EP0788847A1 - Fil en acier pour la fabrication de treillis soudé par résistance électrique - Google Patents

Fil en acier pour la fabrication de treillis soudé par résistance électrique Download PDF

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Publication number
EP0788847A1
EP0788847A1 EP97100966A EP97100966A EP0788847A1 EP 0788847 A1 EP0788847 A1 EP 0788847A1 EP 97100966 A EP97100966 A EP 97100966A EP 97100966 A EP97100966 A EP 97100966A EP 0788847 A1 EP0788847 A1 EP 0788847A1
Authority
EP
European Patent Office
Prior art keywords
wire rod
diameter
wire
less
drum
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97100966A
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German (de)
English (en)
Inventor
Felice Zucchi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alfa Acciai SpA
Original Assignee
Alfa Acciai SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alfa Acciai SpA filed Critical Alfa Acciai SpA
Publication of EP0788847A1 publication Critical patent/EP0788847A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
    • B21C37/04—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of bars or wire
    • B21C37/045—Manufacture of wire or bars with particular section or properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
    • B21B1/163—Rolling or cold-forming of concrete reinforcement bars or wire ; Rolls therefor
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/08—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B15/00—Arrangements for performing additional metal-working operations specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B2015/0071—Levelling the rolled product
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/004—Heating the product
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/04—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing

Definitions

  • the present invention relates to a method for producing highly ductile electrically welded steel nets, particularly for use as reinforcement frames in the manufacture of reinforced-concrete structures.
  • Electrically welded steel nets for reinforced-concrete structures are generally obtained starting from a steel wire rod which is cold-rolled, wound on reels, and then unwound, arranged in a net-like configuration, and electrically welded.
  • the method currently used in the production of electrically welded nets starts, as mentioned, from steel wire rods with a chemical composition that provides for no more than 0.05-0.16% carbon, no more than 0.40-0.80% manganese, no more than 0.08-0.25% silicon according to the diameter of the wire rod, and no more than 0.045% phosphor, no more than 0.045% sulfur, no more than 0.045-0.50% copper and tin, no more than 0.20% chrome and nickel, and no more than 0.05% molybdenum.
  • the wire rod with this chemical composition, has ultimate tensile strengths that vary between 380 N/mm 2 and 530 N/mm 2 from the smallest diameter of 5.5 mm to the largest diameter of 14 mm, yield strengths that vary between 250 N/mm 2 and 350 N/mm 2 , and a breaking elongation of more than 23-27%.
  • the steel wire rod is then subjected to a cold-rolling operation which is inappropriately termed "drawing".
  • This operation has three basic purposes.
  • a first purpose is to obtain from the wire rod a bar having the intended diameter, which is usually 1 mm smaller than the initial wire rod for smaller diameters and 2 mm smaller for larger diameters, and to obtain anchoring ribs on the bar surface.
  • a second purpose is to improve the mechanical characteristics, i.e., to increase the ultimate tensile strength and the yield strength as a consequence of the work-hardening caused by drawing.
  • a third purpose of the drawing operation is to perform mechanical descaling, i.e. , to remove from the wire rod surface the so-called "calamine” constituted by ferrous oxide and ferric oxide, so as to allow a successful subsequent electric welding operation during the assembly of the bars to form the net.
  • the work-hardening caused by cold-rolling in addition to positively increase the ultimate tensile strength and the yield strength, has the drawback of reducing ductility, which is expressed by the ratio between the ultimate tensile strength and the yield strength, as well as percentage elongation.
  • this method which has been used up to now, provides on the average for an electrically welded net which is unlikely to fully meet the above-mentioned standards, since it does not allow to obtain a ratio of at least 1.1 between ultimate tensile strength and yield strength.
  • a principal aim of the present invention is to solve the above problem by providing a method which allows to produce an electrically welded net of higher quality with respect to conventional electrically welded nets obtained by cold-rolling.
  • an object of the invention is to provide a method which allows to produce high-ductility electrically welded nets which are fully satisfactory as regards current statutory provisions covering electrically welded nets for reinforced-concrete structures.
  • Another object of the invention is to provide a method which can be performed with commercially available equipment and facilities.
  • Another object of the invention is to provide a method which allows to produce electrically welded nets at competitive costs.
  • a method for producing electrically welded steel nets particularly for use as reinforcement frames in the manufacture of reinforced-concrete structures, characterized in that it consists in subjecting a steel billet, having a composition containing substantially between 0.16 and 0.22% carbon, to rolling after heating in a furnace up to approximately 1200 o C, and in subsequently subjecting the wire rod produced by the rolling process to a cold-deformation treatment and to assembly in a net-like configuration by electric welding.
  • the method according to the invention substantially consists in starting from a steel billet, preferably having a diameter of 130 mm, which has a composition containing substantially between 0.16 and 0.22% carbon and preferably substantially between 0.80 and 0.95% manganese, substantially between 0.20 and 0.30% silicone, less than 0.045% phosphor, less than 0.045 sulfur, less than 0.55% copper, less than 0.055% tin, less than 0.25% chromium, less than 0.30% nickel, and less than 0.05% molybdenum, which in any case allow to keep the value of C eq below the 0.50 value prescribed by standards, and less than 0.013% nitrogen, as prescribed by weldability standards.
  • This billet is first heated in a preheating furnace, preferably of the "pusher" type, i.e. , a conventional furnace wherein the entire charge, in a single layer, is pushed towards the hot region and subsequently towards the discharge section.
  • This furnace adapted for preheating materials having a low carbon content, is capable of maintaining limited surface oxidation levels which can accordingly be easily removed in view of the intrinsic brittleness. This fact can be explained because in this furnace the inserted billets are not struck by the hot products of combustion but are heated by the reverberatory effect of the radiating roof lying above the inserted charge of billets and contains the flat combustion chamber.
  • the heating cycle in the "pusher" heating furnace includes the loading of the billets at a temperature of no more than 300 o C, retention in the preheating region at a temperature substantially between 600 o C and 700 o C for a period substantially between 35 and 45 minutes, travel through the heating region with an initial region temperature of 800 o C and a final region temperature of 1240 o C, over a period between 45 and 55 minutes, retention in the equalization region at a temperature substantially between 1180 o C and 1220 o C, to complete heat penetration, for a further 25-35 minutes.
  • the billet is discharged and rolled.
  • the temperature measurable on the billet surface is between 1070 and 1090 o C and the surface layer of oxides is poorly anchored, thin, and can be easily eliminated by the first rolling stages. This allows to continue the entire rolling process by a plurality of consecutive reduction steps, maintaining a surface that is practically free from secondary oxidations on the rolled part.
  • the ratio between the volumes of the fuel and of the comburent in the heating furnace is preferably kept between 1:8.5 and 1:9.3 so as to obtain, even in case of unwanted retentions of the billets in the heating regions, a surface oxidation layer compatible with subsequent treatments. This is possible since, in case of accidents along the subsequent rolling mill train or in case of anomalies in the discharge sequences, the billets in the furnace, which have by then reached the correct temperature, can be retained for further time without problems, the environment inside the furnace being partially reducing by the above-mentioned fuel-comburent ratios.
  • the billets After heating, the billets are rolled and then cold-shaped; this is followed by assembly in a net-like configuration by electric welding.
  • Rolling is performed in successive steps in order to gradually reduce the diameter of the billet until a wire rod of the desired diameter, preferably between 6 and 12 mm, is obtained, with rolls preferably shaped so as to obtain anchoring ribs 2 (figure 1) on the surface of the wire rod 1.
