JP2019126840A - CONTINUOUS CASTING METHOD FOR Cu-Zn-Si SYSTEM ALLOY - Google Patents

Abstract

To provide a continuous casting method for a Cu-Zn-Si system alloy capable of sufficiently reducing an oscillation mark depth and inhibiting an occurrence of an altered layer or internal defect, and stably casting an ingot excellent in quality.SOLUTION: A continuous casting method for a Cu-Zn-Si system alloy is adapted to intermittently draw an ingot having a cross-section area of 15 mmor greater and 500 mmor smaller of a cross section orthogonal to a drawing direction and continuously cast it, and comprises a pull-out step having a pull-out distance L (mm), a pull-out time T (s), an accelerating time Ta (s) in pulling-out and a deceleration time Td (s) in pulling-out, and a push-back step having a push-back distance l (mm), a push-back time t (s), an accelerating time ta (s) in pushing-back and a deceleration time td (s) in pushing-back, in which a volume of movement ΔV=S×(L-l) satisfies equation (1):7×S<ΔV<18×S-(L-l)/(T+Ta+Td+t+ta+td) and equation (2):10<(L-l)/(T+Ta+Td+t+ta+td)<100.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a continuous casting method of a Cu-Zn-Si alloy, which continuously produces an ingot of a Cu-Zn-Si alloy.

Conventionally, free-cutting brass, which is a copper alloy having excellent machinability, has been widely used as a material for various parts. This free-cutting brass improves the machinability by adding Pb to the Cu-Zn alloy. However, in recent years, the use of Pb has been restricted from the viewpoint of environmental problems etc., and its use has been greatly restricted.
Therefore, as a copper alloy having excellent machinability even if the content of Pb is significantly reduced, for example, a Cu-Zn-Si-based alloy shown in Patent Document 1 is provided. Since this Cu-Zn-Si alloy does not contain Pb, it is used for various parts such as faucet fittings, water supply fittings, valves, and water meter fittings for water supply pipes that come into contact with drinking water and the like. ing.

In the case of manufacturing such a part, a bar or wire having various cross sections may be used as a processing material.
When manufacturing a bar or wire, it is usually manufactured by subjecting a large ingot to hot bar by extruding or rolling, and subjecting this bar to plastic processing such as drawing. ing. However, when manufacturing a bar by performing extrusion or rolling, a casting process for manufacturing a large ingot, a heating process for heating the ingot, and an extrusion process or rolling process for extruding the heated ingot In addition, it is necessary to carry out many steps, which requires a large amount of manufacturing cost and time.

  Therefore, as a method for efficiently producing a metal rod or wire at low cost, for example, as disclosed in Patent Documents 2-5, a mold is installed in a casting furnace in which molten metal of metal is stored, and rod-shaped There is provided a continuous casting method for continuously casting an ingot. In the above-described mold, a mold having self-lubricating properties such as graphite is usually used.

  By the way, when continuously casting a bar-shaped ingot, as shown in Patent Document 2-4, the drawing step and the pushing-back step are repeatedly performed without continuously drawing the ingot at a constant speed. It is common to repeat the intermittent withdrawal cycle. When the intermittent withdrawal cycle is performed as described above, the solid phase (solidified shell) solidified at the time of withdrawal is moved, the liquid phase flows into the space after the movement, and a new solid phase is formed. Since the solidified shell is thus intermittently formed, a pattern called oscillation mark synchronized with the intermittent drawing cycle is formed on the surface of the ingot.

This oscillation mark corresponds to the boundary of the solidified shell that is intermittently formed in the mold, but depending on the manufacturing conditions, cracks may occur in the portion of the oscillation mark or deep irregularities may occur. May be accompanied by surface defects.
Here, in patent documents 2-4, in order to suppress the defect generation in the above-mentioned oscillation mark, the pattern of the intermittent drawing cycle is specified.

By the way, in the Cu—Zn—Si based alloy disclosed in Patent Document 1, since Zn adheres to the inner wall of the mold, the self-lubricating property of the graphite mold is hindered, and seizure of the solidified shell tends to occur. is there. For this reason, when the pattern of the intermittent drawing cycle is not appropriate, seizing of the solidified shell occurs, and there is a possibility that a deep crack may occur in the portion of the oscillation mark. Moreover, there existed a possibility that the fracture | rupture of a coagulation | solidification shell might generate | occur | produce.
In addition, since the temperature range in which the solid phase and the liquid phase are mixed is wide in the Cu-Zn-Si alloy, a solid-liquid coexistence region exists widely in the mold, and the strength of the solidified shell tends to be insufficient. For this reason, there is a problem that the solidified shell is easily broken at the time of intermittent drawing, and the above-mentioned oscillation mark depth becomes deep.

