Selection of material for mating bolts of stainless steel pipe flanges
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For a project I was working on recently, all the pipelines were made of stainless steel S30408. The manufacturer used bolts made of 35CRMO and 30CRMO, which have been treated to give them a dark color, for one of the stainless steel pumps. When I discussed this with the manufacturer, I pointed out that such bolts are prone to rusting; however, the manufacturer insisted that only high-strength steel bolts could be used, and not bolts made of S30408. Additionally, bolts made of S30408 material are used at all the flange connections on the pipes. Is this a suitable choice? Is the material chosen by the manufacturer appropriate? Is there any basis for it?
If it is high pressure, it’s fine for the manufacturer to use high-strength fasteners. To achieve a second-display effect, rust prevention for fasteners can be applied. You might encounter problems using stainless steel 304 for flange fasteners; what is the pressure rating of the flange?
If you are concerned that the bolt strength may not be sufficient, you can use B8 CL.2 bolts