HOT-ROLLED CORROSION-RESISTANT, HEAT-RESISTANT AND THERMALLY STRESSED STEEL SHEETS
This national standard applies to corrosion-resistant, heat-resistant and thermally-stressed steel sheets with a mass fraction of carbon of 0.45% to 0.55%, manganese of 0.6% to 1.2%, phosphorus of 0.03%, sulfur of 0.03%, silicon of 0.15% to 0.4%, copper of 0.2%, nickel of 0.2%, chromium of 0.15% to 0.45%, molybdenum of 0.025% and titanium of 0.01%.
Classification
Steel sheets are classified into two types according to chemical composition, hot-rolled carbon-containing and hot-rolled alloy-containing steel sheets.
1. Hot-rolled carbon-containing steel sheets are divided into grade 534, grade 572 and grade 611.
2. Hot-rolled alloy-containing steel sheets are divided into grade 544, grade 583, grade 612 and grade 613.
Dimensions and tolerances
The value of the linear dimension of steel sheets should not be greater than 1 050 mm and the nominal thickness should be between 0.5 mm and 6 mm.
The permissible deviations of the thickness of steel sheets should be given in Table 1.
Table 1 Permissible deviations of thickness of steel sheets
Nominal thickness(mm) Permissible deviation of thickness(mm)
0.5〜6 ±0.04
Tensile test
Tests should be conducted to determine the tensile properties of steel sheets. The specimens for testing should be taken in two directions of the sheet; along and across the rolling direction. The sample size, test method and sampling method are consistent with the provisions of GB228-87 “Metallic Materials – Tensile Testing”
Hardness test
Tests should be conducted to determine the hardness of steel sheets. The hardness test should be conducted with Rockwell C and Rockwell B scales. The sample size, test method and sampling method are consistent with the provisions of GB/T231.2 Metallic Materials – Rockwell Hardness Test Part 2: Rockwell Hardness Test (HRB, HRE and HRC Scales).
Impact test
Tests should be conducted to determine the impact properties of steel sheets. Tests should be conducted at room temperature and at temperatures lower than 0 ℃. The sample size, test method and sampling method are consistent with the provisions of GB/T 229 Metallic Materials – Charpy Impact Test.
Metallic coating
Steel sheets should be coated with a zinc/aluminium alloy layer or a zinc layer by hot-dip galvanizing.
The coating thickness of zinc should be given in table 2
Table 2 Coating thickness of zinc
Zenith coating thickness (g/m2) Longitudinal direction Across the rolling direction
Zn-Al alloy layer 60 60
Zinc layer 90 90
Inspection and acceptance
Inspection and acceptance of steel sheets should be conducted in accordance with GB/T2975-1998 Metallographic Structure Sampling Method and GB/T228 Metallic Materials – Tensile Testing Method.
The defects of steel sheets should meet the requirements of GB/T9113-2008 “Steel Sheets Metallic Coating – Structural Quality”.
Packaging and labeling
Packaging and labeling of steel sheets should be done in accordance with GB/T252-1995 “Packaging and Labeling of Steel Plates”.
Marking
The mark of steel sheets should include the following contents;
a) Manufacturer’s name (brand);
b) Steel grade;
c) Steel sheet size;
d) Mass fraction of elements;
e) Year of manufacture;
f) Certificate number.
