JP2591954B2 - Hardening method of rack bar consisting of rack and pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a shaft-shaped member in which one half of a longitudinal direction has a solid outer circumference formed with a rack, and the other half has a hollow pipe part, that is, a rack part. The present invention relates to a quenching method in which substantially the entire length and the entire circumference of a rack bar composed of a pipe portion is moved and quenched by induction heating.

(Prior Art) In a conventional rack bar, a tooth profile is formed over a predetermined length range along the outer peripheral longitudinal direction of a solid material, and the entire member is tempered. Kaisho
As disclosed in JP-A-57-133557 and the like, it was sufficient to apply stationary quenching treatment only to the toothed portion of the rack bar to impart abrasion resistance.

However, rack bars used in recent automobiles, etc.
In order to meet the demand for weight reduction, although a solid material is used for the rack portion, a hollow pipe is connected to the rack portion by pressure welding or the like to form a shaft portion.

In a rack bar composed of a rack portion and a pipe portion of this kind, even if the solid portion of the rack portion is a heat-treated material, the pipe portion is not tempered, and a connection process occurs near the connection portion. The effects on the organization remain. Therefore, when this type of rack bar is subjected to a quenching process over substantially the entire length and the entire circumference, it is possible to provide wear resistance to the tooth profile portion, eliminate the residual influence of the connection structure, and improve the strength of the pipe portion at once. Therefore, instead of the conventional lacquer quenching method, quenching treatment for almost the entire length and the entire circumference of the lacquer bar has been required.

(Procedure leading to completion of the invention) The inventor of the present invention believes that this type of rack bar is a shaft member,
We thought that it would be possible to apply the conventional method when moving and quenching the shaft member by induction heating, and tried quenching treatment by this method. This will be described with reference to FIGS. 2 (a) and 2 (b).

In FIG. 2 (a), W is a rack portion r and a pipe portion p.
The work W is a center bar with a substantially horizontal axis at the heating position.
The shaft is supported by S1 and S2. One of the center shafts S is rotatable by a rotary drive source (not shown), and the other is freely rotatable.
The work W supported by the shafts 1 and 2 is rotatable. C is a heating coil having an inner diameter capable of facing the outer periphery of the pipe portion p with a predetermined gap therebetween, and J 'is an annular cooling socket. The cooling bucket J 'and the heating coil C are connected and integrated by a connecting member U so as to maintain a predetermined interval.

The step of quenching the work W using the above configuration will be described with reference to the operation diagram of FIG. 2 (b).

First, the heating coil C is set at a position facing the left end of the rack r as shown in FIG. 2 (a), and then the rotary drive source is driven to move the workpiece W into the rotating state as indicated by the line A.
After the t _0, starts the power supply to the heating coil C as shown by line and c at time t _1, the cooling Jiketsuto the supply of cooling fluid to J 'starts, the time t ₂ of a predetermined time Motogo Then, relative movement in the axial direction between the work W and the heating coil C is started as indicated by the line d. The work W is moved by the relatively moving heating coil C.
Is sequentially heated to the right, and the cooling fluid injected from the cooling jack J 'following the heated portion is rapidly cooled down. Heating coil C is energized to the heating coil C at the time t ₃ when reaching the right end of the pipe portion p is stopped as indicated by the line, cooling Jiketsuto J 'is the right to the heating coil C is further follow moves the relative movement at the time t ₄ when reaching to the position for cooling the heated portion of the end side is stopped as indicated Sen'ni, cooled as indicated fiber and c at the time t ₅ in which the heated portion is cooled sufficiently The rotation of the work W is stopped by stopping the supply of the cooling fluid to the jet J 'and stopping the drive of the rotary drive source. By the above operation, almost the entire length of the work W is hardened over the entire circumference.

However, the attempt failed. Because, in the above method, the ridge located on the axial rotation front side of the tooth end surface over the entire tooth profile of the rack portion r, that is, the portion within the range indicated by the circle in FIG. It became clear that it became a burn-in (the part which is not quenched).

