JPS6134118A - Manufacture of grain oriented silicon steel sheet having high magnetic flux density and low iron loss - Google Patents

Abstract

PURPOSE:To obtain a steel sheet having both high magnetic flux density and ultralow iron loss by applying a specified annealing until final cold rolling after intermediate annealing, in manufacture in which silicon steel material contg. Mo and havng a specified compsn. is hot rolled, cold rolled contg. intermediate annealing, and finally decarbonizing annealed. CONSTITUTION:Grain oriented silicon steel material contg. by weight, 0.01- 0.06% C, 2.0-4.0% Si, 0.01-0.2% Mn, 0.003-0.1% Mo, 0.005-0.2% Sb and 0.005-0.10% total of one or two kinds of S and Sb is hot rolled, next, cold rolled at least one time or more to final sheet thickness while contg. intermediate annealing. Here, annealing at 150-500 deg.C for 1sec-30min is carried out between said intermediate annealing and final cold rolling. Thereafter, said sheet is decarbonizing annealed also for primary recrystallization, the finishing annealed finally to develop secondary recrystallization grain having (110)[001] orientation. Thus, without inconvenience such as dirt of steel sheet surface in manufacturing process, grain oriented silicon steel sheet having >=1.91 T magnetic flux density B10, and <=1.00W/kg iron loss W17/50 is obtd.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing unidirectional silicon steel sheets with high magnetic flux density and low iron loss, and in particular, in a short period of time from intermediate annealing to final cold rolling. This is intended to improve the magnetic properties more favorably than by applying heat treatment.

(Prior art) It is a product in which crystal grains are highly concentrated in the (lio) [oox] direction, that is, the Gags direction, and are mainly used in transformers and other devices. It is used as the iron core of electrical equipment, and the product is required to have high magnetic flux density and low iron loss. Particularly in the wake of the energy crisis, demand for features that reduce power loss has become much stronger, and the need for unidirectional silicon steel sheets with lower iron loss as transformer core materials has become increasingly important. Come φ.

Methods to lower the iron loss of unidirectional silicon steel sheets include: ■ Increasing the S1 content to increase electrical resistance and lowering iron loss, ■ Decreasing the thickness of the product sheet, ■ Increasing the purity of the steel sheet. Or ■ Mainly metallurgical methods are generally known, such as increasing the Goss accumulation degree of secondary recrystallized grains of steel sheets and reducing the grain size, but these methods are limited by current production methods. It is considered to be close to the value.

Apart from these methods, a method has been proposed in which the secondary recrystallization grains are made finer by forming a secondary recrystallization inhibiting region on the surface of the steel sheet, as disclosed in Japanese Patent Publication No. 54-28647. has been done. However, this method cannot be said to be practical because the control of the secondary recrystallized grain size is unstable.On the other hand, Japanese Patent Publication No. 58-5968 etc. By introducing minute strain into the surface layer of the steel plate using ballpoint pen-shaped balls, the width of the magnetic domain is made finer.
A further method for reducing iron loss was published in Japanese Patent Publication No. 57-225.
Publication No. 2 discloses that the width of the magnetic domain is made finer by irradiating the surface of the final product sheet with a laser beam at intervals of several mm almost perpendicular to the rolling direction to introduce high dislocation density regions into the surface layer of the steel sheet.
Various methods for reducing iron loss have been proposed, and Japanese Patent Application Laid-Open No. 18881/1983 describes a similar method of reducing iron loss by introducing micro-strain into the surface layer of a steel sheet by electric discharge machining to refine the magnetic domain width. has also been proposed. All of these eight methods aim to reduce iron loss by refining the magnetic domain width by introducing minute plastic strain to the surface of the steel sheet after S-order recrystallization, and evenly. Although it is practical and has an excellent iron loss reduction effect, the effect of introducing plastic strain is reduced by heat treatment such as punching and shearing of steel sheets, strain relief annealing after winding, and baking of coatings. It comes with some disadvantages. In addition, when introducing minute plastic strain after the coating process, it is necessary to repaint the first insulation coating to maintain the insulation properties, which significantly increases the number of processes such as the strain imparting process and the repainting process, which increases costs. This also adds disadvantages (problems to be solved by the invention) The recent manufacturing technology for low core loss unidirectional silicon steel sheets has been described above. In addition to using subdivision technology, we have been conducting experiments to explore ways to improve iron loss using metallurgical methods.

