Should stainless steel flanges be fastened with stainless steel bolts or 35CrMo bolts?
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It is well known that stainless steel should not come into contact with carbon steel, so why are some stainless steel flanges designed to use carbon steel bolts? Isn’t 35CrMo just carbon steel? Why not design them all as stainless steel bolts?
There are no specific regulations stating that it must be assembled in this way or that way. Stainless steel bolts are the best choice unless there is a specific reason.
There are barriers made of Teflon or zinc plating, right?
1. Technical feasibility 2. Cost 3. Storage versatility
Look at the coating; it can be used once isolation has been applied. In terms of cost, is carbon steel cheaper? Can stainless steel bolts be used on carbon steel pipes? Coated carbon steel bolts can all be used.
35CrMo should actually be classified as an alloy steel
Stainless steel bolts are relatively soft; over time their threads can become seized, and their strength is also lower than that of carbon steel bolts. They are generally used in areas inside containers where they come into direct contact with the medium.
Is the coating mentioned in that document?
35CRMO is a high-strength steel; it replaces 304 to ensure that the strength meets the requirements of the operating conditions. As for the coating on the bolt surface, it serves other purposes
I think the cost issue is the most important, along with strength. Previously, customers reported on-site that 304 bolts were too tight and would come loose
Carbon steel bolts do not come into contact with the medium inside the pipeline, so there is no impact; however, it is necessary to consider rust prevention for the bolts. It is recommended to use galvanized bolts, with strengths of 4.8 or 8.8 being suitable.