低压铸造和高压铸造的比较(英文版).pdf

LPDC Casting process. The low pressure casting process is similar to the traditional aluminum die casting process. Which is commonly used to make cylinder heads wheel rims, and the sp. parts which requires pressure tight Function requirement. Low pressure casting involves the injection of the molten metal with a low pressure and low velocity. Following are the parameters that you forced to produce the component on the low pressure system. Sr. no. High pressure process Low pressure process 1] High cavity pressure is used to fill the Low pressure is used to fill the cavity casting [ From 600kg/cm.sq. to 1100] [0.2 to 0.5 kg/ cm. Sq.] 2] High gate velocity Low gate velocity [ 30 to 60 m/ sec.] [ 0.15 to 0.6 m/ sec.] 3] Less filling time Much higher filling time as per the 30 to 100 mili sec. Volume of the casting. 4] No isolated coating is required. As the Isolating coating is used as the filling Solidification time is less. Only releasing Time is more than HPDC. Agent is used. 5] High silicon and & non heat treatable Low silicon and heat treatable Material is used. For casting. Material is used. For casting. 6] Turbulent free flow is not so profitable as Turbulent free flow is require as far as The atomization of the flow is required. possible 7] In HPDC mold cavity air can thrown out In LPDC the aim is to drive the mold 100 %.it is compressed at some except. Cavity air out with the metal flow. 8] High rate of production. Low rate of production. 9] High degree of accuracy. Wide tolerance was used. 10] Low foundry rejection as parameters Rej, is more than HPDC as all the having no successive setting. parameters are very sensitive. 11] HPDC part can be produced on LPDC LPDC Part can not be produced on process. Hpdc due core inout is not possible. Design consideration. a] One should see that the feeding wall thickness that is the wall thick near the gate portion should be more [ at least 1.5 times than the other part thickness.] b] Before ensuring the gate position, the solidification behavior within the part is to be seen. The part should be solidify in such a way that it will start away from the gate and advances towards the gate, without enclosing the any pocket or area having the molten metal or the high temperature of the metal. In this case it is very difficult to come out from the shri- nkage porosity in the casting at that portion. So the heavier section of the part should be toward the gate side.so that the temperature of the die should gradually increase towards the gate. And this is the requirement of the LPDC die casting process. c] Heavy wall thickness variation should be avoided.If so change the part design to some extent to avoid further defects. d] Thin wall [ less than 2mm] should be avoided within the casting cavity. e] Ensure the direction of the solidification. That is the heat should be extracted from the die part which are away from the gate. So the heavy sect of the die parts which are away from gate should be avoided. f] Pilot cooling should be considered around the heavy section of the gate, But the cooling cycle should start when entire casting got solidified. This will increase the productivity as well as the quality of the casting.The timing of the cooling cycle is very important as the shrinkage porosity will be left in the unsolidified portion of the casting. Isolating the sprue and connector this type of porosity can be avoided. g] Designing the die and sprue bush the following points should be considered. Sliding part of the die should not have the heavy mass. Heat deception should be more from the sliding part. h] Venting position gate position should be marked out Area of the gate to be decided in such way that the Gate speed within a limit of 0.2 to 0.5 m per second velocity. Material melting process. a] In LPDC casting process the material chemistry plays the major roll of the casting process. The aim of the melting procedure of the metal is to optimize and to reach a certain level of mechanical and the theoretical properties of metal which we have used. It mainly influences the solidification behavior to get the require microstructure, improvement in filling property, and it will reduces the degree of the known defects. b] The pouring temperature of the metal is varying as per the silicon and the alloying elements. But as per the metals used in LPDC casting the temperature should 720 degree to 750 degree centigrade. More the temperature more the oxidation formation. And this oxide incr eases the casting defects. To avoid that the melting temperature should not be more by 30 degree than the pouring temperature. c] Grain refinement Or Titan Boron treatment Grain refining is not necessary for the eutectic Al-Si alloy. But this treatment is specially effective for the non eutectic alloy.That means the silicon having the range from 5 to 10。