JPH07110974B2 - Method for producing directional silicon iron alloy ribbon - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a directional silicon-iron alloy ribbon having an easy axis [001] in the rolling direction of the ribbon.

2. Description of the Related Art Since the ribbon related to the present invention does not have carbon as an essential element, it is referred to as iron instead of steel, and is a directional silicon-iron alloy ribbon. The one widely used is called grain-oriented silicon steel strip.

The grain-oriented silicon steel strip is mainly used in large amounts as an iron core for transformers and other electric appliances.

This grain-oriented silicon steel strip has a Goss orientation, that is, a (110) [001] orientation recrystallized grain texture.
That is, since the (110) crystal plane is parallel to the plate surface of the grain-oriented silicon steel sheet and the easy magnetization axis [001] coincides with the rolling direction, the excitation characteristics in the rolling direction are extremely excellent and the iron loss Also few.

At present, the methods currently used as the method for producing this grain-oriented silicon steel strip include mainly a double rolling method and a single rolling method.

The double rolling method is an improved version of the Goss method, which is the basic method for manufacturing grain-oriented silicon steel, and the manufacturing method will be outlined in some detail. First, Sb was used as a grain growth inhibitor in steelmaking.
And Mn and S or Se are added, the thickness is reduced to about 2 to 3 mm by slabbing and hot rolling, then normalizing is performed, then primary cold rolling is performed at a rolling reduction of about 70%, and 850-1
Intermediate annealing at 050 ℃, secondary cold rolling with a reduction of 60 to 70% to a final plate thickness of 0.3 mm, decarburization annealing at 800 to 850 ℃, 8
Generate secondary recrystallized grains by treating at 00-920 ℃ for 5-50 hours,
This is a method of growing and then purifying annealing at 1100 ° C or higher for about 20 hours for a long time to grow (110) [001] crystal grains in the rolling direction to make a steel strip of about 0.3 mm (Matoba et al. Kawasaki Steel Technical Report vol.7 No.2 (1975) P175-188, Nakanaka et al., Japanese Patent Publication No. 51-13469).

In the one-time rolling method, Al and N are added as grain growth inhibitors by steelmaking, thinned to a plate thickness of about 2.3 mm by slabbing and hot rolling, then AlN precipitation annealing, and then rolling. Rate 81-9
It is a method of making a steel strip similar to the double rolling method by performing 5% strong cold rolling to a final plate thickness of about 0.3 mm, decarburizing annealing, and finish annealing at about 1200 ° C for about 20 hours. (Technical Report of the Institute of Electrical Engineers of Japan (Part II) No. 85 (1979) P.8-10, Taguchi et al.
-15644 publication).

As described above, both of the above methods add a crystal grain growth inhibitor, form a solid solution and precipitate and disperse as MnS or AlN after hot rolling to suppress the growth of primary recrystallized grains in the final finish annealing. In the meantime, the secondary recrystallized grains (110) [001] are promoted to grow to form a (110) [001] recrystallized grain texture in the rolling direction.

Problems to be Solved by the Invention As described above, the conventional method is a method based on the addition of a crystal grain growth inhibitor, and the production method is used to maximize the effect of the crystal grain growth inhibitor. The conditions are fixed, and therefore complicated and strict conditions are imposed on the manufacturing, resulting in high cost.

In addition, there is a strong demand from the users to reduce iron loss,
On the other hand, it has been clarified that the eddy current loss of iron loss can be reduced by reducing the plate thickness. However, when the plate thickness is reduced by the conventional method (11
0) It becomes difficult to increase the degree of integration in the [001] direction,
This results in an increase in iron loss, and for this reason a thickness of about 0.2 mm is said to be the industrial limit in the conventional method, and in a ribbon of 0.2 mm or less, in iron loss and magnetic flux density, It was not possible to obtain sufficiently satisfactory magnetic properties.

Recently, a manufacturing method different from the conventional silicon steel strip, that is, a rapid cooling solidification method is being developed. This method involves spraying the molten metal onto a rotating cold twin roll or single roll, cooling and solidifying in an extremely short time, and then producing an ultrathin ribbon (approximately 0.03 to 0.09 mm thickness).

