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The effect of Ce on hot ductility of Cu-As bearing steel in the temperature ranging from 700 to 1100 °C was investigated using Gleeble-3800 thermal-mechanical simulator. The hot ductility evaluation and fracture morphology observation showed that the hot ductility was obviously improved as Ce content increased from 0 to 0.0290 wt%. Detailed, the upper limit temperature of the ductility trough was decreased from 1057 to 765 °C, and the temperature corresponding to the minimum reduction of area was decreased from 850 to 750 °C. The fracture morphology was overall transformed from the dominantly intergraular brittle failure to the ductile failure characterized by the large and deep dimples. Analysis of metallographic, inclusions and grain boundary elements suggested that increasing Ce content inhibited the proeutectoid ferrite formation, which enhanced hot ductility of the steel bearing Cu and As. Moreover, the competitive grain boundary segregation of the solute Ce and As in steel with 0.0022 wt% Ce without arsenious rare earth inclusions decreased the quantity of As distributed at grain boundaries and thereby improved the hot ductility. When the Ce content reached 0.0290 wt%, a large number of arsenious rare earth inclusions were formed, and the grain boundary segregation of As was further decreased As, which was more beneficial to hot ductility than that with the lower Ce content in austenite single phase region. [ABSTRACT FROM AUTHOR]

In order to study the segregation of arsenic impurities at the metal/oxide interface during high temperature exposure, isothermal oxidation behavior of arsenic bearing steels with various Ce content was systematically investigated. The result showed that oxidation mass gain of arsenic bearing steel in the temperature range of 950–1150 °C was decreased as a whole with increasing Ce content from 0 to 0.035 wt.%. At 1100 and 1150 °C, the best results are obtained for 0.027 and 0.035 wt.% Ce. Moreover, Ce addition could prevent grain boundaries oxidation, which reduced or even eliminated the formation of visible oxide particles along grain boundaries at 1000 and 1050 °C. In case of oxidation at 1050 and 1100 °C, the arsenic enrichment amount at the scale/metal interface was firstly decreased with increasing Ce content from 0 to 0.027 wt.% and then slightly increased as Ce content increased from 0.027 to 0.035 wt.%. This variation was attributed to the separation behavior of oxide scale, the formation of a continuous solid Fe2SiO4 layer and the arsenious rare earth particles promoted by Ce addition. [ABSTRACT FROM AUTHOR]

The significant influence of the welding heat input on the microstructural evolution, precipitation behavior and resultant properties of the coarse grained heat affected zone (CGHAZ) in low carbon Nb-V-Ti-N quaternary microalloyed steel was comparatively studied on a Gleeble 3800 thermomechanical simulator. Metallographic investigations revealed that the dominant microstructure transformed from lath bainite (LB) at heat input of 50 kJ/cm to intragranular acicular ferrite (IAF) at 100 kJ/cm, to IAF and intragranular polygonal ferrite (IPF) at 150 kJ/cm and to IPF, IAF and grain boundary ferrite (GBF) at 200 kJ/cm. In addition, Ti- and Nb-enriched submicron-scale precipitates promoted IAF and IPF nucleation with an orientation relationship 01 1 − MC / / 1 − 11 Ferrite and effectively pinned grain boundaries; V-enriched nanoscale precipitates acted as obstacles for dislocation movement, consequently improving CGHAZ performance. Moreover, the impact absorbed energy at 20 °C and −20 °C first increased from 216 ± 4.3J and 58 ± 2.7J to 219 ± 3.7J and 64 ± 3.0J, respectively, and then decreased to 184 ± 7.5J and 45 ± 2.1J, respectively, when the heat input increased from 50 kJ/cm to 200 kJ/cm. The maximum value was obtained at heat input of 100 kJ/cm, which was primarily attributed to the largest amount of high angle grain boundaries originating from IAF. The microhardness slightly reduced as heat input increased from 50 kJ/cm to 100 kJ/cm and did not obviously decrease as heat input varied from 100 to 200 kJ/cm, which was directly related to the microstructure constituents and nanoscale precipitates. Furthermore, the optimal heat input to obtain a good combination of strength and toughness was 100 kJ/cm, and Nb-V-Ti-N microalloyed steel was suitable for high heat input welding. • The low carbon Nb-V-Ti-N microalloyed steel is suitable for high heat input welding. • The optimum welding heat input is 100 kJ/cm to obtain a strengthened and toughened CGHAZ. • The submicron Nb- and Ti-enriched particles promote intragranular ferrite nucleation and pin grain boundary. • The orientation relationship between nucleation site and the induced ferrite grain is 01 1 − MC / / 1 − 11 Ferrite. • The nanoscale V-enriched precipitates act as obstacles for dislocation movement. [ABSTRACT FROM AUTHOR]

