Slagging and calcium treatment are commonly used methods to control cleanliness and inclusions in steel.However,the inappropriate slagging and calcium treatment operations resulted in the generation of large-sized inc...Slagging and calcium treatment are commonly used methods to control cleanliness and inclusions in steel.However,the inappropriate slagging and calcium treatment operations resulted in the generation of large-sized inclusions and deterioration of steel cleanliness;meanwhile,changed inclusions from Al_(2)O_(3)–SiO_(2)–MnO type to Al_(2)O_(3)–SiO_(2)–CaO type after the calcium treatment during the production of an H-beam steel.Combining the thermodynamic analysis and industrial trials,measurements including reducing the basicity of refining slag to be less than 2.0 and the Al_(2)O_(3)content in slag to be less than 10 wt.%and the cancelation of calcium treatment under the total content less than 15×10^(−6)have been taken.After optimization,the content of total oxygen in tundish decreased by 24%;meanwhile,inclusions were changed from the Al_(2)O_(3)–SiO_(2)–CaO system to the Al_(2)O_(3)–SiO_(2)–MnO system with a low-melting point and a obvious decrease in the number density,area fraction,and maximum size of inclusions.It has achieved the improvement of steel cleanliness while reducing production costs.展开更多
The deformation process of H-beams was simulated by explicit dynamic FEM, and the influence of deformation parameters on the spread of rolling piece was obtained. The results show that the flange width, elongation rat...The deformation process of H-beams was simulated by explicit dynamic FEM, and the influence of deformation parameters on the spread of rolling piece was obtained. The results show that the flange width, elongation ratio between flange and web and flange thickness are the maior influencing factors on the spread of rolling piece, and the inclination and diameter of vertical roll together with web inner width can also influence to some extent on the spread of rolling piece.展开更多
Microstructures and critical phase-transformation temperature of boron-nickel added Nb-treated high strength low alloy （HSLA） H-beams cooled at different cooling rate, with different deformation were investigated. C...Microstructures and critical phase-transformation temperature of boron-nickel added Nb-treated high strength low alloy （HSLA） H-beams cooled at different cooling rate, with different deformation were investigated. Continuous cooling transformation （CCT） diagram of this new type of steel was obtained by using Gleeble 1500 ther- momechanical simulator. Microstructures and hardness, especially micro-hardness of the experimental steel were in- vestigated by optical microscopy （OM）, scanning electron microscope （SEM）, Rockwell and Vickers hardness tests. Phase analysis was also studied by X^ray diffraction （XRD）. The results indicated that with increase of cooling rate, microstructures of continuous cooled specimens gradually transformed from polygonal ferrite and pearlite, grain boundary ferrite and bainite, bainite and martensite to single martensite. The CCT diagram revealed that slow cool- ing was needed to avoid austenite-bainite transformation to ensure toughness of this steel. By plastic deformation of 40%, austenite-ferrite transformation temperature increased by 46℃, due to deformation induced ferrite transfor- mation during continuous cooling, but Rockwell hardness has little change.展开更多
The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-...The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-beam steel sample is consisted of ferrite, pearlite and a small amount of granular bainites as well as fine and dispersive V（C,N） precipitates. The microstructure of the water-cooled steel sample is consisted of ferrite and bainite as well as a small amount of fine pearlites. The microstructure of the water-cooled sample is finer than that of the air-cooled sample with the average intercept size of the surface grains reaching to 3.5 gna. The finish rolling temperature of the thin-walled high strength H-beam steel is in the range of 750 ~C-850 ~C. The lower the finish rolling temperature and the faster the cooling rate, the finer the ferrite grains, the volume fraction of bainite is increased through water cooling process. Grain refinement strengthening and precipitation strengthening are used as major strengthening means to develop 550 MPa grade lightweight high strength thin- walled H-beam steel. Vanadium partially soluted in the matrix and contributes to the solution strengthening. The 550 MPa grade high-strength thin-walled H-beam steel could be developed by direct air cooling after hot rolling to fully meet the requirements of the target properties.展开更多
