Optimization of the Casting Length of Billets and Computation of Minimum Number of Steel Batches

This paper deals with the optimization of the casted billet’s lengths, in the context of diverse received orders. Linear programming is used in order to solve the optimization problem, such that minimum cost for the optimal lengths results. A technological constraint is that the number of resulted billets for each casted length must be an integer one. The authors also propose an algorithm for determining the number of batches of liquid steel needed to cover all pieces at optimal lengths for the diverse orders, and also the scheduling order of the casting process.

Thermal Parameters, Microstructure and Porosity During Transient Solidification of Ternary Al–Cu–Si Alloys

Solidification of ternary Al-Cu-Si alloys begins with the development of a complex dendritic network typified by primary (λ1) and secondary (λ2) dendrite arm spacings which depend on the chemical composition of the alloy and on the casting thermal parameters such as the growth rate and the cooling rate. These thermal parameters control the scale of dendritic arms, the size and distribution of porosity and intermetallic particles in the casting. In this paper, λ1and λ2were correlated with experimental thermal parameters i.e., the tip growth rate and the tip cooling rate. The porosity profile along the casting length has also been experimentally determined. The volumetric fraction of pores increase with the increase in alloying Si and with the increase in Fe concentration at the regions close to the casting cooled surface.

Microstructural Evolution during the Directional Transient Solidification of a Hypomonotectic Al-0.9wt%Pb Alloy

In the present study a hypomonotectic Al-0.9wt%Pb alloy was directionally solidified under transient heat flow conditions and the microstructure evolution was analyzed. The solidification thermal parameters such as the growth rate, the cooling rate and the temperature gradient were experimentally determined by cooling curves recorded by thermocouples positioned along the casting length. The monotectic structure was characterized by metallography and a microstructural transition was observed. From the casting cooled surface up to a certain position in the casting the microstructure was characterized by well-distributed Pb-rich droplets in the aluminum-rich matrix, followed by a mixture of fibers and strings of pearls from this point to the top of the casting. The interphase spacing (λ) and the diameter of Pb-rich particles were also measured along the casting length and experimental growth laws relating these microstructural features to the experimental thermal parameters are proposed.

Unsteady-State Directional Solidification of a Hypoperitectic Pb-9.5wt%Bi Alloy

Although considerable attention has been paid to studies on the unidirectional solidification of peritectic alloys, most of these investigations are carried out under steady-state solidification, where both the growth rate and the thermal gradient can be independently controlled and held constant in time. In this work, a hypoperitectic Pb-9.5wt%Bi alloy was directionally solidified under unsteady-state heat flow conditions and the microstructure evolution was analyzed. Continuous temperature measurements in the casting were monitored during solidification, using a data acquisition system and a bank of six type J thermocouples positioned along the casting length. Thermal parameters such as the growth rate (v) and the cooling rate () were experimentally determined by the experimental cooling curves. The solidification microstructure was characterized by a dendritic morphology along the entire casting length. The primary (l1) and secondary (l2) dendrite arm spacings were measured and experimental growth laws relating them to the solidification thermal parameters v and are proposed.

Cleaness of the First Pipeline Steel Slab along with Casting Direction

To improve the quality controlling of pipeline steel and to avoid mis-down grade, the cleaness including content of non-metallic inclusions, total oxygen and nitrogen of the first continuous casting slags of X70 pipeline steel were investigated. Results showed that, content of total oxygen, nitrogen, large non-metallic inclusions and inclusions areal density decrease with casting length increasing gradually. But at casting length of about 5.0 m which is just during the drastic changeing period of casting speed approaching to stead casting state, the content of large non-metallic inclusions and inclusions areal density increases abruptly induced by the entrapment of mold powders. Thus, to decrease the degradation rate of pipeline slab, the increasing rate of casting speed should be adjusted more evenly.

Study on Cleanliness of Ultra-Low Carbon Steel First Slab

By means of Oxygen and Nitrogen Analyzer, Metallographic Examination, SLIME, SEM, EDS, etc, the cleanliness of ultra-low carbon steel first slab produced by LD-RH-CC, and the comparative analysis with the cleanliness of normal slab is studied. The results show that T[O] and [N] are obviously decreasing with the increasing of casting length. The micro-inclusions and large-inclusions are generally decreasing with the increasing of casting length. The micro-inclusions of the first slab are mainly from deoxidization products and reoxidation of liquid steel. And the sources of large-sized inclusions mainly are reoxidation of liquid steel, slag entrapment in mould or tundish and stuffing sand. The cleanliness of ultra-low carbon steel first slab is closed to those normal slabs at the length of 3.5m.

Macrosegregation and Porosity during Directional Solidification of a Ternary Al-9wt%Si-3wt%Cu Alloy

Macrosegregation and porosity formation have been investigated by both a numerical model and by transient directional solidification experiments. The macrosegregation pattern, the theoretical and apparent densities are presented as a function of the casting length. X-ray fluorescence spectrometry was used to determine the macrosegregation profiles. The measurement of microporosity was performed using pyknometry analysis. The local composition along an Al-9wt%Si-3wt%Cu casting length was used as an input parameter for simulations of microporosity evolution. The results have demonstrated that the presence of Si in the alloy composition has inhibited the inverse copper segregation, which is a typical result of directionally solidified Al-Cu castings. The numerically simulated trend is in good conformity with the experimental scatter.

Influence of Process Papameters by Vibrational Cooling-Shearing Slope on Microstructures of Semi-Solid ZAlSi9Mg Alloy

An experimental vibrational cooling-shearing slope was developed to prepare the ZAlSi9Mg semi-solid alloy. The results show that the molten alloy is nucleated heterogeneously under shearing of the gravitation and vibration on the inclined cooling plate surface. Primary α-Al phase converts gradually from the cellular dendrite into tiny spherical or granular crystal. Under 600°C of pouring temperature, 600mm of casting length and 50Hz of vibration frequency, the semisolid alloy melt with good microstructure can obtained. In the alloy melt the average grain size of the original α-Al phase is 50μm, and its shape factor is 0.71. Mechanical vibration can refine obviously the microstructure of ZAlSi9Mg alloy. Along with increasing of vibration frequency, the original α-Al phases are refined obviously, their roundness is improved.

SEM Characterization of Al3Ni Intermetallics and its Influence on Mechanical Properties of Directionally Solidified Hypoeutectic Al-Ni Alloys

Rod-like Al3Ni intermetallic structures have been widely studied by Bridgman techniques of solidification. However, there is a lack of experiments conducted under unsteady-state solidification conditions. Such conditions are very close to the industrial reality since the thermal solidification variables (tip cooling rate, tip growth rate and thermal gradient) are freely changing as solidification progresses. In this research, Al3Ni structures found in hypoeutectic Al-Ni alloys were characterized under transient solidification conditions. Two Al-Ni alloys (1.0 and 5.0 wt%Ni) were directionally solidified. SEM (Scanning Electron Microscope) micrographs were obtained along the casting length (P). It was possible to observe with adequate magnifications the distribution of rod-like Al3Ni particles along the interdendritic regions. In order to emphasize the examination of morphology and distribution of such particles, the aluminum-rich matrix was dissolved by immersion of the sample in a fluoride acid solution (0.5%HF + 99.5% H2O). The effects of nickel content, dendritic arrangement and Al3Ni distribution on mechanical properties were investigated by tensile tests.