CN115537643A - Preparation method and system for stably producing low-temperature impact nodular cast iron in cast state - Google Patents
Preparation method and system for stably producing low-temperature impact nodular cast iron in cast state Download PDFInfo
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- CN115537643A CN115537643A CN202211269726.6A CN202211269726A CN115537643A CN 115537643 A CN115537643 A CN 115537643A CN 202211269726 A CN202211269726 A CN 202211269726A CN 115537643 A CN115537643 A CN 115537643A
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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
- C22C33/12—Making cast-iron alloys including procedures for adding magnesium by fluidised injection
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- 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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C37/00—Cast-iron alloys
- C22C37/04—Cast-iron alloys containing spheroidal graphite
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Abstract
The invention relates to the technical field of production and manufacturing of low-temperature impact nodular cast iron, in particular to a preparation method and a system for stably producing the low-temperature impact nodular cast iron in an as-cast state, which comprises the following steps: step 1: proportioning the raw material components through furnace burden; step 2: fully mixing the proportioned raw material components; and 3, step 3: smelting the mixed raw material components; and 4, step 4: adding a nodulizer and a plurality of inoculants in the smelting treatment process to complete multiple-effect inoculation treatment; and 5, step 5: taking out of the furnace after passing the metallographic phase inspection, and casting and molding the obtained as-cast low-temperature ductile iron; and 6, a step of: carrying out comprehensive cooling; and 7, step 7: and after cooling treatment is finished, opening the box, shakeout and cleaning to obtain the nodular cast iron casting. The preparation method realizes the stable production of the product by adopting high-quality raw materials and high-efficiency nodulizing agent, and by means of four-time combined inoculation in multi-effect inoculation treatment, control of the casting shakeout time and temperature and other detailed level-to-level technical matters.
Description
Technical Field
The invention relates to the technical field of production and manufacturing of low-temperature impact nodular cast iron, in particular to a novel technology and a novel mechanical system capable of quickly completing efficient preparation of low-temperature impact nodular cast iron in an as-cast state, and especially relates to a preparation method and a system for stably producing low-temperature impact nodular cast iron in the as-cast state.
Background
With the gradual improvement of wind power generation technology, wind power generation by means of self advantages of cleanness and environmental protection is greatly developed. The wind power generation equipment is used in areas with variable environments, so the use environment is severe. As an output shell, a hub, a bearing support and the like of a core casting of wind power equipment, the mechanical performance requirements of the output shell, the hub, the bearing support and the like are higher and higher. Particularly in alpine regions, the requirement on the low-temperature impact performance of castings is particularly important.
In order to meet the requirement of the impact property of the nodular cast iron, more than 95 percent of ferrite matrix and 85 percent of nodularity are two important conditions.
In the as-cast state, the casting is fast in cooling speed, so that the formation and precipitation of graphite and ferrite are not facilitated; the smelting, the composition, the spheroidizing inoculation and the like of the molten iron of the added casting are not scientifically controlled, and the low-temperature impact property of the casting under the casting state condition can not meet the use requirement.
In the prior art, in order to meet the requirement, the casting needs to be subjected to graphitization annealing treatment, so that pearlite of the casting is decomposed to form ferrite and graphite, and the nodular cast iron casting reaches more than 95% of a ferrite matrix. For example, patent document CN201210395218.2 discloses a preparation method of low-temperature-resistant and corrosion-resistant wind-power nodular cast iron, which comprises the following steps: smelting molten iron: firstly, weighing Q10 pig iron and scrap steel according to the mass parts of the Q10 pig iron and the scrap steel of 60-80 and 20-40, and then, according to the mass ratio of the carburant for the ball-milling cast iron to the total mass of the Q10 pig iron and the scrap steel of (3-5): 100, according to the mass ratio of the nickel plate to the total mass of Q10 pig iron and scrap steel, which is (1-1.5): 100, weighing a carburant and a nickel plate for nodular cast iron, then adding the weighed Q10 pig iron, scrap steel, carburant and nickel plate for nodular cast iron into a medium frequency furnace, heating to 1500-1550 ℃, standing for 2-4min, and discharging to obtain iron liquid; spheroidizing and inoculating to obtain the low-temperature-resistant corrosion-resistant wind power nodular cast iron before heat treatment; annealing heat treatment: and (3) loading the low-temperature-resistant corrosion-resistant wind power nodular cast iron obtained in the step (II) before heat treatment into a heat treatment furnace for graphitization annealing, wherein the graphitization annealing process comprises the following steps: firstly, heating the furnace to 920-940 ℃, preserving heat for 2-3h, then cooling the furnace to 730-750 ℃, preserving heat for 2-3h, discharging the furnace for air cooling when the furnace is cooled to 600 ℃, and finishing heat treatment to obtain the low-temperature-resistant and corrosion-resistant wind power nodular cast iron.
However, this way of spheroidizing annealing treatment of nodular cast iron causes the following problems in practical operation: firstly, the environment is polluted and the energy is wasted; and secondly, the production period of the low-temperature impact nodular cast iron casting is prolonged, and the production efficiency of the nodular cast iron casting is reduced.
Therefore, the invention provides a preparation method capable of stably producing low-temperature impact nodular cast iron in an as-cast state, which utilizes multi-effect inoculation treatment to improve the mechanical property and refine grains in the as-cast state to obtain a finer structure of the grains, does not need a subsequent heat treatment mode, can meet the low-temperature impact property requirement of minus 20 ℃ in the as-cast state, simultaneously meets other mechanical property requirements, does not need additional heat treatment, and can effectively solve the problems in the prior art.
