RU2417851C2 - Producing tubes with higher properties of welded seams by contact resistance welding - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to contact welding and may be used in producing pipes for oil wells. Strip 20 is formed and its edges are jointed together and subjected to contact resistance welding to produce pipe. In forming, rounded edge or edge inclined from perpendicular by 25° to 50° is produced in pass arranged directly ahead of contact resistance welding machine. Note that perpendicular length from inclination start to end equals 20% - 40% of strip thickness on, at least, one side of the strip and on the side of its top or bottom surface.

EFFECT: high quality of welded joint.

12 cl, 11 dwg, 6 tbl

Description

FIELD OF THE INVENTION

The present invention relates to a method for manufacturing pipes that require toughness of a weld, such as pipe pipes for oil wells, or pipes that require strength of a weld, such as casing pipes for oil wells.

State of the art

Typically, pipes are subdivided into welded pipes and seamless pipes. A pipe obtained by resistance resistance welding, being a pipe related to welded pipes, is made by folding a sheet by roll forming or the like, and then joining each edge and welding. In welded pipes, the toughness and strength of the weld are usually low compared to these characteristics of the original strip. When using these pipes, an inevitable problem is to provide a specific toughness and weld strength for each application.

For example, since pipes for pipelines for transporting crude oil or natural gas are often laid in cold latitudes, impact strength at low temperature is mainly of interest. In addition, in the case of a casing to protect the production pipe in an oil well, strength is essential for the production of crude oil.

As a rule, for a hot-rolled sheet (strip), which will be the initial strip of the pipe obtained by resistance resistance welding, composition development or heat treatment is carried out taking into account the properties acquired by the initial strip after forming the pipe from it, so that the properties of the initial strip are ensured like toughness and strength.

However, since the characteristics of welds are strongly influenced by the resistance welding method, rather than the development of the composition or heat treatment of the original strip, it is necessary to significantly improve the welding technology.

In many cases, the cause of resistance welding problems with resistance can be the following phenomenon: namely, on the edge of the strip, oxides are formed, referred to as inclusions, and these inclusions are not removed from the edge together with the molten steel outlet during resistance welding and remain on it, and the remaining inclusions cause decrease in toughness, leading to insufficient strength.

Thus, in order to remove inclusions from the weld that are the causes of the destruction of the traditional welded joint obtained by resistance resistance welding, a serious study has so far been carried out regarding the technology of active removal of molten steel from the edge of the strip in the weld. For example, Patent Documents 1-4 describe examples of research regarding the shape of each edge of the strip.

In addition, patent document 5 describes that the lateral edges of the strip have bevels of various shapes in order to facilitate the adjustment of the joint pressure on the edges on both sides of the strip when welding the pipe obtained by resistance resistance welding, and to improve the reliability of the welded joint.

Patent Document 1: JP-A-57-031485

Patent Document 2: JP-A-63-317212

Patent Document 3: JP-A-2001-170779

Patent Document 4: JP-A-2003-164909

Patent Document 5: JP-A-2001-259733

Disclosure of invention

In any of the patent documents 1 to 4, it is understood that each edge of the strip is formed with a slope so as to deflect inclusions along with the outlet of the molten steel. The reason for the formation of the slope is believed to be the fact that the edge of the strip can be easily formed with a slope. However, when the edge of the strip is formed with a straight or flat slope having a constant angle of inclination, defects such as oxides may not be properly removed along with the removal of the molten steel.

In addition, Patent Document 5 discloses various forms of bevels to facilitate regulation of joint pressure. However, no description was found in it regarding the removal of inclusions together with the removal of molten steel and the improvement of the characteristics of welds (especially toughness at low temperature) through such removal of inclusions. Therefore, it is completely unclear which particular shape among the various bevel shapes disclosed in this patent is effective for improving the characteristics of welds (especially toughness at low temperature).

In the current manufacturing process for resistance welded pipes, strips having different thickness classes are roll-formed to convert them into pipes. When using the only means for forming a slope at each edge of the strip, for example, the cutting tool or scraper should be adjusted in its position so as to be installed with an exact gap similar to the thickness of the strip, which caused a significant decrease in production efficiency.

Thus, the object of the invention is to propose a method for efficiently producing resistance-welded pipes having excellent weld characteristics, which can properly accelerate the removal of defects such as oxides, together with the removal of molten steel, in addition, may not cause a decrease in production efficiency.

The invention to achieve this objective is described as follows.

1. A method of manufacturing pipes obtained by resistance resistance welding, which improves the characteristics of welds, characterized in that the strip is molded, then its edges are joined and then these edges are resistance-welded to form a pipe, an edge on one side of the upper surface side and the sides of the lower surface of the strip or on both surfaces of the upper and lower surfaces of the strip before resistance welding are formed with a slope.

2. A method of manufacturing pipes obtained by resistance resistance welding, which improves the characteristics of welds, characterized in that the edges on one side of the upper surface side and the lower surface side of the strip are formed with a slope by cutting or scraping.

3. A method of manufacturing pipes obtained by resistance resistance welding, which improves the characteristics of welds, characterized in that the edges on one side of the upper surface side and the lower surface side of the strip are formed with a slope by means of a groove-shaped roll.

4. A method of manufacturing pipes obtained by resistance resistance welding, which improves the characteristics of welds, characterized in that the edges on one side of the upper surface side and the lower surface side of the strip are formed with a slope by molding in caliber with an edge guiding element (edge guiding element providing centering the edges of their final molding and directing them in the desired position in the welding zone).

5. A method of manufacturing pipes obtained by resistance resistance welding, which improves the characteristics of welds, characterized in that the edges on one side of the upper surface side and the lower surface side of the strip are formed with a slope by cutting or scraping or with a groove-shaped roll, and the edges on the side of the other surface of the strip are formed with a slope by molding in caliber with an edge guide element.

6. A method of manufacturing pipes obtained by resistance resistance welding, which improves the characteristics of welds, according to the preceding sections 1 to 5, characterized in that the edges on one side in the direction of the strip thickness have a circular shape.

7. A method of manufacturing pipes obtained by resistance resistance welding, which improves the characteristics of welds, according to the preceding sections 2 to 3, characterized in that cutting, or scraping, or rolling using a groove-shaped roll is performed before roll forming.

8. A method of manufacturing pipes obtained by resistance resistance welding, which improves the characteristics of welds according to the previous section 2 or the previous sections 5 to 6, characterized in that they use a tool having cutting blades located in the form of a roller, or a grinding stone in the form roller, in which each cutting blade or grinding surface of the stone includes a section approximately parallel to the edge of the strip, and a section inclined to the edge of the strip from the midpoint.

9. A method of manufacturing pipes obtained by resistance resistance welding, which improves the characteristics of welds according to the previous section 2 or the previous sections 5 to 6, characterized in that the edge of the strip is subjected to cutting or grinding, while the tool having cutting blades located in in the form of a roller, or a grinding stone in the form of a roller is brought into contact parallel to the edge of the strip, and the edge of the strip is subjected to cutting or grinding, while the tool having other cutting blades located form rollers or grinding stone in the form of a roller is brought into contact to the inclined edge strip so that the strip edges are formed with a slope.

10. A method of manufacturing pipes obtained by resistance resistance welding, which improves the characteristics of welds, according to the previous section 1 or 2 or the previous sections 4 to 9, characterized in that the slope immediately after cutting or grinding the strip or the slope immediately after rolling the strip using a roll having a shape with a recess is performed in such a way that the angle from the perpendicular is in the range from 23 ° to 50 °, and the length of the perpendicular from the start of the slope to the place of its end is about 50% to 90% of the strip thickness.

11. A method of manufacturing pipes obtained by resistance resistance welding, which improves the characteristics of welds, according to the preceding sections 1 to 10, characterized in that the slope in the strip immediately before resistance resistance welding is performed in such a way that the angle from the perpendicular is in the range from 25 ° to 50 °, and the length of the perpendicular from the beginning of the slope to the place of its end is from 20% to 45% of the strip thickness.

Brief Description of the Drawings

Figure 1 is an explanatory diagram of equipment for the manufacture of pipes obtained by resistance welding, for carrying out the invention;

Figure 2 is a schematic view of the arrowed line AA shown in Figure 1;

Figures 3A and 3B are respectively local detailed schematic views of Figure 2;

FIGS. 4A and 4B are respectively schematic views of an arrowed line BB shown in FIG. 1;

FIG. 5 is a schematic view of the arrowed line AA shown in FIG. 1;

Figures 6A and 6B are respectively local detailed schematic views of Figure 5;

FIG. 7 is a schematic diagram showing an example of an embodiment of performing corner rounding on the side of the upper surface of the strip by means of a grinding stone; FIG.

Figures 8A and 8B are respectively diagrams showing a situation of formation of a slope at the edge on the side of the upper surface of the strip with a roll having a shape with a recess;

Fig.9 is a diagram showing a situation of the formation of a slope at the edge on the side of the upper surface of the strip with a roll having a shape with a recess;

10 is a diagram showing a slope formed at an edge on the side of the upper surface of the strip before roll forming; and

11 is a diagram showing a previous roll having a shape with a recess.

The numbers in the drawings relate accordingly to the following:

1 unwinder

2 right car

3 slope forming means

31 cutting roller or scraper roller

31a cutting roller

31b scraper roller

31c cutting roller

31d scraper roller

32 roll shaped recess

4 caliber molding stand with edge guide

4a end stand for molding in caliber with edge guide

5 roll forming machine

6 induction heater

7 compression roller (resistance welding section)

8 burr cutter

9 calibration mill

10 pipe cutting machine

20 strip

30 pipe

The implementation of the invention

In the invention, the term “strip forming” refers to the operation of gradually folding the strip in the transverse direction so as to give the strip a cross-sectional profile, and the molding process includes an initial stage of roll forming, during which sections near the edges are bent on both side the sides of the strip, and the rolling stage in caliber with an edge guide element, during which the strip is finally brought to a circular profile.

In the invention, the means for forming a slope at the edges on one side of the upper side and the lower side of the strip are of a different type from the means for forming a slope at the edges on the other side of the upper side and the side of the lower surface of the strip the previous side of one surface, that is, the edges are formed with a slope by a variety of means. Thus, the edges are formed with a slope on the side of one surface, then the edges are formed with a slope on the side of the other surface. According to this, even if the strip thickness changes, it is easy to adjust the vertical position of the slope forming apparatus, and thereby edges on both sides of the upper surface side and the lower surface side of the strip can be formed with a slope without compromising production efficiency.

Thus, since the strip on the upstream side of the roll forming is approximately flat, the slope is preferably formed by cutting or scraping. Such a slope forming tool requires a relatively large space for its installation, since the size of its device is relatively large, therefore, this tool is difficult to install inside or after roll forming, since the space between the two side edges of the strip, which are folded or rolled, is reduced. In addition, since it is difficult for the cutting or scraping device to vertically limit the edge of the strip only by this device itself, high positioning accuracy is required to install this device in combination with installing the device to accurately maintain the location through which the strip passes. For this reason, it is necessary to increase the rigidity of the location of each device, which leads to the requirement of even more space for installation. Thus, it is preferable that the cutting or scraping means is installed before the roll forming.

