CN107988545B - Method for preparing nodular cast iron casting by recycling scrap steel - Google Patents

Method for preparing nodular cast iron casting by recycling scrap steel Download PDF

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CN107988545B
CN107988545B CN201711103870.1A CN201711103870A CN107988545B CN 107988545 B CN107988545 B CN 107988545B CN 201711103870 A CN201711103870 A CN 201711103870A CN 107988545 B CN107988545 B CN 107988545B
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casting
steel
scrap steel
silicon oxide
inoculant
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CN107988545A (en
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孙荣乾
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Jiangsu Heng Yue Machinery Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/08—Making cast-iron alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C1/00—Refining of pig-iron; Cast iron
    • C21C1/10—Making spheroidal graphite cast-iron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C37/00—Cast-iron alloys
    • C22C37/04—Cast-iron alloys containing spheroidal graphite
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/36—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases using ionised gases, e.g. ionitriding
    • C23C8/38—Treatment of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/80—After-treatment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

Abstract

The invention discloses a method for preparing a nodular cast iron casting by recycling scrap steel, which comprises the following steps: cleaning scrap steel; shot blasting and removing chips peeled from the surface of the scrap steel; cutting up waste steel materials, and stirring and soaking the waste steel materials by adopting a sodium hydroxide aqueous solution; putting the mixture into a steelmaking furnace, melting the mixture at high temperature, and adding aluminum oxide and silicon oxide for soaking treatment; mixing the raw materials with pig iron to make steel, and casting a casting; and (4) performing post-treatment on the casting, detecting flaws and sorting qualified parts. The scheme of the invention provides a treatment process with high standardization degree aiming at the recycling of various waste steels, the waste steels are applied to the preparation of single-cylinder crankshaft castings, the mechanical properties are better, the input amount of the treated waste steels is increased in the casting process, a proper amount of carburant and alloy materials are added, and the processing is carried out by adopting a proper technology, so that the accuracy of the alloy distribution ratio of the materials is ensured, the comprehensive mechanical properties of the crankshaft, such as strength, elongation, wear resistance, fatigue resistance and the like, are improved, the service life of the crankshaft is prolonged, and the shaft breakage rate in the normal use process is reduced.

Description

Method for preparing nodular cast iron casting by recycling scrap steel
Technical Field
The invention belongs to the technical field of metallurgical casting, and particularly relates to a method for preparing a nodular cast iron casting material by recycling scrap steel.
Background
The nodular cast iron material is spheroidal graphite obtained by spheroidization and inoculation, and the material can effectively improve the mechanical property of cast iron, so the nodular cast iron material is widely applied, particularly in the field of mechanical manufacturing. In the prior art, pure pig iron is mainly used as a raw material to prepare the nodular cast iron-carbon alloy material, so that the product cost is high. The scrap steel is an iron-carbon alloy material which is utilized once or for many times, is a renewable resource with high value, theoretically, the scrap steel can be completely applied to nodular cast iron materials, however, the utilization rate of the scrap steel is low due to the limited prior art, a large amount of scrap steel is idle and wasted every year, the scrap steel is not well utilized, and the resource is greatly wasted. The main reason for the limited reuse of the scrap steel is that a large amount of harmful elements remain in the scrap steel material after the processes of spraying, plating, compounding and the like, and the remaining harmful elements can cause the problems of rigid hot brittleness increase, steel ductility reduction, interface deviation and the like; in addition, in the existing process for preparing the nodular cast iron by mixing the scrap steel and the pig iron, the difference between the components of the scrap steel and the components of the pig iron is large, the setting of process conditions is difficult, and the instability of product quality is easily caused because uniform process conditions cannot be adopted for the scrap steel from different sources due to the difference of the components, so that a process for preparing the nodular cast iron material by recycling the scrap steel with uniform standards needs to be researched.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a nodular cast iron material which has high standardization degree, fully utilizes various waste steels to prepare the nodular cast iron material with good mechanical property and excellent extensibility, and the nodular cast iron material prepared by the process can be applied to the manufacturing of single-cylinder crankshafts in mechanical equipment, and the product quality is not inferior to or even higher than that of the nodular cast iron material prepared by pure pig iron.
