The effect of austenitizing temperature and Cr, Mo and Mn addition on microstructure and mechanical properties of V microalloyed medium carbon steel has been studied by means of metallography and mechanical testing. T...The effect of austenitizing temperature and Cr, Mo and Mn addition on microstructure and mechanical properties of V microalloyed medium carbon steel has been studied by means of metallography and mechanical testing. The addition of Cr, Mn and Mo leads to a decrease in yield strength （YS） by approximate 100 MPa in comparison to the base steel. It is assumed that Mn and Mo increase hardenability by promoting the formation of bainitic sheaves （BS）, i.e. by suppressing the formation of ferrite-pearlite and acicular ferrite （FP-AF）. Cr at the level used in this work is not that effective. Presence and packet size of bainitic sheaves decrease the Charpy V-notch impact energy at 20 ℃ （CVN20） in comparison to ferrite-pearlite and acicular ferrite microstructures.展开更多
The microstructure and mechanical properties of NiCrMoV-and NiCrSi-alloyed medium-carbon steels were investigated after multiple tempering. After austenitising, the steels were hardened by oil quenching and subsequent...The microstructure and mechanical properties of NiCrMoV-and NiCrSi-alloyed medium-carbon steels were investigated after multiple tempering. After austenitising, the steels were hardened by oil quenching and subsequently double or triple tempered at temperatures from 250 to 500 °C. The samples were characterised using scanning electron microscopy and X-ray diffraction, while the mechanical properties were evaluated by Vickers hardness testing, V-notched Charpy impact testing and tensile testing. The results showed that the retained austenite was stable up to 400 °C and the applied multiple tempering below this temperature did not lead to a complete decomposition of retained austenite in both steels. It was also found that the microstructure, hardness and impact toughness varied mainly as a function of tempering temperature,regardless of the number of tempering stages. Moreover, the impact toughness of NiCrMoV steel was rather similar after single/triple tempering at different temperatures, while NiCrSi steel exhibited tempered martensite embrittlement after single/double tempering at 400 °C. The observed difference was mainly attributed to the effect of precipitation behaviour due to the effect of alloying additions in the studied steels.展开更多
<div style="text-align:justify;"> <span style="font-family:Verdana;">The purpose of the present study was to investigate the texture in dissimilar medium carbon steels welded by rotary ...<div style="text-align:justify;"> <span style="font-family:Verdana;">The purpose of the present study was to investigate the texture in dissimilar medium carbon steels welded by rotary friction technique. The Electron Backscatter Diffraction (EBSD) technique was the main technique used to investigate the effect of welding on grain size and grain crystallographic orientation in the welded joint. Moreover, the effect of isothermal heat treatment at 600<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">°</span>C on welded joint has been studied knowing that this annealing allows to decrease the residual stresses. EBSD results revealed different subzones in welded joint. The texture in the weld is essentially composed of three components: Goss {110} <001>, Rotated Cube {100} <110>, and Rotated Goss {110} <110> orientation. The heat treatments applied on welded material had a slight effect on texture and grain size.</span> </div>展开更多
The effect of Al on the morphology of MnS in medium-carbon non-quenched and tempered steel was investigated at three different cooling rates of 0.24, 0.43, and 200°C·s^-1. The formation mechanisms of three t...The effect of Al on the morphology of MnS in medium-carbon non-quenched and tempered steel was investigated at three different cooling rates of 0.24, 0.43, and 200°C·s^-1. The formation mechanisms of three types of MnS were elucidated based on phase diagram information combined with crystal growth models. The morphology of MnS is governed by the precipitation mode and the growth conditions. A monotectic reaction and subsequent fast solidification lead to globular Type I MnS. Type II MnS inclusions with different morphological characteristics form as a result of a eutectic reaction followed by the growth in the Fe matrix. Type III MnS presents a divorced eutectic morphology. At the cooling rate of 0.24°C·s^-1, the precipitation of dispersed Type III MnS is significantly enhanced by the addition of 0.044wt% acid-soluble Al（Als）, while Type II MnS clusters prefer to form in steels with either 0.034wt% or 0.052wt% Als. At the relatively higher cooling rates of 200°C·s^-1 and 0.43°C·s^-1, the formation of Type I and Type II MnS inclusions is promoted, and the influence of Al is negligible. The results of this work are expected to be employed in practice to improve the mechanical properties of non-quenched and tempered steels.展开更多
基金indebted to Ministry of Education and Science of Serbia for financial support(Project OI174004)
文摘The effect of austenitizing temperature and Cr, Mo and Mn addition on microstructure and mechanical properties of V microalloyed medium carbon steel has been studied by means of metallography and mechanical testing. The addition of Cr, Mn and Mo leads to a decrease in yield strength （YS） by approximate 100 MPa in comparison to the base steel. It is assumed that Mn and Mo increase hardenability by promoting the formation of bainitic sheaves （BS）, i.e. by suppressing the formation of ferrite-pearlite and acicular ferrite （FP-AF）. Cr at the level used in this work is not that effective. Presence and packet size of bainitic sheaves decrease the Charpy V-notch impact energy at 20 ℃ （CVN20） in comparison to ferrite-pearlite and acicular ferrite microstructures.
