ELECTRODES & FLUXELECTRODES & FLUX- Can welding be done by bare - Can welding be done by bare electrodes ?electrodes ?- Why do we require coating at all ?- Why do we require coating at all ?- Reasons are instability of arc, lack - Reasons are instability of arc, lack of of shielding, poor mechanical shielding, poor mechanical propertiesproperties- What are the different type of - What are the different type of coatingcoatingTYPE OF COATINGTYPE OF COATINGCellulose materialCellulose material - It is made by hard - It is made by hard or soft wood, pulp & similar or soft wood, pulp & similar substance. Washing, drying & substance. Washing, drying & grading into different mesh sizes.grading into different mesh sizes.

- High arc force, large volume of gas - High arc force, large volume of gas mostly hydrogenmostly hydrogen

RUTILERUTILE - - It is a crystalline form of titanium It is a crystalline form of titanium dioxide. dioxide. Available in beach sand. Concentration - Available in beach sand. Concentration - 87% App.87% App.- Arc Stabilizer.- Arc Stabilizer.- Good Slag remover.- Good Slag remover.BALL CLAYBALL CLAY – It is a compound of silica – It is a compound of silica & & alumina commonly known as alumina commonly known as alumino silicate.alumino silicate.- Slag remover - Slag remover - Gives plasticity in the wet paste.- Gives plasticity in the wet paste.

IRON POWDERIRON POWDER – Sometimes added to – Sometimes added to flux flux coating to add strength to weld coating to add strength to weld- - Gives good mechanical strength, arc Gives good mechanical strength, arc stabilizer. stabilizer.

PURPOSE OF FLUX COATINGPURPOSE OF FLUX COATING

- Gas shielding of arc.- Gas shielding of arc.- Stabilizer of the arc (potassium - Stabilizer of the arc (potassium silicate).silicate).- Provides slag blanket.- Provides slag blanket.- Alloying elements will improve - Alloying elements will improve mechanical mechanical properties (Iron oxide, Ferro properties (Iron oxide, Ferro manganese).manganese).- Gives good penetration.- Gives good penetration.- Welding in all positions - Welding in all positions becomes easy.becomes easy.- Compensate oxidation loss.- Compensate oxidation loss.

ELECTRODE CLASSIFICATIONELECTRODE CLASSIFICATION

BASED ON COVERINGBASED ON COVERING- - Rutile ElectrodeRutile Electrode – – Quite & smooth arc, Quite & smooth arc, Excellent Excellent slag removal, fine ripples, medium slag removal, fine ripples, medium penetration, thick penetration, thick slag. slag.- - Cellulose electrodeCellulose electrode – forceful & noisy arc, – forceful & noisy arc, coarse coarse slag, deep penetration, more gas shield, slag, deep penetration, more gas shield, thin slag thin slag cover. cover.- - Basic ElectrodeBasic Electrode – Adequate penetration, – Adequate penetration, slag slag removal is good, contains more iron removal is good, contains more iron powder, good powder, good mechanical properties. mechanical properties.

BASED ON APPLICATIONSBASED ON APPLICATIONS- Stainless steel electrode- Stainless steel electrode- Low alloy electrodes- Low alloy electrodes- Copper & copper alloy electrode- Copper & copper alloy electrode- Aluminum & alloy electrodes- Aluminum & alloy electrodes- Hard facing electrodes.- Hard facing electrodes.

WHAT IT INDICATESWHAT IT INDICATES E6010 E6010 E – Electrode E – Electrode 60 – min tensile strength 60000 psi 60 – min tensile strength 60000 psi (410 mpa)(410 mpa) 1- Welding position 1- Welding position 0 – Coating current & condition. 0 – Coating current & condition.

