KR20050085008A - Long life rotating body with excellent fatigue strength and method of manufacturing the rotating body - Google Patents

Abstract

A long life rotating body with an excellent fatigue strength and a method of manufacturing the rotating body, the rotating body formed by welding the end parts of stacked two sheets of sheet metal to each other comprising lap fillet welded joints, cold bending worked parts, and punched holes, characterized in that an ultrasonic shock treatment is applied to either of the welded joints, cold bending worked parts, and punched holes to form dents or smoothen the surfaces thereof so as to relieve a residual tensile stress, whereby the long life rotating body with the excellent fatigue strength formed of the sheet metal having the lap fillet welded joints, cold bending worked parts, and punched holes which is subjected to repeated loads by rotation such as road wheels for car, pulleys, gears, and crawler driving wheels can be provided.

Description

Long life rotary body with excellent fatigue strength and manufacturing method {LONG LIFE ROTATING BODY WITH EXCELLENT FATIGUE STRENGTH AND METHOD OF MANUFACTURING THE ROTATING BODY}

The present invention relates to a long-life rotating body having excellent fatigue strength using a metal plate and a method of manufacturing the same. For example, a long-life rotating body having excellent fatigue strength having overlapping edge welded joints, cold bending parts, punched holes, etc. repeatedly loaded by rotation, such as automobile wheel wheels, pulleys, gears, and caterpillar driving wheels. And a method for producing the same.

Rotors such as automobile wheel wheels, pulleys, gears, and caterpillar driving wheels that are repeatedly loaded by rotation have weaknesses in metal fatigue, such as overlapping edge welded joints, cold bends, punching holes, and the like. As a technique for improving the weld bead shape and the fatigue strength by post-treatment such as welding, cold bending, punching, or the like, conventionally, (1) grinding, (2) TIG dressing, (3) shot peening, and (4) Hammer peening has been used. Such a technique is to shape the weld end portion to be the stress concentrating portion to relax the stress concentration or to change the residual stress to improve the fatigue strength. However, even with this technique, there were the following problems.

At this time, grinding and TIG dressing are a method of improving a fatigue strength by shaping the shape of a stress concentration part into a shape with little stress concentration. However, they are effective in improving the fatigue strength of overlapping edge welded joints and punching holes, but they are not effective in cold bending parts, have a significantly low work efficiency, and are not suitable for use in mass production. . In the case of grinding, when the toothing direction is perpendicular to the direction of stress action, processing defects are likely to occur such that processing cracks tend to develop fatigue cracks.

By the way, in the weld part, residual stress is generally introduced by local thermal expansion by welding heat input and thermal contraction by subsequent cooling. In addition, a large residual stress accompanying plastic deformation exists in the cold worked part. This residual stress is one of the major factors that lowers the fatigue strength.

As another means for improving fatigue strength, compressive residual stress is generated, or tensile residual stress is reduced to increase the fatigue strength. Methods such as shot peening and hammer peening are known. In addition, the shot peening treatment is a method of imparting a compressive residual stress by hitting a large number of steel balls of less than 1 mm at a site that is a starting point of fatigue crack generation. Moreover, hammer peening is a method of tapping a process part by operating a pin using compressed air etc.

However, shot peening requires a huge machine and requires a chamber in use, which is also inefficient in mass production and requires various utilities. In addition, since partial selectivity to treat only the necessary place is remarkably inferior, it cannot be used when designability is required.

In addition, the hammer peening has a drawback that it is difficult to use a thin plate because it has a large recoil and gives a plastic deformation that is too large.

In hammer peening, in order to perform low frequency machining of several Hz on the joint, unevenness of the machining surface is severe, and the concave portion becomes the stress concentration part and the starting point of the fatigue crack is not stable, and sometimes the whole joint There exists a problem that fatigue strength may fall rather.

It is also known that an improvement in the shape of the weld end portion can be alleviated by melting the heating material of the weld metal, thereby reducing the tensile residual stress. However, this method also has a problem that the efficiency is remarkably low, and the effect is not so great.

As mentioned above, it is difficult to employ | adopt the conventional technique of improving fatigue strength with respect to rotating bodies including a wheel for automobiles, and even if it can employ | adopt, the degree of fatigue strength improvement remained at a low level. Therefore, although it has responded by increasing the strength of the material, the susceptibility to fatigue of the punched end surface is rapidly increased when the strength of the steel reaches 600 N / mm ² or higher, so that the fatigue improvement effect reaches a limit point. There was this.

