Giáo trình Anh văn chuyên ngành công nghệ hàn Trường CĐ nghề Lilama 2

Passive: The process can also be used to deposit metal to form a surface with alternative properties.. Table 2 – AWS A5.1-69 electrode designations for covered arc-welding electrodes In

LỜI NÓI ĐẦU

T X T Q Q T

T

ứ

ứ d ỹ

ự ỉ ự ủ T S V – ở T

LAMA 2, S Lê Quang Trung, S ễ T

d “Anh văn chuyên ngành công nghệ Hàn” T T

ủ ủ T

d & G d S d d – Q

ẩ S E S WS P … ủ dự

P ú ỹ d Q … ứ

ự T ứ ứ ủ d

dù ắ ỏ ữ R

ý ỉ

Ch úng tôi xin chân thành cảm ơn!

NHÓM BIÊN SOẠN

UNIT 1: TERMINOLOGY AND STANDARD

- Arc :

- Edge :

- Metal:

- Joint : Liê

- Electrode : ự - Welding : Hàn - Welded joint:

- Welding process: Q hàn

- Weld:

- Welding structure:

- Melt (n): Sự nung

- Melt (iv / tv) C

- Melted (pp)

- Molten (adj)

- Mass:

- Cool (iv / tv):

- Clamp: ẹ ữ

- Base metal:

- Circuit:

- Stream: ò

- Temperature:

- Bright: Sáng, sáng chói - Welding machine: Máy hàn - Amperage : dò

- Voltage :

- Generator :

- Transformer :

- Rectifier : ỉ

II GRAMMAR: Passive voice: Form: Subject (S) + Verb ( V) + Object ( O) S + ‘to be’ + V_ ed ( past participle) + (by….) 1 The passive tense „ ‟ „ ‟ „ ‟ ỉ ứ

present, past, past perfect v.v )

of an active tense voice is formed by putting the verb „ be‟ at the same tense as the active verb in front of the past participle of the active verb The subject of the active „agent’ f T „agent’ is very often not

mentioned When it is mentioned it is preceded by „by ’ and placed at the end of the

clause:

Ex: This plate of metal was welded by my father

2 Passive voice at present and past tenses:

S + V + O

S + is / are + V_ ed

Active: We build this bridge

Passive: This bridge is built

S + V ( past simple) + O

S + was / were + V_ ed

Active: They broke the window

Passive: The window was broken

3 Passive voice at continuous tense requires the present continuous form of to be:

S + is / am / are + V_ ing + O

S + is / are + being + V_ ed ( past participle)

Active: They are repairing the bridge

Passive: The bridge is being repaired

4 Auxiliary + infinitive combinations are made passive by using a passive infinitive:

S + should / can + V + O

S + should / can + be + V_ ed ( past participle)

Active: You should shut these doors

Passive: These doors should be shut

Active: You can use the process to deposit metal to form a surface with

alternative properties

Passive: The process can also be used to deposit metal to form a surface with

alternative properties

III PRACTICE

This lesson Arc welding is a method of joining two pieces of metal into one solid piece To do this, the heat of an electric arc is concentrated on the edges of two pieces of metal to be joined The metal melts and, while these edges are still molten, addition melted metal is added This molten mass cools and solidifies into one solid piece

Figure 1

The electric arc is made between the work and the tip and of a small metal wire, the electrode, which is clamped in a holder and held in the hand A gap is made in the welding circuit by holding th f d 6‟‟- ‟‟ w f the parent or base metal being welded The electric current jumps this gap and makes an arc, which is held maintained and moved along the joint to be welded, melting the metal as it is moved

Arc welding is a manual skill requiring a steady hand, good general physical conditions, and good eyesight The operator controls the welding arc and, therefore, the quality of the weld made

Figure 2

Figure 3 Illustrates the action that takes place in the electric arc It closely resembles what is actually seen during welding

T “ ” is seen in the middle of the picture This is the electric arc created by the electric current flowing through the space between the end of the electrode and the work The temperature of this arc is about 60000C, which is more than enough to melt metal The arc is very bright, as well as very hot, and cannot be looked at with the naked eye without risking painful, though usually temporary, injury

