A method for preparing outer circle of copper-chromium contact blank

Abstract

The invention discloses a method for preparing the outer circle of a copper-chromium contact blank, comprising S1, material preparation, S2, clamping, and S3, processing. The invention utilizes an integrated one-time clamping processing technology to process the outer circle of a CuCr alloy bar, which can greatly improve the problem of error in the outer circle dimensional accuracy of the bar and the problem of long processing time caused by positioning requiring secondary clamping due to a taper problem. The invention can also effectively reduce the manual secondary loading and unloading clamping process, reduce labor costs, and realize the processing of the entire bar by clamping once.

Description

Technical Field

[0001] The invention relates to the technical field of metal processing, in particular to a method for preparing the outer circle of a copper-chromium contact blank. Background Art

[0002] This invention proposes a highly efficient method for producing the outer diameter of CuCr contact blanks. This method utilizes a highly automated, integrated loading and unloading process with a clamping mechanism to perform a stable, one-time cutting process of CuCr alloy bars in batches. Compared to existing methods, this method significantly improves processing efficiency, significantly reduces manual steps, and simplifies the operation principle of the equipment.

[0003] The main steps in preparing copper-chromium contacts are annealing, turning the outer diameter, sawing the polished sheet, and then machining the finished product. This complex process requires high labor costs and repeated disassembly and clamping. The most difficult part is the loading, unloading, and clamping process for turning the outer diameter. After clamping on the machine tool chuck, the bar stock is turned. However, due to varying clamping volumes and the varying lengths of the forged ingots, the bar stock exhibits a significant taper during the turning process, making it impossible to turn the entire bar in one go. This requires manual secondary clamping. The consequences are: 1) The large taper of the bar stock causes a discrepancy between the outer diameter of the blank and the pre-prepared tooling during the subsequent finished product processing, impacting subsequent automated robotic clamping and causing the blank to fly out and become scrapped under high-speed conditions during machining. 2) Secondary clamping has two disadvantages: first, the bar stock itself is heavy, resulting in high labor costs for the clamping process; second, the diameter of the same bar stock needs to be turned twice, which involves many human-controlled variables. This makes errors more likely to occur. At the same time, the main application direction of CuCr contact material is the field of electric vacuum switches. It is a material that requires good electrical conductivity, thermal conductivity and breaking performance. Therefore, the Cr particles in the CuCr alloy are required to be dispersed and evenly distributed in the Cu matrix. However, copper has low hardness and strong toughness; chromium has high hardness and high brittleness, which leads to less than ideal process performance of the material.

[0004] In order to improve the accuracy of the bar processing process, reduce the labor cost of the process, and ensure the production qualification rate of this process and subsequent related processes, a highly automated and integrated method for efficiently preparing the outer circle of CuCr contact blanks is proposed. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing the outer circle of a copper-chromium contact blank.

[0006] The technical solution of the present invention is: a method for preparing the outer circle of a copper-chromium contact blank, comprising the following steps:

[0007] S1. Prepare materials

[0008] The copper-chromium forging ingot is placed on a horizontal platform, and cutting fluid is sprayed at the cutting positions at both ends at a pressure of 1-3 MPa and a flow rate of 10-15 mL / s. The end faces are then sawed with a grinding wheel until the end faces are horizontal. The grinding wheel saw feed rate is 0.01-0.02 mm / time, and the total feed rate must be ≤30 mm. Finally, the surface of the copper-chromium forging ingot after sawing is deburred to obtain a processed bar.

[0009] S2. Clamping

[0010] A three-jaw self-centering chuck is mounted on one end of the processing bar stock. The processing bar stock obtained in step S1 is clamped by a manipulator, and the end mounted with the three-jaw self-centering chuck is pressed against the top of the driving shaft. The driven shaft is moved so that the retractable top of the driven shaft moves along the guide rail toward the driving shaft until it is pressed against the other end of the processing bar stock.

