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WO2025056948A1 - A method for hot rolling a steel product - Google Patents

A method for hot rolling a steel product Download PDF

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Publication number
WO2025056948A1
WO2025056948A1 PCT/IB2023/059063 IB2023059063W WO2025056948A1 WO 2025056948 A1 WO2025056948 A1 WO 2025056948A1 IB 2023059063 W IB2023059063 W IB 2023059063W WO 2025056948 A1 WO2025056948 A1 WO 2025056948A1
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WO
WIPO (PCT)
Prior art keywords
copper
amounts
steel
antimony
tin
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.)
Pending
Application number
PCT/IB2023/059063
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French (fr)
Inventor
Evangeline AHTOY
Céline MUSIK
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.)
ArcelorMittal SA
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ArcelorMittal 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 ArcelorMittal SA filed Critical ArcelorMittal SA
Priority to PCT/IB2023/059063 priority Critical patent/WO2025056948A1/en
Priority to PCT/IB2024/058819 priority patent/WO2025057071A1/en
Publication of WO2025056948A1 publication Critical patent/WO2025056948A1/en
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/42—Constructional features of converters
    • C21C5/46—Details or accessories
    • C21C5/4673—Measuring and sampling devices
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/56—Manufacture of steel by other methods
    • C21C5/562—Manufacture of steel by other methods starting from scrap
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • 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
    • C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
    • 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
    • C21D8/0226—Hot 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • 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
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C2005/5288—Measuring or sampling devices
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C2300/00—Process aspects
    • C21C2300/06—Modeling of the process, e.g. for control purposes; CII

Definitions

  • the invention is related to a method of hot rolling a steel product wherein the steel is produced using steel scrap.
  • Steelmaking requires the use of iron-containing material, such as steel scrap, direct reduced iron (DRI) or pig iron.
  • steel scrap is commonly used in the steelmaking process to produce liquid steel. Said scrap can be used at different stages along the steelmaking process and in different steelmaking tools.
  • Converter, Basic Oxygen Furnace (BOF), Electric Arc Furnace (EAF), Smelting Furnace (SF) are some of the tools that can be used in particular for steelmaking production.
  • Copper is nobler than iron and it is enriched at the steel- oxide interface when iron is oxidized at high temperature.
  • the copper-rich liquid phase thus formed also called copper phase, eventually penetrates the steel along the austenite grain boundaries, weakening the bonds and inducing surface cracking during hot working. This cracking phenomenon is known as hot shortness.
  • a method according to the invention comprising the steps of production of a liquid steel, said production step comprising the melting of steel scrap comprising copper, the estimation of the amounts of copper %Cu es t, tin %Sn es t, antimony %Sb es t, sulphur %S es t, in said produced liquid steel, the casting of the liquid steel to produce a semi-product, the reheating of the semi product to a reheating temperature TR, the hot rolling of the reheated semi-product, wherein between the step of estimation and of casting, are performed a step of calculation of optimised amounts of tin %Sno P t, antimony %Sb op t and sulphur %S op t said optimised amounts fulfilling the equation OC(TR).
  • the method of the invention may also comprise the following optional characteristics considered separately or according to all possible technical combinations: the produced liquid steel comprises at least 0.1 % in weight of copper, in the production step, scrap is melted with hot metal and/or direct reduced iron, the produced liquid steel has a composition wherein %Sb ⁇ 0.01%, %As ⁇ 0.1%, %Sn ⁇ 0.05%, %Si ⁇ 0.9%, %Ni ⁇ 4.5%, %P ⁇ 0.46%, %S ⁇ 0.008%, %Mo ⁇ 2.2%, %Cr ⁇ 4.5%, %Mn ⁇ 2.5%, %AI ⁇ 0.6%, %C ⁇ 0.21%, % Nb ⁇ 0.21 %, %Ti ⁇ 0.21%, %V ⁇ 0.21%, %B ⁇ 0.002% and %Cu > 0.1 %, remainder being iron and unavoidable impurities, all amount being expressed in weight percent, the amount of copper in the liquid
  • the step of estimation further comprises the estimation of the amounts of carbon %Cest, boron %B es t, aluminium %Al es t and vanadium %V es t
  • the calculation step comprises the calculation of optimised amounts of carbon %Co P t, aluminium %Alo P t, boron %B op t and vanadium %Vo P t said optimised amounts fulfilling the equation OC(TR).
  • the step of estimation further comprises the estimation of the amounts of nickel %Ni es t, molybdenum %Mo es t, manganese %Mn es t, silicon %Si es t, chromium %Cr es t, arsenic %As es t, phosphorus %P es t, niobium %Nb es t, and titanium %Ti es t
  • the calculation step comprises the calculation of optimised amounts of tin %Sno P t, nickel %Nio P t , molybdenum %Moo P t, manganese %Mno P t, carbon %Co P t, antimony %Sbo P t, silicon %Sio P t, sulphur %So P t, chromium %Cro P t, aluminium %Ao P
  • a(T R ) -0.0003752.
  • )(TR) -5.6944E-05.TR + 0.008839, r
  • (T R ) - 0.0016517.
  • Figure 1 illustrates a plant to produce a hot rolled steel sheet
  • Figure 1 shows a plant for the production of a hot-rolled steel product.
