Cutting material method for difficult material
Cutting material method for difficult material
In recent years, the development of multi-functional and high-functional mechanical products has been very strong, requiring parts to be miniaturized and miniaturized. In order to meet these requirements, the materials used must have high hardness, high toughness and high wear resistance, and materials with these characteristics are particularly difficult to process, so new difficult-to-process materials have emerged. Difficult-to-process materials appear in this way with the development of the times and different professional fields, and their unique machining technology also continues to develop with the development of the times and various professional fields.
On the other hand, with the advent of an information society, information on cutting technology of difficult-to-machine materials can also be exchanged through the Internet. Therefore, in the future, information about cutting data of difficult-to-machine materials will be more substantial, and machining efficiency will inevitably be further improved.
Coated cemented carbide tools are almost suitable for cutting all kinds of difficult-to-machine materials, but the coating performance (single-coated composite coating) varies greatly. Therefore, suitable coated tool materials should be selected according to different machining objects.
Cutting tool shapes for difficult materials
When cutting difficult-to-machine materials, the optimized tool shape can give full play to the tool material performance. Choosing tool geometries that are suitable for the characteristics of difficult-to-machine materials, such as rake angle, rake angle, and cut-in angle, to properly handle the blade tip has a great impact on improving cutting accuracy and extending tool life. However, with the popularization and application of high-speed milling technology, recently, small cuts have been gradually adopted to reduce the load on the cutter teeth, reverse milling has been adopted and the feed rate has been increased.
When drilling difficult materials, increase the angle of the drill tip, perform cross-shaped grinding, and reduce the torque cutting heat. The effective way to reduce the contact area between the cutting and the cutting surface is within the minimum range, which extends the tool life. It is very beneficial to improve the cutting conditions. When the drill is drilling, the cutting heat is easily retained near the cutting edge, and chip removal is also difficult. These problems are more prominent when cutting difficult-to-machine materials, and sufficient attention must be paid.
In order to facilitate chip evacuation, usually a coolant outlet is provided on the back side of the cutting edge of the drill bit, which can supply sufficient water-soluble coolant or mist coolant, etc., to make chip evacuation smoother. Very ideal. In recent years, some coating materials with good lubricating properties have been developed. After these materials are coated on the surface of the drill bit, dry drilling can be used when machining shallow holes of 3 to 5 days with them.
Hole finishing has always used the boring method, but recently it has gradually changed from the traditional continuous cutting method to the continuous cutting method such as contour cutting. This method is more beneficial to improving the chip removal performance and extending the tool life. Therefore, this type of intermittent cutting boring tool was designed and immediately applied to cnc machining of automotive parts. For threaded hole machining, the spiral cutting interpolation method is also currently used, and end mills for thread cutting have been put on the market in large quantities.
As mentioned above, this transition from continuous cutting to discontinuous cutting is a gradual process with the deepening of CBN cutting. When this kind of cutting method is used to cut difficult-to-machine materials, the cutting stability can be maintained, and the tool life is prolonged.
Cutting conditions for difficult materials
The cutting conditions of difficult-to-machine materials have always been set relatively low. With the improvement of tool performance, the emergence of high-speed and high-precision CNC machine tools, and the introduction of high-speed milling methods. At present, the cutting of difficult-to-machine materials has entered a period of high-speed machining and tool life.
The use of a small depth of cut to reduce the load on the cutting edge of the tool, which can increase the cutting speed and feed speed, has become the best way to cut difficult materials. Of course, it is extremely important to choose a tool that adapts to the unique performance tool materials of difficult-to-machine materials, and the cutting path of the tool should be optimized. For example, when drilling materials such as stainless steel, the thermal conductivity of the material is very low. Therefore, it is necessary to prevent a large amount of cutting heat from staying on the cutting edge. Helps extend tool life and ensure stable cutting. When rough machining hard-to-machine materials with a ball-end mill, the tool shape fixture should be well matched, so that the precision of the cutting part of the tool can be improved. To the maximum, it can also extend the tool life.
