JPH06218428A - Manufacture of metallic welded tube - Google Patents

Abstract

PURPOSE:To prevent a blow hole from occurring in a weld bead by removing lubricant attached to the end faces of both side edges of a strip metal through rotary bodies after the whole lower surface of the strip metal is coated by coating rolls with the lubricant in front of a die. CONSTITUTION:The whole lower surface (the surface coming in contact with the die 4) of the strip metal 1 is coated by the coating rolls with the lubricant 2. Then, the lubricant 2 attached to the end faces of both side edges 1a of the strip metal 1 is removed continuously by the rotary bodies 5a. The strip metal 1 is penetrated through the die 4 provided with a taper 4a and molded by butting both side edges 1a against each other from the flat shape to the tubular shape. This butt part 1b is welded by a welding torch to make a metallic welded tube. Since the lubricant can be prevented from melting into the welded bead, a metallic welded tube having a good weld part free from the blow hole in the weld bead can be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention penetrates a metal strip into a die having a circular through-hole having a tapered portion on the inlet side, the diameter of which decreases from the inlet side to the outlet side. When a flat metal strip is formed into a tubular shape with its both edges abutting at once, the abutting parts are welded with a welding torch to produce a metal welded pipe, and the friction between the metal strip and the die is reduced. By applying a lubricant to the entire lower surface of the metal strip with a coating roll in front of the die in order to reduce it, it is possible to prevent a welding defect such as a blow hole from occurring inside the weld bead due to the lubricant. The present invention relates to a method for manufacturing a metal welded pipe.

[0002]

2. Description of the Related Art Conventionally, in order to manufacture a metal welded tube by bending a metal strip in its width direction to a product curvature and forming it into a tubular shape, the metal strip is arranged in a large number of tandems as shown in the perspective view of FIG. The metal strip 1 was sequentially bent in the width direction using a roll forming machine having a forming roll having a caliber or a cage roll 9, and the metal strip formed into a tubular shape was held by the seam guide roll 6 or the squeeze roll 7. The welding torch 8 at the abutting portions 1b of both side edges 1a of the metal strip 1 in the state.
A roll forming method of butt welding by a welding means such as the above has been generally practiced.

However, in this roll forming method, when the outer diameter of the metal welded pipe to be manufactured is changed, all the forming rolls or cage rolls 9, and all the rolls such as the seam guide roll 6 and the squeeze roll 7 are to be changed. Since it is necessary to replace the metal welded pipe to be manufactured with one that corresponds to the outer diameter, there is at least 20 or more roll groups to be replaced for one type of outer diameter. Since it requires a long time and a long time, the production efficiency of the equipment is reduced, and it is not economical because a large number of rolls corresponding to the outer diameter of the metal welded pipe to be manufactured must be prepared. . Further, in such a roll forming method, the outer diameter is 10
When trying to manufacture thin metal welded pipes of less than mm,
Since high accuracy is required for the installation position etc. of each roll set, if there is a setting error in some roll positions of each roll set, the twisting of the metal welded pipe or the abutting portion 1b during forming. There is also a drawback that a step is likely to occur.

Further, a method of drawing a metal strip with a forming die, which is abbreviated as a die draw forming method, to form a tube at once is disclosed in, for example, Japanese Patent Publication No. 39-18657, "Consistent pipe making machine for long thin metal pipes. In the above, a metal thin plate hoop is formed into a tubular shape with a forming die, then sequentially welded, and then disclosed as a technique for continuously performing a step of annealing using a non-oxidation bright annealing furnace by high frequency induction heating,
Japanese Patent Publication No. 4-18925 discloses a method for producing a metal corrugated tube, which is formed into a tubular shape with a forming die and welds the joint points of the tubular body, and then corrugated to continuously perform a bright heat treatment in a non-oxidizing gas atmosphere. Techniques for a series of manufacturing lines for performing the above are disclosed.

