fundamental of welding

8/10/2019 Fundamental of Welding

1/163

Welding


2/163

Table of Contents

1. Section 1 Fundamentals of Welding

2. Section 2 Welding Metallurgy

3. Section 3 Welding Design

4. Section 4 Welding Equipment & Consumables

5. Section 5 WPS & PQR

6. Section 6 Welding Inspections & Techniques

7. Section 7 Welding Defects, Causes & Remedies8. Useful Websites


3/163

Section 1

Fundamentals of Welding



4/163


WeldingDefinition 1:

Welding is a complex, metallurgical process involvingmelting, solidification, gas-metal reactions, surface

phenomena and solid state reactions for joining metals.

Definition 2:

Welding is the joining of multiple pieces of metal by the

use of heat and or pressure. A union of the parts is

created by fusion or re-crystallization across the metal

interface. Welding can involve the use of filler material,

or it can involve no filler.


5/163


6/163


Arc Welding:Definition A fusion process wherein the coalescence of the

metals is achieved from the heat of an electric arc

formed between an electrode and the work.


7/163


Arc Welding Processes Shielded metal arc welding (SMAW)/ stick welding

Sub-merged arc welding (SAW)

Gas metal arc and flux cored arc welding (GMAW)

Flux cored arc welding (FCAW)

Gas tungsten arc welding (GTAW)

plasma arc welding (PAW)

Electrogas welding

Electroslag welding


8/163

Shielded Metal Arc Welding

(SMAW)/ Stick Welding



9/163


DIAGRAM 1


10/163


DIAGRAM 2


11/163

Overview of Process

SMAW is an early arc welding process used for

ferrous and several nonferrous base metals. It uses

a covered electrode consisting of a core wire

around which a concentric clay-like mixture of

silicate binders and powdered materials (such as

fluorides, carbonates, oxides, metal alloys and

cellulose) is extruded. This covering is a source of

arc stabilizers, gases to displace air, metal and slag

to protect, support and insulate the hot weld metal.



12/163

Tools & Equipment

Electrode (consumable & non-consumable)

Electrode Holder

Electrode Cable

Welding Machine (AC or DC Power Source)Work Cable

Clamp

Filler Metal

Welding Helmet

Protective Clothing



13/163

Advantages Many welding applications with small variety of

electrodes.

Simple, portable,& inexpensive equipment

Self flux provided by electrode

Provides all position flexibility

Weld can be made in Confined location



14/163

Limitations

Used for steels, stainless steels, cast irons.

Not used for aluminum and its alloys, or copper and

its alloys (energy density is too high).

Best suitable for joining metals of

sections1/8 to 3/4 in.(3 to 9 mm) thickness.

Groove weld joints in plate thickness normally

require edge preparation to allow proper access tothe root of the joint.

Typical current range is between 50 and 300A.



15/163


Limitations contd Special electrodes can be used as high as 600A and

others as low as 30A, allowing weld metal deposition

rates of between 2 and 17 lb/h (1 & 8 KG/Hr).

High material cost as 60% of the weight of the

purchased electrodes is deposited as filler metal.


16/163


Applications Construction

Pipelines

Shipbuilding

Fabrication job shops.

Maintenance Industries


17/163


Common Defects Porosity Slag inclusions

Incomplete Fusions

Inadequate joint penetration. Undercut

Overlap

Cracks


18/163

SUB-MERGED ARC WELDING (SAW)



19/163


Diagram 1


20/163

Overview of ProcessIn SAW, the arc and molten meta; are shielded by anenvelope of molten flux and a layer of unused

granular flux particles. When the arc is struck , the

tip of the continuously fed electrode is submerged

in the flux and the arc is therefore not visible. The

weld is made without the intense radiation that

characterizes an open arc process and with little

fumes.



21/163

Tools, Equipment & MaterialsElectrode (consumable & non-consumable)

Electrode Holder

Electrode Cable

Power Source (600 to 2000A output)Automatic Wire Feed

Tracking System

Work Lead

Weld Backing

Filler Metal

Welding Helmet

Protective Clothing



22/163

Advantages

Useful for welding both Sheet and plate.

Thin materials speed up to 200in/min (84mm/sec) can

be achieved.

In thick section applications, high metal deposition

rates of 60 to 100 lb/h (27 to 45 kg/h).

Least Expensive in operating cost

Edge preparation is not required due to the usage of

DCEP (Direct Current Electrode Positive).

Consistent weld quality



23/163

Limitations

Welds can only be made in the flat and horizontal

positions.

Used for all grade of carbons, low alloy and allow

steels. Stainless Steel and some nickel alloys are

also effectively welded or used as surfacing filler

metals with the process.

Power Source, Three Phase 220V or 440V Single phase 440V.



24/163

Applications

Used for all grade of carbons, low alloy and alloy

steels. Stainless Steel and some nickel alloys are

also effectively welded or used as surfacing filler

Pipelines.

Jobs require deposition of large quantities of filler

metal.

Fabrication job shops.

Maintenance Industries.

