Slab Quality Research Articles

Optimization of Oscillation Model for Slab Continuous Casting Mould Based on Mould Friction Measurements in Plant Trial

Lubrication and friction between the mould and strand are strongly influenced by mould oscillation, and play an important role in slab quality and operating safety during continuous casting processes. Investigation of mould oscillation is therefore essential for getting a better online control of the mould processes. A feasible approach for the development and optimization of mould oscillation was put forward, which combined online measurement of mould friction, design of negative oscillating parameters and evaluation for powder consumption. Three different control models including sinusoidal and non-sinusoidal oscillation for mould oscillations were developed to investigate and evaluate the effects of oscillation on mould friction and powder lubrication. For the purpose of investigating mould friction between mould and strand, online measurement was carried out on a slab continuous caster equipped with a hydraulic oscillator. Also the comparison of the mould friction in sinusoidal and non-sinusoidal mould oscillation was made for subsequent analysis. The industrial experiment result shows that the combination of inverse control model and non-sinusoidal oscillation mode will contribute to the proper powder consumption, leading to a suitable effect of friction force on strand surface, especially for high speed continuous casting. The proposed method provides reliable basis for guiding and optimizing mould oscillation among control models, sinusoidal oscillation and non-sinusoidal oscillation.

Effect of uneven solidification on the quality of continuous casting slab

Solidification during slab continuous casting is of importance to the quality of steel products. Non-uniform cooling often occurs during slab continuous casting, leading to uneven solidification rate at different locations, especially that along the slab width direction. Considering the realistic cooling intensity along all directions, the effect of uneven solidification on steel quality was discussed. Results indicated that, uneven solidification caused by non-uniform cooling would induce defects like shrinkage cavities, segregation and cracks. Due to the uneven solidification, long-narrow solidification ends would form. At the long-narrow solidification ends, high solid phase fraction inhibited the movement of liquid steel and the supplement of solidification shrinkage, leading to serious partial segregation and shrinkage cavities. The irregular solidification end went against the application of dynamic soft reduction technology as well. Furthermore, uneven solidification would lead to high temperature gradient and high thermal stress in the solidified shell, resulting in cracks in the slabs. Defects in the slab, especially the centre macro-segregation and centre shrinkage cavities, were reduced by optimising the spray nozzle arrangement of the continuous caster.

Stress and Deformation Analysis for Caster Segment Based on ANSYS<sup></sup>

The segment is an important part of the slab caster. the designing and manufacturing of segment directly impact the quality of slab. It is necessary to research and analysis the segment. This paper analyses stress and deformation of segment. Firstly, specify the characteristic of segment structure, legitimately simplify the structure, figure out the force of every bearing box. Secondly, develop the 3-D model with SolidWorks software, then import it into ANSYS software, with which we develop the FEM model. Lastly, analysis FEM stress and deformation of FEM model, so the maximum stress and deformation is obtained. The state of stress is safe, but the stiffness is kind of insufficient. It can be improved in the designing process.

Effect of Slab Quality on the Microstructure and Performance of Q345C Hot Rolling Strip Used for Pipe Pile Foundation

The Effect of slab quality on the microstructure and performance of Q345C hot rolling strip for pipe pile foundation were studied by SEM, EBSD, mechanical test and corrosion test. The results showed that the dendrite size of the slab had a great impact on the grain size of the steel. The fine grain structure can significantly improve the mechanical properties of the steel, but to some extent, reduce its corrosion resistance. In the early and later stage of the corrosion reaction, the coarse grain structure can improve the corrosion resistance. However, in the middle stage of the corrosion reaction, the grain size had no significant effect on the corrosion resistance. The rust layer included the inner layer and the outer layer, in which the inner layer was relatively compact, and they were mainly composed of the oxide of iron.

Problems concerning the surface quality of continuous-cast slabs

This article examines the main types of surface defects on slabs and their causes. A general explanation is given for the nucleation and growth of surface cracks. An analysis is made of the possibility of applying criteria from the fracture mechanics of deformable solids to the conditions that exist during the continuous casting of steel slabs.

Development and Application of CISDI Online Slab Quality Diagnosis & Analysis System

An online slab quality diagnosis & analysis system named CISDI_SQDS ONLINE R2011 has been presented in this paper. The system is based on mechanism of defects, which mainly refer to surface crack & internal crack, heat-transfer & solidification simulation, stress & strain calculation and metallurgical process analysis about continuous casting. Combining with BP neural network, several kinds of quality loss factors are used to describe the possibility of inducement. Meanwhile, the respective crack formation indexes are introduced to be the theoretical reference data for slab quality level evaluation and guiding production. The CISDI_SQDS ONLINE R2011 system was firstly applied on the No.1 Slab Continuous Caster of Bayi Steel in China. It is preliminary proved that the model is reliable and reasonable. It can be widely used as an important theoretical tool for prediction & control for slab quality in continuous casting process.