[0011] S3. Processing

[0012] Adjust the position of the cutting shaft to be level with one end of the processing bar sleeve equipped with a three-jaw self-centering chuck, turn on the driving shaft, and then move the cutting shaft along the direction of the driven shaft. Adjust the cutting speed of the cutting shaft to 10m / min, the back cutting amount to 0.05-0.3mm, and the feed rate to 0.02-0.1mm / r. Use the processing tool on the cutting shaft to cut the outer circle of the processing bar to the target specification, use a robot to take out the processing bar to obtain the outer circle of the copper-chromium contact blank.

[0013] Description: The present invention adopts a centering chuck to effectively reduce the contact area between the end face of the processed bar and the active shaft, avoiding the formation of bending torque during clamping. The thermal deformation of the slender shaft of the ingot is large, and it will produce a large expansion under the action of cutting heat. The fixed supports at both ends of the shaft will be squeezed and bent. When the shaft rotates at high speed, the high centrifugal force will aggravate the deformation of the shaft; and setting the cutting shaft to move in the direction of the driven shaft can effectively reduce the cutting force; at high cutting speeds, by adjusting the back cutting amount and feed rate, the heat, built-up edge and residual area in the cutting process can be effectively reduced, so that the parts can obtain higher precision and surface quality.

[0014] Furthermore, after step S3, the outer circle of the copper-chromium contact blank is subjected to secondary processing;

[0015] The secondary processing steps are as follows: first, polishing the processed bar for 1.5 to 5 minutes, then ultrasonically cleaning it with deionized water for 5 to 8 minutes, taking it out and drying it in a vacuum drying oven at 80 to 120° C. for 3 to 5 minutes, and finally using an inert gas with a volume concentration of 99.99% to blow away the debris on the surface of the processed bar until the surface is clean;

[0016] The polishing method comprises: immersing the processed rod material in a container filled with a composite polishing liquid at a temperature of 45 to 55° C., placing the processed rod material in an ultrasonic magnetic field for reaction for 0.5 to 3 minutes, then adding a dispersant obtained by mixing polyoxyethylene ether and carboxyethyl thiosuccinic acid in a ratio of 1:1 to the container, and continuing the ultrasonic reaction for 1.0 to 4.5 minutes; the volume concentration ratio of the dispersant to the composite polishing liquid is 0.3 to 0.5:1.

[0017] Description: Secondary processing of the outer circle of the copper-chromium contact blank can fully ensure that the cleanliness of the copper-chromium contact surface is further improved. Immersing the polishing liquid under the action of the ultrasonic magnetic field can effectively remove stubborn surface contaminants on the outer circle of the copper-chromium contact blank. The added dispersant can simultaneously disperse and clean and promote the precipitation of surface contaminants, thereby achieving further treatment of the copper-chromium contact surface; drying after ultrasonic cleaning with deionized water can completely clean the composite polishing liquid, avoid the residual polishing liquid on the contact surface causing harm to the operator, and reduce environmental pollution; using inert gas to purge the surface of the processed bar can effectively reduce the processing debris on the surface of the bar. At the same time, the use of inert gas can prevent the metal from reacting with oxygen or other gases in the active gas, thereby affecting the composition of the contact material.

[0018] Furthermore, the inert gas is any one of nitrogen, argon and helium;

[0019] Note: Using the above-mentioned inert gas for purging can efficiently and continuously purge and clean the dried debris on the surface of the contact material, thereby avoiding acidification of the contact material surface.

[0020] Furthermore, the composite polishing liquid comprises the following components: 2 to 3 parts of sodium hexametaphosphate, 5 to 20 parts of brown corundum abrasive, 2 to 3 parts of imidazoline sodium oleate, 2 to 3 parts of hydroxyethylidene diphosphonic acid, and 15 to 20 parts of deionized water;

[0021] Description: Brown corundum abrasive is an abrasive with good wear resistance and high durability. Adding it to the composite polishing liquid can effectively improve the surface finish of the copper-chromium contact; sodium hexametaphosphate can improve the water retention of the polishing liquid and increase the adhesion between the components, thereby promoting the polishing effect; sodium imidazoline oleate can disperse the sodium hexametaphosphate with oil, which can accumulate and precipitate surface impurities, thereby improving the brightness of the copper-chromium contact surface; hydroxyethylidene diphosphonic acid as a corrosion inhibitor can improve the corrosion resistance of metal materials.