As a result, for the unidirectional silicon steel sheet containing MO,
It was found that it was possible to produce a hard steel sheet of 800 to 500 Hv by warm rolling at a temperature of KIIIθ to 500° C. before the final cold rolling, and this was disclosed in Japanese Patent Application No. 58-280848.

Separately, in Japanese Patent Publication No. 18846/1984 and Japanese Patent Publication No. 29182/1984, hot rolling or A manufacturing method for obtaining unidirectional silicon steel sheets with low core loss through interpass aging has been proposed. However, although these methods are useful for improving magnetic properties,
Since the surface of the steel plate is contaminated due to warm rolling, the next step is decarburization/1.
There are many problems that still need to be resolved before it can be applied to actual manufacturing processes, such as adversely affecting the subsequent recrystallization annealing and requiring a long annealing treatment during rolling, which increases costs.

This invention advantageously solves the above-mentioned problems without causing disadvantages such as staining of the steel plate surface during the manufacturing process.B□. A high magnetic flux density with a value of at least 1.91 T and W1? The object of the present invention is to propose a grain-oriented silicon steel sheet that also has ultra-low core loss with an o value of 1.00''/ly or less.

(Means for Solving the Problems) That is, this invention provides C: 0.01 to 0.06 wt.
% (hereinafter simply expressed as %), si: 2.0 to 4.0%
, Mn: 0.01-0.2%, Mo: 0.008
~0.1% and Bb: 0.005 to 04%, and a unidirectional silicon having a composition containing one or both of S and Se in total of 0.005 to 0.10% The steel material is hot rolled, then cold rolled one or more times including intermediate annealing to obtain the final thickness, then subjected to decarburization annealing that also serves as primary recrystallization, and then final finish annealing. In a method for producing a grain-oriented silicon steel sheet, which comprises a series of steps of developing secondary recrystallized grains with (1], O) (001) orientation, during the period from the intermediate annealing to the final cold rolling, 150 1 second to 80℃ in the temperature range of ~500℃
This is a method for producing a unidirectional silicon steel sheet with high magnetic flux density and low core loss, which comprises performing an annealing treatment for 30 minutes.

In this invention, the intermediate annealing includes a rapid cooling treatment with a cooling rate of 5'C/s or more from 900°C to room temperature after annealing, or a process in which the heating rate and cooling rate from room temperature to 900°C are both 5'C/s or more. Those that involve rapid heating and rapid cooling are particularly advantageous.

Hereinafter, this invention will be specifically explained based on the experimental results that led to this invention.

C: 0.045%, Si: 8.40%, Mn:
0.068%, Ss: 0.020% and Sb
: A hot-rolled sheet of silicon steel (thickness: 2.7 mm) with a composition containing 0.025% is uniformly annealed at 900°C for 8 minutes, and then primary cold rolled to approximately 70%. I did it. Then, intermediate annealing, subsequent age annealing, and warm rolling were performed under conditions (1) to (lO) as shown in Table 1. After that, the sample was cold-rolled to form a final cold-rolled sheet with a thickness of 0.45 mm, and then decarburized in wet hydrogen at 820°C.
Next, recrystallization annealing was performed. Thereafter, an annealing separator containing Mgo as a main component was applied to the surface of the steel sheet, and secondary recrystallization annealing was performed at 850°C for 50 hours, followed by annealing at 1180°C in hydrogen.
Purification annealing was performed for 5 hours.

The results of investigating the magnetic properties of the obtained product are also listed in Table 1.

As is clear from the results shown in Table 1, the first intermediate annealing condition is K, followed by aging annealing at 850°C for about 20 seconds (44, 5, 6 and 10). Both Blo and W□V/SO are significantly improved.

On the other hand, when warm rolling was simply performed at 850°C after intermediate annealing according to the method disclosed in Japanese Patent Application No. 58-180848 (47, 8 and 9), normal annealing treatment (/161 ), when rapid cooling treatment is added after annealing (reduction
) and when rapid heating/quenching treatment was added (%8) K, the magnetic properties were somewhat improved, but it cannot be said to be sufficient.

