The Experts below are selected from a list of 1938 Experts worldwide ranked by ideXlab platform
Guo Dong Wang - One of the best experts on this subject based on the ideXlab platform.
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ultra fine microstructure and excellent mechanical properties of high borated stainless steel sheet produced by twin roll Strip Casting
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2019Co-Authors: Zhaojie Wang, Yongwang Li, Xiaoming Huang, Guo Dong WangAbstract:Abstract High borated stainless steel sheets have been widely applied in the nuclear power industry because of good thermal neutron absorption property. However, the large and network-like borides existing around the austenite grains in the conventional ingot Casting steel seriously deteriorate the hot workability and the mechanical properties at ambient temperature. In this work, we tried to acquire ultra-fine microstructure by sub-rapid solidification using a novel twin-roll Strip Casting technology so as to enhance the mechanical properties of 2.1%B austenitic stainless steel. Surprisingly, dispersive and very fine borides mostly smaller than 5 µm were produced in the as-cast microstructure without network-like distribution. The morphologies and crystal structure of borides as well as the stacking faults in borides were investigated in detail. After subsequent hot-rolling and solution treatment, ultra-fine borides were observed with more than 50% of which in a size range of 0.3–1.5 µm, significantly smaller than those of the conventional ingot casted and hot rolled steel. Benefiting from the ultra-fine borides, excellent mechanical properties which had not been reported were obtained. In particular, a total elongation of 14.1% was exhibited, which was twice as high as that of the conventional ingot casted and hot rolled steel. Thus a new structure-function combining high borated stainless steel sheet was achieved. The strengthening and plasticity increasing mechanism was discussed based on Hall-Petch relationship, Orowan mechanism and strain-hardening rate analysis. The fracture behavior in tensile deformation was studied in detail. A characteristic fracture process accompanied with the initiation and coalescence of cavities in austenite matrix was found. This work not only developed a new processing way to produce high borated stainless steel with excellent mechanical properties, but also provided a potential solution for some other hard-worked metallic materials with brittle eutectic phase.
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a novel ultra low carbon grain oriented silicon steel produced by twin roll Strip Casting
Journal of Magnetism and Magnetic Materials, 2016Co-Authors: Yang Wang, Yuanxiang Zhang, Feng Fang, Guangming Cao, R D K Misra, Guo Dong WangAbstract:Abstract A novel ultra-low carbon grain oriented silicon steel was successfully produced by Strip Casting and two-stage cold rolling method. The microstructure, texture and precipitate evolution under different first cold rolling reduction were investigated. It was shown that the as-cast Strip was mainly composed of equiaxed grains and characterized by very weak Goss texture ({110} ) and λ-fiber ( //ND). The coarse sulfides of size ~100 nm were precipitated at grain boundaries during Strip Casting, while nitrides remained in solution in the as-cast Strip and the fine AlN particles of size ~20–50 nm, which were used as grain growth inhibitors, were formed in intermediate annealed sheet after first cold rolling. In addition, the suitable Goss nuclei for secondary recrystallization were also formed during intermediate annealing, which is totally different from the conventional process that the Goss nuclei originated in the subsurface layer of the hot rolled sheet. Furthermore, the number of AlN inhibitors and the intensity of desirable Goss texture increased with increasing first cold rolling reduction. After secondary recrystallization annealing, very large grains of size ~10–40 mm were formed and the final magnetic induction, B 8 , was as high as 1.9 T.
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development of trip aided lean duplex stainless steel by twin roll Strip Casting and its deformation mechanism
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2016Co-Authors: Yan Zhao, Zhenyu Liu, Weina Zhang, Xin Liu, Guo Dong WangAbstract:In the present work, twin-roll Strip Casting was carried out to fabricate thin Strip of a Mn-N alloyed lean duplex stainless steel with the composition of Fe-19Cr-6Mn-0.4N, in which internal pore defects had been effectively avoided as compared to conventional cast ingots. The solidification structure observed by optical microscope indicated that fine Widmannstatten structure and coarse-equiaxed crystals had been formed in the surface and center, respectively, with no columnar crystal structures through the surface to center of the cast Strip. By applying hot rolling and cold rolling, thin sheets with the thickness of 0.5 mm were fabricated from the cast Strips, and no edge cracks were formed during the rolling processes. With an annealing treatment at 1323 K (1050 °C) for 5 minutes after cold rolling, the volume fractions of ferrite and austenite were measured to be approximately equal, and the distribution of alloying elements in the Strip was further homogenized. The cold-rolled and annealed sheet exhibited an excellent combination of strength and ductility, with the ultimate tensile strength and elongation having been measured to be 1000 MPa and 65 pct, respectively. The microstructural evolution during deformation was investigated by XRD, EBSD, and TEM, indicating that ferrite and austenite had different deformation mechanisms. The deformation of ferrite phase was dominated by dislocation slipping, and the deformation of austenite phase was mainly controlled by martensitic transformation in the sequence of γ→e-martensite→α′-martensite, leading to the improvement of strength and plasticity by the so-called transformation-induced plasticity (TRIP) effect. By contrast, lean duplex stainless steels of Fe-21Cr-6Mn-0.5N and Fe-23Cr-7Mn-0.6N fabricated by twin-roll Strip Casting did not show TRIP effects and exhibited lower strength and elongation as compared to Fe-19Cr-6Mn-0.4N.
