JP3700321B2 - Solid-state pressure welded pipe manufacturing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for manufacturing a steel pipe, and more particularly to an apparatus for manufacturing a solid-phase pressure welded steel pipe , which is suitable for forming both ends of an open pipe by abutting and joining in an appropriate temperature range for solid-phase pressure welding .
[0002]
[Prior art]
Welded steel pipes are formed by forming steel plates or steel strips (strips) into a tubular shape and welding their joints, and are made by various manufacturing methods from small to large diameters. The main manufacturing method is electrical resistance welding. (Electronic stitching), forging welding, and electric arc welding.
For small to medium diameter steel pipes, an electric resistance welding method (electric resistance welded steel pipe, electric resistance welded pipe) using high frequency induction heating is mainly used. In this method, a steel strip is continuously supplied, formed into a tubular shape with a forming roll to form an open tube, and then both edge portions of the open tube are heated to a temperature higher than the melting point of the steel by high frequency induction heating, and then a squeeze roll. In this method, the end surfaces of both edge portions are abutted and welded to produce a steel pipe (for example, third edition Steel Handbook, Volume III (2) pages 1056-1092).
[0003]
In the above-described method for manufacturing an ERW pipe using high-frequency induction heating, the end surfaces of both edges of the open pipe are heated to the melting point or higher of the steel, so that the molten steel flows under the influence of electromagnetic force, and the generated oxide is impinged. There has been a problem that welding defects such as a penetrator or molten steel scattering (flash) are likely to occur due to being caught in the joint weld.
In order to solve this problem, for example, Japanese Patent Laid-Open No. 2-299782 proposes a method for producing an electric resistance welded steel pipe having two heating devices. That is, the temperature of both edges of the open tube is heated to the Curie point or higher with the first heating device, further heated to the melting point or higher with the second heating device, and both edges are impacted by the squeeze roll provided immediately downstream. Steel pipes are manufactured by joint welding. In Japanese Patent Laid-Open No. 2-99783, a current of a frequency of 45 to 250 kHz is supplied by a first heating device, both edge portions are preheated, further heated to a melting point or higher by a second heating device, and squeezed by a squeeze roll. There has been proposed an electric welded tube manufacturing apparatus for manufacturing a steel pipe by abutting welding of both edge portions.
[0004]
However, although these ERW pipe manufacturing techniques suggest that the edges are heated uniformly, both edges are heated above the melting point of the steel. A bead is formed on the inner and outer surfaces. Therefore, it is necessary to remove the weld beads on the inner and outer surfaces of the pipe after the abutting welding, and most of them are cut and removed by a cutting tool for bead cutting.
[0005]
For this reason, in this method,
(1) Loss of material and time occurs by adjusting the cutting amount of the bead cutting tool.
(2) Since the cutting tool for bead is a consumable item, it varies depending on the pipe making speed, but it is necessary to change the cutting tool every bead cutting length of 3000 to 4000 m. Therefore, it takes 3 to 5 minutes every hour. Forced to stop line for byte exchange.
[0006]
(3) Particularly in the case of a high speed pipe making with a pipe making speed exceeding 100 m / min, the life of the bead cutting tool is short and the replacement frequency is high.
For example, bead cutting has become a bottleneck, and there is a problem that productivity is low because high-speed pipe making is impossible.
On the other hand, there is a forged steel pipe manufacturing method having extremely high productivity for a relatively small diameter steel pipe. In this method, the continuously supplied steel strip is heated to about 1300 ° C in a heating furnace, then formed into a tubular shape with a forming roll to form an open pipe, and then high pressure air is blown to both edge portions of the open pipe to end face After performing the scale-off, oxygen is blown to the end face with a welding horn, the end face is heated to about 1400 ° C with the heat of oxidation, and the end faces of both edges are brought into contact with a forging roll and solid phase bonded. This is a method for producing a steel pipe (for example, 3rd Edition Steel Handbook, Volume III (2) 1056-1092).
[0007]
However, in this forged steel pipe manufacturing method,
(1) Since the scale-off of the end face is not complete, scale biting occurs in the forging contact portion, and the strength of the seam portion is considerably inferior to that of the base material portion. For this reason, in the flatness test, a flat height ratio h / D = 2t / D (t: plate thickness) can be achieved with an electric-welded steel pipe, whereas a flat height ratio h / D is inferior to about 0.5 with a forged steel pipe. It will be a thing.
[0008]
(2) Since the steel strip is heated to a high temperature, scale is generated on the tube surface, and the surface skin is poor.
The pipe making speed is as fast as 300m / min or more, and the productivity is high, but the seam quality and the surface skin are poor, and there is a problem that it is impossible to manufacture those requiring strength reliability and surface quality such as JIS STK. .
