JP2006002191A - Method for controlling heat treatment condition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling a heat treatment condition, which makes heat treatment (quenching treatment or tempering treatment) using a high-frequency direct-conducting system stably and successively form an adequate quench-hardened layer (a quench-hardened layer) having a value of standard on a part to be heat-treated, even when an abrasion loss of a contact electrode has increased with the increase of the number of heat treatment shots. <P>SOLUTION: The method for controlling the heat treatment condition in the heat treatment using a high-frequency direct-conducting system comprises the steps of: previously determining a plurality of the heat treatment conditions in correspondence with the number N of the heat treatment shots or a gap S between a part to be heat-treated (for instance, a gear tooth part 2 of a rack shaft 1) and a proximity conductor 11; detecting the number N of the heat treatment shots or the gap S, when heat-treating the part; selecting the heat treatment condition corresponding to a detected value among a plurality of the heat treatment conditions, on the basis of the detected value; and heat-treating the part, on the basis of thus selected heat treatment condition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat treatment condition adjusting method when performing heat treatment such as induction hardening or induction tempering, and more specifically, a heat treatment condition adjusting method in high-frequency direct current heat treatment (high-frequency direct current quenching / tempering). About. More specifically, in the present invention, for example, when a heat treatment is performed on a tooth portion of a rack shaft (rack bar) or a back surface portion corresponding to the tooth portion by a high-frequency direct current method, a desired quenching depth, The present invention relates to a heat treatment condition adjusting method for obtaining a hardening width and quenching and tempering hardness.

  In the case of induction hardening of the tooth portion 2 of the rack shaft 1 as shown in FIG. 2 and the back surface portion 3 corresponding to the tooth portion 2, the high frequency direct current hardening apparatus 4 as shown in FIGS. Is often used.

  As shown in FIGS. 2 to 4, the high-frequency direct current quenching apparatus 4 is connected to the first conductor 6 and the first conductor 6 and the second conductor 7 that are superposed via an electrical insulating material 5. And a branch conductor 8 connected to the second conductor 7 side (that is, branched from one end of the first conductor 6 to both sides and connected to the other end of the second conductor 7) (FIGS. 3 and 4), a first contact electrode 9 placed and fixed on the first conductor 6 at a position where the electrical insulating material 5 is interposed, and placed and fixed on the second conductor 7. The second contact electrode 10, the proximity conductor 11 placed and fixed on the second conductor 7, the cooling means 12 (see FIG. 4) provided on the proximity conductor 11, and the first contact electrode 9 and the second contact electrode 10, a high frequency power supply unit 13 (see FIG. 2) connected between the first contact electrode 9 and And a hydraulic cylinder 14 for the pair of rack shaft pressing the second contact are respectively the electrode 10 disposed in the corresponding positions.

  Thus, the rack shaft 1 is placed on the tops α and β of the first contact electrode 9 and the second contact electrode 10 as shown in FIGS. 2 and 3, and the tooth portion 2 contacts the tops α and β. While being supported in contact with each other, it is pressed toward the first contact electrode 9 and the second contact electrode 10 by the hydraulic cylinder 14 to ensure an electrical contact state between the tooth portion 2 and the top portions α and β. It has come to be. In addition, when the rack shaft 1 is arranged on the first contact electrode 9 and the second contact electrode 10 in this manner, the rack shaft 1 is disposed between the tooth portion 2 of the rack shaft 1 and the adjacent conductor 11 in FIGS. As shown in FIG. 2, the gap S is formed, and the tooth portion 2 is arranged close to the proximity conductor 11.

The operation at the time of quenching the teeth 2 of the rack shaft 1 using the high-frequency direct current quenching apparatus 4 having such a configuration will be described as follows. First, when the high-frequency power source 13 is energized, The high-frequency current I ₁ flows from the first conductor 6 to the first contact electrode 9 and the branch conductor 8, passes through the rack shaft 1, passes through the second contact electrode 10 and the adjacent conductor 11, and returns to the high-frequency power supply unit 13. Flows alternately, or vice versa. That is, at a certain point in time, as indicated by an arrow in FIG. 2, a high-frequency current I ₁ ′ flows through the rack shaft 1, and an induced current (eddy current) I ₁ ″ flows through the inductive action of the current flowing through the adjacent conductor 1. Therefore, a current of (I ₁ ′ + I ₁ ″) flows on the surface of the tooth portion 2 of the rack shaft 1. At this time, the current returning to the high frequency power supply unit 13 is I ₂ , but detailed description thereof is omitted.

