EP1600516B1

EP1600516B1 - Lead-free, free-cutting copper alloys

Info

Publication number: EP1600516B1
Application number: EP05017190A
Authority: EP
Inventors: Keiichiro Oishi
Original assignee: Sambo Copper Alloy Co Ltd
Current assignee: Sambo Copper Alloy Co Ltd
Priority date: 1998-10-12
Filing date: 1998-11-16
Publication date: 2007-07-18
Anticipated expiration: 2018-11-16
Also published as: EP1600517A3; KR100352213B1; EP1045041A1; DE69839830D1; DE69840585D1; EP1559802B1; EP1600517B1; EP1600515B1; EP1600516A2; CA2314144A1; KR20010033073A; WO2000022182A1; DE69838115T2; EP1600515A2; EP1600517A2; DE69832097T2; CA2314144C; AU744335B2; JP2000119775A; EP1559802A1

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to lead-free, free-cutting copper alloys.

2. Prior Art

Among the copper alloys with a good machinability are bronze alloys such as the one under JIS designation H5111 BC6 and brass alloys such as the ones under JIS designations H3250-C3604 and C3771. Those alloys are enhanced in machinability by the addition of 1.0 to 6.0 percent, by weight, of lead and provide an industrially satisfactory machinability. Because of their excellent machinability, those lead-contained copper alloys have been an important basic material for a variety of articles such as city water faucets, water supply/drainage metal fittings and valves.
However, the application of those lead-mixed alloys has been greatly limited in recent years, because lead contained therein is an environment pollutant harmful to humans. That is, the lead-containing alloys pose a threat to human health and environmental hygiene because lead is contained in metallic vapour that is generated in the steps of processing those alloys at high temperatures such as melting and casting and there is also concern that lead contained in the water system metal fittings, valves and others are made of those alloys will dissolve out into drinking water.
On that ground, the United States and other advanced countries have been moving to tighten the standards for lead-contained copper alloys to drastically limit the permissible level of lead in copper alloys in recent years. Japan, too, the use of lead-contained alloys has been increasingly restricted, and there has been a growing call for development of free-cutting copper alloys with a low lead content.
The document GB-A-359 570 discloses a copper-silicon-zinc alloy with a content of 65 to 80 % of copper and 2 to 6 % of silicon.
The document US-A-1 954 003 discloses an alloy consisting of from 65 % and up to 94 % copper, from 2 % to 6 % silicon, from 3 % to 28 % zinc, and not more than 2 % aluminum.
The document GB-A-354 966 discloses copper-silicon-zinc alloys with up to 6 % silicon and up to 20 % zinc.
The document US-A-3 900 349 discloses a silicon brass alloy consisting of 3-21 weight % zinc, 2.5 to 7 weight % silicon, said amounts of zinc and silicon being sufficient to produce a structure consisting of alpha plus zeta phases in the brass, from 0.030 weight % up to the percentage by weight of solid solubility of one or more elements of the group consisting of arsenic, antimony and phosphorus, remainder being copper.
The document GB-A-1 443 090 discloses a silicon brass alloy consisting of 3-21 weight % zinc, 2.5 to 6 weight % silicon, said amounts of zinc and silicon being sufficient to produce a structure consisting of alpha plus zeta phases in the brass, from 0.030 weight % up to the percentage by weight of solid solubility of one or more elements of the group consisting of arsenic, antimony and phosphorus, remainder being copper.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a lead-free copper alloy which does not contain the machinability-improving element lead yet is quite excellent in machinability and can be used as safe substitute for the conventional free cutting copper alloy with a large content of lead presenting environmental hygienic problems which permits recycling of chips without problems, thus a timely answer to the mounting call for restriction of lead-contained products.
It is an another object of the present invention to provide a lead-free copper alloy which has a high corrosion resistance as well as an excellent machinability and is suitable as basic material for cutting works, forgings, castings and others, thus having a very high practical value. The cutting works, forgings, castings and others include city water faucets, water supply/drainage metal fittings, valves, stems, hot water supply pipe fittings, shaft and heat exchanger parts.
It is yet another object of the present invention to provide a lead-free copper alloy with a high strength and wear resistance as well as machinability which is suitable as basic material for the manufacture of cutting works, forgings, castings and other uses requiring a high strength and wear resistance such as, for example, bearings, bolts, nuts, bushes, gears, sewing machine parts and hydraulic system parts, hence has a very high practical value.
It is a further object of the present invention to provide a lead-free copper alloy with an excellent high-temperature oxidation resistance as well as machinability which is suitable as basic material for the manufacture of cutting works, forgings, castings and other uses where a high thermal oxidation resistance is essential, e.g. nozzles for kerosene oil and gas heaters, burner heads and gas nozzles for hot-water dispensers, hence has a very high practical value.
