Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper
  • C22C9/04—Alloys based on copper with zinc as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working

Definitions

• the present invention relates to a free-cutting copper alloy having good corrosion resistance, particularly good dezincification corrosion resistance and stress corrosion cracking resistance, high strength and a significantly reduced Pb content, and to a method for producing the free-cutting copper alloy.
• This project relates to free-cutting copper alloys used in parts that are cut, such as appliances and parts used in drinking water consumed daily by people and animals, appliances and parts used in sanitary facilities such as kitchens, bathrooms and toilets, water meters, musical instruments, tableware, drainage appliances and parts, industrial piping parts, electrical and electronic equipment parts, automobile parts, machine parts, stationery, toys, sliding parts, instrument parts, precision machine parts, medical parts, parts related to hydrogen and other liquids and gases, and specific part names include water taps, mixer taps, faucet fittings, stopcocks, valves, joints, valves, shower heads, cocks, gears, shafts, bearings, shafts, sleeves, spindles, sensors, bolts, nuts, flare nuts, pen nibs, insert nuts, cap nuts, nipples
• metals have been used for drinking water and sanitation equipment equipment and parts, water meters, musical instruments, tableware, electrical/home appliance/electronic equipment parts, automobile parts, machine parts, stationery, precision machine parts, medical parts, and industrial water, wastewater, and equipment and parts related to liquids and gases such as hydrogen.
• Part names include water taps, mixer taps, stopcocks, valves, cocks, joints, gears, sensors, nuts, screws, etc.
• Cu-Zn-Pb alloys containing 56-65 mass% Cu, 1-4 mass% Pb, and the balance Zn (known as free-cutting brass rods, forging brass, and casting brass), or Cu-Sn-Zn-Pb alloys containing 80-88 mass% Cu, 2-8 mass% Sn, 1-8 mass% Pb, and the balance Zn (known as bronze castings: gunmetal), were used.
• the European RoHS Directive and ELV Directive allow for a Pb content of up to 4 mass% in free-cutting copper alloys as an exception, but as in the drinking water field, there is active discussion about strengthening regulations on Pb content, including the elimination of exceptions.
• Patent Document 1 0.3 to 4 mass%, preferably 1.8 to 3.2 mass%, of Bi is added to a Cu-Zn alloy, and since the ⁇ phase has poor dezincification corrosion resistance, the ⁇ phase is reduced and the ⁇ phase is divided by the ⁇ phase, and annealing is performed at 350 to 550°C to improve machinability and dezincification corrosion resistance.
• alloys containing Bi instead of Pb have many problems, including the fact that Bi is inferior to Pb in terms of machinability, that Bi may be harmful to the environment and human body like Pb, that Bi is a rare metal and therefore has resource problems, and that Bi makes copper alloy materials brittle.
• the ⁇ phase of a Cu-Zn alloy has been conventionally inferior in dezincification corrosion resistance, and as an improvement measure, it has been substantially required to reduce the ⁇ phase and to perform annealing to divide the ⁇ phase by the ⁇ phase.
• Cu-Zn binary alloys containing a large amount of ⁇ phase contribute to improving machinability, but the ⁇ phase has inferior machinability function compared to Pb, and is inferior in dezincification corrosion resistance and stress corrosion cracking resistance, so they cannot be a substitute for Pb-containing free-cutting copper alloys. Therefore, as free-cutting copper alloys, Cu-Zn-Si alloys containing Si instead of Pb have been proposed in, for example, Patent Documents 2 to 8.
• the Cu content is roughly 58 to 65 mass%, the Si content is 0.2 to 1.5 mass%, and it is said that the machinability is improved by the presence of Si contained in the ⁇ phase and fine P compounds formed by P and Zn, etc., and the area ratio of the ⁇ phase and the ⁇ phase are specified, and excellent machinability is realized in combination with the presence of P compounds and the inclusion of a small amount of Pb.
• the ⁇ phase of a Cu-Zn alloy has poor dezincification corrosion resistance as disclosed in Patent Document 1, and further deteriorates stress corrosion cracking resistance.
• Patent Documents 2 to 7 do not disclose any specific data related to dezincification corrosion resistance and stress corrosion cracking resistance, and it is presumed that the dezincification corrosion resistance and stress corrosion cracking resistance, which are technical issues of the ⁇ phase of the conventional Cu-Zn alloy, have not been improved.
• the Cu content is set to 71.5 to 78.5 mass%
• the Si content is set to 2.0 to 4.5 mass%
• Sn and Al in amounts of 0.1 mass% or more, a large amount of ⁇ phase is formed, thereby further improving machinability and corrosion resistance.
• Patent Document 9 a Cu-Zn-Sn alloy contains small amounts of Si, Pb, P, or Fe, and contains 0.5 mass% or less of Pb, and by devising a manufacturing method, Pb-enriched particles are dispersed in the matrix, and the number density of the Pb-enriched particles present inside the ⁇ phase is increased, thereby obtaining excellent machinability.
• Patent Document 9 also states that a finishing heat treatment at 400 to 600°C is essentially required to improve dezincification corrosion resistance.
• Patent Document 10 relates to a technique for producing a near-net hollow hot forged product using a hollow material in a Cu-Zn-Si-Pb-P alloy, and proposes a copper alloy in which the area ratios of the ⁇ , ⁇ and ⁇ phases are limited.
• Patent Document 11 proposes a copper alloy casting in which Si, Pb, and Sn are selectively contained in a Cu-Zn-Zr-P alloy, and the crystal grains are refined by the action of Zr and P.
• Patent Document 12 proposes a Cu-Zn-Sn-Al alloy that selectively contains Si and Pb and has a limited area ratio of ⁇ and ⁇ phases, thereby providing a copper alloy with excellent resistance to discoloration.
• Patent Document 13 proposes a copper alloy casting containing no Pb in a Cu-Zn-Si-Sn-Al-P alloy.
• Patent Document 14 proposes that in a Cu-Zn-Si-Sn-Al alloy, the apparent Zn content is important for improving the corrosion resistance, and proposes a copper alloy that substantially contains a large amount of Pb or Bi to improve machinability.
• Patent Document 15 describes a Cu-Zn-Si alloy that contains 65 mass% or more of Cu, has good castability and mechanical strength, and is a Pb-free copper alloy casting, and is said to have improved machinability due to the ⁇ phase. It also describes an example in which the alloy contains large amounts of Sn, Al, Mn, Ni, and Sb.
• Patent Documents 1 to 15 there has been no substantial improvement in the dezincification corrosion resistance and stress corrosion cracking resistance of the ⁇ phase present in Cu-Zn alloys, which has traditionally been a major technical challenge. Furthermore, there has been no disclosure of a Cu-Zn alloy that exhibits low cutting resistance and excellent machinability under high-speed cutting conditions with a cutting speed of over 100 m/min, even when the alloy contains less than 0.2% Pb and Bi and does not require the inclusion of Bi.
• the present invention has been made to solve the problems of the prior art, and aims to provide a free-cutting copper alloy that has excellent hot workability and machinability, good resistance to dezincification corrosion and stress corrosion cracking despite containing a large amount of ⁇ phase ( ⁇ 1 phase described below), high strength, a good balance between strength and ductility, and a significantly reduced Pb content, as well as a method for producing the free-cutting copper alloy.
• the present inventors conducted extensive research and obtained the following findings.
• the ⁇ phase includes the ⁇ ' phase
• the ⁇ phase includes the ⁇ ' phase
• the ⁇ phase includes the ⁇ ' phase.
• the ⁇ 1 phase is a modified ⁇ phase and is distinguished from the ⁇ phase and the ⁇ ' phase.
• the ⁇ 1 phase is characterized in that, when observed under a metal microscope using hydrogen peroxide and aqueous ammonia as an etching solution, a grain boundary pattern, i.e., a crystal grain boundary, is observed in the ⁇ 1 phase.
• the ⁇ phase present in general Cu-Zn alloys, Cu-Zn-Bi alloys, Cu-Zn-Si alloys, etc. does not have a crystal grain boundary in the ⁇ phase even when etched with hydrogen peroxide and aqueous ammonia. Therefore, the ⁇ phase and the ⁇ 1 phase can be clearly distinguished.
• the crystal grain boundary is sometimes simply called a grain boundary.
• the hot-worked material includes hot extrusion material, hot forging material, and hot rolled material.
• the cold workability refers to the performance of processing performed in cold, such as drawing, wire drawing, rolling, crimping, and bending. Unless otherwise specified, good or excellent machinability refers to low cutting resistance during peripheral cutting using a lathe and good or excellent chip breakability.
• Conductivity refers to electrical conductivity, thermal conductivity, and electrical conductivity. Cooling rate refers to the average cooling rate within a certain temperature range. One day and night means one day. Actual operation means manufacturing using actual mass production equipment.
• Patent Document 8 it is said that in a Cu-Zn-Si alloy, the ⁇ phase hardly contributes to the machinability of the copper alloy, but rather impedes it.
• Patent Documents 10, 11, and 12 the amount of the ⁇ phase is also significantly limited.
• Patent Document 1 as a method for improving the dezincification corrosion resistance of the ⁇ phase, a process of annealing at 350 to 550°C is required to reduce the ⁇ phase and to divide the ⁇ phase by the ⁇ phase.
• Patent Document 9 it is said that in order to improve the dezincification corrosion resistance of the ⁇ phase, it is necessary to contain more Sn than Si, and it is necessary to heat the alloy to a temperature of 700 to 850°C, hot extrude it, and hold it at 400 to 600°C as a finishing heat treatment for 30 minutes or more, and perform heat treatment under conditions of an average cooling rate from 400 to 200°C of 0.2 to 10°C/sec.
• Patent Documents 2 to 7 it was discovered that in a Cu-Zn-Si alloy, the inclusion of a certain amount of Si in the ⁇ phase has a significant effect on the machinability of the ⁇ phase itself. It is then said that the presence of fine P compounds, the inclusion of a small amount of Pb, and in some cases Bi, act synergistically to provide the alloy with excellent machinability. However, in order to provide the presence of P compounds, it is preferable to provide an average cooling rate of about 0.1°C/min to about 70°C/min in the temperature range from about 530°C to about 450°C after hot working. However, Patent Documents 2 to 7 do not disclose data related to dezincification corrosion resistance and stress corrosion cracking resistance.
• the inventors further worked on modifying the ⁇ phase itself in Cu-Zn-Si alloys.
• the modified ⁇ phase i.e., the ⁇ 1 phase
• machinability especially during high-speed cutting, without the inclusion of Bi
• significantly improved the dezincification corrosion resistance and stress corrosion cracking resistance of the ⁇ phase which have long been issues with Cu-Zn alloys.
• alloys containing the ⁇ 1 phase instead of the ⁇ phase were able to further increase strength without impairing ductility.
• This ⁇ 1 phase is first obtained by dissolving a certain amount of Si and P in the ⁇ phase, and then maintaining the ⁇ phase at 500-670°C and increasing the cooling rate when cooling to room temperature, thereby bringing the metal structure at high temperatures to room temperature.
• the ⁇ 1 phase can be easily distinguished and differentiated from the ⁇ phase of Cu-Zn alloys.
• the surface is polished to a mirror finish and etched with a mixture of hydrogen peroxide and aqueous ammonia.
• aqueous solution of 3 mL of 3 vol% hydrogen peroxide and 22 mL of 14 vol% aqueous ammonia is used.
• the cooling process after hot working requires that the hot-worked material is cooled at a temperature lower than 670°C and higher than 500°C, and that the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C exceeds 300°C/min in the cooling process, and that the material is subsequently cooled at an average cooling rate of at least 300°C/min in the temperature range from 500°C to 300°C.
• the cooling process refers to the operation of the cooling rate by water cooling or a method similar thereto, rather than natural cooling.
• Patent Documents 2 to 7 in order to obtain fine P-containing compounds, the hot-worked material needs to be cooled at an average cooling rate of about 0.1°C/min to about 70°C/min in the temperature range from about 530°C to about 450°C after hot working.
• an average cooling rate of about 0.1°C/min to about 70°C/min in the temperature range from about 530°C to about 450°C after hot working In other words, it is clear that the present application and Patent Documents 2 to 7 are moving in opposite directions (teaching opposite directions).
• the cooling rate at around 520°C after hot working is 60°C/min and the average cooling rate in the temperature range from 520°C to 500°C, which is the cooling treatment start temperature, exceeds 300°C/min, an alloy containing both the ⁇ 1 phase and P compounds may exist in this application.
