JPH1034356A - Method for welding metallic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the performance, especially fatigue strength of a joining part while satisfactorily applying the plastic deformation with a simple method in a diffused welding. SOLUTION: In this method, an insert material is interposed between butting parts of the metallic material to be welded, and the butting parts are hated and pressed. In this case, groove welding is executed so that the thickness of the metallic material is made gradually smaller from the metallic material main body toward the top end face of butting parts, the butting parts are heated and pressed to be deformed plastically, the thickness of butting part after deforming plastically is made larger than the thickness of the metallic material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding method for improving the performance of a bonding portion in diffusion bonding of a metal material.

[0002]

2. Description of the Related Art In a diffusion bonding method for realizing joining without melting a butt portion of a material to be joined, plastic deformation is usually applied to the butt portion in order to increase the reliability of the joined portion. However, while this plastic deformation has many beneficial effects, it can lead to stress concentration and does not always improve the reliability of the joint.
In addition, in the case of a bar or the like, if the joint portion has an excessive bulge, the fatigue strength is reduced, and when the concrete is filled, the concrete is cracked.

[0003] For this reason, a method of controlling plastic deformation for the purpose of improving the performance of a joint has been conventionally disclosed.
For example, in the case of the above-mentioned steel bar, a method of fixing the steel bar on both sides, applying only an initial load, heating and bonding to reduce the swelling of the joint (Japanese Patent Laid-Open No. 2-7) is disclosed.
No. 5478).

In the case of this technique, the effect is certainly recognized as compared with the conventional gas pressure welding, but the effect is not sufficient, and it is possible to further improve the shape of the joint and stabilize the quality of the joint. Requested.

[0005] Further, there is disclosed a method for improving the fatigue strength of a diffusion bonding portion and eliminating an incomplete portion such as a staggered step of the diffusion bonding portion by performing arc welding after the diffusion bonding (Japanese Patent Application Laid-Open No. Hei 5 (1993) -108). -220585).

[0006] In this case, it is necessary to always perform arc welding, which is inefficient and economical. Therefore, there is a demand for a technique capable of improving performance by a simpler method.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to improve the performance of a joint, especially the fatigue strength, by sufficiently applying plastic deformation to the joint by a simple method and preventing the adverse effect of the joint while performing diffusion bonding. It is an object of the present invention to provide a joining method of the resulting metallic material.

[0008]

According to the bonding method of the present invention, when diffusion bonding is performed with an insert material interposed between materials to be joined, a groove is formed on an end face of the material to be joined, and the thickness of the butt portion is increased. The thickness is gradually reduced from the metal material main body to the end face in comparison with the thickness of the material to be joined. It is the first important point in the present invention that such a groove processing is performed on the butted portion.

[0009] The grooved portion is plastically deformed, for example, in the process of raising the temperature, and as a result, the thickness of the joint is set to be equal to or greater than the thickness of the material to be joined. In such a groove shape, the plastic deformation is larger at an end face having a smaller cross-sectional area, and as a result, the joint portion can have an almost uniform cross-sectional shape while causing a large plastic deformation. The second important point of the present invention is that such a uniform cross-sectional shape can be obtained by a simple method called groove processing. Therefore, since a large bulge is not formed, the stress concentration does not occur and the fatigue strength does not decrease.

As a result, the following primary object of plastically deforming the butted portion of the materials to be joined can be achieved.

[0011] Discharge of unnecessary insert material from the joint end face for joining: Adhesion between materials to be joined: Enhancement of diffusion of elements based on the action: Increase of joint area As a result of the above results, significant joint performance Improvement is achieved.

The present invention has been completed by diffusing and joining various types of grooved steel pipes or strips, performing various tests on the joints, and confirming the effects thereof.
The following is a summary of the diffusion bonding method for metal materials.

