Manufacturing process of high-temperature nodular cast iron

Abstract

The invention discloses a manufacturing process of high-temperature nodular cast iron. The manufacturing process comprises the steps of (A) mixing materials including scrap steel, pig iron, foundry returns, ferromanganese, silicon carbide, a carburant, ferrosilicon and ferromolybdenum; (B) conducing smelting, specifically, charging the mixed materials into a furnace to be melted into molten iron;(C) conducting heating and standing, heating the molten iron to 1520-1550 DEG C, stopping heating and conducting standing to reach 1460-1480 DEG C; (D) conducting filling, specifically, preheating a casting ladle, filling a nodulizing agent into the pit side of the bottom of the casting ladle, tamping the nodulizing agent with a hammer, covering the nodulizing agent with a layer of nodulizing insulation covering agent, conducting tamping with the hammer, and covering the nodulizing insulation covering agent with a nucleating agent; (E) conducting nodulizing and inoculation, specifically, filling the molten iron into the casting ladle, preventing the molten iron from making contact with the nodulizing agent, adding the nucleating agent again when the molten iron yield is one half of the total treatment amount, stirring the molten iron and then conducting standing for 1.5-3.0 min; (F) conducting casting; and (G) conducting cooling and unpacking. Through the manufacturing process, the microstructure of a casting can be improved to obtain the good graphite from and reduce the pearlite content, the high-temperature strength can be substantially improved, the use requirements are met, and the service life of products is prolonged.

Description

technical field [0001] The invention relates to a process for manufacturing high temperature ductile iron. Background technique [0002] Ductile iron is a high-strength cast iron material developed in the 1950s. The working temperature of high-temperature ductile iron is generally 500-700 ° C, such as for the volute of a turbocharger; but the existing high-temperature ductile iron is due to its composition and manufacturing process reasons such as figure 1 The spheroidization level of the graphite shown is usually 4, such as figure 2 As shown, its pearlite content is greater than 16%, resulting in 10 minutes of heat preservation at 650°C, and its tensile strength Rm is all below 100MPa. The high temperature performance is difficult to meet the use requirements, which affects the service life. Contents of the invention [0003] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and provide a manufacturing process for high...

AI Technical Summary

Problems solved by technology

[0002] Ductile iron is a high-strength cast iron material developed in the 1950s. The working temperature of high-temperature ductile iron is generally 500-700 ° C, such as for the volute of a turbocharger; but the existing high-temperature ductile iron is due to its composition and manufacturing process reasons such as figure 1 The spheroidization level of the graphite shown is usually 4, such as figure 2 As shown, its pearlite content is greater than 16%, which leads to its tensile strength Rm being below 100MPa after 10 minutes of heat preservation at 650°C. The high temperature performance is difficult to meet the use requirements, which affects the service life.

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