Sulfate and nitrate reducing bacteria are important culprits for microbiologically influenced corrosion(MIC)using sulfate and nitrate as electron acceptors,respectively.Sulfate and nitrate hold different standard elec...Sulfate and nitrate reducing bacteria are important culprits for microbiologically influenced corrosion(MIC)using sulfate and nitrate as electron acceptors,respectively.Sulfate and nitrate hold different standard electrode potentials,which may lead to differences in corrosion,but their effects on corrosion by the same bacteria have not been reported.The corrosion of Q235 steel affected by Pseudodesulfovibrio cashew(P.cashew)in the sulfate and nitrate media under carbon starvation was studied.It was found that sulfate and nitrate did not lead to differences in corrosion under abiotic conditions.However,P.cashew promoted corrosion in both cases,and the consumption of H_(2)was the main mechanism for MIC.In addition,corrosion was more severe in the sulfate media.The higher corrosivity of P.cashew with sulfate as the electron acceptor is closely related to the higher number of sessile cells in the biofilm,higher bacterial motility,more hydrogen production pathways,and the increased gene expression of enzymes related to energy synthesis.展开更多
As the basic protective element, steel plate had attracted world-wide attention because of frequent threats of explosive loads. This paper reports the relationships between microscopic defects of Q345 steel plate unde...As the basic protective element, steel plate had attracted world-wide attention because of frequent threats of explosive loads. This paper reports the relationships between microscopic defects of Q345 steel plate under the explosive load and its macroscopic dynamics simulation. Firstly, the defect characteristics of the steel plate were investigated by stereoscopic microscope(SM) and scanning electron microscope(SEM). At the macroscopic level, the defect was the formation of cave which was concentrated in the range of 0-3.0 cm from the explosion center, while at the microscopic level, the cavity and void formation were the typical damage characteristics. It also explains that the difference in defect morphology at different positions was the combining results of high temperature and high pressure. Secondly, the variation rules of mechanical properties of steel plate under explosive load were studied. The Arbitrary Lagrange-Euler(ALE) algorithm and multi-material fluid-structure coupling method were used to simulate the explosion process of steel plate. The accuracy of the method was verified by comparing the deformation of the simulation results with the experimental results, the pressure and stress at different positions on the surface of the steel plate were obtained. The simulation results indicated that the critical pressure causing the plate defects may be approximately 2.01 GPa. On this basis, it was found that the variation rules of surface pressure and microscopic defect area of the Q345 steel plate were strikingly similar, and the corresponding mathematical relationship between them was established. Compared with Monomolecular growth fitting models(MGFM) and Logistic fitting models(LFM), the relationship can be better expressed by cubic polynomial fitting model(CPFM). This paper illustrated that the explosive defect characteristics of metal plate at the microscopic level can be explored by analyzing its macroscopic dynamic mechanical response.展开更多
The welding characteristics of 5052 aluminum alloy and Q235 low-carbon steel sheet were systematically studied by the refilled friction stir spot welding.The effects of rotation speed and pressure speed on weld formin...The welding characteristics of 5052 aluminum alloy and Q235 low-carbon steel sheet were systematically studied by the refilled friction stir spot welding.The effects of rotation speed and pressure speed on weld forming,tensile strength,and welded joint structure were analyzed in different welding modes.The results indicated two different connection modes:the chimeric mode and the non-chimeric mode.The corresponding depression depth are 2 and 2.4 mm,respectively.In the non-chimeric connection mode,the steel/aluminum metallurgical interface is a smooth transition,the hook structure is obvious,and the welding mechanism mainly depends on the mutual diffusion between atoms.However,in the chimeric mode,a hook structure will be formed at the metallurgical interface of steel and aluminum.The connection mechanism is determined by mechanical interlocking and mutual diffusion.The maximum strength value is 7.48 kN in non-chimeric mode.At this time,the spindle speed is 1300 r/min and the pressure speed is 1 mm/s.There were two types of fractures:the button fracture mode and the peel fracture mode.展开更多
A lot of research has been focused on the necking process during the plastic deformation of sheet metals, but the localized necking is rarely distinguished form diffused necking by experiments, due to the limit of mea...A lot of research has been focused on the necking process during the plastic deformation of sheet metals, but the localized necking is rarely distinguished form diffused necking by experiments, due to the limit of measurement equipment and method. Quenching and Partitioning (Q&P) steel is a 3rd generation advanced high strength steel (AHSS). Its good combination of high strength and ductility ensures potential application in automobile industry. Uniaxial tensile tests of QP980 steel sheet at five strain rates are performed to investigate the necking process and the effect of strain rate on necking behavior of Q&P steel. Digital image correlation (DIC) method is applied during tensile tests, and evolutions of major strain, minor strain and normal strain distributions along gauge section of the tensile specimens are obtained. The diffused and localized necking strains are determined according to SWIFT necking theory and HILL necking theory respectively. The test results indicate that with the increasing of strain rate in the investigated range, the diffused necking strain decreases from 0.152 to 0.120 and localized necking strain decreases from 0.245 to 0.137. Meanwhile, the difference of the two strains decreases form 0.096 to 0.017. Thus it can be concluded that strain rate has an influence on both necking strains during the deformation of QP980 steel sheet. Diffused and localized necking strains are determined by uniaxial tensile tests with the aid of DIC technique and the effect of strain rate on necking strains is evaluated.展开更多