The objects of the present inventions are achieved by the present invention, thus:
In a first aspect, the present invention provides a lead-free, free-cutting copper alloy which comprises 70 to 80 percent, by weight, of copper; 1.8 to 3.5 percent, by weight, of silicon; 0.02 to 0.25 percent, by weight, of phosphorous and the remaining percent, by weight, of zinc and wherein the metal structure of the free cutting copper alloy has at least one phase selected from the γ (gamma) phase and the κ (kappa) phase.
Tin works the same way as silicon. That is, if tin is added to a Cu-Zn alloy, a gamma phase will be formed and the machinability of the Cu-Zn alloy will be improved. For example, the addition of tin in as amount of 1.8 to 4.0 percent by weight would bring about a high machinability in the Cu-Zn alloy containing 58 to 70 percent, by weight, of copper, even if silicon is not added. Therefore, the addition of tin to the Cu-Si-Zn alloy could facilitate the formation of a gamma phase and further improve the machinability of the Cu-Si-Zn alloy. The gamma phase is formed with the addition of tin in an amount of 1.0 or more percent by weight and the formation reaches the saturation point at 3.5 percent, by weight, of tin. If tin exceeds 3.5 percent by weight, the ductility will drop instead. With the addition of tin in less than 1.0 percent by weight, on the other hand, no gamma phase will be formed. If the addition is 0.3 percent or more by weight, then tin will be effective in uniformly dispersing the gamma phase formed by silicon. Through that effect of dispersing the gamma phase, too, the machinability is improved. In other words, the addition of tin in not smaller than 0.3 percent by weight improves the machinability.
Aluminum is, too, effective in promoting the formation of the gamma phase. The addition of aluminum together with tin or in place of tin could further improve the machinability of the Cu-Si-Zn. Aluminum is also effective in improving the strength, wear resistance and high temperature oxidation resistance as well as the machinability and also in keeping down the specific gravity. If the machinability is to be improved at all, aluminum will have to be added in at least 1.0 percent by weight But the addition of more than 3.5 percent by weight could not produce the proportional results. Instead, that could affect the ductility as is the case with aluminum.
As to phosphorus, it has no property of forming the gamma phase as tin and aluminum. But phosphorus works to uniformly disperse and distribute the gamma phase formed as a result of the addition of silicon alone or with tin or aluminum or both of them. That way, the machinability improvement through the formation of gamma phase is further enhanced. In addition to dispersing the gamma phase, phosphorus helps refine the crystal grains in the alpha phase in the matrix, improving hot workability and also strength and resistance to stress corrosion cracking. Furthermore, phosphorous substantially increases the flow of molten metal in casting. To produce such results, phosphorus will have to be added in an amount not smaller than 0.02 percent by weight. But if the addition exceeds 0.25 percent by weight, no proportional effect can be obtained. Instead, there would be a fall in hot forging property and extrudability.
In consideration of those observations, the alloy of the present invention has improved machinability by adding to the Cu-Si-Zn-P alloy at least one element selected from 0.3 to 3.5 percent, by weight, of tin and from 1.0 to 3.5 percent, by weight, of aluminum.
Meanwhile, tin, aluminum and phosphorus are to improve the machinability by forming a gamma phase or dispersing that phase, and work closely with silicon in promoting the improvement in machinability through the gamma phase. In the alloy of the present invention mixed with silicon along with tin or aluminum therefore, machinability is improved by not only silicon, but by tin or aluminum. Even if the addition of silicon is less than 2.0 percent by weight, silicon along with tin or aluminum will be able to enhance the machinability to an industrially satisfactory level as long as the percentage of silicon is 1.8 or more percent by weight. But even if the addition of silicon is not larger than 4.0 percent by weight, the addition of tin or aluminum will saturate the effect of silicon in improving the machinability, when the silicon content exceeds 3.5 percent by weight. On this ground, the addition of silicon is set at 1.8 to 3;.5 percent by weight in the alloy of the present invention.
The alloy of the present invention may additionally comprise at least one element selected from among 0.02 to 0.4 percent, by weight, of bismuth, 0.02 to 0.4 percent, by weight, of tellurium, and 0.02 to 0.4 percent, by weight, of selenium.