Moreover, when the edges on both sides of the upper surface side and the lower surface side of the strip are cut off or scraped off, since when rolling in caliber with an edge guiding element during roll forming, the strip fills the gauge roller with the edge guiding element, the edges of the strip are subjected to high pressure, so that a previously formed slope is sometimes destroyed, and thus the desired shape cannot be obtained. Therefore, it is preferable that the edges are pre-formed with a greater slope than the required slope, taking into account the destruction of the strip edges when rolling in caliber with an edge guide element. However, when edges are formed on both sides with a slope from the side of the upper surface side and the side of the lower surface of the strip, a large slope is difficult to obtain due to the limitation of the strip thickness, it is preferable that the edges are cut or scraped only on one side of the upper surface and the lower side strip surface.

Then, the edges on the side of the other surface, which are not yet formed with a slope, are formed with a slope using rolling in caliber with an edge guide element. Since for the above reason, the edges are formed with a slope only on one side of the upper side and the lower surface of the strip, so as to form both sides of the upper surface and the lower surface side, it is preferable that the edges are on the other side surfaces were formed with a slope during or after roll forming. Accordingly, the inventors drew attention to the phenomenon that the edges of the strip are easily destroyed when rolling in caliber with an edge guide element, and decided to use this phenomenon. That is, when the edge guide element of the caliber rolling roll with the edge guide element is formed with a two-stage slope and the angle of the edge of the edge guide element and the place of its contact with the edge of the strip are optimized depending on the amount of compression (draft) when rolling in caliber with the edge guide element, the edges on side of the other surface, which are not yet formed with a slope, can also be formed with a slope. Since such a slope treatment is performed by rolling itself in caliber with an edge guiding element, even if the two edges between which the space is reduced when the strip is folded sideways by roll rolling are extremely close to each other, the slope treatment can be performed properly .

Thus, even if the strips differ in thickness, rolled up, the two side edges of the strip immediately before welding are formed with a slope, according to what is required depending on the thickness of the strip.

Preferably, this slope is formed at the lateral edges on the side of the upper surface of the strip, in order to prevent this relatively large device from interfering with the roller conveyor located on the inlet side of the roll forming.

Preferably, this slope is formed on the two lateral edges of the strip (20) so that the angle (α) of the inclination from the lateral edge of the strip (20) to the upper or lower surface of the strip (20) is from 23 ° to 50 ° immediately before resistance welding resistance, and the distance (β) between the beginning of the slope on the lateral edge of the strip (20) and the upper or lower surface was from 20% to 40% of the strip thickness.

That is, when the inclination angle (α) is less than 25 °, the molten steel is improperly removed from the central portion of the strip thickness, and inclusions, causing defects, remain, which results in a decrease in impact strength or strength after resistance resistance welding, and when the angle (α) the slope is greater than 50 °, the slope, causing problems, still remains as a flaw on the pipe-product after resistance welding. In addition, when the distance (β) is less than 20% of the thickness, the molten steel is improperly diverted from the central portion of the strip thickness, so that inclusions tend to remain, and when the distance β is more than 40% of the thickness, the slope, causing problems, is still remains in the form of a defect on the pipe-product after resistance welding.

Embodiments of the invention are described below.

Figure 1 shows the production line for pipes obtained by resistance resistance welding, used in the invention. The production line for pipes obtained by resistance resistance welding has a basic configuration in which the strip (20) is wound from the unwinder (1); then this strip is straightened, turning into a flat, by means of a straightening machine (2); then the strip (20) is gradually folded by a machine (5) for roll forming; then the two side edges of the rolled strip (20) are subjected to resistance resistance welding using an resistance resistance welding machine including an induction heating section (6) and a compression roller (resistance resistance welding section) (7) so as to be formed into a pipe ( thirty); then, the section of the weld bead of the pipe (30) is cut off with a tool (8) for cutting the bead; then the pipe (30) after cutting is adjusted in the outer diameter by a calibration mill (9); and then the pipe is cut into segments of a given length by a pipe cutting machine (10). The roll forming machine (5) at the last stage has a predetermined number (here two) of the stands for molding in caliber with an edge guiding element.

In this embodiment, in addition to the basic configuration, the production line has cutting or scraping means (31) for forming a slope at two lateral edges on the side of the upper surface of the strip (20) between the straightening machine (2) and the rolling machine (5) molding. As shown in FIG. 2, showing a schematic view along the arrowted line “A-A” shown in FIG. 1, and in FIGS. 3A and 3B, showing respectively local detailed schematic views of FIG. 2, cutting or scraping means (31 ) rotates by a motor (3e) a cutting tool (31a) including cutting blades arranged in the form of a roller (Fig. 3A), or a scraping stone (31b) in the form of a roller (Fig. 3B), and its cutting or scalloping surface parallel to the axis of the roller. Cutting or scraping means (31) are arranged in a pair in the transverse direction of the strip (20), and the axis of each roller is inclined at a given angle (γ) to the vertical direction, so that two side edges on the side of the upper surface of the strip (20) are formed with a given slope ( the angle of inclination from the lateral edge to the upper surface is γ, and the distance in the direction of the thickness of the strip from the upper surface to the beginning of the slope at the lateral edge is δ). Further, a cutting tool (31a) including cutting blades arranged in a roller shape is referred to as a cutting roller (31a), and a scraping stone (31b) in a roller shape is referred to as a scraping roller (31b).

In addition, in this embodiment, as shown in FIG. 4A, showing a schematic view of the arrowed line BB shown in FIG. 1, and FIG. 4B showing a local detailed schematic view of FIG. 4A, final the stand (4a) of the stand (4) for forming in gauge with an edge guiding element has the shape of an edge guiding element including a two-step slope (the slope angle of the second step is α and the vertical slope of the second step is β), and this form is printed on each side cr mark the strip (20), thereby two lateral edges on the side of the lower surface of the strip (20) (on the side of the outer surface of the pipe (30)) are formed with a given slope (the angle of inclination from the lateral edge to the lower surface is α, and the distance in the thickness direction the strip from the beginning of the slope at the lateral edge to the lower surface is β).

In the production line for pipes obtained by resistance resistance welding, configured as described above, in the case when strips (20) having different thickness classes are successively passed through it when forming a given slope at two lateral edges on the side of the upper surface and the side of the lower surface of each strips (20), two side edges on the side of the upper surface of the strips (20) are cut or scraped, while the cutting roller (31a) or scraper roller (31b) is inclined by a predetermined angle γ and the position of the roll ka (31a) or (31b) in the height direction is adjusted precisely, thereby two side edges on the side of the upper surface of the strip (20) are formed with a predetermined bias. In addition, the shape of the edge guiding element is imprinted on the two lateral edges of the side of the lower surface of the strip (20) by means of the end stand (4a) during molding in caliber with the edge guiding element, thereby two side edges on the side of the lower surface of the strip (20) are formed with a given slope . Thus, since, unlike the prior art, it is not necessary to change a roll having a shape with a recess, depending on the thickness of the strip, or it is not necessary to set the relative position of the cutting tool or the like, which is time-consuming, the two side edges of the strip (20) can be formed with a given slope, depending on the thickness of the strip, without compromising production efficiency.

As mentioned above, in this embodiment, two side edges of the strip (20) before resistance welding can be formed with an appropriate slope corresponding to a change in the thickness of the strip (20). Therefore, the welding quality can be maintained excellent, and a decrease in production efficiency can be avoided, and therefore, it is possible to efficiently produce a pipe obtained by resistance resistance welding having excellent weld characteristics.

In this embodiment of the invention, separately from the cutting or scraper means (31) for forming a bias on two lateral edges on the side of the upper surface of the strip (20), it is possible to provide, if necessary, cutting or scraper means for cutting or scraping two lateral edges located approximately parallel to the lateral edges of the strip (20) on the upstream side of the means (31), so that the lateral edges of the strip (20) can be pre-smoothed.

The production line for pipes obtained by resistance resistance welding used in another embodiment of the invention is approximately similar to the production line of pipes obtained by resistance resistance welding used in the first embodiment of the invention, but differs in that the cutting or bracing means (31) for forming a slope on two lateral edges on the side of the upper surface of the strip (20) is located between the leveling machine (2) and the machine (5) for roll forming.

FIG. 5 shows a schematic view of the cutting or scraper means (31) along the arrow line “AA” shown in FIG. 1. Figures 6A and 6B show local detailed schematic views of a cutting or scraping means (31), respectively. The cutting tool (31c) (Fig. 6A) is a cutting tool in which the cutting blades are arranged in the form of a roller. The cutting surface of the cutting tool (31c) has a shape in which a portion approximately parallel to the axis of the roller is connected to a portion that is inclined in the outer direction with respect to the axis of the roller. Squabble stone (31d) (FIG. 6B) has a roller shape. The scoop surface of the scraping stone (31d) has a shape in which a portion approximately parallel to the axis of the roller is connected to a portion that is inclined externally with respect to the axis of the roller. Hereinafter, the cutting tool (31c) is called the cutting roller (31c) with a slope, and the scraper (31d) is called the scraping roller (31d) with a slope.

When using a cutting roller (31c) or a scraper roller (31d) having such a shape for strips having different thickness classes, the side edges on the side of the upper surface of each strip can be easily formed with a slope having a constant angle and location by one cutting roller (31c) or scraper roller (31d).

To form a slope at the lateral edges on the side of the lower surface of the strip 10, as in the first embodiment of the invention, as shown in FIG. 4A, showing a schematic view of the arrow BB line shown in FIG. 1 and FIG. 4B showing a local detailed schematic view of FIG. 4A, the final stand (4a) of the stand (4) for forming in caliber with an edge guiding element has the shape of an edge guiding element including a two-stage slope (the slope angle of the second stage is α and the vertical slope length and the second stage is β), and such a form is printed on the lateral edges of the strip (20), thereby the two side edges at the bottom side of the strip surface (20) (on the outer surface of the tube (30)) formed with a predetermined bias.

Therefore, in this case as well, in this embodiment, the two lateral edges of the strip (20) can be formed with an appropriate slope corresponding to the change in the thickness of the strip (20) before resistance welding. Therefore, the welding quality can be maintained excellent, and a decrease in production efficiency can be avoided, and therefore, it is possible to efficiently produce a pipe obtained by resistance resistance welding having excellent weld characteristics.

In the first and second embodiments of the invention, the slope is formed so that the edges on the side of the upper surface of the strip and the edges on the side of its lower surface are symmetrical with respect to the central plane of the strip thickness. However, this is not a limitation, and the slope can be formed in such a way that the edges on the side of the upper surface of the strip and the edges on the side of its lower surface are asymmetric with respect to the central plane of the strip thickness.

