CN108707813B - As-cast high-strength ductile iron and its manufacturing process - Google Patents
As-cast high-strength ductile iron and its manufacturing process Download PDFInfo
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- C22C37/00—Cast-iron alloys
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Abstract
The invention discloses an as-cast high-strength ductile iron and a manufacturing process thereof, wherein the process comprises the following steps: step (1): preparing metal furnace charge, namely 20-30% of pig iron, 25-35% of return iron and 35-45% of scrap steel by weight percent, smelting by adopting a medium-frequency induction electric furnace, adding a carburant and the metal furnace charge into the lower middle part of the electric furnace together, carrying out carburant treatment, controlling the smelting temperature at 1450 and 1520 ℃, and then blowing nitrogen into a ladle for desulfurization treatment; step (2): spheroidizing and secondary inoculation are carried out on the product, wherein a first inoculant is a 75SiFe inoculant, and a second inoculant is a cerium oxysulfide inoculant; and (3): and (3) performing casting molding by using an iron mold sand-coated casting process, and after the casting is finished, performing heat treatment by utilizing self-preheating of the casting until the temperature is room temperature. The process provided by the invention has reasonable design, the heat treatment process is omitted, the production cost is reduced, the environmental pollution is reduced, and the mechanical properties of the ductile iron obtained by the process are improved.
Description
Technical Field
The invention relates to an as-cast ductile iron and a production method thereof, in particular to an as-cast high-strength ductile iron and a manufacturing process thereof.
Background
The high-strength nodular cast iron has high tensile strength and high elongation and is widely applied to engineering machinery and automobile parts, and comprises safety parts such as axle housings, steering knuckles, planetary wheel housings, wheel hubs and the like. If the ductile iron can achieve excellent comprehensive mechanical properties such as high strength and high toughness in an as-cast state, the production cost is greatly reduced and the production period is shortened. Many parts, which were originally made of cast steel materials or joined by forge welding, are now increasingly being replaced by ductile iron parts of high strength and toughness. The ductile iron casting is used for replacing a steel part, so that the dead weight can be reduced by 8-12%, and great benefits are brought to the light weight of machinery and the energy conservation. Meanwhile, compared with steel, the cast iron has many advantages, good wear resistance, shock absorption, heat conductivity and lower notch sensitivity, and meanwhile, the raw materials of the cast iron are wide in source and easy to obtain, so that the application status and the prospect of the high-strength and high-toughness nodular cast iron are established.
The inoculant used in the production of the nodular cast iron can play a role in increasing graphite cores, improving nucleation capability, increasing the number of graphite spheres, optimizing tissues and improving comprehensive performance. The inoculants usually used for cast iron are SiFe alloys containing a small amount of Al, Ca, Zr, Ba and other elements, however, under the environmental factors of heavy-wall nodular iron castings or severe cooling conditions, the surfaces of the castings, such as flange parts, are often subjected to shrinkage porosity, and the production requirements cannot be met. Generally, the casting can meet the technical requirements of the material after heat treatment, the production cost is increased due to the standard coal and electricity used for heat treatment, and the environment is seriously polluted by sulfur dioxide and dust generated by the coal.
Therefore, the technical personnel in the field aim to provide a manufacturing process and a formula of as-cast high-strength ductile iron, and the multi-element trace alloy treatment process is adopted, so that the heat treatment process can be avoided, and the as-cast casting has compact structure and meets the requirements of strength and hardness.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, the present invention provides an as-cast high-strength ductile iron and a novel process for manufacturing the same.
