JP2556599B2 - Method for manufacturing corrosion-resistant soft magnetic steel sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a soft magnetic steel sheet having excellent corrosion resistance.

(Prior Art) Although it has been attempted to apply a ferritic stainless steel plate as a corrosion-resistant soft magnetic steel material, the soft magnetic properties of such a material are significantly inferior to those of a silicon steel plate. Therefore, for the purpose of improving the magnetic characteristics, for example, Japanese Patent Publication Sho 39
In the publication No. 816, a predetermined amount of C, Si, Mn, Ni, Fe-Cr alloy,
Although addition of Al and the like has been tried, the maximum magnetic permeability was at most 2850, but the coercive force was 0.9 Oersted in the best data.

For the same purpose, in Japanese Patent Publication No. 39-20644, in order to improve the magnetic characteristics by adding Si or Ti to the Fe-Cr alloy to try to remove oxygen in the alloy, It was difficult to stably obtain high magnetic permeability and low coercive force. That is, in the method of adding such a large number of components, inclusions and precipitates are likely to be generated due to the mixed impurities, and rather soft magnetic characteristics are deteriorated.

On the other hand, in Japanese Examined Patent Publication Nos. 50-37135 and 54-14569, etc., the C and N contents in the steel are controlled by annealing at high temperature for a long time, and in the latter, magnetic properties are imparted by further giving directionality. Although the properties are improved, there is a disadvantage that the manufacturing cost becomes high because the process becomes extremely complicated and the final annealing requires a long time.

(Problems to be Solved by the Invention) Without adding many components as described above, and without requiring complicated steps, stable maximum magnetic permeability of 10,000 or more and coercive force of 0.3 in industrial production. 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 of Oersted or lower.

(Means for Solving the Problem) The inventors have found that the soft magnetic properties of the Fe—Cr alloy steel sheet depend on the texture after finish annealing, and appropriately control the sheet temperature in the cooling process subsequent to hot rolling. The present invention has been completed by finding that it is possible to obtain a texture suitable for improving magnetic properties by carrying out the method.

That is, the present invention provides a Fe-Cr alloy steel containing C: 0.01 wt% (hereinafter simply referred to as%) or less and Cr: 11.0 to 18.0%, and further containing Si and Al in the range of Si + Al: 5.0 or less. As a raw material, the hot rolled sheet temperature is between 800 ℃ and 600 ℃ during the stage of hot rolling this material and the subsequent cooling process to room temperature.
During a cooling rate of 800 ° C / min or less, and then a single cold rolling to obtain the final plate thickness with a reduction ratio of 40 ~
Within the range of 85%, a step of performing cold rolling once or twice or more with intermediate annealing sandwiched, and then 800 times of finish annealing.
The method for producing a corrosion-resistant soft magnetic steel sheet is characterized by comprising a step of applying in a temperature range of up to 1200 ° C.

(Operation) Hereinafter, the operation of the above configuration will be specifically described.

In the present invention, the Fe-Cr alloy steel material is subjected to hot rolling, and subsequently the plate temperature is 800 ° C in the cooling process to room temperature.
It is assumed that cooling is performed at a cooling rate of 800 ° C / min or less from 1 to 600 ° C. The reason for this is as follows.

The soft magnetic properties of Fe-Cr alloy steel sheet after cold rolling / annealing strongly depend on the texture, and the {110} plane is parallel to the rolling plane and the <001> direction is parallel to the rolling direction. Soft magnetic properties can be improved by developing {110} <001> texture called Goss orientation. According to the experimental facts on which the present invention is based, the development of the Goss orientation after finish annealing of the Fe-Cr alloy steel sheet depends on the texture of the hot-pressed plate. That is, {110} <0 near the surface of the hot rolled sheet
When 01> texture occurs, {110} <001> texture is likely to appear in the sheet after cold rolling / annealing, resulting in good orientation and improved magnetic properties. Was discovered. So in hot rolled sheet {110} 〈00
1> As a result of various studies to develop a texture, after the hot rolling, {110} in the temperature range of 800-600 ℃
It was found that the <001> texture developed. It is considered that this is because the crystal grains having the {110} <001> orientation generated by hot rolling grow during the recrystallization process. Therefore, it is advantageous for the magnetic properties to maintain this temperature range for a sufficient time after the hot rolling is completed, but under normal cooling conditions, after the hot rolling, the temperature range of 800 to 600 ° C is 800 ° C / min or less. This object can be achieved by cooling at a cooling rate of preferably 600 ° C./min or less. When the cooling rate exceeds 800 ° C./min, the {110} <001> texture is insufficiently developed, and it becomes difficult to improve the magnetic properties. Although the cooling rate outside the above temperature range may be arbitrary, it is not necessary to reduce the cooling rate at a temperature of 600 ° C. or lower. The hot rolling end temperature may be any temperature of 800 ° C. or higher, but the lower the hot rolling end temperature is, the better the uniformity in the plate surface of the texture of the plate after cold rolling / annealing is, The magnetic characteristics can be improved. According to the method described above, it is possible to obtain a good hot-rolled sheet texture without having to heat-treat the hot-rolled sheet after hot rolling.