Pipelines



25/163

Common Defects

Porosity

Slag inclusions

Incomplete Fusions

Inadequate joint penetration. Undercut

Overlap

Cracks



26/163

GAS METAL ARC WELDING (GMAW)



27/163

Diagram 1



28/163

Diagram 2



29/163

Overview of Process

GMAW process use a continuous solid wire toprovide filler metal, and use gas to shield the arc

and weld metal. The electrode is solid and all of the

shielding gas is supplied by an external source. The

shielding gas used has a dual purpose of protecting

the arc and weld zones from air and providing

desired arc characteristics. Gases are used

depending on the reactivity of the metal and the

design of the joint to be welded.



30/163

GMAW Process Variations

In GMAW, the common variations of shielding gases, power sourcesand electrodes have significant effects that can produce three

different modes of metal transfer across the arc. These are:

1) Spray Transfer

It describes an axial transfer of small discrete droplets of metal at

rates of several hundred per second.2) Globular Transfer

In this process variation, carbon dioxide-rich gases are used to

shield the arc and welding zone.

3) Short Circuiting Transfer

In this transfer, the average current and deposition rates can be

limited by using power sources which allow metal to be transferred

across the arc only during intervals of controlled short circuits

occurring at rates in excess of 50 per second.



31/163

Tools, Equipment, Material

A variable speed motor and motor control

Welding gun

Gas Nozzle on gun

A system of cables, hoses, electrical connections and

casings.

A mount for the spooled or coiled electrode.

A control station containing the relays, solenoids and

timers.

A source of shielding gas.Power Source (2KW to 20 KW)

Water supply

Shielding gas argon, nitrogen, helium



32/163

Advantages

Long welds can be made without starts and stops.

Minimal skill required.

Minimal cleaning of surface before weld

Allows welding in all positions

High deposition frequency around 95-100% with solid

electrodes, 80-85% with gas-shielded cored

electrodes and 80-85% with the self shielded cored

electrodes.



33/163

Limitations Ferrous metals welding in all positions if they are

less than in (6mm) thickness.

Globular and spray transfer are restricted towelding steels in the flat and horizontal positions.



34/163

Applications


f


35/163

Common Defects Porosity

Slag inclusions

Incomplete Fusions

Inadequate joint penetration.

Undercut

Overlap

Cracks


F d t l f W ldi


36/163

FLUXED CORE ARC WELDING (FCAW)



37/163

F d t l f W ldi


38/163

Overview of Process

FCAW process uses cored electrodes instead of

solid electrodes for joining ferrous metals. The flux

core may contain minerals, ferroalloys and

materials that provide shielding gases, deoxidizersand slag forming materials.


F d t l f W ldi


39/163


A variable speed motor and motor control

Welding gun

Gas Nozzle on gun

A system of cables, hoses, electrical connectionsand casings.

A mount for the spooled or coiled electrode.

A control station containing the relays, solenoids

and timers.A source of shielding gas.

Power Source (2KW to 20 KW)

Water supply



40/163


41/163


42/163

F d t l f W ldi


43/163

Common Defects

Porosity

Slag inclusions

Incomplete Fusions


Undercut

Overlap

Cracks



44/163



45/163

Diagram 1




46/163

DIAGRAM 2




47/163

Overview of ProcessGTAW 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 theelectrode and the molten weld pool, and provides

the arc characteristics.




48/163


Welding Torch

Tungsten Electrode

Inert Gas

Pressure regulators and flow meters

Welding face shield

Protective clothing

Gas Nozzle on gun

A source of shielding gas.Power Source (8KW to 30 KW)

Current range 200A to 500A)

High Frequency Oscillator

Welding wire



49/163


50/163



51/163

Applications

Most commonly used for aluminum and

stainless steel.

For steel

Except for thin sections or where veryhigh quality is needed




52/163

Common Defects

Porosity

Incomplete Fusions


Cracks




53/163

Definition:

This is a group of fusion welding processes that

use heat and pressure to make the coalescence.

The heat comes from electrical resistance tocurrent flow at the site of the weld.

The processes include:

Spot Welding Projection Welding

Seam Welding

Resistance Welding



54/163



55/163

Spot Welding A process typically used in high-volume, rapid welding

applications.

The pieces to be joined are clamped between twoelectrodes under force, and an electrical current is sentthrough them.

The advantages of spot welding are many andinclude the fact that it is:

An economical process

Adaptable to a wide variety of materials including lowcarbon steel, coated steels, stainless steel, aluminum,

nickel, titanium, and copper alloys Applicable to a variety of thicknesses

A process with short cycle times

A robust process

Tolerant to fit-up variations

Resistance Welding




56/163

There are three major processes within this group:

1- oxyacetylene welding

2- oxyhydrogen welding

3- pressure gas welding.

Gas Welding




57/163


General Gas Welding Procedures

Oxyfuel gas welding (OEW) is a group of welding processes which

join metals by heating with a fuel gas flame or flares with or without

the application of Pressure and with or without the use of filler

metal.

Fuel gas and oxygen are mixed in the proper proportions in a

mixing chamber which may be part of the welding tip assembly.

Molten metal from the plate edges and filler metal, if used, intermix

in a Common molten pool. Upon cooling, they coalesce to form acontinuous

piece.


58/163



59/163

Brazing

Process OverviewBrazing is a group of welding processes in

which the joint is heated to a suitable

temperature in the presence of a filler metal

having a liquidus above 840 F (450 C) and

below the solidus of the base metal.