Therefore, Patent Document 5 proposes a pattern of intermittent drawing cycles suitable for a Cu-Zn-Si-based alloy, which can sufficiently reduce the depth of oscillation marks and produce an ingot excellent in surface quality. It is possible.
In addition, in this patent document 5, the ingot of 10000 mm < ² > or less in cross-sectional area was made into object.

JP 2000-119775 A Japanese Patent Application Laid-Open No. 05-169197 Unexamined-Japanese-Patent No. 08-168852 Japanese Patent Application Laid-Open No. 05-031561 JP, 2014-091147, A

By the way, in recent years, an ingot having a further smaller cross-sectional area such as 500 mm ² or less in cross-sectional area orthogonal to the drawing direction is required due to the further requirement of near net shape.
In the case of continuously casting such an ingot with such a small cross-sectional area, the influence of the oscillation mark is even greater, and it is necessary to make the oscillation mark depth shallower. In addition, it is also necessary to suppress the occurrence of altered layers and internal defects.

The present invention has been made against the background described above, and is a case where an ingot made of a Cu-Zn-Si alloy and having a cross-sectional area of 500 mm ² or less is continuously cast. An object of the present invention is to provide a continuous casting method of a Cu-Zn-Si alloy capable of sufficiently reducing the mark depth and suppressing the generation of the altered layer and internal defects, and capable of producing an ingot excellent in quality. It is said.

In order to solve this subject, in the continuous casting method of the Cu-Zn-Si alloy according to the present invention, the content of Cu is in the range of 69 mass% to 79 mass%, and the content of Si is 2.0 mass% to 4 An ingot that is made of a Cu—Zn—Si based alloy within a range of less than 0.0 mass% and that has a cross-sectional area of 15 mm ² or more and 500 mm ² or less perpendicular to the drawing direction is intermittently drawn and continuously cast. A continuous casting method of a Cu-Zn-Si based alloy using a continuous casting machine having a casting furnace in which a molten metal of the Cu-Zn-Si based alloy is stored, and a mold connected to the casting furnace. Thus, the ingot is drawn by an intermittent drawing cycle including a drawing step and a push-back step, and a drawing distance L (mm), a drawing time T (second), and an acceleration time during drawing in the drawing step. a (seconds), deceleration time Td (seconds) at the time of withdrawal, push-back distance 1 (mm) in the push-back process, push-back time t (seconds), acceleration time ta at push-back (seconds), push-back Movement calculated from the decelerating time td (seconds) and the cross-sectional area S (mm ² ) of the cross section orthogonal to the drawing direction of the ingot, the drawing distance L (mm) and the push-back distance l (mm) The volume ΔV = S × (L−1) is
(1) Formula: 7 × S <ΔV <18 × S− (L−1) / (T + Ta + Td + t + ta + td)
(2) Formula: 10 <(L-1) / (T + Ta + Td + t + ta + td) <100
It is characterized by satisfying.

In the continuous casting method of the Cu—Zn—Si based alloy having this configuration, the upper limit of the moving volume ΔV = S × (L−1) is defined according to (L−1) / (T + Ta + Td + t + ta + td). When the required volume of molten metal is increased in one cycle by increasing the moving volume ΔV, the amount of molten metal supplied into the mold can be increased by increasing the pushback amount l or increasing (T + Ta + Td + t + ta + td). It can be ensured, and the occurrence of poor hot water can be suppressed.
On the other hand, since the moving volume ΔV = S × (L−1) is larger than 7 × S, seizure of the solidified shell can be suppressed.

Moreover, since (L-1) / (T + Ta + Td + t + ta + td) is set to be greater than 10, it is possible to suppress a decrease in fluidity due to an increase in the solid phase ratio of the molten metal during drawing.
Furthermore, since (L−1) / (T + Ta + Td + t + ta + td) is smaller than 100, the occurrence of the hot water turning defect can be suppressed. In addition, it is possible to suppress an increase in the frictional force between the mold and the solidified shell at the time of drawing, and to suppress the breakage of the solidified shell at the time of drawing.
Thus, the depth of the oscillation mark can be reduced, and the formation of a thick altered layer can be suppressed. In addition, the occurrence of internal defects can be suppressed.

Here, in the continuous casting method of the Cu-Zn-Si alloy according to the present invention, push-back time t (seconds) in the push-back step, acceleration time ta (seconds) at push-back, deceleration time at push-back td (seconds), stop time after pushing back ts (seconds),
(3) Formula: 0.05 <(ta + t + td + ts) <3.0
(4) Formula: 0.4 <ts / (ta + t + td) <10
It is preferable to satisfy

In the Cu—Zn—Si-based alloy, as described above, volatilized Zn is likely to adhere to the inner wall of the mold, and the solidified shell is baked and restrained on the mold, which may reduce the surface quality of the ingot. Here, by setting (ta + t + td + ts) within the above-mentioned range, the seizure of the solidified shell can be further suppressed.
Further, by making ts / (ta + t + td) smaller than 10, the stop time ts after the push-back does not become too long, and the occurrence of the burn-in of the solidified shell can be further suppressed.
On the other hand, by setting ts / (ta + t + td) to be larger than 0.4, a stop time ts after pushing back can be secured, and a solidified shell having a sufficient thickness can be grown, thereby further suppressing the fracture of the solidified shell. can do.

