What is cold cutting and hot cutting of steel plate

Today, let's talk about the cold cutting and hot cutting of steel plate.
There are water jet cutting, cutting, sawing or abrasive cutting; thermal cutting includes flame cutting, plasma cutting and laser cutting.
The flame cutting method of thick steel plate is as simple as that of ordinary low carbon and low alloy steel. However, when cutting thick steel plate, attention should be paid to:
With the increase of the thickness and hardness of the steel plate, the tendency of cracks on the cutting edge increases. In order to prevent the generation of steel plate cutting cracks, the following suggestions shall be followed during cutting:

Cutting crack:
The cutting crack of steel plate is similar to the hydrogen induced crack during welding. If the edge of steel plate is cut, the crack will appear within 48 hours to a few weeks.
Therefore, the cutting crack belongs to the delayed crack. The greater the thickness and hardness of the steel plate, the larger the cutting crack.
The effective way to prevent steel plate cutting crack is to preheat before cutting.
Before flame cutting, the steel plate is usually preheated. The preheating temperature mainly depends on the quality grade and thickness of the steel plate. The preheating method can be carried out by flame torch, electronic heating pad or heating furnace.
In order to determine the preheating effect of steel plate, the required temperature should be tested on the hot quilt surface.
Note: special attention shall be paid to preheating to make the positive steel plate interface evenly heated, so as to avoid local overheating in the area contacting the heat source.
If the whole plate cannot be preheated, the local preheating method can be used instead.
Low speed cutting: another way to avoid cutting cracks is to reduce cutting speed.