JP4946223B2 - Steel pipe manufacturing equipment line - Google Patents

Description

The present invention, at least heating the steel pipe, is provided with a desired steel properties is subjected to cooling, to a steel pipe manufacturing equipment train. Here, “steel pipe” includes a welded steel pipe and a seamless steel pipe.

The characteristics of steel pipes as-rolled, for example, for ERW pipes, are affected by the processing strain during pipe making, but almost reflect the characteristics of the steel strip that is the raw material.For seamless steel pipes, the heat history during pipe making is reflected. It depends on.
Further, in order to impart desired steel pipe characteristics, conventionally, after pipe making, for example, after being charged in a heating furnace and heated, a quenching-tempering treatment is performed. However, since the quenching-tempering process using a heating furnace is a batch process, the process is complicated and takes a long time, and the production efficiency is significantly reduced when the temperature condition is changed. is there.

In order to deal with such problems, it is conceivable to apply the concepts of direct quenching-tempering, controlled rolling, controlled cooling and the like during the manufacture of steel pipes as in the production of thin plates and thick plates. That is, specifically, a heated steel pipe, or after hot pipe forming or after pipe forming, subjected to reduction rolling, etc., and then subjected to water cooling treatment or further tempering treatment, and bainite which is a low temperature transformation product When strengthening as a structure or martensite structure, or when reducing diameter rolling during or after pipe forming, the austenite single phase region immediately above the Ar ₃ transformation point is rolled to accumulate strain in the austenite grains. By transforming unrecrystallized austenite grains to produce fine ferrite grains, or by further cooling, the austenite grain growth is suppressed, or the strain of unrecrystallized austenite grains is released, or By suppressing the growth of ferrite grains after transformation, the strength can be increased.

As a technique for manufacturing a steel pipe by actively cooling after such a heated steel pipe or after hot pipe making or after diameter reduction rolling after pipe making, for example, Patent Document 1 discloses a predetermined technique. After heating or soaking the steel pipe containing C, Si, Mn, Al in the range to the Ac ₃ transformation point to 400 ° C, the rolling reduction of 20% or more is performed at the Ac ₃ transformation point to 400 ° C. There has been proposed a method for producing a steel pipe excellent in ductility-strength balance that is rapidly cooled to room temperature at a cooling rate of 1.5 ° C./s or more. According to the technique described in Patent Document 1, it is preferable that the rapid cooling after the drawing and rolling is performed by a rapid cooling device or the like including spray nozzles such as water, air, and mist.

In Patent Document 2, after heating the steel strip to the Ac ₃ transformation point or higher, it is continuously formed with a forming roll to form an open pipe, both edges of the open pipe are heated, and a squeeze roll is used for abutting joining. Then, the inner and outer beads are removed to form a mother pipe, and the mother pipe is further subjected to drawing rolling with a reduction rate of 30% or more in a temperature range of 400 ° C. or higher (Ar ₃ transformation point + 50 ° C.) and 0.5 s after drawing rolling. A method for producing a high-strength, high-ductility steel pipe that is cooled at a cooling rate of 30 ° C./s or more has been proposed. In the technique described in Patent Document 2, it is preferable to use a water spray cooling device for cooling after drawing rolling.

In Patent Document 3, after heating the steel strip to the Ac ₃ transformation point or higher, it is continuously formed with a forming roll to form an open pipe, both edges of the open pipe are heated, and after butt-joining with a squeeze roll The inner and outer beads are removed to form a mother pipe, and the mother pipe is further squeezed at a reduction rate of 30% or more at a strain rate of 1 s ^-1 or higher in the temperature range of Ar ₃ transformation point to (Ar ₃ transformation point + 100 ° C). A method for producing a steel pipe excellent in strength and ductility has been proposed in which rolling is performed and cooling is performed at a cooling rate of 30 ° C./s or more within 0.5 s after the drawing rolling. According to the technique described in Patent Document 3, it is preferable to use a water cooling device using a spray nozzle or the like for cooling after drawing rolling.

  In Patent Document 4, a mother pipe made using a hot-rolled steel sheet manufactured under a predetermined condition is heated to a temperature not lower than a heating temperature determined by the steel composition and not higher than 1050 ° C., and then subjected to diameter reduction processing. Subsequently, a method for producing a high-strength steel pipe excellent in formability, which is cooled to 250 ° C. or lower at a cooling rate of 3 to 500 ° C./s has been proposed. In the technique described in Patent Document 4, accelerated cooling after diameter reduction processing is preferably performed by equipment such as blower, air-water cooling, and water cooling.

  In Patent Document 5, a mother pipe made using a hot-rolled steel sheet manufactured under a predetermined condition is heated to a temperature not lower than a heating temperature determined by the steel material composition and not higher than 1050 ° C., and then reduced in diameter. Next, air-cooled or cooled to a temperature range of 300 to 600 ° C. at a cooling rate of 150 ° C./s or less, and then cooled to room temperature at a cooling rate of 15 ° C./s or less. Manufacturing methods have been proposed. According to the technique described in Patent Document 5, the cooling after the diameter reduction processing is preferably air cooling, or accelerated cooling by equipment such as a blower, air-water cooling, or water cooling.

  In Patent Document 6, the mother steel pipe is subjected to diameter reduction rolling in a temperature range of 600 ° C. or higher and the structure is mainly composed of ferrite, and heated to a temperature in the range of 800 to 1100 ° C. at a heating rate of 10 ° C./s or more. A method for producing a high-strength, high-workability steel pipe that has been held for 30 seconds or less and then cooled to 500 ° C. or less at a cooling rate of 3 ° C./s or more has been proposed. In the technique described in Patent Document 6, no specific cooling method is specifically mentioned.

Patent Document 7, the predetermined range C, Si, Mn, after a steel pipe containing Al heated heating or soaking the Ac ₃ transformation point to 400 ° C., Ac ₃ cumulative radial contraction rate 20% transformation point to 400 ° C. A method for producing a steel pipe excellent in ductility-strength balance and excellent in straightness has been proposed in which the above-described drawing rolling is performed and then slowly cooled at a cooling rate of less than 1.5 ° C./s. According to the technique described in Patent Document 7, it is preferable that the steel pipe is covered with a slow cooling box for cooling after drawing rolling.

