Classifications

• • 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
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
• • 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
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
• • 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
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/005—Heat treatment of ferrous alloys containing Mn
• • 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
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/008—Heat treatment of ferrous alloys containing Si
• • 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
  • C21D7/00—Modifying the physical properties of iron or steel by deformation
  • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
• • 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
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
• • 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
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
• • 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
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0236—Cold rolling
• • 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
  • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron

Definitions

• the present invention relates to a steel product for use in the mining, construction and general manufacturing industries .
• the present invention also relates to a method of producing the steel product.
• the steel may be any one of low carbon steel, medium carbon steel and high strength low alloy steel (which is also described in the steel industry as a microalloy steel) .
• low carbon steel is understood herein to mean steel having less than 0.3 wt.% C, other elements such as Si and Mn that are added as deliberate additions to the steel , residual/incidental impurities and balance Fe.
• medium carbon steel is understood herein to mean steel having 0.3-2.0 wt.% C, other elements such as Si and Mn that are added as deliberate additions to the steel, residual/incidental impurities, and balance Fe .
• residual/incidental impurities covers elements such as Cu , Sn , Mo , Al , Zn , Ni , and Cr that may be present in very small concentrations, not as a consequence of specific additions of these elements but as a consequence of standard steelmaking practices.
• the elements may be present as a consequence of the use of scrap steel to produce high strength low alloy, low carbon and medium carbon steels .
• high strength low alloy steel is understood herein to mean steel of the following typical composition, in wt.%: C: 0.07-0.30;
• V 0.1 or less
• Nb 0.1 or less
• Al 0.05 or less
• Residual/incidental impurities 1.0 or less;
• the term "residual/incidental impurities" in the context of high strength low alloy steels is understood as described above in relation to low and medium carbon steels .
• the concentrations of elements such as Cu and Mo in the table in the preceding paragraph are total concentrations , i.e. the concentrations of these elements as a total of deliberate additions and residual/incidental impurities.
• the steel product may be any suitable product.
• the steel product may be wire, rod, bar, or strip.
• the steel product may be in the form of a steel product that is made from any one of wire, rod, bar, and strip .
• the steel product may include any product, including but not limited to reinforcement bar for concrete
• reinforcement mesh for the concrete construction and mining industries made by welding together spaced-apart parallel line wires and spaced-apart parallel cross-wires, pipe made from steel strip, couplers for coupling together any elongate products such as reinforcing bars , continuous spirals, ligatures for reinforcing cages for concrete columns and beams, fasteners (including screws, bolts etc.) made from steel bar, rock bolts made from steel bar, and other steel products used in tensile or compression or shear or flexural applications in the concrete construction, construction, mining or manufacturing industries .
• the present invention is based on a surprising finding that it is possible to treat steel by heating steel (hereinafter referred to as "heat treatment") that has been mechanically worked (e.g. cold formed such as by cold rolling) and: (a) maintain or increase the ductility (for example, measured as elongation and described in the specification in terms of elongation and known by the term Agt (uniform elongation) when referring to reinforcing steels and often expressed as Agt ( _o.5% ) ) , (b) maintain or increase the yield stress (YS) (often expressed as Proof Stress (PS) for
• mechanically-worked steel results in an increase in ductility and a decrease in the yield stress and a decrease in the tensile strength of the steel .
• the applicant found that steel that had been mechanically worked to reduce the transverse cross-sectional area of the steel by 5-30% and in some instances up to 75% and then heat treated at a temperature in a range of 150-750°C for a time period of 1 minute to 16 hours maintained and in many instances produced an increase in ductility of at least 25% relative to that of the mechanically worked steel and an increase in yield stress of at least 5% relative to that of the mechanically worked steel .
• mechanically worked steel could be heat treated at higher temperatures and for shorter times or at lower temperatures and for longer times to maintain or increase ductility, yield stress, and tensile strength.
• the invention is not confined to mechanical working that changes the transverse cross-sectional area of a feed steel or a steel product and also extends to situations where cold working changes the shape of the feed steel or the steel product.
• the present invention is based on an extensive research and development program that has focused on testing substantial number of samples of low carbon steels r medium carbon steels , and high strength low alloy steels .
• the samples included samples that were mechanically worked under different conditions and heat treated at different
• the present invention provides a method of producing a steel product that includes heat treating a mechanically worked steel product and maintaining or increasing the ductility and maintaining or increasing the yield stress of the steel .
• the present invention also provides a method of producing a steel product that includes heat treating a mechanically worked steel product and maintaining or
• the present invention also includes a mechanically worked and heat treated steel product.
• the steel product may be any one of the steel products described above, i.e. wire, rod, bar, or strip, and any steel product that is made from any one of wire, rod, bar, and strip and including the specific products mentioned above.
