WO2011004888A1

WO2011004888A1 - Method for continuous casting of bronze or bronze alloy and casting ring used therefor

Info

Publication number: WO2011004888A1
Application number: PCT/JP2010/061682
Authority: WO
Inventors: 司高澤; 浩一吉田; 俊郎阿部; 修司富松
Original assignee: 古河電気工業株式会社
Priority date: 2009-07-10
Filing date: 2010-07-09
Publication date: 2011-01-13
Also published as: JP2012179607A; TW201111068A

Abstract

Disclosed is a method for continuous casting of bronze or bronze alloy which has a high cooling capacity and superior productivity and which improves ingot surface quality. Also disclosed is a casting ring used for said method. The continuous casting method uses a casting ring having an electrical conductivity of 20 to 50%IACS, inclusive, when casting bronze or a bronze alloy using the belt and wheel method.

Description

Copper or copper alloy continuous casting method and casting ring used therefor

The present invention relates to the manufacture of a copper alloy wire used as a copper wire or an automobile wire harness, a robot cable, and other signal wires, and in particular, a method of continuously casting copper or a copper alloy by a belt and wheel method and the same It relates to the casting ring used.

In general, an alloy used as a mold is required to have high temperature strength and high thermal conductivity. The material of the cast ring currently used in the belt and wheel method is mainly a Cu—Cr—Zr alloy or a Cu—Ag alloy of a high conductivity (80 to 95% IACS) copper alloy with good heat conduction. Since the heat conduction is good, the ingot cooling capacity is excellent, and high production capacity can be exhibited (see Patent Document 1).
In the early days of development of belt and wheel casting machines, casting was performed using iron casting rings. The iron cast ring has a conductivity of 17% IACS, and the heat transfer coefficient is small compared to the copper cast ring, so the cooling capacity is weak and it is difficult to increase the casting speed. Moreover, cracking occurred on the ring surface due to the brittleness of iron, and long-term casting work could not be performed.

A unique example is the use of a copper alloy mold material with a low conductivity such as Cu-Cr-Zr-Al, but this mold is not intended for changing cooling conditions but is used for electromagnetic stirring. (For example, refer to Patent Document 2).

JP 2008-173662 A JP 63-145732 A

Generally, a copper alloy cast ring using a Cu—Ag alloy (EC: 92% IACS) or a Cu—Cr—Zr alloy (EC: 80% IACS) is strongly cooled because the heat conduction is good immediately after the molten metal contacts the mold. As a result, cooling of the initial solidified skin is hindered by an air gap caused by solidification shrinkage. Therefore, the cooling after the start of solidification becomes uneven, the thickness of the solidified shell varies, and cracks occur at fragile locations. This fine crack appears as a surface defect when it becomes a rough drawn wire through a rolling process, and causes a serious problem such as disconnection in the wire drawing process. Moreover, the yield is also lowered by peeling after rolling to remove the surface defect portion.
As described above, the high conductivity copper alloy casting ring is excellent in ingot productivity, but has a problem in the surface quality of the ingot.
Accordingly, an object of the present invention is to provide a continuous casting method of copper or copper alloy having a high cooling capacity, excellent productivity, and excellent ingot surface quality, and a casting ring used in the method.

To achieve the above-mentioned problems, create cast rings with various electrical conductivity, search for conditions that balance the surface quality and productivity of the ingot, and cast with cast rings with electrical conductivity of less than 20% IACS. Since the cooling capacity is insufficient and the productivity is remarkably reduced, a casting ring having a predetermined conductivity has been found to overcome this point.
That is, the present invention solves the problem by the following solution means.

(1) A continuous casting method using a casting ring having a conductivity of 20% IACS or more and 50% IACS or less in casting of copper or copper alloy by the belt and wheel method.
(2) The continuous ring according to (1), wherein the cast ring has a conductivity B (% IACS) that satisfies the following formula (I) with respect to the conductivity A (% IACS) of the cast metal. Casting method.
20 ≦ B <0.225 × A + 27.5 (I)
A: Conductivity of cast metal (% IACS)
B: Conductivity of cast ring (% IACS)
(3) In the belt and wheel method, the molten metal in the tundish is poured from the pouring nozzle into a belt and wheel casting machine constituted by a belt and a wheel that is rotated by a turn roll, and then cooled and solidified to form an ingot. (1) or (2), wherein the ingot is continuously drawn from the mold, and the cast ring having the specific conductivity is used as the cast ring constituting the wheel. The continuous casting method described.
(4) A casting ring having a conductivity of 20% IACS or more and 50% IACS or less used in continuous casting of copper or copper alloy by the belt and wheel method.
(5) A belt and wheel type continuous casting apparatus used for continuous casting of copper or a copper alloy, wherein a continuous casting apparatus having a conductivity of 20% IACS to 50% IACS is used.
(6) The belt & wheel type continuous casting apparatus comprises a pouring nozzle for injecting molten metal in a tundish, and a belt & wheel casting machine constituted by a belt and a wheel rotated by a turn roll, The continuous casting apparatus according to (5), wherein the wheel includes a wheel main body and a casting ring having the specific conductivity.

