JP3327510B2 - ERW pipe manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric resistance welding method in which a metal strip is continuously formed into a cylindrical shape by a group of forming rolls, and edges at both ends are joined by an electric induction welding method to form a pipe. The present invention relates to a method for manufacturing a pipe.

[0002]

2. Description of the Related Art As shown in FIG. 5, an ERW pipe is formed by continuously forming a strip of material into a cylindrical shape by a group of forming rolls 1 to form an open pipe 2. The edge portion 2 a is intensively heated by Joule heat by an electric current by an induction heating coil 3 connected to a high frequency power supply, and is pressed and joined laterally by a squeeze roll 4 to form a pipe 5. At this time, the two-roll squeeze roll 4 shown in FIG. 6 often has the same structure regardless of the size of the open pipe 2.

[0003] Such a two-roll squeeze roll is
In general, the pressurizing operation on an open pipe is simple, there are few working errors, and the number of rolls used is small, so that there is a feature that the number of steps for changing the outer diameter of the pipe can be reduced.

However, when manufacturing an electric resistance welded tube,
As shown in FIG. 5, the open pipe 2 passing through the group of forming rolls 1 is further narrowed down by the squeeze roll 4,
Since the edges 2a at both ends are bent and joined,
When a two-roll squeeze roll as shown in FIG. 6 is used, there is a disadvantage that a great frictional resistance is generated between the flange portion 4a of the squeeze roll 4 and the edge portion 2a of the open pipe 2. I have. In FIG. 5,
Reference numeral 6 denotes an external bead cutting bit (hereinafter simply referred to as a “bite”) for cutting a welded external bead 5 a of the pipe 5.

[0005] This open pipe 2 has a large friction resistance.
When the thickness becomes thicker, the outer surface of the edge portion is cut off, and the excess thickness is increased so that the excess thickness is bitten out of the squeeze roll. As a result, as shown in FIG. 7, a biting flaw 7 is formed at a portion of the outer surface side of the edge portion 2a which is in contact with the flange portion 4a.

[0006] The biting flaw 7 is formed by a group of regular rolls 8 (FIG. 5).
8), resulting in rash-like flaws 9 on both sides of the ERW weld as shown in FIG. Since such rashes 9 are minute, they usually do not cause a problem. However, they are extremely harmful to drawing, expanding and bend pipes, and as a result of strict surface inspection, most products Will be rejected.

[0007] As a technique for preventing such rashes 9, there is a method employing a multi-roll squeeze roll. For example, when a four-roll squeeze roll 10 as shown in FIG. 9 is used, the edge 2a of the open pipe 2 can be pressed down and formed from above by the upper roll 10a without difficulty. There is no frictional resistance that would occur when a roll-type squeeze roll is used, and no biting flaw 7 is formed.

[0008]

However, when a multi-roll squeeze roll is used, the number of man-hours required for changing the outer diameter of a pipe increases with an increase in the number of rolls, thereby deteriorating the operation rate. become. Therefore, in a practical operation, it is disadvantageous to use a multi-roll squeeze roll.

In addition, in the electric resistance welding method, it is indispensable that the butt shape of the edges at both ends of the open pipe is properly maintained. However, when a multi-roll squeeze roll is used, the butt shape is not sufficient. It is difficult to accurately reset each roll to a good condition. Therefore, since it is difficult to obtain an appropriate butting shape with good reproducibility, it is necessary to check the butting shape each time the squeeze roll setting is changed, which leads to a deterioration in the operation rate and the pipe production yield.

Although the squeeze roll is a multi-roll type squeeze roll having the above-mentioned problems, in the case of a large-diameter pipe making machine, the roll unit cost is reduced by dividing and reducing the size of the roll, and the cost of polishing and rework is reduced. Therefore, multi-roll squeeze rolls are widely used. In addition, even in a small-diameter thick-wall pipe-making machine, a multi-roll squeeze roll, which is unavoidably disadvantageous in operation, is used in order to prevent the above-mentioned flaw-like flaw.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and it has been found that even small-sized thick-walled pipe-making machines having an outer diameter of 152.4 mm or less and a wall thickness of 9.0 mm or more have a rash-like flaw. An object of the present invention is to provide a method for manufacturing an electric resistance welded pipe that can employ a two-roll squeeze roll that is advantageous in operation without generating the squeeze roll.

[0012]

In order to achieve the above object, a method for manufacturing an electric resistance welded pipe according to the present invention comprises the steps of: (a) forming a squeeze roll on an outer surface of an edge of an open pipe ; line fit of the contact portion with the flange portion
They are arranged in the pipe circumferential direction at intervals in the transport direction . Then, by the depth of cut of bytes placed in this way within 0.8 mm, welding the outer surface Bee
The flaws that occur on both sides of the ERW weld at the same time
Each bar can be efficiently cut and removed one side at a time before entering the fixed roll.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted various tests and studies to achieve the above-mentioned object. As a result, in order to efficiently remove the flaws formed on both sides of the ERW weld when using a two-roll squeeze roll before entering the fixed roll, it is necessary to use a welding tool to weld the outer surface bead. At the same time, they found that cutting was effective.

