CN111455263A - Environment-friendly low-temperature nodular cast iron produced by using low-rare earth alloy and production process thereof - Google Patents
Environment-friendly low-temperature nodular cast iron produced by using low-rare earth alloy and production process thereof Download PDFInfo
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C21C1/00—Refining of pig-iron; Cast iron
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- 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
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- C22C33/12—Making cast-iron alloys including procedures for adding magnesium by fluidised injection
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- C22C37/08—Cast-iron alloys containing chromium with nickel
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Abstract
The invention discloses environment-friendly low-temperature nodular cast iron produced by using a low rare earth alloy and a production process thereof, belonging to the technical field of nodular cast iron and comprising the following elements in percentage by mass: 3 to 4 percent of C, 1.8 to 3 percent of Si, 1.2 to 2.8 percent of Cr, 0.2 to 0.8 percent of Mn, 0.03 to 0.06 percent of Mg, 0.4 to 0.8 percent of Ni, less than or equal to 0.07 percent of P, less than or equal to 0.03 percent of S, less than or equal to 0.02 percent of Ti, and the balance of Fe. The method can improve the ductility and tensile strength of the nodular cast iron and improve the strength and corrosion resistance of the nodular cast iron by strictly controlling the contents of C, Si, Cr, Mn, Mg, Ni, P, S and Ti, is favorable for obtaining low-temperature high toughness, avoids brittle fracture when the nodular cast iron runs in a low-temperature environment, can obtain the low-temperature high-toughness nodular cast iron by adopting high-temperature graphitization annealing heat treatment, can effectively remove free cementite in an as-cast structure, and improves the strength and the hardness.
Description
Technical Field
The invention relates to the technical field of nodular cast iron, in particular to environment-friendly low-temperature nodular cast iron produced by using low rare earth alloy and a production process thereof.
Background
The ductile iron is a high-strength cast iron material developed in the 20 th century and the fifties, the comprehensive performance of the ductile iron is close to that of steel, and the ductile iron is successfully used for casting parts which are complex in stress and high in requirements on strength, toughness and wear resistance based on the excellent performance of the ductile iron. Nodular cast iron has rapidly evolved to a very widely used cast iron material second only to gray cast iron. The term "steel is replaced by iron" is mainly used for nodular cast iron.
The nodular cast iron is spheroidized and inoculated to obtain spheroidal graphite, so that the mechanical properties of the cast iron are effectively improved, and particularly, the plasticity and toughness are improved, so that the strength of the cast iron is higher than that of carbon steel.
The common nodular cast iron has insufficient low-temperature resistance, the nodular cast iron gradually changes from toughness to brittleness along with the reduction of the use temperature of a casting, particularly, the impact value is sharply reduced below the brittleness transition temperature, the use requirements under low temperature and high strength cannot be met, and meanwhile, the corrosion resistance and the strength of the nodular cast iron cannot meet the use requirements.
Disclosure of Invention
The invention aims to provide environment-friendly low-temperature nodular cast iron produced by using low-rare earth alloy and a production process thereof, which have the advantages that the fluidity and the mold filling capacity of molten iron are high by strictly controlling the contents of C, Si, Cr, Mn, Mg, Ni, P, S and Ti, the ductile and tensile strength of the nodular cast iron can be improved, the strength and the corrosion resistance of the nodular cast iron can be improved, the low-temperature high toughness can be obtained, the brittle fracture during the operation in a low-temperature environment can be avoided, the long-term safe operation can be ensured, the low-temperature high-toughness nodular cast iron can be obtained by adopting high-temperature graphitization annealing heat treatment, free cementite in an as-cast structure can be effectively removed, the strength and the hardness are improved, and the problems in the background technology are solved.
