JP2006051540A - Impact plastic working method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impact plastic processing method excellent in fatigue strength.
When a shock is applied to a welded portion between an outer surface of a metal hollow cross-section member and fixed by welding and plastic processing is performed, the position of the member opposite to the welded portion is supported or restrained. An impact plastic working method with excellent fatigue strength, wherein a tensile stress is applied to the welded portion in a state of being applied.
[Selection] Figure 1

Description

  The present invention relates to an impact plastic working method for steel, aluminum, titanium, magnesium, etc., and alloys thereof used in automobiles, home appliances, building structures, ships, bridges, construction machines, various plants and the like.

  A structural member made of metal is subjected to post-processing such as grinding, remelting, and plastic working on the starting portion for the purpose of improving fatigue strength. In plastic processing, impact plastic processing such as shot peening, laser peening, ultrasonic impact treatment, hammer peening, and wire peening is often performed. However, since the thin-walled member having the hollow cross section has low rigidity, when impact plasticity such as shot peening is applied to the welded portion W where the outer surface of the metal hollow cross-section member 1 is welded as shown in FIG. As a result, the member 1 may bend 3 due to elastic deformation, or a recess 4 may be formed around the processed portion 12 due to plastic deformation, as shown in FIG. 7, and a sufficient fatigue strength improvement effect may not be obtained. Although this bending and dent are very slight, they are a major factor for reducing the effect of impact machining. Here, the dent means that the entire periphery 12 including the processed portion is bent and plastically deformed by the processing load 2, and is different from the dent generated in the tool contact portion of the impact plastic processing.

  Regarding prevention of deformation of such a hollow cross-section member, Patent Document 1 discloses a method of inserting a core in order to supplement the rigidity of an extruded material, and Patent Document 2 discloses a method of packing a filler. Further, Patent Document 3 discloses a hollow shape member whose sectional shape on the tensile stress side is changed.

  Furthermore, Patent Documents 4 and 5 disclose a method of performing shot peening on the tensile stress side while applying a bending load to a member as a method for enhancing the fatigue strength of an automobile member.

  Further, although not a hollow cross-section member, as a method for improving the fatigue strength of a metal belt, a method of giving a curvature to a metal plate and performing shot peening is disclosed in Patent Document 6 in which a tooth is generated in a state where tensile stress is generated in a tooth root region of a gear. Patent Document 7 discloses a method for performing shot peening aiming at the original region.

Further, Patent Document 8 discloses a method for improving the fatigue strength of a welded joint, in which two metal plates are mechanically constrained, and then welded with a fillet and subjected to ultrasonic impact treatment near the weld toe. ing. In addition, ultrasonic impact treatment refers to improvement of the surface shape and residual by applying ultrasonic deformation of several tens of KHz generated from an ultrasonic generator to an object through a tool such as a pin and applying plastic deformation. This is a process for stress relaxation / relocation.
JP 2000-117334 A Japanese Patent Laid-Open No. 5-104152 JP 2000-220252 A JP-A-5-33048 Japanese Patent Laid-Open No. 5-78739 JP 2000-225567 A Japanese Patent Laid-Open No. 11-320411 JP 2004-130313 JP

  Among the disclosed technologies, Patent Document 1 discloses a method of inserting a core during bending in order to compensate for a lack of cross-sectional rigidity of a hollow extruded material, and Patent Document 2 discloses a compression stress side for preventing collapse of a hollow profile. Each of the methods for filling different deformation resistance fillings on the tensile stress side is disclosed. All of these are methods of filling the hollow part with high rigidity, and do not fill the material, and support or constrain the opposite side of the welded part across the hollow member and give tensile stress or welded This is a method different from the method of the present invention in which the appendage is grasped and a tensile stress is applied to the weld.

  Further, Patent Document 3 discloses a hollow shape member that protrudes in a trapezoidal shape where a tensile stress is generated during bending, but this is also different from the method of the present invention in which the cross-sectional shape is not changed. is there.

  Furthermore, in Patent Documents 4 and 5, a compressive load is applied to the spring seat provided on the upper surface of the member with both ends of the member as fulcrums for the purpose of improving fatigue strength for the front axle beam and rear axle housing for automobiles. A method is disclosed in which the lower side of the member is brought into a tensile stress state and shot peening is applied to the tensile stress portion. This method is a method in which fatigue strength is improved by subjecting a member to four-point bending loading and widely shot peening a portion where tensile stress is generated. In order to prevent this, tensile stress is generated in the welded part while supporting or constraining the position opposite to the welded part in the metal hollow cross-section member, or tensile stress is applied to the welded part by grasping the welded adduct However, this is a different invention because it is a method of applying impact plastic working.

