GB/T 708-2019Dimension, shape, weight and tolerance for cold-rolled steel strip and sheet (English PDF)

Foreword

This Standard is drafted in accordance with the rules given in GB/T 1.1-2009. This Standard replaces GB/T 708-2006 "Dimension, shape, weight and tolerance for cold-rolled steel plates and sheets". Compared with GB/T 708-2006, the main technical changes of this Standard are as follows: - MODIFY the thickness and width ranges of steel sheets and strips (see

5.1 of this Standard,

5.1 of 2006 edition); - MODIFY the thickness tolerance of steel sheets and strips, which is specified respectively according to the specified minimum yield strength Re < 260 MPa, 260 MPa <= Re < 340 MPa, 340 MPa <= Re <= 420 MPa, Re > 420 MPa (see Table 2, Table 3, Table 4, Table 5 of this Standard, Table 2 of 2006 edition); - ADD the higher precision (PW.B) of width tolerance of slit wide strips and its requirements; MODIFY the width tolerance of slit wide strips (see

6.2.3 of this Standard,

6.2.2 of 2006 edition); - MODIFY the flatness of steel sheets and strips according to the specified minimum yield strength Re < 280 MPa, 280 MPa <= Re < 360 MPa, Re < 260 MPa, 260 MPa <= Re < 340 MPa; MODIFY the requirements for flatness (see

7.1 of this Standard,

7.1 of 2006 edition); - ADD the requirement that steel sheets and strips are supplied according to general precision when the thickness tolerance, width tolerance, length tolerance and flatness are default (see 6.1.6, 6.2.2, 6.3, 7.1.1); - ADD the negotiation terms when the yield strength and requirements are not specified in the thickness tolerance and flatness requirements of steel sheets and strips in the product standard (see 6.1.5, 7.1.5); - MODIFY the requirements for camber (see

7.2 of this Standard,

7.2 of 2006 edition); - MODIFY the "cutting angle" to "out-of-squareness"; ADD the method and requirements for the measurement of out-of-squareness using the diagonal method (see

7.3 of this Standard,

7.3 of 2006 edition); - ADD the requirements for the measurement position of flatness of steel strips (see 8.3.3); - ADD the schematic diagram of the measurement of out-of-squareness using the diagonal method [see 8.5b)]. This Standard was proposed by China Iron and Steel Industry Association. This Standard is under the jurisdiction of National Technical Committee on Steel of Standardization Administration of China (SAC/TC 183). Drafting organizations of this Standard. China Metallurgical Information and Standardization Institute, Tangshan Branch of Hebei Iron and Steel Co., Ltd., Guangxi Liuzhou Iron and Steel Group Co., Ltd., Shougang Group Co., Ltd., Anshan Iron and Steel Co., Ltd., Baoshan Iron and Steel Co., Ltd. Main drafters of this Standard. Hou Jie, Zhang Weixu, Li Qian, Deng Cuiqing, Gan Guiping, Tang Mu, Su Haolu, Hu Ling, Xu Feng, Tan Cuiying. The previous released versions replaced by this Standard are as follows: - GB 708-1965, GB 708-1988, GB/T 708-2006. Dimension, shape, weight and tolerance for cold-rolled steel strip and sheet

1 Scope

China's national standard for the dimensions, shape, weight and tolerances of cold-rolled steel strip and sheet. This is one of the documents on which the whole steel trade is transacted, because it defines what is actually being sold. Steel sheet is bought by weight and used by area, so the thickness tolerance determines how much material a customer receives for his money and whether a stamping will be within its own tolerance. Shape is the subtler and often more consequential requirement: flatness, edge wave, crossbow and camber are the results of uneven rolling and internal stress, and a coil that is dimensionally correct but not flat will not feed straight through a press line, will spring after cutting, and can be unusable for laser cutting whatever its thickness. The standard specifies the terms and definitions, classification and codes, dimensions and dimensional tolerances, shape requirements, methods of measuring dimensions and shape, weight and rounding, and applies to cold-rolled wide strip, slit wide strip and sheet cut from strip of rolling width 600 mm and above.

This Standard specifies terms and definitions, classification and code, dimensions, dimension tolerances, shape requirements, measurement of dimensions and shape, weight and rounding off of numerical values of cold- rolled steel sheets and strips. This Standard applies to cold-rolled wide strips, slit wide strips and sheets cut from strip of which the rolling width is not less than 600 mm (hereinafter referred to as steel sheets and strips). Steel plates may also refer to this Standard.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 8170 Rules of rounding off for numerical values & expression and judgement of limiting values

3 Terms and definitions

For the purpose of this document, the following terms and definitions apply.

3.1 wide strip Steel strips with a width of not less than 600 mm and delivered in rolls.

3.2 slit wide strip Slit from wide strips and delivered in rolls.

3.3 sheet cut from strip Cut form steel strips and delivered in sheets.

4 Classification and code

4.1 Classification according to edge state is as follows:

4.2 Classification according to dimension precision and code is as follows:

4.3 Classification according to flatness precision and code is as follows:

4.4 Classification of dimensions and precision of flatness corresponding to product shape and edge state is shown in Table 1.

9 Weight

9.1 Steel sheets are delivered according to theoretical or actual weight. Steel strips are delivered according to actual weight.

9.2 When steel sheets are delivered according to theoretical weight, the theoretical weight is calculated using nominal dimensions and the carbon steel density of

3.Other steel grades are weighted according to the corresponding standards.

9.3 The theoretical weight of steel sheets is calculated according to the calculation method specified in Table 11.