Copper alloy bar for battery formation test and preparation method thereof

Abstract

The invention discloses a copper alloy bar for a battery formation test and a preparation method of the copper alloy bar. The copper alloy bar comprises the following components in percentage by mass: 2.2 to 3.0 percent of Ni, 0.5 to 0.9 percent of Si, 0.8 to 1.2 percent of Co, 0.1 to 0.3 percent of Mg, 0.001 to 0.2 percent of Nd, 0.001 to 0.1 percent of Mn, 0 to 0.05 percent of X and the balance of Cu and inevitable impurity elements. Wherein the X element is one or more of Ag, In, B and Zr; the structure of the copper alloy bar comprises a precipitated phase, the precipitated phase comprises a (Ni, Co) Si compound strengthening phase and a Mn5Si3 wear-resistant phase, the average size of the (Ni, Co) Si compound strengthening phase is smaller than or equal to 380 nm, the area proportion of the (Ni, Co) Si compound strengthening phase is larger than or equal to 80%, and the average size of the Mn5Si3 wear-resistant phase is smaller than or equal to 3 micrometers. The copper alloy bar has good conductivity, wear resistance and high elasticity, and good electroplating machinability and low power-on temperature rise are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of copper alloys, and particularly relates to a copper alloy bar for battery formation testing and a preparation method thereof. Background Art

[0002] Lithium batteries used in new energy vehicles undergo two stages during the production process: formation and capacity separation. These stages activate battery performance and screen for consistency through charge and discharge. Formation involves the initial charge and discharge to activate the battery's internal materials (e.g., forming the SEI film), while capacity separation involves testing and classifying the battery capacity to eliminate substandard products. Battery formation and capacity separation involves a charge and discharge process, during which lithium battery current, internal resistance, capacitance, and contact stability are measured using a probe. To ensure effective penetration of the electrode oxide film during formation testing, the probe tip must be resistant to wear and deformation (high hardness). Furthermore, the capacity separation probe must exhibit a low temperature rise (high conductivity) when energized, meeting the requirements of formation testing for large-capacity power batteries.

[0003] Therefore, the probes used for testing new energy vehicle batteries must have the following properties: 1) Good conductivity, effectively reducing signal transmission loss.

[0004] 2) High wear resistance to prevent the probe from frequent contact and plugging and unplugging and causing wear.

[0005] 3) Good elasticity to ensure the long-term contact stability of the probe.

[0006] 4) Low contact resistance, small temperature rise when powered on after more than tens of thousands of contact plugging and unplugging, improving test accuracy.

[0007] 5) Good electroplating performance, good surface finish after electroplating.

[0008] Currently, the only copper alloy bars on the market that meet these comprehensive performance requirements are primarily beryllium copper. However, beryllium and its compounds are highly toxic, and inhaling dust can cause beryllium lung disease, a serious health hazard. Furthermore, beryllium easily oxidizes during the smelting process, forming BeO impurities. This leads to significant hot brittleness under high-temperature processing conditions, posing quality risks for probes requiring high-temperature welding. Furthermore, beryllium ore is expensive, making its use prohibitive for large-scale production due to environmental concerns.

[0009] Other copper alloys, such as the Cu-Cr-Zr series of rods, have good electrical conductivity but cannot meet the high wear resistance required by frequent probe contact. Ordinary Cu-Ni-Si series cannot simultaneously achieve both high conductivity and high wear resistance. When the wear resistance of the material reaches its limit, the material conductivity cannot meet the requirements due to significant work hardening. If the aging precipitation effect is increased, the material conductivity can be further improved, but the material strength and wear resistance cannot meet the requirements. The general probe test process requires more than 30,000 contact insertions and removals. Due to severe material wear, the material resistance is greatly increased compared to before wear, and the temperature rise is large when power is applied, making it difficult to meet the basic requirement of temperature rise control below 15°C. The Cu-Ni-Sn series has excellent mechanical properties and wear resistance, but its electrical conductivity is poor and it also cannot meet the use requirements.

[0010] In summary, there is an urgent need to develop a green and environmentally friendly copper alloy rod that is harmless to the environment and human body and has good conductivity, wear resistance, and high elasticity, so as to achieve good electroplating processability and low power-on temperature rise, and meet the production and use conditions of probes for new energy vehicle battery formation testing. Summary of the Invention

[0011] The present invention provides a copper alloy bar for battery formation testing. The copper alloy bar has good electrical conductivity, wear resistance, and high elasticity, and achieves good electroplating processability and low temperature rise when powered on.

[0012] The present invention provides a copper alloy bar for battery formation testing. The mass percentages of the components of the copper alloy bar are as follows: Ni: 2.2-3.0%, Si: 0.5-0.9%, Co: 0.8-1.2%, Mg: 0.1-0.3%, Nd: 0.001-0.2%, Mn: 0.001-0.1%, X: 0-0.05%, and the balance is Cu and unavoidable impurity elements; wherein the X element is one or more of Ag, In, B, and Zr; The structure of the copper alloy rod includes a precipitated phase, which includes a (Ni, Co)Si compound strengthening phase and a Mn5Si3 wear-resistant phase. The average size of the (Ni, Co)Si compound strengthening phase is ≤380nm, the area ratio of the (Ni, Co)Si compound strengthening phase is ≥80%, and the average size of the Mn5Si3 wear-resistant phase is ≤3μm.

