Ultrathin high-strength medium-conductivity bending-resistant copper-nickel-cobalt-silicon alloy and preparation method thereof

Abstract

The invention provides an ultrathin high-strength medium-conductivity bending-resistant copper-nickel-cobalt-silicon alloy and a preparation method thereof, and belongs to the field of copper-nickel-cobalt-silicon alloy preparation. The ultra-thin high-strength medium-conductivity bending-resistant copper-nickel-cobalt-silicon alloy provided by the invention comprises the following chemical components in percentage by mass: 0.5-4.5% of Ni; 0.1 to 2.0 percent of Co; 0.1 to 2.0 percent of Si; a strengthening element: 0.001 to 1.0% and the balance of Cu; the strengthening elements comprise at least two of Mg, Zn, Cr, Mn and Fe; the mass ratio of (Ni + Co) to Si is 3.9 to 4.5. Results of the embodiment show that the thickness of the copper-nickel-cobalt-silicon alloy is 0.04-0.08 mm, the tensile strength reaches 930 MPa, the yield strength reaches 900 MPa, the copper-nickel-cobalt-silicon alloy is not cracked after 90-degree bending parallel to the rolling direction R / T is equal to 0, and the electric conductivity is larger than or equal to 45%.

Description

Technical Field

[0001] The present invention relates to the field of copper-nickel-cobalt-silicon alloy preparation, and in particular to an ultra-thin, high-strength, medium-conductive, bending-resistant copper-nickel-cobalt-silicon alloy and a preparation method thereof. Background Art

[0002] Copper-nickel-cobalt-silicon alloy (Cu-Ni-Co-Si alloy) is a type of advanced copper alloy that achieves high strength, high conductivity and high temperature resistance through multi-component microalloying of nickel, cobalt and silicon, and is therefore widely used in electronics, aerospace, energy and other fields. However, in order to improve the mechanical properties of copper-nickel-cobalt-silicon alloy, it is often necessary to increase the proportion of elements such as Ni and Si. Although this method can obtain high-strength copper-nickel-cobalt-silicon alloy, it will cause its electrical conductivity to drop significantly. The conflict between the mechanical properties and electrical conductivity of copper-nickel-cobalt-silicon alloy has become a major problem that seriously restricts the development of copper-nickel-cobalt-silicon alloy. Therefore, how to provide a copper-nickel-cobalt-silicon alloy with both excellent mechanical properties and electrical conductivity has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0003] The purpose of the present invention is to provide an ultra-thin, high-strength, medium-conducting, bend-resistant copper-nickel-cobalt-silicon alloy and a preparation method thereof. The ultra-thin, high-strength, medium-conducting, bend-resistant copper-nickel-cobalt-silicon alloy provided by the present invention has both excellent mechanical properties and electrical conductivity, as well as excellent bending resistance.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides an ultra-thin, high-strength, medium-conducting, and bend-resistant copper-nickel-cobalt-silicon alloy, which comprises the following chemical components by mass percentage: Ni: 0.5-4.5%; Co: 0.1-2.0%; Si: 0.1-2.0%; strengthening elements: 0.001-1.0% and the balance Cu;

[0006] The strengthening elements include at least two of Mg, Zn, Cr, Mn and Fe; the mass ratio of (Ni+Co) / Si is 3.9-4.5.

[0007] Preferably, the strengthening elements are Mg, Zn, Cr and Mn.

[0008] The present invention provides a method for preparing the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy described in the above technical solution, comprising the following steps:

[0009] (1) melting the alloy raw materials and performing semi-continuous casting to obtain alloy ingots;

[0010] (2) hot rolling, initial rolling and intermediate continuous annealing are performed on the alloy ingot obtained in step (1) to obtain a first annealed ingot;

[0011] (3) subjecting the first annealed ingot obtained in step (2) to intermediate rolling and intermediate continuous annealing in sequence to obtain a second annealed ingot;

[0012] (4) subjecting the second annealed ingot obtained in step (3) to pre-finished product rolling and pre-finished product continuous annealing in sequence to obtain a third annealed ingot;

[0013] (5) The third annealed ingot obtained in step (4) is subjected to finished product rolling and finished product bell-type annealing in sequence to obtain an ultra-thin, high-strength, medium-conductivity, and bend-resistant copper-nickel-cobalt-silicon alloy.

[0014] Preferably, the total processing rate of the initial rolling in step (2) is 85-98%; the processing number of the initial rolling is 12-14 times; and the initial rolling is cold rolling.

[0015] Preferably, the holding temperature of the intermediate continuous annealing in step (2) is 850-950° C.; and the holding time of the intermediate continuous annealing is 90-180 seconds.

[0016] Preferably, the total processing rate of the intermediate rolling in step (3) is 55-65%; the processing passes of the intermediate rolling are 4-6 passes; and the intermediate rolling is cold rolling.

[0017] Preferably, the temperature of the intermediate continuous annealing in step (3) is 850-950° C.; and the holding time of the intermediate continuous annealing is 40-50 seconds.

[0018] Preferably, the total processing rate of the pre-finished product rolling in the step (4) is 55-65%; the processing passes of the pre-finished product rolling are 4-6 passes; and the pre-finished product rolling is cold rolling.

[0019] Preferably, the holding temperature of the pre-finished product during continuous annealing in step (4) is 800-900° C.; and the holding time of the pre-finished product during continuous annealing is 5-10 seconds.

[0020] Preferably, the temperature of the bell-jar annealing of the finished product in step (5) is 300-350° C.; and the holding time of the bell-jar annealing of the finished product is 6-8 hours.

