JP2016033243A - Carburization treatment method and carburization treatment device of steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carburization treatment method of a steel material capable of toughening simply and quickly the surface of the steel material.SOLUTION: In a carburization treatment method of a steel material, a tooth material is subjected to a carburization treatment by bringing carburizing gas into contact with a tooth flank of a gear W heated in a carburization furnace 11. In the carburization treatment method, while rotating the gear W which is a steel material by a revolution number control part 25, the tooth flank of the gear W is pressurized successively by pressurizing gears 22A, 22B so that dislocation is imparted to the tooth flank of the gear W and to its surface layer, and simultaneously carburizing gas g is brought into contact with the tooth flank to which dislocation is imparted, to thereby subject the gear W to the carburization treatment.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a steel carburizing method and a carburizing apparatus for carburizing the steel by bringing a carburizing gas into contact with the surface of the steel heated in a carburizing furnace.

  Conventionally, a carburizing method is known as a method of hardening the surface of a steel part, and such a processing method is applied to steel materials such as gears. When carburizing a steel material, a hydrocarbon-based carburizing gas is brought into contact with the surface of the heated steel material, and carbon of the carburizing gas is dissolved and diffused from the surface of the steel material to the inside thereof. Thereby, while ensuring the toughness of steel materials, the surface layer including the surface can be hardened and the wear resistance of the gear can be improved.

  As such a carburizing method, for example, a carburizing method for steel as shown in FIG. 10 has been proposed (see, for example, Patent Document 1). Here, the structure of the steel material that has been shaped into a near net shape into a gear shape is heated until it becomes an austenite structure, and the heated steel material is contacted with a carburizing gas to carburize the carbon, and then the steel material is quenched. doing. Against the quenched steel material, the steel material is heated again to an austenite structure, and rolled into the shape of a gear by contacting the tooth-shaped die while rotating the heated steel material. The tooth surface of the gear is pressed with a die.

JP-T-2006-523775

  When the carburizing treatment method shown in FIG. 10 is performed, since the steel is surely loaded on the surface during the rolling process after the carburizing treatment, the surface (tooth surface) is tough. Become. However, since this carburizing method is performed in two steps, the manufacturing process becomes complicated and the manufacturing cost increases. Further, in the carburizing treatment of the steel material, since the carburizing gas is simply brought into contact with the surface of the heated steel material, it may take time for the solid solution diffusion of carbon to the steel material.

  This invention is made | formed in view of such a point, The place made into the objective is to provide the carburizing treatment method of the steel materials which can make the surface of steel materials tougher more easily and rapidly. is there.

  As a result of intensive studies, the inventors focused on the fact that dislocations are introduced into the pressurized surface of the steel material and its surface layer when a load is applied to the surface of the heated steel material during carburizing. did. Specifically, as shown in FIG. 11, as a tensile load or a compressive load is applied to a steel material, more dislocations are introduced into the surface of the steel material, and more dislocations are introduced (a larger load is applied). I) The knowledge that the steel material has an increased carbon diffusion rate was obtained. Thereby, the new knowledge that a tough surface can be easily obtained in a shorter time without carving the surface of the reheated steel material after carburizing treatment was obtained.

  The present invention is based on such knowledge, and the method of carburizing steel according to the present invention carburizes the steel by bringing a carburizing gas into contact with the surface of the steel heated in the carburizing furnace. A carburizing method for a steel material, wherein the carburizing method, while rotating the steel material, sequentially pressurizing a part of the surface of the steel material so that dislocation is imparted to the surface of the steel material and its surface layer, Carburizing treatment of the steel material is performed by bringing the carburizing gas into contact with the surface provided with the dislocation.

  According to the present invention, when performing the carburizing process, the steel material in a heated state is rotated, a part of the surface of the rotating steel material is sequentially pressed, and a part of the pressed surface of the steel material is sequentially applied. Dislocations will be given. By bringing the carburizing gas into contact with the surface of the steel material to which dislocations are imparted, carbon can be solid-solved on the surface of the steel material, and the diffusion rate of the solid-solved carbon can be increased as compared with the conventional one. Moreover, since the steel material in which a part of the surface is pressed is rotating, dislocations can be repeatedly imparted to a part of the same surface. Thereby, the diffusion rate of carbon into the steel material can be further increased. As a result, since the carburizing process and the pressurization are performed on the surface of the steel material in the same process, the surface of the steel material can be strengthened more quickly and easily than before.

  In this way, a part of the surface of the steel material is sequentially pressurized, while dislocation is imparted to a part of the surface, the carburizing gas is brought into contact with the surface of the steel material at a time to dissolve carbon in the steel material, and then The heated state of the steel material may be maintained and carbon dissolved in the steel material may be diffused therein.

  However, as a more preferable aspect, the carburizing step of carburizing the steel material by supplying the carburizing gas while heating the steel material in the carburizing furnace, and the supply of the carburizing gas into the carburizing furnace are interrupted, The carburizing treatment of the steel material is performed by discharging a carburizing gas from the carburizing furnace and heating the steel material in the carburizing furnace to diffuse the carbon carburized in the steel material. In the period from the start time to the end time of each carburizing step, the number of rotations of the steel material is an integral number of times, and in the period from the start time to the end time of each diffusion step, the rotation of the steel material The number of rotations of the steel material is controlled so that the number of times becomes an integer number.

  According to this aspect, the carburizing process of the steel material is performed by repeating the carburizing process and the diffusion process. Thereby, the carbon concentrated on the surface of the steel material and its surface layer in the carburizing process can be diffused into the steel material in the diffusion process, and the carbon concentrated on the surface layer can be dispersed inside the steel material. Then, by performing the carburizing process again, the carbon of the carburizing gas can be dissolved in the surface layer of the steel material in which the carbon concentration is reduced. Can be dispersed. Thus, carbon can be rapidly permeated and diffused into the steel material by repeating the carburizing step and the diffusion step.

