Flame Hardening

During flame hardening, you heat the workpiece surface quickly with the gas flame to hardening temperature. This transforms the structure in the edge zone. During subsequent rapid cooling, e.g., by quenching in water, a hard, wear-resistant surface layer forms. Caution: If you cool too slowly or heat the workpiece too strongly, you get a coarse grain and hardness suffers. Conversely, too rough cooling can cause stresses and cracks in the edge zone. Guide the flame evenly over the surface until the desired temper color appears, then quench immediately.