Weld Inspection 1

Weld Inspection

Level 1

Introduction to Welding

Definition Introduction to Welding Welding Terminology Physics of Welding

Definition

Welding: A group of processes used to join metallic and nonmetallic materials. Often done using heat but maybe done using pressure or a combination of heat and pressure. A filler material may or may not be used.

Other processes: riveting, forging, cutting, turning, and bending First used: 2000 BC

Modern methods: 1881

Examples of Welding Processes

Shielded Metal Arc

Gas Tungsten Arc Welding Gas Metal Arc Welding Submerged Arc Welding

Shielded Metal Arc Welding

Gas Metal Arc Welding

Introduction to Welding

Joint between the materials is melted Intermixing occurs

Upon solidification a metallurgical bond results

The weld has the potential to have same strength as the materials being joined

Unlike soldering, brazing and adhesive bonds which are not fusion processes

Arc Welding

Intense heat to melt metal is produced by electric arc Arc between electrode and metal to be joined

Shielded Metal Arc Welding

High current, low voltage, AC or DC

Heat in The Arc

Change the arc length Change the shielding gas

Addition of potassium salts reduces arc voltage

Metal Arc Transfer

Metal is transferred across the arc (consumable electrode) Mechanism of transfer:

Molten metal drop touches and transfers by surface tension

Magnetic pinch effect Gravity (flat welding)

More heat is transferred than non-consumable electrodes Ionization column must be present to conduct electricity (arc)

Electrical Supply

AC

DC, electrode positive DC, electrode negative Selection depends upon:

Process

Type of electrode Arc atmosphere Metal being welded

Properties of Metals

Physical Chemical Mechanical

Physical Properties

Colour

Melting Temperature

Density (weight per unit volume)

Chemical Properties

How the metal reacts in an environment

Corrosion Resistance (ability to resist corrosion)

Mechanical Properties

Strength (ability to resist load without failing) Tensile strength (ability to resist pulling force)

Compressive strength (ability to resist crushing force) Ductility (ability to deform without breaking)

Brittleness (inability to resist fracture) Toughness (ability to resist cracking)

Hardness (ability to resist indent or scratching)

Grain size (important in determining mechanical properties)

Effects of Welding

Heat creates stress, affects ductility and toughness Effects of previous heat treating are lost around the weld If done properly usually stronger than the base metal Can effect the chemical resistance

Expansion and Contraction

Metal expands when heated Metal contracts when cooled

Expansion and contraction creates stress

Welding jigs or fixtures prevent movement but lock in stress

Butt Joint Root Opening

Tee Joint Distortion

Reducing Distortion & Stress

Tack weld

Align parts for contraction Use jigs or fixtures

Preheat parts

Heat treat welded parts Proper welding procedures

Heat Treating

Pre heating

Raise the temperature just prior to welding Entire part is heated

Less contraction and stress on cooling

Heat Treating

Interpass heating

Heating while welding or between passes Minimize expansion and contraction Reduce stress

Heat Treating

Annealing

Heat treatment after welding Heated above critical temperature

900° C for mild steel

Held at temperature for 1 hour per inch of thickness

Slow cooled

Heat Treating

Stress Relieving

Heat treatment after welding

Heated below transition temperature 650° C for mild steel

Held at temperature for 1 hour per inch of thickness Air cooled

Electrical Principles

Voltage

Force that causes electrons to flow in a circuit Similar to pressure

Measured in volts

Electrical Principles

Resistance

Opposition to flow of electrons measured in ohms Air gap is resistance

If voltage is not sufficient to overcome resistance of gap no arc exists

Higher voltage allows a longer arc Arc stops if voltage is not high enough

Electrical Principles

Current

Flow of electrons measured in amperes Compared to flow of water

If there is no arc, no current flows in welding circuit

Units of Measure

Micro [µ] = 1/1,000,000 or .000001 Milli [m] = 1/1,000 or .001 Centi [c] = 1/100 or .01 Deci [d] = 1/10 or .1 Kilo [ K] = 1,000 Mega [M] = 1,000,000

