JP2556571B2 - Method for manufacturing corrosion-resistant soft magnetic steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is particularly concerned with soft magnetic steel sheets having remarkably excellent corrosion resistance, such as motor cores for OA equipment, in-vehicle motor cores, underwater motor cores, etc. The present invention relates to a method for manufacturing a soft magnetic steel sheet suitable for use.

(Prior Art) As a corrosion-resistant soft magnetic material, ferritic stainless steel sheets have been conventionally known, but the soft magnetic properties of such materials are significantly inferior to those of silicon steel. Therefore,
For the purpose of improving magnetic properties, Japanese Patent Publication No. 39-816 discloses that F
It has been attempted to add a predetermined amount of C, Si, Mn, Ni, Al, etc. to the e-Cr alloy, but the maximum magnetic permeability μmax is at most 2 as the magnetic characteristics.
850 and coercive force of 0.9 at best (Oe)
It was nothing more than

Further, for the same purpose, in JP-B-39-20644, in order to improve the magnetic characteristics by adding Si or Ti to the Fe-Cr alloy and removing oxygen in the alloy,
It is difficult to stably obtain high permeability and low coercive force. In other words, in the method in which many elements are added, the mixed impurities rather serve as nuclei to generate inclusions or precipitates. Inspire.

On the other hand, in Japanese Patent Publication No. 50-37135 and Japanese Patent Publication No. 54-14569, etc., the C and N contents in steel are controlled by annealing at high temperature for a long time, and in the latter example, magnetic properties are provided by further imparting directionality. However, it is uneconomical because the process is extremely complicated and especially the final annealing requires a long time.

(Problems to be Solved by the Invention) The present invention is stable in industrial production by optimizing the cold rolling and annealing steps without adding many elements as in the above-mentioned conventional technique. It is an object of the present invention to propose a method for producing a corrosion-resistant soft magnetic steel sheet having excellent soft magnetic properties such as a maximum magnetic permeability of 10,000 or more and a coercive force of 0.3 oersted or less, and also excellent in corrosion resistance.

(Means for Solving the Problems) The inventors have added Si and Al, which are effective in improving the soft magnetic properties in Fe-Cr alloy steel, and added S, Mn.
The present invention has been completed by finding that the soft magnetic characteristics can be improved by controlling the amount and further optimizing the cold rolling and the annealing process after the hot rolling.

That is, the present invention includes C: 0.01 wt% or less, Cr: 11.0 to 18.0 wt% Si + Al: 5.0 wt% or less, and further, Mn and S are S: 0.005 wt% or less and satisfy Mn / S ≧ 100. The steel material contained in the range of
Corrosion resistance softening characterized by performing cold rolling more than once at a final reduction of 40 to 85% and then performing final annealing in two stages of a temperature range of 600 to 800 ° C and a temperature range of 850 to 1200 ° C. It is a method of manufacturing a magnetic steel sheet.

 The present invention will be specifically described below.

First, the experimental results which are the basis of the present invention will be described.

That is, the crystal grain size after the final annealing strongly depends on the S content and the Mn / S content ratio, the crystal grain size increases as the S content decreases, and the crystal grain size increases with the Mn / S ratio for the same S content. The diameter increases and the soft magnetism becomes good.

Cr: 15.0wt% (hereinafter simply referred to as%), Si: 2.0%, Al: 1.
5%, S: 0.001-0.010%, Mn: 0.4-0.5% and C: 0.005
% Alloyed slabs with the balance being essentially Fe, hot-rolled, cold-rolled twice to give a final reduction of 60%, then in H ₂ from 600 ° C 100 ° C / min
Fig. 1 shows the results of examining the relationship between the average crystal grain size and the S content of a thin steel sheet having a thickness of 0.35 mm obtained by performing a final annealing at 1000 ° C for 2 minutes after heating up to 1000 ° C at . From the figure,
It is clear that when the S content is 0.005% or less, the crystal grain size rapidly increases.

Also, Cr: 13.5%, Si: 0.9%, Al: 1.8%, S: 0.002-0.
After hot rolling an alloy steel slab containing 005%, Mn: 0.1 to 0.8% and C: 0.003 to 0.006% and the balance being substantially Fe,
Two cold rolling steps were performed to achieve a final reduction of 60%, and then
2 hours at 660 ° C in H ₂ and then immediately at 500 ° C / min
Figure 2 shows the results of an examination of the relationship between the maximum magnetic permeability and the Mn / S ratio of a thin steel sheet with a thickness of 0.5 mm, which was obtained by performing a final anneal of raising the temperature to 1000 ° C and holding it at 1000 ° C for 2 minutes. . From the figure,
In this component system, it is clear that when Mn / S is 100 or more, the maximum magnetic permeability of 10,000 or more is obtained.