Next, regarding the cold rolling / annealing process, in the present invention, one cold rolling to obtain the final plate thickness is set within the range of the rolling reduction of 40 to 85%, and one or two or more cold rollings between which the intermediate annealing is performed. It is stipulated that the final annealing should be performed in the temperature range of 800 to 1200 ° C. The reason is as follows.

First, a single cold rolling reduction, which is the final plate thickness, has a strong influence on the magnetic properties through the texture of the finish annealed plate. That is, when the final cold rolling reduction of one time is set to 40 to 85% with an optimal value of around 60%, after finishing annealing {11
0} <001> texture is highly integrated, resulting in good soft magnetic properties after finish annealing. The cold rolling reduction rate is 40
% Or more than 85%, the degree of integration of {110} <001> texture after finish annealing becomes low, and it is difficult to obtain the maximum magnetic permeability of 10000 or more soft magnetic properties. Becomes Therefore 40 ~ 85% depending on manufacturing conditions
The cold rolling reduction rate was selected within the range. The number of times of cold rolling may be one time or two or more times with intermediate annealing sandwiched, as long as the above-described cold rolling reduction ratio is satisfied.

Also, finish annealing has the effect of promoting the growth of crystal grains and improving the soft magnetic characteristics, but when the annealing temperature is less than 800 ° C, grain growth slows down and good magnetic properties are obtained even after long annealing. The characteristics are hopeless. On the other hand, the annealing temperature is 1200 ℃
If it exceeds, the effect of improving the magnetic properties due to the increase in the annealing temperature is small, which is economically disadvantageous. For this reason, the finish annealing temperature was set in the range of 800 to 1200 ° C. The intermediate and finish annealing are preferably performed in a non-oxidizing and non-carbonizing atmosphere.

Next, the reasons for defining the chemical composition of the steel material will be described below.

C: 0.01% or less C is a component that deteriorates magnetic properties and corrosion resistance, and
If it exceeds 01%, both properties are significantly deteriorated, and annealing for a long time at high temperature is required for decarburization, so it was made 0.01% or less.

Cr: 11.0 to 18.0% Cr is a component added to Fe to improve corrosion resistance,
Although it is effective in improving soft magnetism as a ferrite-forming component, if it is less than 11.0%, the resistance to oxidative corrosion becomes weak, while if it exceeds 18.0%, the corrosion resistance in general acidic atmosphere deteriorates, and the saturation magnetic flux density The decrease is remarkable. For the above reasons, the Cr content is set to the range of 11.0 to 18.0%.

Si + Al: 5.0% or less Since Si and Al are ferrite-forming components, they are effective not only for suppressing γ-phase precipitation and improving soft magnetism, but also for increasing electrical resistance. Even when Cr is contained by 11.0% or more, soft magnetism can be improved by further adding Si and Al, but when the total content of both exceeds 5.0%, not only the saturation magnetic flux density is lowered but also the heat flux is reduced. Since the hot workability is remarkably impaired, it was set to 5.0% or less. The lower limit is not particularly limited, but is 1 in total from the viewpoint of improving soft magnetism.
% Or more, more preferably 1.5% or more. Both Si and Al are desirably added in the range of 0.5 to 3.5%.

In addition to the above components, addition of Mn or the like which improves workability to such an extent that magnetic properties and corrosion resistance are not affected does not impair the effects of the present invention.

As described above, Mn is a component that improves hot and cold workability, but if it is less than 0.05%, the workability improving effect is poor, while if it exceeds 2.0%, the saturation magnetic flux density is significantly increased. Since it has the disadvantage of lowering it 0.05-2.
It is preferably contained in the range of 0%.

(Example) Example 1 C: 0.005%, Cr: 15.0%, Si: 0.8%, containing Al: 1.2%,
The rest is an alloy steel slab consisting essentially of Fe, heated to 1300 ° C, and hot-rolled to final hot rolling temperatures of 850 ° C, 800 ° C, and 750 ° C, respectively, and immediately after making the plate thickness about 3 mm. Controlled cooling in Ar, Ar to 600 ° C. at various cooling rates and then to room temperature in a nitrogen stream. The hot-rolled sheet that has been subjected to such treatment is pickled, and then subjected to intermediate cold rolling to obtain a sheet thickness of 0.
After making it 875 mm, it is annealed in Ar at 900 ℃ for 2 minutes,
Furthermore, the final cold rolling with a reduction rate of 60% is applied and the plate thickness is 0.35 mm.
And Epstein test pieces with a width of 30 mm and a length of 280 mm were sheared and sampled from these cold-rolled sheets so that the longitudinal direction was parallel to the rolling direction, and finish annealing was performed in Ar at 1050 ° C. for 20 minutes. The results of measuring the maximum magnetic permeability of this test piece with a DC magnetization measuring device are shown as the hot rolling end temperature and 600 ° C after the hot rolling.
1 as a function of cooling rate up to.

