Hello welderwv, I have been to one of Chuck's seminars regarding stainless steels. I have also followed many of his posts here on the forum. He and many others who work with the various grades of stainless steels can certainly provide you with answers to your questions. It is a very broad question however, as there are so many different grades of stainless and applications can dictate many variables as well when fabricating and welding these. Avesta and some of the other materials and electrode manufacturers do have a lot of information to answer many of your inquiries. If you wish to have all of the answers at your fingertips you might end up with a very large technical library. Personally, I would consider that there is this forum and other resources you can access for questions regarding the specifics of welding a given stainless scenario, as well the WPS should spell out this type of information. Just my $.02. Regards, aevald
I would be surprised if you find any definitive information regarding preheating of stainless steels. It is a rare necessity related predominantly to thickness, joint strain, and in the case of duplex perhaps maintaining the proper phase balance.
My recommendation would be to gain as much general knowledge as possible as tothe metallurgy of SS's, but then rely on the advice of people such as Chuck when it comes to specific applications.
Now Chuck will charge a small consulting fee,,,,just kiddin.
I think you will find that the conditions requiring preheat for SS will be quite exceptional.
I pulled this from a rough draft D.10 doc that will soon be published.
Preheating is not normally necessary or recommended with duplex SS's. Most often it is utilized when ambient conditions are such that to increase the possibility of excessive moisture, or when ambient temperature is below 32degF. Although the risk of hydrogen embrittlement is low it has been observed. Therefore, under conditions of high restraint, or high ferrite it may be a consideration.
Preheating can help balance cooling rate when low heat input procedures are being used, especially with thicker material. Because of this, greater control of the final phase balance between ferrite and austenite can be maintained, especially for lower nitrogen materials.
Also, when joining thin mateirals to thick materials it can help eliminate the heat sink effect from the thicker material member.
The temrature to be used can vary a great deal depending upon the conditions discussed, however, 200degF seems to be a common recommendation.
Hello js55, that's some good stuff to know. Thanks for taking the time to forward that on. Regards, Allan
As we know, a stainless steel is determined by it's chromium content. Anything with approximately 10.5% chromium, with or without additional alloys, is considered a stainless steel. There are stainless steels that recommend a preheat is performed. (martensitic and ferritic stainless steels). However, the PH's, austenitics, super austenitics, Duplexes and Super Duplexes "normally" do not require a preheat unless it is to remove the moisture. The Duplex's cooling rate, which determines the austenite/ferrite balance, is normally done with the interpass temperature. However, if a Duplex is given a preheat for whatever reason, it should not exceed the recommended interpass temperature which is 150C for regular Duplex and 100C for the Super Duplexes. But, to say that stainless steels do not require a preheat is not a true statement. Just certain grades is where it is not recommended.
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