Preparation method of high-elasticity tin-phosphor bronze thin strip

Abstract

The application discloses a preparation method of high-elasticity tin-phosphor bronze thin strips, which comprises the following steps: melting and casting, homogenizing annealing, face milling, rough rolling, intermediate annealing, warm rolling, finish rolling, product annealing, cleaning, bending and straightening, slitting, and warehousing; the warm rolling opening rolling temperature is 290-320 DEG C, and the final rolling temperature is 270-280 DEG C; the intermediate annealing temperature is 420-560 DEG C, and the temperature is kept for 6-8 hours; and the product annealing temperature is 220-380 DEG C, and the temperature is kept for 5-6 hours. The application adopts warm rolling after intermediate annealing, and then cold finish rolling, so that one annealing process and one cleaning process are reduced, and the technological process is shortened; meanwhile, through the adjustment and control of the rolling temperature, the processing rate and the annealing temperature, the comprehensive mechanical properties of the low-tin phosphor bronze alloy thin strips are improved.

Description

Technical Field

[0001] This invention belongs to the field of copper alloy processing technology, specifically relating to a method for preparing a high-elasticity tin-phosphorus bronze thin strip. Background Technology

[0002] Tin-phosphorus bronze is a ternary alloy composed of copper with added tin and phosphorus as a deoxidizer. It possesses characteristics such as good elasticity, high strength, strong corrosion resistance, and easy soldering, making it the most widely used and extensively applied copper-based elastic alloy material. In electronic, communication, and electrical equipment, it is used to manufacture various connectors, relays, contactors, terminals, contacts, diaphragms, springs, and other components. With the rapid development of the electronics, communication, and automotive industries in recent years, the demand for tin-phosphorus bronze strip has been increasing daily. At the same time, the miniaturization and long lifespan of various electronic information devices have led to the trend towards micro-, thin, and integrated basic components, thus placing higher demands on the performance of tin-phosphorus bronze strip, such as high strength, high conductivity, high elasticity, high resistance to stress relaxation, and high fatigue strength.

[0003] The current production process for tin-phosphorus bronze strip mainly includes casting, homogenization annealing, milling, cold rough rolling, intermediate annealing, cleaning, intermediate rolling, intermediate annealing, cleaning, finish rolling, low-temperature annealing, cleaning, tension bending and straightening, and slitting and warehousing. Because tin-phosphorus bronze ingots are prone to anti-segregation, homogenization annealing is necessary to eliminate or improve it. Furthermore, tin-phosphorus bronze has a high work hardening rate, requiring multiple intermediate annealing cycles during cold working, resulting in a long production cycle. Currently, high-strength, high-elasticity tin-phosphorus bronze alloys are mainly high-tin-phosphorus bronze alloys in the domestic market. Due to the shortage and high cost of tin resources, and the low conductivity of high-tin-phosphorus bronze alloys, researchers have been developing low-tin or tin-free alloys to replace tin-phosphorus bronze. Some low-tin-phosphorus bronze alloys, such as QSn4-0.3 and QSn4-3, are now in use, but the thin strips prepared using traditional production processes still cannot meet the performance requirements of high-strength, high-elasticity component materials. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a short-process, low-cost production process for low-tin phosphor bronze alloys to prepare high-elasticity tin phosphor bronze strips, thereby meeting the application requirements of high-strength, high-elasticity components.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing a highly elastic tin-phosphor bronze thin strip, comprising the following steps:

[0007] Melting and casting, homogenization annealing, milling, rough rolling, intermediate annealing, warm rolling, finish rolling, finished product annealing, cleaning, tension bending and straightening, slitting, and warehousing;

[0008] The initial rolling temperature is 290–320°C, and the final rolling temperature is 270–280°C.

[0009] The intermediate annealing temperature is 420–560℃, and the holding time is 6–8 hours.

[0010] The finished product is annealed at a temperature of 220–380°C for 5–6 hours.

[0011] Preferably, the tin-phosphor bronze is designated as one of T50800, C51100, or C51180.