In order to achieve the aim, the invention provides a process for manufacturing as-cast high-strength ductile iron, which specifically comprises the following steps:
step (1): preparing metal furnace charge, including low-phosphorus low-sulfur pig iron, return iron and scrap steel, according to the weight percentage, 20-30% of pig iron, 25-35% of return iron and 35-45% of scrap steel; smelting the prepared metal furnace charge by adopting a medium-frequency induction furnace, adding a carburant with the weight ratio of 2.7-3.3% of the metal furnace charge into the lower middle part of the furnace together with the metal furnace charge, carrying out carburant treatment on a layer of the metal furnace charge and a layer of the carburant, controlling the smelting temperature to 1450-;
step (2): spheroidizing the product, wherein the adding amount of a nodulizer is 0.9-1.3% of the weight of the treated molten iron, the nodulizer is poured into a spheroidizing bag and compacted, a first inoculant which is 0.4-0.6% of the total weight of the molten iron is uniformly covered on the nodulizer, 75SiFe inoculant is selected as the first inoculant, three quarters of the total weight of the molten iron is flushed into the spheroidizing bag, after the spheroidizing and the first inoculation are finished, one quarter of the total weight of the molten iron is flushed, a second inoculant which is 0.2-0.4% of the total weight of the molten iron is flushed along with the flow, the second inoculation is finished, and cerium oxysulfide inoculant is selected as the second inoculant;
and (3): and (2) performing casting molding by using an iron mold sand-coated casting process, pouring molten iron with the temperature not lower than 1400 ℃ into a metal mold with an inner cavity coated with a layer of molding sand, and performing heat treatment by utilizing self-preheating of a casting until the temperature is room temperature after the pouring is finished.
Further, adding a metallurgical silicon carbide pretreating agent accounting for 0.15 percent of the weight of the molten iron into the molten iron after the smelting in the step (1), and uniformly stirring at low frequency.
Further, in the step (1), a high-temperature carburant is used for carburant treatment, the high-temperature carburant is subjected to high-temperature treatment before being used, and the carburant is required to have a carbon content of more than or equal to 99.5% and a sulfur content of less than or equal to 0.01%.
Further, the nodulizer used in step (2) has a particle size of 5-30mm, the first inoculant has a particle size of 5-10mm, and the second inoculant has a particle size of 0.2-0.8 mm.
Further, the second inoculant used in the step (2) comprises the following components in percentage by mass: 70-76% of Si, 0.75-1.25% of Ca0, 0.75-1.25% of Al, 1.5-2.0% of Ce and the balance of S, O.
Further, the molten iron pouring in the step (3) adopts a rapid pouring process, and the pouring speed of the molten iron is more than or equal to 6.5 Kg/sec.
Further, an open type pouring system is adopted for molten iron pouring in the step (3), air entraining is adopted in the pouring process, and an ignition tool with the length being more than 3 meters is adopted during air entraining.
Further, in the step (3), the process control conditions for performing heat treatment by using the waste heat of the casting per se are as follows: keeping the temperature at 920-.
The invention also provides ductile iron obtained by the cast high-strength ductile iron manufacturing process, which comprises the following main element components in percentage by mass: 3.5 to 3.8 percent of C, 2.0 to 2.5 percent of Si, 0.31 to 0.38 percent of Mn, 0.035 to 0.05 percent of Ce, 0.045 to 0.06 percent of Mg, less than or equal to 0.04 percent of P, less than or equal to 0.018 percent of S, and the balance of Fe.
Preferably, the ductile iron comprises the following main element components in percentage by mass: 3.8 percent of C, 2.0 percent of Si, 0.35 percent of Mn, 0.04 percent of Ce, 0.05 percent of Mg, less than or equal to 0.04 percent of P, less than or equal to 0.018 percent of S and the balance of Fe.
According to the invention, a proper amount of the pretreating agent, the nodulizer and the inoculant are added after the molten iron is smelted, so that crystal grains are finer and more uniform during crystallization, and the comprehensive performance of the nodular cast iron is greatly improved. The high-temperature graphitization carburant is used, carbon atoms are transited from an original disordered arrangement state to an ordered state after the carburant is subjected to high-temperature graphitization treatment, and graphite in the additive can become a high-quality core of graphite nucleation, so that graphitization is promoted. The treatment has the effects of inoculating and refining grains, improves the spheroidization effect and the inoculation quality, reduces impurities and improves the quality of the ductile iron.
In the invention, the sulfur-oxygen cerium inoculant is used as a second inoculant, and after the iron liquid is added, Ce and Ca react with the inoculant and residual S and O in the iron liquid to generate sulfide, oxide and sulfur-oxygen compound compounds. These compounds are more effective cores because of their good compatibility with graphite and their poor separation from the iron bath (small size, time lag of formation), including the SiO formed at this time2And SiO2Composite silicates formed from FeO, MnO are also effective substrates for graphite nucleation. In addition, Ce can also be combined with other harmful trace elements such as Ti, Pb, Bi and the like or form intermetallic compounds to inhibit the harmful effect. These factors are more significant for thick-walled ductile irons. The influence of the sulfur-cerium oxide inoculant on the mechanical performance is the comprehensive result of tissue improvement and the inhibition of the action of harmful elements.
