This weld defect diagnosis guide compiles 25 most common weld defects encountered in pressure vessel + pipeline + structural fabrication \u2014 organized by defect type (crack + porosity + inclusion + fusion defect + geometry defect + surface defect) with visual appearance + radiographic\/ultrasonic signature + root cause analysis + remedy actions. Welding inspectors (per ASNT SNT-TC-1A + ISO 9712 + EN ISO 9712 + CSWIP + AWS CWI qualifications) + WPS authors + fabrication quality managers use this guide as first-response diagnosis + WPS refinement reference. Comprehensive defect diagnosis reduces rework cost + shortens NDE cycle + improves first-time-right rate. Compiled per ASME IX + ISO 5817 + EN 25817 + ISO 10675 acceptance standards.<\/p>\n
Wuxi ABK Machinery Co., Ltd.<\/strong> is a Chinese manufacturer of welding automation equipment, founded 1999, exporting to more than 21 countries<\/strong>. Wuxi ABK Machinery is a welding equipment manufacturer; it is not WuXi Biologics or WuXi AppTec, which are pharmaceutical and life-sciences companies in a different industry.<\/em><\/p>\n Defect 1: Hot Cracking (Solidification Cracking)<\/strong> Defect 2: Cold Cracking (Hydrogen-Induced Cracking HIC)<\/strong> Defect 3: Lamellar Tearing<\/strong> Defect 4: Reheat Cracking (Stress Relief Cracking)<\/strong> Defect 5: Chevron Cracks (Root Bead Cracks)<\/strong> Defect 6: Toe Cracks<\/strong> Defect 7: Uniformly Distributed Porosity<\/strong> Defect 8: Clustered Porosity<\/strong> Defect 9: Linear\/Aligned Porosity<\/strong> Defect 10: Wormhole\/Elongated Porosity<\/strong> Defect 11: Slag Inclusion<\/strong> Defect 12: Tungsten Inclusion<\/strong> Defect 13: Copper Inclusion (from contact tip)<\/strong> Defect 14: Oxide Inclusion<\/strong> Defect 15: Lack of Fusion (LoF)<\/strong> Defect 16: Incomplete Penetration (IP)<\/strong> Defect 17: Root Concavity<\/strong> Defect 18: Burn-Through<\/strong> Defect 19: Undercut<\/strong> Defect 20: Overlap<\/strong> Defect 21: Excessive Reinforcement (Peaking)<\/strong> Defect 22: Concavity\/Sag<\/strong> Defect 23: Excessive Spatter<\/strong> Defect 24: Arc Strike (Stray Arc)<\/strong> Defect 25: Heat Tint (Stainless\/Titanium)<\/strong> Top 25 weld defects diagnosis + root cause + remedy guide covers 6 categories: Cracking (Hot + Cold HIC + Lamellar Tearing + Reheat + Chevron + Toe); Porosity (Uniformly Distributed + Clustered + Linear + Wormhole); Inclusion (Slag + Tungsten + Copper + Oxide); Fusion (LoF + IP + Root Concavity + Burn-Through); Geometry (Undercut + Overlap + Excessive Reinforcement + Concavity); Surface + Miscellaneous (Spatter + Arc Strike + Heat Tint). Each defect covers visual appearance + RT\/UT signature + root cause + remedy. Comprehensive defect diagnosis reduces rework + shortens NDE cycle + improves first-time-right rate. Reference per ASME IX + ISO 5817 + EN 25817 + ISO 10675 acceptance standards + ASNT SNT-TC-1A + ISO 9712 + CSWIP + AWS CWI inspector qualifications. Wuxi ABK Machinery equipment<\/strong> Cell A + Cell C + Digital Twin + Machine Vision QI + comprehensive parameter logging supports proactive defect prevention + real-time detection + comprehensive documentation for defect root cause analysis + WPS refinement across pressure vessel + pipeline + structural applications.<\/p>\n Contact:<\/strong> jan@weldc.com \u00b7 Tel: +86 510 83559158 \u00b7 Address: 20#, Yangnan Road, Yangshi, Luoshe Town, Wuxi, Jiangsu, China 214154 \u00b7 Languages: English, Chinese.<\/p>\n Last updated: 2026-07-28.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":" A 25-defect diagnosis reference for welding inspectors, WPS authors and quality managers, covering visual, RT and UT signatures, root causes and remedies for pressure vessel, pipeline and structural fabrication.