cutting

Date 09-25-2004 02:43

Cutting may be done by machine, arc, or gas methods. I believe plasma hot cutting methods are preferred in order to limit hydrogen uptake. If hot cutting methods are used, the parent metal shall be preheated before any cutting to the same temperature as intended for welding, and effort shall be made to grind/machine remove the surface scale and coarse grain HAZ associated with the hot cutting method. Removal of the HAZ may not be as critical for subsequent welding by SAW, but for other processes, it can be important. Conduct suface NDE of the grind finished joint surface prior to welding. P91 materials are reputed to stress corrosion crack in air. Chemically clean the joint surfce with a non-residue light solvent immediately prior to welding. Do a google seach on: P91, P9, steel, weld and you will turn up much edifying information.

By snakejhj (*)

Date 09-25-2004 06:39

Thank you.
We prepare use plasma hot cutting method.Is it must be preheated before cutting?Do you understand my chinese english?

By Bonniweldor (**)

Date 09-25-2004 17:53

My intuitioin is that you are "playing with fire" here. A P91 material is typically used for high temperature and high pressure operating conditions which can be lethal or catastrophic if the material fails. The P91 material is air hardenable and as such the welding/cutting of P91 material requires a very sophistcated approach in order to do it successfully and with high confidence of its integrity. You need to do the information searches I suggested because no-one can give the time needed for you to become educated about the welding of this material as you need to be.

Absolutely yes, the P91 material must/shall be preheated before plasma cutting and it must be preheated to a relatively high temperature, as compared to 2.25Cr-1Mo material. Before cutting, you must find out what the necessary preheat temperature is, if you do not yet confidently know this.

By snakejhj (*)

Date 09-26-2004 05:10

I don't really undersaand "playing with fire".But I know this is not good words.My english is very poor.I know the P91 is difficult to welding.So I ask for in there.Thank you very much.I know the P91 must preheatde before cutting and welding.

By Bonniweldor (**)

Date 09-26-2004 13:08

Find someone to do a good translation for you of what I said, before welding or cutting P91 material.