JPS63149077A - Manufacture of pipe composed of titanium or titanium alloy - Google Patents

Abstract

PURPOSE:To obtain the welding bead of high quality by making the distance between the electrode tips at the final side among plural electrodes arranged at the upper part of a butt part, the total welding current given to the plural electrodes and the welding current given to the final electrode within the range satisfying the specified inequality respectively. CONSTITUTION:The strip plate consisting of titanium or titanium alloy is made a tubular body and the pipe is made with TIG welding by the plural nonconsumable electrodes arranging the butt part in the longitudinal of the tubular body. In this case, the distance L between the tips of two electrodes at the final side among plural electrodes is made within the range satisfying inequalities I, II and the total welding current It give to the plural electrodes is made within the range satisfying the inequality III. And the welding current If given to the final electrode among the plural electrodes is made within the range satisfying the inequality IV. Whereas, L: distance mm between tips of electrode, V: pipe making speed mm/min, T: pipe thickness mm, It: total welding current A, If: welding current A of final electrode, Im: mean welding current per each electrode.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a TIG welded pipe manufacturing method using multiple electrodes that improves the pipe manufacturing speed, and in particular, the distance between the electrode tips and the arc tangent current applied to the electrodes are adjusted appropriately. The present invention relates to a method for manufacturing a pipe made of titanium or a titanium alloy (hereinafter collectively referred to as Ti), which can increase the pipe manufacturing speed by setting within a certain range.

[Prior art] In manufacturing welded Ti pipes, for example, a strip plate is continuously curved in the width direction of the plate using a tube forming apparatus shown in FIG. The abutting portions of the formed tubular bodies are continuously welded using a TIG welding machine.

In FIG. 8, (II) is an uncoiler, and the uncoiler (II) is a supply source for the Ti strip (2).

(2) is a forming roll, and the forming rolls (2) are arranged in pairs on a base (6), and the pair rotating horizontally and the pair rotating vertically alternately. It is arranged. Please note that these forming rows/v (2) are uncoiler (
II) Breakdown row/v (8) to form the supplied strip (IV) into a U-shape, fin bath roll (4) to form it into a 0-shape, and Squeeze row holding both ends as butt parts for interrogation /l/
(5), and squeeze row /L/ (sizing row 1v (6) which is welded by the TIG welding machine (7) installed above 51 and finishes the friend pipe to a predetermined outer diameter dimension).

Said uncoiler (II) and molding row/L' (2)
The semi-strip plate (IV) is formed into a tubular body using the above-mentioned tube forming device, and is welded using a TIG welding machine installed above the squeeze throw/l/ (5). It becomes a Ti tube.

Note that the TIG welding machine described above has conventionally used a single-electrode type.

On the other hand, when manufacturing steel pipes or stainless steel pipes, a method of TIG welding using multiple electrodes is known, and various proposals have been made regarding the specific method. Welding device disclosed in Japanese Patent Publication No. 56-28629 and Japanese Patent Publication No. 53-34771 shown in FIG.
The following is a proposal for a welded steel pipe cracking method, etc., as disclosed in No.

In FIG. 9, which shows a welding device according to the former prior art (proposed in Japanese Patent Publication No. 56-28629), (4υ is a tubular body, and the tubular body G1D is a thin steel strip formed by forming a ring Oη. The object to be welded is curved in the width direction of the plate and moves in the direction of the arrow in the figure.

(42 is a welding head, and the welding head (47J) is supported by a holder MQ and is movable and adjustable in the vertical and horizontal directions at right angles to the tubular body CD.

K3, (441, 49 are non-consumable 1! electrodes, and these three electrodes [3C4 (c)) are arranged on the same straight line and held by the welding head (42).

Further, the second electrode 94 placed in the center is held by the welding head 03 so as to be perpendicular to the tubular pair @0, and the first electrode (c) and third electrode (c) placed in front and behind the second electrode 94 are held at right angles to the tubular pair @0. are oblique to the second electrode I, and each support portion (411
It is held by the welding head (43) so as to be pivotable about the fulcrum, and is connected to the
The inclination angle with respect to the second electrode (2) can be finely adjusted.

The former prior art welding device has the above-mentioned configuration so that the fused portion formed by the first and third electrodes is connected to the fused portion formed by the second electrode during the welding operation. It is adjustable and allows welding of thin-walled steel pipes by dividing and supplying the welding current with these three electrodes and forming a series of bath melt pools with the three electrodes. be.

