GENERAL INFORMATIONThe Chinese Society of Metals is pleased to announcethat The Second International Conference on HSLASteels(HSEA’90)will be held in Beijing,China inOctober 1990.Much progress in research and devel-o...GENERAL INFORMATIONThe Chinese Society of Metals is pleased to announcethat The Second International Conference on HSLASteels(HSEA’90)will be held in Beijing,China inOctober 1990.Much progress in research and devel-opment of HSLA steels has been achieved by theworld’s metallurgical and materials community sincethe previous International Conference HSLA Steels’85 was held in Beijing,The aim of the conference isto review and to consolidate the scientific,metallurgical,and economical results and to assessthe future trend of development in the fields.展开更多
GENERAL INFORMATIONThe Chinese Society of Metals is pleased to announcethat The Second International Conference on HSLASteels (HSLA’90) will be held in Beijing,China inOctober 1990.Much progress in research and devel...GENERAL INFORMATIONThe Chinese Society of Metals is pleased to announcethat The Second International Conference on HSLASteels (HSLA’90) will be held in Beijing,China inOctober 1990.Much progress in research and devel-opment of HSLA steels has been achieved by theworld’s metallurgical and materials community since展开更多
General Information The Chinese Society of Metals ispleased to announce that The SecondInternational Conference on HSLA Steels(HSLA ’90) will be held in Beijing, Chinain October, 1990. Much progress in researchand de...General Information The Chinese Society of Metals ispleased to announce that The SecondInternational Conference on HSLA Steels(HSLA ’90) will be held in Beijing, Chinain October, 1990. Much progress in researchand development of HSLA steels has beenachieved by the world’s metallurgical andmaterials community since the previousInternational Conference HSLA Steels ’85展开更多
GENERAL INFORMATIONThe Chinese Society of Metals is pleased to announcethat The Second International Conference on HSLASteels(HSLA’90)will be held in Beijing,China inOctober 1990.Much progress in research and devel-o...GENERAL INFORMATIONThe Chinese Society of Metals is pleased to announcethat The Second International Conference on HSLASteels(HSLA’90)will be held in Beijing,China inOctober 1990.Much progress in research and devel-opment of HSLA steels has been achieved by theworld’s metallurgical and materials community since展开更多
Microalloying elements in high-strength low-alloy steels, such as Nb, Ti and V, precipitate during hot-rolling processes. On the basis of classical theory of nucleation and growth, quanti- tative modeling of isotherma...Microalloying elements in high-strength low-alloy steels, such as Nb, Ti and V, precipitate during hot-rolling processes. On the basis of classical theory of nucleation and growth, quanti- tative modeling of isothermal precipitation was developed, which was tested by the stress rela- xation method, the calculated precipitation-time-temperature curve is in good agreements with the measured results, then the model was applied to predict the precipitation behavior during continuous cooling.展开更多
The simulated heat affected zone (HAZ) of the high strength low alloy (HSLA) steels containing 0%, 0.047%, 0.097% and 0.151% vanadium, respectively, were studied with Gleeble-2000 thermomechanical simulator to det...The simulated heat affected zone (HAZ) of the high strength low alloy (HSLA) steels containing 0%, 0.047%, 0.097% and 0.151% vanadium, respectively, were studied with Gleeble-2000 thermomechanical simulator to determine the influence of vanadium addition on the mechanical properties of the HAZ. The HAZ simulation involved reheating the samples to 1350℃, and then cooling to ambient temperature at a cooling rate of 5℃/s ranging from 800 to 500℃ (△8/5=60s). The mechanical properties including tensile strength and -20℃ impact toughness were conducted. The microstructures of the base steel and the simulated HAZs were investigated using optical microscope, scanning electron microscope ( SEM ) and transmission electron microscope (TEM). Based on the systemutic examination, the present work confirmed that about 0.05% vanadium addition to low carbon low alloy steels resulted in expected balance of strength and toughness of the HAZ. And more than 0.10% levels addition led to detrimental toughness of the HAZ SEM study showed that the simulated 0.097% and 0.151%V HAZs consisted of more coarse ferrite plates with greater and more M-A constituents along austenite grain and ferrite plate bound- aries. The impact fracture surfaces of the simulated 0.097% and 0.151%V HAZs showed typically brittle mode with predominant cleavages. The size of the facet in the fracture surface increased with increasing vanadium level from 0.097% to 0.151%.As a result, the simulated 0.151% V HAZ has the lowest impact toughness of the four specimens.展开更多
