Patent Application
20240133011
The present application claims priority on Japanese Patent Application No. 2022-168247 filed on Oct. 20, 2022, the content of which is incorporated herein by reference.
The present invention relates to a continuous cast wire rod of a Cu—Zn—Sn-based alloy obtained by casting continuously.
The above-described Cu—Zn—Sn-based alloy is widely used as a material for various components.
For example, Japanese Patent No. 4814183 discloses a net-like structure for seawater formed of a wire material made of a Cu—Zn—Sn-based alloy (Cu—Zn—Sn-based alloy wire material). The net-like structure for seawater is used while being immersed in or in contact with seawater as in a case of, for example, a culture net for fishes, a seawater strainer to be installed in a seawater intake port of power generation equipment or seawater desalination equipment, or a seawater strainer of an engine for marine vessel.
Marine organisms such as algae and barnacles may adhere to such a net-like structure for seawater. In a case where these marine organisms adhere, the mesh is clogged, and the flow of seawater is hindered. Accordingly, there is a concern that a desired function as a net-like structure for seawater may not be ensured. Moreover, there is a concern that the net-like structure for seawater may deteriorate in early stages due to corrosion and erosion caused by seawater.
In the above-described Cu—Zn—Sn-based alloy wire material, Cu ions are eluted into seawater, and the adhesion of marine organisms such as algae and barnacles to the net-like structure for seawater is suppressed due to the action of the Cu ions. In addition, the surrounding seawater area is sterilized.
Furthermore, since Sn is contained, excellent corrosion resistance (seawater resistance) is imparted, and corrosion and erosion caused by seawater can be suppressed.
Therefore, the Cu—Zn—Sn-based alloy wire material is particularly suitable as a material for constituting the above-described net-like structure for seawater.
In the production of a metal wire material, usually, the production is performed by a working process including: a step of subjecting a large-sized ingot to hot extruding or hot rolling to form a rod material; and a step of subjecting the rod material to plastic working such as drawing. However, in the production of the rod material by extrusion or rolling, it is necessary to perform many steps such as a casting step of producing a large-sized ingot, a heating step of heating the ingot, and a rolling step or an extrusion step of extruding the heated ingot; and therefore, a great deal of production cost and production time are required.
Therefore, as a method of efficiently producing a metal wire material at low cost, for example, a continuous casting method is provided in which a mold is installed in a casting furnace storing a molten metal, and wire rod-shaped ingots (continuous cast wire rods) are continuously cast, as disclosed in Japanese Unexamined Patent Application, First Publication No. 2010-201505. As the above-described mold, a mold having self-lubricity such as graphite is usually used.
By the way, in the above-described continuous cast wire rod, its cast structure tends to be relatively coarse, and there is a concern that mechanical properties such as strength and elongation may be degraded compared to those of an extruded material.
In addition, in a case where coarse dendrites are present in the continuous cast wire rod, there is a concern that the cold workability may significantly decrease, and it may not be possible to efficiently perform the cold working.
Furthermore, in the continuous cast wire rod of the Cu—Zn—Sn-based alloy, casting defects such as shrinkage cavities and deep oscillation marks are likely to occur, and there is a concern that stable casting may not be possible.
The present invention is contrived based on the above circumstances, and an objective thereof is to provide a continuous cast wire rod of a Cu—Zn—Sn-based alloy having few casting defects and excellent cold workability.
In order to solve the problems, a continuous cast wire rod of a Cu—Zn—Sn-based alloy according to Aspect 1 of the present invention is a continuous cast wire rod of a Cu—Zn—Sn-based alloy containing Cu, Zn, and Sn, containing: Cu: 62.0 mass % or greater and 70.0 mass % or less; Sn: 0.3 mass % or greater and 0.9 mass % or less; Zr: 0.0050 mass % or greater and 0.1000 mass % or less; and P: 0.0050 mass % or greater and 0.1000 mass % or less, with a balance being Zn and impurities, in which a mass ratio Zr/P of Zr to P is 0.3 or greater.
In the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to Aspect 1 of the present invention, the amount of Zr is in a range of 0.0050 mass % or greater and 0.1000 mass % or less, the amount of P is in a range of 0.0050 mass % or greater and 0.1000 mass % or less, and the mass ratio Zr/P of Zr to P is 0.3 or greater. Accordingly, Zr—P compounds are dispersed and a primary crystal α-phase is formed with the Zr—P compound acting as an inoculant nucleus. Thus, fine dendrite formation and granular crystallization of the α-phase crystallized during solidification are achieved, and it is possible to appropriately refine the crystal grain diameter of the cast structure. Therefore, it is possible to obtain a continuous cast wire rod of a Cu—Zn—Sn-based alloy which is excellent in mechanical properties such as strength and elongation.
In addition, since the amount of Cu is in a range of 62.0 mass % or greater and 70.0 mass % or less, an effect of preventing adhesion of marine organisms and a sterilization effect, which are generated by Cu ions, can be obtained.