Moreover, although it is not active cooling, the manufactured steel pipe is water-cooled with spray water while being rotated and transported on a cooling floor provided at the end of the steel pipe manufacturing line in a state where it is cut into a fixed length (about 5 m). Is often done. In addition to cooling with spray water, a water tank is provided in a part of the cooling floor, and a steel pipe is immersed in the water tank for cooling. The cooling in the cooling bed is carried out for the purpose of improving the production efficiency, controlling the structure of the ERW seam, controlling the precipitates (such as preventing carbide from being precipitated in the welded part with SUS material, etc.). Often. In other words, the main purpose is to reduce the temperature of the steel pipe after production, bring it to a state close to room temperature, ease the subsequent handling, and avoid scratches on the surface. is there.
JP 2000-94009 A JP 2001-162305 A Japanese Patent Laid-Open No. 2001-9522 Japanese Patent Laid-Open No. 2001-355035 JP 2001-355036 JP 2002-294403 A JP 2000-96144 A

  However, in the techniques described in Patent Documents 1 to 6, it is substantially difficult to manufacture a straight steel pipe (pipe) using an actual operation line. This is because if the heated pipe is forcibly cooled using a refrigerant in an in-line cooling device, warpage is inevitable. It is easy to suppress the occurrence of warping by forcibly cooling with a refrigerant from both the upper and lower sides in a state where tension is tensioned in thin plate manufacturing and in a state where it is stable by its own weight in thick plate manufacturing. However, in a pipe, usually, only forced cooling from the outer surface side is required, and the inner surface side must be air-cooled. Therefore, the slight cooling unevenness of the cooling on the outer surface side is directly connected to the warp of the steel pipe which is the material to be cooled, and it is practical to forcibly cool down evenly and suppress the occurrence of warp like thin and thick plates. It becomes difficult. In addition, in a pipe, the warp is usually corrected with a straightening machine, but if a severe warp occurs due to forced water cooling, the correction may not be completed.

  For example, when the steel pipe is forcedly cooled from above and below by water spray or the like, the cooling water hits the top side and the bottom side of the steel pipe, but the cooling water hits the side side. Therefore, uneven cooling occurs at each position of the steel pipe. In addition, since the cooling water flows from top to bottom in principle, the top side of the steel pipe where water easily hits is apt to be strongly cooled, and the bottom side where water collects and flows down is also slightly apt to be cooled. For this reason, the steel pipe is warped. Steel pipes that are severely warped often require a considerable amount of time to be taken out of the cooling zone, and there is a problem that productivity is lowered and stable production of the steel pipe is difficult. Moreover, in the steel pipe in which the curvature generate | occur | produced, there exists a problem that a pipe | tube outer surface collides with a conveying apparatus etc. because of a curvature, and a surface flaw often occurs. Further, when warpage occurs in a steel pipe that has been forcibly cooled, there are many cases where the steel pipe is hardened and correction with a straightening machine is difficult, and in some cases, the straightening machine cannot be used.

In addition, the cooling unevenness causes a structure unevenness and a material unevenness in the circumferential direction of the steel pipe, resulting in a problem that a steel pipe (product pipe) having uniform characteristics cannot be obtained. In particular, in a high-tensile steel pipe having a high alloy element content that affects the hardenability, there is a concern that cooling unevenness tends to have a large adverse effect on the steel pipe characteristics.
Further, even if the cooling means for the steel pipe is, for example, an annular cooling nozzle arranged concentrically, the cooling water flows from top to bottom, so that the top side and the bottom side of the steel pipe are easily cooled, and the steel pipe is warped. Will occur.

  In order to suppress the occurrence of warpage and produce a straight steel pipe, it is said that it is effective to make the cooling after heating or diameter reduction rolling slow, as in the technique described in Patent Document 7. Yes. However, if the cooling after heating or heating and shrinking rolling is slow cooling, it is possible to freely create steel pipes having various desired steel pipe characteristics as compared with the case of positively forced cooling. It becomes difficult.

  As described above, when a conventional forced cooling technique using a coolant such as cooling water is applied to a steel pipe, it is impossible to completely prevent the steel pipe from warping. For this reason, the steel pipe manufacturing technology that creates steel pipes of various characteristic levels using steel pipe materials of the same composition using forced cooling technology using a refrigerant has left a problem in terms of manufacturing stability in actual operation. It was. In particular, in the manufacture of high-tensile steel pipes with a tensile strength of 60 kg or higher (590 MPa class) or higher, there is a problem that the amount of alloying elements added is large and warpage due to cooling becomes significant, which is practically impossible. It was.

The present invention solves the problems of the prior art described above, to suppress the occurrence of uneven cooling, cooling, further straight steel pipe can be performed until the forced cooling is manufacturable and provide a steel pipe manufacturing equipment train For the purpose.

  In order to achieve the above-mentioned object, the present inventors diligently studied various factors affecting the occurrence of uneven cooling. As a result, in order to prevent the occurrence of uneven cooling, it has become important to cool the steel pipe by a cooling method that does not use a coolant such as cooling water, and the idea has been to use a metal roll as the cooling means. did. The cooling method using a metal roll is a method in which the outer surface of the steel pipe that is the material to be cooled and the metal roll that is the cooling means are brought into contact with each other to uniformly remove heat from the outer surface of the steel pipe and cool the steel pipe. is there. As a result, it has been found that cooling unevenness that cannot be avoided by water cooling, blower cooling, or the like can be suppressed, the occurrence of warpage of the steel pipe is suppressed, stable steel pipe can be manufactured, and productivity is improved. And it was discovered that according to the cooling method in which the steel pipe and the metal roll are brought into contact with each other and cooled, there is no unevenness in the structure in the circumferential direction, and therefore, a steel pipe without material unevenness can be manufactured. Here, “suppression of warpage” is to suppress to a slight warpage (1 mm or less per 1 m length) at a level that can be corrected with a straightening machine and can be commercialized.

The present invention has been completed based on the above findings and further studies. That is, the gist of the present invention is as follows .

(1 ) A steel pipe manufacturing equipment row in which at least a heating device for heating the raw steel pipe and a cooling device for cooling the raw steel pipe heated by the heating device are arranged in this order, and the cooling device is disposed outside the raw steel pipe. circumferential direction of the cooling device der consisting cooling roll consists substantially all around the over surface contact capable disposed a plurality of metal roll surface is, on the upstream side of the heating device, paying strip An uncoiler for feeding out, a relay welding device for joining the steel strip and the preceding steel strip, a looper for storing and discharging the steel strip, a forming device for roll forming the steel strip into an open pipe, and the open A joint welding device that heats both edge portions of the pipe and performs abutting welding to form a raw steel pipe, and a bead cutting device that cuts a bead of the raw steel pipe are arranged in this order, and the bead cutting device Between the heating device and steel A steel pipe cutting device for cutting the tube to length, steel pipe manufacturing equipment train and bead debris vent device for discharging the bead shavings characterized to Rukoto arranged in this order.