In addition, in FIG. 10, which shows the method for welding steel pipes according to the latter conventional technique (proposed in Japanese Patent Publication No. 53-34771), (II) is a tubular body, and the tubular body t5'I) is The object to be welded is a steel strip plate that is curved in the width direction by a pair of forming rolls.

(52) is a pair of fin bath rolls, and here the final pair of a series of forming roll groups such as breakdown rolls and fin bath rolls, respectively, is illustrated.

(50#('')eφ5) are pairs of squeeze rows, and here, the pair of squeeze rolls (54) placed in the center are used to give the maximum squeeze to the tubular body φ0. There is.

(56), (5 force, 0g), (59) are non-consumable electrodes, and these electrodes (i6) (57) (54 (5
9) are arranged above the abutting portion of the tubular body (51), which is the welded body.

In addition, these electrodes (56) (57) (sa)φ9)
Among them, the preceding three trees are arranged in front of the squeeze row Iv (54) that gives the maximum squeeze to the tubular body,
and a squeeze roll (where the molten part formed by the last electrode (5th day) among the three electrodes gives the maximum squeeze)
The center point of 54) is also noted as being located in the front.

The electrode (59) placed behind the squeeze throw/I/(54) is used to correct the shape of the weld bead surface or to heat the weld boundary, and is used to completely penetrate the weld bead. is not considered to be involved.

This latter method of manufacturing a bath contact tube, which is a prior art technique, involves arranging three or more pairs of squeeze rows μ and arranging a plurality of electrodes in front of the squeeze row p that gives the maximum squeeze.
It suppresses the reaction force generated in the butt part of the tubular body to be welded in the direction of the outer circumferential direction of the tube, and prevents the occurrence of microcracks and undercuts due to the reaction force, thereby achieving a welding speed of 2m/m1KI or more even for high alloys such as stainless steel. It is possible to weld pipes at high speeds.

[Problem that the invention seeks to solve]

The inventors of the present invention have been diligently researching the technology to produce Ti pipes of high quality and at high speed by welding. We focused on the TIG welding method using electrodes and tried to apply it to the production of Ti pipes to improve the pipe manufacturing speed.

This is because, in the conventional Ti tube welding method using the single-electrode 1TIG welding machine mentioned above, a large welding current must be applied to a single electrode in order to obtain sufficient penetration at the butt part of the tubular body traveling at high speed. First, it is difficult to delicately harmonize the large current supplied to this single electrode with the traveling speed of the tubular body, etc., and as a result, the welding current may become too high, causing arc penetration, or may become too low, resulting in poor welding. This single-electrode welding has the disadvantage of causing fatal defects in the quality of the pipe products, such as the occurrence of bead undercuts. For pipes, the speed is 3.5 m/min, and the Ti wall thickness is about 5 mm.
Please note that the pipe production speed of 1 m/min is considered to be the limit. )
There was a practical restriction on increasing the value above that level.

However, it was expected that these problems could be avoided even at high speeds by dividing the welding current to multiple electrodes.

However, when we tried the multi-electrode TIG welding method proposed for steel pipes or stainless steel Q-tubes on Ti pipes, we discovered that the pipe forming speed was increased using the single-electrode TIG bath welding machine, and the following problems occurred. However, in addition to this, welding interruption due to embankment of the molten metal resistance (a phenomenon in which the molten metal in the rear molten part of the leading electrode overflows the embankment, shorting with the succeeding electrode and making it impossible to continue welding) ) or the bath welding bead becoming unstable.

On the other hand, Ti pipes made by bath welding are usually used in the welded state, so the welds have a bead shape.

In other words, particularly strict requirements are placed on the quality of the weld bead of pipe products. Among the factors that determine the quality of the weld bead, the particularly important factors shown in Fig. 4, which is a schematic cross-sectional view of the weld bead, are ■TC: bead center wall thickness, ■Wi:
Inner bead width, ■WO: Outer bead width, etc.@
External bead flatness.

In addition, important manufacturing condition factors that affect the bead quality of the welded Ti pipe mentioned above include pipe forming speed, pipe wall thickness, bath contact current, electrode inclination angle, etc. When using multiple electrodes, It has become clear that in addition to manufacturing condition factors, the distance between the tips of each electrode and the distribution of bath contact current to each electrode are important factors.