[0021] The present invention provides an ultra-thin, high-strength, medium-conducting, bend-resistant copper-nickel-cobalt-silicon alloy, which comprises the following chemical components, calculated by mass percentage: Ni: 0.5-4.5%; Co: 0.1-2.0%; Si: 0.1-2.0%; strengthening elements: 0.001-1.0% and the balance Cu; the strengthening elements comprise at least two of Mg, Zn, Cr, Mn and Fe; and the mass ratio of (Ni+Co) / Si is 3.9-4.5. In the present invention, Ni, Si and Co synergistically precipitate to form Ni2Si phase, while cobalt can partially replace nickel to form (Ni, Co)2Si composite precipitate phase, which is finer in size and has better strengthening effect; at the same time, nickel atoms are solid dissolved in the copper matrix, causing lattice distortion and improving initial hardness; in addition, nickel reduces the stacking fault energy of copper, delays the recrystallization process, and is beneficial to the refinement of the structure after cold working; by adding Si element, Ni2Si or (Ni, Co)2Si composite precipitate phase can be preferentially formed with nickel and cobalt, which significantly improves the strength; Si is segregated at the grain boundaries, hindering grain boundary migration at high temperature; at the same time, Si reduces the stacking fault energy of copper, promotes dynamic recrystallization, and improves hot rolling plasticity; at the same time, adding a small amount of strengthening elements can not only improve the corrosion resistance, processing performance and aging response of the copper alloy, but also inhibit high-temperature grain growth, grain boundary migration and Ni2Si phase coarsening, thereby improving the mechanical properties of the alloy. The results of the embodiments show that the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy provided by the present invention has a thickness of 0.04 to 0.08 mm, a tensile strength of 930 MPa, a yield strength of 900 MPa, no cracking when bent at 90° parallel to the rolling direction with R / T=0, a conductivity of ≥45%, and the best comprehensive mechanical properties when (Ni+Co) / Si=3.9 to 4.5. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the tensile curve of the copper-nickel-cobalt-silicon alloy prepared in Example 3. DETAILED DESCRIPTION

[0023] The present invention provides an ultra-thin, high-strength, medium-conducting, and bend-resistant copper-nickel-cobalt-silicon alloy, which comprises the following chemical components by mass percentage: Ni: 0.5-4.5%; Co: 0.1-2.0%; Si: 0.1-2.0%; strengthening elements: 0.001-1.0% and the balance Cu;

[0024] The strengthening elements include at least two of Mg, Zn, Cr, Mn and Fe; the mass ratio of (Ni+Co) / Si is 3.9-4.5.

[0025] In terms of mass percentage, the ultra-thin, high-strength, medium-conducting, bend-resistant copper-nickel-cobalt-silicon alloy provided by the present invention includes Ni: 0.5-4.5%. As an embodiment of the present invention, the mass percentage of Ni can be 0.8%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5% or 3.8%. In the present invention, Ni, Si and Co synergistically precipitate to form a Ni2Si phase, while cobalt can partially replace nickel to form a (Ni, Co)2Si composite precipitate phase with a smaller size and better strengthening effect; at the same time, nickel atoms are solid-dissolved in the copper matrix, causing lattice distortion and improving the initial hardness; in addition, nickel reduces the stacking fault energy of copper, delays the recrystallization process, and is beneficial to the refinement of the structure after cold working.

[0026] The ultra-thin, high-strength, medium-conducting, bend-resistant copper-nickel-cobalt-silicon alloy provided by the present invention comprises 0.1-2.0% Co by mass. In one embodiment of the present invention, the Co mass percentage may be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, or 1.9%. In the present invention, cobalt can partially replace nickel to form a (Ni,Co)2Si composite precipitate phase, which is finer in size and has a better strengthening effect.

[0027] In terms of mass percentage, the ultra-thin, high-strength, medium-conductivity, and bend-resistant copper-nickel-cobalt-silicon alloy provided by the present invention includes Si: 0.1 to 2.0%. As an embodiment of the present invention, the mass percentage of Si can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8% or 1.9%. By adding Si element, the present invention can preferentially form Ni2Si or (Ni, Co)2Si composite precipitate phases with nickel and cobalt, significantly improving the strength; Si segregates at grain boundaries, hindering grain boundary migration at high temperatures; at the same time, Si reduces the stacking fault energy of copper, promotes dynamic recrystallization, and improves hot rolling plasticity.

[0028] The ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy provided by the present invention includes, by mass percentage, 0.001 to 1.0% strengthening elements. In the present invention, the strengthening elements include at least two of Mg, Zn, Cr, Mn, Fe, Ag, Ti, Sn, and Zr, and more preferably include Mg, Zn, Cr, and Mn.

[0029] In the present invention, when the strengthening element includes Mg, the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy provided by the present invention includes 0.01-0.05% Mg by mass. As one embodiment of the present invention, the Mg mass percentage may be 0.002%, 0.003%, 0.0036%, or 0.004%. In the present invention, magnesium combines with excess silicon to form Mg2Si particles, while promoting a finer and more uniform distribution of the (Ni,Co)2Si precipitate. Magnesium segregates at grain boundaries, hindering grain boundary migration at high temperatures and inhibiting grain growth.

[0030] In the present invention, when the strengthening element includes Zn, the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy provided herein comprises 0.01-0.05% Zn by mass. In one embodiment, the Zn mass percentage may be 0.002%, 0.003%, 0.0036%, or 0.004%. In the present invention, the addition of a small amount of Zn can improve corrosion resistance, processability, and aging response.

[0031] In the present invention, when the strengthening element includes Cr, the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy provided herein comprises 0.01-0.015% Cr by mass. In one embodiment, the Cr mass percentage may be 0.011%, 0.012%, 0.013%, or 0.014%. In the present invention, Cr segregates at grain boundaries, inhibiting high-temperature grain growth and Ni2Si phase coarsening.

[0032] In the present invention, when the strengthening element includes Mn, the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy provided by the present invention preferably also includes 0.001% to 0.01% Mn by mass. In one embodiment of the present invention, the mass percentage of Mn may be 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, or 0.009%. In the present invention, manganese has a higher affinity for oxygen than copper, nickel, and cobalt, forming MnO or MnSiO₃ inclusions, significantly reducing the oxygen content of the melt and preventing ingot porosity and hot brittleness. Manganese also segregates at grain boundaries, inhibiting grain boundary migration and Ni₂Si phase coarsening, thereby improving the alloy's high-temperature strength.

