Explanation of the cause of cracking of the furnace shell of the trolley annealing furnace

     Explanation of the causes of cracks in the furnace shell of the trolley annealing furnace

      Car-type annealing furnace is usually used to produce high-quality home appliance panels and automotive panels, and generally includes the following furnace sections: jet preheating section (JPF), radiant tube heating section (RTF), soaking section (SF), slow cooling section }scs), rapid cooling section (Rcs), outlet section (ES), etc. The trolley-type annealing furnace adopts three-stage waste heat recovery of exhaust gas, push-pull combustion system and matching ON/OFF combustion control system, furnace composite lining, etc. Advanced energy-saving technology.

      The steel structure of the trolley annealing furnace mainly includes the furnace shell support frame and the driving equipment support frame (platform steel structure). Taking into account the potential thermal expansion and contraction of the furnace shell, the supporting frame of each section of the furnace shell and the steel platform are independent of each other. The bottom roller chamber of each furnace section is first installed in place, and the four reference columns are welded based on their own four-corner columns; then the left and right integral end plates are welded. The operating side and the transmission side are each composed of several independently manufactured side plates. Welding and installation from bottom to top, and finally the top roller chamber. The top roller chamber also has 4 reference columns, which can be installed and welded with the 4 furnace bodies from the quasi-family column to complete the manufacture and installation of the trolley annealing furnace shell. The platform is installed on the drive side and is used to store the furnace roof. Principle!_

       According to the working principle of the slow cooling section, the preliminary analysis is that the inconsistency of thermal expansion at this place leads to cracking of the channel steel. The negative pressure generated by the circulating cooling and suction action of the circulating fan will carry the weighted gas into the furnace, making the oxygen content of this section biased. When the steel grade specification E7J is not changed, the furnace condition is stable; and once the steel grade specification is switched and the temperature changes frequently, the cracking will be further deteriorated and the furnace condition will be difficult to maintain stable

       When the steel specification is switched, the temperature difference between the inlet and outlet air in the slow cooling section of the hot-dip galvanizing unit is usually required to be about 200 K. Considering the gap between the cooling air box and the furnace shell, the high-temperature circulating gas will conduct heat exchange at this gap; The I f=steel and channel steel on the square duct frame are welded together with the steel structure of the furnace shell. The thermal difference between the room temperature air outside the furnace and the high temperature gas in the furnace will produce a thermal gradient on the corresponding channel steel. Or because the expansion and rigidity of stainless steel can hardly meet the temperature difference and deformation requirements of the air duct, it will also cause the channel steel to crack.