JP2005279664A - Method for joining mash seam joined tube of titanium-made or titanium alloy-made tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mash seam joining method of a titanium-made or titanium alloy-made joined tube in which generation of welding defects is suppressed, and a joined part of high quality can be obtained. <P>SOLUTION: In the mash seam joining method of the titanium-made or titanium alloy-made joined tube in which a titanium plate or a titanium alloy plate is formed in a tube, parts of both ends overlap each other, and the overlapped part is joined, a rotary electrode is arranged so as to be brought into contact with an outer surface of a tube, a metal bar whose length is not less than the total length of the tube and whose outside diameter is ≥ 1/2 of the inside diameter of the tube, and below the inside diameter of the tube is arranged so as to be brought into contact with the inner surface of the tube, and the overlapped part is joined by turning and moving the rotary electrode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a joint pipe made of titanium and a titanium alloy plate that is often used in a condenser of a thermal power / nuclear power plant, a heat transfer pipe of a multi-stage evaporation type seawater desalination plant, a heat exchanger of an oil refining or petrochemical plant, etc. The present invention relates to a mash seam joining method.

As a method of manufacturing joint tubes made of titanium and titanium alloys that are commonly used in condensers for thermal power and nuclear power plants, heat transfer tubes for multi-stage evaporation seawater desalination plants, heat exchangers for petroleum refining and petrochemical plants, etc. Many TIG welding methods are used.
When producing a welded pipe by welding an unmelted electrode type TIG arc welding of a titanium plate and a titanium alloy plate, as shown in FIG. 3, the end face of the workpiece (test body 1) is butted in an argon gas atmosphere, An arc discharge 8 is generated between the object to be welded (test body 1) and the tungsten electrode 6 disposed so as to face the object to be welded (test body 1), and the object to be welded (test body 1) is butt welded with the heat generated at that time. TIG arc welding provides a simple and high-quality welded joint, making it ideal for welding thin steel plates, especially stainless steel thin plates. In fact, titanium plates that easily oxidize when exposed to high temperatures and oxidizing atmospheres in the atmosphere. Also suitable for welding titanium alloy plates.
However, TIG arc welding is merely fusion welding, and in order to suppress undercuts and ensure good welding, there is an upper limit on the welding speed, productivity is low, and welding costs greatly increase the cost of pipes. In addition, it is sensitive to groove fluctuations due to gaps such as gaps, and if the gap is too wide, it tends to melt off, and depending on the groove properties, blow holes due to argon gas are likely to occur, resulting in poor yield. As a result, the cost of the pipe is further increased.

Currently, visual inspection is performed for burn-through, and X-ray transmission tests are performed for blowholes, so that defective products are selected and excluded, and only non-defective products are shipped. However, it is not definitive if 100% defective products can be excluded. There is a problem such as increasing the inspection cost when trying to increase the inspection accuracy, and some measures are required for quality assurance of the product.
On the other hand, as shown in FIG. 2, mash seam joining is conventionally used as a method for joining tin cans having a diameter of about 50 mm or more, a can length: about 200 mm or less, and a plate thickness of about 0.3 mm, such as a beverage steel can. Many methods are used. This mash seam joining method secures an energizing path by sandwiching a joining can 1 overlapped at a certain interval between a pair of electrode wheels (upper electrode wheel 2 and lower electrode wheel 3), and raises the temperature by resistance heating. This is solid phase bonding that is crushed by plastic flow. At this time, the current density governing resistance heat generation and the pressure density governing plastic flow are parameters that affect the joining, but it is the overlap that governs both these parameters under a constant welding current and force. is there. The superposition allowance and the control of the pressure applied to the electrode wheel influence the mash seam joining phenomenon.

Also, in Patent Documents 1 and 2, etc., a method of mash seam joining a titanium plate and a titanium alloy plate is also known, but these methods both press-mold a joint joint produced by butt welding a steel plate. The present invention relates to joining of tailored blank materials for automobiles.
However, joint pipes made of titanium and titanium alloy plates, which are often used in condensers for thermal power and nuclear power plants, heat transfer tubes for multi-stage evaporation seawater desalination plants, heat exchangers for oil refining and petrochemical plants, etc. Is as small as about 30 mm and the tube length is as long as about 15 mm. When considering the application of the mash seam welding method to such a joined pipe, it is necessary to insert the lower electrode ring 3 smaller than the inner diameter of the joined pipe at least inside the joined pipe. There is a limit to making the lower electrode 3 small. For example, the smaller the lower electrode 3 is, the more insufficient the pressurizing force becomes at a convenient time. Therefore, it has been difficult to apply the conventional mash seam welding method to such a heat exchanger titanium tube having a small tube inner diameter.
Japanese Patent Application No. 2002-111968 Japanese Patent Application No. 2000-290879

  The present invention relates to a mash of titanium and titanium alloys that are often used in condensers for thermal power and nuclear power plants, heat transfer tubes for multi-stage evaporation seawater desalination plants, heat exchangers for petroleum refining and petrochemical plants, etc. As a seam joining method, it is an object to provide a mash seam joining method for titanium and titanium alloy joining pipes, which can suppress the occurrence of welding defects as compared with conventional seam and can obtain a high-quality joint.

