Properties of Magnesia-Hercynite Brick

Properties of magnesia-hercynite brick were studied. The coatability, thermal shock resistance, corrosion resistance to cement clinker and thermal conductivity were compared with those of magnesia-chrome brick and magnesia-spinel brick used widely in sintering zone of cement rotary kiln. The result shows that magnesia-hercynite brick is better than magnesia-chrome brick in thermal chock resistance and corrosion resistance to cement clinker, is similar to magnesia-chrome brick and is better than magnesia-spinel brick in coatability and thermal conductivity.

Effect of Magnesia-Chrome Synthetic Materials on Magnesia-Alumina-Chrome Ramming Mixes

Magnesia-alumina-chrome ramming mixes with same chemical compositions were prepared by using different raw materials such as fused magnesia-chrome synthetic materials and sintered one, wasted bricks and magnesia-alumina spinels. Their physical properties were tested and microstructures were analyzed. The results show that the ramming mixes made of different raw materials bring about different microstructures and properties although the mixes have the same chemical composition, binder content and aggregate size composition.

Corrosion mechanism of magnesia-chromite refractories by ZnO-containing fayalite slags: Effect of funnel glass addition

An efficient approach for lead extraction from waste funnel glass through the lead smelting process has been proposed. To clarify the effect of funnel glass addition on the degradation of magnesia-chromite refractories by ZnO-containing fayalite slag, the corrosion behavior of magnesia-chromite refractories in lead smelting slags with different funnel glass additions from 0wt% to 40wt% was tested. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) was used to acquire the microstructural information of the worn refractory samples. Experimental results showed that the corrosion of magnesia-chromite refractory consisted predominantly of the dissolution of MgO into slag. ZnO and FeO reacted with periclase and chromite to form (Zn,Fe,Mg)O solid solution and (Zn,Fe,Mg)(Fe,Al,Cr)2O4 spinel, respectively. With the addition of funnel glass, the solubility of MgO increased whereas ZnO levels remained stable, thereby resulting in a reduced Mg content and an elevated Zn and Fe content in the (Zn,Fe,Mg)O solid solution and the (Zn,Fe,Mg)(Fe,Al,Cr)2O4 spinel. Considering the stability of the (Zn,Fe,Mg)O solid solution layer and the penetration depth of the slag, the optimal funnel glass addition for lead smelting was found to be 20wt%.

Influence of Microporous Magnesia-rich Spinel Aggregates on Properties of Low Carbon MgO-C Refractories

Two types of low carbon MgO - C refractories with 6% graphite were prepared using microporous magnesiarich spinel （5 - 3 and 3 - 1 mm ） and fused magnesia （5 - 3 and 3 - 1 mm ） as coarse aggregates, respectively, fused magnesia （ ≤1 mm） as fine aggregate, magnesia powder （≤ 0. 088 mm ） , flake graphite powder （ ≤0. 088 mm）, metal Al powder （ 〈0. 074 mm） as matrix, and phenol resin as binder. After curing at 220 ℃ and coke-embedded firing at 1 500 ℃ , the apparent porosity, cold crushing strength, cold modulus of rupture, permanent linear change on heating, thermal shock resistance and slag resistance of the specimens were studied comparatively. The results indicate that： （ 1 ） after curing at 220 ℃ and coke-embedded firing at 1 500 ℃, the specimen with microporous magnesia-rich spinel replacing fused magnesia has lower bulk density and higher apparent porosity than the common low car- bon MgO - C specimen. After curing at 220 ℃, the specimen with microporous aggregate has lower strength than common low carbon MgO - C specimen, but after coke-embedded firing at 1 500℃, it has higher strength and lower permanent linear change on heating; （2） low carbon MgO - C specimen using microporous magnesia-rich spinel to replace fused magnesia aggregate has better thermal shock resistance but worse slag resistance.