Furthermore, since the amount of Sn is in a range of 0.3 mass % or greater and 0.9 mass % or less, it is possible to ensure corrosion resistance (seawater resistance) and to suppress a decrease in castability.
According to Aspect 2 of the present invention, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to Aspect 1, a tensile strength is 370 N/mm2 or greater, and an elongation is 14% or greater.
In the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to Aspect 2 of the present invention, since the tensile strength and elongation are in the ranges as described above, the continuous cast wire rod of a Cu—Zn—Sn-based alloy has sufficiently excellent mechanical properties. Therefore, subsequent cold working can be favorably performed.
According to Aspect 3 of the present invention, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to Aspect 1 or 2, a worked material after a working process has a tensile strength of 420 N/mm2 or greater, an elongation of 22% or greater, and a 0.2% yield strength of 300 N/mm2 or greater and 350 N/mm2 or less, and the working process includes: a first heat treatment of holding at 550° C. for 2 hours and subsequently conducing air cooling; a first cold working at a working ratio of 41%; a second heat treatment of holding at 550° C. for 2 hours and subsequently conducing air cooling; a second cold working at a working ratio of 41%; a third heat treatment of holding at 450° C. for 2 hours and subsequently conducing air cooling; and a third cold working at a working ratio of 11%.
In the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to Aspect 3 of the present invention, since the tensile strength, elongation, and 0.2% yield strength of the worked material after the working process are in the ranges as described above, a worked material having the same mechanical properties as in a case where an extruded material is worked can be obtained.
According to Aspect 4 of the present invention, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to any one of Aspects 1 to 3, a number density of Zr—P compounds containing Zr and P is in a range of 50 pieces/mm2 or greater and 500 pieces/mm2 or less.
In the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to Aspect 4 of the present invention, since the number density of the Zr—P compounds is in a range of 50 pieces/mm2 or greater and 500 pieces/mm2 or less, it is possible to reliably refine the crystal grain diameter of the cast structure.
According to Aspect 5 of the present invention, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to any one of Aspects 1 to 4, Al is further contained in an amount of 0.20 mass % or greater and 0.80 mass % or less.
In the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to Aspect 5 of the present invention, since Al is contained in an amount of 0.20 mass % or greater and 0.80 mass % or less, it is possible to further improve the strength and yield strength. In addition, the molten metal flowability is improved, and casting can thus be more favorably performed.
According to Aspect 6 of the present invention, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to any one of Aspects 1 to 5, Sb is further contained in an amount of 0.02 mass % or greater and 0.06 mass % or less.
In the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to Aspect 6 of the present invention, since Sb is contained in an amount of 0.02 mass % or greater and 0.06 mass % or less, it is possible to further improve the corrosion resistance, the strength, and the yield strength, and to sufficiently ensure the workability.
According to Aspect 7 of the present invention, the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to any one of Aspects 1 to 5 is an up-drawn continuous cast wire rod.
Since the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to Aspect 7 of the present invention is an up-drawn continuous cast wire rod, the influence of gravity can be suppressed, and thus the continuous cast wire rod has a uniform and fine cast structure in a cross section orthogonal to a drawing direction, and is particularly excellent in workability.
According to the aspect of the present invention, it is possible to provide a continuous cast wire rod of a Cu—Zn—Sn-based alloy having few casting defects and excellent cold workability.
Hereinafter, a continuous cast wire rod of a Cu—Zn—Sn-based alloy according to an embodiment of the present invention will be described.
A cross section of the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, which is orthogonal to a longitudinal direction, has a substantially circular shape, and its cross sectional area is in a range of 12 mm2 or greater and 227 mm2 or less.
As will be described later, the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment is preferably an up-drawn continuous cast wire rod produced by an up-drawing type continuous casting apparatus shown in
The continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment has a composition containing Cu: 62.0 mass % or greater and 70.0 mass % or less, Sn: 0.3 mass % or greater and 0.9 mass % or less, Zr: 0.0050 mass % or greater and 0.1000 mass % or less, and P: 0.0050 mass % or greater and 0.1000 mass % or less, with a balance being Zn and impurities.
In the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, a mass ratio Zr/P of Zr to P is 0.3 or greater.
In the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, in addition to Cu, Zr, and Sn, Al may be contained in an amount of 0.20 mass % or greater and 0.80 mass % or less.
In addition, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, Sb may be further contained in an amount of 0.02 mass % or greater and 0.06 mass % or less.
In addition, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, the number density of Zr—P compounds containing Zr and P is preferably in a range of 50 pieces/mm2 or greater and 500 pieces/mm2 or less.
In addition, in the present embodiment, the tensile strength is preferably 370 N/mm2 or greater, and the elongation is preferably 14% or greater.
