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  • Weld Defects

  • Significance of defectsIncomplete fusion can influence brittle fracture in either static or dynamic loads.The effect of lack of fusion is almost same as Lack of penetrationArc strikes consist of un annealed martensite and contains a number of small fissures. These small fissures can lead to brittle fracture when remaining load bearing material has been sufficiently reduced in cross section.

  • A Defect is Rejactable discontinuityA defect is a discontinuity but a discontinuity need not be a defect.Acceptance of a discontinuity is based on different factors. Few examples are as follows:Stresses to which the parts will be subjected during serviceType of Material UsedThe environmentConsequence of failure

  • Acceptance Standards Dictate the type of Inspection and testing.The weld defects can be broadly classified into two types.Planer defects / two dimensional defects (Crack, Lack of Fusion, Lack of Penetration, Severe Undercut These are not acceptable defects)Volumetric Defects / Three Dimensional defects.(Slag inclusion, cavities, Porosities are acceptable to certain extent)

  • General Reasons for Defects

    Lack of Know-howWelding Process CharacteristicsBase metal CompositionDefective welding filler metalJoint designWelding Environment (Wind, fit-up, Temperature etc.)

  • Defects involving inadequate bondingLack of FusionDue to improper manipulation of electrodeIncorrect position of electrodeLow welding currentToo rapid arc advanceImproper joint fit-up

  • INCOMPLETE PENETRATIONIncorrect Joint designImproper welding parameters specifically currentIncorrect electrode sizeIncorrect polarity where DC is usedUn fused root can cause stress concentration that could lead to brittle failure

  • InclusionsSlag InclusionBecause of the string action of the arc slag may be forced down to the molten metal and the high viscosity of weld metal, rapid solidification at a low temperature leads to entrapment.Preheating the base metal to control the rate of solidification will ensure release of slag from molten metal

  • Oxide Films In MIG welding oxides in the form of Globules are found in weld metal. The presence of such films seriously impairs the ductility of weld metal.This defect is rarely detectable except with the aid of a microscope

  • Tungsten InclusionsThese are particles deposition in the weld metal from a tungsten electrode in TIG weldingThese inclusions are not generally considered harmful unless their size and number become excessive.Superimposed high frequency current for arc starting tends to minimize these inclusions

  • Geometric DefectsUndercuts represents a depression into the base metal adjacent to the toe of the weld and it form a notch.A small amount of undercut under pulsating stress often acts as a starting point for fatigue cracks.Correct choice of current range and good manipulation of electrode during welding will avoid undercut

  • Burn through or excess penetrationOccurs because of very high current and low travel speed.It is also called as icicles and are found at the root of the weld.Consumable inserts may be used to avoid excess penetration

  • Improper weld profileThis occurs more in the case of fillet joints Excessive concave or convex beads are examples of this.These are caused because of improper weld parameters, electrode size & weaving.Visual examination is sufficient to decide these defects.

  • METALLURGICAL DEFECTSCRACKSHot crackingCaused because of restraint on the joint and the presence of higher carbon and sulfur.Segregation of weld metal due to bead shape also is a reason for these defects.MPI or LPI are used to detect surface defects while UT is suitable for internal cracks.

  • Cold crackingCold cracking starts in the HAZ of the parent metalIt is associated with combined effects of hydrogen, restraint and martensite formationLow hydrogen electrode and preheating minimizes cold cracking.

  • Crater cracksCracks formed from a circular surface with a depression either in the weld or at the end of a weld.It is caused by a volume concentration of molten metal during solidification usually the result of abrupt interruption of the welding arc in the root run.

  • Gas porosityPorosity is the presence of gas pockets of voids caused by the entrapment of gases evolved during weld metal solidificationPorosity is caused due to improper shielding, rust on the weld face, too much generation of gas in the weld pool.Porosity is considered to be the least dangerous defect but is often an indication of damp electrodes having been used.

  • Arc StrikesLocalized heat affected zone caused by an arc is known as arc strikesArc strikes produce hardening particularly in high carbon steels and alloy steels.EmbrittlementThe carbon and alloy steels containing 0.18% carbon tends to form brittle martensite structure in HAZ.This is avoided by controlled cooling rate.