According to the casting method and the casting apparatus of the present invention, a continuous casting method of copper or copper alloy having high cooling capacity, excellent productivity, and excellent ingot surface quality, and a casting ring used in the method are provided. be able to.

It is a schematic explanatory drawing which shows the process of manufacturing a wire in one embodiment of the continuous casting method by the belt & wheel method of this invention. It is sectional drawing which shows typically preferable embodiment of the belt & wheel casting machine used with the continuous casting method of this invention. It is an expanded sectional view of the III-III line cross section of the casting machine shown in FIG. It is a graph which shows the relationship between the electrical conductivity of the alloy to cast, and the electrical conductivity of a casting ring.

[Casting method / Casting equipment]
FIG. 1 is an explanatory view showing an example of all steps in which an ingot obtained by the continuous casting method of the present invention is further used as a wire. As shown in the figure, for example, the method for producing a copper (or copper alloy) wire is obtained by dissolving molten copper in a reducing atmosphere using a shaft furnace 1 to obtain molten copper. 2 is continuously led into the tundish 3. The molten metal 5 in the tundish 3 is poured from the pouring nozzle 4 into a belt & wheel casting machine 8 constituted by a belt 6 and a wheel 7 that are rotated by a turn roll, and cooled and solidified to form an ingot 9. The ingot 9 is continuously drawn out from the mold. Although not shown separately in the figure, the wheel 7 comprises a cast ring and a wheel body. In a state where the temperature of the solidified ingot 9 is not lowered as much as possible (preferably 800 ° C. or higher), the continuous ingot 10 (two-way roll method or three-way roll method) is rolled to a predetermined wire diameter, and roughing is performed. The wire 11 is used. The rough drawn wire 11 is wound as it is, or further rolled by a wire drawing machine 12 shown in FIG. In FIG. 1, the installation of the wire drawing mill 12 is arbitrary.

Next, FIG. 2 shows a longitudinal sectional view of a preferred embodiment of the belt and wheel casting machine used in the belt and wheel method according to the present invention. FIG. 3 is an enlarged cross-sectional view taken along line III-III in FIG.
The belt-and-wheel casting machine of the moving mold type has a wheel body 21, a casting belt 22 having a cooling action that is movable by a drive roll 24, and a casting ring 23 provided on the outer periphery of the wheel body 21. The belt 22 is made of carbon steel or stainless steel. Carbon steel or stainless steel is applied to the wheel body 21. A material having a specific conductivity described later is applied to the casting ring 23. The molten metal 26 is poured from the pouring nozzle 25 into the casting ring 23 on the outer periphery of the wheel 21. The poured molten metal 26 is cooled in a rotating casting ring and gradually solidifies to form an ingot 27. FIG. 2 schematically shows that the molten metal solidifies to form an ingot. The casting speed is 6 to 15 m / min (100 to 250 mm / sec) which is put into practical use in normal operation, and the ingot cross-sectional area is 1930 mm ² to 6450 mm ² .

[Casting ring]
(conductivity)
In continuous casting by the conventional belt and wheel method, the casting speed is overwhelmingly faster than the known DC casting and horizontal horizontal continuous casting methods, so the solid-liquid coexistence region exists long in the casting direction, and metal copper In a copper alloy, the thickness of the solidified shell tends to vary at the final solidification site. And the cast ring with high conductivity immediately after the molten metal comes into contact with the ring is strongly cooled because it has good heat conduction, so that an air gap due to solidification shrinkage immediately occurs, cooling is inhibited, cooling becomes uneven, It was found that the thickness of the solidified shell was not constant. Thereby, it becomes the surface defect of a rough drawing line, and causes the disconnection by a wire drawing.

