JPH05287438A - Cylindrical member of special form, such as wheel hub for vehicle, and heat treatment therefor - Google Patents

Abstract

PURPOSE:To produce a cylindrical member of special form improved in wear resistance, etc., by casting a cylindrical member of special form, such as wheel hub vehicle, and then performing diffusion treatment by means of high frequency induction heating, etc., so that the hardness and hardening depth in the required part to be subjected to machining become specific values, respectively. CONSTITUTION:The cylindrical member of special form, such as wheel hub for vehicle, is formed by means of casting by using a spheroidal graphite cast iron containing, by weight, 3.0-4.0% C, 2.0-3.0% Si, 0.8-1.5% Cu, and 0.03-0.05% Mg and increased in ferritic matrix. After casting, high-frequency induction heating, etc., are applied to the required part, to be subjected to machining, of the cylindrical member of special form to practically uniformly allow graphite to enter into solid solution in an austenite matrix and perform graphite diffusion treatment, by which the hardness in the required part and also the hardening depth are regulated to HB285-341 and about 15mm, respectively. By this method, the cylindrical member of special form remarkably improved in wear resistance, fatigue limit, etc., in the required part can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deformed tubular member such as a wheel hub for a vehicle in which the wear resistance and fatigue limit of required parts are remarkably improved as compared with conventional products, and a heat treatment method therefor. ..

[0002]

2. Description of the Related Art Conventionally, a wheel hub for a vehicle, which is one of deformed tubular members, is produced by, for example, machining a cast wheel hub as it is, machining it at a required portion, or simply burning it. Since most of them were only machined after heat treatment such as annealing and normalizing, there were problems in wear resistance and fatigue limit in vehicles used under severe conditions. For example, a four-wheel drive rally specification vehicle that travels off-road at high speed and high load, a so-called laser truck that travels at high speed on a car kit, or a construction used at a construction site such as a dam. In mechanical vehicles, etc., a high load, which cannot be considered in a normal vehicle, is applied to each part of the vehicle.
It is customary to use tools. Wheel hubs are also included in one of such parts, but none of them hitherto have been satisfactory in wear resistance and fatigue limit.

[0003]

SUMMARY OF THE INVENTION Therefore, the problem to be solved by the present invention is to provide a vehicle wheel suitable for a vehicle traveling under severe conditions, for example, under a high load.
Like Luhab, it is manufactured by machining after casting,
It is an object of the present invention to develop a deformed tubular member in which the processed portion is subjected to the high load as described above, and a heat treatment method for the deformed tubular member such as a wheel hub for a vehicle.

[0004]

The structure of a deformed tubular member such as a wheel hub for a vehicle, which is made for the purpose of solving the above-mentioned problems, has a weight percentage of C: 3.0 to 4.0, Si: 2.0 to 3.0,
A deformed tubular member such as a wheel hub for a vehicle, which is formed of spheroidal graphite cast iron containing a large amount of ferrite containing Cu: 0.8 to 1.5, Mg: 0.03 to 0.05, is machined after casting. The required hardness is Hв285-341 and the hardening depth is about 1
It is characterized in that it is held and formed to 5 mm, and the constitution of the heat treatment method for deformed tubular members such as wheel hubs for vehicles is C; 3.0 to 4.0, Si; 2.0 to 3.0 in weight%.
For a deformed tubular member such as a wheel hub for a vehicle made of spheroidal graphite cast iron containing a large amount of ferrite containing Cu: 0.8 to 1.5, Mg: 0.03 to 0.05, the required portion to be machined after casting is subjected to high frequency By induction heating, etc., the graphite is almost uniformly dissolved in an austenite matrix to perform the diffusion treatment of the graphite, and the hardness of the required portion after heat treatment is maintained at H 285 to 341 and the hardening depth is maintained at about 15 mm. It is characterized by doing.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to a wheel hub for a vehicle with reference to the drawings. 1 is a sectional view of a part of a test material formed on a deformed tubular member having substantially the same shape as a vehicle wheel hub to be heat-treated by the method of the present invention, and FIG. 2 shows the wheel hub shape of FIG. FIG. 3 is a cross-sectional view showing a state in which a test material is heated by high-frequency induction heating, FIG. 3 is a cross-sectional view showing a hardness measurement position of a portion to be treated in FIG. 2, and FIG. FIG. 5 is a hardness diagram showing the accuracy test results of the hardness of the portion to be treated in the eggplant test material.
FIG. 3 is a diagram showing the hardness of another wheel-hub-shaped test material heat-treated by the method of the present invention.

In a wheel hub for a vehicle, grooves are formed on the outer periphery of a cylindrical portion of a cast product for machining such as gear cutting, for example, at about six positions at equal pitches. In the present invention, the heat treatment according to the present invention is performed in order to improve the wear resistance and the like of the cylindrical portion of the wheel hub. This point will be described below.

