Production method of green sand as-cast high-plasticity nodular cast iron QT800-5

Abstract

The invention relates to the field of metal material casting, and discloses a production method of green sand as-cast high-plasticity nodular cast iron QT800-5, which comprises the following steps: preparing pig iron, waste steel and foundry returns, and using auxiliary materials such as a silicon carbide pretreating agent, a high-temperature graphitization carburant, a rare earth magnesium silicon iron nodulizing agent, a silicon barium nucleating agent and a silicon strontium nucleating agent to prepare the green sand as-cast high-plasticity nodular cast iron QT800-5. The purity and component stability of molten iron are ensured; in the smelting process, purification and adjustment are carried out through temperature control and segmented addition of auxiliary materials, then spheroidizing is carried out through a pouring method, and the microscopic structure of a casting is optimized through ladle-to-ladle inoculation and stream inoculation; the final casting has excellent mechanical properties including the tensile strength larger than or equal to 800 MPa, the yield strength larger than or equal to 480 MPa, the elongation larger than or equal to 5% and the matrix pearlite content larger than or equal to 80%. The production process disclosed by the invention is simplified, is suitable for large-scale industrial production, and has a wide application prospect in lightweight application requiring high-strength and high-plasticity materials.

Description

Technical Field

[0001] The invention relates to the technical field of metal material casting, in particular to a production method of green sand cast high-plasticity ductile iron QT800-5. Background Art

[0002] With the continuous development of industry and manufacturing, especially in the fields of automobiles, engineering machinery, etc., the demand for high strength and high plasticity of materials is increasing. In order to achieve lightweight design of structural parts while ensuring safety and durability, ductile iron material has become an important choice due to its excellent comprehensive performance. Ductile iron is spheroidized to make graphite distributed in a spherical shape, thereby improving the ductility and impact resistance of the material. However, although traditional high-strength ductile iron, such as QT800-2, has high tensile strength and yield strength, its plasticity performance is not ideal and its elongation is low. In some applications that require both strength and toughness, it cannot fully meet the use requirements.

[0003] In practical applications, existing ductile iron materials usually need to go through a multi-step complex heat treatment process to improve the toughness of the material, but this undoubtedly increases production costs and process complexity. At the same time, in the traditional spheroidizing and inoculation process, the molten iron composition is not accurately controlled, which makes the microstructure inside the casting unstable and causes large fluctuations in mechanical properties. Especially in the wet sand casting process, due to the influence of the casting environment and process conditions, it is more likely to produce casting defects such as uneven structure, pores, slag inclusions, etc., which in turn affects the performance and service life of the material. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a production method of high-plasticity ductile iron QT800-5 in green sand casting state, which solves the problems of insufficient plasticity, complex process and high production cost of traditional ductile iron in green sand casting process, and realizes the casting with high strength and high plasticity without the need for heat treatment.

[0005] To achieve the above object, the present invention is implemented by the following technical scheme: a production method of green sand cast high plasticity ductile iron QT800-5, comprising the following steps: Raw material preparation: Pig iron 15%-25%, scrap steel 25%-35% and recycled materials 45%-55% by weight; Preparation of auxiliary materials: use silicon carbide pretreatment agent, high temperature graphitization recarburizer, rare earth magnesium ferrosilicon spheroidizer, silicon barium inoculant and silicon strontium flow inoculant; Melting: Load the furnace in the order of pig iron, scrap steel and recycled materials, add silicon carbide pretreatment agent and high-temperature carburizer, melt at 1400-1450℃, and perform component analysis and adjustment; Spheroidizing treatment: using the flushing method, put 0.95% to 1.05% rare earth magnesium ferrosilicon spheroidizing agent by weight on one side of the bottom of the spheroidizing bag, and evenly cover the spheroidizing agent with a weight content of 0.2% silicon barium inoculant and 2% steel sheet covering agent. The spheroidizing temperature is 1470℃; Ladle inoculation treatment: After spheroidization is completed, the molten iron is poured from the spheroidizing ladle into the pouring ladle. During the ladle inoculation process, a silicon-barium inoculant with a weight content of 0.5% is added along with the molten iron flow; Pouring: The temperature of the molten iron is controlled at 1370-1390°C, and a silicon strontium inoculant with a weight content of 0.06% is added during the pouring. After the pouring is completed, the box is opened to obtain the final casting.