  • Liquid steel 1 contained in a ladle 2 is poured into a tundish 3, which then allows liquid steel to flow through a nozzle into a mold.
  • This liquid steel begins to solidify along the caster 4 until it is fully solidified and cut to form a semi-product 5.
  • This semi-product 5 is generally left to cool at ambient temperature and stored in a slab yard before being sent to the hot rolling plant 6.
  • This hot rolling plant 6 comprises a reheating furnace 7 where the semi-product 5 is reheated before being transferred to the rolling mill 8 where it is rolled and transformed into a steel product which is coiled to form a hot rolled steel coil 9.
  • Figure 1 illustrates an embodiment of a plant to produce a hot rolled steel sheet but the method according to the invention may be performed in other plants allowing to turn liquid steel in a semi product such as a billet, a blank, a bar, an ingot, a slab or a bloom and transformation of this semi-product into a steel product 9 in a hot rolling plant 6, this hot rolling plant 6 comprising a reheating furnace 7 adapted to reheat the semi-product 5.
  • the semi-product 5 after casting is directly sent to the hot rolling plant where it is subjected to a heating step before being rolled.
  • This heating step may be performed in a tunnel furnace.
  • This plant is called a continuous plant or direct casting and rolling plant.
  • the production of liquid steel 1 comprises the melting of steel scrap containing copper.
  • scrap can be melted in an electric arc furnace (EAF), optionally together with pig iron and direct reduced iron (DRI), and then liquid steel is obtained which is subjected to a refining step before being poured into the tundish.
  • Scrap can also be melted in a Smelting Furnace (SF) together with pig iron and/or DRI, and the resulting molten metal sent to a converter or BOF for decarburization and conversion to liquid steel.
  • This liquid steel can then be subjected to refining steps, such as dephosphorization and/or desulfurization steps and/or secondary metallurgy steps.
  • Scrap can also be charged into the BOF.
  • the steel scrap that can be used is referred to, in the Ell-21 Steel Scrap specification, as old scraps (E1 or E3), new scraps (E8), shredded scraps 20 (E40) or fragmentized scraps (E46).
  • the estimation of the composition of the produced liquid steel includes the estimation of the amounts of copper %Cu es t, tin %Sn es t, antimony %Sb es t and sulphur %S es t.
  • the estimation also comprises the estimation of amount of carbon %C es t, boron %B es t, aluminium %Al es t and vanadium %V es t.
  • this estimation additionally comprises estimations of amounts of nickel %Ni es t, molybdenum %Mo es t, manganese %Mn es t, chromium %Cr es t, silicon %Si es t, arsenic %As es t, phosphorus %P es t, niobium %Nb es t and titanium %Ti es t- All percentages are expressed in percent by weight.
  • the steel composition of the liquid steel can be estimated at the end of the elaboration step and before the casting step.
  • the estimation of the steel composition is preferably performed by analysing lollipop samples from the hot metal ladle 2 that is used to fill in the casting tundish 3 or the ingot mould to obtain the semi-finished product. This estimation may also be performed using models.
  • step A of production of the liquid steel from 100 to 1000 kg of steel scrap per ton of hot metal is used.
  • step A from 100 to 950 kg of steel scrap per ton of hot metal is used.
  • step A from 100 to 900 kg of steel scrap per ton of hot metal is used.
  • step A from 100 to 800 kg of steel scrap per ton of hot metal is used.
  • step A from 100 to 600 kg 25 of steel scrap per ton of hot metal is used.
  • step A from 100 to 500 kg of steel scrap per ton of hot metal is used. Even more preferably, in step A, from 200 to 400 kg of steel scrap per ton of hot metal is used.
  • the residual elements are the non-desired elements coming from the steel scrap.
  • the unavoidable impurities come from the elaboration process, e.g. oxides, nitrides.
  • the liquid steel is elaborated it is poured into the tundish 3 and then cast in the caster 4 to produce the semi-product 5.
  • this semi-product 5 is generally left to cool at ambient temperature and stored in a warehouse before being sent to the hot rolling plant 6. Then the semi-product 5 is sent to the reheating furnace 7.
  • copper-rich phase is present on the surface of the semi-product.
  • copper-rich or copper-phase it is meant a phase comprising more than 75% by weight of copper, remainder being mostly iron and other alloying and residual elements present in the liquid steel. It is this copper-rich phase that will penetrate the steel along the austenite grain boundaries and will cause the hot shortness issue.
  • the semi-product to be rolled is charged at the entrance of the reheating furnace 7 where it is pushed forward on the hearth of the furnace by means of a pusher machine.
  • the semi-product is usually pre-heated, heated and soaked as it passes through pre-heating, heating and soaking zone of the reheating furnace. At the end of the soaking zone of the furnace, it is discharged from the furnace by an ejector for subsequent rolling in the rolling mill.
  • the temperature TR of the semi-product at the time of discharged depends on several factors and it can vary in the range of 1100° C to 1350°C.
  • the reheating furnace 7 is preferably a continuous reheating furnace such as a pusher type furnace, a walking hearth furnace, or a walking beam furnace.
  • the reheating temperature TR must be understood as the temperature of the semi-product 5 at the exit of the heating step, before the rolling.