In addition, as a prior art related to a method of improving fatigue strength by applying ultrasonic vibration to a weld joint, US Patent No. 6,171,415, for example, describes ultrasonic vibration along a weld seam heated by a welding arc. A method of imparting is disclosed.

However, this prior art is based on the premise of giving ultrasonic vibration to a high temperature material immediately after welding, and there is no disclosure of a specific object and processing range hitting the ultrasonic vibrator proposed by the present invention.

1 is a side view of a wheel for an automobile, which is one embodiment of the present invention.

2 is a cross-sectional view taken along the line A-A of FIG.

It is a figure explaining with the enlarged view which shows the edge welding joint part which overlapped of two metal sheets.

It is a figure explaining the state of the ultrasonic impact process with respect to the cold bending process part of a metal plate.

It is a figure explaining the situation of the ultrasonic shock process to the punching hole part of a metal plate in a partial enlarged view.

FIG. 6 is a diagram for explaining the situation of FIG. 5 in a perspective view. FIG.

Best Mode for Carrying Out the Invention

An embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6 by taking an automobile road wheel as an example.

1 is a side view of a road wheel for a vehicle that is an embodiment of the present invention.

The automobile wheel wheel of FIG. 1 is manufactured by welding the steel plate and the aluminum plate by the wheel disc material processed by the press forming process which includes the punching process, and the wheel-rim material roll-formed, and 1 shows the punching hole.

Hereinafter, a metal plate means the metal plate containing a steel plate and an aluminum alloy plate.

FIG. 2 is a cross-sectional view of a road wheel for automobiles which is one embodiment of the present invention, and shows A-A cross section of FIG. 1. In FIG. 2, 1 is a hole punched by the metal plate by the press, 2 is what is called a heart part which cold-formed the metal plate, and it corresponds to the cold bending part of this invention by having a bending process component, 3 shows a superimposed corner weld seam which welds the two pieces of metal plate together and joined together.

Due to the repetitive load while driving the vehicle, stress concentration is likely to occur in the welded portion, the cold bent portion, and the punching hole, and the fatigue strength of the portion is the smallest. The strength can be significantly improved.

2 in FIG. 2 represents an ultrasonic vibration terminal, the ultrasonic vibration generating apparatus used in the present invention is oscillated by an oscillator and converted into mechanical vibrations of 19 kHz to 60 kHz by a transducer, the amplitude of which is guided by a wave guide. By amplifying the vibration, the ultrasonic vibration terminal consisting of 2 mm to 6 mm pins is vibrated at an amplitude of 20 to 40 µm, whereby an indentation having a depth of about several hundred µm having excellent smoothness of the surface of the hitting portion can be formed. This ultrasonic vibration generating device can be commonly used in the following embodiments.

It is a figure which shows the edge welding joint part which overlapped of two metal plates, and is the detail of 3 in FIG. In FIG. 3, 6 and 7 are two metal plates, 9 is the edge part, 10 is the root part, the curvature radius p in the edge part 9 is the edge radius, and the angle (theta) shows the edge angle. The rotating body (for example, an automobile road wheel) in the present invention has an indentation having a width of 1 to 5 mm formed by an ultrasonic impact treatment around the edge portion 9 of the overlapped corner joint and subjected to the ultrasonic impact treatment. The edge radius p in the applied edge part is 1 mm or more.

By hitting the periphery of the edge 9 by the ultrasonic vibration terminal described above, an indentation having a width of 1 to 5 mm is formed, and the edge radius p at the edge is set to 1 mm or more, thereby alleviating the stress concentration of the edge 9. Since the tensile residual stress can be changed to the compressive residual stress, the fatigue strength of the rotating body can be significantly improved.

The rotating body (for example, an automobile road wheel) in the present invention has indentations having a width of 1 to 5 mm formed on the surface or front and back surfaces of the root portion 10 of the overlapped corner joint by ultrasonic shock treatment.

By hitting the metal plate surface or front and back surface of the root portion 10 by the ultrasonic vibration terminal described above, an indentation having a width of 1 to 5 mm can be formed, and stress concentration of the root portion 10 can be alleviated, thereby significantly improving the fatigue strength of the rotating body. Can be.

