JPH04323321A - Production of nonoriented silicon steel sheet excellent in blankability - Google Patents

Abstract

PURPOSE:To stably obtain a ferrite hardness of Hv1 135-160, accordingly to obtain superior blankability, and also to improve magnetic properties to a greater extent by means of subsequent stress relief annealing. CONSTITUTION:At the time of producing a nonoriented silicon steel sheet, 0.015-0.050% C, <=0.3% Si, 0.1-1.0% Mn, and 0.1-0.6% Al are incorporated into raw material. Further, at the time of cooling in recrystallization annealing, the steel is cooled down to 700 deg.C at <=10 deg.C/s cooling rate, successively cooled down to ordinary temp. at 10-50 deg.C/s cooling rate, aged at 200-450 deg.C for 5-30sec, and further aged at 10-55 deg.C.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention has excellent punching workability,
The present invention also relates to a method for producing a non-oriented electrical steel sheet that has excellent magnetic properties.

0002

[Prior Art] Among non-oriented electrical steel sheets, those with a low Si content exhibit high magnetic permeability although their iron loss value is inferior, and are inexpensive, so they are used in small motors and EI cores of household electrical appliances. It is widely used in small transformers such as.

By the way, there are two types of electrical steel sheets of this type: fully processed materials, which are punched into a predetermined shape by customers and then used as is, and semi-processed materials, which are subjected to strain relief annealing after punching to obtain the required level of magnetism. Separated. It goes without saying that excellent magnetism is required in any case, but since almost all of them are continuously punched out using a punching machine, excellent continuous punching performance is also an extremely important requirement. It is said that Furthermore, in order to rationalize and save labor in the core production process at customers, composite progressive molds using an automatic locking method, in which a certain number of sheets are stacked in a progressive press during continuous punching and taken out in the core state, are being used. As a result, the ability to obtain strong caulking strength and smooth rotor skew has become an important requirement.

[0004] In order to impart good punchability to an electromagnetic steel sheet, it is said to be effective to adjust its hardness within an appropriate range. Regarding this hardness adjustment, various studies have been conducted on semi-processed materials, but there is almost no research on fully processed materials. The reason for this is that machining strain remains in the electromagnetic steel sheet and inclusions in the steel increase, making it impossible to obtain desired magnetism.

[0005] However, as rationalization and labor saving have progressed as seen today, even if the magnetic properties are sacrificed to some extent,
Excellent punching workability is sometimes required. On the other hand, measures have been taken to compensate for the sacrificed magnetic properties, such as applying strain relief annealing after punching, or making slight changes to the design of small motors and small transformers. Regarding full-process materials, there are techniques disclosed in Japanese Patent Publication No. 49-6456 and Japanese Patent Application Laid-open No. 190521/1983, which emphasize hardness for punching workability.

[0006] Among the above proposals,
The publication discloses a method for obtaining a hardness range of 100 to 120 at HV5. Also, JP-A-60-19052
No. 1 discloses a method of minimizing aging deterioration of magnetism by performing over-aging treatment intended to reduce solid solution C in steel, and the hardness of the base steel shown in the example is Hv. So 95
~129. However, in order to obtain a magnetic steel sheet with good punchability and automatic locking property, and good rotor skew property, HV (1kg) is 135
A base metal hardness of ~160 is required, and the above-mentioned prior art cannot satisfy this property.

That is, when the hardness of the base material is low, sagging is likely to occur on the punched cut surface during continuous punching, resulting in errors in the dimensions of the product after punching. One possible solution to this problem is to reduce the clearance of the punching die, but this method reduces the life of the die. Here, the hardness of the base metal that does not cause errors due to sagging in product dimensions with appropriate mold clearance is HV1 ≧ 135.
is desirable. Furthermore, the fact that there is little sagging makes it suitable for automatic crimping molds, resulting in an iron core with strong crimping strength. However, if the hardness of the base metal exceeds 160 at HV1, the damage to the mold will increase, so the hardness of the base metal should be
It is preferable that HV1≦160.

