What is the difference between low-temperature wax and medium-temperature wax?

What is the difference between low-temperature wax and medium-temperature wax?

Original heweifeng Molten Mold Casting Everyday Learning 2020-08-23 21:27

Last week a friend asked about the difference between low temperature wax and Chinese wax. Because recently there are some things at home, I did not have time to update, please forgive me.

In fact, the title of medium-temperature wax and low-temperature wax belongs to a kind of name for molding material in the early days, although many people still use this title now, but strictly speaking, it should be called medium-temperature molding material and low-temperature molding material.

With the rapid development of science and technology and industrial production, the application range of investment casting process is expanding. Wax material in performance and quantity relative to the rapid development of investment casting industry is difficult to synchronize. Thus, a variety of organic materials, plastics and inorganic salts and other materials have been adopted one after another. Some of them are added to the wax material as fillers, and some of them directly replace the wax material to make molds. As a result, wax molds and wax materials are gradually replaced by mold materials and molds. However, it is still customary to call them “wax molds”. Only this “wax mold” is no longer the same as the “wax mold”.

The classification is complicated by the fact that there are many different types of moldings with different compositions. There are two recognized classification methods:

The first classification is based on the thermal stability of the molding material. Thermal stability is an important performance of the mold material, it has a close relationship with the melting point of the mold material, in general, the higher the melting point of the mold material, the higher its thermal stability; Conversely, the lower the melting point, the lower its thermal stability. Therefore, according to the melting point of the molding material, it can be divided into three categories: high melting point molding material, medium melting point molding material and low melting point molding material. If we consider from the point of view of thermal stability, it is divided into high-temperature molding compound, medium-temperature molding compound and low-temperature molding compound.

Therefore, it is clear that the distinction between low-temperature and high-temperature waxes is made on the basis of the thermal stability of the molding material or wax. This is the first point.

The second classification is based on the composition of the base material of the molding compound. According to the recent development of molding materials, they can be divided into wax-based molding materials, rosin-based molding materials, plastic molding materials, water-soluble molding materials and filled molding materials.

The above classification method is based on the classification method of Wang Leyi [investment casting technology]. The first categorization method seems to be basically the same in the information introduced. However, the latter classification method is different: some network information is divided into four categories: wax-based die, resin-based die, filler die, water-soluble die; Jiang Buju edited [practical investment casting technology] is divided into non-filler die (wax-based die, resin-based die), filler die, water-soluble die, and the above classification is basically the same; the following classification method from the yamaya yoki's [precision casting The following classification is from “Practical Techniques of Precision Casting” by Yoki Yamaya.

Picture

Table 1: Classification of mold materials

In fact, no matter how the mold materials are classified, they are all the same. Basically, they are all the same. Only in modern times there is an additional molding material for rapid prototyping, which is a newly added class of molding material.

Here we are we on the first classification method of centralized mold material for further elaboration.

1, low-temperature mold materials. Low-temperature mold material melting point is generally lower than 70 ℃, lower strength, poor thermal stability (30 ℃), shrinkage, the melt mold size and shape with room temperature changes, surface roughness is coarse. China's common use of 50% paraffin and 50% stearic acid molding compound is typical of this type of molding compound. However, this kind of mold material production process is simple, mold material recovery rate is high, can be reused, the cost is low. It is generally pressed in paste form and operated by hand, and can be dewaxed with hot water. This mold material is generally used together with water glass binder.

2, medium temperature molding material. Mainly rosin - wax-based moldings and filler moldings, melting point between 70-100 ℃, higher strength, thermal stability is better (35 ℃), shrinkage is smaller, good dimensional stability, with the liquid pressed molten mold surface roughness is fine, good replication performance. Can be reused, the formulation of the production process is more complex, higher cost. Water, steam or microwave dewaxing. This kind of mold material is generally used together with silicone sol binder. General use of wax injection machine production.

3, high temperature mold material. Mainly rosin - plastic-based, plastic and salt-based moldings, melting point greater than 100 ℃. The mold material is high strength, good thermal stability, shrinkage, but the production process is complex, can not be reused. Generally use flash burning method, water or organic solvent removal. High cost. Obviously, water-soluble mold material, mold material for 3D printing belongs to this category. In the [investment casting process] on the high temperature mold material is this description: the thermal expansion of this mold material is large, in the demolding, the type shell is often ruptured due to lack of strength.