CN109402492B - External treatment method for carbide-containing nodular cast iron molten iron - Google Patents

External treatment method for carbide-containing nodular cast iron molten iron Download PDF

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CN109402492B
CN109402492B CN201811481137.8A CN201811481137A CN109402492B CN 109402492 B CN109402492 B CN 109402492B CN 201811481137 A CN201811481137 A CN 201811481137A CN 109402492 B CN109402492 B CN 109402492B
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molten iron
iron
mass fraction
spheroidizing
core
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CN109402492A (en
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符寒光
南榕
杨鹏辉
林健
李辉
雷永平
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Beijing University of Technology
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Beijing University of Technology
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C37/00Cast-iron alloys
    • C22C37/04Cast-iron alloys containing spheroidal graphite
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0056Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C33/00Making ferrous alloys
    • C22C33/08Making cast-iron alloys
    • C22C33/10Making cast-iron alloys including procedures for adding magnesium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C37/00Cast-iron alloys
    • C22C37/06Cast-iron alloys containing chromium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C37/00Cast-iron alloys
    • C22C37/10Cast-iron alloys containing aluminium or silicon

Abstract

An external treatment method of molten iron containing carbide nodular cast iron belongs to the technical field of casting. Smelting carbide-containing nodular cast iron molten iron in a medium-frequency induction furnace or a cupola furnace, and controlling the chemical composition and the mass fraction of the molten iron to be 3.34-3.75% of C, 1.59-1.88% of Si, 0.94-1.07% of Cr, 0.45-0.64% of Mn, 1.09-1.26% of Cu, less than or equal to 0.06% of S, less than or equal to 0.08% of P and the balance of Fe; when the temperature of the molten iron reaches 1483-1509 ℃, the molten iron is pre-spheroidized in the spheroidizing ladle, then two core-spun yarns are fed in by a wire feeding machine in sequence, after the treated molten iron is solidified, the spheroidization rate of graphite is high, the graphite spheres are fine in size and uniform in distribution, and carbides are in broken nets and isolated distribution, so that the strength and toughness of the carbide-containing nodular cast iron can be obviously improved.

Description

External treatment method for carbide-containing nodular cast iron molten iron
Technical Field
The invention discloses an external treatment method of nodular cast iron molten iron, in particular to an external treatment method of nodular cast iron molten iron containing carbide, belonging to the technical field of casting.
Background
The nodular cast iron has higher strength and better toughness than common gray cast iron, and is widely applied to industrial production. In order to make up the defects of low hardness and poor wear resistance of the nodular cast iron, a strong carbide generating element is added into the nodular cast iron to obtain the nodular cast iron containing carbide, and after isothermal quenching, the nodular cast iron containing acicular ferrite, spheroidal graphite, high-carbon austenite and a certain content of carbide can be obtained. The grinding ball is used for manufacturing the grinding ball of the ball mill, the abrasion loss of the grinding ball is one third of that of the grinding ball made of low-chromium cast iron, and the grinding ball is free from the phenomena of crushing and out-of-round.