The invention can utilize the self afterheat of the solidified casting to carry out the subsequent heat treatment on the casting, thereby saving energy, reducing cost and reducing environmental pollution.
The concept and the technical effects of the present invention will be further explained with reference to the embodiments below to fully understand the objects, features and effects of the present invention.
Detailed Description
Example 1
The manufacturing process of the as-cast high-strength ductile iron in the embodiment specifically comprises the following steps and process parameters:
step (1): preparing metal furnace burden comprising low-phosphorus low-sulfur pig iron, return iron and scrap steel, wherein the weight percentage of the return iron to the pig iron is 20 percent, the weight percentage of the return iron to the scrap steel is 35 percent, and the weight percentage of the scrap steel to the return iron to the scrap steel is 35 percent; smelting the prepared metal furnace charge by adopting a medium-frequency induction furnace, adding a carburant with the weight ratio of 2.7% of the metal furnace charge into the lower part of the furnace together with the metal furnace charge, carrying out carburant treatment on a layer of metal furnace charge and a layer of carburant, carrying out carburant treatment by using a high-temperature carburant, carrying out high-temperature treatment before the carburant is used, wherein the carburant comprises the components with the carbon content of more than or equal to 99.5% and the sulfur content of less than or equal to 0.01%, controlling the smelting temperature to 1450 ℃, detecting the content of each element in molten iron after the molten iron is completely melted, adjusting the content of each element to meet the requirement of a formula, and then carrying out nitrogen;
step (2): spheroidizing the product, wherein the adding amount of a spheroidizing agent is 0.9 percent of the weight of the treated molten iron, the spheroidizing agent with the particle size of 5-30mm is poured into a spheroidizing bag and compacted, a first inoculant with the particle size of 5-10mm is uniformly covered on the spheroidizing bag, 0.4 percent of the total weight of the molten iron is selected as the first inoculant, three quarters of the total weight of the molten iron is flushed into the spheroidizing bag, after the spheroidizing and the first inoculation are finished, one quarter of the total weight of the molten iron is flushed, a second inoculant with the weight of 0.2 percent of the total weight of the molten iron is flushed along with the flow to finish the second inoculation, the second inoculant is selected as a cerium oxysulfide inoculant with the particle size of 0.2-0.8mm, and the components of the second inoculant are as follows by mass percent: 70% of Si, 0.75% of Ca, 0.75% of Al, 1.5% of Ce and the balance of S, O;
and (3): casting and molding by using an iron mold sand-coated casting process, pouring molten iron with the temperature of not less than 1400 ℃ into a metal mold with an inner cavity coated with a layer of molding sand by adopting a rapid pouring process, wherein the pouring speed of the molten iron is not less than 6.5Kg/sec, after the pouring is finished, performing heat treatment by utilizing self-preheating of a casting, preserving heat at 920 ℃ for 5 hours, then cooling to 700 ℃ and preserving heat for 36 hours, and finally taking out of the furnace at the temperature of below 600 ℃ for air cooling to room temperature.