Major Considerations:

Joint Design

Filler Metal Uniform heating

Protective or reactive shielding




60/163

Various Brazing Processes

Torch Brazing

Furnace Brazing

Induction Brazing Dip Brazing

Infrared Brazing

Diffusion Brazing




61/163

Soldering

Process Overview

Soldering involves heating a joint to a suitable

temperature and using a filler metal (solder)

which melts below 840 F (450 C).

Major Considerations:

Joint Design

Filler Metal

Uniform heating Protective or reactive shielding




62/163

Various Soldering Processes

Dip Soldering (DS)

Iron Soldering (INS)

Resistance Soldering (RS)

Induction Soldering (IS)

Torch Soldering (TS)

Furnace Soldering (FS)

Infrared Soldering (IRS)

Ultrasonic Soldering




63/163

Adhesive BondingProcess Overview

Adhesive Bonding is a joining process which is

gaining acceptance as an assembly method for joining

metals.

Advantages:Minimal Training.

Capable of joining dissimilar metals like metals to

plastics

Bonding very thin sections without distortionVery thin sections to thick sections

Joining heat sensitive alloys

Producing bonds with unbroken surface contours.

Low Cost




64/163

Adhesive Bonding

Dis-advantages:

Joints produced, may not support shear or impact

loads.

Must have adhesive layer less than 0.005 in

(0.13mm) thick. Joints can not sustain operational temperatures

exceeding 500 F (260 C)Surfaces to be bonded

requires special cleaning.

Some adhesives are to be used quickly after mixing. NDT of adhesive joints is difficult.




65/163

Welding Processes in Descon

Shield Metal Arc Welding (SMAW)

Gas Tungsten Arc Welding (GTAW)

Sub-Merged Arc Welding (SAW)Adhesive Bonding

BACK TO TOC



66/163

SECTION 2

Welding Metallurgy


67/163

OVERVIEW OF JOINING

PROCESSES

Welding Metallurgy
http://localhost/var/www/asad%20ahmad/other/Welding/Plz%20dont%20make%20anymore%20desktop%20folder%20plz/Welding%20PPT/Final%20PPT/QA%20QC%20Module/Table%20PPT.xlshttp://localhost/var/www/asad%20ahmad/other/Welding/Plz%20dont%20make%20anymore%20desktop%20folder%20plz/Welding%20PPT/Final%20PPT/QA%20QC%20Module/Table%20PPT.xlshttp://localhost/var/www/asad%20ahmad/other/Welding/Plz%20dont%20make%20anymore%20desktop%20folder%20plz/Welding%20PPT/Final%20PPT/QA%20QC%20Module/Table%20PPT.xlshttp://localhost/var/www/asad%20ahmad/other/Welding/Plz%20dont%20make%20anymore%20desktop%20folder%20plz/Welding%20PPT/Final%20PPT/QA%20QC%20Module/Table%20PPT.xls


68/163

General Metallurgy

Understanding of welding metallurgy requires a broad knowledge

of general metallurgy.

Structure of Metals

Solid metals have a crystalline structure in which the atoms of

each crystal are arranged in a specific in a specific geometric

pattern. This orderly arrangement of the atoms, called a lattice, is

responsible for many of the properties of metals.

g gy

Welding Metallurgy


69/163

Structure of Metals

Welding Metallurgy

Welding Metallurgy


70/163

Solidification Process

Welding Metallurgy

Welding Metallurgy


71/163

Phase Transformations

Critical TemperatureA specific temperature at which metals change their

crystallographic structure.

Phase DiagramA drawing showing metallurgical events such as phase changes

and solidification. ( Sometime referred to as an equilibrium

diagram or a constitution diagram)

Welding Metallurgy

Welding Metallurgy


72/163

IRON CARBON DIAGRAM

g gy
http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/examples/no_clim.html


73/163
http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/examples/no_clim.html


74/163

Welding Metallurgy


75/163

Properties of metals can be divided into five

general groups:

Mechanical

Physical

Corrosion

OpticalNuclear

Properties of Metals

g gy

Welding Metallurgy


76/163

Table of Metal Properties

Welding Metallurgy


77/163

Modulus of elasticity

A convenient way of appraising the ability of a

metal to resist stretching(strain) under stress in the

elastic range is by the ration E between the stress

and the corresponding strain.E= Stress / Strain

Elastic Limit

Elastic behavior of a metal reaches limit at a levelof stress called the elastic limit.

Mechanical Properties

g gy

Welding Metallurgy


78/163

Yield StrengthThe stress level at which the metal exhibits its

specified deviation from the proportionality of

stress and strain.

Tensile Strength

The ratio of the maximum load sustained by a

tensile test specimen to the original cross-sectional

area is called the ultimate tensile strength.


g gy

Welding Metallurgy


79/163

Fatigue StrengthFatigue fractures developed because each

application of the tensile applied stress, even at

nominal tensile stresses lower than yield point

stress, causes the tip of a crack to advance a

minute mount (stable crack growth).

Ductility

The amount of plastic deformation that an

un-welded or welded specimen undergoes in amechanical test carried to fracture is considered a

major of the ductility of the metal or the weld.



80/163

Welding Metallurgy


81/163

Thermal ConductivityThe rate at which heat is transmitted through a

material by conduction is called thermal

conductivity or thermal transmittal.

Melting Temperature:

The temperature at which metal starts melting.

Thermal expansion and contraction:

Change in volume of metals when they heated and

cooled during welding.

