Welding iv

By:P.SIVASANKARAN

WELDING

Welding is a process of joining two or more pieces of the same or dissimilar materials to achieve complete coalescence.

DEFINITION AS PER AWS / ASME

A localised coalescence of metals or non-metals produced either by heating the materials to the welding temperature with or without the application of pressure alone, and with or without the application of filler material.

WELDING PROCESSES

1. Shielded Metal Arc Welding (SMAW)

2. Submerged Arc Welding (SAW)

3. Gas Metal Arc Welding (GMAW )

1. - MIG , MAG

4. Gas Tungsten Arc Welding (GTAW / TIG)

SELECTION OF WELDING PROCESS DEPENDS ON

Thickness & Size of part to be welded

Location and position of weld joints

Joint design

Welding equipment availability

Process and operation requirement

Production cost

SHIELDED METAL ARC WELDING

SMAW process defined as an arc welding process which produces coalescence of metals by heating them with an arc between a covered metal electrode and the work-piece.

Shielding is obtained from decomposition of the electrode covering.

Pressure is not used and filler metal is obtained from the electrode.

SHIELDED METAL ARC WELDING

MODE OF OPERATION

Arc melts parent plate and electrode to form a weld pool which is protected by flux cover.

Operator adjusts electrode feed rate, I.e. hand movement to keep arc length constant. Slag must be removed after depositing each bead. Normally a small degree of penetration, requiring plate edge preparation. Butt welds in thick plate or large fillets are deposited in a number of passes.

The process can also be used to deposit metal to form a surface with alternative properties.

CONSUMABLES

Metal rods 1.5 - 8mm diameter with flux covering (1-5mm radial thickness).

Widely used: 2.5x 250, 3.15 x350/450, 4 mm x 450 mm

The characteristics of manual metal arc electrodes, i.e., arc stability, depth of penetration, rate of deposition, position of welding, depends on the chemical composition of the electrode coating classified by AWS specifications.

SMAW - OPERATING PARAMETERS

Current range : 75-300 A

Open Circuit Voltage : 65 - 80 V

Range of Thickness: 2mm upwards

Deposition rate : 2-11 lb/Hr

Types of joint : All

Welding position : all (depending on flux coating)

Access : Good

Portability : Good

MATERIALS

Mostly confined to ferrous alloys, but can be used for some others.

TYPICAL APPLICATIONS

Structural steel work.

Ship Building

Repair and Hard facing of construction plant.

OVERALL ADVANTAGES

Low Equipment Cost

Usage possible with restricted access.

OVERALL LIMITATIONS

Skilled operator is required for good quality welds.

Slow, mainly because flux must be chipped away.

SAFETY

Arc emits visible and ultraviolet radiation.

High open circuit voltage present while electrode is fitted to holder.

SUBMERGED ARC WELDING

SAW is defined as an arc welding process in which an arc is maintained between an end of a bare wire electrode and work piece.

The arc is fully submerged in a layer of dry granular flux.

Pressure is not used and filler metal is obtained from the electrode.

SUBMERGED ARC WELDING

OVERALL ADVANTAGES High weld metal Quality

Smooth and uniform weld bead with no spatters.

Extremely high deposition rate and welding speed.

Current Range: 450 - 3000 A

High Arc time can be achieved through automation.

Minimum operator fatigue.

OVERALL LIMITATIONS High initial cost

Limited welding positions.

Requirement of special jigs and fixtures.

Difficulty in welding low thickness metals.

Full penetration weld joints not possible from single side.

GAS METAL ARC WELDING

GMAW is defined as an arc welding process which produces coalescence of metals by heating them with an arc between a continuous filler metal (consumable) electrode and the work piece.

Shielding is obtained entirely from an externally supplied gas or gas mixture.

GAS METAL ARC WELDING

TYPE OF OPERATION: Semi-automatic /

Fully automatic.

EQUIPMENT : Power Source

Wire feed Unit

Welding gun or torch

Gas supply system travelling unit, if fully mechanised.

GAS METAL ARC WELDING

An arc is maintained between the end of the bare wire electrode and the work. 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.

GAS METAL ARC WELDING

Contd.

The process can be operated at high currents (250-500A) when metal transfer is in the form of ‘spray’ but except for aluminium, this technique is confined to welding in the flat and horizontal positions. For welding in the vertical and overhead positions. Special low-current techniques must be used, I.e. ‘dip transfer’ or pulsed arc shielded by a stream of Gas.

