1. Roasting
The average thickness of the casting shell of the driving wheel reaches 30 m, and the local thickness reaches 45 M. the roasting temperature is not lower than 85 ° C, and the holding time is not less than 1.5-2 hours.
2. Pouring
The molten steel shall be discharged from the mold shell 15 minutes before being discharged from the furnace and quickly filled with dry sand above the runner to prevent the mold shell temperature from decreasing too much and ensure that the mold shell temperature is not lower than 350 ~ 40 C during pouring;
b. The tapping temperature of molten steel should be controlled at 1 570-1 590 ° C and the pouring temperature should be controlled at 1 5030-1 570 ° C.
C. The pouring speed shall be large flow in the initial stage, fast in the middle stage and medium speed in the middle stage. At the end of the stage (when the metal liquid level rises to within the pouring day), it shall be poured at the slowest speed (limited to continuous flow), so as to fully supplement the liquid shrinkage of molten steel;
d. After pouring the gate cup, use an iron chisel to continuously break the cracks on the gate surface
The solidification layer of the gold layer shall connect the surface of the liquid metal with the atmosphere as much as possible, and give full play to the feeding capacity of the riser.
e. After the casting is poured for 30 minutes, remove the sand filling around the mold shell to improve the cooling conditions of the casting so that it is easier to remove the sand.
342 drive wheel castings were produced by the above process method, and satisfactory results were obtained. a. After sand cleaning, gas cutting, internal stress annealing and shot blasting, the tooth profile of the drive wheel casting is clear, and the dimensional accuracy and surface roughness meet the technical requirements; b. After machining, through detailed inspection by the quality inspection department, no defects such as sand inclusion, slag inclusion, porosity and shrinkage porosity were found in the internal organization; c. On the premise of ensuring the quality of castings, the process yield of castings reaches 67%; d. After quenching treatment, the hardness of the tooth surface meets the requirements of H R C 48-5; e. After the specified process test of the installed machine, it shows that the whole machine runs smoothly and turns flexibly, which fully meets the requirements of design and service performance; f. The successful production of drive wheel castings has accumulated rich experience and created a new way for ZHY casting to produce large and complex precision castings with high technical requirements in the future.