Production method of nodular cast iron with high strength and high elongation

Abstract

The invention provides a production method of nodular cast iron with the high strength and the high elongation. The production method comprises the steps that pig iron with low sulfur and low titanium, ordinary carbon steel and self-produced foundry return are selected as main furnace burden, and 75 silicon iron, 65 high carbon ferromanganese, electrolytic copper and a graphite type recarburizingagent are added; smelting is conducted through an intermediate frequency furnace, a special nodulizing agent and an inoculant are added successively, tapping and nodularizing are conduced, iron liquidis added into a mold cavity of a sand-coated iron mold, the thickness of a sand-coated layer is selected according to the wall thickness of the casting corresponding position, casting pieces are slowly cooled in air, and heat treatment is not required. The strength of a prepared product reaches 670-700 MPa, the yielding strength is 450-500 MPa, the elongation rate is 12.5-14.5%, and the product strength, the yielding strength and the elongation rate of the prepared product far exceed ordinary ductile iron with the same tensile strength. Products with the mark has been used for parts such as balanced suspension brackets of a 80 T mine heavy-load dump truck and a 50 T muck truck, replacing steel castings with the nodular cast iron with the high strength and the high elongation is achieved,the cost is reduced, the weight is reduced, and significant benefits are obtained.

Description

technical field [0001] The invention belongs to the field of casting technology, in particular to a production method of high-strength and high-elongation nodular cast iron. Background technique [0002] According to the standard of GB / T1348-2009, when the strength of ductile iron reaches or exceeds 450MPa, it usually has figure 1 Series material grades shown. And from according to figure 1 Plotted material tensile strength versus elongation curve image 3 It can be seen that the elongation of ductile iron decreases rapidly when the strength gradually increases from 450MPa. When the strength reaches 600-700MPa, the elongation is only 2-3%, which is less than 5%. According to the definition of engineering materials, it belongs to brittleness. The material is therefore limited by the elongation rate, and the application field is not very broad. Especially for some support parts that are subject to impact and alternating loads in the working environment, it is difficult to ...

AI Technical Summary

Problems solved by technology

[0005] 1. The casting process of steel castings is far inferior to that of cast iron. The fluidity of molten steel is not as good as that of molten iron, which is prone to cold shut and pore defects, especially for parts with complex structures and uneven cross-sections, which are prone to filling defects;

[0006] 2. The shrinkage of steel castings is very large, and large risers need to be added to the gating system, which has a great impact on the yield. The yield of steel castings is often less than 50%, and cast iron can usually reach 70-80%;

[0009] Based on the above, although steel castings can achieve high strength and high elongation, compared with ductile iron castings, the process is complicated, and only parts with simpler structures can be produced. The production cycle is long, energy consumption is high, and the yield rate is high. Low cost, 30-40% higher than ductile iron castings

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