Bismuth, tellurium and selenium as well as lead do not form a solid solution in the matrix but disperse in granular form to enhance the machinability and that through a mechanism different from that of the silicon. Hence, the addition of those elements along with silicon could further improve the machinability beyond the level obtained by the addition of silicon alone. From this finding, the alloy of the present invention may further comprise at least one element selected from bismuth, tellurium and selenium mixed to improve further the machinability obtained by the first invention alloy. The addition of bismuth, tellurium or selenium in addition to silicon produces a high machinability such that complicated forms could be freely cut at a high speed. But no improvement in machinability can be realised from the addition of bismuth, tellurium or selenium in an amount less than 0.02 percent, by weight. Meanwhile, those elements are expensive as compared with copper. Even if the addition exceeds 0.4 percent by weight, the proportional improvement in machinability is so small that the addition beyond that does not pay economically. What is more, if the addition is more than 0.4 percent by weight, the alloy will deteriorate in hot workability such as forgeability and cold workability such as ductility. While it might be feared that heavy metals like bismuth would cause problems similar to those of lead, an addition in a very small amount of less than 0.4 percent by weight is negligible and would present no particular problems. The addition of those elements, which work on the machinability of the copper alloy through a mechanism different from that of silicon as mentioned above, would not affect the proper contents of copper and silicon.
The present invention also provides a method of forming a lead-free, free cutting alloy having a metal structure which has at least one phase selected from the γ (gamma) phase and the κ (kappa) phase which comprises alloying copper, silicon, phosphorous and zinc in an amount of 70 to 80 percent, by weight, of copper, 1.8 to 3.5 percent, by weight, of silicon; 0.02 to 0.25 percent, by weight, of phosphorus and the remaining percent by weight of zinc.
The method of the present invention may also further comprise subjecting said lead free, free cutting alloy to a heat treatment for 30 minutes to 5 hours at 400°C to 600°C.
The alloys of the present invention contain machinability improving elements such as silicon and have an excellent machinability because of the addition of such elements. Of those invention alloys, the alloys with a high copper content which have great amounts of other phases, mainly kappa phase, than alpha, beta, gamma and delta phases can further improve in machinability in a heat treatment. In the heat treatment, the kappa phase turns to a gamma phase. The gamma phase finely disperses and precipitates to further enhance the machinability. The alloys with a high content of copper are high in ductility of the matrix and low in absolute quantity of gamma phase, and therefore are excellent in cold workability. But in case cold working such as caulking and cutting are required, the aforesaid heat treatment is very useful. In other words those alloys of the present invention which are high in copper content with gamma phase in small quantities and kappa phase in large quantities (hereinafter referred to as the "high copper content alloy") undergo a change in phase from the kappa phase to the gamma phase in a heat treatment. As a result, the gamma phase is finely dispersed and precipitated, and the machinability is improved. In the manufacturing process of castings, expanded metals and hot forgings in practice, the materials are often force-air-cooled or water cooled depending on the forging conditions, productivity after hot working (hot extrusion, hot forging etc.), working environment and other factors. In such cases, among the alloys of the present invention those with a low content of copper (hereinafter called the "low copper content alloy") are rather low in the content of the gamma phase and contain beta phase. In a heat treatment, the beta phase changes into gamma phase, and the gamma phase is finely dispersed and precipitated, whereby the machinability is improved. Experiments showed that heat treatment is especially effective with high copper content alloys where mixing ration of copper and silicon to other added elements (except for zinc) A is given as 67 ≤ Cu - 3Si + aA or low copper content alloys with such a composition with 64 ≥ Cu - 3Si + aA. It is noted that a is a coefficient. The coefficient is different depending on the added element A. For example, with tin a is - 0.5; aluminum, -2; phosphorus, -3; antimony, 0; arsenic, 0; manganese, +2.5; and nickel, +2.5.
But a heat treatment temperature at less than 400°C is not economical and practical, because the aforesaid phase change will proceed slowly and much time will be needed. At temperatures over 600 C, on the other hand, the kappa phase will grow or the beta phase will appear, bringing about no improvement in machinability. From the practical viewpoint, therefore, it is desired to perform the heat treatment for 30 minutes to 5 hours at 400 to 600°C.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1 shows perspective views of cuttings formed in cutting a round bar of copper alloy by lathe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Example 1

