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How to Heat Treat Mild Steel Using Water and a Surfactant

Mild steel is an iron alloy with a relatively low carbon content. This means it is softer than higher carbon steel, but also more flexible and shock resistant. Heat treating steel using a surfactant, a process known as case hardening, serves to harden the outside of the steel while leaving a softer, more flexible core. This also allows the steel to be quenched in water, rather than the oil or brine bath required for heat treating without a surfactant, and eliminates the need for tempering.

Things You'll Need

Fire bricks
Anvil or heat-resistant stand
Hand torch
Tongs
High-carbon hardening compound

Instructions

- 1
  Stack fire bricks in a half-circle around an anvil or heat-resistant stand. The bricks will serve to reflect heat from the torch back into the work area, helping you heat the steel more quickly.
- 2
  Heat the part of the steel to be hardened using a hand torch until it is glowing a dull cherry red.
- 3
  Remove the steel from the anvil with a pair of tongs and dip it into a high-carbon hardening compound.
- 4
  Return the steel to the anvil and reheat it with the torch until it once again glows dull red.
- 5
  Quench the steel in cold, clean water. Repeat the process as necessary to create a thicker outer layer of hardened steel.

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