JP3320465B2 - Method of welding hollow members - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for welding a joint formed by a hollow member and another member inserted therein.

[0002]

2. Description of the Related Art Conventionally, in a welded joint in which the other member to be welded is inserted and fitted into one member to be welded as a hollow member, and both members are fused and joined, an end portion of the hollow member located outside is used. And a member inserted therein is welded continuously or intermittently over the entire circumference of the end. Also, as described in Akira Kobayashi, Practical Manual for Laser Processing Technology, pages 204 to 207 (New Technology Development Center), a method of continuously or intermittently lap welding the overlapped portion of both members to be welded is also generally used. Used. On the other hand, JP-A-64-22489 discloses a welding method for improving the weldability by improving the shape of an end portion of a hollow member located outside or a member inserted inside. ing.

[0003]

However, the above conventional welding method has the following problems. That is, in the conventional welding method described above, the welded portion is provided continuously or intermittently on one circumference perpendicular to the joint axis direction, and radial residual stress is generated due to contraction, thermal deformation, and the like of the welded portion. ,
Defects such as cracks were likely to occur in the weld. In addition, since the heat-affected zone due to welding heat input, that is, the material-degraded portion, exists on the same circumference, the crack is thermally affected by the axial tensile load, which is the situation where such a welded joint is generally used. Part was easy to propagate. This problem is particularly significant for small-sized joints, and is remarkable when a material that is greatly softened by the influence of heat is used. In some cases, the joint strength is reduced to half of the base metal strength. Furthermore, if there is a difference in the strength of the heat-affected zone between the two members to be welded due to different susceptibility to heat effects due to a difference in material or a difference in heat capacity, the welding heat input is higher. The setting was made in accordance with the member having a large decrease, which was a major obstacle to improving the joint strength.

[0004] The problems in these conventional methods will be specifically described with reference to FIG. FIG. 5 shows an example of a conventional lap welding method, in which a hollow member 1 outside a joint and a member 2 inserted into the hollow member 1 are joined by a weld 3. Around the welded portion 3, there is a heat-affected zone 4 whose material has been deteriorated by welding. 5 indicates the direction of the load applied in the axial direction of the joint. The cracks 6 and 7 due to the load often occur in the heat-affected zone 4 where the strength is reduced as shown in the figure, and the generated cracks 6 and 7 are circles in the direction in which the cracks 6 and 7 propagate by the load (perpendicular to the direction of the load). Since the heat-affected zone 4 is continuous on the circumference, the generated cracks 6 and 7 are easily expanded, leading to breakage.

[0005] If there is a difference in the strength of the heat-affected zone due to the material, heat capacity, etc., between the members 1 and 2 to be joined, cracks will occur in the heat-affected zone of the lower strength member. In FIG. 5, a crack 6 indicates a crack that has occurred in the outer hollow member 1, and a crack 7
Indicates what has occurred in the inserted member 2.

[0006] The welding method disclosed in Japanese Patent Application Laid-Open No. 64-22489 improves the shape of the end of the outer hollow member and the shape of the welded portion of the member inserted therein, so that welding defects due to radial stress can be obtained. However, it has not been possible to solve the problem that the crack is easily propagated in the heat-affected zone.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and a method of welding a hollow member capable of suppressing the growth of a crack generated in a heat-affected zone and improving joint strength. The purpose is to provide.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a process for fitting one member to be welded, which is a hollow member, to another member to be welded; Forming continuously or intermittently from the outside of the one member to be welded, the welded portion longer in the axial direction of the joint than in the direction orthogonal to the axial direction of the joint. .

[0009]

According to the present invention, one member to be welded, which is a hollow member, is fitted with the other member to be welded. Then, a weld portion that is longer or longer in the axial direction of the joint than the direction orthogonal to the axial direction of the joint is formed continuously or intermittently from the outside of one of the members to be welded on the overlapped portion of the two members to be welded.

[0010]

Embodiment 1 First, before describing a specific embodiment of the present invention, an outline of the present invention will be described. As the welding method used in the present invention, a welding method capable of deep penetration of an electron beam, a laser, a plasma arc or the like, or a welding method capable of lap welding such as resistance welding or plug welding using an electric arc is suitable.
In addition, welding may be continuous or continuous, and a long welded portion may be provided in the axial direction of the joint. FIG. 1 shows a welding method according to the present invention. Unlike the conventional method (FIG. 5) in which the welds 3 are provided on the same circle, the welds 3 having a length d in the joint axial direction and a depth d are provided. The crack 6 generated in the heat-affected zone 4 at both ends in the longitudinal direction of the welded portion 3 which receives the largest stress concentration due to the tensile load in the direction does not propagate in the circumferential direction. Therefore, when the welding length L is the same as the conventional method (for example, the same as the joint circumferential length), it is possible to withstand larger tensile loads and fatigue loads.

