The core heat treatment process for 17-4PH is “solution treatment + aging”, which together balances strength and toughness. Different aging temperatures correspond to different mechanical properties.
1. Solution Treatment (Pre-treatment, preparation for aging strengthening)
Purpose:Dissolve carbides, copper precipitates, and other phases in the alloy to homogenize composition, form a supersaturated solid solution, and improve subsequent machinability.
Process Parameters: Heating at 1040–1060°C for 30–60 minutes (longer for thicker parts).
Cooling Method: Rapid quenching in water or oil to prevent premature precipitation and ensure the stability of the solid solution.

2. Aging Treatment (Core strengthening step)
Purpose: Through low-temperature heating, fine copper-rich precipitates form in the supersaturated solid solution, hindering dislocation movement and significantly increasing strength and hardness.
Typical Parameters (4 standard aging temperatures for different property requirements):**
480°C aging: Hold 4 hours, air cool, tensile strength ~1400 MPa, hardness 44–45 HRC, high strength.
550°C aging: Hold 4 hours, air cool, tensile strength ~1275 MPa, hardness 40–42 HRC, balanced strength and toughness.
590°C aging: Hold 4 hours, air cool, tensile strength ~1170 MPa, hardness 36–38 HRC, better toughness.
620°C aging: Hold 4 hours, air cool, tensile strength ~1030 MPa, hardness 30–32 HRC, good toughness, suitable for low-temperature service.

Precautions:
Ensure the workpiece is completely cooled to room temperature before aging to avoid uneven precipitate formation due to residual heat.
Welded parts must undergo post-weld aging treatment because welding can destroy the original strengthening effect; aging restores strength.
Avoid prolonged heating in the 400–450°C range, as this can cause “475°C embrittlement,” reducing impact toughness.
For large or complex parts, control cooling speed during solution treatment to prevent warping or cracking.