CN118441178A - Low-copper high-strength high-bending brass strip and preparation method and application thereof - Google Patents
Low-copper high-strength high-bending brass strip and preparation method and application thereof Download PDFInfo
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- 239000010949 copper Substances 0.000 title claims abstract description 93
- 229910052802 copper Inorganic materials 0.000 title claims abstract description 84
- 238000005452 bending Methods 0.000 title claims abstract description 82
- 229910001369 Brass Inorganic materials 0.000 title claims abstract description 55
- 239000010951 brass Substances 0.000 title claims abstract description 55
- 238000002360 preparation method Methods 0.000 title abstract description 10
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 60
- 229910052742 iron Inorganic materials 0.000 claims abstract description 53
- 239000002245 particle Substances 0.000 claims abstract description 43
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 41
- 239000011159 matrix material Substances 0.000 claims abstract description 7
- 238000004519 manufacturing process Methods 0.000 claims abstract description 6
- 239000012535 impurity Substances 0.000 claims abstract description 3
- 238000010438 heat treatment Methods 0.000 claims description 116
- 238000000137 annealing Methods 0.000 claims description 103
- 238000005096 rolling process Methods 0.000 claims description 61
- 239000000956 alloy Substances 0.000 claims description 59
- 229910045601 alloy Inorganic materials 0.000 claims description 58
- 238000001816 cooling Methods 0.000 claims description 50
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 50
- 239000007789 gas Substances 0.000 claims description 48
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 40
- 238000005098 hot rolling Methods 0.000 claims description 40
- 239000000463 material Substances 0.000 claims description 40
- 238000000034 method Methods 0.000 claims description 34
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 28
- 239000001301 oxygen Substances 0.000 claims description 28
- 229910052760 oxygen Inorganic materials 0.000 claims description 28
- 230000035882 stress Effects 0.000 claims description 28
- 230000008569 process Effects 0.000 claims description 23
- 229910052757 nitrogen Inorganic materials 0.000 claims description 20
- 238000003723 Smelting Methods 0.000 claims description 19
- 238000005507 spraying Methods 0.000 claims description 18
- 239000001257 hydrogen Substances 0.000 claims description 14
- 229910052739 hydrogen Inorganic materials 0.000 claims description 14
- 238000007254 oxidation reaction Methods 0.000 claims description 14
- 238000005554 pickling Methods 0.000 claims description 14
- 230000009466 transformation Effects 0.000 claims description 13
- 230000032683 aging Effects 0.000 claims description 10
- 238000009749 continuous casting Methods 0.000 claims description 8
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 7
- 150000002431 hydrogen Chemical class 0.000 claims description 7
- 238000001556 precipitation Methods 0.000 claims description 4
- 229910000881 Cu alloy Inorganic materials 0.000 abstract description 22
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 90
- 238000005266 casting Methods 0.000 description 32
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 30
- 239000002253 acid Substances 0.000 description 23
- 238000004140 cleaning Methods 0.000 description 21
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 15
- 238000001035 drying Methods 0.000 description 15
- 239000007788 liquid Substances 0.000 description 15
- 238000005728 strengthening Methods 0.000 description 14
- 239000011701 zinc Substances 0.000 description 13
- 238000003801 milling Methods 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 238000004321 preservation Methods 0.000 description 11
- 230000001681 protective effect Effects 0.000 description 11
- 238000010008 shearing Methods 0.000 description 11
- 229910052799 carbon Inorganic materials 0.000 description 10
- 239000000498 cooling water Substances 0.000 description 10
- 230000000694 effects Effects 0.000 description 10
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 9
- 229910052725 zinc Inorganic materials 0.000 description 9
- 239000000243 solution Substances 0.000 description 8
- 238000005406 washing Methods 0.000 description 8
- 238000005336 cracking Methods 0.000 description 7
- 239000006185 dispersion Substances 0.000 description 7
- 230000001276 controlling effect Effects 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 229910001096 P alloy Inorganic materials 0.000 description 5
- RIRXDDRGHVUXNJ-UHFFFAOYSA-N [Cu].[P] Chemical compound [Cu].[P] RIRXDDRGHVUXNJ-UHFFFAOYSA-N 0.000 description 5
- 239000007864 aqueous solution Substances 0.000 description 5
- 239000003610 charcoal Substances 0.000 description 5
- 238000005238 degreasing Methods 0.000 description 5
- 238000005237 degreasing agent Methods 0.000 description 5
- 239000013527 degreasing agent Substances 0.000 description 5
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- 230000008018 melting Effects 0.000 description 5
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- 238000001953 recrystallisation Methods 0.000 description 5
- 239000002893 slag Substances 0.000 description 5
- 230000007704 transition Effects 0.000 description 5
- 238000009966 trimming Methods 0.000 description 5
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- 238000010998 test method Methods 0.000 description 2
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- IYRDVAUFQZOLSB-UHFFFAOYSA-N copper iron Chemical compound [Fe].[Cu] IYRDVAUFQZOLSB-UHFFFAOYSA-N 0.000 description 1
- TVZPLCNGKSPOJA-UHFFFAOYSA-N copper zinc Chemical compound [Cu].[Zn] TVZPLCNGKSPOJA-UHFFFAOYSA-N 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
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- 238000010587 phase diagram Methods 0.000 description 1
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- 230000001105 regulatory effect Effects 0.000 description 1
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Abstract
The invention discloses a low-copper high-strength high-bending brass strip, and a preparation method and application thereof, wherein the low-copper high-strength high-bending brass strip comprises the following components in percentage by mass: 61-62 wt%, P:0.01 to 0.03 weight percent of Fe:0.15-0.2wt% and the balance Zn and unavoidable impurities, wherein the structure of the low-copper high-strength high-bending brass strip comprises a matrix phase and a precipitated phase distributed in the matrix phase, the precipitated phase comprises Fe 3 P and Fe 2 P, wherein the average diameter size of Fe 3 P and Fe 2 P is within 10nm, and the particle density per unit area is above 2000/mum 2. The copper alloy strip disclosed by the invention not only has low production cost of low copper brass, but also has high strength, good conductivity, excellent bending performance and good stress relaxation resistance, can meet the performance requirement of a high-end connecting terminal, and has a wide application prospect in the household electrical appliance industry.
Description
Technical Field
The invention relates to the technical field of copper alloy, in particular to a low-copper high-strength high-bending brass strip and a preparation method and application thereof.
Background
Along with the intense competition of the electronic and electric product industry, the production cost control is more and more important. With the continuous rise of copper prices, the price of copper strip products is more difficult to accept by customers, and the competitiveness and profitability of customers are severely restricted. Aiming at the market current situation, the current household appliance industry proposes to replace an H70 copper strip with H62, so that the use cost of the copper strip of a manufacturer can be effectively reduced by 6%, the current H62 is mainly used for a connecting terminal of a household appliance, and the product requirement state is H10.
However, the bending property of the super-hard H62 brass produced by the current production technology cannot meet the customer requirements, mainly because H62 is alpha+beta double-phase brass, the plasticity and bending property are poorer than those of H70, and mainly because the beta phase of the H62 brass produced by the current technology has higher proportion, so that microscopic cracks are generated at the beta phase during plastic processing or bending; meanwhile, the brass alloy has larger structure grain size, so that H62 cannot meet the requirement of H10 bending for the performance state of the connecting terminal product.
The patent document with publication number CN111926273A discloses a combined processing method of high-strength high-toughness H62 brass, which mainly applies equal channel angular extrusion and subsequent heat treatment processes to commercial H62 alloy with lower strength, and can improve the toughness of the H62 alloy by controlling a tissue structure under the condition of not changing the shape and the size of a sample. The tensile strength of the H62 brass prepared by the processing method can reach more than 530MPa, and the microhardness can be improved to about 170 HV.
