GB/T 7306.1 Pipe threads with 55 degree thread angle where pressure-tight joints are made on the threads Part 1:Parallel internal and taper external threads
GB/T 7306.2 Pipe threads with 55 degree thread angle where pressure-tight joints are made on the threads Part 2:Taper internal and external threads
GB/T 7307 Pipe threads with 55 degree thread angle where pressure-tight joints are not made on the threads