JP2000096195A - Nonoriented silicon steel sheet for motor of electric automobile and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonoriented silicon steel sheet for the motor of an electric automobile combining excellent low to high frequency iron loss and magnetic flux density and to provide a stable producing method therefor. SOLUTION: This nonoriented silicon steel sheet for the motor of an electric automobile is the one having a compsn. contg., by weight, <=0.005% C, 1 to <2.2% Si <=1.5% Al, <=1.5% Mn <=0.005% B, and the balance Fe with inevitable impurities, the sheet thickness is controlled to 0.25 to 0.6 mm, the average crystal grain size is controlled to 50 to 125 μm, the surface is provided with an insulating film, the magnetic flux density is B50>1.70T, and, also, the iron loss and the magnetic flux density satisfy the following inequality: B50>=0.011×(W15/50+W10/400/10)+1.64.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-oriented electrical steel sheet for an electric vehicle motor and a method of manufacturing the same, and more particularly, to a non-oriented electrical steel sheet having a high torque and a low battery power consumption which is optimal for an electric vehicle main motor. Provided are an electromagnetic steel sheet and a method for manufacturing the same.

[0002]

2. Description of the Related Art From the viewpoint of the global environment, the harmful effects of recent energy-intensive civilization have been regarded as a problem. For this reason, further reduction in power consumption is demanded in the field of electrical equipment using non-oriented electrical steel sheets. In particular, in recent years, electric vehicles with low gasoline consumption have attracted much attention due to the problem of exhaust gas. The performance required of a drive motor for an electric vehicle, that is, a main motor, has been reported in, for example, the '92 Motor Technology Symposium and '92 Motor General Session (1992.4.23, Makuhari Messe) sponsored by the Japan Management Association. ing.

It is a high-torque high-density non-oriented electrical steel sheet at the time of start-up or low-speed operation to reduce the motor weight.
This is a high-efficiency, low iron loss non-oriented electrical steel sheet at about 0 Hz).

Conventionally, the core of a drive motor for an electric vehicle,
That is, as a non-oriented electrical steel sheet, for example,
No. 9044 is known. However, the relationship between the iron loss (W15 / 50 and W5 / 1000) and the magnetic flux density B50 in the invention does not go out of the category of the conventional product catalog of non-oriented electrical steel sheets, for example, by one step. , W15 / 50 and B50 were unsatisfactory, and there was a problem that the magnetic flux density was low in spite of the iron loss. More specifically, as in the embodiment, 0.35 mm thickness in 2% Si system, W15 / 50 =
2.96 w / kg, B50 = 1.68 T or 0.35 mm thickness in 1.2% Si system, W15 / 50 = 3.80 w / kg, B50 = 1.62
T, 0.50mm thick, W15 / 50 = 5.00w / kg, B
For example, 50 = 1.63T. For this reason, the drive motor of an electric vehicle has a large size, which has been a hindrance to reducing the weight of the vehicle, and improvement in motor torque has been required. Further, the disclosed 1
Iron loss at 000 Hz was too high for electric vehicles to be practical. In an electric vehicle, a frequency range of about 400 Hz is generally important, and improvement of iron loss at this frequency is required. In addition, conventionally, the effect of the insulating film on the high-frequency magnetic properties of the non-oriented electrical steel sheet was not clear.

[0005]

SUMMARY OF THE INVENTION In view of the above, the present invention provides a non-oriented electrical steel sheet for an electric vehicle motor having excellent high-frequency iron loss and magnetic flux density, and a method for stably manufacturing the same. is there.

[0006]

(1) By weight%, C ≦
0.005%, Si is 1% or more and less than 2.2%, Al ≦
1.5%, Mn ≦ 1.5%, B ≦ 0.005%, the balance consists of unavoidable impurities and Fe, and the plate thickness is 0.25 to
0.6 mm, the average crystal grain size is 50 to 125 μm, the surface has an insulating film of 0.5 to 3 g / m ² , the magnetic flux density B50> 1.70T, and the iron loss and the magnetic flux A non-oriented electrical steel sheet for an electric vehicle motor, wherein the density satisfies the following expression. B50 ≧ 0.011 × (W15 / 50 + W10 / 400/10) +
1.64 (2) By weight%, C ≦ 0.005%, Si is 1% or more,
Less than 2.2%, Al ≦ 1.5%, Mn ≦ 1.5%, B ≦
A slab consisting of 0.005%, the remaining unavoidable impurities and Fe is heated at a temperature of 1200 ° C. or less, hot-rolled, and a hot-rolled sheet having a thickness of 1.0 to 2.0 mm is formed.
Perform hot-rolled sheet annealing at a temperature of 0 ° C. or higher,
5 to 0.6 mm thickness, then annealing at a temperature of 800 ° C. or more to reduce the crystal grain size to 50 to 125 μm,
A method for producing a non-oriented electrical steel sheet for an electric vehicle motor, comprising applying and baking an insulating film of 0.5 to 3 g / m ^{2 to} the surface.

