KR102441839B1 - Manufacturing method of structural steel pipe - Google Patents

Abstract

Provided is a manufacturing method of a steel pipe, which performs heat treatment processes of a pipe as consecutive processes to improve productivity of a steel pipe manufacturing process, and prevents a negligence accident caused by cooling water introduced into and accumulated in a steel pipe by a prior welding process and the like when performing a heat treatment process of the steel pipe before a cutting process of the steel pipe. The manufacturing method of a steel pipe comprises: a molding step of molding a steel plate base material in a prescribed shape; a welding step of welding both edges of the molded steel plate base material to form a steel pipe; a cooling step of cooling the steel pipe; a sizing step of machining the cooled steel pipe into a preset shape; and a cutting step of cutting the steel pipe into a prescribed length.

Description

Manufacturing method of steel pipe {MANUFACTURING METHOD OF STRUCTURAL STEEL PIPE}

The present invention relates to a method for manufacturing a steel pipe.

In general, steel pipes are used in various industries such as construction, automobiles, and home appliances. Such a steel pipe is manufactured by processing a steel base material to form a cylindrical shape, a square column, and the like, and then welding the joint part. Steel pipe can be classified into gas welded steel pipe, submerged arc welding (SAW) steel pipe, electric resistance welding (ERW) steel pipe, etc.

Electrical resistance welded steel pipe, which accounts for most of the steel pipe production, generates heat in an electric induction method to weld the joint. More specifically, resistance heat is generated through electrical resistance or electric induction at both ends of the junction of the metal base material formed in a circular shape, and the junction is welded using this resistance heat. Thereafter, the mechanical properties may be improved through local heat treatment on the welded joint, that is, the weld bead portion.

Referring to Patent Document 1 (Registration Patent Publication No. 10-0761730), in the heat treatment of electric resistance welded steel pipe, by performing local heat treatment on the welded part, the residual stress of the welded joint is removed and a uniform metal structure and improved mechanical Techniques for securing properties are known.

After the welding and local heat treatment processes are performed, the steel pipe is subjected to a cooling process, a sizing process, and a cutting process. After the steel pipe is cut to a predetermined size through the cutting process, heat treatment processes such as tempering and quenching are performed on the entire steel pipe in order to improve mechanical properties while removing residual stress inside the steel pipe.

However, according to such a conventional steel pipe manufacturing process, the heat treatment process cannot be continuously performed as the steel pipe is cut to a predetermined size and then heat treatment is performed to impart mechanical properties, thereby reducing the productivity of the steel pipe. there was.

The problem to be solved by the present invention is to improve productivity by performing the heat treatment process of the molten pipe as a continuous process in the steel pipe manufacturing process. An object of the present invention is to provide a method for manufacturing a steel pipe that can prevent the occurrence of safety accidents caused by cooling water flowing into and stagnating.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A method of manufacturing a steel pipe for solving the above-described problems includes a forming step of forming a steel sheet base material of the present invention into a predetermined shape; A welding step of forming a steel pipe by welding both edges of the formed steel sheet base material; a cooling step of cooling the steel pipe; a sizing step of processing the cooled steel pipe into a preset shape; It may be characterized in that it comprises a cutting step of cutting the steel pipe to a predetermined length.

The method may further include a heat treatment step of performing high frequency heat treatment on the steel pipe before the cutting step.

The method may further include a cooling water removal step of removing the cooling water accumulated in the steel pipe before the heat treatment step.

The removing of the cooling water may include forming a plurality of holes at positions facing the ground surface to communicate the inside and the outside of the steel pipe.

The plurality of holes may be formed at regular intervals in the longitudinal direction of the steel pipe, and in the cutting step, the steel pipe may be cut at a position where the plurality of holes are formed.

In the method for manufacturing a steel pipe of the present invention, the heat treatment may be performed as a continuous process before the cutting process, rather than performing heat treatment on the cut individual steel pipes after cutting the steel pipe into product units in the steel pipe manufacturing process. Accordingly, it is possible to significantly increase productivity while ensuring the strength and formability of the steel pipe.

Furthermore, in the method for manufacturing a steel pipe of the present invention, a safety accident that may occur due to explosive vaporization of the coolant during the heat treatment process can be prevented in advance by performing heat treatment after removing the cooling water that has flowed into the inside of the steel pipe by the previously performed process. have.

Effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a flowchart sequentially illustrating a method for manufacturing a steel pipe of the present invention.
2 is a view schematically showing a steel pipe in which a plurality of holes are formed for removing cooling water in the method for manufacturing a steel pipe of the present invention.
3 is a view schematically showing a steel pipe tilted to remove cooling water in the method for manufacturing a steel pipe of the present invention.
4 is a view schematically showing a steel pipe in which a cutting step is performed in the method for manufacturing a steel pipe of the present invention.
5 is a flowchart sequentially showing another embodiment of the method for manufacturing a steel pipe of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and those of ordinary skill in the art to which the present invention pertains. It is provided to fully inform those skilled in the art of the scope of the present invention, and the present invention is only defined by the scope of the claims.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural, unless specifically stated otherwise in the phrase. As used herein, “comprises” and/or “comprising” does not exclude the presence or addition of one or more other components in addition to the stated components. Like reference numerals refer to like elements throughout, and "and/or" includes each and every combination of one or more of the recited elements. Although "first", "second", etc. are used to describe various elements, these elements are not limited by these terms, of course. These terms are only used to distinguish one component from another. Therefore, it goes without saying that the first component mentioned below may be the second component within the spirit of the present invention.

Unless otherwise defined, all terms (including technical and scientific terms) used herein will have the meaning commonly understood by those of ordinary skill in the art to which this invention belongs. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless clearly specifically defined.

1 is a flowchart sequentially illustrating a method for manufacturing a steel pipe of the present invention.

1 , the method for manufacturing a steel pipe according to an embodiment of the present invention includes a forming step (S110), a welding step (S120), a cooling step (S130), a sizing step (S140), a cooling water removal step (S150), and heat treatment It may include a step (S160) and a cutting step (S170).

Prior to the method for manufacturing a steel pipe according to an embodiment of the present invention, a pretreatment step for the steel sheet base material may be performed. In the pretreatment step, uncoiling, leveling, and edge milling processes may be performed.

The uncoiling process is a process of sequentially unwinding the steel plate base material supplied in a wound state, and the leveling process is by pressing the steel plate base material unwound through the uncoiling process from the upper and lower sides of the steel plate base material using a plurality of rolling rolls. It is a flattening process. And the edge milling process is a process of cutting both sides of the flattened steel plate base material to have the steel plate base material has a preset width. In addition to the pretreatment step, a recoiling process of rewinding the steel sheet base material loosened through the uncoiling process may be performed, and the uncoiling process and the recoiling process may be alternately repeated. In addition, after the edge milling process, a side trimming process of trimming both cut corners may be additionally performed.

In the forming step (S110) according to the present embodiment, the steel sheet base material prepared through the pretreatment step is formed into a cylindrical shape.

Specifically, in the forming step (S110), the steel plate base material is wound in the width direction of the steel plate base material intersecting the longitudinal direction (ie, the conveyance direction of the steel plate base material) of the steel plate base material. That is, the steel plate base material is rolled in a cylindrical shape so that both edges of the steel plate base material in the width direction face each other while going through the forming step ( S110 ).

Here, both side edge portions facing each other become a junction where the junction is made in a welding step to be described later. The joint portion may extend straight in the longitudinal direction of the steel plate base material. Alternatively, the joint portion may extend in the longitudinal direction while forming a thread on the outer periphery of the cylindrical steel plate base material.

On the other hand, the present invention is not limited to that the steel plate base material is formed in a cylindrical shape, the steel plate base material may be formed to have a cross section of a polygonal or other shape. For example, it is also possible to shape the steel plate base material to have a rectangular cross section by folding the base material a plurality of times in the width direction of the steel plate base material. In the welding step (S120) according to the present embodiment, the steel pipe 100 is formed by welding the junction of the steel plate base material that has undergone the forming step (S110). The welding in the welding step (S120) may be performed by electric resistance welding. Electrical resistance welding is a welding method using heat generated by applying electromagnetic waves or current to both edges, and since such electrical resistance welding is a well-known technique, a detailed description thereof will be omitted. On the other hand, the present invention is not limited to the manufacturing method of electric resistance welded steel pipe produced by electric resistance welding, submerged arc welded steel pipe produced by submerged arc welding, arc welded steel tube produced by arc welding, etc. It is also applicable to the manufacturing method of welded steel pipe.

