The mechanical properties of heat affected zone （HAZ） of two commercial high-Nb X80 grade pipeline steels with different alloy elements were investigated using thermal simulation performed on a Gleeble-3500 thermal ...The mechanical properties of heat affected zone （HAZ） of two commercial high-Nb X80 grade pipeline steels with different alloy elements were investigated using thermal simulation performed on a Gleeble-3500 thermal simulator. The results showed that the high-Nb steels have excellent weldability. Ernbrittlement regions appear in coarse grain heat affected zone （CGHAZ） and intercritically heat affected zone （ICHAZ） ~ Softening region appears in fine-grain heat affected zone （FGHAZ）, and the strength here was even lower than 555 MPa as required in the standard. Meanwhile, with the increase of heat input, the strength and the toughness of HAZ of steel with high Nb, C and lower alloy decrease notably. Therefore, take into account the welding procedure during manufacture of weld pipe, suitable amount of alloy elements, such as Cr, Ni, Cu, Mo and so on, is necessary for high Nb X80 heavy- thick steel plate.展开更多
According to the research on the deformation resistance and the ferrite transformation behavior of X80 pipeline steel by using Gleeble 3500 thermal simulator, a mathematical model of the α-phase start transformation ...According to the research on the deformation resistance and the ferrite transformation behavior of X80 pipeline steel by using Gleeble 3500 thermal simulator, a mathematical model of the α-phase start transformation temperature for high-Nb pipeline steel was established, based on the transformation kinetics and thermodynamics. The influence of deformation and cooling rate as well as Nb content on the α-phase starting temperature was thor- oughly investigated. The results given by the model were in good agreement with the experimental results, which showed that the model could predict the α-phase starting temperature for high Nb pipeline steel during cooling process.展开更多
In the present research, microstructure refinement of a high-Nb TiAl alloy （Ti-48Al-8Nb-0.15B） was realized by means of the electromagnetic continuous casting （EMCC） technique. The microstructure of an ingot obtai...In the present research, microstructure refinement of a high-Nb TiAl alloy （Ti-48Al-8Nb-0.15B） was realized by means of the electromagnetic continuous casting （EMCC） technique. The microstructure of an ingot obtained by EMCC was analyzed using scanning electron microscopy （SEM）. As compared with the raw as-cast alloy, the obtained EMCC alloy presented a much finer microstructure with lamellar colonies with a mean size of about 50-70 μm because the electromagnetic stirring broke initial dendrites and enhanced the heterogeneous nucleation. As the grains were refined, the properties of the TiAl alloy were improved significantly. This implies that the EMCC technique could offer the possibility of application for high-Nb TiAl alloys with a refined microstructure and excellent properties to be used as a structural material.展开更多
The term adakite was originally pro- posed to define silica-rich, high Sr/Y and La/Yb vol- canic and plutonic rocks derived from melting of the basaltic portion of oceanic crust subducted beneath volcanic arcs. It was...The term adakite was originally pro- posed to define silica-rich, high Sr/Y and La/Yb vol- canic and plutonic rocks derived from melting of the basaltic portion of oceanic crust subducted beneath volcanic arcs. It was also initially believed that ada- kite only occurs in convergent margins where young and thus still hot oceanic slabs are being subducted, but later studies have proposed that it also occurs in other arc settings where unusual tectonic conditions can lower the solidus of older slabs. Currently, ada- kite covers a range of arc rocks ranging from pristine slab melt, to adakite-peridotite hybrid melt, to melt derived from peridotite metasomatized by slab melt. Adakite studies have generated some confusions because (1) the definition of adakite combines com- positional criteria with a genetic interpretation (melt- ing of subducted basalt), (2) the definition is fairly broad and relies on chemistry as its distinguishing characteristic, (3) the use of high pressure melting experiment results on wet basalts as unequivocal proofs of slab melting and (4) the existence of ada- kitic rocks with chemical characteristics similar to adakites but are clearly unrelated to slab melting. Other studies have shown that adakitic rocks and a number of the previously reported adakites are pro- duced through melting of the mafic lower crust or ponded basaltic magma, high-pressure crystal frac- tionation of basaltic magma and low-pressure crystal fractionation of basaltic magma plus magma mixing processes in both arc or non-arc tectonic environ- ments. Despite the confusing interpretations on the petrogenesis of adakite and adakitic rocks, their in- vestigations have enriched our understanding of material recycling at subduction zones, crustal evolu- tionary processes and economic mineralization.展开更多
基金Item Sponsored by National Natural Science Foundation of China(51171162)Natural Science Foundation of Hebei Province of China(E2011203169)The R&D Project of CITIC-CBMM(2011-D056-3)
文摘The mechanical properties of heat affected zone （HAZ） of two commercial high-Nb X80 grade pipeline steels with different alloy elements were investigated using thermal simulation performed on a Gleeble-3500 thermal simulator. The results showed that the high-Nb steels have excellent weldability. Ernbrittlement regions appear in coarse grain heat affected zone （CGHAZ） and intercritically heat affected zone （ICHAZ） ~ Softening region appears in fine-grain heat affected zone （FGHAZ）, and the strength here was even lower than 555 MPa as required in the standard. Meanwhile, with the increase of heat input, the strength and the toughness of HAZ of steel with high Nb, C and lower alloy decrease notably. Therefore, take into account the welding procedure during manufacture of weld pipe, suitable amount of alloy elements, such as Cr, Ni, Cu, Mo and so on, is necessary for high Nb X80 heavy- thick steel plate.
