COPPER ALLOY CONTAINING TIN, METHOD FOR PRODUCING SAME, AND USE OF SAME

Abstract

The invention relates to a high-strength as-cast copper alloy containing tin, with excellent hot-workability and cold-workability properties, high resistance to abrasive wear, adhesive wear and fretting wear, and improved corrosion resistance and stress relaxation resistance, consisting (in wt. %) of: 4.0 to 23.0% Sn, 0.05 to 2.0% Si, 0.01 to 1.0% Al, 0.005 to 0.6% B, 0.001 to 0.08% P, optionally up to a maximum of 2.0% Zn, optionally up to a maximum of 0.6% Fe, optionally up to a maximum of 0.5% Mg, optionally up to a maximum of 0.25% Pb, with the remainder being copper and inevitable impurities, characterised in that the ratio of Si/B of the element content of the elements silicon and boron lies between 0.3 and 10. The invention also relates to a casting variant and a further-processed variant of the tin-containing copper alloy, a production method, and the use of the alloy.

Claims

1. A high-strength tin-containing copper alloy having excellent hot formability and cold formability, high resistance to abrasive wear, adhesive wear and fretting wear and improved corrosion resistance and stress relaxation resistance, consisting of (in % by weight): 4.0% to 23.0% Sn, 0.05% to 2.0% Si, 0.01% to 1.0% Al, 0.005% to 0.6% B, 0.001% to 0.08% P, with or without up to a maximum of 2.0% Zn, with or without up to a maximum of 0.6% Fe, with or without up to a maximum of 0.5% Mg, with or without up to a maximum of 0.25% Pb, the balance being copper and unavoidable impurities, characterized in that the Si/B ratio of the element contents of the elements silicon and boron is between 0.3 and 10.

2. A high-strength tin-containing copper alloy having excellent hot formability and cold formability, high resistance to abrasive wear, adhesive wear and fretting wear and improved corrosion resistance and stress relaxation resistance, consisting of (in % by weight): 4.0% to 23.0% Sn, 0.05% to 2.0% Si, 0.01% to 1.0% Al, 0.005% to 0.6% B, 0.001% to 0.08% P, with or without up to a maximum of 2.0% Zn, with or without up to a maximum of 0.6% Fe, with or without up to a maximum of 0.5% Mg, with or without up to a maximum of 0.25% Pb, the balance being copper and unavoidable impurities, characterized in that the Si/B ratio of the element contents of the elements silicon and boron is between 0.3 and 10; after casting, the following microstructure constituents are present in the alloy: a) 1% up to 98% by volume of Sn-rich phase (1), b) 1% up to 20% by volume of Al- and B-containing phases, Si-containing and B-containing phases and/or addition compounds and/or mixed compounds composed of the two phases (2), c) balance: solid solution of copper, consisting of low-tin phase (3), wherein the Al-containing and B-containing phases, Si-containing and B-containing phases and/or addition compounds and/or mixed compounds composed of the two phases (2) are ensheathed by tin and/or the Sn-rich phase (1); in the casting, the Al-containing and B-containing phases, Si-containing and B-containing phases and/or addition compounds and/or mixed compounds composed of the two phases (2) which are in the form of aluminum borides and silicon borides and/or in the form of addition compounds and/or mixed compounds of the aluminum borides and silicon borides constitute seeds for homogeneous crystallization during the solidification/cooling of the melt, such that the Sn-rich phase (1) is distributed homogeneously in the microstructure in the form of islands and/or a network; the Al-containing and B-containing phases, Si-containing and B-containing phases and/or addition compounds and/or mixed compounds composed of the two phases (2) which are in the form of boron silicates and/or boron phosphorus silicates and/or aluminum oxide boron silicates and/or aluminum oxide boron phosphorus silicates, together with the phosphorus silicates and aluminum oxides, assume the role of a wear-protective and/or corrosion-protective coating on the semifinished products and components of the alloy.