[0013] The appropriate amount of Ni element provided by the present invention can form a solid solution with the matrix Cu, playing a certain role in solid solution strengthening. At the same time, as the main added element of the present invention, it can form a (Ni, Co) Si compound strengthening phase with Co and Si elements, greatly improving the strength and electrical conductivity of the material. The present invention controls the upper limit of the Ni element content at 3.0%, with the purpose of effectively balancing the comprehensive performance of the material. If the added Ni content is too high, although the mechanical properties of the material are further improved, it is easy to cause the electrical conductivity to decrease. At the same time, it also increases the material's resistance to deformation during hot and cold processing, requiring higher hot processing and heat treatment temperatures, which is not conducive to the control of the alloy's microstructure morphology and uniformity, and indirectly worsens the material's wear resistance and elastic properties. If the Ni element content is too low, the material cannot obtain good mechanical properties and elastic properties.

[0014] On the one hand, the appropriate amount of Si element provided by the present invention forms a (Ni, Co)Si compound strengthening phase to obtain good mechanical properties and electrical conductivity. On the other hand, it can form a Mn5Si3 wear-resistant phase with the Mn element. The Mn5Si3 wear-resistant phase belongs to the hexagonal crystal system, has a complex layered atomic arrangement, and the particle hardness can reach more than 900HV, and has excellent resistance to abrasive wear. The probe product finally processed by the present invention has good resistance to plugging and pulling wear, reduces the significant increase in material resistance due to severe wear, and causes severe temperature rise after power is turned on, affecting the quality of the product. The upper limit of the Si content is controlled at 0.9%. If excessive amount is added, the electrical conductivity and processing plasticity of the material will be greatly reduced.

[0015] The present invention provides an appropriate amount of Co. This element, on the one hand, can partially dissolve in the copper matrix, hindering dislocation motion through lattice distortion and improving alloy strength. Co also acts as a heterogeneous nucleation core, inhibiting grain growth in the copper matrix during solidification and heat treatment, improving the material's microstructure uniformity and grain refinement. Furthermore, it promotes the formation of a (Ni, Co)Si compound strengthening phase, which exhibits a more pronounced precipitation strengthening effect than conventional NiSi phases. Given the same order of magnitude of precipitated phases, the (Ni, Co)Si compound strengthening can improve the material's hardness and strength by more than 20% compared to the NiSi phase, without negatively impacting the material's electrical conductivity. The Co content is capped at 1.2%. Excessive addition reduces melt fluidity during smelting, requiring higher melting temperatures and significantly increasing the risk of gas absorption during casting, leading to defects such as pores and inclusions. Furthermore, during subsequent extrusion hot working, the material's hot deformation and tensile strength are significantly increased, requiring higher heating temperatures and hindering the achievement of fine, uniform grain morphology. Furthermore, excessive Co addition does not significantly improve the material's strength.

[0016] The present invention provides an appropriate amount of Mg element, which, on the one hand, plays the role of purification, deoxidation, and grain refinement, and on the other hand, can form Mg2Si phase with Si element, playing a certain precipitation strengthening role. At the same time, Mg element can also improve the distribution density of precipitation phase, promote the distribution of more precipitation strengthening phases in the grain boundaries, and achieve a good strengthening effect. In addition, Mg element can also improve the cutting and processing performance of the material to a certain extent, which is beneficial for obtaining a good surface finish after the rod is turned into a finished probe, and indirectly improves the subsequent electroplating performance. The improved electroplating effect is also beneficial to improving the conductivity of the probe and reducing the temperature rise effect after power is applied. The upper limit of Mg content is controlled at 0.3%. If excessive addition is added, the brittleness of the material will increase, and the wear resistance, mechanical properties and processing performance of the material will deteriorate.

[0017] The present invention provides an appropriate amount of Nd, which acts as a deoxidizer, preferentially reacting with oxygen during the smelting process to form Nd2O3 oxide, replacing the low-melting-point Cu2O impurity that easily forms, reducing the proportion of oxide inclusion defects and significantly improving casting performance. Furthermore, Nd segregates at grain boundaries to form a Nd-Cu-Si composite phase, which inhibits grain boundary sliding and migration at high temperatures, resulting in excellent relaxation resistance and yield strength. It also improves fatigue crack growth resistance, extending fatigue life by 1-2 times compared to materials without Nd addition, and imparting excellent wear resistance. The upper limit of Nd is controlled at 0.2% to avoid excessive Nd-containing oxides, which can increase the material's hot brittleness and detrimentally affect subsequent extrusion hot working performance.

[0018] The appropriate amount of Mn element provided by the present invention is mainly used to form wear resistance and improve the wear resistance of the material. The upper limit of the Mn content is controlled at 0.1% to avoid excessive addition causing a significant decrease in the conductive performance of the material.

