Effect of Ti(C,N) on Properties of Low-carbon MgO-C Bricks

The effect of Ti （ C, N） on properties of low-carbon MgO - C bricks was investigated. The phase composition and the microstructure of the matrix of low-carbon MgO - C brick containing Ti （ C, N） were studied by XRD and SEM analysis together with EDS. The results showed that Ti （ C, N） distributed in the matrix of lowcarbon MgO - C brick uniformly after being treated at 1 600 ~C for 3 h in coke powder bed, and Ti （C, N） and MgO formed a solid solution. After the treatment at 1 600 ℃ for 3 h in coke powder bed, the bulk density and cold crushing strength of low-carbon MgO - C brick with Ti （ C, N） decreased, and the apparent porosity and linear change rate of specimens increased. The oxidation resistance of low-carbon MgO - C brick with Ti（ C, N） was superior to that of low-carbon MgO - C brick with no additives, but inferior to that of low-car- bon MgO - C brick with Al powder. The slag resistance of the specimen with Ti （ C, N） was excellent as well.

Effects of B_4 C and Si Antioxidant on Oxidation Resistance of Low-carbon MgO-C Brick

Low-carbon MgO - C specimens with dimension of Ф6 mm × 36 mm were prepared using fused magnesia, flake graphite and carbon black as main starting materials, thermoplastic phenolic resin as binder, hexamethyl ene tetramine as curing agent, Si powder （ w （Si） 〉 80%, particle size 〈0. 074 mm） and B℃ （ d90 =36. 5 μm ） as antioxidant, pressing under 200 MPa and drying at 200 ℃ for 24 h. The oxidation resistance tests were conducted at 600 ℃ , 1 000 ℃ and 1 400 ℃ for 2 h, respectively. Effects of B4C and Si antioxidant on oxidation resistance of low-carbon MgO - C brick were studied by comparing the areas of the decarburized layers. The results shaw that： （1） When Si powder addition is 3%, at 600 ℃ and 1 000 ℃, the specimens with 0. 5% B4C perform good oxidation resistance; at 1 400 ℃, the oxidation resistance of the specimens is improved with the addition of B4C increasing, and that of the specimen with 0. 7% B4 C is the best. （2） When B4C addition is 0. 5%, at 600 ℃ and 1 000 ℃ ,the oxidation resistances of the specimens with 3% and 5% Si powder are similar, which are better than that of the specimen with 1% Si powder; and at 1 400 ℃ , the oxidation resistance of the specimens is improved obviously with the addition of Si powder increasing, and that of the specimen with 5% Si powder is the best. （3） Bused on the results, it is believed that the low-carbon MgO - C brick with 0. 5% B4C and 3% Si powder performs the best oxidation resistance.

A novel route to enhance high-temperature mechanical property and thermal shock resistance of low-carbon Mgo-C bricks by introducing ZrSiO_(4)

Conventional MgO-C bricks(graphite content>14 wt.%)produce a great deal of greenhouse gas emission,while low-carbon MgO-C bricks have serious thermal shock resistance during high-temperature service.To enhance the high-temperature mechanical property and thermal shock resistance of low-carbon MgO-C bricks,a novel route of introducing ZrSiO_(4) powder into low-carbon MgO-C bricks was reported in such refractories with 2 wt.% flaky graphite.The results indicate that the low-carbon MgO-C brick with 0.5 wt.%ZrSiO_(4) addition has the maximum hot modulus of rupture at 1400℃ and the corresponding specimen fired in the carbon embedded atmosphere has the maximum residual strength ratio(98.6%)after three thermal shock cycles.It is found that some needle-like AlON and plate-like Al_(2)O_(3)-ZrO_(2) composites were in situ formed in the matrices after the low-carbon MgO-C bricks were coked at 1400℃,which can enhance the high-temperature mechanical property and thermal shock resistance due to the effect of fiber toughening and particle toughening.Moreover,CO_(2) emission of the newly developed low-carbon MgO-C bricks is reduced by 58.3% per ton steel after using them as the working lining of a 90 t vacuum oxygen decarburization ladle.

Effect of B_4C on Oxidation Resistance of Low-Carbon MgO-C Materials

B4C was added into the low-carbon MgO-C materials in order to improve the oxidation resistance. The results show adding 0. 3wt% B4C can get the best oxidation resistance and adding 0. 2 wt% B4C can get the highest hot modulus of rupture. Altogether, adding 0. 2wt% B,C into the low-carbon MgO-C materials can get better oxidation resistance and hot strength.