3. A high-strength tin-containing copper alloy having excellent hot formability and cold formability, high resistance to abrasive wear, adhesive wear and fretting wear and improved corrosion resistance and stress relaxation resistance, consisting of (in % by weight): 4.0% to 23.0% Sn, 0.05% to 2.0% Si, 0.01% to 1.0% Al, 0.005% to 0.6% B, 0.001% to 0.08% P, with or without up to a maximum of 2.0% Zn, with or without up to a maximum of 0.6% Fe, with or without up to a maximum of 0.5% Mg, with or without up to a maximum of 0.25% Pb, the balance being copper and unavoidable impurities, characterized in that the Si/B ratio of the element contents of the elements silicon and boron is between 0.3 and 10; after the further processing of the alloy by at least one annealing operation or by at least one hot forming operation and/or cold forming operation in addition to at least one annealing operation, the following microstructure constituents are present in the alloy: a) up to 75% by volume of Sn-rich phase (1), b) 1% up to 25% by volume of Al-containing and B-containing phases, Si-containing and B-containing phases and/or addition compounds and/or mixed compounds composed of the two phases (2), c) balance: solid solution of copper, consisting of low-tin phase (3), wherein the Al-containing and B-containing phases, Si-containing and B-containing phases and/or addition compounds and/or mixed compounds composed of the two phases (2) are ensheathed by tin and/or the Sn-rich phase (1); the Al-containing and B-containing phases, Si-containing and B-containing phases and/or addition compounds and/or mixed compounds composed of the two phases (2) present, which are in the form of aluminum borides and silicon borides and/or in the form of addition compounds and/or mixed compounds of the aluminum borides and silicon borides, constitute seeds for static and dynamic recrystallization of the microstructure during the further processing of the alloy, which enables the establishment of a homogeneous and fine-grain microstructure; the Al-containing and B-containing phases, Si-containing and B-containing phases and/or addition compounds and/or mixed compounds composed of the two phases (2) which are in the form of boron silicates and/or boron phosphorus silicates and/or aluminum oxide boron silicates and/or aluminum oxide boron phosphorus silicates, together with the phosphorus silicates and aluminum oxides, assume the role of a wear-protective and/or corrosion-protective coating on the semifinished products and components of the alloy.

4. The tin-containing copper alloy as claimed in claim 1, characterized in that the element silicon is present at from 0.05% to 1.5%.

5. The tin-containing copper alloy as claimed in claim 1, characterized in that the element silicon is present at from 0.5% to 1.5%.

6. The tin-containing copper alloy as claimed in claim 1, characterized in that the element aluminum is present at from 0.1% to 0.8%.

7. The tin-containing copper alloy as claimed in claim 1, characterized in that the element boron is present at from 0.01% to 0.6%.

8. The tin-containing copper alloy as claimed in claim 1, characterized in that the element phosphorus is present at from 0.001% to 0.05%.

9. The tin-containing copper alloy as claimed in claim 1, characterized in that the alloy is free of lead aside from any unavoidable impurities.

10. A process for producing end products and components having near-end-product form from a tin-containing copper alloy as claimed in claim 1 with the aid of the sandcasting process, the shell mold casting process, precision casting process, full mold casting process, pressure diecasting process or lost foam process.

11. A process for producing strips, sheets, plates, bolts, round wires, profile wires, round bars, profile bars, hollow bars, pipes and profiles from a tin-containing copper alloy as claimed in claim 1 with the aid of the permanent mold casting process or the continuous or semicontinuous strand casting process.

12. The process as claimed in claim 11, characterized in that the further processing of the cast state comprises the performance of at least one hot forming operation within the temperature range from 600 to 880 C.

13. The process as claimed in claim 10, characterized in that at least one annealing treatment is conducted within the temperature range from 200 to 880 C. with the duration of 10 minutes to 6 hours.

14. The process as claimed in claim 11, characterized in that the further processing of the cast state or of the hot-formed state or of the annealed cast state or of the annealed hot-formed state comprises the performance of at least one cold forming operation.

15. The process as claimed in claim 14, characterized in that at least one annealing treatment is conducted within the temperature range from 200 to 880 C. with the duration of 10 minutes to 6 hours.

16. The process as claimed in claim 14, characterized in that a stress relief annealing/age annealing operation is conducted within the temperature range from 200 to 650 C. with the duration of 0.5 to 6 hours.

