GB/T 33968: Evolution and historical versions
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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| | Sector / Industry | National Standard (Recommended) | | Date of Implementation | 2026-03-01 | | Older Standard (superseded by this standard) | GB/T 33968-2017 | GB/T 33968-2017: Hot Rolled Steel Sections with Improved Weldability---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Hot rolled steel sections with improved weldability
ICS 77.140.60
H44
National Standards of People's Republic of China
Improve welding performance Hot rolled steel
Published on.2017-07-12
2018-04-01 Implementation
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
China National Standardization Administration released
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This standard is proposed by the China Iron and Steel Industry Association.
This standard is under the jurisdiction of the National Steel Standardization Technical Committee (SAC/TC183).
This standard was drafted by. Metallurgical Industry Information Standard Institute, Ma Steel (Group) Holding Co., Ltd., Shandong Iron and Steel Co., Ltd.
芜 Branch, China Metallurgical Building Research Institute Co., Ltd., Hebei Jinxi Iron & Steel Group Co., Ltd.
The main drafters of this standard. Liu Shibo, Wu Baoqiao, Wang Zhongzhong, Duan Bin, Zhao Yichen, Wang Yuxuan, Cheng Ding, Zhao Xinhua, Ma Dezhi, Yan Tie,
Ye Gaoqi, Li Furong.
Improve welding performance Hot rolled steel
1 Scope
This standard specifies the order content, classification, grade indication method, size, shape, weight and allowable deviation of the hot rolled section steel for improving the welding performance.
Poor, technical requirements, test methods, inspection rules, packaging, marking and quality certificates.
This standard applies to the use of quenched and self-tempered processes (QST) to improve the welding performance of hot-rolled H-beam (hereinafter referred to as "H-type
Steel "." Other hot-rolled steel can also refer to this standard.
2 Normative references
The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this article
Pieces. For undated references, the latest version (including all amendments) applies to this document.
Finished chemical composition tolerance of GB/T 222 steel
GB/T 223.3 Methods for chemical analysis of iron, steel and alloy. The diantipyrine methane phosphomolybdic acid gravimetric method for the determination of phosphorus content
GB/T 223.5 Determination of acid-soluble silicon and total silicon content in steels-Reduced molybdosilicate spectrophotometric method
GB/T 223.9 Determination of iron and steel and alloy aluminium content Chrome azure S spectrophotometric method
GB/T 223.11 Determination of chromium content in steels and alloys Visual titration or potentiometric titration
GB/T 223.12 Methods for chemical analysis of iron, steel and alloy - The separation of sodium carbonate - Diphenylcarbazine photometric method for the determination of chromium content
GB/T 223.14 Methods for chemical analysis of iron, steel and alloy - Determination of vanadium content by osmium reagent extraction spectrophotometric method
GB/T 223.18 Methods for chemical analysis of iron, steel and alloy - The sodium thiosulfate separation - Iodometric method for the determination of copper content
GB/T 223.19 Methods for chemical analysis of iron, steel and alloy - The neocuproine-chloroform extraction photometric method for the determination of copper content
GB/T 223.23 Determination of nickel content in steels and alloys Dibutyl oxime spectrophotometric method
GB/T 223.26 Determination of molybdenum content in steels and alloys Thiocyanate spectrophotometric method
GB/T 223.32 Methods for chemical analysis of iron, steel and alloy - The sodium hypophosphite reduction - Iodometric method for the determination of arsenic
GB/T 223.40 Iron and steel alloys - Determination of niobium content - Chlorophenol P spectrophotometric method
GB/T 223.54 Methods for chemical analysis of iron, steel and alloy - The flame atomic absorption spectrophotometric method for the determination of nickel content
GB/T 223.58 Methods for chemical analysis of iron, steel and alloy. The sodium arsenite-sodium nitrite titrimetric method for the determination of manganese content
