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WO2009052551A1 - Tôle en acier faiblement allié à haute teneur en cuivre - Google Patents

Tôle en acier faiblement allié à haute teneur en cuivre Download PDF

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Publication number
WO2009052551A1
WO2009052551A1 PCT/AU2008/001512 AU2008001512W WO2009052551A1 WO 2009052551 A1 WO2009052551 A1 WO 2009052551A1 AU 2008001512 W AU2008001512 W AU 2008001512W WO 2009052551 A1 WO2009052551 A1 WO 2009052551A1
Authority
WO
WIPO (PCT)
Prior art keywords
less
alloy steel
low alloy
steel sheet
high copper
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.)
Ceased
Application number
PCT/AU2008/001512
Other languages
English (en)
Inventor
Mary E Alwin
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.)
BlueScope Steel Ltd
IHI Corp
Nucor Corp
Original Assignee
BlueScope Steel Ltd
IHI Corp
Nucor Corp
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 BlueScope Steel Ltd, IHI Corp, Nucor Corp filed Critical BlueScope Steel Ltd
Publication of WO2009052551A1 publication Critical patent/WO2009052551A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • C22C38/04—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
    • C22C38/02—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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper

Definitions

  • Hot shortness occurs by copper separating during surface oxidation from the oxidizing layer to a layer adjacent the surface of the produced sheet resulting in a commercially unacceptable steel. The occurrence of these undesirable surface conditions could be minimized by careful control of oxidation during heating and taking care not to overheat during hot working.
  • nickel in an amount equal to at least one-half the copper content has been known to be very beneficial to the surface quality of steels containing copper.
  • these procedures and alloying additions were expensive and caused the resulting corrosion resistant steels to be expensive.
  • nickel is an expensive alloy addition and causes the resulting corrosion resistant steel to be expensive.
  • Copper in the concentrations used, was known to be the most potent of all common alloying elements in improving atmospheric-corrosion resistance in carbon steels. Copper was known to be especially effective in amounts up to about 0.35% in regular carbon steel. As noted, the steels with about 0.50% or more copper presented the problem of hot shortness. However, these levels of copper were acceptable in slabs of the order of 100 mm or more, where the adverse effects of hot shortness could be minimized by the later hot reduction of the strip.
  • the tolerance for copper is reduced with the reduction in thickness of the slab.
  • the copper levels should be about 0.20% or below by- weight of copper, to avoid the deleterious effects of hot shortness in the sheet. Indeed, it has been found that the levels of copper typically need to be maintained below 0.10% to avoid the inhibiting impact of hot shortness on the sheet made from such thin slabs.
  • Figures 1 and 2 show the deleterious effects of hot shortness in the surface of a slab of 50 mm in thickness made by a thin slab caster.
  • the problem of hot shortness also has increased the costs in making low alloy steel using electric arc furnaces to form the molten carbon steel .
  • Approximately 75% of the cost of making steel by electric arc furnace is the cost of the scrap used as the starting material for charging the electric arc furnace.
  • Steel scrap has been traditionally separated by copper content to less than 0.15% by weight copper, greater than or equal to 0.15% to up to 0.5% by weight copper, and above 0.5% by weight.
  • Scrap with copper content above 0.5% copper could be mixed with scrap with low copper levels to make an acceptable scrap, which also added to the cost of the scrap commercially available.
  • the scrap which was low copper below 0.15% by weight is the highest cost scrap, with the other two grades of scrap being of less cost.
  • high copper low alloy steel sheet of 10 mm, typically 5 mm, in thickness and less can be produced with the composition described below without the addition of substantial nickel alloy by solidification and cooling in a non-oxidizing atmosphere to less than 1080° C, i.e., below the solidification temperature of copper. In this way, hot shortness is reduced by inhibiting oxidation of the sheet surface.
  • a non-oxidizing atmosphere is an atmosphere typically of an inert gas such as nitrogen or argon, or a mixture thereof, which contains less than about 5% oxygen by weight.
  • the steel composition disclosed is low alloy steel having in molten state at processing between 0.02% and 0.3% carbon, between 0.10% and 1.5% manganese, between 0.01% and 0.5% silicon, greater than 0.01% and less than or equal to 0.15% phosphorus, less than 0.05% aluminum, at least 0.20% copper, less than 0.03% tin, less than 0.10% nickel, a total oxygen level of at least 70 and usually less than 250 ppm, and a free oxygen content between 20 and 70 ppm.
  • the copper content of the high copper low alloy steel may be between 0.20% and 2.0%.
