GB/T 33968-2025 English PDF

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GB/T 33968-2025: Hot rolled steel sections with improved weldability
Status: Valid

GB/T 33968: Historical versions

Standard ID	USD	BUY PDF	Lead-Days	Standard Title (Description)	Status
GB/T 33968-2025	199	Add to Cart	3 days	Hot rolled steel sections with improved weldability	Valid
GB/T 33968-2017	150	Add to Cart	Auto, < 3 mins	Hot Rolled Steel Sections with Improved Weldability	Valid

Basic data

Standard ID: GB/T 33968-2025 (GB/T33968-2025)
Description (Translated English): Hot rolled steel sections with improved weldability
Sector / Industry: National Standard (Recommended)
Classification of Chinese Standard: H44
Classification of International Standard: 77.140.70
Word Count Estimation: 10,191
Date of Issue: 2025-08-29
Date of Implementation: 2026-03-01
Older Standard (superseded by this standard): GB/T 33968-2017
Issuing agency(ies): State Administration for Market Regulation; Standardization Administration of China

GB/T 33968-2025: Hot rolled steel sections with improved weldability

---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT33968-2025
ICS 77.140.70 CCSH44 National Standards of the People's Republic of China Replaces GB/T 33968-2017 Improved weldability of hot-rolled steel sections Published on 2025-08-29 Implemented on 2026-03-01 State Administration for Market Regulation The State Administration for Standardization issued a statement.

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1.Structure and Drafting Rules of Standardization Documents". Drafting. This document replaces GB/T 33968-2017 "Hot-rolled steel sections with improved weldability". Compared with GB/T 33968-2017, except for structural adjustments... Aside from the integration and editorial changes, the main technical changes are as follows. ---Added 550 strength levels (see 4.1); ---The self-tempering temperature for each product grade has been changed (see 6.2, 6.4 in the.2017 edition); ---Added requirements for the chemical composition of the Q550QST grade, and changed the P content requirements for the Q500QST grade (see 7.1.1,.2017). Version 6.1.1); ---The requirements for sulfur content in the thickness direction of hot-rolled H-beams have been changed (see 7.1.2, 6.1.1 in the.2017 edition); ---Added carbon equivalent requirements for the Q550QST grade (see 7.2); ---The mechanical properties of grade Q550QST have been added, and the mechanical property requirements for each grade under different thickness categories have been modified (see 7.3). (2017 version 6.5) ---The method for testing performance in the thickness direction has been changed (see 7.5, 6.8 in the.2017 version); ---The ultrasound testing method has been changed (see 7.6, 6.9.3 in the.2017 version); ---Welding-related technical requirements have been removed (see 6.10 in the.2017 edition); ---The sampling and testing methods for thickness-direction performance and ultrasonic testing have been changed (see 8.2, Chapter 7 of the.2017 edition). Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents. This document was proposed by the China Iron and Steel Association. This document is under the jurisdiction of the National Steel Standardization Technical Committee (SAC/TC183). This document was drafted by. Maanshan Iron & Steel Co., Ltd., China Iron & Steel Research Institute Co., Ltd., and Metallurgical Industry Information and Standardization Research Institute. The main drafters of this document are. Chen Hui, Wu Baoqiao, Wang Yujie, Chen Xuehui, Xia Meng, Liu Baoshi, Xu Haochi, Shen Qiancheng, and Lian Xiaojin. The release history of this document and the document it replaces is as follows. ---First published in.2017 as GB/T 33968-2017; ---This is the first revision. Improved weldability of hot-rolled steel sections 1.Scope This document specifies the classification, grade designation, ordering details, manufacturing process, technical requirements, and inspection procedures for hot-rolled steel sections with improved weldability. The rules, packaging, markings, and quality certificates describe the corresponding test methods. This document applies to hot-rolled H-beams (hereinafter referred to as "H-beams") with improved weldability produced using a quench-and-temper (QST) process. (Steel). Other hot-rolled steel sections should refer to this specification.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included. For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies. This document. GB/T 222 Permissible Deviations in Chemical Composition of Finished Steel and Alloy Products GB/T 223.5 Determination of Acid-Soluble Silicon and Total Silicon Content in Iron and Steel - Reduced Molybdate Spectrophotometric Method GB/T 223.12 Chemical Analysis Methods for Iron and Steel Alloys - Sodium Carbonate Separation-Diphenylcarbazide Spectrophotometric Determination of Chromium GB/T 223.18 Chemical Analysis Methods for Iron and Steel Alloys - Determination of Copper by Sodium Thiosulfate Separation-Iodometric Method GB/T 223.23 Determination of Nickel Content in Iron and Steel and Alloys - Dimethylglyoxime Spectrophotometric Method GB/T 223.26 Determination of molybdenum content in iron and steel and their alloys - Thiocyanate spectrophotometric method GB/T 223.40 Determination of Niobium Content in Iron and Steel and Alloys - Chlorsulfonylphenol S Spectrophotometric Method GB/T 223.59 Determination of phosphorus content in iron and steel and their alloys - Bismuth-phosphomolybdenum blue spectrophotometric method and antimony-phosphomolybdenum blue spectrophotometric method GB/T 223.63 Determination of Manganese Content in Iron and Steel and Alloys - Sodium (Potassium) Periodate Spectrophotometric Method GB/T 223.72 Determination of sulfur content in iron and steel and their alloys by gravimetric method GB/T 223.74 Determination of Non-Combined Carbon Content by Chemical Analysis Methods for Iron and Steel and Alloys GB/T 223.76 Chemical Analysis Methods for Iron and Steel Alloys - Determination of Vanadium by Flame Atomic Absorption Spectrometry GB/T 223.78 Chemical Analysis Methods for Iron and Steel Alloys - Determination of Boron Content by Direct Spectrophotometry Using Curcumin GB/T 228.1 Metallic materials – Tensile testing – Part 1.Test method at room temperature GB/T 229 Metallic materials Charpy impact test method GB/T 2101 General Provisions for Acceptance, Packaging, Marking and Quality Certificate of Section Steel GB/T 2975 Sampling Location and Specimen Preparation for Mechanical Property Testing of Steel and Steel Products GB/T 4336 Determination of Multi-Element Content in Carbon Steel and Medium-Low Alloy Steels by Spark Discharge Atomic Emission Spectrometry (Conventional Method) GB/T 11263 Hot-rolled H-beams and split T-beams GB/T 20066 Sampling and Sample Preparation Methods for the Determination of Chemical Composition of Steel and Iron GB/T 20123 Determination of Total Carbon and Sulfur Content in Iron and Steel - Infrared Absorption Method After Combustion in a High-Frequency Induction Furnace (Conventional Method) GB/T 20125 Determination of Multi-Element Content in Low-Alloy Steels by Inductively Coupled Plasma Atomic Emission Spectrometry GB/T 41749 General requirements for surface quality of hot-rolled steel sections YB/T 081 Metallurgical Technical Standards. Numerical Rounding and Judgment of Test Values YB/T 4811 Ultrasonic Testing Method for Hot-Rolled H-Beams YB/T 4831 Thickness-direction properties of hot-rolled H-beams 3.Terms and Definitions This document does not contain any terms or definitions that need to be defined. 4.Classification and Brand Designation Methods 4.1 Classification H-beams are classified into grades 355, 420, 460, 500, and 550 according to their strength levels. 4.2 Designation Method The steel grade designation consists of three parts. the first letter of the Chinese pinyin for yield strength ("屈"), the numerical value of yield strength, and "QST". For example. Q355QST. Wherein. Q---The first letter of the Chinese pinyin for "yield strength" of steel; 355 --- Yield strength value, unit is megapascals (MPa); QST is an abbreviation for Quenching and Self-tempering. Note. For an explanation of the quenching and self-tempering process (QST), please refer to Appendix A. 5.Order details Contracts or orders placed in accordance with this document shall include at least the following. a) This document number; b) Product Name; c) Brand; d) Specifications, length, and weight (or quantity); e) Special requirements. 6.Manufacturing process 6.1 Smelting Method Steel is smelted in an electric arc furnace or converter, and refined outside the furnace when necessary. 6.2 Delivery Status H-beams should be delivered in a quenched and self-tempered condition, with a self-tempering temperature of not less than 550℃.

