In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, ...In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, attempt has been made to establish equations of the isochronous stress-strain for weld joint that can predict the function of loading and service time in use of the creep data of base metal and weld metal.展开更多
A high-building multi-directional pipe joint(HBMDPJ)was fabricated by wire and arc additive manufacturing using high-strength low-alloy(HSLA)steel.The microstructure characteristics and transformation were observed an...A high-building multi-directional pipe joint(HBMDPJ)was fabricated by wire and arc additive manufacturing using high-strength low-alloy(HSLA)steel.The microstructure characteristics and transformation were observed and analyzed.The results show that the forming part includes four regions.The solidification zone solidifies as typical columnar crystals from a molten pool.The complete austenitizing zone forms from the solidification zone heated to a temperature greater than 1100℃,and the typical columnar crystals in this zone are difficult to observe.The partial austenitizing zone forms from the completely austenite zone heated between Ac1(austenite transition temperature)and1100℃,which is mainly equiaxed grains.After several thermal cycles,the partial austenitizing zone transforms to the tempering zone,which consistes of fully equiaxed grains.From the solidification zone to the tempering zone,the average grain size decreases from 75 to20μm.The mechanical properties of HBMDPJ satisfies the requirement for the intended application.展开更多
The finite element simulation software SYSWELD is used to numerically simulate the temperature field,residual stress field,and welding deformation of Q690D thick plate multi-layer and multi-pass welding under differen...The finite element simulation software SYSWELD is used to numerically simulate the temperature field,residual stress field,and welding deformation of Q690D thick plate multi-layer and multi-pass welding under different welding heat input and groove angles.The simulation results show that as the welding heat input increases,the peak temperature during the welding process is higher,and the residual stress increases,they are all between 330–340 MPa,and the residual stress is concentrated in the area near the weld.The hole-drilling method is used to measure the actual welding residual stress,and the measured data is in good agreement with the simulated value.The type of post-welding deformation is angular deformation,and as the welding heat input increases,the maximum deformation also increases.It shows smaller residual stress and deformation when the groove angle is 40°under the same heat input.In engineering applications,under the premise of guaranteeing welding quality,smaller heat input and 40°groove angle should be used.展开更多
Effects of alloying elements,Si,Nb,Ti,W,Mo,V,Al and rare earth metals on the microstructure and properties of high speed steels(HSSs) have been reviewed.More attention is paid to effects of Si on the secondary hardeni...Effects of alloying elements,Si,Nb,Ti,W,Mo,V,Al and rare earth metals on the microstructure and properties of high speed steels(HSSs) have been reviewed.More attention is paid to effects of Si on the secondary hardening and V on the morphology of eutectic carbides in HSSs.A lot of work has been carried out on the behavior of alloying elements in HSSs in the past decade,and some new types of HSSs containing silicon,aluminum or rare earth metals have been successfully developed in the world.展开更多
Naval grade high strength low alloy(HSLA) steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, dis...Naval grade high strength low alloy(HSLA) steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, distortion and fatigue damage. These problems can be eliminated by solid state welding process such as friction stir welding(FSW). In this investigation, a comparative evaluation of mechanical(tensile, impact,hardness) properties and microstructural features of shielded metal arc(SMA), gas metal arc(GMA) and friction stir welded(FSW) naval grade HSLA steel joints was carried out. It was found that the use of FSW process eliminated the problems related to fusion welding processes and also resulted in the superior mechanical properties compared to GMA and SMA welded joints.展开更多
The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine,and the forming of 6063 rod extrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of 2...The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine,and the forming of 6063 rod extrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of 25 on the platform of DEFORM 2D successfully.From the compression experimental results,the flow stress model of this Al alloy is obtained which could be the constitutive equation in the simulation of low-temperature high-speed extrusion process.From the numerical simulation results,there is a higher strain concentration at the entrance of the die and the exit temperature reaches up to 522℃in low-temperature high-speed extrusion,which approaches to the quenching temperature of the 6063 Al alloy.The results show that the low-temperature high-speed extrusion method as a promsing one can reduce energy consumption effectively.展开更多