[0019] The present invention provides that the addition of Ag element in the X element is mainly to improve the electrical conductivity of the alloy, and can also increase the recrystallization temperature of the alloy, which is conducive to the excessive growth trend of grains in the subsequent heat treatment process. The addition of In element can form a self-lubricating transfer film with copper element, promote the improvement of the material's anti-adhesive wear ability, and indirectly improve fatigue performance and wear resistance. The addition of B element can refine the grains, promote the distribution of more precipitation strengthening phases at the grain boundaries, and improve the mechanical properties, wear resistance and electrical conductivity of the material. The addition of Zr element can purify the melt, degas and deoxidize, and further improve the material's high-temperature softening resistance.

[0020] Preferably, the distribution of the precipitated phase is 1*10 6 ~8*10 6 Pieces / mm 2 The present invention distributes a higher number of precipitated phases per unit area, thereby making the copper alloy rod have higher strength and hardness.

[0021] Preferably, the grain size of the copper alloy rod for battery formation testing is 0.005-0.060 mm.

[0022] Preferably, the copper alloy bar for battery formation testing has a tensile strength of ≥800 MPa, a conductivity of ≥42% IACS, a hardness of ≥250 HV, an elongation of ≥12%, and an elastic modulus of ≥128 GPa.

[0023] On the other hand, the present invention also provides a method for preparing the copper alloy bar for battery formation testing, wherein the process flow of the preparation method includes smelting → semi-continuous casting → extrusion → first drawing → heat treatment → finished product drawing; The copper alloy bar for battery formation testing is batched and smelted according to the mass percentage of each component; The extrusion temperature is 850-950° C., the extrusion ratio is 30-200, and the extrusion speed is 5-15 mm / s.

[0024] Since the alloying elements provided by the present invention include Ni, Co, Si, Mn and other alloying elements, the compressive resistance is relatively large. The present invention needs to provide a higher extrusion ratio to avoid retaining the cast microstructure morphology as much as possible, and the extrusion temperature must also be coordinated with the extrusion ratio provided by the present application to be controlled within a higher range to achieve good local deformation plasticity. However, if the extrusion ratio is too large and the corresponding extrusion temperature control exceeds the upper limit, the precipitated phases (Ni, Co) Si compound strengthening phase, Mg2Si phase, and Mn5Si3 wear-resistant phase will fuse and aggregate. The aggregated precipitated phases tend to aggregate at the grain boundaries. If the precipitated phases aggregate, their size will further increase, the number per unit area will be greatly reduced, and the precipitation strengthening effect will be weakened. The (Ni, Co) Si compound strengthening phase is distributed as the main strengthening phase and has the most significant strengthening effect. If its composition ratio is too low, the material strength, especially the electrical conductivity, will be greatly reduced. Intergranular cracking will occur during subsequent processing, and if the extrusion temperature is too high, it will cause significant growth of the grains after recrystallization, affecting the mechanical properties, elastic properties and electrical conductivity of the obtained copper alloy bar.

[0025] In addition, the present invention controls the extrusion speed to reduce the extrusion temperature loss, and cooperates with the extrusion temperature to obtain a suitable extruded billet ejection temperature, so that the billet can achieve a better solid solution effect while being extruded, while avoiding the billet tearing caused by excessive friction with the mold due to excessive extrusion speed.

[0026] Preferably, the temperature of the extruded billet after extrusion is 800-920° C., and the extruded billet is cooled after being extruded.

[0027] The present invention utilizes the residual temperature of a higher extrusion temperature to achieve a desired solid solution effect on the billet. Since the present invention adds a certain amount of Mn and Mg elements in addition to Ni, Co, and Si, if a conventional solid solution process is used and the solid solution process is repeated multiple times, grain growth and precipitation phase aggregation will occur, causing the precipitation phase to be too large and unevenly distributed, resulting in cracking of the finished product after drawing. Therefore, the present invention utilizes the residual temperature of extrusion for solid solution and controls the temperature of the extruded billet out of the die to achieve a better solid solution effect, that is, the precipitated phase can be completely dissolved in the matrix, and the copper alloy rod after subsequent aging treatment has better mechanical properties and electrical conductivity.

[0028] More preferably, the cooling rate is greater than 100° C. / s.

[0029] By controlling the cooling speed, the present invention can achieve uniform cooling of the interior and core of the blank provided in the present application in a specification of φ20~40mm, thereby achieving a better cooling effect.

[0030] Preferably, vibration is applied during the semi-continuous casting process, and the vibration frequency is 30-80 Hz.

[0031] Since a certain amount of elements such as Co, Ni and Mn are added in the present invention, the viscosity of the copper liquid is relatively high during the melting and casting process. By applying vibrations of a suitable frequency, on the one hand, the copper liquid is promoted to be more evenly and tightly distributed after flowing into the crystallizer, thereby avoiding the problem of subsequent looseness. On the other hand, the vibration process of the appropriate frequency promotes an increase in the number of nuclei formed in the copper liquid during the solidification process, which is beneficial to improving the uniformity of the ingot structure. If the vibration frequency is too high, the copper liquid is prone to splashing and flowing too violently after flowing into the crystallizer, which is detrimental to the casting quality. At the same time, it is also easy to cause element segregation, which is not conducive to improving the uniformity and stability of the ingot performance.