In the case of a production line in which the strip forming direction is vertically opposite to that in the production line shown in FIG. 1 (that is, in which the upper surface of the strip is the outer surface), side edges on the side of the lower surface of the strip can be formed with a slope by cutting or scraping before molding, and the side edges on the side of the upper surface of the strip can be formed with a slope by molding in caliber with an edge guide element .

As mentioned above, the following phenomenon often caused problems for resistance resistance welding, namely: oxides, called inclusions, form on the edge of the strip, and these inclusions are not removed from the edge together with the molten steel outlet during resistance resistance welding, but remain on it , and the remaining inclusions cause a decrease in toughness, leading to insufficient strength.

Thus, in any of the technical solutions of the prior art, it was understood that the edge of the strip is formed with a slope so as to divert inclusions along with the outlet of molten steel. The reason for this slope formation is believed to be that the strip edge is easy to shape. However, when the edge of the strip was formed with a straight or flat slope, in some cases, defects such as oxides were not properly removed along with the removal of the molten steel.

To clarify the causes of this phenomenon, the inventors conducted a serious study on this subject, as a result, the following was found out. Namely: the molten steel formed at the beginning of welding is present on the edge of the strip formed with a slope in a small amount due to the small contact area, then the area increases in the area welded with the draft (pressure welding) during resistance resistance welding, and the amount of molten steel increases accordingly. However, it was found that with a prior art slope formed constant in the direction of the strip thickness, since the angle of extraction (withdrawn amount) of the molten steel was constant in the direction of the strip thickness, even if the molten steel was properly diverted from the area near the edge of the strip thickness, it sometimes improperly diverted from the site near the middle of the strip thickness, causing a phenomenon in which molten steel, which was previously molten, filled the surface of the strip and hardened on it, forming a lid, which sometimes blocked the removal of molten steel, which was to be subsequently removed from the surface being welded.

Thus, the inventors conducted a serious study regarding the method of excellent removal of molten steel continuously over time welding. As a result, they realized that the molten steel had a small amount during welding of the section near the middle of the strip thickness, and the molten steel increased in quantity during welding of the section near the edge of the strip thickness, therefore, a special shape was necessary for continuous removal of an approximately constant amount of molten steel edges.

Based on this result, the inventors investigated various forms, as a result they found that the edge of the strip should be round in shape, whereby continuous removal of molten steel can be excellently performed. That is, when the edge of the strip is given a circular shape, since the contact area during welding of the section near the middle of the strip thickness increases sharply, the discharge amount of molten steel is increased, and since the contact area during welding of the section near the edge of the strip thickness increases gradually, the tap the amount of molten steel is reduced. Such an operation makes possible the stable removal of molten steel and eliminates the fact that the molten steel that was previously diverted from the surface being welded hardens to form a lid blocking the removal of molten steel to be subsequently removed.

In this way, molten steel is appropriately diverted from the edge of the strip so that inclusion can be sufficiently removed, characteristics such as toughness or weld strength can be maintained excellent.

When the rounding of the strip edge is performed on the edges on both sides in the direction of the strip thickness (angles on both sides of the upper surface side and the lower surface side), a large effect is achieved.

When the rounding is performed by a roll having a shape with a recess, since the edge of the strip is subjected to insufficient plastic deformation, it is difficult to obtain a given shape. However, a predetermined contour can be directly obtained by performing rounding by cutting or abrasive grinding. In addition, when forming in caliber with an edge guiding element, the strip is folded so as to give the profile of its cross section a round shape, therefore, the edge of the strip is under great pressure from the side of the edge guiding element. Thus, the edge guide element is preformed with the desired round shape, whereby the shape of the strip edge can be appropriately close to the desired round shape.

Thus, since the strip is approximately flat on the inlet side of the roll forming, it is preferable to give the edges a circular shape by cutting or abrasive grinding. Such a rounding tool requires a certain space for its installation, since the size of its device is relatively large, therefore, this tool is difficult to install inside or after roll forming, since the space between the edges of the strip is reduced. In addition, since it is difficult for the cutting or scraping device to vertically limit the edge of the strip only by this device itself, high positioning accuracy is required to install this device in combination with installing the device to accurately maintain the location through which the strip passes.

For this reason, it is necessary to increase the rigidity of the location of the device, which leads to the requirement of even more space for installation. Moreover, when both of the upper and lower edges (angles on both sides of the upper surface side and the lower surface side), the strips are cut or scraped off, because when rolling in caliber with an edge guiding element (which means, as hereinafter, molding in gauge with edge guiding element) during roll forming, the strip fills the caliber roller with edge guiding element, the edges of the strip are subjected to high pressure, so that the previously formed round shape sometimes breaks, and thus The requested form could not be obtained. Therefore, it is preferable that a large round shape is formed in advance, taking into account the destruction of each edge of the strip when rolling in caliber with an edge guide element. However, when both of the upper and lower edges (angles on both sides of the upper surface side and the lower surface side) of the strip are formed with a round shape, it is difficult to obtain a large round shape due to the limitation of the strip thickness, it is preferable that the edges are cut or abrasively ground only on one side (angles on only one side of the sides of the upper surface and the sides of the lower surface).

Then other edges (angles on the side of the other surface) that are not formed with a round shape are formed with a round shape using rolling in caliber with an edge guide element. Since for the aforementioned reason, only one side is formed with a round shape, in order to form a round shape on both edges, it is preferable that the edges on the opposite side can be formed with a round shape during or after roll forming.

Accordingly, the inventors drew attention to the phenomenon that the edges of the strip are easily destroyed when rolling in caliber with an edge guide element, and decided to use this phenomenon. Thus, when the edge guide element of the caliber rolling roll with the edge guide element is formed with a round shape, and the angle of the edge guide element and the place of its contact with the edge of the strip are optimized depending on the amount of reduction (settlement value) when rolling in caliber with the edge guide element, the edges are on the side, the opposite side of the edges of the strip, which are formed with a circular shape before the roll forming, can also be formed with a circular shape. Since this rounding is carried out by rolling in caliber with an edge guiding element, even if the strip is folded laterally by roller rolling, due to which the distance between the lateral, two edges is reduced or the edges are close to each other, rounding can be performed properly.

Thus, the upper and lower two edges of the strip (angles on both sides from the side of the upper surface and the side of the lower surface of the strip) can be formed with a circular shape immediately before resistance welding.

Preferably, rounding by cutting or scraping is performed over the corners on the side of the upper surface of the strip in order to prevent this relatively large device from interfering with the roller table located on the inlet side of the roll forming. In addition, since the side of the lower surface of the strip becomes the side of the outer surface (outer diameter side) of the pipe after roll forming, it is preferable that the corners on the side of the lower surface are formed with a circular shape during rolling in caliber with an edge guide using a variable guide edge.

The inventors tried to optimize the round shape immediately before resistance welding using cutting, or grinding, or rolling in caliber with an edge guiding element, as a result they realized that the radius R when giving a round shape in the preferred embodiment was 20-50% of the strip thickness. That is, when the radius R immediately before the resistance welding is less than 20% of the strip thickness, the molten steel is in some way improperly removed from the central portion of the strip thickness, so that the inclusions remain in some quantity, leading to a slight decrease in impact strength or strength after contact resistance welding.

When the radius R is greater than 50% of the strip thickness, the distance measured in the direction of the strip width of the circular portion becomes excessively small or excessively large. In the case of an excessively short distance, the molten steel is inappropriately diverted from the central portion of the strip thickness, so that inclusions remain, leading to a decrease in impact strength or strength after resistance resistance welding. On the other hand, in the case of an excessively long distance, upsetting is difficult, and therefore, near the boundary between the weld and the original strip, the phenomenon easily appears that the pipe thickness becomes inadequate (the phenomenon that the pipe thickness becomes lower strip thickness).

In yet another embodiment of the invention, the production line for pipes produced by resistance resistance welding, in addition to the basic configuration shown in FIG. 1, has a roll (32) having a shape with a recess for forming a slope at the edges of the strip (20) between leveling machine (2) and machine (5) for roll forming.

As shown in Figures 8A and 8B, the roll (32) having a recessed shape includes a surface parallel to the edge of the strip, which is approximately vertical, and a surface inclined to the approximately vertical edge of the strip, the surfaces being connected to each other, and is capable of move in a vertical direction. The method of rotation of the roller (32) can be developed, as in the example shown in Fig. 8A, so that the surface parallel to the approximately vertical edge of the strip is made in the form of a body of rotation, and an axis of rotation parallel to the approximately vertical edge of the strip is provided, or the method can be developed, as in the example shown in Fig. 8B, so that the surface parallel to the surface inclined to the approximately vertical edge of the strip is made in the form of a body of revolution, and the axis is rotated I, parallel to the surface inclined to the approximately vertical edge of the strip.

When rolling the strip (20) with such a roll (32) having a shape with a recess, as shown in Figures 8A and 8B, the edges on the side of the upper surface of the strip (20) (the side of the inner surface of the pipe (30)) can be formed with a slope where the slope angle from the surface of the strip edge to the vertical direction (the slope angle to the strip thickness direction) is γ, and the perpendicular length from the beginning of the slope to the place of its end on one side (the slope length in the strip thickness direction) is δ.

In addition, as shown in FIG. 4A, showing a schematic view along arrowed line BB shown in FIG. 1, and FIG. 4B showing a local detailed schematic view of FIG. 4A, in this embodiment of the edge guiding element the final stand (4a) of the stand (4) for forming in caliber with an edge guiding element has the shape of an edge guiding element including a predetermined two-stage slope (the slope angle of the second stage is α and the vertical slope of the second stage is β). This shape of the edge guide element is imprinted on each side edge of the strip (20), thereby two side edges on the side of the lower surface of the strip (20) (on the side of the outer surface of the pipe (30)) can be formed with a given slope.

Thus, when a slope is formed at the edges on the side of the upper surface and the side of the lower surface of the strips having different thickness classes, the edges on the side of the upper surface of the strip (20) (the side of the inner surface of the pipe (30)) are rolled in predetermined places in the direction of the thickness of the strip, using a roll (32) having a shape with a recess, with its vertical position precisely adjusted. On the other hand, at the edges on the side of the lower surface of the strip (20) (the side of the outer surface of the pipe (30)), a bias is printed at predetermined locations in the direction of the thickness of the strip by molding in caliber with an edge guide element. Thus, the edges of both of the upper and lower surfaces of the strip can be formed with a given slope, depending on the thickness of the strip, without compromising production efficiency.

Thus, a surface parallel to the edge of the strip, and a surface inclined to the edge of the strip, and a vertically movable roll (32) having a shape with a recess, are combined with the final stand (4a) of the caliber with an edge guiding element having the shape of an edge guiding element, including a two-stage slope, so that both of the edges on the side of the upper surface and the edges on the side of the lower surface of the strip are formed with a slope. Therefore, even if the slope is formed on strips having different thickness classes, the efficiency does not decrease. In addition, even if the strip varies greatly in thickness, an excessive load does not act on a roll having a shape with a recess; therefore, a roll having a shape with a recess cannot be destroyed.