In view of the above problems, the present invention aims to ensure weld bead quality by grasping the appropriate electrode arrangement of multiple electrodes and the appropriate bath contact current conditions to be applied to each electrode in relation to pipe manufacturing speed and pipe wall thickness. The purpose of the present invention is to provide a technology for manufacturing tubes made of titanium or titanium alloys that can improve the speed of tube manufacturing.

[Means for solving problems]

A method for manufacturing a tube made of titanium or a titanium alloy according to the present invention to solve the above problems is to curve a strip plate made of titanium or a titanium alloy in the width direction of the plate to form a tubular body, and to In a method of manufacturing a tube by TIG welding a directional abutting part using a plurality of non-consumable electrodes arranged above the abutting part, the distance between the tips of the last two electrodes among the plurality of electrodes arranged above the abutting part ( IV) below (I)
, within a range that satisfies formula (II), and the total bath contact current (I t) given to the plurality of electrodes is within a range that satisfies formula (II) below, and the final electrode among the plurality of electrodes is It is characterized in that the applied welding current (If) is within a range that satisfies the following equation (Q'V).

0.0035VTL5≦L≦(L0070VTL5+2
O------(II) 10≦L≦70
・・・・・・(II) 0.09VT +30≦It
≦0.09VTL5+130 ・−・−(In)Q,
5 Im ≦If≦ r m”
@) However, L: Distance between electrode tips (mn1) ■
: Pipe manufacturing speed (rnm/m1 n) T: Pipe wall thickness (Innl) It: Total contact current (A) If: Welding current of final electrode (A) m= Average welding current of each electrode ( A) [Function] In order to solve the above problem, the present inventors studied welding conditions, especially the distance between the tips of multiple electrodes, the welding current applied to each electrode, etc. in relation to pipe forming speed and pipe wall thickness. A friend who goes to

The present invention will be explained below along with the research history.

The tube forming apparatus used for the test welding is shown in FIG. 3.

In FIG. 3, % (II) is an uncoiler, and the uncoiler (II) supplies the Ti strip (IV) to the tube forming apparatus.

(2) is a forming roll, the forming roll /l/(2
) is Breakdown Low/L' (8), Finba Low ~ (4).

Squeeze row/L' (Is and sizing row/L'
(6), etc., and these have basically the same configuration as shown in FIG. 8 above, except for the arrangement of the tube forming apparatus and the number of squeeze rolls αυ.

In addition, five pairs of squeeze rows /l/(2) were arranged in order to minimize the influence of springback of the tubular body at various test tube manufacturing speeds.

(b) is an electrode holder, the electrode holder (b)
holds a plurality of electrodes arranged above the butt part of the tubular body, the distance between the tips of each electrode and the inclination angle can be adjusted, and the electrodes can be moved in the vertical and horizontal directions as a unit. And so.

(The mark is a speed detector, which detects the moving speed of the tubular body by measuring the rotation of the detection row 1v (8).

■ is a plate thickness measuring device, and this measuring device (T) is a forming row A
/ Non-contact ultrasound probe (9) placed in front of (2)
The thickness of the Ti strip (IV) was measured at .

(I) is a current controller, the current controller (I) controls a welding power source (IV) for each electrode (γ),
The welding current given to each electrode (7) was adjusted and set respectively.

A Ti strip (IV) was formed into a tubular body with the configuration shown in Fig. 3 above, and the abutting part was tested under various conditions using multiple electrodes (7) arranged above the abutting part. Performed welding.

During test welding, the area near the welding point was seeded with Ar gas to prevent oxygen from entering the weld bead on the inner and outer surfaces of the tube.

In the test welding, we first determined the electrode arrangement conditions that would solve the problem that arose when applying the conventional technology related to the above-mentioned ferrite and alloy to bath welding of Ti pipes, namely, interruptions in welding due to molten metal build-up. I went there for the purpose.

In addition, the electrode numbers (for example, the first electrode, the second electrode, etc.) described hereinafter refer to the welding start side, that is, the above-mentioned uncoiler (II) side that supplies the Ti strip, and the welding end side, that is, the above-mentioned uncoiler (II) side that supplies the Ti strip. With the sizing row/l/(6) side as the rear, use this front side number.

Further, the inclination angle of the electrode refers to the angle between the electrode and a line drawn perpendicularly to the tubular body at the electrode tip when the electrode tip is tilted forward and the upper end is tilted backward.

