AU646183B2 - Corrosion-resistant copper-based alloy - Google Patents

Description

Our Ref: 435209 P/00/011 Regulation 3:2

AUSTRALIA

64618 Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): Toyo Valve Co., Ltd 1-5-7, Nihonbashi Muromachi Chuo-ku

TOKYO

JAPAN

Sanbo Shindo Kogyo Co., Ltd 8-374, Sanbocho Sakai-shi

OSAKA-FU

JAPAN

DAVIES COLLISON CAVE Patent Trade Mark Attorneys Level 10, 10 Barrack Street SYDNEY NSW 2000 Address for Service: Invention Title: Corrosion-resistant copper-based alloy The fol3owing statement is a full description of this invention, including the best method of performing it known to me:- 5020 AMD/0604a 1 CORROSION--RESISTANT COPPER-BASED ALLOY The present invention relates to copper-based alloys which have been subjected to hot working, e.g. hot extrusion or drawing, and more particularly, it relates to corrosion-resistant copper-based alloys with excellent corrosion resistance resistance against dezincification corrosion and intergranular corrosion), mechanical properties, and machinability.

BACKGROUND OF THE INVENTION In general, the art has widely used copper-based alloys, such as forging brass AS1567-377, free-cutting brass AS1567-385, naval brass AS1567-464, high-tensile brass AS1567-678, aluminium bronze CDA-C16900, and the like.

These prior art copper-based alloys are, however, not satisfactory in regard to both corrosion resistance and machinability. For example, free-cutting brass bars, forging brass bars, etc., have the disadvantage that they are susceptible to dezincification corrosion in warm water, polluted water, or sea water, because of their high zinc contents. On the other hand, naval brass bars, aluminium bronze bars, and high-tensile brass bars, which are considered to be excellent in general corrosion resistance, have poor machinability and, in addition, are unsatisfactory in resistance to dezincification and dealuminization corrosion.

Thus, in recent years, the art has proposed copper-based alloys having improved resistance to dezincification corrosion, obtained by the addition of a very small amount of arsenic to those alloys, e.g.

AMD/0604a 2 65/35 brass-type or 60/40 brass-type copper-based alloys, examples of which are AS1567-335, AS1567-C352, AS1567-486, BS2874-CZ132, and the alloys disclosed in US Patent No.

3,963,526.

However, where a very small amount of arsenic is added to such alloys, e.g. 65/35 brass-type or 60/40 brass-type copper-based alloys, to reduce dezincification corrosion, impurities in the alloys, such as iron and manganese, must be limited to very small amounts. This is because arsenic is an element with high chemical activity, and when relatively large amounts of impurities, such as iron and manganese, are contained in the alloys, the arsenic is consumed by these impurities to produce compounds thereof.

Thus, the amount of arsenic available to form a solid solution, as an effective element in the substrate of the copper-based alloys, becomes insufficient, thereby making it difficult to attain the desired resistance to dezincification corrosion.

Consequently, in order to limit the contents of iron, manganese, and the like to satisfactory low levels, for ,example to 0.1 weight percent to 0.2 weight percent or less, return materials, which have been commercially recovered, must correspondingly be limited in these alloys to small amounts. This results in the necessity to use relatively large amounts of raw materials having high purity. For this reason, material cost of such alloys is high. On the other hand, when large amounts of return materials is used, the amount of these impurities becomes large, and a relatively large amount of arsenic must be used to compensate for the amount of arsenic consumed by these impurities.

This approach, however, gives rise to the following disadvantages. Because arsenic is an element which can readily cause segregation into grain 3 boundaries, the sensitivity of the resulting alloys to intergranular corrosion may be significantly increased by the deposition of arsenic compounds of, for example, iron, manganese, and the like, into the grain boundary, thereby causing severe intergranular corrosion.

Additionally, in some countries, such as Japan, the use of arsenic-containing materials has been subjected to drastic restrictions, in view of safety and health Sconsiderations, and, therefore, it is preferable to avoid the addition of arsenic to these alloys.