As the first series of examples of the present invention, cylindrical ingots with compositions given in Tables 1 to 4, each 100 mm in outside diameter and 150 mm in length, were hot extruded into a round bar 15 mm in outside diameter at 750°C to produce the following test pieces: invention alloys Nos 3004 to 3007 and 3010 to 3012, and 4022 to 4049.
As comparative examples, cylindrical ingots with the compositions as shown in Table 5, each 100 mm in outside diameter and 150 mm in length, were hot extruded into a round bar 15 mm in outside diameter at 750°C to obtain the following round extruded test pieces: Nos. 14001 to 14006 (hereinafter referred to as the "conventional alloys"). No. 14001 corresponds to the alloys "JIS C 3604," No. 14002 to the alloy "CDA C 36000," No. 14003 to the alloy "JIS C 3771" and No. 14004 to the alloy "CDA C 69800." No. 14005 corresponds to the alloy "JIS C 6191". This aluminum bronze is the most excellent of the expanded copper alloys under the JIS designations with regard to strength and wear resistance. No. 14006 corresponds to the naval brass alloy "JIS C 4622" and is the most excellent of the expanded copper alloys under the JIS designations with regard to corrosion resistance.
To study the machinability of the alloys of the invention in comparison with the conventional alloys, cutting tests were carried out. In the tests, evaluations were made on the basis of cutting force, condition of chips cut surface condition.
The tests were conducted this way: The extruded test pieces obtained, as mentioned above, were cut on the circumferential surface by a lathe mounted with a point nose straight tool at a rake angle of - 8 degrees and at a cutting rate of 50 meters/minute, a cutting depth of 1.5 mm, a feed of 0.11 mm/rev. Signals from a three-component dynamometer mounted on the tool were converted into electric voltage signals and recorded on a recorder. From the signals were then calculated the cutting resistance. It is noted that while, to be perfectly exact, an amount of the cutting resistance should be judged by three component forces - cutting force, feed force and thrust force, the judgement was made on the basis of the cutting force (N) of the three component forces in the present example. The results are shown in Table 6 to Table 10.
Furthermore, the chips from the cutting work were examined and classified into four forms (A) to (D) as shown in Fig. 1. The results are enumerated in Table 6 to Table 10. In this regard, the chips in the form of a spiral with three or more windings as (D) in Fig. 1 are difficult to process, that is, recover or recycle, and could cause trouble in cutting work as, for example, getting tangled with the tool and damaging the cut metal surface. Chips in the form of an arc with a half winding to a spiral with two about windings as shown in (C), Fig. 1 do not cause such serious trouble as the chips in the form of a spiral with three or more windings yet are not easy to remove and could get tangled with the tool or damage the cut metal surface. In contrast, chips in the form of a fine needle as (A) in Fig. 1 or in the form of an arc as (B) will not present such problems as mentioned above and are not bulky as the chips in (C) and (D) and easy to process. But fine chips (A) still could creep into the sliding surfaces of a machine tool such as a lathe and cause mechanical trouble, or could be dangerous because they could stick into the worker's finger, eye or other body parts. Those taken into account, it is appropriate to consider the chips in (B) are the best, and the second best are the chips in (A). Those in (C) and (D) are not good. In Table 6 to Table 10, the chips judged to be shown in (B), (A), (C) and (D) are indicated by the symbols "⊚", "o", "Δ" and "x" respectively.
In addition, the surface condition of the cut metal surface was checked after cutting work. The results are shown in Table 6 to Table 10. In this regard, the commonly used basis for indication of the surface roughness is the maximum roughness (Rmax). While requirements are different depending on the application field of the brass articles, the alloys with Rmax < 10 microns are generally considered excellent in machinability. The alloys with 10 microns ≤ Rmax < 15 microns are judged as industrially acceptable, while those with Rmax ≥ 15 microns are taken as poor in machinability. In Table 6 to Table 9, the alloys with Rmax < 10 microns are marked "o", those with 10 microns ≤ Rmax < 15 microns are indicated as "Δ" and those with Rmax ≥15 microns are represented by a symbol "x".