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the impact of hot rolling temperature after reheating in the new generation Strip Casting process on structure property relationship in extra low carbon steel
Steel Research International, 2016Co-Authors: Haitao Liu, Guo Dong Wang, Dongjie Chen, Baoguang Zhang, Aihua Chen, Devesh R K MisraAbstract:There is currently a significant interest in extending the application of novel Strip Casting technology to a wide range of high strength steels because it allows Strip to be cast directly from the liquid metal with minimal rolling. In view of the current interest in developing Strip Casting technology, we explore here the structure-property relation in extra-low carbon steel, with particular emphasis on an important parameter, the rolling temperature after reheating. The as-cast Strip exhibited continuous yielding behavior, significantly lower yield ratio and higher elongation than hot rolled sheets. Coarse and recovered microstructure with Luders-like deformation bands was formed when the reheating temperature was in the range of 800–900 °C and followed by one-pass hot rolling, while coarse-fine mixed microstructure and fine and homogeneous microstructure was formed at 950 and 1000 °C, respectively. These differences in microstructure led to a transition from continuous yielding to discontinuous yielding with increase in reheating temperature from 800 to 1000 °C and followed by hot rolling. The present study underscores that a good combination of yield strength and elongation that is comparable to conventional hot rolled sheets can be successfully obtained through optimization of hot rolling temperature after reheating in the Strip Casting process.
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effects of two stage cold rolling schedule on microstructure and texture evolution of Strip Casting grain oriented silicon steel with extra low carbon
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2016Co-Authors: Hong-yu Song, Zhenyu Liu, Haitao Liu, Wenqiang Liu, Y D Wang, Guo Dong WangAbstract:A 0.27 mm-thick grain-oriented silicon steel sheet with extra-low carbon was successfully produced by a novel processing route including Strip Casting, normalizing, two-stage cold rolling with an intermediate annealing, primary annealing, and secondary recrystallization annealing. The evolutions of microstructure and texture along the whole processing route were investigated with a special emphasis on the effects of two-stage cold rolling schedule. It was found that Goss orientation originated in the first cold rolling due to shear banding and relatively strong Goss texture evolved through the whole thickness after intermediate annealing. This is significantly different from the results in conventional process in which the origin of Goss texture is in the hot rolling stage and Goss texture only develops below the sheet surface. Besides, it was found that cold rolling schedule had significant influences on microstructure homogeneity, evolution of λ-fiber texture in primary annealed state and, thus, on secondary recrystallization. In case of appropriate cold rolling schedule, a homogeneous microstructure with Goss texture, relatively strong γ-fiber texture and medium α-fiber texture was observed in the primary annealed Strip. Although Goss texture in primary annealed state was much weaker than that in two-stage route in conventional process, a perfect secondary recrystallization microstructure was produced and the magnetic induction B8 was as high as 1.85 T. By contrast, when the cold rolling schedule was inappropriate, the primary annealed Strips exhibited inhomogeneous microstructure, together with weak γ-fiber texture, medium α-fiber and λ-fiber texture. Finally, the sheets showed incomplete secondary recrystallization microstructure in which a large number of fine grains still existed.
Haitao Liu - One of the best experts on this subject based on the ideXlab platform.
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the impact of hot rolling temperature after reheating in the new generation Strip Casting process on structure property relationship in extra low carbon steel
Steel Research International, 2016Co-Authors: Haitao Liu, Guo Dong Wang, Dongjie Chen, Baoguang Zhang, Aihua Chen, Devesh R K MisraAbstract:There is currently a significant interest in extending the application of novel Strip Casting technology to a wide range of high strength steels because it allows Strip to be cast directly from the liquid metal with minimal rolling. In view of the current interest in developing Strip Casting technology, we explore here the structure-property relation in extra-low carbon steel, with particular emphasis on an important parameter, the rolling temperature after reheating. The as-cast Strip exhibited continuous yielding behavior, significantly lower yield ratio and higher elongation than hot rolled sheets. Coarse and recovered microstructure with Luders-like deformation bands was formed when the reheating temperature was in the range of 800–900 °C and followed by one-pass hot rolling, while coarse-fine mixed microstructure and fine and homogeneous microstructure was formed at 950 and 1000 °C, respectively. These differences in microstructure led to a transition from continuous yielding to discontinuous yielding with increase in reheating temperature from 800 to 1000 °C and followed by hot rolling. The present study underscores that a good combination of yield strength and elongation that is comparable to conventional hot rolled sheets can be successfully obtained through optimization of hot rolling temperature after reheating in the Strip Casting process.
