BRASS HAVING IMPROVED CASTABILITY AND CORROSION RESISTANCE
Disclosed is a brass having reduced amounts of lead and nickel or not containing them, and having improved castability and corrosion resistance. The brass, comprising Sn in the range of 0.05% to 0.2% by mass, at least one or more elements selected from the group consisting of Sb, As, and P with total amount thereof in the range of 0.05% to 0.32% by mass, Al in the range of 0.1% to 0.5% by mass, Zn in the range of 33.0% to 40.0% by mass, at least one or more elements selected from the group consisting of Pb and Bi with total amount thereof in the range of 0.005% to 0.25% by mass, Ni in the range of 0.5% or less by mass, Si in the range of 0.5% or less by mass, at least one or more elements selected from the group consisting of Fe and B with total amount thereof in the range of 0.0001% to 0.3% by mass, and the balance substantially consisting of Cu and unavoidable impurities, and also an apparent content of Zn in the range of 36% to 41%, is excellent in castability and corrosion resistance.
The present invention relates to a brass having reduced amounts of lead and nickel or not containing them; more specifically, the present invention relates to a brass for casting possessing having improved castability and corrosion resistance, which can be advantageously used, for example, for a water faucet metal fitting containing only minute amounts of lead and nickel, or not containing them.
BACKGROUND ARTA water faucet metal fitting is in general made of a brass or a bronze. From the viewpoint of improving the processability and corrosion resistance of the material, lead (Pb) and nickel (Ni) are added. In recent years, however, the influences of Pb and Ni on the human body and environment have become a concern, and regulations related to Pb and Ni have been actively established in various countries. For example, in California, U.S.A., a regulation of the content of Pb in a water-contacting member of a water tap faucet which should be in the range of 0.25% or less by mass in weighted average has come into effect from January, 2010. In addition, in the U.S.A. and China, a regulation that leaching amounts of Pb and Ni should be not more than 5 μg/L and 20 μg/L, respectively, has already been in effect. Also in countries all over the world including Europe and Korea, other than the U.S.A., the movement of regulations as mentioned above is notable; and therefore, the development of materials which can cope with the regulations of containing amount of Pb or leaching amounts of Pb and Ni has been desired in the art.
As to the typical conventional lead-containing brass, in order to provide a copper alloy having improved metal mold castability and corrosion resistance, JP H08(1996)-337831 A proposes a copper alloy for metal mold casting which comprises 0.05 to 0.2% by weight of Sn, 0.05 to 0.3% by weight of at least one or more elements selected from the group consisting of Sb, As, and P, 0.1 to 0.5% by weight of Al, 33.0 to 37.0% by weight of Zn, 0.5 to 3.0% by weight of Pb, and the balance Cu, with 35.7 to 41.0% by weight of a zinc equivalent, 15% or less of the area occupation rate of the β phase, and 17° C. or lower as the solidification temperature range thereof. According to this patent document, in order to improve machinability of the copper alloy, 0.5 to 3.0% by weight of Pb is added thereto. Moreover, in this patent document, Ni is not disclosed as the element contained in the copper alloy.
PRIOR ART DOCUMENT Patent DocumentPatent Document 1: Japanese Patent H08(1996)-337831 A
SUMMARY OF THE INVENTIONInventor of the present invention recently found that in the brass having reduced amounts of Pb and Ni or not containing them, corrosion resistance inherently imparted to the brass by containing them can be remarkably improved by adding prescribed amounts of antimony (Sb) and tin (Sn) each, and that even though addition of Sb and Sn sometimes can have an effect on casting cracking, the effect can be remedied by adding prescribed amounts of iron (Fe) and/or boron (B). The present invention is based on such finding.
Accordingly, the present invention has an object to provide a brass having reduced amounts of lead and nickel or not containing them, and also having improved castability, corrosion resistance, and the like.