[0006] Preferably, the pig iron is Longfengshan Q10 pig iron, the scrap steel is high manganese scrap steel with a manganese content of ≤1.0%, and the recycled materials are recycled materials of QT600 and above.

[0007] Preferably, the silicon carbide pretreatment agent has a silicon content of 60% to 70%, the high-temperature graphitization recarburizer has a carbon content of ≥98%, the rare earth magnesium ferrosilicon spheroidizer has a magnesium content of 5% to 7%, a silicon content of 40%, and the silicon content of the silicon-barium and silicon-strontium flow inoculants is 70% to 75%.

[0008] Preferably, the smelting step includes: performing thermal analysis and spectral analysis when the temperature of the molten iron reaches 1400-1450° C. to ensure that the chemical composition of the molten iron is: C: 3.75~3.95, Si: 1.45~1.65, Mn: 0.4~0.6, P: ≤0.05, S: ≤0.02.

[0009] Preferably, after the smelting, the molten iron is heated to 1520-1540°C for overheating for 5-10 minutes, then the power is reduced and the iron is left to stand to ensure that impurities float, and then the temperature of the molten iron is reduced to 1470°C for tapping.

[0010] Preferably, the spheroidization temperature of the spheroidization treatment is 1470° C., the weight content of the rare earth magnesium ferrosilicon spheroidizer during the spheroidization process is 0.95% to 1.05%, the weight content of the silicon barium inoculant is 0.2%, and they are evenly covered in the spheroidization bag.

[0011] Preferably, in the ladle inoculation treatment, 0.5% silicon-barium inoculant is added along with the molten iron when it is poured into the casting ladle, so as to ensure that the inoculant is fully dissolved and evenly distributed in the molten iron.

[0012] Preferably, in the pouring step, the temperature of the molten iron is controlled at 1370-1390° C., and 0.06% of a silicon strontium inoculant is added during the pouring process. The casting is unpacked and taken out within 14-20 minutes after the pouring is completed.

[0013] Preferably, the chemical composition of the final casting is: C: 3.5~3.7, Si: 2.4~2.7, Mn: 0.4~0.6, P: ≤0.05, S: ≤0.015, Mg: 0.035~0.055, Cu: 0.2~0.3, Sn: 0.02~0.03.

[0014] Preferably, the mechanical properties of the final casting include: tensile strength ≥800 MPa, yield strength ≥480 MPa, elongation ≥5%, and matrix pearlite content ≥80%.

[0015] The present invention provides a method for producing green sand cast high-plasticity ductile iron QT800-5, which has the following beneficial effects: 1. The present invention can achieve uniform distribution of graphite nodules in castings through precise spheroidization and inoculation treatment, reduce the generation of flake graphite and brittle phase, and thus significantly improve the tensile strength and yield strength of the material. The mechanical properties of the castings are stable, and they perform well in high stress environments while maintaining good ductility and toughness, making them suitable for a variety of load-bearing applications.

[0016] 2. The present invention makes the casting have excellent ductility by reasonably controlling the ratio of raw materials and precise process operation. The uniformity and stability of graphite balls effectively avoid the problem of stress concentration in the casting during the stretching process and improve the elongation. This makes the QT800-5 material have high strength while being able to cope with deformation and impact loads.

[0017] 3. The production method of the present invention directly controls the composition and temperature during the smelting and pouring process, and high-strength and high-plasticity castings can be obtained without additional heat treatment. Compared with the traditional casting production process, this not only simplifies the process, but also greatly reduces the production cost and energy consumption, improves the production efficiency, and is suitable for large-scale industrial applications.

