Preparation method for improving deformation uniformity of Bi-series strip core wire
Bi-based multi-core circular wires were prepared by powder pipe-loading method and drawn and rolled using octagonal molds or square molds, which solved the problem of uneven deformation of the core wire of Bi-based high-temperature superconducting wires, achieving more uniform deformation and better performance.
Patent Information
- Application Number
- CN202510294568.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-13
- Publication Date
- 2025-06-13
AI Technical Summary
In the prior art, the core wire of Bi-based high-temperature superconducting wires is unevenly deformed, resulting in easy wire breakage, core breakage and performance fluctuations.
The Bi-based multi-core circular wire is prepared by powder pipe-loading method, and is drawn and processed through an octagonal mold or a square mold, and rolled to ensure the smooth change of wire shape and improve the uniformity of core wire deformation.
Through this method, the uniformity of the deformation of the Bi-lace core wire is improved, the internal stress of the core wire is reduced, the core and wire breakage are prevented, and the current carrying performance and mechanical properties are improved.
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Figure CN120148964A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of superconducting material preparation, and particularly relates to a preparation method for improving the deformation uniformity of the core wires of Bi-based tapes. Background Art
[0002] The Bi-based high-temperature superconducting wire prepared by the powder-in-tube (PIT) method has become one of the most promising high-temperature superconducting materials for strong electric applications at liquid nitrogen temperature and below due to its high critical current density (J c ) and the characteristics of being easy to be processed into long tapes; its potential application fields include power transmission cables, transformers, fault current limiters, motors and generators, etc. For the purposes of improving the current-carrying performance and reducing the AC loss, the structural design of the Bi-based high-temperature superconducting wire is often a multi-core composite structure and the silver-to-superconductor ratio is reduced as much as possible. During the processing from the billet to the final wire, the amount of material deformation is large and often undergoes multiple assembly and compounding; therefore, the uniformity of the core wires of the wire is an important factor affecting the final performance of the superconducting wire.
[0003] In the prior art, circular dies are used for drawing, and the deformation among the core wires in the Bi-based multi-core round wire obtained is uneven, resulting in the uneven deformation of the core wires of the tape. During the preparation of long wires, problems such as wire breakage, core breakage, and performance fluctuations are likely to occur, seriously restricting its practical potential. Therefore, it is necessary to optimize the wire shape before rolling and the rolling process to improve the deformation uniformity of the core wires. Summary of the Invention
[0004] The object of the present invention is to overcome the deficiencies in the above prior art and provide a preparation method for improving the deformation uniformity of the core wires of Bi-based tapes. This preparation method performs drawing processing on the Bi-based multi-core round wire prepared by the powder-in-tube method using an octagonal die or a square die, and then performs rolling, ensuring a smooth transition of the wire shape change, capable of improving the deformation uniformity of the internal core wires, thereby reducing the internal stress of the core wires and preventing core breakage of the wire, and solving the problems of wire breakage, core breakage, and performance fluctuations that easily occur in Bi-based tapes in the prior art.
[0005] To achieve the above object, the technical solution adopted by the present invention is: a preparation method for improving the deformation uniformity of the core wires of Bi-based tapes, characterized in that the preparation method includes the following steps:
[0006] Step 1: Prepare a Bi-based multi-core round wire by the powder-in-tube method;
[0007] Step 2: Perform drawing on the Bi-based multi-core round wire obtained in Step 1 using an octagonal die or a square die, and then perform detection on the deformation uniformity of the core wires to obtain a Bi-based octagonal or square wire with uniform core wire deformation;
[0008] Step 3: Roll the Bi-based octagonal or square wire obtained in Step 2 to obtain a Bi-based tape.
[0009] The above preparation method for improving the deformation uniformity of the core wire of Bi-based tape is characterized in that the method for preparing the Bi-based multi-core round wire in Step 1 is specifically as follows: The tube assembly complex filled with the precursor powder is drawn to obtain a single-core wire, then multiple single-core wires are assembled into an alloy tube to obtain a multi-core wire, and the multi-core wire is drawn to obtain a Bi-based multi-core round wire.
