JPS6250207B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a metal clad tube, in which the outer peripheral surface of a metal tube such as a steel tube is coated with a thin metal strip such as a stainless steel plate formed into a tubular shape. Conventional methods for manufacturing metal-clad tubes include, for example, polymerizing both side edges of metal strips formed and coated into a tubular shape on the outer peripheral surface of a metal tube to a predetermined width, and heating and welding the overlapped portions by applying an electric current. Alternatively, a thin metal strip is formed into a tubular shape and both edges are butt welded by high frequency welding or TIG welding to separately produce a coated metal pipe and a metal pipe such as a steel pipe, and the inside of the coated metal pipe is There is an insertion method in which a metal pipe such as a steel pipe is inserted and the two are brought into close contact. However, the former method of polymerization welding has disadvantages in that the appearance of the welded portion is not good and the weld strength is not excellent. In addition, when using the latter insertion method, especially when the cladding metal tube is welded by TIG welding, the appearance of the welded part is good and the welding strength is excellent, but the overall welding strength of the metal cladding tube is It has the disadvantage that the manufacturing process is very complicated. That is, in this case, the inner metal tube and the outer coated metal tube are manufactured separately, and there is an insertion process in which the metal tubes are inserted one by one into the coated metal tube, and a fitting process in which a spout for drawing is attached. Then, in order to prevent the coated metal tube from being scratched during drawing, a compound coating is applied and the tube is pulled out and shaped using a draw bench, etc., and then the bend is removed using a straightening machine, the compound is washed off, and the opening is removed. The manufacturing process is complicated and requires a lot of effort.

The problem with this insertion method is that it complicates the manufacturing process.The metal tube and metal strip are fed at a predetermined speed along the axial direction of the metal tube, and the metal strip is attached to the outer circumferential surface of the metal tube using forming rolls. This problem could be solved by forming and covering the metal strip into a tubular shape and continuously butt welding the abutting surfaces of both edges of the metal strip using a TIG arc.
Continuous coating by TIG welding was considered impossible. As a result of research on this point, it was found that the main causes are as follows. When butt welding the both edges of a metal strip wrapped around the outer circumferential surface of a metal tube, in order to obtain a good butt weld, it is necessary to melt the welded joint sufficiently. of heat and a certain welding pressure to provide the appropriate amount of upset. However, in the past, there was no appropriate method for applying a predetermined welding pressure to the welded joint, and as a result, it was not possible to continuously cover the metal pipe with a metal strip using TIG welding. It is something that That is, first, a metal strip of the width necessary to be wrapped around the outer circumference of the metal tube is wrapped around the outer circumferential surface of the metal tube to form it, and this metal strip is pressed from the left and right with squeezing rolls to form a metal strip. An attempt was made to obtain the necessary welding pressure on the abutting surfaces of the strips, but in this case, there was a metal tube inside and the width of the outer metal strip was necessary to wrap around the outer circumference of the metal tube. Since the width of the weld is limited and there is not enough room, the action of the squeegee roll is not fully exerted and the necessary welding pressure cannot be obtained on the abutting surfaces. When welding with a TIG arc, heat is taken away from the butt part to the internal metal tube, resulting in insufficient welding, and when the butt part melts and condenses, there is no margin for the width of the metal strip. Therefore, as the molten part condenses, a hole forms in the abutting part, making welding difficult. Additionally, in an attempt to avoid such inconveniences, an attempt was made to make the width of a metal strip suitably wide, wrap it around the outer circumferential surface of a metal tube and form it, and pressurize this metal strip from the left and right sides with squeeze rolls. However, in this case, the outer circumferential surface of the metal strip is pressed toward both side edges by the squeezing roll, so that the both side edges of the metal strip are overlapped by the margin of width as shown in Figure 10. It has become a state. The TIG arc heats only the upper part of the overlapping part, causing the joint to rise, resulting in incomplete welding and poor welding strength.

The present invention is based on the results of such investigation and research,
The purpose of the present invention is to provide a method for manufacturing a metal clad tube that makes it possible to continuously coat a metal tube with a metal strip by TIG welding, and that makes full use of the advantages of TIG welding and eliminates the drawbacks of the conventional methods described above. do.

An example of implementing the present invention will be described with reference to the attached drawings.