GB/T 223.59 Determination of phosphorus content in steels and alloys - Phosphomolybdate blue spectrophotometric method and antimony-molybdenum blue spectrophotometric method
GB/T 223.60 Methods for chemical analysis of iron, steel and alloy. Perchloric acid dehydration gravimetric method for the determination of silicon content
GB/T 223.61 Methods for chemical analysis of iron, steel and alloy - The ammonium phosphomolybdate volumetric method for the determination of phosphorus content
GB/T 223.62 Methods for chemical analysis of iron, steel and alloy - The butyl acetate extraction spectrophotometric method for the determination of phosphorus content
GB/T 223.63 Methods for chemical analysis of iron, steel and alloy - The sodium (potassium) periodate photometric method for the determination of manganese content
GB/T 223.64 Determination of manganese and steel alloys by flame atomic absorption spectrometry
GB/T 223.67 Determination of steel and alloy sulfur content Methylene blue spectrophotometric method
GB/T 223.68 Methods for chemical analysis of iron, steel and alloy - The potassium iodate titration method for the determination of sulfur after combustion in a tubular furnace
GB/T 223.69 Determination of carbon content in steel and alloys
GB/T 223.71 Methods for chemical analysis of iron, steel and alloy - Determination of carbon content by post-combustion gravimetric method in a tubular furnace
GB/T 223.72 Determination of steel and alloy sulfur content by weight method
GB/T 223.74 Methods for chemical analysis of iron, steel and alloys - Determination of non-combined carbon content
GB/T 223.76 Methods for chemical analysis of iron, steel and alloy - The flame atomic absorption spectrometric method for the determination of vanadium content
GB/T 228.1 Tensile test of metallic materials Part 1. Test method at room temperature
GB/T 229 Charpy pendulum impact test method for metal materials
General requirements for GB/T 2101 steel acceptance, packaging, marking and quality certificates
GB/T 2975 Steel and Steel Products Mechanical Properties Test Sampling Position and Sample Preparation
GB/T 5313 thickness direction performance steel plate
GB/T 4336 Determination of multi-element content of carbon steels and low-alloy steels by spark discharge atomic emission spectrometry (routine)
law)
GB/T 11263 hot-rolled H-section steel and split T-shaped steel
GB/T 20066 Sampling and preparation methods for samples 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 after Combustion in High Frequency Induction Furnace (Conventional Method)
Determination of multi-element content of GB/T 20125 low-alloy steel by inductively coupled plasma atomic emission spectrometry
YB/T 081 Metallurgical Technical Standard Rounding and Determination of Test Values
3 Order contents
Contracts ordered under this standard should include at least the following.
a) the standard number;
b) product name;
c) brand number;
d) Specifications, length and weight (or quantity);
e) Special requirements.
4 Classification, brand representation
4.1 Classification
H-beams are classified by intensity class as 355, 420, 460, and 500.
4.2 Brand Names
Steel grade consists of three parts. "yield strength", initials in Chinese Pinyin, yield strength, and "QST." E.g.
Q345QST. among them.
Q --- The first letter of the "Qu" Chinese pinyin of the yield strength of steel;
355 --- Yield strength in megapascals (MPa);
QST---The English acronym for Quenching and Self-tempering.
Note. See Appendix A for a description of the quenching and self-tempering process (QST).
5 Size, shape, weight and allowable deviation
H-shaped steel size, shape, weight and allowable deviation should be consistent with the provisions of GB/T 11263. After the supply and demand sides negotiate and in the contract
Note that other standards may also be used.
6 Technical Requirements
6.1 Steel grades and chemical composition
6.1.1 The steel grade and chemical composition (smelting analysis) shall comply with the requirements of Table 1. After agreement between the supply and demand sides, and in the contract, it can also be
Supply other grades and chemical composition of steel.