Furthermore, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, a worked material after a working process preferably has a tensile strength of 420 N/mm2 or greater, an elongation of 22% or greater, and a 0.2% yield strength of 300 N/mm2 or greater and 350 N/mm2 or less, and the working process includes: a first heat treatment of holding at 550° C. for 2 hours and subsequently conducing air cooling; a first cold working at a working ratio of 41%; a second heat treatment of holding at 550° C. for 2 hours and subsequently conducing air cooling; a second cold working at a working ratio of 41%; a third heat treatment of holding at 450° C. for 2 hours and subsequently conducing air cooling; and a third cold working at a working ratio of 11%.
Hereinafter, the reasons why the composition, the number density of the Zr—P compounds, the mechanical properties of the continuous cast wire rod, and the mechanical properties of the worked material obtained by working the continuous cast wire rod under predetermined conditions are specified as described above will be described.
(Zr)
By adding Zr together with P, Zr—P compounds containing Zr and P are produced. A primary crystal α-phase is formed with the Zr—P compound particles acting as inoculant nuclei; and thereby, fine dendrite formation and granular crystallization of the α-phase crystallized during solidification are achieved.
Due to the fine dendrite formation and granular crystallization of the α-phase as described above, the workability of the continuous cast wire rod is significantly improved, and it is possible to prevent defects such as cracking from occurring during hot working and cold working. Furthermore, the fluidity of the molten metal during casting is improved, the occurrence of large shrinkage cavities is suppressed, and it is possible to significantly improve the yield during casting.
However, since Zr has a strong affinity for oxygen, Zr oxide and the like are likely to be generated. As a result, the viscosity of the molten metal increases, and entrainment defects such as oxides are likely to occur during casting. In addition, blow holes and microporosities are likely to occur. In addition, since Zr is an element which is likely to react with a carbon mold, there is a concern that surface defects may be likely to occur and the castability may decrease in a case where a large amount of Zr is contained.
Therefore, in the present embodiment, the amount of Zr is set to be in a range of 0.0050 mass % or greater and 0.1000 mass % or less.
In order to reliably produce the Zr—P compounds, the lower limit of the amount of Zr is preferably 0.0200 mass % or greater, and more preferably 0.0380 mass % or greater. Meanwhile, in order to suppress the production of Zr oxide, the upper limit of the amount of Zr is preferably 0.0840 mass % or less, and more preferably 0.0680 mass % or less.
(P)
As described above, P is added together with Zr to produce Zr—P compounds containing Zr and P, and a primary crystal α-phase is formed with the Zr—P compound particles acting as inoculant nuclei. As a result, fine dendrite formation and granular crystallization can be achieved.
However, in a case where a large amount of P is contained, cracking is likely to occur on a surface or in the inside of an ingot during the formation of the ingot, and wire break is likely to occur during working. In addition, since P is an element which is likely to react with a carbon mold, there is a concern that surface defects may be likely to occur and the castability may decrease in a case where a large amount of P is contained.
Therefore, in the present embodiment, the amount of P is set to be in a range of 0.0050 mass % or greater and 0.1000 mass % or less.
In order to reliably produce the Zr—P compound, the lower limit of the amount of P is preferably 0.0200 mass % or greater, and more preferably 0.0360 mass % or greater. Meanwhile, in order to suppress the occurrence of cracking, the upper limit of the amount of P is preferably 0.0800 mass % or less, and more preferably 0.0680 mass % or less.
(Cu)
As described above, a primary crystal α-phase is formed with the Zr—P compound particles acting as inoculant nuclei; and thereby, fine dendrite formation and granular crystallization of the α-phase crystallized are achieved.
By setting the amount of Cu to be 62.0 mass % or greater, a region of the primary crystal α-phase is easily obtained, and it becomes possible to achieve fine dendrite formation and granular crystallization by the above-described actions and effects of Zr and P.
Meanwhile, in a case where the amount of Cu is greater than 70.0 mass %, the primary crystal α-phases (granular crystal grains) are bonded to each other, and the resulting α-phases become the same as the grown dendrite arms. Furthermore, due to the bonding between the crystal grains, problems occur on a casting surface, such as the occurrence of large numbers and large sizes of blow holes and shrinkage cavities. Furthermore, there is also a concern that the strength may decrease as the amount of Cu increases.
Therefore, in the present embodiment, the amount of Cu is set to be in a range of 62.0 mass % or greater and 70.0 mass % or less.
In order to reliably produce the primary crystal α-phase, the lower limit of the amount of Cu is preferably 64 mass % or greater, and more preferably 65 mass % or greater. Meanwhile, in order to suppress the bonding between the primary crystal α-phases (granular crystal grains), the upper limit of the amount of Cu is preferably 68 mass % or less, and more preferably 67 mass % or less.
(Sn)
Sn is an element acting to improve the corrosion resistance, erosion resistance, wear resistance, and strength.
However, in a case where the amount of Sn is too large, the solidification temperature range is widened, and casting defects such as cracking, shrinkage cavities, and porous shrinkage cavities are likely to occur. In addition, there is a concern that the Sn segregation may become remarkable during casting; and as a result, hot ductility deteriorates, and this may lead to a decrease in cold workability and a decrease in ductility.
