Application scope of bolts in the ASME B18 series

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The ASME B18 series, which serves as standards for bolts/nuts, comprises several sub-series; ASME B18.2.1 and ASME B18.2.2 specify the bolt fasteners used for flanges as defined in ASME B16.5. In other standards under ASME B18, there are various hex head screws and studs in metric units. Are there any regulations regarding the scope of application for these standards? Also, are there any standards within them that can be used interchangeably with ASME B18.2.1 and ASME B18.2.2? Although ASME B18.2.1 and ASME B18.2.2 use imperial units, domestic standards HG/T20634 and SH/T3404 also specify metric units for bolts; these can be used interchangeably with the flanges specified in ASME B16.5. So, I would like to know the application scopes of each standard in the ASME B18 series. Is there anyone who knows more details about this? I hope those with extensive experience will not hesitate to share their knowledge!