Since it has excellent tensile strength, the quenching and partitioning （Q ＆ P） treated steel has been widely acclaimed. Some researched is currently being conducted on Q ＆ P steel, but Q ＆ P techniques and relat...Since it has excellent tensile strength, the quenching and partitioning （Q ＆ P） treated steel has been widely acclaimed. Some researched is currently being conducted on Q ＆ P steel, but Q ＆ P techniques and related mechanisms have been mostly research based on conventional transformation-induced plasticity （TRIP） steel. This study researches the effect of Mn on the properties of Q ＆P sheet steel. Two kinds of steel sheet with different levels of Mn content （1.46% Mn and 2.75% Mn） are investigated. After being fully annealed, the steel sheets were quenched to a temperature between Ms and Mr. Allocation treatment then caused the carbon to be partitioned into the remaining austenite.The microstructure and tensile properties were analyzed. The results show that the increment of Mn content can increase the stability of the steel and decrease the sensitivity of the quenching temperature （QT）. The results also indicate that increasing the level of Mn can effectively suppress the formation of bainite.展开更多
The Q345 plate steel austenite recrystallization behavior and strain accumulation during rolling were investigated through thermal simulation and rolling. The effect of the recrystallization behavior on the microstruc...The Q345 plate steel austenite recrystallization behavior and strain accumulation during rolling were investigated through thermal simulation and rolling. The effect of the recrystallization behavior on the microstructure and properties of the steel was discussed and analyzed. The control principles of the pass reduction in the austenite recrystallization region and partial recrystallization region were established. It is found that to increase the thickness of intermediate billet in the finish temperature interval of 880-820℃ is favorable to grain refinement. The result has been applied to the industrial production of the 3 500 mm plate mill of Shougang Group. The average grain size of the steel plate conforms to ASTM No. 10-12, and the grade of band structure has been reduced to below 1.5.展开更多
For large-sized AISI P20 steel block used as plastic die with a thickness of more than 200 mm, appropriate quenching processes are the key to obtain much thick hardened layer. In this paper, different quenching proces...For large-sized AISI P20 steel block used as plastic die with a thickness of more than 200 mm, appropriate quenching processes are the key to obtain much thick hardened layer. In this paper, different quenching processes of AISI P20 steel block such as oil quenching, direct water quenching, water quenching with precooling and water quenching with pre-cooling and self-tempering were numerically investigated by computer simulation based on the detailed discussion on the mathematical models of quenching processes including partial differential equations of heat transfer, thermal physical properties, latent heat, heat transfer coefficient and calculation of phase transformation, The results show that the water quenching with pre-cooling and self-tempering process can not only effectively avoid quenching cracks, but also obtain deeper harden depth than oil quenching.展开更多
基金Project(2022LSL050102)supported by the Laoshan Laboratory,China。
文摘Sulfate and nitrate reducing bacteria are important culprits for microbiologically influenced corrosion(MIC)using sulfate and nitrate as electron acceptors,respectively.Sulfate and nitrate hold different standard electrode potentials,which may lead to differences in corrosion,but their effects on corrosion by the same bacteria have not been reported.The corrosion of Q235 steel affected by Pseudodesulfovibrio cashew(P.cashew)in the sulfate and nitrate media under carbon starvation was studied.It was found that sulfate and nitrate did not lead to differences in corrosion under abiotic conditions.However,P.cashew promoted corrosion in both cases,and the consumption of H_(2)was the main mechanism for MIC.In addition,corrosion was more severe in the sulfate media.The higher corrosivity of P.cashew with sulfate as the electron acceptor is closely related to the higher number of sessile cells in the biofilm,higher bacterial motility,more hydrogen production pathways,and the increased gene expression of enzymes related to energy synthesis.
基金Science and Technology Project of Fire Rescue Bureau of Ministry of Emergency Management(Grant No.2022XFZD05)S&T Program of Hebei(Grant No.22375419D)National Natural Science Foundation of China(Grant No.11802160).
文摘As the basic protective element, steel plate had attracted world-wide attention because of frequent threats of explosive loads. This paper reports the relationships between microscopic defects of Q345 steel plate under the explosive load and its macroscopic dynamics simulation. Firstly, the defect characteristics of the steel plate were investigated by stereoscopic microscope(SM) and scanning electron microscope(SEM). At the macroscopic level, the defect was the formation of cave which was concentrated in the range of 0-3.0 cm from the explosion center, while at the microscopic level, the cavity and void formation were the typical damage characteristics. It also explains that the difference in defect morphology at different positions was the combining results of high temperature and high pressure. Secondly, the variation rules of mechanical properties of steel plate under explosive load were studied. The Arbitrary Lagrange-Euler(ALE) algorithm and multi-material fluid-structure coupling method were used to simulate the explosion process of steel plate. The accuracy of the method was verified by comparing the deformation of the simulation results with the experimental results, the pressure and stress at different positions on the surface of the steel plate were obtained. The simulation results indicated that the critical pressure causing the plate defects may be approximately 2.01 GPa. On this basis, it was found that the variation rules of surface pressure and microscopic defect area of the Q345 steel plate were strikingly similar, and the corresponding mathematical relationship between them was established. Compared with Monomolecular growth fitting models(MGFM) and Logistic fitting models(LFM), the relationship can be better expressed by cubic polynomial fitting model(CPFM). This paper illustrated that the explosive defect characteristics of metal plate at the microscopic level can be explored by analyzing its macroscopic dynamic mechanical response.