As mentioned above, age annealing treatment is performed after intermediate annealing.
The reason why the magnetic properties are improved has not yet been clearly elucidated, but it is thought to be as follows.

In other words, when cold rolling is performed after fine carbides are precipitated within the primary recrystallized grains by such low-temperature aging, (111) [
There is a deformation band (Deforma
tion Band) is preferentially formed, and in the subsequent decarburization and primary recrystallization annealing, the Goss-oriented 1
This is thought to be because conditions are established in which secondary recrystallized grains are preferentially generated and secondary recrystallized grains in the Goss orientation are effectively developed in the subsequent secondary recrystallization annealing.

This idea is different from the conventional one, which aims to finely precipitate carbides during cooling after intermediate annealing.
The idea is that by once lowering the temperature to room temperature, carbides are finely precipitated within the matrix again to form deformation bands preferentially within the deformed grains in the (111) <112> orientation during the next cold rolling. It is something that changes.

Next, the reason why the component composition of the material is limited as described above in this invention will be explained.

C: 0.01 to 0.06% When C is less than 0.01%, it is difficult to control the hot rolling texture and large elongated grains are formed, resulting in deterioration of magnetic properties.On the other hand, when C is less than 0.06% If it is too large, it will take a long time to decarburize in the decarburization process, making it uneconomical, so it should be in the range of 0.01 to 0.06%.

Si: 2.0-4.0% If less than 2.0%, the electrical resistance will be low and the iron loss value will increase due to increased eddy current loss, while if it is more than 4.0%, it will cause brittleness during cold rolling. 2.0 to 4 because cracks are likely to occur
．． It is necessary to keep the pressure within the range of 0%.

Mn: 0.01-0.2% If Mn is less than 0.01%, sufficient MnSe precipitates cannot be formed, while if it is more than 0.2%, Mn
Since the heating temperature must be high to dissolve Se precipitates, (2) must be in the range of 0.01 to 0.2%.

Mo: 0.008-0.1% Regarding Mo K, the inventors first published the
As disclosed in Japanese Patent Publication No. 87 and Japanese Patent Publication No. 56-4618, by adding a small amount of MO up to 0.1%,
It has the effect of suppressing the growth of subsequent recrystallized grains, and the same effect can be expected in the present invention. If MO is more than 0.1%, hot and cold workability will decrease, and iron loss will deteriorate, so M
o must be within the range of 0.1% or less, while o,
If it is lower than ooa%, the effect of suppressing the growth of primary recrystallized grains is small, so Mo needs to be within the range of 0.008 to 0.1%.

S and/or Se: 0.005-0.10%B
All zBe is 0.1% or less, especially S is 0.00
The content of Se is preferably 8 to 0.1%, and the content of Se is preferably 0.008 to 0.1%. That means these are 0.1
%, hot and cold workability deteriorates, and below each lower limit, MnS.

This is because MnSe does not have a particular effect on the primary recrystallized grain growth inhibiting function, but known primary growth inhibitors such as Betayo5 Vr and Sb s Mo, which have already been described in the experimental examples, can be used advantageously in combination. Therefore, a total lower limit of 0.005% for S and Be is sufficient.

Sb: 0.005-0.2%
According to Publication No. 4, it is contained in 0.005 to 0.1%, and also in Japanese Patent Publication No. 51-1146, which the inventors previously disclosed.
According to Publication No. 9, it is known that the growth of primary grains is suppressed by K containing a trace amount of Se or S at 0.005 to 0.2%;
If b is less than 0.005%, the effect of suppressing primary recrystallized grains will be small, whereas if it is more than 0.2%, the magnetic flux density will begin to decrease and the magnetic properties will deteriorate, so Sb should be 0.006 to 0.
It is necessary to keep it within 2%.

In this invention, as mentioned above, CO is contained in the silicon steel material.
, 01-0.06%, 812.0-4.0%, MOo,
Basically, it contains 008 to 0.1% and 8b O, 005 to 0.5%, and a total of 0.005 to 0.1θ% of any one or both of S and Ss. , and other known elements normally added to silicon steel,
For example, Cr5Ti, VSZr%Nb%Ta
%C0qNi, SnsP, As, and the like may be contained in trace amounts. Also, acid-soluble AtO, 01-0.
09%, N O, 001-0.01% or B O,
By containing at least one of the following: 0008 to 0.005%, CuO, and 05 to 0.5%, a product with excellent magnetic properties can be stably obtained. 11 of these are 0.0
If it is 1% or more, supplementation with 5SSe, Sb 1Mo, etc. is not required, but it is of course possible to use them in combination.

