EP4263934A1 - Compacted steel strand with cladded core - Google Patents

Compacted steel strand with cladded core

Info

Publication number
EP4263934A1
EP4263934A1 EP21859356.4A EP21859356A EP4263934A1 EP 4263934 A1 EP4263934 A1 EP 4263934A1 EP 21859356 A EP21859356 A EP 21859356A EP 4263934 A1 EP4263934 A1 EP 4263934A1
Authority
EP
European Patent Office
Prior art keywords
steel
steel strand
corrosion resistant
coating
core wire
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.)
Granted
Application number
EP21859356.4A
Other languages
German (de)
French (fr)
Other versions
EP4263934C0 (en
EP4263934B1 (en
Inventor
Stefan VITKO
Jozef Filo
Robert SUDY
Lubos SOBOTA
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.)
Bekaert NV SA
Original Assignee
Bekaert NV SA
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 Bekaert NV SA filed Critical Bekaert NV SA
Publication of EP4263934A1 publication Critical patent/EP4263934A1/en
Application granted granted Critical
Publication of EP4263934C0 publication Critical patent/EP4263934C0/en
Publication of EP4263934B1 publication Critical patent/EP4263934B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B5/00—Making ropes or cables from special materials or of particular form
    • D07B5/007—Making ropes or cables from special materials or of particular form comprising postformed and thereby radially plastically deformed elements
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B1/00—Constructional features of ropes or cables
    • D07B1/14—Ropes or cables with incorporated auxiliary elements, e.g. for marking, extending throughout the length of the rope or cable
    • D07B1/147—Ropes or cables with incorporated auxiliary elements, e.g. for marking, extending throughout the length of the rope or cable comprising electric conductors or elements for information transfer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C23/00—Extruding metal; Impact extrusion
    • B21C23/22—Making metal-coated products; Making products from two or more metals
    • B21C23/24—Covering indefinite lengths of metal or non-metal material with a metal coating
    • B21C23/26—Applying metal coats to cables, e.g. to insulated electric cables
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21F—WORKING OR PROCESSING OF METAL WIRE
    • B21F37/00—Manufacture of rings from wire
    • B21F37/04—Manufacture of rings from wire of washers
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B1/00—Constructional features of ropes or cables
    • D07B1/06—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core
    • D07B1/0693—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core having a strand configuration
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2201/00—Ropes or cables
    • D07B2201/10—Rope or cable structures
    • D07B2201/1012—Rope or cable structures characterised by their internal structure
    • D07B2201/102—Rope or cable structures characterised by their internal structure including a core
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2201/00—Ropes or cables
    • D07B2201/10—Rope or cable structures
    • D07B2201/104—Rope or cable structures twisted
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2201/00—Ropes or cables
    • D07B2201/20—Rope or cable components
    • D07B2201/2001—Wires or filaments
    • D07B2201/2002—Wires or filaments characterised by their cross-sectional shape
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2201/00—Ropes or cables
    • D07B2201/20—Rope or cable components
    • D07B2201/2001—Wires or filaments
    • D07B2201/201—Wires or filaments characterised by a coating
    • D07B2201/2011—Wires or filaments characterised by a coating comprising metals
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2201/00—Ropes or cables
    • D07B2201/20—Rope or cable components
    • D07B2201/2001—Wires or filaments
    • D07B2201/2014—Compound wires or compound filaments
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2201/00—Ropes or cables
    • D07B2201/20—Rope or cable components
    • D07B2201/2015—Strands
    • D07B2201/2019—Strands pressed to shape
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2201/00—Ropes or cables
    • D07B2201/20—Rope or cable components
    • D07B2201/2047—Cores
    • D07B2201/2052—Cores characterised by their structure
    • D07B2201/2059—Cores characterised by their structure comprising wires
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2201/00—Ropes or cables
    • D07B2201/20—Rope or cable components
    • D07B2201/2047—Cores
    • D07B2201/2052—Cores characterised by their structure
    • D07B2201/2065—Cores characterised by their structure comprising a coating
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2205/00—Rope or cable materials
    • D07B2205/30—Inorganic materials
    • D07B2205/3021—Metals
    • D07B2205/3025—Steel
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2205/00—Rope or cable materials
    • D07B2205/30—Inorganic materials
    • D07B2205/3021—Metals
    • D07B2205/306—Aluminium (Al)
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2205/00—Rope or cable materials
    • D07B2205/30—Inorganic materials
    • D07B2205/3021—Metals
    • D07B2205/3071—Zinc (Zn)
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2205/00—Rope or cable materials
    • D07B2205/30—Inorganic materials
    • D07B2205/3021—Metals
    • D07B2205/3085—Alloys, i.e. non ferrous
    • D07B2205/3092—Zinc (Zn) and tin (Sn) alloys
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2401/00—Aspects related to the problem to be solved or advantage
    • D07B2401/20—Aspects related to the problem to be solved or advantage related to ropes or cables
    • D07B2401/202—Environmental resistance
    • D07B2401/2025—Environmental resistance avoiding corrosion
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2501/00—Application field
    • D07B2501/20—Application field related to ropes or cables
    • D07B2501/2015—Construction industries
    • D—TEXTILES; PAPER
    • D07—ROPES; CABLES OTHER THAN ELECTRIC
    • D07B—ROPES OR CABLES IN GENERAL
    • D07B2501/00—Application field
    • D07B2501/20—Application field related to ropes or cables
    • D07B2501/2015—Construction industries
    • D07B2501/2023—Concrete enforcements

