JPH05277551A - Manufacture of metallic welded pipe - Google Patents

Abstract

PURPOSE:To prevent the occurrence of surface flaw on a metallic welded pipe to be manufactured, to unnecessitate repairs of a die for long period and to prolong the service life of the die. CONSTITUTION:A center part between both parts in the range of 1/10-1/3 of strip width respectively from both side edges in a metallic strip 1 is made to be flat-state or bent to arc-state so as to protrude to the side to be the inside surface of the pipe. At the same time, the bending work is executed so that in the case of the former, the bending angle at the both parts or in the case of the latter, the bending angle at the both parts subtracted by half of the bending angle at the center part, becomes 30-85 deg. angle at the side to be the inside surface of the metallic welded pipe, respectively and thereafter, this bended pipe is passed through the die 4.

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 through hole having a circular cross section, which has a tapered portion whose diameter decreases from the entrance side to the exit side. By doing so, the flat metal strip is formed into a tubular shape in which both side edges thereof are abutted at once, and then the abutting portion is welded to mainly produce a ratio of the wall thickness t to the outer diameter D.
When producing a metal welded pipe with a (t / D) of about 3 to 20%, it is possible to prevent surface flaws from being produced on the produced metal welded pipe, and to eliminate the need for maintenance of the die for a long period of time, as well as the life of the die. The present invention relates to a method for manufacturing a metal welded pipe capable of extending the length.

[0002]

2. Description of the Related Art To manufacture a metal welded tube by bending a metal strip in the width direction to a product curvature and forming it into a tubular shape and welding it, conventionally, a caliber arranged in a large number of tandems as shown in the perspective view of FIG. A state in which the metal strip 1 is sequentially bent in the width direction by using a roll forming machine including a forming roll having 10 or a cage roll 10 and the tubular shaped metal strip 1 is held by the seam guide roll 5 and the squeeze roll 6. Then, the roll forming method has been generally carried out in which the butt portions 1b of both side edges 1a of the metal strip 1 are butt-welded by a welding means 7 such as a welding torch.

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 1 is used.
0, and further seam guide roll 5 and squeeze roll 6
Since it is necessary to replace all of the respective rolls such as the ones corresponding to the outer diameter of the metal welded pipe to be manufactured, there are at least 20 or more roll sets to be replaced for one outer diameter. The exchange requires a lot of labor and a long time, which lowers the production efficiency of the equipment, and is disadvantageous in that 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. there were.

Further, in such a roll forming method, in order to manufacture a thin metal welded pipe having an outer diameter of 10 mm or less, high precision is required for the set position of each roll set, and therefore each roll is required. If there is a setting error in the roll position of some of the sets, there is a drawback that the metal welded pipe is likely to be twisted during welding or a step is likely to occur at the butted portion 1b.

As a method of solving such a drawback and manufacturing a metal welded pipe with a simple facility, the present applicant previously described in Japanese Patent Laid-Open No. 3-207523, "Diameter goes from the inlet side to the outlet side. The metal strip is penetrated through a die that has a through hole with a circular cross section having a tapered portion to make the flat metal strip into a tubular shape in which both side edges are abutted. , A method of manufacturing a metal welded pipe, which is characterized by welding the butt portion.

The method for manufacturing a metal welded pipe proposed by the applicant of the present invention is such that a through hole having a circular cross-section is formed which has a tapered portion on the inlet side whose diameter decreases from the inlet side to the outlet side. By passing the metal strip pulled out from the material coil through the existing die, a flat metal strip is formed into a tubular shape with its both edges abutting at once, and the welded portions are continuously welded to form a metal welded pipe. Is a method of manufacturing.

In such a method for producing a metal welded pipe, since only the forming die, the seam guide roll and the squeeze roll are required tools for forming a flat metal strip into a tubular state in which both side edges of the strip are abutted against each other, the equipment is Is easy and inexpensive, and the outer diameter of the welded metal pipe to be manufactured is easy to change, and since there are few rolls that require highly accurate position setting, a thin metal welded pipe with an outer diameter of 10 mm or less is manufactured. Even in such a case, it has an excellent advantage that it is possible to prevent the twist of the metal welded pipe and the step difference of the butted portion due to the error of the setting position of the roll.

