JPH02213421A - Production of soft-magnetic steel stock - Google Patents

Abstract

PURPOSE:To inexpensively produce a soft-magnetic steel stock having high saturation magnetization and high magnetic permeability by subjecting a billet or cast billet having a specific composition consisting of C, Si, Mn, P, S, Al, N, O, and Fe to specific hot working and annealing. CONSTITUTION:A billet or cast billet having a composition which consists of, by weight, <=0.004% C, <=0.5%, preferably <=0.1%, Si, <=0.5%, preferably <=0.15%, Mn, <=0.015% P, <=0.01% S, 0.5-2.0% solAl, <=0.005% N so that C+N is regulated, preferably, to <=0.007%, where <=0.012% N so that C+N is regulated, preferably, to <=0.015% when 0.005-1.0% Ti is added, <=0.005% O, and the balance Fe with inevitable impurities is heated up to 700-1300 deg.C. Then, the hot working of the above billet or cast billet is completed at >=700 deg.C. The resulting worked stock is annealed finally at 900-1300 deg.C. By this method, the soft-magnetic steel stock having <=0.4Oe coercive force and >=10000G magnetic flux density at 0.5Oe can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to soft magnetic materials, and particularly to soft magnetic materials that require high direct current magnetization characteristics, such as electromagnetic core materials or magnetic shielding materials.

[Conventional technology and issues to be solved]

Soft iron and pure iron, which can be obtained relatively cheaply, and permalloy or super, which are very expensive, are used as DC electromagnet iron core materials, or as magnetic shielding materials for medical equipment, various physical equipment, electronic parts and equipment, etc., which have made remarkable progress and spread in recent years. Malloy is used. By the way, the magnetic flux density (hereinafter referred to as 8□ value) of soft iron and pure iron at 10e is approximately 3000 to 1100.
It is about 0 G, and these are magnetic shielding of MHI (tomographic imaging diagnostic equipment using nuclear magnetic resonance).

It is used as a magnetic shielding material up to several Gauss or as a material for the iron core of an electromagnet.

Among applications where DC magnetization characteristics are important, we will use magnetic shielding as an example to illustrate the problems of the conventional technology.
Pure iron, which is relatively inexpensive and has high saturation magnetization, is exclusively used for magnetic shielding, but it does not meet the strictest type 0 of the JIS standards that specify electromagnetic soft iron (e.g. JIS C25045UYPO), which covers soft iron and pure iron. Even so, the lower limit of the B1 value is specified as 8000 G, and with this characteristic it is difficult to shield magnetic fields as strong as the geomagnetic field, and moreover, the shielding system has to become heavier in order to shield magnetic fields as strong as a few Gauss or less. . Fe-Ni alloys such as permalloy or supermalloy are sometimes used as shielding materials to achieve better shielding, but while these materials are capable of shielding less than the geomagnetic field, they are very expensive. In addition, the saturation magnetization is 1/3 to 2/3 lower than that of pure iron, so it has drawbacks such as the need to increase the wall thickness extremely when shielding from high magnetic fields, so in any case, it is used in large quantities. It is economically difficult to do so.2゜Based on these points, some studies have already been made to increase the magnetic permeability without impairing the high saturation magnetization of pure iron-based materials.For example, No. 45443, JP-A-62-77420, or the Japan Institute of Metals Vol. 23, No. 5 (published in 1984) "Development of extra-thick electrical steel sheets", all of the methods are effective at coarsening ferrite grains. These technologies aim to improve the magnetic permeability associated with
The target may be a technique that is limited to hot-rolled sheets with a relatively thin plate thickness, or a magnetic flux density at 0.50e (hereinafter referred to as 8°1.
It is a technology that cannot achieve a value of 10,000 G or more,
In any case, this is not a sufficient technique for obtaining excellent DC magnetization characteristics.

As described above, at present, there is no material that has high saturation magnetization and exhibits high magnetic flux density in a low magnetic field equivalent to the earth's magnetic field, that is, has high magnetic permeability. The objective is to provide a method that can be used to manufacture

[Means to solve the problem]

In order to solve the above-mentioned problems, the present inventors first
We investigated industrial pure iron, which is the basis of soft magnetic materials for direct current magnetic fields, and clarified its shortcomings.We also investigated ways to improve its characteristics, and obtained the following knowledge.