However, this method has a drawback in that it requires a high technology and a device for controlling an extremely high cooling rate to obtain uniform quality, which results in a high production cost.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for producing a grain-oriented silicon-iron alloy ribbon which has low iron loss characteristics at low cost and thin plate thickness. Especially.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention provides a first method in which a plate material of a silicon-iron alloy composed of 2.5 to 4% by weight of silicon and the balance iron is cold-rolled into an intermediate material. Next cold rolling step, a primary heat treatment step of heat treating the intermediate material to a heat treated material having a recrystallized structure, and a reduction ratio of 70 in the same direction as the rolling direction in the primary cold rolling step. ~ 80% cold rolling
Secondary cold rolling step to make a cold-rolled ribbon having a thickness of 0.2 mm or less, and a crystal having a (110) [001] orientation in the rolling direction by heat-treating the cold-rolled ribbon at 1180 ° C or more. It is characterized in that at least the second heat treatment step of forming a ribbon having a recrystallized grain texture mainly composed of grains is performed.

Operation With the above method, it is possible to obtain a highly oriented grain-oriented silicon iron alloy ribbon in a simple process and in a short time.

Example The present invention was developed from repeated trial and error in order to realize a Goss-oriented recrystallized grain texture in a ribbon of 0.2 mm or less, and is possible only under specially limited production conditions. It is something. That is, the grain growth inhibitor was not added to the alloy, and the cold rolled sheet material (intermediate material) was made into a special recrystallized structure by heat treatment (primary) to reduce the thickness to a prescribed thickness. Narrow rolling reduction of 70-80%
By cold-rolling at 0.2mm or less to form a thin strip, and heat-treating this at 1180 ℃ or higher (secondary),
A recrystallized grain texture of (110) [001] orientation is realized.

The composition and each step will be described in more detail below.

The first characteristic of the present invention is the composition. The conventional grain-oriented silicon steel sheet has a grain growth inhibitor added thereto and its composition is finely regulated, but the present invention does not require this grain growth inhibitor. The composition of the silicon-iron alloy according to the present invention is composed of 2.5 to 4% by weight of silicon, the balance being iron loss and unavoidable impurities. When the amount of silicon is less than 2.5% by weight, the electric resistance is low and the eddy current loss is large, and the iron loss is increased, which is disadvantageous. When the amount of silicon exceeds 4% by weight, brittle cracking occurs during cold rolling. There are many defects, which is a disadvantage. When impurities become precipitates or inclusions, they are (110) [00
1) It is preferable that the amount is as small as possible because it inhibits the growth of crystal grains, but inevitable impurities are tolerated in the current ironmaking technology.

Next, the primary cold rolling step is a step for rolling to a predetermined thickness as an intermediate material to be subjected to the next primary heat treatment step. In order to obtain the final thickness of the ribbon, it is necessary to make it 1.0 mm or less in the primary cold rolling process.

The plate material used in this primary rolling step is a plate material cut from an ingot, or a slab or a hot rolled plate material, but a plate material produced by continuous casting hot rolling or a semi-melting process. It may be a plate material.

Next, the primary heat treatment step is intended to recrystallize the intermediate material cold-rolled in the primary cold rolling step into a normal grain structure, and the temperature is higher than the temperature at which recrystallization starts. I wish I had it. Considering the processing time, it is 950 ℃ or higher,
When the treatment is to be completed in a short time, for example, 1 hour, the temperature is preferably around 1100 ° C.

