A heat treatment process for increasing the hardness of the inner hole of a roller rod

Abstract

The present invention relates to the technical field of heat treatment processes, and provides a heat treatment process for improving the hardness of the inner hole of a roller rod, comprising the following steps: S1. Quenching: The roller rod is subjected to induction heating and then quenching cooling to obtain a hardened roller rod; S2. Tempering: The hardened roller rod is heated at a temperature of 400-500°C to obtain a roller rod with high inner hole hardness; The induction heating is carried out in two times, and the frequencies of the first induction heating and the second induction heating are different. Through the above technical solution, the problem of low hardness of the inner hole of the roller rod in the related art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat treatment processes, and specifically, to a heat treatment process for improving the hardness of the inner hole of a roller rod. Background Art

[0002] In the field of wood-based panel production, double-steel-belt continuous flat presses play a crucial role. The press mainly consists of an upper part of the press, a lower part of the press, and continuous circulating steel belts and roller rod chains respectively surrounding the upper part and the lower part of the press. Among them, the chain drives the roller rod to rotate continuously through a piercing pin to ensure the smooth progress of the entire pressing process.

[0003] With the long-term operation of wood-based panel production, the wear problem of the inner hole of the roller rod has become increasingly serious. Since the roller rod is always under stress during operation and frequently rubs against the piercing pin, its inner hole is constantly tested for wear. Once the inner hole is severely worn, the entire roller rod will directly lose its normal working ability and have to face scrapping. For a standard 31.9-meter-long press, the number of roller rods to be installed is nearly 7,000, and the procurement cost of the roller rods is high, with a total price of about 1.5 million yuan. With such a large-scale configuration of roller rods, if they are frequently scrapped due to inner hole wear, it will not only cause huge economic losses but also seriously affect the production efficiency and continuity of wood-based panels. Therefore, it is very necessary to propose a heat treatment process that can improve the hardness of the inner hole of the roller rod. Summary of the Invention

[0004] The present invention proposes a heat treatment process for improving the hardness of the inner hole of a roller rod, which solves the problem of low hardness of the inner hole of the roller rod in the related art.

[0005] The technical solution of the present invention is as follows: The present invention proposes a heat treatment process for improving the hardness of the inner hole of a roller rod, including the following steps:

[0006] S1. Quenching: The roller rod is induction heated and then quenched and cooled to obtain a hardened roller rod;

[0007] S2. Tempering: The hardened roller rod is heated at 400 - 500 °C and then processed to obtain a roller rod with high inner hole hardness;

[0008] The induction heating is carried out in two times, and the frequencies of the first induction heating and the second induction heating are different.

[0009] As a further technical solution, the frequency of the first induction heating > the frequency of the second induction heating, the frequency of the first induction heating is 300 kHz, and the frequency of the second induction heating is 200 kHz.

[0010] As a further technical solution, the time of the first induction heating is 3 s, the time of the second induction heating is 1 s, and the power of both the first induction heating and the second induction heating is 90 - 120 kW.

[0011] As a further technical solution, the heating rate in S2 is 5 - 10 °C / min, and the time of the heat treatment is 1 - 3 h.

[0012] As a further technical solution, the quenching and cooling in S1 includes the following steps: after the induction heating ends, when the surface temperature of the roller bar drops to 1000 - 1100 °C, the roller bar is cooled by spraying a quenching medium, and a hardened roller bar is obtained after cooling.

[0013] As a further technical solution, the quenching medium is an aqueous solution of polyethylene glycol, the solute of the aqueous solution of polyethylene glycol consists of a first polyethylene glycol and a second polyethylene glycol, and the hydroxyl values of the first polyethylene glycol and the second polyethylene glycol are different.

[0014] As a further technical solution, the hydroxyl value of the first polyethylene glycol is 255 - 312 mgKOH / g, the hydroxyl value of the second polyethylene glycol is 102 - 125 mgKOH / g, and the mass ratio of the first polyethylene glycol to the second polyethylene glycol is 2 - 3:1.

[0015] In the present invention, polyethylene glycols with different hydroxyl values are used as the solute of the quenching medium, and the synergistic effect of the two is exerted. By adjusting the mass ratio of the two, the cooling rate of quenching is coordinated, the hardness difference caused by uneven cooling is reduced, and the hardness of the inner hole of the roller bar is further improved.

[0016] As a further technical solution, the concentration of the aqueous solution of polyethylene glycol is 15 wt% - 25 wt%.

[0017] As a further technical solution, the temperature of the quenching medium is 30 - 60 °C, the spraying time is 6 - 8 s, and the spraying flow density is 10 L / (m 2 ·s).

[0018] As a further technical solution, the material of the roller bar is GCr15.

[0019] As a further technical solution, the outer diameter of the roller bar is 20 mm, the inner hole diameter is 9 mm, the hole depth is 110 mm, the inner hole quenching area is 30 mm from the rod end, and the quenching depth is 1 mm.