The welding step (S120) may further include a local heat treatment step (S121) of improving the mechanical properties of the weld bead portion by dissolving the weld bead generated during the welding process into a solid solution. The local heat treatment step ( S121 ) is a separate process distinct from the heat treatment step ( S160 ), which will be described later, and heat treatment is performed only on the weld bead generated during the welding process of the joint and the portion adjacent thereto. Through this local heat treatment step (S121), it is possible to remove the residual stress of the weld bead portion generated in the welding process, and to secure a metal structure similar to the steel sheet base material and improved mechanical properties.

In the cooling step ( S130 ) according to the present embodiment, cooling of the heated steel pipe 100 is performed. Through the above-described forming step (S110), welding step (S120), local heat treatment step (S121), etc., a lot of heat is applied to the steel pipe 100 so that thermal deformation may occur. Accordingly, in the cooling step ( S130 ) according to the present embodiment, the steel pipe 100 is cooled through air cooling or water cooling.

In the sizing step (S140) according to the present embodiment, the cooled steel pipe 100 is processed into a preset shape. For example, through the sizing step (S140), the precision of the outer diameter dimension of the round steel pipe can be increased, and the cross section of the steel pipe can be processed into a desired shape such as an ellipse, a triangle, a square, or other polygons.

In the conventional steel pipe manufacturing method, the product is cut to a desired length through a cutting process after cooling and sizing, and then heat treatment is performed for each cut unit product to improve strength and durability. In this case, productivity may be reduced as each heat treatment is performed on the unit steel pipe 100 ′ cut to a predetermined length.

In order to solve the problems of the prior art, in an embodiment of the present invention, a heat treatment process is performed on the entire steel pipe 100 before cutting the steel pipe to a preset length after cooling and sizing. However, the cooling water continuously sprayed to prevent thermal deformation in the welding process and heat treatment process during the steel pipe manufacturing process remains in the steel pipe as it is, and during the high frequency heat treatment process, the coolant in the steel pipe evaporates explosively, which may cause a safety accident. Therefore, a process of removing the cooling water is performed simultaneously with or before the heat treatment process.

As such, in this embodiment, the cooling water removal step (S150) is performed after the cooling step (S130) and the sizing step (S140). In the cooling water removal step (S150), the cooling water flowing into the steel pipe 100 and stagnating is removed while undergoing molding, welding, local heat treatment, cooling, and the like.

The cooling water removal step (S150) may include forming a plurality of holes (notching step; S151) at positions facing the ground surface to communicate the inside and the outside of the steel pipe, together or separately from the steel pipe to the ground surface. It may include a tilting step (S152) of tilting to a preset angle.

2 is a view schematically showing a steel pipe having a plurality of holes formed for removing cooling water in the method for manufacturing a steel pipe of the present invention, and FIG. 3 is a view schematically showing a steel pipe tilted for removing cooling water in the method for manufacturing a steel pipe of the present invention It is a drawing. Hereinafter, the cooling water removal step ( S150 ) according to the present embodiment will be described in detail with reference to FIGS. 2 and 3 .

In the notching step ( S151 ) of the coolant removal step ( S150 ), a plurality of holes are formed to drain the coolant to the outside of the steel pipe ( 100 ). Specifically, in the notching step ( S151 ), a plurality of holes 101 are formed at positions facing the ground surface of the steel pipe 100 to communicate the inside and the outside of the steel pipe. Accordingly, the cooling water accumulated in the steel pipe 100 through welding, local heat treatment, etc. may be discharged to the outside through the plurality of holes 101 .

Referring to FIG. 2A , the plurality of holes 101 may be formed at a predetermined interval L1 along the longitudinal direction of the steel pipe 100 . As will be described later, the distance L1 between the plurality of adjacent holes 101 may be set to be substantially equal to the length of the finally manufactured unit steel pipe 100 ′.

The plurality of holes 101 may be formed in such a way that, for example, they are cut by a rotating blade rotating based on an axis parallel to the longitudinal direction of the steel pipe 100 . In this case, a plurality of rotating blades may be installed so that a plurality of holes 101 may be simultaneously cut and formed, but a plurality of holes 101 may be formed in a manner in which one rotating blade sequentially cuts. However, the method of forming the plurality of holes 101 is not limited thereto, and it may be possible to form the holes in other known methods.

The plurality of holes 101 formed in this way may be formed to have a width t in the longitudinal direction of the steel pipe 100 . Here, the width t of the plurality of holes 101 may be substantially the same as the thickness of the rotating blade.