First, the presence or absence of molten metal build-up was investigated by conducting nine test weldings using two electrodes, varying the distance between the electrode tips, etc., and the results shown in Tables 1 and 2 were obtained.

The materials used in these tests conform to JIS standard H463.
It is an industrially pure titanium based on Type 2.

(Leaving space below) 1st Table V: Pipe manufacturing speed ×: Frequent occurrence of embankment for each bath ○: No bath embankment θl: Inclination angle work of the first electrode 1: Bath contact current of the first electrode ■Snow: Second Welding current Ixl of the electrode Distance between the first electrode tip and the second electrode tip However, the inclination angle of the second electrode θ depth - 30° Tube wall thickness T - α 7 mm Tube diameter - za 4 mm.

Table 2 ×: Molten metal heaping force generated ○: Molten metal heaping process 1: Welding current of the first electrode ■2: Welding current L1 of the second electrode! : Distance between the first electrode tip and the second electrode tip. Tilt angle θ1 of the second electrode. s=g300 Pipe wall thickness TmQ, 7 mm Pipe diameter -25.4 mm Pipe forming speed V wal Q m/min.

Next, test conduction was performed under the same conditions as above except that three electrodes were arranged above the abutting part of the tubular body, and by variously changing the distance Lax between the second electrode tip and the third electrode tip. When the presence or absence of molten metal heaping was investigated, the results shown in Tables 3 and 4 were obtained.

The materials used in these tests meet the JIS standard H46.
It is industrially pure titanium based on Type 2 No. 31.

(Leaving space below) Table 3 ■ : Pipe manufacturing speed × : Bath water heaping force generation ○ : n Hot water heaping up welding 1: Welding current of the first electrode ■t: Welding current of the second electrode 3: The welding current of the second electrode Welding current L for 3 electrodes! 3: Distance between the second electrode tip and the second electrode tip However, tube wall thickness Ts*Q, 7m+n, tube diameter = 25.4 mm
The distance between the first electrode tip and the second electrode tip is sm3Qmm.

The inclination angles of the first, second and third electrodes were all 30°.

Table 4: Pipe making speed × : Molten metal heaping occurs ○ : Molten metal heaping does not occur ■1: Welding current of 1st electrolysis ■ :: Welding current of 211th pole 3: 31st! Pole bath contact current L! 3: Distance between the tips of the second electrode and the tip of the second electrode However,
Pipe wall thickness: L6mm, pipe diameter: -25.4rnm.

The distance between the first electrode tip and the second electrode tip is -3Qmm.

The inclination angles of the 1st, 2nd, and 31J poles were all 30°.

When we observed the above test welding process, we found that the molten metal build-up phenomenon occurred between the two electrodes when two electrodes were used, and between the second and third electrodes when three electrodes were used. It has been confirmed that both occur. It has also been found that the molten metal heaping phenomenon occurs when the molten metal bath between the two electrodes is connected as a series of molten metal pools, and the molten metal on the rear side flows backwards.

From the results in Tables 1 to 4, it can be seen that the faster the tube manufacturing speed is, the thicker the wall of the Ti tube is, and the shorter the distance between the electrode tips, the more likely this phenomenon occurs. There was found.

Therefore, the results in Tables 1 to 4 are used as the distance between electrode tips (IV),
The results shown in FIG. 2 were obtained when the results were summarized as a function of the pipe forming speed (IV) and the Ti pipe wall thickness ('r).

In other words, as shown in Figure 2, the molten metal build-up phenomenon is α0
035VTL5 area (A area in the figure)
It turned out that it was necessary to set it to 35VT.

However, if L > 70 (region B in the figure), the electrode tips will be too far apart, which will not only deteriorate the heat input efficiency (there will also be problems with the shielding performance due to Ar gas. Also, if L > 0.0
070VTL5+20 <region f)C in the figure) As the temperature increases, the heat input efficiency deteriorates and the advantage of using multiple electrodes disappears. Further, when L<10 (region D in the figure), the electrode tips are too close together, resulting in severe arc interference and unstable g-contact.

Therefore, in order to prevent the molten metal from building up and to obtain satisfactory weldability, the distance between the final two electrode tips should be set as follows (+
), (I came to the conclusion that it is necessary to set it so that the formula 0 is satisfied.

