Taking a brake caliper casting of MQB platform of Volkswagen as the research object, a series of research on the feeding system and filling system design of the casting mold was carried out. The deck wall thickness of the brake caliper is large, and there is an isolated hot spot area at the bottom of the cylinder barrel. How to change the solidification state of the casting only by adjusting the feeding system without introducing additional production technology, so as to solve the problem of casting shrinkage porosity without affecting efficiency and increasing cost, which provides reference for the process design of other similar castings, It has a strong practical significance.
The design of die feeding system is the focus of this paper. Through the design method, software simulation and actual pouring results, the following conclusions are obtained
(1) The riser should be set at the largest hot spot of the casting, its height should be at least 10 mm higher than the upper end of the casting, and its shape should be a cone-shaped cylinder with narrow top and wide bottom, which is conducive to feeding from top to bottom. There should be an angle between the riser neck and the casting, through which the module number of the riser neck section can be changed indirectly, and the feeding time can be controlled. The modulus ratio of the riser to the riser neck is 1:1.1:0.6 For the best.
(2) By adjusting the distance between the riser and the casting, the opening time of the feeding channel in the casting is controlled. The distance is reduced from 12mm to 10mm, which prolongs the solidification time of the casting deck and makes it possible for the riser to feed upward.
(3) In view of the feeding of isolated hot spot area at the bottom of cylinder barrel, the heat preservation block is used to heat the feeding channel. The distance between the heat preservation block and the casting is 6 mm, the opening time of the channel is prolonged, and the feeding effect of riser is ensured. The volume and distance between the block and the casting were determined by magma simulation, and the parameters of the block were adjusted according to the actual production effect. At the same time, combined with the application of heat sink, the solidification rate of hot spot is accelerated, and the sequential solidification process from remote hot spot, feeding channel and riser is realized.
(4) In order to give full play to the feeding effect of the riser and maximize the feeding efficiency of the riser, the runner at the connection with the riser needs to be solidified as soon as possible after the completion of the mold filling, cut off the connection between the riser and the external runner, make the riser and the casting as a whole and start to solidify, so as to ensure the formation of a shrinkage tube at the top during the feeding process of the riser and realize effective feeding.
The difficulty of nodularproduction is shrinkage porosity. It has been proved by practice that solidification sequence is an important factor affecting whether there is shrinkage porosity defect in the casting. How to intervene the solidification sequence and proceed in the direction conducive to feeding is the key to avoid shrinkage porosity defect. With the improvement of automation production efficiency and the pressure of cost control, some commonly used technologies to solve shrinkage porosity of castings are effective, but they greatly reduce the production efficiency and increase the cost of castings. How to use the design of feeding system and gating system to eliminate shrinkage defects is more urgent, but at present, many methods can not be calculated and deduced by effective formulas Through the research and study of this topic, the author also deeply realized this point. There is still a lot of work to do in the future to make up for the lack of research in the subject. I hope to master this method more deeply and provide help for the actual production.