First, in the wheel hub to be treated, C is 3.0 to 4.0% by weight, Si is 2.0 to 3.0% by weight, and Cu is 0.
As-cast spheroidal graphite cast iron with a large amount of ferrite containing 8 to 1.5% by weight and 0.03 to 0.05% by weight of Mg. Such a composition ratio and content are selected such that when the heat treatment according to the present invention is applied to the cylindrical portion, that is, the treatment target portion, graphite is substantially uniformly solid-dissolved in the austenite matrix, and As a result, the desired hardness, the amount of pearlite, and
This is because we want to obtain the curing depth.

In FIG. 1, a test material is formed in a deformed cylindrical shape having substantially the same shape as an actual wheel hub, and a portion corresponding to a boss portion of an actual vehicle wheel hub is formed as a processing target portion T. It is a sectional view of a thing. In FIG. 1, the processing target portion T is shown by hatching, and six temperature measurement points S _{1 of the} processing target portion T are shown.
In to S _6, the measurement of the heating temperature according to the method of the present invention,
As an example, a thermocouple was used. In the illustrated processing target portion T, as an example, the thick portion has a thickness of about 21 mm, the thin portion has a thickness of about 17 mm, and the width of the processing target portion T (right and left in FIG. 1).
Is set to about 76 mm.

As shown in FIG. 2, a coil-shaped high frequency inductor C is provided for the processing target portion T. This inductor C
Is an unequal pitch because it is heated to a predetermined temperature at a substantially uniform depth as a whole, irrespective of the difference in the wall thickness of the processing target portion T, based on the experience of heat treatment with a high frequency inductor. used. The output of this inductor C is about 20 to 28 kW, or the output is adjusted appropriately, and the frequency 20
A high frequency of 00 Hz was applied and induction heating was performed for about 3 minutes. The heating temperature at the temperature measuring points S _{1 to} S ₆ by this heating is about
The temperature was 930 ° C to 1000 ° C.

After the above heating, the temperature at the measuring point S ₃ is about 800.
Allow to cool for about 2 minutes until the temperature drops to about ℃, and continue.
Using two 19φ (mm) hoses, air was jetted to the heated portion of the processing target portion T, and the processing target portion T was forcibly cooled while rotating. This forced cooling is performed at the measurement point S ₁
Temperature to S ₆ was continued for about 4 minutes down to about 500 ° C..

The processing target portion T subjected to the heat treatment as described above
Of the hardnesses A to D in the processing target portion T shown in FIG.
When the hardness in the thickness direction (depth direction) was measured at a pitch of 1 mm from the outer surface at each of the hardness measurement positions indicated by, the hardness shown in FIG. 4 was obtained.

The hardness was H 285 to 341 at the measuring points at the respective depths at the respective hardness measuring positions A to D. In other words, by the heat treatment according to the method of the present invention, it was possible to obtain the desired hardness Hв250 or more at the hardening depth of 15 mm or more.

Next, a test material formed of spheroidal graphite cast iron, which is the same kind of material as the wheel hub-shaped test material and contains a large amount of ferrite containing 1% of Cu, and which has been heat treated by the method of the present invention, and Cu. The test material is formed of spheroidal graphite cast iron that does not contain the test material, which is heat-treated by the same method as the method of the present invention, and spheroidal graphite cast iron containing a large amount of ferrite containing 1% of Cu. With respect to the test materials not subjected to the heat treatment, the hardness of the part machined by gear cutting was measured, and each test material exhibited the hardness shown in the diagram of FIG. In FIG.
TA is the hardness when a test material made of spheroidal graphite cast iron containing 1% Cu and containing a large amount of ferrite is heat-treated by the method of the present invention, and TC is the same test material as TA, but in the case of "as cast" The hardness of the test material is shown. Incidentally, TB represents the hardness of a test material, which was used in a conventional wheel hub for a vehicle, made of spheroidal graphite cast iron containing no Cu and heat-treated by the method of the present invention.

As is clear from the hardness diagram of FIG. 5, Cu1
%, When a product made of spheroidal graphite cast iron with a large amount of ferrite is heat-treated by the method of the present invention, the region subjected to gear cutting, that is, subjected to high load during use, is the entire range of the processed region as shown by TA. In the depth range of 10 mm or more, the desired hardness of Hв285 or more is developed. But,
Even if the same material as the test material shown in TA is "as-cast" and is not subjected to the heat treatment according to the present invention, the hardness of the required portion (that is, the machined portion) is desired as shown in TC. Is not the value of. Further, as shown in TB, even if the same heat treatment as that of the method of the present invention is performed, in the product made of spheroidal graphite cast iron that does not contain Cu, the required area is not entirely hardened as desired.

