微合金化蠕墨铸铁玻璃模具材质的研究

介绍了微合金化蠕墨铸铁玻璃模具材质的组织、力学性能及热物性，探讨了影响其性能的诸多因素。结果表明：这种材质具有较高的综合性能指标，具有良好的使用性能和显著的经济价值和社会效益。不仅适于与玻璃模具，还可广泛地应用于冶金、塑料和橡胶行业。     

蠕墨铸铁在铁道车辆制动系统中的应用研究

在分析车辆制动器摩擦温度场的基础上 ,研究蠕墨铸铁在铁道车辆制动系统中的使用性能 ;研究结果表明 ,在车辆制动器服役条件下 ,摩擦速度与接触压力的提高 ,摩擦副的摩擦系数显著降低 ,磨损率显著增加 ;在所研究的不同石墨形态的铸铁中 ,蠕墨铸铁不但具有低而稳定的磨损率 ,而且具有高而稳定的制动性能 ,是制造车辆制动器部件的合理选材。     

Agronomic evaluation of fertilizer products derived from Sukulu Hills phosphate rock

Partial acidulation of phosphate rock (PR) or compaction of PR with soluble P fertilizers can improve the usefulness of unreactive PR for use as P fertilizer. A greenhouse study was conducted to evaluate nonconventional phosphate fertilizers derived from a low reactive Sukulu Hills PR from Uganda. Raw PR (which contained 341.0 g kg^–1 Fe₂O₃), beneficiated or concentrate PR, partially acidulated PR (PAPR) and PR compacted with triple superphosphate (TSP) were evaluated. Compacted materials had a P ratio of PR:TSP = 50:50. PAPR materials were made by 50% acidulation with H₂SO₄. TSP was used as a reference fertilizer. Fertilizers were applied to an acidic (pH = 5.4) Hiwassee loam (clayey, kaolinitic, thermic Rhodic Kanhapludults) at rates of 0, 50, 100, 200, 300 and 400 mg P kg^–1 soil. Two successive corn (Zea mays L.) crops were grown for 6 weeks. Compacted concentrate PR + TSP and raw PR + TSP were 94.4 and 89.7% as effective as TSP, respectively, in increasing dry-matter yields for the first corn crop. PAPR from the concentrate was 54.8% as effective as TSP. Raw PR, concentrate PR and the PAPR from the raw PR were ineffective in increasing dry-matter yields. The same trends were obtained when P uptake was used to compare effectiveness. Ineffectiveness of the raw PR and its corresponding PAPR was attributed to a high Fe₂O₃ content in the raw PR. Bray I and Pi paper were found to be nearly equally suitable at estimating available P in the soils treated with responsive fertilizer materials. Mehlich 1 overestimated available P in soil treated with raw PR, concentrate PR or the PAPR from the raw PR.     

不同改良剂对不同含砂率粉土改良性质研究

通过人工室内配制不同含砂率(10%、20%、40%)粉土,对其进行改良试验,研究在不同改良剂(石灰+水玻璃、石灰+粉煤灰)、不同配比作用下3种含砂率粉土的改良效果,研究结果表明:随着含砂率的增加,无论是素土还是改良土,其最大干密度均增大;对于石灰+水玻璃改良土,其最大干密度较素土有明显的降低,而石灰+粉煤灰改良土与之相反;石灰+水玻璃改良土最优含水率与素土略有差别,而石灰+粉煤灰改良土与素土最优含水率基本一致;在同一含砂率下,对于不同配比的石灰+水玻璃改良土,其最大压实度和最优含水率并未发生较大变化,10%石灰+20%粉煤灰的压实度高于其他配比情况;在恒定压实度(95%)下,改良土的无侧限抗压强度明显高于素土的无侧限抗压强度,改良剂对粉土起到一定的"维稳"效果,改良剂掺量才是决定无侧限抗压强度的关键因素。     

蠕墨铸铁CA6110柴油机缸体的试验研究

在现有汽缸体高压造型生产线上进行大马力柴油机蠕墨铸铁缸体的试验,试验铁液化学成分w为3.6%~3.9%C;2.2%~2.4%Si;0.2%~0.5%Mn;P≤0.06%;S≤0.03%,采用自行研制的成分为8%~10%Mg,2%~3%RE的蠕化剂进行冲入法蠕化处理,同时加入0.8%~1.0%Cu和0.03%~0.05%Sn,成功的铸造出蠕墨铸铁CA6110柴油机缸体。对附铸试样和铸件本体进行了金相组织和力学性能检测,结果表明,试样的的蠕化率可达80%~85%,珠光体含量达80%~85%,力学性能σb>480 MPa,δ=1.0%~1.5%,180~200 HBS;缸体铸件本体的蠕化率同样为80%~85%,硬度可达197~214 HBS。试验结果表明:采用的铸造工艺方案是合理的,在铁液中加入的Cu和Sn可明显增加蠕墨铸铁的珠光体数量,提高抗拉强度和硬度,满足大马力柴油机对性能的要求。     

