Electromagnetic coupling cryogenic treatment method for improving shear strength of dissimilar material brazing interface

Abstract

The present application relates to a kind of electromagnetic coupling cryogenic treatment method for improving the shear strength of dissimilar material brazing interface. Mainly solve the technical problems of poor comprehensive performance and short service life of brazing interface existing in existing single cryogenic treatment or magnetic field processing. The technical scheme used in the present application is: the electromagnetic coupling cryogenic treatment method, first, the brazing composite material sample of low alloy steel / copper-zinc alloy / tungsten-cobalt hard alloy is prepared, then the sample is subjected to electromagnetic coupling cryogenic treatment, finally, the treated sample is put into a heating furnace, low-temperature tempering treatment is carried out first, and then medium-temperature tempering treatment is carried out. The two processes of magnetic field and cryogenic treatment used in the present application have the advantages of green environmental protection and high efficiency and energy saving, etc. In the case of not affecting the structural deformation, the overall strengthening from inside to outside can be achieved, which can be applied to various fields.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of material heat treatment, and particularly relates to an electromagnetic coupling cryogenic treatment method for improving the shear strength of dissimilar material brazing interfaces. BACKGROUND

[0002] The cryogenic treatment is mostly realized by using the gasification of liquid nitrogen in a closed container, and the magnetic field treatment is to place workpiece materials in a magnetic field so that the materials reach or approach the state of magnetic saturation. Both the magnetic field treatment and the cryogenic treatment have the advantages of green environmental protection and high energy saving, and can significantly improve the service life of materials by changing the material organization. The effective combination of the two has broad application prospects. However, in order to improve the shear strength of dissimilar material brazing interfaces, the single cryogenic treatment or the single magnetic field treatment is used, and the single treatment method has the problems of poor comprehensive performance of the brazing interface and short service life.

[0003] In summary, a new treatment method is needed to improve the shear strength of dissimilar material brazing interfaces, so as to ensure the comprehensive performance of the brazing interface and prolong the service life. SUMMARY

[0004] The purpose of the application is to solve the above technical problems, and provide an electromagnetic coupling cryogenic treatment method for improving the shear strength of dissimilar material brazing interfaces.

[0005] To solve the above technical problems, the technical scheme adopted by the application is:

[0006] An electromagnetic coupling cryogenic treatment method for improving the shear strength of dissimilar material brazing interfaces, first, a brazing composite material sample of low alloy steel / copper-zinc alloy / tungsten-cobalt hard alloy is prepared, and then the sample is subjected to electromagnetic coupling cryogenic treatment, and the specific steps are as follows:

[0007] (1) A cylindrical piece of low alloy steel and a cylindrical piece of tungsten-cobalt hard alloy are respectively manufactured by machining, the inner diameter of the cylindrical piece of low alloy steel is greater than the outer diameter of the cylindrical piece of tungsten-cobalt hard alloy, and the gap is reserved for filling the copper-zinc alloy brazing material;

[0008] (2) First, the copper-zinc alloy brazing material is filled in the bottom of the low alloy steel cylindrical piece, then the tungsten-cobalt hard alloy cylindrical piece is put into the low alloy steel cylindrical piece, the copper-zinc alloy brazing material is heated and melted by using a high-frequency induction brazing machine, the copper-zinc alloy brazing material fills the reserved gap, the connection of the low alloy steel and the tungsten-cobalt hard alloy is realized, then the whole piece after connection is cooled to room temperature in the quenching oil, and after completion, the whole piece is cut into a plurality of round sheet-shaped samples;

[0009] (3) Put the sample in the center of the electromagnetic induction coil, then place the electromagnetic induction coil in the cryogenic box, start the cryogenic control cabinet, use the cryogenic box to cool the sample, when the temperature is lowered to the set cryogenic temperature for 2h, start the electromagnetic control cabinet to power on the electromagnetic induction coil, and magnetize the sample according to the preset magnetization parameters, when the magnetization is completed and the set cryogenic time is reached, the cryogenic box is warmed up to room temperature, and finally the electromagnetic coupling cryogenic treatment is completed;

[0010] (4) Put the treated sample into the heating furnace, and first perform low-temperature tempering treatment and then perform medium-temperature tempering treatment.

