Abstract:
The invention relates to the field of steel processing and steel production, in particular the production of steel profiles. The invention relates to a method for manufacturing a steel profile, the method comprising the steps of: providing a workpiece ( 2, 44, 52 ), in particular a steel blank, preferably a steel strip blank, forming a weakened point ( 10 ) in the region of a planned bend in the workpiece ( 2, 44, 52 ) and bending the workpiece ( 2, 44, 52 ) to produce a bend in the workpiece ( 2, 44, 52 ). After bending, the weakened point ( 10 ) is reinforced by welding.

Description:
[0001]    This application is a Divisional Application of U.S. patent application Ser. No. 14/115,589, filed 13 Feb. 2014, which is a National Stage Application of PCT/EP2012/058311, filed 4 May 2012, which claims benefit of Serial No. 10 2011 100 633.1, filed 5 May 2011 in Germany and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications. 
     
    
     BACKGROUND 
       [0002]    The invention relates to the field of steel processing and steel production, in particular the production of steel profiles. The invention relates to a method for producing steel profiles. The invention further relates to a steel profile, in particular a steel profile produced according to an aforementioned method. The invention also relates to a sheet pile, in particular a Z sheet pile. The invention further relates to a system for producing a steel profile from a workpiece, in particular a steel blank, preferably a steel strip blank. 
         [0003]    Methods for producing a steel profile, steel profiles, sheet piles and systems for producing a steel profile are basically known from the prior art. In steel mills, steel profiles are often produced by continuous casting, by hot rolling or by cold rolling. Steel profiles made by mass forming of steel blanks are also known. When building sheet pile walls, steel profiles in the form of sheet piles are often used as components of the sheet pile walls. Z-shaped sheet piles and U-shaped sheet piles, in particular, are known in this context, and are connected to each other by various forms of interlock, e.g. by means of “Larssen interlocks”. The sheet piles are generally connected to each other by inserting the interlocks into each other when inserting, ramming or vibrating the sheet piles into the ground. 
       SUMMARY 
       [0004]    The object of the present invention is to provide an improved method for producing steel profiles, an improved steel profile, an improved sheet pile and an improved system for producing a steel profile from a workpiece. 
         [0005]    This object is achieved, according to the invention, by a method for producing steel profiles, the method comprising the steps of: providing a workpiece, in particular a steel blank, preferably a steel strip blank, forming a weakened point in the region of a planned bend in the workpiece and bending the workpiece to produce a bend in the workpiece. 
         [0006]    The invention is based on the realisation that prior art methods have several disadvantages. Prior art methods are energy-intensive, labour-intensive and involve high setup and/or start-up costs. This results in large minimum order volumes and comparatively long delivery periods, so it is essential that production is planned long in advance and that large amounts of stock be kept in order to respond in a flexible manner to customer orders. 
         [0007]    The advantages of the method according to the invention are that steel profiles can be produced autonomously, flexibly and fully automatically, preferably directly from a coil and/or a roll of steel strip, or with flat rolled steel workpieces as starting material. Production costs are also kept low due to comparatively low tooling costs, low labour costs and little loss of material. The well-timed production, well-adapted to demand, that is achieved by applying the method also allows storage costs to be kept low. The method is also energy efficient, clean and ecofriendly in operation. Energy is saved, in particular, when processing thick-walled steel. 
         [0008]    The weakened point in the workpiece preferably runs along a planned bend in the workpiece. 
         [0009]    According to one advantageous embodiment of the method according to the invention, the weakened point is formed by forming an indentation, in particular a notch, in the workpiece. This is a particularly expedient and simple variant for forming a weakened point in the region of a planned bend in the workpiece. 
         [0010]    In the context of the present invention, the expression “notch” is to be understood as an indentation which is formed in the workpiece in such a way that it has an open end. 
         [0011]    In another embodiment of the method according to the invention, the weakened point, in particular an indentation forming the weakened point, is formed by milling, rolling, punching or stamping. Weakened points can thus be formed in the workpiece in a particularly simple manner and, if necessary, automatically. 
         [0012]    A particularly preferred embodiment of the method according to the invention is one in which the weakened point is reinforced after bending by welding, in particular by laser welding, and preferably by a laser hybrid welding technique. Due to such reinforcement of a weakened point provided for bending purposes, a steel profile with particularly high stiffness is produced after bending. 
         [0013]    The welding preferably serves to close completely an indentation that is partly closed as a result of bending. For example, ends of the indentation in the workpiece which contact each other can be joined together undetachably by welding. 
         [0014]    In the context of the present invention, the expression “laser welding” shall be understood to mean the undetachable joining of two ends of a steel profile using an optically focused, high-intensity laser beam. 
         [0015]    According to one embodiment of the method according to the invention, welding is done using a focused laser beam which is aimed from the outer side of the bend in the workpiece to the inner side of the bend, in particular along a zero gap formed by the indentation after bending, the focus of said beam preferably being inside the workpiece. The expression “zero gap” shall be understood within the context of the present invention to mean that the sides of the indentation lie against each other after bending, for example have contact, without forming a chemical combination. 
         [0016]    It is basically possible, by bending the workpiece just once, to weld from the outer side of the bend in the workpiece to the inner side of the bend, or also to weld from the inner side of the bend to the outer side of the bend, regardless of the bend angle. When producing a steel profile, however, some bends cannot be welded by starting from the inner side of the bend, as some inner sides of the bend and/or zero gaps are concealed by adjacent strips in the workpiece and are therefore inaccessible for a laser beam. Welding can also be carried out in a particularly simple manner by means of a laser beam which is directed from the outer side of the bend to the inner side of the bend. A single focused laser beam is preferably used thereby, rather than an oscillating beam or two partial laser beams. 