Effective technical solutions for the refining of steel from nonmetallic inclusions in continuous caster tundishes

The technical solutions proposed for modifying the internal structure of the tundishes in slab continuous casters and intended to increase the quality of slabs and sheet rolled products are subjected to pilot tests.

Industrial Application of the Packaged Soft-Reduction Technology for Slab Continuous Casting

Based on the conception of integration and optimization of process, mechanical, electric and hydraulic system, the advanced CISDI packaged soft-reduction technology for slab continuous casting with our full intellectual property rights has been developed successfully, which consists of the metallurgical process models with strong function and advanced arithmetic, the segment equipments with optimized structure and high strength, the basic automation program with full inspection and control function, the reliable stable hydraulic system and automatic system. It contains two control modules, viz., the static soft-reduction function & dynamic soft-reduction function, and three gap-adjustment modes, viz., the position-control mode, pressure-control mode & soft-clamping mode. From the opinions of equipment protection and production safety, some functional mechanism such as segment ordinal action, gap self-adapting adjustment, forced protection for breakout prediction, and etc., have been adopted. The whole system has been put into the industrial practice on the No.6 slab caster of Liusteel China, which has shown the smooth caster operation, the steady running of system, and the good metallurgical effects on improvement of internal quality of slab like center segregation and center porosity. The industrial application of CISDI soft-reduction technology has brought the rising of output proportion of high-class steel grades and the increasing of qualified rate for slab quality inspection, which has resulted in the distinct economic benefits for Liusteel group.

Three-Dimensional Numerical Simulation of Molten Steel Flow Behavior in Soft-Contact Electromagnetic Continuous Casting Mold

Using finite element method, the molten steel flow process in soft-contact electromagnetic continuous casting mold is simulated. The results show that the molten steel surface were affected by the electromagnetic force and shrink to the centre, near meniscus zone the flow velocity of steel increases and appears an obvious circumfluence, a large number of inclusion float and are absorbed by flux; on the other hand, the turbulent kinetic energy significant increases in circumfluence area, this exacerbates the reaction between flux and liquid steel, the initial size of the solidification organization are refined, and the surface quality of slab are enhanced.

Research on Solidification Heat Transfer Model of Copper Horizontal Continuous Casting

Study the horizontal continuous casting mold solidification heat transfer process is not only to optimize the structure of the mold so that it has a uniform stress field, to improve the quality of slab, to extend the mold life basis, and improve production efficiency and cost-effective method. Therefore, oxygen-free copper horizontal continuous casting process as the research object, the establishment of a level of TU1 billet continuous casting mold solidification heat transfer model for the simulation of oxygen-free copper horizontal continuous casting mold solidification and heat transfer process has laid a theoretical foundation.

Study on Grinding Technology of Granite Thin Slab

With the development of economical society and the stone industry, the product of granite thin slab becomes a trend, and gets the welcome of people. The grinding technology influences the quality of granite thin slab. This paper first introduced the situation of the grinding technology of granite thin slab, analyzed the mechanism of the grinding process of granite thin slab and fractured problem by observing the fractured granite thin slab. Then, based on the Hoek-Brown criterion, we researched the fracture criterion and the critical thickness of granite thin slab when grinding. Finally, we set up the fracture criterion of the granite thin slab and built the mathematical model between the thickness of the granite thin slab and grinding process parameters. According to the thickness of the granite thin slab, grinding process parameters can be formulated, in order to ensure the granite thin slab no fractured.

Control and Optimizing of Unstable State in Continuous Casting Process with Automatic System

Features and control methods in processes of unstable continuous casting of the 4th department of general steelmaking factory of WISCO were introduced, including ladle free-opening, tundish auto-casting, liquid level control and submerged nozzle’s quick replacing of mould, slag detection of ladle and so on. Countermeasures including updating facilities, improving accurate of controlling system, developing new technology were proved to be effective in practice, they can minimize the bad effect of the unsteady state to the producing stability and slab quality.

Optimization of Flow Control Devices in a Stainless Steel Tundish

Optimization of FCD design in a single strand slab tundish producing stainless steel is carried out by physical modelling using a 0.4 scale water model and mathematical modelling study. Reducing the residual metal volume at the end of casting, promoting the near-surface plug flow for inclusions removal and improving the transient slab quality are concerned, the optimized FCD is two dams and an impact pad, among them the dam1 (close to ladle shroud) with two 30 degrees upward inclined drain holes, another dam2 (close to tundish exit) is bottom rectangular-grooved which is beneficial for reducing the residual metal volume. Besides, the height of impact pad and drain holes must be concerned simultaneously, in the present study the height is 20mm and 60mm, respectively. Compared with turbulence inhibitors, impact pad will decrease the melt exposed to air at the steady state of casting. The holes at the higher level of dam may cause slag entrapment during the refilling process of ladle change operation.

