Today I mainly introduce to you, the production process of seamless steel pipe, there are two kinds of hot rolling and cold rolling, let’s take a look at it.
1. Hot rolling (extrusion seamless steel pipe): round billet – heating – perforation – three-roll cross-rolling, continuous rolling or extrusion – off-pipe – sizing (or reducing diameter) – cooling – straightening – hydrostatic test (or flaw detection) – mark – into the warehouse. The seamless steel pipe is formed by perforating a steel ingot or a solid tube blank, and then hot rolled, cold rolled or cold drawn.
The specifications of the seamless steel pipe are expressed by the outer diameter * wall thickness in millimeters. Seamless steel tubes are divided into two types: hot rolled and cold rolled (dial) seamless steel tubes.
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. Cold-rolled (dial) seamless steel pipe in addition to general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, petroleum cracking pipe, other steel pipes, also includes carbon thin-walled steel pipe, alloy thin-walled steel pipe, Stainless thin-walled steel pipe and special-shaped steel pipe.
The outer diameter of hot-rolled seamless pipe is generally larger than 32mm, the wall thickness is 2.5-75mm, the diameter of cold-rolled seamless steel pipe can reach 6mm, the wall thickness can reach 0.25mm, the outer diameter of thin-walled pipe can reach 5mm, the wall thickness is less than 0.25mm, cold Rolling is more accurate than hot rolling.
Generally, the seamless steel pipe is formed by hot-rolled or cold-rolled low-alloy structural steels such as 10, 20, 30, 35, 45, etc., such as 16Mn and 5MnV, or 40Cr, 30CrMnSi, 45Mn2, 40MnB, and the like. Seamless steel pipes made of low carbon steel such as 10 and 20 are mainly used for fluid conveying pipes. 45, 40Cr and other medium carbon steel seamless pipes are used to make mechanical parts, such as the force parts of automobiles and tractors.
Generally, seamless steel pipes are required to ensure strength and flattening test. The hot rolled steel pipe is delivered in a hot rolled state or a heat treated state; the cold rolling is delivered in a heat treated state by heat.
Hot rolling means that the temperature of the rolled piece is high, so the deformation resistance is small, and a large amount of deformation can be achieved. Taking the rolling of the steel sheet as an example, the thickness of the continuous casting blank is generally about 230 mm, and after rough rolling and finish rolling, the final thickness is 1-20 mm.
At the same time, due to the small width-to-thickness ratio of the steel plate, the dimensional accuracy requirement is relatively low, and the shape problem is not easy to occur, and the convexity is mainly controlled. For the organization, it is generally achieved by controlled rolling and controlled cooling, that is, controlling the rolling and finishing temperatures of the finishing rolling.
2. Cold-rolled seamless steel pipe: round billet – heating – perforation – heading – annealing – pickling – oiling (copper plating) – multi-pass cold drawing (cold rolling) – blank tube – heat treatment – straightening – water pressure Test (inspection) – marking – storage.