[0012] Preferably, the casting adopts a horizontal continuous casting process, with a casting temperature of 1180-1200℃, a casting speed of 160-180mm / min, a billet exit temperature of 320-350℃, a billet thickness of 13.5-16.5mm, a width of 420-460mm, and a length of 75-150m.

[0013] Preferably, the homogenization annealing is carried out in a bell furnace with a protective atmosphere containing 75 wt% H2 and 25 wt% N2, at an annealing temperature of 630–650°C, for 5–6 hours.

[0014] Preferably, the total roughing rate is 75-85%, and the number of rolling passes is 6-8.

[0015] Preferably, the total warm rolling rate is 75-90%, and the number of rolling passes is 6-8.

[0016] Preferably, the total finishing rate is 50-75%; the number of rolling passes is 4-5.

[0017] Preferably, the intermediate annealing is carried out in a bell furnace with a protective atmosphere containing 75 wt% H2 and 25 wt% N2, using a staged annealing process, first raising the temperature to 530-560°C and holding it for 3-4 hours, then lowering it to 420-450°C and holding it for 3-4 hours.

[0018] Preferably, the finished product annealing is carried out in a bell furnace with a protective atmosphere containing 75 wt% H2 and 25 wt% N2, using a staged annealing process. First, the temperature is raised to 360-380°C and held for 2-3 hours, then lowered to 220-250°C and held for 3-4 hours.

[0019] Preferably, the cleaning process is as follows: first, alkaline washing with an alkaline concentration of 3-5% at a temperature of 70-80°C; then, acid washing with a sulfuric acid concentration of 10-13% at room temperature; followed by passivation treatment with a benzotriazole solution as the passivating agent at a concentration of 0.05-0.08 g / L at a temperature of 60-80°C; and finally, rinsing with clean water at a cleaning speed of 30-40 m / min.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention employs warm rolling after intermediate annealing, followed by cold finishing rolling, reducing one annealing and cleaning step and shortening the process flow. Simultaneously, by adjusting and controlling the rolling temperature, processing rate, and annealing temperature, this invention improves the comprehensive mechanical properties of low-tin-phosphorus bronze alloy strips. The resulting tin-phosphorus bronze strips exhibit tensile strength of 680–780 MPa, yield strength of 625–740 MPa, elastic modulus of 117–125 GPa, Vickers hardness of 180–220 HV, and electrical conductivity of 18–24% IACS. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. In the embodiments of the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art; unless specifically specified, the technical means used are all conventional means well known to those skilled in the art.

[0023] This invention provides a method for preparing a high-elasticity tin-phosphor bronze thin strip, the process of which includes the following steps:

[0024] Melting and casting, homogenization annealing, milling, rough rolling, intermediate annealing, warm rolling, finish rolling, finished product annealing, cleaning, tension bending and straightening, slitting, and warehousing;

[0025] in,

[0026] The initial rolling temperature is 290–320℃, and the final rolling temperature is 270–280℃.

[0027] The intermediate annealing temperature is 420–560℃, and the holding time is 6–8 hours.

[0028] The annealing temperature of the finished product is 220-380℃, and the holding time is 5-6 hours.

[0029] Tin-phosphorus bronze alloys have poor hot working properties and are prone to cracking when hot rolled above the recrystallization temperature. After many experiments, the inventors selected warm rolling and precisely controlled the optimal rolling temperature between 270 and 320°C.

[0030] In some preferred embodiments, the tin-phosphor bronze is designated as one of T50800, C51100, or C51180, with a tin content of 3.5% to 4.5%, and belongs to a low-tin-phosphor bronze alloy.

[0031] In some preferred embodiments, the casting adopts a horizontal continuous casting process, with a casting temperature of 1180-1200℃, a casting speed of 160-180mm / min, a billet exit temperature of 320-350℃, a billet thickness of 13.5-16.5mm, a width of 420-460mm, and a length of 75-150m.

[0032] In some preferred embodiments, homogenization annealing is carried out in a bell furnace with a protective atmosphere containing 75 wt% H2 and 25 wt% N2, at an annealing temperature of 630–650 °C for 5–6 hours.

