Slag Line Research Articles

NDE weld defect detection and feature extraction using segmentation approach

In this paper, comparative study of morphological edge detection and region growing segmentation technique is introduced to detect and assess the flaws from the radiographic images. In the proposed method, segmentation algorithms are applied to detect the different types of flaws and calculate the necessary features such as major axis length, minor axis length, area, and perimeter. Computing time is optimised and algorithm is simpler to implement. These methodologies are compared and concluded to be effective for all possible nine types of weld flaws detection (slag inclusion, worm hole, porosity incomplete penetration, under cuts, cracks, lack of fusion, and weaving fault slag line). The experimental results show that our proposed method gives good performance for non-destructive evaluation (NDE) of radiographic images.

Properties of ZrO<sub>2</sub>-C Materials with Anti-Oxidants

Submerged Entry nozzle is one of the key functional refractories for continuous casting and the safe and efficiency of the continuous casting is directly influenced by the properties of ZrO2-C materials located at the slag line of the submerged entry nozzle. In general, a little anti-oxidants such as SiC, Si or B4C will be introudced into ZrO2-C materials and anti-oxidants also influence the corrosion resistance of ZrO2-C materials. So this paper researched the properties especially the corrosion resistance of ZrO2-C materials with SiC, Si or B4C additions. The results show that the properties of ZrO2-C materials are relate to the composition of ZrO2-C materials and the corrosion resistance of ZrO2-C materials have no obvious relationship with other properties such as apparent porosity, bulk density, et al. The addition of anti-oxidants will all decrease the corrosion resistance of ZrO2-C material. The decreasing degree of corrosion resistance by Si is the most and the decreasing degree of corrosion resistance by SiC is the least. The corrosion resistance of ZrO2-C material with B4C addition is relate to the kind of the mold slag. To obtain the ZrO2-C material with excellent corrosion resistance antioxidants should not be added into ZrO2-C materials.

Acidic and basic binders for magnesite based aggregate in plaster of tundish

Binders are generally inorganic, organic or organomineral and have an important influence on the performance and corrosion resistance of slag line and deskulling. Since silicate and phosphate binders have some side effects, in this work sulphate binders such as sulphamic acid, H 2NSO 3H; aluminum sulphate, Al 2(SO 4) 3; ammonium sulphate, (NH 4) 2SO 4; magnesium sulphate, MgSO 4; calcium sulphate, CaSO 4; sodium sulphate, Na 2SO 4; and potassium sulphate, K 2SO 4, are investigated. Cold crushing strength at different heat treatments of room temperature, 110 °C, 1100 °C, 1400 °C is measured. Apparent porosity of samples without pulp and bulk density together with pH of the binder solution is evaluated and XRD and SEM studies are performed. Among these sulphate binders MgSO 4 was found to be the best. It is acidic in nature and develops strong bonds to the basic aggregate, MgO, at low temperatures. At high temperatures it dissociates from MgO(s) and SO 3(g) and the remained portion of MgO is the same as host oxide, with no corrosion and easy deskulling. Basic binders such as calcium sulphate, sodium sulphate and potassium sulphate could not strongly bond the MgO aggregates.

Identificação e avaliação dos mecanismos de ataque da escória SiO2-CaO-Al2O3-MgO em tijolos refratários de MgO-C

O presente trabalho tem como objetivo identificar e caracterizar mecanismos responsáveis pelo desgaste dos tijolos refratários de magnésia-carbono de uma panela de aciaria, devido ao ataque da escória SiO2-CaO-Al2O3-MgO. Para tanto, tijolos refratários MgO-C utilizados na linha de escória de uma panela industrial foram comparados com tijolos após o uso (post mortem). A microestrutura da região interfacial escória / refratário foi avaliada por análises mineralógicas (difração de raios X), microscopia eletrônica de varredura e microscopia óptica (lâminas petrográficas). Foi possível constatar que o tijolo post mortem apresenta, além das fases já existentes in natura, novas fases como a alumina, o silicato de cálcio e a gelenita devido à sua reação com a escória. Os resultados sugerem que o principal meio de degradação do tijolo se estabeleça pela infiltração da escória na matriz entre os grãos do tijolo refratário. Isto ocasiona o arrancamento de grãos, comprometendo a microestrutura original do material refratário, diminuindo seu tempo de vida útil.

