JPS61149432A - Manufacture of grain oriented silicon steel sheet having high magnetic flux density and low iron loss - Google Patents

Abstract

PURPOSE:To improve iron loss without deteriorating flux density, by controlling cooling rate and induced strain quantity during cooling after intermediate annealing at cold rolling hot rolled Si steel plate contg. Sb, Mn, S or Se, Mo at two times interposing intermediate annealing. CONSTITUTION:Si steel contg. by weight, 0.01-0.06% C, 2.0-4.0% Si, 0.01-0.2% Mn, further 0.003-0.1% Mo, 0.005-0.5% Sb, 0.005-0.1% S and or Se is hot rolled and cold rolled at two times interposing intermediate annealing to the finally cold rolled sheet. Thereat, the sheet is annealed intermediately, successively cooled at >=10 deg.C/sec rate, given by 1-30% working strain at the cooling stage, then rolled finally at 100-400 deg.C. Primary recrystallization annealing used also for decarbonization is applied to the finally cold rolled sheet, further the final finish annealing is applied to develop secondarily recrystallized grains having {110} <001> orientation, but refining of secondarily recrystallized grains becomes advantageous by said intermediate annealing.

Description

Detailed Description of the Invention (Industrial Application Field) During the manufacturing process of unidirectional silicon steel sheets, when the temperature is lowered after intermediate annealing, the steel sheets are rapidly cooled and strain is introduced to increase magnetic flux density and iron loss. Here, we will describe the results of development research on the advantageous production of unidirectional silicon steel sheets with low .

Unidirectional silicon steel sheets are soft magnetic materials that are mainly used as core materials for transformers and other electrical equipment, and must have good magnetic properties such as excitation properties and iron loss properties.

To obtain a material with excellent magnetic properties, the axis of easy magnetization is
001>Although it is fundamentally important to highly align the axes in the rolling direction, it is also known that secondary recrystallized grain size, specific resistance, surface coating, etc. have a large effect on reducing iron loss. As it is.

Since N. P. Goss proposed a method for manufacturing unidirectional silicon steel sheets by two-stage cold rolling in 1934, numerous improvements have been made to this manufacturing method, and the excitation characteristics and iron loss characteristics have improved over the years. It has been improved since then.

(Prior art) Among them, the most representative one is the Japanese Patent Publication No. 40-1, which uses AJ2N as an inhibitor.
The method disclosed in Japanese Patent Publication No. 5644, and the method disclosed in Japanese Patent Publication No. 13469/1983, which utilizes Sb, MnS and/or 1yln3e as inhibitors.B. It is now possible to obtain products with a value exceeding 1.89 T.

However, the former is characterized by a strong cold rolling process, and the AuN
Since the method utilizes precipitated phases, a high magnetic flux density can be obtained, but the disadvantage is that the secondary recrystallized grains are coarse and the iron loss value is high. Very recently, attempts have been made to solve this problem, such as in Japanese Patent Application Laid-open No. 53-137016 and No. 56-515.
No. 22 proposes a method for further lowering iron loss by introducing minute linear strains at intervals of several I perpendicular to the rolling direction on the surface of a product plate using scratches or a laser beam. However, these methods are not economical to implement on an industrial scale, and the formation of artificial grain boundaries by introducing microstrain requires maintaining a locally high density of dislocations. A major drawback is that it can only be used stably in a low temperature range of about 350°C or less.

On the other hand, regarding the latter method of using sb and MnS and/or MnSe as inhibitors,
Improvements were made and the compound addition of Mo to the material
4613, Japanese Patent Publication No. 57-14737), the magnetic flux density B iff value has recently been reduced to 1.90.
T is exceeded and the iron loss W17150 value is 1. The high magnetic flux density unidirectional silicon steel plate of O5W/Miao is being manufactured stably. However, when attempting to further improve the magnetic properties in actual production on an industrial scale, the following problems arise.

In other words, as the secondary grain size increases to align the <100> axes of the product's secondary recrystallized grains in the rolling direction, the magnetic flux density becomes high (but no commensurate improvement in iron loss is observed). On the other hand, if an attempt is made to reduce the secondary recrystallized grain size, secondary recrystallization defects will occur and the orientation of the 100> axis in the rolling direction will deteriorate, resulting in unidirectional silicon with excellent magnetic flux density and iron loss. It has been difficult to stably obtain steel plates.