On the other hand, the rotor core is skewed to ensure smooth rotation of the motor. Regarding the skew of the self-locking core, the V-shaped protrusion is taken out of the mold in a half-closed state, and the skew is applied when the book is tightened using a processing press. At this time, if the base steel hardness is less than HV1:135, the V-shaped protrusion will be deformed and a sufficient skew angle will not be obtained.

[0009]

[Problems to be Solved by the Invention] As described above, in order to have excellent punching workability, automatic locking performance, and smooth skewing, it is important to set the base steel hardness to HV1 of 135 to 160. . This invention advantageously satisfies the above-mentioned demands, and optimizes the hardness of the base metal by adding innovations to the cooling treatment after recrystallization annealing, thereby improving punching workability, automatic locking performance, and skew performance. The purpose of the present invention is to propose an advantageous manufacturing method for a non-oriented electrical steel sheet, which can be further improved in magnetic properties by subsequent strain relief annealing.

0010

[Means for solving the problem] That is, this invention
: 0.015 to 0.050 wt% (hereinafter simply indicated as %), Si: 0.3% or less, Mn: 0.1 to 1.
0% and Al: 0.1 to 0.6%, after cold rolling, recrystallization annealing is performed at 750 to 950°C for 5 seconds to 5 minutes to obtain non-directional properties. In manufacturing electrical steel sheets, in the cooling process of the recrystallization annealing described above, the steel is cooled to 700°C at a cooling rate of 10°C/s or less, and then cooled to room temperature at a cooling rate of 10 to 50°C/s, and then cooled to 200°C. 5-3 at ~450℃
This is a method for manufacturing a non-oriented electrical steel sheet with excellent punching workability, which comprises performing an aging treatment for 0 seconds and further aging treatment at 10 to 55°C.

[0011] Further, in this invention, 200 to 450
The aging treatment at 5 to 30 seconds at 5°C may be performed continuously during the cooling process, or may also serve as a baking treatment for the insulating coating.

[0012] A series of cooling treatments and aging treatments according to the present invention are intended to precipitate fine carbides and improve the hardness of the base steel, and by such treatment, the hardness of the base steel is HV1:13.
5 to 160 can be obtained, and as a result, a non-oriented electrical steel sheet with excellent punching workability can be obtained. There is a concern that fine carbide precipitation may affect magnetic properties, but it is approximately 1%.
It was only a moderate degree of deterioration, and not something that should be considered a problem.

Furthermore, it has been found that by subjecting the material obtained according to the present invention to strain relief annealing, the magnetic properties are significantly improved. In other words, by applying strain relief annealing,
Not only punching workability but also magnetic properties are further improved.

[0014]

[Operation] Next, in this invention, the reason why the component composition of the material and the manufacturing conditions are limited as described above will be explained. C: 0.015 to 0.050% When the amount of C is less than 0.015%, the solid solution C in the steel is small and the amount of fine carbides is also small, so the hardness of the base steel H
V1:135 cannot be secured. On the other hand, the amount of C is 0.05
If it exceeds 0%, the carbide after aging becomes coarse and the hardness of the base metal becomes HV1:135 or less, so the C content was limited to a range of 0.015 to 0.050%.

Si: 0.3% or less Si is an element useful for improving magnetic properties, but since the present invention is directed to low-grade non-oriented electrical steel sheets, Si is not actively added. However, this does not prevent unavoidable contamination during the manufacturing process, especially at the deoxidizing stage, and with this in mind, the content was limited to 0.3% or less.

[0016] Mn: 0.1 to 1.0% Mn is 0
．． If it is less than 1%, hot embrittlement will increase; on the other hand, 1.
If the Mn content exceeds 0%, the price of the steel sheet will increase, so the amount of Mn should be
It was limited to a range of 0.1 to 1.0%.