Disclosure of Invention
In order to solve one of the technical problems, the invention adopts the technical scheme that: the preparation method for stably producing the low-temperature impact nodular cast iron in an as-cast state comprises the following steps:
step 1: proportioning raw material components of the low-temperature impact nodular cast iron by furnace burden;
adding domestic benxi pig iron, high-quality low-manganese stamping waste steel materials and special returning charge into a medium-frequency induction electric furnace; wherein, the weight proportion of the domestic original stream pig iron, the high-quality low-manganese stamping waste steel material and the foundry returns is 40%:40%:20 percent to reduce the introduction of excessive Sn, cr, ti and V impurity elements;
step 2: fully mixing the proportioned raw material components;
and 3, step 3: smelting the mixed raw material components;
smelting at 1440-1490 ℃ and melting the iron raw material into molten iron, and after the melting is finished, determining the components of the molten base iron by using a spectrometer, a stokehole carbon-silicon instrument and a laboratory carbon-sulfur instrument;
and 4, step 4: adding a nodulizer and a plurality of inoculants in the smelting process, completing multi-effect inoculation by using a low-temperature impact nodular cast iron production system, refining grains after treatment, obtaining as-cast low-temperature nodular cast iron, sampling the obtained as-cast low-temperature nodular cast iron, and performing metallographic examination;
and 5, step 5: taking out of the furnace after passing the metallographic phase inspection, and casting and molding the obtained as-cast low-temperature ductile iron;
and 6, a step of: carrying out comprehensive cooling, wherein the cooling treatment time is 3-4 hours;
and 7, step 7: after cooling treatment is finished, opening the box, shakeout and cleaning to obtain a nodular cast iron casting;
the temperature of the casting opening and the sand falling is stably controlled below 600 ℃.
In any of the above embodiments, preferably, after the molten iron is melted, the low-sulfur and low-nitrogen graphite-type recarburizing agent is added, and the silicon carbide is added in a ratio of 10 kg/ton of molten iron.
In any of the above schemes, preferably, the low-temperature impact nodular cast iron comprises the following raw material components in percentage by mass: c content: 3.55-3.75%, si content: 1.90-2.15%, mn content: 0.25-0.35%, residual Mg content: 0.03-0.05%, P content less than 0.03%, S content less than 0.015%, cu content: less than or equal to 0.08 percent, less than or equal to 0.01 percent of Sn, less than or equal to 0.06 percent of Cr, less than or equal to 0.025 percent of Ti, and the balance of Fe.
In any of the above schemes, preferably, the ingredients of the molten iron in the low-temperature impact nodular cast iron are high-purity pig iron and high-purity scrap steel to reduce the introduction of impurity elements.
In any of the above embodiments, it is preferable that the nodulizing agent is added by a spheroidizing method using a punch method.
In any of the above schemes, preferably, after the casting is poured, the sand box is subjected to first and last box identification, the sand mold circulation speed is controlled, the shakeout time is controlled within 3-3.5 hours, the shakeout temperature of the casting is detected, and the shakeout temperature of the casting is stably controlled within 500-600 ℃.
In any of the above schemes, preferably, the specific steps of completing the multiple-effect inoculation treatment by using the low-temperature impact nodular cast iron production system comprise:
performing first inoculation:
before tapping molten iron, firstly adding 1.0-1.05% of 5-25mm efficient nodulizer by weight percent into a nodulizing chamber in a nodulizing ladle by using a low-temperature impact nodular cast iron production system, covering 0.3% of 3-8 ferrosilicon grain primary inoculant on the nodulizer, and then covering a layer of broken steel sheets on the nodulizing chamber to ensure stable nodulizing reaction;
and (3) performing secondary inoculation:
when the molten iron is transferred from a spheroidizing ladle to a pouring ladle, a low-temperature impact nodular cast iron production system is utilized, a pre-weighed secondary inoculant with the weight percentage of 0.5 percent is uniformly added along with the molten iron in a pouring state, the secondary inoculant adopts 1-3 high-efficiency silicon-calcium-barium inoculant, and Ga and Bi elements contained in the inoculant enable the molten iron to be fully inoculated and have the inoculation recession resistance;
casting the molten iron into a green sand mold at 1380-1400 ℃ after primary inoculation treatment;
and (3) performing third inoculation in the pouring process:
the production system of the low-temperature impact nodular cast iron is utilized to realize that 0.1 percent of 0.2-0.7mm rare earth bismuth silicon stream inoculant (tertiary inoculant) with weight percentage is uniformly added along with molten iron, the Bi element in the inoculant enables graphite spheres to be more round, the generation of special-shaped graphite is reduced, the nodularity is ensured, and the pouring temperature is controlled at 1380-1400 ℃;
fourth inoculation is carried out before sand mould assembling:
3-8 ferrosilicon grain inoculants (fourth inoculants) with the weight percentage of 0.05 percent are added into the grooves prefabricated in front of the filter screen by utilizing a low-temperature impact nodular cast iron production system, and inoculation treatment is carried out when molten iron is poured and filled, so that the molten iron is inoculated more fully, and the casting spheroidization rate is stabilized to be more than 85 percent.
The inoculation and spheroidization effects of the molten iron can be effectively ensured through four times of inoculation, the grain refinement is effectively completed, the casting performance is improved, the as-cast low-temperature ductile iron is obtained, the subsequent annealing heat treatment and shot blasting processes are effectively saved, and the process efficiency is improved.