(Problems to be Solved by the Invention) An object of the present invention is to improve iron loss by eliminating the above drawbacks and effectively making secondary recrystallized grains finer without deteriorating magnetic flux density. It is.

(Means for solving the problems) The present invention provides C: 0.01 to 0.06 wI% Si
:2.0~4.0wt% Mn: 0.01~0
, 2wt%, and Mo: 0.003-0.
1 wt% Sb: 0.005 to 0, 5 wt%, and either one or two of S and Se for a total of 0.005
11 cable steel with a composition containing ~0.1 wt% was hot rolled, then cold rolled twice with intermediate annealing to form a final cold rolled sheet, and then subjected to primary recrystallization annealing that also served as decarburization. , further subjected to final finish annealing (110) < 0
01> In a method for manufacturing a grain-oriented silicon steel sheet comprising a series of steps of developing secondary recrystallized grains in the orientation, the cooling rate during temperature reduction following the above-mentioned intermediate annealing is set to 10°C/s or more, and this cooling A method for producing a unidirectional silicon steel sheet with high magnetic flux density and low core loss, characterized by applying a processing strain of 1 to 30% to the steel sheet in a step, and then final rolling at a temperature of 100 to 400°C. .

In other words, in the process of cold-rolling a grain-oriented silicon steel hot-rolled sheet twice including intermediate annealing, the structure of the steel sheet is improved by simultaneously controlling the cooling rate and the amount of strain introduced when the temperature drops after intermediate annealing. At the same time, by keeping C in a state as close to a solid solution as possible, the effect of the subsequent warm rolling becomes stronger, which is advantageous for refining secondary recrystallized grains, resulting in oriented silicon with extremely low iron loss. It originates from the discovery that it makes a significant contribution to the production of steel.

The effect of warm rolling is that by treating the final cold rolling in the double cold rolling process warmly, the dislocation strain energy of the deformation zone and the matrix surrounding it is increased.
The purpose is to facilitate the generation of Goss grains and improve magnetic properties.

(Effect) The details of the experiment that confirmed the above facts are as follows.

(:, : 0,045wt%, Si: 3
．． 35 wt%, Mn: 0.070 wt%, and M O: 0,012 wt%.

3 e: 0,018wt%, Sb: 0.
A steel ingot containing 025 wt% was heated at 1350° C. for 1 hour and then hot rolled to a thickness of 2.11 Im.

Then, after homogenization annealing at 900℃ for 3 minutes, 0.78m
It was first cold-rolled to a thickness of 1.5 m, and then intermediate annealed at 950°C for 3 minutes.

After this intermediate annealing, from that temperature, there is a step (2) in which 5% rolling is performed with a rolling roll immediately during cooling at 20°C/s, a step (0) in which cold section treatment is immediately performed at 20°C/s, and a step 0 in which the temperature is also rolled at 5°C/s. It was subjected to step 0 of cooling treatment.

Thereafter, final cold rolling by warm rolling was carried out in a temperature range from room temperature to 600° C. to produce a steel plate with a final thickness of 0.3111111. The final cold rolling method was carried out in such a manner that after reaching a predetermined rolling temperature for each bath, it was held for 5 minutes and immediately rolled.

After that, the steel plate surface was degreased and heated to 820℃ in wet hydrogen.
After performing decarburization annealing for 3 minutes at 1200°C, an annealing separator mainly composed of magnesia was applied to the surface of the steel plate, and secondary recrystallization annealing was performed at 850°C for 50 hours, followed by hydrogen annealing at 1200°C for 5 hours. Purification annealing was performed inside.

The magnetic properties of the product thus obtained are shown in FIG.

As is clear from Figure 1, it is noteworthy that in the process of increasing the cooling rate after intermediate annealing and at the same time introducing strain into the steel sheet, the effect of warm rolling becomes more apparent and good magnetic properties are obtained. Ru.