This invention solves the said subject, and the place made into the summary is the following content as described in the claim.
(1) In a mash seam joining method in which a titanium plate or a titanium alloy plate is formed into a tubular shape and part of both end portions are overlapped, and then the overlapped portion is joined, a rotary electrode is provided so as to contact the outer surface of the tube. A metal rod having a length that is equal to or greater than the entire length of the tube and that has an outer diameter that is 1/2 or more of the inner diameter of the tube and less than the inner diameter of the tube so that the inner surface of the tube is in contact with the inner surface of the tube; A method for joining mash seams of titanium or titanium alloy tubes, wherein the overlapping portions are joined together.
(2) The mash seam joining method for titanium or titanium alloy tubes according to (1), wherein the metal rod is made of copper.
(3) The mash seam joining method for a titanium or titanium alloy tube according to (1) or (2), wherein the inner diameter of the tube is 10 mm or more and 50 mm or less.
(4) The mash seam joining method for a titanium or titanium alloy tube according to any one of (1) to (3), wherein the total length of the tube is 0.2 m or more and 30 m or less.

  According to the present invention, a condenser tube of a thermal power / nuclear power plant, a heat transfer tube of a multi-stage evaporation type seawater desalination plant, a joint tube made of titanium and a titanium alloy often used for a heat exchanger of an oil refining or petrochemical plant, etc. When using the mash seam joining method, generation of welding defects is suppressed, and a high-quality joint can be stably obtained.

Embodiments of the present invention will be described below with reference to the drawings.
In the present invention, a condenser of a thermal power / nuclear power plant, a heat transfer pipe of a multi-stage evaporation type seawater desalination plant, a joined pipe made of titanium or a titanium alloy often used for a heat exchanger of an oil refinery or a petrochemical plant, etc. In addition, in order to join a small diameter and long joining tube having an inner diameter of 50 mm or less and a length of 200 mm or more with high quality, as shown in FIG. 1, it has been used for the lower electrode 5 by the conventional mash seam joining method. It has been devised to achieve both power feeding and ensuring rigidity by changing the rotary electrode to a fixed rod electrode (lower electrode rod 5). That is, according to the present invention, in a mash seam joining method in which a titanium plate or a titanium alloy plate is formed into a tubular shape (test body 1), a part of both ends are overlapped, and then the overlapped part is joined. The rotary electrode (upper electrode ring 1) is arranged so as to be in contact, and the length is not less than the entire length of the tube and the outer diameter is not less than 1/2 of the tube inner diameter and less than the tube inner diameter so as to contact the inner surface of the tube. A metal bar (lower electrode bar 5) is disposed, and the rotary electrode is rotated to join the overlapping portions. The welding power source in FIG. 1 is connected to the upper electrode wheel 1 and the lower electrode rod 5, and is energized and pressurized between the specimens 1 that are in contact with the upper electrode wheel 1 and the lower electrode rod 5 at the time of joining. It is used to heat and press the overlapped part in a heated state.

In the present invention, the length of the metal rod, which is a fixed electrode, is stable in the overlapping portion of the tube that is in contact with the rotating electrode (upper electrode ring 1) and the metal rod (lower electrode rod 5) during welding. In order to energize and perform good pressure bonding, the length needs to be equal to or greater than the total length of the pipe.
Also, if the outer diameter of the metal rod is less than 1/2 of the inner diameter of the tube, the weld deformation of the tube cannot be accommodated within the elastic range when pressurized from the upper electrode during mash seam joining. The lower limit of the outer diameter of (lower electrode bar 5) was set to ½ of the inner diameter of the tube, which is a practical limit. On the other hand, the upper limit of the outer diameter of the metal rod (lower electrode rod 5) is determined according to the inner diameter of the tube to be manufactured, and the maximum outer diameter of the metal rod that can be inserted into the tube is less than the inner diameter of the tube.
In a conventional mash seam, when a rotary electrode is used as a lower electrode and a pipe having a small pipe diameter is joined, the rotation radius of the rotary electrode as the lower electrode is reduced, so that the total length of the pipe is 200 mm or more. However, sufficient rigidity cannot be obtained for joining by the cantilever method, and the cantilever supporting the rotating electrode as the lower electrode is bent, and mash seam joining becomes impossible.

