Elimination or Minimization of Oscillation Marks: A Path To Improved Cast Surface Quality

Oscillation marks are the most recognizable feature of continuous casting and can be related to the subsurface defects that can be found on product rolled from continuous cast slabs. The purpose of this work was to develop strategies that can be used on industrial continuous casters to reduce oscillation mark depth and, in particular, to minimize the formation of hook type defects that are prevalent on ultra low carbon grades. The major focus of the work was on developing a technique to allow heat transfer in the meniscus region of the continuous caster to be measured and the effect of mold slag chemistry and chrystallization to be documented. A new experimental technique was developed that allowed the effect of mold flux chemistry and chrystallization on the radiation heat transfer rate to be measured dynamically

HEART UK Consensus Statement on Lipoprotein(a) - a call to action

Lipoprotein(a), Lp(a), is a modified atherogenic low-density lipoprotein particle that contains apolipoprotein(a). Its levels are highly heritable and variable in the population. This consensus statement by HEART UK is based on the evidence that Lp(a) is an independent cardiovascular disease (CVD) risk factor, provides recommendations for its measurement in clinical practice and reviews current and emerging therapeutic strategies to reduce CVD risk. Ten statements summarise the most salient points for practitioners and patients with high Lp(a). HEART UK recommends that Lp(a) is measured in adults as follows: 1)those with a personal or family history of premature atherosclerotic CVD; 2)those with first-degree relatives who have Lp(a)levels > 200nmol/l; 3) patients with familial hypercholesterolemia; 4) patients with calcific aortic valve stenosis and 5) those with borderline (but<15%) 10 year risk of a cardiovascular event. The management of patients with raised Lp(a) levels should include: 1) reducing overall atherosclerotic risk; 2)controlling dyslipidemia with a desirable nonHDL-cholesterol level of <100mg/d (2.5mmol/l) and 3) consideration of lipoprotein apheresis

HEART UK statement on the management of homozygous familial hypercholesterolaemia in the United Kingdom

This consensus statement addresses the current three main modalities of treatment of homozygous familial hypercholesterolaemia (HoFH): pharmacotherapy, lipoprotein (Lp) apheresis and liver transplantation. HoFH may cause very premature atheromatous arterial disease and death, despite treatment with Lp apheresis combined with statin, ezetimibe and bile acid sequestrants. Two new classes of drug, effective in lowering cholesterol in HoFH, are now licensed in the United Kingdom. Lomitapide is restricted to use in HoFH but, may cause fatty liver and is very expensive. PCSK9 inhibitors are quite effective in receptor defective HoFH, are safe and are less expensive. Lower treatment targets for lipid lowering in HoFH, in line with those for the general FH population, have been proposed to improve cardiovascular outcomes. HEART UK presents a strategy combining Lp apheresis with pharmacological treatment to achieve these targets in the United Kingdom (UK). Improved provision of Lp apheresis by use of existing infrastructure for extracorporeal treatments such as renal dialysis is promoted. The clinical management of adults and children with HoFH including advice on pregnancy and contraception are addressed. A premise of the HEART UK strategy is that the risk of early use of drug treatments beyond their licensed age restriction may be balanced against risks of liver transplantation or ineffective treatment in severely affected patients. This may be of interest beyond the UK

Quantifying the Thermal Behavior of Slags (TRP 9903)

Successful operation of a continuous caster is based upon control of heat transfer in the mold. The mold slag is a key component in the success of continuous casting; however, the phenomena that occur in the gap between the shell and the mold are largely unknown as until recently there have been no techniques that allowed visualization and quantification of the solidification behavior of liquid slags. This has lead to slag design being an empirical science or art. Recently a new experimental technique, called Double Hot Thermocouple Technique (DHTT), was developed at Carnegie Mellon University that allowed the solidification behavior of a slag to be observed and quantified under conditions that simulate the thermal conditions that occur in steelmaking environments. This technique allows ladle, tundish and mold slags to be characterized under extreme conditions including those found between the mold wall and the growing shell of a continuous caster. Thus, a program is initiated, under this grant, to quantify and describe the phenomena that occur during the solidification of a slag in a steel mill environment. This will allow slag design to become an engineering science rather than an empirical exercise. The project deliverables were as follows: (1) The further development of a tool that will have broad use in the quantification of slag melting and solidification behavior; and (2) The development of a set of meaningful design criteria for slag application in steel mill environments. The project was broken down into a number of objectives: (a) Develop a systematic understanding of the effect of cooling rate on slag solidification; (b) Develop a systematic understanding on the effect of slag chemistry changes on slag solidification behavior; (c) Develop a method to characterize slag melting; (d) Develop an understanding of the role of the environment on slag solidification and melting; (e) Develop the ability to understand slag solidification under the conditions that occur in a continuous caster; (f) Develop an ability to predict the solidification behavior of slags; and (g) Develop the criteria for optimization of slags in steelmaking environments where they are under thermal gradients