Effect of Metal Additives on Performance of Low-Carbon Magnesia-Carbon Materials

In this paper,both oxidation and corrosion resistance of low-carbon magnesia-carbon materials containing 4.0wt% graphite with metallic Al and Mg-Al alloy powders as antioxidants were investigated.Meanwhile,the microstructures of samples corroded by slag were observed with optical microscope as well.The test results revealed the properties of oxidation and corrosion resistance of low-carbon magnesia-carbon materials could be improved obviously by adding metal Al powder and Mg-Al alloy powder.The rule of improving oxidation resistance was illegibility when metal Al powder and Mg-Al alloy powder were added together.It was harmful to corrosion resistance by mixed adding metal Al powder and Mg-Al alloy powder into the materials,at the same time,the corrosion resistance would decreased with the increasing of Mg-Al alloy content.The corrosion resistance of samples with 0.5wt% or 3.0wt% Mg-Al alloy was better. The oxidation resistance and corrosion resistance of materials with metal Al or Mg-Al alloy respectively were better than that with mixed metal Al and Mg-Al alloy. As a result, Mg-Al alloy was more suitable for low-carbon composite materials than metal Al as additives.

Development of Reproducing Alumina-Magnesia-Carbon Bricks

The reproducing alumina-magnesia-carbon bricks were prepared with the dumped bricks as starting materials. The bulk density, apparent porosity, crushing strength, modolus of rupture and slag resistance of the specimen were analyzed. The results show that the used refractories can be reused and recycled by the right method. The reproducing alumina-magnesia-carbon bricks with better abilities were prepared.

Development and Application of High-Performance Magnesia-Chrome Bricks for RH Degasser

The paper analyses the wear mechanism of magnesia-chrome bricks for snorkel of RH degasser. High-performance magnesia-chrome bricks with good resistance to molten slag and infiltration resistance have been manufactured by means of reasonable fabricating technology. The application results of the developed magnesia-chrome bricks at 300t RH degasser of Baosteel indicate that the lining life has been increased up to 150 heats.

Magnesia-Chrome Refractories for Flash Furnace

The rapid development of our country' s heavy non-ferrous metallurgical technology and the revolution in new type of heavynon-ferrous metallurgical furnace have imposed more critical demand on the refractory materials ,i.e. high quality and long service life. This paper presents the domestic status of the refractories for flash furnace , briefly describes the wear of the refractory used, andit is considered that the domestic in refractories for flash-furnace can be surely realized.

The State-of-art of Magnesia-chrome Refractories for P-S Converter in China's Non-ferrous Industry

The state-of-art of magnesia-chrome refractories from direct-bonded magnesia chrome brick to fused-grain rebounded magnesia chrome brick for P-S converter is dis-cribed. The Cr2O3 content of the brick is continually increased with the reduction of the impurity content of brick , the pre-synthetic raw material it applied and the operating condition of convener is optimized so that the service life of convener is largely enhanced.

Rheology of Steel Fibre Containing Alumina-Magnesia-Extruded Graphite Pellets Self-Flowing Castables

The influences of adding steel fibres of different lengths up to 3 volume percentages, on the rheological behaviour of an alumina-magnesia-extruded graphite pellet containing castables have been studied using a rheometer. Free-flow measurements have shown that the flow is severely affected by increasing the length of steel fibres. The calculated values of rheological constants indicate that 19 mm and 25 mm fibre up to 2 volume percentage is permitted while one volume percentage of 50 mm fibres severely degrades the rheology of the castable.

Study on Properties of Magnesia-Hercynite Brick

Using magnesia and hercynite as materials, we researched the magnesia hercynite brick in order to solve the problem of chrome free brick used in the burning zone of cement rotary kiln. Effect of different firing temperature and different content of hercynite on properties of the brick were studied. The results show that the magnesia hercynite specimen fired at 1600℃ was densified and when the hercynite content is 7%, the cold crushing strength and the adhesive strength of rupture of the specimen have the highest value.

Compositions and Properties of Hydration-Resistant Coating of Magnesia-Calcia Materials

The complex coating on the MgO CaO clinker was prepared by dipping method and adding the second mineral to restrain the formation and expansion of the cracks. Meanwhile, the microstructure and the morphology of the coating and hydration resistance of the MgO CaO clinker were also investigated. The result shows that the coating consists mainly of Ca 2P 2O 7, MgO and CaCO 3, its thickness ranges from 5μm to 20μm, and the coating is dense and even, no micro cracks are observed. Also, the coating adheres closely to the matrix. The hydration resistance of the MgO CaO clinker after treatment is improved greatly, and the castables prepared with the treated MgO CaO clinker have better physical properties than MgO castable.