添加电熔MgO-ZrO_2共晶砂对低碳MgO-C砖性能的影响

在以电熔镁砂、鳞片石墨为原料、酚醛树脂为结合剂的低碳MgO-C砖中,分别添加10%,15%,20%的电熔MgO-ZrO2共晶砂替代镁砂,经200,1000,1500℃处理后,对材料的体积密度、显气孔率、耐压强度、线变化率、热膨胀率和抗氧化性进行了检测,并借助XRD研究了试样的物相组成和显微结构。结果表明,随着电熔MgO-ZrO2共晶砂加入量的增加,试样的体积密度逐渐增大,线变化率逐渐减小,耐压强度和抗氧化性均为先增大后减小,试样的热膨胀率逐渐减小,抗热震性得到提高。材料性能的变化主要与电熔MgO-ZrO2共晶砂的体积密度大、热膨胀系数小、氧化锆的相变、镁铝尖晶石和镁橄榄石等物相的生成相关。

Effect of micro-Al_(2)O_(3) powders on oxidation and corrosion behaviors of low-carbon MgO-C refractories

To solve the problem of poor high-temperature service performance caused by low carbonization of MgO-C refractories,low-carbon MgO–C refractories with excellent thermal shock,oxidation and corrosion resistances were successfully designed by using SiC whiskers as reinforcing phases and introducing micro-Al_(2)O_(3) powders as additives.The results indicated that the addition of micro-Al_(2)O_(3) powders optimized the internal structure of the material,like the columnar β-Si_(3)N_(4) with a stepped distribution and the mosaic structure formed between granular and flaky Mg_(2)SiO_(4),which synergistically strengthened and toughened the material and gave the material excellent mechanical properties and thermal shock resistance.Specifically,the cold modulus of rupture and cold crushing strength after thermal shock were increased by 4.1 and 20.3 MPa,respectively.Moreover,the addition of micro-Al_(2)O_(3) powders promoted the formation of fine particles of Mg_(2)SiO_(4),MgAl_(2)O_(4) and MgO,as well as a dense protective layer of Mg_(2)SiO_(4) in the material under high-temperature environment.Furthermore,spinel and high-temperature solid solution were formed in the corrosion environment.The oxidation and corrosion resistances were greatly improved by 41%and 15%,respectively.

钢包渣线用低碳MgO-C砖的研制

以电熔镁砂和石墨为主要原料,研究了Al粉和Si粉为复合抗氧化剂对低碳镁碳砖性能的影响。结果表明,单一加入Al粉时,高温抗折强度和抗氧化性能较好;复合添加Al-Si粉抗氧化剂时气孔率较小,对体积密度影响不大,热震稳定性和抗熔渣侵蚀性能最佳。

In-situ Formation of Spinel Fibers in MgO-C Refractory Matrixes

In-situ magnesia-rich spinel fiber was formed resulting from the addition of ferrocene into MgO-C refractory matrixes. The formation of in-situ spinel fiber was detected to start at 1300 ℃. The amount, diameter and length of the fibers increased with rising temperature. Ferrocene may have catalytic effects on the growth of the fibers in two aspects. First, the reaction between MgO and C and the decomposition of Al4C3 may be catalyzed at high temperature. Suitable concentration gaseous phase is then created for vapor-vapor reaction which could result in the in-situ formation of fibers. Second, Fe nanoparticle produced from ferrocene can act as catalytic droplets and catalyze the growth of the fibers. The fibers are formed via the vapor-liquid-solid and vapor-solid mechanisms. In terms of chemical thermodynamics, the partial pressure of CO and Mg（g） are found to play an important role in the in-situ fibers formation. Different concentration of vapors affects the size, amount and composition of the fibers at different temperatures. The mechanical properties of MgO-C brick was found to be improved by ferrocene addition.

锆英石加入量对低碳镁碳砖抗剥落性能的影响

为了提高VOD钢包用低碳镁碳砖的抗剥落性能,以粒度为5~3、3~1、<1和<0.088 mm的电熔镁砂,粒度<0.15 mm的天然鳞片石墨,粒度<0.045 mm的金属铝粉和粒度<0.05 mm的锆英石粉为主要原料,热固性酚醛树脂为结合剂,制备了低碳镁碳砖,研究了锆英石加入量(加入质量分数分别为0、1%、2%、5%)对低碳镁碳砖抗剥落性能的影响。结果表明:1)添加1%(w)锆英石试样的高温抗折强度、抗热震性、抗氧化性及抗渣性均达到最大,说明锆英石的加入有助于提高低碳镁碳砖的抗剥落性能。2)添加锆英石的试样经1 400℃埋碳加热0.5 h后,基质中有针状、连续片状空间结构的阿隆(AlON)以及片状氧化铝-氧化锆复合物生成,且通过钉扎增韧以及颗粒增韧提高了高温力学性能和抗热震性。3)加入过量的锆英石会导致氧化锆生成量明显增加,其高温下的体积变化使基质中微裂纹聚集,造成试样的抗剥落性能大幅下降。

