In machining production, it is easy to encounter metal materials that are difficult to cut. However, some workpieces require these materials to be used for processing. In machining, different difficult cutting materials have their own performance characteristics. Corresponding measures should be taken according to specific objects during milling.
Milling of common difficult cutting materials
1. Milling of high manganese steel
Alloy steel with a nominal content of 13% or more of manganese is called high manganese steel. When milling high manganese steel, tool materials with high hardness, certain toughness, large thermal conductivity and good high temperature performance should be selected. In the process of machining, the feed rate and milling depth should not be too small, so as to avoid the cutting edge or tool tip scratching in the hardened layer formed by the last tool walking and accelerating the wear of the milling cutter. On the premise of ensuring sufficient strength of the cutting edge, the cutting edge should be as sharp as possible to reduce the work hardening layer of the material during milling.
2. Milling of high strength steel
High strength steel has high strength and enough toughness, and can withstand high stress; At the same time, the specific strength is large, which can reduce the self weight of the structure. Cutting tool materials with good wear resistance must be selected for milling high-strength steel.
3. Milling of austenitic stainless steel
Stainless steel can be divided into five types according to its metallographic structure: ferritic stainless steel, martensitic stainless steel, austenitic stainless steel, austenitic ferritic stainless steel and precipitation hardening stainless steel. Milling austenitic stainless steel requires good rigidity of the machine tool fixture tool system, high power of the machine tool, less teeth of the milling cutter, and good grinding quality. Forward milling is adopted during milling.
4. Milling of Superalloys
Alloys with high oxidation resistance and high mechanical properties at high temperatures are called superalloys. When milling superalloys, it is required that the rigidity of the machine tool fixture tool system is good, and the machine tool power is large. The geometric parameters and cutting parameters of the tool should be reasonably selected, and new tool materials with good performance should be used as far as possible. In addition, pressure cooling should be applied to the cutting area during cutting, and forward milling should be adopted for milling.
2、 Measures to be taken when milling difficult cutting materials
1. Select the appropriate tool material
Appropriate tool materials should be selected according to the characteristics of difficult cutting materials. Generally, tool materials with good hardness and high temperature hardness and good cutting performance can be selected. Such as cobalt containing high-speed steel and other new high-speed steel, coated high-speed steel. When necessary, new cutting tool materials such as artificial diamond and cubic boron nitride can be used.
2. Choose reasonable geometric parameters of milling cutter
For hard cutting materials with low hardness and good plasticity, the milling cutter should adopt larger rake angle and rake angle; For hard cutting materials with high hardness and strength, such as superalloys, smaller rake angle, larger helix angle and the absolute value of increasing blade inclination should be used.
3. Use proper cutting fluid
Select the appropriate cutting fluid according to the milling cutter material and processing material. When milling difficult cutting materials with high-speed steel milling cutter, synthetic cutting fluid with good adhesion resistance and cooling performance is generally used; When milling with carbide milling cutter, it is best to use oil extreme pressure cutting fluid, such as extreme pressure emulsion, extreme pressure cutting oil, etc.
4. Select reasonable milling amount
Due to the large milling force and high milling temperature when machining difficult cutting materials, the milling amount is smaller than that when milling ordinary steel.
5. Choose a reasonable milling method
For some materials with large plastic deformation, high thermal strength and severe cold hardness, forward milling should be used as far as possible (asymmetric forward milling is used for end milling), so that the bonding contact area of chips is small, the pressure on the milling cutter when the chips are separated from the workpiece is small, and it is easy to get rid of it, as well as improve the durability of the milling cutter and obtain a smaller surface roughness value.