Further, as shown in FIG. 3 (b), when both ends of the pipe portion p were supported and a strain measurement test of the rack portion r with respect to the axis of the pipe portion p was performed, the total length of the rack portion r was 192 mm.
(However, the length of the tooth profile portion is 155 mm). In the case of a workpiece W having a diameter of 24 mmφ and a wall thickness of 4.2 mmt of the pipe portion p, the point P2 is opposite to the tooth profile as shown by an arrow with respect to the point P1, that is, the arc circumference. Strain in the direction, and the amount of strain
1.4 to 2.4 mm, which was 1.1 mm even after tempering, it was found that the tempering effect by tempering could not be expected.

Therefore, the present inventor has found that the cause of burn-in
Has a tooth profile different from that of a normal shaft member having a circular cross section, and the cooling fluid injected toward the tooth profile does not flow down as quickly as the shaft member having a circumferential surface, in other words, the cooling fluid is cut off. Poorly, cooling fluid stays in the tooth valleys, and the accumulated cooling fluid overflows as the workpiece W rotates.
It is assumed that the result is that the scattered particles fall down to the ridge portion of the tooth end face located on the front side in the axial rotation direction of the tooth profile during heating, and the temperature rise of the portion is suppressed to the quenching temperature or lower. Also,
It was assumed that the point of large quenching strain was also the result of the synergistic effect of the small amount of shrinkage caused by the occurrence of burn-through in the tooth profile and the large amount of shrinkage caused by sufficient quenching of the circular arc portion.

Based on the above assumptions, the present inventor tried quenching by narrowing the flow rate of the cooling fluid to such a degree that the flow rate of the cooling fluid did not stay in the toothed valleys, but to the lowest line that maintained the quenchable cooling capacity. The attempt was
Although the burn-through was certainly avoided, only a very shallow quenched layer was formed on the tooth portion, and the work W as a whole could not be finished to a desired strength, and only a result unsuitable for use was obtained.

(Object of the Invention) The present invention relates to a case where a half of the longitudinal direction of a solid bar is formed on the outer periphery of a solid material, and the other half of the rack bar is a hollow pipe portion. However, the conventional method of hardening the shaft member is intended to overcome the problem that the above-mentioned problems occur and cannot be applied. Therefore, all the tooth shapes of the rack portion have abrasion resistance of appropriate hardness up to a predetermined depth. Provided is a method of hardening a rack bar comprising a rack portion and a pipe portion, in which a hardened layer having desired hardness and toughness can be formed in accordance with the thickness of the pipe portion, and extremely low strain hardening can be performed. The purpose is to:

(Summary of the Invention) The gist of the present invention is as follows: (1) A substantially half lengthwise and a full length and a whole circumference of a shaft-like material in which the other half is formed by a hollow pipe portion and the other half is formed by a rack formed on the outer periphery of a solid material. In the case of moving and quenching by induction heating, (2) the shaft member is rotatably supported so as to be substantially axially horizontal, and (3) heating having an inner diameter capable of facing the outer periphery of the pipe portion with a predetermined gap therebetween. A horseshoe-type cooling jacket that can follow the coil and the heating coil and has an opening facing downward is relatively moved from one end to the other end with respect to the shaft material. (4) The quenching accompanying the relative movement is The shaft material is not rotated and the tooth profile is facing down. The pipe portion is rotated while the shaft material is rotating. (5) The heating condition can be switched at the time of transition between the rack portion and the pipe portion due to relative movement. And in the rack It is characterized in that heating to form a quenched hardened layer with a predetermined depth in the tooth profile is performed, and heating to form a quenched hardened layer with a predetermined depth according to the wall thickness is applied to the pipe. A method of hardening a rack bar comprising a rack portion and a pipe portion.

(Operation of the Invention) The present invention uses a horseshoe-type cooling jacket in which the rack bar is non-rotating and the tooth profile is downward when quenching the rack portion, and the heating condition is predetermined, and the opening is downward for cooling. The cooling fluid cuts well, there is no overflow of the cooling fluid in the direction of the tooth profile during heating, and the entire tooth profile of the rack is raised to a predetermined quenching temperature to a predetermined depth to ensure a sufficient flow of cooling fluid. The quenching results in the formation of a predetermined quench hardened layer. The entire tooth profile of the rack is uniformly quenched together with the arc side, so that the shrinkage of each part approaches to reduce the quenching strain. During quenching, the rack bar is rotated and the heating conditions are made different from the heating of the rack according to the wall thickness of the pipe.
It has the effect of uniformly forming a hardened hardened layer that imparts toughness and desired strength over the entire circumference of the pipe portion, and the effect of eliminating residual effects generated in the transitional structure between the rack portion and the pipe portion.