[0017] Al: 0.1 to 0.6% Al is 0
．． When it is less than 1%, fine precipitation of AlN occurs, resulting in significant deterioration of magnetic properties. The reason for this is thought to be that grain growth is suppressed by fine AlN. On the other hand, if the content exceeds 0.6%, not only will the effect of improving magnetic properties by adding Al decrease, but it will also be disadvantageous in terms of cost. Therefore, A
The l content was limited to a range of 0.1-0.6%. The improvement in magnetic properties due to the addition of Al is due to the reduction of inclusions, A
This is thought to be due to the detoxification of IN (coarsening of precipitates) and the increase in specific resistance. Furthermore, Al has a great influence on the precipitation behavior of carbides, and also contributes to improving hardness through aging treatment.

The essential components have been explained above, but in the present invention, P can also be added as an element to increase the hardness of the base steel. However, if the content exceeds 0.1%, cold workability deteriorates, so when adding 0.1%.
It needs to be 1% or less.

Next, the manufacturing conditions of this invention will be explained. Now, after cold rolling the hot-rolled steel sheet having the above-mentioned preferred composition, recrystallization annealing is performed at 750 to 950°C for 5 seconds to 5 minutes, and the cooling process is controlled during the cooling process. By increasing the solid solution C in the steel and precipitating fine carbides in the steel through subsequent aging treatment, the hardness of the base steel is increased to HV1:135 to 160.
This is to ensure that In the above treatment, the cooling rate from the recrystallization annealing temperature to 700°C needs to be 10°C/s or less. This is because when the cooling rate exceeds 10°C/s, the amount of solid solute C in the steel is fixed in a small state.
This is to increase the amount of solid solute C in the steel by setting the temperature to ℃/s or less. The temperature at which solid solution C reaches its maximum is around 723 °C, but in order to ensure industrially stable production, in this invention the lower limit of the temperature at which the above-mentioned controlled cooling should be performed is set at 700 °C.
And so.

[0020] Furthermore, after cooling to 700°C at a rate of 10°C/s or less and solid solute C in the steel increasing, it is necessary to increase the cooling rate to fix the solid solute C in the steel. Therefore, after that, it is cooled to room temperature at a relatively fast rate of 10 to 50° C./s. If the cooling rate is slower than 10°C/s, the solid solute C in the steel will precipitate at the grain boundaries and become cementite, reducing the solid solute C in the steel and not contributing to improving the hardness of the base steel through aging treatment. , a cooling rate of at least 10° C./s is required. On the other hand, in order to ensure a cooling rate exceeding 50°C/s, a large amount of capital investment is required, which increases costs.
The cooling rate from 00°C to room temperature was limited to a range of 10 to 50°C/s.

[0021] Next, the solid solution C fixed as described above is finely precipitated to improve the hardness of the base steel. Aging treatment is extremely important for such fine precipitation;
The following two-step process is required. i.e. 200～
A first stage treatment at 450°C for 5 to 30 seconds generates nuclei for fine carbide precipitation, and a second stage treatment at 10 to 55°C aims at fine carbide precipitation, increasing the hardness of the base steel to H.
V1: Secure 135 to 160.

[0022] In the first stage aging treatment, if the treatment temperature is lower than 200°C, nucleation cannot occur, while at 450°C
If it is higher, coarse carbides will be generated and will not contribute to improving the hardness of the base steel. Further, if the treatment time is shorter than 5 seconds, no nuclei are generated, whereas if the treatment time exceeds 30 seconds, coarse carbides are generated. Therefore, in this invention, the first stage of aging treatment is 200
The treatment was carried out for 5 to 30 seconds at a temperature range of -450°C.

Next, if the aging treatment temperature in the second stage is lower than 10°C, it will take a long time to ensure the hardness of the base steel of HV1:135 to 160, which is impractical, whereas if it exceeds 55°C, the Carbide is generated, and the hardness of the base steel is HV1:135.
It is not possible to secure more than that. Therefore, in this invention, the second
The stage aging treatment temperature was limited to a range of 10 to 55°C.

[0024] By carrying out the above two-stage aging treatment, a base steel hardness of HV1:135 to 160 can be ensured. Note that the first stage aging treatment may be performed during the cooling process after recrystallization annealing, and may also serve as a baking treatment for the insulating coating.