Terminology

Welding Technology Fundamentals Page 441

Procedures Handbook of Arc Welding Page 16.1-1

Butt Joints

Corner Joint

Edge Joint

Engineering Drawings

Orthographic Projection

Orthographic Projection

Orthographic Projection

First and Third Angle

Projection

First and Third Angle

Projection

Drawing Lines

Dimensioning

S = size P = position

Dimensioning

Angles Chamfers

Tapers

Sectional Views

Sectional Views

Mating parts

Thread Illustrations

Team Project 2

Preparation of Joints for

Welding

Preparation of Joints for

Welding

Flanged Preparation

e = member thickness

Used of relatively thin material Medium efficiency

Preparation of Joints for

Welding

Square Butt Preparation with backing

g = root gap

Improves probability or full penetration

Stress raisers that affect fatigue performance

Preparation of Joints for

Welding

Single Vee Preparation

ß = bevel angle, α = groove angle, s = root face, g = root gap, = solid angle

Preparation of Joints for

Welding

Single Bevel Preparation

α = groove angle, s = root face, g = root gap, Ω = angle of incidence

Used for Tee and corner joints

Optimum joint efficiency require back gouging and welding

Preparation of Joints for

Welding

Single U Preparation

α = groove angle, s = root face, g = root gap, β = bevel angle, r = root radius

Reduced volume of weld as compared to Vee, less distortion

Optimum joint efficiency require back gouging and welding

Preparation of Joints for

Welding

Partial U Preparation

α = groove angle, s = root face, g = root gap, d = depth of prepared edge, r = root radius, b = root width

Preparation of Joints for

Welding

Double Vee Preparation

α = groove angle, s = root face, g = root gap,

β = bevel angle, d = depth of of prepared edge Reduced distortion and weld volume compared to

single Vee, back gouging preferred before welding second side

Preparation of Joints for

Welding

Double Vee Preparation with Broad Root Face

α = groove angle, s = root face, g = root gap, d = depth of prepared edge

Used in SAW

Preparation of Joints for

Welding

Double U Preparation

α = groove angle, s = root face, g = root gap,

β = bevel angle, d = depth of of prepared edge Used for thicker sections

Reduced volume of weld as compared to Vee, less distortion

Preparation of Joints for

Welding

Double J Preparation

α = groove angle, s = root face, g = root gap, d = depth of prepared edge, r = root radius

Preparation of Joints for

Welding

Partial Double J Preparation

α = groove angle, s = root face, g = root gap,

Preparation of Joints for

Welding

Mixed Preparation

α = groove angle, r = root radius, l = half width of flat bottom

Welding Symbols

L-P

F

A

R

S (E)

T

N

L-P

F

A

R

S (E)

T

N

Weld-all around

L-P

F

A

R

S (E)

T

N

Field Weld

L-P

F

A

R

S (E)

T

N

Reference Line

L-P

F

A

R

S (E)

T

N

Tail

(Tail omitted when references not used)

L-P

F

A

R

S (E)

T

N

L-P

F

A

R

S

(E)

T

N

Depth of penetration, size or strength

L-P

F

A

R

S

(E)

T

N

L-P

F

A

R

S (E)

T

N

Basic weld symbols

L-P

F

A

R

S (E)

T

N

Finish symbol

L-P

F

A

R

S (E)

T

N

Finish contour

L-P

F

A

R

S (E)

T

N

Groove angle

L-P

F

A

R

S (E)

T

N

Root opening

L-P

F

A

R

S (E)

T

N

L-P

F

A

R

S (E)

T

N

Length and pitch

Basic Weld Symbols

L-P F A R S (E) T N

Basic Groove Weld Symbols

Square

Single V

Single bevel

Double J

Double flare

Fillet and Plug Weld Symbols

Fillet

Single and Double Welds

Single

Double

Bevel Groove

J Groove

Flare

Fillet

Arrow Significance

Arrow Significance Groove

Welds

Arrow Significance Groove

Welds

Arrow Significance Fillet

Welds

Arrow Significance Fillet

Welds

Information in the Tail

L-P F A R S (E) T N

Specification, process or other reference

Welding process

Welding procedure

“Typical” representative of all welds on the drawing

Field Weld

In a place other than original construction

Usually in the erection phase

Melt-thru Symbol

Extent of Welding

If length is not specified

length is between abrupt changes in direction

Length maybe directly dimensioned on drawing

Weld all around symbol

L-P F A R S (E) T N Weld-all around

Uses of Weld All Around

Finishing of Weld

C

Chipping

G

Grinding

M

Machining

R

Rolling

H

Hammering

Break in Arrow

Arrow points to member to be chamfered

Alternate Combined Welding

Symbols (AWS A2.4)

