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Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most destructive diseases in wheat production. Pyramiding of adult-plant resistance (APR) genes is a promising strategy to increase durability of resistance. The stripe rust resistance (R) genes Yr18, Yr28, and Yr36 encode different protein families which confer partial resistance to a broad array of P. striiformis f. sp. tritici races. Here, we developed BC3F5 wheat lines representing all possible combinations of Yr18, Yr28, and Yr36 in a genetic background of the highly P. striiformis f. sp. tritici-susceptible wheat line SY95-71 that is widely used in stripe rust analysis. These lines enabled us to accurately evaluate these genes singly and in combination in a common genetic background. The adult plant resistance experiments were analyzed in the field, where stripe rust epidemics occurred frequently. The field results indicated that these partial R genes act additively in enhancing the levels of resistance, and a minimum of two-gene combinations can generate adequate stripe rust resistance. The Yr28 + Yr36 and Yr18 + Yr28 + Yr36 combinations also showed adequate resistance at the seedling stage, implying that APR gene pyramiding can achieve all-stage resistance. Meanwhile, the three genes were simultaneously introduced into elite wheat lines through gene-based marker selection. Elite lines exhibited strong all-stage resistance to stripe rust. This work provides valuable insights and resources for developing durable P. striiformis f. sp. tritici-resistant varieties and for elucidating the regulation mechanism of partial R gene pyramiding.

In steel continuous casting with submerged entry nozzles at a domestic steel plant, nozzle clogging was largely alleviated and defect rates of hot-rolled and cold-rolled sheets relating to slag entrainment were reduced for a nozzle with an approximately oval exit relative to a nozzle with a rectangular exit. Numerical and physical models were built to investigate the above phenomena. A turbulent model was applied in large eddy simulation to obtain the evolution of turbulent features within the nozzle and mold, while particle image velocimetry was adopted to monitor fluid flow beneath the slag–steel interface. Main results were that the flow speed of the main stream from the approximately oval exit was higher than that from the rectangular exit, while the zone of a velocity magnitude below 0.2 m/s within the approximately oval exit was smaller than that within the rectangular exit, indicating that inclusions tended to reside for longer in the latter. At the same casting speed, that slag entrainment occurred more frequently for the nozzle with a rectangular exit was found to have no direct relationship with the velocity magnitude and vorticity at 1/4 mold width on the top surface. Meanwhile, slag entrainment always occurred at the moment that vorticity changed most rapidly. The current study thus provided new insight into the structural parameter optimization of the submerged entry nozzle.

To control heat transfer between the solidifying shell and the water-cooled mold during continuous casting, the transition metal oxides, ZrO2, Y2O3, and Sc2O3, were separately added into the developed low-reactive CaO-Al2O3-based mold slags to investigate the effect on radiation heat transfer. Two kinds of master mold slags were taken into account, one included 18 pct Al2O3 and 18 pct SiO2, and the other one included 28 pct Al2O3 and 8 pct SiO2. The slag viscosity and melting temperature were measured with rotating cylinder viscometer and hemisphere-point method, respectively. The optical parameters of the slag films having different contents of transition metal oxides were measured by Fourier transform infrared spectrometer, and an optical-process model was constructed to consider the radiation from the shell surface and hot and cold sides of the solid films to the mold plate. When ZrO2, Y2O3, and Sc2O3 contents up to 4 pct, the viscosity at 1573 K fluctuated in the range of 0.05 Pa s, the melting temperature varied within a range of 15 K, except for the case of 2 pct Sc2O3, for which the melting temperature was 27 K lower than that of the master mold slag with 8 pct SiO2 and 28 pct Al2O3. The incorporation of the three transition metal oxides up to 4 pct did not have a notable effect on the viscosity or melting temperature. The addition of ZrO2 and Y2O3 effectively decreased the radiation, whereas Sc2O3 had no direct relationship with radiation. When the ZrO2 (Y2O3) concentration was increased from 0 to 4 pct, the reduction rate of radiation transfer was 26.6 pct (13.3 pct) for the mold slag containing 18 pct Al2O3 and 18 pct SiO2. The current study provides a new direction for developing low-reactive mold slag and reducing heat transfer during continuous casting.

The deformation of a bloom tube mold was investigated using an in-house-developed complex model considering the flow, heat transfer, and solidification as well as the copper tube stress strain. This model was validated by the cooling water temperature rise, solidification shell thickness, copper oxidized zone, and measured copper deformation. Based on this model, the heat transfer characteristics of the mold were analyzed. The deformation trends of the copper tube under different water pressures were compared. The results revealed that the deformation of the wide copper plate was mainly influenced by the cooling water pressure, whereas the deformation on the narrow side was primarily affected by the temperature field. Similarly, the corner distortion of the copper plate resulted mainly from the deformation of the wide and the narrow copper plates.

To moderate the erosion in a slag-line zone and extend the service life of a submerged entry nozzle during continuous casting of high-Mn and high-Al steel, the current study developed a low-reaction CaO-Al2O3-based slag with lower SiO2 and higher Al2O3 contents than that of conventional CaO-SiO2-based slag. The static sessile drop technique and dynamic rotating cylinder method were utilized to investigate the erosion behavior of ZrO2-graphite refractory by the above slags. The main results indicated that silicate-based slag could wet the ZrO2-graphite substrate completely, while the aluminate-based slag spread rapidly in the first 20 minutes, and then a slag drop with an unchanged profile formed on the substrate. The equilibrium contact angles with the substrate at 1623 K were 0 and 79 deg for the CaO-SiO2 and CaO-Al2O3 based slags, respectively. The comparison of the influences of the rotating speed and the temperature revealed that the decrease of erosion rate could be realized by the developed slag. An examination of ZrO2-saturation limit also indicated that the low-reaction slag could dissolve much more ZrO2 oxidation, accompanied by a less-negative effect on the viscosity of the molten slag.

To understand the effect of the non-Newtonian behavior of mold slag on lubrication during continuous casting of steel, the current study investigated the rheology of CaO-SiO2-based mold slag using a rotational viscometer with variable rotating speed. The constitutive equations at different temperatures were determined. Subsequently, the obtained viscosity as a function of temperature and shear rate was incorporated into a validated mathematical model. The main results demonstrated that slag viscosity decreased dramatically with increased shear rate as the experimental temperature approached the break temperature of mold slag, meaning that the mold slag had a property of shear thinning. The predicted evolution of slag viscosity during mold oscillation was consistent with the shear thinning as the shear rate exerted on the slag channel varied. The calculated slag consumption was higher than that for slag treated as a Newtonian fluid, which agreed well with measurements using a miniature continuous caster. This study finds that the consideration of the non-Newtonian behavior of mold slag is significant to understand the lubrication mechanism and optimize related parameters via simulation.