Physical Properties


82/163

Welding Metallurgy


83/163

Type of steel Preheat

Low-Carbon Steel Room Temperature or up to 200 Degrees

Fahrenheit (93 Degrees Centigrade)Medium-Carbon Steel 400500 Degrees Fahrenheit (205260 Degrees

Centigrade)

High-Carbon Steel 500600 Degrees Fahrenheit (260315 Degrees

Centigrade)

Low Alloy NickelLess than (6.4 mm)

thick

More than (6.4 mm)

thick

Room Temperature

500 Degrees Fahrenheit (260 Degrees Centigrade)

Low Alloy Nickel-ChromeSteel

Carbon content below .20%

Carbon content .20% to

.35%

200-300 Degrees Fahrenheit (93-150 Degrees

Centigrade)

600-800 Degrees Fahrenheit (315-425 Degrees

Centigrade)

Welding Metallurgy


84/163


Carbon content above .35% 900-1100 Degrees Fahrenheit (480-595 Degrees

Centigrade)

Low Alloy Manganese Steel 400600 Degrees Fahrenheit (205-315 Degrees

Centigrade)

Low Alloy Chrome Steel Up to 750 Degrees Fahrenheit (400 Degrees

Centigrade)

Low Alloy MolybdenumSteel

Carbon content below .15%

Carbon content above .15%

Room Temperature

400650 Degrees Fahrenheit (205-345 Degrees

Centigrade)

Low Alloy High Tensile

Steel

150300 Degrees Fahrenheit (66-150 Degrees

Centigrade)

Austenitic Stainless Steels Room Temperature

Welding Metallurgy


85/163


Ferritic Stainless Steel 150500 Degrees Fahrenheit (66-260 Degrees

Centigrade)

Martensitic Stainless Steel 150300 Degrees Fahrenheit (66-150 Degrees

Centigrade)

Cast Irons 700900 Degrees Fahrenheit (370-480 DegreesCentigrade)

Note: The actual preheat needed may depend on several other

factors such as the thickness of the base metal, the amount of joint

restraint, and whether or not low-hydrogen types of electrodesare used. This chart is intended as general information; the

specifications of the job should be checked for the specific preheat

temperature to be used.

Welding Metallurgy


86/163

A weld joint consists of weld metal (which has beenmelted), heat affected zones and unaffected base

metals. The metallurgy of each weld area is related

to the base and weld metal compositions, the

welding process and the procedures used.

When a weld is deposited, the first grains to solidify

are nucleated by the un-melted base metals, and

these grains maintain the same crystal orientation.

Depending upon composition and solidification

rates, the weld solidifies in cellular or dendriticgrowth mode. Both modes cause segregation of

alloying elements. Consequently, the weld matter

may be less homogenous than the base metal.

Metallurgy of Welding


87/163

Welding Metallurgy


88/163

The weld heat-affected zone is adjacent to the weld metal.

The heat-affected zone is that portion of the base metal that has

not been

melted, but whose mechanical properties or microstructure

have been altered by the heat of welding.

The width of the heat-affected zone is a function of the heat

input.

Heat-affected zones are often defined by the response of the

welded joint to hardness variation or micro structural changes.

Heat Affected Zone

Welding Metallurgy


89/163

Fusion Weld Structure

HAZWeld metal

HAZBasemetal

Fusion line

Weld preparation


90/163

Thermal Gradients in Haz

Time

Temperature

Fusion lineFusion line + 2mmFusion line + 5 mm


91/163

Welding Metallurgy


92/163

Multi pass Fusion Weld

Last weld run

Previous weld run

Welding Metallurgy


93/163

Weld Properties

Weld metal has different composition & thermal

history to base metal

Welding heat modifies adjacent base metal (HAZ)

Variation in strength, ductility & corrosion

resistance across welds

Welding Metallurgy


94/163

Definition of Weldability

The capacity of a material to be welded under the

imposed fabrication conditions into a specific,

suitably designed structure & to perform

satisfactorily in intended service.

(ANSI / AWS A3.0)


95/163

Welding Metallurgy


96/163

Residual Stresses

Welding Metallurgy


97/163

XX XX

Residual Stress in a Butt Weld

ssx

ssy

ssx

0 TensionCompression

XX XX

sy Tension

Compression

Welding Metallurgy


98/163

When a weld is made:

the metal in and around the weld joint is heated to arange of temperatures as the distance from the weld joint increases.

(temperature gradient)

Because of the Uneven heating, the strength, ductility, grain size and

other metal properties may vary greatly and affect the strength of themetal in the weld area.

Welder will use, as per WPS:

preheating

concurrent (continuous) heating and/or

post heating to avoid temperature

gradients in the weld area.

Heat Treatment of Metals for Welding


99/163

Welding Metallurgy


100/163

Heat Treatment of Metals

During heat treatment there are three factors

of great importance:

1. Temperature to which the metal is heated.

2. Length of time that the metal is held at that

temperature

3. Speed of cooling (a time factor).

BACK TO TOC


101/163

Section 3

Welding Design

Welding Design


102/163

Design Basics

WeldmentA weldment is an assembly that has componentparts joined by welding. It may be a bridge, abuilding frame, an automobile, a truck body, atrailer hitch, a piece of machinery, or an offshore

tubular structure.Basic Objectives:

1) Will perform its intended functions.