High strength low alloy(HSLA) steels have been widely used in pipelines,power plant components,civil structures and so on,due to their outstanding mechanical properties as high strength and toughness,and excellent w...High strength low alloy(HSLA) steels have been widely used in pipelines,power plant components,civil structures and so on,due to their outstanding mechanical properties as high strength and toughness,and excellent weldability.Multi-phase microstructures containing acicular ferrite or acicular ferrite dominated phase have been proved to possess good comprehensive properties in HSLA steels.This paper mainly focuses on the formation mechanisms and control methods of acicular ferrite in HSLA steels.Effect of austenitizing conditions,continuous cooling rate,and isothermal quenching time and temperature on acicular ferrite transformation was reviewed.Furthermore,the modified process to control the formation of multi-phase microstructures containing acicular ferrite,as intercritical heat treatments,step quenching treatments and thermo-mechanical controlled processing,was summarized.The favorable combination of mechanical properties can be achieved by these modified treatments.展开更多
The influence of Nb on microstructure, mechanical property and the transformation kinetics of the coarse grain heat affected zone (CGHAZ) in HSLA steels for different heat inputs, has been investigated. When welded ...The influence of Nb on microstructure, mechanical property and the transformation kinetics of the coarse grain heat affected zone (CGHAZ) in HSLA steels for different heat inputs, has been investigated. When welded at higher heat inputs (100-60 kJ/cm), impact toughness values of the steel without Nb are much higher than those of the steel with Nb, and the lowest span is 153 J at 60 kJ/cm. But only a little higher values are observed at lower heat inputs (40-30 kJ/cm), and the highest span is 68 J at 30 kJ/cm. Dilatation studies indicate that continuous cooling transformation starting temperatures (Ts) of CGHAZ for the steel with Nb are approximately 15-30℃ which are lower than those of the steel without Nb at all heat inputs. For higher heat inputs, Nb in solid solution suppresses ferrite transformation and promotes the formation of granular bainite which has detrimental effect on impact toughness. For lower heat inputs higher Charpy impact energy values in the steel with Nb are associated with the formation of low carbon self-tempered martensite.展开更多
During the last decade,the adjustment of product segments always is a very important task of iron industry,and upgrading of steel products has been impelled actively by Chinese iron and steel industry.With rapidly inc...During the last decade,the adjustment of product segments always is a very important task of iron industry,and upgrading of steel products has been impelled actively by Chinese iron and steel industry.With rapidly increasing of iron & steel production,a series of research achievements have been made in the technology area of high strengthtoughness steel,and also have been applied successfully in the actual production,e.g.the technology of fine grain and ultra-fine grain steels,the technology for the control of microalloying precipitates.Further,It is an important strategic goal of "Twelfth Five-year Plan" for Chinese iron and steel industry that the adjustment of steel product segments and meeting the requirements for upgrading of domestic and oversea equipment manufactory industry.Adopting HSLA steel with better performance,instead of plain steel,could save steel consumption largely,and also release pressures from resource,energy and environment.Without doubt,it is the only way to realize the sustained development of Chinese iron and steel industry by popularizing the application of HSLA steels vigorously.展开更多
The microstructure and the characteristics of the inclusions embedded in ferrite matrix in simulated coarse-grain heat affected zone (CGHAZ) of a Ti-Zr-treated high strength low alloy (HSLA) steel have been investigat...The microstructure and the characteristics of the inclusions embedded in ferrite matrix in simulated coarse-grain heat affected zone (CGHAZ) of a Ti-Zr-treated high strength low alloy (HSLA) steel have been investigated. The microstructure of the simulated CGHAZ dominantly consisted of intragranular acicular ferrite (IAF) combining with a small amount of polygonal ferrite (PF), widmanst tten ferrite (WF), bainite ferrite (BF), pearlite and martensite-austenite (M-A) islands. The PF, WF and BF were generally observed at the prior austenite grain boundaries and the interlocking acicular ferrite was usually found intragranularly. It was found that the inclusions were composed of Ti2O3, ZrO2, Al2O3 locating at the center of the particles and MnS lying on the surface layer of the inclusions. The intragranular complex inclusions promoted the acicular ferrite formation and the refinement of microstructure whilst those at prior austenite grain boundaries caused PF formation on the inclusions. The simulated CGHAZ consisting of such complicated microstructure exhibited desired mechanical properties.展开更多