The invention also provides a low-temperature impact nodular cast iron production system, which comprises a guide funnel matched with a pouring gate of a pouring ladle, wherein the outlet end of the guide funnel is in a horizontal shape, a pouring gas-injection mixed inoculant delivery pipe is installed on the outer side wall of the bottom of the outlet end of the guide funnel, a pouring inoculation fine particle delivery fan is connected to the pouring gas-injection mixed inoculant delivery pipe, the inlet end of the pouring gas-injection mixed inoculant delivery pipe is connected with a pouring inoculation fine spiral delivery device, the pouring inoculation fine particle delivery fan is used for ejecting three-time inoculant particles which are quantitatively delivered from the tail end of the pouring gas-mixed inoculant delivery pipe to a molten iron flow column in the pouring falling process and mixing the three-time inoculant particles with molten iron, the low-temperature impact nodular cast iron production system also comprises a multi-bin combined storage bin, a plurality of different types of inoculant particles are stored in the multi-bin combined storage bin, and the discharging pipes of the multi-bin combined pouring are respectively provided with the fine inoculation device, a primary gas-injection mixed inoculant delivery assembly, a secondary gas-mixed inoculant delivery assembly and a four-time mixed inoculant delivery assembly.
In any of the above aspects, it is preferred that the primary gas-mixed inoculant delivery assembly is used for dosing a primary inoculant into a nodulizing chamber in a nodulizing ladle before tapping molten iron;
the secondary gas-mixed inoculant conveying component is used for uniformly and quantitatively adding a secondary inoculant into the molten iron in a pouring state when the molten iron is transferred from a spheroidizing ladle to a pouring ladle;
the quartic gas-mixed inoculant conveying assembly is used for adding quartic inoculant into a groove prefabricated in front of a filter screen before a sand mould box.
The multi-bin combined bin comprises a main bin body, wherein four primary inoculant storage bins, a secondary inoculant storage bin, a tertiary inoculant storage bin and a quaternary inoculant storage bin are arranged in the main bin body side by side, and the bottom of each inoculant storage bin is connected with a corresponding primary inoculant outlet pipe, a corresponding secondary inoculant outlet pipe, a corresponding tertiary inoculant outlet pipe and a corresponding quaternary inoculant outlet pipe.
The primary gas-mixed inoculant conveying assembly comprises a primary gas-mixed inoculant conveying pipe, a primary inoculation fine spiral conveyor and a primary inoculation fine particle conveying fan are mounted on the primary gas-mixed inoculant conveying pipe, and the inlet end of the primary inoculation fine spiral conveyor is connected with a primary inoculant outlet pipe at the corresponding position of the multi-bin combined bin.
The secondary gas mixed inoculant conveying assembly comprises a secondary gas mixed inoculant conveying pipe, a secondary inoculation fine spiral conveyor and a secondary inoculation fine particle conveying fan are installed on the secondary gas mixed inoculant conveying pipe, and the inlet end of the secondary inoculation fine spiral conveyor is connected with a secondary inoculant outlet pipe at the corresponding position of the multi-bin combined bin.
The pouring gas injection mixed inoculant conveying pipe, the pouring inoculation fine spiral material conveyer and the pouring inoculation fine particle air conveying machine form a tertiary gas mixed inoculant conveying assembly, and the inlet end of the pouring inoculation fine spiral material conveyer is connected with the tail end of the tertiary inoculant outlet pipe.
The quartic gas-mixed inoculant conveying assembly comprises a quartic gas-mixed inoculant conveying pipe, a quartic inoculation fine spiral conveyor and a quartic inoculation fine particle conveying fan are mounted on the quartic gas-mixed inoculant conveying pipe, and the inlet end of the quartic inoculation fine spiral conveyor is connected with a quartic inoculant outlet pipe at the corresponding position of the multi-bin combined bin.
An electromagnetic material control valve is arranged at each inoculant outlet pipe.
Compared with the prior art, the invention has the following beneficial effects:
1. the preparation method for stably producing the low-temperature impact nodular cast iron in the as-cast state removes a subsequent heat treatment process, effectively reduces the production cost of castings, and reduces the extra electric energy loss (the cost is 450-500 yuan for processing one ton of low-temperature impact nodular cast iron castings, and the production cost is 450-500 yuan for each ton of castings due to the fact that a heat treatment link is cancelled).
2. Because the heat treatment link is cancelled, the corresponding heat treatment time and the work of removing the oxide skin by shot blasting are also cancelled correspondingly, the production period of the castings is effectively shortened, the production and turnover efficiency of the castings is improved, and the production period of the castings in each batch can be shortened by 2 working days.
3. The preparation method adopts high-quality raw materials and high-efficiency nodulizer, realizes stable production of products by means of four-time combined inoculation in multi-effect inoculation treatment and control of casting shakeout time and temperature and other details, ensures the graphite form of the low-temperature impact nodular cast iron and the ferrite content in a matrix, and further ensures the impact property and the mechanical property of the low-temperature impact nodular cast iron in an as-cast state.
Drawings
In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below. Throughout the drawings, like elements or components are generally identified by like reference numerals. In the drawings, elements or components are not necessarily drawn to scale.
FIG. 1 is a schematic diagram of the low temperature impact nodular cast iron production system of the present invention.