The effect of different Ce content on the hot ductility of C-Mn steel containing arsenic was investigated at the temperature ranging from 700 to 1100 °C conducting Gleebel-1500 thermal-mechanical simulator. The reduction of area (RA%) was used to evaluate the hot ductility. The 0.16 mass% As widened the ductility trough range and especially, decreased the RA value at 850–950 °C. Conversely, adding Ce in the steel could remedy the arsenic-induced hot ductility deterioration. Moreover, with the increase of Ce content from 0 to 0.035 mass%, the RA value at 800–950 °C significantly increased, compared to that of the arsenic steel. When the content of Ce reached 0.027–0.035 mass%, the RA value at 800–850 °C was even higher than that of steel without As. Besides, the corresponding fracture morphology was changed from intergranular feature to ductile and/or interdendritic feature. Grain refinement by Ce addition, the formation of arsenious rare earth inclusions and grain boundary segregation of Ce were considered to improve the hot ductility of the steel containing As. [ABSTRACT FROM AUTHOR]

In order to depress the embrittlement induced by grain boundary segregation of arsenic in steel, the effect of Ce addition on the formation of arsenious inclusions and arsenic concentration at grain boundaries were systematically investigated in iron melts. The results showed that different types of arsenious rare earth inclusions were formed with different Ce content. As Ce content increased from 0.037 to 0.095wt%, the dominant inclusion in the melt was changed from the Ce-S-O inclusion fully coated by Ce-S-As inclusion to the Ce-S-As inclusion completely covered by Ce-As inclusion. Simultaneously, the single Ce-S-As and Ce-As inclusions were also detected when Ce content was more than 0.055 wt%. The amount and average size of inclusions increased with increasing Ce content. Transmission electron microscope analysis indicated that the Ce-As inclusion was the CeAs phase, which was formed during solidification process. Furthermore, concentration of arsenic on grain boundaries after adding Ce was decreased to the level of the matrix. [ABSTRACT FROM AUTHOR]

The effect of welding heat input characterized by the cooling time taken from 800 °C to 500 °C (t 8/5) on the microstructural evolution, V(C,N) precipitation and resultant mechanical properties of the simulated CGHAZ in high-N V-alloyed steel was comparatively investigated using a Gleeble-1500D thermomechanical simulator. Metallographic analysis indicated that the dominant microstructure transformed from lath bainite to granular bainite when t 8/5 increased from 30 s to 90 s and then changed to intragranular ferrite at t 8/5 of 180 s. The nanoscale V(C,N) precipitates were coarsened as t 8/5 increased, coupled with a slightly increased number density. Furthermore, the orientation relationship [001] α // 1 1 ¯ 0 V(C,N) reduced the interfacial structural energy (MC/α) and enhanced the V(C,N) precipitation in the ferrite matrix. Moreover, the microhardness progressively decreased due to the combined effect of microconstituents, precipitates and grain boundaries. The impact toughness first decreased and then increased, and the optimal value was obtained at t 8/5 of 180 s. Furthermore, the formation of intragranular ferrite, especially acicular ferrite, and the increased fraction of high angle grain boundaries could completely remedy the detrimental effect caused by the increased content of grain boundary ferrite and the coarsened effective grain size and precipitates. In addition, the high nitrogen content of 240 ppm accelerated V(C,N) precipitation in the austenite region, and the submicron V(C,N) precipitates could promote the formation of intragranular ferrite by providing heterogeneous nucleation sites, in combination with the larger prior austenite grain size caused by higher welding heat input. Unlabelled Image • Microalloying of nitrogen (0.024 wt%) for V contained base metal was beneficial for simulated CGHAZ. • Acicular ferrite and high angle grain boundaries are more crucial in toughness than precipitates and effective grain size. • HRTEM observation showed that the orientation relationship [001] α // 1 1 ¯ 0 V(C,N) enhanced V(C,N) precipitation in the ferrite matrix. [ABSTRACT FROM AUTHOR]