An off-line controller design method of a tension and looper system is derived based on hybrid systems approach. By employing a multi-parametric programming method, a nonlinear feedback control law, which is equivalent to the model predictive control, is constructively given. The feature of resulting control system is illustrated with numerical example.
Since it has been pointed out that non-wetting behavior of liquid Zn alloy sometimes occurs on high-tensile strength steels which usually contain Si and Mn, there have been a lot of studies to improve the wettability of liquid Zn. In the present work, we applied a sessile drop method to measure the change in contact angle and diameter of liquid Zn droplet wetted on steels containing Si and Mn with time, in order to evaluate quantitatively the wettability by liquid Zn with those steels. Addition of Si has dropped the contact angle, work of adhesion and spreading velocity. On the other hand, Mn has no relationship with contact angle and work of adhesion but increased the spreding velocity when steels contain Si.
Thermodynamic analysis of precipitation behaviors of Ti, Mn sulfide in hot-rolled steels, was conducted to evaluate the thermodynamic parameters of (Ti, Mn, Fe)S in steels. Thermodynamic parameters of sulfide were assessed based on Q-phase (NaCl type): (Mn, Fe)S and P-phase (NiAs type): (Ti, Fe, Mn)S reported by Miettinen. Since it was found that P-phase and Q-phase coexisted, as distinct complex precipitates without changing their crystal structure even on the conditions which both P-phase and Q-phase precipitated at the same time. The thermodynamic parameters of these two phases were determined using the extraction data and TEM-EDS. The solubility limit of Fe and Mn to TiS, which causes errors in practical steels, was estimated by using the solubility product of TiS evaluated by Mitsui. The calculated precipitation behaviors of Ti, Mn sulfide using developed thermodynamic parameter are in good agreement with the formation of sulfides and carbo-sulfides in hot rolled commercial IF steels.
The effects of alloying elements on structures, mechanical properties and deformation-induced martensite transformation were investigated in five types of Cr-Mn-Ni austenitic stainless steels: 14%Cr-1%Ni-10%Mn-0.13%N, 15%Cr-4%Ni-8%Mn-0.05%N, 15%Cr-4%Ni-8%Mn-0.12%N, 17%Cr-5%Ni-4%Mn-0.10%N and 17%Cr-6.5%Ni-4%Mn-0.05%N. The relationships between the compositions and their properties were discussed. The constitutional diagram using Cr and Ni equivalents as Schaeffler's diagram did not correspond to the observed structures of cold rolled and annealed sheets in Cr-Mn-Ni stainless steels. The constitutional diagram of Cr-Mn-Ni stainless steels was described using the equations for the calculated ferrite content and the Ms temperature. The effects of alloying elements on 0.2% proof stress in Cr-Mn-Ni stainless steels was almost equal to that in Cr-Ni stainless steels. The effect of Mn on austenite stability, which reveals the ease of deformation-induced martensite transformation, in Cr-Mn-Ni stainless steels was larger than that in Cr-Ni stainless steels. Therefore, the new Ni equivalent which exhibits austenite stability was attained by regression analysis between deformation-induced martensite transformation contents and compositions. A high correlation between this Ni equivalent and the formability of Cr-Mn-Ni stainless steels was recognized.
In this study, tensile and creep rupture properties of dissimilar welded joints (9Cr-1Mo-V-Nb/Inconel82/SUS304) were examined at elevated temperatures. Effect of temperatures and stresses on the failure location of the dissimilar welded joint was also investigated. Creep rupture tests were conducted at three temperatures: 823, 873, and 923K, and in stress ranges from 160 to 240 MPa, 80 to 160 MPa, and 40 to 80 MPa, respectively. The results of the elevated temperature tensile tests on the dissimilar welded joint showed that the location of fracture changes dependent on the tensile strength of base metal. The creep rupture strength of the dissimilar welded joint was lower than that of the 9Cr-1Mo-V-Nb steel base metal at all temperatures. In addition, the differences in creep strength between the dissimilar welded joint and base metal were increased as the temperature increased. The fracture type observed after long-term creep rupture tests on the dissimilar welded joint was shifted from the Type V and Type VII fracture at lower temperatures to the Type IV fracture at higher temperatures. It can be predicted that the fracture type of the 100,000 h creep rupture at 823K and 873K for dissimilar welded joint is Type IV fracture of 9Cr-1Mo-V-Nb steel.
Iron is an essential element for plant life in the sea and on land. However, in the sea, especially in open ocean, photosynthesis is limited by iron deficiency because of both limited supply from land and rapid oxidation and sedimentation of dissolved iron. Although previous studies demonstrated that marine phytoplankton under such iron stress can grow actively using steelmaking slag as an iron source. In this study, we followed the temporal change in efficiency of the powdered decarburization slag on the growth of the diatoms Thalassiosira oceanica and T. nordenskioeldii in a modified ESAW medium. To avoid limitation in other nutrients than iron, cultures were spiked with macronutrients in excess concentration. The cultures ran at 20°C for T. oceanica and 10°C for T. nordenskioeldii and growth was determined by in vivo fluorescence of the cultures. The results demonstrated that availability of the iron originating from the slag was high for both species. The bioavailability persisted for at least 23 d for T. oceanica and 30 d for T. nordenskioeldii when the slag was initially added at the concentration of 20 mg/L, probably because of slow but continual dissolution of iron from the slag. This indicates that continual positive effect of iron fertilization can be expected by slag input at an interval of a month or more.