Thus, the art has made efforts to avoid or severely limit the necessity to use arsenic in such alloys, and other elements, rather than arsenic, have been proposed for reducing dezincification corrosion of such alloys.

In regard to copper-based alloys which reduce dezincification corrosion by the addition of elements other than arsenic, Hopper's metal S. Patent 3,404,977) and Okano's metal S. Patent 4,101,317) are notable examples. These alloys improve the resistance to dezincification corrosion by the contribution of tin and nickel, both of which are added to copper-zinc alloys in a relatively large amount.

Hopper's metal, however, is a casting alloy, and it is not well adapted to hot working, e.g.

extrusion or drawing. On the other hand, Okano's metal contains 1.2 to 2.0 weight percent tin, which is a relatively high content, and, depending upon the temperature condition in a hot working step, e.g. hot 3 extrusion, the y phase, constituted by Sn-rich Cu-Zn-Sn-type intermetallic compounds, will appear in the alloy. If such a y phase appears, the alloy will have decreased toughness and exhibit brittleness, so that cracks may readily form at the time of such hot working. Moreover, tin is prone to cause segregation, 4 and, therefore, it is difficult to stabilize the structure of the alloy. This results in a serious drawback in that the corrosion resistance of the alloy has a tendency to vary from part to part. This difficulty can be mitigated to a certain extent by adding a large amount of nickel, by conducting the hot working within an extremely narrow temperature range, and by a heat treatment over a long period of time.

However, this mitigation causes the disadvantages of, for example, significantly deteriorated operating characteristics in the production of the alloy, which becomes a problem in quality control and production yield (or cost). Furthermore, the addition of large amounts of expensive tin and nickel is economically unsound.

i It would, therefore, be of significant advantage to the art to provide corrosion-resistant copper-based alloys having a stable a single phase structure, excellent corrosion resistance (especially, resistance against dezincification corrosion and intergranular corrosion), mechanical properties, and machinability, but without the necessity to use arsenic and without the drawbacks, as explained above. It would be a further advantage to provide corrosion-resistant copper-based alloys which are easy to hot work, e.g. hot extrusion, where quality control in the production process is not a problem, with high production yields, and which alloys have stable quality at a low cost.

It would be of further advantage to the art to oooe provide corrosion-resistant copper-based alloys which are well suited for a wide range of applications, such as valve components (disc, stem, etc.), machinery parts, marine equipment, electric parts, shafts, pump shafts, bushes, tube-shaped members, plate-shaped members, and the like, because the alloys have excellent resistance 5 to corrosion caused by warm water, polluted water, sea water, or the like, and also have excellent machinability and mechanical properties.

Finally it would be an advantage to the art to provide such corrosion-resistant copper-based alloys whose working scrap, such as cutting waste, can be reutilized as a material of bronze casting and the like.

SUMMARY OF THE INVENTION The foregoing advantages are accomplished by copper-based alloys having a metal composition which comprises 61.0 to 65.0 weight percent copper, 1.0 to weight percent lead, 0.7 to 1.2 weight percent tin, 0.2 to 0.7 weight percent nickel, 0.03 to 0.4 weight percent iron, 0.02 to 0.10 weight percent antimony, and 0.04 to .A 0.15 weight percent phosphorus, with the balance being zinc and unavoidable associated impurities. These oo** S: alloys substantially have a a single phase structure, especially when the alloys have been subjected to hot working, e.g. hot extrusion or drawing, hot forging, or pressure die-casting of extruded or drawn materials, and more especially when heat treated. It is particularly preferable that the combined total content of antimony and phosphorus be about between 0.08 and 0.20 weight percent; the combined total content of tin and nickel be about between 1.0 and 1.6 weight percent; and the combined total content of copper and nickel be at least 61.5 weight percent. The preferred heat treatment is particularly useful when conducted at about between 500 and 600 C for about 30 minutes to 3 hours.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a photomicrograph showing the metal structure in normal cross-section magnified by 200 times with respect to the exposed surface of 6 copper-based alloy No. 1 of the Examples, after a dezincification corrosion test according to "ISO 6509".