  • Quality Of WeldingWelding Defects (Root Cause Analysis)

  • Why These Defects Occur?Porosity Lack of supervision Incompetent welder / operator Poor performance of welding equipment In-proper handling / use of welding consumables Poor joints fit-ups Weather condition Quality & characteristic of base metal & etcCracks Lack of supervision Incompetent welder / operator. In-proper use of welding consumables. Weather condition. Quality & characteristic of base metal. In-proper control of preheating & post heating process & etcIncomplete Penetration Lack of supervision Incompetent welder / operator. Poor joints fit-ups Welding current too low Wrongly use of electrode size (too big) Arc length too long Melting filler rod instead of welding Insufficient gas shielding (GTAW SUS)Undercut, Excess Penet. Root Concavity Lack of supervision Incompetent welder / operator Misalignment Welding current too high Poor joints fit-ups Wrong electrode angle

    Lack of supervision Incompetent welder / operator Poor performance of welding equipment In-proper handling / use of welding tools In-proper handling / use of welding consumables Poor joints fit-ups & etcSlag / Tungsten InclusionsIncomplete Fusions Lack of supervision Incompetent welder / operator Poor performance of welding equipment In-proper handling / use of welding tools In-proper handling / use of welding consumables Poor joints fit-ups & etc

  • What Are The Possible Root Causes Lack Of Supervision Inadequate Knowledge And Awareness In Quality Control At All Levels Poor Discipline and Negative Working Attitude Lack Of Responsibility Toward Quality Control At Supervisory Level Inefficient Quality Monitoring & Surveillance Plan Work Environment Poor Work Site Management & Control

  • Areas Of Concern Quality Is Client Driven, Company Has Not Set Clear Quality Goals & Targets And Communicate To Shop Floor Ineffectiveness Of Implementation Of QMS Expectations And Deliverables Are Not Clearly Defined At Supervisors, QA Personnel And QC Personnel Levels Quality Is A QA/QC Function, Supervisors are more Concern In Timely Delivery Of Projects Subcontractors Management Has No Commitment Toward Quality Goals

  • CAUSE EFFECT (FISHBONE) DIAGRAMWELD DEFECT ROOT CAUSE ANALYSIS

    Sheet1

    &C&"Arial,Bold"&14&UCAUSE EFFECT (FISHBONE) DIAGRAM&UWELD DEFECT ROOT CAUSE ANALYSIS

    POROSITY

    Not using of weather protectors

    Poor house keeping

    Welding at dusty environment

    Storing of electrodes and filler metals together with oils, paints.

    Welding at windy environment

    WELDING ENVIRONMENT

    Poor in keeping of welders records and repair rates

    Engaging of unqualified welders

    Lack of job / WPS knowledge

    Poor control and guiding welders

    Lack of responsibility and commitment towards quality

    Poor organizing of site protection from wind

    Lack of Quality awareness/ targets

    Poor controls on electrode baking and handling

    Lack of prcess controlls

    SUPERVISOR ROLE

    Wrong selection of welding process

    Using of SMAW where more appropriate GTAW process

    Using of SMAW where more appropriate SAW process

    Lack of understanding on application of process using

    Using of GMAW where FCAW can be used

    WELDING PROCESS

    Welding unkilled steels

    Welding of pitting corroded plates

    Welding of old and already used materials in the process

    Using of rusted plates

    Using of plates oily/ greased

    BASE MATERIAL QUALITY

    Unstable arc voltage

    Unstable current

    Frequent power tripping

    Improper aligning of rotators

    Non uniform rotation of welding rotators

    Exocentric or over loading on rotators.

    Using of damaged gas hoses

    WELDING EQIPMENT

    Not using HF units for GTAW welding

    No calibration of equipment

    Non uniform travel speed

    WELDING CONSUMABLES

    Wrong selection of type of electrodes / fluxes

    Using of unbaked welding consumables

    Using of contaminated filler metals

    Poor storage and handling of welding consumables

    Using of cold welding consumables

    Using of poor quality shielding / purging gasses

    Using of contaminated electrodes/fluxes

    Using of wrong size electrode

    Poor attitude of welder/ operator

    Lack of skillness

    Lack of commitment towards quality

    Lack of welding/ WPS knowledge

    Not using wind protectors.