[0020] The working principle and beneficial effects of the present invention are as follows:

[0021] In the present invention, a heat treatment process of quenching and tempering the roll bar is carried out successively. During the quenching process, two high-frequency quenching processes with different frequencies are carried out. The first high-frequency quenching enables the surface of the roll bar to complete the preliminary tissue transformation in a short time, ensuring that the surface layer is heated uniformly and rapidly. The second high-frequency quenching further refines the grains and improves the hardness of the inner hole of the roll bar. Specific Embodiments

[0022] The following will describe clearly and completely the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.

[0023] In the following examples and comparative examples:

[0024] The first polyethylene glycol: The model is PEG-400, the hydroxyl value is 255 - 312 mgKOH / g, and the manufacturer is Jiangsu Haian Petrochemical Factory;

[0025] The second polyethylene glycol: The model is PEG-1000, the hydroxyl value is 102 - 125 mgKOH / g, and the manufacturer is Jiangsu Haian Petrochemical Factory.

[0026] Example 1

[0027] A heat treatment process for improving the hardness of the inner hole of a roll bar includes the following steps:

[0028] S1. Quenching: Place the roll bar in a high-frequency inductor for induction heating. When the surface temperature of the roll bar drops to 1000 °C, spray a quenching medium through the spray holes to cool the roll bar by quenching. The spraying flow density is 10 L / (m 2 ·s), the spraying time is 6 s, the temperature of the quenching medium is 30 °C, and a hardened roll bar is obtained after cooling. The quenching medium is an aqueous solution of polyethylene glycol, the concentration of the aqueous solution of polyethylene glycol is 15 wt%, and the solute is the first polyethylene glycol; The specific operation of induction heating is: set the frequency of the first induction heating to 300 kHz, heat for 3 s, and after the heating ends, let it stand for 10 s. Set the frequency of the second induction heating to 200 kHz and heat for 1 s. The power of both induction heatings is 90 kW;

[0029] S2. Tempering: Place the hardened roll bar in a high-temperature furnace, heat it to 400 °C at a heating rate of 5 °C / min, hold it for 3 h, then take it out of the furnace, and cool it to room temperature to obtain the roll bar.

[0030] Example 2

[0031] A heat treatment process for improving the hardness of the inner hole of a roll bar includes the following steps:

[0032] S1. Quenching: Place the roller rod in a high-frequency inductor for induction heating. When the surface temperature of the roller rod drops to 1050 °C, spray a quenching medium through the liquid spray holes to cool the roller rod by quenching. The spraying flow density is 10 L / (m 2 ·s), the spraying time is 7 s, the temperature of the quenching medium is 45 °C. After cooling, a hardened roller rod is obtained. The quenching medium is an aqueous solution of polyethylene glycol, the concentration of the aqueous solution of polyethylene glycol is 20 wt%, and the solute is the first polyethylene glycol. The specific operation of induction heating is as follows: Set the frequency of the first induction heating to 300 kHz, heat for 3 s, and after the heating is completed, let it stand for 10 s. Then set the frequency of the second induction heating to 200 kHz and heat for 1 s. The power of both induction heatings is 100 kW;

[0033] S2. Tempering: Place the hardened roller rod in a high-temperature furnace, heat it at a heating rate of 8 °C / min to 450 °C, hold it for 2 h, then take it out of the furnace and cool it to room temperature to obtain the roller rod.

[0034] Example 3

[0035] A heat treatment process for improving the hardness of the inner hole of a roller rod includes the following steps:

[0036] S1. Quenching: Place the roller rod in a high-frequency inductor for induction heating. When the surface temperature of the roller rod drops to 1100 °C, spray a quenching medium through the liquid spray holes to cool the roller rod by quenching. The spraying flow density is 10 L / (m 2 ·s), the spraying time is 8 s, the temperature of the quenching medium is 60 °C. After cooling, a hardened roller rod is obtained. The quenching medium is an aqueous solution of polyethylene glycol, the concentration of the aqueous solution of polyethylene glycol is 25 wt%, and the solute is the first polyethylene glycol. The specific operation of induction heating is as follows: Set the frequency of the first induction heating to 300 kHz, heat for 3 s, and after the heating is completed, let it stand for 10 s. Then set the frequency of the second induction heating to 200 kHz and heat for 1 s. The power of both induction heatings is 120 kW;

[0037] S2. Tempering: Place the hardened roller rod in a high-temperature furnace, heat it at a heating rate of 10 °C / min to 500 °C, hold it for 1 h, then take it out of the furnace and cool it to room temperature to obtain the roller rod.

[0038] Example 4

[0039] Compared with Example 1, the difference in Example 4 is that the frequency of the first induction heating is 200 kHz and the frequency of the second induction heating is 300 kHz.

[0040] Example 5

[0041] Compared with Example 1, Example 5 is different in that the solute of the polyethylene glycol aqueous solution is the second polyethylene glycol.

[0042] Example 6

[0043] Compared with Example 1, Example 6 is different in that the solute of the polyethylene glycol aqueous solution is composed of the first polyethylene glycol and the second polyethylene glycol with a mass ratio of 2:1.