The effect of microstructure variation on the corrosion behavior of high-strength low-alloy(HSLA) steel was investigated. The protective property of the corrosion product layer was also explored. Experimental result...The effect of microstructure variation on the corrosion behavior of high-strength low-alloy(HSLA) steel was investigated. The protective property of the corrosion product layer was also explored. Experimental results reveal that the type of microstructure has significant effect on the corrosion resistance of HSLA steel. The measurement results of weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy indicate that the steel with acicular ferrite microstructure exhibits the lowest corrosion rate. Martensite exhibits a reduced corrosion resistance compared with polygonal ferrite. It is found that the surface of the acicular ferrite specimen uniformly covered by corrosion products is seemingly denser and more compact than those of the other two microstructures, and can provide some amount of protection to the steel; thus, the charge transfer resistance and modulus values of the acicular ferrite specimen are the largest. However, corrosion products on martensite and polygonal ferrite are generally loose, porous, and defective, and can provide minor protectiveness; thus, the charge transfer resistance values for polygonal ferrite and martensite are lower.展开更多
High strength low alloy steel with 16 mm thickness was welded by using high power laser hybrid welding. Microstrueture was characterized by using optical microscopy, scanning electron microscopy ( SEM ) , transmissi...High strength low alloy steel with 16 mm thickness was welded by using high power laser hybrid welding. Microstrueture was characterized by using optical microscopy, scanning electron microscopy ( SEM ) , transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Low temperature impact toughness was estimated by using Charpy V-notch impact samples selected from the upper part and the lower part at the same heterogeneous joint. Results show that the low temperature impact absorbed energies of weld metal are (202,180,165 J) of upper samples and (178,145,160 J) of lower samples, respectively. All of them increase compared to base metal. The embrittlement of HAZ does not occur. Weld metal primarily consists of refined carbide free bainite and a little granular bainite since laser hybrid welding owns the character of low heat input. Retained austenite constituent film "locates among the lath structure of bainitie ferrite. Refined bainitic ferrite lath and retained austenite constituent film provide better low temperature impact toughness compared to base metal.展开更多
For better processing performance of high carbon low alloy steel wire rod,an investigation about the influence of cementite lamellar spacing on wire 'easy drawing' performance is completed.It is pointed out th...For better processing performance of high carbon low alloy steel wire rod,an investigation about the influence of cementite lamellar spacing on wire 'easy drawing' performance is completed.It is pointed out that too thin cementite lamellar spacing(<80 um) reduces the strain hardening level of wire drawing, and reduce the torsion performance of drawn wire at same time.For the wire or wire rod from industrial production,compared with the micro-structure with troostite,the micro-structure with sorbite or sorbite mixed with pearlite is more suitable to the drawing process with high reduction ratio.展开更多
A formula is derived for determining the influence of temperature and loading rate on dynamic fracture toughness of a high strength low alloy steel (HQ785C) from thermal activation analysis of the experimental results...A formula is derived for determining the influence of temperature and loading rate on dynamic fracture toughness of a high strength low alloy steel (HQ785C) from thermal activation analysis of the experimental results of three-point bend specimens as well as introducing an Arrhenius formula. It is shown that the results obtained by the given formula are in good agreement with the experimental ones in the thermal activation region. The present method is also valuable to describe the relationship between dynamic fracture toughness and temperature and loading rate of other high strength low alloy steels.展开更多
In this study,newly developed low content PCBN was used to evaluate the cutting performance in high speed turning of hardened steel.Using new PCBN and commercially available PCBN tipped inserts under the same cutting ...In this study,newly developed low content PCBN was used to evaluate the cutting performance in high speed turning of hardened steel.Using new PCBN and commercially available PCBN tipped inserts under the same cutting condition,cutting performance with variable cutting speed,feed rate and depth of cuts on tools were measured by observation of flank and crater wear.Its microstructures were analyzed through SEM microscope,measurement of surface roughness on workpiece was also performed. According to cutting performance results,it is shown that new PCBN shows much longer tool life in high speed continuous turning than our conventional PCBN tools,with improved wear and chipping resistance.This result on the machinability of new PCBN for hardened steel will provide effective guidelines to manufacturing engineers,also provide useful economic machining solution for high speed continuous turning for hardened steel.展开更多