The effect of relaxation after finished rolling on structures and properties of four microalloyed steel with different content of Nb and Ti was investigated. By alloy designing and control rolling + relaxation-precipi...The effect of relaxation after finished rolling on structures and properties of four microalloyed steel with different content of Nb and Ti was investigated. By alloy designing and control rolling + relaxation-precipitation-control phase trail storm ati on (RPC) process, a new 800 MPa grade HSLA plate steel could be obtained, the microstructure is composite ultra-fine lath bainite/martensite. The tempering process and mechanical properties of this kind of HSLA steel were investigated. The yield strength can achieve 800 MPa, and the ductility and impact toughness is satisfied.展开更多
Effects of microalloying Ti and B on the microstructures and low temperature toughness of manual metal arc (MMA) deposits were investi- gated.Weld metals containing 200-300 ppm Ti and 29-60 ppm B deposited by manual c...Effects of microalloying Ti and B on the microstructures and low temperature toughness of manual metal arc (MMA) deposits were investi- gated.Weld metals containing 200-300 ppm Ti and 29-60 ppm B deposited by manual coated elec- trodes provided an optimum low temperature toughness.The addition of B in weld metals low- ered the γ→α transformation temperature which promoted the acicular ferrite (AF) transformation. Solid solutioned B suppressed grain boundary ferrite as well as side plate ferrite formation and benefited the acicular ferrite formation.Titanium protected B from oxidizing as well as nitriding and formed Ti-Mn silicate inclusions.Ultra-high volt- age electron microscope analyses showed that TiO structure in the Ti-Mn silicate inclusions was the favorable nucleation site for acicular ferrite forma- tion.展开更多
Effect of boron on microstructure and toughness of simulated CGHAZ of 790 MPa grade HSLA steel was studied.In the CGHAZ,boron improved the toughness of granular bainite(Bg),but deteriorated that of martensite.The maj...Effect of boron on microstructure and toughness of simulated CGHAZ of 790 MPa grade HSLA steel was studied.In the CGHAZ,boron improved the toughness of granular bainite(Bg),but deteriorated that of martensite.The major reason of boron improving toughness of Bg was to reduce the.quantity of M-A constituents.The reasons of martensitic brittleness in microstructure were discussed in detail.The experimental results proved that the order state of dislocations was an important factor of martensitic brittleness caused by boron, and the higher the order degree of dislocations was, the more brittle the martensite was.展开更多
An experinientally quantitative inveetisation has been made on the precipitationand coarsening behaviors of niobium carbide in a high strength low alloy(HSLA) steel. The results suggest that the static coarsening proc...An experinientally quantitative inveetisation has been made on the precipitationand coarsening behaviors of niobium carbide in a high strength low alloy(HSLA) steel. The results suggest that the static coarsening processes duringisothermal reaction in (α+γ) two phase region and during isothermal stay aftercertain amount of deformation of austenite are principally controlled by thediffusion of niobium atoms along dislocation pipes, and the volume fraction ofthe precipitates exerts sisnificant influence on the coarsening processes.Whereas the dynamic coarsening process during hot deformation of austeniteappoars to be dominated by the carbide/matrix interphase reaction.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
Majority of the buildings,including industrial buildings,are constructed using either structural steel (plates and structural shapes) or deformed bar steel reinforced concrete.Such buildings,however,must be designed t...Majority of the buildings,including industrial buildings,are constructed using either structural steel (plates and structural shapes) or deformed bar steel reinforced concrete.Such buildings,however,must be designed to be safe and serviceable during construction and during use and occupancy.These objectives can be easily achieved by the use of steels having superior mechanical properties,ductility,weldability,fire resistance,etc.Over the years,the steel industry has made improvements in steel making technologies resulting in high strength low alloy (HSLA) steels with superior steel properties well suited for building construction.First part of this paper presents the structural design considerations,and the constructional considerations associated with the building structures in general,and steel structures in particular.This second part of the paper looks at the acceptance criteria for HSLA steels for North American building codes and construction.The third part of the paper presents the structural properties of currently available HSLA steels for building construction.The discussion focuses on hot-rolled structural steel shapes as well as deformed steel bars for concrete reinforcement.The paper argues that Niobium microalloying is the key to achieving superior properties in such steels.展开更多
