JP2017025350A - Method and apparatus for hardening surface of steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for hardening (for example, carburizing) the surface of a work piece by blowing processing gas, capable of obtaining an excellent hardened layer in a short time by avoiding the reduction of temperature on the surface of the work piece due to the blowing of the processing gas.SOLUTION: An apparatus A for hardening the surface of a work piece W by blowing processing gas on the surface of the work piece W in a high temperature state comprises at least: first heating means 10 for heating the work piece W to be processed; a nozzle 20 for blowing the processing gas on the work piece W; and second heating means 25 for heating a portion W2 of the work piece W a temperature of which might be reduced due to the blowing of the processing gas. Heating by the second heating means 25 can avoid the temperature reduction of the blown portion.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method and apparatus for hardening a surface of a steel material.

  Drive parts such as engines require quality such as wear resistance and surface fatigue strength in order to perform the required power transmission function. To ensure these qualities, the surface of the steel material is carbon or Carburizing treatment or nitriding treatment for increasing the amount of carbon or nitrogen in the surface layer by impregnating and diffusing nitrogen is performed. A method and apparatus for carburizing or nitriding the surface of a steel material in an air atmosphere have also been proposed. Patent Document 1 describes an example of a carburizing apparatus.

  As shown in FIG. 7, the carburizing apparatus includes a heating unit 10 that heats a workpiece W that is a steel material, and a nozzle 20 that blows a carburizing gas onto the workpiece W, and the workpiece W heated by the heating unit 10. Carburizing treatment is performed by directly blowing a carburizing gas having a concentration less than the explosion limit from the nozzle 20 to the carburizing required portion W1.

JP 2011-026651 A

  In the method and apparatus for carburizing the steel material surface in the atmosphere described in Patent Document 1, the carburizing gas, which is the processing gas, is blown to the carburized portion W1 of the heated workpiece W during the processing. It is inevitable that the surface temperature of the workpiece W is lowered by the gas blowing. When the surface temperature of the workpiece W is lower than the set temperature, the carburizing ability is lowered, and carburizing cannot be performed or the carburizing depth may be insufficient. In order to solve this, it is conceivable that the temperature of the workpiece W is increased in advance by the amount of the temperature drop caused by gas blowing, but when the workpiece W, which is a steel material, is heated to a temperature higher than the desired processing temperature, the crystal grains become coarse. The strength may decrease. Further, the processing gas is decomposed around the workpiece W, and the amount of carburizing gas that reaches the surface of the workpiece W may be reduced. Although it is conceivable to warm the carburizing gas in advance, the carburizing gas cannot be heated to the processing temperature of the workpiece W that is a steel material. Therefore, in actual processing, the inconvenience caused by the temperature drop of the surface is covered by extending the processing time.

  The present invention eliminates the above-mentioned inconvenience caused by the temperature of the workpiece surface being lowered by spraying the processing gas in the method and apparatus for performing the hardening treatment on the surface of the workpiece, which is a steel material, by spraying the processing gas. It is an object of the present invention to provide a more improved method and apparatus for hardening a steel surface that can be performed.

  The steel material surface hardening treatment method according to the present invention is a steel material surface hardening treatment method in which the surface of the steel material is hardened by spraying a treatment gas on the surface of the steel material in a high temperature state, by contacting the treatment gas to be blown. Curing treatment is performed while auxiliary heating is performed by a second heating means different from the heating means for maintaining the steel material at a high temperature in order to reduce the temperature drop of the steel material surface.

  According to the method for hardening a steel surface according to the present invention, the temperature drop on the surface of the steel material caused by the spraying of the processing gas is compensated by the heating by the second heating means, so that the surface temperature of the workpiece is set to a required temperature during the processing. Thus, the required curing process can be completed without increasing the processing time. In addition, since it is not necessary to raise the temperature of the workpiece, which is a steel material, to a temperature higher than that suitable for processing, it is possible to prevent the crystal grains from becoming coarse and lowering the strength, and the processing gas is unnecessarily decomposed. Can also be avoided.

  In one aspect of the steel material surface hardening treatment method according to the present invention, the surface temperature of the steel material (work) is measured at a portion where the treatment gas is sprayed, and the second heating is performed so that the surface temperature becomes a predetermined temperature. The curing process is performed while controlling the heating amount by the means. According to this method, it is possible to reduce the processing variation between workpieces, and to reduce the variation within the workpiece.