That is, by introducing strain at high temperature after intermediate annealing, C is collected at dislocations, and at the same time, by rapid cooling, carbide coarsening at grain boundaries and within grains is prevented, solid solution C or ultrafine Cω increases, and this C is In the final cold rolling followed by the final cold rolling, it effectively affects the dynamic and static strain aging, increasing the deformation band and accumulated strain energy density of the final rolled plate, and reducing the rolling direction to < 00
1> This results in a structure that is advantageous for the generation and growth of secondary recrystallized grains with well-aligned axes.

Therefore, by subsequently performing secondary recrystallization annealing at an appropriate temperature, a fine secondary recrystallized structure in which the <001> axes are well aligned in the rolling direction can be obtained, and a product with extremely low core loss can be obtained.

° As described above, by adding the introduction of dislocations according to the present invention, the refinement of carbides, which has conventionally been controlled only by the cold W speed, can be achieved more effectively.

Therefore, one of the features of the present invention is to introduce strain in the quenching process of intermediate annealing and then to cool the material as it is.

Based on the results of the above basic experiments, we proceeded with the following experiments regarding the degree of strain introduction.

C: 0,043wt%, St: 3.37
wt%, Mn: 0.065 wt%, and M O:
0.012wt%, Se: 0.018v1t%
, Sb: A steel ingot containing 0.025 wt%,
Finished by hot rolling to a thickness of 2.7 mm using a known method, and then homogenized by annealing at 900°C for 3 minutes to 0.78 m1.
After rolling to 100°C and intermediate annealing at 1050°C for 3 minutes, immediately annealing was performed at 1000°C at 90°C at a cooling rate of 15°C/s.
After controlling the humidity of the steel plate at 0'C, 500C, and 200C, and applying a strain of 0.5% to 40% at each temperature, it was heated to 15C.
It was immediately cooled to room temperature at a cooling rate of /s.

Next, final cold rolling was performed by warm rolling by heating at 200° C. to produce a steel plate with a final thickness of 0.3 mm. The final cold rolling method was such that after reaching a predetermined rolling temperature for each pass, it was held for 5 minutes and immediately rolled.

After that, the steel plate surface was degreased and heated to 820℃ in wet hydrogen.
After performing decarburization annealing for 3 minutes at 1200°C, an annealing separator containing magnesia as the main component was applied to the steel plate, and secondary recrystallization annealing was performed at 850°C for 50 hours, followed by hydrogen annealing at 1200°C for 5 hours. Purification annealing was performed inside.

The magnetic properties of the obtained product are shown in FIG. As can be seen from FIG. 2, when the processing strain is less than 0.5%, the introduced dislocation density is insufficient, so that the refinement of C is also insufficient and the expected effect cannot be obtained. Therefore, the amount of strain applied when lowering the temperature is 1
~30% is suitable for the purpose of this invention.

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

When C is less than 0.01wt%, 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 more than 0.06wt%, it takes longer to decarburize in the decarburization process. 0.01~0.06wt as it is not economical.
% range.

When 3i is less than 2.0wt%, the electrical resistance is low and the iron loss value based on increased eddy current loss becomes large;
%, brittle cracks are likely to occur during cold rolling, so it is necessary to keep the content within the range of 2.0 to 4.0 wt%.

When Mn is less than 0.01wt%, it becomes difficult to form sufficient MnSe precipitates, while when it is more than 0.2wt%, heating temperature must be raised to solutionize MnSe precipitates. Therefore, Mn is 0.01 to 0.2
It is necessary to keep it within the range of wt%.

Regarding Mo, the inventors first published the
As disclosed in Japanese Patent Publication No. 7 and Japanese Patent Publication No. 56-4613, the addition of a small amount of Mo, up to 1 wt %, has the effect of suppressing the growth of primary recrystallized grains, and the same effect can be expected in the present invention. If Mo is more than 0.1 wt%, hot and cold workability will decrease, and iron loss will deteriorate, so Mo needs to be within the range of 0.1 wt% or less.
On the other hand, if it is lower than 0.003 wt%, the effect of suppressing the growth of -next crystal grains is small, so Mo is 0.003 to 0.1 wt%.
Must be within the range.