In order to further improve the performance of the carbide-containing nodular cast iron, the Chinese invention patent CN 106834902 discloses a high-wear-resistance carbide-containing ausferrite nodular cast iron and a preparation method thereof, and the carbide-containing ausferrite nodular cast ironThe formula of the nodular cast iron containing carbide austempered iron is improved, the nodular cast iron containing carbide is prepared by using 3.50-3.90% of C, 2.90-3.50% of Si, 1.30-1.70% of Mn, less than 0.08% of P, less than 0.012% of S, 0.01-0.04% of RE, 0.025-0.04% of Mg, 0.08-0.18% of Cr, 0.17-0.32% of V, 0.08-0.18% of Ti, 0.30-0.40% of Cu, 0.001-0.006% of B, the balance of Fe, RE is rare earth metal, preferably Y, Chinese patent CN 105420594, a carbide-containing austempered nodular cast iron hammer is prepared by using a salt bath quenching method, the nodular cast iron containing carbide is prepared by using a casting method, an austempered ductile iron containing carbide, a casting method, an austempered ductile iron containing carbide, a ductile iron containing carbide, a Cr, a C, a Cr, a Ck5 to 16J/cm2The ball falling frequency is more than or equal to 20000, and the wear resistance, impact toughness and comprehensive mechanical property are good. Chinese invention patent CN 105274423 also discloses carbide-containing austempered ductile iron and a preparation method thereof, wherein the ductile iron comprises the following chemical components in percentage by weight: 3.3-3.8 parts of C, 1.5-2.5 parts of Si, 0.2-0.7 part of Cr0.4-1.0 part of Mn0.2-0.6 part of Mo0.02-0.08 part of V, 0.2-0.5 part of Ni0.2, 0.15-0.30 part of Cu0.015-0.030 part of Mg0.015-0.030 part of RE, 0.02-0.05 part of S, less than or equal to 0.080 part of P, and the balance of Fe. The preparation process comprises the following steps: preparing raw materials and smelting in an intermediate frequency furnace; spheroidizing and inoculating the molten iron; and (4) isothermal quenching heat treatment. The invention obtains fine and dispersed carbide tissue by adding trace V element and properly reducing the content of Si, the wear resistance of the nodular cast iron is greatly improved by the tissue, and the impact property of the nodular cast iron is improved by adding a small amount of Ni. The Chinese patent CN104233051 also discloses a carbide-containing austempered ductile iron which comprises the following components in percentage by mass: c, 3.10-3.60; 2.50-3.50% of Si; 0.4 to 1.2 parts of Mn; p is less than or equal to 0.040; s is less than or equal to 0.008; 0.02-0.04% of Mg; RE is 0.02-0.045; 0.30-1.80% of Cr; v is 0.19 to 0.60; the balance being iron. The preparation method comprises the following steps: smelting: preparing raw materials, and heating and smelting; placing VNCR-80 rare earth magnesium nodulizer in a ladle bottom groove, placing VI-370 silicon-barium alloy inoculant, and performing nodulizing inoculation to obtain molten iron; pouring molten iron into a sand mold cavity, and cooling to prepare pearlite matrix nodular cast iron containing carbide and graphite nodules; putting pearlite matrix nodular cast iron into 45% KNO heated to 250-300 DEG C3+55%NaNO3And (3) preserving the heat in the molten salt for 1.5 to 3.0 hours, and then cooling to the normal temperature to obtain the carbide-containing ausferrite-containing nodular cast iron. The nodular cast iron of the invention is austempered nodular cast iron containing carbide, which has high hardness, high strength, good toughness and good wear resistance. The Chinese patent CN105986052 also discloses a CADI nodular cast iron drill steel/pick drill steel with high wear resistance and a production method thereof, wherein 99.9 percent of pure tungsten rod 0.15-0.53 percent and ferrovanadium alloy 0.20-0.50 percent are added into nodular cast iron base molten iron according to the weight percentage of molten iron in a furnace, tungsten-vanadium alloy nodular cast iron base molten iron is smelted, the cast drill steel/pick drill steel is subjected to austenitizing treatment at 860-920 ℃ and equal treatment at 230-320 ℃ after spheroidizing treatment and inoculation treatment of the base molten iron, and cooling, cleaning, shot blasting and mechanical processing are carried out on the drill steel/pick steelAnd (4) carrying out warm quenching treatment, wherein the metallographic structure consists of an austenite body, a carbide and graphite nodules. The CADI nodular cast iron steel chisel/pickaxe chisel produced by the invention has high impact toughness and abrasion resistance, high core toughness, no