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GB/T 11251-2020 English PDF (GBT11251-2020)

GB/T 11251-2020 English PDF (GBT11251-2020)

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GB/T 11251-2020: Alloy structural steel plate and strip

This Standard specifies the order content, size, shape, weight, technical requirements, test methods, inspection rules, packaging, marking and quality certificates of alloy structural steel plate and strip. This Standard applies to alloy structural steel hot-rolled steel plates whose thickness is 4 mm ~ 200 mm (hereinafter referred to as steel plates) and alloy structural steel hot-rolled steel strips (including shear steel plates) whose thickness is not greater than 12 mm and width is less than 600 mm.
GB/T 11251-2020
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 77.140.50
H 46
Replacing GB/T 11251-2009
Alloy structural steel plate and strip
ISSUED ON: MARCH 06, 2020
IMPLEMENTED ON: OCTOBER 01, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of the PEOPLE Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Order content ... 6
4 Size, shape, weight ... 6
5 Technical requirements ... 7
6 Test method ... 11
7 Inspection rules ... 12
8 Packaging, marking and quality certificate ... 13
Appendix A (Normative) Size, shape, weight and allowable deviation of the steel strip ... 14
Alloy structural steel plate and strip
1 Scope
This Standard specifies the order content, size, shape, weight, technical requirements, test methods, inspection rules, packaging, marking and quality certificates of alloy structural steel plate and strip.
This Standard applies to alloy structural steel hot-rolled steel plates whose thickness is 4 mm ~ 200 mm (hereinafter referred to as steel plates) and alloy structural steel hot-rolled steel strips (including shear steel plates) whose thickness is not greater than 12 mm and width is less than 600 mm (hereinafter referred to as steel strips).
2 Normative references
The following documents are indispensable for the application of this document. For dated references, only the dated version applies to this document. For undated references, the latest edition (including all amendments) applies to this document.
GB/T 222, Permissible tolerances for chemical composition of steel products GB/T 224, Determination of depth of decarburization of steels
GB/T 228.1-2010, Metallic materials - Tensile testing - Part 2010: Method of test at room temperature
GB/T 229, Metallic materials - Charpy pendulum impact test method
GB/T 231.1, Metallic materials - Brinell hardness test - Part 1: Test method GB/T 232, Metallic materials - Bend test
GB/T 247, General rule of package, mark and certification for steel plates (sheets) and strips
GB/T 709-2019, Dimension shape weight and tolerances for hot-rolled steel plates and sheets
GB/T 2970-2016, Method for ultrasonic testing of thicker steel plates
GB/T 2975, Steel and steel products - Location and preparation of samples and test pieces for mechanical testing
4.2 The size, shape, weight and allowable deviation of the steel strip shall comply with the provisions of Appendix A.
5 Technical requirements
5.1 Designation and chemical composition
5.1.1 The common designations and chemical composition of the steel shall comply with the provisions of GB/T 3077.
5.1.2 The allowable deviation of chemical composition of the finished steel product shall comply with the provisions of GB/T 222.
5.2 Delivery status
5.2.1 Delivery status of steel plate
5.2.1.1 Steel plates shall be delivered in a high-temperature tempering status. If it is required by the buyer and indicated in the contract, delivery can also be in the status of annealing, normalizing, normalizing + tempering.
5.2.1.2 If it is guaranteed that the steel plate can reach the mechanical properties of 5.3.3, normalizing rolling method can also be used instead of normalizing treatment.
5.2.1.3 According to the requirement of the buyer, If it is indicated in the contract, the steel plate can be delivered by acid pickling.
5.2.1.4 Steel plates shall be trimmed for delivery; it shall be indicated in the contract when they are delivered in other edge conditions. Rolled steel plates can be free from longitudinal edge cutting.
5.2.2 Delivery status of steel strip
Steel strips are generally delivered in a hot rolled status without trimming. According to the requirements of the buyer, steel strips of other special delivery status can be supplied. The specific requirements are negotiated by the supplier and the buyer and indicated in the contract.
