The high-temperature dissolution behavior of carbides during the quenching process significantly influences grain growth,mechanical properties,and secondary carbide precipitation,thereby playing a major role in the he...The high-temperature dissolution behavior of carbides during the quenching process significantly influences grain growth,mechanical properties,and secondary carbide precipitation,thereby playing a major role in the heat treatment process of die steel.This study investigated the changes in carbide type,particle size distribution,and weight percentage in DC53 steel after holding at 1060℃for 2 h,followed by oil quenching.The analysis was conducted using Thermo-Calc,DICTRA computations,and experimental methods including electron backscatter diffraction,transmission electron microscopy and laser particle size analysis.The experimental results showed that four types of carbides(M_(7)C_(3),M_(6)C,M_(23)C_(6),and MC)existed in DC53 steel before quenching.After quenching,M_(23)C_(6)carbides were almost entirely dissolved,while the other three types partially dissolved into the matrix.The volume-weighted geometric mean size of carbides(x_(geo,3))increased from 5.43 to 15.15μm,and the weight percentage decreased from 13.03%to 5.01%.Small-sized carbides(below 5μm)dissolved more readily,which primarily accounted for the reduction in carbide weight percentage during quenching.In contrast,the weight percentage of large-sized carbides(greater than 10μm)varies less.DICTRA computations indicated that M_(7)C_(3)carbides smaller than 7μm can completely dissolve into the matrix after holding at 1060℃for 2 h.The findings provide an effective reference for optimizing carbide control during the heat treatment process of DC53 steel.展开更多
As the main use of TBM(tunnel boring machine)cutter ring(DC53 steel)currently is difficult to meet the requirements of high wear resistance and high toughness synchronously in its service environment,a new HWR0 steel ...As the main use of TBM(tunnel boring machine)cutter ring(DC53 steel)currently is difficult to meet the requirements of high wear resistance and high toughness synchronously in its service environment,a new HWR0 steel with 4%Cr-3%V for TBM cutter ring has been developed to control carbides in steel.Precipitation behavior of carbides in HWR0 steel was investigated through theoretical calculation by Thermo-Calc and experimental measurement using scanning electron microscope,energy dispersive spectrometer,electron probe X-ray micro-analyzer,and laser particle size analyzer.The results show that three different carbides are precipitated during cooling.And the as-cast electroslag remelting ingot of HWR0 steel primarily consists of many blocky or strip-like MC distributed along grain boundaries,few chrysanthemum-like M_(6)C concentrated at grain boundary intersections,and a large quantity of fine M_(23)C_(6)and M_(6)C dispersed in the matrix.Compared with DC53 steel,HWR0 steel has more high-hardness carbides MC,which are discontinuously distributed at the grain boundaries,achieving the dual improvement of wear resistance and impact toughness.Cooling rates significantly influence the carbides distribution and grain size.A slower cooling rate exacerbates the segregation of alloying elements,which leads to the localized enrichment of Mo and the subsequent precipitation of M_(6)C carbides at grain boundary intersections.In contrast,faster cooling rate decreases the element segregation,promotes carbide nucleation and limits the space for carbides growth,which results in finer size and distribution of carbides and grains.Higher cooling rates yield a more homogeneous microstructure with uniform MC compositions and promote the preferential formation of M_(6)C carbides along grain boundaries,which enhances the mechanical properties.展开更多
A better understanding of droplet formation and dripping behavior would be useful in the efficient removal of impurity elements and nonmetallic inclusions from liquid metals. In the present work, we developed a transp...A better understanding of droplet formation and dripping behavior would be useful in the efficient removal of impurity elements and nonmetallic inclusions from liquid metals. In the present work, we developed a transparent experimental apparatus to study the mechanisms of droplet formation and the effects of filling ratio on droplet behavior during the electroslag remelting（ESR） process. A high-speed camera was used to clearly observe, at small time scales, the droplet formation and dripping phenomenon at the slag/metal interface during a stable ESR process. The results illustrate that a two-stage process for droplet formation and dripping occurs during the ESR process and that the droplet diameter exhibits a parabolic distribution with increasing filling ratio because of the different shape and thermal state of the electrode tip. This work also confirms that a relatively large filling ratio reduces electricity consumption and improves ingot quality.展开更多