  In the continuous casting method of the Cu—Zn—Si alloy of the present invention, the drawing distance L (mm) is 10 ≦ L ≦ 18, and the drawing time T (second) is 0.01 ≦ T ≦ 0. 0.08, the acceleration time Ta (seconds) during extraction is 0.14 ≦ Ta ≦ 0.3, the deceleration time Td (seconds) during extraction is 0 ≦ Td ≦ 0.2, and the stop time Ts ( Second) is 0 ≦ Ts ≦ 1.0, the retraction distance l (mm) is 0.5 ≦ l ≦ 3.0, and the temperature of the molten copper alloy in the casting furnace is 970 ° C. or higher. Is preferred.

In this case, since the drawing distance L (mm) is in the range of 10 ≦ L ≦ 18, the seizure of the solidified shell can be further suppressed, and the molten metal is sufficiently supplied at the time of drawing, resulting in occurrence of poor hot water. Can be further suppressed.
Further, the extraction time T (seconds) is in the range of 0.01 ≦ T ≦ 0.08, and the acceleration time Ta (seconds) at the extraction is in the range of 0.14 ≦ Ta ≦ 0.3. Therefore, breakage of the solidified shell can be further suppressed, and occurrence of poor hot water can be further suppressed.
Furthermore, since the decelerating time Td (seconds) at the time of drawing is made within the range of 0 ≦ Td ≦ 0.2, it is possible to suppress the time of the whole drawing process from becoming longer than necessary, and occurrence of hot water runout It can be further suppressed.

In addition, since the stop time Ts (seconds) after drawing is in the range of 0 ≦ Ts ≦ 1.0, the solidified shell can be further sufficiently grown, and the seizure of the solidified shell can be further suppressed. Can do.
Furthermore, since the push-back distance l (mm) is in the range of 0.5 ≦ l ≦ 3.0, the solidification shrinkage component necessary for the push-back distance is satisfied, and the push-back causes the solidified shell to strongly adhere to the mold Constraint can be further suppressed, and the solidified shell formed one cycle before and the solidified shell formed in this cycle can be strongly welded.
Moreover, since the temperature of the molten copper alloy in the casting furnace is 970 ° C. or more, the occurrence of poor hot water can be further suppressed.

According to the present invention, even when an ingot having a cross-sectional area of 500 mm ² or less made of a Cu-Zn-Si alloy is continuously cast, the depth of the oscillation mark can be sufficiently reduced and the altered layer or the interior It is possible to provide a continuous casting method of a Cu—Zn—Si based alloy capable of suppressing the generation of defects and producing an ingot having excellent quality.

It is explanatory drawing which shows an example of the continuous casting apparatus used with the continuous casting method of the Cu-Zn-Si type alloy which is one Embodiment of this invention. It is explanatory drawing which shows the pattern of the intermittent drawing cycle in the continuous casting method of the Cu-Zn-Si type alloy which is one Embodiment of this invention. It is explanatory drawing which shows an example of the other continuous casting apparatus used with the continuous casting method of the Cu-Zn-Si type alloy which is embodiment of this invention. It is a structure observation result of the ingot of the example 1 of this invention. (A) is an oscillation mark, (b) is an internal structure, and (c) is an altered layer. It is a structure observation result of the ingot of the comparative example 1. FIG. (A) is an oscillation mark, (b) is an internal structure, and (c) is an altered layer.

Below, the continuous casting method of the Cu-Zn-Si type alloy which is one Embodiment of this invention is demonstrated.
In the continuous casting method of the Cu-Zn-Si alloy according to the present embodiment, the content of Cu is in the range of 69 mass% to 79 mass%, and the content of Si is 2.0 mass% to less than 4.0 mass%. The casting ingot 1 which consists of a Cu-Zn-Si type alloy made into the range of (1) is continuously cast. Moreover, the ingot 1 produced has a cross-sectional area of 15 mm ² or more and 500 mm ² or less in a cross section orthogonal to the drawing direction.

Here, in the present embodiment, Cu-Zn-Si having a Cu content of 69 mass% or more and 79 mass% or less, a Si content of 2.0 mass% or more and less than 4.0 mass%, and the balance being Zn and incidental impurities The alloy ingot 1 is used.
Further, in the present embodiment, the ingot 1 of the Cu—Zn—Si alloy has a circular cross-sectional shape orthogonal to the drawing direction, and the outer diameter is in the range of 4.4 mm to 25 mm. . That is, the cross-sectional area of the cross section perpendicular to the drawing direction of the ingot 1 of Cu-Zn-Si alloy is a 15.2 mm ² or more 490.9Mm ² within the following ranges.

