Hanging slurry of surface coating for investment casting precision casting

Hanging slurry of surface coating for investment casting precision casting

Last week, we analyzed the production of surface layer slurry. Today, precision casting manufacturer Tianyao Metal continues this topic to talk about the coating of surface coatings, which is commonly referred to as hanging slurry.

The manufacturing of silica sol shell involves the use of surface coating slurry, as the surface coating slurry determines the surface condition of the casting, that is, the surface of the casting. Therefore, the application of surface coating is one of the most important operations that determine the quality of precision castings. So, it is obvious that the coating of the surface layer requires technology and not everyone can do it well. The so-called good here refers to the uniformity of the surface layer coating. Due to the fact that most factories use manual operations, the coating of the surface layer varies greatly, making it difficult to ensure the stable quality of the same batch of castings. However, this does not mean that this situation cannot be changed. If manual work is used, it is still necessary to practice the technique more. It is also possible to use the method of multiple dipping of the slurry, and then rotate and throw the material multiple times (in fact, most factories can make a throwing machine to ensure even surface coating), which can help manpower achieve the goal of uniform surface coating.

Attention must be paid to grooves, fonts, and deep holes (especially through holes). Although we often mention this point in the process, everyone is still very casual, and as a result, a pile of metal beans and other things appear. Therefore, we must follow the instructions in the process and include what we have done in the actual operation in the process. Only in this way can we make the process consistent with the actual operation. This is particularly important for investment casting, which is a multi process, long-term, and multi influencing factor process. In addition, when using a brush, use compressed air instead of being lazy. For the surface layer and second layer, compressed air is a necessary tool. Of course, the pressure needs to be reduced a bit, so there is no need to use compressed air in some right angle or flat areas.

Basic points for surface coating:

1. Slowly immerse the wax parts in a direction that does not hold air, and for grooves, immerse them along the direction of the grooves.

2. After the module is fully immersed, slowly lift it up and discard excess paint while rotating the module irregularly.

3. During the process of incomplete loss of excess paint on the module, gently blow away small bubbles in wax mold holes, grooves, and text areas with fine compressed air, promote coating wetting, and remove excess paint.

The thickness of the surface coating is also a factor that needs to be considered. Generally speaking, for non-ferrous alloys, especially aluminum alloys, a single coating of the surface layer may be able to resist the thermal effects of high-temperature molten metal. However, for black metals such as carbon steel, stainless steel, especially products with thick walls (wall thickness greater than 10mm), it may be difficult to ensure the high-temperature resistance of the surface layer after a single coating. At this point, it is completely possible to apply the surface layer slurry once or twice again, thicken the slurry film, to resist the heat of high-temperature molten metal.

Precision machining