Definitions

  • the invention relates to a steel strand comprising a steel core wire surrounded by steel layer wires that are twisted around this steel core wire.
  • the invention also relates to the use of such a steel strand as a pretensioned strand or as a post-tensioned strand.
  • a steel strand comprising a steel core wire surrounded by steel layer wires that are twisted around this steel core wire is a flexible and robust tension member that finds many applications.
  • the steel core wire and the steel layer wires usually have a circular crosssection.
  • a closed layer of steel layer wires is formed around the steel core wire, i.e. a layer where all steel layer wires touch adjacent steel layer wires, interstices are formed between the steel core wire and the steel layer wires. Humid environments or moisture already present in these interstices may cause condensation and lead ultimately to corrosion and a premature end of life of the steel strand. Compacting the steel strand may reduce the size of the interstices but does not take the interstices completely away.
  • the steel strand is subjected to tensile stresses and the mentioned potential corrosion failure problem is even more present.
  • the steel core wire and the steel layer wires may be provided with a corrosion resistant coating to increase the lifetime of the steel strand.
  • a corrosion resistant coating is a polymer coating. If of a sufficient thickness, the steel layer wires exercise a pressure on the polymer coating so that it starts to flow around the steel layer wires and fill the interstices. However, this polymer coating is not resistant against a downstream heat treatment of the rope. Another drawback is that the rope with a polymer inside cannot be installed and used in warm circumstances.
  • Another corrosion resistant coating is a metallic coating such as a zinc or a zinc alloy coating applied by means of a hot dip operation or electroplating operation. While increasing the lifetime of the steel strand, these metallic coatings are not thick enough to fill the interstices.
  • a steel strand comprising a steel core wire.
  • the steel core wire is surrounded by steel layer wires that are twisted around the steel core wire.
  • the steel core wire is covered with a corrosion resistant core coating provided by strip cladding or by metal extrusion.
  • the steel layer wires are covered with a corrosion resistant layer coating provided by a hot dip operation or by an electroplating or chemical plating process.
  • the steel strand is compacted so that the steel layer wires have a non-circular cross-section and that said corrosion resistant core coating fills the interstices between the steel core wire and the steel layer wires.
  • the steel strand is provided with a two corrosion resistant coatings.
  • a first way to provide the relatively thick core coating is by strip cladding.
  • strip cladding a strip of a corrosion resistant metal and of predetermined and desired thickness can be formed into a tube form. The width of this strip is somewhat greater or equal to the circumference of the steel wire to be covered. The strip is closed in a tube and welded on or around the steel wire. The steel wire with the strip around is then drawn until its final steel core wire diameter.
  • a second way to provide the relatively thick core coating is by means of metal extrusion. According to the technique of metal extrusion, corrosion resistant metal material is pushed through a die of the desired crosssection around the steel wire.
  • a hot dip operation or an electroplating or chemical plating process are the ways apply the relatively thin layer corrosion resistant coating on the steel layer wires.
  • the metal of the thick core coating will start to flow somewhat around the steel layer wires and fill the interstices between the steel core wire and the steel layer wires. In contrast with the polymer material, this metal material is able to resist high temperatures.
  • the steel strand with the metal material inside can be subjected to downstream heat treatments, such as a stress-relieving treatment at about 350 °C to 420 °C. Moreover, the steel strand can be installed and used in warm circumstances.
  • the thick corrosion resistant core coating is of aluminium or of an aluminium alloy.
  • the thick corrosion resistant coating has a weight ranging from 400 g/m 2 to 2500 g/m 2 , preferably from 450 g/m 2 to 2250 g/m 2 , where the smaller weights correspond to the smaller diameters and the higher weights correspond to the greater diameters.
  • a steel strand with an outer diameter of 7.0 mm may have a weight of the thick corrosion resistant coating of 486 g/m 2 .
  • a steel strand with an outer diameter of 15.2 mm may have a weight of the thick corrosion resistant coating of 810 g/m 2 .