The patent document with publication number CN102345031A discloses a high-plasticity brass strip and a production process thereof, wherein the brass strip comprises the following components in percentage by weight: electrolytic copper 61-62, copper-iron alloy 0.3-0.5, and electrolytic zinc the rest, the preparation process comprises: smelting; casting; milling; hot rolling; cold rolling; acid washing and rough rolling; fine shearing, acid washing and finish rolling; acid washing and inspection. The brass strip produced by the process not only can meet the elongation of H68 and H70 marks of stretching processing, and the elongation reaches about 60 percent, but also has the characteristics of smaller surface grain size and larger tensile strength after the same elongation of H62 marks is stretched compared with the H68 and H70 marks.
Although the prior art has studied how to improve the properties such as hardness and plasticity of H62 brass, the bending properties of H62 brass are less of a concern in the prior art. For the connection terminal of home appliances, it is required not only that H62 brass has high strength, but also that it has excellent bending property. In the prior art, less H62 brass can meet the performance requirements simultaneously.
Therefore, based on the application demands of customers, there is a need to develop a brass strip with low copper, high strength and high bending resistance, which has excellent bending performance and good stress relaxation resistance while maintaining the high strength of the material under the condition of adopting low copper and high zinc.
Disclosure of Invention
In order to solve the problems, the invention provides a low-copper high-strength high-bending brass strip, which has high strength, excellent bending performance and good stress relaxation resistance, and can be used for preparing household appliance terminals.
The low-copper high-strength high-bending brass strip comprises the following components in percentage by mass: 61-62 wt%, P:0.01 to 0.03 weight percent of Fe:0.15-0.2wt% and the balance Zn and unavoidable impurities, wherein the structure of the low-copper high-strength high-bending brass strip comprises a matrix phase and a precipitation phase distributed in the matrix phase, the precipitation phase comprises Fe 3 P and Fe 2 P, wherein the average diameter size of Fe 3 P and Fe 2 P is within 10nm, and the particle density per unit area is above 2000/mum 2.
According to the invention, fe and P elements are added into brass, so that Fe 3 P and Fe 2 P exist in an alloy tissue structure, the average diameter size of Fe 3 P and Fe 2 P is within 10nm, the particle density per unit area is more than 2000 particles/mum 2, precipitated phases are distributed at grain boundaries and along the grain boundaries, the effect of pinning the grain boundaries is achieved, the dispersion strengthening effect of a strengthening phase is fully exerted, and the strength and stress relaxation resistance of the material are improved. In addition, fe 3 P or Fe 2 P can also play roles in refining grains and preventing recrystallization in the copper alloy, and further improve the strength, bending property and stress relaxation resistance of the alloy.
Preferably, the average grain size of the low-copper high-strength high-bending brass strip is within 3 mu m.
Preferably, the beta phase proportion in the low-copper high-strength high-bending brass strip is less than 3%.
More preferably, the beta ratio of the low copper high strength high bending brass strip is less than 2%.
Preferably, the low copper high strength high bending brass strip has a hardness of 185-205HV, a tensile strength of 580-630MPa, a yield strength of 550-600MPa, an elongation of >7%, no cracking in the direction of Goodway at 180 ° R/t=0.5, no cracking in the direction of Badway at 180 ° R/t=0.8, and no cracking in the direction of Goodway at 90 ° R/t=1 after bending back and forth for 5 times.
The invention also provides a preparation method of the low-copper high-strength high-bending brass strip, which comprises the following process flows: batch smelting, semi-continuous casting, hot rolling, second-phase pre-ageing+beta/alpha phase transformation heat treatment, rough rolling, first air cushion heat treatment, middle rolling, second air cushion heat treatment, finished product rolling and annealing.
In the second phase preaging and beta/alpha phase transformation heat treatment process, after the temperature of the hot rolling final rolling material is 460-500 ℃, rolling the hot rolled strip blank on line within 10 minutes, placing the hot rolled strip blank in a heat treatment furnace, adjusting the temperature of the rolled heat treatment furnace to 450-470 ℃, preserving heat for 2-3 hours, and then taking out the whole rolled material from the furnace for 5 minutes, hanging the whole rolled material into a water tank, and cooling to normal temperature.
The beta phase proportion of the alloy is controlled within 2.5 percent through second phase preaging and beta/alpha phase transformation heat treatment, meanwhile, the alloy is preaging in the process, the diameter sizes of preaging precipitated second phases Fe 3 P and Fe 2 P are within 5nm, and the particle density per unit area is more than 2000 particles/mu m 2. After the temperature of the hot-rolled final rolling material is up to 460-500 ℃, the hot-rolled final rolling material is placed in a heat treatment furnace and kept at 450-470 ℃ for 2-3 hours, mainly at 450-470 ℃, fe and P in an alloy structure are aged to separate out Fe 3 P and Fe 2 P second phases, after the second phases are separated out, the recrystallization temperature of the alloy can be increased, the growth of crystal grains can be prevented, the advantages are brought to the regulation and control of the subsequent heat treatment structure, and the grain size is ensured to be controlled within a required range. Meanwhile, the temperature is kept between 450 and 470 ℃ for 2 to 3 hours for pre-aging, so that the average diameter of the precipitated Fe 3 P and Fe 2 P second phase particles is ensured to be within 5nm, and the particle density per unit area is more than 2000 particles/mu m 2. In addition, according to a copper-zinc binary equilibrium phase diagram, the solubility of zinc in copper can reach 38.3% at the maximum at 454 ℃, namely the beta phase proportion in the alpha+beta dual-phase brass is minimum at 454 ℃, so that when the heat treatment is carried out for 2-3 hours at 450-470 ℃, the beta phase in the alpha+beta dual-phase brass is converted into alpha phase, and the whole coil is hung into a water tank to be cooled to normal temperature within 5 minutes after being discharged from a furnace, and the process heat treatment is converted into alpha phase to be maintained by adopting the rapid water cooling mode, thereby ensuring that the beta phase proportion of the alloy is controlled within 2.5%, and improving the processing plasticity and the bending property of the material.
Preferably, in the hot rolling process, the heating temperature of the cast ingot is 740-780 ℃, the heat preservation time is 2-3 h, the hot rolling starting temperature is 720-750 ℃, and the hot rolling finishing temperature is 460-500 ℃.
Preferably, in the first air cushion type heat treatment process, a single expansion type air cushion furnace is adopted for annealing, the annealing temperature is 450-470 ℃, the annealing speed is 10-15 m/min, the length of an annealing heating furnace zone is 18-23 m, the length of a cooling zone is 2.5-4.5m, on-line water spraying and water cooling are adopted, and the surface temperature of the copper strip is reduced to room temperature after passing through the cooling zone.
The first air cushion type heat treatment process adopts 450-470 ℃ for annealing, the temperature range is suitable for beta opposite alpha phase conversion, meanwhile, the length of an annealing heating furnace zone is 18-23 m, the length of a cooling zone is 2.5-4.5m, the length of a heating zone is increased by beta opposite alpha phase conversion time, and the cooling zone adopts a rapid water cooling mode to convert and separate out beta phase of the heating zone into alpha phase for retention, so that beta phase in the alloy is further converted into alpha phase after the process, beta phase in the alloy is reduced, and cold working plasticity and bending property of the alloy are improved again. And annealing is carried out at 450-470 ℃, so that Fe and P in the alloy matrix can be further separated out to produce second phases Fe 3 P and Fe 2 P, the conductivity of the alloy is improved, and the like. Meanwhile, the air cushion type heat treatment process adopts a single expansion type air cushion furnace for annealing, and each section of copper belt has short heating furnace area time, so that the situation of recrystallization growth of an alloy structure during annealing and softening can be effectively avoided.
Preferably, the first air cushion type heat treatment adopts micro-oxidation atmosphere annealing, the shielding gas is mixed gas of nitrogen and trace oxygen, the oxygen content is 3-6%, and online pickling is adopted to remove oxides on the surface of the alloy. The average grain size after heat treatment is controlled to be 5 mu m, the beta phase proportion of the alloy is controlled to be within 2.2 percent, and the average diameter size of precipitated phases Fe 3 P and Fe 2 P is ensured to be within 8nm, and the grain density per unit area is more than 2000 grains/mu m 2.
