The manufacture of extra-thin wall steel pipe by LD cluster mill through suitable tool design and process design was described in detail.The defects in steel pipe produced during rolling were analysed and some measure...The manufacture of extra-thin wall steel pipe by LD cluster mill through suitable tool design and process design was described in detail.The defects in steel pipe produced during rolling were analysed and some measures were taken to improve them.Five kinds of extra-thin wall steel pipes have been produced successfully,which are as follows:φ18.5mm×0.25 mm,φ15.5mm×0.25 mm,φ11.4mm×0.2mm,φ14- 24mm×0.12 mm,φ21.74mm×0.12 mm.展开更多
The groove shape of the weld faying part was investigated to obtain an ideal pipe frictiowelded joint that had a fracture in the base metal and no inner flash of it.The steel pipe had inner and outer diameters of 8.0 ...The groove shape of the weld faying part was investigated to obtain an ideal pipe frictiowelded joint that had a fracture in the base metal and no inner flash of it.The steel pipe had inner and outer diameters of 8.0 mm and 13.5 mm,respectively,and the weld faying surface was of a basic flat shape(butt)type.Moreover,stepped and tapered groove shapes were prepared.Pipe groove shapes were welded with a friction speed of 27.5 s_1 and a friction load of 2.79 kN.Joining phenomena during the welding process were observed,and the tensile strength of joints was evaluated.The joints,that fabricated with flat or step groove shapes,made with a friction time at which the friction torque reached the initial peak did not have the tensile strength of the base metal nor a fracture in the base metal.However,the joints fabricated with a friction time that reached past the initial peak had a large flash,and they contained a fracture in the base metal.In contrast,when joints were made with a gently tapered groove shape with a friction time reaching the time of the initial peak,they achieved a fracture in the base metal,despite having an extremely small inner flash.Therefore,the shape at the weld faying part was capable of reducing the flash exhausted from the weld interface.展开更多
In the present investigation, a pipe inner-surface grinding（PISG） technique was developed to fabricate nanostructure in the inner-surface of an austenitic 304 stainless steel pipe. PISG was performed by high speed s...In the present investigation, a pipe inner-surface grinding（PISG） technique was developed to fabricate nanostructure in the inner-surface of an austenitic 304 stainless steel pipe. PISG was performed by high speed shearing with hard sphere tips, leading to gradient distribution of strain, strain rate and strain gradient along depth. Nano-austenite with an average boundary spacing of 20 nm was generated, followed by deformation microstructure characterized by shear bands, multi-and uni-directional twins and planar dislocation arrays. Deformation induced grain refinement of austenitic 304 stainless steel with low stacking fault energy（SFE） covering 4–5 order＇s magnitude of length scales toward nanometer regime was unified.展开更多
In this study,the effect of core bar inserted into weld faying part to obtain an ideal pipe joint with non-generating inner flash via friction welding is described.A steel pipe with inner and outer diameters correspon...In this study,the effect of core bar inserted into weld faying part to obtain an ideal pipe joint with non-generating inner flash via friction welding is described.A steel pipe with inner and outer diameters corresponding to 8.0 mm and 13.5 mm was used,and the weld faying surface was machined to a groove shape of a flat(butt)type.The core bar of various materials was inserted in the weld faying part of the pipes,and those pipes were welded with a friction speed of 27.5 s−1 and friction pressure of 30 MPa.The core bars did not decrease inner flash when joints were fabricated with a core bar of some metallic materials with melting points below that of steel;thus,they were melted during the welding process.The joint with an alumina core bar did not decrease inner flash and was crushed by generating an inner flash.However,a commercially pure tungsten(CP-W)core bar was successfully achieved for decreasing the inner flash.Additionally,all joints with a CP-W core bar did not exhibit the tensile strength of the base metal and a fracture in the base metal,when they were fabricated during the same time,the friction torque reached the initial peak.The joint exhibited a fracture in the base metal when it was fabricated with a CP-W core bar and a taper groove shape that was proposed in the previous study.Furthermore,the core bars were easily removed from the joints;thus the joint with almost no inner flash was successfully obtained.To reduce the inner flash of pipe joints,they should be fabricated with a CP-W core bar inserted into the weld faying part with a taper groove shape.展开更多
A low carbon hypoeutectoid steel(0.19 wt%C)with proeutectoid ferrite and pearlite dual-components was subjected to surface plastic deformation via pipe inner surface grinding(PISG)at room temperature.The deformation m...A low carbon hypoeutectoid steel(0.19 wt%C)with proeutectoid ferrite and pearlite dual-components was subjected to surface plastic deformation via pipe inner surface grinding(PISG)at room temperature.The deformation microstructures for each component were systematically characterized along depth,and the patterns of structural evolution toward nanometer regime as well as the governing parameters were addressed.Proeutectoid ferrite grains were refined down to 17 nm,and the pattern covering a length scale of 4–5 orders of magnitude from micron-to nanometer-scale follows:formation of cellular dislocation structure(CDS),elongated dislocation structure(EDS),ultrafine lamellar structure(UFL)and finally the nanolaminated structure(NL).The pearlite experiences the deformation and refinement,and finally the transforming the ultrafine pearlite(UFP)into nanolaminated pearlite(NLP)with the ferrite lamellae as thin as 20 nm.Refinement for both UFL(UFP)and NL(NLP)can be realized via forming novel extended boundaries within ferrite lamellae.A critical lattice curvature of~2.8°is required for forming such extended boundary,corresponding to a minimum strain gradient of 0.25μm^(-1)for a 100 nm-thick lamella.Refinement below size limit(expressed by lamellar thickness d_Tin nm)is correlated with the strain gradient(χ,inμm^(-1))by:d_T=12.5/x.Refinement contributions from strain gradient caused by PISG processing and material heterogeneity were discussed.展开更多
文摘The manufacture of extra-thin wall steel pipe by LD cluster mill through suitable tool design and process design was described in detail.The defects in steel pipe produced during rolling were analysed and some measures were taken to improve them.Five kinds of extra-thin wall steel pipes have been produced successfully,which are as follows:φ18.5mm×0.25 mm,φ15.5mm×0.25 mm,φ11.4mm×0.2mm,φ14- 24mm×0.12 mm,φ21.74mm×0.12 mm.