Research status of high strength low alloy TRIP (transformation induced plasticity) steels for automobile structural parts is briefly described. Composition and microstruc-ture factors especially the morphology, size ...Research status of high strength low alloy TRIP (transformation induced plasticity) steels for automobile structural parts is briefly described. Composition and microstruc-ture factors especially the morphology, size and volume fraction of retained austenite, which largely influence the strength and ductility of the steel, are reviewed and discussed one after another. Modelling of the inter-critical annealing and martempering processes as well as the designing of the TRIP steel aided by commercial software are introduced. Some special aspects of the dynamic mechanical properties of TRIP steel are firstly reported.展开更多
The plate rigid restraint cracking tests (PRRC) have been used to study the welding cold cracking susceptibilities of four kinds of domestic HSLA steels and the effects of diffusive hydrogen content. In welded joints,...The plate rigid restraint cracking tests (PRRC) have been used to study the welding cold cracking susceptibilities of four kinds of domestic HSLA steels and the effects of diffusive hydrogen content. In welded joints, welding heat input, local preheat temperature, restraint intensity and additional stress induced by local preheating on cold cracking susceptibility of steels have been discussed. On the basis of the above research, the critical cooling time criterion tcr of domestic HSLA steels is established. This criterion is proved to be reliable in real application, and has important significance to assess whether the cold cracking occurs under conditions of welding process.展开更多
The addition of microalloying elements (MAE) to low C-Mn-Si HSLA steels has led to many benefits to the producers,fabricators and end-users.Microstructural improvements such as microstructural refinement,higher disloc...The addition of microalloying elements (MAE) to low C-Mn-Si HSLA steels has led to many benefits to the producers,fabricators and end-users.Microstructural improvements such as microstructural refinement,higher dislocation and sub-grain boundary densities and finer M-A-C distributions have led to higher strength,improved toughness and better formability.These improvements can often be traced to the MA addition.In steels for load-bearing applications,the combination of MAE with hardenability additions (Cr,Mo,B,etc.) and lower transformation temperatures has led to much higher strength levels than what were available a few years ago.The resulting nonpolygonal,bainitic and martensitic ferrite microstructures have not only higher strengths but also adequate levels of improved ductility and toughness.Hot strip,plate and pipe applications have benefitted from these developments.Similar improvements have been found in the microalloyed forging steels,where the change from pearlite-ferrite to bainitic ferrite microstructures has led to higher strengths and improved high-cycle fatigue resistance,with little penalty in ductility and toughness.In the cold rolled gauges,both the so-called Advanced High Strength Steels (DP,TRIP and Complex Phase Steels) and the martensitic direct-quenched and press-quenched steels,along with the Interstitial-Free steels,have benefited from MAE additions,especially in the very popular zinc-coated sheet form.This paper will briefly review each of these topic areas,and the underlying physical metallurgy will be discussed.展开更多
On-line thermo mechanical controlled processing(TMCP) was conducted to develop the third generation high strength low alloy(HSLA) steel with high toughness economically.The ultra-low carbon content ensured a high leve...On-line thermo mechanical controlled processing(TMCP) was conducted to develop the third generation high strength low alloy(HSLA) steel with high toughness economically.The ultra-low carbon content ensured a high level of upper shelf energy while ultrafine lath martensitic structure transformed from super-thin pancaked austenite during controlled rolling and cooling.The reduction of martensite block size decreased ductile-to-brittle transition temperature(DBTT) and compensated the strength loss due to carbon reduction.Consequently,the excellent balance of strength and toughness values was obtained as 950-1060 MPa for yield strength,180 J for Charpy V-notch impact absorbed energy at 30℃,which is much superior to that of traditional martensitic steel.Two mechanisms for the refinement of lath martensite block were proposed:One is the austenite grain refinement in the direction of thickness,and the other is the reduction in the fraction of sub-block boundaries with small misorientation and the increase in the fraction of block boundaries with large misorientation,possibly due to austenite hardening.展开更多
文摘GENERAL INFORMATIONThe Chinese Society of Metals is pleased to announcethat The Second International Conference on HSLASteels(HSEA’90)will be held in Beijing,China inOctober 1990.Much progress in research and devel-opment of HSLA steels has been achieved by theworld’s metallurgical and materials community sincethe previous International Conference HSLA Steels’85 was held in Beijing,The aim of the conference isto review and to consolidate the scientific,metallurgical,and economical results and to assessthe future trend of development in the fields.
