Lesson 1Distortion prevention: stitch welds, backstep technique, clamping, low heat input processes, balanced welding sequence, and pre-bending allowanceThis section explains how to prevent distortion using stitch welds, backstep techniques, clamping, low heat input processes, balanced welding sequences, and pre-bending allowances tailored to joint geometry and material thickness.
Stitch welding and skip sequence planningBackstep technique for shrinkage controlUse of clamps, strongbacks, and fixturesLow heat input processes and passesPre-bending and presetting componentsLesson 2How to prevent hot cracking: filler selection, heat input control, bead sequencing, and use of stabilized/low-carbon fillersThis section explains preventive measures against hot cracking, focusing on filler metal selection, heat input control, bead sequencing, and the use of stabilized or low-carbon fillers to manage solidification mode and residual stresses.
Selecting fillers for proper ferrite balanceUsing stabilized and low-carbon filler gradesHeat input limits and interpass temperatureBead sequencing to spread shrinkagePreheat and cooling control for crack resistanceLesson 3Repair/mitigation of distortion: mechanical straightening, local heating, re-welding strategy, acceptance criteria and rework planningThis section addresses repair and mitigation of distortion, covering mechanical straightening, controlled local heating, strategic re-welding, and evaluation against acceptance criteria to decide between correction, rework, or concession.
Measuring distortion and recording baselinesMechanical jacking, pressing, and peeningLocal heat straightening proceduresRe-welding strategies to counter shrinkageAcceptance criteria and repair documentationLesson 4Distortion and warping mechanisms in circumferential shells and brackets: longitudinal and transverse shrinkage, uneven heat distributionThis section explores distortion and warping mechanisms in circumferential shells and brackets, focusing on longitudinal and transverse shrinkage, uneven heat distribution, and how joint layout and welding sequence affect final geometry.
Longitudinal shrinkage around circumferencesTransverse shrinkage and ovality in shellsBracket-induced local bending and twistHeat input distribution around the jointPredicting distortion from weld size and pathLesson 5Three-pronged prevention methods for fusion/penetration defects: joint prep, parameter control, and techniqueThis section details how joint preparation, parameter selection, and welder technique interact to prevent lack of fusion and penetration defects, emphasizing repeatable setups, verification steps, and documentation of qualified procedures.
Joint design, bevel angle, and root face selectionRoot opening, land, and fit-up tolerancesCurrent, voltage, and travel speed windowsArc length, electrode angle, and manipulationVerification of fusion with visual and NDT checksLesson 6Repair and post-weld remediation of porosity: grinding, re-weld, vacuum backing if needed, and re-inspectionThis section details post-weld remediation of porosity, including grinding out affected areas, controlled re-welding, optional use of backing or vacuum support, and final re-inspection to verify compliance with quality standards.
Identifying porosity extent with NDTGrinding and blending porous regionsRe-welding techniques to avoid repeat poresUse of backing bars or vacuum assistanceFinal inspection, records, and traceabilityLesson 7Hot cracking (solidification cracking/intergranular cracking): root causes in stainless (composition, high sulfur/phosphorus, restraint, heat input)This section analyzes hot cracking mechanisms in stainless welds, linking composition, impurity levels, joint restraint, and heat input to solidification and intergranular cracking, with emphasis on recognizing risk conditions in production.
Solidification cracking in austenitic stainless weldsIntergranular hot cracking along grain boundariesEffects of sulfur and phosphorus impuritiesInfluence of joint restraint and fit-upHeat input, cooling rate, and crack susceptibilityLesson 8Repair strategies for hot cracking: stop-drill and gouge, re-weld with controlled heat input, post-weld cleaning and inspectionThis section covers structured repair of hot cracking, including stop-drilling, gouging or grinding, controlled re-welding, and thorough post-weld cleaning and inspection to ensure cracks are fully removed and do not reinitiate.
Crack mapping, marking, and extent assessmentStop-drill techniques to arrest crack growthGouging and grinding to sound metalControlled re-weld with adjusted heat inputPost-weld cleaning, NDT, and documentationLesson 9Lack of fusion and lack of penetration: how they occur on circumferential butt joints and filletsThis section clarifies how lack of fusion and penetration occur in circumferential butt joints and fillet welds, linking joint geometry, access, position, and technique to typical defect locations and inspection focus areas.
Root fusion problems in pipe butt weldsSidewall fusion loss in narrow groovesLack of penetration in double-sided weldsFillet weld throat and leg size issuesInspection focus zones on circumferential weldsLesson 10Prevention strategies for porosity: cleaning, gas control, travel technique, purge integrity, and weld pool manipulationThis section presents practical strategies to prevent porosity, emphasizing cleaning methods, gas selection and flow control, travel technique, purge integrity checks, and weld pool manipulation to allow gases to escape before solidification.
Pre-weld cleaning and degreasing proceduresShielding gas composition and flow settingsTorch angle and travel speed for gas escapePurge dams, venting, and leak testingStringer versus weave beads for porosity controlLesson 11Repair methods for lack of fusion/penetration: grind-out, re-weld procedures, preheat/interpass controls, and NDT acceptance limitsThis section outlines repair methods for lack of fusion and penetration, including defect removal by grinding, qualified re-weld procedures, preheat and interpass controls, and application of NDT acceptance criteria before final sign-off.
Locating fusion defects with UT and radiographyGrinding and carbon arc gouging techniquesRe-weld parameters for full penetrationPreheat and interpass temperature controlApplying code NDT acceptance limitsLesson 12Porosity causes in stainless welds: contamination, inadequate shielding, purge failures, and entrapment of gasesThis section examines porosity formation in stainless welds, relating contamination, inadequate shielding, purge failures, and gas entrapment to pore morphology, and highlighting how joint design and position influence gas escape paths.
Surface contaminants and moisture sourcesShielding gas flow, turbulence, and draftsBack purging failures in root passesGas entrapment in deep or narrow groovesRecognizing porosity patterns in radiography
