1. Production process
The 693 brake caliper and 812 brake caliper of ZHY casting are produced in the same line, and the production equipment conditions are the same: using alixu sand mixer, disa231-c vertical parting extrusion molding machine, z955 hot core machine, should reach medium frequency induction furnace (6T), plunger type automatic pouring machine. The size of sand box is 675 mm × 550 mm × 300 mm, and the temperature of sand mold is 35 ℃. The jaw part of the casting is formed by coated sand core, the core making process is similar, and theis shown in Figure 1.
The spheroidizing treatment is carried out in a 1t treatment package by wire feeding. The amount of spheroidizing agent line is 22 m / T, the amount of inoculant in the subcontract is 0.5%, the adding speed of flow inoculant is 5 g / s, the pouring temperature is 1 380 ~ 1 430 ℃, and the pouring time is 8 ~ 9 s.
2. Existing problems
According to the above process, after processing, it is found that there are porosity defects, most of which are concentrated in the 1.5mm area under the casting jaw (as shown in Figure 2). The shape of the porosity is basically spherical and water drop, the inner wall of the hole defect is smooth, and the aperture is about 0.5 ~ 2mm.
See Table 1 for the comparison of void rejection rate of two kinds of brake caliper. It can be seen from table 1 that there are subcutaneous pores in the jaw after processing. The average scrap rate of 693 brake caliper is 3.52%, and the highest scrap rate is 5.66%; while the average scrap rate of 812 brake caliper is only 1.32%.