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Research on Microstructure and Properties of Ti Micro-Alloy Super-High Strength Wear-Resistant Steel

Author: HanJie
Tutor: WangZhaoDong
School: Northeastern University
Course: Materials Processing Engineering
Keywords: Ti micro-alloy TiC Precipitation Wear-resistant steel Wear
CLC: TG142.72
Type: Master's thesis
Year: 2012
Downloads: 16
Quote: 0
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Abstract


Great progress has been made in terms of low-alloy martensitic wear-resistant steel in our country. This type wear-resistant steel has excellent strength and toughness and low cost, because its alloying elements are abundant inland, and the rare and precious element is reduced. In recent years, through introducing the second phase into martensite matrix to further improve the comprehensive performance of high strength martensitic wear-resistant steel is a hot, however, it is not good in control the type, form, distribution and size of the second phase at present. Combining with NM500grade martensitic wear-resistant steel at home and abroad, a certain amount of microalloy element Titanium was added on Cr-Mo component system and through controlling the hot-rolled and heat treatment parameters, the precipitation of microalloy element Titanium in martensite was promoted to wear resistance, finally a new super-high strength Ti micro-alloy wear-resistant steel was reached and developed. The main work and obtained achievements are as follows:(1) Using thermal simulation experiment, The effect rules of deformation parameters on dynamic recrystallization is researched with single-pass pressing experiments, and the nucleation way of austenitic dynamic recrystallization is discussed. The mathematical models of the dynamic crystallization deformation and resistance of deformation were built. The static recrystallization behavior of austenite in the holding time after deformation was researched and the plot the static softening curve was drawed by using double-pass press experiments.(2) Thermal simulation experiments was conducted to study the deformed austenite phase transformation during continuous cooling, and dynamic CCT curve was drawn. It is suggested that there are three phase regions under different cooling rate which are pearlite, bainite, martensite, but no pro-eutectoid ferrite. The quantity of precipitates is increased and the size of precipitates is smaller as the cooling rate were increased.(3) Two-stage controlled rolling and four kinds of cooling mode were designed. Results showed that lath martensite with good performance was obtained for direct quenching. The quantity of precipitates is most for fast cooling to about650℃followed with air cooling and relaxation about50seconds followed with laminar cooling to about500℃, but the size of precipitates is smaller under the previous cooling mode.(4) With the helf of the formula of solide solution product and the kinetics equations of Ti (C,N) precipitation, the dissolution equation and the precipitation kinetics of microalloy element Titanium had been established. The temperatures, at which the precipitation is fastest, the nucleation rate of precipitate biggest, had been achieved.(5) Influence of quenching and tempering parameters on the microstructure and properties were studied systemically. Results showed that tested steel could obtain considerable combination of strength and toughness with quenching parameters of880℃and14～18min. Intrastress from quenching could be eliminated with tempering of180℃and40min, and tested steel as tempered could still own high hardness. In addition, the influence of rolling and cooling process on microstructure and properties of tested steel as quenched at880℃had been studied.(6) MLD-10abrasion test machine was used to study the wear behavior of tested steel and other wear-resistant steels. Results showed that: the wear resistance of tested steel is better than others, i.e.NGNM500,DILLIDUR500V. The precipitation of microalloy element Titanium in martensite could contribute to improve wear resistance.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Steel > Special performance of steels > Wear-resistant steel
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