JP2012153931A - Heat treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat treatment method capable of induction-heating a portion required to be heat-treated, and also capable of induction-heating concurrently a portion not required to be heat-treated, so as to be discolored, when induction-heating an object to be heat-treated having the portion required to be heat-treated, and the portions of various sizes and shapes not required to be heat-treated, and capable of confirming whether the object to be heat-treated is heat-treated or not, by observing the portion not required to be heat-treated.SOLUTION: A heating coil 2 electrified with an alternating current is approached to a large diameter part 10, to induction-heat the large diameter part 10, when heat-treating again the large diameter part 10 of a work 5 having the heat-treated large diameter part 10 and a small diameter part 6 not heat-treated. At that time, a magnetic induction body 7 composed of a material of high magnetic permeability is approached therein or brought into contact to/with the small diameter part 6, and the small diameter part 6 is induction-heated to be discolored. The large diameter part 10 is poor in a color change even when induction-heated again, the small diameter part 6 is discolored because heat-treated for the first time, and the reheat-treatment of the large diameter part 10 of the work 5 is determined based on the discoloration of the small diameter part 6.

Description

  The present invention relates to a heat treatment method using induction heating such as induction hardening. The present invention also relates to a technique for inductively heating an object to be heated having a part that requires heat treatment and a part that does not require heat treatment, and the part that requires heat treatment in the object to be heated is heat treated. The present invention relates to a heat treatment method capable of easily confirming that the process has been completed.

Machine parts made of steel are subjected to heat treatment such as quenching and tempering in order to obtain strength to withstand use. In automotive machine parts and the like, a large number of machine parts of the same standard are continuously heat-treated.
For example, when steel material is formed into a predetermined shape by cutting and steel parts that give off metallic luster are induction-quenched, the metallic luster of the quenched part is lost, so it is possible to determine at a glance whether or not it has been quenched. Can do. The same applies to cast steel products. When a cast steel product is induction-quenched, the overall color changes to a slightly dull color, so that it is possible to visually determine whether or not quenching has been performed.

  However, even if a steel part is heat-treated, it may be difficult to distinguish whether it has been heat-treated. For example, if the surface of a machine part is coated with a paint or the like after heat treatment, the color of the surface is not known, and it is almost impossible to identify whether the heat treatment has been completed. In addition, when a steel product having an oxide film on its surface is quenched, as in the so-called black skin steel, the steel surface is black in the first place, so discoloration due to quenching cannot be confirmed.

Furthermore, steel products are often subjected to reheating treatment such as tempering after quenching, but it is difficult to judge from the appearance whether or not the reheating treatment has been performed. That is, when a steel product is quenched, the gloss and hue of the surface change, so whether or not quenching has been performed can be determined by looking at the gloss and hue. However, since the reheat treatment is performed on a member that has been once quenched and has changed gloss or the like, the current gloss change or the like is caused by the first quenching or the reheat treatment that is a subsequent process. I can't tell if it was.
In particular, since the reheating process performed after quenching has a lower processing temperature than the quenching performed previously, a change in gloss due to the reheating process is slight.
In this way, when heat treatment such as tempering is performed after quenching, even if the surface of the machine part is not coated with paint or the like, it has already been discolored by quenching, so it is identified that the heat treatment has been repeated. It is difficult.

Therefore, in order to indicate that the machine part has been heat-treated, there is a method of performing marking and printing (ink adhesion) on the machine part after the heat treatment to determine that the machine part has been heat-treated. However, if this method is adopted, it is necessary to prepare a device for attaching stamps and ink to mechanical parts separately from the heat treatment device, leading to an increase in cost.
In addition, engraving is an action that is performed separately from heat treatment, so even if machine parts have been heat-treated, there is a risk that imprinting leakage or ink adhesion leakage may occur, and quality control must be nervous. . In other words, it must be constantly monitored that a process of applying a mark by another apparatus is always performed in conjunction with the heat treatment.

