EP-4635674-B1 - METHOD OF PRODUCING WELDED PLATE GIRDERS FROM THERMALLY CUT SHEETS

EP4635674B1EP 4635674 B1EP4635674 B1EP 4635674B1EP-4635674-B1

Inventors

Kudla, Krzysztof
Wojsyk, Kwiryn
Makles, Krzysztof
Macherzynski, Michal
Jokiel, Jerzy

Dates

Publication Date: 20260506
Application Date: 20240415

Claims (2)

A method of producing welded plate girders from thermally cut sheets, in which blanks are thermally cut from a sheet of steel sheet with a metallically clean surface prepared for cutting and subjected to a straightening operation, and then, after immobilizing the cut sheet blanks relative to each other, they are welded together in components of the structure or its entirety, characterized in that each thermally cut sheet metal blank is subjected to a symmetrical compression process simultaneously on the top and bottom of the sheet metal blank, using cylinders or rollers, before the welding operation, until a permanent reduction in the thickness of the sheet metal blank is achieved in the range of 0, 5 to 1.5% of the thickness of the initial sheet metal, in an area along its thermally cut edges with a strip of at least 20 mm wide, including the heat affected zone resulting from the thermal cutting operation.
A method for producing welded plate girders according to claim 1, characterized in that the sheet metal blank, after symmetrical compression from the top and bottom of the sheet metal blank using cylinders or rollers, is subjected to a dynamic or static burnishing process along its thermally cut edges.

Description

The subject of the invention is a method for producing welded plate girders from thermally cut sheets with a thickness of 3 to 40 mm, see claim 1. The method according to the invention is intended for use by manufacturers of plate girders and steel structures. Current methods of producing welded structures from thermally cut sheets from metallurgical sheets to a given size include pre-welding cold straightening operations - for example using hydraulic presses or cylinders, tension along the plane of the sheets, local mechanical action with hammers, wedges and various types of clamps, and with optional using flame straightening. The last stages of manufacturing plate girders are tacking and welding the sheets into subassemblies or joining them together and finally checking the final dimensions of the workmanship to determine the level of deformation of the welded structure. Tacking and welding are carried out freely or in stiffening devices designed to reduce or prevent significant shape deviations of the constructed structures. In the latter case, however, there is an uncontrolled increase in both elastic and plastic stresses, leading not only to jamming of the structure in the devices but often to construction cracks. After the plate girder has been manufactured, the deformed elements are straightened. Straightening of plate girders to obtain the assumed dimensional tolerance is perform ed mechanically or thermally. However, due to the currently used materials that are sensitive to heat input and leading to their structural degradation, thermal straightening methods are eliminated from the sheet girder manufacturing process. After the thermal cutting process of sheet metal, a narrow zone of high-value tensile stresses is created near their edges and cutting surfaces, which is the result of the influence of the heat zone, which, when qualitative cutting is carried out under optimal conditions of the thermal cutting process in sheet metals with a thickness of 3 to 40 mm, does not exceed 30 mm, and in the case of laser or plasma cutting, it is generally from 1 to 20 mm. A similarly negative phenomenon of creating high tensile stresses occurs during welding of sheet metal, which adds up to the tensile stresses arising after the thermal cutting process, and when the accumulated tensile stresses exceed the yield strength of the material, an uncontrolled increase in stress occurs, which results in significant deformation of steel structure elements, e.g. T-beam, box-girders, etc. included in the final welded structure. The process of producing steel structure elements from sheet metal in this way inevitably leads to implementation conditions requiring the use of extremely time-consuming and expensive straightening operations of the constructed structure elements. Straightening operations are not only complicated and require highly qualified technical staff, but also extremely time-consuming and expensive, which radically reduces production efficiency. A method for producing steel sheets without dimensional deformations is known from the Polish patent description of the invention PL223629B1. In this method, sheets are obtained from hot-rolled steel sheets and strips, which are tightly rolled in the form of high-mass coils, which are then unwound on a decoiler. The method of producing steel sheets consists in mechanical cleaning of the surface and cold rolling, which introduces deformations of the strip as a result of reducing its thickness in the range from 0.5 to 5%, but most often in the range from 1.0 to 2.5 %, then longitudinal cutting, straightening and cross cutting are performed within one workstation. Longitudinal cutting operations are performed before the straightening operation, which is performed with the vertical adjustment of the rollers in a multi-roll straightener, while cross-cutting operations are performed immediately after the straightening operation, while the belt is running. A method for removing uneven residual stresses arising in thermally cut steel sheets is known from the Japanese invention application JP2000301220A. As a result of thermal cutting, stresses appear in sheet metal, causing elongation, contraction and transverse bending of the sheet. If the deformation of the steel sheet due to the release of residual stresses is large, the shape and length of the cut steel sheet may deviate from the tolerance range. In this method, the stress values are measured in several places, and the residual stress values are corrected depending on the length of the tested element. The method consists in measuring the temperature distribution on the surface of a thermally cut steel sheet that has been straightened using a hot straightening device using a thermometer. Then, based on the measured temperature, the distribution of residual stresses in the tested sheet metal is calculated, on the basis of which parameters are determined and compared with its permissible values. When these parameters are n