This article extensively reviews published research on inclusions in ingot steel and defects on ingot products, methods to measure and detect inclusions in steel, the causes of exogenous inclusions, and the transport and entrapment of inclusions during fluid flow, segregation, and solidification of steel cast in ingot molds. Exogenous inclusions in ingots originate mainly from reoxidation of the molten steel, slag entrapment, and lining erosion, which are detailed in this article. The measures to prevent the formation of exogenous inclusions and improve their removal are provided, which are very useful for the clean steel production of ingot industries.

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State of the art in the control of inclusions during steel ingot casting

A fully coupled fluid flow, heat, and solute transport model was developed to analyze turbulent flow, solidification, and evolution of macrosegregation in a continuous billet caster. Transport equations of total mass, momentum, energy, and species for a binary iron-carbon alloy system were solved using a continuum model, wherein the equations are valid for the solid, liquid, and mushy zones in the casting. A modified version of the low-Reynolds numberk-e model was adopted to incorporate turbulence effects on transport processes in the system. A control-volume-based finite-difference procedure was employed to solve the conservation equations associated with appropriate boundary conditions. Because of high nonlinearity in the system of equations, a number of techniques were used to accelerate the convergence process. The effects of the parameters such as casting speed, steel grade, nozzle configuration on flow pattern, solidification profile, and carbon segregation were investigated. From the computed flow pattern, the trajectory of inclusion particles, as well as the density distribution of the particles, was calculated. Some of the computed results were compared with available experimental measurements, and reasonable agreements were obtained.

Coupled turbulent flow, heat, and solute transport in continuous casting processes

A therapy system for managing a psychiatric disorder of the patient may be controlled based on a patient mood state. Therapy may be delivered to a patient according to a therapy program, and a physiological parameter of the patient may be monitored during or after therapy delivery. The patient mood state may be determined based on the monitored physiological parameter, and the therapy delivery may be controlled based on the determined mood state. In some embodiments, the therapy delivery is stopped prior to determining the patient mood state and the therapy delivery is restarted upon detecting a negative mood state. In other embodiments, therapy delivery is delivered until a positive mood state is detected, at which point the therapy delivery may be stopped.

Psychiatric disorder therapy control

A characteristic of a washout period following the delivery of therapy to a patient according to a therapy program may be determined based on a physiological parameter of the patient. A washout period includes the period of time during which a carryover effect from the therapy delivery dissipates. Monitoring a washout period may be useful for timing the delivery of therapy according to different therapy programs during a therapy evaluation period. For example, at least one physiological signal of the patient may be monitored to automatically determine when a washout period has ended, e.g., when stimulation and carryover effects of therapy delivery according to a first therapy program have substantially dissipated, in order to determine when therapy delivery according to a second therapy program can be initiated.

Timing therapy evaluation trials

Simulation of the continuous casting process by a mathematical model

A mathematical representation has been developed for the filling of cylindrical molds, using a bottom pouring arrangement. In the model allowance has been made for thermal natural convection, solidification and for the presence of the free surface. Turbulence was represented by assigning artificially enhanced parametric values to the viscosity and the thermal conductivity. The results have shown that the temperature profiles are markedly non-uniform, and that solidification would commence quite soon after the pouring process has been initiated. For the conditions considered, the free surface disturbances were not very great, although quite high free surface velocities were predicted by the model.

The Modeling of Fluid Flow and Heat Transfer in Mold Filling

Disclosed is a method of producing maraging steel, which includes producing a consumable electrode for vacuum remelting; and subjecting the consumable electrode to the vacuum remelting. The consumable electrode contains not less 5 ppm Mg. Disclosed is also a maraging steel containing, by mass %, at least, from more than zero to less than 10 ppm Mg, less than 10 ppm oxygen, and less than 15 ppm nitrogen. The steel contains also nitride inclusions having a maximum length of not more than 15 μm and oxide inclusions having a maximum length of not more than 20 μm. Regarding the oxide inclusions, a content rate of spinel form inclusions having a length of not less than 10 μm to a total content of the spinel form inclusions having a length of not less than 10 μm and alumina inclusions having a length of not less than 10 μm exceeds 0.33 (i.e. 33%).

Maraging steel and method of producing the same

A method for producing a steel ingot, which comprises an Mg oxide forming step of preparing a molten steel containing Mg in an amount sufficient for the molten steel to have an oxide composition having MgO as a primary component and a dissociation step of keeping the pressure of the atmosphere around the molten steel to be lower than that in said Mg oxide forming step, to thereby dissociate MgO to Mg and oxygen and reduce the content of Mg in the steel to 50 % or less of that in the Mg oxide forming step through the diffusion thereof into a gas phase; and a preferred method further comprising a solidifying step, which comprises an Mg oxide forming step of preparing a first molten steel containing Mg in an amount sufficient for the molten steel to have an oxide composition having MgO as a primary component, a step of solidifying the molten steel, and a dissociation step of melting the resultant solid again under a pressure of an atmosphere lower than that in the case of the first molten steel, to thereby dissociate MgO to Mg and oxygen and reduce the content of Mg in the steel to 50 % or less of that in the above solid before re-melting through the diffusion thereof into a gas phase.

Method for producing steel ingot

PROBLEM TO BE SOLVED: To provide a method for efficiently and economically producing maraging steel not inferior to maraging steel produced by the conventional method even if scrap made of maraging steel is used as a melting raw material. SOLUTION: In the method for producing maraging steel using a scrap material, a melting raw material of maraging steel in which a part or the whole is composed of a scrap material is melted by an arc type electric furnace in an oxidizing atmosphere, so as to be molten steel, the molten steel is received by a vacuum treatment device, vacuum refining is performed in the vacuum treatment device, also, componential regulation is performed in the process of the vacuum refining, before the vacuum refining or after the vacuum refining, and the same is made into a maraging steel ingot having a nitrogen content of ≤25 ppm. Preferably, the vacuum treatment device is a vacuum induction heating furnace, and more preferably, oxidative refining is performed after the raw material is melted by the arc type electric furnace, so as to be the molten steel. COPYRIGHT: (C)2006,JPO&NCIPI

A method for producing maraging steel

PROBLEM TO BE SOLVED: To provide a method for producing a maraging steel with which Al 2 O 3 inclusion quantity remaining in the maraging steel obtained by performing a vacuum-remelting can be reduced, and the maraging steel with the Al 2 O 3 inclusion reduced. SOLUTION: In the method for producing the maraging steel performing the vacuum-remelting by producing a consumable electrode for vacuum-remelting and using this consumable electrode, the above consumable electrode contains ≥ 5 ppm Mg. This maraging steel contains at least 33% spinel type inclusion of ≥ 10 μm size to the total of the spinel type inclusion of ≥ 10 μm size and the Al 2 O 3 inclusion of ≥ 10 μm size. COPYRIGHT: (C)2004,JPO&NCIPI

Setsuo Mishima

Papers

The Modeling of Fluid Flow and Heat Transfer in Mold Filling

Maraging steel and method of producing the same

Method for producing steel ingot

A method for producing maraging steel

Method for producing maraging steel and maraging steel