fracture, high surface hardness, high abrasion resistance and long service life. The chinese invention patent CN 105838972 also discloses an austenitic nodular cast iron containing carbide, which contains the following element components by percentage: 3.0-3.7% of C, 2.7-3.2% of Si, 1.0-1.5% of Mn, 0.2-0.3% of Nb0.2-0.3% of Ni, 0.2-0.3% of V, 0.02-0.04% of Mg0.02-0.045% of RE and the balance of Fe and inevitable impurities, and the invention also discloses a preparation method of the carbide-containing austenitic ductile iron. The chinese invention patent CN 105132790 also discloses an austenitic nodular cast iron containing vanadium carbide, which comprises the following components in percentage by mass: c, 3.20-3.70; 2.50-3.30% of Si; 0.4-0.8% of Mn; p is less than or equal to 0.040; s is less than or equal to 0.007; 0.01 to 0.04 percent of Ce; 0.01 to 0.04 percent of Mg; 0.30-1.80% of Cr; v is 0.25 to 0.70; the balance being iron. The preparation method comprises the following steps: (1) heating and smelting pig iron, scrap steel, ferromanganese and ferrovanadium; (2) placing a rare earth magnesium nodulizer in the bottom groove of the ladle, and placing an inoculant on the rare earth magnesium nodulizer; pouring at 1350-1430 ℃ for 10-30 seconds, and cooling to obtain nodular cast iron; (3) and heating the cooled nodular cast iron to 850-920 ℃, preserving heat for 2-4 hours, then putting the nodular cast iron into 45% KN03+ 55% NaN03 molten salt at 280-320 ℃, preserving heat for 1-3 hours, taking out and cooling to normal temperature to obtain the vanadium-containing carbide ausferrite nodular cast iron. The vanadium-containing carbide ausferrite-containing nodular cast iron is high-toughness high-hardness carbide-containing ausferrite-containing nodular cast iron with good comprehensive mechanical properties. The Chinese patent CN 104831024 also discloses an austempering heat treatment process for austempering ductile iron grinding balls, which comprises heating pearlite matrix ductile iron grinding balls containing graphite balls and carbides to 900-950 ℃, preserving heat for 1-4 hours, and then rapidly quenching at the quenching temperatureNaNO with the mass percentage concentration of 50 percent at the temperature of 220-300 DEG C2+ 50% KNO3The grinding ball is kept in the nitrate solution for 2 to 4 hours, and then the grinding ball is taken out and cooled to room temperature in the air, and finally the ausferrite nodular cast iron grinding ball is prepared2The falling ball impact fatigue life reaches 13000 times. The Chinese invention patent CN 104831156 also discloses a microalloying treatment method for an ausferrite nodular cast iron grinding ball, which comprises converting the requirements of 0.03-0.07% of B, 0.06-0.12% of Ti and 0.03-0.2% of V set in the mass percentage of the chemical elements of the ausferrite nodular cast iron grinding ball into the mass percentage of BFe, TiFe and VFe alloy, weighing, crushing to 0.5-1.0 mm, adding the nodulizer and inoculant into a bag, and melting the fine BFe, TiFe and VFe alloy particles in the molten iron by using the heat and stirring action of the high-temperature molten iron when tapping iron to be absorbed by the molten iron to complete microalloying treatment. The microalloying treatment method for the ausferrite nodular cast iron grinding ball has the advantages that the absorptivity of B, Ti and V alloy elements is high, the graphite balls and carbides of the ausferrite nodular cast iron grinding ball are uniformly distributed and refined, and the mechanical property is improved.
However, the above methods for treating molten iron containing carbide nodular cast iron have disadvantages of high production cost due to the need to add expensive alloy elements vanadium and niobium, or low mechanical properties due to poor spheroidization effect of graphite and continuous network distribution of carbide.
Disclosure of Invention
The invention aims to change the traditional punching spheroidization method into a three-step method, namely, firstly, a proper amount of vermiculizer is put into a pit of a spheroidization bag, a silicon steel sheet is covered on the pit, after spheroidization, a ladle is transferred to a wire feeding position and is tightly pressed with a bag cover, and then a core-spun yarn containing rare earth, magnesium, antimony and barium and a core-spun yarn containing silicon, calcium and aluminum are sequentially fed in, so that graphite spheroidization and carbide refining and isolated distribution after carbide-containing nodular cast iron is solidified are realized.
