As a kind of alpha titanium alloy, the technical and mechanical properties of GR7 alloy are similar to the industrial pure titanium. When the amount of 0.1-0.2% Pd added into titanium, the corrosion rate of titanium in sulfuric acid and hydrochloric acid is sharply reduced. The corrosion rate of the alloy is almost unchanged when the content of Pd is further increased. However, the corrosion rate increases when the content of Pd is lower than 0.05%. At low acid concentration, titanium palladium alloy which contains 0.13% Pd had satisfactory corrosion resistance. On the contrary, ti-0.2 Pd was more suitable due to the reason that it had better corrosion resistance in high acid concentration.

The analysis data shows that the corrosion resistance of ti-0.2pd in reducing medium is obviously better than the industrial pure titanium, which the welding area is the same as the base material. The stabilizing potential of Ti - 0.2 - Pd is significant positive moving in charge of hydrochloric acid with corrosion speed could be dropped by 10 times compared with the ones in the hydrochloric without air. But the passivation performance of Ti - 0.2 - Pd obviously declined in the acid solution of filling with argon or nitrogen when constantly changing new corrosion solution or sample solution volume is increasing per unit area. Therefore it should be avoided of using Ti - 0.2 Pd under the condition of anaerobic or completely oxidant. GR7 titanium alloy corrosion resistance in oxidizing medium is improved by adding a small amount of palladium, especially the crevice corrosion resistance. Therefore, it is widely used in the corrosion media of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid and chloride.

The technical characteristics of titanium alloy precision forging

The production of titanium and titanium alloy bar with precision forging machine has the characteristics of high production efficiency, precise size, better surface quality and high material utilization. The process characteristics of precision forging are as followings:

(1) The method of hammer head forging frequency is high, which could be up to hundreds or even thousands of times per minute. This kind of loading method reduces the friction coefficient between the metal and the tool.

(2) During hammer head forging, each stroke has small stroke, small deformation amount and contact area with metal, which can greatly reduce deformation force and deformation work, as well as reducing the tonnage of equipment and improving the service life of tools.

(3) The stroke of the hammer head can be free adjustment. The shape of the hammer head can adapt to a larger process size, so it is not necessary to replace the hammer head in producing forging rods of a certain size.

(4)The stroke of the four hammers remains unchanged when forging in order to reach high size accuracy.

(5)The feed quantity can be adjusted according to the temperature change of the billet in the deformation process to achieve isothermal forging.

(6) The metal is compressed according to the four hammers with curved grooves so that the metal can only extend axially, Therefore there is no circumferential edges and cracks during forging, which is different from the compression of flat anvil in free forging.

(7) The forging will produce a high three-way compression stress, which can improve the plasticity of the metal by 3 times, and obtain a high forging ratio (pure titanium 6/1, alloy 4/1).

(8) A high thermal effect will be generated in the billet when the feeding speed and the amount of trace pressure are very large, which will increase the deformation temperature. For example, the structure of forging billet could be deactivated when the temperature rise of TC11 alloy reached 90℃.

Corrosion resistance ability of GR7 titanium rod in a variety of corrosive environments

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