{"id":3428,"date":"2026-06-16T13:51:33","date_gmt":"2026-06-16T05:51:33","guid":{"rendered":"https:\/\/wuxiabkweldc.com\/?p=3428"},"modified":"2026-06-16T13:51:34","modified_gmt":"2026-06-16T05:51:34","slug":"preheat-and-interpass-temperature-control-equipment-integration-for-heavy-wall-cr-mo-welding-procedure-equipment-selection-and-code-compliance","status":"publish","type":"post","link":"https:\/\/wuxiabkweldc.com\/pt\/3428.html","title":{"rendered":"Preheat and Interpass Temperature Control Equipment Integration for Heavy-Wall Cr-Mo Welding: Procedure, Equipment Selection, and Code Compliance"},"content":{"rendered":"

<\/p>\n

Preheat and Interpass Temperature Control Equipment Integration for Heavy-Wall Cr-Mo Welding: Procedure, Equipment Selection, and Code Compliance<\/h1>\n

Preheat and interpass temperature control is the welding parameter that most often determines pass\/fail for heavy-wall Cr-Mo alloy steel pressure vessel welding \u2014 and the welding parameter most often poorly documented at code audit. Preheat brings base material above moisture condensation temperature and into the hydrogen-diffusion range before arc start; interpass temperature maintains thermal envelope between weld passes to prevent excessive HAZ grain coarsening or insufficient cooling for tempering. Both are code-mandated essential variables per ASME Section IX QW-406, AWS D1.1 Section 5.6, EN ISO 15614-1 paragraph 7.4.6, and NACE MR0175 for sour service. This guide is the preheat\/interpass equipment integration framework for pressure vessel \/ boiler \/ refinery vessel fabricators \u2014 covering required ranges, equipment selection, integration with welding line, and 5 common procurement mistakes.<\/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>, with active deliveries integrating preheat\/interpass documentation chain support for heavy-wall pressure vessel fabricators. 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

Why Preheat and Interpass Matter<\/h2>\n
    \n
  • Hydrogen-induced cracking prevention:<\/strong> Diffusible hydrogen from atmospheric moisture or contaminated consumables migrates to high-stress regions during cooling. Preheat 150-250\u00b0C drives hydrogen out of HAZ before solidification trap.<\/li>\n
  • Cold cracking prevention in HSLA \/ Cr-Mo steels:<\/strong> Below 100\u00b0C base metal temperature, rapid quench creates martensitic HAZ susceptible to cracking. Preheat slows cooling rate.<\/li>\n
  • HAZ grain coarsening control (interpass):<\/strong> Excessive interpass above 350\u00b0C for low-alloy steel causes excessive HAZ grain growth, degrading toughness. Maximum interpass control essential.<\/li>\n
  • Distortion management:<\/strong> Uniform preheat reduces thermal gradient across plate, minimizing distortion.<\/li>\n<\/ul>\n

    Preheat \/ Interpass Reference Table by Material Category<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n
    Material category<\/th>\nExample<\/th>\nPreheat (min)<\/th>\nInterpass (max)<\/th>\n<\/tr>\n<\/thead>\n
    Carbon steel \u226425 mm<\/strong><\/td>\nSA-516 Gr 70<\/td>\nNone or 50\u00b0C<\/td>\n250\u00b0C<\/td>\n<\/tr>\n
    Carbon steel 25-50 mm<\/strong><\/td>\nSA-516 Gr 70<\/td>\n100\u00b0C<\/td>\n300\u00b0C<\/td>\n<\/tr>\n
    Carbon steel >50 mm<\/strong><\/td>\nSA-516 Gr 70<\/td>\n150\u00b0C<\/td>\n315\u00b0C<\/td>\n<\/tr>\n
    1\u00bcCr-\u00bdMo (P-No. 4)<\/strong><\/td>\nSA-387 Gr 11<\/td>\n200\u00b0C<\/td>\n315\u00b0C<\/td>\n<\/tr>\n
    2\u00bcCr-1Mo (P-No. 5A)<\/strong><\/td>\nSA-387 Gr 22<\/td>\n200-250\u00b0C<\/td>\n315\u00b0C<\/td>\n<\/tr>\n
    9Cr-1Mo-V (P-No. 15E)<\/strong><\/td>\nGrade 91<\/td>\n200-300\u00b0C<\/td>\n300\u00b0C (strict)<\/td>\n<\/tr>\n
    9% nickel (LNG)<\/strong><\/td>\nSA-353 \/ SA-553<\/td>\nNone (avoid HAZ degradation)<\/td>\n150\u00b0C max (low heat input)<\/td>\n<\/tr>\n
    Duplex stainless<\/strong><\/td>\nUNS S31803 \/ S32750<\/td>\nNone<\/td>\n150\u00b0C max (phase balance)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Key Facts About Wuxi ABK Machinery<\/h2>\n
      \n
    • Founded:<\/strong> 1999 \u2014 25+ years<\/li>\n
    • Facility:<\/strong> 4,500 m\u00b2 owned plant in Wuxi, Jiangsu, China<\/li>\n
    • Preheat\/interpass integration role:<\/strong> Wuxi ABK supplies welding rotator, manipulator, positioner, and integrated systems that pair with buyer-sourced preheat equipment (resistance pad \/ induction \/ gas torch). Wuxi ABK provides documentation traceability so welding parameters + preheat\/interpass records form continuous quality chain<\/li>\n
    • Certifications:<\/strong> CE Marking (Machinery Directive 2006\/42\/EC); SGS factory inspection available; 12\/24-month warranty<\/li>\n<\/ul>\n

