ T ≤ 800 °F) for one hour and used within two hours after removal

 MAG welding (135) with clean solid wires

H2 low hydrogen content consumables ensure a diffusible hydrogen content of ≤ 10 ml/100g of deposited metal, as per EN ISO 3690 standards This requirement can be verified through testing each specific type, brand of consumable, or wire/flux combination utilized It can be assumed that the following options comply with this criterion.

 Low-hydrogen electrodes taken from hermetically sealed containers conditioned in accordance with 5.3.2.1 of ANSI/AWS D1.1 and used within four hours after removal

 SAW welding (121) with dry flux.

Energy input

This energy input applies to submerged arc welds

To estimate the minimum energy input for single pass fillet welds in various processes, one can apply the multiplication factors from Table 18 to the energy calculated for the submerged arc welding (SAW) process.

Table 18 — Multiplication factors relating to welding processes

The arc energy (AE) (in J/in) is calculated as follows:

Figure 14 may be used to determine the leg length of fillet welds as a function of energy input.

Because the HAZ hardness controlled method depends solely on controlling the HAZ hardness, the restraint is not explicitly considered

For the hydrogen controlled method the welds are divided in three levels of restraint

 Low restraint This level describes common fillet and butt welded joints in which a reasonable freedom of movement of members exists

 Medium restraint This level describes fillet and butt welded joints in which, because of members being already attached to structural work, a reduced freedom of movement exists

 High restraint This level describes welds in which there is almost no freedom of movement for members joined (such as repair welds, especially in thick material)

The classification of types of welds at various restraint levels should be determined on the basis of experience, engineering judgement, research, or calculation.

Determination of minimum preheat

Method according to value of CE

Table 19 — Steps of the method

2 Locate zone position of the steel Figure 13

In this method there is a correlation between the material thickness at the joint (see Figures 15 a) to f)), the heat input and the cooling rate at 540 °C (R 540 )

2 Determine the heat input of the welding process

3 Select the correct figure according to the material thickness and estimate the cooling rate

4 Estimate the expected hardness with the cooling rate in relationship to the CE Figure 12

For expected hardness levels of 350 HV or lower, consumables with high-hydrogen content are acceptable However, for hardness levels between 350 HV and 400 HV, it is essential to use consumables with low-hydrogen content.

Hydrogen content controlled method

2 Select the welding process and estimate the hydrogen content of the weld metal

3 Estimate the index grouping using Table 22 including the notes Table 22

4 Estimate the minimum preheat and interpass temperatures for the relevant levels of restraint in Table 23

2 R540 in ºC/s for HAZ hardness of 350 HV and 400 HV 3 400 HV

Figure 12 — Critical cooling rate for 350 HV and 400 HV

2 Carbon equivalent CE 3 Zone II

Figure 13 — Zone classification of steels

2 Average energy input in kJ/inch

Figure 14a) – Shielded metal arc welding (SMAW)

2 Average energy input in kJ/inch

Figure 14b) – Submerged arc welding (SAW) Figure 14 — Relationship between fillet weld size and energy input

Figure 15a) – Single-pass SAW fillet welds with web and flange of same thickness

Figure 15b) – Single-pass SAW fillet welds with ẳ in flanges and varying web thickness

Figure 15c) – Single-pass SAW fillet welds with ẵ in flanges and varying web thickness

Figure 15d) – Single-pass SAW fillet welds with 1 in flanges and varying web thickness

Figure 15e) – Single-pass SAW fillet welds with 2 in flanges and varying web thickness

Figure 15f) – Single-pass SAW fillet welds with 4 in flanges and varying web thickness

1 Energy input in kJ/inch

2 Cooling rate at 540 ºC in ºC/s

NOTE Energy input determined from chart does not imply suitability for practical applications For certain combinations of thicknesses melting can occur through the thickness

Figure 15 — Graphs to determine cooling rates for single-pass submerged arc fillet welds

Table 22 — Susceptibility index grouping as function of hydrogen content level HD and composition parameter P cm

Susceptibility index grouping (see NOTE 2)

NOTE 1 P cm (in %) is given by:

Mo Cr Ni Cu Mn

NOTE 2 Susceptibility index = 12 P cm + log 10 HD

NOTE 3 Susceptibility index groupings, A through G, encompass the combined effect of the composition parameter, P cm and hydrogen level, in accordance with the formula shown in note 2

The exact numerical quantities are obtained from the Note 2 formula using the stated values of P cm and the followings values of HD, given in ml/100 g of weld metal

H 1 = 5; H 2 = 10; H 3 = 30 For greater convenience, susceptibility index groupings have been expressed in the table by means of letters, A through G, to cover the following narrow ranges:

The groupings are used in Table 23 in conjunction with restraint and thickness to determine the minimum preheat and interpass temperature.