[0010] The above preparation method for improving the deformation uniformity of the core wire of Bi-based tape is characterized in that when the diameter of the multi-core wire is greater than 2.02 mm, a die with an entrance angle of 14° is used for drawing, and the processing amount per pass is not less than 20%; when the diameter of the multi-core wire is not greater than 2.02 mm, the processing amount per pass is not greater than 10%.
[0011] In the present invention, by controlling the use of a die with an entrance angle of 14° for drawing when the diameter of the multi-core wire is greater than 2.02 mm, and the processing amount per pass is not less than 20%, it is beneficial for the middle core wire and the edge core wire of the multi-core wire to deform synergistically, improving the core wire density and processing efficiency; by controlling the processing amount per pass not to be greater than 10% after the diameter of the multi-core wire is reduced, the drawing force can be reduced, preventing the occurrence of broken core and broken wire phenomena.
[0012] The above preparation method for improving the deformation uniformity of the core wire of Bi-based tape is characterized in that the processing rate per pass for drawing with the octagonal die in Step 2 is 5.8% - 10%, and the processing rate per pass for drawing with the square die is 12.3% - 16.2%.
[0013] In the present invention, by controlling the processing rate per pass of drawing, the uniform deformation of the multi-core wire is effectively promoted, the drawing force can be reduced, and the occurrence of broken core and broken wire phenomena of the wire can be prevented.
[0014] The above preparation method for improving the deformation uniformity of the core wire of Bi-based tape is characterized in that after drawing with the octagonal die in Step 2, drawing is continued with the square die.
[0015] In the present invention, by processing into an octagonal wire with the octagonal die and then processing the octagonal wire into a square wire with the square die, it can further ensure a smooth transition of the wire shape change, ensure the full deformation of the core wires in each part of the multi-core wire, minimize the internal stress in the core wires to the greatest extent, and prevent the multi-core wire from breaking.
[0016] The above preparation method for improving the deformation uniformity of the core wire of Bi-based tape is characterized in that the specific process of the detection in Step 2 is as follows:
[0017] Step 201: Cut a section of wire at any position of the drawn Bi-based multi-core wire. After successively embedding, rough grinding, fine grinding, and polishing the cut wire, take a cross-sectional photograph of the horizontal wire to obtain a metallographic micrograph.
[0018] Step 202: Use Image J software to obtain the core wire area in the metallographic micrograph obtained in Step 201, and then calculate the average value of the core wire area. And the standard deviation S of the core wire area.
[0019] Step 203: According to the average value of the core wire area obtained in Step 202 And the standard deviation S of the core wire area, calculate the core wire deformation uniformity coefficient A to characterize the core wire deformation uniformity; the core wire uniformity coefficient A is calculated by the following formula:
[0020]
[0021] Where A is the core wire deformation uniformity coefficient; S is the standard deviation of the core wire area, with the unit of μm 2 ; Is the average value of the core wire area, with the unit of μm 2 .
[0022] In the above preparation method for improving the core wire deformation uniformity of Bi-based tape, it is characterized in that when the core wire deformation uniformity coefficient A is 0.085 - 0.102, the core wire deformation in the Bi-based octagonal or square wire is uniform.
[0023] In the present invention, by using Image J software to measure the total core wire area at the cross-section of the Bi-based wire, then obtaining the standard deviation of the core wire area of the wire through the standard deviation calculation formula, and substituting it into the formula to calculate the core wire uniformity coefficient A to characterize the core wire uniformity; by controlling the core wire uniformity coefficient A of the Bi-based octagonal or square wire, the uniformity of the core wire of the wire before rolling is improved, the overall current-carrying performance and mechanical properties of the Bi-based tape are improved, and its engineering application is promoted.
[0024] In the above preparation method for improving the core wire deformation uniformity of Bi-based tape, it is characterized in that in Step three, the rolling is carried out using a flat roll mill, the roll diameter of the flat roll mill is not less than 300 mm, and the processing amount per pass of the rolling is 20% - 30%.
[0025] In the present invention, by using a flat roll mill with a roll diameter not less than 300 mm for rolling, it can ensure the full deformation of the core wire, especially the deformation of the core wire in the difficult deformation area and the free deformation area, which is beneficial to improving the spread of the tape and further increasing the current-carrying performance of the tape; at the same time, by controlling the processing amount per pass of the rolling to be 20% - 30%, the rolling efficiency of the tape is improved.