FIG. 4 shows a cold bent portion of a metal plate, and is an enlarged detail view of 2 in FIG. 2. In FIG. 4, 4 and 4 'represent the ultrasonic vibration terminal used for this invention, and a cold bending process part is provided by giving ultrasonic vibration from the front and back surface of the cold bending process part (for example, the head part of a wheel) of a rotating body. The surface hardness of the convex surface, which is the tensile side surface, and the concave surface, which is the compression side surface, is increased by 10% or more as compared with the untreated portion, and the tensile residual stress of the cold bent portion is in the range of compression from 50% or less of tensile strength.

As a result, the fatigue strength of a cold bending part can be improved remarkably.

Further, by hitting only the concave surface, which is the compression-side surface of the cold bending part, the compression-side surface is smoothed to 10 µm or less with the centerline average roughness Ra, and the residual stress on the tension side is alleviated to 50% or less of the tensile strength. Since no trace of treatment is left on the surface side visible to human eyes during use, fatigue strength can be improved while maintaining designability.

Further, the tip of the ultrasonic vibration terminal striking the concave surface of the metal plate surface is convex, and the tip of the ultrasonic vibration terminal striking the iron surface of the metal plate surface is concave with a radius of curvature larger than the convex surface of the metal plate surface (but FIG. 2). In Fig. 4, the radius of curvature of the tip of the ultrasonic vibration terminal 4 'is exaggerated.) Since the tip of the ultrasonic vibration terminal is easily flattened on the surface of the metal plate, the effect of reducing surface hardness and tensile residual stress can be further enhanced. .

5 and 6 show a situation in which an ultrasonic impact treatment is applied to a punched hole portion of a metal plate, FIG. 5 is a partially enlarged view of FIG. 2, and FIG. 6 is a perspective view thereof.

In Fig. 5, 4 'represents an ultrasonic vibration terminal used in the present invention, and the surface of the punched hole cross section is provided by applying ultrasonic vibration to the cross section of the punched hole portion 5 (for example, the punched hole portion of the wheel) of the rotating body. The notch of is smoothed to 10 µm or less with the centerline average roughness Ra, and there is no hardened structure of hardness of 400 Hv or more in the punched hole cross section, and the microcracks of 200 µm or less generated from the surface of the punched hole cross section are 50% or less of the original length It is flattening to its depth. As a result, the fatigue strength of the punched hole portion can be remarkably improved.

In addition, since the tip of the ultrasonic vibration terminal is easily concave in the punched hole end surface by making the tip of the ultrasonic vibration terminal that drills and strikes the end face of the hole, the flattening of the nucleus, the removal of the hardened structure, and the flattening of the microcracks. The effect can be further enhanced.

In addition, the method of applying a residual stress such as an ultrasonic impact treatment tends to be effective in the material to which the high strength material is compared with the low strength material. This is based on the characteristic that it is difficult to redistribute by the external force which the residual stress which the high strength material introduce | transduced is added.

With reference to FIG. 6, by disposing the left and right ultrasonic vibration terminals 4 'up and down, the ultrasonic striking treatment can be efficiently performed because the left and right ultrasonic vibration terminals 4' do not interfere with each other.

Although the above embodiment has been described using an automobile road wheel as an example, the present invention relates to overlapping edge welded joints, cold bends, and punched holes that are repeatedly loaded by rotation, such as pulleys, gears, and caterpillar drive wheels. Branches can be widely applied to a rotating body using a metal plate.

The present invention solves the problems of the prior art as described above, and overlapping edge weld seams, cold bends, punching holes that are repeatedly loaded by rotation, such as wheels, pulleys, gears, driving wheels of Caterpillar for automobiles An object of the present invention is to provide a rotating body long life rotating body excellent in fatigue strength using a metal plate having a metal plate.

The present invention has been made as a result of earnest examination in order to solve the above-described problems, the overlapping edge weld seams, cold bending machined parts that are repeatedly subjected to the load by rotation, such as wheels, pulleys, gears, drive wheels of caterpillar for automobiles By providing an ultrasonic vibration treatment to the surface of a punching hole, a rotating body long life rotating body having excellent fatigue strength is provided, and the gist thereof is as follows as defined in the claims.

(1) A rotating body having overlapping edge welded joints in which two metal plates are superimposed on each other and welded to each other, wherein an indentation having a width of 1 to 5 mm formed by ultrasonic shock treatment around the edge of the overlapped edge welded joint. And the edge radius at the edge portion to which the ultrasonic shock treatment has been applied is 1 mm or more.