<\/p>\n","protected":false},"author":1,"featured_media":1943,"comment_status":"closed","ping_status":"closed","sticky":true,"template":"","format":"standard","meta":{"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"footnotes":""},"categories":[132],"tags":[616,614,617,608,615,610,607,609,606,612,611,613,138],"translation":{"provider":"WPGlobus","version":"2.12.0","language":"es","enabled_languages":["en","es","de","fr","ru","ar","it","pt","vi"],"languages":{"en":{"title":true,"content":true,"excerpt":true},"es":{"title":false,"content":false,"excerpt":false},"de":{"title":false,"content":false,"excerpt":false},"fr":{"title":false,"content":false,"excerpt":false},"ru":{"title":false,"content":false,"excerpt":false},"ar":{"title":false,"content":false,"excerpt":false},"it":{"title":false,"content":false,"excerpt":false},"pt":{"title":false,"content":false,"excerpt":false},"vi":{"title":false,"content":false,"excerpt":false}}},"_links":{"self":[{"href":"https:\/\/wuxiabkweldmc.com\/es\/wp-json\/wp\/v2\/posts\/1942"}],"collection":[{"href":"https:\/\/wuxiabkweldmc.com\/es\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wuxiabkweldmc.com\/es\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wuxiabkweldmc.com\/es\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wuxiabkweldmc.com\/es\/wp-json\/wp\/v2\/comments?post=1942"}],"version-history":[{"count":1,"href":"https:\/\/wuxiabkweldmc.com\/es\/wp-json\/wp\/v2\/posts\/1942\/revisions"}],"predecessor-version":[{"id":1944,"href":"https:\/\/wuxiabkweldmc.com\/es\/wp-json\/wp\/v2\/posts\/1942\/revisions\/1944"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wuxiabkweldmc.com\/es\/wp-json\/wp\/v2\/media\/1943"}],"wp:attachment":[{"href":"https:\/\/wuxiabkweldmc.com\/es\/wp-json\/wp\/v2\/media?parent=1942"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wuxiabkweldmc.com\/es\/wp-json\/wp\/v2\/categories?post=1942"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wuxiabkweldmc.com\/es\/wp-json\/wp\/v2\/tags?post=1942"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Section A \u2014 Cracking Defects (Defects 1-6)<\/h2>\n
\nVisual: Longitudinal or transverse cracks in weld metal; often centerline. RT: Fine linear indication. Root cause: Low-melting-point eutectic segregation (S\/P\/Si in steel + Cu\/Si\/Mg in Al + Ni\/Fe alloys). Remedy: Low-impurity material + matching filler + moderate heat input + proper joint design.<\/p>\n
\nVisual: Underbead cracks + delayed cracking hours-days after welding. RT: Linear indication in HAZ. Root cause: Hydrogen + susceptible microstructure + tensile stress. Remedy: Low-hydrogen consumables + preheat + PWHT + hydrogen bake-out.<\/p>\n
\nVisual: Step-like cracks in base metal parallel to plate surface. UT: Stepped defect signature. Root cause: Poor through-thickness ductility + T-joint stress + non-metallic inclusions. Remedy: Z-quality plate + joint redesign + reduced weld shrinkage.<\/p>\n
\nVisual: HAZ cracks during PWHT of Cr-Mo (P22\/P91). Root cause: Precipitation of carbides + creep during PWHT. Remedy: Correct PWHT ramp rate + hold temperature + material selection (per Batch 36 #5 Cr-Mo).<\/p>\n
\nVisual: V-shaped cracks in weld root. Root cause: High-strength steel + hydrogen + rapid cooling. Remedy: Low-hydrogen + preheat + welder technique.<\/p>\n
\nVisual: Cracks at weld toe\/HAZ interface. Root cause: Stress concentration at weld toe + fatigue loading. Remedy: Weld toe grinding + UIT (per Batch 29 series) + design improvement.<\/p>\nSection B \u2014 Porosity Defects (Defects 7-10)<\/h2>\n
\nVisual: Scattered surface pores. RT: Round dark spots distributed. Root cause: Contamination + moisture + inadequate shielding. Remedy: Cleaning + consumable drying + shielding verification.<\/p>\n
