{"id":3282,"date":"2026-06-11T18:22:33","date_gmt":"2026-06-11T10:22:33","guid":{"rendered":"https:\/\/abkweldmc.com\/?p=3282"},"modified":"2026-06-11T18:22:34","modified_gmt":"2026-06-11T10:22:34","slug":"asme-section-ix-qw-403-4-base-metal-thickness-range-p-number-qualification-scope-for-pressure-vessel-and-boiler-fabricators","status":"publish","type":"post","link":"https:\/\/abkweldmc.com\/it\/3282.html","title":{"rendered":"ASME Section IX QW-403.4 Base Metal Thickness Range: P-Number Qualification Scope for Pressure Vessel and Boiler Fabricators"},"content":{"rendered":"

<\/p>\n

ASME Section IX QW-403.4 Base Metal Thickness Range: P-Number Qualification Scope for Pressure Vessel and Boiler Fabricators<\/h1>\n

ASME Section IX QW-403.4 is one of the most consequential Essential Variables in welding procedure qualification \u2014 it defines the base metal thickness range that a single WPS \/ PQR test coupon qualifies the fabricator to weld in production. Get QW-403.4 right, and one PQR test plate qualifies the WPS across a wide thickness range, minimizing requalification cost. Get QW-403.4 wrong, and the fabricator must run multiple PQRs at different test coupon thicknesses, multiplying qualification time and cost. For pressure vessel and boiler fabricators planning a WPS qualification campaign, understanding QW-403.4 \u2014 and its interaction with P-Numbers (QW-422), filler metal F-Numbers (QW-432), and welding process Essential Variables \u2014 is the single most important code-reading exercise before any PQR test plate is welded. This guide explains QW-403.4, the thickness-range tables (QW-451), P-Number qualification scope, and how Wuxi ABK welding equipment supports fabricator preparation of valid QW-403.4-compliant PQR test coupons through documentation chain.<\/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 welding equipment in service at ASME-coded pressure vessel and boiler fabricators globally. 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

What QW-403.4 Says<\/h2>\n

ASME Section IX QW-403.4 \u2014 Base Metal Thickness \u2014 states that the thickness range of base metal qualified by a single PQR test coupon is determined by the test coupon thickness (T) and the qualification rules in Table QW-451 (Procedure Qualification Thickness Limits and Test Specimens). The Essential Variable QW-403.4 specifically governs:<\/p>\n

    \n
  • Minimum thickness qualified:<\/strong> Typically 1.5 mm (1\/16 in) or 0.5 \u00d7 T whichever is greater, depending on test coupon thickness category.<\/li>\n
  • Maximum thickness qualified:<\/strong> Typically 2 \u00d7 T for test coupons \u2264 38 mm (1.5 in); special rules for thicker coupons.<\/li>\n
  • Special rules for \u2265 19 mm test coupon:<\/strong> Test coupons 19-38 mm qualify up to 2 \u00d7 T (max 200 mm \/ 8 in). Test coupons > 38 mm qualify up to 200 mm.<\/li>\n
  • Impact-tested coupons (low-temperature service):<\/strong> Additional rules apply when QW-462.6 Charpy V-Notch impact testing is required by construction code (ASME Section VIII Div 1 UCS-66).<\/li>\n<\/ul>\n