The brass according to the present invention comprises:
Sn in the range of O,05% or more by mass to 0.2% or less by mass,
at least one or more elements selected from the group consisting of Sb, As, and P with total amount thereof in the range of 0.05% or more by mass to 0.32% or less by mass,
Al in the range of 0.1% or more by mass to 0.5% or less by mass,
Zn in the range of 33.0% or more by mass to 40.0% or less by mass,
at least one or more elements selected from the group consisting of Pb and Bi with total amount thereof in the range of 0.005% or more by mass to 0.25% or less by mass,
Ni in the range of 0.5% or less by mass,
Si in the range of 0.5% or less by mass,
at least one or more elements selected from the group consisting of Fe and B with total amount thereof in the range of 0.0001% or more by mass to 0.3% or less by mass, and
the balance substantially consisting of Cu and unavoidable impurities; and also
an apparent content of Zn in the range of 36% or more to 41% or less.
Definition:
In the present invention, the term “unavoidable impurities” as used herein means elements present in an amount of less than 0.1% by mass unless otherwise specified. For example, elements such as manganese (Mn) and chromium (Cr) are included in the unavoidable impurities. The amount of the unavoidable impurities is preferably less than 0.05% by mass.
At Least One or More Elements Selected from the Group Consisting of Pb and Bi:
The brass according to the present invention contains at least one or more elements selected from the group consisting of Pb and Bi (bismuth) with the total amount thereof in the range of 0.005% or more by mass to 0.25% or less by mass. In the present invention, amount of Pb can be made very small as mentioned above. According to a preferred embodiment of the present invention, the addition amount of the at least one or more elements selected from the group consisting of Pb and Bi is made in the range of 0.15% or more by mass to 0.25% or less by mass as the total amount of them. In addition, according to another preferred embodiment of the present invention, the addition amount of Pb is made in the range of 0.13% or more by mass to 0.23% or less by mass.
Bi, on behalf of Pb, imparts the brass with processability (for example, machinability) comparable with the processability imparted by Pb. Accordingly, in the present invention, the addition amount of Bi is preferably in the range of 0.13% or more by mass to 0.23% or less by mass.
Ni: The brass according to the present invention contains Ni with the amount of 0.5% or less by mass. In the present invention, amount of Ni can be made very small as mentioned above. According to a preferred embodiment of the present invention, the addition amount of Ni is made 0.2% or less by mass, while more preferably 0.1% or less by mass.
At Least One or More Elements Selected from the Group Consisting of Sb, As, and P:
The brass according to the present invention contains at least one or more elements selected from the group consisting of Sb, As (arsenic), and P (phosphorous) with the total amount thereof in the range of 0.05% or more by mass to 0.32% or less by mass. In the brass according to the present invention, as mentioned above, the addition amount of Ni is so small that there is a tendency that sufficient corrosion resistance cannot be obtained; however, by containing the at least one or more elements selected from the group consisting of Sb, As, and P with the total amount thereof in the range of 0.05% or more by mass to 0.32% or less by mass, the corrosion resistance thereof can be enhanced. This effect can be synergistically expressed by adding a prescribed amount of Sn (this will be mentioned later) as compared with the single addition thereof. If the total addition amount of these elements is more than 0.32% by mass, there is a tendency that the corrosion resistance of the brass is not improved so eminently; and therefore, in view of economy, the upper limit thereof is determined to be 0.32% by mass. According to a preferred embodiment of the present invention, the total addition amount of the at least one or more elements selected from the group consisting of Sb, As, and P is made in the range of 0.056% or more by mass to 0.315% or less by mass. According to another preferred embodiment, addition amount of each of Sb, As, and P is made in the range of 0.01% or more by mass to 0.30% or less by mass, in the range of 0.001% or more by mass to 0.30% or less by mass, and in the range of 0.005% or more by mass to 0.30% or less by mass, respectively.