[0014] However, a cutting tool having a wide cutting surface capable of simultaneously cutting out the flaws generated on both sides of the electric resistance welded portion becomes a very large cutting tool in order to guarantee the strength of the shank and the tip. As a result, the unit cost of the tool increases and the manufacturing cost deteriorates. In general, it is necessary to select the rake angle and blade strength of the cutting tool according to the cutting resistance of the work to be cut.However, the weld outer surface bead softened by induction heating and the pipe base material at room temperature are simultaneously cut with a wide tool. Then, the cut surface of the pipe base material is roughened or peeled, resulting in poor surface properties. Therefore, conventionally, it has not been performed to remove the flaws by cutting with a cutting tool.

[0015] However, the inventors of the present invention's stacked further research, two bytes having a normal width, open
Line to match the second portion in contact with the flange portion of the roll squeeze roll on the outer surface side of the edge portion of Npaipu
Distribute in the pipe circumferential direction at intervals in the transport direction ,
If the cutting depth of these tools is 0.8 mm or less,
It has been found that it is possible to efficiently remove bleeding flaws that occur on both sides of the ERW weld before entering the fixed form roll without causing roughening or tearing on the cut surface of the pipe base material. Thus, the present invention has been established.

That is, the method for manufacturing an electric resistance welded tube according to the present invention comprises:
Both edges of the open pipe are intensively heated with Joule heat generated by high-frequency current, and the outer diameter of the two-roll squeeze roll is 152.4 mm or less.
Thickness in the manufacturing method of the above small-diameter thick-walled electric-resistance-welded pipe 9.0 mm, Lai combined two byte portion in contact with the flange portion of the disk <br/> Izuroru the outer surface side of the edge portion
In emissions conveying direction at intervals are arranged in the circumferential direction of the pipe to the distribution shape, as within 0.8mm cutting depth of these bytes,
At the same time as one bead,
Cut out the biting flaw that occurs on one side and use the other bite
The bite generated on the other side of the ERW weld at the same time
This is for cutting out protruding flaws .

According to such a method for manufacturing an electric resistance welded pipe of the present invention, it is possible to prevent a fog-like flaw generated on both sides of the electric resistance welded portion on the outer surface of the pipe due to the engagement of the squeeze roll from both flange portions. Can be.

In the present invention, the edge of the open pipe
Contacting the flange portion of the squeeze rolls in the outer surface of the part
Peritubular at intervals in the line conveyance direction in accordance with the portion
The width of the cutting surface of the two cutting tools arranged in the direction in the direction may be at least half of the interval between the two flange portions of the squeeze roll, and although it depends on the outer diameter of the pipe, the outer diameter is 152.4 mm. For small diameter tubes up to
mm is sufficient. There is no problem if the curvature of the cutting surface is selected to be slightly larger than the curvature of the outer surface of the pipe. For example, when producing a small-diameter pipe having an outer diameter of 100 to 152.4 mm, a radius of curvature of 100 mm is used. Byte 1
Kind can be enough.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing an electric resistance welded tube according to the present invention will be described with reference to an embodiment shown in FIGS. FIG. 1 is a front view schematically illustrating a method for manufacturing an electric resistance welded tube according to the present invention, and FIG. 2 is a side view of FIG. In FIGS. 1 and 2, FIG.
9 denote the same or corresponding parts,
Detailed description is omitted.

In FIG. 1 and FIG. 2, reference numerals 11a and 11b denote cutting tools which are arranged downstream of the two-roll squeeze roll 4 at a predetermined interval in the line conveying direction.
These cutting tools 11a and 11b are bitten out of both flange portions 4a of the squeeze roll 4 so that one side of each of the biting flaws 7 generated on both sides of the electric resistance welded portion on the outer surface of the pipe 5 and the welding outer surface bead 5a. In the circumferential direction of the pipe so as to cut the
They are arranged separately .

These cutting tools 11a and 11b are attached to a cutting tool holding stand 13 via, for example, actuators 12a and 12b, and
Is operated to move the cutting tools 11a and 11b in the vertical direction. For example, the cutting surface ends of the cutting tools 11a and 11b are moved upward by 200 mm and downward by 1 mm from the outer surface contact position of the pipe 5.
It can be adjusted within the range of 00 mm.

In the method of the present invention, two bytes 11a, 1
1b on the outer surface of the edge 2a of the open pipe 2.
In accordance with the flange portion 4a and the contact portion of the squeeze rolls 4 at intervals in the line conveyance direction circumferential direction of the pipe to the distribution that
Arranged in only shape, it is to cut a cutting depth of bytes within 0.8 mm. Therefore, when the pipe 5 is manufactured by heating both edges 2a of the open pipe 2 by the induction heating coil 3 and pressing and joining the pipe 5 laterally with the two-roll squeeze roll 4, the flange 4a of the squeeze roll 4 is used. Even if biting flaws 7 are generated on both sides of the outer surface electric resistance welded portion of the pipe 5 due to biting from the pipe 5, these biting flaws 7 are cut and removed together with the welding outer surface bead 5a by the two cutting tools 11a and 11b. Is done. as a result,
No rash-like flaws are generated on both sides of the outer surface electric welded portion of the pipe 5 after the fixed shape.