Next, in the secondary cold rolling step, it is determined whether or not crystal grains of (110) [001] orientation grow in the secondary heat treatment step depending on the reduction ratio of the cold rolling in this step. Conventionally, it has been considered difficult to grow crystal grains in the (110) [001] orientation in the rolling direction without a grain grain straightening inhibitor. The present inventor has studied in the field of thin strips, and as a result, 0.2 m
It was found that cold rolling with 70 to 80% rolling reduction in the case of m or less, and grain growth of (110) [001] orientation can be grown in the rolling direction by the heat treatment of the next secondary heat treatment step. It was That is, when cold rolling with a reduction rate of 70 to 80%, the following heat treatment in the second heat treatment step causes (110) [00
The crystal of 1] orientation grows, and the ratio of the crystal grains of (110) [001] orientation occupying almost 100% of the total plate area, and the magnetic property of B ₈ (magnetic flux density at a magnetizing force of 800 A / T) Is over 1.8T. If the rolling rate does not reach 70% or exceeds 80%, the proportion of (110) [001] oriented crystal grains in the total plate area decreases as the degree of deviation from the range of 70-80% increases. However, B ₈ drops to 1.8T or less.

What is important in this secondary cold rolling process is that the rolling direction must be the same as the rolling direction in the primary cold rolling process. However, when rolling between the rolls, the rolls may be rotated 180 ° in the first pass.

Rolling with an inclination from the rolling direction in the primary
0) The degree of integration of [001] oriented crystal grains in the rolling direction is reduced, which is not preferable.

In addition, it is desirable for rolling in this process to pass between the rolls only once to achieve a reduction rate of 70 to 80% at once, in terms of magnetic characteristics and in the simplification of the process, but it is possible to make a total of multiple passes. The reduction rate of 70-80% may be reached. However, in this case, reversing the rolling direction by 180 ° is not preferable because it reduces the degree of integration of (110) [001] oriented crystal grains in the rolling direction and the ratio of the total plate area. Further, it is not preferable that the rolled strip is bent unevenly and the rolled strip bends leftward and rightward on the same plane as the plate surface, because it causes a decrease in the degree of integration.

When the oxide film adheres to the heat-treated material that has been subjected to the first heat treatment step for rolling, it is preferable to remove the oxide film by pickling. Further, the roll surface of the rolling mill is degreased to be clean, and when it is rolled without lubrication, it has good magnetic properties.

Next, in the second heat treatment step, the heat treatment temperature is preferably 1180 ° C. or higher, and considering treatment time, it is preferably around 1250 ° C. For example, even if held at a temperature of 1160 ℃ in vacuum for 6 hours (110)
The growth of crystal grains in the (001) orientation did not occur, and the magnetic flux density B ₈ at a magnetic force of 800 A / m was 1.48 T, and when the structure was observed by an optical microscope, it was a recrystallized structure of normal grains, When treated in vacuum at a temperature of 1250 ° C, the holding time is 2 hours.
B ₈ = 1.85T, and the crystal grains of (110) [001] orientation were almost aligned in the cold rolling direction.

In addition, when the temperature of the cold-rolled ribbon is raised to a processing temperature of 1180 ° C or higher, the temperature range of 1100 to 1150 ° C is 10 to 10 ° C.
Over 60 minutes, or 10 ~ in this temperature range
After holding for 60 minutes, heat treatment at a predetermined temperature of 1180 ° C or higher improved the degree of integration of (110) [001] crystal grains in the rolling direction.

Also, the atmosphere during heat treatment is not in vacuum, but in an inert gas,
Also, in the hydrogen gas or the hydrogen-nitrogen mixed gas, the grain growth in the (110) [001] orientation occurred.

As described above, the present invention is a method that does not use a grain growth inhibitor, unlike the conventional manufacturing method, and therefore, in the conventional manufacturing method, a recrystallized grain texture of (110) [001] orientation is obtained. In the field of ribbons with a thickness of 0.2 mm or less, which was difficult to make, the newly found cold rolling conditions and heat treatment conditions will allow the formation of a (110) [001] oriented recrystallized grain texture. It is a thing.

The cause of selective growth of the (110) [001] crystal grains in the rolling direction under the conditions already described is not clear at present, but one of the factors is that the grain growth inhibitor is not used. Can be mentioned. For this reason, it is relatively hot without inclusions and precipitates, but (110) [001]
It is considered that the crystal grains in the orientation can grow. Also, as one of the factors, the thickness of the ribbon is 0.2 mm
The following are thin. For this reason, the driving energy for recrystallized grain growth is dominated by surface energy rather than grain boundary energy, and the surface energy is the lowest (11
It is considered that the (0) plane appears parallel to the plate surface of the ribbon and that it is easy to grow.

