JPH0857661A - Method for welding thin electric resistance welded tube - Google Patents

Abstract

PURPOSE: To provide a welding method of a thin electric resistant welded tube having high strength at the welding part. CONSTITUTION: As a metallic sheet 1, an aluminum alloy material having <=1mm thickness and 0.65-1.3wt.% silicon content, is used. At the time of executing the welding by 200kHz frequency of a high frequency generator, the range 8 having the distance of <=0.5 times of the sheet thickness from both side end part 5, 5 of the butt-welding metallic sheet 1 is rapidly risen and the ratio of the rising height H to the rising width W becomes 0.4-0.95. Further, the rising height H becomes 0.3-0.75 times of the sheet thickness T of the metallic sheet 1. Therefore, even if the rolling is developed in a gap of squeeze rolls, the rising part is not deformed caused by hitting to the squeeze rolls and also, the fear of the strength shortage caused by the development of butting step difference can be eliminated. In the range 8 having the distance of <=0.5 times of the sheet thickness from both side end parts 5, 5, the low melting point segregated material can be developed.

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 thin electric resistance welded tube suitable as a tube for an aluminum heat exchanger for air conditioning.

[0002]

2. Description of the Related Art A conventional electric resistance welding method is disclosed, for example, in JP-A-62-62.
No. 187580 and a method for manufacturing a thin electric resistance welded tube are disclosed in JP-A-3-81075. An apparatus for carrying out the welding method for these thin-wall electric resistance welded pipes is shown in FIG. In the figure, 1 is a metal strip, 2 is a high frequency oscillator for welding and heating, 3 is a heating coil connected to a high frequency oscillator 2, 4 is a pair of welding squeeze rolls (hereinafter referred to as squeeze rolls), 5 is a metal strip 1. It is the side end of the.

With the above apparatus, both end portions 5, 5 of the long metal strip 1 are butted against each other to form a round tube, and both butted end portions 5, 5 and the vicinity thereof are high-frequency heated and melted by the heating coil 3. At the same time, the squeeze roll 4 pressurizes and presses. Then, if necessary, the bead 6 and the raised portion 7 shown in FIG. 2 are partially removed by cutting, or shaped into a predetermined cross-sectional shape by a sizing roll (not shown). The bead 6 is formed by cooling and melting the molten metal liquid extruded from the joining interface to the outside of the pipe during high-frequency welding. Further, when the joint portion is shaped into a predetermined shape by the sizing roll, the plate thickness of the pipe may be slightly increased due to the action of the roll shaping compression force.

When welding thin-walled tubes for heat exchangers having a plate thickness of 1 mm or less by the above-mentioned method, the thinner the plate thickness and the higher the pressing force, the opposite end portions 5 of the metal strips 1 to be butted. 5, buckling is likely to occur, and a step is likely to occur on the end surfaces of the both end portions 5, 5. 12A shows the buckling portion, and the buckling portion A is a deformed portion of the metal strip material which is generated by pressure during roll forming and welding. Further, B of FIG. 13 shows the above-mentioned step, and the step B means a butt step caused by the height shift of the left and right end portions 5, 5 of the metal strip 1 at the welded portion.

By the way, in the above-mentioned high frequency electric resistance welded pipe welding method, a butting step B of about 0.3 times the plate thickness T of the metal strip 1 may occur due to roll dimensional accuracy, spatter entrainment and the like. When such a butt step B occurs, the joint area of the end faces of the both end portions 5, 5 decreases,
There is a problem that the thickness of the joint portion and the vicinity of the joint portion becomes equal to or less than the plate thickness of the metal strip 1 before welding, resulting in insufficient strength.