In order to achieve the purpose, the invention provides the following technical scheme: the low-rare earth alloy is used for producing environment-friendly low-temperature nodular cast iron and comprises the following elements in percentage by mass: 3 to 4 percent of C, 1.8 to 3 percent of Si, 1.2 to 2.8 percent of Cr, 0.2 to 0.8 percent of Mn, 0.03 to 0.06 percent of Mg0.4 to 0.8 percent of Ni, less than or equal to 0.07 percent of P, less than or equal to 0.03 percent of S, less than or equal to 0.02 percent of Ti, and the balance of Fe.
The invention also provides another technical scheme, and the production process for producing the environment-friendly low-temperature nodular cast iron by using the low-rare earth alloy comprises the following steps:
s1, preparing molten iron: mixing and smelting pig iron, scrap steel, foundry returns, a carburant, silicon carbide and silicon at the smelting temperature of 1500 ℃ to obtain molten iron;
s2, deslagging and cooling: standing the iron liquid prepared in the step S1, adding a deslagging agent into the iron liquid for deslagging, naturally cooling the iron liquid after deslagging, and cooling the iron liquid to 1460 ℃;
s3, spheroidizing: pouring the molten iron in the step S2 into a bag, adding a nodulizer into the bag, properly pounding the upper surface of the bag by using a sand punch, covering a layer of oil-free and rust-free nodular iron scraps, then spreading a proper amount of perlite, after tapping, removing spheroidizing residues, and spreading a layer of perlite or plant ash with enough thickness;
s4, inoculation treatment: adding a primary inoculant and a secondary inoculant into the molten iron prepared in the step S3, and performing deslagging treatment;
s5, casting treatment: when the molten iron prepared in the step S4 is poured, adding a tertiary inoculant along with the flow, and simultaneously carrying out floating silicon inoculation in the ladle in the pouring process;
s6, heat treatment: and (4) heating the cast iron prepared in the step S5 in a heating furnace, annealing after the casting is heated to 900-950 ℃ and is kept warm for 2-5 hours, and discharging and air cooling the casting after the casting is cooled to 600 ℃ along with the furnace.
Further, the nodulizer added in the S3 is rare earth magnesium silicon iron alloy, FeSiMg10RE7 or FeSiMg9RE9, and is nodulized by adopting a punching method, and the nodulizer is intensively placed on one side of the ladle bottom close to the taphole during adding.
Further, the particle size of the nodulizer added in S3 is 10-20 mm.
Furthermore, 0.8-1.6% of 75% ferrosilicon with the granularity of 10-20m needs to be added into the molten iron after the spheroidization treatment in S3, and finally the carbon content is controlled to be 4.6-4.7%.
Further, the secondary inoculant added in S4 is SiFe75, and the particle size of the secondary inoculant is 4-6 mm.
Further, the tertiary inoculant added in S5 has a particle size of 0.4-0.6 mm.
Compared with the prior art, the invention has the beneficial effects that:
the invention relates to an environment-friendly low-temperature nodular cast iron produced by low-rare earth alloy and a production process thereof, which can lead the fluidity and the filling capability of molten iron to be strong by strictly controlling the contents of C, Si, Cr, Mn, Mg, Ni, P, S and Ti, have good casting process, reduce the tendency of crystallization supercooling and white cast, refine graphite, improve the roundness of graphite nodules, improve the ductility and the tensile strength of the nodular cast iron, lead the nodular cast iron to be easy to form, improve the strength and the corrosion resistance of the nodular cast iron, lead the nodular cast iron to be difficult to rust and corrode, use the rare earth magnesium-silicon-iron alloy with low rare earth, FeSiMg10RE7 or FeSiMg9RE9 nodulizer, adopt secondary inoculation, namely the combination of stokehold inoculation and rotary ladle inoculation for strengthening inoculation and improving the inoculation effect, thus can reduce the addition of the inoculant, be beneficial to control the final silicon content, obtain fine and uniform graphite nodules and be beneficial to obtain low-temperature high toughness, the ductile iron with low temperature and high toughness can be obtained by adopting high-temperature graphitization annealing heat treatment, free cementite in an as-cast structure can be effectively removed, and the strength and the hardness are improved.