  Here, in this aspect, since the number of rotations of the steel material is controlled so that the number of rotations of the steel material becomes an integer number during the period from the start time to the end time of each carburizing step, the steel material is pressurized during this period. The number of pressurizations on each surface is the same (an integer number that matches the number of rotations). That is, since the total pressurization time (total number of pressurization times) during which each surface of the rotating steel material is pressurized within the period of one carburizing step is the same, the dislocation introduced into each surface of the steel material is also Close state. Since the carburizing gas is brought into contact with the surface in this state to dissolve the carbon of the carburizing gas (carbon is carburized), the same amount of carbon is solidified on each surface of the steel material without variation during each carburizing step. Can be dissolved.

  Similarly, since the number of rotations of the steel material is controlled so that the number of rotations of the steel material becomes an integer number during the period from the start time to the end time of each diffusion step, each time the steel material is pressurized during this period as well. The number of pressurizations on the surface is all the same (an integer number corresponding to the number of rotations). That is, since each total pressurization time (total number of pressurization times) during which each surface of the rotating steel material is pressed within the period of one diffusion process is the same, the dislocation introduced into each surface of the steel material is also Close state. Since the surface in this state is heated and carbon dissolved in the carburizing step is diffused into the inside, carbon can be diffused from each surface of the steel material to the inside without unevenness during each diffusion step.

  In this way, in the carburizing step and the diffusion step, since the treatment conditions for carbon solid solution diffusion on each surface are the same, it is possible to suppress variations in the carbon solid solution diffusion on each surface of the steel material that is sequentially pressed. it can.

  Here, the “carburizing step” is a step of carburizing the steel material by supplying the carburizing gas while heating the steel material in the carburizing furnace, in other words, heated by supplying the carburizing gas in the carburizing furnace. This is a process in which the carbon of the carburizing gas is dissolved from the surface of the steel material and penetrated. On the other hand, in the “diffusion process”, the supply of carburizing gas to the carburizing furnace is interrupted, the carburizing gas is discharged from the carburizing furnace, and the steel material is heated in the carburizing furnace, so that the carbon carburized in the steel material is removed. This is a step of diffusing, in other words, a step of diffusing carbon dissolved in the carburizing step from the surface of the heated steel material to the inside thereof without bringing the carburizing gas into contact with the surface of the steel material. Therefore, the “carburizing process” in the present application indicates a broader concept including the carburizing process and the diffusion process, and the “carburizing” refers to the carburizing process itself that does not include the diffusion process.

  As another preferred aspect, a carburizing step of carburizing the steel material by supplying the carburizing gas while heating the steel material in the carburizing furnace, interrupting the supply of the carburizing gas into the carburizing furnace, and Carburizing gas is discharged from the carburizing furnace, and the steel material is heated in the carburizing furnace, so that the carburizing treatment of the steel material is performed by repeating the diffusion step of diffusing the carbon carburized in the steel material. Yes, a portion of the surface of the steel material is uniformly pressed from a plurality of positions that are equiangular around the rotation axis around which the steel material rotates, and the plurality of positions that pressurize the surface of the steel material. When the number is N, the number of rotations of the steel material is controlled so that the number of rotations of the steel material is an integer / N times during the period from the start time to the end time of each carburizing step, and From the start to the end of each diffusion process The period, the rotation number of the steel material so that the integral / N times, controls the rotation number of the steel.

  In this aspect, similarly to the above-described aspect, the carburizing process of the steel material is performed by repeating the carburizing process and the diffusion process. Thereby, as above-mentioned, carbon can be rapidly permeated and diffused into the steel material.

  Here, in this aspect, since the pressurization of a part of the surface of the steel material is performed uniformly from a plurality of positions that are equiangular around the rotation axis around which the steel material rotates, the number of the plurality of positions that pressurize the surface of the steel material When N is N, each surface is pressurized N times while the steel material rotates once. In other words, each surface of the steel material is pressurized every 1 / N rotation (that is, every 360 ° / N rotation). For example, in the case of N = 2, the steel material is pressurized at two points rotated 180 ° around the rotation axis, and the surface is added every 1/2 rotation (ie, every 180 ° rotation). When the steel material is rotated once, its surface is pressurized twice.

  Here, during the period from the start time to the end time of each carburizing step, the number of rotations of the steel material is controlled so that the number of rotations of the steel material becomes an integer / N times. The number of pressurizations on the surface is all the same. For example, when N = 2, the number of rotations of the steel material is 1/2 times (0.5 times), 2/2 times (1 time), 3/2 times (1.5 times), 4/2. If the number of rotations of the steel material is controlled so that the number of times is twice (twice), the number of pressurization of each surface of the steel material becomes 1, 2, 3, 4 ..., all the same number of times It becomes.

  In this way, each surface of the rotating steel material is pressurized the same number of times within the period of one carburizing step, that is, the total pressurization time during which each surface is pressurized is the same, Dislocations introduced into each surface of the steel material are also close to each other. Since the carburizing gas is brought into contact with the surface in this state and the carbon of the carburizing gas is dissolved in the steel material (carbon is carburized), the carbon amount of the same level without variation on each surface of the steel material during each carburizing step. Can be dissolved.

  Similarly, by controlling the number of rotations of the steel material so that the number of rotations of the steel material becomes an integer / N times during the period from the start point to the end point of each diffusion step, The number of pressurizations on the surface is all the same. That is, since the total pressurization time during which each surface is pressed within the period of one diffusion step is the same, dislocations introduced into each surface of the steel material are also in a close state.

