JPH0739932A - Manufacture of metallic welded tube - Google Patents

Abstract

PURPOSE:To manufacture a metallic welded tube having a good weld zone by applying a lubricant whose specific gravity is made constant by replenishing a solvent on the underside of a metallic strip before forming, forming with a die and welding it. CONSTITUTION:The lubricant 2 is applied on the metallic strip 1 which is delivered from an uncoiler with an applying roller 3. After forming into a tubular shape by passing the metallic strip 1 through the die 4 having a tapered through hole 5 of a circular section, the welded metallic tube is manufactured by welding the butted part with a welding torch 8. At that time, the lubricant 2 whose specific gravity is made constant by continuously or intermittently replenishing the solvent is applied on the whole of the underside of the metallic strip 1 before forming with the die 4. The specific gravity of the lubricant 2 is measured with a standard specific gravity meter 11 in a specific gravity measuring part 10 and the solvent is replenished from a solvent supplying port 12. In this way, the occurrence of weld defects such as a blow hole in the interior of a weld bead is prevented.

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 two side edges abutted all 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 in front of the die in order to reduce the number of welds, it is possible to prevent welding defects such as blow holes from occurring inside the weld beads due to the lubricant. The present invention relates to a manufacturing method of.

[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 to form a tube and welding, the metal strip is arranged in a large number of tandems as shown in the perspective view of FIG. The metal strip 1'is 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 1'formed into a tubular shape is a seam guide roll 6'or a squeeze roll. A roll forming method in which the butted portions 1b ′ of the side edges 1a ′ of the metal strip 1 ′ while being held by the 7 ′ is butt-welded by a welding means such as a welding torch 8 ′ has been generally performed.

However, in the roll forming method, when the outer diameter of the metal welded pipe to be manufactured is changed, the forming roll or the cage roll 9, and further the seam guide roll 6'and the squeeze roll 7 ', etc. Since it is necessary to replace the rolls with those corresponding to the outer diameter of the metal welded pipe to be manufactured, there are at least 20 or more roll sets to be exchanged for one type of outer diameter. Since it requires labor and a long time, the production efficiency of the equipment is reduced, and since it is necessary to prepare a large number of rolls corresponding to the outer diameter of the metal welded pipe to be manufactured, it is not economical. It was Further, in such a roll forming method, the outer diameter is 1
When manufacturing a thin metal welded pipe having a diameter of 0 mm or less, high accuracy is required for the installation position of each roll set, and there is a setting error in some roll positions of each roll set. However, there is also a drawback that the metal welded pipe is twisted during the forming and a step is likely to occur at the butted portion 1b '.

Further, as shown in FIG. 2, a method of drawing a metal strip with a molding 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. 39-39.
No. 18657 "Consistent pipe making machine for long thin metal pipes"
Is disclosed as a technique for continuously performing a step of forming a thin metal plate hoop into a tube shape with a forming die, sequentially welding, and then annealing using a non-oxidation bright annealing furnace by high-frequency induction heating. In the publication "Metal Corrugated Pipe Manufacturing Method", a series of manufacturing is performed by forming a tube with a forming die and welding the joining points of the tubular body, then performing corrugation processing and continuously performing bright heat treatment in a non-oxidizing gas atmosphere. Line technology is 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. The part of the taper surface on the side where the through-hole is inserted that contacts both edges of the metal strip is damaged, shortening the life of the die, and the die flaw causes flaws on both edges of the metal strip. Since the metal powder that has fallen off from the flaws generated on both side edges of the metal accumulates in the die and causes surface flaws on the metal strip, there is the disadvantage that it is necessary to interrupt the molding and maintain the die frequently. there were.

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 polytetrafluoroethylene as a main component with a fluorocarbon solvent represented by the chemical formula CCl2F-CClF2 to the entire surface). Investigated. However, since the freonsolve of this solvent easily evaporates, the concentration of the lubricant is likely to be high, and the high concentration of the lubricant causes the weld to solidify even at high temperatures due to TIG welding using a welding torch. Since it is not completely sublimated by the time, the lubricant remains and melts into the welded part, causing blowholes etc. inside the bead after welding, and it became clear that it is not possible to obtain a good welded pipe due to welding defects. did.