Sn The brass according to the present invention contains Sn in the range of 0.05% or more by mass to 0.2% or less by mass. In the brass according to the present invention, as mentioned above, the addition amount of Ni is so small that there is a tendency that sufficient corrosion resistance cannot be obtained; however, by containing Sn in the range of 0.05% or more by mass to 0.2% or less by mass, the corrosion resistance thereof can be enhanced. This effect can be synergistically expressed by adding a prescribed amount of the at least one or more elements selected from the group consisting of Sb, As, and P, as compared with the single addition thereof.
At Least One or More Elements Selected from the Group Consisting of Fe and B:
The brass according to the present invention contains at least one or more elements selected from the group consisting of Fe and B with the total amount thereof in the range of 0.0001% or more by mass to 0.3% or less by mass. In the present invention, as mentioned above, by considering the influences on the human body and environment, the addition amounts of Pb and Ni, the containing amounts thereof or the leaching amounts thereof being regulated or intended to be regulated, are controlled to be very small. And therefore, this is based on the finding that deterioration of the corrosion resistance due to these reductions can be compensated by addition of prescribed amount of Sn as well as each of the at least one or more elements selected from the group consisting of Sb, As, and P. On the other hand, by reducing the addition amounts of Pb and Ni and by adding Sn as well as Sb and so forth, there is a possibility that the brass may not have sufficient castability; however, the brass according to the present invention is based on the simultaneous finding that the castability thereof can be remedied by containing the at least one or more elements selected from the group consisting of Fe and B within the range as mentioned above. That is, each of Fe and B facilitates refinement of crystals (especially proeutectic β phase) so that cracking during the time of casting can be effectively avoided. Further, the brass according to the present invention, by virtue of the refinement, can also be imparted with good mechanical properties.
Furthermore, B forms, together with Fe, Cr, and the like (these will be mentioned later), an intermetallic compound thereby forming hard spots which possibly pose problems in the surface processing of the molded product after casting. Accordingly, when a smooth and flat surface is wanted, it is preferable to lower the addition amount of B and/or the amounts of Fe, Cr, and the like. Specifically, the amount of B is preferably 0.005% or less by mass, more preferably 0.003% or less by mass, while still more preferably 0.002% or less by mass; and the amount of Fe is preferably 0.10% or less by mass; and the amount of Cr is preferably less than 0.1% by mass.
Zn: The brass according to the present invention contains Zn in the range of 33.0% or more by mass to 40.0% or less by mass. By making the addition amount of Zn in the range of 33.0% or more by mass, the casting yield thereof can be made higher. Also by making the addition amount of Zn in the range of 40.0% or less by mass, increase of the β-phase region, which is poor in the corrosion resistance, can be suppressed so that deterioration of the dezincification corrosion resistance may be avoided.
Al: The brass according to the present invention contains Al in the range of 0.1% or more by mass to 0.5% or less by mass. By having the addition amount of Al in the range of 0.1% or more by mass, castability thereof can be improved. Specifically, the warm-water fluidity and casting surface texture thereof can be improved. In the present invention, preferable addition amount of Al is 0.3% or more by mass. With this, the warm-water fluidity and casting surface texture thereof can be improved furthermore. Also by having the addition amount of Al in the range of 0.5% or less by mass, deterioration of elongation and impact resistance value can be suppressed.
Si: The brass according to the present invention contains Si in the range of 0.5% or less by mass. As will be described later, the Zn equivalent of Si proposed by Guillet is 10; and thus, it increases an apparent Zn content thereby leading to a possibility that heterogeneous phases such as γ phase and κ phase are crystallized out in the crystal texture. In the present invention, because the addition amount of Si is 0.5% or less by mass, a possibility that heterogeneous phases such as γ phase and κ phase are crystallized out in the crystal texture is low. According to a preferred embodiment of the present invention, the addition amount of Si is 0.1% or less by mass.