[0033] In the present invention, when the strengthening element includes Fe, the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy provided by the present invention preferably also includes Fe: 0.01-0.04% by mass. As one embodiment of the present invention, the mass percentage of Fe can be 0.015%, 0.02%, 0.023%, 0.025%, 0.03%, or 0.035%. In the present invention, Fe can act as a solid solution strengthening element to hinder dislocation movement and improve the strength and hardness of the copper-nickel-cobalt-silicon alloy. At the same time, Fe can react with nickel, cobalt, or silicon to form intermetallic compounds, further improving the strength, wear resistance, and high-temperature stability of the alloy. By controlling the amount of Fe, the embrittlement of the alloy caused by the formation of excessive brittle phases can be avoided.

[0034] The ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy provided by the present invention preferably also includes a balance of copper, measured by mass percentage. In the present invention, the copper is a matrix element of the copper-nickel-cobalt-silicon alloy.

[0035] In the present invention, the mass ratio of (Ni+Co) / Si is 3.9 to 4.5. As an embodiment of the present invention, the mass ratio of (Ni+Co) / Si can be 4.0, 4.1, 4.2, 4.3, or 4.4. By controlling the relationship between the amounts of Ni, Co, and Si, the present invention can further improve the comprehensive mechanical properties of the copper-nickel-cobalt-silicon alloy.

[0036] In the present invention, Ni, Si and Co synergistically precipitate to form Ni2Si phase, while cobalt can partially replace nickel to form (Ni, Co)2Si composite precipitate phase, which is smaller in size and has better strengthening effect; at the same time, nickel atoms are solid dissolved in the copper matrix, causing lattice distortion and improving initial hardness; in addition, nickel reduces the stacking fault energy of copper, delays the recrystallization process, and is beneficial to the refinement of the structure after cold working; by adding Si element, Ni2Si or (Ni, Co)2Si composite precipitate phase can be formed preferentially with nickel and cobalt, significantly improving strength; Si is segregated at grain boundaries, hindering grain boundary migration at high temperature; at the same time, Si reduces the stacking fault energy of copper, promotes dynamic recrystallization, and improves hot rolling plasticity.

[0037] In the present invention, magnesium combines with excess silicon to form Mg2Si particles, while promoting the (Ni, Co)2Si precipitation phase to be finer and more evenly distributed; magnesium is segregated at the grain boundaries, hindering grain boundary migration at high temperature and inhibiting grain growth; the addition of a small amount of Zn can improve corrosion resistance, processing performance and aging response; Cr is segregated at the grain boundaries, inhibiting high-temperature grain growth and Ni2Si phase coarsening; manganese has a higher affinity for oxygen than copper, nickel and cobalt, forming MnO or MnSiO3 inclusions, significantly reducing the oxygen content of the melt and avoiding ingot porosity and hot brittleness; at the same time, manganese is segregated at the grain boundaries, inhibiting grain boundary migration and Ni2Si phase coarsening, and improving the high-temperature strength of the alloy; Fe can act as a solid solution strengthening element, hindering dislocation movement, and improving the strength and hardness of the copper-nickel-cobalt-silicon alloy; at the same time, Fe can react with nickel, cobalt or silicon to form intermetallic compounds, further improving the strength, wear resistance and high-temperature stability of the alloy.

[0038] The present invention also provides a method for preparing the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy described in the above technical solution, comprising the following steps:

[0039] (1) melting the alloy raw materials and performing semi-continuous casting to obtain alloy ingots;

[0040] (2) hot rolling, initial rolling and intermediate continuous annealing are performed on the alloy ingot obtained in step (1) to obtain a first annealed ingot;

[0041] (3) subjecting the first annealed ingot obtained in step (2) to intermediate rolling and intermediate continuous annealing in sequence to obtain a second annealed ingot;

[0042] (4) subjecting the second annealed ingot obtained in step (3) to pre-finished product rolling and pre-finished product continuous annealing in sequence to obtain a third annealed ingot;

[0043] (5) The third annealed ingot obtained in step (4) is subjected to finished product rolling and finished product bell-type annealing in sequence to obtain an ultra-thin, high-strength, medium-conductivity, and bend-resistant copper-nickel-cobalt-silicon alloy.

[0044] The invention performs semi-continuous casting after melting alloy raw materials to obtain alloy ingots.

[0045] The present invention has no special restrictions on the specific type and amount of the alloy raw materials, as long as the composition of the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy meets the requirements.

[0046] The present invention does not specifically limit the temperature and time of the smelting. It can be determined according to the technical common sense of those skilled in the art, as long as the alloy raw materials can be completely melted and evenly mixed. As an embodiment of the present invention, the holding temperature of the smelting can be 1200-1300°C, or 1210°C, 1220°C, 1230°C, 1240°C, 1250°C, 1260°C, 1270°C, 1280°C, or 1290°C; the holding time of the smelting can be 15-30 minutes, or 18 minutes, 20 minutes, 22 minutes, 25 minutes, or 28 minutes. By controlling the holding temperature and holding time of the smelting, the present invention can effectively improve the uniformity of the copper alloy melt and reduce the segregation of the ingot.

[0047] In the present invention, the casting temperature of the semi-continuous casting is preferably 1200-1300°C; the pulling speed of the semi-continuous casting is preferably 60-140 mm / min. As one embodiment of the present invention, the casting temperature of the semi-continuous casting can be 1210°C, 1220°C, 1230°C, 1240°C, 1250°C, 1260°C, 1270°C, 1280°C, or 1290°C; and the pulling speed of the semi-continuous casting can be 70 mm / min, 80 mm / min, 90 mm / min, 100 mm / min, 110 mm / min, 120 mm / min, or 130 mm / min. By controlling the casting temperature and pulling speed of the semi-continuous casting, the present invention can achieve an appropriate cooling rate for the copper alloy melt, thereby obtaining a uniform and fine ingot structure and reducing casting defects such as shrinkage and shrinkage cavities.

[0048] After obtaining the alloy ingot, the present invention sequentially performs hot rolling, initial rolling and intermediate continuous annealing on the alloy ingot to obtain a first annealed ingot.

[0049] The present invention preferably performs a holding treatment on the alloy ingot before hot rolling; the holding temperature for the holding treatment is preferably 850-1000°C, and the holding time for the holding treatment is preferably 8-10 hours. In one embodiment of the present invention, the holding temperature for the holding treatment can be 900-950°C, and the holding time for the holding treatment can be 9 hours. Through the holding treatment, the temperature of the alloy ingot can be brought to the required temperature for hot rolling.