Figure 3

The arc melts the parent, or base, metal and actually digs into it, much as the water through a nozzle on a garden hose digs into the earth The molten metal forms a molten pool or crater and tends to flow away from the arc As it moves away from the arc, it cools and solidifies A slag forms on top of the weld to protect it during cooling

There are several types of welding machines include motor-generators, engine-driven generators, transformers, rectifiers, and combination transformer and rectifiers Each type has its place and purpose The basic function of each is the same-providing a source of controlled electric power for welding This controlled electric power has the characteristic of high amperage at low voltage The high amperage is required to provide sufficient heat at the arc The voltage must be low enough to be safe for handling and yet high enough to maintain the arc The welding machine permits the welder (welding operator) to control the amount of current he uses This, in turn, controls the amount of heat of the arc Some welding machine also permits the operator to select either a forceful

or soft arc and to control its characteristics to suit the job

These are some standard that is used for welding

1 ASME (American Society of Mechnical Engineers), includes:

- ASME Boiler& Pressure Vessel Code

- ASME Code For Pressure Piping

2 AWS (American Welding Society)

- AWS D1.1- Structural Welding Code - Steel

3 API (American Petroleum Institute) :

- API 650 – Welded Steel Tanks For Oil Storage

- API 1104 – Welding Of Pipelines And Related Facilities

4 ISO (Internaytional Standardization Organization)

5 EN (European Standard/Normal)

6 JIS – Japanese Industrial Standards

IV EXERCISE

1 Give main ideas of paragraph?

2 What is arc welding?

3 What happens in the arc?

4 What do the electrodes affect to the arc?

5 List and explain the uses of the standards?

UNIT 2: WELDED JOINT AND WELD

Object: to show the types and position of welded joints

- Welding position V trí hàn

- Flat Hàn

- Vertical Hàn ứ - Overhead Hàn ử - Horizontal Hàn ngang - Butt joint Liên

- Corner joint Liên

- Lap joint Liên

- Tee joint Liên ữ T - Edge joint Liên

- Butt weld hàn giáp

- Fillet weld

- Groove angle Góc vát - Groove weld hàn có vát mép - Spot weld

- Spot hàn - Geometry

- Configuration d

- Preparation Sự ẩ

- Surface

- Weld reinforcement

- Weld concavity õ

- Weld width

- Leg of a fillet weld

- Sealing run hàn lót

II GRAMMAR:

THE COMPARISON OF ADJECTIVES

Shorter adjectives: form of regular comparison

Most common adjectives are short words They form their comparatives and superlatives

as shown:

Notes on the comparison of shorter adjectives

Spelling of comparative and superlative forms:

- Most one-syllable adjectives form their comparatives and superlatives like clean: -er and -est are added to their basic form

- Many one-syllable adjectives end with a single consonant after a single vowel-letter This consonant doubles in the comparative and superlative, as in the case of big: bigger, biggest

- Many one-syllable adjectives end in -e, like nice or safe These add -r and -st to the basic form: safer, safest

- Some adjectives, like dry, end in -y with a cosonant letter before it These adjectives are usually two-syllable In the comparative and superlative -y is replaced by i: drier, driest

Longer adjectives:

Most longer adjectives combine with quantifiers „more‟ / „less‟ to form their comparatives and „ most‟ / „ least‟ to form their superlatives

Ex: This joint is more beautiful than that one

This position is the most difficult job when welding a fabrication

A summary of the basic types of joints and basic types of welds is shown in figure below

In a joint, the adjoining members may contact each other in several ways, as illustrated

by the butt, T, corner, lap and edge joints These general descriptions of the joint geometry, however, do not define the weld joint configuration, since it can be made in various ways Thus, a weld butt joint can be made square, double-square, single-bevel, double-bevel, single-V, double-V, or by four other joint configurations A T-connection can be made with a double fillet, as shown: or it may be made with a single or double-bevel or single or double J V and U weld joints are feasible only for butt and corner welds because of the need for the preparation of both surfaces

Single Double

UNIT 3: WELDING CONSUMABLES

Object: to deliver the uses and characteristics of the metal electrode

- Characteristic:

- Core: Lõi - Cover: Vỏ ỏ

- Shielded Metal Arc Welding (SMAW): Hàn à

- Desired weld: M

- Consist of: Bao

- Cellulose: X

- Rutile: Rutin - Dioxidizing: Ôxy hóa - Binders:

