Seamless steel pipe is a pipe mainly used for fluid transportation. It is hollow in the middle and round or square around. The material is generally carbon steel or stainless steel and has no seams, hence its name. It is mainly produced by rolling, drawing, extruding or perforating methods. Suitable for transportation of most fluids, such as oil, natural gas, coal gas, water, etc.
The Manufacturing Process Of Stainless Steel Seamless Pipe
1.Hot rolling (extruded seamless steel pipe):
round tube blank → heating → perforation → three-roll cross rolling, continuous rolling or extrusion → detubing → sizing (or diameter reduction) → cooling → straightening → hydraulic test (or flaw detection) → Mark → Warehouse
The raw material for rolling seamless pipes is round tube billet. The round tube billet must be cut by a cutting machine into a billet with a length of about 1 meter and sent to the furnace for heating via a conveyor belt. The billet is fed into the furnace and heated to a temperature of approximately 1,200 degrees Celsius. The fuel is hydrogen or acetylene. Temperature control in the furnace is a key issue. After the round tube comes out of the furnace, it must be pierced through a pressure punching machine. Generally, the more common piercing machine is the tapered roller piercing machine. This type of piercing machine has high production efficiency, good product quality, large perforation diameter expansion, and can penetrate a variety of steel types. After perforation, the round tube blank is successively cross-rolled, continuous rolled or extruded by three rollers. After extrusion, the pipe should be removed and calibrated.The sizing machine rotates a tapered drill bit at high speed into the steel blank to drill holes to form a steel pipe. The inner diameter of the steel pipe is determined by the outer diameter length of the drill bit of the sizing machine. After the steel pipe is sized, it enters the cooling tower and is cooled by spraying water. After the steel pipe is cooled, it will be straightened. After straightening, the steel pipe is sent to the metal flaw detector (or hydraulic test) by a conveyor belt for internal flaw detection. If there are cracks, bubbles and other problems inside the steel pipe, they will be detected. After quality inspection, steel pipes must undergo strict manual selection. After the quality inspection of the steel pipe, spray the serial number, specification, production batch number, etc. with paint. And it is hoisted into the warehouse by a crane.
2.Cold drawn (rolled) seamless steel pipe:
round tube blank → heating → perforation → heading → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → billet tube → heat treatment → straightening →Hydraulic test (flaw detection)→Marking→Storage.
The rolling method of cold-drawn (rolled) seamless steel pipe is more complicated than hot-rolled (extruded seamless steel pipe). The first three steps of their production process are basically the same. The difference starts from the fourth step. After the round tube blank is hollowed out, it needs to be headed and annealed. After annealing, special acidic liquid should be used for pickling. After pickling, apply oil. Then it is followed by multiple passes of cold drawing (cold rolling) and then special heat treatment. After heat treatment, it is straightened.
The Differences Between Hot Rolling And Cold Drawn(Rolled)
1.Cold-rolled shaped steel allows local buckling of the section, so that the bearing capacity of the rod after buckling can be fully utilized; while hot-rolled shaped steel does not allow local buckling of the section.
2.The causes of residual stress in hot-rolled steel and cold-rolled steel are different, so the distribution on the cross-section is also very different. The residual stress distribution on the cold-formed thin-walled steel section is curved, while the residual stress distribution on the hot-rolled steel or welded steel section is film-type.
3.The free torsional stiffness of hot-rolled steel is higher than that of cold-rolled steel, so the torsional performance of hot-rolled steel is better than that of cold-rolled steel.
Cold rolling refers to processing steel plates or steel strips into various types of steel through cold drawing, cold bending, cold drawing and other cold processing at normal temperature.