In order to solve the above problems, the plate thickness in the vicinity of the joint may be increased. (1) In roll forming before welding, the plate thickness of the side end 5 of the metal strip 1 is increased. . (2) Raise the vicinity of the joint during welding. For example, as disclosed in JP-A-62-187580, the distance between the extra peaks (see FIG. 2) is set to 3 to 6 times the plate thickness T. (3) Raising the vicinity of the joint in roll shaping after welding. Etc. are possible.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
When the method (1) is performed on the metal strip 1 having a size of not more than mm, there arises a problem that the dimensional accuracy of the end face shapes of the both end portions 5, 5 of the metal strip 1 deteriorates. In the method (2), since the width of the ridge is widened, the following problems occur. That is, when welding a thin-walled electric resistance welded pipe, a phenomenon called so-called rolling occurs, in which the round tubular metal strip 1 swings in the gap L of the squeeze roll 4 shown in FIG. The cause of this rolling phenomenon is mainly due to variations in the left and right molding of the metal strip 1. That is, the deformation amount of one side end portion 5 of the metal strip 1 becomes larger or smaller than that of the other side end portion 5 due to the deflection of the forming roll shaft or the like, and the deformation amount is repeatedly repeated. A difference (variation) in the molding amount occurs periodically on the left and right of 1, and the abutting position swings (rolls) when the both end portions 5, 5 are abutted.

Then, when this rolling occurs, FIG.
As shown by the broken line 4 in FIG. 4, the raised portion 7 hits the squeeze roll 4 and a welding failure occurs. Further, in the method of (3), since it is pressed at room temperature to raise it,
As shown in FIG. 15, at the time of shaping, the heat-softened portion 8 near the joint of the side end portion 5 is deformed by buckling, which causes a problem such as defective shape and insufficient strength.

The present invention has been made to solve the above problems, and provides a welding method for a thin electric resistance welded pipe having a plate thickness of 1 mm or less, in which the welded joint has high strength. To aim.

[0010]

The present invention employs the following technical means in order to achieve the above object. In the invention according to claim 1, both side end portions (5, 5) of the butted metal strips (1) and the vicinity thereof are heated and melted, and
In the method for welding a thin-walled electric resistance welded pipe that is pressure-welded by welding squeeze rolls (4, 4), the metal strip (1) has a plate thickness (T) of 1 mm or less, and both side ends ( 5, 5) within a region that is a distance of 0.5 times or less of the plate thickness (T), the protrusion height with respect to the protrusion width (W) of the both end portions (5, 5) that are pressed and raised. The height (H) is set to 0.4 to 0.95, and the height (H) is set to 0.3 of the plate thickness (T).
It is characterized in that it is increased by 0.75 times.

According to a second aspect of the present invention, in the method for welding a thin electric resistance welded pipe according to the first aspect, a low melting point segregation product is generated in the vicinity of the both end portions (5, 5) which are butted and welded to each other. It is characterized by The invention according to claim 3 is the method for welding a thin electric resistance welded pipe according to claim 1 or 2, wherein the metal strip (1) has at least a silicon content of 0.65.
It is characterized by being an aluminum alloy of up to 1.3% by weight.

The invention according to claim 4 is the invention according to claim 1 or 2.
In the method for welding a thin electric resistance welded pipe described above, the metal strip (1) has a difference in liquidus temperature and solidus temperature of at least 20.
It is characterized by being an aluminum alloy of -40 ° C.
The invention according to claim 5 is any one of claims 1 to 4.
In the method for welding a thin-walled electric resistance welded pipe as described in No. 3, both side ends (5, 5) of the metal strip (1) and the vicinity thereof are heated by a heating coil (3) connected to a high frequency oscillator (2). In addition to melting, the heating oscillation frequency of the high frequency oscillator (2) is set to 100 to 300 kHz.

According to the invention described in claim 6,
The method for welding a thin electric resistance welded pipe according to any one of 4 and 5, wherein the metal strip (1) is an aluminum alloy containing at least a minute amount of silicon and copper. The reference numerals in parentheses of the above-mentioned means indicate the correspondence with the concrete means described in the embodiments described later.

[0014]

According to the inventions of claims 1 to 6, in the method for welding thin-walled electric resistance welded pipes, the thickness is 0.5 times or less the plate thickness from both end portions of the metal strips to be butted and welded. The region which is the distance is rapidly raised, and the ratio of the height of the protrusion to the width of the protrusion is 0.4 to 0.95, and the height of the protrusion is 0.3 to 0.75 of the plate thickness of the metal strip. Doubled.
Therefore, even if rolling of the metal strip occurs in the gap between the squeeze rolls, the raised portion does not contact the squeeze roll and is not deformed, and there is an effect that it is possible to eliminate the risk of insufficient strength due to a butt step. is there.

