The theory of agricultural machinery castings forming, liquid metal forming is often called casting, casting forming technology has a long history. As early as 5000 years ago, our ancestors were able to cast red copper and bronze products. Agricultural machinery castings are the most widely used liquid metal forming process. It is a method of pouring liquid metal into the mold cavity, and then cooling and solidifying it to obtain a certain shape of blank or parts. In machinery and equipment, liquid parts account for a large proportion. In machine tools, internal combustion engines, mining machinery and heavy machinery, liquid parts account for 70% ~ 90% of the total weight; It accounts for 50% ~ 70% of automobiles and tractors; It accounts for 40% ~ 70% of agricultural machinery. The reason why liquid forming technology can be widely used is that it has the following advantages:
(1) It can produce the blank with complex inner cavity and shape. Such as all kinds of box, machine bed, cylinder block, cylinder head, etc.
(2) The process is flexible and adaptable. The size of liquid forming parts is almost unlimited, its weight can be from a few grams to hundreds of tons, and its wall thickness can be from 0.5mm to about 1m. In industry, any metal material that can dissolve into liquid can be used for liquid forming.
For cast iron with poor plasticity, liquid forming is the only way to produce its blank or parts.
(3) The cost of liquid forming parts is low. The waste parts and chips can be directly used in liquid forming, and the equipment cost is low. At the same time, the processing allowance of liquid forming parts is small, and the metal is saved. However, the process of liquid metal forming is too many, and it is difficult to accurately control, which makes the quality of agricultural machinery castings unstable. Compared with the forgings of the same material, the defects such as shrinkage cavity, shrinkage porosity and air hole are easy to occur in the liquid forming because of the loose structure and coarse grain. Its mechanical properties are low. In addition, labor intensity, poor conditions. It has excellent mechanical and physical properties. It can have a variety of comprehensive properties of strength, hardness and toughness. It can also have one or more special properties, such as wear resistance, high and low temperature resistance, corrosion resistance, etc.
The weight and size range of agricultural machinery castings are very wide. The lightest ones are only a few grams, the heaviest ones can reach 400 tons, the thinnest ones are only 0.5 mm, the thickest ones can exceed 1 meter, and the length can range from a few millimeters to more than 10 meters, which can meet the requirements of different industrial departments.