Generally, the production process of seamless steel pipe includes hot rolling and cold drawing.
1. Hot-rolled seamless steel pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes and other steel pipes. Hot-rolled steel pipes are delivered in a hot-rolled or heat-treated state;
Production process of hot-rolled seamless steel pipe: tube blank→heating→piercing→three-roll cross rolling, continuous rolling→pipe removal→sizing→cooling→straightening→hydraulic test→marking→storage, the raw material for rolling seamless pipe It is a round tube blank. The round tube blank should be cut by a cutting machine into a billet with a length of about 1 meter, and sent to the furnace for heating by a conveyor belt. The tube blank is sent into the furnace and heated to about 1200 degrees Celsius. The fuel for heating the tube blank is hydrogen or acetylene. The temperature control in the furnace is a key issue. After the tube is released from the furnace, it must be pierced by a piercing machine.
Generally, the more common piercing machine is the tapered roller steel pipe piercing machine. This kind of piercing machine has high production efficiency, good product quality, large perforation diameter expansion, and can wear a variety of steel types. After piercing, the tube blank is successively cross-rolled and continuous rolled by three rolls. After extrusion, the pipe should be taken off for sizing. Sizing by high-speed rotary cone drill holes into the billet to form a steel tube (the inner diameter of the steel tube is determined by the length of the outer diameter 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 by the conveyor belt for internal flaw detection. If there are cracks, bubbles and other problems inside the steel pipe, they will be detected. After the steel pipe passes the quality inspection, it must also pass strict manual selection. After the quality inspection of the steel pipe, paint the serial number, specification, production batch number, etc. with paint. And hoisted into the warehouse by crane.
2. In addition to general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, and other steel pipes, cold drawn seamless steel pipes also include carbon thin-walled steel pipes, alloy thin-walled steel pipes, Rust thin-walled steel pipes, special-shaped steel pipes. Cold rolling is delivered in a heat-treated state. the
Cold-drawn seamless steel pipe production process: tube blank→heating→piercing→heading→annealing→pickling→oiling→multi-pass cold drawing→billet tube→heat treatment→straightening→hydraulic test→marking→warehousing. The rolling method of cold drawn seamless steel pipe is more complicated than that of hot rolling, and the first three steps of their production process are basically the same. The difference starts from the fourth step. After the round tube is empty, it needs to be headed and annealed. After annealing, use a special acidic liquid for pickling. After pickling, apply oil. Then followed by multiple passes of cold drawing. After heat treatment, it will be straightened. After straightening, the steel pipe is sent to the metal flaw detector by the conveyor belt for internal flaw detection. If there are cracks inside the steel pipe, problems such as air bubbles will also be picked out.
From the appearance: the length of cold drawn seamless pipe is generally shorter than that of hot rolled seamless pipe. In terms of wall thickness, the cold-drawn seamless pipe is more uniform than the hot-rolled seamless pipe. The precision of the hot-rolled pipe is lower and the surface is rough, while the precision of the cold-drawn pipe is higher and the surface roughness is better.
