JP2006281317A - Method and apparatus for manufacturing amorphous magnetic thin strip with excellent thickness uniformity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an amorphous magnetic thin strip that has uniform thickness distribution in both width direction and casting direction, excellent space factor and magnetic properties, based on an index which is a newly found index representing a contact area between a cooling roll and molten metal. <P>SOLUTION: The method for manufacturing an amorphous magnetic thin strip with the excellent thickness uniformity by rapidly solidifying iron-based molten metal on a surface of cooling roll rotated at a high velocity includes: (a) evaluating and controlling the surface of cooling roll using a surface unevenness index Z defined in the formula below; and (b) controlling the surface unevenness index Z within a designated range. The formula is Z=Ra<SP>k</SP>×(W/Sm), where Ra is an arithmetical mean roughness (μm) on the cooling roll surface; W/Sm is the number of roughness peaks existing in a surface roughness measuring distance W (μm) in an axial direction of the cooling roll (Sm is an average distance (μm) of roughness peaks existing on the cooling roll surface); and k is an index. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a manufacturing method and a manufacturing apparatus for manufacturing an amorphous magnetic ribbon having a uniform thickness in the width direction and the casting direction.

  Conventionally, the Fe-B-Si-based amorphous alloy magnetic ribbon has been manufactured by using a single roll method, that is, a Fe-B-Si-based molten metal of a cooling roll rotating at high speed from a slit-like nozzle. It is manufactured by a method of jetting to the surface and rapidly solidifying.

  Fe-B-Si-based amorphous alloy magnetic ribbons (hereinafter sometimes simply referred to as “amorphous magnetic ribbons”) are mainly used as a core material for power transformers and motor cores. However, in order to meet the user's request to improve the device performance by increasing the space factor of the material, it is not only to increase the smoothness of the surface of the amorphous magnetic ribbon, but also to amorphous. It is necessary to make the thickness distribution in the width direction and the casting direction of the magnetic thin ribbon uniform (improve thickness uniformity).

  In order to increase the smoothness of the surface of the amorphous magnetic ribbon, it is necessary to always keep the surface state of the cooling roll in direct contact with the molten metal in an optimum state. There is a strong correlation. That is, as the casting amount increases, the number of wrinkles (surface wrinkles) on the surface of the cooling roll increases and the depth of the surface wrinkles also increases.

  The molten metal ejected onto the surface of the cooling roll adheres and solidifies rapidly along the shape of the surface defects, so that the surface of the amorphous magnetic ribbon has surface defects (for example, irregularities). As a result, undulations (unevenness) are formed. Furthermore, as casting progresses, the surface wrinkles (unevenness) of the cooling roll increases, so that the undulations (irregularities) transferred to the surface of the amorphous magnetic ribbon also increase.

  It is natural that the undulations formed on the surface of the amorphous magnetic ribbon due to the surface defects of the cooling roll cause a decrease in the space factor.

  Therefore, as a measure for suppressing an increase in surface flaws accompanying the progress of casting, a method of polishing the surface of the cooling roll during casting has been proposed (see Patent Documents 1 to 3). By these methods, the smoothness of the surface of the amorphous ribbon is improved, but the thickness uniformity of the amorphous magnetic ribbon is not improved.

  On the other hand, as described above, since the amorphous magnetic ribbon is mainly used for a power transformer and a core material of a motor core, it needs to have excellent magnetic properties.

  In order to secure excellent magnetic properties in an amorphous ribbon, it is necessary to rapidly cool the molten metal and make the solidified structure completely amorphous. This rapid cooling rate (cooling rate) It varies depending on the thermal conductivity, thickness, and thickness of the amorphous magnetic ribbon after rapid solidification.

  That is, when a molten metal is rapidly solidified by using a cooling roll having a predetermined thermal conductivity and a constant roll thickness, to secure a complete amorphous structure and obtain excellent magnetic properties, It is necessary to make the plate thickness distribution uniform in the width direction and casting direction of the amorphous magnetic ribbon.

  Patent Document 4 discloses that an upper limit value is defined in the roughness Ra on the ribbon roll surface side in order to reduce variation in magnetic properties, but it improves the thickness uniformity of the amorphous magnetic ribbon. It is not a thing.

  The thickness of the amorphous magnetic ribbon has been greatly influenced by the solidification rate of the molten metal, and it has been found that the solidification rate is affected by the contact area between the cooling roll and the paddle molten metal. Yes. Therefore, it is important to evaluate and manage the contact area in the uniform control (improvement of thickness uniformity) of the ribbon thickness distribution.

