Preparation method of wear-resistant cobalt-based alloy die for punching nickel strips

Abstract

The present invention belongs to the technical field of high-purity nickel strip processing and preparation for the electronics industry, and discloses a method for preparing a wear-resistant cobalt-based alloy mold for punching metal nickel strips. The inventive method uses vacuum induction melting of the cobalt-based alloy, and then uses high-purity nitrogen as the atomization deposition medium to perform double-scanning atomization deposition. After the double-scanning atomization deposition is completed, the cobalt-based alloy deposition blank is raised to the atomization nozzle, and heated nitrogen is blown through the nozzle of the guide tube to the top center of the cobalt-based alloy columnar deposition blank. At the same time, the deposition blank is slowly lowered at a speed of 10 to 15 mm / min. When the surface temperature of the blank is lower than 800°C, the blowing is stopped, and the blank is cooled with the furnace. The obtained deposition blank is heated, forged, and machined to obtain a cobalt-based alloy mold. The method of the present invention helps to improve the wear resistance and service life of the pure nickel strip punching die, improve product quality, and meet the needs of the electronics, energy batteries and other fields.

Description

Technical Field

[0001] The present invention belongs to the technical field of processing and preparing high-purity nickel strips for the electronics industry, and relates to a technology for preparing mold materials for punching pure nickel strips, and specifically to a process for preparing wear-resistant and high-strength cobalt-based alloy molds by double-scanning atomized deposition. Background Art

[0002] Metal nickel strips and foils have good electrical conductivity, as well as antioxidant and corrosion resistance, and are widely used in electronics, petrochemicals and other fields. In recent years, the application areas of strips made of pure nickel have continued to expand, and the demand has also continued to increase. However, in order to meet the final demand, metal nickel strips or foils need to be punched into appropriate sizes using precision dies. Therefore, very high requirements are placed on the die materials used for punching, requiring high strength, good wear resistance, and long life. However, ordinary domestic tool steels cannot meet the long life requirements. After a period of use, the punching accuracy of nickel strip products made of mold steel will drop significantly. Therefore, it is necessary to develop a high-performance die material that is resistant to high temperatures and wear.

[0003] Unlike nickel-based superalloys, cobalt-based superalloys are not strengthened by ordered precipitation phases that are firmly bonded to the matrix, but by carbides distributed in the austenite matrix. Although cobalt-based superalloys lack coherent strengthening phases and have slightly lower medium-temperature strength, they have higher high-temperature strength above 980°C, as well as good thermal fatigue resistance and wear resistance. The carbides in cobalt-based superalloys are mainly MC, M 23 C6 and M6C. In cobalt-based high-temperature alloys, fine M 23 C6 carbide can form eutectic with the matrix. MC carbide particles are too large to have a significant direct effect on dislocations, and thus have little effect on strengthening the alloy. However, fine dispersed carbides have a good strengthening effect. Carbides located on the grain boundaries (mainly M 23 C6) can prevent grain boundary sliding, thereby improving long-term strength. Furthermore, carbides in cobalt-based superalloys exhibit excellent thermal stability. As temperatures rise, carbides aggregate and grow more slowly than the γ phase in nickel-based alloys, and their re-dissolution into the matrix is also at higher temperatures (up to 1100°C). Therefore, the strength of cobalt-based alloys decreases more slowly as temperatures rise. However, cobalt-based superalloys are typically produced using a casting process, which results in severe internal segregation, large carbide size, and segregation, compromising wear resistance. Summary of the Invention

[0004] In response to the problems of poor wear resistance and short service life of dies used for punching pure nickel strips in the electronics field, the present invention proposes a process for preparing wear-resistant and high-strength dies of cobalt-based high-temperature alloys by double-scanning atomized deposition, which helps to increase the service life of pure nickel strip punching dies, improve product quality, and meet the needs of electronics, energy batteries and other fields.