Q, 0035VTL5≦L≦0.0070VTL5+
2O------(I) 10≦L≦70
(II) In the conventional copper pipe welding method using multiple electrodes described above, the distance between the tips of each electrode was set relatively short so that the molten part of each electrode was connected to form a series of molten metal pools. . However, because a unique phenomenon of bulging of the bath water occurs when connecting the Ti pipe to the bath, it was found that it was necessary to avoid integrating the bath pool and to set conditions different from conventional ones.

As mentioned above, the inventors first understood the conditions for proper arrangement of multiple electrodes to prevent welding interruptions due to molten metal build-up and to enable high-speed pipe manufacturing.

Under the above-mentioned electrode arrangement conditions, we conducted test welding by varying the welding current applied to multiple electrodes in order to determine the appropriate welding current conditions that would increase the tube manufacturing speed and still obtain high-quality weld beads. I did it. The tube forming device used for this test welding is the one shown in Figure 3 above.
Further, as the shielding gas, Ar gas was used as described above.

The bead quality of the bath-welded beads formed by these test welds was examined, and the results shown in Table 5 were obtained.

Regarding the weld bead quality, the bead center wall thickness (To) and O inner bead width (Wi) measured at the weld bead cross section, and θ outer bead measured at the circumferential outer surface of the weld bead. Pass/fail judgment was made for each level of flatness.

To explain this, Fig. 4 is a schematic cross-sectional view of a bath welding bead, where is the tube wall thickness (mm), TO is the bead center wall thickness (mm), Wi is the inner bead width (mfn), and W
o indicates the outer bead width (mm), and the cross section of the weld bead is measured by measuring dimensions corresponding to the respective portions in FIG. 4. Figure 5 shows that the flatness of a weld is evaluated by the sum of the concave dimension (δ1) and convex dimension (δ2) with respect to the straight line connecting the points on both sides of the outer bead, that is, the value of δ1 + δ (μl11). .

Regarding the thickness of the bead center portion (Tc) mentioned above, T
≦Tc≦T +9/100 (mm), (
Regarding the inner bead @ (Wi), 1.5rii≦2.
5 (mm), the outer bead flatness (I
Regarding V), F≦60 (μnt) was defined as an acceptable range.

These criteria values are based on cracks occurring in the weld bead during the flare test conducted to evaluate the quality of the weld bead of welded Ti pipes, noise caused by wall thickness variation, and noise during the ultrasonic deep damage test. It was set with shape conditions that would not cause the problem to occur.

(Leaving space below) According to the results shown in Table 5 above, the one that gave good results was the total welding current (It) #pipemaking speed flash and Ti
When organized as a function of tube wall thickness (II), the results shown in FIG. 1 were obtained.

In other words, as plotted with circles, triangles, and squares in Figure 1, the total welding electric power K (It) to obtain a good weld bead is:
The relationship is It-αOgv'r +a, and their distribution is in the range of 30≦a≦130.

Soshite, zt-+109 VT L5+ 1 ao
When it comes to the super L region (Y region in the figure), the inner bead width (
Wi) is excessive to 25 mtn or more, that is, the total bath contact current (It) is excessive, and t is It-0,09VT.
In the region below +30 (X region in the figure), the inner bead width G'Vi) becomes too small by l,5 mm or less, that is, the total bath contact current (It) becomes too small.

Therefore, in order to obtain a good bath contact bead that satisfies the above-mentioned criteria, it is concluded that the total bath contact current (I t) given to multiple electrodes needs to be within a range that satisfies the following formula (If). reached.

0.09VTL5+30≦It<0.09VTL5+1
30---(II) On the other hand, the outer bead flatness (IV
), the test results shown in Table 5 are as follows:
6,9,10°11.18,21,27. The outer bead flatness (IV) failed under the following conditions:
When ≧Im, even if the other judging factors are good, the test has failed.

These are caused by the fact that the outer bead takes on a convex shape when If≦α5Im, and also by the fact that the bathing current (If) of the final electrode is too small and the bathing at the final electrode is insufficient, and the final bead shape is formed. -17jIf≧Im
At this time, it is determined that the welding current of the final electrode was excessive due to the occurrence of undercuts and roughness on the bead surface, but in any case, the outer bead flatness is ultimately determined by the bath contact of the final electrode. It became clear that it depends on the distribution of current (work 0.).

Therefore, in order to obtain an outer bead flatness that satisfies the above criteria, the parallel current (If) given to the final electrode is:
It was concluded that it is necessary to satisfy the following formula (IV).