 Furthermore, Patent Documents 6 and 7 disclose a method of performing shot peening on a portion subjected to tensile stress, but Patent Document 6 is directed to a metal plate such as a belt, and Patent Document 7 is a gear. The present invention is different from the present invention in that it is applied to a cross section of a member and a supporting position or a welded portion.

Patent Document 8 discloses a method of restraining a processing portion in ultrasonic impact processing, but is a technique related to a restraining method at the time of welding, and defines the tensile stress on the support portion and the welded portion during impact plastic working. It is an invention different from the method of the present invention.
An object of the present invention is to provide an impact plastic working method for a hollow cross-section member having excellent fatigue strength.

In order to solve the above problems, the gist of the present invention is as follows.
(1) Supports a position opposite to the welded portion in the metal hollow cross-section member when the outer surface of the metal hollow cross-section member is subjected to plastic working by applying an impact to the welded portion with the appendage fixed by welding. Or, in a restrained state, an impact plastic working method excellent in fatigue strength, characterized by applying tensile stress to the welded portion,
(2) Furthermore, when the metal hollow cross-section member is subjected to plastic working by impacting at least the weld with the pre-addition from the welded portion, a position recording member on the opposite side of the welded portion in the metal hollow cross-sectional member The impact plastic working method with excellent fatigue strength according to (1), wherein a tensile stress is applied to the welded portion in a state where the position apart from the height of the weld is supported or restrained,
(3) The impact plastic working method with excellent fatigue strength according to the above (1) or (2), wherein the tensile stress is 10 to 90% of the yield stress of the member,
(4) When an impact is applied to the welded portion of the metal hollow cross-section member welded and fixed to the welded portion and plastic processing is performed, the metal adduct in the metal hollow cross-sectional member is grasped and attached to the welded portion. Impact plastic working method with excellent fatigue strength, characterized by applying tensile stress,
(5) The impact plasticity processing method with excellent fatigue strength according to the above (4), wherein the tensile stress is 10 to 80% of the yield stress of the adduct,
It is in.

  The method of the present invention is sufficient because the welded portion and the vicinity thereof are not bent or dented when impact is applied to the welded portion fixed by welding to the outer surface of the metal hollow cross-section member and plastic processing is performed. It can be subjected to impact plastic working and has excellent fatigue strength, and its industrial significance is great.

The present invention is described in detail below.
The present inventor has examined the workability when performing plastic working by applying an impact to a welded portion with an appendage that is welded and fixed to the outer surface of a thin metal hollow cross-section member. As a result, although depending on the support form of both ends of the hollow cross-section member, the above-described deflection 3 shown in FIG. 6 and the dent 4 shown in FIG. 7 may occur, which significantly reduces the effect of impact plastic working. Turned out to be. In particular, in the impact plastic working method in which a large load is concentrated in a narrow region such as laser peening and ultrasonic impact treatment, it has been found that the degree of the flexure 3 and the recess 4 is large. However, in general, it is difficult to reduce the deflection and dent by increasing the thickness of the member, changing the cross-sectional shape, and filling the filler, and other methods must be studied. .

  As a result of earnestly examining the solution, in order to prevent bending due to elastic deformation, in the hollow cross-section member 1, a welded portion with an adjunct that is welded and fixed to the outer surface of the hollow cross-section member 1; It has been found that a method of supporting or restraining the opposite side 13 is effective. Here, “support” means to suppress displacement only in the direction of bending, for example, by supporting it with a block-shaped jig 5 as shown in FIG. 1, and “constraint” means that a jig 6 is used as shown in FIG. This is to suppress the displacement in the vertical and horizontal directions by supporting at least two directions by using the vertical part 6a before and after or the horizontal part 11a above and below the material hand 11.

