Machining titanium products for the oil drilling industry

Titanium is a new type of metal. The properties of titanium are related to the content of impurities such as carbon, nitrogen, hydrogen, and oxygen. The purest titanium iodide has an impurity content of no more than 0.1%, but its strength is low and its plasticity is high. The properties of 99.5% industrial pure titanium are: density ρ=4.5g/cm3, melting point 1725°C, thermal conductivity λ=15.24W/(m.K), tensile strength σb=539MPa, elongation δ=25%, and cross-sectional shrinkage The rate ψ=25%, the elastic modulus E=1.078×105MPa, and the hardness HB195.high strengthThe density of titanium alloys is generally around 4.51g/cm3, which is only 60% of steel. Some high-strength titanium alloys exceed the strength of many alloy structural steels. Therefore, the specific strength (strength/density) of titanium alloy is much greater than that of other metal structural materials, and parts with high unit strength, good rigidity, and light weight can be produced. Titanium alloys are used in aircraft engine components, frames, skins, fasteners and landing gear.High thermal intensityThe service temperature is several hundred degrees higher than that of aluminum alloys. It can still maintain the required strength at moderate temperatures and can work for a long time at temperatures of 450 to 500°C. These two types of titanium alloys still have high strength in the range of 150°C to 500°C. Specific strength, while the specific strength of aluminum alloy drops significantly at 150°C. The working temperature of titanium alloy can reach 500℃, while that of aluminum alloy is below 200℃.Good corrosion resistanceTitanium alloy works in humid atmosphere and seawater medium, and its corrosion resistance is much better than stainless steel; it is particularly resistant to pitting corrosion, acid corrosion, and stress corrosion; it is resistant to alkali, chloride, chlorine-based organic substances, nitric acid, and sulfuric acid. etc. have excellent corrosion resistance. However, titanium has poor corrosion resistance to media with reducing oxygen and chromium salts.Good low temperature performanceTitanium alloys can still maintain their mechanical properties at low and ultra-low temperatures. Titanium alloys with good low-temperature properties and extremely low interstitial elements, such as TA7, can maintain a certain plasticity at -253°C. Therefore, titanium alloy is also an important low-temperature structural material.High chemical activityTitanium has high chemical activity and produces strong chemical reactions with O2, N2, H2, CO, CO2, water vapor, ammonia, etc. in the atmosphere. When the carbon content is greater than 0.2%, hard TiC will be formed in the titanium alloy; when the temperature is high, it will react with N to form a hard surface layer of TiN; above 600°C, titanium absorbs oxygen to form a very hard hardened layer ; As the hydrogen content rises, a brittle layer will also form. The depth of the hard and brittle surface layer produced by absorbing gas can reach 0.1~0.15 mm, and the degree of hardening is 20%~30%. Titanium also has high chemical affinity and is prone to adhesion to friction surfaces.Thermal conductivity is smallThe thermal conductivity of titanium λ = 15.24W/(m·K) is about 1/4 of nickel, 1/5 of iron, and 1/14 of aluminum. The thermal conductivity of various titanium alloys is about 50% lower than that of titanium. %. The elastic modulus of titanium alloy is about 1/2 that of steel, so it has poor rigidity and is easy to deform. It is not suitable for making slender rods and thin-walled parts. The rebound amount of the machined surface during cutting is very large, about 2 to 3 times that of stainless steel. times, causing severe friction, adhesion, and bonding wear on the tool flank surface.