- Extrusion: ù ra, é i

- Tensile Strength : ự kéo - Physical properties: í í - Stabilize: Làm

- Essential: ủ

- DC: Dirrect current: Dòng

- AC: Alternating current: Dòng

- Slag removal: Gỡ Lo ỏ ỉ

- Consistently: Liên ỉ - Depend on: Tùy

- Filler wire: Q

- Electrode wire: Dây hàn - Self-shielding Wire: Dây ự

- Flux cored electrode: Dây õ

- Arc welding electrode: cự

- Covered electrode: Que

- Electrode covering: T

- Welding flux: T hàn - Shielding gas: Khí

- Position: V trí - Relationship: liên quan - Designation: Sự

- Characteristic: tính - Operation: Sự ành

- Compound: Ghép,

II GRAMMAR

RELATIVE CLAUSES

a Defining relative clauses

These describe the preceding noun in such a way as to distinguish it from other nouns of the same class A clause of this kind is essential to the clear understanding of the noun Normally relative clauses should be placed directly after their noun or pronoun:

Example: The noise that the welders made woke everybody up

Relative pronouns used in defining relative clauses

The format is as follows:

Defining relative clauses: things

b Subject

Either which or that, which is more formal:

- This is the construction that / which was finished yesterday

- This is the fabrication that shows the job of my students

c Object of a verb

Which or that, or no relative at all:

- The tool that / which you welded is becoming dangerous

d Object of a preposition

The formal construction is preposition + which, but is more usually to move the preposition to the end of the clause, using which or that or omitting the elative altogether:

- The ladder on which the welders usually stand to join a construction

- The ladder which / that the welders usually stand on to join a construction

e Relative adverb: where

Where can replace „in/ at which‟ „w ‟

- That is the shop where (= in/ at which) students usually practise their tasks after studying theory

III PRACTICE

The first specification for mild-steel covered electrodes, AWS A5.1 was writen in

1940 As the welding industry expanded and the number of types of electrodes for welding steel increased, it became necessary to devise a system of electrode classification to avoid confusion The system used applies to both the mild-steel A5.1 and the low-alloy steel A5.5 specification (Figure 4 – Covered electrode)

Figure 4

Table 1 AWS numbering system

a The prefix “E” designates arc welding electrode

b The first two digits of 4-digit numbers and the first three digits of 5-digit numbers indicate minimum tensile strength

E60XX 60,000 psi Tensile Strength

E70XX 70,000 psi Tensile Strength

E110XX 110,000 psi Tensile Strength

c The next –to- last digit indicates position

EXX1X All positions

EXX2X Flat position and horizontal fillets

d The last two digits together indicate the type of covering and the current to be use

e The suffix (example : EXXXX-A1) indicates the approximate alloy in the deposit -A1 ½% Mo

-G 50 min Ni, 30 min Cr, 20 min Mo, 10min V

(only one of the listed elements is required)

Classifications of mild and low-alloy steel electrodes are based on an “E” prefix and a four or five-digit number The fisrt two digits (or three, in a five-digit number) indicate the minimum required tensile strength in thousands of pounds per spuare inch For example, 60=60.000 psi, 70=70.000psi, and 100=100.000psi the next to the last digit indicates the welding position in which the electrode is capable of making satisfactory welds: 1= all position – flat, horizontal, vertical, and overhead; 2= flat and horizontal fillet welding The last two digits indicate the type of current to be used and the type of covering on the electrode (see table 2)

Originally a color identification system was developed by the National Electrical Manufacturers Association (NEMA) in conjunction with the American Welding Society to identify the electrode’s classification This was a system of color markings applied in a specific relationship on the electrode

Table 2 – AWS A5.1-69 electrode designations for covered arc-welding electrodes

In addition to the classifications specified by the American Welding Society, electrodes can be classsified by the characteristics of the molten metal and molten flux during the welding operation These broad classifications are fast-freeze, fast-fill, and fill-freeze, the terms being descriptive of the operation of the electrode

Fast-freeze electrodes

Fast-freeze electrodes are compounded to deposit weld metal that solidifies rapidly after being melted by arc, and are thus intended specifically for welding in the vertical and overhead positions

