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CSWIP 3.2 Summary




CSWIP 3.2 – Senior Welding Inspector Study Notes


🔥 HEAT TREATMENT

Temperature Classification

  • Upper Critical Temperature (880–920°C):

    • Processes: Annealing, Normalizing, Quenching

  • Lower Critical Temperature (<730°C):

    • Processes: Preheating, Post Weld Heat Treatment (PWHT), Tempering, Recovery

PWHT (Post Weld Heat Treatment)

  • Local PWHT: Heat treatment of a localized section (e.g., weld area)

  • Global PWHT: Full-component or equipment-wide heat treatment

  • Purpose of Soaking (Holding Time):

    • Reduces yield strength temporarily

    • Reduces residual stresses

    • Enhances ductility and toughness

    • May lead to partial increase in yield strength after cooling

  • Effects:

    • Improves toughness

    • Decreases hardness and tensile strength

    • Significantly reduces but does not completely eliminate residual stresses

Tempering

  • Always follows quenching

  • Aims to reduce brittleness and increase toughness by controlled reheating


🔧 WELDING PROCESSES AND CONSUMABLES

MMAW (Manual Metal Arc Welding) – Process 111

  • Electrode Types:

    • Cellulosic (0, 1): No baking required

    • Rutile (2, 3, 4): Dried at 90–120°C

    • Basic (5, 6, 8): Baked at 350°C, then kept at 150°C for up to 4 hours before use

TIG (GTAW) – Process 141

  • Lowest hydrogen content process

  • Defects:

    • Slope-in: Tungsten inclusions

    • Slope-out: Crater (shrinkage) cracks

  • Electrodes:

    • Zirconiated: Used with Aluminum (AC current only)

    • Thoriated: Suitable for Carbon Steel (DCEN)

MIG/MAG (GMAW) – Processes 131/135

  • Transfer Modes:

    • Dip Transfer: Thin plate; prone to lack of fusion and spatter

    • Pulse Transfer: Suitable for all positions and small weld pools

    • Spray Transfer: Thick plates in flat/horizontal positions; clean arc

    • Globular Transfer: High distortion and spatter; used with CO₂

SAW (Submerged Arc Welding) – Process 121

  • Flux Types:

    • Fused: Hygroscopic; no baking required

    • Agglomerated: Moisture-sensitive; must be baked; allows alloying element additions

  • High deposition rate, low distortion, but high dilution

Current and Polarity

  • DC Electrode Positive (DCEP): MMAW, FCAW, GMAW, SAW – deepest penetration

  • DC Electrode Negative (DCEN): Used in GTAW; lower penetration, high deposition rate

  • AC: Balanced arc; commonly used for Aluminum

Arc Blow Control

  • Avoid arc blow by switching from DC to AC

  • Inverter: Converts DC to AC

  • Rectifier: Converts AC to DC

Power Source Characteristics

  • Flat Characteristic (Constant Voltage): Wire feed speed controls current; used for MIG, MAG, SAW

  • Drooping Characteristic (Constant Current): Manual control of arc length; used in TIG, MMAW


⚙️ WELD FRACTURE TYPES

  1. Ductile Fracture

    • Large plastic deformation

    • 45° shear surface; rough, torn appearance

  2. Brittle Fracture

    • Occurs at low temperature

    • Rapid propagation, smooth and flat fracture surface

    • Crystalline appearance

  3. Fatigue Fracture

    • Caused by cyclic loading below yield stress

    • Chevron marks and beach marks visible

    • Initiates from defects, propagates slowly


🧪 DESTRUCTIVE TESTING

Types of Tests

  • Quantitative: Tensile, impact, hardness, CTOD

  • Qualitative: Bend tests, macro/micro examination

Applications

  • WPS Qualification: Transverse tensile, bend, CVN, macro, micro, hardness

  • Welder Qualification: Fillet weld fracture, butt weld nick-break

  • Consumables Testing: Full tensile tests

Tensile Test

  • Measures UTS, YS, elongation (typically over 50mm gauge length)

  • Transverse tensile: Strength of weld metal

  • Z-direction: Through-thickness properties

Bend Test

  • 180° bend over a former (typically 4T)

  • Side Bend: ≥13 mm thickness

  • Face/Root Bend: <13 mm thickness

Hardness Test

  • Rockwell (diamond cone) not permitted on weld metal due to risk of crack initiation

Impact Test

  • CVN and CTOD to assess toughness, transition temperature

  • CTOD: Quantitative toughness test

Macro & Micro Examination

  • Macro: 5x–10x magnification; surface defects

  • Micro: 100x–1000x; microstructure and inclusions


🔩 JOINT DESIGN

  • Single-Side V/Bevel: High distortion, more filler, requires skilled welder

  • Double-Side V/U: Lower distortion, reduced filler

  • U/J Grooves: Risk of solidification cracking due to high depth:width ratio

  • Set-on Nozzle: Risk of lamellar tearing, poor access for UT

  • Set-out Nozzle: Safer design, better UT access

  • Narrow groove angle increases risk of lack of fusion


🧱 WELDABILITY – ISO 1011-2

Solidification Cracking (Hot Cracks)

  • Occurs along centerline during solidification

  • Causes: High tensile stress, high sulfur content, poor joint design

  • Detection: VT, PT, UT, RT

Hydrogen Induced Cold Cracking (HICC)

  • Occurs in HAZ or weld metal

  • Requires:

    • Hydrogen

    • Stress

    • Susceptible microstructure (martensite, high CEV)

    • Temperature

  • Austenitic SS not susceptible

Lamellar Tearing

  • Base metal only, subsurface cracking

  • Common in set-on nozzles and T-joints

  • Best detected by UT with 0° probe


🛠 WELD REPAIR

  • Cut-out: Required when:

    • Crack defect

    • Second-time repair

    • Affects >25% of weld circumference

  • Repair Procedure: Must be reviewed and approved before execution




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