[0005] The object of the present invention is achieved in the following ways:

[0006] A method for preparing a wear-resistant cobalt-based alloy die for punching a metal nickel strip, the method comprising the following steps:

[0007] (1) Ingredients: Take the composition of the cobalt-based wear-resistant alloy punching die, according to the weight percentage of C: 1.4-1.55; Cr:

[0008] 28~32; W: 4.0~5.5; Mo: 1.0~2.5; Si: 1.0~1.5; Mn: 1.0~1.5; Co: the balance;

[0009] (2) Forming furnace: put all the raw materials after batching into the melting crucible of the double nozzle atomization deposition equipment;

[0010] (3) Vacuum induction melting: evacuate the double-nozzle atomizing deposition equipment to a vacuum degree of ≤0.1Pa; power on the vacuum induction melting of the cobalt-based wear-resistant alloy. After the alloy is melted, the temperature range is 1450℃~1500℃, and then the temperature is kept for 10min~15min. Then, the obtained cobalt-based wear-resistant alloy melt is slowly poured into the heated tundish, and the lower part of the tundish is equipped with two atomizing nozzles;

[0011] (4) Double scanning atomization deposition: High-purity nitrogen is used as the atomization deposition medium, and the gas pressure range is 35MPa to 60MPa. The cobalt-based wear-resistant alloy melt is filtered through the ceramic filter of the tundish in the smelting chamber, and then flows to the two atomization nozzles through the guide pipe. It is atomized and deposited by the high-pressure high-purity nitrogen. The cobalt-based wear-resistant alloy melt is atomized and deposited on the depositor rotating in the deposition chamber;

[0012] (5) Slow cooling of the deposited billet: After the double-scan atomization deposition is completed, a cobalt-based alloy deposited billet is obtained. The deposited billet is raised to the atomization nozzle, and high-purity nitrogen is filled into the melting chamber with a nitrogen pressure of 2 bar to 5 bar. At the same time, the deposited billet is kept rotating at a high speed on the depositor and its diameter is kept constant. Nitrogen is blown to the top center of the columnar cobalt-based alloy deposited billet through the nozzle of the guide tube. At the same time, the deposited billet is slowly lowered at a speed of 10 to 15 mm / min. When the surface temperature of the billet is lower than 800°C, the blowing is stopped and the billet is cooled with the furnace;

[0013] (6) Heating the deposited blank: Take out the cobalt-based alloy deposited blank, heat it to 1180°C to 1200°C, and keep it warm for 2h to 3h;

[0014] (7) Forging and machining: Take out the heated deposited blank, forge it into an alloy forging block suitable for the die size, and then machine it into a blanking die.

[0015] Preferably, in step (5), the deposition blank is slowly lowered at a speed of 10 mm / min. The final solidification area of the columnar deposition blank is located slightly above the center of the blank. In comparison, the surface of the cobalt-based alloy deposition blank cools faster, and due to cooling shrinkage, the final solidification area, i.e., the upper center of the blank, is prone to local looseness. The use of a specific controlled cooling method is beneficial to promoting shrinkage compensation of the atomized deposition blank and improving the material density.

[0016] Preferably, in the step (3), the temperature of the heated tundish is 1450°C to 1550°C.

[0017] Preferably, in step (4), the purity of the high-purity nitrogen is ≥99.8%.

[0018] Preferably, in the step (4), both atomizing deposition nozzles have a scanning swing mechanism with a driving frequency of 35 Hz to 100 Hz.

[0019] Preferably, in the step (4), the rotation speed of the depositor is 300 to 400 rpm.

[0020] Preferably, in the step (5), the nitrogen gas is heated to 900° C. to 1000° C. when flowing through the tundish.

[0021] Preferably, in the step (5), when the surface temperature of the blank is between 600°C and 700°C, the blowing is stopped.

[0022] Preferably, in step (5), the rotation speed of the rotary sedimentator is 180 to 240 rpm.

