Understanding Vacuum Furnace Operation for Hardening Process

Vacuum hardening is a heat treatment process done under controlled low pressure, allowing temperatures to soar up to 1,300 °C. This technique aims to produce shiny surfaces on metal parts, eliminating the need for further mechanical work. Essentially, hardening involves heating steel and then cooling it rapidly to boost its hardness, either on the surface or throughout.

This process is achieved in vacuum furnaces, with gas quenching using mainly nitrogen or inert gases, though it can vary based on the material.

A vacuum furnace is an electrically heated furnace in which a vacuum is maintained during heating and soaking process. Most vacuum furnaces are heated using electric resistance elements made of graphite or metals.

The absence of air and in turn oxygen prevents oxidation, it also prevents heat loss through convection, and contamination, allowing materials to be heated to very high temperatures with high purity.

Typically, hardening is followed by tempering, which involves reheating to enhance hardness and wear resistance or to balance toughness and hardness, depending on the material used.

Vacuum furnace consists of several general steps for hardening process.

Steps	Parameters	Events
Step-1	Ambient Temp	Loading Of Material
Step-2	Low/ High Depend Upon Application	Creating Vacuum
Step-3	760-1300 Degree Depend upon MOC, Applications	Gas Purging & Convective Heating
Step-4		Creating Vacuum & Radiation Heating
Step-5		Heating up to Target Temperature
Step-6	0.5- 2 Hours	Holding Temperature
Step-7	N2 or Inert Gas	Quench cooling By Gas

- Loading Of Material: The materials to be processed are placed inside the furnace chamber.

- Creating a Vacuum: The chamber is sealed, and a vacuum is created by using vacuum pump by removing of air.

- Gas Purging & Convective Heating: Convective heating done at just above the atmospheric pressure by purging of N2 Gas inside the Chamber. The temperature is controlled precisely to ensure uniform heating by rotating convective fan inside the chamber up to certain temperature for specific period.

- Creating Vacuum & Radiation Heating: Reagain Vacuum creation done inside the chamber. After the vacuum is established, heating elements such as resistance wires or induction coils begin to heat the materials. The furnace is carefully controlled to ensure uniform heating, and the temperature is closely monitored to achieve the desired material properties.

- Holding Temperatures: The materials are held at the target temperature for a specific period to achieve the desired material properties.

- Cooling / Air Quenching:After the process is complete, the materials are cooled down, often using an inert gas like N2 or Argon to prevent oxidation during cooling.

Vacuum hardening furnaces are utilized across various applications.

- In the production of tool steels, which are used for cutting tools, dies, and Molds.

- In the aerospace, medical, and food processing sectors

- Nickel-based superalloys are employed in turbine blades and aerospace components, while titanium alloys find their applications in aerospace and medical implants.

- Super alloys are crucial in the electronics and semiconductor industries, highlighting the versatility of vacuum hardening furnaces.

At Tekman, we specialize in providing advanced heat treatment solutions and manufacturing vacuum furnaces tailored to meet the needs of various applications. Whether you're in aerospace, automotive, or any other industry requiring high-precision heat treatment, we have the expertise and equipment to help you achieve the best possible results.