[0044] Example 7

[0045] Compared with Example 1, Example 7 is different in that the solute of the polyethylene glycol aqueous solution is composed of the first polyethylene glycol and the second polyethylene glycol with a mass ratio of 3:1.

[0046] Comparative Example 1

[0047] Compared with Example 1, Comparative Example 1 is different in that the induction heating parameters of Comparative Example 1 are: the frequency of induction heating is 300 kHz, and the heating time is 4 s.

[0048] Comparative Example 2

[0049] Compared with Example 1, Comparative Example 2 is different in that the induction heating parameters of Comparative Example 2 are: the frequency of induction heating is 200 kHz, and the heating time is 4 s.

[0050] Comparative Example 3

[0051] Compared with Example 1, Comparative Example 3 is different in that the induction heating parameters of Comparative Example 3 are: the frequency of the first induction heating is 300 kHz, heating for 3 s, after the heating is completed, standing for 10 s, setting the frequency of the second induction heating to 300 kHz, and heating for 1 s.

[0052] Comparative Example 4

[0053] Compared with Example 1, Comparative Example 4 is different in that the induction heating parameters of Comparative Example 4 are: the frequency of the first induction heating is 200 kHz, heating for 3 s, after the heating is completed, standing for 10 s, setting the frequency of the second induction heating to 200 kHz, and heating for 1 s.

[0054] The roller rods prepared in Examples 1-7 and Comparative Examples 1-4 were tested according to the following method:

[0055] 1. Hardness: According to the test method specified in GB / T 230.1-2018 "Metallic materials - Rockwell hardness test - Part 1: Test method", the hardness of the outer surface and inner wall of the roller rod was tested, and the test position was 30 mm from the rod end.

[0056] The test results are shown in the following table:

[0057] Table 1 Performance test results of the roller rods prepared in Examples 1-7 and Comparative Examples 1-4

[0058]

[0059] From the data of Examples 1-7, it can be seen that on the premise that the hardness of the outer surface of the roller rod is not less than 50 HRC, the hardness of the inner hole of the roller rod can be increased to more than 40 HRC, significantly enhancing the wear resistance of the roller rod.

[0060] Compared with Comparative Examples 1-4, the induction heating in Example 1 was carried out in two times, and the frequencies of the first induction heating and the second induction heating were different. As a result, the surface hardness and the inner wall hardness of Example 1 were higher than those of Comparative Examples 1-4, indicating that when the induction heating is carried out in two times and the frequencies of the first induction heating and the second induction heating are different, the hardness of the inner hole of the roller rod can be increased.

[0061] Compared with Example 1, the frequency of the first induction heating in Example 4 < the frequency of the second induction heating. As a result, the inner hole hardness of Example 4 was less than that of Example 1, indicating that when the frequency of the first induction heating > the frequency of the second induction heating, the hardness of the inner hole of the roller rod can be further increased.

[0062] Compared with Examples 1 and 5, the first polyethylene glycol and the second polyethylene glycol were simultaneously added as the quenching medium in Examples 6 and 7. As a result, the inner hole hardness of Examples 6 and 7 was higher than that of Examples 1 and 5, indicating that the first polyethylene glycol and the second polyethylene glycol play a synergistic role and can further increase the hardness of the inner hole of the roller rod.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A heat treatment process for improving the hardness of the inner hole of a roller rod, characterized in that: The following steps are involved: S1. Quenching: After the roller is induction heated and the surface temperature of the roller drops to 1000-1100°C, the roller is cooled by spraying a quenching medium to obtain a hardened roller; S2, tempering: the hardened roller rod is heated to 400~500℃ for heating treatment to obtain a roller rod with high inner hole hardness; The induction heating is performed twice, the first induction heating frequency is 300kHz, the time is 3s, and the second induction heating frequency is 200kHz, the time is 1s; The quenching medium is a polyethylene glycol aqueous solution, the solute of the polyethylene glycol aqueous solution consists of a first polyethylene glycol and a second polyethylene glycol, the hydroxyl value of the first polyethylene glycol is 255-312 mgKOH / g, the hydroxyl value of the second polyethylene glycol is 102-125 mgKOH / g, and the mass ratio of the first polyethylene glycol to the second polyethylene glycol is 2-3:

1.

2. A heat treatment process for improving the hardness of the inner hole of a roller rod according to claim 1, characterized in that: The heating rate in S2 is 5-10°C / min, and the heating treatment time is 1-3h.

3. The heat treatment process for improving the hardness of the inner hole of the roller rod according to claim 1, characterized in that: The concentration of the polyethylene glycol aqueous solution is 15wt%-25wt%.

4. The heat treatment process for improving the hardness of the inner hole of the roller rod according to claim 1, characterized in that: The temperature of the quenching medium is 30-60°C, the injection time is 6-8s, and the injection flow density is 10L / (m 2 ·s).

5. The heat treatment process for improving the hardness of the inner hole of the roller rod according to claim 1, characterized in that: The material of the roller rod is GCr15.

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