  In the method for hardening a steel surface according to the present invention, any suitable heating means can be used as the second heating means as long as it can locally heat a desired position. Laser is preferable, but heating means such as an infrared heater (lamp) may be used.

  The steel material surface hardening treatment method according to the present invention can be applied to any conventionally known hardening treatment method in which the surface of the steel material is hardened by blowing a treatment gas onto the surface of the steel material in a high temperature state. As an example, a carburizing process or a nitriding process by spraying a processing gas can be given.

  The present invention is further an apparatus for performing a hardening treatment on the surface of a steel material by hardening the surface of the steel material by blowing a treatment gas on the surface of the steel material in a high temperature state, and the apparatus is the steel material that is a processing object. A first heating means for heating the steel, a nozzle for blowing a processing gas to the steel material, and a second heating means for heating a portion of the steel material to which the processing gas from the nozzle is blown. An apparatus for performing a hardening treatment on the steel surface is also disclosed.

  In the apparatus for hardening a steel surface according to the present invention, a temperature measuring means for measuring a temperature of a portion of the steel material to which a processing gas from the nozzle is blown, and the second heating based on a measurement result of the temperature measuring means. It is a preferable aspect to further include heating control means for controlling the heating amount of the means.

  In the apparatus for performing the hardening treatment on the surface of the steel material according to the present invention, any suitable heating means can be used as the second heating means as long as it can locally heat a desired position. Laser is preferable, but heating means such as an infrared heater (lamp) may be used.

  The apparatus for hardening a steel surface according to the present invention can be applied to any of the conventionally known hardening treatment apparatuses that harden the surface of the steel by blowing a treatment gas on the surface of the steel in a high temperature state. it can. As an example, a carburizing treatment apparatus or a nitriding treatment apparatus by spraying a treatment gas can be mentioned.

  According to the present invention, in the method and apparatus for hardening a steel surface that hardens the surface of the steel material by blowing the treatment gas onto the surface of the steel material in a high temperature state, the temperature drop generated on the surface of the steel material caused by the blowing of the treatment gas Is compensated by heating by the second heating means, so that the surface temperature of the workpiece, which is a steel material, can be maintained at a required temperature at the time of processing. As a result, the required hardening process can be performed without increasing the processing time. Can be terminated. Moreover, since it is not necessary to raise the temperature of the workpiece | work which is steel materials more than the temperature suitable for a process, it can also avoid that a crystal grain coarsens and intensity | strength falls. In addition, it is possible to suppress unnecessary decomposition of the processing gas.

The schematic diagram which shows an example of the apparatus which can implement the hardening processing method of the steel material surface by this invention. The graph which shows the relationship between carburizing temperature and the amount of carburizing per unit time unit area. The graph (FIG. 3 (a)) which shows the relationship between the temperature and time of the workpiece | work surface in the Example which applied this invention to the carburizing process, and sectional photograph (FIG.3 (b)) which shows the state after a process. The graph (FIG. 4 (a)) which shows the relationship between the temperature of the workpiece | work surface and time in the comparative example in a carburizing process, and sectional drawing (FIG.4 (b)) which shows the state after a process. The graph (FIG. 5 (a)) which shows the relationship between the temperature of the workpiece | work surface and time in the Example which applied this invention to the nitriding process, and sectional photograph (FIG.5 (b)) which shows the state after a process. The graph (FIG. 6 (a)) which shows the relationship between the temperature of the workpiece | work surface and time in the comparative example in a nitriding process, and sectional drawing (FIG.6 (b)) which shows the state after a process. The schematic diagram explaining the conventional apparatus which performs the carburizing process on the steel material surface in air | atmosphere.

  Hereinafter, an embodiment of a method and apparatus for hardening a steel surface according to the present invention will be described with reference to the drawings, taking a carburizing method and a carburizing apparatus as an example.

  As shown in FIG. 1, the carburizing apparatus A includes an appropriate jig 1 for supporting a workpiece W that is a steel material, and the workpiece W is rotatably supported by the jig 1. An annular first heating means 10 is positioned so as to surround the workpiece W, and in this example, a high-frequency heating device is used. As the first heating means 10, any heating means that can heat at least the necessary carburizing portion W <b> 1 required for the workpiece W to a required temperature can be used as appropriate, and an infrared heater (lamp) or the like can also be used. Moreover, the heating by electricity supply may be sufficient.

