Xiangtao Deng

Microstructure and Abrasive Wear Behavior of Medium Carbon Low Alloy Martensitic Abrasion Resistant Steel

The effect of processing parameters such as hot rolling and heat treatment on microstructure and mechanical properties was investigated for a new 0. 2 7 mass % C and Ni, Mo-free low alloy martensitic abrasion resistant steel. The three-body impact abrasive wear behavior was also analyzed. The results showed that two-step controlled rolling besides quenching at 880 °C and tempering at 170 °C could result in optimal mechanical property: the Brinell hardness, tensile strength, elongation and −40 °C impact toughness were 531, 1530 MPa, 11.8% and 58 J, respectively. The microstructure was of fine lath martensite with little retained austenite. Three-body impact abrasive wear results showed that wear mechanism was mainly of plastic deformation fatigue when the impact energy was 2 J, and the relative wear resistance was 1. 04 times higher than that of the same grade compared steel under the same working condition. The optimal hardness and toughness match was the main reason of higher wear resistance.

Extending the boundaries of mechanical properties of Ti-Nb low-carbon steel via combination of ultrafast cooling and deformation during austenite-to-ferrite transformation

We underscore here a novel approach to extend the boundaries of mechanical properties of Ti-Nb low-carbon steel via combination of ultrafast cooling and deformation during austenite-to-ferrite transformation. The proposed approach yields a refined microstructure and high density nano-sized precipitates, with consequent increase in strength. Steels subjected to ultra-fast cooling during austenite-to-ferrite transformation led to 145 MPa increase in yield strength, while the small deformation after ultra-fast cooling process led to increase in strength of 275 MPa. The ultra-fast cooling refined the ferrite and pearlite constituents and enabled uniform dispersion, while the deformation after ultra-fast cooling promoted precipitation and broke the lamellar pearlite to spherical cementite and long thin strips of FexC. The contribution of nano-sized precipitates to yield strength was estimated to be ~247.9 MPa and ~358.3 MPa for ultrafast cooling and deformation plus ultrafast cooling processes. The nano precipitates carbides were identified to be (Ti, Nb)C and had a NaCl-type crystal structure, and obeyed the Baker-Nutting orientation relationship with the ferrite matrix.

超快冷终冷温度对含Nb-V-Ti微合金钢组织转变及析出行为的影响

以复合添加Nb,V和Ti的低碳微合金钢为研究对象,采用热模拟试验机模拟高温轧制＋超快速冷却＋缓冷工艺,采用OM,HRTEM和显微硬度计等对超快冷至不同温度实验钢的组织转变和析出规律进行研究.结果表明,随着超快冷终冷温度的升高,显微组织由贝氏体向珠光体和铁素体转变,碳化物形核位置从贝氏体转变为铁素体,铁素体中的析出物密度大于贝氏体中的,且在620℃达到最大.超快冷至不同温度时析出物的尺寸均小于10 nm,纵横比均接近于1,即析出物形态更接近于球形,且随终冷温度的降低,析出物尺寸逐渐减小.利用Orowan机制计算了析出强化增量,得出在620℃析出强化对屈服强度的贡献最大,可达到25.6%.

Effect of Epsilon Carbides on Mechanical Properties and Wear Resistance of Low Alloy Abrasion Resistance Steel

In this paper, different morphology and size of nano epsilon carbides (e-carbides) were obtained by low temperature tempering for a low alloy abrasion resistance steel, the variation of mechanical properties and three-body impact wear resistance as the variation of carbides were investigated. The results shown that as the formation of needle like type e-carbides, the yield strength, low temperature impact toughness and three-body impact wear resistance were all increased. While when the e-carbides grow up to the bigger rodlike type, the hardness and toughness decreased sharply, as well as the three body impact abrasion wear resistance. The wear mechanisms of the steel obtained different carbides were also analyzed.