Method for fabricating steel wire cable comprising zinc- aluminium alloy plating

Abstract

A method for fabricating a steel wire cable having a Zn—Al alloy plating, the method including: arranging steel wires according to an arrangement rule at a cross section of the steel wire cable; controlling a length of the overall cable by a length of a central standard wire; twisting a bunch of the steel wires comprising a zinc-aluminum alloy plating with a torsion angle of between 2° and 4°; wrapping the steel wire bunch with a polyester wrapping bandage and covering a resulting product with a double-layered protective polyethylene sheath; anchoring the two ends of the steel wire cable by anchors using fillers; and coiling the finished-product of the steel wire cables.

The invention claimed is: 
     
         1 . A method for fabricating a steel wire cable, comprising:
 1) preparing steel wires comprising a zinc-aluminum alloy plating, wherein the zinc-aluminum alloy plating has an aluminum content of between 4.2 and 7.2 wt. % or of between 9.2 and 12.2 wt. %, and a weight of the zinc-aluminum alloy plating is equal to or larger than 300 g/m 2 ;   2) selecting a steel wire, which is to be positioned at a center position of a cross section of the steel wire cable, as a standard wire, applying a certain tension force to two ends of the steel wire to straighten the steel wire and performing stress correction and temperature correction to prepare a steel wire having a standard length; making certain markers at two ends of the steel wire; taking the steel wire having the standard length as a reference, and controlling an overall length of the steel wire cable;   3) relaxing the steel wires, positioning the standard wire at the center position of the cross section of the steel wire cable comprising a plurality of layers of steel wires; twisting the steel wires to the left with a torsion angle of between 2° and 4° to yield a steel wire bunch; wrapping the steel wire bunch to the right by a wrapping bandage to yield a naked steel wire cable as a semi-product; and calculating a relaxed length L /  of other layers of steel wires surrounding the standard wire considering the length of the standard wire and a torsion rate according to the following equation:
     L   0   =L   / ×cos α+ K  
 
   in which, α represents the torsion angle ranging from 2° to 4°; K represents a fabrication allowance, m, which is selected according to specifications and operations; L /  represents the relaxed length, m, of other layers of the steel wires surrounding the standard wire; and L 0  represents the length, m, of the standard wire at the center position;   4) preparing a double-layered protective polyethylene outside the naked steel wire cable, wherein the double-layered protective polyethylene has a density of between 0.942 and 0.978 g/cm 3 , environmental stress crack resistance property of ≥5000 F 0 /h, and a melt index of ≤0.45 g/10 min; before extruding, presetting a die aperture of an extruder and an extrusion velocity according to an outer diameter of the naked steel wire cable and thicknesses of two layers of polyethylene; wherein the die aperture of the extruder is provided with two layers of discharge channel, and the two layers of polyethylene simultaneously cover the naked steel wire cable during the extrusion;   5) determining original cutting positions of the steel wire cable, locally stripping the double-layered protective polyethylene, finding the markers for cutting at two ends of the standard wire at the center position of the steel wire cable; cutting the steel wire cable by using a non-liquid cutting machine and ensuring end faces of the steel wire cable perpendicular to an axis of the steel wire cable; stripping the double-layered protective polyethylene according to a preset length to expose the steel wires;   6) providing an anchor functioning as a main connecting structure to transmit a tension of the steel wire cable to a tower and a girder; performing hot galvanizing or paint coating on the anchor for corrosion resistance, wherein a thickness of the hot galvanizing is equal to or larger than 90 μm, and a thickness of the paint coating is determined according to specifications and design requirements of a steel structure; and casting the anchor by chill casting of heading anchor or by hot casting of anchor, operations of which are as follows:   A. chill casting of the heading anchor comprising:   a. fixing ends of the steel wires in anchor cups on a casting platform, removing oil stains and rusts from portions of the steel wires inside the anchor cups, and synchronously washing inner walls of the anchor cups;   b. uniformly dispersing the ends of the steel wires corresponding to holes of anchor plates, and heading each steel wire by using a heading machine, wherein heading dimensions are as follows: heading diameter ≥1.4 D, heading height ≥1.0 D, and D represents a diameter of the steel wires; and   c. providing and uniformly mixing a chilled filler comprising steel balls, a stone dust, an epoxy resin, a curing agent, di-n-butyl, and a diluent; pouring a mixture of the chilled filler into the anchor cups while vibrating by using a vibration pump to fully fill gaps among the anchor cup and steel wires with the mixture of the chilled filler;   B. hot casting of anchor comprising:   providing a zinc-copper alloy comprising 98±0.2 wt. % of zinc and 2±0.2 wt. % of copper, or a zinc-copper-aluminum alloy comprising 4-7 wt. % of aluminum, 1-2 wt. % of copper, and 91-95 wt. % of zinc; and performing casting as follows:   a. perpendicularly fixing ends of the steel wires in anchor cups on the casting platform, dispersing steel wires comprising a zinc-aluminum alloy plating inside the anchor cups in the form of concentric circles, removing oil stains and rusts from surfaces of the steel wires, and simultaneously washing the inner walls of the anchor cups;   b. keeping the center of the steel wire cable coincide with centers of the anchor cups and preventing steel wires from contacting the anchor cups;   c. sealing bottom openings of the anchor cups to prevent the alloy from leaking via the bottom openings; and preheating the anchor cups; and   d. pouring the zinc-copper alloy or the zinc-copper-aluminum alloy into the anchor cups for one-step casting while avoiding any vibration or disruption;   7) according to fillers for the casting of the anchor, performing tension detection on the steel wire cable with chilled-casted anchor or performing top pressure detection on the steel wire cable with hot-casted anchor before leaving a plant, which comprises:   for the steel wire cable with the chilled-casted anchor, stretching the steel wire cable by an overstretching force which is set to be between 1.1 and 1.5 folds of a designed tension of the steel wire cable and satisfies that a retraction value of a casting body inside the anchor cup after stretching is equal to or less than 6 mm;   unloading the overstretching force to be 20% of the original overstretching force or to be the designed tension of the steel wire cable after the stretching; measuring a length of the steel wire cable at a constant temperature in the dark, and calculating a stressless length of the steel wire cable at a reference temperature according to the following equation:   
       
