KR19990038346A - Method of applying fusion inhibitor to prevent fusion of edge part during final annealing of oriented electrical steel sheet - Google Patents

Abstract

The present invention relates to a method for producing a grain-oriented electrical steel sheet used in iron core materials such as transformers, electric motors, generators and other electronic devices; The purpose of the present invention is to provide a method for applying a fusion inhibitor for improving adhesion of the fusion inhibitor to a steel sheet edge portion to prevent plate adhesion of the edge portion after high temperature annealing.

The present invention for achieving the above object is a low-temperature reheating and hot-rolled silicon steel slab and then cold-rolled two times, including de-carbon annealing to obtain a cold rolled plate, then recovered annealing, and then the MgO as a main component in the cold-rolled sheet In the method for producing a low-temperature reheat oriented electrical steel sheet coated with a fusion inhibitor, dried and wound up, and then finally annealed, the fusion inhibitor is MgO: 13-14% by weight and TiO ₂ : 2% or more to 3% At the time of high temperature annealing of the grain-oriented electrical steel sheet which is composed of less than and remaining water and is formed by applying the fusion preventive agent to the annealed cold rolled sheet and spraying gas to the edge of the cold rolled sheet to which the fusion inhibitor is applied. The summary relates to a method for applying a fusion inhibitor to suppress fusion of edge portions.

Description

Method of applying fusion inhibitor to prevent fusion of edge part during final annealing of oriented electrical steel sheet

The present invention relates to a method for producing a grain-oriented electrical steel sheet used in iron core materials such as transformers, electric motors, generators and other electronic devices, and more particularly, to improve the coating property of the fusion inhibitor on the edge of the steel sheet to improve the applicability of the fusion inhibitor The present invention relates to a method for applying a fusion inhibitor to prevent sticking of a part.

The grain-oriented electrical steel sheet has an aggregate structure in which the orientation of the grains is arranged in the direction of (001) in the direction of (001). This product has extremely excellent magnetic properties in the rolling direction. And it is used as iron core material of other electric equipment. The manufacturing process of the grain-oriented electrical steel sheet is made of about 2-4% of silicon and grain growth inhibitor and melts the component system containing mostly MnS or MnSe to make slab, and then reheating and hot rolling → pre-annealing → intermediate annealing The final product is completed through complex processes such as cold rolling, decarburization annealing, application of anti-deposition agent, and final finishing high temperature annealing. Among the complicated manufacturing processes, the most difficult in manufacturing is the slab reheating process, which is heat-treated at a high temperature. This slab reheating process needs to be maintained at high temperature of about 1400 ℃ for 5 hours in order to completely disperse the precipitates such as MnS and AlN used as grain growth inhibitors. At this time, on the surface of the hot slab, an oxide called pyrite (Fe ₂ SiO ₄ ), in which Si and Fe components are combined, is formed by oxidation with air, and the dioxide melts and flows down from the surface upon reheating due to its low melting point. At this time, the molten oxide is designed to flow out of the furnace partly, but most of it is accumulated in the refractory of the upper part of the furnace, so that the entire internal repair for removing the oxide is inevitable at the end of the work. Therefore, in steel mills characterized by continuous work, economic burdens such as poor workability, reduced productivity, and higher costs are incurred.

Therefore, the present inventors established a component system that is subjected to hot rolling by heat treatment at a reheating temperature of 1250-1300 ° C., which is the same as the processing conditions of general steel, and a new manufacturing method that can be operated without additional equipment supplement or new installation in the existing manufacturing process. Therefore, the Republic of Korea Patent Application No. 93-23751, additional technical elements have been proposed in the Republic of Korea Patent Application 94-21388, 21389, 21390 and 21391. The proposed reheating method is characterized in that it is subjected to decarbonization annealing in two times of cold rolling, and after the cold rolling as described above, recovery annealing is carried out, and then an anti-glaze agent comprising MgO as a main component for preventing plate sticking during high temperature annealing. It apply | coats and performs final annealing of 1200 degreeC or more. By using the low temperature reheating method, it is possible to produce a product having excellent magnetic properties in actual production.

However, there is a problem that the sticking phenomenon of the edge portion is caused by the lack of fusion inhibitor in the edge (Edge) of the steel sheet during the final annealing performed at a high temperature. This problem causes a large amount of plate breakage during recoil work for the final insulation coating, which reduces the error rate extremely.

Thus, the present invention was devised to solve the above-mentioned conventional problems, controlling the composition of the fusion inhibitor so that the fusion inhibitor is properly maintained on the edge portion of the steel sheet, and spraying the gas to the edge portion to attach the plate of the edge portion at high temperature annealing To improve this, its purpose is.