[0050] In the present invention, the total hot rolling processing rate is preferably 80-95%, and the number of hot rolling passes is preferably 9-15. As one embodiment of the present invention, the total hot rolling processing rate can be 82%, 85%, 88%, 90%, or 92%, and the number of hot rolling passes can be 10, 11, 12, 13, or 14. The present invention uses hot rolling to significantly reduce the thickness of the alloy ingot, change its microstructure, and improve its performance.

[0051] The present invention preferably further comprises milling the hot-rolled product. The present invention has no particular limitation on the specific operation and thickness of the milling, as long as the oxide layer on the surface of the alloy ingot can be removed.

[0052] In the present invention, the total processing rate of the initial rolling is preferably 85-98%, the number of initial rolling passes is preferably 12-14, and the initial rolling is preferably cold rolling. In one embodiment of the present invention, the total processing rate of the initial rolling can be 88%, 90%, 92%, or 95%, and the number of initial rolling passes can be 13. The present invention utilizes initial rolling to significantly reduce the thickness of the alloy ingot and to break up the coarse grains within the alloy ingot, thereby optimizing the structure and properties of the alloy ingot.

[0053] The present invention preferably further comprises unwinding the initially rolled product. The present invention has no particular limitation on the specific operation of unwinding, and any unwinding operation well known to those skilled in the art can be used.

[0054] In the present invention, the holding temperature of the intermediate continuous annealing is preferably 850-950°C; the holding time of the intermediate continuous annealing is preferably 90-180s. As an embodiment of the present invention, the holding temperature of the intermediate continuous annealing can be 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C or 940°C; the holding time of the intermediate continuous annealing can be 100s, 110s, 120s, 130s, 140s, 150s, 160s or 170s. The present invention can eliminate work hardening and restore plasticity through intermediate continuous annealing, facilitating subsequent processing. At the same time, it can also regulate the grain size, avoid excessive grain growth, ensure the balance between strength and plasticity, and inhibit the premature precipitation of Ni2Si phase.

[0055] The present invention preferably further comprises brushing the intermediate continuous annealing product. The present invention does not particularly limit the specific operation of the brushing. A brushing operation familiar to those skilled in the art can be employed to clean the surface of the ingot. In one embodiment of the present invention, the brushing can be performed sequentially using a PC brush and a needle brush.

[0056] In the present invention, the thickness of the first annealing ingot is preferably 0.7 to 0.8 mm.

[0057] After obtaining the first annealed ingot, the present invention sequentially performs intermediate rolling and intermediate continuous annealing on the first annealed ingot to obtain the second annealed ingot.

[0058] In the present invention, the total processing rate of the intermediate rolling is preferably 55-65%, the number of intermediate rolling passes is preferably 4-6, and the intermediate rolling is preferably cold rolling. In one embodiment of the present invention, the total processing rate of the intermediate rolling can be 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, or 64%, and the number of intermediate rolling passes can be 5. The present invention utilizes plastic deformation during intermediate rolling to manipulate the alloy's microstructure, laying the foundation for subsequent strengthening.

[0059] In the present invention, the temperature of the intermediate continuous annealing is preferably 850-950°C; the holding time of the intermediate continuous annealing is preferably 40-50s. As an embodiment of the present invention, the holding temperature of the intermediate continuous annealing can be 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C or 940°C; the holding time of the intermediate continuous annealing can be 42s, 42s or 48s. The present invention can eliminate work hardening and restore plasticity through intermediate continuous annealing to facilitate subsequent processing. At the same time, it can also regulate the grain size, avoid excessive grain growth, ensure the balance between strength and plasticity, and inhibit the premature precipitation of the Ni2Si phase.

[0060] In the present invention, the thickness of the second annealing ingot is preferably 0.25 to 0.3 mm.

[0061] After obtaining the second annealing ingot, the present invention sequentially performs pre-finished product rolling and pre-finished product continuous annealing on the second annealing ingot to obtain the third annealing ingot.

[0062] In the present invention, the total processing rate of the pre-rolled product is preferably 55-65%, the number of processing passes of the pre-rolled product is preferably 4-6, and the pre-rolled product is preferably cold-rolled. In one embodiment of the present invention, the total processing rate of the pre-rolled product can be 58%, 60%, or 63%, and the number of processing passes of the pre-rolled product can be 5. The pre-rolled product of the present invention can significantly reduce the size of the annealed ingot and further break up the grains in the alloy, thereby refining the grains and further improving the mechanical properties of the alloy ingot.

[0063] In the present invention, the holding temperature of the continuous annealing of the pre-finished product is preferably 800-900°C; the holding time of the continuous annealing of the pre-finished product is preferably 5-10s; the cooling method after the continuous annealing of the pre-finished product is preferably rapid cooling, more preferably air cooling or water cooling. As an embodiment of the present invention, the holding temperature of the continuous annealing of the pre-finished product can be 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C or 890°C; the holding time of the continuous annealing of the pre-finished product can be 6s, 7s, 8s or 9s. The present invention can eliminate the work hardening caused by the rolling of the pre-finished product through continuous annealing of the pre-finished product, restore plasticity, facilitate subsequent processing, and further refine the grains.

[0064] In the present invention, the thickness of the third annealing ingot is preferably 0.07 to 0.15 mm.

[0065] After obtaining the third annealing ingot, the present invention sequentially performs finished product rolling and finished product bell-type annealing on the third annealing ingot to obtain an ultra-thin, high-strength, medium-conductivity, and bend-resistant copper-nickel-cobalt-silicon alloy.

[0066] In the present invention, the total processing rate of the finished product rolling is preferably 10-28%, and the number of processing passes of the finished product rolling is preferably 1-2. As one embodiment of the present invention, the total processing rate of the finished product rolling can be 12%, 14%, 16%, 18%, 20%, 22%, 24%, or 26%. The present invention regulates the size of the copper-nickel-cobalt-silicon alloy through finished product rolling to achieve a thickness that meets the requirements.

