KR101409002B1 - Heat treatment method of the VGR rack bar for vehicle - Google Patents

Abstract

The present invention relates to an induction heating heat treatment method for a vehicular variable rack ratio (VGR) rack bar and, more particularly, to an induction heating heat treatment method for a vehicular variable rack ratio rack bar (VGR rack bar) by which a tampering operation for satisfying mechanical properties required for a vehicular VGR rack bar and improving durability can be performed in a simple and convenient manner. The induction heating heat treatment method for a vehicular VGR rack bar includes a) a high-frequency heat treatment step in which an induction heating heat treatment is performed by using a high-frequency induction heating device of a frequency of 10 kHz or less, the VGR rack bar is positioned in an inner through-hole of an inductor coil so that the induction heating heat treatment is performed while the VGR rack bar is moved upward and downward, and a water spraying unit to which a water cooling device is connected is positioned below the inductor coil so that water cooling is performed at the same time; and b) a high-frequency tampering step that is performed by using the same high-frequency induction heating device after the heat treatment step, in which the VGR rack is moved upward and downward in a state where an output of the high-frequency induction heating device is lower than an output in the heat treatment step in a state where the water cooling is not performed.

Description

TECHNICAL FIELD [0001] The present invention relates to a heat treatment method for a VBR rack bar for a vehicle,

The present invention relates to a method of induction heating treatment of a variable rack ratio (VGR) RACK BAR for an automobile, and more particularly, to a method and apparatus for satisfying mechanical properties required for automotive VGR reverberation and simplifying and tempering for improving durability. And more particularly, to a VGR (Variable Rack Ratio Rack Bar) induction heating method for automobiles.

The Rack BAR is a part that converts and transmits the rotational motion of the piston by the steering wheel to the rectilinear movement of the RACK. It can realize fuel economy improvement and weight reduction by weight saving, And serves to improve the steering feel of the steering wheel by varying the gear ratio.

Especially, Variable Rack Rack Bar (VGR) is a device that differentiates the reaction force of Steering Wheel at low speed, high speed driving, parking, As shown in FIG.

1 shows a photograph of a VGR reflector. As shown in FIG. 1, the VGR reflector is composed of a cylindrical round bar portion and a tooth portion, and the tooth portion is formed such that the interval between the teeth is relatively wide at the center portion and relatively narrow at both sides. This is to differentiate the reaction force of the steering wheel at low speed, high speed driving and parking. The length of the round bar varies depending on the product. The heat treatment of the leva means heat treatment to the tooth part.

Conventional heat treatment method of LVA is a high-frequency heat treatment using a high-frequency induction heating device, then transferring the heat-treated lambar to a separate heating furnace, and tempering by maintaining it at 240 degrees for 2 hours.

The high frequency heating (or "high frequency induction heating") used for heating the metal is a method for heating a metal located in a coil through which an alternating current (high frequency) current flows by an electromagnetic induction action, Heat is generated by resistance of eddy current loss and hysteresis loss. The heating of the material to be heated (metal or conductor) by using the generated heat energy is referred to as induction heating, and in particular, the use of high frequency current is referred to as high frequency induction heating.

Conventional heat treatment methods of LVA utilize a high frequency induction heating apparatus, and usually heat treatment is performed using a high frequency of 150 kHz or more. The surface hardness (HV 700) is high, but the hardening depth is thinned (0.7 mm) to achieve the desired level of hardening depth, and only the upper part (i.e., the acid part) of the tooth is partially And cracks are generated in the teeth.