  • the total oxygen content may between 70 and 150 ppm, and the free oxygen content may be between 30 and 60 ppm.
  • the sulfur levels should also be a low as practical which is generally below 0.01% and generally in the range between 0.002 and 0.009%, or lower.
  • the high copper low alloy steel may have a corrosion index (I) of at least 6.0 in accordance with ASTM GlOl-Ol where:
  • the high copper low alloy steel sheet may be made by the steps comprising:
  • the high copper low alloy steel sheet may also be made by the steps comprising: (a) preparing a molten melt producing an as-cast low alloy steel comprising
  • the thickness of the high copper low alloy steel sheet (or strip) produced may be less than 2 mm in thickness .
  • the copper content of the high copper low alloy steel may be between 0.20% and 2.0%.
  • non-oxidizing atmosphere is an atmosphere typically of an inert gas such as nitrogen or argon, or a mixture thereof, that contains less than about 5% oxygen by weight.
  • the high copper low alloy steel may also have a corrosion index of at least 6.0 in accordance with ASTM GlOl-Ol where:
  • a high copper low alloy steel sheet of less than 10 mm, typically less than 5 mm, in thickness made by a particular method as described in more detail below.
  • a twin roll caster may be used in making the high copper low alloy steel sheet by the disclosed method as described in more detail below. Again, typically, the high copper low alloy steel strip may be less than 2 mm in thickness.
  • Figures 1 and 2 are micrographs illustrating hot shortness experienced in the prior art with corrosion resistant low alloy steel made by thin slab casting;
  • Figure 3 is a diagrammatic side elevation view of an illustrative twin roll strip caster
  • Figure 4 is an enlarged sectional view of a portion of the illustrative caster of Figure 3;
  • Figure 5 is a graph showing the benefits of the high copper low alloy steel of the present invention compared to prior low alloy steel with copper additions;
  • Figures 6 and 7 are micrographs showing the surface of high copper low alloy steel sheet of 1.7 mm in thickness made by thin strip casting, showing the inhibiting of hot shortness-.
  • FIGS 3 and 4 illustrate a twin roll continuous strip caster which has been operated in making high copper low alloy steel strip in accordance with the present invention.
  • the following description of the described embodiments is in the context of continuous casting steel strip using a twin roll caster.
  • the present invention is not limited, however, to the use of twin roll casters and extends to other types of continuous strip casters and other ways of making steel sheet .
  • FIG 3 shows successive parts of an illustrative production line whereby steel sheet (or strip) can be produced in accordance with a twin roll caster.
  • Figures 3 and 4 illustrate a twin roll caster denoted generally as 11 which produces a cast steel strip 12 that passes in a transit path 10 across a guide table 13 to a pinch roll stand 14 comprising pinch rolls 14A.
  • the strip optionally may be passed into a hot rolling mill 16 comprising a pair of reduction rolls 16A and backing rolls 16B by which it is hot rolled to reduce its thickness.
  • the rolled strip passes onto a run-out table 17 on which it may be cooled by convection and/or by contact with water supplied via water jets 18 (or other suitable means) and by radiation.
  • the rolled strip may then pass through a pinch roll stand 20 comprising a pair of pinch rolls 2OA and thence to a coiler 19. Final cooling (if necessary) of the strip takes place by cooling of the coil after coiling.
  • twin roll caster 11 comprises a main machine frame 21 which supports a pair of horizontally positioned casting rolls 22 each having casting surfaces 22A, assembled side-by-side with a nip 27 between them.
  • Molten metal may be supplied during a casting operation from a ladle (not shown) to a tundish 23, through a refractory shroud 24 to a distributor 25 (also called a removable tundish) and thence through a metal delivery nozzle 26 generally above the nip 27 between the casting rolls 22.
  • Molten metal thus delivered to the nip 27 forms a casting pool 30 above the nip 27 supported on the casting roll surfaces 22A.
  • This casting pool is confined at the ends of the rolls typically by a pair of side closure dams or plates 28, which may be positioned adjacent the ends of the rolls by a pair of thrusters (not shown) comprising hydraulic cylinder units
  • casting pool 30 (generally referred to as the "meniscus" level) may rise above the lower end of the delivery nozzle 26 so that the lower end of the delivery nozzle is immersed within this casting pool.
  • Casting rolls 22 are internally cooled by water or other suitable coolant so that shells of steel solidify on the moving casting surfaces 22A of the rolls 22 during rotation of the rolls. The solidified shells are then brought together at the nip 27 between the casting rolls to produce the cast strip 12, which is delivered downwardly from the nip.
  • frame 21 supports a casting roll carriage which is horizontally movable between an assembly station and a casting station.
