JPH0635064B2 - Method for manufacturing tube made of titanium or titanium alloy - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a TIG welded pipe by a plurality of electrodes for improving a pipe forming speed, and more specifically, a proper range of a distance between electrode tips and a welding current applied to the electrode. The present invention relates to a method of manufacturing a pipe made of titanium or a titanium alloy (hereinafter collectively referred to as Ti) that can be set to increase the pipe making speed.

[Prior Art] In the production of welded Ti pipe, for example, a strip forming apparatus shown in FIG. 8 continuously bends a strip plate in the plate width direction to form a tubular body, and the strip is arranged in the pipe forming apparatus. The butt portion of the tubular body formed by the TIG welding machine is continuously welded into a pipe.

In FIG. 8, (1) is an uncoiler, and the uncoiler (1) is a supply source of the Ti strip (F).

(2) is a forming roll, the forming rolls (2) are arranged in pairs on the base (K), and the horizontally rotating pairs and the vertically rotating pairs are alternately arranged. There is. In addition, these forming rolls (2) are breakdown rolls that form the strip (F) supplied from the uncoiler (1) into a U shape.
(3), fin-pass roll (4) formed in O-shape, squeeze roll (5) for holding both ends of O-shaped strip as butt portions for welding, and squeeze roll (5) It is composed of a sizing roll (6) for finishing a pipe welded by a TIG welding machine (7) disposed above the pipe to a predetermined outer diameter.

Ti supplied to the forming roll (2) from the uncoiler (1)
The strip plate (F) is formed into a tubular body by the pipe forming apparatus and welded by a TIG welding machine arranged above the squeeze roll (5) to form a welded Ti pipe.

The TIG welding machine used heretofore has been a single electrode.

On the other hand, in manufacturing a steel pipe or a stainless steel pipe, a method of TIG welding with a plurality of electrodes is known, and various concrete methods have been proposed, for example, as shown in FIG. -28629 and the welding device disclosed in JP-B-53-34771 shown in FIG.
There is a proposal such as a method for manufacturing a welded steel pipe disclosed in No.

In FIG. 9 showing a welding device according to the former prior art (proposal of Japanese Patent Publication No. 56-28629), (41) is a tubular body, and the tubular body (41) is a ring for forming a thin steel strip. (Four
The object to be welded is curved in the plate width direction in 7) and moves in the direction of the arrow in the figure.

Reference numeral (42) is a welding head, and the welding head (42) is movably adjustable in a vertical direction and a horizontal direction at right angles to the tubular body (41) by being indicated by a holder (46).

Reference numerals (43), (44) and (45) are non-consumable electrodes, and these three electrodes (43), (44) and (45) are arranged on the same straight line and are held by the welding head (42). ing.

The second electrode (44) arranged in the center is held by the welding head (42) so as to be perpendicular to the tubular pair (41), and the first electrode (43) and the first electrode (43) arranged before and after the welding head (42). 3 electrode (45) is the second
The welding head (42) is held at the welding head (42) so as to be rotatable with respect to the electrode (44) diagonally, and with the supporting portion (48) as a fulcrum, respectively, via the spring (50) and the set screw (49). The tilt angle with respect to the second electrode (44) can be finely adjusted.

The former welding device according to the prior art has the above-described structure and is adjustable so that the fusion zone formed by the first and third electrodes is connected to the fusion zone formed by the second electrode during the welding operation. Then, the welding current is dividedly supplied by these three electrodes, and a series of molten pools are formed by the three electrodes, thereby enabling the welding and pipe forming of thin-walled steel pipes.

Further, in FIG. 10 showing a method for producing a welded steel pipe according to the latter prior art (proposal of JP-B-53-34771), (51) is a tubular body, and the tubular body (51) is a steel strip. Is a body to be welded that is curved in the plate width direction by a pair of forming rolls.

Reference numeral (52) denotes a pair of fin rolls, and here, a final pair of a series of forming roll groups, each pair of which includes a break roll and a fin roll, is illustrated.