A method for solving this problem is presented in Patent Document 1. The measure disclosed in Patent Document 1 targets an engine crankshaft as a machine part. The crankshaft of an engine has a part that requires quenching, such as a part of a crankpin, and a part that does not require quenching in the first place.
In the invention disclosed in Patent Document 1, only a necessary part such as a part of a crank pin of a crankshaft is quenched by using known induction hardening, and a part that does not need to be subjected to a quenching process is not heated. Therefore, at the stage where quenching is completed, the gloss (color) of the crankpin portion is converted, but the gloss (color) of the portion that does not require quenching does not change.

  Then, as a subsequent process, the crankpin portion is tempered. In the invention of Patent Document 1, a spiral-shaped induction heating coil for tempering is used, a crankshaft is arranged inside the induction heating coil, an alternating current is passed through the heating coil to excite the induction current at the crankpin portion. , Reheat the crankpin part.

Here, in the invention disclosed in Patent Document 1, a special improvement is added to the heating coil used for tempering, and the portion that has not been heated in the previous quenching process is heated by induction heating.
That is, in the invention disclosed in Patent Document 1, a part of the heating coil is linearly formed like a string and is brought close to the surface of the part that has not been heat-treated in the previous quenching process. Promote induction heating. As a result, the crankpin that should originally be tempered is reheated, and at the same time, the part that has not been quenched (undiscolored part) is also induction-heated, oxidized and colored (discolored).

  Therefore, whether or not the crankpin portion has been tempered can be determined based on the presence or absence of discoloration of the portion that does not require quenching. Therefore, the crankshaft must be tempered at the same time, and at the same time, it can be visually discriminated whether the part that has not been discolored has discolored and has been tempered. There is no.

JP 2007-262437 A

  When the invention disclosed in Patent Document 1 is carried out, it becomes possible to recognize that the machine part has been heat-treated without performing another process such as engraving, but the heating coil for tempering is Only workpieces (machine parts) with a specific shape can be heat-treated. That is, when the type of workpiece (particularly the radial dimension) changes, a situation occurs in which the linear (string) portion of the coil wire cannot contact the workpiece or be sufficiently close to the extent that coloring is possible. Therefore, if the type (size, shape) of the workpiece changes, the tempering heating coil must be replaced with one that matches the changed workpiece. That is, the measure disclosed in Patent Document 1 has a problem that the heating coil lacks versatility.

  The present invention solves the above-described problems of the prior art, and is a heat treatment method capable of visually confirming whether a necessary part of an object to be heated has been heat treated, and is a heat treatment with high versatility of a heating coil. It is an object to provide a method.

  The invention of claim 1 for solving the above-mentioned problem is a heat treatment method in which an object to be heated having a heat treatment required part that requires heat treatment and a heat treatment unnecessary part that does not require heat treatment is heat treated by archery heating. In the heat treatment method, the object to be heated is induction-heated in a state where an object having a magnetic flux transmittance different from that of the object to be heated is arranged in the vicinity thereof.

  The heat treatment method of the present invention raises the temperature of an object to be heated by induction heating. In the heat treatment method of the present invention, the object to be heated is induction-heated in a state where an object having a magnetic flux transmittance different from that of the object to be heated is arranged at or near the heat treatment unnecessary part. For this reason, a portion where an object having a different magnetic flux transmittance is arranged or its vicinity has a different temperature rise compared to other portions, and the color and dullness are different from those of other portions. That is, when the object to be heated is subjected to induction heating, the color or dullness in the area where the object having different magnetic flux transmittance is arranged or the vicinity thereof is different from other areas, so the history of heat treatment can be known. it can.

  The invention according to claim 2 is a case where the article to be heated has an already heated part that has already been heat-treated and a non-heated part that has not been heat-treated, and the already-heated part is heat-treated again by induction heating, 2. The heat treatment method according to claim 1, wherein the object to be heated is induction-heated in a state where the objects having different magnetic flux transmittances are arranged in a non-heated region.