[0023] The wear resistance of cobalt-based superalloys is primarily influenced by contact stress or impact stress on their surfaces. Under stress, surface wear is determined by the flow of dislocations and the interaction characteristics of the contact surfaces. This behavior is related to the low stacking fault energy of the matrix and the transformation of the matrix structure from a face-centered cubic to a hexagonal close-packed crystal structure under stress or temperature. Furthermore, the content, morphology, and distribution of secondary phases, such as carbides, in cobalt-based alloys also influence wear resistance. Evenly distributed carbides contribute to improved wear resistance.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. A double-scanning atomization deposition method is used, and high-purity nitrogen is used as the atomization deposition medium to prepare a cobalt-based wear-resistant alloy with high carbide. The nitrogen gas pressure range used is 35MPa~60MPa. Both atomization deposition nozzles have a scanning swing mechanism with a driving frequency of 35HZ~100HZ, so that the prepared cobalt-based wear-resistant alloy has a uniform composition and a dispersed distribution of carbides.

[0026] 2. After the dual-scan atomization deposition process is complete, the cobalt-based alloy deposition blank is raised to the atomization nozzle. Heated nitrogen gas is blown through the nozzle of the guide tube toward the top center of the columnar cobalt-based alloy deposition blank. The nitrogen gas is heated to approximately 900°C to 1000°C as it flows through the tundish. Simultaneously, the deposition blank is slowly lowered at a speed of 10 mm / min and cooled. When the blank surface temperature falls below 800°C, the gas blowing is stopped and the blank is cooled in the furnace. This specific slow cooling method for the atomized deposition blank and the controlled cooling rate facilitate shrinkage compensation of the atomized deposition blank and improve the material density.

[0027] Therefore, the process of preparing cobalt-based high-temperature alloy wear-resistant and high-strength molds by double-scanning atomized deposition provided by the present invention solves the problems of poor wear resistance and short service life of molds used for punching pure nickel strips in the electronics field, helps to increase the service life of pure nickel strip punching molds, improve product quality, and meet the needs of electronics, energy batteries and other fields. DETAILED DESCRIPTION

[0028] The present invention is further explained below by means of specific examples:

[0029] Example 1:

[0030] Based on the requirements for punching dies for pure nickel strip and foil, a cobalt-based wear-resistant alloy punching die was selected with the following specific composition (by weight percentage): C: 1.4; Cr: 28; W: 4.0; Mo: 1.0; Si: 1.0; Mn: 1.0; and Co: 63.6. Based on the alloy composition and the crucible capacity of the melting equipment, 500 kg of raw materials were batched. All the prepared raw materials were placed in the melting crucible of a dual-nozzle atomization deposition system, which was then evacuated to a vacuum of 0.05 Pa. The cobalt-based wear-resistant alloy was then melted using vacuum induction melting. After the alloy was melted, the temperature was measured at 1450°C and held at that temperature for 10 minutes to achieve uniform composition and temperature within the induction furnace. The molten alloy was then slowly poured into a heated tundish, the lower portion of which contained two atomizing nozzles. The heated tundish temperature is 1450°C. High-purity nitrogen (99.8%) is used as the atomization deposition medium, with a gas pressure range of 35 MPa. Both atomization deposition nozzles feature a scanning oscillation mechanism driven at a 35 Hz frequency. The cobalt-based alloy molten metal is filtered through a ceramic filter within the tundish before flowing through a flow guide tube to two nozzles, where it is atomized and deposited by the high-pressure nitrogen. The atomized cobalt-based superalloy melt is deposited onto a rotating depositor within the deposition chamber at a speed of 300 rpm. After atomization, the deposited billet is raised to the atomization nozzle, and high-purity nitrogen (99.8%) is introduced into the melting chamber at a pressure of 2 bar. While the billet rotates and its diameter remains constant on the depositor, the nitrogen is blown through the nozzles of the flow guide tube toward the top center of the cobalt-based alloy columnar billet. The nitrogen is heated to 900°C as it flows through the tundish. At the same time, the deposition blank is slowly lowered at a speed of 10 mm / min. When the surface temperature of the blank reaches 600°C, the air blowing is stopped and the blank is cooled with the furnace. After the atomization deposition is completed, the cobalt-based alloy deposition blank is taken out and placed in a heating furnace for heating to 1180°C and kept warm for 2 hours. The heated deposition blank is taken out and forged into a forging block suitable for the die size. The cobalt-based high-temperature alloy forging block is machined to prepare a punching die.