Difficult to process materials in the cutting field
During cutting, tool wear usually occurs in two forms:
(1) Wear due to mechanical action, such as chipping or abrasive wear, etc .;
(2) Wear due to heat and chemical action, such as adhesion, diffusion, corrosion and other wear, as well as breakage, thermal fatigue, and thermal cracking caused by softening and melting of the cutting edge.
When cutting difficult-to-machine materials, the above-mentioned tool wear occurs in a short time, which is caused by the fact that there are many factors that promote the tool wear. For example, most difficult-to-machine materials have the characteristics of low thermal conductivity, and the heat generated during cutting is difficult to diffuse, resulting in a high temperature of the tool tip, and the cutting edge is extremely affected by heat. As a result of this effect, the bond strength of the tool material binder will decrease at high temperatures, and particles such as tungsten carbide will be easily separated, thereby accelerating tool wear. In addition, some components of the tool material that are difficult to machine materials are susceptible to reaction under high-temperature cutting conditions, and they may be analyzed, fall off, or generate other compounds, which will accelerate the occurrence of tool wear such as chipping.
When cutting high hardness and high toughness processed materials, the cutting edge temperature is very high, and tool wear similar to that when cutting difficult materials will also occur. For example, when cutting high-hardness steel, the cutting force is greater than that of general steel. Insufficient tool rigidity will cause chipping and other phenomena, making the tool life unstable and shortening the tool life, especially when machining short-cut workpiece materials It will cause crescent crater wear near the cutting edge, and the tool will often break in a short time.
When cutting super heat resistant alloys, due to the high hardness of the material, a large amount of stress is con
Attention should be paid to the cutting of difficult materials
The cutting process is roughly divided into turning, milling, and cutting based on heart teeth (drilling, end milling, etc.). The influence of cutting heat on the cutting edge during these cutting processes is also different. Turning during continuous cutting, the cutting edge has no obvious change in cutting force, cutting heat continuously acts on the cutting edge; milling is a discontinuous cutting, the cutting force acts on the cutting edge intermittently, vibration will occur during cutting, and heating will occur during cutting Cooling alternately during non-cutting, the total heat is less than when turning.
Cutting heat during milling is an intermittent heating phenomenon, and the cutter teeth are cooled when they are not cutting, which will help extend the life of the tool. Japan Institute of Physics and Chemistry made a comparative test on the life of turning and milling tools. The tools used for milling are ball end mills and turning tools are general turning tools. , Cutting speed, etc. can only be roughly the same) and comparative cutting tests under the same environmental conditions, the results show that milling is more beneficial to prolong tool life.
When cutting with a drill with a core edge (ie, cutting speed = 0 m / min), a ball end mill and other tools, the tool life near the core edge is often low, but it is still stronger than when turning.
When cutting difficult materials, the cutting edge is greatly affected by heat, which often reduces the tool life. If the cutting method is milling, the tool life will be relatively long. However, difficult-to-machine materials cannot be all milled from beginning to end, and there will always be times when turning or drilling is required. Therefore, corresponding technical measures should be taken for different cutting methods to improve machining efficiency.
Tool materials for cutting difficult-to-machine materials
CBN high-temperature hardness has the best tool materials, and is most suitable for cutting difficult materials. The new-type coated cemented carbide uses ultra-fine grain alloys as the matrix and uses high-temperature hardness coating materials for coating treatment. This material has excellent wear resistance and can also be used as one of the excellent tool materials for difficult-to-machine materials.
Difficult-to-machine materials such as titanium and titanium alloys have high chemical activity and low thermal conductivity. Diamond tools can be used for cutting. CBN sintered body tools are suitable for cutting materials such as high-hardness steel and cast iron. The higher the CBN content, the longer the tool life and the corresponding amount of cutting. A CBN sintered body that does not use a binder has been developed.
Diamond sintered body tool is suitable for cutting aluminum alloy, pure copper and other materials. Diamond cutters have sharp edges, high thermal conductivity, and less heat retention at the blade tips, which can minimize the occurrence of adhesions such as built-up edges. When cutting pure titanium and titanium alloys, single-crystal diamond tools are used for stable cutting, which can also extend the tool life.
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