According to the second aspect of the present invention, the low-melting-point segregation material is generated in a region that is a distance of 0.5 times or less of the plate thickness from both end portions of the metal strips that are butted and welded. Due to the heat effect during welding heating, the plate thickness near the both side edges is 0.5.
The high temperature deformation resistance is lowered by the liquefaction of the grain boundaries in a region having a distance of not more than twice or the minute low melting point segregated substances. This allows
In the area, the ratio of the height of the ridge to the width of the ridge is 0.4 to 0.
95, the height of the protrusion is 0.3 to 0.
It is possible to generate a sharp uplift of 75 times. Furthermore, stress relaxation due to the liquefied low melting point segregated substance has an effect of suppressing the occurrence of welding defects such as cracks.

According to the third aspect of the present invention, the metal strips are made of an aluminum alloy having a silicon content of at least 0.65 to 1.3% by weight, so that both ends of the metal strips to be butt-welded together are welded. A low melting point segregation product is generated in a region where the vicinity of the portion is a distance of 0.5 times or less of the plate thickness. Therefore,
The same effect as the invention according to claim 2 can be obtained, and the strength of the material itself is improved by injecting silicon, which is a low melting point element, into the welded portion, thereby improving the strength and long life of the electric resistance welded pipe. There is an effect that it can be realized.

According to the invention described in claim 4, the metal strip is made of an aluminum alloy having a difference in liquidus temperature and solidus temperature of 20 to 40 ° C., which is the same as the invention described in claim 3. The effect of can be produced. According to the method for welding a thin electric resistance welded pipe of the present invention as set forth in claim 5, the heating coil has 10
A heating oscillation frequency of 0 to 300 kHz is applied. As a result, the heat input depth to the welded portion is increased, a softened region is formed in the vicinity of both side end portions of the metal strips that are butted and welded to each other, and a bulge is easily generated, and at the same time, to the both side end portions. The pressurization can be stabilized. Further, by liquefying the grain boundaries in the vicinity of the both end portions and forming a low melting point segregation product, there is an effect that stress in the welded portion can be relaxed.

According to the sixth aspect of the present invention, even if the silicon content is reduced by containing a very small amount of copper in addition to silicon in the aluminum alloy constituting the metal strip, the first aspect of the present invention is also possible. The same effect as the invention can be exhibited.

[0019]

【Example】

(First Embodiment) The method of the present invention is suitable for use in the production of aluminum heat exchanger tubes (for example, heat exchanger tubes for air conditioning condensers, air conditioning evaporators, automobile radiators, etc.). The first embodiment of the method of the present invention employs the following welding conditions. That is, in the first embodiment, the gap L of the squeeze roll 4 is used by using the device shown in FIG.
(Refer to FIG. 14) is set to 0.6 to 1.2 mm, and the metal strip 1
As for manganese (Mn) 1.0 to aluminum
Based on A3000 aluminum alloy with 1.5% by weight added, silicon (Si) 0.9% by weight
A plate material made of the added aluminum alloy material is used. The other elements of this aluminum alloy are impurities. The plate thickness T of this aluminum alloy plate is 0.3.
mm.

Further, the frequency of the high frequency oscillator 2 is set to 200 k
A case will be described in which welding is performed using a high-frequency heating source (heating coil) of Hz to manufacture an electric resistance welded pipe having a pipe diameter of 10 to 20 mm. As shown in the enlarged cross-sectional view of the welded portion of FIG. 2, the metal strips 1 to be butt-welded together are welded from both end portions 5 and 5 to 0.5 times or less of the plate thickness (hence 0.15 m).
A sharp ridge 7 is formed in a region (softened region) 8 having a distance of m or less).

Therefore, first, the silicon content (% by weight)
And the height H of the metal strip 1 with respect to the plate thickness T (mm)
As for the relationship with the (mm) ratio, as shown in FIG. 3, as the silicon content increases, the ratio of the height H of the metal strip 1 to the plate thickness T increases. Considering the aluminum (Al) -silicon (Si) phase diagram shown in FIG. 16, the solid-liquid coexistence region (region of α + L in FIG. 16) increases substantially in proportion to the silicon content. Therefore, it is considered that the softened region 8 formed due to the existence of the solid-liquid coexisting phase also increases substantially in proportion to the silicon content. Normal,
In the welding of the electric resistance welded pipe, since the softened region 8 is compressed and plastically deformed by the pressure bonding, the higher the softened region 8 is, the higher the bulge height H is. It is considered that the amount increases substantially in proportion to the amount.

