Summary of the invention
The shortcoming of prior art in view of the above, the object of the present invention is to provide a kind of sedan steering to save as cast condition low temperature strongTough ferritic spheroidal graphite cast iron material and preparation method thereof, this material have higher low-temperature impact toughness, tensile strength, yield strength,Percentage elongation and excellent anti-fatigue performance.
For achieving the above object, first aspect present invention provides a kind of sedan steering to save the tough ferritic spheroidal graphite cast iron material of as cast condition low temperatureMaterial, by mass percentage, is made up of following component:
Surplus is Fe and inevitable trace impurity.
It is large that a kind of sedan steering provided by the present invention is saved the tough ferritic spheroidal graphite cast iron of as cast condition low temperature material-30 DEG C non-notch impact valueIn 100J/cm2; Tensile strength is greater than 480MPa, and yield strength is greater than 360MPa, and percentage elongation is greater than 18%, hardnessHB165-200; Nodularization rate be not less than 85% and ferrite content be not less than 90%; There is very high anti-fatigue performance, antifatigueDetection is passed through more than 100,000 times for high year, within low year, is passed through more than 1,000,000 times.
The preparation method that second aspect present invention provides a kind of sedan steering to save the tough ferritic spheroidal graphite cast iron material of as cast condition low temperature, bagDraw together following steps:
(1) raw material is placed in to electric induction furnace and carries out melting, and add low-sulfur carburant to supplement carbon amount, described raw material be the pig iron,Foundry returns and steel scrap;
(2) in fusion process, the molten iron in electric induction furnace is sampled and detected and element adjustment;
(3), after melting is tapped a blast furnace, carry out spheroidising and Bao Nei inoculation;
(4) cast, and carry out current-following inoculation simultaneously;
(5) naturally cooling.
Preferably, the described pig iron is the Q10 pig iron, forms (mass percent): C: >=3.40% by following component; Si:0.50-1.00%; Mn :≤0.20%; S :≤0.02%; P :≤0.05%; Surplus is Fe and inevitable trace impurity.
Preferably, described foundry returns is the foundry returns that a kind of sedan steering is saved the tough ferritic spheroidal graphite cast iron material of as cast condition low temperature, itsComponent composition (mass percent): C3.1-3.4%; Si3.1-3.3%; Mn0.2-0.3%; S < 0.015%; P < 0.04%;Cu < 0.1%; Sn < 0.01%; Cr < 0.1%; Mo < 0.1%; Ni < 0.1%; Mg0.03-0.05%; Surplus isFe and inevitably trace impurity.
Preferably, described steel scrap chemical composition (mass percent) is: C:< 0.10%; Si:< 0.20; Mn:0.1-0.3%; S：＜0.01％；P：＜0.02％；Cu：＜0.05％；Sn：＜0.01％；Cr：＜0.05％；Mo：＜0.05％；Ni:< 0.1%; Surplus is Fe and inevitable trace impurity.
Preferably, described electric induction furnace is medium-frequency induction furnace.
Preferably, in described step (1), the weight percent of described raw material is: pig iron 10-20%, foundry returns 40-60%, steel scrap 30-40%; The addition of low-sulfur carburant is the 0.9-2.0% of weight of molten iron; The temperature of described melting is1490-1525 DEG C, temperature retention time is 3-30 minute.
Preferred, in described low-sulfur carburant, the quality percentage composition of carbon is greater than 99%, and the quality percentage composition of sulphur is less than0.05%; Granularity is 0.5-5mm.
Preferably, in described step (2), the concrete grammar that sampling detects is: from induction furnace, dip molten iron, and pour into a mould carbonSulphur and spectrum samples, detect with carbon sulphur instrument and spectrometer respectively, obtains hot metal composition.
Preferably, in described step (3), described spheroidising adopts pit type to pour method, in pit, is incorporated as processing ironThe rare earth ferrosilicomagnesium nodulizer of water weight 1.25-1.35%; In spheroidising, in pit, be incorporated as processing weight of molten ironThe bismuth ferrosilicon inovulant of 0.10-0.12% and breeding in wrapping for processing the rare earth ferrosilicon inovulant of weight of molten iron 0.29-0.31%.
Preferred, the mass percent of described rare earth ferrosilicomagnesium nodulizer consists of: magnesium: 5.5-6.2%; Silicon: 44-48%;Calcium: 0.8-1.2%; Rare earth: 0.8-1.2%; Aluminium :≤1.0%; Surplus is iron; Granularity is 3-25mm.
Preferred, the mass percent of described bismuth ferrosilicon inovulant consists of: bismuth 0.75-1.30%, silicon 63-70%, calcium0.8-2.8%, barium 1.0-3.0%, surplus is iron; Granularity be 2-8mm.