In the figure, 1, a material guide funnel; 2. pouring a gas-injection mixed inoculant delivery pipe; 3. casting and inoculating a fine particle conveying fan; 4. pouring and inoculating the fine spiral conveyer; 5. a multi-bin combined bin; 501. a main bin body; 502. storing a primary inoculant in a bin; 503. storing a secondary inoculant in a bin; 504. a third inoculant storage bin; 505. storing the inoculant for four times; 506. a primary inoculant outlet pipe; 507. a secondary inoculant outlet pipe; 508. a tertiary inoculant outlet pipe; 509. a quartic inoculant outlet pipe; 6. a primary air-mixed inoculant delivery pipe; 7. inoculating a fine spiral feeder for the first time; 8. inoculating fine particles at a first time and conveying the fine particles to a fan; 9. a secondary air-mixed inoculant delivery pipe; 10. secondarily inoculating a fine spiral feeder; 11. secondarily inoculating the fine particle conveying fan; 12. a fourth gas-mixed inoculant delivery pipe; 13. inoculating the fine spiral feeder for four times; 14. inoculating the fine particle conveying fan for four times; 15. electromagnetic material control valve.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby. The specific structure of the invention is shown in figure 1.
Example 1:
the preparation method for stably producing the low-temperature impact nodular cast iron in an as-cast state comprises the following steps:
step 1: proportioning raw material components of the low-temperature impact nodular cast iron by furnace burden;
adding domestic benxi pig iron, high-quality low-manganese stamping waste steel materials and special returning charge into a medium-frequency induction electric furnace; wherein the weight proportion of the domestic Benxi pig iron, the high-quality low-manganese stamping waste steel material and the foundry returns is 40%:40%:20 percent;
so as to reduce the introduction of excessive Sn, cr, ti and V impurity elements;
step 2: fully mixing the proportioned raw material components; the fully mixed raw material components can ensure that all the components can be fully fused with each other in the subsequent smelting, and the smelting effect is ensured;
and 3, step 3: smelting the mixed raw material components;
smelting at 1440-1490 ℃ and melting the iron raw material into molten iron, and after the melting is finished, determining the components of the molten base iron by using a spectrometer, a stokehole carbon-silicon instrument and a laboratory carbon-sulfur instrument;
and 4, step 4: adding a nodulizer and a plurality of inoculants in the smelting process, completing multi-effect inoculation by using a low-temperature impact nodular cast iron production system, refining grains after treatment, obtaining as-cast low-temperature nodular cast iron, sampling the obtained as-cast low-temperature nodular cast iron, and performing metallographic examination; the multi-effect inoculation treatment can realize the grain refinement of the cast low-temperature ductile iron, and effectively improve the structural toughness and various mechanical properties, so that the subsequent heat treatment annealing process can be effectively removed, and the operation efficiency of the whole process is improved;
and 5, step 5: taking the cast low-temperature ductile iron out of the furnace after passing metallographic phase inspection, and casting and molding the obtained cast low-temperature ductile iron;
and 6, step 6: carrying out comprehensive cooling, wherein the cooling treatment time is 3-4 hours;
and 7, step 7: after cooling treatment is finished, opening the box, shakeout and cleaning to obtain a nodular cast iron casting;
the temperature of the casting opening and the shakeout is stably controlled below 600 ℃. The stable production of the product is realized through four times of combined inoculation in the multi-effect inoculation treatment and the control of the casting sand falling time and temperature and other details, the graphite form of the low-temperature impact nodular cast iron and the content of ferrite in a matrix are ensured, and the impact performance and the mechanical performance of the low-temperature impact nodular cast iron in an as-cast state are ensured.
In any of the above embodiments, preferably, after the molten iron is melted, the low-sulfur and low-nitrogen graphite type recarburizing agent is added, and the silicon carbide is added in a ratio of 10 kg/ton of molten iron. Can effectively prevent air pollution, reduce the generation of harmful substances, refine the graphite grain diameter, increase the graphite ball number, effectively improve the mechanical property and homogenize the grains.
In any of the above schemes, preferably, the low-temperature impact nodular cast iron comprises the following raw material components in percentage by mass: c content: 3.55-3.75%, si content: 1.90-2.15%, mn content: 0.25-0.35%, residual Mg content: 0.03-0.05%, P content less than 0.03%, S content less than 0.015%, cu content: less than or equal to 0.08 percent, less than or equal to 0.01 percent of Sn, less than or equal to 0.06 percent of Cr, less than or equal to 0.025 percent of Ti, and the balance of Fe.
In any of the above schemes, preferably, the ingredients of the molten iron in the low-temperature impact nodular cast iron are high-purity pig iron and high-purity scrap steel to reduce the introduction of impurity elements.
In any of the above embodiments, it is preferable that the nodulizing agent is added by a spheroidizing method of a pour-in method.
In any of the above schemes, preferably, after the casting is poured, the sand box is subjected to first and last box identification, the sand mold circulation speed is controlled, the shakeout time is controlled within 3-3.5 hours, the shakeout temperature of the casting is detected, and the shakeout temperature of the casting is stably controlled within 500-600 ℃.
The invention also provides a low-temperature impact nodular cast iron production system, which comprises a guide funnel 1 matched with a pouring gate of a pouring ladle, wherein the outlet end of the guide funnel 1 is horizontal, a pouring gas-injection mixed inoculant delivery pipe 2 is installed on the outer side wall of the bottom of the outlet end of the guide funnel 1, the pouring gas-injection mixed inoculant delivery pipe 2 is connected with a pouring fine inoculant delivery fan 3, the inlet end of the pouring gas-injection mixed inoculant delivery pipe 2 is connected with a pouring fine spiral inoculant delivery device 4, the pouring inoculant fine inoculant delivery fan 3 is used for injecting three inoculant particles which are quantitatively delivered from the tail end of the pouring gas-mixed inoculant delivery pipe 2 to a molten iron flow column in a pouring falling process discontinuously and mixing the three inoculant particles with the molten iron, the low-temperature impact nodular cast iron production system also comprises a multi-bin combined storage bin 5, a plurality of inoculant particles in the multi-bin combined storage bin 5 are respectively provided with the pouring fine spiral inoculant delivery device 4, a primary gas-mixed inoculant delivery component and a secondary gas-mixed inoculant delivery component.