Heat Transfer in Steelmaking Ladle

The heat transfer in a steelmaking ladle was studied. The evaluation of heat transfer of the steel was performed by measuring steel temperature in points including all refining steel process. In the ladle, the temperatures in the refractories and the shell were also measured. To evaluate the thermal profile between the hot and cold faces of the ladle in the slag line position, an experiment which shows the importance of thermal contact resistance was carried out. Higher heat losses in the tapping and the vacuum were verified. The temperature measurements of the ladle indicate distinct thermal profiles in each stage of steel refining. Moreover, as each stage of the process depends on the previous one, the complexity of the ladle thermal control is incremental. So a complete model of heat losses in the ladle is complex.

Effect of spinel content on slag attack resistance of high alumina refractory castables

High alumina refractory castables based on the Al 2O 3-MgO-CaO diagram ternary system were prepared using tabular alumina, white electrofused corundum, calcined alumina, synthetic spinel, dead-burned magnesia, dolomite, and calcium aluminate cement as starting raw materials. Two kinds of slags with 9.02 and 4.14 CaO/SiO 2 ratios were studied for slag resistance by means of crucible tests. The corrosion thickness increases with increase in magnesia content in all the designed compositions. The slag penetration decreases with increases in spinel content. Taking into account these results a refractory castable composition for its positioning into a steelmaking ladle was chosen. Microstructural studies by SEM of samples taken from the slag line and wall in a steelmaking ladle were carried out. The correct amount of spinel required for practical applications was determined by the Al 2O 3-MgO-CaO-SiO 2 diagram quaternary system. A detailed model of the attack mechanisms is proposed.

Recent improvements in Arcelor steel ladles through optimization of refractory materials, steel shell and service conditions

Capacity of the ladles is in way to be increased in several steelplants for flat carbon steel products (Dunkirk, Florange). The new steel ladles have been designed, taking into account several key points: the stiffness and the service temperature of the steel shell, which is controlled by the geometry of shell reinforcements and by the efficiency of the thermal insulation layer; the stiffness of the lip-rings, which can be greatly improved by using steel plates protected by refractory concrete; the wear of the slag line in MgO-C bricks, which can limit the ladle campaign if vacuum tank degassing process is used for ULC steels production. Slag control is required. Numerous trials are also in way to limit the wear of the bottom impact zone of the steel ladle, including pre-shaped alumina-spinel cast bottom, in Arcelor Dunkirk.

SLAG LINE DISSOLUTION OF MgO REFRACTORY

Abstract The high temperature dip technique has been used to investigate the corrosion of MgO refractory in SiO2-CaO-FeOx-MgO slag and Al2O3-SiO2-CaO-FeOx-MgO slag at 1530 °C. In both systems, significant slag line corrosion was observed and this corresponded to increasing MgO in the slag. There was significant evidence that a solid spinel phase had attached to the surface of the sample in the case of slag containing 20 wt% alumina. This type of corrosion is due to surface tension induced flow patterns at the refractory slag interface and a semi-empirical model of that phenomenon described the observed progression of corrosion with time for direct dissolution well. However, the model did not work well when indirect dissolution occurred.On a utilise la technique de trempe a haute temperature pour etudier la corrosion du refractaire MgO dans un laitier de SiO2-CaO-FeOx-MgO et dans un laitier de Al2O3-SiO2-CaO-FeOx- MgO a 1530 °C. Dans les deux systemes, on a observe une corrosion importante a la ligne de ni...

