scholarly journals Initial Transfer Behavior and Solidification Structure Evolution in a Large Continuously Cast Bloom with a Combination of Nozzle Injection Mode and M-EMS

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1083
Author(s):  
Wang ◽  
Zhang ◽  
Tie ◽  
Qi ◽  
Lan ◽  
...  
Keyword(s):  
Single Port ◽  
Solidification Structure ◽  
Internal Quality ◽  
Equiaxed Crystal ◽  
Injection Mode ◽  
Solidification Interface ◽  
Nozzle Injection ◽  
Continuously Cast ◽  
Heat Transfer And Solidification

A three-dimensional numerical model combining electromagnetic field, fluid flow, heat transfer, and solidification has been established to study the effect of nozzle injection mode and mold electromagnetic stirring (M-EMS) on the internal quality of a continuously cast bloom. The model is validated by measured data of the magnetic flux density along the stirrer center line. According to the simulation and experimental results, M-EMS can introduce a horizontal swirling flow ahead of the solidification front, promoting the superheat dissipation of molten steel and columnar to equiaxed transition (CET). As the stirring current increases from 0 to 800 A, the superheat at the mold exit in the bloom center decreases by 1.9 K for the single-port nozzle case and 3.8 K for the five-port nozzle case. The resulting increase in the equiaxed crystal ratio is about 5.65% and 4.06%, respectively. In comparison, the injection mode shows a more significant influence on the heat transfer and solidification structure in the bloom under the present casting conditions. The superheat at the mold exit in the bloom center decreases by 5.1‒7.7 K as the injection mode changes from a single-port nozzle to a five-port nozzle, and the increase in the equiaxed crystal ratio ranges between 14.8% and 17%. It is found that the flow velocity of the molten steel in front of the solidification interface for the five-port nozzle is higher than that for the single-port nozzle regardless of the M-EMS power. The washing effect here reinforces both the heat exchange through the solidification interface and the dendrite re-melting or fragmenting, stimulating the formation of an equiaxed crystal at the bloom center. In addition, it is observed that both the central shrinkage and carbon segregation have decreased with the five-port nozzle plus M-EMS. This suggests that the combined application of a five-port nozzle and M-EMS can effectively improve the internal quality of large bloom castings.

scholarly journals The Significance of Central Segregation of Continuously Cast Billet on Banded Microstructure and Mechanical Properties of Section Steel

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 76 ◽  
Author(s):  
Fujian Guo ◽  
Xuelin Wang ◽  
Jingliang Wang ◽  
R. D. K. Misra ◽  
Chengjia Shang
Keyword(s):  
Low Temperature ◽  
Solidification Structure ◽  
Cast Billet ◽  
Equiaxed Crystal ◽  
Secondary Cooling ◽  
Elongation Ratio ◽  
Columnar Crystal ◽  
Central Segregation ◽  
Continuously Cast ◽  
Low Temperature Toughness

The solidification structure and segregation of continuously cast billets produced by different continuous casting processes are investigated to elucidate their effect on segregated bands in hot-rolled section steel. It suggested that segregated spots are mainly observed in the equiaxed crystal zone of a billet. The solidification structure is directly related to superheating and the intensities of secondary cooling. To a certain extent, the ratio of the columnar crystal increases with the increase of superheating and secondary cooling. Moreover, the number of spot segregations decreases with the decrease of the equiaxed crystal ratio. After hot rolling, the segregation spots are deformed to form segregated bands in steels. The severe segregation of Mn in segregated bands corresponds with that in the segregation spots. The elongation ratio and low temperature toughness deteriorate significantly by a high fraction of degenerate pearlite caused by central segregation. With a decrease of central segregation, the total elongation is increased by 10% and the ductile–brittle transition temperature (DBTT) is also reduced from −10 to −40 °C. According to the experimental results, columnar crystal in billets is preferred to effectively reduce the degree of central segregation and further improve low temperature toughness and the elongation ratio.