(Example) The present invention will be described in detail below with reference to FIGS. 1 (a) and 1 (b).

The workpiece W of the embodiment has the same shape as the member subjected to the trial experiment.

As shown in FIG. 2 (a), a normal shaft member is horizontally supported by center axes S1 and S2, and the center shaft S is rotationally driven by driving a rotation drive source. The heating coil C to be used may have a mechanism capable of rotating the shaft member, and the heating coil C used may be a single or multiple winding formed with an inner diameter capable of facing the outer periphery of the pipe portion p of the rack bar W with a predetermined gap therebetween. This is a normal shaft member heating coil provided with a heating conductor.

However, the connecting member U should follow the heating coil.
As the cooling jackets connected by (1), those having a horseshoe shape shown as J in FIG. 1 (a) are used. Thus, the cooling jacket J is connected to the connecting member U with the opening facing downward.
The tips of the both sides hanging down are extended from the lower circumference of the work W supported by the center shafts S1 and S2 to a position slightly lower than the lower circumference of the work W, and are formed from the cooling fluid injection holes provided in the inner circumference having a U-shape. As shown in the figure, the injected cooling fluid can impinge from the radial direction on the arc circumference of the rack portion r with the tooth profile g facing downward, and obliquely downward on the tooth profile g. It is formed as follows. The flow rate of the cooling fluid to be injected is set to a flow rate having a cooling capacity capable of sufficiently quenching and cooling the heated portion.

The case where the work W is quenched by using the heating coil C and the cooling jacket J will be described with reference to the operation diagram of FIG.

It is assumed that the work W is carried into the heating position, for example, with the rack r left. Thus, the work W is moved to the center axis.
In the present invention, when the shaft is supported on the shafts S1 and S2, the tooth profile g of the rack portion r is directed downward. Next, the heating coil C, which has been retracted in the direction of the center axis S, is opposed to and located at the left end of the rack r of the work W.

After positioning as described above, the heating power supply is switched to the rack r.
Shows the tooth profile on top of a predetermined depth of the hardened layer can perform heating capable of forming a predetermined output settings, starts the power supply to the heating coil C as at time t ₀ shown in line B, is Senha As described above, the supply of the cooling fluid to the cooling socket J is started.
The width of the wire indicates the magnitude of the output of the heating power supply.

Then the work W as shown by line d in time t ₁ of a predetermined time Motogo
-Start relative movement to the right at a predetermined speed between the heating coils C. Following the relative movement, the rack r is sequentially heated from the left end side to the right end side to a predetermined quenching temperature, and the cooling jacket J relatively moving following the heated coil C following the heated coil C is rapidly cooled. In this state, the cooling fluid injected from the cooling jacket J moves the rack portion r in a state in which the circular arc is directed upward and the tooth profile is directed downward. The cooling fluid, which has been struck and cooled the heated portion at the struck position, immediately flows down from the opening located below the cooling jacket J. Therefore, there is no possibility that the cooling fluid stays in the tooth-shaped valleys. In addition, since the workpiece W is in a rotated state, there is no possibility that the cooling fluid after hitting the heated portion overflows or scatters in the direction of the tooth profile during heating.

With the relative movement heating coil C starts rotating the workpiece W as driving the rotary drive source as indicated by a line b at the time t ₂ which is shifted from rack-and-pinion unit r into the pipe section p, rack-and-pinion heating power as indicated line The output is switched to a lower output than when the portion r is heated, so that heating is performed so that a thin quenched layer corresponding to the thin wall thickness of the pipe portion p can be formed.

While the pipe section p are sequentially quenched in this state, the heating coil C is energized to the heating coil C as shown by line B in ItaruTsuta time t ₃ to the right end of the pipe portion p is stopped, the heating coil C There further moved to follow cooling Jiketsuto J stops the relative movement as indicated by the right-end side of the line two at a time t ₄ when arriving at a position for cooling the heated portion. With the heated portion of the right end side to stop the rotation of the workpiece W as driving stops rotation driving source as indicated by a line b at time t ₅ of a predetermined time Motogo that is sufficiently cooled, the cooling as indicated Senha The supply of the cooling fluid to the jet J is stopped.

