烘炉时耐火浇注料裂纹产生的机理研究

介绍了耐火浇注料升温试验的方法及过程,对烘炉时耐火浇注料内部温度变化规律及裂纹产生的机理进行了分析,提出了缩短烘炉时间的新的烘炉方法.     

低水泥结合氧化铝空心球轻质浇注料的研究

针对氧化铝空心球的结构特点,采用低水泥结合、浇注成型的方式,对低水泥结合氧化铝空心球轻质浇注料的可行性进行了研究。经过相图理论计算、性能检测及X-射线衍射分析,结果表明,铝酸钙水泥不仅有利于提高材料的常温强度,并且对材料的高温烧结具有促进作用,材料的主要矿物组成为CA6和刚玉,材料的高温性能良好,使用温度可以达到1650℃以上。     

M- S-H formation in MgO-SiO2slurries via wet milling for magnesia based castables

It is believed that the formation of hydration phase, MgO-SiO₂-H₂O (M-S-H), contributes to good workability and reliable comprehensive properties for magnesia based castables. In order to stimulate the formation of M-S-H in magnesia based castables and understand the minimum introduction of microslica amount, wet milling process was used to promote the dissolution of MgO and SiO₂ in this work. The slurry containing different content of microsilica with wet milling technology and the castables with/without wet milling slurry were prepared. The effects of microsilica content on the formation of hydration phases were analyzed by XRD, FT-IR and TG/DSC and the properties of magnesia based castables were evaluated by explosion resistance, CMOR, HMOR and so on. The results showed that the formation of M-S-H was accelerated because of the dissolution of Mg²⁺ and HSiO₃^? in wet milling process. Higher amount of M-S-H led to a tight bonding in the early stage, and a denser structure after firing at high temperature due to the limited formation of brucite and in-situ formation of evenly distributed forsterite phase. In addition, much higher HMOR were obtained when less microsilica was added, attributing to the suppressed formation of low-melting-point liquid. Therefore, 2–3 wt% microsilica addition was recommended in this process.     

Crack-free caustic magnesia-bonded refractory castables

A growing interest in designing high-alumina MgO-bonded refractory castables has been identified in recent years due to the magnesia ability to react: (i) with water at the initial processing stages of these materials (inducing the precipitation of brucite phase) or (ii) with alumina, giving rise to in situ MgAl₂O₄ generation at high temperatures. Nevertheless, despite the great potential of caustic magnesia to be used as a binder in such systems due to its high reactivity, it is still a challenge to control the hydration reaction rate of this oxide and the negative effects derived from the expansive feature of Mg(OH)₂ formation. Thus, this work evaluated the incorporation of different contents of aluminum hydroxyl lactate (AHL) into caustic magnesia-bonded castables, aiming to control the brucite precipitation during the curing and drying steps of the prepared samples, resulting in crack-free refractories. The designed compositions were characterized via flowability, setting behavior, X-ray diffraction, cold flexural strength, porosity, permeability and thermogravimetric measurements. According to the results, instead of Mg(OH)₂, hydrotalcite-like phases [Mg₆Al₂(OH)₁₆(OH)₂.4.5H₂O and Mg₆Al₂(OH)₁₆(CO₃)·4H₂O] were the main hydrated phases identified in the AHL-containing compositions. The addition of 1.0 wt% of aluminum hydroxyl lactate to the designed castable proved to be, so far, the best option for this magnesia source, resulting in the development of a crack-free refractory with enhanced properties and greater spalling resistance under heating.     