As described above, in the present invention, since the grain growth inhibitor is not used, the manufacturing conditions, especially the heat treatment conditions are simple and short, and the manufacturing cost can be reduced. Further, since the thickness of the ribbon is smaller than that of the conventional one, the eddy current loss can be reduced, and the ribbon having excellent magnetic characteristics with low iron loss can be manufactured.

Specific examples will be described below.

[Example 1] 99.9% by weight of electrolytic iron and 99.999% by weight of silicon were blended and melt-cast by high frequency induction heating to prepare 3.5% by weight of silicon residual iron and unavoidable impurities of silicon-iron alloy. A plate material having a thickness of 1.9 mm was cut out from the cast body, cold rolled to a thickness of 0.41 mm, and heat-treated at 1100 ° C. for 1 hour in vacuum. Next, after degreasing the roll surface of the rolling mill to clean this heat-treated plate material, cold rolling with a rolling reduction of 80% in the same direction as the previous cold rolling without lubricant was performed.
A thin strip having a thickness of μm was formed and heat-treated in vacuum at 1220 ° C. for 4 hours. The magnetic properties in the rolling direction of the ribbon after the heat treatment were measured with a BH loop tracer.
The magnetic flux density B _{8 at a} magnetizing force of 800 A / m was 1.88T. The maximum magnetic flux density was 1.
The iron loss value W _17/50 at 7T was 0.95 w / kg.

[Example 2] 99.9% by weight of electrolytic iron and 99.999% by weight of silicon were blended and melt-cast by high frequency induction heating to prepare 2.9% by weight of silicon residual iron and unavoidable impurities of silicon-iron alloy. A plate material having a thickness of 1.7 mm was cut out from the cast body, cold rolled to a thickness of 0.63 mm, and heat-treated at 1070 ° C. for 1 hour in an argon gas. Since the surface of the plate material was oxidized and discolored, it was pickled to remove the oxide film, and the roll surface of the rolling mill was wiped with gauze containing acetone to clean it, and then it was cleaned without lubrication. Cold rolling was carried out in the same direction as cold rolling at a rolling reduction of 75% to obtain a strip of 148 μm. This ribbon was heat-treated by holding it at 1380 ° C. for 3 hours in a mixed gas stream of hydrogen 40% and nitrogen 60%. However, the temperature measurement in this case was performed outside the double magnetic tube and near the heater. Since the ribbon of the sample is placed inside the double magnetic tube and the hydrogen-nitrogen mixed gas is flowing, the temperature of the ribbon cannot be measured accurately, but the temperature indicated by the furnace is higher than 1380 ℃. It is estimated that the temperature is low.

After heat treatment, the magnetic property in the rolling direction is B ₈ = 1.91T, W
_{It was 17/50} = 0.92 w / kg.

[Example 3] A plate material having a thickness of 1.5 mm was cut out from the cast body of the silicon-iron alloy of Example 2, cold-rolled to a thickness of 0.40 mm, heat-treated at 1100 ° C for 1 hour in vacuum, and then rolled. After degreasing the roll surface of the machine to clean it, it was unlubricated and then cold-rolled with a rolling reduction of 71% in the same direction as the previous cold-rolling to obtain a ribbon of 116 μm. Then, heat treatment was performed in vacuum. 1100 ~ 11 at temperature rise
The temperature was maintained at 50 ° C for 30 minutes, then raised to 1250 ° C, maintained for 2 hours, and cooled to room temperature. The magnetic properties of this ribbon in the rolling direction were B ₈ = 1.92T and W _17/50 = 0.84w / kg, which were excellent iron loss properties.