Further, conventionally, the induction heating heat treated lable is subjected to tempering in a separate electric heating furnace after high frequency induction heating. Tempering is a process carried out to give durability to ferrite (ferrite) + pearlite (martensite) transformed (transformed) by high frequency heat treatment. Since martensite is a very hard structure, it can not withstand other objects that hit the Rectangle bar. It is a very hard tissue, so there is a possibility of cracks, and the hardness of the tissue is decreased In order to eliminate the possibility of cracks, temper furring is carried out in order to enhance the durability of the whole leva. In the conventional tempering process, approximately 50 lables are loaded on the tempering jig, and then the tempering jig is charged in the tempering furnace 'electric furnace'. The temperature of the heating furnace is set to 240 deg., And the holding time is set to 2 hours. After completion of tempering, take out the product and perform air cooling.

In such a tempering process by the heating furnace method, there is a disadvantage that the secondary defect such as appearance of the product and scratching is very likely to occur as the product is moved to a heating furnace and tempered. In addition, the fixing of the heating furnace type tempering has a problem that the tempering color is generated in other parts except the high frequency heat treatment part due to the secondary heating in the heating furnace. 'Temper color' is a phenomenon in which the color changes to other parts (round bars) other than the high frequency heat treatment part due to the heat of 240 degrees, which is the biggest disadvantage of the heating furnace tempering process.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a VGR reflector for a vehicle, which satisfies the mechanical properties required by the automotive VGR reflector and does not suffer appearance, scratches, And does not cause a 'temper color' in the round bar portion.

The object of the present invention is not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood from the following description

In order to accomplish the above object, the present invention provides a VGR reverberation induction heating method for automobile, comprising the steps of: a) performing induction heating treatment using a high frequency induction heating apparatus with a frequency of 10 kHz or less, A high frequency heat treatment step in which a VGR lever is positioned, the induction heating treatment is performed while moving the VGR lever upward and downward, and a water splitting part connected to a water cooling device is positioned below the induction coil to perform water cooling simultaneously; And b) performing the same high frequency induction heating apparatus after the heat treatment step, wherein the output of the high frequency induction heating apparatus in a state in which no water cooling is performed is lower than the output in the heat treatment step, And a high-frequency tempering step of performing high-frequency tempering while moving it up and down.

Preferably, in the high-frequency heat treatment step and the high-frequency tempering step, the VGR reflector moves up and down in a state of not rotating.

Preferably, the inner aperture of the inductor coil has a triangular or semicircular shape.

Preferably, in the high-frequency heat treatment step, the output of the high-frequency induction heating device decreases from an upper end portion of the VGR reflector to an intermediate portion thereof and increases again from a middle portion to a lower end portion thereof, Increases from the upper end to the middle portion of the tooth, and decreases from the middle portion to the lower end.

Preferably, in the high frequency tempering step, the lowering speed of the VGR reflector increases from the upper end to the middle portion of the VGR reflector, and decreases from the middle portion to the lower end.

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is not necessary to provide a separate electric heating furnace facility because the mechanical properties required by the automotive VGR reflector are all satisfied and the tempering process proceeds in the same high frequency induction heating apparatus And it is also advantageous in that the appearance of scratches and the occurrence of scratches which are generated in the process of transferring to a conventional electric heating furnace can be blocked. In addition, 'Tampa color' is not generated in the round bar portion where the high-frequency heat treatment of the VGR reflector is not performed, so that the quality of the product can be secured.

1 is a photograph of VGR Rexba.
2 is a flow chart of a VGR reflector induction heating method for a vehicle according to a preferred embodiment of the present invention.
3 is a cross-sectional view of an automotive VGR reflector performing a VGR reflector induction heating heat treatment method for a vehicle, in accordance with a preferred embodiment of the present invention.
4 is a photograph showing a process of performing a VGR reflector induction heating process for a vehicle according to a preferred embodiment of the present invention.
5 is a photograph of another embodiment of a high frequency inductor coil in a VGR reflector induction heating method for automotive vehicles, according to a preferred embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, a V-Allevaq induction heating process for automobiles according to the present invention will be described in detail.

