Discoloration-resistant gold alloy

Abstract

Alloy for the manufacturing of jewels or clock components with minimum concentrations of gold of 75 wt %, of copper between 5% and 21%, of silver between 0% and 21%, of iron between 0.5% and 4% and vanadium between 0.1% and 2.0%, intended to increase the tarnishing-resistance of alloys with a minimum content of gold of 75 wt % under environments in which Sulphur- and chlorine-compounds are present.

Claims

1. A gold alloy for manufacturing jewels or clock components, the gold alloy consisting of the following elements, with the following percent concentration by weight: gold at least 75 wt %, copper between 5 and 21 wt %, silver between 0 and 21 wt %, iron between 0.5 and 4 wt % and vanadium between 0.1 and 2 wt %, and optionally palladium between 0.5 wt % and 4 wt % or iridium in content equal or less than 0.05 wt %.

2. The gold alloy according to claim 1, with concentrations of iron greater than 1 wt % and below or equal to 4 wt % and vanadium greater than 0.2 wt % and below or equal to 2 wt %.

3. The gold alloy with contents according to claim 1, wherein iron is present in contents between 0.5 and 2 wt %, vanadium between 0.2 and 1.5 wt %, and palladium is also present between 0.5 and 2 wt %.

4. The gold alloy according to claim 3, wherein a ratio between a sum of iron and palladium concentrations and vanadium concentration is greater than 4.

5. The gold alloy according to claim 1, wherein copper is present in contents between 16 and 21 wt %, iron between 0.5 and 4 wt % and vanadium between 0.1 and 1 wt %.

6. The gold alloy according to claim 5 with concentrations of iron greater than 1 wt % and below or equal to 4 wt % and vanadium greater than 0.2 wt %, and below or equal to 1 wt %, wherein a ratio between iron and vanadium content is greater than 4.

7. A method for producing a gold alloy for manufacturing of jewels or clock components, the method comprising the steps of: a) melting under stirring, by means of an induction furnace equipped with a graphite crucible, Au 99.999%, Cu 99.999%, Fe 99.99%, Ag 99.99%, V>99.5% pure elements, and optionally Pd 99.95% pure or Ir, under controlled argon atmosphere from 500 mbars to 800 mbars inside a specific melting chamber, the latter being previously subjected to at least three conditioning cycles, said conditioning cycles providing for an achievement of a vacuum lower than 110.sup.2 mbars and a succeeding partial saturation with argon preferably at 500 mbars; b) overheating the melt elements at a temperature of up to 1250 C. and at a residual pressure lower than 110.sup.2 mbars in order to homogenize the chemical composition of the melt elements; c) casting, under controlled atmosphere, the melted metals in graphite molding boxes of rectangular section, upon pressurization, in the melting chamber, with argon at 800 mbars; d) extracting quenched alloy ingots from the molding boxes, said quenching occurring in water; and e) deforming the quenched alloy ingots up to 70%, induced by means of cold plastic processing, said plastic processing providing for a planar lamination of the quenched alloy ingots, an annealing of the quenched alloy ingots at temperatures greater than 680 C. and a subsequent quenching of said quenched alloy ingots in water, the gold alloy thus consisting of the following elements, with the following percent concentration by weight: gold at least 75 wt %, copper between 5 and 21 wt %, silver between 0 and 21 wt %, iron between 0.5 and 4 wt % and vanadium between 0.1 and 2 wt %, and optionally palladium between 0.5 wt % and 4 wt % or iridium in content equal or less than 0.05 wt %.

8. The method according to claim 7, comprising carrying out hardness measurements during all steps according to the preceding claim, said hardness measurements occurring at work-hardened, annealed condition and after a further thermal treatment carried out at 300 C., by using an applied load at least equal to 9.8 N during a time of 15 seconds.

9. The method according to claim 8 comprising smoothing, polishing, and analysis of said elements, said processed elements being smoothed by means of abrasive papers and subsequently polished with diamond pastes with grain size of 1 m, until a constant reflection factor is achieved.

