JP2948352B2 - Manufacturing method of non-oriented electrical steel sheet with excellent punching workability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-oriented electrical steel sheet having excellent punching workability.

[0002]

2. Description of the Related Art Among non-oriented electrical steel sheets, a steel sheet having a low Si content shows a high magnetic permeability although having a low iron loss value, and is inexpensive. It is often used for small transformers such as.

By the way, this type of electrical steel sheet is roughly divided into a full process material which is punched into a predetermined shape by a customer and then used as it is, and a semi-process material which obtains a required level of magnetism by performing strain relief annealing after punching. Separated. In any case, it is natural that excellent magnetism is required. However, since almost all of them are continuously punched by a punching machine, it is also an extremely important requirement that they have excellent continuous punching properties. It has been. Furthermore, to streamline the core manufacturing process at the customer, and to save labor, a composite progressive die using an automatic caulking method, in which a certain number of sheets are stacked in a progressive press during continuous punching and taken out in the state of the iron core, is used. Therefore, it is also an important requirement that a strong caulking strength be obtained and that the rotor be skewed smoothly.

[0004] It is said that it is effective to adjust the hardness of the magnetic steel sheet to an appropriate range in order to impart good punching properties to the magnetic steel sheet. Various studies have been made on the adjustment of the hardness of semi-processed materials, but almost no adjustment of full-processed materials. The reason for this is that the desired magnetic properties cannot be obtained because work strain remains in the magnetic steel sheet or inclusions in the steel sheet increase.

However, as the rationalization and labor saving progress as of today, even if the magnetic properties are sacrificed to some extent,
In some cases, it is required to have excellent punching workability.
On the other hand, with respect to the sacrificed magnetic properties, measures have been taken such as performing strain relief annealing after punching, or supplementing the design of small motors and small transformers with slight changes. Regarding the full process material, there is a technique disclosed in Japanese Patent Publication No. Sho 49-6456 and Japanese Patent Laid-Open No. Sho 60-190521 as an emphasis on hardness for punching workability.

[0006] Among the above proposals, JP-B-49-6456, a method of obtaining a hardness range in the H _V5 100 to 120 is shown. Japanese Patent Application Laid-Open No. 60-190521 discloses a method of performing overaging treatment intended to reduce solid solution C in steel to minimize aging deterioration of magnetism. It was the base steel hardness is from 95 to 129 in H _v. However, with good punching property and automatic crimping properties, and to skew of the rotor to obtain a good electrical steel sheet, with H _V (1kg) 13
A ground iron hardness of 5 to 160 is required, and this property cannot be satisfied by the above-mentioned prior art.

In other words, when the ground iron hardness is low, sagging is likely to occur on the cut and cut surface during continuous punching, which causes an error in the product dimensions after punching. As a solution to this problem, it is conceivable to reduce the clearance of the punching die, but this method reduces the life of the die. Here, H _V1 ≧ 135 is desirable as a base iron hardness that does not generate an error due to sag in product dimensions with an appropriate mold clearance. In addition, the fact that the occurrence of sag is small is suitable for an automatic caulking die, and an iron core having strong caulking strength can be obtained. However, if the ground iron hardness exceeds 160 at H _V1 , damage to the mold is increased. Therefore, it is preferable that the ground iron hardness is H _V1 ≦ 160.

On the other hand, the rotor core is skewed in order to obtain smooth rotation of the motor. Regarding the skew of the automatic caulking core, a V-shaped protruding one is taken out of the mold in a semi-clamped state, and skew is applied when the book is clamped by a working press. At this time, if the ground iron hardness is smaller than H _V1 : 135, the V-shaped projection is deformed, and a sufficient skew angle cannot be obtained.

