Method for producing steel fibers

Abstract

A method of making steel fibers, preferably for use as a concrete additive, and for the supply thereof in making steel fiber concrete, characterized in that to form the steel fibers ( 2 ) first a sheet-metal strip ( 1 ) is notched either on one face or both faces so as to form steel-fiber wires ( 4 ) that are initially connected together by webs ( 5 ), and that further, for subsequently converting the webs ( 5 ) into thin easily mutually separable separation webs forming separation surfaces that are fracture-rough and low in burring upon separation, the steel-fiber strip is subjected to a flexing process in which each web ( 5 ) is subjected to multiple bending deformations about its longitudinal axis in such a way that incipient cracks are produced at the webs ( 5 ) due to fatigue fracture and thus the separation webs are produced.

1 . A method of making steel fibers for use as a concrete additive, and for the supply thereof in making steel fiber concrete, the method comprising the steps of:
 to form the steel fibers, first notching a sheet-metal strip on one face or both faces so as to form steel-fiber wires that are initially connected together by webs, and   thereafter, for converting the webs into thin easily mutually separable separation webs forming separation surfaces that are fracture-rough and low in burring upon separation, flexing the steel-fiber strip by subjecting each web to multiple bending deformations about its longitudinal axis in such a way that incipient cracks are produced at the webs due to fatigue fracture and thus the separation webs are produced.   
     
     
         2 . The method according to  claim 1 , wherein in the notching operation the steel-fiber wires are provided with anchor formations formed by interruptions in the notching operation. 
     
     
         3 . The method according to  claim 1  wherein the steel-fiber wires are formed transversely to the longitudinal direction of the sheet-metal strip. 
     
     
         4 . The method according to  claim 1  wherein the steel-fiber wire strip, which after the notching operation extends over the entire width of the sheet-metal strip, is subdivided by separation blades into two or more steel-fiber substrips. 
     
     
         5 . The method according to  claim 4 , wherein the steel-fiber wire strip is subdivided prior to the flexing process. 
     
     
         6 . The method according to  claim 1  wherein, after the flexing process, the steel-fiber strips pass through a shaping roller for shaping the steel-fiber wires in accordance with intended use. 
     
     
         7 . The method according to  claim 1  wherein, after complete production, the steel-fiber strips are wound into a coil. 
     
     
         8 . The method according to  claim 1  wherein the operation of separating the steel-fiber strips into steel fibers is done at the location of concrete preparation. 
     
     
         9 . The method according to  claim 1  wherein the steel-fiber wires are formed longitudinally of the sheet-metal strip. 
     
     
         10 . The method according to  claim 1 , wherein after the flexing process the upper face and/or the lower face of the strip is roughened up by knurling. 
     
     
         11 . The method according to  claim 1 , wherein the steel-fiber wires oriented longitudinally of the strip are separated from each other. 
     
     
         12 . The method according to  claim 1 , wherein, after separation, the steel-fiber wires are subjected by a shaping tool to a shaping operation corresponding to intended use. 
     
     
         13 . The method according to  claim 1 , wherein, after shaping, the steel-fiber wires are cut to the desired length for the steel fiber. 
     
     
         14 . The method according to  claim 1  wherein the notching produces notches of V-shape. 
     
     
         15 . The method according to  claim 14 , wherein a notch angle is between 30° and 120°. 
     
     
         16 . The method according to  claim 14 , wherein a notch angle is about 60°. 
     
     
         17 . The method according to  claim 1 , wherein the thickness of the webs is 20% to 95% of the thickness of the strip. 
     
     
         18 . The method according to  claim 1 , wherein the depth of the V-shaped notches is so selected that it corresponds to the strength of the starting material and the intended use of the steel fiber. 
     
     
         19 . The method according to  claim 1 , wherein the flexing process includes multiple bending deformation to one side of a plane of the steel-fiber strip until fatigue fracture at the webs. 
     
     
         20 . The method according to  claim 1  wherein the flexing process includes multiple bending deformation to both sides of a plane of the steel-fiber strip until incipient fatigue fracture cracks occur at the webs. 
     
     
         21 . The method according to  claim 20 , wherein the multiple bending deformation of the webs is done through identical angular extents. 
     
     
         22 . The method according to  claim 20 , wherein the multiple bending deformation of the webs is done through increasing or decreasing angles. 
     
     
         23 . The method according to  claim 20 , wherein the multiple bending deformation of the webs is done through an angle less than the notch angle. 
     
     
         24 . The method according to  claim 1  wherein the separation webs are locally broken by slight oppositely directed deflection of immediately adjacent steel-fiber wires. 
     
     
         25 . The method according to  claim 1  wherein semifinished material in strip form of metal is used as the starting material. 
     
     
         26 . A steel-fiber strip or steel-fiber wire strip of metal having a plurality of parallel steel-fiber wires connected together by webs and produced in accordance with  claim 1 , wherein semifinished material in strip form is used as starting material and that, for forming steel-fiber wires initially still connected together by webs, is notched on one face or on both faces and in the notching operation is provided with anchor formations, wherein the webs are converted by multiple bending deformations by means of a flexing process to form thin easily separable separation webs that form low-burring and fracture-rough separation surfaces upon separation and that have fatigue fractures, and the steel-fiber wires and the steel-fiber strips are subjected to a shaping operation such that steel fibers suitable as an additive to concrete are formed in the individual separation operation of the steel fibers from the steel-fiber strip or the steel-fiber wire strip. 
     
     
         27 . The steel-fiber strip or steel-fiber wire strip according to  claim 26 , wherein high-quality steel- or iron-based materials are the metallic starting material. 
     
     
         28 . The steel-fiber strip or steel-fiber wire strip according to  claim 26 , wherein galvanized or copper-plated steel strip are the metallic starting material. 
     
     
         29 . The steel-fiber strip or steel-fiber wire strip according to  claim 26 , wherein the metallic starting material is a material with which particularly high strength values can also be achieved by rolling for the respective material. 
     
     
         30 . The steel fiber produced in accordance with  claim 1 , wherein the steel fiber is formed from semifinished material in strip form that is used as the starting material and that, for forming steel-fiber wires that are initially still connected together by webs, is notched on one face or on both faces and is provided with anchor formations in the notching operation, wherein the webs are converted by multiple bending deformations by means of a flexing process to form thin separation webs that form easily separable separation surfaces n that have low burring and are fracture-rough upon separation, and that have fatigue fractures. 
     
     
         31 . The steel fiber according to  claim 30 , wherein it is of a shape suitable for addition to concrete.