Steel crow-bars

The temperature is very important for the hardening of the instruments. Depending on the type of steel, the optimal temperature for hardening is chosen. Most hardeners got used to determine the temperature by eye depending on the colour of the red-hot steel, but it was proven that depending on the amount of light in the workshop the difference in temperature determination may be 82 ° C.
Each time the tool is heated, the carbon content necessary for the steel to keep its properties (between 0.3 to 0.6%) is lowered and so is the solidity of the instrument. Therefore, it is necessary for the tool to be subjected to carbonation after each hardening procedure. If it is not done, then the piece becomes untolerable to heat already after 4 times repeated procedure. During carbonation the chisel is heated again up to ± 900 ° C and slowly cooled in charcoal or graphite powder. Depending on the size of the tool it may take a few minutes.