In this paper,a Fe-based Mn-Ni–Cr–Mo high strength low alloy(HSLA)steel was prepared by using Vacuum melting,following by hot rolling with 78%deformation and various heat treatment processes.Microstructure were char...In this paper,a Fe-based Mn-Ni–Cr–Mo high strength low alloy(HSLA)steel was prepared by using Vacuum melting,following by hot rolling with 78%deformation and various heat treatment processes.Microstructure were characterized by optical microscope(OM),scanning electron microscope(SEM)equipped with energy dispersive spectrometer.Tensile tests were performed.After direct quenching(Q)from 860℃,the samples were subjected to secondary quenching(L)at different intercritical temperatures within the two-phase region and various tempering temperatures(T).Results show that QLT treatment increases elongation and decreases yield ratio compared with conventional quenching and tempering process(QT).The optimum QLT heat treatment parameter in terms of temperature are determined as Q:860℃,L:700℃,and T:600℃,resulting in the better combined properties with yield strength of 756MPa,tensile strength of 820MPa,tensile elongation of 16.76%and yield ratio of 0.923.展开更多
The present study aims at developing high speed steel (HSS) as roll materialsto replace traditional roll materials such as the alloy cast iron and powder metallurgical (PM)hard alloy, because low-cost alloy cast iron ...The present study aims at developing high speed steel (HSS) as roll materialsto replace traditional roll materials such as the alloy cast iron and powder metallurgical (PM)hard alloy, because low-cost alloy cast iron rolls have poor wear resistance and the cost ofhigh-quality PM hard alloy rolls is too high to be accepted by some users. By means of a centrifugalcasting method, HSS rolls with excellent wear resistance have been developed. Its hardness is 65-67 HRC, and its variation is smaller than 2HRC; its impact toughness excels 15J/cm^2. Usingpre-finishing stands of a high-speed hot wire-rod rolling mill, the wear rate of HSS rolls per onethousand ton of steel is 0. 25mm. However, the manufacturing burden of HSS rolls is obviously lowerthan that of PM hard alloy rolls; it is only 30% of that of PM hard alloy rolls.展开更多
With the rapid development of low alloy steel strength level,more problems caused by welding are exposed day by day.Recently,the efforts have been paid to improve or enchance the low toughness of heated affected zone ...With the rapid development of low alloy steel strength level,more problems caused by welding are exposed day by day.Recently,the efforts have been paid to improve or enchance the low toughness of heated affected zone and welded metal which can enchance the comprehensive mechanical properties that is the core scientific problems of its safe operation by researching crack initiation and crack propragation attracted a rapidly growing interest.This article focuses on the research status and progress of welding technology and joint microstructure and properties of advanced steel materials.The influence of shielding gas on the microstructure evolution of deposited metals,the effect heat input of welded joint performance,interpass temperature and alloy elements on welded joints microstructure and M-A constituent evolution and properties are reviewed in detail.And for the heat affected zone,the grain size and microstructure as well as the shape,size,and distribution of M-A constituent,have a significant impact on the impact toughness.This paper is an attempt to review the effect of different welding process parameters on welded metal and HAZ of HSLA steels.展开更多
High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important t...High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important to understand the formation behaviors of the Cu precipitates.High-resolution transmission electron microscopy(TEM)is utilized to investigate the structure of Cu precipitates thermally formed in a high-strength low-alloy(HSLA)steel.The Cu precipitates were generally formed from solid solution and at the crystallographic defects such as martensite lath boundaries and dislocations.The Cu precipitates in the same aging condition have various structure of BCC,9 R and FCC,and the structural evolution does not greatly correlate with the actual sizes.The presence of different structures in an individual Cu precipitate is observed,which reflects the structural transformation occurring locally to relax the strain energy.The multiply additions in the steel possibly make the Cu precipitation more complex compared to the binary or the ternary Fe-Cu alloys with Ni or Mn additions.This research gives constructive suggestions on alloying design of Cu-bearing alloy steels.展开更多
The effects of the composition and cooling process on the microstructures and properties of hot-rolled ultra-high strength low alloy (HSLA) steel, complex phase steel and martensite steel were studied in the laborat...The effects of the composition and cooling process on the microstructures and properties of hot-rolled ultra-high strength low alloy (HSLA) steel, complex phase steel and martensite steel were studied in the laboratory. And S700MC and MP1200 ultra-high strength steels were trial produced at the 1 880 mm hot-rolling line of Baosteel. Compared with conventional hot-rolled high strength products,the idea that water is alloy was applied in the newly developed hot-rolled ultra-high strength steel. By the use of the economical composition design and controlled cooling after hot-rolling effectively,ultra-high strength steel of different steel grades can be obtained.展开更多
基金supports provided by Natural Science Foundation of Shanghai(contract No.03ZR14022)the“Tenth Five”National Key Technological Research and Development Program(contract No.2001BA803B03)National Natural Science Foundation of China(contract No.50225517)are gratefully acknowledged.