(53), (54), (55) are paired quiz rolls, and here, a pair of squeeze rolls (5
In 4), the maximum squeeze is given to the tubular body (51).

Reference numerals (56), (57), (58), and (59) are non-consumable electrodes, and these electrodes (56), (57), (58), and (59) are the same as those of the tubular body (51) to be welded. It is arranged above the abutting portion.

Of these electrodes (56) (57) (58) (59), the preceding three are placed in front of the squeeze roll (54) that gives the maximum squeeze to the tubular body, and the three The molten portion formed by the final electrode (58) in the electrodes is arranged in front of the center point of the squeeze roll (54) that gives the maximum squeeze.

The electrodes arranged behind the squeeze roll (54)
(59) is for correcting the shape of the weld bead surface or heating the weld boundary, and is not involved in the complete penetration of the weld bead.

In this latter prior art method of manufacturing a welded steel pipe, by disposing three or more pairs of squeeze rolls and arranging a plurality of electrodes in front of the squeeze roll that gives the maximum squeeze,
The reaction force in the outer peripheral direction of the pipe that is generated at the abutting portion of the tubular body to be welded is suppressed, and the generation of minute cracks and undercuts due to the reaction force is prevented, and even for high alloys such as stainless steel, 2 m / min Welding pipes can be produced at the above high speeds.

[Problems to be solved by the invention]

The inventors of the present invention have been eagerly studying the technical development for producing a Ti pipe by welding at high quality and at high speed.
Focusing on the technology disclosed in the above-mentioned proposals for steel pipes or stainless steel pipes, that is, the TIG welding method using a plurality of electrodes, this was applied to the manufacture of Ti pipes to improve the pipe forming speed.

This is because in the conventional Ti pipe welding method using the above-mentioned single electrode TIG welding machine, a large welding current must be applied to a single electrode in order to obtain sufficient penetration at the butt portion of a tubular body traveling at high speed. However, it is difficult to subtly match the large current supplied to this single electrode with the traveling speed of the tubular body.Therefore, if the welding current becomes excessive and the arc penetrates or becomes too small, the welding bead There is a defect that fatal defects occur in the quality of the pipe product such as undercut of the pipe, and in this welding with a single electrode, the pipe forming speed of the Ti pipe is limited to a certain limit (for example, a Ti pipe with a wall thickness of 1 mm or less Then 3.5m / m
For Ti pipes with a wall thickness of about 1.5 mm, the pipe forming speed of 1 m / min was the limit. ) It was practically restricted to increase above.

However, it is expected that these problems can be avoided even at a higher speed level by separately supplying the welding current to the plurality of electrodes.

However, when the TIG welding method using multiple electrodes, which is a proposal for the above-mentioned steel pipe or stainless steel pipe, is tried on a Ti pipe, it is sure that the defects that occur when the pipe making speed is increased by the single electrode TIG welding machine are solved. However, in addition to this, welding was interrupted due to swelling of the molten metal (a phenomenon in which the molten metal at the rear molten part of the leading electrode swelled and then short-circuited with the row electrode to make it impossible to continue welding) and the welding bead became unstable. It became clear that problems such as

On the other hand, since the Ti pipe produced by welding is normally used in a welded state, particularly strict requirements are made on the bead shape of the welded portion, that is, the weld bead quality of the pipe product. Among the factors that determine the weld bead quality, particularly important factors are Tc: bead center wall thickness, Wi: inner bead width, shown in FIG. 4, which is a schematic sectional view of the weld bead.
Wo: Outside bead width, etc., as well as outside bead flatness.

Further, important manufacturing condition factors that affect the bead quality of the welded Ti pipe include a pipe making speed, a pipe wall thickness, a welding current, an electrode inclination angle, and the like. In addition to the condition factors, it was clarified that the distance between the tips of each electrode and the distribution of welding current to each electrode are important factors.

In view of the above problems, the present invention grasps a proper electrode arrangement of a plurality of electrodes and a proper welding current condition to be given to each electrode in relation to a pipe forming speed and a pipe wall thickness, and thereby secures a weld bead quality. The purpose of the present invention is to provide a technique for producing a pipe made of titanium or a titanium alloy, which can improve the pipe making speed.