• the ⁇ 1 phase in the present application significantly improves the machinability of the Cu-Zn-Si alloy, particularly in terms of high-speed cutting, even without the P compounds disclosed in Patent Documents 2 to 7.
• the synergistic effect of the ⁇ 1 phase and fine Pb particles or particles containing Pb and Bi reduces the cutting resistance and promotes chip breakage.
• the unsolved problems of the conventional ⁇ phase that is, the dezincification corrosion resistance and stress corrosion cracking resistance
• the mechanical properties inherit the high strength of the conventional ⁇ phase, and the ductility is improved, resulting in even higher strength and a better balance between strength and ductility.
• the relationship is 1 ⁇ 2- ( ⁇ ) ⁇ 2+([Pb]+[Bi] ) ⁇ 20+([ P ]) ⁇ 15, and the ⁇ 1 phase is characterized in that grain boundaries are observable when etched with a mixture of hydrogen peroxide and aqueous ammonia.
• the free-cutting copper alloy of embodiment 3 of the present invention contains more than 60.5 mass% and less than 65.0 mass% Cu, more than 0.50 mass% and less than 1.20 mass% Si, 0.002 mass% or more and less than 0.20 mass% Pb, more than 0.01 mass% and less than 0.18 mass% P, and more than 0.05 mass% and less than 0.90 mass% Sn, and contains 0.
• the steel sheet contains 0.0001 mass% or more and less than 0.20 mass% Bi, with the balance being Zn and inevitable impurities, and among the inevitable impurities, the total content of Fe, Mn, Co and Cr is less than 0.40 mass%, and the Al content is less than 0.30 mass%, the Cu content is [Cu] mass%, the Si content is [Si] mass%, and the Pb content is [Pb] mass%.
• the present invention is characterized in that the grain boundaries of the ⁇ 1 phase are observable when the ⁇ 1 phase is etched with a mixed solution of hydrogen peroxide and aqueous ammonia.
• the free-cutting copper alloy of embodiment 4 of the present invention contains 61.2 mass% or more and 64.8 mass% or less of Cu, 0.65 mass% or more and 1.10 mass% or less of Si, 0.003 mass% or more and less than 0.10 mass% of Pb, 0.03 mass% or more and 0.15 mass% or less of P, and 0.10 mass% or more and less than 0.50 mass% of Sn, and as optional elements
• the free-cutting copper alloy of aspect 5 of the present invention is characterized in that it is any one of the free-cutting copper alloys of aspects 1 to 4 of the present invention and is used for appliances and parts related to drinking water and sanitation facilities, valves, cocks, industrial piping parts, water meters, musical instruments, automobile parts, electrical and electronic equipment parts, machine parts, stationery, toys, sliding parts, instrument parts, precision machine parts, and medical parts.
• the manufacturing method of the free-cutting copper alloy of aspect 6 of the present invention is a manufacturing method of the free-cutting copper alloy of any one of aspects 1 to 4 of the present invention, which has one or more hot working steps, and is characterized in that the hot working temperature in the final hot working step is more than 540°C and less than 750°C, and in the cooling process after hot working, the cooling treatment of the hot-worked material is started at a temperature lower than 670°C and higher than 500°C, and in the cooling treatment, the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C exceeds 300°C/min, and the average cooling rate in the temperature range from 500°C to 300°C exceeds 300°C/min.
• the manufacturing method of the free-cutting copper alloy of aspect 7 of the present invention is a manufacturing method of the free-cutting copper alloy of any one of aspects 1 to 4 of the present invention, which has one or more hot working steps and heat treatment steps, and is characterized in that in the final heat treatment step, annealing is performed under conditions of holding at a temperature above 520°C and below 630°C for 1 minute to 5 hours, and after annealing, cooling treatment is started at a temperature above 500°C, the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C is more than 300°C/min, and the average cooling rate in the temperature range from 500°C to 300°C is more than 300°C/min.
• a free-cutting copper alloy that has excellent hot workability, good machinability, dezincification corrosion resistance, and stress corrosion cracking resistance, high strength, an excellent balance between strength and ductility, and a significantly reduced Pb content, and a method for producing the free-cutting copper alloy.
• Alloy No. S01 has a composition of Zn-63.3 mass% Cu-0.95 mass% Si-0.069 mass% P-0.063 mass% Pb-0.017 mass% Bi.
• hot extrusion was performed at 630°C, and cooling treatment was started at 580°C, and both the average cooling rate in the temperature range from 580°C to 300°C and the average cooling rate in the temperature range from 500°C to 300°C were set to 1020°C/min.
• FIG. 1B is a cross-sectional metallographic photograph showing the results of a dezincification corrosion test performed on the alloy of FIG. 1A in accordance with the ISO 6509 test method, the photograph including the portion showing the maximum corrosion depth.
• This is a photograph of the structure of a copper alloy in an embodiment, and the copper alloy was obtained by subjecting Alloy No. S11 to Step No. E2.
• Alloy No. S11 has a composition of Zn-62.5 mass% Cu-0.96 mass% Si-0.064 mass% P-0.072 mass% Pb.
• Step No. E2 hot extrusion was performed at 550 ° C., and the average cooling rate in the temperature range from 500 ° C. to 300 ° C.
• 2B is a cross-sectional metallographic photograph showing the results of a dezincification corrosion test performed on the alloy of FIG. 2A in accordance with the ISO 6509 test method, the photograph including the portion showing the maximum corrosion depth.
• Alloy No. S11 has a composition of Zn-62.5 mass% Cu-0.96 mass% Si-0.064 mass% P-0.072 mass% Pb.
• Process No. E13H hot extrusion was performed at 550 ° C., and the average cooling rate in the temperature range from 500 ° C. to 300 ° C. was set to 20 ° C./min to obtain a rod having a diameter of 50 mm and a length of 200 mm. The rod was heated, and the rod was placed horizontally and hot forged at 630 ° C.
• FIG. 3A and the alloy in FIG. 2A have different cooling treatment start temperatures.
• 3B is a cross-sectional metallographic photograph showing the results of a dezincification corrosion test performed on the alloy of FIG. 3A in accordance with the ISO 6509 test method, the photograph including the portion showing the maximum corrosion depth. This is a photograph of the structure of a copper alloy in an embodiment, and the copper alloy was obtained by subjecting Alloy No. S43 to Step No. E6.
• Alloy No. S43 has a composition of Zn-63.3 mass% Cu-0.98 mass% Si-0.084 mass% P-0.060 mass% Pb-0.28 mass% Sn.
• Step No. E6 a casting cast into a die having a diameter of 55 mm was cut to a diameter of 50 mm and a length of 200 mm. The casting was heated, the casting was placed horizontally and hot forged at 630 ° C. to a thickness of 20 mm, and the cooling treatment was started at 565 ° C., and both the average cooling rate in the temperature range from 565 ° C. to 300 ° C. and the average cooling rate in the temperature range from 500 ° C. to 300 ° C. were set to 900 ° C. / min.
• 4B is a cross-sectional metallographic photograph showing the results of a dezincification corrosion test performed on the alloy of FIG. 4A in accordance with the ISO 6509 test method, the photograph including the portion showing the maximum corrosion depth.
• 1 is a photograph of the structure of a copper alloy in an embodiment, and the copper alloy was obtained by subjecting Alloy No. S02 to Process No. A34H and Process No. G1.
• Alloy No. S02 has a composition of Zn-62.9 mass% Cu-0.98 mass% Si-0.071 mass% P-0.071 mass% Pb.
• Process No. A34H the alloy was obtained by hot extrusion at 615°C and setting the average cooling rate from 500°C to 300°C to 18°C/min.
• 5B is a cross-sectional metallographic photograph showing the results of a dezincification corrosion test performed on the alloy of FIG. 5A in accordance with the ISO 6509 test method, the photograph including the portion showing the maximum corrosion depth.
• This is a photograph of the structure of a copper alloy in an embodiment, and the copper alloy was obtained by subjecting alloy No. S02 to process No. E14H. In detail, alloy No.
• S02 has a composition of Zn-62.9 mass% Cu-0.98 mass% Si-0.071 mass% P-0.071 mass% Pb.
• hot extrusion was performed at 550 ° C., and the average cooling rate from 500 ° C. to 300 ° C. was set to 20 ° C./min to obtain a rod having a diameter of 50 mm and a length of 200 mm.
• the rod was heated, and the rod was placed horizontally and hot forged at 630 ° C. to a thickness of 20 mm, and then naturally cooled.
• the average cooling rate in the temperature range from 500 ° C. to 300 ° C. was 25 ° C./min.
• 6B is a cross-sectional metallographic photograph showing the results of a dezincification corrosion test performed on the alloy of FIG. 6A in accordance with the ISO 6509 test method, including a portion showing the maximum corrosion depth.
• a free-cutting copper alloy and a method for producing the free-cutting copper alloy according to an embodiment of the present invention will be described.
• These include drinking water and sanitation equipment, musical instruments, tableware, electrical, home appliance and electronic device parts, automobile parts, machine parts, stationery, precision machinery parts, medical parts, as well as industrial water, wastewater, hydrogen and other liquid and gas related equipment and parts.
• Specific part names include water taps, mixer taps, stopcocks, valves, cocks, fittings, water meters, gears, sensors, nuts, screws, etc.
• compositional relations f1, f2, and f0 as follows.
• Compositional relationship f1 [Cu] - 4.6 x [Si] + 0.5 x ([Pb] + [Bi]) - [P]
• f1 [Cu] - 4.6 x [Si] + 0.5 x ([Pb] + [Bi]) - [P] - [Sn]
• compositional relation f2 [Pb]+[Bi]
• f0 [Sn] / [Si] It is.
• the area ratio of the ⁇ phase is represented as ( ⁇ )%, the area ratio of the ⁇ phase as ( ⁇ ), the area ratio of the unmodified ⁇ phase as ( ⁇ ), and the area ratio of the modified ⁇ 1 phase as ( ⁇ 1)%.
• the area ratio of each phase is also referred to as the amount of each phase, the proportion of each phase, or the proportion occupied by each phase.
• a plurality of organization relationship expressions are defined as follows.
• the area ratio of the ⁇ phase is ( ⁇ )%
• the area ratio of the ⁇ phase is ( ⁇ )%
• the area ratio of the ⁇ 1 phase which is a modified ⁇ phase
• the relationship is 1 ⁇ 2- ( ⁇ ) ⁇ 2+([Pb]+[Bi] ) ⁇ 20 +([P]) ⁇ 15
• the ⁇ 1 phase is characterized in that grain boundaries are observable when etched with a mixture of hydrogen peroxide and aqueous ammonia.
• the area ratio of the ⁇ phase is ( ⁇ )%
• the area ratio of the ⁇ phase is ( ⁇ )%
• the area ratio of the ⁇ 1 phase which is a modified ⁇ phase
• there are the following relationships: 30 ⁇ f3 ( ⁇ ) ⁇ 70
• 30 ⁇ f4 ( ⁇ 1) ⁇ 70
• 0 ⁇ f5 ( ⁇ ) ⁇ 1
• 35 ⁇ f6 ( ⁇ 1) ⁇ ([Si])
• the relationship is 1 ⁇ 2- ( ⁇ ) ⁇ 2+([Pb]+[Bi] ) ⁇ 20 +([P]) ⁇ 15
• the ⁇ 1 phase is characterized in that grain boundaries are observable when etched with a mixture of hydrogen peroxide and aqueous ammonia.
• a free-cutting copper alloy according to a third embodiment of the present invention contains more than 60.5 mass% and less than 65.0 mass% Cu, more than 0.50 mass% and less than 1.20 mass% Si, 0.002 mass% or more and less than 0.20 mass% Pb, more than 0.01 mass% and less than 0.18 mass% P, and more than 0.05 mass% and less than 0.90 mass% Sn, and any optional elements.
• a free-cutting copper alloy according to a fourth embodiment of the present invention contains 61.2 mass% or more and 64.8 mass% or less of Cu, 0.65 mass% or more and 1.10 mass% or less of Si, 0.003 mass% or more and less than 0.10 mass% of Pb, 0.03 mass% or more and 0.15 mass% or less of P, and 0.10 mass% or more and less than 0.50 mass% of Sn, and any optional elements.