[0009]

As described above, it is important to set the ground iron hardness to 135 to 160 in H _V1 in order to have excellent punching workability and automatic caulking property and to perform skew smoothly. is there. The present invention advantageously satisfies the above-mentioned requirements, and aims at optimizing the hardness of the ground iron by modifying the cooling treatment after recrystallization annealing, thereby improving the punching workability, the automatic caulking property, and the skew property. It is an object of the present invention to propose an advantageous method for manufacturing a non-oriented electrical steel sheet.

[0010]

That is, the present invention provides:
C: 0.015 to 0.040 wt% (hereinafter simply indicated as%), Si:
After performing cold rolling on a hot-rolled steel sheet containing 0.3% or less and Mn: 0.1 to 1.0%, with the balance being substantially Fe,
In producing a non-oriented electrical steel sheet by performing recrystallization annealing at 750 to 950 ° C. for 5 seconds to 5 minutes, the cooling process of the recrystallization annealing is performed by increasing the temperature up to 700 ° C. to 10 ° C./s.
Cool at the following cooling rate, and then to 10-50 ° C /
After cooling at a cooling rate of s, aging treatment is performed at 250 to 450 ° C for 5 to 30 seconds, and further aging treatment is performed at 10 to 55 ° C. It is a manufacturing method. In addition, the present invention provides a C: 0.015-0.0.
040%, Si: 0.3% or less, Mn: 0.1 to 1.0%, and P: 0.1
%, The balance being substantially Fe, after cold-rolling a hot-rolled steel sheet at 750-950 ° C.
In producing a non-oriented electrical steel sheet by performing recrystallization annealing for seconds to 5 minutes, in the cooling process of the above recrystallization annealing, cooling to 700 ° C. at a cooling rate of 10 ° C./s or less, and then to room temperature Cooling at a cooling rate of 10-50 ° C / s, aging at 250-450 ° C for 5-30 seconds, and further aging at 10-55 ° C. A non-oriented electrical steel sheet.

Further, in the present invention, it is preferable that the temperature of 250-450 ° C., 5
The aging treatment for up to 30 seconds may be performed continuously during the cooling process or may also serve as a baking treatment of the insulating film.

A series of cooling and aging treatments according to the present invention are intended to precipitate fine carbides and improve the hardness of the steel, and the hardness of the steel H _H1 : 135 to 16
0 can be obtained, and as a result, a non-oriented electrical steel sheet having excellent punching workability can be obtained. The effect of the precipitation of fine carbides on the magnetic properties was small, and the deterioration was about 1%, which was not a problem.

[0013]

Next, the reason why the composition of the material and the manufacturing conditions in the present invention are limited as described above will be described. C: 0.015 to 0.040% If the C content is less than 0.015%, the solid solution C in the steel is small and the amount of fine carbides is also small, so that the ground iron hardness H _V1 : 13
5 cannot be secured. On the other hand, when the C content exceeds 0.040%,
Since the carbide after aging treatment becomes coarse and the ground iron hardness H _V1 becomes 135 or less, the C content is limited to the range of 0.015 to 0.040%.

Si: 0.3% or less Si is an element useful for improving magnetic properties. However, since the present invention is directed to a low-grade non-oriented electrical steel sheet, Si addition, which increases costs, is actively performed. Absent. However, it does not prevent unavoidable contamination during the manufacturing process, especially in the deoxidation stage, and in consideration of this point, the range is limited to 0.3% or less.

Mn: 0.1-1.0% If Mn is less than 0.1%, hot brittleness increases, while
If it exceeds 1.0%, the price of the steel sheet will increase, so the Mn content
Limited to the range of 0.1-1.0%.

Although the essential components have been described above, in the present invention, P can be added as an element for increasing the base iron hardness. However, if the content exceeds 0.1%, the cold workability deteriorates. Therefore, when the content is added, the content needs to be 0.1% or less.

