JPS5974224A - Producton of non-directional silicon steel sheet having extremely outstanding magnetic characteristic - Google Patents

Abstract

PURPOSE:To produce a high grade non-directional silicon steel sheet having a low iron loss and a high magnetic flux density by decreasing considerbly S, O and N among the impurities contained unavoidably in a blank material for a silicon steel and annealing a base strip under specific conditions after hot rolling then cold rolling the strip at a high draft. CONSTITUTION:A blank material for a silicon steel contg., by weight %, <=0.005 % C, 2.5-4.0% Si, 0.25-1.00% Al, and 0.1-1.0% Mn is hot rolled by an ordinary method. A base strip is annealed and is then made into a final plate thickness by one time of a cold rolling method, in succession to which the strip is subjected to continuous finish annealing. The S, O and N among the impurities contained unavoidably in the blank materal are considerably decreed to <=15ppm, <=20ppm and <=25ppm respectively in the above-mentioned stage. The annealing of the base strip is accomplished under the conditions of 900-1,050 deg.C and 2- 15min. The draft in the cold rolling is set at >=65%. The non-directional silicon steel sheet having an extremely outstanding magnetic characteristic is thus produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a non-oriented silicon steel sheet with extremely excellent magnetic properties, and particularly an advantageous method for manufacturing a high-grade non-oriented silicon steel sheet with low iron loss and high magnetic flux density 1f. This is what we are trying to propose.

Generally, non-oriented silicon steel sheets are graded by iron loss, and currently the highest grade according to JIS standards is grade 8-9 (plate thickness 0.
85 u at w”/5o<0.95, W”'/5o
<z. 4ow/IH, W10/5o with plate thickness 0.50mm
<1.15.

W15/5. <2.90 W/}, ). However, as iron core materials for large power generators and the like, there is a strong demand for high-grade non-oriented silicon steel sheets in the 8-8 class to 8-7 class, which have even lower iron loss in order to reduce power loss.

The present invention advantageously meets these demands, and aims to provide a method for manufacturing a high-grade non-oriented silicon steel sheet with low core loss and high magnetic flux density.

By the way, methods for manufacturing non-oriented silicon steel sheets can be roughly divided into a single cold rolling method and a double cold rolling method.

The former is a process in which hot-rolled steel strip is cold-rolled once to achieve the final product thickness and then subjected to continuous finish annealing, and although the cost is low, sufficient grain growth is not achieved due to the intense cold-rolling reduction. Iron loss is relatively high. Therefore, it is mainly used as a manufacturing method for low-grade products of grades 5-12 and below.

On the other hand, the latter two-step cold rolling method is a process in which intermediate annealing is performed after the first cold rolling, and then the second cold rolling is performed again.
In this case, the magnetic properties are strongly influenced by the intermediate annealing conditions and the second cold rolling. Generally, when iron loss is important, a method is adopted in which the final cold rolling is lightly reduced, and the strain energy introduced earlier during continuous finish annealing is used to cause significant grain growth to improve iron loss. However, according to this method, the texture is randomized, so the magnetic flux density is low.

Iron core materials for large generators are required to have a high magnetic flux density so that they can be used in magnetic fields higher than 1.5 T.

This invention relates to the improvement of the manufacturing method of non-oriented silicon steel sheets by the two-time cold rolling method, which is one of the two manufacturing methods that have been developed. The present invention proposes a manufacturing method capable of obtaining a high-grade non-oriented silicon steel sheet of 87 to 8 class.

This invention is based on a new technology that can significantly reduce the impurities that inevitably get mixed into steel, in line with recent advances in steelmaking technology. As a result of this research, it was discovered that if the impurities, especially sulfur (denoted as 8 below), oxygen (O) and nitrogen (N) are extremely reduced and the cold rolling conditions are appropriately controlled, is based on the new knowledge that excellent magnetic properties can be obtained due to different recrystallization behavior.

That is, this invention has C: 0.005% by weight or less, S
i: 2.5-4.0 M completion%, Aj: 0.25
~1.00 wt% and Mn: 0.1 = 1.0
A material for silicon steel containing % by weight is hot-rolled according to a conventional method, then subjected to household annealing, and then cold-rolled once to obtain the final thickness, followed by continuous finish annealing to produce a non-oriented silicon steel plate. (a) Of the impurities that inevitably mix into the material, S.

For 0 and N, respectively, S: 1 5 ppm or less, 0: 20 ppm or less and N: 25 p
(b) Household annealing at 900-1050°C, 2-15
(c) A manufacturing method of a patented silicon steel sheet, characterized in that the manufacturing method is carried out under conditions of 1 minute, and (c) the reduction sign of cold rolling is 65% or more.