[0026] The present invention has the following advantages compared with the prior art:
[0027] 1. By subjecting the Bi-based multi-core round wire prepared by the powder-in-tube method to drawing using an octagonal die or a square die and then rolling, the present invention can ensure a smooth transition in the shape change of the wire, improve the uniformity of the deformation of the internal core wires, and the octagonal wire and the square wire are more conducive to rolling than the circular wire; compared with using a circular die for drawing in the prior art, using an octagonal die or a square die can effectively deform the core wires at the edge positions, minimize the internal stress of the core wires to the greatest extent, and prevent the core wires of the multi-core wire from breaking.
[0028] 2. By detecting the uniformity of the core wires of the drawn wire, the present invention enables the wire with sufficient deformation to be rolled, and then a strip with fully deformed core wires is obtained, so as to improve the spread of the strip and increase the current-carrying performance of the strip.
[0029] 3. The preparation process of the present invention is simple, reasonably designed, and has a low manufacturing cost, and can be used for the industrial production of Bi-based strips.
[0030] 4. The present invention calculates the uniformity coefficient of the core wires by using the standard deviation of the cross-sectional area of the wire core, as a quantitative index for evaluating the uniformity of the core wires of the Bi-based wire. This quantitative index is accurately measured, simple to operate, and convenient to promote.
[0031] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings
[0032] Figure 1 It is the rolling deformation diagram of the Bi-based wire of the present invention.
[0033] Figure 2 It is the metallographic diagram of the cross-section of the Bi-2223 octagonal wire in Example 1 of the present invention.
[0034] Figure 3 It is the metallographic diagram of the cross-section of the 121-core wire in Comparative Example 1 of the present invention.
[0035] Figure 4 It is the metallographic diagram of the cross-section of the Bi-2223 octagonal wire in Example 2 of the present invention.
[0036] Figure 5 It is the metallographic diagram of the cross-section of the 121-core wire in Comparative Example 2 of the present invention.
[0037] Figure 6 It is the metallographic diagram of the cross-section of the Bi-2223 square wire in Example 3 of the present invention.
[0038] Figure 7 It is the metallographic diagram of the cross-section of the 121-core wire in Comparative Example 3 of the present invention. Detailed Embodiments
[0039] Example 1
[0040] The preparation method of this example includes the following steps:
[0041] Step 1: The tube - containing composite with precursor powder is drawn to obtain single - core wire. Then, 121 single - core wires are assembled into a silver alloy tube in a set core - wire structure to obtain a 121 - core wire. The 121 - core wire is drawn using a die with an entry angle of 14°. The processing amount per pass is not less than 20%. When the diameter of the 121 - core wire is no more than 2.02 mm, the processing amount per pass is not more than 10%, and a Bi - 2223 multi - core round wire with a diameter of 1.51 mm is obtained. The precursor powder contains Bi - 2212 and CaCuO 2 ;
[0042] Step 2: The Bi - 2223 multi - core round wire obtained in Step 1 is drawn successively using two octagonal dies with sizes of 1.47 mm×1.47 mm×1.44 mm×1.36 mm and 1.46 mm×1.46 mm×1.42 mm×1.22 mm, and then the uniformity of core - wire deformation is detected to obtain a Bi - 2223 octagonal wire with uniform core - wire deformation. The specific process of the detection is as follows:
[0043] Step 201: A section of wire is intercepted at an arbitrary position of the drawn Bi - 2223 multi - core round wire. The intercepted wire is successively inlaid, coarsely ground, finely ground, and polished, and then a metallographic micrograph of the cross - section is taken.
[0044] Step 202: The core - wire areas of all Bi - 2223 multi - core round wires in the metallographic micrograph of the cross - section taken in Step 201 are obtained using Image J software, and then the average value of the core - wire areas is calculated to be 4372 μm 2 and the standard deviation S of the core - wire areas is 371 μm 2 ;
[0045] Step 203: According to the average value of the core - wire areas and the standard deviation of the core - wire areas obtained in Step 202, the core - wire deformation uniformity coefficient A is calculated to be 0.085;
[0046] Step 3: The Bi - 2223 octagonal wire obtained in Step 2 is rolled using a flat - roll mill with a roll diameter of 300 mm, and the pass reduction rate is 30% to obtain a Bi - 2223 strip.
