The quality of stainless steel mainly depends on the difference of nickel content. Nickel is a high-quality corrosion-resistant element. The perfect combination with chromium in stainless steel further consolidates the corrosion resistance and acid-base resistance. However, for low-carbon nickel steel to obtain pure austenite structure, the nickel content should reach 24%, and the corrosion resistance of steel in some media can be significantly changed only when the nickel content is 27%. Therefore, for the heating pipe, 800, 840, 316L and other materials can be selected for better corrosion and high temperature resistance. The nickel content of 800 stainless steel heating pipe is 30%, 840 pipe is 20%, and 316L stainless steel heating pipe is 10%. However, if the worse 304 pipe is used, the nickel content is only 8%.
Advantages of stainless steel heating pipe: good heat resistance, dry burning resistance and low cost. At present, there are many kinds of stainless steel heating pipes, and the price difference of various materials is large. Similarly, stainless steel materials have great differences in quality and performance. Therefore, when purchasing stainless steel pipes for heating pipes, it is necessary to detect the content of specific elements, so as to eliminate shoddy products and buy low-quality products at a high price.
In addition to this intuitive method, we have the following methods to test its quality.
1. Conduct electrical strength test
Under the electrical strength of cold state and working temperature, high-quality products should be able to withstand withstand withstand voltage of 50Hz for one minute. After cutting off the current for 5mA, there is no breakdown and flashover.
2. Conduct overload test
Under the condition of full heat release, power on for 1.5 hours with 1.27 times the rated power, cut off the power for cooling, and repeat this speculation for 30 times to see if the heating tube is damaged.
3. Conduct leakage current test
Put the heating tube under the condition of full heating and energize it with a voltage of 1.15 times. If the leakage current is less than 0.5mA, it is a high-quality electric heating tube.
4. Conduct sealing test
This sealing test is mainly conducted for the shell of the electric heater. Put the heating pipe in acidified water, and then expose both ends of the heating pipe to see whether the performance requirements meet the requirements of items 1 and 3.
5. Perform the sealer test
The main performance requirements are consistent with the fourth item, but the experimental conditions are different. The experimental conditions are that the electric heating tube is placed in an environment with a temperature of 60 ℃ and a humidity of 95% for one day.