This invention will be specifically explained below based on the experimental results that led to this invention.

1l80 silicon steel slab with the composition shown in Table IK
After heating at °C for 1 hour, it was hot rolled to a thickness of 1.0
111+, 1,4 1111, 1.7 m and j3. Hot-rolled sheets were prepared in Q order. Each of these hot-rolled sheets was heated to 850°C.

After household annealing for 5 minutes at 900°C, 950°C, 1000°C, and 1060°C, surface scale was removed by pickling, and the product was finished by cold rolling to a thickness of 0.50 mm. Continuous finish annealing was then performed at 1000°C for 8 minutes.

The results of investigating the relationship between the household annealing temperature and the magnetic properties of each of the obtained steel sheets are shown in Figures Sill to 2 for each cold rolling section.

Table 1 From the same figure, it can be seen that the magnetic properties improve as the household annealing temperature increases, but the levels of iron loss and m-east density differ depending on the material composition and cold rolling reduction.

8: 80 ppm, O: 22 ppm
, N: 2. The magnetic properties of the hot-rolled sheet obtained from slab A containing 6 ppm remain at grade S-9 no matter what household annealing temperature or cold rolling reduction ratio is taken. On the other hand, the hot-rolled sheet made of slab B with extremely low 8°0 and N content in the steel has excellent magnetic properties in both cold-rolling regions, and has a cold-rolling density of 65% or more and Obiyaki slanting drama 90
Those processed at 0°C to 1050°C have iron loss w”/, o
: 1.05 ”/to, below, w”Zo : 2.50
”/Shows excellent magnetic properties of S-7 class under Tottori.

This point 8: 15 ppm or less, O: 20 ppm
Below, N: If any of the components is contained in a large amount below 25 ppm at ℃, no significant improvement in magnetic properties can be expected and grade 8-7 cannot be obtained even if household annealing and cold rolling are performed under optimal conditions. .

Next, the reason why the component composition is limited to the above range in this invention will be described.

C: If more than 0.005% of C remains in steel, it deteriorates the magnetic properties due to magnetic aging.
It was set to 0.005% or less.

If Sl is less than 2.5%, it is possible to manufacture high-grade products of grade S-8 or higher, but if it exceeds 4.0%, cold rolling workability deteriorates, so Eli: 2.5 to 4.0 %.

Kl is required to be 0.25% or more in order to improve magnetic properties, but if it exceeds 1.00%, cold rollability deteriorates, so A7: o, ga ~ 1.00%.

Mn is added to suppress hot embrittlement caused by S, but if it is less than 0.1%, it is not effective in preventing cracking.
On the other hand, if the amount exceeds 1.0%, the magnetic properties deteriorate, so Mn
: 0.1 to 1.0%.

S, O and N are 15 ppm and 20 ppm respectively
m.

If the content exceeds 25 ppm, fine inclusions will increase, which will inhibit the growth of crystal grains in the steel sheet during continuous finish annealing, and the significant improvement in magnetism as expected in this invention cannot be expected. Below, 0:20 ppm
Hereinafter, it is particularly important to keep N:Z to 5 ppm or less.

Now, the molten steel whose composition has been adjusted as described above is cast into a steel slab by continuous casting or by an ingot-blowing method. The thus obtained steel slab is hot rolled by a known method and finished to a thickness of 2.0 to 8.0 mm.

Next, cold rolling is performed, and the reason why the cold rolling conditions are limited as described above in this invention is as follows.

2-15 at 900-1050°C in single cold rolling method
The purpose of household annealing for 1 minute is to homogenize the structure of the hot-rolled sheet and to coarsen the grain size. is not sufficiently improved, and magnetic properties of class 8-7 cannot be obtained. On the other hand, household annealing at a temperature exceeding 1050° C. or for a longer time than 15 minutes causes the crystal grains of the hot-rolled sheet to become excessively large, causing cracking of the sheet during rolling.

In addition, the reason why the cold rolling reduction ratio in the double cold rolling method was set to 65% or more was because
If the reduction is less than 65%, grade 8-7 cannot be obtained, and for example, if the product thickness is Q, 35m, it is necessary to hot-roll the steel slab to a thickness of 1.01m or less, but in this case, the steel plate To avoid problems such as poor shape and sheet breakage, the cold rolling height was set at 65% or more in the case of the single cold rolling method.

The reason why the magnetic properties are greatly improved as described above is that
The decrease in fine inclusions and precipitates associated with the reduction of S, O, and N affects the recrystallization behavior during final annealing, and this difference in recrystallization behavior may result in the desired texture shape. , has been confirmed as a result of numerous experiments.

