Liquid iron inoculation process for ductile iron pipes

Abstract

The invention discloses a liquid iron inoculation process for ductile iron pipes, which comprises the following steps of: (1) inoculating in a spheroidizing ladle, and adding an inoculator accounts for 0.4 to 0.6 weight percent of the liquid iron into the spheroidizing ladle; (2) performing stream inoculation, adding an inoculator in an amount which is 0.1 to 0.25 weight percent of the liquid iron into a pouring ladle; and (3) performing pipe powder inoculation, spraying pipe powder on the inner surface of a pipe die before pouring and during pipe drawing in a ratio of 20-30g / m<2>. The key improvement is that: a tundish inoculation step is added between the step (1) and the step (2), wherein an inoculator in an amount which is 0.15 to 0.25 weight percent of the liquid iron is added into the tudish, and after the inoculator is completely melted, the liquid iron is transferred into the pouring ladle for stream inoculation. The liquid iron inoculation process has the advantages that: a tundish inoculation process is added between the spheroidizing ladle inoculation and the stream inoculation to realize long-acting inoculation of the liquid iron; the residual magnesium in the spheroidizing liquid iron can be effectively reduced; the tensile strength and the yield strength are improved; and meanwhile, conditions are created for reducing high-temperature annealing temperature and stabilizing the size of the ductile iron pipe finished products.

Description

technical field [0001] The invention relates to a production process of molten iron for ductile iron pipes, in particular to an inoculation process of molten iron for ductile iron pipes. Background technique [0002] Centrifugal ductile iron pipes are widely used in construction projects such as water and gas transmission due to their high strength and good toughness. Therefore, improving and stabilizing the quality of centrifugal ductile iron pipes to achieve higher standards is an urgent problem that ductile iron pipe manufacturers need to solve. The main factors affecting the quality of ductile iron pipes are as follows. The first point The chemical composition of blast furnace molten iron, such as sulfur, titanium, silicon, etc.; the second point is the control of the carbon equivalent of molten iron after spheroidizing; the third point is the control of magnesium content in molten iron after spheroidizing. The present invention is mainly aimed at the improvement of the...

AI Technical Summary

Problems solved by technology

Since the pipe wall specified in the new industry standard for ductile iron pipes is thinner than that in the current industry standard, it is difficult to incubate molten iron according to the current inoculation process to achieve the strength and toughness of ductile iron pipes under the new industry standards Isomechanical properties