• compositional equations f0, f1, f2, structure equations f3, f4, f5, structure-composition equation f6, metal structure, etc. as described above.
• Cu is a main element of the free-cutting copper alloy of this embodiment, and in order to overcome the problems of the present invention, it is necessary to contain at least 60.5 mass% or more of Cu.
• the Cu content is 60.5 mass% or less, depending on the contents of Si, Zn, P, Pb, Bi, and Sn and the manufacturing process, the proportion of ⁇ 1 phase exceeds 80%, and ductility is reduced.
• the modification of the ⁇ phase is not performed sufficiently, and dezincification corrosion resistance, stress corrosion cracking resistance, and machinability are deteriorated.
• the lower limit of the Cu content is more than 60.5 mass%, preferably 61.2 mass% or more, more preferably 61.5 mass% or more, and even more preferably 62.0 mass% or more.
• the Cu content is 65.0 mass% or more, the proportion of ⁇ 1 phase decreases, depending on the contents of Si, Zn, P, Pb, Bi, and Sn and the manufacturing process. As a result, excellent machinability is not obtained and strength is also reduced. Therefore, the Cu content is less than 65.0 mass%, preferably 64.8 mass% or less, and more preferably 64.5 mass% or less.
• (Si) Si is a main element of the free-cutting copper alloy of this embodiment, and Si contributes to the formation of metal phases such as ⁇ , ⁇ , ⁇ , ⁇ , ⁇ 1, and ⁇ phases.
• metal phases such as ⁇ , ⁇ , ⁇ , ⁇ , ⁇ 1, and ⁇ phases.
• the ⁇ phase is modified, and the ⁇ 1 phase is generated through a predetermined cooling treatment described below.
• the ⁇ 1 phase (modified ⁇ phase) improves machinability and significantly improves the dezincification corrosion resistance and stress corrosion cracking resistance, which were drawbacks of the conventional ⁇ phase.
• a typical composition of the modified ⁇ 1 phase is about 61 mass% Cu, about 1.2 mass% Si, about 37.5 mass% Zn, and about 0.1 mass% P.
• the ⁇ phase has a typical composition of about 66 mass% Cu, about 0.7 mass% Si, and about 33 mass% Zn.
• the inclusion of Si slightly improves the machinability of the ⁇ phase
• the inclusion of Si improves the dezincification corrosion resistance and stress corrosion cracking resistance of the ⁇ phase.
• the modified ⁇ 1 phase and the improved ⁇ phase improve the dezincification corrosion resistance and stress corrosion cracking resistance of the alloy in particular.
• a certain amount of ⁇ phase is necessary, and for example, if there is no ⁇ phase, the ⁇ phase will not be modified.
• the ⁇ phase In order to improve the dezincification corrosion resistance, stress corrosion cracking resistance, ductility, and machinability of the alloy, the ⁇ phase must be 20% or more, preferably 30% or more, in terms of area ratio.
• Si is an essential element for modifying the ⁇ phase to the ⁇ 1 phase, and the more Si, the more the ⁇ phase is modified, resulting in a ⁇ 1 phase with better properties.
• the Si content is preferably 0.60 mass% or more, more preferably 0.65 mass% or more, and even more preferably 0.75 mass% or more.
• the amount of Si reaches a certain amount, the modification of the ⁇ 1 phase is saturated. Furthermore, if the content of Si is too high, the conductivity is reduced.
• the ⁇ phase appears, and the dezincification corrosion resistance, stress corrosion cracking resistance, and machinability are deteriorated. Meanwhile, in Patent Documents 2 to 8, the ⁇ phase is said to improve machinability.
• the present application which is mainly composed of the ⁇ 1 phase and the ⁇ phase
• the presence of the ⁇ phase rather deteriorates the machinability, reduces the ductility of the alloy, and deteriorates the dezincification corrosion resistance and stress corrosion cracking resistance. Therefore, it is preferable to limit the amount of Si and the amount of the ⁇ phase.
• the amount of Si is less than 1.20 mass%, preferably 1.10 mass% or less. If conductivity is emphasized, the amount of Si is 1.0 mass% or less.
• Zn Zn is a main constituent element of the free-cutting copper alloy of this embodiment, and is an element necessary for improving machinability, strength, high-temperature properties, and castability.
• Zn is the balance, if forced to state, the Zn content is less than about 38.5 mass%, preferably less than 38.0 mass%, and more than about 32.0 mass%, and preferably more than 33.0 mass%.
• P is an essential element for reforming the ⁇ phase into the ⁇ 1 phase.
• the cooling treatment is started at a temperature above 500°C and below 670°C, and the ⁇ phase is reformed into the ⁇ 1 phase by cooling the temperature range from the cooling treatment start temperature to 500°C and the temperature range from 500°C to 300°C at a cooling rate of more than 300°C/min, and the ⁇ phase is reformed into the ⁇ 1 phase, and the ⁇ 1 phase is obtained.
• the reforming of the ⁇ phase into the ⁇ 1 phase significantly improves the dezincification corrosion resistance and stress corrosion cracking resistance, which were problems with the conventional ⁇ phase.
• the presence of the ⁇ 1 phase can reduce the cutting resistance and improve the chip breakability during cutting.
• compounds containing P reduce the cutting resistance and improve the chip breakability, but when a cooling treatment is started at a temperature above about 550°C or 530°C at a cooling rate of more than 300°C/min, compounds containing P do not exist or exist in small amounts. From the viewpoint of improving machinability, the effect of modifying the ⁇ phase to the ⁇ 1 phase is greater than the effect of the presence of a compound containing P in the ⁇ phase.
• the modification of the ⁇ phase to the ⁇ 1 phase provides better machinability than the presence of a compound containing P in the ⁇ phase.
• the inclusion of P improves the dezincification corrosion resistance and stress corrosion cracking resistance of the ⁇ phase, and leads to a significant improvement in the dezincification corrosion resistance and stress corrosion cracking resistance of an alloy consisting of the ⁇ 1 phase and the ⁇ phase.
• the lower limit of the P content In order to reform the ⁇ phase into the ⁇ 1 phase, the lower limit of the P content must be at least 0.01 mass% or more. In consideration of a better reform into the ⁇ 1 phase, the amount of unavoidable impurities, the cooling treatment start temperature, and the cooling rate after the start of the cooling treatment, which will be described later, the P content is preferably 0.03 mass% or more, and more preferably 0.04 mass% or more. In addition, P easily forms compounds with Zn, Si, Mn, Fe, Cr, Co, Al, etc. When P forms compounds and the amount of P dissolved in the ⁇ phase in the alloy after hot working is reduced, the reforming from the ⁇ phase to the ⁇ 1 phase is hindered.
• the formation of compounds between Zn and Si, which are the main elements of the alloy of the present application, and P begins at about 550°C, and the amount of P compounds increases as the cooling rate slows.
• the formation of compounds between Mn, Fe, Cr, Co, which are unavoidable impurities, and P begins at a temperature above about 550°C, and the formation of P compounds is further promoted as the amount of these elements increases.
• the presence of Mn, Fe, Cr, and Co hinders the reforming to the ⁇ 1 phase, resulting in an increase in the cutting resistance of the alloy, poor chip splitting ability, and poor dezincification corrosion resistance and stress corrosion cracking resistance. Therefore, the total content of Fe, Mn, Co and Cr must be less than 0.40 mass%, preferably less than 0.30 mass%.
• the P content is less than 0.18 mass%, preferably 0.15 mass% or less, and more preferably 0.12 mass% or less.
• the ⁇ 1 phase containing Si and P provides good machinability as an alloy, but the inclusion of a small amount of Pb further improves the machinability.
• about 0.001 mass% of Pb is dissolved in the matrix, and any excess amount of Pb exists as fine Pb particles with a diameter of about 0.1 to about 2 ⁇ m.
• the inclusion of about 0.1 mass% of Pb hardly contributes to improving the machinability.
• FIG. 6 shows the relationship between the amount of Pb and machinability when the machinability of a Cu-Zn-Pb alloy containing 62-65 mass% Cu, about 3.2 mass% Pb, and the balance Zn is taken as 100%, and shows that a Pb content of 0.1 mass% only has an effect of improving the machinability by about 5%, from about 25% to about 30% in terms of the machinability index.
• a small amount of Pb has a significant effect on the machinability, and is effective at a content of 0.002 mass% or more.
• the Pb content is preferably 0.003 mass% or more, and more preferably 0.01 mass% or more.
• the Pb content is preferably 0.03 mass% or more, and the machinability of the alloy is greatly improved by the ⁇ 1 phase with significantly improved machinability and the inclusion of a small amount of Pb. It is well known that Pb improves the machinability of copper alloys, and for this purpose, about 3 mass% of Pb is required in a binary alloy of Cu-Zn, as typified by free-cutting brass bar C3604.
• an alloy with excellent machinability is completed by having a ⁇ 1 phase containing Si and P and a small amount of Pb particles, or Pb and Bi particles described later, present in the metal structure.
• the upper limit of Pb is set to less than 0.20 mass%.
• the content of Pb is preferably less than 0.10 mass%, and is optimally 0.08 mass% or less in consideration of the effects on the human body and the environment.
• Bi Like Pb, Bi is dissolved in the matrix in an amount of about 0.0001 mass%, and any Bi in excess of this amount exists as particles with a diameter of about 0.1 to about 2 ⁇ m. When both Pb and Bi are added, most of the Bi and Pb are mixed and exist as particles with a diameter of about 0.1 to about 2 ⁇ m. In this embodiment, it was found that by including Bi together with Pb in the presence of the ⁇ 1 phase, machinability equivalent to or greater than that obtained when Pb and Bi are each contained alone can be obtained. The function of improving machinability by Bi was considered to be inferior to that of Pb, but in this embodiment, it was found that it exhibits the same effect as Pb, and in some cases, even exceeds that of Pb. Incidentally, Bi deteriorates the stress corrosion cracking resistance of brass, but when it exists as a particle of a mixture of Pb and Bi, or when the amount of Bi is small, there is almost no effect on stress corrosion cracking.
• Bi When Bi is contained, at least 0.0001 mass% or more of Bi is required in order to have good machinability as an alloy.
• the Bi content is preferably 0.001 mass% or more, more preferably 0.002 mass% or more.
• the amount of Bi is less than 0.20 mass%, preferably less than 0.10 mass%, and further preferably 0.08 mass% or less.
• Bi can be a sufficient substitute for Pb, the effect of Bi on the human body is unknown, Bi is one of the rare metals and has an impact on the environment, and on the other hand, Bi is included in the raw material as an unavoidable impurity.
• the total content of Pb and Bi (compositional formula f2 described later) is set to less than 0.20 mass%, preferably less than 0.10 mass%.
• the amount of Pb, which is harmful to the human body is limited to less than 0.20 mass%, including Bi in some cases, and excellent machinability is the goal.
• Sn Sn is dissolved in the ⁇ 1 phase, which further improves the dezincification corrosion resistance of the ⁇ 1 phase and improves the dezincification corrosion resistance of the alloy.
• Sn When Sn is contained, in order to obtain this effect, Sn needs to be contained in an amount exceeding 0.05 mass%, preferably 0.10 mass% or more.
• Sn is originally distributed more in the ⁇ phase and ⁇ 1 phase than in the ⁇ phase, and a small amount of Sn improves the dezincification corrosion resistance, but when the Sn concentration is high, the ⁇ phase is easily formed and the ductility is reduced.
• the formation of the ⁇ phase not only leads to a decrease in ductility as an alloy, but also reduces machinability and deteriorates the dezincification corrosion resistance.
• the content of Sn needs to be kept below 0.90 mass%, preferably below 0.70 mass%, and more preferably below 0.50 mass%.
• Sn is distributed in large amounts in the ⁇ and ⁇ 1 phases, and it has been found that a high Sn content can cause problems in modifying the ⁇ phase, which contains Si and P. Specifically, it has been found that when the amount of Sn is greater than the amount of Si, the modification of the ⁇ phase becomes insufficient, and the effect of the Sn content in improving dezincification corrosion resistance is offset. As will be described later, the amount of Si must exceed the amount of Sn.
• inevitable impurities include Mn, Fe, Al, Ni, Mg, Se, Te, Sn, Bi, Co, Ca, Zr, Cr, Ti, In, W, Mo, B, Ag, and rare earth elements.