         
           
             
               
                 L 
                 CO 
               
               = 
               
                 
                   L 
                   CP 
                 
                 
                   1 
                   + 
                   
                     
                       P 
                       20 
                     
                     EA 
                   
                   + 
                   
                     α 
                      
                     
                       ( 
                       
                         t 
                         - 
                         
                           t 
                           0 
                         
                       
                       ) 
                     
                   
                 
               
             
           
         
         in which, L C0  represents the stressless length, m, of the steel wire cable at the reference temperature; L CP  represents a length, m, of the steel wire cable loaded with a tension force of P 20 ; P 20  represents 20% of the overstretching force, N; A represents a nominal area, mm 2 , of the steel wire bunch of the steel wire cable; E represents an elastic modulus, MPa; α represents a coefficient of linear expansion of a stay cable which is equal to 0.000012/° C.; t represents the constant temperature, ° C., when measuring a length of the stay cable; and to represents a designed reference temperature, ° C., of the stay cable; and 
         for the steel wire cable with hot-casted anchor, applying, to the steel wire cable, a top pressure which is 1.25 folds of the designed tension of the steel wire cable and satisfies that a retraction value of the casting body inside the anchor cup after the top pressure detection is equal to or less than 6 mm; and 
         8) packing an outer surface of the steel wire cable, coiling layers of the steel wire cables successively by using a coil frame, wherein an inner diameter of a resulting coil is equal to or larger than 20 folds of an outer diameter of the steel wire cable and is equal to or larger than 1.6 m. 
       
     
     
         2 . The method of  claim 1 , wherein when determining the length of the standard wire in 2), stress correction and temperature correction are carried out according to the following equation:
     L=L   0 ×[(1+ F/EA )+α( T− 20)]
   in which, L represents a length (m) of the steel wire in a stressed state, L 0  represents a designed length, m, of the steel wire in an unstressed state, F represents a tensioning force, N, E represents an elastic module, MPa, of the steel wire, and fabrication of the standard wire adopts a measured value, A represents an area of a cross section, m 2 , of the steel wire, and fabrication of the standard wire adopts the measured value, a represents an expansion coefficient of the steel wire, and T represents a temperature of the environment.   
     
     
         3 . The method of  claim 1 , wherein in extrusion process in 4), a magnetic field is arranged above the steel wire cable to make the steel wire cable in a suspension state; after the extrusion process, the double-layered protective polyethylene and the naked steel wire cable are concentrically arranged. 
     
     
         4 . The method of  claim 1 , wherein an outer surface of the double-layered protective polyethylene is provided with helical lines or embossments, and a drag coefficient is equal to or smaller than 0.8. 
     
     
         5 . The method of  claim 1 , wherein structures of the anchors in 6) adopt a nut-screwing type anchor, an anchor plate gap adjusting type anchor, or a fork-ear pin joint type anchor at two ends of the steel wire cable. 
     
     
         6 . The method of  claim 1 , wherein in 7), an error of the stressless length of the steel wire cable at the reference temperature satisfies the following requirements:
 when L C0 ≤100 m, the error is less than or equal to 10 mm; and   when L C0 >100 m, the error is less than or equal to L C0 /20000+5 mm.   
     
     
         7 . The method of  claim 1 , wherein the wrapping bandage is a bandage made from a polyester fiber; the wrapping bandage has a width of between 40 and 60 mm and a tensile strength of equal to or high than 500 N/25 mm 2 .