[0018] 4. The present invention adopts a raw material ratio of up to 50% of recycled materials, which effectively utilizes resources and reduces the demand for primary raw materials. Through scientific batching and smelting operations, the recycling of materials is realized, production costs are saved, and it helps to reduce raw material procurement and energy consumption costs, thereby improving the economic benefits of the enterprise.

[0019] 5. The present invention optimizes the microstructure of the casting by using silicon carbide pretreatment agent and multiple inoculants. The effects of high temperature graphitization carburizer and rare earth magnesium ferrosilicon spheroidizer ensure that impurities in molten iron are effectively controlled, graphite spheroidization effect is good, and the internal structure of the final casting is dense and uniform, reducing the defects of pores and inclusions.

[0020] 6. The uniformity and density of the internal structure of the casting are improved in the present invention, and the QT800-5 material produced shows good cutting performance during mechanical processing. It has high stability and small tool wear during processing, which can improve production efficiency, reduce processing costs, and provide better support for downstream application links.

[0021] 7. The QT800-5 material produced by the present invention has high strength and high plasticity, and can reduce the wall thickness of the casting while meeting the mechanical performance requirements, thereby achieving lightweight. It is particularly suitable for fields such as automobiles and mechanical equipment that have special requirements for lightweight and high strength, and helps to improve product performance and save energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the process flow of the production method of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings of the present invention specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] At present, the highest grade of cast ductile iron in China is QT800-2, which is a pearlite matrix ductile iron with a pearlite content of ≥80%. According to the national standard GB / T1348-2019 material specification for ductile iron, the tensile performance indicators of QT800-2 ductile iron samples are shown in Table 1, with a tensile strength of ≥800MPa, a yield strength of ≥480MPa, and a minimum elongation of only 2%.

[0025] Table 1. Tensile performance indicators of QT800-2 specimens in GB / T1348-2019

[0026] The higher the tensile strength, the lower the elongation, which is determined by the matrix structure characteristics of cast iron. There is currently no way to overcome this material defect.

[0027] Please refer to the attached Figure 1 The embodiment of the present invention provides a method for producing green sand cast high-plasticity ductile iron QT800-5, which ensures that the final casting has excellent properties of high strength and high plasticity through a series of optimized process steps and precise component control. The following are the specific implementation steps of the method: 1. Raw material preparation The raw materials used in the present invention include pig iron, scrap steel and recycled materials, and the weight percentage ratio of each component is: Pig iron: 15% to 25%, Longfengshan Q10 pig iron is used. This pig iron has high purity and suitable carbon content, which helps to form high-quality molten iron during smelting, and reduces the content of harmful impurities, ensuring the stability of subsequent processes.

[0028] Scrap steel: 25% to 35%, high manganese scrap steel with a manganese content of ≤1.0% is selected. An appropriate amount of manganese helps to enhance the strength of the casting, while too high a manganese content will affect the ductility of the material, so the proportion of manganese is strictly controlled in the present invention.

[0029] Return material: 45% to 55%, QT600 and above grades are used. The alloy elements in the return material can be recycled after smelting, which reduces production costs and stabilizes the chemical composition of castings.

[0030] Pig iron and recycled materials can provide the necessary carbon and silicon, while scrap steel is used to adjust the balance of alloying elements. The reasonable combination of the three materials ensures good meltability and appropriate chemical composition of molten iron, laying the foundation for the production of high-quality ductile iron.

[0031] 2. Preparation of auxiliary materials In order to ensure the graphite nodule morphology and matrix structure of the casting, the present invention adopts the following auxiliary materials: Silicon carbide pretreatment agent: The silicon content is 60% to 70%. It is added in the early stage of smelting to increase the silicon content in the molten iron, play the role of increasing silicon and deoxidation, help stabilize the composition of the molten iron, and enhance the nucleation effect of graphite balls.