         [0017]    According to another embodiment of the inventive method, an indentation forming the weakened point and which is formed on an inner side of the bend is reduced in size or closed during bending, or an indentation forming the weakened point and which is formed on an outer side of the bend in the workpiece is enlarged during bending. This is a particularly expedient embodiment of the method, in which an indentation constituting the weakened point is formed in a particularly suitable way for bending purposes. The method is also simplified in this manner, since an indentation in the material can be formed prior to bending in such a way that the indentation can be adapted accordingly to the bending to be carried out. It is preferred that the indention can be matched to an intended bend angle. 
         [0018]    According to another expedient embodiment of the inventive method, an indentation forming the weakened point is provided in the workpiece, wherein the indentation formed on an inner side of the bend in the workpiece is closed after bending by welding, in particular by laser welding. A method is thus defined with which an indentation which is initially reduced in size on bending is closed by welding to reinforce the steel profile. 
         [0019]    In another embodiment of the method according to the invention, sides which define an indentation forming the weakened point are undetachably joined together. In this way, a weakened point provided for bending purposes is additionally reinforced after bending. 
         [0020]    According to another expedient embodiment of the method according to the invention, bending is done by free bending, folding or die bending. In this way, the workpiece can be bent in a particularly simple and automated manner to form a steel profile. 
         [0021]    According to yet another preferred embodiment of the inventive method, the workpiece is provided by unrolling a steel strip roll, in particular a coil. In the context of the present invention, the expression “coil” shall be understood to mean a wound metal strip, for example in the form of a steel strip coil. 
         [0022]    According to another preferred embodiment of the method according to the invention, an indentation is introduced into a workpiece in the form of a steel strip blank, prior to bending, said indentation being oriented transverse to the longitudinal direction of the steel strip blank and open to a lateral edge of the steel strip blank. The indentation may be provided, for example, in the form of a slot-like indentation which is laterally introduced into the steel strip blank by means of a stamping tool, a high-energy laser beam or a steel saw, for example. The longitudinal direction of the steel strip blank is preferably the direction in which the steel strip blank moves during the production process, for example on a production line. This can also be the direction, more specifically, in which a steel strip unwound from a steel strip coil is fed to the production line. 
         [0023]    The indentation allows steps in the production process to be carried out in a first region of the steel strip blank without this affecting a second region of the steel strip blank that is separated from the first region by the indentation. 
         [0024]    According to a preferred development of the aforementioned embodiment, the indentation projects into the steel strip blank in such a way that a bending moment in a first region of the steel strip blank which limits a first portion of the indentation, is not transmitted to a second region of the steel strip blank which limits a second portion of the indentation. This substantially simplifies the production process for a steel profile when steel strip blanks are used. The bending according to the inventive method can be carried out without any necessity arising to separate individual sections of the steel strip blank completely from each other prior to bending. The indentations are each introduced with a predefined depth into the steel strip blank in such a way that a bending moment in a first region of the steel strip blank is not transmitted to a second region of the steel strip blank, the two regions nevertheless remaining joined together in a predefined portion of the steel strip blank. 
         [0025]    In the production process according to the invention, for producing a steel profile, the first region of the steel strip blank is located in a bending device, for example, such that the workpiece can be bent therein. The indentation serves in this case to prevent the bend being applied to a second region of the steel strip blank that is still located in the weakening device, for example. 
         [0026]    The object specified at the outset is also achieved, according to the invention, by a steel profile, in particular a steel profile produced by an aforementioned method, in the form of a workpiece which has a weakened point in a bending region. 
         [0027]    The present invention is based on the realisation that prior art steel profiles have a number of disadvantages. Until now, prior art steel profiles could only be bent by applying a very large amount of energy. Depending on the bending technique deployed, material accumulations and distortions ensue, for example on the inner side of the bend in the workpiece, that have to be removed during finishing. 
         [0028]    One advantage of the steel profile according to the invention is that a bending technique for forming a steel profile can be carried out in a particularly simple and energy efficient manner. Material costs are also kept low. 
         [0029]    According to one advantageous embodiment of the inventive steel profile, the weakened point is formed as an indentation in the workpiece. The weakened point is thus provided in a particularly simple and expedient form. 
         [0030]    In one particularly preferred embodiment of the steel profile according to the invention, the workpiece has a substantially V-shaped indentation in the bending region, the sides of the indentation preferably forming an angle ranging from 90° to 135°. 
         [0031]    According to yet another preferred embodiment of the inventive steel profile, the workpiece has a substantially W-shaped indentation in the bending region. A W-shaped indentation in this sense can also be formed by two V-shaped indentations provided adjacent to each other. After bending, the sides of the W-shaped indentation, i.e. the respective sides of the two V-shaped indentations, lie against each other and form a zero gap. This zero gap can then be closed by welding, in particular by laser welding. 
         [0032]    One key advantage of a W-shaped indentation is that, when bending the workpiece, only a particularly small region is deformed, i.e. is cold formed. In the case of a W-shaped indentation which is open towards the inner side of the bend, only the region of the workpiece which faces away from the inner side of the bend is deformed during bending. As a result, the strength of the workpiece material is only slightly affected by bending. This is particularly important when using steel profiles, as the deformed region is harder, but also more brittle. 
         [0033]    According to another preferred embodiment of the inventive steel profile, the workpiece has an indentation which is V-shaped in a first region and W-shaped in a second region, in particular in a bottom region of the indentation, the sides of the V-shaped region preferably forming an angle ranging from 50° to 110°. After the workpiece has been bent, the sides of the W-shaped region of the indentation lie against each other and form a zero gap. The sides of the V-shaped region of the indentation also lie against each other after bending and form a zero gap. Three zero gaps are thus formed: one zero gap in the V-shaped region and two zero gaps in the W-shaped region, i.e. between the sides of the two V-shaped indentations forming the W-shaped region. These zero gaps are then preferably closed by welding, in particular by laser welding. 