[0007]

SUMMARY OF THE INVENTION The present invention solves the drawbacks of the method for producing a metal welded pipe by the die draw forming method described above, so that the specific gravity is constant over the entire lower surface of the metal strip in front of the die. A method for manufacturing a metal welded pipe, which can prevent a welding defect such as a blowhole from occurring inside the weld bead due to the lubricant by applying a lubricant whose concentration is adjusted continuously or intermittently The challenge is to provide.

[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. By passing the metal strip through the die 4 having the through hole 5 formed therein, the flat metal strip 1 is formed into a tubular shape with its both side edges 1a abutting, and then the abutting portion 1b is welded torch 8 When manufacturing a metal welded pipe to be welded with, a lubricant is previously applied to the entire lower surface of the metal strip 1 by a coating roll 3 in order to reduce the friction between the metal strip 1 and the die 4, and the specific gravity of the lubricant 2 is always maintained. If the concentration is controlled, that is, if the specific gravity becomes high, by adjusting the specific gravity value by replenishing the solvent, it is possible to prevent the concentration of the lubricant 2 from increasing and prevent the lubricant from remaining on the welded portion. For welding inside the bead The inventors have completed the present invention by discovering that it is effective in preventing welding defects that occur.

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 is a side view showing a state in which a metal welded pipe is manufactured while controlling the lubricant concentration by the method of the present invention, and FIG. 2 is a tube in which the metal strip is pulled out by a die in the method of the present invention. FIG. 4 is a perspective view showing the state of molding, FIG. 3 is a view showing the relationship between the lubricant concentration and specific gravity, and FIG. 4 is a view showing the relationship between the lubricant concentration and the number of blow holes generated.

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 polytetrafluoroethylene as a main component has a chemical formula CCl on the entire surface (the outer surface of the metal welded tube and the lower surface).
₂ F-CClF ₂ A cross-section having a tapered portion on the inlet side, which is diluted with a fluorocarbon solve and whose specific gravity is measured at the specific gravity measuring section 10, and whose diameter decreases from the inlet side to the outlet side. It is penetrated by a die 4 having a circular through hole 5 and is formed into a tubular shape in which both side edges 1a thereof are abutted from a flat plate, and then the abutting portion 1b is TIG welded with a welding torch 8 to form a metal. It is manufactured into a welded pipe.

The features of the method for producing a metal welded pipe according to the present invention are that the lubricant 2 is uniformly applied to the metal strip 1 by the application roll 3 before forming, and the specific gravity of the lubricant 2 is Timely measurement in the measuring unit 10, the value is
The solvent is added from the solvent replenishing port 12 so as to be 1.60 to 1.62, and the concentration of the lubricant 2 is controlled so as to be always in a constant range. Here, if the specific gravity exceeds 1.62, blowholes are generated in the welded portion, and if it is less than 1.60, the lubrication effect is reduced, and the metal band is flawed during molding. Therefore, the range is preferably 1.60 to 1.62. .

In the specific gravity measuring unit 10, any method may be used as a means for measuring the specific gravity of the lubricant 2. However, since the solvent Clonsolve is a quick-drying substance, it easily evaporates, so that it is a simple standard. It is preferable to use a hydrometer.

[0013]

As described above, in the method of the present invention, the die 4 having the through-hole 5 having a circular cross section, which has a tapered portion on the inlet side whose diameter decreases from the inlet side to the outlet side, is formed. 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 pipe by welding with, the specific gravity of the lubricant 2 applied to the entire lower surface of the metal strip 1 in order to reduce friction is measured in the specific gravity measuring section 10, and an appropriate amount of solvent is supplied from the solvent supply port 12. However, the specific gravity value is always adjusted to 1.60 to 1.62 to prevent the concentration of the solvent from increasing, and because the entire surface is evenly coated, the lubricant 2 does not remain in the welded portion and weld defects are prevented. It is possible.

