Vacuum Heat Treatment

The vacuum heat treatment is a process of heating and cooling steels inside a furnace where almost all the air and gases have been removed, creating a very low-pressure environment (vacuum).

Its main objective is to perform heat treatments without oxidation, without decarburization, and with very precise temperature control.

How does it work?

The process generally follows these stages:

1. Loading the material

The steel parts are placed in the vacuum furnace.

2. Creation of the vacuum

Air is extracted using vacuum pumps, reducing the internal pressure to very low levels.

3. Heating

The parts are heated to the required temperature according to the treatment:

• Hardening
• Tempering
• Annealing
• Solution treatment
• Stress relief

4. Maintenance

The temperature is maintained for a certain time to homogenize the metallurgical structure.

5. Cooling

Depending on the steel and the desired result, cooling can be done with:

• High-pressure nitrogen
• Argon
• Helium
• Oil (in some special systems)

Main advantages

✅ No surface oxidation

In a conventional furnace, the following appear:

• Scale
• Oxides
• Discoloration

In vacuum, the surface comes out practically shiny.

✅ No decarburization

In atmospheric furnaces, surface carbon can be lost.

This causes:

• Lower surface hardness
• Lower wear resistance

The vacuum prevents this problem.

✅ Greater dimensional uniformity

With very precise control:

• Less deformation
• Less warping
• Better dimensional stability

This is especially important for:

• Molds
• Dies
• Precision tooling

✅ Better surface finish

Many parts come out ready for:

• Final grinding
• Polishing
• Subsequent coatings

without the need to clean oxides.

Typical applications

Tooling and dies

Widely used for:

• Aluminum extrusion dies
• Punches
• Injection molds
• Cutting tools

Tool steels

For example:

• H13
• D2
• M2
• P20

Aerospace industry

For critical components where it is required:

• High metallurgical cleanliness
• Dimensional accuracy
• Excellent surface finish

Application in aluminum extrusion dies

Since you work in extrusion, this is probably the most relevant case.

Dies made from steels like H13 typically receive:

1. CNC machining.
2. Vacuum hardening.
3. Multiple tempering.
4. Nitriding (optional).

Benefits:

• Greater hardness.
• Higher wear resistance.
• Less deformation of the die.
• Better service life.
• Lower risk of premature cracks.

Example: H13 steel for extrusion dies

A typical cycle can be:

1. Preheating: 650–850 °C.
2. Austenitizing: 1,000–1,040 °C.
3. Vacuum hardening.
4. Cooling with high-pressure nitrogen.
5. Triple tempering between 540–620 °C.

Typical result:

• Hardness: 44–50 HRC.
• Excellent toughness.
• Good resistance to thermal shock.