         [0034]    One key advantage of an indentation of this kind is that, when bending the workpiece, only a very small region is deformed. With an indentation of this kind that is open to the inner side of the bend, said region is one that faces away from the inner side of the bend, for example. As a result, the strength of the workpiece material is only slightly affected by bending. Furthermore, it is possible with indentations of this kind to produce large bend angles while simultaneously exerting a minimal effect on the material. In addition, good bending characteristics are obtained regardless of the direction in which the workpiece is rolled, i.e. the direction in which the roller turns during production of the blank. After bending the workpiece provided with an indentation of this kind, the workpiece has a greater thickness at the apex of the bend than in the unbent region of the workpiece. If, for example, the workpiece is bent by an angle of 110°, the apex has a thickness that is approximately 1.7 times the thickness of the workpiece in the unbent region. 
         [0035]    According to another preferred development of the two aforementioned embodiments, the sides of the W-shaped indentation adjoin the sides of the V-shaped indentation, in particular in such a way that the respective outer sides of the W-shaped indentation adjoin the sides of the V-shaped indentation. This can be understood in such a way that specifically the free ends of the outer sides of the W-shaped indentation adjoin the sides of the V-shaped indentation. The sides of the V-shaped indentation do not adjoin each other, but extend respectively from the ends of the W-shaped indentation to the inner side of the bend in the workpiece, i.e. to the open side of the indentation, for example. In this way, it is possible, in particular, to produce an indentation that is open to the inner side of the bend. 
         [0036]    The angle between the sides of the V-shaped indentation is preferably equal to the bend angle of the workpiece. It is also preferred that the respective outer sides of the W-shaped indentation are oriented substantially parallel to each other. It is further preferred that the width of the W-shaped indentation increases with an increasing angle between the sides of the V-shaped indentation. 
         [0037]    In another expedient design of the steel profile according to the invention, the workpiece has a weld seam, in particular a laser weld seam, for reinforcing the weakened point in the bending region. This results in a steel profile that is particularly stable and simple to produce. 
         [0038]    The object specified at the outset is also achieved according to the invention by a sheet pile, in particular a Z sheet pile formed by a steel profile which is produced by a method of the kind described above. A sheet pile produced by the inventive method has a greater thickness, in particular at the apexes of the bends, than at the unbent regions of the sheet pile. According to DIN 10248, sheet piles generally have a thickness in the order of about 12 mm in the unbent regions of the sheet. 
         [0039]    The object specified at the outset is also achieved according to the invention by a sheet pile, in particular a Z sheet pile, comprising: a lock member for connecting the sheet pile to a lock member of another sheet pile or of a support element, comprising a neck strip extending substantially at right angles from a wall section of the sheet pile and comprising a claw strip extending from the neck strip, wherein the claw strip is oriented substantially at an angle of at least 90°, in particular at an angle of 100° to 130°, to the neck strip, and one end of the claw strip faces the wall section. A neck strip extending substantially at right angles from an wall section of the sheet pile should preferably be understood in the context of the present invention to mean that the the neck strip is oriented at an angle of approximately 90° to the wall section. 
         [0040]    The lock member of the sheet pile is preferably produced according to the invention by a method of the kind described in the foregoing. This is preferably done by bending a steel strip blank by the method described above into the shape of the lock member. The lock member is specifically used to engage with a lock member of another sheet pile. This is preferably done by inserting the lock member into a lock member of another sheet pile when it is being rammed or vibrated into the ground. 
         [0041]    According to a preferred embodiment of the sheet pile according to the invention, the neck strip is oriented at an angle of at most 90°, in particular at an angle of approximately 20° to 60°, preferably 35° to 45°, to the wall section. 
         [0042]    The object specified at the outset is also achieved according to the invention by a sheet pile, in particular a Z sheet pile, comprising: a lock member for connecting the sheet pile to a lock member of another sheet pile or of a support element, comprising a neck strip extending substantially at right angles from a wall section of the sheet pile, a head strip extending from the neck strip, in particular substantially at right angles thereto, a front strip extending from the head strip, in particular substantially at right angles thereto and a claw strip extending from the front strip, wherein the claw strip is oriented substantially at an angle of at least 90°, in particular at an angle of 100° to 130°, to the front strip and extends from the front strip in a U-shaped region formed by the neck strip, the head strip and the front strip. A neck strip extending substantially at right angles from an wall section of the sheet pile should preferably be understood in the context of the present invention to mean that the the neck strip is oriented at an angle of approximately 90° to the wall section. A head strip extending substantially at right angles from the neck strip should preferably be understood in the context of the present invention to mean that the head strip is oriented at an angle of approximately 90° to the neck strip. A front strip extending substantially at right angles from a head strip should preferably be understood in the context of the present invention to mean that the front strip is oriented at an angle of approximately 90° to the head strip. 
         [0043]    The lock member of the sheet pile is preferably produced according to the invention by a method of the kind described in the foregoing. This is preferably done by bending a steel strip blank by the method described above into the shape of the lock member. The lock member is specifically used to engage with a lock member of another sheet pile. This is preferably done by inserting the lock member into a lock member of another sheet pile when it is being rammed or vibrated into the ground. 