• free-cutting copper alloys particularly free-cutting brass containing Zn at about 30 mass% or more, are not primarily made from high-quality raw materials such as electrolytic copper and electrolytic zinc, but from recycled copper alloys.
• downstream processes downstream processes, processing processes
• most members and parts are cut, generating a large amount of discarded copper alloy at a ratio of 40 to 80 parts by mass per 100 parts by mass of material.
• Examples include cutting chips, scraps, burrs, runners, and products with manufacturing defects. These discarded copper alloys are the main raw materials. If the separation of cutting chips and scraps is insufficient, Pb, Fe, Mn, Si, Se, Te, Sn, P, Sb, As, Bi, Ca, Al, Zr, Ni and rare earth elements are mixed in as raw materials from free-cutting brass with Pb added, free-cutting copper alloys that do not contain Pb but contain Bi, special brass alloys that contain Si, Mn, Fe and Al, and other copper alloys. Cutting chips also contain Fe, W, Co, Mo, etc., which are mixed in from tools. Recycled waste products contain plated products, so Ni, Cr and Sn are mixed in. Pure copper scrap used instead of electrolytic copper contains Mg, Sn, Fe, Cr, Ti, Co, In, Ni, Se and Te. Brass-based scrap used in place of electrolytic copper and electrolytic zinc is often plated with Sn, resulting in Sn contamination.
• scrap containing these elements is used as a raw material, at least to the extent that it does not adversely affect the properties.
• the essential element Pb is contained in an amount of approximately 3 mass%, and furthermore, as impurities, Fe is permitted at 0.5 mass% or less, and Fe + Sn (total amount of Fe and Sn) is permitted up to 1.0 mass%.
• free-cutting brass bars can contain high concentrations of Fe and Sn.
• Fe, Mn, Co and Cr dissolve in the ⁇ and ⁇ phases of Cu-Zn alloys to a certain concentration, but if Si or P is present, they are likely to combine with the Si and P, posing the risk of consuming the Si and P needed to modify the ⁇ phase.
• Si Fe, Mn, Co and Cr
• Fe-Si compounds Mn-Si compounds, Co-Si compounds, Cr-Si compounds, etc.
• P Fe, Mn, Co and Cr form Fe-P compounds, Mn-P compounds, Co-P compounds, Cr-P compounds, etc. in the metal structure.
• These intermetallic compounds are very hard, so they not only increase the cutting resistance but also shorten the tool life.
• the amounts of Fe, Mn, Co, and Cr must be limited, and each content is preferably less than 0.30 mass%, more preferably less than 0.20 mass%, and even more preferably 0.15 mass% or less.
• the total content of Fe, Mn, Co, and Cr must be less than 0.40 mass%, preferably less than 0.30 mass%, more preferably less than 0.25 mass%, and even more preferably 0.20 mass% or less.
• the Al content which is mixed in from special brass rods, brass castings, etc., must be limited because a high content affects the modification of the ⁇ phase and Al forms compounds with P or Si.
• the Al content must be less than 0.30 mass%, preferably less than 0.15 mass%, and more preferably 0.10 mass% or less.
• Ni is often mixed in from scraps, etc. Although Ni has a relatively small effect on mechanical properties such as machinability, it is necessary to limit it in consideration of its effect on the human body.
• the Ni content is preferably less than 0.20 mass%, more preferably less than 0.10 mass%.
• Ag is generally regarded as Cu and has almost no effect on various properties, so there is no need to particularly limit it, but the Ag content is preferably less than 0.05 mass%.
• Te and Se are elements themselves that have free machinability, and although rare, there is a risk of being mixed in large amounts.
• the respective contents of Te and Se are preferably less than 0.10 mass%, more preferably less than 0.05 mass%, and even more preferably 0.02 mass% or less.
• corrosion-resistant brass contains As and Sb to improve the corrosion resistance of brass.
• the content of each of As and Sb is preferably less than 0.05 mass%, and more preferably 0.02 mass% or less.
• the content of each of the other elements, such as Mg, Ca, Zr, Ti, In, W, Mo, B, and rare earth elements, is preferably less than 0.05 mass%, more preferably less than 0.03 mass%, and further preferably 0.02 mass% or less.
• the content of rare earth elements is the total amount of one or more of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Tb, and Lu.
• the total amount of inevitable impurities other than Fe, Mn, Co, Cr and Al is preferably less than 0.70 mass%, and more preferably less than 0.50 mass%.
• compositional formula f1 [Cu] - 4.6 x [Si] + 0.5 x ([Pb] + [Bi]) - [P] - [Sn].
• Sn content is 0.05 mass% or less
• Bi is not contained
• [Bi] in f1 is 0.
• Sn is 0.05 mass% or less, the effect on compositional formula f1 is small, so it is not specified in compositional formula f1. Even if the amount of each element is within the range specified above, if the compositional relational formula f1 is not satisfied, the properties targeted by this embodiment cannot be satisfied.
• the lower limit of the compositional relational formula f1 is 57.5 or more, preferably 58.0 or more, and more preferably 58.2 or more.
• the proportion of the ⁇ phase increases, the ⁇ phase is sufficiently modified, and excellent machinability is maintained, while good dezincification corrosion resistance and stress corrosion cracking resistance can be provided, and good ductility and cold workability can be obtained.
• the upper limit of the compositional relational formula f1 affects the proportions of the ⁇ phase and the ⁇ 1 phase, and if the compositional relational formula f1 is greater than 60.5, the proportion of the ⁇ 1 phase decreases, making it difficult to obtain excellent machinability and reducing the strength. Therefore, f1 is 60.5 or less, preferably 60.2 or less, and more preferably 60.0 or less.
• compositional formula f0 Sn is contained to further improve the dezincification corrosion resistance.
• Sn is contained in a large amount in the ⁇ phase, and the more Sn is contained, the more the dezincification corrosion of the ⁇ 1 phase is delayed.
• f0 is preferably less than 0.8, more preferably less than 0.6, and even more preferably less than 0.5.
• the free-cutting copper alloy of this embodiment contains a large amount of the conventional ⁇ phase, and in this application, ⁇ 1 phase, while having good dezincification corrosion resistance, stress corrosion cracking resistance, and mechanical properties, and also has the completely contradictory properties of machinability, which requires a kind of brittleness that reduces resistance during cutting and allows chips to be broken into small pieces, and ductility.
• machinability which requires a kind of brittleness that reduces resistance during cutting and allows chips to be broken into small pieces, and ductility.
• composition relational formula f1 As for Fe, Mn, Co, Cr, Al, and other unavoidable impurities specified separately, they are not specified in the composition relational formula f1 because their effect on the composition relational formula f1 is small so long as they are within the range of the category treated as unavoidable impurities.
• Tables 1 to 4 show the results of comparing the compositions of the Cu-Zn-Si alloys described in the above-mentioned Patent Documents 1 to 15 with the alloy of this embodiment.
• Patent Document 8 differ in the contents of the main elements Si and Cu
• the present embodiment and Patent Document 9 differ in the content of the main element Si
• the present embodiment and Patent Document 15 differ in the content of the main element Cu.
• Patent Documents 1, 13, and 15 state that Pb is not contained, and the Pb content is different.
• the ⁇ phase in the metal structure is significantly restricted from the viewpoints of machinability, dezincification corrosion resistance, corrosion resistance, etc.
• the ⁇ 1 phase in the present application is different from the ⁇ phase in Patent Documents 8, 10, 11, and 12, but the ⁇ phase is restricted to 5% or less, 25% or less, 15% or less, and 0.9% or less, respectively.
• Patent Document 10 relates to a near-net-shape tubular hot forged product, and uses a tubular material.
• heat treatment is performed at a temperature of 350 to 550° C. or 400 to 600° C. in order to reduce the ⁇ phase and to break up the ⁇ phase.
• the steel contains 0.2 mass% or more of Sn, contains Sn and Si to improve the dezincification corrosion resistance of the ⁇ phase, and requires hot extrusion at a temperature of 700° C. or more to improve machinability and heat treatment at 400 to 600° C. to improve corrosion resistance.
• the proportion of the ⁇ phase is approximately 5 to 20%, and the content of Si is 0.01 to 0.50 mass%, and may be controlled to 0.2 mass% or less.
• Patent Documents 12, 13, and 14 Al is considered to be essential in order to improve discoloration resistance, castability, and dezincification corrosion resistance.
• Patent Document 14 in order to improve dezincification corrosion resistance, Sn and Al are contained in an amount of at least 0.1 mass% each, and in order to obtain excellent machinability, it is necessary to contain large amounts of Pb and Bi.
• Patent Document 15 a corrosion-resistant copper alloy casting is obtained that does not contain Pb, requires a ⁇ phase, and contains 65 mass% or more Cu and Si, as well as trace amounts of Al, Sb, Sn, Mn, Ni, B, etc., and has good mechanical properties and castability.
• Patent documents 2 to 7 all require that the cooling process after hot working is performed so that the average cooling rate in the temperature range from about 530°C to about 450°C is about 0.1°C/min to about 70°C/min, and that the resulting P compounds are present in the metal structure. They also state that the ⁇ phase is effective for machinability, and make no mention of modifying the ⁇ phase. They are silent about dezincification corrosion resistance and stress corrosion cracking resistance, and no data is disclosed. Furthermore, except for Patent document 7, no data is disclosed about cutting resistance under high-speed cutting conditions.
• the cooling process after hot working is started at a temperature lower than 670°C and higher than 500°C, and the average cooling rate in the temperature range from the cooling process start temperature to 500°C and the average cooling rate in the temperature range from 500°C to 300°C exceed 300°C/min, which is basically the opposite of Patent documents 2 to 7.
• Patent Documents 2 to 7 there is no mention whatsoever of the ⁇ phase being modified or the modified ⁇ phase, i.e., the ⁇ 1 phase.
• the ⁇ 1 phase is formed under the following conditions. During hot working, a ⁇ phase is formed in which a certain amount of Si and P are dissolved. Then, cooling treatment is started at a temperature higher than 500°C, and in the cooling treatment, the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C exceeds 300°C/min, and the average cooling rate in the temperature range from 500°C to 300°C exceeds 300°C/min.
• the ⁇ 1 phase is formed by the above.
• Patent documents 2 to 7 disclose metal structures etched with a mixture of hydrogen peroxide and aqueous ammonia, but in none of them are grain boundaries observed within the ⁇ phase.
• Patent documents 2 to 7 do not define the start temperature of the cooling treatment after hot working, but even if the start temperature of the cooling treatment falls below 530°C, the average cooling rate from the start temperature of the cooling treatment to 500°C is about 0.1°C/min or more and about 70°C/min or less, so the ⁇ 1 phase (modified ⁇ phase) is not observed.
• Beta1 phase differs from conventional beta phase in that it significantly improves dezincification corrosion resistance and stress corrosion cracking resistance, and further improves machinability, surpassing that when P compounds are present.
• the beta1 phase must be present in the metal structure at an area ratio of more than 25%.
• Patent Documents 2 to 7 claim that the gamma phase is effective in improving machinability.
• the metal structure of the present application is composed of ⁇ phase, ⁇ 1 phase, and in some cases, small amount or 0% of ⁇ phase, excluding non-metallic inclusions.
• the difference between the ⁇ phase and the ⁇ 1 phase is that when the ⁇ 1 phase is etched with a mixture of hydrogen peroxide and ammonia water, a grain boundary pattern, i.e., grain boundaries, are observed within the ⁇ 1 phase, but in the case of the ⁇ phase, no grain boundaries are observed within the ⁇ phase.
• the ⁇ 1 phase in this embodiment is obtained by dissolving a certain amount of Si and P in the ⁇ phase at high temperature during hot working, and then maintaining the state of 500 to 670°C, and then cooling from that temperature range (cooling at an average cooling rate in the temperature range from the cooling treatment start temperature to 500°C and an average cooling rate in the temperature range from 500°C to 300°C both exceeding 300°C/min, and continuing to cool to near room temperature) to bring the state of the metal structure at 500 to 670°C to room temperature.
• the cooling rate in the temperature range from the high temperature cooling start temperature to 300°C is increased to rapidly cool the material, and the material is cooled to room temperature of 100°C or less. This brings the state of the metal structure at high temperature to room temperature.
