Stress-Relief Annealing Protocols for CNC Machined Brass Lock Housings
Engineering Overview: Metallurgical guide on thermal stress-relief annealing (280°C) for extruded brass cylinder bodies to eliminate residual stresses and seasonal cracking.
Technical & Engineering Specifications
| Standard | ASTM B154 Ammonia Vapor Verification |
|---|---|
| Soak Time | 120 Minutes Slow Air Cool |
| Eliminates | Stress Corrosion Cracking (SCC) & Residual Warp |
| Temperature | 280°C - 300°C Controlled Atmosphere Furnace |
| Thermal Process | Sub-Critical Stress-Relief Annealing |
Preventing Stress Corrosion Cracking (SCC)
Heavy cold extrusion and high-speed CNC multi-axis milling induce severe residual tensile stresses in brass lock cylinder bodies.
Thermal Annealing Protocol
- Furnace Cycle: Heated to $280^\circ ext{C}$ to $300^\circ ext{C}$ for 2 hours, followed by slow controlled air cooling.
- Outcome: Relieves 90% of internal residual stresses without reducing bulk Vickers hardness, preventing seasonal cracking under ASTM B154 ammonia testing.
Frequently Asked Engineering & Selection Questions
Q1: Why must brass lock bodies undergo stress-relief annealing?
It removes internal mechanical stresses caused by CNC milling, preventing the brass from developing cracks in humid or ammonia-rich air.