Flash welding method and flash welding apparatus for welding together steel billets having undercut ends

Abstract

Apparatus and method for welding together steel billets having cut ends, each cut end comprising a deformation in a cross section of the billet made by one side surface of the billet, the method comprising the steps of: determining the orientation of the cut end of the front portion of the billet to be welded to the rear portion of the previously welded billet; determining based on the orientation whether the billet to be welded to the previously welded billet needs to be rotated about the longitudinal axis of the billet to align the cut end at the front portion of the billet with the cut end at the rear portion of the previously welded billet so that the weld to be formed by the flash welding device can be successfully deburred by a skiving cutter; operating a billet rotating component based on the determined rotation to rotate the billet about the longitudinal axis of the billet to form a ring-shaped bar for continuous rolling into a rolled product; flash welding the aligned billets using the flash welding device; and deburring excess welding material from the flash welded joint of the formed ring-shaped bar using one or more skiving cutters.

Description

Technical Field

[0001] The present disclosure relates to methods and apparatus for welding steel billets together to form endless bars for continuous rolling into rolled products. In particular, the apparatus and method disclosed herein are for welding steel billets having down cut ends together. Background Art

[0002] In a rolling mill, square billets, typically 150mm x 150mm x 12m, weighing 2 tons, are each heated in a reheating furnace and then rolled into various cross-sections and sizes. Since the final steel product is usually sold in commercial lengths of 12 meters, the 2-ton billet will always have a variable final length of less than 12 meters for different sizes and types of finished products. This loss can be 5% or more. To mitigate this, the heated billets can be flash welded before entering the first stand of the rolling mill. The tail end of the first billet is welded to the front end of the second billet, and so on. This can be called "ring bar rolling" or "ring weld rolling". The result is virtually zero end loss.

[0003] Steel billets are mainly made by continuous casting machines, whereby molten steel solidifies continuously into square profile billets of infinite length while passing through such machines. Various methods and equipment must be used to cut the solidified square billets into convenient lengths of billets, typically 12 m, for subsequent rolling in a subsequent rolling process in a hot rolling mill as an intermediate steel product to produce rolled steel as a finished product. Thus, the intermediate billets are used to subsequently charge a reheating furnace in another workshop in the rolling mill for flash welding to form ring bars and rolling into final rolled products.

[0004] When the billet leaves the reheating furnace, the tail end of the first billet and the front end of the second billet are heated by passing a high current through them to partially melt these ends. These ends are then pressed together so that they fuse to form a flash weld, and the welded billet can then be rolled continuously. Just before the flash welded joint passes through the first rolling station, the excess weld at the joint is shaved off so that it will not be rolled into the finished product as a surface defect. Scraping the excess weld can be challenging. To date, in order to obtain a scraped clean joint, uniform square cross-sections of the billets to be welded need to be welded together.

[0005] It is in the above context that the present disclosure has been conceived. Summary of the invention

[0006] There are three types of billet cutting during billet manufacturing, and each type has a different effect on the cross-section of the billet cut surface; "flame cutting", "diagonal cutting" and "undercutting".

[0007] Flash welding of "flame cut" and "diagonal cut" billet ends has been successful because these billet ends have a suitably uniform square cross section, but successful flash welding of billets having deformed "undercut" billet ends has not been possible because of their severe deformation at the billet ends. Each undercut end comprises a deformation in the cross section of the billet made by one side surface of the billet, the deformation gradually extending inwardly into the profile of the billet in the end region of the billet relative to the normal square cross-sectional profile of the end portion of the billet remote from the billet, wherein the deformation is produced by a previous cutting operation (e.g., a cutting operation in a continuous casting process used to manufacture the billet).

[0008] This occurs because: although the normal flash welding process of the cut billet ends can be performed (i.e., melting the billets with an electric arc and pressing them together to form the weld), the resulting weld joint cannot be properly scraped clean by burr removal and will be rolled into the final product as a surface defect or "scab" and rejected as scrap.

[0009] The present inventors have realised that, with relatively uniform square cross-sections, such as those produced by 'flame cutting' and 'diagonal cutting', the orientation of the blank along its axis relative to the next blank to be flash welded is unimportant and the excess weld will be successfully shaved off regardless of the relative orientation of the blanks. However, with irregular cross-sections of the ends of the blanks, such as from 'down cuts', a completely shaved clean weld joint cannot be achieved, particularly where the weld in the 'down cut' joint cannot be accessed by the deburring cutter and the excess weld will therefore be rolled into a surface defect in the final product.