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effects of two stage cold rolling schedule on microstructure and texture evolution of Strip Casting grain oriented silicon steel with extra low carbon
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2016Co-Authors: Hong-yu Song, Zhenyu Liu, Haitao Liu, Wenqiang Liu, Y D Wang, Guo Dong WangAbstract:A 0.27 mm-thick grain-oriented silicon steel sheet with extra-low carbon was successfully produced by a novel processing route including Strip Casting, normalizing, two-stage cold rolling with an intermediate annealing, primary annealing, and secondary recrystallization annealing. The evolutions of microstructure and texture along the whole processing route were investigated with a special emphasis on the effects of two-stage cold rolling schedule. It was found that Goss orientation originated in the first cold rolling due to shear banding and relatively strong Goss texture evolved through the whole thickness after intermediate annealing. This is significantly different from the results in conventional process in which the origin of Goss texture is in the hot rolling stage and Goss texture only develops below the sheet surface. Besides, it was found that cold rolling schedule had significant influences on microstructure homogeneity, evolution of λ-fiber texture in primary annealed state and, thus, on secondary recrystallization. In case of appropriate cold rolling schedule, a homogeneous microstructure with Goss texture, relatively strong γ-fiber texture and medium α-fiber texture was observed in the primary annealed Strip. Although Goss texture in primary annealed state was much weaker than that in two-stage route in conventional process, a perfect secondary recrystallization microstructure was produced and the magnetic induction B8 was as high as 1.85 T. By contrast, when the cold rolling schedule was inappropriate, the primary annealed Strips exhibited inhomogeneous microstructure, together with weak γ-fiber texture, medium α-fiber and λ-fiber texture. Finally, the sheets showed incomplete secondary recrystallization microstructure in which a large number of fine grains still existed.
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effect of cooling rate on bending behavior of 6 5 wt si electrical steel thin sheets fabricated by Strip Casting and rolling
Materials Characterization, 2016Co-Authors: Xianglong Wang, Guo Dong Wang, Zhenyu Liu, Haitao Liu, Zhonghan Luo, Shenglin Chen, Fengquan Zhan, Li LyuAbstract:Abstract Thin sheets of 6.5 wt.% Si electrical steel with the thickness of 0.35 mm were fabricated by Strip Casting and rolling. Influences of different cooling processes after annealing, including air cooling, water quenching, brine quenching and brine ice quenching, on the bending behavior at room temperature were systematically investigated. The results showed that with increase of the cooling rate, the room-temperature bending properties could be much improved, the fracture deflection values of the air cooled, water quenched, brine quenched and brine ice quenched specimens were measured to be 2.82 mm, 3.36 mm, 4.17 mm and 5.85 mm, respectively, moreover, obvious plastic deformation could be observed in the brine ice quenched specimen. The fracture modes of the air cooled and water quenched specimens were trans-granular cleavage fracture, while for the brine and brine ice quenched specimens, because the phosphorus segregation at grain boundary during high temperature could be preserved to room temperature by rapid quenching, the fracture modes were inter-granular fracture. The ordered phases in all specimens were observed and analyzed by TEM. The average sizes of B2 ordered domains in the air cooled, water quenched, brine quenched and brine ice quenched specimens were measured to be 107 nm, 2.7 nm, 1.6 nm, and 1.2 nm, respectively, and the DO 3 ordered domain with the average size of 2 nm could only be detected in the air cooled specimen. Therefore, the reduction of the order degree caused by fast cooling was believed to be mainly responsible for the improvement of bending properties, which might have led to significant decrease of the order-strengthening effect.
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effects of rolling temperature on microstructure texture formability and magnetic properties in Strip Casting fe 6 5 wt si non oriented electrical steel
Journal of Magnetism and Magnetic Materials, 2015Co-Authors: Haitao Liu, Fei Gao, Zhenyu Liu, Guo-huai Liu, Guangming Cao, Zhonghan Luo, Fengquan Zhang, Shenglin Chen, Guo Dong WangAbstract:Abstract Fe-6.5 wt% Si non-oriented electrical steel sheets with a thickness of 0.50 mm were produced by using a new processing route: Strip Casting followed by hot rolling, intermediate temperature (150–850 °C) rolling and final annealing. The present study focused on exploring the effects of rolling temperature varying from 150 to 850 °C on the microstructure and texture evolution, the formability and final magnetic properties. The microstructure and texture evolution at the various processing steps were investigated in detail by using OM, XRD, EBSD and TEM. It was found that the formability during rolling, the microstructure and texture before and after annealing and final magnetic properties highly depended on rolling temperature. The formability during rolling was gradually improved with increasing rolling temperature due to the slipping of dislocation. In particular, the rolling temperature dominated the formation of in-grain shear bands in the rolled microstructure, which played an important role in the development of final recrystallization microstructure and texture. In the case of lower temperature (150–450 °C) rolling, an inhomogeneous microstructure with a large amount of in-grain shear bands was formed in the rolled sheets, which finally resulted in a fine and inhomogeneous annealing microstructure dominated by mild λ-fiber texture composed of cube and {001}〈210〉 components and α*-fiber texture concentrated on {115}〈5–10 1〉 component. By contrast, in the case of higher temperature (650–850 °C) rolling, a relatively homogeneous microstructure without in-grain shear bands was formed instead in the rolled sheets, which finally led to a coarse and relatively homogeneous annealing microstructure characterized by strong α-fiber and γ-fiber texture. Accordingly, on the whole, both the magnetic induction (B 8 and B 50 ) and iron loss (P 15/50 and P 10/400 ) decreased with raising rolling temperature.