Meanwhile, although depending on the blending ratio with Cu, Zn, and the like, the γ-phase, which is a hard phase having a higher Sn concentration than that of the matrix (α-phase), is remarkably generated, so that breaking is easy to occur during wire drawing. In addition, due to the selective corrosion of they-phase, and there is a concern that the seawater resistance may decrease.
Therefore, in the present embodiment, the amount of Sn is set to be in a range of 0.3 mass % or greater and 0.9 mass % or less.
In order to further improve the corrosion resistance, erosion resistance, wear resistance, and strength, the lower limit of the amount of Sn is preferably 0.60 mass % or greater, and more preferably 0.62 mass % or greater. Meanwhile, in order to further improve the castability, hot workability, and cold workability, the upper limit of the amount of Sn is preferably 0.68 mass % or less, and more preferably 0.66 mass % or less.
(Zr/P)
Zr and P are added together for the purpose of forming fine dendrites of copper alloy crystal grains. Each of Zr and P can only slightly refine copper alloy crystal grains in the same manner as other general additive elements. However, in a case where Zr and P coexist in an appropriate range, fine dendrites can be effectively formed. However, in a case where the ratio of Zr to P is small, it is difficult to achieve fine dendrite formation.
Therefore, in the present embodiment, the mass ratio Zr/P of Zr to P is set to be 0.3 or greater.
The lower limit of the mass ratio Zr/P of Zr to P is preferably 0.5 or greater, and more preferably 0.6 or greater. Meanwhile, the upper limit of the mass ratio Zr/P is preferably 4 or less, and more preferably 2 or less.
(Al)
Al is an element acting to improve the strength and yield strength by strengthening the matrix. In addition, Al acts to improve the molten metal flowability. Meanwhile, in a case where a large amount of Al is contained, there is a concern that the elongation may decrease.
Therefore, in the present embodiment, Al may be contained in an amount of 0.20 mass % or greater and 0.80 mass % or less in order to improve the strength, yield strength, and molten metal flowability.
The lower limit of the amount of Al is more preferably 0.30 mass % or greater, and even more preferably 0.40 mass % or greater. Meanwhile, the upper limit of the amount of Al is more preferably 0.70 mass % or less, and even more preferably 0.60 mass % or less.
(Sb)
Sb is an element acting to improve the corrosion resistance. Meanwhile, in a case where a large amount of Sb is contained, there is a concern that the workability may decrease.
Therefore, in the present embodiment, Sb may be contained in an amount of 0.02 mass % or greater and 0.06 mass % or less in order to improve the corrosion resistance.
The lower limit of the amount of Sb is more preferably 0.027 mass % or greater, and even more preferably 0.034 mass % or greater. Meanwhile, the upper limit of the amount of Sb is more preferably 0.054 mass % or less, and even more preferably 0.047 mass % or less.
(Number Density of Zr—P Compounds)
As described above, a primary crystal α-phase is formed with the Zr—P compound acting as an inoculant nucleus; and thereby, fine dendrite formation and granular crystallization of the α-phase crystallized during solidification are achieved.
However, in a case where the amount of the Zr—P compounds is too large, the primary crystal α-phases (granular crystal grains) are bonded to each other, and the resulting α-phases become the same as coarse dendrites obtained by growing dendrite arms. In addition, in a case where the primary crystal α-phases are not bonded to each other, there is a concern that the crystal grains may become too fine and the elongation may decrease.
Therefore, in the present embodiment, the number density of the Zr—P compounds is set to be in a range of 50 pieces/mm2 or greater and 500 pieces/mm2 or less.
In order to ensure the effects of the fine dendrite formation and the granular crystallization, the lower limit of the number density of the Zr—P compounds is preferably 60 pieces/mm2 or greater, and more preferably 90 pieces/mm2 or greater. Meanwhile, in order to further suppress the bonding between the primary crystal α-phases (granular crystal grains), the upper limit of the number density of the Zr—P compounds is preferably 400 pieces/mm2 or less, and more preferably 300 pieces/mm2 or less.
(Tensile Strength and Elongation)
In the continuous cast wire rod of a Cu—Zn—Sn-based alloy, a balance between strength and elongation is important for cold drawability.
Therefore, in the present embodiment, the tensile strength is preferably 370 N/mm2 or greater, and the elongation is preferably 14% or greater.
The lower limit of the tensile strength is more preferably 380 N/mm2 or greater, and even more preferably 390 N/mm2 or greater. Meanwhile, the upper limit of the tensile strength is preferably 420 N/mm2 or less, and more preferably 410 N/mm2 or less.
In addition, the lower limit of the elongation is more preferably 16% or greater, and even more preferably 18% or greater. Meanwhile, the upper limit of the elongation is preferably 29% or less, and more preferably 27% or less.
