The heating furnaces used in the manufacture of seamless steel pipes include billet heating furnaces and steel pipe heat treatment furnaces. The accuracy and uniformity of temperature control are two important indicators for judging the quality of heating equipment, and an important guarantee for the heating process. Therefore, the manufacturer should strictly implement the thermocouple service life and calibration period regulations, and the furnace temperature uniformity test.
The formulation of the heating process should comprehensively consider the inherent properties of the furnace equipment, the type and quantity of the tube blank or steel pipe, and strictly control the heating rate, holding time and cooling rate to avoid cracks, overheating or overburning.
Taking the heating of the pipe billet in the perforation stage as an example, considering the low thermal conductivity of stainless steel at room temperature, that is, slow heat transfer and large expansion coefficient, there should be a long preheating time in the furnace, and the heating rate in the initial heating stage should be slow to prevent Thermal cracks are generated.
When the billet temperature exceeds a certain temperature, the thermal conductivity and plasticity of stainless steel increase rapidly. At the same time, if the stainless steel stays in the high-temperature section for too long, it will produce α phase, that is, ferrite. When the α phase exceeds a certain ratio, the metal thermoplasticity will drop sharply. In severe cases, the perforation will not be possible, and the high temperature and long-term heat preservation will also make the internal crystal grains coarse. Therefore, during the soaking stage, it should be heated quickly and completed in a short time.
In addition, attention should be paid to controlling the adjustment of the atmosphere in the furnace and maintaining a weak oxidizing atmosphere, which can not only reduce the degree of surface oxidation but also prevent surface carbon from increasing.
As a seamless pipe manufacturer, Huzhou Nanxun Yintuo Special Material Technology Co., Ltd. produces super austenitic stainless steel seamless pipes and tubes that are favored by customers. If you need to buy seamless pipes, you can contact us.