[0032] Preferably, the semi-continuous casting casting pulling rate is 30-80 mm / min, the primary cooling water inlet temperature is 20-40°C, the primary cooling water outlet temperature is 35-60°C, the cooling water pressure is 0.6-1.0 MPa, the casting temperature is 1200-1320°C, the ingot out of the crystallizer temperature is 700-950°C, and secondary cooling is adopted to obtain a φ150-260 mm ingot by drawing.

[0033] The present invention controls the pulling rate so that the cooling and solidification of molten copper in the crystallizer is more complete, thereby avoiding the risk of molten copper leaking out of the crystallizer. At the same time, it can also prevent the width of the solidification zone from being too large, reduce the contact area between the solidified copper ingot and the crystallizer during the casting process, reduce the frictional resistance between the ingot and the crystallizer, and reduce the negative impact of excessive frictional resistance on the surface quality of the ingot, such as cracking.

[0034] The present invention controls the first cooling water outlet and inlet temperatures and the cooling water pressure, so that the cooling intensity of the outer layer of the ingot during the solidification process is appropriate and the cross-section is cooled more evenly, thereby avoiding the problem of stress cracking. At the same time, it can also reduce the coarse grain size of the ingot, segregation, shrinkage and other quality defects caused by too low cooling intensity.

[0035] The present invention controls the casting temperature so that the fluidity of the copper liquid flowing into the crystallizer is better, thereby avoiding defects such as shrinkage and segregation. At the same time, defects such as casting pores formed by air absorption by the copper liquid can be avoided as much as possible, and the reaction between the elements such as Ni and Co provided by the present invention and the carbon-containing auxiliary materials in the solution, which may cause a high carbon content in the ingot and brittle cracking, can be avoided.

[0036] The present invention controls the temperature of the ingot out of the crystallizer to effectively control the quality of the alloy solidification process. If the temperature out of the crystallizer is too low, it means that the solidification rate in the primary cooling process is too high, and the ingot is prone to stress cracking risk; if the temperature out of the crystallizer is too high, there is a risk of copper leakage.

[0037] Preferably, the first drawing comprises multiple passes, and the processing rate of each drawing pass is 15-40%.

[0038] By controlling the processing rate of each drawing pass, the present invention avoids defects such as tensile cracks caused by excessive reduction due to excessive processing rate in a single drawing pass. It also avoids large deformation near the outer diameter of the round bar and small deformation at the center of the bar. This can cause uneven deformation at the edge and center of the bar, thereby generating certain stresses and easily causing stress cracking during subsequent heat treatment.

[0039] Preferably, the total processing rate of the first drawing is 60-90%. The present invention controls the total processing rate to achieve sufficient work hardening while avoiding the risk of brittle cracking due to excessive hardening.

[0040] Preferably, the heat treatment temperature T is: T=extrusion die temperature / 2+40, the holding time is 2-10 h, and then cooling is performed, and the cooling rate is <5°C / min.

[0041] The holding temperature provided by the present invention corresponds to the temperature of the billet after being ejected from the die in the previous extrusion process, that is, the higher the temperature after being ejected from the die, the higher the temperature required for the precipitation strengthening heat treatment of the material. Because the temperature after being extruded from the die in the present invention is the solid solution temperature of the material, the higher the solid solution temperature, the higher the subsequent precipitation strengthening aging heat treatment temperature needs to be, which is conducive to the precipitation phase being able to fully precipitate from the matrix. Conversely, the lower the solid solution temperature, the required aging heat treatment temperature can meet the requirements of fully precipitating the precipitation phase from the matrix under relatively low conditions. If the corresponding aging heat treatment temperature is too high under low temperature solid solution conditions, the material is prone to over-aging, and the material strength and elastic properties are seriously attenuated.

[0042] The cooling rate after aging heat treatment is limited to a lower range to avoid stress formation due to rapid extreme cooling, which can lead to cracking risks due to uneven stress distribution during the subsequent bar straightening process. Excessive stress can also negatively impact the bar's subsequent turning performance.

[0043] Preferably, the processing rate of the finished product drawing is 15-30%. By controlling the processing rate of the finished product drawing, the present invention avoids excessive processing deformation that may lead to a decrease in the material's electrical conductivity. It also helps to avoid the formation of excessive residual stress that may lead to a decrease in the straightness of the bar. If the straightness is reduced, a large deformation straightening process is required, and the material's mechanical properties will be weakened after the Bauschinger effect occurs.