Further, in a general high-frequency welding method for electric resistance welded pipes, there may be a maximum butt step B of about 0.3 times the plate thickness T, and the ridge height H is at least the step B. Will be needed. Therefore, as can be seen from FIG. 3, if the metal strip 1 is made of an aluminum alloy material having a silicon content of 0.65% by weight or more, the butting step B
The protrusion height H necessary for compensating for the decrease in the joint area due to is obtained, and the necessary strength of the welded portion can be secured.

In FIG. 3, the part indicated by the broken line shows the characteristic of the region that can be estimated based on the experiments and studies by the present inventor. The broken line portions in FIGS. 4, 5, 9, 10, and 11 below also show the characteristics of the similar estimable region. Next, the silicon content (% by weight) and the plate thickness T of the metal strip 1
Consider the relationship with the ratio of the ridge width W (mm) to (mm). As shown in FIG. 4, as the silicon content increases, the ratio of the ridge width W to the plate thickness T of the metal strip 1 increases. According to the aluminum-silicon phase diagram of FIG. 16, it is considered that the ridge width W increases substantially in proportion to the silicon content for the same reason as the case where the ridge height H increases. Generally, in the case of welding an electric resistance welded pipe, rolling in the gap L of the squeeze roll 4 is unavoidable as shown in FIG. 14, and therefore the raised portion 7 must be prevented from hitting the quiz roll 4. .

Here, the rolling angle θ is an angle at which the center of the raised portion 7 swings to the left and right as shown in FIG. 14, and the rolling amount D is a distance at which the center of the raised portion 7 swings to the left and right to the maximum. Considering industrial mass production of the thin-walled electric resistance welded pipe of the present invention, it is desirable that the rolling angle is about 5 ° or less at an angle θ. If the gap L of the squeeze roll 4 is too narrow with respect to the protrusion width W, the raised portion 7 hits, and if the gap L is too wide, FIG.
As shown in FIG. 7, both end portions 5, 5 of the metal strip 1 overlap each other in the radial direction. Therefore, the gap L
Needs to be set to a certain amount of gap, and empirically,
It is preferable to set the plate thickness T of the metal strip 1 to about 2 to 4 times (2T to 4T).

However, as described above, the gap L is widened (L =
4T), considering that rolling occurs at an angle θ of about 5 °, in order to prevent the squeeze roll 4 from hitting the ridge portion 7, the ridge width W is set to about 1. It is necessary to limit it to 0 times or less. As shown in FIG. 4, this limitation of the ridge width W can be realized by using an aluminum alloy material having a silicon content of 1.3% by weight or less as the metal strip 1, and as a result, the angle θ =
Even if rolling of about 5 ° occurs, the raised portion 7 does not contact the squeeze roll 4.

As described above, the use of an aluminum alloy material having a silicon content of 1.3% by weight or less as the metal strip 1 indicates that the ridge height of the metal strip 1 with respect to the plate thickness T is as shown in the characteristic diagram of FIG. The ratio of the height H is 0.75 or less. Furthermore, as shown in FIG. 5, it was found that the ratio of the height H (mm) of the ridge to the width W (mm) of the ridge increases as the silicon content (% by weight) increases. Regarding this FIG. 5, it is necessary to have the ridge height H equal to or larger than the maximum step (the silicon content is 0.65 wt% or more) and the restriction that prevents the ridge 7 from hitting the squeeze roll 4 by rolling. (Since the silicon content is 1.3% by weight or less), the ratio of the height H of the ridge to the width W of the ridge is 0.4 to 0.9.
Within the range of 5, the raised portion 7 does not hit the squeeze roll 4 and the strength due to the butting step B does not become insufficient.

From this example, the silicon content is 0.65.
In the range of up to 1.3% by weight, the difference between the liquidus temperature (line a in FIG. 16) and the solidus line (line b) in the aluminum alloy material forming the metal strip 1 is 20 to 40. It can be seen that a good weld can be formed when the temperature difference is in the range of 20 to 40 ° C. and the difference between the liquidus temperature and the solidus temperature of the aluminum-silicon alloy material is in the range of 20 to 40 ° C.