文摘GENERAL INFORMATIONThe Chinese Society of Metals is pleased to announcethat The Second International Conference on HSLASteels (HSLA’90) will be held in Beijing,China inOctober 1990.Much progress in research and devel-opment of HSLA steels has been achieved by theworld’s metallurgical and materials community since
文摘General Information The Chinese Society of Metals ispleased to announce that The SecondInternational Conference on HSLA Steels(HSLA ’90) will be held in Beijing, Chinain October, 1990. Much progress in researchand development of HSLA steels has beenachieved by the world’s metallurgical andmaterials community since the previousInternational Conference HSLA Steels ’85
文摘GENERAL INFORMATIONThe Chinese Society of Metals is pleased to announcethat The Second International Conference on HSLASteels(HSLA’90)will be held in Beijing,China inOctober 1990.Much progress in research and devel-opment of HSLA steels has been achieved by theworld’s metallurgical and materials community since
文摘Microalloying elements in high-strength low-alloy steels, such as Nb, Ti and V, precipitate during hot-rolling processes. On the basis of classical theory of nucleation and growth, quanti- tative modeling of isothermal precipitation was developed, which was tested by the stress rela- xation method, the calculated precipitation-time-temperature curve is in good agreements with the measured results, then the model was applied to predict the precipitation behavior during continuous cooling.
文摘The simulated heat affected zone (HAZ) of the high strength low alloy (HSLA) steels containing 0%, 0.047%, 0.097% and 0.151% vanadium, respectively, were studied with Gleeble-2000 thermomechanical simulator to determine the influence of vanadium addition on the mechanical properties of the HAZ. The HAZ simulation involved reheating the samples to 1350℃, and then cooling to ambient temperature at a cooling rate of 5℃/s ranging from 800 to 500℃ (△8/5=60s). The mechanical properties including tensile strength and -20℃ impact toughness were conducted. The microstructures of the base steel and the simulated HAZs were investigated using optical microscope, scanning electron microscope ( SEM ) and transmission electron microscope (TEM). Based on the systemutic examination, the present work confirmed that about 0.05% vanadium addition to low carbon low alloy steels resulted in expected balance of strength and toughness of the HAZ. And more than 0.10% levels addition led to detrimental toughness of the HAZ SEM study showed that the simulated 0.097% and 0.151%V HAZs consisted of more coarse ferrite plates with greater and more M-A constituents along austenite grain and ferrite plate bound- aries. The impact fracture surfaces of the simulated 0.097% and 0.151%V HAZs showed typically brittle mode with predominant cleavages. The size of the facet in the fracture surface increased with increasing vanadium level from 0.097% to 0.151%.As a result, the simulated 0.151% V HAZ has the lowest impact toughness of the four specimens.
基金the China National Funds for Distinguished Young Scientists (Grant No.51325401)the National Magnetic Confinement Fusion Energy Research Project (Grant No.2015GB119001)the National Natural Science Foundation of China (Grant Nos.51501126,51474156 and U1660201) for grant and financial support
文摘High strength low alloy(HSLA) steels have been widely used in pipelines,power plant components,civil structures and so on,due to their outstanding mechanical properties as high strength and toughness,and excellent weldability.Multi-phase microstructures containing acicular ferrite or acicular ferrite dominated phase have been proved to possess good comprehensive properties in HSLA steels.This paper mainly focuses on the formation mechanisms and control methods of acicular ferrite in HSLA steels.Effect of austenitizing conditions,continuous cooling rate,and isothermal quenching time and temperature on acicular ferrite transformation was reviewed.Furthermore,the modified process to control the formation of multi-phase microstructures containing acicular ferrite,as intercritical heat treatments,step quenching treatments and thermo-mechanical controlled processing,was summarized.The favorable combination of mechanical properties can be achieved by these modified treatments.
文摘The influence of Nb on microstructure, mechanical property and the transformation kinetics of the coarse grain heat affected zone (CGHAZ) in HSLA steels for different heat inputs, has been investigated. When welded at higher heat inputs (100-60 kJ/cm), impact toughness values of the steel without Nb are much higher than those of the steel with Nb, and the lowest span is 153 J at 60 kJ/cm. But only a little higher values are observed at lower heat inputs (40-30 kJ/cm), and the highest span is 68 J at 30 kJ/cm. Dilatation studies indicate that continuous cooling transformation starting temperatures (Ts) of CGHAZ for the steel with Nb are approximately 15-30℃ which are lower than those of the steel without Nb at all heat inputs. For higher heat inputs, Nb in solid solution suppresses ferrite transformation and promotes the formation of granular bainite which has detrimental effect on impact toughness. For lower heat inputs higher Charpy impact energy values in the steel with Nb are associated with the formation of low carbon self-tempered martensite.
