Hydraulic housing/hydraulic casting
Casting method of hydraulic castings: die casting machine is a machine used for pressure casting. under the action of pressure, the die casting machine hydraulically shoots molten metal into the mold for cooling and molding. after mold opening, solid metal castings can be obtained, which are initially used for die casting type, etc. Among them, hydraulic systems are mainly used to provide pressure to die casting machines, in which hydraulic castings are required. the use conditions of hydraulic castings in die casting machines are very high, such as high, and do not allow cracks, cold insulation, shrinkage, loose, slag and other defects, so the casting process for hydraulic castings is very high. The structure shown in Figure 1-3 is a typical hydraulic casting applied to the hydraulic system of die casting machine. The wall thickness of the hydraulic cavity of the casting is relatively thick, so the hot joints are distributed at the section outside the hydraulic cavity. Usually, cold iron is added at the hot joints to make the molten iron in the cavity relatively uniform cooling. At the same time, large riser or heating riser must be used in combination, reduce the generation of defects such as loose shrinkage holes at the hot joints. Although through the above efforts, to a certain extent, the hydraulic casting can be produced, but the fully qualified yield is low, even if the qualified product, but also need to be removed to the large riser or heat riser, high production costs. On the other hand, in the casting process, the structure of the runner, the structure of the sand core or the design of the sand core material is unreasonable, and the molten iron enters the cavity unevenly, and the temperature difference is large, which will affect the casting to a certain extent. The quality of the casting is easy to produce defects such as shrinkage porosity, which affects its use effect.
In addition, the structure of the above-mentioned hydraulic casting includes a casting body a, a valve body mounting hole a1 and an oil pressure cavity a2 provided inside the casting body a, the casting material is ductile iron qt500-7, the weight is 140kg, the thickness of the thickest part is 135mm, and the product belongs to thick large section ductile iron. The machining roughness of the mounting surface of the casting valve body is ra1.6μm, which is extremely high, and the hydraulic pressure requirement of 40mpa must be met at the same time. The casting shall not have leakage and seepage, which cannot be realized by conventional casting methods. The hydraulic cavity and valve body mounting hole of the above hydraulic casting are formed by sand core, specifically, the sand core is directly made of chromite sand and adhesive. This structure will have the problems of insufficient sand mold strength and uneven cooling during pouring process, during the casting process of molten iron, there may be phenomena such as sand falling out of the surface tissue, which affects the insufficient density of the tissue of the hydraulic cavity and the mounting hole of the valve body or casting defects such as pores and slag inclusions, resulting in the problems of less than ra1.6μm in machining roughness and leakage and seepage.
In addition, the existing casting process of the above-mentioned hydraulic castings, due to the feed inlet of the pouring system, as well as the entire casting process steps and parameter control is not ideal, easily lead to the appearance of the casting ring gas, slag defects and so on.