KR960003174B1 - Method for preparation of non-oriented electrical steel sheet having high flux-density - Google Patents

Abstract

reheating steel slab at 1050-1270 deg.C and hot rolling it at 850-930 deg.C; annealing the hot rolled steel plate at 800-1100 deg.C and acid-cleaning; and cold rolling it; and annealing the cold rolled steel plate at 800-1100 deg.C. The slab comprises (in wt.) C of below 0.02%, Si of below 3.5%, Mn of below 0.5%, S of below 0.01%, N of 0.008%, Cu of below 0.05-0.50% Al of below 0.5%, P of 0.05-0.15% and balance Fe with inevitable impurities.

Description

Manufacturing method of non-oriented electrical steel sheet having excellent iron loss and magnetic flux density

The present invention relates to a non-oriented electrical steel sheet used as iron cores of various motors and small transformers, and more particularly, to a method for manufacturing a non-oriented electrical steel sheet having excellent iron loss and magnetic flux density, which can save energy due to low iron loss and high magnetic flux density. will be.

Major magnetic properties required for non-oriented electrical steel sheet include iron loss, magnetic flux density and permeability. Among these magnetic properties, the iron loss and the magnetic flux density have a relationship in which the efficiency thereof is in conflict with the Si content. That is, when there is much Si, iron loss becomes low, but magnetic flux density becomes low, and when there is little Si, magnetic flux density becomes high but iron loss also becomes high. Therefore, for large motors that are continuously used for a long time or have a high power consumption, the Si content is increased by increasing the Si content in terms of energy saving, while the Si content is lowered for small motors or home appliances that are used for a short time. Increasing density is the key to more economical material selection.

However, while the consumption rate of electric energy continues to increase due to population growth and improved living standards, it is difficult to respond to sufficient supply measures for energy demand through expansion of power generation facilities. Therefore, steel companies can supply energy-saving electric equipment. In order to achieve high efficiency of iron core material as well as low noise and high precision, the core of electric equipment has made great efforts to develop high efficiency non-oriented electrical steel sheet with low magnetic flux loss and high magnetic flux density.

As part of this effort, in the early 80's, Nippon Steel Mill developed an advanced non-oriented electrical steel sheet called New Core, which was manufactured by lowering the S component, adding 0.1% Sn and 1.0% Mn. will be.

However, the steel sheet had excellent iron loss of 3.0 w / kg or less in magnetic properties, but the magnetic flux density was 1.69 Tesla or less, which was insufficient in efficiency. Subsequently, Nippon Steel Mill developed M43, which is manufactured in a fully process with an iron loss of 2.8 w / kg and a magnetic flux density of 1.69 Tesla, but with only a slight improvement in iron loss. It can not escape.

On the other hand, Japanese Patent Laid-Open No. 63-23262 discloses a method for lowering iron loss and increasing magnetic flux density by containing 0.02-0.20% of Sn and 0.1-1.0% of Cu by weight. However, in the method of manufacturing non-oriented electrical steel sheet containing such component elements, grain growth is suppressed by Sn, and when the hot rolling temperature is lower than 750 ° C, the magnetic flux density does not increase even though the iron loss is low. There was this.

An object of the present invention is to solve the drawbacks of the conventional methods, to provide a method for manufacturing a non-oriented electrical steel sheet having a low magnetic flux and high magnetic flux density.

The present invention for achieving the above object by weight% C: 0.02% or less, Si: 3.5% or less, Mn: 0.5% or less, S: 0.01% or less, N: 0.008% or less, Cu: 0.05-0.50%, Al: Slab composed of 0.5% or less, especially the main management element P: 0.05-0.15%, balance Fe and other unavoidable impurities, after reheating, including hot rolling, hot roll annealing, pickling, and one cold rolling or intermediate annealing The present invention relates to a method for producing a non-oriented electrical steel sheet having excellent iron loss and magnetic flux density which are subjected to final cold-rolled sheet annealing after two cold rollings.

Hereinafter, numerical limitations of the component element content and heating temperature will be described.

C is a harmful component that increases the iron loss, so it may cause self-aging, so it is preferable to set it to 0.02% or less and 0.005% or less to omit the decarburization process.

Mn is to prevent brittle fracture at the time of hot rolling and to reduce iron loss by compensating for the resistivity of steel caused by the decrease of Al content, but when it is 0.50% or more, the manufacturing cost of the product is increased to 0.5% or less.

S is contained in an appropriate amount of Mn and the like to be 0.01% or less in order to keep the heating temperature at a relatively low temperature when reheating the slab to form MnS harmless to grain growth.

N is good to lower the amount contained in the steelmaking step, but it is difficult to manage the nitrogen content level of silicon steel below 10ppm, and usually exceeds 30ppm, so it should be 0.008% or less.

Al combines with N to form AIN, and at Al content of 0.005-0.15%, it becomes harmful form of crystal growth. Therefore, in low-oriented non-oriented electrical steel sheet having Si content of 1.0-1.5% or less, Al should be 0.005% or less as possible. In the medium-oriented non-oriented electrical steel sheet having a Si content of 1.0-1.5% or more, Al content of 0.15% or more should be adjusted so that AlN precipitates in a form that is harmless to crystal growth when the slab is reheated. In addition, manufacturing costs and rising factors should be 0.50% or less.

Cu is an element that develops the texture and increases the resistivity in favor of increased corrosion resistance and magnetism. In addition, by forming a fine precipitate to precipitate S in the form of coarse Cu ₂ S to inhibit grain growth and the development of a texture that is favorable for magnetism, the magnetic properties are improved. Less than 0.05% of magnetism is poor, and more than 0.5% may cause surface cracking before hot rolling. Therefore, the range of Cu is made 0.05-0.50%.

