Gr7 titanium alloy

Gr7(T-0.2P.) titanium alloy is an a-type titanium alloy made by adding a small amount of precious metal Pd to industrial pure titanium. The addition of Pd not only significantly improves the corrosion resistance of the alloy in reducing media, but also improves Its corrosion resistance in oxidizing media. Among the various chloride-containing media with high temperature and high concentration, the crevice corrosion resistance of Gr7 alloy is the best. Gr7 also has various properties similar to the various grades of industrial pure titanium, so the alloy is widely used in the chemical industry, especially in the petrochemical sector. Since the addition of Pd increases the cost of titanium, Gr7 is selected when industrial pure titanium cannot meet the requirements of use. The main products of Gr7 alloy are plates, bars, pipes, forgings and wires.

Gr7 titanium alloy chemical composition (mass fraction/%)

Gr7 titanium alloy product specifications and supply status

Thermal performance: melting temperature range1665℃±5℃.

Thermal conductivity of Gr7 titanium alloy

Specific heat capacity of industrial pure titanium

The influence of palladium on the corrosion resistance of titanium

When the amount of Pa added to titanium reaches 0.1%-0.2%, the corrosion rate of titanium in sulfuric acid and hydrochloric acid is significantly reduced, and the content of Pa is further increased, and the corrosion rate of the alloy is almost unchanged. When the Pd content is less than 0.05%, the corrosion rate increases instead. When the acid concentration is low, the titanium-palladium alloy containing 0.13% (mass fraction) Pa has satisfactory corrosion resistance; but when the acid concentration is high, Ti-0.2Pa has better corrosion resistance, so T -0.2Pa is more suitable.

Corrosion resistance of Gr7 titanium alloy in chloride

The crevice corrosion resistance of Gr7 titanium alloy is better than pure titanium. Gr7 titanium alloy still has the ability to resist crevice corrosion at higher temperatures. For example, crevice corrosion occurs when pure titanium is used in 3% NaCi to 170 ℃, while crevice corrosion does not occur when the use temperature of Gr7 titanium alloy reaches 250 ℃. corrosion.

Effect of Inhibitor on Corrosion Resistance of Gr7 Titanium Alloy

Like pure titanium, Gr7 titanium alloy can improve its corrosion resistance in reducing media through corrosion inhibitors, and the required corrosion inhibitor concentration is lower than pure titanium.

Application examples

Gr7 titanium alloy is mainly used in the environment of dilute hydrochloric acid, dilute sulfuric acid, and dilute phosphoric acid. It is also widely used in titanium equipment to prevent crevice corrosion. For example, the tubular heat exchanger made of Gr7 titanium alloy used in the environment of dilute hydrochloric acid, sulfuric acid, and phosphoric acid is used as a part of spinneret in the textile industry, and a large number of titanium equipment flange lining rings are manufactured in the acetaldehyde device. As with diamond gaskets, Gr7 is also used in other devices to manufacture flanges and joints with gaps in parts. In addition, the alloy is also used as a structural material for C2H2C12.

①Gr7 manufacturing equipment is also used in the production of nitric acid. Gr7 titanium alloy is also suitable for environments where oxidizing and reducing conditions alternate. When this alloy is used for the sealing surface, 0.2 mm surfacing can be welded on the sealing surface. For example, using Gr7 titanium alloy in a 27%NH4C1+6.4%NaC1 solution at 135 ℃, this method can effectively prevent the occurrence of cracks in the titanium equipment corrosion.

② Acetaldehyde is widely used in the synthesis of basic chemical products such as acetic acid, butanol and quaternary alcohol. Acetaldehyde is produced by direct oxidation of ethylene, using dilute hydrochloric acid solution of palladium chloride and copper chloride as a catalyst to directly oxidize ethylene to acetaldehyde through air or oxygen. During the oxidation process, the reaction temperature is 100-150 ℃, the pressure is several or tens of atmospheres, and the pH value of the solution is 1.2-1.5 (strongly acidic), that is, the reaction is carried out under high temperature, high pressure, and strong acid environment, resulting in production equipment (Oxidation tower, rectification tower, pipes, pumps, valves), etc. have all suffered severe corrosion. Titanium has good corrosion resistance due to the corrosion inhibition effect of Cu2+ and O2 in the medium, and is suitable for making acetaldehyde production equipment.

As early as 1963, titanium equipment was used in the production of acetaldehyde, including complete sets of equipment such as titanium reactor linings, heat exchangers, pipes, pumps and valves. The size of the titanium container reached φ3>9.6 m, making it the largest titanium device at that time. A complete set of equipment for the production of titanium acetaldehyde has become a finalized design. A 60,000-ton/year acetaldehyde plant requires 11 sets of titanium equipment with a total weight of 20t.

Some solvent plants, synthetic pharmaceutical plants, and petrochemical plants in my country have successfully used titanium equipment related to acetaldehyde production, including oxidation towers, heat exchangers, catalyst regenerators, and acetaldehyde liquid coolers. Titanium equipment is widely used in acetaldehyde production equipment imported from abroad in my country. The main material is industrial pure titanium. Where there is severe crevice corrosion, Ti-0.3Mo-O.8Ni alloy, Ti-Pd alloy or Ti-Pd alloy plating is used.