[0044] Compared with the prior art, the present invention has the following beneficial effects: The present invention controls the average size and area ratio of the (Ni, Co)Si compound strengthening phase, so that the copper alloy rod provided by the present invention has higher strength, hardness and conductivity; the present invention forms and controls the average size of the Mn5Si3 wear-resistant phase, so that the copper alloy rod provided by the present invention has higher wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a metallographic photograph of the finished product of Example 1 of the present invention; Figure 2 This is a metallographic photograph of the finished product of Comparative Example 1 of the present invention; Figure 3 This is the (Ni, Co)Si compound strengthening phase morphology of the finished product of Example 1 of the present invention; Figure 4 This is the wear-resistant phase morphology of the finished product MnSi in Example 1 of the present invention. DETAILED DESCRIPTION

[0046] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0047] The present invention provides 4 embodiments and 5 comparative examples, and the specific ingredients are shown in Table 1.

[0048] Example 1 1) Melting: Add raw materials according to the required composition ratio and melt them. The melting temperature is 1350°C.

[0049] 2) Casting: Semi-continuous casting is used for production, with a casting pulling rate of 40 mm / min, a vibration frequency of 70 Hz, a primary cooling water inlet temperature of 35°C, a primary cooling water outlet temperature of 50°C, a cooling water pressure of 0.8 MPa, a casting temperature of 1220°C, an ingot outlet temperature of 780°C, and secondary cooling. φ250 mm ingots are obtained by drawing.

[0050] 3) Extrusion: Hot extrusion was performed using a horizontal extruder at a temperature of 900°C, an extrusion ratio of 40, an extrusion speed of 9 mm / s, and a temperature control of 840°C for the extruded billet. Immediately after extrusion, the billet was extremely cooled at a cooling rate of >100°C / s. A φ28 mm billet was obtained.

[0051] 4) Drawing: After pickling, the extruded billet is subjected to diameter-reducing drawing. Drawing is performed in four passes, with a processing rate of 15-40% for each pass and a total processing rate of 63%. A φ17mm billet is obtained.

[0052] 5) Heat treatment: Heat treatment is performed on the drawn bar, with a holding temperature of 460°C and a holding time of 5 hours. After the holding time is up, the bar is slowly cooled, and the cooling rate is controlled to be less than 5°C / min.

[0053] 6) Finished product drawing: The heat-treated bars are subjected to finished product drawing with a processing rate of 22%. Finished bars with a diameter of 15 mm are obtained.

[0054] Example 2 1) Melting: Add raw materials according to the required composition ratio and melt them. The melting temperature is 1350°C.

[0055] 2) Casting: Semi-continuous casting is used for production, with a casting pulling rate of 60 mm / min, a vibration frequency of 60 Hz, a primary cooling water inlet temperature of 25°C, a primary cooling water outlet temperature of 55°C, a cooling water pressure of 0.8 MPa, a casting temperature of 1240°C, an ingot outlet temperature of 800°C, and secondary cooling. φ250 mm ingots are obtained by drawing.

[0056] 3) Extrusion: Hot extrusion was performed using a horizontal extruder at an extrusion temperature of 860°C, an extrusion ratio of 40, an extrusion speed of 12 mm / s, and a controlled extrusion temperature of 810°C. Immediately after extrusion, the extruded billet was extremely cooled at a cooling rate of >100°C / s. A φ28 mm billet was obtained.

[0057] 4) Drawing: After pickling, the extruded billet is subjected to diameter-reducing drawing. Drawing is performed in four passes, with a processing rate of 15-40% for each pass and a total processing rate of 63%. A φ17mm billet is obtained.

[0058] 5) Heat treatment: Heat treatment is performed on the drawn bar, with a holding temperature of 445°C and a holding time of 7 hours. After the holding time is up, the bar is slowly cooled, and the cooling rate is controlled to be less than 5°C / min.

[0059] 6) Finished product drawing: The heat-treated bars are subjected to finished product drawing with a processing rate of 22%. Finished bars with a diameter of 15 mm are obtained.

[0060] Example 3 1) Melting: Add raw materials according to the required composition ratio and melt them. The melting temperature is 1350°C.

[0061] 2) Casting: Semi-continuous casting is used for production, with a casting pulling rate of 70 mm / min, a vibration frequency of 60 Hz, a primary cooling water inlet temperature of 25°C, a primary cooling water outlet temperature of 55°C, a cooling water pressure of 0.8 MPa, a casting temperature of 1250°C, an ingot outlet temperature of 850°C, and secondary cooling. φ200 mm ingots are obtained by drawing.

[0062] 3) Extrusion: Hot extrusion was performed using a horizontal extruder at a temperature of 880°C, an extrusion ratio of 41, an extrusion speed of 10 mm / s, and a temperature control of 820°C at the exit of the extrusion billet. Immediately after exiting the die, the billet was extremely cooled at a cooling rate of >100°C / s. A φ22 mm billet was obtained.

[0063] 4) Drawing: After pickling, the extruded billet is subjected to diameter-reducing drawing. Drawing is carried out in three passes, with the processing rate of each pass controlled at 15-40%, and the total processing rate at 70%. A φ12mm billet is obtained.

[0064] 5) Heat treatment: Heat treatment is performed on the drawn bar, with a holding temperature of 450°C and a holding time of 6 hours. After the holding time is up, the bar is slowly cooled, and the cooling rate is controlled to be less than 5°C / min.