[0011] Further, the inner surface of the cylindrical part and the outer surface of the cylindrical part are polished and cleaned by ultrasonic waves.

[0012] Further, the thickness of the round sheet sample is 3mm-8mm.

[0013] Further, the heating temperature of the high-frequency induction brazing machine is 870 DEG C, and the holding time is 20min, and the quenching process of the alloy steel is completed at the same time of brazing.

[0014] Further, the cryogenic temperature is -190 DEG C to -80 DEG C, and the cryogenic time is 2h-24h.

[0015] Further, the temperature rising and falling rate in step (3) is set to 2 DEG C / min.

[0016] Further, the magnetization parameters are: the magnetization intensity is 0.5T-1.5T, and the magnetization time is 5s-15s; the magnetization treatment sample is performed in several times, and the magnetization time of each time is 1s, and the interval time is 3s.

[0017] Further, the low-temperature tempering temperature is 150 DEG C, and the holding time is 20min.

[0018] Further, the medium-temperature tempering temperature is 360 DEG C, and the holding time is 2h.

[0019] The beneficial effects of the present application are:

[0020] (1) The magnetic field and the cryogenic treatment adopted in the present application have the advantages of green environmental protection and high energy saving, and can achieve overall strengthening from inside to outside without affecting the structural deformation, and can be applied to various fields.

[0021] (2) The electromagnetic field in the process treatment equipment can adjust the magnetic field parameters by external power supply, and combined with different cryogenic parameters, the influence law of different treatment parameters on key performance can be analyzed, so as to obtain the optimal process and the corresponding optimal shear performance.

[0022] (3) Compared with single processing mode, the phase transition of the sample is increased, the dislocation is increased, and the grain is refined after the electromagnetic coupling cryogenic treatment equipment is strengthened, and the shear performance of the sample is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram of the sample prepared by the present application;

[0024] Figure 2 is a schematic diagram of the sample subjected to electromagnetic coupling cryogenic treatment of the present application;

[0025] Figure 3 is a process route diagram of the electromagnetic coupling cryogenic treatment of the present application;

[0026] Figure 4 is a microstructure diagram of the copper-zinc alloy brazing surface obtained by using Comparative Example 1;

[0027] Figure 5 is a microstructure diagram of the copper-zinc alloy brazing surface obtained by using Comparative Example 2;

[0028] Figure 6 is a microstructure diagram of the copper-zinc alloy brazing surface obtained by using Example 1 of the present application;

[0029] In the figure: 1 - induction coil, 2 - cylindrical part, 3 - gap, 4 - cylindrical part, 5 - brazing material, 6 - sample, 7 - electromagnetic control cabinet, 8 - electromagnetic induction coil, 9 - cryogenic tank, 10 - cryogenic control cabinet. DETAILED DESCRIPTION

[0030] The present application will be described in detail below in combination with the drawings and examples.

[0031] An electromagnetic coupling cryogenic treatment method for improving the shear strength of the brazing interface of dissimilar materials, first, a brazing composite material sample of low alloy steel / copper-zinc alloy / tungsten-cobalt hard alloy is prepared, and then the sample is subjected to electromagnetic coupling cryogenic treatment, and the specific steps are as follows:

[0032] (1) The cylindrical part of low alloy steel and the cylindrical part of tungsten-cobalt hard alloy are respectively manufactured by machining, the inner diameter of the cylindrical part is larger than the outer diameter of the cylindrical part, to ensure that there is a gap to fill the copper-zinc alloy brazing material; the inner surface of the cylindrical part and the outer surface of the cylindrical part to be welded are polished bright and cleaned by ultrasonic wave.