In other words, from the viewpoint of obtaining high magnetic permeability, adding A1 not only enables effective deoxidation and improves magnetic permeability by reducing the amount of oxygen and oxide inclusions, but also increases magnetic permeability. Solute N has a negative impact on AII.
■Additionally, by adding a certain required amount, it is possible to agglomerate the finely dispersed AΩN particles, suppressing the negative effects of the A+IN particles themselves as much as possible, and at the same time reducing the amount of ferrite. It also has the effect of promoting the coarsening of crystal grains, both of which are effective in improving magnetic permeability. In particular, by adding more than 0.5%, the transformation temperature can be significantly raised or the ferrite single phase can be increased. Therefore, it is possible to perform annealing at a temperature exceeding 900°C without introducing strain due to transformation, and this high temperature annealing effectively removes lattice strain and improves ferrite crystal grains. This results in coarsening of the solid solution Al! Although the effect of improving the magnetic permeability of itself is considered, the synergistic effect of these makes it possible to obtain extremely excellent magnetic permeability. Addition of Affi exceeding 0.02% should be avoided from the viewpoint of preferentially fixing and contributing to property improvement, not requiring special effort to reduce the N content, and maintaining high saturation magnetization of the material. Also, if the C and N contents are high, in addition to lowering the transformation temperature or increasing the necessary amount of additive, solid solution C
, N may cause property deterioration due to an increase in lattice strain or the formation of carbides and nitrides, so this is to avoid these.

The present invention was completed by discovering that there is an upper limit for the amounts of C and N.

That is, the features of the present invention are as follows.

(1) In weight%, C: 0.004% or less, Si:
0.5% or less, Mn: 0.50% or less, P: 0
．． 015% or less, S: 0.01% or less, 5offi, mouth: 0.5-2.0%, N: 0.005% or less, oxygen: 0.005% or less, the balance consisting of Fe and inevitable impurities. Steel slabs or cast slabs at temperatures above 700°C and 1300°C
℃ or less, hot working is completed at a temperature of 700℃ or higher, and finally annealing is performed at 900 to 1300℃. A method for producing a soft magnetic steel material, the method comprising obtaining a soft magnetic steel material having the following properties.

(2) In weight%, C: 0.004% or less, Si:
0.1% or less, Mn: O, t5% or less, P: 0
．． 015% or less, S: 0.01% or less, 5ofi, Al
A steel slab or cast slab with a composition consisting of l: 0.5 to 2.0%, N: 0,005% or less, oxygen: 0.005% or less, and the balance Fe and unavoidable impurities is heated to 700°C or higher13
By heating to 00℃ or lower, finishing hot working at a temperature of 700℃ or higher, and finally annealing at 1000 to 1300℃, the coercive force is 0.4Oe or lower and the magnetic flux density at 0.50e is 10,000G or higher. A method for producing a soft magnetic steel material, the method comprising obtaining a soft magnetic steel material having the following properties.

(3) In weight%, C: 0.004% or less, Si:
0.5% or less, Mn: 0.50% or less, P: 0
．． 015% or less, S: 0.01% or less, 5oj1. mouth:
0.5-2.0%, N: 0.012% or less, Oxygen: 0.005% or less, Ti: 0.005-1.0
%, the balance Fe and unavoidable impurities are heated to 700°C or higher and 1300°C or lower, and
Hot processing is completed at a temperature of 0℃ or higher, and the final temperature is 900℃ or higher.
By annealing at 1300℃, the coercive force is 0.4Oe.
Hereinafter, a method for manufacturing a soft magnetic steel material, which is characterized in that a soft magnetic steel material having a magnetic flux density of 10000 G or more at 0.5 Oe is obtained.

The reasons for limiting the composition and manufacturing conditions in the present invention will be explained below.

Like N, it is desirable to reduce carbon as much as possible in order to ensure excellent magnetic permeability, but it is difficult to reduce carbon to an extreme degree in industrial production, and it also causes an extremely high cost. In addition, in order to increase the transformation temperature by adding A,
If the addition amount is not kept low, the required addition amount will increase, which will result in a decrease in saturation magnetization, which is contrary to the intent of the present invention. Therefore, C is 0
．． The upper limit is 004 vt%.

SL contributes to improving magnetic permeability, but in the present invention, the purpose of improving magnetic permeability is to satisfy the problem by addition of SL.
There is a concern that the saturation magnetization will decrease due to the addition of a large amount of
．． The upper limit is 5 wt%, preferably 0.1 wt%.

Mn is an element that deteriorates DC magnetization characteristics, and it is desirable to reduce it, but extreme reduction will lead to higher costs and an increase in N content, and fixing S will not have the effect of preventing hot embrittlement. Therefore, as long as Mn/S is not less than 10, 0.50 vt%, preferably 0.15
It may be added up to wt%.