Based on ANSYS, an analytical model was established for H beam during controlled cooling. The tempera-ture fields during controlled cooling and air cooling were analyzed and the microstructure and mechanical propertie...Based on ANSYS, an analytical model was established for H beam during controlled cooling. The tempera-ture fields during controlled cooling and air cooling were analyzed and the microstructure and mechanical properties for different parts of H-beam were discussed in detail. After the H-beam was controlled cooled for 4.5 s, its mean surface temperature decreased from 850 to 460 ℃, and the lowest and the highest temperatures were measured at edge of flange and at R corner, respectively. Whereas, for the H-beam air cooled for 30 s, the mean temperature at R corner and web was 700 and 540 ℃, respectively. The microstructures for different parts of H-beam consisted of ferrite and pearlite, and the grain size at R corner was coarser than those at flange and web. The difference of yield and tensile strengths of web, flange and R corner was within 30 MPa, and the elongation was similar. The changes of microstructure were in good agreement with that of temperature field. In addition, the results show that the uni formity of microstructure and mechanical properties can be improved by increasing water flow rate at R corner.展开更多
It has been observed that H^- current could be improved by adding Ar to H2 plasma. But due to a slower pumping speed for Ar with the existing pumping scheme, the tank pressure will increase quickly during the length o...It has been observed that H^- current could be improved by adding Ar to H2 plasma. But due to a slower pumping speed for Ar with the existing pumping scheme, the tank pressure will increase quickly during the length of a beam pulse. Since H^- stripping loss depends on the tank pressure and gas species, part of the H^- beam can be converted to H^0 and then H^0 can be converted into H^＋ with background H2 and Ar gas thickness. Therefore, the H^- beam current, measured by a Faraday cup, situated at a distance L from GG （ground grid）, will decrease because it will be converted into a H^＋ current. This gives a ratio of the Faraday cup net current to the H^- beam current before stripping at background partial pressure of Ar.展开更多
H型钢立板焊接路径规划效率低下、路径质量欠佳以及转弯冗余过多等问题一直是制约其焊接效率与质量提升的关键难题。为攻克这一难题,提出了一种基于改进快速探索随机树(rapidly-exploring random tree,RRT)法的机器人焊接路径优化方法...H型钢立板焊接路径规划效率低下、路径质量欠佳以及转弯冗余过多等问题一直是制约其焊接效率与质量提升的关键难题。为攻克这一难题,提出了一种基于改进快速探索随机树(rapidly-exploring random tree,RRT)法的机器人焊接路径优化方法。首先,引入人工势场机制引导采样树的扩展方向,从而提升算法的收敛效率;其次,结合粒子群优化算法,基于路径拆分与优选段落重组策略,构建连贯顺畅的连通路径;最后,提出创建线段间自适应半径圆弧的方法,对路径进行精细化的平滑处理,进一步提升路径质量。实验结果表明,所提方法在收敛速度、路径平滑度与可行性方面均优于传统RRT算法,能够更好地满足H型钢立板复杂焊缝环境下的焊接路径规划需求。展开更多
基金support from the National Key R&D Program(Nos.2023YFB3506802 and 2023YFB3709900)the National Natural Science Foundation of China(Grant Nos.52174293 and U22A20171)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.FRF-BD-20-04A)the High Steel Center(HSC)at North China University of Technology.
文摘Slagging and calcium treatment are commonly used methods to control cleanliness and inclusions in steel.However,the inappropriate slagging and calcium treatment operations resulted in the generation of large-sized inclusions and deterioration of steel cleanliness;meanwhile,changed inclusions from Al_(2)O_(3)–SiO_(2)–MnO type to Al_(2)O_(3)–SiO_(2)–CaO type after the calcium treatment during the production of an H-beam steel.Combining the thermodynamic analysis and industrial trials,measurements including reducing the basicity of refining slag to be less than 2.0 and the Al_(2)O_(3)content in slag to be less than 10 wt.%and the cancelation of calcium treatment under the total content less than 15×10^(−6)have been taken.After optimization,the content of total oxygen in tundish decreased by 24%;meanwhile,inclusions were changed from the Al_(2)O_(3)–SiO_(2)–CaO system to the Al_(2)O_(3)–SiO_(2)–MnO system with a low-melting point and a obvious decrease in the number density,area fraction,and maximum size of inclusions.It has achieved the improvement of steel cleanliness while reducing production costs.
文摘The deformation process of H-beams was simulated by explicit dynamic FEM, and the influence of deformation parameters on the spread of rolling piece was obtained. The results show that the flange width, elongation ratio between flange and web and flange thickness are the maior influencing factors on the spread of rolling piece, and the inclination and diameter of vertical roll together with web inner width can also influence to some extent on the spread of rolling piece.