[0022] Furthermore, in step S1, the cutting fluid comprises the following components by mass percentage: 2.0-3.0% of monolaurin, 3.5-4.5% of triethanolamine, 2.5-3.0% of sodium phosphate, 1.0-2.0% of benzotriazole, 0.05-0.1% of silicone defoamer, and the balance of water;

[0023] Description: The cutting fluid prepared by the above formula has good cleaning and penetrating effects, can effectively improve the cutting force of the tool, prevent the tool from being passivated, and is friendly to the tool, effectively extending the service life of the tool; the combined addition of triethanolamine and silicone defoaming agent can effectively reduce the retention of foam, so that the debris on the surface of the copper-chromium contact adheres to the foam and falls off faster; the addition of benzotriazole can play a protective role, ensuring that the surface of the copper-chromium material does not undergo oxidation reaction under the high heat during the cutting process; the addition of monolaurin can effectively improve the smoothness of the material surface, and also play a cooling role, reducing surface scratches caused by excessive cutting speed, thereby improving the smoothness of the copper-chromium material; this formula does not contain harmful ingredients, is operator-friendly, and non-irritating to the skin.

[0024] Furthermore, in step S1, the standard for the horizontality of the end surface of the processed bar is: the end surface flatness is not greater than 0.001 mm, and the roughness is 0.8 to 1.2 μm;

[0025] Note: By limiting the flatness and roughness of the end face, the accuracy of the copper-chromium contact parts can be improved, and it is also easier to clamp the driving shaft and the driven shaft.

[0026] Furthermore, in step S1, the deburring process includes the following steps: spraying a sand powder mixture onto the surface of the sawn copper-chromium ingot using a high-pressure spray gun, then continuously blowing the surface of the copper-chromium ingot with compressed air for 0.5 to 3 minutes, and finally wiping it with cotton cloth for standby use; the spraying time is 3 to 5 minutes, and the spraying air pressure of the high-pressure spray gun is 1.0 to 2.2 L / cm2;

[0027] Note: Spraying a sand powder mixture on the surface of the copper-chromium forging ingot with a high-pressure spray gun, blowing with compressed air, and wiping with cotton cloth can reduce processing waste caused by differences in burrs and further improve processing efficiency.

[0028] Furthermore, the sand powder mixture is a mixture of resin sand, fumed aluminum oxide and deionized water in a ratio of 1-1.5:0.3-0.5:1-1.5.

[0029] Note: The addition of vapor-phase alumina can help flow, increase the fluidity of the sand powder mixture on the surface of the copper-chromium contact, and thus improve the burr cleaning efficiency; at the same time, the addition of vapor-phase alumina can dehydrate and adsorb the residual organic solvent in the cutting fluid, play a further treatment role, and avoid the influence of residual organic solvent on subsequent processing.

[0030] Furthermore, the machining tool is a blade made of any one of diamond, cubic boron nitride, and ceramic.

[0031] Note: The above materials used for machining tools have the characteristics of high hardness, good wear resistance and strong thermal stability.

[0032] The beneficial effects of the present invention are:

[0033] (1) The present invention utilizes an integrated one-time clamping processing technology to process the outer diameter of the CuCr alloy bar, which can greatly improve the problem of bar outer diameter size accuracy error and time-consuming positioning caused by the need for secondary clamping due to the taper problem. It can also effectively reduce the manual secondary loading and unloading clamping process, reduce labor costs, and achieve one-time clamping to complete the processing of the entire bar.

[0034] (2) The present invention not only ensures that the consistency of the ends of the processed bar is maintained within a range of no more than 0.1 / 1000mm, and the outer diameter accuracy of the turning is within ±0.1, but also improves the processing efficiency, reduces the manual operation process, and greatly improves the unstable factor of the outer diameter of the finished contact of the alloy bar in the automated batch processing process. Compared with the original process, the processing efficiency of the present invention is improved by nearly 40%.