An Investigation of the Crystallization of a Continuous Casting Mold Slag Using the Single Hot Thermocouple Technique

The conditions under which crystallization develops in a mold slag must be understood in order to select or design a mold flux for use in the continuous casting of steels. In this paper, the crystallization of an industrial mold slag was quantified using a single hot thermocouple technique which, when combined with a video camera based observation system, allowed observation of the onset and growth of the crystals which were precipitated from the melt. The beginning of crystallization was determined by direct observation and the growth rate of crystals were measured by frame by frame image analysis of recordings of the progress of crystallization. Isothermal experiments were performed at different temperatures and a Time-Temperature-Transformation (TTT) diagram was determined for this industrial mold slag. X-ray diffraction of quenched samples was used to determine the type of crystalline phases that were precipitated. The TTT diagram was divided into two separate regions which corresponded to the precipitation of dicalcium silicate (Ca2SiO4) at temperatures over 1050°C and of Cuspidine (Ca4Si2O7F2) at temperatures below 1050°C. The evolution crystal fraction was described by Avrami's equation. This work indicates that industrial mold slags are easily undercooled, that crystallization occurs throughout the melt, that crystals grow initially as equiaxed dendrites and that the onset of crystallization is a function of cooling rate and must be described by either TTT or CCT curves

Development of Double and Single Hot Thermocouple Technique for in Situ Observation and Measurement of Mold Slag Crystallization

To overcome the limitations of differential thermal analysis (DTA) and direct casting experimentation in the measurement and understanding of the solidification phenomena of mold slags, the double and single hot thermocouple techniques (DHTT and SHTT) for the direct observation and measurement of mold slag crystallization were developed. These methods enable the solidification and melting process of transparent slags to be observed "in situ" under conditions where the temperature or temperature gradient can be measured and controlled. The SHTT allows a sample to be subjected to rapid cooling rates or to be held under isothermal conditions. The DHTT allows large temperature gradients to be developed between the two thermocouples and allows a simulation of the transient conditions which can occur in the infiltrated slag film that occurs between the mold and the solidifying shell in the mold of a continuous caster. By these techniques both isothermal and non-isothermal phenomena can be studied. A number of mold slags are optically transparent or translucent at steelmaking temperatures while the crystalline phase which precipitates upon cooling is opaque and can be clearly observed using optical microscopy. Thus the SHTT and DHTT are connected to an image capturing and analysis system that allows the onset and growth of the opaque crystals which precipitate from the slags to be documented. The development and application of these techniques to mold slag crystallization will be discussed in this paper

Clean Steel: Advancing the State of the Art (TRP 0003)

This project had 3 objectives: (1) to determine the kinetic factors governing inclusion removal from liquid steels at a slag metal interface; (2) to develop a methodology to enable steels of less than 1 ppm total oxygen to be produced with an average inclusion diameter of less than 5 {micro}m; and, (3) to determine the slag-metal interface conditions necessary for ultra clean steels. In objectives 1, and 3, the major finding was that dissolution rates of solid particles in slags were found to be significant in both ladle and tundish slags and must be included in a model to predict steel cleanliness. The work towards objective 2 indicated that liquid steel temperature was a very significant factor in our understanding of clean steel potential and that undercooled steels equilibrated with low oxygen potential inert gases have the potential to be significantly cleaner than current steels. Other work indicated that solidification front velocity could be used to push particles to produce clean steels and that reoxidation must be severely curtailed to allow the potential for clean steels to be realized

Inclusion Optimization for Next Generation Steel Products

The project objective is to determine the conditions under which the inclusions in liquid steel can act as heterogeneous nucleants for solidification. The experimental approach consisted of measuring the undercooling of a pure iron droplet in contact with different oxides to determine which oxides promote iron solidification by providing a suitable surface for nucleation and which oxides and under which conditions the metal can be deeply undercooled. The conclusions suggest that deep undercoolings are possible at low oxygen content provided the oxygen potential is such that substrate decomposition does not occur. If the oxygen content increases the undercooling decreases