AWS ELECTRODE CLASSIFICATION SYSTEM FOR CARBON & LOW - ALLOY STEEL

ELECTRODES (SMAW)

AWS Specification A5.1

E 60 1 0

Electrode

Strength in PSI Position

Type of Coating & Current

E 80 1 8 - B1

Electrode

80 PSI Min.

All Position

For AC or DCEP

Chemical Composition of Weld Metal Deposit

POSITION

DIGIT POSITION

1 Flat, Horizontal, Vertical, Overhead

2 Flat & Horizontal Only

3 Flat, Horizontal, Vertical down,

Overhead

TYPE OF COATING & CURRENT

DIGIT TYPE OF COATING CURRENT 0 Cellulose Sodium DCEP

1 Cellulose Potassium AC or DCEP or DCEN

2 Titania Sodium AC or DCEN

3 Titania Potassium AC or DCEP

4 Iron Powder Titania AC or DCEP or DCEN

5 Low Hydrogen Sodium DCEP

6 Low Hydrogen Potassium AC or DCEP

7 Iron Powder Iron Oxide AC or DCEP or DCEN

8 Iron Powder Low Hydrogen AC or DCEP

CHEMICAL COMPOSITION OF WELD DEPOSIT

Suffix %Mn %Ni %Cr %Mo %V

A1 1/2

B1 1/2 1/2

B2 1-1/4 1/2

B3 2-1/4 1

C1 2-1/2

C2 3-1/4

C3 1 0.15 0.35

D1&D2 1.25-2.00 0.25-0.45

G 0.50 0.3Min 0.20Min 0.10Min

AWS ELECTRODE CLASSIFICATION SYSTEM FOR CARBON STEEL ELECTRODES (GMAW)

ER 70 S- XElectrode or rod

Strength in PSI

Chemical Composition & Shielding

Solid Electrode Wire

SPECIFICATIONS FOR GMAW ELECTRODES

BASE MATERIAL TYPE AWSSPECIFICATION

Carbon Steel A5.18

Low Alloy Steel A5.28

Al Alloy A5.10

Cu Alloy A5.7

Magnesium A5.19

Nickel Alloys A5.14

Stainless Steel A5.9

Titanium A5.16

AWS CLASSIFICATIONS FOR GTAW ELECTRODES

AWS COMPOSITION COLOR CLASS. CODE

EWP Pure Tungsten Green

EWCe-2 97.3% Tungsten, 2% Cerium Oxide Orange

EWLa-1 98.3% Tungsten,1% lanthanum Oxide Black

EWTh-1 98.3% Tungsten,1% lanthanum Oxide Yellow

EWTh-2 97.3% Tungsten,2% lanthanum Oxide Red

EWZr-1 99.1% Tungsten,0.25%Zirconium Oxide Brown

EWG 94.5% Tungsten,remainder not specified Gray

ALLOY STEELS

Steel is considered to be alloy - steel when the maximum of the range given for the content of alloying elements exceeds one or more of the following limits

Manganese 1.65%Silicon 0.60%Cu 0.60% or

in which the limits of any of the following elements is specified or requiredAl, Boron, Cr 3.99%Cobalt, Columbium, Mo, Ni, Ti, Tungsten, Vanadium or any other element added to obtain the desired alloying element.

ALLOY STEELS

AWS Filler Metal Specifications

Suffix Letter designate the chemical composition of the deposited weld metal

Suffix Letter indicate the following chemistry

Suffix Letter Chemistry A C - Mo Steel B Cr - Mo Steel C or NI Ni Steel D Mn - Mo Steel NM Ni - Mo Steel G, K, M and W Other Low Alloy Steel

ALLOY STEELS

To Weld Alloy Steel successfully four factors must be considered

1. Always use a low - hydrogen welding procedure, process & filler metal

2. Select a filler metal that matches the strength level of the alloy steel

3. Select a filler metal that comes close to matching the composition of alloy steel

4. Use proper welding procedure

CARBON STEELS & LOW - ALLOY STEELS

Wrought Iron No Carbon ( < 0.08%)Low Carbon Steels 0.15 % Carbon (Max)

0.25 - 1.5 % ManganeseMild Steel 0.15 - 0.29 % CarbonMedium Carbon Steel 0.25 - 0.50 % Carbon

0.60 - 1.65 % Manganese

High Carbon Steels 0.50 - 1.03 % Carbon0.30 - 1.00% Manganese

Low Alloy Steels 0.29 % Carbon (Max.)Total Metal Alloys <= 2.0 %

Cast Iron 2.1 % Carbon

CARBON STEELS & LOW - ALLOY STEELS

STEEL ELECTRODES AISILow Carbon Steels E60XX & E70XX1008

1025

Medium Carbon Steel E70XX 10301050

High Carbon Steels Pre - Heating &PWHT 1055(200 - 310o C) 1095

Low Alloy Steels E80XX, E90XX

LOW - ALLOY STEELS

Low Nickel Steel AISI 2315, 2515, 2517Carbon 0.12 - 0.30%Mn 0.40 - 0.60%Si 0.20 - 0.45%Ni 3.25 - 5.25 %

