JP6536453B2 - Breakdown roll and manufacturing method of welded steel pipe - Google Patents

Description

  The present invention relates to a breakdown roll capable of reliably forming the edge portion of a steel strip and a method of forming the steel strip edge portion.

  When manufacturing ERW steel pipe, which is a type of welded steel pipe, generally, a steel strip formed as a material is formed into a cylindrical shape by a group of rolls in a state of running a steel strip which is a material, Welding of the width direction end parts (edge parts) is performed.

  The manufacturing process of the welded steel pipe will be described in more detail with reference to FIG. First, the steel strip 1 is fed horizontally to the forming roll row 2 at a constant speed while being leveled. For example, in order from the entry side, the forming roll row 2 is a break-down roll 3 and 4 that bends both end portions in the width direction of the steel strip upward (performs edge bending); It has a cage roll 5 for pressing in between (venting) and a fin pass roll 6 for finish forming into a circular cross section. The steel strip processed into a cylindrical shape by processing with this forming roll row 2 is heated by the induction coil 7 with the edge portions butted together, these edge portions are held together by the squeeze roll 8, crimped and welded, and a tube 9 is molded.

  Further, in the subsequent stage, the bead produced on the tube 9 is cut and removed by bead cutting means 10 or the like installed on the inner and outer surfaces of the tube 9. After the flaw inspection with the ultrasonic flaw detector 11, annealing of the welded portion in the seam annifier 12 and cooling with the water injection nozzle 13 are sequentially performed as necessary. Thereafter, the size is adjusted by the squeeze rolling mill 14 and then cut to a desired axial length by the cutter 15 on the transfer line to complete the welded steel pipe.

  It is very important that the welded steel pipe manufactured in this manner is symmetrical in cross-sectional shape with the butt portion (welded portion) as a boundary. If the cross-sectional shape is asymmetrical, not only the appearance of the product is undesirable but also the quality such as strength is adversely affected. It should be noted that the rejection rate of products due to such a left-right asymmetry of the cross-sectional shape is such that the higher the steel strip material is, the larger the steel pipe thickness (steel strip thickness) is. The bigger it gets, the higher it gets.

  By the way, what influences the asymmetry of the cross-sectional shape of this welded steel pipe most is the forming state in the breakdown roll which bends the edge part of the steel strip first. The following patent documents 1 and 2 are mentioned as a literature indicated about shaping of an edge part in a breakdown roll.

  The breakdown roll used in Patent Document 1 is shown in FIG. As shown in FIG. 6A, the breakdown roll 3 includes two upper rolls 18 and two lower rolls 16. The upper roll 18 is located on the surface (upper surface in the figure) of the steel strip 1 and is movable in the vertical direction (the thickness direction of the steel strip) and in the lateral direction (the width direction of the steel strip). It has the shape of The lower roll 16 is located on the back surface (lower surface in the figure) side of the steel strip 1 and has a shape that is symmetrical left and right and engaged with the upper roll 18, and the position is fixed during sheet passing. The upper roll 18 and the lower roll 16 are also called edge rolls because they press the edge portion of the steel strip 1. As a mechanism for moving the upper roll 18 vertically and horizontally, a servomotor 19 for vertical movement, a servomotor 20 for horizontal movement, a worm jack 25 for vertical movement, and a screw screw 26 for horizontal movement are provided. The upper roll 18 and the lower roll 16 are respectively held by roll shafts 37 and 38, and these roll shafts 37 and 38 are attached to roll stands 39 and 40 provided in the form of columns on the left and right.

  As shown in FIG. 6 (b), a sensor 21 for measuring the bending shape of the steel strip 1 is provided at the rear stage of the breakdown roll 3. The position adjustment means 22 controls the vertical movement servomotor 19 and the horizontal movement servomotor 20 based on the measured value by the sensor 21 so that the curved shape of the edge portion becomes left and right symmetrical, and the vertical direction of the upper roll 18 Position and horizontal position are adjusted. The operation confirmation of the position adjustment means 22 is performed using the display 24.

  Moreover, patent document 2 is mentioned as another document which disclosed the edge bend roll which used two upper rolls and two lower rolls. Patent Document 2 discloses that accurate shaping can be performed by changing the swing angle of the upper roll or the lower roll.