Fast- freeze electrodes provide deep penetration and maximum admixture The weld bead is flat with distinct ripples Slag formation is light, and the arc is easy to control

Applications for fast-freeze electrodes are:

1 General-purpose fabrication and maintenance welding

2 Vertical-up and overhead plate welds requiring X-ray quality

3 Pipe welding

4 Welds to be made on galvanized, plated, painted, or unclean surfaces

5 Joints requiring deep penetration, such as square-edge butt welds

6 Sheet- metal welds, including edge, conner, and butt welds

Fast-fill electrodes

Fast-fill electrodes are compounded to deposit metal rapidly in the heat of the arc and are, thus, well suited to high-speed welding on horizontal surfaces The weld metal solidifies some what slowly; therefore this type of electrode is not well suited for out-of-position welds

Arc-penetration is shallow with minimum admixture The bead is smooth, free of ripples, flat or slightly convex Spatter is negligible Slag formation is heavy, and the slag peels off rapidly

Applications for fast-fill electrodes are:

1 Production weld on plate having a thickness of 3/16 or more

2 Flat horizontal fillets, laps, and deep groove butt welds

3 Welds on medium-carbon crack-sensitive steel when low-hydrogen electrodes are not available (Preheat may be required)

Fill-freeze electrodes

Fill-freeze electrodes are compounded to provide a compromise between fast-free and fast-fill characteristics, and thus provide medium deposition rates and medium penetration

Applications for fill-free electrodes include:

1 Downhill fillet and lap welds

2 Irregular or short welds that change direction or position

3 Sheet-metal lap or fillet welds

4 Fast-fill joints having poor fitup

5 General-purpose welding in all position

Table 3 Welding parameter

Approximate Electrode Amperage Settings

Fast Freeze Fill Freeze Fast Fill Low Hydrogen E6010 - E6011 E6013 - E7014 E7024 - E7028 E7018

Diameter of Current Setting Current Setting Current Setting Current Setting Electrode

Inches(Millimeters) Amperes Amperes Amperes Amperes

UNIT 4: WELDING TECHNOLOGY

Object: To introduce general about welding technology

- Submerged arc welding: Hàn d (Hàn h

- Gas shielded arc welding: Hàn g trong môi tr í

- TIG (Tungsten inert gas welding): Hàn ự w f í

- Pulsed arc welding: Hàn

- Manual arc welding: Hàn

- Automatic arc welding: Hàn ự

- Double arc welding: Hàn

- Multi-arc welding: Hàn

- Twin electrode welding: Hàn 2 ự

- Semi-automatic arc welding: Hàn ự

The passive voice with may, can, should and must

S + can / may / should / must + V + O

S + can / may / should / must + be + V_ ed (Past participle)

Active: You should shut these doors

Passive: These doors should be shut

Active: You can use the process to deposit metal to form a surface with alternative

properties

Passive: The process can be used to deposit metal to form a surface with alternative

properties

III PRACTICE:

MANUAL METAL ARC WELDING

Manual metal arc (MMA) welding, also known as shielded metal arc welding (SMAW), stick welding, or electric arc welding is a constant current drooping arc process (Figure 5)

In manual metal arc welding the heat source is an electric arc, which is formed between a consumable electrode and the parent plate The arc is formed by momentarily touching the tip of the electrode onto the plate and then lifting the electrode to give a gap of 3 mm – 6 mm between the tip and the plate When the electrode touches the plate, current commences to flow and as it is withdrawn the current continues to flow in the form of a small spark across the gap, which will cause the air in the gap to become ionised, or made conductive As a result of this the current continues to flow even when the gap is quite large The heat generated is sufficient to melt the parent plate and also melt the end of the electrode – the molten metal so formed is transferred as small globules across the arc into the molten pool

TUNGSTEN INERT GAS WELDING

Tungsten inert gas welding is a constant current drooping arc process It is also known as TIG, gas tungsten arc welding – GTAW, wolfram inert gas – WIG, and under the trade names of argon arc and helium arc (Figure 6)

Figure 6

Type of Operation

Usually manual, but can be mechanised

Mode of Operation

An arc is maintained between the end of a tungsten electrode and the work The electrode

is not consumed and the current is controlled by the power source setting The operator must control the arc length and also add filler metal if needed to obtain the correct weld; consequently, a high degree of skill is needed for the best results The arc is unstable at low currents Special provision is made for starting (high frequency or surge injection) and for welding thin materials (pulse TIG)