  • Casting rolls 22 are counter-rotated through drive shafts (not shown) driven by an electric motor and transmission.
  • Rolls 22 have copper peripheral walls formed with a series of longitudinally extending and circumferentially spaced cooling passages supplied with coolant.
  • the rolls may typically be about 500 mm in diameter and generally up to about 2000 mm long, in order to produce strip product of about 2000 mm wide.
  • Removable tundish 25 is of conventional construction. It is formed as a dish made of a refractory material such as for example magnesium oxide (MgO) . One side of the tundish receives molten metal from the ladle and is provided with an overflow spout and an emergency plug as shown in Figure 4.
  • Delivery nozzle 26 is formed as an elongate body made of a refractory material such as for example alumina graphite. Its lower part is tapered so as to converge inwardly and downwardly above the nip between casting rolls 22.
  • Nozzle 26 may have a series of horizontally spaced generally vertically extending flow passages to produce a suitably low velocity discharge of molten metal throughout the width of the casting rolls 22 and to deliver the molten metal onto the roll surfaces 22A of the rolls 22 where initial solidification occurs.
  • the nozzle 26 may have a single continuous slot outlet to deliver a low velocity curtain of molten metal directly above the nip between the rolls .
  • the nozzle may be immersed in the molten metal pool 30.
  • the casting pool 30 is confined at the ends of the rolls by a pair of side closure plates 28 which are adjacent to and held against stepped ends of the rolls 22 when the roll carriage is at the casting station.
  • Side closure plates 28 are illustratively made of a strong refractory material, for example boron nitride, and have scalloped side edges to match the curvature of the stepped ends of the rolls 22.
  • the side plates 28 can be mounted in plate holders which are movable at the casting station by actuation of a pair of hydraulic cylinder units (or other suitable means) to bring the side plates into engagement with the stepped ends of the casting rolls 22 to form end closures for the casting pool 30 of metal supported on the casting roll surfaces 22A during a casting operation.
  • the twin roll caster may be of the kind illustrated and described in some detail in, for example, United States Patent Nos .
  • the steel strip had the following chemical composition: 0.048% carbon, 0.636% manganese, 0.117% phosphorus, 0.005% sulfur, 0.252% silicon, 0.261% copper, 0.034% nickel, 0.027% chromium, 0.015% molybdenum, 0.006% tin, 0.001% aluminium, 0.001% titanium, 0.001% zinc, 0.0072% nitrogen a total oxygen level between 70 and 100 ppm, a free oxygen content of 45 ppm, and other impurities normally found in steel scrap. The total oxygen level was not directly measured. The steel was also tested and not found to have any measurable amounts of vanadium, lead, calcium or boron.
  • This steel was designated heat #232613 (trial #1), and was made into four coils (i.e., numbers 1,2,3 and 4) which were tested.
  • a second high copper low-alloy steel sheet was made by twin-roll caster into thin cast strip of 1.7 mm in thickness.
  • the steel strip had the following chemical composition: 0.049% carbon, 0.554% manganese, 0.043% phosphorus, 0.009% sulfur, 0.227% silicon, 0.417% copper, 0.030% nickel, 0.067% chromium, 0.011% molybdenum, 0.005% tin, 0.001% aluminium, 0.001% lead, 0.001% titanium, 0.001% zinc, 0.0065% nitrogen, a total oxygen level between 70 and 100 ppm, a free oxygen content 52 ppm, and other impurities normally found in steel scrap. The total oxygen content not directly measured.
  • the composition was also tested for vanadium, niobium, calcium and boron and none were measured. This steel was designated heat #137162 (trial #2), and was made into four coils (i.e., numbers 1,2,3 and 5) which were tested. There was not a roll #4 tested, because it was a pup.
  • Figure 5 shows the dramatic improvement in inhibiting hot shortness with the high copper low alloy steel sheet of the present invention.
  • the solid line illustrates the tolerance of prior art sheet to hot shortness as a function of percent copper from available data.
  • the dotted line is an extension of the solid line showing the projected levels of copper that can be tolerated without hot shortness in sheet below 10 mm in thickness. As can be seen from Figure 5, those copper levels are below 0.15% and closer to and below 0.1%.
  • the levels of copper that can be tolerated without substantial hot shortness in the high copper low alloy steel sheet of the present invention under 5 mm in thickness is more than 0.2%, and 0.4% copper, and higher, with a cast strip of 1.7 mm thickness.
  • high copper low alloy steel as high as 1.5% copper has been cast without hot shortness at a thickness of 1.9 mm with the present invention.
  • Figures 6 and 7 are micrographs of the surfaces of the high copper low alloy sheet or strip showing an absence of hot shortness . The benefits in inhibiting hot shortness are most evident by comparing Figures 6 and 7 with Figures 1 and 2 above.
  • the high copper low alloy steel also may have a the corrosion index (I) of at least 6.0 where:

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Continuous Casting (AREA)

Abstract

L'invention concerne une tôle en acier faiblement allié à haute teneur en cuivre de moins de 5 mm d'épaisseur, obtenue en préparant un bain de fusion produisant un acier faiblement allié brut de coulée contenant, en poids, de 0,02 % à 0,3 % de carbone, de 0,10 % à 1,5 % de manganèse, de 0,01 % à 0,5% de silicium, une teneur supérieure à 0,01 % et inférieure ou égale à 0,15 % de phosphore, moins de 0,05 % d'aluminium, plus de 0,20 % de cuivre,, moins de 0,03 % d'étain, moins de 0,10 % de nickel, une teneur totale en oxygène égale à au moins 70 ppm et habituellement inférieure à 250 ppm, une teneur en oxygène libre comprise entre 20 et 70 ppm, le reste étant constitué de fer et d'impuretés, et en solidifiant le bain en tôles de moins de 10 mm d'épaisseur dans une atmosphère non oxydante à une température inférieure à 1080 °C. La teneur en cuivre peut être comprise entre 0,2 % et 2,0 % en poids. L'acier peut présenter un indice de corrosion (I) égal à au moins 6,0 selon ASTM G101, avec : I = 26,01 (% cu) + 3,88 (% Ni) + 1,20 (% Cr) + 1,49 (% Si) + 17,28 (% P) - 7,29 (% cu)(% Ni) - 9,10 (% Ni)(% P) - 33,39 (% cu)2. L'acier peut être produit par coulée entre cylindres et peut présenter une épaisseur inférieure à 2 mm.
PCT/AU2008/001512 2007-10-23 2008-10-14 Tôle en acier faiblement allié à haute teneur en cuivre Ceased WO2009052551A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US11/877,376 2007-10-23
US11/877,376 US20080264525A1 (en) 2004-03-22 2007-10-23 High copper low alloy steel sheet

Publications (1)

Publication Number Publication Date
WO2009052551A1 true WO2009052551A1 (fr) 2009-04-30

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US (1) US20080264525A1 (fr)
WO (1) WO2009052551A1 (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100215981A1 (en) * 2009-02-20 2010-08-26 Nucor Corporation Hot rolled thin cast strip product and method for making the same
JP5702683B2 (ja) * 2011-07-29 2015-04-15 株式会社神戸製鋼所 ばら積貨物船用耐食鋼材およびばら積貨物船の船倉
CN103305760B (zh) * 2012-03-14 2015-12-02 宝山钢铁股份有限公司 一种薄带连铸550MPa级高强耐候钢制造方法
KR20190072321A (ko) * 2017-12-15 2019-06-25 주식회사 포스코 표면품질이 양호한 고Cu 스테인리스 강의 제조방법
MX2021009518A (es) 2019-02-08 2021-09-08 Nucor Corp Acero con ultra alta resistencia a la corrosion atmosferica o a la intemperie, y con laminado con alta friccion del mismo.
MX2022003382A (es) * 2019-09-19 2022-07-11 Nucor Corp Acero de resistencia ultra-alta a la intemperie para aplicaciones de estampado en caliente.
WO2021052314A1 (fr) 2019-09-19 2021-03-25 宝山钢铁股份有限公司 Plaque/bande d'acier patinable résistante au feu et son procédé de fabrication
CN112522576B (zh) 2019-09-19 2022-11-18 宝山钢铁股份有限公司 一种薄规格高耐蚀钢及其生产方法

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WO2005090627A1 (fr) * 2004-03-22 2005-09-29 Nucor Corporation Feuille d'acier faiblement allie a forte teneur en cuivre

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AUPN733095A0 (en) * 1995-12-22 1996-01-25 Bhp Steel (Jla) Pty Limited Twin roll continuous caster
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