Figure 2 is a photomicrograph showing the metal structure in normal cross-section magnified by 200 times with respect to exposed surfaces of copper-based alloy No. 2 of the Examples, after the same test as described above.

Figure 3 is a photomicrograph showing the metal structure in normal cross-section magnified by 200 times with respect to exposed surfaces of copper-based alloy No. 3 of the Examples, after the same test as described above.

Figure 4 is a photomicrograph showing the metal structure in normal cross-section magnified by 200 times with respect to exposed surfaces of copper-based alloy No. 4 of the Examples, after the same test as described above.

Figure 5 is a photomicrograph showing the metal structure in normal cross-section magnified by 100 2 times with respect to exposed surfaces of copper-based alloy No. 6 of the Examples, after the same test as described above.

Figure 6 is a photomicrograph showing the metal structure in normal cross-section magnified by 100 times with respect to exposed surfaces of copper-based alloy No. 7 of the Examples, after the same test as described above.

Figure 7 is a photomicrograph showing the S:..."metal structure in normal cross-section magnified by 200 times with respect to exposed surfaces of copper-based alloy No. 9 of the Examples, after the same test as described above.

Figure 8 is a photomicrograph showing the metal structure in normal cross-section magnified by 200 times with respect to exposed surfaces of copper-based 7 alloy No. 10 of the Examples, after the same test as described above.

DETAILED DESCRIPTION OF THE INVENTION As briefly noted above, a feature of the present invention is that of the present alloys having a marked increase in the volume of a single phase structure or substantially an a single phase structure, as opposed to conventional alloys.

The increase in the volume of the a phase for such brass materials, e.g. cast materials, extruded materials, and drawn materials, is caused in the present alloys when the copper content is 62 weight percent or more, although this increase also depends upon the nickel content. To obtain a substantially a single phase structure, the copper content should be at least 63 weight percent. However, when the present appropriate heat treatment is conducted after hot working, e.g. extrusion, it is possible to obtain a stable a single phase structure when the copper content is as low as 61.0 weight percent, due to the synergistic effect with nickel, as described below. While it is, thus, possible to obtain the a phase with increased copper content, alone (which also improves corrosion resistance), decreases in mechanical properties, e.g.

S tensile strength and hardness, of the alloy occur with such increased copper contents. Thus, taking into consideration the fact that dezincification corrosion occurs in the structure of any phase, e.g. the P phase, other than the a phase, and considering the decrease in mechanical properties with higher copper contents, the copper content should be between about 61.0 and 65.0 weight percent. This is also an economical range in which a stable a phase structure can be obtained, especially after heat treatment. The mechanical 8 properties of this range are not significantly deteriorated. Preferably, however, the copper should also be in amounts that the combined total content of copper and nickel is at least 61.5 weight percent.

Tin is added in order to improve the corrosion resistance. While the tin content in the above-described Okano's metal is relatively large, i.e.

1.2 to 2.0 weight percent, through experiments it was found that a stable a phase structure is obtained, especially after heat treatment, when the amount of tin in the alloy is much smaller. Thus, satisfactory corrosion resistance can be obtained with these smaller amounts, especially with the nickel, antimony, and phosphorus contents, as described below. With an addition of less than 0.7 weight percent tin, a significant improvement in the corrosion resistance cannot be obtained. It was further found that with more .eeD than 1.2 weight percent of tin, the y phase, which is brittle, is prone to appear. Thus, the tin content should be between about 0.7 and 1.2 weight percent, which is also consistent with desired economy, since tin is an expensive metal.

:Lead is added in order to improve the machinability of the alloy. With an addition of less than 1.0 weight percent lead, satisfactory machinability cannot be obtained, whereas with the addition of too much lead, the hot working, e.g. hot extrusion, in the production process is difficult. It is noted that the """maximum amount of lead in the above-described Okano's S0 metal is 2.0 weight percent. As described above, the minimum present conL.nt of copper is decreased to 61.0 weight percent, and, with this, the hot working, e.g.

hot extrusion, is easy and stably produced, even with a lead addition of more than 2.0 weight percent. However, with an addition of more than 3.5 weight percent lead, 9 the elongation, impact value, and the like decrease.

