基于CAFE法优化易切削钢9SMn28锰、硅、硫含量

应用CAFE法,模拟了不同锰、硅、硫含量对易切削钢9SMn28凝固组织的影响,并通过热力学计算分析了原因,优化了钢中的锰、硅、硫含量,得出结论如下:Mn含量在0.9%～1.3%时,随Mn的增加,柱状晶减小;当Mn含量从0.9%到1.2%时,晶粒逐渐细化。Si含量在0.02%～0.10%时,随Si的增加,柱状晶略有减小;当Si含量从0.02%到0.08%时,晶粒逐渐细化。S含量在0.24%～0.36%时,随S的增加,柱状晶减小,晶粒逐渐细化。因此,从凝固组织方面考虑,易切削钢9SMn28的Mn、Si、S含量应分别为1.2%、0.08%、0.36%。同时,对优化了的锰、硅、硫含量进行模拟,有效的改善了9SMn28的凝固组织。

高锰无磁钢40Mn18Cr3的冶炼

针对高锰无磁钢40Mn18Cr3的化学成分和力学性能特点,对冶炼工艺进行研究及改进,采取电炉—LF精炼—真空脱气—浇注钢锭的冶炼工艺,并控制真空前湿度和时间,使锰成分和气体含量达到标准要求,保证轧材全部合格。

Soil Manganese and Iron Released due to Calcium Salts:Bioavailability to Pepper (Capsicum frutescens L.)

Releases of manganese and iron ions from an albic soil (Albic-Udic Luvisol), a yellow-red soil (Hap-Udic Ferrisol) and a yellow-brown soil (Arp-Udic Luvisol) induced by calcium salt addition and their bioavailability to pepper (Capsicum frutescens L.) were studied in a pot experiment. Addition of Ca(NO3)2 decreased soil pH and increased both exchangeable and DTPA (diethylenetriamine pentaacetic acid)-extractable Mn and Fe in soils. Meanwhile, total Mn accumulation in the shoots of Capsicum frutescens L. on the salt-treated soils increased significantly (P ＜ 0.01) compared with the control, suggesting that salt addition to soil induced Mn toxicity in Capsicum frutescens L. Although exchangeable and DTPA-extractable Fe increased also in the salt-treated soils, Fe uptake by the shoots of Capsicum frutescens L. decreased. The effect of added salts in soils on dry matter weight of pepper varied with the soil characteristics, showing different buffer capacities of the soils for salt toxicity in an order of yellow-brown soil ＞ albic soil ＞ yellow-red soil. Fe/Mn ratio in shoots of Capsicum frutescens L. decreased with increasing salt addition for all the soils, which was ascribed to the antagonistic effect of Mn on Fe accumulation. The ratio of Fe/Mn in the tissue was a better indicator of the appearance of Mn toxicity symptoms than Mn concentration alone.

Elemental Composition and Geochemical Characteristics of Iron-Manganese Nodules in Main Soils of China

Elemental composition and geochemical characteristics of iron-manganese nodules from nine main soils in China were studied by chemical and multivariate statistical analyses to better understand the reactions and functions of iron-manganese nodules in soils and sediment. Compared to the corresponding soils, Mn, Ba, Cd, Co and Pb had strong accumulation, Ni had moderate accumulation, while Ca, Cu, Fe, Na, P, Sr and Zn accumulated to a minor degree in the iron-manganese nodules. In contrast, Si, Al, K, Mg and Ti were reduced in the iron-manganese nodules. The contents of Ba, Cd, Co, Cu, Ni, Pb and Zn were positively and significantly correlated with that of MnO2 in the iron-manganese nodules, while the contents of Cr, Cu, Ni, Pb and Zn were positively and significantly correlated with that of Fe2O3 in soils. Based on a principle component analysis, the elements of iron-manganese nodules were divided into four groups: 1) Mn, Ba, Cd, Co, Cu, Li, Ni, Pb and Zn that were associated with Mn oxides, 2) Fe, Cr and P that were associated with Fe oxides, 3) Si, K, and Mg that were included in the elemental composition of phyllosilicate, and 4) Ca, Na, Al and Ti that existed in todorokite, birnessite, lithiophorite and phyllosilicate. It was suggested that accumulation, mineralization and specific adsorption were involved in the formation processes of soil iron-manganese nodules.

TG–FTIR analysis of pyrolusite reduction by major biomass components

Pyrolusite reduction processes by three major biomass components cellulose,hemicelluloses and lignin,represented by CP,HP and LP,respectively,were investigated by thermogravimetric analyzer coupled with Fourier transform infrared spectrometry(TG-FTIR).The Sestak-Berggren(SB) equation was used to evaluate the kinetics of reduction processes.TG analysis reveals that the main reduction processes occur at 250-410 ℃,220-390 ℃,and 190-410 ℃ for CP,HP,and LP,respectively.FT-IR and XRD results indicate that various reducing volatiles(e.g.aldehydes,furans,ketones and alcohols) are produced from the pyrolysis with the three major components,which directly reduce MnO_2 in ore to MnO.The processes are described by the SB equation with three parameters(m,n,p).Their non-zero values suggest that pyrolusite reduction is controlled by the diffusion of reducing gaseous products through an ash/inert layer associated with minerals.The apparent activation energies for pyrolusite reduction by CP,HP and LP are 40.48,25.70 and 40.10 kJ·mol^(-1),respectively.

Investigation of the Composition and Structure of Ferrous and Manganese-Ferrous Minerals out of Lake-Marsh Ores

Minerals which enter lake-marsh ores composition are very diverse. There are two large classes of ores： ferrous and manganese-ferrous ores. Each class is divided into groups according to its mineral composition. In this investigation, ferrous ore sample （Chagodostcha） and manganese-ferrous ore samples （Totyma-2 and Mologa-2） were considered. All samples in the initial state are contaminated with a-quartz and Ab-An feldspars. Thus for purification of the samples, direct flotation method with kerosene agent were used. As a result, almost all impurities were removed from the samples. With the X-ray diffraction method, the authors identified following phases： goethite （ferrous ore） and birnessite （manganese-ferrous ores）. Also, the authors used electron probe microanalysis of the original and purified probes and it showed the presence of such impurities as Ca, K, Mg and Ba in birnessite from the manganese-ferrous ores, and AI and Mn impurities in goethite from the ferrous ore. All ore minerals are in a nanocrystalline state （crystallite size is about 10 nm）.