( 2 ) In the steel pipe manufacturing equipment row, the cooling roll is provided in a plurality of stages in ( 1 ).
( 3 ) A steel pipe manufacturing equipment row according to ( 1 ) or ( 2 ), wherein a reduced diameter rolling device for reducing the diameter of the material steel pipe is disposed between the heating device and the cooling device.
( 4 ) In ( 2 ), a water cooling device is disposed after the first stage of the multi-stage cooling roll and / or before the final stage of the multi-stage cooling roll. Steel pipe manufacturing equipment line.

( 5 ) The steel pipe manufacturing equipment column according to any one of ( 1 ) to ( 4 ), wherein pickling equipment and Ni flash plating equipment are arranged in this order on the downstream side of the cooling device .

  According to the present invention, a steel pipe excellent in straightness can be manufactured easily and stably even in a steel pipe manufacturing method in which forced cooling is performed, and a remarkable industrial effect is achieved. Further, according to the present invention, there is an effect that a steel pipe having various characteristics can be freely and stably made from a material having the same composition.

In the present invention, after subjected to heat treatment on the material steel pipe, it shall be the product pipe subjected to cooling processing. In addition, you may perform the diameter reduction rolling process which performs diameter reduction rolling to the heated raw material steel pipe after heat processing and before cooling processing. In addition, as the material steel pipe used in the present invention, either a seamless steel pipe or a welded steel pipe can be suitably used. Further, the composition may be appropriately determined according to the use and purpose, and is not particularly limited. The raw material steel pipe may be manufactured by applying a normal pipe making method using billets for seamless steel pipes, skelpes or the like obtained by stripping hot-rolled steel sheets or cold-rolled steel sheets for welded steel pipes.

Also not a, subjected to heat treatment on the material steel pipe, heating the entire tube to a desired heating temperature. The heat treatment method used in the present invention can be applied by any method as long as the entire tube is uniformly heated, and is not particularly limited. An optimum heating method may be selected according to the purpose, and examples include a method in which a raw steel pipe is charged in a heating furnace and heated, a method by induction heating, a method by current heating, and the like.

The heating temperature of the material steel pipe in pressurized thermal treatment may be appropriately determined depending on the composition and application of the material steel pipe to be used is not particularly limited. For example, for the purpose of strengthening the transformation structure, it is desirable to heat to a temperature above the Ac ₃ transformation point. In addition, when combined with reduced diameter rolling or the like, there is no problem even when heating to a temperature below the Ac ₃ transformation point. In addition, it is desirable to heat to a temperature equal to or higher than the Ac ₃ transformation point from the viewpoint of ensuring the toughness of welded parts such as ERW steel pipes.

The material steel pipe heated by pressurized heat treatment, subjected to condensation径圧rolling process for performing contraction径圧rolling, then may be subjected to cooling processing. Reduced diameter rolling is performed mainly for the purpose of minimizing the change in thickness and reducing only the outer diameter. However, a specific rolling texture can be formed to provide desired steel pipe characteristics. The diameter reduction rolling conditions may be appropriately determined according to the intended characteristics and applications, and need not be particularly limited. In addition to reduced diameter rolling, there is no problem even if hot working such as drawing is performed as necessary.

The raw material steel pipe whose whole pipe is heated or the steel pipe subjected to the diameter reduction rolling is then fed by the conveying means and cooled by the cooling means. In addition, the cooling start temperature of the material steel pipe in the present invention may be appropriately determined according to the composition and use of the material steel pipe to be used, and is not particularly limited, but the temperature of the ferrite single phase region or the ferrite + cementite region It is desirable to start cooling from a temperature higher than the Ar ₁ transformation point, since it is not possible to make use of the strengthening of the structure even if it is cooled from above. Moreover, in order to utilize the strength improvement by the structure strengthening, it is desirable to cool from a temperature not lower than the Ar ₃ transformation point, which is an austenite single phase region.

Cooling process using a cooling means comprising a cooling roll, a process of cooling the heated material steel pipe.
The cooling treatment is preferably carried out within 1 s after the heat treatment or after the diameter reduction rolling, particularly for the purpose of strengthening the structure and refining the crystal grains. If a long time exceeding 1 s is required to start the cooling process, the tissue may not be frozen in the previous step, and the intended purpose may not be achieved. If the time until the start of the cooling treatment is within 1 s, it is possible to prevent the structure obtained in the previous step from changing to some extent regardless of the composition of the material steel pipe to be used. In order to shorten the time until the start of the cooling process, it is important to increase the conveying speed or the rolling speed, or to arrange the cooling means in the immediate vicinity of the heating means or the downstream side of the rolling means.

Cooling roll to be used as a cooling means is arranged in the circumferential direction a plurality of metal roll that is contactable disposed substantially over the entire circumference of the material steel pipe outer surface. Examples of the plurality of metal rolls include a 2-roll system, a 3-roll system, a 4-roll system, and the like as shown in FIG. 2, but the invention is not limited to these. The cooling roll is made of a plurality of metals so that the outer diameter of the steel pipe that is the material to be cooled is substantially the same as or slightly larger than the outer diameter of the steel pipe that is the material to be cooled. It is desirable to configure a roll.

The cooling roll contacts the outer surface of the heated material steel pipe to extract heat from the material steel pipe, lowers the temperature of the steel pipe material, and cools it. As a result, the heated material steel pipe can be uniformly cooled, and a straight product pipe free from warpage can be obtained.
In particular, in order to obtain a stable cooling effect, it is desirable to maintain the surface temperature of the metal roll constituting the cooling roll at a predetermined temperature. This is because when the steel pipe is continuously cooled by contact between the metal roll constituting the cooling roll and the steel pipe, the metal roll is warmed and the subsequent cooling ability is lowered. By keeping the metal roll at a predetermined temperature, it is possible to prevent the cooling ability of the metal roll from being lowered, and to prevent uneven cooling in the longitudinal direction of the pipe and fluctuation of the cooling effect for each pipe. In consideration of cooling efficiency, the predetermined temperature is preferably 100 ° C. or lower. The temperature is more preferably 50 ° C. or lower.

  In order to keep the surface temperature of the metal roll constituting the cooling roll at a predetermined temperature, it is desirable that the metal roll be a metal roll cooled by a refrigerant instead of air cooling. The metal roll itself may be cooled by applying a coolant. However, when the metal roll itself is cooled by applying a coolant, for example, when a large amount of coolant (water) is applied, the steel pipe is directly drawn by the coolant (water). This is the same as the case of cooling the steel pipe, and severe warping occurs in the steel pipe. For this reason, it is preferable that a cooling pipe is provided inside the metal roll, and the metal roll is cooled from the inside with a refrigerant.

Further, in cooling process, it is preferable to use a cooling means in which a plurality stages arranged cooling roll. By using a cooling means in which a plurality of cooling rolls are arranged, it is possible to ensure a wide range of cooling ability to low temperatures, and desired cooling without strictly adjusting the surface temperature of the metal roll. The speed can be secured. In particular, since cooling to a low temperature is possible, steel pipes having various characteristics can be easily made from materials having the same composition. In addition, since the cooling control is easier as the number of installation stages of the cooling rolls is larger, it is preferable to have a plurality of stages. The composition of the steel pipe, the temperature, thickness, depending on the temperature or the like, the desired cooling rate, so that the desired cooling temperature lowering amount, preferably a suitably determined child the number of stages of the multiple stages of cooling rolls.

In addition, when making steel pipes having various characteristics from the steel pipes with the same composition, in addition to the cooling start temperature, the cooling start time, and the cooling speed, the temperature drop amount ΔT (= cooling start temperature−cooling completion) It is important to increase the temperature. The temperature drop ΔT due to cooling is preferably 100 ° C. or higher, more preferably 200 ° C. or higher.
Cooling rate in the cooling process may be appropriately determined according to purposes and are not particularly limited. The faster the cooling rate, the easier it is to strengthen the structure by low-temperature transformation products such as martensite and bainite, and the finer crystal grains can be expected. The overall cooling rate is desirably 50 ° C./s or more on average. From the viewpoint that the initial cooling rate is important for the purpose of strengthening the structure, the cooling rate in the first-stage cooling roll is preferably 30 ° C./s or more.

Further, cooling process, in addition to the cooling means using the cooling roll, may be further cooled process for performing water cooling. In the present invention, water cooling is only used as an auxiliary means for cooling means using a cooling roll for improving cooling capacity or reducing the number of cooling rolls installed within a range that does not affect the occurrence of warpage. can do. Water cooling is preferably performed after cooling with at least one cooling roll from the viewpoint of preventing warpage. It should be noted that there is no problem even if the water cooling is performed a plurality of times alternately with the cooling by the cooling roll as long as warpage does not occur.

  In addition, in water cooling, although it is good also as cooling using an upper and lower nozzle, in order to suppress cooling nonuniformity, it is more preferable to set it as cooling using an annular nozzle. Needless to say, the annular nozzle to be used has a structure having an inner diameter larger than the outer diameter of the steel pipe in order to avoid interference with the steel pipe as the material to be cooled. Needless to say, in the water cooling using the upper and lower nozzles, the upper and lower nozzles are arranged so as to avoid contact with the steel pipe as the material to be cooled.

  The water cooling is more preferably cooling in a nucleate boiling mode in which the vapor film is constantly destroyed. In the cooling in the film boiling mode in which the material to be cooled is wrapped in the vapor film, the cooling rate obtained is low, and there is a possibility that a desired cooling rate cannot be secured. The cooling in the nucleate boiling mode can be achieved by increasing the distance between the steel pipe, which is the material to be cooled, and the cooling nozzle, and / or increasing the pressure of the cooling water, and / or increasing the amount of cooling water. it can.

  Moreover, in order to ensure the uniformity of cooling, in the cooling process by the cooling roll, it is preferable to feed the steel pipe as the material to be cooled while rotating around the pipe axis. This is because, since the cooling roll is composed of a plurality of metal rolls, there is a gap that does not come into contact with the steel pipe between the metal rolls, which may cause uneven cooling in the steel pipe. Therefore, in order not to fix a portion where the steel pipe and the metal roll do not contact, it is preferable to feed the steel pipe while rotating it around the pipe axis. In addition, rotation around a pipe axis can also be provided by arrangement | positioning of the some roll group which comprises a cooling device and a reduced diameter rolling apparatus. For example, by setting the set position of each roll constituting each roll group to a position different from the preceding and following roll groups, the roll is covered by the influence of slight cooling unevenness between the roll groups and slight differences in the rolling shape. It may be used that the coolant is fed while rotating. Thereby, fixation of the part which a steel pipe and metal rolls do not contact can be prevented, generation | occurrence | production of a cooling nonuniformity can be prevented, and much more uniform cooling is attained.

Further, after cooling treatment noted above, it is preferable to further pickling, or even subjected to Ni flash plating. In particular, when water cooling is used in combination in the cooling treatment, it is preferably performed. Steel pipes that have been subjected to heat treatment and cooling treatment are often in a state where scales are formed on the surface, the surface is rough, and the surface properties are deteriorated. Therefore, it is preferable to clean the surface by pickling treatment. Moreover, since it may become easy to rust after a pickling process, it is preferable to perform Ni flash plating and to protect the surface. Note that the Ni flash plating process functions effectively when the steel pipe is used in applications where a chemical conversion process or a coating process is performed.

Next, a description will be given of steel pipe manufacturing equipment train of the present invention.
As shown in FIG. 1, the steel pipe manufacturing equipment line according to the present invention is based on a structure in which at least a heating device 1 and a cooling device 2 are arranged in this order. Needless to say, a driving device 3 for feeding the material steel pipe P to the lower process side such as a heating device and a cooling device is provided.
Although the heating apparatus 1 is an apparatus which heats the raw steel pipe P and is preferably an induction heating apparatus, it is needless to say that the heating apparatus 1 is not limited to this and may be a heating furnace. In addition, when it is set as the induction heating apparatus, heating temperature can be adjusted with the feeding speed of the steel pipe P, and the input electric power to the induction heating apparatus.

  The cooling device 2 is a device that cools the heated material steel pipe P. In the present invention, the outer surface of the material steel pipe P is made of a plurality of metals arranged so as to be surface contactable over substantially the entire circumference in the circumferential direction. A cooling device including a cooling roll 21 constituted by a roll 211 is used. Examples of the plurality of metal rolls include a 2-roll system, a 3-roll system, a 4-roll system, and the like, as shown in FIG. The cooling roll is a cooling means that removes heat by contact between the outer surface of the steel pipe that is the material to be cooled and the metal roll, and the outer diameter of the steel pipe that is the material to be cooled is substantially the same or slightly larger. It is desirable that the steel pipe, which is the material to be cooled, is composed of a plurality of metal rolls so that it can be brought into contact with the entire circumference of the steel pipe.