METAL INERT GAS WELDING

With a 'flat' volts/amps characteristic an attempted alteration in arc length (volts) will have little effect, hence arc length (volts) remains constant but a significant change in current will result This is often referred to as the 'self-adjusting arc' Metal Inert Gas (MIG) welding is a 'flat' arc process (constant voltage process) Also known as Metal Active Gas (MAG); CO2; Metal-arc Gas Shielded, flux core and GMAW (US) MIG can

be used on all materials, in all positions, with high productivity and low heat input There

is no CO2 MIG welding with stainless steel Normally DC positive though some flux cored processes uses DC negative (Figure 7)

Figure 7

Type of Operation

Manual, mechanised, semi-automatic and automated (robotics)

Mode of Operation

An arc is maintained between the end of the bare wire electrode and the work piece The wire is fed at a constant speed, selected to give the required current, and the arc length is controlled by the power source The operator is not therefore concerned with controlling the arc length and can concentrate on depositing the weld metal in the correct manner Hence the name 'semi-automatic' for manual operation, in which wire, gas and power are fed to a hand held gun via a flexible conduit

The process can be operated at high currents (250 - 500 A) when metal transfer is in the form of a 'spray', but, except for aluminium, this technique is confined to welding in the flat and horizontal positions For vertical and overhead welding special low current techniques must be used, i.e 'dip' transfer or pulsed arc The arc and weld pool are shielded by a stream of gas The electrode can be solid or flux cored

SUBMERGED ARC WELDING

A flat arc process - (constant voltage process) It is used in beam, boom, tractor and multi-head type rigs (figure 8)

of the flux melts to provide a protective blanket over the weld pool The remainder of the flux is unaffected and can be recovered and re-used, provided it is dry and not contaminated

A semi-automatic version is available in which the operator has control of a welding gun that carries a small quantity of flux in a hopper

flux-4 Explain the principle of SMAW?

5 Explain the principle of MIG/MAG?

6 Explain the principle of TIG?

7 Explain the principle of SAW?

UNIT 5: IMPERFECTION WELDING

Object: to study imperfection welding

- Tungsten inclusion: ẫ vonfram

- Burn through: Cháy xuyên ủ

II GRAMMAR:

THE ARTICLE: A / AN AND THE

1 The indefinite article (a/an)

Indefinite article is used before a singular noun which is countable when it is mentioned for the first time and represents no particular person or thing:

Example:

a butt joint a lap joint a position a way

2 The use of a / an

The „a‟ is used before a word beginning with a consonant, or a vowel with a consonant sound:

Example:

a steel a bar of steel a joint

The „an‟ is used before words beginning with a vowel ( a, e, i, o, u) or words beginning with a mute h:

Example:

an iron an imperfection an irregular

or individual letters spoken with a vowel sound:

Example:

an L-plate

3 The definite article (the)

The definite article is used before a noun which has become definite as a result

of being mentioned in second time or afterward:

The body of the weld

The area of the arc strike

The damage on the parent material

At the end of

The side of the weld

III PRACTICE

1 Defects detected by surface inspection

Defects, which can be detected by visual inspection, can be grouped under five headings

Longitudinal, in weld metal (centreline) Longitudinal, in parent plate

Figure 9

Figure 10

An imperfection at the toe or root of a weld caused by weld metal flowing

on to the surface of the parent plate without fusing to it

Causes - slow travel speed, large electrode, tilt angle, poor pre-cleaning

Spatter

Stray globules of weld material, on parent plate outside the weld

Causes - damp electrodes, too high voltage, too high current, flux missing

Stray flash (stray arcing)

The damage on the parent material resulting from the accidental striking of an arc away from the weld A small volume of base material is melted when the arc is struck This molten pool is quenched due to the rapid diffusion of heat through the plate This may lead to the formation of a crater that lends itself to cracking, or a change in grain structure by creating a martensitic or brittle grain structure in the area of the arc strike These discontinuities may lead to extensive cracking in service

