Nodular cast iron is a high-strength cast iron material developed in the 1950s. Its comprehensive properties are close to steel. Based on its excellent properties, it has been successfully used to cast some parts with complex stress and high requirements for strength, toughness and wear resistance. Nodular cast iron has rapidly developed into a widely used cast iron material second only to gray cast iron. The so-called “replacing steel with iron” mainly refers to nodular cast iron.
Nodular cast iron is spheroidized and inoculated to obtain spherical graphite, which effectively improves the mechanical properties of cast iron, especially the plasticity and toughness, so as to obtain higher strength than carbon steel.
Reaumur of France made white core malleable iron in 1722. Later, Seth Boyden of the United States invented black core malleable iron in 1826.
By the 1920s. Due to the research and progress in the influence of carbon, silicon and other main components in cast iron and the addition of other alloy elements, melting method and inoculation effect, the so-called high-grade cast iron appeared. Therefore, the material has been considerably improved, and the scope of application has been expanded to a certain extent. However, due to the fundamental disadvantage of low toughness, its application scope has not been expanded rapidly.
In 1947, morrogh discovered cast iron with spheroidal graphite in the as cast state.
In 1948, nodular cast iron was prepared by adding CE to gray cast iron with high carbon, low sulfur and low phosphorus and keeping its residue above 0.02%. Almost at the same time, inco gagnebin and others obtained the same nodular cast iron by adding Mg to cast iron and keeping its residue above 0.04%.
During the Second World War, due to the lack of chromium resources necessary for the production of wear-resistant martensitic white cast iron, it was urgent to study the substitute elements of CR. Therefore, a systematic investigation has been carried out on whether various metals and transition metals chemically combined with carbon can form carbides, including magnesium. Cu80-mg20 alloy and ni80-m920 alloy have been used to slow down the intense splashing during magnesium addition. The results show that magnesium not only has a good effect as a substitute element of chromium, but also has a significant desulfurization effect when magnesium has a certain degree of residue in molten iron. Based on these new findings, the effect of adding magnesium to gray cast iron was also studied after white cast iron. 3.5% C, SI2 The tensile strength of 25% and Ni 2% gray cast iron with 0.5% Mg is much higher than the original expectation (about 13kgf / mm2 for ordinary gray cast iron), up to 78kgf / mm2.