การหมุน 304 ลักษณะสเตนเลสและแนวทางกระบวนการ

การหมุน 304 สแตนเลส: ลักษณะสำคัญและแนวทางกระบวนการ

ภาพรวม

ออสเตนนิติก 304 สแตนเลสถูกนำมาใช้กันอย่างแพร่หลายเนื่องจากมีความต้านทานต่อการกัดกร่อน, ความร้อน, และอุณหภูมิต่ำ. มักพบในอาหาร, เคมี, and nuclear equipment. อย่างไรก็ตาม, its machinability is poor, making it hard to process. When turning this material, several challenges must be considered.

Main Challenges During Turning

1. High Cutting Force

304 stainless steel has good toughness and plasticity (elongation ≥ 40%, area reduction ≥ 60%). Its hardness is around 187 HB. During cutting, large plastic deformation occurs. The cutting force needed is about 2450 MPa—more than 25% higher than that for 45# เหล็ก.

2. การแข็งตัวของงาน

During machining, the structure becomes unstable. Austenite may convert into martensite, especially under heat. A hard layer forms on the surface. This hardened layer can reach a depth of 0.1 ถึง 0.3 mm and hardness of up to 1500 MPa.

3. High Cutting Temperature

Due to poor thermal conductivity (only 1/3 that of 45# เหล็ก), heat builds up in the cutting area. The temperature can be 200–300°C higher than when cutting 45# เหล็ก. This affects both the part and the cutting tool.

4. Tool Wear and Adhesion

304 stainless steel tends to stick to the tool, causing wear. Small particles can also chip the tool, reducing its life. This affects both cutting precision and surface finish.

Recommended Turning Methods

To improve results, a suitable turning process must be selected. This includes tool material, shape, cutting settings, and cooling method.

Tool Material

1. Cemented Carbide

YG-type cemented carbide is preferred. It offers good toughness, สึกหรอ, and heat resistance. YG8N, which includes niobium, performs even better in rough and semi-finish turning.

2. High-Speed Steel

New types of high-speed steel (เช่น, W6Mo5Cr4V2Al or W12Mo3Cr4V3N) are better than traditional types. These resist wear and improve performance.

Tool Geometry

The tool should have a sharp edge and larger front and back angles. This helps reduce cutting resistance and wear.

Cutting Parameters

ความเร็วในการตัด affects temperature and tool life most.
Feed Rate (เอฟ) influences tool wear.
Cutting Depth (AP) affects work hardening.

All parameters must be adjusted carefully to balance performance and tool life.

Cutting Fluids

Proper cooling is critical. Use fluids with strong cooling and lubricating effects.

For rough turning: Use emulsions (good cooling, ต้นทุนต่ำ).
For semi-finishing and finishing: Use sulfurized oils with added S or Cl.
For high precision: Use mixtures like carbon tetrachloride, kerosene, and oleic acid.

Spray and high-pressure cooling methods help remove heat more effectively.

สรุป

การหมุน 304 stainless steel is difficult due to its strength, ทนความร้อน, and work hardening. Tool choice, cutting settings, and cooling methods must be carefully selected to improve machining quality and tool life.