[0067] The present invention preferably further comprises unwinding the finished rolled product. The present invention has no particular limitation on the specific operation of unwinding, and any unwinding method well known to those skilled in the art can be used.

[0068] In the present invention, the temperature of the finished product bell-jar annealing is preferably 300-350°C; and the holding time of the finished product bell-jar annealing is preferably 6-8h. As an embodiment of the present invention, the temperature of the finished product bell-jar annealing can be 310°C, 320°C, 330°C or 340°C; and the holding time of the finished product bell-jar annealing can be 7h. The present invention can achieve complete recrystallization and softening through the finished product bell-jar annealing, eliminate work hardening, and completely recrystallize the deformed grains after cold rolling and restore plasticity; at the same time, it can also achieve grain size control and avoid premature precipitation of Ni2Si.

[0069] The present invention preferably further includes pickling the finished bell-annealed product. In the present invention, the mass concentration of the acid in the pickling solution used during pickling is preferably 10-25%; the mass concentration of the passivating solution in the pickling solution is preferably 0.025-0.070%. As one embodiment of the present invention, the mass concentration of the acid in the pickling solution used during pickling can be 11%, 12%, 15%, 18%, 20%, 22%, or 24%; the mass concentration of the passivating solution in the pickling solution can be 0.030%, 0.035%, 0.040%, 0.045%, 0.050%, 0.055%, 0.060%, or 0.065%. Pickling can remove rolling oil and oxide layers from the surface of the copper-nickel-cobalt-silicon alloy.

[0070] In the present invention, the thickness of the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy is preferably 0.04 to 0.08 mm.

[0071] The present invention achieves optimal bending performance by adjusting chemical composition and performing multiple solid solution processes to uniformly distribute substructures in the grains; and achieves the best strengthening effect and electrical conductivity through graded aging.

[0072] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0073] Example 1

[0074] An ultra-thin, high-strength, medium-conductivity, and bending-resistant copper-nickel-cobalt-silicon alloy, comprising the following chemical components by mass percentage: Ni: 4.15%; Co: 2.0%; Si: 1.5%; Mg: 0.05%; Zn: 0.04%; Cr: 0.012%; Mn: 0.006% and the balance Cu; the (Ni+Co) / Si mass ratio is 4.1;

[0075] The preparation method of the ultra-thin, high-strength, medium-conductivity, and bend-resistant copper-nickel-cobalt-silicon alloy comprises the following steps:

[0076] (1) melting the alloy raw materials and performing semi-continuous casting to obtain an alloy ingot; the holding temperature of the melting is 1280° C., and the holding time of the melting is 25 minutes; the casting temperature of the semi-continuous casting is 1250° C., and the casting speed of the semi-continuous casting is 80 mm / min;

[0077] (2) the alloy ingot obtained in the step (1) is kept at 950° C. for 10 hours and then hot rolled, milled, rolled, unrolled, intermediate continuous annealed and brushed to obtain a first annealed ingot; the total processing rate of the hot rolling is 93%, and the number of hot rolling passes is 13; the total processing rate of the initial rolling is 95%, and the number of initial rolling passes is 12, and the initial rolling is cold rolled; the holding temperature of the intermediate continuous annealing is 850° C., and the holding time of the intermediate continuous annealing is 120 seconds;

[0078] (3) subjecting the first annealed ingot obtained in step (2) to intermediate rolling and intermediate continuous annealing in sequence to obtain a second annealed ingot; the total processing rate of the intermediate rolling is 60%, the number of intermediate rolling passes is 5, and the intermediate rolling is cold rolling; the temperature of the intermediate continuous annealing is 900° C., and the holding time of the intermediate continuous annealing is 50 seconds;

[0079] (4) the second annealed ingot obtained in step (3) is subjected to pre-finished product rolling and pre-finished product continuous annealing in sequence to obtain a third annealed ingot; the total processing rate of the pre-finished product rolling is 60%, the number of processing passes of the pre-finished product rolling is 5, and the pre-finished product rolling is cold rolling; the holding temperature of the pre-finished product continuous annealing is 850° C., the holding time of the pre-finished product continuous annealing is 10 seconds, and the cooling method of the pre-finished product after the continuous annealing is air cooling;

[0080] (5) The third annealed ingot obtained in the step (4) is subjected to finished product rolling, unwinding, finished product bell-shaped annealing and pickling in sequence to obtain an ultra-thin, high-strength, medium-conductive, bend-resistant copper-nickel-cobalt-silicon alloy with a thickness of 0.05 mm; the total processing rate of the finished product rolling is 26%, and the number of processing passes of the finished product rolling is 1; the temperature of the finished product bell-shaped annealing is 350° C., and the holding time of the finished product bell-shaped annealing is 8 h; the mass concentration of the acid in the pickling solution used in the pickling is 15%, and the mass concentration of the passivation solution is 0.05%.

[0081] Example 2

[0082] An ultra-thin, high-strength, medium-conductivity, and bending-resistant copper-nickel-cobalt-silicon alloy, comprising the following chemical components by mass percentage: Ni: 1.5%; Co: 1.2%; Si: 0.6%; Mg: 0.03%; Zn: 0.04%; Cr: 0.01%; Mn: 0.005% and the balance Cu; the mass ratio of (Ni+Co) / Si is 4.5;

[0083] The preparation method of the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy comprises the following steps:

[0084] (1) melting the alloy raw materials and performing semi-continuous casting to obtain an alloy ingot; the holding temperature of the melting is 1280° C., and the holding time of the melting is 25 minutes; the casting temperature of the semi-continuous casting is 1250° C., and the casting speed of the semi-continuous casting is 80 mm / min;

[0085] (2) the alloy ingot obtained in the step (1) is kept at 950° C. for 10 hours and then hot rolled, milled, rolled, unrolled, intermediate continuous annealed and brushed to obtain a first annealed ingot; the total processing rate of the hot rolling is 93%, and the number of hot rolling passes is 13; the total processing rate of the initial rolling is 95%, and the number of initial rolling passes is 12, and the initial rolling is cold rolled; the holding temperature of the intermediate continuous annealing is 850° C., and the holding time of the intermediate continuous annealing is 120 seconds;