The points of the present invention are the following four points.
First, when the cold rolling reduction is small, the texture of the product is improved and the magnetic flux density is improved. For this reason, it is necessary to reduce the thickness of the hot rolled sheet. Second, in order to further improve the magnetic flux density, it is necessary to perform high-temperature ripening annealing in hot-rolled sheet annealing. Third, excellent control of both high-frequency iron loss and magnetic flux density can be achieved by controlling the crystal grain size of the product. Fourth, high-frequency characteristics are improved by controlling the amount of the insulating film applied.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The amount of C is 0.005% or less. If the content exceeds 0.005% C, there is a problem in magnetic aging. Si amount 1
% To less than 2.2%. The higher the Si content,
It is known that iron loss is reduced. The reason for the limitation is S
When the i amount is less than 1%, the iron loss aimed at by the present invention is unsatisfactory, and when it is 2.2% or more, the magnetic flux density is unsatisfactory, so it must be avoided.

The amount of Al is limited to 1.5% or less. Although Al also reduces iron loss, it is avoided when the amount of Al exceeds 1.5% because the magnetic flux density is unsatisfactory. The Mn content is 1.5% or less. M
n is effective and necessary to prevent red-hot brittleness in hot rolling and to improve the edge roughness of the hot-rolled sheet, but if too much, there is a problem of cost increase, so n is set to 1.5% or less.

The B content is set to 0.005% or less. B improves the hysteresis loss, but if it exceeds 0.005%, the continuous cast slab is broken, so that it is avoided. Other components, P,
Impurities such as S, N, Ti, Nb, and V are as small as possible to improve iron loss.

In addition to the above elements, Sn, Ni, Cu, Sb, and C, which are known as elements that do not impair magnetic properties, are known.
Addition of r, Mo or the like does not impair the effects of the present invention, but is preferably 0.1% or less in view of the cost of addition.

The slab heating temperature of hot rolling is 1200 ° C. or less. The low temperature is good for the purpose of preventing the deterioration of the high frequency iron loss, and its limit is 1200 ° C. Next, normal hot rolling is performed, but the thickness of the hot rolled sheet is limited to 1.0 to 2.0 mm.

The thinner the hot-rolled sheet, the better the magnetic flux density is. However, if the thickness is less than 1.0 mm, the finishing temperature during hot rolling is remarkably reduced, resulting in insufficient power for reduction. If it exceeds 2.0 mm, the magnetic flux density deteriorates and must be avoided.

Next, the hot rolled sheet is annealed. There are long-time batch annealing and short-time continuous annealing in the annealing of the hot-rolled sheet, but any method is acceptable. Although the annealing temperature varies depending on the annealing time, 700 ° C. or more is necessary to secure the magnetic flux density.

Before or after the hot rolled sheet annealing, pickling is performed, and then cold rolling is performed. Cold rolling is performed by ordinary reversal or tandem, but reversals such as Sendzimer mill are preferable in terms of magnetic flux density. In addition, it is also preferable to perform warm rolling at a temperature of about 100 to 300 ° C. to improve the magnetic flux density, as is well known.

The thickness of the cold-rolled sheet is 0.25 to 0.6 mm. When the thickness is less than 0.25 mm, the steel plate is thin and has a low rigidity, so that it is easily deformed at the tip of the teeth of the motor and the like, and the noise is increased and the winding becomes difficult. If it exceeds 6 mm, avoid high frequency iron loss due to dissatisfaction.