Drawings
FIG. 1 is a flow chart of the production process of the invention for producing environment-friendly low-temperature nodular cast iron by using low rare earth alloy.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
The low-rare earth alloy is used for producing environment-friendly low-temperature nodular cast iron and comprises the following elements in percentage by mass: 3% of C, 1.8% of Si, 1.2% of Cr, 0.2% of Mn, 0.03% of Mg, 0.4% of Ni, 0.06% of P, 0.03% of S, 0.02% of Ti and the balance of Fe.
C is an element formed by strengthening graphite, carbon and silicon have great influence on the performance of a casting, the carbon content is high, casting defects such as graphite floating, broken graphite and the like are easily generated, free cementite is easily generated due to the low carbon content, and casting defects such as shrinkage cavity, shrinkage porosity and the like are easily generated, and the proper carbon content is selected, so that the fluidity and the mold filling capacity of molten iron are high, and the casting process is good, and therefore, the carbon content is selected from 3-4%.
Si is an important element for controlling graphitization and ferrite quantity in the nodular cast iron, the low-temperature impact toughness of the nodular cast iron is reduced while a ferrite matrix is strengthened, the tendency of crystal supercooling and white cast can be reduced by the Si, the graphite can be refined, the roundness of graphite spheres is improved, but the Si is high and is easy to form special-shaped graphite, and the low-temperature brittleness is improved, so that the Si content is selected from 1.8-3%.
Cr can change the physical structure and chemical properties of the nodular cast iron, so that the nodular cast iron has a wider application field, and the chromium content is 1.2-2.8.
Mn is stable and can refine pearlite, strength and hardness are improved, plasticity and toughness are reduced, brittle transition temperature is obviously improved, structure segregation is easy to form, and formation of carbide is promoted, so that the manganese content is selected to be 0.2-0.8%.
Mg can improve the ductility and tensile strength of the nodular cast iron, so that the nodular cast iron is easy to mold, and therefore, the magnesium content is selected to be 0.03%.
Ni can improve the strength and corrosion resistance of the nodular cast iron, and the nodular cast iron is not easy to rust and corrode, so that the nickel content is selected to be 0.8%.
P is a harmful element and is easy to segregate at the eutectic cell boundary to generate phosphorus eutectic, the low-temperature toughness of the nodular cast iron is reduced strongly, and similarly, Ti also has the adverse effects of increasing the brittleness of the casting and reducing the strength, and the content of P and Ti is controlled to be beneficial to improving the performance of the casting, so that P is less than or equal to 0.07 percent and Ti is less than or equal to 0.02 percent.
S is an extremely harmful element in the nodular cast iron, the mass percentage content of the S is the key for stabilizing the nodularity of the nodular cast iron and improving the nodularity quality of a casting, the S reacts with the nodularity element, a nodulizer is consumed, nodularization is unstable, the quantity of inclusions is increased, casting defects are caused, the lower the sulfur content is, the better the sulfur content is, therefore, the S is less than or equal to 0.03%, and the fluidity and the mold filling capacity of molten iron are high by strictly controlling the contents of C, Si, Cr, Mn, Mg, Ni, P, S and Ti, so that the casting process is good.
