A kind of method that adopts converter blowing smelting and purify production cast iron
Technical field
The present invention relates to smelting iron and steel industry, specifically belong to the category of smelting purification explained hereafter cast iron.
Background technology
The basic situation of steel and cast iron industry: iron and steel scrap mainly be take as raw material passes through oxidation and the reducing process production steel of blowing smelting electric arc furnace in the American-European developed country that waits, and in recent years accounts for 90% of its steel ultimate production.Within 2002,2005,2011, Chinese crude steel output is about respectively 1.8,3.5,700,000,000 tons, within 2011, account for 45% of the world, main take iron ore and produce steel as oxidation and reducing process that raw material passes through blast furnace, blowing smelting converter, wherein mainly use electric arc furnace to produce special steel, only account for 10% of China.Within 2010, Chinese steel scrap generation is approximately 1.1 hundred million tons, and wherein the self-produced steel scrap amount of steel mill is 0.3 hundred million tons, and social steel scrap output is 0.8 hundred million tons of left and right.The converter of large-scale steel mill and arc furnaces consume steel scrap are about 0.9 hundred million tons, and casting, hardware, little steel mill consume steel scrap and be about 0.3 hundred million tons.
Within 2012, Chinese ironcasting output is about 3,500 ten thousand tons, mainly take foundry iron and a small amount of high-quality steel scrap to pass through induction furnace remelting and recarburization process is produced cast iron as raw material.And have a small amount of cast iron enterprise to rely on large blast furnace steel-making enterprise that molten iron is provided, reduce cast iron smelting cost.The output of the high-purity pig iron of the high-end foundry goods of domestic product is about 3,000,000 tons at present, and mainly the steel mill by the high-quality iron ore place of production produces, and substantially meets the demand of domestic high-end foundry goods.But the blast furnace number of the enterprise for the production of the high-purity pig iron of high-end foundry goods is limited, blast furnace need to rely on high-quality iron ore and produce high-purity pig iron simultaneously, and cast iron enterprise relies on blast furnace enterprise to provide the high-end foundry goods of molten iron production to be subject to regional impact serious.
Iron and steel scrap is generally divided into heavy-duty waste steel iron (heavily useless), thickness >=6mm, medium-sized iron and steel scrap (in useless), thickness >=4mm, system material type iron and steel scrap (system is useless), thickness >=2mm, it is the mixture of various Industry Waste iron and steel, light material type iron and steel scrap (gently useless), is the mixture of various industry and life iron and steel scrap, the iron and steel scrap of generation after burning scrap iron and referring to burn away the refuse.Also has the foundry returns of motor iron, shock wave iron, iron and steel bits, parts scrap iron, Iron and Steel Production etc.Special iron and steel scrap divides 3 classes, and high-meltiing alloy iron and steel scrap, as stainless steel, bearing etc., is electroplated iron and steel scrap, automobile waste iron and steel.Heavily useless, in the composition consistence such as useless, shock wave iron, cast iron foundry returns better, foreign matter content is low, price is high, is high-quality iron and steel scrap.The complicated component of uniting and giving up, gently giving up and burning scrap iron, foreign matter content is high, can have the oxide compound of part iron, can contain a small amount of greasy dirt and silt, and price is low, in large supply, is low-quality iron and steel scrap.In general scrap iron, contain higher C, Si, Mn, S, P, in steel scrap, can contain higher C, Si, Mn, Ni, Cu, Cr, Sn, and other numerous trace elements, all elements distributed pole is inhomogeneous.Iron and steel scrap can be divided three classes with the type of impurity, the one, the element of low melting point, as Hg, As, Cd, Zn, Mg, Ce, Bi, Pb, Sb, Sn, Al, Cu, S, P etc., the 2nd, high-melting-point element, as Ni, Co, Ti, Cr, V, B, Nb, Mo, W etc., the 3rd, non-metallic inclusion and gas, as oxide compound, sulfide, O
2, N
2, H
2, etc.The element of low melting point and compound " hot-short " that easily at lower temperature, expanded by heating causes material, the relatively active inclusion that easily forms of Partial Elements, Partial Elements is difficult to volatilization and oxidation in remelting processing.High-melting-point element fusing point is very high, easily remains in foundry goods and forms processing hard spot, is difficult for decomposing in remelting processing.Inclusion and gas content are too much, and inclusion particle is excessive, can make casting compactness decline, and easily produce segregation, shrinkage porosite, crackle etc., as the inclusion of > 10um easily produces fatigue cracking.Remelting processing be take the physical process of refuse and is basis, the difficulty of removing is large or cost is very high, above-mentioned three dvielements and compound have some very large on the impact of cast iron, therefore only have, the content of detrimental impurity are controlled in certain scope, could produce the cast prod of uniform quality.The kind of iron-bearing material and composition are very complicated, although it is all the very good material under the oxidation of blowing smelting stove, reduction chemical reaction process, use under the condition of remelting processing in traditional cast iron industry, and all kinds of iron-bearing materials are cannot be widely used.Automobile steel scrap contains conventional non-ferrous metal Al, Cu, Zn, Mg, Sn, Pb, Hg, Ni, Ti, W, Ag, Cr, Be etc., if harmful element exceeds standard, will having a strong impact on the stability of cast iron quality, is the obstacle that cast iron industry is used traditional remelting processing maximum.