Ladle glaze: major source of oxide inclusions during ladle treatment of steel

Samples of ladle lining covered by glaze were taken from industrial ladles of different ages at Uddeholm Tooling AB, Hagfors, Sweden. It was found in the samples taken at and below the slag line that a slag infiltrated layer was covered by an outer layer containing many MgO 'islands' of various sizes. The microstructure of the infiltrating slag was the same as the matrix of the outer layer. The slag was found to decompose into the compound 3CaO.Al2O3 and a liquid phase during the cooling process. The former phase along with tiny MgO particles from the ladle glaze was found to be one of the major sources of inclusions during the degassing and flotation periods of ladle treatment. Thermodynamic analysis indicated that the reaction between the ladle glaze and the slag from the electric arc furnace resulted in the formation of MgO–Al2O3 spinel and an oxide solution, which were also the main inclusions found at the initial stages of ladle treatment. Evidence of this reaction was found in the lining samples taken above the slag line.

From viscosity and surface tension to marangoni flow in melts

This article covers some of our recent work on slag viscosity, the surface tension of liquid Cu-O alloys, and the relative role of Marangoni and bulk flow on refractory wear in iron-silicate slags. A viscosity model developed for slags containing SiO2, Al2O3, Fe2O3, CaO, MgO, MnO, FeO, PbO, NiO, Cu2O, ZnO, CoO, and TiO2 is capable of representing the effects of temperature, silica, and network-modifier cations within a wide range of temperatures and compositions. It forms a useful part of a computational package for multiphase-equilibrium (MPE) calculations and for predicting slag viscosities. The models are well applicable to a range of industrial slags (blast furnace, new iron making, base-metal and Platinum Group Metals (PGM) smelting, and coal-ash slags). The package has also some capability of predicting the viscosity of slags containing suspended solids. The surface tension of liquid copper-oxygen alloys has also been analyzed. The adsorption behavior of oxygen in liquid copper is well represented by the combined Langmuir-Gibbs isotherm. According to the rate data for silica-rod dissolution in liquid iron-silicate slags at 1573 K, the preferential attack at the slag line diminishes as the linear velocity of flow at the surface of the rotating silica rod reaches 9 to 16 cm/s. A tentative analysis gives the critical condition, that relates the critical Reynolds (Re) and Marangoni (Ma) number by the equation Re*2=0.13 Ma*.

Effect of Marangoni‐induced flow on the rate of refractory dissolution in molten slags

Dissolution rate of silica rods in iron‐saturated silicate slags containing 15–30% SiO2 was measured using the rotating cylinder technique at 1300°C, under a controlled atmosphere of deoxidized Ar‐gas. These measurements were aimed at quantifying the magnitude of Marangoni‐induced flow near the slag–refractory region. The Marangoni effect was found to be significant under stagnant conditions, but gradually became dominated by bulk flow when the linear velocity of the flowing melt was increased, and reached values in the range of 0.09–0.16 m/s. This implies that, in highly agitated vessels, the Marangoni effect is unlikely to play a dominant role in refractory wear at the slag line. Also, the silica dissolution rate and mass transfer coefficient were examined, and it was found that with increasing silica content of the slag, the dissolution rate and mass transfer coefficient decreased. Furthermore, the relationship between Marangoni number and Reynolds number was calculated, and boundary flow conditions determined using the experimental critical velocity.

Chemical wearing mechanism of refractory materials in a steel ladle slag line

Wearing of the ladle slag line is the biggest refractory material problem with ladles. The purpose of this work was to study the wearing mechanism of refractory materials in a steel ladle slag line. The studied refractory materials were MgO–C bricks, doloma brick, corundum castable and spinel castable. Rotating‐furnace and sessile‐drop tests were conducted with converter and ladle slags. The corrosion index, infiltration zone and refractory/slag mineralogical reactions were studied. The wear mechanisms of refractory materials were studied using SEM, XRF and XRD analysing techniques. The driving force behind chemical wearing is the chemical potential differences of the components between lining and slag. In general, the main principles of chemical wearing depend on the structure and mineralogical character of the refractory material.

Ladle service under the conditions of vacuum-oxygen decarburization

The Izhstal plant has created a technology for treating corrosion-resistant steel by the method of VOD in a 30-ton ladle. The lining of the ladle is made of periclase-chromite refractories produced by the Magnezit Works JSC. The effect of the process parameters and lining patterns on the endurance of the ladle was studied in development of the process. The main factors determining the wear of the functional layer of the lining are the density of its joints, the composition of the slag of the refining period, the intensity of the mixing, and the thermal regime of the ladle between the heats. The pattern of the lining has been improved by reinforcing the slag line. The mixing regimes and the composition of the killing mixture have been improved where the consumption of lime and the proportion of aluminum to silicon are concerned. These measures have increased the endurance of the ladles by a factor of 2.2 and that of the refractory roofs by a factor of 2.5.

