JP2008023555A - Welding method for making tube of metal having large spring back - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding method for making a tube of metal having a large spring back capable of preventing generation of microcracks in a surface of a weld bead of an inside surface of the tube, and consistently executing the high-speed welding for making the tube. <P>SOLUTION: At a forward position of a squeeze roll 2 for executing the welding, the gap width between end faces 4 of butted parts is increased by using a fin roll having a fin 11. The butted parts are tightly fitted to each other at a squeeze point 2C by pressing the squeeze roll 2 to increase the angle on the butt-inlet side in front of the squeeze roll and to decrease the angle on the butt-outlet side behind the squeeze point, respectively. In an extensive area behind the squeeze point 2C, the gap width between the end faces 5 of the butted parts is decreased as being away from the squeeze point, and as a result, generation of microcracks in the surface of the weld bead can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for continuously forming a pipe by butt-welding both end faces of a hoop using a squeeze roll while rolling a metal hoop having a large spring back into a cylindrical shape by roll forming.

  In the metal tube-forming welding method, a method is used in which a metal strip hoop is rolled into a cylindrical shape by roll forming, and both ends of the hoop are butt-welded using a squeeze roll to continuously form a tube. When a metal having a large spring back is formed, even if both end faces of the hoop are brought into contact with each other by the squeeze roll, the butt may be opened by the spring back on the downstream side of the squeeze roll.

  FIG. 1 and FIG. 2 are schematic views for explaining the influence of a spring back acting on a welded portion when pipe-forming welding is performed using a general squeeze device. When making a thin metal plate with a small Young's modulus and high yield strength, such as titanium, the butt can be brought into close contact at the squeeze point 2C by pressing the rounded hoop with the squeeze roll 2 as shown in FIG. However, the property of opening the butt before and after the squeeze point 2C, that is, the spring back is strong. In FIG. 1, the rear end face 5 is in a state opened by a springback. When rolling a long hoop of such a thin metal plate into a cylindrical shape by roll forming, the two edge surfaces of the plate are brought into close contact with each other using a squeeze roll 2, and the butted portions are welded to form a continuous pipe. The spring back acts before the solidification of the portion is completed, and as shown in FIG. 3, a fine crack 19 having a width on the order of several μm to several tens of μm is formed on the surface of the central portion in the width direction of the pipe inner surface weld bead. In some cases, a material having a larger springback is more likely to be expressed. Also, this phenomenon does not occur when the final solidification position of the melted part is close to the squeeze point because pressing with a squeeze roll is effective, but if the final solidified position of the melted part moves away from the squeeze point, Cracking occurs because the action is weakened. For example, as shown in FIG. 2B, if the shape of the melted portion is 7 when the pipe making speed is low, the final solidified position of the melted portion is close to the squeeze point 2C. Although pressing works effectively, when the pipe making speed increases, the welding heat input increases with the speed increment, so the size of the molten pool expands, and it is formed when the pipe making speed is high. Like the shape 8 of the melted part, the final solidification position of the melted part moves away from the squeeze point. As a result, the above-described fine cracking phenomenon is likely to occur.

  Conventionally, to solve this problem, by arranging a plurality of small diameter rolls in the tube forming axis direction using a restraining jig, the spring back of the material is suppressed, and a straight region with a minimum amount of butt gap is secured and welded. Pipe making method (Patent Document 1: Multiple diameter squeeze device with small diameter rolls) and pipe making method (Patent Document 2: Warm heating construction) to reduce the spring back of the material by pipe making welding with the tubular body heated Tube method), and further, a method of reducing spring back during butt welding by alternately forming the left and right regions of the material into a small radius at the roll forming stage before butt welding (Patent Document 3: Asymmetric bending) Pipe making method) has been proposed. All of these proposals are aimed at minimizing the springback of the material. However, all of these proposals have a special dedicated jig, forming roll structure, heat treatment, etc. It is necessary to incorporate equipment, and applying these special equipment to various pipe sizes involves engineering difficulties and requires a large capital investment, which is not an economical solution. In addition, neither method completely suppresses the action of the springback to zero.

  As shown in FIG. 4, the present inventors also arranged a squeeze roll 2 ′ having a very small diameter so as to be as close as possible to the rear of the squeeze roll 2, and pressed down the spring back in the vicinity of the final solidification position of the melting part. We have devised a method and tried it, but it is difficult to control the amount of squeeze in order to prevent the above-mentioned fine cracks from occurring and to obtain a good bead shape. Is difficult and has not yielded satisfactory results.