Description

DESCRIPTION OF TABLES AND FIGURES

(1) TABLE 1 shows the composition and the main physical characteristics of the alloys disclosed in the present document. For each composition, the values tabulated in columns L*.sub.0, a*.sub.0, b*.sub.0 are evaluated with the use of a spectrophotometer Konica Minolta CM-3610d. These measurements are performed under reflection conditions with the use of a light source D65-6504K, a di/de observation angle of 8, and a measurement area of 8 mm (MAV). The measurements are carried out on samples immediately after a careful processing of their surfaces. The surface processing of samples of the various compositions disclosed herein includes smoothing with abrasive papers followed by polishing. Smoothing is performed by means of abrasive papers, whereas polishing is carried out with diamond pastes having a grain size of up to 1 m. This processing is carried out until a constant reflection factor is reached. Such a processing is essential, and it is carried out in order to remove traces of any compound which can alter the surface composition of the alloy and its actual color, thereby having the potential to distort the experimental measurements. The hardness values shown herein are measured alter a flatbed lamination hardening of the material to 70% (column 70% hardened), alter an annealing treatment at 680 C. (column Annealed), and after a heat-treatment hardening performed at a temperature of 300 C. (column Aged). Hardness tests are carried out with an applied load of 9.8 N (HV1) which is maintained for 15 seconds, as specified by standard ISO 6507-1.

(2) Table 2 shows the E(L*,a*,b*) values measured alter 150 hours of exposure to thioacetamide vapors (column Exposure to thioacetamide vapors (150 hrs)) and after 175 hours of immersion in a saturated solution of sodium chloride at neutral pH and at a thermostated temperature of 35 C. (column Immersion in saturated aqueous NaCl (175 hrs)). The values shown for parameters E(L*,a*,b*) relate to spectrophotometric measurements of the values of coordinates L*,a*,b* as taken at defined time intervals. The values thus obtained for coordinates CIE 1976 L*a*b* allow the kinetics of surface discoloration of the test sample to be quantified by evaluating the parameter E*(L*,a*,b*)=[(L*L*.sub.0).sup.2+(a*a*.sub.0).sup.2+(b*b*.sub.0.sup.2)].sup.1/2 over time. This parameter is calculated with respect to the values of coordinates L*.sub.0, a*.sub.0, b*.sub.0 for the test alloy (values shown in table 1).

(3) FIG. 1 shows the change in surface color for an alloy 5 N ISO 8654 while exposed to a generic ambient atmosphere at 25 C.

(4) FIG. 2 shows the color changes E(L*,a*,b*) for composition 5 N ISO 8654, composition L11 and composition L01 as evaluated while carrying out tests according to standard ISO 4538.

(5) FIG. 3 shows the color changes E(L*,a*,b*) for compositions L01, L02, L03 and L04 as evaluated while carrying out tests according to standard ISO 4538.

(6) FIG. 4 shows the color changes E(L*,a*,b*) for compositions 3 N ISO 8654 and L05 as evaluated while carrying out tests according to standard ISO 4538.

(7) FIG. 5 shows the color changes E(L*,a*,b*) for composition 5 N ISO 8654, composition L11 and composition L01 as evaluated while carrying out tests by immersing the various samples in a saturated solution of sodium chloride NaCl at neutral pH and at a thermostated temperature of 35 C.

(8) FIG. 6 shows color changes E(L*,a*,b*) for compositions L01, L03 and L06 as evaluated while carrying out tests by immersing the various samples in a saturated solution of sodium chloride NaCl at neutral pH and at a thermostated temperature of 35 C.

(9) FIG. 7 shows the color changes E(L*,a*,b*) for compositions L01, L03 and L06 as evaluated while carrying out tests according to standard ISO 4538.

(10) FIG. 8 shows the micro-structure of an alloy comprising iron in a content of 1.8 wt %, vanadium in a content of 0.4 wt %, and iridium in a content of 0.01 wt %.