Causes - operator error

1.3 Contour defects

The profile of a finished weld may

considerably affect performance of the joint

under load bearing conditions Specifications

normally include details of acceptable weld

profiles to be used as a guide

Excess weld metal

Also excess convexity, excess reinforcement

Additional weld metal above the surface plane

of the parent material or greater than the

desired throat on

fillet welds

Lack of fusion

A continuous or intermittent groove along the

side of the weld with the original weld prep

face still intact

Causes - not enough runs, operator error

Incompletely filled groove

A continuous or intermittent channel in the

surface of the weld, running along its length,

due to insufficient weld material The channel

may be along the centre or along one or both

edges of the weld

Causes - not enough runs - procedure error,

electrode too small Also called insufficient

throat

Figure 13

1.4 Root defects (Figure 14)

Figure 14

Incomplete root penetration

Failure of weld metal to extend into the root of the weld

Causes - poor weld prep, root gap too small, root face too big, small included angle, heat input too low

Lack of root fusion

Lack of union at the root of a joint

Causes - poor weld prep, uneven bevel, root face too large, linear misalignment, cleaning

Excess penetration bead

Excess weld metal protruding through the root of a fusion weld made from one side only

Causes - high heat input, poor weld prep - large included angle

Root concavity (suck-back, underwashing)

A shallow groove which may occur in the root of a butt weld

Causes - purge pressure, wide root gap, and residual stresses in root

Lack of fusion. Lack of union in a weld a between weld metal and parent metal

b between parent metal and parent metal

c between weld metal and weld metal

Lack of sidewall fusion. Lack of union between weld metal and parent metal at a side

of a weld

Lack of inter-run fusion. Lack of union between adjacent runs of weld metal in a

multi-run joint

Figure 16

defect is more irregular in shape than a gas pore

Oxide inclusion Metallic oxide entrapped during welding

Tungsten inclusion An inclusion of tungsten from the electrode during TIG

welding

Copper inclusion An inclusion of copper due to the accidental melting of the

contact tube or nozzle in self adjusting or controlled arc welding or due to pick up by contact between the copper nozzle and the molten panel during TIG welding

Puckering The formation of an oxide covered weld run or bead with

irregular surfaces and with deeply entrained oxide films, which can occur when materials forming refractory oxides (e.g aluminium and its alloys) are being welded

Figure 17

Elongated cavities A string of gas pores situated parallel to the weld axis

(Linear porosity.)

Blowhole A cavity generally over 1.5mm in diameter formed by

entrapped gas during the solidification of molten metal

Wormhole An elongated or tubular cavity formed by entrapped gas

during the solidification of molten metal

UNIT 6: WELDING PROCEDUCE

Object: to study the WPS and the uses

- Welding procedure: Quy trình hàn

- Welding processes: P

- Welding procedure specification (WPS): ỹ quy trình hàn

- Approved welding procedure specification: ỹ quy trình hàn

- Preliminary welding procedure specification (pWPS): ỹ quy trình hàn

- Welding procedure test: Thử àn

- Welding procedure approval record (WPAR): ẩ quy trình hàn

- W d d f d WPQR PQR quy trình hàn

- Welding operator: T

- Direction of welding: hàn

- Downhill welding in the inclined position: hàn trê

- Uphill welding in the inclined position: Hàn d (Hàn leo)

- Edge preparation: S ng-phanh ( ẩ mép hàn)

- Filler metal: Kim

- DCEN (Direct current electrode negative): ò ự

- DCEP (Direct current electrode positive): ò ự d

- Weight of electrode deposited per ampere per hour:

- Weight of metal deposited per ampere per hour: ắ

II GRAMMAR

CONDITIONAL SENTENCES

Type 0: Cause and effect:

Example:

If you heat ice, it melts

These sentences are statements of universal truth and general validity, and in this type of sentence, if corresponds closely in meaning to when (ever) Statements in this form commonly appear in factual discussion or explanatory material The tense in both the conditional and the main clause are the same

Type 1: Open conditions:

In these sentences, the conditional clauses represent open conditions; that is, conditions that may or may not be fulfilled

Ex: f ‟ d

The common sequence of tenses in this type of sentence is:

(If) present tense, (Main) Future (or modal verb) or imperative

Ex: If you want to join this construction better, you should prepare carefully

If you work without any detective blankets, your eyes will be damaged