    Using of long arcs

    Welding on wet / oily surfaces

    Using of wrong size and clod electrodes

    WELDER / OPERATORSKILLS

    Using of wrong welding parameters

    Using of high or low flow gasses

    Welding on wet / oily surfaces

    Using of excessive electrode stickout

    Poor eye sight, over fatigue and personal reasons

    Using of too narraow groove

    Using of tack welds in the groove for single side joints

    Using of unqualified welder for tack welding

    Gas cutting notches on edge preoeration

    Poor accessibility for welding

    Using of unskilled gas cutters, gougers and grinders

    Not using proper run and run off plates

    Not keeping joint foreasy welding position

    Not grinding rusted /mill scales and gouged surfaces

    JOINT FITUPS

    Large gps

    Sheet2

    Sheet3

  • CAUSE EFFECT (FISHBONE) DIAGRAMWELD DEFECT ROOT CAUSE ANALYSIS

    Sheet1

    &C&"Arial,Bold"&14&UCAUSE EFFECT (FISHBONE) DIAGRAM&UWELD DEFECT ROOT CAUSE ANALYSIS

    SLAG / TUNGSTEN INCLUSIONS

    WELDING PROCESS

    Wrong selection of welding process

    Using of SMAW where more appropriate GTAW process

    Using of SMAW where more appropriate SAW process

    Lack of understanding on application of process using

    JOINT FITUPS

    Using of too narraow groove

    Using of tack welds in the groove for single side joints

    Using of unqualified welder for tack welding

    Gas cutting notches on edge preoeration

    Poor accessibility for welding

    Using of unskilled gas cutters, Gougers and grinders

    Not using proper run and run off plates

    Not keeping joint foreasy welding position

    WELDING TOOLS

    Using of incorrect tools

    Non availability of proper tools

    Using defective tools

    Not using any tools

    WELDER / OPERATORSKILLS

    Poor attitude of welder/ operator

    Lack of skill

    Lack of commitment towards quality

    Lack of welding/ WPS knowledge

    Using of wrong welding parameters

    Not using welding tools for inter pass cleaning

    Not following of foreman instructions

    Using of too low current

    Not cleaning interpass

    Using too low welding speed

    Using of too low voltage

    Poor eye sight, over fatigue and personal reasons

    WELDING EQIPMENT

    Not using HF units for GTAW welding

    Unstable arc voltage

    Unstable current

    Prequent power tripping

    Improper aligning of rotators

    Non uniform rotation of welding rotators

    Exocentric or over loading on rotators.

    No calibration of equipment

    Non uniform travel speed

    SUPERVISOR ROLE

    Poor in keeping of welders records and repair rates

    Engaging of unqualified welders

    Poor control and guiding welders

    Lack of responsibility and commitment towards quality

    Poor organizing of tools

    Lack of Quality awareness/ targets

    Poor monitoring

    Lack of process controls

    Lack of job / WPS knowledge

    Not keeping job in appropriate position

    Poor planning and coordination with fitting group

    WELDING CONSUMABLES

    Wrong selection of electrodes/fluxes

    Using of wrong size electrode

    Wrong selection of Tungsten electrode

    Poor quality of electrodes/fluxes

    Using of damaged contaminated electrodes / fluxes / filler metals size electrode

    Sheet2

    Sheet3

  • CAUSE EFFECT (FISHBONE) DIAGRAMWELD DEFECT ROOT CAUSE ANALYSIS

    Sheet1

    &C&"Arial,Bold"&14&UCAUSE EFFECT (FISHBONE) DIAGRAM&UWELD DEFECT ROOT CAUSE ANALYSIS

    LACK OF FUSION

    BASE MATERIAL QUALITY

    Using of contaminated base metals

    Using of plates oily/ greased

    WELDING CONSUMABLES

    Using of wrong size electrode

    Using of poor quality shielding / purging gasses

    Using of damaged contaminated electrodes fluxes / filler metals

    WELDING EQIPMENT

    Not using HF units for GTAW welding

    Unstable arc voltage

    Unstable current

    Frequent power tripping

    Improper aligning of rotators

    Non uniform rotation of welding rotators

    Exocentric or over loading on rotators.

    Non uniform welding travel speed

    No calibration of equipment

    Welding at dusty environment

    WELDING ENVIRONMENT

    Not using of weather protectors

    Welding at windy environment

    JOINT FITUPS

    Using of too narraow groove

    Using of tack welds in the groove for single side joints

    Using of unqualified welder for tack welding

    Poor accessibility for welding

    Not using proper run and run off plates

    Not keeping joint foreasy welding position

    Not grinding rusted /mill scales and gouged surfaces

    Inadquate bevel angle

    Using of square butt joints.