Electrode With the C-1, C - 2 Suffix

if C < 0.15% No preheat, except for heavy section

if C > 0.15% Preheat up to 260o C

Stress Relieving Advisable

LOW - ALLOY STEELS

Low Ni - Cr Steel AISI 3120, 3135, 3140, 3310, 3316Carbon 0.14 - 0.34%Mn 0.40 - 0.90%Si 0.20 - 0.35%Ni 1.10 - 3.75 %Cr 0.55 - 0.75%

Electrode E80XX & E90XX

if C < 0.15% No preheat, except for heavy section

if C > 0.20% Preheat up to 316o C

Stress Relieving Advisable

LOW - ALLOY STEELS

Low Manganese Steel AISI 1320, 1330, 1335, 1340, 1345

Carbon 0.18 - 0.48%Mn 1.60 - 1.90%Si 0.20 - 0.35%

Electrode E80XX & E90XX With A-1, D-1 or D-2 Suffix

Low Range of C & Mn No preheat

if C >= 0.25% Preheat desirable(121o C- 149o C)

High Range Mn Mandatory

Thicker Section (240o C- 290o C)

Stress Relieving Advisable

LOW - ALLOY STEELS

Low Alloy Cr Steel AISI 5015 to 5160

Carbon 0.12 - 1.10%Mn 0.30 - 1.00%Si 0.20 - 0.30%Cr 0.20 - 1.60%

Electrode E80XX & E90XX With B Suffix

Low Range of C & Cr No preheat

High Range C & Cr 399o C

Thicker Section (240o C- 290o C)

Stress Relieving Advisable

LOW - ALLOY STEELS

Low Alloy Cr Steel AISI 5015 to 5160

C.E. = C% + Mn% + Ni% + Cr% + Mo% + Cu% 6 20 10 40

if C.E. < 0.40% Material is readily weldable

C.E. > 0.40% Special Controls RequiredPreheatingLow Hydrogen Processes

Procedure Should be Qualified

STAINLESS STEELS

Also called Corrosion - Resistant Steels

They do not rust

Strongly resist attack by great many liquids, gases

& chemicals

Good low - temperature toughness & ductility

Good Strength & Resistance to High Temp.

Iron as main element

Chromium - 11 to 30 %

STAINLESS STEELS

AISI Identification System

Three Digit Number e.g. AISI 304

First Digit indicates Group

Last Two indicates specific alloy Series Metallurgical Principle MagneticDesign. Group Elements

2XX Austenitic Cr-Ni-Mn Non Magnetic3XX Austenitic Cr-Ni -do-4XX Martensitic Cr Magnetic4XX Ferritic Cr -do-5XX Martensitic Cr-Mo -do-

LOW HYDROGEN ELECTRODESLOW HYDROGEN ELECTRODESThese electrodes are having These electrodes are having covering that is low in hydrogen covering that is low in hydrogen bearing compound.bearing compound.

- Hydrogen has limited solubility - Hydrogen has limited solubility in steel.in steel.- Solubility is high in liquid state- Solubility is high in liquid state- Beyond solubility limit, it - Beyond solubility limit, it retained in weld retained in weld called traps. called traps.- Localization of hydrogen takes - Localization of hydrogen takes place which place which creates under bead crack, creates under bead crack, Hydrogen Hydrogen induced crack. induced crack.

SELECTION OF ELECTRODESSELECTION OF ELECTRODES

- Composition & strength of BM- Composition & strength of BM- Penetration requirement- Penetration requirement- Position of welding.- Position of welding.- Fit up condition- Fit up condition- Skill of welding personnel- Skill of welding personnel- Cost of welding operation.- Cost of welding operation.- Service requirement of weld - Service requirement of weld joint.joint.