The technical scheme is as follows: the method for preparing the nodular cast iron casting by recycling the scrap steel comprises the following steps:
(1) primarily cleaning the scrap steel by using a high-pressure water gun to remove surface stains; draining, soaking in a mixed pickling agent, wherein the mixed pickling agent comprises 0.1-0.5 mol/L hydrochloric acid and 0.2-0.6 mol/L ethanol, soaking for 10-20 min, taking out, cleaning by using a high-pressure water gun again, and draining;
(2) heating the cleaned scrap steel to 500-650 ℃, carrying out shot blasting for 2-4 min, then heating to 700-750 ℃ at the speed of 2-5 ℃/min, and carrying out shot blasting for 1-3 min; removing chips peeled from the surface of the scrap steel;
(3) cutting up the waste steel material, and adopting the waste steel material with the concentration of 0.1-0.2 g/Kg2Stirring and soaking the O in a sodium hydroxide aqueous solution for 1-3 hours, and then centrifuging to obtain a treated steel product;
(4) throwing the broken steel into a steelmaking furnace, heating to 1600-1700 ℃ at the speed of 5-20 ℃/min under the condition of nitrogen blowing, stirring by adopting a stirring rod made of a high-temperature-resistant material for 1-3 h, and then adding a proper amount of alumina and silicon oxide, wherein the adding proportion of the alumina to the silicon oxide is 2-4: 1, transferring molten steel after treating for 0.5-3 h, and filtering residues; cooling the molten steel to 750-805 ℃ at the speed of 5-10 ℃/min, and then cooling to room temperature;
(5) feeding raw materials into a high-temperature furnace, wherein 48 wt% of the raw iron material and 52 wt% of the reclaimed material obtained in the step (4) are added; adding a proper amount of mixed carburant and a proper amount of copper, tin, magnesium and silicon, carrying out heat smelting in a digital high-temperature furnace, adjusting the addition amount of each component according to the alloy components detected by the digital high-temperature furnace, wherein when the iron content of each alloy is 78-82%, the carbon content is 5.3-5.6%, the rare earth content is 4.3-4.6%, the copper content is 0.1-0.2%, the tin content is 0.01-0.012%, the magnesium content is 7.4-7.7% and the impurity content of other alloys is 1.8-2.1%, adding a first inoculant into molten iron for treatment for 2-5 min, then carrying out casting, pouring 35% of the cast molten iron, and adding a second inoculant in batches until the casting is finished; after casting, firstly cooling to 750-875 ℃ at the speed of 5-10 ℃/min, then completely cooling to room temperature, and taking out the cast part;
(6) heating the casting to 780-810 ℃, preserving heat for 30-38 min, and quenching after performing plasma carbonitriding in the heat preservation process;
(7) heating the casting to 550-600 ℃, performing shot blasting for 1-2 min, then heating again to 780-810 ℃, preserving heat for 30-38 min, and performing quenching treatment after performing plasma carbonitriding in the heat preservation process;
(8) and carrying out flaw detection treatment after fine machining on the cast parts, and sorting qualified parts.
Further, in order to enable low-melting-point impurity metals in the scrap steel to better infiltrate into the high-temperature-resistant material and be brought out by the high-temperature-resistant material, the silicon oxide treated by hydrofluoric acid in the step (4) is prepared by the following specific treatment method: placing silicon oxide in a closed treatment bin with a vibration function to enable the silicon oxide to be in a vibrated state, spraying hydrofluoric acid to the silicon oxide to enable the surface of the silicon oxide to be corroded to form a rough interface, and then alternately washing the treated silicon oxide by hot and cold clean water to remove the hydrofluoric acid on the surface.