[0031] The wear-resistant cobalt-based alloy prepared in this embodiment has a bulk density of 8.51 g / cm 3 , the friction coefficient is 0.0032 (the wear resistance is tested using a vertical friction and wear tester, with the pressure set to 98N and the speed set to 300 rpm).

[0032] Example 2:

[0033] Based on the material requirements for punching dies for pure nickel strip and foil, a cobalt-based wear-resistant alloy punching die was designed. The specific composition (by weight percentage) is C: 1.55; Cr: 32; W: 5.5; Mo: 2.5; Si: 1.5; Mn: 1.5; and Co: 55.45. The ingredients were prepared based on the alloy composition and the crucible capacity of the melting equipment. All the raw metals, prepared according to the alloy composition, were placed in the melting crucible of a dual-nozzle atomization deposition system. The dual-nozzle atomization deposition system was evacuated to a vacuum of 0.1 Pa, and power was applied to vacuum induction melting of the cobalt-based wear-resistant alloy. After melting, the alloy was measured at a temperature of 1500°C and held at that temperature for 15 minutes to achieve uniform composition and temperature within the induction furnace. The alloy was then slowly poured into a heated tundish with two atomizing nozzles at the bottom. The heated tundish temperature was 1550°C. High-purity nitrogen was used as the atomization deposition medium, with a gas pressure range of 60 MPa. Both atomizing nozzles feature a scanning and oscillating mechanism driven at a frequency of 100 Hz. After being filtered through a ceramic filter within the tundish, the cobalt-based alloy melt flows through a draft tube to the two nozzles, where it is atomized and deposited by high-pressure nitrogen. The atomized cobalt-based superalloy melt is deposited onto a rotating depositor within the designed deposition chamber at a speed of 400 rpm. After atomization, the deposited billet is raised to the atomizing nozzles, and high-purity nitrogen (≥99.8%) is introduced into the melting chamber at a pressure of 5 bar. While the billet rotates at a high speed of 240 rpm on the depositor, its diameter remains constant. Nitrogen is blown through the draft tube nozzles toward the top center of the cobalt-based alloy columnar billet. The nitrogen is heated to 1000°C as it flows through the tundish. At the same time, the deposition blank is slowly lowered at a speed of 10 mm / min. When the surface temperature of the blank reaches 700°C, the air blowing is stopped and the blank is cooled with the furnace. After the atomization deposition is completed, the cobalt-based alloy deposition blank is taken out and placed in a heating furnace for heating to 1200°C and kept warm for 3 hours. The heated deposition blank is taken out and forged into a forging block suitable for the mold size. The cobalt-based high-temperature alloy forging block is machined to prepare a punching mold.

[0034] The bulk density of the wear-resistant cobalt-based alloy in this embodiment is 8.42 g / cm 3 , the friction coefficient reaches 0.0036, (the wear resistance is tested using a vertical friction and wear tester, the pressure is set to 98N, and the speed is 300 rpm).

[0035] Comparative Example 1

[0036] The remaining steps and conditions are the same as those in Example 1, except that a single nozzle atomization deposition device is used, and the single atomization deposition nozzle does not have a scanning swing mechanism. The cobalt-based alloy product obtained in this example has a bulk density of 8.23 g / cm 3; Friction coefficient 0.0062. (A vertical friction and wear tester was used to test the wear resistance, with the pressure set to 98N and the speed set to 300 rpm) Comparative Example 2

[0037] The remaining steps and conditions are the same as those in Example 1, except that after the atomized deposition is completed, the atomized deposition ingot is directly deposited and cooled, and air is blown until the ingot cools with the furnace. The cobalt-based alloy product obtained in this example has a bulk density of only 7.91 g / cm 3 .

