CN2056233U - New-type cupola for melting iron and steel chips - Google Patents

Abstract

The utility model relates to a new-type cupola for melting iron and steel chips, which is the improvement on the basis of a normal cupola. The utility model is characterized in that a secondary combustion heat exchanger (2) is installed at the inside of a chimney (1), and a ventilating port (8) is arranged on a hearth (6); the air vent ratio is big, and the constancy of the air vent ratio is regulated by the self-melting nature. The furnace hearth of the normal cupola is deepened, and the external wall of the top of a cupola body (7) is provided with a shower (4); the upper part of the furnace hearth zone is provided with a water jacket (9), and a secondary combustion air outlet (12) is arranged on the chimney (1). The good quality molten iron of the melting of 100% loosening iron and steel chips can be directly used for the production of the ductile iron and the grey cast iron by taking the measurement.

Description

New-type cupola for melting iron and steel chips

It is new cupola--the new cupola of molten steel iron filings of furnace charge fusing high quality cast iron with whole steel chips, case-iron shavings that the utility model relates to a kind of.

The annual product of paying that all produces millions of tons in China's machine-building is produced--steel chips, iron smear metal (hereinafter to be referred as the iron and steel bits).China is only limiting to the recovery of metal recovery department aspect the comprehensive utilization of steel scrap at present, make ripe briquetting (loss 30-40%) or cold extrusion and become agglomerate (being only limited to) with sheet iron and short-term steel cuttings, return steel plant's melting again, human and material resources, financial resources have been wasted, and quite a few unmanned reclaim or reclaim untimelyly oxidized away in vain, promptly wasted precious resources, worsened environment again, make the used iron charge of China's casting industry, be in the situation that is becoming tight supply day.

As everyone knows: furnace cupola is to be the melting unit of furnace charge with certain proportioning with the pig iron, steel scrap, foundry returns, ferroalloy, coke, flux.And whole loose steel scraps can not have three as the main cause of soaring furnace charge: one of reason is the specific area of the steel scrap big ratio of weight (surface area with), be general piece material 30-50 doubly, and the affinity of iron atom and oxygen is stronger, be easy to oxidation, and conventional soaring atmosphere is oxidisability.At high temperature go into the very easily oxidation of diffusing shape steel scrap of stove, even the form with briquetting in furnace charge allocates 10% into, then make more serious oxidation takes place in the stove, the ferrous oxide iron-holder in the slag is up to 8-10%, when worsening slag, also make the molten iron severe oxidation.Very high with this molten iron pouring cast part percent defective.Then be cast the boundary always and be considered as the forbidden zone as for founding the direct pouring cast part of molten iron for the furnace cupola iron charge with 100% loose iron and steel bits.Former two is because steel scrap composition and cast iron composition differ bigger therefore.And conventional furnace cupola does not possess the ability that nature is adjusted cast iron composition, even adjust composition with artificial way of adding ferroalloy, but because of the affinity of alloying element and oxygen is big, oxidization burning loss is serious, especially with iron oxide content height in the slag for very.This be because:

Be that silicon, manganese are to carry out oxidization burning loss in the mode of displacement iron.So be furnace charge with the iron and steel bits, the FeO content height in the slag, it is uneconomic adjusting cast iron composition with the interpolation ferroalloy.For this reason, only limit on the casting circle at present use the iron and steel bits of briquetting to allocate the effect of playing dilution carbon amount in the furnace cupola piece material into 10% proportioning.Former three is that loose steel scrap is tiny therefore, and gap each other is little, goes into to cause behind the stove furnace gas difficulty that rises, furnace gas is by rising operation on the furnace wall basically, in the very play of furnace wall etch down of the washing away of high temperature gas flow and scum stream, etch 20-30mm per hour, stove is difficult to long-term work.

Purpose of the present invention just provides a kind of furnace cupola that can produce reproducibility or weak reducing atmosphere, makes steel scrap can melt the new cupola of high quality cast iron as furnace charge.

