chiba 4x8 sheets metal prices corrugated roofing sheets ppgl is currently the most widely used ferritic stainless steel, mostly used in kitchen utensils, construction industry and other fields, it has the advantages of low cost, high thermal conductivity, low coefficient of linear expansion and so on. However, due to the inherent characteristics of ferritic stainless steel, slabs are prone to transverse crack defects during the production process.
Most of the transverse cracks of the slab are concentrated in the middle of the inner arc side surface of the slab. The cracks on the surface of the slab are small and difficult to be found. After rolling, they expand into large cracks. The hole defect of the steel plate poses a great threat to the production organization and safety.
According to the analysis, the transverse crack defect of chiba 4x8 sheets metal prices corrugated roofing sheets ppgl billet is the result of a combination of factors, but the main reason is that the arc in the secondary cooling section of continuous casting is poor, the secondary cooling is uneven, and the high temperature strength of the steel itself is low. , the brittle transition temperature is high. To this end, the corresponding process control measures are:
1. The existence of hard and brittle second-phase particles in steel will affect the nature of cracks. There are a large number of carbide precipitations on the ferrite grain boundaries. This kind of precipitates along the grain boundaries will accelerate the expansion of cracks, resulting in casting The billet is more prone to brittle fracture. Strictly control the composition of steel grades, especially the control of the mass fraction of carbon and nitrogen. On the premise of not excessively increasing the production cost, wC+wN is required to be less than 0.03%.
2. Appropriately speed up the continuous casting speed, and achieve forced cooling by improving the quality of the nozzle, the injection angle, and increasing the cooling water volume, increasing the water flow rate, and reducing the water temperature within a certain range, so as to strengthen the uniformity of the surface cooling of the billet and reduce the The difference between the temperature at the center of the slab and the temperature at the corners, the slab is rapidly cooled around 500 °C to avoid the generation of brittle phases.
3. Improve the arc alignment accuracy of the casting machine, avoid excessive stress on the solid-liquid interface at the initial stage of solidification, and prevent the occurrence of intergranular cracks. The arc accuracy is 0.27mm.
4. The casting billet is ground with temperature, and the grinding temperature is controlled to above 120℃, and the sequence and rolling of the billet are completed within one week.