Problem Analysis Of Channel Steel

The 400mm unit in a steel mill is a profile unit that produces medium Angle steel and channel steel, with an annual output of 650,000 tons, of which channel steel product specifications are 638 ~ 1208, and the output accounts for about 25% of the total output. The segmented operation of finished channel steel is carried out by a 400t cold shear machine. The shear quality of the channel steel has a great influence on the subsequent process, especially the welding quality. If there are defects such as shoulder collapse, burr, tear, and cut Angle at the shear fracture, there will be a large gap in the joint of the channel steel, which will affect the welding quality, especially the strength index, resulting in a greater security risk.
With the increase of production rhythm and output, the above shear defects are more and more prominent, and the internal control rate of shear quality is only 94.2%. And the service life of the cutting edge is getting shorter and shorter, and the average shift is replaced once, resulting in an increase in production costs and labor intensity of employees. In view of these problems, the paper analyzes the process, technology and operation seriously, and puts forward the corresponding improvement measures, and obtains good results.
1. Process reasons
The design capacity of the unit is 200,000 t/a, but the output has reached 600,000 t/a, and the problem of insufficient production capacity in the cold bed area is very prominent. Compared with the production Angle steel, the cooling speed of the channel steel is slow, resulting in high temperature of the channel steel during shearing, which is prone to defects such as shoulder collapse, burr and tear, and has a greater impact on the life of the cutting edge.
2. Cutting edge design reasons
The basic basis of channel cutting edge design is the pass shape of the finished channel steel, as shown in Figure 1 (taking 100# channel steel as an example). This design is prone to the following problems in the shearing process: First, the two shoulders of the channel steel are relatively thick compared with other parts, the required shear force is also large, the cutting edge wear is faster, and the cutting edge is used for a period of time. This part of the relative wear amount is large, resulting in large shoulder gap, easy to appear shoulder collapse phenomenon; Second, compared with the waist, due to the influence of the shear Angle, when the cutting edge is worn, the shear quantity becomes smaller when cutting the two legs, and the leg shear changes from the usual cutting to tearing, and the end face of the channel leg is easy to appear burrs; Third, the leg inclination of the upper and lower cutting edge is basically the same as that of the finished channel steel pass, so that the leg is basically stressed at the same time when cutting, the shear force is large, and the cutting edge is worn faster. On the one hand, the shear impression of the leg end is serious, and on the other hand, after the aging of the cutting edge, it is easy to tear the shear part of the channel steel and there are more burrs. The latter two points are the main reasons affecting the shear quality of channel steel.