At present, the forming technology of bucket teeth mainly includes sand casting, metal mold casting, lost foam casting and liquid die forging.
1. Sand casting
The common sand mold casting bucket tooth is the main bucket tooth forming technology now, because this kind of craft uses the sand core many, the process is complex, and the sand mold inevitably has the rough place, causes the casting surface rough, wants to obtain the surface smooth casting is difficult. It is time-consuming and laborious for workers in the manufacturing process. At the same time, the technical requirements for workers are high. For some steel materials, cracks will appear, which are not only easy to cold crack, but also easy to hot crack. At the same time, it is easy to react with molding sand to produce chemical and mechanical sand sticking. In addition, the grain size of bucket teeth in sand mold casting is relatively coarse, and the structure is loose and uneven. There are some defects in the casting, such as porosity, shrinkage cavity, slag inclusion, etc. some of the above shortcomings lead to the unstable quality of the products, poor mechanical properties and high reject rate, so sand casting technology is generally suitable for the production of bucket teeth blank parts.
2. Lost foam casting
The lost foam casting technology used in the production of steel and iron castings has become mature. Lost foam casting has many advantages in technology, because it does not need to take the mold core, it can form more complex parts; at the same time, there is no parting surface, so the casting parts have no defects such as flash and burr. These advantages make the technology not limited by the model, and has high accuracy. However, EPC also has its disadvantages and shortcomings in investment The pattern can only be used once, and can not be repeated. The production process of the core equipment is high, and the process control is difficult. During the casting process, there are a lot of gases in the thermal decomposition of the polystyrene foam, which causes the carbon increase and hydrogen increase in the casting. The comparison between the lost foam casting and sand casting is made from the structure of the casting. There are no structural changes. Although there are no defects in traditional sand casting such as core and sand removal, when the molten metal is pouring, the foam pattern decomposes and consumes heat to reduce the temperature of the front end of the liquid metal, which is likely to cause defects in the metal casting such as porosity. For the bucket teeth, these defects seriously affect their service life. The development and application of foam pattern material in EPC is a weakness in our country’s EPC technology, resulting in the production of bucket teeth in EPC process.
3. Metal mold casting
Compared with sand mold casting, metal mold casting has the advantages of higher mechanical properties, lower surface roughness, higher dimensional accuracy, stable mass production and mold can be used repeatedly. Due to the rapid cooling rate and grain refinement of metal materials, the tensile strength is increased by about 1 / 4 and the yield strength is increased by about 1 / 5. However, due to the high cost and long cycle of metal mold casting, mass production of castings has limitations, and the large undercooling degree brings about casting defects such as cracks and insufficient pouring, which are also limited by the size and shape of castings. In a word, it is difficult to produce qualified bucket teeth by metal mold casting process.