High-purity pig iron refers to that the detrimental impurity constituent contents such as phosphorus, sulphur, manganese, titanium are low, the micronutrient levelss such as Cr, V, Mo, Sn, Sb, Pb, Bi, Te, As, B, Al are very low, be mainly used in wind power casting, nuclear power foundry goods, large section, have the iron casting of low-temperature impact toughness and fatigue property requirement etc.
It is raw material that tradition cast iron industry be take foundry iron and high-quality iron and steel scrap, mainly uses two kinds of ironmaking flow processs: cupola furnace+remelting induction furnace duplex and the refining of remelting induction furnace list.The flow process of cupola furnace+remelting induction furnace duplex is mainly: cupola furnace → remelting induction furnace.General use heavily useless, in slightly low iron-bearing material and coke or the Sweet natural gas etc. of foreign matter content such as useless, in cupola furnace, by burning, oxidation and reduction reaction, generate the molten iron of desulfurization, then refine processing equally through induction furnace list.Remelting induction furnace list refining, is mainly used foundry iron, the lower iron-bearing material of foreign matter content such as heavily useless.By induction heating, both can use the hereditary nucleus of the pig iron, also can complete graphited process by carburetting and art of inoculation etc.It is raw material that cast iron enterprise relies on large blast furnace steel-making enterprise that molten iron is provided, the main ironmaking flow process of using: blast-melted → remelting induction furnace duplex.Cupola furnace or remelting processing are produced cast iron cannot use complicated component, foreign matter content is high, in large supply, price is low low-quality iron and steel scrap, as it is useless, gently useless and burn scrap iron etc. to unite.
Whether can use a kind of mode, make cast iron enterprise needn't leave no choice but rely on the high-grade foundry goods of molten iron production of blast furnace enterprise, expand the use range of iron and steel scrap and auxiliary material in cast iron raw material simultaneously, reduce the requirement of cast iron raw material to impurity, reduce the cost of cast iron raw material, can produce high-purity pig iron and corresponding high-end foundry goods, blast furnace needn't rely on high-quality iron ore also can produce high-purity pig iron simultaneously.This development to cast iron industry is very beneficial.
Summary of the invention
The invention provides a kind of method that adopts converter blowing smelting and purification process to produce cast iron, the present invention can make cast iron enterprise needn't rely on the high-grade foundry goods of molten iron production of blast furnace enterprise, and produce molten iron by combustion Jiao or gas-fired cupola fusing iron-bearing material, and can effectively use low-quality iron and steel scrap and auxiliary material at a low price, expand the use range of cast iron raw material, iron-bearing material is not needed to strict control, effectively decompose high-meltiing alloy, electroplate iron and steel scrap, automobile waste iron and steel.Blast furnace enterprise needn't rely on high-quality iron ore simultaneously, and common iron ore is molten into molten iron by blast furnace, through the present invention, also can produce high-purity pig iron.
Technical scheme of the present invention comprises following operation:
the charging batching phase, in body of heater, add iron-bearing material and auxiliary material; Preliminary melting period, heat up, make oxidation sludge;
heating by O2 blowing oxidation period, is blown into gas to melt, makes oxidation sludge;
blowing purification and reduction period, be blown into gas to melt, makes reducing slag;
iron carbide or greying.
The present invention is when using converter of basic lining smelting technology, and the addition manner of auxiliary material is: in operation
pack into before steel water and operation
skim before add auxiliary material amount be 8~29%(W of iron-bearing material total amount); In operation
before packing steel water into, drop in advance auxiliary material, the auxiliary material of input is auxiliary material 20~90% of the total amount that feeds intake; In operation
skim before add or the auxiliary material of portion-wise addition remainder; Described in it, auxiliary material is oxide-based, carburelant class, iron oxide-based of lime base class, manganese; Wherein lime base class is lime, fluorite, rhombspar, quartz sand or/and silicon carbide, and its ratio is fluorite 10~20%(W), rhombspar 5~15%(W), silicon carbide or quartz sand 0~20%(W), lime is 40~80%(W); Adding lime base class auxiliary material is 3~10%(W of iron-bearing material total amount); Wherein manganese oxide-based is one or more combination in rich manganese slag, rich manganese ore, manganese monoxide, Manganse Dioxide, and adding the oxide-based of manganese is 0~1%(W of iron-bearing material total amount); Wherein carburelant class is coke grain, graphite ore, carbon dust, broken graphite electrode slab, silicon carbide, and adding carburelant class is 3~8%(W of iron-bearing material total amount); Wherein iron oxide-based is the iron rust in iron fine powder, iron ore, iron scale, iron scale, brown iron oxide, iron-bearing material, and adding the oxide-based of iron is 2~10%(W of iron-bearing material total amount).In operation
and/or
in skim after add lime base class auxiliary material; Auxiliary material is lime, fluorite, quartz sand, and ratio is fluorite 0~20%(W), quartz sand 20~40%(W), lime 40~80%(W), be 2~9%(W of iron-bearing material total amount); In operation
in skim after add the oxide-based of manganese and carburelant class, making containing manganese total amount is iron-bearing material total amount 0~2%(W), making carbon containing total amount is iron-bearing material total amount 2~4%(W).