  On the other hand, a method of dealing with this problem by contriving the condition surface of welding can be considered.

  That is, the welding torch position is set to the 1 ′ point upstream of the squeeze point 2C, and the molten part is moved forward to form the molten part shape 9 formed by the welding torch 1 ′. This is a method of bringing the solidification position closer to the squeeze point 2C, and a schematic diagram is shown in FIG. According to this method, although cracking due to springback is mitigated, the gap amount at both end faces of the butt increases as it goes upstream from the squeeze point. There is also a limit. For example, in the case of a thin-walled titanium tube with a thickness of 0.5 mm, in order to maintain a sound weld quality without melting through, the movable distance of the welding torch position is limited to a range of several mm to a maximum of about 10 mm. Therefore, a great improvement by this method cannot be expected.

  Although the combination of the above-mentioned forming and conventional technologies related to welding can be expected to have a synergistic effect of preventing microcracking on the pipe inner surface weld bead surface, the effect of springback cannot be completely suppressed, and in the future It is expected that the technical limits will be exposed in the demand for higher strength materials and higher pipe forming speeds. In addition, as a countermeasure, both proposals require that special welding jigs, complicated forming roll structures, heat treatment equipment, etc. be incorporated in the conventional welding tube line. Applying to is accompanied by engineering difficulties and requires a large amount of capital investment, which is not an economical solution. In addition, when both ends of the plate are in close contact using a squeeze roll with a strong springback material and the abutting part is welded to make a continuous pipe, in principle, the end edge surface is the most suitable for the welding target position. Adjacent to the close squeeze point must be adopted. In this case, for example, in TIG welding, it is necessary to pass through the narrow part where the flanges of the squeeze rolls are closest to each other and irradiate the TIG arc with the aim of the butted part. At this time, the distance between the TIG arc and the squeeze roll flange is extremely short, and the TIG arc falls into an unstable state. In severe cases, the TIG arc is shorted to the squeeze roll flange. To do. In addition, due to the high temperature of the squeeze roll caused by the proximity of the TIG arc, it may lead to troubles in equipment and quality, but the proposal of an effective solution for these problems is Not done.

JP 09-216094 A Japanese Patent Publication No. 01-054122 Japanese Patent Publication No. 05-05373

  The present invention proposes an effective method for preventing fine cracks generated on the inner surface of a pipe inner weld bead in pipe making welding of a welded pipe made of a metal-like hoop having a large spring back such as titanium. The application range is not particularly limited to the steel type, plate thickness, and pipe diameter of the pipe material. The present invention also provides means for avoiding the adverse effects of arc instability and high temperature of the squeeze roll, which are caused when the distance between the welding arc and the squeeze roll flange used in the pipe-forming welding of the weld pipe is close. For the purpose. The present invention basically uses a conventional welded pipe-making line, and aims to obtain a large improvement effect by remodeling of an extremely small facility.

The gist of the present invention for solving the above problems is as follows.
(1) In a pipe making and welding method in which a metal belt-like hoop having a large spring back is rolled into a cylindrical shape, both ends of the hoop are brought into close contact with each other using a squeeze roll, and butt-welded to continuously make a pipe. A method of pipe-welding a metal with a large spring back, characterized in that the gap width between the butted end faces of the hoop before entering the squeeze roll for carrying out welding is expanded by the fins of the finned roll.
(2) In the pipe-forming welding method according to (1), the pipe-welding method for a metal with a large spring back is characterized in that a target position for welding is set within the following range.
0mm ≦ L ≦ 25mm
However, L represents the distance (mm) from the squeeze point of the squeeze roll which performs welding to the back welding target position.

  That is, as shown in FIG.6 (c), the present inventors expand the gap width between the butted end faces of the hoop before entering the squeeze roll for performing welding by the fins 11 of the finned roll, Without damaging or deforming the abutting portion, the entry side angle of the abutting portion end surface 4 ahead of the squeeze point 2C is enlarged, and conversely, the exit side angle of the abutting portion end surface 5 behind the squeezing point 2C is reversed. Experiments have found that it is possible to reduce the size. As a result of earnest and experiment, it is clear that this effect reduces the gap width of the butt portion in a wide area behind the squeeze point 2C, and as a result, can prevent the occurrence of fine cracks on the surface of the weld bead. became.