Although the above-mentioned embodiments describe examples in which the present invention is applied to a wheel hub for a vehicle, the present invention is not only a wheel hub for a vehicle but also a cast product using spheroidal graphite cast iron. After casting, it is subjected to machining such as cutting with a metalworking machine, and this processed part receives a mechanical high load during use, for example, a hole into which a shaft is fitted, such as a gear, belt wheel, chain wheel, or Can be applied to a deformed cylindrical member such as a cylindrical shaft covered by the cylindrical body.

[0016]

As described above, the present invention is a deformed tubular member such as a wheel hub for a vehicle, which is subjected to machining such as gear cutting after casting, and this portion is subjected to a high load. The member is subjected to high-frequency induction heating or the like to dissolve the graphite in a substantially uniform solid solution in an austenite material to diffuse the graphite, and the hardness of the machined portion after the heat treatment is set to H 285 to 341,
Since it is designed to hold the hardening depth of about 15 mm, if this is applied to a vehicle wheel hub, it is possible to obtain a vehicle wheel hub that is superior in wear resistance compared to conventional wheel hubs. become. Therefore, the wheel hub for a vehicle according to the present invention is applied to a severe load, for example, a vehicle with a high load such as a race specification vehicle, a rally specification vehicle, or a construction machine vehicle or a freight vehicle. Very useful as a wheel hub.

Further, the present invention can be applied to machine parts having a boss-shaped portion which receives a high load, and the like, because it can obtain the same effect in a deformed cylindrical member other than the wheel hub, and is very useful. Furthermore, even if the same material as the conventional product is used,
Since it is possible to obtain a product having a quality higher than that of a conventional product, it is possible to form a high quality product with a low cost material. Moreover, since the heat treatment is applied only to the required portion, the other portions remain as the soft material, and therefore, there is an advantage that it is easy to perform the subsequent processing.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a part of a test material formed on a deformed tubular member having substantially the same shape as a vehicle wheel hub to be heat-treated by the method of the present invention.

FIG. 2 is a cross-sectional view showing a state in which the wheel-hub-shaped test material of FIG. 1 is heated by high-frequency induction heating.

FIG. 3 is a cross-sectional view showing a hardness measurement position of a processing target portion in FIG.

FIG. 4 is a hardness diagram showing the accuracy test results of the hardness of the processing target portion in the vehicle wheel hub-shaped test material heat-treated by the method of the present invention.

FIG. 5 is a hardness comparison diagram comparing the hardness of the gear-cut portion of another test material in the shape of a wheel hub heat-treated by the method of the present invention and a test material not subjected to such treatment.

[Explanation of symbols]

T Processing target part C Inductor S _{1 to} S ₆ Temperature measurement point A to D Hardness measurement position

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichi Matsubara 2-8-3 Tonomachi, Kawasaki-ku, Kawasaki-ku, Kanagawa Daiichi Kogyo Kogyo Co., Ltd. (72) Inventor Hiroshi Kobayashi Kawasaki, Kawasaki-shi, Kanagawa 2-8-3, Tonomachi, Kawasaki Daiichi Kogyo Kogyo Co., Ltd. (72) Inventor Kunio Ikeda 2-8-3, Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Daiichi Kogyo Kogyo Co., Ltd.

Claims (3)

[Claims] 1. C: 3.0 to 4.0, Si: 2.0 to 3.0, in weight%.
In a deformed tubular member such as a wheel hub for a vehicle formed of spheroidal graphite cast iron containing a large amount of ferrite containing Cu: 0.8 to 1.5, Mg: 0.03 to 0.05, a required portion to be machined after casting A deformed tubular member such as a wheel hub for a vehicle, which has a hardness of H 285 to 341 and a hardening depth of about 15 mm. 2. C .: 3.0 to 4.0, Si: 2.0 to 3.0 in weight%.
For a deformed tubular member such as a wheel hub for a vehicle made of spheroidal graphite cast iron containing a large amount of ferrite containing Cu: 0.8 to 1.5, Mg: 0.03 to 0.05, the required portion to be machined after casting is subjected to high frequency By induction heating, etc., the graphite is almost uniformly dissolved in an austenite matrix to perform the diffusion treatment of the graphite, and the hardness of the required portion after heat treatment is maintained at H 285 to 341 and the hardening depth is maintained at about 15 mm. A vehicle wheel characterized by
Heat treatment method for deformed tubular members such as luhab. 3. The diffusion treatment of graphite is performed by heating in a range of about 930 ° C. to 1000 ° C. for a short time by heating means such as high frequency induction heating, and after heating, cooling to room temperature is performed at about 800 ° C.
Approximately 2.5 ℃ / sec to 1 depending on the temperature of 550 ℃
The heat treatment method for a deformed tubular member such as a wheel hub for a vehicle according to claim 2, wherein the cooling is performed at a cooling rate of 2.5 ° C / sec.