Quality Control Problems and Countermeasures of Stainless Steel Plate Continuous Casting Billets

The quality of the continuous casting slab of stainless steel plate will directly affect the quality of the final product, so it is necessary to analyze the factors affecting the quality of the continuous casting slab and the corresponding control measures.

Continuous casting of stainless steel plate
The quality problems of continuous casting stainless steel slabs often arise from surface defects, which are mainly caused by the uneven solidification of molten steel in the crystallizer, so the main influencing factors are the cleanliness of molten steel, casting temperature and the performance of mold slag.
Molten steel cleanliness control
When the molten steel in the continuous casting machine is in the solidification period, the harmful elements sulfur and phosphorus will transfer and accumulate to the unsolidified molten steel, forming a liquid film with a low melting point such as iron sulfide and phosphide on the grain boundary, resulting in embrittlement of the grain boundary, weakening the The high-temperature strength and plasticity of stainless steel plate products, and the higher the sulfur and phosphorus content, the greater the harm caused, which makes the austenitic stainless steel continuous casting slab prone to surface depressions and cracks, so in order to optimize the surface quality of the stainless steel continuous casting slab , to strictly control the sulfur and phosphorus content in the slab.
Molten steel casting temperature control
The greater the superheat of the molten steel, the thinner the billet shell formed in the mold will be, and the weaker the performance of the cast billet to withstand external forces will be, and the formation of defects such as depressions and cracks will easily occur in the weak part of the billet shell, and the mold production The shrinkage of the slab becomes smaller, and the gap between the slab shell and the mold will also become smaller, making it more difficult for the mold slag to flow in. In severe cases, the mold slag will be partially blocked, causing heat transfer and lubrication in the mold. The inhomogeneity of the slag film between the crystallizer and the slab makes the thickness of the slab shell not uniform, and the weak part of the slab shell is prone to defects such as depressions and longitudinal cracks. Therefore, the stainless steel plate should be cast with low superheat within the range permitted by the process. For example, the superheat of 2Crl3 stainless steel is best controlled within the range of 50-60°C.
Secondary cooling zone temperature control
The secondary cooling of the continuous casting slab of stainless steel plate will have a certain influence on the formation of the surface and internal cracks of the slab. The influencing factors are not only the casting speed, steel type, slab size and surface roughness of the slab, but also affected by the cooling water. The flow rate of each section, average droplet size, flow velocity, impact angle and wetting effect and other factors are affected.
Therefore, some appropriate measures can be taken for processing control. One is to prevent excessive surface temperature return when the slab is air-cooled. Usually, the surface temperature rise rate of the slab in the secondary cooling air-cooling section should be controlled to be less than 100°C/m to prevent cracks from being generated due to the tensile stress on the solidification front surface; secondly The slab should not be straightened in the brittle temperature zone, which is usually around 700°C to 900°C. The surface temperature of the slab at the straightening point should be controlled to be greater than 900°C; the third is that the temperature of the slab exiting the continuous casting machine should be greater than 800°C, which is conducive to hot delivery of the slab or direct rolling production.