GAS METAL ARC WELDING

GMAW - OPERATING PARAMETERS

Current range : 65-500 A

Metal Transfer modes:

Globular - in CO2 welding ( Non-axial metal transfer) for Structures

Spray Transfer - Thk > =6mm; in MIG ( Axial Transfer) for piping ( with Argo-CO2 shield) high thickness range.

Dip Transfer ( Short Circuit ) - suitable for thin sheet metal works ( thk @ 3 mm or less)

: Dip transfer, pulsed arc –Above 0.5mm Spray transfer 6mm upwards

Deposition rate :12-10 Kg/Hr (2-20 Lb/Hr)

Types of joint : All including spot welds

Access : Fair

Portability : Fair

Consumables

Electrodes, bare wire (m.s. is normally copper coated) 0.6-1.6mm dia. Layer wound on spools 0.5-12 Kg (1-25lb) weight. Composition of wire selected to suit parent material; wire specifications covered by BS 2901. Electrodes, flux cored are available for high deposition rate welding.

Shielding gas in cylinders containing compressed gas which will expand to 7Cu.M (250 Cu.Ft) at atmospheric pressure. Composition to suit parent material – usually carbon dioxide (CO2) for mild steel, argon for non-ferrous materials and argon with 1.5% oxygen or 5-20% CO2 for high strength and corrosion resisting ferrous alloys.Other mixtures are used in special circumstances.

TYPICAL APPLICATIONS

CO2 Welding ( MAG )- For structures

MIG Welding with Argon / Helium/ Mixed Gases - for Low Alloy, Mild Steel, Aluminium alloy, Copper and Copper allloys

Spray Transfer method - for heavy wall thickness pipes, structures

Dip Transfer ( Short Circuit) - for Thin sheet metal working. Vehicle manufacturing.

OVERALL ADVANTAGES

Continuous process

Reduced finishing operations

Thin sheets can be welded in all positions by dip transfer mode.

OVERALL LIMITATIONS

No independent control of filler addition.

Range of action limited by wire feed.

SAFETY

Arc emits visible and ultraviolet radiation.

GAS TUNGSTEN ARC WELDING

GTAW is defined as an arc welding process which produces coalescence of metals by heating them with an arc between a tungsten (non- consumable) electrode and the work piece.

Gas Tungsten Arc Welding (GTAW) uses a non consumable tungsten electrode which must be shielded with an inert gas.

The arc is initiated between the tip of the electrode and work to melt the metal being welded, as well as the filler metal, when used.

A gas shield protects the electrode and molten weld pool, and provides the required arc characteristics.

GAS TUNGSTEN ARC WELDING

STRAIGHT POLARITY

REVERSE POLARITY

OVERALL ADVANTAGES Superior quality welds

Welds can be made with or without filler metal

Precise control of welding variables (heat)

Free of spatter

Slag free

Low distortion

OVERALL LIMITATIONS Requires greater welder dexterity than MIG or

stick welding

Lower deposition rates

More costly for welding thick sections

RECOMMENDED ELECTRODES / FILLER WIRES

COATED ELECTRODES FILLER WIRESASME AWS ASME AWS

CARBON STEEL SFA 5.1 E 7018 SFA 5.18 ER 70 S2CARBON MOLY SFA 5.5 E 7018 A1 SFA 5.28 ER 80 SB2

11/4 Cr - 1/2 Mo P11 SFA 5.5 E 8018 B2 SFA 5.28 ER 80 SB2

21/4 Cr - 1 Mo P22 SFA 5.5 E 9018 B3 SFA 5.28 ER 90 SB3

5 Cr - 1/2 Mo P5 SFA 5.4 E 502 SFA 5.9 ER 502

9Cr - 1 Mo P9 SFA 5.4 E 505 SFA 5.9 ER 50518 Cr 8 Ni SFA 5.4 E 308 SFA 5.9 ER 30816 Cr 13 Ni Mo SFA 5.4 E 316 SFA 5.9 ER 31618 C 10 Ni cb SFA 5.4 E 347 SFA 5.9 ER 34718 Cr 10 Ni Tl SFA 5.4 E 347 SFA 5.9 ER 34723 Cr 12 Ni SFA 5.4 E 309 SFA 5.9 ER 30925 Cr 20 Ni SFA 5.4 E 310 SFA 5.9 ER 310Miscelleneous SFA 5.11 E Ni Cr Fe2 SFA 5.14 ER Ni Cr3

BASE MATERIAL

STANDARD REBAKING PROCEDURE FOR LOW HYDROGEN ELECTRODES

1. Rebake the electrodes at 250-300 Deg. C for one hour.

2. Cool them in the same oven to 100 Deg. C

3. Transfer them to a holding oven maintained at 60-70 Deg. C

4. Draw from this oven for use.

5. Do not keep the rutile type electrodes in the same oven.

WELDING PROCEDURE SPECIFICATION (WPS)

• WPS shall be written as per ASME Section IX or IS 7307

• ( For Cross Country Pipelines: API 1104)

• WPS is a written qualified welding procedure prepared to provide direction for making production welds to code requirements.