Next, the manufacturing conditions of the present invention will be described. By the way, after performing cold rolling on the hot-rolled steel sheet having the above-mentioned preferable component composition, recrystallization annealing is performed at 750 to 950 ° C. for 5 seconds to 5 minutes, and by controlling a cooling process in the cooling process, By increasing the solid solution C in the steel and then aging treatment to precipitate fine carbides in the steel, the ground iron hardness H _V1 : 135 to 160 is secured. In the above treatment, the cooling rate from the recrystallization annealing temperature must be 10 ° C / s or less up to 700 ° C. This is because if the cooling rate exceeds 10 ° C./s, the solid solution C in the steel is fixed in a small state, so that the solid solution C
This is for the purpose of increasing. The temperature at which the solid solution C is maximized is around 723 ° C., but in order to secure an industrially stable production amount, in the present invention, the lower limit of the temperature at which the above-mentioned controlled cooling is performed is set to 700 ° C.

After cooling to 700 ° C. at a rate of 10 ° C./s or less and increasing the solute C in the steel, it is necessary to increase the cooling rate to fix the solute C in the steel. Therefore, thereafter, it is cooled to room temperature at a relatively early rate of 10 to 50 ° C./s.
Here, if the cooling rate is lower than 10 ° C./s, the solute C in the steel precipitates at the crystal grain boundaries and becomes cementite, so that the solute C in the steel decreases. , A cooling rate of at least 10 ° C./s is required. On the other hand, in order to secure a cooling rate exceeding 50 ° C / s, a great deal of capital investment is required, and the cost increases.
The cooling rate from to room temperature was limited to the range of 10 to 50 ° C / s.

Then, the solid solution C fixed as described above is finely precipitated to improve the ground iron hardness. Aging treatment is extremely important for such fine precipitation,
The following two-stage process is required. Ie 250-450
The first stage treatment at 5 ° C. for 5 to 30 seconds produces nuclei of carbide fine precipitation, then the second stage treatment at 10 to 55 ° C. achieves fine precipitation of carbides, and ground iron hardness H _V1 : 135 to 160 To secure.

In the first stage of the aging treatment, the treatment temperature is
If the temperature is lower than 250 ° C, nucleation cannot be performed, whereas if the temperature is higher than 450 ° C, coarse carbides are formed and do not contribute to the improvement of the hardness of the steel. If the treatment time is shorter than 5 seconds, no nucleus is generated, while if it exceeds 30 seconds, coarse carbides are generated. Therefore, in the present invention, the first stage of the aging treatment is performed in a temperature range of 250 to 450 ° C. for 5 to 30 seconds.

Next, if the aging temperature in the second stage is lower than 10 ° C., it takes a long time to secure the ground iron hardness H _V1 : 135 to 160, which is not practical. Coarse carbides are formed, and the ground iron hardness H _V1 : 135 or more cannot be secured. Therefore, in the present invention, the aging temperature in the second stage is 10
Limited to the range of 5555 ° C.

By performing the above-mentioned two-stage aging treatment, a ground iron hardness H _{V1 of} 135 to 160 can be secured. The first
The aging treatment in the step may be performed during the cooling process after the recrystallization annealing, and may also serve as the baking treatment of the insulating film.

As the insulating film, any of the conventionally known phosphate type, (bi) chromate type, and a mixed type of (bi) chromate and organic resin can be used. When these are the main components, for example, in the case of a phosphate system, additives are nitrate, nitrite, boric acid, surfactant, chromic anhydride, (bi) chromate and the like. In the case of (bi) chromate, an organic reducing agent, boric acid and the like are used. Further, in the case of a (bi) chromic acid-organic resin type, an organic reducing agent, boric acid, and one or more copolymers of an acrylic resin, a styrene type, a vinyl acetate type and a veova type as the organic resin are used. In order to improve the heat resistance of the insulating film, colloidal silica, colloidal alumina, further titania, silica,
Fine powder of a metal oxide such as alumina may be blended.

