CNC Parts- Positioning Pin Base

Analysis of Heat Treatment Quality Incident
Customer Technical Requirements:
Material: JIS S45C (equivalent to international 45# steel)
Heat Treatment Requirements: Overall quenching, target hardness HRC 40-45
Quantity: 100 pieces

Quality Abnormalities:
After heat treatment, the Rockwell hardness testing showed:
1. Insufficient hardness in initial inspection (actual HRC < 35, not up to technical requirements).
2. 100% cracking after secondary quenching and tempering, .

Root Cause Analysis:
1. Process: When the first quenching did not meet technical requirements, annealing treatment was performed in accordance with industry standards, to relieve stress before re-quenching. There is no process issues.
2. Material: S45C is a medium carbon steel, and its reasonable hardenability range should be HRC 25-35. The requirement of HRC 40-45 exceeds the material limits, resulting in excessive quenching stress.

Solution:
Material Change—Use Martensitic Stainless Steel AISI 420 (National Standard 4Cr13)
Material Characteristics:
• Conventional quenching hardness HRC 45-50
• High hardenability
• Good stress release capability

Result Verification:
After improvements, 100 pieces were produced, and testing showed: zero cracking.
Hardness distribution: HRC 42-44 (meets requirements).
Dimensional stability: Qualified.