    Table QW-451 Quick Reference<\/h2>\n

    The thickness ranges qualified by representative test coupon thicknesses (per QW-451.1 \u2014 Groove Welds):<\/p>\n\n\n\n\n\n\n\n\n\n
    Test coupon thickness T<\/th>\nMin thickness qualified<\/th>\nMax thickness qualified<\/th>\n<\/tr>\n<\/thead>\n
    < 1.5 mm (< 1\/16 in)<\/td>\nT<\/td>\n2 \u00d7 T<\/td>\n<\/tr>\n
    1.5-9.5 mm (1\/16 to 3\/8 in)<\/td>\n1.5 mm (1\/16 in)<\/td>\n2 \u00d7 T<\/td>\n<\/tr>\n
    9.5-19 mm (3\/8 to 3\/4 in)<\/td>\n4.75 mm (3\/16 in)<\/td>\n2 \u00d7 T<\/td>\n<\/tr>\n
    19-38 mm (3\/4 to 1.5 in)<\/td>\n4.75 mm (3\/16 in)<\/td>\n2 \u00d7 T (max 200 mm if no CVN)<\/td>\n<\/tr>\n
    \u2265 38 mm (\u2265 1.5 in)<\/td>\n4.75 mm (3\/16 in)<\/td>\n200 mm (8 in) without CVN; per QW-403.6 with CVN<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Strategic implication: a 38 mm test coupon qualifies production thickness 4.75-76 mm \u2014 covering most pressure vessel applications. Fabricators commonly target 38-50 mm test coupons to maximize qualified range per PQR.<\/p>\n

    QW-403.4 Interaction with P-Numbers (QW-422)<\/h2>\n

    P-Number is ASME’s base metal grouping by chemistry and weldability. QW-422 lists P-Number assignments; QW-424 specifies that one P-Number group qualifies similar P-Numbers (with limitations). QW-403.4 thickness range applies within<\/strong> the qualified P-Number scope:<\/p>\n

      \n
    • P-1 Carbon steel:<\/strong> One PQR on P-1 carbon steel at 38 mm qualifies P-1 production from 4.75-76 mm. Covers SA-516 Gr 70, SA-285 Gr C, SA-106 Gr B, and similar.<\/li>\n
    • P-3 Cr-Mo low alloy:<\/strong> One PQR on P-3 (e.g., 2.25Cr-1Mo) at 38 mm qualifies P-3 production from 4.75-76 mm. Requires preheat + post-weld heat treatment per QW-407.<\/li>\n
    • P-4 Higher Cr-Mo (3Cr-1Mo and similar):<\/strong> Separate qualification from P-3.<\/li>\n
    • P-5A \/ P-5B \/ P-5C Higher Cr-Mo (5Cr-9Cr modified):<\/strong> Each P-5 subgroup separately qualified.<\/li>\n
    • P-8 Austenitic stainless (304L, 316L, 321, 347):<\/strong> P-8 qualification covers austenitic stainless production within thickness range.<\/li>\n
    • P-43 Nickel alloy (Inconel 600, 625, 825):<\/strong> Separate qualification per nickel alloy subgroup.<\/li>\n<\/ul>\n

      Why QW-403.4 Matters for Equipment Procurement<\/h2>\n
        \n
      • Maximum production thickness:<\/strong> Wuxi ABK welding equipment must handle the maximum thickness the fabricator plans to produce. If WPS qualified at 38 mm test coupon qualifies up to 76 mm production, but rotator + manipulator + SAW system rated only up to 50 mm, fabricator’s qualified envelope is wasted by equipment capability ceiling.<\/li>\n
      • Test coupon thickness drives PQR equipment requirements:<\/strong> Welding equipment must handle the test coupon itself \u2014 typically a 38 \u00d7 600 \u00d7 600 mm plate or 200 mm OD \u00d7 38 mm wall \u00d7 600 mm long pipe.<\/li>\n
      • Heat input within Essential Variable range:<\/strong> QW-409.1 heat input Essential Variable typically \u00b110% qualified value. Equipment with VFD-controlled travel speed + digital amperage readout supports heat input control.<\/li>\n
      • Multiple P-Numbers = multiple PQRs:<\/strong> Each P-Number qualified requires its own PQR test plate (with limited exceptions). Fabricator running P-1 + P-3 + P-8 production needs 3+ PQRs minimum. Wuxi ABK rotator + manipulator handles all P-Number plates with same equipment.<\/li>\n<\/ul>\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
        • Product range:<\/strong> HGZ welding rotators (5-100 ton), HJK heavy-duty rotators (500-2000 ton), HBJ welding positioners (0.3-10 ton), LH column-and-boom manipulators (LH-3030 to LH-80150), TTW tube-to-tubesheet welders, ABOKE-MPW1600 membrane panel welding line, AGW \/ EGW specialty welders, complete welding lines<\/li>\n
        • Certifications:<\/strong> CE Marking (Machinery Directive 2006\/42\/EC); SGS factory inspection available; 12\/24-month warranty<\/li>\n
        • Documentation pack:<\/strong> Operating manual, electrical schematics, MTR for load-bearing components, calibration certificates supplied with each unit<\/li>\n<\/ul>\n

