Design of Pouring Technology for Negative Pressure Disappear Mold Cast Material Mill Lining Plate
Introduction
In order to ensure the quality of castings, the design of pouring technology for negative pressure disappears the mould cast material mill lining plate is very important. This paper will introduce a scientific and reasonable pouring technology for negative casting vanish mould cast material mill lining plate, meanwhile, a series of corresponding measures are studied emphatically.
1、Materials and requirements
The mill lining plate cast material adopted in this article is HT200 cast iron. The mechanical properties of this kind of cast iron are good, with high strength and good machinability. The size of the mill lining plate is 1500mm×400mm×450mm, and the technical requirements are as follows:
1) Cavity size and curved surface tolerance must be strictly controlled;
2) The wall thickness of the cast plate should be equal, and the outer surface of the casting should be flat;
3) The allowable deviation of the outer wall thickness should not exceed 0.50mm;
4) The inner wall of the mould should be smooth and free from defects such as slag coke and sand holes;
5) The permissible burr on the edge of the casting should not exceed 0.50mm.
2、Mould design
In order to meet the requirements of the casting quality, the mould used for pouring the lining plate must have certain requirements. According to the size and materials of the castings, a matching mould design is developed.
1) The size of the mould should be matched with the size of the liner in order to ensure the smooth forming of the liner. The size of the mould should be slightly larger than the size of the liner so that the liner can be elongated. At the same time, the position of the feeding port should be at the thinnest part of the liner;
2) The cross-section of the mould should be designed reasonably, and it is necessary to keep the pouring port with a certain distance from the parting surface to prevent the molten iron from flowing into the pouring port;
3) The filling rate and the falling speed of the molten iron should be taken into account in the design of the mould. The filling rate should be easy to control and the falling speed should be adjustable;
4) The exhaust port is correspondingly set on the mould, and a certain size of the negative pressure disappear cavity should be set.
3、Reasonable selection of mould materials
Due to the high temperature of molten iron, different materials have different requirements for the mould when dealing with the mould temperature and other aspects. Therefore, it is necessary to select the appropriate mould material according to the temperature and other factors.
According to the temperature of the molten iron in this article which is about 1300 degrees, the choice of mould material should be based on the factors of temperature, thermal conductivity and hardness. In this article, the mould material selected is HT200, which has high temperature resistance, strong thermal conductivity and good thermal shock resistance.
4、Analyze the pouring system
The pouring system used in negative pressure vanishing mould cast material mill lining plate is the furan resin sand casting process. The equipment used includes an electric furnace, a forcing medium, a ladle, a spout and a pouring cup.
1) The electric furnace is used to melt the cast iron material and purify the molten iron material by adding the appropriate alloying elements;
2) The ramming material is used to fill the negative pressure chamber of the mould;
3) The crucible is used to transport the molten iron material to the spout;
4) The spout which is connected to the crucible is used to guide the molten iron material into the mould;
5) The pouring cup is used to control the filling rate and pouring speed of the molten iron material.
5、Rational design of gating system
The design of gating system of negative pressure vanish mould cast material mill lining plate directly affects the quality of castings. In this part, a rational gating system is designed to ensure the quality of castings.
1) Firstly, the number and size of the gating system are determined. According to the size and requirements of the liner, the number of risers adopted should be determined, and the development of a rational gating system is also taken into account.
2) Secondly, the shape and size of the gating system should be determined. According to the pouring system and the pouring pattern, the shape and size of the gate and the pouring system should be determined to ensure the smoothness of the pouring process.
3) Finally, the position of the gate and tundish should be determined. The position of the gate should be designed reasonably to make the molten iron fill the mould smoothly and evenly.
6、Design of pouring process
In order to realize the good pouring process of negative pressure cast material mill lining plate, the process parameters of pouring should be reasonably determined.
1) Firstly, the pouring temperature is determined. The pouring temperature should be determined according to the type of cast iron material and the requirement of flux addition. The suitable pouring temperature of HT200 cast iron is 1260 degrees.
2) Determine the pouring time. The pouring time should be determined according to the thickness of the casting, the filling time of molten iron and the feeding speed. The bigger the casting, the longer the feeding time and the longer the pouring time.
3) The setting of the rising speed. The setting of the rising speed should be determined according to the size and weight of the casting and the filling rate of the molten iron. In this article, the rising speed is set at about 100mm/min.
4) The setting of the falling speed. The setting of the falling speed should be determined according to the thickness, weight and filling rate of the casting. The falling speed should be set slow at first and gradually speed up. In this article, the falling speed is set at about 100mm/min first and gradually increased to 130mm/min.
7、Analysis of other factors
1) Flux addition: Flux addition is necessary before pouring. The flux is used to reduce the oxygen content in the molten iron and improve the quality of the castings.
2) Insulation: the insulation is carried out after pouring and the temperature of the mould should be kept in a higher temperature range at this time, so as to make the casting cool more uniformly and slowly.
3) Knock out mold: knock down mould is an important part of pouring process. The knock down mould process should be done after pouring. The purpose of the knock down mould is to make the mould loose so that the casting can be separated from the mould.
Conclusion
Through the design of pouring technology for negative pressure vanish mould cast material mill lining plate, a reasonable pouring technology is proposed in this article. The pouring technology is characterized by rational selection of mould material, reasonable design of mould, pouring process and other factors. With the application of this pouring technology, high quality castings can be obtained.