Anti-hydration Magnesia-spinel Bricks in Cement Industry

Hydration cracks of magnesia-spinel bricks in cement industry have been serious problems for both refractory producers and refractory users for a long time.When magnesia-spinel bricks are kept for more than 6months,the bricks tend to have reaction with water or moisture and result in cracks and loss on their structural strength. Those bricks cannot be used anymore and cause substantial loss for the related parties. In 2013,the Siam Refractory Industry Co.,Ltd.,Thailand,successfully developed and applied a special nano-technology to create ＂Anti-Hydration Magnesia-Spinel Bricks ＂ for cement industry which can have the storage time more than two years even in high humidity areas. The cement producers can ensure that all bricks still have good properties as the new ones.

Corrosion of Magnesia-chrome Brick by Smelting Reduction Slag with Iron Bath

Effects of FeO content （0, 5%, 10%, and 15% in mass, respectively ） in lab-synthesized smelting redttc- tion slag with iron bath and test temperature （1 450, 1 500, 1550, anti 1 600 ℃ ） on corrosion am,amount and microstructure of fused rebonded magnesia - chrome brick with 26.02 massqc of Cr2O3 were researched by rotary cylinder method. The results show that ： （ 1 ） the corro- sion amolult of magnesia -chrome brick by slag without FeO is higher than that by the slag with 5% FeO, and the vorrosion amount increases when FeO content increa- ses from 5% to 15% ; （2） the test temperature is one of the important factors affecting the slag corrosion resist- ance of magnesia - chrome brick, and the corrosion of smelting reduction slag to brick increases with the temperature rising.

碳化复合桩(MCP)原理与应用试验研究

介绍了一种基于MgO碳化固化软弱土技术的碳化复合桩(MCP),通过透气管桩向MgO搅拌桩注入CO_(2)气体进行碳化形成新型复合桩。进行了室内模型试验,通过对碳化过程和碳化后的温度、物理、力学等特性的分析,论证了该技术在粉土和淤泥质土中的适应性,结果表明,在MgO充分水化的条件下,不同深度的碳化反应较为均匀;在透气管桩外围存在有效碳化距离和最大碳化距离,在有效碳化距离内可获取良好的碳化效果,揭示了MCP的形成机理与影响因素。在室内试验基础上开展了现场应用试验,结果表明,MCP施工工艺方便、成桩效果好且桩身强度均匀,碳化桩体标贯击数均值为39;其单桩竖向极限承载力为1920 kN,相对于PHC管桩提升37%。室内与现场试验表明,MCP复合桩兼具固碳与加固效果,对岩土工程低碳化发展具有重要意义。

生物酶辅助氧化镁碳化过程砂土加固试验研究

基于微生物或酶诱导碳酸盐沉积(即MICP和EICP)过程的固土技术具备固化强度高、环境友好等特点,但是目前也存在处理效率低、耗时长等局限。为克服这些局限,研究一种新型高效的生物固土技术,即基于植物脲酶辅助氧化镁碳化(酶辅助碳化)过程的固土法,探索其处理方法、效果和作用机理,并与单纯的氧化镁碳化、EICP和水泥等方法进行比较。结果表明,采用酶辅助碳化加固法时,一遍处理强度可达0.92 MPa,且试样的强度显著高于单纯氧化镁处理(0.30 MPa)、EICP处理(0.28 MPa)和水泥处理(0.69 MPa)。酶辅助碳化加固法处理试样的制备方式对强度影响较大。与注入法相比,采用拌和法处理的试样强度高了3倍。此外,添加少量脱脂奶粉后,酶辅助碳化加固法处理试样的强度进一步提升了约70%,达到1.30 MPa。通过微观结构和矿物成分分析发现,酶辅助碳化处理后,固化物填满了砂颗粒之间的孔隙,将砂颗粒结合在一起,形成稳定网格空间结构,与不添加脲酶的试样相比,其中的水合碳酸镁混合物含量较高,中间产物水镁石含量较低。