Table 23 — Minimum preheat and interpass temperature for three levels of restraint

Minimum preheat and interpass temperature (°C)

> 76,2 116 129 149 149 160 160 160 a Thickness is that of the thicker part welded.

Comparison of the different methods

General

In comparing the methods it is first of all importance to recall their origins

 The CE-method uses a critical hardness approach based on data predominantly from CTS fillet weld testing using mainly carbon manganese steels but including some low alloy steels

 The CET-method is an empirical approach based mainly on y-groove testing but incorporates some CTS fillet weld data Steels tested cover both carbon manganese and low alloy types

 The CE N -method is an empirical approach based predominantly on y-groove test data, many of which comes from low alloy steels

The P cm-method combines a critical hardness approach with a hydrogen control method While the hardness control method primarily applies to carbon manganese and certain low alloy steels, it does not include quenched and tempered steels Conversely, the hydrogen control approach is designed for high hardenability, high strength, low alloy steels where controlling hardness is not feasible.

As can be seen in Table A.1, there are some differences in the precise compositional ranges covered, that for the

CE N method probably providing the widest coverage

Table A.1 — Parent metal composition range

NS = Not specified NA = Not applicable

The plate thickness ranges covered are similar for CE, CET and P cm with an upper limit of 100 mm, while the upper limit for CE N is 200 mm

The CE N - and CET-methods do not differentiate between butt and fillet welds when predicting preheat temperatures, although the CET-method offers some guidance for fillet welds In contrast, the CE- and P cm -methods provide comprehensive guidance for both types of welds Notably, the CE-method may recommend higher preheat temperatures for fillet welds compared to butt welds due to the effect of combined plate thickness Additionally, the P cm -method determines preheat temperatures for fillet welds based on the hardening in the heat-affected zone (HAZ) for specific steels, while it treats fillet and butt welds the same for other steels with equivalent weld thickness.

Hydrogen levels

In the CE N and CET methods, hydrogen input can vary from 1 ml/100 g to 20 ml/100 g for CET, while CE N does not specify a limit Conversely, the CE and P cm methods utilize a scale or group that encompasses a range of hydrogen levels.

Heat input

The CE- and CE N-methods allow for the determination of heat input for butt welds without preheating, while for fillet welds, only the CE- and P cm-methods can be utilized However, most P cm-methods do not account for heat input, limiting the benefits of increased heat input in reducing HAZ hardness, except in the case of fillet welds without preheat This is particularly evident in butt welds at 25 mm, where a heat input of 3 kJ/mm consistently results in the highest preheat when using the P cm-method (refer to Table A.5).

Figure 6 demonstrates how heat input affects preheat temperature in the CET-method, based on the carbon equivalent This effect is comparable to the CE N-method, where heat input up to 4 kJ/mm also impacts preheat temperatures within a specific range, depending on the carbon equivalent.

Prediction comparison

This article presents a comparison of predicted preheats for various steel types and compositions, considering different hydrogen levels, plate thicknesses, and weld types Table A.2 details the minimum yield strength, chemical compositions, and carbon equivalents of ten selected steels, including unalloyed normalized CMn-steels, low alloyed normalized steel, TMCR-steels, and quenched and tempered steels, with yield strengths ranging from 235 MPa to 960 MPa The results for a hydrogen content of 13.6 ml/100g weld metal are summarized in Table A.5 for both fillet and butt welds Notably, the CET-method indicates that preheat temperatures for single run fillet welds can be reduced by 60 °C compared to butt welds of the same thickness, while multi run fillet welds require the same preheat temperatures as butt welds due to similar restraint Further detailed comparisons for butt welds are provided in Tables A.3 and A.4, along with graphical representations in Figures A.1 to A.12.

The CET-method appears to be more conservative than the CE-method for mild steels, as illustrated in Figure A.1 Notably, when the carbon equivalent is low (CE < 0.4%), the minimum preheat temperatures are established based on this method.

The CE-method yields significantly lower preheat temperature values compared to the CET-method Conversely, for low alloyed steels with elevated CE values, the CE-method indicates higher preheat temperatures than those derived from the CET-method.