Cast iron raw material divides iron-bearing material and auxiliary material.Auxiliary material divides slag making auxiliary material, element auxiliary material; slag making auxiliary material is mainly for generation of slag; slag making auxiliary material object is to provide oxidation and reduction atmosphere; absorption impurity, accelerates the fusing of iron-bearing material, adjusts the required acid base concentration of melting; protection furnace lining; reduce heat radiation and air-breathing, fusing heat is provided, slag will have the ability of good mobility, viscosity and absorption impurity.
Basic furnace is used lime base class slag making auxiliary material, mainly contain lime, quartz sand (silicon carbide), fluorite, rhombspar, clay, alumina etc., acid lined furnace is used silica-based class slag making auxiliary material, auxiliary have quartz sand (silicon carbide), lime, clay, alumina, a fluorite etc., they lose less in redox reaction, wherein CaO, SiO
2be mainly used in adjusting the potential of hydrogen of slag, MgO is mainly for the protection of basic lining, CaF
2be mainly used in strengthening the mobility of alkaline slag making, Al
2o
3the main viscosity that increases alkaline slag making.In basic furnace and acid lined furnace minute for the oxidation sludge of oxidizing reaction and for the reducing slag of reduction reaction.The oxide compound of iron is slag making auxiliary material, is again iron-bearing material, very large to reduction period fluctuation in melting period.Carburelant, silicon carbide are element auxiliary material, can be decomposed into C, Si element, also can generate CO, SiO
2heating.Element auxiliary material is according to the ratio of the required alloying element of trade mark of casting iron, before reduction period or in reduction period, adjust, as carbon, silicon, manganese, can be by adding the adjustment such as coke, carbon dust, silicon carbide, rich manganese slag, rich manganese ore, ferrosilicon, ferromanganese, the element auxiliary material foreign matter content adding before reduction period can be higher, and the element auxiliary material adding at reduction period needs foreign matter content lower.
CaO/SiO in basic furnace
2represent the size of basicity, high alkalinity is conducive to protect furnace lining, dephosphorization, desulfurization.In some iron-bearing materials, silicon is obviously not enough, makes content SiO in slag
2too low, in charging period, to oxidation, add quartz sand early stage, the deficiency that can supplement silicone content in iron-bearing material, can partly replace quartz sand slag making with silicon carbide.
SiO in acid lined furnace
2/ CaO represents the size of acidity, and high acidity is conducive to protect furnace lining, high SiO
2the slag of content, easily causes SiO
2be reduced to the atmosphere of element silicon, reduce the consumption of reduction period ferrosilicon or silicon carbide.Being extremely oxidized early stage in charging period, can replace part quartz sand with silicon carbide, although element silicon is at a large amount of scaling loss oxidation period, SiO
2after ratio strengthens, element silicon residual quantity obviously increases, and element silicon can reduce the scaling loss of carbon simultaneously, increases the heat of melting period and oxidation period, and the thermal discharge of the Oxidation of SiC of unit mass is approximately (the generating CO) 2.5 times of carbon.
For containing the very low iron-bearing material of manganese, in charging period, to oxidation, add the oxide compound of manganese early stage, be conducive to reduce slag melting.In oxidizing reaction, the loss of manganese element is very large, increases the content of the oxide compound of manganese in slag, can reduce the oxidation of manganese in iron-bearing material, adds the oxide compound of manganese in oxidation latter stage, can increase possibility of " Hui Meng ", the consumption of minimizing reduction period ferromanganese.Furnace temperature is high, and FeO is few, and basicity is high, and time manganese degree is high.
FeO is a value constantly changing in redox reaction, first be present in the iron rust of iron-bearing material, manually add afterwards the fusing point of the adjustment slags such as part iron scale, add iron ore etc. to emit oxygen, by oxygen blast, improve the quantity of FeO, oxidation atmosphere is provided, indirectly pass [O], fully oxidation impurities wherein the most important thing is to impel the oxidation of phosphorus, with the same also oxidable other impurity of acid lined furnace in basic furnace.FeO is finally reduced by C, produces CO gas, and floating is cleaned impurity, and carbon also can constantly reduce the quantity of FeO in oxidation atmosphere simultaneously, and while tapping a blast furnace, the content of FeO can drop to 0.05~0.5%(W containing ferro element).If the impurity of need oxidation in iron and steel scrap, volatilize, dissolve, discharging is less, can reduce the amount of being blown into of oxygen enrichment, the output of CO gas is reduced, accelerate the speed of intensification, reduce energy loss.
Pre-estimate the ratio of the carbon of iron-bearing material, infer the interpolation quantity of carbon in batching, reduce the consumption of reduction period carburelant, the object of adding carbon is the high carbon containing requirement that reaches cast iron, be different from steel-making decarburization and reach the low carbon containing requirement of steel, and be conducive to produce heat, improve melting speed, reduce melt temperature of fusion, reduction FeO, generates CO, supplements the carbon content deficiency of using steel scrap to cause, silicon carbide can supplement carbon and silicon, also can produce heat.
By desulfurization, dephosphorization technology, can effectively remove S, P.General dephosphorization is more difficult than desulfurization, also can desulfurization in the time of dephosphorization under reducing atmosphere.Blast furnace, cupola furnace, remelting electric furnace, acid electric furnace dephosphorization difficulty are large, general dephosphorization not, a desulfurization.
