石墨种类对尖晶石碳材料性能与结构的影响

以质量分数分别为88%的镁铝尖晶石、8%的石墨、1%的B4C、3%的铝硅合金粉为原料,外加7%的酚醛树脂和2. 5%的酒精制备了尖晶石碳材料,研究了石墨种类(鳞片石墨(+199和-199)、超细鳞片石墨SG、膨胀石墨EG)对该材料性能与结构的影响。结果表明:1)石墨含量至8%(w)时,石墨在基质中的分布不连续。鳞片石墨(+199和-199)对试样抗热震性和常温强度影响不大。加入3%(w)的超细鳞片石墨对试样的抗热震性较佳; 2)热震后试样的残余强度随膨胀石墨含量的增加稍有提高,而强度保持率最高试样的常温抗折强度则较低,综合考虑加入1%(w)的膨胀石墨较为适宜; 3)尖晶石碳棒头材料中石墨组成为鳞片石墨(+199和-199)和膨胀石墨,制备了多支塞棒进行了工业试验,结果表明该塞棒棒头不开裂,抗冲刷性能较好。     

膨胀石墨对镁碳耐火材料显微结构和性能的影响

以膨胀石墨为碳源,部分取代镁碳耐火材料(含5wt％的鳞片石墨)中的鳞片石墨,借助X射线衍射仪、场发射扫描电镜、能谱仪以及三点弯曲测试仪等研究了膨胀石墨的添加对热处理后镁碳材料的显微结构、力学性能、抗热震性和抗氧化性的影响.结果表明:镁碳材料中引入0.2wt％的膨胀石墨在高温下可促进材料基体内片状AlN相形成,进而使试样的抗折强度和弯曲模量达到最大,分别为12.35 MPa和2.82 GPa;但是过量的添加将对材料的致密度产生负面影响,从而降低了材料的抗折强度和弯曲模量;膨胀石墨的添加显著提高了镁碳材料的抗热震性但对材料的抗氧化性不利;当膨胀石墨的加入量为0.5wt％时,镁碳材料的综合性能最好,若想加大膨胀石墨的添加量,需对其抗氧化性进行改善.     

六方氮化硼复合氧化铝耐火材料的性能研究

以粒度为3~1和≤1 mm的板状刚玉为骨料,板状刚玉细粉、α-Al2O3微粉和Si粉为细粉,分别添加质量分数为3%的六方氮化硼、3%和10%的鳞片石墨制备了Al2O3-BN和低碳、高碳Al2O3-C三种试样,并对比了其常温物理性能、高温强度、抗氧化性、抗热震性和抗渣侵蚀性。结果表明:1)Al2O3-BN耐火材料的常温、高温物理性能与低碳铝碳材料相差不大,并优于传统高碳铝碳材料;2)Al2O3-BN耐火材料具有比碳复合耐火材料更好的抗热震性和抗氧化性,抗渣性与低碳铝碳材料的相当;3)考虑到材料的整体性能,六方氮化硼可以替代石墨作为原料,用于制备综合性能优异的氧化铝质复合耐火材料。     

膨胀石墨对MgO-C耐火材料性能的影响

含石墨的MgO-C耐火材料具有优异的抗渣性和抗热震性,是炼钢工业最重要的耐火材料。然而,较高的石墨或碳含量会导致MgO-C耐火材料的高温强度降低,耐火衬的热导率增加。因此,需要减少碳含量且不降低抗热震性。印度的研究人员利用膨胀石墨代替鳞片石墨,并研究了MgO-C材料的性能。试验基础配比(w)为:粗、中颗粒的高纯电熔镁砂65%,镁砂细粉28%,鳞片石墨5%,Al粉1%,B4C粉1%,外加热塑性酚醛树脂4%。以质量分数分别为0.2%、0.5%、0.8%的     

铝锆碳质长水口损毁机制的研究

采用SEM、EDS对使用后的铝锆碳质长水口内壁及渣线部位材料的蚀损过程进行了分析研究.结果 表明:1)铝锆碳质长水口内壁蚀损过程为碳首先被氧化和溶解形成脱碳层,之后钢水中的夹杂物FeO与脱碳层中的Al2O3反应形成铁铝尖晶石,随着FeO继续附着,在脱碳层表面形成FeO富集区并生成低熔点相,致使脱碳层在高速钢水的冲刷下逐渐蚀损;2)长水口渣线部位蚀损首先为碳向钢液中溶解,之后为中间包渣侵蚀材料中的氧化物,两个过程交替进行,从而导致了长水口渣线部位材料的蚀损;3)适当降低长水口制品中的碳含量,可以减少铝锆碳质长水口内壁以及渣线部位材料中碳的氧化及溶解所导致的材料结构的破坏,可望延长长水口的使用寿命.     