Further, in order to improve the spheroidizing effect, the mixed carburant in the step (5) comprises the following components:
65-85% of artificial graphite;
15-35% of calcined acicular petroleum coke;
in parts by weight.
Further, the first inoculant in the step (5) is ZFCCM inoculant; the second inoculant is CAINO-SUPER inoculant.
Further, in the step (5), the adding mass ratio of the first inoculant to the second inoculant is 5-10: 1.
further, the casting process in the step (5) is controlled within 5-8 min.
Further, in order to ensure good comprehensive performance of the casting, other alloy impurities in the step (5) comprise metal nickel, chromium, molybdenum and manganese, and the total weight of nickel and chromium is less than or equal to 0.2% and less than or equal to 0.2% compared with the total weight of molten iron.
Has the advantages that: (1) the scheme of the invention provides a treatment process with high standardization degree aiming at the reuse of various types of steel scraps, and the steel scraps are treated uniformly to ensure the quality consistency before the steel scraps are reused, so that the problems of large hot brittleness, low ductility and the like caused by the residue of harmful substances in the steel scraps are avoided; on the other hand, the problem of unstable product quality in the later period caused by large component difference when the scrap steel is reused is solved; (2) the invention provides a method for reusing waste steel for castings for mechanical equipment, in particular to the manufacture of single-cylinder crankshaft castings in the mechanical equipment, and particularly provides process conditions for preparing the castings by utilizing the waste steel, the crankshaft castings prepared by the process have the performance which is not inferior to or even higher than that of crankshaft castings prepared by raw materials of pig iron, and the product quality is improved while the input of production material cost is reduced.
Detailed Description
The technical solution of the present invention is described in detail by the following examples, but the scope of the present invention is not limited to the examples.
Example 1: a method for preparing a nodular cast iron single-cylinder crankshaft casting by recycling scrap steel comprises the following steps:
(1) primarily cleaning the scrap steel by using a high-pressure water gun to remove surface stains; draining, soaking in a mixed pickling agent, wherein the mixed pickling agent comprises 0.4mol/L hydrochloric acid and 0.35mol/L ethanol, soaking for 15min, taking out, cleaning with a high-pressure water gun again, and draining;
(2) heating the cleaned scrap steel to 630 ℃, carrying out shot blasting for 3min, then heating to 720 ℃ at the speed of 4 ℃/min, and carrying out shot blasting for 2 min; removing chips peeled from the surface of the scrap steel;
(3) cutting waste steel material into pieces with the concentration of 0.15g/Kg2Stirring and soaking the O sodium hydroxide aqueous solution for 2 hours, and then centrifuging to obtain the processed steel;
(4) putting the crushed steel into a steelmaking furnace, heating to 1650 ℃ at the speed of 15 ℃/min under the condition of nitrogen blowing, stirring by adopting a stirring rod made of high-temperature resistant material for 2.5h, and then adding a proper amount of alumina and silicon oxide, wherein the adding proportion of the alumina to the silicon oxide is 3: 1, transferring molten steel after treating for 1.5, and filtering residues; cooling the molten steel to 780 ℃ at the speed of 8 ℃/min, and then cooling to room temperature; the silicon oxide is silicon oxide treated by hydrofluoric acid, and the specific treatment method comprises the following steps: placing silicon oxide in a closed treatment bin with a vibration function to enable the silicon oxide to be in a vibrated state, spraying hydrofluoric acid to the silicon oxide to enable the surface of the silicon oxide to be corroded to form a rough interface, and then alternately washing the treated silicon oxide by hot and cold clean water to remove the hydrofluoric acid on the surface;
