Machining method for avoiding induction heating cracks of loading machine pin shaft key groove

By using a double-circle structure in the induction heating coil and jet quenching medium in the medium frequency induction quenching machine tool, the problem of microcracks in the arc keyway during the induction heating and quenching process of the loader pin shaft is solved, and the crack-free processing effect is achieved. The customer's organization and hardened layer depth requirements.

CN119242887APending Publication Date: 2025-01-03BAOMEILONG (SHANDONG) INTELLIGENT TECH CO LTD
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Patent Information

Application Number
CN202411242431.9
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2024-09-05
Publication Date
2025-01-03

AI Technical Summary

Technical Problem

During the induction heating and quenching process of loader pin shaft, microcracks are prone to appear at the arc keyway, which affects its load-bearing capacity and reliability.

Method used

The induction heating coil structure of the medium frequency induction quenching machine tool is redesigned as a double-circle structure, the inner heating coil is used for induction heating, and the quenching medium is sprayed through the outer ring for cooling, and the process parameters are optimized to avoid deformation and cracks in the arc keyway.

Benefits of technology

No microcracks were found through magnetic powder flaw detection. The customer checked the tissue and the depth of the hardened layer to meet the requirements. 23,000 pieces have been supplied in batches, proving the effectiveness of this method.

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Abstract

The invention discloses a processing method for avoiding induction heating cracks of a loading machine pin shaft key groove, which is characterized in that a transformer of a medium-frequency induction quenching machine tool is connected with an induction heating coil, the heating power is 140-145kW, and the frequency is 2-2.5 kHz; the induction heating coil comprises a support, a heating coil is arranged on the support, an outer ring is arranged outside the heating coil, and a quenching medium inlet and a quenching medium jet orifice are formed in the outer ring in the circumferential direction. In the machining process, the lower end of the pin shaft is inserted into the center of the heating coil and heated for 3-3.5 s, then the pin shaft moves downwards at the speed of 210-215 mm / min, a quenching medium is sprayed to the pin shaft, heating is stopped after the pin shaft moves till the upper end of the pin shaft is located at the center of the heating coil, the pin shaft continues to move downwards to the position 15 mm away from the center of the heating coil, and meanwhile the quenching medium continues to be sprayed. According to the invention, the structure of the induction heating coil is redesigned, and technological parameters are optimized and adjusted, so that the quenched pin shaft does not deform at the arc-shaped key groove, and no micro-crack is found through magnetic powder inspection.
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Description

Technical Field

[0001] The invention relates to the technical field of pin processing, and in particular to a processing method for avoiding induction heating cracks in a keyway of a pin of a loader. Background Art

[0002] During the induction heating and quenching process of the special pin shaft of the loader, a medium frequency induction quenching machine is used for induction heating and quenching. At present, the induction heating coils used in the medium frequency induction quenching machine are all single-loop structure designs. While the pin shaft workpiece is induction heated, the workpiece is sprayed with water to cool the workpiece using the spray holes on the induction heating coil to complete the quenching process. However, according to the test report feedback from customers, micro cracks appear at the arc keyway on the surface of some pin shaft workpieces. When the pin shaft is subjected to strong shear, impact, bending and torsion, the micro cracks may cause stress concentration, thereby reducing the bearing capacity and reliability of the pin shaft. Therefore, in view of this phenomenon, further research on the heat treatment process of the pin shaft is needed. Summary of the invention

[0003] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art and provide a processing method for avoiding induction heating cracks in the keyway of a loader pin shaft. The structure of the induction heating coil is redesigned, and the pin shaft workpiece is induction heated by the inner heating coil, and then the outer ring is used to spray quenching medium on it to cool it. Then, by optimizing and adjusting the process parameters, the pin shaft after quenching does not deform at the arc keyway, and no microcracks are found after magnetic particle inspection.

[0004] The technical solution of the present invention is:

[0005] A processing method for avoiding induction heating cracks in a keyway of a loader pin shaft, wherein a medium frequency induction quenching machine is used to process the pin shaft, wherein an induction heating coil is connected to a transformer of the medium frequency induction quenching machine tool, wherein the heating power of the induction heating coil is 140-145 kW and the frequency is 2-2.5 kHz; the induction heating coil comprises a bracket, wherein a connecting plate is arranged at the bottom of the bracket, and the connecting plate is connected to the transformer; a heating coil is arranged on the bracket, and an outer ring is arranged outside the heating coil, wherein a plurality of quenching medium inlets are arranged in the circumferential direction of the outer ring, and a quenching medium injection port is arranged on the end surface of the outer ring close to the pin shaft; During working hours, the induction heating coil is placed horizontally and the pin is installed vertically on the medium frequency induction quenching machine. The pin moves downward and the lower end of the pin is inserted into the center of the heating coil and heated for 3-3.5s. Then, it moves downward at a speed of 210-215mm / min and sprays quenching medium to the pin through the quenching medium injection port. After moving to the center of the heating coil where the upper end of the pin is, heating is stopped. The pin continues to move downward to 15mm from the center of the heating coil. During the movement, the quenching medium is continued to be sprayed for cooling for 12-14s. The pressure of the quenching medium is 0.2-0.4MPa, and the quenching process of the pin is completed.

[0006] Preferably, the diameter of the heating coil is 100-105 mm, and the diameter of the outer ring is 140-145 mm.

[0007] Preferably, the quenching medium is a 10-15 wt. % PAG aqueous solution.

[0008] Preferably, the angle between the quenching medium injection port and the moving direction of the pin shaft is 40°-45°.

[0009] Preferably, the pin shaft is made of 40Cr alloy structural steel.

[0010] Preferably, the keyway of the pin shaft is filled with rock wool for protection.

[0011] Preferably, the heating coil is provided with a water inlet and a water outlet, and circulating cooling water is introduced into the heating coil.

[0012] Preferably, the temperature of the circulating cooling water is 20-40°C and the water pressure is 0.1-0.3 MPa.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The present invention redesigns the structure of the induction heating coil, uses the inner heating coil to induction heat the pin workpiece, and then uses the outer ring to spray quenching medium to cool it. By optimizing and adjusting the process parameters, the pin after quenching does not deform at the arc keyway, and no microcracks are found after magnetic particle inspection. The customer's inspection organization and hardened layer depth meet the requirements. It has been supplied in batches for 2 years, with a total of about 23,000 pieces. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the induction heating coil of the present invention.

[0016] Figure 2 This is a magnetic particle inspection photograph of the pin shaft processed in Example 1 of the present invention at the keyway.

[0017] Figure 3 This is a magnetic particle inspection photograph of the pin shaft processed in Example 2 of the present invention at the keyway.

[0018] Figure 4 This is a magnetic particle inspection photograph of the pin shaft processed in Example 3 of the present invention at the keyway.

[0019] Figure 5 This is a magnetic particle inspection photograph of the pin shaft processed in comparative example 1 of the present invention at the keyway.

[0020] Figure 6 This is a magnetic particle inspection photograph of the pin shaft processed in comparative example 2 of the present invention at the keyway.

[0021] Figure 7 This is a magnetic particle inspection photograph of the pin shaft processed in comparative example 3 of the present invention at the keyway.

[0022] Figure 8 This is a magnetic particle inspection photograph of the pin shaft processed in comparative example 4 of the present invention at the keyway.

[0023] Fig. 9 This is a magnetic particle inspection photograph of the pin shaft processed in comparative example 5 of the present invention at the keyway.

[0024] Fig.10 This is a magnetic particle inspection photograph of the pin shaft processed in comparative example 6 of the present invention at the keyway.

[0025] In the figure, 1, bracket; 2, connecting plate; 3, bolt; 4, heating coil; 5, insulating plate; 6, outer ring; 7, quenching medium inlet. DETAILED DESCRIPTION

[0026] In order to enable persons skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0027] The present invention redesigns the induction heating coil structure in the medium frequency induction hardening machine tool, adjusting it from the original single-loop structure to a double-loop structure. Figure 1 As shown: the induction heating coil includes a bracket 1, a connecting plate 2 is arranged at the bottom of the bracket 1, and the connecting plate 2 is fixedly connected to the transformer of the medium frequency induction quenching machine tool by bolts 3. A heating coil 4 is arranged on the bracket 1, and a water inlet and a water outlet are arranged on the heating coil 4. While heating the pin shaft workpiece, circulating cooling water is introduced into the heating coil 4 to prevent the heating coil 4 from overheating and melting, wherein the temperature of the circulating cooling water introduced is 30°C and the water pressure is 0.2MPa; the outer ring 6 is bolted to the outside of the heating coil 4 through three insulating plates 5, and four quenching medium inlets 7 are arranged circumferentially on the outer ring 6, and a quenching medium injection port is arranged on the end face of the outer ring 6 close to the pin shaft, and the angle between the quenching medium injection port and the moving direction of the pin shaft is 40°-45°. The heating power of the induction heating coil is 140-145kW, and the frequency is 2-2.5kHz.

