7 Most Common Knife Heat Treat Failures
Overheating causes grain growth within the steel which will result in the blade not being hardened correctly. The remedy for this is to normalize the steel and repeat your heat treating process.
Old quench oil
Quench oil loses some properties each time it is used and will lose its effectiveness over time. To ensure a consistent result from your quench it is advised to change your oil after 10 uses. This varies according to the oil used so check with your oils manufacturer.
No thermal cycle
If you are not doing a full thermal cycle on your knives you are doing yourself a dis-service. The only exception to this rule is for air hardened steels which according to knife steel nerds should not be normalized.
Wrong heating for steel
If you are doing a heat treat on 1084 but are using temperatures for 1095 you will not be getting the optimal hardness out of the steel and may in fact cause the steel to get too hot. Be sure to check what the recommended temperature ratings are for the steel you are working with.
Overheating when grinding
When you are working the bevels of your knife post heat treatment you may notice the edge of your steel bluing. This means the steel has gotten too hot and is soft in these areas. The good news is that you can re-perform the heat treat and potentially save your work. A good rule of thumb is to dip the blade in water between grinds to keep the steel cool and preserve your heat treat.
Tempering too hot
If you temper your steel too hot it will lose some of its hardness. The only remedy at that point is to redo your heat treatment process. Be sure to check what the recommended temperature range and time in the oven for whatever steel you are working with. A little research will save you time and materials.
Warping after quench
Warping can be caused by a number of factors but can easily be resolved. After quench be sure to examine the blade to ensure it is still straight. If you notice a slight warp and the steel is around 500 degrees you can clamp the blade between two flat pieces of steel and let it cool. Do not do this with a cold blade unless you want to create a custom two piece knife as it will likely cause a catastrophic failure.
You will experience one or many of these failures over time but don't give up. Have fun with the process, be safe, and always forge ahead.
To learn more about the heat treating process you can visit our Comprehensive guide to the basics of heat treating here.