JPH11156556A - Clad metal butt resistance welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of a welding defect due to too much/too little welding electric current among each metal group of a low electric resistance and of a high electric resistance respectively even when a butt resistance welding is conducted among clad metals themselves composed of a high electric resistance metal and a low electric resistance metal. SOLUTION: High resistance layers 1a and 2a composed of a high resistance metal with a high electric resistance, and low resistance layers 1b and 2b formed on a surface of the high resistance layers 1a and 2a, comprising of a low resistance metal whose electric resistance is lower than that of the high resistance metal, comprise the first and the second clad metals 1 and 2, and the butt resistance welding is conducted among/between each end face. At this time, a groove 3 is installed only to and between the low resistance layers 1b and 2b of the butted first and second clad metals, and at the starting stage of resistance welding to flow a welding electric current, priority is given to the high resistance layers 1a and 2a of the first and second clad metals and 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for butt resistance welding of clad materials.

[0002]

2. Description of the Related Art Conventionally, clad materials composed of different kinds of materials are known, and such clad materials can be utilized by utilizing the merits of the respective materials, and thus are applied to various parts. For example, in recent years, attempts have been made to apply a clad material of iron-aluminum to a cylinder bore constituting an engine block in order to reduce the weight and size of a vehicle and improve the cooling performance of an engine.

When the iron-aluminum clad material is applied to a sliding member such as a cylinder bore as described above, if the pipe is formed so that iron is the sliding inner surface and aluminum is the outer surface, the sliding inner surface made of iron is Abrasion resistance can be ensured, heat generated by combustion and sliding can be released to the outer surface side of aluminum having good heat conduction, and the weight of the cylinder bore and the like can be reduced.

In order to manufacture a tubular member from a clad material as described above, it is necessary to butt-weld end faces of the clad material. At present, various butt resistance welding methods such as butt welding (upset welding), butt seam welding, flash welding and high-frequency resistance welding are used as a method of butt welding plates. In such a butt resistance welding, generally, a welding current is applied while the end faces of the workpiece are butt-pressed and pressurized, and the contact portions between the end faces are heated by resistance heating to melt a part of the base material. It is a joining method.

[0005]

However, when the clad members composed of the above-mentioned different materials are butt-welded to each other by resistance welding, the welding current mainly flows through the material side having a low electric resistance. There is a problem that a welding defect due to an excess or deficiency of a welding current is easily generated between each other and between materials having high electric resistance.

That is, there is a relation of Q = I ² Rt between the calorific value: Q, the welding current: I, the electric resistance: R, and the energizing time: t. Since it is difficult to generate heat, a large current condition is obtained, and the generated heat is also easily diffused, so that the bonding interface is greatly expanded and deformed toward the outer surface side. On the other hand, between materials having a high electric resistance, the resistance heating becomes insufficient due to an excessively small welding current, so that the joining strength is reduced or the joining becomes impossible.

[0007] When fusion welding such as arc welding or laser welding is applied to the welding of clad materials, brittle intermetallic compounds composed of molten dissimilar materials are formed at the joining interface, and the joining strength may be significantly reduced. . For example, the iron-
In the case of aluminum clad material, Fe ₂ Al ₅ , Fe
A brittle intermetallic compound such as Al ₃ is formed at the joint interface, and almost no joint strength is obtained.

The present invention has been made in view of the above circumstances, and even when clad materials made of a material having a high electrical resistance and a material having a low electrical resistance are butt-welded to each other, the materials having a low electrical resistance and the materials having a high electrical resistance are welded. An object of the present invention is to provide a method for butt resistance welding of clad materials that can prevent the occurrence of welding defects due to excessive or insufficient welding current in each of the materials.