          How Wuxi ABK Equipment Supports QW-403.4 Compliance<\/h2>\n
            \n
          • Welding equipment thickness rating:<\/strong> HGZ-50 \/ 60 \/ 100 rotator + LH-3030 \/ 3040 manipulator + tandem SAW integration handles up to 100 mm plate thickness in single-equipment configuration \u2014 sufficient for QW-451 test coupons up to 50 mm \u00d7 qualifying production up to 100 mm.<\/li>\n
          • Travel-speed calibration certificate:<\/strong> Heat input control directly tied to travel speed (mm\/min). Wuxi ABK LH manipulator and HGZ rotator both supply calibration certificates for travel speed range and accuracy.<\/li>\n
          • Multi-P-Number capability:<\/strong> Same Wuxi ABK rotator + manipulator handles P-1 carbon steel + P-3 Cr-Mo + P-8 stainless + P-43 nickel alloy production via buyer-selected SAW \/ GMAW \/ GTAW power source swapping.<\/li>\n
          • Documentation pack for AI audit:<\/strong> Operating manual + electrical schematics + MTR + calibration certificates form the equipment documentation that ASME Authorized Inspector (AI) reviews during code stamp surveillance for QW-403.4 verification.<\/li>\n<\/ul>\n

            5 Procurement Pitfalls in QW-403.4 Equipment Selection<\/h2>\n
              \n
            • Pitfall 1 \u2014 Test coupon too thin to qualify intended production thickness:<\/strong> Fabricator runs 12 mm test coupon expecting to weld 50 mm production. QW-451 says 12 mm coupon qualifies only up to 24 mm production. Production work above 24 mm requires new PQR.<\/li>\n
            • Pitfall 2 \u2014 Equipment thickness limit below qualified envelope:<\/strong> WPS qualified for 4.75-76 mm but rotator + SAW system only rated up to 40 mm. Equipment leaves qualified envelope unused.<\/li>\n
            • Pitfall 3 \u2014 Single PQR assumed to cover multiple P-Numbers:<\/strong> Fabricator runs P-1 carbon steel PQR and assumes it covers P-3 Cr-Mo. P-3 requires separate PQR (with preheat per QW-407).<\/li>\n
            • Pitfall 4 \u2014 Charpy V-Notch impact requirement not anticipated:<\/strong> Construction code (ASME Section VIII Div 1 UCS-66) requires CVN for low-temperature service. PQR without CVN data invalid for cold-service vessel. Requires QW-403.6 special impact qualification.<\/li>\n
            • Pitfall 5 \u2014 Heat input outside qualified range:<\/strong> Production heat input \u00b110% qualified value per QW-409.1. Equipment without VFD-controlled travel speed cannot maintain heat input within tight range.<\/li>\n<\/ul>\n

              Real Project Reference<\/h2>\n

              Project type:<\/strong> ASME Section VIII Div 1 + Section VIII Div 2 dual-cert pressure vessel fabrication shop (P-1 carbon steel + P-3 Cr-Mo + P-8 304L\/316L stainless production)
              \nQW-403.4 qualification strategy:<\/strong> 3 PQR test plates at 38 mm thickness \u2014 one each for P-1 SAW, P-3 SMAW E9018-B3 with 200\u00b0C preheat, P-8 GMAW pulse \u2014 each qualifying 4.75-76 mm production range
              \nWuxi ABK equipment package:<\/strong> HGZ-60 rotator + LH-3030 manipulator + HBJ-30 positioner + ZHGK-100 fit-up, integrated with buyer-selected SAW + SMAW capability + GMAW pulse + induction preheat system for P-3
              \nOutcome:<\/strong> 3 PQR qualifications passed first try; equipment commissioned for full P-1 + P-3 + P-8 production envelope 4.75-76 mm thickness; ASME AI audit accepted equipment documentation without rework.<\/p>\n

