US20150203940A1 - Brass alloy and method for manufacturing the same

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US20150203940A1

Publication number: US20150203940A1
Application number: US14/160,941
Authority: US
Inventors: Ching-Shing Kang; Sung-Wei Yeh; Chin-Hsiang Shih
Original assignee: Metal Industries Research and Development Centre
Current assignee: Metal Industries Research and Development Centre
Priority date: 2014-01-22
Filing date: 2014-01-22
Publication date: 2015-07-23

A brass alloy, with a total weight percentage thereof counted as 100 wt %, includes the following elements: 60 wt % to 65 wt % of copper, 0.1 wt % to 0.35 wt % of bismuth, 0.15 wt % to 0.5 wt % of antimony, a balance of zinc, and an inevitable impurity.

BACKGROUND

1. Technical Field
The present invention relates to a brass alloy, and in particular, to a brass alloy that does not contain lead, is easily cut, and resists dezincification.
2. Related Art
Generally, 38% to 42% of zinc is added to brass alloy used for processing. To be better processed, the brass usually contains 2% to 3% of lead to increase the strength and workability. The leaded brass alloy has desirable formability (making it easy to manufacture products of various shapes), machinability and attrition resistance, and is hence widely applied to machining components of various shapes. The leaded brass alloy accounts for a large share in the copper industry, and is recognized as an important basic material in the world. However, during manufacturing or using of the leaded brass, lead is easily dissolved out in the form of solid or gas. Medical research points out that lead causes a great damage to human hematopoietic and nervous systems, and especially kidneys and other organs of children. All countries in the world are seriously concerned about pollutions and hazards caused by lead. The US National Sanitation Foundation (NSF), Japanese Industrial Standards (JIS), Deutsches Institut für Normung e.V. (DIN), and Restriction of Hazardous Substances Directive (RoHS) of the European Union have limited and forbidden the use of leaded brass alloy in succession.
In addition, when zinc content in brass alloy exceeds 20 wt %, a dezincification corrosion phenomenon occurs easily. Especially, when the brass alloy contacts an environment with high chloride ion content, for example, a sea water environment, the dezincification corrosion phenomenon is accelerated. The dezincification severely destroys the structure of the brass alloy, reduces surface strength of a brass product so as to even leads to perforating of a brass pipe, and thus the dezincification greatly reduces a service life of the brass product and causes usage problems.
Therefore, it is necessary to provide a brass alloy that can replace the leaded brass alloy, and can achieve dezincification corrosion resistance while still having desirable casting performance, machinability, corrosion resistance, and mechanical properties, so as to solve the foregoing problems.

SUMMARY

The present invention is directed to a brass alloy that has desirable dezincification resistance and does not contain lead.
To achieve the foregoing objective, the present invention provides a brass alloy, with a total weight percentage thereof counted as 100 wt %, the brass alloy including the following elements: 60 wt % to 65 wt % of copper, 0.1 wt % to 0.35 wt % of bismuth, 0.15 wt % to 0.5 wt % of antimony, a balance of zinc, and an inevitable impurity.
To achieve the foregoing objective, the present invention further provides a method for manufacturing a brass alloy, comprising the following steps of: providing copper and manganese; heating the copper and manganese until a temperature rises to between 1100 and 1150 degrees centigrade, so that the copper and manganese are formed to a molten copper-manganese alloy; decreasing the temperature of the molten copper-manganese alloy to between 950 and 1000 degrees centigrade; covering a surface of the molten copper-manganese alloy with a rice husk ash; adding zinc to the molten copper-manganese alloy, so as to form a molten copper-manganese-zinc alloy; removing slag from the molten copper-manganese-zinc alloy; adding antimony, bismuth, aluminum, or tin to the molten copper-manganese-zinc alloy, to form a molten metal alloy; increasing a temperature of the molten metal alloy to between 1000 and 1050 degrees centigrade, and adding a copper-boron alloy and a phosphorus-copper alloy, to form a molten brass alloy; and tapping the molten brass alloy out of a furnace and casting the molten brass alloy to form the brass alloy.
According to the brass alloy of the present invention, after different metal having a predetermined weight percentage is added, a brass alloy material is manufactured by using a high-frequency melting furnace, wherein the manufactured brass alloy material has machining properties equivalent to those of the conventional leaded brass, desirable tensile strength and elongation, and good dezincification resistance. The manufactured brass alloy is easily cut, does not contain lead, and is suitable for replacing the conventional leaded brass to manufacture products such as a faucet or accessories of bathroom products.
In order to make the aforementioned and other objectives, features, and advantages of the present invention clearer, embodiments accompanied with figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the present disclosure, and wherein:

FIG. 1 is a flow chart of a method for manufacturing a brass alloy according to an embodiment of the present invention; and

FIG. 2 shows test result photos about mechanical properties of brass alloys.