As is evident from me results of the cutting tests shown in Table 6 to Table 10, the invention alloys 3004 to 3007 and 3010 to 3012 are all equal to the conventional lead- contained alloys Nos. 14001 to 14003 in machinability. Especially with regard to formation of the chips, those invention alloys are favourably compared not only with the conventional alloys Nos. 14004 to 14006 with a lead content of not higher than 0.1 percent by weight but also Nos. 14001 to 14003 which contain large quantities of lead.
In another series of tests, the alloys of the present invention were examined in comparison with the conventional alloys in hot workability and mechanical properties. For the purpose, hot compression and tensile tests were conducted the following way.
First, two test pieces, first and second test pieces, in the same shape 15 mm in outside diameter and 25 mm in length were cut out of each extruded test piece obtained as described above. In the hot compression tests, the first test piece was held for 30 minutes at 700°C, and then compressed 70 percent in the direction of axis to reduce the length from 25 mm to 7.5 mm. The surface condition after the compression (700°C deformability) was visually evaluated. The results are given in Table 6 to Table 10. The evaluation of deformability was made by visually checking for cracks on the side of the test piece. In Table 6 to Table 10, the test pieces with not cracks found are marked "o", those with small cracks are indicated in "Δ" and those with large cracks are represented by symbol "x".
The second test pieces were put to a tensile test by the commonly practiced test method to determine the tensile strength, N/mm² and elongation, %.
As the test results of the hot compression and tensile tests in Table 6 to Table 10 indicate, it was confirmed that the alloys of the present invention are equal to or superior to the conventional alloys Nos. 14001 to 14004 and No. 14006 in hot workability and mechanical properties and are suitable for industrial use.
Furthermore, the alloys of the present invention were put to dezincification and stress corrosion cracking tests in accordance with the test methods specified under "ISO 6509" and "JIS H 3250" respectively to examine the corrosion resistance and resistance to stress corrosion cracking in comparison with the conventional alloys.
In the dezincification test by the "ISO 6509" method, a sample taken from each extruded test piece was imbedded in a phenolic resin material in such a way that part of the side surface of the sample is exposed, the exposed surface perpendicular to the extrusion direction of the extruded test piece. The surface of the example was polished with emery paper No. 1200, and then ultrasonic-washed in pure water and dried. The sample thus prepared was dipped in a 12.7 g/l aqueous solution of cupric chloride dihydrate (CUCl₂.2H₂O) 1.0% and left standing for 24 hours at 75°C. The sample was taken out of the aqueous solution and the maximum depth of dezincification was determined. The measurements of the maximum dezincification depth are given in Table 6 to Table 10.
As is clear from the results of dezincification tests shown in Table 6 to table 10, the alloys of the present invention are excellent in corrosion resistance and favourable comparable with the conventional alloys Nos. 14001 to 14003 containing great amounts of lead.
In the stress corrosion cracking tests in accordance with the test method described in "JIS H 3250," a 150-mm long sample was cut out from each extruded test piece. The sample was bent with its centre placed on an arc shaped tester with a radius of 40 mm in such a way that one end and the other end subtend an angle of 45 degrees. The test sample thus subjected to a tensile residual stress was degreased and dried, and then placed in an ammonia environment in the desiccator with a 12.5% aqueous ammonia (ammonia diluted in the equivalent of pure water). To be exact, the test sample was held some 80 mm above the surface of aqueous ammonia in the desiccator. After the test sample was left standing in the ammonia environment for two hours, 8 hours and 24 hours, the test sample was taken out from the desiccator, washed in sulphuric acid solution 10% and examined for cracks under a magnifier of 10 magnifications. The results are given in Table 6 to Table 10. In those tables, the alloys which have developed clear cracks when held in the ammonia environment for two hours are marked "xx." The test samples which had no cracks at passage of two hours but were found to have clear cracks at 8 hours are indicated by "x." The test samples which had no cracks at 8 hours, but were found to have clear cracks at 24 hours were indicated by "Δ". The test samples which were found to have no cracks at all at least 24 hours are given a symbol "o."