The first air cushion type heat treatment adopts micro-oxidation atmosphere to carry out brass heat treatment, and a thin oxide film can be formed on the surface of the high-zinc brass alloy during the heat treatment, so that dezincification of brass in the annealing process can be effectively avoided, but the oxygen content cannot exceed 6%, otherwise, the surface of the copper strip is seriously oxidized due to the excessively high oxygen content, and the surface oxide layer is difficult to eliminate by on-line pickling.
Preferably, in the second air cushion heat treatment process, a single expansion air cushion furnace is adopted for annealing, the annealing temperature is 450-470 ℃, the annealing speed is 30-50 m/min, the length of an annealing heating furnace zone is 18-23 m, the length of a cooling zone is 2.5-4.5m, on-line water spraying and water cooling are adopted, and the surface temperature of the copper strip is reduced to room temperature after passing through the cooling zone.
Preferably, the second air cushion type heat treatment adopts micro-oxidation atmosphere annealing, the shielding gas is mixed gas of nitrogen and trace oxygen, the oxygen content is 3-6%, and online pickling is adopted to remove oxides on the surface of the alloy.
The second air cushion type heat treatment has the same effect as the first air cushion type heat treatment, the average grain size of the alloy structure after the second air cushion type heat treatment is controlled within 3 mu m, and the beta phase ratio of the alloy is controlled within 2.0 percent. Meanwhile, the average diameter size of the precipitated phases Fe 3 P and Fe 2 P is ensured to be within 10nm, the particle density per unit area is more than 2000 particles/mu m 2, the dispersion strengthening effect of the strengthening phase is fully exerted, and the strength, the bending property, the electric conductivity and the stress relaxation resistance of the material are improved. The alpha phase is a face-centered cube, the plasticity is good, the cold working is suitable, the beta phase is a body-centered cube, and the disordered beta phase can be converted into the ordered beta / phase at the temperature of 454-468 ℃, and the ordered beta / phase is obviously fragile, so that when the ordered beta / phase brass is in plastic deformation, microscopic cracks are generated at the beta / phase due to the fact that the beta / phase is hard and fragile and difficult to deform, the microscopic cracks are gradually increased along with the increase of plastic deformation, and the processing cracks or bending cracks and the like are caused. The preparation method controls the beta phase of the brass with low copper and high zinc within 2 percent, greatly reduces the influence of beta on plasticity, greatly improves the bending property of the brass, controls the grain size of the alloy within 3 mu m, and further improves the bending property, strength and the like of the alloy material.
Preferably, the hot rolling power is controlled to be more than 90%; the rough rolling processing rate is controlled to be 85-95 percent; the medium rolling processing rate is controlled between 70 and 85 percent. The hot rolling processing rate reaches more than 90%, the cast structure of the casting blank can be completely broken, the grains of the structure are effectively thinned, and the plasticity, the strength and the bending property of the material are improved. Meanwhile, the hot rolling reaches more than 90%, the high processing rate at high temperature can effectively eliminate the tiny slackening of the cast state, the compactness of the material is improved, and the plasticity and bending performance of the material are improved. The rough rolling processing rate reaches more than 85% and the medium rolling processing rate reaches more than 70%, the texture fiber can be effectively textured, and the texture grain refinement can be effectively reduced by matching with the subsequent air cushion type heat treatment, so that the grain size and the like required by the alloy are achieved, and the high strength, the excellent bending performance and the like are realized.
Preferably, the power for the finished product rolling is controlled to be 20-25%.
Preferably, the annealing is low-stress-relief Wen Qidian annealing, the single-expansion air cushion furnace is adopted for on-line stress-relief annealing, the annealing temperature is 360-400 ℃, the annealing speed is 100-150 m/min, the unit tension in the furnace is 30-35 kg/mm 2, the shielding gas is the mixed gas of nitrogen and hydrogen, and the content of the hydrogen in the mixed gas is 2-4%. By the destressing low-temperature gas cushion annealing, the internal stress of the material can be eliminated by a low-temperature rapid mode and a high tension in the recrystallization temperature range of the material. Under the process, the material can recover the grain structure of the material processing in the recrystallization temperature range, so that the internal stress of the material processing is effectively eliminated, the material is recovered only for a long time but not recrystallized due to the low temperature speed, and the strength of the material is not obviously changed. Therefore, under the process, the internal stress of the material is eliminated, and the plasticity of the material is improved, so that the bending performance of the material is further improved.
The invention also provides application of the low-copper high-strength high-bending brass strip in a connecting terminal of a household appliance. The copper alloy strip has the hardness of 185-205HV, the tensile strength of 580-630MPa, the yield strength of 550-600MPa, the elongation rate of >7 percent, no cracking in the direction of Goodway at 180 DEG R/T=0.5, no cracking in the direction of Badway at 180 DEG R/T=0.8, no cracking in the direction of Goodway when 180 DEG R/T=1, and no cracking in the back and forth bending for 5 times, and can meet the performance requirement of the connecting terminal of customer household appliances.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) According to the invention, fe and P elements are added into brass, so that Fe 3 P and Fe 2 P exist in an alloy tissue structure, and through second-phase pre-ageing and beta/alpha phase transformation heat treatment, the size and unit area particle density of Fe 3 P and Fe 2 P are controlled by matching with two air cushion heat treatments, the average grain size and the proportion of beta phase of the alloy tissue are effectively controlled, material grains are thinned, and the hardness, bending property and stress relaxation resistance of the material are improved.
(2) The copper alloy strip disclosed by the invention has low production cost of low copper brass, and simultaneously has high strength, good conductive performance, excellent bending performance and good stress relaxation resistance, the hardness is 185-205HV, the tensile strength is 580-630MPa, the yield strength is 550-600MPa, the elongation is more than 7%, the bending Goodway direction 180 DEG R/T=0.5 is not cracked, the bending Badway direction 180 DEG R/T=0.8 is not cracked, and the bending back and forth for 5 times is not cracked when the bending Goodway direction 90 DEG R/T=1, so that the performance requirement of a high-end connecting terminal can be met, and the copper alloy strip has a wide application prospect in the home electronics industry.
Detailed Description
To make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments.
The chemical compositions of the copper alloy strips in the examples of the present invention are shown in table 1.
TABLE 1 chemical composition (wt%) of copper alloy strip
| Cu | P | Fe | Zn |
| 61-62 | 0.01-0.03 | 0.04-0.1 | Allowance of |
The preparation process flow of the copper alloy strip in the embodiment of the invention comprises the following steps: batch smelting, semi-continuous casting, hot rolling, second-phase pre-ageing+beta/alpha phase transformation heat treatment, surface milling, rough rolling, edge cutting, first air cushion type heat treatment, middle rolling, second air cushion type heat treatment, finished product rolling, stretch bending straightening, stress relief low Wen Qidian type annealing and cleaning. The method comprises the following specific steps:
S1, batch smelting
Adding electrolytic copper into a smelting furnace, heating and melting, and tightly covering the smelting furnace melt with dry charcoal, wherein the covering thickness is 80-100 mm; then the temperature is raised to 1340-1380 ℃, and pure iron sheets (the specification of the pure iron sheets is 0.5-1.0mm thick, 30-60mm wide and 80-120mm long) are added according to the component proportion. After adding iron sheet for 20-40 min, the temperature is reduced to 1100-1120 ℃, zinc ingot and copper-phosphorus alloy are added according to the inverse proportion of the components, slag is fished after heat preservation is continued for 20-30 min, and casting is started.
