JPH01228A - Manufacturing method of non-oriented electrical steel sheet with high tensile strength - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing a non-oriented electrical steel sheet with high tensile strength, and a method for manufacturing a high-strength magnetic material with low core loss for high-speed rotating machines and for use in electromagnetic switches. The present invention relates to a method of manufacturing a magnetic material suitable for use as a magnetic material with excellent wear resistance.

(Prior Art) Conventionally, the rotational speed required for rotating equipment is about 100,000 rpm at most, and laminated electromagnetic steel plates have been used as the material for the rotor.

Recently, ultra-high speed rotation of 200,000 to 300,000 rpm has become necessary, and there is a possibility that the centrifugal force applied to the Rogue exceeds the strength of the electromagnetic steel sheet.

For this reason, ultra-high-speed rotating machines usually use solid rotors made of cast steel, which have sufficient strength, instead of electromagnetic steel sheets. However, in this case, the cost is high because it requires a complicated machining process of cutting the rotor from a cast steel block, and there is also the problem that the eddy current loss is greater than in the laminated type, which significantly reduces the efficiency of the motor. Because the contact surfaces of electromagnetic switches wear out as they are used, magnetic materials are desired that have not only good magnetic properties but also excellent wear resistance.

In response to these needs, non-oriented electrical steel sheets with high tensile strength have recently been studied, and several proposals have been made. High at .0%, and Mn: 0
．． 1-11.5%, Ni: 0.1-20.0%, Co:
0.5-20.0%, Ti: 0.05-3.0%, W,
:0.05-3.0%, MO:0.05-3.0%, A
10.5-13.0% of one or two solid solution strengthening components
The material is a slab containing 1.0 to 20.0% of carbon dioxide, and after hot rolling, the hot rolled plate is repeatedly warm rolled at 100 to 600°C to the final thickness, and then annealed to improve the tensile strength. 50kg/
This is a method for manufacturing a high tensile strength non-oriented electrical steel sheet having a tensile strength of 1.5 mm or more.

This has a high Si content that is difficult to roll, so tedious warm rolling is required, but there is a risk of plate breakage occurring more often during rolling, resulting in lower productivity and lower yields. There is room for

In Japanese Patent Application Laid-Open No. 61-84360, N i : 8~
20%, Mo: 0.2-5.0%, Al: o, t-2.
0%, Ti: 0.1-1.0%, Cr 1.0-
A high tensile strength soft magnetic material for high speed rotating electric motors containing 10.0% has been proposed. This is particularly true for Ni and also for Mo.
, it is an extremely expensive material because it contains a large amount of Cr.

Furthermore, Japanese Patent Application Laid-Open No. 61-9520 discloses that Si: 2.5 to 7.
．． 0%, Ti: 0.05~3.0%, W: 0.05~
3.0%, Mo:Q, Q5~3.0%, Ni:0.1~
20.・High tensile strength non-oriented electrical steel sheet is manufactured by rapid solidification method using molten steel containing 1.0 to 20.0% of one or more of A1: 0.5% to 13.0%. It is something to do. Because this process is special, it cannot be manufactured using normal electromagnetic steel sheet manufacturing equipment, and it is considered difficult to produce it industrially.

(Problems to be Solved by the Invention) As described above, there have been proposals for manufacturing non-oriented electrical steel sheets with high tensile strength, but it is difficult to manufacture them industrially stably using ordinary electrical steel sheet manufacturing equipment. The reality is that we have not yet reached that point.

Furthermore, as mentioned above, high tensile strength non-oriented electrical steel sheets are used as materials for ultra-high-speed rotating electric equipment and electromagnetic switches, so in addition to having high tensile strength, they also need to have a low iron core and excellent magnetic flux density. be.

The present invention has a yield strength YP≧55 kg/as” and a tensile strength TS≧ suitable as a material for ultra-high rotation machines and electromagnetic switches.
6Qkg/w', hardness Hpv≧150, high strength, wear resistance, and magnetic flux density B50≧1.60T, which is a high tensile strength non-oriented electrical steel sheet that combines excellent magnetic properties with B50≧1.60T. The purpose is to stably manufacture it on an industrial scale with good workability without causing plate breakage or the like.

(Means for Solving the Problems) The present inventors have conducted various experiments and studies in order to achieve the above object. That is, in the present invention, C: 0.01% or less, Si: 2
．． 0% or more and 3.5% or less, Mn: 0.1% or more 1O30
% or less, P: 0.20% or less, Al170.10% or more and 1.50% or less, B2 0.008% or less, and if necessary, contains Ni 6.0% or less, the balance being iron and unavoidable A slab containing impurities is hot-rolled, rapidly cooled at an average cooling rate of 1000°C/min or more from the hot-rolling finishing exit to the coiling interval, and coiled at a temperature of 550″CJi650°C or less to remove P at grain boundaries. This is a method for manufacturing a non-oriented electrical steel sheet with high tensile strength and excellent magnetic properties by suppressing segregation at 1IaL, then annealing the sheet as it is unannealed or annealing the hot rolled sheet, cold rolling, and annealing it.

First, let's talk about the steel components.