Sb is derived from Japanese Patent Publication No. 38-821, which was previously disclosed by the inventors.
According to Publication No. 4, it contains o, oos ~ 0.1 wt%,
Similarly, the inventors previously disclosed the Japanese Patent Publication No. 51-13
According to Publication No. 469, by containing a trace amount of Se or S at o, oos to o, 2 wt%,
- It is known that the growth of several grains is suppressed, and if Sb is less than 0.005 wt%, the effect of suppressing primary recrystallized grains is small, while if it is more than 0.5 wt%, the magnetic flux density decreases. Since the magnetic properties are deteriorated for the first time, sb needs to be within the range of 0.005 to 0.5 wt%.

Both S and Se are 0.1 wt% or less, especially S is 0.008 to 0.1 wt%, and Se is 0.003 to 0.
, 1wt%. That means these are 0,
If it exceeds 1 wt%, hot and cold workability deteriorates, and if the lower limit is not reached, MnS.

This is because MnSe does not have a particular effect on the primary recrystallization grain growth inhibition function, but as already mentioned in the experimental example, known primary grain growth inhibition by Sb, Mo, etc. can be used advantageously in combination. The lower limit value of Se and O in total is sufficient to be o, ooswt%.

In this invention, c:o is added to the silicon steel material as described above.
, o1-0.06wt%, 3i:2.0-4. wt%
, Mn: 0.01 to 0.2 wt%, and
Mo2 0.003-0.1wt%, 3b: o,
oos~o, swt% and any one of S and Se
Basically, it contains one or two species in a total amount of o, oos to o, 10 wt%, but in addition, known elements that are usually added to silicon steel, such as Cr, Ti, V,
Zr.

Nb, Ta, Co, Ni, Sr1. There is no problem with the inclusion of trace amounts of P, As, and the like.

Also, acid-soluble Ai: 0.01 to 0.09 wt%, N: 0.
001~0.01wt% or 3: 0.003~0
．． 005wt% or cu: 0.06~0.5w
A product with excellent magnetic properties can be stably obtained by containing Aβ of 0.0%.
If it is 1wt% or more, it is not necessary to support s, se, Sb, Mo, etc., but it is also possible to use them in combination.

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

First, a slab having the above composition is obtained by a conventionally known agglomeration-blooming method or continuous casting method. Then this slab is 12
The plate is heated to 50°C or higher and subjected to known hot rolling to obtain a plate with a thickness of 1.2
~5 Obtain a single layer hot rolled sheet.

Then, after finishing to an intermediate thickness of 0.50 mm to 1.51 mm by cold-open rolling through uniform annealing if necessary, intermediate annealing is performed.

These homogenizing annealing and intermediate annealing are for the purpose of recrystallization treatment to homogenize the crystal structure after rolling, and are usually performed at temperatures ranging from 800°C to 11°C.
The temperature is maintained at 00°C for 30 seconds to 10 minutes.

When the temperature immediately before processing exceeds 1000°C, dislocations tend to disappear when the temperature is lowered following intermediate annealing, but when the temperature drops below 400°C, C becomes difficult to move, so the desired effect is not achieved. It fades. Therefore, the temperature before processing is preferably between 1000°C and 400°C.

Next, in the method of the present invention, the cooling rate during temperature reduction following intermediate annealing is set at 10°C/s or more, a working strain of 1 to 30% is applied to the steel plate in this cooling stage, and the subsequent final rolling is performed. It is an essential condition that the process be carried out at a temperature of 100 to 400°C. Here, the processing strain may be imparted to the steel plate by any known method such as tensioning or rolling.

The reason why the cooling rate during temperature reduction is set to 10° C./s or more is to prevent excessive C precipitation at dislocations or grain boundaries introduced into the steel sheet.

In addition, if the processing strain is less than 1%, the introduced dislocation density is insufficient, so the C refinement is insufficient and the expected effect cannot be obtained, and if it exceeds 30%, the texture becomes unfavorable to secondary recrystallization. No effect can be obtained. Therefore, the amount of processing strain applied during temperature reduction was set to 1 to 30%.