17. The use of the tin-containing copper alloy as claimed in claim 1 for adjustment gibs and sliding gibs, for friction rings and friction disks, for slide bearing faces in composite components, for sliding elements and guide elements in internal combustion engines, valves, turbochargers, gears, exhaust gas aftertreatment systems, lever systems, braking systems and joint systems, hydraulic aggregates, or in machines and installations in mechanical engineering in general.

18. The use of the tin-containing copper alloy as claimed in claim 1 for components, wire elements, guiding elements and connection elements in electronics/electrical engineering.

19. The use of the tin-containing copper alloy as claimed in claim 1 for metallic articles in the breeding of seawater-dwelling organisms, for percussion instruments, for propellers, wings, marine propellers and hubs for shipbuilding, for housings of water pumps, oil pumps and fuel pumps, for guide wheels, runner wheels and paddle wheels for pumps and water turbines, for gears, worm gears, helical gears and for forcing nuts and spindle nuts, and for pipes, seals and connection bolts in the maritime and chemical industry.

Description

[0244] Further important working examples of the invention are elucidated in tables 1 to 11. Cast blocks of the tin-containing copper alloy of the invention were produced by permanent mold casting. The chemical composition of the castings is apparent from tab. 1 and 3.

[0245] Tab. 1 shows the chemical composition of alloy variant 1. This material is characterized by an Sn content of 7.35% by weight, an Si content of 0.74% by weight, an Al content of 0.34% by weight, a boron content of 0.33% by weight and a P content of 0.015% by weight, and a balance of copper.

TABLE-US-00001 TABLE 1 Chemical composition of working example 1 (in % by weight) Cu Sn Si Al B P 1 balance 7.35 0.74 0.34 0.33 0.015

[0246] After the casting, the microstructure of working example 1 is shaped by a very homogeneous, island-like distribution of a comparatively small proportion of the phase (1, about 20% by volume) and of the hard particles 2 in the solid copper solution 3 (FIG. 1). The hardness of this type of alloy is 108 HB (tab. 2).

TABLE-US-00002 TABLE 2 Hardness of the permanent mold casting blocks of working example 1 Hardness Alloy HB 2.5/62.5 1 108

[0247] Tab. 3 shows the chemical composition of a further alloy variant 2. This material contains, as well as 15.09% by weight of Sn and 0.027% by weight of P, the further elements Si (0.80% by weight), Al (0.54% by weight), boron (0.24% by weight) and a balance of copper.

TABLE-US-00003 TABLE 3 Chemical composition of working example 2 (in % by weight) Cu Sn Si Al B P 2 balance 15.09 0.80 0.54 0.24 0.027

[0248] One characteristic feature of the invention is that the microstructure in the cast state, with rising Sn content of the alloy, depending on the casting/cooling operation, consists of increasing proportions of phase. The arrangement of this Sn-rich phase is transformed from a finely distributed island form, with increasing Sn content of the alloy, to a dense network form.

[0249] In the microstructure of alloy type 2, the phase is present with a distinctly higher content (up to 70% by volume). This microstructure is shown in FIG. 3 in 200-fold magnification and in FIG. 4 in 500-fold magnification. Reference numeral 1 in each case indicates the Sn-rich phase arranged in a network-like manner in the microstructure. In addition, the hard particles 2 that are ensheathed by tin and/or the Sn-rich phase are apparent. The microstructure constituent of the solid copper solution is labeled by reference numeral 3.

[0250] The increase in hardness of the material with rising Sn content is expressed by the distinctly higher value of 210 HB of alloy 2 (tab. 4).

TABLE-US-00004 TABLE 4 Hardness of the permanent mold casting blocks of working example 2 Hardness Alloy HB 2.5/62.5 2 210

[0251] The homogeneous distribution of the phase arranged in the form of islands and/or a networking the microstructure of the tin-containing copper alloy of the invention emphasizes the effect of the hard particles as crystallization seeds for the formation of the phase.

[0252] One aspect of the invention relates to a process for production of strips, sheets, plates, bolts, wires, bars, profile bars, hollow bars, pipes and profiles from the tin-containing copper alloy of the invention with the aid of the permanent mold casting process or the continuous or semicontinuous strand casting process.