S2, semi-continuous casting
Controlling the temperature of the copper liquid at 1100-1120 ℃, opening a stopper rod, putting the copper liquid into a crystallizer, then opening cooling water, starting a tractor when the copper liquid in the crystallizer reaches about two thirds of the height of the crystallizer, starting the drawing casting work at 20-30 mm/min, starting vibration, and covering the vibration with graphite powder spraying in the whole drawing casting process, wherein the frequency of the vibrator is 30-50 times/min and the amplitude is 3-6 mm; the ingot is cast to 0.5-1.0 m to reach a stable speed casting stage, and the casting speed is controlled to be 100-140 mm/min. The primary cooling water flow of the crystallizer is 30-50 m 3/h, the water pressure is 0.4-0.6 MPa, the water inlet temperature is 20-28 ℃, and the water outlet temperature is controlled at 40-50 ℃. Ingot casting specifications were 230 x 620mm x 800mm.
S3, hot rolling
The heating temperature of the cast ingot is 740-780 ℃, the heat preservation time is 2-3h, the hot rolling starting temperature is 720-750 ℃, the hot rolling processing rate is above 90%, the hot rolling finishing temperature is 460-500 ℃, and the bandwidth after hot rolling expansion is 650+ -5 mm.
S4, second phase preaging+beta/alpha phase transformation heat treatment
After the temperature of the hot-rolled final rolling material is 460-500 ℃, rolling the hot-rolled strip blank on line within 10 minutes, placing the hot-rolled strip blank in a heat treatment furnace, adjusting the temperature of the rolled heat treatment furnace to 450-470 ℃, preserving heat for 2-3 hours, and then taking out the hot-rolled strip blank from the furnace for 5 minutes, hanging the whole rolled strip blank into a water tank, and cooling to normal temperature. The beta phase proportion of the alloy is controlled within 2.5 percent through second phase preaging and beta/alpha phase transformation heat treatment, meanwhile, the alloy is preaging in the process, the average diameter size of preaging precipitated second phases Fe 3 P and Fe 2 P is within 5nm, and the particle density per unit area is more than 2000 particles/mu m 2.
S5, milling surface
The single-sided milling amount is 0.5-1.5 mm.
S6, rough rolling
The rough rolling processing rate is controlled between 85 and 95 percent.
S7, trimming
The unilateral shearing is 7-10 mm, and the bandwidth after shearing is 630+/-0.5 mm.
S8, first air cushion type heat treatment
And annealing by adopting a single-expansion air cushion furnace, wherein the annealing temperature is 450-470 ℃, and the annealing speed is 10-15 m/min. The length of the annealing heating furnace zone is 18-23 m, the length of the cooling zone is 2.5-4.5m, on-line water spraying and water cooling are adopted, and the surface temperature of the copper strip is reduced to the room temperature after passing through the cooling zone. Heating and annealing in micro-oxidation atmosphere, wherein the protective gas is a mixed gas of nitrogen and trace oxygen, the oxygen content is 3-6%, and on-line pickling is adopted to remove oxides on the surface of the alloy, the sulfuric acid concentration is 100-130 g/l, the temperature is less than or equal to 40 ℃, and Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 65-70 ℃. The average grain size after heat treatment is controlled to be 5 mu m, and the beta phase ratio of the alloy is controlled to be within 2.2 percent. Meanwhile, the average diameter size of the precipitated phases Fe 3 P and Fe 2 P is ensured to be within 8nm, and the particle density per unit area is more than 2000 particles/mu m 2.
S9, middle rolling
The medium rolling processing rate is controlled between 70 and 85 percent.
S10, second air cushion type heat treatment
And annealing by adopting a single-expansion air cushion furnace, wherein the annealing temperature is 450-470 ℃, and the annealing speed is 30-50 m/min. The length of the annealing heating furnace zone is 18-23 m, the length of the cooling zone is 2.5-4.5m, on-line water spraying and water cooling are adopted, and the surface temperature of the copper strip is reduced to the room temperature after passing through the cooling zone. Adopting micro-oxidation atmosphere annealing, wherein the protective gas is a mixed gas of nitrogen and trace oxygen, the oxygen content is 3-6%, and on-line pickling is adopted to remove oxides on the surface of the alloy, the sulfuric acid concentration is 100-130 g/l, the temperature is less than or equal to 40 ℃, and Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 65-70 ℃. The average grain size after heat treatment is controlled within 3 μm, and the beta phase ratio of the alloy is controlled within 2.0%. Meanwhile, the average diameter size of the precipitated phases Fe 3 P and Fe 2 P is ensured to be within 10nm, the particle density per unit area is more than 2000 particles/mu m 2, the dispersion strengthening effect of the strengthening phase is fully exerted, and the strength, the bending property, the electric conductivity and the stress relaxation resistance of the material are improved.
S11, rolling finished products
When the finished product is rolled, a 20-roller finishing mill is adopted, and the processing rate is controlled to be 20-25%.
S12, stretch bending and straightening
When in stretch bending and straightening, the straightening elongation is 0.15-0.2%, and the straightening unit tension is 20-25 kg/mm 2.
S13, low stress relief Wen Qidian type annealing
The single-expansion type air cushion furnace is adopted for on-line stress relief annealing, the annealing temperature is 360-400 ℃, the annealing speed is 100-150 m/min, the unit tension in the furnace is 30-35 kg/mm 2, the protective gas is the mixed gas of nitrogen and hydrogen, and the content of the hydrogen in the mixed gas is 2-4%.
S14, cleaning
Degreasing is carried out firstly, a degreasing agent adopts sodium hydroxide aqueous solution, the PH range is 7-9, and the solution temperature is 60-70 ℃; then carrying out acid washing, wherein the concentration of sulfuric acid is 100-130 g/l, the temperature is less than or equal to 40 ℃, and the Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 65-70 ℃.
S15, separating and packaging the finished product.
The thickness of the copper alloy strip prepared by the embodiment of the invention is 0.15-0.3 mm, the hardness of the product is 185-205HV, the tensile strength is 580-630MPa, the yield strength is 550-600MPa, the elongation is more than 7%, the copper alloy strip is not cracked in the direction of Goodway, 180 DEG R/T=0.5 and 180 DEG R/T=0.8 in the direction of Badway, and is not cracked when being bent back and forth for 5 times in the direction of Goodway and 90 DEG R/T=1, so that the performance requirement of a connecting terminal of a customer household appliance can be met.
The technical scheme and effect of the present invention are illustrated below with reference to specific examples.
Specific compositions of the copper alloy strips of examples 1 to 4 and comparative examples 1 to 3 are shown in Table 2, and key process parameters are shown in Table 3.
Example 1
The copper alloy strip of this example was prepared as follows:
1) Batch smelting
Adding electrolytic copper into a smelting furnace, heating and melting, and tightly covering the smelting furnace melt with dry charcoal, wherein the covering thickness is 90mm; then the temperature is raised to 1370 ℃, and pure iron sheets (the pure iron sheets are 0.5-1.0mm thick, 30-60mm wide and 80-120mm long) are added according to the component proportion. After adding the iron sheet for 35 minutes, the temperature is reduced to 1116 ℃, zinc ingots and copper-phosphorus alloy are added according to the inverse proportion of the components, slag is fished after the heat preservation is continued for 28 minutes, and casting is started.
2) Semi-continuous casting
The temperature of the copper liquid is controlled at 1116 ℃, a stopper rod is opened, the copper liquid is put into a crystallizer, then cooling water is opened, a tractor is started when the copper liquid in the crystallizer reaches about two thirds of the height of the crystallizer, the drawing casting work is started at 27mm/min, vibration is started, the frequency of the vibrator is 36 times/min, the amplitude is 5mm, and the whole drawing casting process is covered by graphite powder spraying; the ingot is cast to 0.5-1.0 m to reach a stable speed casting stage, and the casting speed is controlled to be 128mm/min. The primary cooling water flow of the crystallizer is 43m 3/h, the water pressure is 0.52MPa, the water inlet temperature is 24 ℃, and the water outlet temperature is controlled at 44 ℃. Ingot casting specifications were 230 x 620mm x 800mm.