After cold rolling, it is degreased and subjected to ordinary continuous annealing. The annealing temperature is 800 ° C. or higher. At this time,
In particular, it is necessary to control the crystal grain size from 50 μm to 125 μm. If it is less than 50 μm, iron loss at a low frequency deteriorates, and if it exceeds 125 μm, high-frequency iron loss deteriorates, so that it is avoided. The crystal grain size is controlled by the temperature or the soaking time, but since the crystal grain growth rate varies depending on the amounts of Si, Al, Mn and the amount of impurities, it is necessary to carefully determine the annealing conditions. . If the temperature is less than 800 ° C., even if the soaking time is about 5 minutes, the crystal grain size is less than 50 μm, which is economically impossible. The upper limit of the temperature is the temperature at which the crystal grain size becomes 125 μm. The temperature differs depending on the system. Further, in order to prevent the deterioration of the high-field iron loss due to the surface oxidation of the steel sheet by this annealing, Japanese Patent Application Laid-Open No.
A reducing atmosphere is preferred as described in US Pat. After annealing, a mixture of organic and inorganic substances, an all-organic or all-inorganic insulating coating is applied and baked. The coating amount of the film is limited to 0.5 to 3 g / m ² per one side. 0.
If it is less than 5 g / m ² , an abnormal value occurs due to insulation failure in high-frequency iron loss, and if it exceeds 3 g / m ² , the space factor deteriorates, and the effective magnetic flux density as a motor core deteriorates. . The baking temperature is usually 100 to 600C. Hereinafter, examples of the present invention will be described.

Example 1 The amount of C is 0.002%, the amount of S is 0.0009%, the amount of N is 0.0011%, and the amount of B is 0.0
001%, and the other components were cast into a vacuum melting ingot as shown in Table 1.
Hot rolling was performed to obtain a 1.6 mm hot rolled sheet. After the pickling, the hot-rolled sheet was annealed at 750 ° C. for 6 hours in a nitrogen gas. Next, after pickling, cold rolling was performed with a Sendzimer mill to a thickness of 0.5 mm, followed by degreasing and annealing. Annealing was carried out in 50% hydrogen + 50% nitrogen at 900 to 1000 ° C. for 30 seconds to adjust the crystal grain size to about 90 μm. The crystal grain size is
A straight line was drawn in the thickness direction of the steel sheet in the light microscopic structure, and the number of crystal grain boundaries intersecting with the straight line was counted and determined. Then, a mixed insulating film of epoxy resin and chromic acid was applied at 2 g /
m ² baking, cut the resulting product to 100mm square sample was measured magnetic average L, and C directions.

[0019]

[Table 1]

As shown in Table 1, it can be seen that excellent low frequency to high frequency iron loss and excellent magnetic flux density can be obtained with the component system in the range of the present invention. The magnetic flux density B50 was measured at 50 Hz, and whether or not the maximum magnetic flux density when a maximum magnetizing force of 5000 A / m was given changed with frequency from DC to 1 KHz was investigated. The value was constant regardless of the frequency.

Example 2 C ≦ 0.002%, Si: 1
% To less than 2.2%, Al ≦ 1.5%, S ≦ 0.00
A vacuum melting material of 01% and N ≦ 0.002% was heated at 1150 ° C. to produce a 1.8 mm hot-rolled sheet. Then, JP-A-8-
In the graph of Japanese Patent No. 49044, the conventional hot-rolled sheet without annealing, soaking at 670 ° C. for 2 hours in nitrogen, and 900 of the present invention were used.
After performing hot-rolled sheet annealing in nitrogen at 30 ° C. for 30 seconds and pickling,
It was tandem cold rolled and finished to 0.25 to 0.6 mm. This was degreased and subjected to continuous annealing at 800 to 1050 ° C for 20 seconds for 6 seconds.
0% H ₂ + 40% N ₂ atmosphere, crystal grain size 50%
１２５125 μm was obtained. Next, the epoxy resin was baked at 2 g / m ² per side. Cut out 100mm square sample,
The magnetism was measured by averaging the L and C directions to obtain FIG. The comparative example was plotted with no hot-rolled sheet annealing and 670 ° C. annealing, and the present invention example was plotted with a 900 ° C. hot-rolled sheet annealing material.

As shown in FIG. 1, excellent low to high frequency iron loss and magnetic flux density were exhibited under the conditions of the present invention. When the range of the present invention was expressed by a mathematical expression, it was found that the range satisfied the following two expressions at the same time. B50> 1.70T B50 ≧ 0.011 × (W15 / 50 + W10 / 400/10) +
1.64

Although not an object of the present invention, W5 / 1000
Is also measured in the present invention, for example, W15 / 50 + W10 / 100
With the value of 0/10 being 4.5 and the B50 being 1.73T, all the plots of the present invention show characteristics that are significantly improved from the invention examples shown in the graph of the known JP-A-8-49044. I knew it was being done.