DETAILED DESCRIPTION OF THE INVENTION

(11) The different compositions disclosed in the present invention are melted by using an induction fornace equipped with a graphite crucible, and they are melted in graphite molding boxes of rectangular section. The homogeneity of the bath during melting is ensured by electromagnetic induction stirring. The pure elements (Au 99.999%, Cu 99.999%, Pd 99.95%, Fe 99.99%, Ag 99.99%, V99.5%) are melted and cast under a controlled atmosphere. Particularly, melting operations are carried out only after at least 3 cycles of conditioning of the atmosphere of the melting chamber. This conditioning includes reaching a vacuum level up to pressures below 110.sup.2 mbar, followed by partially saturating the atmosphere with argon to 500 mbars. During melting, argon pressure is maintained at pressure levels in a range from 500 mbars to 800 mbars. When pure elements are completely melted; the liquid is overheated up to a temperature of about 1250 C. in order to homogenize the chemical composition of metal bath. During overheating, a vacuum level of less than 110.sup.2 mbar is reached again, which is useful to eliminate a portion of the slag produced while the pure elements are being melted. At this point, the melting chamber is partially re-pressurized to 800 mbars with argon, and then the molten material is poured into the graphite molding box. Once solidification has occurred, the resulting melts are extracted from the molding box, quenched in water to prevent phase changes to solid state, and then plastically cold-deformed by flatbed lamination.

(12) During the cold plastic processing process, the different compositions synthesized according to the melting procedure described above are deformed up to 70%, then subjected to a heat annealing treatment at temperatures above 680 C., and subsequently quenched in water to prevent a phase change to solid state. During the entire process, all the compositions shown herein are subjected to hardness testing in the hardened and annealed state. Additional hardness measurements are made after a heat-treatment hardening carried out at a temperature of 300 C. Hardness tests are performed with an applied load of 9.8 N (HV1) which is maintained for 15 seconds, as specified by standard ISO 6507-1.

(13) Samples are taken from the materials processed by the processing procedures described above, i.e. after melting, lamination, heat-treatment annealing and subsequent quenching, for metallographic analysis. These samples are smoothed, polished and analyzed in order to evaluate the microstructural properties of the synthesized compositions. Similarly, additional samples of material are taken from the materials processed by the processing procedures described above, and they are subjected to color measurements and accelerated corrosion testing.

(14) The surface of the samples subjected to color measurements and accelerated corrosion testing are carefully smoothed by means of abrasive papers and subsequently polished with diamond pastes with a grain size of up to 1 m, until the achievement of a constant reflection factor. Such a surface processing of the samples is essential, and it is carried out in order to remove traces of any compound which can alter the surface composition of the alloy and its actual color, thereby distorting the experimental measurements.

(15) Color measurements were made using a spectrophotometer Konica Minolta CM-3610d immediately after the preparation of the samples and during the various corrosion tests. These measurements are carried out under reflection conditions with the use of a light source D65-6504K, a di/de observation angle of 8, and a measurement area of 8 mm (MAV).

(16) The resistance to surface color change of the different compositions proposed herein is evaluated in accordance with the test procedures prescribed by standard ISO 4538. This standard establishes apparatus and procedure for evaluating the corrosion- and oxidation-resistance of metal surfaces under an atmosphere containing volatile sulphides. To this aim, the specimens are exposed to thioacetamide vapors CH.sub.3CSNH.sub.2 under an atmosphere having a relative humidity of 75% which is maintained with the use of a saturated solution of sodium acetate trihydrate CH.sub.3COONa.3H.sub.2O.

(17) Furthermore, in order to evaluate the resistance to surface color change under environments characterized by the presence of chlorides, further tests are carried out by immersing the samples in a saturated solution of NaCl at neutral pH and at a thermostated temperature of 35 C.

(18) Color changes occurring in the compositions analyzed by accelerated corrosion testing are a function of the time t of exposure to the aggressive action of test environments. Such changes can be evaluated experimentally by taking spectrophotometric measurements of coordinate values L*,a*,b* from the surface of the test alloy samples at defined time intervals. The values thus obtained for coordinates CIE 1976 L*a*b* allow the kinetics of surface discoloration of the test material to be quantified by evaluating the parameter E*(L*,a*,b*)=[(L*L*.sub.0).sup.2+(a*a*.sub.0).sup.2+(b*b*.sub.0.sup.2)].sup.1/2 over time. This parameter must be evaluated with respect to coordinates L.sup.*.sub.0, a*.sub.0, b*.sub.0 of the test material as measured immediately after smoothing with abrasive papers and subsequent polishing with diamond pastes with a grain size of up to 1-m. These operations are carried out until a steady reflection factor is reached. Such a surface processing of the sample is essential, and it is carried out in order to remove traces of any compound which can alter the surface composition of the alloy and its actual color, thereby having the potential to distort the experimental measurements. The results of these tests allow experimental curves E*(L*,a*,b*) vs. time to be obtained, which are indispensable to analyze the kinetics of color change in the analyzed compositions and, therefore, to quantitatively analyze the chemical stability in considered test environments.