The invention relates to an external treatment method of carbide-containing nodular cast iron molten iron, which can be realized by the following process steps:
① smelting nodular cast iron molten iron containing carbide in a medium frequency induction furnace or a cupola furnace, controlling the chemical composition and the mass fraction of the molten iron to be 3.34-3.75% C, 1.59-1.88% Si, 0.94-1.07% Cr, 0.45-0.64% Mn, 1.09-1.26% Cu, less than or equal to 0.06% S, less than or equal to 0.08% P and the balance Fe, discharging the molten iron into a spheroidizing bag when the temperature of the molten iron reaches 1483 and 1509 ℃, placing a vermiculizer in a pit at the bottom of the spheroidizing bag in advance, covering a silicon steel sheet on the vermiculizer, flattening the vermiculizer and the silicon steel sheet, then discharging and pre-spheroidizing, directly impacting the molten iron into the pit with the vermiculizer during iron discharge, adding the vermiculizer in an amount of 0.45-0.55% of the mass fraction of the molten iron entering the spheroidizing bag in a stoking way, removing slag from the surface after the reaction;
② transferring the spheroidizing bag and molten iron in the bag in the step ① to a wire feeding position of a wire feeding machine and tightly pressing the spheroidizing bag and the bag cover, firstly feeding 1# core-spun wires with the diameter of 4.0-5.5mm by the wire feeding machine, wherein the adding amount of the 1# core-spun wires accounts for 0.6-0.8% of the mass fraction of the molten iron in the spheroidizing bag, continuously feeding 2# core-spun wires with the diameter of 3.5-4.5mm after the 1# core-spun wires are all fed into the spheroidizing bag for 3-5 minutes, the adding amount of the 2# core-spun wires accounts for 0.6-0.7% of the mass fraction of the molten iron in the spheroidizing bag, opening the bag cover after the 2# core-spun wires are all fed into the spheroidizing bag for 6-8 minutes, removing slag, and pouring the molten iron in the spheroidizing bag into a casting mold when the temperature of the molten iron is reduced to 134.
The chemical composition and the mass fraction of the vermiculizer are 42.13 to 43.68 percent of Si,2.31 to 2.68 percent of Ca,9.48 to 10.55 percent of RE,4.24 to 4.80 percent of Mg, less than or equal to 1.20 percent of Al and the balance of Fe.
The chemical composition and the mass fraction of the silicon steel sheet are 3.14-3.39% of Si, 0.40-0.53% of Al, < 0.08% of C, < 0.15% of Mn, < 0.03% of P, < 0.01% of S, and the balance of Fe.
The chemical composition and the mass fraction of the core-spun yarn of the No. 1 are 4.21-4.56% of Mg, 0.45-0.69% of La, 0.45-0.69% of Ce, 2.68-3.23% of Sb, 39.05-39.80% of Si, 2.84-3.09% of Ba, < 0.45% of Al, < 0.45% of Ti and the balance of Fe.
The chemical composition and the mass fraction of the 2# cored wire are 58.37-58.94% of Si, 4.16-4.70% of Ca, 10.38-10.61% of Al, 1.20-1.55% of N, 1.69-1.92% of Ti and the balance of Fe.