[0010] In this regard, it has been recognized that problems arise in flash welding such "undercut" billet ends when presented for flash welding capable of being on any of the four sides due to the random orientation of the billet along its axis.

[0011] Viewed from one aspect, the present disclosure provides a method for welding together steel billets having undercut ends. Each undercut end includes a deformation in the cross section of the billet made by one side surface of the billet, the deformation gradually extending inwardly into the profile of the billet in the end region of the billet relative to the normal square cross-sectional profile of the billet remote from the end portion of the billet, the deformation being produced by a previous cutting operation. The method uses a flash welding device and one or more skiving cutters to remove excess weld material to form a ring-shaped bar for continuous rolling into a rolled product.

[0012] The method includes the following steps: determining the orientation of the lower cut end of the front portion of the billet to be welded to the rear portion of the previously welded billet; determining based on the orientation whether the billet to be welded to the previously welded billet needs to be rotated around the longitudinal axis of the billet to align the lower cut end at the front portion of the billet with the lower cut end of the rear portion of the previously welded billet so that the weld to be formed by the flash welding device can be successfully deburred by the scraping cutter; operating the billet rotating component based on the determined rotation to rotate the billet around the longitudinal axis of the billet to form a ring-shaped bar for continuous rolling into rolled products; using the flash welding device to flash weld the aligned billets; and using one or more scraping cutters to deburr excess welding material from the flash welded joint of the formed ring-shaped bar.

[0013] Welding steel billets having undercut ends to form ring bars has not been previously accomplished and will allow manufacturers using ring bar rolling to have components for making rolled steel products from any cut billet because excess weld material formed during the flash welding process can be reliably removed and scab in the finished rolled product can be avoided.

[0014] This is accomplished by rotating the blank about its longitudinal axis to bring the undercut ends of the blank into complementarity or oppositional alignment so that excess weld material of the flash weld joint can be successfully deburred in a subsequent processing step. If the undercut ends of the blank are not aligned in this manner, the deformation prevents the skiving cutter from reaching the excess weld material to successfully deburr the weld joint.

[0015] Successful burr removal is possible with "flame cut" and "diagonal cut" blanks where the blank orientation is random, because these blanks retain their square cross-section and as such can be flash welded and successfully deburred regardless of their orientation.

[0016] Rolled products produced from the ring-shaped bar can include products such as reinforcing bars (also known as rebars), steel sheets, and steel plates.

[0017] In an embodiment, the cutting operation to form the undercut end is characterized in that it has been performed by a mechanical shear, the mechanical shear comprising a fixed shear and a mobile shear arranged on opposite sides of the blank, wherein the mobile shear moves toward the fixed shear to cut through the cross section of the blank in the middle; and wherein the resulting deformation causes the surface of one side of the blank to extend inwardly into the profile of the blank by at least 25 mm or more or at least 10% of the thickness of the normal cross-sectional profile of the blank. In other embodiments, the surface of one side of the blank is to extend inwardly into the profile of the blank by at least 10 mm or more or 15 mm or more or 20 mm or more or 30 mm or more or 35 mm or more or 40 mm or more. In other embodiments, the surface of one side of the blank is to extend inwardly into the profile of the blank by at least 5% of the thickness of the normal cross-sectional profile of the blank, or at least 7% of the thickness of the normal cross-sectional profile of the blank, or at least 12% of the thickness of the normal cross-sectional profile of the blank, or at least 15% of the thickness of the normal cross-sectional profile of the blank, or at least 17% of the thickness of the normal cross-sectional profile of the blank, or at least 20% of the thickness of the normal cross-sectional profile of the blank. At the opposite surface, a certain degree of deformation away from the normal blank profile may be formed so that the opposite surface extends outwardly, although typically by a smaller amount over a shorter length.

[0018] In an embodiment, the deformed undercut end region of the blank includes at least 10 centimeters at the end of the blank. This is due to the forces to which the end of the blank is subjected during the cutting operation. In other embodiments, the deformed undercut end region of the blank includes at least 5 centimeters at the end of the blank, or at least 7 centimeters at the end of the blank, or at least 12 centimeters at the end of the blank, or at least 15 centimeters at the end of the blank, or at least 17 centimeters at the end of the blank, or at least 20 centimeters at the end of the blank, or at least 25 centimeters at the end of the blank, or at least 30 centimeters at the end of the blank.