ZrO_2含量对镁锆不烧砖性能的影响

以w(MgO)=97%的电熔镁砂和w(ZrO2)=14.33%的预合成电熔镁锆料为原料,以酚醛树脂为结合荆,用400 t摩擦压砖机机压成型制备了w(ZrO2)分别为0、2%、4%、6%和8%的镁锆不烧砖,研究了ZrO2含量对镁锆不烧砖的常温性能、高温强度、抗热震性的影响,同时还重点研究了其抗渣性能(采用回转抗渣法,渣为碱度3.6的精炼炉渣,侵蚀温度1 650℃),并借助SEM和EDAX分析了部分抗渣后试样的显微结构.结果表明:(1)随着引入的ZrO2含量提高,镁锆不烧砖的常温力学性能总体呈上升趋势,w(zrO2)由0增加到8%时,1 600℃3 h处理后镁锆不烧砖的高温抗折强度(1 500℃下)从0.5 MPa提高到2 MPa.(2)引入的ZrO2改善了不烧砖的抗热震性,w(ZrO2)由0增加到8%时,试样经1 000℃风冷1次后的抗折强度保持率由20%提高至70%以上.(3)ZrO2的引入可以改善镁质材料的抗渣渗透性,尤其是电熔钱锆合成料以细粉形式引入时效果更佳;但ZrO2的引入又对抗渣侵蚀性有所不利,尤其是引入w(ZrO2)达6%～8%时,会造成主晶相方镁石和c-ZrO2,的热膨胀不匹配效应加剧,使材料产生较大裂纹甚至剥落,导致抗渣渗透性随之恶化.当引入的w(ZrO2,)≤4%时,材料以侵蚀损毁为主,蚀损深度约12 mm;而w(ZrO2)>4%时,以渗透和剥落损毁为主,最高蚀损深度达到30 mm左右.因此,综合考虑,镁锆不烧砖中ZrO2,含量以4%(质量分数)为宜.     

铝锆碳质耐火材料的性能研究

为提高铝锆碳耐火材料的性能,研究了烧成温度对铝锆碳耐火材料气孔率、体积密度、常温耐压强度的影响,得出了适宜的烧成温度范围和最佳的锆莫来石加入量,并对此进行了理论分析。同时,还研究了烧成温度对材料抗氧化性的影响。     

加入碳纤维对铝碳耐火材料性能及显微结构的影响

为了提高铝碳耐火材料的性能,以电熔白刚玉(3~1、≤1 mm)为骨料,电熔白刚玉(≤0.074 mm)、鳞片石墨(≤0.15 mm)为基质,Si粉为抗氧化剂,热固性酚醛树脂为结合剂,碳纤维为添加剂,制成铝碳耐火材料,研究了碳纤维添加量对相组成、显微结构、常温物理性能、高温抗折强度和抗氧化性能的影响。结果表明:1)经220℃处理后,碳纤维与树脂结合紧密;1 100℃处理后,碳纤维与树脂之间存在一定的间隙,碳纤维表面未蚀变,但其表面有少量碳化硅晶须生成;1 400℃处理后,碳纤维表面发生蚀变,形成C-Si系物质,同时其表面形成大量碳化硅晶须;2)碳纤维在不显著改变铝碳耐火材料显气孔率和体积密度的基础上,能显著提高试样经220℃和1 400℃处理后的常温耐压强度和抗折强度及1 400℃下的高温抗折强度;3)碳纤维的加入使铝碳耐火材料抗氧化性能下降。     

发展连铸用耐火材料建议书

近年来,我国连铸有较快的发展,1990年连铸比达22.4%,已建成122台总设计生产能力为2530万吨的连铸机.武钢二炼钢厂实现了全连铸,宝钢和鞍钢的3台大板坯连铸机也先后投产,特钢连铸已经起步,与此同时连铸用耐火材料得到了相应的发展,基本适应了连铸生产的需要.如研究开发了熔融石英质、铝碳质长水口和浸入式水口,铝碳—锆碳质复合浸入式水口,整体塞棒,铝锆碳质滑板,锆质定径水口,中间包用绝热板和涂料,以及连铸钢包用浇注料和镁碳、铝镁碳衬砖等.但与国     

高钛金属化球团熔分用电炉炉衬材质探讨

针对攀钢高钛金属化球团熔分用电炉的工况条件,选择炭砖及七种含碳耐火材料作为研究对象,借助热力学计算和动态抗渣试验探讨应用这些材料的可行性.结果表明,在不考虑氧化的前提下镁质或铝质耐火材料中引入高含量C和SiC组分有利于提高其抗熔分渣侵蚀能力;综合考虑认为,引入高SiC含量的镁碳化硅碳材料或铝碳化硅碳材料是高钛金属化球团熔分用电炉炉衬的最佳候选.     