文摘In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, attempt has been made to establish equations of the isochronous stress-strain for weld joint that can predict the function of loading and service time in use of the creep data of base metal and weld metal.
基金financially supported by the National Key R&D Program of China(No.2017YFB1103200)the Independent Innovation Research Fund Project of Huazhong University of Science and Technology(No.2018KFYXMPT002)。
文摘A high-building multi-directional pipe joint(HBMDPJ)was fabricated by wire and arc additive manufacturing using high-strength low-alloy(HSLA)steel.The microstructure characteristics and transformation were observed and analyzed.The results show that the forming part includes four regions.The solidification zone solidifies as typical columnar crystals from a molten pool.The complete austenitizing zone forms from the solidification zone heated to a temperature greater than 1100℃,and the typical columnar crystals in this zone are difficult to observe.The partial austenitizing zone forms from the completely austenite zone heated between Ac1(austenite transition temperature)and1100℃,which is mainly equiaxed grains.After several thermal cycles,the partial austenitizing zone transforms to the tempering zone,which consistes of fully equiaxed grains.From the solidification zone to the tempering zone,the average grain size decreases from 75 to20μm.The mechanical properties of HBMDPJ satisfies the requirement for the intended application.
文摘The finite element simulation software SYSWELD is used to numerically simulate the temperature field,residual stress field,and welding deformation of Q690D thick plate multi-layer and multi-pass welding under different welding heat input and groove angles.The simulation results show that as the welding heat input increases,the peak temperature during the welding process is higher,and the residual stress increases,they are all between 330–340 MPa,and the residual stress is concentrated in the area near the weld.The hole-drilling method is used to measure the actual welding residual stress,and the measured data is in good agreement with the simulated value.The type of post-welding deformation is angular deformation,and as the welding heat input increases,the maximum deformation also increases.It shows smaller residual stress and deformation when the groove angle is 40°under the same heat input.In engineering applications,under the premise of guaranteeing welding quality,smaller heat input and 40°groove angle should be used.
文摘Effects of alloying elements,Si,Nb,Ti,W,Mo,V,Al and rare earth metals on the microstructure and properties of high speed steels(HSSs) have been reviewed.More attention is paid to effects of Si on the secondary hardening and V on the morphology of eutectic carbides in HSSs.A lot of work has been carried out on the behavior of alloying elements in HSSs in the past decade,and some new types of HSSs containing silicon,aluminum or rare earth metals have been successfully developed in the world.
基金The Director,Naval Material Research Laboratory(NMRL),Ambernath for financial support through CARS project No:G8/15250/2011 dated29.02.2012
文摘Naval grade high strength low alloy(HSLA) steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, distortion and fatigue damage. These problems can be eliminated by solid state welding process such as friction stir welding(FSW). In this investigation, a comparative evaluation of mechanical(tensile, impact,hardness) properties and microstructural features of shielded metal arc(SMA), gas metal arc(GMA) and friction stir welded(FSW) naval grade HSLA steel joints was carried out. It was found that the use of FSW process eliminated the problems related to fusion welding processes and also resulted in the superior mechanical properties compared to GMA and SMA welded joints.
基金Project(2008A09030004) supported by the Major Science and Technology Project of Guangdong Province,ChinaProject(30815009) supported by the Foundation of State Key Laboratory of Advanced Design and Manufacture for Vehicle Body
文摘The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine,and the forming of 6063 rod extrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of 25 on the platform of DEFORM 2D successfully.From the compression experimental results,the flow stress model of this Al alloy is obtained which could be the constitutive equation in the simulation of low-temperature high-speed extrusion process.From the numerical simulation results,there is a higher strain concentration at the entrance of the die and the exit temperature reaches up to 522℃in low-temperature high-speed extrusion,which approaches to the quenching temperature of the 6063 Al alloy.The results show that the low-temperature high-speed extrusion method as a promsing one can reduce energy consumption effectively.
