Control method for increasing the number of graphite nodules in solid solution strengthened ferritic ductile iron with thick and large section

Abstract

The invention discloses a control method for increasing the number of graphite nodules by solid solution strengthening ferrite nodular cast iron with a thick and large cross section, which comprises the following steps: selecting materials: 50-70 percent of pig iron and 30-50 percent of scrap steel; smelting: adding the materials into an electric furnace for smelting, wherein the tapping temperature of the molten iron is 1420-1450 DEG C; spheroidizing: adding a spheroidizing agent, adding a covering agent on the spheroidizing agent, and then spheroidizing, wherein the spheroidizing temperatureis 1420-1450 DEG C; inoculating: adding a silicon-aluminum-calcium-barium type inoculant during a primary inoculation, and respectively adding the inoculant on the surface of the covering agent and the other side of a ladle dam before tapping, wherein the distribution proportion is 50 percent; adding a trace amount of alloy Sb along with the flow of the molten iron during casting, wherein the adding amount of the alloy Sb is 0.003-0.005% of the total amount of the molten iron, molding, casting and cooling: ensuring that the casting opening temperature is controlled to be <= 300 DEG C, and thecasting is obtained by air cooling after the casting is opened. The control method has the advantages of obtaining higher number of the graphite nodules, ensuring a metallographic structure and goodconsistency of performance indexes, thereby improving the quality of the castings and prolonging the service life.

Description

technical field

[0001] The invention relates to the technical field of casting metals, in particular to a control method for increasing the number of graphite balls in solid-solution strengthened ferritic nodular cast iron with thick and large sections. Background technique

[0002] In the current national standard "GB / T1348-2009 Ductile Iron Castings", 7.5.1 graphite form requires that the graphite is mainly spherical, and the nodularization level is not lower than the nodularization level 4 stipulated in GB / T9441. If there are special requirements, nodularization The level is agreed upon by both parties. Spheroidization level 4 refers to the spheroidization rate ≥ 70%. In Appendix F, the spheroidization rate is defined as the percentage of spherical graphite and flocculent graphite. At the same time, it is mentioned in the appendix that the spheroidization level is not only related to the measurement method, but also related to The material grade of the casting is related...

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