(Mechanical Properties of Worked Material)
With regard to the continuous cast wire rod of a Cu—Zn—Sn-based alloy, a wire material (worked material) worked into a predetermined wire diameter is subjected to bending, and thus becomes, for example, a member constituting a net-like structure for seawater. Therefore, with regard to the continuous cast wire rod of a Cu—Zn—Sn-based alloy, the mechanical properties of the worked material after working under predetermined conditions are particularly important.
Therefore, in the present embodiment, a worked material after a working process preferably has a tensile strength of 420 N/mm2 or greater, an elongation of 22% or greater, and a 0.2% yield strength of 300 N/mm2 or greater and 350 N/mm2 or less, and the working process include: a first heat treatment of holding at 550° C. for 2 hours and subsequently conducing air cooling; a first cold working at a working ratio of 41%; a second heat treatment of holding at 550° C. for 2 hours and subsequently conducing air cooling; a second cold working at a working ratio of 41%; a third heat treatment of holding at 450° C. for 2 hours and subsequently conducing air cooling; and a third cold working at a working ratio of 11%.
The lower limit of the tensile strength of the above-described worked material is preferably 430 N/mm2 or greater, and more preferably 435 N/mm2 or greater. Meanwhile, the upper limit of the tensile strength of the above-described worked material is preferably 460 N/mm2 or less, and more preferably 450 N/mm2 or less.
The lower limit of the elongation of the above-described worked material is preferably 26% or greater, and more preferably 30% or greater. Meanwhile, the upper limit of the elongation of the above-described worked material is preferably 41% or less, and more preferably 37% or less.
The lower limit of the 0.2% yield strength of the above-described worked material is preferably 310 N/mm2 or greater, and more preferably 315 N/mm2 or greater. Meanwhile, the upper limit of the 0.2% yield strength of the above-described worked material is preferably 340 N/mm2 or less, and more preferably 330 N/mm2 or less.
Next, an up-drawing type continuous casting apparatus 10 used in the production of the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment will be described with reference to
The continuous casting apparatus 10 includes a casting furnace 11, a continuous casting mold 20 connected to the casting furnace 11, and pinch rolls 17 which draw a cast wire material 1 produced from the continuous casting mold 20.
The casting furnace 11 heats and melts a melting raw material to produce and store a molten copper having a predetermined composition, and the casting furnace 11 includes a crucible 12 which stores the melting raw material and the molten copper, and a heating apparatus (not shown) for heating the crucible 12.
The cast wire material 1 produced from the continuous casting mold 20 is interposed between the pinch rolls 17 which draw the cast wire material 1 out in a drawing direction F. In the present embodiment, the cast wire material 1 is intermittently drawn out.
The continuous casting mold 20 includes a cylindrical mold 21 into which the supplied molten copper is injected, and a cooling portion 28 which cools the mold 21.
In the present embodiment, as shown in
The mold 21 has a substantially cylindrical shape, and the mold 21 has a casting hole 24 penetrating from one side to the other side.
The cooling portion 28 is a water-cooling jacket disposed on the outer peripheral side of the mold 21, and is configured to circulate cooling water to cool the mold 21.
Next, a method of producing the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment by using the above-described continuous casting apparatus 10 will be described.
First, a melting raw material is charged into the crucible 12 from a raw material input port of the casting furnace 11. As the raw material, a Cu single element, a Zn single element, a Sn single element, a Cu—Zn base alloy, a Cu—Sn base alloy, and the like can be used. In addition, a raw material containing Zn and Sn may be melted together with a copper raw material. Furthermore, a recycled material and a scrap material of the present alloy may be used.
Next, the melting raw material charged into the crucible 12 is heated and melted by the heating apparatus to produce a molten copper prepared to have the above-described component composition.
The molten copper is heated to a predetermined casting temperature and held in the crucible 12. Then, the 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, solidified, and becomes the cast wire material 1. The cast wire material 1 is continuously produced by being intermittently drawn out by the pinch rolls 17.
In a case where the casting temperature is low, misrun occurs due to a decrease in fluidity of the molten metal, and deep oscillation marks, internal defects, and altered layers are formed. Meanwhile, in a case where the casting temperature is high, there is a concern that seizure to the mold may occur.
Therefore, in the present embodiment, the casting temperature is preferably in a range of 980° C. or higher and 1,100° C. or lower.
In addition, in a case where the casting speed is low and the cooling rate during solidification is low, crystal growth or coalescence of crystal grains is promoted even with the Zr—P compound particles acting as inoculant nuclei. Therefore, there is a concern that the crystal grains may not be sufficiently refined. Meanwhile, in a case where the casting speed is high, the molten metal is not sufficiently supplied during drawing-out, and there is a concern that deep oscillation marks, internal defects, and altered layers may be formed. In addition, the frictional force between the mold and the solidified shell during drawing-out also increases, and there is a concern that the solidified shell may break during drawing-out, and deep oscillation marks may be formed.
Therefore, in the present embodiment, the casting speed is preferably in a range of 0.8 m/min or higher and 3.3 m/min or less.
