JP4267499B2 - Non-oriented electrical steel sheet with excellent magnetic properties - Google Patents

Description

  The present invention relates to a non-oriented electrical steel sheet used as an iron core material for electrical equipment and a method for producing the same, and particularly to a non-oriented electrical steel sheet having excellent magnetic properties.

  In recent years, due to the increase in energy saving of electric appliances worldwide, non-oriented electrical steel sheets used as iron core materials for rotating machines have been required to have higher performance characteristics. In particular, there is a strong need to reduce the iron loss that leads to the loss of rotating machines, and the reduction of iron loss has been achieved by increasing the specific resistance by increasing the Si and Al contents and increasing the crystal grain size. Furthermore, increasing the purity of steel not only promotes crystal grain growth, but also reduces the influence of precipitates formed by impurities in the steel, so that the purity of steel has been increased in recent years.

  For example, in Patent Document 1, S, N: 0.0020% or less, Ti, V, As: 0.0020% or less, Nb: 0.0030% or less, a method of promoting grain growth and reducing iron loss It is disclosed. In Patent Document 2, S: 0.0010% or less promotes crystal grain growth, and Sb + 1 / 2Sn: 0.001-0.05% is contained, thereby suppressing nitriding of the steel sheet caused by S: 0.0010% or less. Thus, a method for reducing iron loss is disclosed.

  In addition, for the purpose of promoting grain growth and reducing iron loss in strain relief annealing, Patent Document 3 adds REM, Patent Document 4 adds Ca alloy, Patent Document 5 uses Mg or Mg, Although a method of adding Ca and REM in combination is disclosed, these grains grow by making S unavoidable in steel a coarse and thermally stable sulfide with REM, Ca and Mg. The purpose is to promote.

  Furthermore, Patent Document 6 describes a method for prescribing the amount of Ni and Cu mixed for the purpose of positive use of scrap in steelmaking, and Patent Document 7 describes a technique for reducing the cost of steelmaking when 1.5% or more of Mn is added. As scrap utilization, a method for reducing a nitride layer or an oxide layer on the surface of a steel sheet by optimizing the amount of Su, Cu, Ni, and Cr mixed at that time is disclosed.

Japanese Patent Laid-Open No. 8-283835 JP-A-10-317111 JP-A-8-325678 JP-A-10-183309 JP 2002-302746 A JP 7-305114 A JP 2003-96548 A

  The present inventors have found that the deterioration of iron loss due to nitriding of steel sheet occurs not only when S described in Patent Document 2 is 0.0010% or less, but also when S exceeds 0.0010%. did. This invention is made | formed in view of such a problem, and provides an electromagnetic steel plate with a low iron loss.

(1) By mass%, Si: 3.5% or less, Mn: 1.5% or less, Al: 0.1% or more and 3.0% or less, C: 0.0050% or less, Ti: 0.0030% Hereinafter, N: 0.0050% or less, S: 0.0011% or more and 0.0030% or less, Ni: 0.05% or more and 1.0% or less, Cu: 0.05% or more and 1.0% or less , Ca + Mg + (REM / 4) contains 0.0005-0.0024 % , consists of the balance Fe and inevitable impurities, and is the sum total of SasMnS (S generating MnS) and SasCu2S (S generating Cu2S) ( A non-oriented electrical steel sheet characterized in that Sas [MnS + Cu2S] is 0.0010% or less by mass%.
(2) The non-oriented electrical steel sheet according to (1), wherein the non-oriented electrical steel sheet according to (1) contains at least 0.3% of Cu and Ni at least 1/2 of the Cu content.
( 3 ) The non-oriented electrical steel sheet according to any one of (1) to ( 2) , wherein Ti is 0.0010% by mass or less.

  ADVANTAGE OF THE INVENTION According to this invention, the nitriding of a steel plate is suppressed and the electromagnetic steel plate with a low iron loss can be provided.

