JPH0772301B2 - Iron loss reduction method for grain-oriented silicon steel sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for advantageously reducing the iron loss of grain-oriented silicon steel sheets used for transformers and the like.

The grain-oriented silicon steel sheet is mainly used as an iron core for transformers and other electric devices, and is required to have good magnetic properties. In particular, it is important that the energy loss when used as an iron core, that is, the iron loss is low, and the demand for a grain-oriented silicon steel sheet having a particularly low iron loss is increasing more and more due to the deterioration of the energy situation in recent years.

In order to reduce iron loss, the crystallographic orientation (11
0) Various attempts have been made to achieve a higher degree of alignment by the [001] orientation, increase the electrical resistance of the steel sheet by increasing the Si content, and further reduce impurities.

However, the reduction of iron loss by these metallurgical methods has almost reached the limit due to the improvement of technology in recent years.

(Prior Art) Various methods for improving iron loss have been proposed in addition to metallurgical methods. Among these, the one currently industrialized is the iron wire reduction method by laser irradiation disclosed in JP-B-57-2252. By this method,
Although it has become possible to significantly reduce iron loss, it is inevitable that the initial cost and running cost will increase due to the high cost of the device and the short life of the laser excitation lamp. Also, the laser used is often not visible light,
Safety measures are also essential.

(Problems to be Solved by the Invention) By the way, the inventors have previously reduced the iron loss by a more advantageous means in terms of productivity, workability, safety and cost without the above-mentioned drawbacks. As a method for obtaining it, a method for reducing iron loss in grain-oriented silicon steel sheets by radiation of plasma flame is applied.
Proposed in No. 60-236271.

The present invention is a further advancement of the practicality of the above method, and a method for obtaining a stable iron loss improving effect when the iron loss reducing technology by plasma flame radiation is actually applied to a factory production line. The purpose is to propose.

(Means for Solving Problems) In Japanese Patent Application No. 60-236271, the inventors have determined the output current of the plasma flame and the relative velocity between the plasma flame and the steel plate from a nozzle having a nozzle hole diameter of 2.0 mm or less. It was disclosed that a significant reduction in iron loss can be obtained by appropriately selecting and radiating a plasma flame in a direction substantially perpendicular to the rolling direction of the steel sheet.

Therefore, as a result of further intensive experiments and studies in order to find a condition capable of stably reducing iron loss even in actual operation, the inventors have made it possible to change the distance between the nozzle tip emitting the plasma flame and the steel plate surface as much as possible. The inventors have newly found that reducing the size is effective for achieving the intended purpose, and have completed the present invention.

That is, the present invention, when continuously radiating the plasma flame to the grain-finished grain-oriented silicon steel sheet, the variation in the distance between the tip of the nozzle radiating the plasma flame and the steel sheet surface is suppressed.
This is a method of reducing the iron loss of grain-oriented silicon steel sheets by suppressing the thickness to 3 mm or less.

The present invention will be specifically described below based on the experimental results.

Plasma flame was radiated from the torch with a nozzle hole diameter of 0.05 to 2.0 mm onto the surface of grain-finished grain-oriented silicon steel sheets with a thickness of 0.23 m and 0.30 mm. Ar gas was used as the gas for generating the plasma flame, and the plasma output current, the relative velocity between the nozzle and the steel plate, and the distance between the nozzle tip and the steel plate surface were varied over a wide range. The plasma flame was radiated in a continuous linear shape in a direction substantially perpendicular to the rolling direction of the steel sheet, and the radiation interval in the rolling direction was 7.5 mm.

The effect of plasma flame radiation was investigated by measuring the iron loss W17 / 50 at a magnetic flux density of 1.7 Tesla and a frequency of 50 Hz before and after plasma flame radiation of a steel plate by a single-plate magnetometer.