Complete Penetration

Note:

CJP = Complete joint penetration

or CP = Complete penetration

Groove Welds

Key parameters:

Depth of penetration

Bevel angle

Root opening

Three Basic Angles

Θ

₁

= Bevel angle

Θ

₂

= Groove angle

Θ

₃

= Angle at root

Dimensioning Double Groove

Welds

Depth of Penetration &

Groove Weld Size

L-P F A R S (E) T N L-P F A R S (E) T N

Depth of Penetration &

Groove Weld Size

E may be greater or smaller than S

Practice

Single Groove

Partial Penetration

Practice

Single Groove

Partial Penetration

Practice

Single Groove

Partial Penetration

Practice

Single Groove

Partial Penetration

Practice

Double Groove

Partial Penetration

Practice

Double Groove

Partial Penetration

Practice

Double Groove

Partial Penetration

Practice

Double Groove

Partial Penetration

Practice

Double Groove

Full Penetration

Practice

Double Groove

Full Penetration

Practice

Double Groove

Full Penetration

Practice

Square Groove

Square Groove

Square Groove

Symmetrical Double Groove

Welds

Optional Joint Preparation

Complete Penetration With

Back-gouging

Complete Penetration With

Back-gouging

Complete Penetration With

Back-gouging

Flare Weld

Surface Finish

Most common is flush

Welds With Backing

Basic Symbol

M = Material of backing bar

R = Removal of backing bar after

welding

Welds With Backing

Backing bar size can be placed in tail

S = Steel

R = Removed

Combination Groove and Fillet

Sequence of Preparation

Sequence of Preparation

Solid lines indicate preparation before fitting

CSA W59

Fillet Welds

Note: vertical side (line) always on left

Equal-legged

Fillets

Fillet Size

S = Specified size (size on symbol)

S

_eff

= Effective size (size that corresponds to

specified size)

S

_m

= Measured size (based on actual measurement)

Fillet Size

Some countries specify the size of fillet by throat

rather than leg

In Canada and USA we use leg

ISO (ISO/TC44/SC7) recognizes both, but requires

identification:

“z” designates leg size

“a” designates throat size

Unequal-legged Fillet Welds

Size is shown in brackets as:

(S

₁

x S

₂

)

Not leg specific

Unequal-legged Fillet Welds

Unequal-legged Fillet Welds

Often the which leg size is governed by

geometry of joint

Fillet Sizes (With Gaps)

Gaps less than 1mm (CSA W59)

Fillet Sizes (With Gaps)

Gaps greater than 1mm (CSA W59)

or 1/16 (AWS D1.1)

Maximum gap

5mm for material < 75mm thick

8mm for material > 75mm thick

Measured size increased

by amount of gap

Fillet Welds in Skewed

Connections

Beyond this range, weld is considered partial

penetration (CSA W59 and AWS D1.1)

Fillet Welds in Skewed

Connections

It is necessary to show a sketch of the weld with

dimensions

Length of Fillet Welds

Length of Fillet Welds

(Not Specified)

Considered to run length of joint to change of

direction

Length of Fillet Welds

(Not Specified)

Fillet

All-around

Intermittent Fillet Welds

Intermittent Fillet Welds

Common Centre Symbols Aligned

Intermittent Fillet Welds

Staggered Centres Staggered Symbols

Fillets Welds

With Terminal Ends

Fillets Welds

Surface Finish & Contour

Plug and Slot Welds

Plug Welds

Key Parameters:

