Through the careful analysis of the physicochemical and processing characteristics of graphite materials, the reasons for the easy occurrence of chipping and dross falling during the graphite parts’ machining process were found, and the measures and methods for solving the problems were proposed.
Graphite material Introduction
Graphite is a crystalline carbon with a relatively low relative density (2.1 to 2.3) and a high melting point (3850±50°C). It is resistant to high temperatures and has a strong resistance to sudden cold heat. At the same time, graphite materials has sufficient mechanical strength and Impact resistance performance. Graphite body is hexagonal. Due to the weak bonding force between the layers, the internal porosity is large, the material is brittle, the tensile strength is low, the graphite material is easy to cut, and the mechanical processing performance is good. There are two main types of graphite supply: cylindrical and square.
The prone to quality problems in the processing of graphite
In the process of graphite machining, it is easy to produce cracks or breakages; it is easy to produce chipping, dross, and edges can easily form sawtooth.
Solution to the problem
1 Reasonable choice of tool
Graphite is a non-metal material that can be easily cut. In general, cutting tools of any grade material can be used to process the graphite parts. For the parts with less general requirements and surface quality requirements, the high-speed steel cutters with lower prices can be selected to meet the processing requirements and more economical and suitable. Because the graphite material is pressed from the powder, only suitable for dry cutting, high-speed steel tool wear resistance is poor, in the process of machining, the wear of the cutting tool is aggravated by graphite particles, which makes the tool blunt, which not only has a certain influence on the machining geometry, but also makes the surface roughness of the profile worse and the sawing of the edge is aggravated. Therefore, high-speed steel cutters are not suitable for graphite parts with high surface quality and dimensional accuracy requirements. The use of better wear-resistant material tools or coated tools to replace the high-speed steel tool with poor wear resistance can effectively improve the machining conditions, such as the use of cemented carbide YG8 tools, high-speed steel coating TiCN tools, carbide coating Tools, etc., can not only improve the surface quality of parts, but also can improve the production efficiency by adjusting cutting parameters such as increasing the number of spindle rotations and feedrate.
2 Reasonably arrange the path
In the processing of the inner contour, should be as far as possible select the milling; at the same time avoid large engagement of the cutting edge, to prevent edge chipping, drop slag;
When machining planes or grooves, it is not suitable to select the vertical feed on the workpiece. Slash or spiral feed should be selected as far as possible to effectively prevent the parts from cracking or breaking. Attention must be paid to the tool after it is dulled.
In order to prevent the occurrence of slagging at the working face of the part, and to form a cavity, when forming the path of the knife, avoid forming islands on the working face and cutting off the workpiece as far as possible.
3 Reasonable choice of cutting parameters
In general, because the graphite material is easy to cut, in the processing process, cutting parameters such as high rotation speed, rapid feed, and large engagement of the cutting edge can be selected to effectively improve the processing efficiency. However, the chipping and slag dropping may easily occur during the graphite machining. In particular, edges and other places are easy to form saw teeth, in these parts should be appropriate to reduce the speed and feed rate, should not use large engagement of the cutting edge, in the processing, should take variable speed cutting, in the surrounding area appropriate to reduce the cutting parameters, the middle position can be high speed, fast feed processing.
4 Others
When the through hole is processed on the graphite material, the drill hole of the drill bit is likely to produce dregs, and when the through hole is processed, the cutting surface should be closely attached to the surface of other materials, such as a thin graphite sheet or an aluminum gasket, which can effectively Control hole produces dregs.
To prevent crushing of the parts, moderate force must be applied when clamping graphite parts.
Inspection of graphite parts
In addition to the dimensions required to detect the pattern, due to the special nature of the graphite material fragile and cracking, it is necessary to detect the internal and external defects of the graphite components. The non-destructive testing of graphite components mainly includes x-ray inspection and fluoroscopy; X-ray can inspection of internal defects of parts; Fluorescence inspection of surface defects of parts. X-ray inspections are generally performed after roughing, and fluoroscopy is generally performed after finishing.
Surface treatment
The surface treatment should be performed after the graphite product is machined. Surface treatment is generally spraying silicone Heat-resistant paint on the surface of parts, graphite parts after painting are silver-gray, it looks very beautiful.
