KR810001851B1 - Production of grain oriented silicon steels intended for electromagnetic application - Google Patents

Abstract

Si steel strip is manufd. from a slab contg. (by wt.) 2-4% Si, 0.05-0.1% Mn, 0.02-0.035% S, 0.02-0.06% C, 0.002-0.01% N2, 0.01-0.1% V, and trace impurities. The slab is hot rolled into strip, then cold rolled with final redn. >= 70%, followed by decarburising esp. a continuous decarburising anneal at 900-1050≰C. The hot rolled strip is pref. annealed at 900-1100≰C, then selectively cooled at 5-16≰C/ second to 750-900≰C. Alternatively, the hot rolled steel may be cold rolled in two passes with an intermediate anneal similar to that described above.

Description

Method for manufacturing grain-oriented electromagnetic silicon steel strip

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for producing silicon steel strips oriented for electromagnetic particles, and more particularly to steel having a (110) [001] structure as a cubic lattice structure, ie, Miller indices. These steels are mainly used as iron core materials for transformers and other electrical machinery, and they must have high magnetic permeability as well as low core loss at a given flux density.

In order to optimize such magnetic properties, a method is adopted in which each particle in the polycrystalline lattice of steel is arranged in a straight line with the crystal direction so that the best magnetism is arranged on the lattice plane and parallel to the rolling direction. Just do it.

One conventional method for producing grain-oriented steel sheets is based on the fact that the finely dispersed precipitates of manganese sulfide finally form a well-oriented structure with the particles. The present invention facilitates dispersion by using vanadium nitride precipitates in dispersing such manganese sulfide, and the magnetic properties of strips prepared from starting materials containing these two precipitates in various processes in the manufacturing process. It is conceived that it can increase by selecting appropriately.

In one aspect of the present invention, the method for producing silicon steel strips for electromagnetics is 2-4% silicon by weight, 0.05-0.1% manganese, 0.02-0.035% sulfur, 0.02-0.06% carbon, nitrogen 0.002- After hot-rolling a plate containing 0.01% and 0.01-0.1% vanadium, it is cold rolled to at least 70% of the thickness and decarburized at 900-1050 ° C.

Preferably, cold rolling is a single process, in which case the heated band should be optionally annealed at 900-1100 ° C. to selectively cool. As another method, a two-stage low temperature rolling method using an intermediate annealing may be used. In this case, the intermediate annealing is a process of selectively cooling in the same manner as the annealing of the heated band, but the annealing of the heating band may be omitted as necessary. Secondary cold rolling should be at least 70%.

In case of cold rolling, the plate should be reheated properly to about 1.90-3.00mm as much as possible. It should be 2.30-2.85mm. By doing so, the cold rolling accuracy is very good when rolling about 0.28-0.35mm, which is required in terms of product value. Done. Cut the edges of the heating band after this process and continue annealing at 900-1100 ° C. for 2-5 minutes. The temperature at this time is preferably 950-1075 ° C.

It is well known that the choice of cooling rate after annealing is important for the case of vanadium bearing steel in finally obtaining the best magnetism. After cooling the temperature at 750-900 ° C to 5-16 ° C / sec, cooling to room temperature more rapidly by natural air cooling, forced air or gas spray cooling, or water spray cooling, etc., gives proper results.

This process is a two-stage cooling process, which is required to deposit vanadium nitride in a specific form after annealing the heating band, and prevents the formation of coarse particles generated during the long-term cooling process up to room temperature. It is not intended to.

After the heating band annealing, the steel may be pickled and cold rolled to the final thickness, which may or may not be subjected to low temperature aging. The final cold rolled thickness thus obtained is 70-95%.

After cold rolling, the steel is decarburized in a continuous annealing process at 900-1050 ° C., preferably 950-1050 ° C., for about 4 minutes in a moist hydrogen atmosphere or a nitrogen / hydrogen wet mixed gas atmosphere. This decarburization temperature range is clearly higher than the temperature range of 800-850 ° C., which has been used in steel fabrication prior to grain orientation, and also appears in the case of complete secondary recrystallization of this material in the case of relatively low temperature decarburization conventionally employed. It has proved to be able to solve various difficulties. The strip after the decarburization process is subjected to magnesia coating and box annealing at a temperature of 1100 ° C. or more for about 24 hours.

The present invention will be described in detail according to the embodiment.

Example 1

The steel melt obtained from the smelting process was inoculated with vanadium in a ladle, so that 0.022% carbon, 0.026% sulfur, 0.0056% nitrogen, 0.092% manganese, 2.86% silicon and 0.062% vanadium and iron as residual components. And an impurity composition. Reheating the plate made of ingot having such composition at 1400 ℃ and rolling the heating band at 960 ℃ of the final processing temperature to make the thickness 2.85mm becomes a band in which the precipitate of manganese sulfide and vanadium nitride, a grain growth inhibitor, is dispersed. It is annealed at 1050 ° C. for 5 minutes and then cooled to 850 ° C. at an average rate of 10.5 ° C. per second to oil quenching to room temperature. This process was cold rolled to a thickness of 0.35 mm. In this process, aging annealing was performed at 200 ° C. for 5 minutes in a rolling apparatus at six equal intervals.