Solution of the present invention is as follows:

According to calculation of thermodynamics, under hot conditions, promptly temperature is 705 ℃ greater than 978K() time, because CO compares CO ₂Free energy low, then CO is a stable state, CO ₂Be labile state, so take place:

CO ₂Reduction reaction, and this reaction is condition with temperature greater than 978K, temperature is high more, reacts fast more, thorough more.In view of this, improving furnace gas temperature is the necessary condition that obtains reducing atmosphere, the lumpiness of the air port row's number that adapts with it, air port ratio, tuyere angle, flow, blast, coke, the reactivity of coke, coke ratio etc. then are adequate condition, only possess necessary condition and adequate condition and could obtain reducing atmosphere.For improving furnace gas temperature, we install a second-time burning heat exchanger (2) in the chimney (1) above original cupola charging mouth, second-time burning heat exchanger (2) be by heat transfer property preferably material make, the setting of second-time burning heat exchanger (2) is in order to absorb physics heat and the potential chemical heat in the waste gas effectively, second-time burning heat exchanger (2) can be made helix tube type, various ways such as the multitube interconnection system or the tubular type of crawling, an air inlet termination air blast of second-time burning heat exchanger (2), the other end is received bellows (11) by airduct (3).For second-time burning heat exchanger (2) is heated evenly, and the chemical potential that CO had in the furnace gas is also emitted, on chimney (1) wall, have second-time burning air inlet (12), intake is regulated by control valve (13), by suitable adjusting to intake, can make the CO content in the combustion gas reach minimum, most of CO fully burns in the furnace gas, emit its contained potential chemical heat, in order to preheated air.

In order to dwindle zoneofoxidation, enlarge the reducing zone, the present invention adopts the single air outlet operation, be about to second exhaust outlet (14) Close All of the big spacing of existing furnace cupola two rows, on burner hearth (6), only adopt an exhaust outlet (8) to operate, to enlarge the reducing zone, if build new furnace cupola, one exhaust outlet (8) then only is set on burner hearth (6), and exhaust outlet (8) is made moulding by oneself with refractory material, exhaust outlet (8) to be shaped as the inside little, the outside is big, and following rake angle big (20 °), the air port is than being 5.5-6.5%, the air port that the unique distinction of this exhaust outlet (8) is to regulate furnace cupola by self-fluxing nature is than being constant, and the purpose of using big air port ratio is to slow down the tuyere area gas flow rate, is beneficial to the reduction reaction of tuyere area CO2.

Under reducing atmosphere, two kinds of metallurgical reactions take place in the solid steel scrap, the reduction reaction of iron oxide and carburization reaction:

The carburizing process of iron and steel bits is owing to the contact action of the big iron and steel bits of activity (owing to its specific area is big) with CO, impel it to decompose, the CO branch parses active very big carbon black (cigarette carbon), is adsorbed on the surface of steel scrap, constantly diffusion is dissolved in the iron simultaneously, makes carburization.

Reduction along with steel, iron filings, the decline gradually of carburizing and furnace charge, temperature raises, be fused into liquid at fusion zone, iron drips, and passes high-temperature region (tropical excessively), be superheated to higher temperature, because iron drips with red-hot coke and contacts well, quicken carburization reaction simultaneously, also carried out increasing simultaneously pasc reaction.

Increase pasc reaction: in tropical excessively high-temperature region, the SiO in the fuel ash ₂With etch furnace lining and the SiO that brings into of furnace charge ₂, gasify earlier and afterwards increase silicon.

Through furnace cupola has been made the obtained reproducibility high-temperature furnace gas of above-mentioned improvement, just finish the reduction and the fusing of steel scrap, make the reduction of the overheated and alloying element of molten iron.But the primitive component and the cast iron composition of the smear metal of whole invar iron differ bigger, far can not satisfy the composition requirement of cast iron, also will make following improvement:

The cupola well of conventional furnace cupola is deepened, be bath formula cupola well (10), be used to store molten iron and slag.Remove the forehearth of conventional furnace cupola,, make the high-temperature region be displaced downwardly to cupola well because of arranging the following rake angle of internal orifice (8) big (20 °).Moreover the coke of crucible zone participates in metallurgical reaction always, constantly consume, so the red-hot coke of high-temperature region, top constantly descends and brought a large amount of thermals source to cupola well; Pass iron that the overheated zone obtained maximum temperature in addition and drip with slag and come together in cupola well molten bath district, all make cupola well keep high temperature, cause cupola well to possess the thermodynamic condition of metallurgical reaction.Owing to be full of coke, molten iron and slag in the cupola well bath, and three's contact conditions is quite abundant, in carburizing, carrying out determining the multiple metallurgical reaction of the molten iron ultimate constituent, by control, can regulate the content of alloying element in molten iron to each group element content of slag.