Cu and Unavoidable Impurities:
In the brass according to the present invention, the balance after the above-mentioned element components comprises substantially copper (Cu) and unavoidable impurities. According to a preferred embodiment of the present invention, the brass according to the present invention contains Cu in the range of 55% or more by mass to 709′o or less by mass. When the addition amount of Cu is made in the range of 70% or less by mass, cracking due to crystallization of dendrite of the proeutectic α phase can be suppressed. Also when the addition amount of Cu is 55% or more by mass, deterioration of the castability, corrosion resistance, and mechanical properties as the brass can be suppressed. According to a more preferred embodiment of the present invention, the lower limit of the addition amount of Cu is 58% by mass, and the upper limit thereof is 66% by mass.
In addition, the brass according to the present invention may contain various additives in order to improve properties of the brass. Also in the present invention, it is preferable that amounts of the unavoidable impurities be as small as possible, though presence of them is not excluded.
In the present invention, Cr forms, together with Fe, B, and the like, an intermetallic compound thereby forming hard spots which possibly pose problems in the surface processing of the molded product after casting. Therefore, when a smooth and flat surface is wanted, it is preferable to lower the amount of Cr. Specifically, the amount thereof is preferably less than 0.1% by mass, while more preferably less than 0.01% by mass.
In the present invention, Mn improves strength of the brass. When Mn is added, an intermetallic compound of Mn and Si is formed thereby forming hard spots which possibly pose problems in the surface processing of the molded product after casting. Therefore, in order to suppress the influence to the castability as mentioned above, it is preferable that amount of Mn be made as small as possible. Specifically, the amount thereof is preferably less than 0.1% by mass, while more preferably less than 0.01% by mass.
Apparent Zn Content:
According to a preferred embodiment of the present invention, an apparent Zn content in the brass of the present invention is in the range of 36% or more to 41% or less. When the apparent Zn content is within this range, the brass not having cracks by casting can be obtained. In the present specification, the apparent Zn content means the amount calculated by the following equation proposed by Guillet. This equation is based on the concept that the addition of additive elements other than Zn exhibits the same tendency as the addition of Zn.
Apparent Zn content (%)=[(B+tq)/(A+B+tq)]×100
In the equation, A=% by mass of Cu and B=% by mass of Zn, wherein t represents the Zn equivalent of the additive element, and q represents % by mass of the addition amount of the additive element. The Zn equivalent of each element is Si=10, Al=6, Sn=2, Pb=1, Fe=0.9, Mn=0.5, and Ni=−1.3. The Zn equivalent of Bi has not been clearly defined yet. In the present specification, however, the Zn equivalent of Bi is calculated to be 0.6 in view of reference documents and the like. For the other elements, the value is regarded as “1,” because the addition amount of them is very small and thus the influence on the Zn equivalent value is small, too.
Ratio of the β Phase:
According to a preferred embodiment of the present invention, in the brass of the present invention, the ratio of the β phase in the crystal texture thereof is 15% or less. When the crystal texture as mentioned above is formed, the brass having improved corrosion resistance can be realized. In addition, according to a more preferred embodiment of the present invention, the ratio of the β phase is 8% or less. By so doing, the brass for metal mold casting having improved corrosion resistance useful for a water faucet metal fitting can be realized. This is especially suitable for a pressure-resistant part of a water faucet metal fitting. Meanwhile, in the present invention, the ratio of the fi phase is based on the area ratio of the cross section of the crystals. For example, the ratio of the β phase may be determined as the area ratio of the β phase, for example, by subjecting a photograph of a crystal texture taken with an optical microscope to image processing.
Use:
The brass according to the present invention has the amounts of Pb and Ni reduced to very small, or does not contain these elements;
but on the other hand, the castability and corrosion resistance thereof are equal to or higher than the brass which contains Pb and Ni. Thus, the brass is preferably used in a water faucet metal fitting material. Specifically, the brass according to the present invention is preferably used as a material for a water supply metal fitting, a drainage metal fitting, a valve, and the like.