基金National Natural Science Foundation of China(No.52275306)Beijing Municipal Natural Science Foundation(No.3232021)for their support.
文摘The welding characteristics of 5052 aluminum alloy and Q235 low-carbon steel sheet were systematically studied by the refilled friction stir spot welding.The effects of rotation speed and pressure speed on weld forming,tensile strength,and welded joint structure were analyzed in different welding modes.The results indicated two different connection modes:the chimeric mode and the non-chimeric mode.The corresponding depression depth are 2 and 2.4 mm,respectively.In the non-chimeric connection mode,the steel/aluminum metallurgical interface is a smooth transition,the hook structure is obvious,and the welding mechanism mainly depends on the mutual diffusion between atoms.However,in the chimeric mode,a hook structure will be formed at the metallurgical interface of steel and aluminum.The connection mechanism is determined by mechanical interlocking and mutual diffusion.The maximum strength value is 7.48 kN in non-chimeric mode.At this time,the spindle speed is 1300 r/min and the pressure speed is 1 mm/s.There were two types of fractures:the button fracture mode and the peel fracture mode.
文摘A lot of research has been focused on the necking process during the plastic deformation of sheet metals, but the localized necking is rarely distinguished form diffused necking by experiments, due to the limit of measurement equipment and method. Quenching and Partitioning (Q&P) steel is a 3rd generation advanced high strength steel (AHSS). Its good combination of high strength and ductility ensures potential application in automobile industry. Uniaxial tensile tests of QP980 steel sheet at five strain rates are performed to investigate the necking process and the effect of strain rate on necking behavior of Q&P steel. Digital image correlation (DIC) method is applied during tensile tests, and evolutions of major strain, minor strain and normal strain distributions along gauge section of the tensile specimens are obtained. The diffused and localized necking strains are determined according to SWIFT necking theory and HILL necking theory respectively. The test results indicate that with the increasing of strain rate in the investigated range, the diffused necking strain decreases from 0.152 to 0.120 and localized necking strain decreases from 0.245 to 0.137. Meanwhile, the difference of the two strains decreases form 0.096 to 0.017. Thus it can be concluded that strain rate has an influence on both necking strains during the deformation of QP980 steel sheet. Diffused and localized necking strains are determined by uniaxial tensile tests with the aid of DIC technique and the effect of strain rate on necking strains is evaluated.
文摘Since it has excellent tensile strength, the quenching and partitioning （Q ＆ P） treated steel has been widely acclaimed. Some researched is currently being conducted on Q ＆ P steel, but Q ＆ P techniques and related mechanisms have been mostly research based on conventional transformation-induced plasticity （TRIP） steel. This study researches the effect of Mn on the properties of Q ＆P sheet steel. Two kinds of steel sheet with different levels of Mn content （1.46% Mn and 2.75% Mn） are investigated. After being fully annealed, the steel sheets were quenched to a temperature between Ms and Mr. Allocation treatment then caused the carbon to be partitioned into the remaining austenite.The microstructure and tensile properties were analyzed. The results show that the increment of Mn content can increase the stability of the steel and decrease the sensitivity of the quenching temperature （QT）. The results also indicate that increasing the level of Mn can effectively suppress the formation of bainite.
文摘The Q345 plate steel austenite recrystallization behavior and strain accumulation during rolling were investigated through thermal simulation and rolling. The effect of the recrystallization behavior on the microstructure and properties of the steel was discussed and analyzed. The control principles of the pass reduction in the austenite recrystallization region and partial recrystallization region were established. It is found that to increase the thickness of intermediate billet in the finish temperature interval of 880-820℃ is favorable to grain refinement. The result has been applied to the industrial production of the 3 500 mm plate mill of Shougang Group. The average grain size of the steel plate conforms to ASTM No. 10-12, and the grade of band structure has been reduced to below 1.5.
文摘For large-sized AISI P20 steel block used as plastic die with a thickness of more than 200 mm, appropriate quenching processes are the key to obtain much thick hardened layer. In this paper, different quenching processes of AISI P20 steel block such as oil quenching, direct water quenching, water quenching with precooling and water quenching with pre-cooling and self-tempering were numerically investigated by computer simulation based on the detailed discussion on the mathematical models of quenching processes including partial differential equations of heat transfer, thermal physical properties, latent heat, heat transfer coefficient and calculation of phase transformation, The results show that the water quenching with pre-cooling and self-tempering process can not only effectively avoid quenching cracks, but also obtain deeper harden depth than oil quenching.
