Spatial distribution of chromium in soils contaminated by chromium-containing slag

To evaluate the metal chromium (Cr) contamination of soil at a chromium-containing slag site by ferrochromium production, the contaminated sites, under slag heap, in the vicinity of slag heap and arable soils near the outlet of sewer channel, and unpolluted site 5 km away from one ferroalloy plant in Hunan Province, China, were selected. The concentrations of total Cr and water soluble Cr in bulk soil samples and profile depth samples were determined. The results show that the soils in the vicinity of slag heap have the highest total Cr content followed by the soils under the slag heap and near the outlet of sewer channel of the factory. The mean concentrations of total Cr in the top soils at above three contaminated locations exceed the critical level of Secondary Environmental Quality Standard for Soil in China by 3.5, 5.4 and 1.8 times. In most Cr polluted soils, total Cr has a relative accumulation in soil depth of 40-60 cm, but this trend is not found in unpolluted soils. The average concentrations of water soluble Cr (Ⅵ) in top soils under slag heap and in the vicinity of slag heap are 176.9 times and 52.7 times higher than that in the uncontaminated soils, respectively. However, water soluble Cr (Ⅵ) contents in soils near sewer channel are all low and the values are close to that in the uncontaminated soils. Although water soluble Cr (Ⅵ) content in soil profiles decreases with soil depths, it in soils under slag heap maintains a high level even at a depth of 100-150 cm. The results imply that the transportation of Cr (Ⅵ) can result in a potential risk of groundwater system in this area.     

Immobilization of Cr (VI) in stainless steel slag and Cd,As, and Pb in wastewater using blast furnace slag via a hydrothermal treatment

The immobilization of hexavalent chromium in stainless steel slag using blast furnace slag as the immobilizing agent and by performing a hydrothermal treatment was investigated. The results showed that there was no immobilization in the absence of the blast furnace slag. On the other hand, the hexavalent chromium in stainless steel slag could be immobilized through the hydrothermal reaction when blast furnace slag was used at 250 °C for 24 h. A leaching test was performed to evaluate the degree of immobilization of hexavalent chromium in the products formed by the hydrothermal reaction. It was found that the degree of immobilization was very high. Based on the results obtained, the immobilization mechanism of hexavalent chromium in stainless steel slag, resulting from the hydrothermal treatment of blast furnace slag, could be elucidated. Finally, the immobilization of cadmium, lead, and arsenic using blast furnace slag as the immobilization agent was also studied while focusing on the effects of the hydrothermal treatment.     

铸件表面合金化层性能研究

针对采用水玻璃、树脂等作为粘结剂进行铸件表面合金化时，合金层中容易产生气孔、夹渣缺陷的问题，研究了一种铸件表面合金化新工艺，即加入一种YB成型剂将合金粉末压制成块的方法进行表面合金化，在铸钢ZG65Mn本体表面得到高含Cr、W等元素的合金化层。结果表明，通过消失模铸造工艺，使用YB成型剂较好地消除了水玻璃等粘结剂造成的气孔、夹渣，合金化层和本体之间实现了冶金结合；合金化层具有较好的耐磨性和耐热性能，加入WC后耐磨性可达本体材料的4．82倍，抗氧化性能提高50％左右，且合金化粉末压块放置操作简便、可靠。     

高硼铸钢锤头的研究和应用

利用新研制的高硼耐磨铸钢制造锤头,由于其硼化物的显微硬度高(1400～1600Hv)且孤立分布,基体是强韧性好的板条状马氏体,锤头使用中不易磨损和剥落,基体抗疲劳能力强,不易产生裂纹,锤头耐磨性好,使用寿命达到高锰钢锤头的4倍以上,比中铬合金钢锤头和镍硬I号铸铁锤头寿命分别提高55.8%和41.9%。高硼铸钢锤头合金加入量少,生产工艺简便,生产成本与高锰钢相当,比中铬合金铸钢和镍硬I号铸铁降低40%以上。使用高硼铸钢锤头,使材料消耗降低,减少了更换次数,提高了生产作业率。     

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.     

