MS&T'11 Poster Session: Iron and Steel
Program Organizers: Chris Wood, TMS
Tuesday 11:00 AM
October 18, 2011
Room: Exhibit Hall C
Location: Greater Columbus Convention Center
136 Effect of Prestrain and Bake Hardening Heat Treatment on Fracture Toughness and Fatigue Crack Growth Resistance of Two Dual-Phase Steels: Leonardo Godefroid1; Warley Horta1; Fabiano Machado2; Margareth Andrade3; 1Federal University of Ouro Preto; 2Iochpe Maxion S.A.; 3Centro Tecnológico de Minas Gerais
Fracture toughness (J integral, R-curve) and fatigue crack growth (da/dN) resistance have been studied in two ferrite-martensite DP-600MPa steels broadly used in the automotive industry, with 7% to 12% of martensite volume fraction, and with different silicon and chromium additions. The effect of 10% prestrain followed by a bake hardening heat treatment was verified. This thermo-mechanical treatment was used to simulate the stamping and the paint baking of the wheels. All the mechanical properties are affected by the thermo-mechanical history for both steels. An inverse relationship was found between yield stress and J integral, and between yield stress and fatigue threshold. This behavior was related with small changes in the microstructure of the steels.
137 Effects of Coiling Temperature on the Mechanical Properties and Microstructures of Low Alloy Martensitic Steels: Duhan Kim1; Eunji Yu1; Sung-Kyung Han2; Sung-Ju Kim2; Jongryoul Kim1; 1Hanyang University; 2HYUNDAI STEEL COMPANY
The relationship between mechanical properties and microstructures of high strengthen hot-rolled steels were investigated by the change of their coiling temperature. Low carbon steel containing 1.2 wt% Mn was normalized at 1200 ℃, hot-rolled at continuous milling line, and then was water cooled down to the coiling temperature. With the increase of the coiling temperature, the tensile strength was decreased by the formation of ferrite phase and the substructural changes inside lath martensite, which resulted in the increase of the elongation. A more detailed study on the relationship between mechanical properties and microstructures was conducted by scanning electron microscopy, electron backscattered diffraction and transmission electron microscopy. The optimum microstructure for high strength and ductility martensitic steel will be suggested.
138 Insulated Sprayed Roll Technique "ISRT" and Solid Shell Resistance of Inner Quality of Continuously Cast Steel Slabs: Mostafa El-Bealy1; 1Ain Shams University, (CC)
In order to get a better inner quality of continuously cast steel slabs, ceramic sprayed roll technique as an insulated material has been developed to increase the slab thermo-mechanical rigidity against the thermo-mechanical stresses between a pair of rolls. The idea behind this technique is increasing in the slab solid shell resistance "Ic" by optimizing the homogeneity of cooling conditions between a pair of rolls. This is by minimizing a rapid fluctuation in the surface temperature especially at roll contact area. The mathematical model of thermal, solidification, solid shell resistance and cooling conditions has been developed. The model predications indicate that the increasing in the thickness "c" of this layer or decreasing its thermal conductivity "c" is proportional to decreasing the peak of surface temperature at roll contact area. The predictions also point out that the improving of the solid shell resistance depends on the optimum selection of c and c with cooling conditions between rolls. Also, the predications were used to explain and discussed the mechanism of ceramic layer characteristics with Ic and thermo-mechanical rigidity of steel slab.
139 Investigation on the Inclusions in the First Slab of Ultralow Carbon Steel: Wenjun Duan1; Qichun Peng1; 1WuHan University of Science and Technology
By the ways of optical microscope observation, scanning electron microscopy, the energy spectrum analysis and total oxygen content, the content change of inclusions in the first slab of ultra-low carbon Al-killed steel was investigated under the unsteady casting conditions. The result shows that the content of the inclusions decreases progressively along the casting direction, occurs inflection point in 3.5m of the first slab, and then it appears to be leveling off，the content of the inclusions in 5m has fallen to its lowest level, approaching to normal slabs. Microscopic inclusions are mainly aluminum deoxidizing products, the distribution of particle size under 15μm is in the majority. The large inclusions over 50μm is relatively few, however, the content of the large inclusions is higher than that of normal slabs. Most of that are aluminum inclusions. This was related to the entrapment of mould powder at the beginning of casting.
140 Kinetic Process of Nozzle Clogging during Continuous Casting of Lower Carbon Al-Killed Steel: Suzhou Wu1; 1Wuhan University of Science and Technology
Nozzle clogging is serious problem for steel continuous casting, especially for low-aluminium killed steel. For the submerged-entry nozzle (SEN) clogging process, previous studies often adopt experimental means to analysis type, morphology and composition of the clogging materials, and then to speculate and to verify the thermodynamic mechanism, a lot of previous research in this area has been done. Nozzle Clogging is a complex process containing thermodynamics and kinetics of physical processes and chemical processes. In current paper, with the help of experimental means such as optical microscope, scanning electron microscopy and transmission electron microscopy, SEN clogging material morphology and composition have been investigated. Effect of decarburization reaction layer on the initiation process of nozzle clogging has been investigated. The kinetic condition of inclusions adhesion to nozzle wall is also been discussed.
141 Numerical Simulation on Influence of Parameters of RH on Decarburization Process for IF Steel: Xinyu Zhao1; Jiongming Zhang1; 1University of Science and Technology in Beijing
It is necessary to reducing element carbon at the process of IF steel making. RH has become the most widely used refining equipment for decarburization because of its good effect. A mathematical model is created for circulate decarburization process of RH, considering the equilibrium of elements according to 210t RH for IF steel. The results imply that: the mathematical model is credible. The mass fraction of initial oxygen is required to exceed 0.06% to ensure the effect of decarburization when that of initial carbon is 0.03%. Also the rate of decarburization will increase by adding the lift gas flow. While the mostly significant impact on decarburization rate is the diameters of snorkel. The average mass fraction of carbon at the end of decarburization is about 0.0049% if the diameters of snorkel are 350mm. However that is only 0.0011% if the diameters of snorkel are 650mm.
142 Optimization of Secondary Cooling Parameters in Continuous Casting Using CAFÉ Model: JING Cailiang1; Wang Xinhua1; Xu Zhigang1; Wang Wanjun1; Yin Na1; 1School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing
A method for evaluating the continuous casting parameters based on CAFÉ (Finite Element- Cellular Automaton coupling) model was established in this paper, in which the effect of different phases and electromagnetic stirring (EMS) on solidification process were taken into consideration. By this model the current secondary cooling parameters were discussed and optimized. Successful applications in industrial practice indicate that this method can work well in estimation of continuous casting parameters.
143 Research of Iron Slag Appearance of Blast Furnace Hearth: Qi Chenglin1; Zhang Jianliang1; Liu Qinyuan1; 1University of Science and Technology Beijing
The studies of microscopic behavior in blast furnace hearth were important. Some samples were obtained at of tuyere and tap-hole when disassembling BF to study the mechanism of micro-reduction and separation of iron and slag. The results confirm that the main process of the “shelling” separation of slag and iron can be observed clearly from microstructure in the lower part of BF. The respective phenomena were presented in different zones of BF hearth: The separation of iron and slag happens and the hot metal were assembled into dense sphere again due to the high temperature in the front of tuyere; However, at the bottom of tuyere, little iron ball which didn’t pass high temperature region was still iron and slag mixture. The separation of iron and slag was significant at tap-hole, but iron ball still kept the framework of ore pellet, and slag flowed out from the crack of ore.
144 Retained Austenite Characteristics and Tensile Properties in TRIP Assisted Steel: Sang-Wook Lee1; 1; 1HYSCO
Retained austenite characteristics and carbide formation behavior in newly developed 0.15%C-1.0%Si-2.5%Mn-Cr-Mo TRIP-aided steel with martensite matrix structure (TRIP-aided martensitic steel; TM steel) were investigated. If the 0.2%C-1.5%Si-1.5%Mn TM steel (base TM steel) was processed by annealing at 900°C and then partitioning at temperatures lower than 250°C, volume fraction of 3vol% and carbon concentration of 1.0mass% of retained austenite were completed in the steel with tensile strength of about 1300MPa. Fine cementite films were appeared in the martensite lath structure even just after quenching which are not found in the other types of TRIP-aided steels different matrix structure. Addition of Cr, Mo into the base TM steel raised upper limit partitioning temperature where high volume fraction and stability of retained austenite are maintained.
145 Study on the Combustion Process of Pulverized Coal and Carbonaceous Matter Dust in BF: Buxin SU1; Jianliang Zhang1; Qinyuan Liu1; Xiaomei CHE1; Yuandi FU1; Jiaqi JIN1; 1University of Science and Technology Beijing
Using the sampling device for unburnt pulverized coal(UPC) before the tuyere and combining the UPC microscopic morphology which are in BF dust, there is a detailed study of the combustion process of coal before the tuyere. In this study, we analyzed the shape and distribution of the carbonaceous matter in the Blast Furnace Dust by SEM and MM (Metallographic Microscope) and got the unburned pulverized coal and coke’s proportions in the dust by quantitative analysis. Based on the coke ratio and the coal ratio, we calculated the unburned pulverized coal’s and coke’s availabilities in BF. What’s more, we provided some effective methods for increasing the amount of the coal injection and decreasing BF’s coke ratio.
146 The Influence of Geometrical Factors of the Deformation Zone on Changing for Deformation Shift Degree for the Axial Zone of Rolled High Bars: Borys Sereda1; Anton Kovalenko1; Dmytro Sereda1; Tatjana Vasilchenko1; 1ZSEA
Data storage about characteristics of the tensely- deformed condition of the rolling metal for various combinations of the geometrical factors for the deformation zone while using results of the planned experiments is reasonable to carry them out, approximating them in the view of regressional differences. During seven-factorial experiment the Λ plasticity criterion was founded. Results of approximation of one of the basic integrated indicators degree the deformation of an axial zone shift of depending on geometrical factors of the deformation have been considered. It is received that the greatest influence on Λ in the investigated interval of the variation for deformation zone factors renders relative cogging of samples. The given models can be used by development work of reduction modes and blooming of thick sheet rolling mills providing intensive development of metal structure and (or) the minimum probability defect production as a result of its discontinuity.
147 The Variations of Compressive Strength of Containing Carbon Pellets Preheated under Reducing Atmosphere: Bing Dai1; zhe jiang1; 1unversity of science and technology
By simulating the temperature rising process of blast furnace interior, the compressive strengths of the pellets which were preheated to different temperatures under reducing atmosphere were measured, the compositions and microstructures of pellets at 900℃, 1000℃ and 1100℃ were also analyzed by XRD and SEM. When pellets heated to 900℃, nearly all Fe2O3 was reduced into FexO, so the strength was minimum; at 1000℃, a small amount of iron that formed small pieces of iron crystal appeared, so that the strength began to rise; when heated to 1100℃, a large area of iron crystal was found, which formed iron framework, due to that the strength increased sharply. The reasons for compressive strength changes of pellets were analyzed.
148 Thermodynamics Analysis and Control of TiN Precipitation during Solidification of Q345EN Steel: Yanzhao Luo1; Jiongming Zhang1; Chao Xiao1; Zhiming Liu1; 1university of science and technology beijing
The formation of Ti and N as a secondary inclusion precipitated during solidification is of great interest because it has an important impact on the quality of final products. In the present study the formation reaction of TiN was discussed based on the thermodynamic calculation in Q345EN steel. The activity coefficient values of titanium and nitrogen at 1873 K were obtained and the relational expression of their activity coefficients and temperature was calculated. The results show that TiN inclusions only form in solid phase, but under the chemical composition of this Q345EN steel, TiN inclusions can’t be produced in solid phase. Only in a solidification front, the formation reaction of TiN can take place owing to the enrichment of Ti and N. It is considered the best way to reduce TiN’s precipitation is to go through the mushy region rapidly, and control titanium and nitrogen contents in steel simultaneously.
149 Three Dimensional Modeling of Raceway of Dissected Blast Furnace: Yang Guangqing1; zhang jianliang1; shao jiugang1; chen weiwei1; guo hongwei1; 1University of Science and Technology Beijing
In order to obtain a practical raceway shape, refractory was injected through tuyere before blast furnace blowing out. After dissecting the blast furnace, the attained raceway shape is elliptical cavity, the end of which far from the tuyere expands to the upper of the furnace, depth :700mm, width :450mm, height:600mm. Aiming at the dissected blast furnace, the raceway was stimulated by using commercial software CFX based on Computational Fluid Dynamics, and the model is validated against the result of dissected blast furnace. Finally the flow filed of raceway was analyzed through this model.