However, the methods disclosed in Japanese Patent Publication No. 39-18657 and Japanese Patent Publication No. 4-18925, which are abbreviated as the die draw forming method, are as follows.
Since it is a method of directly drawing a flat metal strip from a through hole having a taper on the entrance side of the die to form a tubular shape,
Compared to the roll forming method described above, the equipment cost is significantly reduced, and even when changing the outer diameter of the metal welded pipe to be manufactured, it is only necessary to prepare a die corresponding to the outer diameter of the metal welded pipe, so production efficiency However, in this method, both side edges of the metal strip first come into contact with the tapered surface of the through hole of the die, and further, while the molding proceeds in the through hole of the die, the width direction which is received during forming is increased. Since the bending moment is minimum on both side edges of the metal strip, both side edges of the metal strip are parallel to the through hole of the die (minimum diameter portion).
Since it is drawn into the tapered part on the side of the through hole of the die with almost no bending until just before,
Both edges of the metal strip slide on the tapered surface of the die through hole while only contacting the tapered surface of the die through hole with a high surface pressure. When the edges of both sides of the strip are flawed, the part of the tapered surface on the side of the through hole of the die that contacts the edges of the metal strip is damaged, shortening the life of the die. There is a drawback that it is necessary to interrupt the molding and frequently perform maintenance of the die because the metal powder that has fallen off from the generated flaws accumulates in the die and causes surface flaws on the metal strip.

As a result of various investigations by the applicant of the present invention in order to eliminate such a defect, the lower surface of the metal strip (the metal welded tube It is effective to apply a quick-drying lubricant obtained by diluting a fine fluororesin powder containing a polytetrafluoride telomer as a main component with a fluorocarbon solvent represented by the chemical formula CCl ₂ F-CClF ₂ to the entire surface). I clarified that there is. This lubricant is applied by rolls. According to this application method, when the metal strip is thin, the lubricant is applied to the upper surface (the inner surface of the metal welded pipe) from the end of both side edges of the metal strip by the applied roll pressure. When the forming die is penetrated as it is, the lubricant adhered to the end portions of both side edges of the metal strip remains at the abutting portions of both side edges of the metal strip after forming. This residual lubricant is almost sublimated due to the high temperature due to TIG welding using a welding torch, etc., but it does not necessarily sublime completely until the welded part solidifies, and if a part of the lubricant remains as it is,
It has been found that the residual lubricant dissolves in the welded portion to generate blowholes inside the bead after welding, resulting in a defect that a good welded pipe cannot be obtained as a welding defect.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks in the method for producing a metal welded pipe by the die draw forming method, and inserts a tapered portion whose diameter decreases from the inlet side to the outlet side. When a flat metal strip is formed into a tubular shape with its two side edges abutting each other by penetrating the metal strip through a die having a through hole having a circular cross section on the side, the metal strip and the die are In order to reduce friction, the lubricant is applied to the entire lower surface of the metal strip by the application roll in front of the die, so that the lubricant does not cause welding defects such as blowholes inside the bead. It is an object of the present invention to provide a method for manufacturing a metal welded pipe capable of performing the above.

[0008]

As a result of various studies to solve the above-mentioned problems, the inventors of the present invention have a circular cross section having a tapered portion on the entrance side whose diameter decreases from the entrance side to the exit side. A metal welded pipe in which a flat metal strip is formed into a tubular shape with its both edges abutted at once by penetrating the metal strip through a die having a through hole, and then the abutting portion is welded with a welding torch. In manufacturing the die, both side edges of the metal strip are formed by applying a lubricant to the entire lower surface of the metal strip by a coating roll in front of the die and then using a rotating body made of a grindstone of a lubricant removing device provided in front of the die. It is sufficient to continuously remove the lubricant adhering to the end face of the metal strip.When the rotating body of the lubricant remover is made of a grindstone, the grinding amount on the lower surface side of both edges of the metal strip is larger than the grinding amount on the upper surface side. With the composed shape things have completed the present invention by investigating that it is more effective.