As is indicated by the results of the stress corrosion cracking test given in Table 6 to Table 10, it was confirmed that the alloys of the present invention, in which nothing particular was done to improve corrosion resistance, were both equal to the conventional alloy No. 14005, an aluminum bronze containing no zinc, in stress corrosion cracking resistance and were superior in stress corrosion cracking resistance to the conventional naval brass alloy No. 14006, the one which has a highest corrosion resistance of all the expanded copper alloys under the JIS designations.

[Table 1]

No.	alloy composition (wt%)
No.	Cu	Si	Sn	Al	P	Zn
3001*	71.8	2.4	3.1			remainder
3002*	78.2	2.3		3.3		remainder
3003*	75.0	1.9	1.5	1.4		remainder
3004	74.9	3.2			0.09	remainder
3005	71.6	2.4	2.3		0.03	remainder
3006	76.5	2.7		2.4	0.21	remainder
3007	76.5	3.1	0.6	1.1	0.04	remainder
3008*	77.5	3.5	0.4			remainder
3009*	75.4	3.0	1.7			remainder
3010	76.5	3.3			0.21	remainder
3011	73.8	2.7			0.04	remainder
3012	75.0	2.9	1.6		0.10	remainder

* out of the scope of the invention

[Table 2]*

No.	alloy composition (wt%)
No.	Cu	Si	Sn	Al	Bi	Te	Se	Zn
4001	70.8	1.9	3.4		0.36			remainder
4002	76.3	3.4	1.3			0.03		remainder
4003	73.2	2.5	1.9				0.15	remainder
4004	72.3	2.4	0.6		0.29	0.23		remainder
4005	74.2	2.7	2.0		0.03		0.26	remainder
4006	75.4	2.9	0.4			0.31	0.03	remainder
4007	71.5	2.1	2.6		0.11	0.05	0.23	remainder
4008	79.1	1.9		3.3	0.28			remainder
4009	76.3	2.7		1.2		0.13		remainder
4010	77.2	2.5		2.0			0.07	remainder
4011	79.2	3.1		1.1	0.04	0.06		remainder
4012	76.3	2.3		1.3	0.13		0.04	remainder
4013	77.4	2.6		2.6		0.22	0.03	remainder
4014	77.9	2.2		2.3	0.09	0.05	0.11	remainder
4015	73.5	2.0	2.9	1.2	0.23			remainder
4016	76.3	2.5	0.7	3.2		0.04		remainder
4017	75.5	2.3	1.2	2.0			0.12	remainder
4018	77.1	2.1	0.9	3.4	0.03	0.03		remainder
4019	72.9	3.2	3.3	1.7	0.11		0.04	remainder
4020	74.2	2.8	2.7	1.1		0.33	0.03	remainder

* alloys of table 2 out of the scope of the invention

[Table 3]

No.	alloy composition (wt%)
No.	Cu	Si	Sn	Al	Bi	Te	Se	P	Zn
4021*	74.2	2.3	1.5	2.3	0.07	0.05	0.09		remainder
4022	70.9	2.1			0.11			0.11	remainder
4023	74.8	3.1				0.07		0.06	remainder
4024	76.3	3.2					0.05	0.02	remainder
4025	78.1	3.1			0.26	0.02		0.15	remainder
4026	71.1	2.2			0.13		0.02	0.05	remainder
4027	74.1	2.7			0.03	0.06	0.03	0.03	remainder
4028	70.6	1.9	3.2		0.31			0.04	remainder
4029	73.6	2.4	2.3			0.03		0.04	remainder
4030	73.4	2.6	1.7				0.31	0.22	remainder
4031	74.8	2.9	0.5		0.03	0.02		0.05	remainder
4032	73.0	2.6	0.7		0.09		0.02	0.08	remainder
4033	74.5	2.8				0.03	0.12	0.05	remainder
4034	77.2	3.3	1.3			0.03	0.12	0.04	remainder
4035	74.9	3-1	0.4		0.02	0.05	0.05	0.08	remainder
4036	79.2	3.3		2.5	0.05			0.12	remainder
4037	74.2	2.6		1.2		0.12		0.05	remainder
4038	77.0	2.8		1.3			0.05	0.20	remainder
4039	76.0	2.4		3.2	0.10	0.04		0.05	remainder
4040	74.8	2.4		1.1	0.07		0.04	0.03	remainder

* out of the scope of the invention

[Table 4]

No.	alloy composition (wt%)
No.	Cu	Si	Sn	Al	Bi	Te	Se	P	Zn
4041	77.2	2.7		2.1		0.33	0.05	0.05	remainder
4042	78.0	2.6		2.5	0.03	0.02	0.10	0.14	remainder
4043	72.5	2.4	1.9	1.1	0.12			0.03	remainder
4044	76.0	2.6	0.5	2.0		0.20		0.07	remainder
4045	77.5	2.6	0.7	3.1			0.21	0.12	remainder
4046	75.0	2.6	0.8	2.2	0.04	0.05		0.06	Remainder
4047	71.0	1.9	3.1	1.0	0.15		0.02	0.04	remainder
4048	73.3	2.1	2.6	1.2		0.04	0.03	0.05	remainder
4049	74.8	2.5	0.6	1.1	0.03	0.03	0.04	0.07	remainder

[Table 5]