The metal roll constituting the cooling roll is cooled by air cooling or using a refrigerant, or provided with a cooling pipe inside and cooled from the inside by the refrigerant, and the surface temperature is maintained at a predetermined temperature. It is preferable from the viewpoint of securing a desired cooling capacity.
In the cooling device 2 of the present invention, in order to secure a desired amount of temperature drop due to cooling, it is preferable that the cooling rolls 21 are arranged in a plurality of stages from the viewpoint of preventing the occurrence of uneven cooling. As shown in FIGS. 2A to 2C, the cooling roll 21 is composed of a plurality of metal rolls 211. Therefore, at the boundary between the metal rolls 211, the steel pipe P, which is a material to be cooled, There is a non-contact portion (gap). Since the cooling rate of the steel pipe decreases at that portion, the cooling rolls 21 are arranged in a plurality of stages, and the angle of the arrangement of the metal rolls at each stage is set so that the gaps between the metal rolls do not overlap. It is desirable to arrange by shifting. FIG. 3 is a plan view schematically showing an example of the case where the 2-roll cooling roll shown in FIG. 2A is used.

  In addition, since the steel pipe P to be fed tends to come into contact with the lower metal roll of the cooling roll, the cooling of the upper portion of the steel pipe P may tend to be insufficient. Therefore, it is preferable to feed the steel pipe P while rotating it around the pipe axis by the driving device 3. Thereby, further uniform cooling becomes possible. For this reason, it is preferable that the drive device 3 has a function of adding rotation around the pipe axis to the steel pipe P in addition to the function of simply feeding the steel pipe P to the lower process side.

Further, the plurality of metal rolls of the cooling roll may be either a driving type or a non-driving type. In the case of the drive type, a sensor for synchronizing with the feeding speed of the steel pipe P immediately before the cooling means 2 may be provided.
In the present invention, the reduced diameter rolling device 4 may be disposed between the heating device 1 and the cooling device 2. The reduced diameter rolling device 4 is disposed in order to perform a desired reduced diameter rolling on the steel pipe. As the reduced diameter rolling apparatus 4 used in the present invention, any ordinary reduced diameter rolling apparatus is suitable, and the form thereof is not particularly limited as long as the desired reduced diameter rolling can be performed on the steel pipe. FIG. 4 schematically shows an example of the equipment. In addition, in a plurality of roll groups of the reduced diameter rolling apparatus, by rotating the set arrangement of each roll so as to have an angle different from that of the preceding and following roll groups, it is also possible to impart rotation around the pipe axis to the steel pipe. it can.

  Moreover, in the steel pipe manufacturing equipment row | line | column of this invention, in addition to the roll 21 for cooling, you may arrange | position the water cooling apparatus 5 as an auxiliary | assistant cooling means in the cooling apparatus 2. FIG. The water cooling device 5 is preferably disposed at least downstream of the first-stage cooling roll 21. Only cooling by the water cooling device 5 tends to cause warping of the steel pipe, and there is a risk that the pipe cannot be passed through the cooling device. Therefore, the water cooling device 5 is arranged at least downstream of the first-stage cooling roll 21 so as to be cooled by water after being cooled by the first-stage cooling roll. An example in which the water cooling device 5 is disposed between the first-stage cooling roll and the second-stage cooling roll is shown in FIG. 5 (a), the last stage (n-th stage) of the cooling roll 21, FIG. 5 (b) shows an example in which the water cooling device 5 is installed between the last stage (n-1 stage).

  The water cooling device 5 may be any structure that can cool the steel pipe with water, and the structure is not particularly limited. However, as shown in FIG. 6, the water cooling device 5 has an annular structure in which a plurality of cooling nozzles 51 are arranged in an annular shape. It is preferable to use a water cooling device. Although it is good also as a structure which has arranged the cooling nozzle in the top part side and the bottom part side of the up-and-down direction of the steel pipe which is to be cooled, since cooling water flows from the upper part to the lower part, the cooling on the steel pipe top part side is large and the bottom part Cooling water tends to accumulate on the side, and uneven cooling tends to occur. If the water-cooling device has an annular structure, uniform cooling is easily achieved by simple adjustment of the ejection pressure and the like. The cooling nozzle may be either a spray method or a high pressure water discharge method. Further, depending on the situation, the cooling nozzle may cause scratches on the surface of the steel pipe that is the material to be cooled. Therefore, it is desirable to attach a donut-shaped cover that accommodates the entire cooling nozzle 51.

In addition, it is desirable that the cooling device 5 is provided with a draining device, for example, a gas jet type, which prevents the cooling water from flowing out before and after the cooling device 5.
In order to secure a desired cooling rate, the water cooling device 5 is preferably capable of cooling in the nucleate boiling mode. Specifically, a water-cooling device capable of cooling in the nucleate boiling mode has a distance between the steel pipe, which is the material to be cooled, and the cooling nozzle, and / or a water pressure of 1.5 kgf / cm ² or more on the steel pipe surface. It is preferable to use a device capable of increasing the pressure of cooling water that can be added and / or increasing the amount of cooling water that can supply a sufficient amount capable of destroying the vapor film.

  In the steel pipe manufacturing equipment line of the present invention, the pickling device 6 or the plating device 7 may be disposed downstream of the cooling device 2 described above. As shown in FIG. 7, the pickling apparatus 6 includes a pickling tank 61 and a neutralization tank 62, and the plating processing apparatus 7 has a plating processing tank 71. The acid used in the pickling tank 61 is not particularly limited, but it is preferable to add a small amount of an additive to hydrochloric acid or sulfuric acid depending on the situation. Moreover, it is preferable from a viewpoint of pickling efficiency improvement to control liquid temperature in the range of room temperature-100 degreeC. It goes without saying that the steel pipe that has been heated and cooled is immersed in the pickling tank 61, and further immersed in the neutralization tank 62 for neutralization.

Further, depending on the situation, the Ni flash plating layer may be subsequently formed by the plating apparatus 7 including the plating tank 71. In the plating treatment tank 71, Ni flash plating can be formed by using a NiSO ₄ aqueous solution whose pH is adjusted to the range of room temperature to 100 ° C. to about pH 1 to ₄ . Thereby, the steel pipe surface is protected and the corrosion resistance is improved, and the adhesion with the film formed by chemical conversion treatment or coating treatment is further improved.