As a result of observing the cross section in the vicinity of the welded portion in the above-mentioned specific example, in the metal strip 1 made of an aluminum alloy material having a silicon content of 0.9% by weight, both side end portions 5 which are butted and welded to each other. 5, segregation of liquefied and agglomerated silicon, which is the element for lowering the melting point, occurs at the grain boundary in a region of 0.5 times or less of the plate thickness, and the ratio of the height H of the ridge to the width W of the ridge is 0. There was a sharp uplift of 4 or more.

However, if the silicon content is 0.3% by weight
In the metal strip 1 made of the aluminum alloy material which has been reduced to 1, the segregation of silicon did not occur, and neither did a sharp bulge. From this, the above-mentioned abrupt ridge is in the vicinity of the welded portion due to the influence of heat at the time of welding (a region that is a distance of 0.5 times or less of the plate thickness from both end portions 5 and 5 welded by being butted against each other). It is considered that this occurs because the high temperature deformation resistance is generated in the region (softened region) 8 due to the liquefaction of the grain boundaries or the minute low melting point segregated substances.

Therefore, as shown in FIG. 6, copper, magnesium, and
By adding a low melting point element such as zinc to form the segregated substance 10, it is possible to prevent the bump 7 from hitting the squeeze roll 4 and prevent the insufficient strength due to the butt step. it can. Further, liquefaction of the low-melting-point segregation product 10 or the like causes stress relaxation, which can suppress the occurrence of welding defects such as cracks.

As shown in FIG. 7 (a), the metal strip 1 of the aluminum alloy material of the above specific example is used as the core material.
By using a clad material obtained by laminating a skin material 11 to which a low melting point element such as copper, magnesium or zinc is added,
As shown in FIG. 7 (b), the low melting point element is introduced into the vicinity of the welded portion at the time of welding to form the segregated substance 10, so that the bump 7 is not brought into contact with the squeeze roll 4 and the butt step is formed. It is possible to prevent the lack of strength due to.

Further, by adding the above-mentioned element for lowering the melting point, the strength of the material itself can be increased to improve the strength and the service life of the electric resistance welded pipe. The skin material 11 serves as a brazing material or sacrificial corrosion material for the heat exchange tube.
In the first embodiment described above, the Mn content in the aluminum alloy of the metal strip 1 is relatively high, but addition of Mn to such an extent almost changes the difference between the solidus temperature and the liquidus temperature of the aluminum alloy. Since it is not present, it is not a factor that influences the formation of the sharp ridge shape intended by the present invention.

In the first embodiment, the combination of Al--Si is used to increase the difference between the solidus temperature and the liquidus temperature, but any element capable of increasing the temperature difference can be used. However, the combination is not limited to Al-Si. (Second embodiment) In the first embodiment, the silicon content of the aluminum alloy constituting the metal strip 1 is 0.65.
However, in the second embodiment, by adding copper (Cu) to the aluminum alloy, Even if the silicon content is small, the above-mentioned predetermined sharp ridge shape is obtained.

In the second embodiment, using the apparatus shown in FIG. 1, the gap L (see FIG. 14) of the squeeze roll 4 is set to 0.45 to 1.2 mm and the aluminum strip clad material is used as the metal strip 1. The core material of this clad material is based on an A3000 series aluminum alloy in which manganese (Mn) is added to aluminum in an amount of 1.0 to 1.5% by weight, on which silicon (Si) is added by 0.5% by weight and copper is added. 0.
Using aluminum alloy material added 8 wt% each,
A4000 series (Al-Si series) aluminum alloy, A7000 series (Al-Zn-Mg series) aluminum alloy or the like is used as a skin material (brazing material, sacrificial corrosion material) attached to both surfaces of the core material. The plate thickness of the aluminum alloy clad material is 0.2 to 0.3 mm, and the clad ratio of the skin material applied to both surfaces of the core material is 5 to 20%.