  The invention according to claim 3 is the heat treatment method in which the object to be heated is heat-treated by induction heating, the object to be heated has an already heated part that has already been heat-treated and a non-heated part that has not been heat-treated, This is a heat treatment method in which an already-heated part is heat-treated again by induction heating, and an object to be heated is induction-heated in a state where an object having a different magnetic flux transmittance is arranged in a non-heated part.

According to the second and third aspects of the present invention, when the heated portion is induction-heated, an object having a different magnetic flux transmittance is arranged in the non-heated portion, so that the induced current flowing through the non-heated portion changes. For example, when an object having a high magnetic flux transmittance is arranged in the non-heated part, the induced current flowing through the non-heated part increases. In other words, an object having a high magnetic flux transmittance induces magnetism in the non-heated part and generates an induced current in the non-heated part, and part or all of the non-heated part is inductively heated to raise the temperature and further discolor. It can be visually confirmed that the heated portion of the heated object has been heat-treated again by the conductor.
On the other hand, when an object having a low magnetic flux transmittance is arranged in the non-heated part, the induced current flowing in the non-heated part is inhibited. That is, an object having a low magnetic flux transmittance interferes with magnetism in the non-heated part and the induced current flowing through the non-heated part decreases, and part or all of the non-heated part becomes heated, and the degree of discoloration is in other parts Is different. Therefore, it can be visually confirmed that the already heated portion of the object to be heated has been heat-treated again by the conductor.

  Further, the non-heated part may have a smaller diameter than the already heated part, and the non-heated part may be an end portion of the object to be heated. (Claim 4)

  According to a fifth aspect of the present invention, in the induction heating, a conductor is brought close to the object to be heated, and the object to be heated is induction heated by flowing an alternating current through the conductor, the conductor is spiral, and the object to be heated The object to be heated is disposed inside the conductor so that the object is axial, and the axis of the object to be heated follows the center of the spiral of the conductor. This is a heat treatment method.

  In the invention of claim 5, the object to be heated is arranged inside the conductor so that the conductor is spiral, the object to be heated is axial, and the axis of the object to be heated is along the center of the spiral of the conductor. Therefore, when alternating current is supplied to the conductor, an induced current flows on the object to be heated, and the object to be heated is heated.

  The inventions of claims 1 to 5 can also be applied to an object to be heated having a film on a part of the surface. In other words, when induction heating is performed on a part where the film is present, induction current is generated by inducing magnetism in the non-heated part, and part or all of the non-heated part is induction-heated and discolored, or the induced current does not easily flow. It is possible to leave a metallic luster intentionally in a part in the state. Thereby, even if the film exists on the surface of the heated part, it can be confirmed that the object to be heated has been heat-treated.

  In the present invention, it can be confirmed by looking at the non-heated part that the already heated part of the article to be heated has been heat-treated again. Therefore, it is possible to reliably prevent a situation in which the heated object is shipped in a state where the heated portion of the heated object is not heat-treated again.

It is a perspective view which shows the state which has arrange | positioned the to-be-heated material (workpiece | work) in the induction heating coil which implements the heat processing method of this invention. It is a perspective view of the to-be-heated material which implements the heat processing method of this invention, (a) shows the workpiece | work immediately after machining, (b) shows the mode after quenching the said workpiece | work, (c) is this invention. The mode after performing tempering by applying the heat treatment method of the embodiment is shown. It is a perspective view of the magnetic derivative used with the heat processing method of this invention. It is a conceptual diagram of the magnetic force line which passes a to-be-heated object at the time of supplying alternating current to the induction heating coil of FIG. In FIG. 4, it is a conceptual diagram of the magnetic force line which passes a to-be-heated object at the time of making the magnetic derivative which consists of a high magnetic permeability material contact | abut the edge part of the non-heating part of a to-be-heated object. It is a perspective view of the to-be-heated material (work) heat-processed with the heat processing method of the other Example of this invention, (a) shows the workpiece | work just after machining, (b) shows the mode after quenching the said workpiece | work. (C) shows a state after tempering by applying the heat treatment method of the embodiment of the present invention. It is a perspective view of the to-be-heated material (work) heat-processed with the heat processing method of the further another Example of this invention, (a) shows the workpiece | work immediately after machining, (b) is the state after quenching the said workpiece | work. (C) shows a state after tempering by applying the heat treatment method of the embodiment of the present invention. It is the perspective view which made the magnetic derivative contact | abut to the cylindrical side wall of the non-heating site | part of the to-be-heated object of FIG. It is a block diagram of the induction hardening apparatus which hardens the workpiece | work immediately after machining. It is sectional drawing which shows a mode at the time of hardening the workpiece | work immediately after machining with the induction hardening apparatus of FIG.