[0033] (2) first install copper-zinc alloy brazing material at the bottom of low alloy steel cylinder, then install tungsten-cobalt hard alloy cylinder into low alloy steel cylinder, use high frequency induction brazing machine to heat and melt copper-zinc alloy brazing material, make copper-zinc alloy brazing material fill the reserved gap, realize the connection of low alloy steel and tungsten-cobalt hard alloy, then put the whole piece after connection into quenching oil to cool to room temperature, complete the whole piece into several round sheet samples; the heating temperature of high frequency induction brazing machine is 870℃, the holding time is 20min, and the quenching process of alloy steel is completed at the same time of brazing.

[0034] The thickness of the round sheet sample is 3mm-8mm. Too large thickness will make the required pressure too large, exceeding the loading range of the electronic universal testing machine; too small thickness will cause insufficient rigidity of the sample, which may cause damage to the sample.

[0035] (3) put the sample into the center of the electromagnetic induction coil, then place the electromagnetic induction coil in the cryogenic tank, open the cryogenic control cabinet, use the cryogenic tank to cool the sample, when the temperature is cooled to the set cryogenic temperature for 2h, start the electromagnetic control cabinet to power on the electromagnetic induction coil, magnetize the sample according to the preset magnetization parameters, when the magnetization is completed and the set cryogenic time is reached, the cryogenic tank is warmed to room temperature, and finally the electromagnetic coupling cryogenic treatment is completed.

[0036] The cryogenic parameters are: the cryogenic temperature is -190℃ to -80℃, and the temperature of -190℃ is the limit temperature interval of liquid nitrogen cooling; the cryogenic time is 2h-24h. Too long cryogenic time has limited effect on improving shear performance, but will cause high cost of cryogenic treatment; too short cryogenic time cannot guarantee sufficient cooling of the sample; the heating and cooling rate is set to 2℃ / min, too high rate will cause too fast temperature change of the material, causing unnecessary stress; too small rate will prolong the cooling time, and the cost of cryogenic treatment will be higher.

[0037] The magnetization parameters are: the magnetization intensity is 0.5T-1.5T, and the magnetic field intensity of 1.5T can basically magnetize general metal materials; the magnetization time is 5s-15s, too long magnetization time will cause eddy current effect of the material and softening; too short magnetization time will cause the magnetization effect not obvious.

[0038] The magnetization of the sample is carried out in batches, and the magnetization time of each time is 1s, and the interval time is 3s. This is mainly to prevent too long power-on time from causing electromagnetic heating, which affects the cryogenic temperature field.

[0039] (4) put the treated sample into the heating furnace, first perform low-temperature tempering treatment and then perform medium-temperature tempering treatment.

[0040] The low-temperature tempering temperature is 150℃, and the holding time is 20min. The low-temperature tempering can effectively reduce the residual stress.

[0041] The medium-temperature tempering temperature is 360℃, and the holding time is 2h. The medium-temperature tempering can not only maintain the strength of the material, but also appropriately improve the toughness.

[0042] The low-alloy steel used in the embodiment is AISI 4140 alloy steel, the tungsten-cobalt hard alloy is YG-11C hard alloy, and the copper-zinc alloy is Cu-Zn-Ni-Mn alloy, and their compositions are shown in Table 1, Table 2 and Table 3 respectively.

[0043] Table 1 Chemical composition of AISI 4140 alloy steel (mass fraction, wt. %)

[0044]

[0045] Table 2 Composition of YG-11C hard alloy (mass fraction, wt %)

[0046]

[0047] Table 3 Composition of Cu-Zn-Ni-Mn alloy (mass fraction, wt %)

[0048]

[0049] Example 1

[0050] The electromagnetic coupling cryogenic treatment method for improving the shear strength of the brazed interface of dissimilar materials in this embodiment first prepares a brazed composite material sample of AISI 4140 alloy steel / Cu-Zn-Ni-Mn alloy / YG11C hard alloy, and then performs electromagnetic coupling cryogenic treatment on the sample. The specific steps are as follows:

[0051] (1) As shown in Figure 1 , the cylindrical piece 2 of AISI 4140 alloy steel and the cylindrical piece 4 of YG11C hard alloy are respectively manufactured by machining. The inner diameter of the cylindrical piece 2 is larger than the outer diameter of the cylindrical piece 4, so as to ensure that there is a gap 3. The brazing gap 3 is about 0.2mm, so as to fill the Cu-Zn-Ni-Mn alloy brazing filler 5. The surfaces to be welded of the inner surface of the cylindrical piece 2 and the outer surface of the cylindrical piece 4 need to be polished and cleaned by ultrasonic wave.