• the invention provides an opportunity to use the same starting material, such as a high strength low alloy steel, low carbon steel, and medium carbon steel, and produce a range of required mechanical properties by appropriate selection of mechanical working and heat treatment time and heat treatment temperature .
• the present invention also provides a method of producing a steel product that includes selecting a feed steel as a starting material for the product and selecting mechanical working and heat treatment time and heat treatment temperature conditions of the feed steel or a product made from the feed steel to provide required
• the invention provides an opportunity for small or large quantities of readily available steel materials to be used to manufacture :
• medium strength e.g. >500 MPa yield stress
• high ductility e.g. Uniform Elongation > 1.5% Agt
• a 750 MPa yield stress type (a) steel in accordance with the invention represents a potential material saving of 33% for the same performance as a
• a mesh manufactured from the material with the same properties and used in mining applications represents a potential material saving of at least 30% for the same performance and with consequent occupational health and safety benefits, i.e. handling of a lighter product. Whilst not critical, being able to also increase the ductility is a potential benefit.
• ductile mesh manufactured in this manner would potentially allow in the order of 20-25% reduction in the mass of steel required to reinforce a concrete slab on ground or tilt-up concrete products , for example .
• high tensile strength or medium tensile strength products have an added advantage of providing an opportunity to significantly reduce embodied energy (greenhouse gases) in the product and the potential to reduce concrete use in columns and beams and associated reductions in transport and other materials handling costs.
• Elongation is a measure of ductility. Elongation is expressed herein as Uniform Elongation - Agt. The term
• Total elongation is also used as a measure of ductility of steel products, particularly sheet.
• the increase in elongation of the heat treated steel relative to that of the mechanically worked steel may be greater than 5% .
• the increase in elongation of the heat treated steel may be greater than 10%.
• the increase in elongation of the heat treated steel may be greater than 15% .
• the increase in elongation of the heat treated steel may be greater than 20%.
• the increase in elongation of the heat treated steel may be greater than 30%.
• the increase in elongation of the heat treated steel may be greater than 50%.
• the increase in elongation of the heat treated steel may be greater than 100%.
• the increase in elongation of the heat treated steel may be greater than 150%.
• the increase in elongation of the heat treated steel may be greater than 200%.
• the increase in the yield stress of the heat treated steel relative to that of the mechanically worked steel may be greater than 5% .
• the increase in the yield stress of the heat treated steel may be greater than 10%
• the increase in the yield stress of the heat treated steel may be greater than 15%
• the increase in the yield stress o£ the heat treated steel may be greater than 20%
• the increase in the yield stress of the heat treated steel may be greater than 30% .
• the increase in the yield stress of the heat treated steel may be greater than 40% .
• the heat treatment step may be carried out at any suitable temperature . There are a number of ctors that may have an impact on the selection of the heat treatment
• each heat treatment temperature has a time window within which the yield stress and ductility are increased to a level above a desired minimum. This window narrows as the heat treatment
• composition Another factor is the target properties, such as ductility and yield stress.
• the heat treatment step may be carried out at a temperature below the austenitising temperature of the steel . It is noted that in any given situation the actual temperature of the steel during the heat treatment will be a time- temperature dependent relationship and a function of the steel composition. Therefore, the temperature of the furnace may be above the austenitising temperature of the steel.
• the heat treatment step may be carried out at a temperature below 1000°C.
• the heat treatment step may be carried out at a temperature below 800°C.
• the heat treatment step may be carried out at a temperature below 750°C.
• the heat treatment step may be carried out at a temperature below 700°C.
• the heat treatment step may be carried out at a temperature below 600°C.
• the heat treatment step may be carried out at a temperature below 550°C.
• the heat treatment step may be carried out at a temperature below 500°C.
• the heat treatment step may be carried out at a temperature below 450°C.
• the heat treatment step may be carried out at a temperature below 400°C.
• the heat treatment step may be carried out at a temperature below 300°C.
• the heat treatment step may be carried out at a temperature below 250°C.
• the heat treatment step may be carried out at a temperature above 200°C.
• the heat treatment step may be carried out at a temperature above 150°C.
• the heat treatment step may be carried out at a temperature above the austenitising temperature of the steel provided the heat treatment time is selected to be
• the heat treatment step may be carried out for any suitable time .
• the heat treatment step may be carried out for less than 16 hours.
• the heat treatment step may be carried out for less than 10 hours.
• the heat treatment step may be carried out for less than 6 hours .
• the heat treatment step may be carried out for less than 5 hours .
• the heat treatment step may be carried out for less than 4 hours .
• the heat treatment step may be carried out for greater than 1 hour.
• the heat treatment step may be carried out for greater than 45 minutes.
• the heat treatment step may be carried out for greater than 30 minutes.
• the heat treatment step may be carried out for greater than 10 minutes.
• the heat treatment step may be carried out for greater than 5 minutes .
• the heat treatment step may be carried out for greater than 1 minute .
• the heat treatment step may be carried out for greater than 30 seconds.
• the heat treatment step may be carried out in any suitable atmosphere.
• the atmosphere may be an oxidising atmosphere or a reducing atmosphere .
• the heat treatment step may be carried out in air.
• the heat treatment step may be carried out without a protective atmosphere. This is an important advantage of the invention .
• the heat treatment step may be carried out using any suitable means. Specifically, any suitable source of heat energy may be used to carry out the heat treatment.
• the mechanically worked steel product may be any suitable form of product.
• the mechanically worked steel product may be in the form of any one of wire, rod, bar, or strip .
