CN108950366B - Method for processing nodular cast iron part with good wear resistance - Google Patents
Method for processing nodular cast iron part with good wear resistance Download PDFInfo
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- CN108950366B CN108950366B CN201810765254.0A CN201810765254A CN108950366B CN 108950366 B CN108950366 B CN 108950366B CN 201810765254 A CN201810765254 A CN 201810765254A CN 108950366 B CN108950366 B CN 108950366B
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- 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
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D5/00—Heat treatments of cast-iron
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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
- C22C33/10—Making cast-iron alloys including procedures for adding magnesium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/06—Cast-iron alloys containing chromium
- C22C37/08—Cast-iron alloys containing chromium with nickel
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/10—Cast-iron alloys containing aluminium or silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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- 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
Abstract
The invention discloses a method for processing a nodular cast iron part with good wear resistance, which comprises the following steps: designing chemical components of nodular cast iron; smelting the raw materials by using a medium-frequency induction furnace; step three, after the step two is finished, adding an inoculant for primary inoculation, and then casting to prepare a nodular cast iron part; and step four, cooling the obtained nodular cast iron part, then repeatedly heating to 940-. The invention provides a method for processing a nodular cast iron part with good wear resistance, wherein the nodular cast iron part mainly comprises pearlite and ferrite in an as-cast structure, a small amount of acicular martensite is contained on the surface of the part, and the wear resistance of the surface of the nodular cast iron is improved by more than 10% compared with that of a common nodular cast iron part.
Description
Technical Field
The invention belongs to the field of alloy materials, particularly belongs to the field of nodular cast iron materials, and particularly relates to a method for processing a nodular cast iron product with good wear resistance.
Background
The cast iron is an iron-carbon alloy and is characterized by high carbon content, more than 2% of carbon element by mass and more impurity elements such as silicon, manganese, phosphorus, sulfur and the like. The graphite which is spread out in the cast iron exists mostly as carbide or in a free state, and a very small amount of the graphite is dissolved in ferrite. The graphite lattice type in the cast iron is a simple hexagonal lattice, the atomic distance in the basal plane is 0.142nm, the bonding force is strong, but the surface distance between the two basal planes is 0.340nm, the bonding force is weak, so the basal plane of the graphite is easy to slide, and the strength, the hardness, the plasticity and the toughness of the graphite are extremely high, and the graphite often exists in a sheet shape. The graphite in the nodular cast iron is spherical, the strength and the toughness of the nodular cast iron are higher than those of other cast irons such as gray cast iron, the nodular cast iron has excellent castability, high damping performance and good machinability, and compared with steel with similar performance, the nodular cast iron has relatively low price, so that the nodular cast iron is widely applied to industry, wear-resistant parts such as crankshafts, camshafts, hot rolls and the like are usually made of the nodular cast iron, and the dosage of the nodular cast iron is the second place of all metal materials in the manufacturing industry.
Ductile iron, also known as ductile iron, has graphite that acts as a crack stopper, giving it excellent properties of human and ductility. The diversity of the nodular cast iron makes the nodular cast iron suitable for more applications and is considered as a substitute of steel, but the strength of the iron matrix is discontinuous because the spheroidal graphite is embedded in the iron matrix, and the spheroidal graphite is a crack source under impact load, so that the matrix is easy to crack. Because graphite is a soft base phase, parts for manufacturing cast iron are often poor in wear resistance, stress is easily concentrated to generate scrap nodules due to the existence of the graphite phase, and the graphite phase on the surface of cast iron is exposed in media such as air, lubricating oil and the like to generate carbonization corrosion, so that the graphite phase on the surface needs to be removed in order to improve the toughness and wear resistance of the surface of the nodular cast iron.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method for processing ductile iron with good wear resistance. The technical effect to be achieved by the invention is realized by the following scheme:
the invention provides a method for processing a nodular cast iron part with good wear resistance, which comprises the following steps:
the method comprises the following steps of firstly, designing the nodular cast iron to comprise the following chemical components in percentage by mass: 3.7 to 3.85 percent of C, 1.6 to 1.9 percent of Si, 0.55 to 0.60 percent of Mn, less than or equal to 0.07 percent of P, less than or equal to 0.02 percent of S, less than or equal to 0.06 percent of Cr, 0.005 to 0.008 percent of B, 0.3 to 0.5 percent of Mo0.3, 0.3 to 0.6 percent of Cu0.02 to 0.03 percent of Mg, 1.0 to 1.15 percent of Ni1.03 to 0.045 percent of V, and the balance of Fe and inevitable impurities; the nodular cast iron mainly adopts pig iron and scrap steel as raw materials, and ferromolybdenum, red copper, ferromanganese and ferrovanadium as the rest raw materials; the nodulizer is FeSiMg8Re7, and the adding amount is 1.0-1.3% of the total mass of the raw materials;
step two, smelting the raw materials by using a medium frequency induction furnace, and smelting the raw materials into molten liquid under the conditions of 1400 ℃ and 1450 ℃; adopting a pouring method for treatment, drying a casting ladle, putting a nodulizer into the casting ladle, covering the surface with a ferrosilicon alloy, pouring 70-80% of melt into the casting ladle immediately when the temperature of the raw material melt exceeds 1400 ℃, and pouring the rest raw material melt after the spheroidization reaction is finished;
step three, after the step two is finished, adding an inoculant accounting for 0.55-0.60% of the mass of the raw materials for primary inoculation, discharging the mixture from the furnace at 1450-1480 ℃ for casting, wherein the casting temperature is 1380-1400 ℃, and preparing a nodular cast iron part;
and step four, cooling the obtained nodular cast iron part, then repeatedly heating to 940-.
The invention starts from the chemical components of the nodular cast iron, and firstly carries out adaptive blending on the components of the nodular cast iron. In order to obtain a suitable ductile iron structure, it is necessary to select and add suitable elements. In the invention, Si, Mn, Mo, Cu and Ni are selected as main alloy addition elements, and a small amount of B, Mg and V are doped at the same time, and further, the content of P, S, Cr is controlled. In the main alloy additive elements, proper amount of Si and Ni can jointly influence the graphitization process in the nodular cast iron smelting process, the critical temperature of austenite transformation can be reduced, the austenite area is enlarged, the carbon content of a eutectoid point can be reduced, and the effects of strong stability and pearlite refinement are achieved. The Cu can promote graphitization during eutectic transformation, the critical temperature of austenite transformation is reduced, the formation of pearlite is promoted, the formation of free cementite is reduced or eliminated, the toughness of the nodular cast iron is improved, the pearlite can be obviously refined by the Mo, the strength and the hardenability of the nodular cast iron are improved, and the pearlite and ferrite in the pearlite can be simultaneously strengthened and refined by the cooperation of the Cu and the Mo, so that the strength and the hardness of the nodular cast iron are obviously improved. It is obvious from the actual production that small amounts of B, Mg and V are doped, and small amounts of B, Mg and V are dissolved into the microstructure of the nodular cast iron in a solid way, so that the wear resistance and hardenability of the nodular cast iron can be improved, but the addition amount is not excessive, otherwise, the comprehensive mechanical property of the nodular cast iron is adversely affected, and the macroscopic toughness is reduced in a cliff type. The chemical components of the nodular cast iron are strictly controlled, and the final microstructure is a synergistic result of the interaction of multiple additive elements and the control of impurity elements such as P, S, Cr, so that the microstructure of the nodular cast iron is seriously influenced by the change of the content of a single additive element or multiple additive elements, and the mechanical property of the prepared nodular cast iron product is influenced.
In the fourth step, the growth of a microstructure capable of improving the surface hardness is promoted by carrying out heat preservation and cooling processes at a specific temperature (the specific temperature corresponds to a specific microstructure), and finally, the microstructure is naturally cooled to room temperature in the atmospheric environment after being cooled to 500 ℃ at a cooling speed of 10-15K/s, so that the optimal surface state is obtained, and the surface wear resistance is improved.
Further, in the first step, the mass ratio of the pig iron to the scrap steel is (7-8): 1. the proportion of raw material pig iron and scrap steel is controlled, on one hand, the composition of nodular cast iron is effectively controlled, and on the other hand, the production cost of the cast iron is controlled.
Further, in the first step, the addition amount of the nodulizer is 1.2% of the total mass of the raw materials.
Further, in the second step, the ferrosilicon alloy is one or more of FeSi90Al1.5, FeSi75Al0.5-A, FeSi75Al0.5-B, FeSi75Al1.5-A, FeSi75Al1.5-B, FeSi65 and FeSi 45.
Further, in the second step, the grain size of the ferrosilicon alloy is 1-2 mm. The covering layer in the nodular cast iron smelting process is preferably ferrosilicon alloy, the ferrosilicon alloy and oxygen have high chemical affinity, the ferrosilicon alloy is a very good diffusion deoxidizer, and the strength and hardness of the nodular cast iron can be remarkably improved.
Furthermore, in the second step, the primary molten liquid rushing-in amount is 74-76%. The primary molten liquid feeding amount and the secondary molten liquid feeding amount are strictly set, so that the spheroidization reaction amount is carried out within the process control range.
Further, in the third step, the inoculant is one of CBSALLOY inoculant, INOFSBA-A antimony-silicon inoculant, Si73Sr1.0 silicon-strontium inoculant and Si73Sr1.5 silicon-strontium inoculant.
Further, in the third step, the particle size of the inoculant is 0.1-0.5 mm.
Further, in the fourth step, the cooling medium is a water-soluble cooling medium. Preferably, in the fourth step, the water-soluble cooling medium is one of a saturated sodium chloride solution, a saturated sodium carbonate solution and a saturated sodium bicarbonate solution. The water-soluble cooling medium can quickly cool the nodular cast iron, and organic residues can not be brought to the surface of the nodular cast iron even if the water-soluble cooling medium is in direct contact with the nodular cast iron, so that adverse effects on the surface are avoided.
The invention has the following advantages:
the invention provides a method for processing a nodular cast iron part with good wear resistance, wherein the nodular cast iron part mainly comprises pearlite and ferrite in an as-cast structure, a small amount of acicular martensite is contained on the surface of the part, and the wear resistance of the surface of the nodular cast iron is improved by more than 10% compared with that of a common nodular cast iron part.
Detailed Description
The present invention will be described in detail with reference to examples.
Firstly, pig iron and scrap steel are used as raw materials, and ferromolybdenum, red copper, ferromanganese and ferrovanadium are used as other additive materials for casting nodular cast iron, wherein the raw materials are all commercially available materials, and the mass ratio of the pig iron to the scrap steel is 7.6: 1. the casting method of the nodular cast iron part comprises the following steps:
① selecting corresponding raw materials according to the component design, smelting the raw materials by using a medium frequency induction furnace, smelting the raw materials into a melt at 1420-1430 deg.C (real-time temperature control, smelting temperature is controlled within the range), processing by using a flushing method, drying a casting ladle, putting a nodulizer into the casting ladle, covering the surface with ferrosilicon FeSi90Al1.5 powder with the average particle size of 1mm, flushing 75% of the melt into the casting ladle when the temperature test result of the raw material melt exceeds 1420 deg.C after smelting, and flushing the rest of the raw material melt after the spheroidization reaction.
In the step, FeSiMg8Re7 is adopted as a nodulizer, and the adding amount is 1.2 percent of the total mass of the raw materials. In this step, other commercially available and compatible nodulizers can be used as the nodulizer, and the addition amount can be adaptively adjusted according to the change of the actual situation. The type and amount of the ferrosilicon alloy may be adjusted adaptively according to the actual situation, and preferably may be one or more of FeSi90Al1.5, FeSi75Al0.5-A, FeSi75Al0.5-B, FeSi75Al1.5-A, FeSi75Al1.5-B, FeSi65, and FeSi 45.
② after the previous step, adding CBSALLOY inoculant accounting for 0.55% of the raw material mass for primary inoculation, tapping at 1450 ℃ for casting, wherein the casting temperature is 1390 ℃, and the grain size of the inoculant used in the step is 0.1 mm.
In the manufacturing method between the nodular cast irons, the process steps provided by professional terms are taken as the prior art, such as the 'punching method', and the description of the cast iron processing process in the prior art is provided, and the prior art is not taken as the invention point of the invention, so that the detailed description is not repeated, but the process steps are not taken as the basis for the description of the invention lacking the necessary technical characteristics.