文摘During the last decade,the adjustment of product segments always is a very important task of iron industry,and upgrading of steel products has been impelled actively by Chinese iron and steel industry.With rapidly increasing of iron & steel production,a series of research achievements have been made in the technology area of high strengthtoughness steel,and also have been applied successfully in the actual production,e.g.the technology of fine grain and ultra-fine grain steels,the technology for the control of microalloying precipitates.Further,It is an important strategic goal of "Twelfth Five-year Plan" for Chinese iron and steel industry that the adjustment of steel product segments and meeting the requirements for upgrading of domestic and oversea equipment manufactory industry.Adopting HSLA steel with better performance,instead of plain steel,could save steel consumption largely,and also release pressures from resource,energy and environment.Without doubt,it is the only way to realize the sustained development of Chinese iron and steel industry by popularizing the application of HSLA steels vigorously.
文摘The microstructure and the characteristics of the inclusions embedded in ferrite matrix in simulated coarse-grain heat affected zone (CGHAZ) of a Ti-Zr-treated high strength low alloy (HSLA) steel have been investigated. The microstructure of the simulated CGHAZ dominantly consisted of intragranular acicular ferrite (IAF) combining with a small amount of polygonal ferrite (PF), widmanst tten ferrite (WF), bainite ferrite (BF), pearlite and martensite-austenite (M-A) islands. The PF, WF and BF were generally observed at the prior austenite grain boundaries and the interlocking acicular ferrite was usually found intragranularly. It was found that the inclusions were composed of Ti2O3, ZrO2, Al2O3 locating at the center of the particles and MnS lying on the surface layer of the inclusions. The intragranular complex inclusions promoted the acicular ferrite formation and the refinement of microstructure whilst those at prior austenite grain boundaries caused PF formation on the inclusions. The simulated CGHAZ consisting of such complicated microstructure exhibited desired mechanical properties.
文摘The effect of relaxation after finished rolling on structures and properties of four microalloyed steel with different content of Nb and Ti was investigated. By alloy designing and control rolling + relaxation-precipitation-control phase trail storm ati on (RPC) process, a new 800 MPa grade HSLA plate steel could be obtained, the microstructure is composite ultra-fine lath bainite/martensite. The tempering process and mechanical properties of this kind of HSLA steel were investigated. The yield strength can achieve 800 MPa, and the ductility and impact toughness is satisfied.
文摘Effects of microalloying Ti and B on the microstructures and low temperature toughness of manual metal arc (MMA) deposits were investi- gated.Weld metals containing 200-300 ppm Ti and 29-60 ppm B deposited by manual coated elec- trodes provided an optimum low temperature toughness.The addition of B in weld metals low- ered the γ→α transformation temperature which promoted the acicular ferrite (AF) transformation. Solid solutioned B suppressed grain boundary ferrite as well as side plate ferrite formation and benefited the acicular ferrite formation.Titanium protected B from oxidizing as well as nitriding and formed Ti-Mn silicate inclusions.Ultra-high volt- age electron microscope analyses showed that TiO structure in the Ti-Mn silicate inclusions was the favorable nucleation site for acicular ferrite forma- tion.
文摘Effect of boron on microstructure and toughness of simulated CGHAZ of 790 MPa grade HSLA steel was studied.In the CGHAZ,boron improved the toughness of granular bainite(Bg),but deteriorated that of martensite.The major reason of boron improving toughness of Bg was to reduce the.quantity of M-A constituents.The reasons of martensitic brittleness in microstructure were discussed in detail.The experimental results proved that the order state of dislocations was an important factor of martensitic brittleness caused by boron, and the higher the order degree of dislocations was, the more brittle the martensite was.
文摘An experinientally quantitative inveetisation has been made on the precipitationand coarsening behaviors of niobium carbide in a high strength low alloy(HSLA) steel. The results suggest that the static coarsening processes duringisothermal reaction in (α+γ) two phase region and during isothermal stay aftercertain amount of deformation of austenite are principally controlled by thediffusion of niobium atoms along dislocation pipes, and the volume fraction ofthe precipitates exerts sisnificant influence on the coarsening processes.Whereas the dynamic coarsening process during hot deformation of austeniteappoars to be dominated by the carbide/matrix interphase reaction.