First, a metal tube 1 and a metal strip 2 having a width suitably wider than the width necessary to wrap around the outer periphery of the metal tube 1 are fed at a predetermined speed along the tube axis direction of the metal tube 1. 1. As shown in FIG. 1, a metal strip 2 is wound around the outer peripheral surface of a metal tube 1 into a tubular shape using forming rolls. However, both side edges 2 of the metal strip 2
₁ and 2 ₂ should be in contact with each other without overlapping.
Next, as shown in the third figure, the metal tube 1 and the metal strip 2 formed by wrapping it around its outer peripheral surface into a tubular shape pass between an upper roll 3 and a lower roll 4. The upper roll 3 is located above the portion 5 where the side edges 2 ₁ and 2 ₂ of the metal strip 2 are in contact with each other, and the upper roll 3 and the side edges of the lower roll 4 are connected to each other as shown in FIGS. 3 and 2. In other words, at a position different from the position where both side edges of the metal strip touch, an escape groove 3' having an appropriate width along the tube axis direction is provided. Therefore, the outer peripheral surface of the metal strip 2 formed into a tubular shape is pressurized in the circumferential direction by the upper and lower rolls 3 and 4, and both side edges 2 ₁ and 2 ₂ of the metal strip 2 are As shown in FIGS. 2 and 4, the metal strips 2 are brought into close contact with each other in parallel over the entire thickness of the metal strip 2, and along the tube axis direction on the outer circumferential surface of the metal strip 2 other than the close contacting side edges 5 through the relief grooves 3'. A bulge 6 is formed due to the extra material width (as shown in FIGS. 2 and 4). The width of this bulging portion 6 is the portion 5 of the side edges 2 ₁ , 2 ₂ of the metal strip 2 that are in close contact with each other.
The welding pressure required for butt welding is set to a predetermined value. In other words, this bulge 6 is a bulge corresponding to the extra material width of the metal strip 2. The portions 5 of the metal strip 2 where the edges 2 ₁ , 2 ₂ are in close contact with each other are pressed from above by the upper roll 3, so that they are brought into close contact in a parallel state as described above, resulting in a superposed state as shown in FIG. Must not be. Next, a metal band plate 2 is formed into a tubular shape on the outer peripheral surface of the metal tube 1, and has a bulge portion 6 on the outer peripheral surface with both side edges 2 ₁ , 2 ₂ in parallel and close together and along the tube axis direction. It passes through a die 7 having notches 7' at positions corresponding to the close contact parts 5 on both side edges 2 ₁ and 2 ₂ of the strip.
Then, as it passes, the bulge 6 due to the extra material width on the outer peripheral surface of the metal strip 2 is pressurized by the die 7, and the both side edges 2 of the metal strip 2 are pressed as shown in FIGS.
₁ , 2 ₂ are gradually stretched into the parallel close-contact parts 5 , and due to this pressure both side edges 2 ₁ ,
2. The _two parallel close contact parts 5 are brought into pressure contact and abutted 5', and this abutted part 5' is passed through the notch 7' of the die 7 to the seventh
As shown in the figure, the metal tube 1 is slightly lifted above the outer circumferential surface of the metal tube 1, and a predetermined welding pressure and an appropriate amount of upset necessary for welding are applied to the abutting portion 5'. Note that the inner diameter of the die 7 can be adjusted as appropriate using a fastener provided externally. Next, the abutting portions 5' of the both side edges 2 ₁ , 2 ₂ of the metal band plate 2 formed into a tubular shape are closely parallel to the outer peripheral surface of the metal tube 1 over the entire thickness of the metal band plate 2 and are placed in a predetermined position on the outer circumferential surface of the metal tube 1. In order to maintain the state in which the welding pressure of The squeegee roll 9 is placed, and the abutting portion 5' is welded using TIG arc welding torches 10 provided at appropriate positions immediately behind the presser metal fitting 8 and before and before the squeegee roll 9. In this case, as described above, the abutting portions 5' of both side edges 2 ₁ and 2 ₂ of the metal strip 2 are parallel and close together over the entire thickness of the metal strip 2, and are slightly raised above the outer circumferential surface of the metal tube 1. Since a predetermined welding pressure and upset amount are applied to this part, and the state of this abutting part is maintained by the pressing member, the heat from the welding torch 10 is transferred to the internal metal pipe 1 by conduction. The heat is sufficiently applied to the abutting portion without being taken away by the heat, and the abutting portion melts easily and reliably (the state shown in Figure 8). Since a predetermined welding pressure is applied to this abutment portion based on the extra material width of the metal strip 2 that formed the bulged portion 6, as the molten portion condenses, this extra material width The parts are successively pushed into the molten part and melted, forming a strong weld bead. A metal tube 1 and a metal strip 2 formed into a tubular shape on its outer peripheral surface.
is sent at a predetermined speed in the tube axis direction, so the welding by the welding torch 10 is performed continuously along the tube axis direction, and the metal strip 2 is brought into close contact with the outer peripheral surface of the metal tube 1 in a tubular shape. . Then, a metal clad tube is manufactured by shaping the outer diameter with a sizing roll. (State shown in FIG. 9) In the above embodiment, the upper and lower rolls 3 are used as means for forming the bulge 6 having an extra material width along the tube axis direction of the metal strip 2 formed into a tubular shape. , 4 is used, but grooves corresponding to the relief grooves may be provided on the side surface of the die so that the pressure roll passes through the die. Moreover, the means for pushing and stretching the bulging portion 6 to the abutting portions of both side edges of the metal strip is not limited to the die, and a pressure roll may also be used. Furthermore, although a carbon steel pipe is mainly used for the internal metal pipe 1, the material need not be limited to this, and the shape may be round, square, hollow, or non-hollow. Further, the metal band plate 2 is also mainly made of stainless steel, but the material is not limited to this as long as it can be TIG welded.