  The immersion in the pickling tank 61, the neutralization tank 62, and the plating treatment tank 71 may be performed by one tube at a time, or a continuous immersion treatment apparatus 8 as shown in FIG. 8 may be used. The continuous dipping treatment apparatus 8 is preferably a paddle drive system comprising a charging means 81, a paddle 82, and a guide 83. One or more steel pipes P are inserted into the nail bottom of the paddle 82 by the charging means 81, and after being immersed in the chemical solution in the processing tank and processed along with the rotation of the paddle 82, along the guide 83, It is carried out of the tank.

Further, on the upstream side of the heating device 1, as shown in FIG. 9, an uncoiler 11 for discharging the steel strip A, which is a normal ERW steel pipe manufacturing equipment row, and the steel strip A and the preceding steel strip B are provided. A relay welding device 12 for performing weld welding, a looper 13 having a function as a buffer for storing and discharging the steel strip, a roll forming device 14 for roll-forming the steel strip A (B) to form an open pipe Po, and an open pipe P For example, a joining welding device 15 that heats both edge portions of _o using, for example, an induction heating coil 15a and abuttingly welds them with a squeeze roll 15b to form a raw steel pipe P, and a bead formed on the inner and outer surfaces of the seam portion of the raw steel pipe P You may arrange | position the bead cutting device 16 which cuts with the cutting jigs 16a and 16b in this order. It goes without saying that other means such as a contact chip may be used instead of the induction heating coil 15a. The example shown in FIG. 9 is an example in which a normal ERW steel pipe manufacturing equipment line is continuously arranged on the upstream side of the heating device 1, but the present invention is not limited to this. Needless to say, it may be a batch-type process in which pipes are formed in a normal ERW steel pipe manufacturing equipment line, cut into a desired length, cooled, and then inserted into the heating device 2 and the cooling device 1.

  Moreover, in the steel pipe manufacturing equipment row | line | column of this invention, as shown in FIG. 10, the steel pipe cutting apparatus which cut | disconnects a steel pipe to desired length in the downstream of the bead cutting apparatus 16 of FIG. 17 can be arranged. In this case, it is preferable to dispose an inner surface bead waste removing device 18 for removing inner surface bead waste downstream of the steel pipe cutting device 17. The steel pipe cutting device 17 is preferably a rotary hot saw or the like made of, for example, a disk saw blade, which is usually used for cutting a steel pipe. Further, the inner surface bead scraping device 18 preferably discharges the inner surface bead scrap from the inside of the steel pipe using, for example, air blow.

  Further, in the present invention, a bending straightening machine for correcting the bending of the steel pipe is arranged in-line or offline on the downstream side of the welding joining device 15 and the upstream side of the heating device 19 and / or on the downstream side of the cooling device 2. You may set up.

Example 1
Using a skelp obtained by rolling a hot-rolled steel plate (thickness: 3.2 mm) with the composition shown in Table 1, the ERW with an outer diameter of φ89.1 mm is produced by the ERW steel pipe manufacturing facility shown in FIG. A steel pipe was made. The obtained electric resistance welded steel pipe was used as a raw steel pipe (length: about 10 to 40 m), and the raw steel pipe was subjected to heat treatment, diameter reduction rolling, and cooling treatment using the steel pipe manufacturing equipment row shown in FIG. The material steel pipe was confirmed to be a straight pipe through a sizer before heat treatment.

  In the heat treatment, heating was performed to the heating temperatures shown in Table 2 by the induction heating type heating device 1. After the heat treatment, diameter reduction rolling was performed so as to obtain a steel pipe having an outer diameter shown in Table 2. In some steel pipes, only the post-heat treatment cooling treatment was performed with the apparatus shown in FIG. The diameter-reduction rolling was performed with a diameter-reduction rolling apparatus 4 composed of 6 stands. Each stand was adjusted so that the inner diameter of the roll gradually decreased. After the diameter reduction rolling, it was then cooled by the cooling device 2. In addition, the cooling device 2 used was one in which six stages of cooling rolls composed of three metal rolls as shown in FIG. In consideration of the bulging of the steel pipe after the diameter reduction rolling, the inner roll diameter of the final stage of the diameter reduction rolling is set so that the cooling roll in each stage is in contact with almost the entire circumference of the outer surface of the steel pipe that is the material to be cooled. Rather than using a metal roll adjusted slightly larger. Moreover, the metal roll was provided with piping inside, and was a roll of an internal cooling system using a refrigerant. The refrigerant used was based on water with a small amount of additive added. As a result, the surface temperature of the metal roll was adjusted to 100 ° C. or less at the start of pipe passing.

In some steel pipes, in addition to the six-stage cooling roll 21 as shown in FIG. 5 (b), the last-stage (sixth stage) cooling roll 21 and the previous stage (five-stage) The cooling device provided with the water cooling device 5 was used at one place between the cooling rolls 21) or all (5 places) between the cooling rolls. The water-cooling device is a water-cooling device in which the nozzles are arranged in an annular shape, and is a device capable of cooling in the nucleate boiling mode, in which high-pressure water (7 kgf / mm ² or more) (nozzle discharge pressure) is discharged from the nozzles. Moreover, in some steel pipes, some of the six-stage cooling rolls were not used, that is, the steel pipes were cooled by opening some of the cooling rolls. Further, in some steel pipes, the feeding speed of the steel pipe was changed to change the cooling start time, the cooling start temperature, and the temperature drop amount ΔT due to cooling.

Here, the “steel pipe feeding speed” refers to the speed of the steel pipe on the inlet side of the cooling device. The feeding speed to the heating device is 60 rpm, but when performing diameter rolling after heat treatment, the feeding speed of the steel pipe increases according to the degree of reduction of the cross-sectional area as the cross-sectional area of the pipe decreases. Will do.
In addition, as a comparative example, 1 mm behind the last stage of the cooling roll was separated by 300 mm from the uppermost surface and the lowermost surface of the steel pipe through position, and cooled only by a laminar water cooling device.

The steel pipe subjected to the cooling treatment is cut into a standard size of 10 to 11 m in length by a steel pipe cutting device, and is then loosened by spray cooling or water immersion to a temperature at which it can be handled while being rotated and transferred in a cooling bed. Cooled.
In addition, the surface temperature of the steel pipe was measured by installing a radiation thermometer in each part of the steel pipe manufacturing equipment line. The cooling rate was measured using a delivery thermometer of the reduced diameter rolling device, a delivery thermometer of the first stage cooling roll in the cooling device, and a delivery pipe thermometer of the final sixth stage cooling roll. It calculated from the surface temperature of this and the passage time of a steel pipe. In addition, when the water cooling apparatus was used between the cooling roll groups, the surface temperature was estimated based on the measured values that were not affected by spraying.