  • optimised amounts of tin %Sno P t, antimony %Sb op t and sulphur %S op t are calculated so as to fulfil the following equation:
  • optimised amounts of tin %Sno P t, carbon %Co P t, antimony %Sbo P t, sulphur %So P t, aluminium %Alo P t, vanadium %Vo P t and boron %B op t are calculated so as to fulfil the following equation:
  • optimised amounts of tin %Sno P t, nickel %Nio P t , molybdenum %Moo P t, manganese %Mno P t, carbon %Co P t, antimony %Sbo P t, silicon %Sio P t, sulphur %So P t, chromium %Cro P t, aluminium %Ao P tl, vanadium %Vo P t, arsenic %Aso P t, phosphorus %Po P t, niobium %Nbo P t, titanium %Tio P t, and boron %Bo P t are calculated so as to fulfil the following equation,
  • the produced liquid steel has preferably a composition wherein %Sb ⁇ 0.01%, %As ⁇ 0.1%, %Sn ⁇ 0.05%, %Si ⁇ 0.9%, %Ni ⁇ 4.5%, %P ⁇ 0.46%, %S ⁇ 0.005%, %Mo ⁇ 2.2%, %Cr ⁇ 4.5%, %Mn ⁇ 2.5%, %AI ⁇ 0.6%, %C ⁇ 0.21 %, % Nb ⁇ 0.21%, %Ti ⁇ 0.21%, %V ⁇ 0.21%, %B ⁇ 0.002% and %Cu > 0.1% remainder being iron and unavoidable impurities, all amount being expressed in weight percent. Copper amount is preferably from 0.1 to 0.3% by weight.
  • the composition of the liquid steel is adjusted so that the copper content at the steel surface is below the copper solubility limit, thereby preventing or at least limiting its penetration into the steel along the austenite grain boundaries and causing hot shortness.
  • a trial was performed with three steel samples S1 to S2 having a composition as defined in table 2, remainder being iron and unavoidable impurities.
  • the solid samples were subjected to a heating step at TR equal to 1235°C to simulate the reheating step of an industrial installation and observations by a microscope were performed to identify presence of infiltrations in the steel bulk. Results are also included in table 2.
  • N means that no infiltrations have been observed while Y means that infiltrations of the copper-rich phase have been observed in the steel bulk.
  • optimised amounts of tin, sulphur and antimony were calculated using formula 1 and coefficients indicated in table 1.
  • Compositions of liquid steel were then adjusted and new samples, respectively named S1 bis, S2bis were cast and subjected to same heating step and observations as previously indicated.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

A method for hot rolling a steel semi-product, comprising the steps of producing a liquid steel, said production step comprising the melting of steel scrap comprising copper, estimating the amounts of copper %Cuest, tin %Snest, antimony %Sbest, sulphur %Sest, in said produced liquid steel, casting the liquid steel to produce a semi-product, reheating the semi product to a reheating temperature TR and hot rolling the reheated semi-product. The method further comprises the calculation of optimized amounts of tin, antimony, and sulfur.

Description

A method for hot rolling a steel product
[001] The invention is related to a method of hot rolling a steel product wherein the steel is produced using steel scrap.
[001] Steelmaking requires the use of iron-containing material, such as steel scrap, direct reduced iron (DRI) or pig iron. Today, steel scrap is commonly used in the steelmaking process to produce liquid steel. Said scrap can be used at different stages along the steelmaking process and in different steelmaking tools. Converter, Basic Oxygen Furnace (BOF), Electric Arc Furnace (EAF), Smelting Furnace (SF) are some of the tools that can be used in particular for steelmaking production.
[002] In order to reduce the CO2 global footprint of the steelmaking process, there is a global trend to use more and more scrap in steel production. However, said scrap may be of different types, in particular depending on its origin, and thus have different qualities in terms notably of shape, density, chemistry and presence of impurities. Steel scrap contains residual elements, such as copper, chromium, molybdenum, nickel, tin, antimony, zinc and/or arsenic. The use of steel scrap is therefore not widespread for all steel grades as these residual elements can have a detrimental effect on the properties of the steel.
[003] When steel is produced using direct reduced iron and/or pig iron, small amounts of residual elements are inevitably left behind in the molten metal. When steel scrap is used, the amount of residual elements is much greater than in the case of pig iron coming from a blast furnace or direct reduced iron.
[004] Recently, it has been observed by the present inventors that the production of steel using a significant amount of steel scrap raises problems during some manufacturing steps such as hot rolling.
[005] One of the impurities contained in steel scrap that is difficult to remove in the steelmaking process is copper. Copper is nobler than iron and it is enriched at the steel- oxide interface when iron is oxidized at high temperature. The copper-rich liquid phase thus formed, also called copper phase, eventually penetrates the steel along the austenite grain boundaries, weakening the bonds and inducing surface cracking during hot working. This cracking phenomenon is known as hot shortness.
