According to JIS G3452, pipes shall be manufactured by electric resistance welding or butt welding. Pipes shall be delivered as manufactured. However, the cold-finished pipes shall be annealed after manufacturing. This is done to relieve stress that has built up during the manufacturing process and to improve the pipe’s ductility and toughness.
The standard for both ends of pipes is that they shall be either threaded or plain-ended. Pipes of a nominal diameter 350A or over shall have plain ends, while those of 300A or under may have either type of end. When the buyer specifies, pipes may be ordered with beveled ends instead. The shape of the bevel is to be agreed upon between the buyer and manufacturer, but absent such an agreement, it shall conform to the illustration below.
JIS B 0203 describes the standards for taper threads on threaded pipes. The taper threads specified in JIS B 0203 shall be applied on both ends of the pipe, and a socket as described in JIS B 2301 or JIS B 2302 shall be screwed into one end of the threads. The other end of the pipe, which will not have a socket screwed into it, shall be provided with a thread-protecting ring or protected by other suitable means. If the purchaser specifies, the threaded pipe may dispense with a socket. The taper threads shall be inspected by JIS B 0253 before use.
• Before pipes and sockets are threaded, they zinc-coated. If the inspection passes, the pipes and sockets shall be cleaned by sandblasting, pickling, etc., then hot dip galvanized. The zinc used shall be distilled zinc ingot Class 1 specified in JIS H 2107 or at least equivalent thereto. Other general matters of zinc-coating shall be by JIS H 8641. Zinc coating protects the metal from corrosion and makes it last longer. It is essential in places where pipes and sockets are exposed to moisture or chemicals.