However, since this method of manufacturing a metal welded pipe is a method in which a flat metal strip is directly drawn out through a through hole having a taper on the entrance side of the die to form a tubular shape,
The corners of both edges of the metal strip contact the tapered surface of the through hole of the die first, and the bending moment in the width direction that is received during the forming is further increased during the forming in the through hole of the die. Since it is the smallest in the section, both side edges of the metal strip are hardly subjected to bending until it is formed just before the parallel section (the smallest diameter section) of the through hole of the die. Therefore, since both side edges of the metal strip are drawn into the tapered portion on the side of the through hole of the die with almost no bending work, the corners of the both side edges of the metal strip are on the side of the side of the through hole of the die. When sliding for a long time because it slides on the tapered surface on the side of the through hole of the die while it is in contact with the tapered surface with high surface pressure, flaws will occur on both side edges of the metal strip and the side of the die through hole The taper surface of the die is damaged, 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 causes surface flaws on the metal strip. There is a drawback that it is necessary to interrupt the molding and perform maintenance of the die.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the method for producing a metal welded pipe proposed by the present applicant,
It is an object of the present invention to provide a method for producing a metal welded pipe which can prevent surface defects from occurring in the produced metal welded pipe, can maintain the die for a long time, and can extend the life of the die.

[0010]

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 method for producing a metal welded pipe in which a flat metal strip is formed into a tubular shape with its both side edges abutted by penetrating the metal strip through a die having a through hole, and then the abutted portions are welded. In the above, the central part sandwiched between the both edges of the metal strip in the range of 1/10 to 1/3 of the plate width is flattened or projected to the inner surface side of the metal welded pipe. At the same time, when the central portion is flattened, the bending angles of the two portions are also curved so that the central portion projects toward the inner surface of the metal welded pipe. If Bend the half of the bending angle of the center part of the two parts to the inner surface of the metal welded pipe so that the bending angle is 30 degrees or more and 85 degrees or less. It is enough to pass through the metal strip, and from the both edges of the metal strip, 1/10 of the strip width
If the lubricant is applied to the outer surface side of the metal welded pipe before the bending work is performed so that the bending angles of both parts within the range of ⅓ are the predetermined bend angles, the surface of the metal welded pipe will be more enhanced. The present invention has been completed by investigating that defects can be prevented and damage to the die can be suppressed.

The method for producing a metal welded pipe according to the present invention will be described in detail below with reference to the drawings. 1 is a side view showing an example of a state in which a metal welded pipe is manufactured by the method of the present invention, FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 3 shows the shape of the metal strip in FIG. FIG. 4 is a sectional explanatory view showing the shape of a metal strip of another embodiment corresponding to FIG.

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 passes through the pass line adjusting roll 9 and then the die 4 is formed by the lubricant applying device 2. Lubricant is applied to the contacting surface (the side that becomes the outer surface of the metal welded pipe), and the edge bend rolls 3a and 3b, which are the features of the present invention, bend the side edges 1a to a predetermined width. After receiving, a state in which both side edges 1a thereof are abutted at once by a die 4 having a through hole having a circular cross-section having a tapered portion on the inlet side whose diameter decreases from the inlet side to the outlet side. The welded metal pipe is formed into a tubular shape, and the butt portion 1b is butt-welded by the squeeze roll 6 and the welding means 7 while the edge position is guided by the seam guide roll 5. 8 is manufactured.

In such a process, the central portion sandwiched by the edge bend rolls 3a, 3b from both side edges 1a of the metal strip 1 to both portions in the range of 1/10 to 1/3 of the plate width is flattened. At the same time (see FIG. 3) or bent into an arc shape so as to project to the side that will be the inner surface of the metal welded pipe (see FIG. 4), the central portion sandwiched between the two parts was made flat. In this case, the bending angle α of the both portions is the same as the bending angle 2θ of the central portion when the central portion sandwiched between the both portions is bent in an arc shape so as to protrude toward the inner surface of the metal welded pipe. It is necessary to perform bending so that the bending angle (α−θ) in both the parts obtained by subtracting half of the above is 30 ° or more and 85 ° or less on the inner surface side of the metal welded pipe.