[0086] (3) subjecting the first annealed ingot obtained in step (2) to intermediate rolling and intermediate continuous annealing in sequence to obtain a second annealed ingot; the total processing rate of the intermediate rolling is 60%, the number of intermediate rolling passes is 5, and the intermediate rolling is cold rolling; the temperature of the intermediate continuous annealing is 900° C., and the holding time of the intermediate continuous annealing is 50 seconds;

[0087] (4) the second annealed ingot obtained in step (3) is subjected to pre-finished product rolling and pre-finished product continuous annealing in sequence to obtain a third annealed ingot; the total processing rate of the pre-finished product rolling is 60%, the number of processing passes of the pre-finished product rolling is 5, and the pre-finished product rolling is cold rolling; the holding temperature of the pre-finished product continuous annealing is 850° C., the holding time of the pre-finished product continuous annealing is 10 seconds, and the cooling method of the pre-finished product after the continuous annealing is air cooling;

[0088] (5) The third annealed ingot obtained in the step (4) is subjected to finished product rolling, unwinding, finished product bell-shaped annealing and pickling in sequence to obtain an ultra-thin, high-strength, medium-conductive, bend-resistant copper-nickel-cobalt-silicon alloy with a thickness of 0.05 mm; the total processing rate of the finished product rolling is 26%, and the number of processing passes of the finished product rolling is 1; the temperature of the finished product bell-shaped annealing is 350° C., and the holding time of the finished product bell-shaped annealing is 8 h; the mass concentration of the acid in the pickling solution used in the pickling is 15%, and the mass concentration of the passivation solution is 0.05%.

[0089] Example 3

[0090] An ultra-thin, high-strength, medium-conductivity, and bending-resistant copper-nickel-cobalt-silicon alloy, comprising the following chemical components by mass percentage: Ni: 2.0%; Co: 1.15%; Si: 0.75%; Mg: 0.02%; Zn: 0.05%; Cr: 0.015%; Mn: 0.003% and the balance Cu; the (Ni+Co) / Si mass ratio is 4.2;

[0091] The preparation method of the ultra-thin, high-strength, medium-conductivity, and bend-resistant copper-nickel-cobalt-silicon alloy comprises the following steps:

[0092] (1) melting the alloy raw materials and performing semi-continuous casting to obtain an alloy ingot; the holding temperature of the melting is 1280° C., and the holding time of the melting is 25 minutes; the casting temperature of the semi-continuous casting is 1250° C., and the casting speed of the semi-continuous casting is 80 mm / min;

[0093] (2) the alloy ingot obtained in the step (1) is kept at 950° C. for 10 hours and then hot rolled, milled, rolled, unrolled, intermediate continuous annealed and brushed to obtain a first annealed ingot; the total processing rate of the hot rolling is 93%, and the number of hot rolling passes is 13; the total processing rate of the initial rolling is 95%, and the number of initial rolling passes is 12, and the initial rolling is cold rolled; the holding temperature of the intermediate continuous annealing is 850° C., and the holding time of the intermediate continuous annealing is 120 seconds;

[0094] (3) subjecting the first annealed ingot obtained in step (2) to intermediate rolling and intermediate continuous annealing in sequence to obtain a second annealed ingot; the total processing rate of the intermediate rolling is 60%, the number of intermediate rolling passes is 5, and the intermediate rolling is cold rolling; the temperature of the intermediate continuous annealing is 900° C., and the holding time of the intermediate continuous annealing is 50 seconds;

[0095] (4) the second annealed ingot obtained in step (3) is subjected to pre-finished product rolling and pre-finished product continuous annealing in sequence to obtain a third annealed ingot; the total processing rate of the pre-finished product rolling is 60%, the number of processing passes of the pre-finished product rolling is 5, and the pre-finished product rolling is cold rolling; the holding temperature of the pre-finished product continuous annealing is 850° C., the holding time of the pre-finished product continuous annealing is 10 seconds, and the cooling method of the pre-finished product after the continuous annealing is air cooling;

[0096] (5) The third annealed ingot obtained in the step (4) is subjected to finished product rolling, unwinding, finished product bell-shaped annealing and pickling in sequence to obtain an ultra-thin, high-strength, medium-conductive, bend-resistant copper-nickel-cobalt-silicon alloy with a thickness of 0.05 mm; the total processing rate of the finished product rolling is 26%, and the number of processing passes of the finished product rolling is 1; the temperature of the finished product bell-shaped annealing is 350° C., and the holding time of the finished product bell-shaped annealing is 8 h; the mass concentration of the acid in the pickling solution used in the pickling is 15%, and the mass concentration of the passivation solution is 0.05%.

[0097] Comparative Example 1

[0098] A copper-nickel-cobalt-silicon alloy, comprising the following chemical components by mass percentage: Ni: 3.15%; Si: 1.25%; Mg: 0.03%; Zn: 0.02%; Cr: 0.013%; Mn: 0.004% and the balance Cu;

[0099] The preparation method of the ultra-thin, high-strength, medium-conductivity, and bend-resistant copper-nickel-cobalt-silicon alloy comprises the following steps:

[0100] (1) melting the alloy raw materials and performing semi-continuous casting to obtain an alloy ingot; the holding temperature of the melting is 1280° C., and the holding time of the melting is 25 minutes; the casting temperature of the semi-continuous casting is 1250° C., and the casting speed of the semi-continuous casting is 80 mm / min;

[0101] (2) the alloy ingot obtained in the step (1) is kept at 950° C. for 10 hours and then hot rolled, milled, rolled, unrolled, intermediate continuous annealed and brushed to obtain a first annealed ingot; the total processing rate of the hot rolling is 93%, and the number of hot rolling passes is 13; the total processing rate of the initial rolling is 95%, and the number of initial rolling passes is 12, and the initial rolling is cold rolled; the holding temperature of the intermediate continuous annealing is 850° C., and the holding time of the intermediate continuous annealing is 120 seconds;