• the steel product may be in the form of any one of wire, rod, bar, or strip.
• the rod and bar products may range from products which have small to large aspect ratios of length to diameter.
• the rod and bar products may range from products which have diameters that are close to the length of the products to products that have diameters or transverse cross-sectional areas that are significantly less than the length of the products .
• the steel product may be in the form of a steel product that is made from any one of wire, rod, bar, and strip.
• a non-exclusive range of steel products is set out above.
• One particular steel product of interest to the applicant is reinforcement mesh for the concrete construction and mining industries made by welding together spaced-apart parallel line wires and spaced-apart parallel cross-wires.
• Another particular steel product of interest to the applicant is reinforcing bar of all kinds, such as in straight lengths and formed into ligatures or continuous spirals or other commonly available shapes (noting that there are many such shapes) .
• the invention and the properties achieved by the invention are not limited by the shape of the steel product.
• the mechanically worked steel product may be a cold rolled or drawn or any other suitable mechanically worked product that results in a change of cross-sectional shape of the product, without necessarily changing the transverse cross-sectional area, such that there has been energy input required to cause the shape change .
• the shape change may be from a circular to an oval transverse cross- section of the same cross-sectional area as the circular shape .
• the mechanically worked steel product may be a cold rolled or drawn or any other suitable mechanically worked product that has a reduced transverse cross-sectional area after it has been mechanically worked.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 2% less than the transverse cross-sectional area of the steel product before the mechanical working.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 5% less than the transverse cross-sectional area of the steel product before the mechanical working .
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 10% less than the transverse cross-sectional area of the steel product be ore the mechanical working .
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 15% less than the transverse cross-sectional area of the steel product before the mechanical working.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 20% less than the transverse cross-sectional area of the steel product before the mechanical working.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 40% less than the transverse cross-sectional area of the steel product before the mechanical working.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 50% less than the transverse cross-sectional area of the steel product before the mechanical working.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 60% less than the transverse cross-sectional area of the steel product before the mechanical working.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 70% less than the transverse cross-sectional area of the steel product before the mechanical working .
• the method may include cooling the heat treated product from the heat treatment temperature at any suitable cooling rate .
• the heat treated product may be quenched by being water-cooled.
• the heat treated product may be cooled in ambient air.
• the cooling rate does not have a significant impact on properties, namely ductility, yield stress and tensile strength.
• quenching the heat treated product may have a significant impact on the properties in some situations, such as when quenching from heat treatment temperatures of at least 750°C after a particular time. In one example, after
• the steel may be a low carbon steel, as described above .
• the steel may be a medium carbon steel, as described above .
• the steel may be a high strength low alloy steel, as defined above.
• the high strength low alloy steel may contain greater than 0.040 wt.% V.
• the high strength low alloy steel may contain greater than 0.050 wt.% V.
• the high strength low alloy steel may contain greater than 0.060 wt.% V.
• the high strength low alloy steel may contain greater than 0.005 wt.% N.
• the high strength low alloy steel may contain greater than 0.015 wt.% N.
• the high strength low alloy steel may contain greater than 0.018 wt.% N.
• the high strength low alloy steel may contain other alloying elements , such as Nb .
• the present invention provides a method of producing a steel product that includes :
• the method may include multiple sequences of steps (a) and (b) and (c) .
• the present invention provides a method of producing a steel product that includes :
• the method may include multiple sequences of steps (a) and (b) .
• the present invention provides a method of producing a steel product that includes : (a) mechanically working a feed steel,
• the method may include multiple sequences of steps (a) and (b) and (c) .
• the present invention provides a method of producing a steel product that includes : (a) mechanically working a feed steel,
• the method may include multiple sequences of steps (a) and (b) and (c) .
• the increase in elongation of the heat treated steel may be greater than 5% relative to that of the mechanically worked feed steel .
• the increase in elongation of the heat treated steel may be greater than 10%.
• the increase in elongation of the heat treated steel may be greater than 20%.
• the increase in elongation of the heat treated steel may be greater than 30%.
• the increase in elongation of the heat treated steel may be greater than 50%.
• the increase in elongation of the heat treated steel may be greater than 100%.
• the increase in elongation of the heat treated steel may be greater than 150%.
• the increase in elongation of the heat treated steel may be greater than 200%.
• the increase in the yield stress of the heat treated steel may be greater than 10%.
• the increase in the yield stress of the heat treated steel may be greater than 20%.
• the increase in the yield stress of the heat treated steel may be greater than 30%.
• the increase in the yield stress of the heat treated steel may be greater than 40%.
• the method may also include forming the steel product into another steel product.
• the feed steel may be any one of low carbon steel, medium carbon steel, and high strength low alloy steel.
• the feed steel may be in any suitable form.
• the feed steel may be in the form of any one of wire, rod, bar, or strip .
• the mechanical working step may comprise reducing the transverse cross-sectional area, i.e. the diameter, of wire, rod and bar. It is also noted that the mechanical working step may comprise reducing the transverse cross-sectional area, i.e. the thickness, of the strip.