    WELDING PROCESS

    Wrong selection of welding process

    Using of SMAW where more appropriate GTAW process

    Using of SMAW where more appropriate SAW process

    Lack of understanding on application of process using

    Using of GMAW where FCAW can used

    WELDER / OPERATORSKILLS

    Poor attitude of welder/ operator

    Lack of skill

    Lack of commitment towards quality

    Lack of welding/ WPS knowledge

    Using of wrong welding parameters

    Using of excessive electrode stickout

    Using of low flow gasses

    Using of low current

    Using of high welding travel speed

    Using of improper bead laying sequence

    Lack of qualification

    Using of long arcs

    Poor eye sight, over fatigue and personal reasons

    SUPERVISOR ROLE

    Poor in keeping of welders records and repair rates

    Engaging of unqualified welders

    Lack of job / WPS knowledge

    Lack of responsibility and commitment towards quality

    Poor organizing of site protection from wind

    Lack of Quality awareness/ targets

    Lack of prcess controlls

    Poor control and guiding welders

    Poor planning and coordination with fitting group

    Sheet2

    Sheet3

  • CAUSE EFFECT (FISHBONE) DIAGRAMWELD DEFECT ROOT CAUSE ANALYSIS

    Sheet1

    &C&"Arial,Bold"&14&UCAUSE EFFECT (FISHBONE) DIAGRAM&UWELD DEFECT ROOT CAUSE ANALYSIS

    INCOMPLETE PENETRATION

    WELDING CONSUMABLES

    Using of wrong size electrode

    Using of poor quality shielding /purging gasses

    Using of Ecentric coated cectrodes

    Using of damged contaminated electrodes/ fluxes / filler metals

    WELDER / OPERATORSKILLS

    Poor attitude of welder/ operator

    Lack of skill to manipulate beads

    Lack of commitment towards quality

    Lack of welding/ WPS knowledge

    Using of wrong welding parameters

    Using of excessive electrode stickout

    Using of long arcs

    Using of low or high flow gasses

    Using of too low currents

    Using of too high welding travel speed

    Using of improper welding manipulation

    Poor eye sight, over fatigue and personal reasons

    WELDING EQIPMENT &ACCESSORIES

    Not using HF units for GTAW welding

    Unstable arc voltage

    Unstable current

    Frequent power tripping

    Non uniform welding travel speed

    No calibration of equipment

    JOINT FITUPS

    Using of too narrow groove

    Using of tack welds in the groove for single side joints

    Using of unqualified welder for tack welding

    Poor accessibility for welding

    Not using proper run and run off plates

    Not keeping joint foreasy welding position

    Inadquate bevel angle

    Wrong selection of welding process

    WELDING PROCESS

    Using of SMAW where more appropriate GTAW process

    Lack of understanding on application of process using

    Using of GMAW where FCAW can used

    SUPERVISOR ROLE

    Poor in keeping of welders records and repair rates

    Engaging of unqualified welders

    Lack of job / WPS knowledge

    Poor control and guiding welders

    Lack of responsibility and commitment towards quality

    Poor organizing of site protection from wind

    Lack of Quality awareness/ targets

    Poor planning and co ordination with fitting group

    Lack of prcess controlls

    Sheet2

    Sheet3

  • CAUSE EFFECT (FISHBONE) DIAGRAMWELD DEFECT ROOT CAUSE ANALYSIS

    Sheet1

    &C&"Arial,Bold"&14&UCAUSE & EFFECT (FISHBONE) DIAGRAM&UWELD DEFECT ROOT CAUSE ANALYSIS

    CRACKS

    WELDING PROCESS

    Wrong selection of welding process

    Using of high hydrogen inducing process ( for Ex. using SMAW instead of GTAW process)