  In addition, since the gap width of the butt portion is reduced in a wide area behind the squeeze point 2C, a weldable area where no melt-down occurs and fine cracks on the weld bead surface do not occur is the squeeze point. Enlarged backwards. As a result, problems with equipment and quality caused by arc instability and temperature rise of the squeeze roll, which have been caused by the close distance between the welding arc and the squeeze roll flange, have been This can be solved by arranging the torch position backward.

  In the present invention, a metal having a large spring back is a metal having a proof stress (unit MPa) × 1000 / Young's modulus (unit MPa) of 1.40 or more. Specifically, pure titanium (JIS type 1 and type 2), stainless steel (SUS304), and the like can be mentioned.

  According to the present invention, in the case of continuous welding pipe making of a metal with a large spring back, a fine cracking of the pipe inner surface weld bead surface is prevented, and a manufacturing method that enables high-speed and stable welding pipe forming is provided, industrially, It can have a beneficial effect.

  The best mode for carrying out the present invention will be described below with reference to FIGS. 6, 7, and 8.

  First, a method for reducing the gap width of the butted portion in the region behind the squeeze point 2C will be described with reference to FIGS. In the present invention, the abutting portion is brought into close contact at the squeeze point 2C using the squeeze roll 2, and the fin portion 11 and the plate holding portion 13 are formed between the abutting portion end surfaces 4 of the hoop before entering the squeeze roll 2. 6 (b), FIG. 6 (c), and FIG. 8 are arranged between the hoop end faces of the butted portion, and the gap width is set as shown in FIG. It expands from 4a of (not arranged) to 4a ′ of FIG.

  As a result, the entry side angle of the abutting portion end face 4 ahead of the squeeze point 2C is enlarged, but at this time, the exit side angle of the abutting portion end face 5 rearward from the squeeze point 2C is reduced, and as a result, the squeeze point The gap width of the abutting portion at the rear is 5a or 5b in FIG. 6A where no finned roll is arranged, but as shown in 5a ′ and 5b ′ in FIG. 6C, respectively. A tendency to narrow was confirmed.

  This phenomenon occurs when the position 12 where the fin portion 11 in FIG. 6 (b) contacts and expands the hoop end surface is the “power point” and the squeeze point 2C where the butted portion is in close contact is the “fulcrum”. This can be easily explained by considering the behavior of the abutting portion behind the squeeze point, which is the “action point”, according to the “principle of”.

  When the principle of the present invention is considered in this way, the effect of the present invention is brought about as a reduction in the butt gap width in the rear region of the squeeze point. The thickness of the fin to be inserted is increased, and the other is to reduce the distance F between the force point 12 and the squeeze point 2C as a fulcrum.

  However, when an extremely thick fin is inserted, or when the distance F between the force point 12 and the squeeze point 2C is extremely short, the material is severely bent, resulting in damage to the end face of the butt portion or the butt shape. Defects such as deformation may occur, which may adversely affect welding. Therefore, when actually applying the present invention, it is necessary to determine the fin thickness and the fin insertion position so as not to be excessively bent in consideration of the material, plate thickness, pipe diameter, etc. of the material hoop to be formed. There is.

  The present inventors have used two types of outer diameter φ20 mm pure titanium welded pipe hoop materials having a plate thickness of 0.5 mm and 1.4 mm, and set the butt gap width before and after the squeeze roll while making a pipe without welding. An experiment was conducted to confirm the effect of reducing the gap width behind the squeeze by using the finned roll by measuring using a CCD camera. During the experiment, the fin thickness was changed from 2.9 mm to 6.5 mm, and the position where the fin was inserted was changed from a position 80 mm away from the squeeze point to a position 140 mm away, and the influence and appropriate range were searched. did.

  Table 1 shows the results. By expanding the gap between the butt end faces of the hood before entering the squeeze roll using a finned roll, the butt gap width at the position 30 mm behind the squeeze has been reduced, confirming the effect of the present invention. It was. Further, it was proved that the effect of reducing the gap width behind the squeeze is greater as the fin thickness is thicker and the position where the fin is inserted is closer to the squeeze point. In Table 1, the W value calculated using the thickness of the fin and the distance from the fin insertion position to the squeeze point is defined as an index that can predict the improvement effect by the fin insertion. The gap at the butt end face at the fin position when the fin is used is 4a ', the gap when the fin at the same position is not used is 4a, and the gap enlargement ratio Ga is defined as Ga = 4a' / 4a. The distance between the fin action point 12 and the squeeze point 2C is defined as F, and W is defined as W = Ga / F. In the experiment, a relationship that the gap width behind the squeeze is reduced as the W value increases is obtained. However, it was also confirmed that when the fin thickness is too thick or the fin insertion position is too close to the squeeze point, the butt shape is deformed.