[Means for solving problems]

A method for manufacturing a tube made of titanium or a titanium alloy according to the present invention for solving the above-mentioned problems is a method in which a strip plate made of titanium or a titanium alloy is curved in the plate width direction to form a tubular body, and the length of the tubular body is long. A method for manufacturing a tube by TIG welding with a plurality of non-consumable electrodes on which direction-directed butts are arranged, wherein the last side 2 of the plurality of electrodes arranged above the butted parts is manufactured.
The distance (L) between the electrode tips of the book is set within the range that satisfies the following expressions (I) and (II), and the total welding current (I
t) within the range that satisfies the following formula (III), and the welding current (If) given to the final electrode among the plurality of electrodes is
It is characterized in that it falls within the range that satisfies the expression (V).

0.0035VT ^1.5 ≤ L ≤ 0.0070VT ^1.5 +20 ...... (I) 10 ≤ L ≤ 70 ...... (II) 0.09VT ^1.5 +30 ≤ It ≤ 0.09VT ^1.5 +130 ...... (III) 0.5 Im ≤ If ≤ Im ...... ( IV) However, L: Distance between electrode tips (mm) V: Pipe forming speed (mm / min) T: Pipe wall thickness (mm) It: Total welding current (A) If: Welding current of final electrode (A) Im : Average welding current per electrode (A) [Operation] In order to clarify the above-mentioned problems, the inventors of the present invention have determined the welding conditions, in particular, the distance between the tips of a plurality of electrodes, the welding current applied to each electrode, etc. Research was conducted in relation to tube wall thickness.
The present invention will be described below along with its research history.

The pipe forming apparatus used for the test welding is shown in outline in FIG.

In FIG. 3, (1) is an uncoiler, and the uncoiler (1) supplies a Ti strip (F) to a pipe forming apparatus.

(2) is a forming roll, and the forming roll (2) is composed of an array of breakdown rolls (3), fin pass rolls (4), squeeze rolls (15), sizing rolls (6), etc. These are basically the same in configuration except for the number of squeeze rolls (15) and the pipe forming apparatus shown in FIG.

The squeeze roll (15) is designed to minimize the influence of the spring back of the tubular body on various test pipe making speeds.
Placed in pairs.

(H) is an electrode holder, and the electrode holder (H) holds a plurality of electrodes so that they are arranged above the abutting portion of the tubular body, and the distance between the tips of the electrodes and the tilt angle can be adjusted. It is held and movable integrally in the vertical and horizontal directions.

(S) is a velocity detector, and the velocity detector (S) detects the moving velocity of the tubular body by measuring the rotation of the detection roll (8).

(T) is a plate thickness measuring instrument, and the measuring instrument (T) is a forming roll.
The thickness of the Ti strip (F) was measured with a non-contact ultrasonic probe (9) arranged in front of (2).

(I) is a current controller,
(I) controls the welding power source (P) of each electrode (7) and adjusts and sets the welding current applied to each electrode (7).

With the structure shown in FIG. 3, the Ti strip (F) is formed into a tubular body, and a plurality of electrodes (7) are arranged above the butted portion.
The butt joint was subjected to test welding under various conditions.

In the test welding, the vicinity of the welding point was shielded with Ar gas in order to prevent oxygen from mixing with the weld beads on the inner and outer surfaces of the pipe.

The purpose of test welding is to understand the problems that occurred when applying the above-mentioned conventional techniques for steel and alloy steel to welding of Ti pipes, that is, the electrode placement conditions that can eliminate the interruption of welding due to rising of the molten metal. I went.

In addition, the electrode numbers described below (for example, the first electrode, the second electrode, etc.) are the welding start side, that is, the uncoiler (1) side that supplies the Ti strip is the front side, and the welding end side, that is, the sizing. The roll (6) side is the rear side, and the number is from this front side.

The tilt angle of the electrode means the angle formed by the electrode and the line drawn perpendicularly to the tubular body at the electrode tip with the tip of the electrode tilted forward and the upper end tilted backward.