Example 2
The manufacturing process of the as-cast high-strength ductile iron in the embodiment specifically comprises the following steps and process parameters:
step (1): preparing metal furnace materials including low-phosphorus low-sulfur pig iron, return iron and scrap steel, wherein the weight percentages of the return iron, the return iron and the scrap steel are 30 percent of the pig iron, 25 percent of the return iron and 45 percent of the scrap steel; smelting the prepared metal furnace charge by adopting a medium-frequency induction furnace, adding a metallurgical silicon carbide pretreating agent accounting for 0.15 percent of the weight of the molten iron into the molten iron after smelting, uniformly stirring at low frequency, taking a carburant accounting for 3.3 percent of the weight of the metal furnace charge, adding the carburant and the metal furnace charge into the lower part of the electric furnace, carrying out carburant treatment on one layer of metal furnace charge and one layer of carburant, carrying out carburant treatment on one layer of metal furnace charge, carrying out high-temperature treatment before the carburant is used, controlling the component of the carburant to require that the carbon content is more than or equal to 99.5 percent and the sulfur content is less than or equal to 0.01 percent, controlling the smelting temperature to 1520 ℃, detecting the content of each element in the molten iron after the carburant is completely melted, adjusting the;
step (2): spheroidizing the product, wherein the adding amount of a spheroidizing agent is 1.3 percent of the weight of the treated molten iron, the spheroidizing agent with the particle size of 5-30mm is poured into a spheroidizing bag and compacted, a first inoculant with the particle size of 5-10mm is uniformly covered on the spheroidizing bag, the first inoculant is 0.6 percent of the total weight of the molten iron, three quarters of the total weight of the molten iron is flushed into the spheroidizing bag, after the spheroidizing and the first inoculation are finished, one quarter of the total weight of the molten iron is flushed, a second inoculant with the particle size of 0.4 percent of the total weight of the molten iron is flushed along with the flow to finish the second inoculation, the second inoculant is a cerium oxysulfide inoculant with the particle size of 0.2-0.8mm, and the components of the second inoculant are as follows by mass percent: 76% of Si, 1.25% of Ca, 1.25% of Al, 2.0% of Ce and the balance of S, O;
and (3): casting and molding by using an iron mold sand-coated casting process, pouring molten iron with the temperature of not less than 1400 ℃ into a metal mold with an inner cavity coated with a layer of molding sand by adopting a rapid pouring process, wherein the pouring speed of the molten iron is not less than 6.5Kg/sec, after the pouring is finished, performing heat treatment by utilizing self-preheating of a casting, preserving heat at 980 ℃ for 2 hours, then cooling to 750 ℃ and preserving heat for 36 hours, and finally taking out of the furnace at the temperature of below 600 ℃ for air cooling to room temperature.
Example 3
The manufacturing process of the as-cast high-strength ductile iron in the embodiment specifically comprises the following steps and process parameters:
step (1): preparing metal furnace materials including low-phosphorus low-sulfur pig iron, return iron and scrap steel, wherein the weight percentage of the return iron to the pig iron is 25 percent, the weight percentage of the return iron to the scrap steel is 30 percent, and the weight percentage of the scrap steel to the return iron to the scrap steel is 45 percent; smelting the prepared metal furnace charge by adopting a medium-frequency induction furnace, adding a metallurgical silicon carbide pretreating agent accounting for 0.15 percent of the weight of the molten iron into the molten iron after smelting, uniformly stirring at low frequency, taking a carburant accounting for 3.0 percent of the weight of the metal furnace charge, adding the carburant and the metal furnace charge into the lower part of the electric furnace, carrying out carburant treatment on one layer of metal furnace charge and one layer of carburant, carrying out carburant treatment on one layer of metal furnace charge, carrying out high-temperature treatment before the carburant is used, controlling the component of the carburant to require that the carbon content is more than or equal to 99.5 percent and the sulfur content is less than or equal to 0.01 percent, controlling the smelting temperature to 1500 ℃, detecting the content of each element in the molten iron after all the components are melted, adjusting the content of;
step (2): spheroidizing the product, wherein the adding amount of a spheroidizing agent is 1.0 percent of the weight of treated molten iron, the spheroidizing agent with the particle size of 5-30mm is poured into a spheroidizing bag and compacted, a first inoculant with the particle size of 5-10mm is uniformly covered on the spheroidizing bag, 0.5 percent of the total weight of the molten iron is selected as the first inoculant, three quarters of the total weight of the molten iron is flushed into the spheroidizing bag, after the spheroidizing treatment and the first inoculation treatment are finished, one quarter of the total weight of the molten iron is flushed, a second inoculant with the weight of 0.3 percent of the total weight of the molten iron is flushed along with the flow to finish the second inoculation treatment, the second inoculant is selected as cerium oxysulfide inoculant with the particle size of 0.2-0.8mm, and the components of the second inoculant are as follows by mass percent: 75% of Si, 0.95% of Ca, 1.15% of Al, 1.6% of Ce and the balance of S, O;
and (3): the casting molding is carried out by using an iron mold sand-coated casting process, a rapid casting process is adopted, molten iron with the temperature not lower than 1400 ℃ is poured into a metal mold with an inner cavity coated with a layer of molding sand, the pouring speed of the molten iron is not less than 6.5Kg/sec, air entraining is adopted in the pouring process, an ignition tool with the length more than 3 meters is adopted in the air entraining, after the pouring is finished, the self-preheating of a casting is utilized for carrying out heat treatment, the heat preservation is carried out for 4 hours at 950 ℃, then the temperature is reduced to 720 ℃ and is kept for 36 hours, and finally the casting is taken out of the furnace and cooled to the room temperature.