Further, various studies were conducted on the optimization of the cold rolling and annealing steps performed on the hot-rolled sheet of Fe-Cr alloy whose components were adjusted as described above.

Cr: 15.0%, Al: 1.0%, Si: 1.2%, S: 0.004%, Mn: 0.6
% And C: 0.005%, the balance being substantially Fe, the alloy steel slab was hot-rolled, then cold-rolled and then finally annealed to obtain an X-ray of a thin steel sheet with a thickness of 0.35 mm. (200)
A reflection pole figure is shown in FIG. Here, the final reduction rate of cold rolling is 30 to 90%, and the final annealing is 750 ° C in H ₂ atmosphere.
After 2 minutes, 1050 ° C. was continuously performed for 3 minutes. As is clear from the figure, the final reduction rate of 60% was obtained for the above steel types.
When the degree is adjusted, the {110} plane is the rolling plane <001>
The so-called Goss orientation in which the directions are parallel to the rolling direction appears most strongly, and a unidirectional texture that exhibits excellent soft magnetism when magnetized in the rolling direction is obtained.

In addition to the grain growth, the final annealing is performed in the temperature range of the first stage for the cold-rolled sheet having the above-mentioned preferable composition.
It has been found that it is effective for texture control to apply the second temperature range from 850 to 1200 ° C at 600 to 800 ° C. That is, in the first stage final annealing, the crystal grains having the above Goss orientation are selectively recrystallized, and then the second stage high temperature final annealing is performed to grow the crystal grains, thereby obtaining a highly unidirectional texture. It is possible to obtain

Cr: 15.0%, Si: 1.5%, Al: 0.8%, Mn: 0.45%, C: 0.00
After hot rolling an alloy steel slab containing 6% and S: 0.003%, or 0.022% and the balance being essentially Fe,
The X-ray (200) reflection peak intensity corresponding to the Goss orientation of a 0.35 mm-thick steel sheet obtained by performing cold rolling and then final annealing was calculated as a function of the annealing temperature in the second stage final annealing.
It is shown in FIG. Here, the final reduction rate of cold rolling is 60%, the annealing time is 4 minutes for the first stage and 2 minutes for the second stage, and
Immediately after completion of the final annealing of the second stage, the temperature was raised to the final annealing temperature of the second stage at a heating rate of 500 ° C./min. The second stage annealing was performed in an Ar atmosphere.

In the figure, (A) is S: 0.003%, the first stage annealing temperature is 720 ° C, (B) is S: 0.003%, the first stage annealing temperature is the same as the second stage annealing temperature, and the temperature is A When the temperature is the same as the second-stage annealing temperature in A., the temperature was raised after the first-stage annealing in A and held for the same time as the time until the second-stage annealing was completed, (C) was S: 0.022%, The one-stage annealing temperature of 720 ° C is shown respectively. As is clear from the figure, in the component system in which S is reduced, the integration degree of the Goss orientation is increased and the higher unidirectional texture is obtained when the first stage annealing temperature is maintained at 720 ° C. I understand.

By appropriately controlling the components and the cold rolling and annealing steps in this manner, excellent soft magnetism can be obtained.

(Operation) The reason why the component composition is limited to the above range in the present invention will be described below.

C: 0.01% or less C is an element that deteriorates magnetic properties and corrosion resistance.
%, Both properties are significantly deteriorated, and decarburization requires annealing at high temperature for a long time, so 0.01% or less.

Cr: 11.0 to 18.0% Cr is an element that imparts corrosion resistance when added to Fe.
If the content is less than%, the resistance to oxidative corrosion becomes low, while if it exceeds 18%, the corrosion resistance in an acidic atmosphere deteriorates. Cr is a ferrite-forming element and is effective in improving soft magnetism, but when the content exceeds 18%, the saturation magnetic flux density is significantly reduced. Therefore, the Cr content is set to 11 to 18%.

Si + Al: 5.0% or less Si and Al are ferrite-forming elements, and have the effect of not only improving soft magnetism but also increasing electric resistance. Cr
Even if the content is 11% or more, addition of Si and Al can suppress γ-phase precipitation and improve soft magnetism, but if it is too small, the effect of improving electric resistance and magnetic permeability is poor, and if it is too large, saturation flux Not only does it reduce the density, but it also becomes brittle.