Next, a description will be given of the results of an experiment performed to confirm the effects of the method of the present invention. [Part 1] C: 0.23% by weight, Si: 0.13% by weight,
From a steel strip containing Mn: 0.81% by weight and Al: 0.04% by weight, the balance being Fe and unavoidable impurities, 10 m /
An ERW steel pipe having an outer diameter of 152.4 mm and a wall thickness of 14.3 mm was produced at a constant pipe-making speed of 1 minute. The distance between the flange portions of the two-roll squeeze roll used in this production was 20 mm.

During the manufacture of the above-mentioned ERW steel pipe, the flaws formed on both sides of the ERW weld on the outer surface of the pipe due to the protruding from the flange portion of the squeeze roll and the bead on the outer surface of the weld are removed by a 15 mm tool bit. It is manufactured by moving the tip of the cutting surface of two cutting tools whose center distance L (see FIG. 2) is 5 mm in a range of 1.2 mm below the pipe outer surface contact position, and corresponds to each cutting depth. After collecting the product to be inspected, it was subjected to an outer surface inspection, and a defect having a flaw having a depth of 0.1 mm or more was determined as a defective material, and a defect rate was determined.

The results are shown in FIG. 3. As shown in FIG. 3, as the cutting depth of the outer surface of the pipe increases, the defect rate of the outer surface inspection decreases. In this experiment, the height of the biting flaw was about 0.3 mm. Therefore, when the cutting depth was 0.3 mm or more, there was no defective material. However, when the cutting depth exceeded 0.8 mm, the defect rate of the outer surface inspection increased. This is because when the cutting depth exceeds 0.8 mm, the cut surface of the pipe base material is roughened or peeled, resulting in poor surface properties. That is, by setting the cutting depth of the two cutting tools arranged in the distribution direction in the circumferential direction of the pipe to 0.8 mm or less, while maintaining a good cutting surface property, the both sides of the electric resistance welded portion on the outer surface of the pipe are provided. It has been found that the occurrence of fogging flaws can be prevented.

[Part 2] With all the pipe-making tools removed from the squeeze roll unit of the pipe-making machine,
A two-roll squeeze roll having an outer diameter of 152.4 mm was incorporated, and the time required for immediately forming a pipe was measured. Further, the same measurement was performed on a 4-roll squeeze roll having the same outer diameter. In addition, each roll assembling work was performed by two people. The results are shown in FIG. 4. As compared with the case of the four-roll squeeze roll, the time required for assembling the roll is shorter in the case of the two-roll squeeze roll, which is advantageous in terms of improving the pipe production efficiency. There was found.

[0027]

As described above, according to the method for manufacturing an electric resistance welded pipe of the present invention, the two roll type squeeze rolls are formed on both sides of the electric resistance welded portion on the outer surface of the pipe due to biting from both flange portions. Can be effectively prevented
Using a two-roll squeeze roll that is advantageous in actual operation,
An electric resistance welded tube having good surface properties can be stably manufactured.

[Brief description of the drawings]

FIG. 1 is a front view schematically illustrating a method for manufacturing an electric resistance welded tube according to the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a graph showing a relationship between an outer surface cutting depth and an outer surface inspection failure rate.

FIG. 4 is a graph showing the time required for assembling rolls of a two-roll squeeze roll and a four-roll squeeze roll.

FIG. 5 is a front view schematically illustrating a conventional method for manufacturing an electric resistance welded tube.

6 is a schematic view of a two-roll squeeze roll as viewed from the side in FIG.

FIG. 7 is a schematic cross-sectional view of biting flaws generated on both sides of an outer surface electric resistance welded portion of a pipe due to biting from a flange portion of a two-roll squeeze roll.

FIG. 8 is a schematic cross-sectional view of a fog-like flaw generated on both sides of an electric resistance welded portion when the biting flaw illustrated in FIG. 7 is crushed by a fixed roll group.

FIG. 9 is a schematic view of a four-roll squeeze roll.

[Explanation of symbols]

 2 Open pipe 2a Edge 3 Induction heating coil 4 2-roll squeeze roll 4a Flange 11a byte 11b byte

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 13/00 B23K 37/08 B23D 1/20

Claims (1)

(57) [Claims] 1. Both edges of an open pipe are intensively heated by Joule heat generated by a high-frequency current, and an outer diameter of 152.degree.
4mm or less, in the manufacturing method of wall thickness 9.0mm or more small-diameter thick-walled electric-resistance-welded pipe, the two outer surface bead cutting tool, fit the parts in contact with the flange portion of the squeeze rolls in the outer surface of the edge portion Space in the line transport direction
And arranged in distribution shape in the circumferential direction of the pipe, the cutting depth of the outer surface bead cutting tool as within 0.8 mm, one of the outer
Electro-welding at the same time as the external bead on the face bead cutting tool
Cut out the flaw that occurs on one of the contact parts, and remove the outer surface of the other.
ERW at the same time as the outer bead on the bead cutting tool
A method for manufacturing an electric resistance welded tube, characterized in that a biting flaw generated on the other of the portions is cut .