  • a steel strand with an outer diameter of 18.0 mm may have a weight of the thick corrosion resistant coating of 2119 g/m 2 .
  • the thin corrosion resistant layer coating is of zinc or of a zinc alloy.
  • a zinc aluminium coating has a better overall corrosion resistance than zinc.
  • the zinc aluminium coating is temperature resistant. Still in contrast with zinc, there is no flaking with the zinc aluminium alloy when exposed to high temperatures.
  • a zinc aluminium coating may have an aluminium content ranging from 2 per cent by weight to 12 per cent by weight, e.g. ranging from 3 % to 11 %.
  • One preferable composition lies around the eutectoid position: Aluminium about 5 per cent.
  • the zinc alloy coating may further have a wetting agent such as lanthanum or cerium in an amount less than 0.1 per cent of the zinc alloy. The remainder of the coating is zinc and unavoidable impurities.
  • Another preferable composition contains about 10% aluminium. This increased amount of aluminium provides a better corrosion protection then the eutectoid composition with about 5% of aluminium.
  • a highly preferable composition in the context of the present invention is a zinc aluminium alloy that comprises 2 % to 10 % aluminium and 0.2 % to 3.0 % magnesium, the remainder being zinc.
  • An example is 5% Al, 0.5 % Mg and the rest being Zn.
  • the thin corrosion resistant layer coating may have a weight ranging from 150 g/m 2 to 450 g/m 2 .
  • the smaller weights correspond to the smaller diameters and the higher weights correspond to the greater diameters.
  • the steel strand may have an outer diameter ranging from 6.0 mm to 25.0 mm, preferably from 6.5 mm to 20.0 mm.
  • the steel strand can be used as a pre-tensioned strand or as a post-tensioned strand.
  • the steel strand can be used in elevated transportation systems, in ACSR power cables, as guardrail, stay cable strand, umbilical or pre-cast concrete reinforcing elements.
  • FIGURE 1 shows a cross-section of a steel strand according to a first aspect of the present invention.
  • FIGURE 1 shows a cross-section of a steel strand 10.
  • the steel strand 10 has a steel core wire 12 and six steel layer wires 14 that are twisted around the steel core wire 12.
  • the steel core wire 12 is provided with an aluminium strip clad core coating 16.
  • the steel layer wires 14 are provided with a zinc aluminium magnesium layer coating 18.
  • the steel strand 10 is compacted so that the steel layer wires 14 obtain a trapezium-like cross-section.
  • the steel layer wires 14 form a closed layer around the steel core wire 12 and push the aluminium strip clad core coating 16 to flow and fill the interstices between the steel core wire 12 and the steel layer wires 14.
  • the aluminium strip clad core coating 16 fills all interstices and holes inside the steel strand and prevents moisture from penetrating inside the steel strand 10. At the same time the aluminium strip clad core coating 16 gives corrosion resistance to steel core wire 12.
  • the zinc aluminium magnesium layer coating 18 gives corrosion resistance to the steel layer wires 14.
  • a steel strand according to the invention can be made along following lines.
  • composition of the starting material is usually a microalloyed high-carbon composition as follows: (all percentages being percentages by weight):
  • % C a carbon content (% C) ranging from 0.50% to 1 .20%, e.g. 0.60% to 1.0%;
  • % Mn manganese content
  • % Si silicon content ranging from 0.10% to 1 .50%, e.g. from 0.15% to 0.70%;
  • phosporus content (% P) below 0.03%, e.g. below 0.01 %.
  • Micro-alloying elements such as chromium, vanadium, aluminium or nickel may or may not be present in amounts up to 0.50%.
  • the steel core wire is drawn until an intermediate steel wire diameter.
  • An aluminium strip is formed and welded or extruded around the steel wire and the thus formed composite is further drawn until a final diameter.
  • the steel layer wires are drawn until an intermediate steel wire diameter.
  • the steel layer wires are then guided through a hot dip bath of zinc-aluminium-magnesium.
  • the thus coated steel layer wires are then further drawn until their final wire diameter.
  • the steel layer wires are twisted around the steel core wire with the aluminium strip to form a non-compacted steel strand. Thereafter, the steel strand is finally subjected to a compacting treatment.
  • the compacted steel rope according to the invention is preferably subjected to a stress-relieving treatment in order to lower the relaxation and to improve the straightness.
  • a suitable temperature for carrying out such a stress-relieving treatment is 380 °C.
  • the compacted steel rope according to the invention can obtain following tensile strength grades: 1700 MPa, 1860 MPa, 1960 MPa and 2060 MPa.