[0065] 6) Finished product drawing: The heat-treated bar is subjected to finished product drawing with a processing rate of 16%. A φ11mm finished bar is obtained.

[0066] Example 4 1) Melting: Add raw materials according to the required composition ratio and melt them. The melting temperature is 1350°C.

[0067] 2) Casting: Semi-continuous casting is used for production, with a casting pulling rate of 80 mm / min, a vibration frequency of 75 Hz, a primary cooling water inlet temperature of 22°C, a primary cooling water outlet temperature of 50°C, a cooling water pressure of 0.8 MPa, a casting temperature of 1300°C, an ingot outlet temperature of 900°C, and secondary cooling. φ200 mm ingots are obtained by drawing.

[0068] 3) Extrusion: Hot extrusion was performed using a horizontal extruder at a temperature of 930°C, an extrusion ratio of 41, an extrusion speed of 7 mm / s, and a temperature control of 860°C at the exit of the extrusion billet. Immediately after exiting the die, the billet was subjected to extreme cooling at a cooling rate >100°C / s. A φ22 mm billet was obtained.

[0069] 4) Drawing: After pickling, the extruded billet is subjected to diameter-reducing drawing. Drawing is carried out in three passes, with the processing rate of each pass controlled at 15-40%, and the total processing rate at 70%. A φ12mm billet is obtained.

[0070] 5) Heat treatment: Heat treatment is performed on the drawn bar, with a holding temperature of 470°C and a holding time of 3.5h. After the holding time is up, the bar is slowly cooled, and the cooling rate is controlled to be less than 5°C / min.

[0071] 6) Finished product drawing: The heat-treated bar is subjected to finished product drawing with a processing rate of 16%. A φ11mm finished bar is obtained.

[0072] Comparative Example 1 1) Melting: Add raw materials according to the required composition ratio and melt them. The melting temperature is 1300°C.

[0073] 2) Casting: Semi-continuous casting is used for production, and φ250mm ingots are obtained by drawing.

[0074] 3) Extrusion: Use a horizontal extruder for hot extrusion processing, extrusion temperature: 960℃, extrusion ratio: 20, extrusion speed: 12mm / s, and the billet is slowly cooled to room temperature after extrusion.

[0075] 4) Solution treatment: The extruded billet is subjected to solution heat treatment at a holding temperature of 880°C for 1 hour. After heating, it is quickly immersed in water for cooling.

[0076] 5) Drawing: After pickling, the extruded billet is subjected to diameter reducing and drawing processing.

[0077] 6) Heat treatment: Heat treatment is performed on the drawn bar, with a holding temperature of 460°C and a holding time of 5 hours.

[0078] 7) Finished product drawing: The heat-treated bar is subjected to finished product drawing to obtain a φ15mm finished bar.

[0079] Comparative Example 2 1) Melting: Add raw materials according to the required composition ratio and melt them. The melting temperature is 1400°C.

[0080] 2) Casting: Semi-continuous casting is used for production, and φ250mm ingots are obtained by drawing.

[0081] 3) Extrusion: Use a horizontal extruder for hot extrusion processing, extrusion temperature: 980℃, extrusion ratio: 18, extrusion speed: 10mm / s, and the billet is slowly cooled to room temperature after extrusion.

[0082] 4) Solution treatment: Solution heat treatment is performed on the extruded billet. The holding temperature is 950℃ and the holding time is 1 hour. After heating, the billet is quickly immersed in water for cooling.

[0083] 5) Drawing: After pickling, the extruded billet is subjected to diameter-reducing drawing to obtain the required finished product with a diameter of 15mm. 6) Heat treatment: Heat treatment is performed on the drawn bar, with a holding temperature of 400°C and a holding time of 3 hours.

[0084] Comparative Example 3 1) Melting: Add raw materials according to the required composition ratio and melt them. The melting temperature is 1350°C.

[0085] 2) Casting: Semi-continuous casting is used for production, and φ200mm ingots are obtained by drawing.

[0086] 3) Extrusion: Use a horizontal extruder for hot extrusion processing, extrusion temperature: 850℃, extrusion ratio: 8, extrusion speed: 4mm / s, and the billet is slowly cooled to room temperature after extrusion.

[0087] 4) Solution treatment: Solution heat treatment is performed on the extruded billet at a holding temperature of 800°C for 2 hours. After heating, the billet is quickly immersed in water for cooling.

[0088] 5) Drawing: After pickling, the extruded billet is subjected to diameter-reducing drawing to obtain the required finished product with a diameter of 15mm. 6) Heat treatment: Heat treatment is performed on the drawn bar, with a holding temperature of 460°C and a holding time of 4 hours.

[0089] Comparative Example 4 1) Melting: Add raw materials according to the required composition ratio and melt them. The melting temperature is 1400°C.

[0090] 2) Casting: Semi-continuous casting is used for production, and φ250mm ingots are obtained by drawing.