Technology Research and Application of Dynamic Secondary Cooling of Continuous Casting

Secondary cooling is one of the important techniques of continuous casting. A mathematical model for heat transfer during solidification in continuous casting was established in researching on influence of the solidifying process on slab quality. The dynamic secondary cooling system has been analyzed with consideration of the principles, nozzles arrangement method and mathematical model of solidification process. The model was applied on some continuous casting machines. It indicates that the dynamic cooling model is better than conventional ones.

Technology Research and Application of Dynamic Secondary Cooling of Continuous Casting

Secondary cooling is one of the important techniques of continuous casting. A mathematical model for heat transfer during solidification in continuous casting was established in researching on influence of the solidifying process on slab quality. The dynamic secondary cooling system has been analyzed with consideration of the principles, nozzles arrangement method and mathematical model of solidification process. The model was applied on some continuous casting machines. It indicates that the dynamic cooling model is better than conventional ones.

Impact of Mould Powder Density on Surface Quality and Near-Surface Zone Microstructure of Cast Slab

Impact of Mould Powder Density on Surface Quality and Near-Surface Zone Microstructure of Cast Slab

DESENVOLVIMENTO DE FLUXANTE ISENTO DE FLÚOR APLICADO EM AÇOS BAIXO CARBONO

The mould flux is a mixture of non-metallic oxides that, in contact with liquid steel melts, becomes a liquid slag which the mainly function is to lubricate and control heat transfer between mould and strand during the continuous casting process. The mould flux without fluoride has the advantage of decreasing the wear of machine and the SEN in comparison to common mould flux. The application in Continuous Casting of Slabs has been a great challenge in relation to the operational viability together with internal and surface quality of slabs. Another differential is the decrease of environmental issues on account of the contamination of secondary cooling water by the fluorides. It is considered that properties of mould flux as chemical composition, viscosity, softening, melting flowing temperatures, fusion rate, etc, should be suitable to the chemical composition and the mechanical properties at elevated temperatures of steel and also the operational parameters such as casting temperature, casting speed, mould frequency, among others. This work presents a preliminary analysis in relation to operational viability, analysis of surface quality of slabs, measurements of fluorides content in the water of secondary cooling of machine. In addition to that, the analyses of operational features as measurements of wear of SEN, mould flux consumption, slag pool and behavior of thermocouples of detection system break outs (MSD) are considered

The Industrial Application of Dynamic Soft-Reduction Technology on the No.1 Slab Continuous Caster in No.2 Steelmaking Plant of Xinyu Steel

Through the one-month intense industrial test, the CISDI packaged soft-reduction technology of slab continuous casting has been put into practice to the No.1 slab caster of the No.2 steelmaking plant in Xinyu steel, China. The whole system has many advantages, such as the advanced algorithm and idea, the reasonable platform structure and the improved control function, which has been running stably and reliably. During the test process, a new calibrating method of roll gap has been adopted, which resulted in the perfect precision of gap control and the rational pressure feedback of hydraulic cylinder. By comparison of the macrographs of slab samples for the various steel grades, definitely, it can be concluded that, the application of the dynamic soft-reduction function will improve the internal quality of slab obviously, which has notable metallurgical effects on the center segregation defect of slab.

Quality Control of Casting Slab for 510L Steel

Slab quality affects the quality of hot rolled sheet significantly. There were serious transverse corner cracks on continuous casting slab of 510L steel plate in Panzhihua Steel before. Based on this, some effective countermeasures are put forward, such as the optimization of ratio of heat flux on narrow side and broad side of casting slab and mold powder, as well as the stabilization of casting speed and working condition of caster. With these countermeasures, transverse corner cracks on continuous casting slab have been significantly reduced, and the lines and peeling defects on hot rolled sheet reduce from 30% to 0.

Analysis of Distribution of Nonmetallic Inclusions in Aluminum DC-Cast Billets and Slabs

Inclusion distribution was studied in commercial aluminum DC-cast billets and slabs using a newly developed deep-etching method. Analyses revealed a nonuniform distribution of nonmetallic inclusions across billet diameters and lengths, and also across slab thicknesses and widths. In as-cast billets, more inclusions were found at the beginning and end of the billet length; more were present near the cross-section center than near the surface. In slabs, inclusions were located mostly within 13 mm of the surface and in a band between the centerline and the surface. Few inclusions were found 60 to 100 mm from the slab surface or at the centerline. In addition, comparing slab quality after casting using three types of ceramic foam filters (CFFs; i.e., 30 ppi, 50 ppi, and 50 ppi + HF) revealed significant differences in inclusion size, number, and distribution. Casting slabs using a finer pore-size filter (50 ppi) reduced the number of non-metallic inclusions greatly. The inclusion distribution patterns observed in the solidified slabs are discussed in terms of melt flow during casting.