Next, a series of manufacturing steps in this invention will be explained.

First, the process of melting the material can be performed using an LD converter, an electric furnace, an open hearth, or other known q steelmaking methods, and vacuum treatment and vacuum melting can be used together.

Continuous casting is currently being applied to the next generation of slabs due to its economical and technical advantages, such as improving yields, significantly reducing production costs by eliminating process steps, and uniformity of components and quality in the longitudinal direction of the slab. In addition, conventional agglomeration methods can also be suitably used.

In this invention, any conventionally known method can be used to add at least one of 8S813, 8b and MO contained in the material to the molten steel,
For example, it can be added to molten steel in an LD converter, at the end of RH degassing, or during ingot formation.

The continuously cast slab or the ingot is hot rolled in a known manner. Normally, a slab is rolled into a hot-rolled steel sheet, and the thickness of the resulting hot-rolled sheet is controlled by the subsequent cold rolling process, but it is usually advantageous to have a thickness of about 2 to 5 mm.

The hot rolled sheet is then uniformly annealed and then cold rolled. After cold rolling, the temperature is raised or cooled before and after intermediate annealing, but in order to obtain a product with high magnetic flux density and ultra-low iron loss, it is necessary to pay attention to the heating and cooling rates. In other words, the inventors
As disclosed in No. 14 Publication No. 19, rapid cooling treatment after intermediate annealing,
Alternatively, further improvement in properties is observed when rapid heating/quenching treatment conditions are applied as disclosed in JP-A-69-856B5.

In this regard, in this invention as well, the cooling rate after intermediate annealing before short-time aging treatment is set at 5'C/S from 900°C to room temperature.
or higher (preferably 10°C or higher), or the temperature increase rate before intermediate annealing is 5°C or higher from room temperature to 900°C (preferably 10°C or higher), and the temperature cooling rate after intermediate annealing is 5° from 900°C to room temperature. It is preferable to set the temperature to C/S or higher (preferably 10° C/S or higher).

Next, the steel plate that has been subjected to such intermediate annealing is subjected to aging annealing treatment before final cold rolling, and this aging treatment is performed at a temperature range of 150 to 500°C, as shown in Figure 1. 1
Annealing for seconds to 80 minutes, more preferably 200°C to 60°C
It is necessary to carry out annealing treatment for 1 second to 100 seconds in a temperature range of 0°C.

FIG. 1 summarizes the relationship between the temperature and time in aging treatment and the iron loss value of the product plate for silicon steels having five preferred compositions according to the present invention.

Although this aging treatment may be performed separately from the intermediate annealing, it is more preferable to perform the aging treatment in a continuous annealing line according to the heat pattern described above.

After such short-time aging annealing, final cold rolling is then performed. During the final cold rolling process, the inventors filed a patent application in 1973.
Although warm rolling or inter-bath aging treatment may be performed as disclosed in No. 8-280848, it is usually cold rolled at room temperature to the final plate thickness (0.20 to 0.85rIL1rL thickness) K. .

After finishing the final cold rolling, the steel plate that has reached the product thickness is then subjected to decarburization. The purpose of this annealing is to convert the cold-rolled structure into a primary recrystallized structure and at the same time to remove harmful C when the final annealing develops 8th recrystallized grains with (110)[001) orientation. Any known method can be used, such as annealing in hydrogen at 850° C. for about 8 to 15 minutes.

Final annealing is performed to sufficiently develop the 8th recrystallized grains with the (110) <001> orientation, and is usually carried out by box annealing where the temperature is immediately raised to 1000°C or higher and maintained at that temperature. . This final annealing is usually performed by box annealing after applying an annealing separator such as magnesia. In this invention, K is 880°C in order to develop 8th recrystallized grains that are extremely aligned in the (110) [001> orientation.
It is more advantageous to perform retention annealing at a low temperature of 900°C.
Alternatively, heat-removal annealing may be performed at a temperature increase rate of 0.5 to 15° C.4, for example.