7 Technical Requirements

7.1 Steel grades and chemical composition 7.1.1 The steel grade and chemical composition (smelting analysis) shall conform to the specifications in Table 1.Alternatively, this may be agreed upon by both the supplier and the buyer and specified in the contract. We supply steel profiles of other grades and chemical compositions. Table 1 Chemical Composition (Smelting Analysis) Brand Chemical composition (mass fraction) /%, not greater than C Si Mn PS Cu Ni Cr Mo V Nb Q355QST 0.12 0.40 1.60 0.030 0.030 0.45 0.25 0.25 0.07 0.06 0.05 Q420QST 0.12 0.40 1.60 0.030 0.030 0.35 0.25 0.25 0.07 0.06 0.05 Q460QST 0.12 0.40 1.60 0.030 0.030 0.35 0.25 0.25 0.07 0.08 0.05 Q500QST 0.12 0.40 1.60 0.030 0.030 0.45 0.25 0.25 0.07 0.09 0.05 Q550QST 0.16 0.50 1.80 0.030 0.030 0.45 0.25 0.25 0.07 0.10 0.06 7.1.2 When the buyer requires H-beams to guarantee properties in the thickness direction, the sulfur content shall comply with the provisions of Table 2. Table 2 Sulfur Content Requirements (Smelting Analysis) Thickness-direction performance level sulfur content (mass fraction)/% Z15 ≤0.010 Z25 ≤0.007 Z35 ≤0.005 7.1.3 The permissible deviation of the chemical composition of finished steel products shall comply with the provisions of GB/T 222. 7.2 Carbon Equivalent The carbon equivalent (CEV) of H-beams should conform to the specifications in Table 3. Table 3 Carbon Equivalent Brand Carbon equivalents a, b CEV/%, not greater than Q355QST 0.38 Q420QST 0.40 Q460QST 0.43 Q500QST 0.45 Q550QST 0.49 Carbon equivalent is calculated using the following formula based on smelting analysis. CEV=C Mn/6 (Cr Mo V)/5 (Ni Cu)/15. b. With consultation between the supplier and the buyer, and as specified in the contract, the weld crack sensitivity index (Pcm) may be used instead of carbon equivalent to assess the weldability of steel, and its value... The calculation of Pcm is to be negotiated between the supplier and the buyer. Pcm is calculated using the following formula. Pcm = C Si/30 Mn/20 Cu/20 Ni/60 Cr/20 Mo/15 V/10 5B. 7.3 Mechanical Properties 7.3.1 The mechanical properties of H-beams shall conform to the provisions of Table 4. ......

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