weld defects 2
DESCRIPTION
notesTRANSCRIPT
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Weld Defects
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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.
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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
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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)
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General Reasons for Defects
Lack of Know-howWelding Process CharacteristicsBase metal CompositionDefective welding filler metalJoint designWelding Environment (Wind, fit-up, Temperature etc.)
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Defects involving inadequate bondingLack of FusionDue to improper manipulation of electrodeIncorrect position of electrodeLow welding currentToo rapid arc advanceImproper joint fit-up
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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
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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
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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
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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
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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
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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
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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.
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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.
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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.
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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.
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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.
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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.
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Quality Of WeldingWelding Defects (Root Cause Analysis)
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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
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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
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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
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CAUSE EFFECT (FISHBONE) DIAGRAMWELD DEFECT ROOT CAUSE ANALYSIS
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&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
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Sheet3
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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
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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
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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
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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
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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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