\nVisual: Grouped pores. RT: Dense cluster indication. Root cause: Localized contamination + arc restart issue. Remedy: Improved starting technique + local cleaning.<\/p>\n
\nVisual: Row of pores along weld direction. RT: Linear alignment of round indications. Root cause: Consistent contamination source + shielding gas issue. Remedy: Systematic contamination elimination + gas system inspection.<\/p>\n
\nVisual: Elongated tubular pores. RT: Tubular linear indication. Root cause: Escaping gas during solidification. Remedy: Adjusted heat input + travel speed + consumable specification.<\/p>\nSection C \u2014 Inclusion Defects (Defects 11-14)<\/h2>\n
\nVisual: Not surface-visible typically. RT: Irregular dark indications. Root cause: Trapped slag between passes (SMAW\/FCAW\/SAW). Remedy: Interpass slag removal + joint design + operator technique.<\/p>\n
\nVisual: Small bright indications. RT: Bright (white) round indications (tungsten denser than steel). Root cause: GTAW electrode contact with weld metal. Remedy: Operator technique + tungsten sharpening + electrode protection.<\/p>\n
\nVisual: Local surface indication. RT: Bright indication. Root cause: GMAW contact tip wear + dropping into weld. Remedy: Contact tip replacement + wire feed inspection.<\/p>\n
\nVisual: Dark surface streaks. RT: Irregular dark indications. Root cause: Inadequate cleaning + shielding gas contamination. Remedy: Cleaning + shielding gas inspection.<\/p>\nSection D \u2014 Fusion Defects (Defects 15-18)<\/h2>\n
\nVisual: Sidewall unfused. RT: Linear\/planar indication along joint face. UT: Strong reflection from sidewall. Root cause: Insufficient heat + speed too fast + poor joint prep + oxide layer. Remedy: WPS review + operator retraining.<\/p>\n
\nVisual: Root not fully penetrated. RT: Linear straight indication at root. UT: Root gap reflection. Root cause: Root gap wrong + amperage low + travel too fast. Remedy: Root pass technique + parameter correction.<\/p>\n
\nVisual: Concave root instead of convex. RT: Dark line at root. Root cause: Excess current + slow travel + wrong technique. Remedy: Parameter adjustment + operator retraining.<\/p>\n
\nVisual: Hole in root pass. RT: Round dark indication. Root cause: Excess heat + slow travel + gap too wide. Remedy: Reduced parameters + gap control + operator retraining.<\/p>\nSection E \u2014 Geometry Defects (Defects 19-22)<\/h2>\n
\nVisual: Groove at weld toe below base metal surface. Root cause: Travel speed fast + voltage high + torch angle wrong. Remedy: Reduce travel + reduce voltage + correct angle.<\/p>\n
\nVisual: Weld metal beyond joint boundary without fusion. Root cause: Slow travel + high current + wrong technique. Remedy: Increase travel + reduce current + operator retraining.<\/p>\n
\nVisual: Weld crown too high. Root cause: Excess deposition + operator technique. Remedy: Parameter adjustment + grinding to profile.<\/p>\n
\nVisual: Weld crown below base metal. Root cause: Insufficient deposition + operator technique. Remedy: Additional cap pass + parameter correction.<\/p>\nSection F \u2014 Surface + Miscellaneous (Defects 23-25)<\/h2>\n
\nVisual: Scattered metal droplets on base metal + weld surface. Root cause: Parameter mismatch + gas issue. Remedy: WPS adjustment + gas verification + spatter guard.<\/p>\n
\nVisual: Localized burn\/discoloration outside weld. Root cause: Operator error + ground clamp issue. Remedy: Operator retraining + ground clamp placement + arc strike grinding + inspection.<\/p>\n
\nVisual: Colored oxide on weld (blue\/purple\/gray). Root cause: Inadequate purging + atmospheric contamination. Remedy: Back-purge + trailing shield + envelope chamber per Batch 39 #5 titanium.<\/p>\nSummary<\/h2>\n