That is, if the total amount of both is 5% or more, not only the addition effect is low but also the hot workability is remarkably impaired, so it is set to 5% or less. The lower limit is 1% or more, more preferably 1.5% or more, from the viewpoint of improving magnetism. Both Si and Al are preferably added in the range of 0.5 to 3.5%.

S: 0.005% or less When S is distributed in the steel as fine precipitates of FeS, CrS or MnS, it inhibits grain growth and deteriorates soft magnetism.
The presence of FeS and CrS in steel impairs the hot and cold workability and causes surface defects and the like. That is, when the S content exceeds 0.005%, FeS, CrS, and MnS single or complex fine compounds are dispersed and precipitated in the steel, which inhibits grain growth and deteriorates soft magnetism as shown in FIG. To let
The S content was 0.005% or less.

Mn / S ≧ 100 Mn is an element that suppresses the precipitation of FeS and CrS in steel and precipitates MnS.If the Mn / S ratio is less than 100, FeS and CrS precipitate and the hot and cold Workability is impaired. On the other hand, the Mn / S ratio is 10
When it is 0 or more, most of S is precipitated as MnS, so that the workability is improved, and the grain size is not hindered due to the coarsening of the precipitate, as shown in FIG. Good soft magnetism can be obtained. For this reason
It was decided to add Mn having an Mn / S content ratio of 100 or more. Since the saturation magnetic flux density decreases as the Mn content increases, it is desirable to add 1.0% or less.

 Next, the reasons for defining the manufacturing method will be described.

Final rolling reduction in cold rolling: 40-85% As shown in Fig. 3, the degree of integration of Goss orientation is 60
Since the peak is around 40% and it becomes high in the range of 40 to 85%,
When the rolling reduction is within this range, the directionality is improved and excellent soft magnetism can be obtained. Therefore, depending on the process conditions 40 ~
The reduction rate was selected within the range of 85%.

Final annealing: 1st stage 600-800 ° C, 2nd stage 850-1200 ° C Regarding the final annealing conditions, 1st stage 600-800 ° C, 2nd stage
The temperature shall be in the range of 850-1200 ℃. The annealing atmosphere is not particularly limited, but it is desirable to use a non-oxidizing atmosphere in order to remove oxide scale easily or not.

As mentioned above, the 1st-stage annealing aims to preferentially recrystallize the Goss orientation from the rolling structure, and
If it is less than 1, it takes a very long time to recrystallize itself, which is disadvantageous. On the other hand, if it exceeds 800 ° C., recrystallization is not selective with respect to the Goss orientation and it is difficult to effectively give directionality. Limited to the range of 600-800 ℃. Next, regarding the second stage annealing, in the component system according to the present invention, it is possible to raise the annealing temperature to obtain good soft magnetism in a short time, but when it exceeds 1200 ° C, the soft magnetism due to the increase of the annealing temperature is obtained. The improvement effect is small and therefore economically disadvantageous. On the other hand, if the temperature is less than 850 ° C., grain growth is slow and it is not possible to obtain good soft magnetism even after annealing for a long time. Therefore, the second stage annealing temperature was set in the range of 850 to 1200 ° C.

Although the annealing time is not particularly specified, good results can be obtained in both the intermediate annealing and the final annealing (first step, second step) with a relatively short annealing time of 30 seconds to 10 minutes. The heat pattern of the final two-stage annealing was maintained at the temperature of the first stage, cooled to an arbitrary temperature of room temperature or higher, then reheated and maintained at the temperature of the second stage, after being maintained at the temperature of the first stage. , Raise the temperature to the second
Other than the normal pattern such as keeping the temperature at 600-800 ℃
It is also possible to raise the temperature for a certain period of time or more and then keep the temperature in the second stage. At this time, the holding time in
The temperature rise time at ˜800 ° C. is preferably 30 seconds to 10 minutes, but is not limited thereto.