Therefore, the inventors consider lowering the conductivity of the casting ring, and the casting ring with low conductivity, that is, poor heat conduction, has a low solidification rate, so that it is possible to perform initial cooling more stably. The relationship between the conductivity of the copper or copper alloy to be treated and the conductivity of the cast ring was investigated.

As a result of examination using various alloys having different electrical conductivities, it was found that the electrical conductivity (% IACS) of the cast ring is preferably 20% IACS or more and 50% IACS or less. That is, in a preferred embodiment of the present invention, the use of a specific low-conductivity copper alloy casting ring can extremely effectively suppress the formation of an air gap immediately after pouring. Therefore, the heat transfer hindrance due to the air gap in the initial stage of solidification is alleviated and stable cooling can be performed, and as a result, a uniform and stable solidified shell having no fragile portions can be formed. Moreover, the nucleation frequency is increased by increasing the supercooling, and the ingot structure near the ingot surface can be refined. With these effects, the surface quality of the ingot can be improved, and cracking of the ingot surface can be suppressed. Furthermore, the surface defect of the rough drawn wire can be suppressed by improving the ingot quality, and the yield can be improved as well as the quality of the rough drawn wire is improved.

From the above, when casting copper or a copper alloy, it is desirable to select a material whose conductivity of the casting ring is 20% IACS to 50% IACS, preferably 20% IACS to 40% IACS. By being more than the said lower limit, cooling efficiency can fully be ensured and it is preferable. By being below the upper limit, the quality of the ingot surface can be favorably maintained, which is preferable. In the present invention, the conductivity means a value measured by the measurement method employed in the examples unless otherwise specified.

In a preferred embodiment of the present invention, the conductivity between the cast alloy and the cast ring is preferably set in the range of the following formula (II).
20 ≦ b <0.225 × a + 27.5 (II)
a: Cast alloy conductivity (% IACS)
b: Casting ring conductivity (% IACS)
The technical significance of the lower limit is as described above. The mathematical formula on the right side constituting the upper limit is derived experimentally, and below this value, it is possible to produce a good cast alloy without peeling and without disconnection.

(alloy)
Considering the above points, the alloy materials constituting the cast ring include Cu—Cr—Zr—Al alloy, Cu—Cr alloy, Cu—Be alloy, phosphor bronze, Corson alloy, Cu—Zn alloy and the like. preferable. Preferred examples of typical component compositions for each alloy are described below.
Cu—Cr (—Zr—Al) alloy Cr 0.2 mass% to 2.0 mass% (preferably 0.3 mass% to 1.5 mass%, more preferably 0.5 mass% to 1.5 mass%) mass%)
Zr 0 mass% to 0.5 mass% (preferably 0.08 mass% to 0.30 mass%)
Al 0 mass% to 3.0 mass% (preferably 0.3 mass% to 2.0 mass%)
Remaining copper and inevitable impurities / Cu—Be alloy Be 0.3 mass% to 3.0 mass% (preferably 0.5 mass% to 2.0 mass%)
Co 0.1% to 1.0% by mass (preferably 0.2% to 0.6% by mass)
Remaining copper and inevitable impurities / phosphor bronze Sn 1 mass% to 5 mass% (preferably 1 mass% to 4 mass%)
P 0.03 mass% to 0.4 mass% (preferably 0.03 mass% to 0.1 mass%)
Remaining copper and inevitable impurities / Corson alloy Ni 2 mass% to 5 mass% (preferably 3 mass% to 5 mass%)
Si 0.5% to 1.3% by mass (preferably 0.7% to 1.3% by mass)
Remaining copper and inevitable impurities / Cu—Zn alloy Zn 10% to 40% by mass (preferably 20% to 40% by mass)
Remaining copper and inevitable impurities

[Casting alloy]
In consideration of the characteristics in the belt and wheel method as described above and the phenomenon at the time of casting, in the casting method to which the casting ring of the present invention is applied, it is particularly effective and preferable to cast the following alloy.
Cu-Sn alloy Sn 0.1 mass% to 0.8 mass%
Remaining copper and inevitable impurities / Cu-Ag alloy Ag 0.02 mass% to 4.0 mass%
Remaining copper and inevitable impurities / Corson alloy Ni 1.5% by mass to 5.0% by mass
Si 0.4% to 1.3% by mass
Remaining copper and inevitable impurities / Cr alloy Cr 0.3 mass% to 1.5 mass%
Remaining copper and inevitable impurities, Cu-Cr-Zr alloy Cr 0.5 mass% to 1.5 mass%
Zr 0.05 mass% to 0.5 mass%
Remaining copper and inevitable impurities

