Importance of heating temperature for stainless steel strip rolling

At the beginning of rolling and producing stainless steel strips, the problems often encountered are relatively high rolling temperature, small temperature range during rolling, and high temperature deformation resistance of materials. Therefore, if the heating temperature of the billet used for rolling is lower than the required range, it cannot ensure that the billet has sufficient plastic deformation capacity during rolling, but if the heating temperature of the billet is higher than the required range, it will lead to metallographic structure. The ferrite content is greatly increased, and the consequence is that many surface defects will be generated in the finished stainless steel strip, which will affect the subsequent cold working performance.

And why is this suitable heating temperature so important? In fact, because the thermal conductivity of stainless steel is relatively low, it takes a relatively long time for the heat absorbed from the surface to be transferred to the center during the heating process. If the heating speed of stainless steel is too fast, the heat absorbed by the surface will come It cannot be well transmitted to the center, which leads to a larger temperature difference between the core and the surface of the billet, that is, a large temperature difference between the core and the surface inside the billet will cause the thermal expansion of the material surface to be higher than the thermal expansion of the core, so that the billet is easy to form cracks .
Therefore, when heating the stainless steel plate below 600°C, the heating speed must be strictly controlled. At this time, the heating process should follow the principles of slow heating, smooth heating curve and long time in the furnace. Usually, the furnace temperature in the low temperature section should not be higher than 800°C. .
Another point to note is that in the process of heating stainless steel plates, according to the characteristics of longer rolling time of stainless steel materials and larger temperature drop at the head and tail of the strip, in order to enhance the quality of the strip, the heating temperature of the stainless steel slab is usually controlled In the range of 1250-1270°C, the cross-sectional temperature difference after heating should be controlled within 30°C, and overheating and overburning should not occur during the heating process of the billet. Because once the stainless steel is overheated or overburned, the grains will become coarser, and the corresponding oxidation will occur between the grain boundaries, which will weaken the plastic deformation performance of the stainless steel.
In addition, during the heating process of stainless steel in the heating furnace, the requirements for the uniformity of the furnace gas temperature are relatively high, and the number of changes in steel types is large, coupled with the frequent work of roller table grinding and equipment inspection on the rolling line, so the waiting for rolling of the heating furnace The time will be relatively long, and the heat load of the furnace will vary greatly. In order to better adapt to various temperature control requirements in the production process, the heating furnace should be equipped with a better temperature control system, which can better heat the stainless steel. The speed and heating temperature are controlled without affecting the service life of the furnace.