Desulfurization is thermo-negative reaction, mainly by CaO base slag, and minute high and low oxygen atmosphere desulfurization.In the oxidation period of alkalescence and acid electric furnace, under oxygen blast, high oxidation iron, low alkali atmosphere, a small amount of sulphur easily generates SO
2gas, discharges with furnace gas, makes to reduce to 0.9~0.6 containing S total amount, and in reduction period, wash heat and the refining furnace of electric furnace, at hypoxemia and suboxide, when furnace temperature is higher, basicity is higher or carbon content is higher, S easily forms sulfide slag and discharges.Or/and divide the desulfurization of stove reduction method, phosphorus sulphur in wash heat and refining furnace.
Produce low phosphorus pig iron and can use low-phosphorous iron-bearing material, for adopting iron and steel scrap ironmaking, in grey cast iron product containing P total amount often than high in steel, the P total amount Chang Yugang that contains of wriggling in China ink, spheroidal graphite cast iron product approaches, if need a small amount of dephosphorization, can, by electric furnace, wash heat, refining furnace by a small amount of dephosphorization of reduction method, make to reduce to 0.8~0.4 containing P total amount.Basic electric furnace is at dephosphorization oxidation period, and arc furnace electrode is to slag direct heating, and the temperature of slag is high, and mobility and reaction conditions are good, and has a large amount of gas floatings and induction stirring, and dephosphorization effect is best, can make to reduce to 0.2~0.6 containing P total amount.For using high phosphorus iron-bearing material to produce low phosphorus pig iron, can be oxidized and reduction method Dephosphorization.
By dephosphorization under reducing atmosphere in deslagging process and refining furnace, can reduce the content of oxygen in cast iron, sulphur, inclusion simultaneously.During iron and steel liquid C content >=1% (W), easily make oxygen level≤50ppm, then by blowing argon gas and strong reductor deoxidation, when oxygen level≤10ppm, easy dephosphorization.In electric furnace or refining furnace, add CaAl, CaSi, CaC
2deng after, first calcium react with sulphur, oxygen, and slag liquid interface oxygen gesture is further reduced, and is less than Critical oxygen potential, the almost simultaneously reaction such as phosphorus, carbon, nitrogen of calcium generates calcium phosphate etc.Calcium phosphate easily generates poisonous substance, need deal carefully with.Deslagging process dephosphorization, general first useization slag hearth melting furnace slag, rear pulverization process, pours ladle into iron and steel liquid, also can when electrosmelting terminal, add slag charge, after fusing and molten steel pour ladle into simultaneously, during change slag, also can add other alloys.Normal principal constituent (the CaO+BaO)-Al2O that uses
3-CaF
2slag system, wherein CaO regulates basicity, desulfurization, dephosphorization, Al2O3 and SiO
2adjust viscosity, MgO protects furnace lining, CaF
2fusing assistant, Al deoxidation, heating, C, SiC, CaC
2deoxidation, heating, foaming.
Operation of the present invention
in gas that melt is blown into be oxygen or oxygen enrichment, flux, carrier of oxygen pressure is 0.2~1.4MPa, oxygen-supplying amount is 5~60m
3/ t, wherein the oxygen level of oxygen enrichment is 30%~93%.
Operation of the present invention
in, the gas that melt is blown into is N
2, CO
2, in Ar one or more.
Of the present invention melt is blown into gas, its mode for to insert gas blow pipe or/and bottom blowing in electric furnace.
Gas blow pipe of the present invention can adopt water-cooled copper, common steel tube, high temperature coating aluminized steel tube, hot metal pipe, vitrified pipe, metal ceramic tube from top, fire door, sidepiece be blown into gas, high temperature coating aluminized steel tube, hot metal pipe, vitrified pipe, metal ceramic tube can contact steel water.
Of the present invention melt is blown into gas, for bottom, there is no the body of heater of blowing function, can imbed the gas permeable brick of gas blow pipe and isolation melt at bottom of furnace body opening, lay cooling water circulation securing system, make body of heater have Bottom Blowing function.
Element in iron and steel scrap divide have oxidizable: Ca, Mg, S, Al, Ce, Ti, Si, B, V, Nb, Mn, Cr, P, C etc.; Dysoxidizable: Pb, Sb, As, W, Mo, Ni etc.; Substantially be not oxidized: Sn, Co, Cu etc.[O] that the oxygen that the present invention enters by top bottom blowing and the oxide compound of iron discharge, height [O] atmosphere forming, fully be oxidized oxidizable impurity, FeO is generating a large amount of CO gas with the reacting of C, CO and other gases that are blown into carry the impurity of easy fusing, volatilization and oxidation in the process of floating, sneak into slag and discharge.The N that the gases such as CO that produce during the present invention smelts and bottom are blown into
2, the gas such as Ar can effectively float and carry impurity, to non-metallic inclusion, gas, lower boiling and low melting point, there is extremely strong cleansing power, as all low in the boiling point of the elements such as Hg, Cd, Zn, Sb, As, Bi and compound, easily form steam condition and be eliminated.Air blowing high-temperature stirring is conducive to the decomposition of impurity in high-melting-point element and raw material, as the ash in Mo, Co, W, bulk graphite, carburelant grades.