The frequency of the high frequency oscillator 2 is set to 200
Welding was performed using a high-frequency heating source (heating coil 3) at a frequency of kHz to manufacture an electric resistance welded pipe having a pipe diameter of 10 to 20 mm.
As a result, in the second example, as shown in the sample in the table of FIG. 18, a good shape of the raised portion could be obtained. FIG.
Table 8 summarizes the addition amounts of Si and Cu as the additive elements, the frequency of the high-frequency oscillator during welding, and the welding results for each sample. The welding results are described for five indicators (H / T, W / T, H / W, solid-liquid coexistence temperature range, and presence / absence of segregation).

Here, the samples in the table of FIG. 18 are the first embodiment of the present invention, and the samples are comparative examples with respect to the embodiments of the present invention. In addition, in the table of FIG.
The solid-liquid coexistence temperature range is a temperature difference between the solidus temperature and the liquidus temperature. H / T, W / T, H / W
Is an index showing the form of the raised portion 7, and since the raised portion 7 is important to obtain a good welded portion as described above, it is important to determine H / T (height with respect to the plate thickness T). H
The larger the ratio is, the more preferable. Further, the smaller W / T (the ratio of the width W to the plate thickness T) is more preferable. Further, the larger the H / W (height H with respect to the width W), the more preferable.

Considering from this point of view, the sample of the second embodiment was able to obtain a good shape of the raised portion similar to the sample of the first embodiment. Thus, the second
In the embodiment, even if the amount of silicon added is reduced to 0.5% by weight by adding copper, the same good effect as in the first embodiment can be exhibited. In the second embodiment, the case where silicon and copper are added to aluminum has been described, but a low melting point segregation product can be formed, and the temperature difference between the solidus temperature and the liquidus temperature is 20 ° C to 40 ° C. If it is an aluminum alloy that can be expanded up to about ° C, it is possible to substitute it with additives (magnesium, zinc, etc.) other than silicon and copper.

Next, in the above method for welding a thin electric resistance welded pipe, the metal strip 1 is made of an aluminum alloy having a silicon content of 0.9% by weight, and the frequency of the high-frequency oscillator 2 which is a heating heat source is changed to 200 to 400 kHz. The case will be described. Generally, in the high frequency electric resistance welding method, the current penetration depth at the end face of the metal strip 1 is inversely proportional to the square root of the frequency.

Therefore, the higher the oscillator frequency, the more the heat is concentrated in the narrow region of the end face of the metal strip 1, so that the softened region 8 becomes narrower and the ridge width W becomes narrower as shown in FIG. 8 (a). On the contrary, as the oscillator frequency is lower, the heat is dispersed in a wider region of the end surface of the metal strip 1, so that the softened region 8 becomes wider and the ridge width W becomes wider as shown in FIG. 8B. FIG.
Oscillator frequency (kHz) and plate thickness T (m of metal strip 1
It shows the relationship with the ratio of the ridge width W (mm) to m). In order to prevent the raised portion 7 from hitting the squeeze roll 4 by rolling, the ratio of the raised width W to the plate thickness T of the metal strip 1 needs to be 1.0 or less. Therefore, the oscillator frequency needs to be 100 kHz or higher.

FIG. 10 shows the oscillator frequency (kHz)
And the height H of the metal strip 1 with respect to the plate thickness T (mm)
It shows the relationship with the ratio of (mm). 9 and 10
As will be understood from the above, as the oscillator frequency increases, the ratio of the ridge width W to the plate thickness T of the metal strip 1 and the ratio of the ridge height H to the plate thickness T of the metal strip 1 decrease.
Considering that the maximum butt difference B of about 0.3 times the plate thickness T is generated as described above, the oscillator frequency needs to be 300 kHz or less as shown in FIG.

FIG. 11 shows the oscillator frequency and the ridge width W (m
It shows the relationship with the ratio of the height H (mm) of the ridge to the height m. As the oscillator frequency increases, the ridge width W increases.
The ratio of the bulge height H to Therefore, in order to prevent the insufficient strength due to the rolling and the butt step B, the oscillator frequency is set to 100 to 3 from the above FIGS.
It is necessary to set it to 00 kHz. By setting in this way, the ratio of the height H of the ridge to the width W of the ridge is
The range is 0.40 to 0.75.

In addition, as a method of solving the strength shortage due to the butt step B, the distance between the heating coil 3 and the welding point is increased, the preheating process is set, or the pipe forming speed is reduced, and the like. It is also possible to disperse the heat input to the end surface of the band 1 to form a region (softened region) which is easily deformed in the vicinity of the joint portion during welding, and sharply raise this region.

