JPH0732036A - Manufacture of metallic welded tube - Google Patents

Abstract

PURPOSE:To prevent burning and the shortening of the life of a die by heating a metallic strip in a heating furnace in front of a die, after a lubricant is applied on the entire lower surface of the strip with an applicator roll, and continuously drying the lubricating oil stuck to the strip. CONSTITUTION:A planar metallic strip 1 is formed at a stroke into a tubular shape with both side edges abutted on each other by putting the strip 1 through a die 4 in which a through-hole is formed and provided with a round cross section and a tapered part 4a on the entrance side with the diameter gradually made smaller from the entrance side to the exit side. Then, this abutted part is welded with a welding torch 8 to produce a metallic welded tube. At that time, the metallic strip 1 is applied with a lubricant 2 on the entire lower surface by an applicator roll 3 in front of the die 4 so that the friction at the contact surface of the metallic strip 1 with the die 4 is reduced when the die 4 is put through and that flaws for example are not generated on the surface of the strip 1; and this applied lubricant 2 is continuously dried in a heating furnace 5 that is provided in farther front of the die 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention allows a metal band to penetrate a die having a through hole having a circular cross section, which has a tapered portion whose diameter decreases from the entrance side to the exit side. This reduces the friction between the metal strip and the die when manufacturing a metal welded pipe by welding a flat metal strip into a tubular shape with its both edges abutted together and then welding the abutting parts with a welding torch. In order to prevent the seizure and shortening of die life due to the lubricant not completely drying when the lubricant is applied to the entire lower surface of the metal strip by the application roll in front of the die, It is about the method.

[0002]

2. Description of the Related Art Conventionally, in order to manufacture a metal welded pipe by bending a metal strip in its width direction to a product curvature to form a tubular shape and welding, the metal strip is arranged in a large number of tandems as shown in the perspective view of FIG. Using a roll forming machine equipped with a forming roll having a caliber or a cage roll 9, the metal strip 1 is sequentially bent in the width direction and bent to a product curvature to form a tubular shape, and then formed into a tubular shape. A roll forming method is generally used in which the metal strip 1 is held by the seam guide rolls 6 and the squeeze rolls 7, but the abutting portions 1b of both side edges 1a of the metal strip 1 are butt welded by a welding means such as a welding torch 8.

However, in such a roll forming method, when the outer diameter of the metal welded pipe to be manufactured is changed, the forming roll or cage roll 9, further the seam guide roll 6 and the squeeze roll 7 are used.
It is necessary to replace all of the rolls, etc., with ones that correspond to the outer diameter of the metal welded pipe to be manufactured, so there must be at least 20 roll sets to be replaced for one outer diameter. Therefore, it requires a lot of labor and a long time to replace the rolls, which lowers the production efficiency of the equipment, and it is economical because many sets of rolls corresponding to the outer diameter of the metal welded pipe to be manufactured must be prepared. There was a drawback that was not. Furthermore, in such a roll forming method,
If an attempt is made to manufacture a thin metal welded pipe having an outer diameter of 10 mm or less, high accuracy is required for the installation position of each roll set, etc. If there is such a problem, there is a drawback that the metal welded pipe is likely to be twisted during forming and a step is likely to occur at the butted portion 1b.

Further, a method, which is abbreviated as a die draw forming method, for drawing a metal strip from a forming die to form a tube at once is disclosed in, for example, Japanese Examined Patent Publication No. 39-18657, "Consistent pipe making of long thin metal pipes. Machine to form a metal thin plate hoop into a tubular shape with a molding 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.
A flat metal strip is made at once by passing the metal strip through a die that has a through hole with a circular cross section that has a tapered portion on the inlet side that decreases in diameter from the entrance side to the exit side. Since it is a method of forming a tubular shape with both side edges abutting, the equipment cost is significantly reduced compared to the roll forming method described above, and even when changing the outer diameter of the metal welded pipe to be manufactured, the metal welded pipe Since there is no need to reduce the production efficiency because it is only necessary to prepare a die corresponding to the outer diameter of the die, this method causes both side edges of the metal strip to contact the tapered surface of the through hole of the die first and Since the bending moment in the width direction that is received during forming is the minimum at both side edges of the metal strip while the forming is progressing in the hole, both side edges of the metal strip are parallel to the through holes of the die (minimum (Before just before the diameter part), it is drawn into the tapered part on the side of the through hole of the die with almost no bending work, so both side edges of the metal strip are on the tapered surface on the side of the through hole of the die. Since it slides on the tapered surface of the side of the through hole of the die when it is only in contact with a high surface pressure, when forming for a long period of time, flaws occur on both side edges of the metal strip and The part of the taper surface where both edges of the metal strip contact each other is worn out, shortening the life of the die, and further, the metal powder that has fallen off from the flaws generated on both edges of the metal strip accumulates in the die and accumulates on the metal strip. There is a drawback that it is necessary to interrupt the molding and frequently perform maintenance of the die because it may cause surface defects.