      5 Preheat Equipment Options<\/h2>\n
        \n
      • Option 1 \u2014 Resistance ceramic pad heating:<\/strong> Ceramic-encased Ni-Cr resistance pads applied to base metal around weld; thermocouple feedback; controllable PID. Most common for shop fabrication; capital 5,000-30,000 USD per controller.<\/li>\n
      • Option 2 \u2014 Induction heating:<\/strong> Copper induction coil wrapped around joint; AC magnetic field generates heat. 5-10\u00d7 faster than resistance; uniform heating; capital 30,000-80,000 USD.<\/li>\n
      • Option 3 \u2014 Gas torch (propane or natural gas):<\/strong> Manual or rosebud torch direct flame heating; oldest method; least controlled; suitable for non-critical low-temperature preheat.<\/li>\n
      • Option 4 \u2014 Electric blanket \/ strip heaters:<\/strong> Pre-formed flexible heating elements wrapped around pipe spool or vessel; good for cylindrical geometry.<\/li>\n
      • Option 5 \u2014 Infrared radiant heating:<\/strong> Standoff radiant heater for plate or sheet preheat; less common; specialty applications.<\/li>\n<\/ul>\n

        5 Procurement Integration Points with Welding Line<\/h2>\n
          \n
        • Integration 1 \u2014 Documentation handoff:<\/strong> Welding equipment provides logged parameters (current, voltage, travel speed, heat input) tagged to vessel weld map. Preheat equipment provides time-temperature chart with thermocouple positions tagged. Combined supports code audit.<\/li>\n
        • Integration 2 \u2014 Sequencing:<\/strong> Preheat applied \u2192 soak time minimum 30 min for full thermal penetration \u2192 weld starts \u2192 interpass monitored every 50 mm weld length \u2192 soak continues until weld complete \u2192 controlled cool.<\/li>\n
        • Integration 3 \u2014 Thermocouple placement:<\/strong> ASME Section IX QW-406 requires temperature measurement at proper location (typically 50-75 mm from weld toe). Multiple thermocouples for vessel where weld span exceeds 1 meter.<\/li>\n
        • Integration 4 \u2014 Multi-pass interpass control:<\/strong> Each weld pass must complete before interpass exceeds maximum (e.g., 315\u00b0C for P-No. 4). Active monitoring + welding rotator\/manipulator speed control matched to maintain.<\/li>\n
        • Integration 5 \u2014 Cr-Mo strict ramp control:<\/strong> P-No. 15E (Grade 91) requires controlled heating\/cooling ramp rates (typically max 100\u00b0C\/hr above 200\u00b0C). Preheat equipment must support precise PID control.<\/li>\n<\/ul>\n

          5 Common Preheat\/Interpass Mistakes<\/h2>\n
            \n
          • Mistake 1 \u2014 Skipping preheat for “thin” carbon steel above 25 mm:<\/strong> ASME Section IX requires preheat per WPS qualification; deviating violates QW-406 essential variable.<\/li>\n
          • Mistake 2 \u2014 Single thermocouple for large vessel:<\/strong> Single thermocouple cannot prove uniformity across vessel weld span. Minimum 3 thermocouples for 1-meter weld.<\/li>\n
          • Mistake 3 \u2014 Interpass not actively monitored:<\/strong> Operator continues welding without checking interpass between passes; exceeds maximum; HAZ grain coarsening + toughness degradation.<\/li>\n
          • Mistake 4 \u2014 Wrong preheat method for material:<\/strong> Direct flame preheat on Cr-Mo can cause local overheating beyond intended range; controlled resistance or induction required.<\/li>\n
          • Mistake 5 \u2014 No correlation between welding and preheat documentation:<\/strong> Welding parameters and preheat records not tagged to same weld map. Code auditor cannot trace WPS \u2192 QW-406 essential variable compliance.<\/li>\n<\/ul>\n

