BT20 Titanium bar

The nominal composition of BT20 Titanium bar is Ti-6.5Al-2Zr-1Mo1V, which has good comprehensive mechanical properties. The main strengthening mechanism is through the solid solution strengthening of the a-stabilizing element Al. Adding neutral elements Zr and B to stabilize the elements Mo and V can improve manufacturability and are increasingly used in the aircraft manufacturing industry.

It is used as a load-bearing member at room temperature (-60 to 400°C) among titanium alloys. It is mainly developed to meet the needs of aircraft body structural parts... The characteristics of near β-type titanium alloys are: it has the high strength, high toughness and high hardenability of metastable β-type titanium alloys, and also has α+ Tensile Ductility and Elastic Modulus of β-Type Titanium Alloys.

BT20 titanium alloy is mainly used in aerospace, mostly used to make aircraft engine compressor components, followed by structural parts of rockets, missiles and high-speed aircraft.

Production details

BT20|TA15|Ti-6.5Al-2Zr-1Mo1V titanium bar is smelted by vacuum consumable arc three times to obtain finished ingots with a diameter of Φ750mm.

Process:

-For the billet forging, firstly, the high temperature of the β-phase region is carried out for 1 time of drawing, and then 2 times of upsetting and drawing are performed at the same temperature;

-it is drawn for 3 times at a lower temperature in the two-phase region, and finally it is rounded into a bar.

- After forging, the bars are air-cooled and annealed at 800 °C for 1 h, and then transversely sampled and processed into national standard samples for microstructure and performance testing.

Chemical composition(max) VT20/BT15

note:Ti is a basis; the percentage of Ti is given approximately.

Advantageous features

High intensity

The density of titanium alloy is generally about 4.5g/cm3, which is only 60% of steel. The strength of pure titanium is close to that of ordinary 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 and components with high unit strength, good rigidity and light weight can be produced. At present, titanium alloys are used in aircraft engine components, skeletons, skins, fasteners and landing gear.

High thermal strength

The operating temperature is several hundred degrees higher than that of aluminum alloys, and the required strength can still be maintained at moderate temperatures, and it can work for a long time at a temperature of 450 to 500 °C. The specific strength of aluminum alloy decreases significantly at 150 °C. The working temperature of titanium alloy can reach 500 ℃, and the working temperature of aluminum alloy is below 200 ℃.

Good corrosion resistance

Titanium 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, organic substances, nitric acid, sulfuric acid etc. have excellent corrosion resistance. However, titanium has poor corrosion resistance to media with reducing oxygen and chromium salts.

Good performance at low temperature

Titanium alloys can still maintain their mechanical properties at low and ultra-low temperatures. Titanium alloys with good low temperature performance 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.

Chemically active

Titanium has great chemical activity and produces strong chemical reactions with o, n, h, co, co2, water vapor, ammonia, etc. in the atmosphere. When the carbon content is greater than 0.2%, a hard tic will be formed in the titanium alloy; when the temperature is high, it will also form a titanium alloy product. Hard surface layer; when the temperature is above 600 ℃, titanium absorbs oxygen to form a high hardness The hardened layer; the increase of hydrogen content will also form an embrittlement layer. The depth of the hard and brittle surface layer produced by absorbing gas can reach 0.1 to 0.15 mm, and the hardening degree is 20% to 30%. The chemical affinity of titanium is also large, and it is easy to adhere to the friction surface.

Small thermal conductivity and elastic modulus

The thermal conductivity of titanium λ=15.24w/(m.k) 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, so its rigidity is poor and it is easy to deform. It is not suitable to make slender rods and thin-walled parts. times, resulting in severe friction, adhesion and bond wear on the flank of the tool.

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