3) Hot rolling
The heating temperature of the cast ingot is 765 ℃, the heat preservation time is 2.8h, the hot rolling starting temperature is 735 ℃, the hot rolling is carried out to 16mm, the processing rate is 93.04%, meanwhile, the hot rolling finishing temperature is 495 ℃, and the bandwidth after hot rolling expansion is 650+/-5 mm.
4) Second phase preaging+beta/alpha phase transition heat treatment
After the temperature of the hot-rolled final rolling material is 495 ℃, rolling the hot-rolled strip blank on line within 10 minutes, placing the hot-rolled strip blank in a heat treatment furnace, adjusting the temperature of the rolled heat treatment furnace to 470 ℃, preserving heat for 2.1 hours, and then taking out the hot-rolled strip blank from the furnace for 5 minutes, hanging the whole rolled strip blank into a water tank, and cooling to normal temperature. The beta phase proportion of the alloy is 2.15 percent after the second phase pre-ageing and beta/alpha phase transformation heat treatment, meanwhile, the alloy is pre-aged in the working procedure, the average diameter size of the pre-ageing precipitated second phases Fe 3 P and Fe 2 P is within 3.4nm, and the particle density per unit area is more than 3944 particles/mu m 2.
5) Milling surface
The single-sided milling amount is 0.75mm.
6) Rough rolling
Rough rolling to 1.2mm, and controlling the processing rate to 91.72%.
7) Trimming edge
The unilateral shearing is 7.5mm, and the bandwidth after shearing is 630+/-0.5 mm.
8) First air cushion type heat treatment
And (3) annealing by adopting a single-expansion air cushion furnace, wherein the annealing temperature is 465 ℃, the annealing speed is 11m/min, the length of an annealing heating furnace zone is 21m, the length of a cooling zone is 3m, water cooling is performed by adopting on-line water spraying, and the surface temperature of the copper strip is reduced to room temperature after passing through the cooling zone. Adopting micro-oxidation atmosphere annealing, wherein the protective gas is a mixed gas of nitrogen and trace oxygen, the oxygen content is 5.5%, and on-line pickling is adopted to remove oxides on the surface of the alloy, the sulfuric acid concentration is 127g/l, the temperature is less than or equal to 40 ℃, and the Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 68 ℃. The average grain size after heat treatment was controlled to 3.7 μm, and the beta ratio of the alloy was controlled to 1.95%. While ensuring that the average diameter size of the precipitated phases Fe 3 P and Fe 2 P is 4.8nm and the particle density per unit area is 3110 particles/μm 2.
9) Middle rolling
The middle rolling is carried out until the thickness reaches 0.39mm, and the processing rate is controlled to be 67.5 percent.
10 Secondary air cushion heat treatment
And (3) annealing by adopting a single-expansion air cushion furnace, wherein the annealing temperature is 465 ℃, the annealing speed is 33m/min, the length of an annealing heating furnace area is 21m, the length of a cooling area is 3m, water cooling is performed by adopting on-line water spraying, and the surface temperature of the copper strip is reduced to room temperature after passing through the cooling area. Adopting micro-oxidation atmosphere annealing, wherein the protective gas is a mixed gas of nitrogen and trace oxygen, the oxygen content is 3-6%, and on-line pickling is adopted to remove oxides on the surface of the alloy, the sulfuric acid concentration is 125g/l, the temperature is less than or equal to 40 ℃, and Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 65-70 ℃. The average grain size after heat treatment was controlled to 2.2 μm, and the beta phase ratio of the alloy was controlled to 1.8%. Meanwhile, the average diameter size of the precipitated phases Fe 3 P and Fe 2 P is ensured to be 6.3nm, the particle density per unit area is 3318 particles/mu m 2, the dispersion strengthening effect of the strengthening phase is fully exerted, and the strength, the bending property, the electric conductivity and the stress relaxation resistance of the material are improved.
11 Rolling of finished products
When the finished product is rolled, a 20-roller finishing mill is adopted, the rolling is carried out until the thickness is 0.3mm, and the processing rate is controlled to be 23.08%.
12 Stretch bending and straightening
When the stretch bending is performed, the straightening elongation is 0.16 percent, and the straightening unit tension is 22kg/mm 2.
13 Low Wen Qidian anneal for stress relief
And (3) carrying out on-line stress relief annealing by adopting a single expansion type air cushion furnace, wherein the annealing temperature is 395 ℃, the annealing speed is 120m/min, the unit tension in the furnace is 32kg/mm 2, the shielding gas is a mixed gas of nitrogen and hydrogen, and the content of the hydrogen in the mixed gas is 2.8%.
14 Cleaning)
Degreasing is carried out firstly, a degreasing agent adopts sodium hydroxide aqueous solution, the PH range is 8.6, and the solution temperature is 68 ℃; then carrying out acid washing, wherein the concentration of sulfuric acid is 125g/l, the temperature is less than or equal to 40 ℃, and the Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 68 ℃.
15 Dividing and packaging the finished product.
Example 2
The copper alloy strip of this example was prepared as follows:
1) Batch smelting
Adding electrolytic copper into a smelting furnace, heating and melting, and tightly covering the smelting furnace melt with dry charcoal, wherein the covering thickness is 86mm; then the temperature is raised to 1350 ℃, and pure iron sheets (the pure iron sheets have the specification of 0.5-1.0mm thick, 30-60mm wide and 80-120mm long) are added according to the component proportion. After adding the iron sheet for 25 minutes, the temperature is reduced to 1115 ℃, zinc ingots and copper-phosphorus alloy are added according to the inverse proportion of the components, slag is fished after the heat preservation is continued for 27 minutes, and casting is started.
2) Semi-continuous casting
Controlling the temperature of copper liquid at 1115 ℃, opening a stopper rod, putting the copper liquid into a crystallizer, then opening cooling water, starting a tractor when the copper liquid in the crystallizer reaches about two thirds of the height of the crystallizer, starting the drawing casting work at 26mm/min, starting vibration, wherein the frequency of the vibrator is 35 times/min, the amplitude is 4mm, and the whole drawing casting process is covered by graphite powder spraying; the ingot is cast to 0.5-1.0 m to reach a stable speed casting stage, and the casting speed is controlled to be 125mm/min. The primary cooling water flow of the crystallizer is 37m 3/h, the water pressure is 0.45MPa, the water inlet temperature is 22 ℃, and the water outlet temperature is controlled at 47 ℃. Ingot casting specifications were 230 x 620mm x 800mm.
3) Hot rolling
The heating temperature of the cast ingot is 745 ℃, the heat preservation time is 3h, the hot rolling starting temperature is 725 ℃, the hot rolling is carried out to 15mm, the processing rate is 93.47%, the hot rolling finishing temperature is 475 ℃, and the bandwidth after hot rolling expansion is 650+/-5 mm.
4) Second phase preaging+beta/alpha phase transition heat treatment
After the temperature of the hot-rolled final rolling material is 475 ℃, the hot-rolled strip blank is rolled on line and placed in a heat treatment furnace within 10 minutes, the temperature of the rolled heat treatment furnace is regulated to 465 ℃, the heat is preserved for 2.4 hours, and then the whole rolled material is hung into a water tank to be cooled to normal temperature within 5 minutes after being discharged from the furnace. The beta phase proportion of the alloy is 2.1 percent after the second phase preaging and beta/alpha phase transformation heat treatment, meanwhile, the alloy is preaging in the working procedure, the average diameter size of preaging precipitated second phases Fe 3 P and Fe 2 P is 3.1nm, and the particle density per unit area is 2800 particles/mu m 2.
5) Milling surface
The single-sided milling amount is 0.75mm.
6) Rough rolling
Rough rolling to 1.0mm, and the processing rate is controlled to be 92.59%.
7) Trimming edge
The unilateral shearing is 7.5mm, and the bandwidth after shearing is 630+/-0.5 mm.