Next, embodiments of this invention will be described.

Example: Molten steel produced in a converter was immediately degassed, and then Mn
After adjusting the composition by adding alloy components such as + si I A1, a slab was obtained by continuous casting. The component analysis values for this slab were as follows.

C: 0.008%, Si: 8.21%, Mn
:Sail 15%.

S: 0.0006%, At: 0.60%,
P: 0.010%.

0: 0.0004%, N: 0.0018% This slab was heated at 1150° C. for 1 hour, and then hot rolled into a hot rolled sheet having a thickness of 2.0 mm. 95 on this hot rolled plate
Continuous annealing was performed at 0°C for 5 minutes.

Next, the surface scale of the annealed hot-rolled sheet was pickled and removed, and then finished by cold rolling to a thickness of 0.50111 (rolling down 75%), followed by 1000°C H, near 0%, N,
: Continuous finish annealing was performed for 8 minutes in an 80% dry atmosphere. As a comparative example, slabs having the following component compositions were processed in the same process and their magnetic properties were compared.

c: 0.004%, Si: 8.28%, M
n: 0.16%.

s: o, ooao%, Al: 0.62%, P
: 0,012%.

Table 2 shows the results of investigating the magnetic properties of each steel sheet obtained with 0: 0.0025% and N: 0.0028%.

Table 2 Comparative examples in which S, o, and N deviated from the appropriate ranges of the present invention did not have very good magnetic properties even if they were subsequently subjected to appropriate cold rolling. The invention material, in which both N and N were significantly reduced, exhibited excellent magnetic properties of grade 8-7, and was superior in grade 2 properties to the comparative example.

As described above, according to the present invention, even in the -fold cold rolling method,
It is possible to easily obtain high-grade non-oriented silicon steel sheets that have excellent magnetic properties with low iron loss and high magnetic flux density.
It's advantageous.

[Brief explanation of drawings]

Figures 1 to 4 show the rolling reduction of 50% for the single cold rolling method, respectively.
Matrix annealing tolerance and W at 65%, 70% and 75%
10/l5o(a), W15/, o(b), and B5o(c); FIG. Patent Applicant: Kawasaki Steel Corporation Figure 1 Figure 2 Figure 3 Figure 4 Procedural Amendment (Method) March 1, 1981 1. Display of the Case 1984 Patent Application No. 184164 2. Title of the Invention Method for manufacturing non-oriented silicon steel sheet with extremely excellent magnetic properties 3
, Relationship to the case of the person making the amendment Patent applicant (125) Kawasaki Steel Corporation 5 Date of amendment order February 22, 1981 1, page 12, lines 6 to 10 of the specification amended as follows: do. [4. Brief description of the drawings Figure 1 a, b and 0 are graphs showing the relationship between the household annealing temperature and W 10/ , W IZ[I0 and B50 at a cold rolling rate of 50%, respectively; Figure 2 a
, b and O are the household annealing temperature at a cold rolling rate of 65% and W 107 , W 1515°0 and B, respectively. Graph showing the relationship between
, b and C are the household annealing temperature and WIO at a cold rolling rate of 7%, respectively. , W i. Graphs a, b and O shown in FIG. 4 show the relationship between household annealing temperature and W 107. at a cold rolling rate of 75%, respectively. ,
, W is a graph showing the relationship between 1515° and B11. ” 2. Figure 1-4 is corrected as shown in the attached sheet. Fig. 1 (revised - 4'l! 114 ce J/f (-C), C: g-size ≧ Oko 1 no Fig. 8 Fig. 4

Claims (1)

[Claims] L O: 0.005 weight or less, Si: 2.5
~4.0% by weight, At: 0.25~1.00% by weight
A material for silicon steel containing 0.1 to 1.0% by weight of In:' is hot-rolled according to a conventional method, then mother-of-the-plate annealing is performed, and the final thickness is obtained by the 11 cold rolling method, followed by continuous rolling. When manufacturing non-oriented silicon steel sheets by final annealing, (a) Regarding impurities that are inevitably mixed into the material, each of oxygen and nitrogen shall be considered: 15 p.
pm or less, oxygen: 20 ppm or less and nitrogen: 2
(b) Suppress mother zone annealing to 5 ppm or less, 90
A patented method for producing a grain-oriented silicon steel sheet, characterized in that the cold rolling is carried out under conditions of 0 to 1050''C for 2 to 15 minutes, and (c) the reduction ratio of cold rolling is 66% or more.