[0032] High temperature graphitization recarburizer: carbon content ≥98%. By increasing the carbon content in molten iron, it promotes the formation and uniform distribution of graphite, ensuring that the casting forms a stable graphite nodule structure when cooling.

[0033] Rare earth magnesium ferrosilicon nodulizer: contains 5% to 7% magnesium and 40% silicon. Rare earth elements and magnesium can effectively nodulize graphite in molten iron, making it spherical, reducing the formation of flake graphite and worm-like graphite, and improving the toughness and plasticity of castings.

[0034] Silicon-barium inoculant and silicon-strontium inoculant: silicon content is 70% to 75%. Added during smelting and pouring, it further increases the number and uniformity of graphite nodules and prevents structural defects in castings.

[0035] The key elements in the molten iron are optimized and controlled through the precise proportion of auxiliary materials. Silicon carbide pretreatment agent and high-temperature carburizer adjust the carbon-silicon ratio, rare earth magnesium ferrosilicon nodulizer ensures the formation and stability of graphite nodules, and silicon-barium and silicon-strontium inoculants further refine the structure and improve the overall performance of the casting.

[0036] 3. Melting The smelting process is the core link of casting production. The present invention realizes high-quality molten iron smelting through the following steps: Charging order: Load the medium frequency furnace in the order of "pig iron-scrap steel-return materials". During the charging process, silicon carbide pretreatment agent and high temperature carburizer are added in stages along with the scrap steel to ensure uniform distribution of elements.

[0037] Temperature control and composition analysis: The melting temperature is controlled at 1400-1450℃ to ensure that the raw materials are fully dissolved and evenly mixed. Thermal analysis and spectral analysis are carried out at this time to ensure that the chemical composition of the molten iron meets the requirements: C: 3.75-3.95, Si: 1.45-1.65, Mn: 0.4-0.6, P: ≤0.05, S: ≤0.02.

[0038] Heating and overheating treatment: After the molten iron is fully melted, the temperature is raised to 1520-1540℃ and overheated for 5-10 minutes. This process helps remove gas and impurities in the molten iron, allowing surface impurities to float up, and then the power is reduced and allowed to stand to ensure that impurities can be easily removed after floating up.

[0039] Reasonable temperature control and composition analysis ensure that the carbon, silicon, manganese and other elements in the molten iron are within the appropriate proportion range. Superheat treatment makes the molten iron purer, which is conducive to the smooth progress of subsequent spheroidization and inoculation treatment.

[0040] 4. Spheroidization Spheroidization is the key step to make graphite spherical: Nodulizer addition: Place 0.95% to 1.05% rare earth magnesium ferrosilicon nodulizer at the bottom of the spheroidizing bag, and cover it with 0.2% silicon-barium inoculant and 2% steel sheet covering agent.

[0041] Spheroidizing temperature control: The spheroidizing temperature is strictly controlled at 1470℃ to ensure the reaction of magnesium with sulfur and oxygen in molten iron, eliminate impurities and stabilize the morphology of graphite balls.

[0042] Spheroidizing reaction process: When the molten iron is poured into the spheroidizing bag, the rare earth elements and magnesium work together to effectively reduce the oxygen and sulfur content in the molten iron and form spheroidal graphite. This organizational characteristic makes QT800-5 castings have excellent toughness and ductility.

[0043] Magnesium and rare earth elements react rapidly in molten iron to eliminate the interference of sulfur and oxygen. The precise addition of nodularizer and temperature control ensure the stability of the graphite nodule formation process and effectively avoid the appearance of worm-like or flake graphite.

[0044] 5. Incubation treatment The molten iron after spheroidization needs to be inoculated: Pour ladle operation: After spheroidization is completed, remove the reaction slag on the surface, pour the molten iron from the spheroidizing ladle into the pouring ladle, and add 0.5% silicon-barium inoculant during the pouring process.