  The carburizing apparatus A includes a nozzle 20 at a position where the carburizing gas can be sprayed toward the substantially central portion of the workpiece W in the axial direction of the carburizing required portion W1. Carburizing gas from a gas cylinder 21 equipped with a pressure adjusting device is fed to the nozzle 20 via a mass flow controller 22. The fed carburizing gas is sprayed from the nozzle 20 toward the carburizing required portion W1 of the workpiece W.

  The carburizing apparatus A includes a radiation thermometer 23 as temperature measuring means capable of measuring the surface temperature of the work W at a site where the carburizing gas is sprayed. The temperature measuring means is preferably the radiation thermometer 23, but is not limited thereto. The region where the temperature measuring means measures the temperature is preferably the entire region of the carburizing required portion W1, and is preferably a temperature measuring means capable of outputting the average temperature, but in the axial direction of the carburizing required portion W1. Even if the temperature in the vicinity of the center position is measured and the value is output, the intended purpose can be achieved. The temperature information of the radiation thermometer 23 is sent to the control unit 24.

  The carburizing apparatus A includes a laser oscillation unit 25 as a second heating unit that can heat the portion W2 of the workpiece W, the temperature of which decreases when the carburizing gas is blown from the nozzle 20. The laser oscillation means 25 may be a conventionally known one. Due to the laser energy from the laser oscillating means 25, the portion W2 where the temperature has decreased is heated. The region heated by the second heating means is preferably all of the region where the temperature of the workpiece W is lowered by the blowing of the carburizing gas. For this reason, the laser oscillation means 25 sets the laser irradiation region as the axis of the workpiece W. Those that can be adjusted in the direction or those that can be heated as a surface by changing the beam diameter of the laser are preferable. Since the workpiece W, which is a steel material, has thermal conductivity, local heating may be used. In addition, although 30 is a casing in FIG. 1, it is omissible.

  In one aspect, the radiation thermometer 23 and the laser oscillation means 25 are position-controlled so that the temperature monitoring part by the radiation thermometer 23 and the laser irradiation part from the laser nozzle of the laser oscillation means 25 are the same part. . In that case, it is desirable that the “same part” is a substantially central part in the axial direction of the carburizing required part W1 in the workpiece W. Accordingly, it is possible to reliably heat the temperature-decreasing portion without performing special position control on the radiation thermometer 23 and the laser oscillation means 25 during the carburizing process.

  The laser output from the laser oscillating means 25 is controlled by a signal from the control unit 24 described above. In one aspect, the control unit 24 determines that the temperature of the carburization required portion W1 of the work W is based on the temperature information from the radiation thermometer 23 by blowing the carburizing gas from the initial temperature, that is, the temperature before the carburizing gas blowing. This is a mode in which the controller 24 controls the laser oscillation means 25 so as to continuously determine how much the temperature has decreased and to output laser energy sufficient to compensate for the temperature decrease. By controlling the output of the laser oscillating means 25 in this way, it becomes possible to continuously maintain the temperature of the part W1 requiring carburization of the workpiece W at a required temperature, and the desired carburizing process proceeds, and the desired The carburizing time for obtaining the carburizing depth can be shortened.

  It is possible to predict how much the temperature of the workpiece surface is lowered by the blowing of carburizing gas during the carburizing process from the actual operation results of the actual machine or by calculation. In that case, the control unit 24 is provided with information on the predicted temperature drop without using the temperature information from the radiation thermometer 23, and the output of the laser oscillation means 25 is controlled based on the information. It may be. In that case, the radiation thermometer 23 as temperature measuring means can be omitted.

  There may be one “second heating means”, or two or more “second heating means” may be arranged in the axial direction of the carburization-needed portion W1 of the workpiece W. Further, a heating means that can heat a part that needs to be heated as a surface, for example, a heating means such as an infrared heater (lamp) can be used.