Incidentally, one example of data of a specific example used in the above method is as follows.

Metal pipe (steel pipe) Outer diameter φ18, 85 Thickness 0, 8 mm Metal strip (stainless steel SUS304) Thickness 0, 2 mm Width 60.5 mm (including extra material width approx. 0.65 mm) Welding current (high frequency superimposed argon arc) High frequency 16, 8A (15KHz) DC 45, 4A Welding speed 10m/min As mentioned above, the present invention consists of a metal tube and a metal strip having a width appropriately wider than the width necessary to wrap around the outer circumference of the metal tube. A step of forming a metal strip by wrapping the metal strip around the outer peripheral surface of the metal tube using forming rolls while feeding the metal strip at a predetermined speed along the tube axis direction of the metal tube so that both edges of the metal strip are in contact with each other without overlapping; The outer circumferential surface of a metal strip formed into a tubular shape on the outer circumferential surface of a metal tube using a pressure roll or die that has relief grooves of an appropriate width along the tube axis direction at positions different from the positions where both side edges of the strip touch. Pressure is applied to bring the both side edges of the metal strip into close contact with each other in parallel over the entire plate thickness, and the expansion due to the excess material width is applied to the outer circumferential surface of the metal band other than the close-contacted side edges through the relief groove. A process of forming a protruding part along the tube axis direction, and forming a tube shape on the outer peripheral surface of the metal tube using a pressure roll or a die having notches at positions corresponding to the close contact areas of both side edges of the metal strip. Pressure is applied to the outer circumferential surface of a metal band plate having parallel and closely spaced bulges along the tube axis direction on the outer circumferential surface, and the bulges are pushed out to both side edges of the metal band plate that are in close contact with each other and the notch. a step of applying a predetermined welding pressure to the edges of the metal strips by bringing them into contact with each other in a state where they are slightly raised above the outer peripheral surface of the metal tube; The metal clad tube is formed by a process of butt welding the abutting surfaces at both side edges with a welding torch while maintaining the condition of the abutting surfaces at both side edges via a presser member, and closely covering the outer circumferential surface of the metal tube with the metal strip. Since it is manufactured in this manner, it has the following effects.

In other words, when butt welding is performed using a welding torch such as a TIG arc, in order to ensure welding, the welding torch, unlike electrode rolls, does not have a pressing force, so both edges of the metal strip must be It is necessary that the parts are parallel and closely abutted throughout the entire thickness, and that when this abutting surface is melted by the high-temperature arc during welding, sufficient welding pressure is applied to that part. . However, in the present invention, as described above, first of all, the both side edges of the metal band plate, which is formed by wrapping it into a tubular shape around the outer peripheral surface of the metal tube by applying pressure with a pressure roll or die, are rolled over the entire thickness of the metal band. The metal strips are brought into close contact with each other in parallel, and a bulge is formed along the tube axis direction by using an extra width of material prepared in advance on the outer circumferential surface of the metal strip other than the close contact portion, so that the abutting portions of both side edges of the metal strips are formed. The bulging portion is held as a welding margin to apply welding pressure to the metal strip, and secondly, the bulging portion is pushed out to the close contact portion of both side edges of the metal strip by applying pressure from a pressure roll or die, and the close contact portion is Since the metal strips are brought into contact with each other, the close contact parts on both side edges of the metal strips have elasticity that acts in the direction of repulsion from each other as the bulges move, while maintaining a parallel and close state throughout the thickness of the metal strips. Even if a force is applied and the metal tube is located inside, the close contact areas on both side edges of the metal strip strongly abut, and a predetermined welding pressure is applied to the area. Therefore, butt welding can be easily and reliably performed by welding with a welding torch while maintaining the abutting state of both side edges of the metal strips via appropriate pressing members. Therefore, it is necessary to wrap a metal band plate of the width necessary to wrap it around the outer circumference of a metal tube in the conventional case where no bulge is formed on the outer circumferential surface of the metal band formed into a tubular shape. When welding and pressurizing the outer circumferential surface, sufficient welding pressure cannot be obtained and there is insufficient welding margin, and the welding heat is absorbed by the internal metal tube, resulting in insufficient welding or melting. It is possible to reliably eliminate inconveniences such as holes forming in welded joints due to condensation of parts. In addition, the method of forming the above-mentioned side edges of the metal strip in parallel and close together in advance to form a bulge on the outer circumferential surface other than the abutting surface to function as a welding margin is not adopted, but instead of forming an extra wide part in advance. As in the case where the width of a metal strip is pressed against the edges of both sides of the metal strip, the edges of the metal strip overlap without meeting each other, causing a TIG arc. It is also possible to reliably eliminate the inconvenience of heating only the upper portion of the overlapping portion, causing the joint to rise, resulting in incomplete welding and poor welding strength. By taking advantage of TIG welding's good external appearance and high welding strength, which are the features of TIG welding, we are able to attach a metal strip to the outer circumferential surface of the metal tube without having to take the complicated process of conventional insertion methods. Metal-clad tubes can be manufactured by winding and forming into a tubular shape, abutting the edges on both sides, and continuously butt welding the abutting surfaces. The manufacturing efficiency of cladding tubes can be significantly improved, and the product price can also be reduced.