DETAILED DESCRIPTION

With a method for manufacturing a brass alloy according to an embodiment of the present invention, the brass alloy has machinability equivalent to that of a conventional leaded brass, desirable tensile strength and elongation, and good dezincification resistance, and does not contain lead, and therefore is a perfect alloy material to replace the conventional leaded brass to manufacture products. With its weight percentage counted as 100 wt %, the brass alloy includes the following elements: 60 wt % to 65 wt % of copper, 0.1 wt % to 0.35 wt % of bismuth, 0.15 wt % to 0.5 wt % of antimony, a balance of zinc, and an inevitable impurity. The brass alloy may further include one or a mixture of more than one selected from aluminum, tin, phosphorus, manganese, and boron, and total content of the selected mixture accounts for 0.2 wt % to 2 wt % of the brass alloy. In addition, during manufacturing, an inevitable impurity is brought into the brass alloy due to purity of a material, and total content of the inevitable impurity may be less than 0.1 wt % of nickel, less than 0.1 wt % of chromium, or less than 0.1 wt % of iron.
Preferably, the brass alloy of the present invention only includes 60 wt % to 65 wt % of copper, 0.1 wt % to 0.35 wt % of bismuth, 0.15 wt % to 0.5 wt % of antimony, a balance of zinc, and an inevitable impurity.
In another embodiment, the brass alloy of the present invention only includes 60 wt % to 65 wt % of copper, 0.1 wt % to 0.35 wt % of bismuth, 0.15 wt % to 0.5 wt % of antimony, one or a mixture of more than one selected from aluminum, tin, phosphorus, manganese, and boron, total content of the selected mixture accounting for 0.2 wt % to 2 wt % of the brass alloy, a balance of zinc, and an inevitable impurity.
In another embodiment, the brass alloy of the present invention includes 60.5 wt % to 64.5 wt % of copper, 0.15 wt % to 0.3 wt % of bismuth, 0.2 wt % to 0.35 wt % of antimony, 0.1 wt % to 0.25 wt % of aluminum, 0.05 wt % to 0.4 wt % of manganese, 0.1 wt % to 0.6 wt % of tin, 0.05 wt % to 0.2 wt % of phosphorus, 0.002 wt % to 0.005 wt % of boron, a balance of zinc, and an inevitable impurity.
A metallographic structure of the brass alloy of the present invention mainly includes an α phase, a β phase, a soft and fragile intermetallic compound distributed at a grain boundary or in a grain, wherein copper and zinc are main elements which is formed to 6/4 brass alloy (includes 60% Cu and 40% Zn approximately), and bismuth can be added to become a cutting breakpoint in the structure so as to replace of lead. However, with excessively high bismuth content, hot tearing occurs easily during casting, so the bismuth content is reduced while antimony and phosphorus are used to produce an intermetallic compound with copper, so as to increase machinability, which is also conducive to dezincification resistance. The addition of elements such as aluminum, tin, and manganese is also conducive to the dezincification resistance and casting fluidity. The addition of boron refines grains, and can scatter the distribution of the intermetallic compound, so as to increase the dezincification resistance and mechanical properties.
FIG. 1 is a flow chart of a method for manufacturing a brass alloy according to an embodiment of the present invention. The method for manufacturing a brass alloy includes the following steps:
Step S100: Provide copper and manganese. In this step, a copper-manganese alloy may be provided to serve as a material for providing the copper and manganese.