Diameter of hole

Angle of countersink

Depth of filling

Spacing of welds

Contour and surface finish

Plug Weld, Countersink

Plug Weld, Depth of Filling

Plug Weld, Spacing

Safety Considerations

Pressurized Gases

High temperatures and hot surfaces Electrical hazards

Fume generation Non-ionizing radiation Ionizing radiation

Molten droplets of metal Explosive hazards

Oxy-Fuel Cutting

Torch tip selection Oxygen pressure Acetylene pressure Cutting Speed Tip alignment Torch Position

Tip Alignment

Torch Position

Torch Position

Torch 90 degrees to the surface of the metal

Torch Position

Cutting Conditions

Good Cut

Cutting Conditions

Preheat flames too small Cutting speed too slow

Cutting Conditions

Preheat flame too long Top surface melted over Cutting edge irregular Excess slag

Cutting Conditions

Oxygen pressure too low Top edge melted

Cutting Conditions

Oxygen pressure too high Nozzle too small

Cut control lost

Cutting Conditions

Cutting speed too slow

Cutting Conditions

Cutting speed too fast

Pronounced break in drag line Cut edge irregular

Cutting Conditions

Torch travel unsteady

Cutting Conditions

Cut lost

Not properly restarted Bad gouges at restart point

Shielded Metal Arc Welding

Acronyms: AC Alternating Current DC Direct Current CC Constant Current CV Constant Voltage

DCEN Direct Current Electrode Negative DCEP Direct Current Electrode Positive OCV Open Circuit Voltage

Current and Polarity

Current and Polarity

DCEP Deeper penetration than DCEN

DCEN Electrode melts faster, less heat to the base metal

Used for welding thin materials

AC Produce a neutral or reducing gas (to protect the weld puddle) Medium depth of penetration

Current and Polarity

Manual processes such as SMAW require CC welding machine

CC machines sometimes called droopers or droop curve machines

A CC machine adjusts to maintain a constant current as small changes in arc length occur

Constant Current Machine

25% change in voltage 4% change in current

Welding Machines

Current Type (AC, DC, or AC/DC)

Input power requirements (117, 240 0r 550 Volts) Rated current output

Duty Cycle

Open Circuit Voltage

Duty Cycle

How long a welding machine can be used at maximum current

Based on a ten minute cycle

E.g. 60% duty cycle machine can be used at maximum current for a maximum of 6 minutes out of every 10 minutes. It can be used for longer periods at lower current settings

Duty Cycle

Open Circuit Voltage

Voltage of the welding machine when on but not being used. Typically 80 volts compared to closed circuit voltage of

5 to 30 volts

A high OCV is required to initiate the arc.

Welding Leads

Electrode lead Work lead

Electrical resistance increases as diameter decreases and length increases

Voltage and current are affected when leads are too small in diameter

Welding Leads

Welding Technology Fundamentals Page 58

Wire Diameter

Suggested Filter Lenses

Sensible 7 thru 14 Shade Adjustability On The Outside Of The Helmet While You Are Welding

SMAW Electrodes

Specified by: AWS

A5.1 carbon steel

A5.3 aluminum and aluminum alloys A5.4 corrosion resistant steels A5.5 low alloy steels

A5.6 copper and copper alloys A5.11 nickel and nickel alloys A5.15 gray and ductile cast iron CSA W 48-01

carbon steel covered electrodes

chromium and chromium-nickel covered electrodes low alloy steel covered electrodes

Electrode Coverings

1. Add filler metal

2. Create a protective gas shield 3. Create a flux to remove impurities 4. Create slag to protect bead as it cools

5. Add alloys to improve mechanical and chemical properties 6. Determine the polarity of electrode

Electrode Size

CSA W47-01

Electrode Size

AWS

Lengths: 9, 12, 14, and 18 inches

Diameters: 1/16, 5/64, 3/32, 1/8, 5/32, 3/16, 7/32, 1/4, 5/16, 3/8 inches

Freezing Characteristics

Electrodes manufactured to melt rapidly are called fast-fill electrodes

Electrodes manufactured to freeze rapidly are called fast-freeze electrodes

Electrodes manufactured to compromise between fast-fill and fast-freeze are called fill-freeze

Electrode Designations

E 6010

AWS

Electrode

Minimum tensile strength in thousand psi Welding position

Minimum Tensile strength

Minimum tensile strength of the as deposited metal

Welding Position

1 All position

2 Flat and horizontal fillets only 3 Flat position only

Team Assignment 5

Assignment

What electrodes are low hydrogen?