Here, the range of bending on both sides of the metal strip 1 is 1/10 of the plate width from both side edges 1a of the metal strip 1.
The range limited to 1/3 is that if the bending range is from the side edges 1a of the metal strip 1 to less than 1/10 of the plate width, the side edges 1a of the metal strip 1 are excessively bent and the metal strip 1 This is because the side edges 1a are not satisfactorily abutted with each other, and a lap (edge overlap) is likely to occur at the abutting portion 1b. This is because, similarly to the case where the whole is bent, both side edges 1a of the metal strip 1 are in strong contact with the tapered surface of the die 4 and the effect of bending is hardly obtained. In addition, when the center portions sandwiched by the edge bend rolls 3a and 3b from both side edges 1a of the metal strip 1 to both sides in the range of 1/10 to 1/3 of the plate width are made flat, When the bending angle α in both parts is bent in an arc shape so that the central part projects toward the inner surface of the metal welded pipe, half of the bending angle 2θ in the central part is subtracted from both parts. The bending angle (α-θ) must be bent so that the inner surface of the metal welded pipe is 30 degrees or more and 85 degrees or less. These angles are less than 30 degrees. Since both sides of the metal strip 1 have not been significantly bent, both side edges 1a of the metal strip 1 strongly contact the tapered surface of the through hole of the die 4 and the effect of bending is almost obtained. Because there ’s no Therefore, when bending is performed with the single-stage edge bend rolls 3a and 3b, the forming amount becomes excessive, and the surface pressure between the edge bend rolls 3a and 3b on both sides of the metal strip 1 increases and the roll circumference also increases. This is because the edge bend rolls 3a and 3b are not preferable because of scratches and wear on the edge bend rolls 3a and 3b due to the speed difference between the speed and the metal strip 1.

[0015]

As described above, the metal strip 1 is passed through the die 4 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. In this way, in the method for manufacturing the metal welded pipe 8 in which the flat metal strip 1 is formed into a tubular shape in which both side edges 1a thereof are abutted at one time and then the abutted portion 1b is welded, 1/10 to 1 of board width
The central part sandwiched between both parts in the range of / 3 is flattened or bent in an arc shape so as to project to the side which becomes the inner surface of the metal welded pipe, and at the same time, the central part is flattened. The bending angle α in both parts
However, in the case where the central portion is bent in an arc shape so as to project to the side that becomes the inner surface of the metal welded pipe, the bending angle (α-θ in both portions obtained by subtracting half θ of the bending angle 2θ of the central portion ) Is bent by the edge bend rolls 3a and 3b so as to form an angle of 30 degrees or more and 85 degrees or less on the side that becomes the inner surface of the metal welded pipe, and then passes through the through hole of the die 4, In particular, at the first stage of passing the metal strip 1 into the die 4, the contact area between the inner surface of the through hole of the die 4 and both sides of the metal strip 1 can be increased and the contact surface pressure can be lowered, so that the product as a manufactured product can be obtained. Not only can the occurrence of surface defects in the metal welded pipe 8 be reduced,
The tapered surface of the through hole of the die 4 is not damaged and the life of the die 4 is not shortened, and further, the metal powder that has fallen off from the flaws on the both side edges 1a of the metal strip 1 accumulates in the through hole of the die 4. The situation in which a phenomenon occurs and the molding must be interrupted to perform maintenance of the die 4 does not occur.

It is known that, in the drawing process, applying backward tension to the material from the die entry side is an effective means for reducing the load on the die. However, tension applying means such as a tension reel is required to apply a stable backward tension to the material that can be passed through the die, but it is often difficult to implement because the equipment is expensive. However, in the method of the present invention, at least the side edges 1a of the metal strip 1 are formed by the edge bend rolls 3a and 3b on the entrance side of the die 4.
Therefore, since the bending work is performed on both portions in the range of 1/10 to 1/3 of the plate width, this bending work has the same effect as applying the backward tension. That is, since the bending is performed, the edge bend rolls 3a and 3b can stably obtain a larger braking force than a tension pad or the like by friction alone. Therefore, the life of the die 4 can be greatly extended by increasing the value of.

