Process control of metal mold produced high chrome casting balls
In recent years, high chromium metal mold casting grinding ball has been widely used. In cement, electric power and mining industry and in the water, mud production, replaced, the pebble ball has achieved significant social benefits, market demand, and increasing. How to ensure the quality and meet users’ needs, production process control has become a key factor.
1.The quality control of molten iron is the premise of production platform, standard production and product.
Since the melting of high chromium materials generally uses acid induction, electric furnace, itself has no desulfurization, dephosphorization, the raw materials should be low sulfur and low phosphorus, and control other harmful impurities to prevent increase, increase Brittleness, chromium Iron, pig iron, should be fixed source, molten iron must be refined at the bottom of the balance if the refining is not good, when there are more gas and sundries in the molten iron, it will make zinc parts produce blowhole and inclusion t obvious influence, affect the performance of cast ball, lead to the increase of broken rate. Due to the high melting point of the high chromium material, the melting temperature should be higher, appropriate, is the basis of quality assurance.
2.Preheating and working temperature of metal mold
With the increase of the metal mold’s preheating temperature, the metal mold’s filling property is increased. Still, the metal mold’s life is reduced, the group and microstructure of the casting are changed, and the Mechanical Properties of the casting are reduced. Some substances on the surface of the chemical reaction should produce pores; type temperature is too low, will reduce the filling of liquid metal, but also because the liquid metal quickly formed a hard shell, Molten Iron, precipitation, outgassing, the body does not exhaust and resulting in pores, the water in the coating is not dry enough to produce choking fire. The service life of the metal mold can be reduced. The metal mold’s preheating temperature can be controlled at 100-150 °C and the working temperature at 100-200 °C.
3.Pouring temperature
Pouring temperature, degree depends on the casting size. The relative pouring temperature of grinding balls over 70mm in diameter should be lower to improve the metal mold’s life and the mechanical properties of casting balls. Under certain other conditions in production, the big ball’s hardness of the same kind of hot metal is lower, so the big ball should be cast at a lower temperature under the premise of guaranteeing the quality. Too High, the pouring temperature makes the metal life and casting mechanical properties and produces defects such as blowhole. Similarly, too low pouring temperature can also reduce the filling property of liquid metal, resulting in cold separation, porosity, shrinkage, and shrinkage depression.
4.Coating and brushing control
The main function of coating in the production of ball casting is to protect the metal mold and, metal, liquid separate to avoid production, gas hole, so there are special requirements for coating. The main aspects of its control are that the coating property should be good and easy to be brushed, and easy to be carried away by the casting after pouring. Otherwise, the coating layer will gradually thicken and burst, which will not affect the external and visual quality. And because, need to scratch, light repaint to improve labor intensity. Production, mining, quartz powder, clay, and a small amount of syrup can be achieved, requirements and easy to control, and paint preparation.
Paintbrush one must be uniform and thorough, in this way, both to protect the metal, but also to prevent reactivity, the formation of pores.
5.Feeding of the molten iron
The feeding of high chromium cast ball is one of the critical problems in production. Such as feeding up to, less than the requirements, then its material superiority can not be reflected, thus, will produce, hardness, reduce, broken rate increase, increase, and so on, problems. Under the conditions of suitable mold temperature and pouring temperature, the qualified product can be produced stably with the yield rate of about 65%, the smallest pressure of the gate, and the force head not less than 80mm. For Group and casting, the feeding task of the sprue is 80%-100% of the diameter of the ball, 25% of the diameter of the sprue, and the diameter of the balls.
6.Remained questions
To ensure the feeding, resulting in low process yield. Suppose you can use a kind of heat preservation effect, better. The material branch’s economic and convenient production to replace the existing sand mold part will improve, high product quality and process yield, play a positive role.