Landscapes

  • Ropes Or Cables (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Coating With Molten Metal (AREA)

Abstract

A steel strand (10) comprises a steel core wire (12). This steel core wire (12) is surrounded by steel layer wires (14) that are twisted around the steel core wire(12). The steel core wire (12) is covered with a thick corrosion resistant core coating (16) provided by strip cladding or by metal extrusion. The steel layer wires (14) are covered with a thin corrosion resistant layer coating (18) provided by a hot dip operation or by an electroplating or chemical plating process. The steel strand(10) is compacted so that said steel layer wires (14) have a non-circular cross-section and that the thick corrosion resistant core coating fills the interstices between the steel core wire (12) and the steel layer wires (14) in order to give the steel strand (10) an improved corrosion resistance and increased lifetime.

Description

Title: COMPACTED STEEL STRAND WITH CLADDED CORE
Description
Technical Field
[0001 ] The invention relates to a steel strand comprising a steel core wire surrounded by steel layer wires that are twisted around this steel core wire.
[0002] The invention also relates to the use of such a steel strand as a pretensioned strand or as a post-tensioned strand.
Background Art
[0003] A steel strand comprising a steel core wire surrounded by steel layer wires that are twisted around this steel core wire is a flexible and robust tension member that finds many applications.
[0004] The steel core wire and the steel layer wires usually have a circular crosssection. When a closed layer of steel layer wires is formed around the steel core wire, i.e. a layer where all steel layer wires touch adjacent steel layer wires, interstices are formed between the steel core wire and the steel layer wires. Humid environments or moisture already present in these interstices may cause condensation and lead ultimately to corrosion and a premature end of life of the steel strand. Compacting the steel strand may reduce the size of the interstices but does not take the interstices completely away. When used as a pre-tensioned steel strand or as a post-tensioned steel strand, the steel strand is subjected to tensile stresses and the mentioned potential corrosion failure problem is even more present.
[0005] The steel core wire and the steel layer wires may be provided with a corrosion resistant coating to increase the lifetime of the steel strand.
[0006] An example of a corrosion resistant coating is a polymer coating. If of a sufficient thickness, the steel layer wires exercise a pressure on the polymer coating so that it starts to flow around the steel layer wires and fill the interstices. However, this polymer coating is not resistant against a downstream heat treatment of the rope. Another drawback is that the rope with a polymer inside cannot be installed and used in warm circumstances.
[0007] Another corrosion resistant coating is a metallic coating such as a zinc or a zinc alloy coating applied by means of a hot dip operation or electroplating operation. While increasing the lifetime of the steel strand, these metallic coatings are not thick enough to fill the interstices.
Disclosure of Invention
[0008] It is a general object of the invention to avoid or mitigate the drawbacks of the prior art.
[0009] It is a particular object of the invention to provide a steel strand that can operate under tensile forces and that has an increased lifetime.
[0010] It is another object of the invention to fill in a sustainable way the interstices between the steel core wire and the steel layer wires.
[0011 ] According to a first aspect of the invention, there is provided a steel strand. The steel strand comprises a steel core wire. The steel core wire is surrounded by steel layer wires that are twisted around the steel core wire. The steel core wire is covered with a corrosion resistant core coating provided by strip cladding or by metal extrusion. The steel layer wires are covered with a corrosion resistant layer coating provided by a hot dip operation or by an electroplating or chemical plating process. The steel strand is compacted so that the steel layer wires have a non-circular cross-section and that said corrosion resistant core coating fills the interstices between the steel core wire and the steel layer wires.