[0019] In an embodiment, the method further comprises controlling the flash time and upset distance of the flash welding device to be sufficient to cause excess weld material to protrude beyond the contour of the blank on one side of the deformed surface of the undercut end of the blank, so as to allow the excess weld material to be successfully deburred by one or more skiving cutters.

[0020] In an embodiment, the skiving cutter can be configured to cut within the contour of the normally square cross-section of the welded annular bar on at least one side of the deformed surface of the undercut end of the blank so that the depth of the cut is sufficient to remove all excess weld material from the flash weld joint.

[0021] In an embodiment, rotation of a blank to be welded to a previously welded blank about its longitudinal axis will cause the undercut ends of blanks to be welded together in the same direction to be complementarily aligned or cause the undercut ends of blanks to be welded together in opposite directions to be oppositely aligned so that the weld to be formed by the flash welding device can be successfully deburred by the skiving cutter.

[0022] In an embodiment, the formed ring-shaped bar for continuous rolling into a rolled product is rolled in one or more rolling stands such that the rolled product is free of surface defects or profile variations from burr removal of excess weld material.

[0023] Viewed from another aspect, the present disclosure provides an apparatus for welding together steel billets having cut ends, each cut end comprising a deformation in the cross-section of the billet made by one side surface of the billet, the deformation gradually extending inwardly into the profile of the billet in the end region of the billet relative to the normal square cross-sectional profile of the billet away from the end portion of the billet, the deformation being produced by a previous cutting operation, the weld to form a ring-shaped bar for continuous rolling into a rolled product.

[0024] In an embodiment, the apparatus includes: a billet orientation determining component for determining the orientation of the lower cut end of the front portion of the billet to be welded to the rear portion of the previously welded billet, and based on the orientation, determining whether the billet to be welded to the previously welded billet needs to be rotated around the longitudinal axis of the billet to align the lower cut end at the front portion of the billet with the lower cut end of the rear portion of the previously welded billet; a billet rotating device, configured to rotate the billet around its longitudinal axis to achieve alignment based on the determined rotation; a flash welding device, for flash welding the aligned billets to form a ring-shaped bar for rolling; one or more scraping cutters, for deburring excess welding material from the weld joint between the billets, the determined rotation enabling the weld to be formed by the flash welding device to be successfully deburred by the scraping cutter.

[0025] In an embodiment, the blank rotating component rotates the blank to be welded to the previously welded blank about its longitudinal axis so that the undercut ends of the blanks to be welded together in the same direction are complementarily aligned or the undercut ends of the blanks to be welded together in opposite directions are oppositely aligned so that the weld to be formed by the flash welding device can be successfully deburred by the skiving cutter.

[0026] In an embodiment, the flash welding device is configured such that the flash time and upset distance of the flash welding device are sufficient to cause excess weld material to protrude beyond the contour of the blank on one side of the deformed surface of the undercut end of the blank to allow the excess weld material to be successfully deburred by one or more skiving cutters.

[0027] In an embodiment, the reheating furnace is arranged to heat each billet prior to flash welding so that the resulting ring-shaped bar is ductile enough to be rolled into a rolled product.

[0028] In an embodiment, the billet orientation determination means comprises one or more cameras coupled to one or more processors, positioned between the reheat furnace and the flash welding device, in order to determine the orientation of the undercut end of the billet. This allows the billet orientation determination to be performed at a distance from the rest of the apparatus, so that the heat of the reheat furnace, the billet, or the flash welding device does not damage the billet orientation determination means. The billet orientation determination may also be performed automatically by a processor, which analyzes the billet observed in the camera feed, determines the orientation of the billet, and determines the appropriate rotation of the billet to align it with the preceding billet to be welded to.

[0029] In an embodiment, the apparatus further comprises one or more rolling stands for continuously rolling the formed ring-shaped bar into rolled products, such as those mentioned above.

[0030] In an embodiment, the skiving cutter comprises a separate cutting member for each contoured surface of the annular bar so that excess welding material can be removed from each of these contoured surfaces.

[0031] In an embodiment, the skiving cutter is configured to cut within the contour of the normally square cross-section of the annular bar being welded on at least one side of the deformed surface of the undercut end of the blank so that the depth of the cut is sufficient to remove all excess weld material from the flash weld joint.