After cold rolling the strip is decarburized for 4 minutes at 1050 ° C. in hydrogen with a dew point of + 60 ° C. followed by coating and box annealing by known methods. The steel produced by this method had an iron core loss of 1.30 w / kg at 1.7T and 50 Hz and a permeability of 1.92T at H = 1.0 kA / m.

Example 2

The heating band prepared in the same manner as in Example 1 was annealed at 1000 ° C. for 5 minutes, cooled to 850 ° C. at a rate of 7.7 ° C./sec, and then quenched with oil. After aging similar to Example 1, it was cold rolled to 0.35 mm, decarburized at 1050 ° C. for 5 minutes, and the strip was coated and box annealed by a known method.

The steel thus produced had an iron core loss of 1.34 w / kg at 1.7 T and 50 Hz and a permeability of 1.89 T at H = 1.0 KA / m.

Example 3

The heating band prepared according to the method described above is annealed at 1050 ° C. for 5 minutes, cooled to 750 ° C. at a rate of 11.0 ° C./sec, and then cold rolled to 0.35 mm through the aging process as described above. After decarburizing at 1050 ° C. for 5 minutes, the strip is coated and box annealed by known methods. The iron core loss of the steel thus produced was 1.39 w / kg at 1.7 T and 50 Hz, and the permeability was 1.89 T at H = 1.0 KA / m.

Example 4

The heating band prepared according to Example 1 was annealed at 1000 ° C. for 2 minutes, cooled to 900 ° C. using air at a rate of 15 ° C./sec, and then quenched with oil at a temperature of about room temperature. Cold rolling to 0.35 mm while aging treatment, decarburized at 1000 ℃ for 4 minutes, and then box annealed at 1200 ℃ 24 hours. The iron core loss of the steel thus produced was 1.32 w / kg at 1.7 T and 50 Hz, and the permeability was 1.89 T at H = 1.0 KA / m.

Example 5

Iron core loss of steel quenched at room temperature after cooling the heating band manufactured as in Example 4 to 900 ° C at a rate of 6 ° C / sec without annealing at an initial temperature of 1.34w at 1.7T and 50Hz / kg and permeability was 1.89T at H = 1.0KA / m.

Example 6

The heating band prepared as in Example 1 was annealed at 1050 ° C. for 2 minutes, cooled to 900 ° C. at a rate of 8 ° C./sec, and then quenched at room temperature. After quenching, cold rolling was carried out while aging to 0.35 mm, decarburized at 1050 ° C. for 4 minutes, and box annealing at 1200 ° C. for 24 hours. The iron core loss of the steel thus produced was 1.37 w / kg at 1.7 T and 50 Hz, and the permeability was 1.93 T at H = 1.0 KA / m.

Example 7

The heating belt prepared according to Example 1 was annealed at 1025 ° C. for 2 minutes, cooled to 900 ° C. at a rate of 16 ° C./sec, and then quenched to room temperature. The quenched heating belt is aged and cold rolled, decarburized at 1050 ° C for 4 minutes, and then box annealed at 1200 ° C for 24 hours. The iron core loss of the steel thus prepared was 1.37 w / kg at 1.7 T and 50 Hz, and the permeability was 1.88 T at H = 1.0 KA / m.

Example 8

The heating band processed according to Example 7 was decarburized at 1000 ° C. for 4 minutes. The iron core loss of this steel was 1.34w / kg at 1.7T and 50Hz and 1.89T at H = 1.0KA / m.

Example 9

The steel treated as in Example 1 was annealed at 950 ° C. for 5 minutes, cooled to 850 ° C. at a rate of 5 ° C./sec, and then cooled to room temperature with forced air. The specimens were cold rolled without aging and decarburized at 1050 ° C for 4 minutes and then box annealed at 1200 ° C for 24 hours.

The iron core loss of the steel thus produced was 1.36 w / kg at 1.7 T and 50 Hz and the permeability was 1.91 T.

Claims (1)

As described above in the text, the composition of the plate by weight percent of silicon 2-4%, manganese 0.05-0.1%, sulfur 0.02-0.035%, carbon 0.02-0.06%, nitrogen 0.002-0.01%, vanadium 0.01-0.1% and impurities A method for producing a grain-oriented electromagnetic silicon steel strip, characterized in that the sheet is hot rolled and finally cold rolled to at least 70% and then decarburized in a temperature range of 900-1050 ° C.