Fig. 2 is a flow chart of a VGR reverberation induction heating method for a vehicle according to a preferred embodiment of the present invention. Fig. 3 is a schematic diagram of a vehicle VGR reverberation heat treatment method for performing a VGR reverberation induction heating method for automobiles according to a preferred embodiment of the present invention. Fig.

Referring to FIGS. 2 and 3, the method for heat treatment of VGR Reve induction heating for automobiles according to the present invention comprises the steps of: a) performing a high-frequency heat treatment step using a high-frequency induction heating apparatus at a relatively low frequency (9 kHz) Wherein the high frequency induction heating apparatus performs tempering at a lower output than the high frequency heat treatment step.

In the high frequency induction heating apparatus, the surface hardness and the hardening depth are determined according to the output frequency. In the present invention, an induction heating apparatus using a low frequency of 10 kHz or less is used in order to satisfy the physical property required in a VGR relay for an automobile. The heat treatment at a frequency of 10 kHz has a relatively low surface hardness (HV 600 level) and a deep curing depth (about 4.5 mm). The reason for using the induction heating apparatus having a relatively low output frequency of 10 kHz or less in the present invention is that the depth of the teeth of the lever is approximately 2.2 mm so that the depth of the lower surface of the tooth of the tooth is set to be the hardening depth.

More specifically, a description will be given of a manner in which the VGR lever shown in FIG. 1 is subjected to a high frequency induction heating heat treatment. 4 is a photograph showing a process of performing a VGR reflector induction heating process for an automobile according to a preferred embodiment of the present invention

As shown in FIG. 4, the VGR lever is vertically erected to fix the upper side, and then subjected to a high-frequency heat treatment while moving downward along both guides. The VGR reflector 10 is inserted into the inner hole 22 of the inductor coil 20 connected to the high frequency induction device and is subjected to high frequency induction heat treatment while descending along the inner hole 22. As shown in the drawing, the water dispersing unit 30 connected to the water cooling unit is positioned below the inductor coil 20, and water cooling is simultaneously performed during induction heating heat treatment. Water supplied from the outside through the water supply pipe 32 is sprayed on the surface of the VGR reverber 10 heated by the high-frequency induction heating through the water distributing unit 30. [ This is to change the structure of VGR Rexbae from ferrite + pearlite structure to martensite structure through quenching.

In the present invention, the high frequency induction heating heat treatment is performed only for the portion of the VGR reflector portion 12. The heat treatment portion is divided into three portions of an upper end portion, a middle portion and a lower end portion, and a high frequency induction heating heat treatment is performed while changing the descending speed and the output of the high frequency induction heating device.

The upper part is the part where the high-frequency heat treatment is started, and the heating performance of the inductor coil is lower than that of the intermediate part. Also, even if the heating performance of the high frequency inductance coil is raised to a continuous operation, the depth of the curing may become thin because the VGR lever falls as soon as the output of the device starts. Therefore, the high-frequency induction heating heat treatment is performed by setting the output of the device to be relatively high (phase) and the falling speed to be relatively low (low). In the embodiment of the present invention (high-frequency induction heating apparatus of 9 kHz), the output of the apparatus was set to 6.3 and the descending speed was set to 7.0.

Next, in the middle portion, the heating performance of the high frequency inductance coil is at its maximum, and the high frequency heat treatment is performed as the VGR lever is lowered. Therefore, the high-frequency induction heating heat treatment is performed by setting the output of the device relatively low (middle) and the descending speed relatively (high) relative to the upper end. In the embodiment of the present invention (high frequency induction heating apparatus of 9 kHz), the output of the apparatus was set to 6.0 and the descending speed was set to 9.0.

Finally, at the lower end, if the output of the high frequency induction heating apparatus is stopped, the depth of the hardening may be reduced. Therefore, the hardening depth is maintained by varying the output and the descending speed to the same extent as in the upper end portion. At the lower end, the output of the device is relatively high (up) and the descending speed is relatively low (down). In the embodiment of the present invention (high-frequency induction heating apparatus of 9 kHz), the output of the apparatus was set to 6.3 and the descending speed was set to 7.0.

