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1.
徐友宁 《机械工人(冷加工)》1981,(5)
图1是挤压不锈钢零件的模子,孔径为φ0.12毫米,由于孔小,加工比较困难。我们用线切割加工两半模子新工艺制成了高速钢及硬质合金模具。1.线切割:按图2切出半模,此半模比半圆稍大0.03毫米,外径为φ10d,同时,中心还切出了φ0.12毫米的半孔。2.钳工研磨至光洁度(?)11以上,并保证每件正好是半圆,这 相似文献
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设计制造复杂的硬质合金成形刀具,已成为大多数机加为主的工厂的当务之急,此文立足现有技术条件,总结了一些这方面的小经验。 相似文献
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小秦岭金矿带枣香河重金属及氰化物分布特征及污染成因 总被引:1,自引:0,他引:1
为了研究小秦岭金矿带河流中重金属及氰化物分布特征及污染成因,利用野外调研、室内淋溶试验、数据测试分析等手段,对枣香河河水和底泥中重金属和氰化物进行了时空剖析。其研究表明,河水水质污染严重,水质类别主要是劣Ⅴ类和Ⅴ类水,污染河段占93.09%,河水中主要污染物为汞、铅及氰化物。通过对近年河水断面水质对比分析得出,重金属、氰化物已经造成枣香河水的持续污染。河流中重金属主要以底泥的形式存在,底泥中铜、铅污染最严重。河水污染成因主要为山区采矿活动、山外傍河选冶作业;河水的稀释、混合作用;底泥的吸附作用、生物化学的降解作用等。影响因素主要为污染物总量及其降解速率、水系沉积物颗粒粒径、地形地貌等。 相似文献
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某矿区土壤及作物中汞的分析与评价 总被引:1,自引:0,他引:1
文中对某金矿区农田土壤及作物进行了调查。采集样品分析其中汞的含量,结果表明,农田土壤汞的含量范围为0.21~20.30mg/kg,均值为2.23mg/kg,高出对照区土壤值6.96倍;与土壤环境质量二级标准比较,最大超标倍数19.3,平均超标1.23倍,超标样本达到58.67%,土壤受到汞的轻度污染。作物中汞的含量范围为0.001~1.35mg/kg,均值为0.196mg/kg,平均值超过食品卫生限量标准18.6倍;作物中汞的含量分布规律是叶菜类果实类块根类,达到警戒水平的样本在74.28%以上。该研究成果可为环境污染的防治提供科学依据。 相似文献
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某河流底泥重金属污染地质累积指数评价 总被引:1,自引:0,他引:1
通过对双桥河流域进行环境调查,采集了底泥样品,分析了重金属含量,应用地质累积指数对河流底泥进行了评价。其结果表明:汞的地质累积指数为-1.01~2.39,76.92%采样点为Ⅱ级,属于中度污染;铅的地质累积指数为-0.07~2.19,3.85%采样点达到Ⅲ级,属中度污染到强污染,65.38%采样点达到Ⅱ级,属中度污染;镉的地质累积指数为-0.32~1.55,30.77%采样点达到Ⅱ级,属中度污染,50.00%采样点达到Ⅰ级,属无污染到中度污染;铬、砷基本没有污染;铜、锌地质累积指数平均值为0≤Igeo<1,达到Ⅰ级,属于无污染到中度污染;汞、铅的污染较为严重。 相似文献
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Soil, crop and residents' hair over Xiaoqinling gold mining region, China, which was selected as a case study, were sampled and analyzed for Hg, Cd, Pb, Cu, Cr, As and Zn concentrations. The concentrations of heavy metals in soil or crop and hair samples were used to assess their potential ecological risks, or to find the responses to these metals as evidences to prove the potential risk was coming down to observed harm, respectively. The results showed that, these metals in soil were ranked by severity of ecological risk as Hg>Cd>Pb>Cu>Cr>As>Zn, based on their single-element indexes. In the view of the potential ecological risk indexes, of all soil samples, about half had significantly high or high potential ecological risk, which covered more than 74% of the studied region. Most of the risks were 97.41% from Hg, Pb and Cd, especially, 84.37% from Hg. Both the single-element and potential ecological risk indexes indicated that, the ecological risk grades had a special spatial characteristic, and increased from northwest to southeast generally. This was agreed with the spatial distribution of the strength in gold mining activities over the studied region. The concentrations of Hg and Pb were higher than their relative backgrounds in the corps, and were even 9.48 and 25.09 times higher than their relative backgrounds in residents' hair, respectively. All these showed that the heavy metals in the soil had a high potential ecological risk, especially, had been affecting these crops' growing and yield, and even the residents' health through food strains. Obviously, these metals' potential ecological harm had been coming down to observed harm to the ecology. 相似文献
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