What electrodes cannot be used with AC?

Which electrodes have iron powder addition?

Cellulose is used to improve penetration, what electrodes will provide good root penetration?

What electrodes cannot be used for DCEP?

Low Hydrogen Electrodes

E 7018

E4918 (CSA W48-01) Low hydrogen Fill-freeze All position 70,000 psi, 490 Mpa

Moderately heavy slag easy to remove

Smooth quiet arc, very low spatter, medium penetration AC or DCEP

Iron powder addition

Electrodes

Assignment: Prepare a similar description for E7015, E7016, E7028, E8018, E6010, E6019

Hint: Use references: Welding Technology Fundamentals, Page 74-78, Procedure Handbook of Arc Welding Chapter 6.2, and CSA W48-01 appendix D

Electrode Storage

Low Alloy

Steel

Electrodes

Electrode Designations

E 10016-D2

AWS

Electrode

Minimum tensile strength in thousand psi Welding position

Utilization

Alloy addition

Low Alloy Electrodes

Assignment: 1. Describe the electrodes E9018-B3L and E6218-B3L

2. Create memory rules to help recall which electrodes are low hydrogen, and which electrodes cannot be used with AC

Chromium and Chromium

Nickel Electrodes

E 316L-16

Alloy designation Electrode Position Use-ability

15 all position DC only

16 all position AC/DC, (DC if available) 25 flat or horizontal position only, DC

26 flat or horizontal position AC/DC (DC if available) Low carbon

Chromium and Chromium

Nickel Electrodes

Team Assignment 6:

1. What electrode is used to join 304 stainless steel to 304 stainless steel?

2. What electrode is used to join 316L stainless steel to 316L stainless steel?

3. What electrode is used to join 304L stainless steel to 316L stainless steel?

Hint: Procedure handbook of Arc Welding chapter 7.2

Flat Welding Position

Striking an arc

Arc Blow

Stringer Bead

Width of bead 2 to 3 times electrode diameter Height of bead 1/8th_{bead width}

Weaving Bead

Width less than 6 times

Work Angle

Reading The Bead

Reading The Bead

Current too low

Reading The Bead

Reading The Bead

Arc length too short

Reading The Bead

Reading The Bead

Travel speed too slow

Reading The Bead

Gas Tungsten Arc Welding

Current & Heat Distribution

Cleaning Action

Shielding Gases

Argon

Easier to start and maintain arc Lower flow rates

Less expensive

Helium Hotter arc

Deeper penetration Faster welding speeds

Electrodes

Zirconia: AC only, Aluminum Thoria: Steel and SS

Pure: Aluminum

Current Selection

Pulsed GTAW

Arc Starting

High frequency start Electrode contact

Laying A Bead

Pool formed Electrode moved to back of puddle, filler added to front of puddle

Rod is withdrawn electrode is moved to front of puddle

GTAW Variations

Autogenous Automatic Hot Wire Multi-Electrode

Team Assignment 7

Prepare a welding procedure including all the details your team is capable of to perform a full penetration Butt weld to join two 3-1/2” schedule 40, 316L pipe for use in a pressure chemical application.

Gas Metal Arc Welding

Metal Transfer

Short Circuit Globular Transfer Spray Transfer

Short Circuit

Thin material Out of position Low heat transfer

Globular Transfer

Spray Transfer

At least 90% Argon

Pulsed Spray Transfer

Above and below transition current Out of position

Power Supply

Constant Potential Inductance Slope Adjustment No current adjustment

Wire Feeder

Shielding Gas

Type of transfer

Penetration and bead shape Speed of Welding

Mechanical Properties of weld

Shielding Gas

Argon: aluminum, nickel, copper magnesium excellent arc stability

good penetration and bead profile finger like penetration

CO2 steel

reactive gas

will not support spray transfer greater spatter and fumes good fusion and penetration Helium heavy sections of Al, Cu and Mg

higher thermal conductivity additional heat to base metal

Shielding Gas

Argon-Oxygen 1 to 8% Oxygen Stainless steel

increases droplet rate more fluid puddle reduces undercut

Argon- CO2 Carbon and low alloy steels

Most popular 5 to 18% More fluid puddle Higher welding speeds

Argon- Helium Aluminum, copper, nickel alloys Increased heat input

Electrode Wire

ER49S-B2

Electrode Rod Solid Alloy Tensile Strength [MPa]