2) Will have the required reliability and safety

3) Is capable of being fabricated, inspected,transported and placed in service at minimum

total cost


103/163

Welding Design


104/163

Design Program

Analyses of existing designWhen designing an entirely new machine or structure,

information should be obtained about similar units,

including those of other manufacturers or builders.

If a new design is to replace an existing design , the

strengths and weaknesses of the existing design should be

determined first. Following questions can help in that:

1) Hat are the opinions of customers and the sales force

about the existing products?

2) Hat has been the performance history of the existing

products?

3) What features should be retained, discarded, or added?

4) What suggestions for improvements have been made?

Welding Design


105/163

Major Design Factors

Strengths and stiffness requirements Realistic Safety factor

Good appearance

Deep, symmetrical sections

Rigidity

Tubular sections or diagonal bracing

Standard rolled sections, plate and bar

Accessibility for maintenance

Standard commercially available components

Welding Design


106/163

Designing the Weldment

General Pointers for effective weldemnt design:1) Design for easy handling of materials, inexpensive

tooling, and accessibility of joints for reliable welding

2) Check with the shop for idea that can contribute cost

savings.3) Establish realistic tolerances base on end use and

suitability for service. Excessively close tolerances

serve no useful purpose, and increase cost.

4) Minimize the no of piecers

Welding Design


107/163

Designing the Welded Joints

Definitions

Joints - Arrangements of members being joined

Butt, tee, lap, corner, flare

Welds - Geometry of weld detail selected to makethe joint

Butt, fillet, plug & slot

Welding Design


108/163

Joint Types

Butt Tee

Lap Corner

Edge

Welding Design


109/163

Weld Types

Butt weld Between mating members

Best quality

High weld preparation cost

Fillet weld

Easy preparation

Asymmetric loads, lower design

loads Plug & slot welds

Modified fillet welds in lap joints,

using holes through one member

Welding Design


110/163

Fillet Welds

Simple & cheap to assemble & weld

Stress concentrations at toes & root

Notch at root (fatigue, toughness)

Critical dimension is throat

thickness

Root gap affects throat thickness

Radiography & ultrasonic testing is

of limited use

Large fillets use a lot of weld metal

& therefore are uneconomic

Welding Design


111/163

Fillet Weld Terms

Root

ToeWeld face

Toe Throatthickness

Apparent leg length

Gap

Welding Design


112/163

Types: Double welded butt

Permanent or temporary backing

Single welded butt

Lower stress concentration

Easier ultrasonic testing or radiography

Expensive preparation

Butt Welds

Welding Design


113/163

Butt Weld Types

Single veecan be single

or double welded

Single bevel Double vee

Backed butt (permanent or temporary)

B tt W ld T

Welding Design


114/163

Butt Weld TermsFusion face

Root face

Rootgap

Included angle

Bevel angle

Root run Toe

Toe

Reinforcement


115/163

Welding Design


116/163

Structural Tubular Connections

Tubular members are being used in structures such as

drill rigs, space frames, trusses, booms and earth

moving & mining equipment.

They have the advantage of minimizing defections underload because of their grater rigidity when compare to

standard structural shapes.

Various types of welded tubular connections, the

component designations and nomenclature are shown in

next figure.


117/163

AS1101 2 D i S b l

Welding Design


118/163

AS1101.2 Drawing Symbols

Tail

Arrow points to weldlocation

OTHER SIDE

ARROW SIDE

Weld type symbol

Reference line


119/163


120/163

Section 4

Welding Equipments & Consumables

Welding Equipment & Consumables


121/163

Welding Electrode

http://zhwelding.en.alibaba.com/product/50110638/50501470/Welding_Materials/Welding_Electrode.htmlhttp://zhwelding.en.alibaba.com/product/50110638/50501474/Welding_Materials/Solder_Wire.html


122/163

Solder Wire

http://zhwelding.en.alibaba.com/product/50110638/50501474/Welding_Materials/Solder_Wire.htmlhttp://zhwelding.en.alibaba.com/product/50110635/51162437/Hand_Tools/electrode_holder.html


123/163

Electrode Holder

http://zhwelding.en.alibaba.com/product/50110635/51162437/Hand_Tools/electrode_holder.htmlhttp://zhwelding.en.alibaba.com/product/50110635/51162536/Hand_Tools/electrode_holder.htmlhttp://zhwelding.en.alibaba.com/product/50110635/51159071/Hand_Tools/electrode_holder.htmlhttp://zhwelding.en.alibaba.com/product/50110635/51159069/Hand_Tools/electrode__holder.htmlhttp://zhwelding.en.alibaba.com/product/50110635/50501478/Hand_Tools/Tool_Set/showimg.htmlhttp://zhwelding.en.alibaba.com/product/50110637/50501477/Welding_Equipment_and_Tools/Welding_and_Cutting_Torch.html


124/163

CO2Regulator Welding & Cutting Torch

Electric Welder

Welding Equipment and Tools

Air HosesBACK TO TOC
http://zhwelding.en.alibaba.com/product/50110637/50504615/Welding_Equipment_and_Tools/Welding_Equipment_and_Tools.htmlhttp://zhwelding.en.alibaba.com/product/50110637/50501453/Welding_Equipment_and_Tools/Air_Hoses.htmlhttp://zhwelding.en.alibaba.com/product/50110637/50504615/Welding_Equipment_and_Tools/Welding_Equipment_and_Tools.htmlhttp://zhwelding.en.alibaba.com/product/50110637/50501466/Welding_Equipment_and_Tools/Electric_Welder.htmlhttp://zhwelding.en.alibaba.com/product/50110637/50501454/Welding_Equipment_and_Tools/Cutting_Torch.htmlhttp://zhwelding.en.alibaba.com/product/50110637/50501477/Welding_Equipment_and_Tools/Welding_and_Cutting_Torch.htmlhttp://zhwelding.en.alibaba.com/product/50110636/51132600/Regulators_and_Gauges/Regulator.html


125/163

Section 5

WPS & PQR


126/163

WPS & PQR


127/163

Welder Performance Qualification (WPQ)

Welders or welding operators ability to produce

welded joints that meet prescribed standards.

