The existing problems in titanium alloy grinding and the treatment scheme
Characteristics of titanium alloys
Titanium alloys are roughly divided into three categories: α titanium alloy, β titanium alloy, and α+β titanium alloy. The most widely used titanium alloy specification is TC4 (Ti-6AI-4V), which is a titanium alloy with an α+β phase structure.
Titanium alloys have the characteristics of high strength, good thermal stability, high high temperature strength, high chemical activity, and low thermal conductivity. The higher the temperature, the higher the hardness. It is one of the most difficult materials to process. It is very difficult to polish and the grinding performance is very poor. 36#-80# particle size is usually used for grinding titanium alloys.
Problems in grinding
1. The bonding problem of the grinding wheel is serious.
During the grinding process, the titanium alloy on the surface falls off and adheres to the grinding wheel. The bonding surface will fall off with the abrasive grains on the grinding wheel during subsequent grinding, which will cause serious damage to the grinding wheel.
2. The workpiece is prone to burns, deformation and cracks
Due to the characteristics of titanium alloy that the higher the temperature, the higher the hardness, the grinding force required is large, the temperature generated is too high, and the heat transmitted to the workpiece is difficult to be discharged. Its heat will destroy the titanium alloy, which is easy to cause the workpiece to burn, deform, and even crack.
Suitable abrasives
Because titanium alloy is a non-ferrous metal, it is more suitable for grinding with silicon carbide (SiC) or green silicon carbide (GreenSiC), or superhard diamond abrasives (Diamond). The use of green silicon carbide and silicon carbide grinding wheels has less adhesion, and there are fewer burns and cracks. Therefore, green silicon carbide grinding wheels are generally used.
Solution to grinding problems
The reason why the grinding wheel is prone to bonding during the grinding process of titanium alloy and the workpiece is prone to burning, deformation and cracking is due to the high grinding temperature. High grinding temperature will cause severe plastic deformation, thereby damaging the surface of the workpiece, and the abrasive and the metal will produce a bonding effect through physical or chemical adsorption.
The most fundamental solution is to solve the heat dissipation problem. The common practice is to effectively improve the grinding ratio and achieve more removal with as little grinding wheel loss as possible.
Traditional practice
Traditional practice; slowing down the grinding wheel speed will also reduce the grinding temperature, and better grinding effect will be achieved than high-speed rotation; but in this case, due to the slow speed, the grinding wheel consumption will be accelerated, the more time and frequency of dressing, the slower the processing efficiency will be, which will also affect its processing cost invisibly, and also have a certain impact on the plane accuracy/dimensional accuracy of the workpiece; therefore, this is not the best way.
Ideal practice; achieve good heat dissipation effect under the condition of constant speed. Grind at the highest speed allowed by the grinding wheel or grinder, and use the grinding wheel or grinding fluid or processing conditions to achieve better heat dissipation effect, and try not to lose the rotation speed of the grinding wheel as much as possible to avoid wasting the cost of the grinding wheel.
However, the requirements for titanium alloy grinding fluid, in addition to cooling and flushing, are more importantly to inhibit the adhesion and chemical reaction of titanium and abrasive particles. It is advisable to use a water-soluble grinding fluid containing a variety of extreme pressure additives.
Titanium alloy grinding fluid has excellent biological stability and anti-rust performance. The longest service life can exceed two years; it has good anti-rust performance and reduces the consumption of cutting fluid. At the same time, titanium alloy grinding fluid does not contain harmful substances such as chlorine, nitrite, phenol, etc. It is an environmentally friendly grinding fluid that will not irritate the skin and protect the health of the operator. If you want to use the existing grinding wheel to improve efficiency, you can try to reduce the speed of the grinding wheel to see if the effect is achieved. If so, it proves that the problem is caused by the grinding temperature, and you can start from this condition to see how other conditions should be set.
In general, it is to use the heat dissipation of the grinding wheel, plus the coordination between other heat dissipation methods, such as whether the cutting fluid is properly coordinated; let it provide better heat dissipation.
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