[0032] In an embodiment, the apparatus further comprises one or more skiving cutters for deburring the weld, so that the ring-shaped bar can be continuously rolled into a rolled product by one or more rolling stands without surface defects from excess welding material. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1a is a diagram of a "flame cut" blank showing that the blank retains its original square cross-section after the cutting operation.

[0034] Figure 1b Illustration of the "flame cut" end of a steel billet and its arrangement for successful flash welding and burr removal.

[0035] Figure 2a is a photograph of a "diagonally cut" billet showing minimal deformation of this type of billet.

[0036] Figure 2b Illustration of the diagonally cut end of a steel billet and its arrangement for successful flash welding and burr removal.

[0037] Figure 3a is a diagram of a "down-cut" billet, which illustrates the deformation characteristics of this kind of billet.

[0038] Figure 3b is a view of a "down-cut" blank 301 showing the deformation of the end regions of the blank and the retention of the normal square cross-sectional profile of the blank away from these end regions.

[0039] Figure 3c The illustration shows a steel billet with an undercut end presented for flash welding with orthogonally aligned deformations and resulting defects due to failed flash welding and burr removal.

[0040] Figure 3d Illustration of a steel billet with an undercut end presented for flash welding with variously orthogonally aligned deformations and resulting defects, failed flash welds and burr removal.

[0041] Figure 3e The illustration shows a steel billet with undercut ends presented for flash welding with deformations aligned in opposite directions and the resulting successful flash welding and burr removal.

[0042] Figure 3f The illustration shows a steel billet with undercut ends presented for flash welding with deformations aligned in opposite directions and the resulting successful flash welding and burr removal.

[0043] Figure 4 is a schematic diagram of an apparatus for successfully welding "down cut" billets together into ring-shaped bars for rolling into rolled products.

[0044] Figure 5 is a flow chart detailing a method for successfully welding "down cut" billets together into ring shaped bars for rolling into rolled products. DETAILED DESCRIPTION

[0045] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of the presently preferred embodiments of the invention and is not intended to represent the only form in which the invention may be practiced. It is to be understood that the same or equivalent functions may be achieved by different embodiments intended to be included within the spirit and scope of the invention. In addition, the terms "comprises, comprising" or any other variation thereof are intended to cover non-exclusive inclusions, such that a device and method step that includes a list of elements or steps includes not only those elements, but may also include other elements or steps that are not explicitly listed or inherent. An element or step that continues with "including...a" does not exclude the presence of additional identical elements or steps that include that element or step, without further constraints.

[0046] Reference now Figure 4 , which shows a schematic illustration of an embodiment of an apparatus for successfully welding "down cut" billets together into ring-shaped bars for rolling into rolled products in accordance with aspects of the present disclosure. Figure 4 Shown is a series of such billets to be welded together into annular bars, a "down cut" billet 401, a conveyor 402 for conveying the billets along the processing line, a reheating furnace 406, a flash welding device 407 and associated control components 408, a skiving cutter 410, and a rolling stand 412.

[0047] The reheating furnace 406 is arranged and operated to heat the steel billet 406 so that the billet will be suitably ductile for rolling into a rolled product 413 by a rolling station 412 .

[0048] The flash welding device 407 is controlled by a control component 408 and is configured to move along the conveyor 402 with the steel billets so as to successfully flash weld the steel billets together to form a weld joint 409 therebetween.

[0049] The skiving cutter 410 is used to remove excess weld material from the weld joint 409, which is also known as deburring. This produces Figure 4 The deburred weld joint 411 is seen in FIG. 1 , and if this process does not occur or occurs unsuccessfully, the resulting rolled product 413 will include surface defects or "scabs" caused by squeezing in excess weld material.

[0050] The rolling station 412 is configured to roll the formed ring-shaped bar into a rolled product 413 , such as a steel bar or a steel plate, and to smooth any depression or scraping deformation formed in the surface ring-shaped bar after passing through the scraping cutter 410 .

[0051] Figure 1a is a diagram of a "flame cut" billet showing that the billet retains its original square cross section after the cutting operation in the continuous casting process. "Flame cutting" is performed using fuel gas and oxygen. Since no mechanical forces act in the process, the resulting cross section of the billet end retains its original square cross section (see Figure 1a ). This type of billet ends are preferred by manufacturers for flash welding during, for example, ring bar rolling, because their square cross section allows them to be welded together using a standard flash welding process, completely without regard to billet orientation and without any resulting defects. However, this method has the disadvantage that there will be some losses in the case of combustion by fuel gas and oxygen.