The obtained steel pipe was evaluated for warpage and mechanical properties.
The warpage was evaluated by visually observing a steel pipe of a standard size at the last part of the cooling bed. Those that were warped in appearance were marked with ×, and those other than that were marked with ○. According to this criterion, X corresponds to a warp of about 1 mm or more per meter.
Tensile properties were evaluated as mechanical properties. From the obtained steel pipe, an ASTM arc-shaped piece was collected so that the tensile direction was the longitudinal direction of the pipe, and a tensile test was performed to obtain the yield strength YS, tensile strength TS, and elongation El.

  The obtained results are shown in Table 3.

Steel pipes No. 1 and No. 13 are electric resistance welded steel pipes (comparative example) that are not subjected to heat treatment or cooling treatment. Steel pipes No. 4 and No. 14 are steel pipes (comparative examples) in which only heat treatment and diameter reduction rolling are performed and cooling treatment is not performed.
Steel pipes No.5 to No.10, No.12, No.15, No.16 are subjected to heat treatment, reduced diameter rolling, and cooling treatment using a cooling roll composed of at least a plurality of metal rolls. steel tube (reference example), also steel No.2~No.3 is heated, and a plurality of metal roll set at a configured has been subjected to the cooling process using a cooling roll steel (reference example ). Steel pipes No. 12 and No. 16 are steel pipes that have been subjected to cooling treatment using both a cooling roll and water cooling. Steel pipe No. 11 is a steel pipe that has been subjected to heat treatment, diameter reduction rolling, and cooling treatment, but is a steel pipe (comparative example) in which the cooling treatment is performed only by water cooling.

All of the reference examples are straight steel pipes without warping. It can be seen that a straight steel pipe can be obtained without warping by cooling the steel pipe using a cooling roll composed of at least a plurality of metal rolls.
In addition, as shown in the reference example, when cooling a steel pipe using a cooling roll composed of a plurality of metal rolls, the feeding speed of the steel pipe, the number of installation stages and the number of utilization stages of the cooling roll are changed. Therefore, it is possible to adjust the cooling start time, the cooling start temperature, and the temperature drop ΔT due to the cooling as appropriate, using the steel pipe of the same composition, having the desired steel pipe characteristics, without generating warp and straight It can be seen that various steel pipes can be made freely.

For example, steel pipes No. 2, No. 3, No. 10, and No. 12 have cooling start temperatures above the Ar ₃ transformation point, and steel pipes No. 5 to 9, No. 15, and No. 16 are cooled. This is an example in which the starting temperature is below the Ar ₃ transformation point and above the Ar ₁ transformation point, but there is no warpage, and the strength is increased compared to steel pipes No. 1, No. 4, and No. 14, which are comparative examples. It shows what you can do.
Steel pipe Nos. 5 to 9, No. 15, and No. 16 are presumed to have high strength utilizing the fine graining of ferrite grains, and No. 2, No. 3, No. 10, and No. No. 12 is presumed to be strengthened with the formation of acicular ferrite or even bainitic ferrite structure.

  Steel pipes No. 3, No. 7, and No. 8 perform cooling using only a part of the cooling rolls of the six-stage cooling rolls, reduce diameter rolling, and feed the steel pipes. In this example, the speed is increased to change the cooling start time and the temperature drop amount ΔT due to cooling. Even if these cooling conditions are changed, no warpage of the steel pipe is observed, and it can be seen that according to the cooling device of the present invention, a steel pipe free from warpage can be easily obtained. In addition, by setting the cooling start time to within 1 s and ΔT to 100 ° C or higher, the steel composition used can achieve a high strength of about 10 MPa or more in tensile strength. It is easy to make steel pipes with different characteristics.

  Steel pipes No. 12 and No. 16 are examples in which cooling by a water cooling device is added in addition to cooling by a cooling roll composed of a plurality of metal rolls. Steel pipe No. 12 is between the last stage (sixth stage) and the fifth stage (one place) of the cooling roll, and steel pipe No. 16 is all between the stages of the cooling roll (five places). It is the example which installed and cooled the water rejection apparatus which has arrange | positioned the nozzle annularly shown in FIG. Even when cooling by a water cooling device is added, no warpage is observed, and if it is used in combination with a cooling roll composed of a plurality of metal rolls as in the present invention, strong cooling is applied by water cooling. However, it can be cooled without causing warpage, and further, the cooling rate and the amount of temperature drop due to cooling can be further increased, thereby further increasing the strength. In addition, a water-cooling device having an annular structure was effective in preventing warpage. Also. It can be seen that it is advantageous to dispose the water cooling device between the cooling rolls from the viewpoint of preventing warpage.

  Steel pipe No. 11, which is a comparative example, is an example in which cooling is performed using an upper and lower laminar type water cooling device, warping occurs, and the product cannot be made into a product. In addition, the cooling start temperature in the steel pipe No. 11 is the temperature at the entrance side of the first stage cooling roll that is not affected by the water spray from the water cooling device, and ΔT is the cooling start temperature, although cooling unevenness is considered. From the temperature on the cooling device delivery side (before the cooling floor), the calculated value was taken into account the decrease in the amount of heat removed from the atmosphere.

In addition, the cooling rate by the cooling roll composed of the metal roll is about 100 to 200 ° C./s in the first stage cooling roll, and is substantially equal even if the increase in the feeding speed due to the reduced diameter rolling is taken into consideration The cooling rate is shown, and cooling in the cooling roll composed of metal rolls indicates that stable cooling can be performed.
In addition, the cooling rate of the entire cooling device of the present invention is about 170 to 200 ° C./s when the water cooling device is not used together, becomes 250 ° C./s or more when the water cooling device is used together, and is based on simple water cooling (85 It can be seen that the cooling can be enhanced compared to (° C./s). In addition, when cooling is performed by reducing the number of use stages of the cooling roll, the cooling rate tends to be slightly slow due to the effect of the longer air cooling portion, but the degree is small. In any case, it can be seen that a cooling rate that cannot be achieved by simple water cooling can be secured.