[0009]
[Problems to be solved by the invention]
In order to advantageously solve the above problem, it is preferable to use the solid-phase pressure welding pipe method, which is the idea of the present inventors. This is because the edge of the open tube is induction-heated (called edge preheating) to a temperature range (referred to as preheating temperature range) above the Curie point (about 770 ° C) and below the melting point, and then the temperature of the edge portion within the preheating temperature range by air cooling. This is an unprecedented tube-forming method in which after homogenization, induction heating (referred to as main heating) is performed in the proper temperature range (1300 ° C to 1500 ° C) for solid-phase pressure welding, and abutting and pressure welding are performed. Steel pipes manufactured by this solid-state pressure welded pipe method do not require bead cutting unlike conventional welded pipes, enabling high-speed pipe forming and high productivity, and also due to oxidation, which is a drawback of conventional forged pipes No seam quality and surface skin degradation.
[0010]
An object of the present invention is to provide a solid-phase pressure welded steel pipe suitable for carrying out the above-described solid-phase pressure welded pipe method capable of producing a steel pipe having high seam quality and surface texture without requiring bead cutting. It is to provide a manufacturing apparatus.
[0011]
In the present invention, first and second work coils that inductively heat both edge portions of an open pipe formed from a steel strip in two stages, and both edge portions are abutted and pressed downstream to form a seam portion. in the manufacturing apparatus of a steel pipe having a squeeze roll, is arranged to squeeze roll abuts the seam portion, further squeeze rolls opposed to smoothing roll for smoothing by pressing the seams from the tube, and the 1. An insertion bar equipped with an impeder that enhances the heating efficiency of at least one of the edge portions of the second work coil is provided in the pipe, and if necessary, the smoothing roll is squeezed instead of facing the squeeze roll. seam temperature is disposed at a position not cooled to 900 ° C. or less downstream of the roll, this that the restraining roll comprising a tube outer which was opposite thereto for restraining the variation in pipe diameter due to the smoothing An apparatus for manufacturing a solid-phase pressure-steel pipe characterized by.
[0012]
It is preferable that the apparatus further includes an atmosphere holding mechanism that maintains the atmosphere around the edge portion being induction-heated in a low oxygen state or a reducing state.
The atmosphere holding mechanism is provided with a box surrounding the edge portion outside the pipe and supplying low oxygen gas or reducing gas to the box, or by providing a gas supply path in the insertion bar and surrounding the edge portion. It is preferable that low oxygen gas or reducing gas is supplied into the pipe, and it is more preferable that these are combined.
[0013]
The squeeze roll, the smoothing roll and the restraining roll that are in contact with the seam portion preferably have a bending strength of 15 kg / mm ² or more and a thermal shock temperature difference of 150 ° C. or more. , Silicon carbide, zirconia, or alumina ceramics are most suitable.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic diagram showing an example of a solid-phase pressure welded steel pipe manufacturing apparatus (the present invention apparatus) according to the present invention, where (a) is without a separate restraining roll and (b) is with a separate restraining roll. Each case is shown. In FIG. 1, 1 is a first work coil, 2 is a second work coil, 3 is a squeeze roll, 4 is a smoothing roll, 5 is an interpolation bar, 6 is a first impeder, and 7 is a second impeder. , 10 is a seam part, 20 is an open pipe, 21 is an edge part, 30 is a pressure contact, 40 is a seam pipe, 51 is a rolling reaction force receiving roll, 52 is a support frame, 60 and 61 are restraining rolls, and 100 is preheated Section 200 is the main heating section.
[0015]
An example of a reference device not provided with an impeder is shown in FIG.
As shown in FIG. 1, the apparatus of the present invention performs induction heating of both edge portions 21, 21 of an open tube 20 formed from a steel strip in two stages in order to carry out the solid phase pressure welding tube method. 1, a second work coil 1, 2 and a squeeze roll 3 that forms a seam portion 10 by abutting and pressure-contacting both edge portions downstream thereof. The edge preheating section 100 is set by the first work coil 1, and the main heating section 200 is set by the second work coil 2. Here, a point where the edge portion 21 of the open pipe 20 is abutted and pressed (the start point of the seam portion 10) is referred to as a pressure contact 30, and a pipe body downstream of the pressure contact 30 is referred to as a seam pipe 40.
[0016]
However, as shown in FIGS. 3A and 3B, the seam portion 10 in the seam tube 40 is in contact with the seam portion 10 that has been solid-phase-welded, depending on the temperature reached by the edge portion 21 or the degree of narrowing by the squeeze roll 3. An increase in thickness of 5% or more of the tube thickness may occur inside or outside the tube.
