Ceramsite sand technology has matured in China in recent years. Although there is no industry standard in the country at present, with the continuous development of lost foam casting technology in recent years, the efforts of the majority of lost foam casting workers, the original and auxiliary materials used in lost foam casting, Process equipment, jewel sand production and technical management, etc., have fully adapted to the requirements of lost foam casting production. At present, the domestic foundry manufacturers have a number of different sizes of lost foam casting production line online production. Among them, there are many types such as "simple" type (excluding automatic sand treatment) and "automatic" type (except for placing models and pouring manually). However, regardless of the type, the matching of process equipment must be calculated when designing the lost foam casting production line. However, few people are involved in the current domestic technical data.
1. Casting process design principles
(1) Control the gating system is always full of jewel sand
The pouring process of negative pressure lost foam casting is the process of vaporization and disappearance of plastic mold while filling the molten steel. If the runner is not full, sand collapse is very easy to occur due to the limited strength of the coating layer, resulting in the lack of meat in the casting.
(2) Control the molten steel to return from the bottom, which is conducive to smooth filling and is not easy to form an empty cavity.
(3) due to the suction of vacuum, under the action of gravity and suction, the filling speed of molten steel is accelerated, and the pouring system is suitable for larger.
2. Gating system form
Selection of pouring method: vertical pouring, bottom pouring, casting spacing of 70~100mm put a row of 13 pieces (1 ton furnace, ladle capacity of 1 ton).
(1) The difference between negative pressure lost foam casting and sand casting is that the general steel castings are open, while the negative pressure lost foam casting adopts a closed system, and it must be closed at the inner gate. This is mainly due to the fact that the runner before the in-gate must be kept full.
(2) The size and opening position of the gate Molten steel enters the model, the plastic mold begins to burn and gasify and disappear, and the front end of the liquid flow forms a temporary cavity. In order to prevent the molten steel from melting the model at high temperature, forming a large empty cavity and sand collapse, the speed of filling the molten steel is roughly the same as the speed of disappearance of the model, and the filling speed of molten steel is suitable and fast. The gate is slightly larger than in previous designs.
The position of the inner gate shall be 20-30mm on the lowest position of casting pouring. According to the design of the gating system of ordinary sand mold casting, the size of the inner gate is calculated, and the cross-sectional size of the inner gate is 30 × 2Omm after enlarging <1/3.
In order to prevent the casting from being close to the runner, the model deforms and melts at high temperature, the inner gate is properly lengthened, and the design length is 5Omm. jewel sand
(3) Runner
The cross-sectional dimension of the runner is 70 x 6Omm.
(4) Sprue
The sprue section size is 70 x 7Omm.
(5) pouring cup
The pouring head is greater than 200-250mm.
Be sure to set up a pouring cup. The main function of the gate cup is to accumulate molten steel, so that the sprue section is filled instantaneously and the molten steel flows down neatly and steadily.
3. Negative pressure selection
Pay attention to adjust and control the degree of negative pressure at 0 when pouring. 02-0. 03Mpa range, after pouring to maintain the same degree of negative pressure about lOmin