The plurality of holes 101 may be formed to be elongated along the circumferential direction of the steel pipe 100 . Referring to FIG. 2B , the length R1 of the plurality of holes 101 along the circumferential direction may be less than or equal to half of the length R2 of the remaining uncut portions. In other words, the plurality of holes 101 may be formed to have a ratio of 1/3 or less to the circumference of the steel pipe 100 . This is the maximum ratio that can cool the cutting edge and the cutting portion of the steel pipe 100 due to the stagnant coolant even if a predetermined coolant is not additionally added in the process of forming the plurality of holes 101 . When the circumferential length of the plurality of holes 101 is formed to be greater than the above ratio, the process for forming the holes may take a lot of time, and the strength of the hole formed portion is significantly lowered, causing stress in the tilting process to be described later. If you do, you are vulnerable to breakage.

In the tilting step S152 of the cooling water removal step S150 , the steel pipe 100 is tilted at a preset angle with respect to the ground surface to drain the cooling water to the outside of the steel pipe 100 .

In general, in the steel pipe manufacturing process, the steel pipe 100 is moved in a direction parallel to the ground surface, and the process is sequentially performed. In this case, since the cooling water flowing into the steel pipe 100 and stagnating cannot be smoothly discharged through welding, local heat treatment, etc., in this embodiment, the steel pipe 100 that has undergone the cooling step S130 and the sizing step S140 The cooling water flows along the slope of the steel pipe 100 by making it inclined with respect to the ground surface. That is, the steel pipe 100 is made to form a gradient with respect to the ground surface perpendicular to the direction of gravity.

However, when the steel pipe 100 is inclined with respect to the ground surface in this way, stress may occur on the continuously connected surface of the steel pipe 100 . Referring to FIG. 3 , a force that bends the steel pipe 100 in an upward direction may act at a portion where the gradient starts from the left portion in which the steel pipe 100 is arranged and moved in parallel on the ground surface. Conversely, a force that bends the steel pipe 100 in the downward direction may act on the right side where the gradient is terminated and the steel pipe 100 is aligned and moved on the ground surface.

Accordingly, stress is applied in the section where the inclination of the steel pipe 100 changes, and when the stress is higher than the yield strength of the steel pipe, permanent deformation or cracks may occur. In particular, stress may be concentrated in a region where the plurality of holes 101 are formed, and cracks may occur. In this case, not only the product quality is lowered but also the productivity is lowered, and in this embodiment, the inclination angle α of the steel pipe 100 with respect to the ground surface in the tilting step is set in consideration of this. That is, the inclination angle α is set to be smaller than the inclination angle when a stress corresponding to the yield strength of the steel pipe 100 is applied so that a stress lower than the yield strength can be applied to the portion where the inclination is changed, particularly the portion where the hole is formed. do.

Meanwhile, as illustrated, the steel pipe 100 is expressed as being inclined upward along the process progress direction. In this case, the remaining cooling water inside the steel pipe 100 flows in a direction opposite to the process progress direction. Through this, the residual cooling water inside the steel pipe 100 entering the heat treatment step S160 that is performed after the tilting step S152 can be minimized. However, the present invention is not limited thereto, and it is also possible to make the steel pipe 100 inclined downward along the process progress direction.

In the embodiment shown in FIG. 3 , it is illustrated that the steel pipe 100 having a plurality of holes 101 is tilted, but unlike this, the cooling water is removed only by placing a gradient in the moving direction of the steel pipe 100 without forming a hole. It is also possible to

Of course, it will be possible to drain the steel pipe 100 only by forming a plurality of holes without providing a gradient in the moving direction.

After the cooling water removal step (S150) is performed, the heat treatment step (S160) is performed. For example, in the heat treatment step ( S160 ), tempering may be performed to increase the toughness of the steel pipe 100 . Alternatively, high frequency heat treatment using a coil may be performed in the heat treatment step ( S160 ).

However, this heat treatment step (S160) is a process in which heat treatment is performed on the entire steel pipe 100, unlike the local heat treatment step (S121) described above. That is, in the heat treatment step ( S160 ), heat is uniformly applied along the outer circumferential direction of the steel pipe 100 .

Through this, the steel pipe 100 can have uniform mechanical properties in the circumferential direction, and strength and formability can be improved.

Above all, since the heat treatment step ( S160 ) is performed before the cutting step ( S170 ), the steel pipe manufacturing process can be continuously performed, thereby greatly improving productivity.

After the heat treatment step (S160) is completed, the cutting step (S170) of cutting the steel pipe 100 to a predetermined length is performed.

