JPH01198428A - Production of non-oriented silicon steel sheet having excellent magnetic characteristic - Google Patents

Abstract

PURPOSE:To prevent generation of ridging by specifying the values of Si+Al and Mn of a specifically composed steel to obtain an alpha-gamma transformed steel and subjecting this steel to hot rolling under specific conditions. CONSTITUTION:The ingot contg. <=0.01% C, 1.65-2.4% (Si+Al), <=0.006% S, <=2.0% Mn, and the components satisfying the formula is heated and is then subjected to the hot rolling at a finishing temp. of 700 deg.C-A1 transformation point. Or the ingot may be reheated after rough rolling of >=10% draft at 1000-1200 deg.C prior to this hot rolling. The resulted steel sheet is coiled at <=600 deg.C and is annealed at 600-750 deg.C before or after pickling. The annealed sheet is cold rolled down to a desired sheet thickness and is then subjected to continuous annealing under ordinary conditions. The alpha-gamma transformed steel is not obtainable in both cases in which the content of the Si+Al exceeds the upper limit unless the Mn is added at the excess ratio to deteriorate the magnetic characteristics and in which said content is below the lower limit. The formula is not satisfied and the ridging prevention is not possible if the content of the Si+Al is above the lower limit and, therefore, the austenite region is expanded by positively adding the Mn to the steel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing non-oriented electrical steel sheets that do not cause creasing.

[Prior Art] Conventionally, materials for electrical steel sheets of JIS intermediate grade (50A310 to 50A470) usually have a Si content of 1.5 to 1.5.
2.5% steel is used. However, it is generally known that when such a material is used, uneven surface defects called ridging are likely to occur during cold rolling.

In order to prevent this ridging, for example,
No. 4614 discloses a method of annealing a hot rolled sheet at a temperature higher than the recrystallization temperature. However, with this method, for electrical steel sheets with a Si content of 1.5 to 2.5%,
An annealing temperature of 50 to 900°C must be ensured,
There were drawbacks such as deterioration in energy consumption and productivity.

It is said that the occurrence of ridging is caused by the texture during hot rolling. The present inventor focused on this point as a method to prevent ridging, and found that if α-γ transformed steel is used as a material, the texture changes due to α-γ transformation during hot rolling or the subsequent cooling process, which prevents ridging. I discovered that it can be prevented.

However, when the C content is 0.005%, the Si content corresponding to the α-γ region limit is 1.5%, and for materials containing more than this, α-γ transformation steel should be applied. I couldn't. In addition, since AQ has the same effect as Si on α-γ transformation, it is effective only in the range of (Si + Al) 51.5%, and cannot be applied to materials with a higher (Si + Al) content. I couldn't do that.

Note that in order to expand the γ region, it is sufficient to increase C, but increasing C significantly deteriorates the magnetic properties and is therefore not practical.

[Problems to be solved by the invention] The present invention has been made in view of the above facts, and
To realize a method for manufacturing a non-oriented electrical steel sheet that can prevent the occurrence of ridging without requiring high-temperature hot-rolled sheet annealing as described above even when using a material with +Al) of 1.5% or more. It is for.

[Means for Solving the Problems] The present invention for solving the problems described above includes C50°01%,
(Si+Al): 1.65-2.4%, S≦0.00
6%, Mn≦2.0%) and (.

Si+Al)-0,5Mn: After heating a steel piece containing a component satisfying 1.4 to 1.8%, 1,000 to 1,10
Rough rolling is performed at a temperature of 0°C with a reduction ratio of 210% or more, then heating is performed again, hot rolling is performed at a finishing temperature of 700°C to A, the transformation point, and coiling is performed at a winding temperature of 600°C or less, and pickling is performed. Non-directional with excellent magnetic properties, characterized by hot-rolled plate annealing at 600-750°C before or after pickling, cold rolling to the desired thickness, and continuous annealing under normal conditions. This is a method for manufacturing electrical steel sheets.

Another aspect of the present invention for solving the above problems is that C≦0.01%, (Si+Al): 1°65 to 2.
4%, S≦0.006%, Mn≦2゜0%) and (
Si+Al)-0,5Mn: After heating a steel piece containing components satisfying 1.4 to 1.6%, 1s 000 to
1. ．． Rough rolling is performed at a temperature of 100°C with a reduction ratio of 210% or more, then heating is performed again, hot rolling is performed at a finishing temperature of 700°C to At transformation point, and coiling is performed at a winding temperature of 600°C or less, before pickling. Alternatively, a non-directional electromagnetic material with excellent magnetic properties is produced by hot-rolled plate annealing at 600-750°C after pickling, followed by cold rolling to the desired thickness, and continuous annealing under normal conditions. This is a method for manufacturing steel plates.

