Thermal and nuclear power plants built in coastal areas use seawater as cooling water for condensers. The function of the condenser is to condense the steam into water. Generally, condensers use copper alloy pipes, such as aluminum brass pipes. Such pipes can only be used satisfactorily in clean seas. The problem is that seawater deteriorates rapidly, and aluminum brass pipes are subject to hydrogen sulfide-containing seawater. Severe corrosion, leaks often occur. The advantages of using a titanium condenser are corrosion resistance and long life. The corrosion resistance of titanium alloy plates is manifested in two aspects: chemical resistance and corrosion resistance. The corrosion caused by chlorides and the pitting corrosion caused by marine life and sediments have strong resistance; on the other hand, it can resist the accelerated corrosion caused by high-speed seawater and local eddy currents, because the titanium surface can quickly The damaged protective oxide film is repaired. Even in the seawater with a velocity of 2m / s, the corrosion rate of Chin surface is very low. Therefore, the condenser made by milling can increase the flow rate of seawater, which is conducive to improving the cooling effect.
Titanium alloy plate has high specific strength, good fatigue performance and corrosion resistance, so it is also suitable for steam turbine blades, mainly the last few stages of the low-pressure section. Turbine blades are usually made of martensitic chromium stainless steel. The specific gravity of steel is large. For high-speed rotating steam turbines, the steel blades must withstand huge centrifugal forces. In addition, chloride phase sulfides are often incorporated in water vapor, which is caused by condenser leaks and other reasons. These media cause pitting on the surface of the blade, and crevice corrosion is formed between the root and tip of the blade or at the rib, and the corroded part will become the source of cracks. The fatigue performance of Crl3 steel is also not ideal. In the corrosive environment with saturated sodium chloride solution, especially in the case of low pH and dissolved oxygen, the fatigue strength of Crl3 steel is greatly reduced.
If titanium blades are used instead of steel blades, the situation will be greatly improved. The titanium blade is light, and the centrifugal force at the root of the blade can be reduced by 40% at the same speed. In addition, the corrosion resistance of titanium blades to salty steam is much better than that of steel, and the fatigue performance of Chinganjin is also higher than that of stainless steel. In air, the fatigue strength of Ti-6A1-4Y alloy is about 30% higher than that of Cr13 steel, and the fatigue strength of Crl3 steel in sodium chloride solution is also reduced by 2 / 3-4 / 5, compared with that, The fatigue properties of titanium alloys are not affected. Therefore, considering the pros and cons of fatigue performance under corrosive conditions, the most important factor is to replace steel with titanium.
Titanium alloy plate can also be used as a generator retaining ring. In the entire turbine generator system, the guard ring is an important component. Large-scale generators require the guard ring to have high strength, good fracture resistance, insensitivity to stress corrosion cracking in aqueous media, and non-magnetic. The current guard ring is made of austenitic Fe-Mn-Cr alloy, which has a strong tendency to stress corrosion cracking, and there is also a problem in achieving high strength reliability. In contrast, the specific strength of the titanium alloy plate retaining ring can easily meet the design requirements, and it is non-magnetic and insensitive to stress corrosion, so it is suitable to use titanium to make the retaining ring.