[0024]

【Example】

Example 1 Hot-rolled steel sheets (A to D) having the composition shown in Table 1 were subjected to cold rolling, and then recrystallization annealing was performed at 800 ° C. for 1 minute. ° C / s, then cool to room temperature at a cooling rate of 25 ° C / s.
After a first-stage aging treatment at 50 ° C. for 10 seconds, a second-stage aging treatment was performed at 25 ° C. The results obtained by examining the punching workability of the product thus obtained are also shown in Table 1. In addition, FIG. 1 shows the results obtained by examining the change with time of the ground iron hardness.

[0025]

[Table 1]

As is clear from FIG. 1, the steel sheet obtained according to the present invention has an improved ground iron hardness as compared with the comparative material, and an appropriate ground iron hardness was obtained. Also, according to the investigation of the punching workability by automatic caulking, the number of punches up to a burr height of 50 μm was about 80,000 for the comparative material,
Approximately 140,000 times were obtained according to the present invention, and the punching property was significantly improved. The swaging strength was also good. Further, with respect to the skew property, although the one obtained according to the present invention had a sufficient skew angle, the skew deviation occurred in the comparative material.

Example 2 A hot-rolled steel sheet (E) having the composition shown in Table 1 was subjected to cold rolling, and then recrystallization annealing was performed at 800 ° C. for 1 minute. 7 ° C / s, followed by 20
After cooling at a cooling rate of ° C / s, a first-stage aging treatment was performed at 400 ° C for 7 seconds during the cooling, and then a second-stage aging was performed at 25 ° C. For the steel sheet (F), the first-stage aging treatment was performed at 460 ° C. for 40 seconds, and for (G), cooling after recrystallization annealing was performed at a cooling rate of 7 ° C./s to remove the aging treatment. For (H), the cooling after the recrystallization annealing was all quenched until the aging treatment at a cooling rate of 25 ° C./sec.
The results obtained by examining the punching workability of the product thus obtained are also shown in Table 1. In addition, FIG. 2 shows the result of examining the change with time of the base iron hardness.

As is apparent from FIG. 2, in the present invention, 3
A day later, H _V1 : 135 was secured, and 10 days later, H _V1 : 150. The number of punches was 150,000 times, and the caulking and skew properties were also good. On the other hand, in each of Comparative Examples (F), (G), and (H), no improvement in the ground iron hardness was observed, the number of punches was about 80,000, and good results were obtained in both caulking and skew. Was not obtained.

Example 3 A hot-rolled steel sheet (I) having the composition shown in Table 1 was subjected to cold rolling, followed by recrystallization annealing at 800 ° C. for 1 minute. After cooling at 5 ° C / s and then to room temperature at a cooling rate of 25 ° C / s, then applying a (bi) chromate-organic resin-based treatment liquid,
A first-stage aging treatment also serving as baking for 15 seconds was performed, and then a second-stage aging treatment was performed at 35 ° C. For comparison, for the (J) steel, the aging temperature in the second stage was 8 ° C.
And for (K) steel, the aging temperature in the second stage is 70 ° C.
And The results obtained by examining the punching workability of the product thus obtained are also shown in Table 1. In addition, FIG. 3 shows the result of examining the change with time of the base iron hardness.

As is apparent from FIG.
H _V1 : 140 was secured after one day, and H _V1 : 150 after five days. On the other hand, in the case of the comparative example (J), H _V1 : 130 even after 100 days, and in the case of the comparative example (K),
After 100 days, H _V1 : 110. In addition, the punchability was good, with 1.5 million punchings, in each case due to the application of the (bi) chromate-organic resin coating.
Regarding the caulking property, the invention example (I) was good,
Comparative Examples (J) and (K) were slightly inferior. Further, with respect to the skew property, the invention example [I] was good, but the comparative examples (J) and (K) were extremely poor. This is due to the hardness of the ground iron, and is due to the deformation of the V projection.