First, the results shown in Tables 1 and 2 were obtained when the presence or absence of molten metal rise was examined by variously changing the distance between the electrode tips and the like by test welding using two electrodes.

The materials used in these tests are JIS standard H463.
1 It is a pure titanium for industrial use based on the 2nd type.

Next, except that three electrodes are arranged above the abutting portion of the tubular body, the same conditions as above are taken, and the test welding is performed by variously changing the distance L ₂₃ between the second electrode tip and the third electrode tip. When the presence or absence of rising of the molten metal was examined, the results shown in Tables 3 and 4 were obtained.

The materials used in these tests are JIS H46.
31 Industrial pure titanium based on the 2nd type.

Observing the process of the test welding, the rising phenomenon of the molten metal was observed between the two electrodes when two electrodes were used, and between the second electrode and the third electrode when three electrodes were used. It was confirmed that each of them occurred. It was also found that the rising phenomenon of these melts occurs when the melt on the rear side flows backward when the melts at the molten portion between the two electrodes are connected as a series of melt pools.

From the results shown in Tables 1 to 4, it was found that such a molten metal rise phenomenon is likely to occur as the pipe forming speed increases, the thickness of the Ti pipe increases, and the distance between the electrode tips decreases. did.

Then, the results shown in Tables 1 to 4 were arranged as a function of the distance between electrode tips (L), the pipe forming speed (V), and the wall thickness (T) of the Ti pipe, and the results shown in FIG. 2 were obtained.

That is, as shown in FIG. 2, the melt rise phenomenon is L <0.00.
It occurs in the region of 35VT ^1.5 (A region in the figure). From this, in order to prevent the rise of the molten metal, L ≧ 0.0035VT ^1.5
I found that I needed to.

However, if L> 70 (region B in the figure), the tips of the electrodes are too far apart from each other and the heat input efficiency is deteriorated, and also a problem arises in the shielding property by Ar gas. L> 0.0070VT
^{At 1.5} +20 (C region in the figure), the heat input efficiency deteriorates and the advantage of using multiple electrodes disappears. Furthermore, L <10
In the region (D area in the figure), the tips of the electrodes are too close to each other, the interference of the arc is intense, and the welding becomes unstable.

Therefore, in order to prevent the molten metal from rising and to obtain a satisfactory weldability, the distance between the last two electrode tips should be
We came to the conclusion that it is necessary to make settings so that equations (I) and (II) are satisfied.

0.0035VT ^1.5 ≤ L ≤ 0.0070 VT ^1.5 +20 (I) 10 ≤ L ≤ 70 (II) In the above-mentioned conventional steel pipe welding method using multiple electrodes, the molten parts of each electrode are connected to form a series of molten metal pools. The distance between the tips of the electrodes was set to be relatively short so as to form them. However, in welding of Ti pipes, a unique phenomenon of molten metal rise occurs, so rather it was found that it is necessary to avoid integration of the molten metal pool and to set different setting conditions from the conventional one.

As described above, the inventors first grasped the proper arrangement condition of the plurality of electrodes that prevents the interruption of welding due to the rising of the molten metal and enables high-speed pipe making.

Then, under the above-mentioned electrode arrangement conditions, for the purpose of grasping an appropriate welding current condition for increasing the pipe forming speed and still obtaining a high quality welding bead, various welding currents etc. given to a plurality of electrodes are changed to perform test welding. I went. The pipe forming apparatus used for this test welding is the one shown in FIG.
As the shield gas, Ar gas was used as described above.

When the bead quality of the weld beads formed by these test weldings was examined, the results shown in Table 5 were obtained.

Regarding the weld bead quality, the thickness of the center part of the bead (Tc) measured on the cross section of the weld bead and the inner bead width (W
Pass / Fail judgment was made for each of i), and C outer bead flatness measured on the outer circumferential surface of the weld bead.