Embodiments of the present invention will be described below with reference to the drawings.
The heat treatment method according to the embodiment of the present invention reheats a workpiece by induction heating, and targets a workpiece having a history of heating once.
That is, the heat treatment method of the embodiment of the present invention is directed to the workpiece 5 that has been once quenched by the induction hardening device (induction heating device) 100 as shown in FIG. 9, and the quenched workpiece 5 is shown in FIG. 1. It is the method of reheating with the reheating induction heating apparatus 1 shown.
More specifically, in the heat treatment method of the present embodiment, the workpiece 5 formed by cutting or the like is quenched with an induction hardening apparatus 100 as shown in FIG. It reheats with the reheating induction heating apparatus 1 as shown in FIG.

  Prior to the description of the reheat method, which is a configuration peculiar to the present invention, the workpiece 5 to be heat-treated (reheated) by the reheat induction heating apparatus 1 of the present embodiment will be described. The workpiece 5 is formed of a steel material, can be induction-heated, and can be subjected to heat treatment such as quenching. The workpiece 5 has a large diameter portion 10 and a small diameter portion 6 as shown in FIG. In the present embodiment, the large diameter portion 10 is a heat treatment required site, and the small diameter portion 6 is a heat treatment unnecessary site that does not require heat treatment.

  And the workpiece | work 5 used with the heat processing method (reheat method) of this embodiment is a thing by which the required part was induction-hardened previously. That is, the workpiece 5 is formed by cutting carbon steel into a shape having a large diameter portion (required heat treatment portion) 10 and a small diameter portion (heat treatment unnecessary portion) 6 as shown in FIG. At the beginning of cutting, the whole has a metallic luster. Further, the workpiece 5 used in the heat treatment method (reheat method) of the present embodiment is a large-diameter portion using an induction hardening apparatus 100 as shown in FIG. Only 10 was quenched.

  Here, the induction hardening apparatus 100 is the same as that of a known shape, and for example, a one-turn-type high-frequency heating coil 101 can be used. Then, while energizing the high-frequency heating coil 101, the workpiece 5 or the high-frequency heating coil 101 is moved in the axial direction, and only the large-diameter portion 10 of the workpiece 5 is quenched. Specifically, as shown in FIG. 10, the high-frequency heating coil 101 is moved from one end (left end) to the other end (right end) of the large-diameter portion 10 of the work 5 while energizing the high-frequency heating coil 101. Let As a result, the workpiece 5 is quenched by induction heating only of the large diameter portion 10. That is, the small diameter portion 6 is not quenched. Therefore, as shown in FIG. 2B, the workpiece 5 is discolored only on the surface of the large-diameter portion 10, and the small-diameter portion 6 still has a metallic luster.