As the insulating coating, any of the conventionally known phosphate-based, (heavy)chromate-based, and mixed systems of (heavy)chromate and organic resin can be used. When these are the main ingredients, for example, in the case of a phosphate type, additives include nitrates, nitrites, boric acid, surfactants, chromic anhydride, (bi)chromates, and the like. In the case of (bi)chromate, organic reducing agents, boric acid, etc. are used. Furthermore, in the case of a (heavy) chromic acid-organic resin system, an organic reducing agent, boric acid, and a copolymer of one or more of acrylic, styrene, vinyl acetate, and beoba-based organic resins are used. In order to improve the heat resistance of the insulation coating, colloidal silica, colloidal alumina, titania, silica,
Fine powder of metal oxide such as alumina may also be blended.

[0026]

【Example】

Example 1 Hot rolled steel sheets (A to D) having the compositions shown in Table 1 were cold rolled and then recrystallized at 800°C for 1 minute, and during the cooling process up to 700°C for 5 °C/
s, followed by cooling to room temperature at a cooling rate of 25°C/s, followed by a first stage aging treatment at 350°C for 10 seconds, followed by a second stage aging treatment at 25°C. Table 1 also shows the results of examining the punching workability of the product thus obtained. In addition, the results of investigating the change in the hardness of the steel base over time are shown in Figure 1.

[0027]

[Table 1]

As is clear from FIG. 1, the steel plate obtained according to the present invention showed an improvement in base metal hardness compared to the comparative material, and an appropriate base metal hardness was obtained. In addition, according to a survey of punching workability using automatic clamping, it was found that the burr height was 50 μm.
The number of punches obtained according to the present invention was approximately 140,000 times, while the comparative material was approximately 80,000 times.
Punching performance has been significantly improved. The caulking strength was also good. Furthermore, regarding the skew property, although the product obtained according to the present invention had a sufficient skew angle,
Skew deviation occurred in the comparison material.

Regarding magnetic properties, for example, sample materials A and B of Example 1 have a W17/50 of 8.2 to 8.2 after aging.
3 (W/kg), and the W17/50 after strain relief annealing is 6.1 (W/kg), which is better than sample material C of comparative example 1, but inferior to sample material D. . The reason for this is
This is due to the effects of both the deterioration of magnetism due to C addition and the improvement of magnetism due to Al addition. That is, in this invention, the hardness of the base metal is ensured by adding C, and the magnetic deterioration caused by C is compensated for by adding Al.

Example 2 A hot rolled steel sheet (E) having the composition shown in Table 1 was cold rolled and then recrystallized annealed at 800°C for 1 minute. Cooled at a cooling rate of 7°C/s, then 20°C/s, and during cooling,
After performing a first stage aging treatment at 400°C for 7 seconds, a second stage aging treatment was performed at 25°C. In addition, for steel plate (F), the first stage aging treatment was performed at 460°C for 40 seconds, and for (G), cooling after recrystallization annealing was all performed at 7°C/s.
For (H), all cooling after recrystallization annealing was performed at a cooling rate of 25° C./sec up to the aging treatment. Table 1 also shows the results of examining the punching workability of the product thus obtained. Furthermore, the results of investigating the change in the hardness of the steel base over time are shown in Figure 2.

As is clear from FIG. 2, in this invention, 2
After 1 day, we were able to secure HV1:135, and after 10 days,
HV1:150. The number of punches was 150,000 times, and both caulking and skewing properties were good. On the other hand, in the comparative examples (F), (G), and (H), no improvement in the hardness of the base metal was observed, the number of punches was approximately 80,000 times, and good results were obtained in terms of caulking property and skew property. was not obtained.

Example 3 A hot rolled steel sheet (I) having the composition shown in Table 1 was cold rolled and then recrystallized annealed at 800°C for 1 minute, and in the cooling process up to 700°C. 5°C/s, then cooled down to room temperature at a cooling rate of 25°C/s, then applied a (bi)chromate-organic resin treatment solution, and then baked at 280°C for 15 seconds. A step aging treatment was performed, and then a second step aging treatment was performed at 35°C. For comparison, the second stage aging temperature for (J) steel was 8°C, and the second stage aging temperature for (K) steel was 70°C. Table 1 also shows the results of examining the punching workability of the product thus obtained. Also,
Figure 3 shows the results of investigating changes in the hardness of the steel base over time.