基金Item Sponsored by Fok Ying Tung Education Foundation of China(101048)Provincial Natural Science Foundation of Hebei Province of China(E2008000835)
文摘According to the research on the deformation resistance and the ferrite transformation behavior of X80 pipeline steel by using Gleeble 3500 thermal simulator, a mathematical model of the α-phase start transformation temperature for high-Nb pipeline steel was established, based on the transformation kinetics and thermodynamics. The influence of deformation and cooling rate as well as Nb content on the α-phase starting temperature was thor- oughly investigated. The results given by the model were in good agreement with the experimental results, which showed that the model could predict the α-phase starting temperature for high Nb pipeline steel during cooling process.
基金financially supported by the National Science Foundation of China(Grant No.51171053 and No.51471062)
文摘In the present research, microstructure refinement of a high-Nb TiAl alloy （Ti-48Al-8Nb-0.15B） was realized by means of the electromagnetic continuous casting （EMCC） technique. The microstructure of an ingot obtained by EMCC was analyzed using scanning electron microscopy （SEM）. As compared with the raw as-cast alloy, the obtained EMCC alloy presented a much finer microstructure with lamellar colonies with a mean size of about 50-70 μm because the electromagnetic stirring broke initial dendrites and enhanced the heterogeneous nucleation. As the grains were refined, the properties of the TiAl alloy were improved significantly. This implies that the EMCC technique could offer the possibility of application for high-Nb TiAl alloys with a refined microstructure and excellent properties to be used as a structural material.
文摘The term adakite was originally pro- posed to define silica-rich, high Sr/Y and La/Yb vol- canic and plutonic rocks derived from melting of the basaltic portion of oceanic crust subducted beneath volcanic arcs. It was also initially believed that ada- kite only occurs in convergent margins where young and thus still hot oceanic slabs are being subducted, but later studies have proposed that it also occurs in other arc settings where unusual tectonic conditions can lower the solidus of older slabs. Currently, ada- kite covers a range of arc rocks ranging from pristine slab melt, to adakite-peridotite hybrid melt, to melt derived from peridotite metasomatized by slab melt. Adakite studies have generated some confusions because (1) the definition of adakite combines com- positional criteria with a genetic interpretation (melt- ing of subducted basalt), (2) the definition is fairly broad and relies on chemistry as its distinguishing characteristic, (3) the use of high pressure melting experiment results on wet basalts as unequivocal proofs of slab melting and (4) the existence of ada- kitic rocks with chemical characteristics similar to adakites but are clearly unrelated to slab melting. Other studies have shown that adakitic rocks and a number of the previously reported adakites are pro- duced through melting of the mafic lower crust or ponded basaltic magma, high-pressure crystal frac- tionation of basaltic magma and low-pressure crystal fractionation of basaltic magma plus magma mixing processes in both arc or non-arc tectonic environ- ments. Despite the confusing interpretations on the petrogenesis of adakite and adakitic rocks, their in- vestigations have enriched our understanding of material recycling at subduction zones, crustal evolu- tionary processes and economic mineralization.