Effect of argon blow through a monoblock stopper in continuous casting of steel on the service of the stopper and nonmetallic inclusions in the cast steel

Kinetic equations of the dependence of the wear of corundum-graphite monoblock stoppers in the slag line and the head on the temperature of the steel in the intermediate ladle in continuous casting are derived as a result of a full-scale experiment. The equations make it possible to calculate the casting time at any possible temperature of casting with the use of corundum-graphite monoblock stoppers of a standard composition (TU 14-8-371-81). In addition to increasing substantially the number of casting cycles in a batch, argon blow through monoblock stoppers with porous inserts improves the quality parameters of cast steel ShKh-15 with respect to segregation bands, globules, central porosity, carbide segregation, content of sulfides and oxides, and subshrinkage segregation.

Use of unfired periclase-carbon refractories in parts of linings of 350-ton steel-teeming ladles

Workers of the Azovstal’Company have established the causes of the decrease in the endurance of slag-line areas of linings of 350-ton steel-teeming ladles. In 1995–1996 they conducted industrial tests and introduced a process for lining the slag areas of 350-ton teeming ladles with unfired periclase-carbon refractories. The mean service life of a lining of a 350-ton teeming ladle with a slag line made of periclase-carbon refractories amounts to 23 heats on the average without hot repairs of the slag line during the campaign. The wear of the periclase-carbon lining in the slag line is 3.6–4.3 mm per heat. The specific consumption of refractories and materials for a lining has been decreased by 0.6–0.8 kg per ton of converter steel. Such an operating capacity for the periclase-carbon refractories in slag lines is provided by the composition and structure of the refractories, which possess a high heat resistance and resist the effect of the molten metal and slag.

Interaction of CaO–FeO–SiO2 Slags with Partially Stabilized Zirconia

Calcia‐ and magnesia‐partially‐stabilized zirconia samples were corroded under static and dynamic conditions in three slags from the CaO–FeO–SiO2 system. Low–basicity and high–FeO slags corroded tht samples by leaching magnesia from the cubic phase in the specimen, causing its destabilization and ultimate dissolution. However, a higher–basicity slag which proved the most corrosive of the three promoted bulk dissolution of the cubic phase instead, the rate of which was controlled by the thickness of the adjacent slag boundary layer. The levels of sample corrosion both at and below the slag line are used to illustrate the effects of experimental variables, including slag composition, specimen density, and slag motion.

銅製錬スラグの高温酸化による改質

Slags produced from iron and steel making industry or non-ferrous smelting plants are now considered one of the important domestic resources in various fields. Although the most copper smelting slags have been used in cement plant as a component of iron oxide in clinker, the market is not big enough to consume the amount of slag available, and furthermore, advanced usage of slag with higher value will be expected.In this study, the copper slags are oxidized in air at 1, 000°C for 1-20 hours. After oxidation the X-ray diffraction pattern, infra-red absorption spectra, and EPMA images showed an existence of iron oxide (Fe203, Fe2O4), CaO-Al2O3-Si02 system, and discrete Si02 in different phases. The dissolution test with HCl, H2SO4 and NaOH solution was carried out for Fe and SiO2 in the samples. The results indicate that the oxidized slags exhibit high resistance against the dissolution of both Fe and SiO2. According to the Seger cone test, the oxidized slags were stable at higher temperature than that for non-oxidized slags. As a result of slag lining tests on a steel plate, the strong anchoring effect was observed at the interface probably due to the reaction between iron plate and Fe ions in slag. The alkali-aggregate reaction of slags in concrete was examined by the ASTM chemical method, resulting in finding all spots inside the safe range of figure.

The use of doors with a hardened slag lining

The use of doors with a hardened slag lining