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Precautions before and after use of trolley annealing furnace

Precautions before and after use of trolley annealing furnace

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[Abstract]:
Inordertofacilitatetheheatingoflargeworkpieces,atrolleytypefurnacesuitableforheatingingotsandbilletsispresented,andawelltypefurnaceisalsopresentedforheatinglongrods.Sincethe1920s,variousmechanizedandactivefurnaceshaveemerged,whichcanimprovetheoutputrateoffurnacesandtheworkingconditions.Withthedevelopmentoffuelresourcesandtheadvancementoffuelconversiontechnology,thefueloftrolleyannealingfurnacehasgraduallychangedfromsolidfuelssuchaslumpcoal,cokeandpulverizedcoaltogaseousandliquidfuelssuchasproducergas,citygas,naturalgas,dieseloilandfueloil,andvariousincinerationscorrespondingtothefuelsusedhavebeendeveloped.Burningequipment.Thestructure,heatingtechnology,temperaturecontrolandatmosphereoftrolleyannealingfurnacewilldirectlyaffectthequalityofprocessedproducts.Intheheatingfurnaceofcasting,improvingtheheatingtemperatureofmetalscanreducethedeformationresistance,buttoohightemperaturecancausegraingrowth,oxidationoroverheating,whichseriouslyaffectsthequalityoftheworkpiece.Intheprocessofheattreatment,ifthesteelisheatedtoapointabovethecriticaltemperatureandthensuddenlycooled,thehardnessandstrengthofthesteelcanbeimproved;ifthesteelisheatedtoapointbelowthecriticaltemperatureandthenslowlycooled,thehardnessofthesteelcanbereducedandthetoughnesscanbeimproved.Inordertoobtainworkpieceswithaccuratescaleandsmoothappearance,ortoreducemetaloxidationinordertoachievethepurposeofprotectingdiesandreducingprocessingallowance,variouskindsoflessoxidation-freeheatingfurnacescanbeselected.Inanopenflamefurnacewithlittleornooxidation,therecoverygasisproducedbyincompleteincinerationoffuel,inwhichtheoxidationlossratecanbereducedtolessthan0.3%byheatingtheworkpiece.Controllableatmospherefurnaceismanuallypreparedatmosphere,whichcanbeusedforgascarburizing,carbonitriding,brightquenching,normalizing,annealingandotherheattreatmenttoachievethepurposeofchangingthemetallographicarrangementandimprovingthemechanicalpropertiesoftheworkpiece.Inthemovableparticlefurnace,theburninggasoffuelorotherfluidizersappliedexternallyareusedtoflowthroughthegraphiteparticlesorotherlazyparticlelayersonthebedforcibly.Theworkpieceburiedintheparticlelayersmaybeheatedintensively,andallkindsofnon-oxidizingheatingsuchascarburizingandnitridingcanalsobecarriedout.Inthesaltbathfurnace,moltensaltliquidisusedasheatingmediumtopreventoxidationanddecarbonizationoftheworkpiece.Castironsmeltingincupolaisusuallyinfluencedbycokequality,airsupplymethod,burdenconditionandairtemperature,whichmakesthesmeltingprocessdifficulttobestableandhighqualityhotmetaldifficulttobeobtained.Hotblastcupolacaneffectivelyimprovehotmetaltemperature,reducealloyburningloss,andreducetheoxidationrateofhotmetal,thusproducinghigh-gradecastiron.Withtheappearanceofcorelessinductionfurnace,cupolahasgraduallybeenreplaced.Thesmeltingoperationofthisinductionfurnaceisnotconstrainedbyanygradeofcastiron.Itcanquicklychangefromsmeltingonegradeofcastirontosmeltinganothergradeofcastiron,whichisconducivetoimprovingthequalityofmolteniron.Somespecialalloysteels,suchasultra-lowcarbonstainlesssteelandsteelsforrollsandsteamturbinerotors,needtomeltmoltensteelfromopen-hearthfurnaceorgeneralelectricarcfurnace,removeimpuritiesinrefiningfurnacethroughvacuumdegassingandargonagitation,andfurtherrefinehighpurityandlargecapacityofhigh-qualitymoltensteel.Flamefurnaceshaveawiderangeoffuelsandlowprices,whichmakeiteasytoadoptdifferentstructuresandreduceproductioncosts.However,flamefurnacesaredifficulttooperateaccurately,whichcausesevereenvironmentalpollutionandlowthermalefficiency.Thecharacteristicsoftheelectricfurnacearethatthefurnacetemperatureisuniformandeasytocompleteactivecontrol,andtheheatingqualityisgood.Accordingtothemethodofenergyconversion,electricfurnacecanbedividedintoresistancefurnace,inductionfurnaceandarcfurnace.Furnaceheatingcapacitycalculatedbyunittimeperunitareaoffurnacebottomiscalledfurnaceyield.Thefastertheheatingrateofthefurnaceandthelargertheloadofthefurnace,thehighertheproductivityofthefurnace.Ingeneral,thehigherthefurnaceyield,thelowertheunitheatconsumptionperkilogramofmaterial.Therefore,inordertoreduceenergyconsumption,full-loadproductionshouldbecarriedout,furnaceproductionrateshouldbeimprovedasfaraspossible,andtheactiveshareoffuelandcombustion-supportingairshouldbeadjustedforincinerationequipmenttopreventexcessorlackofair.Inaddition,thelossofheatstorageandheatdissipationoffurnacewall,heatlossofwatercoolingcomponents,radiationheatlossofvariousopenings,heatlossofoff-furnacefluegasandsoonshouldbereduced.Theratiooftheheatabsorbedbymetalsormaterialswhenheatedtotheheatsuppliedtothefurnaceiscalledfurnacethermalefficiency.Continuousfurnacesaremoreefficientthandiscontinuousfurnacesbecauseoftheirhighproductivityanduninterruptedoperation.Theheatsystemofthefurnaceisinastablestateandthereisnoperiodiclossofheatstorageonthewall.Thereisalsoasectionofpreheatingburdeninthefurnace,andsomewasteheatofthefluegasisduetoapreheatingfurnaceinsidethefurnace.Inthematerialsection,someresidualheatofthefluegasisabsorbedbythecoldworkpieceenteringthefurnac
In order to facilitate the heating of large workpieces, a trolley type furnace suitable for heating ingots and billets is presented, and a well type furnace is also presented for heating long rods. Since the 1920s, various mechanized and active furnaces have emerged, which can improve the output rate of furnaces and the working conditions.