A method for manufacturing a metal welded pipe according to the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a pipe in which flat metal strips are abutted at once by penetrating the metal strips through a die while continuously removing the lubricant adhered to the both side edges of the metal strip by the method of the present invention. 2 is a side view showing an example of a molding state, FIG. 2 is a plan view of the apparatus shown in FIG. 1, FIG. 3 is an enlarged sectional view taken along the line AA in FIG. 2, and FIG. 4 is a lubricant removing apparatus. FIG. 5 is a side view showing another example of the rotating body of FIG. 5, FIG. 5 is a sectional explanatory view of the molded pipe immediately before welding when the rotating body of the lubricant removing device shown in FIG. 3 is used, and FIG. 6 is shown in FIG. It is a cross-sectional explanatory drawing of the shaping | molding pipe just before welding when the rotary body of a lubricant removal device is used.

The outline of the method for producing a metal welded pipe according to the present invention will be described with reference to FIG. 1. The metal strip 1 unwound from the uncoiler comes into contact with the die 4 of the metal strip 1 by the coating roll 3 of the lubricant coating device. A fine fluororesin powder containing polytetrafluoride telomer as a main component has a chemical formula of CCl ₂ F-on the entire surface (the surface which is the outer surface of the metal welded tube and the lower surface).
A lubricant 2 such as a quick-drying lubricant diluted with CFCF ₂ represented by CFCF is applied, and then a metal strip 1 is applied.
After the lubricant 2 adhering to the end faces of both side edges 1a is continuously removed by the rotating body 5a of the lubricant removing device 5, the portion with the taper 4a whose diameter decreases from the inlet side to the outlet side is removed. It is penetrated by a die 4 having a through hole with a circular cross section on the entrance side, and is formed into a tubular shape in which both side edges 1a are abutted from a flat plate, and then the abutting portion 1b is TIG with a welding torch 8. It is welded and manufactured into a welded metal tube.

The most characteristic feature of the method for producing a metal welded pipe according to the present invention is that the metal strip 1 is applied in front of the die 4 by the application roll 3 of the lubricant application device.
After applying the lubricant 2 on the entire lower surface of the
This is to continuously remove the lubricant 2 adhering to the end faces of the both side edges 1a of the metal strip 1 by the rotating body 5a of the lubricant removing device 5 provided in front of.

As an element for removing the lubricant 2 of the lubricant removing device 5, the metal strip 1 is provided in front of the entrance side of the die 4.
Both edges of the metal strip 1 are rotated by abutting on both edges 1a of the
For removing the lubricant 2 adhering to 1a, for example, a roll lined with a metal brush or buff or a rotating body 5a such as a grindstone is used, but a roll lined with a metal brush is used. In the case of, when the plate thickness of the metal strip 1 is thin, the metal strip 1 may pass between the metal lines (between the brushes) forming the brush, and the lubricant 2 may not be completely removed. There is a problem in that the removal of the lubricant 2 is not always uniform because it is difficult to bring the metal wire forming the brush into contact with the side edges 1a of the metal strip 1 in the same thickness direction at all times. Further, in the case of a roll having a lined buff, the buff wears quickly and its maintenance is troublesome, and the buff may fuzz and adhere to both side edges 1a of the metal strip 1. Because there is a problem Preferably grindstone always have excellent contact and wear resistance on both side edges 1a of the plate metal strip irrespective thickness 1 metal strip 1.

As the shape of this grindstone, a cylindrical shape as shown in FIG. 4 can be used, but in this case, when the side edges 1a of the flat metal strip 1 are formed into a tubular shape with butting against each other. As shown in FIG. 6, both side edges 1a of the metal strip 1 are abutting portions 1b which are almost entirely in contact with each other. Therefore, if the lubricant 2 drops onto the both side edges 1a of the metal strip 1 and adheres again, the abutting portions 1b will be removed. When welding is performed by the welding torch 8, the lubricant 2 may melt into the welded portion and cause welding defects such as blowholes inside the bead after welding.

Therefore, as the shape of this grindstone, a drum is cut at a right angle to its axis and at a portion having the smallest cross-sectional area as shown in FIG. 3, that is, both side edges of the metal strip 1.
If a shape in which the amount of grinding on the lower surface side of 1a is larger than the amount of grinding on the upper surface side is used, the corners of the lower surface of both side edges 1a of the metal band 1 will be removed. Wear of the die 4 is reduced in the process of forming the flat metal strip 1 into a tubular shape with its both side edges 1a abutting each other by penetrating a portion with 4a into a through hole having a circular cross section on the inlet side. It is preferable because the life of the die is extended and the cost can be reduced. Further, both side edges of the flat metal strip 1
As shown in FIG. 5, both side edges 1a of the metal strip 1 become abutting portions 1b abutting with an opening formed on the outer surface side when the tubular portions 1a are abutted to each other. The bead generated when welding is performed with the welding torch 8 does not significantly project to the outer surface side, and post-processing such as bead grinding can be easily performed.

