The gear shaft is a large rotating shaft with large section and slow cooling, so the as-cast microstructure of the casting is coarse. Therefore, the diffusion annealing and quenching and tempering heat treatment process is adopted to eliminate the coarse grains generated during the casting process, thereby ensuring the intrinsic quality of the product. . The casting process diagram of the gear shaft is as follows.
The operation points are made of quartz clay sand. In order to increase the retractability of the sand type, 15 (by volume) sawdust is added during the sand mixing. Use a scraper to scrape out the metal-type hanging sand layer of each section, and ensure that the hanging sand layer is uniform. The thickness of the hanging sand layer is 1525mm, and the compactness is appropriate.
Brush the water-based zircon powder coating on the sand surface. After flattening, brush the paint again and let it dry. The metal type after hanging sand molding is baked in a drying kiln for 45 hours, and the temperature is 200250. When the box is assembled, the positioning of each mold is aligned, the sealing surface is blocked by mud, and the gap in the cavity after the box is closed. They are all smoothed with zircon powder coating paste, and finally the sand and other impurities in the cavity are drained. When tapping, the steel is selected and poured at a low temperature. When the liquid level of the molten steel rises to 1/2 of the riser, the molten steel is injected from the riser, and after pouring, the riser is refilled twice with hot molten steel. After the pouring is completed, the heating electrode is inserted into the center of the riser with an insertion depth of 500 mm, and the electric heating process curve is as shown.
After the electric heating is completed for 24 hours, the box is punched, the sand layer and the flash edge of the casting surface are removed, and then the furnace is slowly cooled to room temperature. The casting is subjected to diffusion annealing treatment to eliminate the coarse weiss structure generated during the casting process and to refine the grains. The annealing process is shown in 3.
Test results Casting gear shaft blanks, some of the surface has some sticky sand, the feeder is good for shrinkage, after roughing, the casting surface has no casting defects such as air holes, sand inclusions, shrinkage holes, etc. After ultrasonic testing, it meets the technical requirements of the drawings. Therefore, the ZG35CrMoV converter gear shaft can be produced by this casting method, which can completely replace the forged steel parts, and the cost saving in the mass production is about 30.
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