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development of microstructure and texture in Strip Casting grain oriented silicon steel
Journal of Magnetism and Magnetic Materials, 2015Co-Authors: Yang Wang, Haitao Liu, Yuanxiang Zhang, Feng Fang, Guo Dong WangAbstract:Abstract Grain oriented silicon steel was produced by Strip Casting and two-stage cold rolling processes. The development of microstructure and texture was investigated by using optical microscopy, X-ray diffraction and electron backscattered diffraction. It is shown that the microstructure and texture evolutions of Strip Casting grain oriented silicon steel are significantly distinct from those in the conventional processing route. The as-cast Strip is composed of coarse solidification grains and characterized by pronounced 〈001〉//ND texture together with very weak Goss texture. The initial coarse microstructure enhances {111} shear bands formation during the first cold rolling and then leads to the homogeneously distributed Goss grains through the thickness of intermediate annealed sheet. After the secondary cold rolling and primary annealing, strong γ fiber texture with a peak at {111}〈112〉 dominates the primary recrystallization texture, which is beneficial to the abnormal growth of Goss grain during the subsequent high temperature annealing. Therefore, the secondary recrystallization of Goss orientation evolves completely after the high temperature annealing and the grain oriented silicon steel with a good magnetic properties ( B 8 =1.94 T, P 1.7/50 =1.3 W/kg) can be prepared.
T. Haga - One of the best experts on this subject based on the ideXlab platform.
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Strip Casting using a roll caster equipped with a scraper
'EDP Sciences', 2020Co-Authors: T. HagaAbstract:An Al-Mg Strip without center segregation could be cast using a single-roll caster equipped with a scraper at speed of 40 m/min. The scraper was useful for flattening a free solidified surface and for cooling the solidification layer by pushing the solidification layer to the roll. Clad Strips consisting of 1) an Al-Mn base Strip and an Al-Mg overlay Strip and 2) an Al base Strip and an Al-Sn-Cu overlay Strip could be cast using an unequal-diameter twin-roll caster equipped with a scraper at speeds of 30 m/min and 15 m/min, respectively. The base Strip and overlay Strip were strongly bonded at the interface between the base Strip and the overlay Strip. The elements of the overlay Strip did not diffuse into the base Strip. The scraper played two roles in the Casting of the clad Strip: prevention of the mixture of two kinds of molten metal and making the surface of the base Strip a semisolid of high solid fraction
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feasibility study of twin roll Casting process for magnesium alloys
Journal of Materials Processing Technology, 2007Co-Authors: Hisaki Watari, N. Koga, T. Haga, Keith DaveyAbstract:Abstract This paper is concerned with the development of a Strip Casting technology for manufacturing magnesium alloy sheets. The aim of the work is to establish a manufacturing process and technology to facilitate the economical manufacture of high-quality magnesium alloy sheets. Magnesium alloy AZ31, AZ61, AM60 and AZ91 were used to investigate the appropriate manufacturing conditions for use in twin roll Strip Casting. Temperatures of the molten materials and roll speeds were varied to find the appropriate manufacturing conditions. The effects of manufacturing conditions on possible forming were clarified in terms of roll speeds and roll gaps between upper and lower rolls. In addition, microscopic observation of the microstructure of the finished Casting was performed. It was clarified that a magnesium sheet of 2.5–4.5 mm thickness could be produced at a speed of 20 m/min by a horizontal copper roll caster. Mill stiffness and a method of predicting the cast sheet's thickness were investigated to determine the appropriate manufacturing conditions. It was also found that the cast magnesium sheet of AZ31, AZ61, AM60 and AZ91 manufactured by roll Strip Casting could be used for plastic forming if the appropriate magnesium sheets were produced after the roll Casting process. By a warm deep-drawing test, it also demonstrated that a limiting drawing ratio of 2.4 was possible in the case of AZ91 sheet that was difficult to be manufactured by conventional extrusion process or DC Casting and hot-rolling process for magesium alloy sheets with high aluminium contents.