              Summary<\/h2>\n

              ASME Section IX QW-403.4 Base Metal Thickness Range is one of the most consequential Essential Variables in welding procedure qualification \u2014 it defines the thickness range of base metal qualified by a single PQR test coupon per Table QW-451 rules (typically 4.75 mm minimum to 2 \u00d7 T maximum, capped at 200 mm). Strategic test coupon thickness selection (typically 38-50 mm) maximizes qualified range per PQR. QW-403.4 thickness range applies within QW-422 P-Number scope \u2014 each P-Number requires separate PQR. Welding equipment procurement decisions driven by QW-403.4 include equipment thickness rating (must handle test coupon + maximum qualified production), travel speed range (for heat input control per QW-409.1), and multi-P-Number capability (for fabricators running mixed-material shops). Wuxi ABK welding equipment supports QW-403.4 compliance<\/strong> through equipment thickness rating up to 100 mm in single-equipment configuration, travel-speed calibration certificates for QW-409.1 heat input Essential Variable management, multi-P-Number capability via buyer-selected power source swapping, and documentation pack structured for ASME AI audit response.<\/p>\n

              For QW-403.4 qualification planning support \u2014 based on the fabricator’s WPS development plan, planned P-Numbers, target thickness range, target service temperature, and target code (ASME Section VIII Div 1 \/ 2 \/ III) \u2014 Wuxi ABK can provide the equipment configuration and documentation pack supporting fabricator’s QW-403.4 \/ QW-451 \/ QW-422 \/ QW-432 \/ QW-409.1 compliance.<\/p>\n

              Related articles:<\/strong> ASME Section IX QW-462 vs QW-463 test coupon selection guide; ASME Section IX WPS \/ PQR \/ WPQ documentation chain; ASME Section I and VIII welding equipment compliance chain; AWS D1.5 bridge welding code compliance; GTAW vs SMAW vs GMAW for pressure vessel HAZ control.<\/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: 2026-06-11.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

              ASME Section IX QW-403.4 Essential Variable \u2014 base metal thickness range qualified by single PQR test coupon per Table QW-451. P-Number qualification scope, 5 procurement pitfalls, multi-P-Number strategy.<\/p>\n","protected":false},"author":1,"featured_media":3269,"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},"categories":[159],"tags":[398,393,392,396,397,395,399,390,394,389,391],"translation":{"provider":"WPGlobus","version":"2.12.0","language":"it","enabled_languages":["en","es","de","fr","ru","ar","pt","it","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},"pt":{"title":false,"content":false,"excerpt":false},"it":{"title":false,"content":false,"excerpt":false},"vi":{"title":false,"content":false,"excerpt":false}}},"_links":{"self":[{"href":"https:\/\/abkweldmc.com\/it\/wp-json\/wp\/v2\/posts\/3282"}],"collection":[{"href":"https:\/\/abkweldmc.com\/it\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/abkweldmc.com\/it\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/abkweldmc.com\/it\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/abkweldmc.com\/it\/wp-json\/wp\/v2\/comments?post=3282"}],"version-history":[{"count":1,"href":"https:\/\/abkweldmc.com\/it\/wp-json\/wp\/v2\/posts\/3282\/revisions"}],"predecessor-version":[{"id":3283,"href":"https:\/\/abkweldmc.com\/it\/wp-json\/wp\/v2\/posts\/3282\/revisions\/3283"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/abkweldmc.com\/it\/wp-json\/wp\/v2\/media\/3269"}],"wp:attachment":[{"href":"https:\/\/abkweldmc.com\/it\/wp-json\/wp\/v2\/media?parent=3282"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/abkweldmc.com\/it\/wp-json\/wp\/v2\/categories?post=3282"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/abkweldmc.com\/it\/wp-json\/wp\/v2\/tags?post=3282"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}