Iron-chromium-aluminum and nickel-chromium electrothermal alloys generally have strong oxidation resistance, but because the furnace contains various gases, such as air, carbon atmosphere, sulfur atmosphere, hydrogen, nitrogen atmosphere, etc. All have a certain impact. Although all kinds of electrothermal alloys have been subjected to anti-oxidation treatment before leaving the factory, they will cause damage to the components to a certain extent in the links of transportation, winding, and installation, which will reduce the service life. In order to prolong the service life , the customer is required to carry out pre-oxidation treatment before use. The method is to heat the installed electric heating alloy element in dry air to 100-200 degrees below the maximum allowable temperature of the alloy, keep it warm for 5-10 hours, and then The furnace can be cooled slowly.
It is understood that the diameter and thickness of the heating wire is a parameter related to the maximum operating temperature. The larger the diameter of the heating wire, the easier it is to overcome the deformation problem at high temperature and prolong its own service life. When the heating wire operates below the maximum operating temperature, the diameter shall not be less than 3mm, and the thickness of the flat strip shall not be less than 2mm. The service life of the heating wire is also largely related to the diameter and thickness of the heating wire. When the heating wire is used in a high temperature environment, a protective oxide film will be formed on the surface, and the oxide film will age after a period of time, forming a cycle of continuous generation and destruction. This process is also the process of continuous consumption of elements inside the electric furnace wire. Electric furnace wire with larger diameter and thickness has more element content and longer service life.
Classification
Electrothermal alloys: according to their chemical element content and structure, they can be divided into two categories:

One is the iron-chromium-aluminum alloy series,

The other is the nickel-chromium alloy series, which have their own advantages as electric heating materials, and are widely used.

The main purpose
Metallurgical machinery, medical treatment, chemical industry, ceramics, electronics, electrical appliances, glass and other industrial heating equipment and civil heating appliances.

Advantages and disadvantages
1. The main advantages and disadvantages of the iron-chromium-aluminum alloy series: Advantages: the iron-chromium-aluminum electric heating alloy has a high service temperature, the maximum service temperature can reach 1400 degrees, (0Cr21A16Nb, 0Cr27A17Mo2, etc.), long service life, high surface load, and good oxidation resistance , high resistivity, cheap and so on. Disadvantages: Mainly low strength at high temperature. As the temperature increases, its plasticity increases, and the components are easily deformed, and it is not easy to bend and repair.

2. The main advantages and disadvantages of nickel-chromium electric heating alloy series: Advantages: high temperature strength is higher than that of iron-chromium-aluminum, not easy to deform under high temperature use, its structure is not easy to change, good plasticity, easy to repair, high emissivity, non-magnetic, corrosion resistance Strong, long service life, etc. Disadvantages: Because it is made of rare nickel metal material, the price of this series of products is up to several times higher than that of Fe-Cr-Al, and the use temperature is lower than that of Fe-Cr-Al.

good and bad
First of all, we need to know that the heating wire reaches the red hot state, which has something to do with the organization of the heating wire. Let’s remove the hair dryer first and cut off a section of heating wire. Use an 8V 1A transformer, and the resistance of the heating wire or the heating wire of the electric blanket should not be less than 8 ohms, otherwise the transformer will burn out easily. With a 12V 0.5A transformer, the resistance of the heating wire should not be less than 12 ohms, otherwise the transformer will burn out easily. If the heating wire reaches a red-hot state, the redder the better, you should use an 8V 1A transformer, and its power is greater than that of a 12V 0.5A transformer. In this way, we can better test the advantages and disadvantages of the heating wire.

4 Attention Item Editing
1. The maximum operating temperature of the component refers to the surface temperature of the component itself in dry air, not the temperature of the furnace or the heated object. Generally, the surface temperature is about 100 degrees higher than the furnace temperature. Therefore, considering the above reasons, in the design Pay attention to the operating temperature of the components. When the operating temperature exceeds a certain limit, the oxidation of the components themselves will be accelerated and the heat resistance will be reduced. Especially the iron-chromium-aluminum electric heating alloy components are easy to deform, collapse, or even break, which shortens the service life. .

2. The maximum operating temperature of the component has a considerable relationship with the wire diameter of the component. Generally, the maximum operating temperature of the component should have a wire diameter not less than 3mm, and the thickness of the flat strip should not be less than 2mm.

3. There is a considerable relationship between the corrosive atmosphere in the furnace and the maximum operating temperature of the components, and the existence of the corrosive atmosphere often affects the operating temperature and service life of the components.

4. Due to the low high-temperature strength of iron-chromium-aluminum, the components are easily deformed at high temperatures. If the wire diameter is not selected properly or the installation is improper, the components will collapse and short-circuit due to high-temperature deformation. Therefore, it must be taken into account when designing components. its factor.

5. Due to the different chemical compositions of iron-chromium-aluminum, nickel, chromium and other series electric heating alloys, the use temperature and oxidation resistance are determined by the difference in resistivity, which is determined in the iron-chromium heat alloy material Al element of resistivity, Ni-Cr electric heating alloy material determines the resistivity of the element Ni. Under high temperature conditions, the oxide film formed on the surface of the alloy element determines the service life. Due to the long-term interval use, the internal structure of the element is constantly changing, and the oxide film formed on the surface is also aging and destroyed. The elements within its components are constantly being consumed. Such as Ni, Al, etc., thereby shortening the service life. Therefore, when selecting the wire diameter of the electric furnace wire, you should choose a standard wire or a thicker flat belt.