[0052] Figure 1bIllustration of the "flame cut" end of a steel billet and its arrangement for successful flash welding and burr removal. This process can be done using Figure 4 405. In addition, the flash welding device 407 and the skiving cutter 410 can be operated in a conventional manner to form a weld joint 409 that can completely remove burrs. As shown, the "flame cut" blanks 101-A and 101-B are flash welded using the flash welding device to form a ring-shaped bar 101-AB and a flash welded joint 102 with excess weld material. One or more skiving cutters can be used to successfully remove burrs from the flash welded joint 102 of the formed ring-shaped bar 101-AB.

[0053] Figure 2a is a photograph of a "diagonally cut" billet, which shows the minimum deformation of this type of billet. The "diagonally cut" billet is cut diagonally by a mechanical shear during the continuous casting process. This has a certain degree of deformation of the resulting cross section of the billet, but still maintains a square cross section and is also useful for flash welding (see Figure 2a ) are acceptable to manufacturers because their cross-section allows them to be welded together using a standard flash welding process, regardless of the blank orientation and without any resulting defects.

[0054] Figure 2b Illustration of the diagonally cut end of a steel billet and its arrangement for successful flash welding and burr removal. This process can be done using Figure 4 405. In addition, the flash welding device 407 and the scraping cutter 410 can be operated in a conventional manner to form a weld joint 409 that can completely remove burrs. As shown, the "diagonal cut" blanks 201-A and 201-B are flash welded using the flash welding device to form a ring-shaped bar 201-AB and a flash weld joint 202 with excess welding material. One or more scraping cutters can be used to successfully remove burrs from the flash weld joint 202 of the formed ring-shaped bar 201-AB.

[0055] Figure 3ais a diagram of a "undercut" billet, which illustrates the deformation characteristics of this type of billet. In the "undercut" method, the cross-section of the end of the billet is severely deformed due to the cutting movement of the shear during the continuous casting process. The mechanical shear can cut the billet from one side across the outline of the billet. The cutting action of the mechanical shear causes the profile of the billet end of the 'undercut' surface of the billet to bend on the longitudinal axis to extend inward away from its end compared to the normal profile of the billet. For example, the undercut billet profile can be bent inwardly from the normal billet profile at a distance of about 25mm or more over a length of 100mm at the end of the billet. For a 150mm by 150mm billet, this can represent a 17% deformation in the 'undercut' surface of the billet profile at its end relative to the billet profile along its length. At the opposite surface, a certain degree of deformation away from the normal billet profile can be formed, so that the opposite surface extends outward, although typically by a smaller amount over a shorter length.

[0056] Figure 3b is a diagram of a "undercut" blank 301 showing the deformation of the end regions of the blank 303 and the normal square cross-sectional profile 302 of the blank remaining away from these end regions. The shading of the diagram (which is only for illustration and does not indicate the physical properties of the blank) is to mark which part of the "undercut" blank 301 constitutes the end region 303; wherein the deformation in the cross section of the blank, performed by one of the side surfaces of the blank, gradually extends inwards into the profile of the blank relative to the normal square cross-sectional profile 302 of the blank away from the end portion of the blank. The dotted lines 304 are to mark the ends of the normal square cross-sectional profile 302 of the "undercut" blank 301 and the beginning of the deformed undercut end regions 303, each of which includes at least 10 cm of the length of the blank.

[0057] Figure 3cBillets 311-A and 311-B with down cut ends are illustrated, which are presented for flash welding with orthogonally aligned deformation and resulting defects, failed flash welding and burr removal. The top side of the billet (the side that the mechanical shear cuts and deforms in the down cut operation) is marked by shading, which is not used to illustrate any physical characteristics of the billet. As shown, the "down cut" billets 311-A and 311-B are flash welded using a flash welding device to form an annular bar 311-AB and a flash welded joint 312 with excess weld material. Here, this is to illustrate what would happen if the billets 311-A and 311-B were flash welded while orthogonally oriented and no billet rotating parts were used to align them (such as would be the case according to the present disclosure). One or more skiving cutters are used to deburr the excess weld material from the flash welded joint 312 of the formed annular bar 311-AB, however, this fails in removing all of the excess weld material. This is due to the skiving cutter being unable to reach the material as it is in a random orientation within the normal cross section of the billet and causing the material to be rolled into the final product as a surface defect or "scab" and the resulting product being rejected as scrap.