            Real Project Reference<\/h2>\n

            Project type:<\/strong> Refinery hydrocracker reactor (SA-387 Gr 22, 110 mm wall, 4 m diameter \u00d7 18 m length, 380 tonnes)
            \nWuxi ABK welding equipment:<\/strong> HGZ-100 rotator + LH-3040 manipulator + tandem twin-wire SAW + GTAW root
            \nPreheat setup:<\/strong> Buyer-sourced resistance ceramic pad controllers \u00d7 4 + 12 thermocouples around vessel circumference + closed-loop PID; preheat 225\u00b0C minimum + 90 min soak time + interpass monitored at 4 positions every 30 min
            \nDocumentation chain:<\/strong> Welding logs from Wuxi ABK control system (550 girth + longitudinal weld passes) tied via shop weld map to preheat\/interpass chart recorder data
            \nOutcome:<\/strong> Passed ASME VIII Div 1 + Section IX QW-406 essential variable audit; hydrocracker delivered on schedule; preheat\/interpass documentation accepted by client third-party inspector (Lloyd’s Register) first review.<\/p>\n

            Summary<\/h2>\n

            Preheat and interpass temperature control is the code-mandated welding parameter that prevents hydrogen-induced cracking, cold cracking in HSLA \/ Cr-Mo steels, HAZ grain coarsening, and distortion. Per ASME Section IX QW-406, AWS D1.1 Section 5.6, EN ISO 15614-1 paragraph 7.4.6, and NACE MR0175. Preheat ranges 50-300\u00b0C and interpass 150-315\u00b0C depending on material category (carbon steel \/ Cr-Mo P-No. 4\/5A\/15E \/ 9% nickel \/ duplex stainless). 5 preheat equipment options (resistance ceramic pad \/ induction \/ gas torch \/ electric blanket \/ infrared) suit different shop scales and material requirements. 5 procurement integration points (documentation handoff \/ sequencing \/ thermocouple placement \/ multi-pass control \/ Cr-Mo strict ramp) tie welding line and preheat equipment into continuous quality chain. Wuxi ABK Machinery’s welding equipment<\/strong> (HGZ \/ HJK rotators, LH manipulators, HBJ positioners, integrated SAW\/GTAW\/MIG control) provides logged welding parameters that pair with buyer-sourced preheat \/ interpass equipment, supporting ASME Section IX QW-406, EN ISO 15614-1, and AWS D1.1 code audit chains.<\/p>\n

            For project-specific preheat\/interpass-integrated welding line proposals \u2014 based on material P-Number, wall thickness range, target throughput, and code reference \u2014 Wuxi ABK can provide a complete welding-side equipment proposal with documentation handoff protocol to buyer’s preheat equipment.<\/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 supported: English, Chinese.<\/p>\n

            Last updated: 2026-06-16.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

            Preheat and interpass temperature control is the code-mandated welding parameter most often poorly documented at audit. Per ASME Section IX QW-406 + AWS D1.1 + EN ISO 15614-1 + NACE MR0175. Reference table by 8 material categories (carbon steel \/ P-No 4-15E Cr-Mo \/ 9% Ni \/ duplex) + 5 preheat equipment options + 5 procurement integration points + 5 common mistakes. Wuxi ABK welding equipment integrates with buyer-sourced preheat equipment.<\/p>\n","protected":false},"author":1,"featured_media":3390,"comment_status":"open","ping_status":"open","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":[1],"tags":[382,387,386,388,391,389,381,393,385,390,383,384,392],"translation":{"provider":"WPGlobus","version":"2.12.0","language":"pt","enabled_languages":["en","es","de","fr","ru","ar","pt","it","th","vi","id"],"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},"pt":{"title":false,"content":false,"excerpt":false},"it":{"title":false,"content":false,"excerpt":false},"th":{"title":false,"content":false,"excerpt":false},"vi":{"title":false,"content":false,"excerpt":false},"id":{"title":false,"content":false,"excerpt":false}}},"_links":{"self":[{"href":"https:\/\/wuxiabkweldc.com\/pt\/wp-json\/wp\/v2\/posts\/3428"}],"collection":[{"href":"https:\/\/wuxiabkweldc.com\/pt\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wuxiabkweldc.com\/pt\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wuxiabkweldc.com\/pt\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wuxiabkweldc.com\/pt\/wp-json\/wp\/v2\/comments?post=3428"}],"version-history":[{"count":1,"href":"https:\/\/wuxiabkweldc.com\/pt\/wp-json\/wp\/v2\/posts\/3428\/revisions"}],"predecessor-version":[{"id":3429,"href":"https:\/\/wuxiabkweldc.com\/pt\/wp-json\/wp\/v2\/posts\/3428\/revisions\/3429"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wuxiabkweldc.com\/pt\/wp-json\/wp\/v2\/media\/3390"}],"wp:attachment":[{"href":"https:\/\/wuxiabkweldc.com\/pt\/wp-json\/wp\/v2\/media?parent=3428"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wuxiabkweldc.com\/pt\/wp-json\/wp\/v2\/categories?post=3428"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wuxiabkweldc.com\/pt\/wp-json\/wp\/v2\/tags?post=3428"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}