The production process of producing environment-friendly low-temperature nodular cast iron by using the low-rare earth alloy comprises the following steps:
s1, preparing molten iron: mixing and smelting pig iron, scrap steel, foundry returns, a carburant, silicon carbide and silicon at the smelting temperature of 1500 ℃ to obtain molten iron;
s2, deslagging and cooling: standing the molten iron prepared in the step S1, adding a deslagging agent into the molten iron for deslagging, naturally cooling the molten iron after deslagging, and effectively removing impurities in the molten iron when the temperature of the molten iron is reduced to 1460 ℃ to ensure that the molten iron has no slag;
s3, spheroidizing: pouring the molten iron in S2 into a ladle, adding a nodulizer into the ladle, properly pounding the upper surface of the molten iron by using a sand punch, covering a layer of oil-free and rust-free nodular iron scraps, then spreading a proper amount of perlite, after tapping, scraping spheroidization residues, spreading a layer of perlite or grass ash with enough thickness, adding the nodulizer into S3, namely rare earth magnesium silicon iron alloy, FeSiMg10RE7 or FeSiMg9RE9, spheroidizing by adopting a pouring method, wherein the nodulizer is intensively placed at one side of the ladle bottom close to an iron tapping hole when being added, adding 0.8-1.6 percent of 75 percent ferrosilicon into the molten iron after the spheroidization treatment in S3, the granularity is 10-20m, finally ensuring the carbon content to be 4.6-4.7 percent, adding the nodulizer into S3, and using low-rare earth silicon iron alloy, FeSiRE 10RE 5 or FeSiMg9, and a second-shot nucleating agent before ladle inoculation, wherein the nodulizer is used for secondary inoculation, and the nodulizer is a second-time of inoculation, the spheroidization method, The inoculation effect is improved, so that the addition of the inoculant can be reduced, the control of the final silicon amount is facilitated, fine and uniform graphite nodules are obtained, the low-temperature high toughness is facilitated, the brittle fracture during the operation in a low-temperature environment is avoided, the long-term safe operation can be ensured, and the maintenance is not performed or is very little performed;
s4, inoculation treatment: adding a primary inoculant and a secondary inoculant into the molten iron prepared in the step S3, and performing deslagging treatment, wherein the secondary inoculant added in the step S4 is SiFe75, and the particle size of the secondary inoculant is 4-6 mm;
s5, casting treatment: when the molten iron prepared in the step S4 is poured, adding a tertiary inoculant along with the flow, simultaneously performing floating silicon inoculation in the ladle in the pouring process, wherein the granularity of the tertiary inoculant added in the step S5 is 0.4-0.6 mm;
s6, heat treatment: and (3) heating the cast iron prepared in the step (S5) in a heating furnace, keeping the temperature for 2-5 h after the cast iron is heated to 900-950 ℃, annealing, cooling the cast iron to 600 ℃ along with the furnace, discharging the cast iron out of the furnace for air cooling, and performing high-temperature graphitization annealing heat treatment to obtain the low-temperature high-toughness nodular cast iron, so that free cementite in an as-cast structure can be effectively removed.
Example two
The low-rare earth alloy is used for producing environment-friendly low-temperature nodular cast iron and comprises the following elements in percentage by mass: 3.2% of C, 2% of Si, 1.4% of Cr, 0.3% of Mn, 0.04% of Mg, 0.5% of Ni, 0.05% of P, 0.03% of S, 0.02% of Ti and the balance of Fe, and the preparation steps of the embodiment are the same as those of embodiment 1, and are not repeated.
EXAMPLE III
The low-rare earth alloy is used for producing environment-friendly low-temperature nodular cast iron and comprises the following elements in percentage by mass: 3.4% of C, 2.6% of si, 1.6% of Cr, 0.4% of Mn, 0.05% of Mg, 0.6% of Ni, 0.04% of P, 0.02% of S, 0.01% of Ti, and the balance of Fe, and the preparation steps in this embodiment are the same as those in embodiment 1, and thus are not repeated.
Example four
The low-rare earth alloy is used for producing environment-friendly low-temperature nodular cast iron and comprises the following elements in percentage by mass: 3.6% of C, 2.8% of Si, 1.8% of Cr, 0.5% of Mn, 0.03% of Mg, 0.5% of Ni, 0.03% of P, 0.01% of S, 0.01% of Ti and the balance of Fe, and the preparation steps of the embodiment are the same as those of embodiment 1, and thus are not repeated.