P is a particularly important element of the present invention, and the addition of 0.05-0.15% of P in Cu-added steels results in a particularly well-developed texture of the (110) and (120) faces. If it is less than 0.05%, it is disadvantageous in forming the aggregate. If it exceeds 0.15%, cold rolling is difficult and the grain growth is damaged. It is also a major element in reducing iron loss by increasing resistivity.

The slab reheating temperature is difficult to roll when carried out at a reheating temperature of 1050 ° C. or lower, and when heated to 1270 ° C. or higher, fine CuS is formed.

Hot rolling is finished rolling at 850-930 ° C. and wound at 700-750 ° C. to develop a typical hot rolled {200} <110> texture of ferrite.

After hot-rolled sheet annealing for 3-5 minutes at 800-1100 ℃, pickling. Cold rolling is performed either once or two times cold rolling, including intermediate annealing at 800-1050 ℃.

Final cold rolled annealing is for cold rolled steel sheet 800 ℃ or more and 1100 ℃ After annealing for 10 minutes or less, the grains are grown and aggregates are developed.

Hereinafter, the present invention will be described in detail based on examples.

Example 1

The slabs composed of the component ranges as shown in Table 1 and the balance of Fe and unavoidable impurities are heated to the slab reheating temperature of Table 2 and hot rolled, followed by hot-rolling annealing at 1050 ° C. for 3 minutes in a nitrogen atmosphere, and then 0.5 mm thick. Cold rolled. The cold rolled material was annealed at 1030 ° C. for 2 minutes in a mixed gas atmosphere of hydrogen and nitrogen.

Table 2 shows the magnetic properties of the material produced by the production method of the present invention.

TABLE 1

(Unit: weight%)

When comparing the composition range of the invention steel and the composition range of the comparative steel, the composition ratio of most chemical components is almost similar, but there are many differences in the composition ratio of P. That is, P of invention steel A is 0.08 weight%, but P of comparative steel is 0.04 weight%.

TABLE 2

* B ₅₀ : Magnetic flux density value when the magnetic field strength is 5000A / m

W _15/50 : Velocity value at magnetic flux density 1.5Tesla, 50Hz

As can be seen from Table 2, the magnetic flux density was the same when the inventive steel A was reheated at 1240 ° C and 1050 ° C at different temperatures, but the magnetic flux density was the same, but it was better when reheated to 1050 ° C in iron loss. . This result is due to the formation of Cu and S when the slab reheating temperature is low to grow to an appropriate grain size (about 80㎛) to the minimum iron loss.

On the other hand, when the inventive steel A was compared with the comparative steel, the invention steel A was superior to the comparative steel in both iron loss and magnetic flux density. These results are due to the fact that the magnetic properties are improved by increasing the resistivity while improving the degree of development of the texture by the addition effect of P.

Example 2

The slab composed of component ranges as shown in Table 3 and the balance of Fe and unavoidable impurities is re-heated at 1150 ° C and 1270 ° C, hot rolled, and the hot rolled plate is annealed by hot-rolling annealing for 3 minutes in a nitrogen atmosphere of 1050 ° C, and then 0.5 mm thick. Cold rolled. The cold rolled sheet was annealed at 1030 ° C. for 2 minutes in a mixed gas atmosphere of hydrogen and nitrogen. Table 4 shows the measurement results of the magnetic properties of the materials manufactured by such a manufacturing method.

TABLE 3

(Unit: weight%)

TABLE 4

As shown in Table 4, both the iron loss and the magnetic flux density were superior to the case where the slab heating temperature was low.

These results show that Cu and S form coarse Cu ₂ S due to the addition of P and the low slab reheating temperature, and the grain size grows to the minimum value of iron loss. Because

The present invention relates to a method for manufacturing a non-oriented electrical steel sheet by adjusting the amount of P in the components of the slab and reheating temperature of 1050-1250 ℃, more economically compared to the electrical steel sheet according to the prior art The non-oriented electrical steel sheet excellent in iron loss and magnetic flux density can be manufactured.

Claims (2)

After reheating the steel slab, the hot-rolled slab is finished hot-rolled at a temperature of 850-930 ° C, the hot rolled plate is hot-annealed at a temperature of 800-1100 ° C and then pickled, and then cold rolled plate after one cold rolling In the method for producing a non-oriented electrical steel sheet comprising the step of performing a final cold-rolled sheet annealing at a temperature of 800-1100 ℃, the composition of the steel slab in weight%, C: 0.02% or less, Si: 3.5% Or less than Mn: 0.5% or less, S: 0.01% or less, N: 0.008% or less, Cu: 0.05-0.50%, Al: 0.5% or less, P: 0.05-0.15%, residual Fe and inevitable impurities; And a reheating temperature of the slab is 1050-1270 ° C., wherein the iron loss and magnetic flux density are excellent. After reheating the steel slab, hot-rolling the reheated slab at a temperature of 850-930 ° C., hot-rolling the hot rolled plate at a temperature of 800-1100 ° C. and then pickling, followed by an intermediate at a temperature of 800-1050 ° C. In the method for producing a non-oriented electrical steel sheet comprising the step of performing the final cold roll annealing cold rolled sheet at a temperature of 800-1100 ℃ after two cold rolling including annealing, the steel slab is composed of weight percent , C: 0.02% or less, Si: 3.5% or less, Mn: 0.5% or less, S: 0.01% or less, N: 0.008% or less, Cu: 0.05-0.50%, Al: 0.5% or less, P: 0.05-0.15 %, Balance Fe and inevitable impurities; And a reheating temperature of the slab is 1050-1270 ° C., wherein the iron loss and magnetic flux density are excellent.