         [0044]    The lock member (referred to in this paragraph as the second lock member) of the sheet pile is used, in particular, for engagement with a lock member of the kind described above, comprising a neck strip and a claw strip (referred to in this paragraph as the first lock member). When the two lock members are engaged with each other, the two front strips lie against each other and are oriented substantially parallel to each other. The claw strips of the two lock members also lie against each other, that is to say, the claw strip of the first lock member extends parallel to the claw strip of the second lock member. The neck strip of the first lock member extends from the wall section of the sheet pile in the U-shaped region of the second lock member formed by the neck strip, the head strip and the front strip of the first lock member. The claw strip projects into a region of the first lock member formed by the neck strip and the claw strip of the first lock member. The two wall sections of the sheet piles which are joined together by means of the lock members are aligned substantially parallel to each other and lie in the same plane. When two lock members of the kind described in the foregoing are joined together, interspace are formed that are very small in volume compared to those in lock member connections in the prior art. As a result, the amount of sealant needed to fill the interspaces after the lock members have been inserted into each other is less. It is further preferred that the first lock member is formed at a first end of the sheet pile, with another lock member, preferably a lock member corresponding to the second lock member, being formed at a second end of the sheet pile. Numerical analyses based on the finite element method, and tests with lock members have shown that the inventive connection between two lock members as described in the foregoing is particularly resilient against tensile forces. This is particularly the case with a first lock member in which the neck strip is oriented at right angles to the wall section and the claw strip extends at an angle of 120° to 140° to the neck strip. This is also the case with a second lock member, in which the neck strip is oriented substantially at right angles to the wall section, the head strip is oriented substantially at right angles to the neck strip, the front strip is oriented substantially at right angles to the head strip and the claw strip extends from the neck strip at an angle of 120° to 140° to the front strip. If, when lock members of this kind are joined together, a tensile force is exerted in the direction of extension of the wall sections of the lock members (the material thickness of the sheet pile being approximately 10 mm), the lock members do not fail until a tensile force of 136 kN is exerted (kN: kilonewtons). In comparison thereto, joins between Larssen profiles such as those known from the prior art fail when a tensile force of 80 kN is exerted. The aforesaid tensile forces were determined with samples that were each 100 mm in length. 
         [0045]    According to one preferred development of the sheet pile according to the invention, the neck strip is oriented at an angle of at most 90°, in particular at an angle of approximately 30° to 70°, preferably 45° to 55°, to the wall section, the head strip being oriented at an angle of at most 90°, in particular at an angle of approximately 20° to 50°, preferably 30° to 40°, to the neck strip and/or the front strip being oriented at an angle of at most 90°, in particular at an angle of approximately 30° to 70°, preferably 45° to 60°, to the head strip. 
         [0046]    According to one preferred development of the sheet pile according to the invention, the claw strip is oriented substantially at an angle of 120° to 140° to the front strip. 
         [0047]    The numerical analyses and tests with lock members, described above, have shown that the development described above is particularly resilient against tensile forces when two lock members are joined together. If a tensile force is exerted in the direction of extension of the wall sections of the lock members (the material thickness of sheet pile being approximately 10 mm), the lock members do not fail until a tensile force of 112 kN is exerted. When a tensile force of 110 kN is exerted, for example, the wall sections of the joined lock members are pulled apart by between 50 and 60 mm, compared to the original position when no force is exerted. In comparison thereto, the wall sections of the joined lock members as described above are pulled apart by 90 to 100 mm, compared to the original position when no force is exerted, In other words, the offset between the wall sections when a tensile force is exerted is less in comparison to the join between two lock members as described above. Another advantage is that when a force in the order of about 80 kN is exerted, less stress and strain ensues in than in the case of the lock members described above. This is particularly advantageous for the welded points. 
         [0048]    According to one advantageous embodiment of the inventive sheet pile, one end of the claw strip is rounded. This means, for example, that the end of the claw strip has no sharp edges, from the perspective of the sheet pile cross-section. The end of the claw strip is preferably rounded by milling. When joining the sheet piles by inserting the lock members into each other, any sharp edges would result in material being cut away from the interlocks. The cuttings that ensue accumulate between the lock members are cause them to become wedged, in part. Inserting the lock members into each other is severely affected, or is rendered impossible when a particular amount of cuttings has accumulated between the lock members. The interlocks are also damaged by the sharp edges cutting away material, and their stability is simultaneously impaired. Rounding the ends of the claw strips prevents such cutting away of material, which means that the lock members of two sheet piles can be inserted into each other in a particularly simple manner, without damage being caused to the interlocks. 
         [0049]    The object specified at the outset is also achieved, according to the invention, by a sheet pile wall comprising at least two sheet piles, in particular Z-sheet piles of the kind described above. 
         [0050]    The object specified at the outset is also achieved, according to the invention, by a system for producing a steel profile from a workpiece, in particular from a steel blank, preferably a steel strip blank, said system comprising a weakening device for forming a weakened point in the workpiece, in particular an indentation, in the region of a planned bend in the workpiece, and a bending device for bending the workpiece in the region of the weakened point. 
         [0051]    The present invention is based on the realisation that prior art systems for producing steel profiles are particularly complex, cause high levels of power consumption as well as high setup and start-up costs. 
         [0052]    One advantage of the system according to the invention is that steel profiles can be produced with the system in a particularly simple and automated manner. 
         [0053]    The weakening device may preferably be provided in the form of a milling unit, a punching unit, a stamping unit and/or a rolling unit. Preferably, the bending device may also include a folding unit, a die bending unit and/or a bending unit for free bending of the workpiece. 
         [0054]    According to one preferred variant of the inventive system, the system includes a feeding device for providing the workpiece, in particular the steel blank, preferably the steel strip blank. In this way, a workpiece for producing the steel profile can be fed automatically to the system. 
         [0055]    The feeding device may preferably be provided as an automatic grappler that takes workpieces from a stack of workpieces. It is further preferred that the feeding device can be a unrolling unit for unrolling a steel strip coil. 
