Manufacturing Process
Heat Treatment
热处理
Controlled heating and cooling to change mechanical properties such as hardness, strength or ductility.
Process Steps
- Parts loaded
- Heat cycle
- Quench/temper as specified
- Hardness test
What heat treatment does
Direct answer: heat treatment changes the microstructure of a metal by controlled heating and cooling. Hardness, strength, ductility, residual stress and magnetic behaviour all follow from that microstructure — which is why the same steel can be soft enough to deep draw on Monday and hard enough to cut another steel on Friday.
Which treatment does what
| Treatment | What it changes | Typical use on stamped parts |
|---|---|---|
| Stress relief | Removes locked-in stress without changing hardness | After forming or heavy machining, to stop a part moving during later operations or in service |
| Annealing | Softens, restores ductility, removes stress | Between deep drawing stages when a part has work-hardened too far to be drawn again |
| Normalising | Refines grain structure | Before machining or forming where structure uniformity matters |
| Hardening + tempering | High hardness with controlled toughness | Punches, die inserts, wear surfaces — tooling rather than parts |
| Case hardening | Hard surface, tough core | Wear faces where through-hardening would make the part brittle |
| Magnetic annealing | Restores permeability and lowers coercivity | Pure iron and soft-magnetic parts (DT4E and similar) after forming — critical for solenoid valve housings |
Why a stamped part needs it
- Ductility runs out. Cold forming work-hardens the material. When the next draw stage would crack the wall, the part is annealed and the sequence continues.
- Geometry moves after forming. Residual stress releases during later operations or in service, and a part that measured right at first article drifts out of tolerance. Stress relief fixes the cause rather than chasing the measurement.
- The magnetic circuit depends on it. Forming raises coercivity and lowers permeability in soft magnetic steels. Magnetic annealing restores them — and on a solenoid valve housing that is the difference between a working magnetic circuit and a weak one.
How to specify it on a drawing
Name the treatment and the result, not just the process. A heat-treatment note should state:
- The treatment and where it sits in the route (for example "stress relief after forming, before plating").
- The property that must be achieved — hardness in HRC or HV, tensile strength, or for magnetic parts permeability and coercivity.
- Any dimensional allowance: hardening distorts, so surfaces that must stay tight are either ground after treatment or given allowance.
How Balford handles it
Production heat treatment — quench and temper, annealing, magnetic annealing and demagnetising — runs through audited, long-term partners with controlled-atmosphere furnaces and traceable records, because those are the processes that need certified cycles rather than a convenient furnace. The tool room keeps a small furnace for emergency die repairs, and bulk die hardening is outsourced on the same basis.
Frequently asked
Does heat treatment distort a part?
Yes — hardening in particular. The distortion has to be allowed for: either by grinding the critical surfaces after treatment, by leaving stock where it does not matter, or by choosing a treatment that changes the part less. It is a drawing-level decision, not something to discover at first article.
What is magnetic annealing and when is it needed?
It is a controlled high-temperature anneal that restores the soft magnetic properties of a formed part. Deep drawing raises coercivity and lowers permeability, so a solenoid valve housing or magnetic sleeve made from pure iron is annealed after forming to bring the magnetic circuit back to specification.
What is the difference between annealing and normalising?
Both soften steel, but annealing cools slowly in the furnace for maximum softness and stress relief, while normalising cools in air for a finer, more uniform grain structure. Annealing is what a drawn part gets between stages; normalising is a structural treatment.
Do you heat treat parts in-house?
Not the production cycles. They run through audited partners with certified furnaces and records; the in-house furnace is for emergency tool repairs. Every batch comes back with a record that goes into the project file alongside the material certificate.
Related: surface treatment · deep drawing · deep draw stamping · solenoid valve housings · quality & certifications