At this time, the ultrasonic shock treatment refers to a process of hitting the metal plate surface by the ultrasonic vibration terminal.

(2) A rotating body having overlapping edge welded joints in which two metal plates are superimposed on each other to weld the ends, wherein widths 1 to 5 formed on the surface or front and back surfaces of the root portion of the overlapped edge welded joint by ultrasonic shock treatment Long life rotating body excellent in fatigue strength, characterized by having an indentation of mm.

(3) A rotating body having a cold bent portion of a metal plate, by applying an ultrasonic impact treatment to the tensile side surface of the cold bent portion, the surface hardness of the tensile side surface is increased by 10% or more compared with the untreated portion, A long-life rotating body having excellent fatigue strength, characterized in that the tensile residual stress of the cold bending part is in the range of compression from 50% or less of tensile strength.

(4) A rotating body having a cold bent portion of a metal plate, by applying an ultrasonic shock treatment to the compressed side surface of the cold bent portion, the compressed side surface is smoothed to 10 μm or less with a centerline average roughness Ra (JlS B 0601). The surface hardness of the tensile side surface is increased by 10% or more compared with the untreated portion, and the tensile residual stress of the cold bent portion is in the range of compression from 50% or less of tensile strength to excellent longevity. Rotating body.

(5) A rotating body of a metal plate having a punching hole, wherein by applying an ultrasonic shock treatment to the end face of the punching hole, the nutch of the surface of the end face of the punching hole is smoothed to 10 m or less at the center line average roughness Ra, and the punching hole Long life rotator with excellent fatigue strength, characterized in that the cross section does not have a hardened structure of 400 Hv or more in hardness, and fine cracks of 200 μm or less generated from the surface of the punched hole cross section are flattened to a depth of 50% or less of the original length. .

(6) The long-life rotating body excellent in the fatigue strength according to any one of (1) or (5), wherein the tensile strength of the metal plate is 400 N / mm ² or more.

(7) In the method of manufacturing a metal plate rotating body having a nested welded joint, a cold bent and / or a punched portion, wherein the ground end, the root, the cold worked portion of the metal plate, and the punched portion are welded. Ultrasonic shock treatment is performed using an ultrasonic vibration terminal whose tip is convex or concave in accordance with the shape of a to-be-processed part, etc., The manufacturing method of the long life rotating body excellent in fatigue strength characterized by the above-mentioned.

The effect of this invention is demonstrated by the Example of the steel road wheel for automobiles in this invention. In the 13-inch road wheel for automobiles, the treatment method was changed to compare the fatigue strength. In addition, wheel, disk material thickness used here 3.2mm, is processed from the material strength of 690 N / mm ² and a thickness of 4.0 mm, strength of 330N / mm ^2.

Fatigue tests were conducted with a rotating bending moment load. The repeat speed is 700 rpm, the bolt tightening torque is 98 Nm, and the test moment is 1.47 kNm.

In addition, as an initial crack before a process, the nipple of 200 micrometers in depth was artificially inserted into the edge of a punching hole, the part was cut out after a test, and the crack length was measured. The results are shown in Table 1.

No. 1 is an example of the invention, and the front and back surfaces of the bent portion, the punched hole cross section, and the overlapping edge welded joints were each subjected to a blow treatment using ultrasonic vibration terminals having convex ends, so that the surface of the steel sheet subjected to the ultrasonic impact treatment was smoothed. In addition, since the residual stress also became a compressive residual stress, the fatigue life became long, and the evaluation was "0 K" (good).

No. 2, No. 3 is an example of the invention, the front and back surfaces of the bent portion and the overlapped corner joints are subjected to the blow treatment using ultrasonic vibration terminals having a convex tip, and punching hole cross sections are subjected to the blow treatment using a concave ultrasonic vibration terminal. Since the surface of the steel sheet subjected to the ultrasonic impact treatment was further smoothed, the fatigue life was further increased, and the evaluation was "OK" (good). In addition, the ultrasonic blow treatment was performed in the invention examples of Nos. The surface hardness (Vickers hardness) of the applied steel sheet surface was increased by about 30% compared with the untreated portion.