Step S102: Heat the copper and manganese until a temperature rises to between 1100 and 1150 degrees centigrade, so that the copper and manganese are formed to a molten copper-manganese alloy. In this step, the copper-manganese alloy may be put to a high-frequency melting furnace, and is molten and heated in the melting furnace, until the temperature rises to between 1100 and 1150 degrees centigrade; wherein this operation lasts 30 minutes, so that the copper-manganese alloy is molten so as to forms a molten copper-manganese alloy. The foregoing operation can prevent the molten copper and manganese from absorbing a large amount of external air because of an excessively high temperature, and prevent form a cracking effect on the formed alloy material.
The high-frequency melting furnace has features such as a high melting rate, a high temperature rise, being clean and pollution-free, and being capable of self-stirring (under the effect of a magnetic line of force) during melting; and in the high-frequency melting furnace, a silicon carbide graphite crucible is used as a furnace liner for magnetization.
Step S104: Decrease the temperature of the molten copper-manganese alloy to between 950 and 1000 degrees centigrade. In this step, when the temperature in the melting furnace rises to between 1100 and 1150 degrees centigrade and is maintained for 30 minutes, a power supply of the high-frequency melting furnace is turned off, so that the temperature in the melting furnace declines to between 950 and 1000 degrees centigrade, and at the same time, the molten copper-manganese alloy still maintains a molten state.
Step S106: Cover a surface of the molten copper-manganese alloy with a rice husk ash.
In this step, the surface of the molten copper-manganese alloy whose temperature is between 950 and 1000 degrees centigrade is covered with the rice husk ash, and this operation can effectively separate the molten copper-manganese alloy liquid from air and prevent zinc, which is to be added subsequently, from melting, boiling, and volatilizing at the high temperature between 950 and 1000 degrees centigrade.
Step S108: Add zinc to the molten copper-manganese alloy, so as to form a molten copper-manganese-zinc alloy. In this step, zinc is added to the melting furnace, and is submerged into the molten copper-manganese alloy, so that the zinc and the molten copper-manganese alloy dissolve into each other to form the molten copper-manganese-zinc alloy.
Step S110: Remove slag from the molten copper-manganese-zinc alloy. In this step, first, under the magnetization effect of the furnace liner of the silicon carbide graphite crucible, the molten copper-manganese-zinc alloy is stirred and mixed, and then the rice husk ash is taken out. Subsequently, a slag removal operation is performed by using a slag remover.
Step S112: Add antimony, bismuth, aluminum, or tin to the molten copper-manganese-zinc alloy, to form a molten metal alloy. In this step, pure antimony, pure bismuth, pure aluminum, or pure tin may be added to the molten copper-manganese-zinc alloy.
Step S114: Increase a temperature of the molten metal alloy to between 1000 and 1050 degrees centigrade, and add a copper-boron alloy and a phosphorus-copper alloy, to form a molten brass alloy. In this step, the copper-boron alloy and the phosphorus-copper alloy are added to the molten metal alloy.
Step S116: Tap the molten metal alloy out of the furnace and cast the molten metal alloy to the brass alloy. In this step, after the molten metal alloy is stirred evenly, a tapping temperature is controlled between 1030 and 1050 degrees centigrade, and finally the molten metal alloy is tapped out of the furnace and cast to be an unleaded brass alloy with desirable workability, and good dezincification resistance and mechanical properties.
The element contents of the brass alloy material of the present invention are measured as follows, wherein the unit is weight percentage (wt %):


