COPPER ALLOY CONTAINING TIN, METHOD FOR PRODUCING SAME, AND USE OF SAME
20200181738 ยท 2020-06-11
Assignee
Inventors
Cpc classification
B22D21/025
PERFORMING OPERATIONS; TRANSPORTING
International classification
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, 0.005 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, 0.005% 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, 0.005% 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 Si-containing and B-containing phases (2), c) balance: solid solution of copper, consisting of low-tin phase (3), wherein the Si-containing and B-containing phases (2) are ensheathed by tin and/or the Sn-rich phase (1); in the casting, the Si-containing and B-containing phases (2) which are in the form of 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 Si-containing and B-containing phases (2) which are in the form of boron silicates and/or boron phosphorus silicates, together with the phosphorus silicates, 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, 0.005% 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 20% by volume of Si-containing and B-containing phases (2), c) balance: solid solution of copper, consisting of low-tin phase (3), wherein the Si-containing and B-containing phases (2) are ensheathed by tin and/or the Sn-rich phase (1); the Si-containing and B-containing phases (2) present, which are in the form of 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 Si-containing and B-containing phases (2) which are in the form of boron silicates and/or boron phosphorus silicates, together with the phosphorus silicates, 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 boron is present at from 0.01% to 0.6%.
7. 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%.
8. The tin-containing copper alloy as claimed in claim 1, characterized in that the alloy is free of lead aside from any unavoidable impurities.
9. 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.
10. 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.
11. The process as claimed in claim 10, 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.
12. The process as claimed in claim 9, 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.
13. The process as claimed in claim 10, 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.
14. The process as claimed in claim 13, 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.
15. The process as claimed in claim 13, 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.
16. 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.
17. 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.
18. 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
[0225] 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.
[0226] Tab. 1 shows the chemical composition of alloy variants 1 and 2. These materials are characterized by an Sn content of 7% by weight, a P content of 0.015% by weight and by a different element ratio of the elements silicon and boron, and a balance of copper.
TABLE-US-00001 TABLE 1 Chemical composition of working examples 1 and 2 Cu Sn P Si B 1 balance 7.18 0.015 0.66 0.26 2 balance 7.08 0.015 0.19 0.40
[0227] After the casting, the microstructure of working examples 1 and 2 is shaped by a very homogeneous, mostly island-like distribution of a comparatively small proportion of the phase (about 15 to 20% by volume) and of the hard particles. The microstructure of the cast state of alloy 1 is shown in
[0228] The hardness of these types of alloy is 105 HB for alloy 1 and 98 HB for alloy 2 (tab. 2).
TABLE-US-00002 TABLE 2 Hardness of the permanent mold casting blocks from working examples 1 and 2 Hardness Alloy HB 2.5/62.5 1 105 2 98
[0229] Tab. 3 shows the chemical composition of a further alloy variant 3. This material contains, as well as about 15% by weight of Sn and 0.024% by weight of P, the further elements Si (0.77% by weight) and boron (0.20% by weight).
TABLE-US-00003 TABLE 3 Chemical composition of working example 3 Cu Sn P Si B 3 balance 15.03 0.024 0.77 0.20
[0230] 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. In the cast microstructure of alloy type 3, the S phase is present with a distinctly higher content (up to about 70% by volume). This microstructure is shown in
[0231] The increase in hardness of the material with rising Sn content is expressed by the distinctly higher value of 190 HB of alloy 3 (tab. 4).
TABLE-US-00004 TABLE 4 Hardness of the permanent mold casting blocks from working example 3 Hardness Alloy HB 2.5/62.5 3 190
[0232] 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.
[0233] 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., yield point R.sub.p0.2 and hardness is achieved.
[0234] 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.
[0235] 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.
[0236] 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.
[0237] For lowering of the residual stresses of the components, it is advantageously additionally possible to conduct a stress relief/age annealing operation within a temperature range from 200 to 650 C. with the duration of 0.5 to 6 hours.
[0238] 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.