• The WPS or other documents may be used to provide direction to the welder or welding operator to assure compliance with the code requirements.

• WPS shall describes all of essential, non-essential and supplementary variables for each welding process.

PROCEDURE QUALIFICATION RECORD (PQR)

• PQR shall be written as per ASME Section IX or IS 7307.

• PQR is a record of the welding data used to weld a test coupon.

• The PQR is a record of variables recorded during the welding of the test coupons.

• It is a record of what happened during a particular welding test.

WELDERS PERFORMANCE QUALIFICATION (WPQ)

• WPQ shall be written as per ASME Section IX or IS 7310.

• WPQ test shall be welded in accordance with qualified WPS.

• Each manufacturer or contractor shall qualify each welder or welding operator for each welding process to be used in production welding.

Company Name Larsen & Toubro Limited - ECC Construction Group

Welding Procedure Specification no L&T/CPCL/ Rev. 0 Date 29.12.2K

Supporting PQR No.(s) Rev. - Date -

Welding Process(es) SMAW Type(s) Manual

JOINTS (QW-402)

Joint Design Double 'V' Groove

Backing Yes / No

Backing Material (Type) Nil

(Refer to both packing and retainers)

Metal Non Fusing Metal

Non mettalic Other

BASE METALS(QW-403)

P.No. 01 Group No 02 to P.No. 01 Group No. 02____orSpecification Type & Grade ASTM SA 516 GR 70 to Specification Type & Grade ASTM SA 516 GR 70 or

Chem.Analysis and Mech. Prop. -

to Chem.Analysis and Mech. Prop. -

Thickness Range

Base Metal Groove 4.76 - 50 mm Fillet All

Pipe Dia Range Groove All Fillet AllOther -

FILLER METALS(QW-404)

Process

Spec. No (SFA)

Aws. No(Class)

F.No.

A.No

Size of Filler metals

Electrode Flux(class)

Flux Trade Name

Consumable Insert

Other

NA

NA

04

01

2.5, 3.15 & 4.0mm

NA

QW-482 WELDING PROCEDURE SPECIFICATIONS (WPS)

(See QW-200.1,Section IX ASME Boiler and Pressure Vessel Code)

5.1

E7018

SMAW

2.5+0.5mm mm

1.5 .5mm

60º

t

WPS No. L&T/CPCL/ Rev. 0

POSITIONS (QW-405) POST WELD HEAT TREATMENT(QW-407)

Position(s) of Groove Any Temparature Range 595 to 650 Deg. C

Welding Progression : Up Yes Down X Heating & Cooling Rate 160 Deg. C / Hr

Positions of Fillet All GAS (QW-408)

Percent Composition

PREHEAT(QW-406) Gas(es) Mixture Flow Rate

Preheat Temp. Min 150 Deg. C for T > 19mm Shielding NA

Interpass temp.Max 250 Deg.C Trailing NA

Preheat Maintanence - Backing NA

(Contininous or special heating w here applicable should be recorded)

ELECTRICAL CHARECTRASTICS (QW-409)

Current AC or DC DC Polority SMAW - RP

Amps (Range) 60-180 Volts Range 18 - 24 V

(Amps and volts range should be recorded for each electrode size,position, and thick etc.

Tungsten electrode Size and Type NA

Mode of metal Transfer for GMAW NA

Eletrode Wire feed speed range NA

TECHNIQUE (QW-410)

String or Weave Bead Both

Orifice or Gas Cup Size NA

Intial and Interpass Cleaning (Brushing,Grinding etc.) Wire Brushing, Grinding

___________________________________________________________________________________________

Method of Back Gouging Grinding

Ocillation NA

Contact tube to Work distance --

Multiple or Single pass (per side) Multipass

Multiple or Single Electrodes Single

Travel Speed ( Range) See Table

Peening NA

Other NA

___________________________________________________________________________________________

Weld Layers ProcessAmp

RangeVolt

Range

Travel speed Range

Others

Class Dia Type Polority mm/min

01 SMAW E7018 2.5 DC RP 60-90 18-20 60-120 --

02 SMAW E7018 2.5 DC RP 60-90 18-20 60-120 --

03 SMAW E7018 3.15 DC RP 90-130 18-22 60-120 --

04 SMAW E7018 4.0 DC RP 130-180 18-24 60-120 --

Prepared by Reviewed and Approved by Reviewed and Accepted by

for LTCG for LTCG for CLIENT / CONSULTANT

Filler Metals Current

QW-482 (Back)

(Pure Tungsten,2% Thoriated etc)

Spray arc,short circuiting etc.

