Method for producing two brand numbers of low-temperature ductile irons by adopting molten iron

Abstract

The invention discloses a method for producing two brand numbers of low-temperature ductile irons by adopting molten iron. The method comprises the following steps: simultaneously adding pig iron, steel scrap, scrap returns, recarburizing agent and scrap iron into a medium-frequency induction furnace, then adding 75 silicon iron; then adjusting Si and Mn to be in a scope required by base iron; melting the molten iron till the temperature reaches 1480-1500 DEG C, pouring the molten iron into a porous plug desulfurization molten iron ladle, simultaneously adding a desulfurization agent, introducing nitrogen into the porous plug so that the desulfurized molten iron rolls over; feeding the desulfurized molten iron to an induction electric furnace, simultaneously adding the recarburizing agent which needs to be supplemented in the furnace, increasing the temperature of the molten iron in the furnace to be 1500-1520 DEG C, preserving heat, standing for 5-10 minutes and adjusting chemical components of the molten iron in the furnace; preprocessing the molten iron and carrying out spheroidizing inoculation, pouring at a temperature of 1330-1350 DEG C and adding 0.15% sulphur oxide stream inoculants during the pouring process; opening a box when the temperature of casting is less than or equal to 300 DEG C. The method is capable of producing products of two different brand numbers (QT350-22AL and QT400-18AL), thus providing convenience for the production.

Description

technical field [0001] The invention relates to a production method of low-temperature ductile iron, in particular to a method for producing low-temperature ductile iron of different grades by using a raw iron molten iron. Background technique [0002] Ductile iron has the advantages of excellent mechanical properties, processing properties, wear resistance, shock absorption properties and low manufacturing cost. It is not only widely used, but also continuously replaces cast steel materials to manufacture high-demand structural parts. However, the disadvantage of ordinary nodular cast iron is that it has poor low-temperature impact resistance, and it is restricted in application to workpieces that are subjected to dynamic loads at low temperatures. [0003] In order to meet the low temperature (-40°C) impact toughness requirements and strength (-20°C) requirements, foreign countries generally use Ni0.5 ~ 2wt% to produce low-temperature ductile iron. For example, Denmark an...

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Problems solved by technology

[0004] At present, in the production process of low-temperature ductile iron, one kind of raw iron can often only produce one brand of ductile cast iron, and the production of different brands of ductile cast iron requires different raw materials, which causes inconvenience in production.

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