  From the above experimental results, an appropriate range of fin thickness and fin insertion position was extracted for each of two pure titanium welded pipe hoops having different plate thicknesses. For example, when the plate thickness is 0.5 mm, the preferable range of W is 0.013 to 0.022. Moreover, when plate | board thickness is 1.4 mm, the suitable range of W is 0.018-0.026.

  Regarding the structure of the roll with fins, the plate part 11 plays the role of suppressing the butt shape defect such as offset by pressing the tube surface near the butt part in a well-balanced manner with the fin part 11 that plays the role of expanding the end face of the butt part. The fin roll is a mechanism that smoothly rotates so as not to cause seizure with the material. As the roll material, the fin portion 11 is a portion that easily wears due to intense contact with the material, so that it is desirable that the surface is hard. A hardened SKD 11 or a super hard roll may be used if the cost permits. . The plate holding part 13 may be made of the same material as that of the fin part. However, a copper alloy is applied as a countermeasure in order to easily damage the product value in the pipe making of the titanium hood which is easily seized with steel because the pipe surface is liable to generate flaws. is doing. The receiving roll 14 is disposed on the opposite side of the finned roll with the tubular body interposed therebetween, and plays a role of supporting the pressing load by the finned roll from below. It is preferable to use a rotating structure similar to the finned roll, and use the same material as the plate holding portion 13.

  Since the hoop material with a large spring back and the pipe making speed are high, when the conventional pipe making and welding method has caused fine cracks on the surface of the weld bead, the present invention uses the above method to reduce the squeeze point. Since it is possible to reduce the gap width of the rear butting portion, as shown in FIG. 7, when the molten pool 17 is formed using the welding torch 1, the weld bead surface is formed at the end position 17 ′. It became possible to prevent the occurrence of fine cracks.

  Further, the effect of the present invention can be obtained by greatly expanding the weldable range, which was conventionally limited to an extremely narrow range near the squeeze point, to the rear of the squeeze point. That is, in the wide area behind the squeeze point, the gap width of the abutting portion is reduced, so that the position of the welding torch is arranged as 1 ″ in FIG. Even if the welding is performed at a different position, the melt-off does not occur easily, and the fine cracks on the surface of the weld bead are less likely to occur. It was possible to solve problems in terms of equipment and quality caused by arc instability and temperature increase of the squeeze roll, as shown in Fig. 7 (b). The shape of the melted portion is 18 when the shape of the melted portion is 17 and the welding torch position is 1 ″.

  The greater the distance L between the squeeze point 2C and the welding torch 1, the less likely it will be that the arc becomes unstable or the squeeze roll temperature rises. However, if the distance L is too large, the occurrence of fine cracks on the weld bead surface becomes prominent. Therefore, it is necessary to reduce the pipe making speed, and melt-down occurs. Although shown also in the Example, the maximum value of the distance L was set to 25 mm behind the squeeze point from the results of the pipe forming test. In the present invention, the placement of the welding torch in front of the squeeze point welds the butt portion where the gap width is expanded by the action of the fins, so the possibility of occurrence of burnout is extremely high and should be adopted. No. From the above, the distance L was set in the range of 0 mm ≦ L ≦ 25 mm (where L represents the distance (mm) from the squeeze point of the squeeze roll to be welded to the rear welding target position).

  A sufficient improvement effect is already brought about by the above-mentioned form. However, as a method for further improving and improving the improvement effect, as shown in FIG. 9, a pair of squeeze squeeze is newly provided behind the squeeze roll 2 to be welded. You may combine the method of arrange | positioning roll 2 "and pressing down a springback.

  As a welding method applied in the present invention, TIG welding is generally used. However, plasma welding, laser welding, or the like in which the heat source is thinner than TIG can be applied for the purpose of pursuing higher speed. In addition, a welding method using a plurality of torches may be selected because of the necessity of speeding up by preheating and adjusting the bead shape.