[0035] (3) The present invention adopts a centering chuck to effectively reduce the contact area between the end face of the processed bar and the driving shaft, avoiding the formation of bending torque during clamping. By arranging a retractable center on the driven shaft, it can effectively avoid the problem that the chuck cannot be clamped or flies out during the processing after clamping; and the present invention arranges the cutting shaft to move along the direction of the driven shaft, which can effectively reduce the deformation effect of the copper-chromium ingot under the cutting force by using reverse feed. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of components during the cutting process of the present invention.

[0037] Among them, 1-driving axis, 2-cutting axis, 3-driven axis, 4-guide rail, 5-processing bar. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below in conjunction with specific implementation methods to better demonstrate the advantages of the present invention.

[0039] Example 1

[0040] like Figure 1 As shown, a method for preparing the outer circle of a copper-chromium contact blank comprises the following steps:

[0041] S1. Prepare materials

[0042] A copper-chromium forged ingot was placed on a horizontal platform, and cutting fluid was sprayed at both cutting ends at a pressure of 2 MPa and a flow rate of 13 mL / s. The end faces were then sawed with a grinding wheel until the end faces were horizontal. The grinding wheel saw feed rate was 0.015 mm / time, and the total feed rate was 15 mm. Finally, the surface of the sawed copper-chromium forged ingot was deburred to obtain a processed bar 5. The cutting fluid comprised the following components by mass percentage: 2.5% monolaurin, 4.0% diethylene glycol, 2.7% sodium phosphate, 1.5% benzotriazole, 0.08% silicone defoamer, and the balance water.

[0043] The standards for machining the end surface of bar 5 are: end surface flatness is 0.0008mm, roughness is 1.0μm;

[0044] The deburring process includes the following steps: spraying a sand powder mixture onto the surface of the sawn copper-chromium ingot through a high-pressure spray gun, then continuously blowing the surface of the copper-chromium ingot with compressed air for 1.5 minutes, and finally wiping it with cotton cloth for later use; the spraying time is 4 minutes, and the spray pressure of the high-pressure spray gun is 1.5L / cm 2 ;

[0045] The sand powder mixture is a mixture of resin sand, fumed aluminum oxide and deionized water in a ratio of 1.3:0.4:1.3;

[0046] S2. Clamping

[0047] A three-jaw self-centering chuck is mounted on one end of the processing bar 5. The processing bar 5 obtained in step S1 is clamped by a manipulator, and one end of the processing bar 5 mounted with the three-jaw self-centering chuck is pressed against the top of the driving shaft 1. The driven shaft 3 is moved so that the retractable top on the driven shaft 3 moves along the guide rail 4 toward the driving shaft 1 until it is pressed against the other end of the processing bar 5.

[0048] S3. Processing

[0049] The cutting shaft 2 is adjusted to be level with one end of the processing bar 5 provided with a three-jaw self-centering chuck, the driving shaft 3 is turned on, and then the cutting shaft 2 is moved in the direction of the driven shaft 3. The cutting parameters of the cutting shaft 2 are adjusted as follows: cutting speed of 10 m / min, back cutting depth of 0.15 mm, and feed rate of 0.08 mm / r. The outer diameter of the processing bar 5 is cut to the target specification using the processing tool on the cutting shaft 2. The processing bar 5 is removed by a manipulator to obtain the outer diameter of the copper-chromium contact blank.