  • At least the finishing rolls of the rolling mill trains are preferably made of tungsten carbide, have excellent resistance to wear when hot, and allow to obtain, for the rolled wire rod, a smooth, roughness-free surface so as to prevent the formation of an excessive anchoring base for the formation of the final oxidation layer.
  • the ribbed wire rod 1 is provided with ribs having: for a diameter of 6 mm, a height that is substantially between 0.30 and 0.60 mm and preferably equal to 0.60 mm; for a diameter of 8 mm, a height which is substantially between 0.40 and 0.80 mm and preferably equal to 0.70 mm; for a diameter of 10 mm, a height which is substantially between 0.50 and 1 mm and preferably equal to 0.90 mm; for a diameter of 12 mm, a height which is substantially between 0.60 and 1.20 mm and preferably equal to 1 mm.
  • the wire rod produced by the rolling process has, on the average, an ultimate tensile strength of 552-620 N/mm 2 , a yield strength of 360-400 N/mm 2 , and a breaking elongation of more than 22%.
  • the wire rod 1 at the end of the rolling process, has a surface oxide layer with a thickness substantially between 0.010 mm and 0.045 mm, and that said thickness value is determined by the setting up of the rolling cycle.
  • the wire rod is wound in coils having preferably an inside diameter of 800-900 mm, an outside diameter of 1100-1200 mm, and a height of 800-1100 mm.
  • the subsequent cold-deformation treatment can be constituted by a straightening process in a first embodiment of the method according to the invention or, in a second embodiment thereof, by a further winding process.
  • straightening is performed, it is preferably carried out by means of a conventional working bench comprising, in sequence, a station for unwinding the coil, a unit for the advancement of the rolled material, a rotary-drum straightening unit, for example of the type shown in figure 3 and generally designated by the reference numeral 10, and a station for cutting the straightened bars to size.
  • a conventional working bench comprising, in sequence, a station for unwinding the coil, a unit for the advancement of the rolled material, a rotary-drum straightening unit, for example of the type shown in figure 3 and generally designated by the reference numeral 10, and a station for cutting the straightened bars to size.
  • the rotary drum 10 has an axial passage for the wire rod delimited by a plurality of bushes 11 which are arranged inside the rotary drum in an eccentric alternating manner, with an eccentricity substantially between 2 and 8 mm with respect to the axis of the rotary drum, which is made to rotate about said axis.
  • the arrangement of the bushes 11 in the drum 10, which is made to rotate, causes a plurality of alternating bendings of the wire rod, with deflections which are substantially equal to the eccentricity of the bushes 11.
  • the straightening performed with the rotary drum 10 enhances certain mechanical characteristics of the wire rod and leads to a ratio between the ultimate tensile strength and the yield strength of the final product which fully complies with the above-mentioned standards.
  • the straightening thus performed affects the structure of the wire rod in full, since it does not act on separate planes, which would in any case limit the regions affected by yielding, but on the entire cross-section. Since the drum 10 rotates at a rate preferably on the order of 3000 rpm, and since the linear speed of the wire rod passing therethrough is approximately 2 m/sec, the bending force produced by the eccentric arrangement of the bushes 11 is distributed uniformly over all possible planes.
  • the wire rod By virtue of its passage within the drum 10, the wire rod also undergoes substantially complete descaling, fully eliminating the oxide layer from its surface and allowing to perform trouble-free subsequent electric welding during the production of the net.
  • this operation is preferably performed by means of an apparatus of the type shown schematically in figure 4.
  • Said apparatus comprises, in sequence, an unwinding device 21 which gradually unwinds the coil of wire rod, a first descaling unit 22, a lubricator 23, a yielding and pulling bench 24, and a coil winding device 25.
  • the descaling unit 22 is substantially constituted by a bench 30 with a plurality of pairs of rollers with a grooved profile 31, which have mutually parallel axes and are arranged so as to form a path for the wire rod having one or more S-shaped portions, so as to obtain, during the passage of the wire rod, its alternating bending with a camber of substantially 10 to 20 mm, which causes the separation of the oxide layer covering the wire rod surface.
  • the lubricator 23 is constituted by a conventional lubricator which delivers onto the wire rod surface a lubricant having the purpose of preventing the turns of wire rod from overlapping during the pulling and winding on a drum performed downstream.
  • the yielding and pulling device comprises, in sequence, a first winding traction unit 40, shown in figure 8, which is substantially constituted by a motorized drum around which the wire rod arriving from the descaling unit 23 is wound in turns and then conveyed through two yielding benches 41 and 42, which are substantially constituted by a first set of rolls with a groove-shaped profile 43 and by a second set of rolls with a groove-shaped profile 44, arranged so as to produce the S-shaped deformation of the wire rod on two mutually perpendicular planes, i.e., on a horizontal plane and on a vertical plane, as shown in particular in figure 6.
  • the rolls 43 are arranged so as to have axes which are parallel and spaced with respect to each other so as to produce a sequence of alternating bendings of the wire rod with a maximum camber of substantially between 80 and 120 mm and with a distance between two maximum camber points of two contiguous regions bent on opposite sides that is substantially between 180 and 210 mm.
  • another drum winder again of the type shown in figure 8, i.e., provided with a motorized drum around which the wire rod arriving from the yielding benches 41 and 42 is wound.
  • the apparatus is completed by a coil winder 25, which packages the wire rod in coils.
  • the wire rod by passing through the apparatus shown in figure 4, is pulled, unwound, made to yield on a horizontal plane, made to yield on a vertical plane, wound again, pulled, and unwound again with an advancement rate varying between 3 and 9 m/s for larger-diameter wire rods and between 6 and 12 m/s for smaller-diameter wire rods.
  • This treatment heats the wire rod up to 70-80 o C, producing a work-hardening of the material which raises the ultimate tensile strength and the yield strength and allows at the same time to obtain a ratio between ultimate tensile strength and yield strength and a percentage elongation value which fully comply with the pertinent standards.
  • the resulting wire rod is then electrically welded in a per se known manner to obtain the electrically welded net.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Wire Processing (AREA)
  • Reinforcement Elements For Buildings (AREA)
EP97100966A 1996-02-07 1997-01-22 Fil en acier pour la fabrication de treillis soudé par résistance électrique Withdrawn EP0788847A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITMI960222 1996-02-07
IT96MI000222A IT1282011B1 (it) 1996-02-07 1996-02-07 Procedimento per la produzione di reti in acciaio elettrosaldate ad alta duttilita',particolarmente per l'impiego come armature