  Also in the production of ERW welded pipes, finned rolls are used during pipe making. However, the purpose of using the finned roll is completely different from the present invention. In the present invention, a finned roll is used to expand the gap width between the butt end faces of the hoop before entering the squeeze roll for performing welding. On the other hand, in the manufacture of ERW welded pipes, fin pass rolls are used for finish forming after rough forming by breakdown rolls, and bending and drawing are performed by fin pass rolls. Does not increase the gap width.

  Table 2 shows the case of a pure titanium welded pipe having an outer diameter of φ20 mm and a wall thickness of 0.5 mmt in comparison with the case of pipemaking welding according to the present invention pipe-welded by a conventional method. The same conditions as in Table 1 were adopted for the fin thickness and fin insertion position. Welding was performed using one TIG welding torch. Pipe-forming welding was carried out at five speeds of 6 m / min, 6.5 m / min, 7 m / min, 7.5 m / min, and 8 m / min, and the occurrence of fine cracks on the surface of the weld bead was compared. For the welding torch position, the distance from the squeeze point was changed from 0 mm to the rearward at a maximum pitch of 30 mm at a 5 mm pitch, and the effect on the stability of the arc and the temperature rise of the squeeze roll. The squeeze roll temperature rise is remarkable and the level at which actual damage can occur, ○ indicates that the arc is almost stable, the squeeze roll rises in temperature but within the allowable range, and ◎ indicates no problem.) The occurrence of fine cracks on the weld bead surface was compared. As the welding heat input conditions, optimum conditions were selected for each pipe making speed, and the conventional method and the present invention method were set to the same welding heat input conditions.

  No. 1-No. 3 is a comparative example by the conventional method. As the welding torch position is moved backward from the squeeze point, the fine crack initiation limit speed of the weld bead surface shifts to the low speed side, while the tendency of occurrence of defects due to arc instability and squeeze roll temperature rise has weakened.

  No. 4-No. 6 is an embodiment of the present invention. In any case, the welding torch position is a position aimed at the squeeze point. No. In No. 4, by inserting a 3.5 mm thick fin at a position 100 mm away from the squeeze point, Compared with the conventional method in which no fin 1 is inserted, the fine crack initiation limit speed is improved by 0.5 m / min on the high speed side. No. 5, no. In No. 6, the W value is increased by increasing the thickness of the fin from 3.5 mm to 4.5 mm and 5.5 mm, and the fine crack generation limit speed on the surface of the weld bead is accordingly increased from 7.0 m / min to 7. The speed was further improved to 5 m / min and 8.0 m / min. All of these improvement trends are in good agreement with the results obtained in the experiment of Table 1, and it is confirmed that a certain improvement can be obtained by the present invention.

  No. 7-No. 11 is an example of the present invention. The fin of 5.5 mm thickness same as 6 is used. By using a fin with a thickness of 5.5 mm, the improvement effect of reducing the butt gap width at the rear of the squeeze was great, and the weldable range was expanded to a target position 25 mm behind the squeeze point. No. 6 to No. As the welding torch position is moved backward from the squeeze point to 11, the critical crack generation limit speed on the surface of the weld bead gradually shifts to the lower speed side, but there is a problem due to arc instability or squeeze roll temperature rise. The outbreak trend was improved in stages.

  No. No. 12 also used a fin with a thickness of 5.5 mm, but as a result of separating the welding torch position to 30 mm behind the squeeze point, the melted part melted down. It was presumed that the butt gap width was too wide, so that melt-out occurred, and this was taken as a comparative example in order to show the limit of the effect of the present invention. As described above, it is appropriate that the distance L between the squeeze point and the welding torch is set in a range of 0 mm ≦ L ≦ 25 mm from the result of pipe-forming welding of a pure titanium welded pipe having an outer diameter of φ20 mm and a thickness of 0.5 mmt. Proved.

  No. In Example 13, a thicker 6.5 mm thick fin was used. However, it was found that welding was not stable because the shape of the butted portion was deformed, and melt-off occurred frequently, making pipe-forming welding impossible.

  No. No. 14 The fins with a thickness of 6.5 mm are used as in the case of 13, but the processing level of the butt portion is reduced by separating the fin insertion position from the squeeze point to 140 mm, and the squeeze is made without damaging or deforming the butt portion. Successfully sent to the point. As a result, no. As in the case of No. 4, a sound weld was obtained by pipe forming welding at a speed of 7.0 m / min.