    Using of high dilution welding process

    Lack of understanding on application of process

    BASE MATERIAL QUALITY

    Using of quenched & tempered steels

    Using of high Ceq. materials

    Using of high Sulphur & Phosphorus steels

    Using of unkilled & high impurities content steels

    Using of damaged contaminated electrodes / fluxes

    Using of cold welding consumables

    Using of unbaked welding consumables

    Using of poor quality shielding / purging gasses

    WELDING CONSUMABLES

    Wrong selection of type of electrodes/fluxes

    Using of wrong size electrode

    Using of contaminated filler metals

    Selection of non compatible welding consumables

    Poor storage and handling of welding consumables

    WELDING EQIPMENT

    No calibration of equipment

    Unstable arc voltage

    Unstable current

    Non uniform rotation of welding rotators

    Using of damaged gas hoses

    Non uniform travel speed

    WELDING ENVIRONMENT

    Not using of weather protectors

    Poor house keeping

    Welding at dusty environment

    Welding at windy environment

    WELDER / OPERATORSKILLS

    Not maintaining preheat, interpass temp. and not covering joints with fire blankets

    Lack of skill

    Lack of commitment towards quality

    Lack of welding/ WPS knowledge

    Using of wrong welding parameters

    Incorrect welding sequence

    Not using wind protectors.

    Welding on wet / oily surfaces

    Using of wrong size and cold electrodes

    Using of too high travel speed

    Using of improper bead laying sequence

    Poor eye sight, over fatigue and personal reasons

    Using of long arcs

    Not using appropriate tempil stiks

    Poor in keeping of welders records and repair rates

    Engaging of unqualified welders

    Lack of job / WPS knowledge

    Poor control and guiding welders

    Lack of responsibility and commitment towards quality

    Poor organizing of site protection from wind

    Lack of Quality awareness/ targets

    Poor controls on electrode baking and handling

    Lack of process controls

    Using of poor preheating methods and not arranging fire blankets

    SUPERVISOR ROLE

    Poor planning and coordination with fitting group

    JOINT FITUPS

    Using of mismatch joints

    Using of unqualified welder for tack welding

    Not removing gouged surfaces by grinding

    Using of unskilled gas cutters, Gougers and grinders

    Not using proper run and run off plates

    Not keeping joint foreasy welding position

    Using toomuch strong backs and making restraint joints.

    Using of square butt joints for high Sulphour & Phosphorus steels

    Large gaps

    Sheet2

    Sheet3

  • CAUSE EFFECT (FISHBONE) DIAGRAMWELD DEFECT ROOT CAUSE ANALYSIS

    Sheet1

    &C&"Arial,Bold"&14&UCAUSE EFFECT (FISHBONE) DIAGRAM&UWELD DEFECT ROOT CAUSE ANALYSIS

    UNDERCUTS, EXCESS PENETRATION, ROOT CONCAVITY

    WELDING EQIPMENT

    Not using HF units for GTAW welding

    Unstable arc voltage

    Unstable current

    Frequent power tripping

    Improper aligning of rotators

    Non uniform rotation of welding rotators

    Exocentric or over loading on rotators.

    Non uniform welding travel speed

    No calibration of equipment

    JOINT FITUPS

    Using of too narrow groove or large groove

    Using of tack welds in the groove for single side joints

    Using of unqualified welder for tack welding

    Poor accessibility for welding

    Not using proper run and run off plates

    Not keeping joint foreasy welding position

    Inadquate bevel angle

    WELDING CONSUMABLES

    Using of wrong size electrode

    Using of poor quality shielding gasses

    Using of Ecentric coated cectrodes

    Using of damaged contaminated electrodes / fluxes, filter metals

    WELDER / OPERATORSKILLS

    Poor attitude of welder/ operator

    Lack of skill to manipulate beads

    Lack of commitment towards quality

    Lack of welding/ WPS knowledge

    Using of wrong welding parameters

    Using of excessive electrode stickout

    Using of long arcs

    Using of low or high flow gasses

    Using of too high or low currents

    Using of too high or low welding travel speed

    Using of improper welding technic

    Poor eyes sight, over fatigue and personal reasons

    WELDING PROCESS

    Using of SMAW where more appropriate GTAW process

    Using of SMAW where more appropriate SAW process

    Lack of understanding on application of process using

    Using of GMAW where FCAW can used

    Wrong selection of welding process

    SUPERVISOR ROLE

    Poor in keeping of welders records and repair rates

    Engaging of unqualified welders

    Lack of job / WPS knowledge

    Poor control and guiding welders

    Lack of responsibility and commitment towards quality

    Poor organizing of site protection from wind

    Lack of Quality awareness/ targets

    Lack of prcess controlls

    Poor planning and coordination with fitting group

    Sheet2

    Sheet3

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