P and S are impurity elements, and it is desirable to reduce them within a range that does not lead to increased costs, and each is 0.015
vt%, with an upper limit of 0.01 wt%.

As mentioned above, the element is an essential additive element in the present invention. In other words, AI causes fixation of solid solution N, agglomeration of IN particles, and an increase in transformation temperature, thereby realizing high-temperature annealing by expanding the ferrite region, thereby coarsening ferrite grains and reducing internal strain. It achieves this and improves magnetic permeability, and further improves solid solution Afi
It is also considered to have an effect of improving its own magnetic permeability, and in the present invention, it is an element that must be added in order to obtain excellent DC magnetization characteristics. This effect of An can be obtained by adding 0.5 wt% or more in the state of 5offi and AQ, but on the other hand, 2. If added in excess of Owt%, the saturation magnetization will decrease, which is undesirable, so the addition amount range for A] is SoA, A
0.5-2. It was set as Owt%.

Like C, N penetrates into the Fe lattice, causing a lot of lattice distortion and deteriorating the DC magnetization characteristics. Further, it is desirable that N be as low as possible in order to prevent the generation of too many Al1 particles. This idea also leads to making the added AQ exist as an effective solid solution An, so that the amount of N is 0.
In the present invention, Ti, which is a strong nitride-forming element, is added as necessary, as will be described later. Ti is added for the purpose of reducing the above-mentioned adverse effects of N without imposing a strict upper limit on the amount of N, which would lead to high costs. Therefore, in this case, the upper limit of N is set to 0.012. Let it be wt%.

Furthermore, as is clear from the above findings, in order to more reliably ensure DC magnetization characteristics, it is desirable to regulate the total amount of N and C.

In other words, in the case of no Ti addition, C+N is 0.007wt.
% or less, in case of Ti addition, C+N is 0.014wt
% or less.

Like Mn, oxygen is also an element that deteriorates DC magnetization characteristics, and in particular, the deterioration effect on magnetic permeability due to the formation of nonmetallic inclusions is large and must be sufficiently reduced when producing the present invention. However, the upper limit is 0.005 wt.
% was specified.

As mentioned above, Ti is a strong nitride-forming element, and 0
．． 005-1. By adding within the range of Owt%,
Even in materials whose N content is not sufficiently reduced, that is, which are inexpensive, it is possible to avoid significant impairment of DC magnetization characteristics due to the fixation effect of solid solution N. Further, when the N content is relatively low, the amount of nitride particles produced is small, and a slight improvement in DC magnetization characteristics can be expected. On the other hand, adding more than the above upper limit results in deterioration of DC magnetization characteristics.

Next, the manufacturing conditions for the steel of the present invention will be explained.

In the present invention, very normal hot working conditions are adopted as the hot rolling conditions, and the steel slab or cast slab with the above composition is rolled at 700%
Hot working is performed by heating the product to a temperature above 1300°C and below 1300°C. However, the increase in deformation resistance during hot working and the increase in the time spent on hot working due to low-temperature rolling always lead to higher costs and extreme Low-temperature rolling may lead to grain refinement due to recrystallization during annealing, so in the present invention, a lower limit temperature of 700° C. is set for the finishing temperature.

The final annealing must be carried out within a range that does not touch the transformation temperature, which is determined mainly by the amount of additive, but it must be carried out at a temperature of at least 900°C or higher, preferably 1000°C or higher. The extremely excellent DC magnetization characteristics intended by the steel of the present invention cannot be achieved, and specifically, by adding approximately 1 wt% of An to 0.001 vt%C, 10,0020 wt%N, the steel of the present invention The annealing temperature becomes 900 to 1300°C, preferably 900 to 1300°C. is 1000-13
The temperature was 00°C. Note that the heating holding time varies depending on the heat capacity of the material, but it is desirable to hold it for 30 minutes or more, and regarding cooling after heating holding, it is desirable to perform slow cooling from the viewpoint of not introducing thermal strain as much as possible.

Of course, if care is taken to ensure uniform cooling, thermal strain is less likely to be introduced, and in this case it is not necessarily necessary to cool slowly.

As described above, with the chemical components and manufacturing conditions according to the present invention,
In particular, by limiting the annealing temperature, it is possible to obtain a steel material with high Bo, s value, and saturation magnetization, that is, excellent soft magnetic properties in a DC magnetic field.