From the above wide range of experimental results, it was found that by appropriately selecting the output current of the plasma flame and the relative speed of the nozzle and the steel plate, a significant reduction in iron loss can be obtained.
As a result of further consideration by the inventors, the iron loss reduction effect also depends on the distance between the nozzle tip and the steel plate surface, and when the variation from the optimum distance is too large, a sufficient iron loss reduction effect can be obtained. Newly found that there is no.

Fig. 1 shows that although the nozzle hole diameter, output current, and relative speed between the nozzle and the steel plate are different, when the distance between the nozzle tip and the steel plate surface is optimal, the iron loss reduction ΔW17 / 50 is 0.05 w / kg.
In each of the above cases, the results of examining the effect of the variation (Δl) in the distance between the nozzle tip and the steel plate surface on the iron loss reduction effect (ΔW17 / 50) are shown. Here, Δl is based on the distance at which the largest iron loss reduction effect is obtained, and is a (-) sign when the nozzle is closer to the steel plate than this reference point,
On the other hand, when moving away, it is represented by (+) sign. ΔW17 / 50
Is the difference between iron loss ΔW17 / 50 (1.7T, 50Hz iron loss) before plasma flame radiation and iron loss W17 / 50 after radiation.

The distance at which the iron loss reducing effect is maximum, that is, the reference point, varies depending on the hole diameter of the nozzle used for plasma radiation, the output current, and the relative speed between the nozzle and the steel plate, but as shown in FIG. It was also found that if the variation of the distance from the reference point is within ± 3 mm, an iron loss reduction effect of 0.02 W / kg or more can be obtained.

Generally, when plasma flame radiation is realized in a factory production line, it is unavoidable that the distance between the radiation nozzle and the steel plate surface fluctuates to some extent due to flapping of the steel plate, but in order to obtain a stable iron loss reduction effect, From the above experimental results, it is necessary to suppress this fluctuation width to 3 mm or less.

In order to suppress the fluctuation width to 3 mm or less, it is effective to radiate a plasma flame while applying either tensile stress, bending stress or a combined stress thereof in the rolling direction of the steel sheet. In addition, there is also a method in which the distance between the steel plate and the nozzle is detected by a sensor such as a laser and the signal is fed back to move the nozzle to an appropriate position to keep the distance between the steel plate and the nozzle constant.

(Operation) The reason why the iron loss is reduced by the plasma flame radiation is considered to be that the part where the plasma flame is radiated becomes magnetically hard and the magnetic domains are subdivided by it.

The grain-oriented silicon steel sheet used in this invention is Mn S, Mn Se, AlN
Hot rolled steel sheet containing Sb and Sb as an inhibitor is cold-rolled once or twice with intermediate annealing to final thickness, then decarburization annealed, and then annealed and separated with MgO as a main component. It is a steel sheet that has been subjected to finish annealing at a high temperature of about 1200 ° C after applying the agent, and has completed secondary recrystallization.

Normally, the steel sheet that has been finish-annealed is covered with a forsterite coating, but the plasma radiation in the present invention is such that the forsterite coating is not present and the forsterite coating is not present. You may perform it from the coating film which has a salt as a main component.

Further, the radiation of the plasma flame is preferably perpendicular to the rolling direction of the steel sheet, but may deviate within 45 ° with respect to that direction. Furthermore, the radial spacing in the rolling direction is 2 m
m to 30 mm is preferable, and other than that, the effect may be small, or rather may lead to deterioration of iron loss.

An inert gas such as Ar is generally used as the gas for generating the plasma flame, but other gases and mixed gases may be used. The nozzle diameter of the plasma flame radiation nozzle is preferably 2.0 mm or less.

(Example) Example 1 The iron loss of two finish-annealed grain-oriented silicon steel coils (A) and (B) having a sheet thickness of 0.23 mm was measured using a continuous iron loss measuring device.
It was measured every 10 m. After that, the coil (A) was placed on a roll with a radius of 100 mm, and while applying a tensile stress of 5 kg / mm ² in the rolling direction of the steel sheet, a plasma flame was applied to this coil at a right angle to the rolling direction of the steel sheet on the roll. It radiated linearly in various directions. At this time, the variation of the distance between the plasma flame radiation nozzle, the tip and the steel plate surface was 0.8 mm at maximum.