[0009]

A butt resistance welding method for a clad material according to the present invention, which solves the above problems, comprises a high resistance layer made of a high resistance material having a high electric resistance, and a high resistance layer formed on a surface of the high resistance layer; The end faces of the first and second clad materials, which are made of a low-resistance layer made of a low-resistance material having a lower electric resistance than the high-resistance material, are held in abutted state, and the butted end faces of the first and second clad materials are held together. By applying a welding current to the first and second cladding materials while applying pressure, the high-resistance layers of the first and second cladding materials and the first
And a butt resistance welding method of the clad material for joining the low resistance layers of the second clad material by resistance welding, wherein only the space between the low resistance layers of the butted first and second clad materials is opened. The method is characterized in that a current is preferentially supplied between the high-resistance layers of the first and second clad materials at an initial stage of resistance welding in which a welding current starts to flow.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the butt resistance welding method for a clad material according to the present invention, a high resistance layer made of a high resistance material having a high electric resistance is formed on the surface of the high resistance layer, and the electric resistance is higher than that of the high resistance material. The end faces of the first and second clad members made of a low-resistance layer made of a low-resistance material having low resistance are abutted and resistance-welded.

That is, the end face of the first clad material and the end face of the second clad material are brought into contact with each other with the high resistance layers and the low resistance layers facing each other.
In the method of the present invention, the end face of the first clad material and the end face of the second clad material are brought into contact with each other and the low-resistance layer of the first clad material and the low-resistance layer of the second clad material are brought into contact with each other. Only a groove is provided. For this reason, in the initial stage of the resistance welding in which the welding current starts to flow, the current flows preferentially between the high resistance layer of the first clad material and the high resistance layer of the second clad material where no groove is provided. Accordingly, even between the high-resistance layers having high electric resistance, good resistance heat is generated, so that it is possible to prevent the welding strength from being too small, and further reduce the bonding strength and the connection failure due to insufficient resistance heat generation.

When a current flows preferentially between the high-resistance layers as described above and the high-resistance layers heated by resistance heating are softened or softened / melted, the first and second clad materials are pressed by the pressing force. Are welded in a crushed state. As a result, the first and second cladding materials are close to each other, and the groove provided between the low-resistance layers of the first and second cladding materials is filled with the low-resistance material of each low-resistance layer, The low resistance layers of the first and second cladding materials also contact each other. Therefore, a welding current flows between the low-resistance layers of the first and second cladding materials, and the low-resistance layers are reliably welded to each other by resistance heat generation. Since the groove provided between the low-resistance layers is filled with the low-resistance material as described above, the bonding interface between the low-resistance layers is reduced due to an excessive welding current. It is possible to suppress a large bulging deformation to the side.

Therefore, when the cladding materials composed of the high-resistance layer having a high electric resistance and the low-resistance layer having a low electric resistance are butt-welded to each other, the welding current is excessive or insufficient in each of the high-resistance layers and the low-resistance layers. Therefore, it is possible to suppress the occurrence of welding defects caused by the above, and to secure sufficient welding quality of such butt resistance welding of the clad material.

Here, as the shape and size of the groove, a current preferentially flows between the high-resistance layers of the first and second clad materials in an initial stage of resistance welding in which a welding current starts to flow. In addition, the first and second high-resistance layers of the first and second clad materials, which have been softened or softened and melted by resistance heat generation, are crushed by the pressing force applied to the butted end surfaces of the first and second clad materials. If the low-resistance material of the clad material is filled in the gap of the groove, and the shape and the size are such that the low-resistance layers of the first and second clad materials can contact each other,
There is no particular limitation. For example, as a cross-sectional shape, a V-shape,
An I-shape (L-shape), U-shape, L-shape, or the like can be used.

However, in the initial stage of resistance welding, the first
And a welding current flows only between the high-resistance layers of the second clad material to more reliably generate resistance heat between the high-resistance layers, and furthermore, the high-resistance layers caused by insufficient resistance heating. From the viewpoint of more reliably preventing poor welding, the shape and size of the groove are set such that only the high-resistance layers of the first and second clad materials come into contact with each other at the initial stage when the welding current starts to flow, and It is preferable that the low resistance layers of the second clad material are set so as not to contact each other at all.