Example 4 A hot-rolled steel sheet (L, M) having the composition shown in Table 1 was subjected to cold rolling, and then was subjected to recrystallization annealing at 800 ° C. for 1 minute. After cooling at a cooling rate of 10 ° C./s (L) and 50 ° C./s (M) to room temperature, a phosphate-based treatment liquid was applied. After a first-stage aging treatment also serving as baking for seconds, a second-stage aging treatment was performed at 25 ° C.
For comparison, the cooling rate up to 700 ° C was
A comparative example (N, O) was prepared in the same manner except that the temperature was changed to 12 ° C./s. The results obtained by examining the punching workability of the product thus obtained are also shown in Table 1. In addition, FIG. 4 shows the result of examining the change with time of the ground iron hardness.

In the case of Invention Example (L), H _V1 : 135 after 20 days
Was secured. In the invention example (M), H _V1 : 13 after 2 days
5 was secured. The punching property was 100,000 to 150,000 times, and both the caulking property and the skew property were good. On the other hand, (N) and (O) of Comparative Examples could not secure H _V1 : 135, and were inferior in both caulking property and skew property.

[0033]

According to the present invention, the ground iron hardness H
_V1 : 135 to 160 can be obtained stably, and thus a non-oriented electrical steel sheet having excellent punching workability can be obtained stably.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph showing a change over time in ground iron hardness.

FIG. 2 is a graph showing the change over time of the ground iron hardness.

FIG. 3 is a graph showing the change over time in the hardness of ground iron.

FIG. 4 is a graph showing the change over time of the ground iron hardness.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiaki Iida 2-88, Wakihama Kaigandori, Chuo-ku, Kobe-shi, Hyogo Kawasaki Steel Corporation Hanshin Works (72) Inventor Yasuo Kato 1 Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Prefecture Chome (without address) Kawasaki Steel Corporation Mizushima Works (56) References JP-A-4-323321 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21D 9/46 501 C21D 8/12 C22C 38/00 303 C22C 38/04

Claims (4)

(57) [Claims] (1) C: 0.015 to 0.040 wt%, Si: 0.3 wt% or less and Mn: 0.1 to 1.0 wt%, the balance being substantially Fe
After cold rolling on a hot-rolled steel sheet with a composition of 750 to 9
In producing a non-oriented electrical steel sheet by performing recrystallization annealing at 50 ° C. for 5 seconds to 5 minutes, in the cooling process of the recrystallization annealing, cooling to 700 ° C. is performed at a cooling rate of 10 ° C./s or less. Punching characterized by successively cooling to a normal temperature at a cooling rate of 10 to 50 ° C./s, aging at 250 to 450 ° C. for 5 to 30 seconds, and further aging at 10 to 55 ° C. A method for manufacturing non-oriented electrical steel sheets with excellent workability. 2. Hot rolled steel containing 0.015 to 0.040% by weight of C, 0.3% by weight or less of Si, 0.1 to 1.0% by weight of Mn and 0.1% by weight or less of P, and the balance being substantially Fe. In order to manufacture a non-oriented electrical steel sheet by subjecting a steel sheet to cold rolling and then performing recrystallization annealing at 750 to 950 ° C. for 5 seconds to 5 minutes, the cooling process of the recrystallization annealing is performed at 700 ° C.
After cooling at a cooling rate of 10 ° C / s or less, and then cooling to room temperature at a cooling rate of 10-50 ° C / s,
A method for producing a non-oriented electrical steel sheet having excellent punching properties, comprising aging at 5 to 30 seconds at 10C and further aging at 10 to 55C. 3. The method according to claim 1, wherein during the aging treatment,
A method for producing a non-oriented electrical steel sheet having excellent punching workability, wherein the holding at 50 to 450 ° C. for 5 to 30 seconds is continuously performed during the cooling process. 4. The method according to claim 1, 2 or 3, wherein
A method for producing a non-oriented electrical steel sheet having excellent punching workability, wherein aging treatment at 5 ° C. for 5 to 30 seconds also serves as a baking treatment of an insulating film.