Stainless steel elbows are widely used in petrochemical, instrumentation, food, and other industries because of their good corrosion resistance. For professional pipe fittings manufacturers, stainless steel elbows are a high-value-added product, and their quality and output directly affect the benefits of the enterprise. At present, the domestic pipe fittings manufacturers all adopt the radial cold pressing production process when processing stainless steel elbows. The use of this process is mainly due to the high elongation of stainless steel pipe fittings and the characteristics of hot brittleness. But in the actual production process, we found that there are some disadvantages:
① The forming effect of the elbow is not good, and the pipe fittings are prone to dents, which increases the number of repairs and increases the cost of repairs.
②The mold is not easy to disassemble and assemble, which increases auxiliary man-hours and reduces production efficiency. The above problems have seriously affected the quality and output of products. For this reason, at the beginning of 2000, we made a technical breakthrough and adopted the axial cold pressing process to produce stainless steel elbows, which achieved very remarkable results.
1. Principle of the radial cold pressing process
The main factor that determines the plastic deformation of steel is elongation, the elongation of stainless steel pipes (such as 1Crl8Ni9Ti) is 45%, and the elongation of carbon steel pipes (such as 20 steel) is 25%, so stainless steel has good cold pressing Plastic deformation features. In the past, our company used the radial cold pressing process commonly used in China. The pressing process of the elbow is rough as follows: the pressure of the hydraulic machine works radially from top to bottom along the surface of the pipe fitting, the short side of the pipe joint faces upward, and the long side of the pipe joint faces upward. The side is facing down, and the core is loaded into the pipe joint, the pipe El is inserted into the horseshoe, and the pipe joint frame is placed on the lower mold. When pressing, the upper mold presses the pipe from top to bottom, and the pipe is deformed accordingly.
The deformation characteristics of the specific pressing situation can be roughly summarized as the following points:
(1) The outer circular arc tube wall (except the nozzle) is in the range of tensile deformation, and its deformation law is that the middle part becomes a circular arc, and the two flanks are straightened.
(2) The inner circular arc tube wall (except the nozzle) is squeezed, and its bending deformation is always a concave arc in the middle, and the two side wings are bulging.
(3) The deformation of the inner arc of the nozzle is in a state of extrusion to form a concave arc
2. problem analysis
In the actual production process, it is found that the following problems exist in this process.
(1) To ensure that the elbow is fully formed, the process requires that a core and a horseshoe must be placed in the pipe joint during pressing. Its structure is complex and processing is difficult.
(2) From the deformation characteristics of the pipe, it can be seen that the bending force acts along the radial direction of the pipe fitting surface, and the stress generated on the pipe fitting surface is very large, causing the unfilled section in the pipe to sag, resulting in one-time forming of the elbow Not good, increased repair time and cost.
(3) During the pressing process, the inner and outer arcs of the pipe are prone to bulges and depressions, making it difficult to remove the core and horseshoe placed inside the pipe after the pressing is completed, which increases the auxiliary time spent on removing the core, reducing production efficiency. From the above analysis, it can be seen that the above defects will inevitably appear in this process, and if the deformation is carried out along the axial direction, this problem can be better solved in terms of form. Therefore, axial deformation can be considered. Pressing process.
Post time: Jun-29-2023