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CN-121294997-B - Preparation method of green sand as-cast high-strength high-plasticity spheroidal graphite cast iron

CN121294997BCN 121294997 BCN121294997 BCN 121294997BCN-121294997-B

Abstract

The application discloses a preparation method of green sand as-cast high-strength high-plasticity spheroidal graphite cast iron, and belongs to the technical field of metal material casting. The method comprises the following steps of S1, smelting raw materials, namely charging pig iron, scrap steel and return furnace materials, then adding silicon carbide and carburant in sections, dissolving all the raw materials into molten iron, removing slag, taking out slag, adding silicon carbide for pretreatment, S2, spheroidizing and inoculating, namely adding the spheroidizing agent into a spheroidizing ladle, covering a steel sheet covering agent and a silicon barium calcium inoculant, adding the molten iron, spheroidizing and inoculating the ladle bottom, adding a composite inoculant with molten iron in the pouring process, S3, pouring, namely adding the composite inoculant when the molten iron is poured into a casting mold, and cooling to obtain a product, wherein the composite inoculant comprises, by weight, 70.0% -80.0% of Si, 0.05% -0.15% of Sr, 0.2% -0.6% of Ti, 0.1% -0.3% of Nb and the balance of Fe. The spheroidal graphite cast iron prepared by reasonable formula improvement and process improvement has good strength and toughness and good comprehensive performance.

Inventors

  • ZHU QIJUN
  • HU FUXING
  • LV CHAO
  • ZHANG HAIBIAO
  • ZHANG BAOQIANG
  • FANG SHUAI

Assignees

  • 山东湖西王集团铸业有限公司

Dates

Publication Date
20260508
Application Date
20251014

Claims (6)

  1. 1. The preparation method of the green sand as-cast high-strength high-plasticity spheroidal graphite cast iron is characterized by comprising the following steps of: S1, smelting raw materials, namely charging pig iron, scrap steel and return furnace materials into a furnace, adding a carburant, melting all the raw materials into molten iron, removing slag and slag, taking out molten iron from a medium-frequency electric furnace for carrying out molten iron composition thermal analysis and spectral analysis when the temperature of the molten iron reaches 1400-1450 ℃, and then adding silicon carbide for pretreatment; S2, spheroidizing and inoculating, namely adding a spheroidizing agent into a spheroidizing ladle, wherein the spheroidizing agent is covered with a steel sheet covering agent and a silicon barium calcium inoculant, adding molten iron, performing spheroidizing and ladle bottom inoculating, pouring molten iron into a pouring ladle from the spheroidizing ladle after the temperature is reduced by 80-100 ℃, and adding a composite inoculant with the molten iron in the ladle pouring process for ladle pouring inoculating; S3, pouring, namely pouring molten iron into a casting mold, adding a composite inoculant to perform in-mold inoculation while pouring, and cooling to obtain a product; The composite inoculant comprises, by weight, 70.0% -80.0% of Si, 0.05% -0.15% of Sr, 0.2% -0.6% of Ti, 0.1% -0.3% of Nb and the balance of Fe; the weight ratio of Sr, ti and Nb in the composite inoculant is 1 (4-8): 2-4; the adding amount of the compound inoculant in the step S2 is 0.4% -0.5%; The adding amount of the composite inoculant in the step S3 is 0.1% -0.2%; The green sand as-cast high-strength high-plasticity spheroidal graphite cast iron comprises, by weight, 3.4% -3.6% of C, 2.8% -3.0% of Si, less than or equal to 0.25% of Mn, less than or equal to 0.035% of P, 0.005% -0.01% of S, 0.4% -0.6% of Cu, 0.4% -0.6% of Ni, and the balance of Fe and unavoidable impurities.
  2. 2. The method for preparing spheroidal graphite cast iron according to claim 1, wherein the spheroidizing agent comprises, by weight, 30% -35% of Si, 6.5% -8% of Mg, 1.5% -2.5% of Ce, 0.8% -1.2% of La, 0.01% -0.03% of Y, 0.01% -0.02% of Sr, and the balance of Fe.
  3. 3. The method for preparing ductile iron according to claim 2 wherein the weight ratio of La, sr, and Y is (40-80): (1-1.5): 1.
  4. 4. The method for preparing ductile iron according to claim 1 wherein the adding amount of the spheroidizing agent in step S2 is 0.95% -1.05% of the total weight of the molten iron.
  5. 5. The method for preparing spheroidal graphite cast iron according to claim 1, wherein the silicon-barium-calcium inoculant comprises, by weight, 68.0% -72.0% of Si, 4.5% -5.0% of Ba, 0.8% -1.0% of Ca, 1.5% -2.0% of Al and the balance of Fe.
  6. 6. The spheroidal graphite cast iron prepared by the preparation method according to any one of claims 1 to 5 is applied to a chassis system of a heavy truck.