基金financially supported by the National Science Fund for Distinguished Young Scholars (No. 51325401)the International Thermonuclear Experimental Reactor (ITER) Program Special Project (No. 2014GB125006)+1 种基金the Major State Basic Research Development Program of China (No. 2014CB046805)the National Natural Science Foundation of China (No. 51474156)
文摘The effect of microstructure variation on the corrosion behavior of high-strength low-alloy(HSLA) steel was investigated. The protective property of the corrosion product layer was also explored. Experimental results reveal that the type of microstructure has significant effect on the corrosion resistance of HSLA steel. The measurement results of weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy indicate that the steel with acicular ferrite microstructure exhibits the lowest corrosion rate. Martensite exhibits a reduced corrosion resistance compared with polygonal ferrite. It is found that the surface of the acicular ferrite specimen uniformly covered by corrosion products is seemingly denser and more compact than those of the other two microstructures, and can provide some amount of protection to the steel; thus, the charge transfer resistance and modulus values of the acicular ferrite specimen are the largest. However, corrosion products on martensite and polygonal ferrite are generally loose, porous, and defective, and can provide minor protectiveness; thus, the charge transfer resistance values for polygonal ferrite and martensite are lower.
文摘High strength low alloy steel with 16 mm thickness was welded by using high power laser hybrid welding. Microstrueture was characterized by using optical microscopy, scanning electron microscopy ( SEM ) , transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Low temperature impact toughness was estimated by using Charpy V-notch impact samples selected from the upper part and the lower part at the same heterogeneous joint. Results show that the low temperature impact absorbed energies of weld metal are (202,180,165 J) of upper samples and (178,145,160 J) of lower samples, respectively. All of them increase compared to base metal. The embrittlement of HAZ does not occur. Weld metal primarily consists of refined carbide free bainite and a little granular bainite since laser hybrid welding owns the character of low heat input. Retained austenite constituent film "locates among the lath structure of bainitie ferrite. Refined bainitic ferrite lath and retained austenite constituent film provide better low temperature impact toughness compared to base metal.
文摘For better processing performance of high carbon low alloy steel wire rod,an investigation about the influence of cementite lamellar spacing on wire 'easy drawing' performance is completed.It is pointed out that too thin cementite lamellar spacing(<80 um) reduces the strain hardening level of wire drawing, and reduce the torsion performance of drawn wire at same time.For the wire or wire rod from industrial production,compared with the micro-structure with troostite,the micro-structure with sorbite or sorbite mixed with pearlite is more suitable to the drawing process with high reduction ratio.
文摘A formula is derived for determining the influence of temperature and loading rate on dynamic fracture toughness of a high strength low alloy steel (HQ785C) from thermal activation analysis of the experimental results of three-point bend specimens as well as introducing an Arrhenius formula. It is shown that the results obtained by the given formula are in good agreement with the experimental ones in the thermal activation region. The present method is also valuable to describe the relationship between dynamic fracture toughness and temperature and loading rate of other high strength low alloy steels.
基金Suported by Advanced Technolgy center prject(No.10020604)
文摘In this study,newly developed low content PCBN was used to evaluate the cutting performance in high speed turning of hardened steel.Using new PCBN and commercially available PCBN tipped inserts under the same cutting condition,cutting performance with variable cutting speed,feed rate and depth of cuts on tools were measured by observation of flank and crater wear.Its microstructures were analyzed through SEM microscope,measurement of surface roughness on workpiece was also performed. According to cutting performance results,it is shown that new PCBN shows much longer tool life in high speed continuous turning than our conventional PCBN tools,with improved wear and chipping resistance.This result on the machinability of new PCBN for hardened steel will provide effective guidelines to manufacturing engineers,also provide useful economic machining solution for high speed continuous turning for hardened steel.
基金This work was supported by the Project funded by China Postdoctoral Science Foundation,the Fundamental Research Funds for the Central Universities(No.FRF-TP-19-002A1)Domain Foundation of Equipment Advance Research of 13th Five-year Plan(No.61409220124).
文摘In this paper,a Fe-based Mn-Ni–Cr–Mo high strength low alloy(HSLA)steel was prepared by using Vacuum melting,following by hot rolling with 78%deformation and various heat treatment processes.Microstructure were characterized by optical microscope(OM),scanning electron microscope(SEM)equipped with energy dispersive spectrometer.Tensile tests were performed.After direct quenching(Q)from 860℃,the samples were subjected to secondary quenching(L)at different intercritical temperatures within the two-phase region and various tempering temperatures(T).Results show that QLT treatment increases elongation and decreases yield ratio compared with conventional quenching and tempering process(QT).The optimum QLT heat treatment parameter in terms of temperature are determined as Q:860℃,L:700℃,and T:600℃,resulting in the better combined properties with yield strength of 756MPa,tensile strength of 820MPa,tensile elongation of 16.76%and yield ratio of 0.923.
文摘The present study aims at developing high speed steel (HSS) as roll materialsto replace traditional roll materials such as the alloy cast iron and powder metallurgical (PM)hard alloy, because low-cost alloy cast iron rolls have poor wear resistance and the cost ofhigh-quality PM hard alloy rolls is too high to be accepted by some users. By means of a centrifugalcasting method, HSS rolls with excellent wear resistance have been developed. Its hardness is 65-67 HRC, and its variation is smaller than 2HRC; its impact toughness excels 15J/cm^2. Usingpre-finishing stands of a high-speed hot wire-rod rolling mill, the wear rate of HSS rolls per onethousand ton of steel is 0. 25mm. However, the manufacturing burden of HSS rolls is obviously lowerthan that of PM hard alloy rolls; it is only 30% of that of PM hard alloy rolls.
文摘With the rapid development of low alloy steel strength level,more problems caused by welding are exposed day by day.Recently,the efforts have been paid to improve or enchance the low toughness of heated affected zone and welded metal which can enchance the comprehensive mechanical properties that is the core scientific problems of its safe operation by researching crack initiation and crack propragation attracted a rapidly growing interest.This article focuses on the research status and progress of welding technology and joint microstructure and properties of advanced steel materials.The influence of shielding gas on the microstructure evolution of deposited metals,the effect heat input of welded joint performance,interpass temperature and alloy elements on welded joints microstructure and M-A constituent evolution and properties are reviewed in detail.And for the heat affected zone,the grain size and microstructure as well as the shape,size,and distribution of M-A constituent,have a significant impact on the impact toughness.This paper is an attempt to review the effect of different welding process parameters on welded metal and HAZ of HSLA steels.
基金Supported by Startup Fund for Youngman Research at SJTU(SFYR at SJTU)National Basic Research Program of China(Grant No.2011CB012904)China Postdoctoral Science Foundation(Grant No.2013M541517)
文摘High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important to understand the formation behaviors of the Cu precipitates.High-resolution transmission electron microscopy(TEM)is utilized to investigate the structure of Cu precipitates thermally formed in a high-strength low-alloy(HSLA)steel.The Cu precipitates were generally formed from solid solution and at the crystallographic defects such as martensite lath boundaries and dislocations.The Cu precipitates in the same aging condition have various structure of BCC,9 R and FCC,and the structural evolution does not greatly correlate with the actual sizes.The presence of different structures in an individual Cu precipitate is observed,which reflects the structural transformation occurring locally to relax the strain energy.The multiply additions in the steel possibly make the Cu precipitation more complex compared to the binary or the ternary Fe-Cu alloys with Ni or Mn additions.This research gives constructive suggestions on alloying design of Cu-bearing alloy steels.
文摘The effects of the composition and cooling process on the microstructures and properties of hot-rolled ultra-high strength low alloy (HSLA) steel, complex phase steel and martensite steel were studied in the laboratory. And S700MC and MP1200 ultra-high strength steels were trial produced at the 1 880 mm hot-rolling line of Baosteel. Compared with conventional hot-rolled high strength products,the idea that water is alloy was applied in the newly developed hot-rolled ultra-high strength steel. By the use of the economical composition design and controlled cooling after hot-rolling effectively,ultra-high strength steel of different steel grades can be obtained.