From the figure, it is clear that when the temperature range from 800 ℃ to 600 ℃ is cooled at a cooling rate of 800 ℃ / min or less after hot rolling, the maximum magnetic permeability exceeds 10,000 and good soft magnetic characteristics are obtained. Is.

Example 2 100 kg ingots having various component compositions shown in Table 1 were prepared.

The ingot was hot-sheared into several sheets as a sheet bar having a plate thickness of 30 mm and air-cooled. 1250 ° C for each ingredient
Re-heated, and hot-rolled to a hot rolling finish temperature of 830 ° C to a plate thickness of 2.0 mm, cooled to 600 ° C at a cooling rate of 680 ° C / min, and then air-cooled to obtain a hot-rolled sheet. . After pickling these hot-rolled sheets, they were cold-rolled to a sheet thickness of 1.0 mm. An Epstein test piece having a width of 30 mm and a length of 280 mm was shear-sampled from the thus obtained cold-rolled sheet so that the longitudinal direction was parallel to the rolling direction, and annealed in hydrogen at 850 ° C. for 1 hour.
Table 1 also shows the results of measuring the maximum magnetic permeability and coercive force of these test pieces by a DC magnetization measuring device and the results of investigating the corrosion resistance by a salt spray test at 35 ° C. for 16 hours.
The results of the corrosion resistance test are shown as those in which no rust is visually observed (○), those with light rust (△), and those rusted over an area of 10% or more (×). Steel No. 9
However, since the cracks occurred during the ingot slabbing, the subsequent treatment was impossible.

From the table, it is clear that the conforming example according to the present invention has a maximum magnetic permeability of 10,000 or more and a coercive force of 0.3 Oe or less and also has good corrosion resistance.

Example 3 Steel No. among the sheet bars produced in Example 2
After reheating 1 each of 2, 4 and 7 to 1300 ° C, hot rolling to a hot rolling finish temperature of 860 ° C to give a plate thickness of 4 mm,
After cooling to 600 ℃ at a cooling rate of 160 ℃ / min,
Air cooled. After pickling these hot-rolled sheets, the sheet thickness is 0.5
Cold rolling was performed to ˜3.5 mm, and then intermediate annealing was performed at 950 ° C. for 2 minutes in a hydrogen atmosphere. After that, cold rolling was performed at various reduction ratios up to a plate thickness of 0.35 mm, and the width of each plate obtained
Epstein test pieces of 30 mm and 280 mm in length are sheared and sampled so that the longitudinal direction is parallel to the rolling direction, and 750 to 1250
Final annealing was performed at 30 ° C. for 30 minutes in a hydrogen atmosphere. The final magnetic permeability of these test pieces was measured by a direct current magnetometer and the corrosion resistance was investigated by a salt spray test at 35 ° C for 16 hours. Of these, Table 2 shows the maximum magnetic permeability and the corrosion resistance test results of the test pieces whose final annealing temperature was 850 ° C.

Also, the intermediate cold-rolled finish plate thickness is 0.875 mm (final reduction of 60%).
2 shows the maximum magnetic permeability of the test piece as a function of the final annealing temperature. The corrosion resistance was evaluated according to the same criteria as in Example 2.

According to this example, good soft magnetic properties are obtained when the final cold rolling reduction of the final plate thickness is in the range of 40 to 85%, and the final annealing temperature is good in the range of 800 to 1200 ° C. It is clear that excellent magnetic properties can be obtained.

(Effect of the Invention) According to the method of the present invention, it is possible to economically manufacture a corrosion-resistant soft magnetic steel sheet that has both excellent soft magnetic characteristics and corrosion resistance, which is a great industrial advantage.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the maximum magnetic permeability, the hot rolling finish temperature and the cooling rate, and FIG. 2 is a graph showing the relationship between the maximum magnetic permeability and the final annealing temperature.

Claims (1)

(57) [Claims] 1. A Fe-Cr alloy steel containing C: 0.01 wt% or less and Cr: 11.0 to 18.0 wt% and further containing Si and Al in the range of Si + Al: 50 wt% or less. The temperature of hot-rolled sheet is 800 ℃ during the stage of hot rolling
To 600 ° C at a cooling rate of 800 ° C / min or less, and then one cold rolling to obtain the final plate thickness with a reduction rate of 40 to 85%.
In the range of 1), the corrosion resistance softening is characterized by comprising a step of performing cold rolling once or two times or more with an intervening annealing, and then performing a step of finish annealing in a temperature range of 800 to 1200 ° C. Method for manufacturing magnetic steel sheet.