除尘灰对Si质消失模铸钢涂料烧结性的影响

使用BST401抗折弯仪测试烧结试样的抗弯强度,研究除尘灰对Si质消失模铸钢涂料烧结特性的影响.结果表明,随着除尘灰含量增加和烧结温度提高,试样的抗弯强度有增大的趋势,当除尘灰含量为4％、在1 500℃烧结时,试样的抗弯强度显著增大,符合消失模铸钢涂料的要求.经对现场浇注试样进行涂层断面扫描电镜(SEM)分析,发现涂层断面与钢液接触部分烧结良好,耐火骨料连成整片,因此可实现涂料烧结壳从铸件表面自动剥离.     

消失模铸钢涂料耐火骨料烧结性的研究

以石英粉和铝矾土组成复合耐火骨料,在不同温度下进行烧结,使用BST401抗折弯仪测试烧结试样的抗弯强度,研究不同配比的耐火骨料的烧结性。研究表明,随着复合骨料中铝矾土含量的增加和烧结温度的升高,试样的抗弯强度都有增大的趋势。当铝矾土含量为60%、石英粉含量为40%、试样在1500℃时抗弯强度显著增大。并对烧结试样进行扫描电镜(SEM)分析,试样烧结良好,符合消失模铸钢涂料耐火骨料的要求。     

膨润土对石英涂料烧结性的影响

为解决石英粉涂料耐火度偏高、烧结性差的问题,研究膨润土的添加对石英涂料烧结的促进作用。以添加不同比例的Ca基膨润土和Na基膨润土烧结后的石英涂料试样为研究对象,运用抗折弯仪测量试样的抗弯强度,扫描电镜(SEM)观察其微观形貌,通过X射线衍射(XRD)分析其烧结后的成分,并对Ca基与Na基膨润土进行了对比。结果表明,两种膨润土都能促进石英粉骨料的烧结,Ca基膨润土的添加效果要好于Na基膨润土,当Ca基膨润土含量为4%时,能够满足消失模铸钢水基涂料的要求。     

Si质消失模铸钢涂料耐火骨料烧结机理的研究

在单一的石英粉耐火骨料中加入4％的除尘灰作为烧结助剂,在1 400℃、1 500℃下分别进行保温烧结,使用BST401抗折弯仪测试烧结试样的抗弯强度,与单一的石英粉骨料进行对比,研究耐火骨料的烧结机理.研究表明,除尘灰的加入促进了石英粉的液相烧结,而对固相烧结基本没有影响;在烧结过程中,液相烧结对整个烧结过程的贡献远大于固相烧结.并对烧结试样进行扫描电镜(SEM)分析,耐火骨料在1 500℃时产生了适量的液相,试样烧结良好,符合消失模铸钢涂料耐火骨料的要求.     

消失模铸钢水基涂料粘结剂与悬浮剂的试验研究

采用抗弯强度表征涂料的强度,应用单因素试验方法研究了不同粘结剂和悬浮剂对消失模铸钢水基涂料强度和悬浮性的影响。结果表明,随着不同粘结剂含量的增加,涂料抗弯强度都有增大的趋势,各粘结剂含量相同的情况下,马铃薯改性淀粉作为粘结剂时其抗弯强度显著大于乳胶粉和糊精粘结剂,因此,选用马铃薯改性淀粉作为消失模铸钢水基涂料的粘结剂,含量1.5%~2.0%。随着不同悬浮剂含量的增加,涂料悬浮性都有增大的趋势。含量相同的Ca基膨润土和Na基膨润土,涂料的悬浮性差别不大。含量小于2.5%时,HCE对涂料悬浮性的影响优于CMC;含量大于2.5%时,HCE和CMC对涂料悬浮性的影响没有差别。考虑成本因素,选择Ca基膨润土和CMC作为复合悬浮剂,Ca基膨润土含量2.5%~3.5%,CMC含量1.5%~2.0%,所配制涂料综合性能优良,能够满足实际生产需要。     

云母粉对石英基消失模涂料烧结性能的影响

采用单因素梯度法,研究了云母粉对石英基消失模涂料烧结性能的影响。对以云母粉为助烧结剂的涂料试样进行了抗弯强度测试、SEM观察和XRD分析。结果表明,云母粉的加入促进了涂料的烧结,随着云母粉添加量的增加,涂料的烧结性能随之提高。当云母粉的添加量为1%时,涂料具有优良的使用性能和工艺性能。     