  For preventing the dent 4 in the periphery 12 including the weld due to plastic deformation, it is effective to generate a tensile stress 7 in the weld W as shown in FIG. It has been found that not only the resistance of 4 but also the reduction of the deflection 3 is effective. The generation of the tensile stress can be realized by applying a tensile load or a bending load to the member 1, and among these, the supporting point of the jig 5 on the opposite side 13 to the welded portion W is used as a fulcrum, and the jig 8 is provided on both sides of the welded portion W. It was found that by applying a compressive load, a tensile stress can be applied to the welded portion W, and as a result, both the bending 3 and the dent 4 of the processed portion can be suppressed. In such a three-point bending type loading, the tensile stress around the welded portion W can be increased. If the distance 9 between the welded portion W and the position 8 to which the compressive load is applied is smaller than the height 10 of the metal hollow cross-section member 1 (height from the member surface on the welded portion W side to the lower surface on the opposite side), sufficient bending is achieved. It has also been found that tensile stress can be effectively generated when the member is separated by at least 10 heights, because deformation and tensile stress to the surface cannot be applied. Further, even if a uniform tensile stress 14 is generated on the surface by applying a tensile load F to the entire hollow cross-section member 1 as shown in FIG.

  Further, as a result of examining the magnitudes of the tensile stresses 7 and 14 to be generated, if the tensile stress at the welded portion W that does not consider the influence of the appendage 15 or the defect is less than 10% of the yield stress of the member, the effect is very large. However, if it exceeds 80% of the yield stress of the member, the welded portion W is a stress concentrated portion, so plastic deformation starts in a wide area of the welded portion W, and the thickness of the member is reduced or the cross-sectional shape is deformed. Therefore, it has been found that it is preferable to set the yield stress to 10 to 80%. In order to more effectively suppress the bending and the dent, it is more preferable to set the yield stress to 30 to 60%.

  Next, it has been found that a method of grasping the welded appendage 15 and applying a tensile stress to the welded portion W is also effective. There are appendages 15 on the same side as the welded portion W, and for example, many of them are joined for the purpose of connecting other members as in the bracket of the target example shown in FIG. In many cases, the stress applied causes fatigue failure. As shown in FIG. 9, when a tensile stress is applied to the appendage 15 existing on the same side as the welded portion W, a tensile stress 7 is also generated around the welded portion and lifted. The dent around the part can be prevented, and the effect of impact plastic working can be sufficiently obtained. As a method for applying the tensile stress to the appendage 15, the tensile stress may be applied by using a jig that directly grips the welding appendage after using the support jig 8. In the case of a bracket, as shown in FIG. 10, a method of inserting a link member 16 into a bracket that is an appendage 15 and axially fixing it with pins and / or bolts 17 and applying a tensile stress to the link member 16 is simple. And effective. The direction of the tensile stress applied to the appendage 15 is not particularly limited, and the effect of the present invention can be obtained in any direction, but the metal hollow cross-section member 1 is pulled in a direction close to the load direction applied in practical use. It is preferable to apply stress.

  Furthermore, it is preferable that the magnitude of the tensile stress applied to the welded portion W by grasping the welded appendage 15 is 10 to 80% of the yield stress of the appendage 15. This is because if the stress is less than 10%, the effect of preventing bending and dent is small, but if it exceeds 80%, plastic deformation becomes prominent in the vicinity of the welded part of the additive, resulting in deformation of the additive and reduction in thickness. It is. In addition, the tensile stress here means the largest tensile stress generated in the appendage 15.

  The member to which the method of the present invention is applied is not particularly specified, and a metal and its alloy such as steel, aluminum, titanium, and magnesium, and a portion where they are processed into a member having a hollow cross section by joining, plastic working, or the like. As long as it has a welded portion with an adjunct that is welded and fixed to the outer surface of the metal hollow cross-section member, regardless of the presence or absence of openings, adducts at both ends, the shape of the entire member, etc. It is possible to apply the method of the invention. Also, the type of welded joint is not particularly specified, and the method of the present invention can be applied to fillet welding, lap welding, and butt welding. The welding conditions are not particularly limited with respect to welding.

(Example)
Using a hot-rolled or cold-rolled steel sheet having the thickness and yield stress shown in Table 1, a hollow cross-section member having the shape and dimensions shown in FIG. 8 (hollow member height dimension 50 mm, width dimension 70 mm) is manufactured. An addendum 15 having a U-shaped cross section having the same material and thickness was welded to the upper surface by fillet welding by carbon dioxide arc welding using a welding material having the same strength as the steel plate. For the arc weld toes of these specimens, the method of the present invention, that is, the impact plastic working method under the conditions shown in Table 3 in a state where the opposite side of the weld W is supported and tensile stress is applied to the weld W. Applied. For comparison, a test piece that was impact plastic processed by supporting the other part without supporting the opposite side of the welded part was also manufactured.