In the carburizing process, the carburizing amount changes depending on the temperature. FIG. 2 shows an example of this. Carburizing temperature and F when C ₃ H ₈ (1%) (other N ₂ ) is used as the carburizing gas and carburizing treatment is performed at a carburizing gas partial pressure of 740 Pa and a carburizing time of 33 minutes. An example of the relationship between values (the amount of carburization per unit time unit area) is shown. As shown in the graph, the F value increases with the increase in the carburizing temperature, and in actual carburizing treatment, when the temperature of the work W is decreased by blowing the carburizing gas, the carburizing amount decreases accordingly. When such a temperature drop occurs, it is necessary to lengthen the treatment time in order to ensure a desired carburization amount. In the case of the present invention, the temperature drop generated on the surface of the steel material (work W) by being in contact with the sprayed processing gas is different from the heating means for maintaining the steel material (work W) in a high temperature state. Since the curing process is performed while supplementing by auxiliary heating by the heating means (output from the laser oscillation means 25), the above-described temperature drop can be eliminated, and a desired carburizing amount can be ensured without lengthening the processing time. be able to.

  In the above description, the carburizing process has been described as an example. However, the method and apparatus according to the present invention may be applied in another form in which the surface of the work is hardened by blowing a processing gas onto the surface of the work, for example, a nitriding process. It can be applied as it is.

  Hereinafter, advantages of the present invention will be described with reference to Examples and Comparative Examples.

[Example 1: Carburizing treatment]
The apparatus described based on FIG. 1 was used. As the workpiece W, a steel material (S25C) which is a cylindrical body having a diameter of 18 mm and a height of 40 mm was used. The workpiece W was attached to the rotatable jig 1, and the workpiece W was rotated at 100 rpm. High frequency induction heating means was used as the first heating means 10. A radiation thermometer 23 was used as the temperature measuring means, and the center position in the axial direction of the workpiece W requiring carburization W1 could be measured. Laser oscillating means 25 provided with a nozzle was used as the second heating means, and the laser irradiation part was set so as to be the central position in the axial direction of carburizing required part W1.

When the workpiece W was heated by high frequency induction heating and reached a predetermined temperature (950 ° C.), the carburizing gas was sprayed from the nozzle 20 toward the axial center position of the workpiece W in the carburizing required portion W1.
The experimental conditions are as shown in Table 1.

  FIG. 3A shows the relationship between the elapsed time (s) from the start of the experiment and the temperature measured by the radiation thermometer 23 (the temperature at the central position in the axial direction at the carburizing required portion W1 of the workpiece W). In the experiment, when the surface temperature of the workpiece W reached 950 ° C. by high-frequency induction heating, the laser oscillation means 25 was activated at the same time as the blowing of the processing gas from the nozzle 20 was started. And based on the temperature information from the radiation thermometer 23, the output of the laser oscillation means 25 was controlled so that measurement temperature could continue and maintain 950 degreeC. As a result, the surface temperature of the workpiece W could be maintained at approximately 950 ° C. even after the start of spraying.

  The structure of the work W after spraying for 10 minutes was observed. FIG. 3B is a cross-sectional photograph showing a state after processing. As shown in the photograph, a carburized layer having a desired depth (about 100 μm) was formed on the surface of the workpiece W.

[Comparative Example 1]
Carburizing treatment was performed in the same manner as in Example 1. However, the laser oscillating means 25 was not operated even when the processing gas was blown from the nozzle 20. FIG. 4A shows the relationship between the elapsed time (s) from the start of the experiment and the temperature measured by the radiation thermometer 23 (the temperature at the central position in the axial direction in the carburizing portion W1 of the workpiece W). Moreover, the cross-sectional photograph of the workpiece | work W after performing spraying for 10 minutes was shown in FIG.4 (b).

  Since the laser oscillation means 25 was not operated after spraying, the surface temperature of the workpiece W was lowered to approximately 607 ° C. As a result, a carburized layer was not formed on the surface of the workpiece W as shown in FIG.

  The temperature drop of the workpiece W can be reduced by adjusting the flow rate of the processing gas. For example, the surface temperature of the workpiece W can be maintained at 723 ° C. or more without operating the laser oscillation means 25. Can do. However, in this case, a longer treatment time is required to form a carburized layer having the same thickness.

[Example 2: Nitrogen treatment]
Nitrogen treatment was performed in the same manner as in Example 1. The apparatus and workpiece W used are the same as those in the first embodiment. The experimental conditions are shown in Table 2.
The experimental conditions are as shown in Table 2.

