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Flame Hardening

Flame hardening involves quench-hardening of the material surface followed by low-temperature tempering.

Flame hardening of parts with ductile centres results in high surface-layer hardness of up to approximately 800 HV. A pre-requisite is that materials initially have a minimum carbon content of 0.3 %.

Flame Hardening

Flame hardening is a thermo-physical process which is classed as a surface-layer hardening process.  Heating to the austenising temperature is usually by radiant heat, which is created by burning natural gas with technical-grade pure oxygen, in addition there is also thermal conduction.

Austenising is followed by quenching with water, special hardening oil, synthetic quenching material or compressed air, depending on the hardening process and material.

Flame hardening is generally only used to harden the specific areas of a component that must withstand especially high-abrasion.  However,  the compressive stress induced in the surrounding areas also increases the fatigue strength and rolling contact fatigue strength.

This process, including the customised fabrication of the thermal sources necessary for the heat treatment are carried out exclusively in our branch in Gevelsberg, by the Peddinghaus Oberflächenhärtung GmbH company.



Because we have the machinery and dedicated burner fabrication capability, we are able to treat even the largest of components:

  • Spin hardening Ø 2000 mm x 950 mm high – component weights up to 7000 kg
  • Progressive spin hardening Ø 650 mm x 5000 mm long – component weights up to 6000 kg

The treatment of components with part weights of up to 10 000 kg is possible using the progressive spin hardening method.

Suitable Materials

Because primarily the attained hardness is dependant on the carbon content, steels suitable for flame hardening are the heat-treatable steels with a carbon content above 0.3 %, medium- and high-alloy materials, such as, e.g. X155CrVMo12.

Advantages of Flame Hardening

  • Large, cumbersome components can be hardened
  • The transition of the hardened case to original state is smoother, so that when the original material has a high strength, no sharp transition develops below the hardened zone

Greater heating depths are achieved using spin hardening

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