1 is a process chart showing a coating method of an fusion inhibitor;

2 is a graph showing the relationship between the mixing ratio of the fusion inhibitor and the coating amount according to the mixing time.

In order to achieve the above object, the present invention, after reheating and hot-rolling silicon steel slab to obtain a cold rolled sheet by cold rolling two times, including de-carbon annealing, recovery annealing, and then MgO by weight% in the cold-rolled sheet : 13-14%, TiO ₂ : More than 2% and less than -3% and the fusion inhibitor composed of the remaining water is applied, the gas is sprayed on the edge of the cold-rolled plate coated with the fusion inhibitor, dried and wound up, and then It comprises a finishing annealing.

Hereinafter, the present invention will be described in detail.

Low-temperature reheat oriented electrical steel sheet is usually obtained by performing two cold rolling including decarbonization annealing. At this time, the obtained cold rolled plate is damaged during the final cold rolling oxide layer of the edge portion formed during the decarbonization annealing. As described above, when the fusion inhibitor is applied to the cold rolled plate where the oxide layer is damaged on the edge portion, the applicability of the edge portion is deteriorated, and eventually, the plate sticking phenomenon occurs at the edge portion during the final annealing of 1200 ° C. or higher to secure magnetic properties. That is, applicability is deteriorated by the oxide layer breakage of the edge portion, which is caused by the fusion inhibitor applied to the edge portion flowing into the center of the steel sheet.

As a result of the cause analysis, the present invention adjusts the mixing ratio of the fusion inhibitor, and injects gas into the edge portion to improve the applicability of the fusion inhibitor on the edge portion. First, the present invention is applied to a grain-oriented electrical steel sheet coated with a fusion inhibitor for high temperature final annealing, and is applicable to a manufacturing process of a grain-oriented electrical steel sheet produced by decarbonization annealing in the middle of two cold rolling. The grain-oriented electrical steel sheet manufactured by this manufacturing process is weight percent, Si: 2.9-3.3%, C: 0.025-0.055%, P: 0.015% or less, dissolved Al: 0.012-0.027%, N: 0.0090-0.012%, Examples include S: 0.007% or less, Mn: 0.45% or less, Cu: 0.60% or less, balance Fe and other unavoidable impurities.

The grain-oriented electrical steel sheet based on such a component system is a basic condition for lowering the reheating temperature for hot rolling. Silicon steel slab of the composition as described above can secure the magnetic properties even if the reheating temperature is usually worked at 1250 ℃ reheating temperature of ordinary carbon steel, when the reheating temperature exceeds 1340 ℃ electrical steel slab begins to melt Because of the temperature, it is reheated at 1250-1340 ° C, the most economical temperature in steel mills. The reheated slab is hot rolled, subjected to two cold rolling, including decarbonization annealing, and then recovered and annealed at a temperature of 400-600 ° C.

The fusion inhibitor is sprayed and deposited on the steel sheet recovered and annealed as described above in a conventional manner to apply the same. An example of the coating method is shown in FIG. That is, as shown in FIG. 1, the fusion inhibitor is sprayed on the upper portion of the annealed cold rolled sheet 1 with the nozzle 2, and the lower portion of the fusion inhibitor 3 located at the lower portion of the annealed cold rolled sheet 1 is sprayed. Coating is performed using a coater (4). The steel sheet to which the fusion inhibitor has been applied is dried and wound up. At this time, the anti-fusion agent used was conventionally composed of MgO: 12% by weight (hereinafter referred to as '%'), TiO _2: 1.5% and the rest of the water, the present invention is MgO: 13-14% by weight to improve the coating force , TiO ₂ : Use a fusion inhibitor composed of more than 2% and less than -3% and the remaining water. If the amount of MgO added is less than 13%, the coating force is insufficient to improve the coating force, and if it exceeds 14%, base coating is poor due to the excessive coating amount. In addition, when the amount of TiO ₂ added is less than 2%, the coating strength is also insufficient due to the improvement in coating power, and when the amount of TiO ₂ exceeds 3%, the plate adhesion is improved, but the glossiness due to the excessive TiO ₂ is increased. It can be bad. The composition of this anti-fusion agent was limited to the amount as a result of several executions, and the empirical formula was obtained from the amount of the data, and the following relations 1 and 2 were obtained.

[Relationship 1]

7.22 × M-4.44 × T = 85-90

[Relationship 2]

M × T = 26-35

Where M is the amount of MgO added, T is the amount of TiO ₂ added, and T is obtained by substituting an arbitrary value of MgO: 12-13% by weight in the above relation 1, and substituting the value into the formula 2 to yield If satisfied, the value obtained can be set to the value of TiO ₂ . For reference, TiO ₂ in the fusion inhibitor composition serves to prevent the denitrification of nitrogen in the steel composition in the final annealing process by forming a film of TiO _{2 on} the steel sheet.