  Since the carburizing gas is brought into contact with the surface in this state and the carbon of the carburizing gas is dissolved in the steel material, the same amount of carbon can be dissolved in each surface of the steel material without variation during each carburizing step. . Furthermore, since the surface of this state is heated and carbon dissolved in the carburizing step is diffused into the inside, carbon can be diffused from each surface of the steel material to the inside without any variation during each diffusion step.

  In this way, in the carburizing step and the diffusion step, since the treatment conditions for carbon solid solution diffusion on each surface are the same, it is possible to suppress variations in the carbon solid solution diffusion on each surface of the steel material that is sequentially pressed. it can.

  As a more preferable aspect, in the carburizing treatment, the steel material is heated to a recrystallization temperature or higher. According to this aspect, by heating the steel material to the recrystallization temperature or higher in the carburizing treatment, dislocations imparted to the pressurized surface of the steel material can be eliminated during the carburizing treatment. In steel materials in which a part of the surface is pressurized while rotating, the introduction and disappearance of dislocations on the surface of the steel material is repeated during the carburizing process, so that the solid solution diffusion of carbon can be performed more efficiently. .

  As the present invention, a carburizing apparatus that suitably performs the above-described carburizing method for steel is also disclosed. The carburizing apparatus according to the present invention is a carburizing apparatus for a steel material for carburizing the steel material by bringing a carburizing gas into contact with the surface of the heated steel material, and the carburizing apparatus heats the steel material. The carburizing furnace for carburizing the steel by bringing the carburizing gas into contact with the steel, the pressurizing member for pressing a part of the surface of the steel disposed in the carburizing furnace, and the surface of the steel by the pressurizing member A rotation drive unit that rotates the steel material such that a part of the steel material is sequentially pressurized.

  According to the present invention, while the steel material in the carburizing furnace is rotated by the rotation drive unit, a part of the surface of the steel material is sequentially pressed by the pressing member so that dislocation is imparted to the surface of the steel material and its surface layer. The carburizing treatment of the steel material can be performed by bringing the carburizing gas into contact with the surface to which the dislocation has been imparted.

  In this way, by bringing the carburizing gas into contact with the surface of the steel material to which dislocations are imparted, carbon can be solid-solved on the surface of the steel material, and the diffusion rate of the solid-solved carbon can be increased as compared with the conventional one. .

  Moreover, since the steel material in which a part of the surface is pressurized by the pressure member during the carburizing process is rotated by the rotation driving unit, dislocation can be repeatedly imparted to a part of the same surface. Thereby, the diffusion rate of carbon into the steel material can be further increased. As a result, since the carburizing process and the pressurization are performed on the surface of the steel material in the same process, the surface of the steel material can be strengthened more quickly and easily than before.

  As a more preferred aspect, the carburizing apparatus is configured to control the number of rotations of the steel material by controlling a carburizing gas control unit that controls supply timing and discharge timing of the carburizing gas to the carburizing furnace, and the rotation driving unit. And a carburizing step for carburizing the heated steel material by supplying the carburizing gas into the carburizing furnace, and the carburizing gas control part into the carburizing furnace. And diffusing the carburized carbon in the heated steel material by interrupting the supply of the carburizing gas and exhausting the carburizing gas from the carburizing furnace, so as to repeat the process in the carburizing furnace. The carburizing gas supply timing and discharge timing are controlled, and the rotation frequency control unit adjusts the rotation frequency of the steel material during a period from the start time to the end time of each carburizing step. It becomes times, and the period up to the end time from the start of each diffusion step, the rotation number of the steel material so that the integer times, controls the rotation number of the steel.

  According to this aspect, the carburizing gas control unit controls the supply timing and discharge timing of the carburizing gas in the carburizing furnace, thereby repeating the carburizing process and the diffusion process for the steel material in the carburizing furnace. Thereby, the carburizing process of steel materials is performed, and carbon can be rapidly permeated and diffused into the steel materials as described above.

  Here, in the present aspect, the rotational drive unit is controlled by the rotational speed drive control unit in the period from the start time to the end time of each carburizing process, and in the period from the start time to the end time of each diffusion process. The number of rotations is controlled. Specifically, the rotation number control unit controls the number of rotations of the steel material so that the number of rotations of the steel material becomes an integer number during these periods.

  As a result, as described above, the total pressurization time during which each surface of the rotating steel material is pressed is the same both within one carburization step and within one diffusion step. Therefore, the dislocations introduced into each surface of the steel material are also close to each other. As a result, the same amount of carbon can be dissolved in each surface of the steel material without variation during each carburizing step, and the carbon can be solidified from each surface of the steel material without variation from each surface during each diffusion step. It can be dissolved and diffused.

  In this way, in the carburizing step and the diffusion step, since the treatment conditions for carbon solid solution diffusion on each surface are the same, it is possible to suppress variations in the carbon solid solution diffusion on each surface of the steel material that is sequentially pressed. it can.

  As another more preferable aspect, the carburizing treatment apparatus includes a carburizing gas control unit that controls supply timing and discharge timing of the carburizing gas to the carburizing furnace, and rotation of the steel material by controlling the rotation driving unit. A rotation frequency control unit for controlling the number of rotations, and a plurality of the pressure members, and each of the pressure members has a surface of the steel material at an equiangular position around a rotation axis around which the steel material rotates. The carburizing gas control unit is configured to pressurize the heated steel material by supplying the carburizing gas into the carburizing furnace, and the carburizing furnace in the carburizing furnace. And the diffusion step of diffusing the carbon that has been carburized into the heated steel material by interrupting the supply of the carburizing gas to the steel and discharging the carburizing gas from the carburizing furnace. Previous When the carburizing gas supply timing and discharge timing are controlled and the number of pressurizing members is set to N, the rotation number control unit is configured to perform the rotation of the steel material during a period from the start time to the end time of each carburizing step. The number of rotations of the steel material is controlled to be an integer / N times, and the number of rotations of the steel material is an integer / N times during the period from the start time to the end time of each diffusion step. Thus, the number of rotations of the steel material is controlled.