[0052] (2) As shown in Figure 1As shown, firstly, Cu-Zn-Ni-Mn alloy brazing filler 5 is inserted into the bottom of the AISI 4140 alloy steel cylindrical part 2. Then, YG11C cemented carbide cylindrical part 4 is inserted into the AISI 4140 alloy steel cylindrical part 2. A high-frequency induction brazing machine is used to energize the induction coil 1, heating and melting the Cu-Zn-Ni-Mn alloy brazing filler 5 to fill the gap 3, thereby achieving the connection between AISI 4140 alloy steel and YG11C cemented carbide. During the brazing process, the quenching process of AISI 4140 alloy steel is also completed. Then, the connected integral part is placed in quenching oil to cool to room temperature. After completion, the integral part is cut into several circular plate-shaped samples 6; the thickness of the circular plate-shaped sample 6 is 4mm.

[0053] (3) Figure 2 As shown, sample 6 is placed at the center of electromagnetic induction coil 8, and magnetizing cores are placed at both ends. Then, electromagnetic induction coil 8 is placed in cryogenic chamber 9, cryogenic control cabinet 10 is turned on, and cryogenic chamber 9 is used to cool sample 6. After cooling to the set cryogenic temperature for 2 hours, electromagnetic control cabinet 7 is turned on to power electromagnetic induction coil 8 and sample 6 is magnetized according to preset magnetization parameters. After magnetization is completed and the set cryogenic time is reached, cryogenic chamber 9 is heated to room temperature, and electromagnetic coupling cryogenic treatment is finally completed.

[0054] (4) Place the treated sample 6 into a heating furnace and perform low-temperature tempering followed by medium-temperature tempering.

[0055] like Figure 3 As shown, in step (2) above, the heating temperature of the high-frequency induction brazing machine is 870℃ and the holding time is 20min. In step (3) above, the cryogenic temperature is -190℃, the cryogenic time is 24h, the heating and cooling rate is set to 2℃ / min, the magnetization intensity is 1.5T and the magnetization time is 15s. The magnetization treatment of the sample is carried out in batches, with each magnetization time being 1s and the interval time being 3s. In step (4) above, the low-temperature tempering temperature is 150℃ and the holding time is 20min. The medium-temperature tempering temperature is 360℃ and the holding time is 2h.

[0056] Example 2

[0057] In step (3) of Example 1, the cryogenic temperature was set to -135℃, the cryogenic time was set to 13h, the heating and cooling rate was set to 2℃ / min, the magnetization intensity was set to 1T, and the magnetization time was set to 10s. The magnetization treatment of the sample was carried out in several sessions, with each magnetization lasting 1s and an interval of 3s. The remaining steps were the same as in Example 1.

[0058] Example 3

[0059] The deep cooling temperature in step (3) of Example 1 is set to -80°C, the deep cooling time is set to 2h, the magnetization intensity is set to 0.5T, the magnetization time is set to 5s, and the magnetization treatment of the sample is performed in several times, each time of magnetization is 1s, and the interval time is 3s. The rest of the steps are the same as those in Example 1.

[0060] The thickness of the circular sheet sample 6 in the above examples can also be selected randomly between 3mm and 8mm.

[0061] The deep cooling temperature in the above examples can also be selected randomly between -190°C and -80°C, and the deep cooling time can also be selected randomly between 2h and 24h.

[0062] The magnetization intensity in the above examples can also be selected randomly between 0.5T and 1.5T, and the magnetization time can also be selected randomly between 5s and 15s.

[0063] The low-alloy steel and the tungsten-cobalt hard alloy are not limited to AISI 4140 alloy steel and YG-11C hard alloy, and the above-mentioned AISI 4140 alloy steel and YG-11C hard alloy can also be replaced by other materials with similar functions.