Description

Preparation method of green sand as-cast high-strength high-plasticity spheroidal graphite cast iron Technical Field The application relates to a preparation method of green sand as-cast high-strength high-plasticity spheroidal graphite cast iron, and belongs to the technical field of metal material casting. Background Along with the improvement of national environmental protection and load limiting requirements, the light weight of the automobile becomes an important development direction of all host factories, and the demand is put forward for high-strength high-plasticity spheroidal graphite cast iron materials, and when components such as a balance shaft bracket, a plate spring support, a bracket, a knuckle and the like are manufactured in a heavy truck chassis system, the conventional spheroidal graphite cast iron is often manufactured into a structure with a certain thickness, so that the weight of the heavy truck chassis is increased, and the energy consumption of the heavy truck is increased in the running process. In the prior art, most of inoculants adopted for spheroidal graphite cast iron are silicon-based inoculants, which are widely applied to industrial production, but have obvious limitations that the inoculant effect is easy to fade, the number of graphite balls in unit area is small, the strength and the elongation of the final spheroidal graphite cast iron product are further influenced, and as the chassis system castings of the heavy truck are developed towards the high-strength toughening and light-weight directions, the traditional inoculants are difficult to meet the increasingly higher performance requirements. Chinese patent CN 119433337A discloses a method for producing green sand casting high plasticity spheroidal graphite cast iron QT800-5, by using auxiliary materials such as silicon carbide pretreatment agent, high temperature graphitization carburant, rare earth magnesium silicon iron nodulizer, silicon barium and silicon strontium inoculant, etc., to ensure purity and stable components of molten iron, common inoculants such as rare earth magnesium silicon iron nodulizer, silicon barium and silicon strontium inoculant are adopted in the above patents to inoculate spheroidal graphite cast iron, but the inoculant inoculation effect is easy to decline, and the prepared casting can not achieve thin wall weight reduction effect. Therefore, developing a preparation method of spheroidal graphite cast iron with higher extensibility, strength and plasticity and capable of achieving the thin-wall weight reduction effect is a technical problem to be solved. Disclosure of Invention In order to solve the problems, the preparation method of the as-cast high-strength high-plasticity spheroidal graphite cast iron is provided, and can promote graphite nucleation, increase the number of graphite nodules in unit area, enable the graphite nodules to be finer and more uniform, enable the roundness to be higher, prolong the inoculation validity period and improve the extensibility, strength and plasticity of the spheroidal graphite cast iron. In one aspect of the application, a method for preparing green sand as-cast high-strength high-plasticity spheroidal graphite cast iron is provided, which comprises the following steps: s1, smelting raw materials, namely charging pig iron, scrap steel and return furnace materials, then adding silicon carbide and carburant in sections, dissolving all the raw materials into molten iron, removing slag and slag, taking out molten iron from an intermediate frequency electric furnace for carrying out molten iron composition thermal analysis and spectral analysis when the temperature of the molten iron reaches 1400-1450 ℃, and then adding silicon carbide for pretreatment; S2, spheroidizing and inoculating, namely adding a spheroidizing agent into a spheroidizing ladle, wherein the spheroidizing agent is covered with a steel sheet covering agent and a silicon barium calcium inoculant, adding molten iron, performing spheroidizing and ladle bottom inoculating, pouring molten iron into a pouring ladle from the spheroidizing ladle after the temperature is reduced by 80-100 ℃, and adding a composite inoculant with the molten iron in the ladle pouring process for ladle pouring inoculating; S3, pouring, namely pouring molten iron into a casting mold, and adding a composite inoculant to perform in-mold inoculation while pouring to obtain a product; The composite inoculant comprises, by weight, 70% -80% of Si, 0.05% -0.15% of Sr, 0.2% -0.6% of Ti, 0.1% -0.3% of Nb and the balance of Fe. In the preparation process of the spheroidal graphite cast iron, silicon carbide is adopted to pretreat molten iron, and the molten iron is not melted due to the high melting point of the spheroidal graphite cast iron, but the molten iron is melted, and the slowly melted silicon carbide can form particles, so that graphite nucleation matrixes can be increased, and the metallurgical quality of t