文摘Microstructures and critical phase-transformation temperature of boron-nickel added Nb-treated high strength low alloy （HSLA） H-beams cooled at different cooling rate, with different deformation were investigated. Continuous cooling transformation （CCT） diagram of this new type of steel was obtained by using Gleeble 1500 ther- momechanical simulator. Microstructures and hardness, especially micro-hardness of the experimental steel were in- vestigated by optical microscopy （OM）, scanning electron microscope （SEM）, Rockwell and Vickers hardness tests. Phase analysis was also studied by X^ray diffraction （XRD）. The results indicated that with increase of cooling rate, microstructures of continuous cooled specimens gradually transformed from polygonal ferrite and pearlite, grain boundary ferrite and bainite, bainite and martensite to single martensite. The CCT diagram revealed that slow cool- ing was needed to avoid austenite-bainite transformation to ensure toughness of this steel. By plastic deformation of 40%, austenite-ferrite transformation temperature increased by 46℃, due to deformation induced ferrite transfor- mation during continuous cooling, but Rockwell hardness has little change.
基金Funded by the "11th Five" National Science and Technology Support Project(No.2006BAE03A13)
文摘The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-beam steel sample is consisted of ferrite, pearlite and a small amount of granular bainites as well as fine and dispersive V（C,N） precipitates. The microstructure of the water-cooled steel sample is consisted of ferrite and bainite as well as a small amount of fine pearlites. The microstructure of the water-cooled sample is finer than that of the air-cooled sample with the average intercept size of the surface grains reaching to 3.5 gna. The finish rolling temperature of the thin-walled high strength H-beam steel is in the range of 750 ~C-850 ~C. The lower the finish rolling temperature and the faster the cooling rate, the finer the ferrite grains, the volume fraction of bainite is increased through water cooling process. Grain refinement strengthening and precipitation strengthening are used as major strengthening means to develop 550 MPa grade lightweight high strength thin- walled H-beam steel. Vanadium partially soluted in the matrix and contributes to the solution strengthening. The 550 MPa grade high-strength thin-walled H-beam steel could be developed by direct air cooling after hot rolling to fully meet the requirements of the target properties.
基金Item Sponsored by National Science and Technology Support Project of China(2007BAE30B05)
文摘Based on ANSYS, an analytical model was established for H beam during controlled cooling. The tempera-ture fields during controlled cooling and air cooling were analyzed and the microstructure and mechanical properties for different parts of H-beam were discussed in detail. After the H-beam was controlled cooled for 4.5 s, its mean surface temperature decreased from 850 to 460 ℃, and the lowest and the highest temperatures were measured at edge of flange and at R corner, respectively. Whereas, for the H-beam air cooled for 30 s, the mean temperature at R corner and web was 700 and 540 ℃, respectively. The microstructures for different parts of H-beam consisted of ferrite and pearlite, and the grain size at R corner was coarser than those at flange and web. The difference of yield and tensile strengths of web, flange and R corner was within 30 MPa, and the elongation was similar. The changes of microstructure were in good agreement with that of temperature field. In addition, the results show that the uni formity of microstructure and mechanical properties can be improved by increasing water flow rate at R corner.
文摘It has been observed that H^- current could be improved by adding Ar to H2 plasma. But due to a slower pumping speed for Ar with the existing pumping scheme, the tank pressure will increase quickly during the length of a beam pulse. Since H^- stripping loss depends on the tank pressure and gas species, part of the H^- beam can be converted to H^0 and then H^0 can be converted into H^＋ with background H2 and Ar gas thickness. Therefore, the H^- beam current, measured by a Faraday cup, situated at a distance L from GG （ground grid）, will decrease because it will be converted into a H^＋ current. This gives a ratio of the Faraday cup net current to the H^- beam current before stripping at background partial pressure of Ar.
文摘H型钢立板焊接路径规划效率低下、路径质量欠佳以及转弯冗余过多等问题一直是制约其焊接效率与质量提升的关键难题。为攻克这一难题,提出了一种基于改进快速探索随机树(rapidly-exploring random tree,RRT)法的机器人焊接路径优化方法。首先,引入人工势场机制引导采样树的扩展方向,从而提升算法的收敛效率;其次,结合粒子群优化算法,基于路径拆分与优选段落重组策略,构建连贯顺畅的连通路径;最后,提出创建线段间自适应半径圆弧的方法,对路径进行精细化的平滑处理,进一步提升路径质量。实验结果表明,所提方法在收敛速度、路径平滑度与可行性方面均优于传统RRT算法,能够更好地满足H型钢立板复杂焊缝环境下的焊接路径规划需求。
