Nitrogen case hardening method of orientation silicon steel

Abstract

The invention discloses a nitriding method of an oriented silicon steel, which is mainly characterized in that the plasma nitriding treatment is performed in a plasma nitriding chamber; the infiltration capacity and the distribution of N elements, and the size of nitride are controlled through controlling the conditions in the plasma nitriding chamber, wherein, the N element and nitride are permeated into the oriented silicon steel; the plasma nitriding chamber satisfies the conditions that nitriding temperature ranges from 500 to 700 DEG C, the nitriding time is 10 to 30 seconds, nitriding atmosphere comprises H2 which accounts for 0 to 10 percent, NH3 which accounts for 0 to 5 percent, and N2 which accounts for the rest, the vacuum degree of the plasma nitriding chamber ranges from 1000 to 2000Pa, and the polar plate pressure is 700 to 1000V. The plasma nitriding method is adopted in the manufacture of the oriented silicon steel can lead the nitriding effect to be uniform, enhance the inhibitory capacity of an inhibitor, and increase the technologic stability.

Description

technical field [0001] The invention relates to a nitriding technology of oriented silicon steel, in particular to a plasma nitriding technology method of oriented silicon steel. Background technique [0002] Oriented silicon steel refers to a silicon steel sheet with a Gaussian texture along the rolling direction, that is, (110)[001] texture, and it has the best magnetic properties in the rolling direction. The Goss texture of grain-oriented silicon steel is formed during the secondary recrystallization process of the cold-rolled sheet, and this process is based on the suppression of the primary recrystallization of the cold-rolled sheet. Inhibition of primary recrystallization is mainly through fine precipitated phases and segregated elements in steel, so one of the key points in the manufacturing process of grain-oriented silicon steel is how to form inhibitors with suitable size and distribution. After these phases that act as inhibitors are formed, they should not fail...

AI Technical Summary

Problems solved by technology

This is because the surface quality of the steel plate has a significant impact on the effect of chemical heat treatment, and the nitrogen infiltrated by chemical heat treatment is relatively unstable.

[0012] Second, the nitriding efficiency is low

Because the nitrogen infiltrated by chemical heat treatment needs to enter the steel plate by diffusion through heat energy, the infiltrated nitrogen is mainly concentrated on the surface layer, and the infiltration speed is relatively slow

[0013] Third, during the nitriding process, the decomposition of ammonia gas on the pipeline and furnace wall reduces the nitriding efficiency of ammonia gas, and at the same time, because of the nitriding effect on the equipment, it also increases the difficulty of equipment maintenance

[0015] 1. Since the infiltrated N is highly concentrated on the interface of the material, the inhibitor is unevenly distributed along the thickness direction, so the performance of the finished product is unstable

[0016] 2. Since the N in the surface layer can easily return to the atmosphere, the N content that finally enters the steel plate matrix from the surface layer is unstable, so the product performance fluctuates greatly

[0017] 3. Since the process of N finally entering the matrix is ​​a slow heat treatment process, the formed inhibitor must have a coarser shape, generally above 50nm, and the product performance is lower than the highest level of the high-temperature process.

[0018] 4. Because the nitriding amount is highly dependent on the surface state of the steel plate, the uneven distribution of the nitriding amount on the surface will be caused by the uneven distribution of the surface oxide layer or residual oil, resulting in uneven secondary recrystallization of the finished product on the two-dimensional plane

However, this method will reduce the quality of the glass film, and the nitriding amount is not easy to control uniformly along the thickness direction of the slab, and the processing time is also very long, so the applicability is poor

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