After taking above measure, the problem that occurs is furnace lining etch aggravation, make the conventional furnace cupola can't long-term work, address this problem, furnace lining can be worked long hours, produce needs to satisfy, the utility model changes conventional cupola body formula bellows into separate type bellows (11), bellows (11) inwall and furnace body outer wall are gapped, be provided with the device that drenches with rain (4) at the top of body of heater (7), the device that drenches with rain (4) has a plurality of spray apertures around the outer wall of body of heater (7) shape ringwise on annular drenches with rain device (4), its spray apertures axis and body of heater (7) outer wall angle at 45, during work, make the outer wall of whole body of heater (7) form cascade, cooling water is taken away the heat that the furnace wall gives out, when coolant water temperature kept substantially constant (changing little), the furnace wall kept certain thickness.One ring-shaped water jacket (9) is set on the top of crucible zone, elimination thermal current, high temperature iron, slag liquid plume wash away and erosion the crucible zone furnace lining, stove can be worked long hours, production shows in the our factory, said structure is functional, in fusing time is 10 hours, and the fusion zone lining thickness corrodes 120mm by original 170mm, has satisfied the production needs.

The utility model has the advantages that and on existing furnace cupola basis, to reequip, furnace cupola after the repacking can produce reproducibility or weak reducing atmosphere, with avoid loose iron and steel bits in stove oxidation or make slight oxidation steel scrap reduced, melt the high-quality molten iron with 100% loose steel scrap and can be directly used in production spheroidal graphite cast-iron and grey cast-iron, be to adjust cast iron composition in fusing by adjusting slag character, saved ferroalloy, and because the present invention has the molten refining feature of reproducibility, oxide content is low, molten steel quality is excellent, the casting wasted product rate is low, iron and steel bits rate of recovery height (＞95%) has successfully solved the difficult problem that conventional furnace cupola can not be made furnace charge with 100% loose iron and steel bits material.

Embodiment of the present utility model is as shown in drawings:

Accompanying drawing 1 is the utility model structural representation.

Accompanying drawing 2 is structure diagrams of second-time burning heat exchanger (2).

Accompanying drawing 3 is A-A cutaway views of accompanying drawing 2.

In the utility model, second-time burning heat exchanger (2) is to adopt the multitube interconnection system, and pipe is to adopt steel pipe.The second-time burning air outlet of opening on chimney (1) wall (12) is the tangent line perforate along chimney (1), makes second-time burning air outlet (12) form the tangent line air intake, causes the burning of flame uniformity, has increased the being heated evenly property of heat exchanger.

Exhaust outlet (8) is to adopt high plumbous refractory material, and the self-control moulding is put into when building by laying furnace lining, and the air port ratio is 5.9%.

In the present embodiment, be that the cupola well of 350mm adds and is deep to 750mm with the original degree of depth of conventional furnace cupola, be melting pool type cupola well of the present utility model (10).

In order when melting, to increase the concentration of oxidation in the wind, with further raising overheated zone temperature, the utility model is provided with an oxygen enrichment blow valve (5) at bellows (11) air inlet place, the size of oxygen enrichment blow valve (5) matches with the size of oxygen cathete, whether the oxygen enrichment air-supply is adopted, and can decide according to producing needs.

Adopt the utility model that conventional furnace cupola is made improvements, can't influence the original purposes of conventional furnace cupola.

Production example of the present utility model is as follows:

One of production instance: produce 550 type straightener alloy nodular cast iron smoothing rolls and other ball foundry goods with 100% loose steel, iron smear metal fusing QT600-3 trade mark base iron.

1, charge composition:

Iron and steel bits batch heavy (Kg) coke charge (Kg) lime stone (Kg)

100％????250????30????10

Annotate: the iron and steel bits are loose condition (of surface), and corrosion is lighter.Steel cuttings respectively is 50% approximately.

2, hot metal composition and spheroidising

	C	Si	Mn	S	P
						Food ingredient %	1.5～1.7	0.9～1.0	0.4～0.6	0.07～0.08	0.07～0.08
Base iron composition %	3.5～3.6	1.1～1.2	0.4～0.6	0.04～0.06	0.075
						Element variation %+increase-subtract	＋100～115	＋20～25	－－	－30～50	－－
Slag composition %	Sio 236～38	CaO 40～46	MgO 8～10	FeO 1～1.5	MnO <0.4

Molten iron temperature: 1500～1550 ℃, leucoscope iron notch thermometric.Slag is an alkalescence, and basicity is 1.37, and this slag has excellent desulfurizing effect, and silicon slightly increases.

Spheroidising: nodulizer is the 4# magnesium-rare earth that the Baotou produces, addition 1.3%, and inovulant is the 75# ferrosilicon, addition is 0.8%, pours 0.7% cathode copper, 0.03% tin at iron notch during the water outlet of spheroidising secondary.

3, alloy ductile iron chemical composition, metallographic and mechanical performance

Chemical composition %:

C????Si????Mn????S????P????Mg????Re????Cu????Sn

Metallographic structure:

Nodulizing grade is that one-level, graphite size are 90-95% ball light body for one-level, matrix.