• the ⁇ 1 phase is obtained. Even if the above-mentioned cooling treatment is performed on the ⁇ phase of a Cu-Zn alloy that does not contain both the predetermined amount of Si and P, the ⁇ 1 phase cannot be obtained. Similarly, even if an alloy containing Si and P is subjected to a cooling treatment at a temperature lower than 500°C, for example, from 450°C at a cooling rate exceeding 300°C/min, the ⁇ 1 phase cannot be obtained. Note that a certain amount of ⁇ phase is required to modify the ⁇ phase, and if the ⁇ phase does not exist or is small, the ⁇ 1 phase cannot be obtained.
• the degree of modification of the ⁇ phase is also affected by the amount of Si and P, the amount of unavoidable impurities, the cooling treatment start temperature, the average cooling rate in the temperature range from the start of the cooling treatment to 500°C, and the average cooling rate in the temperature range from 500°C to 300°C.
• the degree of modification of the ⁇ phase is improved, that is, when the ⁇ 1 phase is further modified, a material having better machinability and good dezincification corrosion resistance and stress corrosion cracking resistance can be obtained.
• the ⁇ 1 phase (modified ⁇ phase) overcomes the drawbacks of the ⁇ phase of Cu-Zn alloys, namely, the dezincification corrosion resistance and stress corrosion cracking resistance of the alloy, which have been major issues. That is, as an example, in concrete figures, the corrosion progress of dezincification corrosion can be reduced by about 60% or more, and similarly, the crack progress of stress corrosion cracking can be delayed by about 50% or more.
• dezincification corrosion of Cu-Zn alloys containing ⁇ phases is a major problem, and since dezincification corrosion occurs along the ⁇ phase, the amount of ⁇ phase is limited to 25% or less or 20% or less, and a heat treatment of 350 to 550 ° C. is performed to further reduce the amount of ⁇ phase and to break up the ⁇ phase.
• strength it depends largely on the area ratio of the constituent phases, but the modified ⁇ phase, i.e., ⁇ 1 phase, has higher strength and better ductility than the ⁇ phase, so the alloy has a good balance of strength and ductility.
• the area ratio of the ⁇ 1 phase In the Cu-Zn-Si-P-Pb alloy, which is the free-cutting copper alloy of this embodiment, in order to obtain good machinability while minimizing the Pb content, the area ratio of the ⁇ 1 phase must be at least more than 25%. Furthermore, in order to improve machinability and strength, the area ratio of the ⁇ 1 phase is preferably 30% or more, more preferably 33% or more. On the other hand, if the amount of the ⁇ 1 phase is too large, for example 95%, the ⁇ phase is not modified. Since the ⁇ phase is modified in the presence of the ⁇ phase, a certain amount of the ⁇ phase is required.
• the ⁇ 1 phase significantly slows down the progress of dezincification corrosion and stress corrosion cracking compared to the ⁇ phase, but is still inferior to the ⁇ phase in dezincification corrosion resistance and stress corrosion cracking resistance.
• the ⁇ phase is selectively dezincified and the dezincification corrosion depth reaches about 500 ⁇ m.
• the ⁇ 1 phase is selectively dezincified, but the dezincification corrosion depth is about 20 to about 200 ⁇ m depending on the degree of modification to the ⁇ 1 phase and the area ratio of the ⁇ 1 phase, and the progress of dezincification corrosion is greatly suppressed.
• the dezincification corrosion resistance is greatly improved by modifying the ⁇ phase to the ⁇ 1 phase, but even if it is improved, it is inferior to the ⁇ phase in dezincification corrosion resistance and ductility, so if the area ratio of the ⁇ 1 phase is high, the dezincification corrosion resistance and ductility of the alloy are low.
• the area ratio of the ⁇ 1 phase needs to be set to 80% or less, preferably 70% or less, and more preferably 65% or less.
• the present application is basically composed of ⁇ phase and ⁇ 1 phase, and a treatment is carried out to modify the ⁇ phase to ⁇ 1 phase, but the ⁇ phase is hardly affected by the treatment.
• a certain amount of ⁇ phase is necessary to modify the ⁇ phase. If there is too much ⁇ 1 phase, the ductility of the alloy is problematic, and an appropriate amount of ductile ⁇ phase is necessary, and conversely, if there is too much ⁇ phase, the strength is low.
• the ⁇ phase containing Si only improves the machinability slightly compared to the ⁇ phase not containing Si, and the amount of ⁇ phase is limited from the viewpoint of machinability.
• the ⁇ phase plays the role of a cushioning material during cutting, or plays the role of a stress concentration source at the boundary with the hard ⁇ 1 phase during cutting, and even if the alloy contains up to about 75% of the ⁇ phase, the cutting resistance of the alloy is maintained low and the chips are broken.
• the ⁇ phase plays the role of a cushioning material during cutting and also plays the role of a stress concentration source at the boundary with the hard ⁇ 1 phase, the ⁇ phase is preferably in a fine granular shape.
• the amount of the ⁇ phase must be 20% or more, preferably 30% or more, and more preferably 35% or more.
• the upper limit of the ⁇ phase is less than 75%, preferably 70% or less, and more preferably 67% or less.
• the ⁇ phase is a phase that contributes to machinability in Cu-Zn-Si alloys having a Cu concentration of about 69 to about 80 mass% and a Si concentration of about 2 to about 4 mass%.
• Patent Document 15 states that the ⁇ phase is essential in Pb-free Cu-Zn-Si alloys, and Patent Documents 2 to 6 also state that the ⁇ phase containing Si has good machinability, and at the same time, the ⁇ phase containing Si also has good machinability.
• the structure-composition relational formula f6 is a simple conditional formula for obtaining good machinability as an alloy.
• the amount of ⁇ 1 phase, the amount of Si, the amount of Pb and Bi, and the amount of P contained in the alloy within the composition range of the present application are arranged as positive effects, and the amount of ⁇ phase is arranged as negative effects.
• the amount of ⁇ 1 phase is multiplied by the amount of Si to the 1/2 power, the sum of the amounts of Pb and Bi is multiplied by a coefficient of 20, and the amount of P is multiplied by a coefficient of 15, and the sum of these is multiplied by the amount of ⁇ phase to the coefficient of 2, and then subtracted.
• the performance of the ⁇ 1 phase (modified ⁇ phase) is directly affected by the Si concentration and is also affected by the P concentration, and when a very small amount of Pb or Bi is contained, the machinability is improved.
• the ⁇ phase inhibits machinability.
• f6 should be greater than 27, preferably greater than 33, more preferably greater than 35, and even more preferably greater than 38, which approaches the machinability of a free-cutting brass bar containing 3 mass% Pb.
• 1A to 6B show photographs of the metal structures of various alloys and photographs of the results of the ISO6509 dezincification corrosion test.
• 1A is a photograph of the structure of a copper alloy in an embodiment, and the copper alloy was obtained by subjecting Alloy No. S01 to Process No. A2.
• Alloy No. S01 has a composition of Zn-63.3 mass% Cu-0.95 mass% Si-0.069 mass% P-0.063 mass% Pb-0.017 mass% Bi.
• FIG. 1B is a cross-sectional metallographic photograph showing the results of a dezincification corrosion test performed on the alloy of FIG.
• 2A is a photograph of the structure of a copper alloy in the embodiment, and the copper alloy was obtained by subjecting Alloy No. S11 to Process No. E2.
• Alloy No. S11 has a composition of Zn-62.5 mass% Cu-0.96 mass% Si-0.064 mass% P-0.072 mass% Pb.
• Process No. E2 the alloy was hot extruded at 550°C, and the average cooling rate in the temperature range from 500°C to 300°C was set to 20°C/min to obtain a rod having a diameter of 50 mm and a length of 200 mm.
• FIG. 2B is a cross-sectional metallographic photograph showing the results of a dezincification corrosion test performed on the alloy of FIG. 2A in accordance with the ISO 6509 test method, the photograph including the portion exhibiting the maximum corrosion depth.
• 3A is a photograph of the structure of a copper alloy in an embodiment, and the copper alloy was obtained by subjecting Alloy No. S11 to Process No. E13H. In detail, Alloy No.
• S11 has a composition of Zn-62.5 mass% Cu-0.96 mass% Si-0.064 mass% P-0.072 mass% Pb.
• Hot extrusion was performed at 550 ° C., and the average cooling rate in the temperature range from 500 ° C. to 300 ° C. was set to 20 ° C./min to obtain a rod having a diameter of 50 mm and a length of 200 mm.
• the rod was heated, and the rod was placed horizontally and hot forged at 630 ° C. to a thickness of 20 mm, and cooled at an average cooling rate of 35 ° C./min.
• the cooling process was started at 455 ° C., and the average cooling rate in the temperature range from 455 ° C.
• FIG. 3B is a cross-sectional metallographic photograph showing the results of a dezincification corrosion test performed on the alloy of FIG. 3A in accordance with the ISO 6509 test method, the photograph including the portion exhibiting the maximum corrosion depth.
• 4A is a photograph of the structure of a copper alloy in an embodiment, and the copper alloy was obtained by subjecting Alloy No. S43 to Step No. E6.
• Alloy No. S43 has a composition of Zn-63.3 mass% Cu-0.98 mass% Si-0.084 mass% P-0.060 mass% Pb-0.28 mass% Sn.
• FIG. 4B is a cross-sectional metallographic photograph including a portion exhibiting maximum corrosion depth, showing the results of a dezincification corrosion test performed on the alloy of FIG.
• 5A is a photograph of the structure of a copper alloy in an embodiment, and the copper alloy was obtained by subjecting Alloy No. S02 to Process No. A34H and Process No. G1.
• Alloy No. S02 has a composition of Zn-62.9 mass% Cu-0.98 mass% Si-0.071 mass% P-0.071 mass% Pb.
• Process No. A34H the alloy was obtained by hot extrusion at 615°C and an average cooling rate from 500°C to 300°C of 18°C/min.
• Process No. A34H the alloy was obtained by hot extrusion at 615°C and an average cooling rate from 500°C to 300°C of 18°C/min.
• FIG. 5B is a cross-sectional metallographic photograph including a portion exhibiting maximum corrosion depth, showing the results of a dezincification corrosion test performed on the alloy of FIG. 5A in accordance with the ISO 6509 test method.
• 6A is a photograph of the structure of a copper alloy in an embodiment, and the copper alloy was obtained by subjecting alloy No. S02 to process No. E14H. In detail, alloy No.
• S02 has a composition of Zn-62.9 mass% Cu-0.98 mass% Si-0.071 mass% P-0.071 mass% Pb.
• hot extrusion was performed at 550 ° C., and the average cooling rate from 500 ° C. to 300 ° C. was set to 20 ° C./min to obtain a rod having a diameter of 50 mm and a length of 200 mm.
• the rod was heated, and the rod was placed horizontally and hot forged at 630 ° C. to a thickness of 20 mm, and then naturally cooled.
• the average cooling rate in the temperature range from 500 ° C. to 300 ° C. was 25 ° C./min.
• FIG. 6B is a cross-sectional metallographic photograph including a portion exhibiting maximum corrosion depth, showing the results of a dezincification corrosion test performed on the alloy of FIG. 6A in accordance with the ISO 6509 test method.
• grain boundary patterns i.e., grain boundaries
• the grain boundaries refer to linear patterns penetrating the ⁇ 1 phase grains observed in the ⁇ 1 phase, as shown in Figure 1A.
• grain boundaries are recognized in the modified ⁇ phase, i.e., the ⁇ 1 phase, whereas in FIG.
• FIG. 3A shows slight black streaks are observed in the ⁇ phase, but no grain boundaries penetrating the ⁇ phase crystal grains are seen. In FIG. 6A, even a hint of grain boundaries is not seen in the ⁇ phase. Instead, in FIG. 3A and FIG. 6A, black granular precipitates of about 0.5 to 3 ⁇ m are present mainly in the ⁇ phase and at the phase boundary between the ⁇ phase and the ⁇ phase.
• the granular precipitates are mainly P compounds, but also include Pb particles, mixed particles of Pb and Bi, compounds of Fe, oxides, and sulfides, and can be distinguished by microscopic observation, but are a little difficult to distinguish in printed photographs.
• Precipitates that deviate from the size of the above precipitates and exist in the ⁇ phase are not P compounds.
• FIG. 3A and FIG. 6A there are about 1,000 mainly P compounds within the field of view of the printed photographs.