The invention relates to an external treatment method of carbide-containing nodular cast iron molten iron, which comprises the steps of smelting the carbide-containing nodular cast iron molten iron in a medium-frequency induction furnace or a cupola furnace, and controlling the chemical composition and the mass fraction of the molten iron to be 3.34-3.75% of C, 1.59-1.88% of Si, 0.94-1.07% of Cr, 0.45-0.64% of Mn, 1.09-1.26% of Cu, less than or equal to 0.06% of S, less than or equal to 0.08% of P and the balance of Fe. Wherein 0.94-1.07% Cr is added, chromium is mainly used as a strong carbide forming element, and the chromium-containing cast iron is added to produce high-hardness (Cr, Fe) in the solidification process3C and (Cr, Fe)7C3. When the temperature of the molten iron reaches 1483-1509 ℃, the molten iron is discharged to a spheroidizing ladle. A vermiculizer is pre-placed in a pit at the bottom of the nodulizing ladle, and the chemical composition and the mass fraction of the vermiculizer are 42.13-43.68% of Si, 2.31-2.68% of Ca, 9.48-10.55% of RE, 4.24-4.80% of Mg, less than or equal to 1.20% of Al and the balance of Fe. The vermiculizer is added to mainly realize the pre-spheroidization of the molten iron, prevent the molten iron from splashing and effectively eliminate the shrinkage porosity defect of the casting. The vermiculizer is covered with a silicon steel sheet, the chemical composition and the mass fraction of the silicon steel sheet are 3.14 to 3.39 percent of Si,0.40 to 0.53 percent of Al,<0.08%C,<0.15%Mn,<0.03%P,<0.01% S, balance Fe. The silicon steel sheet covered on the vermiculizer can ensure the mild pre-spheroidization reaction, and also has the functions of thinning graphite nodules and eliminating graphite floating. The vermiculizer and the silicon steel sheet are flattened and tamped, and then tapping and pre-spheroidizing are carried out. Molten iron is not directly impacted into the pits added with the vermiculizer during tapping, so that the molten iron is prevented from splashing. The adding amount of the vermiculizer accounts for 0.45-0.55 percent of the mass fraction of the molten iron entering the spheroidizing bag, and the adding amount of the silicon steel sheet accounts for 1.9-2.0 percent of the mass fraction of the molten iron entering the spheroidizing bag; after the pre-spheroidizing reaction is finished, the slag on the surface of the molten iron needs to be cleaned, so that the subsequent molten iron treatment effect is ensured.
After the molten iron is subjected to pre-spheroidizing treatment, the spheroidizing bag and the molten iron in the bag are transferred to a wire feeding position of a wire feeding machine and are tightly pressed with a bag cover, and a 1# core-spun wire with the diameter of 4.0-5.5mm is fed by the wire feeding machine, wherein the chemical composition and the mass fraction of the 1# core-spun wire are 4.21-4.56% of Mg, 0.45-0.69% of La, 0.45-0.69% of Ce, 2.68-3.23% of Sb, 39.05-39.80% of Si, 2.84-3.09% of Ba, less than 0.45% of Al, less than 0.45% of Ti and the balance of Fe. The adding amount of the No. 1 cored wire accounts for 0.6-0.8 percent of the mass fraction of the molten iron in the spheroidizing bag. The addition of the No. 1 core-spun yarn can ensure that the molten iron realizes good spheroidization, and the spheroidization does not fade. After the 1# core-spun yarn is completely fed into the balling ladle for 3-5 minutes, the 2# core-spun yarn with the diameter of 3.5-4.5mm is continuously fed, and the chemical composition and the mass fraction of the 2# core-spun yarn are 58.37-58.94% of Si, 4.16-4.70% of Ca, 10.38-10.61% of Al, 1.20-1.55% of N, 1.69-1.92% of Ti and the balance of Fe. The 2# core-spun yarn is added, so that graphite and carbide can be refined, and the carbide is promoted to be in broken net and isolated distribution. The adding amount of the No. 2 cored wire accounts for 0.6 to 0.7 percent of the mass fraction of the molten iron in the spheroidizing bag; and after the 2# core-spun yarn is completely fed into the spheroidizing ladle for 6-8 minutes, opening a ladle cover, slagging off, and pouring molten iron into the casting mold when the temperature of the molten iron is reduced to 1342-.
Compared with the prior art, the invention has the following characteristics:
1) the molten iron is treated by the method, splashing does not occur in the molten iron spheroidizing process, and the safety is high;
2) the method for treating the molten iron has the advantages that the slag raking amount is reduced by more than 40 percent compared with that of the molten iron treated by the common flushing spheroidizing method, so that the environment is effectively protected;
3) after the molten iron is treated by the method and solidified, the spheroidization rate of graphite is high, the graphite nodules are small in size and uniform in distribution, and carbides are distributed in a broken net and in an isolated distribution.