  Regarding the surface of the cooling roll, in addition to this, a technique (Patent Document 5) that defines the roughness in combination with a Cr plating roll, a technique (Patent Document 6) that defines a satin-like surface, and a technique that is defined by the grain number ( Patent Document 8), a technique for determining the manufacturing conditions by measuring roll roughness online (Patent Document 7) and the like have been disclosed, both of which are for the purpose of improving the surface quality and controlling the plate thickness. There is no suggestion about that.

  As described above, in the amorphous magnetic ribbon, uniform control of the ribbon thickness distribution (improving thickness uniformity) is an important issue in terms of both improving the space factor and ensuring excellent magnetic properties. However, a method for solving this problem by controlling the surface of the roll has not been proposed so far.

JP-A-61-209755 JP-A-3-161149 JP-A-3-165955 Japanese Patent Laid-Open No. 2003-340554 JP-A-56-30061 JP-A-56-117868 JP-A-3-221245 JP 2000-328206 A

  In view of the present situation, the present invention has found a new index representing the contact area between the cooling roll and the molten metal, and based on this index, the surface of the cooling roll is accurately evaluated and managed, and further adjusted. An object of the present invention is to produce an amorphous magnetic ribbon having a uniform thickness distribution in the width direction and the casting direction and excellent in space factor and magnetic properties.

First, the present inventor has intensively studied an index representing the contact area between the cooling roll and the molten metal. As a result, the present inventor
(X) When the surface roughness index Z defined by the following formula is used, the surface of the cooling roll can be accurately evaluated and managed,
Z = Ra ^k (W / Sm)
Here, Ra: Centerline average roughness of the surface of the cooling roll (μm)
W / Sm: Over the surface roughness measurement length W (μm) in the cooling roll axis direction
The number of irregularities present (Sm: irregularities present on the surface of the cooling roll
Mean interval (μm))
k: index (y) The surface roughness index Z can be used as an index that quantitatively represents the contact area (rate), and
(Z) It has been found that if the surface roughness index Z is controlled within a predetermined range and the surface state of the cooling roll is adjusted, an amorphous magnetic ribbon having excellent thickness uniformity can be produced.

  This invention was made | formed based on the said knowledge, and the summary is as follows.

(1) In a method for producing an amorphous magnetic ribbon by rapidly solidifying an iron-based molten metal on the surface of a cooling roll rotating at high speed,
(A) The surface state of the cooling roll is evaluated and managed using the surface roughness index Z defined by the following formula,
(B) A method for producing an amorphous magnetic ribbon having excellent thickness uniformity, wherein the surface roughness index is controlled within a predetermined range.
Z = Ra ^k (W / Sm)
Here, Ra: Centerline average roughness of the surface of the cooling roll (μm)
W / Sm: Over the surface roughness measurement length W (μm) in the cooling roll axis direction
The number of irregularities present (Sm: irregularities present on the surface of the cooling roll
Mean interval (μm))
k: exponent

  (2) The method for producing an amorphous magnetic ribbon having excellent thickness uniformity according to (1), wherein k = 0.5 in the surface roughness index Z.

  (3) In the surface unevenness index Z, the variation in Z in the plate width direction and the casting direction is controlled to 40 or less. The amorphous magnetic ribbon excellent in thickness uniformity according to (2), Production method.

(4) An apparatus for producing an amorphous magnetic ribbon by rapidly solidifying an iron-based molten metal on the surface of a cooling roll rotating at high speed,
(A) An evaluation / management device that evaluates and manages the surface state of the cooling roll using the surface unevenness index Z defined by the following formula, and
(B) An apparatus for producing an amorphous magnetic ribbon excellent in thickness uniformity, comprising a controller for controlling the surface roughness index within a predetermined range.
Z = Ra ^k (W / Sm)
Here, Ra: Centerline average roughness of the surface of the cooling roll (μm)
W / Sm: Over the surface roughness measurement length W (μm) in the cooling roll axis direction
The number of irregularities present (Sm: irregularities present on the surface of the cooling roll
Mean interval (μm))
k: exponent

  (5) The apparatus for producing an amorphous magnetic ribbon having excellent thickness uniformity according to (4), wherein k = 0.5 in the surface roughness index Z.

  (6) Production of an amorphous magnetic ribbon having excellent thickness uniformity according to (5), wherein in the surface roughness index Z, variation in Z in the sheet width direction and casting direction is 40 or less. apparatus.

  According to the present invention, the surface of the cooling roll is accurately evaluated and managed based on the surface unevenness index Z, and further, by adjusting the surface unevenness index Z to an appropriate range, the plate thickness in the width direction and the casting direction is determined. An amorphous magnetic ribbon having a uniform distribution and excellent space factor and magnetic properties can be produced.