The present invention is described in detail below. As a result of investigating the nitriding of the steel sheet surface which deteriorates the magnetic properties, the present inventors have deteriorated the magnetic properties by nitriding during finish annealing or strain relief annealing even in a relatively high range where S in the steel is 0.0011% or more. I found out that there was a case. As a result of investigating the cause, it was found that the amount of S producing MnS or Cu ₂ S was extremely small in steel sheets that deteriorated in magnetic properties due to nitriding, and Ni and Cu were added as a countermeasure. It was found that nitriding during annealing can be suppressed and the magnetic properties can be improved. Furthermore, the inventors have found that wrinkles can be prevented by preventing the generation of wrinkles on the steel sheet surface due to excessive Cu addition, and by defining the amount of Ni added according to the amount of Cu. Hereinafter, the experimental results that led to the present invention will be described.
(Experiment 1)
In a laboratory vacuum melting furnace, by mass%, C: 0.0014%, Si: 3.1%, Mn: 0.2%, Al: 1.0%, Ti: 0.0008%, N: 0.0020%, S: 0.0013% And as shown in Table 1, steel pieces containing Ca, Mg, and REM were also produced. These steel slabs were heated at 1100 ° C for 60 minutes, then immediately hot rolled to a sheet thickness of 2.0 mm, and subjected to hot rolled sheet annealing at 1000 ° C for 60 seconds, with a single cold rolling. The plate thickness was 0.35 mm.

The cold-rolled sheet thus obtained was subjected to a finish annealing at 1050 ° C. for 30 seconds in an atmosphere N ₂ 70% -H ₂ 30% (volume ratio), and then the iron loss was measured, and Ca, Mg, REM, N and Sas [MnS + Cu ₂ S] were analyzed. As a result, as shown in Table 1, in samples ₂ , 3, 5 to 8 where Sas [MnS + Cu ₂ S] is 0.0010% or less, the nitriding amount ΔN (N amount after annealing−steel N amount) exceeds 0.0010%. It was found that the iron loss was worsened for samples 1 and 4 that were not nitrided. Although all samples were in the range of S: 0.0012 to 0.0014%, Sas [MnS + Cu ₂ S] of samples _{2, 3, 5 to 8} was 0.0010% or less because of MnS and Cu ₂ It was found that Ca, Mg, and REM, which had a stronger affinity for S than S, were contained in Ca + Mg + (REM / 4) in an amount of 0.0005% or more.

(Experiment 2)
In a laboratory vacuum melting furnace, in mass%, C: 0.0019%, Si: 1.6%, Mn: 0.5%, Al: 0.8%, Ti: 0.0006%, N: 0.0017%, S: 0.0017%, Cu: Steel pieces containing 0.25%, Ni: 0.1%, and containing Ca, Mg, and REM as shown in Table 2 were also produced. These steel slabs were heated at 1150 ° C for 60 minutes, then immediately hot rolled to a sheet thickness of 2.0mm, and subjected to hot rolled sheet annealing at 1100 ° C for 60 seconds, with a single cold rolling. The plate thickness was 0.50 mm.

The cold-rolled sheet thus obtained was subjected to a finish annealing at 975 ° C. for 15 seconds in an atmosphere N ₂ 70% -H ₂ 30% (volume ratio), and then the iron loss was measured, and Ca, Mg, REM, N and Sas [MnS + Cu ₂ S] were analyzed. As a result, as shown in Table 2, it was found that samples ₂ , 3, 5 to 8 having Sas [MnS + Cu ₂ S] of 0.0010% or less were not nitrided and that good iron loss was obtained.

(Experiment 3)
In a laboratory vacuum melting furnace, by mass, C: 0.0024%, Si: 2.5%, Mn: 0.2%, Al: 0.8%, Ti: 0.0010%, N: 0.0025%, S: 0.0015%, Ca: A steel slab containing 0.0004%, Mg: 0.0006%, and Cu: 0.55% and changing Ni from 0.1 to 0.79% was produced. These steel slabs were heated at 1100 ° C for 60 minutes, and then immediately hot-rolled to a sheet thickness of 2.3 mm, subjected to hot-rolled sheet annealing at 1050 ° C for 60 seconds, and then cold-rolled once. The plate thickness was 0.50 mm.