Further, when the high-resistance layers of the first and second clad materials heated by the resistance heat generation are crushed by the pressing force, the low-resistance layers are reliably brought into contact with each other.
From the viewpoint of more reliably preventing the junction interface between the low-resistance layers of the second clad material from bulging and deforming to the outer surface side, when the groove has a V-shaped cross-sectional shape, the groove angle is reduced. Preferably, the angle is about 20 to 30 °, and the width of the groove (the maximum distance between the low-resistance layers of the first and second cladding materials).
Is preferably about 1 to 2 mm. If the V-shaped groove angle is too small or the width of the groove is too narrow, it is not possible to effectively suppress large bulging deformation of the bonding interface between the low-resistance layers. If the groove angle of the shape is too large or the width of the groove is too wide, the high resistance layers of the first and second clad materials heated by the resistance heat will be low when the high resistance layers are crushed by the pressing force. It is difficult to reliably contact the resistance layers.

The combination of the high-resistance material and the low-resistance material constituting the clad material is not particularly limited, and can be appropriately selected according to the required characteristics of the product to be applied. For example, a combination of iron as a high-resistance material and aluminum as a low-resistance material, a combination of titanium as a high-resistance material, and aluminum as a low-resistance material, and the like can be used.

The thicknesses of the high-resistance layer and the low-resistance layer are not particularly limited, either, and can be appropriately set according to the required characteristics of the product to be applied. The high-resistance material and the low-resistance material constituting the first clad material and the high-resistance material and the low-resistance material constituting the second clad material are usually the same, but are formed by resistance welding. If the bonding strength is secured, it is possible to use different high-resistance materials or low-resistance materials for the first clad material and the second clad material.

The type of resistance welding is not particularly limited, either.
Various butt resistance welding methods such as butt welding (upset welding), butt seam welding, flash welding and high frequency resistance welding can be employed. The welding conditions can also be appropriately set according to the type of the high-resistance material and the low-resistance material, the shape and size of the groove, and the like. However, a welding electrode for flowing a welding current to the first and second clad materials is:
It is preferable to make contact with the respective high resistance layers of the first and second cladding materials. According to this aspect, it is possible to directly conduct electricity from the welding electrode to the high-resistance layers of the first and second clad materials. The welding current can flow preferentially, and the resistance heating can be more reliably generated between the high resistance layers.

Although the embodiments of the present invention have been described above, it should be noted that the following technical matters can be extracted from the description in addition to the technical matters described in the claims. (1) The shape and size of the groove are such that only the high-resistance layers of the first and second clad materials are in contact with each other at the initial stage of resistance welding when the welding current starts to flow, and the first and second clad materials are in contact with each other. 2. The method according to claim 1, wherein the low resistance layers are set so as not to contact each other at all. (2) The shape and size of the groove are such that only the high-resistance layers of the first and second clad materials are in contact with each other and the first and second clad materials are in contact with each other at the initial stage of resistance welding when the welding current starts to flow. So that the low-resistance layers do not contact each other at all, and
When the high resistance layers of the first and second clad materials heated by the resistance heating are crushed by the pressing force, the grooves are filled with the low resistance material of the low resistance layer so that the first and second claddings are filled. 2. The method according to claim 1, wherein the low resistance layers of the two clad materials are set so as to contact each other.

[0021]

EXAMPLES Hereinafter, examples embodying the present invention will be described.
This will be described with reference to the drawings. (Embodiment 1) In this embodiment, an iron-aluminum clad plate was used as the first and second clad materials. That is, as shown in the cross-sectional view of FIG. 1, the first and second cladding materials 1 and 2 are composed of high resistance layers 1a and 2a made of iron (S45C) as a high resistance material having high electric resistance, and high resistance layers 1a and 2a. Low resistance layers 1b and 2b formed on the surfaces of 1a and 2a and made of aluminum (A1050) as a low resistance material having low electric resistance.