JP, 2004-202552, A Japanese Patent Application Laid-Open No. 7-116739

  However, in the case of the break-down roll in which the upper roll and the lower roll each consist of two edge rolls as in the prior art, the edge portion of the steel strip may not be sufficiently bent depending on the steel type, plate width and plate thickness. In particular, when the material of the steel strip is a high strength material or the thickness of the steel strip is large, it is difficult to sufficiently bend the edge portion of the steel strip. In particular, when the thickness of the steel strip is 15 mm or more, spring back occurs in the subsequent stage, and there is a frequent problem that the forming of the edge becomes insufficient.

  If the formation of the edge portion is insufficient, the sheet is passed through the subsequent fin pass roll having a function of making the cross-sectional shape of the steel strip closer to a circular shape with the edge portion rising. As a result, streaky wrinkles occur on the surface of the fin pass roll. When a subsequent steel strip is passed using a wrinkled fin pass roll, the wrinkles are transferred to the steel strip, a continuous wrinkle called roll mark is generated on the surface of the steel strip, and a product failure occurs.

  In addition, in the fin pass roll provided downstream of the breakdown roll, the load applied at the time of forming is measured as a forming load current (sometimes referred to simply as "load current"), and an excessive load is applied to the roll at the time of forming It is monitoring that it does not cost. When passing through the fin pass roll with the edge portion rising, the load on the fin pass roll increases and the forming load current increases. As described above, if the forming of the edge portion at the breakdown roll is insufficient, the forming load current at the fin pass roll exceeds the rated current for a certain period of time, or the forming load current at a certain value or more is instantaneous This causes the line to stop more frequently due to overload.

  In Patent Documents 1 and 2, in order to solve the problem of molding failure of the edge portion in the breakdown roll, the curved shape of the edge portion is measured by a sensor, and the position of the roll (vertical position according to the measurement result The adjustment of the horizontal position, the inclination, etc.) is also performed. However, adopting such a method requires a complicated operation mechanism and program for adjusting the position of the upper roll, requires a large-scale facility construction, and maintains these programs, etc. Require a great deal of cost.

  The present invention was conceived in view of the above problems, and it is a steel strip (for example, having a thickness of 15 mm or more) which is easy to form without requiring large-scale equipment construction and the like and which has difficulty in forming the edge portion. It is an object of the present invention to provide a breakdown roll which is less likely to cause forming defects even if it is a steel strip or the like, and a method of forming a steel strip edge using this breakdown roll.

The means for solving the above problems are as follows.
[1] A breakdown roll for bending an edge portion of a steel strip upward, comprising: an upper roll group located on the upper surface side of the steel strip; and a lower roll group located on the lower surface side of the steel band The upper roll group includes two upper edge rolls pressing the edge portion of the steel strip and an upper center roll pressing the widthwise central portion of the steel strip, and the lower roll group includes the edge of the steel strip Breakdown roll with two lower edge rolls pressing the part.
[2] The breakdown roll according to the above [1], having a spacer member for fixing the widthwise position of the upper edge roll, the upper center roll, and the lower edge roll.
[3] The method for forming a steel strip edge portion performed using the breakdown roll according to the above [1] or [2], wherein the upper edge roll and the lower edge roll sandwich the steel strip edge portion, The forming method of a steel strip edge part which performs shaping | molding by pressing the upper surface center part of a steel strip downward with an upper center roll, bending the width direction both ends of a band upwards.
[4] Select the upper edge roll, upper center roll, and lower edge roll according to the steel strip to be passed through, fix the widthwise position of the upper edge roll, upper center roll, and lower edge roll, and select The method for forming a steel strip edge portion according to the above [3], wherein the upper roll group including the edge roll and the lower edge roll and the lower roll group are fixed in the vertical direction,

  According to the present invention, even when a steel strip in which forming of the edge portion is difficult is passed through the breakdown roll, it is possible to suppress the occurrence of forming defect of the edge portion.