Mechanical performance:

Tensile strength 6b=689.5N/mm ²(69Kgf/mm ²)

Hardness HB 190～210

It is Hv964.8 that foundry goods is handled hardness through laser surface hardening

With the spheroidal graphite cast-iron that this method is produced, machined shows that processing characteristics is good, and to 118 comprehensive percent defective statistics of smoothing roll, percent defective is 1.69%, and percent defective is starkly lower than the like product of producing with conventional furnace cupola.

Two of production instance: with gray iron castings such as 100% loose iron and steel bits batching fusing HT200 trade mark molten iron production bucket elevator large pulleys.

1, charge composition

Iron and steel bits (respectively being 50%) batch heavy (Kg) coke charge lime stone

100％????250????30????5

2, chemical composition and rate of change, slag composition

Chemical composition	C	Si	Mn	S	P
						Food ingredient %	1.5～1.7	0.9～1.0	0.4～0.6	0.07～0.08	0.07～0.08
Hot metal composition %	3.1～3.3	1.5～1.6	0.4～0.6	0.09～0.11	0.07
						Element variation rate %	+90～100	+40～50	--	+20～30	--
Slag composition %	SiO 245～55	CaO 19～23	MgO 4～5	FeO 1～1.5	MnO 0.3～0.4

As can be known, it is acid that slag is from table, and basicity is 0.6, increases the silicon performance and is better than basic slag.

3, mechanical performance:

Tensile strength 6b 216.5N/mm ²(22Kgf/mm ²)

Hardness HB 170～190

The grey cast-iron machinability of producing with this method is good, and bleb and slag blister defective obviously reduce, and the comprehensive percent defective of foundry goods is starkly lower than the like product of producing with conventional furnace cupola.

Conclusion: new cupola of the present utility model, melt the high-quality molten iron with 100% loose steel scrap and can be directly used in production spheroidal graphite cast-iron and ash product cast iron.Every physical and chemical index of cast iron all reaches the regulation of GB5675-85, ISO-1083.In fusing, adjust cast iron composition, saved ferroalloy by adjusting slag character.Because this new cupola has the reduction melting feature, oxide content is low, and molten steel quality is excellent, and the casting wasted product rate reduces, iron and steel bits rate of recovery height (＞95%).Successfully solved conventional furnace cupola and can not make the difficult problem of furnace charge with 100% loose iron and steel bits material.

The utility model remarkable in economical benefits, through rough calculation, melt the conventional furnace cupola of hot metal ratio per ton (making furnace charge with the pig iron) and reduce production costs 390 yuan, can not only greatly reduce production costs, demonstrate again significant economic results in society, fully utilized national precious resources, the potential economic value of iron and steel bits is brought into play. With 7,300,000 tons of calculating of China's cast iron output in 1985, if adopt the utility model, only can be country this every year and economize on the use of funds about 28.5 hundred million yuan.

Claims (8)

1, a kind of new cupola of molten steel iron filings is that conventional furnace cupola is improved, and it is characterized in that:

A: chimney (1) is installed a second-time burning heat exchanger (2) of being made by the material of good heat-transfer, to absorb physics heat and the potential chemical heat in the waste gas;

B a: exhaust outlet (8) only is set, on burner hearth (6) to enlarge the reducing zone;

C: the cupola well of conventional furnace cupola is deepened to be bath formula cupola well (10).

2, furnace cupola according to claim 1 is characterized in that the outer wall at body of heater (7) top is provided with the device that drenches with rain (4), takes away the heat that distribute the furnace wall; Water jacket (9) is set on the top of crucible zone, water jacket (9) at crucible zone ringwise so that stove can long-term work.

3, furnace cupola according to claim 2, what it is characterized in that air port (8) is shaped as that the inside is little, the outside is big, and the air port is than for 5.5-6.5%, regulates the air port than being constant by self-fluxing nature.

4, furnace cupola according to claim 3 is characterized in that the air port ratio in air port (8) is 5.9%.

5, furnace cupola according to claim 3 is characterized in that having on the chimney (1) second-time burning air outlet (12).

6, furnace cupola according to claim 5 is characterized in that second-time burning air outlet (12) is out the tangential direction at chimney, forms the tangent line air intake.

7, furnace cupola according to claim 5 is characterized in that second-time burning heat exchanger (2) is to adopt the multitube interconnection system, also can adopt the tubular type of crawling, helix tube type, is beneficial to heat absorption.

8, furnace cupola according to claim 7 is characterized in that bellows (11) are to adopt and the body of heater separate mode, and bellows (11) inwall and furnace body outer wall are gapped.

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