Production Method:
It is preferable that the brass according to the present invention be produced by the method which comprises heat treatment after casting thereby decreasing the ratio of the β phase in the crystal texture thereof. Because the corrosion resistance thereof increases with decrease of the ratio of the β phase, the brass having improved corrosion resistance can be obtained. According to a preferred embodiment of the present invention, the heat treatment is carried out in the temperature range of 450° C. to 550° C. and the time range of 30 minutes to 3 hours. When the heat treatment is carried out in the way as mentioned above, the brass having the ratio of the β phase in the range of 15% or less, preferably in the range of 8% or less, can be obtained. The brass obtained in this way has improved corrosion resistance.
In the present invention, when the heat treatment is carried out in the temperature range of 450° C. to 550° C., the region of the β phase decreases and the concentrations of Sn and Sb in the β phase increase, so that the corrosion resistance in the β phase improves dramatically. When the heat treatment is carried out in the temperature range of 550° C. or lower, increase of the region of the β phase can be suppressed thereby suppressing deterioration of the corrosion resistance. Also when the heat treatment is carried out in the temperature range of 450° C. or higher, uneven distribution of elements in particular region of a grain boundary is resolved without requiring time, so that the region of the β phase can be decreased.
In the present invention, when the heat treatment is carried out in the time range of 30 minutes to 3 hours, the effect that the phase becomes smaller can be obtained. In addition, this effect can be sufficiently obtained within 3 hours of the heat treatment. The heat treatment longer than 3 hours does not give a significant effect of it; and thus, in view of economy, it is preferable that the upper limit of the time for the heat treatment be within 3 hours.
In addition, molded products using the brass according to the present invention as a material may be produced by any of mold casting and sand casting by virtue of good castability thereof. However, the effect of the good castability can be more clearly enjoyed in the mold casting. Further, the brass according to the present invention has good machinability and thus can be machined after casting. Furthermore, after continuous casting, the brass according to the present invention may be extruded into a bar for machining and a bar for forging, or alternatively may be drawn into a wire rod.
EXAMPLESThe following Examples further illustrate the present invention. However, it should be noted that the present invention is not limited to these Examples.
Evaluation Tests:Evaluation tests each conducted in the following Examples will be described in detail.
(1) Casting Cracking Resistance TestThe casting cracking resistance was evaluated by a both end restriction test method. In this test, a mold 1 having a shape shown in
In the test, in such a state that the restriction parts were rapidly quenched while the both ends were restricted, the solidification of the central part was allowed to proceed. In this case, whether or not cracking took place at the central part of a test piece as the final solidified part by the resultant solidification shrinkage stress was examined.
The casting cracking resistance was evaluated as ⊚ (Excellent) when cracking did not take place; as ∘ (Good) when cracking partially took place but the cracking was not such a level that the test piece was broken; and as × (Bad) when cracking took place resulting in breaking of the test piece.
(2) Corrosion Resistance TestA cast ingot having a diameter of 35 mm and a length of 100 mm was produced by metal mold casting. This cast ingot was used as a test piece and was tested according to the technical standards JBMA T-303-2007 established by Japan Copper and Brass Association. The corrosion resistance was evaluated as ⊚ (Excellent) when the maximum erosion depth was 100 μm or less; as ∘ (Good) when the maximum erosion depth was 150 μm or less; and as × (Bad) when the maximum erosion depth was more than 150 μm.
Examples 1-1 to 10-8Brasses having chemical compositions shown in the following Tables were produced by casting. Specifically, electrolytic Cu, electrolytic Zn, virgin Bi metal, electrolytic Pb, virgin Sn metal, virgin Sb metal, Cu-30% Ni mother alloy, electrolytic Al, Cu-15% Si mother alloy, Cu-2% B mother alloy, Cu-30% Mn mother alloy, Cu-10% Cr mother alloy, Cu-15% P mother alloy, Cu-10% Fe, Cu-20% As mother alloy and the like were provided as raw materials; and then, they were melted in a high frequency melting furnace while regulating the composition thereof. Firstly, the melt was cast into a mold for a both end restriction test to evaluate the casting cracking resistance.
Subsequently, the melt was cast into a cylindrical mold to produce a cast ingot having a diameter of 35 mm and a length of 100 mm. The cast ingot was used as a sample for the evaluation of the corrosion resistance. The evaluation results are shown in the following Tables.
