Matching flat washers
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For a certain non-metallic pipe, the design specifies the use of 35CrMo/30CrMo fully threaded studs/nuts, along with flat washers per GB/T97.2. However, according to GB/T 97.2, washers with a hardness grade of 200 HV are suitable for: hex head bolts and screws with a performance grade of up to 8.8 and product grades of A and B; hex nuts with a performance grade of up to 8 and product grades of A and B; hex head bolts, screws, and hex nuts made of stainless steel or materials with similar chemical compositions; as well as self-tapping screws with a hardened surface. Washers with a hardness grade of 300 HV are suitable for: --Hex head bolts and screws with a performance grade of up to 10.9 and a product grade of A and B; --Hex nuts with a performance grade of up to 10 and a product grade of A and B. Are these two applications compatible? How to solve it.
Your bolts are the same as those I used recently. This specification offers only 200HV and 300HV options; the hardness of 300HV is higher than that of bolts and nuts, so it should not be used. Therefore, only 200HV is an option.