(5) feeding raw materials into a high-temperature furnace, wherein 48 wt% of the raw iron material and 52 wt% of the reclaimed material obtained in the step (4) are added; adding a proper amount of mixed recarburizer and a proper amount of copper, tin, magnesium and silicon, carrying out heat smelting in a digital high-temperature furnace, and adjusting the addition amount of each component according to alloy components detected by the digital high-temperature furnace, wherein when the iron content of each alloy is 80%, the carbon content is 5.6%, the rare earth content is 4.6%, the copper content is 0.2%, the tin content is 0.012%, the magnesium content is 7.5%, and the content of other alloy impurities is 2.088%, the other alloy impurities comprise metallic nickel, chromium, molybdenum and manganese, and the total weight of nickel and chromium is less than or equal to 0.2% and less than or equal to 0.2% compared with the total weight of molten iron; adding a first inoculant into molten iron, treating for 3min, casting, adding a second inoculant in batches when pouring out 35% of the molten iron until casting is finished, and controlling the casting process within 6 min; after the casting is finished, cooling to 850 ℃ at the speed of 8 ℃/min, then completely cooling to room temperature, and taking out the cast part;
the mixed carburant comprises the following components:
78% of artificial graphite;
22% of needle petroleum coke after calcination;
counting by weight parts;
the first inoculant is ZFCCM inoculant; the second inoculant is CAINO-SUPER inoculant; the adding mass ratio of the first inoculant to the second inoculant is 6: 1;
(6) heating the casting to 800 ℃, preserving heat for 35min, and carrying out quenching treatment after carrying out plasma carbonitriding in the heat preservation process;
(7) heating the casting to 570 ℃, carrying out shot blasting for 2min, then heating to 800 ℃ again, carrying out heat preservation for 35min, carrying out plasma carbonitriding in the heat preservation process, and then carrying out quenching treatment;
(8) and carrying out flaw detection treatment after fine machining on the casting, and sorting qualified single-cylinder crankshaft castings.
Example 2: a method for preparing a nodular cast iron single-cylinder crankshaft casting by recycling scrap steel comprises the following steps:
(1) primarily cleaning the scrap steel by using a high-pressure water gun to remove surface stains; draining, soaking in a mixed pickling agent comprising 0.1mol/L hydrochloric acid and 0.2mol/L ethanol for 10min, taking out, cleaning with a high-pressure water gun, and draining;
(2) heating the cleaned scrap steel to 500 ℃, carrying out shot blasting for 2min, then heating to 700 ℃ at the speed of 2 ℃/min, and carrying out shot blasting for 1 min; removing chips peeled from the surface of the scrap steel;
(3) cutting waste steel material into pieces with the concentration of 0.1g/Kg2Stirring and soaking the O sodium hydroxide aqueous solution for 1h, and then centrifuging to obtain the processed steel;
(4) putting the crushed steel into a steelmaking furnace, heating to 1600 ℃ at the speed of 5 ℃/min under the condition of nitrogen blowing, stirring by adopting a stirring rod made of high-temperature-resistant materials for 1h, and then adding a proper amount of alumina and silicon oxide, wherein the adding proportion of the alumina to the silicon oxide is 2: 1, transferring molten steel after treating for 0.5h, and filtering residues; cooling the molten steel to 750 ℃ at the speed of 5 ℃/min, and then cooling to room temperature; the silicon oxide is silicon oxide treated by hydrofluoric acid, and the specific treatment method comprises the following steps: placing silicon oxide in a closed treatment bin with a vibration function to enable the silicon oxide to be in a vibrated state, spraying hydrofluoric acid to the silicon oxide to enable the surface of the silicon oxide to be corroded to form a rough interface, and then alternately washing the treated silicon oxide by hot and cold clean water to remove the hydrofluoric acid on the surface;