Drawings
FIG. 1 is a graph showing the distribution of graphite nodules in molten iron after solidification according to example 1 of the present invention;
FIG. 2 microstructure of example 1 of the present invention after solidification of molten iron.
Detailed Description
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.
Example 1:
the method for treating molten iron containing carbide nodular cast iron outside the furnace can be realized by the following process steps:
① smelting nodular cast iron molten iron containing carbide in a 1500 kg medium frequency induction furnace, controlling the chemical composition and mass fraction of the molten iron to be 3.75% C, 1.59% Si, 1.07% Cr, 0.45% Mn, 1.26% Cu, 0.036% S, 0.057% P and the balance Fe, discharging the molten iron to a spheroidizing bag when the temperature of the molten iron reaches 1509 ℃, placing a vermiculizer in advance in a pit at the bottom of the spheroidizing bag, wherein the chemical composition and mass fraction of the vermiculizer are 42.13% Si, 2.68% Ca, 9.48% RE, 4.80% Mg, 1.03% Al and the balance Fe, covering a silicon steel sheet on the vermiculizer, the chemical composition and mass fraction of the silicon steel sheet are 3.14% Si, 0.53% Al, 0.05% C, 0.11% Mn, 0.019% P, 0.008% S and the balance Fe, flattening the silicon steel sheet, adding the vermiculizer into the molten iron ladle, directly adding the vermiculizer into the molten iron ladle after the molten iron temperature reaches 1509 ℃ and the molten iron temperature, removing the molten iron by mass fraction, and adding the vermiculizer, wherein the molten iron surface of the molten iron is completely, and the molten iron is added with the molten iron;
②, transferring the ① nodulizing ladle and molten iron in the ladle to a wire feeding position of a wire feeding machine and pressing the nodulizing ladle and the ladle cover, firstly feeding 1# core-spun wire with the diameter of 5.5mm by the wire feeding machine, wherein the chemical composition and the mass fraction of the 1# core-spun wire are 4.56% of Mg, 0.45% of La, 0.69% of Ce, 2.68% of Sb, 39.80% of Si, 2.84% of Ba, 0.25% of Al, 0.33% of Ti and the balance of Fe, the addition amount of the 1# core-spun wire is 0.8% of the mass fraction of the molten iron in the nodulizing ladle, after the 1# core-spun wire is completely fed into the nodulizing ladle for 5 minutes, continuously feeding 2# core-spun wire with the diameter of 3.5mm, the chemical composition and the mass fraction of the 2# core-spun wire are 58.94% of Si, 4.16% of Ca, 10.61% of Al, 1.20% of N, 1.92% of Ti and the balance of Fe, the addition amount of the 2# core-spun wire is 0.7% of the mass fraction of the molten iron in the nodulizing ladle, opening the casting mould, uniformly distributing the graphite carbide, and uniformly casting the nodulizing ladle when the molten iron is broken graphite is obtained, and the casting mould has the advantages of casting mould.