The main function of the low-temperature impact nodular cast iron production system designed in the invention is to complete the relevant steps of multi-effect inoculation treatment in the production process.
In any of the above aspects, it is preferred that the primary air-mixed inoculant delivery assembly is used for dosing a primary inoculant into a nodulizing chamber in a nodulizing ladle before tapping molten iron;
the secondary gas-mixed inoculant conveying assembly is used for uniformly and quantitatively adding a secondary inoculant into the molten iron in a pouring state when the molten iron is transferred from the spheroidizing ladle to the pouring ladle;
the quartic air-mixed inoculant conveying assembly is used for adding quartic inoculant into a groove prefabricated in front of a filter screen before a sand mold box assembly.
Example 2:
the preparation method for stably producing the low-temperature impact nodular cast iron in the as-cast state comprises the following steps:
step 1: proportioning raw material components of the low-temperature impact nodular cast iron by furnace burden;
adding domestic benxi pig iron, high-quality low-manganese stamping waste steel materials and special returning charge into a medium-frequency induction electric furnace; wherein, the weight proportion of the domestic original stream pig iron, the high-quality low-manganese stamping waste steel material and the foundry returns is 40%:40%:20 percent;
so as to reduce the introduction of excessive Sn, cr, ti and V impurity elements;
step 2: fully mixing the proportioned raw material components;
the fully mixed raw material components can ensure that all the components can be fully fused with each other in the subsequent smelting, and the smelting effect can be ensured;
and 3, step 3: smelting the mixed raw material components;
smelting at 1440-1490 ℃ and melting the iron raw material into molten iron, and after the melting is finished, determining the components of the molten base iron by using a spectrometer, a stokehole carbon-silicon instrument and a laboratory carbon-sulfur instrument;
according to the confirmation result, the molten iron composition is adjusted according to the following standard: c content: 3.55-3.85%, mn content: 0.25-0.35%, P content less than 0.03%, S content less than 0.015%, cu content: less than or equal to 0.08 percent, less than or equal to 0.01 percent of Sn, less than or equal to 0.06 percent of Cr, less than or equal to 0.025 percent of Ti, standing at the high temperature of between 150 and 1540 ℃ after the components are qualified, and performing qualification detection on the white mouth tendency of the base iron;
and 4, step 4: adding a nodulizer and a plurality of inoculants in the smelting process, completing multi-effect inoculation by using a low-temperature impact nodular cast iron production system, refining grains after treatment, obtaining as-cast low-temperature nodular cast iron, sampling the obtained as-cast low-temperature nodular cast iron, and performing metallographic examination;
the multi-effect inoculation treatment can realize the grain refinement of the cast low-temperature ductile iron, and effectively improve the structure toughness and various mechanical properties, thereby effectively removing the subsequent heat treatment annealing process and improving the operation efficiency of the whole process;
and 5, step 5: taking out of the furnace after passing the metallographic phase inspection, and casting and molding the obtained as-cast low-temperature ductile iron;
and 6, step 6: carrying out comprehensive cooling, wherein the cooling treatment time is 3-4 hours;
and 7, step 7: after cooling treatment is finished, opening the box, shakeout and cleaning to obtain a nodular cast iron casting;
the temperature of the casting opening and the sand falling is stably controlled below 600 ℃.
The stable production of the product is realized by means of four-time combined inoculation in the multi-effect inoculation treatment and the control of the sand falling time and temperature of the casting, and the like, and the stable production of the product is realized, the graphite form of the low-temperature impact nodular cast iron and the ferrite content in the matrix are ensured, and the impact performance and the mechanical performance of the low-temperature impact nodular cast iron in an as-cast state are ensured.
In any of the above embodiments, preferably, after the molten iron is melted, the low-sulfur and low-nitrogen graphite-type recarburizing agent is added, and the silicon carbide is added in a ratio of 10 kg/ton of molten iron.
Can effectively prevent air pollution, reduce the generation of harmful substances, refine the graphite grain diameter, increase the graphite ball number, effectively improve the mechanical property and homogenize the grains.
In any of the above schemes, preferably, the low-temperature impact nodular cast iron comprises the following raw material components in percentage by mass: c content: 3.55-3.75%, si content: 1.90-2.15%, mn content: 0.25-0.35%, residual Mg content: 0.03-0.05%, P content less than 0.03%, S content less than 0.015%, cu content: less than or equal to 0.08 percent, less than or equal to 0.01 percent of Sn, less than or equal to 0.06 percent of Cr, less than or equal to 0.025 percent of Ti, and the balance of Fe.
In any of the above schemes, preferably, the molten iron in the low-temperature impact nodular cast iron is prepared from high-purity pig iron and high-purity scrap steel to reduce the introduction of impurity elements.
In any of the above embodiments, it is preferable that the nodulizing agent is added by a spheroidizing method using a punch method.
In any of the above schemes, preferably, after the casting is poured, the sand box is subjected to first and last box identification, the sand mold circulation speed is controlled, the shakeout time is controlled within 3-3.5 hours, the shakeout temperature of the casting is detected, and the shakeout temperature of the casting is stably controlled within 500-600 ℃.