         [0056]    According to another embodiment of a system according to the invention, a cutting device is provided for dividing a steel strip fed from a steel strip coil into workpieces. In this way, steel strip workpieces can be cut to the required size and/or length for producing a steel profile. 
         [0057]    According to a further preferred embodiment of the system according to the invention, a cutting device is designed to introduce an indentation which is oriented substantially transverse to the longitudinal direction of the steel strip coil and which is open to a lateral edge of the steel strip coil. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0058]    Preferred embodiments of the invention shall now be described with reference to the drawings, in which: 
           [0059]      FIG. 1  shows an embodiment of a method according to the invention, 
           [0060]      FIG. 2  shows an embodiment of a steel profile according to the invention, 
           [0061]      FIG. 3  shows a first embodiment of a system according to the invention, 
           [0062]      FIGS. 4A-C  show further embodiments of a method according to the invention, 
           [0063]      FIG. 5  shows two first embodiments of two sheet piles according to the invention, 
           [0064]      FIG. 6  shows a cross-sectional view of a first embodiment of a sheet pile wall according to the invention, 
           [0065]      FIG. 7  shows a second embodiment of a system according to the invention, 
           [0066]      FIG. 8  shows a perspective view of one embodiment of a workpiece, 
           [0067]      FIG. 9  shows a perspective view of the steel strip coil shown in  FIG. 8   m  in an intermediate state, 
           [0068]      FIG. 10  shows two second embodiments of two sheet piles according to the invention, 
           [0069]      FIG. 11  shows a perspective view of a second embodiment of a sheet pile wall according to the invention, 
           [0070]      FIG. 12  shows a cross-sectional view of a second embodiment of a sheet pile wall according to the invention and 
           [0071]      FIG. 13  shows a cross-section of a portion of a lock member. 
       
    
    
     DETAILED DESCRIPTION 
       [0072]      FIG. 1  shows an embodiment of a method according to the invention for producing a steel profile  1 . A workpiece  2  is shown in each case in a view from the side, transverse to a longitudinal direction  3  of workpiece  2 . 
         [0073]    In step A, workpiece  2  is provided in the in the form of a rectangular steel strip blank  4 , which has a height  5  and a length  6 . 
         [0074]    In step B, weakened points  10  in the form of indentations  11  are formed in a region  12  of a planned bend  13  in workpiece  2 . A tool unit  15 , used as a weakening device  14 , removes a fragment from workpiece  2 . V-shaped indentations  11  having two side  16  of substantially equal length are formed in the process. 
         [0075]    In step C, workpiece  2  is bent in bending region  12  by means of a bending device  20  in such a way that an indentation  11  formed in step B on an inner side  21  of the bend in workpiece  2  is closed. In the bent state, the sides  16  of the indentation  11  formed in step B come into contact with each other. 
         [0076]    In another step of the method (not shown), the sides  16  are joined together undetachably by laser welding in such a way that the weakened point originally provided as indentation  11  is reinforced to form a steel profile  1  with a high stiffness. The laser welding is carried out in such a way that the gap formed when sides  16  come into contact with each other is closed by a laser weld seam. Technically, the gap formed may also be a zero gap, in which case the sides do not need to be adapted for welding. 
         [0077]      FIG. 2  shows a side view of an embodiment of a steel profile  1  according to the invention, produced by a method according to the invention from the workpiece  2  shown in  FIG. 1 . 
         [0078]    Identical members, or members having identical functions, are marked therein with the same reference signs. 
         [0079]    The indentations formed in the production process are closed by bending. The steel profile has weld seams  30  with which the indentations are securely closed in order to reinforce the steel. On the inner sides  31  of the bend or the outer side of the bend, the weld seams run in the viewing direction along steel profile  1  and extend partly into workpiece  2  along the sides  1  shown in  FIG. 1 . 
         [0080]      FIG. 3  shows an embodiment of a system  40  according to the invention for producing a steel profile from a workpiece. A feeding device  41  removes steel strip from a steel strip coil  42  so that the steel strip can be divided in a cutting device  43  into workpieces  44  of a suitable size for the further production process. The system also has a second feeding device  50  which removes a workpiece  52  from a pallet  51  of workpieces for the further production process. 
         [0081]    Transfer elements  55  guides workpieces  44 ,  52  to be processed to a weakening device  56 , which is provided in the form of a milling unit  57 . 
         [0082]    After milling unit  57  has formed an indentation in the workpiece, workpiece  44 ,  52  is guided by transfer elements  55  to a bending device  60  for bending workpiece  44 ,  52 . 
         [0083]    After bending, workpieces  44 ,  52  are fed to a laser device  61 , in which the indentations in the workpieces are closed. After welding, steel profiles  58  can be put to the side on a stack  59  by transfer elements  55 . 
         [0084]    The system  40  is controlled by a central controller  62 . 
         [0085]      FIGS. 4A-B  show a second embodiment of a method according to the invention. More specifically,  FIGS. 4A-B  each show two intermediate states of a workpiece  400  before bending (top) and after bending (bottom). 
         [0086]      FIG. 4A  shows an end portion  401  of a workpiece  400 , in which end  402  is rounded, i.e. without sharp edges. In the intermediate state shown at the top in  FIG. 4A , an indentation  410  in workpiece  400  has a W-shaped region  411  and a V-shaped region  412 . W-shaped region  411  consists of a first V-shaped portion  420  and a second V-shaped portion  421 . A first side  413  of V-shaped region  412 , on the left when seen in the direction of viewing, adjoins a first side  422  of the first V-shaped portion  420  an. A second side  423  of V-shaped portion  420  adjoins a first side  424  of the second V-shaped portion  421 . A second side  425  of the second V-shaped portion  421  adjoins a second side  414  of V-shaped portion  412 . 