石墨加入量对低碳镁碳砖性能的影响

通过检测含有2%～14%石墨镁碳砖1400℃的高温抗折强度、1500℃的热膨胀系数、1000℃×2 h煅烧后的抗氧化性,比较低碳镁碳砖与传统镁砖的性能差异,研究了石墨加入量对低碳镁碳砖性能的影响。结果表明:在有2%Al存在的情况下,低碳镁碳砖高温抗折强度与石墨加入量无关;石墨加入量为6%时,可保证低碳镁碳砖具有较优良的抗剥落性及抗氧化性。

SiC-Al_2O_3复合粉体的合成以及在低碳镁碳砖中的应用

本文以蜡石和天然石墨为原料,通过碳热还原法合成了SiC-Al2O3复合粉体,考察了加热温度对SiC-Al2O3复合粉体合成的影响;并将SiC-Al2O3粉体作为添加剂加入到低碳镁碳砖中,考察了其对低碳镁碳砖抗氧化性和抗渣侵蚀和抗渣渗透性能的影响,并对其作用机理进行了探讨.研究结果表明,加热温度对于SiC-Al2O3复合粉体的合成具有重要的影响;通过在蜡石中添加适量的天然石墨,并将蜡石和石墨的混合物在惰性气氛下加热到1 650℃时,可以很容易地合成SiC-Al2O3复合粉体.在低碳镁碳砖中添加SiC-Al2O3复合粉末能明显提高其对氧化性炉渣的抗侵蚀和渗透性能,而对其抗氧化性能的影响不大.这是由于与炉渣接触时,SiC-Al2O3复合粉体易于进入渣中,使接触界面的炉渣部分的炉渣黏度大幅度增加,阻碍了炉渣向耐火材料的进一步侵蚀和渗透.

B_4C-C复合粉体的合成及其在低碳镁碳砖中的应用

以炭黑和硼酸为原料,采用碳热还原法合成了部分石墨化B4C-C复合粉体,并将其作为碳源和抗氧化剂用于低碳镁碳砖中.研究了加热温度对B4C-C复合粉体合成的影响,分析了其物相结构、成分、形貌和粒度.通过测定低碳镁碳砖的常规物理性能、抗氧化性和热震稳定性,考察了复合粉体对低碳镁碳砖性能的影响.结果表明,随加热温度升高,B4C-C复合粉体的石墨化度增大,B4C含量下降,1900℃时石墨化度达23.26%,B4C含量为20%左右,复合粉体中除部分微米、亚微米级的B4C外,85%以上为纳米级的B4C和部分石墨化炭黑.添加复合粉体的低碳镁碳砖具有良好的常规物理性能、抗氧化性和热震稳定性.

不同碳含量的镁碳砖抗渣侵蚀性能研究

用感应炉浸渍试验法研究低碳镁碳砖和普通镁碳砖对攀枝花钢铁(集团)公司钢包渣的抗侵蚀能力。采用SEM和EDS分析方法研究侵蚀后试样的显微结构及化学组成的变化。结果表明,普通镁碳砖脱碳层厚度是低碳镁碳砖脱碳层厚度的2.4倍,碳氧化后其组织结构疏松,并且生成大量低熔点CMS和CaSiO3。这些低熔点化合物形成连续相渗透于MgO颗粒周围,分解镁砂,使骨料破坏,加速MgO-C砖的损毁。而低碳镁碳砖碳氧化后形成微细化气孔,此微孔中生成的高熔点化合物MA容易过饱和而沉淀,因此增加了固-固直接结合程度,使脱碳层的组织结构较为致密,提高了材料的抗渣侵蚀性能。