The CET-method applies low heat inputs, resulting in a stronger influence of carbon equivalent on minimum preheat temperatures compared to the CE-method Consequently, the CE-method leads to lower preheat temperatures for mild steels and higher temperatures for low alloyed steels When welding low alloyed steels, the preheating range between low and high heat inputs is significantly broader than indicated by the CET-method As illustrated in Figure A.1b), the CE-method assesses the impact of heat input on preheat temperature more robustly, particularly for low alloyed high strength steels Figure A.1c) demonstrates the relationship between hydrogen content and preheat temperature at 1 kJ/mm, where the CET-method assumes a proportional ratio between carbon equivalent and hydrogen content As carbon equivalents increase, the influence of hydrogen content on preheat temperature also rises However, the CE-method shows no effect for carbon equivalent values below 0.45% and plate thicknesses under 25 mm, as noted in Table A.5.

50 strong dependency of the preheat temperature from the hydrogen content This ratio becomes smaller with increasing carbon equivalents

Figure A.2 compares the CE N - and CET-methods, showing good conformity for normalized steels However, for high strength steels, the CE N -method predicts higher preheat temperatures than the CET-method Additionally, Figure A.3 indicates that the P cm -proposal generally results in higher preheat temperatures than the CET-method, particularly for mild steels Notably, in the P cm -method for butt welds, the heat input does not affect the preheat temperature.

In comparing the CE- and CE N-methods, the CE-method generally predicts lower preheat temperatures, particularly evident in the case of mild steels and high heat input welding.

The CE N-method, similar to the CET-method, may be overly conservative, as illustrated in Figure A.5, which compares the P cm- and CE-methods, showing that AWS typically requires higher preheat temperatures In contrast, Figure A.6 highlights that the CE N-method results in lower preheat temperatures for mild steels However, this trend reverses with high strength steels, where the CE N-method necessitates higher preheating.

Figures A.7 to A.12 present the results for 50 mm plates, showing an expected increase in preheat temperatures when comparing 25 mm and 50 mm plates However, the fundamental predictions across different methods remain consistent It is important to view these results as recommendations rather than definitive guidelines Despite variations among the four methods, they serve as proposals for welding procedure test plates, as outlined in EN ISO 15614-1 The aim is to assist users fabricating a specific steel for the first time in identifying safe and economical welding conditions Users should select the method that best suits their application, while experienced fabricators may opt for lower preheat temperatures based on their practical experience, regardless of the calculated recommendations.

Summary and conclusions .5 0

Different methods have unique features that present both advantages and disadvantages for users, depending on their application When selecting a method, it is essential to consider its origins to ensure the best alignment with practical situations and original test data, which can lead to more accurate predictions It is advisable to use the chosen method that best fits the practical scenario for determining preliminary welding conditions, which should then be validated through appropriate procedure testing and qualifications.

Table A.2 presents various steel grades used for comparing predicted preheats, detailing their typical chemical compositions and minimum yield strengths The steel grades include S235J2G3, S355N, S355M, S460N, S460M, S690QL, and S960QL, with yield strengths ranging from 235 N/mm² to 960 N/mm² Each grade is defined by its specific chemical composition, including elements such as carbon, silicon, manganese, chromium, copper, molybdenum, niobium, nickel, titanium, vanadium, and their respective carbon equivalents This information is crucial for understanding the mechanical properties and applications of these steel grades in various engineering contexts.

Table A.3 presents a comparison of preheat temperatures for various steel types with a plate thickness of 25 mm The data includes preheat temperatures in °C for five different steel types, labeled Steel 1 through Steel 5, under various conditions For instance, Steel 1 shows a preheat temperature of 0.23 °C under specific conditions, while Steel 2 reaches 0.39 °C The table also highlights the variations in preheat temperatures across different methods, indicating significant differences such as Steel 3 at 0.46 °C and Steel 4 at 0.50 °C Additionally, the results reveal that preheat temperatures can vary widely, with some values dropping as low as -91 °C for certain conditions Overall, the data underscores the importance of selecting appropriate preheat temperatures based on the steel type and method used.