Laser-assisted machining of compacted graphite iron

Compacted graphite iron (CGI) is a material currently under study for the new generation of engines, including blocks, cylinder liners, and cylinder heads. Its unique graphite structure yields desirable high strength, but makes it difficult to machine, thus resulting in a machining cost. Laser-assisted machining (LAM) is adopted to improve its machinability and hence machining economics. The machinability of CGI is studied by varying depth of cut, feed, and material removal temperature and then evaluating resultant cutting forces, specific cutting energy, surface roughness, and tool wear. At a material removal temperature of 400 °C and a feed of 0.150 mm/rev at a cutting speed of 1.7 m/s, it is shown that tool life is 60% greater than conventional conditions at a feed of 0.100 mm/rev. Surface roughness is improved 5% as compared to conventional machining at a feed of 0.150 mm/rev. CGI microstructure evaluated post machining by sectioning and polishing shows no change. An economic analysis shows that LAM can offer an approximately 20% cost savings for the machining of an engine cylinder liner.     

Modelling the compaction curve of fine-grained soils

A theoretical model for the compaction curve of fine-grained soils at various compaction efforts for the entire range of water content is presented in this study. The prediction method is based on the assumption that the compaction curve represents the state surface at the yield state in an unsaturated condition. Thus, for each applied compaction effort, the compaction curve relates to one yielding point on the saturated normal consolidation line (NCL). For a given soil, the model requires the NCL, S_rc, and one point from any compaction curve to predict the compaction curves for different compaction efforts. Moreover, the lines of equal suctions on the compaction curves can be determined if the SWCC, the wetting path, is known. The model introduced here provides additional theoretical understanding of the soil׳s volume change behavior of the compaction curve. The model was verified in two ways: first it was verified quantitatively, by experimental results, and second it was verified qualitatively, by examining the relationships from other models in the literature. The model was further applied to experimental data reported in the literature on previous static and dynamic compaction tests. The results show that the model fits the experimental data very well. Finally, a simple chart, based on this model and using only liquid limits, is presented to estimate γ_dmax and OMC quickly.     

Granulometry,cluster analysis and spatial distribution of manganese contaminated soils,Kgwakgwe, southeastern Botswana

The particle size distribution (PSD) of 400 Mn contaminated soil samples was established, and generated data were statistically analysed and spatially presented. The PSD for the 53 µm – 4 µm size fraction soil samples ranged from 11.05 to 100 wt %, whereas that for < 4 µm was from 0.3 to 30 wt %. Texturally, samples were dominantly silt loam, although silt and sandy loam were also present, as well as loam, loamy sand and clay classes. Six clusters were identified with cluster one being the most dominant occurring in sandy loam, silt loam and loamy sand. The < 53 µm fraction had three dominant areas, and the < 4 µm fraction had several unevenly presented populations as reflected in the maps. Because of its spatial distribution, the < 4 µm fraction may pose hazards to human health. Furthermore, predominance of Mn limits land use to subsistence agriculture with possibly low crop yield.     

Stormwater quality associated with a silt trap (empty and full) discharging into an urban watercourse in Scotland

The aim was to assess the influence of a full silt trap at the end of a stormwater drainage pipe on the water quality of stormwater discharged into a semi‐natural urban watercourse. For approximately eleven weeks, the water qualities of the preliminarily treated stormwater and of the receiving watercourse (Braid Burn) were studied. The mean outflow concentrations of suspended solids were 2.0 mg/l and 34.1 mg/l during dry and wet weather conditions, respectively. Suspended solids concentrations of up to 141.6 mg/l were recorded during storm events. Suspended solids values for treated stormwater were often too high compared to international secondary wastewater treatment standards of around 30 mg/l. Pollutants including heavy metals (e.g., zinc, copper and nickel) accumulated in the silt trap. However, high outflow velocities during heavy rainfall events did not result in clearly defined sediment layers due to sediment re‐suspension. Metals did not accumulate in the receiving watercourse.     

蠕墨铸铁加工研究现状

蠕墨铸铁因为其优秀的力学性能越来越多地被应用在工业当中,特别是在汽车工业中制造高性能和轻质量的柴油发动机方面,已经成为替代灰铸铁的理想材料。然而,蠕墨铸铁优秀的力学性能,使得蠕墨铸铁加工成为一个难题,加工过程存在速度过快刀具过早失效或速度过慢表面质量不达标等问题。基于存在的问题和目前的研究进展,综述了蠕墨铸铁切削机制、内部成分、切削刀具等对加工蠕墨铸铁的影响,并进一步对刀具角度、表面涂层、切削参数、冷却方法等研究进行了介绍,指出了蠕墨铸铁的未来研究方向和发展趋势。