Nodular cast iron gear box with high impact toughness at ultralow temperature, and making method thereof

Abstract

The invention relates to a nodular cast iron gear box with high impact toughness at ultralow temperature. The nodular cast iron gear box comprises, by mass, 3.50-3.80% of C, 1.7-1.9% of Si, 0.10-0.15% of Mn, 0.035% or less of P, 0.015% or less of S, 1.0-1.3% of Ni, and the balance of Fe and inevitable impurities. A making method comprises the following steps: melting highly pure Q10 pig iron, Q235 carbon structural iron and returns in an intermediate frequency induction electric furnace, adding nickel plates, and adjusting the percentages of all chemical components; nodulizing by adopting an exposure ladle pour-over technology, and sequentially packing a nodulizing agent, an inoculant and a covering agent in a layered manner; and carrying out primary stream inoculation during tapping, carrying out ladle inoculation, and carrying out secondary stream inoculation during casting. The making method improves the elongation and the low-temperature impact toughness, reinforces the matrix structure, guarantees reasonable graphite sphere number and high nodulizing rate, improves the toughness and plasticity, does not need graphitization annealing heat treatment, and saves the production cost.

Description

technical field [0001] The invention relates to a ductile iron gearbox with ultra-low temperature and high impact toughness and a manufacturing method thereof, belonging to the field of casting technology. Background technique [0002] The toughness of ductile iron generally decreases with the decrease of temperature. When the temperature is lower than a certain temperature, brittle fracture will occur due to the sharp decrease of toughness, which is the so-called ductile-brittle transition. In recent years, my country's rail transit industry has developed rapidly. Electric locomotives operate in a vast area with a large latitude span. In cold regions, the temperature in winter can reach below -40°C. Based on the consideration of locomotive speed and safety, nodular cast iron for electric locomotives The requirements for low temperature impact toughness of gearboxes are also getting higher and higher. China Railway Corporation's TJ / JW 065-2015 "Interim Technical Conditions f...

AI Technical Summary

Problems solved by technology

China's invention patent application No. 201310114040.4 discloses a low-temperature high-toughness ductile iron bearing seat and its manufacturing method, which is said to improve the low-temperature impact toughness of ductile iron castings. , it is also necessary to carry out graphitization annealing treatment on the castings in two stages of high temperature and low temperature, the process is complicated, and the manufacturing cost is increased

Images