The casting method is utilized to prepare 10 batches of cylindrical ductile iron workpieces, the length of each workpiece is 10cm, and the diameter of each workpiece is 2 cm. The measurement results of the element content by using an oxygen-nitrogen analyzer and an ICP emission spectrometer are as follows (the test results are the mass percentages of the corresponding elements):
after the preparation of the nodular cast iron product is finished, the next step of treatment is carried out, and the specific treatment process is as follows:
and cooling the obtained nodular cast iron product, then repeatedly heating to 950 ℃ and preserving heat for 2h, then cooling to 820 ℃ and preserving heat for 1h, then cooling to 600 ℃ and preserving heat for 0.6h, then placing the nodular cast iron product in a saturated sodium chloride aqueous solution, cooling to 500 ℃ at a cooling speed of 15K/s, and naturally cooling to room temperature in an atmospheric environment.
In the nodular cast iron parts, 100PCS is prepared for each batch of products, then 5PCS is randomly extracted from each batch for testing the mechanical property, and then the average value is obtained, wherein the comparative example is a test result obtained by adopting the same test method for the columnar parts with the same size and made of common nodular cast iron, and the results are as follows:
from the test results, the tensile strength of the nodular cast iron in the embodiment of the invention is slightly higher than that of the nodular cast iron composed of similar components in the prior art, and the surface hardness and the wear resistance are improved by over 10 percent.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the embodiments of the present invention and not for limiting the same, and although the embodiments of the present invention are described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the embodiments of the present invention, and these modifications or equivalent substitutions cannot make the modified technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (1)
1. A processing method of a nodular cast iron part with good wear resistance comprises the following steps:
the method comprises the following steps of firstly, designing the nodular cast iron to comprise the following chemical components in percentage by mass: 3.7 to 3.85 percent of C, 1.6 to 1.9 percent of Si, 0.55 to 0.60 percent of Mn, less than or equal to 0.07 percent of P, less than or equal to 0.02 percent of S, less than or equal to 0.06 percent of Cr, 0.005 to 0.008 percent of B, 0.3 to 0.5 percent of Mo0.3, 0.3 to 0.6 percent of Cu0.02 to 0.03 percent of Mg, 1.0 to 1.15 percent of Ni1.03 to 0.045 percent of V, and the balance of Fe and inevitable impurities; the nodular cast iron mainly adopts pig iron and scrap steel as raw materials, and the mass ratio of the pig iron to the scrap steel is (7-8): 1, adopting ferromolybdenum, red copper, ferromanganese and ferrovanadium for the rest; the nodulizer is FeSiMg8Re7, and the addition amount of the nodulizer is 1.2% of the total mass of the raw materials;
step two, smelting the raw materials by using a medium frequency induction furnace, and smelting the raw materials into molten liquid under the conditions of 1400 ℃ and 1450 ℃; treating by adopting a punching method, drying a casting ladle, putting a nodulizer into the casting ladle, and covering the surface of the casting ladle with a silicon-iron alloy, wherein the silicon-iron alloy is one or more of FeSi90Al1.5, FeSi75Al0.5-A, FeSi75Al0.5-B, FeSi75Al1.5-A, FeSi75Al1.5-B, FeSi65 and FeSi 45; the particle size of the ferrosilicon alloy particles is 1-2 mm; when the temperature of the raw material melt exceeds 1400 ℃, 74-76% of the melt is immediately poured into the casting ladle;
step three, after the step two is finished, adding an inoculant which accounts for 0.55-0.60% of the mass of the raw materials for primary inoculation, wherein the inoculant is one of CBSALLOY inoculant, INOFSBA-A antimony silicon inoculant, Si73Sr1.0 silicon strontium inoculant and Si73Sr1.5 silicon strontium inoculant, and the particle size of the inoculant is 0.1-0.5 mm; taking out of the furnace at 1450-1480 ℃ for casting, wherein the casting temperature is 1380-1400 ℃ to prepare a nodular cast iron part;
step four, the obtained nodular cast iron part is cooled and then heated to 940-; the cooling medium is a water-soluble cooling medium; the water-soluble cooling medium is one of saturated sodium chloride solution, saturated sodium carbonate solution and saturated sodium bicarbonate solution.
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| CN115074610B (en) * | 2022-07-05 | 2022-12-06 | 襄阳金耐特机械股份有限公司 | Preparation method of low-residual-stress and high-elastic-modulus nodular cast iron, nodular cast iron and application |
| CN115094301A (en) * | 2022-07-20 | 2022-09-23 | 南京浦江合金材料股份有限公司 | Spheroidizing method of microparticle rare earth magnesium silicon iron nodulizer |
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