In any of the above schemes, preferably, the specific steps of completing the multiple-effect inoculation treatment by using the low-temperature impact nodular cast iron production system comprise:
performing first inoculation:
before tapping molten iron, firstly adding 1.0-1.05% of 5-25mm efficient nodulizer by weight percent into a nodulizing chamber in a nodulizing ladle by using a low-temperature impact nodular cast iron production system, covering 0.3% of 3-8 ferrosilicon grain primary inoculant on the nodulizer, and then covering a layer of broken steel sheets on the nodulizing chamber to ensure stable nodulizing reaction;
and (3) performing secondary inoculation:
when the molten iron is transferred from a spheroidizing ladle to a pouring ladle, a low-temperature impact nodular cast iron production system is utilized, a pre-weighed secondary inoculant with the weight percentage of 0.5 percent is uniformly added along with the molten iron in a pouring state, the secondary inoculant adopts 1-3 high-efficiency silicon-calcium-barium inoculant, and Ga and Bi elements contained in the inoculant enable the molten iron to be fully inoculated and have the inoculation recession resistance;
pouring the molten iron into a green sand mold at 1380-1400 ℃ after primary inoculation treatment;
and (3) performing third inoculation in the pouring process:
the production system of the low-temperature impact nodular cast iron is utilized to realize that 0.1 percent of 0.2-0.7mm rare earth bismuth silicon stream inoculant (tertiary inoculant) with weight percentage is uniformly added along with molten iron, the Bi element in the inoculant enables graphite spheres to be more round, the generation of special-shaped graphite is reduced, the nodularity is ensured, and the pouring temperature is controlled at 1380-1400 ℃;
fourth inoculation is carried out before sand mould assembling:
3-8 ferrosilicon grain inoculants (fourth inoculants) with the weight percentage of 0.05 percent are added into the grooves prefabricated in front of the filter screen by utilizing a low-temperature impact nodular cast iron production system, and inoculation treatment is carried out when molten iron is poured and filled, so that the molten iron is inoculated more fully, and the casting spheroidization rate is stabilized to be more than 85 percent.
The inoculation and spheroidization effects of the molten iron can be effectively ensured through four times of inoculation, the grain refinement is effectively completed, the casting performance is improved, the as-cast low-temperature ductile iron is obtained, the subsequent annealing heat treatment and shot blasting processes are effectively saved, and the process efficiency is improved.
The invention effectively achieves the purposes of improving the internal grain refinement of the as-cast casting, effectively improving the structural toughness and various mechanical properties of the as-cast casting, effectively removing the subsequent heat treatment annealing process and improving the operation efficiency of the whole process by utilizing a novel combined inoculation treatment mode of four times with different time periods.
The secondary inoculant is uniformly added into the molten iron in a pouring state during adding, so that the full contact of the inoculant and the molten iron can be better ensured, and the inoculant can better perform an inoculation effect after entering the molten iron; the mode that the tertiary inoculant is uniformly added along with the molten iron during adding can better ensure that the inoculant is fully contacted with the molten iron poured into the green sand mold, and can also ensure that the inoculant can better achieve the effect of tertiary inoculation after entering the molten iron.
Meanwhile, the fourth inoculation treatment is added in the sand box, so that the liquid casting in a molding state after pouring can be ensured to finish final inoculation before cooling, and the inoculation effect of the whole casting product in the casting state is further ensured.
The invention also provides a low-temperature impact nodular cast iron production system, which comprises a guide funnel 1 matched with a pouring gate of a pouring ladle, wherein the outlet end of the guide funnel 1 is horizontal, a pouring gas-injection mixed inoculant delivery pipe 2 is installed on the outer side wall of the bottom of the outlet end of the guide funnel 1, the pouring gas-injection mixed inoculant delivery pipe 2 is connected with a pouring fine inoculant delivery fan 3, the inlet end of the pouring gas-injection mixed inoculant delivery pipe 2 is connected with a pouring fine spiral inoculant delivery device 4, the pouring inoculant fine inoculant delivery fan 3 is used for injecting three inoculant particles which are quantitatively delivered from the tail end of the pouring gas-mixed inoculant delivery pipe 2 to a molten iron flow column in a pouring falling process discontinuously and mixing the three inoculant particles with the molten iron, the low-temperature impact nodular cast iron production system also comprises a multi-bin combined storage bin 5, a plurality of inoculant particles in the multi-bin combined storage bin 5 are respectively provided with the pouring fine spiral inoculant delivery device 4, a primary gas-mixed inoculant delivery component and a secondary gas-mixed inoculant delivery component.
The main function of the low-temperature impact nodular cast iron production system designed in the invention is to complete the relevant steps of multi-effect inoculation treatment in the production process.
In any of the above aspects, it is preferred that the primary air-mixed inoculant delivery assembly is used for dosing a primary inoculant into a nodulizing chamber in a nodulizing ladle before tapping molten iron;
the secondary gas-mixed inoculant conveying assembly is used for uniformly and quantitatively adding a secondary inoculant into the molten iron in a pouring state when the molten iron is transferred from the spheroidizing ladle to the pouring ladle;
the quartic gas-mixed inoculant conveying assembly is used for adding quartic inoculant into a groove prefabricated in front of a filter screen before a sand mould box.