8) First air cushion type heat treatment
And (3) annealing by adopting a single-expansion air cushion furnace, wherein the annealing temperature is 460 ℃, the annealing speed is 12m/min, the length of an annealing heating furnace zone is 21m, the length of a cooling zone is 3m, water cooling is performed by adopting on-line water spraying, and the surface temperature of the copper strip is reduced to room temperature after passing through the cooling zone. Adopting micro-oxidation atmosphere annealing, wherein the protective gas is a mixed gas of nitrogen and trace oxygen, the oxygen content is 5%, and on-line pickling is adopted to remove oxides on the surface of the alloy, the sulfuric acid concentration is 115g/l, the temperature is less than or equal to 40 ℃, and Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 68 ℃. The average grain size after heat treatment was controlled to 3.5. Mu.m, and the beta ratio of the alloy was controlled to 1.9%. Meanwhile, the diameter size of the precipitated phases Fe 3 P and Fe 2 P is 4.2nm, and the particle density per unit area is more than 3358 particles/mu m 2.
9) Middle rolling
The middle rolling is carried out until the thickness reaches 0.32mm, and the processing rate is controlled to be 68 percent.
10 Secondary air cushion heat treatment
And (3) annealing by adopting a single-expansion air cushion furnace, wherein the annealing temperature is 460 ℃, the annealing speed is 39m/min, the length of an annealing heating furnace area is 21m, the length of a cooling area is 3m, water cooling is performed by adopting on-line water spraying, and the surface temperature of the copper strip is reduced to room temperature after passing through the cooling area. Adopting micro-oxidation atmosphere annealing, wherein the protective gas is a mixed gas of nitrogen and trace oxygen, the oxygen content is 3-6%, and on-line pickling is adopted to remove oxides on the surface of the alloy, the sulfuric acid concentration is 120g/l, the temperature is less than or equal to 40 ℃, and Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 67 ℃. The average grain size after heat treatment was controlled to 2.15 μm, and the beta ratio of the alloy was controlled to 1.75%. Meanwhile, the average diameter size of the precipitated phases Fe 3 P and Fe 2 P is ensured to be 5.8nm, the particle density per unit area is 3576 particles/mu m 2, the dispersion strengthening effect of the strengthening phase is fully exerted, and the strength, the bending property, the electric conductivity and the stress relaxation resistance of the material are improved.
11 Rolling of finished products
When the finished product is rolled, a 20-roller finishing mill is adopted, the finished product is rolled to 0.25mm, and the processing rate is controlled to be 21.88%.
12 Stretch bending and straightening
When the stretch bending is performed, the straightening elongation is 0.17 percent, and the straightening unit tension is 23kg/mm 2.
13 Low Wen Qidian anneal for stress relief
And (3) carrying out on-line stress relief annealing by adopting a single expansion type air cushion furnace, wherein the annealing temperature is 380 ℃, the annealing speed is 120m/min, the unit tension in the furnace is 33kg/mm 2, the shielding gas is a mixed gas of nitrogen and hydrogen, and the content of the hydrogen in the mixed gas is 2.9%.
14 Cleaning)
Degreasing is carried out firstly, a degreasing agent adopts sodium hydroxide aqueous solution, the PH range is 8.2, and the solution temperature is 67 ℃; then carrying out acid washing, wherein the concentration of sulfuric acid is 115g/l, the temperature is less than or equal to 40 ℃, and the Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 67 ℃.
15 Dividing and packaging the finished product.
Example 3
The copper alloy strip of this example was prepared as follows:
1) Batch smelting
Adding electrolytic copper into a smelting furnace, heating and melting, and tightly covering the smelting furnace melt with dry charcoal, wherein the covering thickness is 88mm; then the temperature is raised to 1360 ℃, and pure iron sheet (the pure iron sheet has the specification of 0.5-1.0mm thick, 30-60mm wide and 80-120mm long) is added according to the component proportion. After 29 minutes of adding the iron sheet, the temperature is reduced to 1114 ℃, zinc ingots and copper-phosphorus alloy are added according to the inverse proportion of the components, slag is fished after the heat preservation is continued for 26 minutes, and casting is started.
2) Semi-continuous casting
Controlling the temperature of copper liquid at 1114 ℃, opening a stopper rod, putting the copper liquid into a crystallizer, then opening cooling water, starting a tractor when the copper liquid in the crystallizer reaches about two thirds of the height of the crystallizer, starting the drawing casting work at 23mm/min, starting vibration, wherein the frequency of the vibrator is 45 times/min, the amplitude is 4mm, and the whole drawing casting process is covered by graphite powder spraying; the ingot is cast to 0.5-1.0 m to reach a stable speed casting stage, and the casting speed is controlled to be 126mm/min. The primary cooling water flow of the crystallizer is 40m 3/h, the water pressure is 0.48MPa, the water inlet temperature is 25 ℃, and the water outlet temperature is controlled at 46 ℃. Ingot casting specifications were 230 x 620mm x 800mm.
3) Hot rolling
The heating temperature of the cast ingot is 765 ℃, the heat preservation time is 2.5h, the hot rolling starting temperature is 740 ℃, the hot rolling is carried out until reaching 14mm, the hot rolling processing rate is 93.91%, meanwhile, the hot rolling finishing temperature is 475 ℃, and the bandwidth after hot rolling expansion is 650+/-5 mm.
4) Second phase preaging+beta/alpha phase transition heat treatment
After the temperature of the hot-rolled final rolling material is 475 ℃, the hot-rolled strip blank is rolled on line and placed in a heat treatment furnace within 10 minutes, the temperature of the rolled heat treatment furnace is adjusted to 460 ℃, the heat is preserved for 2.8 hours, and then the whole rolled material is hung into a water tank to be cooled to normal temperature within 5 minutes after being discharged from the furnace. The beta phase proportion of the alloy is 2.0% after the second phase preaging and beta/alpha phase transformation heat treatment, meanwhile, the alloy is preaging in the process, the average diameter size of preaging precipitated second phases Fe 3 P and Fe 2 P is 3nm, and the particle density per unit area is 3112 particles/mu m 2.
5) Milling surface
The single-sided milling amount is 0.75mm.
6) Rough rolling
Rough rolling to 0.9mm, and the processing rate is controlled to be 92.8%.
7) Trimming edge
The unilateral shearing is 7.5mm, and the bandwidth after shearing is 630+/-0.5 mm.
8) First air cushion type heat treatment
And (3) annealing by adopting a single-expansion air cushion furnace, wherein the annealing temperature is 458 ℃, the annealing speed is 13m/min, the length of an annealing heating furnace area is 21m, the length of a cooling area is 3m, and the surface temperature of the copper strip is cooled to the room temperature after passing through the cooling area by adopting on-line water spraying and water cooling. Adopting micro-oxidation atmosphere annealing, wherein the protective gas is a mixed gas of nitrogen and trace oxygen, the oxygen content is 4%, and on-line pickling is adopted to remove oxides on the surface of the alloy, the sulfuric acid concentration is 118g/l, the temperature is less than or equal to 40 ℃, and Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 66 ℃. The average grain size after heat treatment was controlled to 3.3. Mu.m, and the beta ratio of the alloy was controlled to 1.9%. At the same time, the average diameter size of the precipitated phases Fe 3 P and Fe 2 P is 4.2nm, and the particle density per unit area is 3678 particles/mu m 2.
9) Middle rolling
The middle rolling is carried out until the thickness reaches 0.265mm, and the processing rate is controlled to be 70.56 percent.