Electrode Wire

Torch Position

Team Assignment 8

Flux Cored Arc Welding

Electrodes

1. Gas shielded 2. Self Shielded 3. Metal Cored

Gas Shielded Electrodes

Used with same equipment as GMAW Constant voltage

Constant wire speed Most are designed for DCEP

Gas is usually CO₂or 75% Ar / 25%CO₂ Rutile wire: spray transfer only

stable arc, smooth bead

good penetration & out of position Basic wire: short circuit and globular transfer

considerable spatter

Self Shielded Electrodes

Very similar to an inside out SMAW electrode Flat and out of position wire

Immune to moisture pickup

DCEN or DECP, with long stick-out Most fume generation

Metal Cored Electrodes

Core contains: arc stabilizers deoxidizers metal powders Used with shielding gas

Short circuit/globular/spray transfer Out of position with pulsed spray transfer

Electrode Designations

EXXXT-1

Electrode Tensile Strength

Tubular or C = metal cored

Grouping (27 groups / CSA W48-01) Welding Position

1= all, 2 = F groove and F&H fillet

Refer to CSA W48-01 figure B1

Power Supply

Constant Potential Inductance

Slope Adjustment No current adjustment

Submerged Arc Welding

Three to ten times faster than SMAW

Electrodes

Typical wire size: 1/16, 5/64, 3/32” Also cored and strip

Available for mild steel, low alloy, stainless steel and nickel-base alloys

Fluxes

Manufacturing: Fused (mixed, melted, fused, crushed, screened & packaged)

Bonded (blended dry, binder added, dried, sized & packaged) Alloy Content

of Weld: Active (Controlled amounts of Mn & or Si to improve resistance to porosity and cracking)

Neutral (contains little or no deoxidizers)

Power Supplies

DCEN, DCEP, AC

DCEP recommended for deep penetration DCEN recommended for: fillets (clean plate)

hard facing

hard to weld steels greater build-up AC recommended for: tandem arc

Joint Preparation

Joint Preparation

Backing Required

Electrode & Flux Specification

F XX X X-E L XX X

Flux

Tensile Strength

Heat Treat Condition A = as welded, P = PWHT

Temp of impact strength

Z = impact testing not required

Electrode

Mn L = low, M = medium,

H = high, C = composite electrode If solid K = killed steel Carbon or chemical analysis

Team Assignment 9

Make a short presentation (7 to 10 minutes) to act as a review for your class mates on one of the welding methods. SMAW GTAW GMAW FCAW SAW

Heating

Preheating: Just prior to welding Interpass heating During welding Post weld heat treatment : After welding

Preheating

Why?

Reduce local shrinkage stresses

Reduce cooling rate through critical temperature (870º to 720º C) to prevent excess hardening & lowering ductility in weld & HAZ

Reduce cooling rate around 205º C to allow more time for hydrogen to to diffuse from weld and adjacent plate material to avoid hydrogen embrittlement and cracking

How Much Preheat?

Base metal chemistry Plate thickness

Restraint

Rigidity of members

Guides for Preheat

Specification

Note usually given as minimum preheat and is determined by measuring temperature for some distance around the weld

Observe minimum ambient temperatures

Remember Q&T steels can be damaged if preheat is to high

W59-03 Appendix P

W59-03 Appendix P

W59-03 Appendix P

Methods of Preheating

Production of small parts maybe best in a furnace Natural gas premixed with air

Acetylene or propane torches Electric strip heaters parallel to joint

Measuring Preheat

Temperature

With the exception of Q&T steels temperatures can be exceeded by 40º C

If temperature indicating crayons are used it is best to have one above and one below target temperature Pyrometers, thermocouples and infrared sensors are also Used, calibration and proper use are important