[0050] The cutting shaft is made of diamond material;

[0051] Perform secondary processing on the outer circle of the copper-chromium contact blank;

[0052] The secondary processing steps are as follows: first, the processed bar is polished for 2 minutes, then ultrasonically cleaned with deionized water for 7 minutes, removed and placed in a vacuum drying oven at 100°C for 4 minutes, and finally, the surface of the processed bar is purged of debris with an inert gas with a volume concentration of 99.99% until the surface is clean;

[0053] The polishing method comprises: immersing the processed rod in a container filled with a composite polishing liquid at a temperature of 50° C. and placing it in an ultrasonic magnetic field for reaction for 0.5 minutes, then adding a dispersant prepared by mixing polyoxyethylene ether and carboxyethyl thiosuccinic acid in a ratio of 1:1 to the container, and continuing the reaction for 1.5 minutes; the volume concentration ratio of the dispersant to the composite polishing liquid is 0.4:1;

[0054] Wherein, nitrogen is used as the inert gas;

[0055] The composite polishing liquid includes the following components: 2 parts of sodium hexametaphosphate, 10 parts of brown corundum abrasive, 2 parts of imidazoline sodium oleate, 2 parts of hydroxyethylidene diphosphonic acid, and 17 parts of deionized water.

[0056] Example 2

[0057] The difference from Example 1 is that in step S1, cutting fluid is sprayed toward the cutting points at both ends at a pressure of 1 MPa and a flow rate of 10 mL / s.

[0058] Example 3

[0059] Different from Example 1, in step S1, cutting fluid is sprayed toward the cutting points at both ends at a pressure of 3 MPa and a flow rate of 15 mL / s.

[0060] Example 4

[0061] The difference from Example 1 is that in step S1, the feeding amount of the grinding wheel saw is 0.01 mm / time, and the total feeding amount is 15 mm.

[0062] Example 5

[0063] The difference from Example 1 is that in step S1, the feeding amount of the grinding wheel saw is 0.03 mm / time, and the total feeding amount is 15 mm.

[0064] Example 6

[0065] Different from Example 1, in step S1, the cutting fluid includes the following components in percentage by mass: 2.0% of monolaurin, 3.5% of diethylene glycol, 2.5% of sodium phosphate, 1.0% of benzotriazole, 0.05% of silicone defoamer, and the balance of water.

[0066] Example 7

[0067] Different from Example 1, in step S1, the cutting fluid includes the following components in percentage by mass: 3.0% of monolaurin, 4.5% of diethylene glycol, 3.0% of sodium phosphate, 2.0% of benzotriazole, 0.1% of silicone defoamer, and the balance of water.

[0068] Example 8

[0069] The difference from Example 1 is that in step S1 , the standards for processing the end surface of the bar 5 to be level are: the end surface flatness is 0.0008 mm, and the roughness is 0.8 μm.

[0070] Example 9

[0071] The difference from Example 1 is that in step S1 , the standards for processing the end surface of the bar 5 to be level are: the end surface flatness is 0.0008 mm, and the roughness is 1.2 μm.

[0072] Example 10

[0073] The difference from Example 1 is that in step S1, the sand powder spraying parameters in the deburring process are: the spraying time is 3 minutes, the spraying air pressure of the high-pressure spray gun is 1.0 L / cm 2 .

[0074] Example 11

[0075] The difference from Example 1 is that in step S1, the sand powder spraying parameters in the deburring process are: spraying time is 5 minutes, the spraying air pressure of the high-pressure spray gun is 2.2L / cm 2 .

[0076] Example 12

[0077] Different from Example 1, in step S1, the sand powder mixture in the deburring process is a mixture of resin sand, fumed alumina and deionized water in a ratio of 1:0.3:1.

[0078] Example 13

[0079] Different from Example 1, in step S1, the sand powder mixture in the deburring process is a mixture of resin sand, fumed alumina and deionized water in a ratio of 1.5:0.5:1.5.

[0080] Example 14

[0081] Different from Example 1, in step S3, the cutting parameters of the cutting shaft 2 are adjusted as follows: cutting speed of 10 m / min, back cutting depth of 0.05 mm, and feed rate of 0.02 mm / r.

[0082] Example 15

[0083] Different from Example 1, in step S3, the cutting parameters of the cutting shaft 2 are adjusted as follows: cutting speed of 10 m / min, back cutting depth of 0.3 mm, and feed rate of 0.1 mm / r.