  Also in this aspect, the carburizing gas control unit controls the supply timing and discharge timing of the carburizing gas in the carburizing furnace, thereby repeating the carburizing process and the diffusion process for the steel material in the carburizing furnace. Thereby, the carburizing process of steel materials is performed, and carbon can be rapidly permeated and diffused into the steel materials as described above.

  In this aspect, the rotation drive unit is controlled by the rotation speed drive control unit during the period from the start time to the end time of each carburization process, and from the start time to the end time of each diffusion process, and the number of rotations of the steel material Take control. Specifically, the rotation number control unit controls the number of rotations of the steel material so that the number of rotations of the steel material becomes an integer / N times during these periods.

  As a result, as described above, the total pressurization time during which each surface of the rotating steel material is pressed is the same both within one carburization step and within one diffusion step. Therefore, the dislocations introduced into each surface of the steel material are also close to each other. As a result, the same amount of carbon can be dissolved in each surface of the steel material without variation during each carburizing step, and carbon can be diffused from each surface of the steel material without variation during each diffusion step. can do.

  According to the present invention, the surface of a steel material can be made a tough surface easily and quickly by carburizing treatment.

The figure for demonstrating the carburizing processing apparatus of the gear which concerns on embodiment of this invention. The typical perspective view which showed the state of the gearwheel shown in FIG. The figure which showed the temperature profile of the gearwheel which concerns on 1st Embodiment, and the state of carburizing gas. The figure for demonstrating the introduction and disappearance of the dislocation to the tooth surface of a gear, and carburization of the surface layer of a tooth surface. The figure which showed the temperature profile of the gearwheel which concerns on 2nd Embodiment, and the state of carburizing gas. (A) is the figure which showed the relationship between the carburizing gas density | concentration in the furnace which concerns on the comparative example for comparing with 2nd Embodiment, and the rotation frequency of a gear, (b) is rotation of the gear at the carburizing process start time. The figure which showed the position, (c) is the figure which showed the rotational position of the gearwheel at the time of completion | finish of a carburizing process. (A) is the figure which showed the relationship between the carburizing gas density | concentration in a furnace and the rotation frequency of a gear in 2nd Embodiment, (b) is the start (end) time of a carburizing process, and the start (end) of a diffusion process. The figure which showed the rotational position of the gear of a time. (A) is the figure which showed the relationship between the carburizing gas density | concentration in the furnace which concerns on the comparative example of 3rd Embodiment, and the rotation frequency of a gear, (b) is the rotation position of the gear at the time of carburizing process start (end). The figure which showed (c), the figure which showed the rotational position of the gearwheel at the time of completion | finish of a carburizing process. (A) The schematic diagram of the principal part of the carburizing apparatus which concerns on the modification of 1st-3rd embodiment, (b) The schematic diagram of the principal part of the carburizing apparatus which concerns on another modification of 1st-3rd embodiment. The figure which showed the manufacturing method of the conventional steel materials. The figure explaining the load loaded on steel materials, and the diffusion rate of carbon.

Several embodiments according to the steel carburizing method of the present invention will be described below with reference to the drawings.
[First Embodiment]
1. Steel Material (Material to be Processed) The steel material to be carburized according to the present embodiment is a steel material made of, for example, a ferrite structure and a pearlite structure, and in this embodiment is a spur gear shown in FIG. Examples of the steel material include chromium steel (JIS standard: SCr415-435), chromium molybdenum steel (JIS standard: SCM415-435), and the like, and carbon is dissolved and diffused from the surface to the inside by carburizing treatment. As long as it can be used, the material is not particularly limited.

  Moreover, in this embodiment, although the spur gear was illustrated as a steel material (material to be processed), it may be a shape that can pressurize the surface uniformly and sequentially with a pressurizing member to be described later while rotating. Gears made of steel such as spur gears, helical gears, bevel gears, and worm gears may be used, and cylindrical or columnar steel materials may be used as shown in FIG.

2. About the carburizing apparatus In this embodiment, the gear W which is the steel material mentioned above is prepared, and the gear W is carburized using the carburizing apparatus shown in FIG. The carburizing apparatus 10 will be briefly described below. FIG. 1 is a schematic diagram for explaining a carburizing apparatus for a gear W according to an embodiment of the present invention. FIG. 2 is a schematic perspective view showing a state of the gear shown in FIG. In the second and third embodiments described later, the carburizing process is performed using the same carburizing apparatus as that shown in FIGS. 1 and 2, and the difference is the control apparatus.

  As shown in FIG. 1, the carburizing apparatus 10 according to the present embodiment includes a carburizing gas by placing a gear W in a carburizing furnace and bringing a carburizing gas (processing gas) G into contact with the processing surface of the gear W. This is a device for diffusing carbon (element) of G from the treated surface of the gear W to the surface layer thereof.

  Specifically, the carburizing apparatus 10 includes a carburizing furnace 11, and the carburizing furnace 11 performs carburizing processing of the gear by bringing the carburizing gas G into contact with the gear W while heating the gear W. The carburizing furnace 11 is connected on one side to a carburizing gas supply source 31 that supplies a carburizing gas G via a flow rate adjusting device 32, and on the other side, the carburizing gas G in the carburizing furnace 11 is sucked from the carburizing furnace 11. It is connected to an exhaust pump 33 for discharging. The flow rate adjusting device 32 and the exhaust pump 33 are electrically connected to a control device 40 described later, and the supply timing and discharge timing of the carburizing gas G to the carburizing furnace 11 are controlled.