Japanese Patent Application No. 10-183234 (Patent Document 1) is known as a known technique related to high frequency direct current quenching of the rack shaft 1 (rack bar) by the high frequency direct current quenching apparatus 4 having the above-described structure. .
Japanese Patent Laid-Open No. 10-183234

  When quenching the teeth 2 of the rack shaft 1 and the like using the high-frequency direct current quenching apparatus 4 as described above, the initial stage of the heat treatment operation (the use start time of the high-frequency direct current quenching apparatus 4, i.e., the first When the contact electrode 9 and the second contact electrode 10 have not yet started to wear), a desired hardened and hardened layer can be formed on the surface of the tooth portion 2 and the like. However, as the number of heat treatment shots (number of shots; number of heat treatments performed) N increases, the top portions α and β of the first contact electrode 9 and the second contact electrode 10 are gradually worn by contact with the rack shaft 1. The rack shaft 1 gradually approaches the proximity conductor 11 side, and the gap S between the tooth portion 2 of the rack shaft 1 that is the quenching target portion and the proximity conductor 11 is reduced. When the heat treatment is performed under the same heat treatment conditions without changing the heat treatment conditions, the rack shaft 1 has a quenching depth, a quenching width, and a quenching as shown in FIGS. (Tempering) Hardness changes greatly, which may cause a problem that exceeds the standard value. In the above-mentioned Japanese Patent Application Laid-Open No. 10-183234, no countermeasure is proposed for solving such a problem.

  The present invention has been made to solve the above-described problems, and its purpose is to increase the number of heat treatment shots in high-frequency direct current heat treatment (quenching or tempering). A method for adjusting the heat treatment conditions so that a good heat treatment hardened layer (quenched hardened layer) within the standard value can be stably and continuously formed in the heat treatment target part even if the wear amount of the contact electrode increases. It is to provide.

In order to achieve the above object, in the present invention, a high frequency heat treatment object is supported by a pair of contact electrodes, and a high frequency current is directly passed through the pair of contact electrodes to a heat treatment target part of the high frequency heat treatment object. In addition, an induction current is caused to flow through the heat treatment target portion by an induction action of a high frequency current flowing in a proximity conductor disposed in proximity to the high frequency heat treatment target object to heat the heat treatment target portion, and then to a required quenching temperature. In the heat treatment condition adjustment method in the heat treatment of the high-frequency direct current method in which the heat treatment target part is heat treated by cooling the heated heat treatment target part,
(A) a step of predetermining a plurality of heat treatment conditions corresponding to the number of heat treatment shots or a gap between the heat treatment target portion and the adjacent conductor;
(B) detecting the number of heat treatment shots or the gap during heat treatment;
(C) selecting a heat treatment condition corresponding to the detected value from the plurality of heat treatment conditions based on the detected value;
(D) performing a heat treatment based on the heat treatment conditions selected thereby;
To have.
In the present invention, the heat treatment conditions are related to the quenching depth, the quenching width, and the quenching and tempering hardness of the heat treatment target part.
Moreover, in this invention, the said heat processing object part is made to be the back part of the rack shaft corresponding to the tooth part of a rack shaft, or the said tooth part.

  According to the first aspect of the present invention, in the heat treatment condition adjusting method in the heat treatment of the high frequency direct current method, a plurality of heat treatment conditions are previously set corresponding to the number of heat treatment shots or the gap between the heat treatment target part and the adjacent conductor. A step of determining, a step of detecting the number of heat treatment shots or a gap during heat treatment, a step of selecting a heat treatment condition corresponding to the detected value from a plurality of heat treatment conditions based on the detected value, and a selection thereby In accordance with the heat treatment condition adjusting method of the present invention, the number of heat treatment shots can be increased even when the wear amount of the contact electrode is increased. By changing the heat treatment conditions accordingly, the heat treatment hardened layer (quenched hardened layer) within the required standard value is always stably maintained in the part to be hardened. It is possible to form Te.