[Brief description of drawings]

1 is a perspective view showing an outline of an apparatus for carrying out the method of the present invention.

FIG. 2 is an enlarged cross-sectional view of a welded portion by the apparatus of FIG.

FIG. 3 is a characteristic diagram showing the relationship between the silicon content and the ratio of the ridge height to the plate thickness of the metal strip.

FIG. 4 is a characteristic diagram showing the relationship between the silicon content and the ratio of the ridge width to the plate thickness of the metal strip.

FIG. 5 is a characteristic diagram showing the relationship between the silicon content and the ratio of the height of the ridge to the height of the ridge.

FIG. 6 is an enlarged cross-sectional view of a welded portion that is welded by adding a low melting point element.

FIG. 7 is an enlarged cross-sectional view of a clad material and a welded portion welded using the clad material.

FIG. 8 is an enlarged cross-sectional view of a welded portion that is welded by changing the oscillator frequency.

FIG. 9 is a characteristic diagram showing a relationship between an oscillator frequency and a ratio of a ridge width to a plate thickness of a metal strip.

FIG. 10 is a characteristic diagram showing a relationship between an oscillator frequency and a ratio of a protrusion height to a plate thickness of a metal strip.

FIG. 11 is a characteristic diagram showing a relationship between an oscillator frequency and a ratio of a ridge height to a ridge width.

FIG. 12 is an enlarged cross-sectional view illustrating buckling at a welded portion.

FIG. 13 is an enlarged cross-sectional view illustrating a butt step at a welded portion.

FIG. 14 is an enlarged cross-sectional view of a welding portion exemplifying rolling.

FIG. 15 is an enlarged cross-sectional view illustrating buckling at a welded portion.

FIG. 16 is an equilibrium diagram of an Al—Si alloy.

FIG. 17 is an enlarged cross-sectional view illustrating the overlap at the welded portion.

FIG. 18 is a table showing welding results according to the first and second examples of the present invention in comparison with comparative examples.

[Explanation of symbols]

1 ... Metal strip, 2 ... High frequency oscillator, 3 ... Heating coil, 4
... Squeeze roll, 5 ... Side end, 7 ... Protuberance, 8 ... Region (softened region), 10 ... Segregation product, T ... Plate thickness, H ... Protrusion height, W ... Protrusion width.

(72) Inventor Tetsuji Shinbo, 1-1, Showa-cho, Kariya, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Inventor, Mitsuo Hashiura, 1-1, Showa-cho, Kariya, Aichi Nippondenso Co., Ltd. Within

Claims (6)

[Claims] 1. A method for welding a thin electric resistance welded pipe in which both ends and the vicinity thereof of butted metal strips are heated and melted and pressure-welded with a welding squeeze roll, wherein the metal strip has a plate thickness of 1 mm. Below, in a region that is a distance of 0.5 times or less of the plate thickness from the both side ends to be butt-welded and welded, the ridge height with respect to the ridge width of the both side ends to be urged by pressurization. Ratio is 0.4 ~
The method for welding a thin-walled electric resistance welded pipe, wherein the height of the protrusion is set to 0.95 and the height of the protrusion is set to 0.3 to 0.75 times the plate thickness. 2. The method for welding a thin electric resistance welded pipe according to claim 1, wherein a low melting point segregation product is generated in the vicinity of the both end portions to be butt-welded and welded. 3. The method for welding a thin electric resistance welded pipe according to claim 1, wherein the metal strip is an aluminum alloy having a silicon content of at least 0.65 to 1.3% by weight. 4. The thin electric resistance welded pipe according to claim 1, wherein the metal strip is an aluminum alloy having a difference between a liquidus temperature and a solidus temperature of 20 to 40 ° C. Welding method. 5. The both sides of the metal strip and the vicinity thereof are heated and melted by a heating coil connected to a high frequency oscillator, and the frequency of the high frequency oscillator is set to 100.
The welding method for a thin electric resistance welded pipe according to any one of claims 1 to 4, wherein the welding speed is set to 300 kHz. 6. The thin electric resistance welded pipe according to claim 1, wherein the metal strip is an aluminum alloy containing at least minute amounts of silicon and copper. Welding method.