10 Secondary air cushion heat treatment
And (3) annealing by adopting a single-expansion air cushion furnace, wherein the annealing temperature is 458 ℃, the annealing speed is 45m/min, the length of an annealing heating furnace area is 21m, the length of a cooling area is 3m, water cooling is performed by adopting on-line water spraying, and the surface temperature of the copper strip is reduced to room temperature after passing through the cooling area. Adopting micro-oxidation atmosphere annealing, wherein the protective gas is a mixed gas of nitrogen and trace oxygen, the oxygen content is 3-6%, and on-line pickling is adopted to remove oxides on the surface of the alloy, the sulfuric acid concentration is 111g/l, the temperature is less than or equal to 40 ℃, and Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 69 ℃. The average grain size after heat treatment was controlled to 1.9. Mu.m, and the beta ratio of the alloy was controlled to 1.70%. Meanwhile, the average diameter size of the precipitated phases Fe 3 P and Fe 2 P is ensured to be 5.4nm, the particle density per unit area is 3842 particles/mu m 2, the dispersion strengthening effect of the strengthening phase is fully exerted, and the strength, the bending property, the electric conductivity and the stress relaxation resistance of the material are improved.
11 Rolling of finished products
When the finished product is rolled, a 20-roller finishing mill is adopted, the rolling is carried out until the thickness is 0.2mm, and the processing rate is controlled to be 24.53%.
12 Stretch bending and straightening
When the stretch bending is performed, the straightening elongation is 0.16 percent, and the straightening unit tension is 23kg/mm 2.
13 Low Wen Qidian anneal for stress relief
And (3) carrying out on-line stress relief annealing by adopting a single expansion type air cushion furnace, wherein the annealing temperature is 380 ℃, the annealing speed is 130m/min, the unit tension in the furnace is 33kg/mm 2, the shielding gas is a mixed gas of nitrogen and hydrogen, and the content of the hydrogen in the mixed gas is 2.5%.
14 Cleaning)
Degreasing is carried out firstly, a degreasing agent adopts sodium hydroxide aqueous solution, the PH range is 8, and the solution temperature is 65 ℃; then carrying out acid washing, wherein the concentration of sulfuric acid is 120g/l, the temperature is less than or equal to 40 ℃, and the Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 67 ℃.
15 Dividing and packaging the finished product.
Example 4
The copper alloy strip of this example was prepared as follows:
1) Batch smelting
Adding electrolytic copper into a smelting furnace, heating and melting, and tightly covering the smelting furnace melt with dry charcoal, wherein the covering thickness is 95mm; then the temperature is raised to 1370 ℃, and pure iron sheets (the pure iron sheets are 0.5-1.0mm thick, 30-60mm wide and 80-120mm long) are added according to the component proportion. After 28 minutes of adding the iron sheet, the temperature is reduced to 1118 ℃, zinc ingots and copper-phosphorus alloy are added according to the inverse proportion of the components, slag is fished after the heat preservation is continued for 24 minutes, and casting is started.
2) Semi-continuous casting
Controlling the temperature of copper liquid at 1118 ℃, opening a stopper rod, putting the copper liquid into a crystallizer, then opening cooling water, starting a tractor when the copper liquid in the crystallizer reaches about two thirds of the height of the crystallizer, starting the drawing casting work at 25mm/min, starting vibration, wherein the frequency of the vibrator is 39 times/min, the amplitude is 5.5mm, and the whole drawing casting process is covered by graphite powder spraying; the ingot is cast to 0.5-1.0 m to reach a stable speed casting stage, and the casting speed is controlled to be 130mm/min. The primary cooling water flow of the crystallizer is 48m 3/h, the water pressure is 0.55MPa, the water inlet temperature is 26 ℃, and the water outlet temperature is controlled at 47 ℃. Ingot casting specifications were 230 x 620mm x 800mm.
3) Hot rolling
The heating temperature of the cast ingot is 775 ℃, the heat preservation time is 2.2h, the hot rolling starting temperature is 741 ℃, the hot rolling is carried out until reaching 13mm, the hot rolling processing rate is 94.35%, the hot rolling finishing temperature is 480 ℃, and the bandwidth after hot rolling expansion is 650+/-5 mm.
4) Second phase preaging+beta/alpha phase transition heat treatment
After the temperature of the hot-rolled final rolling material is up to 480 ℃, rolling the hot-rolled strip blank on line within 10 minutes, placing the hot-rolled strip blank in a heat treatment furnace, adjusting the temperature of the rolled heat treatment furnace to 455 ℃, preserving heat for 3 hours, and then taking out the hot-rolled strip blank from the furnace for 5 minutes, hanging the whole rolled strip blank into a water tank, and cooling to normal temperature. The beta phase proportion of the alloy is 1.95 percent after the second phase pre-ageing and beta/alpha phase transformation heat treatment, meanwhile, the alloy is pre-aged in the process, the average diameter size of the pre-ageing precipitated second phases Fe 3 P and Fe 2 P is 2.7nm, and the particle density per unit area is 3607 particles/mu m 2.
5) Milling surface
The single-sided milling amount is 0.75mm.
6) Rough rolling
Rough rolling to 0.8mm, and the processing rate is controlled to be 93.04%.
7) Trimming edge
The unilateral shearing is 7.5mm, and the bandwidth after shearing is 630+/-0.5 mm.
8) First air cushion type heat treatment
And (3) annealing by adopting a single-expansion air cushion furnace, wherein the annealing temperature is 455 ℃, the annealing speed is 14m/min, the length of an annealing heating furnace zone is 21m, the length of a cooling zone is 3m, and the surface temperature of the copper strip is cooled to room temperature after passing through the cooling zone by adopting on-line water spraying and water cooling. Adopting micro-oxidation atmosphere annealing, wherein the protective gas is a mixed gas of nitrogen and trace oxygen, the oxygen content is 5%, and on-line pickling is adopted to remove oxides on the surface of the alloy, the sulfuric acid concentration is 122g/l, the temperature is less than or equal to 40 ℃, and Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 68 ℃. The average grain size after heat treatment was controlled to 2.9 μm, and the beta phase ratio of the alloy was controlled to 1.85%. At the same time, the average diameter size of the precipitated phases Fe 3 P and Fe 2 P is 3.8nm, and the particle density per unit area is 3856 particles/mu m 2.
9) Middle rolling
The middle rolling is carried out until the thickness reaches 0.195mm, and the processing rate is controlled to be 75.63 percent.
10 Secondary air cushion heat treatment
And (3) annealing by adopting a single-expansion air cushion furnace, wherein the annealing temperature is 455 ℃, the annealing speed is 48m/min, the length of an annealing heating furnace zone is 21m, the length of a cooling zone is 3m, and the surface temperature of the copper strip is cooled to room temperature after passing through the cooling zone by adopting on-line water spraying and water cooling. Adopting micro-oxidation atmosphere annealing, wherein the protective gas is a mixed gas of nitrogen and trace oxygen, the oxygen content is 3-6%, and on-line pickling is adopted to remove oxides on the surface of the alloy, the sulfuric acid concentration is 115g/l, the temperature is less than or equal to 40 ℃, and Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 67 ℃. The average grain size after heat treatment was controlled to 1.6 μm, and the beta phase ratio of the alloy was controlled to 1.65%. Meanwhile, the diameter size of the precipitated phases Fe 3 P and Fe 2 P is guaranteed to be 4.8nm, the particle density per unit area is 4151/mu m 2, the dispersion strengthening effect of the strengthening phase is fully exerted, and the strength, the bending property, the conductivity and the stress relaxation resistance of the material are improved.
11 Rolling of finished products
When the finished product is rolled, a 20-roller finishing mill is adopted, the rolling is carried out until the thickness is 0.15mm, and the processing rate is controlled to be 23.08%.
12 Stretch bending and straightening
When the stretch bending is performed, the straightening elongation is 0.18 percent, and the straightening unit tension is 24kg/mm 2.
13 Low Wen Qidian anneal for stress relief
And (3) carrying out on-line stress relief annealing by adopting a single expansion type air cushion furnace, wherein the annealing temperature is 365 ℃, the annealing speed is 120m/min, the unit tension in the furnace is 33kg/mm 2, the shielding gas is a mixed gas of nitrogen and hydrogen, and the content of the hydrogen in the mixed gas is 2.6%.