[006] There is so a need for a method to produce a hot rolled steel using steel scrap wherein hot shortness risk is reduced and even suppressed. i)This problem is solved by a method according to the invention comprising the steps of production of a liquid steel, said production step comprising the melting of steel scrap comprising copper, the estimation of the amounts of copper %Cuest, tin %Snest, antimony %Sbest, sulphur %Sest, in said produced liquid steel, the casting of the liquid steel to produce a semi-product, the reheating of the semi product to a reheating temperature TR, the hot rolling of the reheated semi-product, wherein between the step of estimation and of casting, are performed a step of calculation of optimised amounts of tin %SnoPt, antimony %Sbopt and sulphur %Sopt said optimised amounts fulfilling the equation OC(TR). %SnoPt + S(TR). %SbOpt + H(TR). %SoPt + A(TR) > %Cuest, where a(TR), E(TR), r|(TR) are coefficients representing the respective impacts of, tin, antimony, and sulphur, on the solubility of copper according to the reheating temperature TR, and A(TR), is a coefficient representing the impact of the reheating temperature TR on the solubility of copper and adjustment of the final respective amounts of tin, antimony, and sulphur in the liquid steel so that it matches optimised calculated amounts.
[007] The method of the invention may also comprise the following optional characteristics considered separately or according to all possible technical combinations: the produced liquid steel comprises at least 0.1 % in weight of copper, in the production step, scrap is melted with hot metal and/or direct reduced iron, the produced liquid steel has a composition wherein %Sb < 0.01%, %As < 0.1%, %Sn < 0.05%, %Si < 0.9%, %Ni < 4.5%, %P < 0.46%, %S < 0.008%, %Mo < 2.2%, %Cr < 4.5%, %Mn < 2.5%, %AI < 0.6%, %C < 0.21%, % Nb < 0.21 %, %Ti < 0.21%, %V < 0.21%, %B < 0.002% and %Cu > 0.1 %, remainder being iron and unavoidable impurities, all amount being expressed in weight percent, the amount of copper in the liquid steel is from 0.1 to 0.3% by weight, the reheating temperature TR is from 1100°C to 1350°C, the semi-product is a slab, a(TR)= -0.0003752. TR - 0.112106, S(TR) = 0.00044767.TR - 1.53167, r|(TR) = - 0.0016517. TR + 1.02667 and A(TR) = 0.0001998.TR- 0.04817. the step of estimation further comprises the estimation of the amounts of carbon %Cest, boron %Best, aluminium %Alest and vanadium %Vest, the calculation step comprises the calculation of optimised amounts of carbon %CoPt, aluminium %AloPt, boron %Bopt and vanadium %VoPt said optimised amounts fulfilling the equation OC(TR). %SnoPt + y(TR).%CoPt + s(TR).%SboPt + n(TR).%SoPt + K(TR).%AloPt + X(TR).%VoPt + <j(TR).%BoPt + A(TR) > %Cuest wherein OC(TR), Y(TR), , S(TR), T|(TR), K(TR), X(TR), O(TR) are coefficients representing the respective impacts of, tin, carbon, antimony, sulphur, aluminum, vanadium and boron on the solubility of copper according to the reheating temperature, and A(TR) is a coefficient representing the impact of the reheating temperature on the solubility of copper, a(TR)= -0.0003752. TR - 0.112106, y(TR) = -0.0003549.TR + 0.2229, s(TR) =
0.00044767. TR - 1.53167, r|(TR) = -0.0016517.TR + 1.02667, K(TR) = -0, 0001236.TR + 0.12294, X(TR) = -4.5172E-05.TR + 0.02392, Q(TR) = -0.001334.TR + 1.5078 and A(TR) = 0.000393. TR - 0.27398 the step of estimation further comprises the estimation of the amounts of nickel %Niest, molybdenum %Moest, manganese %Mnest, silicon %Siest, chromium %Crest, arsenic %Asest, phosphorus %Pest, niobium %Nbest, and titanium %Tiest, and the calculation step comprises the calculation of optimised amounts of tin %SnoPt, nickel %NioPt , molybdenum %MooPt, manganese %MnoPt, carbon %CoPt, antimony %SboPt, silicon %SioPt, sulphur %SoPt, chromium %CroPt, aluminium %AoPtl, vanadium %VoPt, arsenic %AsoPt, phosphorus %PoPt, niobium %NboPt, titanium %TioPt, boron %BoPt, said optimised amounts fulfilling the following equation,
OC(TR). %SnoPt + P(TR).%NioPt + x(TR).%MooPt + 5(TR).%MnoPt + y(TR).%CoPt + s(TR).%SboPt + <HTR) %SioPt + r|(TR) %SoPt + <p(TR).%CroPt + K(TR).%AloPt + A(TR).%VoPt + |i(TR).%AsoPt + v(TR).%PoPt + 6(TR).%NboPt + p(TR).%TioPt + <j(TR).%BoPt + A(TR) S %Cuest wherein OC(TR), p(TR), X(TR), 5(TR), y(TR), s(TR), ^(TR), n(TR), q>(TR), K(TR), X(TR), M-(TR), V(TR), 0(TR), P(TR), C(TR) are coefficients representing the respective impact of, tin, nickel, molybdenum, manganese, carbon, antimony, silicon, sulphur, chromium, aluminum, vanadium, arsenic, phosphorus, niobium, titanium and boron on the solubility of copper according to the reheating temperature and A(TR) is a coefficient representing the impact of the reheating temperature on the solubility of copper. a(TR)= -0.0003752. TR - 0.112106, P(TR) = -2.395E-05.TR+ 0.02462, X(TR) = - 0,0002872. TR + 0.01797, 5(TR) = -0, 0001287.TR + 0.14394, y(TR) = -0.0003549.TR + 0.2229, S(TR) = 0.00044767. TR - 1.53167, <|)(TR) = -5.6944E-05.TR + 0.008839, r|(TR) = - 0.0016517. TR + 1.02667, q>(TR) = 5.6556E-06.TR - 0.01346, K(TR) = -0, 0001236.TR + 0.12294, X(TR) = -4.5172E-05.TR + 0.02392, p(TR) = -3.6111 E-05.TR + 0.04027, V(TR) = - 0,758E-06.TR + 0.00343, 0(TR) = -7.033E-06.TR + 0.00207, p(TR) = 1.289E-06.TR + 0.01007, Q(TR) = -0.001334.TR + 1.5078 and A(TR) = 0. 0008089.TR- 0.80722.