Next, the heat treatment method (reheat method) of this embodiment will be described.
As described above, the heat treatment method of the embodiment of the present invention is a method in which the work 5 once quenched by the induction hardening device (induction heating device) 100 is reheated by the reheating induction heating device 1 shown in FIG. is there.
The basic configuration of the reheat induction heating apparatus 1 is the same as that of a known one, and includes a reheat heating coil 2 as shown in FIG. The reheating heating coil 2 has a structure that is not significantly different from that of an induction heating coil employed in a known induction heating device (for example, induction hardening device), and is a hollow conductor through which cooling water can be passed. It is. The reheating heating coil 2 is supplied with electric power from an AC power source (not shown). In this embodiment, a commercial power supply with a frequency of 50 Hz or 60 Hz is used as an AC power supply, but a high-frequency inverter is further provided to convert the frequency to several KHz to several MHz, or a transformer is provided to transform and heat conditions. Depending on the frequency, the frequency and voltage can be appropriately set and used.

  As shown in FIG. 1, the reheating heating coil 2 is composed of a spiral conductor. The diameter of the spiral of the reheating heating coil 2 is such that at least the work 5 (a shaft-like member to be heated) can be disposed inside. The reheating heating coil 2 reheats only the large-diameter portion 10 of the workpiece 5, and the total length of the effective operating portion is equal to the length of the large-diameter portion 10 of the workpiece 5 described later.

  Next, the magnetic derivative 7 which is a characteristic configuration of the present embodiment will be described. The magnetic derivative 7 is made of a material having a high magnetic permeability, and has a cylindrical (disc-shaped) outer shape as shown in FIG. That is, the material of the magnetic derivative 7 has a high magnetic flux transmittance, and a stainless steel material such as SUS403, an iron material, or the like can be used. Further, as a material having a higher magnetic permeability, iron, an iron-based alloy, a permalloy-based alloy, a ferrite compound, or the like can be employed. Furthermore, a silicon steel material (silicon steel plate) can also be used.

Next, the process of the heat treatment method of this embodiment will be described.
In the heat treatment method (reheat method) of this embodiment, only the large-diameter portion 10 as described above is quenched and discolored, and the small-diameter portion 6 is a non-heated workpiece 5 having a metallic luster. And the workpiece | work 5 which has the said already heated site | part (large diameter part 10) and a non-heated site | part (small diameter part 6) is mounted | worn with the reheating induction heating apparatus 1 shown in FIG. Further, in this embodiment, as shown in FIGS. 2C and 5, the magnetic derivative 7 is pressed against the end of the small diameter portion 6 that is a non-heated portion. And in this state, it supplies with electricity to the heating coil 2 for reheating, and the workpiece | work 5 is induction-heated.

  Here, when attention is paid to the positional relationship between the work 5 and the reheating heating coil 2 in the heat treatment method of the present embodiment, the reheating heating coil 2 reheats only the large-diameter portion 10 of the work 5 as described above. The total length of the effective operating portion is substantially equal to the length of the large-diameter portion 10 of the workpiece 5 described later, and the reheating heating coil 2 covers only the large-diameter portion 10 of the workpiece 5. That is, the reheating heating coil 2 does not heat the small diameter portion 6, and the reheating heating coil 2 is only slightly applied to the retracted portion of the small diameter portion 6.

  Therefore, in the conventional reheating method, only the large-diameter portion 10 of the workpiece 5 is induction-heated by the reheating heating coil 2, but in this embodiment, the magnetic derivative 7 is provided at the end of the small-diameter portion 6 that is a non-heated portion. Is pressed, the small-diameter portion 6 is also heated. That is, in the liver-and-kidney configuration of the present embodiment, when reheating is performed, the magnetic derivative 7 is pressed against the end of the small-diameter portion 6 that is a non-heated portion, as shown in FIGS. Yes, thereby increasing the temperature of the small diameter portion 6 that has not been heated in the past, and changing the color of the small diameter portion 6. The reason for this will be described below by comparing FIG. 4 and FIG.

