flame straightening

[fazel1]

where can I find sobject about flame straightening in ASME Code SecI or SecVIII . is it permitted for chrom molybdenum steels such as A335-P22? is it permitted for carbon steels ? what is the maximum temperature for this treatment?

 

[metengr]

What is your specific application?

Flame straightening is not endorsed nor prohibited by ASME Boiler and Pressure Vessel Code. This is a process, and as such, must be controlled by a detailed process procedure that is reviewed and accepted by the Authorized Inspector.

If you intend to use general heat and force to reshape or move an object, yes, I have seen it performed under controlled conditions with a procedure and only used on carbon steel. If you intend to simply re-round an object using only spot heating (aka flame straightening), this will not work.

Typically, the application of flame straightening for structural beams or shafts requires very localized or spot heating (torch heating). Because of spot heating affects, flame straightening will in most cases exceed the lower critical transformation temperature especially for low alloy steels. There can be no stress relief or reheat treatment of the object after spot heating because it will undo the residual stresses applied during spot heating.

I would not permit the use of "flame straightening" to re-shape a pressure containing object. The application of general heat and mechanical force can be used, provided the temperature used during general heating is kept 50 deg F below the published lower critical transformation temperature. For 2.25% Cr-1%Mo (P22) low alloy steel the published lower critical transformation temperature is 1480 deg F.

 

[chicopee]

To impart a camber on steel beams, heavy structural steel fabricators will use flame heating at localized areas along the length of the beams. It is a very interesting procedure used by Natioanl Eastern Corp in Plainville,Ct. Get hold of them to learn more about it.

I am of the understanding that in the older days of riveted fire tube boilers that this process was used to restore a sagging shell that may have been overheated due to lets say excessive scale accumulation on the waterside. One case explained to me was that this steel worker from Worcester ,MA who specialty was to do that, spent hours heating to cherry red condition and then hammering the heck out of that deformed section to restore the drum back to its approximate original shape. I dont believe that it is an acceptable ASME/NB repair method for pressure parts.

 

[deanc]

chicopee

Called "saggs and bags" See RD-2020 in the NBIC.

Heat shrinking;in carbon steel your shrink will generally be 1/2 of your heated expansion.

If this is to be done on ASME work I (as a AI)would ask for a controlled procedure. Temps.,cooling,heating,and metalurgical concerns.