PREHEATING & POST HEATINGPREHEATING & POST HEATING

It is to elevate base metal temp before It is to elevate base metal temp before or after welding operation.or after welding operation.PurposePurpose - to reduce cooling rate - to reduce cooling rate- To avoid cold cracks- To avoid cold cracks- To avoid hydrogen entrapment- To avoid hydrogen entrapment- To remove moisture- To remove moisture

Carbon equivalentCarbon equivalent = C+Mn/6+ = C+Mn/6+(Cr+Mo+V)/5 + (Ni+Cu)/15(Cr+Mo+V)/5 + (Ni+Cu)/15

0.40 Below – Preheating optional0.40 Below – Preheating optional 0.40 - 0.60 – Preheating 150 to 0.40 - 0.60 – Preheating 150 to 200 deg c200 deg c 0.60 & above – Preheating & Post 0.60 & above – Preheating & Post heating – heating – 200 – 370 deg C 200 – 370 deg C

POST WELD HEAT TREATMENTPOST WELD HEAT TREATMENT

- - Rate of heatingRate of heating- Soaking & soaking time- Soaking & soaking time- Rate of cooling- Rate of cooling

WELDING DEFECTSWELDING DEFECTSIn the correct sense, a defect is a In the correct sense, a defect is a rejectable discontinuity or a flaw of rejectable discontinuity or a flaw of rejectable in nature. Certain flaws rejectable in nature. Certain flaws acceptable in one type of product need not acceptable in one type of product need not be accepted nature in another product. A be accepted nature in another product. A defect is definitely a discontinuity but a defect is definitely a discontinuity but a discontinuity need not necessary be a discontinuity need not necessary be a

defectdefect..ACCEPTANCE / REJECTION CRITERIAACCEPTANCE / REJECTION CRITERIA

- - Stress to which the parts will be Stress to which the parts will be subjected.subjected.- Type of material used.- Type of material used.- The temp & pressure to which the parts - The temp & pressure to which the parts will be will be stressed & Its thickness stressed & Its thickness - Consequence of failure & cost - Consequence of failure & cost &accessibility of &accessibility of repair. repair.

DEFECT CHARACTERISTICSDEFECT CHARACTERISTICS

- - Size of defectSize of defect- Sharpness or notch effect- Sharpness or notch effect- Orientation of defect- Orientation of defect- Location of defect (surface, root, weld - Location of defect (surface, root, weld metal, HAZ, metal, HAZ, Parent metal. Parent metal.BROAD CLASSIFICATIONSBROAD CLASSIFICATIONSPlaner defectPlaner defect (two dimensional) - cracks, (two dimensional) - cracks, lack of fusion, lack of penetration, lack of fusion, lack of penetration, laminationlamination

Voluminar defectVoluminar defect (three dimensional) – (three dimensional) – Slag inclusion, Porosity, cavity, root Slag inclusion, Porosity, cavity, root concavity.concavity.

Geometric defectsGeometric defects Misalignment, undercut, concavity , Misalignment, undercut, concavity , convexity, excessive reinforcement, convexity, excessive reinforcement, improper reinforcement, overlap, burn improper reinforcement, overlap, burn through, incomplete penetration, lack of through, incomplete penetration, lack of fusion, surface irregularity fusion, surface irregularity

Incomplete penetrationIncomplete penetration – Lack of – Lack of penetration & excessive penetration.penetration & excessive penetration.- Excessive thick root face or insufficient - Excessive thick root face or insufficient root opening root opening can be avoided by use proper joint can be avoided by use proper joint geometry.geometry.- Insufficient heat input.- Insufficient heat input.- Slag flooding ahead of welding – Use - Slag flooding ahead of welding – Use small small electrodes in root . electrodes in root .

- Misalignment - id matchingMisalignment - id matching- Bridging or root opening.- Bridging or root opening.INCOMPLETE FUSIONINCOMPLETE FUSION- Insufficient heat input, wrong size of - Insufficient heat input, wrong size of electrode, electrode, improper joint design – follow correct improper joint design – follow correct WPSWPS- Incorrect electrode position – maintain - Incorrect electrode position – maintain correct correct position. position.- Weld metal running ahead of arc – lower - Weld metal running ahead of arc – lower the current the current & speed & speedSLAG INCLUSIONSLAG INCLUSION- Improper joint design-increase groove - Improper joint design-increase groove angle of joint.angle of joint.- Oxide inclusions – proper gas shielding.- Oxide inclusions – proper gas shielding.- Poor electrode manipulative techniques.- Poor electrode manipulative techniques.- Change electrode or flux to improve slag - Change electrode or flux to improve slag control.control.- Failure by welder to remove slag- Failure by welder to remove slag