[Brief explanation of the drawing]

Figures 1 to 4 show an example of the implementation of the present invention, and Figure 1 is an explanatory diagram of the process of wrapping a metal strip plate into a tubular shape around the outer peripheral surface of a metal tube using forming rolls. , Fig. 2 shows that both side edges of a metal strip formed into a tubular shape are brought into close contact with each other in parallel throughout the thickness of the metal strip by applying pressure from the upper and lower rolls, and the outer circumferential surface other than the closely-contacted portions is pressed along the tube axis direction. FIG. 3 is an explanatory diagram of a state in which a bulge of extra material width is formed, and FIGS. 4 to 7 are explanatory diagrams of the manufacturing apparatus used in the method of the present invention.
The figure shows a metal strip formed into a tubular shape on the outer circumferential surface of a metal tube by applying pressure with a pressure roll or die, with both side edges parallel to each other and having a bulge with an extra material width on the outer circumferential surface other than the closely-contacted areas. An enlarged view showing the process in which the bulging part of the plate is stretched and transferred to the close contact parts of both side edges, and the close contact parts of both side edges are abutted and welding pressure is applied to the part. Figure 8 is a cross-sectional view showing the abutting surfaces of both side edges of the metal strip being melted by an arc welding torch to form a welded joint, and Figure 9 is a cross-sectional view of the metal strip manufactured by the method of the present invention. FIG. 10, a cross-sectional view showing a cladding tube, shows two sides of a metal strip in a case where, unlike the present invention, the material width of the metal strip is simply increased appropriately, the material is wrapped around the outer circumferential surface of the metal tube, and the material is pressed with a pressure roll. It is an explanatory view showing the state of the edge. 1... Metal tube, 2... Metal strip, 2 ₁ , 2 ₂ ...
...Both sides edges of the metal strip, 3...Top roll, 3'
... Relief groove, 4 ... Lower roll, 5 ... Close contact part,
5'...Abutment part, 6...Bulging part, 7...Dice,
7'... Notch, 8... Presser fitting, 9... Squeeze roll, 10... Welding torch.

Claims (1)

[Claims] 1. While feeding a metal tube and a metal strip having a width suitably wider than the width necessary to wrap around the outer periphery of the metal tube along the axial direction of the metal tube at a predetermined speed,
A process of wrapping a metal strip around the outer circumferential surface of a metal tube using forming rolls so that both edges of the metal strip are in contact with each other without overlapping. Pressure is applied to the outer circumferential surface of a metal strip formed into a tubular shape on the outer circumferential surface of a metal tube using a pressure roll or die having relief grooves of appropriate width along the outer circumferential surface of the metal tube, so that both side edges of the metal strip are pressed over the entire plate thickness. forming a bulge along the tube axis direction by the excess material width on the outer circumferential surface of the metal strip other than the closely-contacting side edges of the metal strip through the escape groove; A metal that is formed into a tubular shape on the outer circumferential surface of a metal tube by a pressure roll or die that has notches at positions corresponding to both side edges, and has both side edges parallel and close together and has a bulge on the outer circumferential surface along the tube axis direction. Pressure is applied to the outer circumferential surface of the band plate, and the bulging portion is pushed to both side edges of the metal band plate that are in close contact with each other through the notch, and the both side edges of the metal band plate that are in close contact with each other are raised above the outer circumferential surface of the metal tube. a step of applying a predetermined welding pressure to the part by abutting the parts in a slightly raised state;
a step of welding the abutting surfaces at both side edges of the metal strip with a welding torch while maintaining the condition of the abutting surfaces via appropriate pressing members to closely cover the outer circumferential surface of the metal tube with the metal strip; A method for manufacturing a metal clad tube, characterized by comprising: