If the cutting tool is made of bad steel, then ordinary hardening in water will not save it. To correct its softness and increase wear resistance, cyanidation can be carried out before hardening using yellow blood salt, also known as potassium iron sulfide, yellow blue, or blood alkali salt.
This is a powder in the form of crystals, which, when heated, saturates the surface layer of steel with carbon and nitrogen. The wear resistance and corrosion resistance of the tool processed in blue increases many times faster than what happens during carburization. Cyanidation can bring a hoe, knife, axe, chisel and other tools or machine parts back to normal. This does not require much time, so the method is convenient to use at home.
What you will need:
- yellow blood salt;
- forge or gas cutter;
- container with water.
First of all, let's check the hardness of the metal using a makeshift method - we scratch it with a file.
Let's hit the nail.
The result is obvious.
Process of cyanidation and hardening of tools
A tool whose hardness needs to be increased must be sharpened before processing, since after cyanidation and hardening this will be much more difficult to do. After sharpening, its cutting edge becomes red hot.
The hot instrument is immersed with its cutting edge into the powder of yellow blood salt. Upon contact, the crystals will begin to melt, which is accompanied by the appearance of toxic smoke. In this regard, it is better to carry out work under a hood or outside.
Immediately after applying the crystals, the tool is returned to heating.
It needs to be reheated and dipped in salt again.
This is repeated 2-3 times. If the tool has a thin cutting edge, like a hoe or a knife, then the thickness of carburization obtained in 3 approaches will already be sufficient.
After this, it is heated to the quenching temperature and cooled in water.
Using the example of a hoe, you can evaluate how much stronger its blade has become after hardening with preliminary cyanidation.
Before treatment, it was deformed when it hit a nail, but after treatment it was able to easily cut it.
Having the opportunity to purchase yellow blood salt, you can transform cheap instruments from soft “plasticine” steels into normal ones. This method will also improve the wear resistance of gears, splines and other mechanical parts. If a heavy load is placed on the product, then after hardening with cyanidation, the steel should also be tempered to prevent its brittleness.
After sharpening, the edge of the blade is as sharp as a razor blade.