[0047] The rolling deformation of the wire is as Figure 1As shown in the figure, the core wire in Region I has the largest deformation, the smallest core wire thickness, and the largest spread, which is called the easy deformation region; the core wire in Region II has relatively small deformation and a relatively large core wire thickness, which is called the difficult deformation region; Region III is the region where the core wire has the smallest deformation, the largest core wire thickness, and the smallest spread. In this region, the deformation of the core wire is restricted the least, which is called the free deformation region.
[0048] The cross-section of the Bi-2223 octagonal wire obtained in this embodiment was subjected to metallographic analysis. As Figure 2 shown, obvious deformation occurred in the core wire of this cross-section, especially in the core wire of the difficult deformation region, indicating that the method of the present invention can pre-deform the core wire in the difficult deformation region before rolling, thereby improving the deformation uniformity of the Bi-2223 strip.
[0049] Comparative Example 1
[0050] The difference between this comparative example and Example 1 is that in Step 2, circular dies with diameters of Ф1.45 mm and Ф1.39 mm were used for drawing in sequence to obtain a 121-core wire with a diameter of Ф1.39 mm.
[0051] The cross-section of the 121-core wire obtained in this comparative example was subjected to metallographic analysis as Figure 3 shown. Compared with that of Example 1, Figure 2 the core wire at the edge of the 121-core wire in this comparative example has relatively small deformation and poor core wire uniformity; it shows that the method of the present invention can improve the core wire uniformity of the wire before rolling.
[0052] Example 2
[0053] The preparation method of this embodiment includes the following steps:
[0054] Step 1: The tube-complex filled with the precursor powder was drawn to obtain a single-core wire. Then, 121 single-core wires were assembled into a silver alloy tube in a set core wire structure to obtain a 121-core wire; the 121-core wire was drawn using a die with an entrance angle of 14°. The processing amount per pass was not less than 20%. When the diameter of the 121-core wire was not more than 2.02 mm, the processing amount per pass was not more than 10% to obtain a Bi-2223 multi-core round wire with a diameter of 1.51 mm; the precursor powder contains Bi-2212 and CaCuO 2 ;
[0055] Step 2: Use four octagonal dies with dimensions of 1.47mm×1.47mm×1.44mm×1.36mm, 1.46mm×1.46mm×1.42mm×1.22mm, 1.45mm×1.45mm×1.41mm×1.11mm, and 1.44mm×1.44mm×1.39mm×0.99mm to draw the Bi-2223 multi-core round wire obtained in Step 1 in sequence, and then perform a core wire deformation uniformity test to obtain Bi-2223 octagonal wire with uniform core wire deformation; the specific process of the test is as follows:
[0056] Step 201: Cut a section of wire at an arbitrary position of the drawn Bi-2223 multi-core round wire, and successively perform sample embedding, rough grinding, fine grinding, and polishing on the cut wire, and then take a metallographic micrograph of the cross-section;
[0057] Step 202: Use Image J software to obtain the core wire areas of all Bi-2223 multi-core round wires in the metallographic micrograph of the cross-section taken in Step 201, and then calculate the average value of the core wire areas to be 3606.9μm 2 and the standard deviation S of the core wire areas to be 305μm 2 ;
[0058] Step 203: Calculate the core wire deformation uniformity coefficient A to be 0.085 according to the average value of the core wire areas and the standard deviation of the core wire areas obtained in Step 202;
[0059] Step 3: Use a flat roll mill with a roll diameter of 300mm to roll the Bi-2223 octagonal wire obtained in Step 2, and the pass reduction rate is 25%, to obtain Bi-2223 strip.
[0060] Perform metallographic analysis on the cross-section of the Bi-2223 octagonal wire obtained in this example. As Figure 4 shown, obvious deformation appears in the core wires in this cross-section, especially the core wires in the difficult-to-deform area, indicating that the method of the present invention can pre-deform the core wires in the difficult-to-deform area before rolling, thereby improving the deformation uniformity of the Bi-2223 strip.
