Titanium has an excellent strength-to-weight ratio, which is usually only 60% of the density of steel. Titanium has a lower modulus of elasticity than steel, so the texture is harder and the deflection is better. Titanium is also superior to stainless steel in corrosion resistance and has low thermal conductivity. These properties mean that titanium will produce higher and more concentrated cutting forces during processing.
It is prone to vibrations that cause chattering during cutting; and it also easily reacts with the cutting tool material during cutting, which exacerbates crater wear. In addition, its thermal conductivity is poor, and since the heat is mainly concentrated in the cutting zone, the tool for machining titanium alloy parts must have high heat hardness.
Characteristics of titanium alloy cutting process
In actual milling, the conditions required for the machining of titanium alloy parts are not always fully met, as ideal stability conditions are not always available. In addition, many titanium parts are complex in shape and may contain many fine or deep cavities, thin walls, bevels, and thin brackets. To successfully machine such parts, large overhangs and small diameter tools are required, which can affect tool stability.
When processing titanium alloys, potential stability problems are often more likely to occur.
When milling titanium, the tool is required to work with at least a minimum feed rate - typically 0.1 mm per tooth.
If the tendency to vibrate is thrown, the problem of blade damage or shortened tool life will be inevitable. Possible solutions include accurately calculating the feed per tooth and making sure it is at least 0.1 mm.
With the development of processing technology, in recent years, titanium alloys have been widely used in the manufacture of aircraft engine compressor sections, engine covers, exhaust devices and other structural components such as aircraft frame frames. The titanium alloy parts of a new type of aero engine in our company account for about 11% of the total number of parts.
According to the nature of titanium alloy and the characteristics of the cutting process
Titanium alloy processing methods should consider the following aspects:
1. Use a small front angle and a large back angle to increase the contact length between the chip and the rake face, reduce the friction between the workpiece and the flank face, and use a circular arc edge to increase the strength and avoid sharp corners. Burned and chipped. Keep the blade sharp to ensure smooth chip removal and avoid chipping. The cutting speed should be low to avoid excessive cutting temperature; the feed rate is moderate, too large and easy to burn the knife. If it is too small, the blade will wear too fast because it works in the hardened layer; the cutting depth can be large, so that the tip is in the hardened layer. The following work is beneficial to improve tool durability.
2. Use carbide tools as much as possible. For example, tungsten-cobalt cemented carbide and titanium alloy have low chemical affinity, good thermal conductivity and high strength. Ultra-fine grained carbide with impact resistance can be selected for interrupted cutting at low speeds. High-speed steel with high temperature performance can be used for forming and complex tools.
