Theoretically, steels should receive a similar pre-heat when flame cutting, as when welding. Practically, this is seldom required because the HAZ is narrow compared to a welded material and the cut component almost always undergoes further operations that would remove material that was adversely affected. (e.g. machining or grinding operations)

It therefore depends on your application, what the required pre-heat should be. At any rate, the pre-heat should not be higher than you would use for welding, unless you are going to retain the affected area of the material without any subsequent heat treatment. It may then be prudent to use a high enough pre-heat, to force a bainite transformation. Under these circumstances, the pre-heat will have to be maintained as a post heat for the necessary time to ensure the bainite transformation takes place.

Hope this helps

Regards
Niekie Jooste

You say you have a Procedure (in writing I assume), some one must have put some thought and effort in to the Procedure and came up with a good reason for the preheat. That person may know more about what the material will be use for, exposed to or the kind of stress it will see.

Preheat is sometimes used to reduce thermal stresses also, and you say you are working with a forged material. There maybe concern that some yelding may take place from uneven thermal growth.

If you were just wacking the end off a piece of Cr. Mo. pipe I couldnt agree more, but a forging may be another story.

For thicker materials, preheating simply helps to make a smoother cut which in turn means less grinding. I don't think any one likes to grind any more than they absoloutly have to...