  Here, the carburizing gas G supplied from the carburizing gas supply source 31 is not particularly limited as long as it is a gas capable of carburizing the steel material that is the gear W. For example, acetylene gas, butane gas, propane Examples thereof include hydrocarbon gases such as gas and ethane gas.

  Further, in the carburizing furnace 11, a pair of pressure members 21 </ b> A and 21 </ b> B that pressurize a part of the surface of the gear W are arranged. The pressure members 21 </ b> A and 21 </ b> B are members arranged so as to mesh with the gear W, and are arranged around the rotation axis of the gear W at positions having an equal angle of 180 °.

  Each pressurizing member 21A (21B) includes a pressurizing gear 22A (22B) and a rotary shaft 23A (23B) rotatably supporting the pressurizing gear 22A (22B), and the rotary shaft 23A (23B). ) Is connected to a pressurizing device 24 that pressurizes in the direction of the rotation axis of the gear W. The material of the pressurizing gears 22A and 22B is not particularly limited as long as the gears can be displaced during pressurization, and the tooth surfaces of the pressurizing gears 22A and 22B are harder than the tooth surface of the gear W. A surface is preferred.

  Each pressurizing gear 22A (22B) is disposed in a housing portion 11a that is a part of the carburizing furnace 11, and each housing portion 11a has a cooling gas supply source 35 that cools each pressurizing gear 22A (22B). It is connected to the. The cooling gas supply source 35 is filled with a cooling gas composed of an inert gas for cooling the pressurizing gear 22A (22B).

  The carburizing apparatus 10 also rotates the gear W so that a part of the surface of the gear W (that is, the tooth surface) is sequentially pressed by the pressurizing gears 22A and 22B of the pressurizing members 21A and 21B. A drive unit (motor) 25 is disposed. Further, as shown in FIG. 2, a pair of heaters 28, 28 for heating the tooth surfaces of the gear W are arranged in the carburizing furnace 11.

  Furthermore, the carburizing apparatus 10 includes a control device 40. The control device 40 includes a carburizing gas control unit 41 and a rotation number control unit 42. The carburizing gas control unit 41 and the exhaust pump 33 output a control signal that depends on the flow rate of the carburizing gas, thereby controlling the flow rate adjusting device 32 and supplying the carburizing gas G to the carburizing furnace 11. The timing and the discharge timing of the carburizing gas G are controlled. The rotation number control unit 42 controls the rotation number by the gear W by controlling the rotation driving unit 25.

3. About the carburizing method In this embodiment, the gear W mentioned above is prepared and the carburizing process of the gear W is performed using the carburizing apparatus shown in FIG. 1 and FIG. FIG. 3 is a view showing the temperature profile of the gear W and the state of the carburizing gas G according to the first embodiment, and FIG. 4 shows the introduction and disappearance of dislocations on the tooth surface of the gear W and the surface layer of the tooth surface. It is a figure for demonstrating carburization of.

3-1. Heating Step First, as shown in FIG. 4, the gear W is heated by the heaters 28 and 28 to a temperature equal to or higher than the recrystallization temperature Tr of the steel material constituting the gear W. More preferably, ferrite structure and pearlite structure, the steel to transform to austenite structure A ₁ transformation point or more, more preferably heated to A ₃ transformation point or above the temperature (carburization temperature). For example, steel chromium steel (e.g. JIS standard: SCr420) or chromium molybdenum steel (e.g. JIS standard: SCM420) when you select the, _{A 1} transformation point around 730 ° C., _{A 3} transformation point is around 900 ° C. Therefore, the austenite structure is transformed by heating to at least 730 ° C. or higher, preferably 900 ° C. to 1200 ° C. Here, although the gear W is heated by the heaters 28, 28, the gear W may be heated in a separate heating furnace in advance.

Further, in the present embodiment, as described later, by introducing a dislocation into the tooth surface of the gear W, for contacting the carburizing gas G to the tooth surface dislocations are introduced, more than the recrystallization temperature Tr and A less than ₁ transformation point Even if the gear W is heated in the temperature range, it is possible to increase the solid solution diffusion of carbon to the tooth surface as compared with the conventional case.

3-2. Carburizing step Next, a carburizing step is performed. In the carburizing process, the carburizing gas control unit 41 outputs a control signal to the flow rate adjusting device 32 and the exhaust pump 33. Thus, a predetermined amount of carburizing gas G is supplied into the carburizing furnace 11 by the flow rate adjusting device 32, and a part of the carburizing gas G in the carburizing furnace 11 is discharged by the exhaust pump 33.

  At the same time, while the gear W is rotated by the rotation drive unit 25, the dislocation is performed while sequentially pressing the tooth surfaces of the gear W with the pressurizing gears 22A and 22B so that the dislocation is imparted to the tooth surfaces of the gear W. The gear W is carburized by bringing the carburizing gas G into contact with the applied tooth surface. Note that the concentration of the carburizing gas G in the furnace, the carburizing time, and the heating temperature (carburizing temperature) are set so that the cementite structure does not precipitate on the surface of the gear W.

  As a result, as shown in FIG. 4, dislocation is introduced into the tooth surface w of the gear W and its surface layer by being pressurized by the pressure gears 22 </ b> A and 22 </ b> B. Since the gear W is rotating, the tooth surface w into which the dislocation has been introduced comes into contact with the carburizing gas G while rotating to a position facing the heater 28. Thereby, carbon of the carburizing gas is dissolved from the surface where the dislocation is introduced. At the same time, since the gear W is heated to a temperature higher than the recrystallization temperature Tr of the steel material, the tooth surface w and the dislocations introduced into the tooth surface w disappear. Thus, the rotation of the gear W causes the carbon of the carburizing gas to be dissolved and dissolved while repeating the introduction and disappearance of dislocations, so that the carbon diffusion rate is increased compared to the conventional ones, and the amount of carbon dissolved Can be increased (or the desired amount of carbon can be dissolved more rapidly). In this way, the tooth surface w of the gear W can be strengthened.