That is, in the method of performing diffusion bonding by interposing an insert material between butted portions of a metal material to be joined and applying heat and pressure to the butted portion, the metal is spread from the metal material body to the end face of the butted portion. Beveling is applied so that the thickness of the material gradually decreases, and the butted part is plastically deformed by heating and pressing.
Metallic material joining method in which the thickness of the butted portion after plastic deformation is equal to or greater than the thickness of the metallic material. "

In the above, the melting point of the insert material is generally lower than the melting point of the material to be welded. The heating temperature is desirably higher than the melting point of the insert material and lower than the melting point of the material to be welded. However, the heating temperature does not necessarily need to be higher than the melting point of the insert material, and the insert material may be a solid phase. That is, in the method of the present invention, it is desirable that the diffusion bonding is a liquid phase diffusion bonding because it shortens the bonding time, but it is not necessarily required to be the liquid phase diffusion bonding.

The groove processing in which the thickness gradually decreases from the main body to the end face of the butted portion means that the thickness of the end face of the material to be joined is a thickness for a plate, a wall thickness for a pipe, and a circular shape for a strip. It means that the radius of the cross section is tapered from the portion of the main body to the end face, and is gradually reduced. In this case, it is not necessary to taper both the upper and lower surfaces of the plate and the inner and outer surfaces of the tube. Only the upper surface of the plate or the inner surface of the tube may be tapered.

It is desirable that the flat portion of the end face to be the abutting face be left.

The plastic deformation is mainly performed at the time of temperature rise, but is not limited to the time of temperature rise.

As the metal material, all metal materials are targeted, and particularly steel is mainly targeted. The shape of the metal material is plate,
There is no particular limitation on pipes and strips.

When the metal material to be joined is a metal material having a low melting point such as aluminum, the liquid phase diffusion bonding is more desirable as described above, so the insert material should be a material having a lower melting point than aluminum. Is desirable. Further, depending on the use, an insert material that improves corrosion resistance, particularly, crevice corrosion resistance, may be used.

[0020]

Next, the limiting factors of the present invention will be described.

1. Groove processing FIG. 1 is a diagram illustrating a groove on an end face of a pipe.
In FIG. 1, the lengths of the tapered portions on the inner surface and the outer surface of the pipe are distinguished, but need not be distinguished, and the gradient and length of the taper on the outer surface and the inner surface may be the same. It is. Although FIG. 1 shows that a constant curvature R is provided at the shoulder portion of the taper, it is desirable to provide a curvature, but the curvature need not always be provided. Also, in FIG. 1, the indication Tout and the like of the thickness of the end face are made, but the thickness of this part can be adjusted by controlling plastic deformation, so that the limitation of the Tout and the like is not necessarily required. .

When the inner and outer surfaces of the taper are the same, the length (L) of the taper in the axial direction for decreasing the thickness is determined by the relationship with the width (W) of the heating coil, and it is desirable to satisfy the expression (1). W / 16 ≦ L ≦ W / 2 (1) This is because when the material to be joined is plastically deformed, the region where the temperature is rising is preferentially deformed. If the heating area is deformed, it expands greatly.If it is too wide, the temperature of the grooved portion will be low, and even if plastic deformation is applied, the part far from the joint will not be deformed. This is because it is not more. The slope of the taper can be adjusted by plastic deformation, so that there is no particular limitation.

2. Plastic deformation The purpose of forming a groove on the end face of the material to be joined is to suppress excessive bulging after joining, and to avoid stress concentration due to shape discontinuity at the joint. Plastic deformation may be applied to the materials to be joined in accordance with the conditions. Since control is easy, it is preferable that heating is applied by high-frequency heating and pressurization is applied by hydraulic pressure, and these can be easily implemented by a normal method.

The thickness of the butted portion must be equal to or greater than the thickness of the material to be joined, while it is desirable that the thickness be less than 1.1 times the thickness of the material to be joined.

After the plastic deformation, if the thickness of the joining portion is smaller than the thickness of the material to be joined, the sectional area of the joining becomes smaller than the sectional area of the material to be joined, and it becomes difficult to secure the strength. is there.