[0012] Briefly stated, the steel strand is provided with a two corrosion resistant coatings. A relatively thick metallic coating around the steel core wire and relatively thin metallic coatings around the steel layer wires. [0013] A first way to provide the relatively thick core coating is by strip cladding. According to the technique of strip cladding, a strip of a corrosion resistant metal and of predetermined and desired thickness can be formed into a tube form. The width of this strip is somewhat greater or equal to the circumference of the steel wire to be covered. The strip is closed in a tube and welded on or around the steel wire. The steel wire with the strip around is then drawn until its final steel core wire diameter.
[0014] A second way to provide the relatively thick core coating is by means of metal extrusion. According to the technique of metal extrusion, corrosion resistant metal material is pushed through a die of the desired crosssection around the steel wire.
[0015] A hot dip operation or an electroplating or chemical plating process are the ways apply the relatively thin layer corrosion resistant coating on the steel layer wires.
[0016] When finally compacting the steel strand, the metal of the thick core coating will start to flow somewhat around the steel layer wires and fill the interstices between the steel core wire and the steel layer wires. In contrast with the polymer material, this metal material is able to resist high temperatures. The steel strand with the metal material inside can be subjected to downstream heat treatments, such as a stress-relieving treatment at about 350 °C to 420 °C. Moreover, the steel strand can be installed and used in warm circumstances.
[0017] Preferably the thick corrosion resistant core coating is of aluminium or of an aluminium alloy.
[0018] Most preferably, the thick corrosion resistant coating has a weight ranging from 400 g/m2 to 2500 g/m2, preferably from 450 g/m2 to 2250 g/m2, where the smaller weights correspond to the smaller diameters and the higher weights correspond to the greater diameters.
A steel strand with an outer diameter of 7.0 mm may have a weight of the thick corrosion resistant coating of 486 g/m2. A steel strand with an outer diameter of 15.2 mm may have a weight of the thick corrosion resistant coating of 810 g/m2.
A steel strand with an outer diameter of 18.0 mm may have a weight of the thick corrosion resistant coating of 2119 g/m2.
[0019] Preferably the thin corrosion resistant layer coating is of zinc or of a zinc alloy.
[0020] A zinc aluminium coating has a better overall corrosion resistance than zinc. In contrast with zinc, the zinc aluminium coating is temperature resistant. Still in contrast with zinc, there is no flaking with the zinc aluminium alloy when exposed to high temperatures.
[0021 ] A zinc aluminium coating may have an aluminium content ranging from 2 per cent by weight to 12 per cent by weight, e.g. ranging from 3 % to 11 %.
[0022] One preferable composition lies around the eutectoid position: Aluminium about 5 per cent. The zinc alloy coating may further have a wetting agent such as lanthanum or cerium in an amount less than 0.1 per cent of the zinc alloy. The remainder of the coating is zinc and unavoidable impurities.
[0023] Another preferable composition contains about 10% aluminium. This increased amount of aluminium provides a better corrosion protection then the eutectoid composition with about 5% of aluminium.
[0024] A highly preferable composition in the context of the present invention is a zinc aluminium alloy that comprises 2 % to 10 % aluminium and 0.2 % to 3.0 % magnesium, the remainder being zinc. An example is 5% Al, 0.5 % Mg and the rest being Zn.
[0025] Other elements such as silicon (Si) may be added to the zinc aluminium alloy coatings mentioned above. [0026] The thin corrosion resistant layer coating may have a weight ranging from 150 g/m2 to 450 g/m2. Here again, the smaller weights correspond to the smaller diameters and the higher weights correspond to the greater diameters.