0.5 Irn≦If≦Im
... Song QV) In relation to the pipe forming speed (to) and the pipe wall thickness (°C), the distance between the electrode tips (L) is calculated from the above (I) and (II).
), and the total current applied to the electrodes (
By setting I t) within a range that satisfies the above formula and setting the bath contact current (I f) given to the final electrode within a range that satisfies the above (II), it is possible to form Ti pipes using multiple electrodes. It becomes possible to increase the speed and obtain a high quality weld bead.

〔Example〕

FIG. 6 shows an example in which a Ti tube is connected and formed using two electrodes.

In Figure 6, what is plotted with O and It is shown in relation to the bath contact current (Step 2).

The conditions other than the n-contact current (II1, Iz) are as follows:
Showa 6m/min, pipe wall thickness (II) = α49mm, pipe diameter -
25.4mm, distance between electrode tips (IV) -4Qm
m and the inclination angle of the two electrodes were kept constant at −20°. The material to be welded is pure titanium (JIS: H4631 2nd
species).

In addition, the 0 mark plotted in Figure 6 indicates that the weight percentage is 0.
．． Titanium alloy containing 8% Ni and α3% MO (ASTM:
B538Grada 12) was welded under the same conditions as the pure titanium described above, and the results are as shown in Table 6 below.

Table 6 Wi-J: Inner bead width pass/fail, Tc-J: Bead center thickness pass/fail, F-T: Outer bead flatness pass/fail.

O: Pass, ×: Fail.

I engineering: Solution chamber bff of the first core pole, ae2: Welding current of the second core pole (other conditions are the same as in Table 5). The line segments shown in Figure 6 indicate the above pipe forming speed ( V) and tube wall thickness ■, Is --Iz-1-21
5 is Q, 09VT +30 and l1m-1x+31
5 is 0.09VT"'+130, ItsIx is I
tnwm engineering f and Isrw31x are α5Im-If
are synonymous with each other.

Based on the results of each bath welded pipe manufacturing shown in the plot of FIG. Within the range that satisfies the equation (!I) of the present invention, the region of f - a - g is a range that satisfies the formula (! It is. In addition, as shown in the plot in the figure, all weld beads of raw pipes manufactured within this bath contact current range passed the judgment, and this range is appropriate for welding Ti pipes. One thing will be understood.

In areas other than area a, the following problems were mainly observed.

In the b-f-b region, there was a tendency for the inner bead width to be too small, which was determined to be due to a lack of total welding current.

In the region of ・-g-・, there is a tendency for the inner bead width to become excessive, which is considered to be caused by an excess of total welding current.

In the region d, the outer bead tends to have a convex shape, which tends to cause poor flatness of the outer bead, and in the region e, underdots tend to occur, resulting in poor flatness of the outer bead. It turned out that the problem was caused by the welding current of the two electrodes being too low or too high.

As for the titanium alloy, as shown in the plot in Figure 6, satisfactory results were obtained for all welding currents in the a region, although it was observed that the inner bead width tended to be slightly smaller than that of pure titanium. Therefore, in practice, it is desirable to select the total bath contact current on the higher side within the above range.

FIG. 7 is a schematic diagram showing the electrode arrangement of an example in which the inclination angles of a plurality of electrodes were investigated in the Ti tube welding method according to the present invention.

In FIG. 7, αθ is five pairs of squeeze rows p, and the squeeze rows/I/aS are the same as those of the tube forming apparatus shown in FIG. 3 above. Ill is a tubular body, and the tubular body α advances in the direction of the arrow in the figure, is arranged in front of the squeeze row fi/(to), and by nine breakdown rows μ and fin pass rows, Ti band plate It is molded by curving it in the board width direction.

(A) is two electrodes, the electrode (A) is arranged above the abutting part of the tubular body αυ, and the tip of the second electrode is arranged in the center of the squeeze row/L' (to). It is arranged so that it is on the center line of the object.

θ1 is the inclination angle of the first electrode, whereas LIz is the inclination angle of the second electrode, and LIz is the 11th! The distance between the pole tip and the second electrode tip is shown.

With the above arrangement, the distance between the electrode tips Ll! 2Q
The influence of bath contact was investigated by fixing it at mm or 3 Q + nm and changing the tilt angle θ1 of the first electrode.

