Quality standards for stainless steel vary.
It is important to first consult the relevant product standards and also follow the terms previously agreed between buyer and supplier.
Having a clear understanding of stainless steel quality standards (including standards for corrosion resistance testing, material standards and national standards for stainless steel plate specifications, etc.) can better guide companies in developing procurement specifications and acceptance for stainless steel.
1. Scope of application
The scope of application of GB/T24511-2017 is for hot-rolled and heat-resistant stainless steel plates and strips (including cold-rolled steel plates) and cold-rolled and heat-resistant stainless steel plates and strips (including rolled steel) for pressure equipment with a minimum width of 600mm.
2. Content
The contract (order) for ordering in accordance with GB/T24511-2017 will include the following content:
- Product's name;
- Note;
- Default number;
- Dimensions and precision;
- Weight or quantity;
- Type of surface finish;
- Delivery status;
- Other special requirements.
3. Dimension and accuracy
1. The actual thickness of the steel plate must conform to the allowable thickness deviation (the thickness has two-dimensional accuracy: normal thickness accuracy PTA and upper thickness accuracy PT. B).
2. The allowable width deviation of the steel plate must meet the following requirements:
In the case of cold-rolled steel sheets and strips,
Case 1: 1.5~2.5mm thick cold-rolled steel plate: allowable width deviation is +2mm;
Case 2: Cold-rolled steel plate with thickness >2.5~3.5mm: allowable width deviation is +3mm;
Case 3: Cold-rolled steel plate >3.5~8mm thick: allowable width deviation is +4mm.
In the case of hot-rolled steel sheets and strips,
Case 1: the edge cutting width is 600~2100mm, and the allowable width deviation is +6mm;
Case 2: If there is no cutout, the permitted width deviation must be negotiated between the supplier and the applicant.
3. Allowable length deviation
The allowable length deviation of hot plate, hot-rolled steel plate and cold-rolled steel plate shall be in accordance with corresponding regulations: +0.5% × nominal length, 0 (that is, 0 ~ + 0, 5% × nominal length).
4. Shape, sickle bending, cutting inclination and irregularities
See GB/T24511-2017 for corresponding accuracy requirements.
5. Dimension and contour measurement method
See GB/T24511-2017 for corresponding measurement methods.
4. Weight
1. Weight of steel plate: steel plate will be delivered according to the theoretical or actual weight.
The nominal size of the steel plate is used to calculate the theoretical weight, but the calculated thickness is the arithmetic mean of the maximum and minimum allowable thickness of the steel plate.
2. Weight of steel strip: steel strip will be delivered according to the actual weight.
5. Chemical composition
The steel type and chemical composition (casting analysis) must comply with relevant regulations.
The allowable deviation of the chemical composition of finished steel sheets and strips shall be in accordance with GB/T222.
Equivalent pitting index in stainless steel PREN=Cr%+3.3Mo%+16N%.
6. Delivery Status
After cold rolling or hot rolling, the steel plate and strip will undergo heat treatment in accordance with the stainless steel heat treatment system specified in GB/T24511-2017, and will be delivered after pickling or similar treatment.
7. Mechanical property and process property
The mechanical properties of heat-treated steel plates and strips at room temperature must comply with relevant regulations.
8. Intergranular corrosion
As required by the applicant, austenitic stainless steel and austenitic-ferritic stainless steel can be subjected to intergranular corrosion testing, and the evaluation standard must be indicated in the contract.
9. Surface processing and quality requirements
There are several types of surface processing of steel plates and strips, and it is up to the Claimant to specify the type of processing according to the demand for use and indicate it in the contract.
Hot rolled thick steel sheet, hot rolled steel strip and coiled steel sheet
Steel sheets and strips must not present defects that impair their use.
The surface of the pickled steel plates and strips must not show oxide scale or residues from the pickling process.
Local defects on the surface of the steel sheet can be removed by grinding and cleaning, but the minimum sheet thickness must be maintained.
A small amount of irregular parts is acceptable for steel strips.
Cold rolled steel strip and spiral cut steel sheet
The steel plate must be free from any defects that could impair its use.
Small holes, scratches, indentations, pinholes, roller prints and color differences less than half the thickness tolerance are acceptable and will not affect its use.
Local grinding is permitted, but the minimum steel plate thickness must be maintained.
The steel strip must also be free from any defects that could affect its use.
However, as defects often cannot be removed in steel strips delivered in coils, a small quantity of irregular parts is permitted.
For unpolished steel strips, the surface may have small pits, scratches, indentations, pits, roller marks and color differences to a depth of less than half the thickness tolerance.
The edge of the steel strip must be flat.
The cut edge of the steel strip must not have an irregular cut with a depth greater than half the width tolerance, and there must be no burrs greater than the thickness tolerance of the steel strip.
The uncut steel strip must not have cracks greater than the width tolerance.