It is preferable that the slope formed by the roll (32) having a shape with a recess and the final stand (4a) of the gauge with the edge guiding element is made so that the slope angle (α) or (γ) immediately before resistance welding, measured from the edge of the strip to the vertical direction ranged from 25 ° to 50 °, and the length (α) or (γ) of the perpendicular from the beginning of the slope to the place of its end on one side was from 20% to 40% of the strip thickness.

That is, when the slope angle (α) or (γ) is less than 25 °, the molten steel is inappropriately removed from the central portion of the strip thickness, so that inclusions causing defects remain, resulting in a decrease in impact strength or strength after resistance welding resistance, and when the angle (α) or (γ) of the slope is more than 50 °, the slope, causing problems, still remains as a defect on the pipe after resistance welding. In addition, when the distance (β) or (δ) is less than 20% of the strip thickness, the molten steel is inappropriately removed from the central portion of the strip thickness, so that inclusions tend to remain, and when the distance (β) or (δ) is greater than 40 % of the thickness, the slope, causing problems, still remains in the form of a flaw on the pipe-product after resistance welding.

Thus, in this embodiment of the invention, since the edges of the strip can be properly formed with a slope before resistance welding, it is possible to efficiently fabricate a resistance-welded pipe having very excellent toughness and welding strength.

In this embodiment, the edges on the side of the upper surface of the strip (20) (the side of the inner surface of the pipe (30)) are formed with a slope before the roll forming, and the edges on the side of the lower surface of the strip (20) (the side of the outer surface of the pipe (30)) with a slope by molding in caliber with an edge guide element. However, in some cases, the edges on the side of the lower surface of the strip (20) (the side of the outer surface of the pipe (30)) can be formed with a slope before roll forming, and the edges on the side of the upper surface of the strip (20) (side of the inner surface of the pipe (30 )) can be formed with a slope by molding in caliber with an edge guide element.

The above description was made on the assumption of a production line in which the side of the upper surface of the strip (20) corresponds to the side of the inner surface of the pipe (30). However, it is obvious that the invention can be similarly applied to the production line for pipes obtained by resistance resistance welding, in which the side of the upper surface of the strip (20) corresponds to the side of the outer surface of the pipe (30).

In yet another embodiment of the invention, the production line for resistance welded pipes has, in addition to the basic configuration shown in FIG. 1, a roll (32) having a recessed shape to form a slope at the edges of the strip (20) between the leveling machine (2) and the roll forming machine (5).

As shown in FIG. 9, the roll (32) having a recessed shape has a rolling surface (32a) including a vertical rolling surface (32a ₁ ) and a rolling surface (32a ₂ ) inclined at an angle γ and has flange sections 3b on the upper and lower edges of the rolling surface (32a) and has a vertical axis of rotation. In this case, the width of the rolling surface (32a) is approximately the same as the thickness of the strip (20), and the upper and lower flange sections (3b) pinch the strip (20) so as to limit the strip (20) in the vertical direction (direction of strip thickness) .

When rolling the strip (20) with such a roll (32) having a shape with a recess, as shown in Fig. 9, the edges on the side of the upper surface of the strip (20) (the side of the inner surface of the pipe (30)) can be formed with a slope in which the slope angle relative to the strip edge surface to the vertical direction (the slope angle to the strip thickness direction) is γ, and the perpendicular length from the beginning of the slope to the end point (slope length in the strip thickness direction) on one side is δ.

In addition, in this embodiment, as shown in FIG. 4A, showing a schematic view of the arrowed line BB shown in FIG. 1, and FIG. 4B showing a local detailed schematic view of FIG. 4A, final the stand (4a) of the stand (4) for rolling in gauge with an edge guiding element has the shape of an edge guiding element including a predetermined two-stage slope (the slope angle of the second stage is α and the vertical length of the slope of the second stage is β). This shape of the edge guide element is imprinted on each side edge of the strip (20), thereby two side edges on the side of the lower surface of the strip (20) (on the side of the outer surface of the pipe (30)) can be formed with a given slope.

It is preferable that the slope formed by the recessed roll (32) and the slope formed by the end stand (4a) of the gauge with the edge guiding element are made so that the slope angle (α) or (γ) immediately before resistance welding measured from the surface of the strip edge to the vertical direction, ranged from 25 ° to 50 °, and the length (β) or (δ) of the perpendicular from the beginning of the slope to the place of its end on one side was from 20% to 40% of the strip thickness .

That is, when the slope angle (α) or (γ) is less than 25 °, the molten steel is inappropriately removed from the central portion of the strip thickness, so that inclusions causing defects remain, resulting in a decrease in impact strength or strength after resistance welding resistance, and when the angle (α) or (γ) of the slope is more than 50 °, the slope, causing problems, still remains as a defect on the pipe after resistance welding. In addition, when the slope height (β) or (δ) is less than 20% of the strip thickness, the molten steel is improperly diverted from the central portion of the strip thickness, so that inclusions tend to remain, and when the slope height (β) or (γ) is greater than 40% of the strip thickness, the slope, causing problems, still remains in the form of a flaw on the pipe-product after resistance welding.

Thus, in this embodiment, since the edges of the strip can be properly formed with a slope before resistance welding, it is possible to produce a pipe obtained by resistance welding, having very excellent toughness and welding strength.

In this embodiment, the edges on the side of the upper surface of the strip (20) (the side of the inner surface of the pipe (30)) are formed with a slope before the roll forming, and the edges on the side of the lower surface of the strip (20) (the side of the outer surface of the pipe (30)) with a slope by rolling in caliber with an edge guide element. However, in some cases, the edges on the side of the lower surface of the strip (20) (the side of the outer surface of the pipe (30)) can be formed with a slope before roll forming, and the edges on the side of the upper surface of the strip (20) (side of the inner surface of the pipe (30 )) can be formed with a slope by rolling in caliber with an edge guide element.

In addition, although the above description was made on the assumption of a production line in which the side of the upper surface of the strip (20) corresponds to the side of the inner surface of the pipe (30), it is obvious that the invention can be similarly applied to the production line for pipes obtained by resistance welding resistance, in which the side of the upper surface of the strip (20) corresponds to the side of the outer surface of the pipe (30).

In addition, the inventors conducted a study of means for forming a slope at each edge of the strip without compromising production efficiency even with varying thicknesses.

As a result, the tool for forming a slope varies between the edges on the side of the upper surface of the strip and the edges on the side of the lower surface of the strip, therefore, many means are used to form the slope. That is, the edges on the side of the upper surface of the strip and the edges on the side of its lower surface are formed with a slope by a plurality of means, while being formed with a slope of the edge on the side of one surface, then formed with a slope of the edge on the side of the other surface. Thus, even if the thickness changes, the vertical position of the slope forming means is easy to precisely adjust, and thereby both of the upper and lower edges of the strip can be formed with a slope without compromising production efficiency.

In this case, since the strip before the roll forming is approximately flat, it is preferable that the edges of the strip on one side of the surfaces are formed with a slope by cutting or grinding before the roll forming. However, since the edges of the strip are not cold-hardened, the following event may occur, that is, as previously mentioned, that is, the edges of the strip are strongly deformed under the influence of strong pressure on the edges of the strip during molding in caliber with an edge guide element, therefore, most of the formed slope can to be destroyed.

Thus, the inventors at different times conducted a study of how the edge of the strip is deformed so that the slope is destroyed during molding in the caliber with the edge guide element. Forming in caliber with an edge guide is usually done in two or three stands.

As a result, the following was discovered. Thus, in the first caliber stand with an edge guiding element, since the edges of the strip on the inlet side are substantially free of hardening, the slope is destroyed by about 40% to 60% of the length in the direction of the thickness of the strip. In the second caliber stand with an edge guiding element, since the strip edges are riveted due to the high pressure loading by the first caliber stand with an edge guiding element, 10% to 30% of the remaining slope is destroyed. In addition, if a certain number of stands are added behind the second stand, then in each stand from 10% to 30% of the slope remaining in the previous stand is destroyed.

On the other hand, as a result of studying the optimal shape of the slope immediately before resistance welding by molding after molding in gauge with an edge guiding element, it turned out that it is preferable that the angle from the perpendicular (angle of inclination to the direction of the strip thickness) be in the range from 25 ° to 50 °, and it is preferable that the perpendicular length (the length of the slope in the direction of the strip thickness) from the beginning of the slope to the place of its end be 20% to 40% of the strip thickness.

That is, when the angle from the perpendicular is less than 25 °, the molten steel is improperly diverted from the central portion of the strip thickness, and inclusions, causing defects, remain, which results in a decrease in impact strength or strength after resistance resistance welding, and when the angle is from the perpendicular greater than 50 °, the slope, causing problems, still remains as a defect on the pipe-product after resistance welding. Furthermore, when the distance (β) is less than 20% of the strip thickness, the molten steel is inappropriately diverted from the central portion of the strip thickness, so that inclusions tend to remain, and when the length is more than 40% of the strip thickness, the slope causing problems causes still remains in the form of a flaw on the pipe-product after resistance welding.

From these results it was found that in the retrograde calculation of the slope to be pre-formed on the edges of the strip on the side of one surface by cutting or grinding before roll rolling (before molding in caliber with an edge guiding element), it is preferable that the length of the perpendicular from the beginning of the slope to its place end ranged from 50% to 90% of the strip thickness.

Preferably, for forming a slope at the edges of the strip on the side of the other surface, a caliber molding with an edge guide element in the middle of the roll forming is used. The reason for this is as follows. Since when forming in caliber with an edge guiding element, the caliber roll with an edge guiding element is filled with a strip, the edges of the strip are subjected to high pressure during molding in caliber with an edge guiding element. Therefore, when forming in caliber with an edge guiding element, it is preferable that the shape of the edge guiding element is designed to include at least two steps of the slope, and the shape of the edge guiding element is imprinted on the strip using high pressure on the edges of the strip.

The slope formed during molding in caliber with an edge guiding element, as mentioned above, is performed so that the angle from the perpendicular (slope angle to the direction of the strip thickness) is 25 ° to 50 °, and the perpendicular length (slope length in the direction of the strip thickness ) from the beginning of the slope to the place of its end ranged from 20% to 40% of the strip thickness, which corresponds to the optimal shape of the slope after molding in caliber with an edge guide element and immediately before resistance welding.