14 Cleaning)
Degreasing is carried out firstly, a degreasing agent adopts sodium hydroxide aqueous solution, the PH range is 8.2, and the solution temperature is 68 ℃; then carrying out acid washing, wherein the concentration of sulfuric acid is 118g/l, the temperature is less than or equal to 40 ℃, and the Cu 2+ in the acid liquor is less than or equal to 1.2g/l; cleaning and drying, wherein the temperature of the oven is 66 ℃.
15 Dividing and packaging the finished product.
Comparative example 1
The copper alloy strip of this example contains 61.5% by mass of the following element Cu and the balance Zn, but no P and Fe elements were added, and was prepared in the same manner as in example 4.
Comparative example 2
The copper alloy strip of this example contains the following elements by mass percent, cu 61.5%, P0.02%, fe 0.07%, and the balance Cu. The preparation procedure differs from example 4 in that: without step 4) the second phase pre-ageing + beta/alpha phase transition heat treatment.
Comparative example 3
The copper alloy strip of this example contains the following elements by mass percent, cu 61.5%, P0.02%, fe 0.07%, and the balance Cu. The preparation procedure differs from example 4 in that: the air cushion type heat treatment in the step 8) and the step 10) is changed into bell jar type annealing, the annealing process is heating to 455 ℃ and preserving heat for 5 hours, the heating rate of the heating section is 80 ℃/h, and the cooling rate of the cooling section is 65 ℃/h.
The copper alloy strips prepared in examples 1 to 4 and comparative examples 1 to 3 were tested for mechanical properties, electrical conductivity, texture, etc., and the results are shown in Table 4. The test method is as follows:
and (3) mechanical property detection: room temperature tensile test according to GB/T228.1-2010 metal materials tensile test part 1: room temperature test method is tested on an electronic universal mechanical property tester, and a sample with a 20mm width and a 5mm/min stretching speed are adopted.
Metallographic structure grain size test: according to the intercept point method in GB/T6394-2007 method for measuring average grain size of metals, the grain size in a photograph taken by a metallographic microscope of 1000 times is tested. The sample had a width of 10mm and a length of 10mm.
The copper alloy finished product prepared in examples 1-4 has the hardness of 185-205HV, the tensile strength of 580-630MPa, the yield strength of 550-600MPa, the elongation rate of more than 7%, the bending Goodway direction 180 DEG R/T=0.5 and the bending Badway direction 180 DEG R/T=0.8, and the bending back and forth for 5 times when the bending Goodway direction 90 DEG R/T=1, and the bending is not broken. Meanwhile, the beta phase proportion of the finished product is within 3%, the grain size is within 3 mu m, the average diameter size of precipitated phases Fe 3 P and Fe 2 P is within 10nm, the grain density per unit area is above 2000 particles/mu m 2, and the alloy strip has high strength, excellent bending performance and good stress relaxation resistance.
TABLE 2 chemical composition/wt% of copper alloy strips of examples and comparative examples according to the present invention
| Numbering device | Cu | P | Fe | Zn |
| Example 1 | 61.2 | 0.016 | 0.06 | Allowance of |
| Example 2 | 61.6 | 0.022 | 0.08 | Allowance of |
| Example 3 | 61.9 | 0.028 | 0.095 | Allowance of |
| Example 4 | 61.5 | 0.02 | 0.07 | Allowance of |
| Comparative example 1 | 61.5 | - | - | Allowance of |
| Comparative example 2 | 61.5 | 0.02 | 0.07 | Allowance of |
| Comparative example 3 | 61.5 | 0.02 | 0.07 | Allowance of |
TABLE 3 control of critical process parameters for each example, comparative example, of the present invention
TABLE 4 tissue structure and Properties of examples, comparative examples of the present invention
Finally, it should be noted that the above embodiments are merely illustrative of the technical solution of the present invention, and not limiting thereof; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (10)
1. The low-copper high-strength high-bending brass strip is characterized by comprising the following components in percentage by mass: 61-62 wt%, P:0.01 to 0.03 weight percent of Fe:0.15-0.2wt% and the balance Zn and unavoidable impurities, wherein the structure of the low-copper high-strength high-bending brass strip comprises a matrix phase and a precipitation phase distributed in the matrix phase, the precipitation phase comprises Fe 3 P and Fe 2 P, wherein the average diameter size of Fe 3 P and Fe 2 P is within 10nm, and the particle density per unit area is above 2000/mum 2.
2. The low copper high strength high bending brass strip in accordance with claim 1, wherein the average grain size of the low copper high strength high bending brass strip is within 3 μm.
3. The low copper high strength high bending brass strip defined by claim 1 or claim 2, wherein the ratio of β -phase in the low copper high strength high bending brass strip is <3%.
4. The low copper high strength high bending brass strip according to claim 3, wherein the hardness of the low copper high strength high bending brass strip is 185-205HV, the tensile strength is 580-630MPa, the yield strength is 550-600MPa, the bending Goodway direction 180 ° R/t=0.5 does not crack, the Badway direction 180 ° R/t=0.8 does not crack, and the bending back and forth 5 times at Goodway direction 90 ° R/t=1 does not crack.
5. The method for preparing the brass strip with low copper content, high strength and high bending according to any one of claims 1 to 4, which is characterized by comprising the following process flows: batch smelting, semi-continuous casting, hot rolling, second-phase pre-ageing+beta/alpha phase transformation heat treatment, rough rolling, first air cushion heat treatment, middle rolling, second air cushion heat treatment, finished product rolling and annealing.
In the second phase preaging and beta/alpha phase transformation heat treatment process, after the temperature of the hot rolling final rolling material is 460-500 ℃, rolling the hot rolled strip blank on line within 10 minutes, placing the hot rolled strip blank in a heat treatment furnace, adjusting the temperature of the rolled heat treatment furnace to 450-470 ℃, preserving heat for 2-3 hours, and then taking out the whole rolled material from the furnace for 5 minutes, hanging the whole rolled material into a water tank, and cooling to normal temperature.
6. The method for preparing the brass strip with low copper content, high strength and high bending as claimed in claim 5, wherein in the first and second air cushion heat treatment processes, a single expansion type air cushion furnace is adopted for annealing, the annealing temperature is 450-470 ℃, the length of an annealing heating furnace area is 18-23 m, the length of a cooling area is 2.5-4.5m, on-line water spraying and cooling are adopted, the surface temperature of the copper strip after passing through the cooling area is reduced to room temperature, wherein the annealing speed of the first air cushion heat treatment is 10-15 m/min, and the annealing speed of the second air cushion heat treatment is 30-50 m/min.
7. The method for preparing a brass strip with low copper content, high strength and high bending strength according to claim 6, wherein the first and the second air cushion type heat treatments adopt micro-oxidation atmosphere annealing, the shielding gas is a mixed gas of nitrogen and oxygen, the oxygen content is 3-6%, and online pickling is adopted to remove oxides on the surface of the alloy.
8. The method for producing a brass strip having a low copper content and a high strength and a high bending strength according to claim 6 or 7, wherein the hot rolling heating power is controlled to be 90% or more; the rough rolling processing rate is controlled to be 85-95 percent; the medium rolling processing rate is controlled to be 70-85%, and the power for finished product rolling is controlled to be 20-25%.
9. The method for preparing the brass strip with low copper content, high strength and high bending content according to claim 8, wherein the annealing is carried out by adopting a single expansion type air cushion furnace for on-line stress relief annealing, the annealing temperature is 360-400 ℃, the annealing speed is 100-150 m/min, the unit tension in the furnace is 30-35 kg/mm 2, the shielding gas is a mixed gas of nitrogen and hydrogen, and the content of the hydrogen in the mixed gas is 2-4%.
10. Use of the low copper high strength high bending brass band material as defined in any of claims 1-4 in connection terminals of household appliances.
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