(5) feeding raw materials into a high-temperature furnace, wherein 30 wt% of raw iron materials and 70 wt% of reclaimed materials obtained in the step (4) are added; adding a proper amount of mixed recarburizer and a proper amount of copper, tin, magnesium and silicon, carrying out heat smelting in a digital high-temperature furnace, and adjusting the addition amount of each component according to the alloy components detected by the digital high-temperature furnace, wherein when the iron content in each alloy is 81.09%, the carbon content is 5.3%, the rare earth content is 4.3%, the copper content is 0.1%, the tin content is 0.01%, the magnesium content is 7.4%, and the impurity content of other alloys is 1.8%, the impurities of other alloys comprise metallic nickel, chromium, molybdenum and manganese, and the total weight of nickel is less than or equal to 0.2% and the total weight of chromium is less than or equal to 0.2%; adding a first inoculant into molten iron, treating for 2min, casting, adding a second inoculant in batches when pouring out 35% of the molten iron until casting is finished, and controlling the casting process within 5 min; after the casting is finished, cooling to 750 ℃ at the speed of 5 ℃/min, then completely cooling to room temperature, and taking out the cast part;
the mixed carburant comprises the following components:
65% of artificial graphite;
35% of needle petroleum coke after calcination;
counting by weight parts;
the first inoculant is ZFCCM inoculant; the second inoculant is CAINO-SUPER inoculant; the adding mass ratio of the first inoculant to the second inoculant is 5: 1;
(6) heating the casting to 780 ℃, preserving heat for 30min, and carrying out quenching treatment after carrying out plasma carbonitriding in the heat preservation process;
(7) heating the casting to 550 ℃, carrying out shot blasting for 1min, then heating to 780 ℃ again, carrying out heat preservation for 30min, carrying out plasma carbonitriding in the heat preservation process, and then carrying out quenching treatment;
(8) and carrying out flaw detection treatment after fine machining on the cast parts, and sorting qualified parts.
Example 3: a method for preparing a nodular cast iron single-cylinder crankshaft casting by recycling scrap steel comprises the following steps:
(1) primarily cleaning the scrap steel by using a high-pressure water gun to remove surface stains; draining, soaking in a mixed pickling agent, wherein the mixed pickling agent comprises 0.5mol/L hydrochloric acid and 0.6mol/L ethanol, soaking for 20min, taking out, cleaning with a high-pressure water gun, and draining;
(2) heating the cleaned scrap steel to 650 ℃, carrying out shot blasting for 4min, then heating to 750 ℃ at the speed of 5 ℃/min, and carrying out shot blasting for 3 min; removing chips peeled from the surface of the scrap steel;
(3) cutting waste steel material into pieces with the concentration of 0.2g/Kg2Stirring and soaking the O sodium hydroxide aqueous solution for 3 hours, and then centrifuging to obtain the processed steel;
(4) putting the crushed steel into a steelmaking furnace, heating to 1700 ℃ at the speed of 20 ℃/min under the condition of nitrogen blowing, stirring by adopting a stirring rod made of high-temperature-resistant materials for 3 hours, and then adding a proper amount of alumina and silicon oxide, wherein the adding proportion of the alumina to the silicon oxide is 4: 1, transferring molten steel after treating for 3 hours, and filtering residues; cooling the molten steel to 805 ℃ at the speed of 10 ℃/min, and then cooling to room temperature; the silicon oxide is silicon oxide treated by hydrofluoric acid, and the specific treatment method comprises the following steps: placing silicon oxide in a closed treatment bin with a vibration function to enable the silicon oxide to be in a vibrated state, spraying hydrofluoric acid to the silicon oxide to enable the surface of the silicon oxide to be corroded to form a rough interface, and then alternately washing the treated silicon oxide by hot and cold clean water to remove the hydrofluoric acid on the surface;
