As a manufacturing enterprise specializing in stainless steel coil production, we rely on a complete system covering smelting, rolling, finishing and testing, dedicated to providing stable, reliable and performance-compliant stainless steel coil products for various industries.
The performance of stainless steel coils is fundamentally determined by alloy composition ratios. We cover four major series: austenitic, ferritic, martensitic and duplex stainless steels. All mainstream grades comply with domestic and international standards such as GB/T 3280, ASTM A240 and JIS G3459. The key material properties are as follows:
In terms of mechanical properties, all grades undergo strict heat treatment process control: the 304/316L series have a tensile strength ≥520MPa, yield strength ≥205MPa, elongation ≥35%, and hardness (HV) <90; the 201 series has a tensile strength ≥535MPa and elongation ≥30%; the precipitation-hardening 17-4PH material can achieve a tensile strength of over 860MPa, meeting the requirements of high-strength working conditions.
The quality of stainless steel coils stems from full-process process control. We adopt a closed-loop production model of "raw material refinement - rolling forming - heat treatment - finishing and packaging". The key process links are as follows:
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Raw Material Selection and Smelting: High-purity molten iron, ferrochromium, nickel plates, molybdenum iron and other raw materials are selected. Smelting is carried out in a 100-ton electric arc furnace, combined with an LF refining furnace for composition fine-tuning, ensuring that the deviation of the chemical composition ratio of molten steel is ≤±0.05%, and the content of harmful elements P and S is strictly controlled at ≤0.030% (≤0.045% for the 304/316L series).
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Rolling Process:
- Hot-rolled coils: After heating the slab to 1250℃, rolling is performed by a multi-stand continuous rolling mill. The thickness control range is 3.0-80.0mm, and the width is 3.5-1550mm. An on-line thickness monitoring system is adopted during the rolling process, and the thickness tolerance is controlled within ±10%.
- Cold-rolled coils: A 20-high reversing cold rolling mill is used for precision rolling through multiple passes at room temperature. The thickness range is 0.025-4.0mm, and the width can be customized from 3.5-1550mm. Tension control technology is used to ensure the flatness of the plate shape is ≤3mm/m.
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Heat Treatment and Surface Treatment:
- Heat treatment: Vertical bright annealing furnaces are equipped with a fully digital temperature control system. The solution temperature is set according to material characteristics (1050-1100℃ for 304/316L, 1150-1200℃ for 310S), and the holding time is accurately controlled within 2-4 hours to ensure uniform structure.
- Surface treatment: Various surface conditions are available, including annealed and pickled (2B finish), mechanical grinding (180G/240G/320G brushed finish, 400G/600G mirror finish), passivation treatment, etc. The surface roughness Ra ≤0.8μm (2B finish), and the mirror gloss can reach the 8K standard.
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Slitting and Packaging: High-precision slitting machines and cross-cutting machines are used, with a slitting width tolerance of ±0.01mm. The standard inner diameter of the coil is 508mm/610mm, the outer diameter is ≤2133mm (84 inches), and the coil weight can be customized from 1 to 20 tons. The packaging adopts a double-layer protection of waterproof paper + stretch film, fixed with wooden pallets, meeting the anti-corrosion and anti-deformation requirements for sea transportation and long-distance transportation.
- 304 stainless steel coil: Passes the ASTM A480 neutral salt spray test, with no red rust after 48 hours of continuous testing in a 5% NaCl solution;
- 316L stainless steel coil: No corrosion after 72 hours of salt spray testing in a 5% NaCl solution, and its corrosion resistance to media such as sulfuric acid and phosphoric acid is more than 3 times that of the 304 series;
- All grades pass the passivation film integrity test, with a surface passivation film thickness ≥8nm.
- Delivery status: Cold-rolled coil (annealed, pickled + flattened), hot-rolled coil (annealed, pickled/black skin), slit coil (fixed width and weight);
- Grain size: Austenitic steel ≤Grade 8, ferritic steel ≤Grade 7;
- Bending performance: Products with thickness ≤3mm can withstand 180° cold bending test, with a bending radius ≤1.5 times the plate thickness and no cracks;
- Environmental standards: Complies with RoHS and REACH certifications, with heavy metal content below the limit requirements and 100% recyclable.
We have established a three-level inspection mechanism of "raw materials - process - finished products", equipped with professional testing equipment such as direct-reading spectrometers, tensile testing machines, hardness testers, salt spray test chambers, and ultrasonic flaw detectors, ensuring that each batch of products leaves the factory qualified:
- Raw Material Inspection: Conduct spectral analysis of the chemical composition of incoming alloy raw materials to ensure that the element content meets the smelting standards;
- Process Inspection: Real-time monitoring of thickness and plate shape during the rolling process, sampling inspection of hardness, tensile strength and elongation after heat treatment. An on-line visual inspection system is used for surface quality, with a defect detection rate ≥99%;
- Finished Product Inspection: Extract 3-5 samples from each batch of products for chemical composition re-inspection, mechanical performance testing, salt spray corrosion testing and dimensional accuracy calibration. At the same time, NDT non-destructive testing (ultrasonic/eddy current flaw detection) options are provided to meet the needs of high-end industrial scenarios;
- Quality Traceability: Assign a unique traceability code to each coil, covering information such as raw material batch, smelting time, rolling parameters and test data, enabling full life cycle traceability.