Note that the present invention also includes cases where hot rolling is performed by direct pressure hot rolling. Further, the steel materials to be manufactured by the present invention include hot-worked materials and cold-worked materials (including warm-worked materials).

The same applies hereafter). Therefore, it does not matter whether the final annealing specified by the present invention is performed after hot working or after hot oil knee cold working. Needless to say, this also includes cases where intermediate annealing is performed during hot working or cold working, or where each of the above-mentioned workings is performed in several stages.

In addition, the steel materials targeted by the present invention include thick plates and thin single strip materials (
(shaped steel, etc.), forged materials, etc.

〔Example〕

Example 1 Table 1 shows the chemical composition of the steel used in Examples and Comparative Examples. mA-E has a thickness of 110m after melting.
The steel ingot was formed into a 15 m thick plate by hot rolling at 1200°C. Steels A-C are compatible with the chemical composition of the present invention, and IID, E, F, and G are comparative steel types. Table 1 also shows the results of examining the transformation point when the temperature was raised to 1300°C at a heating rate of 0.5°C/S. In addition, this transformation point measurement result shows that the present invention steel mentioned in the example has a ferrite single phase.

Table 2 shows the results of measuring the DC magnetization characteristics of the invention steel and comparative steel. Test specimens with an outer diameter of 45 ma+, an inner diameter of 33 mm, and a thickness of 6+ m were taken from the center of the plate thickness after hot rolling. However, this is the result of annealing it and measuring the DC magnetization characteristics, and this annealing corresponds to the final annealing defined in the present invention. In addition, the annealing was carried out for a heating holding time of 1 to 3 hours, and a cooling rate of about 100° C./hr.

In Table 2, Nα1 is an example based on the present invention in which steel A was annealed at 1100°C. In this example, the ferrite single phase is achieved due to the low carbon content and addition of carbon.
High-temperature annealing is possible without introducing transformation strain or grain refinement due to transformation.In fact, by annealing at a high temperature of 1100°C, significant coarsening of ferrite grains with a diameter of 2 m or more is achieved, and at the same time, lattice strain is reduced. Removal has also been achieved, with a Bo value of approximately 13,000 G and a maximum permeability of 6.
Extremely excellent characteristics exceeding 0,000 were obtained.

Nα2 is! This is an example in which 11A was annealed at 1000°C. In this example, the annealing temperature is lower than &1, the ferrite grain size is about 0.5 to 1.0 m, and although it is smaller than the Nα1 example, the maximum magnetic permeability is 23,900, and good characteristics are obtained.

Nα3.4 are both examples by @B and C.

Here too, the ferrite is made into a single phase by adding A1, and both can be annealed at a high temperature exceeding 1000℃, and due to the synergistic effect of coarsening the ferrite crystal grains and removing internal strain, &3 has a maximum magnetic permeability of 56000. , Demon 4
Excellent characteristics with a maximum magnetic permeability of 37,200 were obtained.

The above examples with Nα1 to 4 all have a maximum permeability of 20
000 or more and a coercive force of less than 0.4 Oe, which not only fully satisfies the characteristics specified in JIS C2504 SUYPO, but also has a
Since even the 3a and s values exceed 11,000 G, it is possible to achieve magnetic shielding comparable to that of the earth's magnetism.

&5.6.7 is comparative steel by taD, E, F. m
D, E, and F all correspond to industrial pure iron and deviate from the chemical composition specified by the present invention. Therefore, as shown in &5.6, even if annealing is performed at 1000°C or higher, no significant coarsening of ferrite crystal grains can be expected, and furthermore, strain is introduced during the transformation from austenite to ferrite, making it impossible to provide good properties. , Nα7 are the results when the annealing temperature is lower than the transformation point, but neither of them has good characteristics.

Example 2 Table 3 shows the chemical composition of the steel used in the example and comparative example. @I~U has a thickness of 110a after melting
The steel ingot was made into a steel ingot of 1200"C, hot rolled at 1200"C to a plate thickness of 15III11, and then annealed.11
Steels 1 to S, WY, Z, and bd are compatible with the chemical composition of the present invention, and steels T, U, V, and a are comparative steel types. Table 4 summarizes the results of measuring the DC magnetization characteristics of the invention steel and comparative steel. In this example, the heating holding time for annealing was 1 to 3 hours, and the cooling rate was about 100° C./hr to 500° C./hr.

In Table 4, Na1. Examples 0 to 13 are examples in which the amount of Mn added was varied within the specified range of the present invention.