With the development of fuel resources and the advancement of fuel conversion technology, the fuel of trolley annealing furnace has gradually changed from solid fuels such as lump coal, coke and pulverized coal to gaseous and liquid fuels such as producer gas, city gas, natural gas, diesel oil and fuel oil, and various incinerations corresponding to the fuels used have been developed. Burning equipment.
The structure, heating technology, temperature control and atmosphere of trolley annealing furnace will directly affect the quality of processed products. In the heating furnace of casting, improving the heating temperature of metals can reduce the deformation resistance, but too high temperature can cause grain growth, oxidation or overheating, which seriously affects the quality of the workpiece. In the process of heat treatment, if the steel is heated to a point above the critical temperature and then suddenly cooled, the hardness and strength of the steel can be improved; if the steel is heated to a point below the critical temperature and then slowly cooled, the hardness of the steel can be reduced and the toughness can be improved.
In order to obtain workpieces with accurate scale and smooth appearance, or to reduce metal oxidation in order to achieve the purpose of protecting dies and reducing processing allowance, various kinds of less oxidation-free heating furnaces can be selected. In an open flame furnace with little or no oxidation, the recovery gas is produced by incomplete incineration of fuel, in which the oxidation loss rate can be reduced to less than 0.3% by heating the workpiece.
Controllable atmosphere furnace is manually prepared atmosphere, which can be used for gas carburizing, carbonitriding, bright quenching, normalizing, annealing and other heat treatment to achieve the purpose of changing the metallographic arrangement and improving the mechanical properties of the workpiece. In the movable particle furnace, the burning gas of fuel or other fluidizers applied externally are used to flow through the graphite particles or other lazy particle layers on the bed forcibly. The workpiece buried in the particle layers may be heated intensively, and all kinds of non-oxidizing heating such as carburizing and nitriding can also be carried out. In the salt bath furnace, molten salt liquid is used as heating medium to prevent oxidation and decarbonization of the workpiece. Cast iron smelting in cupola is usually influenced by coke quality, air supply method, burden condition and air temperature, which makes the smelting process difficult to be stable and high quality hot metal difficult to be obtained. Hot blast cupola can effectively improve hot metal temperature, reduce alloy burning loss, and reduce the oxidation rate of hot metal, thus producing high-grade cast iron.
With the appearance of coreless induction furnace, cupola has gradually been replaced. The smelting operation of this induction furnace is not constrained by any grade of cast iron. It can quickly change from smelting one grade of cast iron to smelting another grade of cast iron, which is conducive to improving the quality of molten iron. Some special alloy steels, such as ultra-low carbon stainless steel and steels for rolls and steam turbine rotors, need to melt molten steel from open-hearth furnace or general electric arc furnace, remove impurities in refining furnace through vacuum degassing and argon agitation, and further refine high purity and large capacity of high-quality molten steel.
Flame furnaces have a wide range of fuels and low prices, which make it easy to adopt different structures and reduce production costs. However, flame furnaces are difficult to operate accurately, which cause severe environmental pollution and low thermal efficiency. The characteristics of the electric furnace are that the furnace temperature is uniform and easy to complete active control, and the heating quality is good. According to the method of energy conversion, electric furnace can be divided into resistance furnace, induction furnace and arc furnace. Furnace heating capacity calculated by unit time per unit area of furnace bottom is called furnace yield. The faster the heating rate of the furnace and the larger the load of the furnace, the higher the productivity of the furnace. In general, the higher the furnace yield, the lower the unit heat consumption per kilogram of material. Therefore, in order to reduce energy consumption, full-load production should be carried out, furnace production rate should be improved as far as possible, and the active share of fuel and combustion-supporting air should be adjusted for incineration equipment to prevent excess or lack of air. In addition, the loss of heat storage and heat dissipation of furnace wall, heat loss of water cooling components, radiation heat loss of various openings, heat loss of off-furnace flue gas and so on should be reduced.
The ratio of the heat absorbed by metals or materials when heated to the heat supplied to the furnace is called furnace thermal efficiency. Continuous furnaces are more efficient than discontinuous furnaces because of their high productivity and uninterrupted operation. The heat system of the furnace is in a stable state and there is no periodic loss of heat storage on the wall. There is also a section of preheating burden in the furnace, and some waste heat of the flue gas is due to a preheating furnace inside the furnace. In the material section, some residual heat of the flue gas is absorbed by the cold workpiece entering the furnace, which reduces the temperature of the flue gas leaving the furnace.
In order to complete the active control of furnace temperature, atmosphere or pressure.
Gas is liquefied gas, natural gas, coke oven gas, city gas, converter gas, mixed gas, producer gas, blast furnace gas, etc.