1. Introduction of Titanium

It was only in 1948 that the Dupont Company of the United States used the magnesium method to produce tons of sponge titanium-this marked the beginning of the industrial production of sponge titanium, that is, titanium. Titanium alloys are widely used in various fields because of their high specific strength, good corrosion resistance, and high heat resistance.

Titanium is abundant in the earth's crust and ranks ninth in content, much higher than common metals such as copper, zinc and tin. Titanium is widely present in many rocks, especially in sand and clay.

Second, the characteristics of titanium

High strength: 1.3 times that of aluminum alloy, 1.6 times that of magnesium alloy, 3.5 times that of stainless steel, the champion among metal materials.

High thermal strength: the use temperature is several hundred degrees higher than that of aluminum alloy, and it can work for a long time at a temperature of 450 ~ 500 ℃.

Good corrosion resistance: acid resistance, alkali resistance, atmospheric corrosion resistance, particularly strong resistance to pitting corrosion and stress corrosion.

Low temperature performance: Titanium alloy TA7 with extremely low interstitial elements can maintain a certain plasticity at -253 ℃.

High chemical activity: The chemical activity is very high at high temperature, and easily reacts with gas impurities such as hydrogen and oxygen in the air to form a hardened layer.

The thermal conductivity is small and the elastic modulus is small: the thermal conductivity is about 1/4 of nickel, 1/5 of iron, 1/14 of aluminum, and 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 of that of steel.

Third, the classification and use of titanium alloy

Titanium alloys can be divided into heat-resistant alloys, high-strength alloys, corrosion-resistant alloys (titanium-molybdenum, titanium-palladium alloys, etc.), low-temperature alloys and special functional alloys (titanium-iron hydrogen storage materials and titanium-nickel memory alloys) Wait.

Although the application history of titanium and its alloys is not long, but because of its superior performance, it has won many glorious titles. The first title won was "Space Metal". It is light in weight, high in strength and resistant to high temperatures, and is particularly suitable for manufacturing aircraft and various spacecraft. About three-quarters of the titanium and titanium alloys currently produced in the world are used in the aerospace industry. Many parts that originally used aluminum alloys have been replaced with titanium alloys.

Fourth, titanium and titanium alloys have many excellent characteristics, mainly reflected in the following aspects:
1. High strength. Titanium alloy has high strength, its tensile strength is 686-1176MPa, and the density is only about 60% of steel, so the specific strength is very high.
2. High hardness. The hardness HRC of the titanium alloy (annealed state) is 32-38.
3. Low elastic modulus. The elastic modulus of titanium alloy (annealed state) is 1.078 × 10－1.176 × 10MPa, which is about half of steel and stainless steel.
4. Excellent high and low temperature performance. At high temperatures, titanium alloys can still maintain good mechanical properties, their heat resistance is much higher than aluminum alloys, and the working temperature range is wider. At present, the working temperature of new heat-resistant titanium alloys can reach 550-600 ℃; at low temperatures However, the strength of the titanium alloy is increased compared to that at room temperature, and it has good toughness. The low-temperature titanium alloy can maintain good toughness at -253 ° C.
5. Titanium has strong corrosion resistance. Titanium quickly forms a thin and dense titanium oxide film in the air below 550 ° C, so its corrosion resistance is superior to most stainless steels in oxidizing media such as the atmosphere, seawater, nitric acid, sulfuric acid, and strong alkalis.