[0028] During processing, the induction heating coil is placed horizontally and connected to the transformer through a connecting plate. The pin is installed vertically on the medium frequency induction quenching machine. The pin moves downward and the lower end of the pin is inserted into the center of the heating coil 4 and heated for 3-3.5s. The pin moves downward at a speed of 210-215mm / min while spraying the quenching medium to the pin through the quenching medium injection port. After the upper end of the pin is located at the center of the heating coil 4, the heating is stopped. The pin continues to move downward to 15mm from the center of the heating coil. During the movement, the quenching medium is continued to be sprayed to cool for 12-14s. The pressure of the quenching medium is 0.2-0.4MPa, and the quenching process of the pin is completed. Among them, the pin is made of 40Cr alloy structural steel; during the processing, the keyway of the pin is filled with rock wool.

[0029] Example 1

[0030] The processing method of this embodiment to avoid induction heating cracks in the keyway of the loader pin is as follows:

[0031] During processing, the pin moves downward and the lower end of the pin is inserted into the center of the heating coil and heated for 3 seconds. Then, it moves downward at a speed of 210 mm / min and sprays quenching medium to the pin through the quenching medium injection port. The angle between the quenching medium injection port and the moving direction of the pin is 45°. After the pin moves to the center of the heating coil at the upper end, the heating is stopped. The pin continues to move downward to 15 mm from the center of the heating coil. During the movement, the quenching medium is continued to be sprayed for cooling for 12 seconds. The pressure of the quenching medium is 0.3 MPa, and the quenching process of the pin is completed.

[0032] Among them, the diameter of the heating coil 4 of this embodiment is 100 mm, and the diameter of the outer ring 6 is 140 mm; the heating power of the induction heating coil is 140 kW, and the frequency is 2 kHz; the quenching medium is a 15 wt. % PAG aqueous solution.

[0033] Example 2

[0034] The processing method of this embodiment to avoid induction heating cracks in the keyway of the loader pin is as follows:

[0035] During processing, the pin moves downward and the lower end of the pin is inserted into the center of the heating coil and heated for 3 seconds. Then, it moves downward at a speed of 210 mm / min and sprays quenching medium to the pin through the quenching medium injection port. The angle between the quenching medium injection port and the moving direction of the pin is 45°. After the pin moves to the center of the heating coil at the upper end, the heating is stopped. The pin continues to move downward to 15 mm from the center of the heating coil, and continues to spray quenching medium for cooling for 12 seconds. The pressure of the quenching medium is 0.2 MPa, and the quenching process of the pin is completed.

[0036] Among them, the diameter of the heating coil 4 of this embodiment is 100 mm, and the diameter of the outer ring 6 is 140 mm; the heating power of the induction heating coil is 140 kW, and the frequency is 2 kHz; the quenching medium is a 10 wt. % PAG aqueous solution.

[0037] Example 3

[0038] The processing method of this embodiment to avoid induction heating cracks in the keyway of the loader pin is as follows:

[0039] During processing, the pin moves downward and the lower end of the pin is inserted into the center of the heating coil and heated for 3.5 seconds. Then, it moves downward at a speed of 215 mm / min and sprays quenching medium to the pin through the quenching medium injection port. The angle between the quenching medium injection port and the moving direction of the pin is 40°. After the pin moves to the center of the heating coil at the upper end, the heating is stopped. The pin continues to move downward to 15 mm from the center of the heating coil, and continues to spray quenching medium for cooling for 14 seconds. The pressure of the quenching medium is 0.35 MPa, and the quenching process of the pin is completed.

[0040] Among them, the diameter of the heating coil 4 of this embodiment is 105mm, and the diameter of the outer ring 6 is 145mm; the heating power of the induction heating coil is 145kW, and the frequency is 2.5kHz; the quenching medium is a 15wt.% PAG aqueous solution.

[0041] Comparative Example 1

[0042] In comparative example 1, when processing the pin shaft of a loader, a single-circle induction heating coil is used, and a circle of spray holes is provided on the induction heating coil. The processing method is as follows:

[0043] During processing, the lower end of the pin is inserted into the center of the induction heating coil and heated for 3 seconds, then moved down at a speed of 220 mm / min until the upper end of the pin is located at the center of the induction heating coil. During the heating process, the quenching medium is sprayed onto the pin through the nozzle for cooling for 12 seconds to complete the quenching process of the pin.

[0044] The diameter of the heating coil 4 is 85 mm, the heating power of the induction heating coil is 200 kW, and the frequency is 2.94 kHz; the quenching medium is clean water.

