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Vacuum heat treatment of electrical pure iron

Electrical pure iron, also known as industrial pure iron, is a high-quality steel with iron content above 99.5%. It is a low carbon, low sulfur and low phosphorus iron.

Industrial pure iron is mainly used for electromagnetic relay, pure iron for iron core, soft magnetic pure iron, pure iron for magnetic particle clutch, pure iron for electronic lock, electric pure iron for automobile piston, pure iron strip for magnetic shielding, aviation instruments and meters, military pure iron, pure iron plate for galvanized pot, pure iron sheet for electronic components, solenoid valve, pure iron for magnetic separator, hairless pure iron, pure iron for electronic tube, and easy turning electric pure iron.

There are two common specifications:

One is used as deep drawing material, which can be stamped into extremely complex shapes;

The other is used as electromagnetic material, which has high inductance and low diamagnetism, and is widely used in electronic and electrical products, electrical components, magnetic materials, amorphous products, relays, sensors, automobile brakes, textile machines, electric meter solenoid valves and other products.

At present, there are two methods to smelt electric pure iron in China: ordinary furnace and vacuum furnace. Because of the high carbon content of electrical pure iron smelted in ordinary furnaces, even if the parts are vacuum heat treated, its magnetic properties are difficult to meet the requirements of technical indicators. However, due to the low carbon content of the electrical pure iron smelted in the vacuum furnace, the magnetic properties of the parts after vacuum heat treatment are far superior to the requirements of the technical indicators. Even if the parts are processed with raw materials in the supply state (annealing), some items of their magnetic properties can also meet the requirements of the technical indicators. Therefore, it creates favorable conditions for the design and processing of electromagnetic parts.

With the improvement of electric pure iron smelting technology, its carbon content has decreased significantly, so the magnetic properties of materials in different states have been greatly improved. Since the electrical pure iron smelted in vacuum furnace has been selected to replace the electrical pure iron smelted in ordinary furnace, over the years, there has been no phenomenon that the processing of parts has been affected by the unqualified magnetic properties of raw materials. Moreover, the magnetic properties of parts have also been greatly improved, especially the improvement of coercive force and permeability.

As the carbon content of electrical pure iron smelted in vacuum furnace is low, the hardness of the material is also reduced accordingly, so it is vulnerable to mechanical processing. Therefore, proper cutting amount shall be selected during mechanical processing. In the case of a certain carbon content, mechanical processing has a great impact on the electrical pure ferromagnetic properties. Mechanical processing stress can reduce the magnetic permeability of materials and increase the coercive force. In order to eliminate the adverse effects of machining stress on the magnetic properties of parts and keep the magnetic properties of parts in the best state, the parts are generally subject to vacuum annealing.

There are three kinds of heat treatment methods for electrical pure iron: 1 Artificial aging. 2High temperature purification annealing. 3Stress relief annealing.

Cold working causes various crystal defects (dislocations, stacking faults, etc.) in pure iron, and causes internal stress, which increases the difficulty of domain wall movement and Hc, μ The value of m decreases. In order to eliminate these adverse effects, stress relief annealing or recrystallization annealing can be carried out. The annealing temperature is high and the grain is coarse, which is favorable for magnetic properties. Therefore, the maximum temperature without phase transformation is generally adopted for stress relief annealing to avoid grain refinement when phase transformation occurs during cooling. Therefore, the recrystallization annealing process commonly used to eliminate cold working stress of pure iron is: charging below 600 ℃, heating up to 800 ℃ in the furnace, slowly heating up to 830~890 ℃, holding for 4h, then cooling down to 700 ℃ at a cooling rate of no more than 50 ℃/h, and finally discharging from the furnace when cooling down to 500 ℃. The whole annealing is carried out in hydrogen or vacuum. The annealing process curve is shown in the figure.

Heat treatment equipment selection: The RVA series vacuum heat treatment furnace produced by SIMUWU is a high-quality product for vacuum heat treatment process of industrial pure iron. Good temperature control accuracy and uniformity ensure the effective implementation of vacuum heat treatment process. SIMUWU focuses on the manufacturing of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum gas quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.