In addition, in a case where the cooling rate is low during casting, the degree of undercooling becomes low, and only a part of the Zr—P compounds acts as the inoculant nucleus. Therefore, the refining effect is not sufficient. In addition, since crystal grain growth or coalescence of crystal grains is promoted, there is a concern that it may be difficult to refine the crystal grains. Meanwhile, in a case where the cooling rate is high during casting, the molten metal temperature decreases and the molten metal solidifies before the Zr—P compounds act as the inoculant nucleus, so that there is a concern that the refining effect may not be obtained.
Therefore, in the present embodiment, the cooling rate during casting is preferably in a range of 22° C./sec or higher and 75° C./sec or lower.
In addition, in a case where the continuous cast wire rod has a small cross sectional area, the cooling rate during casting increases, and there is a concern that a sufficient refining effect may not be obtained. Meanwhile, in a case where the continuous cast wire rod has a large cross sectional area, the cooling rate during casting decreases, and there is a concern that a sufficient refining effect may not be obtained. In addition, there is a concern that a sufficient solidified shell strength may not be obtained, and due to the drawing stress applied during casting, the oscillation marks may become large, or breaking may be likely to occur.
Therefore, in the present embodiment, the cross sectional area of the continuous cast wire rod is preferably in a range of 28 mm2 or greater and 226 mm2 or less.
In the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment having the above-described configuration, the amount of Zr is in a range of 0.0050 mass % or greater and 0.1000 mass % or less, the amount of P is in a range of 0.0050 mass % or greater and 0.1000 mass % or less, and the mass ratio Zr/P of Zr to P is 0.3 or greater. Accordingly, the Zr—P compounds are sufficiently dispersed. Thus, fine dendrite formation and granular crystallization of the α-phase crystallized during solidification are achieved, and it is possible to appropriately refine the crystal grain diameter of the cast structure. Therefore, the continuous cast wire rod has excellent mechanical properties and workability, and is particularly suitable as a material for a Cu—Zn—Sn-based alloy wire material constituting a net-like structure for seawater or the like.
In addition, since the amount of Cu is in a range of 62.0 mass % or greater and 70.0 mass % or less, an effect of preventing adhesion of marine organisms and a sterilization effect, which are generated by Cu ions, can be obtained.
Furthermore, since the amount of Sn is in a range of 0.3 mass % or greater and 0.9 mass % or less, it is possible to ensure corrosion resistance (seawater resistance) and to suppress a decrease in castability.
In addition, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, in a case where the number density of the Zr—P compounds containing Zr and P is in a range of 50 pieces/mm2 or greater and 500 pieces/mm2 or less, it is possible to reliably refine the crystal grain diameter of the cast structure, and to further improve the mechanical properties and workability.
Furthermore, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, in a case where the tensile strength is 370 N/mm2 or greater and the elongation is 14% or greater, the mechanical properties are sufficiently excellent, and subsequent cold working can be favorably performed. Therefore, the continuous cast wire rod is particularly suitable as a material for a Cu—Zn—Sn-based alloy wire material constituting a net-like structure for seawater or the like.
In addition, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, in a case where a worked material after a working process has a tensile strength of 420 N/mm2 or greater, an elongation of 22% or greater, and a 0.2% yield strength of 300 N/mm2 or greater and 350 N/mm2 or less, it is possible to obtain a worked material (wire material) having excellent mechanical properties. The working process includes: a first heat treatment of holding at 550° C. for 2 hours and subsequently conducing air cooling; a first cold working at a working ratio of 41%; a second heat treatment of holding at 550° C. for 2 hours and subsequently conducing air cooling; a second cold working at a working ratio of 41%; a third heat treatment of holding at 450° C. for 2 hours and subsequently conducing air cooling; and a third cold working at a working ratio of 11%.
Furthermore, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, in a case where Al is further contained in an amount of 0.20 mass % or greater and 0.80 mass % or less, it is possible to further improve the strength and yield strength. In addition, the molten metal flowability is improved, and casting can thus be more favorably performed.
In addition, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, in a case where Sb is contained in an amount of 0.02 mass % or greater and 0.06 mass % or less, it is possible to further improve the corrosion resistance, and to sufficiently ensure the workability.
In addition, in the continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the present embodiment, in a case where the continuous cast wire rod is an up-drawn continuous cast wire rod produced by an up-drawing type continuous casting apparatus, the influence of gravity can be suppressed, and thus the continuous cast wire rod has a uniform and fine cast structure in a cross section orthogonal to the drawing direction, and is particularly excellent in workability.
The continuous cast wire rod of a Cu—Zn—Sn-based alloy according to the embodiment of the present invention has been described as above, but the present invention is not limited thereto, and can be appropriately modified without departing from the technical features of the invention.