Table A.3 presents the temperature data in °C for various steel grades, including Steel 6 through Steel 10, along with their corresponding carbon equivalents (CE, CET) as per EN 1011-2/ISO/TR 17671-2, JIS B8285, and P cm according to ANSI/AWS D1.1 The table includes values for different conditions, highlighting the variations in carbon content and temperature effects on steel properties Notably, the data indicates significant differences in performance metrics across the steel grades at specified temperatures, emphasizing the importance of understanding carbon equivalents in steel selection for engineering applications.

Table A.4 presents a comparison of preheat temperatures for various steel types with a plate thickness of 50 mm The data includes preheat temperatures in °C for five different steel grades, labeled Steel 1 through Steel 5 Each steel type is evaluated under different conditions, with specific values for HD, Q, CE, CET, CE N, and P cm The results indicate varying preheat temperatures, with notable values such as 116 °C for multiple conditions across the steel types The table highlights the importance of preheat temperature in the processing of steel, showcasing how different methods impact the required temperatures for optimal performance.

Table A.4 presents the temperature data in °C for various steel grades, including Steel 6 through Steel 10, along with their respective carbon equivalents (CE, CET) as per EN 1011-2/ISO/TR 17671-2 and JIS B8285, and P cm according to ANSI/AWS D1.1 The values indicate the relationship between temperature and carbon content, highlighting the variations across different steel types For instance, Steel 6 shows a CE of 0.39 at -20°C, while Steel 10 has a CE of 0.70 at the same temperature This data is crucial for understanding the properties and applications of these steel grades in various industrial contexts.

Table A.5 presents a comparison of minimum preheat temperatures for various steel types, specifically at a hydrogen level of 13.6 ml/100 g The data includes minimum heat input values in kJ/mm for both butt and fillet welds at a preheat temperature of 20 ºC For butt welds, the minimum heat input ranges from 0.5 to 1.9 kJ/mm, while for fillet welds, it varies from 0.65 to 2.9 kJ/mm Notably, some values are marked as beyond the range of data This comparison highlights the differences in heat input requirements across different steel types, which is crucial for optimizing welding processes.

Table A.5 presents the minimum heat input values in kJ/mm for various steel types (Steel 6 to Steel 10) under different preheat conditions For butt welds with a preheat of 20 ºC, the minimum heat input ranges from 0.5 to 3.0 kJ/mm, with specific values noted for each steel type Similarly, for fillet welds at the same preheat temperature, the minimum heat input also varies, with values starting from 1.0 kJ/mm The data indicates that certain conditions lead to a range of heat inputs, while some values fall beyond the available data range.

Table A.5 presents the minimum heat input (kJ/mm) required for various steel types (Steel 1 to Steel 5) during welding, specifically under a preheat temperature of 20 ºC For butt welds, the minimum heat input varies across different steel types, with values ranging from 0.65 to 3.75 kJ/mm In contrast, for fillet welds, the minimum heat input also shows variability, with values from 0.65 to 5.65 kJ/mm Notably, some data points are marked as beyond the range of available data This information is crucial for ensuring proper welding techniques and achieving optimal results in steel fabrication.

Table A.5 presents the minimum heat input (kJ/mm) required for various steel types (Steel 6 to Steel 10) at a preheat temperature of 20 ºC, detailing both butt and fillet welds For butt welds, the minimum heat input varies across different steel types, with values ranging from 0.23 to 1.15 kJ/mm Similarly, for fillet welds, the minimum heat input also shows variation, with values from 0.6 to 1.15 kJ/mm The diagrams in Figures A.1 to A.12 illustrate the calculated preheating temperatures for selected steels, categorized by heat input and hydrogen content, with Figures A.1 to A.6 focusing on 25 mm plate thickness and Figures A.7 to A.12 on 50 mm plate thickness Accurate preheating temperatures related to heat input and hydrogen content are detailed in Table A.3 for 25 mm plates and Table A.4 for 50 mm plates.

Heat input Q = 1, 2 and 3 kJ/mm

Hydrogen content HD = 3, 7 and 13,6 ml/100g

2 T 0 according to the CET-method ● YS = 355

Figure A.1b) – Influence of heat input

Figure A.1c) – Influence of hydrogen content

Figure A.1 — Comparison of preheat temperature T o according to CE - and CET -methods; plate thickness

2 T 0 according to CET-method ▲ YS = 460

Figure A.2 — Comparison of preheat temperature T o according to CE N - and CET -methods; plate thickness

2 T 0 according to CET-method ▲ YS = 460

Figure A.3 — Comparison of preheat temperature T o according to P cm - and CET -methods; plate thickness