  FIG. 5A shows the relationship between the elapsed time (s) from the start of the experiment and the temperature measured by the radiation thermometer 23 (the temperature at the central position in the axial direction of the workpiece W where nitriding is required). In the experiment, when the surface temperature of the workpiece W reached 780 ° C. by the high frequency induction heating, the laser oscillation means 25 was activated simultaneously with the start of the blowing of the processing gas from the nozzle 20. Similarly to Example 1, based on the temperature information from the radiation thermometer 23, the output of the laser oscillation means 25 was controlled so that the measured temperature could be maintained at 780 ° C. As a result, the surface temperature of the workpiece W could be maintained at approximately 780 ° C. even after the start of spraying.

  The structure of the work W after spraying for 10 minutes was observed. FIG. 5B is a cross-sectional photograph showing a state after processing. As shown in the photograph, a nitriding layer having a desired depth (about 150 μm) was formed on the surface of the workpiece W.

[Comparative Example 2]
Nitrogen treatment was performed in the same manner as in Example 2. However, the laser oscillating means 25 was not operated even when the processing gas was blown from the nozzle 20. FIG. 5A shows the relationship between the elapsed time (s) from the start of the experiment and the temperature measured by the radiation thermometer 23 (the temperature at the central position in the axial direction of the workpiece W where the carburization is required). Moreover, the cross-sectional photograph of the workpiece | work W after performing spraying for 10 minutes was shown in FIG.5 (b).

  Since the laser oscillation means 25 was not operated after spraying, the surface temperature of the workpiece W was lowered to about 510 ° C. As a result, even after 10 minutes, no nitriding layer was formed on the surface of the workpiece W as shown in FIG.

  Even in the nitriding treatment, the temperature drop of the workpiece W can be reduced by adjusting the flow rate of the processing gas. For example, the surface temperature of the workpiece W can be reduced without operating the laser oscillation means 25. It can be maintained at 723 ° C. or higher. However, in this case, a longer treatment time is required to form a nitriding layer having the same thickness.

A ... Carburizing device,
W ... Work (steel),
W1 ... Carburization required part required for workpiece W,
W2 ... the region where the temperature drops due to the blowing of carburizing gas,
1 ... Jig,
10: First heating means,
20 ... Nozzle that blows carburizing gas,
21 ... Gas cylinder,
22 ... Mass flow controller,
23: Radiation thermometer as temperature measuring means,
24 ... control unit,
25... Laser oscillation means as second heating means,
30. Casing.

Claims (8)

A method of hardening a steel surface to harden the surface of the steel material by blowing a treatment gas on the surface of the steel material in a high temperature state,
It is characterized in that a hardening process is performed while auxiliary heating is performed by a second heating means different from a heating means for maintaining the steel material in a high temperature state due to a temperature drop on the surface of the steel material caused by contact with the sprayed processing gas. Hardening method for steel surface.   It measures the surface temperature of the steel material at the site where the processing gas is sprayed, and performs the hardening process while controlling the heating amount by the second heating means so that the surface temperature becomes a predetermined temperature. The method for hardening a steel surface according to claim 1.   The method of hardening a steel material according to claim 1 or 2, wherein a laser is used as the second heating means.   The steel material surface hardening treatment method according to any one of claims 1 to 3, wherein the steel material surface hardening treatment is either carburizing treatment or nitriding treatment. An apparatus for performing a hardening treatment on the surface of a steel material by hardening a surface of the steel material by blowing a treatment gas on the surface of the steel material in a high temperature state,
A first heating means for heating the steel material that is the object to be treated;
A nozzle for blowing a processing gas on the steel material;
A second heating means for heating a portion of the steel material to which the processing gas from the nozzle is sprayed;
The apparatus which performs the hardening process of the steel material surface characterized by including at least. Temperature measuring means for measuring the temperature of the portion of the steel material to which the processing gas from the nozzle is sprayed;
Heating control means for controlling the heating amount of the second heating means based on the measurement result of the temperature measuring means;
The apparatus which performs hardening processing of the steel material surface of Claim 5 characterized by the above-mentioned.   The apparatus for performing a hardening treatment on a steel material surface according to claim 5 or 6, wherein the second heating means is a laser.   The said apparatus is either a carburizing processing apparatus or a nitriding processing apparatus, The apparatus which performs the hardening process of the steel material surface as described in any one of Claims 5-7 characterized by the above-mentioned.

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