• the mechanical working step may result in a change of cross-sectional shape of the product, without necessarily changing the transverse cross- sectional area, such that there has been energy input required to cause the shape change .
• the steel product may be any suitable form of product .
• the steel product may be in the form of a steel product that is made from any one of wire, rod, bar, and strip.
• the mechanical working step (a) may include cold rolling or drawing or any other suitable mechanical working step that reduces the transverse cross-sectional area of the feed steel.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 2% less than the transverse cross-sectional area of the steel product before the mechanical working .
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 5% less than the transverse cross-sectional area of the steel product be ore the mechanical working .
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 10% less than the transverse cross-sectional area of the steel product before the mechanical working.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 15% less than the transverse cross-sectional area of the steel product before the mechanical working.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 20% less than the transverse cross-sectional area of the steel product before the mechanical working.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 40% less than the transverse cross-sectional area of the steel product before the mechanical working.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 50% less than the transverse cross-sectional area of the steel product before the mechanical working.
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 60% less than the transverse cross-sectional area of the steel product before the mechanical working .
• the reduced transverse cross-sectional area of the mechanically worked steel product may be at least 70% less than the transverse cross-sectional area of the steel product before the mechanical working .
• the heat treatment step may be carried out at a temperature below the austenitising temperature of the steel.
• the heat treatment step may be carried out at a temperature below 1000°C.
• the heat treatment step may be carried out at a temperature below 800°C.
• the heat treatment step may be carried out at a temperature below 750°C.
• the heat treatment step may be carried out at a temperature below 700°C.
• the heat treatment step may be carried out at a temperature below 600°C.
• the heat treatment step may be carried out at a temperature below 550°C.
• the heat treatment step may be carried out at a temperature below 500°C.
• the heat treatment step may be carried out at a temperature below 450°C.
• the heat treatment step may be carried out at a temperature below 400°C.
• the heat treatment step may be carried out at a temperature below 300°C.
• the heat treatment step may be carried out at a temperature below 250°C.
• the heat treatment step may be carried out at a temperature above 200°C.
• the heat treatment step may be carried out at a temperature above 150°C.
• the heat treatment step may be carried out for less than 16 hours.
• the heat treatment step may be carried out for less than 10 hours.
• the heat treatment step may be carried out for less than 6 hours .
• the heat treatment step may be carried out for less than 5 hours .
• the heat treatment step may be carried out for less than 4 hours .
• the heat treatment step may be carried out for greater than 1 hour .
• the heat treatment step may be carried out for greater than 45 minutes.
• the heat treatment step may be carried out for greater than 30 minutes.
• the heat treatment step may be carried out for greater than 10 minutes.
• the heat treatment step may be carried out for greater than 5 minutes .
• the heat treatment step may be carried out for greater than 1 minute .
• the heat treatment step may be carried out for greater than 30 seconds.
• the heat treatment step (b) may be carried out in any suitable atmosphere .
• the present invent also provides a steel product made by the above method.
• the steel product may have a yield stress of at least 500 MPa yield stress and a Uniform Elongation of at least 1.5% Agt.
• the present invention also provides a mechanically worked and heat treated high strength low alloy steel product that has a steel composition, an elongation and a yield stress as described above .
• the steel product may have a tensile strength as described.
• the present invention also provides a mechanically worked and heat treated low carbon steel product that has a steel composition, an elongation and a yield stress as described above.
• the steel product may have a tensile strength as described.
• the present invention also provides a mechanically worked and heat treated medium carbon steel product that has a steel composition, an elongation and a yield stress as described above .
• the steel product may have a tensile strength as described.
• the steel product may be in the form of a steel product that is made from any one of wire, rod, bar, and strip as described above .
• the steel product is a mesh product that includes parallel line wires and parallel cross-wires welded together at the intersections of the wires, with the wires being steel wires, with the wires being at least 3 mm in diameter, and with the wires having been mechanically worked and heat treated prior to being welded together to form the mesh, such that the wires have a yield stress of at least 650 MPa and a Uniform Elongation of at least 1.5% Agt.
• the steel product is a mesh product that includes parallel line wires and parallel cross-wires welded together at the intersections of the wires, with the wires being at least 3 mm in diameter, with the wires being steel wires, with the wires having been mechanically worked prior to being welded together to form the mesh, and with the mesh being heat treated, such that the wires having a yield stress of at least 650 MPa and a Uniform Elongation of at least 1.5% Agt.
• the steel product is a ligature formed from a steel wire that is at least 3 mm in diameter, and with the wire having been mechanically worked and heat treated prior to being formed into the ligature, such that the wires have a yield stress of at least 650 MPa and a Uniform Elongation of at least 1.5% Agt.
• the steel product is a ligature formed from a steel wire that is at least 3 mm in diameter, and with the wire having been mechanically worked prior to being formed into the ligature, with the ligature being heated treated, such that the wires have a yield stress of at least 650 MPa and a Uniform Elongation of at least 1.5% Agt.