Even if the fusion inhibitor thus formed is applied to the recovery-annealed steel sheet, the fusion inhibitor is pushed toward the center of the cold rolled sheet (although the amount thereof is reduced than before). It is necessary to reapply the fusion inhibitor again by blowing it to the edge and then dry it. The gas at this time may be used air, nitrogen gas, argon gas, etc., more preferably nitrogen gas. In the case of air, a small amount of oil can be sprayed onto the cold rolled plate, which can deteriorate the surface quality, and argon is too expensive. In this case, the gas injection direction may be injected in the edge direction from the center of the cold rolled sheet so that the fusion inhibitor flowing from the edge portion can be blown back to the edge portion. The gas injection pressure is somewhat different depending on the injection direction. That is, when the spraying direction is sprayed to the edge part while maintaining the angle of less than 90 ° to the opposite direction of the steel plate advancing direction, when sprayed at a pressure of 3-5㎏ / ㎠ to prevent the fusion preventive agent of the edge part is pushed to the center can do.

Application of the fusion inhibitor in the manner described above can prevent the pasting of the edge portion during final annealing, which will be described later. That is, after applying the fusion inhibitor as described above, dried, and wound up. The final annealing, in which the final annealing is maintained at a temperature rise rate of 700-1200 ° C. over 15 ° C./hr in a hydrogen gas atmosphere containing 10% or less nitrogen, is cracked for 10 hours at a temperature of 1150 ± 10 ° C. For example, it goes through a heat cycle to cool after.

As can be seen from the above, the present invention is characterized in that it provides a method for applying a fusion inhibitor in the method for producing a grain-oriented electrical steel sheet, and other operating conditions are one example, thereby limiting the scope of the present invention It should not be construed as.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

Si: 2.98%, C: 0.042%, P: 0.013%, dissolved Al: 0.019%, N: 0.0098%, S: 0.005%, Mn: 0.37%, Cu: 0.44% To make a slab of 200mm thickness and hot-rolled after cold reheating for 3.5 hours at a temperature of 1290 ℃ to make a hot rolled plate of 1.8-2.2mm thickness. The hot rolled sheet was then annealed at 950 ° C, pickled and cold rolled to adjust the thickness to 0.75 mm, and decarbonized annealing was carried out in a wet gas atmosphere at 25 ° C of 25% H ₂ + 75% N ₂ for 52 minutes at 840 ° C. And cold rolling at the final thickness of 0.30 mm. Subsequently, the recovery annealing was performed in a dry atmosphere at 550 ° C., and the fusion preventive agent, which was prepared as shown in Table 1 and mixed for 20 minutes, was applied to the recovery and annealing cold rolled plates, followed by nitrogen gas at 4.2 kg / cm 2 at the edge of the cold rolled plates. After spraying with pressure and drying, each was wound up into a large coil and subjected to final finishing annealing. At this time, the final finishing annealing was 100% hydrogen atmosphere, and the final product was made through a thermal cycle of cooling after cracking for 15 hours at a temperature of 1150 ° C while maintaining the temperature rising rate of 700-1200 ° C at 18 ° C / hr. . The electrical steel sheet obtained by such a process is first coated with the fusion inhibitor, and then investigated the coating amount of the fusion inhibitor immediately after drying, and after the final annealing to investigate the plate adhesion and insulation quality characteristics, the results are shown in Table 1 Shown in The coating amount was measured after cutting the central portion of the steel sheet to 7cm × 7cm size.

division Amount of MgO added to the fusion inhibitor (% by weight) Amount of adhesion (g / 49㎠) Edge plate attached Appearance quality Nitrogen injection Nitrogen fine injection Example 1 12 0.92 × × Good Example 2 13 1.02 ○ × Good Example 3 14 1.03 ○ × Good Example 4 16 1.16 ○ × Organizational exposure Example 5 20 1.67 ○ ○ Organizational exposure ○: No edge plate ×: No edge plate

As shown in Table 1, Example (1-5) is only to determine the appropriate addition amount of MgO in the composition of the fusion inhibitor in the present invention, an embodiment in which nitrogen gas is injected and 13-14% by weight of MgO added It can be seen that edge plate pasting does not occur in the case of (2-3).

Example 2

The recovery-annealed cold-rolled sheet of Example 1 was applied as shown in Table 2 and mixed for 20 minutes mixed fusion inhibitor, and then sprayed with nitrogen gas at a pressure of 4.2kg / ㎠ to the edge of the cold-rolled sheet and dried, respectively It was wound up to a large coil and subjected to final finishing annealing under the same conditions as in Example 1. The electrical steel sheet obtained by such a process is first coated with the fusion inhibitor and investigated the coating amount of the fusion inhibitor immediately after drying, and after the final annealing to investigate the plate adhesion and insulation quality characteristics, the results are shown in Table 2 Shown in

division Fusion prevention agent (wt%) Amount of adhesion (g / 49㎠) Edge plate attached Appearance quality Nitrogen injection Nitrogen fine injection Amount of MgO TiO ₂ amount Conventional Example 1 12 1.5 1.25 × × Good Conventional Example 2 12 5 1.48 × × Discoloration Inventive Example 1 13 2.0 1.40 ○ × Good Inventive Example 2 13 2.5 1.48 ○ × Good Comparative Example 1 13 3.0 1.50 ○ × usually Comparative Example 2 13 5.0 1.50 ○ × Discoloration ○: No edge plate ×: No edge plate

As shown in Table 2, in the case of the conventional example (1-2), the edge portion pasting occurred regardless of the injection of nitrogen gas, but in the case of the present invention (1-2), the fusion inhibitor is appropriately adjusted. In addition, it can be seen that the injection of nitrogen gas can prevent the edge portion sticking.

On the other hand, while applying the fusion inhibitor of the composition of the conventional example (1) and the invention example (1) to the cold-rolled sheet recovered and annealed, the amount of adhesion according to the mixing time of the fusion inhibitor is investigated, looking at the result shown in FIG. In the case of the conventional example, the adhesion amount does not change significantly with time, but in the case of the present invention, it can be seen that the adhesion amount greatly increases with time. In view of this, it can be seen that the fusion inhibitor of the present invention has excellent applicability. In addition, in the comparative example examined for the anti-fusion agent of MgO: 20% and TiO ₂ : 5.0% in FIG. 1, although the adhesion amount changes over time, the workability may be impaired by causing clogging and the like for MgO coating. It can be seen that there is an appropriate composition ratio of the fusion inhibitor.

Example 3

After applying the fusion inhibitor composed of MgO: 13%, TiO ₂ : 2% to the recovery-annealed cold-rolled sheet of Example 1, and then sprayed with nitrogen gas to the edge of the cold-rolled sheet at a pressure as shown in Table 3 and dried Each was wound up to a large coil and subjected to final finishing annealing under the same conditions as in Example 1. The electrical steel sheet obtained by such a process was first coated with the fusion inhibitor, and then investigated the coating amount of the fusion inhibitor immediately after drying, and after the final annealing to investigate the plate adhesion and insulation quality characteristics, the results are shown in Table 3 Shown in

division Nozzle pressure (㎏ / ㎠) Edge attachment amount (g / 49㎠) Adhesion amount at the center of steel plate (g / 49㎠) Whether the edge part is attached Comparative Example 3 0 1.40 1.4 × Comparative Example 4 One 1.40 × Inventive Example 3 3 1.68 ○ Inventive Example 4 4 1.92 ○ Inventive Example 5 5 1.71 ○ Comparative Example 6 6 1.22 × ○: No edge plate ×: No edge plate

As shown in Table 3, in the case of Inventive Example (3-5) having a nitrogen gas injection pressure of 3-5 kg / cm 2, edge plate adhesion did not occur.

As described above, according to the present invention, the plated portion of the steel sheet edge during the final annealing is prevented by the proper application of the fusion inhibitor, and thus the failure rate is not generated during the rewinding of the coil for the final insulation coating. There is an effect that can be improved.

Claims (4)

The silicon steel slab is reheated at low temperature, hot rolled, and then cold rolled twice, including decarbonized annealing, to obtain a cold rolled plate, then recovered and annealed. In the method for producing a low-temperature reheating oriented electrical steel sheet which is subsequently finished annealing, The fusion inhibitor is composed of MgO: 13-14% by weight, TiO _2: 2% or more and less than -3% and the remaining water; The fusion inhibitor formed as described above is applied to the annealed cold rolled sheet, and the gas is sprayed and dried on the edge of the cold rolled sheet to which the fusion inhibitor is applied. Method for applying fusion inhibitor to suppress fusion. The method of claim 1, wherein the silicon steel slab is in weight%, Si: 2.9-3.3%, C: 0.025-0.055%, P: 0.015% or less, dissolved Al: 0.008-0.027%, N: 0.0080-0.012%, S: 0.007% or less, Ni: 0.02-0.08%, Mn: 0.32% or less, Cu: 0.60% or less, balance Fe and other inevitable impurities. The method of claim 1, wherein the gas is nitrogen gas. The method of claim 1 or 3, wherein the gas is injected at a pressure of 3-5 kg / cm 2.