[0038] Generally, the friction coefficient of H3 mold steel is 0.128, the friction coefficient of C12MoV mold steel is 0.313, the friction coefficient of H13 mold steel is 0.323, and the bulk density is 7.85g / cm 3 .

[0039] It can be seen that the wear-resistant life of the cobalt-based wear-resistant alloy obtained by the method of the present invention is significantly improved.

Claims

1. A method for preparing a wear-resistant cobalt-based alloy die for punching nickel strips, characterized in that The method comprises the following steps: (1) Ingredients: Take the composition of the cobalt-based wear-resistant alloy blanking die, according to the weight percentage: C: 1.4-1.55; Cr: 28-32; W: 4.0-5.5; Mo: 1.0-2.5; Si: 1.0-1.5; Mn: 1.0-1.5; Co: the remaining ingredients; (2) Furnace loading: Place all the raw materials after batching into the melting crucible of the double nozzle atomization deposition equipment; (3) Vacuum induction melting: evacuate the double-nozzle atomizing deposition equipment to a vacuum degree of ≤0.1Pa; power on the vacuum induction melting of the cobalt-based wear-resistant alloy. After the alloy is melted, the temperature range is 1450℃~1500℃, and then the temperature is kept for 10min~15min. Then, the obtained cobalt-based wear-resistant alloy melt is slowly poured into the heated tundish, and the lower part of the tundish is equipped with two atomizing nozzles; (4) Double scanning atomization deposition: High-purity nitrogen is used as the atomization deposition medium, and the gas pressure range is 35MPa~60MPa. The cobalt-based wear-resistant alloy melt is filtered through the ceramic filter of the tundish in the smelting chamber, and then flows to the two atomization nozzles through the guide pipe. It is atomized and deposited by the high-pressure high-purity nitrogen. The cobalt-based wear-resistant alloy melt is atomized and deposited on the depositor rotating in the deposition chamber; both atomization deposition nozzles have a scanning swing mechanism, and the driving frequency is 35HZ~100HZ; (5) Slow cooling of the deposited billet: After the double-scanning atomization deposition is completed, the cobalt-based alloy deposited billet is obtained. The deposited billet is raised to the atomization nozzle, and high-purity nitrogen is filled into the melting chamber with a nitrogen pressure of 2 bar to 5 bar. At the same time, the deposited billet is kept rotating at a high speed on the depositor and the diameter is kept unchanged. The nitrogen is blown to the top center of the columnar cobalt-based alloy deposited billet through the nozzle of the guide tube. At the same time, the deposited billet is slowly lowered at a speed of 10 mm / min. When the surface temperature of the billet is lower than 800 ° C, the blowing is stopped and the billet is cooled with the furnace; the nitrogen is heated to 900 ° C to 1000 ° C when it flows through the tundish; (6) Heating the deposited billet: Take out the cobalt-based alloy deposited billet, heat it to 1180℃~1200℃, and keep it warm for 2h~3h; (7) Forging and machining: Take out the heated deposited blank, forge it into an alloy forging block suitable for the die size, and then machine it into a blanking die.

2. The method for preparing a wear-resistant cobalt-based alloy die for punching a metal nickel strip according to claim 1, characterized in that In the step (3), the temperature of the heated tundish is 1450°C to 1550°C.

3. The method for preparing a wear-resistant cobalt-based alloy die for punching a metal nickel strip according to claim 1, characterized in that In the step (4), the purity of the high-purity nitrogen is ≥99.8%.

4. The method for preparing a wear-resistant cobalt-based alloy die for punching a metal nickel strip according to claim 1, characterized in that In the step (4), the rotation speed of the depositor is 300 to 400 rpm.

5. The method for preparing a wear-resistant cobalt-based alloy die for punching a metal nickel strip according to claim 1, characterized in that In the step (5), the high-speed rotation adopts a rotation speed of 180 to 240 rpm.

6. The method for preparing a wear-resistant cobalt-based alloy die for punching a metal nickel strip according to claim 1, characterized in that In the step (5), when the surface temperature of the green body is between 600°C and 700°C, the air blowing is stopped.