Formulate the production process and deformation regulations of cold rolling and drawing of pipelines. In the steel pipe cold rolling and cold drawing unit, before the product is put into production, there are clear regulations on the selection of its production process, deformation parameters and processing equipment, as the basis for organizing production and operation. This job is to develop a process specification. According to the cold working method used, the process specification can be divided into a drawing table (cold drawing deformation) and rolling table (cold rolling deformation) and a rolling and drawing table (cold rolling and drawing deformation).
Due to the characteristics of multi-process, multi-cycle and multi-variety in the production of cold-formed steel pipes, in order to make the production reasonable and orderly, it is very important to formulate process regulations.
The content of the process flow table includes pipe size, deformation method and hole type, the deformation amount of each hole type and deformed pipe size, processing equipment, auxiliary processes and tooling types, etc. In addition to material processing characteristics and pipe technical conditions, in the preparation of specific production conditions are also taken into account when formulating the process specification sheet. Each cold-drawn cold-rolling mill has its own process specification according to its own production conditions, which is constantly revised and improved in production practice.
Regarding the usage of cold rolling and cold drawing, it is divided into three schemes: cold rolling, single cold drawing and cold drawing.
(1) Single cold rolling scheme. Compared with cold drawing, cold rolling has a better stress state and larger hole deformation, which can shorten the intermediate process and production cycle, reduce consumption and cost, and is suitable for processing high-alloy steel pipes with poor plasticity and non-ferrous metals that are difficult to deform. . The disadvantages are low productivity and poor production flexibility.
(2) Combined scheme of cold rolling and cold drawing. The combination of cold rolling and drawing can give full play to the advantages of large-scale cold rolling deformation and flexible cold drawing production, reduce processes, shorten the production cycle, improve productivity and expand varieties. When the cold rolling and drawing combination scheme is adopted, the steel pipe is usually rolled on the cold rolling mill to the fixed wall or a certain pass before the fixed wall, and then drawn to the finished pass.
(3) Single cold drawing scheme. The single-piece cold-drawing scheme is not an ideal cold-drawing scheme due to small deformation, large deformation, many intermediate processes, long production cycles, and large consumption of metals and accessories. However, the structure of the drawing machine is simpler than that of the cold rolling mill, the investment is less, the operation is convenient, the manufacture and replacement of tools are convenient, the production flexibility is large, and the productivity is high. Therefore, it is widely used in single-pass cold drawing of carbon steel, low alloy steel and general non-ferrous metal pipes.
The selection principle of cold rolled tube blank is basically the same as that of cold drawing, but when determining the size of the tube blank and intermediate tube, the requirements of cold rolling mill pass system should be considered.
The selection of hole shape deformation is to determine the degree of deformation of the hole shape (section compression ratio, elongation coefficient), diameter reduction and diameter reduction. When conditions permit, a large amount of hole pattern deformation should be selected to reduce the machining hole pattern. When selecting the pass deformation of the cold rolling mill, it is necessary to consider the strength of the main components of the rolling mill, the material plasticity, the quality requirements of the pipe, etc. In actual production, dimensional accuracy, surface condition and tool life are often the factors that limit the pass deformation. For the output and quality of the product, the deformation of the finished product should be smaller. In the multi-roll cold rolling mill, the pass deformation (especially the reduction) is smaller than that in the two-roll cold rolling mill.
The factors affecting the hole shape deformation of the cold drawing machine are: the cold working properties of the metal (including the strength and plasticity of the metal), the strength of the pipe body (the drawing phenomenon cannot occur during the cold drawing process), the ability of the cold drawing machine, the selected Drawing method and Die Type. The factors that should be considered in the selection of deep drawing hole deformation are: the number of continuous deep drawing holes (no heat treatment is performed in the middle of the hole pattern), heat treatment quality, pickling and lubrication.
Determination of the deformation pass is determined by the following formula: where is the total elongation coefficient from the processing of the pipe to the finished product; F0 is the cross-sectional area of the pipe; FK is the cross-sectional area of the finished product; μC is the average elongation coefficient.
By adopting the method of combining cold rolling and cold drawing, the size of the intermediate pipe during the cold rolling to cold drawing process can be determined according to the structure of the cold rolling mill and the cold drawing machine and the existing pass system of the cold rolling mill. Then the cold rolling and cold drawing passes are calculated separately. The sum of the two is the total deformation process.