[0027] The steel strand may have an outer diameter ranging from 6.0 mm to 25.0 mm, preferably from 6.5 mm to 20.0 mm.
[0028] According to a second aspect of the invention, the steel strand can be used as a pre-tensioned strand or as a post-tensioned strand.
[0029] The steel strand can be used in elevated transportation systems, in ACSR power cables, as guardrail, stay cable strand, umbilical or pre-cast concrete reinforcing elements.
Brief Description of Figure in the Drawing
[0030] FIGURE 1 shows a cross-section of a steel strand according to a first aspect of the present invention.
Mode(s) for Carrying Out the Invention
[0031] FIGURE 1 shows a cross-section of a steel strand 10. The steel strand 10 has a steel core wire 12 and six steel layer wires 14 that are twisted around the steel core wire 12. The steel core wire 12 is provided with an aluminium strip clad core coating 16. The steel layer wires 14 are provided with a zinc aluminium magnesium layer coating 18.
[0032] The steel strand 10 is compacted so that the steel layer wires 14 obtain a trapezium-like cross-section. The steel layer wires 14 form a closed layer around the steel core wire 12 and push the aluminium strip clad core coating 16 to flow and fill the interstices between the steel core wire 12 and the steel layer wires 14. [0033] The aluminium strip clad core coating 16 fills all interstices and holes inside the steel strand and prevents moisture from penetrating inside the steel strand 10. At the same time the aluminium strip clad core coating 16 gives corrosion resistance to steel core wire 12.
[0034] The zinc aluminium magnesium layer coating 18 gives corrosion resistance to the steel layer wires 14.
[0035] A steel strand according to the invention can be made along following lines.
[0036] The composition of the starting material (wire rod) is usually a microalloyed high-carbon composition as follows: (all percentages being percentages by weight):
- a carbon content (% C) ranging from 0.50% to 1 .20%, e.g. 0.60% to 1.0%;
- a manganese content (% Mn) ranging from 0.10% to 1.0%, e.g. from 0.20% to 0.80%;
- a silicon content (% Si) ranging from 0.10% to 1 .50%, e.g. from 0.15% to 0.70%;
- a sulphur content (% S) below 0.03%, e.g. below 0.01%;
- a phosporus content (% P) below 0.03%, e.g. below 0.01 %. Micro-alloying elements such as chromium, vanadium, aluminium or nickel may or may not be present in amounts up to 0.50%.
[0037] Starting from wire rod, the steel core wire is drawn until an intermediate steel wire diameter. An aluminium strip is formed and welded or extruded around the steel wire and the thus formed composite is further drawn until a final diameter.
[0038] Starting also from wire rod, the steel layer wires are drawn until an intermediate steel wire diameter. The steel layer wires are then guided through a hot dip bath of zinc-aluminium-magnesium. The thus coated steel layer wires are then further drawn until their final wire diameter. [0039] The steel layer wires are twisted around the steel core wire with the aluminium strip to form a non-compacted steel strand. Thereafter, the steel strand is finally subjected to a compacting treatment.
[0040] Examples of a 1 + 6 steel strand (6 steel layer wires):
- diameters of the steel core wire resp. (steel only): 2.64 mm, 5.60 mm, 6.50 mm;
- diameters of the steel core wire with aluminium strip: 3.00 mm, 6.35 mm, 8.07 mm;
- diameters of the coated and drawn steel layer wires: 2.53 mm, 5.60 mm, 6.46 mm;
- diameter of the compacted steel strand: 7.0 mm, 15.2 mm, 18.0 mm.
[0041] The compacted steel rope according to the invention is preferably subjected to a stress-relieving treatment in order to lower the relaxation and to improve the straightness. A suitable temperature for carrying out such a stress-relieving treatment is 380 °C.
[0042] The compacted steel rope according to the invention can obtain following tensile strength grades: 1700 MPa, 1860 MPa, 1960 MPa and 2060 MPa.
List of Reference Numbers
10 Steel strand
12 Steel core wire
14 Steel layer wire
16 Thick corrosion resistant core coating
18 Thin corrosion resistant layer coating

