Although most regular steel products are not as prone to cracking, cut edge cracking is a common phenomenon for thicker gauge or grade steels that exhibit substantially high carbon content, such as wear-resistant steels and high-carbon steels. high resistance.
These steels are essential materials for many industries such as construction and mining, where durability and resistance are essential. As annoying as cut edge cracking can be, there are some useful ways to prevent it, and we share some of the most effective tips on how to eliminate cut edge cracking!
But first, you could ask:
WHAT IS CUT EDGE CRACKING AND WHY DOES IT HAPPEN?
When thermally cutting thicker gauge steels, cracks can form from the cut edges. Cut edge cracking is caused by reasons similar to cold welding cracking, including:
hydrogen content cracking
Cut Edge Residual Stresses
a high carbon equivalent
Cut edge cracking is also known as delayed cracking, as it takes 48 hours to several weeks after cutting for cracks to show. It is a phenomenon closely related to hydrogen cracking in welds under thermal cutting methods.
The likelihood of cut edge cracks occurring in your steel products will increase with the hardness of the steels and the thickness of the steel plates.
WHAT CAN I DO TO AVOID IT?
1. Preheating
Preheating before cutting is undoubtedly the best way to eliminate the risk of cracking of the cut edge. Preheating is most commonly applied before oxyfuel cutting. It can be carried out using burner lances, electric heating mats or by heating in an oven.
The preheating temperature depends on the grade of steel and the thickness of the plate. For detailed information, we at CUMIC provide professional help for your queries. The required temperature must be measured on the opposite side to that on which heating occurs.
Also, don't forget to maintain a low temperature gradient across the plate cross section to avoid local overheating in the heat source contact area!
2. Low cutting speed
If preheating cannot be performed, maintaining a low cutting speed may be the best alternative option. Although a little less consistent than preheating when it comes to preventing cracking of the cut edge, low cutting speed is still one of the most useful methods.
If preheating is not used, the maximum allowable cutting speed depends on the steel grade and plate thickness. Therefore, we strongly recommend a combination of preheating and low cutting speed to further reduce the susceptibility to cut edge cracking.
3. Slow cooling
Regardless of whether or not the above two methods are used, a slow cooling rate can help reduce the risk of cracking of the cut edge. Slow cooling can be achieved if the pieces are stacked together while still hot from the cutting process and covered with an insulating blanket. Let the parts cool slowly to room temperature.
4. Postheating
Another way to prevent cracking of the cut edge is to heat the pieces immediately after cutting. This will prolong the time at temperature to allow hydrogen to escape from the steel plates. The residual stresses at the cutting edge can also potentially decrease to some extent.
When applying the post-heating method, the soaking temperature should be the same as the preheating temperature introduced above, and the soaking time should be at least 5 minutes per mm of plate thickness.
For postheating, multiple methods can be used, including burner lances, electrical heating mats, or heat treatment in an oven.