The nozzle diameter of the plasma torch was 0.15 mm, and the gas used was Ar. The output current of the plasma flame was 7A and the voltage was 30V. The scanning speed of the nozzle was 200 mm / s, and the radial interval in the rolling direction was 8 mm.

The coil (A) thus radiated with the plasma flame was further applied to a continuous iron loss measuring device to measure the iron loss at the same position as the position measured before the plasma flame radiating flame.

Table 1 shows the maximum value, the minimum value, and the average value of the decrease ΔW17 / 50 (w / kg) in iron flame loss due to plasma flame radiation.

On the other hand, with respect to the coil (B), a plasma flame was radiated in the same manner as the coil (A), but the roundness of the roll was poor, and the variation in the distance between the nozzle tip and the steel plate surface was 4.5 mm at maximum.
Met. ΔW17 / 50 at this time is also shown in Table 1 as a comparative example.

As shown in Table 1, when Δl _max is as large as 4.5 mm,
There was a large variation in the iron loss reduction of plasma flame radiation depending on the location, and there was a portion where the iron loss did not decrease, while Δl _max
In the case of the invention example with 0.8 mm, the iron loss was reduced by 0.09 W / kg or more at any position by applying the plasma flame radiation, and the average value was 0.14 W / kg, which was a large decrease.

Example 2 After the iron loss of two finish-annealed grain-oriented silicon steel coils (C) and (D) having a plate thickness of 0.23 mm was measured by a continuous iron loss measuring device, the steel plate was subjected to a plasma flame treatment as follows. Radiated. The radiation was done in the flat area between the two rolls,
The coil (C) uses a laser sensor and feeds back the signal to the nozzle moving device to keep the distance between the steel plate surface and the nozzle tip constant. The maximum distance variation at this time was 0.5 mm.

On the other hand, the coil (D) radiated with the nozzle fixed without using a sensor. As a result, the maximum variation in the distance between the nozzle tip and the steel plate surface was 5.3 mm.

The nozzle diameter of the plasma torch was 0.15 mm, and the gas used was Ar. The output current of the plasma flame was 7A and the voltage was 30V. The operation speed of the nozzle was 200 mm / s, and the radial interval in the rolling direction was 8 mm.

In this way, the coil (C) that radiated the plasma flame,
Further, (D) was applied to a continuous iron loss measuring device to measure the iron loss at the same position as the measuring position before the plasma flame radiation.

Table 2 shows the maximum value, minimum value and average value of the iron loss reduction ΔW17 / 50 (W / kg) due to plasma flame radiation.

As shown in Table 2, when Δl _max is as large as 5.3 mm,
Although there was a large variation in the iron loss reduction of plasma flame radiation depending on the location, there was a position where iron loss did not decrease, while Δl _max
In the case of the invention example of 0.5 mm, by applying plasma flame radiation, the iron loss was reduced by 0.07 W / kg or more at any position, and the average value was also significantly reduced to 0.12 W / kg.

(Effects of the Invention) Thus, according to the invention, the iron loss of the directional silicon plate can be stably reduced even in an actual factory production line.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of the variation (Δ1) in the distance between the tip of the plasma flame radiation nozzle and the steel plate surface on the iron loss reduction effect (ΔW17 / 50).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Toho Sugiyama, 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division (56) Reference JP-A-59-229419 (JP, A) JP-A-SHO 56-56605 (JP, A) JP-A-60-89523 (JP, A)

Claims (1)

[Claims] 1. When continuously radiating a plasma flame to a grain-finished grain-oriented silicon steel sheet, it is possible to suppress the variation in the distance between the tip of the nozzle radiating the plasma flame and the surface of the steel sheet to 3 mm or less. A characteristic iron loss reduction method for grain-oriented silicon steel sheets.