  As described above, in the case of a pure titanium welded tube having an outer diameter of 20 mm and a thickness of 0.5 mm, the improvement effect of the present invention was confirmed.

  Table 3 shows a case of a pure titanium welded pipe having an outer diameter of φ20 mm and a wall thickness of 1.4 mm compared with the case of pipemaking welding according to the present invention pipe-welded by a conventional method. The same conditions as in Table 1 were adopted for the fin thickness and fin insertion position. Welding was performed using one TIG welding torch. Pipe-forming welding was carried out at five speeds of 1.4 m / min, 1.8 m / min, 2.2 m / min, 2.6 m / min, and 3.0 m / min, and microcracking occurred on the surface of the weld bead. Compared. For the welding torch position, the distance from the squeeze point was changed from 0 mm to a maximum of 30 mm at a 5 mm pitch in the same way as in Table 2, and the effect on the arc stability and squeeze roll temperature rise (△ is rarely (It may become unstable, the temperature rise of the squeeze roll is remarkable and the actual damage may occur, ○ is the arc is almost stable, the temperature rise of the squeeze roll is within the allowable range, and ◎ is no problem at all.) Were compared and the occurrence of fine cracks on the surface of the weld bead was compared. As the welding heat input conditions, optimum conditions were selected for each pipe making speed, and the conventional method and the present invention method were set to the same welding heat input conditions.

  No. 1-No. 3 is a comparative example by the conventional method. As the welding torch position is moved backward from the squeeze point, the fine crack initiation limit speed of the weld bead surface shifts to the low speed side, while the tendency of occurrence of defects due to arc instability and squeeze roll temperature rise has weakened.

  No. 4-No. 5 is an embodiment of the present invention. In any case, the welding torch position is a position aimed at the squeeze point. No. In No. 4, by inserting a fin having a thickness of 2.9 mm into a position 100 mm away from the squeeze point, no. Compared to the conventional method in which no fin 1 is inserted, the fine crack initiation limit speed is improved by 0.4 m / min on the high speed side. No. In No. 5, the W value increases by increasing the fin thickness from 2.9 mm to 4.0 mm, and the fine crack initiation limit speed on the weld bead surface increases from 2.6 m / min to 3.0 m / min. And further improved on the high speed side. All of these improvement trends are in good agreement with the results obtained in the experiment of Table 1, and it is confirmed that a certain improvement can be obtained by the present invention.

  No. 6-No. No. 10 is an embodiment of the present invention. The fin of 4.0 mm thickness same as 5 is used. By using a fin with a thickness of 4.0 mm, the butt gap gap width behind the squeeze is greatly improved, and the weldable range is expanded to a target position 25 mm behind the squeeze point. No. 5 to No. As the welding torch position is moved backward from the squeeze point to 10, the critical crack occurrence limit on the surface of the weld bead gradually shifts to the lower speed side, but the problem is due to arc instability or squeeze roll temperature rise. The outbreak trend was improved in stages.

  No. No. 11 also uses a fin with a thickness of 4.0 mm, but as a result of separating the welding torch position to 30 mm behind the squeeze point, the melted part melted off. It was presumed that the butt gap width was too wide, so that melt-out occurred, and this was taken as a comparative example in order to show the limit of the effect of the present invention. As described above, it is appropriate that the distance L between the squeeze point and the welding torch is set in the range of 0 mm ≦ L ≦ 25 mm from the result of pipe-forming welding of a pure titanium welded tube having an outer diameter of φ20 mm and a wall thickness of 1.4 mm. Proved.

  No. In No. 12, a thicker 4.5 mm thick fin was used, but the shape of the butted portion was deformed because it was too strong, welding was not stable, and melt-off occurred frequently, making it impossible to make pipes. .

  No. No. 13 2.9mm-thick fins are used as in 4, but the W value increases when the fin insertion position is brought close to the position of 80mm from the squeeze point. As a result, the W value is approximately equal to 4.5mm. No. using thick fins. As in the case of No. 5, a sound weld was obtained even in high-speed pipe-forming welding at a speed of 3.0 m / min.

  As described above, in the case of a pure titanium welded tube having an outer diameter of 20 mm and a wall thickness of 1.4 mm, the improvement effect of the present invention was confirmed.