[0084] Example 16

[0085] The difference from Example 1 is that secondary processing is performed after step S3. The steps of the secondary processing are: first, the processed rod is polished for 1.5 minutes, then ultrasonically cleaned with deionized water for 5 minutes, taken out and placed in a vacuum drying furnace at 80°C for 5 minutes, and finally, the surface of the processed rod is purged of debris with an inert gas with a volume concentration of 99.99% until the surface is clean.

[0086] Example 17

[0087] The difference from Example 1 is that secondary processing is performed after step S3. The steps of the secondary processing are: first, the processed rod is polished for 5 minutes, then ultrasonically cleaned with deionized water for 8 minutes, taken out and placed in a vacuum drying furnace at 120°C for 3 minutes, and finally, the surface of the processed rod is purged of debris with an inert gas with a volume concentration of 99.99% until the surface is clean.

[0088] Example 18

[0089] The difference from Example 1 is that secondary processing is performed after step S3. The composite polishing liquid used for the secondary processing includes the following components: 2 parts of sodium hexametaphosphate, 5 parts of brown corundum abrasive, 2 parts of imidazoline sodium oleate, 2 parts of hydroxyethylidene diphosphonic acid, and 15 parts of deionized water.

[0090] Example 19

[0091] The difference from Example 1 is that secondary processing is performed after step S3. The composite polishing liquid used for the secondary processing includes the following components: 3 parts of sodium hexametaphosphate, 20 parts of brown corundum abrasive, 3 parts of imidazoline sodium oleate, 3 parts of hydroxyethylidene diphosphonic acid, and 20 parts of deionized water.

[0092] Control Example

[0093] Comparative Example 1: General turning: Place the bar on the lathe, clamp the outer diameter of one end with the chuck, and the other end is based on the length of the bar. While ensuring the taper, determine whether to add a tailstock at the tail for auxiliary tightening processing;

[0094] Comparative Example 2: Different from Example 1, the cutting fluid does not contain monolaurin.

[0095] Comparative Example 3: Different from Example 1, the deburring process includes: directly using compressed air to continuously blow the surface of the copper-chromium forging ingot for 1.5 minutes, and finally wiping it with cotton cloth.

[0096] Comparative Example 4: Different from Example 1, the sand powder mixture is a mixture of resin sand and deionized water in a ratio of 1.3:1.3.

[0097] Comparative Example 5: Unlike Example 1, no secondary processing is performed.

[0098] Comparative Example 6: Different from Example 1, the composite polishing liquid includes the following components: 2 parts of sodium hexametaphosphate, 2 parts of hydroxyethylidene diphosphonic acid, and 17 parts of deionized water.

[0099] Experimental example

[0100] 1. Explore the impact of processing methods on processing efficiency and taper

[0101] Batch processing of copper-chromium contacts was performed according to the methods of Example 1 and Comparative Example 1 of the present invention. Taper tests were performed on the left, middle, and right three measuring points of 10 bars with a specification of Φ53×(700-800) at random. The processing efficiency was also measured. The taper test data are shown in Table 1:

[0102] Table 1 Test table of the taper of the copper-chromium contacts prepared in Example 1 and Comparative Example 1

[0103]

[0104] The processing efficiency of general turning is 15 pieces / h; the processing efficiency of the present invention's processing method of early preparation + later integration is statistically 20 pieces / h.

[0105] Conclusion: It can be seen from the data in Table 1 that the taper of the copper-chromium contact prepared by this method is closer to the required Φ53 processing requirement, while the taper of the copper-chromium contact prepared by the general turning processing method in Control Example 1 deviates slightly from the required Φ53 compared with the present invention. The present invention significantly improves the accuracy of the bar processing process, and the products produced are more qualified.

[0106] 2. Investigate the influence of cutting fluid components on the performance of copper-chromium contact materials

[0107] The copper-chromium contact materials prepared in Example 1, Example 6, Example 7 and Comparative Example 2 were respectively taken and performance tests were performed. The results are shown in Table 2:

[0108] Table 2 Performance test table of copper-chromium contacts of Example 1, Examples 6-7 and Comparative Example 2

[0109]

[0110] Conclusion: From the data in Table 2, it can be seen that the components of the cutting fluid have a certain influence on the roughness of the copper-chromium contact end face, and it is confirmed that the addition of monolaurin to the cutting fluid can reduce the smoothness of the end face, thereby affecting the processing accuracy of the product; the components of the cutting fluid have little effect on the performance of the copper-chromium contact.