[0253] The alloy of the invention can additionally be subjected to further processing. This firstly enables the production of particular and often complicated geometries. Secondly, in this way, the demand for an improvement in the complex operating properties of the materials, particularly for wear-stressed components and for components and connection elements in electronics/electrical engineering is met, since there is a significant increase in stress on the system elements in the corresponding machines, engines, gears, aggregates, constructions and installations. In the course of this further processing, a significant improvement in the toughness properties and/or a significant increase in tensile strength R.sub.m, yield point R.sub.p0.2 and hardness is achieved.

[0254] Owing to the excellent hot formability of the alloy of the invention, the further processing of the cast state can advantageously include the performance of at least one hot forming operation within the temperature range from 600 to 880 C. By means of hot rolling, it is possible to produce plates, sheets and strips. Extrusion enables the manufacture of wires, rods, tubes and profiles. Finally, forging processes are suitable for producing near-end-shape components with complicated geometry in some cases.

[0255] A further advantageous means of further processing the cast state or the hot-formed state or the annealed cast state or the annealed hot-formed state comprises the performance of at least one cold forming operation. In particular, this process step significantly increases the material indices R.sub.m, R.sub.p0.2 and the hardness. This is important for applications where there is mechanical stress and/or intense abrasive and/or adhesive wear stress on the components. In addition, the spring properties of the components made of the alloy of the invention are significantly improved as a result of a cold forming operation.

[0256] For corresponding recrystallization of the microstructure of the invention after a cold forming operation, it is possible to conduct at least one annealing treatment within a temperature range from 200 to 880 C. with the duration of 10 minutes to 6 hours. The very fine-grain structure that thus forms is an important prerequisite for establishing the combination of properties of high-strength and hardness and of sufficient toughness of the material.

[0257] For lowering of the residual stresses of the components, it is advantageously additionally possible to conduct a stress relief annealing operation within a temperature range from 200 to 650 C. with the duration of 0.5 to 6 hours.

[0258] For the fields of use having particularly severe complex component stress, it is possible to choose a further processing operation comprising at least one cold forming operation or the combination of at least one hot forming operation and at least one cold forming operation in conjunction with at least one annealing operation within a temperature range from 200 to 800 C. with the duration of 10 minutes to 6 hours and leads to a recrystallized microstructure of the alloy of the invention. The fine-grain structure of the alloy established in this way assures a combination of high strength, high hardness and good toughness properties. In addition, for lowering of the residual stresses of the components, a stress relief annealing treatment within the temperature range from 200 to 650 C. with the duration of 0.5 to 6 hours is possible.

[0259] For manufacture of semifinished products in strip form from working example 1 (tab. 1), three different production sequences were selected. They differ primarily in the number of cold forming/annealing cycles and in the level of the degrees of cold forming and annealing temperatures employed (tab. 5).

TABLE-US-00005 TABLE 5 Manufacturing programs for working example 1 No. Manufacture 1 Manufacture 2 Manufacture 3 1 Permanent mold casting 2 Hot rolling at 780 C. + water quenching 3 Annealing 700 C./3 h + air cooling 4 Cold rolling: from 6.05 to 0.93 mm ( 85%) 5 Stress relief Annealing Annealing annealing at 680 C./3 h 450 C./3 h 280 C./2 h 6 Cold rolling Cold rolling ( 60%): ( 30%): from 0.93 to from 0.93 to 0.37 mm 0.65 mm 7 Stress relief Stress relief annealing annealing 280-400 C./2-4 h 240-360 C./2 h

[0260] After the permanent mold casting and the hot rolling, the corresponding blocks or semifinished products are characterized by an exceptionally smooth surface. As a result of the dynamic recrystallization of the microstructure that has taken place during the hot rolling operation, the hot-formed state of alloy variant 1 has sufficient cold formability. For further improvement of the cold formability of the hot-formed semifinished products, the performance of annealing treatment within the temperature range from 600 to 880 C. with the duration of 3 hours was found to be advantageous. Thus, it was possible to cold-roll the hot-rolled plates without cracking with a cold-forming of about 85%.