[0045] Comparative Example 2

[0046] The difference from Example 1 is that a single-turn induction heating coil is used to replace the double-turn induction heating coil of Example 1.

[0047] Comparative Example 3

[0048] The difference from Example 1 is that the heating power of the induction heating coil is 200 kW, the frequency is 2.94 kHz, and the downward movement speed of the pin is 220 mm / min.

[0049] Comparative Example 4

[0050] The difference from Example 1 is that clean water is used to replace the PAG aqueous solution in Example 1.

[0051] Comparative Example 5

[0052] The difference from the first embodiment is that the diameter of the heating coil 4 is 90 mm, and the diameter of the outer ring 6 is 120 mm.

[0053] Comparative Example 6

[0054] The difference from Example 1 is that during the processing, the keyway of the pin shaft does not need to be blocked with rock wool for protection.

[0055] The pins prepared in Examples 1-3 and Comparative Examples 1-6 were tested for performance, and the test results all met the following usage standards:

[0056] 1) Surface hardness ≥57HRC, 3mm deep hardness ≥50HRC, 5mm deep hardness ≥30HRC, 8mm deep hardness ≤50HRC, 15mm deep hardness is 241-285HB;

[0057] 2) After quenching, the structure from the surface to a depth of 1.5 mm is 100% martensite.

[0058] The pins processed in Examples 1-3 and Comparative Examples 1-6 were subjected to magnetic particle inspection. Figure 2-4 As shown in FIG. 1 , the pin workpieces processed in Example 1-3 have no cracks at the keyway, while Figure 5-10 As shown, the pin workpiece processed in Comparative Examples 1-6 has cracks at the keyway.

Claims

1. A processing method for avoiding induction heating cracks in the keyway of a loader pin, characterized in that: A medium frequency induction hardening machine is used to process the pin shaft. An induction heating coil is connected to the transformer of the medium frequency induction hardening machine. The heating power of the induction heating coil is 140-145 kW and the frequency is 2-2.5 kHz. The induction heating coil comprises a bracket (1). A connecting plate (2) is arranged at the bottom of the bracket (1). The connecting plate (2) is connected to the transformer. A heating coil (4) is arranged on the bracket (1). An outer ring (6) is arranged outside the heating coil (4). A plurality of quenching medium inlets (7) are arranged in the circumferential direction of the outer ring (6). A quenching medium inlet (7) is arranged on the end surface of the outer ring (6) close to the pin shaft. During processing, the induction heating coil is placed horizontally, the pin shaft is moved vertically downward, and the lower end of the pin shaft is inserted into the center of the heating coil (4) and heated for 3-3.5 seconds, and then the pin shaft is moved downward at a speed of 210-215 mm / min while spraying quenching medium onto the pin shaft through the quenching medium injection port. After the pin shaft moves to the center of the heating coil (4), the heating is stopped, and the pin shaft continues to move downward to 15 mm from the center of the heating coil (4). During the movement, the quenching medium is continuously sprayed to cool for 12-14 seconds. The pressure of the quenching medium is 0.2-0.4 MPa, and the quenching process of the pin shaft is completed.

2. The processing method for avoiding induction heating cracks of the loader pin keyway according to claim 1, characterized in that: The diameter of the heating coil (4) is 100-105 mm, and the diameter of the outer ring (6) is 140-145 mm.

3. The processing method for avoiding induction heating cracks of the loader pin keyway according to claim 1, characterized in that: The quenching medium is a 10-15 wt. % PAG aqueous solution.

4. The processing method for avoiding induction heating cracks of the loader pin keyway according to claim 1, characterized in that: The angle between the quenching medium injection port and the moving direction of the pin shaft is 40°-45°.

5. The processing method for avoiding induction heating cracks of the loader pin keyway according to claim 1, characterized in that: The pin shaft is made of 40Cr alloy structural steel.

6. The processing method for avoiding induction heating cracks of the loader pin keyway according to claim 1, characterized in that: The keyway of the pin shaft is filled with rock wool for protection.

7. The processing method for avoiding induction heating cracks of the loader pin keyway according to claim 1, characterized in that: The heating coil (4) is provided with a water inlet and a water outlet, and circulating cooling water is introduced into the heating coil (4).

8. The processing method for avoiding induction heating cracks in the keyway of a loader pin as claimed in claim 7, characterized in that: The temperature of the circulating cooling water is 20-40°C, and the water pressure is 0.1-0.3MPa.