No.	Alloy composition (wt%)
No.	Cu	Si	Sn	Al	Mn	Pb	Fe	Ni	Zn
14001	58.8		0.2			3.1	0.2		remainder
14001a	58.8		0.2			3.1	0.2		remainder
14002	61.4		0.2			3.0	0.2		remainder
14002a	61.4		0.2			3.0	0.2		remainder
14003	59.1		0.2			2.0	0.2		remainder
14003a	59.1		0.2			2.0	0.2		remainder
14004	69.2	1.2				0.1			remainder
14004a	69.2	1.2				0.1			remainder
14005	remainder			9.8	1.1		3.9	1.2
14005a	remainder			9.8	1.1		3.9	1.2
14006	61.8		1.0			0.1			remainder
14006a	61.8		1.0			0.1			remainder

[Table 6]

No.	machinability			corrosion resistance	hot workabitily	mechanical properties		stress resistance corrosion cracking resistance
No.	form of chippings	condition of cut surface	cutting force (N)	maximum depth of corrosion (µm)	700°C deformability	tensile strength (N/mm²)	elongation (%)	stress resistance corrosion cracking resistance
3001	⊚	Δ	128	40	○	553	26	○
3002	⊚	○	126	130	Δ	538	32	○
3003	⊚	○	126	50	○	526	28	○
3004	⊚	○	119	<5	○	533	36	○
3005	⊚	○	125	50	○	525	28	○
3006	⊚	○	120	<5	○	546	38	○
3007	⊚	○	121	<5	○	552	34	○
3008	⊚	○	122	80	○	570	36	○
3009	⊚	○	123	50	○	541	29	○
3010	⊚	○	118	<5	○	560	35	○
3011	⊚	○	119	20	○	502	34	○
3012	⊚	○	120	<5	○	534	31	○

[Table 7]

No.	machinability			corrosion resistance	hot workability	mechanical properties		stress resistance corrosion cracking resistance
No.	form of chippings	condition of cut surface	cutting force (N)	maximum depth of corrosion (µm)	700°C deformability	tensile strength (N/mm²)	elongation (%)	stress resistance corrosion cracking resistance
4001	⊚	○	119	40	Δ	512	24	○
4002	⊚	○	122	50	○	543	30	○
4003	⊚	○	123	50	○	533	30	○
4004	⊚	○	117	80	Δ	520	31	○
4005	⊚	○	119	50	○	535	32	○
4006	⊚	○	116	60	○	532	31	○
4007	⊚	○	122	50	○	528	26	○
4008	⊚	○	124	100	Δ	554	30	○
4009	⊚	○	119	130	○	542	34	○
4010	⊚	○	119	120	○	562	35	○
4011	⊚	○	122	100	Δ	563	34	○
4012	⊚	○	119	130	○	524	40	○
4013	⊚	○	120	110	○	548	37	○
4014	⊚	○	120	120	Δ	539	36	○
4015	⊚	○	121	40	○	528	28	○
4016	⊚	○	122	60	○	597	32	○
4017	⊚	○	120	50	○	520	33	○
4018	⊚	○	123	60	○	553	31	○
4019	⊚	○	118	40	○	606	24	○
4020	⊚	○	120	40	○	561	26	○

[Table 8]

No.	machinability			corrosion resistance	hot work ability	mechanical properties		stress resistance corrosion cracking resistance
No.	form of chip pings	condition of cut surface	cutting force (N)	maximum depth of corrosion (µm)	700°C deformability	tensile strength (N/mm²)	elongation (%)	stress resistance corrosion cracking resistance
4021	⊚	○	120	50	○	540	29	○
4022	⊚	○	123	<5	○	487	32	Δ
4023	⊚	○	117	<5	○	524	34	○
4024	⊚	○	117	40	○	541	37	○
4025	⊚	○	115	<5	Δ	526	43	○
4026	⊚	○	122	30	○	498	30	Δ
4027	⊚	○	118	30	○	516	35	○
4028	⊚	○	120	<5	○	529	27	○
4029	⊚	○	121	<5	○	544	28	○
4030	⊚	○	118	<5	○	536	30	○
4031	⊚	○	116	<5.	○	524	31	○
4032	⊚	○	114	<5	○	515	32	○
4033	⊚	○	118	<5	○	519	37	○
4034	⊚	○	118	<5	○	582	31	○
4035	⊚	○	117	<5	○	538	32	○
4036	⊚	○	118	<5	Δ	600	34	○
4037	⊚	○	117	20	○	523	34	○
4038	⊚	○	116	<5	Δ	539	38	○
4039	⊚	○	118	20	○	544	34	○
4040	⊚	○	117	40	○	522	31	○

