Pressure casting is characterized by high speed and high pressure, which is also the basic characteristic of pressure casting which is different from other casting processes. The filling process involves mechanical, thermal and hydrodynamic phenomena. Pressure, injection speed, metal temperature change, The process becomes very complicated.Pressure filling process is theoretically divided into three stages: the first stage, the metal liquid into the cavity at high speed, the impact of the gate opposite the wall, and along the wall in the other direction of the rapid expansion of the formation of the shell ; The second stage, followed by the metal into the cavity to continue to fill the cavity; the third stage, the cavity of the metal liquid in the role of pressure under the pressure of the rapid compaction cooling. Metal flow casting defects are mostly produced in this process It can be seen that the factors that affect the quality of the die casting are multifaceted, but the most important is the filling conditions (porosity, dimensional accuracy and surface quality in the casting). The variable factors in the filling process are complex and diverse Which is divided into two aspects: dynamic and static, including static casting machine performance, casting structure, mold structure, mold material, stripper, accumulator pressure, , Limit switch, and the viscosity of the hydraulic oil temperature of the molten metal and the like; metal comprising an amount of the dynamic pressure chamber, a punch suffered running resistance, the mold temperature curve and a negative pressure at the vacuum casting.
They have a great impact on the speed and the ram pressure exerted on the molten metal, thus filling conditions affect the most important parameters. Wherein the dynamic aspect of many variables, it is also difficult to control the maximum.
As a system, there are feed and outlet, slagging links, consisting of many elements, the purpose is to make the alloy solution in a suitable way to make the alloying solution a suitable for the quality of a die cast, the casting system occupies a very important position and is a decisive factor. The flow of the cavity into the cavity at the same time to maximize the discharge of gas within the system.The so-called appropriate flow, that is, does not produce liquid flow collision, volume gas, air, smooth speed.As the casting has its own characteristics, There is a computer simulation analysis software can help to see a result, but for bad results, or rely on people based on practice and experience to change the program. Gate entrance direction and distribution of the exhaust has an important impact on the direction of the entrance To ensure that the flow along the wall-like filling, favorable exhaust, the distribution of which way to consider the distribution can be more orderly filling, do not hold their breath.In addition, according to the metal liquid flow analysis, combined with overflow slot settings, in the appropriate parts open exhaust ducts, the gas discharge cavity. fitted with exhaust groove, defines the overflow tank, only cold gas and sewage can be discharged metal cavity, but also controls charging of the molten metal Type flow pattern, reduce or prevent the formation of vortices.
2) die casting process parameters in the production of die-casting, die-casting machine, die-casting alloy and die-casting type is the three elements.Printing process is the three elements of the right combination and the use of the process, focusing on the impact of casting Quality factors, so that a variety of process parameters to meet the needs of die-casting production. Die casting process parameters are many, the greater the impact of porosity there are two points: the direction of the inlet and the distribution of the way on whether the orderly filling at the same time smooth Exhaust is very important, which is the first level of the length of the injection (may be called the exhaust stroke) and the speed of a great relationship. If the injection early (referring to the melt into the runner), pressure chamber, Gas is not sufficient, will produce rolling gas; late will produce a cold, less cast. The first level of injection is to discharge the chamber and cavity gas and set, can achieve results, depending on a "critical speed ", The critical speed is filled with the pressure chamber is not involved in the volume of gas, the production should be as far as possible to meet the pressure chamber filling on the casting hole defects are also significant, full of high, slow injection is not easy to volume, pressure Room air below, into the cavity So that the diameter of the pressure chamber should be taken as small as possible without affecting the filling rate, and the presence of the short press chamber can meet this requirement, ensuring a high degree of filling and no reduction in filling flow. Process to meet the molding requirements of the conditions, try to use low temperature, low injection speed, to reduce the impact, splash and eddy current formation.