基金supported by the Central Guide Local Science and Technology Development Project of Hubei Province of China(No.2023EGA008)the Wuhan Natural Science Foundation Exploration Project(Chenguang Project,2024040801020309)。
文摘The high-temperature dissolution behavior of carbides during the quenching process significantly influences grain growth,mechanical properties,and secondary carbide precipitation,thereby playing a major role in the heat treatment process of die steel.This study investigated the changes in carbide type,particle size distribution,and weight percentage in DC53 steel after holding at 1060℃for 2 h,followed by oil quenching.The analysis was conducted using Thermo-Calc,DICTRA computations,and experimental methods including electron backscatter diffraction,transmission electron microscopy and laser particle size analysis.The experimental results showed that four types of carbides(M_(7)C_(3),M_(6)C,M_(23)C_(6),and MC)existed in DC53 steel before quenching.After quenching,M_(23)C_(6)carbides were almost entirely dissolved,while the other three types partially dissolved into the matrix.The volume-weighted geometric mean size of carbides(x_(geo,3))increased from 5.43 to 15.15μm,and the weight percentage decreased from 13.03%to 5.01%.Small-sized carbides(below 5μm)dissolved more readily,which primarily accounted for the reduction in carbide weight percentage during quenching.In contrast,the weight percentage of large-sized carbides(greater than 10μm)varies less.DICTRA computations indicated that M_(7)C_(3)carbides smaller than 7μm can completely dissolve into the matrix after holding at 1060℃for 2 h.The findings provide an effective reference for optimizing carbide control during the heat treatment process of DC53 steel.
基金financial support of the Central Guide Local Science and Technology Development Project of Hubei Province of China(No.2023EGA008)the Wuhan Natural Science Foundation Exploration Project(Chenguang Project)(No.2024040801020309).
文摘As the main use of TBM(tunnel boring machine)cutter ring(DC53 steel)currently is difficult to meet the requirements of high wear resistance and high toughness synchronously in its service environment,a new HWR0 steel with 4%Cr-3%V for TBM cutter ring has been developed to control carbides in steel.Precipitation behavior of carbides in HWR0 steel was investigated through theoretical calculation by Thermo-Calc and experimental measurement using scanning electron microscope,energy dispersive spectrometer,electron probe X-ray micro-analyzer,and laser particle size analyzer.The results show that three different carbides are precipitated during cooling.And the as-cast electroslag remelting ingot of HWR0 steel primarily consists of many blocky or strip-like MC distributed along grain boundaries,few chrysanthemum-like M_(6)C concentrated at grain boundary intersections,and a large quantity of fine M_(23)C_(6)and M_(6)C dispersed in the matrix.Compared with DC53 steel,HWR0 steel has more high-hardness carbides MC,which are discontinuously distributed at the grain boundaries,achieving the dual improvement of wear resistance and impact toughness.Cooling rates significantly influence the carbides distribution and grain size.A slower cooling rate exacerbates the segregation of alloying elements,which leads to the localized enrichment of Mo and the subsequent precipitation of M_(6)C carbides at grain boundary intersections.In contrast,faster cooling rate decreases the element segregation,promotes carbide nucleation and limits the space for carbides growth,which results in finer size and distribution of carbides and grains.Higher cooling rates yield a more homogeneous microstructure with uniform MC compositions and promote the preferential formation of M_(6)C carbides along grain boundaries,which enhances the mechanical properties.
基金financially supported by the National Natural Science Foundation of China (No. 51274266)the Joint Research Fund of National Natural Science Foundation of China and Baosteel Group Corporation (No. U1360103)the Fundamental Research Funds for Central Universities of China (No. N150202003)
文摘A better understanding of droplet formation and dripping behavior would be useful in the efficient removal of impurity elements and nonmetallic inclusions from liquid metals. In the present work, we developed a transparent experimental apparatus to study the mechanisms of droplet formation and the effects of filling ratio on droplet behavior during the electroslag remelting（ESR） process. A high-speed camera was used to clearly observe, at small time scales, the droplet formation and dripping phenomenon at the slag/metal interface during a stable ESR process. The results illustrate that a two-stage process for droplet formation and dripping occurs during the ESR process and that the droplet diameter exhibits a parabolic distribution with increasing filling ratio because of the different shape and thermal state of the electrode tip. This work also confirms that a relatively large filling ratio reduces electricity consumption and improves ingot quality.
