At present, the majority of aircraft engine parts use titanium alloy materials, according to the assembly needs, precision machining surface size and surface roughness need grinding processing to ensure the quality of parts surface.Due to the physical and mechanical properties of titanium alloy material itself, surface burns and surface integrity degradation are easy to occur during grinding. At present, it is urgent to solve the problem of grinding titanium alloy material, so it is very necessary to choose the right grinding wheel.
1 performance analysis of titanium alloy materials
The types of titanium alloys can be divided into three types: titanium dioxide, titanium dioxide and titanium plus titanium dioxide.With small specific gravity, high specific strength, high temperature resistance, corrosion resistance, super memory, non-magnetic, low elastic modulus, biocompatibility number, this series of excellent make it in a wide range of applications.Titanium has a melting point of 1668 ° c and a boiling point of 3400 ° c, which is higher than that of ferronickel. Therefore, lightweight heat resistance provides an excellent basis for its long-term operation at 500 ° c.The new titanium alloy has a higher long-term operating temperature and is 10 times stronger than aluminum alloy at 300-350℃.Commonly used: + MPa titanium alloy strength up to 1.2GPa, specific gravity 0.44mpa, specific strength 23-27, are higher than alloy steel.The tensile strength of titanium alloy can be more than 1.5GPa, and a great force must be exerted on its processing, which is a typical hard material.
The thermal conductivity of titanium is 0.036 CAL, and the thermal conductivity of TC11 titanium alloy is worse.The elastic modulus of titanium is about 1/2 of that of steel.
Titanium alloy contains oxygen, hydrogen, nitrogen, carbon, and sometimes silicon, iron and other impurities, these elements have a strong reaction, in the gap type existence in the lattice, can make the strength of titanium alloy increase, plastic decline, and even fracture toughness, low temperature toughness, fatigue strength, corrosion resistance, cold forming and weldability become bad.Titanium alloy in high temperature high chemical, in a certain grinding temperature, the formation of titanium oxidation, nitriding protective film, make the surface layer hardening brittle, reduce the elasticity, increase the degree of processing hardening, easy to adhere to the grinding, blocking the grinding wheel, resulting in grinding overheating, surface integrity reduction.
Selection of titanium alloy grinding wheel
2.1 titanium alloy grinding requires small adhesion of grinding wheel, small wear, not easy to block and low grinding temperature
This mainly includes the particle size of the abrasive binder structure size.Common grinding wheel consists of abrasive binder and porosity.The function of abrasive is to grind the processed material to form a suitable surface.The function of binders is to bond abrasives together to form a certain shape and hardness, so that the abrasive particles in the grinding process to maintain a stable track of movement, and can be self-released.Porosity is in the process of grinding chip, cooling and lubrication.Common abrasives include corundum series (alumina), and silicon carbide series.Silicon carbide grinding wheel should be chosen for grinding titanium alloy.
2.2 selection of binder
Binders are divided into resin and ceramic:
1) ceramic binder particles have strong capacity, good thermal stability and chemical stability, waterproof, heat resistance, corrosion resistance, small wear, long time to maintain the grinding performance, porous, not easily blocked, high productivity.Brittleness, can not withstand the larger impact load.
2) resin bonded grinding wheel has high strength, elasticity, good impact resistance, poor thermal stability, poor corrosion resistance, and will soften and lose strength under high temperature.
Ceramic bond grinding wheel should be selected for grinding titanium alloy.
2.3 selection of granularity
Titanium alloys are usually ground with a size of 36#-80#.
2.4 grinding wheel organization hardness
Titanium alloy grinding should usually choose the soft hardness or medium hardness, the organization of loose large hole grinding wheel.