CaO pellets with different porosity were carbonated at 700℃ in CO2 atmosphere. The carbonation rate was controlled by the diffusion of CO2, regardless of the difference in porosities. For the low-porosity pellet, carbonation reaction only occurred on the surface, with a denseCaCO3 film thus formed, which combined well with the substrate material; while for the pellet of high-porosity, the carbonation reaction occurred simultaneously both on surface and inside pores, and each CaO grain was surrounded by CaCO3 film that contained microfissures. Hydration test results showed that carbonation treatment could effectively improve the hydration resistance of CaO materials regardless of porosity, but the carbonated high-porosity pellet was prone to breakage due to poor combination between the carbonated CaO grains. Therefore, for the purpose to improve the hydration resistance by carbonation treatment, it is recommended that the CaO materials should be either with less appreciable apparent porosity or with a limited carbonation ratio for the high-porosity CaO material.

MgO–CaO refractories added with different sized ZrO2 powders were sintered at 1600℃, the effect of the ZrO2 powders on performance of MgO–CaO refractories was investigated. The results showed that the densification of the MgO–CaO refractories was appreciably promoted when a small amount of ZrO2 was added owing to the formation of small size CaZrO3 facilitated to sintering, and the densification was promoted further with increasing the amount of ZrO2 due to the volume expansion caused by the reaction of the added ZrO2 and CaO to form CaZrO3 in the refractories, and the addition of nano-sized ZrO2 was more effective. The thermal shock resistance of the MgO–CaO refractories was improved by modification of the microstructure due to the formed CaZrO3 particles that predominately located on the grain boundaries and triple points in the whole microstructure, and the addition of nano-sized ZrO2 was more effective attributed to its well dispersion and the critical addition amount was effectively decreased to 6%. The slaking resistance of the MgO–CaO refractories was appreciably improved by addition of ZrO2 due to its effect on decreasing the amount of free CaO in the refractories, promotion of densification as well as modification of microstructure, the nano-sized ZrO2 addition was more effective due to its higher activity. The slag corrosion resistance of the MgO–CaO refractories was enhanced by addition of ZrO2 due to the increase of the viscosity of the liquid phase and thus inhibited further penetration of slag at elevated temperatures.

The mixing behaviour in a 150t ladle furnace induced by two-nozzle jetting was investigated on the basis of a water model simulation of 1: 4. The effects of nozzle arrangements, including separation angle, radial position and asymmetry as well as tracer adding position, on the mixing time were studied. The most favourable mixing was achieved when the two nozzles were symmetrically arranged at half radii in the ladle, with 45

The effect of SiC used as antioxidant in carbon-containing CaO–ZrO2 refractories and the behaviour of SiC in CO gas were studied. SiC was found to react initially with CO to form SiO2(s) and C(s) at 1200℃, and then the formed SiO2 reacted with CaO in the refractories to form belite (2CaO·SiO2). The refractory microstructure was modified by addition of SiC. Due to the deposition of SiO2 in the large (2–10 μm) pores of the refractory through the reaction of SiO(g) with CO, the percentage of large pores decreased and a dense layer, mainly consisting of belite, was formed near the surface of the refractory after it was heated at high temperature (1500℃). The oxidation resistance of CaO–ZrO2–C refractories was improved by reaction of SiC with CO to deposit C(s) and decrease the size of the large pores. The oxidation resistance of such refractories can be improved significantly when such a dense layer is formed near their surfaces.

An alumina–magnesia precast block was prepared by using high-alumina fused corundum as aggregate, and fused magnesia, ultra-fine Al2O3 and SiO2 powders as matrix materials. A small linear expansion for the precast block was achieved through spinel formation from the reaction of MgO with Al2O3 in the matrix. The precast block showed a lower apparent porosity, higher modulus of rupture and better slag corrosion resistance compared to the traditional Al2O3–MgO–C brick. In addition, the practical application of the precast block to the ladle lining proved it to possess a better thermal insulation which could effectively prevent the temperature drop of molten steel during the refining process. It can be considered that the alumina–magnesia precast block could possibly be applied as a new type of ladle lining material for the production of low-carbon and ultra-low-carbon steel.