[008] Other features and advantages of the invention will be apparent from the following description, which is by way of illustration and in no way limitative, with reference to the appended figures in which:
Figure 1 illustrates a plant to produce a hot rolled steel sheet
[009] Elements in the figures are illustration and may not have been drawn to scale. [0010] Figure 1 shows a plant for the production of a hot-rolled steel product. Liquid steel 1 contained in a ladle 2 is poured into a tundish 3, which then allows liquid steel to flow through a nozzle into a mold. This liquid steel begins to solidify along the caster 4 until it is fully solidified and cut to form a semi-product 5. This semi-product 5 is generally left to cool at ambient temperature and stored in a slab yard before being sent to the hot rolling plant 6. This hot rolling plant 6 comprises a reheating furnace 7 where the semi-product 5 is reheated before being transferred to the rolling mill 8 where it is rolled and transformed into a steel product which is coiled to form a hot rolled steel coil 9.
[0011] Figure 1 illustrates an embodiment of a plant to produce a hot rolled steel sheet but the method according to the invention may be performed in other plants allowing to turn liquid steel in a semi product such as a billet, a blank, a bar, an ingot, a slab or a bloom and transformation of this semi-product into a steel product 9 in a hot rolling plant 6, this hot rolling plant 6 comprising a reheating furnace 7 adapted to reheat the semi-product 5.
[0012] In another embodiment of a plant to produce a hot-rolled steel product, not illustrated here, the semi-product 5 after casting is directly sent to the hot rolling plant where it is subjected to a heating step before being rolled. This heating step may be performed in a tunnel furnace. This plant is called a continuous plant or direct casting and rolling plant.
[0013] In the method according to the invention, the production of liquid steel 1 comprises the melting of steel scrap containing copper. Different production routes can be used, scrap can be melted in an electric arc furnace (EAF), optionally together with pig iron and direct reduced iron (DRI), and then liquid steel is obtained which is subjected to a refining step before being poured into the tundish. Scrap can also be melted in a Smelting Furnace (SF) together with pig iron and/or DRI, and the resulting molten metal sent to a converter or BOF for decarburization and conversion to liquid steel. This liquid steel can then be subjected to refining steps, such as dephosphorization and/or desulfurization steps and/or secondary metallurgy steps. Scrap can also be charged into the BOF.
[0014] For example, the steel scrap that can be used is referred to, in the Ell-21 Steel Scrap specification, as old scraps (E1 or E3), new scraps (E8), shredded scraps 20 (E40) or fragmentized scraps (E46).
[0015] In the method according to the invention, the estimation of the composition of the produced liquid steel includes the estimation of the amounts of copper %Cuest, tin %Snest, antimony %Sbest and sulphur %Sest. In a preferred embodiment the estimation also comprises the estimation of amount of carbon %Cest, boron %Best, aluminium %Alest and vanadium %Vest. In a most preferred embodiment this estimation additionally comprises estimations of amounts of nickel %Niest, molybdenum %Moest, manganese %Mnest, chromium %Crest, silicon %Siest, arsenic %Asest, phosphorus %Pest, niobium %Nbest and titanium %Tiest- All percentages are expressed in percent by weight.
[0016] The steel composition of the liquid steel can be estimated at the end of the elaboration step and before the casting step. The estimation of the steel composition is preferably performed by analysing lollipop samples from the hot metal ladle 2 that is used to fill in the casting tundish 3 or the ingot mould to obtain the semi-finished product. This estimation may also be performed using models.
[0017] Preferably, in step A of production of the liquid steel., from 100 to 1000 kg of steel scrap per ton of hot metal is used. Preferably, in step A, from 100 to 950 kg of steel scrap per ton of hot metal is used. Preferably, in step A, from 100 to 900 kg of steel scrap per ton of hot metal is used. Preferably, in step A, from 100 to 800 kg of steel scrap per ton of hot metal is used. Preferably, in step A, from 100 to 600 kg 25 of steel scrap per ton of hot metal is used. Preferably, in step A, from 100 to 500 kg of steel scrap per ton of hot metal is used. Even more preferably, in step A, from 200 to 400 kg of steel scrap per ton of hot metal is used.