3-3. Diffusion process Next, a diffusion process is performed. In the diffusion step, the flow rate adjusting device 32 interrupts the supply of the carburizing gas G into the carburizing furnace 11 and the exhaust pump 33 discharges the carburizing gas from the carburizing furnace 11 with a control signal from the carburizing gas control unit 41. .

  At this time, continuing from the carburizing step, while rotating the gear W by the rotation drive unit 25, the tooth surface of the gear W is applied by the pressurizing gears 22A and 22B so that dislocation is imparted to the tooth surface of the gear W. The pressure is applied sequentially. In addition, the heating of the gear W by the heaters 28 and 28 is continuously performed.

  In this way, the tooth surface w and the surface layer into which the dislocation has been introduced rotate and move to a position facing the heater 28 and are heated. As a result, the tooth surface into which dislocations are introduced and the solid solution carbon of the surface layer diffuse. At the same time, since the gear W is heated to a temperature higher than the recrystallization temperature Tr of the steel material, the tooth surface w and the dislocations introduced into the tooth surface w disappear. In this way, since carbon dissolved in the gear W is diffused while repeating the introduction and disappearance of dislocations, the carbon diffusion rate can be increased as compared with the conventional ones.

3-4. Quenching process Next, a quenching process is performed. In the quenching step, the carburized gear is cooled to transform at least the surface steel structure, which is the carburized layer, into a martensitic structure. In this step, the entire austenite structure of the carburized layer is transformed into a martensite structure by cooling the entire gear below the martensite transformation point Ms at a predetermined cooling rate by oil cooling, air cooling, or water cooling. Can be made.

  Further, a tempering step may be further performed after the quenching step. In this tempering step, the quenched gear is cooled by heating the gear at a temperature below the austenite transformation point. Thereby, the toughness of a gear can be improved.

[Second Embodiment]
FIG. 5 is a view showing the temperature profile of the gear and the state of the carburizing gas according to the second embodiment. FIG. 6A is a diagram showing the relationship between the carburizing gas concentration in the furnace and the number of rotations of the steel according to the comparative example for comparison with the second embodiment, and FIG. 6B is the gear at the start of the carburizing process. (C) is a diagram showing the rotational position of the gear at the end of the carburizing process.

  FIG. 7A is a diagram showing the relationship between the carburizing gas concentration in the furnace and the number of rotations of the steel material in the second embodiment, and FIG. 7B is the start (end) time of the carburizing process and the start of the diffusion process ( It is the figure which showed the rotational position of the gearwheel at the time of completion | finish.

  The second embodiment is different from the first embodiment in the control of the supply / discharge of the carburizing gas supplied into the furnace and the control of the number of rotations of the gears at that time. Therefore, the description of other common parts is partially omitted.

  As shown in FIG. 5, in the present embodiment, solid solution diffusion of carbon to the gear W is performed in the carburizing furnace 11 while alternately performing the carburizing process and the diffusion process shown in the first embodiment. . In the carburizing process, the carburizing gas G is supplied into the carburizing furnace 11, and in the diffusion process, the supply of the carburizing gas G into the carburizing furnace 11 is interrupted and the carburizing gas G is discharged from the carburizing furnace 11. In both the carburizing step and the diffusion step, the gears W are continuously heated by the heaters 28, 28, and the pressurizing gears 22A, 21B of the pressurizing members 21A, 21B are rotated while the gears W are rotated by the rotation drive unit 25. 22B pressurizes the tooth surface of the gear W evenly.

  By repeating the carburizing step and the diffusion step, the carbon concentrated in the tooth surface of the gear W and its surface layer in the carburizing step is diffused in the gear in the diffusion step, and the carbon concentrated in the surface layer is diffused inside the gear W. Can be dispersed. Then, by performing the carburizing process again, the carbon of the carburizing gas can be dissolved in the surface layer of the gear W in which the carbon concentration is reduced, and the carbon concentrated in the surface layer is further converted into the gear W in the diffusion step. Can be dispersed inside. Thus, carbon can be rapidly permeated and diffused into the gear W by repeating the carburizing step and the diffusion step.

  By the way, as shown in FIG. 6A, when so-called pulse carburizing is performed in which the carburizing process and the diffusion process are repeated, it is assumed that the gear carburizing depth varies. For example, in the period T1 from the start time Ts to the end time Te of the carburizing process, from the rotation position at the start time Ts shown in FIG. 6B to the rotation position at the end time Te shown in FIG. When carburizing is performed by rotating the gear W a plurality of times, the rotation position at the start time Ts and the rotation position at the end time Te are different.

  More specifically, for example, when the gear W is rotated from the rotation position at the start time Ts shown in FIG. 6B, the pressurization gear 22B pressurizes in the order of the X point and the Y point on the surface of the gear W. Then dislocations are introduced. However, at the rotational position at the end time Te shown in FIG. 6 (c), the point X on the surface of the gear W is pressurized by the pressurizing gear 22B and the dislocation is introduced. The Y point on the surface is not pressurized and dislocations are not introduced. In such a state, since the process proceeds to the diffusion process at the start time point Rs, the carbon carburization / diffusion state of the gear at the X point and the Y point is different. When such a state is repeated when the carburizing step and the diffusion step are repeated, it is assumed that the carburizing depth of each tooth surface of the gear varies.