消失模铸造涂料耐火骨料的烧结性研究

以含量为40％的石英粉和60％的铝矾土组成复合耐火骨料,在1400℃、1500℃下分别进行保温烧结,使用BST401抗折弯仪测试烧结试样的抗弯强度,与单一的石英粉骨料进行对比,研究耐火骨料的烧结机理.研究表明,铝矾土的加入促进了石英粉的液相烧结,而对固相烧结基本没有影响;在烧结过程中,液相烧结对整个烧结过程的贡献远大于固相烧结.并对烧结试样进行扫描电镜(SEM)分析,复合耐火骨料在1 500℃时产生了适量的液相,试样烧结良好,符合消失模涂料耐火骨料的要求.     

醇基涂料抗粘砂及剥离机理分析与研究

以M70莫来石为耐火骨料的铸钢用醇基涂料为研究对象,对浇注、涂料残片断面进行扫描电镜和能谱分析。结果表明,涂料在浇注过程中由于与钢水接触,使得涂料温度接近耐火骨料的耐火度,从而使涂料发生化学和物理变化,产生的致密结构能够阻止钢水渗进砂子,有效防止粘砂。     

消失模铸钢醇基涂料的开发

以锆铝石粉为耐火骨料,酚醛树脂和硅溶胶混合使用做粘结剂,CMC和钠基膨润土混合使用做悬浮剂,采用异丙醇作载体,开发出消失模铸钢醇基涂料。通过试验确定了消失模铸钢醇基涂料的最佳配比,并对涂料综合性能进行了测试。     

消失模铸造的合理浇注速度研究

利用基础理论计算出消失模铸造的速度流量随着静压头、气隙的厚度、气隙的周长、透气性的增大而增大,随涂料层厚度、消失模密度、液态金属的浇注温度的增大而减小,并在生产实践中验证.     

Preparation of YSZ solid electrolyte by slip casting and its properties

Fully stabilized YSZ solid electrolyte was prepared by slip casting. The density was measured according to the Archimedes principle and the linear shrinkage was calculated from measuring the sizes of samples before and after sintering. XRD analysis was conducted to verify the phase structure of both the starting YSZ powder and the prepared YSZ electrolyte. The microstructure of fracture surface and the electrical properties of the samples sintered at different temperatures were investigated via SEM and a complex impedance method, respectively. By comparison of the properties and features among the samples, a slip casting method was established to be a simple way to manufacture high-quality YSZ electrolyte at the sintering temperature of 1550℃ for 3 h, which provides a new approach for YSZ electrolyte with com-plex shapes and mass production.     

Sintering process and grain growth of Mn-Zn ferrite nanoparticles

The density, microstructure and magnetic properties of non-doped Mn-Zn ferrite nanoparticles sintered compacts were investigated. The compacts of non-doped Mn-Zn ferrite nanoparticles were sintered by segmented-sintering process at lower sintering temperature. The density of sintered samples was measured by Archimedes method, and the phase composition and microstructure were examined by XRD and SEM. The sintered Mn-Zn ferrite magnetic measurements were carried out with Vibrating Sample. The results show that the density of sintered compacts increases with the rising of sintering temperature, achieving 4.8245 g·cm-3 when sintered at 900 ℃, which is the optimal density of Mn-Zn functional ferrite needed and from the fractured surface of sintered samples, it can be seen that the grain grows well with small grain size and homogeneous distribution.     

Sintering Behavior of Elemental Powders with FeB Addition in the Composition of Martensitic Stainless steel

The effect of sintering additive for the development of high-strength martensitic stainless steel from elemental powders was studied. The sintering parameters investigated were: sintering temperature, sintering time, and wt.% of FeB. In vacuum sintering, effective sintering took place between 1300 and 1350 °C with 1-1.5 wt.% FeB addition. The maximum sintered density and ultimate tensile strength (UTS) were achieved after sintering at 1350°C for 60 min with 1 wt.% FeB. Secondary pores were observed in samples containing more than 1.5 wt.% FeB sintered at 1350 °C for 60 min. More than 1.5 wt.% FeB content and temperature above 1350°C caused slumping of the specimens. Maximum UTS of 505 MPa was achieved with 1 wt.% FeB content. Above 0.5 wt.% FeB content, maximum increase in density was observed. Fracture morphologies of the sintered samples are reported.     