纳米NiO掺杂Carbores'P对Al2O3-C耐火材料力学性能的影响

为提高低碳铝碳耐火材料的力学性能,以≤1 mm的棕刚玉、Si粉和Carbores’P为原料,外加纳米NiO为催化剂,制备Al2O3-C基质试样,利用XRD、SEM、激光拉曼光谱研究纳米NiO对Carbores’P炭化产物的影响。以棕刚玉(粒度为5~3、3-1、≤1 mm)、电熔白刚玉粉、Si粉、鳞片石墨、Carbores’P、纳米NiO为原料制备低碳Al2O3-C试样,研究纳米NiO掺杂Carbore’P对试样力学性能的影响。结果表明:1400℃埋碳热处理后,添加纳米NiO能提高基质的石墨化度,促进碳纳米管和SiC晶须的生成;正是由于它们的生成,提高了Al2O3-C试样的致密度、常温强度和断裂前的位移量,使试样韧性增强。     

锆莫来石对Al2O3-ZrO2-C材料性能的影响

以电熔白刚玉、锆莫来石、鳞片石墨、SiC粉和酚醛树酯为原料,通过改变锆莫来石的加入量和粒度制备了7种不同的A l2O3-ZrO2-C试样,主要研究了锆莫来石加入量和试样的粒度组成对A l2O3-ZrO2-C材料的体积密度、显气孔率、常温耐压强度、气孔孔径分布和透气度等性能的影响。结果表明:1)锆莫来石加入量对A l2O3-ZrO2-C材料的体积密度、显气孔率、耐压强度、气孔孔径分布和透气度都有一定的影响,但影响都不大;2)试样的粒度组成对A l2O3-ZrO2-C材料的体积密度和透气度的影响较大,但对显气孔率、常温耐压强度、气孔孔径分布的影响较小。     

金属Al-Si结合Al2O3-C滑板的性能和使用

自主研制开发了节能型低碳金属Al-Si结合Al2O3-C滑板,其工艺特点是低温烧成,产品特性是低碳,与常用的Al2O3-C和Al2O3-ZrO2-C滑板相比,具有较高的热态强度,较好的抗热震性和抗氧化性。经大中型钢包的批量使用表明,其连续使用次数是高温烧成Al2O3-C滑板的两倍,与Al2O3-ZrO2-C滑板相当,用后滑板扩孔均匀,拉毛较少,裂纹微细。经残砖分析,认为金属Al-Si结合Al2O3-C滑板使用时的损毁过程可能是:表面工作层的非氧化物首先被氧化,导致结构疏松,强度降低,在铸孔处由高温钢水冲刷引起铸孔扩大,在滑动面处因机械摩擦造成滑动面拉毛。     

Effect of h-BN on the microstructure and fracture behavior of low carbon Al2O3-C refractories

h-BN is an ideal substitution candidate for graphite due to its similar crystal structure, better oxidation resistance. In this work, the effect of h-BN on microstructure and comprehensive properties of Al₂O₃-C refractories are investigated, and the specimen containing 0.5 wt% h-BN (G0.5N0.5) possesses the best comprehensive properties. The addition of h-BN could reduce the diameter of SiC whiskers, which leads to the highest strength of specimen G0.5N0.5 (42.63 ± 3.10 MPa). Moreover, the fracture behavior of the specimens is demonstrated using wedge splitting test. The results show that the specimen G0.5N0.5 possesses the highest crack initiation and propagation resistance, which could be attributed to the collaborative effect of h-BN and SiC whiskers. Noteworthily, the addition h-BN could improve the thermal shock resistance. The specimens containing h-BN possess the higher residual ratio, compared with the specimen containing no h-BN (G1N0), and the specimen G0.5N0.5 shows the highest residual strength (14.12 ± 0.67 MPa). Furthermore, the oxidation resistance could be enhanced with introducing the h-BN.     

Synthesis of SiC whiskers via catalytic reaction method in self-bonded SiC composites

Catalyzed by in-situ formed Fe nanoparticles (NPs), 3C–SiC whiskers were prepared from expanded graphite and Si powders after firing at 1573 K for 3 h in Argon. The density functional theory calculations revealed that Fe catalysts facilitated the formation of SiC nucleus and the epitaxial growth of SiC whiskers via reducing the bonding strength in CC dimer as well as Si–O and C–O bonds. Moreover, using SiC, expanded graphite and silicon powders as starting materials Fe-catalyzed self-bonded SiC composites were fabricated. Lots of SiC whiskers were synthesized in the as-prepared composites, leading to remarkable enhancements in high temperature mechanical behavior, oxidation resistance and cryolite resistance of the self-bonded SiC composites.     

