Stainless Steel Products CNC Precision Machining Parts

1. Material selection and property compatibility

Core grade characteristics:

304/316 austenitic stainless steel: It has strong corrosion resistance and is suitable for medical and food equipment (such as surgical instruments, food processing valves). It should be noted that 304 is prone to corrosion in salt spray environments, while 316 contains molybdenum to enhance its corrosion resistance.

17-4PH precipitation-hardening stainless steel: High strength (tensile strength ≥1300MPa), high-temperature resistance, used in aerospace turbine components and nuclear reaction equipment, and needs to be strengthened through heat treatment (aging at 550℃).

420 martensitic stainless steel: High hardness (HRC50-55), suitable for cutting tools and bearings, but has relatively weak corrosion resistance and requires surface passivation treatment.

303 free-cutting stainless steel: With a high sulfur content (0.3%), it has excellent cutting performance and is suitable for mass production of nuts and bolts, but it has poor weldability.

Material challenge

The work hardening is severe (hardness increases by 1.4 to 2.2 times), and the cutting parameters need to be controlled to prevent rapid tool wear.

It has poor thermal conductivity (only one-third that of carbon steel), and is prone to heat accumulation leading to deformation. Therefore, high-pressure coolant (such as an emulsion with a concentration of 15%) and low cutting speed (such as 300-800 RPM) are required.

2. Optimization of processing technology

Tool and Parameter Control

Tool selection: Cemented carbide coated tools (such as TiCN coating) or ceramic tools to enhance wear resistance; The five-axis linkage machining center is suitable for complex curved surfaces (such as aviation blades), and the tool holder repeatability accuracy should be ≤0.005mm.

Cutting parameters: For roughing, large-diameter flying knives (such as Φ20mm) are used, with a cutting depth of 2-5mm and a feed rate of 0.2-0.5mm/rev. Ball-end cutters for fine machining, with a rotational speed of 8000-12000rpm and a feed rate of 0.1-0.3mm/rev, can achieve a surface roughness of Ra0.8μm.

Cooling strategy: High-pressure coolant (10-20bar pressure) combined with micro-lubrication (MQL) to reduce thermal deformation and built-up edge formation.

Special process treatment

Deep hole processing: Use gun drills or BTA drills, combined with an internal chip removal system to prevent chip breakage and blockage.

Thread processing: When tapping with a tap, the torque needs to be controlled (for example, the torque of an M8 bolt should be ≤50N·m), and the continuity should be verified in conjunction with a gauge. Rolling threads enhances surface strength (hardness increases by 20%).

3. Quality Control and Inspection

Dimensional accuracy: Tolerance grades reach IT5-IT7. For example, the diameter tolerance of shafts is ±0.01mm, and the coaxiality is ≤0.02mm. The key dimensions are inspected by using a three-coordinate measuring machine (CMM).

Surface quality: Polished to #8 mirror finish (Ra≤0.2μm) for medical implants, sandblasted (Ra3.2μm) or brushed for industrial equipment; Electrolytic polishing enhances corrosion resistance (no rust after salt spray test for ≥96 hours).

Mechanical properties: Hardness test (HRC/HV), tensile strength (≥520MPa), impact toughness (≥20J); Metallographic testing is used to verify the grain size (ASTM E112 standard).

Corrosion resistance: According to the salt spray test (ISO 9227), 316 stainless steel shows no red rust after being exposed to 5%NaCl solution for ≥1000 hours.

4. Design optimization and innovation

Structural optimization

Lightweight design: Topology optimization reduces material usage (such as a 30% reduction in the weight of automotive shafts), and combines with hollow structures to enhance the stiffness-to-weight ratio.

Modular design: Quick-release interfaces (such as snap-on connections) enhance assembly efficiency and reduce the risk of welding deformation.

Heat dissipation design: Add heat dissipation fins or thermal conductive coatings (such as alumina) to enhance thermal management efficiency.

Surface engineering

Coating technology: PVD titanium plating (2-5μm thickness) to enhance wear resistance; DLC coating reduces the coefficient of friction (≤0.1).

Passivation treatment: Nitric acid passivation forms a protective film of chromium oxide, increasing corrosion resistance by 2 to 3 times.