Operation of the present invention
in, can be to body of heater extracting vacuum.At reduction period, to use water-ring pump and vapor jet pump or use separately water-ring pump, extracting vacuum auxiliary furnace bottom blowing enter gas, after reaching vacuum tightness 10~300Pa, 5~the 20min that bleeds, reduces the content of gas and inclusion, further removes obnoxious flavour, inclusion and volatile substances.
When adding reducing slag, by Bottom Blowing or top blast gas, can be in converter or/and refining furnace, or/and extracting vacuum is simultaneously blown into N
2, CO
2, Ar, can first blow N
2, blow CO again
2or Ar, also can only blow CO
2or Ar, remove inclusion and gas, be specially 0.05~1.0m
3/ min, 5~20 min.Use water-ring pump and vapor jet pump or use separately water-ring pump extracting vacuum, and being blown into gas, after reaching vacuum tightness 10~300Pa, 5~20min bleeds.For producing high trade mark cast iron, require foreign matter content very low, can extend gassing time, extracting vacuum, can improve refining effect simultaneously, is conducive to improve the removing effect of inclusion, gas, low melting point, and prevents that gas secondary from sneaking into.
In cast iron, there are a large amount of tiny non-iron, carbonaceous points, SiO
2, FeO, MnO, Al
2o
3deng oxide fine particle, be about 5,000,000/cm
3, size is between 0.2~1.0 μ m, and MnS, FeS sulfides particulate are about 4,000 ten thousand/cm
3, size is between 2~23 μ m.The amount of inclusions of size below 10 μ m is about 90%, under general nature state, the inclusion of > 50um can initiatively float, Bottom Blowing technique can make the inclusion floating of > 5um rapidly, but also has some effects for the heterogeneous nucleation quantity of < 1um.If in cast iron because air void causes density decline 0.2T/ m
3, mean that the perviousness of cast iron gas is equivalent to approximately improve 37%.Every oxidation 1%(W) CO that C generates, or the every reduction of C 6%(W) the CO that generates of FeO, because gas density is little, after expanded by heating, its volume is approximately nearly thousand times of total iron and steel liquid.N
2, CO, CO
2, Ar gas etc. is dissolved in iron and steel hardly, the ultra-large volume ratio between the gas in purification process and iron and steel liquid, is the major cause that effectively floats carrying clamp foreign material, obnoxious flavour and clean low-boiling point material etc., significant to improving cast iron quality.
Body of heater of the present invention, the purposes of body of heater can be smelting furnace, holding furnace, can addition of vacuum de-gassing vessel.Can be the holding furnace of air blowing electric-arc heating, as LF refining furnace, can be also blowing induction heating, vacuum stove, as vacuum induction furnace (VIDP).
The iron-bearing material that cupola furnace of the present invention and blast furnace are molten into steel water comprises: the combination of one or more in the oxide compound of iron and steel scrap, conversion pig, foundry iron, the spheroidal graphite pig iron, reduced iron, half steel, iron; That iron and steel scrap comprises is heavily useless, in useless, system is useless, light useless, burn one or more the combination in scrap iron, steel scrap, scrap iron, motor iron, shock wave iron, iron and steel bits, parts scrap iron, iron and steel foundry returns, high-meltiing alloy iron and steel scrap, plating iron and steel scrap, automobile waste iron and steel, high-quality iron and steel scrap or low-quality iron and steel scrap, be the raw material of cupola furnace and blast furnace.The oxide compound of iron comprises the iron rust in iron fine powder, iron ore, iron scale, iron scale, brown iron oxide, iron-bearing material etc.
The present invention is intended to by firing Jiao or gas-fired cupola melting waste steel iron, and by the oxidation in the high temperature blowing smelting of converter and the processes such as chemical reaction of reduction, effectively remove the impurity in iron-bearing material and auxiliary material, substitute in traditional cast iron remelting processing cannot blowing smelting removal of contamination physics reflow process, control oxidation rate and the loss of carbon, add in time and adjust the content of the elements such as the required carbon of trade mark of casting iron, silicon, manganese.
The present invention to the preliminary melting of low-quality iron and steel scrap, and uses the iron ore of low-quality or iron fine powder by the preliminary melting of blast furnace by combustion Jiao or gas-fired cupola, generates steel water, for converter.The cycle of bessemerizing is short, main rely in steel water and heat that the Si, the C that add, Mn oxidation discharge heats up, need high FeO oxidation atmosphere when dephosphorization, rear and C spontaneous combustion forms a large amount of CO gas, and being blown into the gases such as Ar, in iron-bearing material, impurity has the ability of removing very by force.
The present invention can also can produce high-grade foundry goods for the production of low-grade foundry goods, and provides the cast iron raw materials such as the high consummate pig iron or molten iron for iron foundry.The present invention can produce ash mouth, the China ink of wriggling, spheroidal graphite, malleable, white cast iron, heat-resisting, anti-corrosion, antifriction cast iron, synthetic, inoculated cast iron, the products such as D type cast iron.