The multi-bin combined bin 5 comprises a main bin body 501, four primary inoculant storage bins 502, a secondary inoculant storage bin 503, a tertiary inoculant storage bin 504 and a quaternary inoculant storage bin 505 which are arranged side by side are arranged in the main bin body 501, and the bottom of each inoculant storage bin is connected with a corresponding primary inoculant outlet pipe 506, a corresponding secondary inoculant outlet pipe 507, a corresponding tertiary inoculant outlet pipe 508 and a corresponding quaternary inoculant outlet pipe 509.
The primary gas-mixed inoculant conveying assembly comprises a primary gas-mixed inoculant conveying pipe 6, a primary inoculation fine spiral conveyor 7 and a primary inoculation fine particle conveying fan 8 are installed on the primary gas-mixed inoculant conveying pipe 6, and the inlet end of the primary inoculation fine spiral conveyor 7 is connected with a primary inoculant outlet pipe 506 at the corresponding position of the multi-bin combined bin 5.
The secondary gas mixed inoculant conveying assembly comprises a secondary gas mixed inoculant conveying pipe 9, a secondary inoculation fine spiral conveyor 10 and a secondary inoculation fine particle conveying fan 11 are installed on the secondary gas mixed inoculant conveying pipe 9, and the inlet end of the secondary inoculation fine spiral conveyor 10 is connected with a secondary inoculant outlet pipe 507 at the corresponding position of the multi-bin combined bin 5.
The pouring gas injection mixed inoculant conveying pipe 2, the pouring inoculation fine spiral conveyor 4 and the pouring inoculation fine particle conveying fan 3 form a tertiary gas mixed inoculant conveying assembly, and the inlet end of the pouring inoculation fine spiral conveyor 4 is connected with the tail end of the tertiary inoculant outlet pipe 508.
The quartic gas-mixed inoculant conveying component comprises a quartic gas-mixed inoculant conveying pipe 12, a quartic inoculation fine spiral conveyer 13 and a quartic inoculation fine particle conveying fan 14 are installed on the quartic gas-mixed inoculant conveying pipe 12, and the inlet end of the quartic inoculation fine spiral conveyer 13 is connected with a quartic inoculant outlet pipe 509 at the corresponding position of the multi-bin combined bin 5.
An electromagnetic material control valve 15 is arranged at each inoculant outlet pipe.
According to the invention, the multi-bin combined bin 5 is adopted to provide different quantitative types of inoculants for multi-effect inoculation, and the inoculants can be effectively quantitatively and fixedly conveyed according to the requirement through the primary gas-mixed inoculant conveying assembly, the secondary gas-mixed inoculant conveying assembly, the tertiary gas-mixed inoculant conveying assembly and the fourth gas-mixed inoculant conveying assembly, so that the aim of effectively matching the whole cast nodular cast iron production and preparation process to complete the multi-effect inoculation is finally achieved.
When the low-temperature impact nodular cast iron production system is used, enough inoculant particles of corresponding varieties are directly put into the four primary inoculant storage bins 502, the secondary inoculant storage bin 503, the tertiary inoculant storage bin 504 and the fourth inoculant storage bin 505 in sequence, and corresponding electromagnetic material control valves 15, corresponding conveying fans and fine spiral conveyers are directly opened when the inoculant needs to be added in each step, so that quantitative discharging can be realized by using the fine spiral conveyers, outward feeding and blowing are realized by using the fine particle conveying fans, and quantitative conveying of materials is completed.
By carrying out metallographic examination on the cast-state casting body sampling casting prepared by the method, the nodularity is stabilized to be more than 85%, the content of the molten iron in the matrix is more than 90%, and the requirements of low-temperature impact nodular cast iron are met. The cast-state casting body is sampled, the low-temperature impact (-20 +/-2 ℃) of the impact property of the V-shaped notch stably reaches more than 12J (average value), the hardness is 135-180HB, the tensile strength reaches more than 400MPa, the yield strength is more than 250MPa, the elongation is more than 18%, and the mechanical property requirement and the service performance requirement of the casting are met. The method can obtain the product with similar effect to that obtained by the conventional heat treatment mode in the cast state, and obtains good economic benefit.
The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; the modifications or the substitutions do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present invention, and the technical solutions are all covered in the scope of the claims and the specification of the present invention; it will be apparent to those skilled in the art that any alternative modifications or variations to the embodiments of the present invention may be made without departing from the scope of the invention.
The details of the present invention are not described in detail, but are known to those skilled in the art.
Claims (8)
1. The preparation method for stably producing the low-temperature impact nodular cast iron in the as-cast state is characterized by comprising the following steps: the method comprises the following steps:
step 1: proportioning raw material components of the low-temperature impact nodular cast iron by furnace burden;
adding domestic benxi pig iron, high-quality low-manganese stamping waste steel materials and special returning charge into a medium-frequency induction electric furnace; wherein, the weight proportion of the domestic original stream pig iron, the high-quality low-manganese stamping waste steel material and the foundry returns is 40%:40%:20 percent to reduce the introduction of excessive Sn, cr, ti and V impurity elements;
step 2: fully mixing the proportioned raw material components;
and 3, step 3: smelting the mixed raw material components;
smelting at 1440-1490 ℃ and melting the iron raw material into molten iron, and after the melting is finished, determining the components of the molten base iron by using a spectrometer, a stokehole carbon-silicon instrument and a laboratory carbon-sulfur instrument;
and 4, step 4: adding a nodulizer and various inoculants in the smelting treatment process, completing multi-effect inoculation treatment by using a low-temperature impact nodular cast iron production system, refining grains after treatment, obtaining as-cast low-temperature nodular cast iron, and performing metallographic examination after sampling the obtained as-cast low-temperature nodular cast iron;
and 5, step 5: taking out of the furnace after passing the metallographic phase inspection, and casting and molding the obtained as-cast low-temperature ductile iron;
and 6, step 6: carrying out comprehensive cooling, wherein the cooling treatment time is 3-4 hours;
and 7, step 7: after cooling treatment is finished, opening the box, shakeout and cleaning to obtain a nodular cast iron casting;
the temperature of the casting opening and the sand falling is stably controlled below 600 ℃.