[0033] In some preferred embodiments, the total roughing rate is 75-85%, and the number of rolling passes is 6-8.

[0034] In some preferred embodiments, the total warm rolling yield is 75-90%, and the rolling passes are 6-8.

[0035] In some preferred embodiments, the total finishing rate is 50-75%; the number of rolling passes is 4-5.

[0036] In some preferred embodiments, intermediate annealing is carried out in a bell furnace with a protective atmosphere containing 75 wt% H2 and 25 wt% N2, using a staged annealing process, first raising the temperature to 530–560°C and holding it for 3–4 hours, then lowering it to 420–450°C and holding it for 3–4 hours.

[0037] In some preferred embodiments, the finished product annealing is carried out in a bell furnace with a protective atmosphere containing 75 vol% H2 and 25 vol% N2, using a staged annealing process, first raising the temperature to 360-380°C and holding it for 2-3 hours, then lowering it to 220-250°C and holding it for 3-4 hours.

[0038] In some preferred embodiments, the cleaning method is as follows: first, alkaline washing with an alkaline concentration of 3-5% and a temperature of 70-80°C; then, acid washing with a sulfuric acid concentration of 10-13% and a temperature of room temperature; followed by passivation treatment with a benzotriazole solution as the passivating agent at a concentration of 0.05-0.08 g / L and a temperature of 60-80°C; finally, rinsing with clean water; the cleaning speed is 30-40 m / min.

[0039] Example 1

[0040] This embodiment uses C51100 tin-phosphor bronze alloy to prepare high-elasticity tin-phosphor bronze thin strips. The process flow is as follows:

[0041] The tin-phosphorus bronze alloy raw material was smelted and then cast using a horizontal continuous casting process. The casting temperature was 1200℃, the casting speed was 165mm / min, the billet exit temperature was 325℃, the billet thickness was 16mm, the width was 450mm, and the length was 100m. The billet was then fed into a bell furnace with a protective atmosphere containing 75% wt% H2 and 25% wt% N2 for homogenization annealing at 650℃ for 5 hours. After annealing, the billet was milled, with 0.8mm milled on the top and bottom surfaces and 2mm milled on each side. The milled billet was then rough rolled in 7 passes, with a total machining rate of 83.3%. Finally, it was fed into a bell furnace with a protective atmosphere containing 75% wt% H2 and 25% wt% N2 for intermediate annealing. The temperature was first raised to 550℃ and held for 3 hours, then lowered to 40℃. The product is heated to 20℃ and held for 4 hours; then cooled to 320℃ and removed from the furnace for warm rolling, with 7 rolling passes and a final rolling temperature of 280℃, achieving a total processing rate of 85.4%; it is then cooled to room temperature and subjected to finish rolling, with 5 rolling passes and a total processing rate of 65.7%; finally, it is placed in a bell furnace containing a protective atmosphere of 75 wt% H2 and 25 wt% N2 for annealing, with the temperature first raised to 380℃ and held for 2 hours, then lowered to 240℃ and held for 3 hours; after annealing, the product is cleaned, first with alkali washing (5% alkali concentration, 70℃), then with acid washing (10% sulfuric acid concentration, room temperature); then passivation treatment is performed using benzotriazole solution (0.05 g / L concentration, 80℃), and finally rinsed with clean water at a speed of 35 m / min; finally, it is stretched, straightened, slit, and stored.

[0042] The tin-phosphor bronze strip prepared in this embodiment has a thickness of 0.12 mm, a tensile strength of 778 MPa, a yield strength of 725 MPa, an elastic modulus of 125 GPa, a Vickers hardness of 208 HV, and a conductivity of 22% IACS.