• Figures 1A, 2A, 4A, and 5A fine granular P compounds and the like are absent or present in small amounts, and the number of precipitates is at least 1/10 or 1/50 of that in Figures 3A and 6A. From these, whether grain boundaries exist in the ⁇ 1 phase or the ⁇ phase depends on whether the cooling treatment start temperature is higher or lower than about 500°C, and whether a large amount of P compounds exists depends on whether the cooling treatment start temperature is higher or lower than about 500°C.
• the hot extruded material, hot rolled material and hot forged material are preferably high strength materials having a tensile strength of 460 N/ mm2 or more in the hot worked state without cold working.
• the tensile strength is more preferably 490 N/mm 2 or more, and even more preferably 520 N/mm 2 or more.
• the tensile strength of the currently used Pb-added copper alloy, C3604 is about 390 to 420 N/mm 2 and the elongation is about 30 to 35%, so that the increased strength can lead to weight reduction.
• the cutting material may be subjected to cold working such as light crimping or bending, and it is necessary that the material does not crack. Machinability requires a certain degree of brittleness in the material because the cutting chips are broken, but it is a contradictory property to cold workability.
• f7 is about 470.
• the applications of this embodiment include electrical and electronic equipment parts, automobile parts for which EVs are becoming more common, and other highly conductive members and parts.
• phosphor bronze JIS standard, C5191, C5210 containing 6 mass% or 8 mass% Sn is often used for these applications, and the electrical conductivity of these is about 14% IACS and 12% IACS, respectively. Therefore, if the electrical conductivity of the copper alloy of this embodiment is 15% IACS or more, no problem will occur with respect to electrical conductivity. Note that the upper limit of the electrical conductivity is not particularly specified because the improved conductivity will hardly cause any practical problems.
• the free-cutting copper alloy of this embodiment is characterized by having excellent deformability at 540 to 750° C., and can be hot extruded into a bar with a small cross-sectional area and hot forged into a complex shape. Due to the energy situation and the good granular shape of the ⁇ phase, the hot working temperature is preferably less than 750° C., more preferably less than 720° C., and from the viewpoint of hot deformation resistance, it is preferably more than 540° C., more preferably more than 560° C.
• the metal structure of the alloy of this embodiment varies not only with the composition but also with the manufacturing process. It is not only affected by the hot working temperature and heat treatment conditions of hot extrusion and hot forging, but also by the average cooling rate during the cooling process of hot working and heat treatment. As a result of intensive research, it was found that the metal structure is greatly affected by the cooling treatment start temperature, the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C, and the average cooling rate in the temperature range from 500°C to 300°C during the cooling process of hot working and heat treatment.
• the melting is carried out at about 950 to about 1200°C, which is about 100 to about 300°C higher than the melting point (liquidus temperature) of the alloy of this embodiment.
• the molten metal at about 900 to about 1100°C, which is about 50 to about 200°C higher than the melting point, is poured into a predetermined mold and cooled by several cooling means such as air cooling, slow cooling, and water cooling. After solidification, the constituent phases change in various ways.
• the hot working includes hot extrusion, hot forging, and hot rolling.
• the final hot working step is performed under the following conditions.
• the material temperature (extrusion temperature) immediately after hot working is higher than 540 ° C and lower than 750 ° C, depending on the extrusion ratio (hot working rate) and the equipment capacity.
• the extruded rod is wound into a coil, or if the cross-sectional area of the extruded rod is large, it is extruded as a straight rod onto a table.
• the lower limit of the hot extrusion temperature is related to the deformation resistance during hot extrusion, and the lower the extrusion temperature, the finer the ⁇ -phase crystal grains become, and the better the dezincification corrosion resistance, stress corrosion cracking resistance, and machinability become.
• the extrusion temperature is preferably 560 ° C or higher due to the relationship between the equipment capacity and the cooling treatment start temperature described later.
• the upper limit is related to the shape of the ⁇ -phase, and a stable metal structure can be obtained by controlling it at a narrower temperature.
• the metal structure becomes a single ⁇ phase, or the proportion of ⁇ phase becomes 90% or more, and the shape of the ⁇ phase crystal grains becomes needle-like, or coarse ⁇ phase crystal grains tend to appear.
• the strength is slightly lowered, the balance between strength and ductility is slightly worsened, and the long side is large and the coarse ⁇ phase crystal grains become an obstacle to cutting, resulting in poor machinability. Furthermore, the dezincification corrosion resistance and stress corrosion cracking resistance are also poor.
• the extrusion temperature is preferably 720°C or lower.
• the shape of the ⁇ phase crystal grains is related to the compositional relational formula f1, and when the compositional relational formula f1 is 59.0 or less, the extrusion temperature is preferably lower than 720°C. By extruding at a lower temperature than the copper alloy containing Pb, it is possible to provide good machinability and strength.
• the ⁇ phase can be modified, and a material having better machinability, dezincification corrosion resistance, and stress corrosion cracking resistance can be obtained. That is, in the cooling process after hot extrusion, the cooling process is first started at a temperature lower than 670°C and higher than 500°C, and the average cooling rate in the temperature range from the cooling process start temperature to 500°C and the average cooling rate in the temperature range from 500°C to 300°C are set to at least 300°C/min, preferably more than 600°C/min, and more preferably 900°C/min or more.
• the average cooling rate in the temperature range from the cooling process start temperature to 500°C and the average cooling rate in the temperature range from 500°C to 300°C are roughly the same, or in some cases, the former is slightly faster. If the material is cooled at a more preferable cooling rate, the ⁇ 1 phase is further modified. When the ⁇ 1 phase is further modified, a material having better machinability and good dezincification corrosion resistance and stress corrosion cracking resistance can be obtained.
• the upper limit of the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C and in the temperature range from 500°C to 300°C is sufficient as a cooling rate that can be performed in normal production equipment, and is not particularly specified, but if mentioned, the cooling rate is preferably about 9000°C/min or less.
• the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C and the average cooling rate in the temperature range from 500°C to 300°C are 300°C/min or less, grain boundaries cannot be observed in the ⁇ phase.
• the degree of reforming to the reformed ⁇ phase i.e., ⁇ 1 phase, is greater as the cooling rate is faster.
• the cooling rate becomes a little slower as the temperature approaches room temperature, but it is desirable to continue cooling in the temperature range from 500°C to 300°C.
• the cooling treatment start temperature also affects the modification of the ⁇ phase.
• the cooling treatment is started at a temperature lower than 550°C, if the cooling rate from 550°C to the cooling treatment start temperature is slow, compounds of P and Zn, or P and Zn, Si begin to form, and the formation of P compounds is further promoted at 530°C or lower.
• a cooling rate of more than 300°C/min P compounds are hardly formed, but if the cooling treatment start temperature is lower than 550°C, P compounds are observed in the metal structure.
• the cooling treatment start temperature must be lower than 670°C, and is preferably lower than 650°C.
• the hot working temperature is defined as the temperature of the hot worked material that can be measured approximately 2 or 3 seconds after the end of hot extrusion, hot forging, or hot rolling.
• the metal structure is affected by the temperature immediately after processing, which has caused large plastic deformation.
• hot forging hot extrusion material is mainly used as the material, but continuous cast rods are also used. Since the material for forging is not the final hot processing, no cooling measures are required. Compared to hot extrusion, hot forging has a high processing speed, is processed into a complex shape, and in some cases, the wall thickness may be strongly processed to about 3 mm. In addition, the weight of each forged product is several tens of grams to several kilograms, and small ones are rapidly cooled during forging and the cooling rate thereafter is also fast. Therefore, the heating temperature of the material during forging is higher than the heating temperature of the ingot during hot extrusion.
• the temperature of the hot forged product i.e., the material temperature about 2 seconds or 3 seconds after forging, is preferably higher than 540°C and lower than 750°C.
• Hot forging is also related to the compositional relational formula f1, and when the compositional relational formula f1 is 59.0 or less, the hot forging temperature is preferably lower than 720 ° C. Although it depends on the processing rate of hot forging, the lower the temperature, the smaller the crystal grain size of the ⁇ phase, the change in the shape of the ⁇ phase crystal grains from needle-like to granular, the higher the strength, the better the balance between strength and ductility, and the better the machinability, dezincification corrosion resistance, and stress corrosion cracking resistance.
• the cooling rate after hot forging a material having good dezincification corrosion resistance, good stress corrosion cracking resistance, and good machinability can be obtained. That is, in the cooling process after hot forging, the cooling treatment is first started at a temperature lower than 670°C and higher than 500°C, and the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C and the average cooling rate in the temperature range from 500°C to 300°C are set to at least 300°C/min, preferably more than 600°C/min, and more preferably 900°C/min or more.
• the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C and the average cooling rate in the temperature range from 500°C to 300°C are roughly the same, or the former is slightly faster.
• the average cooling rate is set to more than 300°C/min, the ⁇ phase is modified, and when the metal structure is etched with a mixture of hydrogen peroxide and ammonia water and observed with a metal microscope at a magnification of 500 times, grain boundaries can be observed in the modified ⁇ phase. If the average cooling rate in the temperature range from 500°C to 300°C is 300°C/min or less, grain boundaries cannot be observed in the ⁇ phase.
• the degree of modification to the modified ⁇ phase i.e., the ⁇ 1 phase
• the degree of modification to the modified ⁇ phase is greater as the cooling rate is faster.
• the cooling rate from a temperature lower than 300°C to room temperature becomes slightly slower as the temperature approaches room temperature, but it is desirable to continue cooling in the temperature range from 500°C to 300°C.
• the upper limit of the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C and the temperature range from 500°C to 300°C is not particularly specified, but if mentioned, the cooling rate is preferably about 9000°C/min or less.
• the cooling treatment start temperature also affects the modification of the ⁇ phase.
• the cooling treatment is started at a temperature lower than 550 ° C, if the cooling rate from 550 ° C to the cooling treatment start temperature is slow, compounds of P and Zn, or P and Zn, Si begin to form, and the formation of P compounds is further promoted at 530 ° C or lower.
• a cooling rate of more than 300 ° C / min P compounds are hardly formed, but if the cooling treatment start temperature is lower than 550 ° C, P compounds are observed in the metal structure.
• the cooling treatment start temperature needs to be lower than 670 ° C, and is preferably lower than 650 ° C.
• the product is placed in a simple furnace with an atmospheric temperature set at about 550 to 600°C for several tens of seconds to several minutes, and then a cooling process is started, whereby a more uniform and stable forged product can be obtained.
• shot blasting is an effective means after the completion of the hot forging-cooling treatment.
• the ingot is heated and rolled repeatedly 5 to 15 times.
• the material temperature at the end of the final hot rolling is preferably above 540°C and below 750°C, and more preferably below 670°C.
• the rolled material is cooled, but as with hot extrusion, the cooling process begins at a temperature above 500°C and below 670°C, and the average cooling rate in the temperature range from the cooling process start temperature to 500°C and the average cooling rate in the temperature range from 500°C to 300°C are set to at least 300°C/min, preferably above 600°C/min, and more preferably 900°C/min or more.
• the cooling rate slows slightly as the temperature approaches room temperature, but it is desirable to continue cooling in the temperature range from 500°C to 300°C.
• the cooling rate is preferably about 9000°C/min or less.
• Cool Treatment In the present application, if the cooling treatment cannot be started at a temperature higher than 500°C after the final hot working, or if the average cooling rate in the temperature range from 500°C to 300°C exceeds 300°C/min, the ⁇ phase cannot be reformed. In addition, when making a small diameter rod, wire, etc., the ⁇ phase is not basically reformed even if a process such as cold working and annealing in which heat is applied is included.
• annealing is performed under conditions of a temperature higher than 520°C and lower than 630°C for 1 minute to 5 hours, and in the cooling after annealing, the cooling treatment is started at a temperature higher than 500°C, the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C exceeds 300°C/min, and the average cooling rate in the temperature range from 500°C to 300°C exceeds 300°C/min, thereby reforming the ⁇ phase and forming the ⁇ 1 phase.
• the annealing temperature is preferably 530° C.
• the average cooling rate in the temperature range from 500° C. to 300° C. is preferably set to more than 600° C./min, more preferably 900° C./min or higher, from the viewpoint of the degree of modification of the ⁇ 1 phase.
• this heat treatment is applied to hot-worked materials that cannot be cooled under predetermined conditions after hot working, and materials that have been subjected to cold working after hot working and are annealed one or more times.
• cold working may be applied to the hot extruded material in order to obtain high strength, improve dimensional accuracy, or to make the extruded rod or coil material into a straight shape with less bending.