Certification

The results of welding procedure or performance

qualification must be certified by an authorized

representative of the organization performing thequalified tests.

WPS & PQR


128/163

Welder Procedure Major Parts

Welding procedure consists of three parts as follows:

A detailed written explanation of how the weld is to be

made

A drawing or sketch showing the weld joint design

and the conditions for making each pass or bead

A record of the test results of the resulting weld.

WPS & PQRWhy we need WPS for welding


129/163

Why we need WPS for weldingAs welding becomes a modern engineering

technology it requires that the various elementsinvolved be identified in a standardized way.

A welding procedure is used to make a record of all of

the different elements, variables, and factors that are

involved in producing a specific weld or weldment.

Welding procedures should be written whenever it is

necessary to:

Maintain dimensions by controlling distortion

Reduce residual or locked up stresses

Minimize detrimental metallurgical changesConsistently build a weldment the same way

Comply with certain specifications and codes.

WPS & PQR


130/163

Essential Variables

Essential variables are those factors which must be

recorded and if they are changed in any way, the

procedure must be retested and re-qualified.

Non- Essential Variables

Nonessential variables are usually of less importance

and may be changed within prescribed limits and the

procedure need not be re-qualified.

WPS & PQREssential Variables


131/163

Essential Variables

Essential variables involved in the procedure usuallyinclude the following:

The welding process and its variation

The method of applying the process

The base metal type, specification, or composition

The base metal geometry, normally thickness

The base metal need for preheat or postheat

The welding position

The filler metal and other materials consumed in

making the weldThe weld joint, that is, the joint type and the weld

Electrical or operational parameters involved

Welding technique.


132/163


133/163


134/163

WPS & PQRSpecific References from ASME Section 9


135/163

Specific References from ASME Section 9

Article II Welding Procedure QualificationsQW-200 General . . . . . . . . . . . . . . . . . . . . . .13

QW-210 Preparation of Test Coupon . . . . 16

QW-250 Welding Variables. . . . . . . . . . . . . 18

Article III Welding Performance Qualifications

QW-300 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

QW-310 Qualification Test Coupons . . . . . . . . . . . . . 50

QW-320 Retests and Renewal of Qualification. . . . . 51

QW-350 Welding Variables for Welders . . . . .. . . . . . 52QW-360 Welding Variables for Welding Operators . .53

QW-380 Special Processes . . . . . . . . . . . . . . . . . . . . . 54

BACK TO TOC
http://localhost/var/www/asad%20ahmad/other/Welding/Plz%20dont%20make%20anymore%20desktop%20folder%20plz/Welding%20PPT/Final%20PPT/QA%20QC%20Module/ASME%20IX.pdfhttp://localhost/var/www/asad%20ahmad/other/Welding/Plz%20dont%20make%20anymore%20desktop%20folder%20plz/Welding%20PPT/Final%20PPT/QA%20QC%20Module/ASME%20IX.pdfhttp://localhost/var/www/asad%20ahmad/other/Welding/Plz%20dont%20make%20anymore%20desktop%20folder%20plz/Welding%20PPT/Final%20PPT/QA%20QC%20Module/ASME%20IX.pdfhttp://localhost/var/www/asad%20ahmad/other/Welding/Plz%20dont%20make%20anymore%20desktop%20folder%20plz/Welding%20PPT/Final%20PPT/QA%20QC%20Module/ASME%20IX.pdf


136/163

Section 6

Welding Inspection & Techniques


137/163


NDE R i t


138/163

NDE Requirements

All NDE methods must include the following to render

valid examination results:

A trained operator

A procedure for conducting the tests

A system for reporting the results

A standard to interpret the results



139/163

Non-Destructive Examination Methods

Visual inspection, with or without optical aids (VT)

Liquid Penetrant (PT)

Magnetic Particle (MT)

Radiography (RT)

Eddy Current (ET) Ultrasonic (UT)

Acoustic emission (AET)

Heat Transfer

Ferrite Testing



140/163

Visual inspection (VT)

With eyes where access

With mirror

Illumunator

Boroscopy For record keeping using the camera



141/163

References

ASME Section I, Power Boilers

ASME Section VIII, Divisions 1 & 2. Pressure

Vessels

ASME B31.1, Power Piping

API 620 & API 650, Welded Steel Tanks


Acceptance Standards


142/163

Acceptance StandardsThe following minimum acceptance standards

apply to visual examinations performed on all weldsduring and after welding. The following indications

are unacceptable:

All external surface cracks.

Undercut on the surface which is greater than 1/32inch deep or ten percent (10%) of the wall

thickness, whichever is less.