Therefore, in the apparatus of the present invention, the squeeze roll 3 is disposed so as to abut the seam portion 10, and the insertion bar 5 fitted with the smoothing roll 4 for smoothing the seam portion 10 by pressing from the inside of the tube is inserted into the tube. Prepared. The insertion bar 5 is preferably made of a highly rigid iron material or the like. As shown in FIG. 1, the smoothing roll 4 has a support frame 52 with a rolling reaction force receiving roll 51 that can roll on the inner surface of the seam tube 40 fixed to the insertion bar 5. To support.
[0017]
Thereby, even if the thickness increase as shown in FIG.
In addition, in the induction heating using only the first and second work coils 1 and 2, when the tube thickness is large, the heating efficiency is low and high-speed pipe forming is difficult, or the end surface of the edge portion 21 is uniform. In some cases, it may be difficult to raise the temperature to a temperature range where solid-phase pressure welding is possible.
[0018]
Therefore, as shown in this example , in the present invention , at least one of the first and second impeders 6 and 7 is attached to the interpolation bar 5, and at least one of the edge preheating section 100 and the main heating section 200 is installed. Improves the impedance of the inner surface of the open tube 20 and increases the concentration of the induced current at the edge. It is preferable to use a ferromagnetic material such as ferrite for the impeder. Either one of the first and second impeders 6 and 7 may be mounted, but the heating efficiency is further improved by mounting both. The first and second impeders 6 and 7 may be integrated.
[0019]
Since the thickening and smoothing can be performed with the seam portion 10 being hot while the load is low, as shown in FIG. 1 (a), the seam portion 10 between the squeeze roll 3 and the smoothing roll 4 closest to the pressure contact 30 is provided. The position of the smoothing roll 4 is determined so as to be rolled while pressing . However, if it can not place a smoothing roll 4 in the vicinity of the squeeze roll 3 with restrictions such as on the dimensions on and arrangement of the apparatus, as shown in FIG. 1 (b), the seam portion 10 at its downstream 900 ° C. or less The constraining rolls 60 and 61 are separately provided outside the pipe at a position where they do not cool down. By receiving the pressing force from the smoothing roll 4 and the rolling reaction force receiving roll 51 with the constraining rolls 60 and 61, the pipe due to the pressing force is provided. The variation in diameter may be prevented.
[0020]
Further, in order to suitably prevent the deterioration of the seam quality caused by oxidation as seen in forged pipes, the apparatus of the present invention further includes an atmosphere holding mechanism for maintaining the atmosphere around the edge portion being induction heated in a low oxygen state. It is preferable to provide.
FIG. 2 is an explanatory view of such an atmosphere holding mechanism, wherein (a) shows a box type, (b) shows an in-pipe purge type, and (c) shows a composite type. In FIG. 2, 70 is a box, 80 is a gas supply passage provided in the insertion bar, 81 is a gas jet port communicating with the gas supply passage 80, and the same or corresponding parts as in FIG. The description is omitted.
[0021]
As shown in this figure, the atmosphere holding mechanism is provided with a box 70 surrounding the edge portion (that is, the edge portion 21 in the preheating section 100 and the main heating section 200) outside the pipe, and supplies low oxygen gas to the box 70. (A) Alternatively, a gas supply path 80 having a gas outlet 81 opened in the pipe is provided in the insertion bar 5 to supply low oxygen gas into the pipe around the edge portion 21 (b). In addition, it is more preferable if these are combined. As the low oxygen gas, an inert gas such as N ₂ gas or Ar gas is suitable. Furthermore, if a reducing gas such as H ₂ gas, CO gas, or propane gas is used, the tolerance for intruding air is increased.
[0022]
In addition, the squeeze roll, the smoothing roll, and the constraining roll provided as necessary, which come into contact with the seam portion, are subjected to a bending stress of 15 kg / mm ² or more due to the reaction force from the tube during the thickening smoothing, In addition, the temperature difference between the vicinity of the pressure contact point on the contact surface of the roll with respect to the tubular body and the other region often reaches 150 ° C. or more.
Therefore, in order to extend the life of these rolls, the material of the rolls is preferably selected from those having characteristics of a bending strength of 15 kg / mm ² or more and a thermal shock temperature difference of 150 ° C. or more. Note that the thermal shock temperature difference used in the evaluation here means that a 3 mm x 4 mm x 40 mm square bar (spec for JIS 4-point bending test) was used as a material test piece, and the test piece was heated to a predetermined temperature. Later, the temperature difference (difference between heating temperature and water temperature) at which cracks do not occur in the test piece when dropped in water. In view of the current technical level, silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), zirconia (ZrO ₂ ), or alumina (Al ₂ O ₃ ) ceramics are optimal as such materials. is there.