By the above operation, the entire periphery of the work W is hardened over the entire length, but different hardening processes are performed so that the rack portion r and the pipe portion p are adapted to each other, and the work W is released from the shaft support by the centers S1 and S2. Then, it is carried out of the heating position, and all the steps are completed.

When the strain measurement test shown in FIG. 3 (b) was performed on the workpiece W subjected to the above process, the strain amount was 1.25 to 1.27 mm in the as-quenched state, and the strain amount was 0.6 in the tempered state. mm test results were obtained. This value indicates that no mechanical correction is required as a post-process.

Further, as a result of the hardness measurement test, no quenching was found at the ridge portion on the end face side of the rack portion r, and a hardened hardened layer having a predetermined hardness was formed to a predetermined depth on all the tooth profiles, and the pipe portion p In addition, it was shown that a quenched layer of 1.25 mm was formed on the surface layer for a wall thickness of 4.2 mmt, and the pipe portion p was treated so as to have both strength and toughness.

(Other Embodiments) In the above embodiment, the switching of the heating condition for each of the rack portion r and the pipe portion p is performed by changing the output of the heating power supply. Is also good.

In the above embodiment, the case where the relative movement quenching is performed from the rack part r side to the pipe part p side is described. However, even if the relative movement quenching is performed from the pipe part p side to the rack part r side, no problem occurs. However, it goes without saying that the same operation and effect as those of the embodiment can be obtained. However, in this case, the rotating work W must be stopped without inertia and the tooth profile must be directed downward at the time of shifting to the rack portion r.

The present invention is directed to a rack bar having a structure in which a solid member and a pipe member are connected. For example, a rack bar having a pipe-like structure in which one side of a solid member is formed with a hole along an axis. It can be widely applied to quenching of similar shaft materials.

(Effects of the Invention) According to the present invention, a rack bar composed of a rack portion and a pipe portion has abrasion resistance of appropriate hardness up to a predetermined depth in all tooth shapes of the rack portion by performing only one relative movement hardening. The desired hardness and toughness can be imparted to the pipe portion in accordance with the wall thickness thereof, and a finish can be obtained in which the quenching distortion is suppressed to a small extent, thereby eliminating the need for mechanical correction in the subsequent steps. Therefore, the present invention dramatically improves the method of relative displacement quenching by induction heating, and can respond to the demand for the reduction of the weight of the rack bar with a product having a high quality finish. It is awarded as having great effect.

[Brief description of the drawings]

1 (a) is a front view of a cooling jacket used in the method of the present invention, FIG. 1 (b) is an operational diagram for explaining the method of the present invention, and FIGS. 2 (a) and (b) are FIGS. 3 (a) and 3 (b) are front views and operation diagrams, respectively, showing the case where the subject material of the present invention is subjected to the conventional shaft material quenching method. FIGS. It is sectional drawing and a front view of a material.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C21D 9/08 C21D 9/08 D

Claims (1)

(57) [Claims] An induction heating method for moving and quenching the substantially entire length and the entire circumference of a shaft portion in which one half of the longitudinal direction is formed by a rack around the outer periphery of a solid material and the other half is formed by a hollow pipe portion. The shaft member is rotatably supported so as to be substantially axially horizontal, and a heating coil having an inner diameter capable of facing the outer periphery of the pipe portion with a predetermined gap therebetween, and an opening facing downward with respect to the heating coil is provided. Move the horseshoe-type cooling jacket relative to the shaft from one end to the other end,
The quenching associated with the relative movement is performed in such a manner that the rack portion is in a state in which the shaft is non-rotating and the tooth profile is directed downward, and the pipe portion is in a state in which the shaft is rotating, and the rack portion and the rack are associated with the relative movement.
Heating is set so that the heating conditions can be switched at the time of transition between pipe sections. Heating that can form a quenching and hardening layer with a predetermined depth on the rack section is performed, and quenching and hardening with a predetermined depth according to the wall thickness is performed on the pipe section. A quenching method for a rack bar comprising a rack portion and a pipe portion, wherein heating is performed to form a layer.