[0102] (3) subjecting the first annealed ingot obtained in step (2) to intermediate rolling and intermediate continuous annealing in sequence to obtain a second annealed ingot; the total processing rate of the intermediate rolling is 60%, the number of intermediate rolling passes is 5, and the intermediate rolling is cold rolling; the temperature of the intermediate continuous annealing is 900° C., and the holding time of the intermediate continuous annealing is 50 seconds;

[0103] (4) the second annealed ingot obtained in step (3) is subjected to pre-finished product rolling and pre-finished product continuous annealing in sequence to obtain a third annealed ingot; the total processing rate of the pre-finished product rolling is 60%, the number of processing passes of the pre-finished product rolling is 5, and the pre-finished product rolling is cold rolling; the holding temperature of the pre-finished product continuous annealing is 850° C., the holding time of the pre-finished product continuous annealing is 10 seconds, and the cooling method of the pre-finished product after the continuous annealing is air cooling;

[0104] (5) The third annealed ingot obtained in the step (4) is subjected to finished product rolling, unwinding, finished product bell-type annealing and pickling in sequence to obtain a copper-nickel-cobalt-silicon alloy with a thickness of 0.05 mm; the total processing rate of the finished product rolling is 26%, and the number of processing passes of the finished product rolling is 1 pass; the temperature of the finished product bell-type annealing is 350° C., and the holding time of the finished product bell-type annealing is 8 h; the mass concentration of acid in the pickling solution used during the pickling is 15%, and the mass concentration of the passivation solution is 0.05%.

[0105] Comparative Example 2

[0106] A copper-nickel-cobalt-silicon alloy, comprising the following chemical components by mass percentage: Ni: 6.15%; Co: 0.2%; Si: 2.5%; Mg: 0.05%; Zn: 0.01%; Cr: 0.01%; Mn: 0.005% and the balance Cu;

[0107] The preparation method of the copper-nickel-cobalt-silicon alloy comprises the following steps:

[0108] (1) melting the alloy raw materials and performing semi-continuous casting to obtain an alloy ingot; the holding temperature of the melting is 1280° C., and the holding time of the melting is 25 minutes; the casting temperature of the semi-continuous casting is 1250° C., and the casting speed of the semi-continuous casting is 80 mm / min;

[0109] (2) the alloy ingot obtained in the step (1) is kept at 950° C. for 10 hours and then hot rolled, milled, rolled, unrolled, intermediate continuous annealed and brushed to obtain a first annealed ingot; the total processing rate of the hot rolling is 93%, and the number of hot rolling passes is 13; the total processing rate of the initial rolling is 95%, and the number of initial rolling passes is 12, and the initial rolling is cold rolled; the holding temperature of the intermediate continuous annealing is 850° C., and the holding time of the intermediate continuous annealing is 120 seconds;

[0110] (3) subjecting the first annealed ingot obtained in step (2) to intermediate rolling and intermediate continuous annealing in sequence to obtain a second annealed ingot; the total processing rate of the intermediate rolling is 60%, the number of intermediate rolling passes is 5, and the intermediate rolling is cold rolling; the temperature of the intermediate continuous annealing is 900° C., and the holding time of the intermediate continuous annealing is 50 seconds;

[0111] (4) the second annealed ingot obtained in step (3) is subjected to pre-finished product rolling and pre-finished product continuous annealing in sequence to obtain a third annealed ingot; the total processing rate of the pre-finished product rolling is 60%, the number of processing passes of the pre-finished product rolling is 5, and the pre-finished product rolling is cold rolling; the holding temperature of the pre-finished product continuous annealing is 850° C., the holding time of the pre-finished product continuous annealing is 10 seconds, and the cooling method of the pre-finished product after the continuous annealing is air cooling;

[0112] (5) The third annealed ingot obtained in the step (4) is subjected to finished product rolling, unwinding, finished product bell-type annealing and pickling in sequence to obtain a copper-nickel-cobalt-silicon alloy with a thickness of 0.05 mm; the total processing rate of the finished product rolling is 26%, and the number of processing passes of the finished product rolling is 1 pass; the temperature of the finished product bell-type annealing is 350° C., and the holding time of the finished product bell-type annealing is 8 h; the mass concentration of acid in the pickling solution used during the pickling is 15%, and the mass concentration of the passivation solution is 0.05%.

[0113] Comparative Example 3

[0114] A copper-nickel-cobalt-silicon alloy, comprising the following chemical components by mass percentage: Ni: 0.8%; Co: 0.2%; Si: 0.5%; Mg: 0.03%; Zn: 0.03%; Cr: 0.011%; Mn: 0.008% and the balance Cu;

[0115] The preparation method of the copper-nickel-cobalt-silicon alloy comprises the following steps:

[0116] (1) melting the alloy raw materials and performing semi-continuous casting to obtain an alloy ingot; the holding temperature of the melting is 1280° C., and the holding time of the melting is 25 minutes; the casting temperature of the semi-continuous casting is 1250° C., and the casting speed of the semi-continuous casting is 80 mm / min;

[0117] (2) the alloy ingot obtained in the step (1) is kept at 950° C. for 10 hours and then hot rolled, milled, rolled, unrolled, intermediate continuous annealed and brushed to obtain a first annealed ingot; the total processing rate of the hot rolling is 93%, and the number of hot rolling passes is 13; the total processing rate of the initial rolling is 95%, and the number of initial rolling passes is 12, and the initial rolling is cold rolled; the holding temperature of the intermediate continuous annealing is 850° C., and the holding time of the intermediate continuous annealing is 120 seconds;

[0118] (3) subjecting the first annealed ingot obtained in step (2) to intermediate rolling and intermediate continuous annealing in sequence to obtain a second annealed ingot; the total processing rate of the intermediate rolling is 60%, the number of intermediate rolling passes is 5, and the intermediate rolling is cold rolling; the temperature of the intermediate continuous annealing is 900° C., and the holding time of the intermediate continuous annealing is 50 seconds;

[0119] (4) the second annealed ingot obtained in step (3) is subjected to pre-finished product rolling and pre-finished product continuous annealing in sequence to obtain a third annealed ingot; the total processing rate of the pre-finished product rolling is 60%, the number of processing passes of the pre-finished product rolling is 5, and the pre-finished product rolling is cold rolling; the holding temperature of the pre-finished product continuous annealing is 850° C., the holding time of the pre-finished product continuous annealing is 10 seconds, and the cooling method of the pre-finished product after the continuous annealing is air cooling;

[0120] (5) The third annealed ingot obtained in the step (4) is subjected to finished product rolling, unwinding, finished product bell-type annealing and pickling in sequence to obtain a copper-nickel-cobalt-silicon alloy with a thickness of 0.05 mm; the total processing rate of the finished product rolling is 26%, and the number of processing passes of the finished product rolling is 1 pass; the temperature of the finished product bell-type annealing is 350° C., and the holding time of the finished product bell-type annealing is 8 h; the mass concentration of acid in the pickling solution used during the pickling is 15%, and the mass concentration of the passivation solution is 0.05%.

