At present, the widely used CNC tool materials mainly include diamond tools, cubic boron nitride tools, ceramic tools, coated tools, carbide tools and high-speed steel tools.There are many grades of cutting tool materials and their properties vary greatly.The main performance indexes of various tool materials are listed below.The cutting tool material for NC machining must be selected according to the workpiece and the nature of the machining.The selection of cutting tool material should be reasonable with the processing object match, cutting tool material and the processing object match, mainly refers to the mechanical properties, physical properties and chemical properties of the two match, in order to obtain the longest tool life and the largest cutting productivity.
1.Matching of cutting tool material with mechanical properties of machining objects The matching of cutting tool material with mechanical properties of machining objects mainly refers to the matching of cutting tool with mechanical properties such as strength, toughness and hardness of workpiece materials.Tool materials with different mechanical properties are suitable for different workpiece materials.(1) the hardness sequence of tool materials is: diamond tool > cubic boron nitride tool > ceramic tool > carbide > high speed steel.The bending strength sequence of tool materials is: > high speed steel carbide > ceramic tool > diamond and cubic boron nitride tool.(3) the order of toughness of the tool material is: high speed steel > carbide > cubic boron nitride, diamond and ceramic tools.The workpiece material with high hardness must be processed with the tool with higher hardness. The hardness of the tool material must be higher than the hardness of the workpiece material, generally required to be above 60HRC.The harder the tool material is, the better its wear resistance will be.For example, when the amount of cobalt in cemented carbide increases, its strength and toughness increase and hardness decreases, and it is suitable for rough machining.When the cobalt content decreases, its hardness and wear resistance increase, and it is suitable for finishing.Tools with excellent high temperature mechanical properties are especially suitable for high speed cutting.The high temperature performance of ceramic cutting tools enables them to cut at a high speed, which is 2 ~ 10 times faster than carbide.
2.The cutting tool materials and the physical properties of the processing object match the tools with different physical properties, such as, high thermal conductivity and low melting point of high-speed steel tools, high melting point and low thermal expansion of ceramic tools, high thermal conductivity and low thermal expansion of diamond tools, etc., suitable for processing the workpiece materials are different.When machining the workpiece with poor thermal conductivity, the tool material with good thermal conductivity should be used to make the cutting heat quickly spread out and reduce the cutting temperature.Due to high thermal conductivity and thermal diffusivity, diamond is easy to be released from the cutting heat and will not produce great thermal deformation, which is particularly important for precision machining tools with high dimensional accuracy requirements.The heat resistance temperature of various tool materials: diamond tool 700 ~ 8000C, PCBN tool 13000 ~ 15000C, ceramic tool 1100 ~ 12000C, TiC(N) base cemented carbide 900 ~ 11000C, WC base ultra-fine grain cemented carbide 800 ~ 9000C, HSS 600 ~ 7000C.The order of thermal conductivity of various tool materials: PCD>PCBN>WC cemented carbide >TiC(N) cemented carbide >HSS> si3n4-based ceramic > a1203-based ceramic.The order of the thermal expansion coefficient of various tool materials is: HSS>WC cemented carbide >TiC(N)>A1203 base ceramic >PCBN>Si3N4 base ceramic >PCD.The order of thermal shock resistance of various tool materials is HSS>WC hard alloy > si3n4-base ceramic >PCBN>PCD>TiC(N) hard alloy > a1203-base ceramics.
3.The matching problem of cutting tool material and the chemical property of the processing object mainly refers to the matching of the chemical property parameters such as the chemical affinity, chemical reaction, diffusion and dissolution of the cutting tool material and the workpiece material.Different materials of the tool suitable for processing the workpiece materials are different.(1) all kinds of cutting tool material adhesion temperature (and steel) for PCBN> ceramic > cemented carbide >HSS.(2) the oxidation resistance temperature of various cutting tool materials is as follows: ceramic >PCBN> carbide diamond >HSS.The diffusion strength of the cutter material (for steel) is: diamond > si3n4-base ceramic >PCBN> a1203-base ceramic.The diffusion strength (to titanium) was a1203-base ceramic >PCBN>SiC>Si3N4> diamond.
4.Generally speaking, PCBN, ceramic tools, coated carbide and TiCN base carbide tools are suitable for numerical control processing of ferrous.
Post time: Jan-21-2021