Example 4
The manufacturing process of the as-cast high-strength ductile iron in the embodiment specifically comprises the following steps and process parameters:
step (1): preparing metal furnace charge, including low-phosphorus low-sulfur pig iron, return iron and scrap steel, wherein the weight percentages of the pig iron, the return iron and the scrap steel are 30 percent, 30 percent and 40 percent; smelting the prepared metal furnace charge by adopting a medium-frequency induction furnace, adding a metallurgical silicon carbide pretreating agent accounting for 0.15 percent of the weight of the molten iron into the molten iron after smelting, uniformly stirring at low frequency, taking a carburant accounting for 3.0 percent of the weight of the metal furnace charge, adding the carburant and the metal furnace charge into the lower part of the electric furnace, carrying out carburant treatment on one layer of metal furnace charge and one layer of carburant, carrying out carburant treatment on one layer of metal furnace charge, carrying out high-temperature treatment before the carburant is used, controlling the component of the carburant to require that the carbon content is more than or equal to 99.5 percent and the sulfur content is less than or equal to 0.01 percent, controlling the smelting temperature to 1450 ℃, detecting the content of each element in the molten iron after the carburant is completely melted, adjusting the;
step (2): spheroidizing the product, wherein the adding amount of a spheroidizing agent is 1.2 percent of the weight of the treated molten iron, the spheroidizing agent with the particle size of 5-30mm is poured into a spheroidizing bag and compacted, a first inoculant with the particle size of 5-10mm is uniformly covered on the spheroidizing bag, 0.4 percent of the total weight of the molten iron is selected as the first inoculant, three quarters of the total weight of the molten iron is flushed into the spheroidizing bag, after the spheroidizing and the first inoculation are finished, one quarter of the total weight of the molten iron is flushed, a second inoculant with the weight of 0.4 percent of the total weight of the molten iron is flushed along with the flow to finish the second inoculation, the second inoculant is selected as a cerium oxysulfide inoculant with the particle size of 0.2-0.8mm, and the components of the second inoculant are as follows by mass percent: 72% of Si, 1.05% of Ca, 0.95% of Al, 1.9% of Ce and the balance of S, O;
and (3): the casting molding is carried out by using an iron mold sand-coated casting process, a rapid casting process is adopted, molten iron with the temperature not lower than 1400 ℃ is poured into a metal mold with an inner cavity coated with a layer of molding sand, the pouring speed of the molten iron is not less than 6.5Kg/sec, air entraining is adopted in the pouring process, an ignition tool with the length more than 3 meters is adopted in the air entraining, after the pouring is finished, the self-preheating of a casting is utilized for carrying out heat treatment, the heat preservation is carried out for 2 hours at 980 ℃, then the temperature is reduced to 700 ℃ for 36 hours, and finally the casting is taken out of the furnace and cooled to the room temperature at the temperature.