Explaining this, Fig. 4 is a schematic view of the weld bead cross section, where T is the wall thickness of the pipe (mm), Tc is the wall thickness of the center of the bead (m).
m) and Wi are the inner bead width (mm), Wo is the outer bead width (mm), and the measurement of the weld bead cross section is performed by measuring the dimensions corresponding to the respective portions in FIG. FIG. 5 is a schematic view of the profile of the circumferential surface of the weld bead measured with a surface roughness meter, and the flatness of the outer bead is the concave portion size (in relation to the straight line connecting both points of the outer bead). δ ₁ )
And the convex dimension (δ ₂ ), that is, δ ₁ + δ
Evaluation is performed with a value of ₂ (μm).

And, regarding the thickness (Tc) of the central portion of the ibid, T ≦ Tc
With ≦ T + 9/100 (mm), (B) Inner bead width (Wi)
With respect to 1.5, and with respect to the bead flatness (F) of C, F ≦ 60 (μm).

Note that these judgment reference values are such that cracks occur in the weld bead portion in the flare test performed to evaluate the weld bead quality of the welded Ti pipe, and noise occurs in the ultrasonic flaw detection test due to wall thickness variation. It was set with a shape condition that does not.

From the results shown in Table 5 above, good results were summarized as a function of the total welding current (It) applied to the electrode, the pipe making speed (V) and the Ti pipe wall thickness (T). The results shown in the figure were obtained.

That is, the total welding current (It) for obtaining a good welding bead as plotted by circles, triangles and squares in FIG.
There is a relationship of 0.09VT ^1.5 + a, and their distribution is 30 ≦ a
The range was ≦ 130.

Then, in the region where It = 0.09VT ^1.5 +130 (Y region in the figure), the inner bead width (Wi) becomes excessively larger than 2.5 mm, that is, the total welding current (It) becomes excessive, and
In the region of less than 0.09VT ^1.5 +30 (region X in the figure), the inner surface bead width (Wi) is less than 1.5 mm, that is, the total welding current (It) is too small.

Therefore, in order to obtain a good welding bead that satisfies the above criteria, the total welding current (It) given to multiple electrodes should be
We have come to the conclusion that it must be within the range that satisfies the formula (II).

0.09VT ^1.5 + 30 ≦ It ≦ 0.09VT ^1.5 +130 (III) On the other hand, when the outer surface bead flatness (F) is examined in detail, the test Nos. 5, 6, 9, 10, 11, 1 shown in Table 5 are shown.
The external bead flatness (F) was unacceptable under the conditions of 8, 21, 27, and 32, and these are related to the distribution of the welding current (If) to the final electrode, and If ≤ 0.5 Im. When and if ≧ Im, it fails even if the other judgment factors are good.

These have a function of forming the final bead shape due to insufficient welding at the final electrode due to the welding current (If) of the final electrode being too small because the outer bead has a convex shape when If ≦ 0.5 Im. It is judged that the welding current of the final electrode was excessive due to undercuts and roughening of the bead surface when If ≧ Im. Finally, it became clear that it depends on the distribution of the welding current (If) of the final electrode.

Therefore, in order to obtain the outer bead flatness that satisfies the above-mentioned criteria, the welding current (If) given to the final electrode is as follows (IV)
We came to the conclusion that the formula needs to be satisfied.

0.5 Im ≦ If ≦ Im (IV) As described above, in relation to the pipe forming speed (V) and the pipe wall thickness (T), the distance between the electrode tips (L) is set to the above (I), (II ), And the total current (It) given to the electrode is
Welding current applied to the final electrode within the range that satisfies equation (I)
By setting (If) in the range that satisfies the above (IV), it becomes possible to increase the pipe forming speed of the Ti pipe by using a plurality of electrodes and to obtain a high-quality weld bead.

〔Example〕

FIG. 6 shows an embodiment in which a Ti tube is welded and formed by using two electrodes.

In FIG. 6, the results plotted in ○ and × marks are the results of the internal tests No. 1 to 15 of the welding results shown in Table 5 above, and the welding current (I ₁ ) of the first electrode and the second electrode Welding current (I ₂ )
It is shown in the relationship with.