For this reason, the lead content should be between about 1.0 and 3.5 weight percent.

Nickel is added in order to improve the corrosion resistance by the synergistic effect with tin and to improve the mechanical properties of the alloy.

Since nickel has a negative zinc equivalent, the a phase structure has increased volumes with increased amounts of nickel. Therefore, with the addition of nickel, it lu is possible to not only prevent an increase in the volume of the P phase but also to prevent the appearance of an Sn-rich y phase, i.e. Cu-Zn-Sn-type intermetallic compounds, and this is true even when the copper content is decreased to as little as 61.0 weight percent. Heat treatment after hot working, e.g. hot extrusion, makes possible to obtain a stable a phase structure and to improve toe corrosion resistance, and particularly resistance against dezincification corrosion. Moreover, the addition of nickel makes it possible to obtain •"2V alloys with high mechanical strength, even though they have a stable a phase structure. However, with an addition of less than 0.2 weight percent nickel, such effects are minimal. On the other hand, there is no necessity for improvements in corrosion resistance and increased mechanical strength achieved by nickel contents above about 0.7 weight percent, and, in fact, there is a problem with higher contents from an economic point of view. For this reason, the nickel content should be between about 0.2 and 0.7 weight percent.

Moreover, in consideration of the synergistic effect with tin, it is preferable that the conmbined total content of nickel and tin should be between about and 1.6 weight percent.

Antimony is added in order to suppress the dezincification corrosion together with the addition of 10 tin and phosphorus. Because antimony is an element with high chemical activity, it not only forms a solid solution in the substrate of the alloy, but also forms a solid solution together with lead to a certain extent, particularly in the case of lead-containing brass.

Therefore, an effective amount of antimony must be determined in relation to the added amount of antimony forming a solid solution. According to the results of experiments, it is necessary in the case of i lead-containing brass to add at least about 0.02 weight percent lead for the purpose of ensuring the effective action of resistance to dezincification corrosion. On the other hand, with an addition of more than 0.10 weight percent antimony, the alloy becomes brittle, and particularly, the hot-processing characteristics of the alloy are deteriorated. Thus, in casps where the addition of antimony is only intended to improve the o.o.

corrosion resistance, it is possible that the industrial S"usefulness of the alloy may be deteriorated. For these reasons, the antimony content should be between about Sp "0.02 and 0.10 weight percent, especially in consideration of its interrelationship with tin, phosphorus and lead.

Phosphorus is added in order to suppress the dezincification corrosion, together with the addition of tin and antimony, as described above. Phosphorus is an *Celement with high chemical activity, similar to antimony, so it can readily form compounds with iron and can affect the corrosion resistance. While deposited or o..

soliC solutions of unformed iron can produce compounds with phosphorus to improve the corrosion resistance, phosphorus is consumed by iron, so that the desired effect achieved by the addition of phosphorus is decreased. Therefore, the appropriate amount of phosphorus to be added should be determined in 11 consideration of the amount of phosphorus which will be consumed by the iron. Moreover, with the addition of too much phosphorus, segregation is caused in the grain boundary, so that sensitivity to intergranular corrosion is significantly increased, along with a decrease in the ductility. According to the zisults of the experiments, in the above-described Okano's metal, if phosphorus is not added in an amount of 0.2 weight percent or more, phosphorus can hardly form a solid solution in the ±0 substrate of the alloy because phosphorus preferentially forms compounds with iron. With an additr.ion of phosphorus in an amount of 0,2 weight percent or more, the sensitivity to grain-boundary corrosion is increased and the compounds are deposited in the grain boundary, thereby deterioratin- the corrosion resistance. For this reason, the iron content should be in small amounts, as described below, and the appropriate addition range of phosphorus should be between about 0.04 and 0.15 weight percent, in consideration of its interrelationship with tin and antimony.