[0014]

EXAMPLE A 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 was used as a metal strip 1.
Before applying to, the specific gravity is measured by the specific gravity measuring unit 10 and the value is 1.60 to 1.62 (concentration:
It is controlled so that it is between 3% by volume and 30% by volume, and a stainless steel strip with a plate thickness of 0.7 mm and a plate width of 30.7 mm (SUS
304) is applied to the entire lower surface (the side that becomes the outer surface of the metal welded pipe), and the taper (taper angle: 10 mm) decreases from the entrance side (diameter: 35 mm) to the exit side (diameter of the smallest diameter part: 10 mm). 22 °) is formed in the through-hole having a circular cross-section having a portion marked with 22 °) on the inlet side, and the inner surface of the through-hole is made of a tungsten carbide die coated with a film of titanium carbide and titanium nitride by a chemical vapor deposition method. The stainless steel strip was pierced at a pipe speed of 4 m / min to form a tubular shape in which both side edges were abutted at once, and this abutted portion was immediately TIG welded using a welding torch {welding condition: current (120 A) Argon gas flow rate (10 l /
As a result, it was possible to manufacture a metal welded pipe having a good welded portion with a diameter of 10 mm, which was free from blowholes caused by the residual lubricant even after about 3 hours from the start of operation and had no flaws. .

[0015]

[Comparative Example] As a result of producing a metal welded pipe under exactly the same conditions as in the Example except that the concentration of the lubricant was not controlled,
About 3 hours after the start of operation, the concentration of lubricant is about 50% by volume.
As the lubricant remains, blowholes are continuously generated inside the bead, and the average number of defects is about 100.
Only a welded metal tube with a defective welded area of over 10 m / m was produced.

[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 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
By measuring the specific gravity of the lubricant with the specific gravity measuring section installed in front of the coating roll and applying the solvent to the metal strip while controlling the specific gravity so that the specific gravity is within a certain range, Since it is possible to prevent the lubricant from remaining, it is possible to manufacture a metal welded pipe having a good weld portion in which no blowhole exists in the weld bead. In addition, in order to measure the specific gravity of the lubricant, a particularly expensive device is not required, and a simple method of using a standard hydrometer can be used.
It is easy for anyone to measure and does not require excessive equipment costs. As described above, the industrial value of the method of the present invention having various advantages is extremely great. Furthermore, the present invention is not only effective for a lubricant using freonsolve as a solvent, but also applicable to concentration adjustment by controlling the specific gravity of a lubricant whose concentration changes with time during operation.

[Brief description of drawings]

FIG. 1 is a side explanatory view showing a state in which a metal welded pipe is manufactured while controlling a lubricant concentration by the method of the present invention.

FIG. 2 is a perspective view showing a state in which a metal band is pulled out by a die of the method of the present invention and formed into a tubular shape all at once.

FIG. 3 is a diagram showing a relationship between a concentration of a lubricant and a specific gravity.

FIG. 4 is a diagram showing a relationship between the concentration of a lubricant and the number of blow holes generated.

FIG. 5 is a perspective view of a method for manufacturing a metal welded pipe by a conventional roll forming method.

[Explanation of symbols]

 1 Metal strip 1'Metal strip 1a Both side edges 1a 'Both side edges 1b Butt portion 1b' Butt portion 2 Lubricant 3 Coating roll 4 Dice 5 Through hole 6 Seam guide roll 6'Seam guide roll 7 Squeeze roll 7'Squeeze roll 8 Welding Torch 8'Welding torch 9 Forming roll or cage roll 10 Specific gravity measuring part 11 Standard specific gravity meter 12 Solvent supply port 13 Lubricant tank 14 Pump

Claims (1)

[Claims] 1. A metal band (1) is attached to a die (4) having a through hole (5) having a circular cross section having a tapered portion on the entrance side whose diameter decreases from the entrance side to the exit side. ), The flat metal strip (1) is formed into a tubular shape with both side edges (1a) butted together, and the butted portion (1b) is welded with a welding torch (8). When manufacturing a welded pipe, a lubricant that keeps the specific gravity constant by continuously or intermittently replenishing the entire lower surface of the metal strip (1) with a solvent before forming with the die (4). Welding torch (8)
A method for producing a metal welded pipe, which is produced by welding at.