Chromium accumulation, microorganism population and enzyme activities in soils around chromium-containing slag heap of steel alloy factory

The environmental risk of chromium pollution is pronounced in soils adjacent to chromate industry. It is important to investigate the functioning of soil microorganisms in ecosystems exposed to long-term contamination by chromium. 45 soil samples obtained from different places of the slag heap in a steel alloy factory were analyzed for chromium contamination level and its effect on soil microorganisms and enzyme activities. The results show that the average concentrations of total Cr in the soil under the slag heap, adjacent to the slag heap and outside the factory exceed the threshold of Secondary Environmental Quality Standard for Soil in China by 354%, 540% and 184%, respectively, and are 15, 21 and 9 times higher than the local background value, respectively. Elevated chromium loadings result in changes in the activity of the soil microbe, as indicated by the negative correlations between soil microbial population and chromium contents. Dehydrogenase activity is greatly depressed by chromium in the soil. The results imply that dehydrogenase activity can be used as an indicator for the chromium pollution level in the area of the steel alloy factory.     

铬在铁合金厂周边土壤-蔬菜系统中的迁移转化及健康风险

分析湖南省某铁合金厂附近重金属铬在土壤中的分布及迁移特征,在土壤-植物系统中的迁移转化规律,以及铬污染蔬菜对人体的健康风险。结果表明：铁合金厂外排污口、污灌区和对照区土壤的铬含量平均值分别为2239.5,995.33和104.9mg/kg。总铬在排污口附近土壤中主要富集在地表下200-400mm;在污灌区,主要富集于地表下0-200mm;而在对照区,铬浓度从上至下逐渐降低且各层之间富集浓度相差不大。结果也表明芹菜、莴苣和白菜均能够把土壤中吸收的致毒性较强的六价铬转化成低毒的三价铬,且蔬菜中的铬含量平均值为11.95mg/kg。铬在土壤–蔬菜中的生物富集因子大小依次为：白菜〉莴苣〉芹菜。居民每天摄入的铬含量严重超过食物中最大铬允许摄入量,表明铬污染对当地居民存在一定的健康风险。     

不锈钢药芯焊丝中铁粉/长石对焊接烟尘中Cr(Ⅵ)的影响

采用汉诺威电弧质量分析仪、高速摄像机和激光粒度仪等研究了不锈钢药芯焊丝中铁粉/长石比对不锈钢药芯焊丝电弧稳定性、焊接烟尘平均颗粒尺寸、烟尘中Cr(Ⅵ)含量及其生成率.结果表明,短路过渡生成的焊接烟尘平均颗粒尺寸比粒状过渡小,烟尘中Cr(Ⅵ)/总Cr(n/N)的比值大;在同一焊接参数下,当药芯中铁粉/长石比例在1.8时,短路过渡时间最短为1033μs,焊接电弧稳定、焊接烟尘颗粒平均尺寸为1154 nm, Cr(Ⅵ)的含量及Cr(Ⅵ)/总Cr(n/N)的比最小,分别为1555.8 mg/kg和24%.     

Response of soil fungal community to long-term chromium contamination

To further study the fungal community in heavy metal contaminated ecosystems, soil samples were collected from an abandoned chromium (Cr) factory, and fungal community was analyzed by Illumina sequencing of Internal Transcribed Spacer (ITS) amplicons. The results showed that Cr contamination changed the composition and structure of soil fungal community, but didn't change the diversity. Fungus showed various responses to Cr contamination. LEfSe analysis revealed that the biomarker changed a lot in the Cr-contaminated samples in comparison with that in the control samples. The changes in fungal community may be caused by the direct toxic effects on fungi by high concentration of Cr and the significant change in soil properties resulting from Cr contamination. Among all the Cr fractions, organic matter-bound Cr and exchangeable Cr showed significant effects on the fungal community and organic matter also showed a significant effect on soil fungal community.     

CORROSION OF 1Cr13 STAINLESS STEEL IN SOILS

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ⅥB族金属Cr, Mo和W晶格稳定性的密度泛函理论研究

采用总能赝势平面波方法计算了ⅥB族过渡金属Cr,Mo和W不同晶体结构的晶格常数、总能和态密度,总能计算结果确定3种元素的晶格稳定性顺序为?Ghcp-bcc>?Gfcc-bcc>0,其中bcc结构最稳定,与实验结果一致。电子结构的计算结果表明:Cr,Mo和W的s态电子极大向p态转化,部分向d态转化,增强了化学键的结合能力,形成了较高的晶体结合能,使得重金属的晶格更稳定。     

Environmental availability and profile characteristics of arsenic, cadmium, lead and zinc in metal-contaminated vegetable soils

Environmental availability and profile characteristics of arsenic (As), cadmium (Cd), lead (Pb) and zinc (Zn) were studied in contaminated vegetable soils from the Pb/Zn mining and smelting areas in Hunan Province of China, and the potential environmental risks of these metals were also assessed. The results show that the concentrations of As, Cd, Pb and Zn in vegetable soils are higher than the levels of Soil Environmental Quality of China (GB15618-1995). The mobility of metals in soil profiles is mainly characterized by the low pH and organic matter content of soil. The major part of As, Cd, Pb and Zn is restricted to the upper soils and the contamination of these metals in soils is significantly influenced by the long-term Pb/Zn mining and smelting activities. Based on the results from the BCR sequential extraction, the fraction of Cd in the soil profiles is predominantly existed in the acid-extractable form and the large amount of Pb is closely associated with reducible fraction. The environmental availability of Cd and Pb is predominantly higher than that of As and Zn in the soil profiles, suggesting Cd and Pb have more huge potential risk for human health and surrounding environment.     