[0043] Example 2

[0044] This embodiment uses T50800 tin-phosphor bronze alloy to prepare high-elasticity tin-phosphor bronze thin strips. The process flow is as follows:

[0045] The tin-phosphorus bronze alloy raw material was smelted and then cast using a horizontal continuous casting process. The casting temperature was 1180℃, the casting speed was 165mm / min, the billet exit temperature was 330℃, the billet thickness was 16mm, the width was 450mm, and the length was 100m. The billet was then fed into a bell furnace containing a protective atmosphere of 75% wt% H2 and 25% wt% N2 for homogenization annealing at 635℃ for 6 hours. After annealing, the billet was milled, with 0.8mm milled on the top and bottom surfaces and 2mm milled on each side. The milled billet was then rough rolled in 7 passes, with a total machining rate of 80.6%. Finally, it was fed into a bell furnace containing a protective atmosphere of 75% wt% H2 and 25% wt% N2 for intermediate annealing. The temperature was first raised to 530℃ and held for 4 hours, then lowered to 4... The product is heated to 30℃ and held for 4 hours; then cooled to 320℃ and removed from the furnace for warm rolling, with 7 rolling passes and a final rolling temperature of 280℃, achieving a total processing rate of 87.5%; then cooled to room temperature and subjected to finish rolling, with 4 rolling passes and a total processing rate of 57.1%; finally, it is placed in a bell furnace containing a protective atmosphere of 75 wt% H2 and 25 wt% N2 for annealing, with the temperature first raised to 360℃ and held for 2 hours, then lowered to 220℃ and held for 4 hours; after annealing, the product is cleaned, first with alkali washing (5% alkali concentration, 70℃), then with acid washing (13% sulfuric acid concentration, room temperature); then passivation treatment is performed using benzotriazole solution (0.08 g / L concentration, 80℃), and finally rinsed with clean water at a speed of 35 m / min; finally, it is stretched, bent, slit, and stored.

[0046] The tin-phosphor bronze strip prepared in this embodiment has a thickness of 0.15 mm, a tensile strength of 745 MPa, a yield strength of 675 MPa, an elastic modulus of 117 GPa, a Vickers hardness of 184 HV, and a conductivity of 24% IACS.

[0047] Example 3

[0048] This embodiment uses C51180 tin-phosphor bronze alloy to prepare high-elasticity tin-phosphor bronze thin strips. The process flow is as follows:

[0049] The tin-phosphorus bronze alloy raw material was smelted and then cast using a horizontal continuous casting process. The casting temperature was 1200℃, the casting speed was 165mm / min, the billet exit temperature was 325℃, the billet thickness was 16mm, the width was 450mm, and the length was 100m. The billet was then fed into a bell furnace with a protective atmosphere containing 75% wt% H2 and 25% wt% N2 for homogenization annealing at 650℃ for 6 hours. After annealing, the billet was milled, with 0.8mm milled on the top and bottom surfaces and 2mm milled on each side. The milled billet was then rough rolled in 8 passes, with a total machining rate of 84.7%. Finally, it was fed into a bell furnace with a protective atmosphere containing 75% wt% H2 and 25% wt% N2 for intermediate annealing. The temperature was first raised to 545℃ and held for 4 hours, then lowered to 4... The product is heated to 50℃ and held for 3 hours; then cooled to 320℃ and removed from the furnace for warm rolling, with 7 rolling passes and a final rolling temperature of 280℃, achieving a total processing rate of 86.4%; it is then cooled to room temperature and subjected to finish rolling, with 5 rolling passes and a total processing rate of 66.7%; finally, it is placed in a bell furnace containing a protective atmosphere of 75 wt% H2 and 25 wt% N2 for annealing, with the temperature first raised to 360℃ and held for 3 hours, then lowered to 220℃ and held for 3 hours; after annealing, the product is cleaned, first with alkali washing (5% alkali concentration, 70℃), then with acid washing (10% sulfuric acid concentration, room temperature); then passivation treatment is performed using benzotriazole solution (0.05 g / L concentration, 80℃), and finally rinsed with clean water at a speed of 35 m / min; finally, it is stretched, bent, slit, and stored.

[0050] The tin-phosphor bronze strip prepared in this embodiment has a thickness of 0.1 mm, a tensile strength of 685 MPa, a yield strength of 637 MPa, an elastic modulus of 121 GPa, a Vickers hardness of 213 HV, and a conductivity of 18% IACS.