Preferred, the mass percent of described rare earth ferrosilicon inovulant consists of: rare earth 1.5-2.0%, silicon 70-76%, calcium0.75-1.25%, aluminium 0.75-1.25%, surplus is iron; Granularity is 2-8mm.
Preferably, in described step (4), the temperature of described cast is 1435-1390 DEG C; The inovulant of described current-following inoculationFor silicon ferrozirconium inovulant, addition is the 0.1-0.2% of pouring molten iron weight; The casting mold of described cast is selected from clay-bonded sand wet type. WaterDivide type equally, high pressure moulding.
Preferred, described silicon ferrozirconium inovulant mass percent consists of: silicon 62-69%, and zirconium 4.0-5.0%, manganese 4.0-5.0%,Calcium 1.0-2.0%, surplus is iron; Granularity is 0.2-0.7mm.
Purposes of the present invention is: have compared with high/low-temperature impact toughness, tensile strength, yield strength, percentage elongation and excellent resistingThe tough ferritic spheroidal graphite cast iron material of the as cast condition low temperature automobile steering knuckle of fatigue behaviour is manufactured.
The present invention selects low-carbon (LC) and suitable high silicon, increases graphitizability on the one hand, obtains and stablizes more ferrite;On the other hand, the solubility of carbon in ferrite is lower, and the carbon overwhelming majority is with the appearance of graphite form, and low-carbon (LC) is conducive to reduce stoneThe China ink amount of separating out; Suitably high silicon solid solution, in ferrite, makes ferrite obtain larger solution strengthening, makes tensile strength, bendsTake intensity and hardness obviously improves, take into account again required percentage elongation and low-temperature impact toughness. The selection of other elements, also abundantConsider that they are definite afterwards on the impact of tensile strength, yield strength, hardness, percentage elongation and low-temperature impact toughness. In addition adopt,With the rare earth ferrosilicomagnesium nodulizer of high-quality, guarantee spheroidization of graphite, reduce shrinkage porosite. Adopt bismuth ferrosilicon inovulant and rare earth ferrosilicon pregnantEducate that agent is bred in wrapping, silicon ferrozirconium inovulant current-following inoculation, breed by these efficient intensive inoculation combining, can carryHigh graphite nodule roundness, grain refinement, graphite is tiny. Because: (1) bismuth is surface active element, can increase iron liquid excessively coldSpend and iron liquid nucleation rate is increased, increasing graphite and ferrite quantity, refinement graphite, refinement ferrite crystal grain; (2) rare earthFerrosilicon inovulant contains a certain amount of Ca, Ce. Ca, Ce react with sulphur, oxygen in iron liquid and form sulfide, oxide and sulphurOxygen complex chemical compound, these compounds and graphite have coherence relation, become graphite nuclei; These core adhesions are strong, more steadyFixed, run through whole process of setting, therefore graphite nucleation rate is high, increase graphite, crystal grain thinning; (3) silicon ferrozirconium inovulantContain zirconium, manganese, the oxygen of zirconium in molten iron is combined, and is conducive to eliminate the pore in foundry goods. Meanwhile, the ZrC of formation is as stoneChina ink core, increases graphite. Manganese can reduce silicon ferrozirconium inovulant fusing point, is conducive to silicon ferrozirconium inovulant and dissolves in molten ironDiffusion, is suitable for molten steel pouring temperature wider range. The anti-ageing ability of moving back of this inovulant is strong, reduces chilling tendency, improves graphiteForm, crystal grain thinning. The comprehensive above-mentioned Overlay that breeds: grain refinement, graphite is tiny, and intensity and low-temperature flexibility are improvedAll there is important function. Naturally cooling after cast, gained as cast condition material matrix tissue is stable, and mechanical property meets necessary requirement.
The present invention is put into production, easy and simple to handle, and gained as cast condition stable material quality, meets the demands, and is applicable to large-scale mass production.
Prepare a kind of sedan steering and save the tough ferritic spheroidal graphite cast iron material of as cast condition low temperature, its chemical composition mass percent is: C:3.37％，Si：3.29％，Mn：0.26％，S：0.008％，P：0.026％，Cu：0.02％，Sn：0.003％，Cr：0.010%; Mo:0.02%; Ni:0.007%; Mg:0.036%, all the other are Fe and inevitable trace impurity.
