Research on Casting Large Coal Mining Equipment Parts by Lost Foam Technology

Lost foam casting means that during the casting process, the model gasifies and disappears. The model here refers to the mold used in casting, referred to as EPC casting. Ordinary sand casting is to pour molten metal into a specific mold, and remove the mold after the molten metal is formed to form the required casting. The lost foam casting process is different. The lost foam casting process uses foam plastics to make molds and embeds them in sand molds. Sand molds usually use dry sand or dry sand with binders, which are controlled by vibration or negative pressure. It is processed and then filled with molten metal. The high-temperature molten metal heats up the foam plastic, and through the process of softening, liquefaction and gasification, it finally forms a casting.

1. Characteristics of lost foam casting process

The lost foam casting technology is used to cast high precision castings. Because the lost foam casting process basically has no machining allowance, it is a new type of precise molding process. The characteristic of this process is that it does not need to take out the wood sample, and there is no parting compared with the ordinary casting process. Surface, no sand core, the large-scale coal mining equipment cast by this method has no flash, burr, and draft angle, which greatly reduces the dimensional error caused by the combination and matching of the core type.

Compared with the ordinary large-scale coal mining equipment casting process, the design of the lost foam casting process is more flexible, and the structural design of the casting is more free. When using ordinary casting methods, large and complex coal mining equipment castings need to manufacture part of the equipment first. Then spliced and assembled, the lost foam casting process does not need this method, and the foam can be spliced to cast, which greatly simplifies the casting steps and assembly difficulty. It reduces the difficulty of mechanical processing, saves manpower and material resources, improves casting quality and expands economic benefits.

The lost foam casting process does not need to use the sand core in the traditional casting process. The lost foam process uses dry sand to fill and compact, and the inner cavity and hole of the casting are produced by the flow of the dry sand, so the problem of inaccurate sand core size is disappearing. It no longer exists in the large-scale coal machine equipment of mold casting, and also avoids the problem of inaccurate position of the lower core.

The lost foam casting process also has the advantages of cleanliness and environmental protection. During the casting process of large coal machinery equipment, there is no chemical binder in the molding sand, and the foam plastic is harmless to the environment. During the process of lost foam casting large coal machinery equipment, the harmful There are very few substances, and the only discharges are concentrated relative to the discharge location, easy to collect, and the discharge time is short. The molding of the lost foam adopts dry sand molding, and the amount of sand falling out of the casting is significantly reduced. At the same time, the input of personnel workload and the workload of cleaning are significantly reduced. Noise attenuation and dust control have been improved in the casting process of large coal mining equipment.

Another feature of the lost foam casting process is that it can improve economic benefits. Because of the lost foam process, the recovery rate of the molding sand is high, the amount of chemical adhesives is less, and the waste is less. The increase in the degree of automation reduces the amount of manual labor input and improves the production environment.

2. Problems faced by coal mining equipment

The coal machinery equipment industry is now facing the problems of market chaos and lack of a sound mechanism for competition. State-owned enterprises, private enterprises, foreign-funded enterprises, and machine repair companies are all engaged in large-scale coal machinery equipment. In many areas, the density of coal machinery equipment companies is relatively high, and large coal machinery equipment Equipment accessories cities and large coal machinery equipment manufacturers are scattered all over the world. The large coal machinery equipment industry has no strict industry guidelines and no standard pricing mechanism. Many companies engage in price wars, which lowers the quality of manufacturing processes.

In the production of coal machinery equipment accessories, there are still problems such as backward product manufacturing technology, single detection means and experimental means, and old processing equipment. At present, my country's basic mechanical processing methods are backward, casting technology has not been innovated, heat treatment and welding quality cannot meet the requirements and other problems frequently occur, and there is still a long way to go before the performance parameters achieved by the design requirements.

3. Application of lost foam casting technology in large coal machinery equipment

3.1 Manufacturing of foam plastic pattern

The pattern manufacturing of the lost foam is the most important in the lost foam casting process, and the material selection, processing and manufacturing methods and techniques of the pattern should attract sufficient attention from researchers. The production of the lost foam mold should mainly meet the following requirements. The gasification temperature should be low, which can make the lost foam mold easier to gasify and decompose. The amount of gas generation should be low, which can reduce decomposition products. The gasification speed is fast, the gasification is complete, and the residue after gasification should be as little as possible. The weight reduction of the lost foam itself is conducive to transportation and manufacturing, and is conducive to casting. The strength and stiffness of the material should be improved as much as possible to reduce damage during transportation and use. Only when the structural stability of the model is good can a mold with excellent quality be produced. In the process of mold making, it is necessary to be familiar with the drawing design content, design ideas, and timely modify the lost foam design drawings and manufacturing process in order to manufacture a reasonable mold.

3.2 Case study of the application of lost foam in the production of large coal machinery equipment accessories

Under the condition of negative pressure, the lost foam casting technology was used to improve the fluidity of molten metal, the exhaust port was scientifically and reasonably arranged, and the vertical shaft sky wheel with a weight of 2.5 tons and a diameter of 3 meters was successfully cast, and the expected design purpose was achieved. . The main advantage of the lost foam casting process in the production of large coal machinery equipment is that the fluidity of the molten metal liquid becomes better under negative pressure conditions, and it also solves the problem of the collapse of the original sand mold.