As conditions other than the welding current (I ₁ , I ₂ ), the pipe forming device is as shown in FIG. 3 described above, the pipe forming speed (V) = 6 m / min, the pipe wall thickness (T) = 0.49 mm, Tube diameter = 25.4 mm, distance between electrode tips (L) =
The angle of inclination was 40 mm and the inclination angle of the two electrodes was 20 °, which were constant. The material to be welded is pure titanium (JIS: H4631).
Second type).

Also, what is plotted with □ in Fig. 6 is 0% by weight.
The results are shown in Table 6 below, which was obtained by welding a titanium alloy containing 8% Ni and 0.3% Mo (ASTM: B338 Grade 12) under the same conditions as the pure titanium.

In addition, the line segment shown in FIG. 6 is 0.09VT ^{1.5 in} relation to the above-mentioned pipe making speed (V) and pipe wall thickness (T), where I ₁ = −I ₂ +215.
+30 and I ₁ = -I ₂ +315 is 0.09VT ^1.5 +130, I ₁ = I ₂
Is synonymous with Im = If, and I ₁ = 3I ₂ is synonymous with 0.5 Im = If.

From the results of each welded pipe shown in the plot of FIG. 6 and the observation of the process, each region of a to g in the figure will be explained. The region of d-a-e satisfies the formula (III) of the present invention. The range of f−a−g is the range satisfying the formula (IV) of the present invention, and therefore the region a is the proper welding current range of the present invention satisfying the formulas (III) and (IV). . Further, as shown by the plot in the figure, the weld beads of the pipe welded in this welding current range have all passed the determination,
It will be appreciated that the range is adequate for welding Ti tubes.

The following problems were mainly observed in areas other than region a.

In the b-f-d region, the inner bead width, which was determined to be due to the shortage of the total welding current, tended to be too small.

In the c-g-c region, it was observed that the inner bead width, which was determined to be due to the excess of the total welding current, tended to be excessive.

It is recognized that the outer bead tends to be convex in the area d, and the outer bead flatness tends to be poor, and the undert is likely to occur in the area e to cause the outer bead flatness to be poor. It was found that this is caused by the welding current being too low or too high.

As for the titanium alloy, as shown in the plot of FIG. 6, satisfactory results were obtained with the welding current in the region a, but the inner bead width tended to be slightly smaller than that of pure titanium. Therefore, it is desirable to select the total welding current on the higher side within the above range.

FIG. 7 is a schematic view showing an electrode arrangement of an example in which the tilt angles of a plurality of electrodes are investigated in the Ti pipe welding method according to the present invention.

In FIG. 7, (15) is 5 pairs of squeeze rolls, and the squeeze rolls (15) are the same as those of the pipe forming apparatus shown in FIG. Further, (11) is a tubular body, the tubular body (11) proceeds in the direction of the arrow in the figure, Ti band plate by the breakdown roll and fin pass roll arranged in front of the squeeze roll (15). Is formed by curving in the plate width direction.

(7) is two electrodes, the electrode (7) is the tubular body (11)
Of the squeeze rolls (15) arranged on the center line of the squeeze rolls (15).

θ ₁ is the tilt angle of the first electrode, θ ₂ is the tilt angle of the second electrode, and L ₁₂ is the distance between the first electrode tip and the second electrode tip.

With the above arrangement, the distance L ₁₂ between the electrode tips is 20 mm.
Alternatively, it was fixed to 30 mm, the inclination angle θ ₁ of the first electrode was changed, welding was performed, and the effect was investigated and examined.

Other conditions are pure titanium (JIS: H463
1 type 2), pipe wall thickness (T) = 0.7 mm, pipe diameter = 25.4 mm, first electrode welding current (I ₁ ) = 300 A, second electrode welding current (I ₂ ) = 20
The setting was 0 A and the pipe forming speed (V) = 10 m / min.

The results shown in Table 7 were obtained by these investigations.

As shown in Table 7, when the inclination angle θ ₁ of the first electrode is on the negative side, that is, the electrode tip faces the non-supply side of the tubular body and the upper part of the electrode is inclined to the supply side, humping is performed. A bead (a phenomenon in which an intermittent spot pattern is formed on the outer surface of the bead portion) occurred.