As a result of various investigations by the present inventors in order to eliminate such a defect, as a result of various studies, the entire lower surface of the metal strip (metal welded pipe) which is in contact with the forming die is reduced so that the friction between the die and the metal strip during forming is reduced. The entire surface of the outer surface of (1) is coated with a quick-drying lubricant prepared by diluting a fine fluororesin powder containing polytetrafluoroethylene as a main component with a fluorocarbon solvent represented by the chemical formula CCl ₂ F-CClF _2. It was found to be effective. However, since Flonsolve is an ozone depleting substance and has been decided to be completely abolished, the present inventors have selected, as an alternative lubricant, a fluororesin-based powder or a melamine resin-based powder dispersed in water.
When this lubricant is completely dried, there is no particular problem in pultrusion molding and welding, but if it is not sufficiently dried, a lubricating film will not be formed, so seizure between the die and the metal strip during molding will occur. It has been found that the dies and the die life are shortened.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks in the method for manufacturing a metal welded pipe by the die draw forming method, and has a tapered portion whose diameter decreases from the inlet side to the outlet side. When forming a flat metal strip into a tubular shape in which both side edges are abutted at once by penetrating the metal strip into a die in which a through hole having a circular cross section on the entrance side is formed, a metal strip and a die In order to reduce the friction of the above, when the lubricant is applied to the entire lower surface of the metal band by the application roll in front of the die, the lubricant is not completely dried, so that seizure or reduction of die life can be prevented. An object is to provide a method for manufacturing a welded pipe.

[0008]

As a result of various investigations to solve the above-mentioned problems, the present inventors have found that 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. When manufacturing, if the lubricant applied to the entire lower surface of the metal strip by the coating roll in front of the die is continuously dried by the heat of heating the metal strip in a heating furnace The present invention has been completed by researching good points.

An embodiment of a method for manufacturing a metal welded pipe according to the present invention will be described in detail below with reference to the drawings. Figure 1
After applying the lubricant to the entire lower surface of the metal strip by the method of the present invention, the metal strip is continuously heated by a heating furnace, and then the metal strip is penetrated through the die to butt the side edges of the flat metal strip at once. It is a side surface explanatory view showing the state where welding is performed, forming into a tubular state of the state. In FIG. 2, the installation position of the heating furnace in FIG. 1 is changed to the front of the coating roll,
Immediately after preheating the metal strip with this heating furnace, apply a lubricant to the entire lower surface of the metal strip, and then penetrate the metal strip through the die to form a flat metal strip into a tubular shape with its side edges abutting at once. It is a side surface explanatory view showing the state where welding is performed while forming. FIG. 3 is a diagram showing a temperature change of the thermocouple attached to the surface of the metal band when the heating furnace is penetrated in the two examples.

An outline of the method for producing a metal welded pipe according to the present invention will be described with reference to the embodiment shown in FIG. 1. A metal strip 1 unwound from an uncoiler (not shown) is coated with metal by a coating roll 3 of a lubricant coating device. A lubricant 2 such as a lubricant in which a fluororesin-based powder or a melamine resin-based powder is dispersed in water is applied to the entire surface of the strip 1 in contact with the die 4 (the outer surface of the metal welded pipe and the lower surface). The lubricant 2 applied while penetrating through the heating furnace 5 is dried, and then a through-hole having a circular cross-section having a portion with a taper 4a whose diameter decreases from the inlet side to the outlet side is formed on the inlet side. The formed die 4 penetrates the metal strip 1 and is formed into a tubular shape with its both side edges 1a abutted from a flat plate shape, and then the abutted portion 1b is TIG welded with a welding torch 8 to form a metal welded pipe. Manufacturing The most characteristic feature of the method for producing a metal welded pipe according to the present invention shown in FIG. 1 is that the entire surface of the lower surface of 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, the lubricant 2 applied on the metal strip 1 by the heating furnace 5 provided between the lubricant applying device and the die 4.
Is to be dried continuously.