[0017]

[Example] A stainless steel strip (SUS3) having a plate thickness of 0.7 mm and a plate width of 30.7 mm coated with a lubricant made of fine fluororesin powder
04) from each side edge within a range of about 4 mm (about 1 of the plate width
/7.7) the central part sandwiched between both parts is made flat, and both parts are driven by a radius of 4 mm so as to form an angle of about 57.3 degrees to the inside surface of the metal welded pipe. After performing bending work with edge bend roll,
From the entrance side (diameter: approx. 30 mm) to the exit side (diameter of the smallest diameter part: 10 mm)
The taper (taper angle:
22 °) is formed on the inside of the through hole having a circular cross section, and the inner surface of the through hole is coated with a titanium carbide film and a titanium nitride film by a chemical vapor deposition method on a tungsten carbide die. When the stainless steel strip was formed into a tubular shape with its both edges abutted all at once by penetrating the stainless steel strip, the abutting portion was TIG welded using a welding torch. Compared to the conventional method in which both sides within a predetermined range from both side edges of the steel strip are not bent to the side that becomes the inner surface of the metal welded pipe at a predetermined angle, both side edges of the stainless steel strip are The amount of stainless steel powder that has fallen off from the stainless steel strip accumulated in the through holes of the die due to damage is significantly reduced. Pull-out force required a scan steel steel strip to pull allowed to pass through the through hole of the die from 3.66kN 3.0
It decreased to 4 kN.

[0018]

As described above in detail, in the method for manufacturing a metal welded pipe according to the present invention, a through hole having a circular cross section having a tapered portion on the inlet side whose diameter decreases from the inlet side to the outlet side. In the method for producing a metal welded pipe, in which a flat metal strip is formed into a tubular shape in which both side edges thereof are abutted at once by penetrating a metal strip in a die in which the abutting portions are welded, From the both side edges of the metal strip, flatten the central part sandwiched between both parts of a predetermined ratio of the plate width, or bend it in an arc shape so as to project to the side that becomes the inner surface of the metal welded pipe, When the central portion is in a flat state, the bending angles of the both portions are different, and when the central portion is bent in an arc shape so as to project to the side which becomes the inner surface of the metal welded pipe, the bending of the central portion is made. After performing bending work so that the bending angle in both parts subtracting half of the angle becomes the predetermined bending angle on the side that will be the inner surface of the metal welded pipe, it is a simple method to pass through the through hole of the die. Despite that, it has the remarkable effect that it can prevent surface flaws that occur in the welded metal pipe to be manufactured, does not require maintenance of the die for a long time, and can extend the life of the die. If a lubricant is applied to the outer surface of the metal welded pipe before bending the both edges at a predetermined proportion of the plate width so that the bending angle becomes the predetermined bending angle, it becomes more metallic. It is possible to prevent surface flaws occurring in the welded pipe and suppress damage to the die, which is of great industrial value.

[Brief description of drawings]

FIG. 1 is a side view showing an example of a state in which a metal welded pipe is manufactured by the method of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA in FIG.

FIG. 3 is an explanatory cross-sectional view showing the shape of the metal band in FIG.

FIG. 4 is a cross-sectional explanatory view showing the shape of a metal strip of another embodiment corresponding to FIG.

FIG. 5 is a perspective view showing an example of a state in which a conventional metal welded pipe is manufactured.

[Explanation of symbols]

 1 Metal band 1a Both side edges 1b Butt portion 2 Lubricant applying device 3a, 3b Edge bend roll 4 Die 5 Seam guide roll 6 Squeeze roll 7 Welding means 8 Metal welding pipe 9 Path line adjusting roll 10 Forming roll or cage roll

Claims (2)

[Claims] 1. A flat plate shape is obtained by penetrating a metal band through a die having a through hole having a circular cross section having a tapered portion whose diameter decreases from the entrance side to the exit side. In a method for manufacturing a metal welded pipe in which a metal strip is formed into a tubular shape in which both side edges are abutted at a stroke and then the abutted portions are welded, a metal strip having a width of 1/10 to 1/3 of a width of each side edge is formed. When the central part sandwiched between both parts of the range is flattened or bent in an arc shape so as to project to the side that becomes the inner surface of the metal welded pipe, and when the central part is flattened, If the bending angle in both the parts is bent in an arc shape so that the central part projects toward the inner surface of the metal welded pipe, the bending angle in both parts obtained by subtracting half the bending angle of the central part Angle, after each performing inner surface and made to be 30 degrees or more and 85 degrees or less angle to the side bending of metal welded pipe, preparation of metal welded pipe, characterized in that passing the die. 2. From the both side edges of the metal strip, 1 / of the plate width
The metal according to claim 1, wherein a lubricant is applied to the outer surface side of the metal welded pipe before bending is performed so that the bending angle of both parts in the range of 10 to 1/3 becomes a predetermined bending angle. Welded pipe manufacturing method.