[Function] First, the limitations and reasons for the added components of the steel slab, which is the material of the present invention, will be explained.

When C exceeds 'o, oi%, magnetic aging occurs significantly and the magnetic properties deteriorate, so the upper limit was set at 0.01%.

(Si+Al) is an essential element for improving magnetic properties, and has an important effect on α-γ transformation as described above. That is, when 5(Si+Al) exceeds 2.4%, α-γ transformed steel cannot be obtained unless Mn is excessively added. Since excessive addition of Mn deteriorates the magnetic properties as described later, the upper limit of the addition of (Si+Al) was set at 2.4%.・Also, when (Si + Al) is 1.65% ungrooved, as will be described later, in steel with normal Mn content, α-γ
This is because it cannot become transformed steel and desired magnetic properties cannot be obtained.

S combines with Mn to produce MnS, which inhibits grain growth during annealing and worsens the iron loss value (W/Kg).
The upper limit was set at 0.006%.

Mn is an element effective in increasing the specific resistance and improving the iron loss value. Furthermore, Mn is also a γ-producing element, and by increasing the amount added, the γ-producing region is expanded. but,
If Mn is added excessively, the α-γ transformation point will drop significantly and magnetism will be lost, and a situation will occur where the α-γ transformation point will be passed during hot rolling, which will cause plate thickness fluctuations. The upper limit of in was set to 2.0%.

By adding an appropriate amount of Mn in this way, it is possible to reduce the amount of (Si+Al) added necessary to ensure magnetic properties equivalent to conventional ones, and as a result, magnetic flux density and magnetostriction can be improved. can.

Furthermore, the present inventors have found that within the above component range, in order to realize α-γ transformed steel, it is necessary to use the following formula (1) as the component to be titrated.

(Si+Al)-0,5Mn=1.4-1.8%-1-
(1) The meaning of the above formula (1) will be explained below.

Mn is an element that exists in hot metal itself, and cannot be eliminated. In a normal hot metal component, Mn is about 0.1%, and at this time, the content of (Si+Al) satisfying equation (1) is 1.45 to 1.65%. Normally, when the content of (S i +Al ) is < f m in this range, no shear or zinc occurs C). However, according to the present invention, (S i + Al) (
1) In electrical steel sheets with a content of t, es% or more, the above formula (1) is not titrated and ridging cannot be prevented, so Mn is actively added. This allows the austenite region to be expanded, and as a result, ridging can be prevented even in steel where (Si+Al)≧1.65%.

Next, the reason for limiting the conditions when hot rolling a steel slab having the above components will be described.

First, rough rolling is performed before hot finish rolling at a rolling reduction rate of 10.
% or more is that the rough rolling imparts strain to the rolled material to make the crystal grains finer, and the subsequent reheating to about 1,200° C. makes the material structure regular. If the rolling reduction rate is less than 10%, the above effect cannot be obtained sufficiently.
The lower limit was set at 10%. Moreover, the reason why the temperature of the rolled material at this time was set to 1,000 to 1.200°C is that the rolling reduction required to form crystals becomes extremely large in a temperature range outside this range.

In this way, the occurrence of ridging can be further prevented by refining the crystal grains by performing rolling at a light reduction rate during hot rolling. However, performing light reduction and reheating during hot rolling as described above is disadvantageous in terms of efficiency and energy cost, so it is necessary to take into account the composition of the steel and the generation of zinc. You can do it accordingly.

The higher the hot rolling finishing temperature, the better the texture and the higher the magnetic flux density of the product. However, when the temperature of the rolled material passes through A, the transformation point, in the latter half of the rolling schedule, the thickness variation of the rolled material increases, so the finishing temperature needs to be below A, the transformation point. In addition, the finishing temperature is 700℃
If it is less than 7, the rollability and magnetic flux density will deteriorate, so the lower limit is 7.
The temperature was 00°C.

The winding temperature after hot rolling was set to 600° C. or lower because the lower the temperature, the better the pickling properties during the subsequent pickling.

Pickling is necessary to perform descaling by pickling before rolling in order to prevent scale from adhering to the rolls during cold rolling and causing surface flaws in the rolled product.

Next, hot-rolled sheet annealing is performed to improve magnetic properties.

The annealing temperature for hot-rolled sheet annealing is less than 600°C, which has no effect on improving magnetic flux density.
If the temperature is higher than 600°C, nitridation will occur in the N2 atmosphere, deteriorating the magnetic properties, and as mentioned above, high-temperature annealing will also deteriorate the energy consumption and productivity. The temperature was set at ~750°C. In addition, either of the pickling and hot-rolled sheet annealing steps may be performed first.

The rolling reduction ratio in cold rolling is not particularly limited, but if it is less than 70%, the load during hot rolling becomes large, and if it exceeds 95%, cold rolling becomes difficult.