[0045] Inoculation effect: Silicon-barium inoculant further increases the nucleation rate of graphite, ensures uniform distribution of graphite nodules during cooling, and reduces the hard and brittle phase caused by grain growth.

[0046] Adding silicon-barium inoculant during the pouring process can promote the nucleation of graphite nodules during the flow of molten iron, prevent graphite agglomeration when the casting is cooled, and improve the microstructure uniformity and quality stability of the casting.

[0047] 6. Pouring The pouring process directly determines the final organizational structure of the casting: Pouring temperature control: Use thermocouples to measure the temperature of molten iron to ensure that pouring is carried out within the range of 1370-1390°C. This temperature range can not only ensure good fluidity of molten iron, but also prevent the coarsening of casting structure caused by excessive temperature.

[0048] Inoculation: 0.06% silicon strontium inoculant is added during pouring to further control the growth rate of graphite nodules and ensure that a fine and uniform graphite nodule structure can be formed when the casting solidifies.

[0049] Cooling and unpacking: After pouring, the casting is cooled for 14 to 20 minutes. After the temperature drops, the casting is unpacked and cleaned and inspected.

[0050] Through precise temperature control and in-stream inoculation, the present invention ensures that the formation and growth of graphite nodules are controlled during the process of molten iron flowing into the casting mold, significantly reduces casting defects such as cold shut and slag inclusion, and ensures the density and mechanical properties of the casting.

[0051] 7. Chemical composition and mechanical properties of the final casting The chemical composition and mechanical properties of QT800-5 ductile iron castings prepared by the above process are as follows: Chemical composition: C: 3.5~3.7 Si: 2.4~2.7 Mn: 0.4~0.6 P: ≤0.05 S: ≤0.015 Mg: 0.035~0.055 Cu: 0.2~0.3 Sn: 0.02~0.03 Mechanical properties: Tensile strength ≥800MPa Yield strength ≥480MPa Elongation ≥5% Matrix pearlite content ≥80% The production process of the present invention enables the casting to have high strength, high plasticity and excellent ductility, and can achieve high-level mechanical properties without additional heat treatment. This makes QT800-5 material particularly suitable for use in fields such as automotive parts and mechanical structural parts that have strict requirements on material strength and toughness.

[0052] The QT800-5 ductile iron casting of the present invention has significantly improved plasticity and toughness while maintaining high strength, and is suitable for use as a structural part that needs to bear dynamic loads in automobiles, mechanical engineering, etc. Since the process is simple and low-cost, excellent mechanical properties can be directly obtained without subsequent heat treatment, which is particularly suitable for large-scale industrial production and has good application prospects and competitiveness in the market.

[0053] The present invention successfully developed high-performance green sand casting QT800-5 ductile iron through careful material selection, auxiliary material optimization, strict smelting and spheroidization process, and precise temperature control and inoculation treatment. This production method has the advantages of simple operation, reliable process, and low cost. The casting product quality is stable and the performance is superior. It is an ideal choice for the production of modern high-performance engineering materials.

[0054] In order to better understand the present invention, the above method is described in detail below in conjunction with specific embodiments.

[0055] Embodiment 1: The embodiment of the present invention provides a method for preparing green sand cast high-strength and high-plasticity ductile iron QT800-5, which comprises the following steps: 1. Raw materials preparation: The weight percentages of raw materials are as follows: pig iron: 20%, scrap steel: 30%, recycled materials: 50%; 2. Preparation of auxiliary materials: 30kg of silicon carbide pretreatment agent, 53kg of high-temperature graphitized recarburizer, 1.0% of rare earth magnesium ferrosilicon spheroidizer, 0.7% of silicon barium inoculant and 0.06% of silicon strontium inoculant. The carbon content of high-temperature graphitized recarburizer is ≥98%, and the main components of other auxiliary materials are shown in Table 2.