  Therefore, in the second embodiment, the number of rotations of the gear W is controlled as follows. Specifically, as shown in FIG. 7A, the rotation number control unit 42 rotates the gear W an integer number of times (T1 and T2) from the start time Ts to the end time Te of each carburizing step. A times, B times ...). Similarly, as shown in FIG. 7A, the number-of-rotations control unit 42 determines that the number of rotations of the gear W is an integer number (a times) in the periods R1, R2 from the start time Rs to the end time Re of each diffusion process. , B times ...).

  That is, in this embodiment, when the gear W is at the rotational position shown in FIG. 7B at the start time Ts of each carburizing step, the gear W is also shown in FIG. 7B at the end time Te of each carburizing step. The same rotational position is shown. Furthermore, even when the gear W is at the rotational position shown in FIG. 7B at the start time Rs of each diffusion process, the gear W is also at the same rotational position as shown in FIG. 7B at the end time Re of each diffusion process. It becomes.

  In this way, each surface of the rotating gear W is pressurized in both the carburizing process period T1, T2,... And in the one diffusion process period R1, R2,. Since the number of times of pressure is the same, the dislocation introduced into each tooth surface w of the gear W is also close. Thereby, in each carburizing step, the same amount of carbon can be dissolved in each tooth surface of the gear W without variation, and each tooth surface of the gear W in each diffusion step period T1, T2,. Therefore, carbon can be dissolved in a solid solution without variation.

  As a result, in the carburizing step and the diffusion step, the treatment conditions for carbon solid solution diffusion on each surface become the same, so that the solid solution diffusion of carbon on each tooth surface of the gear W and its surface layer that are sequentially pressed is performed. The variation can be suppressed.

[Third Embodiment]
FIG. 8A is a diagram showing the relationship between the carburizing gas concentration in the furnace and the number of rotations of the gear according to the comparative example of the third embodiment, and FIG. 8B shows the rotational position of the gear at the start of the carburizing process. The figure shown, (c) is the figure which showed the rotational position of the gearwheel at the time of completion | finish of a carburizing process.

  The third embodiment is different from the second embodiment in a method for controlling the number of rotations of the gear. Therefore, the description of other common parts is partially omitted. In the present embodiment, as described above, there are 2 (= N) pressing gears 22A and 22B of the pressing members 21A and 21B. Each of the pressurizing gears 22A and 22B is disposed so as to pressurize the tooth surface of the gear W evenly at a position at an equal angle (180 °) around the rotation axis around which the gear W rotates.

  Therefore, in the present embodiment, the rotation number control unit 42 is arranged so that the rotation number of the gear W is an integer / 2 times (integer / N times) during the period from the start time to the end time of each diffusion process. Control the number of rotations of W. Furthermore, the rotation frequency control unit 42 sets the rotation frequency of the gear W so that the rotation frequency of the gear W becomes an integer / 2 times (integer / N times) during the period from the start time to the end time of each diffusion process. Control.

  That is, in the present embodiment, the tooth surface is pressurized by one of the pressurizing gears 22A and 22B every 1/2 rotation (ie, every 180 rotations) of the gear W. When one rotation is made, the tooth surface is pressurized twice.

  Here, as shown in FIG. 8A, in the periods T1 and T2 from the start time Ts to the end time Te of each carburizing step, the number of rotations of the gear W is A / 2 times, B / 2 times (A, By controlling the number of rotations of the gear W so that B is an integer), the number of pressurizations of the tooth surfaces to which the gear W is pressed in the periods T1 and T2 are all the same.

  For example, the number of rotations of the gear W is 1/2 (0.5), 2/2 (1), 3/2 (1.5), 4/2 (2) ... If the number of rotations of the gear W is controlled to be such a number, the number of pressurization of each tooth surface of the gear W becomes 1, 2, 3, 4,... That is, when the rotation position of the gear W is the rotation position shown in FIG. 8B at the start time Ts of the carburization process, the rotation position of the gear W is changed to that shown in FIG. ), Or the rotational position shown in FIG. 8 (c) rotated 180 ° from the rotational position of FIG. 8 (b), each tooth surface is pressurized with the same number of pressurizations during that period. .

  Similarly, in the periods R1 and R2 from the start time Rs to the end time Re of each diffusion step, the gear W is set so that the number of rotations of the gear W is a / 2 times and b / 2 times (a and b are integers). By controlling the number of rotations, the number of pressurizations of the tooth surfaces to which the gear W is pressed in the periods R1 and R2 are all the same.

  In this way, since each tooth surface of the rotating gear W is pressurized by the same number of times within the period of one carburizing step and one diffusion step, the dislocation introduced into each tooth surface of the gear W is also close. It becomes a state. As a result, the same amount of carbon can be dissolved in each tooth surface of the gear W without variation in the periods T1 and T2 of each carburizing step, and in the periods R1 and R2 of each diffusion step, the gear W Carbon can be diffused from each tooth surface w to the inside without variation.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed.

  For example, in this embodiment, the pressurizing gear is used for the gear to be carburized. For example, as shown in FIG. 9A, the steel material to be carburized is a columnar steel material W having a peripheral surface. In the case of ', pressurizing cylindrical members 22A' and 22B 'may be used.

  Furthermore, in this embodiment, two pressure members are provided at an equal angle (180 °) around the rotation axis of the gear, but for example, as shown in FIG. 9B, three pressure gears are provided. (22A, 22B, 22C), and when these are arranged at an equal angle (120 °) around the rotation axis of the gear, the period from the start point to the end point of each carburizing step and each diffusion step In addition, the number of rotations of the gear W may be controlled so that the number of rotations of the gear becomes an integer / 3. Further, the gear W can be uniformly heated by disposing the heater 28 ′ between these pressure members.