Moreover, because both antimony and .phosphorus, as described above, have a property of readily causing segregation in the grain boundary, the combined total amount of both elements in excess of 0.20 weight percent decreases the ductility, and, particularly, the hot-processing characteristics are deteriorated. On the other hand, to ensure more stable corrosion resistance by the interaction of these elements and tin, it is preferable to add antimony and phosphorus at a combined total amount in the range of about 0.08 to 0.20 weight percent.

Iron also has the effect of making the alloy crystals very fine, thereby enhancing the strength of the alloy, although the addition of too little iron decreases this effect to an unsatisfactory extent.

12 Because phosphorus, as described above, also has the effect of making the crystal grains very fine, somewhat to the same degree or more than that of iron, phosphorus can make a significant contribution by its synergistic effect with iron, e.g. to the degree of making the crystal grains similarly very fine, as well as improving the mechanical properties. With an addition of less than about 0.03 weight percent iron, such a synergistic effect of phosphorus and iron is not exhibited to a i satisfactory extent. On the other hand, according to the r.sults of the experiments, the solid solution of unformed or deposited iron has an adverse effect on the corrosion resistance in that it can form compounds with phosphoris, as described above, and thereby significantly decrease the adverse effect of iron on the corrosion resistance. With an addition of more than 0.4 weight percent iron, however, the amount of phosphorus-iron compounds is increased to consume phosphorus, such that the amount of phosphorus added to the substrate of the alloy becomes insufficient, thereby making it impossible to obtain the desired corrosion :resistance. Furthermore, because of the possibility of compounds deposited in the grain boundary becoming high, the sensitivity to intergranular corrosion is increased.

With an increase in the amount of iron-phosphorus compounds, the machinability is also decreased. Taking into consideration the improvement in the corrosion S"resistance and mechanical properties, the maintenance of 5555 machinability, and the economy in the use of return materials, the iron content should, therefore, be between about 0.03 and 0.4 weight percent.

Because hot extrusion is usually conducted at a high temperature, e.g. of 700 to 770' C, extruded or drawn materials have an unequilibrium structure, and it is possible that the P phase, having an adverse effect 13 on the corrosion resistance, may remain. At the same time, the local segregation of zinc, tin, iron, nickel, antimony, and phosphorus (particularly tin, antimony, and phosphorus) occurs, mainly, in the crystal grain boundary.

For these reasons, in the preferred form of the present invention, the extruded or drawn materials, after hot extrusion or drawing, are subjected to a heat treatment annealing), so that any remaining P 1. phase is eliminated, local mis-distribution of elements at the grain boundary is eliminated, and the concentration and distribution of elements in the grains at the grain boundary becomes uniform. This makes it possible not only to enhance the corrosion resistance, .I including the resistance against intergranular corrosion, but also to prevent decreases in the ductility of the alloy, arising from an increase in the 0 concentrations of tin, antimony, and phosphorus at the grain boundary. According to the results of the experiments, it -s found that with annealing tem. Iratures of greater than about 6000 C, the disappearance of the P phase becomes difficult, whereas at temperatures lower than about 500 C, long annealing times are required to dissolve the local mis-distribution of elements at the grain boundary and o0e0 to allow the P phase to disappear. Furthermore, with annealing times of less than 30 minutes, the above-described annealing effect is not exhibited to a satisfactory extent. On the other hand, with annealing times of more than 3 hours, the above-described annealing effect remains substantially unchanged and the longer annealing times are economically wasteful. For these reasons, it is preferable that hot extruded or drawn materials are subjected to heat treatments at about 5000 and 600* C for about 30 minutes to 3 hours.

AMD/0604a 14

EXAMPLES

As examples, copper-based alloys having the respective compositions shown in Table 1 were hot-extruded into a rod shape having a diameter of 20 mm, followJe by subjecting the rods to heat treatment, i.e. annealing, at 550 0 C for minutes, resulting in copper-based alloys Nos. 1 to 3 of the present invention.

As comparative examples, copper-based alloys have the respective compositions shown in Table 1 were hot-extruded into a rod shape having a diameter of 20 mm, under the same conditions as those used for the above-described copper-based alloys Nos. 1 to 3, resulting in copper-based alloys Nos. 4 to 8 which had not been subjected to heat treatment, and copper-based alloys Nos. 9 and 10 which had been subjected to heat treatment at 500 0 C for 3 hours.