[0023]
【Example】
The solid-phase pressure welded steel pipe manufacturing apparatus of the present invention shown in FIG. 2 (b) is installed in a steel pipe manufacturing line, and after forming the pipe diameter φ21.7 to 114.3 mm × wall thickness 1.9 to Carbon steel pipes for 4.5 mm piping and general structure (JIS G3452 SGP, G3444 STK equivalent) were manufactured. The insertion bar 5 is an iron cylinder provided with a gas jet 81 that opens into the pipe. The first and second impeders 6 and 7 are configured by inserting and fixing hollow ferrite on the outer periphery of the insertion bar 5. , N ₂ gas was 800 NL / min supplied to cylindrical hollow portion from one end of the interpolation bar 5, squeeze roll 3 in contact with the seams 10, bending the material of the smoothing roll 4 strength 85 kg / mm ^2, thermal shock temperature difference A silicon nitride ceramic having 800 ° C. was obtained.
[0024]
As a result, the steel pipe of the same size and the same size as the above is solid phase pressure welded pipe in a conventional apparatus that does not contact the seam portion 10 with the squeeze roll 3 and does not have the insertion bar 5 and smoothes the seam portion by bead cutting. Compared to the time when the prototype was manufactured by the method, the maximum molding speed was improved from 100 m / min to 350 m / min, and the seam quality was the average of the flat height ratio h / D in the flat test. Improved from 0.5 to 0.2.
[0025]
【The invention's effect】
As described above, according to the present invention, high productivity without the need for the bead cutting suitable can moreover practice of solid phase pressure forming tube method which can produce steel pipe excellent seam quality and surface texture ensuring a solid There is an excellent effect that a production apparatus for a phase-welded steel pipe is obtained.
[Brief description of the drawings]
1A and 1B are schematic views showing an example of the apparatus of the present invention, in which FIG. 1A shows a case without a separate restraining roll, and FIG. 1B shows a case with a separate restraining roll.
FIGS. 2A and 2B are explanatory views of an atmosphere holding mechanism, wherein FIG. 2A shows a box type, FIG. 2B shows an in-pipe purge type, and FIG. 2C shows a composite type.
FIG. 3 is an explanatory view of a thickening occurring in a seam portion.
FIGS. 4A and 4B are schematic views showing an example of a reference device without an impeder, where FIG. 4A shows a case without a separate restraining roll, and FIG. 4B shows a case with a separate restraining roll.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st work coil 2 2nd work coil 3 Squeeze roll 4 Smoothing roll 5 Interpolation bar 6 1st impeder 7 2nd impeder
10 Seam part
20 open tube
21 Edge
30 pressure contacts
40 seam tube
51 Rolling reaction force receiving roll
52 Support frame
60, 61 Restraint roll
70 boxes
80 Gas supply path
81 Gas outlet
100 Preheating section
200 heating section

Claims (6)

Equipped with first and second work coils that inductively heat both edges of an open tube formed from steel strip in two stages and a squeeze roll that forms a seam by abutting and pressing the edges downstream In the steel pipe manufacturing apparatus, the squeeze roll is disposed so as to abut the seam portion, and further, an insertion bar equipped with a smoothing roll that is smoothed by pressing the seam portion from the inside of the pipe so as to face the squeeze roll is provided in the pipe. And a solid-state pressure welded steel pipe manufacturing apparatus , wherein the interpolating bar is equipped with an impeder for increasing the heating efficiency of at least one of the edge portions of the first and second work coils . Instead of making the smoothing roll face the squeeze roll, it is arranged downstream of the squeeze roll at a position where the seam temperature is over 900 ° C., and the diameter of the tube due to the pressing force of the smoothing roll faces the smoothing roll. apparatus for manufacturing a solid-phase pressure-steel pipe further claim 1 Symbol placement with a restraint roll restraining outside the tube variations in. The apparatus for producing a solid-phase pressure welded steel pipe according to claim 1 or 2 , further comprising an atmosphere holding mechanism for maintaining an atmosphere around the edge portion being induction heated in a low oxygen state or a reducing state. The atmosphere holding mechanism provides a box surrounding the edge portion outside the tube to supply low oxygen gas or reducing gas to the box, and / or provides a gas supply path to the insertion bar to surround the edge portion. The solid-state pressure welded steel pipe manufacturing apparatus according to claim 3, wherein the apparatus is configured to supply a low oxygen gas or a reducing gas into the pipe. Abuts the seam, squeeze roll, smoothing roll and constraining rolls, bending strength 15 kg / mm ² or more, according to any one of claims 1 to 4 comprising a material having a thermal shock temperature difference 0.99 ° C. or more properties Production equipment for solid phase pressure welded steel pipe. The apparatus for producing a solid-phase pressure welded steel pipe according to claim 5 , wherein the material is a silicon nitride-based, silicon carbide-based, zirconia-based, or alumina-based ceramic.

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