• the present invention is based on an extensive research and development program that focused on testing a substantial number of samples of low carbon steel, medium carbon steel and high strength low alloy.
• the samples included samples mechanically worked under different
• the steel wire was made from low carbon steel, medium carbon steel, and high strength low alloy steel .
• the steel wire was made by rolling a larger diameter steel rod or wire to smaller diameters .
• the samples included (a) 10 mm diameter rod rolled to 9.5 mm wire, (b) 8 mm diameter rod rolled to 7.7 mm, 7.6 mm, 7.5 and 6.75 mm wire, (c) 10.5 mm rod rolled to 9.5 mm, (d) 8.5 mm rod rolled to 6.75 mm, (e)
• Heat treatment furnace a fan forced air furnace and a resistance heated furnace.
• Figures 26-32 focus on low carbon steel samples, and Figure 33 focuses on medium carbon steel samples.
• Figure 1 is a graph of elongation (Agt) versus heat treatment time (0-30 minutes) for HSLA samples heat treated at 300, 400, 500, 600, and 700°C, with the samples comprising 9.5 mm diameter wire samples cold rolled from 10 mm diameter rod in accordance with the invention. It is evident from Figure 1 that the ductility of the samples increased with heat
• Figure 2 is a graph of yield stress (Proof Strength - MPa) versus heat treatment time (0-30 minutes) for HSLA samples heat treated at 300, 400, 500, 600, and 700°C, with the samples comprising 9.5 mm diameter wire samples cold rolled from 10 mm diameter rod in accordance with the
• the yield stress of the samples heat treated at the higher temperatures decreased (e.g. 500, 600, and 700°C) as the heat treatment times increased. However, there was no decrease in yield stress with heat treatment time for the samples that were heat treated at lower temperatures (300 and 400°C) . The increase in yield stress was achieved with relatively short heat treatment times across the range of heat treatment temperatures . This is potentially significant in terms of processing times and costs .
• Figure 3 is a graph of tensile strength (MPa) versus heat treatment time (0-30 minutes) for samples heat treated at 300, 400, 500, 600, and 700°C, with the samples comprising 9.5 mm diameter HSLA wire samples mechanically worked by being cold rolled from 10 mm diameter rod in accordance with the invention.
• the cold rolling amounts to a 9.75% reduction in transverse cross-sectional area. It is evident from Figure 3 that there was an increase in tensile strength of the cold rolled samples at short (less than 4 minutes) heat treatment times at each of the heat treatment temperatures.
• the tensile strength of the samples that were heat treated at the higher temperatures e.g. 500, 600, and 700 °C
• Figure 4 includes a graph of elongation (measured as Uniform Elongation - Agt) versus heat treatment time (0-5 hours) for 9.5 mm diameter HSLA wire samples cold rolled from 10 mm diameter rod and heat treated at 300 °C in accordance with the invention.
• the cold rolling amounts to a 9.75% reduction in transverse cross-sectional area.
• This graph is described as the "NlOPLUS” curve in the Figure.
• Figure 4 also includes comparative data for 6.75 mm diameter low carbon steel wire samples cold rolled from 8.5 mm diameter rod and heat treated in the same way.
• the cold rolling amounts to a 37% reduction in transverse cross-sectional area.
• This graph is described as the "6.75EX8.5" curve in Figure 4.
• Figure 4 illustrates increases in ductility that might be expected as a consequence of the heat treatment of either steel samples .
• Figure 5 includes graphs of yield stress (reported as Proof Stress - MPa) versus heat treatment time (0-5 hours) for the Figure 4 samples (HSLA and low carbon steel) heat treated at 300°C.
• Figure 6 includes graphs of tensile strength (MPa) versus heat treatment time (0-5 hours) for the Figure 4 samples (HSLA and low carbon steel) heat treated at 300°C.
• Figure 7 is a graph of elongation (Agt) versus heat treatment temperature (0-500 °C) for HSLA samples heat treated for 4 hours, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm diameter rod in accordance with the invention. The samples were cold rolled to different extents, with the highest reduction being around 12% in transverse cross-sectional area. It is evident from Figure 7 that there was an increase in ductility in the cold drawn samples at heat treatment temperature greater than 200°C and that the ductility increased as the heat treatment temperature increased .
• Figure 8 is a graph of yield stress (Proof Stress MPa) versus heat treatment temperature (0-500°C) for HSLA samples heat treated for 4 hours, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm diameter rod in accordance with the invention .
• the samples were cold rolled to different extents, with the highest reduction being around 12% in transverse cross- sectional area. It is evident from Figure 8 that the yield stress of each of the cold drawn samples initially increased and then decreased as the heat treatment temperature
• Figure 9 is a graph of tensile strength (MPa) versus heat treatment temperature for HSLA samples heat treated for 4 hours, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm diameter rod in accordance with the invention. The samples were cold rolled to different extents, with the highest reduction being around 12% in transverse cross-sectional area. It is evident from Figure 9 that the tensile strength of each of the cold rolled samples initially increased and then decreased as the heat treatment temperature increased. The tensile strength was higher for the samples having higher cold reductions .
• FIG. 10 is a graph of elongation (Agt) versus heat treatment time (0-7 hours) for HSLA samples heat treated at 100°C, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm diameter rod. The samples were cold rolled to different extents, with the highest reduction being around 12% in transverse cross- sectional area. It is evident from Figure 10 that there was an overall slight decrease in ductility in the cold drawn samples across the range of heat treatment times . This decrease is consistent with a strain ageing mechanism.
• the ductility change was conventional and the teaching is that the heat treatment temperature of 100 °C was too low.
• the ductility was higher for the samples having lower cold reductions .
• Figure 11 is a graph of yield stress (Proof Strength - MPa) versus heat treatment time (0-7 hours) for HSLA samples heat treated at 100°C, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold drawn from 8 mm diameter rod in accordance with the invention. The samples were cold drawn to different extents, with the highest reduction being around 12% in transverse cross-sectional area. It is evident from Figure 11 that there was an increase
• Figure 12 is a graph of tensile strength (MPa) versus heat treatment time (0-7 hours) for HSLA samples heat treated at 100°C, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm
• Figure 13 is a graph of elongation (Agt) versus heat treatment time (0-16 hours) for HSLA samples heat treated at 300°C, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm diameter rod in accordance with the invention .
• the samples were cold rolled to different extents, with the highest reduction being around 12% in transverse cross-sectional area. It is evident from Figure 13 that after an initial sudden decrease in ductility (which is consistent with normal ageing) there was a
• Figure 14 is a graph of yield stress (Proof Stress -
• Figure 15 is a graph of tensile strength (MPa) versus heat treatment time (0-16 hours) for HSLA samples heat treated at 300°C, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm diameter rod in accordance with the invention .
• the samples were cold rolled to different extents, with the highest reduction being around 12% in transverse cross-sectional area.
• Figure 16 is a graph of elongation (Agt) versus heat treatment time (0-30 minutes) for HSLA samples heat treated at 300°C, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm diameter rod in accordance with the invention . These samples were cold rolled and heat treated under the same conditions as the Figure 13 samples. The samples were cold rolled to different extents, with the highest reduction being around 12% in transverse cross-sectional area. This graph focuses on the first 30 minutes of heat treatment time highlighted in the discussion of Figure 13.
• Figure 17 is a graph of yield stress (Proof Stress -
• Figure 18 is a graph of tensile strength (MPa) versus heat treatment time (0-30 minutes) for HSLA samples heat treated at 300°C, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm diameter rod in accordance with the invention. The samples were cold rolled to different extents, with the highest reduction being around 12% in transverse cross-sectional area. These samples were cold rolled and heat treated under the same conditions as the Figure 15 samples. This graph focuses on the first 30 minutes of heat treatment time highlighted in the discussion of Figure 15. It is evident from Figure 18 that there was a steady increase in tensile strength with heat treatment time at 300°C for each of the samples. The tensile strength was higher for the samples having higher cold reductions .
• MPa tensile strength
• Figure 19 is a graph of elongation (Agt) versus heat treatment time (0-30 minutes) for HSLA samples heat treated at 500°C, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm diameter rod in accordance with the invention. The samples were cold rolled to different extents, with the highest reduction being around 12% in transverse cross-sectional area. It is evident from Figure 19 that after an initial decrease in ductility (which is consistent with normal ageing) there was a steady increase in ductility with heat treatment time at 500 °C for each of the samples, with the ductility being higher for the samples having lower cold reductions .
• Figure 20 is a graph of yield stress (Proof Stress - MPa) versus heat treatment time (0-30 minutes) for HSLA samples heat treated at 500°C, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm diameter rod in accordance with the invention. The samples were cold rolled to different extents, with the highest reduction being around 12% in transverse cross- sectional area. It is evident from Figure 20 that there was an initial increase in yield stress at the heat treatment temperature of 500 °C for each of sample, with the yield stress of each sample reaching a maximum yield stress after 10 minutes . The yield stress of each sample decreased with heat treatment times greater than 10 minutes. The yield stress was higher for the samples having higher cold reductions . The yield stress of the samples was higher across the whole heat treatment temperature range than the yield stress of the samples prior to heat treatment.
• Figure 21 is a graph of tensile strength (MPa) versus heat treatment time (0-30 minutes) for HSLA samples heat treated at 500°C, with the samples comprising 7.5 mm, 7.6 mm, and 7.7 mm diameter wire samples cold rolled from 8 mm diameter rod in accordance with the invention. The samples were cold rolled to different extents, with the highest reduction being around 12% in transverse cross-sectional area. It is evident from Figure 21 that there was an initial increase in tensile strength at the heat treatment
• Figure 22 is a graph of elongation (Agt) versus heat treatment time (0-20 minutes) for 6.75 mm diameter HSLA wire samples cold rolled from 8 mm diameter rod and heat treated at 750°C over a time period up to 20 minutes and then water quenched in accordance with the invention.
• the cold rolling amounts to a 29% reduction in transverse cross-sectional area. It is evident from Figure 22 that after an initial decrease in ductility (which is consistent with normal strain ageing) there was a steady increase in ductility with heat treatment time at 750°C until 7 minutes, followed by a sudden decrease in ductility and a sudden increase before levelling out at around 10-12 minutes.
• Figure 23 is a graph of yield stress (Proof Strength - MPa) and tensile strength (MPa) versus heat treatment time (0-20 minutes) for 6.75 mm diameter HSLA wire samples cold rolled from 8 mm diameter rod and heat treated at 750°C and then water quenched in accordance with the invention. It is evident from Figure 23 that water quenching samples that were heat treated for up to 7 minutes and then quenched had an improvement in yield stress and tensile strength. Heat treatment times less than 8 minutes followed by quenching resulted in a significant increase in tensile strength and a significant reduction in yield stress.
• Figure 24 is a graph of elongation (Agt) versus heat treatment time (0-20 minutes) for 6.75 mm diameter HSLA wire samples cold rolled from 8 mm diameter rod and heat treated at 500°C and then water quenched in accordance with the
• Figure 25 is a graph of yield stress (Proof Strength - MPa) and tensile strength (MPa) versus heat treatment time (0-20 minutes) for 6.75 mm diameter HSLA wire samples cold rolled from 8 mm diameter rod and heat treated at 500°C and then water quenched in accordance with the invention. It is evident from Figure 25 that water quenching heat treated samples had substantially no impact on yield stress and tensile stress. In other words, at this heat treatment temperature there is no downside in water quenching treated steel. It is noted nevertheless that these heat treatment conditions produced an increase in yield stress and tensile strength.
• Figures 26-31 focus on the results of research and development work on low carbon steel samples .