It should be noted that the occurrence of molten metal swelling, which is indicated by X in Table 7, is observed. This is because when the welding conditions are examined, the electrode tip distance L ₁₂ is 0.0035 VT ^1.5 or less. .

In addition, since the same tendency was observed when the humping beat was generated when three electrodes were used, the inclination angle of the first electrode should be 0 ° or more.

The distance between the tips of the multiple electrodes is 10 mm to 70 mm.
As a result, and by arranging in an octagonal shape, the upper parts of them are in contact with each other and cannot be arranged substantially. It is desirable that the inclination angle be 15 ° to 30 °.

Moreover, it is desirable to select these inclination angles in the direction of increasing the inclination angle as the pipe making speed increases. However, when this inclination angle exceeds 45 °, a new problem such as arc instability in practice arises. To do.

Therefore, the tilt angle of the electrode should be set in the range of 0 ° to 45 °, preferably in the range of 15 ° to 30 ° and in harmony with the pipe making speed.

〔The invention's effect〕

As described above, according to the present invention, a high quality weld bead is obtained by welding the abutting portion of the tubular body formed from the titanium or titanium alloy strip with a plurality of electrodes satisfying these conditions. It is possible to improve the pipe making speed to a width, and for example, in the case of welding pipe making with a single electrode, the limits are 3.5 m / min (wall thickness 1 mm or less) and 1.5 m / min (wall thickness of about 1.5). The former is 10 m / min, and the latter is 5 m / min, and the pipe-making speed can be improved to more than double speed, respectively, and a great effect can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the total welding current (It) of the present invention and VT ^1.5 . FIG. 2 is a graph showing the relationship between the electrode tip distance L and VT ^{1.5 according to} the present invention. FIG. 3 is a schematic view of a pipe forming apparatus used for carrying out the present invention. FIG. 4 is a schematic sectional view of a weld bead. FIG. 5 is a schematic view of the profile of the outer bead surface measured. FIG. 6 is a graph showing the relationship between the welding current I ₁ of the first electrode, the welding current I ₂ of the second electrode, and the pass / fail result of the example. FIG. 7 is a schematic diagram showing the two-electrode arrangement of the embodiment. FIG. 8 is a schematic view showing a conventional pipe forming apparatus. FIG. 9 is a front view showing a conventional welding device. FIG. 10 is a perspective view showing a conventional welding device. F ... Strip plate, 1 ... Uncoiler, 2 ... Forming roller,
3 ... Breakdown roller, 4 ... Fin pass roller, 15 ... Squeeze roll, 6 ... Sizing roll, 7 ... Electrode, 8 ... Detection roll, 9 ... Probe, H
... Holder, I ... Current controller, S ... Speed detector, T ... Plate thickness measuring instrument.

Claims (1)

[Claims] 1. A TI or a plurality of non-consumable electrodes having a longitudinal abutting portion of the tubular body arranged thereon to form a tubular body by curving a strip plate made of titanium or a titanium alloy in the plate width direction.
In the method of manufacturing a tube by G welding, the final side 2 of the plurality of electrodes arranged above the abutting portion
The distance (L) between the electrode tips of the book is set within the range that satisfies the following expressions (I) and (II), and the total welding current (I
t) within the range that satisfies the following formula (III), and the welding current (If) given to the final electrode among the plurality of electrodes is
A method for producing a tube made of titanium or a titanium alloy, characterized in that the content is within the range that satisfies the formula (V). 0.0035VT ^1.5 ≤ L ≤ 0.0070VT ^1.5 +20 ...... (I) 10 ≤ L ≤ 70 ...... (II) 0.09VT ^1.5 +30 ≤ It ≤ 0.09VT ^1.5 +130 ...... (III) 0.5 Im ≤ If ≤ Im ...... ( IV) However, L: Distance between electrode tips (mm) V: Pipe forming speed (mm / min) T: Pipe wall thickness (mm) It: Total welding current (A) If: Welding current of final electrode (A) Im : Average welding current per electrode (A)