The reason for performing continuous annealing is to perform rapid heating/rapid cooling to improve the texture, and batch annealing cannot achieve this effect. Further, the continuous annealing conditions may be those normally used, but the following points should be taken into consideration. first,
When the annealing temperature is less than 600℃, sufficient growth of crystal grains cannot be obtained, and when the annealing temperature exceeds 10001℃, the crystal grains become excessively large, and the desired magnetic properties cannot be obtained in either case. Soaking The soaking time must be at least 30 seconds; if it is shorter than that, the grain size within the steel sheet will not be uniform and the magnetic properties will vary, so the soaking time must be at least 30 seconds.

[Example code] Next, examples of the method of the present invention will be described.

Ingredients shown in Table 1, Thickness: 230 mm Width:
, hot rolling a 1000 mm continuous cast slab to a thickness of 2.3 mm under the hot rolling conditions shown in the same table, followed by pickling and batch annealing the hot rolled sheet under the conditions shown in the same table. It was performed by annealing. Thereafter, it was cold rolled to a plate thickness of 0.5 mm and continuously annealed under the conditions shown in the same table. As for the magnetic properties at that time, the same table shows the iron loss value w 115/B (1) and the measurement results of the magnetic flux density B6o, and the results of examining the presence or absence of the occurrence of sliding on the steel plate surface are shown as Example 1 #4. Indicated.

Furthermore, as another example of the method of the present invention, as shown in Table 1, the same ingredients as in Example 1 were used, and the thickness was 23 Omm.
x Width: After heating a continuous casting slab of 1000 mm, it was roughly rolled to a slab thickness of 150 mm, and then reheated to 1200°C, and subsequently, as shown in the same table, it was manufactured under the same conditions and similar to the above-mentioned example. After producing electrical steel sheets through the process, the results of similarly measuring the iron loss value Wt6/150, the magnetic flux density Boo, and the presence or absence of ridging were shown as Examples 5 to 8.

Similarly, as a comparative example, it is outside the component range of the present invention,
Comparative example 1 is a slab with a component system that does not take α-γ transformation into consideration.
Production was carried out under the conditions shown in the same table as -4.

(Hereinafter, blank space) As a result, in Comparative Examples 2 and 4, in which the S1 content was 1.5% or less and hot rough rolling was not performed, no welding and zinc occurred, but the iron loss value WIIS150 was 5 (W/
Kg) or more, which is a very large value.

In addition, Comparative Example 1 and Comparative Example 3 with Si content of 1.5% or more
Zinc is occurring.

On the other hand, in Examples 1 to 4 of the present invention in which the values of (Si+Al) and Mn were selected to appropriate values, electrical steel sheets with excellent magnetic properties were manufactured without causing ridging. was completed.

Furthermore, in addition to selecting appropriate values for (S i + Al ) and Mn, ridging also occurred in Examples 5 to 8 of the present invention, which were reheated after rough hot rolling. It was possible to produce an electrical steel sheet with excellent magnetic properties without using any of the above methods.

[Effects of the invention] As described above, according to the present invention, (Si+Al) and Mn
By setting the value of to an appropriate value, in addition to utilizing α-γ transformation, ridging can occur by performing hot rough rolling and then reheating and continuing hot rolling. It is possible to produce an electrical steel sheet with excellent magnetic properties without deteriorating energy consumption or productivity by hot-rolled sheet annealing at a relatively low temperature.

Claims (2)

[Claims] (1) C≦0.01%, (Si+Al): 1.65-2
．． 4%, S≦0.006%, Mn≦2.0%, and (
Si+Al)-0.5Mn: After heating a steel billet containing a component satisfying 1.4 to 1.6%, it is hot rolled at a finishing temperature of 700°C to A_1 transformation point, and then rolled at a coiling temperature of 600°C or less. The magnetic property is characterized by hot-rolled plate annealing at 600 to 750°C before or after pickling, cold rolling to the desired thickness, and continuous annealing under normal conditions. A method for producing excellent non-oriented electrical steel sheets. (2) C≦0.01%, (Si+Al): 1.65-2
．． 4%, S≦0.006%, Mn≦2.0%, and (
Si+Al)-0.5Mn: 1,000 to 1,20 after heating a steel piece containing a component satisfying 1.4 to 1.6%
Rough rolling is performed at a temperature of 0°C with a reduction ratio of 10% or more, then heating is performed again, hot rolling is performed at a finishing temperature of 700°C to A_1 transformation point, coiling is performed at a winding temperature of 600°C or less, and acid A non-directional sheet with excellent magnetic properties, characterized by hot-rolled sheet annealing at 600-750°C before washing or pickling, followed by cold rolling to the desired sheet thickness, and continuous annealing under normal conditions. manufacturing method of magnetic steel sheet.