JPS5817248B2 - Low core loss non-oriented electrical steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-oriented electrical steel sheet with low core loss and excellent magnetism, in which the inclusion components and their amount in the steel are controlled.

As is well known, in order to improve iron loss in non-oriented electrical steel sheets, it is necessary to sufficiently increase the grain size in the final annealing, and for this purpose various inclusions that impede grain growth, such as A720a and S t 029Mn. S.

Al! It is an effective means to reduce the amount of N and the like as much as possible.

Also, inclusions having a low solution temperature, such as MnS. 81a
N4, etc., with other inclusions having a high solution temperature, such as RE.
There is also the idea of making it harmless by substituting it with M-8, Ca-8, 5b-8, etc. to prevent grain growth caused by fine precipitation in the subsequent process, and related to this,
For example, JP-A No. 52 = 2824 (Ce addition), JP-A No. 52
There is l-62115 (REM added).

In addition, JP-A-51-6062 adds Zr.
4 has been proposed.

However, all of these require the addition of necessary expensive additives in order to exhibit sufficient effects, which inevitably increases costs.

The object of the present invention is about 115 to 1/10 compared to the prior art.
If a product with characteristics equal to or better than conventional products can be obtained with zero additional cost, it is in category C.

In order to achieve the above object, the present inventors conducted various studies on the components, forms, and amounts of inclusions contained in steel.

As a result, crystal grain growth is achieved by forming spherical composite inclusions that combine calcium manganese sulfide and one or both of aluminum oxide and aluminum nitride, which are naturally contained in non-oriented electrical steel. It was possible to make it harmless.

In order to form spherical composite inclusions that face each other, it is necessary to use CaO, Ca, which is significantly cheaper than conventional additives, at the steelmaking stage.
It uses a flux whose main component is F2,
A non-oriented electrical steel sheet with low iron loss can be obtained at extremely low cost.

The micrograph and EPMA analysis results in FIG. 1 show inclusions contained in the final product of the present invention and inclusions that are included in conventional products.

As is clear from FIG. 1, the inclusions of the present invention are present in sample 1.
Sample 2 is a combination of (CaMn)-8 around Al2O3, and sample 2 is a combination of A7N and (CaMn)-8, both of which form spherical composite inclusions (C-based inclusions). Its size is about 5μ.

On the other hand, inclusions in ordinary materials are lumpy Al as in sample 1.
2O3 and stretched (MnCa)-8, or as in Sample 2, massive Al2O3 and stretched Mn5 (A-based inclusions); in any case, both exist separately.

Therefore, MnS existing in an elongated shape in the inclusions of the normal material
Or (MnCa) S inhibits crystal grain growth, but in the present invention, it is rendered harmless as a spherical composite inclusion as described above, and does not inhibit crystal grain growth.

Figure 2 shows the ratio of the number of inclusions of the present invention (i.e., spherical composite inclusions in which calcium manganese sulfide is combined with one or both of aluminum oxide and aluminum nitride) to the total number of sulfide-based inclusions and iron. Loss (Wl 5150 (W/9)
).

In this case, the amount of inclusions is measured according to JIS. GO555 (Microscopic test method for non-metallic inclusions in steel.

Based on.

As can be seen from FIG. 2, the iron loss improves as the number of inclusions of the present invention increases, but a remarkable effect can be obtained when the number ratio is set to a factor of 20 or more.

Especially when it comes to 50 sections or more, JIS-C2552-197
It can be seen that the iron loss is improved to a level equivalent to 89 described in No. 8.

Note that other sulfide inclusions include, for example, FeS,
MnS etc. were confirmed.

Figure 3 shows how the relationship between the amount of S in steel and iron loss differs between when the steel contains the inclusions of the present invention (approximately 50 times the total amount of sulfide inclusions) and when it contains inclusions of ordinary steel. This shows whether there is a difference.

As is clear from this figure, when compared at the same 〇 level, the material of the present invention has a much lower core loss value, and the difference is particularly large as the level 〇] is lower.

This is because the lower the [■], the more completely the sulfides are transformed into composite inclusions.

An example of the method for manufacturing the low core loss non-oriented electrical steel sheet of the present invention is as follows.

First, molten steel produced in a steelmaking furnace is subjected to vacuum treatment.

This vacuum treatment decarburizes the molten steel and removes about 4% of the oxygen in the molten steel.
After reducing the amount to 00 ppl [1 or less, Al and Si are added during vacuum treatment for the purpose of removing residual oxygen and containing components.

A flux containing CaO and CaF2 as main components is added to the molten steel during vacuum treatment while leaving an appropriate amount of Al2O3 mainly produced by this addition of AA and forming a part of A7N to remove S and perform the present invention. Forms inclusions.