3Cr13不锈钢低温双辉等离子渗铬

对3Cr13不锈钢在700 ℃进行低温等离子渗铬处理,并观察处理后试样的组织,进行了截面成分检测、硬度检测、X射线衍射物相分析以及电化学腐蚀性能测试.结果表明,表面覆盖4～5 μm 的铬沉积层后在沉积层的下边形成了一定区域的脱碳层,表面硬度达728 HV0.05;表层物相主要为Fe、Cr、Cr_(1.36)Fe_(0.52)及Cr_(23)C_6;在2.5%HCl溶液中耐腐蚀性能提高约6倍,抗点蚀能力有一定的增强,提高了耐晶间腐蚀的能力.     

铝及铝合金表面铬酸盐转化膜的组成和结构研究——Ⅰ.离子束分析、X光电子能谱和俄歇电子能谱测试

本文报道了用离子束分析(RBS和ERD方法)、X光电子能谱(XPS)和俄歇电子能谱(AES)测试方法对铝及铝合金不同基材表面经不同铬酸处理液处理所得的铬酸盐转化膜测定分析的结果。转化膜主要由三价铬化合物CrOOH·nH_2O组成,六价铬只存在于转化膜的表面层。转化膜中含有少量氟及铝化合物,在含有[Fe(CN)_6]~(3-)的铬酸处理液所得的转化膜中还含有铁氰化物。     

土壤中SRB及Cl-对1Cr18Ni9Ti不锈钢腐蚀的相互影响

利用交流阻抗测试技术、扫描电镜及表面能谱、失重法、微生物分析等方法 ,研究了在不同Cl-含量的土壤中 ,硫酸盐还原菌对 1Cr18Ni9Ti不锈钢腐蚀的影响规律 .13 6d的试验结果表明 ,不同Cl-含量土壤中SRB菌量在2 3 0 0 0～ 3 5 0 0 0 (个 /克土 )之间 ,Cl-的加入并没有显著影响SRB的生长 ,随着Cl-的加入土壤中SRB的菌量有增大的趋势 ;随着土壤中Cl-含量的增大 ,不锈钢腐蚀电位负偏移 ,而且在接菌土壤中的腐蚀电位比在灭菌土壤中负移幅度更大 ;不锈钢在灭菌土壤中没有发生点蚀现象 ,而在接菌土壤中发生了严重的点蚀 ,最大点蚀深度随着土壤中Cl-含量的增加而增大 ,这说明在土壤中SRB及Cl-的共同作用下 ,增大了不锈钢的点蚀敏感性 .不锈钢在灭菌土壤中的阻抗图谱表现为一个半径很大的容抗弧 ,而在接菌土壤中的阻抗图表现为两个时间常数的双容抗弧     

2Cr13钢的表面气体渗氮处理

用光学金相显微镜、扫描电子显微镜、X射线衍射(XRD)仪及显微硬度计对经气体渗氮处理的2Cr13钢试样进行了组织结构分析,并利用销-盘摩擦磨损试验机对渗氮的盘与未渗氮销摩擦副进行摩擦磨损试验.结果表明,520℃×20 h渗氮可使2Cr13马氏体不锈钢的渗氮层深度达到165 μm,处理后试样的显微硬度约为处理前的2.5倍.处理后试样的耐磨性能得到了较大的提高,渗氮盘试样的磨损表面未出现裂纹,而未渗氮销的磨损表面存在严重的裂纹.     

消除低铬白口铸铁铸造缺陷的措施

本文对低铬白口铸铁材料的缩松、气孔、夹渣及热裂等铸造缺陷进行原因分析,通过改进铸造工艺参数、净化铁水、控制原材料等措施,基本解决了低铬白口铸铁的铸造缺陷问题,可以在一定范围内进行推广应用。     

Cr12MoV钢宽带激光淬火试验研究

运用宽带扫描技术对Cr12MoV钢进行激光表面淬火研究，分析了不同工艺参数对硬化层深度、宽度和显微硬度的影响及硬化层显微组织特征。结果表明，单道激光淬火宽度〉16mm，在最佳工艺下（激光功率2．6kW，扫描速度6mm／s，离焦量65mm），硬化层平均硬度达916HV0．1，是基体硬度的1．8倍。宽带激光淬火造成的组织细化和过饱和的隐晶马氏体的形成是硬度提高的主要原因。     