Among the copper-based alloys in the comparative examples, No. 4 is the same as No. 1, except that it had not been subjected to heat treatment. Also, copper-based alloys Nos. 5, 6, 7, 8, 9 and 10 correspond to free-cutting brass AS1567-385, forging brass AS1567-377, naval brass AS1567-464, high-tensile brass AS1567-678, AS1567-352, and Okano's metal (US Patent No. 4,101,317), respectively.

e *o a *e C C C C CC C a.

a a a [Table 11 Allay composition w t Alloy No. H le at Cu Pb 'Sn Fe Ni Sb P Mn Al As Zn treatment 1 61.75 2.78 0.92{0.23 0.57 0.07 0.04 Balance Treated Examples 2 62.96 1.78 1.10 0.18 0.42 0.05 0.07 Balance Treated 3 64. 10 2. 23 0. 78 0. 30 0. 37 0. 03 -0.11 Balance Trea'ted 4 61.75 2. 78 0. 92 0.23 0. 57 0.07 0. 04 Balance Untreated 58. 58 3. 12 0.26 0. 25 0.07 Balance U atrealed 6 58. 86 2. 08 0.29 0. 24 0. 10 Balance Untreated Compara- tive 7 60.23 0.04 0.79 0.06 Balance Untreated examples 8 57.45 0.31 0.17 0.46 0.04 0.81 0.70 Balance Untreated 9 62. 81 1. 97 0. 05 0. 03 0. 14 0. 25 Balance Treated 64.27 1.84 1.45 0.79 0.71 Balance Treated 16 These copper-based alloys were respectively tested for their mechanical properties, e.g. tensile strength, elongation, hardness, and machinability, and the results are shown in Table 2. The machinability was evaluated with drill-test values, which are the usually applied CDA standard. The drill-test value refers to the piercing-time ratio of the sample to that of the standard sample (free-cutting brass), and the greater the value of the ratio, the greater the machinability.

As can be seen from the test results shown in Table 2, the copper-based alloys Nos. 1 to 3 of the present invention (although all of -them contain relatively larger amounts of elements, such as tin, phosphorus and antimony, which have the usual property of improving the corrosion resistance but decreasing the elongation) exhibit remarkable elongation. This is because these elements in the present invention form a uniform solid solution In the substrate of the alloy.

It will also be noted that these alloys exhibit "2U excellent machinability because of the lead content.

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17 (Table 2) St Mechanical properties Machinability Alloy No. Tensile strength Elongation Hardness Dtill-test-value N/mm 2 HR (B) 1 452 26.8 68 91 Examples 2 453 36.14 69 68 3 450 314.14 j 68 14 459 21.6 71 87 441 25.14 66 100 6 458 33.14 69 72 Compar'a- tive 7 429 37.8 614 examples 8 6146 18.0 81 9 380 31.0 62 435 28.14 65 57 S S S 5555.

18 Furthermore, the above-described copper-based alloys were subjected to the dezincification corrosion test according to the method defined by "ISO 6509", and the results (depth of dezincification corrosion maximum and average values as well as the corrosion form) is shown in Table 3. These values are much smaller than the acceptable depth of dezincification corrosion defined by BS2872-1989, which is the same test method as ISO 6509, and are much smaller than the 1_ acceptable depth of dezincification corrosion defined by AS1628 Amendment No. 4-1989-08-04.

In the dezincification corrosion test defined by "ISO 6509", the sample obtained from each of copper-based alloys Nos. 1 to 10 was embedded in a phenol resin material with its exposed sample surface being at right angles to the direction of extension of *extruded or drawn materials, and the sample surface was polished using a series of emery paper up to #1200 fineness, followed by ultrasonic cleaning and then drying. The corrosion test sample, thus obtained, was immersed in an 1.0% aqueous solution (12.7 g/l) of S*.i cupric chloride dihydrate (CuCl 2H 2 and maintained at 75° C for 24 hours, after which it was removed from the aqueous solution and the extent of dezincification and intergranular corrosion and the form of corrosion were determined by photomicrographs. The maximum and average values of the depth of dezincification corrosion were also measured. Typical examples of the above-mentioned photomicrographs (for copper-based alloys Nos. 1 to 4, 6, 7, 9 and 10) are shown in Figures 1 to 8.