Preheating Quench &

Tempered Steel

Q & T steel have been heat treated heating above a certain temperature will destroy the properties of that heat treatment

The assembly may require preheat but it must not be to high The material must cool rapidly enough to re-establish the original properties

Interpass Temperatures

Usually steel which requires preheat is required to remain at that temperature between passes

On massive weldments the heat input from welding may not be sufficient to maintain the required temperature Just as it is desirable to control the cooling rate of the weld as a whole it is also important to control cooling between passes

Heat from additional sources maybe required to maintain interpass temperatures

Post Weld Heat Treatment

Annealing Normalizing Stress Relief

Full Annealing

Purpose:

Make steel soft and ductile Reduce stresses

Heat steel to 100º F above critical temperature Hold for 1 hour per inch of thickness

Slow cool, usually in furnace

Normalizing

Purpose:

Reduce stresses, usually after welding Greater hardness & tensile strength than

full annealing

Heat steel to 100º F above critical temperature Hold for 1 hour per inch of thickness

Stress Relief

Purpose:

Provides dimensional stability Softens martensitic areas Improves fracture resistance Heat slowly to about 625º C

Hold for a period of time Slowly cool

Welding Procedures

CWB Pre-qualified Joints Not pre-qualified Joints

CWB Pre-Qualified Joints

CSA W59-03 Section 10

SMAW, FCAW and SAW only Weld Procedure Specification Submit to CWB for Approval Qualify Welders

CWB Not Pre-Qualified Joints

Welding Procedure Specification Procedure Qualification

CWB Approval Qualify Welders

ASME Weld Procedures

No pre-approved joints

Each welding procedure will have a procedure qualification record

Three types of variables: Essential Supplementary Non-essential

What is Included in a Welding

Procedure?

One welding procedure specification One or more data sheets

Welding Procedure

Specification

Scope

Welding Procedure Base Metal

Base Metal Thickness Preparation of Base Material Filler Material

Shielding Gas Position

Minimum Preheat and Interpass Temperatures Electrical Characteristics

Welding Technique

Treatment of Underside of Groove Weld Metal Cleaning

Quality of Welds Storage of Electrodes

Data Sheet

CWB Welder Qualification

Classification Process Mode of Application Position

Classification

S With backing

T Without backing

FW = fillet & tack welds, ASW = arc spot weld, WT = tack welds

Process

SMAW FCAW GMAW SAW ESW EGW

Mode of Application

Manual Semi-automatic Machine Welding Automatic

Position

Class F Flat position & horizontal fillets Class H Flat and horizontal positions Class V Flat, horizontal & vertical positions

Electrode Designations

F4 Exx15, Exx16, Exx18 F3 Exx00, Exx10, Exx11 F2 Exx12, Exx13, Exx14

F1 Exx22, Exx24, Exx27, Exx28

Team Assignment 10

Review a weld procedure and present your teams understanding to your class

Verification Functions

Develop inspection plans & check lists Ordering and delivery of material Welding procedure specifications Welder qualifications

Proper fit up and welding processes Heat Treatment Inspection Inspection Records Nondestructive Testing

Procurement Verification

Vendor approval

Quantity & Dimensions Material Specification Special Requirements Heat treatment Inspection Nondestructive Testing QA Requirements Documentation Requirements

Receiving Inspections

Quantity Inspections Dimensions

Identification

Mill test reports or other required documentation Manufacturing defects

Weather or transportation damage

Documentation Verification

Mill Test Reports

Certificates of Compliance Partial Data Reports

SMAW Electrode Storage

Low Hydrogen Minimum 120º C Used within 4 hours

Alternate exposure times maybe approved Portable storage devices maybe approved E49 within 10 hours in portable storage Non-Low Hydrogen Stored warm and dry

Kept free from oil and grease

Preparation for Welding

Assembly Groove Welds

Backing

Preheat & Interpass

Temperatures

Sweep

Misalignment

Fillet Weld Size

Groove Weld Profile

Butt Weld Profile

Butt Weld Profile

Incomplete Penetration

Porosity

Slag

Inclusions

Solidification

Crack

Lamellar Tearing

Excess Convexity

Excessive Reinforcement

Undercut

Discontinuities Related to

Specific Welding Methods

SMAW SAW

GMAW & FCAW GTAW

SMAW

Spatter Lower current Check polarity Shorter arc

If molten metal running in front of arc, change electrode angle

Watch for arc blow

Ensure electrodes are not wet

SMAW

Undercut Reduce current Reduce travel speed Reduce electrode size Change electrode angle Avoid excessive weaving