[0061] Comparative Example 2
[0062] The difference between this comparative example and Example 2 is that in Step 2, circular dies with diameters of Ф1.45mm, Ф1.39mm, Ф1.33mm, and Ф1.28mm are used for drawing in sequence to obtain a 121-core wire with a diameter of Ф1.28mm.
[0063] Perform metallographic analysis on the cross-section of the 121-core wire obtained in this comparative example as Figure 5 shown, compared with that of Example 2 Figure 4In contrast, for the 121-core wire in Comparative Example 1, the core wires at the edge part have less deformation and poorer uniformity of core wire deformation; it shows that the method of the present invention can improve the uniformity of core wires of the wire before rolling.
[0064] Example 3
[0065] The preparation method of this example includes the following steps:
[0066] Step 1: The canned composite containing precursor powder is drawn to obtain a single-core wire, and then 121 single-core wires are bundled and assembled into a silver alloy tube according to the set core wire structure to obtain a 121-core wire; the 121-core wire is drawn using a die with an entry angle of 14°, and the processing amount per pass is not less than 20%. When the diameter of the 121-core wire is not greater than 2.02 mm, the processing amount per pass is not greater than 10%, and a Bi-2223 multi-core round wire with a diameter of 1.51 mm is obtained; the precursor powder contains Bi-2212 and CaCuO 2 ;
[0067] Step 2: The Bi-2223 multi-core round wire obtained in Step 1 is drawn successively using four octagonal dies with dimensions of 1.47 mm × 1.47 mm × 1.44 mm × 1.36 mm, 1.46 mm × 1.46 mm × 1.42 mm × 1.22 mm, 1.45 mm × 1.45 mm × 1.41 mm × 1.11 mm, and 1.44 mm × 1.44 mm × 1.39 mm × 0.99 mm, and then continued to be drawn successively using four square dies with dimensions of 1.32 mm × 0.88 mm, 1.31 mm × 0.79 mm, 1.29 mm × 0.71 mm, and 1.28 mm × 0.64 mm, and then the uniformity of core wire deformation is detected to obtain a Bi-2223 square wire with uniform core wire deformation; the specific process of the detection is as follows:
[0068] Step 201: A section of wire is intercepted at an arbitrary position of the drawn Bi-based multi-core round wire, and the intercepted wire is successively subjected to sample embedding, rough grinding, fine grinding, and polishing, and then a metallographic micrograph of the cross-section is taken.
[0069] Step 202: Using Image J software, obtain the core wire areas of all the Bi-based multi-core round wires in the metallographic micrograph of the cross-section taken in Step 201, and then calculate the average value of the core wire areas to be 2535 μm 2 and the standard deviation S of the core wire areas to be 255.3 μm 2 ;
[0070] Step 203: According to the average value of the core wire areas and the standard deviation of the core wire areas obtained in Step 202, calculate the core wire deformation uniformity coefficient A to be 0.101;
[0071] Step 3: Use a flat rolling mill with a roll diameter of 300 mm to roll the Bi-2223 square wire obtained in Step 2, with a pass reduction rate of 20%, to obtain a Bi-2223 strip.
[0072] Perform metallographic analysis on the cross-section of the Bi-2223 square wire obtained in this embodiment, as Figure 6 shown. Obvious deformation occurred in the core wires in this cross-section, especially in the core wires in the difficult-to-deform area, indicating that the method of the present invention can pre-deform the core wires in the difficult-to-deform area before rolling, thereby improving the deformation uniformity of the Bi-2223 strip. Moreover, the shape of the Bi-2223 square wire is quasi-square, which is closer to the strip shape and is more conducive to subsequent rolling.
[0073] Comparative Example 3
[0074] The difference between this comparative example and Example 3 is that in Step 2, round dies with diameters of Ф1.45 mm, Ф1.39 mm, Ф1.33 mm, Ф1.28 mm, Ф1.23 mm, Ф1.18 mm, Ф1.13 mm, Ф1.08 mm, Ф1.04 mm, and Ф1.0 mm are used for drawing in sequence to obtain a 121-core wire with a diameter of Ф1.0 mm.