[0261] In the course of manufacture 1, the cold-rolled strips were annealed at the temperature of 280 C. with a duration of 2 h. The indices of the strips thus subjected to stress relief are apparent from tab. 6. In spite of high strength and hardness values, the strips of the alloy have adequate toughness properties as measured by the value for elongation at break A5.

TABLE-US-00006 TABLE 6 Microstructure characteristics and mechanical indices of the strips of working example 1 in the final state (manufacture 1) Electrical conductivity R.sub.m R.sub.p0.2 A5 Hardness Alloy [% IACS] [MPa] [MPa] [%] HB 1.0/10 1 9.6 867 838 9.3 279

[0262] In the course of manufacture 2, the strips of alloy variant 1, after the first cold rolling operation, were annealed at 680 C. for 3 hours. This was followed by the cold rolling of the strips with a cold-forming of about 60%. To complete the manufacture, the strips were subjected to thermal stress relief at different temperatures between 280 and 400 C. with a duration of 2 and 4 hours. The indices of the resulting material states are listed in tab. 7.

TABLE-US-00007 TABLE 7 Microstructure characteristics and mechanical indices of the strips of working example 1 in the end state (manufacture 2) Stress Elec- relief trical Hard- annealing Grain conduc- ness Al- temperature size tivity R.sub.m R.sub.p0.2 A5 HB loy [ C.] [m] [% IACS] [MPa] [MPa] [%] 1.0/10 1 280 C./2 h 9.5 804 740 8.7 268 280 C./4 h 9.6 801 713 8.9 276 340 C./2 h 1-2 10.0 592 445 31.6 198 340 C./4 h 1-2 10.1 596 446 24.8 184 400 C./2 h 3-4 9.8 551 359 50.2 152 400 C./4 h 3-4 9.9 512 340 45.4 155

[0263] It can be inferred from tab. 7 that the microstructure of the strips subjected to stress relief at 280 C. include deformation features, and therefore no value can be reported for grain size. At about 340 C., the recrystallization of the microstructure sets in, which leads to a significant drop in strengths and in the hardness. For this reason, in the course of manufacture 3, the annealing temperature after the first cold forming operation was lowered to 450 C. The annealing operation at this temperature for three hours was followed by the cold rolling of the strips with the cold-forming of about 30%. The final stress relief annealing for two hours at temperatures between 240 and 360 C. led to the indices shown in tab. 8.

[0264] The microstructure with 500-fold magnification of the final state of the strip of working example 1 that has been subjected to stress relief annealing at 240 C./2 h is shown in FIG. 2. What can be seen is the fine-grain microstructure with the hard phases 2 intercalated in the solid copper solution 3. The hard particles are ensheathed by tin and/or the Sn-rich phase.

[0265] The results point to high values for strength and hardness. Nevertheless, the high values for elongation at break A5 indicate the excellent ductility of the material states.

TABLE-US-00008 TABLE 8 Microstructure characteristics and mechanical indices of the strips from working example 1 in the end state (manufacture 3) Stress Elec- relief trical Hard- annealing Grain conduc- ness Al- temperature size tivity R.sub.m R.sub.p0.2 A5 HB loy [ C.] [m] [% IACS] [MPa] [MPa] [%] 1.0/10 1 240 C./2 h 4-5 9.8 759 693 21.0 228 280 C./2 h 4-5 9.7 748 679 27.9 222 320 C./2 h 5-6 9.7 731 627 29.3 215 360 C./2 h 4-5 9.8 619 403 36.8 154

[0266] The strips of working example 2 of the invention, the chemical composition of which can be found in tab. 3, were produced by the manufacturing program shown in tab. 9. The hot rolling of the permanent mold casting formats was effected at the temperature of 750 C. with subsequent cooling in water. After the permanent mold casting and the hot rolling, the corresponding blocks or semifinished products were characterized by an exceptionally smooth surface.

[0267] After the hot-rolling operation, the strips were cold-rolled with a low cold-forming level of about 3%. One portion of the strips designated 2-A were subsequently annealed at the temperatures of 500, 550 and 600 C. for 3 hours and examined.

[0268] The second portion of the strips cold-rolled to 7.04 mm, designated 2-B, were further manufactured by means of cyclical performance of annealing and cold-forming operations.