Next, the continuous casting apparatus 10 used for the continuous casting method of the Cu-Zn-Si alloy which is this embodiment is demonstrated with reference to FIG.
The continuous casting apparatus 10 includes a casting furnace 11, a continuous casting mold 20 connected to the casting furnace 11, and a pinch roll 17 that pulls out the ingot 1 produced from the continuous casting mold 20. .

The casting furnace 11 heats and melts the melting raw material to produce and hold a molten copper having a predetermined composition. The crucible 12 holds the melting raw material and the molten copper, and heating means for heating the crucible 12 ( (Not shown).
The pinch roll 17 sandwiches the ingot 1 produced from the continuous casting mold 20 and pulls it in the drawing direction F. In the present embodiment, the ingot 1 is intermittently pulled out.

The continuous casting mold 20 includes a cylindrical mold 21 into which the supplied molten copper metal is injected, and a cooling unit 28 that cools the mold 21.
Here, in this embodiment, as shown in FIG. 1, the continuous casting mold 20 is disposed on the molten copper in the casting furnace 11 via the refractory heat insulating material 15, and the ingot 1 is drawn upward. It has composition.

The mold 21 has a substantially cylindrical shape, and is provided with a cast hole 24 penetrating from one side to the other side.
As shown in FIG. 2, the cooling unit 28 is a water cooling jacket disposed on the outer peripheral side of the mold 21 and configured to cool the mold 21 by circulating cooling water.

Next, a continuous casting method of a Cu—Zn—Si-based alloy according to the present embodiment using the above-described continuous casting apparatus 10 will be described.
First, molten raw material is introduced into the crucible 12 from the raw material inlet of the casting furnace 11. As a raw material, Cu simple substance, Zn simple substance, Si simple substance, Cu-Zn master alloy, Cu-Si master alloy, etc. can be used. Alternatively, the raw material containing Zn and Si may be dissolved together with the copper raw material. In addition, recycled and scrap materials of the present alloy may be used.

Next, the melting raw material charged in the crucible 12 is heated and melted by the heating means to produce a molten copper prepared in the above-described component composition.
This molten copper is heated to a predetermined temperature and held in the crucible 12. Then, this molten copper is supplied to the continuous casting mold 20.

The molten copper supplied into the continuous casting mold 20 is cooled in the mold 21 and solidified to form the ingot 1. The ingot 1 is intermittently produced by the pinch rolls 17 so that the ingot 1 is continuously produced.
Here, the continuous casting method of the Cu—Zn—Si alloy according to the present embodiment is characterized by the pattern of the intermittent drawing cycle of the ingot 1.

In the continuous casting method of the Cu—Zn—Si based alloy according to the present embodiment, as shown in FIG. 2, the drawing step of moving the ingot 1 solidified in the mold 21 in the drawing direction F, and the ingot 1 The intermittent drawing cycle including the push-back process of moving toward the side opposite to the drawing direction F is repeatedly performed.
The pattern drawing of the intermittent drawing cycle shown in FIG. 2 is described as a set value, and in an actual continuous casting apparatus 10, it may be partially curved due to mechanical loss and the like.

Then, the withdrawal distance L (mm), the withdrawal time T (seconds), the acceleration time Ta during withdrawal (seconds), the deceleration time Td (seconds) during withdrawal, and the push-back distance l (mm) in the withdrawal process. ), Push-back time t (seconds), push-back acceleration time ta (seconds), push-back deceleration time td (seconds), and cross-sectional area S of a cross section orthogonal to the drawing direction F of the ingot 1 Moving volume ΔV = S × (L−l) calculated from (mm ² ), drawing distance L (mm) and pushing back distance l (mm) satisfies the following equations (1) and (2) doing.
(1) Formula: 7 × S <ΔV <18 × S− (L−l) / (T + Ta + Td + t + ta + td) (2) Formula: 10 <(L−l) / (T + Ta + Td + t + ta + td) <100

Further, the push-back time t (seconds) in the push-back process, the acceleration time ta (seconds) at the time of push-back, the deceleration time td (seconds) at the time of push-back, and the stop time ts after push-back are (3) Expressions and (4) are satisfied.
(3) Formula: 0.05 <(ta + t + td + ts) <3.0
(4) Expression: 0.4 <ts / (ta + t + td) <10

Furthermore, the drawing distance L (mm) is 10 ≦ L ≦ 18, the drawing time T (seconds) is 0.01 ≦ T ≦ 0.08, and the acceleration time Ta (seconds) at drawing is 0.14 ≦ Ta ≦ 0. 3. Deceleration time Td (sec) at the time of withdrawal 0 T Td 0.2 0.2, stop time Ts (sec) at the time of withdrawal 0 T Ts 1.0 1.0, push-back distance l (mm) 0.5 ≦ It satisfies l ≦ 3.0.
Furthermore, the temperature of the molten copper alloy in the casting furnace is set to 970 ° C. or higher.