4 is a view schematically showing a steel pipe in which a cutting step is performed in the method for manufacturing a steel pipe of the present invention. Referring to this, in the cutting step (S170), the steel pipe 100 may be cut to a preset length (L2). That is, the unit steel pipe 100' may be manufactured with a preset length L2.

Here, the preset length L2 of the unit steel pipe 100 ′ may be substantially equal to the distance L1 between the plurality of adjacent holes 101 . In other words, in the cutting step ( S170 ), the steel pipe 100 may be cut based on the point where the plurality of holes 101 are formed. As such, the plurality of holes 101 formed in the cooling water removal step ( S150 ) may be used as guides for guiding the cutting position in the cutting step ( S170 ). In addition, since a plurality of pre-formed holes 101 are utilized, the process time of the cutting step S170 can be reduced.

After the cutting step (S170) according to the present embodiment, a post-processing of the unit steel pipe 100' may be performed. In the post-processing stage, an inspection to determine whether there is a defect or whether the specification is satisfied may be performed. For example, a hydrostatic test that checks for leaks and defects by adding water to the inside of a steel pipe and pressurizing it at a certain pressure, and ultrasonic flaw inspection that uses ultrasonic waves to inspect the condition or presence of defects in the base material and weld bead Non-destructive testing processes, such as, may be performed.

In addition, in the post-treatment step, a process for preventing corrosion, such as application of rust preventive oil, and a process of determining whether the product is acceptable by checking the dimensions and appearance of the final product, and packaging according to the specifications desired by the consumer may be performed. In the post-processing step, other various inspections and processes may be added.

In the embodiment of the present invention described above, the cooling water removal step (S150) and the heat treatment step (S160) are performed between the sizing step (S140) and the cutting step (S170). However, it is also possible that the order of the cooling water removal step and the heat treatment step is performed differently.

5 is a flowchart sequentially showing another embodiment of the method for manufacturing a steel pipe of the present invention. The method for manufacturing a steel pipe according to this embodiment includes a forming step (S210), a welding step (S220), a cooling step (S230), a cooling water removal step (S240), a heat treatment step (S250), a sizing step (S260), and a cutting step (S270) ) is included. Since the process of each step in this embodiment is similar to the process of each step in the above-described embodiment, a description thereof will be omitted.

According to another embodiment of the present invention, unlike the above-described embodiment, the heat treatment step (S250) may be performed between the cooling step (S230) and the sizing step (S260). In addition, the cooling water removal step (S240) should be performed prior to the heat treatment step (S250), and is performed between the cooling step (S240) and the heat treatment step (S250).

Even according to this other embodiment of the present invention, since the heat treatment step ( S250 ) is performed before the cutting step ( S270 ), the steel pipe manufacturing process can be continuously performed, thereby greatly improving productivity. In addition, by performing a notching step (S241) of forming a plurality of holes for cooling water drainage in the steel pipe before or simultaneously with the heat treatment step (S250) and/or a tilting step (S242) of forming a gradient in the steel pipe for cooling water drainage, It is possible to prevent safety accidents that may occur due to explosive vaporization of the coolant during the heat treatment process.

Further, in the cooling water removal steps (S150 and S240) in the embodiment and other embodiments of the present invention, notching (S151, S241) and tilting (S152, S242) are omitted, and the cooling water is removed by a cooling water removal robot (not shown). can This is because forming the plurality of holes 101 in the steel pipe 100 and tilting it to remove the coolant may cause stress concentration at a specific point of the steel pipe, and thus there is a risk of deterioration in quality such as deformation.

To replace this, the cooling water removal robot includes a case, a rotor disposed in front of the case, a first motor disposed in the case to rotate the rotor, a wheel disposed in the case to assist the movement of the coolant removal robot, and a case; It may include a second motor disposed on the wheel to rotate, and an electronic control unit for controlling the first motor and the second motor by a user's manipulation.

The cooling water removal robot rides on the inside of the steel pipe 100 and moves along the axial direction to remove the cooling water inside the steel pipe 100 . In this case, the outer diameter of the rotor may be provided to match the inner diameter of the steel pipe 100 , and a vortex is generated by the axial movement of the cooling water removal robot and the rotation of the shaft based on the axis of the steel pipe 100 of the rotor, and the cooling water may be discharged to the outside along the opposite hole of the steel pipe 100 (a hole located opposite to the hole into which the coolant removal robot entered). That is, the rotor may act like a screw to discharge the cooling water inside the steel pipe 100 to the outside.