FIG. 1 shows a production line for resistance welded pipes according to an embodiment of the invention, which is configured based on the above considerations. The production line for pipes obtained by resistance resistance welding has a basic configuration in which the strip (20) is wound from the unwinder (1); then this strip is straightened, turning into a flat, by means of a straightening machine (2); then the strip (20) is gradually folded by a machine (5) for roll forming; then the two side edges of the rolled strip (20) are subjected to resistance resistance welding using an resistance resistance welding machine including an induction heating section (6) and a compression roller (resistance resistance welding section) (7) so as to be formed into a pipe ( thirty); then, the section of the weld bead of the pipe (30) is cut off with a tool (8) for cutting the bead; then the pipe (30) after cutting is adjusted in the outer diameter by a calibration mill (9); and then the pipe is cut into segments of a given length by a pipe cutting machine (10). The roll forming machine (5) at the last stage has a stand (4) for forming in caliber with an edge guiding element having a predetermined number of stands (there are two stands).

In this embodiment, in addition to the basic configuration, the production line has a pair of cutting tools, each of which has cutting blades located in the form of a roller (or grinding stones in the form of a roller), (3) in the transverse direction of the strip (20) between the straightening machine (2) and a roll forming machine (5). Thus, as shown in FIG. 10, two side edges on the side of the upper surface of the strip (20) (the side of the inner surface of the pipe (30)) are formed with a slope in which the angle to the direction of the thickness of the strip (slope angle) γ is from 25 ° up to 40 °, and the slope length in the direction of the strip thickness (slope height) γ is from 50% to 90% of the strip thickness.

In addition, as shown in FIG. 4A, showing a schematic view along arrowed line BB shown in FIG. 1, and FIG. 4B showing a local detailed schematic view of FIG. 4A, the end stand (4a) of the stand ( 4) for molding in caliber with an edge guiding element, it has the shape of an edge guiding element that includes a predetermined two-stage slope (the slope angle of the second stage is α, and the vertical length of the slope of the second stage is β). This shape of the edge guide element is imprinted on the lateral edges of the strip (20), thereby two lateral edges on the side of the lower surface of the strip (20) (on the side of the outer surface of the pipe (30)) are formed with a slope in which the angle to the direction of the thickness of the strip (slope angle ) is from 25 ° to 40 °, and the slope length in the direction of the strip thickness (slope height) is from 20% to 40% of the strip thickness.

Thus, when a slope is formed at the edges on the side of the upper surface and the side of the lower surface of the strips having different thickness classes, the edges on the side of the upper surface of the strip (20) (the side of the inner surface of the pipe (30)) are cut or scraped at predetermined locations in the direction strip thickness using cutting tools, each of which has cutting blades arranged in the form of a roller (or grinding stones in the form of a roller), (3) with their vertical position precisely adjusted. On the other hand, at the edges on the side of the lower surface of the strip (20) (the side of the outer surface of the pipe (30)), a bias is printed at predetermined locations in the direction of the thickness of the strip by molding in caliber with an edge guide element. Thus, the edges of both of the upper and lower surfaces of the strip can be formed with a given slope, depending on the thickness of the strip, without compromising production efficiency.

In this case, the strip width is sometimes significantly reduced due to the destruction of the edge during molding in caliber with an edge guide element. Therefore, in order to adjust the width of the strip, the strip is preliminarily increased in width by an amount corresponding to such a decrease in the strip width, and this strip is used to manufacture the pipe obtained by resistance resistance welding. Thus, it is easy to manufacture a pipe obtained by resistance resistance welding having the required outer diameter.

Thus, in this embodiment of the invention, since the edges of the strip can be properly formed with a slope before resistance welding, it is possible to efficiently fabricate a resistance-welded pipe having very excellent toughness and welding strength.

In this embodiment, the edges on the side of the upper surface of the strip (20) (the side of the inner surface of the pipe (30)) are formed with a slope before the roll forming, and the edges on the side of the lower surface of the strip (20) (the side of the outer surface of the pipe (30)) with a slope by molding in caliber with an edge guide element. However, in some cases, the edges on the side of the lower surface of the strip (20) (the side of the outer surface of the pipe (30)) can be formed with a slope before roll forming, and the edges on the side of the upper surface of the strip (20) (side of the inner surface of the pipe (30 )) can be formed with a slope by molding in caliber with an edge guide element.

The above description was made on the assumption of a production line in which the side of the upper surface of the strip (20) corresponds to the side of the inner surface of the pipe (30). However, it is obvious that the invention can be similarly applied to the production line for pipes obtained by resistance resistance welding, in which the side of the upper surface of the strip (20) corresponds to the side of the outer surface of the pipe (30).

Example 1

The following is a description of the examples.

Figure 1 shows a pipe making machine used in the examples. A pipe manufacturing method using this pipe making machine is as follows. The strip (20) is wound off the unwinder (1); then the strip straightens, turning into flat, by means of a straightening machine (2); then the strip is gradually folded in the transverse direction by a roll forming machine (5); then, the two lateral edges of the transversally rolled strip are subjected to resistance resistance welding using an resistance resistance welding machine (including an induction heating section (6) and a compression roller (resistance resistance welding section) (7) so as to be formed into a pipe ( 30); then, the section of the welded bead of the pipe (30) is cut off with a tool (8) for cutting the bead; then the pipe (30) after cutting is adjusted in the outer diameter by a calibration mill (9); and then the pipe is cut into a section and a predetermined length by a pipe cutting machine (10). The roll forming machine (5) has a crimping first stand (13) from the side of the first stage and a stand (4) for rolling in caliber with an edge guide element in the last stage.

In addition to the aforementioned basic configuration, on the upstream side of the roll forming machine (5) and on the upstream side of the straightening machine (2), as a cutting or scraping means (31), a tool including roller-shaped cutting blades shown in Figure 2, such that the roller-shaped cutting blades cut portions on the upper surface side of the two lateral edges of the strip (20) so that these portions can be formed with a slope having a predetermined angle of inclination (γ) and a predetermined inclination distance (δ) , and caliber rolling roll 4, with the edge guide element of the first stand (4A) for rolling in gauge with the edge guide element, is designed in such a way that it has an edge guide element including a two-stage inclination, as shown in FIG. 4A, such that the portions are on the side of the lower surface of the two side the edges of the strip (20), which is folded in the transverse direction, are rolled so that these sections can be formed with a slope having a given slope angle (α) and a given slope distance (β).

(Example 1 of the invention)

In example 1 of the invention, using the pipe manufacturing machine shown in FIG. 1, steel pipes (pipes) having 600 mm in outer diameter were made of a steel strip (strip A) having 1920 mm in width and 19.1 mm in thickness. Then, steel pipes (pipes) having 600 mm in outer diameter were made of a steel strip (strip B) having 1920 mm in width and 11.3 mm in thickness. During the manufacture of the pipes, a slope was formed on the lateral edges on the side of the upper surface of the strip by means of cutting or scraping means (31), and formed on the lateral edges on the side of the lower surface of the strip by means of a caliber rolling roll with an edge guide element of the first stand (4A) for rolling in caliber with edge guiding element, respectively. The slope is made in such a way that it has a slope angle (α) of 30 ° and a slope distance (β) of 5 mm (26% of the strip thickness) on both sides of the upper surface side and the lower surface side in strip A, and the slope is made in such a way that it has a slope angle (α) of 30 ° and a slope distance (β) of 2.5 mm (26% of the strip thickness) on both sides of the upper surface side and the lower surface side on strip B. When changing strip from strip A (19.1 mm in thickness) to strip B (11.3 mm in thickness), the position is cut or about skoblilnogo means (31) is moved down at 7 to 8 mm in order to accurately adjust the cutting position.

Test specimens were cut from the weld of the manufactured steel pipes, and these samples were subjected to a Charpy test to evaluate pipe performance. Charpy test specimens were taken one at a time for each of ten different points in the pipe length direction such that the longitudinal direction of the test specimen was parallel to the direction along the pipe circumference and the longitudinal center of the notch corresponded to the central position in the thickness of the weld. Test specimens were made as impact test specimens having a 2 mm V-notch conforming to JIS5 (Japanese Industrial Standard 5) and subjected to a shock test at a temperature of -46 ° C, and the absorbed energy and ratios were measured brittle fracture surface. The absorbed energy of 125 Joules or more, and the brittle fracture surface ratio of 35% or less, were respectively determined as an acceptable range of performance.

(Example 2 of the invention)

In example 2 of the invention, the slope angle (α) from example 1 is changed to an angle of 40 °, and except for this, the pipes are manufactured and tested according to Charpy to evaluate their performance in the same manner as in example 1.

(Comparative example 1)

In comparative example 1, the pipe making machine shown in FIG. 1 was used. In addition, in addition to the basic configuration of this machine, instead of the cutting or scraper means (32) located on the input side of the roll forming machine (5), that is, on the output side of the straightening machine (2), a rolling roll (31) was located having a shape with a recess, as shown in FIG. 9, such that the two lateral edges of the strip (20) are rolled so that two edges on both sides of the upper surface side and the lower surface side can be simultaneously formed with a slope having given angle (α) grade and the set pitch (β) of grade. In a gauge roll with an edge cage (4) for rolling in gauge with an edge cage, the edge guide does not have a two-stage slope in any roll, as in a typical case.

Using the pipe making machine shown in FIG. 1, steel pipes (pipes) having 600 mm in outer diameter were made of a steel strip (strip A) having 1920 mm in width and 19.1 mm in thickness. Then, steel pipes (pipes) having 600 mm in outer diameter were made of a steel strip (strip B) having 1920 mm in width and 11.3 mm in thickness. During the manufacture of the pipes, sections on both sides of the upper surface side and the lower surface side of the side edges of the strip were rolled by a roll (12) having a shape with a recess so that these sections were formed with a slope. The slope shape was designed to have the same shape as in Example 1 of the invention. When changing the strip from strip A (19.1 mm in thickness) to strip B (11.3 mm in thickness), the operation of the pipe making machine temporarily stopped, and the roll (12), which has a shape with a recess, was replaced from the roll to form a slope for a strip having 19.1 mm in thickness, on a roll for a strip having 11.3 mm in thickness.

The manufactured steel pipes were subjected to a Charpy test to evaluate pipe performance, as in Example 1 of the invention.

(Example 1 prior art)

The pipe making machine is configured by removing the grooved roll (32) to form a slope and cutting or scraping means (31) from the pipe making machine shown in FIG. 1 in comparative example 1. During the manufacture of the pipe, the strip ( 20) did not form with a slope at two lateral edges and retained a rectangular section profile. Other than this, steel pipes were fabricated and tested according to Charpy to evaluate their performance in the same manner as in comparative example 1.

Charpy impact strength values and brittle fracture surface relations of a steel pipe weld made in accordance with these examples were measured, and the measurement results are shown in Table 1. Also, Table 1 shows the production efficiency in each of the examples. Production efficiency is shown in relative terms of the reciprocal of production time to the value (normalized to 1) from Example 1 of the prior art.