Example 2:
the method for treating molten iron containing carbide nodular cast iron outside the furnace can be realized by the following process steps:
① smelting nodular cast iron molten iron containing carbide in a cupola furnace of 2 tons, controlling the chemical composition and mass fraction of the molten iron to 3.34% C, 1.88% Si, 0.94% Cr, 0.64% Mn, 1.09% Cu, 0.028% S, 0.051% P and the balance Fe, tapping the molten iron into a spheroidizing bag when the temperature of the molten iron reaches 1483 ℃, placing a vermiculizer in advance in a pit at the bottom of the spheroidizing bag, wherein the chemical composition and mass fraction of the vermiculizer are 43.68% Si, 2.31% Ca, 10.55% RE, 4.24% Mg, 0.86% Al and the balance Fe, covering a silicon steel sheet on the vermiculizer, the chemical composition and mass fraction of the silicon steel sheet are 3.39% Si, 0.40% Al, 0.07% C, 0.12% Mn, 0.021% P, 0.006% S and the balance Fe, leveling the silicon steel sheet, then tapping the vermiculizer and adding the vermiculizer into the molten iron ladle to complete the spheroidizing reaction, wherein the molten iron directly enters the spheroidizing bag and the molten iron is added into the spheroidizing bag after the molten iron reaches 1483.3.3, the weight fraction of the molten iron;
②, transferring the spheroidizing ladle and molten iron in the ladle in the step ① to a wire feeding position of a wire feeding machine and pressing the spheroidizing ladle and the ladle cover, firstly feeding a 4.0mm diameter 1# core-spun wire by the wire feeding machine, wherein the chemical composition and the mass fraction of the 1# core-spun wire are 4.21% Mg, 0.69% La, 0.45% Ce, 3.23% Sb, 39.05% Si, 3.09% Ba, 0.37% Al, 0.29% Ti and the balance Fe, the addition amount of the 1# core-spun wire is 0.6% of the mass fraction of the molten iron in the spheroidizing ladle, after the 1# core-spun wire is completely fed into the spheroidizing ladle for 3 minutes, continuously feeding a 4.5mm diameter 2# core-spun wire, the chemical composition and the mass fraction of the 2# core-spun wire are 58.37% Si, 4.70% Ca, 10.38% Al, 1.55% N, 1.69% Ti and the balance Fe, after the addition amount of the 2# core-spun wire is 0.6% of the mass fraction of the molten iron in the spheroidizing ladle, opening the spheroidizing ladle, uniformly casting the graphite ladle, and uniformly casting the spheroidizing ladle to obtain an isolated graphite cast iron with the advantages of small carbide, and reducing the size and the size of the graphite cast iron.
Example 3:
the method for treating molten iron containing carbide nodular cast iron outside the furnace can be realized by the following process steps:
① smelting nodular cast iron molten iron containing carbide in a 1000 kg medium frequency induction furnace, controlling the chemical composition and mass fraction of the molten iron to be 3.51% C, 1.74% Si, 0.98% Cr, 0.53% Mn, 1.21% Cu, 0.042% S, 0.049% P and the balance Fe, discharging the molten iron to a spheroidizing bag when the temperature of the molten iron reaches 1496 ℃, placing a vermiculizer in advance in a pit at the bottom of the spheroidizing bag, wherein the vermiculizer has the chemical composition and mass fraction of 42.60% Si, 2.57% Ca, 9.92% RE, 4.57% Mg, 0.85% Al and the balance Fe, covering a silicon steel sheet on the vermiculizer, the chemical composition and mass fraction of the silicon steel sheet are 3.28% Si, 0.49% Al, 0.05% C, 0.12% Mn, 0.018% P, 0.005% S and the balance Fe, flattening the silicon steel sheet, and then discharging the vermiculizer and adding the vermiculizer into the molten iron ladle to perform an impact reaction, wherein the molten iron is added into the molten iron and the molten iron is added into the spheroidizing bag directly after the molten iron reaches the molten iron and the molten iron is heated molten iron;
②, transferring the spheroidizing ladle and molten iron in the ladle in the step ① to a wire feeding position of a wire feeding machine and pressing the spheroidizing ladle and the ladle cover, firstly feeding a 1# core-spun wire with the diameter of 4.5mm by the wire feeding machine, wherein the chemical composition and the mass fraction of the 1# core-spun wire are 4.49% of Mg, 0.52% of La, 0.48% of Ce, 2.90% of Sb, 39.74% of Si, 2.93% of Ba, 0.18% of Al, 0.12% of Ti and the balance of Fe, the addition amount of the 1# core-spun wire is 0.7% of the mass fraction of the molten iron in the spheroidizing ladle, after the 1# core-spun wire is completely fed into the spheroidizing ladle for 4 minutes, the 2# core-spun wire with the diameter of 4mm is continuously fed, the chemical composition and the mass fraction of the 2# core-spun wire are 58.61% of Si, 4.57% of Ca, 10.44% of Al, 1.39% of N, 1.82% of Ti and the balance of Fe, after the addition amount of the 2# core-spun wire is completely fed into the spheroidizing ladle, the molten iron is uniformly distributed, and the spheroidizing ladle is uniformly distributed when the molten iron is broken graphite is poured into the spheroidizing ladle, the graphite is uniformly distributed, and the graphite.