  Further, as shown in FIG. 9, the impact plastic working method shown in Table 3 is performed in a state where the link member 16 is inserted into the appendage 15 and fixed with a pin, and tensile stress is applied to the appendage 15 via the link member 16. A test piece to which was applied was also produced.

  Thereafter, the hollow cross-section member 1 is subjected to a load control fatigue test by a three-point bending load so that the weld has tensile stress as shown in FIG. 8, the stress ratio (= minimum load / maximum load) is 0.1, room temperature The fatigue stress was compared with the nominal stress range of the surface where the fracture life was 2 million times.

The fatigue strength of each specimen is also shown in Table 1 and Table 2.
In the case of shot peening treatment (No. 1 to 13), the method No. 1 of the present invention is compared with the comparative examples such as No. 1 and 2 which do not support the back surface of the processed part and No. 3 where the tensile stress is 0. 4 to 13 have improved fatigue strength by 15% or more. When the back surface of the processed part is supported, when the tensile stress is 10 to 80% of the yield stress (No. 5 to 7), even greater fatigue strength is shown, and this is an example of the present invention in the case of 30 to 60%. No. 6 showed a significant improvement in fatigue strength. Furthermore, in Example Nos. 9 to 13 of the present invention in which tensile stress was applied to the same side as the welded portion via a weld appendage, a greater fatigue strength was exhibited than when the tensile stress was applied while supporting the back surface of the weld. ing. Even in this case, the effect of improving the fatigue strength was greater than in the case of No. 10-12 where the tensile stress was 10-80% of the yield stress of the adduct. The same tendency was observed in other impact treatment methods such as hammer peening, water jet peening, laser peening, and ultrasonic impact treatment.

Also, looking at the relationship between the distance between the processed part and the support part and the member height, No. 17, 18, 20 in the case of hammer peening, No. 66, 67, 70 in the case of ultrasonic impact treatment, all When the distance between the processed portion and the support portion is smaller than the member height, the fatigue strength is slightly improved, but when the distance is higher than the member height, a greater fatigue strength is exhibited. In Tables 1 and 2, “〃” is used as “same meaning as the row immediately above”.

It is an external view of the three-point bending loading at the time of impact plastic working in the present invention. It is an external view of the tensile stress loading at the time of impact plastic working in this invention. It is a figure which shows the example of application of this invention. It is a figure which shows another example of application object of this invention. It is an external view of another three-point bending load at the time of impact plastic working in this invention. It is a figure which shows bending generation | occurrence | production in the conventional method. It is a figure which shows the dent generation | occurrence | production of the process part periphery in a conventional method. It is a figure which shows the fatigue test condition in the example of this invention. It is an external view of the other tensile stress loading at the time of impact plastic working in this invention. It is a figure which shows the example of the grabbing method for the time of tensile stress loading in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal hollow cross-section member 2 Load at the time of impact plastic working 3 Deflection of whole member 4 Depression around welded part 5 Support jig 6 Restraint jig 7 Tensile stress 8 Support jig 9 for loading 9 Distance between loading jig and processing part 10 Member Height 11 Restraint jig for loading (material hand)
12 Around welded portion 13 Opposite side of welded portion 14 Uniform tensile stress 15 on member 15 Addition 16 Link member 17 Pin (bolt)

Claims (5)

  When an impact is applied to the welded portion of the metal hollow cross-section member welded and fixed to the adduct and plastic processing is performed, the position opposite to the welded portion of the metal hollow cross-section member is supported or restrained. An impact plastic working method excellent in fatigue strength, wherein a tensile stress is applied to the welded portion in a state.   2. The fatigue strength according to claim 1, wherein a tensile stress is applied to the welded portion in a state in which the position of the metal hollow cross-section member separated from the welded portion by at least the height of the member is supported or restrained. Excellent impact plastic working method.   The impact plastic working method with excellent fatigue strength according to claim 1 or 2, wherein the tensile stress is 10 to 80% of the yield stress of the metal hollow cross-section member.   When an impact is applied to the welded portion of the metal hollow cross-section member welded and fixed to the welded portion and plastic processing is performed, the additional material in the metal hollow cross-sectional member is grasped and tensile stress is applied to the welded portion. An impact plastic working method excellent in fatigue strength, characterized by imparting.   The impact plastic working method with excellent fatigue strength according to claim 4, wherein the tensile stress is 10 to 80% of the yield stress of the adduct.

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