[0121] The properties of the copper-nickel-cobalt-silicon alloys prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were tested, and the results are shown in Tables 1 and Figure 1 As shown:

[0122] Table 1 Properties of copper-nickel-cobalt-silicon alloys prepared in Examples 1 to 3 and Comparative Examples 1 to 3

[0123]

[0124] Among them, the test methods for tensile strength and yield strength are: GB / T 34505-2017 Room temperature tensile test method;

[0125] The test method for elongation is: GB / T 34505-2017 Room temperature tensile test method;

[0126] The test method for hardness is: GB / T 4340.1 Metallic materials Vickers hardness test Part 1: Test method;

[0127] The test method for bending at 90° parallel to the rolling direction is: GB / T 232 Metal material bending test method;

[0128] The test method for conductivity is: GB / T 351-2019 Metallic Materials-Resistivity Measurement Method.

[0129] The tensile curve of the copper-nickel-cobalt-silicon alloy prepared in Example 3 is as follows: Figure 1 As shown in Table 1 and Figure 1 It can be seen that after omitting the addition of cobalt element, although comparative example 1 can still maintain good electrical conductivity, its tensile strength and yield strength decrease significantly, and its hardness is low, and its mechanical properties cannot meet the requirements; although the tensile strength, yield strength and hardness of the copper-nickel-cobalt-silicon alloy prepared in comparative example 2 meet the technical requirements, it is obvious that its electrical conductivity is less than 40% IACS, and its electrical conductivity is poor, and it is impossible to achieve a joint improvement in mechanical properties and electrical conductivity, and also cannot meet the technical requirements; and comparative example 3 significantly reduces the content of the added elements in the copper-nickel-cobalt-silicon alloy, The influence of the added elements on the electrical conductivity of the copper alloy is reduced, so that its electrical conductivity reaches more than 47% IACS. However, this method causes a significant decrease in the mechanical properties of the copper-nickel-cobalt-silicon alloy. That is, Comparative Example 3 sacrifices mechanical properties to improve electrical conductivity, and still cannot meet the technical requirements. The copper-nickel-cobalt-silicon alloy provided by Examples 1 to 3 of the present invention not only has a tensile strength of more than 930 MPa and a yield strength of more than 900 MPa, but also does not crack when bent at 90° parallel to the rolling direction with R / T=0. At the same time, the electrical conductivity can reach more than 45%, taking into account the joint improvement of mechanical properties and electrical conductivity.

[0130] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy, characterized in that: Calculated by mass percentage, it includes the following chemical components: Ni: 0.5-4.5%; Co: 0.1~2.0%; Si: 0.1-2.0%; Strengthening elements: 0.001-1.0% and the balance Cu; The strengthening elements include at least two of Mg, Zn, Cr, Mn and Fe; the mass ratio of (Ni+Co) / Si is 3.9-4.

5.

2. The ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy according to claim 1, characterized in that: The strengthening elements are Mg, Zn, Cr and Mn.

3. The method for preparing the ultra-thin, high-strength, medium-conductivity, bend-resistant copper-nickel-cobalt-silicon alloy according to claim 1 or 2, characterized in that: The following steps are involved: (1) melting the alloy raw materials and performing semi-continuous casting to obtain alloy ingots; (2) hot rolling, initial rolling and intermediate continuous annealing are performed on the alloy ingot obtained in step (1) to obtain a first annealed ingot; (3) subjecting the first annealed ingot obtained in step (2) to intermediate rolling and intermediate continuous annealing in sequence to obtain a second annealed ingot; (4) subjecting the second annealed ingot obtained in step (3) to pre-finished product rolling and pre-finished product continuous annealing in sequence to obtain a third annealed ingot; (5) The third annealed ingot obtained in step (4) is subjected to finished product rolling and finished product bell-type annealing in sequence to obtain an ultra-thin, high-strength, medium-conductivity, and bend-resistant copper-nickel-cobalt-silicon alloy.

4. The preparation method according to claim 3, characterized in that The total processing rate of the initial rolling in the step (2) is 85-98%; the processing number of the initial rolling is 12-14 times; and the initial rolling is cold rolling.

5. The preparation method according to claim 3, characterized in that The holding temperature of the intermediate continuous annealing in the step (2) is 850-950° C.; the holding time of the intermediate continuous annealing is 90-180 seconds.

6. The preparation method according to claim 3, characterized in that The total processing rate of the intermediate rolling in the step (3) is 55-65%; the processing passes of the intermediate rolling are 4-6 passes; and the intermediate rolling is cold rolling.

7. The preparation method according to claim 3, characterized in that The temperature of the intermediate continuous annealing in step (3) is 850-950° C.; the holding time of the intermediate continuous annealing is 40-50 seconds.

8. The preparation method according to claim 3, characterized in that The total processing rate of the pre-finished product rolling in the step (4) is 55-65%; the processing passes of the pre-finished product rolling are 4-6 passes; and the pre-finished product rolling is cold rolling.

9. The preparation method according to claim 3, characterized in that The holding temperature of the continuous annealing of the pre-finished product in the step (4) is 800-900° C.; the holding time of the continuous annealing of the pre-finished product is 5-10 seconds.

10. The preparation method according to claim 3, characterized in that The temperature of the finished product bell-jar annealing in step (5) is 300-350° C.; the holding time of the finished product bell-jar annealing is 6-8 hours.

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