Heating wire

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 and nitrogen atmosphere, etc., these gases are used under high temperature conditions. It has certain influence. Although all kinds of electrothermal alloys are treated with anti-oxidation treatment before leaving the factory, they will cause damage to components to some extent in transportation, winding, installation, etc., and reduce the service life to prolong the service life. The customer is required to carry out pre-oxidation treatment before use. The method is to heat the installed electrothermal alloy component in the dry air to a temperature below 100-200 degrees of the maximum allowable temperature of the alloy, and keep it for 5-10 hours. The furnace can be cooled slowly.

Diameter thickness

The diameter of the heating wire is the parameter related to the highest 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 service life. The heating wire shall run below the maximum service temperature and shall maintain a diameter of not less than 3 mm and a thickness of not less than 2 mm. 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 is formed on the surface, and the oxide film will age after a certain period of time, forming a cyclic process of continuous generation and destruction, and this process is a process of continuously consuming internal elements of the electric furnace wire. The electric furnace wire with larger diameter and thickness has more elements and a longer service life.

classification

Electrothermal alloys can be divided into two categories according to their chemical elements and their structure:

One is the iron-chromium-aluminum alloy series, and the other is the nickel-chromium alloy series, which have various advantages as electrothermal materials, and are widely used.

The main purpose

Industrial heating equipment and civil heating equipment for metallurgical machinery, medical, chemical, ceramics, electronics, electrical appliances, glass, etc.

Advantages and disadvantages

1. Main advantages and disadvantages of iron-chromium-aluminum alloy series: Advantages: Iron-chromium-aluminum electrothermal alloy has high use temperature, the highest temperature can reach 1400 degrees, (0Cr21A16Nb, 0Cr27A17Mo2, etc.), long service life, high surface load and good oxidation resistance. , high resistivity, low price, etc. The lack of advertising points: mainly low temperature strength, plasticity increases with the use of temperature, components are easily deformed, not easy to bend and repair.

2, nickel-chromium electrothermal alloy series main advantages and disadvantages: advantages: high temperature strength is higher than iron chrome aluminum, high temperature is not easy to deform, its structure is not easy to change, plasticity is good, easy to repair, its high emissivity, non-magnetic, corrosion resistance Strong, long service life, etc. Disadvantages: Due to the use of the scarce nickel metal material, the price of this series of products is up to several times higher than that of iron-chromium-aluminum, and the use temperature is lower than that of iron-chromium-aluminum.

Good or bad

First, we need to know to reach the red hot heating wire heating wire which organization has a relationship. We first removed the blower and intercepted a piece of heating wire. With an 8V 1A transformer, the electric wire resistance of the heating wire or electric blanket should not be less than 8 ohms, otherwise the transformer will burn easily. With a 12V 0.5A transformer, the resistance of the heating wire should not be less than 12 ohms, otherwise the transformer will easily burn out. If the heating wire is red hot, the better the red, the 8V 1A transformer should be used, which is larger than the 12V 0.5A transformer. In this way, we can better test the advantages and disadvantages of the heating wire.

Attention item

1. The maximum use temperature of the component refers to the surface temperature of the component itself in dry air, not the temperature of the furnace or the object to be heated. Under normal circumstances, the surface temperature is about 100 degrees higher than the furnace temperature. Therefore, considering the above reasons, the design element should pay attention to the use temperature, when the temperature exceeds a certain limit, the amount of the element itself to accelerate oxidation, heat resistance is reduced, in particular iron chrome aluminum alloy heating element, deformation, collapse or even rupture, shortened service life .

2, the highest temperature of the element member has a considerable diameter relationship, in general, the highest temperature element should not be less than its diameter 3mm, sling thickness not less than 2mm.

3, furnace elements and corrosive atmosphere maximum temperature relationship is also considerable, and often affected by the presence of a corrosive environment temperature and the element lifetime.

4, since the high-temperature strength of low iron chrome aluminum, so deformable element, such as improper mounting or the improper selection of wire diameter at a high temperature, are deformed due to high temperature caused by the collapse element, short circuit, etc., so that the element design must take into account the Its factors.

5, iron chrome aluminum, nickel, chromium and other series of electrothermal alloys due to their different chemical composition, their use temperature, oxidation resistance to determine the length of use temperature with different azoles of resistivity, determined in the iron chromium hot alloy material The AL element of the resistivity, the composition of the nickel-chromium electrothermal alloy material that determines the resistivity is the Ni element. In the high temperature state, the oxide film formed on the surface of the alloy component determines the service life. Due to the use of the long-term interval, the internal structure of the component is constantly changing, and the oxide film formed on the surface is also aging and destroyed. The internal elements of its components are constantly being consumed. Such as Ni, AL, etc., thus shortening the service life, therefore, the choice of wire or thicker flat belt should be used when selecting the wire diameter of the electric furnace.

Technical processing

Iron chrome aluminum or tungsten, molybdenum electrothermal alloy wire is closely wound and can be used vertically. The surface is insulated, anti-oxidation and self-diffusion treatment. The surface has good insulation and oxidation resistance, and it is hardly oxidized at the rated power temperature and is free from nickel-chromium oxide contamination.

The service life of this product is several times to several tens of times higher than that of ordinary electric heating wire. The main performances are as follows:

1) Insulation resistance: universal meter detection is infinite

2) Surface insulation and oxidation layer thickness: 3-12 microns

3) Single layer withstand voltage of insulation is greater than AC 50V without breakdown

4) Operating voltage: 6-380V

5) Thermal shock performance: can withstand 500-6000 thermal and thermal shocks without deformation