Figure A.4 — Comparison of preheat temperature T o according to CE - and CE N -methods; plate thickness

2 T 0 according to P cm -method ▲ YS = 460 ■ YS = 960 ● YS = 355

Figure A.5 — Comparison of preheat temperature T o according to CE - and P cm -methods; plate thickness

Figure A.6 — Comparison of preheat temperature T o according to P cm - and CE N -methods; plate thickness

2 T 0 according to CET-method ▲ YS = 460 ■ YS = 960 ● YS = 355

Figure A.7 — Comparison of preheat temperature T o according to CE - and CET -methods; plate thickness

Figure A.8 — Comparison of preheat temperature T o according to CE N - and CET -methods; plate thickness

Figure A.9 — Comparison of preheat temperature T o according to P cm - and CET -methods; plate thickness

2 T 0 according to CE N -method ▲ YS = 460 ■ YS = 960 ● YS = 355

Figure A.10 — Comparison of preheat temperature T o according to CE - and CE N -methods; plate thickness

2 T 0 according to P cm -method ▲ YS = 460 ■ YS = 960 ● YS = 355

Figure A.11 — Comparison of preheat temperature T o according to CE - and P cm -methods; plate thickness

Figure A.12 — Comparison of preheat temperature T o according to P cm - and CE N -methods; plate thickness

CE, CET, CE N , P cm carbon equivalent % d plate thickness mm

PHT Post weld heat treatment ° C

EN 499, Welding consumables – Covered electrodes for manual metal arc welding of non alloy and fine grain steels – Classification

EN 1011-1, Welding – Recommendations for welding of metallic materials – Part 1: General guidance for arc welding

EN 1011-2:2001, Welding – Recommendations for welding of metallic materials – Part 2: Arc welding of ferritic steels

EN 10025, Hot rolled products of non-alloy structural steels – Technical delivery conditions (includes amendment

EN 10113-2, Hot-rolled products in weldable fine grain structural steels– Part 2: Delivery conditions for normalized rolled steels

EN 10113-3, Hot-rolled products in weldable fine grain structural steels – Part 3: Delivery conditions for thermomechanically rolled steels

EN 10137-2, Plates and wide flats made of high yield strength structural steels in the quenched and tempered or precipitation hardened conditions – Part 2: Delivery conditions for quenched and tempered steels

EN ISO 3690, Welding and allied processes – Determination of hydrogen content in ferritic arc weld metal (ISO

EN ISO 4063, Welding and allied processes – Nomenclature of processes and reference numbers (ISO 4063:1998)

EN ISO 6947, Welds – Working positions – Definitions of angles of slope and rotation (ISO 6947:1993)

EN ISO 15614-1 outlines the specifications and qualifications for welding procedures related to metallic materials, specifically focusing on arc and gas welding of steels, as well as arc welding of nickel and nickel alloys This standard, known as ISO 15614-1:2004, serves as a crucial guideline for ensuring the quality and reliability of welding processes in various applications.

ISO 2560, Welding consumables – Covered electrodes for manual metal arc welding of non-alloy and fine grain steels – Classification

ISO/TR 17671-1, Welding – Recommendations for welding of metallic materials – Part 1: General guidance for arc welding

ISO/TR 17671-2:2002, Welding – Recommendations for welding of metallic materials – Part 2: Arc welding of ferritic steels

CR ISO 15608:2000, Welding – Guidelines for a metallic material grouping system (ISO/TR 15608:2000)

ANSI/AWS D 1.1, Structural Welding Code – Steel

JIS B 8285, Welding procedure qualification test for pressure vessels

JIS Z 3118, Method of measurement for hydrogen evolved from steel welds

SEW 088, Schweiògeeignete Feinkornbaustọhle – Richtlinien fỹr die Verarbeitung, besonders fỹr das

Schmelzschweiòen / Achtung: Enthọlt Beiblatt 1 und Beiblatt 2

IIW Doc IX-1630-91, Characterization of the cold cracking behaviour of steels during welding

IIW Doc IX-1631-91, Determination of suitable minimum preheating temperatures for cold crack-free welding of steels

Tiêu đề	Welding — Comparison of Standardised Methods for the Avoidance of Cold Cracks
Trường học	International Organization for Standardization
Chuyên ngành	Welding
Thể loại	Technical report
Năm xuất bản	2004
Thành phố	Geneva

Định dạng
Số trang	82
Dung lượng	1,19 MB