  In addition, when there are N (plural) pressure members and these are arranged at an equal angle (360 ° / N) around the rotation axis of the gear, the start of each carburizing step and each diffusion step The number of rotations of the gear W may be controlled so that the number of rotations of the gear becomes an integer / N in the period from the time point to the end point.

  DESCRIPTION OF SYMBOLS 10: Carburizing process apparatus, 11: Carburizing furnace, 11a: Accommodating part, 21A, 21B: Pressurizing member, 22A, 22B, 22C: Pressurizing gear, 23A, 23B: Rotating shaft, 24: Pressurizing apparatus, 25: Rotating Drive unit, 28: heater, 31: carburizing gas supply source, 32: flow rate adjusting device, 33: exhaust pump, 35: cooling gas supply source, 40: control device, 41: carburizing gas control unit, 42: rotation number control unit , W: Gear (steel)

Claims (7)

It is a carburizing method of a steel material for carburizing the steel material by bringing a carburizing gas into contact with the surface of the steel material heated in a carburizing furnace,
In the carburizing method, while rotating the steel material, the surface of the steel material and a surface layer thereof are sequentially pressurized so that a part of the surface of the steel material is pressed, and the dislocation is applied to the surface. A method for carburizing a steel material, comprising carburizing the steel material by bringing a carburizing gas into contact therewith. A carburizing step of carburizing the steel material by supplying the carburizing gas while heating the steel material in the carburizing furnace; interrupting the supply of the carburizing gas into the carburizing furnace; and carburizing gas from the carburizing furnace. And by diffusing carbon that has been carburized into the steel material by heating the steel material in the carburizing furnace, the carburizing treatment of the steel material is performed,
In the period from the start time to the end time of each carburizing process, the number of rotations of the steel material is an integer number of times, and in the period from the start time to the end time of each diffusion process, the rotation number of the steel materials is an integer number of times. The method of carburizing a steel material according to claim 1, wherein the number of rotations of the steel material is controlled so that A carburizing step of carburizing the steel material by supplying the carburizing gas while heating the steel material in the carburizing furnace; interrupting the supply of the carburizing gas into the carburizing furnace; and carburizing gas from the carburizing furnace. And by diffusing carbon that has been carburized into the steel material by heating the steel material in the carburizing furnace, the carburizing treatment of the steel material is performed,
Pressurization of a part of the surface of the steel material is performed uniformly from a plurality of positions that are equiangular around the rotation axis around which the steel material rotates, and the number of the plurality of positions that pressurize the surface of the steel material is determined. N,
In the period from the start time to the end time of each carburizing step, the number of rotations of the steel material is controlled so that the number of rotations of the steel material is an integer / N times, and the time from the start of each diffusion step is ended. 2. The carburizing method for steel according to claim 1, wherein the number of rotations of the steel material is controlled so that the number of rotations of the steel material becomes an integer / N times during a period up to the time point.   The said carburizing process WHEREIN: The said steel materials are heated more than recrystallization temperature, The carburizing process method of the steel materials in any one of Claims 1-3 characterized by the above-mentioned. A steel carburizing apparatus for carburizing the steel by bringing a carburizing gas into contact with the surface of the heated steel,
The carburizing apparatus is a carburizing furnace for carburizing a steel material by bringing the carburizing gas into contact with the steel material while heating the steel material.
A pressurizing member that pressurizes a part of the surface of the steel material disposed in the carburizing furnace;
A carburizing apparatus comprising at least a rotation drive unit that rotates the steel material such that a part of the surface of the steel material is sequentially pressurized by the pressing member. The carburizing apparatus includes a carburizing gas control unit that controls supply timing and discharge timing of the carburizing gas to the carburizing furnace,
A rotation frequency control unit that controls the rotation frequency of the steel material by controlling the rotation drive unit; and
The carburizing gas controller supplies the carburizing gas into the carburizing furnace, thereby carburizing the heated steel material, and interrupting the supply of the carburizing gas into the carburizing furnace and the carburizing furnace. By controlling the supply timing and discharge timing of the carburizing gas in the carburizing furnace so as to repeat the diffusion step of diffusing the carbon carburized in the heated steel material by discharging the carburizing gas from the inside,
In the period from the start point to the end point of each carburizing step, the rotation number controller is an integer number of rotations of the steel member, and in the period from the start point to the end point of each diffusion step, the steel member The carburizing apparatus according to claim 5, wherein the number of rotations of the steel material is controlled so that the number of rotations is an integer number. The carburizing apparatus includes a carburizing gas control unit that controls supply timing and discharge timing of the carburizing gas to the carburizing furnace,
A rotation frequency control unit that controls the rotation frequency of the steel material by controlling the rotation drive unit; and
There are a plurality of the pressure members, and each pressure member is arranged so as to uniformly press a part of the surface of the steel material at a position that is equiangular around the rotation axis around which the steel material rotates,
The carburizing gas controller supplies the carburizing gas into the carburizing furnace, thereby carburizing the heated steel material, and interrupting the supply of the carburizing gas into the carburizing furnace and the carburizing furnace. By controlling the supply timing and discharge timing of the carburizing gas in the carburizing furnace so as to repeat the diffusion step of diffusing the carbon carburized in the heated steel material by discharging the carburizing gas from the inside,
When the number of the pressure members is N, the rotation number control unit is configured so that the number of rotations of the steel material is an integer / N times during a period from the start time to the end time of each carburizing step. Controlling the number of rotations of the steel material, and controlling the number of rotations of the steel material so that the number of rotations of the steel material is an integer / N during the period from the start time to the end time of each diffusion step. The carburizing treatment apparatus for steel according to claim 5.

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