(Example) Example 1 Various alloy steels having the composition shown in Table 1 were made into 50 kg ingots by a vacuum melting method, and the surface was ground to give 1300
It was heated to ℃ and immediately hot-rolled into a sheet bar having a thickness of 25 mm. Then after grinding the surface of this sheet bar
It was heated to 1250 ° C and hot-rolled to obtain a hot-rolled sheet having a thickness of 3.0 mm. After pickling this hot-rolled sheet, it was cold-rolled for the first time to make a sheet with a thickness of 1.2 mm, subjected to intermediate annealing at 950 ° C for 3 minutes in an Ar atmosphere, and then cold-rolled for 2 hours. Thickness 0.
It was a cold rolled sheet of 5 mm. A 30 mm × 280 mm Epstein test piece was cut out from this cold-rolled sheet so that its long side was parallel to the rolling direction, kept at 760 ° C for 4 minutes in an Ar atmosphere, once air-cooled to room temperature and then raised again to 1050 Two-stage annealing was performed at 2 ° C for 2 minutes. In addition, a thickness of 1.5 mm on a part of the seat bar
Hot-rolled, pickled, and cold-rolled to give a cold-rolled sheet with a thickness of 0.65 mm. Epstein test pieces are cut from this with the long side parallel to the rolling direction, and then placed in an Ar atmosphere. Temperature rises from 600 ℃ to 800 ℃ at 50 ℃ / min at 800 ℃
To 1050 ° C. at a temperature of 500 ° C./min and a final two-stage annealing in which the temperature was maintained at 1050 ° C. for 2 minutes. Table 2 shows the results of examining the magnetic properties and corrosion resistance of each test piece subjected to these treatments.

The maximum magnetic permeability and the coercive force (Bm = 1.0T) were measured using a DC magnetization measuring device. In addition, the corrosion resistance was evaluated by the following criteria after performing a 24-hour salt spray test according to JIS Z2371.

◯: Almost no rust is visually observed, Δ: Light distribution of spot rust, ×: Rust of 10% or more in area ratio, Example 2 Various alloy steels having the composition shown in Table 3 were made into 500 kg ingots by the vacuum melting method, heated to 1300 ° C. after surface grinding, subjected to slab rolling and hot rolling, and then had a thickness of 2.5 mm.
It was wound as a hot rolled coil. 950 ℃ 3 in this hot rolled coil
Annealing was performed for 0 seconds, pickled, and then cut, and then a reduction rate was changed by sandwiching an intermediate annealing at 950 ° C. for 2 minutes in an H ₂ atmosphere.
It was cold-rolled once to give a final plate thickness of 0.35 mm. A 30 mm × 280 mm Epstein test piece was sampled from this cold-rolled sheet with its long side parallel to the rolling direction and placed in an H ₂ atmosphere.
Hold at 640 ℃ for 1 minute and immediately raise the temperature at 500 ℃ / min to 700-1
A final two-stage annealing was carried out at 250 ° C. for 4 minutes. The magnetic properties and corrosion resistance of the test pieces subjected to this treatment were evaluated in the same manner as in Example 1. Fig. 5 shows the final cold rolling reduction of 30 to 80% and the maximum magnetic permeability of the test piece subjected to the final second stage annealing temperature of 1050 ° C. Fig. 6 shows the final cold rolling reduction of 60%. %, And the maximum magnetic permeability of the test piece subjected to the treatment of the final second stage annealing temperature of 700 to 1250 ° C.
Also, the final cold rolling reduction is 60%, the final second stage annealing temperature is 1050 ° C.
A corrosion resistance test was performed on the test piece that was subjected to the treatment. The results are also shown in Table 3.

(Effects of the Invention) According to the present invention, by optimizing the alloy components and the cold rolling / annealing process, it is possible to impart directionality to the corrosion-resistant soft magnetic steel sheet and obtain excellent magnetic properties, and it is economical. The industrial advantage is also great because it will provide an advantageous method.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the average particle size and the S content, FIG. 2 is a graph showing the relationship between the maximum magnetic permeability and the Mn / S content ratio, and FIG. 3 is the X-ray (200) reflection pole figure, 4 is a graph showing the relationship between the X-ray (200) reflection peak intensity and the final second stage annealing temperature, FIG. 5 is a graph showing the relationship between the maximum magnetic permeability and the final cold rolling reduction, and FIG. 6 is It is a graph which shows the relationship between the maximum magnetic permeability and the maximum second stage annealing temperature.

Claims (1)

(57) [Claims] 1. C: 0.01 wt% or less, Cr: 11.0 to 18.0 wt% Si + Al: 5.0 wt% or less, and Mn and S are S: 0.005 wt% or less and satisfy Mn / S ≧ 100. The steel material contained in the range of
Corrosion resistance softening characterized by performing cold rolling more than once at a final reduction of 40 to 85% and then performing final annealing in two stages of a temperature range of 600 to 800 ° C and a temperature range of 850 to 1200 ° C. Method for manufacturing magnetic steel sheet.