Next, the reason why the subsequent final rolling temperature was set at 100°C to 400°C is that when the rolling temperature is below 100°C, the activity occurs < 1
11> The interaction between the slip system and C decreases, dislocation growth becomes inactive, and hardness does not increase.On the other hand, when the temperature exceeds 400℃, dislocations disappear and recover, making it difficult to maintain hardness, and in both cases, primary recrystallization aggregation occurs. This is because the structure becomes inappropriate and fine secondary recrystallization aggregates III cannot be obtained.

In addition, the finished plate thickness follows the custom of 0.1511 to 0.511IIll, but recently the finished plate thickness has been reduced, for example 0.
．． 23. There is a growing trend to improve core loss by making the steel 0.15+g-, but trying to make it thinner in this way has the problem of increasing secondary recrystallization defects and making the crystal grains of the finished product larger. However, the present invention is particularly effective as a countermeasure against this problem.

The cold-rolled sheet subjected to final cold rolling in this way is then given a grade of 750 to 85
Decarburization and crystal annealing are performed in wet hydrogen at 0°C. This annealing removes C in the steel and forms a primary recrystallized texture that is advantageous for developing secondary recrystallized grains with (110) <001> orientation in the next final annealing.

Next, an annealing separator containing magnesia as a main component is applied to the surface of the steel sheet, and then final annealing is performed using a winding annealing furnace. Final annealing is performed to sufficiently develop secondary recrystallized grains with (110}<001> orientation, and is usually box annealed to immediately raise the temperature to 1000°C or higher.
This is done by holding it at that temperature (11G
) In order to develop a secondary recrystallized structure that is extremely aligned in the <001> orientation, it is advantageous to carry out holding annealing at a low temperature of about 820°C to 900°C, and in some cases, for example at a temperature of 0.5°C to 15°C. Body thermal annealing may be performed at a low temperature increase rate of about °C/hr.

(Example) Next, the present invention will be explained with reference to examples.

Example 1 C: 0,055wt%, 3i: 3. so
wt%, Mn: 0.080wt%, Mo: 0,
030wt%, 3e: 0,021℃%, Sb
: A steel ingot containing 0.025 wt% with the remainder being iron is hot rolled to a thickness of 2.71, homogenized at 900°C for 3 minutes, and then cold rolled to 70%. was then subjected to intermediate annealing at 950°C for 3 minutes.

Then, it is immediately rolled at 10% and rolled at 50°C/s.
It was cooled to room temperature. Next, the method of holding at 250℃ for 3 minutes and immediately rolling was repeated to obtain a final plate thickness of 0.3m.
Finished with m steel plate. After that, following customary decarburization annealing at 820°C in wet hydrogen for 3 minutes, an annealing separator mainly composed of magnesia was applied, and 50°C at 840°C was applied.
A final annealing was performed using a combination of time holding and holding at 1200° C. for 5 hours. (The magnetic properties of the q product are B le
= 1.92 T, W 17/50=0.96
It was W/kg.

[Brief explanation of drawings]

FIG. 1 is a graph showing the influence of cooling conditions after intermediate annealing and final rolling temperature on product magnetism, and FIG. 2 is a graph showing the influence of strain introduction temperature and amount of strain introduced, respectively. Fig. 1 5WL rolling surface ('C) Fig. 2 ffi knowledge E cell (5ζ)

Claims (1)

[Claims] 1. Contains C: 0.01 to 0.06 wt%, Si: 2.0 to 4.0 wt%, Mn: 0.01 to 0.2 wt%, and Mo: 0.003 to 0.06 wt%. 1 wt% Sb: 0.005 to 0.5 wt% and a silicon steel having a composition containing one or both of S and Se in a total of 0.005 to 0.1 wt%, and then an intermediate The final cold-rolled plate is obtained by cold rolling twice with annealing in between, then primary recrystallization annealing which also serves as decarburization, and final finish annealing {11
0} In a method for producing a unidirectional silicon steel sheet comprising a series of steps of developing secondary recrystallized grains with <001> orientation, the cooling rate during temperature reduction subsequent to the above intermediate annealing is set to 10°C/s or more. , 1 to 3 in this cooling stage
After applying 0% processing strain to the steel plate, 100 to 400
A method for producing a unidirectional silicon steel sheet with high magnetic flux density and low core loss, characterized by performing final rolling at a temperature of ℃.