As described above, in the present invention, the high-frequency induction heating process is performed on the VGR laser while the descending speed and the output of the high frequency induction heating apparatus are changed, thereby maintaining the curing depth constant.

In the present invention, after the high frequency induction heating, the tempering process proceeds in the same facility. The tempering process in the present invention using a high frequency induction heating apparatus is also a process for imparting durability to a VGR laker changed from a ferrite + pearlite structure to a martensite structure by a high frequency heat treatment, This is done to prevent cracks and cracks from being generated in the bars. In the tempering process, the output is lower than the output of the induction heating apparatus in the high frequency induction heating step, which means that the tempering temperature is lower than the temperature in the high frequency induction heating. In the 9 kHz high frequency induction heating system, the induction heat treatment stage has an output state of about 5 to 8, but maintains a lower output state of 2 to 3 at the time of high frequency tempering.

Thus, in the high-frequency tempering process using the high-frequency induction heating apparatus of the present invention, tempering is performed not only on the entire VGR reflector but also on the teeth 12 of the high-frequency heat treated VGR reflector, i.e., the heat treatment section, There is no occurrence of any other temper color, and there is no need to provide a facility such as an electric heating furnace, and there is an advantage that it does not cause secondary defects such as scratches and scratches generated at the time of movement.

In the high-frequency tempering process, no artificial cooling is performed. The previous high-frequency heat treatment aims to transform the structure of the VGR Rexbae into the Martensite structure from the ferrite + pearlite structure by spraying the cooling water. However, the high frequency tempering is performed by applying the cooling water to the transformed tissue martensite By applying secondary heat, the heat dissipates the internal stress in the existing martensite, thereby lowering the surface hardness and improving the durability.

Preferably, in the high frequency tempering process, as in the preceding high frequency heat treatment step, the high frequency tempering is performed while varying the lowering speed by dividing into the upper part, the middle part and the lower part. Since the output of the high frequency induction heating apparatus is lower than that in the high frequency heat treatment, it is possible to perform the tempering process by adjusting the descending speed only. However, the present invention is not limited thereto. It is needless to say that the tempering process may be performed by varying the output with the descending speed as in the high frequency heat treatment step.

Meanwhile, in the high-frequency heat treatment step and the high-frequency tempering step, the VGR reverber 10 is inserted into the inner hole 22 of the inductor coil 20 in a non-rotating state and descends along the inner hole 22. The VGR reflector is lowered in the non-rotating state, and the shape of the inner through hole of the inductor coil is not circular but the shape of the VGR reflector is changed to correspond to the shape of the end surface of the VGR reflector in order to make the hardening depth of the heat- And a semicircular shape or a triangular shape as shown in Fig. That is, in FIG. 4, the inner through hole 22 of the inductor coil 20 has a semicircular shape. In FIG. 5, the inner through hole 22 of the inductor coil 20 has a triangular shape.

After the high-frequency tempering is completed, the heat treatment of the VGR reverberation is completed through air cooling.

Table 1 shows the physical properties required for VGR VREBA.

Item Requirements Exterior There should be no foreign matter or harmful flaws. Surface hardness HRC 51 ~ 59 Curing Depth (HV450) 3.2 ± 0.4mm (base to hit), 1.0 ± 0.5mm (base to base) group Martensite structure Degree of deformation Should be within 1.0mm crack There should be no cracks

[Example]

After the high frequency induction heating apparatus of 150 kW × 9 kHz was purchased, the VGR lager was fixed in the same manner as shown in FIG. 4, and high frequency heat treatment was performed using a high frequency induction heating apparatus. In the high-frequency heat treatment step, the high-frequency induction heat treatment was performed by setting the output 6.3 at the upper end, the descending speed 7.0, the output 6.0 at the middle portion, the descending speed 9.0, the output 6.3 at the lower end, and the descending speed 7.0. At this time, the VGR reflector was lowered in the non-rotating state, and water cooling was simultaneously performed by the water-cooling supply device at the same time as the high-frequency induction heating treatment.