  When the configuration of this embodiment is not employed and the magnetic derivative 7 does not exist at the end of the small diameter portion 6 that is a non-heated portion, the distribution of the magnetic lines of force in the small diameter portion 6 is as shown in FIG. The small-diameter portion 6 is more distant from the heating coil 2 in the radial direction than the large-diameter portion 10. Therefore, the small-diameter portion 6 is less likely to pass magnetic lines than the large-diameter portion 10 and is not easily induction-heated. That is, as shown in FIG. 4, most of the magnetic force lines 11 that have passed through the large diameter portion 10 deviate from the work 5 without passing through the small diameter portion 6. As a result, the amount of magnetic lines 21 passing through the small-diameter portion 6 is small and the induced current generated by the magnetic lines 21 is small, so that the small-diameter portion 6 is not induction heated to the extent that it is colored.

  On the other hand, as shown in FIGS. 2 (c) and 5, alternating current is supplied to the reheating heating coil 2 in a state where the magnetic derivative 7 is pressed against the end of the small-diameter portion 6 that is a non-heating portion, When induction heating of the workpiece 5 is started, not only the desired heat treatment is performed on the large diameter portion 10 of the workpiece 5, but also the small diameter portion 6 is heated. That is, when a configuration in which the magnetic derivative 7 is pressed against the end portion of the small-diameter portion 6, which is a configuration specific to the embodiment, the distribution of magnetic lines of force changes as shown in FIG. That is, in this embodiment, the magnetic derivative 7 having a high magnetic permeability is brought into contact with the end of the small diameter portion 6 as a unique configuration. As a result, a part of the magnetic force lines 11 deviating in FIG. 4 are drawn to the magnetic derivative 7 side as shown in FIG. 5, and the amount of magnetic force lines passing through the small diameter portion 6 increases. As a result, the induced current generated in the small-diameter portion 6 increases, and the small-diameter portion 6 undergoes induction heating and changes color.

Here, before the work 5 is induction-heated by the reheating induction heating device 1, only the large-diameter portion 10 is already quenched by the induction hardening device 100 in advance, and the induction heating by the reheating induction heating device 1 this time is performed. However, since it corresponds to the tempering step, the surface of the large diameter portion 10 has already been discolored before being attached to the reheating induction heating device 1, and even if induction heating is performed by the reheating induction heating device 1, The surface appearance of the large-diameter portion 10 is poor in color change. However, since the small diameter part 6 is induction-heated for the first time by the reheating induction heating device 1, the surface of the small diameter part 6 is clearly changed from a metallic luster to a brown color.
Therefore, the operator can know the thermal history of the workpiece 5 by looking at the color and gloss of the small diameter portion 6.

That is, as shown in FIG. 2A, when both the large-diameter portion 10 and the small-diameter portion 6 have metallic luster, the workpiece 5 is not subjected to any heat treatment. Specifically, when both the large-diameter portion 10 and the small-diameter portion 6 have a metallic luster, the workpiece 5 is not quenched or reheated.
As shown in FIG. 2B, when only the large-diameter portion 10 is darkened and the small-diameter portion 6 has a metallic luster, the workpiece 5 is hardened but reheated. There is no state.
On the other hand, as shown in FIG. 2C, when both the large diameter portion 10 and the small diameter portion 6 are discolored and darkened, the workpiece 5 is quenched and further reheated thereafter. Has also been completed.
Therefore, it is possible to determine whether or not the large-diameter portion 10 has undergone a tempering process (reheat) by viewing the color of the small-diameter portion 6.

Next, reference guidelines for implementing the present invention will be described.
In the present invention, when reheating is performed as described above, the magnetic derivative 7 is brought into contact with the end of the small-diameter portion 6 that is a non-heated portion. An induced current is generated in the part, and the temperature of the non-heated part is raised to change the color. Therefore, selection of the material of the magnetic derivative 7 and determination of the size have a great influence on the effect of the present invention.

  As described above, the material of the magnetic derivative 7 may be a stainless steel material such as SUS403, an iron material, an iron alloy, a permalloy alloy, a ferrite compound, or a silicon steel material (silicon steel plate). Among these, stainless steel materials, iron materials, and the like are the most readily available materials, but even if these are used, sufficient effects can be expected.

