Heat Treatment for Machined Parts
Stress relief, solution, aging, hardening and annealing, sequenced into the machining route with grinding stock planned and hardness verified.
Heat Treatment Sequenced Into Machining
Heat treatment is not a standalone service bolted on at the end; it is a route decision that changes whether your part arrives straight or springs after delivery. KGL plans the sequence: roughing, stress relief, semi-finish, final precision cuts, hardening where the drawing needs it, then grinding and CMM verification.
When to Choose It
| Goal | Process | Where it fits |
|---|---|---|
| Release machining stress after heavy roughing | Stress relief (aging) anneal | steel and aluminum, before finish cuts |
| Harden wear surfaces on tool steel and alloy steel | Quench and temper, then grind | to HRC 55 typical max on ground faces |
| Aluminum strength state per drawing | Solution and aging (T6 family) | 6061-T6, 7075-T6/T351 |
| Restore corrosion resistance and formability | Solution treatment | 17-4PH and stainless conditions |
| Soften for rework or re-machining | Full anneal | per material datasheet |
Specifications We Control
| Item | Specification |
|---|---|
| Scope | Stress relief, solution, aging, quench and temper, annealing, case processes per drawing |
| Control | Batch furnace with calibrated thermocouples; charge traceability per part number |
| Typical practice | 20# steel stress relief 540 to 560 °C, soak about 1.5 h, controlled cooling |
| Verification | Hardness test (Rockwell / Vickers) on return; dimensional check after |
| Documentation | Heat treatment certificate with batch number in the shipment package |
How We Run It and Check It
Two rules we apply without being asked. First, aging and stress relief happen between roughing and finishing whenever stock removal is heavy, because the alternative is discovering the distortion after your incoming inspection. Second, any part that gets hardened gets ground on the critical faces afterwards, since a hardened part straight out of the furnace will not hold a tolerance you can use.
Full detail on steel-specific routes and states: heat treatment standards on the steel material page.
Material side: carbon and alloy steel machining, stainless steel. Related capability: surface grinding.
Cross entrances: by material | CNC machining | inspection and QC.
Frequently Asked Questions
When does a part need stress relief between operations?
When roughing removes a lot of stock or the wall is thin. Our standing practice on heavily machined steel and aluminum: rough, stress relieve, then semi-finish and finish, so the distortion happens before the precision cuts, not after delivery. On one 20# steel rotor support program the aging step ran at 540 to 560 degrees C with controlled cooling before the precision turning.
Can you harden steel and still hold tolerance?
Yes, by planning for it: harden, then grind the critical faces on our surface grinders, and verify on the CMM. Parts harden to HRC 55 and come back flat, because grinding stock was already reserved in the route.
What is the difference between T6 and T351 on aluminum?
Both are solution treated and artificially aged. T351 adds stress relief by stretching, which matters on 7075 plates that will be machined heavily; we buy 7075-T351 when distortion control on large stock removals is the priority, 7075-T6 where the section is smaller.
Do you handle the logistics of outside heat treatment?
Yes, heat treatment runs through audited partners under KGL purchase control, with batch traceability, hardness verification on return, and the certificate filed under your part number for repeat orders.
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Quote with engineering feedback within 24 hours; prototypes in 7 to 15 days.
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