POROSITYPOROSITY

- - Improper arc length, welding current, Improper arc length, welding current, electrode electrode manipulation – change welding manipulation – change welding condition & condition & techniques. techniques.- Excessive moisture in electrode-use - Excessive moisture in electrode-use correct baking correct baking & holding temp. & holding temp.- Excessive Hydrogen & nitrogen in weld - Excessive Hydrogen & nitrogen in weld atmosphere atmosphere by use low hydrogen electrodes. by use low hydrogen electrodes.- High solidification rate – use preheat- High solidification rate – use preheat- Dirty metal or filler metal.- Dirty metal or filler metal.

WELD DEFECTS

INC

OM

PL

ET

E

PE

NE

TR

AT

ION

LA

CK

OF

F

US

ION

WELD DEFECTS

INCOMPLETE PENETRATION

WELD DEFECTS

CONTINUOUS INCOMPLETE PENETRATION

WELD DEFECTS

BU

RN

T

HR

OU

GH

RO

OT

C

ON

CA

VIT

Y

WELD DEFECTS

TR

AN

SV

ER

SE

C

RA

CK

CR

AC

K A

DJ

AC

EN

T T

O T

HE

R

OO

T

WELD DEFECTS

PO

RO

SIT

Y

WELD DEFECTS

MIS

MA

TC

HC

RA

CK

WELD DEFECTS

SL

AG

IN

CL

US

ION

TU

NG

US

TE

N IN

CL

US

ION

WELD DEFECTS

WELD DEFECTS

UN

DE

R

CU

TE

XC

ES

SIV

E P

EN

ET

RA

TIO

N

WELD DEFECTS

WELDING EXAMPLES RELATED TO BAD PRACTICES

EFFECT OR VARIATION OF EFFECT OR VARIATION OF PARAMETERSPARAMETERS

CURRENT TOO LOWCURRENT TOO LOW• Poor penetrationPoor penetration• Slag inclusionSlag inclusion• Irregular ripplesIrregular ripples• Uneven bead heightUneven bead height

CURRENT TOO HIGHCURRENT TOO HIGH• Excessive penetrationExcessive penetration• More spatterMore spatter• Poor ripple appearancePoor ripple appearance• PorosityPorosity• UndercutUndercut

ARC TOO SHORTARC TOO SHORT• Irregular ripplesIrregular ripples• Electrode freezing the jobElectrode freezing the jobARC TOO LONGARC TOO LONG• Wide ripplesWide ripples• More spatters, blow holesMore spatters, blow holesTRAVEL TOO FASTTRAVEL TOO FAST• Narrow width of beadNarrow width of bead• Porosity Porosity TRAVEL TOO LOWTRAVEL TOO LOW• More width & height of beadMore width & height of bead• Slag inclusionSlag inclusion

DISTORATION & RESIDUAL DISTORATION & RESIDUAL STRESSSTRESS

• Distortion or residual shape change occur Distortion or residual shape change occur during welding.during welding.

• These imperfections adversely affect These imperfections adversely affect further assembly.further assembly.

• Designers are often constrained to design Designers are often constrained to design structure free from distortionstructure free from distortion

• Distortion control is often tackled by shop Distortion control is often tackled by shop floor engineers.floor engineers.

• This is a after effect of welding that This is a after effect of welding that remains permanent in the component till remains permanent in the component till the equilibrium is disturbed.the equilibrium is disturbed.

PROCESSPROCESS – – Localized application of heat Localized application of heat causes plastic deformation. As a result causes plastic deformation. As a result thermal shrinkage occur near that zone & thermal shrinkage occur near that zone & the metal or weldment changes its shape the metal or weldment changes its shape during cooling.during cooling.

METHOD TO PREVENTMETHOD TO PREVENT • Minimizing weld joints.Minimizing weld joints.• Minimizing weld sizes.Minimizing weld sizes.• Minimizing unsupported lengthMinimizing unsupported length• Selection of appropriate edge Selection of appropriate edge

preparationpreparation• Use of intermittent welding.Use of intermittent welding.• Using proper jigs & fixturesUsing proper jigs & fixtures• Using welding sequence Using welding sequence • Minimizing heat input rateMinimizing heat input rate