Нарезка

Oxygen fuel cutting of HARDOX wear plate is as simple as cutting of regular Mild Steel. When cutting of thicker HARDOX plates special attention is needed. For thick and hard plates the risk of developing cut edge cracks increases. By following the recommendations and guidelines given below cut edge cracking and component softening can be prevented.

Cutting methods
HARDOX wear plate can very well be cut using both cold and thermal cutting methods. The cold methods are abrasive water jet cutting, shearing, sawing or abrasive grinding, while thermal methods are oxy-fuel, plasma and laser cutting.


This leaflet contains general suggestions and calculation models. SSAB Oxelösund AB does hereby expressly exclude any liability whatsoever for their suitability for individual applications. It is the responsibilty of the user of the manual to adapt the recommendations contained herein to the requirements of individual applications.

Cut edge cracking
Cut edge cracking is a phenomenon that is closely related to hydrogen cracking in welds and occurs when thermal cutting methods are used. If cut edge cracks should occur, they will become visible between 48 hours and up to several weeks after the cutting. So cut edge cracking can be regarded as delayed cracking. The risk of cut edge cracking increases with the steel hardness and plate thickness.

Preheating
Preheating prior to cutting is the best way of eliminating the risk of cut edge cracking. Preheating is most commonly applied prior to oxy-fuel cutting. As shown in Table 2, the preheating temperature depends on the steel grade and the plate thickness.
Preheating can be carried out by means of burner lances, electric heating mats or by heating in a furnace. The required temperature should be measured on the opposite side from that at which heating takes place.
N.B. It is important to maintain a low temperature gradient across the plate crosssection in order to avoid local overheating at the contact area of the heat source.

Low cutting speed
Another way of avoiding cut edge cracking is to maintain a low cutting speed. This could be an alternative if preheating cannot be carried out. Cutting at low speed is less reliable than preheating for preventing cut edge cracking. If preheating is not employed, the maximum permissible cutting speed depends on the steel grade and the plate thickness, as shown in Table 3.
A combination of preheating and low cutting speed is recommended for reducing further the susceptibility to cut edge cracking. Slow cooling
Regardless of whether or not preheating of the cut parts is employed, a slow cooling rate will reduce the risk of cut edge cracking. Slow cooling can be achieved if the parts are stacked together while still warm from the cutting process, and are covered with an insulating blanket. Allow the parts to cool slowly down to room temperature.

Post-heating
Heating of the parts immediately after cutting is another method that can be used. This will prolong the time at temperature to allow the hydrogen to escape from the plate and, to some extent, reduce the residual stresses at the cut edge. The soaking temperature should be the same as that given in Table 2, and the soaking time should be at least 5 minutes per mm of plate thickness. Burner lances, electric heating mats or heat treatment in a furnace can be used for postheating.

Reducing the risk of softening
The resistance of the steel to softening depends on its chemistry, microstructure and the way in which it has been processed.
The smaller the part that is thermally cut, the greater the risk of the whole component being softened. If the temperature of the steel exceeds 200 –250