• the hot extruded material is cold drawn at a working ratio of about 2 to about 30%, or in some cases drawn, and then straightened.
• the thin bar, wire, or rolled material is repeatedly subjected to cold working and annealing, and after the final heat treatment, is subjected to cold working and straightening with a final working ratio of 0 to about 30%. The closer the final working ratio is to 0%, the less likely the material is to crack when cold working such as light crimping or bending is performed on the material.
• low-temperature annealing In the case of bars, wires, forgings, and rolled materials, low-temperature annealing may be performed in the final process at a temperature below the recrystallization temperature, mainly for the purpose of removing residual stress, straightening the bar (straightness of the bar), and adjusting and improving the metal structure.
• the ⁇ 1 phase modified by the hot working process and heat treatment is damaged when heat is applied to the alloy. For example, heating at 300°C for 2 hours damages the modification of the ⁇ phase, and the modified ⁇ 1 phase reverts to the original ⁇ phase, and the improved machinability, dezincification corrosion resistance, and stress corrosion cracking resistance become the properties of the alloy made of the original ⁇ phase. Therefore, low-temperature annealing is not recommended, but is permissible at temperatures below about 150°C.
• the alloy composition, compositional formula, metal structure, structure-structure formula, and structure-composition formula are specified as described above, so that even with a low Pb content, excellent machinability can be obtained, and the alloy has good dezincification corrosion resistance and stress corrosion cracking resistance, excellent hot workability, high strength, and an excellent balance of strength and ductility.
• a prototype test of copper alloy was carried out using a low-frequency melting furnace and semi-continuous casting machine that are used in actual operation. Additionally, prototype tests of copper alloys were carried out using laboratory equipment.
• the alloy compositions are shown in Tables 5 to 7.
• the manufacturing processes are shown in Tables 8 to 17. In the compositions, "Mm” stands for misch metal and indicates the total amount of rare earth elements. Each manufacturing process is described below.
• the cooling rate of hot working such as hot extrusion, hot forging, or hot compression is the average cooling rate from the end of hot working to the start of cooling treatment.
• a billet with a diameter of 240 mm was produced using a low-frequency melting furnace and a semi-continuous casting machine that are in actual operation.
• the raw materials used were those that conformed to those used in actual operation.
• the billet was cut to a length of 800 mm and heated.
• a round bar with a diameter of 20.9 mm was extruded using an indirect extruder with a nominal capacity of 2750 tons, and the extruded material (round bar) was wound into a coil in a tank located a short distance from the extruder.
• This tank is capable of water cooling with an adjustable amount of water.
• the cooling process water cooling
• the cooling process was started at the same time as the extruded material was placed in the tank.
• the temperature was measured using a radiation thermometer, and the temperature of the extruded material was measured when it was extruded from the extruder, when the cooling process was started, and until it reached 500°C and 300°C.
• a radiation thermometer Model IGA8Pro/MB20 manufactured by LumaSense Technologies Inc. and a contact thermometer were used in combination.
• process AA i.e. process No. A1-A5, A11H-A14H
• the extrusion temperature was 630°C
• process AB i.e. process No. A21-A25, A31H-A34H
• the extrusion temperature was 615°C
• process No. AD i.e. process No. A41-A44, A46H, A47H
• the extrusion temperature was 720°C.
• a cooling process was started, and the time until the extrusion material reached 500°C and 300°C was measured.
• the average cooling rate in the temperature range from the cooling treatment start temperature to 300°C is described as the cooling rate in the temperature range from 500°C to 300°C.
• the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C can be easily calculated from the average cooling rate in the temperature range from the cooling treatment start temperature to 300°C and the average cooling rate in the temperature range from 500°C to 300°C. It was confirmed that the cooling rate in the temperature range from the cooling treatment start temperature to 500°C is the same as the cooling rate in the temperature range from 500°C to 300°C, or is slightly faster under some conditions.
• process No. A25 and process No. A31H the bar material obtained in process No. A21 was used and further annealed at low temperatures in the laboratory at 130°C for 5 hours and 300°C for 2 hours.
• process AA, process AB, and process AD materials were subjected to microscopic observation, cutting tests, dezincification corrosion tests, and tensile tests.
• step B raw materials were melted in a laboratory at a predetermined component ratio as shown in Table 12.
• the molten metal was poured into a metal mold having a diameter of 100 mm and a length of 200 mm to prepare billets.
• Some billets had impurities such as Fe intentionally added to them.
• the concentration of the intentionally added impurities such as Fe was approximately the same level as or lower than that of commercially available brass containing Pb.
• These billets were heated, and in process No. B1, the extrusion temperature was set to 670°C, and the material was extruded into a round bar with a diameter of 20 mm.
• the cooling process was started at 540°C, and the material was cooled from 500°C to 300°C at an average cooling rate of 960°C/min. It was confirmed that the average cooling rate from 540°C to 500°C was roughly the same as the average cooling rate from 500°C to 300°C. Thereafter, the material was cooled continuously under the same cooling conditions, and the material was cooled to a temperature of about 100°C or less.
• the extrusion temperature was set to 670°C, and the material was extruded into a round bar with a diameter of 20 mm, and the material was cooled from 500°C to 300°C at an average cooling rate of 40°C/min without performing the cooling process.
• Process No. B1 and B3H were subjected to a microscope observation, a cutting test, a dezincification corrosion test, and a tensile test, and a part of Process No. B3H was used as a hot forging material for Process D.
• the extrusion temperature was 590°C
• the material was extruded to a diameter of 50 mm
• no cooling treatment was performed
• the average cooling rate from 500°C to 300°C was 25°C/min to produce a forging material.
• Process C forging and hot compression materials: castings (Process No. C1, C2)
• the castings used as forging materials were prepared in a laboratory by melting raw materials in a prescribed composition ratio, and casting the molten metal at about 1000°C into an iron mold with an inner diameter of 35 mm and a depth of 200 mm (Process No. C1), and casting into an iron mold with an inner diameter of 55 mm and a depth of 200 mm (Process No. C2).
• the castings reached about 700°C, they were removed from the mold and allowed to cool naturally without undergoing a cooling treatment.
• the average cooling rate from 500°C to 300°C was 35°C/min in process No. C1 and 23°C/min in process C2.
• the average cooling rate from after forging to the start of cooling treatment was 100 ° C./min except for process No. D15H and D13H, and 120 ° C./min in process No. D15H.
• cooling treatment was not performed and the material was naturally cooled.
• the cooling treatment start temperature was 475 to 695 ° C.
• process No. D13H were 475 to 695 ° C. in process No. D13H. Except for D13H, the cooling rate was changed from 240°C/min to 1980°C/min.
• the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C was the same as the average cooling rate in the temperature range from 500°C to 300°C, while in D8 and D15H, the former was slightly faster.
• the average cooling rate from the cooling treatment start temperature of 475°C to 300°C was recorded as the average cooling rate in the temperature range from 500°C to 300°C.
• hot forging and cooling were performed under the same conditions as in process No.
• Process E is a process for laboratory forging, and the raw materials used were the actual extrusion bar of process No. A50, the laboratory extrusion bar of process No. B2, and the laboratory casting of process No. C2, each of which was cut to a length of 180 mm. These round bars were placed horizontally and forged to a thickness of 20 mm using a hot forging press with a capacity of 150 tons.
• step E12H the average cooling rate in the temperature range from the cooling treatment start temperature to 300° C. was recorded as the average cooling rate in the temperature range from 500° C. to 300° C.
• step E14H the cooling No treatment was performed, and natural cooling was performed, with an average cooling rate from 500° C. to 300° C. being 25° C./min.
• Hot compression test (step F) The hot extrusion rods of the actual machine in process No. A13H, A34H, and A47H, the hot extrusion rods of the laboratory in process No. B3H, and the castings in process C1 were used as materials, and were finished to ⁇ 15 mm and height 27 mm on a lathe. Then, as shown in Table 16, a 10-ton Amsler-type testing machine equipped with a heating furnace was used to hot compress the specimens to a height of 8 mm at 650°C under the condition of a strain rate of 0.02/sec. In process No. F1 to F3, the hot compressed specimens were removed from the heating furnace and cooled at a cooling rate of 50°C/min.
• the cooling treatment was started at 560°C, and the average cooling rate in the temperature range from 500°C to 300°C was 2100°C/min, and the treatment method was continued below 300°C, and the specimens were cooled to room temperature.
• the cooling treatment was started at 560°C, and the average cooling rate from the cooling treatment start temperature to 300°C was 200°C/min.
• Process No. F5H no special cooling treatment was performed, and the average cooling rate from 500°C to 300°C was 40°C/min.
• the average cooling rate in the temperature range from the cooling treatment start temperature (560°C) to 500°C and the average cooling rate in the temperature range from 500°C to 300°C were roughly the same.
• step G In process G, as shown in Table 17, the bar material and forgings obtained in process Nos. A1, A21, A41, A13H, A34H, A47H, D1, and D13H were heat-treated in a laboratory to examine changes in properties. All annealing was performed under conditions of holding at 580°C for 30 or 60 minutes. In process Nos. G1, G2, and G3, after annealing, the cooling treatment was started at 560°C, and the average cooling rate in the temperature range from the cooling treatment start temperature to 300°C was 1800°C/min. The average cooling rate in the temperature range from the cooling treatment start temperature (560°C) to 500°C and the average cooling rate from 500°C to 300°C were roughly the same. In process Nos.
• Process Nos. G11H and G12H after annealing at 580°C, the cooling treatment start temperature was set to 470°C, and cooling was performed at an average cooling rate of 1500°C/min from 470°C to 300°C.
• Process Nos. G13H and G14H after annealing at 580°C, no special cooling treatment was performed, and cooling was performed at an average cooling rate of 25°C/min from 500°C to 300°C.
• Comparative material As a comparative material, a ⁇ 20 mm rod made of free-cutting brass C3604 containing 3 mass% Pb was prepared. In addition, a ⁇ 50 mm rod and a ⁇ 20 mm rod made of forging brass C3771 containing 2 mass% Pb were prepared. Alloys X, Y, and Z were used, all of which were commercially available. Alloy Y was subjected to hot forging and cooling treatment under the same conditions as in process Nos. E14H and E1. Alloy Z was subjected to hot forging and cooling treatment under the same conditions as in process Nos. D13H and D1.
• Alloy X was subjected to metallurgical microscope observation, cutting test, dezincification corrosion test, and tensile test. Alloy Y was subjected to metallurgical microscope observation, cutting test, dezincification corrosion test, and tensile test. Alloy Z was subjected to metallurgical microscope observation, dezincification corrosion test, and stress corrosion cracking test.
• the above test materials were evaluated for the following items. The evaluation results are shown in Tables 18 to 56.
• the area ratio of the ⁇ phase i.e., the unmodified ⁇ phase, is listed in each table as f4A, to distinguish it from the area ratio of the ⁇ 1 phase (f4).
• the metal structure was observed by the following method, and the area ratio (%) of each phase, including the ⁇ phase, ⁇ phase, and ⁇ phase, was measured by image analysis.
• ⁇ phases in which grain boundaries were observed were classified as ⁇ 1 phases and were distinguished from the ⁇ phase.
• the ⁇ ' phase, ⁇ ' phase, and ⁇ ' phase were included in the ⁇ phase, ⁇ phase, and ⁇ phase, respectively.
• the ⁇ phase has a granular, elliptical shape and is often accompanied by twin crystals.
• the ⁇ phase and ⁇ 1 phase exist around the granular, elliptical ⁇ phase. This is how the ⁇ phase, ⁇ phase, and ⁇ 1 phase were distinguished.
• each test material was cut parallel to the longitudinal direction or parallel to the flow direction of the metal structure.
• the surfaces were then mirror-polished and etched with a mixture of hydrogen peroxide and aqueous ammonia.
• aqueous solution 3 mL of 3 vol% hydrogen peroxide and 22 mL of 14 vol% aqueous ammonia was used.
• the polished metal surface was immersed in this aqueous solution for about 2 to 10 seconds at room temperature of about 15 to about 25°C.
• the corrosion resistance was improved compared to when the ⁇ phase was present, so the immersion time for etching had to be longer, about 5 to 10 seconds.