(5) feeding raw materials into a high-temperature furnace, wherein 50 wt% of raw iron materials and 70 wt% of reclaimed materials obtained in the step (4) are added; adding a proper amount of mixed recarburizer and a proper amount of copper, tin, magnesium and silicon, carrying out heat smelting in a digital high-temperature furnace, and adjusting the addition amount of each component according to the alloy components detected by the digital high-temperature furnace, wherein when the iron content in each alloy is 80.388%, the carbon content is 5.6%, the rare earth content is 4.6%, the copper content is 0.2%, the tin content is 0.012%, the magnesium content is 7.4%, and the impurity content of other alloys is 1.8%, the impurities of other alloys comprise metallic nickel, chromium, molybdenum and manganese, and the total weight of nickel is less than or equal to 0.2% and the total weight of chromium is less than or equal to 0.2%; adding a first inoculant into molten iron, treating for 5min, casting, adding a second inoculant in batches when pouring out 35% of the molten iron until casting is finished, and controlling the casting process within 8 min; after the casting is finished, cooling to 875 ℃ at the speed of 10 ℃/min, then completely cooling to room temperature, and taking out the cast part;
the mixed carburant comprises the following components:
85% of artificial graphite;
15% of needle petroleum coke after calcination;
counting by weight parts;
the first inoculant is ZFCCM inoculant; the second inoculant is CAINO-SUPER inoculant; the adding mass ratio of the first inoculant to the second inoculant is 10: 1;
(6) heating the casting to 810 ℃, preserving heat for 38min, and carrying out quenching treatment after carrying out plasma carbonitriding in the heat preservation process;
(7) heating the casting to 600 ℃, carrying out shot blasting for 2min, then heating to 810 ℃ again, carrying out heat preservation for 38min, carrying out plasma carbonitriding in the heat preservation process, and then carrying out quenching treatment;
(8) and carrying out flaw detection treatment after fine machining on the casting, and sorting qualified single-cylinder crankshaft castings.
In the above embodiments 1 to 3, the waste steel is applied to the preparation of the single-cylinder crankshaft casting for the mechanical equipment, and all the waste steel has good mechanical properties, the input amount of the treated waste steel is increased in the casting process, the carburant and the alloy material are added in a proper amount, and the processing is performed by adopting a proper technology, so that the accuracy of the alloy distribution ratio of the material is ensured, the comprehensive mechanical properties such as the strength, the elongation, the wear resistance and the fatigue resistance of the crankshaft are improved, the service life of the crankshaft is prolonged, and the shaft breakage rate in the normal use process is reduced, table 1 shows the comparison result of the mechanical property data of the single-cylinder crankshaft casting (hereinafter referred to as the current casting) which is prepared by using pure pig iron as a raw material and adopting the existing process and the single-cylinder crankshaft castings prepared in the embodiments 1 to 3 of the present invention, and the data in table 1 shows that the crankshaft casting manufactured.
TABLE 1 comparison of mechanical property data of single-cylinder crankshaft castings manufactured by using pure pig iron as a raw material and adopting the conventional process with those of single-cylinder crankshaft castings prepared in examples 1 to 3 of the present invention
Product(s) Strength (MPa) Elongation (%)
Cast-in-place part 830 4.0
Example 1 875 4.6
Example 2 900 4.4
Example 3 840 3.8
As noted above, while the present invention has been shown and described with reference to certain preferred embodiments, it is not to be construed as limited thereto. Various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (7)

1. A method for preparing a nodular cast iron casting by recycling scrap steel is characterized by comprising the following steps:
(1) primarily cleaning the scrap steel by using a high-pressure water gun to remove surface stains; draining, soaking in a mixed pickling agent, wherein the mixed pickling agent comprises 0.1-0.5 mol/L hydrochloric acid and 0.2-0.6 mol/L ethanol, soaking for 10-20 min, taking out, cleaning by using a high-pressure water gun again, and draining;
(2) heating the cleaned scrap steel to 500-650 ℃, carrying out shot blasting for 2-4 min, then heating to 700-750 ℃ at the speed of 2-5 ℃/min, and carrying out shot blasting for 1-3 min; removing chips peeled from the surface of the scrap steel;
(3) cutting up the waste steel material, and adopting the waste steel material with the concentration of 0.1-0.2 g/Kg2Stirring and soaking the O in a sodium hydroxide aqueous solution for 1-3 hours, and then centrifuging to obtain a treated steel product;