[0111] 3. Investigate the effects of deburring process parameters, methods, and sand powder mixture composition on the performance of copper-chromium contact materials

[0112] The copper-chromium contact materials prepared in Example 1, Examples 10 to 13, and Comparative Example 3 were respectively taken and subjected to performance tests. The results are shown in Table 3:

[0113] Table 3 Performance test table of copper-chromium contacts prepared in Example 1, Examples 10-13, and Comparative Examples 3 and 4

[0114]

[0115]

[0116] Conclusion: From the data in Table 3, it can be seen that the deburring process can effectively remove the chips after the copper-chromium contact is cut, and the contact has good conductivity. In Control Example 3, no high-pressure spray gun was used to spray the sand powder mixture onto the surface of the copper-chromium ingot after sawing. It can be seen that the chips have an impact on the performance of the copper-chromium contact, which reduces the conductivity of the copper-chromium contact to a certain extent. In Control Example 4, no gaseous alumina was added to the sand powder mixture, resulting in poor fluidity of the sand powder, thereby causing the burr treatment effect on the surface of the copper-chromium contact to deteriorate. At the same time, from the surface roughness of Control Examples 3 and 4, it can be seen that the jet grinding of the sand powder mixture and the sand powder mixture with stronger fluidity can further improve the improvement of the surface roughness of the copper-chromium contact.

[0117] 4. Investigate the influence of secondary processing on the qualified rate of the outer circle of copper-chromium contact blanks

[0118] Copper-chromium contacts were batch-processed according to the preparation methods of Example 1 and Comparative Example 5, and the taper test was performed on the left, middle, and right three measurement points of 10 bars with a specification of Φ53×(700-800) at random. If the average taper value at the three points was between 52.9 and 53.1, it was judged to be qualified, and if it was out of the range, it was judged to be unqualified. The qualified rate data are shown in Table 4:

[0119] Table 4 Qualified rate measurement table of Example 1 and Comparative Example 5

[0120] Group Pass rate Example 1 98.9％ Comparative Example 5 95.1％

[0121] Conclusion: From the data in Table 4, it can be seen that the qualified rate of the first processing of the control example 5 is slightly lower than that of the embodiment 1. Therefore, it can be concluded that the secondary processing of the embodiment 1 can greatly improve the compliance rate of the copper-chromium contact, thereby improving the preparation efficiency of the outer circle of the copper-chromium contact blank.

[0122] 5. Investigate the influence of the composition of composite polishing liquid on the performance of copper-chromium contacts

[0123] Copper-chromium contacts were prepared from Example 1, Examples 18-19, and Comparative Example 6, and their performance was tested. The results are shown in Table 5:

[0124] Table 5 Performance test table of copper-chromium contacts prepared in Example 1, Examples 18-19, and Comparative Example 6

[0125]

[0126] Conclusion: From the data in Table 5, it can be seen that the contact material prepared in Example 1 has the highest conductivity, hardness and density, indicating that the composition of the composite polishing liquid selected in Example 1 is optimal. Compared with Control Example 6, it can be found that the polishing effect of the polishing liquid in Control Example 6 that does not contain sodium imidazoline oleate is limited, thereby affecting the performance parameters of the copper-chromium contact.