  The reason why the intermittent drawing cycle pattern and the copper alloy molten metal temperature are defined as described above in the Cu—Zn—Si alloy continuous casting method according to the present embodiment will be described below.

<(1) Formula>
The equation (1) defines a moving volume ΔV = S × (L−l) which is a volume of the ingot drawn in one intermittent drawing cycle.
When the moving volume ΔV is increased, the amount of molten metal supply required in one cycle increases, and poor hot water is likely to occur. Here, (L-1) / (T + Ta + Td + t + ta + td) is obtained by dividing the drawing length (L-1) in one cycle by the total time of the drawing process and the pushing-back process. Here, the molten metal supply amount can be secured by reducing the drawing length (L-l) in one cycle, or lengthening the total time of the drawing process and the push-back process, so that the hot water rotation defect It is possible to suppress the occurrence of

  From the above, in this embodiment, the upper limit of the movement volume ΔV is defined according to (L−1) / (T + Ta + Td + t + ta + td). That is, the movement volume ΔV = S × (L−1) can be increased by reducing (L−1) / (T + Ta + Td + t + ta + td). The upper limit of the moving volume ΔV is preferably less than 16 × S− (L−1) / (T + Ta + Td + t + ta + td), and more preferably less than 15 × S− (L−1) / (T + Ta + Td + t + ta + td).

On the other hand, when ΔV is 7 × S or less, that is, when the length (L−l) of the ingot drawn in one intermittent drawing cycle is 7 mm or less, seizure of the solidified shell is likely to occur. is there.
From the above, in the present embodiment, the lower limit of the moving volume ΔV is set to exceed 7 × S. The lower limit of the moving volume ΔV is preferably more than 9 × S, and more preferably more than 10 × S.

<(2) Formula>
As described above, the expression (2) is obtained by dividing the drawing length (L-1) in one cycle by the total time of the drawing process and the pushing back process.
Here, when (L-1) / (T + Ta + Td + t + ta + td) is 10 or less, the total time of the drawing process and the pushing back process becomes longer with respect to the drawing length (L-1) in one cycle. The solid phase ratio of the molten metal is increased, the fluidity of the molten metal is lowered, and there is a possibility that a hot water runout may occur.
From the above, in the present embodiment, the lower limit of (L−1) / (T + Ta + Td + t + ta + td) is exceeded by 10. The lower limit of (L−l) / (T + Ta + Td + t + ta + td) is preferably 15 or more, and more preferably 31 or more.

On the other hand, when (L-1) / (T + Ta + Td + t + ta + td) is 100 or more, the total time of the drawing process and the pushing back process is short with respect to the drawing length (L-1) in one cycle, and the amount of molten metal supplied is not good. It becomes enough and there is a possibility that hot water runout may occur.
From the above, in the present embodiment, the upper limit of (L−1) / (T + Ta + Td + t + ta + td) is less than 100. The upper limit of (L−l) / (T + Ta + Td + t + ta + td) is preferably less than 97, and more preferably less than 33.

<(3) equation>
The equation (3) defines the total time (ta + t + td + ts) of the push-back process.
Here, by setting (ta + t + td + ts) to more than 0.05, the total time of the push-back process is ensured, the solidified shell grows sufficiently, and the fracture of the solidified shell can be suppressed.
On the other hand, by setting (ta + t + td + ts) to less than 3.0, the total time of the push-back process does not become unnecessarily long, the seizure of the solidified shell can be suppressed, and the fracture of the solidified shell can be suppressed. it can.
From the above, in the present embodiment, the total time (ta + t + td + ts) of the push-back process is set within the range of 0.05 <(ta + t + td + ts) <3.0.
The lower limit of (ta + t + td + ts) is preferably greater than 0.06, and more preferably greater than 0.08. Further, the upper limit of (ta + t + td + ts) is preferably less than 2.3, and more preferably less than 1.8.

<(4) Formula>
Equation (4) defines the ratio ts / (ta + t + td) between the stop time ts after pushback and the movement time (ta + t + td) of the ingot 1 in the pushback process.
Here, by setting ts / (ta + t + td) to exceed 0.4, a stop time ts after pushing back is ensured, the solidified shell grows sufficiently, and the fracture of the solidified shell can be suppressed. .
On the other hand, by setting ts / (ta + t + td) to less than 10, the stop time ts after pushing back does not become longer than necessary, and the seizure of the solidified shell can be suppressed and the fracture of the solidified shell can be suppressed. Can do.
From the above, in this embodiment, the ratio ts / (ta + t + td) between the stop time ts after push-back and the movement time (ta + t + td) of the ingot 1 in the push-back step is 0.4 <ts / (ta + t + td) <10.
The lower limit of ts / (ta + t + td) is preferably 0.41 or more. The upper limit of ts / (ta + t + td) is preferably less than 9.0, and more preferably less than 7.0.

