Among the electric heating products, the most used ones are metal electric heating tubes (the best ones are nickel-chromium heating wires, and the worst is iron-chromium heating wires), mainly nickel-chromium wire electric heating tubes (also divided into iron electric heating tubes). , stainless steel electric heating tube, copper electric heating tube); there is a layer of magnesium oxide (material with good insulation effect and good thermal conductivity) between the metal tube and the heating wire. According to the national standard requirements, it is generally required to withstand the high temperature of 1250V to test its electrical strength. . Among the water storage type electric water heaters, most of them also adopt such a heating method, which is a relatively mature and relatively inexpensive electric heating method, and thus is widely used. The iron electric heating tube is used on the electric water heater. Because it is easy to rust, it is rarely used. The stainless steel electric heating tube is currently used more, but it is more prone to scale than the copper metal electric heating tube, but the copper electric heating tube is relatively The cost is higher, the best of which is the copper electric heating tube, but the current application rate only accounts for 10% of the metal electric heating tube.