Compared with prior art, the invention has the advantages that: utilize and be blown into O
2, oxidation atmosphere is provided, for oxidation impurities, in oxidation and reduction process, generate a large amount of CO gas floatings and carry impurity, utilize the N being blown into
2, CO
2, Ar, eliminate obnoxious flavour, floating is carried impurity.By redox chemical reaction, various high-temperature stirring, blowing purification, the mode such as vacuumize, eliminate the various impurity that produce in iron-bearing material, auxiliary material and production, eliminate the harm of low melting point element, high-melting-point element, non-metallic inclusion and gas, stablize the consistence of raw material, coupling is produced the required element of various cast iron, the iron carbide that interpolation, generation, inoculated cast iron are required or the foundation structure of various forms of graphite, reach the object of the various cast irons of production.
Embodiment
Steel water → converter → refining furnace+(vacuumizing)+iron carbide or greying → high trade mark foundry goods.
charging batching
Object: analytical element content, pre-estimate steel water and need to generate carbon in cast iron kind, silicon, manganese equal proportion, rationally add auxiliary material.
Analyze C, P, S equal size, according to the control requirement to the content of P, S, determine oxidation period and the reduction period dephosphorization scheme of skimming, determine the scheme of reduction period desulfurization, tentatively determine that reduction period adds the scheme of alloying element content.
The steel water of cupola furnace and blast furnace fusing is packed into converter, in oxidation period, adds in addition 0~15%(W that solid iron-bearing material is steel water total amount), inhibited oxidation heat-up rate, is convenient at lower temperature dephosphorization etc. assorted.
The amount of adding auxiliary material before the charging batching phase packs steel water into and before the skimming of heating by O2 blowing oxidation period is 8~29%(W of iron-bearing material total amount); Before packing in advance steel water into, drop into 20~50% auxiliary material, before being oxidized the dephosphorization of skimming mid-term, add or portion-wise addition auxiliary material afterwards.
Wherein lime base class is lime, fluorite, rhombspar, quartz sand or/and silicon carbide, and its ratio is fluorite 10~20%(W), rhombspar 5~15%(W), silicon carbide or quartz sand 0~20%(W), lime is 40~80%(W); Adding lime base class auxiliary material is 3~10%(W of iron-bearing material total amount), in oxidation period, make CaO/SiO
2ratio be about 1.5~6, with silicon carbide or quartz sand, supplement the deficiency of element silicon in iron-bearing material, make siliceous total amount account for 1~4% of cast iron raw material total amount, wherein comprise the silicon content in iron material; Wherein manganese oxide-based is one or more combination in rich manganese slag, rich manganese ore, manganese monoxide, Manganse Dioxide, and adding the oxide-based of manganese is 0~1%(W of iron-bearing material total amount); Wherein carburelant class is coke grain, graphite ore, carbon dust, broken graphite electrode slab, silicon carbide, and adding carburelant class is 3~8%(W of iron-bearing material total amount); Wherein iron oxide-based is the iron rust in iron fine powder, iron ore, iron scale, iron scale, brown iron oxide, iron-bearing material, and adding the oxide-based of iron is 2~10%(W of iron-bearing material total amount).Above-mentioned auxiliary material is mixed, can reduce the consumption of carbon, increase the quantity of carbon atom.
After the impurity such as dephosphorization of skimming of oxidation period and/or the skimming after the impurity such as sulphur removal of reduction period, separately make a small amount of new lime base class auxiliary material and cover melt; Auxiliary material is lime, fluorite, quartz sand, ratio is fluorite 0~20%(W), quartz sand 20~40%(W), lime 40~80%(W), 2~9%(W for iron-bearing material total amount), or replace 20~70%(W with silicon carbide) quartz sand, CaO/SiO in slag
2ratio be about 1.2~3; After the skimming of oxidation period, add the oxide-based of manganese and carburelant class, making containing manganese total amount is iron-bearing material total amount 0~2%(W), making carbon containing total amount is iron-bearing material total amount 2~4%(W).
heating by O2 blowing oxidation period
object:persistently overheating, oxygen blast is fluxed, and forms high oxidation atmosphere, oxidation impurities, and gas stirring molten bath, floating inclusion, skims, dephosphorization, removal of inclusions and gas.For phosphorous higher iron-bearing material, or produce low phosphorus pig iron part, oxidation period, dephosphorization was very important.
the fusing of acceleration raw material:heating by O2 blowing, accelerates raw material fusing, mends slag.
Use oxygen or oxygen enrichment to flux, by top Bottom Blowing or top blast gas, be blown into oxygen, blow gas pressure is 0.2~1.2MPa, and oxygen enrichment oxygen level is 50~93%, and blowing oxygen quantity is 10~40Nm
3/ T, according to furnace diameter and go deimpurity degree to select blowing oxygen quantity, iron-bearing material impurity is higher or produce the cast iron of the high trade mark, need to be blown into more oxygen.Before skimming dephosphorization oxidation period, supplement the quantity of slag, adjust basicity etc., carry out the dephosphorization of skimming and prepare.Adopt water cooled oxygen lance or oxygen blow steel pipe, insert slag degree of depth < 100mm, angle is 30~45 °.Adopt the oxygen rifle of hyperthermal material also can insert in steel water, can improve oxidation rate, reduce the loss of oxygen.
the impurity such as dephosphorization of skimming:oxidation mid-term, reaches dephosphorization condition, and the impurity being oxidized at lower temperature, adopts stream slag and the mode of skimming automatically, takes off in time oxidation sludge in batches, adds and make new oxidation sludge, removes the impurity such as phosphorus, prevents that oxidation impurities from reducing again.