Company Name Larsen & Toubro Limited - ECC Construction Division

Procedure Qualification Record No. L&T/CPCL/ 01 Rev. 0 Date 15.02.2001

WPS No. L&T/CPCL/ 01 Rev. 0 Date

Welding Process(es) SMAW Type(s) Manual

JOINTS (QW-402)

BASE METALS(QW-403) POSTWELD HEAT TREATMENT(QW-407)

Material Spec. : ASTM SA 516 Temperature : 620 Deg. C

Type or Grade : Gr. 70 Time : One Hour

P.No. 01 to P.No. 01 Other :

Thickness of Test Coupon : 25mm Rate of Heating : 160 Deg. C/ HrDiameter of Test Coupon : NA Rate of Cooling: 130 Deg. C/ HrOther : NA GAS (QW408) Percent Composition Gas(es) (Mixture) Flow Rate

Shielding NA

FILLER METALS(QW-404) Trailing NA

SFA Specification 5.1 Backing NA

Aws. Classification E7018 ELECTRICAL CHARECTRASTICS (QW-409)

Filler Metal F.No. 04 Current DC .

Weld metal Analysis A.No 01 Polarity SMAW - RP .

Size of Filler metals 2.5, 3.15 & 4.0mm Amps 130 Ave Volts 18-21 V .

Other : NA .Tungsten Electrode Size NA .

Other NA

Weld Metal Thickness

POSITION(QW-405) TECHNIQUE(QW-410)

Position of Groove : 6G . Travel Speed : 60 - 120 mm / Min

Weld Progression (Uphill, Downhill) Uphill . String or Weave Bead:Root - String,Fillup-Weave

Other NA .Oscillation _________2.5 D

Multipass or Single pass (per side) Multipass

PREHEAT (QW-406 ) Multiple or Single Electrode Single

Preheat Temp : 150 Deg. C Other NA

Inter pass temp : NA

Other NA .

(See QW-200.1,Section IX ASME Boiler and Pressure Vessel Code)

Groove design of Test Coupon

QW-482 PROCEDURE QUALIFICATION RECORDS (PQR)

Record of Actual conditions used to Weld Test Coupon

2.5+0.5mm mm

1.5 .5mm

60º

25mm

PQR No. L&T/CPCL/01

Specimen Width Thickness Area Ultimate Type of No. unit Stress Mpa failure & Loc.T1 12.6 25.1 316 496.74 Fractured awayT2 12.6 25.1 316 496.16 from the welded

area

Specimen Notch Specimen Test Drop WeightNo. Location Size Temp Ft. LBS % Shear Mils Break (Y / N)

NA NA NA NA NA NA NA NA

Result - Satisfactory : yes No penetration into parent metal:yes metal : yes ______No _________

Macro--Results NA

Other Results NA

Type of test NADeposit analysis NAother NA

Welder's Name A.ARUL SELVAM Clock no _____________ Stamp no ______________Tests conducted by : __________________________Laboratory test No ______________________________M/s sargam metals Laboratory Test No SM/MT/256A/2000-2001 dated 14.02.2001We certify that the statements in this record are correct and that the test welds were prepared, welded,and tested in accordance with the requirements of section IX of the ASME Code.

Manufacturer : Larsen & Toubro Limited - ECC Division, ChennaiDate : 15.02.2001 By : P Sampathkumar

for L&T-ECCD for M/s SGS India Limited

Fillet - Weld (QW-180)

3. Face Bend FB3 No Significant defect2. Face Bend FB2

4. Face Bend FB4 No Significant defect

Impact Values

Toughness Tests (QW-170)

QW-483 (Back)

Tensile Test (QW -150)

Ultimate TotalLoad KN

Guided - Bend Tests (QW -160)

1.5706697021.568835768

Type and Figure No

No Significant defect

ResultNo Significant defect1. Face Bend FB1

WELD SYMBOLSWELD SYMBOLS

Insert Weld Symbol

Thermal Cutting Methods