(19) Compositions and main physical characteristics of the alloys considered in the present document are shown in table 1. On the contrary, table 2 shows the values of E(L*,a*,b*) as measured after 150 hours of exposure of the analyzed compositions to thioacetamide vapors, and after 175 hours of immersion of the analyzed compositions in the solution containing sodium chloride.

(20) Additions of iron and vanadium of more than 1% and 0.1 wt % respectively, allow surface color change to be decreased under an atmosphere containing volatile sulphides. In this way, it is not required to add palladium in order to improve the chemical stability of the analyzed compositions, thereby avoiding the decrease of surface brightness due to the presence of this element within the alloy. Similarly, expensive additions of platinum are not required.

(21) The curves shown in FIG. 2 can then be analyzed. Since time t=0 corresponds to conditions immediately after the polishing of the samples 5 N ISO8654, L11, L01, then the value of E*(L*,a*,b*, t=0) for the three different given compositions is zero. As can be seen, after 150 hours of exposure to thioacetamide vapors, for an alloy containing iron in a content of 1.8 wt % and vanadium in a content of 0.4 wt % (L01), color change E(L*,a*,b*) is 2.9. Under the same conditions, an alloy 5 N ISO 8654 undergoes a change of 5.6, whereas such a parameter for an alloy (L11) according to document EP 1 512765A1 has a value of 4.1.

(22) Furthermore, for alloys having a composition failing within this embodiment of the invention, the kinetics of discoloration occurring during testing differs from those of the two compositions taken as a reference. As can be also seen in FIG. 2, with reference to the alloy 5 N ISO 8654, a rapid color change occurs within the first 24 hours of the test. Subsequently, the kinetics of color change decreases, but the parameter E(L*,a*,b*) continues to increase throughout the 150 hours of testing analyzed. The alloy L11 also shows a similar behavior, but after about 120 hours of exposure to thioacetamide vapors, the values of parameters E(L*,a*,b*) for this composition reach a plateau of almost constant values. On the contrary, color change for composition L01 is stabilized after only 80 hours of testing.

(23) Again, the presence of iron in the composition of the alloy allows the miscibility of vanadium in gold to be increased. Keeping a ratio greater than 4 between of iron and vanadium levels, allows obtaining solid solutions and preventing second phases from separating out from the mixture.

(24) The curves shown in FIG. 3 can then be analyzed. Since time t=0 corresponds to the conditions immediately after the polishing of the samples L01, L02, L03, L04, then the value of E*(L*,a*,b*, t=0) for the four different given compositions is zero. Compositions in which palladium is replaced with iron show a decreased resistance to color change under environments characterized by the presence of volatile sulphides. After 150 hours of exposure to the thioacetamide vapors, an alloy with 1.8 wt % of palladium and 0.4 wt % of vanadium (L03) undergoes a change E(L*,a*,b*) of 4.1, thus showing a surface color change which is comparable to that of the composition L11. However in this case, (FIG. 3), is not possible to observe a stabilization of the parameter E(L*,a*,b*) for the composition L03 within the first 150 hours of testing.

(25) Moreover, the addition of vanadium is essential to increase the chemical stability of considered compositions. Under atmospheres containing volatile sulphides, a simple addition of 1.8 wt % of iron (L02) results in a color change which is completely equivalent to that shown by the reference alloy 5 N ISO 8654 (FIG. 3).

(26) If palladium is substituted for iron, the effects generated by the presence of vanadium are less obvious. As also shown in FIG. 3, alter 150 hours of exposure to thioacetamide vapors, a composition only characterized by palladium in a content of 1.8 wt % (L04) undergoes a color change E(L*,a*,b*) of 3.8. For a composition in which vanadium is also present, this parameter has a value of 4.1. In this case, the presence of vanadium does not affect the chemical stability of quaternary gold-silver-copper-palladium system. Furthermore, the compositions L03 and L04 are not only characterized by the same chemical stability, but also by the same kinetics of color development throughout the entire test range.