Copper	Zinc	Bismuth	Antimony	Manganese	Aluminum	Tin	Phosphorus	Boron
(Cu)	(Zn)	(Bi)	(Sb)	(Mn)	(Al)	(Sn)	(P)	(B)

Test 1 (T1)	56.14	41.54	0.006	0.492	0.4163	0.494	0.783	0.122	0.0013
Test 2 (T2)	56.01	41.5	0.002	0.513	0.4667	0.5604	0.820	0.121	0.0011
Test 3 (T3)	56.88	40.02	0.440	0.536	0.548	0.584	0.856	0.131	0.0012
Test 4 (T4)	58.68	38.52	0.3092	0.4114	0.7219	0.2188	0.9789	0.1585	0.0007
Test 5 (T5)	60.5	38.03	0.3121	0.2223	0.085	0.173	0.5921	0.083	0.001

Results of dezincification resistance tests are as follows:

Average	598.1	440.3	407.4	153.4	80
dezincification
depth
(micrometer)

The dezincification corrosion resistance tests are carried out in accordance with the standard AS-2345-2006. 12.8 grams of copper chloride is added to 1000 C.C of deionized water, and materials in the tests 1 to 5 are put in the copper chloride solution and stay for 24 h, so as to measure the dezincification depth. The element contents of the material and the results of the dezincification resistance tests indicate that when a weight percentage of copper is greater than 60 wt %, the average dezincification depth decreases significantly. Especially, when the weight percentage of the copper is 60.5 wt %, the average dezincification depth declines to about 80 micrometers. The foregoing tests indicate that when the copper content is above 60%, a small quantity of dezincification resisting elements need to be added to obtain a dezincification depth less than 100 micrometers.
Then, seven groups of tests are planned, and the weight percentage of copper in the brass alloy in each group is greater than or equal to 60.5 wt %, so as to carry out tensile strength tests, elongation tests, dezincification depth tests, and relative cutting rate tests.
The element contents of the brass alloy material are measured as follows, wherein the unit is weight percentage (wt %):


Material	Copper	Zinc	Bismuth	Antimony	Manganese	Aluminum	Tin	Phosphorus	Boron
No.	(Cu)	(Zn)	(Bi)	(Sb)	(Mn)	(Al)	(Sn)	(P)	(B)

1	60.50	38.03	0.3121	0.2223	0.085	0.173	0.5921	0.083	0.001
2	63.47	35.16	0.2	0.31	0.140	0.126	0.325	0.052	0.0026
3	62.27	35.19	0.2	0.313	0.572	0.348	0.686	0.05	0.003
4	61.73	37.36	0.137	0.27	0.192	0.018	0.059	0.194	0.0013
5	61.49	37.164	0.273	0.188	0.053	0.138	0.616	0.076	0.0019
6	64.03	34.45	0.186	0.3	0.067	0.128	0.677	0.104	0.0047
7	63.79	35.0	0.262	0.309	0.087	0.053	0.337	0.103	0.0047

The tensile strength tests, elongation tests, machinability tests, and dezincification corrosion resistance tests for Material No. 1 to Material No. 7 are carried out, wherein the test samples are in a casting condition.
In the tensile strength tests and elongation tests, the test samples undergo extension tests in a casting condition at a room temperature, and comparison samples are leaded brass alloy, namely C36000 alloy, having the same condition and the same specification.
The machinability tests are carried out by using the same cutting tool with the same cutting speed and the same amount of feed; the cutting speed is 25 meters/minute (m/min.), the amount of feed is 0.2 millimeters/revolution (mm/r), a cutting depth is 0.5 mm, and the diameter of a test bar is 20 mm. The C36000 alloy material is acted as a reference, the relative cutting rate is obtained by measuring a cutting resistance.
Relative cutting rate=Cutting resistance of the C36000 alloy material/Cutting resistance of the test sample.
The dezincification corrosion resistance tests are carried out in accordance with the standard AS-2345-2006. 12.8 grams of copper chloride is added to 1000 C.C of deionized water, and Material No. 1 to Material No. 7 and the C36000 alloy material are put in the copper chloride solution and stay for 24 h, so as to measure the dezincification resistance.
The element contents of the C36000 alloy material are measured as follows, wherein the unit is weight percentage (wt %):


Material	Copper	Zinc	Bismuth	Antimony	Manganese	Aluminum	Tin	Lead	Iron
No.	(Cu)	(Zn)	(Bi)	(Sb)	(Mn)	(Al)	(Sn)	(Pb)	(Fe)

C36000 alloy	60.53	36.26	0	0	0	0	0.12	2.97	0.12
material

Results of the tensile strength tests, elongation tests, machinability tests, and dezincification corrosion resistance tests are as follows:


Material	Tensile strength	Elongation	Dezincification	Relative
number	(N/mm²)	(%)	layer	cutting rate

1	352	23	⊚	⊚
2	264	20	⊚	⊚
3	341	27	⊚	⊚
4	269	13	⊚	⊚
5	338	26	⊚	⊚
6	236	13	⊚	⊚
7	241	19	⊚	⊚
C36000	394	9	X	⊚
alloy