Next, the present invention will be described in more detail on the basis of examples. However, for example, the sample and the production conditions thereof are only specific examples, and the present invention is not limited thereto.
[Example 1]
As shown in Tables 1 to 3, cast rings having an ingot cross-sectional area of 3220 mm ² each having a conductivity of 13 to 80% IACS were used. The component composition of the alloy constituting the cast ring is described together with the following examples and comparative examples. Tough pitch copper containing 0.7% Sn (see Table 1), Cu-1% Cr alloy (see Table 2), and Cu-2.5% Ni-0.6% Si Corson alloy at a casting speed of 20 ton / hour. The alloy rough drawn wire (see Table 3) was manufactured by the SCR method and drawn to Φ0.1 mm. Tables 1 to 3 show the detection results of the eddy current flaw detector at the time of rough drawing wire manufacture and the results of product quality judgment based on the presence or absence of disconnection when the wire was drawn with rough drawing wire.

[Measurement of conductivity]
The conductivity of the casting ring was measured on the polished surface of the casting ring using an AutoSigma 3000 manufactured by GE Inspection Technologies. The conductivity of the cast ring was measured at room temperature (23 ° C.).

As for the detection results of the eddy current flaw detectors shown in Tables 1 to 3, “s” indicates a minute defect that does not lead to disconnection, and “m” indicates a defect that rarely causes disconnection when the skin is not peeled off. Then, the serious defect causing the disconnection was regarded as “l”, and the number of each detected per ton was counted. Furthermore, each defect was weighted as s = 1, m = 20, and l = 100, and the total evaluation value of the flaw detection results was evaluated. Those having a total value d of less than 50 were evaluated as “◎”, those having 50 or more as “◯”, and those having 100 or more as “×”. In addition, the amount of peel and disconnection judgment is “×” when the Φ8 mm rough drawing wire 5000 kg is peeled off at 0 to 0.3 mm thickness on one side and drawn to Φ0.1 mm as shown. Those that were not disconnected were evaluated as “◯”.
In “Evaluation” in the rightmost column of Tables 1 to 3, “○” indicates that the skin peel on one side was 0 mm or 0.1 mm, and “0” indicates that the skin peel on one side was 0 mm and 0.1 mm. A case where the wire was broken and the wire was not broken when the peel on one side was 0.2 mm was evaluated as “Δ”, and a wire which was broken when the peel on one side was 0.2 mm was evaluated as “x”.

Both of these alloys were superior in both flaw detection results and disconnection judgments when using a cast ring of 20% to 50% IACS. In addition, when a casting ring of less than 20% IACS was used, the cooling capacity was insufficient, so that the molten metal was not supplied to the center of the ingot, which caused a large shrinkage and caused a disconnection failure. It can be seen that a cast ring that does not exceed 50% IACS is preferable because it prevents the occurrence of fine cracks on the ingot surface and deterioration of the surface quality as described above.

[Example 2]
For various alloys having the conductivity shown in Table 4, casting and wire drawing were performed under the same conditions as in Example 1 using a cast ring having the indicated conductivity, and evaluation was performed in the same manner as in Example 1. Went. Of these results, those with particularly good results and those with poor results are shown in Table 4 and FIG. The “more desirable conductivity b” shown in Table 4 is a value obtained by applying the alloy conductivity a to (0.225 × a + 27.5) of the following formula (II), whereas “casting ring conductivity” "Rate" is the conductivity of the cast ring actually used. In this case, “conformity with b” means “conformity between the conductivity of the cast ring actually used and the following formula (II)”, and the conductivity of the cast ring actually used is the formula (II) “○” indicates that the value was within the range of b, and “Δ” indicates that the conductivity of the cast ring actually used was larger than the upper limit of b in the following formula (II) and not more than 50% IACS. evaluated.
As a result of experiments with various alloys having different electrical conductivities, it has become clear that it is particularly desirable to select a cast ring material according to the following formula (II).
20 ≦ b <0.225 × a + 27.5 (II)
a: Cast alloy conductivity (% IACS)
b: Casting ring conductivity (% IACS)

[Example 3]
It is an Example when changing a casting speed.
Various casting rings with a Cu-2.5% Ni-0.6% Si Corson alloy with an ingot cross-sectional area of 3220 mm ² and electrical conductivity shown in Table 5 were used, and the casting speed was changed. Casting was carried out in the same manner as in Example 1.
The casting speed Vr, which is a relative speed, was evaluated based on the casting speed V performed with a casting ring of 80% IACS based on the normal casting speed V ₀ (200 mm / second). It is Vr = _V / V _0.
If the casting speed is too high with respect to the cooling speed, the ingot temperature becomes too high, the ingot strength decreases and cracks occur, or a large shrinkage remains in the center of the ingot, causing disconnection. . Therefore, the judgment of pass / fail of the implementation results was evaluated as “◯” when the rough drawing wire of 5000 mm of Φ8 mm was peeled and drawn 0.1 mm on one side, and “×” when the wire was not broken.
The results are shown in Table 5.