scholarly journals Comparison of Transverse Uniform and Non-Uniform Secondary Cooling Strategies on Heat Transfer and Solidification Structure of Continuous-Casting Billet

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 543 ◽  
Author(s):  
Yanshen Han ◽  
Xingyu Wang ◽  
Jiangshan Zhang ◽  
Fanzheng Zeng ◽  
Jun Chen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Continuous Casting ◽  
Surface Temperature ◽  
Water Flux ◽  
Solidification Structure ◽  
Equiaxed Crystal ◽  
Secondary Cooling ◽  
Cooling Strategy ◽  
Crystal Density ◽  
Heat Transfer And Solidification

Water flux distribution largely influences the heat transfer and solidification of continuously-cast steel billets. In this paper, a secondary cooling strategy of transverse non-uniform water flux (i.e., higher flux density on billet center), was established and compared with the uniform cooling strategy using mathematical modeling. Specifically, a heat transfer model and a cellular automaton finite element coupling model were established to simulate the continuous casting of C80D steel billet. The water flux was measured using different nozzle configurations to assist the modeling. The mathematical results were validated by comparing the surface temperature and the solidification structure. It is shown that the non-uniform cooling strategy enables the increase of corner temperature and reduction in surface temperature difference, while a higher reheating rate is found on the surface center of the billet. Moreover, the non-uniform cooling strategy can enhance the cooling effect and refine the solidification structure. Accordingly, the liquid pool length is shortened, and the equiaxed crystal density is increased along with the decreased equiaxed crystal ratio. The uniform cooling strategy contributes to reducing internal cracks of billet, and the non-uniform one is beneficial for surface quality and central segregation. For C80D steel, the non-uniform cooling strategy outperforms the uniform one.

Thermal and Dynamics Analysis of Meniscus-Controlled Materials Processing

2005 ◽  
Author(s):  
B. Yang ◽  
L. L. Zheng
Keyword(s):  
Heat Transfer ◽  
Growth Conditions ◽  
Materials Processing ◽  
Flow And Heat Transfer ◽  
Solidification Interface ◽  
Silicon Tube ◽  
Stable Growth ◽  
Operating Window ◽  
Heat Transfer And Solidification

Fundamental physical processes involved in meniscus-controlled materials processing include meniscus formation and dynamics, movement of solidification interface, and the interaction at the crystal-liquid-vapor tri-junction. Final product shape that can be grown by different techniques depends on the meniscus shape, heat transfer and solidification interface. The fluid flow and heat transfer in the melt and dynamics of meniscus are critical for determining the stable growth conditions for better quality of the grown crystals. In this paper, a theoretical thermal and dynamic model have been developed to describe the heat transfer and dynamics of meniscus and its interaction with solidification. A simplified form of the model will also be developed to allow the investigation of ribbon (or tube) growth that exhibits one-dimensional feature in the most regions. This model will be used to conduct parametric study, and the important process and geometry conditions will be investigated such as the crystal dimension, die-top height, pull rate, and die-top temperature. The dynamic response of meniscus to the potential perturbations during growth such as pull rate and die-top temperature variations, and misalignment between the die and silicon tube will be investigated extensively. From this study, an operating window for stable meniscus will be obtained, and growth procedure that leads to improving the grown crystal quality will be identified.

scholarly journals Influence of Operating Conditions on Internal Quality of Large Cross Section Continuously Cast Blooms

1981 ◽  
Vol 67 (8) ◽  
pp. 1269-1277 ◽  
Author(s):  
Yoshiharu IIDA ◽  
Masayuki ONISHI ◽  
Tetsuo UEDA ◽  
Shinobu OKANO ◽  
Yutaka SHINSHO
Keyword(s):  
Cross Section ◽  
Operating Conditions ◽  
Internal Quality ◽  
Large Cross Section ◽  
Continuously Cast

