GB/T 2520-2017Cold-reduced electrolytic tinplate (English PDF)

1 Application Scope

China's national standard for cold-reduced electrolytic tinplate. It specifies the classification and designation, the order content, the dimensions, the technical requirements, the test methods, the inspection rules and the packaging and marking of electrolytically tinned cold-rolled steel sheet and strip. Tinplate is the material of the food can, and it exists because tin is one of the few metals that is both non-toxic in contact with food and passive enough not to affect the taste. The steel gives the strength and the cost; the tin gives the corrosion resistance and the solderability; and a lacquer over the tin handles the products the tin alone cannot. The coating is extraordinarily thin - a fraction of a micrometre, measured in grams per square metre - and it is applied electrolytically rather than by dipping precisely because it can be controlled that finely and because the two faces can be coated differently, which matters since the inside of a can faces the food and the outside faces the printing. That difference is one of the things the designation must carry. The standard therefore specifies the coating mass on each surface and its designation, the steel grade and temper, which govern whether the material can be drawn into a can body or must be formed as a three-piece can, the surface finish, the passivation and the oiling, the mechanical properties, and the dimensional tolerances. The tin coating mass itself is determined by the coulometric method of GB/T 1838. Issued on 7 September 2017 and in force since 1 June 2018, it replaced GB/T 2520-2008 and has since been superseded by GB/T 2520-2026.

This Standard specifies the classification and codes, ordering content, dimensions, shapes, weights and tolerances, technical requirements, test methods, inspection rules, packaging, marking and quality certification of cold-reduced electrolytic tinplate. This Standard applies to single cold-reduced electrolytic tinplate of nominal thickness

0.14 mm ~

0.80 mm and double cold-reduced electrolytic tinplate of nominal thickness

0.12 mm ~

0.36 mm (hereinafter referred to as tinplate).

2 Normative References

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

GB/T 222, Permissible Tolerances for Chemical Composition of Steel Products

GB/T 223.4, Iron, Steel and Alloy - Determination of Manganese Content - Potentiometric or Visual Titration Method

GB/T 223.5, Steel and Iron - Determination of Acid-soluble Silicon and Total Silicon Content - Reduced Molybdosilicate Spectrophotometric Method

GB/T 223.9, Iron, Steel and Alloy - Determination of Aluminium Content - Chrom Azurol S Photometric Method

3 Terms and Definitions

3.1 electrolytic tinplate Cold-reduced low-carbon steel plate or strip which is tinplated on both sides through continuous electrolytic tinning.

3.2 differentially coated electrolytic tinplate Electrolytic tinplate of different tin coating weights on the two sides.

3.3 single cold-reduced; SR Steel baseplate is cold-reduced to obtain the required thickness, and then annealed and skin-passed.

3.4 double cold-reduced; DR Reduction in which steel baseplate goes through first cold-reducing and annealing, and then cold-reduced with large rolling reduction.

3.5 box annealing; BA The process in which cold-reduced steel strip is annealed in the wind-up state and the controlled atmosphere, in accordance with the set cycles of time and temperature.

3.6 continuous annealing; CA The process in which cold-reduced steel strip is annealed in the unfolding state and controlled atmosphere, in accordance with the set cycles of time and temperature.

4 Classification and Codes

4.1 The classification and codes of tinplate shall be as specified in Table 1.

5 Ordering Content

The contract or order placed in accordance with this Standard shall include the following content.

8 Test Methods

8.1 The dimensions and shapes of tinplate shall be measured with appropriate tools.

8.2 The thickness measuring position is any point not less than 10 mm from both sides of tinplate.

8.3 The appearance of tinplate is examined by visual inspection.

8.5 For the hardness test, usually 3 points are measured for one sample. When the maximum difference (i.e. the maximum value - the minimum value) of the 3 points is greater than 1.0, add 2 points for measurement, take out the maximum and minimum values of the 5 points, calculate the mean value of the 3 points as the test value. In case of any dispute in the test result, then remove the tin coating and conduct the test once again.

8.6 When the nominal thickness of tinplate is smaller than

0.20 mm, use HR15Tm for hardness measurement, and then convert into HR30Tm as specified in Annex C.

8.7 The inspection items, sample quantities, sampling methods or sampling locations and test methods shall be as specified in Table 9.