In addition, when diffusion welding of small diameter steel pipes, it is necessary to cut off a groove because the inner surface cannot be repaired after welding, but the outer surface can be repaired after welding. Absent. For this reason, when diffusion welding of a small-diameter steel pipe according to the present invention, groove preparation on the inner surface is indispensable, but groove preparation on the outer surface side can be omitted in consideration of joint performance.

3. Metal material In the present invention, the material to be joined is not particularly limited,
It is possible to appropriately select from materials applicable to diffusion bonding according to the application, and for example, a bar material such as a steel bar for reinforced concrete, a steel pipe of each material, and other metal materials can be applied.

The materials to be joined to be joined are not necessarily limited to the same or the same kind, and different kinds of materials can be applied.

4. Insert Material The insert material used in the present diffusion bonding is not particularly limited, either, and can be appropriately selected according to the material of the material to be joined. Further, an amorphous metal or the like can be applied, and it is more general. As the amorphous metal, Ni
-Si-B-Cr alloy amorphous ribbon (thickness 25μ)
m, melting point 1140 ° C.) and the like, for example, commercially available products such as M8F-50 manufactured by Allied Chemical Company.

Since the present invention is a diffusion bonding method, the heating temperature for bonding is usually lower than the melting point of the material to be bonded. In addition, when the melting point of the insert material is lower than that of the base material, heating to a temperature equal to or higher than the melting point of the insert material makes the liquid phase diffusion bonding method among the diffusion bonding methods. This liquid-phase diffusion bonding method is more likely to obtain a sound bonded part because of its better conformity with the material to be bonded.

The method of interposing the insert material between the materials to be joined is not particularly limited, but spot welding, an adhesive method, or the like can be applied.

5. Others When the metal is heated in the atmosphere, there is a concern that the joint end face is particularly oxidized. When the joint end face is oxidized, joint defects are likely to occur, which may deteriorate the joint performance. Therefore, it is desirable to perform the heating in an inert gas atmosphere.

Although various heating methods are conceivable, high-frequency induction heating is desirable because the temperature can be easily controlled and the atmosphere can be easily controlled.

Further, depending on the type of the material to be joined, the cooling rate after joining may affect the joining performance. Therefore, the cooling rate of the joining portion may be controlled.

According to the present joining method, a joint having excellent joint performance and little deformation of the material to be joined can be obtained.

[0036]

EXAMPLES Next, the effects of the present invention will be described with reference to examples.

Example 1 0.24% as a material to be joined
C-0.25% Si-1.13% Mn-0.48% Cr
Outer diameter 130m including alloy element of -0.026% Ti
The following tests were conducted using a quenched (950 ° C.)-tempered (620 ° C.) tempered seamless steel pipe having a thickness of 15 mm and a thickness of 15 mm. Here, the tensile strength of the steel pipe was 860 MPa.

Table 1 shows the groove conditions used in the test.

[0039]

[Table 1]

1.4% B-7.3% as insert material
It has a composition of Si-5.3% Cr-remaining Ni, and has a melting point of 114.
Using a ribbon having a thickness of 0 ° C. and a thickness of 30 μm, bonding was carried out under a nitrogen gas shield under the conditions of a heating temperature of 1250 ° C. and a holding time of 300 seconds in various butt shapes described later. The pressurization was performed using a hydraulic cylinder, and was controlled so as to have a predetermined compression displacement in consideration of thermal expansion so as to have a uniform cross section or the like.

FIG. 2 is a schematic view of a joining system used for joining the first embodiment and a second embodiment described later.

The heating was performed by a high frequency induction heating method, and the heating coil width W was set to 50 mm. Therefore, the groove of satisfies the desirable range of expression (1).

With regard to the test number and the groove, the butt portion was 1.00 to 1..
The pressure was adjusted so as to be 03 times, and the amount of plastic deformation was controlled. Regarding the test number and the amount of plastic deformation, the amount of plastic deformation was controlled so that the inner surface side where the groove was formed almost coincided with the inner surface of the steel pipe, and the amount of protrusion on the outer surface side at that time was 1.18 times the wall thickness of the steel pipe. Had become. In addition, the bonding conditions of the test numbers were the same as the conditions at the groove. The deformation at that time (the thickness of the butted portion) was 1.38 times the wall thickness of the steel pipe.

