Common problems and solutions for billet annealing

How does a billet obtain a fine-wavelength body-line structure with excellent performance?
The heating and annealing treatment will make the steel material soft, and the quenching treatment will make the steel hard. In comparison, if the "normalization" treatment is applied, the layered wave-like iron structure can be obtained, which can effectively improve the machinability and resistance of the steel. Grindability, at the same time, it has the advantages of no cracks, less deformation and convenient operation. However, normalized induction heat treatment is a difficult heat treatment technology, because it is cooled by air cooling, and it will be affected by many factors, such as slab annealing heating equipment, cooling effect in summer and winter, workpiece size is air-cooled. Different rates, even winds, can affect the cooling rate. Therefore, normalized intermediate frequency heat treatment uses various methods to maintain uniformity, and can use sunshades, curtains, potholes, fans, and the like. The electric heating billet equipment production line produced by Haituo can use a closed cooling tower to cool the workpiece.



Difference between heat treatment and annealing treatment of normalized billet heating equipment
Normalization treatment is heated to A3 point or above Acm point 40~60 °C for a period of time, so that the steel structure becomes a uniform Worth field structure, and then cooled to room temperature in a static heat treatment program. For the hypoeutectoid steel, the grain refinement can be obtained with good strength and toughness; for the hypereutectoid steel, the ferritic carbon iron can be prevented from forming a network precipitate on the iron grain boundary of the Worthfield. To reduce the toughness of the material. Haituo billet heating equipment is designed and manufactured by engineers with many years of experience.

How to eliminate the residual stress of the workpiece?
The stress relief annealing is to cool to room temperature after heating for a period of time from 450 to 650 ° C below the transformation point, which can eliminate the residual stress generated in the cutting, stamping, casting and welding process of the steel. For carbon steel, the reference billet heating temperature is 625 ± 25 ° C; for alloy steel, the reference heating temperature is 700 ± 25 ° C. The holding time will also vary. For carbon steel, the holding time is 1 hour for every 25mm thickness. For alloy steel, the holding time is 2 hours for every 25mm thickness, and the cooling rate is 25mm every time. Cooled at a cooling rate of 275 ° C / hour or less. The continuous casting billet heating furnace Haituo is more professional.




How to prevent medium frequency induction heating deformation?
To prevent the occurrence of induction heating deformation of the billet, it is preferred to slowly heat and perform a preheat treatment. In general steel, when preheating temperature is selected, the preheating temperature can be selected according to the following criteria:
(1) The preheating temperature is below the metamorphic point. For example, ordinary steel is about 650~700 °C, and high speed steel is about 800~850 °C.
(2) The preheating temperature is about 500 °C.
(3) Two-stage preheating, first preheating at a reliable section of the work at about 500 °C, and after preheating for a period of time, the preheating temperature is raised to below the A1 metamorphic point.
(4) Three-stage preheating, for large steels containing high alloys, such as high-speed steel, sometimes need to be preheated at 1000~1050 °C for the third stage.