He Zhenming

Abrasion-resistant as-cast manganese steel with nodular carbide modified by calcium

Calcium systems agents, which are cheap and abundant on earth, are used for the modification of high-carbon medium-manganese steel. After the treatment, needle-like and network-forming carbide turns to a nodular form in the as-cast state. This is an economical and practical method, and it also is a new investigation

Distribution of Al2O3 particles in Al-4.5 Cu alloy composite and its influences on crystal growth

During solidification,to Al2O3 particle/ A1—4.5Cu—2.0Mg alloy composite,when matrix grows in the form of cell or cellular dendrite, particles are pushed off by the interface of solid liquid and most of them distribute between cells or cellular dendrites and some arrange linearly along crystal boundary.It isn’t found that solute (cerium) makes the crystal boundary distribution of particles change dramatically. There are effects of particles on the process of crystal growth,which change crystal growth from unidirectional and vertical to leaning and fine cell.

Control of solidification structure of wear-resistant austenite-bainite polyphase steel with nodular eutectic

A new austenite-bainite polyphase steel with nodular carbides can be obtained by controlling the solidification structure of the steel melt, which only contains manganese and silicon, with modification of Si-Ca-B compound and air-hardening. The result indicates that the nodular carbide is in the eutectic form of austenite and (Fe, Mn)3C, which is formed between the austenitic dendrites during solidification due to element segregation. The modifying elements (calcium, silicon, etc.) have the following functions: (1) their chemical compounds (CaS, SiO2) are formed preferentially during solidification to act as heterogeneous nuclei for nodular eutectic crystallization, (2) the eutectic can be turned into the nodular shape after modification because of the decrease in the amount of the adsorbed impurity elements (oxygen and sulphur) and silicon enriched on the eutectic growth interface. The quantity of nodular eutectic makes up 10%–20%, with a size of 15–25 μm. The hardness and the toughness of this steel are 40–50 HRC and 20–40 J, respectively, and hence its wear-resistance can be more greatly increased than that of the austenite-manganese steel and the austenite-bainite steel.