Further, the outline of the method for manufacturing a metal welded pipe according to the present invention will be described with reference to the embodiment shown in FIG.
The metal strip 1 unwound from the uncoiler (not shown) is first sufficiently heated and preheated in the process of penetrating the inside of the heating furnace 5, and immediately after leaving the heating furnace 5, the metal strip 1 is applied by the coating roll 3 of the lubricant coating device. A lubricant 2 such as a lubricant in which a fluororesin-based powder or a melamine resin-based powder is dispersed in water is applied to the entire surface of the strip 1 in contact with the die 4 (the outer surface of the metal welded pipe and the lower surface). , The lubricant 2 applied until it reaches the die 4 is dried, and then a through-hole having a circular cross section having a portion with a taper 4a whose diameter decreases from the inlet side to the outlet side is formed on the inlet side. The formed die 4 penetrates the metal strip 1 and is formed into a tubular shape with its both side edges 1a abutted from a flat plate shape, and then the abutted portion 1b is TIG welded with a welding torch 8 to form a metal welded pipe. Because it is manufactured The most characteristic feature of the method for producing a metal welded pipe according to the present invention shown in FIG. 2 is that the lubricant 2 is applied to the entire lower surface of the metal strip 1 by the application roll 3 of the lubricant application device in front of the die 4. Lubricant 2 applied to metal strip 1 by heating furnace 5 provided before application
Is to preheat to a temperature at which it can be dried continuously.

The heating furnace 5 is a metal at a temperature sufficient to dry the lubricant 2 applied to the entire lower surface of the metal strip 1 by the application roll 3 of the lubricant application device and to a temperature at which no temper color is applied. It is indispensable that the belt 1 can be heated, and it is preferable that the belt 1 is of a half-divided type so as to be able to quickly and easily deal with any operational inconvenience.

[0013]

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 with its both side edges 1a abutted by penetrating the strip 1 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 a lubricant 2 on its entire lower surface by a coating roll 3 in front of the die 4, and the coated lubricant 2 is provided in a heating furnace 5 provided in front of the die 4 (the embodiment shown in FIG. 1). In the case of No. 2, it is a heating furnace which is installed rearward by the coating roll 3 and directly heats the lubricant 2 adhering to the metal strip 1. In the case of the embodiment shown in FIG. It is attached to the metal strip 1 by the heat given by the installed furnace, which is a heating furnace that preheats the metal strip 1 to a temperature at which the lubricant 2 applied to the metal strip 1 is dried before reaching the die 4. Lubricant 2 is continuously dried, then die 4 Since the metal strip 1 is formed into a tubular shape in which both side edges 1a of the metal strip 1 are butted against each other, the metal strip 1 is penetrated through the die 4 and is shaped into a tubular shape in which both side edges 1a are butted against each other. The seizure does not occur and the die life is not shortened.

[0014]

【Example】

Example 1 A tungsten carbide die 4 was formed with a through hole having an entrance side diameter of 35 mm, an exit side diameter of 10 mm and a taper angle of 22 ° as a through hole to form a titanium carbide and titanium nitride film by a chemical vapor deposition method. Installed in pipe making equipment. Then, an austenitic stainless steel strip having a wall thickness of 0.7 mm and a plate width of 30.7 mm is prepared as the metal strip 1, and the bottom surface of the metal strip 1 is coated with a fluorine resin lubricant 2 having a concentration of 20% by volume. While applying the solution, the die 4 is passed through so that the abutting portions 1b of the both side edges 1a are upward, and the production of a stainless welded pipe with a wall thickness of 0.7 mm and an outer diameter of 10 mm is performed under a pipe forming speed of 4 m / min. Tried in. Then, seizure occurred in the die 4, and many flaws were generated on the surface of the welded pipe. Therefore, the lubricant 2 and the die 4
A heating furnace 5 composed of a half-divided tubular electric furnace having a furnace core diameter of 40 mm and a furnace length of 500 mm was installed between the and, and the temperature inside the furnace was adjusted to 573 K, and a welded tube was manufactured by the same method as described above. . Then,
It was possible to manufacture a good welded tube without the above-mentioned seizure and without any flaws on the surface. This is because the temperature inside the heating furnace 5 is set to 573K, so that the surface temperature of the metal strip 1 is heated to about 400K as shown by the solid line in Fig. 3 at the pipe making speed of 4m / min. It is considered that the water as the solvent of the agent 2 was evaporated and the lubricating coating was completely formed.