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high speed twin roll Strip Casting of al mg si alloys with high iron content
Materials Transactions, 2005Co-Authors: Kenta Suzuki, Shinji Kumai, Yuichi Saito, T. HagaAbstract:Thin Strips of the 6063 aluminum alloy and the alloys with increased nominal Fe contents (0.7–6 mass%Fe) were fabricated directly from the molten alloys using a vertical-type high speed twin-roll Strip caster equipped with a pair of water-cooled pure copper rolls. The estimated cooling rates from the DAS measurement were about 4500 and 100 � C/s at the near the surface region and the mid-thickness region of the Strip respectively. Refinement of Al–Fe–Si intermetallic compound particles was also successfully achieved, however, segregated coarse particles were also observed at the mid-thickness region. The cast Strips were cold-rolled and heat-treated to form 0.5 mm-thick thin sheets. They were either naturally aged at room temperature (T4) or artificially aged (T6), and then subjected to bending, tensile and hardness tests. No detrimental effect of Fe was appeared concerning the bendability even in the alloy containing 3 mass%Fe. No cracking took place even in the 180 � bending (hemming) test. The reduction of age-hardenability was evident for the alloy with 1 mass%Fe and more. The alloy sheet containing 0.7 mass%Fe exhibited not only a good bendability in the T4 condition but also the larger proof stress and UTS than those of the master alloy in the T6 condition. This means that the capacity of Fe impurity in a 6063 alloy (0.35 mass% according to JIS) can be doubled by using the present roll caster. Strip Casting at a high cooling rate using the present roll caster is considered to be a promising method for reducing the detrimental effect of impurity iron from the scrap melt.
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semi solid manufacturing process of magnesium alloys by twin roll Casting
Journal of Materials Processing Technology, 2004Co-Authors: Hisaki Watari, M.t. Alonso Rasgado, Keith Davey, T. Haga, S IzawaAbstract:Abstract An experimental approach has been employed to ascertain the effectiveness of semi-solid roll Strip Casting of magnesium alloys by a twin-roll caster. The demand for light-weight products with high strength has grown recently due to the rapid development of automobile and aircraft technology. One key to such development has been utilization of magnesium alloys, which can potentially reduce the total product weight. However, the problems of utilizing magnesium alloys are still mainly related to high manufacturing cost. One of the solutions to this problem is to develop magnesium Casting–rolling technology in order to produce magnesium sheet products at competitive cost for commercial applications. In this experiment, magnesium alloys AZ31B, AZ91D, AM50A and AM60B were used for twin-roll Strip Casting. Temperature of the molten materials and roll speeds of upper and lower rolls, which could be adjusted independently, were varied to find appropriate manufacturing conditions. Effects of cooling and contact condition on possible forming were clarified in terms of contact condition between molten material and the rolls. Microscopic observation of the crystals of the finished Casting was performed. It has been found that 2.0–3.0 mm thick magnesium sheets could be produced at a speed of 25 m/min. It has been found that the hot rolled cast magnesium sheets produced by semi-solid manufacturing process could be used for plastic forming.
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twin roll Casting of aluminum alloy Strips
Journal of Materials Processing Technology, 2004Co-Authors: T. Haga, Kenta Tkahashi, Masaaki Ikawaand, Hisaki WatariAbstract:Abstract Two kinds of twin roll caster for aluminum alloys were devised in the present study. Vertical type was adopted. The Strip, which was thinner than 3 mm, could be cast at speeds higher than 60 m/min. Aluminum alloy, which freezing zone is very wide like A5182, could be cast using the twin roll caster of the present study at speeds up to 150 m/min. Features of the twin roll casters are as below. Copper rolls were used and lubricant was not used in order to increase the Casting speed. Heat transfer between melt and the roll was improved by hydrostatic pressure of the melt. Separating force was very small in order to prevent sticking of the Strip to the roll. Low superheat Casting was carried out in order to improve microstructure of the Strip. A5182 Strip, which had equiaxed structure, could be cast. Some heat treatment was tried and tested in order to improve the mechanical property of A5182 Strip. A3003 Strip was cast by low superheat Strip Casting. A3003 Strip showed thermo-softening resistance. Semisolid Strip Casting of A356 alloy was tried using a twin roll caster equipped with a cooling slope. Mechanical property, especially elongation, was improved. Result of 180° bending test was improved, too. Semisolid Strip Casting was useful for high speed roll Casting, and the Casting speed increased up to 180 m/min.
Zhenyu Liu - One of the best experts on this subject based on the ideXlab platform.