Surface porosity.

Lack of fusion on the surface.

Incomplete penetration (when inside surface is

accessible for examination) except for partial

penetration welds.


Penetrant Testing (PT)


143/163

g ( )

For Open to the Surface Defects Pin Hole

Under Cutting

Cracks

Grinding Marks etc.

Types of PT Solvent Remover

Simple Method

Penetrant

Developer Cleaner



144/163

Reference Codes

ASME Sec. V

Client Specifications

Acceptance StandardsASME VIIIClient Specifications.


MT (Magnetic Particle Testing)


145/163

( g g)

For Open to the Surface Defects Just below the Surface Under Cutting

Use only for Ferro Magnetic Material

Types of MT

Visible Method (Iron Oxide Ink)

Black & White Contrast

Fluorescent Method

Fluorescent Magnetic Ink

UV Light


Magnetic Particle Testing Equipment (MT)


146/163

Magnetic Particle Testing Equipment (MT)

Hand Yoke AC & DC Central Conductor Unit

Magnetizing Coil

Prude Conductor

Field IndicatorReferences Code

ASME V

ClientsSpecifications

Equipment

AC Hand Yoke type Equipment



147/163

Acceptable Standards

ASME VIII

Client Specifications.


Ultrasonic Flaw Detection (UT)


148/163

Ultrasonic Flaw Detection (UT)1) Ultrasonic Flaw Detection Machine

Internal Defects

Thickness Measurements

PrinciplesHigh Frequency Sound Waves

0.5 MHz to 25 MHzHuman Hearing Range 20 MHz to 20 KHz

Scan of the Body on maximum Thickness upto 5 meters

Depending upon Probe Capacity

Defect SizingDefect Location

Thickness Measurement

Permanent Record at the Shape of graph


149/163


150/163


Radiographic Testing (RT)


151/163

Radiographic Testing (RT)1) Ultrasonic Flaw Detection Machine

Internal Defect detection

EquipmentXray Machine

Gama Rays ProjectorRadio Isotope Source

IR192\

CO 60

CS 137Video

BACK TO TOC
http://localhost/var/www/asad%20ahmad/other/Welding/Plz%20dont%20make%20anymore%20desktop%20folder%20plz/Welding%20PPT/Final%20PPT/QA%20QC%20Module/Clippings/XRAY.MPG


152/163

Section 7Welding Defects, Causes &

Remedies

Welding Defects, Causes & Remedies


153/163

Each weld should be:Adequately designed to meet the intended service for

the required life.

Fabricated with specified materials and in accordance

with the design concepts.

Operated and maintained properly.Quality considerations are:Physical features, normally examined by inspectors

Hardness

Chemical compositionMechanical properties

Porosity

Slag Inclusions

http://localhost/var/www/asad%20ahmad/other/Welding/Plz%20dont%20make%20anymore%20desktop%20folder%20plz/Welding%20PPT/Final%20PPT/QA%20QC%20Module/Clippings/Pourisity.MPG


154/163

Slag Inclusions

Entrapped slag discontinuities typically occur only with

the flux shielded welding processes: shielded metal arc,

flux cored arc, submerged arc, and electro slag welding.

Entrapped slag is:

A reaction product of the flux and the molten weld metal

Oxides, nitrides and other impurities may dissolve in the

slag to refine the weld metal

Factors preventing release of slag:



155/163

Factors preventing release of slag:

High viscosity weld metal

Rapid solidification

Insufficient welding heat

Improper manipulation of the electrode

Undercut on previous passes

Common Causes and Remedies of Porosity



156/163

Cause Remedies

Excessive hydrogen, nitrogen, or oxygen in

welding atmosphere

Use low-hydrogen welding process, filler metals

high in deoxidizers, increase shielding gas flow

High solidification rate Use preheats or increases heat input.

Dirty base metal Clean joint faces and adjacent surfaces.

Dirty filler wire Use special cleaned and packaged filler wire,

and stored in clean area.Improper arc length, welding current or electrode

manipulation

Change welding conditions and techniques.

Volatization of zinc form brass Use copper-silicon filler metal, reduce heat

input.

Galvanized steel Use E6010 electrodes and manipulate the arc

heat to volatize the zinc ahead of the molten

weld pool.

Excessive moisture in electrode covering or on

joint surface

Use recommended procedures for baking and

storing electrodes preheat the base metal.

High sulphur base metal Use electrodes with basic slagging recreations

Common Causes and Remedies of Slag Inclusions



157/163

g

Cause Remedies

Failure to remove slag Clean surface and previous weld bead

Entrapment of refractory oxides Power Wire brush the previous weld

bead

Tungsten in the weld metal Avoid contact between the electrode

and the work. Use larger electrode

Irnproper joint design Increase groove angle of joint

Oxide inclusions Provide proper gas shielding

Slag flooding ahead of the welding arc Reposition work to prevent loss of

slag control

Poor electrode manipulative technique Change electrode or flux to improve

slag control

Entrapped pieces of electrode Use undamaged electrodes Covering

Common Causes and Remedies of Inadequate Joint Penetration



158/163

q

Causes Remedies

Excessively thick root face or

insufficient root opening

Use proper joint geometry

Insufficient heat input Follow welding procedure

Slag flooding ahead of welding

arc.