碳氮化钛对低碳镁碳砖性能的影响

研究了碳氮化钛加入到低碳镁碳砖中对其性能的影响,并采用XRD物相分析、SEM显微分析研究了碳氮化钛对低碳镁碳砖基质部分烧后性能的影响。结果表明:镁碳砖基质部分经1600℃3h埋炭处理后,碳氮化钛仍均匀分布在基质中,并和MgO发生一定程度的固溶;加有碳氮化钛的镁碳砖经1600℃3h埋炭处理后,体积密度有所降低,气孔率升高,线膨胀率增大,常温耐压强度有所减小;碳氮化钛对镁碳材料的抗氧化性有所改善,但不及传统的金属铝粉;材料同样表现出良好的抗渣性。

复合添加Al和TiO_2对低碳镁碳砖基质物相组成及性能的影响

以电熔镁砂、超细鳞片石墨为主要原料,以热固性酚醛树脂为结合剂,添加Al和TiO2制备低碳镁碳砖,研究复合引入Al粉和TiO2对低碳镁碳砖基质物相组成及性能的影响。结果表明,埋炭热处理后,添加剂与基质反应生成新相MgAl2O4和TiN或Ti(C,N),使低碳镁碳砖的抗氧化性能明显提高,材料的强度显著增加;此外,添加剂的复合引入有利于改善单独引入Al粉时镁碳砖埋炭处理后易水化的问题。

碳氮化钛的加入量对低碳镁碳砖性能的影响

研究碳氮化钛不同加入量对低碳镁碳砖各种性能的影响,并采用扫描电镜(SEM)分析碳氮化钛在低碳镁碳砖中的分布和转化情况。结果表明,碳氮化钛的加入量为3%时,镁碳砖的常温物理性能较好,高温抗折强度最高,抗氧化性最好;碳氮化钛加入量的变化对镁碳砖在埋炭气氛下的抗渣性能影响不明显;碳氮化钛均匀地分布在低碳镁碳砖中,在高温下碳氮化钛可能参与了氧化反应。

低碳镁碳砖抗氧化剂的研究

研究了Al、Si和B4C几种抗氧化添加剂对低碳镁碳砖抗氧化性能的影响.利用热重法分析了加热过程中耐火材料试样的失重率;测定耐火材料的脱碳层厚度;探讨了抗氧化添加剂的作用机理;并明确了适合于低碳镁碳砖用抗氧化添加剂的种类.研究结果表明,与添加Al和Si相比,添加B4C能更好地提高低碳镁碳砖的抗氧化性能.通过在低碳镁碳砖中添加B4C,可明显提高低碳镁碳砖的抗氧化性,有望提高其抗渣侵及抗热震性能。

金属复合低碳镁碳渣线砖氧化剥落分析

金属Al/Si复合低碳MgO-C砖在冶炼品种钢的210 t钢包渣线试用,取得良好使用效果。采用XRD、SEM、EDS对用后残砖分段带进行了物相和显微结构分析,结果表明:用后残砖可分为原砖带、原砖渐变带和氧化带三个段带;原砖渐变带里Al和Si与C和N2反应,原位生成Al4C3、AlN和SiC,有利于提高高温强度和热震稳定性;氧化带里的AlN和SiC先后逐渐被氧化,并与MgO反应生成镁铝尖晶石和镁橄榄石,结构比较疏松,抗热震稳定性有所减弱。可以认为该砖的损毁原因主要是氧化后的结构剥落。今后改进的方向主要为改善材料氧化后的热震稳定性。

石墨粒度对低炭镁炭砖性能的影响

以电熔镁砂和4种粒度(≤0.149mm、 ≤0.074mm、≤0.044mm和≤0.01mm)的天然鳞片 石墨为主原料,在石墨含量为4%的条件下,研究了 石墨粒度对低炭镁炭砖的物理性能、抗氧化性和热震 稳定性的影响。结果表明:用细石墨取代较粗石墨 (粒度≤0.149mm)制成的镁炭砖,其物理性能、抗氧 化性和热震稳定性都有了明显的改善,且都以加入粒 度≤0.074mm石墨的效果最好。其原因是细石墨的 加入改善了镁炭砖的基质结构。

复合石墨对低碳镁碳砖抗渣性能的影响

以电熔97镁砂为主要原料,研究了石墨复合时对低碳镁碳砖性能的影响以及以酚醛树脂与高温沥青为复合结合剂对低碳镁碳砖性能的影响。结果表明,当加入1%300目、4.5%100目石墨时,试验砖的综合性能较好;当加入5.5%300目石墨时,抗渣渗透性能较好;而当石墨全部使用100目时,抗氧化性能最好;高温沥青加入1%时,可以提高其高温抗折强度,对常温耐压强度和体积密度、气孔率的影响不大,但降低抗氧化性能,继续加入则各性能大大降低。