基金sponsorship provided by Innovate UK through the Knowledge Transfer Partnership Programme(KTP010269 Sheffield Hallam University and Tyzack Machine Knives Ltd.)
文摘The microstructure and mechanical properties of NiCrMoV-and NiCrSi-alloyed medium-carbon steels were investigated after multiple tempering. After austenitising, the steels were hardened by oil quenching and subsequently double or triple tempered at temperatures from 250 to 500 °C. The samples were characterised using scanning electron microscopy and X-ray diffraction, while the mechanical properties were evaluated by Vickers hardness testing, V-notched Charpy impact testing and tensile testing. The results showed that the retained austenite was stable up to 400 °C and the applied multiple tempering below this temperature did not lead to a complete decomposition of retained austenite in both steels. It was also found that the microstructure, hardness and impact toughness varied mainly as a function of tempering temperature,regardless of the number of tempering stages. Moreover, the impact toughness of NiCrMoV steel was rather similar after single/triple tempering at different temperatures, while NiCrSi steel exhibited tempered martensite embrittlement after single/double tempering at 400 °C. The observed difference was mainly attributed to the effect of precipitation behaviour due to the effect of alloying additions in the studied steels.
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;">The purpose of the present study was to investigate the texture in dissimilar medium carbon steels welded by rotary friction technique. The Electron Backscatter Diffraction (EBSD) technique was the main technique used to investigate the effect of welding on grain size and grain crystallographic orientation in the welded joint. Moreover, the effect of isothermal heat treatment at 600<span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">°</span>C on welded joint has been studied knowing that this annealing allows to decrease the residual stresses. EBSD results revealed different subzones in welded joint. The texture in the weld is essentially composed of three components: Goss {110} <001>, Rotated Cube {100} <110>, and Rotated Goss {110} <110> orientation. The heat treatments applied on welded material had a slight effect on texture and grain size.</span> </div>
文摘研究了5CrMnMo 钢渗碳并经马氏体(M)与贝氏体(B)复相处理后的力学性能与冲击磨损机理。结果表明,冲击加滑动产生脱层磨损;渗碳后马氏体(M)/下贝氏体(B_下)组织中 B_下量增加,韧性塑性可明显提高,B_下量达到一定值时,其抗冲击磨损能力最高;无论是先 M后 B_下组织还是先 B_下后 M 组织,只要含有一定量的 B_下都能提高材料的韧性塑性和耐磨性,但先 B_下后 M 的组织性能更好。看来渗碳加 M 与 B_下复相处理可作为提高中碳钢冷作模具寿命的一条新的有效途径。
基金financially supported by the National Natural Science Foundation of China (Nos. 51174020 and 51374018)the National High-Tech Research and Development Program of China (No. 2013AA031601)
文摘The effect of Al on the morphology of MnS in medium-carbon non-quenched and tempered steel was investigated at three different cooling rates of 0.24, 0.43, and 200°C·s^-1. The formation mechanisms of three types of MnS were elucidated based on phase diagram information combined with crystal growth models. The morphology of MnS is governed by the precipitation mode and the growth conditions. A monotectic reaction and subsequent fast solidification lead to globular Type I MnS. Type II MnS inclusions with different morphological characteristics form as a result of a eutectic reaction followed by the growth in the Fe matrix. Type III MnS presents a divorced eutectic morphology. At the cooling rate of 0.24°C·s^-1, the precipitation of dispersed Type III MnS is significantly enhanced by the addition of 0.044wt% acid-soluble Al（Als）, while Type II MnS clusters prefer to form in steels with either 0.034wt% or 0.052wt% Als. At the relatively higher cooling rates of 200°C·s^-1 and 0.43°C·s^-1, the formation of Type I and Type II MnS inclusions is promoted, and the influence of Al is negligible. The results of this work are expected to be employed in practice to improve the mechanical properties of non-quenched and tempered steels.