  When examining the index representing the contact area between the cooling roll and the molten metal, the inventor first investigated the relationship between the ribbon thickness and the contact area. The result is shown in FIG.

  Here, the production conditions are at%, Fe: 80.5%, Si: 6.5%, B: 12%, C: 1%, and an alloy having a melting temperature of 1320 to 1340 ° C. is shown in FIG. Cast with a single roll casting machine. As the cooling roll of the casting apparatus, a roll having a diameter of 1200 mm, a width of 250 mm, a material of Cu-2% B, a thickness of 20 mm, and a thermal conductivity of 105 W / (m · k) was used. The nozzle opening shape was 0.7 mm × 100 mm slit shape. The gap between the cooling roll and the nozzle during casting was 250 μm.

  The thickness of the amorphous magnetic ribbon after casting and the roll contact area ratio were measured every 1000 m of ribbon. Here, the roll contact area ratio is determined by observing the roll surface of the ribbon with a microscope, and identifying the portion of the projection on the ribbon surface where fine wrinkles caused by friction with the roll are observed as the contact portion. , And binarized by image processing.

  Black squares and black circles in FIG. 1 indicate the results of investigating amorphous magnetic ribbons of different lots under the same casting conditions. It can be seen from FIG. 1 that there is a good correlation between the amorphous magnetic ribbon thickness and the contact area. FIG. 1 shows that the contact area increases despite the same casting conditions. That is, the aspect of the unevenness existing on the surface of the cooling roll greatly affects the thickness of the amorphous magnetic thin plate. Therefore, if this unevenness can be quantified by some index, the amorphous magnetic ribbon thickness can be controlled based on the correlation between this index and the amorphous magnetic ribbon thickness.

  Since it is impossible to grasp and quantify a number of irregularities on the surface of the cooling roll, the present inventor has focused on the number of irregularities as an alternative.

  An index represented by the following formula is known as an index indicating the average interval of the unevenness, and its reciprocal number “1 / Sm” represents the number of unevenness per unit length. Therefore, it means that there are many surface irregularities, so that this Sm is large.

Therefore, the present inventor can accurately evaluate the roughness of the surface according to the measurement curve by combining “Ra” and “1 / Sm” in some form to evaluate the roughness of the surface of the cooling roll according to the unevenness state. Since the number of irregularities present on the surface is taken into account, the idea that the surface state of the cooling roll can be evaluated more appropriately is reached, and as the surface irregularity index (new index),
Z = Ra ^k (W / Sm)
Here, Ra: Centerline average roughness of the surface of the cooling roll (μm)
W / Sm: Over the surface roughness measurement length W (μm) in the cooling roll axis direction
The number of irregularities present (Sm: irregularities present on the surface of the cooling roll
Mean interval (μm))
k: An index was defined.

  The index Z is an index for comprehensively evaluating the uneven state of the roll surface, including quantitative evaluation of the unevenness. Physically, it means the contact area between the surface of the cooling roll and the molten metal, and increasing Z means that the contact area between the cooling roll and the molten metal is increased.

  k is an index for appropriately changing the weight of the roughness Ra in Z, and is a value determined from equipment conditions, for example, the material and diameter of the cooling roll, and is determined in advance through preliminary experiments. W is a measurement length of roughness, and represents a length to be evaluated in the plate width direction. Therefore, W is an arbitrarily determined value and can be set up to the plate width of the amorphous magnetic ribbon.

  Therefore, if W is increased, it becomes a macro evaluation, and if it is small, it becomes a micro evaluation. However, in order to make the thickness distribution in the width direction uniform, it is actually meaningful to set W as the plate width. In addition, W cannot be increased due to limitations of the measurement apparatus and measurement accuracy, and is set to 1/4 or less, preferably 10 mm or less of the plate width.

  The inventors of the present invention cast an amorphous magnetic ribbon using a cooling roll having a diameter of 1200 mm and a width of 250 mm (apparatus shown in FIG. 3), and the thickness of the amorphous magnetic ribbon at the end of casting, The Ra and Sm of the cooling roll after casting were measured as W = 2500 μm. The fact that the end of the amorphous magnetic ribbon was used as the measurement sample was because the evaluation of the state of the cooling roll could only be performed after the casting was completed. This is because the portion of the amorphous magnetic ribbon that can be evaluated in this way is the tail end.