EXAMPLE five
The low-rare earth alloy is used for producing environment-friendly low-temperature nodular cast iron and comprises the following elements in percentage by mass: 3.8% of C, 2.9% of Si, 2% of Cr, 0.6% of Mn, 0.04% of Mg, 0.5% of Ni, 0.02% of P, 0.01% of S, 0.01% of Ti and the balance of Fe, and the preparation steps of the embodiment are the same as those of embodiment 1, and are not repeated.
The invention also provides the following comparative examples
Comparative example 1: the alloy comprises the following elements in percentage by mass: 3.2 to 3.8 percent of C, 2.1 to 2.6 percent of Si, 0.6 percent of Mn, less than or equal to 0.07 percent of P, less than or equal to 0.03 percent of S, less than or equal to 0.02 percent of Ti and the balance of Fe, and the preparation steps adopt the traditional preparation process, so the details are not repeated.
Comparative example 2: the alloy comprises the following elements in percentage by mass: 3.4 to 3.5 percent of C, 2.3 to 2.4 percent of Si, 0.5 percent of Mn, less than or equal to 0.05 percent of P, less than or equal to 0.02 percent of S, less than or equal to 0.02 percent of Ti and the balance of Fe, and the preparation steps adopt the traditional preparation process, so the details are not repeated.
The warm nodular cast iron prepared in the above 5 examples and 2 comparative examples was subjected to the performance test, and the test results are as follows:
| tensile strength | Ductility of the alloy | Strength of | Corrosion resistance | Degree of roundness | Toughness of | |
| Example 1 | 50MPa | Good wine | Good wine | Good wine | Difference (D) | Difference (D) |
| Example 2 | 45MPa | Superior food | Superior food | Superior food | Superior food | Superior food |
| Example 3 | 40MPa | Superior food | Good wine | Superior food | Good wine | Superior food |
| Example 4 | 35MPa | Good wine | Difference (D) | Good wine | Good wine | Good wine |
| Example 5 | 30MPa | Difference (D) | Good wine | Difference (D) | Difference (D) | Difference (D) |
As can be seen from the above table, the tensile strength, ductility, strength, corrosion resistance, roundness and toughness of the graphite nodules in the second embodiment are all excellent, and the tensile strength, ductility, strength, corrosion resistance, roundness and toughness of the graphite nodules can be greatly improved by the nodular cast iron produced by the second embodiment.
In conclusion, the invention uses the low rare earth alloy to produce the environment-friendly low-temperature nodular cast iron and the production process thereof, the contents of C, Si, Cr, Mn, Mg, Ni, P, S and Ti are strictly controlled, so that the fluidity and the mold filling capability of molten iron are strong, the casting process is good, the tendency of crystallization supercooling and white cast can be reduced, graphite can be refined, the roundness of graphite nodules is improved, the ductility and the tensile strength of the nodular cast iron can be improved, the nodular cast iron is easy to mold, the strength and the corrosion resistance of the nodular cast iron can be improved, the nodular cast iron is not easy to rust and corrode, the rare earth magnesium-silicon-iron alloy with low rare earth, FeSiMg10RE7 or FeSiMg9RE9 nodulizer is used, secondary inoculation is adopted, namely the combination of stokehold inoculation and rotary ladle inoculation is combined to strengthen inoculation and improve the inoculation effect, thus the addition of the inoculant can be reduced, the control of the final silicon amount is beneficial to obtain fine and uniform graphite nodules, the method is favorable for obtaining low-temperature high toughness, avoids brittle fracture when the nodular cast iron runs in a low-temperature environment, can ensure long-term safe running, is not maintained or has little maintenance, can obtain the nodular cast iron with low temperature and high toughness by adopting high-temperature graphitization annealing heat treatment, can effectively remove free cementite in an as-cast structure, and improves the strength and the hardness.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.