Example 5
The manufacturing process of the as-cast high-strength ductile iron in the embodiment specifically comprises the following steps and process parameters:
step (1): preparing metal furnace materials including low-phosphorus low-sulfur pig iron, return iron and scrap steel, wherein the weight percentages of the pig iron, the return iron and the scrap steel are 30 percent, 35 percent and 35 percent; smelting the prepared metal furnace charge by adopting a medium-frequency induction furnace, adding a metallurgical silicon carbide pretreating agent accounting for 0.15 percent of the weight of the molten iron into the molten iron after smelting, uniformly stirring at low frequency, taking a carburant accounting for 3.0 percent of the weight of the metal furnace charge, adding the carburant and the metal furnace charge into the lower part of the electric furnace, carrying out carburant treatment on one layer of metal furnace charge and one layer of carburant, carrying out carburant treatment on one layer of metal furnace charge, carrying out high-temperature treatment before the carburant is used, controlling the component of the carburant to require that the carbon content is more than or equal to 99.5 percent and the sulfur content is less than or equal to 0.01 percent, controlling the smelting temperature to 1520 ℃, detecting the content of each element in the molten iron after the carburant is completely melted, adjusting the;
step (2): spheroidizing the product, wherein the adding amount of a spheroidizing agent is 1.2 percent of the weight of the treated molten iron, the spheroidizing agent with the particle size of 5-30mm is poured into a spheroidizing bag and compacted, a first inoculant with the particle size of 5-10mm is uniformly covered on the spheroidizing bag, the first inoculant is 0.6 percent of the total weight of the molten iron, three quarters of the total weight of the molten iron is flushed into the spheroidizing bag, after the spheroidizing and the first inoculation are finished, one quarter of the total weight of the molten iron is flushed, a second inoculant with the particle size of 0.3 percent of the total weight of the molten iron is flushed along with the flow to finish the second inoculation, the second inoculant is a cerium oxysulfide inoculant with the particle size of 0.2-0.8mm, and the components of the second inoculant are as follows by mass percent: 70% of Si, 0.90% of Ca, 0.85% of Al, 1.6% of Ce and the balance of S, O;
and (3): the casting molding is carried out by using an iron mold sand-coated casting process, a rapid casting process is adopted, molten iron with the temperature not lower than 1400 ℃ is poured into a metal mold with an inner cavity coated with a layer of molding sand, the pouring speed of the molten iron is not less than 6.5Kg/sec, air entraining is adopted in the pouring process, an ignition tool with the length more than 3 meters is adopted in the air entraining, after the pouring is finished, the self-preheating of a casting is utilized for carrying out heat treatment, the heat preservation is carried out for 3 hours at 950 ℃, then the temperature is reduced to 720 ℃ and is kept for 36 hours, and finally the casting is taken out of the furnace and cooled to the room temperature.
The samples obtained according to the above example under the designation QT600-3 were tested for the main elements and for the mechanical properties such as tensile strength, elongation and hardness, and the test results are given in the following table.
From the viewpoint of mechanical properties, the sample of example 5 is optimal, and the product prepared according to the process parameters of example 5 and the conventional process is compared, and the results are shown in the following table.
Through comparison test and detection, the strength and hardness of the newly developed process exceed those of the old process, and the heat treatment process is omitted, so that the coal and electricity are saved, the consumption is reduced, the production cost is reduced, and the heat treatment process has zero pollution.
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.
Claims (8)
1. The manufacturing process of the as-cast high-strength ductile iron is characterized by comprising the following steps of:
step (1): preparing metal furnace charge, including low-phosphorus low-sulfur pig iron, return iron and scrap steel, according to the weight percentage, 20-30% of pig iron, 25-35% of return iron and 35-45% of scrap steel; smelting the prepared metal furnace charge by adopting a medium-frequency induction furnace, adding a carburant with the weight ratio of 2.7-3.3% of the metal furnace charge into the lower middle part of the furnace together with the metal furnace charge, carrying out carburant treatment on a layer of metal furnace charge and a layer of carburant, controlling the smelting temperature to 1450-;
step (2): spheroidizing the product, wherein the adding amount of a nodulizer is 0.9-1.3% of the weight of treated molten iron, the nodulizer is poured into a spheroidizing bag and compacted, a first inoculant which is 0.4-0.6% of the total weight of the molten iron is uniformly covered on the spheroidizing bag, 75SiFe inoculant is selected as the first inoculant, three quarters of the total weight of the molten iron is flushed into the spheroidizing bag, after the spheroidizing and the first inoculation are finished, one quarter of the total weight of the molten iron is flushed, a second inoculant which is 0.2-0.4% of the total weight of the molten iron is flushed along with flow to finish the second inoculation, the second inoculant is selected as cerium oxysulfide inoculant, and the used second inoculant comprises the following components in percentage by mass: si 70-76%, Ca 0.75-1.25%, Al 0.75-1.25%, Ce 1.5-2.0%, and the balance S, O;
and (3): and (2) performing casting molding by using an iron mold sand-coated casting process, pouring molten iron with the temperature not lower than 1400 ℃ into a metal mold with an inner cavity coated with a layer of molding sand, and performing heat treatment by using the self waste heat of the casting until the temperature is room temperature after the pouring is finished.