[0018] In this patent, the residual elements are the non-desired elements coming from the steel scrap. The unavoidable impurities come from the elaboration process, e.g. oxides, nitrides.
[0019] Once the liquid steel is elaborated it is poured into the tundish 3 and then cast in the caster 4 to produce the semi-product 5. As previously explained this semi-product 5 is generally left to cool at ambient temperature and stored in a warehouse before being sent to the hot rolling plant 6. Then the semi-product 5 is sent to the reheating furnace 7.
[0020] Due to the use of copper-containing scrap a copper-rich phase is present on the surface of the semi-product. By copper-rich or copper-phase it is meant a phase comprising more than 75% by weight of copper, remainder being mostly iron and other alloying and residual elements present in the liquid steel. It is this copper-rich phase that will penetrate the steel along the austenite grain boundaries and will cause the hot shortness issue.
[0021] Classically, the semi-product to be rolled is charged at the entrance of the reheating furnace 7 where it is pushed forward on the hearth of the furnace by means of a pusher machine. The semi-product is usually pre-heated, heated and soaked as it passes through pre-heating, heating and soaking zone of the reheating furnace. At the end of the soaking zone of the furnace, it is discharged from the furnace by an ejector for subsequent rolling in the rolling mill. The temperature TR of the semi-product at the time of discharged depends on several factors and it can vary in the range of 1100° C to 1350°C. The reheating furnace 7 is preferably a continuous reheating furnace such as a pusher type furnace, a walking hearth furnace, or a walking beam furnace.
[0022] If the production plant is a continuous plant or direct casting and rolling plant then the reheating temperature TR must be understood as the temperature of the semi-product 5 at the exit of the heating step, before the rolling.
[0023] In the method according to the invention, before the casting, optimised amounts of tin %SnoPt, antimony %Sbopt and sulphur %Sopt, are calculated so as to fulfil the following equation:
(Formula 1) CC(TR). %SnoPt + S(TR). %SboPt + r|(TR).%SoPt + A(TR) > %Cuest wherein OC(TR), S(TR) and T|(TR), are coefficients representing the respective impacts of, tin, antimony and sulphur, on the solubility of copper according to the reheating temperature, and A(TR), is a coefficient representing the impact of the reheating temperature on the solubility of copper.
[0024] By equal it is meant equal to +/-10%, or even +/-5% or even +1-2%.
[0025] In another embodiment of the method according to the invention, optimised amounts of tin %SnoPt, carbon %CoPt, antimony %SboPt, sulphur %SoPt, aluminium %AloPt, vanadium %VoPt and boron %Bopt are calculated so as to fulfil the following equation:
(Formula 2) CC(TR). %SnoPt + y(TR).%CoPt + s(TR).%SboPt + r|(TR).%SoPt + K(TR).%AloPt + A(TR).%VOP( + c(TR).%BoPt + A(TR) > %Cuest wherein OC(TR), Y(TR), S(TR), T|(TR), K(TR), X(TR) and c(TR) are coefficients representing the respective impacts of, tin, carbon, antimony, sulphur, aluminum, vanadium and boron on the solubility of copper according to the reheating temperature, and A(TR), is a coefficient representing the impact of the reheating temperature on the solubility of copper.
[0026] In another embodiment of the method according to the invention, optimised amounts of tin %SnoPt, nickel %NioPt , molybdenum %MooPt, manganese %MnoPt, carbon %CoPt, antimony %SboPt, silicon %SioPt, sulphur %SoPt, chromium %CroPt, aluminium %AoPtl, vanadium %VoPt, arsenic %AsoPt, phosphorus %PoPt, niobium %NboPt, titanium %TioPt, and boron %BoPt are calculated so as to fulfil the following equation,
(Formula 3) CC(TR). %SnoPt + P(TR).%NioPt + x(TR).%MooPt + 8(TR).%MnoPt + y(TR).%CoPt + s(TR).%SboPt + <|)(TR) 0/oSioPt + r|(TR) %SoPt + <p(TR).%CroPt + K(TR).%AloPt + X(TR).%VoPt + P(TR).%ASOPI + v(TR).%PoPt+ 6(TR).%NboPt+ p(TR).%TioPt + <J(TR).%BOP( + A(TR) > %Cuest wherein CC(TR), P(TR), /(TR), 8(TR), Y(TR), S(TR), <|>(TR) , T|(TR), <P(TR), K(TR), X(TR), JJ.(TR), V(TR), 0(TR), P(TR), C(TR) are coefficients representing the respective impacts of, tin, nickel, molybdenum, manganese, carbon, antimony, silicon, sulphur, chromium, aluminum, vanadium, arsenic, phosphorus, niobium, titanium and boron on the solubility of copper according to the reheating temperature, and A(TR), is a coefficient representing the impact of the reheating temperature on the solubility of copper.
[0027] Example of coefficients for each formula are given in below table 1.
Figure imgf000008_0001
Table 1
[0028] Those coefficients are given by means of example and have been determined using Thermocalc® software, using Ssol4 database for antimony and arsenic and TCFe12 for the other elements, and based on the composition range as defined in claim 4. It is of course possible to use other software and/or other compositions, which would result in slightly modified coefficients.