FIG. 1 is an explanatory view showing a breakdown roll of the present invention. Fig.2 (a) is a graph which shows the relationship between the plate thickness in Example 1, and the bending amount (edge bending amount) of the edge part of a steel strip, and FIG.2 (b) is in order to demonstrate the definition of edge bending amount. FIG. FIG. 3 is a graph showing roll mark occurrence rates of the comparative example and the inventive example in the second embodiment. FIG. 4 is a graph showing the molding load current in the fin pass roll of the comparative example and the inventive example in the third embodiment. FIG. 5 is a flow chart showing the manufacturing process of the ERW steel pipe. FIG. 6 is a view showing a conventional break-down roll, FIG. 6 (a) is a front view of the break-down roll, and FIG. 6 (b) is a flow chart showing a control mechanism of curved shape of both ends of steel strip It is.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an example of the configuration of the breakdown roll according to the present invention.

  Breakdown roll 41 has upper roll group 35 located on the upper surface side of steel strip 1 and lower roll group 36 located on the lower surface side of steel strip 1. When the steel strip 1 is passed through the breakdown roll 41, the edge portion of the steel strip 1 is formed to rise toward the upper surface side.

  The upper roll group 35 includes two upper edge rolls 28 and 30 and an upper center roll 29. The lower roll group 36 has two lower edge rolls 31, 32. The upper roll group 35 has a shape obtained by dividing a radial crown-shaped roll into three in the width direction. The lower roll group 36 has a shape obtained by dividing a reverse crown-shaped roll in the width direction and taking out only the width direction end.

The upper edge roll 28 located on the left side of FIG. 1 allows the steel strip 1 to be bent upward,
It has a cross-sectional shape that tapers upward toward the end of the steel strip 1. The lower edge roll 31 has a cross-sectional shape of meshing with the cross-sectional shape of the upper edge roll 28. The left and right upper edge rolls 28 and 30 and the left and right lower edge rolls 31 and 32 are respectively shaped to be laterally symmetrical so that the edge portions of the steel strip 1 can rise symmetrically to the left and right.

  The upper edge roll 28 and the lower edge roll 31 are adjusted in the width direction (X direction) position of the steel strip 1 before sheet passing so that the edge portions of the steel strip 1 can be pressed. In the example of FIG. 1, the end face of the steel strip 1 is located at the biting portion (tapered portion) of the upper edge roll 28 and the lower edge roll 31.

  The upper center roll 29 is located on the upper surface side of the steel strip 1 and at the center in the width direction (X direction) of the steel strip 1. By positioning the upper center roll 29 at the widthwise central portion of the steel strip 1, the edge can be raised so as to be symmetrical. In FIG. 1, the X-direction center line of the upper center roll 29 and the X-direction center line of the steel strip 1 coincide with each other by a dashed line A. Note that these two lines do not have to exactly match each other. For example, the center line of the upper center roll 29 in the X direction and the steel strip 1 within about 3% of the length between the roll stands The X direction center line may be shifted to the left or right.

  The cross-sectional shapes and the curvatures of the upper edge roll 28 and the lower edge roll 31 can be appropriately changed according to the steel type of the steel strip 1 to be passed, the bending amount of the edge portion, and the like.

  A plurality of upper center rolls may be provided. When a plurality of upper center rolls are provided, a group of upper center rolls is disposed so as to be symmetrical with respect to the center line A (dotted line in FIG. 1). From the viewpoint of cost reduction of the apparatus, it is preferable to use one upper center roll.

  Although not illustrated in FIG. 1, the lower roll group 36 may also be provided with a lower center roll that presses the lower surface central portion of the steel strip 1. In particular, in the case of a steel strip having a large width, it is effective to provide a lower center roll. However, if the lower roll group is provided with the lower center roll, wrinkles are likely to be generated on the lower surface of the steel strip at the gap between the lower center roll and the lower edge roll. The roll group may not be able to apply a sufficient pressure to make the forming of the edge insufficient. Further, when the lower center roll is provided in the lower roll group, the stress is also dispersed to the widthwise central portion at the time of bending of the edge portion, and there is also a problem that the edge portion becomes difficult to bend. In consideration of these points, it is preferable that the lower roll group is not provided with the lower center roll, that is, the lower roll group is preferably composed of two lower edge rolls.

