Study on the nanocarbon containing Al2O3 – C continuous casting refractories with reduced fixed carbon content

Self Cite

The functional refractories used in steel casting operations are usually made up of alumina‐carbon compositions having graphite as the major source of carbon. In recent times, to reduce the carbon content and to enhance the performance by designing microstructure at nano‐sized level, several nano carbon sources and organic binders are introduced to traditional carbon‐based refractories. The homogenous distribution of nano carbon sources within the refractory composition is important to get the advantages of its use. In the present work, nanocarbon black is used along with graphite in the alumina‐carbon system. Three different mixing procedures are followed and how mixing effects the physical and mechanical properties is evaluated. The mixing order with proper nanocarbon distribution throughout the batch composition provided significant improvement in the properties. The microstructural analysis and in situ phase developments in the samples at different temperatures are also studied.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of mixing on the properties of nanocarbon containing Al₂O₃‐C continuous casting refractories

Pilli

Sarkar

2019

Self Cite

“…Therefore, increasing the strength of Al 2 O 3 -C refractories has always been the focus of numerous investigations. [12][13][14][15][16][17] Recent researches demonstrated that the ceramic reinforcement phases of carbon containing refractories play a major role in the enhancement of mechanical properties. [18][19][20][21][22] One of the best-known methods to increase the strength of the matrix of Al 2 O 3 -C refractories is the in situ formation of SiC whiskers by adding metallic Si powder.…”

Section: Introductionmentioning

confidence: 99%

Enhanced mechanical properties of lightweight Al₂O₃‐C refractories reinforced by combined one‐dimensional ceramic phases

Chen

Yan

Schafföner

et al. 2021

We prepared a new lightweight Al2O3‐C refractory material with a higher strength by using microporous corundum aggregates instead of dense tabular corundum aggregates, which was reinforced by in situ formed SiC whiskers, multi‐walled carbon nanotubes (MWCNTs), and mullite rods. A comparative study of the microstructure, mechanical properties, and fracture behavior was carried out for dense and lightweight Al2O3‐C refractories coked at 1200°C and 1400°C, respectively. By using the microporous corundum aggregates, a better aggregate/matrix interface bonding and an optimized distribution of SiC whiskers were obtained. The SiC whiskers formed inside the microporous corundum aggregates and simultaneously in the matrix by a vapor‐solid reaction mechanism, resulting in an enhancement at the microporous aggregate/matrix interface. Furthermore, the in situ formed MWCNTs and well‐developed mullite rods at 1200°C in the matrix also contributed to the better interface structure. Thus, due to the improved microporous aggregate/matrix interface, the crack propagation along the aggregate/matrix interface was suppressed, resulting in an increased crack propagation within the aggregates. Consequently, the synergy between microporous corundum aggregates and combined one‐dimensional ceramic phases caused a lower bulk density but a markedly higher strength, a higher fracture energy, and a higher toughness of lightweight Al2O3‐C refractories compared to the dense ones. Overall, our study allows to overcome the traditional concept that a higher strength of refractories is reached by a higher density.

“…5 Despite the above advantages, a major drawback regarding the use of Al 2 O 3 -C refractories is the carbon pick-up in the steel flow during casting. The application of nano carbons in the form of nano-carbon black (CB), multiple-wall carbon nanotubes (MWCNTs), carbon nanofibers (CNFs), etc, has increasingly attracted attention because of its great potential in developing low carbon containing refractories with enhanced properties, 8,9 but the poor dispersion and the high cost limit its further applications in industrial scale. Therefore, it is of great importance to develop low carbon containing Al 2 O 3 -C refractories, especially when the steel industry moves toward clean steel technology and low carbon economy.…”

Section: Introductionmentioning

confidence: 99%

“…7 However, the decrease in carbon content usually leads to a dramatic reduction of the resistance to both thermal shock and slag corrosion. The application of nano carbons in the form of nano-carbon black (CB), multiple-wall carbon nanotubes (MWCNTs), carbon nanofibers (CNFs), etc, has increasingly attracted attention because of its great potential in developing low carbon containing refractories with enhanced properties, 8,9 but the poor dispersion and the high cost limit its further applications in industrial scale. 10 The in situ formation of nano carbon fibers and/or nano ceramic whiskers was found to have similar advantages as those obtained by the direct incorporation of nanoscale additives.…”

Section: Introductionmentioning

confidence: 99%

Microstructure, properties, and application of low carbon Al₂O₃‐C refractories used as submerged entry nozzles

Bao

Bao³

et al. 2019

With the aim to achieve the application of low carbon Al2O3‐C refractory as submerged entry nozzle (SEN) materials, a comprehensive study on the microstructure, thermo‐mechanical properties, as well as application performance during use in the continuous casting was carried out by comparing with the traditional one. Both hot and cold modulus of ruptures of the low carbon Al2O3‐C refractory were superior to the traditional one, and its thermal shock resistance still kept in an acceptable level. The increase in the amount of SiC whiskers and the enhancement in the sintering are considered as the strengthening mechanism. In the industrial trial, the rapid loss of graphite caused by the large level fluctuation made the traditional Al2O3‐C refractory more susceptible to flux corrosion. For the low carbon Al2O3‐C refractory, however, the dense structure and the adhesion of viscous slag layer suppressed the slag penetration. Besides, the remaining SiC phases were also difficult to be wetted and dissolved by the flux. As a consequence, a better corrosion resistance was obtained, achieving a decrease of 27.6% in the average depth of the corrosion groove after working for 8 hous.