  In the casting of amorphous magnetic ribbon, in order to investigate the relationship between the change in the absolute plate thickness due to the change in the amount of molten alloy supplied and the change in the relative plate thickness due to the contact area between the cooling roll and the molten metal This was carried out by changing the nozzle opening shape and the jet pressure of the molten metal, and changing the surface roughness of the cooling roll before casting the amorphous magnetic ribbon in order to change the values of Ra and Sm.

  By this series of castings, an amorphous magnetic ribbon having a thickness of 22 to 70 μm was produced. When the thickness of the amorphous magnetic ribbon exceeded 70 μm, partial crystallization occurred and did not show good magnetic properties. Therefore, the evaluation was conducted on an amorphous magnetic ribbon with a thickness of 70 μm or less. did. The correlation between the thickness of the amorphous magnetic ribbon and the index Z was investigated by changing k from the measured Ra and Sm. FIG. 2 shows changes in the plate thickness with respect to changes in the index Z when Z = 20 is set as a reference value (zero) under each casting condition.

  In FIG. 2, Δ is a change in the plate thickness when the surface roughness of the cooling roll is changed under casting conditions in which the plate thickness is about 25 μm in the vicinity of Z = 20, and □ is a plate thickness in the vicinity of Z = 20. The change in sheet thickness when the surface roughness of the chill roll is changed under casting conditions with a thickness of about 35 μm. ◇ indicates the surface roughness of the chill roll under the casting conditions where the sheet thickness is about 45 μm near Z = 20. The change in the plate thickness when the thickness is changed, and the circle indicates the change in the plate thickness when the surface roughness of the cooling roll is changed under casting conditions in which the plate thickness is about 55 μm near Z = 20.

  In FIG. 2, k = 0.5 is the result of the present inventors analyzing from the experiment using the apparatus shown in FIG. 3, and the best correlation is obtained when k = 0.5. Because they found out. Note that k may deviate from 0.5 due to differences in equipment conditions, for example, the material and diameter of the cooling roll, etc. If the equipment changes, the value of k is determined in advance in a preliminary experiment. There is a need to.

  It can be seen from FIG. 2 that there is a good correlation between the change in sheet thickness and the index Z. That is, under the same casting conditions (for example, casting conditions where the plate thickness is about 25 μm in the vicinity of Z = 20: Δ in FIG. 2), it is found that the plate thickness increases as the index Z increases. Furthermore, even when the absolute plate thickness is increased (for example, when casting is performed in the vicinity of Z = 20 and the plate thickness is about 45 μm: ◇ in FIG. 2), the amount of change in the plate thickness with respect to Z is It turned out not to change.

  Further, since this correlation is a linear relationship, it has been found that the change in the plate thickness depends not on the absolute value of Z but on the amount of change (for example, if Z is changed from 20 to 60 and 40, The thickness varies by 10 μm).

  From the experiment and analysis, the present inventors have found that an amorphous magnetic ribbon having excellent thickness uniformity in the width direction and the casting direction can be produced by controlling the variation of the index Z within a predetermined range. .

  Actually, when an amorphous magnetic ribbon is used as a core material for power transformers, motor cores, etc., in order to exhibit excellent space factor and magnetic properties, It is necessary to suppress the thickness variation in the width direction and the casting direction to a certain level or less.

  As a result of investigations by the present inventors, it was found that the thickness variation in the width direction and the casting direction is acceptable if it is 10 μm or less, and more preferably 5 μm or less when used in a laminated state. As a result of obtaining the variation of the index Z with the plate thickness variation of 10 μm or less from FIG. 2, it was found that the Z variation needs to be controlled to 40 or less.

  Therefore, in order to produce an amorphous magnetic ribbon having excellent thickness uniformity in the width direction and casting direction, and excellent space factor and magnetic properties, it is necessary to control the variation of the surface unevenness index Z to 40 or less. .

  Next, examples of the present invention will be described. The conditions of the examples are one example of conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is limited to this one example of conditions. Is not to be done. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example)
At%, cast an alloy consisting of Fe: 80.5%, Si: 6.5%, B: 12%, C: 1% at a melting temperature of 1320 to 1340 ° C. with a single roll casting apparatus shown in FIG. did. As the cooling roll of the casting apparatus, a roll having a diameter of 1200 mm, a width of 250 mm, a material of Cu-2% Be, a thickness of 20 mm, and a thermal conductivity of 105 W / (m · k) was used. The nozzle opening shape was 0.7 mm × 100 mm slit shape. The gap between the cooling roll and the nozzle during casting was 250 μm. Moreover, the jet pressure of the molten alloy was adjusted so that the plate thickness was 30 μm.