[0091] 3) Extrusion: Use a horizontal extruder for hot extrusion processing, extrusion temperature: 920℃, extrusion ratio: 25, extrusion speed: 10mm / s, and the billet is slowly cooled to room temperature after extrusion.

[0092] 4) Solution treatment: Solution heat treatment is performed on the extruded billet at a holding temperature of 980°C for 0.4h. After heating, the billet is quickly immersed in water for cooling.

[0093] 5) Drawing: After pickling, the extruded billet is subjected to diameter reducing and drawing processing.

[0094] 6) Heat treatment: Heat treatment is performed on the drawn bar, with a holding temperature of 460°C and a holding time of 5 hours.

[0095] 7) Finished product drawing: The heat-treated bar is subjected to finished product drawing to obtain a φ15mm finished bar.

[0096] Comparative Example 5 1) Melting: Add raw materials according to the required proportions and melt.

[0097] 2) Casting: Use horizontal continuous casting to produce φ25 coil wire.

[0098] 3) Coiling: The horizontal continuous casting billet is subjected to coiling. After stretching and hardening, it is softened and annealed at 500°C for 5 hours. The coiling and annealing processes are repeated 4 times in between.

[0099] 4) Finished product drawing: The annealed billet is subjected to finished product drawing to obtain a φ15mm finished bar.

[0100] Comparative Example 6 The difference compared with Example 1 is that during the semi-continuous casting process, the vibration frequency is 120 Hz.

[0101] Comparative Example 7 The difference compared with Example 1 is that no vibration is performed during the semi-continuous casting process.

[0102] Comparative Example 8 The difference compared with Example 1 is that the extrusion temperature is 990°C and the outlet temperature of the extruded billet is 930°C.

[0103] The obtained examples and comparative examples were tested for mechanical properties, electrical conductivity and / or microstructure. The specific test indicators and test standards are as follows: 1) Tensile strength and elongation test: GB / T 228.1-2010 Tensile tests on metallic materials - Part 1: Room temperature tensile test method.

[0104] 2) Metallographic microscopic test: YS / T 449-2002 Microstructure examination method of copper and copper alloy castings and processed products.

[0105] 3) Elastic modulus test: GB / T 22315-2008 Test method for elastic modulus and Poisson's ratio of metallic materials.

[0106] 4) Electrical conductivity: GB / T 351-2019 Metal materials - Measurement method for resistivity.

[0107] 5) Temperature rise test: Refer to GB / T 20234.1-2023 Connection devices for conductive charging of electric vehicles Part 1: General requirements. After processing the rods into corresponding probes, perform 30,000 plug-in and pull-out tests. Use a probe life tester to perform temperature rise testing.

[0108] Performance Analysis: As shown in Tables 1-3, the tensile strength, hardness, elastic modulus, and conductivity of Comparative Example 1 were all lower than those of the Examples. Furthermore, the high-temperature, offline solutionization process resulted in a coarse grain structure and inferior microstructure uniformity compared to the Examples. Although the temperature rise of the rods from Comparative Example 1 after processing into probes was less than 15°C during power-on testing, the material's low strength and poor wear resistance resulted in severe surface wear and a significant increase in resistance after 30,000 plug-in and pull-out cycles. The temperature rise exceeded 15°C after 1.5 hours of power-on, failing to meet the required operating conditions.

[0109] In Comparative Example 2, by increasing the Ni and Si contents, the material strength and hardness are significantly improved, but the electrical conductivity is relatively low. Therefore, the material heats up significantly after being energized, and the temperature rises above 15°C, making it impossible to meet the use conditions.

[0110] Comparative Example 3 is similar to Comparative Example 2. Although the material has better mechanical properties, wear resistance, and elastic properties, its electrical conductivity is relatively low.

[0111] The conductivity of Example 4 is relatively excellent, so the temperature rise after being processed into the probe and before being plugged in and out is relatively low. However, due to the low material strength and poor wear resistance, the surface of the material is severely worn after 30,000 plugging and unplugging, and the resistance increases significantly. After being powered on for 1.5 hours, the temperature rise is higher than 15°C, which cannot meet the requirements of the use conditions.

[0112] Although the production process of Comparative Example 5 is simple and the processing cost is low, its mechanical properties and conductive properties are inferior to those of the embodiment, and the temperature rise test after power-on cannot meet the requirements of the use conditions.

[0113] In Comparative Example 6, due to the excessive vibration frequency during the melting and casting process, elements such as Co, Si, and Ni were severely segregated, the uniformity of the ingot structure deteriorated, the uniformity of the distribution of the precipitation strengthening phase in the material also deteriorated, and the mechanical and conductive properties of the material were inferior to those of the embodiment.

[0114] Since no vibration was added in Comparative Example 7, the density of the ingot structure was average, and the overall grain size and morphology were large and uneven. The mechanical properties and electrical conductivity of the material were inferior to those of the embodiment.

[0115] In Comparative Example 8, due to the high extrusion temperature, on the one hand, the extruded grains grew significantly, and on the other hand, the fine grain strengthening effect could not be fully achieved. At the same time, the grain growth caused the number of grain boundaries to decrease. After the subsequent aging heat treatment, the precipitation strengthening phase was unevenly distributed in the grain boundaries, the material strengthening effect was weakened, and the mechanical properties, wear resistance and electrical conductivity were all inferior to those of the embodiment.

