The difference between the castings and the forgings of a gear

Gear forging is usually made of steel heated to austenite state, and then pressed by mould, and the parts formed by external force forging are formed. The casting has some defects, such as segregation, shrinkage, porosity and so on. Taking gear forgings as an example, iron and steel after forging can retain metal flow linearly, which can significantly improve the mechanical properties of metal materials.
First, the mechanical performance difference, after two processing of the forging, there will be a hardening process, this process will lead to fine arrangement, mechanical properties without direction, superior to the casting;
Two. The molding method difference castings are melted through the melting furnace, pouring into the model and cooling, and the forging is made up of repeated restrictions under the pressure effect.
A. casting parts consist of direct casting of molten steel with poor grain size, low metal density and poor mechanical properties.
Gear forging: cast by high temperature forging, grain size is fine, density is slightly higher, mechanical performance is stable.
B. from the non processing appearance survey: the casting pieces are small granular, can see the slit (casting grinding gear); free forging, the appearance of the appearance after the black, the appearance of a slightly flaky appearance, can see the cast fold; die forging, at first glance, a bit similar to the casting, but the appearance of the granular is still relatively delicate. And die forging is often done in small parts, big components difficult to do.
C. from the processing surface: cast iron is a significant difference from the forgings. The cast iron has no gloss (after grinding is still bright). The chips of the chips are all broken chips, and the gray cast iron will have powder like chips. The cast steel processing surface and the forgings are not very different and have glossiness.
Gear forging has no molding defects such as shrinkage holes, so forgings are better than mechanical castings. The advantage of the casting is the convenience of producing and forming. The fine mechanical properties of the scale are not high enough to be formed at one time. It is mainly about the difference of molding methods.
Judging from the appearance, it can be seen that the surface of the casting is thicker, and there are segregation and shrinkage holes, while the surface of the gear forging is smooth and glossy. Because the gear forging is forged by external force, and the casting is solidified.