Table 1 Means for forming a slope before roll forming Means for forming a slope during roll forming Inclination angle immediately before resistance resistance welding Charpy Impact Value Brittle Fracture Surface Ratio Production efficiency Example 1 of the invention Cutting roller Caliber roll with edge guide Slope angle (α) = 30 ° Slope distance (β) in the strip A = 5.0 mm Slope distance (β) in the strip B = 2.5 mm 180 joule fifteen% one Example 2 of the invention Cutting roller Caliber roll with edge guide Slope angle (α) = 40 ° Slope distance (β) in the strip A = 5.0 mm Slope distance (β) in the strip B = 2.5 mm 190 joules 13% one Comparative Example 1 Groove-shaped rolling roll Not provided Slope angle (α) = 30 ° Slope distance (β) in the strip A = 5.0 mm Slope distance (β) in the strip B = 2.5 mm 170 joules eighteen% 0.7 Prior Art Example 1 Not provided Not provided No bias 20 joules 58% one

As can be seen from Table 1, in a steel pipe product according to Example 1 of the prior art, the weld has low impact strength and a high brittle fracture surface ratio, that is, the toughness is lowered and the reliability of the products is low. In the steel pipe product according to comparative example 1, the weld has a high impact strength and a low brittle fracture surface ratio compared to the prior art example 1, that is, the toughness is excellent and the reliability of the products is high, but the production efficiency is lowered. In contrast to these examples, in a steel pipe according to each of examples 1 and 2 of the invention, it is clear that the weld has an impact strength equal to or higher than the impact strength in comparative example 1, in addition, the production efficiency is high, being approximately at that same level as in example 1 of the prior art.

Although the slope formed in the example is designed so that the side of the upper surface of the strip and the side of its lower surface are symmetrical with respect to the central plane of the strip thickness, this is not a limitation, and the slope can be formed so that the edges are on the side of the upper surface of the strip and the edge on the side of its lower surface are asymmetric with respect to the central plane of the strip thickness. When a pipe making machine is used, which is vertically opposite to the machine shown in FIG. 1 (i.e., the side of the upper surface of the strip corresponds to the side of the outer surface of the pipe), it is preferable that in areas on the side of the lower surface of the side edges of the strip, a slope is formed by cutting or scraping before molding , and in areas on the side of the upper surface of the lateral edges of the strip, a slope was formed by rolling in caliber with an edge guiding element.

Example 2

Here, pipes obtained by resistance resistance welding, having 600 mm in diameter, were manufactured using a strip (steel strip) having 1920 mm in width and 19.1 mm in thickness. Then, pipes obtained by resistance resistance welding, having 600 mm in diameter, were made of a strip (steel strip) having 1920 mm in width and 11.3 mm in thickness.

Then, test pieces were cut from the weld of the manufactured pipes produced by resistance resistance welding, and these samples were subjected to a Charpy test to evaluate pipe performance. Charpy test specimens were taken one at a time for each of ten different points in the pipe length direction such that the longitudinal direction of the test specimen was parallel to the direction along the pipe circumference and the longitudinal center of the notch corresponded to the central position in the thickness of the weld. Test specimens were made as impact test specimens having a 2 mm V-notch conforming to JIS5 (Japanese Industrial Standard 5) and subjected to a shock test at a temperature of -46 ° C, and the absorbed energy and ratios were measured brittle fracture surface. The absorbed energy of 125 Joules or more and the brittle fracture surface ratio of 35% or less were respectively determined as an acceptable performance range.

(Example 21 of the invention)

By way of example 21 of the invention, the above-mentioned pipes obtained by resistance resistance welding were manufactured according to the first embodiment of the invention. In their manufacture, the cutting roller (31a) shown in Fig. 3A was used as a cutting or scraping tool (31) to form a slope on both side edges on the side of the upper surface of the strip. The inclination angle (α) for the slope was 30 ° on both sides of the upper surface side and the lower surface side. When changing the strip thickness from 19.1 mm to 11.3 mm, the vertical position of the cutting roller (31a), to be precisely adjusted, was moved down by 7.8 mm.

(Example 22 of the invention)

By way of example 22 of the invention, the aforementioned resistance weld pipes were manufactured according to the first embodiment of the invention. In their manufacture, a scraper roller (31b) shown in Fig. 3B was used as a cutting or scraping tool (31) to form a slope on both lateral edges on the side of the upper surface of the strip. The inclination angle (α) for the slope was 40 ° on both sides of the upper surface side and the lower surface side. When changing the strip thickness from 19.1 mm to 11.3 mm, the vertical position of the scraper roller (31b), to be precisely adjusted, was moved down by 7.8 mm.

(Example 23 of the invention)

By way of example 23 of the invention, the aforementioned resistance weld pipes were manufactured according to a second embodiment of the invention. In their manufacture, a cutting roller (31 s) with a slope, shown in Fig. 6A, was used as a cutting or scraping tool (31) to form a slope on both lateral edges on the side of the upper surface of the strip. The inclination angle (α) for the slope was 30 ° on both sides of the upper surface side and the lower surface side. When changing the strip thickness from 19.1 mm to 11.3 mm, the vertical position of the cutting roller (31c), to be precisely adjusted, was moved down by 7.8 mm.

(Example 24 of the invention)

By way of example 24 of the invention, the aforementioned resistance weld pipes were manufactured according to a second embodiment of the invention. In their manufacture, as a cutting or scraper means (31), a scraper roller (31d) with a slope, shown in Fig. 6B, was used to form a slope on both lateral edges on the side of the upper surface of the strip. The inclination angle (α) for the slope was made 40 ° on both sides of the upper surface side and the lower surface side. When changing the strip thickness from 19.1 mm to 11.3 mm, the vertical position of the scraper roller (31d) with a slope, to be precisely adjusted, was moved down by 7.8 mm.

(Comparative example 2)

By way of comparative example 2, the aforementioned resistance welded pipes were manufactured using the production line shown in FIG. 1, with a roll having a recessed shape being provided between the straightening machine (2) and the roll forming machine (5). and this rolling roll having a recessed shape was used to form a slope on both side edges on the upper surface side and on the lower surface side of the strip. The inclination angle (α) for the slope was 30 ° on both sides of the upper surface side and the lower surface side. In the manufacture of the pipes, the cutting or scraper means (31) was removed, and the shape of the edge guide element of the end stand (4a) for forming in caliber with the edge guide element was made in such a way as to include a conventional single-stage slope. When changing the strip thickness from 19.1 mm to 11.3 mm, the production line was temporarily stopped, and the rolling roll having a recessed shape was replaced from a roll for a strip having a thickness of 19.1 mm with a roll for a strip having 11.3 mm in thickness.

(Example 2 prior art)

As an example 2 of the prior art, the aforementioned resistance welded pipes were manufactured using the production line shown in FIG. 1, while both side edges of the strip were smoothly ground between the straightening machine (2) and the roll forming machine (5) . In the manufacture of the pipes, the cutting or scraper means (31) was removed, and the shape of the edge guide element of the end stand (4a) for forming in caliber with the edge guide element was made in such a way as to include a conventional single-stage slope. When the strip thickness changed from 19.1 mm to 11.3 mm, production continued without stopping the production line.

Charpy impact strengths and brittle fracture surface relations of pipe weld obtained by resistance welding made in accordance with these examples were measured and the measurement results are shown in Table 2. This table also shows the ratio of production efficiency in each example to production efficiency in comparative example 2, which is taken equal to 1.

table 2 Means for forming a slope on the upper surface side Means for forming a slope on the bottom side Inclination angle immediately before resistance resistance welding Charpy Impact Value Brittle Fracture Surface Ratio Production efficiency Example 21 of the invention Cutting roller Caliber forming roll with edge guide 30 degrees 180 joule fifteen% 1,5 Example 22 of the invention Scoop roller Caliber forming roll with edge guide 40 degrees 180 joule fifteen% 1.5 Example 23 of the invention Slant cutter roller Caliber forming roll with edge guide 30 degrees 180 joule fifteen% 1,5 Example 24 of the invention Slope roller Caliber forming roll with edge guide 40 degrees 180 joule fifteen% 1,5 Reference Example 2 Groove-shaped rolling roll Not provided 30 degrees 170 joules eighteen% 1,0 Example 2 Prior Art Not provided Not provided No bias 20 joules 58% 1,5

As can be seen from Table 2, in pipes obtained by resistance resistance welding, according to examples 21 to 24 of the invention, the weld has high impact strength and low brittle fracture surface ratio, that is, the toughness is excellent and the reliability of the products is high. In contrast, in pipes obtained by resistance resistance welding according to Example 2 of the prior art, the weld has low impact strength and a high brittle fracture surface ratio, that is, the toughness is lowered and the reliability of the products is low. In addition, examples 21 to 24 of the invention are significantly improved in terms of production efficiency compared to comparative example 2.

Therefore, it was confirmed that, in accordance with the invention, it is possible to efficiently produce a pipe obtained by resistance resistance welding having excellent weld characteristics.

Example 3

The following is a description of the example. In this example, the equipment for manufacturing pipes shown in FIG. 1 or equipment partially modified compared to this equipment was used. The pipe manufacturing equipment is composed of an unwinder (1), a straightening machine (2), a machine (5) for roll forming, means (6) of induction heating (induction heating coils), a compression roll (7), means (8) for cutting the burr (a tool for cutting a burr), a calibration mill (9) and a pipe cutting machine (10), which are located in this order. A roll forming machine (5) includes a plurality of rolling stands located in stages from a rough forming step including a crimping first stand (13) to a finishing step including a forming roll (4) of caliber with an edge guiding element.

In this equipment for the manufacture of pipes, a strip (sheet) (20) is unwound by an unwinder (1); then the strip straightens, turning into flat, by means of a straightening machine (2); then the strip is gradually folded in the transverse direction by a plurality of rolling stands arranged in stages from the rough forming step to the finishing step of the roll forming machine (5); and then the strip is subjected to finishing molding with a molding roll (4) of caliber with an edge guide element. Since the folding of the strip (20) in the transverse direction essentially starts from the crimp first stand (13), the term “section before roll forming” refers to the section from the output side of the straightening machine (2) to the input side of the crimp first stand (13) .

After finishing molding, the strip (20) is formed in the form of an open pipe, and the two edges in the transverse direction (the direction along the circumference of the open pipe) of the strip are heated by means of induction heating (6) and then brought into contact by compression (they are subjected to resistance contact welding) by a compression roller (7 ) to form a pipe. Then the weld bead of the pipe is removed by cutting using means (8) for cutting the bead, and then the pipe is rolled with a constant diameter on a calibration mill (9), and then the pipe is cut into sections of a given length by a pipe cutting machine (10).

In the pipe manufacturing equipment shown in FIG. 1 as an example of an embodiment of the invention, abrasive grinding means (31) are arranged on the upstream side of the roll forming to round out (see FIG. 7) to each corner on the side of the upper surface of the strip. In addition to this, the corners of the edge guide element, the forming roll (4) of the caliber with the edge guide element are formed with a round shape instead of a slope, so that each corner on the side of the lower surface of the strip (side of the outer diameter of the pipe) is formed into a round shape in gauge with a edge guide element.