  Further, the present invention according to claim 2 is that the heat treatment conditions are related to the quenching depth, the quenching width, and the quenching and tempering hardness of the heat treatment target part. According to the heat treatment condition adjusting method of the present invention, the required quenching depth, quenching width, and quenching and tempering hardness can always be stably and continuously obtained even when the wear amount of the contact electrode increases. Can do.

  Further, the present invention according to claim 3 is such that the heat treatment target portion is a tooth portion of the rack shaft or a back surface portion of the rack shaft corresponding to the tooth portion. According to the adjustment method, even if the contact electrode that is in contact with the tooth portion or back surface portion of the rack shaft is worn, the desired hardened layer depth, hardened layer width, and hardened layer are always applied to the tooth portion or back surface portion of the rack shaft. A hardened (tempered) hardened layer can be obtained.

  Hereinafter, a heat treatment condition adjusting method according to an embodiment of the present invention will be described with reference to FIG. Here, as an example of the heat treatment object (work), for example, a case in which the tooth portion 2 of the rack shaft is heat treated (quenched or tempered) will be described. In the following description, the same reference numerals as those used in the above description and FIG. 2 are used.

  For example, when the rack shaft 1 is employed as the heat treatment object (work), it is not necessary to exchange the first contact electrode 9 and the second contact electrode 10 up to about 10,000 times as the number of heat treatment shots. However, it is necessary to change the heat treatment conditions at least about every 2,000 times. In this embodiment, the heat treatment shot number N is adopted as the detection value, but instead of this, the gap S between the tooth portion 2 of the rack shaft 1 and the adjacent conductor 11 may be used as the detection value. Good. In addition, the heat treatment conditions include those corresponding to the quenching depth, quenching width and quenching and tempering hardness, but the quenching depth is selected in the following description, but is limited to this. It is not a thing.

  Table 1 below shows an example of the relationship between the heat treatment shot number N and a plurality of predetermined heat treatment conditions.

  As shown in Table 1 above, when the number N of heat treatment shots is in the range of 1 to 2,000, heat treatment (for example, quenching) under condition 1 is performed. Next, when the number N of heat treatment shots is in the range of 2,001 to 4,000, heat treatment is performed under condition 2 different from condition 1. Thereby, substantially the same quenching depth as in the case of condition 1 can be obtained. Next, Condition 3 is set when the heat treatment shot number N is in the range of 4,001 to 6,000, Condition 4 is set when the heat treatment shot number N is in the range of 6,001 to 8,000, and the heat treatment shot number N is 8,001. Condition 5 is adopted in the range of 90,000. The heat treatment shot number N can be automatically detected by a simple measuring instrument such as a counter during the heat treatment operation, and the heat treatment conditions can be changed relatively manually and automatically at a relatively low cost. is there. Therefore, based on the detected value for the number of heat treatment shots N, the optimum heat treatment conditions for the actual heat treatment operation are selected from a plurality of predetermined heat treatment conditions according to the number of heat treatment shots N and quenched (or quenched). (Return) heat treatment is performed.

  FIG. 1 shows changes in the quenching depth when the heat treatment condition adjusting method in the high frequency direct current quenching according to the present invention is performed. That is, in FIG. 1, the horizontal axis represents the number N of heat treatment shots and conditions 1 to 5 determined in advance corresponding thereto, and the vertical axis represents the quenching depth. As shown in the figure, the quenching depth gradually increases as the number N of heat treatment shots increases, but the quenching depth returns to the original value (value within the standard value) by appropriately changing the summer treatment conditions. This adjustment is repeated up to 10,000 which is the final number of heat treatment shots, and the quenching depth is set within a very narrow range of standard values by sequentially changing and setting conditions 1 to 5 be able to.