<Pullout distance L (mm)>
By setting the drawing distance L (mm) in the drawing step to 18 or less, it is possible to further suppress the hot water run-off defect at the time of drawing.
On the other hand, by setting the drawing distance L (mm) in the drawing process to 10 or more, it becomes possible to secure the moving volume ΔV at a certain level or more.
The lower limit of the drawing distance L (mm) in the drawing process is preferably 13 or more. Moreover, it is preferable that the upper limit of the drawing distance L (mm) in the drawing step is 17 or less.

<Extraction time T (seconds)>
By setting the withdrawal time T (seconds) in the withdrawal step to 0.01 or more, it is possible to suppress an excessive increase in the frictional force between the mold and the solidified shell. Thereby, the fracture | rupture of a solidification shell can be suppressed.
On the other hand, by setting the withdrawal time T (seconds) in the withdrawal step to 0.08 or less, it is possible to suppress an increase in solid phase ratio of the molten metal during withdrawal, and it is possible to suppress the occurrence of hot water runout Become.
The lower limit of the drawing time T (seconds) in the drawing step is preferably 0.02 or more, and more preferably 0.04 or more. The upper limit of the drawing time T (seconds) in the drawing process is preferably 0.07 or less, and more preferably 0.05 or less.

<Acceleration time Ta (seconds) at withdrawal>
By setting the acceleration time Ta (seconds) at the time of drawing to 0.14 or more, it can be suppressed that the frictional force between the mold and the solidified shell becomes excessively large. Thereby, breakage of the solidified shell can be suppressed.
On the other hand, by setting the acceleration time Ta (seconds) at the time of drawing to 0.3 or less, it is possible to suppress an increase in the solid phase ratio of the molten metal during the drawing, and to suppress the generation of the hot water runout.
The lower limit of the acceleration time Ta (seconds) at the time of extraction is preferably 0.15 or more, and more preferably 0.2 or more. Further, the upper limit of the acceleration time Ta (seconds) at the time of extraction is preferably 0.28 or less, and more preferably 0.25 or less.

<Deceleration time Td (seconds) when pulling out>
By setting the deceleration time Td (seconds) at the time of drawing to 0.2 or less, it is possible to suppress an increase in the solid phase ratio of the molten metal during the drawing, and it is possible to suppress the occurrence of the hot water rotation defect.
The lower limit of the deceleration time Td (seconds) at the time of extraction is preferably 0.005 or more, and more preferably 0.01 or more. The upper limit of the deceleration time Td (seconds) at the time of extraction is preferably 0.19 or less, and more preferably 0.18 or less.

<Stop time after withdrawal Ts (seconds)>
By setting the stop time Ts (seconds) after drawing to 1.0 or less, the seizing of the solidified shell can be suppressed, and the breakage of the solidified shell can be suppressed.
Note that the upper limit of the stop time Ts (seconds) is preferably 0.9 or less, and more preferably 0.8 or less.

<Pushback distance l (mm)>
By setting the push-back distance l (mm) in the push-back process within the range of 0.5 or more and 3.0 or less, the solidification shrinkage necessary for the push-back distance is satisfied, and the solidifying shell While being able to suppress being strongly restrained, it is possible to strongly weld the solidified shell formed one cycle before and the solidified shell formed in this cycle.
The upper limit of the push-back distance l (mm) in the push-back step is preferably 2.8 or less, and more preferably 2.0 or less.

<Temperature of the molten copper alloy in the casting furnace>
By setting the temperature of the molten copper alloy to 970 ° C. or higher, the fluidity of the molten metal can be ensured and the occurrence of poor hot water can be suppressed.
The lower limit of the temperature of the molten copper alloy is preferably 980 ° C. or higher, and more preferably 1000 ° C. or higher. Moreover, about the upper limit of the temperature of molten copper alloy, in order to suppress the seizure of a solidification shell, it is preferable to set it as the liquidus temperature +100 degreeC or less of copper alloy.

Next, the state of solidification in the mold 21 when the intermittent drawing cycle is repeatedly performed as described above will be described.
First, the molten copper in the casting furnace 11 flows into the mold 21 by moving the ingot 1 in the drawing direction F by the drawing process.
Next, the molten copper in the mold 21 is cooled and solidified to form a solidified shell.
Then, in the push-back process, the seizing of the solidified shell and the mold 21 is prevented, and the solidified shell formed one cycle before and the solidified shell formed in this cycle are combined.
After the solidified shell is formed with a sufficient thickness in the mold 21, the ingot 1 is moved again in the drawing direction F by the drawing process.
Thus, the rod-shaped ingot 1 is continuously produced by repeating the intermittent drawing cycle.

