Mg alloy seamless tubes(MASTs)were prepared through three-high rotary piercing process,effect of billet temperature,feed angle and plug advance on microstructure,texture and mechanical properties of tubes were investi...Mg alloy seamless tubes(MASTs)were prepared through three-high rotary piercing process,effect of billet temperature,feed angle and plug advance on microstructure,texture and mechanical properties of tubes were investigated.The effect on the deformation mechanism and improving mechanical properties mechanism of this process for MASTs were studied.The results show that the grain size could be refined to 11.3-31.1%of the initial grain size and the microstructure was more uniform due to the accumulation of strain.The formation of high strain gradient at the grain boundary activated the non-basal slip.This piercing process could change the grain orientation of as-extruded billet and eliminate the initial basal texture to produce new favorable texture.And the process could accelerate the continuous dynamic recrystallization process.After piercing,yield strength of pierced tubes decreased by 6.7%,ultimate tensile strength(UTS)and elongation increased by 32.4 and 45%,respectively,at optimal parameters.The plate-shapedβ_(1)-Mg_(17)Al_(12) orientation transformed from basal plates to prismatic plates,facilitating the increase in UTS and ductility.The decrease size of nanoscale precipitates could reduce the cracking possibility.The critical resolved shear stress ratios of pyramidal(10−11)slip and(11−22)slip to basal slip for the sample including prismatic plates both decreased compared to that including basal plates.This could enhance the ductility of tube sample.Moreover,grain boundary sliding could contribute to a better ductility via coordinating deformation and reducing stress concentration during piercing process.展开更多
With the aid of FE （finite element） code MSC.Superform 2005, 2-D coupled thermo-mechanical simulation of center-crack occurrence in round billet during 2-roll rotary rolling process was presented using Oyane ductile...With the aid of FE （finite element） code MSC.Superform 2005, 2-D coupled thermo-mechanical simulation of center-crack occurrence in round billet during 2-roll rotary rolling process was presented using Oyane ductile fracture criteria. A simple modeling is put forward based on the spiral motion of the workpiece as an essential characteristic in movement. The influence of the feed angle and the entry cone angle of the main roll on the process was taken into account in the modeling. The soundness for simplifying the 3-D rotary rolling into a 2-D problem was discussed. By adopting the parameters of Diescher piercer in 140mm mandrel mill of Bao Steel, the distribution and development of strain/stress were analyzed, and the eigen value of ductile fracture as well. The critical percentage of diameter reduction was obtained from the simulation. The result showed a good agreement with the experimental value, and therefore was of widely guiding significance to the practical process for rationally formulating the deformation parameters of steel tube piercing.展开更多
研究了三辊斜轧穿孔法生产Φ50 mm×5 mm TA2管坯的生产工艺。通过TA2棒坯不同加热温度对穿透率的影响、不同径向压下量对穿孔后管坯直径的影响、穿孔头尺寸对管坯壁厚的影响、棒坯直径与管坯直径关系的研究,确定了三辊斜轧穿孔法...研究了三辊斜轧穿孔法生产Φ50 mm×5 mm TA2管坯的生产工艺。通过TA2棒坯不同加热温度对穿透率的影响、不同径向压下量对穿孔后管坯直径的影响、穿孔头尺寸对管坯壁厚的影响、棒坯直径与管坯直径关系的研究,确定了三辊斜轧穿孔法生产纯钛管坯的具体工艺参数：棒坯规格Φ48 mm,棒坯加热制度930~950℃/40~50min,顶头前探量26~32 mm,径向压下量15%~20%。展开更多
基金the PhD Scientific Research Startup Foundation of Shanxi Province(No.20202002)the Fundamental Research Program of Shanxi Province(No.202103021223287)+1 种基金the Shanxi Province Key Technology Project(No.20191102009)the Shanxi Province Key Project of Research and Development Plan(No.201903D121049).
文摘Mg alloy seamless tubes(MASTs)were prepared through three-high rotary piercing process,effect of billet temperature,feed angle and plug advance on microstructure,texture and mechanical properties of tubes were investigated.The effect on the deformation mechanism and improving mechanical properties mechanism of this process for MASTs were studied.The results show that the grain size could be refined to 11.3-31.1%of the initial grain size and the microstructure was more uniform due to the accumulation of strain.The formation of high strain gradient at the grain boundary activated the non-basal slip.This piercing process could change the grain orientation of as-extruded billet and eliminate the initial basal texture to produce new favorable texture.And the process could accelerate the continuous dynamic recrystallization process.After piercing,yield strength of pierced tubes decreased by 6.7%,ultimate tensile strength(UTS)and elongation increased by 32.4 and 45%,respectively,at optimal parameters.The plate-shapedβ_(1)-Mg_(17)Al_(12) orientation transformed from basal plates to prismatic plates,facilitating the increase in UTS and ductility.The decrease size of nanoscale precipitates could reduce the cracking possibility.The critical resolved shear stress ratios of pyramidal(10−11)slip and(11−22)slip to basal slip for the sample including prismatic plates both decreased compared to that including basal plates.This could enhance the ductility of tube sample.Moreover,grain boundary sliding could contribute to a better ductility via coordinating deformation and reducing stress concentration during piercing process.
文摘With the aid of FE （finite element） code MSC.Superform 2005, 2-D coupled thermo-mechanical simulation of center-crack occurrence in round billet during 2-roll rotary rolling process was presented using Oyane ductile fracture criteria. A simple modeling is put forward based on the spiral motion of the workpiece as an essential characteristic in movement. The influence of the feed angle and the entry cone angle of the main roll on the process was taken into account in the modeling. The soundness for simplifying the 3-D rotary rolling into a 2-D problem was discussed. By adopting the parameters of Diescher piercer in 140mm mandrel mill of Bao Steel, the distribution and development of strain/stress were analyzed, and the eigen value of ductile fracture as well. The critical percentage of diameter reduction was obtained from the simulation. The result showed a good agreement with the experimental value, and therefore was of widely guiding significance to the practical process for rationally formulating the deformation parameters of steel tube piercing.