• Figure 26 is a graph of elongation (Agt) versus heat treatment time (0-30 minutes) for samples heat treated at 500°C, with the samples comprising 9.5 mm and 6.75 mm diameter low carbon steel wire samples cold rolled from 10 mm diameter and 8.5 mm rod respectively in accordance with the invention. The cold rolling amounts to a 18% and 37% reduction in transverse cross-sectional area, respectively. It is evident from Figure 26 that after an initial decrease in ductility (which is consistent with normal strain ageing) there was a steady increase in ductility with heat treatment time at 500°C.
• Figure 27 is a graph of yield stress (Proof Strength - MPa) versus heat treatment time (0-30 minutes) for samples heat treated at 500°C, with the samples comprising 9.5 mm and 6.75 mm diameter low carbon steel wire samples cold rolled from 10.5 mm diameter and 8.5 mm rod respectively in
• the cold rolling amounts to a 18% and 37% reduction in transverse cross-sectional area, respectively.
• the yield stress of the more heavily mechanically worked sample i.e. the 6.75 mm sample
• initially increased up to 2 minutes heat treatment time
• then decreased with heat treatment time with a period of 7 minutes treatment time passing before the yield stress decreased to the initial start strength, i.e. cold worked strength.
• the initial increase in yield stress is a surprising result and indicates that there is a heat treatment window in which it is possible to achieve an increase in yield stress.
• the yield stress of the less heavily mechanically worked sample i.e. the 9.5 mm sample
• Figure 28 is a graph of tensile strength (MPa) versus heat treatment time (0-30 minutes) for samples heat treated at 500°C, with the samples comprising 9.5 mm and 6.75 mm diameter low carbon steel wire samples cold rolled from 10.5 mm diameter and 8.5 mm rod respectively in accordance with the invention. The cold rolling amounts to a 18% and 37% reduction in transverse cross-sectional area, respectively. It is evident from Figure 28 that the tensile strength of the less heavily mechanically worked sample (i.e. the 9.5 mm sample) initially increased (up to 8 minutes heat treatment time) and then decreased with heat treatment time.
• MPa tensile strength
• the initial increase in tensile strength is a surprising result and indicates that there is a heat treatment window in which it is possible to achieve an increase in tensile strength.
• the Figure 28 result is a significant result because it indicates that it is possible to heat treat such heavily worked steel and achieve the Figure 26 increase in ductility and the Figure 27 increase in yield stress without a loss of tensile
• Figure 29 is a graph of yield stress (Proof Strength - MPa) , tensile strength (MPa) , and elongation (A gt ) versus heat treatment time (0-15 minutes) for samples heat treated at 500°C, with the samples comprising 10.7 mm diameter low carbon steel wire samples cold rolled from 12 mm diameter rod in accordance with the invention. The cold rolling amounts to a 20% reduction in transverse cross-sectional area of the samples. The plots for each parameter are shown as lines of best fit for the actual data points . It is evident from Figure 29 that yield stress, tensile strength and ductility Increased steadily with heat treatment time. The increase in yield stress is a surprising result. The yield stress of the samples was higher across the whole heat treatment temperature range than the yield stress of the samples prior to heat treatment .
• Figure 30 is a graph of yield stress (Proof Strength
• the initial increase in yield stress is a surprising result and indicates that there is a heat treatment window in which it is possible to achieve an increase in yield stress .
• the yield stress of the samples was higher across the whole heat treatment temperature range than the yield stress of the samples prior to heat treatment. It is also evident from Figure 30 that ductility increased steadily with heat treatment time .
• Figure 31 is a graph of yield stress (Proof Strength
• the initial increase in yield stress is a surprising result and indicates that there is a heat treatment window in which it is possible to achieve an increase in yield stress.
• the yield stress of the samples was higher across the whole heat treatment temperature range than the yield stress of the samples prior to heat treatment. It is also evident from Figure 31 that ductility increased steadily with heat treatment time.
• Figure 32 is a graph of yield stress (Proof Strength - MPa) , tensile strength ( Pa) , and elongation (A gt ) versus heat treatment time (0-15 minutes) for samples heat treated at 500°C, with the samples comprising 4.75 mm diameter low carbon steel wire samples cold rolled from 5.5 mm diameter rod in accordance with the invention.
• the wire samples were passed through a straightener before being heat treated.
• the cold rolling amounts to a 25% reduction in transverse cross- sectional area of the samples .
• the only difference between the experimental procedure for this experiment and the experiment reported in Figure 31 relates to the type of straightener used.
• the straightening roll was a smaller diameter straightening roll than the straightening roll used for the item (h) samples .
• Figure 33 is a graph of yield stress (Proof Strength - MPa) , tensile strength (MPa) , and elongation (A gt ) versus heat treatment time (0-15 minutes) for samples heat treated at 500°C, with the samples comprising 3.06 mm diameter medium carbon steel wire samples cold rolled from 5.5 mm diameter rod in accordance with the invention. The cold rolling amounts to a 69% reduction in transverse cross-sectional area,
• the initial increase in yield stress is a surprising result and indicates that there is a heat treatment window in which it is possible to achieve an increase in yield stress .
• the yield stress of the samples was higher across the whole heat treatment temperature range than the yield stress of the samples prior to heat treatment. It is also evident from Figure 33 that ductility increased steadily with heat treatment time .
• the finding is a significant finding for the following reasons : ⁇ It is possible to significantly reduce the amount of steel required to manufacture products without a loss of force capacity of the steel in the products . The reduced amount of steel required for products improves the economics of construction and reduces the carbon
• the method is inexpensive in that it can be carried out with low capital and operating costs.
• steel wire can be processed in accordance with the invention to increase the yield stress and ductility of the wire and then coiled.
• the coiled product can be formed into end use products such as spirals, ligatures etc.
• standard wire can be produced and coiled and then processed to produce products such as mesh sheets and ligatures etc. and these products can be processed in accordance with the invention to increase the yield stress and ductility of the products .