The cold-rolled sheet thus obtained was subjected to finish annealing at 1000 ° C. for 30 seconds in an atmosphere N ₂ 70% -H ₂ 30% (volume ratio), and then analysis of Sas [MnS + Cu ₂ S], N The presence or absence of linear wrinkles on the steel sheet surface was investigated. As a result, as shown in Table 3, the nitriding suppression effect was obtained in spite of Sas [MnS + Cu ₂ S] being 0.0010% or less in all samples, but samples 1 to 3 having a low Ni content were obtained. Then, linear wrinkles on the steel sheet surface were confirmed.

  Such a linear wrinkle was not seen in Experiment 2 with a small amount of Cu added, so it only occurs when the amount of Cu added is large, and increase the amount of Ni added as in Samples 4 to 6 in this experiment. It was found that it no longer occurs. As a result of further investigations, when Cu is contained in an amount of 0.3% or more, Cu concentrated on the surface of the slab at the time of hot rolling is melted to form linear wrinkles, and when Ni is added more than 1/2 of Cu. It was found that Ni, which was concentrated on the slab surface at the same time as Cu, was alloyed with Cu to raise the melting temperature, so that linear flaws could be suppressed.

Thus, nitriding during annealing by the amount of S forming the sulfides MnS and Cu ₂ S (Sas [MnS + Cu ₂ S]) in the steel sheet was first discovered by the present invention, and REM Therefore, it cannot be inferred from Patent Documents 3 to 5, in which Ca and Mg are simply added to modify sulfides.

  Also, as an invention containing both Ni and Cu, Patent Document 6 defines the amount of Ni and Cu mixed for the purpose of positive use of scrap in steelmaking, but this also includes Sn mixed in as scrap The present invention discloses that the surface defects generated by the synergistic action are suppressed, and there is no suggestion about the suppression of nitriding of the steel sheet caused by the type and amount of sulfide in the present invention.

  In addition, Patent Document 7 shows the use of scrap in steelmaking as a cost reduction measure when adding 1.5% or more of Mn, and by appropriate amount of Sn, Cu, Ni, Cr mixed at that time, nitride layer and oxidation on the steel sheet surface Although it is described that the effect of reducing the layer can be enjoyed, there is no suggestion about the effect of the present invention because not only the influence of the sulfide but also the example of the nitriding suppression effect is not shown.

  Next, the reasons for limiting the numerical values of the components in the product of the present invention will be described.

  Si is an effective element for increasing the electric resistance, but if added excessively, the cold rolling property is remarkably deteriorated, so the upper limit was made 3.5%.

  Mn is an element effective for increasing the electrical resistance like Si, but if added over 1.5%, the saturation magnetic flux density is drastically reduced and the magnetic properties are deteriorated. In addition, the transformation depends on other components. Therefore, the upper limit of the annealing temperature is restricted and the desired magnetism cannot be obtained, so 1.5% was made the upper limit.

  Al, like Si, is an effective element for increasing electrical resistance, and is also useful as a deoxidizer. For these purposes, since it is necessary to add 0.1% or more of Al, it was specified to be 0.1% or more. In particular, 0.2% or more is preferably added in order to prevent deterioration of grain growth due to fine AlN generation. In addition, the specific resistance can be increased to almost the same as Si with the same addition amount, but since the increase in hardness is smaller than that of Si, it is an essential element in high-grade grades, and addition of 0.8% or more is particularly desirable. However, if added in a large amount, castability deteriorates, so 3.0% was made the upper limit.

  Since C is well known to cause magnetic aging, it is defined as 0.0050% or less. However, Ti and precipitates are formed, and the grain growth particularly during strain relief annealing is deteriorated, so 0.0020% or less is desirable.

  Since Ti forms nitrides, carbides, and carbonitrides and significantly deteriorates grain growth, it is specified to be 0.0030% or less. However, 0.0010% or less is desirable especially when promoting crystal grain growth during strain relief annealing.

  N is defined as 0.0050% or less in order to generate Al, Ti and nitride, and to significantly deteriorate the grain growth.

  S is an important element in the present invention. Although it is desirable to reduce as much as possible from the viewpoint of promoting crystal grain growth, 0.0011% is set as the lower limit and the upper limit is set to 0.0030% at which deterioration of crystal grain growth becomes remarkable because the manufacturing cost increases.

