How to Increase the Strength of Stainless Steel Extended Screws？

Release time：2020-01-16 18:44 Browse：

1. Select High-Strength Stainless Steel

The strength of stainless screws depends on their alloy composition. Common grades and properties:

Recommendations:

• General use: 304HC (A2-70) or 316HC (A4-70) (cold-work hardened).

• High strength: 17-4PH or A286 (heat-treated).

2. Cold Work Hardening

Austenitic stainless steels (e.g., 304, 316) can be strengthened via:

• Cold heading: Increases strength (e.g., 304HC to 700–900 MPa) by grain refinement.

• Thread rolling: Improves fatigue resistance by 20–30% vs. cut threads.

Applicability:

• Works for austenitic steels (304/316) (e.g., A2-70, A4-70).

• Not for martensitic steels (e.g., 410), which rely on heat treatment.

3. Heat Treatment (For Precipitation-Hardening Steels)

17-4PH (Grade 630) can be heat-treated for maximum strength:

1. Solution treatment (1020–1060°C, water-quenched) → Soft state for machining.

2. Aging (480–620°C, 1–4 hours) → Precipitates strengthen to 1000–1300 MPa.

Advantages:

• Strength rivals alloy steel (e.g., Grade 12.9) while retaining corrosion resistance.

• Ideal for aerospace, medical, and high-end machinery.

4. Structural Design Optimization

(1) Thread Reinforcement

• Use fine-pitch threads (e.g., M8×1.0 instead of M8×1.25) for higher load distribution.

• Optimize thread root radius to reduce stress concentration.

(2) Enhanced Stability for Extended Screws

• Add unthreaded shank to minimize bending stress.

• Use reinforced thread run-out (e.g., undercut + radius transition).

(3) Anti-Loosening Design

• Apply double nuts or nylon lock nuts.

• Use thread-locking adhesive (e.g., Loctite 243).

5. Surface Treatments

• Shot peening: Induces compressive stress, boosting fatigue strength (+20–40%).

• Electroless nickel plating (ENP): Improves wear/corrosion resistance without weakening.

6. Practical Solutions by Need