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Heat Treatment Of Steel (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Heat Treatment Of Sheet Steel (AREA)

Priority Applications (13)

Applications Claiming Priority (2)

Related Child Applications (2)

Publications (1)

Family

ID=51688747

Family Applications (1)

Country Status (11)

Families Citing this family (3)

Citations (2)

Family Cites Families (17)

• 2013
  • 2013-04-13 AU AU2013205082A patent/AU2013205082B2/en active Active
• 2014
  • 2014-04-13 JP JP2016506734A patent/JP2016517915A/ja active Pending
  • 2014-04-13 EP EP14782460.1A patent/EP2984190A4/en not_active Withdrawn
  • 2014-04-13 BR BR112015025895A patent/BR112015025895A2/pt not_active IP Right Cessation
  • 2014-04-13 CN CN201910420128.6A patent/CN110331346A/zh active Pending
  • 2014-04-13 US US14/784,248 patent/US20160068925A1/en not_active Abandoned
  • 2014-04-13 SG SG11201507872VA patent/SG11201507872VA/en unknown
  • 2014-04-13 NZ NZ712644A patent/NZ712644A/en unknown
  • 2014-04-13 KR KR1020157031725A patent/KR102427244B1/ko active Active
  • 2014-04-13 WO PCT/AU2014/000416 patent/WO2014165934A1/en not_active Ceased
  • 2014-04-13 CN CN201480020343.2A patent/CN105164282B/zh active Active
  • 2014-04-13 CA CA2908922A patent/CA2908922A1/en not_active Abandoned
  • 2014-04-13 AU AU2014252700A patent/AU2014252700A1/en not_active Abandoned
• 2018
  • 2018-03-15 US US15/922,116 patent/US20180202014A1/en not_active Abandoned
• 2019
  • 2019-02-14 AU AU2019201022A patent/AU2019201022B2/en active Active
  • 2019-04-26 JP JP2019086032A patent/JP2019178424A/ja active Pending
• 2021
  • 2021-04-21 AU AU2021202437A patent/AU2021202437A1/en not_active Abandoned
  • 2021-12-01 JP JP2021195465A patent/JP2022046474A/ja active Pending

Patent Citations (2)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events