The sheath of cartridge heater is the outermost protective layer, which not only plays a role in protecting the internal resistance wire and magnesium oxide powder but also is the key part for heat transfer between the heater and the heated medium. In common temperature ranges (50℃-200℃), many users only pay attention to the power and size of the cartridge heater, but ignore the importance of the sheath material, resulting in problems such as corrosion, deformation, scaling of the heater, and even damage to the heated medium. Actually, the sheath material of cartridge heater directly affects its corrosion resistance, high-temperature resistance, heat transfer efficiency and service life, and different common temperature ranges and heating media require different sheath materials.
At present, the common sheath materials of cartridge heater mainly include 304 stainless steel, 316L stainless steel, 310S stainless steel and Teflon. These materials have obvious differences in performance and are suitable for different temperature ranges and application scenarios. For cartridge heater, selecting the appropriate sheath material according to the working temperature and heating medium is the premise to ensure its stable operation and long service life.
304 stainless steel is the most common sheath material of cartridge heater, which is suitable for low-temperature ranges (50℃-90℃) and neutral heating media (such as ordinary water, air, and neutral chemical reagents). 304 stainless steel has good corrosion resistance, wear resistance and heat transfer performance, and its cost is relatively low, which can meet the basic heating needs of low-temperature scenarios. For example, in small water dispensers, laboratories and other scenarios where ordinary water or neutral reagents are heated, the cartridge heater with 304 stainless steel sheath can work stably for a long time. According to experience, the service life of 304 stainless steel sheath cartridge heater in low-temperature neutral media can reach more than 10000 hours. However, 304 stainless steel has poor corrosion resistance to acidic and alkaline media, and is not suitable for medium and high-temperature scenarios, because it will oxidize and deform at temperatures above 100℃ for a long time.
316L stainless steel is an upgraded version of 304 stainless steel, which adds molybdenum element, greatly improving its corrosion resistance and high-temperature resistance. It is suitable for medium-temperature ranges (100℃-120℃) and acidic, alkaline or corrosive heating media (such as acidic solutions, alkaline reagents, and industrial oil containing impurities). For example, in hydraulic systems, plastic processing equipment and other scenarios where industrial oil or corrosive reagents are heated, the cartridge heater with 316L stainless steel sheath can effectively resist the corrosion of the medium and avoid sheath damage. In addition, 316L stainless steel has good heat transfer performance, which can ensure that the heat generated by the cartridge heater is quickly transferred to the medium, avoiding local overheating. It should be noted that 316L stainless steel is not suitable for high-temperature scenarios above 200℃, because its high-temperature oxidation resistance is still insufficient.
310S stainless steel is a high-temperature resistant stainless steel material, which is suitable for high-temperature ranges (200℃) and harsh working environments (such as high-temperature air, high-temperature oil, and high-temperature chemical reaction kettles). 310S stainless steel contains high content of chromium and nickel, which has excellent high-temperature oxidation resistance and corrosion resistance, and can withstand long-term baking at 200℃ without deformation or oxidation. For example, in mold heating, high-temperature drying of electronic components and other scenarios, the cartridge heater with 310S stainless steel sheath can maintain stable performance. In addition, 310S stainless steel has good mechanical strength, which can adapt to the vibration and friction in high-temperature industrial production. However, the cost of 310S stainless steel is relatively high, and it is not necessary to use it in low and medium-temperature scenarios, which will increase the use cost.
Teflon sheath is a special material, which is suitable for low and medium-temperature ranges (50℃-120℃) and strong corrosive media (such as strong acid, strong alkali, and oxidizing reagents). Teflon has excellent corrosion resistance, almost no reaction with any corrosive medium, and has good non-stick performance, which can avoid scaling and adhesion of the medium on the surface of the cartridge heater. For example, in the chemical industry, where strong acid and strong alkali reagents are heated, the cartridge heater with Teflon sheath is the best choice. However, Teflon has poor high-temperature resistance, and will melt and deform at temperatures above 120℃, so it is not suitable for high-temperature scenarios. In addition, Teflon has poor wear resistance, and needs to avoid friction and collision during installation and use.
In conclusion, the sheath material of cartridge heater has a decisive impact on its performance and service life in common temperature ranges. 304 stainless steel is suitable for low-temperature neutral media, 316L stainless steel is suitable for medium-temperature corrosive media, 310S stainless steel is suitable for high-temperature harsh environments, and Teflon is suitable for low and medium-temperature strong corrosive media. Selecting the appropriate sheath material according to the specific working temperature and heating medium can ensure the stable operation of the cartridge heater and reduce the later maintenance cost. Different application scenarios have different requirements for sheath materials, and professional material selection guidance can help users avoid unnecessary losses.