  The upper roll group (or lower roll group) is attached to one roll shaft (shaft). In FIG. 1, the roll shaft is hidden inside the spacer member 33 formed in a tubular shape. The left and right ends of these roll shafts are attached to a vertically extending roll stand 34. By moving the roll axis up and down along the roll stand 34, the upper roll group 35 can be displaced in the vertical direction (the Z direction in the drawing). The lower roll group 36 may also be vertically displaceable, but in view of maintaining the pass line, it is preferable to use a fixed type.

  Each of the rolls constituting the upper roll group 35 can adjust the position in the width direction (X direction in the drawing) of the steel strip 1 along the roll axis before sheet passing. Specifically, when assembling the upper roll group 35, the upper edge roll 28 or the upper center roll 29 and the spacer member 33 are alternately passed through the shaft (roll axis). The spacer member 33 is a hollow cylindrical member, and the rolls are arranged and fixed at a distance corresponding to the axial length. For example, in the example of FIG. 1, between the roll stand 34 on the left and the upper edge roll 28, between the upper edge roll 28 and the upper center roll 29, between the upper center roll 29 and the upper edge roll 30, and on By providing cylindrical spacer members each having a predetermined axial length between the edge roll 30 and the right roll stand 34, the X direction (width direction) position of each roll is fixed.

  Similarly, in the lower roll group, the X position of the lower edge rolls 31, 32 can be adjusted before passing the plate, and the X of the lower edge rolls 31, 32 can be adjusted by the spacer member 33 having a predetermined axial length. It is possible to fix the direction position.

  Next, a method of forming the edge portion of the steel strip 1 using the breakdown roll 41 will be described.

  First, according to the steel type of the steel strip to be passed, the width and thickness of the steel strip, the desired amount of edge deformation, etc., the optimum curvature, the shape upper edge rolls 28, 30, the upper center roll 29, and the lower edge roll Select 31, 32 Next, the X-direction positions of the upper edge rolls 28, 30, the upper center roll 29, and the lower edge rolls 31, 32 are set, and the spacer member 33 having an optimum axial length is selected. The spacer member 33, the upper edge rolls 28, 30, and the upper center roll 29 are fitted to the roll shaft to form the upper roll group 35. Further, the lower roll group 36 is formed by fitting the spacer member 33 and the lower edge rolls 31 and 32 on the roll shaft. The roll shaft on which the optimal upper roll group 35 and lower roll group 36 are attached is mounted on the roll stand 34. Thus, the widthwise positions of the upper edge rolls 28, 30, the upper center roll 29, and the lower edge rolls 31, 32 are fixed according to the axial length of the spacer member 33.

  Next, the space | interval of the up-down direction (Z direction) of the upper roll group 35 and the lower roll group 36 is adjusted, and it fixes. The distance in the Z direction can also be appropriately adjusted in accordance with the type of steel strip to be passed, the width and thickness of the steel strip, the desired amount of edge deformation, and the like.

  Thereafter, the steel strip 1 is passed through the breakdown roll 41 to form an edge portion. At the time of sheet passing, the upper edge rolls 28, 30 and the lower edge rolls 31, 32 press the edge portions of the upper and lower surfaces of the steel strip 1 to rise upward (upper surface side). At the same time, the upper center roll 29 presses the upper central portion of the steel strip 1 downward, making it easy to bend the left and right ends of the steel strip 1 upward. Thereby, even if it is a steel strip in which shaping | molding of the edge part was difficult in the apparatus which does not have an upper center roll like before, it can suppress that shaping | molding defect arises.

  As a steel strip with a difficult shaping | molding of an edge part, the steel strip with a thick plate thickness, and / or the high strength steel strip etc. are mentioned, for example. More specifically, a steel strip having a thickness of 15 mm or more and / or a material having a strength of X65 grade or more can be mentioned. According to the present invention, with a steel strip having a thickness of up to about 22 mm, the occurrence of molding defects can be suppressed to a very low level.

  In the present invention, by suppressing molding defects of the edge portion, it is possible to prevent the generation of roll marks in the fin pass roll of the latter stage, and to improve the product yield. Furthermore, the sheet passing property can be improved and the production efficiency of the line can also be increased by preventing the molding load current in the subsequent fin pass roll from becoming excessive.