Claims (7)
1. The method for producing the environment-friendly low-temperature nodular cast iron by using the low-rare earth alloy is characterized by comprising the following elements in percentage by mass: 3 to 4 percent of C, 1.8 to 3 percent of Si, 1.2 to 2.8 percent of Cr, 0.2 to 0.8 percent of Mn, 0.03 to 0.06 percent of Mg, 0.4 to 0.8 percent of Ni, less than or equal to 0.07 percent of P, less than or equal to 0.03 percent of S, less than or equal to 0.02 percent of Ti, and the balance of Fe.
2. The process for producing environmentally friendly low temperature ductile iron using low rare earth alloy according to claim 1, comprising the steps of:
s1, preparing molten iron: mixing and smelting pig iron, scrap steel, foundry returns, a carburant, silicon carbide and silicon at the smelting temperature of 1500 ℃ to obtain molten iron;
s2, deslagging and cooling: standing the iron liquid prepared in the step S1, adding a deslagging agent into the iron liquid for deslagging, naturally cooling the iron liquid after deslagging, and cooling the iron liquid to 1460 ℃;
s3, spheroidizing: pouring the molten iron in the step S2 into a bag, adding a nodulizer into the bag, properly pounding the upper surface of the bag by using a sand punch, covering a layer of oil-free and rust-free nodular iron scraps, then spreading a proper amount of perlite, after tapping, removing spheroidizing residues, and spreading a layer of perlite or plant ash with enough thickness;
s4, inoculation treatment: adding a primary inoculant and a secondary inoculant into the molten iron prepared in the step S3, and performing deslagging treatment;
s5, casting treatment: when the molten iron prepared in the step S4 is poured, adding a tertiary inoculant along with the flow, and simultaneously carrying out floating silicon inoculation in the ladle in the pouring process;
s6, heat treatment: and (4) heating the cast iron prepared in the step S5 in a heating furnace, annealing after the casting is heated to 900-950 ℃ and is kept warm for 2-5 hours, and discharging and air cooling the casting after the casting is cooled to 600 ℃ along with the furnace.
3. The process for producing environmentally friendly low temperature ductile iron according to claim 2, wherein the nodulizer added in S3 is a rare earth sendust, FeSiMg10RE7 or FeSiMg9RE9, and is nodulized by a punching method, and the nodulizer is added while being concentrated on the side of the ladle bottom close to the taphole.
4. The process for producing environmentally friendly low temperature ductile iron using low rare earth alloy according to claim 2, wherein the nodulizer added in S3 has a particle size of 10-20 mm.
5. The process for producing environmentally friendly low temperature ductile iron using low rare earth alloy according to claim 2, wherein 0.8-1.6% ferrosilicon of 75% with a grain size of 10-20m is added to the molten iron after spheroidizing in S3, and the carbon content is finally 4.6-4.7%.
6. The process for producing environmentally friendly low temperature ductile iron using low rare earth alloy according to claim 2, wherein the secondary inoculant added in S4 is SiFe75, and the particle size of the secondary inoculant is 4-6 mm.
7. The process for producing environmentally friendly low temperature ductile iron using low rare earth alloy according to claim 2, wherein the grain size of the tertiary inoculant added in S5 is 0.4-0.6 mm.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114058935A (en) * | 2021-08-03 | 2022-02-18 | 常州市大华环宇机械制造有限公司 | Ultralow-temperature ferrite nodular cast iron and preparation method thereof |
| CN115537644A (en) * | 2022-09-30 | 2022-12-30 | 新兴铸管股份有限公司 | Corrosion-resistant nodular cast iron pipeline and preparation method thereof |
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2020
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114058935A (en) * | 2021-08-03 | 2022-02-18 | 常州市大华环宇机械制造有限公司 | Ultralow-temperature ferrite nodular cast iron and preparation method thereof |
| CN115537644A (en) * | 2022-09-30 | 2022-12-30 | 新兴铸管股份有限公司 | Corrosion-resistant nodular cast iron pipeline and preparation method thereof |
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Application publication date: 20200728 |