Molding technology of large nodular cast iron roll

Furan resin self hardening sand is used for molding and core making, and alcohol based zircon coating is used to prevent sand sticking. As the roll needs 100% ultrasonic testing as a whole, if the rigidity (strength) of nodular cast iron mold is not enough, it is easy to have problems such as unqualified due to excessive ultrasonic flaw detection defects. In order to prevent these defects, it is necessary to increase the amount of resin in molding sand to improve the strength of sand mold.

The height of the roll ductile iron casting is 4500mm. With the height of the riser and the plug pulling gate cup, the whole ductile iron casting is more than 7m. Considering the convenient operation, three box modeling is adopted. Although the external mold structure is relatively simple, to ensure uniform wall thickness, we must first ensure accurate sand mold size. Uniform size in the mold cavity is the key to ensure wall thickness. Diameter of inner hole sand core φ 1880 mm is a large sand core. It is difficult to lower the core, the positioning accuracy of the sand core is low, and the depth of the lower mold is high. Therefore, before closing the box, it is necessary to carefully measure the cavity dimensions at multiple positions of the upper and lower mold to ensure the perpendicularity of the sand core.

Due to the high indenter of molten iron, ductile iron casting defects such as sand expansion, sticking tip and fire escape are easy to occur. The pressure head is high and the box lifting force is large. In addition to the conventional method of placing pressure iron and fastening the sand box with bolts, the steel plate shall be welded on the parting surface and the sand enclosure reinforcement shall be carried out on the parting surface of the sand box to prevent fire escape.

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