At this time, in the example of the present invention, the variation of the surface unevenness index Z = Ra ^0.5 · (2500 / Sm) of the cooling roll was controlled to 40 or less using the online polishing apparatus shown in FIG. In the conventional method, the operation was performed without using an online polishing apparatus. Before casting, both the inventive example and the conventional method were adjusted to Z = 20 uniformly in the width direction.

  In the present invention example, the Z value in the strip width direction after casting is 23 to 38, the variation is 40 or less, and the Z value is 20 to 38 at the maximum even before and after casting. The variation was only 40 and less in the casting direction. On the other hand, in the conventional method, since online polishing is not used, the number of cooling roll surface flaws increases as the casting progresses, the value of Z gradually increases, and the value of Z in the strip width direction after casting increases. The variation of Z exceeded 40, and the variation of Z exceeded 40, and even when compared before and after casting, the value of Z reached 83 at the maximum.

  As a result, in the example of the present invention, the thickness distribution is within a range of 30 to 34 μm in the width direction of the amorphous magnetic ribbon and 30 to 33 μm in the casting direction, and an amorphous magnetic ribbon having excellent thickness uniformity is manufactured. We were able to. On the other hand, in the conventional method, the plate thickness distribution is 30 to 46 μm in the width direction and 30 to 41 μm in the casting direction, and the plate thickness variation cannot be set to a target of 10 μm or less.

  Table 1 shows the magnetic properties and space factor of the ribbon. From Table 1, it can be seen that the amorphous magnetic ribbon according to the present invention is excellent in magnetic properties and space factor.

  As described above, according to the present invention, the surface of the cooling roll is accurately evaluated and managed based on the surface unevenness index Z, and further, the surface unevenness index Z is adjusted to an appropriate range. It is possible to produce an amorphous magnetic ribbon having a uniform plate thickness distribution in the direction and casting direction and excellent in space factor and magnetic properties. As described above, the present invention provides an amorphous magnetic ribbon having an excellent space factor and magnetic properties, and thus has high industrial applicability.

It is a figure which shows the correlation with the contact area of a cooling roll and a molten metal, and ribbon thickness. It is a figure which shows the correlation of Z (= Ra ^0.5 * (2500 / Sm)) and plate | board thickness change (micrometer). It is sectional drawing which shows the example of the single roll method for implementing this invention method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thin strip 2 Winding roll 3 Cooling roll 4 Molten alloy 5 Tundish 6 Nozzle 7 Stopper 8 Polishing apparatus

Claims (6)

In a method for producing an amorphous magnetic ribbon by rapidly solidifying an iron-based molten metal on the surface of a cooling roll rotating at high speed,
(A) The surface state of the cooling roll is evaluated and managed using the surface roughness index Z defined by the following formula,
(B) A method for producing an amorphous magnetic ribbon having excellent thickness uniformity, wherein the surface roughness index is controlled within a predetermined range.
Z = Ra ^k (W / Sm)
Here, Ra: Centerline average roughness of the surface of the cooling roll (μm)
W / Sm: Over the surface roughness measurement length W (μm) in the cooling roll axis direction
The number of irregularities present (Sm: irregularities present on the surface of the cooling roll
Mean interval (μm))
k: exponent   2. The method for producing an amorphous magnetic ribbon having excellent thickness uniformity according to claim 1, wherein k = 0.5 in the surface roughness index Z. 3.   3. The method for producing an amorphous magnetic ribbon having excellent thickness uniformity according to claim 2, wherein in the surface unevenness index Z, variation in Z in the plate width direction and casting direction is controlled to 40 or less. An apparatus for producing an amorphous magnetic ribbon by rapidly solidifying an iron-based molten metal on the surface of a cooling roll rotating at high speed,
(A) An evaluation / management device that evaluates and manages the surface state of the cooling roll using the surface unevenness index Z defined by the following formula, and
(B) A device for producing an amorphous magnetic ribbon excellent in thickness uniformity, comprising a control device for controlling the surface roughness index within a predetermined range.
Z = Ra ^k (W / Sm)
Here, Ra: Centerline average roughness of the surface of the cooling roll (μm)
W / Sm: Over the surface roughness measurement length W (μm) in the cooling roll axis direction
The number of irregularities present (Sm: irregularities present on the surface of the cooling roll
Mean interval (μm))
k: exponent   5. The apparatus for producing an amorphous magnetic ribbon having excellent thickness uniformity according to claim 4, wherein k is 0.5 in the surface roughness index Z.   6. The apparatus for producing an amorphous magnetic ribbon excellent in thickness uniformity according to claim 5, wherein in the surface roughness index Z, the variation in Z in the plate width direction and the casting direction is 40 or less.

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