[0058] Figure 3d Billets 321-A and 321-B with downcut ends are illustrated, which are presented for flash welding with deformations that are differently orthogonally aligned and resulting defects, failed flash welding and burr removal. The top side of the billet (the side that the mechanical shear cuts and deforms in the downcut operation) is marked by shading, which is not used to illustrate any physical characteristics of the billet. As shown, the "downcut" billets 321-A and 321-B are flash welded using a flash welding device to form an annular bar 321-AB and a flash welded joint 322 with excess weld material. Again, this is to illustrate what would happen if the billets 311-A and 311-B were flash welded while being differently orthogonally oriented and no billet rotating member was used to align them (such as would be the case according to the present disclosure). One or more skiving cutters are used to deburr the excess weld material from the flash welded joint 322 of the formed annular bar 321-AB, however this fails in removing all of the excess weld material. This is due to the skiving cutter being unable to reach the material as it is in a random orientation within the normal cross section of the billet and causing the material to be rolled into the final product as a surface defect or "scab" and the resulting product being rejected as scrap.

[0059] To achieve successful flash welding of billets with undercut billet ends, the inventors have developed a modified process. This includes ensuring that each billet is aligned or transformed into alignment so that the two bent ends are aligned before welding, such as in Figure 3e (opposite undercut alignment) or Figure 3f (Complementary undercut alignment) is aligned to the desired alignment shown in FIG.

[0060] Figure 3e Billets 331-A and 331-B with downcut ends are illustrated, which are presented for flash welding with deformation aligned in opposite directions and the resulting successful flash welding and burr removal. The top side of the billet (the side cut and deformed by the mechanical shear in the downcut operation) is marked by shading, which is not used to illustrate any physical characteristics of the billet. As shown, the "downcut" billets 331-A and 331-B are flash welded using a flash welding device to form an annular bar 331-AB and a flash welded joint 332 with excess weld material. Excess weld material can be successfully deburred from the flash welded joint 332 of the formed annular bar 331-AB using one or more skiving cutters because excess material is only given on two sides in the oppositely aligned configuration. Here, the flash welding time or upset distance or skiving cutter can be adapted to ensure that the excess weld material reliably formed in the desired side surface of the billet (which can be inside the normal cross-sectional profile of the billet) by flash welding can be reliably removed by the skiving cutter. If the flash welding time and upset distance have been adapted to cause the weld material to reliably extend beyond the normal cross-sectional profile of the blank, the skiving cutter may be adapted to cut on both sides within the normal cross-sectional profile of the blank, thereby exhibiting an undercut deformation, although this may not be necessary.

[0061] Figure 3fBillets 341-A and 341-B with downcut ends are illustrated, which are presented for flash welding with deformations that are complementarily aligned in the same direction and the resulting successful flash welding and burr removal. The top side of the billet (the side that the mechanical shear cuts and deforms in the downcut operation) is marked by shading, which is not used to illustrate any physical characteristics of the billet. As shown, the "downcut" billets 341-A and 341-B are flash welded using a flash welding device to form an annular bar 341-AB and a flash welded joint 342 with excess weld material. Excess weld material can be successfully deburred from the flash welded joint 342 of the formed annular bar 341-AB using one or more scraping cutters because the excess material is only given on one side in the complementarily aligned configuration. Here, the flash welding time or upset distance or scraping cutter can be adapted to ensure that the excess weld material reliably formed by flash welding in the desired side surface of the billet (which can be inside the normal cross-sectional profile of the billet) can be reliably removed by the scraping cutter. If the flash welding time and upset distance are suitable to cause the weld material to reliably extend beyond the normal cross-sectional profile of the billet, the skiving cutter may be adapted to cut on both sides inside the normal cross-sectional profile of the billet, thereby presenting an undercut deformation, although this may not be necessary.

[0062] like Figure 4 As shown in, the billet lathe 405 can be controlled to rotate the billet before welding so that the undercut billet ends are aligned. In the flash welding process, for example, compared with the normal flash time and upset distance for flash welding the billet, the flash time can be extended and the upset distance can be increased.

[0063] The flash time of the flash welding device 407 is the time that a high current arc exists between the ends of the billet and is used to partially melt the ends of the billet, and the upsetting distance is the distance that the billet travels on the conveyor 402 while being squeezed together so as to achieve the function of fusing the partially melted ends of the billet to form an annular bar.

