Classifications

• • 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
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/06—Deoxidising, e.g. killing
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium

Definitions

• the invention relates to the use of alloys consisting essentially of aluminum-lithium for the purpose of deoxldizing, depurating, killing and refining any kind of carbonor alloy-steel.
• the alloys used in the process of the invention contain from 50 to 99.7% of aluminum and from 0.3 to 8% of lithium; they may also suitably contain at least one element selected from the group consisting of rare earths (TR), Ca, Ba, Fe and B, in percentage ranges as follows:
• the present invention relates to alloys consisting of or comprising aluminium-lithium for the purpose of deoxidizing, depurating, killing and refining low, high and medium carbon steels, and also alloy-steels.
• the invention provides also the method for the production of such steels deoxidated, depurated, killed and refined by the above mentioned alloys, which greatly improve their physicalmechanical characteristics.
• the present invention relates to aluminium-alloys which comprise from 50 to 99.7% of aluminium and from 0.3 to 8% of lithium. All percentage referred in the present application are by weight.
• the most detrimental non-metallic impurities contained in the steels, at the elementary or combined state, are: oxygen, hydrogen, nitrogen and sulphur.
• aluminium has been employed to deoxidate, kill and refine steels, but it produces alumina inclusions and forms aluminium nitride which may impart poor engineering properties to the steel. Moreover the aluminium seems to influence the distribution and the type of the metal sulfide inclusions and, depending on the quantity of aluminium added to the liquid steel, the sulfide inclusions may assume such distributions which are highly harmful to the characteristics of the steels.
• Li-Al alloys were afterwards no more considered for depurating molten steel, as can be drawn e.g. from the Revue de Metallurgie, 1963, where methods for adding metal lithium to molten steel are considered and where it is concluded that such methods-often asso- United States Patent 6 ciated with argon bubbling through the molten steelare unsatisfactory because of explosion danger and because only a small percentage of the added lithium is utilized while the greatest part is lost through evaporation; the boiling point of Li being of 1325 C.
• lithium additions to molten steel can notably improve its mechanical characteristics, in that it lowers the oxygen, nitrogen, hydrogen and sulphur content of the steel, it allows a reduction of inclusions and exerts a grain refining action.
• the Li content may not be higher than 8%, otherwise when adding the alloy to the ladle it may cause dangerous molten steel projection, refractories corrosions, contamination of the steel by A1 0 inclusions, etc.
• a Al-Li-Fe alloy having 8% of Li, 10% of Fe and 82% of Al is a quite stable one.
• One portion of rare earths added to the new alloys hereabove described correspond, for the purpose of the present invention, approximately 0.5 parts of cerium or to 0.2 parts of lanthanum.
• alloys of the present invention such as: Si, Mn, Ni, Ti, Zr, Fe, Y, Mg.
• Si, Mn, Ni, Ti, Zr, Fe, Y, Mg Various other elements may be added to the alloys of the present invention such as: Si, Mn, Ni, Ti, Zr, Fe, Y, Mg.
• an economic advantage may be obtained or a special steel endowed with peculiar characteristics.
• the alloys in order to attain the principal object of the present invention, the alloys must have an A1 content higher than 50%, the lithium content being always comprised bewteen 0.3 and 8%.
• the following percentages of Li: 0.3, 1.2 and 8%, in the Al alloys are critical experiments A, B, C were carried out.
• Example I, II and III the performances of steels treated with the alloys of the invention are reported.
• Alloy Al-Li with 1% Li total inclusions 107 p.p.m.; FeO 7.4%; A1 0 16%; SiO 32%; MnO 22%; others 22.6%.
• Alloy Al-Li with 1.5% Li total inclusions 91 p.p.m.; FeO 9%; A1 0 15%; SiO MnO 25%; others 20%.
• the temperature of the molten steel was in the range of 1590 C.-l630 C. The same steel and technique were used throughout. Li-Al-Ca alloys with pure Al, total inclusions p.p.m. 187, FeO 18%,
• alloys from c onwards (not considering aluminum metal, named a, and alloy b, only used for comparative purposes), which are mentioned only as illustrative but not as limitative of the invention, have been successfully applied:
• All the alloys of the present invention may be employed for the production of low, medium and high carbon steels, and also for the production of low, medium and high alloy steels as for example stainless steel, chrome and manganese steels.
• addition percentage of these alloys to the steel may vary depending on the steel-type treated and also on the employment field which the steel is destined to. In any case these additions are limited as follows: from 0.01 to 0.16%, i.e. from grs. to 1600 grs. per ton of liquid steel.
• the new alloys are added to the steel by plunging it down to the bottom of the filled ladle; alternatively the alloy may be introduced at the bottom of the ladle where thereafter the molten steel is poured.
• the alloy uniformly reacts with all the liquid mass.
• alloy in the furnace or in the ingot moul in shapes such as stars, pellets, wires, etc.
• the present invention may be successfully used in all those fields of metallurgical industry wherein Al has been used up to date to kill and refine steel, as well as to control its grain size to obtain higher purity qualities.
• the invention is hereafter illustrated by the examples in which, for comparison purposes, the same steel are treated with A1 alone and with alloys, consisting of or comprising Al-Li. All percentages are by weight.
• Trglalrted o The following steels. glfig a 33;, m 2 am 2.7
• Type I c 0.24Mn 0.72-Si 0.26-P 0.024 0.03
• S Type II C 0.32-Mn 1.60Si 0.25-P 0.02S 0.03
• Type of inclusions according to ASTM 45/63 Type III C 0.42Mn- 0.75--Si 0.25P 0.015S 0.03
• AHOY number A B G D E treated in the molten state as 1nd1cated, thereafter normal- Treated with ized at 850 C.
• Type I steel AI a 53.20 30.70 30.00 51.20 4.95 .Al-TR b 53.25 30 .80 30.60 53 .40 5.80 Al-Li-TR 11 53.25 31.40 31.40 56.30 6.74
• Type II steel a 65.20 44.50 27.2 55.00 6.32 .Al-TR b 65.60 44.60 27.8 56.70 6.48 Al-Li-TR 11 66.20 44.95 23.6 60 .50 7.30
• Type III steel Al a 65.6 39.10 24.2 37.5 2.54 Al-TR b 65.7 40.20 25.1 39 .4 2.81 AI-Li-TR n 66.3 41.60 27.8 .6 3.42

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Treatment Of Steel In Its Molten State (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=11145347

Family Applications (1)

Country Status (9)

Cited By (16)

Family Cites Families (2)

• 1967
  • 1967-04-19 LU LU53462D patent/LU53462A1/xx unknown
  • 1967-04-24 AT AT383667A patent/AT279660B/de not_active IP Right Cessation
  • 1967-04-24 SE SE5722/67A patent/SE342652B/xx unknown
  • 1967-04-28 BE BE697768D patent/BE697768A/xx unknown
  • 1967-05-02 ES ES340068A patent/ES340068A1/es not_active Expired
  • 1967-05-09 DE DE19671558462 patent/DE1558462B1/de active Pending
  • 1967-05-19 GB GB23327/67A patent/GB1182155A/en not_active Expired
  • 1967-05-22 CH CH714967A patent/CH492024A/de not_active IP Right Cessation
• 1971
  • 1971-10-18 US US00190402A patent/US3795505A/en not_active Expired - Lifetime

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