The processing of stainless steel bars (round bars, square bars, hexagonal bars, etc.) usually includes raw material preparation, forming, heat treatment, finishing and other steps. The specific process is as follows:
1. Raw material preparation
Material selection:
Common grades: 304, 316, 303 (free cutting), 416 (martensite), 17-4PH (precipitation hardening)
Morphology: continuous casting billet, hot rolled billet
Inspection:
Composition analysis (spectrometer)
Surface inspection (cracks, inclusions)
2. Hot processing (hot rolling/forging)
(1) Hot rolling
Heating: Heat the billet to 1100~1250℃ (austenitizing temperature)
Rolling: forming round bars, square bars, etc. through multiple rolling mills
Cooling: air cooling or water cooling (controlling grain size)
Applicable products: large diameter bars (Φ≥20mm)
(2) Forging
Free forging: used for small batches and large size bars (such as nuclear power steel)
Die forging: production of high-precision special-shaped bars (such as automobile crankshafts)
3. Cold working (cold drawing/cold rolling)
(1) Cold drawing (Cold Drawing)
Steps:
Pickling: Remove hot rolling scale (HNO3+HF mixed acid)
Phosphating/lubricating: Reduce drawing friction
Drawing: Gradually reduce the diameter through the die (can improve the dimensional accuracy to ±0.02mm)
Annealing: Eliminate work hardening (austenitic steel: 1010~1120℃; martensitic steel: 700~800℃)
Features:
High surface finish (Ra≤0.8μm)
Applicable to small diameter bars (Φ1~50mm)
(2) Cold rolling
Formed by rolling mill, suitable for flat bars or special-shaped bars
4. Heat treatment
Select the process according to the type of stainless steel:
Stainless steel type Heat treatment process Purpose
Austenite (304/316) Solution treatment (1050~1100℃ rapid cooling) Eliminate stress and improve corrosion resistance
Martensite (416/420) Quenching (980℃ oil cooling) + tempering Improve hardness and strength
Precipitation hardening (17-4PH) Solution + aging (H900, etc.) Precipitation strengthening phase
5. Finishing
(1) Surface treatment
Polishing: Mechanical/electrolytic polishing to mirror finish (BA surface)
Polishing: Centerless grinder to improve dimensional accuracy (±0.005mm)
Sandblasting: Matt surface (No.4 or brushed effect)
(2) Cutting
Sawing: Band saw/circular saw (conventional length cutting)
Turning: CNC lathe processing threads, steps, etc.
Laser/water jet cutting: High-precision special-shaped cutting
(3) Other processing
Drilling/tapping: Making bolts and shaft parts
Bending/welding: Pay attention to the crack risk of martensitic steel
6. Quality inspection
Dimension inspection: Micrometer, laser diameter gauge
Mechanical properties: Tensile test, hardness test (HRC/HB)
Corrosion resistance: Salt spray test (ASTM B117)
Non-destructive testing: Ultrasonic flaw detection (UT), penetrant testing (PT)
7. Packaging and storage
Rust prevention: Apply anti-rust oil or VCI anti-rust film
Packaging: Wooden box/strapping to avoid collision
Marking: Sign indicating brand, size, batch
Stainless Steel Bar
Cherry
Website: www.jinyoumetal.com
Email: Cherry@jinyoumetal.com
WhatsApp/WeChat: +86 13373795593
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