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
  • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the object of this invention is a process wherein the charge material (liquid pig iron, with scrap,slag, flux and if the case may be also iron ore) is contained :in-a vertical symmetrical vessel, revolving at a suitable speed and sense about its vertical axis and will be refined by blowing onto its surface, by means of suitable devices, oxidizing refining gas, particularly technically pure oxygen.
• the charge material liquid pig iron, with scrap,slag, flux and if the case may be also iron ore
• Another technical proposed solution consists in in creasing the temperature inside the converter by burning therein suitable fuels, particularly the carbon monoxide which is formed during the refining process.
• the process forming the object of the present invention consists in refining'a charge including liquid pig iron, steel scrap and/or iron in pigs, flux and possiblyiron ore and/or other cooling material by blowing one.
• this rise of the bath along the walls of the converter is utilized in order so to increase the amount of the charge, so that the ratio: total converter inner volume/weight of the charge, is equal at the utmost to 0.4 m lt versus a ratio of about 0.8 to l m /t which can be obtained in a vertical stationary converter.
• this increase of charge does not prevent the refining times from being kept within the limits of a conventional LD process; in fact due to revolution, the thickness of the bath will be at any point suitable for a quick and effective refining.
• the speed of revolution of the converter appears to'be rather critical-to the purposes of both the metallurgical process and the protection of the refractory.
• the thickness of the bath in fact, must be such as to prevent the primary jet from reaching the lining of the converter and at same time must be not so great as to promote the generation of dead zones little interested or not interested to the refining reactions. It has been found that preferably the revolution speed must be such as to allow the formation of a paraboloid the height of which stands in a relation with the internal diameter of the converter according to a ratio comprised between 0.7 and 1.5.
• the speed of revolution of the converter must be established in relation to the dimensions of the converter itself, so that at the rated speed, the peripheral speeds of the basic or acid refractory and of the metal bath, at the separating surfaces thereof will be equal, avoiding, as aforesaid, that wear which hindered a large diffusion of those processes, for instance the Kaldo process, where said relative movements exist.
• Another feature of the present invention connected to the primary blowing, consists in that the slag is kept apart from the basic or acid lining so that said slag cannot attack the lining.
• the slag which is lighter than the liquid metal, will locate on the surface of the paraboloid generated by. the roation of the bath and tends to rise, heaping near the upper end of said paraboloid. This fact would involve the double drawback of wearing quickly the refractory zone concerned with the heaping of the slag, and of leaving the bath at the point or points of impact of the oxygen and/or the oxidizing gas, free from slag, slowing down the refining process.
• the impact point of the primary jet onto the surface of the paraboloid must be at a distance from the axis of the converter, measured on the radius of the cross section-of the converter at that point, comprised between percent and 40 percent of the value of the internal diameter of the converter itself.
• the blowing of the primary jet is carried out by means of a lance with a vertical single nozzle which is eccentrically located and adjustable both vertically and horizontally, the eccentricity of which is comprised between 10 percent and 40 percent of the value of the internal diameter of the converter, said lance being so located that its head will be at a distance from the impact point comprised between 20 percent and 65 percent of the value of the internal diameter of the converter.
• the blowing is carried out through a lance located at the centre, along the vertical axis of the converter; in this case'said lance is provided with one or more nozzles, downwards directed with their axes inclined with respect to the axis of the lance itself through an angle from 15 to 45.
• This-lance is vertically adjustable and its distance measured along the axis of the nozzles, from said nozzles to the impact point of said jets on the surface of the bath, equals a value from 18 percent to 65 percent of the value of the internal diameter of the converter.
• Another feature of the present invention consists in that the heat developed by the combustion of CO to CO is absorbed directly by the metal bath, rotated by means known per se, as disclosed in the first path of this specification.
• an amount up to percent of said CO will be effectively burnt, utilizing the combustion heat in order to melt amounts of scrap from 20 percent to more than 50 percent of the total charge and/or corresponding amounts of pig iron in pigs and/or iron ores, with no need of preheating or of the addition of other fuel.