By adopting the method for treating the carbide-containing nodular cast iron molten iron outside the furnace, splashing does not occur in the molten iron spheroidizing process, and the safety is very high; the invention treats the molten iron outside the furnace, the slag removing amount is reduced by more than 40 percent compared with the molten iron treated by the common flushing spheroidization method, after the treated molten iron is solidified, the spheroidization rate of graphite is high, the sizes of graphite spheres and carbides are fine, the graphite spheres and the carbides are uniformly distributed, the carbides are in broken net and isolated distribution, the strength and the toughness of the nodular cast iron containing the carbides can be obviously improved, and the invention has good economic and social benefits when being popularized and applied.

Claims (1)

1. The method for treating the molten iron containing carbide ductile cast iron outside the furnace is characterized by comprising the following steps of:
① smelting nodular cast iron molten iron containing carbide in a medium frequency induction furnace or a cupola furnace, controlling the chemical composition and the mass fraction of the molten iron to be 3.34-3.75% C, 1.59-1.88% Si, 0.94-1.07% Cr, 0.45-0.64% Mn, 1.09-1.26% Cu, less than or equal to 0.06% S, less than or equal to 0.08% P and the balance Fe, discharging the molten iron into a spheroidizing bag when the temperature of the molten iron reaches 1483 and 1509 ℃, placing a vermiculizer in a pit at the bottom of the spheroidizing bag in advance, covering a silicon steel sheet on the vermiculizer, flattening the vermiculizer and the silicon steel sheet, then discharging and pre-spheroidizing, directly impacting the molten iron into the pit with the vermiculizer during iron discharge, adding the vermiculizer in an amount of 0.45-0.55% of the mass fraction of the molten iron entering the spheroidizing bag in a stoking way, removing slag from the surface after the reaction;
②, transferring the spheroidizing bag and molten iron in the bag in the step ① to a wire feeding position of a wire feeding machine and tightly pressing the spheroidizing bag and the bag cover, firstly feeding 1# core-spun wires with the diameter of 4.0-5.5mm by the wire feeding machine, wherein the adding amount of the 1# core-spun wires accounts for 0.6-0.8% of the mass fraction of the molten iron in the spheroidizing bag, continuously feeding 2# core-spun wires with the diameter of 3.5-4.5mm after the 1# core-spun wires are all fed into the spheroidizing bag for 3-5 minutes, the adding amount of the 2# core-spun wires accounts for 0.6-0.7% of the mass fraction of the molten iron in the spheroidizing bag, opening the bag cover after the 2# core-spun wires are all fed into the spheroidizing bag for 6-8 minutes, removing slag, and pouring the molten iron in the spheroidizing bag into a casting mold when the temperature of the molten iron is reduced to;
the chemical composition and the mass fraction of the vermiculizer are 42.13-43.68% of Si, 2.31-2.68% of Ca, 9.48-10.55% of RE, 4.24-4.80% of Mg, less than or equal to 1.20% of Al and the balance of Fe;
the chemical composition and the mass fraction of the silicon steel sheet are 3.14-3.39% of Si, 0.40-0.53% of Al, less than 0.08% of C, less than 0.15% of Mn, less than 0.03% of P, less than 0.01% of S and the balance of Fe;
the chemical composition and the mass fraction of the No. 1 cored wire are 4.21-4.56% of Mg, 0.45-0.69% of La, 0.45-0.69% of Ce, 2.68-3.23% of Sb, 39.05-39.80% of Si, 2.84-3.09% of Ba, < 0.45% of Al, < 0.45% of Ti and the balance of Fe;
the chemical composition and the mass fraction of the 2# cored wire are 58.37-58.94% of Si, 4.16-4.70% of Ca, 10.38-10.61% of Al, 1.20-1.55% of N, 1.69-1.92% of Ti and the balance of Fe.
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