[0029] Once those optimised amounts are calculated composition of the liquid steel is adjusted accordingly and liquid steel with adjusted composition is then cast to produce the semi-product. [0030] The produced liquid steel has preferably a composition wherein %Sb < 0.01%, %As < 0.1%, %Sn < 0.05%, %Si < 0.9%, %Ni < 4.5%, %P < 0.46%, %S <0.005%, %Mo < 2.2%, %Cr < 4.5%, %Mn < 2.5%, %AI < 0.6%, %C < 0.21 %, % Nb < 0.21%, %Ti < 0.21%, %V <0.21%, %B < 0.002% and %Cu > 0.1% remainder being iron and unavoidable impurities, all amount being expressed in weight percent. Copper amount is preferably from 0.1 to 0.3% by weight.
[0031] In the method of the invention, the composition of the liquid steel is adjusted so that the copper content at the steel surface is below the copper solubility limit, thereby preventing or at least limiting its penetration into the steel along the austenite grain boundaries and causing hot shortness.
[0032] A trial was performed with three steel samples S1 to S2 having a composition as defined in table 2, remainder being iron and unavoidable impurities. The solid samples were subjected to a heating step at TR equal to 1235°C to simulate the reheating step of an industrial installation and observations by a microscope were performed to identify presence of infiltrations in the steel bulk. Results are also included in table 2.
[0033] N means that no infiltrations have been observed while Y means that infiltrations of the copper-rich phase have been observed in the steel bulk.
[0034] Then according to the invention, optimised amounts of tin, sulphur and antimony were calculated using formula 1 and coefficients indicated in table 1. Compositions of liquid steel were then adjusted and new samples, respectively named S1 bis, S2bis were cast and subjected to same heating step and observations as previously indicated.
Figure imgf000010_0001
Table 2
[0035] One can observe that for samples S1 and S2 which are not according to the invention, infiltrations are observed while for samples S1bis and S2bis, for which optimised composition have been calculated and implemented and which have thus been produced with a method according to the invention no infiltrations are observed.

Claims

CLAIMS 1 ) A method for hot rolling a steel semi-product, comprising the steps of: A. Producing a liquid steel (1 ), said production step comprising the melting of steel scrap comprising copper, B. Estimating the amounts of copper %Cuest, tin %Snest, antimony %Sbest, sulphur %Sest, in said produced liquid steel (1 ), C. Casting the liquid steel (1 ) to produce a semi-product (5), D. Reheating the semi product (5) to a reheating temperature TR, E. Hot rolling the reheated semi-product, wherein between steps B and C, following steps are performed: ii) Calculating optimised amounts of tin %SnoPt, antimony %Sbopt and sulphur %SoPt said optimised amounts fulfilling the following equation: OC(TR). %SnoPt + S(TR). %SboPt + T|(TR). %SoPt + A(TR) > %Cuest wherein OC(TR), S(TR), T|(TR) are coefficients representing the respective impacts of, tin, antimony, and sulphur, on the solubility of copper according to the reheating temperature TR, and A(TR), is a coefficient representing the impact of the reheating temperature TR on the solubility of copper. iii) Adjusting final respective amounts of tin, antimony, and sulphur in the liquid steel so that it matches optimised calculated amounts. 2) A method according to claim 1 wherein the produced liquid steel (1 ) comprises at least 0.1 % in weight of copper. 3) A method according to anyone of claim 1 or 2 wherein in the production step A, scrap is melted with hot metal and/or direct reduced iron. 4) A method according to anyone of claim 1 to 3 wherein the produced liquid steel has a composition wherein %Sb < 0.01 %, %As < 0.1 %, %Sn < 0.05%, %Si < 0.9%, %Ni < 4.5%, %P < 0.46%, %S < 0.008%, %Mo < 2.2%, %Cr < 4.5%, %Mn < 2.5%, %AI < 0.6%, %C < 0.21 %, % Nb < 0.21 %, %Ti < 0.21 %, %V < 0.21 %, %B < 0.002% and %Cu > 0.1 %, remainder being iron and unavoidable impurities, all amount being expressed in weight percent. 5) A method according to anyone of the previous claims wherein the amount of copper in the liquid steel is from 0.1 to 0.3% by weight. 6) A method according to anyone of claim 1 to 5 wherein the reheating temperature TR is from 1100°C to 1350°C. 7) A method according to anyone of claims 1 to 6 wherein the semi-product is a slab. 8) A method according to anyone of claims 1 to 7 wherein a(TR)= -3.75e-04.TR - 0.11211 , S(TR) = 4.48e-04.TR - 1 .53167, T|(TR) = -1 ,65e-03.TR + 1 .02667 and A(TR) = 2.00e-04.TR- 0.04817. 