In all the reference examples, since the surface temperature of the metal roll of the cooling roll is adjusted to 100 ° C. or less, the surface skin deterioration due to seizure or the like can be avoided.
(Example 2)
From the steel pipes No.1, No.4, No.9, No.12 manufactured under the conditions shown in Table 2, 15 test materials (tubes) each having a length of 100 mm were sampled, 5 of which were still steel pipes. Five were pickled, five were pickled, and Ni flash plated. About the obtained test material (tube), the surface skin was observed and a corrosion test was performed to observe the progress of corrosion.

The pickling treatment was performed by immersing in a 15% aqueous hydrochloric acid solution (liquid temperature: room temperature to 70 ° C.) for 30 minutes, and the surface scale was removed.
In addition, the Ni flash plating treatment is performed in the 159 g / L NiSO4 aqueous solution (pH: 2-3, liquid temperature: 50-70 ° C.) after the above pickling treatment, neutralization treatment and water cooling treatment. The treatment was immersed for ˜10 minutes, and a Ni flash plating layer was formed on the surface of the test material (tube).

In addition, when performing pickling treatment and Ni flash plating treatment, the sample was treated in such a direction that the inside of the steel pipe was expanded at the tip of the tongue, so that the surface side did not become an unsteady portion. Therefore, only the surface side was evaluated.
The surface skin was observed by visually observing the appearance surface of the test material (tube) after the above-described treatment, and also judged by tactile sensation.

The corrosion test is a test in which the test material after the above treatment is allowed to stand for 30 days in an atmospheric environment and an indoor environment. After the test, the corrosion condition on the surface of the test material is visually observed, Evaluation was made with a good one having little progress as ◯, a one with much progress of corrosion as x, and a middle as Δ.
Table 4 shows the obtained results.

In the steel pipe No. 1 in the state as a steel pipe, the skin of the hot-rolled steel sheet remained and the surface skin was good. On the other hand, steel pipes No. 4, No. 9, and No. 12 are heated and reduced in diameter, and the surface skin is slightly rough, and rust formation is progressing in a very small area. The surface skin is not good.
The corrosion condition of the steel pipe No. 1 was good (◯) because no rusting was observed, the progress of corrosion was small. On the other hand, in the steel pipes No. 4 and No. 9, there is a portion that seems to be formed due to the point-like rust originally present or slightly formed, and it cannot be said that the corrosion condition is good. Moreover, in Steel Pipe No. 12, although it cannot be completely determined whether it is caused by water cooling, the corrosion condition is not good.

When these steel pipes are pickled, the surface skin will be improved and there will be no problem, but the corrosion will be observed in all samples, and rust will be observed and corrosion will not progress well. Become. It is thought that rusting was promoted by the disappearance of the oxide film by pickling.
When a Ni flash plating layer is formed on the surface after pickling, the surface skin is almost the same as that of pickling skin, but the corrosion condition is clearly improved. It is thought that the formation of the Ni flash plating layer protects the exposed surface after pickling.

An example of a steel pipe manufacturing equipment train is an explanatory view schematically showing. It is explanatory drawing which shows typically an example of a structure of the roll for cooling used as a cooling device with the steel pipe manufacturing equipment row | line | column of this invention. It is explanatory drawing which shows an example of arrangement | positioning of the roll for cooling typically. It is explanatory drawing which shows typically an example of arrangement | positioning of the reduced diameter rolling equipment used with the steel pipe manufacturing equipment row | line | column of this invention . It is explanatory drawing which shows typically an example of arrangement | positioning of the roll for cooling used as a cooling device in the steel pipe manufacturing equipment row | line | column of this invention, and a water cooling device. It is explanatory drawing which shows an example of a water-cooling apparatus typically. It is explanatory drawing which shows typically an example of arrangement | positioning of a pickling processing apparatus and a plating processing apparatus. It is explanatory drawing which shows typically an example of the structure of a continuous immersion processing apparatus. An example of a steel pipe manufacturing equipment train is an explanatory view schematically showing. It is explanatory drawing which shows typically an example of the steel pipe manufacturing equipment row | line | column of this invention .

Explanation of symbols

1 Heating device (induction heating device)
11 Uncoiler
12 Relay welding equipment
13 Looper
14 Roll forming equipment
15 Joining and welding equipment
15a induction heating coil
15b squeeze roll
16 Bead cutting machine
16a, 16b Cutting jig
17 Steel pipe cutting device
18 Internal bead scraper 2 Cooling device
21 Cooling roll
211 Metal roll 3 drive
31 Drive roll 4 Reduced diameter rolling device (reducer)
5 Water cooling device
51 Cooling nozzle 6 Pickling device
61 Pickling tank
62 Neutralization layer 7 Plating treatment equipment
71 Plating tank 8 Continuous immersion treatment equipment
81 Loading means
82 paddle
83 Guide P Steel pipe P ₀ Open pipe A, B Band steel

Claims (5)

A steel pipe manufacturing equipment row in which at least a heating device that heats the raw steel pipe and a cooling device that cools the raw steel pipe heated by the heating device are arranged in this order, and the cooling device includes a peripheral surface of the outer surface of the raw steel pipe. cooling device der consisting cooling roll consists substantially all around the plurality of metal roll whose surface is contactable disposed over the direction is,
On the upstream side of the heating device, an uncoiler for discharging the steel strip, a relay welding device for relay welding the steel strip and the preceding steel strip, a looper for storing and discharging the steel strip, and rolling the steel strip A forming apparatus for forming an open pipe, a joining and welding apparatus for heating and welding both edges of the open pipe to form a raw steel pipe, and a bead cutting apparatus for cutting a bead of the raw steel pipe in this order. Arranged in
And characterized between the heating device and the bead cutting device, and the steel pipe cutting device for cutting a steel pipe to a predetermined length, the disposed to Rukoto in this order and a bead debris vent device for discharging the bead cutting chips Steel pipe manufacturing equipment line. The steel pipe manufacturing equipment row according to claim 1 , wherein the cooling rolls are arranged in a plurality of stages. The steel pipe manufacturing equipment row according to claim 1 or 2 , wherein a diameter reduction rolling device for reducing the diameter of the raw steel pipe is disposed between the heating device and the cooling device. The steel pipe production according to claim 2 , wherein a water cooling device is disposed after the first stage of the multi-stage cooling roll and / or before the final stage of the multi-stage cooling roll. Equipment column. The steel pipe manufacturing equipment row according to any one of claims 1 to 4 , wherein pickling equipment and Ni flash plating equipment are arranged in this order on the downstream side of the cooling device.

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