能量色散X射线荧光光谱仪在镁砂成分测定中的应用

能量色散X射线荧光光谱仪(X射线能谱仪)具有体积小、价格低、分析速度快等优点而被广泛应用于高分子、陶瓷、混凝土、生物等材料的成分和形态分析,但是在耐火材料行业没有相关方法标准的规定。为了实现X射线能谱仪对镁砂中SiO_(2)、Al_(2)O_(3)、Fe_(2)O_(3)、TiO_(2)、CaO、MgO含量的快速分析,通过优化仪器参数,优选样片制备方法,进行精密度和准确度试验,能谱法和波谱法比对试验。结果表明:以熔铸玻璃片法制取样片,采用X射线能谱仪,可以快速测试镁砂样品中SiO_(2)、Al_(2)O_(3)、Fe_(2)O_(3)、TiO_(2)、CaO、MgO的含量,其相对标准偏差为0.09%~1.85%,具有满意的精密度和准确度。能谱法与波谱法的检测差值满足现用标准GB/T 21114—2019规定的允许差要求,数据可靠。

粉煤灰对轻烧氧化镁制备磷酸镁水泥性能影响的研究

文中分析了粉煤灰(FA)对轻烧氧化镁制备磷酸镁水泥(MPC)性能的影响。随着FA替代率的增加,MPC的凝结时间逐渐降低,流动度逐渐提高,抗压强度先升高后降低。当FA替代率为10%时,MPC的各项性能较佳,凝结时间为42.0 min,流动度为200 mm,28 d抗压强度为82.6 MPa。

粉煤灰掺量对轻烧氧化镁基制备3d打印用磷酸镁水泥性能的影响

以实现轻烧氧化镁为原料制备低碳磷酸镁水泥材料的3d打印为目标,采用自主研发的混搅挤功能一化建筑3d打印设备,探究了不同粉煤灰掺量对以轻烧氧化镁为基制备磷酸镁水泥材料性能与打印性能的影响规律,并结合XRD与SEM微观试验进一步分析粉煤灰对其水化产物及晶体样貌的影响。结果表明:与重烧氧化镁相比,由轻烧氧化镁制备磷酸镁水泥的凝结时间大幅缩短;粉煤灰的加入对材料凝结时间影响较小,均在2~3 min左右,但对抗压强度与界面粘结强度有负面影响,当粉煤灰掺量为磷酸镁水泥质量的30%时,抗压强度及界面粘结强度分别下降约34.24%、48.94%;粉煤灰掺量在20%以内时,可有效改善轻烧氧化镁基磷酸镁水泥材料的干缩率,提高体积稳定性;粉煤灰中的活性物质参与水化反应,生成的水化产物与磷酸镁水泥展现出良好的化学相容性,使结构内部更为密实;当粉煤灰掺量为20%~25%时,制备的3d打印用轻烧氧化镁基磷酸镁水泥具有良好的工作性能、体积稳定性能、挤出性能以及建造性能,且满足3d打印对水泥基材料的力学要求。

偏高岭土改性轻烧氧化镁基磷酸镁水泥的3D打印性能

本文采用自主研发的混搅挤功能一体化建筑3D打印设备,实现了轻烧氧化镁基磷酸镁水泥材料的3D打印,探究了不同掺量偏高岭土(MK)对3D打印轻烧氧化镁基磷酸镁水泥性能的影响规律,并结合XRD与SEM试验进一步分析MK掺量对3D打印轻烧氧化镁基磷酸镁水泥水化产物及晶体形貌的影响。结果表明:3D打印轻烧氧化镁基磷酸镁水泥的凝结时间与力学性能均随着MK掺量的增加呈先上升后下降的趋势;当MK掺量为胶凝材料质量的4%~6%时,MK的加入有效改善了轻烧氧化镁基磷酸镁水泥浆体的打印性能,此时的轻烧氧化镁基磷酸镁水泥具有良好的挤出性能、建造性能与力学性能,能够满足3D打印应用要求;MK的加入不会改变轻烧氧化镁基磷酸镁水泥水化产物晶体的组成,但会产生大量无定形的非晶体水化产物,进一步填充水化产物与颗粒间的空隙,改善结构密实程度。