5.3 Mechanical property
5.3.1 For steel plates that are delivered in high-temperature tempering status, the surface Brinell hardness shall comply with the provisions of GB/T 3077. 5.3.2 For steel plates that are delivered in the annealing status, the mechanical properties shall comply with the provisions in Table 1.
According to the requirements of the buyer, the 25CrMnSi and 30CrMnSi steel plates can be tested for the banded structure; the result shall not be greater than grade 3.
5.7 Ultrasonic testing
The steel plate shall be subjected to ultrasonic testing in accordance with the provisions of GB/T 2970-2016; the results shall meet the requirements of grade II.
5.8 Surface quality
5.8.1 There shall be no cracks, bubbles, folds, inclusions, scars, and obvious scratches on the surface of the steel plate and steel strip; the steel plate and steel strip shall not have visual layering. If the above surface defects are allowed to be cleaned, the cleaning depth shall not exceed half the thickness tolerance of the steel plate or steel strip. Defects whose depth and height does not exceed half the thickness tolerance of the steel plate and steel strip are allowed; the minimum thickness of the steel plate and steel strip shall be ensured.
5.8.2 Steel plates and steel strips that are delivered by acid pickling are allowed to have unobvious rough surface and light-yellow film that is caused by acid pickling.
5.8.3 Steel strips are allowed to be delivered with partial surface defects; but the length of the defective part shall not exceed 6% of the total length of each coil of steel strip.
5.8.4 There shall be no gaps and edge cracks on the edges of untrimmed steel strips; other edge defects whose actual depth is not greater than half the width tolerance is allowed, and the minimum width of the steel strip shall be guaranteed. The edges of the trimmed steel strip are allowed to have burrs whose size is not greater than 0.50 mm.
5.9 Special requirements.
According to the requirements of the buyer, if it is negotiated between the supplier and the buyer, and specified in the contract, steel plates or steel strips of the following special requirements can be supplied:
a) Sulfur content range: 0.015%~0.035%;
b) Inspect the content of residual lead, arsenic, antimony, tin and titanium; c) Inspect the oxygen and nitrogen content in the steel;
8 Non-metallic inclusions 1 pc/ batch
Any steel plate or
coil
Method A in GB/T
10561-2005
9 Ultrasonic testing
Piece by
piece - GB/T 2970-2016
10 Surface quality
Piece by
piece - Visual inspection
11 Size, shape Piece by piece -
Micrometer, sample
plate
7 Inspection rules
7.1 Inspection and acceptance
7.1.1 The delivery inspection and acceptance of steel plates and steel strips shall be carried out by the supplier's quality and technical supervision department.
7.1.2 The supplier shall ensure that the delivered steel plates meet the requirements of this Standard or the contract. If necessary, the buyer has the right to inspect and accept according to any inspection item that is specified in this Standard or the contract.
7.2 Batch rules
Steel plates and steel strips shall be inspected and accepted in batches; each batch shall consist of steel plates and steel strips of the same designation, the same furnace number, the same thickness, and the same heat treatment
furnace (the continuous furnace is the same heat treatment system).
7.3 Sampling quantity and sampling position
7.3.1 The sampling quantity and sampling position of the steel plates shall comply with the requirements of Table 3.
7.3.2 For steel plates that are heat-treated in stacks, respectively take one piece of steel plate for inspection from the top and bottom of each batch. For steel plates that are heat-treated by continuous furnaces, respectively take one steel plate for inspection from the beginning and the end of a batch of heat treatment; take one sample from each piece of steel plate for inspection. When the batch number does not exceed 10 steel plates, only take one steel plate for inspection, and take one sample at each end of the steel plate.
7.3.3 For steel plates that are heat-treated in coils, respectively take one sample from the outer end of the upper and lower layers of the heat treatment furnace for each batch.

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