SMAW

Rough Welding Check polarity Check current

Ensure electrodes are not wet

SMAW

Porosity Remove scale rust and moisture Use low hydrogen electrodes Use shorter arc length

SMAW

Lack of Fusion Increase current

Stringer bead technique Ensure joint is clean

Check joint fit-up and design

Over Lap

SMAW

Incomplete Penetration Increase current Decrease travel speed

Use smaller diameter electrode Increase root gap

SMAW

Cracking Hydrogen induced cracking Low hydrogen electrodes Store electrodes properly Use preheat

Smaller diameter electrodes

SMAW

Cracking Hot Cracking Proper fit-up

Proper electrode selection

Ensure root pass is of sufficient size Check rigidity of joint

SMAW

Cracking Solidification Cracking

If originating in crater use back step technique

If centre bead decrease travel speed

SAW

Cracking Fillet Welds

If members 25 mm or greater ensure gap of 1 to 1.5 mm to help with shrinkage

Check polarity, usually DCEP but DCEN sometimes used to reduce penetration to help deal with cracking

Check wire size, larger wire often used when cracking is a problem Check condition of root pass and fit-up Check bead shape (1-1/4 to 1)

SAW

Cracking Fillet Welds & T Welds

Groove angles should be at least 60º If different materials, weld puddle towards the most weld-able material Increasing stick out reduces cracking tendency

Ground at the start end of the weld Decreasing welding speed and current reduces cracking tendency

SAW

Cracking Butt Welds

If bead is hat shaped , check voltage and travel speed, may need to be reduced

If the first bead from the second side, after back gouging is cracking check to make sure the width is greater than depth

If the steels are of poor weld-ability often reducing current and/or travel speed or increasing stick out reduces

GMAW & FCAW

Fillet Welds Undercut & overlap are common

Check manipulation of the gun to ensure welding of both base metals

Slag

Check for slag removal between passes Gas Shielding is affected by ambient air movement

GTAW

Porosity Check shielding gas flow rates, leaks etc.

Check arc length (too long cannot be protected) Tungsten Inclusions

Check for touching the electrode into the puddle Check for current being to high

Team Assignment 11

Identify weld discontinuities in samples provided. Record results

Bend Tests

Face Bend Root Bend

Bend Tests

Bend Tests

All Weld Metal Tensile Test

Vickers Hardness Test

Hardness Tests

Three groups:

 Elastic hardness

 Resistance to cutting or abrasion

 Resistance to penetration

Resistance to Penetration

Brinell Hardness Test

A hard steel ball or carbide sphere is forced into the surface under a specified load.

Diameter is measured to determine Brinell Hardness

Resistance to Penetration

Rockwell Hardness Method

Measures the net increase in depth of the impression after a minor load is applied and after the major load is applied 14 different scales

C, A & D are the most common scales 15-N, 30-N & 45-N are the most common Superficial scales

Resistance to Penetration

Vickers Hardness Test

Considered a micro hardness method Uses a square based diamond pyramid The surface dimensions of the indent are measured and converted to hardness Used for measuring case hardening and heat affected zones of welds

Resistance to Penetration

Tukon Hardness Method

Micro hardness technique Employs a diamond indenter

Usually combined with a Vickers unit

Resistance to Penetration

Knoop Hardness Method Micro hardness technique

Impact Tests

Measures the decrease in fracture resistance caused by sudden loading in the

presence of a notch Methods:

Charpy Izod

Units: foot pounds of joules

Charpy Impact Tests

Izod Impact Tests

Transition Temperature

Impact test results must include temperature

Most materials exhibit a change from notch tough to notch brittle over a very narrow temperature range called the transition temperature

Transition temperature is determined by conducting impact tests at different temperatures until an abrupt change in energy required to break the specimen is noted