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development of trip aided lean duplex stainless steel by twin roll Strip Casting and its deformation mechanism
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2016Co-Authors: Yan Zhao, Zhenyu Liu, Weina Zhang, Xin Liu, Guo Dong WangAbstract:In the present work, twin-roll Strip Casting was carried out to fabricate thin Strip of a Mn-N alloyed lean duplex stainless steel with the composition of Fe-19Cr-6Mn-0.4N, in which internal pore defects had been effectively avoided as compared to conventional cast ingots. The solidification structure observed by optical microscope indicated that fine Widmannstatten structure and coarse-equiaxed crystals had been formed in the surface and center, respectively, with no columnar crystal structures through the surface to center of the cast Strip. By applying hot rolling and cold rolling, thin sheets with the thickness of 0.5 mm were fabricated from the cast Strips, and no edge cracks were formed during the rolling processes. With an annealing treatment at 1323 K (1050 °C) for 5 minutes after cold rolling, the volume fractions of ferrite and austenite were measured to be approximately equal, and the distribution of alloying elements in the Strip was further homogenized. The cold-rolled and annealed sheet exhibited an excellent combination of strength and ductility, with the ultimate tensile strength and elongation having been measured to be 1000 MPa and 65 pct, respectively. The microstructural evolution during deformation was investigated by XRD, EBSD, and TEM, indicating that ferrite and austenite had different deformation mechanisms. The deformation of ferrite phase was dominated by dislocation slipping, and the deformation of austenite phase was mainly controlled by martensitic transformation in the sequence of γ→e-martensite→α′-martensite, leading to the improvement of strength and plasticity by the so-called transformation-induced plasticity (TRIP) effect. By contrast, lean duplex stainless steels of Fe-21Cr-6Mn-0.5N and Fe-23Cr-7Mn-0.6N fabricated by twin-roll Strip Casting did not show TRIP effects and exhibited lower strength and elongation as compared to Fe-19Cr-6Mn-0.4N.
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effects of two stage cold rolling schedule on microstructure and texture evolution of Strip Casting grain oriented silicon steel with extra low carbon
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2016Co-Authors: Hong-yu Song, Zhenyu Liu, Haitao Liu, Wenqiang Liu, Y D Wang, Guo Dong WangAbstract:A 0.27 mm-thick grain-oriented silicon steel sheet with extra-low carbon was successfully produced by a novel processing route including Strip Casting, normalizing, two-stage cold rolling with an intermediate annealing, primary annealing, and secondary recrystallization annealing. The evolutions of microstructure and texture along the whole processing route were investigated with a special emphasis on the effects of two-stage cold rolling schedule. It was found that Goss orientation originated in the first cold rolling due to shear banding and relatively strong Goss texture evolved through the whole thickness after intermediate annealing. This is significantly different from the results in conventional process in which the origin of Goss texture is in the hot rolling stage and Goss texture only develops below the sheet surface. Besides, it was found that cold rolling schedule had significant influences on microstructure homogeneity, evolution of λ-fiber texture in primary annealed state and, thus, on secondary recrystallization. In case of appropriate cold rolling schedule, a homogeneous microstructure with Goss texture, relatively strong γ-fiber texture and medium α-fiber texture was observed in the primary annealed Strip. Although Goss texture in primary annealed state was much weaker than that in two-stage route in conventional process, a perfect secondary recrystallization microstructure was produced and the magnetic induction B8 was as high as 1.85 T. By contrast, when the cold rolling schedule was inappropriate, the primary annealed Strips exhibited inhomogeneous microstructure, together with weak γ-fiber texture, medium α-fiber and λ-fiber texture. Finally, the sheets showed incomplete secondary recrystallization microstructure in which a large number of fine grains still existed.
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effect of cooling rate on bending behavior of 6 5 wt si electrical steel thin sheets fabricated by Strip Casting and rolling
Materials Characterization, 2016Co-Authors: Xianglong Wang, Guo Dong Wang, Zhenyu Liu, Haitao Liu, Zhonghan Luo, Shenglin Chen, Fengquan Zhan, Li LyuAbstract:Abstract Thin sheets of 6.5 wt.% Si electrical steel with the thickness of 0.35 mm were fabricated by Strip Casting and rolling. Influences of different cooling processes after annealing, including air cooling, water quenching, brine quenching and brine ice quenching, on the bending behavior at room temperature were systematically investigated. The results showed that with increase of the cooling rate, the room-temperature bending properties could be much improved, the fracture deflection values of the air cooled, water quenched, brine quenched and brine ice quenched specimens were measured to be 2.82 mm, 3.36 mm, 4.17 mm and 5.85 mm, respectively, moreover, obvious plastic deformation could be observed in the brine ice quenched specimen. The fracture modes of the air cooled and water quenched specimens were trans-granular cleavage fracture, while for the brine and brine ice quenched specimens, because the phosphorus segregation at grain boundary during high temperature could be preserved to room temperature by rapid quenching, the fracture modes were inter-granular fracture. The ordered phases in all specimens were observed and analyzed by TEM. The average sizes of B2 ordered domains in the air cooled, water quenched, brine quenched and brine ice quenched specimens were measured to be 107 nm, 2.7 nm, 1.6 nm, and 1.2 nm, respectively, and the DO 3 ordered domain with the average size of 2 nm could only be detected in the air cooled specimen. Therefore, the reduction of the order degree caused by fast cooling was believed to be mainly responsible for the improvement of bending properties, which might have led to significant decrease of the order-strengthening effect.
