Heat treatment process for improving hardness of inner hole of roller rod

Abstract

The invention relates to the technical field of heat treatment processes, and provides a heat treatment process for improving the hardness of an inner hole of a roller rod, which comprises the following steps: S1, quenching: carrying out induction heating on the roller rod and then carrying out quenching cooling to obtain a hardened roller rod; s2, tempering is conducted, specifically, the hardened roller rod is heated to 400-500 DEG C to be subjected to heating treatment, and then the roller rod with the high inner hole hardness is obtained; the induction heating is performed twice, and the frequency of the first induction heating is different from that of the second induction heating. According to the technical scheme, the problem that the hardness of the inner hole of the roller rod is low in the prior art is solved.

Description

Technical Field

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

[0002] In the field of wood-based panel production, the double steel belt continuous flat press plays a vital role. The press is mainly composed of the upper part of the press, the lower part of the press, and the continuous circulating steel belt and roller chain that surround the upper part and the lower part of the press respectively. Among them, the chain drives the roller to run continuously with the help of the needle to ensure the smooth progress of the entire pressing process.

[0003] With the long-term operation of artificial board production, the wear problem of the inner hole of the roller rod is becoming more and more serious. Since the roller rod is always under stress during the working process and frequently rubs against the threading needle, its inner hole is constantly subjected to the test of wear. Once the inner hole is seriously worn, it will directly cause the entire roller rod to lose its normal working ability and have to face scrapping. For a standard 31.9-meter-long press, the number of roller rods required to be installed is nearly 7,000, and the procurement cost of the roller rod is high, with a total price of about 1.5 million yuan. Such a large-scale roller rod configuration, if frequently scrapped due to inner hole wear, will not only cause huge economic losses, but also seriously affect the production efficiency and continuity of artificial boards. Therefore, it is 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 invention proposes a heat treatment process for improving the hardness of the inner hole of a roller rod, thereby solving 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, comprising the following steps: S1. Quenching: The roller rod is induction heated and then quenched to obtain a hardened roller rod; 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, and the frequency of the first induction heating is different from the frequency of the second induction heating.

[0006] As a further technical solution, the frequency of the first induction heating is greater than 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.

[0007] As a further technical solution, the time of the first induction heating is 3 seconds, the time of the second induction heating is 1 second, and the power of the first induction heating and the second induction heating are both 90-120 kW.

[0008] As a further technical solution, the heating rate in S2 is 5-10°C / min, and the heating treatment time is 1-3h.

[0009] As a further technical solution, the quenching cooling described in S1 includes the following steps: after the induction heating is completed, after the surface temperature of the roller rod drops to 1000~1100℃, the roller rod is cooled by spraying a quenching medium to obtain a hardened roller rod after cooling.

[0010] As a further technical solution, 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, and the first polyethylene glycol and the second polyethylene glycol have different hydroxyl values.

[0011] 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.

[0012] In the present invention, polyethylene glycol with different hydroxyl values ​​is used as the solute of the quenching medium to exert the synergistic effect of the two. 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 rod is further improved.

[0013] As a further technical solution, the concentration of the polyethylene glycol aqueous solution is 15wt%~25wt%.

[0014] As a further technical solution, 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).

[0015] As a further technical solution, the material of the roller rod is GCr15.

[0016] As a further technical solution, the outer diameter of the roller rod is 20 mm, the inner hole diameter is 9 mm, the hole depth is 110 mm, the inner hole quenching area is 30 mm away from the rod end, and the quenching depth is 1 mm.

[0017] The working principle and beneficial effects of the present invention are: In the present invention, the roller rod is subjected to a heat treatment process of quenching and tempering in sequence. During the quenching process, two high-frequency quenching processes with different frequencies are carried out. The first high-frequency quenching enables the roller rod surface to complete a preliminary structural transformation in a short time, ensuring that the surface layer is heated quickly and evenly. The second high-frequency quenching further refines the grains and improves the hardness of the inner hole of the roller rod. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In the following examples and comparative examples: The first polyethylene glycol: model is PEG-400, hydroxyl value is 255~312mgKOH / g, the manufacturer is Jiangsu Hai'an Petrochemical Plant; The second polyethylene glycol: model is PEG-1000, the hydroxyl value is 102~125mgKOH / g, and the manufacturer is Jiangsu Hai'an Petrochemical Plant.