Claims

1. A method for preparing the outer circle of a copper-chromium contact blank, characterized in that: The following steps are involved: S1. Prepare materials Place the copper-chromium forging ingot on a horizontal platform, spray cutting fluid at the cutting ends at a pressure of 1-3 MPa and a flow rate of 10-15 mL / s, then use a grinding wheel to saw the end faces until the end faces are horizontal. The grinding wheel saw feed rate is 0.01-0.02 mm / time, and the total feed rate must be ≤30 mm. Finally, deburr the surface of the copper-chromium forging ingot after sawing to obtain a processed bar (5); S2. Clamping A three-jaw self-centering chuck is sleeved on one end of the processing bar (5), and after the processing bar (5) obtained in step S1 is clamped by a robot, one end sleeved with the three-jaw self-centering chuck is pressed against the top of the driving shaft (1), and the driven shaft (3) is moved so that the retractable top on the driven shaft (3) moves along the guide rail (4) toward the driving shaft (1) until it is pressed against the other end of the processing bar (5); S3. Processing The position of the cutting shaft (2) is adjusted to be flush with one end of the processing bar (5) provided with a three-jaw self-centering chuck, the driving shaft (3) is turned on, and then the cutting shaft (2) is moved in the direction of the driven shaft (3), the cutting speed of the cutting shaft (2) is adjusted to 10 m / min, the back cutting amount is adjusted to 0.05-0.3 mm, and the feed rate is adjusted to 0.02-0.1 mm / r, the outer circle of the processing bar (5) is cut to the target specification, and the processing bar (5) is taken out by a robot to obtain the outer circle of the copper-chromium contact blank; S4, secondary processing The processed rod is first polished for 1.5 to 5 minutes, then ultrasonically cleaned with deionized water for 5 to 8 minutes, taken out and dried in a vacuum drying oven at 80 to 120°C for 3 to 5 minutes, and finally inert gas with a volume concentration of 99.99% is used to purge the surface of the processed rod until the surface is clean. The polishing method comprises: immersing a processed rod in a container filled with a composite polishing liquid at a temperature of 45-55° C., placing the processed rod in an ultrasonic magnetic field for reaction for 0.5-3 minutes, then adding a dispersant obtained by mixing polyoxyethylene ether and carboxyethyl thiosuccinic acid in a ratio of 1:1 to the container, and continuing the reaction for 1-4.5 minutes; the volume concentration ratio of the dispersant to the composite polishing liquid is 0.3-0.5:1; and the composite polishing liquid comprises the following components: 2-3 parts of sodium hexametaphosphate, 5-20 parts of brown corundum abrasive, 2-3 parts of imidazoline sodium oleate, 2-3 parts of hydroxyethylidene diphosphonic acid, and 15-20 parts of deionized water.

2. The method for preparing the outer circle of a copper-chromium contact blank according to claim 1, characterized in that: The inert gas may be any one of nitrogen, argon and helium.

3. The method for preparing the outer circle of a copper-chromium contact blank according to claim 1, characterized in that: In step S1, the cutting fluid includes the following components in percentage by mass: 2.0-3.0% of monolaurin, 3.5-4.5% of diethylene glycol, 2.5-3.0% of sodium phosphate, 1.0-2.0% of benzotriazole, 0.05-0.1% of silicone defoamer, and the balance of water.

4. The method for preparing the outer circle of a copper-chromium contact blank according to claim 1, characterized in that: In step S1, the standard for the horizontality of the end face of the processed bar (5) is: the end face flatness is not greater than 0.001 mm, and the roughness is 0.8~1.2 μm.

5. The method for preparing the outer circle of a copper-chromium contact blank according to claim 1, characterized in that: In step S1, the deburring process includes the following steps: spraying a sand powder mixture onto the surface of the sawn copper-chromium ingot by a high-pressure spray gun, then continuously blowing the surface of the copper-chromium ingot with compressed air for 0.5 to 3 minutes, and finally wiping it with cotton cloth for standby use; the spraying time is 3 to 5 minutes, and the spraying air pressure of the high-pressure spray gun is 1.0 to 2.2 L / cm 2 .

6. The method for preparing the outer circle of a copper-chromium contact blank according to claim 5, characterized in that: The sand powder mixture is a mixture of resin sand, fumed aluminum oxide and deionized water in a ratio of 1-1.5:0.3-0.5:1-1.

5.

7. The method for preparing the outer circle of a copper-chromium contact blank according to claim 1, characterized in that: In step S3, the cutting shaft is made of any one of diamond, cubic boron nitride, and ceramic.

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