  According to the continuous casting method of the Cu-Zn-Si alloy of the present embodiment configured as described above, the pattern of the intermittent drawing cycle is set so as to satisfy the above-mentioned equations (1) and (2). Since it is specified, it is possible to suppress the hot water rotation defect in the mold and the seizure of the solidified shell, etc., and it is possible to stably cast an ingot having a small oscillation mark depth and few denatured layers and internal defects. .

  Further, in the present embodiment, since the conditions of the stopping step and the pushing-back step are defined so as to satisfy the above-mentioned equations (3) and (4), the occurrence of melt flow defects in the mold is suppressed. However, the solidified shell can be sufficiently grown, and an ingot having excellent quality can be produced.

  Furthermore, in the present embodiment, the withdrawal distance L (mm), the withdrawal time T (seconds), the acceleration time Ta during withdrawal (seconds), the deceleration time Td during withdrawal (seconds), and the stop time Ts after withdrawal (seconds Since the push-back distance l (mm) and the temperature of the molten copper alloy in the casting furnace are respectively defined in the above-mentioned ranges, it is possible to carry out casting more stably.

As mentioned above, although the continuous casting method of the Cu-Zn-Si system alloy which is an embodiment of the present invention was explained, the present invention is not limited to this, It changes suitably in the range which does not deviate from the technical idea of the invention. Is possible.
For example, although the present embodiment has been described as producing an ingot having a circular cross section, the present invention is not limited thereto, and may be an ingot having a polygonal cross section, or an ingot having a tubular cross section. It may be Moreover, the irregular-shaped ingot which a cross section has a convex part and a recessed part may be sufficient.

  Moreover, in the above-mentioned embodiment, although it demonstrated as a structure which pulls out an ingot upwards, it is not limited to this, For example, like the continuous casting apparatus 110 shown in FIG. It is good also as a structure which arrange | positions in the side surface of the crucible 112 of 111, and draws the ingot 1 in the horizontal direction with the pinch roll 117. FIG.

Further, in the above-described embodiment, it has been described that a mold provided with a cooling jacket is used. However, the structure of the mold is not limited, and for example, a mold in which a water-cooled probe made of a double tube is inserted in the mold. Also good.
Furthermore, in the present embodiment, although the material of the mold 21 is graphite, it may be boron nitride having self-lubricating property as in the case of graphite.

  In this embodiment, the Cu content is 69 mass% or more and 79 mass% or less, the Si content is 2.0 mass% or more and less than 4.0 mass%, and the balance is Cu-Zn-Si composed of Zn and inevitable impurities. Although the ingot made of an alloy has been described as an object, the present invention is not limited to this, and an additive element other than Cu and Si may be included.

Below, the result of the confirmation experiment performed in order to confirm the effect of this invention is demonstrated.
First, a dissolved raw material was prepared so as to have a component composition containing Cu: 76.10 mass%, Si: 3.10 mass%, and the balance being Zn and an unavoidable impurity.
The prepared molten material was charged into a crucible 12 of a casting furnace 11 shown in FIG. 1 in an amount of 500 kg and melted by heating with a heating means.

As a mold, an ingot having a circular cross section with an outer diameter of 6 mm (a cross sectional area of 28.26 mm ^{2 in} a cross section perpendicular to the drawing direction) was prepared.
Then, according to the intermittent drawing cycle shown in Tables 1 and 2, the ingot was drawn and casting was performed at 300 kg.

The obtained ingot was cut along a plane parallel to the drawing direction, and the cross-section was observed with an optical microscope, and the defect depth in the oscillation mark was measured. Then, the defect depth of less than 20 μm was evaluated as ◎, the defect depth of 20 μm or more and less than 100 μm was evaluated as ◯, and the defect depth of 100 μm or more was evaluated as ×. Moreover, what was broken of the ingot at the time of casting was evaluated as xx.
Further, the thickness of the altered layer formed on the surface layer of the ingot was measured. And the thing whose thickness of an alteration layer is less than 190 micrometers was evaluated as (double-circle), the thing of 190 micrometers or more and less than 200 micrometers, (circle), and 200 micrometers or more were evaluated as x.
Furthermore, the internal tissue was observed to confirm the presence or absence of internal defects.
The evaluation results are shown in Table 2. Moreover, the observation result of the invention example 1 is shown in FIG. 4, and the observation result of the comparative example 1 is shown in FIG.

