Pickling wear-resistant plate is a high-quality hot-rolled thin wear-resistant plate as raw material, after the pickling unit removes the oxide layer, cutting edge, finishing, surface quality and use requirements between hot-rolled plate and cold-rolled plate, compared with cold-rolled plate low cost, cost-effective, is an ideal alternative to cold-rolled plate, widely used in automotive, compressor, machinery manufacturing, parts processing and other industries. In production, transverse folding defects sometimes appear on the surface of the strip, that is, many irregular strip dimples or raised creases can be seen on the surface of the strip, which is perpendicular to the running direction of the strip, seriously affecting the quality improvement and application.
It is concluded that the defects of wear-resistant plate are mainly due to the existence of yield platform and obvious upper and lower yield points of low carbon aluminum killed steel. When the uncoiling tension is too large or the deformation is too large during the bending and straightening process, the surface stress of the strip reaches or exceeds the yield strength of the material, which will cause plastic deformation of the wear-resistant plate strip, and is concentrated in a certain area, thus forming uneven transverse folding defects. Its control measures are:
1. Strictly control the content of C and N elements in low carbon steel. The carbon content is generally taken as the lower limit of the design value, which is controlled at about 0.03%, and the nitrogen content is generally controlled below 0.005%.
2. Properly adjust laminar flow mode and coiling temperature to improve the yield strength of strip steel. For ordinary cold rolled materials, the yield strength can be increased by 15 ~ 20 MPa when the coiling temperature is reduced by 30 ~ 50 ℃.
3. Improve the shape quality of the strip after rolling, evenly distribute the stress of the strip cross-section, and avoid stress concentration. Due to the difference in cross section temperature of strip steel, the transverse temperature of strip steel drops unevenly during laminar flow cooling, resulting in stress difference, which will lead to transverse folding defects. This kind of problem can be solved effectively by adopting the production process of small and medium wave.
4, control the uncoiling temperature below 40 ℃. Because the temperature has a certain effect on the strength of steel, when the temperature of steel is in the range of 40 ~ 100 ℃, the decline trend of its yield strength is obvious. Practice shows that when the uncoiling temperature of the steel coil is controlled at about 35 ℃, the probability of transverse folding of the strip steel is significantly reduced.
5, when the winding line is flat and unwinding, the deep bending roll is put in, which can make the stress of the strip cross section tend to be uniform and avoid stress concentration.
To sum up, the corresponding measures can be taken to eliminate the transverse folding defects of wear-resistant plates by eliminating the yield platform, improving the yield strength and reducing the uncoiling stress.