(27) In case in which palladium is present in the alloy in substitution for iron, the effect of vanadium becomes appreciable only after the content of silver is increased and the content of copper is decreased. This is the case of an alloy comprising silver in contents between 5% and 16 wt %, palladium in contents between 0.2% and 5 wt %, and vanadium in contents between 0.2% and 1.5 wt %. The curves shown in FIG. 4 can then be analyzed. Since time t=0 corresponds to the conditions immediately after the polishing of the samples 3 N IS08654, L05, then the value of E*(L*,a*,b*, t=0) for the two different given compositions is zero. For example (FIG. 4), after 150 hours of exposure to the thioacetamide vapors, an alloy comprising silver and copper in contents of 12.5% by weight and additions of palladium and vanadium of 1.8% and 0.4 wt % respectively (L05) shows a color change E(L*,a*,b*) of 3.6. Under the same conditions, a standard alloy 3 N ISO 8654 undergoes a change of 4.8. In this particular embodiment of the invention, the additions of palladium allow the miscibility of vanadium in gold to be increased.

(28) Tests performed by immersing the samples into the solution of sodium chloride (FIG. 5) confirm the chemical stability of the alloy L11 disclosed in document EP1512765A1. After 175 hours of immersion in the chloride-containing solution, such a composition undergoes a color change E(L*,a*,b*) of 1.9, while such a parameter for a composition 5 N ISO 8654 has a value of 3.6. Under the same conditions, the composition L01 undergoes a change of 2.7. Accordingly, simple additions of iron or vanadium cannot optimize the strength of gold alloys in solutions in which chlorides are dissolved.

(29) To this aim, a further embodiment of the invention provides for additions of palladium in a range from 0.5% to 2 wt %, iron in a range from 0.5% to 2 wt %, and vanadium in a range from 0.1% to 1.5 wt %.

(30) After 175 hours of immersion in the chloride-containing solution, an alloy characterized by 0.9 wt % of iron, 0.9 wt % of palladium and 0.4 wt % of vanadium (L06) undergoes a color change E(L*,a*,b*) of 2.1. The curves shown in FIG. 6 can then be analyzed. Since time t=0 corresponds to the conditions immediately after the polishing of the samples L01, L03, L06, then the value of E*(L*,a*,b*, t=0) for the three different given compositions is zero. As can be seen in FIG. 6, the color change of the alloy L1 is quick within the first 48 hours of testing and after about 150 hours of immersion, and the values of the parameter E(L*,a*,b*) reach a plateau of almost constant values. On the contrary, the composition L06 undergoes a rapid color change within the first 24 hours, and similarly to what happens with the composition L11, the parameter E(L*,a*,b*) of the composition L06 is also stabilized after about 150 hours of testing.

(31) This further embodiment of the invention allows the resistance to color change to be increased in solutions in which chlorides are dissolved. However, at the same time, the chemical stability under environments containing volatile sulphides is maintained. The curves shown in FIG. 7 can then be analyzed. Since time t=0 corresponds to the conditions immediately alter the polishing of the samples L01, L03, L06, then the value of E*(L*,a*,b*, t=0) for the three different given compositions is zero. As shown in FIG. 7, alter 150 hours of exposure to thioacetamide vapors, the composition L06 undergoes a color change E(L*,a*,b*) of 3.3. This color change reaches a plateau of intermediate values compared to those of the compositions L01 and L03.

(32) Furthermore, compositions in which the ratio of the sum of the concentrations of iron and palladium to the concentration of vanadium is greater than 4, are solid solutions which are homogeneous and free of second phases.

(33) By replacing palladium with iron, it is possible to obtain an increased surface brightness. As shown in table 1, the composition L01 is characterized by a parameter L* of 86.66, whereas such a parameter for the composition L04 has values lower than and equal to 85.21. The L* values obtained by partially replacing palladium with iron, as in the case of the composition L06, are intermediate values compared to those set forth above.

(34) Iron and vanadium are chemical elements capable to decrease the shade saturation of gold alloys. The higher the concentration of these elements, the lower the values of coordinates a* and b* and the more the colors will become achromatic.

(35) To overcome this problem, a further embodiment of the invention discloses compositions in which silver may not be present and which comprise copper in a content between 16% and 23 wt %, iron in a content between 0.5% and 4 wt %, and vanadium in a content between 0.1% and 1 wt %. For example, with the composition L07 in which iron is present at a concentration of 2.5 wt % and the content of vanadium is 0.6 wt %, it is possible to obtain an a* value of 6.45 which is similar to that reported for the composition L01. However, the absence of silver causes a decrease in parameter b* (yellow). In fact, the composition L07 is characterized by a b* value of 12.90, whereas this parameter takes a value of 15.49 for the composition L01. Also with this particular embodiment of the invention, which includes compositions in which the ratio between the concentrations of iron and vanadium is more than 4, solid solutions are obtained which are homogeneous and free of second phases.