The other conditions are that the material is pure titanium (JIS: H463
1 Type 2], Pipe wall thickness (T) = Q, 7 mm,
Pipe diameter x 2j% 4mm, first electrode welding current (I
s) = 30OA, welding current of the second electrode (Iri-2o
oA, pipe forming speed (V) = 10 m/min.

These investigations yielded the results shown in Table 7.

(Leaving space below) Table 7 ○: Healthy bead Δ: Humping bead occurrence ×; Bath water heaving occurrence θ1: Inclination angle of the first electrode θ2: Inclination angle of the second electrode As shown in Table 7, When the inclination angle θ1 of one electrode is on the negative side, that is, the tip of the electrode faces the opposite supply side of the tubular body, and the upper part of the electrode falls toward the supply side, a humping bead (intermittent spots on the outer surface of the bead) appears. A phenomenon in which a spotted pattern is formed) occurred.

Incidentally, in Table 7, the occurrence of molten metal bulges indicated by x marks is observed, but when examining the conduction conditions, it can be seen that this is because the distance Lss between the electrode tips is equal to or less than α0035VT.

Since a similar tendency was observed in the occurrence of humping beats when three electrodes were used, the inclination angle of the first electrode should be 0° or more.

Furthermore, the distance between the tips of multiple electrodes is 1 Q mm to 70 mm, and arranging them in a square shape means that the upper parts of each electrode are in contact with each other, and it is virtually impossible to arrange the electrodes, and the above-mentioned test welding Based on our experience, it is desirable that the plurality of electrodes be arranged in parallel, that is, at the same angle of inclination of 15° to 30°.

It is also desirable to select these angles of inclination so that they become larger as the pipe manufacturing speed increases, but if this angle exceeds 45°, new problems such as instability of the arc arise in practical use. do.

Therefore, the inclination angle of the electrode should be set in a range of C or more and 4r or less, preferably in a range of 15° or more and 30° or less, and should be set in harmony with the pipe forming speed.

〔Effect of the invention〕

Fortunately, according to the present invention, by bath-welding the abutting portions of tubular bodies formed from titanium or titanium alloy sheets using multiple electrodes that satisfy these conditions, a high-quality bath-welded bead can be obtained and still be large. It is possible to greatly improve the pipe manufacturing speed. 3.5 for welded pipe making
m/mjl+ (wall thickness 1mm or less), 1°5 rn/
It is possible to obtain great effects, such as increasing the pipe-making speed by more than twice as fast as 8rn/mil for the former and 5 m/min for the latter, which was considered to be the limit of rniu (wall thickness L5). .

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the total welding current rt and vTL5 of the present invention. FIG. 2 is a graph showing the relationship between the distance between electrode tips and VTL5 of the present invention. FIG. 3 is a schematic diagram of a tube forming apparatus used in carrying out the present invention. Figure 4 is a schematic cross-sectional view of a weld bead. Figure 6 shows welding 1 of the first electrode in the example! A graph showing the relationship between flow II, welding current 2 of the second electrode, and pass/fail results. FIG. 7 is a schematic diagram showing the two-electrode arrangement of the embodiment. FIG. 8 is a schematic diagram showing a conventional tube forming apparatus. FIG. 9 is a front view showing a conventional welding device. FIG. 1O is a perspective view showing a conventional welding device. F--Strip plate, 1--Anchoy two, 2--Forming roller, 3--Plain down row, 4--Finn bath loaf, 15--Squeeze roll, 6--Sizing roll, 7... Electrode, 8... Detection low A/
, 9... probe. H...Holder, ■...Current controller, S...
・Speed detector, T...Plate thickness measuring device. VT “5 (IIM257min) Fig. 2 5.000 10,000 15,000”
5(””/min)

Claims (1)

[Claims] A strip plate made of titanium or a titanium alloy is curved in the width direction of the plate to form a tubular body, and the longitudinal abutting portion of the tubular body is TIGed by a plurality of non-consumable electrodes arranged on the longitudinal abutting portion of the tubular body. In the method of manufacturing a pipe by welding, the distance (L) between the tips of the two final electrodes among the plurality of electrodes arranged above the abutting part is set within a range that satisfies the following formulas (I) and (II). The total welding current (It) given to the plurality of electrodes is given below (I
Made of titanium or a titanium alloy, the welding current (If) given to the final electrode among the plurality of electrodes is within a range that satisfies the following formula (IV). Method of manufacturing tubes. 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) 0.5Im≦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 each electrode (A)