Good dephosphorization, make molten bath have good oxidisability, suitable alkalescence, control furnace temperature on the low side, reduce speed that furnace temperature rises, make slag have good mobility etc., slag making in batches, deslagging and the oxidation sludge more renewing, progressively reduce P concentration, all contributes to improve dephosphorization effect.Basic electric furnace dephosphorization oxidation period is thermopositive reaction, and the fundamental order of smelting oxidation is Si → Mn → Cr → P → C, and Si need be oxidized to approximately 0.15% (W), and after partial oxidation Mn, Cr, P could be oxidized, and oxidation Si, Mn, both provided heat, be convenient to again dephosphorization, C < 1.5%(W) time, oxygen position, interface is controlled by Cr, C > 1.5%(W) time, by C, controlled, when C content is high to dephosphorization, to protect chromium very important.Continue oxygen blast, add the oxide compound of iron in batches, adjustment FeO is 12%~25%(W) oxidisability slag, every crowd of interval > 5min, weight is 1~3%(W), adjustment basicity is R=CaO/SiO
2=1.5~6.Melt need be controlled in 1300 ℃~1670 ℃ alap temperature, otherwise the easy vigorous reaction of C progressively disappears FeO, is prone to rephosphorization phenomenon.Portion-wise addition bushel iron ore such as makes at oxide compound and the iron-bearing material of iron, extend duration of blast, can cause automatic stream slag, be conducive to automatically discharge the low weight phosphoric acid salt of density in slag, reduce the loss of the oxide compound of iron, also can prevent that furnace temperature from rising too fast simultaneously, oxidation atmosphere declines, and phosphoric acid salt etc. reduce again, and initiatively skims, take off the quantity of slag and can reach 70%~80% at most, and separately make new slag covering melt.SiO
2, B
2o
3deng being acid, in alkaline environment, reductibility is little, and the density of Ti, B and oxide compound thereof is all low, easily sneaks into slag to get rid of, but is reduced phase reduction under the easy high temperature of oxide compound of V, Mn, Nb, Cr, P etc.
the formation of high temperature oxidation atmosphere:to bath lancing, because of the very high concentrations of Fe in melt, part 2Fe+O
2=2FeO, being oxidized main is indirect biography oxygen by FeO, FeO+M=MO; Small part passes oxygen, FeO=Fe+[O by the FeO on interface to diffusion in iron and steel liquid], and oxygen diffusion is in iron and steel liquid, O
2=2[O]; Also there is a small amount of direct oxidation, 2M+O
2=2MO; Be deposited in the unfused iron ore of furnace bottom and also can provide oxygen, FeO=Fe+[O], Fe
2o
3=2FeO+[O], be thermo-negative reaction, speed of response is come slowly than oxygen blast thermopositive reaction.The oxidation that oxidation atmosphere is impurity element provides condition, is that electric furnace technique is gone deimpurity important step.
oxidation order:under smelting condition, the fundamental order of part elemental oxygen is 1400 ℃ of Ca → Mg → a small amount of Fe → a small amount of S → Al → Ce → Ti → B → Si → V → Nb → Mn(Nb, Mn >, easily by C, reduced) → Cr → P → C → Fe, Sn → Mo → W → Ni → Pb → Sb → As → Co → Cu etc.Wherein Sn, Sb, As, Pb partly volatilize and are oxidized, and W, Mo, Ni are oxidized on a small quantity, and Co, Cu are not oxidized substantially.Oxidation order is also relevant with concentration, and concentration is high, easily oxidized.
generate phosphoric acid salt:5FeO+2Fe
3p=P
20
5+ 11Fe, generates 4(CaO) .P
20
5and 3(CaO) .P
20
5deng;
generate SO 2 :oxidation period oxygen more active than sulphur, under oxygen blast, high oxidation iron, low alkali atmosphere, a small amount of sulphur easily generates SO
2gas, discharges FeS+2[O with furnace gas]=Fe+SO
2↑, MnS+2[O]=Mn+SO
2↑.
be oxidized latter stage:when skimming dephosphorization etc. oxidation period, furnace temperature is progressively raising, the difficulty of dephosphorization continues to increase, progressively enter and be oxidized latter stage, stop after oxygen blast, at liquid level, sprinkle carburelant, making carbon containing total amount is iron-bearing material total amount 2~4%(W), supplement the carbon content of molten iron, according to the requirement of manganese content in trade mark of casting iron, the appropriate oxide compound that adds manganese, for iron-bearing material total amount 0~2%(W), allow molten bath enter approximately 3~15min of nature boiling state, make FeO be converted in a large number Fe, the oxide compound of manganese is reduced by carbon, supplement the content of manganese in molten iron, take off oxidation sludge, impurity in the oxide compound of removing carburelant and manganese, make thin reducing slag and cover melt, to reduce air-breathing and cooling.Fully stir molten steel, in molten bath sampling core, analyze the constituent contents such as C, Mn, Si, S, P, for the later stage is timely, adjust constituent content foundation is provided.