C is a component that deteriorates magnetic properties, and is 0.01 (weight l)%
Containing more than 0.01% increases iron loss.
The following shall apply. Note that C may be brought into the above range by decarburizing with a hot-rolled plate or a cold-rolled plate instead of decarburizing with steel manufacturing.

Si increases the specific resistance of steel, reduces eddy current, lowers iron loss, and increases tensile strength, but if the content is 2.
If it is less than 0%, the effect is small. Moreover, if it exceeds 3.5%, the steel becomes brittle and the magnetic flux density of the product further decreases, so it should be set to 3.5 or less.

Mn increases the tensile strength of steel, increases specific resistance, and reduces iron loss, but if it is less than 0.1%, the effect is small, and preferably from more than 1.0% to 5.0%. 10.0%
If it exceeds 0.1-1, the magnetic flux density of the product will decrease.
It shall be 0.0%.

P is an element that has a remarkable effect of increasing tensile strength, but 0.2
If it exceeds 0.2%, embrittlement becomes severe and it becomes difficult to perform hot rolling, cold rolling, etc. on an industrial scale, so the upper limit is set to 0.20%.

When using a product such as an iron core from a steel plate with its end face punched or sheared, if it is exposed to an atmosphere of 150° C. or higher for a long time, the appearance may be poor and the elongation may deteriorate if Po exceeds 0.3%.

This is thought to be due to the fact that the fractured surface of the high tensile strength steel plate is relatively likely to contain microcranks, strain aging, etc.

Therefore, if elongation after aging is a problem in the application, adopt a method for processing the end face to make it smooth and free from distortion.

■ Punching with sandpaper and removing the sheared surface layer are effective. Further, if the Po component is set to 0.03% or less, the above problem does not occur.

As a deoxidizing material, AI+ is required to have at least o and io%, and by including Al, strength is improved and iron loss is reduced due to increased specific resistance, but if it exceeds 1.50%, it becomes brittle. is a problem, so 0.1O to 1.50%
shall be.

B has the effect of suppressing the embrittlement caused by segregation at grain boundaries and the segregation of P at grain boundaries, but if it exceeds 0.008%, it will become extremely brittle, so the upper limit is set at 0.008%.

Furthermore, Ni is contained if necessary. Ni has little negative effect on magnetic characteristics and is effective in improving tensile strength, but 6.0
If it exceeds 6.0%, the magnetic flux density will decrease significantly, so it is set to 6.0% or less.

A steel slab containing the above-mentioned components and the remainder consisting of iron and unavoidable impurities is melted in a converter and manufactured by continuous casting or ingot-blowing rolling.

The steel slab is heated in a known manner and then heated to a temperature of e.g.
Hot rolled to a thickness of ~3.5fi. The cooling rate from the finishing exit of hot rolling to coiling, the subsequent coiling temperature, and the cooling conditions after coiling are important for improving the cooling ductility of the steel sheet.

First, the area between the finishing exit and the winding is cooled at an average cooling rate of 1000° C./min or more. This cooling rate is slow <1000℃/
If it is less than 100%, P segregates at grain boundaries, resulting in embrittlement.

Subsequently, it is wound up at a temperature of more than 550°C and less than or equal to 650°C, and cooled to at least 300°C at an average cooling rate of 100°C/hour or more. In this way, by setting the cooling rate after winding to 100° C./hour or more and cooling it to at least 300° C., the winding temperature can be made higher than 550° C. and below 650° C., which is advantageous for the winding operation, without lowering the temperature. In addition, embrittlement of the steel is prevented.

The reason why the winding temperature is set to exceed 550° C. is to improve workability without causing poor winding or the like when winding the coil. On the other hand, in the case of winding at a temperature exceeding 650'C, even if the cooling rate is specified thereafter, P segregates at the grain boundaries or the grain size increases, resulting in frequent plate breakage during subsequent rolling.

After winding, steel with a slow cooling rate becomes brittle, so to prevent this, the steel is cooled at an average cooling rate of 100° C./hour or more. Further, this cooling needs to be carried out to at least 300° C., and if the temperature at the cooling end point that defines the cooling rate is high, the cooling performance will deteriorate.

If it is necessary to perform cold rolling after hot rolling, or to further improve the magnetic properties, hot rolled sheet annealing is performed at 500 to 1000°C for 5 seconds to 15 minutes, and then cold rolling is performed. do.

Hot-rolled sheet annealing is performed within the above temperature and time ranges at 500
This is because if the temperature is lower than 1000°C or shorter than 5 seconds, the annealing effect that further enhances the magnetic properties cannot be obtained.
If the rolling time is longer than 15 minutes, the crystal grains will become coarser, leading to sheet breakage during cold rolling or lowering the strength of the final product.

After cold rolling, annealing is performed at 70.0 to 900'C for 5 seconds to 15 minutes.The reason is that at 700C or less than 5 seconds,
A sufficient annealing effect for reducing core loss and improving magnetic flux density cannot be achieved, and a compressed structure remains or flatness remains unimproved. If the temperature exceeds 900°C or exceeds 15 minutes, the crystal grains will become coarse and the strength will decrease, and a high tensile strength steel plate will not be obtained.