[Example 4] 99.9% by weight of electrolytic iron and 99.999% by weight of silicon were blended and melted to form a 3.3% by weight silicon balance iron and an unavoidable impurity silicon-iron alloy. This cast body was heated to about 1200 ° C. in argon gas and then hot-rolled to a plate thickness of 2.5 mm. After hot rolling, it was gradually cooled to room temperature. The oxide film was removed by pickling, the thickness was 0.5 mm by cold rolling, and heat treatment was performed at 1100 ° C. for 1 hour in a hydrogen-nitrogen mixed gas. After that, after cleaning the roll surface of the rolling mill, this heat-treated 0.5 mm plate material was rolled down in the same direction as the previous time and cold rolling by 76%.
% Cold-rolled into 120 μm thin strips. This ribbon was heated at 1360 ° C. in the double magnetic tube furnace used in Example 2
Heat treated for hours. In the atmosphere of hydrogen-nitrogen mixed gas, the amount of nitrogen was increased especially when the temperature was raised, and the amount of hydrogen was increased at a constant temperature of 1360 ° C. The magnetic properties of the ribbon after this heat treatment were B ₈ = 1.90 T and W _17/50 = 0.96 w / kg.

EFFECTS OF THE INVENTION As described above, the present invention is a primary cold rolling method in which a plate material of a silicon-iron alloy composed of 2.5 to 4% by weight of silicon and the balance iron is cold-rolled into an intermediate material having a predetermined thickness. Step, a primary heat treatment step of heat-treating the intermediate material to be a heat-treated material of a recrystallized structure, and a reduction ratio of 70 to 80% in the same direction as the rolling direction in the primary cold rolling step of the heat-treated material. Cold rolled to 0.2 m
A secondary cold rolling step to form a cold-rolled strip having a thickness of m or less, and a heat treatment of the cold-rolled strip at 1180 ° C. or higher, and a crystal having a (110) [001] orientation in the rolling direction. A method for producing a directional silicon-iron alloy ribbon, which comprises at least a second heat treatment step of forming a ribbon having a recrystallized grain texture mainly composed of grains, by using a conventional grain growth inhibitor. Compared with the method using, the heat treatment of, for example, finish annealing, i.e., the second heat treatment step, is a remarkably simple process, and the treatment time is about 1/5 to 1/10 of the conventional time of about 20 hours. It is a manufacturing method that can be shortened to 2 to 4 hours, and a manufacturing method that can reduce costs. In addition, it has been possible to reduce the magnetic flux density in a ribbon of 0.2 mm or less, which has been difficult in the past, to reduce the iron loss value without surface coating and without applying domain refinement technology.
_17/50 can be 1.0 w / kg or less, and it is a manufacturing method capable of providing a high-performance, low-cost oriented silicon iron alloy ribbon.

Claims (4)

[Claims] 1. A primary cold rolling step of cold-rolling a sheet material of a silicon-iron alloy consisting of 2.5 to 4% by weight of silicon and the balance iron to form an intermediate material, and heat-treating the intermediate material to form a recrystallized structure. The first heat treatment step to be a heat treatment material having, and the reduction ratio 70 in the same direction as the rolling direction in the first cold rolling step of the heat treatment material.
~ 80% cold rolling, the secondary cold rolling step to make a cold rolling strip with a thickness of 0.2 mm or less, and the cold rolling strip
Characterized by at least passing through a second heat treatment step of heat treatment at 1180 ° C. or higher, and a ribbon having a recrystallized grain texture mainly composed of crystal grains having a (110) [001] orientation in the rolling direction. And a method for producing a directional silicon-iron alloy ribbon. 2. The first and second heat treatment steps, wherein the heat treatment is performed in a vacuum, an inert gas, a hydrogen gas, or a mixed gas of hydrogen and nitrogen. 2. A method for producing a directional silicon-iron alloy ribbon according to claim 1. 3. The directional silicon-iron alloy according to claim 1, wherein in the secondary cold rolling step, the surface of the roll used for rolling is degreased and then rolled without lubrication. Thin strip manufacturing method. 4. In the second heat treatment step, when the temperature is raised to 1100
The method for producing a directional silicon-iron alloy ribbon according to claim 1, characterized in that the temperature zone of 〜1150 ° C is held or passed over 10 to 60 minutes.