结合剂对镁质浇注料性能的影响

主要研究了SiO2 微粉、MgCl2 ·6H2 O和ρ Al2 O3 3种结合剂对镁质浇注料的耐压强度、显气孔率和抗水化性能的影响。结果表明 :采用SiO2 微粉和MgCl2 ·6H2 O为结合剂时 ,镁质浇注料 110℃2 4h处理后的耐压强度和抗水化性能优于采用ρ Al2 O3 的 ;采用MgCl2 ·6H2 O和 ρ Al2 O3 为结合剂时 ,浇注料 110 0℃ 3h热处理后的耐压强度明显下降 ;经 16 0 0℃ 3h热处理后 ,浇注料的耐压强度随着SiO2 微粉含量的增加先增大后减小 ,而MgCl2 ·6H2 O的影响较小 ,随着 ρ Al2 O3 加入量的增大浇注料的耐压强度明显降低。     

Slag corrosion mechanism of lightweight Al2O3–MgO castable in different atmospheric conditions

The slag resistance of ladle lining refractory in different atmospheric conditions is of utmost importance due to the strong variation of atmospheric environment in ladle during the process cycle. In this study, by adopting dynamic induction furnace corrosion test, the corrosion mechanism of lightweight Al₂O₃–MgO castable with different environmental oxygen partial pressure was investigated through macro and microanalysis, XRD, and thermodynamic simulation. The atmospheric condition was set to P (O₂) = 0.21 atm or P(Ar) = 1.0 atm. The attained results showed that a reduced slag corrosion but intensified slag penetration happened at low environmental oxygen partial pressure condition. With P(O₂) = 0.21 atm, Mn and Fe in slag were present in the form of divalent and/or trivalent cations and were incorporated into spinel to form MnFe₂O₄ solutions and MgAl₂O₄ solutions during the corrosion process. Since Fe, Mn ions were largely consumed, liquid with high viscosity formed and the continuing infiltration was suppressed. Under P(Ar) = 1.0 atm, Fe ions in the slag were totally reduced into elemental iron while Mn existed mainly in the state of MnO, and the amount of liquid slag was therefore reduced, leading to significantly weakened corrosion on castable aggregates. Corrosion reaction products under this condition were mainly MgAl₂O₄ and CA₆.     

Revisiting CA6 formation in cement-bonded alumina-spinel refractory castables

This work revisits the proposed mechanisms presented in the literature for CA₆ formation in Al₂O₃-MgO and Al₂O₃-MgAl₂O₄ castables bonded with calcium aluminate cement. New experimental tests, thermodynamic simulations and re-evaluation of the chemical composition and microstructural aspects observed for samples fired in the temperature range of 1150 °C to 1500 °C were carried out. Based on these data, a new interpretation of the CA₆ generation process, as well as the features which influence the location and morphology of this phase were proposed. CA₆ formation via solid and liquid states are suggested to take place in all evaluated compositions, where the former (solid-state) is the main reaction predicted for the silica-free refractories (AM0MS and AS0MS), whereas the liquid-state one prevails in the AM1MS and AS1MS materials. The CA₆ crystal morphology should be affected by these different reaction mechanisms. According to the experimental results, it was also discussed the role of the calcium hexaluminate features in the overall corrosion behavior of the designed refractories when they were placed in contact with molten slag at high temperatures. Such aspects have not been previously reported in published papers related to this subject.     

钢包渣线浇注料基质组成及其抗渣性

采用特级高铝矾土熟料和电熔镁砂为主要原料,研究了Al2O3-MgO系浇注料中MgO/Al2O3质量比对浇注料基本性能的影响,并分析对比了基质中添加适量工业氧化格、镁锆合成料及矾土尖晶石对浇注料抗渣性的影响及其规律。结果表明：恰当控制基质中MgO/Al2O3质量比及在基质中添加适量的工业氧化铬等组分,可明显提高浇注料的抗渣性。     

水泥加入量对氧化铝-尖晶石质自流浇注料强度的影响

研究了氧化铝－尖晶石质自流浇注料的力争性能和显微结构。结果表明：当水泥加入量＜10％时,浇注料的强度随水泥加入量的增加而增大;当水泥加入量＞10％时,浇注料的强度无明显增加。此外,水泥加入量过大会影响浇注料的流动性。     

骨料对Al_2O_3-尖晶石钢包浇注料性能的影响

研究了三种不同骨料对Al2O3-尖晶石钢包浇注料性能的影响。结果表明：用电冶矾土刚玉骨科制得的浇注料具有较好的流动性、高温烧结性和抗渣性,但热震稳定性比电熔白刚玉有所降低。这主要与电冶矾土刚玉的组成和显微结构有关。