Method for producing nodular cast iron

A method for producing nodular cast iron by using a nodulizer and a spheroidizing device;

• the nodulizer being prepared by providing a rectangular steel tube (13) comprising a pressure regulating through hole (17) arranged on a middle part of a side surface thereof;
• for the rectangular steel tube, the pressure regulating through hole (17) being arranged on a middle part of an end surface of a relatively small area;
• injecting an alloy melt of a rare earth magnesium ferrosilicon nodulizer comprising magnesium ≦20%, silicon ≦65%, and Re ≦3% from the pressure regulating through hole (17) into the rectangular steel tube (13) to condense and cool;
• a diameter of the pressure regulating through hole (17) being 8-14 mm;
• using a steel plate having a same thickness as a wall of the rectangular steel tube to close a part of an opening of each of two ends of the rectangular steel tube by means of welding for controlling a reaction time and reaction state of the nodulizer;
• the spheroidizing device comprising:
• a strut head (1), a steering shaft (2), a mobile location (3), a pressure lever (4), a balance steel (5), a column and a positioning ruler (6), a first bolt (8), and a third bolt and a nut thereof (12);
• the strut head (1) being movable and fixable at a required position by using the third bolt and the nut thereof (12) disposed on the column and the positioning ruler (6) as an rotational axis of the pressure lever (4), arranging the steering shaft (2) on the pressure lever (4), and connecting the first bolt (8) of the steering shaft (2) to the strut head (1);
• a bottom surface of the strut head (1) being flat;
• a fire-proof material coated on the strut head (1) being a frame welded by a threaded steel and an iron wire;
• the column and the positioning ruler (6) being welded as a whole body;
• the mobile location (3) being arranged on an end part of the positioning ruler;
• the balance steel (5) being hanged on the other end of the pressure lever (4);
• the method comprising spheroidizing, and the spheroidizing comprising the following steps:
• a) placing an integrated rare earth magnesium ferrosilicon nodulizer (18) coated with the rectangular steel tube at a preset position inside a spheroidizing ladle (7), disposing the strut head (1) on the spheroidizing ladle (7), and fixing the strut head (1);
• b) inputting a ferrosilicon inoculant into the spheroidizing ladle (7);
• c) inputting melted iron into the spheroidizing ladle (7) for spheroidizing;
• and
• d) removing the strut head (1) from the spheroidizing ladle (7) after the spheroidizing.