[0239] For manufacture of semifinished products in strip form from working examples 1 and 2 (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 examples 1 and 2 No. Manufacture 1 Manufacture 2 Manufacture 3 1 Permanent mold casting 2 Hot rolling at 780 C. + water quenching 3 Cold rolling: 1: from 7.39 to 2.1 mm ( 72%) 2: from 7.34 to 2.1 mm ( 71%) 4 Stress relief Annealing Annealing annealing at 680 C./3 h 450 C./3 h 280 C./2 h 5 Cold rolling Cold rolling ( 60%): ( 30%): 1: from 2.1 to 1: from 2.1 to 0.84 mm 1.47 mm 2: from 2.1 to 2: from 2.1 to 0.84 mm 1.47 mm 6 Stress relief Stress relief annealing annealing 280-400 C./2-4 h 240-360 C./2 h
[0240] 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 both alloy variants 1 and 2 has excellent cold formability. Thus, it was possible to cold-roll the hot-rolled plates without cracking with a cold-forming of about 70%.
[0241] 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 both alloys have extremely good toughness properties as measured by the high values for elongation at break A5.
TABLE-US-00006 TABLE 6 Microstructure characteristics and mechanical indices the strips of working examples 1 and 2 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 9.8 820 767 12.9 244 2 12.6 757 660 14.1 256
[0242] An indication of the importance of the Si/B element ratio of the elements silicon and boron is given by the comparison of the individual data for the strips made from alloys 1 and 2. Owing to the higher Si/B ratio of alloy 1 of about 2.5, the boron silicates, phosphorus silicates and/or boron phosphorus silicates are formed to an enhanced degree during the casting and during the thermal and thermomechanical production steps. For this reason, in various tests, the superiority of alloy 1 with regard to the corrosion resistance by comparison with alloy 2 was established. In addition, the values for R.sub.m and R.sub.p0.2 of the strips made from alloy 1 are at a much higher level. As a result of the lower Si/B ratio at about 0.5, a higher Si content was bound in the hard particles in the microstructure of alloy 2. This results particularly in a higher electrical conductivity and increased elongation at break A5, which results in better ductility of the alloy 2. Even the results from the manufacture 1 suggest that the properties can be matched exactly to the respective fields of use with a variation of the chemical composition of the invention.
[0243] In the course of manufacture 2, the strips of alloy variants 1 and 2, 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. The indices of the resulting material states are listed in tab. 7.
[0244] In the same way as after manufacture 1, the states of working example 1 show the higher strength values, whereas working example 2 features higher values for electrical conductivity and for elongation at break A5. Furthermore, 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.
TABLE-US-00007 TABLE 7 Microstructure characteristics and mechanical indices of the strips of working examples 1 and 2 in the end state (manufacture 2) Stress Hard- relief ness annealing Grain Electrical HB Al- temperature size conductivity R.sub.m R.sub.p0.2 A5 1.0/ loy [ C.] [m] [% IACS] [MPa] [MPa] [%] 10 1 280 C./2 h 9.9 790 752 9.5 249 280 C./4 h 10.0 780 730 9.9 266 340 C./2 h 2 10.0 571 430 45.6 173 340 C./4 h 2 9.9 565 417 43.0 168 400 C./2 h 4-5 9.8 529 342 54.5 143 400 C./4 h 4-5 9.9 523 327 56.8 143 2 280 C./2 h 12.7 739 694 17.8 248 280 C./4 h 12.9 733 678 21.3 242 340 C./2 h 2-3 13.0 500 371 51.0 150 340 C./4 h 2-3 12.5 490 353 52.2 143 400 C./2 h 5-6 12.8 466 200 59.0 127 400 C./4 h 5-6 12.3 475 296 57.0 124
[0245] 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.
[0246] 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
[0247] The results point to a completely recrystallized microstructure having exceptionally high values for strength and hardness. Nevertheless, the high values for elongation at break A5 indicate the excellent ductility of the material states. After manufacture 3 as well, the strength values of the states of alloy 1 are above those of alloy 2. By contrast, the states of alloy 2 offer advantages with regard to elongation at break A5 and electrical conductivity.
