Technical characteristics and application of the vacuum die casting technology
The vacuum die casting method is to eliminate or significantly reduce die casting pores and dissolved gases by gas extraction in the die casting process, die casting mold cavity, thereby increasing the die-casting mechanical properties and surface quality of advanced die-casting process.
Recently, vacuum aluminum alloy die-casting to the gas extraction cavity, there are two main forms:
(1) direct exhaust from the mold;
(2) set the mold in a vacuum tank pumping. Vacuum aluminum alloy die casting, mold the exhaust position and exhaust area design is essential. Exhaust there is a "critical area", is related to the amount of gas out with the cavity, the pumping time and filling time. When the area of the exhaust is greater than the critical area, the effect of vacuum aluminum die casting; the contrary is not obvious.
The choice of the vacuum system is also very important requirements before the vacuum pump shut down, the cavity of the vacuum can be maintained until the filling is completed. Most of the gas in the pores of die casting die casting technology for the N2 and H2, and little of O2, O2 and active metal the reaction of a solid oxide, which provides a theoretical basis for the die casting technology. The die casting before heat, oxygen filling into the cavity to replace one of the air.
Can easily lead to the involvement of the gas affect the quality of the die casting pressure casting filling process is completed within a very short time. Oxygenase die casting machines and vacuum die casting machine is developed for that purpose, in the pressure die casting machine to obtain the rapid development, some die-casting machines combined body tilt in the form. Computer control of die-casting process automation and die-casting and die casting flexible manufacturing cell (FMC) have gradually been developed.
(1) the oxygen pressure casting aluminum liquid metal before filling the cavity, the pressure chamber and the cavity filled with oxygen instead of air and other gases. Its characteristics are: to eliminate or reduce porosity, improve casting quality; simple structure, convenient operation, less investment.
(2) vacuum pressure casting is first die-casting cavity air extraction, and then pressed into the liquid metal. Its characteristics are: to eliminate or reduce the die-casting inside the pores, to improve the mechanical properties and surface quality of the castings; die-casting, greatly reducing the cavity of the anti-stress, you can use lower than the pressure and the casting of the poor performance of the alloy.
Vacuum die casting method advantages
① vacuum die casting method can eliminate or reduce the die casting inside the pores, to improve the mechanical properties of the die-casting and surface quality, to improve the performance of plating;
(2) vacuum die casting method greatly reduces the back pressure of the cavity, can be used to lower the performance less than the pressure and the casting alloy, and may die casting with small machine large castings;
③ vacuum die casting method to improve the filling conditions, die-casting thin casting;
The ④ vacuum die casting method and compared to the ordinary die-casting method, the production efficiency is almost the same.
Vacuum die casting method shortcomings
① mold sealing structure, manufacture and installation more difficult, and therefore higher cost;
(2) vacuum die casting method is not properly controlled, the effect is not very significant.
Compared with ordinary die-casting method
Vacuum die compared with the ordinary die-casting method has the following characteristics:
(1) porosity is greatly reduced;
(2) The vacuum die casting, high hardness, the microstructure is small;
(3) vacuum aluminum die casting, high mechanical properties.
Application of vacuum die casting method of production of aluminum-magnesium alloy die casting has been shown to welding, heat treatment and other processing means, the room temperature performance upgrade: such as the now successful in the cold chamber die casting machine, vacuum die casting method to produce AM60B magnesium alloy car wheels, clamping force for of 2940kN the hot chamber die casting machine, vacuum die casting method to produce AM60B magnesium alloy automobile steering wheel, and die-casting elongation rate from 8% to 16%.
Properly controlled, vacuum die casting method can give satisfactory improvement in die-casting performance. Mold sealing cost of upgrading, with the adoption of the technology and mass production brought about by the cost-sharing, will be a good solution. Compared to traditional die-casting method, the laminar flow filling method / ultra-low-speed die casting production efficiency is low, the gate clean-up difficult, difficult to apply mass production; die casting method is complex process, process parameters difficult to control , it is difficult in the actual production of large-scale application; vacuum die casting method, process simple, easy to operate, with almost the same productivity and ordinary die-casting method, easy to promote in the actual production. Since the since the emergence of the vacuum die casting method showed great vitality, with the improvement of related technologies, their applications are increasingly being used!