[0056] Table 2. Content of main components of auxiliary materials

[0057] 3. Melting: The furnace is loaded in the order of pig iron - low manganese scrap steel - recycled materials. Silicon carbide and recarburizer are added in stages along with the low manganese scrap steel. After the raw materials are dissolved, slag collecting agent is sprinkled on the surface of the molten iron, and the surface slag is removed by a slag remover.

[0058] When the temperature of the molten iron reaches 1400-1450°C, the molten iron is taken out from the medium frequency electric furnace for thermal analysis and spectral analysis of the molten iron composition to ensure the chemical composition in the furnace: C: 3.85, Si: 1.54, Mn: 0.539, P: 0.011, S: 0.012.

[0059] When the temperature of molten iron in the medium frequency electric furnace rises to 1530℃, let it stand for 5 minutes, reduce the power, sprinkle slag agent to remove the slag, and then tap the iron when the temperature of molten iron drops to 1470℃.

[0060] 4. Spheroidization treatment: The spheroidizing method adopts the flushing method. A rare earth magnesium ferrosilicon spheroidizing agent with a weight content of 1.0% is placed on one side of the bottom of the spheroidizing bag. The spheroidizing agent is evenly covered with a silicon-barium inoculant with a weight content of 0.2% and a steel sheet covering agent with a weight content of 2%. When the amount of molten iron reaches 50% of the amount of iron produced, the spheroidizing reaction begins to occur. The spheroidizing treatment temperature is 1470℃. 5. Incubation treatment of inverted package: After the spheroidization treatment is completed, the reaction slag on the surface of the molten iron is scraped off, and the molten iron is transferred from the spheroidization ladle to the casting ladle. During the pouring process of the molten iron, a silicon-barium inoculant with a weight content of 0.5% is added along with the molten iron flow; 6. Pouring: After the inoculation treatment, the temperature of the molten iron is measured to be 1385°C using a thermocouple temperature measuring gun, and the molten iron is poured into the mold. During the pouring, a silicon strontium inoculant with a weight content of 0.06% is added along with the molten iron flow.

[0061] The final casting chemical composition is C: 3.56%, Si: 2.47%, Mn: 0.517%, P: 0.011%, S: 0.007%, Mg: 0.042%, Cu: 0.256%, Sn: 0.026%.

[0062] According to the above steps, the experimental results are shown in Table 3 below. Table 3 shows the actual test results of the castings produced by the above process, including tensile strength, yield strength and elongation.

[0063] Table 3. Experimental results of Example 1

[0064] Experimental analysis: Tensile strength: The measured values ​​are all higher than 800MPa, indicating that the castings have excellent strength.

[0065] Yield strength: The measured yield strength is stable at above 504MPa, which is significantly higher than the standard value of 480MPa.

[0066] Elongation: All measured values ​​meet or reach 5%, proving that the material has high strength while maintaining good ductility.

[0067] The production method demonstrated in this example successfully prepared high-performance QT800-5 ductile iron castings, verifying that through refined process control and the rational use of auxiliary materials, castings with tensile strength ≥ 800 MPa, yield strength ≥ 480 MPa, and elongation ≥ 5% can be produced. These materials have good market prospects in lightweight applications that require high strength and toughness, such as automotive parts and key structural parts in mechanical engineering.

[0068] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing green sand cast high plasticity ductile iron QT800-5, characterized in that: The following steps are involved: Raw material preparation: Pig iron 15%-25%, scrap steel 25%-35% and recycled materials 45%-55% by weight; Preparation of auxiliary materials: use silicon carbide pretreatment agent, high temperature graphitization recarburizer, rare earth magnesium ferrosilicon spheroidizer, silicon barium inoculant and silicon strontium flow inoculant; Melting: Load the furnace in the order of pig iron, scrap steel and recycled materials, add silicon carbide pretreatment agent and high-temperature carburizer, melt at 1400-1450℃, and perform component analysis and adjustment; Spheroidizing treatment: using the flushing method, put 0.95% to 1.05% rare earth magnesium ferrosilicon spheroidizing agent by weight on one side of the bottom of the spheroidizing bag, and evenly cover the spheroidizing agent with a weight content of 0.2% silicon barium inoculant and 2% steel sheet covering agent. The spheroidizing temperature is 1470℃; Ladle inoculation treatment: After spheroidization is completed, the molten iron is poured from the spheroidizing ladle into the pouring ladle. During the ladle inoculation process, a silicon-barium inoculant with a weight content of 0.5% is added along with the molten iron flow; Pouring: The temperature of the molten iron is controlled at 1370-1390°C, and a silicon strontium inoculant with a weight content of 0.06% is added during the pouring. After the pouring is completed, the box is opened to obtain the final casting.