TABLE-US-00008 TABLE 8 Microstructure characteristics and mechanical indices of the strips from working examples 1 and 2 in the end state (manufacture 3) Stress Hard- relief ness annealing Grain Electrical HB Al- temperature size conductivity R.sub.m R.sub.p0.2 A5 1.0/ loy [ C.] [m] [% IACS] [MPa] [MPa] [%] 10 1 240 C./2 h 5-10 9.9 739 653 25.3 228 280 C./2 h 5-10 9.9 723 648 27.1 219 320 C./2 h 5-10 9.9 708 582 28.3 213 360 C./2 h 5-10 10.0 570 400 47.0 153 2 240 C./2 h 5-10 12.8 668 598 26.7 204 280 C./2 h 5-10 12.9 653 557 32.4 197 320 C./2 h 5-10 12.7 636 544 34.3 189 360 C./2 h 5-10 12.9 536 390 43.6 149
[0248] The strips of working example 3 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 using calmed air in water. The advantage of accelerated cooling of the hot-formed semifinished product in water is manifested in the form of better cold formability. For instance, the hot-rolled strip that has been quenched in water can subsequently be cold-rolled with a cold-forming of 24%. By contrast, the strip that has been cooled under air after hot rolling permits only cold rolling with a cold-forming of about 5%.
TABLE-US-00009 TABLE 9 Manufacturing program for working example 3 No. Manufacture 1 Permanent mold casting 2 3-A, 3-B 3-C Hot rolling at 750 C. + water Hot rolling at 750 C. + quenching air cooling 3 Cold rolling Cold rolling 3-A/B: from 7.20 to 5.50 mm 3-C: from 7.38 to 7.04 mm ( 24%) ( 5%) 4 3-A and 3-C Annealing: 500 C./3 h, 550 C./3 h, 600 C./3 h + air cooling 3-B Annealing: 600 C./4 h + air cooling 5 Cold rolling 3-B: from 5.50 to 3.67 mm ( 33%) 6 3-B Annealing: 550 C./4 h + air cooling 7 Cold rolling 3-B: from 3.67 to 2.05 mm ( 44%) 8 3-B Annealing: 500 C./3 h + air cooling 9 Cold rolling 3-B: from 2.05 to 1.40 mm ( 32%) 10 3-B Stress relaxation annealing: 200 C./2 h, 240 C./2 h, 280 C./2 h, 320 C./2 h
[0249] The grain size and hardness of the cold-rolled state and of the cold-rolled and annealed state are shown in tab. 10. As a result of the annealing treatment, the microstructure properties balance out at a high level with rising annealing temperatures.
TABLE-US-00010 TABLE 10 Grain size and hardness of the cold-rolled (after manufacturing step 4 in tab. 8) and subsequently annealed strips from working example 3 Heat Grain size Hardness Alloy/state treatment [m] HB 2.5/62.5 3-A cold-rolled 15-20 247 (hot-rolled with water 500 C./3 h + air 5-10 188 quenching + cold-rolled 550 C./3 h + air 10-15 178 from 7.2 to 5.5 mm) 600 C./3 h + air 15-20 170 3-C cold-rolled 15-20 210 (hot-rolled with air 500 C./3 h + air 15-20 182 cooling + cold-rolled 550 C./3 h + air 20-25 174 from 7.38 to 7.04 mm) 600 C./3 h + air 20-25 174
[0250] The microstructure of strip 3-A was finally heat-treated with the parameters Of 500 C./3 h+air and 600 C./3 h+air and is shown in
[0251] The strip 3-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.
[0252] 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 5 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, which is expressed by the very low values for elongation at A11.3.
TABLE-US-00011 TABLE 11 Microstructure characteristics and mechanical indices of the strips from working example 3 in the final state Stress Electr. relief Con- Al- annealing Grain duct. loy/ temperature size [% R.sub.m R.sub.p0.2 A11.3 state [ C.] [m] IACS] [MPa] [MPa] [%] HV1 3-B Cold-rolled 2-3 6.3 574 477 0.4 282 200 C./2 h 3-4 6.5 734 693 0.3 294 240 C./2 h 3-4 6.5 731 658 0.6 283 280 C./2 h 2-3 6.5 702 621 0.7 281 320 C./2 h 2-3 6.7 703 628 0.7 275
[0253] 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 high level. However, there is naturally a deterioration in the ductility of the invention with rising Sn content owing to the rising 5 component of the microstructure.
LIST OF REFERENCE NUMERALS
[0254] 1 Sn-rich phase [0255] 2 Hard particles ensheathed by tin and/or the Sn-rich S phase [0256] 3 Solid copper solution consisting of tin-deficient a phase