Table 1 Chemical composition (smelting analysis)
Grade
Chemical composition (mass fraction)/%, not more 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
Q460QSTa 0.12 0.40 1.60 0.030 0.030 0.35 0.25 0.25 0.07 0.08 0.05
Q500QSTa 0.12 0.40 1.60 0.040 0.030 0.45 0.25 0.25 0.07 0.09 0.05
a For Q460QST and Q500QST grades with performance requirements in the thickness direction, the S content should not exceed 0.010%.
6.1.2 The allowable deviation of the chemical composition of finished steel products shall comply with the provisions of GB/T 222.
6.2 carbon equivalent
The carbon equivalent of H-shaped steel shall comply with Table 2.
Table 2 Carbon Equivalents
Grade
Carbon equivalent a,bCEV/%
no greater than
Q355QST 0.38
Q420QST 0.40
Q460QST 0.43
Q500QST 0.45
a The carbon equivalent should be calculated using smelting analysis components according to the following formula.
CEV=C Mn/6 (Cr Mo V)/5 (Ni Cu)/15
b After negotiation between the supplier and the buyer, and in the contract, it is also acceptable to use the weld crack sensitivity index (Pcm) instead of the carbon equivalent to evaluate the weldability of the steel.
The value is negotiated between the supplier and the buyer. Pcm is calculated as follows.
Pcm=C Si/30 Mn/20 Cu/20 Ni/60 Cr/20 Mo/15 V/10 5B
6.3 Smelting method
Steel is smelted by an electric furnace or a converter and, if necessary, externally refined.
6.4 Delivery status
H-beams should be delivered in a quenched and tempered condition. The self-tempering temperature is not lower than 600°C.
6.5 Mechanical Properties
The mechanical properties and process performance of H-beams are to comply with the requirements of Table 3.
Table 3 Mechanical properties and process performance
Grade
Upper yield strength b,c
ReH
MPa
tensile strength
Rm
MPa
After breaking elongation d
A50 A200
Impact energy absorption
KV2a
(20°C)
Yield ratio e
ReH/Rm
Not less than not more than
Q355QST 355 470 21 18 54 0.85
Q420QST 420 520 18 16 54 0.85
Q460QST 460 550 17 15 54 0.85
Q500QST 500 610 16 14 54 0.85
a The shock absorption energy at other temperatures is negotiated between the supplier and the buyer.
b When the yield phenomenon is not obvious, Rp0.2 can be used instead of the upper yield strength.
c For Q460QST and Q500QST grades, when the thickness is greater than 80mm, the yield strength values can be reduced to 450MPa and 485MPa, respectively.
d Samples use full section specimens.
e Yield ratio ReH/Rm is the terms of the agreement.
6.6 Impact
6.6.1 H-shaped steel with a thickness of not less than 6mm shall be subjected to impact tests. Impact test specimen size is 10mm × 10mm × 55mm standard
Samples. When it is not enough to prepare a standard sample, a small size sample should be used. When a 7.5mm x 10mm x 55mm sample is used, the sample is tested.
The test result should not be less than 75% of the specified value; when using 5mm × 10mm × 55mm, the test result should not be less than 50% of the specified value,
However, larger size specimens should be preferred.
6.6.2 Charpy (V-shaped) impact test results for H-beams are calculated from the arithmetic mean of a group of three specimens, allowing one of the specimens to have a low value.
In the specified value, but not less than 70% of the prescribed value. If the test result does not meet the above requirements, it should be from the same H-beam (or the same
On the blank) Take 3 more specimens for testing. The arithmetic mean of the 6 specimens before and after the two groups shall not be lower than the specified value, allowing 2 specimens smaller than
The specified value, but only less than 70% of the specified value of the sample is allowed.
6.7 Surface quality
The surface quality of H-shaped steel shall comply with the provisions of GB/T 11263. After the supply and demand sides negotiate and indicate in the contract, they can also press
YB/T 4427 or related standards.
6.8 thickness direction performance
The thickness direction performance shall meet the requirements of GB/T 5313.