Publications (1)

Publication Number Publication Date
EP0788847A1 true EP0788847A1 (fr) 1997-08-13

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EP97100966A Withdrawn EP0788847A1 (fr) 1996-02-07 1997-01-22 Fil en acier pour la fabrication de treillis soudé par résistance électrique

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EP (1) EP0788847A1 (fr)
IT (1) IT1282011B1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114888075A (zh) * 2022-04-13 2022-08-12 大冶特殊钢有限公司 一种钎具用80Mn14Ti钎芯的轧制方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE635211A (fr) * 1962-07-23
DE2621330A1 (de) * 1976-05-14 1977-11-24 Fels Werke Peine Salzgitter Verfahren zum herstellen von bewehrungsstaeben aus stahl
FR2378578A1 (fr) * 1977-01-27 1978-08-25 Arbed Piece de laminage en metal dur
GB2109281A (en) * 1981-11-18 1983-06-02 Allied Steel Wire Ltd Cold worked rod or wire

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE635211A (fr) * 1962-07-23
DE2621330A1 (de) * 1976-05-14 1977-11-24 Fels Werke Peine Salzgitter Verfahren zum herstellen von bewehrungsstaeben aus stahl
FR2378578A1 (fr) * 1977-01-27 1978-08-25 Arbed Piece de laminage en metal dur
GB2109281A (en) * 1981-11-18 1983-06-02 Allied Steel Wire Ltd Cold worked rod or wire

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114888075A (zh) * 2022-04-13 2022-08-12 大冶特殊钢有限公司 一种钎具用80Mn14Ti钎芯的轧制方法
CN114888075B (zh) * 2022-04-13 2024-06-07 大冶特殊钢有限公司 一种钎具用80Mn14Ti钎芯的轧制方法

Also Published As

Publication number Publication date
IT1282011B1 (it) 1998-03-06
ITMI960222A0 (fr) 1996-02-07
ITMI960222A1 (it) 1997-08-07

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