优质低铬白口铸铁生产新工艺

优质低铬白口铸铁生产新工艺其核心就是将变质处理、孕育处理、微合金化技术三位一体,互为作用.笔者以优质低铬白口铸铁生产新工艺内容的形式来体现冶金处理技术还应具备哪些相关的动力学条件才能充分发挥其本身工艺效果展开了讨论.     

低品位硫化铜矿细菌浸出

采用正交实验方法,考察了矿石粒度、矿浆含量、接种量对大冶露天矿石和井下矿石的摇瓶浸出过程的影响.结果表明:粒度对露天矿和井下矿的酸耗影响大,对井下矿的浸出率影响高度显著; 矿浆含量对酸耗影响大,对浸出率则不显著; 在接种的初期,接种量对酸耗与浸出率都有影响,2d后接种量的影响消失; 井下矿浸出的最优工艺条件为:粒度<0.154mm,矿浆含量10%,接种量10%; 露天矿浸出的最优工艺条件为:粒度<0.154mm,矿浆含量20%,接种量7.5%.     

Sb-Ba复合随流孕育对大断面球铁低温冲击性能的影响北大核心CSCD

采用随流孕育的方式向铁液中分别加入普通孕育剂75SiFe和含Sb和Ba孕育剂进行孕育处理,浇注尺寸规格为180 mm×180 mm×200 mm的大断面球墨铸铁试块。运用光学显微镜(OM)、扫描电子显微镜(SEM)、拉力试验机、冲击试验机等检测方法,研究Sb-Ba复合随流孕育对大断面低温球墨铸铁组织和性能的影响。结果表明,与用普通孕育剂75SiFe相比,运用含Sb和Ba复合孕育剂对铁液进行随流孕育能显著改善大断面低温球墨铸铁微观组织和力学性能。该工艺可提高试样的石墨球化级别、改善石墨形态、增加石墨球数量、细化石墨球,可有效避免孕育衰退,使铸件组织和力学性能达到较佳匹配。冲击试验表明,低温韧性得到了明显提高,其(-40℃)冲击功平均值不低于为12 J。     

孕育剂量对激冷球铁凸轮轴组织和性能的影响

试验了孕育剂量对凸轮轴组织和性能的影响。在轴颈心部碳化物质量分数≤15%条件下，降低孕育剂量可有效减少激冷层的石墨数量，提高激冷层的硬度和激冷深度；同时，降低孕育剂量，可增加铁液的激冷敏感性，有利于凸轮轴的生产控制。     

薄壁铸态铁素体球墨铸铁型内孕育块的研究

研究了压力成型孕育块的熔解特性及孕育剂组成。结果表明，在75硅铁孕育块含有适量的Bi和冰晶石并具有合适的形状时，可以减小孕育滞后，提高孕育均匀性，满足生产薄壁铸态铁素体球墨铸铁件的孕育要求。     

Influence of Mg2N2 powder on microstructures and mechanical properties of AZ31 Mg alloy

In order to obtain an effective and reliable grain refiner for Mg-Al alloys, 1% (mass fraction) Mg3N2 was added into AZ31 Mg alloy. The microstructures of the Mg alloys were studied by optical microscopy, scan electron microscopy and X-ray energy dispersive spectroscopy, and the mechanical properties were determined. The results show that adding a small amount of Mg3N2 to AZ31 Mg alloy can refine the grain size from 103 to 58 μm. The ultimate tensile strength and elongation of AZ31 Mg alloy are 174.1MPa and 8.3%, respectively. After the addition of 1% Mg3N2, the ultimate tensile strength and elongation of AZ31 Mg alloy are increased up to 198.7 MPa and 11.8%, respectively. The grain refinement mechanism is that AIN is formed after Mg3N2 is added.Both A1N and Mg phases are of HCP lattice structure, and the disregistry between Mg phases and AIN along (0001)Mg//(0001)AlN is 3.04%, which is very effective for heterogeneous nucleation.     

在高锰钢改性处理中钒渣的冶金物化条件与作用

在高锰钢改性处理中,V渣 Ti Zn复合孕育剂起着良好的孕育处理作用.本文主要从热力学角度分析了V渣作为炼钢工业副产品得到二次利用的可行性,并讨论了冶金综合处理工艺和冶金物化条件对充分发挥V渣复合孕育效果的作用.     

优质高铬白口铸铁生产新工艺

介绍将变质处理、孕育处理和微合金化技术结合使用于优质高铬白口铸铁生产的新工艺。其特点是在铸态实现马氏体基体,通过亚温处理进一步改善组织,提高材料的综合性能。     

Energy of activation in cassava silages

The formation of lactic acid in cassava laboratory silos was determined at five temperatures using a strain of Lactobacillus sp as inoculant. The acidification kinetics were followed during the first 2 days. Dry matter, pH and other fermentation byproducts were also determined. The optimum temperature for the production of lactic acid was 30°C. Rate constants (k) were calculated by fitting each lactic acid curve to the Gompertz model and these were fitted to the Arrhenius equation and the energy of activation was calculated. An unusually low value for the energy of activation in biological systems was found (8300 ± 750 cal mol^?1). The relatively high dry matter content (45% DM) in cassava silage could impose a type of barrier to diffusion of lactic acid. Local accumulation of lactic acid could affect the evolution of the biological reaction. Thus, this result could be explained by a diffusional limitation of lactic acid in the fermenting mass.     

低碳球墨铸铁的显微组织分析

用透射电镜和扫描电镜研究了经Sx变质处理的低碳球墨铸铁的显微组织,对基体和石墨进行了分析.结果表明,低碳球墨铸铁的铸态组织为石墨＋珠光体,石墨是多晶体,珠光体中的铁素体和渗碳体在晶体结构上有对应关系.