First of all, we have to clarify what are the main metal CNC machining methods in current industrial production.
Generally speaking, metal CNC machining methods are mainly divided into 4 categories:
- Casting: Metal Casting is the heating and melting of metal ingots and blocks into a liquid, which is then poured into a mold to obtain various shapes and sizes.
- Forging: Metal Forging is the use of pressure to change plastic ingots or profiles into various shapes and sizes. To make metal plastic, heating is generally used, but the heating temperature should be lower than the melting temperature.
- Welding: Industry Welding is a method of welding the place where two blanks are connected with a welding rod.
- Cutting: Laser Cutting is the further cutting of the blank into the desired shape and correct size with a cutting tool.
Casting, forging, and welding do not produce chips during processing, so it is called chip-free processing. At the same time, during processing, heating is generally required, so it is also called thermal processing And cutting produces chips, which is a kind of cold working.
So, what are the characteristics of the forged parts compared to the other three processing methods?
Generally speaking, the impact stress that forgings can withstand is the strongest. In machines, some parts must be made by forging. For example, in the parts used in aircraft, forgings account for about 85%.
Specifically, the parts produced by forging have the following characteristics:
1. The Strength Of The Parts Is High
Strength refers to the force that a unit area can withstand. The unit area stress of forged parts is larger than that of castings, so the cross-sectional area of forgings is smaller than that of castings, and the parts are lighter.
The reason why forgings can withstand higher strength per unit area is:
(1) Through forging, the internal organization of the parts is made more compact.
When we observe the internal organization of metal through a microscope, we can see that metal is composed of many crystals like rock candy.
If the molten metal is cast into a casting, the grains of the crystals are very coarse. At the same time, there are shrinkage holes and air holes inside.
Shrinkage cavities are caused by the shrinkage of the metal during cooling, and porosity is caused by the inclusion of gas in the casting.
In addition, castings have a defect called segregation, which is inconsistent in mechanical properties due to uneven distribution of impurities (such as sulfur, phosphorus, etc. contained in steel).
However, after casting a Chengdu ingot, after forging, the coarse particles are crushed into fine grains, which are pressed together, and the shrinkage and pores will shrink, so the structure of the part becomes more solid. The strength is also increased.
(2) Forgings can make the streamline of the parts meet the requirements.
2. Material Saving
Using forging services as a blank can not only improve the strength of the parts, but also save materials.
- Using forging to make blanks can save materials.
- Forging can remedy the shortage of bar section size.
- Some shapes can be made by bending.
- The concave and convex shape on the surface can be stamped with a mold.
3. Increase Productivity
By forging, productivity can also be increased. For example, if a steam turbine blade is produced by a bar car, it will go through many processes and cut off a lot of metal. And adding the use of die forging, first making a similar shape, and then a little grinding, you can save labor and material.
Links:Why Are Some Metal Parts Produced By Forging Rather Than Other Machining Methods?