In this case, the rotor may include a hub and a plurality of blades spaced apart along the circumference of the hub, and radially outer ends of each of the plurality of blades may be in contact with the inner circumferential surface of the steel pipe 100 . On the other hand, since the elastic coating agent is applied to the radially outer end of each of the plurality of blades, it is possible to prevent the inner peripheral surface of the steel pipe 100 from being damaged.

Furthermore, a tip formed of a shape memory alloy, a pressure sensor for measuring pressure, and a thermoelectric module may be embedded between the radially outer end of each of the plurality of blades and the elastic coating agent.

The tip is formed of a shape memory alloy and may be provided to grow outward in the radial direction at a specific temperature or higher, and further is formed of a plurality of shape memory alloys (arranged along the radial direction) growing at different temperatures to each preset It is step-controlled according to the temperature and can grow outward in the radial direction step by step.

The pressure sensor and the heat transfer module may be controlled by an electronic control unit, and the electronic control unit may control the temperature of the tip by controlling the heat transfer module until a predetermined appropriate pressure is maintained based on a value sensed by the pressure sensor. In this case, the appropriate pressure may be a pressure at which the radially outer end of each of the plurality of blades is in contact with the inner circumferential surface of the steel pipe 100 . This is to reflect the fact that the diameter of the steel pipe 100 varies depending on the use, and to cover all the steel pipes 100 having mutually different diameters by adjusting the outer diameters of the plurality of blades with one cooling water removal robot.

For example, the electronic control unit controls the second motor to move the cooling water removal robot to the inside of the steel pipe 100 to temporarily stop it, and then, through the electric heat module until the sensing value of the pressure sensor reaches a preset appropriate pressure. After growing the tip radially outward and reaching an appropriate pressure, the coolant removal robot controls the first and second motors while maintaining the temperature of the tip to maintain the outer diameters of the plurality of blades. The cooling water may be discharged to the outside of the steel pipe 100 by rotating the rotor while the inside is moving at a constant speed along the axial direction.

As mentioned above, although embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art to which the present invention pertains can realize that the present invention can be embodied in other specific forms without changing its technical spirit or essential features. you will be able to understand Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (5)

A forming step of forming a steel sheet base material into a predetermined shape;
A welding step of forming a steel pipe by welding both edges of the formed steel sheet base material;
a cooling step of cooling the steel pipe;
a sizing step of processing the cooled steel pipe into a preset shape;
a cooling water removal step of removing the cooling water accumulated in the steel pipe;
a heat treatment step of performing induction heat treatment on the steel pipe; and
A cutting step of cutting the steel pipe to a predetermined length,
and forming a plurality of holes at positions facing the ground surface to communicate the inside and the outside of the steel pipe in the cooling water removal step,
The plurality of holes are formed at regular intervals in the longitudinal direction of the steel pipe, and in the cutting step, the steel pipe is cut at a position where the plurality of holes are formed,
In the cooling water removal step, the cooling water is removed by the cooling water removal robot,
The cooling water removal robot includes a case, a rotor disposed in front of the case, a first motor disposed in the case to rotate the rotor, and a wheel disposed in the case to assist the movement of the cooling water removal robot; a second motor disposed in the case to rotate the wheel, and an electronic control unit configured to control the first motor and the second motor by a user's manipulation,
The cooling water removal robot rides on the inside of the steel pipe and moves along the axial direction to remove the cooling water inside the steel pipe,
A vortex is generated by the axial movement of the cooling water removal robot and the rotation of the rotor with the shaft formed based on the axis of the steel pipe, and the cooling water is discharged to the outside along the plurality of holes,
The rotor includes a hub and a plurality of blades spaced apart along the circumference of the hub,
An elastic coating is applied to the radially outer end of each of the plurality of blades,
A tip, a pressure sensor for measuring pressure, and a thermoelectric module are embedded between the radially outer end of each of the plurality of blades and the elastic coating agent,
The tips grow at different temperatures and are formed of a plurality of shape memory alloys arranged along the radial direction of the plurality of blades, step-controlled according to each preset temperature, and grow outward in the radial direction of the plurality of blades step by step do,
The electronic control unit controls the thermoelectric module based on the sensing value of the pressure sensor until the pressure generated by the radial outer end of each of the plurality of blades in contact with the inner circumferential surface of the steel pipe is maintained at a predetermined appropriate pressure. A method of manufacturing a steel pipe, characterized in that to control the temperature of the tip. delete delete delete delete

Images