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How to Heat Treat A36 Steel

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A36 steel is the grade for one of the most common types of structural steels used today. A36 grade steel is considered low-alloy; however, because the carbon can range up to 0.29 percent at the most and mild steel is anything below 0.25 percent, A36 is considered the safest mild steel. As such, direct heat treating is not applicable. Case hardening is the process for treating A36 steel.

Place the fire bricks around the fireproof table inside the brazing hearth, make sure that your brazing hearth and gas-air torch are in good condition and fill a large container with cold water and another with Kasenit or your chosen brand. Keep these last two nearby but not in your way. Check your safety equipment before proceeding.

Set the steel bar on the hearth table, and set the tongs within reach. Turn on and light the gas-air torch. Make sure that it is heating one end of the steel bar. When the bar turns thoroughly red from heat, turn off the torch and pick up the tongs.

Remove the heated steel bar from the hearth with the tongs. Immediately plunge the bar into the Kasenit container. Allow it to cool a little while inside while holding it with the tongs.

Remove the steel bar from the Kasenit with the tongs. Replace it inside the hearth on the table. Turn on the torch again and reheat the steel bar until it is once again red-hot.

Turn off the torch and use the tongs to remove the bar again. This time, put the steel inside the cold water until it is cooled. Repeat the heating, Kasenit, reheating and cooling process again if desired.


Make sure that you have A36 steel before case hardening it if at all possible.

Fire bricks aid in keeping the heat oriented at the steel bar.


A36 steel will soften when heated. It is not advisable to directly heat-treat A36 steel.

Always wear protective gear when handling high heat objects.