A carbon free precast block was prepared by using high-alumina fused corundum as aggregate, and fused magnesia and ultra-fine Al2O3 and SiO2 powders as matrix materials. A small linear expansion for the precast block was achieved through spinel formation from the reaction of MgO with Al2O3. The precast block showed a lower apparent porosity, higher hot modulus of rupture and better slag corrosion resistance compared to the traditional Al2O3-MgO- C brick. Moreover, the practical application of the precast block to the ladle lining proved it to possess a better thermal insulation which could effectively prevent the temperature drop of molten steel during the refining process. It can be assumed that the carbon free precast block could possibly be accepted as a new type of ladle lining material for the production of low-carbon and ultra-low–carbon steel.

CaO aggregate was sintered from reagent-grade lightweight CaCO3 powder by the addition of 0–20% (molar ratio) MgO and ZrO2, respectively. The results showed that the CaO derived from lightweight CaCO3 was highly sinterable and compact CaO aggregate with relative density above 96% was obtained after sintering at 1400 °C for 2 h, but further increase of compactness was restrained due to the occurrence of abnormal grain growth. The densification of the aggregate was promoted due to the behavior of oxide addition on restraining the grain growth of CaO. With increasing the amount of oxide addition, the microstructure of CaO aggregate underwent a restructuration process. Homogeneous microstructure, with well growing MgO grains occupying most of the boundary triple points of CaO grain, formed by the addition of 20% MgO. Especially when 20% ZrO2 was added, CaZrO3 layer formed around CaO grains. The slaking resistance of the aggregate was appreciably improved due to the promotion of densification, the formation of CaO solid solution (while MgO added) and the modification of microstructure.

Owing to the status that the price of thermal insulating agent for liquid metal has been raising constantly in recent years, the present work investigated the properties of carbonized corn straw using as thermal insulating agent of liquid metal. The results showed that the carbonized corn straw possessed higher content of fixed carbon, smaller repose angle (or better flowing property) and lower heat conductivity coefficient compared to carbonized rice husk. Both the laboratory test and practical application of using carbonized corn straw as thermal insulating agent of liquid metal showed that it had a better thermal insulating performance, whereas a bigger collapse ratio and agglomeration were found. Thus, a satisfied application performance of thermal insulating can be achieved by using a mixture of carbonized corn straw and carbonized rice husk. The application of carbonized corn straw as thermal insulating agent of liquid metal not only develops a new effective way to use corn straw, but also contributes to decrease the production cost of metallurgical industries.

MgO-CaO materials is one type of the refractories for substitution of MgO-Cr2O3 refractories that has been widely used in metallurgy and cement industries, but the application of MgO-CaO materials has been inhibited for its poor thermal shock resistance that is often improved by addition of ZrO2 but it results in increase of the cost. The present work investigated preparation of MgO-CaO materials by addition of nano-sized ZrO2. The results showed that the densification of the MgO-CaO refractories was promoted and the direct bonding rate of the materials was increased by addition of nano-sized ZrO2. The thermal shock resistance of the MgO-CaO refractories was appreciably improved by modification of the microstructure due to the formed fine CaZrO3 crystallines homogenously locating on the grain boundaries and triple points of the whole microstructure. The critical amount of ZrO2 addition for the purpose to improve thermal shock resistance was effective decreased.

通过水力模型实验，研究了水口结构对南钢板坯连铸机结晶器内钢水流动特性的影响。研究结果表明：使用现有水口结晶器内液面波动大且存在明显裸露并有严重的卷渣现象，适当增加浸入式水口出口面积，在不改变水口其它结构参数和插入深度条件下，能够获得液面波动小，保护渣覆盖良好且没有卷渣的钢水流动特性，不仅能够实现提高拉速的要求，还能提高铸坯质量。