[Table 9]

No.	machinability			corrosion resistance	hot workability	mechanical properties		stress resistance corrosion cracking resistance
No.	form of chippings	condition of cut surface	cutting force (N)	maximum depth of corrosion (µm)	700°C deformability	tensile strength (N/mm²)	elonga tion (%)	stress resistance corrosion cracking resistance
4041	⊚	○	120	20	○	565	31	○
4042	⊚	○	119	<5	○	567	34	○
4043	⊚	○	121	<5	○	530	29	○
4044	⊚	○	120	<5	○	548	31	○
4045	⊚	○	121	<5	○	572	32	○
4046	⊚	○	119	<5	○	579	29	○
4047	⊚	○	123	<5	○	542	26	○
4048	⊚	○	123	<5	○	540	28	○
4049	⊚	○	120	<5	○	439	33	○

[Table 10]

No.	machinability			corrosion resistance	hot work ability	mechanical properties		stress resistance corrosion cracking resistance	high-temperature oxidation
No.	form of chipings	condition of cut surface	cutting force (N)	maximum depth of corrosion (µm)	700°C deforma bility	tensile strength (N/mm²)	elongation (%)	stress resistance corrosion cracking resistance	increase in weight by oxidation (mg/10cm²)
14001	○	○	103	1100	Δ	408	37	xx	1.8
14002	○	○	101	1000	x	387	39	xx	1.7.
14003	○	Δ	112	1050	○	414	38	xx	1.7
14004	x	○	223	900	○	438	38	x	1.2
14005	x	○	178	350	Δ	735	28	○	0.2
14006	x	○	217	600	○	425	39	x	1.8

Claims

A lead-free, free-cutting copper alloy which comprises 70 to 80 percent, by weight, of copper, 1.8 to 3.5 percent, by weight, of silicon; 0.02 to 0.25 percent, by weight, of phosphorous; optionally at least one element selected from among 0.3 to 3.5 percent, by weight, of tin and 1.0 to 3.5 percent, by weight, of aluminium, and/or optionally least one element selected from among 0.02 to 0.4 percent, by weight, bismuth, 0.02 to 0.4 percent, by weight, of tellurium, and 0.02 to 0.4 percent, by weight, of selenium; and the remaining percent, by weight, of zinc and wherein the metal structure of the free cutting copper alloy has at least one phase selected from the γ (gamma) phase and the κ (kappa) phase.
A lead-free cutting copper alloy according to claim 1 wherein when cut on a circumferential surface by a lathe provided with a point nose straight tool at a rake angle of -8 (minus 8) and at a cutting rate of 50 m/min, a cutting depth of 1.5 mm, a feed rate of 0.11 mm/rev yields chips having one or more shapes selected from the group consisting of an arch shape and a fine needle shape.
A lead free, free-cutting copper alloy according to any one of the preceding claims which is subjected to a heat treatment for 30 minutes to 5 hours at 400 to 600°C.
A method of forming a lead-fee, free cutting alloy having a metal structure which has at least one phase selected from the γ (gamma) phase and the κ (kappa) phase which comprises alloying copper, silicon, phosphorous and zinc in an amount of 70 to 80 percent, by weight, of copper,1.8 to 35 percent, by weight, of silicon; 0.02 to 0.25 percent, by weight, of phosphorus optionally alloying at least one element selected from tin and aluminium in an amount of 0.3 to 3.5 percent, by weight, of tin and 1.0 to 3.5 percent, by weight, of aluminium, and for optionally alloying at least one element selected from bismuth, tellurium and selenium in an amount of 0.02 to 0.4 percent, by weight, bismuth, 0.02 to 0.4 percent, by weight, of tellurium, and 0.02 to 0.4 percent, by weight, of selenium; optionally alloying at least one element selected from bismuth, tellurium and selenium in an amount of 0.02 to 0.4 percent, by weight, bismuth, 0.02 to 0.4 percent, by weight, of tellurium, and 0.02 to 0.4 percent, by weight, of selenium; and the remaining percent by weight of zinc.
The method of any of claim 4 wherein said silicon is provided as a Cu-Si alloy.
The method of any one of claims 4 to 5 wherein said lead-free, free cutting alloy is subjected to a heat treatment for 30 minutes to 5 hours at 400 to 600°C.