  The breakdown roll of the present invention is preferably used for the production of welded steel pipes (including round steel pipes and square steel pipes). According to the present invention, it is possible to reduce the rate of forming defects in the initial edge deformation of a steel strip which is particularly important in the manufacturing process of welded steel pipes.

  When the breakdown roll of the present invention is used in the manufacturing process of a welded steel pipe as shown in FIG. 5, it is applied to the most entry side (first stage) breakdown roll in the line (symbol 3 in the figure). It is preferable to do. In the first-stage breakdown roll, the edge portion of the flat steel strip 1 is deformed and is most likely to cause forming defects, but the rate of forming defects is reduced by using the breakdown roll of the present invention be able to. The breakdown roll of the present invention may be applied to the subsequent stage (second stage) breakdown roll (symbol 4 in the figure). In the second-stage (symbol 4) breakdown roll, the distance between the upper edge rolls (and the lower edge rolls) is narrower than in the first-stage (symbol 3) breakdown roll, and the width of the steel strip 1 is greater The widthwise position of the upper edge roll and the lower edge roll is adjusted so as to press the direction central portion side (ventral side).

  The breakdown roll of the present invention has the function of bending the edge portion of the steel strip. As described above, in the case where the present invention is applied to the first-stage breakdown roll of a welded steel pipe line and in the case where the present invention is applied to the second- and subsequent-stage breakdown rolls, Although the positions are different, in any case, the edge portions pressed by the breakdown roll of the present invention are shifted from the both widthwise end faces of the steel strip toward the center by a length of 1/4 or less of the width of the steel strip. It is sufficient if it is at the

  The breakdown roll of the present invention can use an existing breakdown roll device. The existing breakdown roll equipment comprises, for example as shown in FIG. 6 (a), two movable upper edge rolls and two fixed lower edge rolls. The present invention can be applied to this equipment simply by attaching an upper center roll anew in the vicinity of the central portion of the upper roll axis and fixing the position in the width direction using a spacer member having a length matched to the gap. it can. For example, large-scale equipment work such as in the case of introducing a position control program for the upper edge roll, which is conventionally used to suppress molding defects, is not necessary, and existing roll stands and rolls are simple and simple. Application of the present invention is possible at low cost.

  In the present invention, the widthwise position of each roll can be adjusted and fixed by the spacer member. Therefore, when it is necessary to adjust the position in the width direction of each roll, such as when passing through steel strips having different sheet widths or when the steel strips meander, round the upper roll group or the lower roll group It is possible to adjust the widthwise position of each roll only by changing the inexpensive spacer member without changing to the product of the above.

Example 1
Various sheet thicknesses are used using the breakdown roll of the present invention shown in FIG. 1 (example of the present invention) or the breakdown roll comprising an upper roll and a lower roll in which an edge roll and a center roll are integrated as a comparative example. Edge formation of the steel strip 1 was carried out. The plate width of the steel strip 1 was 1300 mm to 1380 mm. The amount of edge bend after molding was measured by the method shown in FIG. 2 (b). Specifically, a straight measure of 200 mm in length is placed on the upper surface side of the edge portion of the bent steel strip 1, and the upper surface of the steel strip 1 in the gap formed between the steel strip 1 and the straight measure The largest of the distances to the lower surface of the straight measure was taken as the amount of edge bend (maximum length of the gap).

  FIG. 2A shows the relationship between the plate thickness and the amount of edge bend. The dotted line in the figure indicates the required bending amount (11 mm) of the amount of edge bend calculated from the curvature of the fin pass roll provided at the rear stage of the breakdown roll. If the amount of edge bend is less than the required amount of bending, it is evaluated that the forming of the edge is not sufficient. The result of the comparative example is indicated by ▪ in the figure, and the inventive example is indicated by ● in the figure. In the comparative example, the amount of edge bend is smaller than the required amount of bending, and the forming of the edge portion is insufficient. On the other hand, in the example of the present invention, the edge bend amount is larger than the required bending amount and the edge portion is sufficiently shaped even in the example in which the plate thickness where deformation of the edge portion is most difficult is the largest (22 mm).

