(1) The elastic modulus of titanium alloy is low, about 1/2 of that of steel. It is easy to rebound on the surface after removal, and it is easy to produce strong friction with the flank of the tool;

(2) Low plasticity, high hardness, small contact area between chips and rake face, high cutting stress of the tool tip, and easy wear of the tool tip and cutting edge, usually the cutting speed is about 30m/min;

(3) The chemical activity is high. At high temperature, titanium and most of the components in the air produce a strong chemical reaction, especially with oxygen and nitrogen, producing interstitial solid solution, forming a hard layer with high hardness, and having a strong knife The abrasion effect;

(4) The affinity is large. Due to the strong friction between the chip and the cutting face, under the action of high cutting temperature and high cutting pressure, the titanium element in the tool material and the workpiece material is mutually compatible, resulting in occlusion and adhesion. Knives and knives are prone to adhesive wear.

Titanium alloy cutting tool selection:

(1) The material of the tool (according to the processed material, processing application type, processing environment and on-site processing requirements).

Choose tool materials with good red hardness, high bending strength, good thermal conductivity, and poor affinity with titanium alloys. YG cemented carbide is more suitable. Due to the poor heat resistance of high-speed steel, tools made of cemented carbide should be used as much as possible. Commonly used cemented carbide tool materials include YG8, YG3, YG6X, YG6A, 813, 643, YS2T and YD15.

(2) Geometry (divided into shank geometry and cutting edge geometry, which mainly affect the surface quality, chip removal effect, cutting edge strength, burrs, vibration lines, etc.).

(3) Coating (extend the tool life, increase the cutting speed and feed of the tool, obtain higher production efficiency, and improve the wear resistance of the tool).

Coated inserts and YT-type cemented carbide will have a violent affinity with titanium alloys, which will aggravate the bonding wear of the tool, and are not suitable for cutting titanium alloys. For complex and multi-edge tools, high-vanadium high-speed steel (such as W12Cr4V4Mo) ), high-cobalt high-speed steel (such as W2Mo9Cr4VCo8) or aluminum high-speed steel (such as W6Mo5Cr4V2Al, M10Mo4Cr4V3Al) and other tool materials, suitable for making drills, reamers, end mills, broaches, taps and other tools for cutting titanium alloys.

(4) According to on-site operation requirements, coordinate the efficiency and processing cost, and fully consider the performance of the existing machine tools, using relatively conservative cutting parameters, which can effectively extend the tool life and obtain a more reasonable processing efficiency.

Using diamond and cubic boron nitride as tools for cutting titanium alloys can achieve significant results. For example, the cutting speed can reach 200 m/min under the condition of emulsion cooling with natural diamond tools; if the cutting fluid is not used, the allowable cutting speed is only 100 m/min at the same amount of wear.

In the process of cutting titanium alloy, the matters that should be paid attention to are:

(1) Due to the small modulus of elasticity of titanium alloy, the clamping deformation and force deformation of the workpiece during processing will reduce the processing accuracy of the workpiece; the clamping force should not be too large when the workpiece is installed, and auxiliary support can be added when necessary.

(2) If a cutting fluid containing hydrogen is used, it will decompose and release hydrogen at high temperatures during the cutting process, which will be absorbed by titanium and cause hydrogen embrittlement; it may also cause high-temperature stress corrosion cracking of titanium alloys.

(3) The chloride in the cutting fluid may also decompose or volatilize toxic gas during use. Safety protection measures should be taken when using it, otherwise it should not be used; after cutting, the parts should be thoroughly cleaned with a chlorine-free cleaning agent in time to remove chlorine residues Things.

(4) It is forbidden to use lead or zinc-based alloy tools and fixtures in contact with titanium alloys, and copper, tin, cadmium and their alloys are also forbidden to use.

(5) All tools, fixtures or other devices in contact with the titanium alloy must be clean; the cleaned titanium alloy parts should be prevented from being contaminated by grease or fingerprints, otherwise it may cause salt (sodium chloride) stress corrosion in the future.

(6) Under normal circumstances, there is no risk of ignition when cutting titanium alloys. Only in micro-cutting, the small chips cut off will ignite and burn. In order to avoid fire, in addition to pouring a large amount of cutting fluid, it is also necessary to prevent the accumulation of chips on the machine tool. The tool should be replaced immediately after being blunt, or the cutting speed should be reduced, and the feed rate should be increased to increase the thickness of the chip. In case of fire, fire extinguishing equipment such as talcum powder, limestone powder, dry sand should be used to extinguish the fire. Carbon tetrachloride and carbon dioxide fire extinguishers are strictly prohibited, and watering is prohibited, because water can accelerate combustion and even cause hydrogen explosion.

Shenzhen Lixin-iMachining Co., Ltd.

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