Progress in Research and Development of Refractory Oxide-Nonoxide Composites

Some of the progress made in our laboratories in collaboration with industry in research and development work on high performance oxide-nonoxide composites for metallurgical applications has been reviewed. (1) SiAlON bonded corundum composites for blast furnace usage have been produced by reduction-nitridation sintering at high temperature, using bauxite instead of alumina in the matrix. (2) Low carbon Al2O3-SiAlON slide plate materials successfully used in high quality steel continuous casting have been developed in which most or all of the graphite in Al2O3-C brick is replaced by bauxite-based β-SiAlON. (3) Al/Si metal bonded Al2O3-C material characterized by low carbon content, low firing temperature and in-situ formation of carbides and nitrides at high temperature during service are found to possess very high hot strength and very good thermal shock resistance and have also been successfully used as slide plates in ladles and tundishes for high quality steel casting.     

Role of nano-ZrO2 powder in in-situ formation of ceramic whiskers in Al2O3-C slide plate materials

The effects of nano-ZrO₂ powder on the evolution of phase composition and microstructure of Al₂O₃–C materials during firing have been investigated using tabular alumina, Si powder, Al powder, graphite and nano-ZrO₂ powder as starting materials. The residual content of Al and Si gradually decreased with increasing temperature, and the added nano-ZrO₂ facilitates the reactions involving Si and Al. The quantity of in-situ synthesized AlN and SiC whiskers exhibiting continuous interlocking networks increased gradually with temperature. Nano-ZrO₂ facilitates more ceramic whiskers generated in samples, which play a strengthening and toughening role in the materials, thus improving the thermal shock resistance and high temperature strength of Al₂O₃–C materials. In addition, physical properties are improved due to the nano-ZrO₂ filling the pores and increasing the density of materials.     

Strengthening of Al2O3-C slide gate plate refractories with microcrystalline graphite

The novel carbon sources (including nano-carbon black, carbon nanotubes and graphene oxide nanosheets, etc.) have been extensively researched in low carbon Al₂O₃-C refractory systems. In the present work, ultrafine microcrystalline graphite (UMCG) and nickel-loaded ultrafine microcrystalline graphite (NMCG) were added into low carbon Al₂O₃-C slide gate plate refractories to partially replace graphite flake (GF), respectively. The mechanical properties, phase compositions and microstructures were investigated by three-point bending test, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. Also, the reaction mechanisms of in-situ formed ceramic phases were discussed by thermodynamic analysis. The results indicate that the existence of UMCG powders can facilitate the in-situ formation of intertwined ceramic whiskers, leading to increased densification and mechanical properties of low carbon Al₂O₃-C slide gate plate. Moreover, multi-walled carbon nanotubes and ceramic phases intensively interlock with each other in the Al₂O₃-C refractories containing NMCG powders, which results in their better mechanical properties; the cold modulus of rupture are 36.03±0.12 MPa and 32.14±0.17 MPa for the specimens after coking at 1200 °C and 1350 °C, respectively. This work puts forward a practical application for the microcrystalline graphite as a candidate carbon source in Al₂O₃-C slide gate plate refractories.     

Effect of Additives on Properties of MgO—ZrO2—C Material

The paper describes the effect of additives Al,Si,SiC and A4C on the expanson of MgO-ZrO2-C material after being coked.Theresults indicate that Al and Si were oxi-dized to form Al2O3 and SiO2 respectively,and then re-acted with CaZrO3 or stabilizer in c-ZrO2 to form calcium aluminate,spinel(MA),dicalcium silicate(C2S) and forsterite (M2S) ,Meznwhile,α-C2S ras transformed to γ-C2S and c-ZrO2 to m-ZrO2 when temperature changed.All the above reactions resulted in the decrease of the amount of Al4C3 and SiC and the increase in bulk volume,which caused the stucture of MgO-ZrO2-C material de-stroyed.Hence,contrary to the MgO-C material,when adding Al,and Si,the MgO-ZrO2-C material would be structurally deteriorated after heat-treatment and its strength and corrosion resistance decreased.     

金属-氮化物结合刚玉质滑板的结构与性能

由80%～90%板状刚玉及20%～10%金属铝组成的坯料经氮化处理(温度1100℃)后,再进行表面氧化处理(温度800℃),可制得显气孔率为2%的Al-AlN-Al2O3滑板材料,其1400℃高温抗折强度高达48.7 MPa. 该滑板材料浇钢的使用寿命是Al2O3-C滑板的2倍. 显微结构分析表明,部分金属铝氮化形成AlN的体积膨胀效应及其对刚玉晶粒的结合作用,提高了材料的结构致密度和强度,赋予材料优良的抗钢液侵蚀性能. 部分金属铝的高温塑性状态、金属铝及氮化铝的高导热性、刚玉与氮化铝的复相热失配等,是材料具有高抗热震性能的主要原因.