Here, the thickness of the high resistance layers 1a and 2a is 1
mm, and the thickness of the low-resistance layers 1b and 2b is 4 mm. The specific electric resistance (ρ _a ) of the high resistance layers 1a and 2a is 9.
8 × 10 ⁻⁶ Ωcm, the specific resistance (ρ _b ) of the low resistance layers 1 b and 2 _b is 2.7 × 10 ⁻⁶ Ωcm, and the high resistance layer 1 a
And the electrical resistance per unit length and length of 2a (r _a )
Is 9.8 × 10 ⁻⁵ Ω / cm, and the electric resistance (r _b ) per unit width and unit length of the low-resistance layers 1b and 2b is 6.7 × 1
0 ⁻⁶ Ω / cm. Therefore, the high resistance layers 1a and 2a
a (I _a = 1 / r _a ) and low-resistance layers 1b and 2
b and the current distribution (I _b = 1 / r _b ) are I _a : I _b
= 1: 14.7, and the current flowing through the low resistance layers 1b and 2b is much larger than the current flowing through the high resistance layers 1a and 2a.

With the end face of the first clad material 1 and the end face of the second clad material 2 abutting each other, the low resistance layer 1b of the first clad material 1 and the low resistance layer 2 of the second clad material 2
The end surfaces of the low-resistance layers 1b and 2b of the first and second clad materials 1 and 2 were processed so that the groove 3 having a V-shaped cross section was provided only between the low-resistance layers 1b and 2b. And as shown in FIG.
High resistance layers 1a and 2 of first and second cladding materials 1 and 2
The end face of the first clad material 1 and the end face of the second clad material 2 were abutted so that a and the low resistance layers 1b and 2b of the first and second clad materials 1 and 2 faced each other. At this time, the groove angle (α) of the V-shaped groove 3 formed between the low resistance layer 1b of the first cladding material 1 and the low resistance layer 2b of the second cladding material 2 is 30 degrees. It is. The width of the groove 3 (the maximum distance between the low-resistance layers 1b and 2b of the first and second cladding materials 1 and 2) is about 2.1 mm (4 tan (α / 2) × 2 ≒ 2.1 mm). .

In this state, the first clad material 1 and the second clad material 2 are pressed against the butt end surfaces thereof, and the first clad materials 1 and 2 are brought into contact with the high resistance layers 1a and 2a of the first and second clad materials 1 and 2, respectively. Resistance welding was performed by applying a DC welding current to the second electrodes 4 and 5. FIG. 3 shows the energizing conditions at this time. In FIG. 3, I ₁ denotes a first welding current, I ₂ denotes a second welding current, P ₁ denotes a first pressing force, P ₂ denotes a second pressing force, and P ₃ denotes a third pressing force. The horizontal axis indicates time, and the unit is cycle (1 cycle = 1 /
60 sec). The upset margin was 6 mm.

FIG. 4 shows the metal structure at the joint interface between the first and second clad materials 1 and 2 after resistance welding.
At the joining interface between the high-resistance layers 1a and 2a, the high-resistance layers 1a and 2a are joined together by a large plastic flow caused by a pressing force such that the high-resistance layers 1a and 2a protrude on both front and back sides (upper and lower sides in FIG. 4). I have. Further, since the grain flow generated in the rolling direction of the high resistance layers 1a and 2a (horizontal direction in FIG. 4) does not disappear at the bonding interface, the material is melted at the bonding interface of the high resistance layers 1a and 2a. It is not considered to be.

On the other hand, at the joining interface between the low resistance layers 1b and 2b, the low resistance layers 1b and 2b are crushed by the pressing force, and the high resistance layers 1a and 2a are connected to the low resistance layers 1b and 2b.
4b, the outer surface side (FIG. 4)
Slightly upward, and the grain flow is also pushed upward, but the plastic flow is not as large as that of the high-resistance layers 1a and 2a. This is because the groove 3 provided between the low-resistance layers 1b and 2b is filled with the low-resistance material of the low-resistance layers 1b and 2b.