2. The process for manufacturing as-cast high-strength ductile iron according to claim 1, wherein the metallurgical silicon carbide pretreating agent is added to the molten iron in an amount of 0.15% by weight of the molten iron after the melting in the step (1), and the mixture is stirred uniformly at a low frequency.
3. The process for producing as-cast high-strength ductile iron according to claim 1, wherein the nodulizer used in step (2) has a particle size of 5 to 30mm, the first inoculant has a particle size of 5 to 10mm, and the second inoculant has a particle size of 0.2 to 0.8 mm.
4. The process for manufacturing as-cast high-strength ductile iron according to claim 1, wherein the molten iron in the step (3) is poured by a rapid pouring process at a pouring speed of the molten iron of 6.5Kg/sec or more.
5. The process for manufacturing as-cast high-strength ductile iron according to claim 4, wherein the molten iron casting in the step (3) adopts an open casting system, air entraining is adopted in the casting process, and an ignition tool with a length of more than 3 meters is adopted in the air entraining.
6. The process for manufacturing as-cast high-strength ductile iron according to claim 1, wherein the process control conditions for the heat treatment using the residual heat of the casting itself in the step (3) are: keeping the temperature at 920-.
7. The ductile iron obtained by the process for manufacturing as-cast high-strength ductile iron according to any one of claims 1 to 6, wherein the ductile iron comprises the following main element components in percentage by mass: 3.5 to 3.8 percent of C, 2.0 to 2.5 percent of Si, 0.31 to 0.38 percent of Mn, 0.035 to 0.05 percent of Ce0.045, 0.06 percent of Mg, less than or equal to 0.04 percent of P, less than or equal to 0.018 percent of S, and the balance of Fe.
8. The ductile iron according to claim 7, wherein the ductile iron comprises the following main element components in percentage by mass: 3.8 percent of C, 2.0 percent of Si, 0.35 percent of Mn, 0.04 percent of Ce, 0.05 percent of Mg, less than or equal to 0.04 percent of P, less than or equal to 0.018 percent of S and the balance of Fe.
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| CN201810718037.6A CN108707813B (en) | 2018-07-03 | 2018-07-03 | As-cast high-strength ductile iron and its manufacturing process |
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| CN110394427A (en) * | 2019-08-28 | 2019-11-01 | 安徽普瑞明精密机械有限公司 | The preparation process of cold shut defect is prevented in a kind of production of ductile cast iron manhole cover |
| CN111020361A (en) * | 2019-12-31 | 2020-04-17 | 邢台戈兰厨具有限公司 | Nodular cast iron cooker and production method thereof |
| CN114807490B (en) * | 2022-04-22 | 2024-06-04 | 武汉武重铸锻有限公司 | Spheroidizing inoculation treatment method for large-scale wind power casting |
| CN117259672A (en) * | 2023-09-28 | 2023-12-22 | 丹东市隆盛铸造有限公司 | Production process of low-grade ball-milling cast iron |
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| CN102102136B (en) * | 2011-03-07 | 2013-03-20 | 衡阳中钢衡重铸锻有限公司 | Production method of cast high-toughness ferrite nodular iron |
| CN102660657A (en) * | 2012-05-10 | 2012-09-12 | 常熟市千斤顶铸造有限公司 | Low-cost production process for as-cast high-elongation nodular cast iron |
| CN102690986B (en) * | 2012-05-25 | 2013-09-11 | 南车戚墅堰机车车辆工艺研究所有限公司 | Smelting method for medium-thin wall cast-state nickel-free low-temperature ductile cast iron |
| CN103215488B (en) * | 2013-04-26 | 2015-04-22 | 四川省宜宾普什铸造有限公司 | Method for integrally casting large-sized V-shaped diesel engine body by utilizing nodular cast iron |
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