Cold Working Processes of Steel Pipes
What are the advantages of cold working processes compared with hot rolled processes?
(1) Cold working processes can be adopted to produce thin wall pipes,extremely thin wall pipes and large diameter thin-wall pipes, small diameter pipes, capillary pipes, and all kinds of special-shaped and variable section pipes or pipe fittings.
(2) Cold working processes can be used to produce steel pipes with high dimensional accuracy and high surface finish.
(3) The cold working steel pipe can obtain high comprehensive mechanical properties, because the process of cold working contributes to refining the metal grain and matching the corresponding heat treatment.
What are the main features of the cold rolled processes?
(1) There is hardly any metal consumption.
(2) The amount of deformation is large. The reduction of the pipe wall (reduced 75%-85%) and the reduction of the diameter (reduced 65%) can be obtained by using the conical mandrel (periodic cold rolled processes), thus the production cycle can be shortened.
(3) Because of the large amount of reduction, the uneven thickness and tolerances of the pipe wall can be reduced significantly.
(4) The state of deformation stress is good and the size of the pipe product is accurate. Also, the quality of the internal and external surface is good, and the surface will not present the longitudinal cracks occurring in the cold drawn processes.
(5) A large number of finished pipes can be made of a few pipe materials with different wall thicknesses.
(6) The disadvantages of cold rolled steel pipes are that the variety can not be diversified, the tool is difficult to manufacture, and the equipment is kind of complicated due to the limitation of tools or process requirements.
(7) The cold rolled process is widely used in the production of the high alloy steel pipes, the carbon steel pipes and the alloy steel pipes.
What are the characteristics of the cold drawn processes?
(1) Cold drawn processes have high productivity and high flexibility. Because the tool is simple and easy to adjust, steel pipes in a variety of shapes can be produced by this method, and the pipes include the capillary pipe, the thick wall pipe, the small diameter pipe and any kinds of special-shaped pipe which are difficult or impossible to be produced by other methods.
(2) The steel pipes produced through the cold drawn processes have superior quality. The equipment adopted for the cold drawn processes is relatively simple, and the cost of tools is low.
(3) The disadvantage of the cold drawn process is that the production cycles are more. Because the deformation amount per pass is generally no more than 40% and there are many auxiliary processes, the metal consumption becomes more compared to the metal consumption in the cold rolled process.
(4) The cold drawn process is mainly used for producing all kinds of carbon steel pipes, some low alloy steel pipes and the alloy steel pipes. In recent years, the cold reduced process has been introduced. This process has the advantage of high productivity. The amount of deformation is up to 50% to 60% and the small diameter pipes (3 to 4mm) can be manufactured through the cold drawn process.
Source: China Steel Pipes Manufacturer – Yaang Pipe Industry (www.ugsteelmill.com)