[0064] For example, a flash time greater than 20 seconds may be used and an upset distance greater than 40 mm may be used. The flash time and / or upset distance can be varied to be sufficient to form a weld in the aligned billet ends that, when scraped by the skive cutter / deburrer, ensures that surface defects are avoided. This can be achieved by extending the flash time and upset distance to cause the excess weld 409 to protrude further beyond the profile of the billet, allowing the skive cutter(s) 410 to better access the joint to successfully deburr the joint.

[0065] The billet orientation determining component 403 is used to determine the orientation of the cut end of the incoming steel billet 401, and is coupled to the billet rotating component 405 via the control component 404, so that the billet to be welded to the previously welded billet can be rotated around its longitudinal axis to align the cut end at the front of the billet with the cut end at the rear of the previously welded billet, so that the weld joint 409 to be formed by the flash welding device 407 can be successfully deburred by the scraping cutter 410.

[0066] A camera coupled to a processor that is configured, for example, by software, to operate a billet rotation device at the charging side of the reheating furnace 406 can be used to detect and correct the orientation of billets that may be rotating inside the reheating furnace 406 (i.e., as a billet orientation determination component 403). The same camera and rotation device configuration can additionally or alternatively be used at the discharge side of the reheating furnace (e.g., in the case where the billets are rotated inside a walking hearth furnace). Figure 3e or Figure 3f In the configuration shown in , a processor-coupled camera can capture an image of the tail end of the first blank and can rotate the next blank to match the tail end of the previous blank. In this way, the random orientation of the blanks has been limited to only complementary alignment or opposite orientations, and successful clean scraping of the excess weld joint will be performed accordingly.

[0067] The skiving cutter(s) 410 (which performs the burr removal) may also be configured to make a deeper cut for the undercut(s) with inwardly bent ends in order to remove the excess weld formed. As seen in the annular bars 331-AB and 341-AB of FIG. 3 , this deeper cut may result in a slight depression in the cross-section of the billet at the joint. This slight depression will disperse after passing through at least one or both of the rolling stands 413, so that the cross-section of the rolled product is balanced along the length without any defects or scabs in the finished product. In this way, the problem of flash welding of "undercut" billets can be overcome.

[0068] Figure 5 A flow chart detailing a method for successfully welding "down cut" billets together into ring-shaped bars for rolling into rolled products is shown.

[0069] In step 501, the orientation of the undercut end of the front portion of a blank to be welded to the rear portion of a previously welded blank is determined.

[0070] In step 502, it is determined based on the determined orientation whether the blank to be welded to the previously welded blank needs to be rotated about the longitudinal axis of the blank to align the undercut end at the front of the blank with the undercut end at the rear of the previously welded blank so that the weld to be formed by the flash welding device can be successfully deburred by the skiving cutter.

[0071] In step 503, a billet rotating component is operated based on the determined rotation to rotate the billet around a longitudinal axis of the billet for flash welding to form a ring-shaped bar for continuous rolling into a rolled product.

[0072] In step 504, flash welding of the aligned blanks is performed using a flash welding device.

[0073] In step 505, one or more skiving cutters are used to deburr excess welding material from the flash welded joint of the formed ring-shaped bar.

[0074] In step 506, the formed ring-shaped bar is continuously rolled into a rolled steel product.

[0075] The object of the present invention is to make a flash welding machine more versatile, able to accept all kinds of billet end cuts including undercut ends, with clear advantages due to flexibility.

Claims

1. A flash welding method for welding together steel billets having undercut ends to form annular bars for continuous rolling into rolled products, each undercut end comprising a deformation in the cross section of the billet made by a side surface of the billet, the side surface gradually extending inwardly into the profile of the billet in the end region of the billet relative to the normally square cross-sectional profile of the billet remote from the end region of the billet, the method using a flash welding device and one or more skiving cutters for removing excess weld material, the method comprising the steps of: orienting an undercut end of a front portion of a blank to be welded to a rear portion of a previously welded blank; determining, based on the orientation, whether the blank to be welded to the previously welded blank needs to be rotated about the longitudinal axis of the blank to align the undercut end at the front of the blank with the undercut end of the rear of the previously welded blank so that a flash welded joint to be formed by the flash welding device can be deburred by the skive cutter so that all excess weld material is removed; operating a blank rotating component based on the determined orientation to rotate the blank about the longitudinal axis of the blank; flash welding the aligned blanks using the flash welding device; as well as The flash weld joint is deburred using the one or more skive cutters such that all excess weld material is removed from the annular bar.