[0064] Comparative Example 1 (conventional heat treatment)

[0065] The sample is prepared according to steps (1) and (2) in Example 1, and then the sample is treated according to step (4) in Example 1. This comparative example can be considered as a conventional heat treatment group.

[0066] Comparative Example 2 (deep cooling treatment)

[0067] The sample is prepared according to steps (1) and (2) in Example 1, and the deep cooling treatment process parameters are programmed in the control system, the cooling rate is set to 2°C / min, and when the temperature is cooled to -190°C, the temperature is kept for 24h, and then the temperature is raised to room temperature at a rate of 2°C / min. Then the sample is treated according to step (4) in Example 1. This comparative example can be considered as a deep cooling treatment group.

[0068] In order to show the beneficial effects of the present application, the shear strength test and microstructure analysis are carried out on the sample prepared by the method of the present application and the sample prepared by conventional heat treatment and deep cooling treatment, and the specific results are as follows.

[0069] 1. Shear strength test

[0070] The equipment used for the shear strength test is an electronic universal testing machine. The equipment generates a downward pressure on the surface of the pressure head to press down the YG-11C hard alloy part at the center, thereby completing the shearing of the brazing interface. According to the load collected in the test, the shear strength can be calculated in combination with the structure size of the brazing surface, and the expression is as follows:

[0071]

[0072] In the formula, P is the load, D is the diameter of the brazing surface, and H is the height of the brazing surface.

[0073] 2. Result analysis

[0074] Table 4 is the shear strength test result of the brazing interface after the above-mentioned Examples 1-3 and Comparative Examples 1-2, and three samples are set in each scheme, and the final result is taken as an average value.

[0075] Table 4 is the shear strength test result of the brazing interface after the above-mentioned Examples 1-3 and Comparative Examples 1-2, and three samples are set in each scheme, and the final result is taken as an average value.

[0076]

[0077] As can be seen from Table 4, the shear strength of the conventional heat treatment (Comparative Example 1) is 223.803 MPa, the shear strength of the cryogenic treatment (Comparative Example 2) is 275.591 MPa, and in the electromagnetic coupling cryogenic treatment of the present application, the shear strength of Example 1 is the highest, which is 295.234 MPa, which is increased by 23.14% and 31.92% compared with Comparative Examples 1 and 2, respectively. In addition, as can be seen from Comparative Examples 1-3, lower cryogenic temperature, longer cryogenic time, stronger magnetization intensity and longer magnetization time are beneficial to improve the shear strength of the brazing interface.

[0078] 3. Microstructure analysis

[0079] The sample for microstructure observation can be uniformly made into a size of 10 mm x 10 mm x 5 mm, and is polished using 500#, 1000#, 1500# and 2000# series of sandpaper in sequence. After polishing, the sample surface is treated using a polishing machine, and when the sample surface is smooth like a mirror surface and has no scratches, the sample surface can be etched using an etching liquid, and when the surface appears gray-black, it is considered that the etching is completed. The sample surface is cleaned using an ultrasonic cleaning instrument, and is dried using a hair dryer and packaged, and the microstructure sample preparation is completed. The etching liquid is 5% ferric chloride and 10% hydrochloric acid alcohol.

[0080] The morphology of Comparative Example 1, Comparative Example 2 and the optimal group (Example 1) of the present application is selected as shown in Figure 4 , 5and 6. The materials from left to right in the figure are YG-11C cemented carbide, Cu-Zn-Ni-Mn alloy and AISI 4140 alloy steel, and the Cu-Zn-Ni-Mn alloy in the three groups of processes is composed of dark block α-Cu(s.s) phase and light strip β-Cu(s.s) phase. The proportion of β-Cu(s.s) phase in the total material is 8.4%, 24.2% and 31.3% respectively from conventional heat treatment to electromagnetic coupling cryogenic treatment, which indicates that the α-Cu(s.s) phase in the material is converted to the β-Cu(s.s) phase with higher plasticity, and the toughness of the material is improved; dendritic structure appears on the surface of the matrix after cryogenic treatment and electromagnetic coupling cryogenic treatment, which can change the direction of fracture multiple times and inhibit the propagation of cracks; the average value of α-Cu(s.s) phase after conventional heat treatment, cryogenic treatment and electromagnetic coupling cryogenic treatment is 50.10 μm, 33.04 μm and 25.84 μm respectively, which indicates that the grain size of Cu-Zn-Ni-Mn alloy gradually decreases from conventional heat treatment to electromagnetic coupling cryogenic treatment, and the strength and toughness of the interface material gradually improve. Based on the above analysis, the electromagnetic coupling cryogenic treatment process can change the microstructure of Cu-Zn-Ni-Mn alloy, thereby improving the shear strength of the brazing interface.