- Examples shown in Table 4 especially clarify the significance and influence of the following elements.
- Examples 11-1, 11-2, 11-8, 12-1, 12-2, and 12-8: Sb, As, and P
- Examples 11-3, 11-4, 12-3, and 12-4: Sn
- Examples 11-5, 11-6, 12-5, and 12-6: Al
- Examples 11-7 and 12-7: Si
- Examples 13-1 to 13-5, and 14-1 to 14-5: Pb and Bi
- Examples 13-6 and 14-6: Ni
- Examples 13-7 and 14-7: Mn
- Examples 13-8 and 14-8: Cr
- Examples 15-1 to 15-8 and 16-1 to 16-8 give the compositions which are considered to be more preferable.
- Examples shown in Table 5 especially clarify the significance and influence of the following elements.
- Examples 17-1, 17-3, 17-5, 17-7, 18-1, 18-3, 18-5, and 18-7: Sb, As, and P
- Examples 17-2, 17-4, 17-6, 17-8, 18-2, 18-4, 18-6, and 18-8: Sn
- Examples shown in Table 6 especially clarify the significance and influence of the following elements.
- Examples 19-1 to 19-8, 20-1 to 20-8, 21-1, 21-3, 21-5, and 21-7: Sb, As, and P
- Examples 19-1 to 19-8, 20-1 to 20-8, 21-2, 21-4, 21-6, and 21-8: Sn
- Examples 22-1 to 22-8: apparent Zn content
- Examples 22-1, 22-2, 22-5, and 22-6: Al
- Examples 22-3, 22-4, 22-7, and 22-8: Zn
- Examples shown in Table 7 especially clarify the significance and influence of the following elements.
- Examples 23-1 to 23-8: unavoidable impurities
- Examples 23-1, 23-2, 23-5, and 23-6: Mn
- Examples 23-3, 23-4, 23-7, and 23-8: Cr
- Examples 24-1 and 24-5: Si
- Examples 24-1 and 24-5: apparent Zn content
- Examples 24-2, 24-3, 24-6, and 24-7: Cu and unavoidable impurities
Claims
1. A brass comprising:
- Sn in the range of 0.05% or more by mass to 0.2% or less by mass,
- at least one or more elements selected from the group consisting of Sb, As, and P with total amount thereof in the range of 0.05% or more by mass to 0.32% or less by mass,
- Al in the range of 0.1% or more by mass to O.5% or less by mass,
- Zn in the range of 33.0% or more by mass to 40.0% or less by mass,
- at least one or more elements selected from the group consisting of Pb and Bi with total amount thereof in the range of 0.005% or more by mass to 0.25% or less by mass,
- Ni in the range of 0.5% or less by mass,
- Si in the range of 0.5% or less by mass,
- at least one or more elements selected from the group consisting of Fe and B with total amount thereof in the range of 0.0001% or more by mass to 0.3% or less by mass, and
- the balance substantially consisting of Cu and unavoidable impurities; and also
- an apparent content of Zn in the range of 36% or more to 41% or less.
2. The brass according to claim 1, wherein ratio of β phase in crystal texture thereof is 15% or less.
3. The brass according to claim 2, wherein the brass is obtained, after casting, by heat treatment carried out in a temperature range of 450° C. to 550° C. and a time range of 30 minutes to 3 hours.
4. A method for producing the brass according to claim 1, wherein the said method comprises, after casting, the heat treatment carried out in a temperature range of 450° C. to 550° C. and a time range of 30 minutes to 3 hours.
5. A water faucet metal fitting comprising the brass according to claim 1.
6. The water faucet fitting according to claim 5, wherein the said water faucet fitting is produced by metal mold casting.
Type: Application
Filed: Jan 25, 2016
Publication Date: Jul 28, 2016
Inventor: Toru UCHIDA (Fukuoka-ken)
Application Number: 15/005,325
