JPH06658A - Formation of joint for stainless steel products and different metallic material - Google Patents

Abstract

PURPOSE:To improve joining strength and to cleanly finish a joint part in the case of formation of a joint by subjecting stainless steel products and a different metallic material softer than the stainless steel products to friction press welding. CONSTITUTION:The joint surface of the different metallic material, such as aluminum alloy material, is projected and formed to a circular conical shape and the joint surface of the stainless steel products 3 is previously formed to a recessed shape to be fitted to a circular conical shape. These joint surfaces are subjected to friction press welding to the state of fitting the surfaces to each other. The joint surface of the recessed shape of the stainless steel products 3 is subjected to nickel plating 5 and thereafter the materials are subjected friction press welding if the different metallic material 1 is an aluminum alloy material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a joint between a stainless steel material and a dissimilar metal material softer than the stainless steel material.

[0002]

2. Description of the Related Art In a space-related plant, a nuclear power generation-related plant, a chemical-related plant, etc., a metal pipe made of a material most suitable for forming a pipeline is used.

Based on the fact that a plurality of types of insertion fluids branch or merge, it is necessary to properly use the metal material of the piping constituent material in the middle of the same piping system, and to use a joint having a different metal material in the middle of the piping. When installation is required, it is effective to adopt mechanical connection such as a flange joint structure or a nipple joint structure in the joint portion of the metal pipe made of each constituent material.

However, in a pipe line where importance is placed on the airtightness of fluid, the fluid may leak in a joint structure for mechanical connection. For example, in space equipment parts, there is a combination of stainless steel pipe and aluminum alloy pipe.
These pipes are connected by a nipple joint structure, but in the nipple joint structure, leakage easily occurs due to vibration or thermal stress. Therefore, in such piping, it is desirable to have a joint structure in which metals are directly butt-welded,
Since this welded joint is a dissimilar metal weld, its implementation is technically difficult. For example, when friction welding is performed between a stainless steel material and an aluminum alloy material, since the aluminum alloy material is softer than the stainless steel material, the vicinity of the joint surface of the aluminum alloy material is crushed by friction welding and sticks out to the periphery of the joint portion. The phenomenon of swelling occurs.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a method for forming a joint by friction welding a stainless steel material and a dissimilar metal material that is softer than the stainless steel material, and has a good joint strength and a clean joint. An object of the present invention is to provide a method for forming a joint between a finished stainless steel material and a dissimilar metal material.

[0006]

A method for forming a joint between a stainless steel material and a dissimilar metal material according to the present invention for solving the above-mentioned problems is achieved by friction welding a stainless steel material and a dissimilar metal material softer than the stainless steel material. A method of forming a joint by forming a joint surface of the dissimilar metal material in a conical shape and forming a joint surface of the stainless steel material into a concave shape that fits with the conical shape, and joining these The surfaces are fitted together and friction welded. When the dissimilar metal material is an aluminum alloy material, the concave joint surface of the stainless steel material is nickel-plated and then friction-welded.

[0007]

In the method of forming the joint between the stainless steel material and the dissimilar metal material, the conical joint surface of the dissimilar metal material and the concave joint surface of the stainless steel material to be fitted thereto are frictionally pressure-bonded to each other. Therefore, the conical tip of the dissimilar metal material enters the inner depth of the concave joint surface of the stainless steel material. Therefore, it is possible to prevent the dissimilar metal material, which is softer than the stainless steel material, from moving to the periphery of the joint when frictionally welded. When the dissimilar metal material is an aluminum alloy material, the stainless steel material and the aluminum alloy material are metals that are difficult to bond to each other, but nickel easily bonds to both the stainless steel material and the aluminum alloy material. The joint strength of the joint is improved by plating the joint surface of the shape with nickel.

[0008]

Embodiments of the method for forming a joint between a stainless steel material and a dissimilar metal material to which the present invention is applied will be described below with reference to the drawings. As an example of the pipe dissimilar metal joint, a method for producing a pipe joint made of a stainless steel material such as SUS304L and an aluminum alloy material such as A6061-T4 will be described.

To make a pipe joint of a stainless steel material and an aluminum alloy material, a rod-shaped stainless steel material and a rod-shaped aluminum alloy material are friction-welded to each other to form a shaft joint, and then a hole is formed in the central portion of the pipe joint. And Before the stainless steel material and the aluminum alloy material are friction-welded to each other, the joint surface of both metal rods is formed as shown in FIG. The joint surface of the aluminum alloy material 1 is formed in the conical projection portion 2, and the joint surface of the stainless steel material 3 is formed in the concave portion 4 that fits with the conical projection portion 2 of the aluminum alloy material 1. Then, nickel plating 5 is applied to the surface of the recess 4 of the stainless steel material 3.

After the joint surfaces of the two metal rods are formed as described above, the rod-shaped stainless steel material 3 and the rod-shaped aluminum alloy material 1 are friction-welded with the joint surfaces facing each other as shown in FIG. In the figure, the aluminum alloy material 1 round bar is set on the spindle 6, and the stainless steel material 3 round bar is set on the clamp 7, and the aluminum alloy material 1 on the spindle 6 side is rotated as shown by the arrow. Friction welding is carried out by linearly moving 3 as shown by an arrow and pressing it.

As shown in FIG. 2, the friction welding process comprises a heating process and an upsetting process.
After the preheating process, which is heating at low pressure, is completed, a full-scale heating process begins. The time of the upset process is the time until the friction welding is completed.