Example 2 The heating furnace 5 in Example 1 was installed immediately before the coating roll 3 for coating the entire lower surface of the metal strip 1 with the fluorine resin lubricant 2 having a concentration of 20% by volume. A welded pipe was manufactured under the same conditions as in Example 1 except that the temperature inside the heating furnace 5 was adjusted to 623K. As a result, it was possible to manufacture a good welded pipe in which seizure did not occur and the surface had no flaws, as in Example 1. Since the temperature inside the heating furnace 5 is set to 623 K, the surface temperature of the metal strip 1 is coated with the lubricant 2 as shown by the broken line in FIG. 3 at the pipe making speed of 4 m / min. It is considered that since the water is heated to 370 K or more until the temperature reaches, the water as the solvent of the lubricant 2 is evaporated and the lubricating film is completely formed. The temperature of the heating furnace 5 may be set any number of times as long as the lubricating coating can be formed. However, when the surface temperature of the metal strip 1 is stainless steel of 473 K or more, the temper color adheres. Caution must be taken.

[0016]

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 flat metal strip is formed into a tube with both edges abutted by passing the metal strip through a die having holes, and then the welded torch is used to weld the abutted parts to form a metal welded pipe. When manufacturing,
A lubricant is applied to the entire lower surface of the metal strip in front of the die by a coating roll, and the lubricant is completely dried by continuously drying the applied lubricant by the heat of heating the metal strip in a heating furnace. Even if the metal strip penetrates the die, seizure does not occur, and it is possible to manufacture a good metal welded pipe having no surface flaw, and its industrial value is extremely great.

[Brief description of drawings]

FIG. 1 is a drawing showing a method of the present invention in which a lubricant is applied to the entire lower surface of a metal strip, and then the metal strip is continuously heated in a heating furnace.
FIG. 6 is a side view showing a state in which welding is performed while forming a flat metal strip into a tubular shape in which both side edges are abutted at once by penetrating the metal strip through the die.

FIG. 2 is a schematic view showing that the heating furnace in FIG. 1 is installed in front of a coating roll, and the metal strip is preheated by the heating furnace, and immediately after that, a lubricant is applied to the entire lower surface of the metal strip, and then the die is coated with the metal strip. It is a side surface explanatory view showing the state where welding is performed, forming the tubular metal band which penetrates and forms the tubular shape of which both side edges were abutted at once.

FIG. 3 is a diagram showing a temperature change of a thermocouple attached to a surface of a metal band when a heating furnace is penetrated in two examples.

FIG. 4 is a perspective view of a method for manufacturing a metal welded pipe by a conventional roll forming method.

[Explanation of symbols]

 1 Metal band 1a Both side edges 1b Butt part 2 Lubricant 3 Application roll 4 Die 4a Taper 5 Heating furnace 6 Seam guide roll 7 Squeeze roll 8 Welding torch 9 Forming roll or cage roll

Claims (2)

[Claims] 1. A metal band (1) is formed on 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. The flat metal strip (1) is formed into a tubular shape with its both side edges (1a) butted together, and then the butted portion (1b) is welded with a welding torch (8) for metal welding. In manufacturing the pipe, in front of the die (4), a lubricant (2) is applied to the entire lower surface of the metal strip (1) by a coating roll (3), and then the metal strip (1) is heated by a heating furnace (5). A method for producing a metal welded pipe, characterized in that the lubricant (2) adhering to the metal strip (1) is continuously dried by heating. 2. A heating furnace (5) in front of the die (4).
Change the installation position to the front of the coating roll (3) and
Immediately after preheating (1), the metal strip is applied by the coating roll (3).
The method for producing a metal welded pipe according to claim 1, wherein a lubricant (2) is applied to the entire lower surface of (1) and the lubricant (2) attached to the metal strip (1) is continuously dried.