6.9 Ultrasonic testing
6.9.1 H-section steels with thickness direction performance requirements shall be ultrasonically examined.
6.9.2 After negotiations between the supply and demand sides, and in the contract, it is indicated that other H-beams may also be subjected to ultrasonic testing.
6.9.3 Ultrasonic testing may be performed on steel in accordance with GB/T 2970 or ASTM A898/A898M or related agreements. Its inspection quantity, qualified
The level should be specified in the contract.
6.10 Welding
6.10.1 H-beams welded without preheating shall meet the following conditions.
a) The hydrogen content in the welding material should be less than 10mL/100g;
b) the ambient temperature is greater than 0 °C;
c) The weldment is not in a complex rigid constraint during welding.
6.10.2 Other welding conditions and processes shall also comply with the relevant welding specification requirements.
7 Test methods
The inspection items, sampling quantities, sampling methods and test methods for each batch of steel shall comply with the requirements in Table 4.
Table 4 Inspection items, sampling quantity, sampling method and test method
No. Inspection Item Sampling Quantity Sampling Method Test Method
1 chemical composition 1/furnace GB/T 20066
GB/T 223, GB/T 4336,
GB/T 20123, GB/T 20125
2 Stretch 1
3 impact 3
GB/T 2975
GB/T 228.1
GB/T 229
4 thickness direction performance 3 GB/T 5313 GB/T 5313
5 Ultrasonic testing See 6.9 See 6.9 See 6.9
6 surface quality by root - visual, measuring tools
7 Dimensions, shape by root - Appropriate measuring tools
8 Inspection Rules
8.1 Inspection and Acceptance
The inspection and acceptance of H-beams shall be performed by the technical quality supervision department of the supplier. The acquirer has the right to check and accept according to this standard.
8.2 Group Batch Rules
H-beams shall be inspected and accepted in batches. Each batch shall consist of the same brand, the same furnace number, and the same specification of H-shaped steel. Each batch weight is not
Greater than 60t.
8.3 Retest and determination
The re-examination and determination of H-beams shall comply with the provisions of GB/T 2101.
8.4 Numerical Rounding
The numerical rounding of inspection results shall comply with the provisions of YB/T 081.
9 Packaging, Signs and Quality Certificates
The packaging, marking and quality certificate of the steel section shall comply with the provisions of GB/T 2101.
Appendix A
(Informative Appendix)
Quenching plus self-tempering process (QST)
A.1 The quenching and self-tempering process (QST) was developed from the thermomechanical rolling (TMCP) process. QST(Quenchingandself-
Tempering) is an evolved TMCP process that interrupts quenching and self-return on-line by controlling the composition and production process.
Fire to produce fine-grained steel to obtain the required mechanical properties. The schematic diagram is shown in Figure A.1.
A.2 QST fine grain steel is transformed into martensite and/or bainite by passing martensitic tempering through the Ar3 line (Cooling process
Graded quenching above the ferrite transition temperature) [by interrupting the quenching time by controlling the time in the quenching medium (water)] to the minimum self-return
Fire temperature 600 °C to obtain the desired performance. Staged quenching can be performed in conventional hot rolling (AR) or controlled rolling (CR) or thermomechanical rolling
After (TMCP).
A.3 The choice of rolling process is usually selected by the manufacturer based on the chemical composition, thickness and required properties of the product.
Explanation.
TMR---thermo-mechanical rolling;
AR --- hot rolling;
CR --- controlled rolling;
QST --- quenched and tempered;
MTT---Martensite tempering temperature;
STT --- self-tempering temperature.
Figure A.1 QST process schematic
references
[1] Ultrasonic testing method for GB/T 2970 thick steel plate
[2] YB/T 4427 General requirements for surface quality of hot-rolled section steel
[3] ASTMA898/A898M hot rolled structural steel ultrasonic straight beam inspection method
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