In addition, there was no hardened structure with a hardness of 40OHv or more in the punched hole cross section, and a 200 μm nugget introduced into the surface of the punched hole cross section was flattened to a depth of about 30% of the original length. Moreover, the trace of the process in a welding part can also be confirmed.

No. 4 is a comparative example, since the processing surface was rough because no processing was performed after the processing, and the residual stress had many parts which became tensile residual stress, and thus the fatigue life was shortened, and the evaluation was "NG" (defect).

No. 5 is a comparative example, and the grinding | polishing process was applied to the cross section of the punched hole after processing, but the smoothness of the surface was improved, but since the residual stress was not improved, fatigue life became short and evaluation was "NG" (defect).

No. 6 is a comparative example. Since the shot peening treatment was applied to the surface of the bent portion after machining, the smoothness and residual stress of the surface were also improved, and the fatigue life was long, but nothing else was done. We stayed at and evaluation was "NG" (bad).

No.7 is an example of the strength of the wheel and disc material of 330 N / mm ² , and the front and back edges of the bent portion and the overlapping edge welded joints are subjected to the impact treatment by using convex ultrasonic vibration terminals. Although the cross section performed the hitting process using the concave ultrasonic vibration terminal, the surface of the steel plate which performed the ultrasonic shock treatment was further smoothed and the long life was obtained, and evaluation was "OK" (good).

According to the present invention, an ultrasonic vibration treatment is applied to the surfaces of overlapping edge welded joints, cold bends, and punched holes that are repeatedly loaded by rotation, such as automobile wheel wheels, pulleys, gears, and caterpillar driving wheels. It is possible to provide a rotating body excellent in fatigue strength and a long-life rotating body, which has a remarkable effect useful industrially.

Claims (7)

A rotor having an edge welded joint welded to an end by overlapping two metal plates with each other, the ultrasonic impact treatment having an indentation having a width of 1 to 5 mm formed by an ultrasonic shock treatment around the edge of the overlapped edge welded joint. A long life rotary body having excellent fatigue strength, characterized in that the edge radius at the edge portion to which the edge is applied is 1 mm or more. At this time, the ultrasonic shock treatment refers to a process of hitting the metal plate surface by the ultrasonic vibration terminal. A rotating body having an edge welded joint formed by superimposing two metal plates on each other and welding the ends thereof, wherein the metal plate surface or front and back surfaces of the root portion of the edge welded joint have indentations having a width of 1 to 5 mm formed by ultrasonic impact treatment. Long life rotating body with excellent fatigue strength. A rotating body having a cold bent portion of a metal plate, by applying an ultrasonic impact treatment to the tensile side surface of the cold bent portion, the surface hardness of the tensile side surface is increased by 10% or more compared with the untreated portion, and the cold bend A long-life rotating body having excellent fatigue strength, characterized in that the tensile residual stress of the processed portion is in the range of 50% or less of tensile strength to compression. A rotating body having a cold bent portion of a metal plate, by applying an ultrasonic impact treatment to the compressed side surface of the cold bent portion, the compressed side surface is smoothed to 10 μm or less with a centerline average roughness Ra (JlS B 0601). The surface hardness of the tension-side surface is increased by 10% or more compared with the untreated portion, and the tensile residual stress of the cold-bending portion is in the range of compression from 50% or less of tensile strength, and has excellent fatigue strength. A rotating body of a metal plate having a punching hole, by applying an ultrasonic impact treatment to the end face of the punching hole, the surface nits of the end face of the punching hole are smoothed to 10 µm or less at the center line average roughness Ra, and the hardness of the punching hole end face is 400 A long-life rotating body having excellent fatigue strength, wherein there is no hardened structure of Hv or more, and fine cracks of 200 µm or less generated from the surface of the punched hole cross section are flattened to a depth of 50% or less of the original length. The long-life rotating body having excellent fatigue strength according to any one of claims 1 to 5, wherein the metal plate is a steel material having a tensile strength of 400 N / mm ² or more. In the manufacturing method of the metal plate rotating body which has a superimposed edge weld joint part, a cold bending process part, and / or a punching process part, it is possible to avoid the edges, the root part, the cold work part of a metal plate, punching process part, etc. of a weld joint part. An ultrasonic shock treatment is applied using an ultrasonic vibration terminal whose tip of the pin according to the shape of the processing portion is convex or concave, so as to produce a long-life rotating body having excellent fatigue strength.