As can be seen from the test results of Table 3, copper-based alloys Nos. 1 to 3 of the present invention exhibited a depth of dezincification corrosion (maximum value) of 0.03 mm or less, and it will be 19 appreciated that this is excellent resistance to dezincification and intergranular corrosion, as compared with copper-based alloys Nos. 4 to 10 of the comparative examples. Because the tin content of copper-based alloys Nos. 1 to 3 is relatively small, the segregation of tin and the like is unlikely to occur. It was also confirmed by these results that there was no significant variation in the corrosion resistance and the like, resulting from the difference in the conditions of heat lu treatment. Thus, the control of the heat-treatment is not critical in that very little variations in corrosion resistance occurred as a result of the variations in heat treatment used by the present invention.

a.

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S.

S S S Depth of dezincification corrosion A3~loy (mm) No.

Maximum Average Corrosion form 1 0.03 0.01 or less Intergranular corrosion Examples 2 0.02 0..01 or less Intergranular corrosion 3 0.02 0.01 or less Intergranular corrosion 14 0.3 0.18 or less Intergranular corrosion 5 1.2 1.00 Overall corrosion 6 1.1 0.90 Overall corrosion Comparative 7 0.6 0.142 Overall corrosion examples- 8 0.8 0.52. Overall corrosion 9 0.13 0.10 Intergranular corrosion 10 0.18 0.10 7 -selective corrosion S S

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Claims (10)

1. A corrosion-resistant copper-based alley having a metal composition comprising 61.0 to 65.0 weight percent copper, to 3.5 weight percent lead, 0.7 to 1.2 weight percent tin, 0.2 to 0.7 weight percent nickel, 0.03 to 0.4 weight percent iron, 0.02 to 0.10 weight percent antimony, and 0.04 to 0.15 weight percent phosphorus, with the balance being zinc and associated impurities, and having an alloy structure changed to a substantially a single phase structure by heat treatment.

2. The alloy of claim 1 which is a hot worked alloy.

3. The alloy of claim 2 which is a hot extruded or hot drawn alloy.

4. The alloy of claim 1 which is a hot forged or pressure die-cast hot extruded or hot drawn alloy.

The alloy of claim 1 wherein the temperature of the heat treatment is about 500°C to 600 0 C.

6. The alloy of claim 5 wherein the time of heat treatment is about 30 minutes to 3 hours.

7. The alloy of claim 1, wherein the combined total coo• content of antimony and phosphorus is 0.08 to 0.20 weight percent.

8. The alloy of claim 1, wherein the combined total content of tin and nickel is 1.0 to 1.6 weight percent.

9. The alloy of claim 1, wherein the combined total content of copper and nickel is at least 61.5 weight percent.

10. A corrosion-resistant copper-based alloy substantially as hereinbefore described with reference to the accompanying figures. DATED this 26th day of November 1993. TOYO VALVE CO., LTD. and SANBO SHINDO KOGYO CO., LTD. By Their Patent Attorneys C, DAVIES COLLISON CAVE ABSTRACT OF THE DISCLOSURE The present invention relates to corrosion-resistant, copper-based alloys having a metal composition which comprises 61.0 to 65.0 weight percent copper, 1.0 to 3.5 weight percent lead, 0.7 to 1.2 weight percent tin, 0.2 to 0.7 weight percent nickel, 0.03 to 0.4 weight percent iron, and a combination of 0.02 to 0.10 weight percent antimony and 0.04 to 0.15 weight percent phosphorus in a combined total amount of 0.08 to 0.20 weight percent, with the balance being zinc and unavoidable associated impurities, and substantially having an alpha single phase structure, and where the alloys have been subjected to hot working, e.g. extrusion or drawing, and then to heat treatment at 500° 1c to 600* C for 30 minutes to 3 hours. *e