Star Cracks in Continuously Cast Deep-Drawing Tin Steel Slab

2014 ◽  
Vol 782 ◽  
pp. 235-238
Author(s):  
Jaroslav Duška ◽  
Gabriel Grimplini ◽  
Marek Molnár ◽  
Lucia Hrabčáková ◽  
Atila Drotár
Keyword(s):  
Deep Drawing ◽  
Small Radius ◽  
Internal Quality ◽  
Cast Slab ◽  
Steel Slab ◽  
Continuous Slab ◽  
Slab Casting ◽  
Continuously Cast ◽  
Gradual Expansion

The final quality of flat products is directly related to surface and internal quality of continuously cast slabs. This aspect is very important especially in case of IF and deep-drawing tin grades, in which even the smallest defects can cause problem in the final processing of the material, especially during forming by stamping, when the material fails. This work is devoted to the analysis of the surface defect of star crack type. The presence of defect was visually detected after scarfing process during removal of surface layer on the small radius side of the slab. This type of defect occurs particularly in cases, when steel is contaminated by copper in the process of continuous slab casting. In view of the copper melting point (1083°C) and the surface temperature of the cast slab shell at the mold exit (about 1200°C) in the process of steel cooling at continuous casting, Cu penetrates along the boundaries of primary austenitic grain, or separate particles are precipitated at the grain boundaries. Initial cracks are formed in the area of primary cooling in the mold. Thermal and mechanical stresses acting in the surface area of slab shell when the slab passes thorough the rollers of secondary cooling cause gradual expansion of crack defects along boundaries of grains contaminated by copper.

Influence of technology parameters of free-cutting steel continuous casting on the billet internal structure

2020 ◽  
Vol 76 (2) ◽  
pp. 139-142
Author(s):  
A. T. Kunakbaeva ◽  
A. M. Stolyarov ◽  
M. V. Potapova
Keyword(s):  
Regression Analysis ◽  
Continuous Casting ◽  
Internal Structure ◽  
Sulfur Content ◽  
Manganese Content ◽  
High Quality ◽  
Correlation And Regression Analysis ◽  
Cutting Steel ◽  
Continuously Cast

Free-cutting steel gains specific working properties thanks to the high content of sulfur and phosphorus. These elements, especially sulfur, have a rather high tendency to segregation. Therefore, segregation defects in free-cutting steel continuously cast billets can be significantly developed. The aim of the work was to study the influence of the chemical composition of freecutting steel and casting technological parameters on the quality of the macrostructure of continuously cast billets. A metallographic assessment of the internal structure of cast metal made of free-cutting steel and data processing by application of correlation and regression analysis were the research methods. The array of production data of 43 heats of free-cutting steel of grade A12 was studied. Steel casting on a five-strand radial type continuous casting machine was carried out by various methods of metal pouring from tundish into the molds. Metal of 19 heats was poured with an open stream, and 24 heats – by a closed stream through submerged nozzles with a vertical hole. High-quality billets had a cross-sectional size of 150×150 mm. The macrostructure of high-quality square billets made of free-cutting steel of A12 grade is characterized by the presence of central porosity, axial segregation and peripheral point contamination, the degree of development of which was in the range from 1.5 to 2.0 points, segregation cracks and strips – about 1.0 points. In the course of casting with an open stream, almost all of these defects are more developed comparing with the casting by a closed stream. As a result of correlation and regression analysis, linear dependences of the development degree of segregation cracks and strips both axial and angular on the sulfur content in steel and on the ratio of manganese content to sulfur content were established. The degree of these defects development increases with growing of sulfur content in steel of A12 grade. These defects had especially strong development when sulfur content in steel was of more than 0.10%. To improve the quality of cast metal, it is necessary to have the ratio of the manganese content to the sulfur content in the metal more than eight.