It is the schematic for demonstrating the principle of this invention, and is the figure which showed the behavior of the butt | matching part before and behind the squeeze in a conventional method. It is the schematic for demonstrating the mechanism in which a bead surface fine crack generate | occur | produces in the conventional method, (a) is a side view, (b) is a top view. The image figure at the time of carrying out cross-sectional observation of the fine crack of the pipe inner surface of a welding part. Schematic for demonstrating the method of pressing down a spring back using a small diameter squeeze roll as a measure for improving a bead surface fine crack. It is the schematic for demonstrating the method of changing a welding torch position and improving a bead surface fine crack, (a) is a side view, (b) is a top view. It is the schematic for demonstrating the principle of this invention, (a) is a top view which does not have a finned roll, (b) (c) has a roll with a fin, (b) is a side view, (c ) Is a plan view. It is the schematic explaining the Example of this invention, (a) is a side view, (b) is a top view. It is the schematic of the roll with a fin used by this invention, and is AA arrow sectional drawing of FIG. In order to heighten the effect of the present invention, it is a schematic diagram for explaining a method of providing another stage squeeze roll behind the squeeze roll and pressing the spring back, (a) is a side view, (b) is a plan view. is there.

Explanation of symbols

1 welding torch 1 ′ welding torch moved forward 1 ”welding torch moved backward 2 squeeze roll 2C squeeze point 2 ′ small-diameter squeeze roll (for springback suppression)
2 ”additional squeeze roll (3 spring tube for preventing spring back)
4 End face of the butt part at the front of the squeeze roll 5 End face of the butt part at the rear of the squeeze roll 5 'End face of the butt part at the rear of the squeeze roll when using a small diameter squeeze roll to suppress the spring back 5 "Small diameter squeeze to suppress the spring back End face of butt part behind small diameter roll when using roll 6 Shape of melted part formed when pipe making speed is medium 6 '6 butt part end face 7 The shape of the melted part formed when the pipe making speed is low 7 'The size of the spring back that acts on the end of the melted part of 7 is represented by the gap width between the end faces of the butted parts 8 Shape of the melted part formed when the pipe making speed is high 8 'Large spring back acting at the end of the melted part of 8' 8 9 represents the shape of the melted portion formed by the welding torch 1 'moved forward, and the size of the springback acting on the end of the melted portion of 9'9. What is expressed by the gap width between the end surfaces 10 Weld beads 11 Fin portions of the finned roll 12 Positions where the fin portion 11 contacts and expands the hoop end surface 13 Plate restraining portion 14 of the finned roll 14 Receiving roll 4a When not used, the gap width between the butt end faces at the position 12 in front of the squeeze roll 4a ′ is the gap width between the butt end faces at the position 12 when using the finned roll, and is equal to the width dimension of the fin bottom. .
5a Gap width between abutting portion end faces at the rear position of the squeeze roll when no finned roll is used 5a ′ Gap width between the end faces of the abutting section when using the finned roll, Corresponding to the position 5b Gap width between the abutting portion end faces at the further rear position of 5a when the finned roll is not used 5b 'Gap between the abutting portion end faces at the rear position of the squeeze roll when using the finned roll The width corresponding to the position of 5b 17 The shape of the melted part formed by the welding torch 1 aiming at the squeeze point 17 'The size of the spring back acting at the end of the melted part of 17 is between the abutting part end faces 18 Welding torch 1 ”placed behind the squeeze point The shape of the melted part formed by 18 '18 The size of the spring back acting at the end of the melted part of 18 is expressed by the gap width between the end faces of the butted parts. 19 Fine generated on the surface of the center part in the width direction of the pipe inner surface weld bead Crack F Distance between the position 12 where the fin portion 11 is in contact with the hoop end surface and spreads out and the squeeze point 2C: (mm)
L Distance from squeeze point to welding target position: (mm)

Claims (2)

  In a pipe making and welding method in which a metal strip hoop with a large spring back is rolled into a cylindrical shape by rolling, the both ends of the hoop are brought into close contact with each other using a squeeze roll, and butt welding is performed to continuously make a pipe. A metal pipe-forming welding method having a large spring back, wherein a gap width between butt end faces of a hoop before entering a squeeze roll to be implemented is expanded by fins of a finned roll. 2. The method of pipe-forming and welding a metal with a large spring back according to claim 1, wherein a welding target position is set within the following range.
0mm ≦ L ≦ 25mm
However, L represents the distance (mm) from the squeeze point of the squeeze roll which performs welding to the back welding target position.

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