文摘The groove shape of the weld faying part was investigated to obtain an ideal pipe frictiowelded joint that had a fracture in the base metal and no inner flash of it.The steel pipe had inner and outer diameters of 8.0 mm and 13.5 mm,respectively,and the weld faying surface was of a basic flat shape(butt)type.Moreover,stepped and tapered groove shapes were prepared.Pipe groove shapes were welded with a friction speed of 27.5 s_1 and a friction load of 2.79 kN.Joining phenomena during the welding process were observed,and the tensile strength of joints was evaluated.The joints,that fabricated with flat or step groove shapes,made with a friction time at which the friction torque reached the initial peak did not have the tensile strength of the base metal nor a fracture in the base metal.However,the joints fabricated with a friction time that reached past the initial peak had a large flash,and they contained a fracture in the base metal.In contrast,when joints were made with a gently tapered groove shape with a friction time reaching the time of the initial peak,they achieved a fracture in the base metal,despite having an extremely small inner flash.Therefore,the shape at the weld faying part was capable of reducing the flash exhausted from the weld interface.
基金supported financially by the Hundred Outstanding Creative Talents Projects in University of Hebei ProvinceChina, the Project Program of Heavy Machinery Collaborative Innovation Center+1 种基金the Natural Science Foundation of Hebei Province, China (No. E2018203312)the Postdoctoral Science Foundation of Hebei Province, China
文摘In the present investigation, a pipe inner-surface grinding（PISG） technique was developed to fabricate nanostructure in the inner-surface of an austenitic 304 stainless steel pipe. PISG was performed by high speed shearing with hard sphere tips, leading to gradient distribution of strain, strain rate and strain gradient along depth. Nano-austenite with an average boundary spacing of 20 nm was generated, followed by deformation microstructure characterized by shear bands, multi-and uni-directional twins and planar dislocation arrays. Deformation induced grain refinement of austenitic 304 stainless steel with low stacking fault energy（SFE） covering 4–5 order＇s magnitude of length scales toward nanometer regime was unified.
文摘In this study,the effect of core bar inserted into weld faying part to obtain an ideal pipe joint with non-generating inner flash via friction welding is described.A steel pipe with inner and outer diameters corresponding to 8.0 mm and 13.5 mm was used,and the weld faying surface was machined to a groove shape of a flat(butt)type.The core bar of various materials was inserted in the weld faying part of the pipes,and those pipes were welded with a friction speed of 27.5 s−1 and friction pressure of 30 MPa.The core bars did not decrease inner flash when joints were fabricated with a core bar of some metallic materials with melting points below that of steel;thus,they were melted during the welding process.The joint with an alumina core bar did not decrease inner flash and was crushed by generating an inner flash.However,a commercially pure tungsten(CP-W)core bar was successfully achieved for decreasing the inner flash.Additionally,all joints with a CP-W core bar did not exhibit the tensile strength of the base metal and a fracture in the base metal,when they were fabricated during the same time,the friction torque reached the initial peak.The joint exhibited a fracture in the base metal when it was fabricated with a CP-W core bar and a taper groove shape that was proposed in the previous study.Furthermore,the core bars were easily removed from the joints;thus the joint with almost no inner flash was successfully obtained.To reduce the inner flash of pipe joints,they should be fabricated with a CP-W core bar inserted into the weld faying part with a taper groove shape.
基金the Hundred Outstanding Creative Talents Projects in Hebei University,Chinathe Project Program of Heavy Machinery Collaborative Innovation CenterChina and the National Natural Science Foundation of China(No.51171182)。
文摘A low carbon hypoeutectoid steel(0.19 wt%C)with proeutectoid ferrite and pearlite dual-components was subjected to surface plastic deformation via pipe inner surface grinding(PISG)at room temperature.The deformation microstructures for each component were systematically characterized along depth,and the patterns of structural evolution toward nanometer regime as well as the governing parameters were addressed.Proeutectoid ferrite grains were refined down to 17 nm,and the pattern covering a length scale of 4–5 orders of magnitude from micron-to nanometer-scale follows:formation of cellular dislocation structure(CDS),elongated dislocation structure(EDS),ultrafine lamellar structure(UFL)and finally the nanolaminated structure(NL).The pearlite experiences the deformation and refinement,and finally the transforming the ultrafine pearlite(UFP)into nanolaminated pearlite(NLP)with the ferrite lamellae as thin as 20 nm.Refinement for both UFL(UFP)and NL(NLP)can be realized via forming novel extended boundaries within ferrite lamellae.A critical lattice curvature of~2.8°is required for forming such extended boundary,corresponding to a minimum strain gradient of 0.25μm^(-1)for a 100 nm-thick lamella.Refinement below size limit(expressed by lamellar thickness d_Tin nm)is correlated with the strain gradient(χ,inμm^(-1))by:d_T=12.5/x.Refinement contributions from strain gradient caused by PISG processing and material heterogeneity were discussed.
