What is the structural design of the casting?
Dalian castings are cleaned manually by means of wire brushes, chisels, files, air shovels and other tools. Manual cleaning has high labor intensity, poor sanitary conditions and low efficiency. However, for some castings with complex shapes, manual cleaning is more appropriate. Qualified products refer to castings whose appearance quality and internal quality meet the current national or industrial standards, the production process and quality are stable, and the user's evaluation can meet the service performance, 60<c<80; First class products refer to castings whose appearance quality and internal quality meet the current national or industrial standards, the production process and quality are stable, and the quality evaluated by users reaches the domestic advanced level. From the origin of metal casting to now, both at home and abroad, people in gravity casting to a large extent use molten metal, then pour it into the pre cast mold, with the help of self weight feeding and solidification of the metal, so as to obtain the designed castings. Whether it is black metal or non-ferrous metal, people still use the above methods to produce castings.
Many workers have done a lot of work on the theory of sequential solidification, but so far, how to make the castings designed by ourselves achieve the ideal sequential solidification and successfully meet the sequential feeding solidification of castings with the help of it. So as to achieve the goal of good internal quality of castings, which has not yet provided an ideal calculation control method. This method can be said to be an effective method to properly arrange the shrinkage cavity and porosity of castings due to insufficient shrinkage. During solidification, the concentration of solute in the precipitated phase is different from that in the liquid phase. In most cases, the concentration of solute in the liquid phase is too rich to diffuse, which makes the chemical composition of the successively solidified part uneven.
The casting continues to cool after solidification, and the solid shrinkage is hindered to produce the casting internal stress. When the internal stress reaches a certain value, the casting will be deformed or even cracked. Sand holes are also common defects of cylinder block castings, which are mostly seen on the upper mold surface of the casting, but also exposed after processing on the inner surface of the cylinder barrel. The design of the gating system is unreasonable. Macropores formed at the hot spot or the last solidified part of a casting due to poor feeding during solidification The distribution characteristic is concentrated shrinkage; When the crystallization temperature range of the alloy is wide, there is a wide solidification region of liquid and solid phases after the crust on the surface of the casting. Continue to solidify, and the solid phase continues to increase. Die forging is divided into open die forging and closed die forging. Forgings are obtained by pressing and deforming metal blanks in a certain shape forging die chamber, which can be divided into cold heading, roll forging, radial forging, extrusion and so on.