• the blowing of the secondary jet is embodied according to the present invention so that this secondary jet hit directly neither the surface of the meta] bath nor that of the refractory; particularly, said secondary jet is delivered through nozzles the diameter of which varies from 1/50 to 1/150 of the distance measured along the axis of the nozzles themselves, from said nozzles to the molten bath.
• the blowing of the secondary jet can be obtained by means of a second lance vertically and horizontally adjustable, the eccentricity of said second lance varying from nil to the value of the eccentricity of the primary lance, said second lance having one or more nozzles and being introduced into the converter so that said nozzles will be at a depth, measured from the mouth of the vessel, from 10 percent to 40 percent of the value of the internal diameter of the converter.
• auxiliary nozzles suitably located along the circumference of the head of the lance spaced apart from the endless than two diameters of the lance, or along the circumference of the lance body.
• the auxiliary nozzles are downwards turned and are inclined with respect to the axis of the lance through an angle from 10 to 30; their position inside the converter is soselected as to establish their distance from the plane of the mouth at a value from percent to 40 percent of the internal diameter of the converter itself.
• the blowing of the secondary jet can also be made of a second lance provided with one or more nozzles, located ecce-ntrically and horizontally or vertically'adjustable, with an eccentricity variable from 10 percent to 40 percent of the value of the internal diameter of the converter.
• This second lance is introduced into the converter so that said nozzles will be located at a variable depth measured from the mouth of the converter; the maximum effect will be reached at a depth from 10 percent to 40 percent of the internal diameter of the converter.
• the rate of this secondary jet can vary from 40 percent to 100 percent of the value of the rate of the primary jet, said secondary rate being adjustable, independently from that of the primary jet, during the process, from zero to the optimum value. 1
• the over-heating caused by the combustion of CO is such as to render useless the addition of slag fluidizing substances, and furthermore it-is capable of allowing,
• the process according to this invention results to be particularly flexible; it can be utilized not only in those plants where scarce amounts of liquid pig ioron are available, but also in plants where the liquid pig iron contains high amounts of sulphurand phosphorus as well as of other oxidizable impurities. Also in this case the process according to this invention is capable of by any other process, in correspondingly short times.
• Table 1 shows the data of certain heats, selected in the groups of heats carried out for testing the various type of blowing.
• Column 1 shows the data of one of thefirst heats carried out to ascertain thevalidity of the process, and wherein only primary oxygen has been blown.
• EXAMPLE 1 This example relates to the heat reported in Table l 7 under N0. 5. In this heatthe effectiveness of the process has been tested under the standpoint of the refining as well as of the final yield. The sequence of the operations has been as follows:
• the primary oxygen was blown by an eccentric lance with one nozzle and the secondary oxygen was blown by a lance also eccentric and with two nozzles having a 32 mm diameter.
• the percent ratio, between the rate of secondary O and the rate of the primary 0 was equal to 100.
• the ratio between the final sulphur and the initial sulphur is 0.33 and the ratio between the final phosphorus and'the initial phosphorus is about 0.062.
• the oxygen and nitrogen content of the steel resulted to be less than 0.001 percent.
• the iron yield was 93.6 percent.
• a rabbling cycle consists in starting the converter and causing it to reach the rated speed, then stopping the converter, and subsequently starting it in opposite This example relates to the heat reported in Table 1, under N0. 6.
• the Table 2 shows the refractory consumption alter 50 non continuous heats.
• ter was 0.6 percent of the distance from said nozzles to the metal bath.
• Liquid pig iron 83 74 65 83 71 83 56 80 Scrap........... 13 22 30 13 13 40 14 Lime 4 4 5 V 4 4 4 6 Percent composition of the liquid pig iron:

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Carbon Steel Or Casting Steel Manufacturing (AREA)
• Treatment Of Steel In Its Molten State (AREA)

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Citations (18)

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• 1971
  • 1971-05-06 US US3793001D patent/US3793001A/en not_active Expired - Lifetime
  • 1971-05-10 ZA ZA713041A patent/ZA713041B/xx unknown
  • 1971-05-10 CA CA112,526A patent/CA946624A/en not_active Expired
  • 1971-05-18 BR BR301671A patent/BR7103016D0/pt unknown
  • 1971-05-19 ES ES391376A patent/ES391376A1/es not_active Expired
  • 1971-05-19 BE BE767385A patent/BE767385A/xx unknown
  • 1971-05-19 JP JP3392271A patent/JPS5014964B1/ja active Pending
  • 1971-05-19 FR FR7118191A patent/FR2090211B1/fr not_active Expired
  • 1971-05-19 AT AT435071A patent/AT325080B/de not_active IP Right Cessation
  • 1971-05-19 NL NL7106878A patent/NL159719B/xx not_active IP Right Cessation
  • 1971-05-19 LU LU63191D patent/LU63191A1/xx unknown
  • 1971-05-24 GB GB1665171A patent/GB1364255A/en not_active Expired

Patent Citations (18)

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