Adjust electrode or work position

Electrode diameter too large Use small electrodes in root or increase

root opening

Misalignment of second side weld Improve visibility or back gouge

Failure to back gouge when

specified

Back gouge to sound metal if required in

welding procedure specification.

Bridging of root opening Use wider root opening or smaller

electrode in root pass.

Common Causes and Remedies of Cracking



159/163

Causes Remedies

WELD CRACKING

Highly rigid joint Preheat

Reliever residual stresses mechanically

Minimize shrinkage stresses using back step or

block welding

Excessive dilution Sequence

Change welding current and travel speed

Weld with covered electrode negative, butter thejoint faces prior to welding

Defective electrodes Change to new electrode, bake electrode to remove

moisture

Poor fit-up Reduce root opening, build up the edges with metal.

Small weld bead Increase electrode size, raise welding current,

reduce travel speed

Higher sulphur base metal Use filler metal low in sulphur.

Angular distortion Change to balanced welding on both sides of joint.

Crater cracking Filler crater before extinguishing the arc, use a

welding current decay device when terminating the

weld bead.

Common Causes and Remedies of Cracking



160/163

g

HEAT AFFECTED ZONE

Hydrogen in welding atmosphere Use low-hydrogen welding process,

preheat and hold for 2h after welding or

post weld heat treat immediately

Hot cracking Use low heat input, deposit thin layers,

change base metal.Low ductility Use preheat anneal the base metal.

High residual stresses Redesign the weldment change welding

sequence, apply intermediate stress-relief

heat treatment.

High hartdenability room Preheat increase beat input, heat treatwithout cooling to temperature.

Brittle phase in the microstructure. Solution heat treat prior to welding.

SAWAN GAS DEVELOPMENT PROJECT PROJECT No. : 6430 / 6431

COMMON WELDING DEFECTS, CAUSES AND CURES DURING THE WELDING OF D.S.S

DEFECTS CAUSES CURES

Common Welding Defects, causes and cures during the welding of DSS


161/163

1

2

3

4

5

6 DECREASE IN CORROSION RESISTANCE

HEAT INPUT AS PER WPS

CHROMIUM DEPLETION MAINTAIN INTERPASS

TEMPERATURE AS PER WPS

FORMATION OF CHROMIUM

NITRIDES

MAINTAIN ELECTRICAL

CHARACTERISTICS AS PER WPS

IMPROPER SET UP AND FIXTURING TACK OR CLAMP PARTS SECURELY

CONTAMINATION WITH C.S. POOR SHOP DISCIPLINE USE SEPARATE CONSUMABLES /

TOOLS FOR C.S. AND D.S.S.

USE PROPER BEAD SEQUENCEIMPROPER BEAD SEQUENCE

DO PURGING AS PER WPS

USE PROPERLY PREPARED AND

SHARP TIPPED TUNGSTENELECTRODE

CURRENT AND VOLTAGE SHOULD

BE AS PER WPS

MAINTAIN TRAVEL SPEED AS PER

WPS

MAINTAIN TRAVEL SPEED AS PER

WPS

ELECTRICAL CHARACTERISTICS AS

PER WPS

PROPER ROOT GAP TO BE

MAINTAINED

IMPROPER POINTING OR GRINDING

OF TUNGSTEN ELECTRODE

EXCESSIVE ARC LENGTH

HIGH HEAT INPUT

TACK WELD PARTS WITH

ALLOWANCE FOR DISTORTION

IMPROPER TRAVEL SPEED

POOR JOINT DESIGN

IMPROPER ROOT GAP

IMPROPER TACK WELDING AND /

OR FAULTY JOINT PREPARATION

WELDING DISTORTION

ARC DESTABILIZATION

POOR PENETRATION

OXIDATION IMPROPER PURGING


162/163

Useful Web Sites

Useful Web Sites


163/163

http://www.aws.org/American Welding Society

http://www.ewi.org/Welding and Joining Information Network

http://www.adtdl.army.mil/cgi-bin/atdl.dll/tc/9-237/toc.htm Welding

Theory and Application, Department of the Army, Washington, DC,

7 May 1993

http://www.lincolnwelding.com Lincon Electric (welding supply co.)

http://www.weldingengineer.com/ Welding Procedures and Welding

Techniques

http://www.cigweld.com.au/litPocketGuide.asp Welding

Consumables & Equipments
http://www.aws.org/http://www.ewi.org/http://www.adtdl.army.mil/cgi-bin/atdl.dll/tc/9-237/toc.htmhttp://www.lincolnwelding.com/http://www.weldingengineer.com/http://www.cigweld.com.au/litPocketGuide.asphttp://www.cigweld.com.au/litPocketGuide.asphttp://www.weldingengineer.com/http://www.lincolnwelding.com/http://www.adtdl.army.mil/cgi-bin/atdl.dll/tc/9-237/toc.htmhttp://www.adtdl.army.mil/cgi-bin/atdl.dll/tc/9-237/toc.htmhttp://www.adtdl.army.mil/cgi-bin/atdl.dll/tc/9-237/toc.htmhttp://www.adtdl.army.mil/cgi-bin/atdl.dll/tc/9-237/toc.htmhttp://www.adtdl.army.mil/cgi-bin/atdl.dll/tc/9-237/toc.htmhttp://www.ewi.org/http://www.aws.org/

fundamental of welding

Documents