2. The method for preparing low-temperature impact ductile iron according to claim 1, characterized in that: after molten iron is melted, adding the low-sulfur low-nitrogen graphite carburant, and adding silicon carbide according to the proportion of 10 kg/ton of molten iron.
3. The method for preparing low-temperature impact ductile iron according to claim 2, characterized in that: the low-temperature impact nodular cast iron comprises the following raw material components in percentage by mass: c content: 3.55-3.75%, si content: 1.90-2.15%, mn content: 0.25-0.35%, residual Mg content: 0.03-0.05%, P content less than 0.03%, S content less than 0.015%, cu content: less than or equal to 0.08 percent, less than or equal to 0.01 percent of Sn, less than or equal to 0.06 percent of Cr, less than or equal to 0.025 percent of Ti, and the balance of Fe.
4. The method for preparing low-temperature impact ductile iron according to claim 3, characterized by comprising the following steps: the molten iron in the low-temperature impact nodular cast iron is prepared from high-purity pig iron and high-purity scrap steel so as to reduce the introduction of impurity elements.
5. The method for preparing the low-temperature impact ductile iron stably produced in the as-cast state according to claim 4, wherein: wherein the nodulizer is added by adopting a nodulizing mode of a punching method.
6. The method for preparing low-temperature impact ductile iron according to claim 5, characterized by comprising the following steps: after casting is poured, marking the sand box by using a first box and a last box, controlling the circulation speed of the sand mould, ensuring that the shakeout time is controlled within 3-3.5 hours, detecting the shakeout temperature of the casting, and stably controlling the shakeout temperature of the casting to be 500-600 ℃.
7. Low temperature strikes nodular cast iron production system, its characterized in that: the low-temperature impact nodular cast iron production system is characterized by comprising a guide funnel matched with a pouring gate of a pouring ladle, wherein the outlet end of the guide funnel is horizontal, a pouring and gas-injecting mixed inoculant conveying pipe is arranged on the outer side wall of the bottom of the outlet end of the guide funnel, a pouring and gas-injecting mixed inoculant conveying pipe is connected with a pouring and inoculating fine particle conveying fan, the inlet end of the pouring and gas-injecting mixed inoculant conveying pipe is connected with a pouring and inoculating fine spiral feeder, the pouring and inoculating fine particle conveying fan is used for ejecting tertiary inoculant particles which are quantitatively conveyed from the tail end of the pouring and gas-mixing inoculant conveying pipe to a molten iron flow column in a pouring falling process in a discontinuous mode and mixing the tertiary inoculant particles with the molten iron, the low-temperature impact nodular cast iron production system further comprises a multi-bin combined material discharging pipe, the inside of the multi-bin combined material bin is used for storing various different types of inoculant particles, and the pouring and inoculating fine spiral feeder, a primary gas-mixing inoculant conveying assembly, a secondary gas-mixing inoculant conveying assembly and a quartic gas-mixing inoculant conveying assembly are respectively arranged at each position of the multi-bin combined material bin.
8. The low-temperature impact nodular cast iron production system of claim 7 wherein: the primary gas-mixed inoculant conveying assembly is used for quantitatively adding a primary inoculant into a spheroidizing chamber in a spheroidizing ladle before tapping molten iron;
the secondary gas-mixed inoculant conveying assembly is used for uniformly and quantitatively adding a secondary inoculant into the molten iron in a pouring state when the molten iron is transferred from the spheroidizing ladle to the pouring ladle;
the quartic gas-mixed inoculant conveying assembly is used for adding quartic inoculant into a groove prefabricated in front of a filter screen before a sand mould box.
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| JPH10317093A (en) * | 1997-05-19 | 1998-12-02 | Toyota Motor Corp | High rigidity spheroidal graphite cast iron and its production |
| US20180148805A1 (en) * | 2015-05-18 | 2018-05-31 | Toshiba Kikai Kabushiki Kaisha | Method for treating molten cast iron |
| CN110592466A (en) * | 2019-10-23 | 2019-12-20 | 淄博乾能铸造科技股份有限公司 | Production method of as-cast low-temperature ductile iron |
| CN112404369A (en) * | 2020-10-27 | 2021-02-26 | 宜昌船舶柴油机有限公司 | Argon blowing stream inoculation device and method for large nodular cast iron cylinder |
| CN113523205A (en) * | 2021-07-06 | 2021-10-22 | 武汉武重铸锻有限公司 | Novel spheroidizing inoculation treatment method |
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| JPH10317093A (en) * | 1997-05-19 | 1998-12-02 | Toyota Motor Corp | High rigidity spheroidal graphite cast iron and its production |
| US20180148805A1 (en) * | 2015-05-18 | 2018-05-31 | Toshiba Kikai Kabushiki Kaisha | Method for treating molten cast iron |
| CN110592466A (en) * | 2019-10-23 | 2019-12-20 | 淄博乾能铸造科技股份有限公司 | Production method of as-cast low-temperature ductile iron |
| CN112404369A (en) * | 2020-10-27 | 2021-02-26 | 宜昌船舶柴油机有限公司 | Argon blowing stream inoculation device and method for large nodular cast iron cylinder |
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