In the casting ring having the electrical conductivity in the range specified in the present invention, the formation of the air gap can be suppressed, so that it can be cooled strongly rather than the casting ring with high conductivity in the initial stage of solidification, and moreover than the iron casting ring. Due to the high conductivity, the overall cooling capacity could be higher than that of the high conductivity ring. In experiments using cast rings of various conductivity, the casting speed could be increased up to 1.2 times from the current level in the range of 20-50% IACS.

[Example 4]
Various alloys were cast, rolled and drawn in the same manner as in Example 1 using cast rings having different electrical conductivities. The crystal grain size (μm) of the ingot was measured by the intersection method in the direction perpendicular to the crystal grain growth direction at a location 2 mm from the ingot surface. The evaluation was performed in the same manner as in Example 1.
The results obtained are shown in Table 6.

Compared with the comparative example, by using a casting ring with a low conductivity within the range specified in the present invention, the supercooling near the mold increases and the nucleation frequency increases, and the ingot structure near the ingot surface becomes finer. It became clear that the ingot surface quality could be improved. As a result, surface defects could be reduced, and wire could be drawn without disconnection even with a smaller amount of skin peeling.

The conductivity (unit:% IACS) and composition of the cast ring used in Examples 1 to 3 are shown below. This composition is an example when the cast ring is formed of a copper alloy, and may be formed of another copper alloy or the like as long as the electrical conductivity condition is satisfied.
Table 7 corresponds to Table 3, Table 8 corresponds to Table 4, and Table 9 corresponds to Table 5.

1 Shaft furnace 2 樋
3 Tundish 4 Spout 5 Molten Metal 6 Belt 7 Wheel 8 Belt & Wheel Casting Machine 9 Ingot 10 Continuous Rolling Machine 11 Rough Drawing Wire 12 Wire Drawing Roller 13 Wire Drawing Material 14 Pallet 21 Wheel 22 Belt 23 Casting Ring 24 Drive Roll 25 Note Hot water nozzle 26 Molten metal 27 Ingot

While this invention has been described in conjunction with its embodiments, we do not intend to limit our invention in any detail of the description unless otherwise specified and are contrary to the spirit and scope of the invention as set forth in the appended claims. I think it should be interpreted widely.

This application claims priority based on Japanese Patent Application No. 2009-164248 filed in Japan on July 10, 2009, which is incorporated herein by reference. Capture as part.

Claims

A continuous casting method using a casting ring having a conductivity of 20% IACS or more and 50% IACS or less in casting of copper or copper alloy by the belt and wheel method.
The continuous casting method according to claim 1, wherein the casting ring has a conductivity B (% IACS) satisfying the following formula (I) with respect to a conductivity A (% IACS) of the cast metal.
20 ≦ B <0.225 × A + 27.5 (I)
A: Conductivity of cast metal (% IACS)
B: Conductivity of cast ring (% IACS)
In the belt and wheel method, the molten metal in the tundish is poured from a pouring nozzle into a belt and wheel casting machine constituted by a belt and a wheel that is rotated by a turn roll, and is cooled and solidified to form an ingot. 3. The continuous casting method according to claim 1, wherein the casting is a casting method for continuously drawing a lump from the mold, and a casting ring having the specific conductivity is used as a casting ring constituting the wheel. 4. .
Cast ring with conductivity of 20% IACS or more and 50% IACS or less used in continuous casting of copper or copper alloy by belt & wheel method.
A belt and wheel type continuous casting apparatus used for continuous casting of copper or copper alloy, wherein a continuous casting apparatus having a conductivity of 20% IACS or more and 50% IACS or less is used.
The belt & wheel type continuous casting apparatus comprises a pouring nozzle for injecting molten metal in a tundish, and a belt and wheel casting machine constituted by a belt and a wheel rotated by a turn roll, The continuous casting apparatus according to claim 5, comprising a wheel main body and a casting ring having the specific conductivity.