The addition amount of this flux is at least 0.5 kg/T-8 tee 1 or more in order to obtain the amount of inclusions of the present invention, and the upper limit is about 20 kg/T-8 tee 1, while CaF2 is about 5 to 40 It is a weight ratio.

The added flux that does not form the inclusions of the present invention hardly floats in the molten steel and is contained in the steel. For example, according to actual results, Ca is a small amount of 50 ppm or less.

The thus treated molten steel is then subjected to the continuous casting method (
or ingot method) to create a slab (or steel ingot),
It is made into a hot coil by predetermined hot rolling, and then cold rolled and annealed one or more times to produce a non-oriented electrical steel sheet with low iron loss.

The amount of C in the final product is limited to 0.005% or less.

This is because if it exceeds this range, the deterioration of magnetism will increase due to magnetic aging during use of the steel plate.

Next, Si is contained in order to obtain the required magnetic properties, and in particular, since the present invention is aimed at high-grade non-oriented electrical steel, it is necessary to contain Si in an amount of 1.5% or more.

However, if the amount is too large, cold rolling becomes difficult, so the upper limit was limited to 4.0.

Further, Sol and Al are contained in a range of 2.5 or less for the purpose of further improving magnetic properties.

Examples will be described in detail below.

Mn is added to improve brittleness during rolling, and must have a coefficient of 010 or higher.

However, as the content increases, the cost increases.
The upper limit should be kept at 1.0%.

Oxygen and nitrogen are both elements that are unfavorable for magnetism (iron loss), and each should be 50 pp [[1 or less].

The decarburization and deoxidation of molten steel blown in a converter is promoted by an RH type vacuum degassing device, and when the C content in the steel becomes 0.005 parts or less (oxygen content 0.0460 parts or less) Then, 7.0 to 8 Okg/t-Steel of Al was added to completely deoxidize the steel, and AA was contained at 0.450 to 0.6so.

Thereafter, Si was added to make the Si content in the range of 2.90 to 3.15.

Thereafter, the following treatments were performed on samples A to G shown in Table 1, respectively.

First, for samples A, B, and C, a flux consisting of CaO and CaF2 with a particle size of 3 to 5 mm (7) was mixed with CaO 3 to 8 kg/
t-8teel, CaF20.6~1. ．． 6kg
/ Add t-8teel, sample, E is CaO0,
1~0.3kg/t-5teel, CaF2o
, 9/t-8teel was added to o5-0.06, followed by stirring for 15 minutes.

On the other hand, no flux was added to samples F and G.

The degree of vacuum at the end of the process was 0.03-0.05 torr.

For samples A, B, and C, desulfurization (sections 45 to 68) and deoxidation were also performed by adding Franks.

The molten steel thus obtained was subjected to a single rolling annealing process including continuous casting, hot rolling, and hot coil annealing according to a conventional method to produce a product of 0351n111.

Table 1 shows the component composition and magnetic properties (iron phase).

The nonmetallic inclusions formed by the addition of flux are mainly a mixture of spherical composite inclusions in which Al2O3 and (CaMn)-8 are combined and spherical composite inclusions in which AlN(CaMn)-8 is combined. confirmed.

As is clear from Table 1, even if flux is added, the amount of spherical composite inclusions is small and the amount of spherical composite inclusions is less than 20%. Comparative material E and normal materials F and G without flux have iron loss values. is high and corresponds to class 5-12 of JIS-C2552-1978, whereas materials A, B, and C of the present invention have a high
-io.

It is possible to obtain low iron loss values up to S-9 equivalent products.

Furthermore, the flux used in the production of the non-oriented electrical steel sheet of the present invention has the advantage that it is cheaper than conventional additives and that high-quality products can be obtained at low cost.

[Brief explanation of the drawing]

Figure 1 shows a micrograph (x:rooo) and EPMA analysis results showing inclusions contained in the invention material and the conventional material.
The figure shows the relationship between the amount of spherical composite inclusions in the total amount of sulfide inclusions and iron loss. Figure 3 shows the relationship between the amount of S in steel and iron loss depending on the presence or absence of spherical composite inclusions. This is a chart showing how things change.

Claims (1)

[Claims] 1% by weight, C = 0.005, Stl, 5-4.0
%, Mn 0.10 to 1.0%, 5ol Al and 2 to 5%, and oxygen and nitrogen are each 50 pIM [1 or less], and calcium manganese sulfide is added to one or both of aluminum oxide and aluminum nitride. The number ratio of spherical composite inclusions that are coalesced is 20 or more of the total amount of sulfide inclusions,
A low iron loss non-oriented electrical steel sheet consisting of the remainder iron and unavoidable impurities.