[0015]

As described above, in the method of the present invention, the die 4 having the through-hole having the circular cross section, which has the portion having the taper 4a whose diameter decreases from the entrance side to the exit side, is formed on the entrance side. The flat metal strip 1 is formed into a tubular shape by piercing the metal strip 1 in a state in which both side edges 1a thereof are abutted, and then the abutting portion 1b is welded torch 8
When manufacturing a metal welded tube by welding with a metal, the friction of the contact surface of the metal strip 1 with the die 4 when penetrating the die 4 is reduced so that a flaw or the like does not occur on the surface of the metal strip 1. The strip 1 is coated with the lubricant 2 on the entire lower surface of the strip 1 by the coating roll 3 in front of the die 4, and then the lubricant removing device 5 provided between the coating roll 3 and the die 4.
Since the lubricant 2 adhering to the end faces of the both side edges 1a is continuously removed by the rotating body 5a, the metal formed into a tubular shape is penetrated through the die 4 and the both side edges 1a are abutted at once. When the abutting portion 1b of the strip 1 is welded by the welding torch 8, the gas in which the lubricant 2 has sublimated does not remain as a blow hole in the welded portion.

[0016]

【Example】

Example 1 A stainless steel strip with a plate thickness of 0.7 mm and a plate width of 31.3 mm (SU
S304) has a chemical formula CCl ₂ on the entire lower surface (the side which becomes the outer surface of the metal welded tube) of fine fluororesin powder containing polytetrafluorotelomer as a main component so that the concentration thereof is 50% by volume.
After applying a lubricant quick-drying diluted by Furonsorubu represented by F-CClF _2, both side edges of the strip of stainless steel steel by the lubricant removal device having a rotating body consisting of a cylindrical grinding wheel as shown in FIG. 4 Each of them is ground by 0.3 mm to remove the lubricant, and the taper (taper angle: 22 degrees) is reduced from the entrance side (diameter: about 35 mm) to the exit side (diameter of the smallest diameter part: about 10 mm). ) A through hole having a circular cross section having a portion marked with) is bored, and the inside surface of the through hole is coated with a film of titanium carbide and titanium nitride by a chemical vapor deposition method into a tungsten carbide die to form a pipe. The stainless steel strip was pierced at a speed of 4 m / min and formed into a tubular shape in which both side edges were abutted at once, and immediately this abutted portion was welded to a TIG using a welding torch.
As a result of welding, it was possible to manufacture a metal welded pipe having a good weld portion with a diameter of 10 mm, which was free of blowholes caused by the lubricant being melted into the weld bead.

Example 2 As a rotating body of the lubricant removing device, a rotating body made of a grindstone having a curved surface with a radius of 10 mm as shown in FIG. 3 is used to remove the corners on the lower surface side of both side edges of the stainless steel strip. As a result of producing a metal welded pipe under the same conditions as in Example 1 except that grinding was performed as described above, as in Example 1, it was possible to obtain a favorable welded pipe having a diameter of 10 mm without a blowhole generated due to the lubricant being melted into the weld bead. A metal welded tube having a weld could be produced. In the case of Example 1, the die was worn out by making a pipe of about 2000 m, but in this example, the wear of the die was extremely reduced by removing the corners of the lower surfaces of both side edges of the metal strip together with the lubricant. The dies can be sufficiently used even in the pipe making of 3000 to 4000 m, and the cost can be reduced with the improvement of the product yield.

[0018]

[Comparative Example] Exactly the same conditions as in Example 1 except that the plate width of the stainless steel strip (SUS304) was 30.7 mm and that both edges of the stainless steel strip were not ground after the lubricant was applied. As a result of producing the metal welded pipe in the above, the melted lubricant inside the weld bead continuously generated blow holes, and only the welded metal with a defective welded portion could be produced.