高Cr微渣堆焊耐磨焊条的研制

对高Cr微碴堆焊耐磨焊条进行了研究，解决了焊条的各种工艺性能，使焊缝金属具有超高硬度和好的耐磨性，该焊条熔敷效率高，焊道上仅有微渣，达到了多层多道焊不需敲渣的目的。     

ZGMn13Cr2钢水韧处理中的脱碳行为

研究了不同水韧条件下ZGMn13Cr2钢的脱碳行为,分析了实际脱碳深度与理论计算之间的关系,并对传统的计算模型进行了修正。结果表明,水韧处理加热温度越高,保温时间越长,脱碳越严重。当加热温度为1000 ℃时,实际脱碳深度与理论脱碳深度相似;加热温度为1050 ℃和1100 ℃时,由于氧化反应的加剧以及碳化物的作用,实际脱碳深度大于理论脱碳深度,传统的计算模型不再适用,采用修正的计算模型能对ZGMn13Cr2钢水韧处理中的脱碳深度起到一定的预测作用。     

70Cr3Mo钢支承辊辊坯的生产试制

采用电渣重熔工艺生产试制了70Cr3Mo钢支承辊辊坯。产品检验结果表明,辊坯的化学成分、超声波探伤、高倍检验全部合格。     

Preparation, characterization and photocatalytic activity of sulfuric acid-modified titanium-bearing blast furnace slag

The feasibility of reducing Cr(VI)from the aqueous solution by sulfuric acid-modified titanium-bearing blast furnace slag(SATBBFS)as a photocatalyst was investigated.The photocatalysts were examined by X-ray diffraction(XRD),UV-vis diffuse reflectance spectra,thermogravimetric analysis(TG)and Fourier transform infrared spectroscopy(FTIR).The photocatalytic activities of the different catalysts were evaluated by the photocatalytic reduction of Cr(VI)under UV-vis light irradiation.The results show that the photocatalytic activities of SATBBFS catalysts are strongly dependent on CaTiO3-to-TiO2 mass ratio,adsorption capacity and surface acidity,and SATBBFS calcined at 400°C shows a higher photocatalytic activity compared with other catalysts.     

用稀土变质低铬白口铸铁生产高硬度耐磨铸件

利用国内丰富的稀土、钒渣或钒钛生铁熔制低铬白口铸铁，通过采用适当的成分设计，稀土复合孕育变质处理和热处理可以在明显降低生产成本的情况下获得与高铬钼铸铁接近的高硬度性能，明显改善零件在小能量高速冲击凿削与冲刷磨损的复合式工况条件下的使用性能。     

超临界汽轮机高压内缸用ZG13Cr9Mo1VNbN不锈钢铸件冶炼浇注工艺研究

通过合理配料,粗炼炉严格脱硫、脱磷、熔化铁合金,出钢过程留钢留渣,进入LF炉后升温化渣,扩散脱氧、微调合金元素含量,真空脱气处理,成功冶炼超临界汽轮机高压内缸用超纯净ZG13Cr9Mo1VNbN不锈钢钢水。     

Minimization of Copper Losses in Copper Smelting Slag During Electric Furnace Treatment

In the quest to achieve the highest metal recovery during the smelting of copper concentrates, this study has evaluated the minimum level of soluble copper in iron-silicate slags. The experimental work was performed under slag-cleaning conditions for different levels of Fe in the matte and for a range of Fe/SiO₂ ratios in the slag. All experiments were carried out under conditions where three phases were present (copper?Cmatte?Cslag), which is the condition typically prevailing in many slag-cleaning electric furnaces. The %Fe in the electric furnace matte was varied between 0.5?wt.% and 11?wt.%, and two different Fe/SiO₂ ratios in the slag were used (targeted values were 1.4 and 1.6). All experiments were performed at 1200°C. From thermodynamic considerations, from industrial experience, and from the results obtained in this study, the minimum soluble copper content in the electric furnace slag is expected to be near 0.55?wt.% Cu. This level does not account for a portion of the copper present as mechanically entrained matte/metal droplets. Taking this into account, the current authors believe an overall copper level in discard slag between 0.7?wt.% and 0.8?wt.% can be obtained with optimal operating conditions. For these conditions, the copper losses in the slag are roughly 75% as dissolved copper and 25% as entrained matte and copper. Such conditions include operating the electric furnace at metallic copper saturation, maintaining the %Fe in the electric furnace matte between 6?wt.% and 9?wt.%, not exceeding a slag temperature of 1250°C, and controlling the Fe/SiO₂ ratio in the smelting furnace slag at ??1.5. In addition, magnetite reduction needs to be performed efficiently during the slag-cleaning cycle so as to maintain a total magnetite content of ??7?wt.% in the discard slag. The authors further consider that under exceptionally well-controlled conditions, a copper content in electric furnace discard slag between 0.55?wt.% and 0.7?wt.% can be obtained, by minimizing entrained matte and copper solubility in the discard slag.