Abstract

A 600 MPa-grade fine-grain anti-seismic rebar and a fabrication method therefor, the method comprising molten steel smelting, deoxidation and alloying, molten steel LF furnace refining, molten steel casting, steel billet heating and steel billet controlled rolling/controlled cooling processes. In the fabrication method, prior to steel production active lime is added to the bottom of a ladle so as to carry out slag splashing, and then bottom blowing of nitrogen is carried out during the entire steel production process. This reduces the [S] content in the molten steel, thereby improving the molten steel cleanliness and promoting an increase in the plasticity and toughness of the steel. A certain amount of vanadium-containing pig iron is added into an LF refining furnace to replace a portion of expensive vanadium alloy, thus increasing the V content of the molten steel while reducing the amount of the vanadium alloy used and reducing alloying costs during converter steel production. During the steel rolling process, pre-water-cooling is used prior to the finishing step to allow for a low initial finishing temperature, and then a post-finishing multi-phase staged controlled cooling process is applied. Thus, the grain size of the microstructure ferrite of the rebar may be greater than or equal to 12.0-grade, allowing for an outstanding fine-grain strengthening and toughening effect. The production cost of the fabrication method is lower than vanadium microalloying hot rolling processes by 40 yuan/t of steel or more, thus increasing the market competitiveness and application prospects of the final product, while offering outstanding economic and social benefits.

IPC Classes  ?

• C22C 38/02 - Ferrous alloys, e.g. steel alloys containing silicon
• C22C 38/04 - Ferrous alloys, e.g. steel alloys containing manganese
• C22C 38/24 - Ferrous alloys, e.g. steel alloys containing chromium with vanadium
• C22C 38/26 - Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
• C22C 38/38 - Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
• C21C 7/00 - Treating molten ferrous alloys, e.g. steel, not covered by groups
• C21C 7/06 - Deoxidising, e.g. killing
• C21C 7/064 - DephosphorisingDesulfurising
• C21D 8/06 - Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
• C21D 8/08 - Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement
• C21D 9/52 - Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articlesFurnaces therefor for wiresHeat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articlesFurnaces therefor for strips
• C22C 33/04 - Making ferrous alloys by melting
• C22C 33/06 - Making ferrous alloys by melting using master alloys

Abstract

A 500 MPa-grade high-strength high-toughness anti-seismic rebar and a fabrication method therefor, the method comprising molten steel smelting, deoxidation and alloying, molten steel argon station refining, molten steel casting, steel billet heating and steel billet controlled rolling/controlled cooling processes. In the present fabrication method, during the steel refining process, a certain amount of vanadium-containing pig iron is added into an LF refining furnace to replace a portion of expensive vanadium alloy, thus increasing the V content of the molten steel while reducing the amount of the vanadium alloy used. A small amount of silicon-nitrogen alloy is added during the steel-making deoxidation and alloying process, increasing the nitrogen content of the molten steel, and promoting the transfer of V and Nb from a solid solution state to a carbon nitride precipitation phase during the rolling process. Thus, finely dispersed V (C,N) and Nb (C,N) precipitate phases are formed and precipitated in large quantities, reducing the phase change temperature, and markedly improving the precipitation strengthening of the steel. The present fabrication method has a low production cost. Rebar fabricated by means of the method has the advantage of having excellent and stable mechanical properties, a fine and uniform microstructure, good plasticity and toughness, and excellent anti-seismic properties, durability and connectability.

IPC Classes  ?

• C22C 38/02 - Ferrous alloys, e.g. steel alloys containing silicon
• C22C 38/04 - Ferrous alloys, e.g. steel alloys containing manganese
• C22C 38/24 - Ferrous alloys, e.g. steel alloys containing chromium with vanadium
• C22C 38/26 - Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
• C22C 33/04 - Making ferrous alloys by melting
• C21C 5/28 - Manufacture of steel in the converter
• C21C 7/00 - Treating molten ferrous alloys, e.g. steel, not covered by groups
• C21C 7/06 - Deoxidising, e.g. killing
• C21C 7/072 - Treatment with gases
• C21D 8/06 - Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
• C21D 8/08 - Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement

Abstract

A 600 MPa-grade large-specification high-strength corrosion-resistant anti-seismic rebar and a fabrication method therefor, the method comprising molten steel smelting, deoxidation and alloying, molten steel LF refining, molten steel casting, steel billet heating and steel billet controlled rolling/controlled cooling processes. In the present fabrication method, a certain amount of vanadium-containing pig iron is added to replace expensive vanadium alloy, thus increasing the vanadium content of the molten steel while reducing the amount of the vanadium alloy used. By adding a certain amount of chromium, the passivation and corrosion resistance of the steel are improved, the corrosion rate thus being only 1/2 that of ordinary 600 MPa-grade high-strength rebar. In addition, the hardenability and the secondary hardening effect are markedly improved, the pearlite content is increased, the tensile strength of the steel is improved, and the anti-seismic properties are improved. The present fabrication method has a low production cost, high process applicability and controllability, and other such characteristics. Rebar produced by means of the method has the advantage of having excellent and stable mechanical properties, a fine and uniform microstructure, good plasticity and toughness, and excellent corrosion resistance and anti-seismic properties.

IPC Classes  ?

• C22C 38/02 - Ferrous alloys, e.g. steel alloys containing silicon
• C22C 38/04 - Ferrous alloys, e.g. steel alloys containing manganese
• C22C 38/24 - Ferrous alloys, e.g. steel alloys containing chromium with vanadium
• C22C 33/06 - Making ferrous alloys by melting using master alloys
• C21C 7/06 - Deoxidising, e.g. killing
• C21D 8/08 - Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement