The manufacturing process of seamless steel pipes does involve a variety of methods, and there are roughly the following five methods:
1.Hot rolling method: This is the core process of seamless steel pipe manufacturing. First, the round tube blank is heated to a certain high temperature to make it soft and easy to shape. Subsequently, a series of rolling mills perform continuous extrusion and drawing operations to gradually shape the round tube blank into the desired tubular shape. This method is particularly suitable for producing seamless steel pipes with larger diameters and thicker walls.
2.Cold drawing method: Cold drawing method is carried out at room temperature or slightly lower than room temperature. It usually involves pre-treatment, such as pickling and cold treatment, of hot-rolled or cold-rolled steel billets to improve their workability. The billet is then pulled into a specially made mold, and its diameter and wall thickness are gradually reduced through the drawing operation until the required specifications are reached. Seamless steel pipes produced by the cold drawing method have high precision and high surface finish, and are especially suitable for manufacturing steel pipes with smaller diameters and thinner wall thicknesses.
3.Cold rolling method: Cold rolling method is similar to hot rolling method, but the main difference is that cold rolling is performed at room temperature. A continuous rolling operation is performed on the steel billet through a cold rolling mill, which can be shaped into a seamless steel pipe without heating. The steel pipes produced by this method also have high precision and high surface quality, but are generally suitable for steel pipes with smaller diameters and wall thicknesses.
4.Hot extrusion method: Hot extrusion method is a process suitable for producing large-diameter, thick-walled seamless steel pipes. It requires heating the billet to a high temperature and then extruding it into a tube shape through an extruder. The advantage of this method is that it can produce seamless steel pipes with larger sizes and thicker wall thicknesses, but the production efficiency and cost may be relatively high.
5.Closing method: Closing method is a special seamless steel pipe manufacturing process. It usually involves heating two or more semicircular steel billets to a certain temperature and pressing them into a complete tubular structure through the rollers of a closing machine. This method is mainly used to produce large-diameter, thick-walled seamless steel pipes, and has high requirements on the quality of the steel billet and the accuracy of the rolls.
Each of the above methods has its own unique characteristics and scope of application. The specific method chosen depends on the required steel pipe specifications, performance requirements, production costs and other factors.