  Further, according to experiments by the present inventors, as the length of the magnetic derivative 7 (the length in the axial direction of the workpiece 5 indicated by the arrow A in FIG. 5) is increased, the amount of magnetic field lines that are induced in the small diameter portion 6 is increased. Become more. Therefore, by increasing the length of the magnetic derivative 7, the induced current generated in the small diameter portion 6 can be increased. That is, if induction heating cannot be performed to the extent that the small diameter portion 6 is discolored, increasing the length of the magnetic derivative 7 increases the amount of magnetic lines of force induced by the small diameter portion 6 and increases the induced current generated in the small diameter portion 6. Can be made.

  However, the diameter of the small-diameter portion 6 is considerably smaller than the diameter of the large-diameter portion 10, and even when the magnetic derivative 7 is brought into contact with the small-diameter portion 6, induction heating cannot be performed to the extent that the small-diameter portion 6 is discolored. It is desirable to change the material of the magnetic derivative 7 to one having a higher magnetic permeability. That is, permalloy alloys, ferrite compounds, silicon steel materials (silicon steel plates), etc. have higher magnetic permeability than stainless steel materials, iron materials, etc., so these materials are selected as the magnetic derivative 7.

  In addition, when the magnetic derivative 7 is brought into contact with the small diameter portion 6 (non-heated portion) and induction heating is performed, if the discoloration of the small diameter portion 6 becomes excessive, the magnetic derivative 7 is not brought into contact with the small diameter portion 6 and a gap is formed. The degree of discoloration can be adjusted by bringing them close to each other. That is, if there is a gap between the small diameter portion 6 and the magnetic derivative 7, the amount of magnetic lines of force induced by the small diameter portion 6 is reduced as compared with the case where the small diameter portion 6 and the magnetic derivative 7 are in contact. Therefore, when the gap is provided, excessive induction heating of the small diameter portion 6 is suppressed.

  That is, when the magnetic derivative 7 is brought into contact with the small diameter portion 6, the induced current generated in the small diameter portion 6 becomes excessive, and the small diameter portion 6 is excessively discolored. By separating the magnetic derivative 7 from 6 and bringing it close, the small-diameter portion 6 can be induction-heated so as to change its color to an appropriate color.

Conversely, if the entire small diameter portion 6 is discolored without installing the magnetic derivative 7, a magnetic repellent 8 made of a low magnetic permeability material is installed as shown in FIG. 6 (c). To do.
As a result, the lines of magnetic force passing through the small diameter part 6 do not reach the end part, and only the base end part of the small diameter part 6 is heated and discolored.

As a result, as shown in FIG. 6C, as a result of reheating, the open end side of the small diameter portion 6 has a metallic luster, and only the portion near the large diameter portion 10 is discolored.
Therefore, as shown in FIG. 6 (a), when both the large diameter portion 10 and the small diameter portion 6 have a metallic luster, the workpiece 5 is not hardened or reheated. As shown in FIG. 6B, when only the large-diameter portion 10 is dark and the small-diameter portion 6 has a metallic luster, the workpiece 5 is hardened but reheated. When only a part of the small-diameter portion 6 has a metallic luster as shown in FIG. 6C, the workpiece 5 is quenched and the subsequent reheating is completed. It can be said that it is a thing.
Therefore, it is possible to determine whether or not the large-diameter portion 10 has undergone a tempering process (reheat) by viewing the color of the small-diameter portion 6.

The use of the magnetic repellent body 8 is not limited to reheating but may be used for quenching by the high-frequency heating coil 101 as a previous process.
For example, when there is a concern that the small-diameter portion 6 is also heated during the quenching process, at the end of the small-diameter portion 6 that is a non-heated portion, as shown in FIG. The magnetic derivative 7 is pressed. As a result, the small-diameter portion 6 is not discolored during the quenching process, and the small-diameter portion 6 can be discolored for the first time in the next reheating step.

