GB_T 9948-2025 Seamless steel pipes for petrochemical and chemical plants

GB/T9948-2025 was drafted in accordance with the provisions of GB/T1.1-2020 \"Guidelines for standardization work – Part 1: Structure and drafting rules for standard documents\". This document replaces GB/T9948-2013 \"Seamless steel tubes for petroleum cracking\", GB/T6479-2013 \"Seamless steel tubes for high-pressure fertilizer equipment\", GB/T24592-2009 \"High-pressure alloy steel tubes for polyethylene\", and GB/T33167-2016 \"Stainless steel seamless tubes for industrial furnaces in petrochemical hydrogenation units\". This document is based primarily on GB/T9948-2013, and incorporates the contents of GB/T6479-2013, GB/T24592-2009, and GB/T33167-2016. Compared with GB/T9948-2013, apart from structural adjustments, content integration, and editorial changes, the main technical differences are as follows: a) The ordering details have been revised, with the addition of information regarding the delivery status (see Chapter 5; Chapter 4 in the 2013 version) ； b) The manufacturing method of stainless steel pipes was changed (see 6.3.2, 6.2.3 in the 2013 edition) ； c) The manufacturing method for 35CrNi3MoV steel pipes for polyethylene was added (see 6.3.3) ； d) The delivery condition of the stainless steel pipe was changed (see 6.4.2, 6.3 in the 2013 edition) ； e) Grades 10Mn, Q355B, Q355C, Q355D, Q355E, 10Cr9Mo1VNbN, 10MoWVNb, 12SiMoVNb, 35CrNi3MoV, 022Cr19Ni13Mo3, 06Cr18Ni11Ti, 06Cr18Ni11Nb and their heat treatment procedures have been added (see Table 1) ； f) The heat treatment procedure for grade 15CrMo was modified (see Table 1, Table 4 of the 2013 version) ； g) The chemical compositions of 12 grades such as 10Mn and Q355B have been added, along with unified numerical codes and grade comparisons (see Table 2 and Table A.1) ； h) The chemical composition of grades 10 and 20, as well as the chemical composition requirements for other Cu grades, have been modified (see Table 2, Table 3 of the 2013 version) ； i) Increased requirements for the content of residual elements (melting composition) in steel (see 7.1.2) ； j) The carbon equivalent requirements for Q355B, Q355C, Q355D, and Q355E have been increased (see 7.1.5) ； k) The reduction in cross-sectional area of steel pipes and the mechanical property requirements for 12 grades including 10Mn and Q355B have been increased (see Table 4) ； l) The tensile strength, yield strength, and Brinell hardness values of the steel pipes were changed (see Table 4, Table 5 in the 2013 version) ； m) Added requirements for the specified plastic elongation strength of steel pipes at high temperatures (see 7.3.4, Appendix B) ； n) Recommended data for endurance strength at 100,000 hours have been added (see 7.3.5, Appendix C) ； o) The hydraulic testing requirements have been changed (see 7.4.1, 6.5 of the 2013 edition) ； p) The requirements for the mechanical properties regarding flattening and bending have been modified (see 7.5.1 and 7.5.2, and 6.6.1 and 6.6.2 of the 2013 edition) ； q) The requirements for the flaring test have been changed (see 7.5.3, 6.6.3 in the 2013 edition) ； r) Added requirements for low-magnification and non-metallic inclusions for 35CrNi3MoV (see 7.6, Table 8) ； s) Changed the total requirements for the fine and coarse grade counts of various types of inclusions A, B, C, and D (see Table 8, 6.8 of the 2013 version) ； t) Added requirements for grain size (see 7.8) ； u) The surface quality requirements for 35CrNi3MoV steel pipes used for polyethylene have been increased (see 7.10.5) ； v) The non-destructive testing requirements have been modified (see 7.11, 6.10 in the 2013 edition) ； w) Additional technical requirements for stainless steel pipes used in industrial furnaces of petrochemical hydrogenation units have been added (see 7.13, Appendix E) ； x) The allowable tolerances for outer diameter and wall thickness have been changed (see Tables 9 and 10, and Tables 1 and 2 of the 2013 edition) ； y) The outer diameter and wall thickness requirements for 35CrNi3MoV steel pipes used in polyethylene are increased (see 7.14.1.5) ； z) Changed the requirements regarding normal length and cut-to-length (see 7.14.2, 7.14.3, and 5.2.1, 5.2.2 of the 2013 edition) ； aa) The bending requirement for 35CrNi3MoV steel pipes used in polyethylene has been increased (see 7.14.4.3) ； bb) Changed the requirements for the end shape (see 7.14.6, 5.5 of the 2013 edition) ； cc) The densities of grades 022Cr19Ni13Mo3, 06Cr18Ni11Ti, and 06Cr18Ni11Nb have been increased (see Table 11) ； dd) The allowable weight tolerance has been changed (see 7.14.9 and 5.6.3 of the 2013 edition) ； ee) The sampling quantities, sampling methods, and testing methods for magnetic particle and penetrant inspection tests have been increased (see Table 12) ； ff) Added a roughness inspection method for 35CrNi3MoV steel pipes used in polyethylene (see 9.4).

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