The welding method of the present invention has a great effect in a small joint in which the size of the weld 3 occupies a relatively large area with respect to the joint body. This is particularly noticeable when the value is 5 or more.

By adjusting the parameters such as welding current, welding speed, and beam output singly or in combination, the heat input at the welded portion is reduced by the member having the greater strength decrease due to the heat effect of welding. Control may be performed so that In FIG. 2, the heat-affected zone 4 of the members 1 and 2
The strength of the joints is different due to the difference in heat capacity due to the respective materials and wall thicknesses even in the same welded portion 3, and when the joint receives an axial load 5 exceeding the allowable limit, the heat affected zone Among 4, the stress concentrates on the A portion and the B portion, and the crack is generated on the lower strength side of the A portion or the B portion. Therefore, as shown in FIG. 2, a member whose strength is greatly reduced due to the thermal influence of welding (member 1 in FIG. 2).
Side has low heat input, and sufficient penetration can be obtained on the side of the member (member 2 in FIG. 2) with a small decrease in strength (d1 <d
2, w1 <w2) By controlling the welding heat input so as to obtain a large heat input, the occurrence of cracks on the low-strength member side is suppressed,
The joint strength may be improved.

Next, a specific embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows a first embodiment of the present invention. In this embodiment, the inner diameter is 0.5 mm and the outer diameter is 0.7 mm shown in FIG.
A stainless steel wire (outer diameter 0.48 mm, strand diameter 0.
06mm, 49 strands, Nd · YAG laser (beam output 3J, pulse width 3ms, spot diameter 0.4)
mm), three spot weldings 13a, 13b and 13c long in the axial direction of the joint were performed.

In the conventional method of providing spots on the circumference,
When welding is performed under the same conditions, since the distance between the heat-affected zones of adjacent welding spots is small, the tube 11 breaks in a form in which a crack connects the welding spots, whereas the average tensile strength is 6 kg. In this embodiment, since the crack growth is suppressed, the fracture is mainly caused by the stainless wire 1
2 and the average tensile strength increased to 12 kg.

[0015]

Second Embodiment FIG. 4 shows a second embodiment of the present invention. This embodiment is an example of a joint requiring higher strength than that of the first embodiment, and one end is attached to both ends of a stainless steel SUS304 tube 11 having an inner diameter of 0.5 mm, an outer diameter of 0.7 mm, and a length of 6 mm.
A stainless steel wire (outer diameter 0.48 mm, element wire diameter 0.06 mm, 49 strands) shown as 2a and a stainless steel wire (outer diameter 0.47 mm) shown as 12b are inserted so as to abut at the center of the tube 11, and Nd · Three points of spot welding (13a, 13b, 13c and 13d, 13e,
13f) was performed long in the joint axial direction.

Stainless steel wire 12a and tube 11
In the joint of (1), the wire diameter constituting the wire is small, and the wire side which is greatly affected by heat has low heat input, and the heat input of each spot is adjusted to 2.4, 2.8 and 3.
It was set to 2J / pulse. Also, stainless single wire 12b
And the tube 11 has a large heat input on the single wire side where the strength reduction due to the heat is small, and 4.0, 3.6, 3.2J.
/ Pulse.

The strength of the joint is as follows:
17 kg (12 kg in the same configuration in the first embodiment) at the junction of the tube 11 and the heat effect on the wire, and the connection between the stainless steel single wire 12 b and the tube 11 is also reduced by the heat effect on the tube. Good joint strength of 20 kg was obtained.

In the present invention, specific means such as a welding method and the shapes and dimensions of target members are not limited to the above-described embodiment.

[0019]

As described above, according to the welding method of the present invention, when another member is inserted and fitted into one hollow member and joined by lap welding, the growth of a crack generated in the weld heat affected zone is improved. And joint strength can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a welding method of the present invention.

FIG. 2 is a cross-sectional view showing a case where welding heat input is controlled in the present invention.

FIG. 3 is a perspective view showing Embodiment 1 of the present invention.

FIG. 4 is a perspective view showing a second embodiment of the present invention.

FIG. 5 is a view showing a conventional welding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hollow member 2 Member to be inserted 3 Weld part 4 Heat affected part 5 Load 6,7 Crack 11 Tube 12,12a Stainless wire 12b Stainless single wire 13a-13f Spot welding

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification symbol FI B23K 26/00 310 B23K 26/00 310J // B23K 101: 06 101: 06 (58) Field surveyed (Int.Cl. ⁷ , DB name) B23K 9/028 B23K 15/00 B23K 26/00 B23K 31/00

Claims (1)

(57) [Claims] A step of fitting the other member to be welded into one member to be welded as a hollow member; and a step of fitting an overlapped portion of both members to be welded from outside the one member to be welded. Forming a weld continuously or intermittently in the axial direction of the joint than in a direction perpendicular to the axial direction of the joint.