[0019]

As described above in detail, in the method for manufacturing a metal welded pipe according to the present invention, a penetrating hole having a circular cross section having a tapered portion whose diameter decreases from the inlet side to the outlet side is provided. A metal welded pipe is formed by penetrating a metal strip through a die having holes to form a flat metal strip into a tubular shape with its both edges abutted together, and then welding this abutting portion with a welding torch. When manufacturing
The lubricant is applied to the entire lower surface of the metal strip by a coating roll in front of the die, and then the lubricant adhering to the end faces of both side edges of the metal strip is continuously applied by the rotating body of the lubricant removing device provided in front of the die. Since it was possible to prevent the lubricant from being melted into the weld bead, it is possible to manufacture a metal welded pipe having a good weld portion without blowholes in the weld bead. When a grindstone is used as the rotating body of the lubricant removing device, the continuous removing function of the lubricant adhering to the end faces of both side edges of the metal band is stable. If you use a body with a shape such that the grinding amount on the lower surface side of both edges of the metal band is larger than the grinding amount on the upper surface side, the corners of the lower surface of both side edges of the metal band will be removed. The die wear is reduced in the process of forming the flat metal strip into a tubular shape with both side edges abutting by penetrating the tapered portion of the die into the through hole with a circular cross section on the entrance side. It is preferable because the life of the metal strip is extended and the cost can be reduced. Further, when the flat metal strip is formed into a tubular shape in which both side edges are abutted with each other, both side edges of the metal strip have openings formed on the outer surface side. Butt that abuts in the state Since, it is not the bead that occurs when welding the butt portion in the welding torch is greatly protrudes to the outer surface side, it is the post-processing such as bead grinding can be easily performed. As described above, the industrial value of the method of the present invention having various advantages is extremely great.

[Brief description of drawings]

FIG. 1 is a tubular state in which a lubricant is attached to both side edges of a metal strip by the method of the present invention while the metal strip is passed through a die and flat metal strips are abutted against each other. It is a side surface explanatory view showing an example of the state where it is forming into.

FIG. 2 is an explanatory plan view of the device shown in FIG.

3 is an enlarged cross-sectional view taken along the line AA in FIG.

FIG. 4 is a side view showing another example of the rotating body of the lubricant removing device.

5 is a cross-sectional explanatory view of a formed pipe immediately before welding when the rotating body of the lubricant removing device shown in FIG. 3 is used.

6 is a cross-sectional explanatory view of a formed pipe immediately before welding when the rotating body of the lubricant removing device shown in FIG. 4 is used.

FIG. 7 is a perspective view of a method for producing a metal welded pipe by a conventional roll forming method.

[Explanation of symbols]

 1 Metal strip 1a Both side edges 1b Butt portion 2 Lubricant 3 Application roll 4 Die 4a Taper 5 Lubricant removing device 5a Rotating body 6 Seam guide roll 7 Squeeze roll 8 Welding torch 9 Forming roll or cage roll

Claims (3)

[Claims] 1. A metal band (1) is attached to a die (4) having a through hole having a circular cross section having a tapered portion (4a) whose diameter decreases from the entrance side to the exit side. ) Is formed into a tubular shape with both side edges (1a) butted together, and then the butted portion (1b) is welded by a welding torch (8). When manufacturing a welded pipe, a lubricant is applied to the entire lower surface of the metal strip (1) by a coating roll (3) in front of the die (4).
After applying (2), the rotating body (5a) of the lubricant removing device (5) provided in front of the die (4) causes both side edges (1) of the metal strip (1).
A method for producing a metal welded pipe, characterized in that the lubricant (2) adhering to the end face of a) is continuously removed. 2. The method for producing a metal welded pipe according to claim 1, wherein a grindstone is used as the rotating body (5a) of the lubricant removing device (5). 3. A metal strip as the rotating body (5a) made of a grindstone.
The method for producing a metal welded pipe according to claim 2, wherein a shape in which a grinding amount on the lower surface side of both side edges (1a) of (1) is larger than a grinding amount on the upper surface side is used.