Difficulties associated with measurement of the surface temperature of the workpiece during the rolling process made direct measurement of the heat transfer coefficients at these locations almost impossible. Indirect method of measurement which involves use of radiation pyrometers has been adopted generally (Kim and Huh, 2000; Polukhin, 1975). The disadvantage of this technique of temperature measurement was that the other modes of cooling were not monitored. Consequently, the accuracy of the results so obtained depends largely on the effectiveness of the radiation mechanism, and the surface heat flux of the material becomes a direct function of the radiation mechanism. Harding (1976) argued that this is misleading since convection was a more important heat transfer mechanism than was generally thought. Polukhin (1975) and Hills (Obinabo, 1991) also considered a combined effect of convection and radiation mechanisms and related it to the surface heat flux of the workpiece. Meanwhile, in their classical experiments on heat flow in continuous casting of steel ingots, Savage and Pritchard (Hills, 1963) obtained a relationship that expresses the surface flux as a function of time. This was done by measuring the rise in the temperature of the cooling water. The data so generated was used to estimate the total quantity of heat removed from the surface of the cooling steel ingot. The expression obtained from the heat flux was of the form
Abstract— Casting of steel is an operation which is sensitive to a number of factors. It should be performed with great control and steadiness in such a way to produce safe casting operation and sound steel mechanical properties, and ensure a continuous process with limited delays. In this study, effects of factors encountered in the process of continuous casting of steel billets on the thickness of solidified steel layer in the mould area were mathematically modeled in order to identify the most predominant ones. Of these factors modeled are mould thickness, mould material thermal conductivity and molten steel superheat. Simplified calculation were performed in which heat transfer equations governing the process solidification were solved using an explicit method of finite difference technique. The results showed that the most effective factor on solidified steel thickness in the mould is the magnitude of molten steel superheat prior to entering the mould. Thermal conductivity of mould material showed little effect due to the small thickness of mould wall. Changing mould thickness showed some effect of solidification but were not significant . Index Terms — solidification, heat transfer, finite difference, explicit method, superheat .
An anchor-shaped geometrical design for a Submerged Entry Nozzle for the slab con- tinuous casting of steel is presented in this work. To evaluate its performance, transient 3D multiphase numerical simulations were carried out using the Computational Fluid Dynamics technique. The performance of the proposed nozzle is numerically com- pared with that of a conventional cylindrical nozzle. Computer results show that the chance of formation of Karman’s vortexes and powder entrapment becomes small for the anchor-shaped SEN.
Fig. 3 shows the variation of the dendrite growth direction from slab surface towards the slab center for sample - A solidified under a constant casting speed. It can be seen that near the surface, all primary dendrites (shown as white dotted lines) are oriented in the same downward direction. A small distance away from the slab surface, the primary dendrites undergo a change in growth direction from downwards to upwards. Some primary dendrites are seen to follow their original downward growth direction, while other dendrites are seen to have an upwards growth direction. Further away, it can be seen that all primary dendrites are oriented in the upward direction, which is exactly opposite in close proximity to the surface. Thus, it seems that the observed change in the dendrite growth direction might be due to a change in the fluid flow direction ahead of the moving front. Generally, a portion of the liquid steel after exiting from the submerged entry nozzle with relatively high flow velocity directly hits the narrow face mold walls  . After striking the mold walls, a portion of the liquid steel may travel upwards towards the
A time-dependent law for the secondary dendrite arm coarsening behaviour has to be known, for the current example being a simple cube-root time law consistent with standard expectation  and ﬁtted to experimental data for the grades and casting machines in question. The same law is then used in the calculation throughout the cast section, with the amount of coarsening and inclusion growth therefore limited by the local solidiﬁcation time as calculated by the macro/micro model.
Finally, the material part in Equation (1) reveals mold dwell time “t” and casting speed “v” in nominator and dominator of Equation (1), respectively, for non-dimen- sional mathematical requirements. Also, different mate- rials formula of exponent creep material m appeared in both the nominator and dominator of Equation (1) repre- sented the effect of different types of steels on MTMR. Wherever, Morozenskii et al.  have reported that steel containing 0.17% C to 0.2% C has a minimum strain to fracture compared to the steels with higher or lower carbon levels where the creep properties varies with car- bon content of different types of steel alloys. This affects the solidification and shell formation and therefore, af- fects resistance of thermo-mechanical stresses [22,23]. Equation (1) shows also the effect of thermal linear ex- pansion coefficient “β” revealed in its dominator where it was concluded that the shape and width of the air gap which has a large responsibility about the mold heat flow depends mainly on β and local temperature distribution [23,24]. Therefore, the value of β affects directly the re- sistance of thermo-mechanical stresses where the in- creasing in β may decrease MTMR.
Our approach to process parameter optimization in con- tinuous casting of steel involves a numerical simulator of the casting process and various stochastic optimization techniques among which evolutionary algorithms play the key role. The initial version of the optimization system  was designed to search for process parameter values that would result in as high as possible quality of contin- uously cast steel. Based on empirical metallurgical crite- ria, it was able to deliver improved parameter settings that proved beneficial in practice. However, using a simple evo- lutionary algorithm, it spent thousands of process simula- tions to find high-quality solutions. As the time aspect is critical, the purpose of further exploration [9, 7] was to re- duce the number of needed process simulations. These ap- plied studies were all using the weighted-sum technique of aggregating multiple criteria into a scalar cost function. As opposed to that, in a recent work  an attempt was made to handle multiple criteria by means of evolutionary mul- tiobjective optimization. Based on the initial findings, this paper refines the problem definition by introducing an addi- tional technological constraint, justifies the algorithm set- tings by checking the algorithm performance metrics and analyzes the new numerical results.
We present an empirical study of process parameter tuning in industrial continuous casting of steel where the goal is to assure the highest possible quality of the cast steel through proper parameter setting. The process is assumed to be under steady-state conditions and the considered optimization task is to set 18 coolant flows in the caster secondary cooling zone to achieve the target surface temperatures along the slab. A numerical model of the casting process was employed to first investigate the properties of the parameter search space, and then iteratively improve parameter settings. For this purpose, two stochastic optimization algorithms were used: a steady-state evolutionary algorithm and next-descent local optimization. The results indicate the difficulty of the optimization task arises not from a complicated fitness landscape but rather from high dimensionality of the problem.
In the High Pressure Die Casting (HPDC) process, liquid aluminum alloy is injected to a die cavity within temperature range 670–710 o C on a high speed, around 30–100 m/s and injection pressure around 50–80 MPa [7,8]. This condition might cause erosion and die soldering. Erosion that formed on dies is the early stage of die soldering. where the erosion depends on the firmness and the hardness of die material [9,10]. Hardening is applied to the die surface to resist erosion, and tempering is applied to keep the hardness high in die casting temperature . H13 tool steel is usually used as die- casting and generally gets a double tempering until it reaches 48-50 HRC .
The methoding design was revisited and found that the gases could not escape from the sample casting cavity since the samples were horizontally straight away connected to the pouring cup. Revised methoding was done in such a way to accommodate the samples in normal to the pouring cup plane so as to vent out the gases fully while the sample cavity was getting filled which is shown in the revised Methoding sketch2 (Fig.8). Then the samples were recast and RT was done. All the samples were qualified in RT.
Various strength tests are conducted on concrete having seven different types of mix proportions for 7 days and 28 days. The graphs obtained from the results clearly indicate that the addition of 1.5% of steel fiber in crumb rubber concrete significantly increases the overall strength than the concrete with other mix proportions. It is concluded that the addition of 1.5% steel fiber addition to the crumb rubber concrete is an optimum choice compared to the other percentages considered.
steel, but the product value is not very high. On the other hand, fewer nodes have a higher product of Mn and S than the equilibrium product in low P steel, but the product value is very high compared to those in high P steel. As shown in Fig. 8, high P steel has a wider temperature range from liquidus temperature to solidus temperature than that of low P steel. Since S is an element with a high diﬀusion coeﬃcient, there is more time for S to conduct back solid diﬀusion in high P steel, which decreases the segregation degree of S in the last solidiﬁed zones as shown in Fig. 9. Since the solidus temperature is quite diﬀerent, it may be reasonable if we assume that the undercooling for MnS precipitation is 50 K and 70 K for low and high P steel respectively. Then the S that precipitated as MnS is 0.00413% and 0.00243%, respectively for low and high P steels. Therefore, high P decreases not only the precipitation temperature of MnS but also the precipitation amount of MnS during liquid/solid transformation. In addition, the higher the precipitation temperature, the quicker the growth rate for sulﬁdes, and the more sulﬁde precipitating at high temperature, the higher the tendency to allure sulﬁde precipitating from the matrix at low temperature. Thus, the retarding eﬀect of P on sulﬁde precipitation during solidiﬁcation may have some active eﬀects on small sulﬁde precipitation at low temperature. 3.3.2 Eﬀect of phosphorus on sulﬁde precipitation
In this paper, a systematic analysis of the failure performance of the slab after continuous hot rolling is carried out. The results show that the microstructure of Q345D steel plate is F + P, individual Class A inclusions exceeding standard, specifications for 15-25um. The results show that elongation of unqualified specimens is common in inclusions exceeding the standard or banded tissue level. The phenomenon of stratification is common in cold fracture test specimen. The inclusions are predominantly Class A sulfides and Class C silicates. By comparing the rolling temperature and other parameters, it is found that the dendritic segregation is the main factor affecting the performance when the ribbon and billet are cast.
composite oxides when the ladle enters into working position; there is also a small amount of MnS wrapped around the oxide. Such inclusions mainly come from alloying deoxidation products and the top slag modifier, where they will affect the slagging function in the early stage of refining. The size range of the inclusions is relatively small, the maximum size not exceeding 25 μm and the smallest one only being about 5 μm. The welding performance, corrosion resistance, and fatigue resistance of the material will be seriously destroyed by such complex inclusions existing in the steel. However, the generation of such inclusions can be effectively reduced by the composition’s adjustment of refining slag .
The project of “Investigation to improve the secondary steel manufacturing process by adopting mathematical models“ was considered to contribute to the Strategic Steel Research in Sudan. The project was suggested as a close collaboration between Depart of mechanical engineering- University of Karrary and the steel factories in Sudan. Steel cleanliness, which is aim of this project, is a focal point for Sudan young steel industry in order to maintain and strengthen their in-market and global competitiveness. The steady velocity and temperature fields were obtained by computationally solving,the Reynolds-Averaged Navier-Strokes (RANS) equations together with the energy equation, using the standard k-ε model of turbulence. These flow fields were then used to predict the inclusion removal by numerically solving the inclusion transport equation. For the mixing time characteristics transient solution was performed. The calculations were carried out using the commercial Computational Fluid Dynamics (CFD) software ANSYS-FLUENT 6.3.26.
Total materials requirement (TMR) for the recycling of elements and materials (Urban Ore TMR) from end-of-life electric home appliances (cathode ray tube TV, liquid crystal display TV, refrigerator, washing machine, air conditioner and microwave oven) have been estimated and evaluated. The estimation were carried out using scenario analyses, in which the number of recycled elements and/or materials was changed considering additional energy for advanced recycling. As the results of the estimation, the urban ore TMR of gold, silver, copper and stainless steel were lower than TMR when they are smelted from natural ore (natural ore TMR) for all the scenarios. The urban ore TMR for iron (steel), aluminum and die-casting aluminum were mainly aﬀected by the dilution ratio using pure element for the recycling. The recyclability of the elements and materials are discussed from the view point of TMR. [doi:10.2320/matertrans.MAW200908]
Direct near net shape casting is an attractive process for the production of sheet metal because of its economical proﬁt and the production of a new microstructure due to the fast solidiﬁcation rate. To explore further advantages of direct near net shape casting, the diﬀerences in the mechanical properties between the as-cast and annealed strips of a steel with comparatively high contents of the impurities (Cu, P and S) were investigated in this paper with an emphasis on the microstructural eﬀects. This process not only produced ﬁne microstructures but also resulted in nano-scale copper sulﬁdes. The as-cast strip has higher yield and tensile strengths and maintains high work hardening ability at higher stress levels than that of the annealed strip. Both the as-cast and annealed strips have a superior balance of strength and work hardening ability compared to the strips without the impurities. The nano-scale copper sulﬁde particles in the as-cast strip contributed most to the increase in the yield strength. The as-cast strip also could not produce the good work hardening ability without the nano-size particles. Further improvements in strength and work hardening ability can be attained by controlling the particles’ size and the volume fraction in the strip.