Concrete preparation method is as follows:
The first step, adopts the Q10 pig iron (to be made up of following mass percent component: C: >=3.40%; Si:0.50-1.00%;Mn :≤0.20%; S :≤0.02%; P :≤0.05%; Surplus is Fe and inevitable trace impurity. ), foundry returns(formed by following mass percent component: C3.1-3.4%; Si3.1-3.3%; Mn0.2-0.3%; S < 0.015%; P < 0.04％；Cu＜0.1％；Sn＜0.01％；Cr＜0.1％；Mo＜0.1％；Ni＜0.1％；Mg0.03-0.05％；Surplus is Fe and inevitable trace impurity), (waste steel quality percentage component consists of C:< 0.10% to steel scrap; Si:＜0.20；Mn：0.1-0.3％；S：＜0.01％；P：＜0.02％；Cu：＜0.05％；Sn：＜0.01％；Cr：＜0.05%; Mo:< 0.05%; Ni:< 0.1%; Surplus is Fe and inevitable trace impurity), three's proportioning: rawIron 500kg, foundry returns 3000kg, steel scrap 1500kg; In electrosmelting of intermediate frequency, carry out melting, and add low-sulfur carburant(wherein, the quality percentage composition of carbon is greater than 99%, and the quality percentage composition of sulphur is less than 0.05%; Granularity is 0.5-5mm)In stove, supplement carbon amount, smelting temperature is 1490-1525 DEG C, and temperature retention time is 3-30 minute;
Second step, samples detection to the molten iron in intermediate frequency furnace in fusion process, and described sampling testing process is: fromIn medium-frequency induction furnace, dip one spoonful of molten iron, cast carbon sulphur sample and spectrum samples, detect also with carbon sulphur instrument and spectrometer respectivelyCarry out element adjustment;
The 3rd step, melting after tapping a blast furnace, adopt pit type pour method carry out spheroidising and for the first time inoculation (bag in wombReason): in pit, the rare earth ferrosilicomagnesium nodulizer (matter that the 1.25-1.35% granularity that is incorporated as processing weight of molten iron is 3-25mmAmount percentage consists of: Mg:5.5-6.2%; Si:44-48%; Ca:0.8-1.2%; Rare earth 0.8-1.2%; Al :≤1.0%;Surplus is Fe; Granularity is 3-25mm); And be that 2-8mm bismuth ferrosilicon breeds for processing the 0.10-0.12% granularity of weight of molten ironAgent (quality percentage composition is: bismuth 0.75-1.30%, silicon 63-70%, calcium 0.8-2.8%, barium 1.0-3.0%, Yu Weitie) andFor the 0.29-0.31% granularity of processing weight of molten iron is that (quality percentage composition is 2-8mm rare earth ferrosilicon inovulant: rare earth1.5-2.0%, silicon 70-76%, calcium 0.75-1.25%, aluminium 0.75-1.25%, Yu Weitie) breed in wrapping;
The 4th step: then pour into a mould, pouring temperature 1435-1390 DEG C, carries out current-following inoculation, inovulant is that silicon ferrozirconium breedsAgent (mass percent consists of: silicon 62-69%, zirconium 4.0-5.0%, manganese 4.0-5.0%, calcium 1.0-2.0%, Yu Weitie), grainDegree is 0.2-0.7mm, and addition is the 0.1-0.2% of pouring molten iron weight; Casting mold is clay-bonded sand wet type, horizontal parting or high pressureMoulding.
The 5th step: naturally cooling after cast.
Knuckle body material testing result is in shown in table 1, Fig. 1; In table 1, GB/T9441-2009 " spheroidal graphite is pressed in metallographic structureCast iron metal lographic examination " detect and pass judgment on.
In this embodiment, the chemical composition mass percent of gained as cast condition low temperature is tough ferritic spheroidal graphite cast iron material is: C:3.25%,Si：3.21％，Mn：0.25％，S：0.007％，P：0.028％，Cu：0.04％，Sn：0.004％，Cr：0.015％，Mo:0.02%; Ni:0.006%; Mg:0.041%, all the other are Fe and inevitable trace impurity.
Concrete preparation method is referring to embodiment 1. In the present embodiment, the Q10 pig iron, foundry returns, steel scrap three proportioning are: Q10Pig iron 750kg, foundry returns 2500kg, steel scrap 1750kg. All the other content step are all in the same manner as in Example 1.
Knuckle body material testing result is in table 1, and metallograph and Fig. 1 are similar.
The tough ferritic spheroidal graphite cast iron material of as cast condition low temperature prepared by embodiment 1-3, for the manufacture of certain knuckle in car, has comprehensiveClose higher low-temperature impact toughness, tensile strength, yield strength, percentage elongation and excellent anti-fatigue performance feature.
In sum, the present invention has effectively overcome various shortcoming of the prior art and tool high industrial utilization.
Above-described embodiment is illustrative principle of the present invention and effect thereof only, but not for limiting the present invention. Anyly be familiar with thisThe personage of technology all can, under spirit of the present invention and category, modify or change above-described embodiment. Therefore,Such as in affiliated technical field, have and conventionally to know that the knowledgeable completes under disclosed spirit and technological thought not departing fromAll equivalences are modified or are changed, and must be contained by claim of the present invention.