To this end, steel strips having 1920 mm wide and 19.1 mm thick and steel strips having 1920 mm wide and 15.3 mm thick were used as strips, and in both cases steel pipes were made ( pipes obtained by resistance resistance welding) with an outer diameter of pipe products of 600 mm.

Test specimens were cut from the weld of the pipes obtained by resistance resistance welding, and these samples were subjected to a Charpy test to evaluate the performance of the pipes. Charpy test specimens were taken one at a time for each of ten different points in the pipe length direction such that the longitudinal direction of the test specimen was parallel to the direction along the pipe circumference and the longitudinal center of the notch corresponded to the central position in the thickness of the weld. Test specimens were made as impact test specimens having a 2 mm V-notch conforming to JIS5 (Japanese Industrial Standard 5) and subjected to a shock test at a temperature of -46 ° C, and the absorbed energy and ratios were measured brittle fracture surface.

The absorbed energy of 125 Joules or more and the brittle fracture surface ratio of 35% or less were respectively determined as an acceptable performance range. The following four types of conditions were used as production conditions.

As an example 31 of the invention, pipes were fabricated using the pipe manufacturing equipment shown in FIG. 1. In the manufacture of pipes, each corner on the side of the upper surface of the strip was given a round shape by abrasive grinding before roll forming, then each corner on the side of the lower surface of the strip (side of the outer diameter of the pipe) was given a round shape by molding in caliber with an edge guide element. The radius R of the given round shape was made of 7 mm (37% of the strip thickness of 19.1 mm and 46% of the strip thickness of 15.3 mm).

When changing the strip thickness from 19.1 mm to 15.3 mm, the position of the grinding stone, to be precisely adjusted, was moved down 3.8 mm.

By way of example 32 of the invention, the pipes were manufactured using pipe manufacturing equipment in which, instead of the abrasive grinding means (3) shown in FIG. 1, a cutting roller (not shown in the drawing) was arranged. In the manufacture of pipes, each corner on the side of the upper surface of the strip was given a round shape by cutting with a roller using a cutting roller before roll forming, then each corner on the side of the lower surface of the strip (side of the outer diameter of the pipe) was given a round shape by molding in caliber with an edge guide element . The radius R of the given round shape was made of 4 mm (21% of the strip thickness of 19.1 mm and 26% of the strip thickness of 15.3 mm).

When changing the strip thickness from 19.1 mm to 15.3 mm, the position of the cutting roller, to be precisely adjusted, was moved down 3.8 mm.

As a comparative example, 3 pipes were manufactured using pipe manufacturing equipment in which instead of the abrasive grinding means (3) shown in FIG. 1, a roll having a shape with a recess was arranged to form side edges (not shown in the drawing) , and the corners of the edge guide element of the forming roll (4) of the caliber with the edge guide element were made so as to have an approximately rectangular shape. In the manufacture of pipes, each corner on both sides of the upper surface side and the lower surface side of the strip was circularly shaped by rolling in a grooved shaped roll using a grooved shaped roll to form side edges in front of the roll forming. The radius R of the round shape was 3 mm (16% of the strip thickness of 19.1 mm and 19% of the strip thickness of 15.3 mm).

When changing the strip thickness from 19.1 mm to 15.3 mm, the position of the cutting roller, to be precisely adjusted, was moved down 3.8 mm. When the strip thickness was changed from 19.1 mm to 15.3 mm, the production line was temporarily stopped, and the recessed roll was replaced from the roll for a strip having 19.1 mm in thickness to a strip roll, having 15.3 mm in thickness.

As an example 3 of the prior art, pipes are made using pipe making equipment in which a roll having a recess is removed from the pipe making equipment used in comparative example 3 to form side edges. Each of the angles on both sides of the upper surface side and the lower surface side of the strip was still approximately rectangular (approximately rectangular).

Charpy impact strengths and brittle fracture surface relations of a welded seam of steel pipes manufactured in accordance with these conditions were measured, and the measurement results are shown in Table 3. This table also shows the manufacturing time in each example as a relative indicator of each manufacturing time to manufacturing time in comparative example 3, which is assumed to be 1.

Table 3 Means for forming corners on the side of the upper surface of the strip Means for forming corners on the side of the lower surface of the strip Side Edge Shape Charpy Impact Value Brittle Fracture Surface Ratio Preparation time Example 31 of the invention Abrasive grinding Caliber forming roll with edge guide Rounding, radius 7 mm 250 joules 8% 0.7 Example 32 of the invention Cutting roller Caliber forming roll with edge guide Rounding, radius 4 mm 280 joules 7% 0.7 Reference Example 3 Forming roll with recess (same between upper and lower sides) Forming roll with recess (same between upper and lower sides) Rounding, radius 3 mm 180 joule fifteen% one Example 3 Prior Art Not provided Not provided Approximately rectangular 25 joules 55% 0.7

As can be seen from Table 3, in examples 31 and 32 of the invention, the weld has high impact strength and low brittle fracture surface ratio, that is, the toughness is excellent and the reliability of the products is high. In contrast, in Example 3 of the prior art, the weld has low impact strength and a high brittle fracture surface ratio, i.e., toughness is lowered and product reliability is low.

In addition, in examples 31 and 32 of the invention, the manufacturing time is significantly reduced compared with comparative example 3, showing that in accordance with the invention, it is possible to effectively manufacture a pipe product obtained by resistance resistance welding, having excellent weld characteristics.

Example 4

Here, pipes obtained by resistance resistance welding, having 600 mm in diameter, were manufactured using a strip (steel strip) having 1920 mm in width and 19.1 mm in thickness. Then, pipes obtained by resistance resistance welding, having 600 mm in diameter, were made using a strip (steel strip) having 1920 mm in width and 11.3 mm in thickness.

Then, test pieces were cut from the weld of the manufactured pipes produced by resistance resistance welding, and these samples were subjected to a Charpy test to evaluate pipe performance. Charpy test specimens were taken one at a time for each of ten different points in the pipe length direction such that the longitudinal direction of the test specimen was parallel to the direction along the pipe circumference and the longitudinal center of the notch corresponded to the central position in the thickness of the weld. Test specimens were made as impact test specimens having a 2 mm V-notch conforming to JIS5 (Japanese Industrial Standard 5) and subjected to a shock test at a temperature of -46 ° C, and the absorbed energy and ratios were measured brittle fracture surface. The absorbed energy of 125 Joules or more and the brittle fracture surface ratio of 35% or less were respectively determined as an acceptable performance range.

(Example 41 of the invention)

By way of example 41 of the invention, the above-mentioned pipes obtained by resistance resistance welding were manufactured according to an embodiment of the invention. In their manufacture, the edges on the side of the upper surface of the strip (the edges on the side of the inner surface of the pipe) were formed with approximately a straight slope with a slope angle (α) of 30 ° using a roll (32) having the shape with a recess shown in Figures 8A and 8B. Then, the edges on the side of the lower surface of the strip (the edges on the side of the outer surface of the pipe) were formed with approximately a straight slope with a slope angle (α) of 30 ° by molding in caliber with an edge guiding element. When changing the strip thickness from 19.1 mm to 11.3 mm, the position of the roll (32), having a shape with a recess, in order to be precisely adjusted, was moved down by 7.8 mm.

(Comparative example 4)

As comparative example 4, in the manufacture of the aforementioned pipes by resistance welding, after processing on a straightening machine or before roll forming, both of the edges on the side of the upper surface of the strip and the edges on the side of its lower surface were simultaneously formed with an approximately straight slope with an angle (α ) a slope of 30 ° using a conventional roll (32) having the shape with a recess shown in FIG. 4. When changing the strip thickness from 19.1 mm to 11.3 mm, the production line was temporarily stopped and the recessed roll was replaced from a roll for a strip having 19.1 mm in thickness to a roll for a strip having 11 , 3 mm in thickness.

(Example 4 prior art)

As an example 4 of the prior art, in the manufacture of the aforementioned tubes by resistance welding, after processing on a straightening machine or before roll forming, each edge of the strip was vertically smoothly ground, then the tubes obtained by resistance welding were manufactured by conventional roll molding. When changing the strip thickness from 19.1 mm to 11.3 mm, the production line was temporarily stopped, but the operation was resumed to continue production.

Charpy impact strengths and brittle fracture surface relations of pipe weld obtained by resistance resistance welding made in accordance with these examples were measured, and the measurement results are shown in Table 4. Table 4 also shows the ratio of production efficiency in each example to production efficiency in comparative example 4, which is taken equal to 1.

Table 4 Means for forming a slope before roll forming Means for forming a slope during roll forming Inclination angle immediately before resistance resistance welding Charpy Impact Value Brittle Fracture Surface Ratio Production efficiency Example 41 of the invention Recessed Roll Caliber forming roll with edge guide 30 ° 180 joule fifteen% 1.3 Reference Example 4 Recessed Roll Not provided 30 ° 170 joules eighteen% 1,0 Example 4 prior art Not provided Not provided No bias 20 joules 58% 1.3

As can be seen from Table 4, in pipes obtained by resistance resistance welding, according to Example 41 of the invention, the weld has high impact strength and low brittle fracture surface ratio, that is, the toughness is excellent and the reliability of the products is high. In contrast, in pipes obtained by resistance resistance welding according to Example 4 of the prior art, the weld has low impact strength and a high brittle fracture surface ratio, that is, the toughness is lowered and the reliability of the products is low. In addition, example 41 of the invention is significantly improved in terms of production efficiency compared to comparative example 4.

Therefore, it was confirmed that, in accordance with the invention, it is possible to efficiently produce a pipe obtained by resistance resistance welding having excellent weld characteristics.

Example 5

Here, pipes obtained by resistance resistance welding, having 600 mm in diameter, were manufactured using a strip (steel strip) having 1920 mm in width and 19.1 mm in thickness.

Then, test pieces were cut from the weld of the manufactured pipes produced by resistance resistance welding, and these samples were subjected to a Charpy test to evaluate pipe performance. Charpy test specimens were taken one at a time for each of ten different points in the pipe length direction such that the longitudinal direction of the test specimen was parallel to the direction along the pipe circumference and the longitudinal center of the notch corresponded to the central position in the thickness of the weld. Test specimens were made as impact test specimens having a 2 mm V-notch conforming to JIS5 (Japanese Industrial Standard 5) and subjected to a shock test at a temperature of -46 °, and the absorbed energy and surface ratios were measured brittle destruction. The absorbed energy of 125 Joules or more and the brittle fracture surface ratio of 35% or less were respectively determined as an acceptable performance range.

