GB/T 39754-2021Hot dip coating steel sheet and strip for corrugated pipe (English PDF)

3.1 Hot-dip zinc coating

Z a coating that is obtained by immersing the pre-treated steel strip or steel sheet in a molten zinc solution of which the zinc content is not less than 99% 3.2 aluminum-silicon coating; AS a coating that is obtained by immersing the pretreated steel strip or steel sheet in a plating solution of which the aluminum content is 90%±2% and the silicon content is 10%±2%

3.3 Aluminum-zinc alloy coating

AZ a coating that is obtained by immersing the treated steel strip or steel sheet in a plating solution of which the aluminum content is 55%±3%, the silicon content is 1.6%±0.3%, and the balance is zinc

3.4 Base steel thickness

the thickness of steel sheet substrate without metal coating or other coating

3.5 Corrugated steel pipe

CSP a coated steel strip or steel sheet is processed into a corrugated steel pipe

3.6 Corrugated steel pipe sheet

a steel sheet or strip that is used to produce corrugated steel pipe (structural corrugated steel pipe, spiral corrugated steel pipe) with coating

3.7 Corrugated steel pipe

a large size steel pipe of which the hot-rolled steel sheet is pickled and then rolled into a corrugated sheet, which is hot-dip galvanized or hot-dipped with other coatings by the solvent method, and then assembled with these coated corrugated steel sheets

NOTE: Hot-rolled steel sheet is usually used.

3.8 Helical corrugated steel pipe

a steel pipe that is made of coated steel strip through spiral winding process

NOTE: Include various coated helical corrugated steel pipes, corrugated pipes of special material and corrugated pipes of various structures, such as carbon steel corrugated pipes, weather resistant corrugated pipe, stainless steel corrugated pipes.

4.1 Codes

4.1.1 Usage code

The usage code is the initial letter "B" of the Chinese pinyin of the word "Bo" (meaning corrugated in English) in "Bo Wen Guan" (meaning corrugated pipe).

4.1.2 Steel grade code

If the second letter of the steel grade code is C, it represents that the base steel is specified as a cold-rolled base steel. If the second letter is D, it represents that the base steel is specified as a hot-rolled base steel.

4.1.3 Coating type code

The pure zinc coating is expressed as Z. The aluminum-zinc coating is expressed as AZ. The aluminum-silicon coating is expressed as AS.

4.2 Expression method for designation

The designation of steel sheet and strip is composed of four parts: product usage code, steel grade code, specified minimum tensile strength value and coating type code. The specified minimum tensile strength value and the coating type code are connected with a plus sign "+".

Example 1: BC290+Z It means that the product is steel for corrugated pipes, the base steel is cold-rolled, the minimum tensile strength specified is 290MPa, and is a zinc-coated product.

Example 2: BD380+AZ It means that the product is steel for corrugated pipes, the base steel is hot-rolled, the minimum specified tensile strength is 380MPa, and is a aluminum-zinc coating product.

4.3 Designation and recommended usage

The designation and usage of steel sheet and strip shall comply with Table 1.

NOTE: Usually, the issuance date in the product inspection document is specified as the product's manufacturing completion date.

7.9 Surface treatment method

7.9.1 Chromic acid passivation (C), trivalent chromium passivation

(C3) and chromium-free passivation (CN)

The surface treatment can reduce the black rust on the surface of the product during transportation and storage. When using chromic acid passivation treatment, there is a risk of rubbing black spots on the surface. During trivalent chromium passivation treatment, hexavalent chromium substances harmful to human health in the passivation film is restricted. During chromium-free passivation treatment, the passivation film does not contain chromium and chromium ions.

7.9.2 Chromic acid passivation + oiling

(CO), trivalent chromium passivation + oiling (CO3) and chromium-free passivation + oiling (CON)

The surface treatment can further reduce the black rust on the surface of the product during transportation and storage. During trivalent chromium passivation treatment, the hexavalent chromium substances harmful to human health in the passivation film is restricted. During chromium-free passivation