In the foregoing table, as for the dezincification layer: “
” represents that the dezincification depth is less than 100 μm: “◯” represents that the dezincification depth is between 100 μm and 200 μm; and “X” represents that the dezincification depth is greater than 200 μm.
In the foregoing table, as for the relative cutting rate: “
” represents that the relative cutting rate is greater than 85%; “◯” represents that the relative cutting rate is greater than 70%.
It can be known from the foregoing table that when the weight percentage of copper is 60.05 wt % to 64.03 wt % and other metal is added (for example, bismuth and antimony), the machinability can be equivalent to that of the C36000 alloy and a small dezincification depth can be obtained. It can be seen from FIG. 2 that the cutting and breaking in the seven groups of tests (Material No. 1 to Material No. 7) are short and small chips, which indicates good machinability.
It can be seen from the foregoing that, after different metal having a predetermined weight percentage is added, a brass alloy material is manufactured by using a high-frequency melting furnace, wherein the manufactured brass alloy material has machining properties equivalent to those of the conventional leaded brass, desirable tensile strength and elongation, and good dezincification resistance. The manufactured brass alloy is easily cut, does not contain lead, and is suitable for replacing the conventional leaded brass to manufacture products such as a faucet or accessories of bathroom products.
Described in the foregoing are merely implementation manners or embodiments for presenting the technical means employed in the present invention for solving the problems, and these implementation manners or embodiments are not intended to limit the implementation scope of the present invention patent. Any equivalent change and modification made in consistency with the content of the scope of the present invention patent application or in accordance with the scope of the present invention patent shall fall within the scope of the present invention patent.

Test 4 (T4)

Test 5 (T5)

What is claimed is:

1. A brass alloy, with a total weight percentage thereof counted as 100 wt %, the brass alloy comprising the following elements: 60 wt % to 65 wt % of copper, 0.1 wt % to 0.35 wt % of bismuth, 0.15 wt % to 0.5wt % of antimony, a balance of zinc, and an inevitable impurity.

2. The brass alloy according to claim 1, further comprising one or a mixture of more than one selected from aluminum, tin, phosphorus, manganese, and boron, wherein total content of the selected mixture accounts for 0.2 wt % to 2 wt % of the brass alloy.

3. The brass alloy according to claim 1, wherein total content of the inevitable impurity is less than 0.1 wt % of nickel, less than 0.1 wt % of chromium, or less than 0.1 wt % of iron.

4. A method for manufacturing a brass alloy, comprising the following steps of:

providing copper and manganese;

heating the copper and manganese until a temperature rises to between 1100 and 1150 degrees centigrade, so that the copper and manganese are formed to a molten copper-manganese alloy;

decreasing the temperature of the molten copper-manganese alloy to between 950 and 1000 degrees centigrade;

covering a surface of the molten copper-manganese alloy with a rice husk ash;

adding zinc to the molten copper-manganese alloy, so as to form a molten copper-manganese-zinc alloy;

removing slag from the molten copper-manganese-zinc alloy;

adding antimony, bismuth, aluminum, or tin to the molten copper-manganese-zinc alloy, to form a molten metal alloy;

increasing a temperature of the molten metal alloy to between 1000 and 1050 degrees centigrade, and adding a copper-boron alloy and a phosphorus-copper alloy, to form a molten brass alloy; and

tapping the molten brass alloy out of a furnace and casting the molten brass alloy to form the brass alloy.

5. The method for manufacturing a brass alloy according to claim 4, wherein the step of removing slag from the molten copper-manganese-zinc alloy further comprises removing the slag by using a slag remover.

6. The method for manufacturing a brass alloy according to claim 4, wherein the step of heating the copper and manganese until a temperature rises to between 1100 and 1150 degrees centigrade lasts 30 minutes.

7. The method for manufacturing a brass alloy according to claim 4, wherein the brass alloy, with a total weight percentage thereof counted as 100 wt %, comprises the following elements: 60 wt % to 65 wt % of the copper, 0.1 wt % to 0.35 wt % of the bismuth, 0.15 wt % to 0.5wt % of the antimony, a balance of the zinc, and an inevitable impurity.

8. The method for manufacturing a brass alloy according to claim 4, wherein total content of aluminum, tin, phosphorus, manganese, and boron accounts for 0.2 wt % to 2 wt % of the brass alloy.

9. The method for manufacturing a brass alloy according to claim 4, wherein a copper-manganese alloy is provided as a material for providing the copper and the manganese.

10. A brass alloy, with a total weight percentage thereof counted as 100 wt %, comprising 60.5 wt % to 64.5 wt % of copper, 0.15 wt % to 0.3 wt % of bismuth, 0.2 wt % to 0.35 wt % of antimony, 0.1 wt % to 0.25 wt % of aluminum, 0.05 wt % to 0.4 wt % of manganese, 0.1 wt % to 0.6 wt % of tin, 0.05 wt % to 0.2 wt % of phosphorus, 0.002 wt % to 0.005 wt % of boron, a balance of zinc, and an inevitable impurity.