Quenching and tempering (salt bath quenching + tempering)

Quenching and tempering is the combination of hardening and subsequent tempering that gives a part high strength, toughness and dimensional stability, depending on the hardenability of the material and the cross-section. It is well suited to dynamically loaded components.

What is quenching and tempering?

Quenching and tempering is the hardening + tempering of structural steels. Hardening produces a hard structure; tempering then reduces brittleness and sets the target balance of hardness, strength and toughness according to the drawing.

At Kalírna Zlín we prefer salt bath quenching because of minimal distortion and excellent reproducibility. Depending on the geometry and weight of the part, we also use a polymer quenchant.

Benefits for your parts

  • Uniform properties – hardness and stability depending on the hardenability of the material and the cross-section

  • Minimal distortion thanks to uniform heat extraction in the salt bath

  • High fatigue strength and toughness for dynamically loaded parts

  • Batch-to-batch reproducibility – precise control of temperature profiles and times

  • Laboratory testing and documentation (hardness, metallography) by agreement

Typical applications and materials

Typical parts: shafts, piston rods, gears, pins, levers, forgings and machine components.
Typical steels: 42CrMo4, C45E and other structural steels.

Technical information (important for your enquiry)

  • Quenching medium: primarily salt bath; polymer quenchant possible depending on the part

  • Required result: target hardness / strength according to the drawing (e.g. HRC)

  • Possible follow-up steps as required: straightening and laboratory testing

How an order proceeds

  1. Technical consultation – drawing, target properties, tolerances and test surfaces

  2. Choice of medium and fixturing – salt bath / polymer depending on the part

  3. Hardening + tempering – setting the final properties (single- or multi-stage)

  4. Inspection and handover – hardness; metallography and report by agreement

Primarily for structural steels (e.g. 42CrMo4, C45E). For case-hardening steels it depends on the function of the part and whether through hardening or surface hardening is required.

We use a salt bath, correct fixturing/handling and stabilizing steps (tempering and, where needed, straightening). For sensitive parts we recommend a pilot batch.

As standard we measure hardness according to the drawing (e.g. HRC); by agreement we carry out metallographic evaluation and issue a test report.