The pickling conditions of titanium rods and titanium alloy rods are determined by the types (characteristics) of the oxide layer and the existing reaction layer, and the types of this layer are subject to high-temperature heating processes and increased processing temperatures (for example, forging, casting, welding, etc.) )Impact. At a lower processing temperature, it may be about 600 degrees: the following high-temperature heating temperature conditions only generate a thin oxide layer. Under high-temperature conditions, it forms an oxygen-rich dispersion zone near a certain oxide layer, and it is also necessary to go through pickling Remove this oxygen-rich dispersion layer. A variety of different methods for removing scale can be selected: the mechanical method of removing the thick oxide layer and hard outer layer, the method of removing oxide scale in a molten salt bath, and the method of removing oxide scale by acid elution in acid solution
In many cases, a combination of several methods can be used. For example, a combination of a mechanical method of removing oxide scale and then pickling, or a combination of salt bath and then pickling. In the case of an oxide layer and a dispersion layer formed at a higher temperature, a special method should be used^ but when heated to 600 degrees at a high temperature: most of the oxide layer formed can be dissolved after the usual pickling Drop.
The mechanical method of removing the oxide scale usually adopts the method of sandblasting, polishing, brushing and then pickling to remove the oxide layer formed under high-temperature conditions. In any case, it is necessary to adopt measures to prevent mechanically disposed of foreign impurities from passing through the metal surface, because the subsequent thermal processing or thermal treatment process may cause cracks due to the reduction of plasticity. Corundum, emery or steel grit is usually used when disposing of forgings. When disposing of plates, shot blasting is also used to remove the oxide scale. In order to achieve the surface quality of titanium, cold rolling or fine grinding is then performed. It can be unevenly removed by salt bath or pickling to remove more than 750 degrees: the thick adhesive oxide layer formed at the temperature, and the oxide scale can be removed beyond words only by grinding. In this case, it is difficult to choose a lower grinding speed (5*10m/s). This can prevent overheating of the grinding surface because a hardened layer develops due to oxygen absorption in the overheated area.
It is necessary to corrode or polish the deoxidized surface to improve the surface quality several times. Before the disposal, the external surface should be degreased. It can be dewaxed in organic solvents to prevent stress crack corrosion as much as possible. It should not be rich in chlorides or hydrocarbons with similar effects, or in alkaline solutions rich in water. During degreasing. Titanium is stable to this medium, as long as the dirt adhered to the surface can be dissolved, but the titanium surface itself does not corrode. In order to corrode the thinner oxide layer, an acid solution can be used for corrosion. Adjust the composition of the acid solution in the pickling tank according to the desired appearance or characteristics. In most cases, it is rich in hydrofluoric acid as the basic substance, and hydrochloric acid or sulfuric acid is also used in individual cases.
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