(Example 51 of the invention)

By way of example 51 of the invention, the above-mentioned pipes obtained by resistance resistance welding were manufactured according to an embodiment of the invention. In their manufacture, the edges on the side of the upper surface of the strip (the edges on the side of the inner surface of the pipe) were formed with approximately a straight slope with a slope angle (γ) of 30 ° using a roll (32) having the shape with a recess shown in FIG. 9. Then, the edges on the side of the lower surface of the strip (the edges on the side of the outer surface of the pipe) were formed with approximately a straight slope with a slope angle (α) of 30 ° by rolling in caliber with an edge guiding element.

(Example of invention 52)

By way of example 52 of the invention, the aforementioned resistance weld pipes were manufactured according to an embodiment of the invention. In their manufacture, the edges on the side of the upper surface of the strip (the edges on the side of the inner surface of the pipe) were formed with approximately a straight slope with a slope angle (α) of 45 ° using a roll (32) having the shape with a recess shown in FIG. 9. Then, the edges on the side of the lower surface of the strip (the edges on the side of the outer surface of the pipe) were formed with approximately a straight slope with a slope angle (α) of 40 ° by rolling in caliber with an edge guiding element.

(Comparative example 5)

As comparative example 5, in the manufacture of the aforementioned pipes by resistance welding, after processing on a straightening machine or before roll forming, both of the edges on the side of the upper surface of the strip and the edges on the side of its lower surface were simultaneously formed with an approximately straight slope with an angle (α ) of a slope of 20 ° using a cutting tool, then the pipes obtained by resistance resistance welding were fabricated by conventional roll forming.

(Example 5 prior art)

By way of example 5 of the prior art, after processing on a straightening machine or before roll forming, each edge of the strip was vertically smoothly ground, then the pipes obtained by resistance resistance welding were fabricated by conventional roll forming.

Charpy impact strength values and brittle fracture surface relations of pipe weld obtained by resistance resistance welding made in accordance with these examples were measured, and the measurement results are shown in Table 5.

Table 5 Means for forming a slope before roll forming Means for forming a slope during roll forming Inclination angle immediately before resistance resistance welding Charpy Impact Value Brittle Fracture Surface Ratio Example 51 of the invention Recessed Roll Caliber roll with edge guide On the side of the inner surface -30 °
On the side of the outer surface -30 ° 250 joules four% Example 52 of the invention Recessed Roll Caliber roll with edge guide On the side of the inner surface -30 °
On the side of the outer surface -30 ° 230 joules 13% Reference Example 5 Cutting tool Not provided On the side of the inner surface -20 °
On the side of the outer surface -20 ° 100 joules 40% Example 5 Prior Art Not provided Not provided No bias 20 joules S8%

As can be seen from Table 5, in pipes obtained by resistance resistance welding, according to examples 51 and 52 of the invention, the weld has high impact strength and low brittle fracture surface ratio, that is, the toughness is excellent and the reliability of the products is high. On the contrary, in pipes obtained by resistance resistance welding, according to comparative example 5 and example 5 of the prior art, the weld has low impact strength and a high brittle fracture surface ratio, that is, the toughness is lowered and the reliability of the products is low.

Thus, it was confirmed that, in accordance with the invention, it is possible to efficiently produce a pipe obtained by resistance resistance welding having excellent weld characteristics.

Example 6

Here, resistance weld pipes having 600 mm in diameter were manufactured using a strip (steel strip) having a width of 1920 mm and 19.1 mm in thickness, in accordance with the following Example 61 of the invention, Example 62 of the invention, comparative example 6 and example 6 of the prior art, respectively.

Then, test pieces were cut from the weld of the manufactured pipes produced by resistance resistance welding, and these samples were subjected to a Charpy test to evaluate pipe performance. Charpy test specimens were taken one at a time for each of ten different points in the pipe length direction such that the longitudinal direction of the test specimen was parallel to the direction along the pipe circumference and the longitudinal center of the notch corresponded to the central position in the thickness of the weld. Test specimens were made as impact test specimens having a 2 mm V-notch conforming to JIS5 (Japanese Industrial Standard 5) and subjected to a shock test at a temperature of -46 °, and the absorbed energy and surface ratios were measured brittle destruction. The absorbed energy of 125 Joules or more and the brittle fracture surface ratio of 35% or less were respectively determined as an acceptable performance range.

(Example 61 of the invention)

By way of example 61 of the invention, the above-mentioned pipes obtained by resistance resistance welding were manufactured according to an embodiment of the invention. In their manufacture, after processing on a straightening machine or before roll forming, the edges on the side of the upper surface of the strip (edges on the side of the inner surface of the pipe) were machined using a cutting tool (cutting roller) having cutting blades arranged in the form of a roller, thus which are formed with an approximately straight slope with a slope angle of 30 and a slope height of 70% of the strip thickness. Then, the edges on the side of the outer surface of the pipe (the edges on the side of the lower surface of the strip) were formed with approximately a straight slope with a slope angle of 30 ° and a slope height of 30% of the strip thickness by means of a second stand during molding in caliber with an edge guiding element, performed in two stands.

(Example 62 of the invention)

By way of example 62 of the invention, the above-mentioned pipes obtained by resistance resistance welding were manufactured according to an embodiment of the invention. In their manufacture, after processing on a straightening machine or before roll forming, the edges on the side of the upper surface of the strip (the edges on the side of the inner surface of the pipe) were machined using a grinding stone in such a way that they are formed with approximately a straight slope with a slope angle of 40 °, and a slope height of 85% of the strip thickness. Then, the edges on the side of the outer surface of the pipe (the edges on the side of the lower surface of the strip) were formed with approximately a straight slope with a slope angle of 40 ° and a slope height of 25% of the strip thickness by a third stand during molding in caliber with an edge guiding element, performed in three stands.

(Comparative example 6)

As comparative example 6, in the manufacture of the aforementioned resistance welded pipes after processing on a straightening machine or before roll forming, both of the edges on the side of the upper surface of the strip and the edges on the side of its lower surface were machined using a grinding stone in the form of a roller and thereby formed with an approximately straight slope with a slope angle of 20 ° and a slope height of 40% of the strip thickness. Then, molding was carried out using a caliber stand with an edge guiding element of three stands having an edge guiding element with a conventional one-step slope.

(Example 6 prior art)

As an example 6 of the prior art, in the manufacture of the aforementioned tubes by resistance welding, after processing on a straightening machine or before roll forming, each edge of the strip was vertically smoothly ground, then the tubes obtained by resistance welding were manufactured by conventional roll molding.

Charpy impact strengths and the brittle fracture surface relationship of pipe weld obtained by resistance welding made in accordance with these examples were measured, and the measurement results are shown in Table 6. In comparative example 6, the slope was reduced in height to 10% or less than the strip thickness after molding in caliber with an edge guiding element and immediately before resistance welding, i.e. the slope height was significantly reduced by forming in alibre with kromkonapravlyayuschim element.

Table 6 Slope formation before roll forming Slope formation during roll forming Charpy Impact Value Brittle Fracture Surface Ratio Gradient Slope angle Grade height Gradient Slope angle Grade height Example 61 of the invention Cutting roller (side of the upper surface of the strip) 30 ° 70% strip thickness Caliber rolling with edge guide (side of the bottom surface of the strip) 30 ° 30% strip thickness 180 joule fifteen% Example 62 of the invention Roller-shaped grinding stone (side of the upper surface of the strip) 40 ° 85% strip thickness Caliber rolling with edge guide (side of the bottom surface of the strip) 40 ° 25% strip thickness 180 joule fifteen% Comparative and example 6 Roller-shaped grinding stone (upper and lower surfaces of the strip) 20 ° 40% strip thickness Not provided No bias No bias 80 joules 45% Example 6 prior art Not provided No bias No bias Not provided No bias No bias 20 joules 58%

As can be seen from Table 6, in pipes obtained by resistance resistance welding, according to Examples 61 and 62 of the invention, the weld has high impact strength and low brittle fracture surface ratio, that is, the toughness is excellent and the reliability of the products is high. On the contrary, in pipes obtained by resistance resistance welding, according to comparative example 6 and example 6 of the prior art, the weld has low impact strength and a high brittle fracture surface ratio, that is, the toughness is lowered and the reliability of the products is low.

Claims (12)

1. A method of manufacturing pipes, including forming the strip, joining the edges of the strip and resistance resistance welding to produce a pipe, while forming a rounded edge or edge with a slope of 25 ° to 50 ° with a perpendicular length from the beginning of the slope to its end equal to 20% -40% of the strip thickness on at least one side of the strip and on the side of its upper or lower surface in a gauge installed directly in front of the resistance welding machine. 2. The method according to claim 1, characterized in that before forming the strip, the edges of the strip are formed with a slope or rounded by cutting or grinding or rolling. 3. The method according to claim 2, characterized in that the rolling before molding is carried out using a roll having a shape with a recess. 4. The method according to claim 2, characterized in that they use a tool having cutting blades in the form of a roller or a grinding stone in the form of a roller, each cutting blade or grinding surface of the stone includes a section approximately parallel to the edge of the strip, and a section inclined to the edge of the strip from the midpoint. 5. The method according to claim 4, characterized in that the edge of the strip is subjected to cutting or grinding with a tool having cutting blades in the form of a roller, or with a grinding stone in the form of a roller that is installed parallel to the edge of the strip, the edge of the strip is brought into contact with it, and subjected to cutting or grinding and then a tool with cutting blades in the form of a roller or a grinding stone in the form of a roller, which is arranged along an inclined strip to the edge, brought into contact and formed the edges of the strip with a slope. 6. The method according to claim 1, characterized in that the edges of the strip are formed with a slope by means of a roll having a shape with a recess. 7. The method according to claim 1, characterized in that before forming the strip perform cutting, or grinding, or rolling using a roll having a shape with a recess. 8. The method according to claim 1, characterized in that the edges on one side of the side of the upper surface and the side of the lower surface of the strip are formed with a slope by molding in caliber with an edge guide element. 9. The method according to claim 1, characterized in that the edges on one side of the side of the upper surface and the side of the lower surface of the strip are formed with a slope by cutting or grinding or with a roll having a shape with a recess, and the edges on the other side of the strip are formed with a slope by molding in caliber with an edge guide element. 10. The method according to claim 9, characterized in that the cutting, or grinding, or rolling using a roll having a shape with a recess is performed before forming the strip. 11. A method according to any one of claims 9 or 10, characterized in that they use a tool having cutting blades in the form of a roller, or a grinding stone in the form of a roller, in which each cutting blade or grinding surface of the stone includes a section approximately parallel to the edge strip, and the section inclined to the edge of the strip from the midpoint. 12. The method of any one of claims 9 or 10, characterized in that the edge of the strip is subjected to cutting or grinding with a tool having cutting blades in the form of a roller, or with a grinding stone in the form of a roller that is brought into contact parallel to the edge of the strip, and the edge of the strip is subjected cutting or grinding with a tool having cutting blades in the form of a roller or grinding stone in the form of a roller, which are brought into contact along an inclined to the edge of the strip and the edges of the strip are formed with a slope.

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