         [0087]    Proceeding from left to right when seen in the direction of viewing, indentation  410  is defined by the following adjoining elements: first side  413  of V-shaped region  412 , first side  422  of first V-shaped portion  420 , second side  423  of first V-shaped portion  420 , first side  424  of second V-shaped portion  421 , second side  425  of second V-shaped portion  421  and second side  414  of V-shaped region  412 . 
         [0088]    The opening angle between first side  413  and second side  414  is approximately 110°. 
         [0089]    At the bottom,  FIG. 4A  shows workpiece  400  in an intermediate state after bending. During bending, the workpiece was bent to a bend angle of approximately 110°, thus resulting in an opening angle of approximately 70° between an end portion  401  and a right-hand portion  430  of workpiece  400 , as seen in the direction of viewing. After bending, the sides of the respective V-shaped regions or portions lie against each other and/or form a zero gap, i.e. side  413  forms a zero gap with side  414 , side  422  forms a zero gap with side  423  and side  424  forms a zero gap with side  425 . 
         [0090]      FIG. 4B  shows a workpiece  440  having an indentation  441  which is formed substantially like indentation  410 . Identical members, or members having identical functions, are marked therein with the same reference signs. In the indentation  441  shown in  FIG. 4B , the opening angle between first side  413  and second side  414  is approximately 90°. During bending, sides  413  and  414  of the V-shaped region  412  and sides  422  and  423  and sides  424  and  425  of W-shaped region  411  form a respective zero gap, such that an angle of approximately 90° is produced between the sections  445  and  446  which are bent towards each other. 
         [0091]      FIG. 4C  shows a workpiece  450  having an indentation  451  which is formed substantially like indentations  410  ( FIG. 4A) and 441  ( FIG. 4B ). Identical members, or members having identical functions, are marked therein with the same reference signs. In indentation  451  shown in  FIG. 4C , the opening angle between first side  413  and second side  414  is approximately 50°. During bending, sides  413  and  414  of the V-shaped region  412  and sides  422  and  423  and sides  424  and  425  of W-shaped region  411  form a respective zero gap, such that an angle of approximately 130° is produced between the sections  455  and  456  which are bent towards each other. 
         [0092]      FIG. 5  shows a respective section  510 ,  520  of a first sheet pile  511  and a second sheet pile  521 . The first sheet pile  511  has a lock member  512  in engagement with a lock member  522  of the second sheet pile  521 . In references to  FIG. 5 , stated angles with positive values greater than 0° are to be understood as angles measured in the clockwise direction  530 ; 
         [0093]    stated angles with negative values less than 0° are to be understood as angles measured in the anti-clockwise direction. 
         [0094]    The lock member  512  of the first sheet pile  511  is formed by a neck strip  513  and a claw strip  514 . Neck strip  513  extends from a wall section  515  of the first sheet pile  511  at a substantially right angle (approximately −90°). The bending of a workpiece necessary to achieve such angle can be carried out, for example, via the intermediate state of workpiece  440  shown in  FIG. 4A . Claw strip  514  extends from neck strip  513  at an angle α of approximately −110°. The bending of a workpiece necessary to achieve such an angle, e.g. of approximately 110°, can be carried out, for example, via the intermediate state of workpiece  400  shown in  FIG. 4A . The end of claw strip  514  simultaneously forms an end  502  of the first sheet pile  511 . Said end  502  is rounded and has no sharp edges, at least from the perspective of the sheet pile cross-section. Lock member  522  of the second sheet pile  521  is formed by a neck strip  523 , a head strip  524 , a front strip  525  and a claw strip  526 . Neck strip  523  extends from a wall section  527  of the second sheet pile  521  at a substantially right angle (approximately +90°). Head strip  524  extends from neck strip  523  at a substantially right angle (approximately −90°). Front strip  525  extends from head strip  524  at a substantially right angle (approximately −90°). The bending of a workpiece necessary to achieve such a right angle can be carried out, for example, via the intermediate state of workpiece  440  shown in  FIG. 4B . Claw strip  526  extends from front strip  525  at an angle β of approximately −110° thereto. The bending of a workpiece necessary to achieve such an angle, e.g. of approximately 110°, can be carried out, for example, via the intermediate state of workpiece  400  shown in  FIG. 4A . The end of claw strip  526  simultaneously forms an end  503  of the second sheet pile  521 . Said end  503  is rounded and has no sharp edges, at least from the perspective of the sheet pile cross-section. 
         [0095]    Neck strip  523 , head strip  524  and front strip  525  form a U-shaped region  528  of sheet pile  521 . In combination with wall section  527 , U-shaped region  528  forms a sickle-shaped region of sheet pile  521 . Claw strip  526  projects thereby into an inner space  529  formed by U-shaped region  528  and/or the sickle-shaped region. In the arrangement shown in  FIG. 5 , wall sections  515  and  527  are aligned parallel to each other and are arranged in the same plane. 
         [0096]    If wall sections  515  and  527  are moved towards each other, lock members  512  and  522  abut each other with their front strips  513  and  523 . In the event of tensile forces acting between the sheet piles  511  and  521 , i.e. when the sheet piles are driven apart by strong forces in the direction of extension of the wall sections, the lock members engage each other in such a way that end  502  of claw strip  514  abuts front strip  525  and end  503  of claw strip  526  abuts neck strip  513 . The interlocks remain locked when pressure is exerted, for example transversely to the longitudinal direction of extension of sheet piles  511  and  521 . Only by displacing the interlocking sheet piles in the viewing direction of  FIG. 5  can the sheet piles be separated from each other. 