Claims

1. A method for improving the shear strength of a brazed joint between dissimilar materials by electromagnetic coupling cryogenic treatment, characterized by: First, the low alloy steel / copper zinc alloy / tungsten cobalt hard alloy brazing composite material sample is prepared, and then the sample is subjected to electromagnetic coupling cryogenic treatment, the specific steps are as follows: (1) The low alloy steel cylinder and the tungsten cobalt hard alloy cylinder are respectively manufactured by machining, the inner diameter of the cylinder is larger than the outer diameter of the cylinder, and the gap is reserved for filling the copper zinc alloy brazing filler; (2) First, the copper zinc alloy brazing filler is filled in the bottom of the low alloy steel cylinder, then the tungsten cobalt hard alloy cylinder is filled in the low alloy steel cylinder, the high-frequency induction brazing machine is used to heat and melt the copper zinc alloy filler, the copper zinc alloy filler is filled in the reserved gap, and the connection between the low alloy steel and the tungsten cobalt hard alloy is realized, then the whole piece after connection is placed in the quenching oil and cooled to room temperature, and then the whole piece is cut into several disc-shaped samples; (3) Put the sample in the center of the electromagnetic induction coil, then put the electromagnetic induction coil in the cryogenic box, start the cryogenic control cabinet, use the cryogenic box to cool the sample, when the temperature is lowered to the set cryogenic temperature 2h, start the electromagnetic control cabinet to power on the electromagnetic induction coil, and magnetize the sample according to the preset magnetization parameters, when the magnetization treatment is completed and the set cryogenic time is reached, the cryogenic box is heated to room temperature, and finally the electromagnetic coupling cryogenic treatment is completed; (4) Put the treated sample into the heating furnace, first perform low temperature tempering treatment and then perform medium temperature tempering treatment; The magnetization parameters are: the magnetization intensity is 0.5T~1.5T and the magnetization time is 5s~15s; the magnetized sample is magnetized in several times, and each magnetization time is 1s, and the interval time is 3s; The low temperature tempering temperature is 150℃, and the holding time is 20min; The medium temperature tempering temperature is 360℃, and the holding time is 2h.

2. The electromagnetic coupling cryogenic treatment method for improving the shear strength of the brazing interface of dissimilar materials according to claim 1, characterized in that: The inner surface of the cylinder and the outer surface of the cylinder to be welded are polished and cleaned with ultrasonic wave.

3. The electromagnetic coupling cryogenic treatment method for improving the shear strength of the brazing interface of dissimilar materials of claim 1, wherein: The thickness of the disc-shaped sample is 3mm~8mm.

4. The electromagnetic coupling cryogenic treatment method for improving the shear strength of the brazing interface of dissimilar materials of claim 1, wherein: The heating temperature of the high-frequency induction brazing machine is 870℃, and the holding time is 20min, and the quenching process is completed during brazing.

5. The electromagnetic coupling cryogenic treatment method for improving the shear strength of the brazing interface of dissimilar materials of claim 1, wherein: The cryogenic temperature is-190℃~-80℃, and the cryogenic time is 2h~24h.

6. The electromagnetic coupling cryogenic treatment method for improving the shear strength of the brazing interface of dissimilar materials of claim 1, wherein: The temperature rising and falling rate in step (3) is set to 2℃ / min.

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