If the total of SasMnS and SasCu ₂ S exceeds 0.0010%, the crystal grain growth and iron loss during finish annealing or strain relief annealing deteriorate, so the upper limit of the total was set to 0.0010%.

Since Ca, Mg, and REM can produce more stable sulfides at higher temperatures than MnS and Cu ₂ S, in a steel containing 0.0011 to 0.0030% S, the sum of SasMnS and SasCu ₂ S is 0.0010%. It is contained for the purpose of the following. However, when Ca + Mg + (REM / 4) is less than 0.0005%, sulfide is hardly generated, so the lower limit of Ca + Mg + (REM / 4) is set to 0.0005%.

  Cu is an essential element in the present invention, and exhibits a nitriding suppression effect when combined with Ni. However, since Cu is less than 0.05%, the effect is lost, so 0.05% was made the lower limit. Furthermore, in addition to the effect of suppressing nitriding, a texture preferable for magnetic properties can be obtained. In order to enjoy the effect, it is desirable that the amount of addition be 0.2% or more. However, if it exceeds 1.0%, precipitates are generated and the magnetic properties are deteriorated, so the upper limit was made 1.0%.

  Ni is an essential element in the present invention, and a nitriding suppression effect is manifested by combined addition with Cu, but since Ni is less than 0.05%, the effect is lost, so 0.05% was made the lower limit. Furthermore, when adding Cu 0.3% or more, in order to suppress the linear flaw on the surface of the steel sheet generated by the concentration of Cu, it is necessary to add 1/2 or more of the Cu content. The upper limit is set to 1.0% in consideration of the effect and cost.

In a laboratory vacuum melting furnace, in mass%, C: 0.0015%, Si: 2.6%, Mn: 0.2%, Al: 1.4%, Ti: 0.0018%, S: 0.0021%, N: 0.0018%, Ca: Steel slabs containing 0.0005%, Mg: 0.0004%, Cu: 0.01 to 0.72%, and Ni: 0.03 to 0.77% were produced. These steel slabs were heated at 1050 ° C for 60 minutes, then immediately hot rolled to a sheet thickness of 2.3 mm, hot rolled at 1000 ° C for 60 seconds, and cold-rolled once. The plate thickness was 0.50 mm, and a finish annealing was performed at 1000 ° C. for 30 seconds in an atmosphere of N ₂ 70% -H ₂ 30%.

Table 4 shows the results obtained by measuring and observing Sas [MnS + Cu ₂ S], N, iron loss W15 / 50, magnetic flux density B50, and presence or absence of linear wrinkles of each sample thus obtained. In any sample, Sas [MnS + Cu ₂ S] is 0.0010% or less, and samples 1 to 6, 11, 16, and 21 with Cu: less than 0.05% and Ni: less than 0.05% have ΔN (N amount after annealing− The amount of steel slab N) was high, and it was confirmed that nitriding occurred.

Further, in samples 16 to 17 and 21 to 23 where Cu was 0.3% or more and Ni was less than 1/2 of Cu, linear wrinkles occurred. From the above, in a steel plate with Sas [MnS + Cu ₂ S] of 0.0010% or less, Cu: 0.05% or more and Ni: 0.05% or more, and further Cu: 0.3% or more, 1% of Cu It was found that samples 7 to 10, 12 to 15, 18 to 20, 24, and 25 containing Ni of 2 or more can obtain good characteristics without nitriding and linear defects. It was also found that the magnetic flux density (B50) was improved as the Cu addition amount increased.

In a laboratory vacuum melting furnace, in mass%, C: 0.0023%, Si: 1.0%, Mn: 0.5%, Al: 1.2%, Ti: 0.0013%, S: 0.0012%, REM: 0.0032%, Cu: Steel pieces containing 0.03-0.65% and Ni: 0.02-0.32% were produced. These steel slabs were heated at 1130 ° C for 60 minutes, and then immediately hot-rolled to a sheet thickness of 2.3 mm, subjected to hot-rolled sheet annealing at 1100 ° C for 60 seconds, with a single cold rolling. The plate thickness was 0.50 mm, finish annealing was performed at 850 ° C. for 15 seconds in an atmosphere N ₂ 85% -H ₂ 15%, and further, strain relief annealing was performed at 750 ° C. for 2 hours in an atmosphere N ₂ 100%.