As is clear from FIG. 3, in this invention, 2
HV1:140 can be secured after 5 days, and after 5 days H
V1:155. On the other hand, in the comparative example (J)
In the case of Comparative Example (K), the HV is 1:130 even after 100 days, and in the case of the comparative example (K), the HV is 1:1 after 100 days.
It was 110. In addition, as for punching properties, due to the application of the (heavy) chromate-organic resin coating, the number of punchings was 1.5 million times, which was good. Regarding the caulking property, the invention example (I) was good, but
Comparative Examples (J) and (K) were slightly inferior. Furthermore, regarding the skew property, the invention example [I] was good, but the comparative example (
J) and (K) were extremely inferior. This is due to the hardness of the base metal, and is due to the deformation of the V projection.

Furthermore, regarding the magnetic properties, Sample Material I of Example 3 and Sample Material J of Comparative Example 3 were good, but Sample Material K of Comparative Example 3 was poor. This is due to the presence or absence of the effect of Al addition.

Example 4 Hot-rolled steel sheets (L, M) having the chemical compositions shown in Table 1 were cold-rolled and then recrystallized at 800°C for 1 minute, and during the cooling process, the temperature was increased to 700°C. up to 10℃
/s, then 10℃/s (L) up to room temperature and 50℃
After cooling at a cooling rate of /s (M), a phosphate-based treatment solution was applied, a first aging treatment was performed at 350°C for 15 seconds, and a second aging treatment was performed at 25°C. It underwent a stage aging process. For comparison, comparative examples (N,
O). Table 1 also shows the results of examining the punching workability of the product thus obtained. In addition, the results of investigating the change in the hardness of the steel base over time are shown in FIG. 4.

In the case of invention example (L), HV1 after 10 days
:135 was secured. Moreover, in the invention example (M), HV1:135 was secured after 2 days. Also, the punchability is 10~
After 150,000 cycles, both caulking and skewing properties were good. On the other hand, the comparative examples (N) and (O) have an HV of 1:135.
could not be ensured, and both caulking and skewing properties were poor.

[0037]

[Effect of the invention] Thus, according to this invention, the hardness of the base metal
HV1:135 to 160 can be stably obtained, and therefore a non-oriented electrical steel sheet with excellent punching workability can be stably obtained. Furthermore, by subsequently performing strain relief annealing, the magnetic properties can be further improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing changes in the hardness of the base steel over time.

FIG. 2 is a graph showing changes in the hardness of the base steel over time.

FIG. 3 is a graph showing changes in the hardness of the base steel over time.

FIG. 4 is a graph showing changes in the hardness of the base steel over time.

Claims (3)

[Claims] [Claim 1] C: 0.015 to 0.050 wt
%, Si: 0.3 wt% or less, Mn: 0.1 to 1.
After cold rolling a hot rolled steel sheet containing 0 wt% and Al: 0.1 to 0.6 wt%, 750 to 95
In manufacturing a non-oriented electrical steel sheet by performing recrystallization annealing at 0°C for 5 seconds to 5 minutes, the cooling process of the recrystallization annealing is performed at 10°C/s up to 700°C.
Cool at the following cooling rate and continue to cool down to room temperature for 10 to 50 minutes.
After cooling at a cooling rate of ℃/s, 200-450℃
Aging treatment is performed for 5 to 30 seconds at 10 to 55℃.
A method for manufacturing a non-oriented electrical steel sheet with excellent punching workability, characterized by subjecting it to aging treatment. [Claim 2] In Claim 1, during the aging process, 2
A method for producing a non-oriented electrical steel sheet with excellent punching workability, comprising continuously holding the temperature at 00 to 450°C for 5 to 30 seconds during the cooling process. [Claim 3] In Claim 1 or 2, 200~
A method for manufacturing a non-oriented electrical steel sheet with excellent punching workability, wherein aging treatment at 450° C. for 5 to 30 seconds also serves as baking treatment for an insulating coating.