2. The method for producing green sand cast high plasticity ductile iron QT800-5 according to claim 1, characterized in that: The pig iron is Longfengshan Q10 pig iron, the scrap steel is high manganese scrap steel with a manganese content of ≤1.0%, and the recycled materials are QT600 and above recycled materials.

3. The method for producing green sand cast high plasticity ductile iron QT800-5 according to claim 1, characterized in that: The silicon carbide pretreatment agent has a silicon content of 60% to 70%, the high temperature graphitization recarburizer has a carbon content of ≥98%, the rare earth magnesium ferrosilicon spheroidizer has a magnesium content of 5% to 7%, a silicon content of 40%, and the silicon content of the silicon-barium and silicon-strontium flow inoculants is 70% to 75%.

4. The method for producing green sand cast high plasticity ductile iron QT800-5 according to claim 1, characterized in that: The smelting step includes: performing thermal analysis and spectral analysis when the temperature of the molten iron reaches 1400-1450° C. to ensure that the chemical composition of the molten iron is: C: 3.75~3.95, Si: 1.45~1.65, Mn: 0.4~0.6, P: ≤0.05, S: ≤0.

02.

5. The method for producing green sand cast high plasticity ductile iron QT800-5 according to claim 1, characterized in that: After the smelting, the molten iron is heated to 1520-1540° C. for overheating for 5-10 minutes, and then the power is reduced and allowed to stand to ensure that impurities float up, and then the temperature of the molten iron is reduced to 1470° C. for tapping.

6. The method for producing green sand cast high plasticity ductile iron QT800-5 according to claim 1, characterized in that: The spheroidizing temperature of the spheroidizing treatment is 1470° C. During the spheroidizing process, the weight content of the rare earth magnesium ferrosilicon spheroidizing agent is 0.95% to 1.05%, and the weight content of the silicon barium inoculant is 0.2%, and they are evenly covered in the spheroidizing bag.

7. The method for producing green sand cast high plasticity ductile iron QT800-5 according to claim 1, characterized in that: In the ladle inoculation treatment, 0.5% silicon-barium inoculant is added into the molten iron when it is poured into the casting ladle, so as to ensure that the inoculant is fully dissolved and evenly distributed in the molten iron.

8. The method for producing green sand cast high plasticity ductile iron QT800-5 according to claim 1, characterized in that: In the pouring step, the temperature of the molten iron is controlled at 1370-1390° C., and 0.06% of a silicon-strontium inoculant is added during the pouring. The casting is taken out of the box within 14-20 minutes after the pouring is completed.

9. The method for producing green sand cast high plasticity ductile iron QT800-5 according to claim 1, characterized in that: The chemical composition of the final casting is: C: 3.5~3.7, Si: 2.4~2.7, Mn: 0.4~0.6, P: ≤0.05, S: ≤0.015, Mg: 0.035~0.055, Cu: 0.2~0.3, Sn: 0.02～0.03。 10. The method for producing green sand cast high plasticity ductile iron QT800-5 according to claim 1, characterized in that: The mechanical properties of the final casting include: tensile strength ≥800 MPa, yield strength ≥480 MPa, elongation ≥5%, and matrix pearlite content ≥80%.

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