Based on the above-mentioned joint forming method, nine shaft joints of stainless steel material and aluminum alloy material were prepared as shown in Table 1. Aluminum alloy material 1 has a diameter of 19
mm round bar to form the joint surface of the joint,
The end on the joining side of the round bar was shaved to have a diameter of D ₁ of 16 mm, and its tip was formed as a conical protrusion 2 having a cross sectional angle θ of 90 degrees. Stainless steel material 3 has a diameter of 19
mm round bar is used, and the end on the joining side of the round bar is shaved to have a diameter of D ₂ of 14 mm in order to form the joint surface of the joint, and the end is a conical shape of aluminum alloy material 1. A conical shape having a cross-sectional angle θ of 90 degrees and a diameter D ₃ of 13 mm was shaved off to form a concave portion 4 so that the protruding portion 2 could be fitted. Then, nickel plating 5 was applied to the surface of the concave portion 4 of the stainless steel material 3 and its periphery in a thickness of about 10 μm.

Table 1 shows, for each joint, the pressures P ₁ , P ₂ , P ₃ , and times T ₂ , T ₃ of the friction welding processes shown in FIG. 2 as well as the round bar and aluminum of the stainless steel material 3 before the pressure welding. Alloy material 1
The total length with the round bar, the length of the joint after pressure welding, and the shrinkage allowance obtained by subtracting the length after pressure welding from the length before pressure welding were noted. In friction welding, the pressure is increased to P ₃ during the time T ₃ in the preheating process, and the pressure is increased during the time T _{2 in} the subsequent heating process.
The pressure is raised to P ₁ and the pressure contact pressure is raised to P ₂ in the upset process. The rotation speed of the aluminum alloy material 1 for friction welding was 2768 times / minute.

[0014]

[Table 1]

Of the shaft couplings shown in Table 1, 1, 2, 4, 5, 7,
The shaft joint of No. 8 was a pipe joint with a hole in the center. This pipe joint was tested for tensile strength and elongation at break, and Table 2 shows conditions and results of each joint. The tensile strength of all the joints was the same, and the joints had sufficient strength. Regarding the breaking position, the aluminum alloy portion of the base material was broken in the joints 1, 2, and 7, and the joint portion was broken in the other joints. Since the joint with the base metal fractured and the joint with the fractured joint show similar tensile strength, it can be seen that the joint of this joint has the same tensile strength as the base metal. .

[0016]

[Table 2]

Next, among the shaft couplings shown in Table 1, the shaft couplings 3, 6, 9 were subjected to microscopic observation of the cross section of the joint to measure the hardness of the joint.

As a result of microscopic observation, a nickel plating layer was found on the entire joint surface of each joint, and a plastically deformed structure was observed on the stainless steel material side of the joint, but it was remarkable on the aluminum alloy material side. No deformed tissue was observed. Figure 3
A cross-sectional micrograph of the joint of 3 is shown at 100 times. (A) is a cross section near the tip of the conical shape at the joint, and (a) is a cross section near the conical slope at the joint. Is. Reference numeral 1 is an aluminum alloy material, 3 is a stainless steel material, and 5 is a nickel plating layer.

The joint hardness was similar for all 3, 6, and 9 joints. As shown in the measurement results of the joint 3 in FIG. 4, the hardness decreases on the aluminum alloy side as it approaches the joint, and the hardness shows a minimum value at a position of about 2 mm from the joint interface, and on the stainless steel side. The hardness increased as it approached the joint.

[0020]

When a joint is formed by the method for forming a joint between a stainless steel material and a dissimilar metal material according to the present invention, the conical joint surface of the dissimilar metal material is wedged inwardly of the concave joint surface of the stainless steel material. Enter like. Therefore, most of the dissimilar metal material, which is softer than the stainless steel material, is less likely to enter the concave portion of the joint surface of the stainless steel material and to be extruded to the periphery, and the joint surface is finished cleanly. When an aluminum alloy material is used as the dissimilar metal material, sufficient joint strength as a joint can be obtained by interposing nickel plating.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a joint formed by joining a stainless steel material and an aluminum alloy according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between pressure and time in each step of friction welding performed in an example of the present invention.

FIG. 3 is a photomicrograph of a cross section of a joint portion of a joint 3 according to an example of the present invention, in which (A) is a cross section near the tip of a conical shape,
(A) is a cross section near the conical slope.

FIG. 4 is a diagram showing a result of measuring hardness of a joint 3 according to an example of the present invention.

[Explanation of symbols]

 1 Aluminum alloy material 2 Conical protrusion 3 Stainless steel material 4 Recess 5 Nickel plating 6 Spindle 7 Clamp

Claims (2)

[Claims] 1. A method of friction-welding a stainless steel material and a dissimilar metal material softer than the stainless steel material to form a joint, wherein a joint surface of the dissimilar metal material is formed in a conical shape, and the stainless steel material is formed. Is formed into a concave shape that fits with the conical shape, and the joining surfaces are frictionally welded to each other in a fitted state. A method for forming a joint between a stainless steel material and a dissimilar metal material. 2. The dissimilar metal material is an aluminum alloy material, and the concave joint surface of the stainless steel material is nickel-plated and then friction-welded.
A method for forming a joint between the described stainless steel material and a dissimilar metal material.