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Majority of the buildings,including industrial buildings,are constructed using either structural steel (plates and structural shapes) or deformed bar steel reinforced concrete.Such buildings,however,must be designed to be safe and serviceable during construction and during use and occupancy.These objectives can be easily achieved by the use of steels having superior mechanical properties,ductility,weldability,fire resistance,etc.Over the years,the steel industry has made improvements in steel making technologies resulting in high strength low alloy (HSLA) steels with superior steel properties well suited for building construction.First part of this paper presents the structural design considerations,and the constructional considerations associated with the building structures in general,and steel structures in particular.This second part of the paper looks at the acceptance criteria for HSLA steels for North American building codes and construction.The third part of the paper presents the structural properties of currently available HSLA steels for building construction.The discussion focuses on hot-rolled structural steel shapes as well as deformed steel bars for concrete reinforcement.The paper argues that Niobium microalloying is the key to achieving superior properties in such steels.
基金supported by the National Natural Science Foundation of China(No.50171038)the Chinese Society for Metals and China-Belgium Bilateral Project(No.2001-242).
文摘Research status of high strength low alloy TRIP (transformation induced plasticity) steels for automobile structural parts is briefly described. Composition and microstruc-ture factors especially the morphology, size and volume fraction of retained austenite, which largely influence the strength and ductility of the steel, are reviewed and discussed one after another. Modelling of the inter-critical annealing and martempering processes as well as the designing of the TRIP steel aided by commercial software are introduced. Some special aspects of the dynamic mechanical properties of TRIP steel are firstly reported.
文摘The plate rigid restraint cracking tests (PRRC) have been used to study the welding cold cracking susceptibilities of four kinds of domestic HSLA steels and the effects of diffusive hydrogen content. In welded joints, welding heat input, local preheat temperature, restraint intensity and additional stress induced by local preheating on cold cracking susceptibility of steels have been discussed. On the basis of the above research, the critical cooling time criterion tcr of domestic HSLA steels is established. This criterion is proved to be reliable in real application, and has important significance to assess whether the cold cracking occurs under conditions of welding process.
文摘The addition of microalloying elements (MAE) to low C-Mn-Si HSLA steels has led to many benefits to the producers,fabricators and end-users.Microstructural improvements such as microstructural refinement,higher dislocation and sub-grain boundary densities and finer M-A-C distributions have led to higher strength,improved toughness and better formability.These improvements can often be traced to the MA addition.In steels for load-bearing applications,the combination of MAE with hardenability additions (Cr,Mo,B,etc.) and lower transformation temperatures has led to much higher strength levels than what were available a few years ago.The resulting nonpolygonal,bainitic and martensitic ferrite microstructures have not only higher strengths but also adequate levels of improved ductility and toughness.Hot strip,plate and pipe applications have benefitted from these developments.Similar improvements have been found in the microalloyed forging steels,where the change from pearlite-ferrite to bainitic ferrite microstructures has led to higher strengths and improved high-cycle fatigue resistance,with little penalty in ductility and toughness.In the cold rolled gauges,both the so-called Advanced High Strength Steels (DP,TRIP and Complex Phase Steels) and the martensitic direct-quenched and press-quenched steels,along with the Interstitial-Free steels,have benefited from MAE additions,especially in the very popular zinc-coated sheet form.This paper will briefly review each of these topic areas,and the underlying physical metallurgy will be discussed.
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2010CB630805)the National Natural Science Foundation of China (Grant No. 51071089)
文摘On-line thermo mechanical controlled processing(TMCP) was conducted to develop the third generation high strength low alloy(HSLA) steel with high toughness economically.The ultra-low carbon content ensured a high level of upper shelf energy while ultrafine lath martensitic structure transformed from super-thin pancaked austenite during controlled rolling and cooling.The reduction of martensite block size decreased ductile-to-brittle transition temperature(DBTT) and compensated the strength loss due to carbon reduction.Consequently,the excellent balance of strength and toughness values was obtained as 950-1060 MPa for yield strength,180 J for Charpy V-notch impact absorbed energy at 30℃,which is much superior to that of traditional martensitic steel.Two mechanisms for the refinement of lath martensite block were proposed:One is the austenite grain refinement in the direction of thickness,and the other is the reduction in the fraction of sub-block boundaries with small misorientation and the increase in the fraction of block boundaries with large misorientation,possibly due to austenite hardening.