  Conditions 1 to 5 correspond to the number N of heat treatment shots as described above, but the number of heat treatment shots N depends on the type of rack shaft 1 and the materials of the first contact conductor 9 and the second contact conductor 10. The setting also differs from the numerical values described in Table 1 above, and the heat treatment conditions corresponding thereto are not limited to the above conditions 1 to 5. Further, in the present embodiment, the quenching depth is selected as the heat treatment condition, but it may correspond to a quenching width and a quenching (tempering) hardness. In addition to the number N of heat treatment shots, the gap S between the rack shaft 1 and the adjacent conductor 11 may be used as a detection value, and conditions may be determined corresponding to this. The gap S can be automatically detected by a simple distance measuring device during the heat treatment operation.

  According to such a heat treatment condition adjusting method, high-frequency direct current firing applied when heat treatment such as induction hardening and tempering is performed on the tooth portion 2 of the rack shaft (or the back surface portion 3 corresponding to the tooth portion 2). When performing heat treatment / tempering, the number of heat treatment shots N, or the heat treatment associated with the increase in the clearance S between the heat treatment target portion (tooth portion 2 or back surface portion 3) of the rack shaft 1 and the adjacent conductor 11 is performed. The change of the hardened layer can be suppressed to a narrow range, and a stable hardened layer can always be formed continuously.

  Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications and changes can be made based on the technical idea of the present invention. For example, in the above-described embodiment, the case where the tooth portion 2 of the rack shaft 1 is heat treated has been described. However, the heat treatment condition adjusting method of the present invention can also be applied to the case where the back surface portion 3 of the rack shaft 1 is heat treated. Furthermore, it goes without saying that the heat treatment condition adjusting method of the present invention can be applied to various heat treatment objects to which the heat treatment of the high frequency direct current method other than the rack shaft 1 is applied.

It is a graph which shows the relationship between the number of heat processing shots by the heat processing condition adjustment method which concerns on one Embodiment of this invention, and a quenching depth. It is a side view of a high frequency direct current hardening apparatus. It is an AA line expanded sectional view in FIG. FIG. 4 is an enlarged sectional view taken along line BB in FIG. 3. It is a graph which shows the relationship between the heat processing shot number by the conventional heat processing condition adjustment method, and quenching depth. It is a graph which shows the relationship between the number of heat processing shots by the conventional heat processing condition adjustment method, and quenching (tempering) hardness.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rack shaft 2 Tooth part 3 Back part 4 High frequency direct current hardening apparatus 9 1st contact conductor 10 2nd contact conductor 11 Proximity conductor N The number of heat processing shots S Clearance (alpha), (beta) Top part

Claims (3)

A high-frequency heat treatment object is supported by a pair of contact electrodes, and a high-frequency current is directly passed through the pair of contact electrodes to a heat treatment target part of the high-frequency heat treatment object, and is disposed in proximity to the high-frequency heat treatment object. By inducing an induced current through the heat treatment target part by the induction action of the high-frequency current flowing in the adjacent conductor, heating the heat treatment target part, and then cooling the heat treatment target part heated to a required quenching temperature, In the heat treatment of the high-frequency direct current method in which the heat treatment target part is heat treated, a method for adjusting heat treatment conditions,
(A) a step of predetermining a plurality of heat treatment conditions corresponding to the number of heat treatment shots or a gap between the heat treatment target portion and the adjacent conductor;
(B) detecting the number of heat treatment shots or the gap during heat treatment;
(C) selecting a heat treatment condition corresponding to the detected value from the plurality of heat treatment conditions based on the detected value;
(D) performing a heat treatment based on the heat treatment conditions selected thereby;
A method for adjusting a heat treatment condition, comprising:   The heat treatment condition adjusting method according to claim 1, wherein the heat treatment condition relates to a quenching depth, a quenching width, and a quenching and tempering hardness of the heat treatment target part.   The heat treatment condition adjusting method according to claim 1, wherein the heat treatment target portion is a tooth portion of a rack shaft or a back surface portion of the rack shaft corresponding to the tooth portion.

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