         [0097]      FIG. 6  shows a section of a sheet pile wall  600  comprising two sheet piles. The sheet piles shown in  FIG. 6  are similar to the sheet piles shown in  FIG. 5 . Identical members, or members having identical functions, are marked therein with the same reference signs. A first sheet pile  511  is produced with a substantially Z-shaped profile and includes a first wall section  515  which has a lock member  512  at one end  610  (right). A second sheet pile  521  is produced with a substantially Z-shaped profile and includes a first wall section  527  which has a lock member  522  at one end  620  (left). 
         [0098]    From the first wall section  515  of first sheet pile  511 , a second wall section  640  of first sheet pile  511  extends at an angle ç of approximately +50° to first wall section  515 . From the second wall section  640 , a third wall section  613  of first sheet pile  511  extends at an angle ρ of approximately −50° to the second wall section  640 . At one end  611 , third wall section  613  has a lock member  612  which has substantially the same structure as lock member  522  of second sheet pile  521 , that is to say, lock member  612  has the same shape as lock member  522  when mirrored in a plane  630 . 
         [0099]    From the first wall section  527  of second sheet pile  521 , a second wall section  641  of second sheet pile  521  extends at an angle π of approximately −50° to first wall section  527 . From the second wall section  641 , a third wall section  614  of second sheet pile  527  extends at an angle ξ of approximately +50° to second wall section  641 . At one end  621 , third wall section  614  has a lock member  622  which has substantially the same structure as lock member  512  of the first pile sheet, that is to day, lock member  622  has the same shape as lock member  512  when mirrored in a plane  630 . 
         [0100]      FIG. 7  shows a second embodiment of a system  700  according to the invention for producing a sheet pile  701  from a steel strip blank  702 . Steel strip blank  702  is unrolled from a steel strip coil  703  by means of a feeding device  704  and fed in feeding direction  710  to the following components of system  700  in conveying direction  710 . A conveying device  711  is used to convey steel blank  702  in feeding direction  710  along and/or through the individual components of system  700 . 
         [0101]    Steel strip blank  702  proceeds from feeding device  704  to a milling device  712 , by means of which indentations provided as weakened points are introduced into steel strip blank  702 . 
         [0102]    Milling device  712  has two milling units  713  and  714 . By means of milling unit  713 , indentations are firstly introduced from below into steel strip blank  702 . By means of milling unit  714 , indentations are then introduced from above into steel strip blank  702 . 
         [0103]    A laser cutting device  720  is used to introduce slot-shaped cut-outs into steel strip blank  702 . The cut-outs each run transversely to feeding direction  710  from an outer edge of steel strip blank  702  in a substantially straight line into steel strip blank  702 . More specifically, two cuts are made at predefined distances in feeding direction  710 , namely inwardly by a predefined depth from the lateral edge of steel strip blank  702 . The cuts are made, in particular, in order to perform the bends to be made in the following production process, without the bending moments being transmitted to the entire steel strip blank  702  located on conveying device  710 . The cuts are introduced at those points in steel strip blank  702  where the workpieces are subsequently severed from steel strip blank  702  in the subsequent production process. 
         [0104]    A bending device  725  of system  700  is adapted to bend steel strip blank  702  at different points. In the region of the bends, the zero gaps formed during bending are closed by means of a laser device  730 . After welding, the individual workpieces are severed from steel blank  702  by means of a cutting device  740 . The finished workpieces can then be stored on a stack  750 , for example for transport. 
         [0105]      FIG. 8  shows a perspective view of a portion of a workpiece  800  according to the invention, embodied in the form of steel strip blank  801 . Indentations  810  are introduced into steel strip blank  801 , which extend transversely to the longitudinal direction of extension  815  of steel strip blank  801  and laterally into steel strip blank  801  and which are open to a lateral edge  816  of the steel strip blank. A first region  820  defines a first portion  821  of indentation  810 . A second region  830  defines a second portion  831  of indentation  810 . A bending moment  840  can be exerted thereby on second region  830  of steel strip blank  801 , in the form of a torque about axis  841  represented by a broken line. I.e. the region of the steel strip blank shown under broken line  841 , when seen in the viewing direction, remains in its position, whereas the edge of steel strip blank  801  shown above broken line  841 , seen in the viewing direction, is exposed to a torque about axis  841 . Due to indentation  810 , a bending moment  841  of this kind is not transmitted to first region  820  of steel strip blank  801 . I.e. a bend can be performed in second region  830 , without this bending being transmitted to first region  820  and/or having any effect on first region  820 . 
         [0106]      FIG. 9  shows a perspective view of the steel strip blank  801  shown in  FIG. 8 , in an intermediate state after bending. I.e. the steel strip blank  801  shown in  FIG. 8  was subjected to bending operations that are performed during the production process on steel strip blank  801  in order to produce a sheet pile.  FIG. 9  basically shows two sheet piles  901  and  902  that are separated from each other in a subsequent step in the production process. 
         [0107]      FIG. 10  shows a respective section  1010 ,  1020  of a first sheet pile  1011  and a second sheet pile  1021 . The first sheet pile  1011  has a lock member  1012  in engagement with a lock member  1022  of the second sheet pile  1021 . In references to  FIG. 10 , stated angles with positive values greater than 0° are to be understood as angles measured in the clockwise direction  1030 ; stated angles with negative values less than 0° are to be understood as angles measured in the anti-clockwise direction. 
         [0108]    Lock member  1012  of the first sheet pile  1011  is formed by a neck strip  1013  and a claw strip  1014 . Neck strip  1013  extends from a wall section  1015  of the first sheet pile  1011  at an angle ω of +38°. Claw strip  1014  extends from neck strip  1013  at an angle ψ of approximately +123°. The end of claw strip  1014  simultaneously forms an end  1002  of the first sheet pile  1011 . Said end  1002  is rounded and has no sharp edges, at least from the perspective of the sheet pile cross-section. 
