Titanium and titanium alloy has many perfect properties and processing advantages as new material.
Today TopTiTech introduces some properties for you:
1. Machining performance
Titanium alloy has high chemical activity at high temperatures, and it is easy to chemically react with gas impurities such as hydrogen and oxygen in the air to form a hardened layer, which further aggravates the wear of the tool; in the cutting of titanium alloy, the workpiece material is very easy to stick to the surface of the tool. junction, coupled with high cutting temperature, so the tool is prone to diffusion wear and adhesive wear. Compared with 45 steel, although the cutting force of titanium alloy is only 2/3-3/4, the contact area between the chip and the rake face is smaller (only 1/2-2/3 of 45 steel), so the stress on the cutting edge is greater, and the tooltip or cutting edge is easy to wear; the friction coefficient of titanium alloy is large, but the thermal conductivity is low (only 1/4 and 1/16 of iron and aluminum, respectively); the contact between the tool and the chip The length is short, and the cutting heat is accumulated in a small area near the cutting edge and is not easily dissipated. These factors make the cutting temperature of titanium alloys very high, resulting in accelerated tool wear and poor machining quality. Due to the low elastic modulus of titanium alloy, the workpiece rebounds greatly during cutting, which is easy to cause aggravation of tool flank wear and workpiece deformation.
2. Grinding performance
The wear of the titanium alloy grinding wheel also increases the contact area between the grinding wheel and the workpiece, resulting in the deterioration of the heat dissipation conditions, the sharp increase in the temperature of the grinding zone, and the formation of large thermal stress on the grinding surface layer, resulting in local burns of the workpiece, resulting in Grinding cracks. Titanium alloy has high strength and high toughness, which makes the grinding debris difficult to separate, the grinding force increases, and the grinding power consumption increases accordingly. Titanium alloy has low thermal conductivity, small specific heat, and slow heat conduction during grinding, which causes heat to accumulate in the grinding arc area, resulting in a sharp increase in the temperature of the grinding area.
3. Extrusion performance
Titanium and titanium alloy extrusion dies should be made of new heat-resistant mold materials, and the conveying speed of the billet from the heating furnace to the extrusion cylinder should be fast. Since metals are easily contaminated by gases during heating and extrusion, appropriate protective measures should also be used. Appropriate lubricants should be selected during extrusion to prevent sticking of the mold, such as the use of sheath extrusion and glass-lubricated extrusion. Due to the large deformation thermal effect and poor thermal conductivity of titanium and titanium alloys, special attention should be paid to preventing overheating during extrusion deformation. The extrusion process of titanium alloy is more complicated than that of aluminum alloy, copper alloy, and even steel, which is determined by the special physical and chemical properties of titanium alloy. When the titanium alloy is formed by conventional hot back extrusion, the temperature of the die is low, the temperature of the surface of the billet in contact with the die drops rapidly, and the temperature of the inside of the billet increases due to the heat of deformation. Due to the low thermal conductivity of titanium alloys, after the surface temperature drops, the heat of the inner layer billet cannot be transferred to the surface layer in time for supplementation, and a surface hardened layer will appear, making it difficult to continue the deformation. At the same time, the surface layer and the inner layer will have a large temperature gradient, and even if they can be formed, it is easy to cause deformation and uneven tissue.
4. Forging processing performance
Titanium alloys are very sensitive to forging process parameters. Changes in forging temperature, deformation, deformation, and cooling rate will cause changes in the microstructure and properties of titanium alloys. In order to better control the microstructure and properties of forgings, in recent years, advanced forging technologies such as hot die forging and isothermal forging have been widely used in the forging production of titanium alloys.
The plasticity of titanium alloy increases with the increase in temperature. In the temperature range of 1000-1200 ℃, the plasticity reaches the maximum value, and the allowable deformation degree reaches 70%-80%. The titanium alloy forging temperature range is narrow, and it should be strictly controlled according to the (α+β)/β transition temperature (except for ingot opening), otherwise, the β grains will grow violently, reducing the room temperature plasticity; α titanium alloys are usually in (α +β) Forging in two-phase region, because the forging temperature above (α+β)/β phase transformation line is too high, it will lead to β brittle phase, and the initial forging and final forging of β titanium alloy must be higher than (α+β)/ beta transition temperature. The deformation resistance of titanium alloys increases rapidly with the increase of deformation speed, and the forging temperature has a greater impact on the deformation resistance of titanium alloys. Therefore, conventional forging must be completed with the least cooling in the forging die. The content of interstitial elements (such as O, N, and C) also has a significant effect on the enforceability of titanium alloys.