(36) Moreover, the presence of iron causes an increase in surface brightness. An alloy with 2.5 wt % of palladium (L09) is characterized by an L* value of 83.77. The composition L07 in which iron is present in a content of 2.5 wt % is characterized by an L* value of 86.09. When iron content is increased to 3.1 wt %, even in the absence of vanadium (L08), the parameter L* takes a value of 86.33.

(37) A last embodiment of the invention may comprise iridium in contents of less than 0.05 wt %. These additions allow the crystal structure of the compositions considered to be tuned. FIG. 8 shows the micro-structure of an alloy comprising iron in a content of 1.8 wt %, vanadium in a content of 0.4 wt %, and iridium in a content of 0.01 wt %, which has been plastically cold-deformed up to 70% and annealed at 680 C. The composition is characterized by a grain size of 7 according to standard ISO 643. A similar grain size allows the manufactured articles to show a good polishing ability. Increased additions of iridium can further increase the grain size index and have adverse effects on the chemical stability of the alloy.

(38) TABLE-US-00001 TABLE 1 Color CIE L*a*b* Hardness HV1 Alloy Composition [wt %] L*0 a*0 b*0 70% Hardened Annealed Aged L01 Au75 Ag4.1 Cu18.7 Fe1.8 86.86 6.45 15.49 267 170 265 V0.4 L02 Au75 Ag4.2 Cu19.0 Fe1.8 86.88 6.47 15.50 261 162 273 L03 Au75 Ag4.1 Cu18.7 Pd1.8 85.54 7.32 14.17 256 160 285 V0.4 L04 Au75 Ag4.2 Cu19.0 Pd1.8 85.21 8.23 14.47 254 156 298 L05 Au75 Ag11.4 Cu11.4 Pd1.8 87.27 5.16 17.30 239 154 215 V0.4 L06 Au75 Ag3.6 Cu19.2 Pd0.9 85.77 6.85 14.10 273 165 275 Fe0.9 V0.4 L07 Au75 Cu21.9 Fe2.5 V0.6 86.09 6.45 12.90 295 192 323 L08 Au75 Cu21.9 Fe3.1 86.33 5.78 12.75 272 163 302 L09 Au75 Cu22.5 Pd25 83.77 8.11 11.74 245 163 286 L10 Au75 Ag4.1 Cu18.7 Fe1.8 86.80 6.43 15.49 265 172 260 V0.4 Ir0.01 L11 Au76 Pt3 Cu21 84.52 9.10 13.10 270 165 300 5N ISO Au75 Ag4.5 Cu20.5 86.94 9.60 17.50 230 165 325 8654 3N ISO Au75 Ag12.5 Cu12.5 89.30 5.68 22.45 220 145 230 8654

(39) TABLE-US-00002 TABLE 2 E(L*, a*, b*) Exposure to Immersion in a thioacetamide saturated vapors aqueous solution Alloy Composition [wt %1] (150 hours) of NaC1 L01 Au75 Ag4.1 Cu 18.7 Fe1.8 2.9 2.7 V0.4 L02 Au75 Ag4.2 Cu19.0 Fe1.8 4.7 2.9 L03 Au75 Ag4.1 Cu18.7 Pd1.8 4.1 1.8 V0.4 L04 Au75 Ag4.2 Cu19.0 Pd18 3.3 2.4 L05 Au75 Ag11.4 Cu11.4 Pd1.8 3.6 2.0 V0.4 L06 Au75 Ag3.6 Cu19.2 Pd0.9 3.3 2.1 Fe0.9 V0.4 L07 Au75 Cu21.9 Fe2.5 V0.6 4.2 2.6 L08 Au75 Cu21.9 Fe3.1 4.4 3.0 L09 Au75 Cu22.5 Pd25 4.7 2.0 L11 Au76 Pt3 Cu21 4.1 1.9 5N ISO Au75 Ag4.5 Cu20.5 5.6 3.6 8654 3N ISO Au75 Ag12.5 Cu12.5 4.8 3.3 8654