For example, in the present embodiment, an up-drawn continuous cast wire rod produced using the up-drawing type continuous casting apparatus shown in
In addition, in the present embodiment, the production of a continuous cast wire rod having a circular cross section and having a cross sectional area of 12 mm2 or greater and 227 mm2 or less has been described, but the present invention is not limited thereto, and the continuous cast wire rod may have a polygonal cross section or a tubular cross section. In addition, the continuous cast wire rod may have an irregular shape with a cross section having a protruding portion and a recessed portion. In addition, the cross sectional area of the cross section orthogonal to the longitudinal direction thereof is not particularly limited.
A description will be given below of the results of confirmatory experiments performed to confirm the effects of the present invention.
Melting raw materials were prepared so that the compositions shown in Tables 1 and 2 were obtained. 500 kg of the prepared melting raw material was charged into a crucible 12 of a casting furnace 11 shown in
As a mold, a mold for producing a cast wire rod having a circular cross section and an outer diameter of 6 mm (cross sectional area of the cross section orthogonal to a drawing direction: 28.26 mm2) was prepared.
Then, cast wire rods were drawn out under the casting conditions shown in Tables 3 and 4; and thereby, 300 kg of the melting raw material was cast.
The obtained cast wire material was cut along a center line parallel to the drawing direction to prepare a sample for microstructure observation, which was for observing oscillation and internal defects, and a sample for EPMA measurement. In addition, the cast wire material was cut in a direction orthogonal to the drawing direction to prepare a sample for microstructure observation.
The above-described various samples were polished using emery paper in the order of #240, #400, #800, and #1500 under conditions of a pressure of 100 N and a speed of 100 r/min for 1000 s in each case. Next, buffing was performed using a polishing agent in the order of 9 μm-particles, 3 μm-particles, and 1 μm-particles under conditions of a pressure of 30 N and a speed of 100 r/min for 1000 s in each case.
After that, the resulting materials were immersed in an etching liquid (a mixture of a hydrogen peroxide solution and ammonia water) at a temperature of 30° C. to 40° C. and subjected to ultrasonic cleaning for 30 to 60 s. Next, the resulting materials were immersed in water at room temperature, subjected to ultrasonic cleaning for 30 to 60 s, and dried.
(Microstructure of Cross Section Orthogonal to Drawing Direction)
The cross section orthogonal to the drawing direction of the cast wire rod was observed by an optical microscope.
As shown in
In contrast, in Invention Example 14, as shown in
In addition, in Comparative Example 11, the amount of Zr and the amount of P were less than the ranges of the present embodiment, but as shown in
In contrast, in invention Example 14, as shown in
(Zr—P Compound)
EPMA measurement was performed using the sample for EPMA measurement obtained as described above, and a dispersion status of the Zr—P compounds was observed. The observation visual field was set to 69 μm×49 μm, and the measurement was performed once at a substantially center position of the sample for EPMA measurement. Various conditions for the EPMA measurement were set as follows.
A granular compound in which a detection intensity of each of Zr and P was level 3 or higher and a diameter was 1 μm was recognized as the Zr—P compound.
(Oscillation Depth)
The obtained cast wire material was cut into 10 mm along the center line parallel to the drawing direction. Polishing was performed thereon using emery paper in the order of #240, #400, #800, and #1500 under conditions of a pressure of 100 N and a speed of 100 r/min for 1,000 s in each case. Next, buffing was performed using a polishing agent in the order of 9 μm-particles, 3 μm-particles, and 1 μm-particles under conditions of a pressure of 30 N and a speed of 100 r/min for 1000 s in each case.
After that, the resulting materials were immersed in an etching liquid (a mixture of a hydrogen peroxide solution and ammonia water) at a temperature of 30° C. to 40° C. and subjected to ultrasonic cleaning for 30 to 60 s. Next, the resulting materials were immersed in water at room temperature, subjected to ultrasonic cleaning for 30 to 60 s, and dried.
The structure was observed by an optical microscope at a100-fold magnification.
As shown in
A sample having an oscillation depth of less than 0.05 mm was evaluated as “A”, a sample having an oscillation depth of 0.05 mm or greater and less than 0.1 mm was evaluated as “B”, and a sample having an oscillation depth of 0.1 mm or greater was evaluated as “C”.
(Internal Defect)
The obtained cast wire material was cut into 100 mm along the center line parallel to the drawing direction. The cut material was divided into 10 equal pieces of 10 mm, and polished using emery paper in the order of #240, #400, #800, and #1500 under conditions of a pressure of 100 N and a speed of 100 r/min for 1000 s in each case. Next, buffing was performed using a polishing agent in the order of 9 μm-particles, 3 μm-particles, and 1 μm-particles under conditions of a pressure of 30 N and a speed of 100 r/min for 1000 s in each case.
After that, the resulting materials were immersed in an etching liquid (a mixture of a hydrogen peroxide solution and ammonia water) at a temperature of 30° C. to 40° C. and subjected to ultrasonic cleaning for 30 to 60 s. Next, the resulting materials were immersed in water at room temperature, subjected to ultrasonic cleaning for 30 to 60 s, and dried.