Table 5 shows the results obtained by measuring and observing Sas [MnS + Cu ₂ S], N, iron loss W15 / 50, magnetic flux density B50, and presence or absence of linear wrinkles of each sample thus obtained. In any sample, Sas [MnS + Cu ₂ S] is 0.0010% or less, and samples 1 to 6, 11, 16, and 21 with Cu: less than 0.05% and Ni: less than 0.05% have ΔN (N amount after annealing− The amount of steel slab N) was high, and it was confirmed that nitriding occurred. Further, in samples 16-18 and 21-24 where Cu was 0.3% or more and Ni was less than 1/2 of Cu, linear wrinkles occurred.

From the above, in a steel sheet with Sas [MnS + Cu ₂ S] of 0.0010% or less, Cu: 0.05% or more and Ni: 0.05% or more, and further Cu: 0.3% or more Cu It was found that samples 7 to 10, 12 to 15, 19, 20, and 25 containing Ni of 1/2 or more can obtain good characteristics without nitriding and linear flaws. It was also found that the magnetic flux density (B ₅₀ ) was improved as the Cu addition amount increased.

In a laboratory vacuum melting furnace, in mass%, C: 0.0021%, Si: 2.1%, Mn: 0.2%, Al: 0.3%, Ti: 0.0007%, S: 0.0025%, Mg: 0.0024%, Cu: Steel pieces containing 0.04 to 0.80% and Ni: 0.01 to 0.45% were produced. These steel slabs were heated at 1080 ° C for 60 minutes, and then immediately hot-rolled to a thickness of 2.3 mm, then subjected to hot-rolled sheet annealing at 950 ° C for 60 seconds, with a single cold rolling. Finish annealing was performed at 975 ° C. for 30 seconds in a plate thickness of 0.35 mm and atmosphere N ₂ 80% -H ₂ 20%.

Table 6 shows the results obtained by measuring and observing Sas [MnS + Cu ₂ S], N, iron loss W15 / 50, magnetic flux density B50, and presence or absence of linear defects of each sample thus obtained. In any sample, Sas [MnS + Cu ₂ S] is 0.0005% or less, and Cu is less than 0.05% and Ni is less than 0.05%. Samples 1 to 6, 11, 16, and 21 have ΔN (N amount after annealing− The amount of steel slab N) was high, and it was confirmed that nitriding occurred. Further, in samples 16-18 and 21-24 where Cu was 0.3% or more and Ni was less than 1/2 of Cu, linear wrinkles occurred.

From the above, Sas [MnS + Cu ₂ S] is 0.0010% or less of the steel sheet, Cu: 0.05% or more and Ni: 0.05% or more, and further Cu: 0.3% or more Cu It was found that samples 7 to 10, 12 to 15, 19, 20, and 25 containing Ni of 1/2 or more can obtain good characteristics without nitriding and linear flaws. It was also found that the magnetic flux density (B ₅₀ ) was improved as the Cu addition amount increased.

Claims (3)

In mass%, Si: 3.5% or less, Mn: 1.5% or less, Al: 0.1% to 3.0%, C: 0.0050% or less, Ti: 0.0030% or less, N : 0.0050% or less, S: 0.0011% or more and 0.0030% or less, Ni: 0.05% or more and 1.0% or less, Cu: 0.05% or more and 1.0% or less , Ca + Mg + (REM / 4) containing 0.0005-0.0024 % as the balance, consisting of the balance Fe and inevitable impurities, and the sum of SasMnS (S producing MnS) and SasCu2S (S producing Cu2S) (hereinafter Sas) A non-oriented electrical steel sheet characterized in that [MnS + Cu2S] is 0.0010% or less by mass%.   2. The non-oriented electrical steel sheet according to claim 1, wherein the non-oriented electrical steel sheet comprises, by mass%, 0.3% or more of Cu and 1/2 or more of the content of Ni. Ti is 0.0010 mass% or less, The non-oriented electrical steel sheet according to any one of claims 1 and 2 .