Flame Cutting

High strength and abrasion resistant steel can be oxyfuel cut like mild steel. However, like mild steel, the extremely high heat transforms and tempers the surrounding cold material. We speak of the surrounding area as the "heat affected zone" (HAZ).  Flame cutting creates a risk of softening the steel in the HAZ.

In addition, flame cutting creates a risk of cut edge cracking. Cut edge cracks may take between 48 hours and two weeks to appear. To reduce the risk of cut edge cracking, steel mills recommend both preheating the steel prior to flame cutting and controlling the cut speed during the cutting process. Even where preheating is not recommended, it is necessary that the temperature of the steel be at least room temperature (21C) prior to cutting. Keeping the steel warm prior to cutting is one of the major benefits of storing steel indoors.

Plasma arc cutting, laser cutting and waterjet cutting significantly reduce HAZ and reduce the risk of cut edge cracking. Underwater cutting will also minimize HAZ and reduce the risk of cracking. Our experience suggests that laser cutting can be slower than plasma cutting for high strength and abrasion resistant steel, while waterjet cutting is often more expensive. We use plasma and oxyfuel cutting and a combination of preheating, controlled cut speeds, and underwater cutting to reduce HAZ and to reduce the risk of cut edge cracking.

Most steel mills generally provide their own guidelines on flame cutting and preheat temperatures.  ThyssenKrupp Steel provides the following guidelines:

Flame Cutting N-A-XTRA 700
Preheat Temperatures N-A-XTRA 700
Preheat Temperatures XAR

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