The quality standards of stainless steel are different.
First, it is necessary to refer to the relevant product standards, and second, it is necessary to follow the prior agreement between the supplier and the supplier.
Understanding stainless steel quality standards (including stainless steel corrosion resistance testing standards, stainless steel material standards, national standards for stainless steel plate specifications, etc.) can better guide enterprises to develop stainless steel procurement and acceptance specifications.
1. Scope of application
First of all, the scope of application of GB/T24511-2017 standard is: hot rolled stainless steel and heat-resistant steel plates and strips (including rolled steel plates), cold rolled stainless steel and heat-resistant steel plates and strips (including rolled steel plates) for pressure equipment with a width of no less than 600m.
The contract (order) for ordering according to GB/T24511-2017 shall include the following contents:
- Product Name;
- Standard number;
- Dimensions and accuracy;
- Weight or quantity;
- Type of surface finish;
- Delivery status;
- Other special requirements.
3. Dimension and accuracy
1. The actual thickness of the steel plate shall comply with the allowable thickness deviation (the thickness has two-dimensional accuracy: ordinary thickness accuracy PTA and higher thickness accuracy PT. B).
2. The allowable width deviation of steel plate shall meet the following requirements:
In case of cold rolled steel sheet and strip,
Case 1: 1.5~2.5mm thick cold-rolled steel plate: the allowable width deviation is+2mm;
Case 2: Cold rolled steel plate with thickness>2.5~3.5 mm: the allowable width deviation is+3 mm;
Case 3: Cold rolled steel plate>3.5~8mm thick: the allowable width deviation is+4mm.
In case of hot rolled steel plate and strip,
Case 1: the width of the edge cutting is 600~2100mm, and the allowable deviation of the width is+6mm;
Case 2: If there is no trimming, the allowable width deviation shall be negotiated between the supplier and the demander.
3. Allowable deviation of length
The allowable length deviation of hot plate, hot rolled rolled rolled steel plate and cold rolled rolled steel plate shall comply with the corresponding regulations: +0.5% × nominal length, 0 (i.e. 0~+0.5% × Nominal length).
4. Shape, sickle bending, cutting slope and unevenness
Refer to GB/T24511-2017 for corresponding accuracy requirements.
5. Dimension and outline measurement method
Refer to GB/T24511-2017 for corresponding measurement methods.
1. Steel plate weight: steel plate shall be delivered according to theoretical or actual weight.
The nominal size of the steel plate is used for theoretical weight calculation, but the calculated thickness is the arithmetic mean of the maximum and minimum allowable thickness of the steel plate.
2. Steel strip weight: the steel strip shall be delivered according to the actual weight.
5. Chemical composition
The steel grade and chemical composition (smelting analysis) shall comply with relevant regulations.
The allowable deviation of the chemical composition of finished steel plates and strips shall comply with GB/T222.
Stainless steel pitting equivalent index PREN=Cr%+3.3Mo%+16N%.
6. Delivery status
After cold rolling or hot rolling, the steel plate and strip shall be subject to heat treatment according to the heat treatment system of stainless steel specified in GB/T24511-2017, and shall 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 shall comply with relevant regulations.
8. Intergranular corrosion
As required by the demander, austenitic stainless steel and austenitic-ferritic stainless steel can be subject to intergranular corrosion test, and the evaluation standard shall be indicated in the contract.
9. Surface processing and quality requirements
There are many types of surface processing of steel plates and steel strips, and the Demander shall specify the processing type according to the use demand and indicate it in the contract.
Hot rolled thick steel plate, hot rolled steel strip and coiled steel plate
The steel plate and strip are not allowed to have defects that affect the use.
The surface of the steel plate and strip after pickling is not allowed to have oxide scale and pickling.
It is allowed to grind and clean local defects on the steel plate surface, but the minimum thickness of the steel plate shall be guaranteed.
The steel strip is allowed to have a small amount of abnormal parts.
Cold rolled steel strip and coiled cut steel plate
The steel plate shall be free from defects that may affect its use.
Minor pits, scratches, indentations, pits, roller prints and color differences with individual depth less than half of the thickness tolerance are allowed, which will not affect the use.
Local grinding is allowed, but the minimum thickness of steel plate shall be ensured.
The steel strip shall be free from defects that may affect its use.
However, since there is generally no opportunity to remove defects for steel strip delivered in coils, a small amount of abnormal parts are allowed.
For the unpolished steel strip, the surface is allowed to have slight pits, scratches, indentations, pits, roll marks and color differences with individual depth less than half of the thickness tolerance.
The edge of the steel strip shall be flat.
The trimmed edge of the steel strip shall not have uneven cutting with a depth greater than half of the width tolerance and burr greater than the thickness tolerance of the steel strip;
The non-trimming steel strip shall not have cracks greater than the width tolerance.