For this joint, a joint tensile test (test piece: JIS Z3124) and a bending test (test piece: JIS Z3122)
Specimens (Fig. 2) for pipes and fatigue tests (specimen: JIS
Z3103).

The conditions of the fatigue test were as follows: A four-point bending fatigue test was conducted at a bending stress of 200 MPa, and the life (number of times) until fracture was examined.

Table 2 is a list showing the test results.

[0047]

[Table 2]

In the joint tensile test, no interface fracture occurred.
The base material was broken. The test number having a protruding portion from the wall thickness of the steel pipe and the test number showed a slight but high strength.
The side bending test was also passed under any of the groove conditions.

In the fatigue test, the groove having the test number of the conventional method has sufficient characteristics in use, but by performing the groove processing, the fatigue life is improved by one order or more, and the effect of the method of the present invention is improved. It is obvious. Among them, there are slight cases in which R is not provided at the groove shoulder as shown in the test numbers, but the fatigue life tends to be reduced. However, even if compared with the test number of the conventional method, it can be improved sufficiently.

Example 2 0.23% C-0.36% S
i-Size D51 of a steel bar for reinforced concrete of SD345 grade having a composition of 1.44% Mn (nominal diameter 5
0.8 mm).

The joining conditions were 18.5 for the insert material.
Using a 25 μm-thick ribbon made of% Cr-7.5% Si-1.5% B-remaining Ni, bonding was performed at 1200 ° C for 300 seconds. Heating was performed in a nitrogen gas shield, and heating was performed by high frequency induction.

There are two types of bevels, one that is not beveled and one that has a butt portion of φ30 mm at the center and is beveled at an angle of 45 ° around the periphery. The plastic deformation was controlled so that the butted portion was almost the same as the diameter of the rebar in a test piece with groove processing. In addition, those not subjected to beveling were joined under the same conditions as the test piece with beveled. At this time, the outer diameter swelling amount was 1.29 times the outer diameter of the material.

From these joints, tensile test pieces (JIS Z312
No. 14), a side bending test piece (a test piece for a pipe of JIS Z3122 (FIG. 2)) and a fatigue test piece were collected and subjected to each test. Fatigue test is load controlled pulsating tensile fatigue test (specimen:
According to JIS Z3103), the upper limit of the applied stress that did not break at a repetition rate of 5.8 Hz and a repetition rate of 2 × 10 ⁶ was defined as the fatigue strength.

Table 3 shows the test results.

[0055]

[Table 3]

In each of the tensile tests, the base material was broken, which was good. The results of the bending test were also good.

In the fatigue test, the test number without the groove processing was 148 N / mm ² ,
In case of beveling, 186 N / mm ² and about 2
The improvement effect of the fatigue strength by as much as 5% was recognized.

[0058]

According to the present joining method, a simple method can be used.
It is possible to provide a diffusion bonding method capable of obtaining excellent bonding joint performance without giving a large swelling while giving sufficient plastic deformation, and this is a valuable technology for related industries.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a groove shape of a pipe.

FIG. 2 is a schematic diagram of a joining system used for joining in an embodiment of the present invention.

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 1 ... Heating coil and gas shield jig 2 ... Tube, plate or strip material 3 ... Cooling jacket 4 ... Clamp 5 ... High frequency power supply 6 ... Control panel

Claims (1)

[Claims] In a method for diffusion bonding by interposing an insert material between butted portions of a metal material to be joined and applying heat and pressure to the butted portions, the metal material extends from the metal material body to an end face of the butted portion. The beveling process is applied so that the thickness of the butt gradually decreases, and the butt portion is plastically deformed by heating and pressing, and the thickness of the butt portion after the plastic deformation is set to be equal to or greater than the thickness of the metal material. Method of joining metal materials.