In Comparative Example 1 in which the value of the equation (1) deviates from the upper limit of the present invention, the defect depth in the oscillation mark is 100 μm or more, the thickness of the deteriorated layer is 200 μm or more, and internal defects were also observed. It is inferred that the movement volume ΔV is too large to cause a hot water rotation defect.
In Comparative Example 2 in which the value of the equation (1) deviates from the lower limit of the present invention, the defect depth in the oscillation mark is 100 μm or more, and the thickness of the altered layer is 200 μm or more. It is presumed that the length of the ingot drawn in one intermittent drawing cycle was short and the solidified shell was seized.

In Comparative Example 3 in which the value of the equation (2) deviates from the upper limit of the present invention, the defect depth in the oscillation mark is 100 μm or more, and the thickness of the altered layer is 200 μm or more. It is presumed that the total time of the drawing process and the pushing back process is shorter than the drawing length in one cycle, and the molten metal supply amount is insufficient to cause a hot water rotation defect.
In Comparative Example 4 in which the value of the equation (2) deviates from the lower limit of the present invention, the defect depth in the oscillation mark is 100 μm or more, and the thickness of the altered layer is 200 μm or more. The total time of the drawing process and the pushing-back process becomes longer than the drawing length in one cycle, the solid phase ratio of the molten metal increases during the drawing process, and the fluidity of the molten metal decreases. It is guessed.

On the other hand, in the invention examples 1-6 satisfying the formulas (1) and (2), the depth of defect in the oscillation mark is less than 100 μm and the thickness of the deteriorated layer is less than 200 μm. It was. In addition, no internal defects were found.
Furthermore, in Invention Examples 1-3 and 6 that satisfy the expressions (3) and (4), the thickness of the deteriorated layer was suppressed to less than 190 μm.
Moreover, in the invention example 1, the defect depth in the oscillation mark is less than 20 μm, and the thickness of the deteriorated layer is less than 190 μm, so that it is possible to obtain a very high quality ingot.

  From the above, according to the example of the present invention, it was confirmed that the depth of the oscillation mark can be sufficiently reduced and the occurrence of internal defects can be suppressed, and it is possible to stably cast an ingot excellent in quality. .

DESCRIPTION OF SYMBOLS 1 Ingot 10 Continuous casting apparatus 11 Casting furnace 20 Continuous casting mold (mold)
21 Mold

Claims (3)

It consists of a Cu-Zn-Si based alloy in which the content of Cu is in the range of 69 mass% to 79 mass% and the content of Si is in the range of 2.0 mass% to less than 4.0 mass%, and is orthogonal to the drawing direction A continuous casting method of a Cu—Zn—Si-based alloy in which an ingot having a cross-sectional area of 15 mm ² or more and 500 mm ² or less is intermittently drawn and continuously cast,
Using a continuous casting machine having a casting furnace in which a molten metal of the Cu-Zn-Si alloy is stored and a mold connected to the casting furnace, an intermittent drawing cycle including a drawing process and a pushing-back process is performed. , And is configured to pull out the ingot,
Drawing distance L (mm), drawing time T (seconds), acceleration time Ta (seconds) at drawing, deceleration time Td (seconds) at drawing,
The pushback distance l (mm), pushback time t (seconds), acceleration time ta (seconds) at pushback, and deceleration time td (seconds) at pushback in the pushback process,
Moving volume ΔV = S × (L−l) calculated from the cross sectional area S (mm ² ) of the cross section orthogonal to the drawing direction of the ingot, the drawing distance L (mm) and the push-back distance l (mm) And
(1) Formula: 7 × S <ΔV <18 × S− (L−1) / (T + Ta + Td + t + ta + td)
(2) Formula: 10 <(L-1) / (T + Ta + Td + t + ta + td) <100
A continuous casting method of a Cu-Zn-Si alloy characterized by satisfying The pushback time t (seconds) in the pushback process, the acceleration time ta (seconds) at pushback, the deceleration time td (seconds) at pushback, and the stop time ts (seconds) after pushback
(3) Formula: 0.05 <(ta + t + td + ts) <3.0
(4) Expression: 0.4 <ts / (ta + t + td) <10
The continuous casting method for a Cu—Zn—Si based alloy according to claim 1, wherein: The drawing distance L (mm) is 10 ≦ L ≦ 18,
The withdrawal time T (seconds) is 0.01 ≦ T ≦ 0.08,
The acceleration time Ta (seconds) at the time of extraction is 0.14 ≦ Ta ≦ 0.3,
The deceleration time Td (seconds) at the time of drawing is 0 ≦ Td ≦ 0.2,
The stop time Ts (seconds) after withdrawal is 0 ≦ Ts ≦ 1.0,
The push-back distance l (mm) is 0.5 ≦ l ≦ 3.0,
The temperature of the molten copper alloy in the casting furnace is at least 970 ° C.,
The continuous casting method of the Cu-Zn-Si type alloy according to claim 1 or 2 characterized by being.