Furnace temperature is at 1450~1670 ℃, and the oxidizing reaction of C progressively enters very active state, FeO+C=Fe+CO, C+[O]=CO, FeO is fully reacted with C, C consumes in a large number, generates CO, the floating of CO and the N in oxygen enrichment
2stir, gas carrying clamp foreign material are fully floated, be conducive to discharge inclusion and gas.
Also can adopt gas injection carburetting, carburelant can be used silicon carbide, coke granule etc., adds reducing slag and covers melt.Every reduction 6%(W) FeO, the 1%(W needing) C, the oxidation rate of C is about 0.3~1.2%/h.
Fully stir molten steel, in molten bath sampling core, analyze the constituent contents such as C, Mn, Si, S, P, for the later stage is timely, adjust constituent content foundation is provided.
blowing purification and reduction period
Skimming oxidation period is completely called reduction period during this period of time to the liquid that taps a blast furnace, and main task is to have made reducing slag, to the further deoxidation of iron liquid, sometimes also simultaneously desulfurization, continues discharge inclusion and gas by airs blowing, prevents that gas secondary from sneaking into, adjust alloy element component, control tapping temperature well.Reduction period can be at electric arc furnace or/and complete in refining furnace, deslagging process, vacuum technology.If need to be in deslagging process, refining furnace and vacuum oven further removal of contamination and gas, need to select higher tapping temperature, note changing the acid-basicity of furnace rear refining furnace body, general refining furnace be acidity, reducing slag need be become to acid slag from basic slag.
Add reductive agent, close fire door, guarantee to react and proceed, guarantee that burner hearth has good stopping property as far as possible, to keep white slag to form fast, skim after desulfurization, need to again supplement reducing slag and reductive agent, and can multiple slagging, desulfurization, make new slag and cover melt, but reductive agent needs portion-wise addition, prevents the waste of reductive agent.At reduction period, skim, the impurity such as deoxidation, desulfurization, take off the quantity of slag and can reach 60~80% at most.Conventional reductive agent has carbon dust, silicon carbide, ferrosilicon, ferromanganese, ferro-silico-manganese, aluminium etc.Deoxidation, desulfurization need be carried out simultaneously, and along with the carrying out of reduction process, slag loses deoxidation, sweetening power gradually, need to skim in time, supplement reductive agent and reducing slag, approximately every 5~10min, add a collection ofly, and adjust the mobility of slag.
When adding reducing slag, by Bottom Blowing or top blast gas, can be in converter or/and refining furnace, or/and extracting vacuum is simultaneously blown into N
2, CO
2, Ar, can first blow N
2, blow CO again
2or Ar, also can only blow CO
2or Ar, remove inclusion and gas, be specially 0.05~1.0m
3/ min, 5~20 min.Use water-ring pump and vapor jet pump or use separately water-ring pump extracting vacuum, and being blown into gas, after reaching vacuum tightness 10~300Pa, 5~20min bleeds.For producing high trade mark cast iron, require foreign matter content very low, can extend gassing time, extracting vacuum, improves refining effect simultaneously, is conducive to improve the removing effect of inclusion, gas, low melting point, and prevents that gas secondary from sneaking into.
According to the ratio of non-ferro element in trade mark of casting iron, add in time element auxiliary material, adjust alloying constituent, iron liquid temp is elevated to tapping temperature, tapping temperature scope is 1320 ℃~1650 ℃, carries out the preparation of tapping a blast furnace.
Produce low phosphorus pig iron and can use low-phosphorous iron-bearing material, for adopting iron and steel scrap ironmaking, in grey cast iron product containing P total amount often than high in steel, the P total amount Chang Yugang that contains of wriggling in China ink, spheroidal graphite cast iron product approaches, if need a small amount of dephosphorization, can, by electric furnace, wash heat, refining furnace by a small amount of dephosphorization of reduction method, make to reduce to 0.4~0.8 containing P total amount.Converter of basic lining oxidation period dephosphorization effect better, can make to reduce to 0.3~0.7 containing P total amount.For using high phosphorus iron-bearing material to produce low phosphorus pig iron, can be oxidized and reduction method Dephosphorization.Use principal constituent (CaO+BaO)-Al2O
3-CaF
2slag system, by dephosphorization under reducing atmosphere in deslagging process and refining furnace, reduce the content of oxygen in cast iron, sulphur, inclusion simultaneously.
iron carbide or greying
Iron carbide refers to that carbon exists with atomic way in molten iron, and after solidifying, with the form appearance of iron carbide, greying refers to that carbon independently exists in crystal mode at molten iron and after solidifying.Iron carbide or greying all can be in converter or/and refining furnace, or/and keep completing in vacuum state, prevent that secondary air from sneaking into.For producing white cast iron, can select higher tapping temperature, by air blowing, stir and fully decompose the graphite crystallization body in molten iron, carbon is dissolved in iron liquid with atomic condition.For producing spheroidal graphite and vermicular cast iron, should select higher tapping temperature, grey cast iron should be selected lower tapping temperature, tapping temperature more in high de-agglomeration iron liquid the effect of graphite better, eliminate as far as possible the hereditary defect of graphite, then add the pig iron of some amount or less graphite crystal and graphite nucleating agent, at lower temperature, breed graphite.