[0020] Example 1 A heat treatment process for improving the hardness of the inner hole of a roller rod comprises the following steps: S1. Quenching: Place the roller into a high-frequency inductor for induction heating. When the roller surface temperature drops to 1000°C, spray the quenching medium through the spray hole to quench the roller. The spray flow density is 10L / (m 2 ·s), the spraying time is 6s, the temperature of the quenching medium is 30°C, and a hardened roller rod is obtained after cooling, wherein the quenching medium is a polyethylene glycol aqueous solution, the concentration of the polyethylene glycol aqueous solution is 15wt%, and the solute is the first polyethylene glycol; the specific operation of induction heating is: the frequency of the first induction heating is set to 300kHz, heating for 3s, after the heating is completed, standing for 10s, setting the frequency of the second induction heating to 200kHz, heating for 1s, and the power of the two induction heatings is 90kW; S2. Tempering: Place the hardened roller rod in a high temperature furnace, heat it to 400°C at a heating rate of 5°C / min, keep it at that temperature for 3 hours, then take it out of the furnace and cool it to room temperature to obtain the roller rod.

[0021] Example 2 A heat treatment process for improving the hardness of the inner hole of a roller rod comprises the following steps: S1. Quenching: Place the roller into a high-frequency inductor for induction heating. When the roller surface temperature drops to 1050°C, spray the quenching medium through the spray hole to quench the roller. The spray flow density is 10L / (m 2·s), the spraying time is 7s, the temperature of the quenching medium is 45°C, and a hardened roller rod is obtained after cooling, wherein the quenching medium is a polyethylene glycol aqueous solution, the concentration of the polyethylene glycol aqueous solution is 20wt%, and the solute is the first polyethylene glycol; the specific operation of induction heating is: the frequency of the first induction heating is set to 300kHz, heating for 3s, after the heating is completed, standing for 10s, setting the frequency of the second induction heating to 200kHz, heating for 1s, and the power of the two induction heatings is 100kW; S2. Tempering: put the hardened roller rod into a high temperature furnace, heat it to 450℃ at a heating rate of 8℃ / min, keep it at that temperature for 2h, then take it out of the furnace and cool it to room temperature to obtain the roller rod.

[0022] Example 3 A heat treatment process for improving the hardness of the inner hole of a roller rod comprises the following steps: S1. Quenching: Place the roller into a high-frequency inductor for induction heating. When the roller surface temperature drops to 1100°C, spray the quenching medium through the spray hole to quench the roller. The spray flow density is 10L / (m 2 ·s), the spraying time is 8s, the temperature of the quenching medium is 60°C, and a hardened roller rod is obtained after cooling, wherein the quenching medium is a polyethylene glycol aqueous solution, the concentration of the polyethylene glycol aqueous solution is 25wt%, and the solute is the first polyethylene glycol; the specific operation of induction heating is: the frequency of the first induction heating is set to 300kHz, heating for 3s, after the heating is completed, standing for 10s, setting the frequency of the second induction heating to 200kHz, heating for 1s, and the power of the two induction heatings is 120kW; S2. Tempering: Place the hardened roller rod in a high temperature furnace, heat it to 500°C at a heating rate of 10°C / min, keep it at that temperature for 1 hour, then take it out of the furnace and cool it to room temperature to obtain the roller rod.

[0023] Example 4 Compared with Example 1, the difference of 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.

[0024] Example 5 Compared with Example 1, the difference of Example 5 is that the solute of the polyethylene glycol aqueous solution is a second polyethylene glycol.

[0025] Example 6 Compared with Example 1, the difference of Example 6 is that the solute of the polyethylene glycol aqueous solution consists of the first polyethylene glycol and the second polyethylene glycol in a mass ratio of 2:1.

[0026] Example 7 Compared with Example 1, the difference of Example 7 is that the solute of the polyethylene glycol aqueous solution consists of the first polyethylene glycol and the second polyethylene glycol in a mass ratio of 3:1.