  The example in which the magnetic derivatives 7 and 8 are brought into contact with or close to the end of the small-diameter portion 6 (non-heated portion that does not require heat treatment) of the workpiece 5 has been described above. It can also be arranged at a place other than the end. This will be described with reference to FIG. FIG. 8 is a perspective view virtually showing magnetic lines of force generated by bringing a magnetic derivative into contact with the side wall (curved surface) of the non-heated portion of the object to be heated in FIG.

  In the example shown in FIG. 8, the magnetic derivative 9 is brought into contact with the curved side wall of the small diameter portion 6 (non-heated portion). In this case, the lines of magnetic force 22 gather at the part where the magnetic derivative 9 is brought into contact, and therefore, in the small diameter portion 6, the induced current generated at the part where the magnetic derivative 9 is brought into contact and the vicinity thereof increases. Therefore, only this part and its periphery discolor by induction heating.

  As a material of the magnetic derivative 9, a high permeability material similar to that of the magnetic derivative 7 is adopted. That is, the material of the magnetic derivative 9 is selected such that it can induce and heat the magnetic field lines to such an extent that the portion in contact with the small diameter portion 6 is appropriately discolored.

  In the example shown in FIG. 8, since the magnetic derivative is brought into contact with the side wall (curved surface) of the non-heated part, it is preferable that the contact surface of the magnetic derivative is constituted by a curved surface along the side wall of the non-heated part.

  1 to 8, the small-diameter portion 6 at the end is a non-heated portion, but the present invention can be implemented even when the non-heated portion is disposed in the central portion of the work.

  When the large-diameter portion 10 (FIGS. 4 to 8) of the workpiece 5 is coated with a coating or the like and a film is attached or another oxide film is attached, the large-diameter portions 10 and 25 are attached. Even if induction heating is performed, the appearance of the large diameter portions 10 and 25 hardly changes in appearance. Therefore, even if the large-diameter portions 10, 25, and 26 are induction-heated, it is not possible to determine whether or not induction-heating is performed only by looking at the large-diameter portions 10, 25, and 26. Therefore, when the present invention is implemented and magnetic lines 7 to 9 induce magnetic lines of force (magnetism) in the non-heated part, the color is always changed by induction heating, so that the workpieces 5 and 16 are easily heated by induction. Can be recognized.

1 Reheating induction heating device 2 Reheating heating coil (conductor)
5 Workpiece (shaft-shaped member)
6 Small diameter part (heat treatment unnecessary part, non-heated part)
7,9 Magnetic derivative 8 Magnetic repellent body 10 Large diameter part (heat-treated part, already heated part, coated part)

Claims (5)

  In a heat treatment method in which an object to be heated having a heat treatment required part that requires heat treatment and a part that does not require heat treatment is subjected to heat treatment by archery heating, an object having a magnetic flux permeability different from that of the object to be heated is provided at or near the heat treatment unnecessary part A heat treatment method characterized by inductively heating an object to be heated in a disposed state.   The object to be heated has a heated part that has already been heat-treated and a non-heated part that has not been heat-treated, and the heated part is heat-treated again by induction heating, and the magnetic flux transmittance is introduced into the non-heated part. The heat treatment method according to claim 1, wherein the object to be heated is induction-heated in a state in which objects having different sizes are arranged.   In a heat treatment method in which an object to be heated is heat-treated by induction heating, the object to be heated has an already heated part that has already been heat-treated and an unheated part that has not been heat-treated, and the already-heated part is heat-treated again by induction heating. A heat treatment method in which an object to be heated is induction-heated in a state where objects having different magnetic flux transmittances are arranged in a non-heated part.   4. The heat treatment method according to claim 2, wherein the non-heated portion is heat-treated on the heated object that is smaller in diameter than the already heated portion and is an end of the heated object.   Induction heating is a method of inductively heating an object to be heated by bringing a conductor close to the object to be heated and passing an alternating current through the conductor, the conductor is spiral, and the object to be heated is axial. The heat treatment method according to any one of claims 1 to 4, wherein the object to be heated is arranged inside the conductor so that the axis of the object to be heated is along the center of the spiral of the conductor.

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