[0051] Comparative Example 1

[0052] This comparative example uses C51100 tin-phosphor bronze alloy to prepare tin-phosphor bronze thin strips. The process flow is as follows:

[0053] The tin-phosphorus bronze alloy raw material was smelted and then cast using a horizontal continuous casting process. The casting temperature was 1200℃, the casting speed was 165mm / min, the billet exit temperature was 325℃, the billet thickness was 16mm, the width was 450mm, and the length was 100m. The billet was then placed in a bell-shaped furnace containing a protective atmosphere of 75% wt% H2 and 25% wt% N2 for homogenization annealing at 650℃ for 5 hours. After annealing, the billet was milled, with both the upper and lower surfaces milled. The billet was milled to 0.8 mm, with 2 mm milled on each side. After milling, the billet underwent rough rolling in 7 passes, achieving a total machining rate of 83.3%. It was then placed in a bell furnace with a protective atmosphere of 75 wt% H₂ and 25 wt% N₂ for intermediate annealing at 550℃ for 7 hours. Following annealing, it underwent cold intermediate rolling in 7 passes, achieving a total machining rate of 85.4%. Finally, it was placed in a bell furnace with a protective atmosphere of 75 wt% H₂ and 25 wt% N₂ for a second intermediate annealing. The furnace was annealed at 600℃ for 6 hours. After annealing, it was cleaned by first alkali washing (5% alkali concentration, 70℃) and then acid washing (10% sulfuric acid concentration, room temperature). Passivation was then performed using a benzotriazole solution (0.05 g / L) at 80℃, followed by rinsing with clean water at a speed of 35 m / min. After cleaning, it underwent finishing rolling in 5 passes, achieving a total yield of 65.7%. The furnace was then fed into a feedstock containing 75 wt% H₂ and 25 wt% N₂. The finished product is annealed in a bell-shaped furnace under a protective atmosphere. The temperature is first raised to 380℃ and held for 2 hours, then lowered to 240℃ and held for 3 hours. After annealing, the finished product is cleaned. First, it is alkali washed with a 5% alkali solution at 70℃. Then, it is acid washed with a 10% sulfuric acid solution at room temperature. Then, it is passivated with a benzotriazole solution at a concentration of 0.05 g / L at 80℃. Finally, it is rinsed with clean water at a speed of 35 m / min. Finally, it is bent, straightened, slit, and stored.

[0054] The tin-phosphor bronze strip prepared in this comparative example has a thickness of 0.12 mm, a tensile strength of 664 MPa, a yield strength of 566 MPa, an elastic modulus of 112 GPa, a Vickers hardness of 202 HV, and a conductivity of 15% IACS.

[0055] Comparative Example 2

[0056] This comparative example uses C51100 tin-phosphor bronze alloy to prepare tin-phosphor bronze thin strips. The process flow is as follows:

[0057] The tin-phosphorus bronze alloy raw material was smelted and then cast using a horizontal continuous casting process. The casting temperature was 1200℃, the casting speed was 165mm / min, the billet exit temperature was 325℃, the billet thickness was 16mm, the width was 450mm, and the length was 100m. The billet was then fed into a bell furnace containing a protective atmosphere of 75 wt% H2 and 25 wt% N2 for homogenization annealing at 650℃ for 5 hours. After annealing, the billet was milled, with 0.8mm milled on both the top and bottom surfaces and the sides. Each milling pass is 2mm. The milled billet is then rough-rolled in 7 passes, achieving a total machining yield of 83.3%. It is then placed in a bell-shaped furnace with a protective atmosphere of 75% wt% H2 and 25% wt% N2 for intermediate annealing. The temperature is first raised to 550℃ and held for 3 hours, then lowered to 420℃ and held for 4 hours. After annealing, it undergoes cold intermediate rolling in 7 passes, achieving a total machining yield of 85.4%. Finally, it is placed in a bell-shaped furnace with a protective atmosphere of 75% wt% H2 and 25% wt% N2 for a second intermediate annealing. The annealing process involves first raising the temperature to 600℃ and holding it for 3 hours, then lowering it to 480℃ and holding it for another 3 hours. After annealing, the mixture is cleaned, first with an alkaline wash at 70℃ (5% alkali concentration), then with an acid wash at room temperature (10% sulfuric acid concentration). Next, it undergoes passivation treatment with a benzotriazole solution at 80℃ (0.05 g / L), followed by rinsing with clean water at a speed of 35 m / min. After cleaning, the mixture is finished rolled in 5 passes, achieving a total yield of 65.7%. The mixture is then fed into a feedstock containing 75% VT. The finished product was annealed in a bell-shaped furnace under a protective atmosphere of 25% N2. The temperature was first raised to 380℃ and held for 2 hours, then lowered to 240℃ and held for 3 hours. After annealing, the finished product was cleaned. First, it was alkali washed with 5% alkali solution at 70℃. Then it was acid washed with 10% sulfuric acid solution at room temperature. Then it was passivated with benzotriazole solution at 0.05 g / L at 80℃. Finally, it was rinsed with clean water at a speed of 35 m / min. Finally, it was bent, straightened, slit and put into storage.

[0058] The tin-phosphor bronze strip prepared in this comparative example has a thickness of 0.12 mm, a tensile strength of 671 MPa, a yield strength of 572 MPa, an elastic modulus of 112 GPa, a Vickers hardness of 204 HV, and a conductivity of 16% IACS.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a highly elastic tin-phosphor bronze thin strip, characterized in that, Includes the following steps: Melting and casting, homogenization annealing, milling, rough rolling, intermediate annealing, warm rolling, cold finishing rolling, finished product annealing, cleaning, tension bending and straightening, slitting, and warehousing; The initial rolling temperature is 290~320℃, and the final rolling temperature is 270~280℃; The intermediate annealing temperature is 420~560℃, and the holding time is 6~8h; The finished product is annealed at 220~380℃ for 5~6 hours. The tin-phosphor bronze is designated as one of T50800, C51100, and C51180. The total roughing rate is 75-85%, and the number of rolling passes is 6-8. The total processing rate of the warm rolling is 75-90%, and the number of rolling passes is 6-8. The total cold finishing rate is 50-75%, and the rolling passes are 4-5. The intermediate annealing is carried out in a bell furnace with a protective atmosphere containing 75 vol% H2 and 25 vol% N2, using a staged annealing process. First, the temperature is raised to 530~560℃ and held for 3~4 hours, then lowered to 420~450℃ and held for 3~4 hours. The finished product annealing is carried out in a bell furnace with a protective atmosphere containing 75% wt% H2 and 25% wt% N2, using a staged annealing process. First, the temperature is raised to 360~380℃ and held for 2~3 hours, then lowered to 220~250℃ and held for 3~4 hours.

2. The method for preparing the high-elasticity tin-phosphor bronze thin strip according to claim 1, characterized in that, The casting process adopts a horizontal continuous casting process, with a casting temperature of 1180~1200℃, a casting speed of 160~180mm / min, a billet exit temperature of 320~350℃, a billet thickness of 13.5~16.5mm, a width of 420~460mm, and a length of 75~150m.

3. The method for preparing the high-elasticity tin-phosphor bronze thin strip according to claim 1, characterized in that, The homogenization annealing is carried out in a bell furnace with a protective atmosphere containing 75 wt% H2 and 25 wt% N2, at an annealing temperature of 630~650℃, and held for 5~6 hours.

4. The method for preparing a high-elasticity tin-phosphor bronze thin strip according to claim 1, characterized in that, The cleaning process is as follows: first, alkaline washing with an alkaline concentration of 3-5% at a temperature of 70-80℃; then, acid washing with a sulfuric acid concentration of 10-13% at room temperature; followed by passivation treatment with a benzotriazole solution at a concentration of 0.05-0.08 g / L at a temperature of 60-80℃; and finally, rinsing with clean water. The cleaning speed is 30-40 m / min.