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Flame hardening involves rapidly heating a metal and then cooling it. The aim is to harden the metal while making it malleable for subsequent working. It requires the direct impingement of a high-temperature flame from a suitably designed and positioned burner with quenching capabilities. This process is often used on the tooth flank of a gear wheel or the surface of a rail.
Advantages of flame hardening
There are several advantages with flame hardening. Although the process requires a skilled operator and cannot be as easily automated as other heat treatment processes, it allows for the short-term application of high intensity heating ensuring the hardening effects are localised and the depth of hardening controllable. This imparts a hard, wear-resistant surface to the component whilst improving the fatigue strength through the development of residual surface compressive stresses. Because only the surface is heated and quenched, heat treatment distortion is minimized thereby improving the overall resistance of the metal component.
Advanced gas burner technology for flame hardening projects
Our range of LINDOFLAMM® special burners are the ideal tool for flame hardening applications. These hardening burners include an integrated water shower to cool down the material after it has been heated to the specified hardening temperature.
Benefits at a glance:
- Rapid annealing of desired material areas
- Minimal heating of surrounding material with acetylene as fuel gas
- Quench hardening upon effective cooling
- Burner selection adapted to customer demands
- Special burners with integrated water shower
- Customised gas supply solutions
Recommended gases for flame hardening
Achieving a very high, controlled temperature is key in flame hardening. As fuel gas, acetylene has proven to have the best heating properties for this process. Mixed with oxygen, the acetylene flame can reach a temperature of 3160°C. It is the fuel gas of choice for Linde’s LINDOFLAMM® special burner portfolio.
The Linde service offering
Linde is at the forefront of process innovations and applications expertise. We support our innovative LINDOFLAMM® burners with a range of complementary services, including advice and help ranging from the process at hand, like flame hardening to more general parameters like the set-up of your gas supply system.
Materials suitable for flame hardening:
- Low/medium carbon steel (depending upon required surface hardness and core properties)
- High carbon steel (use increases the risk of cracking, and careful control is required)