Example 3 0.003% C, 1.2% S
i, 0.03% Al, Mn: 0.3%, 0.001%
S, 0.0015% N, 0.002% B, 0.02%
P, 0.07% Cu, 0.05% Ni, 0.03% S
n, 0.01% Cr, 0.001% Ti, 0.003%
The soaking time of the slab containing Nb was set to 2 hours while changing the slab heating temperature. Next, the thickness of the hot rolled sheet was also changed and hot rolled. The hot rolled sheet was subjected to a soaking treatment at 1000 ° C. for 20 seconds in a nitrogen gas. Next, it was pickled and warm-rolled at about 200 ° C. with a Sendzimir mill to obtain 0.35 mm.
mm thickness. Next, a soaking time of 5 minutes at an annealing temperature of 1000 ° C.
Annealing in hydrogen for 2 seconds to form a mixed insulating film of epoxy resin, magnesium hydroxide and chromic acid at 1 g /
After baking m ² , the magnetism was measured with Epstein.
The crystal grain size of the product was constant at 95 μm.

[0025]

[Table 2]

As shown in Table 2, the hot rolling conditions were within the range of the present invention, and excellent magnetic properties were obtained.

Example 4 C: 0.001%, Si:
2.1%, Al: 0.45%, Mn: 0.1%, S:
1 slab containing 0.0004%, N: 0.0029%
After heating at 160 ° C. for 2 hours, hot-rolling to 1.9 mm, performing hot-rolled sheet annealing at 1100 ° C. for 25 seconds, and then pickling,
Cold-rolled to 0.3 mm with a Sendzimer mill, and then continuous annealing was performed under the conditions shown in Table 3 at a soaking temperature of 20 seconds to apply an insulating film (epoxy resin, a mixture of magnesium hydroxide and chromic acid) on one side. Was baked under the conditions shown in FIG. Table 3 shows the results obtained by the Epstein measurement.

[0028]

[Table 3]

As shown in Table 3, when the annealing temperature, crystal grain size and insulating film of the cold rolled sheet were controlled within the range of the present invention, excellent magnetic properties were obtained. When the amount of the insulating film was outside the upper limit, the space factor was deteriorated, and when the amount was outside the lower limit, the high-frequency iron loss showed an abnormal value.

[0030]

As described above, a non-oriented electrical steel sheet for an electric vehicle motor having excellent low to high frequency iron loss and magnetic flux density can be provided. As a result, it is possible to provide a high-torque and compact motor for an electric vehicle, which contributes to a reduction in the weight of the electric vehicle and a reduction in battery consumption.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between iron loss and magnetic flux density of a product obtained in Example 2.

Claims (2)

[Claims] (1) C ≦ 0.005% by weight and Si is 1% by weight
% To less than 2.2%, Al ≦ 1.5%, Mn ≦ 1.5
%, B ≦ 0.005%, balance unavoidable impurities and Fe
It has a thickness of 0.25 to 0.6 mm, an average crystal grain size of 50 to 125 μm, has an insulating film of 0.5 to 3 g / m ^{2 on} the surface, and has a magnetic flux density B50> 1. At 70T,
A non-oriented electrical steel sheet for an electric vehicle motor, wherein the iron loss and the magnetic flux density satisfy the following expressions. B50 ≧ 0.011 × (W15 / 50 + W10 / 400/10) +
1.64 2. In% by weight, C ≦ 0.005% and Si is 1%.
% To less than 2.2%, Al ≦ 1.5%, Mn ≦ 1.5
%, B ≦ 0.005%, balance unavoidable impurities and Fe
The slab is heated at a temperature of 1200 ° C. or less, hot-rolled to form a hot-rolled sheet having a thickness of 1.0 to 2.0 mm, and then subjected to hot-rolled sheet annealing at a temperature of 700 ° C. or more, After cold rolling to a sheet thickness of 0.25 to 0.6 mm, and then annealing at a temperature of 800 ° C. or more to reduce the crystal grain size to 50 to 125 μm, a 0.5 to 3 g / m ² insulating film is formed on the surface. Apply
A method for producing a non-oriented electrical steel sheet for an electric vehicle motor, the method comprising baking.