Further, no boundary line is seen at the joining interface between the low resistance layers 1b and 2b, and the low resistance layer 1b of the first clad material 1 and the low resistance layer 2b of the second clad material 2 are firmly joined. You can see that it is. In addition, the first and second
At the joining interface between the cladding materials 1 and 2, a boundary between the high resistance layer 1 a and the low resistance layer 1 b of the first cladding material 1 and a boundary between the high resistance layer 2 a and the low resistance layer 2 b of the second cladding material 2 are formed. Has no gaps.

X-ray diffraction was performed on the bonding interface between the first and second clad materials 1 and 2 after the resistance welding. As shown in FIG. 5, no brittle intermetallic compounds (Fe ₂ Al ₅ , FeAl _3, etc.) that reduced the bonding strength were detected. The value on the horizontal axis in FIG. 5 indicates the diffraction angle (2θ) when the incident angle of the X-ray is θ. As shown in FIG. 6, the tensile strength of the clad material itself and the joint was measured, and the tensile strength at the joint was equivalent to that of the clad material itself. It was confirmed that it could be secured.

Therefore, according to this embodiment, the butt welding with high productivity (DC butt welding in this embodiment)
Iron-aluminum cladding materials can be butt-welded while ensuring sufficient welding quality. For example, cylinder bores for vehicle engines with reduced weight and improved cooling performance can be produced at high cost at low cost. Becomes

(Embodiment 2) The present embodiment shown in FIG.
In addition, the shape of the groove 3 provided between the low resistance layers 1b and 2b of the second clad materials 1 and 2 is changed. That is, the groove 3 has an I-shaped (L-shaped) cross section,
The width of the groove 3 (the maximum distance between the low-resistance layers 1b and 2b of the first and second cladding materials 1 and 2) is about 2 mm. Other configurations are the same as those of the first embodiment.

In the first and second embodiments, butt welding is described as an example. However, it goes without saying that the present invention can be applied to other butt resistance welding methods such as butt seam welding, flash welding, and high frequency welding. Absent.

[0032]

As described above in detail, according to the butt resistance welding method of the clad material of the present invention, the occurrence of welding defects due to excessive or insufficient welding current in each of the high resistance layers and the low resistance layers. Therefore, sufficient welding quality can be ensured even when the clad material consisting of the high resistance layer with high electric resistance and the low resistance layer with low electric resistance is butt-welded to each other. Become.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a clad material according to a first embodiment.

FIGS. 2A and 2B are diagrams illustrating a butt resistance welding method of a clad material of Example 1, and FIG. 2A is a cross-sectional view illustrating an initial stage in which a welding current starts flowing between a first and a second clad material; (b) is a sectional view showing a state after the completion of the resistance welding.

FIG. 3 is a diagram showing welding conditions of resistance welding according to the first embodiment.

FIG. 4 is a photograph showing a metal structure at a bonding interface of a clad material after completion of resistance welding according to Example 1.

FIG. 5 is a graph showing a result of performing X-ray diffraction on a bonding interface of a clad material after completion of resistance welding according to Example 1.

FIG. 6 is a graph showing the results of measuring the tensile strength of the clad material itself and the joint according to Example 1.

FIG. 7 is a cross-sectional view illustrating a modification of the groove shape according to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st clad material 2 ... 2nd clad material 1a, 2a ... High resistance layer 1b, 2b ... Low resistance layer 3 ... Groove

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[Procedure amendment]

[Submission date] December 24, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B23K 11/24 338 B23K 11/24 338

Claims (1)

[Claims] 1. A high resistance layer made of a high resistance material having a high electric resistance, and a low resistance layer formed on a surface of the high resistance layer and made of a low resistance material having a lower electric resistance than the high resistance material. By holding the end surfaces of the first and second clad materials in abutted state and applying a welding current to the first and second clad materials while pressing the butted end surfaces of the first and second clad materials, A butt resistance welding method of a clad material for joining the high resistance layers of the first and second clad materials together and the low resistance layers of the first and second clad materials by resistance welding. A groove is provided only between the low-resistance layers of the first and second clad materials, and priority is given between the high-resistance layers of the first and second clad materials at an initial stage of resistance welding where a welding current starts to flow. To let current flow Butt resistance welding method of the clad material, characterized in that the.