Na 23-26 is 5oJ1. The influence of AQ amount, &28
1 and 29 to 31 respectively investigated the influence of the amount of C and the influence of the amount of Si.

Examples 14 to 16 are examples in which Ti is added. Here too, the addition of Ajl has made ferrite into a single phase, and the addition of Ti has also fixed N, resulting in Nα1
4.16 has been found to have good characteristics. Especially &15
Based on the present invention, in which Ti is added to steel equivalent to HAMA 22.
This is an example, and sufficient N fixation is achieved by the addition of Ti, and a significant improvement is recognized compared to the comparative example of Na22.

Nci21 is a comparative example in which Ti was added in an amount exceeding the specified range of the present invention, and significant deterioration of the DC magnetization characteristics was observed.

Nα22 is a comparative example in which the amount of N added is high and Ti is not added, and the precipitation state of AIIN is stable, so even if annealing is performed, it is not possible to achieve sufficient coarsening of ferrite crystal grains. Moreover, since the amount of solid solute N is also high, good characteristics are not obtained.

Na17 and Na18 are examples in which steels P and Q were annealed at 1000°C.

The above Nα10-18, Ha 24-26, Nα27,
Examples of Ha 29 to 31 all have a coercive force of 0.4
Excellent DC magnetization characteristics of Oe or less, tlo, and s values of 10,000 G or more have been achieved, and JIS C2504
Not only does it meet the characteristics specified by SUYPO, it can also be used as a magnetic shielding material to create a magnetic field environment that is at a level below that of earth's magnetism.

Also, Nα19.20 is Ti in relation to the amount of N and the amount of C+N.
The effect of addition was investigated, both of which were N) 0.005%.
, C+N>0.007%, but since Nα20 is a Ti-added material, good characteristics are obtained.

〔Effect of the invention〕

As described above, the soft magnetic steel material obtained by the present invention has excellent DC magnetization characteristics, and therefore can be easily magnetized even in a weak magnetic field, and can be used as a high-performance iron core material or a high-performance magnetic shielding material. It is useful as a.

Claims (5)

[Claims] (1) In weight%, C: 0.004% or less, Si: 0.5
% or less, Mn: 0.50% or less, P: 0.015% or less, S: 0.01% or less, sol. Al: 0.5-2.0
%, N: 0.005% or less, Oxygen: 0.005% or less,
A steel slab or cast slab with a composition consisting of the balance Fe and unavoidable impurities is heated to 700°C or more and 1300°C or less, and then heated to 700°C.
By completing hot working at a temperature above and finally annealing at 900 to 1300°C, the coercive force is 0.
．． 4Oe or less, magnetic flux density 10000 at 0.5Oe
A method for producing a soft magnetic steel material, the method comprising obtaining a soft magnetic steel material having a magnetic flux of G or more. (2) In weight%, C: 0.004% or less, Si: 0.1
% or less, Mn: 0.15% or less, P: 0.015% or less, S: 0.01% or less, sol. Al: 0.5-2.0
%, N: 0.005% or less, Oxygen: 0.005% or less,
A steel slab or cast slab with a composition consisting of the balance Fe and unavoidable impurities is heated to 700°C or more and 1300°C or less, and then heated to 700°C.
By completing hot working at a temperature above and finally annealing at 1000 to 1300°C, the coercive force is 0.4 Oe or less and the magnetic flux density is 1000 at 0.5 Oe.
A method for producing a soft magnetic steel material, the method comprising obtaining a soft magnetic steel material having 0G or more. (3) A method for manufacturing a soft magnetic steel material according to claim (1) or (2), characterized in that C+N is 0.007% or less in weight%. (4) In weight%, C: 0.004% or less, Si: 0.5
% or less, Mn: 0.50% or less, P: 0.015% or less, S: 0.01% or less, sol. Al: 0.5-2.0
%, N: 0.012% or less, Oxygen: 0.005% or less,
A steel slab or cast slab with a composition consisting of Ti: 0.005 to 1.0%, the balance Fe and unavoidable impurities is heated at 700°C or higher13
By heating to 00℃ or less, finishing hot working at a temperature of 700℃ or higher, and finally annealing at 900 to 1300℃, a coercive force of 0.4Oe or less and a magnetic flux density of 10,000G or more at 0.5Oe can be achieved. A method for producing a soft magnetic steel material, the method comprising obtaining a soft magnetic steel material having the following properties. (5) A method for manufacturing a soft magnetic steel material according to claim (4), characterized in that C+N is 0.014% or less in weight%.