[0027] Comparative Example 1 Compared with Example 1, the difference of Comparative Example 1 is 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.

[0028] Comparative Example 2 Compared with Example 1, the difference of Comparative Example 2 is 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.

[0029] Comparative Example 3 Compared with Example 1, the difference of Comparative Example 3 is that the induction heating parameters of Comparative Example 3 are: the frequency of the first induction heating is 300 kHz, heating for 3 seconds, after the heating is completed, standing for 10 seconds, setting the frequency of the second induction heating to 300 kHz, heating for 1 second.

[0030] Comparative Example 4 Compared with Example 1, the difference of Comparative Example 4 is that the induction heating parameters of Comparative Example 4 are: the frequency of the first induction heating is 200 kHz, heating for 3 seconds, after the heating is completed, standing for 10 seconds, setting the frequency of the second induction heating to 200 kHz, heating for 1 second.

[0031] The rollers prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were tested according to the following method: 1. Hardness: According to the test method specified in GB / T 230.1-2018 "Rockwell hardness test for metallic materials - Part 1: Test method", the hardness of the outer surface and inner wall of the roller rod is tested at a position 30 mm from the rod end.

[0032] The test results are shown in the following table: Table 1 Performance test results of rollers prepared in Examples 1 to 7 and Comparative Examples 1 to 4

[0033] From the data of Examples 1 to 7, it can be seen that, under the premise that the outer surface hardness of the roller rod is not less than 50 HRC, the present solution can increase the inner hole hardness of the roller rod to above 40 HRC, thereby significantly enhancing the wear resistance of the roller rod.

[0034] Compared with Comparative Examples 1 to 4, the induction heating of Example 1 is performed twice, and the frequency of the first induction heating is different from the frequency of the second induction heating. As a result, the surface hardness and the inner wall hardness of Example 1 are higher than those of Comparative Examples 1 to 4, indicating that when the induction heating is performed twice, and the frequency of the first induction heating is different from the frequency of the second induction heating, the hardness of the inner hole of the roller rod can be improved.

[0035] Compared with Example 1, the frequency of the first induction heating in Example 4 is less than the frequency of the second induction heating. As a result, the inner hole hardness of Example 4 is less than that of Example 1, indicating that when the frequency of the first induction heating is greater than the frequency of the second induction heating, the hardness of the inner hole of the roller rod can be further improved.

[0036] Compared with Examples 1 and 5, Examples 6 and 7 simultaneously add the first polyethylene glycol and the second polyethylene glycol as quenching media. As a result, the inner hole hardness of Examples 6 and 7 is 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 improve the hardness of the inner hole of the roller rod.

[0037] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should 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: The roller rod is induction heated and then quenched to obtain a hardened roller rod; 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, and the frequency of the first induction heating is different from the frequency of the second induction heating.

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 frequency of the first induction heating is greater than 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.

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 time of the first induction heating is 3 seconds, the time of the second induction heating is 1 second, and the power of the first induction heating and the second induction heating are both 90-120 kW.

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 heating rate in S2 is 5-10°C / min, and the heating treatment time is 1-3h.

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 quenching cooling in S1 includes the following steps: after the induction heating is completed, when the surface temperature of the roller rod drops to 1000-1100° C., the roller rod is cooled by spraying a quenching medium to obtain a hardened roller rod after cooling.

6. A heat treatment process for improving the hardness of the inner hole of a roller rod according to claim 5, characterized in that: The quenching medium is a polyethylene glycol aqueous solution, the solute of which consists of a first polyethylene glycol and a second polyethylene glycol, and the first polyethylene glycol and the second polyethylene glycol have different hydroxyl values.

7. A heat treatment process for improving the hardness of the inner hole of a roller rod according to claim 6, characterized in that: 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.

8. The heat treatment process for improving the hardness of the inner hole of the roller rod according to claim 6, characterized in that: The concentration of the polyethylene glycol aqueous solution is 15wt%-25wt%.

9. The heat treatment process for improving the hardness of the inner hole of the roller rod according to claim 5, 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).

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

Images