Nondestructive Quality Evaluation of Tomatoes

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 544c-544
Author(s):  
A. Hakim ◽  
A. Purvis ◽  
E. Pehu ◽  
I. Voipio ◽  
E. Kaukovirta
Keyword(s):  
Quality Evaluation ◽  
Tomato Fruit ◽  
Quality Attributes ◽  
Internal Quality ◽  
Attractive Alternative ◽  
Fluorescence Techniques ◽  
Nondestructive Quality ◽  
Alternative Techniques ◽  
Evaluation Techniques

Both external and internal quality of fruits such as tomatoes can be evaluated by different methods, but all most all of the methods are destructive. For this reason, there is a need to reassess some of the alternative techniques. Nondestructive quality evaluation is an attractive alternative. The principles of different nondestructive quality evaluation techniques such as optical, physical, and fluorescence techniques applied to tomato fruit is explained. Successful application of these techniques that could be used for evaluation of different quality attributes are illustrated. The advantages of nondestructive quality evaluation techniques are that they are very fast, easy, labor- and time-intensive, and inexpensive. These techniques could also be useful to evaluate the quality of other vegetables.

scholarly journals Quantitative Correlation and Control Strategy for Element Content Fluctuation along Casting Direction in Central Area of Continuous Casting Billet

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 452
Author(s):  
Dongwei Guo ◽  
Zibing Hou ◽  
Zhiqiang Peng ◽  
Qian Liu ◽  
Jianghai Cao
Keyword(s):  
Control Strategy ◽  
Central Area ◽  
Solidification Structure ◽  
Equiaxed Crystal ◽  
Correlation Relationship ◽  
Zone Formation ◽  
Zone Width ◽  
Quantitative Correlation ◽  
Central Segregation ◽  
And Control

The statistical correlation was applied to analyze the specific and quantitative correlation relationship between the solidification structure and central segregation along the casting direction in carbon steel billet. On this basis, the segregation formation mechanism of the solute element and related control strategy were investigated. It is found that the equiaxed crystal zone fluctuation along the casting direction determines the fluctuation degree of central segregation. At the same time, the central segregation at a certain position is mostly affected by the equiaxed crystal zone width at the hysteretic position. Moreover, the casting speed can influence the columnar to equiaxed transition (CET) fluctuation along the casting direction by affecting the flow of molten steel in the billet. Overall, the segregation mechanism of solute elements along the casting direction can be summarized into two aspects: First, with the growth of columnar crystals in the initial stage, the segregated solutes are continuously enriched and distributed in the equiaxed crystal zone after CET. The fluctuation of the equiaxed crystal zone will affect the distribution of the enriched solute in the billet and cause the fluctuation of the central segregation. Second, due to the solidification shrinkage at the end of solidification, the solute-enriched liquid phase at the hysteretic position is pumped to the solidification endpoint and forms the central V-shaped segregation. Meanwhile, the stable solidification structure (columnar crystal length or equiaxed crystal zone width) along the casting direction and control measures preceded equiaxed crystal zone formation are beneficial to reduce the central V-shaped segregation.

scholarly journals Internal Quality Evolution of Open-Source Software Systems

2021 ◽  
Vol 11 (12) ◽  
pp. 5690
Author(s):  
Mamdouh Alenezi
Keyword(s):  
Open Source ◽  
Open Source Software ◽  
Software Evolution ◽  
Quality Metrics ◽  
Internal Quality ◽  
Software Systems ◽  
Software Metric ◽  
Significant Difference ◽  
The Relationship

The evolution of software is necessary for the success of software systems. Studying the evolution of software and understanding it is a vocal topic of study in software engineering. One of the primary concepts of software evolution is that the internal quality of a software system declines when it evolves. In this paper, the method of evolution of the internal quality of object-oriented open-source software systems has been examined by applying a software metric approach. More specifically, we analyze how software systems evolve over versions regarding size and the relationship between size and different internal quality metrics. The results and observations of this research include: (i) there is a significant difference between different systems concerning the LOC variable (ii) there is a significant correlation between all pairwise comparisons of internal quality metrics, and (iii) the effect of complexity and inheritance on the LOC was positive and significant, while the effect of Coupling and Cohesion was not significant.

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