(Example 2)
Among the steel strips used in Example 1, the thickness of the steel strip is 9 to 22 mm using the breakdown roll of the present invention shown in FIG. 1 or the same breakdown roll as that used in the comparative example of Example 1. After passing the product, it was passed through a fin pass roll at a later stage. After passing through the fin pass roll, the ratio (generation frequency) of the steel strip in which appearance wrinkles (roll marks) were generated on the surface was calculated. The results are shown in FIG. Incidentally, although two bar graphs are illustrated in the comparative example of FIG. 3, these show the occurrence rates of roll marks in steel pipes manufactured at different timings. In the comparative example, although the steel strip in which the roll mark was generated was detected around 10%, it was 0% in the inventive example. Thus, it has been shown that the present invention can suppress the occurrence of roll marks on fin pass rolls.

(Example 3)
Comparison of the breakdown roll of the present invention shown in FIG. 1 or the comparison of Example 1 for the first stage of the three previous breakdown rolls in a line provided with three fin pass rolls after the three breakdown rolls Breakdown rolls similar to those used in the examples were used to deform the edges of the steel strip with various thickness. The breakdown rolls in the second and third stages were all the same as the breakdown rolls used in the comparative example of the first embodiment. The result of measuring the load current in the first stage fin pass roll (F1), the second stage fin pass roll (F2), and the third stage fin pass roll (F3) is shown in FIG. The allowable value of the load current of F1 in this line was 400 A, and the allowable value of the load current of F2 and F3 was 350 A.

  In the comparative example, in each of the three fin pass rolls, the thicker the plate thickness is, the more the load current tends to increase. Under conditions where the plate thickness is 12 mm or more, the load current allowable value is exceeded. The outage rate was very high.

  On the other hand, in the example of the present invention, the magnitude of the load current was relatively stable even when the plate thickness changed. Even in the case of the maximum plate thickness (22 mm), there were cases where the load current temporarily exceeded the allowable value, but when compared to the comparative example, the line stop rate was significantly reduced.

DESCRIPTION OF SYMBOLS 1 Steel strip 2 Forming roll row 3, 4 Breakdown roll 5 Cage roll 6 Fin pass roll 7 Induction coil 8 Squeeze roll 9 Tubular body 10 Bead cutting means 11 Ultrasonic flaw detector 12 Seam anila 13 Water jet nozzle 14 Drawing rolling mill 15 Cutter 16 Lower roll 17 Lower roll rotation motor 18 Upper roll 19 Vertical movement servomotor 20 Horizontal movement servomotor 21 Sensor 22 Position adjustment means 24 Display 25 Vertical movement worm jack 26 Horizontal movement screw 28 and 30 Upper edge Roll 29 Upper center roll 31, 32 Lower edge roll 33 Spacer member 34 Roll stand 35 Upper roll group 36 Lower roll group 37, 38 Roll shaft 39, 40 Roll stand 41 Breakdown roll

Claims (4)

A break-down roll that bends the edge of a steel strip upwards,
An upper roll group located on the upper surface side of the steel strip and a lower roll group located on the lower surface side of the steel strip;
The upper roll group consists of two upper edge rolls for pressing the edge portion of the steel strip and an upper center roll for pressing the widthwise central portion of the steel strip,
The lower roll group is a breakdown roll consisting of two lower edge rolls that press the edge portion of the steel strip.   The breakdown roll according to claim 1, further comprising a spacer member for fixing the widthwise position of the upper edge roll, the upper center roll, and the lower edge roll. It is a manufacturing method of a welded steel pipe performed using a breakdown roll according to claim 1 or 2,
By pressing the edge portion of the steel strip with the upper edge roll and the lower edge roll and bending the both widthwise end portions of the steel strip upward, pressing the upper central portion of the steel strip downward with the upper center roll A method of manufacturing a welded steel pipe for forming. Select the upper edge roll, upper center roll, and lower edge roll according to the steel strip to be passed through,
Fix the widthwise position of the upper edge roll, upper center roll, and lower edge roll,
After fixing the vertical position of the upper roll group and the lower roll group with the selected upper edge roll and lower edge roll,
The manufacturing method of the welded steel pipe of Claim 3 which shape | molds.

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