         [0109]    Lock member  1022  of second sheet pile  1021  is formed by a neck strip  1023 , a head strip  1024 , a front strip  1025  and a claw strip  1026 . Neck strip  1023  extends from a wall section  1027  of second sheet pile  1021  at an angle χ of approximately −49.5°. Head strip  1024  extends from neck strip  1023  at an angle φ of approximately +30.5°. Front strip  1025  extends from head strip  1024  at an angle σ of approximately +57°. Claw strip  1026  extends from front strip  1025  at an angle ψ of approximately +123°. The end of claw strip  1026  simultaneously forms an end  1003  of the second sheet pile  1021 . Said end  1003  is rounded and has no sharp edges, at least from the perspective of the sheet pile cross-section. In the arrangement shown in  FIG. 10 , wall sections  1015  and  1027  are aligned parallel to each other and are arranged in the same plane. 
         [0110]    In the event of tensile forces acting between the sheet piles  1011  and  1021 , i.e. when the sheet piles are driven apart by strong forces, the lock members engage each other in such a way that end  1002  of claw strip  1014  abuts front strip  1025  and claw strip  1026 , and end  1003  of claw strip  1026  abuts neck strip  1013  and claw strip  1014 . The interlocks remain locked when pressure is exerted, for example transversely to the longitudinal direction of extension of sheet piles  1022  and  1021 . Only by displacing the interlocking sheet piles in the viewing direction of  FIG. 10  can the sheet piles be separated from each other. 
         [0111]      FIGS. 11 and 12  each show a section of a sheet pile wall  1100  comprising two sheet piles.  FIG. 11  shows a perspective view, and  FIG. 12  shows a cross-section of sheet pile wall  1100 . The sheet piles shown in  FIGS. 11 and 12  are similar in structure to the sheet piles shown in  FIG. 10 . Identical members, or members having identical functions, are marked therein with the same reference signs. A first sheet pile  1011  is produced with a substantially Z-shaped profile and includes a first wall section  1015  which has a lock member  1012  at one end  1110  (right). A second sheet pile  1021  is produced with a substantially Z-shaped profile and includes a first wall section  1027  which has a lock member  1022  at one end  1120  (left). 
         [0112]    From the first wall section  1015  of first sheet pile  1011 , a second wall section  1140  of first sheet pile  1011  extends at an angle ν of approximately −50° to first wall section  1015 . From the second wall section  1140 , a third wall section  1113  of first sheet pile  1011  extends at an angle μ of approximately +50° to second wall section  1140 . At one end  1111 , third wall section  1113  has a lock member  1112  which has substantially the same structure as lock member  1022  of second sheet pile  1021 , that is to say, lock member  1112  has the same shape as lock member  1022  when mirrored in a plane  1130 . 
         [0113]    From the first wall section  1027  of second sheet pile  1021 , a second wall section  1141  of second sheet pile  1021  extends at an angle λ of approximately +50° to first wall section  1027 . From the second wall section  1141 , a third wall section  1114  of second sheet pile  1027  extends at an angle κ of approximately −50° to second wall section  1141 . At one end  1121 , the third wall section  1114  has a lock member  1122  which has substantially the same structure as lock member  1012  of the first sheet pile, that is to say, lock member  1122  has the same shape as lock member  1012  when mirrored in a plane  1130 . 
         [0114]      FIG. 13  shows a cross-section of a portion of the lock member  1022  shown in  FIG. 10 . This cross-section illustrates the welding operation that is carried out after the bending step. More particularly,  FIG. 13  shows a claw strip  1026  and a portion of a front strip  1025 . After bending, a zero gap is formed by the sides of the indentation, for example by sides  413  and  414  as depicted in  FIG. 4A . To close (weld) the zero gap, a laser beam  1310  is directed from the outer side  1320  of the bend to the inner side  1321  of the bend. Laser beam  1310  runs substantially along the zero gap inside workpiece  1300 . After welding, a weld root  1330  is formed on the bend outer side  1320  of the weld seam, and a weld root  1331  is formed on the bend inner side  1321  of the weld seam. Inside workpiece  1300 , two regions  1340  and  1341  are formed after welding. Region  1340  is formed by a substantially triangular weld core  1345  which is fully fused during welding. Region  1341  is formed by a transitional region between weld core  1345  and region  1346  of the workpiece, which is not involved in the welding operation. Welding from bend outer side  1320  ensures that a wedge-shaped weld root is formed, the tip of which is oriented towards bend inner side  1321 . The focus  1350  of laser beam  1310  is inside workpiece  1300 , in particular in region  1340 . This focal position, i.e. the position of the focus inside the workpiece (proceeding from the point at which the laser beam hits the workpiece), ensures a broad root, with the result that a wide area of the bend outer side is affected. In the case of W-shaped indentations, in particular, which project out in dovetail fashion in the bent state, it is thus possible to fuse the zero gaps formed during bending. The region deformed during bending is also fused, with the result that the joint is under less strain after cooling than in the pre-bent state. 
         [0115]    Laser beam  1310 , which is used for welding, preferably has a power rating of 10 kW to 14 kW (kilowatts). For a bend angle of approximately 110°, the power rating of the laser welding beam is preferably about 14 kW, with a preferred focal position of approximately −14 mm; for a bend angle of approximately 90°, the nominal power of the laser welding beam is preferably about 12 kW, with a preferred focal position of approximately −16 mm, and for a bend angle of approximately 50° the nominal power of the laser welding beam is preferably about 10 kW, with a preferred focal position of approximately −8 mm. The laser welding beam preferably moves during welding along the workpiece to be welded, in the viewing direction of  FIG. 13 , with a speed of 1.5 to 1.8 m/min (metres per minute).