Understanding the Process of Flame Hardening

01 December 2020

A lot of metal parts and components normally require additional processes for them to achieve wear-resistant surface, improved core strength, and other dependable properties. These enhancements allow them to be useable for specific applications and conditions.

Achieving these enhancements can be done in two ways. First, metal parts and components can be subjected under the process of altering the chemical composition of their surface. Some processes that can be utilised for this type of enhancement include carburising, nitriding, cyaniding, and carbonitriding. Another way of achieving the aforementioned enhancements is through the hardening of their surface layer only, which can be done by either flame hardening or induction hardening.

General Overview of Flame Hardening

One process that can be done to strengthen the surface layer of metal parts and components is flame hardening. It is a fairly common surface hardening process that utilises high-temperature flame in heating the surface layer of materials. Through this process, metal parts and components are expected to obtain surfaces that are tough and resistant to wear and corrosion.

Generally, there are two flame hardening techniques that can be utilised for metal parts and components. 

  1. Shell Hardening: Shell hardening is done by heating the parts and components completely before quenching them entirely. Some types of shell hardening are stationary hardening, spin hardening, and cycle hardening. 
  2. Line Hardening: Line hardening involves the heating and quenching of parts and components simultaneously, with some parts subjected under a cooling spray jet in advance. Progressive hardening and combination hardening are some of the few types of line hardening.

Steels that have a carbon content of 0.4 to 0.7% can be processed by flame hardening. Other materials that can also be processed by this process are cast iron and cast steel products. Materials that have sensitive materials can undergo flame hardening, given that emulsions with an oil-like quenching behaviour will be used instead of water.

Flame Hardening Working Principles

As previously stated, flame hardening utilises high-temperature flame in performing the hardening process. Metals under this surface hardening process are normally heated to their austenitizing temperature, allowing their surfaces to change without affecting their respective cores. As these metal materials reach their austenitizing temperatures, they are often quenched immediately. The quenching process allows them to develop much harder and more corrosion-resistant surfaces.

Crucial factors that can determine the results of the flame hardening would normally include the heat of the flame, the duration of the heating, the speed and temperature of the quenching process, and the entire composition of the material or workpiece.

Useful Benefits of Flame Hardening

The flame hardening process can be beneficial for manufacturers and businesses since it can give higher hardness for increased longevity, provide more efficient productivity, reduce downtime and maintenance costs, and decrease distortion, processing time, and the need for machining and grinding. Some products that can be subjected under flame hardening include rolls, shafts, sheaves, rope drums, slew rings, machine ways, rails, dies, moulds, gears, and sprockets.

To know more about the flame hardening process, you can talk to us at Alpha Detroit Heat Treatment.

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