[0116] As can be seen from Table 3, Examples 1 to 4 all have relatively low power-on temperature rises before and after plugging and unplugging. The power-on temperature rise is still relatively low after 30,000 plugging and unplugging cycles, meeting the requirements.

[0117] like Figure 1As shown in the figure, the copper alloy rod obtained in Example 1 has a fine structure and uniform distribution, and has a significant fine grain strengthening effect. It is also conducive to the precipitation strengthening phase being dispersed and evenly distributed in the grain boundaries. like Figure 2 As shown, the average grain size of the copper alloy rod prepared in Comparative Example 1 is large and the size distribution is uneven. The large-sized grain morphology is not conducive to the uniform dispersion distribution of the subsequent precipitation strengthening phase. The mechanical properties, electrical conductivity and wear resistance of the material are not as good as those of the embodiment.

[0118] like Figure 3 and Figure 4 As shown, the structure of the copper alloy rod prepared in Example 1 has a suitable size of (Ni, Co) Si compound strengthening phase ( Figure 3 The middle arrow marks the (Ni, Co) Si compound strengthening phase) and the Mn5Si3 wear-resistant phase ( Figure 4 The middle arrow mark is the Mn5Si3 wear-resistant phase).

[0119] Table 1 Composition of components in Examples 1-4 and Comparative Examples 1-8 (wt%) Table 2 Microstructure and properties of finished rods of Examples 1-4 Table 3 Properties of finished bars of Examples 1-4 and Comparative Examples 1-8 Table 3 Test performance of the rods of Examples 1-4 and Comparative Examples 1-8 after processing the probe

Claims

1. A copper alloy bar for battery formation testing, characterized in that: The mass percentages of the components of the copper alloy bar are: Ni: 2.2-3.0%, Si: 0.5-0.9%, Co: 0.8-1.2%, Mg: 0.1-0.3%, Nd: 0.001-0.2%, Mn: 0.001-0.1%, X: 0-0.05%, and the balance is Cu and unavoidable impurity elements; Wherein the X element is one or more of Ag, In, B, and Zr; The structure of the copper alloy rod includes a precipitated phase, which includes a (Ni, Co)Si compound strengthening phase and a Mn5Si3 wear-resistant phase. The average size of the (Ni, Co)Si compound strengthening phase is ≤380nm, the area ratio of the (Ni, Co)Si compound strengthening phase is ≥80%, and the average size of the Mn5Si3 wear-resistant phase is ≤3μm.

2. The copper alloy bar for battery formation testing according to claim 1, characterized in that: The distribution of the precipitated phase is 1*10 6 ~8*10 6 Pieces / mm 2 .

3. The copper alloy bar for battery formation testing according to claim 1, characterized in that: The copper alloy rod for battery formation testing has a tensile strength of ≥800 MPa, a conductivity of ≥42% IACS, a hardness of ≥250 HV, an elongation of ≥12%, and an elastic modulus of ≥128 GPa.

4. A method for preparing a copper alloy bar for battery formation testing according to any one of claims 1 to 3, characterized in that: The process flow of the preparation method includes smelting → semi-continuous casting → extrusion → first drawing → heat treatment → finished product drawing; The copper alloy bar for battery formation testing according to any one of claims 1 to 3 is prepared and smelted according to the mass percentage of each component; The extrusion temperature is 850-950° C., the extrusion ratio is 30-200, and the extrusion speed is 5-15 mm / s.

5. The method for preparing the copper alloy bar for battery formation testing according to claim 4, characterized in that: The temperature of the extruded billet after extrusion is 800-920°C, and the extruded billet is cooled after being extruded.

6. The method for preparing the copper alloy bar for battery formation testing according to claim 5, characterized in that: The cooling speed is greater than 100° C. / s.

7. The method for preparing the copper alloy bar for battery formation testing according to claim 4, characterized in that: Vibration is applied during the semi-continuous casting process, and the vibration frequency is 30-80 Hz.

8. The method for preparing the copper alloy bar for battery formation testing according to claim 4, characterized in that: The semi-continuous casting has a casting pulling rate of 30-80 mm / min, a primary cooling water inlet temperature of 20-40° C., a primary cooling water outlet temperature of 35-60° C., a cooling water pressure of 0.6-1.0 MPa, a casting temperature of 1200-1320° C., an ingot outlet temperature of 700-950° C., and adopts secondary cooling to obtain a φ150-260 mm ingot by drawing.

9. The method for preparing the copper alloy bar for battery formation testing according to claim 4, characterized in that: The first drawing process includes multiple passes, and the processing rate of each drawing process is 15-40%.

10. The method for preparing the copper alloy bar for battery formation testing according to claim 4, characterized in that: The heat treatment temperature T is: T=extrusion die temperature / 2+40, the holding time is 2-10 h, and then cooling is performed, and the cooling rate is <5°C / min.

Images