Effect of silicon addition on the microstructure and corrosion behavior of sintered stainless steel

The influence of silicon addition on the physical properties and the corrosion behavior of sintered austenitic 304L stainless steel was evaluated. The density of the sintered stainless steel changed depending upon the amount of silicon added. A “pseudo-peritectic” reaction developed during the sintering of high silicon content alloys and resulted in an increased sintering rate and enhanced densification. The corrosion resistance of the various sintered stainless steels was evaluated from the results of potentiodynamic polarization curves and corrosion rate measurements and from the appearance of the corroded surfaces. The results indicated that the corrosion resistance was improved with the addition of more than 2 wt.% Si.     

The effects of nanoparticle addition on SiC and AlN powder–polymer mixtures: Packing and flow behavior

The development of methods to increase sintered density and improve dimensional tolerances is a crucial issue in powder metallurgy and ceramic processing. Increasing the packing density of starting powders is one effective route to achieve high sintered density and dimensional precision. The current paper presents an in-depth study on the effect of nanoparticle addition on the powder content of SiC and AlN powder–polymer mixtures. In particular, bimodal mixtures of nanoscale and sub-micrometer particles were found to have significantly increased powder volume fraction (solids loading) in the mixtures for injection molding. This observation to increasing packing density by using nanoparticles is surprising and novel since nanoparticles are known to inherently exhibit poor packing behavior. Additionally, for a given volume fraction of powder, the bimodal μ-n suspensions had a lower viscosity at any shear rate compared to the monomodal μ-suspensions. The ability to lower the suspension viscosity by adding nanoparticles to micron-sized particles has important implications for processing of particulate suspensions by powder injection molding (PIM), extrusion, slip casting and tape casting. Samples made from bimodal powders exhibited slower polymer removal during debinding and higher densification with lower shrinkage on sintering compared to the corresponding samples made from monomodal powder mixtures.     

Investigation of carbon contamination in lost foam castings of low carbon steel

Lost foam casting(LFC) process is a special casting method in which polymeric foam patterns with refractory coatings are utilized as a mould component. In this work, four types of foam: expandable polyethylene(EPE), expandable polypropylene(EPP) and expandable polystyrene(EPS) foams with two different densities were employed as pattern materials. LFC and conventional green sand mould casting methods were used to cast a low carbon steel, A216 Grade WCB. Both casting processes were carried out at 1,580 °C. Chemical analysis results showed that the carbon contamination level was high and was influenced by pattern type. Metallographic investigations revealed a significant increase in the percentage of pearlite phase in all LFC samples. Densities of manufactured samples were calculated in order to evaluate porosity of the products. It was determined that the densities of the LFC samples were lower than the green sand mould cast reference sample(RS). Vickers hardness tests were also carried out and increments in hardness values with increased carbon content was observed.     

Cr镀层对金刚石/铝硼硅玻璃复合材料中金刚石氧化反应的抑制研究

为研究在镀铬金刚石/铝硼硅玻璃复合材料中Cr镀层对金刚石氧化反应的抑制作用,将不同镀层厚度的镀铬金刚石和铝硼硅玻璃在相同工艺下烧制成试样,检测试样的体积膨胀率和抗折强度,观察其断面形貌;同时分析烧结后金刚石单颗粒抗压强度和金刚石-结合剂界面的成分。结果表明：Cr镀层具有消耗和隔绝氧元素的双重保护作用,能有效抑制金刚石的氧化。同时,镀层厚度对金刚石氧化反应影响显著：镀层太薄,不能在高温烧结过程中持续保护金刚石;镀层太厚,会由于应力匹配问题产生裂纹或成片剥落,使金刚石暴露在有氧环境中,反而失去保护作用。对于粒度号为140/170的金刚石,最佳镀层厚度为1.58μm。     

涂层厚度对气化模铸钢件表面含碳量的影响

用EPS做模型，干砂造型在负压的状态下浇注ZG25，系统研究涂层厚度对气化模铸造碳钢件表面含碳量变化。结果表明，适当的涂层厚度，铸件表面含碳量不会变化，随着涂层厚度的增加，铸件表面脱碳区－增碳区－正常区。