2. The method according to claim 1, wherein: The undercut end of each blank is characterized by: The side surfaces extend inwardly into the profile of the blank by at least 25 mm or by at least 10% of the thickness of the normally square cross-sectional profile of the blank.

3. The method according to claim 1 or 2, wherein: The end region comprises at least 10 centimetres at the end of the blank.

4. The method according to claim 1 or 2, further comprising controlling the flash time and upset distance of the flash welding device to be sufficient to cause the excess weld material to protrude beyond the contour of the blank on the side surface to allow the flash weld joint to be deburred by the one or more skiving cutters so that all excess weld material is removed.

5. The method according to claim 1 or 2, wherein: The skiving cutter is configured to cut within the contour of the normally square cross-section of the annular bar at least on the side surface so that the depth of the cut is sufficient to remove all excess weld material from the flash weld joint.

6. The method according to claim 1 or 2, wherein: Said rotation of the blank to be welded to the previously welded blank about its longitudinal axis will complementarily align the undercut ends of the blanks to be welded together in the same direction or oppositely align the undercut ends of the blanks to be welded together in opposite directions so that the flash welded joint can be deburred by the skiving cutter so that all excess welding material is removed.

7. The method according to claim 1 or 2, wherein: The ring-shaped bar is rolled in one or more rolling stands such that the rolled product is free of surface defects from the excess weld material.

8. A flash welding apparatus for welding together steel billets having undercut ends to form annular bars for continuous rolling into rolled products, each undercut end comprising a deformation in the cross section of the billet made by a side surface of the billet which in the end region of the billet gradually extends inwardly into the profile of the billet relative to the normally square cross-sectional profile of the billet remote from the end region of the billet, the apparatus comprising: a billet orientation determining component for determining an orientation of a cut end at a front portion of a billet to be welded to a rear portion of a previously welded billet, and determining based on the orientation whether the billet to be welded to the previously welded billet needs to be rotated about a longitudinal axis of the billet to align the cut end at the front portion of the billet with the cut end at the rear portion of the previously welded billet; a blank rotating device configured to rotate the blank about the longitudinal axis of the blank to achieve the alignment based on the determined orientation; a flash welding device for flash welding the aligned blanks to form the annular bar; one or more skiving cutters for deburring the flash welded joints between the blanks so that excess weld material is removed; The determined orientation determined by the blank orientation determining means in use enables the flash weld joint to be deburred by the skive cutter such that all excess weld material is removed.

9. The device according to claim 8, wherein: The blank rotating component, in use, rotates the blank to be welded to the previously welded blank about its longitudinal axis to complementarily align the undercut ends of the blanks to be welded together in the same direction or to oppositely align the undercut ends of the blanks to be welded together in opposite directions, so that the flash welded joint can be deburred by the skiving cutter so that all excess welding material is removed.

10. The device according to claim 8 or 9, wherein: The flash welding apparatus is configured such that the flash time and upset distance of the flash welding apparatus are sufficient to cause the excess weld material to protrude beyond the contour of the blank on the side surface to allow the flash weld joint to be deburred by one or more skiving cutters so that all excess weld material is removed.

11. Apparatus according to claim 8 or 9, further comprising a reheating furnace arranged to heat each billet prior to flash welding so that the ring-shaped bar is sufficiently ductile to be rolled into a rolled product.

12. The device according to claim 11, wherein The billet orientation determination component includes one or more cameras coupled to one or more processors, positioned between the reheat furnace and the flash welding device to determine the orientation of the undercut end of a billet.

13. The apparatus according to claim 8 or 9, further comprising one or more rolling stands for continuously rolling the ring-shaped bar into a rolled product.

14. The apparatus according to claim 8 or 9, wherein: The skiving cutter comprises a separate cutting element for each contoured surface of the annular bar.

15. The apparatus according to claim 8 or 9, wherein: The skiving cutter is configured to cut within the contour of the normally square cross-section of the annular bar at least on the side surface so that the depth of the cut is sufficient to remove all excess weld material from the flash weld joint.

16. The apparatus according to claim 8 or 9, wherein: The one or more skiving cutters deburr the flash weld joint so that the ring bar can be continuously rolled into a rolled product by one or more rolling stands without surface defects from excess weld material.

Images