9) A method according to anyone of claims 1 to 8 wherein the step B of estimation further comprises the estimation of the amounts of carbon %Cest, boron %Best, aluminium %Alest and vanadium %Vest, the calculation step E i) comprises the calculation of optimised amounts of carbon %CoPt, aluminium %AloPt, boron %Bopt and vanadium %VoPt said optimised amounts fulfilling the following equation: a(TR). %SnoPt + y(TR).%CoPt + s(TR).%SboPt + r|(TR).%SoPt + K(TP). %AIOPI + 7(TR).%VoPt + <j(TR).%BoPt + A(TR) > %Cuest wherein a(TR), y(TR), , s(TR), r|(TR), K(TR), X(TR), O(TR) are coefficients representing the respective impacts of, tin, carbon, antimony, sulphur, aluminum, vanadium and boron on the solubility of copper according to the reheating temperature, and A(TR), is a coefficient representing the impact of the reheating temperature on the solubility of copper. 10)A method according to claim 9 wherein a(TR)= -3.75e-04.TR - 0.11211 , y(TR) = -3.55e-04.TR + 0.2229, S(TR) = 4.48e-04.TR - 1 .53167, T|(TR) = -1 ,65e-03.TR +
1.02667, K(TR) = -1.24e-04.TR + 0.12294, A(TR) = -4.52e-05.TR + 0.02392, O(TR) = -1 ,33e-03.TR + 1 .5078 and A(TR) = 3.95e-04.TR - 0.27398 11 ) A method according to anyone of claims 9 or 10 wherein the step B of estimation further comprises the estimation of the amounts of nickel %Niest, molybdenum %Moest, manganese %Mnest, silicon %Siest, chromium %Crest, arsenic %Asest, phosphorus %Pest, niobium %Nbest, and titanium %Tiest, and the calculation step E i) comprises the calculation of optimised amounts of tin %SnoPt, nickel %NioPt , molybdenum %MooPt, manganese %MnoPt, carbon %CoPt, antimony %SboPt, silicon %SioPt, sulphur %SoPt, chromium %CroPt, aluminium %AoPtl, vanadium %VoPt, arsenic %AsoPt, phosphorus %PoPt, niobium %NboPt, titanium %TioPt, boron %BoPt, said optimised amounts fulfilling the following equation,
OC(TR). %SnoPt + P(TR).%NioPt + x(TR).%MooPt + 5(TR).%MnoPt + Y(TR).%COPI + s(TR).%SboPt + (|)(TR).%SioPt + r|(TR).%SoPt + (p(TR).%CroPt + K(TR). %AIOPI + X(TR).%VOPI + p(TR).%AsoPt + v(TR).%PoPt + 0(TR).%NboPt + p(TR).%TioPt + <j(TR).%BoPt + A(TR) > %CUest wherein OC(TR), P(TR), X(TR), 5(TR), Y(TR), S(TR), 4>(TR), T|(TR), <P(TR), K(TR), A(TR), P(TR), V(TR), 0(TR), P(TR), O(TR) are coefficients representing the respective impact of, tin, nickel, molybdenum, manganese, carbon, antimony, silicon, sulphur, chromium, aluminum, vanadium, arsenic, phosphorus, niobium, titanium and boron on the solubility of copper according to the reheating temperature, and A(TR), is a coefficient representing the impact of the reheating temperature on the solubility of copper.
12) A method according to claim 11 wherein a(TR)= -3.75e-04.TR - 0.11211, P(TR) = -2.40E-07.TR+ 0.02462, X(TR) = -2.87e-05. TR + 0.01797, 5(TR) = -1.29e-04.TR + 0.14394, Y(TR) = -3.55e-04.TR + 0.2229 S(TR) = 4.48e-04.TR - 1.53167, ^(TR) = - 5.69e-05.TR + 0.00884, T|(TR) = -1.65e-03.TR + 1.02667, cp(TR) = 5.66e-06.TR - 0.01346, K(TR) = -1.24e-04.TR + 0.12294 X(TR) = -4.52e-05.TR + 0.02392, p(TR) = - 3.61 e-05.TR + 0.04027, V(TR) = -7.58e-06.TR + 0.00343, 0(TR) = -7.03e-06.TR + 0.00207, P(TR) = 1.29e-06.TR + 0.01007, O(TR) = -1.33e-03.TR + 1.5078 and A(TR) = 8.09e-04.TR- 0.80722.
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WO2011114178A1 (en) * 2010-03-19 2011-09-22 Arcelormittal Investigación Y Desarrollo Sl Process for the production of grain oriented electrical steel
EP3296417A1 (en) * 2016-01-05 2018-03-21 Jiangyin Xingcheng Special Steel Works Co., Ltd Microalloyed steel for car carbon wheel hub bearing and manufacturing method therefor
WO2020084332A1 (en) * 2018-10-23 2020-04-30 Arcelormittal Hot-rolled steel plate and a method of manufacturing thereof
WO2022168167A1 (en) * 2021-02-02 2022-08-11 日本製鉄株式会社 Thin steel sheet

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011114178A1 (en) * 2010-03-19 2011-09-22 Arcelormittal Investigación Y Desarrollo Sl Process for the production of grain oriented electrical steel
EP3296417A1 (en) * 2016-01-05 2018-03-21 Jiangyin Xingcheng Special Steel Works Co., Ltd Microalloyed steel for car carbon wheel hub bearing and manufacturing method therefor
WO2020084332A1 (en) * 2018-10-23 2020-04-30 Arcelormittal Hot-rolled steel plate and a method of manufacturing thereof
WO2022168167A1 (en) * 2021-02-02 2022-08-11 日本製鉄株式会社 Thin steel sheet
EP4289988A1 (en) * 2021-02-02 2023-12-13 Nippon Steel Corporation Thin steel sheet

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