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effects of rolling temperature on microstructure texture formability and magnetic properties in Strip Casting fe 6 5 wt si non oriented electrical steel
Journal of Magnetism and Magnetic Materials, 2015Co-Authors: Haitao Liu, Fei Gao, Zhenyu Liu, Guo-huai Liu, Guangming Cao, Zhonghan Luo, Fengquan Zhang, Shenglin Chen, Guo Dong WangAbstract:Abstract Fe-6.5 wt% Si non-oriented electrical steel sheets with a thickness of 0.50 mm were produced by using a new processing route: Strip Casting followed by hot rolling, intermediate temperature (150–850 °C) rolling and final annealing. The present study focused on exploring the effects of rolling temperature varying from 150 to 850 °C on the microstructure and texture evolution, the formability and final magnetic properties. The microstructure and texture evolution at the various processing steps were investigated in detail by using OM, XRD, EBSD and TEM. It was found that the formability during rolling, the microstructure and texture before and after annealing and final magnetic properties highly depended on rolling temperature. The formability during rolling was gradually improved with increasing rolling temperature due to the slipping of dislocation. In particular, the rolling temperature dominated the formation of in-grain shear bands in the rolled microstructure, which played an important role in the development of final recrystallization microstructure and texture. In the case of lower temperature (150–450 °C) rolling, an inhomogeneous microstructure with a large amount of in-grain shear bands was formed in the rolled sheets, which finally resulted in a fine and inhomogeneous annealing microstructure dominated by mild λ-fiber texture composed of cube and {001}〈210〉 components and α*-fiber texture concentrated on {115}〈5–10 1〉 component. By contrast, in the case of higher temperature (650–850 °C) rolling, a relatively homogeneous microstructure without in-grain shear bands was formed instead in the rolled sheets, which finally led to a coarse and relatively homogeneous annealing microstructure characterized by strong α-fiber and γ-fiber texture. Accordingly, on the whole, both the magnetic induction (B 8 and B 50 ) and iron loss (P 15/50 and P 10/400 ) decreased with raising rolling temperature.
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fabrication of high permeability non oriented electrical steels by increasing 0 0 1 recrystallization texture using compacted Strip Casting processes
Journal of Magnetism and Magnetic Materials, 2015Co-Authors: Haitao Liu, Fei Gao, Zhenyu Liu, Yu Sun, Hong-yu Song, Dian-qiao Geng, Jurgen Schneider, Guo Dong WangAbstract:Abstract In this paper we will report on the application of the twin-roll Casting technique to get a 2 mm thick material of Fe-3.2%Si alloy, which was finally hot rolled, cold rolled and annealed. After a mild hot rolling to a thickness of 1 mm and a mild cold rolling to a thickness of 0.35 mm, we obtained a high intensity of λ-fiber (〈0 0 1〉|| ND) and η-fiber (〈0 0 1〉|| RD) texture concentrated on cube ({0 0 1}〈0 1 0〉) component and a diminishing intensity of the γ-fiber (〈1 1 1〉|| ND) texture, and a large average grain size in the final processed material. The experimental results for the evolution of the microstructure and texture along the used processing routes were described within the paper in detail. The formation mechanism for the desired recrystallization textures were explained in terms of oriented nucleation, micro-growth selection, accumulated deformation stored energy, geometric softening and orientation pinning. It will be demonstrated that this new processing route using the compact Strip Casting offers the possibility to fabricate high permeability non-oriented electrical steels without additional fabrication steps like hot band annealing or two step cold rolling with intermediate annealing as in the case of conventional processing route.
Nicole Stanford - One of the best experts on this subject based on the ideXlab platform.
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effect of molybdenum on phase transformation and microstructural evolution of Strip cast steels containing niobium
Journal of Materials Science, 2019Co-Authors: Lu Jiang, Nicole Stanford, Peter Hodgson, Ross K W Marceau, Thomas DorinAbstract:Molybdenum (Mo) is known to have a complex effect on phase transformations and precipitation in steels manufactured by conventional Casting. The present work aims to examine the effect of Mo on phase transformations in Nb-containing steels produced by Strip Casting. Advanced experimental techniques have been utilised to simulate the Strip Casting process, and the microstructural features of the rapid solidification are retained for further study. Two cooling conditions from the austenite phase field were examined, isothermal holding and continuous cooling. It was found that at high cooling rates, the addition of Mo delayed the nucleation of bainite and lowered the bainite start temperature, but did not alter the bainite growth rate. The addition of Mo was also found to result in a slower transformation rate of polygonal ferrite under both isothermal and continuous cooling conditions. Thermodynamic simulations indicated that Mo did not affect the growth velocity of the polygonal ferrite, and quantitative metallography showed the nucleation density was significantly reduced by Mo addition. For the slowest continuous cooling rate, the addition of Mo completely inhibited pearlite formation, with bainitic ferrite forming instead. This has been suggested to be the result of the suppression of pearlite nucleation, rather than inhibition of growth.
