Stainless steel pipe Performance of 321 stainless steel heating tube heater
The advantages of 321 stainless steel heating pipe are: good heat resistance, dry burning resistance, mature technology and low cost. At present, there are many kinds of 321 stainless steel heating pipes used by the manufacturers of instant electric water heaters, and the price difference of various tubes is large. The same is 321 stainless steel electric heating pipe, its quality performance difference is very big. The difference between the material quality of 321 stainless steel electric heating pipe is mainly the difference of nickel content. Nickel is an excellent corrosion-resistant material. The corrosion resistance and process performance of 321 stainless steel can be improved by combining with chromium in 321 stainless steel. However, in order to obtain pure austenite structure of low carbon nickel steel, the nickel content should reach 24%, and only when the nickel content is 27%, the corrosion resistance of the steel in some media will be significantly changed. Therefore, from the material point of view eight hundred The results show that, 840, 316L are relatively good corrosion and high temperature resistant 321 stainless steel electric heating pipe, the nickel content of 800321 stainless steel pipe reaches 30%, and that of 840 pipe reaches 20%, but if the nickel content is lower three hundred and four The nickel content of 321 stainless steel tube is only 8%. Therefore, the product of 321 stainless steel heating pipe with high nickel content and high temperature and corrosion resistance is also very advantageous.
321 stainless steel heating tube heating body performance is good or bad, material performance is only one aspect, product performance and water quality have a very big relationship. The instantaneous electric water heater is heated in the flowing state of water. When the electric water heater works, the temperature of the outer pipe of the heating pipe can reach 90 ¡æ ~ 120 ¡æ. Calcium and magnesium ions in water will start to precipitate at 60 ¡æ and form scale. Therefore, the 321 stainless steel electric heating body in the thermal electric water heater also faces the problem of scaling, but the scaling condition can be greatly improved compared with the traditional water storage water heater. The possibility and speed of scale formation are as follows
30% ¡« 50% of the electric water heater with storage. China has a vast area and complicated water quality. Some areas directly use the underground water source which has not been treated too much. There are many calcium ions and magnesium ions in the water. It is easy to cause the surface scaling of 321 stainless steel heating body, which makes the heat transfer performance of the heating body worse and the surface temperature of the outer tube higher. At the same time, this kind of scaling is loose. The performance of the electric heating tube is still in contact with water, but the heat transfer is relatively poor. The upper surface of the outer tube and the inner surface of the scale will vaporize and form cavitation. That is to say, when heated, water will form water vapor and then become a bubble. When the bubble reaches a certain size, it will break and produce vacuum at the moment of rupture. There is a positive pressure on the surface of the heating tube when bubbles are generated, and a negative pressure is generated when the bubbles break. The surface of the heating tube is constantly affected by the change of the stress, and a cavitation phenomenon is slowly produced, which causes damage to the electric heating body of 321 stainless steel. In addition, if there are too many chloride ions and sulfate ions in the water, the surface of 321 stainless steel electric heating pipe will be pitted. For example, groundwater is used in Central Plains and Xinjiang areas of China, which contains more chloride ions and acid ions. In these areas, the holes of 321 stainless steel heating body are caused by pitting corrosion, causing water to enter into the electric heating pipe, resulting in leakage and poor insulation, Cause the protection function inside the machine to fail to work and need to be repaired. It can be said that more than 60% of 321 stainless steel electric heater is damaged due to scaling or pitting corrosion. If the market sales of enterprises can reach a certain scale, then different heating pipes can be selected according to the water quality in different areas. For example, using 800321 stainless steel heating pipe to these areas with poor water quality can not only reduce the repair rate of products, but also improve the performance of products, and the cost of mass production will not increase much. But if the sales can not reach a certain scale, the cost of using 800321 stainless steel pipe will be very high.