Temperature control in precision casting

Temperature control in precision casting

Precision casting belongs to the field of hot working, therefore, temperature is a very important influencing factor for casting, and it is also an important parameter that needs to be controlled during the casting process. In our university days, there was a course called "Casting Temperature Measurement Technology", which specifically taught various temperature controls during the casting process. As a foundry practitioner or someone related to casting, it is still necessary to understand some temperature control techniques in the field of casting. Today, precision casting manufacturer Tianyao Metal will talk to you about temperature control in precision casting.

Most casting techniques belong to hot mold casting. The molds here include metal molds, gypsum molds, ceramic molds, and so on. Talking about metal molds, such as metal molds and die-casting molds, due to the large heat storage capacity and good cooling effect of metal molds, it is necessary to preheat the mold before the metal liquid enters the mold, otherwise it may cause defects such as insufficient casting and cold shut. Therefore, in metal mold and die casting production, mold temperature will be a parameter that casting engineers need to control. And it must be indicated in the process document. However, measurements do not necessarily need to be taken. In general aluminum alloy metal mold and die casting production, the mold needs to be heated for a period of time before use to raise the temperature of the mold to a certain range. For example, metal molds generally reach temperatures between 200 ℃ and 300 ℃. Whether the temperature of the mold is appropriate mainly depends on the on-site workers themselves. One is time management, and the other is mold testing. Generally, on-site workers will conduct trial pouring and inspect the appearance of the castings after pouring. If the appearance of the casting meets the quality requirements of the casting, it is considered that the mold preheating is appropriate. In addition, some units also use trial casting to preheat the mold, which means wasting more liquid metal. Some people may think that even after talking for a while, you haven't been able to control the temperature! Actually, it's not the case. Just take a look below and you'll know. Is the mold constantly being heated and the temperature continuously increasing during use? At this point, you will notice that the workers will spray paint and take a break. This is not laziness, but controlling the mold temperature to lower it. Someone said, isn't it necessary to preheat the mold?, Being taller is not better. No, absolutely not! As the temperature increases, the probability of shrinkage and porosity will greatly increase, and the grains will become coarse. Although this control is passive. Of course, there is also proactive control: adding cooling water to the mold. Not to mention casting, just wax molds. If the mold is hot, it should also be cooled with cooling water to control the temperature of the mold.

The temperature control of the mold shell in investment casting is also a principle, but it is more precise. Electric furnaces or natural gas furnaces are generally used. High temperature uses a hot gas furnace, and low temperature uses an electric furnace. Compared to metal molds, the temperature of investment casting shell is more precisely controlled.

Precision machining