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effect of deformation on microstructure and mechanical properties of dual phase steel produced via Strip Casting simulation
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Zhiping Xiong, Nicole Stanford, Andrii Kostryzhev, Elena V PerelomaAbstract:Abstract The Strip Casting is a recently appeared technology with a potential to significantly reduce energy consumption in steel production, compared to hot rolling and cold rolling. However, the quantitative dependences of the steel microstructure and mechanical properties on Strip Casting parameters are unknown and require investigation. In the present work we studied the effects of strain and interrupted cooling temperature on microstructure and mechanical properties in conventional dual phase steel (0.08C–0.81Si–1.47Mn–0.03Al wt%). The Strip Casting process was simulated using a Gleeble 3500 thermo-mechanical simulator. The steel microstructures were studied using optical, scanning and transmission electron microscopy. Mechanical properties were measured using microhardness and tensile testing. Microstructures consisting of 40–80% polygonal ferrite with remaining martensite, bainite and very small amount of Widmanstatten ferrite were produced. Deformation to 0.17–0.46 strain at 1050 °C refined the prior austenite grain size via static recrystallisation, which led to the acceleration of ferrite formation and the ferrite grain refinement. The yield stress and ultimate tensile strength increased with a decrease in ferrite fraction, while the total elongation decreased. The improvement of mechanical properties via deformation was ascribed to dislocation strengthening and grain boundary strengthening.
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microstructures and mechanical properties of dual phase steel produced by laboratory simulated Strip Casting
Materials & Design, 2015Co-Authors: Zhiping Xiong, Nicole Stanford, Andrii Kostryzhev, Elena V PerelomaAbstract:Abstract Conventional dual phase (DP) steel (0.08C–0.81Si–1.47Mn–0.03Al wt.%) was manufactured using simulated Strip Casting schedule in laboratory. The average grain size of prior austenite was 117 ± 44 μm. The continuous cooling transformation diagram was obtained. The microstructures having polygonal ferrite in the range of 40–90%, martensite with small amount of bainite and Widmanstatten ferrite were observed, leading to an ultimate tensile strength in the range of 461–623 MPa and a corresponding total elongation in the range of 0.31–0.10. All samples exhibited three strain hardening stages. The predominant fracture mode of the studied steel was ductile, with the presence of some isolated cleavage facets, the number of which increased with an increase in martensite fraction. Compared to those of hot rolled DP steels, yield strength and ultimate tensile strength are lower due to large ferrite grain size, coarse martensite area and Widmanstatten ferrite.
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Effect of Cooling Rate on Phase Transformations in a High-Strength Low-Alloy Steel Studied from the Liquid Phase
Metallurgical and Materials Transactions A, 2015Co-Authors: Thomas Dorin, Nicole Stanford, Adam Taylor, Peter HodgsonAbstract:The phase transformation and precipitation in a high-strength low-alloy steel have been studied over a large range of cooling rates, and a continuous cooling transformation (CCT) diagram has been produced. These experiments are unique because the measurements were made from samples cooled directly from the melt, rather than in homogenized and re-heated billets. The purpose of this experimental design was to examine conditions pertinent to direct Strip Casting. At the highest cooling rates which simulate Strip Casting, the microstructure was fully bainitic with small regions of pearlite. At lower cooling rates, the fraction of polygonal ferrite increased and the pearlite regions became larger. The CCT diagram and the microstructural analysis showed that the precipitation of NbC is suppressed at high cooling rates, and is likely to be incomplete at intermediate cooling rates.
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Static recrystallisation study of as-cast austenitic stainless steel
Materials Science and Engineering: A, 2013Co-Authors: G. K. Mandal, Nicole Stanford, Peter Hodgson, John H. BeynonAbstract:This investigation will assist the generation of the fundamental knowledge required to develop advanced high strength and formable steels using thin Strip Casting processes. During thin Strip Casting the low temperature, high strain rate and the lack of deformation that can be applied in a hot rolling pass may not be sufficient for the onset of dynamic recrystallisation (DRX). Therefore, the refinement of the hot rolled deformed microstructure has to be finished by post-dynamic softening events (metadynamic and/or static). The present investigation reveals the softening mechanisms of as-cast austenitic stainless steel after hot rolling based on static recrystallisation. The static recrystallisation kinetics of austenitic stainless steel can be successfully modelled using a standard Avrami equation with an Avrami exponent of 1.15. It is observed that static recrystallisation proceeds heterogeneously, as a result of a non-uniform distribution of stored energy in the deformed material. The presence of many annealing twins inside recrystallised grains is also observed.