On the other hand, the above-described method of the present invention suppresses generation of welding defects and welding deformation as compared with the conventional case when welding a small-diameter / long-sized joining pipe having a minimum inner diameter of 10 mm and a maximum length of 30 m, for example. It is possible to manufacture a titanium or titanium alloy tube that can provide a simple joint.
In the method of the present invention, the lower limit of the pipe inner diameter to be joined is set to 10 mm in consideration of the minimum size that can be manufactured industrially. On the other hand, the upper limit of the inner diameter of the pipe is set to 50 mm as the upper limit of the size at which the quality improvement effect of the joint cannot be fully expected by the method of the present invention by the conventional mash seam welding method.
In the method of the present invention, there is no particular upper limit on the total length of the pipes to be joined, but 30 m is set as industrially meaningful. On the other hand, the lower limit of the total pipe length is the minimum size that can be manufactured industrially, and the conventional mash seam welding method cannot be expected to improve the quality of the joint. Considering the minimum size, the lower limit of the total length of the pipe was set to 200 mm.
In the present invention, the material of the metal bar (lower electrode bar 5) is preferably copper having high thermal conductivity and high-temperature strength characteristics in terms of the function of current heating as an electrode for mash seam welding.

The effects of the method of the present invention will be described below with reference to examples.
After forming a 0.5 mm thick titanium plate shown in Table 1 into a tubular shape, the present invention and conventional mash seam joining and TIG welding were performed under the joining conditions shown in Tables 1 and 2. In addition, each mash seam joining performed overlap joining with the overlap shown in Table 1, and TIG welding performed butt welding. Table 2 also shows the results of measuring the number of burn-outs during joining, the occurrence rate of blowhole defects in the joints of the joined pipes, and the occurrence of tube shape defects.

In addition, about the blowhole, since the generation | occurrence | production condition and size were discriminate | determined from the X-ray transmission photograph and it confirmed that the size was about 0.1 mm, it evaluated by the generation | occurrence | production number per unit line length. Moreover, about the burn-through, the occurrence state was grasped by an appearance test, and the occurrence number per unit length of the joining line was evaluated.
Implementation Nos. 1, 2, 6, 7, 11 and 12 were mash seam joined under the conditions satisfying the conditions defined in the present invention. There was no occurrence of blowhole defects, and a titanium tube having a good joint was obtained.
On the other hand, in Examples Nos. 3, 8 and 13, mash seam bonding was performed under conditions that deviated from the lower limit of the outer diameter of the metal rod, which is the lower electrode defined in the present invention. Although no blowhole defect occurred in the joint, the tube did not return while being plastically deformed, and the roundness could not be secured, resulting in a defective shape.
In Examples Nos. 4, 9, and 14, mash seam joining was performed using a rotating electrode as a conventional lower electrode (without using a metal rod), so that the cantilever was bent at a convenient time, resulting in poor contact with the electrode. The energization path could not be secured, and crimping joining became impossible.
Since execution No. 5, 10 and 15 joined using the conventional TIG welding method, the welding part melted down and the blowhole defect incidence rate of the joined part became high, and the quality defect of the joined part arose.

It is a figure which shows the aspect which uses a metal bar for a lower electrode in order to manufacture a small diameter joining pipe | tube by the mash seam joining of the titanium plate and titanium alloy plate by this invention. It is a figure which shows the aspect which manufactures the joining pipe | tube by the mash seam joining conventionally used. It is a figure which shows the aspect which manufactures the welded pipe of a titanium plate and a titanium alloy plate by TIG arc welding which is the fusion bonding conventionally used.

Explanation of symbols

1 Test Specimen 2 Upper Electrode Wheel 3 Lower Electrode Wheel 4 Welding Power Supply 5 Lower Electrode Rod 6 Tungsten Electrode 7 Welding Power Supply 8 Arc

Claims (4)

In a mash seam joining method in which a titanium plate or a titanium alloy plate is formed into a tubular shape and part of both end portions are overlapped, and then the overlapped portion is joined, a rotary electrode is disposed so as to contact the outer surface of the tube, A metal rod having a length not less than the entire length of the tube and having an outer diameter not less than 1/2 of the tube inner diameter and less than the tube inner diameter is disposed so as to contact the inner surface of the tube, and the rotary electrode is rotated to move the overlap. A method for joining mash seams of titanium or titanium alloy pipes, characterized in that joining portions are joined.   The mash seam joining method for titanium or a titanium alloy tube according to claim 1, wherein the metal rod is made of copper.   The method for mash seam joining of titanium or titanium alloy tubes according to claim 1 or 2, wherein the inner diameter of the tube is 10 mm or more and 50 mm or less.   The mash seam joining method for a titanium or titanium alloy tube according to any one of claims 1 to 3, wherein the total length of the tube is 0.2 m or more and 30 m or less.

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