After the high-frequency induction heating treatment was finished, the high-frequency induction heating device was subjected to high-frequency templating while the VGR lever was lowered from the non-rotating state while the water-cooling supply device was not operated. The output of the high frequency induction heating device was maintained at 2.3, and the descending speed was set to 7.0 at the upper end, 9.0 at the middle portion, and 7.0 at the lower end as in the high frequency heat treatment. After the high-frequency templating was completed, the air cooling was dried.

Heat treatment The physical properties of the finished VGR lakers were measured. The surface hardness was measured by using a Rockwell hardness tester. The hardening depth was measured by micro Vickers cutting the VGR lavel vertically, and the texture of the heat treated portion was measured by changing the metallographic microscope to martensitic texture. The value of strain was measured using a strain gauge and the crack was measured with a magnetic particle detector.

The measurement results are shown in Table 2.

Item Measurement result Surface hardness   HRC 55 Curing Depth 3.4mm (base to hit), 1.2mm (base to base) group Martensite structure Degree of deformation  none crack  none

As can be seen in Table 2, the VGR reflector performed by the heat treatment method of the present invention achieved excellent quality satisfying all of the required physical properties.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention may be embodied otherwise without departing from the spirit and scope of the invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the scope of the present invention, but are intended to be illustrative, and the scope of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of the claims should be construed as being included in the scope of the present invention.

10: VGR Rexba
12:
14:
20: inductor coil
30: Water distribution
32: Water supply pipe

Claims (7)

A method for heat treating a VBR RVA induction heating for automobile,
a) induction heating heat treatment using a high frequency induction heating apparatus having a frequency of 10 kHz or less, placing a VGR lever in an inner through hole of the inductor coil, performing induction heating treatment while moving the VGR lever up and down, A high-frequency heat treatment step in which a water splashing part connected to a water-cooling device is positioned at the bottom of the water-cooling device,
b) performing the same high frequency induction heating apparatus after the heat treatment step, wherein the output of the high frequency induction heating apparatus is lower than the output in the heat treatment step in a state in which water cooling is not performed, And a high-frequency tempering step of performing high frequency tempering while moving the VGR reverberation induction heating furnace. The method according to claim 1,
In the high frequency heat treatment step and the high frequency tempering step,
And the VGR lever is moved up and down in a state in which the VGR lever does not rotate. The method according to claim 1,
Wherein the inner hole of the inductor coil has a triangular shape or a semicircular shape. The method according to claim 1,
In the high-frequency heat treatment step,
Wherein the heat treatment of the middle portion of the VGR reflector is performed at a low output of the high frequency induction heating apparatus and at a high descending speed as compared with the heat treatment at both ends (upper end portion and lower end portion) of the VGR reflector. Induction heating heat treatment method. The method according to claim 1,
In the high-frequency heat treatment step,
The output of the high-frequency induction heating device decreases from the upper end portion of the VGR reflector toward the middle portion, increases again from the middle portion to the lower end portion,
Wherein the decreasing rate of the VGR reflector increases from an upper end portion of the VGR reflector to an intermediate portion thereof and decreases from an intermediate portion to a lower end portion of the VGR reflector. The method according to claim 1,
In the high frequency tempering step,
Wherein the tempering of the intermediate portion of the VGR reflector progresses in a state where the lowering speed is higher than the tempering at both ends (upper end portion and lower end portion) of the VGR reflector. The method according to claim 1,
In the high frequency tempering step,
Wherein the decreasing rate of the VGR reflector increases from an upper end portion of the VGR reflector to an intermediate portion thereof and decreases from an intermediate portion to a lower end portion of the VGR reflector.

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