In annealing this cold-rolled sheet, decarburization may be carried out in a decarburizing atmosphere if necessary.

(Example) Example I C: 0.0021%, Si: 3.2%, Mn: 1.4%
, P: 0.095%, Al 70.670%, B: 0.
Steel slab specimen A containing 1.45% Ni with the balance being iron and unavoidable impurities, and steel slab specimen B containing 1.45% Ni were hot rolled to a plate thickness of 2.3 mm. and the average cooling rate from hot rolling finish rolling to coiling is 500
~b degree is 400~800℃, cooling rate from coiling to 300℃ is 50~b No plate annealing, or hot rolled plate annealing conditions (400~110℃)
0)℃ x (5 to 900) seconds, and after cold rolling to a plate thickness of 0.5m, (650 to 92
5) 'CX annealing for 30 seconds to improve mechanical properties and W
The iron loss of L5150 and the magnetic flux density of B50 were measured.

Incidentally, an Epstein specimen measuring 30 cranes x 320 m (half in the rolling direction and half in the perpendicular direction) was used for the magnetic measurement.

(The following margins are continued on the next page) As is clear from the results shown in Table 1, samples A5, A7, B9, Bll, and B14 manufactured under the conditions of the present invention
is rolled without plate breakage, and the yield strength YP is 6.
4 to 67 kg/w”, tensile strength TS is 73 to 76 k
g/w” and has high strength characteristics, and also has iron tJW151
50. It is also excellent in magnetic flux density B50.

Example 2 c:o in weight%, oot3~0.0043%, Si:2
．． 8-3.23%, Mn:Q, Q4%-3.01%, p
:0.008~0.500%, At':0.50~2.
00%, B: 0.000-0.0108%, Ni: 0.
A steel slab specimen containing 75% to 1.90%, the remainder consisting of iron and unavoidable impurities, was hot rolled to a plate thickness of 2.3%.
mm, the average cooling rate from hot rolling finish rolling to coiling is 2000°C per minute, the coiling temperature is 600°C, and from coiling to 300°C.
Average cooling rate up to 100℃ per hour, 800℃
After hot-rolled sheet annealing for 30 seconds, the steel sheet was cold rolled to a thickness of 0.5 fl and annealed at 750° C. for 30 seconds. The mechanical properties and magnetic properties of the steel sheet were measured.

Incidentally, an Epstein test piece with magnetic properties of 301 m x 320 tm was sheared in half from the rolling direction and from the right angle direction, and the core loss of Wl 5150, the core loss of B50, and the magnetic flux density of B50 were measured.

The results are shown in Table 2.

(The following margins are continued on the next page) As is clear from the results shown in Table 2, Samples 1 to 9 produced under the conditions of the present invention were rolled without plate breakage, and the yield strength YP was 62~72kg/Tsuru3, tensile strength TS is 70~82kg/m'', and has high strength characteristics.
Furthermore, it is excellent in iron loss Wl 515 G and magnetic flux density B50.

(Effects of the Invention) As described above, according to the present invention, non-oriented electrical steel sheets with high tensile strength for use in ultra-high-speed rotating machines with high strength and good magnetic properties, and electromagnetic switches can be stably manufactured with good workability. Ru.

Agent: Patent Attorney Tatsuo Cha Noki

Claims (2)

[Claims] (1) In weight% C: 0.01% or less Si: 2.0% or more and 3.5% or less Mn: 0.1% or more and 10.0% or less P: 0.20% or less Al: 0.10% When hot rolling a slab containing 1.50% or less B: 0.008% or less, with the balance consisting of iron and unavoidable impurities, the average cooling rate from the hot rolling finishing exit to the winding is After cooling at 1000°C/min or more and winding at a temperature of more than 550°C and less than 650°C, at least 3
Cooled to 00°C to suppress P segregation to grain boundaries, then left unannealed or annealed at a temperature of 500°C to 1000°C for 5 seconds to 15 minutes, cold rolled to 700°C. A method for manufacturing a non-oriented electrical steel sheet with high tensile strength, which comprises annealing at a temperature of 5 seconds or more and 15 minutes or less at a temperature of 900°C or higher. (2) C: 0.01% or less Si: 2.0% or more and 3.5% or less Mn: 0.1% or more and 10.0% or less P: 0.20% or less Al: 0.10% When hot rolling a slab containing 1.50% or less B: 0.008% or less Ni: 6.0% or less, with the balance consisting of iron and unavoidable impurities, the slab is unrolled from the hot rolling finishing outlet. After cooling at an average cooling rate of 1000°C/min or more between the ladle and winding at a temperature of more than 550°C and no more than 650°C, at least 30°C at an average cooling rate of 100°C/hour or more.
Cooled to 0°C to suppress P segregation to grain boundaries, then annealed without annealing or annealed at a temperature of 500°C to 1000°C for 5 seconds to 15 minutes, cold rolled,
A method for producing a non-oriented electrical steel sheet with high tensile strength, the method comprising annealing at a temperature of 00°C or more and 900°C or less for 5 seconds or more and 15 minutes or less.