- In order to reduce the internal cracks of the casting slab, the mold cooling and secondary cooling section should not be forced to cool, and start to check the water volume and secondary cooling ratio of the mold
Optimization of water volume.
- Eliminate the remaining water jacket, the wall thickness of the water jacket is changed from 6mm to 8mm, and the material is changed from carbon steel to stainless steel. This kind of water jacket is not easy to deform, the inner wall is smooth, and the water flow field in the mold water gap is uniform.
- By adjusting different tension and correction pressures, take corresponding low-power samples, explore the best tension and correction pressure, and comprehensively consider the hydraulic conditions, the red billet pressure is gradually optimized from 510MPa to 310MPa, and the hydraulic valve table is replaced to make the red billet The pressure remains stable
- Improve the quality of cooling water.
- Fine operation. The stability of the crystallizer liquid level is judged by the condition of the immersed nozzle slag line after use. The stability of the crystallizer liquid level control is greatly improved, and the fluctuation of the crystallizer liquid level is increased from about ±10mm to ±5mm, and at the same time Ensure that the immersion nozzle is centered, and the filling of the protective slag is relatively standardized.
- Strictly control the superheat of molten steel in the tundish. The original tundish molten steel has a relatively high degree of overheating at 20-30°C, and the columnar crystals of the cast slab are relatively developed. The probability of internal cracks and loose center of the cast slab is increased. Through the study of the temperature of the tundish, the molten steel in the tundish is now strictly controlled. The degree of superheat is 15～25℃.
- Change the current situation of turbulence in the cooling water of continuous casting equipment, change the direction of the waterway, optimize the water cooling nozzle and water volume, and basically achieve a small amount of water flowing to the red billet.
- Improve the purity of molten steel and increase the Mn/S in steel. In the past, argon was blown and stirred during the whole process of the converter steel tapping, and then the small argon was softly blown for 3 minutes, and it was optimized to be the whole process of argon blowing and stirring during the steel tapping process, and the small argon gas was 4 minutes to promote the full collision, growth and floating of the deoxidized products; Increase the manganese content in the 20MnSi and 20MnSiV finished products and reduce the sulfur content in the finished products, thereby increasing the Mn/S in the steel. Before optimization, Mn/S many heats are below 15, and after optimization, all of them are above 18. The above measures are reduced The hot embrittlement tendency of sulfur in the grain boundary in steel.
In the process of casting aluminum castings, it is easy to produce defects such as internal porosity, shrinkage holes, pores, etc. After these defective castings are machined, the surface dense layer components are removed and the internal structural defects are exposed. For automotive cast aluminum parts with sealing requirements, such as cylinder blocks, cylinder heads, intake manifolds, brake valve bodies, etc., when performing pressure sealing tests, the existence of defective micropores will cause a large amount of leakage of the sealing medium. Waste products, and these defects are often found only after machining and pressure testing, resulting in serious waste of working hours, raw materials and energy.
In order to solve the problem of high scrap rate of automotive aluminum castings and save the aluminum castings that may be scrapped due to the above-mentioned defects, certain treatment measures must be taken in production. At present, the most commonly used technology is impregnation treatment, that is, leak plugging. The so-called "impregnation" is to infiltrate the infiltrant into the micropores of aluminum castings under certain conditions. After solidification, the filler that penetrates into the pores is connected to the inner wall of the casting pores to block the micropores so that the parts can Process technology that meets the conditions of pressurization, anti-seepage and anti-leakage.