The structure was observed by an optical microscope at a 100-fold magnification, and a circular or elliptical hole or fracture in a region of a depth of 20 μm or greater was defined as an internal defect.
A sample in which no internal defects were observed was evaluated as “O”, and a sample in which internal defects were observed was evaluated as “X”.
(Mechanical Properties of Cast Wire Rod)
The obtained cast wire material was cut into a length of 150 mm, and a tensile test was performed thereon using a tensile tester AG-100kNX under conditions where an inter-grip distance was 70 mm, an inter-gauge point distance was 50 mm, and a tensile speed was 15 MPa/sec to evaluate the tensile strength, 0.2% yield strength, and elongation. The evaluation results are shown in Tables 5 and 6.
(Mechanical Properties of Worked Material)
The surface layer of the obtained cast wire material was peeled off, and the following working process was performed.
The material was held at 550° C. for 2 hours, and then air-cooled (first heat treatment). Next, first cold working was performed at a working ratio of 41%. Next, the material was held at 550° C. for 2 hours, and then air-cooled (second heat treatment). Next, second cold working was performed at a working ratio of 41%. Next, the material was held at 450° C. for 2 hours, and then air-cooled (third heat treatment). Next, third cold working was performed at a working ratio of 11%.
The obtained worked material was cut into a length of 150 mm, and a tensile test was performed thereon under the above-described conditions to evaluate the tensile strength, 0.2% yield strength, and elongation. The evaluation results are shown in Tables 5 and 6.
In Comparative Example 1, the amount of Cu was 60.3 mass %, which was less than the range of the present embodiment, and the composition was out of the region of the primary crystal α-phase; and therefore, fine dendrite formation and granular crystallization by the actions and effects of Zr and P could not be achieved, and the cast wire rod and the worked material were low in strength and 0.2% yield strength.
In Comparative Example 2, the amount of Cu was 72.4 mass %, which was greater than the range of the present embodiment. Internal defects such as blow holes occurred, the oscillation depth was deep, and the cast wire rod was low in internal quality and surface quality. In addition, the cast wire rod and the worked material were low in strength and 0.2% yield strength.
In Comparative Example 3, the amount of Sn was 0.21 mass %, which was less than the range of the present embodiment, and the cast wire rod and the worked material were low in strength and 0.2% yield strength.
In Comparative Example 4, the amount of Sn was 1.36 mass %, which was greater than the range of the present embodiment, casting defects occurred, and the cast wire rod was low in internal quality and surface quality. In addition, the cast wire rod and the worked material were low in elongation.
In Comparative Example 5, the amount of Zr was 0.0037 mass %, which was less than the range of the present embodiment, the mass ratio Zr/P of Zr to P was 0.25, which was outside the range of the present invention, and the worked material was low in strength.
In Comparative Example 6, the amount of Zr was 0.1230 mass %, which was greater than the range of the present embodiment, the oscillation depth was deep, and the cast wire rod was low in surface quality.
In Comparative Example 7, the amount of P was 0.0037 mass %, which was less than the range of the present embodiment, the oscillation depth was deep, and the cast wire rod was low in surface quality. In addition, the worked material was low in strength.
In Comparative Example 8, the amount of P was 0.1740 mass %, which was greater than the range of the present embodiment, casting defects occurred, and the cast wire rod was low in internal quality and surface quality. In addition, the cast wire rod and the worked material were low in strength, 0.2% yield strength, and elongation.
In Comparative Example 9: the mass ratio Zr/P of Zr to P was 0.18, which was outside the range of the present embodiment, and the worked material was low in strength and 0.2% yield strength. In addition, the cast wire rod was low in internal quality and surface quality.
In Comparative Example 10, the amount of Zr was 0.4410 mass %, which was greater than the range of the present embodiment, the amount of P was 0.2020 mass %, which was greater than the range of the present invention, casting defects occurred, and the cast wire rod was low in internal quality and surface quality. In addition, the cast wire rod and the worked material were low in strength and 0.2% yield strength.
In Comparative Example 11, neither Zr nor P contained, and the cast wire rod and the worked material were low in strength and 0.2% yield strength.
In contrast, in Invention Examples 1 to 18 in which the composition was within the range of the present embodiment, the occurrence of internal defects in the cast wire rod was suppressed, and the cast wire rod and the worked material were excellent in strength, 0.2% yield strength, and elongation.
In Inventive Examples 2, 7 to 13, and 15, the oscillation depth was slightly deeper, but it could be removed by peeling, and no problems occurred in the production of the worked material.
As a result of the above confirmatory experiments, it was confirmed that according to Invention Examples, it is possible to provide a continuous cast wire rod of a Cu—Zn—Sn-based alloy having few casting defects and excellent cold workability.
While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the invention. Accordingly, the invention is not to be considered as being limited by the foregoing description and is only limited by the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-168247 | Oct 2022 | JP | national |