Claims

8 Claims
1 . A steel strand comprising a steel core wire, said steel core wire surrounded by steel layer wires that are twisted around said steel core wire, said steel core wire covered with a corrosion resistant core coating provided by strip cladding or by metal extrusion, said steel layer wires covered with a corrosion resistant layer coating provided by a hot dip operation or by an electroplating or chemical plating process, said steel strand being compacted so that said steel layer wires have a noncircular cross-section and that said corrosion resistant core coating fills the interstices between the steel core wire and the steel layer wires.
2. The steel strand according to claim 1 , wherein said corrosion resistant core coating is of aluminium or an aluminium alloy.
3. The steel strand according to claim 1 or 2, where said corrosion resistant core coating has a weight ranging from 400 g/m2 to 2500 g/m2.
4. The steel strand according to any one of the preceding claims, wherein said corrosion resistant layer coating is of zinc or a zinc alloy.
5. The steel strand according to claim 4, wherein said corrosion resistant layer coating has a weight ranging from 150 g/m2 to 450 g/m2.
6. The steel strand according to claim 4 or claim 5, wherein said corrosion resistant layer coating is a zinc aluminium alloy. 9
7. The steel strand according to claim 6, wherein said corrosion resistant layer coating is a zinc aluminium magnesium alloy.
8. The steel strand according to any one of the preceding claims, wherein said steel strand has an outer diameter ranging from 10.0 mm to 30.0 mm.
9. The steel strand according to any one of the preceding claims, wherein said steel strand is in a stress-relieved state.
10. Use of the steel strand according to any one of the preceding claims as a pretensioned strand.
11. Use of the steel strand according to any one of claims 1 to 9 as a posttensioned strand.
EP21859356.4A 2020-12-17 2021-12-14 Compacted steel strand with cladded core Active EP4263934B1 (en)

Applications Claiming Priority (2)

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EP20214792 2020-12-17
PCT/EP2021/085721 WO2022129067A1 (en) 2020-12-17 2021-12-14 Compacted steel strand with cladded core

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EP (1) EP4263934B1 (en)
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Also Published As

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WO2022129067A1 (en) 2022-06-23
US20240052565A1 (en) 2024-02-15
EP4263934C0 (en) 2025-08-13
EP4263934B1 (en) 2025-08-13
CN116710611A (en) 2023-09-05

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