(4) throwing the broken steel into a steelmaking furnace, heating to 1600-1700 ℃ at the speed of 5-20 ℃/min under the condition of nitrogen blowing, stirring by adopting a stirring rod made of a high-temperature-resistant material for 1-3 h, and then adding a proper amount of alumina and silicon oxide, wherein the adding proportion of the alumina to the silicon oxide is 2-4: 1, transferring molten steel after treating for 0.5-3 h, and filtering residues; cooling the molten steel to 750-805 ℃ at the speed of 5-10 ℃/min, and then cooling to room temperature;
(5) feeding raw materials into a high-temperature furnace, wherein 48 wt% of the raw iron material and 52 wt% of the reclaimed material obtained in the step (4) are added; adding a proper amount of mixed carburant and a proper amount of copper, tin, magnesium and silicon, carrying out heat smelting in a digital high-temperature furnace, adjusting the addition amount of each component according to the alloy components detected by the digital high-temperature furnace, wherein when the iron content of each alloy is 80-81.09%, the carbon content is 5.3-5.6%, the rare earth content is 4.3-4.6%, the copper content is 0.1-0.2%, the tin content is 0.01-0.012%, the magnesium content is 7.4-7.7% and the impurity content of other alloys is 1.8-2.1%, adding a first inoculant into molten iron for treating for 2-5 min, then carrying out casting, pouring 35% of the cast molten iron, and adding a second inoculant in batches until the casting is finished; after casting, firstly cooling to 750-875 ℃ at the speed of 5-10 ℃/min, then completely cooling to room temperature, and taking out the cast part;
(6) heating the casting to 780-810 ℃, preserving heat for 30-38 min, and quenching after performing plasma carbonitriding in the heat preservation process;
(7) heating the casting to 550-600 ℃, performing shot blasting for 1-2 min, then heating again to 780-810 ℃, preserving heat for 30-38 min, and performing quenching treatment after performing plasma carbonitriding in the heat preservation process;
(8) and carrying out flaw detection treatment after fine machining on the cast parts, and sorting qualified parts.
2. The method for producing spheroidal graphite cast iron castings according to the recycling of scrap steel according to claim 1, characterized in that: the silicon oxide treated by hydrofluoric acid in the step (4) is prepared by the following specific treatment method: placing silicon oxide in a closed treatment bin with a vibration function to enable the silicon oxide to be in a vibrated state, spraying hydrofluoric acid to the silicon oxide to enable the surface of the silicon oxide to be corroded to form a rough interface, and then alternately washing the treated silicon oxide by hot and cold clean water to remove the hydrofluoric acid on the surface.
3. The method for producing spheroidal graphite cast iron castings according to the recycling of scrap steel according to claim 1, characterized in that: the mixed carburant in the step (5) comprises the following components:
65-85% of artificial graphite;
15-35% of calcined acicular petroleum coke;
in parts by weight.
4. The method for producing spheroidal graphite cast iron castings according to the recycling of scrap steel according to claim 1, characterized in that: the first inoculant in the step (5) is ZFCCM inoculant; the second inoculant is CAINO-SUPER inoculant.
5. The method for producing spheroidal graphite cast iron castings according to the recycling of scrap steel according to claim 4, characterized in that: in the step (5), the adding mass ratio of the first inoculant to the second inoculant is 5-10: 1.
6. the method for producing spheroidal graphite cast iron castings according to the recycling of scrap steel according to claim 4, characterized in that: in the step (5), the casting process is controlled within 5-8 min.
7. The method for producing spheroidal graphite cast iron castings according to the recycling of scrap steel according to claim 1, characterized in that: in the step (5), other alloy impurities comprise metallic nickel, chromium, molybdenum and manganese, and the total weight of nickel and chromium is less than or equal to 0.2% and less than or equal to 0.2% compared with the total weight of molten iron.
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