• each phase ( ⁇ phase, ⁇ phase, ⁇ 1 phase, ⁇ phase) was manually filled in using the image processing software "Photoshop CC". To distinguish between ⁇ phase and ⁇ 1 phase, if one or more ⁇ grain boundaries were observed in one field, all ⁇ phase in that field was filled in as ⁇ 1 phase. Next, the images were binarized using the image analysis software "WinROOF2013" to determine the area ratio of each phase.
• the average area ratio of the five fields was calculated for each phase, and the average was used as the area ratio of each phase.
• Compounds containing P and Si, precipitates, oxides, Pb or Bi particles, sulfides, and crystallized materials were excluded, and the total area ratio of all constituent phases was set to 100%.
• a grain boundary pattern i.e., a crystal grain boundary
• the ⁇ phase is regarded as a ⁇ 1 phase and is distinguished from a normal ⁇ phase.
• the crystal grain boundary refers to a linear pattern penetrating the ⁇ 1 phase crystal grains observed in the ⁇ 1 phase, as shown in FIG. 1A.
• compounds and precipitates of P and Si may exist in the metal structure.
• P compounds when the amount of P was 0.06 mass% and the average cooling rate from 500°C to 300°C was 15 to 50°C/min, about 500 to about 1000 P compounds were observed in a field of view with a magnification of 500 times (80 mm x 120 mm when printed).
• the P compounds were evaluated as "C” (fair) because there were few P compounds present. If there were 300 or more compounds, the P compounds were evaluated as "B” (present). The presence or absence, and the amount of P compounds present, is one indicator of whether appropriate treatment has been carried out.
• FE-SEM field emission scanning electron microscope
• JSM-7000F manufactured by JEOL Ltd.
• EDS Electronic Back Scattering Diffracton Pattern
• tensile strength/elongation Each test material was processed into a JIS Z 2241 No. 10 test piece, and the tensile strength and elongation were measured. If the tensile strength of the hot extrusion material or hot forging material that has not been subjected to the cold working process is preferably 460 N/mm 2 or more, more preferably 490 N/mm 2 or more, and even more preferably 520 N/mm 2 or more, it is the highest level among free-cutting copper alloys, and it is possible to reduce the thickness and weight of components used in various fields, or increase the allowable stress.
• the value of the characteristic relational expression f7 S ⁇ (E+100)/100 ⁇ 1/2 , which indicates the balance between strength and ductility, is preferably 540 or more, which is a measure of a high-strength, high-ductility material.
• f7 is more preferably 570 or more, and even more preferably 600 or more. It can be said to be at a very high level among free-cutting copper alloys.
• Many parts used in faucets, valves, joints, pressure vessels, and air conditioners/refrigeration equipment are made from hot forged or hot extruded rods.
• the currently used Pb-added copper alloy, C3604 has a tensile strength of approximately 390-420 N/ mm2 , an elongation of 30-35%, and an f7 of approximately 470, whereas this embodiment has high strength and good dezincification corrosion resistance and stress corrosion cracking resistance, making it possible to reduce weight.
• machinability test using a lathe The machinability was evaluated by a cutting test using a lathe as described below.
• the circumference of the test material with a diameter of 18 mm was cut under dry conditions with a rake angle of 0°, a nose radius of 0.4 mm, a relief angle of 6°, a cutting speed of 40 m/min or 110 m/min, a cutting depth of 1.0 mm, and a feed rate of 0.11 mm/rev.
• the effect of the cutting speed was also investigated.
• the signals emitted from a three-part dynamometer (AST-type tool dynamometer AST-TL1003, manufactured by Miho Electric Manufacturing Co., Ltd.) attached to the tool were converted into electrical voltage signals and recorded on a recorder. These signals were then converted into cutting resistance (principal force, feed force, thrust force, N).
• cutting resistance principal force, feed force, thrust force, N.
• the cutting test was performed twice, going back and forth from A ⁇ B ⁇ C ⁇ ... C ⁇ B ⁇ A, and measurements were taken four times for each sample.
• the cutting resistance was calculated using the following formula.
• the cutting resistance is the largest due to the principal force, and the magnitude of the principal force determines the cutting resistance to a large extent. Therefore, the principal force was used as the cutting resistance, and the average value of four measured values was calculated to determine the cutting resistance.
• the cutting resistance (principal force) of a commercially available free-cutting brass bar C3604 (Alloy X, ⁇ 20 mm) made of a Zn-59 mass%Cu-3 mass%Pb-0.2 mass%Fe-0.3 mass%Sn alloy was taken as 100, and the relative value of the cutting resistance of the sample (machinability index) was calculated and a relative evaluation was performed. In other words, the higher the machinability index, the lower the cutting resistance and the better the machinability.
• Cutting resistance depends on the shear strength and tensile strength of the material, and the stronger the material, the higher the cutting resistance tends to be. For example, in the case of a copper alloy that has good chip breakability equivalent to C3604 but is about 1.2 times stronger than C3604, the cutting resistance is proportional to the material strength, so the cutting resistance is roughly 20% higher than C3604. For this reason, in the case of a copper alloy with high strength, if the cutting resistance is about 40% higher than C3604, it is considered to be good for practical use.
• the tensile strength and shear strength of the extruded material are approximately 1.2 times higher than C3604, so the machinability evaluation criteria in this embodiment were evaluated with a machinability index of about 72 as the border (boundary value).
• the machinability index is 80 or more, it is evaluated as having excellent machinability (rating: A, excellent) and having machinability equivalent to C3604. If the machinability index was 72 or more and less than 80, the machinability was evaluated as good (evaluation: B, good). If the machinability index was 66 or more and less than 72, the machinability was evaluated as fair (evaluation: C, fair). If the machinability index was less than 66, the machinability was evaluated as poor (evaluation: D, poor). In this application, the aim was to achieve good machinability, so a machinability index of 72 or more was considered to be acceptable.
• Dezincification corrosion test ISO6509 dezincification corrosion test
• the dezincification corrosion test was performed according to the ISO 6509 dezincification corrosion test. This test method is adopted in many countries and is also specified in the JIS standard, JIS H 3250.
• the procedure for the dezincification corrosion test was as follows: first, the test material was embedded in a phenolic resin material, specifically, the exposed sample surface was embedded in the phenolic resin material perpendicular to the extrusion direction of the extruded material. The sample surface was polished with emery paper up to No. 1200, then ultrasonically cleaned in pure water and dried.
• Each sample was immersed in an aqueous solution (12.7 g/L) of 1.0% cupric chloride dihydrate (CuCl 2 .2H 2 O) and held for 24 hours under a temperature condition of 75° C. Then, the sample was taken out of the aqueous solution.
• the specimens were re-embedded in phenolic resin material with the exposed surface perpendicular to the extrusion direction, longitudinal direction, or flow direction of the forging. The specimens were then cut to obtain the cross section of the corroded area as the longest cut. The specimens were then polished. The corrosion depth was observed at 10 points in the field of view of the microscope using a metallurgical microscope at a magnification of 100 to 500.
• the deepest corrosion point was recorded as the maximum dezincification corrosion depth.
• the maximum corrosion depth is 200 ⁇ m or less, it is considered that there is no problem in terms of practical corrosion resistance.
• the maximum corrosion depth is preferably 100 ⁇ m or less. In this test, the maximum corrosion depth exceeding 200 ⁇ m was evaluated as unacceptable (evaluation: D, poor). The maximum corrosion depth exceeding 100 ⁇ m and not more than 200 ⁇ m was evaluated as good (evaluation: B, good). The maximum corrosion depth not more than 100 ⁇ m was evaluated as excellent (evaluation: A, excellent).
• a stress corrosion cracking test In order to determine whether or not the material can withstand a stress corrosion cracking environment, a stress corrosion cracking test was carried out according to the following procedure. First, a rod of ⁇ 20 mm was cut to a weight of 120 ⁇ 1 g (119 to 121 g) as a test material, and formed into a hexagonal flare nut forging material with a side length of 27 mm and a length of 26 mm under the conditions of Table 14, step D, using a 500-ton hot forging press. Furthermore, as shown in Table 14, some samples were shot-treated in the same manner as step No. D7, and the forged material was heat-treated under several conditions as shown in Table 17 (steps G2, G3, G12H, and G14H).
• Ammonia water of a predetermined concentration was placed in a desiccator, and the flare nut with the load stress applied was placed 60 mm away from the liquid surface, and after holding for a predetermined time, the flare nut was removed.
• the test was carried out in a room controlled at 25 ⁇ 1 ° C (24 to 26 ° C) by air conditioning.
• the stress corrosion cracking test was carried out in the following two ways.
• Stress corrosion cracking test-1 Ammonia water with an ammonia concentration of 14 vol% was used, 1000 ml of ammonia water was placed in a desiccator, and a sample loaded with a torque of 70 N ⁇ m was exposed in the desiccator for 48 hours and 96 hours. The sample was washed with 10 vol% sulfuric acid, then visually observed, and evaluated for the presence or absence of cracks. This test was conducted in accordance with JIS H 3250 except for the exposure time. The exposure time in JIS H 3250 was 2 hours, whereas this method was more than 20 times longer, making it a severe stress corrosion cracking test.
• Stress corrosion cracking test-2 In another stress corrosion cracking test, 200 ml of ammonia water with an ammonia concentration of 28 vol% was placed in a desiccator, and a sample loaded with a torque of 150 N ⁇ m was exposed to the desiccator and held for 75 hours. The sample was removed from the desiccator, washed with 10 vol% sulfuric acid, and then visually observed for cracks. Compared to stress corrosion cracking test-1, the ammonia concentration was higher and the load torque was larger, so the following criteria were used. The largest crack visible to the naked eye was judged as "D" (poor) when it was 1/2 or more of the length of the sample, i.e., a crack of 13 mm or more was clearly observed by visual inspection.
• a rating of "C” was deemed acceptable.
• compositional relations f0 to f2 the requirements for the metal structure, the structure relations f3 to f5, and the structure-compositional relations f6, it is possible to obtain a hot extrusion material and a hot forging material with good machinability, good dezincification corrosion resistance and stress corrosion cracking resistance, high electrical conductivity of 15% IACS or more, high strength, good ductility, and a high balance between strength and ductility (characteristic relations f7) with a small amount of Pb. Furthermore, although the presence of P compounds has the effect of significantly improving machinability, the ⁇ 1 phase, which is a modified ⁇ phase, further improves machinability.
• the dezincification corrosion was selective corrosion of the ⁇ 1 phase, and the rate of progress of the dezincification corrosion seemed to be slightly increased when the proportion of ⁇ 1 phase was high (process Nos. A1 to A5, D1 to D5, E1 to E5, F1 to F3, G1 to G3, etc.).
• the hot-worked material is annealed at a temperature above 520°C and below 630°C for 1 minute to 5 hours, and after annealing, the cooling treatment is started at a temperature above 500°C, and the average cooling rate in the temperature range from the cooling treatment start temperature to 500°C and the average cooling rate in the temperature range from 500°C to 300°C are more than 300°C/min. It has been confirmed that the ⁇ phase is modified, and in particular the dezincification corrosion resistance and stress corrosion cracking resistance are significantly improved (Process Nos. G1 to G3, Figures 5A and 5B).
• the alloy of this embodiment in which the content of each added element, the compositional relationship formula, and each structural relationship formula are within the appropriate range, has excellent hot workability, and has good machinability, mechanical properties, dezincification corrosion resistance, and stress corrosion cracking resistance. Furthermore, in order to obtain excellent properties in the alloy of this embodiment, it can be achieved by setting the manufacturing conditions for hot extrusion and hot forging, and the conditions for heat treatment within the appropriate ranges.
• the free-cutting copper alloy of this embodiment has a small Pb content, excellent hot workability and machinability, high strength, and an excellent balance between strength and elongation. Therefore, the free-cutting copper alloy of this embodiment is suitable for appliances and parts related to drinking water and sanitary facilities, food appliances, electric and electronic equipment parts, automobile parts, machine parts, stationery, toys, musical instruments, sliding parts, instrument parts, precision machine parts, medical parts, beverage appliances and parts, water meters, and parts related to liquids and gases such as industrial water, wastewater, and hydrogen.
• the present invention can be suitably applied as a component material for items used in the aforementioned fields under the names of water taps, stop valves, mixer taps, shower heads, valves, joints, cocks, gears, axles, bearings, trumpets, shafts, sleeves, spindles, sensors, bolts, nuts, flare nuts, pen tips, insert nuts, cap nuts, nipples, spacers, screws, and the like.

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