TABLE-US-00009 TABLE 9 Manufacturing program for working example 2 No. Manufacture 1 Permanent mold casting 2 2-A, 2-B Hot rolling at 750 C. + water quenching 3 Cold rolling 2-A/B: from 7.26 to 7.04 mm ( 3%) 4 2-A Annealing: 500 C./3 h, 550 C./3 h, 600 C./3 h + air cooling 2-B Annealing: 600 C./4 h + air cooling 5 2-B Cold rolling: from 7.04 to 6.18 mm ( 12%) 6 2-B Annealing: 550 C./4 h + air cooling 7 2-B Cold rolling: from 6.18 to 4.60 mm ( 26%) 8 2-B Annealing: 500 C./3 h + air cooling 9 2-B Cold rolling: from 4.60 to 3.32 mm ( 28%) 10 2-B Stress relaxation annealing: 200 C./2 h, 240 C./2 h, 280 C./2 h

[0269] The grain size and hardness of the cold-rolled state and of the cold-rolled and annealed state for the strips 2-A are shown in tab. 10. Owing to the dynamic recrystallization of the microstructure that has taken place during the hot rolling of the cast blocks, the structure even after the first cold rolling operation is in homogeneous form with a grain size of 20 to 25 m. The toughness properties can also be improved by means of annealing treatment within the temperature range from 200 to 650 C. Thus, FIG. 5 shows the microstructure of working example 2 after annealing at 500 C. for three hours. The phase (dark-colored) is distributed extremely homogeneously in the microstructure of the material. A further reduction in the proportion of the phase is achieved by an annealing operation at 600 C./3 h (FIG. 6).

[0270] With regard to the cast state, the hard particles are present more completely in the phase regions. This emphasizes the function of the hard particles as crystallization/precipitation seeds even in the course of thermomechanical further processing of the alloy.

TABLE-US-00010 TABLE 10 Grain size and hardness of the cold-rolled and subsequently annealed strips 2-A (after manufacturing step 4 in tab. 9) from working example 2 Heat Grain size Hardness Alloy/state treatment [m] HB 2.5/62.5 2-A cold-rolled 20-25 220 (hot-rolled + cold- 500 C./3 h + 15-20 211 rolled from 7.26 to air 7.04 mm) 550 C./3 h + 15-20 196 air 600 C./3 h + 20-25 184 air

[0271] The microstructure of strip 2-A that has finally been heat-treated with the parameters of 500 C./3 h+air and 600 C./3 h+air is shown in FIG. 5 and FIG. 6. The microstructure of both states includes, as well as the Sn-rich phase 1, the hard particles 2 ensheathed by tin and/or the Sn-rich phase. Also visible is the solid copper solution 3 consisting of tin-deficient phase. After the annealing at a higher temperature of 600 C., the microstructure of strip 2-A is in coarse-grain form (FIG. 6) .

[0272] The second portion of the strips designated 2-B was subjected to further processing with multiple cold rolling/annealing cycles. The indices of the final states that have been subjected to stress relaxation at different temperatures are listed in tab. 11.

[0273] With each cycle that consists of a cold rolling step and an annealing treatment, the microstructure of working example 3 of the invention is continually stretched in a linear manner. The linear arrangement of the very high component, resulting from the high Sn content of the alloy, leads to high hardness values close to 300 HV1. At the same time, there is an increase in the brittle character of the alloy.

TABLE-US-00011 TABLE 11 Grain size and hardness of the finally manufactured strips 2-B (after manufacturing step 10 in tab. 9) from working example 2 Stress relief annealing temperature Grain size Alloy/state [ C.] [m] HV1 2-B 200 C./2 h <2 294 240 C./2 h 2-3 283 280 C./2 h 2-3 281

[0274] As a result, it can be concluded that the alloy of the invention has excellent castability and hot formability over the entire Sn content range from 4% to 23% Sn. Cold formability is also at a very high level. However, there is naturally a deterioration in the ductility of the invention with rising Sn content owing to the rising component of the microstructure.

LIST OF REFERENCE NUMERALS

[0275] Sn-rich phase [0276] Hard particles ensheathed by tin and/or the Sn-rich phase [0277] Solid copper solution consisting of tin-deficient phase