First, seamless steel pipe classification
Seamless steel pipe is generally divided into precision seamless steel pipe, cold drawn seamless steel pipe, hot-rolled seamless steel pipe, seamless cast pipe (thermal expansion seamless steel pipe is only a seamless pipe products, can not be regarded as one of the classification of seamless steel pipe ).
Hot-rolled (extruded seamless steel pipe) Production process and process circle: tube → heating → perforation → three-roll inclined rolling, rolling or extrusion → off → sizing (or reducing diameer) → cooling → straightening → water Pressure test (or flaw detection) → mark → storage cold drawn (rolling) seamless steel pipe
(Cold-rolled) → billet → heat treatment → straightening  → Water pressure test (inspection) → mark → storage
Seamless cast steel pipe as the name suggests is the use of centrifugal steel casting into a steel tube, and then processed into a seamless steel pipe production process.
Second, seamless steel pipe manufacturers and suppliers
Domestic seamless steel pipe technology is relatively mature, able to produce seamless steel pipe manufacturers can be said there are thousands, but this caused manufacturers of production equipment and production capacity can be described as a far cry from. Strength to produce a diameter of 1200mm seamless steel pipe, small diameter of 10mm to produce seamless pipe, are considered seamless tube manufacturers. For non-industry people alone from the network to distinguish these manufacturers is very difficult, not to mention there are many traders lie that they are the manufacturer, how strong their own production strength. So the procurement staff if you want to purchase seamless steel pipe must be clearly identified. Of course, seamless steel pipe and straight seam steel pipe is different, seamless steel pipe suppliers also have a lot of strength is very strong units, their inventory even to tens of thousands of tons. If it is in their procurement there can also be assured. In fact, the main fear is not afraid to encounter illegal vendors shoddy, real ones.