[0075] Perform metallographic analysis on the cross-section of the 121-core wire obtained in this comparative example as Figure 7 shown. Compared with that of Example 3 Figure 6 , the core wires at the edge part of the 121-core wire in this comparative example have less deformation and poorer deformation uniformity of the core wires, indicating that the method of the present invention can improve the uniformity of the core wires of the wire before rolling.
[0076] Example 4
[0077] The difference between this example and Example 3 is that in Step 2, six square dies with sizes of 1.25 mm × 1.25 mm, 1.16 mm × 1.16 mm, 1.2 mm × 1 mm, 1.5 mm × 0.75 mm, 1.33 mm × 0.66 mm, and 1.28 mm × 0.64 mm are used to draw the Bi-2223 multi-core round wire in sequence, and then the uniformity of the core wire deformation is detected to obtain the average value of the core wire area of 2554 μm 2 and the standard deviation S of the core wire area of 260 μm 2 and a Bi-2223 square wire with a core wire deformation uniformity coefficient A of 0.102.
[0078] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent structural transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims
1. A method for improving the uniformity of deformation of a core wire of a Bi-based tape, characterized in that: The preparation method comprises the following steps: Step 1: Prepare Bi-based multi-core round wire by powder tube method; Step 2: Using an octagonal die or a square die to draw the Bi-based multi-core round wire obtained in step 1, and then performing a core wire deformation uniformity test to obtain a Bi-based octagonal or square wire with uniform core wire deformation; Step 3: rolling the Bi-based octagonal or square wire obtained in step 2 to obtain a Bi-based strip.
2. A method for improving the uniformity of deformation of the core wire of a Bi-based tape according to claim 1, characterized in that: The method for preparing Bi-based multi-core round wire described in step 1 is specifically: drawing a tube-filled composite containing precursor powder to obtain a single-core wire, then assembling multiple single-core wires into an alloy tube to obtain a multi-core wire, and drawing the multi-core wire to obtain a Bi-based multi-core round wire.
3. A method for improving the uniformity of deformation of Bi-based tape core wire according to claim 2, characterized in that: When the diameter of the multi-core wire is greater than 2.02 mm, a die with an entry angle of 14° is used for drawing, and the processing amount of each drawing pass is not less than 20%; when the diameter of the multi-core wire is not greater than 2.02 mm, the processing amount of each drawing pass is not greater than 10%.
4. A method for improving the uniformity of deformation of the core wire of a Bi-based tape according to claim 1, characterized in that: The processing rate of each drawing pass using the octagonal die in step 2 is 5.8% to 10%, and the processing rate of each drawing pass using the square die is 12.3% to 16.2%.
5. The method for improving the uniformity of deformation of the core wire of a Bi-based tape according to claim 1, characterized in that: After the drawing using the octagonal die as described in step 2, the drawing is continued using the square die.
6. A method for improving the uniformity of deformation of the core wire of a Bi-based tape according to claim 1, characterized in that: The specific process of the detection in step 2 is as follows: Step 201, cutting a section of the wire at any position of the drawn Bi-based multi-core wire, mounting, coarse grinding, fine grinding and polishing the cut wire in sequence, and then photographing the cross section of the wire to obtain a metallographic micrograph; Step 202: Use Image J software to obtain the core wire area in the metallographic micrograph obtained in step 201, and then calculate the average value of the core wire area. and the standard deviation S of the core wire area; Step 203: according to the average value of the core wire area obtained in step 202 The core wire deformation uniformity coefficient A is calculated based on the standard deviation S of the core wire area to characterize the core wire deformation uniformity; the core wire uniformity coefficient A is calculated by the following formula: Where A is the core wire deformation uniformity coefficient; S is the standard deviation of the core wire area, in μm 2 ; is the average value of the core area, in μm 2 .
7. A method for improving the uniformity of deformation of the core wire of a Bi-based tape according to claim 6, characterized in that: When the core wire deformation uniformity coefficient A is 0.085-0.102, the core wire in the Bi-based octagonal or square wire is uniformly deformed.
8. The method for improving the uniformity of deformation of the core wire of a Bi-based tape according to claim 1, characterized in that: The rolling in step 3 is performed by a flat roll mill, the roll diameter of the flat roll mill is not less than 300 mm, and the processing amount of each rolling is 20% to 30%.