Example l CO, 048%, Si B, 45%, Mn 0.072
%, BeO,020%, SbO,025% and Mo
After blooming a steel ingot containing 0.080%, hot rolling it to a thickness of 2.7 am, homogenizing it at 900°C for 8 minutes, and then cold rolling it to 70%. Then, intermediate annealing was performed at 960° C. for 8 minutes. During this intermediate annealing, the temperature increase rate is 400C/S- from room temperature to 600℃.
, 15℃/8.5 from 500℃ to 900℃, and the cooling rate is 15℃/8.5 from 900℃ to 500℃.
From 00°C to room temperature, cooling was performed using B 5 'C/B. Thereafter, it was aged at 400° C. for 80 seconds, and then finally cold-rolled to a thickness of 0.2 mm and a thickness of 0.80 mm. Thereafter, decarburization and primary recrystallization annealing were performed in wet hydrogen at 820°C, followed by secondary recrystallization annealing at 850°C for 60 hours and final annealing at 1180°C for 5 hours in hydrogen.

The magnetic properties of the obtained product were as follows.

o, syg thickness B□. :1.91 T% Wl, 7. ,
. : 0.92% 0.80mm thickness BIO: 1-9
1 Ts W1d6: 0-98 w/y Example 2 GO, 046%, Si 8.88%, Mn 0.07
8%, SeO,019%, SbO,020% and M
o A continuous cast slab containing 0.019% was hot rolled to a thickness of 2.7 fim, homogenized annealed at 900°C for 8 minutes, then cold rolled to approximately 80%, and then rolled at 950°C. Intermediate annealing was performed for 8 minutes. During this intermediate annealing, the temperature increase rate was 85℃ from room temperature to 500℃, /S, 50
The temperature increases at a rate of 12°C/S from 0°C to 900°C, and the temperature decreases at a rate of 16°G/13 from 900°C to 500°C.
It was rapidly cooled at 40 c'C/B from 500°C to room temperature.

Thereafter, it was subjected to age annealing at 600° C. for 20 seconds, and then cold rolled at room temperature to produce final cold rolled sheets with thicknesses of 0.20 and 0.28 mm. Thereafter, decarburization and primary recrystallization annealing were performed in wet hydrogen at 820°C, followed by eighth recrystallization annealing at 850°C for 50 hours and purification annealing at 1180°C for 7 hours in hydrogen.

The magnetic properties of the obtained product were as follows.

0.20 mm M B,. : 1.91 T, W
l,,AO: 0.76%0.28mm thickness BIO:
1.91 T% W17/, o: 0.82 w,
4゜ (Effect of the invention) Thus, according to the present invention, the magnetic flux density and iron loss characteristics can be improved compared to conventional ones by a simple operation of performing annealing treatment for one short time after intermediate annealing and before final cold rolling. can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the aging temperature and time and the steel value in the aging annealing treatment according to the present invention.

Claims (1)

[Claims] 1. C: 0.01 to 0.06 wt%, Si: 2.0 to 4.0 wt%, Mn: 0.01 to 0.2 wt%, Mo: 0.008 to 0.1 wt% % and Sb: 0.005 to 0.2 wt%, and a unidirectional silicon steel material having a composition containing one or both of S and Se in total of 0.005 to 0.10 wt%. is hot rolled, then subjected to one or more cold rolling including intermediate annealing to obtain the final plate thickness, subjected to decarburization annealing which also serves as primary recrystallization, and then subjected to final finish annealing ( 110) [0
01] In a method for producing a grain-oriented silicon steel sheet that includes a series of steps for developing oriented secondary recrystallized grains, after the intermediate annealing described above and before the final cold rolling, the process is performed at a temperature range of 150 to 500°C for 1 second. A method for producing a grain-oriented silicon steel sheet having high magnetic flux density and low iron loss, the method comprising performing an annealing treatment for 30 minutes to 30 minutes. 2. The method according to claim 1, wherein the intermediate annealing is accompanied by rapid cooling treatment from 900°C to room temperature after annealing at a cooling rate of 5°C/S or more. 3. The method according to claim 1, wherein the intermediate annealing involves rapid heating/quenching treatment at a rate of 5°C/S or more over a temperature range from room temperature to 900°C.