涡流贫化法回收铜渣中的金、银、铜

采用熔融铜渣为原料,经过涡流贫化过程,回收铜渣中的金、银、铜,贫化渣进一步升温还原得到含铜铁水,最终可制备成耐磨铸铁。结果表明,通过涡流贫化,铜渣中的Fe_3O_4被还原为FeO,然后FeO与SiO_2结合,生成Fe_2SiO_4。经过涡流贫化后,金、银、铜的回收率分别达到了99.44%、93.97%和93.14%。贫化渣中Fe_3O_4和铜的含量分别为1.53%和0.61%(质量分数)。贫化渣涡流还原后得到的含铜铁水制备的耐磨铸铁成分满足高铬耐磨铸铁国标要求。     

利用铬渣制备耐火材料

从铁合金生产中排出的是一种有害废渣,而且排放量日益增加,对环境造成极大危害.本研究采用铁合金厂排放的含铬废渣,将废渣与镁砂以不同比例混合,测试了试样的体积密度、气孔率、常温耐压强度等常温性能,并用电镜对部分试样进行显微结构观察和矿物成分分析.结果表明:铬渣镁砂复合耐火材料的生产是可行的,在经过烧成后材料中生成大量的尖晶石和镁橄榄石相,试样的性能良好,完全可满足耐火材料使用的要求.当铬渣的加入量超过40%(质量分数, 下同)时,复合材料的性能下降较大,综合各项指标来看,为保证使用性能,铬渣的加入量应小于40%.     

The weldability and properties of joints welded in new-generation creep resistant steels: HCM12A steel

HCM12A (ASME T122) steel, containing 10-12% chromium and 2% tungsten, is made by the Japanese companies Sumitomo Metal Industries and Mitsubishi Heavy Industries, and is intended for fresh steam superheaters. The aim is to increase the resistance to corrosion at elevated temperatures over that of steels containing 9% chromium, e.g. P91, P92, and E911. This steel, a modification of HCM12 alloy, has a di-phase structure of tempered martensite and some 30% delta ferrite. The resistance to creep of HCM12 steel is higher than that of HCM12 alloy and is close to that of P92 material (see Fig. 8 in Ref. 7). Basic characteristics of HCM12A steel are quoted in an article published earlier.     

Chromium depletion profiles after preferential removal of chromium from alloys

Chromium depletion profiles and surface concentrations were determined from vacuum annealed and oxidized 18/8 type stainless steels by serial sectioning after neutron irradiation, energy dispersive X-ray analysis and Auger electron spectroscopy.It was established that with vacuum annealing and with selective oxidation of chromium in austenitic stainless steel the rate of chromium loss from the alloy is controlled by a balance of chromium diffusion in the metal and the rate of interchange of chromium from the alloy surface to the vacuum or oxide respectively. An analysis for the variation of the metal surface chromium concentration with time was derived. According to this analysis the metal surface chromium concentration decreases with increasing oxidation or vacuum annealing time, the rate of decrease depending on two parameters, chromium diffusivity in the metal and an interface transfer coefficient.     

引流砂对钢液氧含量的计算分析

从对提高钢铁产品洁净度的实际意义出发,对引流砂进行了简单介绍,在此基础之上计算分析了某钢厂使用的引流砂对钢液中氧含量的影响。经过理论计算,得出了由于引流砂随着钢包的开浇进入中包后滞留在熔渣中,增加了熔渣的氧化性。根据氧在熔渣和钢液中的平衡关系可知,引流砂会增加钢液中氧含量,降低了钢液的洁净度。     

电弧炉生产低磷合金钢P22管坯工艺实践

介绍了以废钢和没有经预处理脱磷的高磷铁水为原料,采用电弧炉生产低磷合金钢P22(P含量小于0.008%)的冶炼工艺。通过电弧炉早期造渣提前脱磷,用石灰作脱磷剂,采用大渣量、多次换渣等工艺,高碱度与高氧化铁的合理匹配和熔池的强烈搅拌以及高温抑制回磷技术,实现电弧炉初炼钢水P含量小于0.003%。通过控制铁合金增磷和炉渣回磷技术措施,采用电弧炉冶炼工艺,可批量生产出高质量的低磷合金钢P22连铸管坯。     

The Electrodeposition and Properties of Black Lead Peroxide Coatings

Electrodeposited coatings of tin-nickel alloy and of nickel/chromium on steel and on brass were exposed to atmospheric corrosion out-of-doors in four localities and indoors. The alloy coatings remained bright in all tests, but suffered some disfigurement out-of-doors especially near the sea, from pore-spotting. The nickel/chromium coatings lost some lustre, especially if sheltered from rain, and became stained by corrosion product from the basis metal. For comparable thicknesses of coating, indoors and outdoors, except by the sea, tinnickel retained a better over-all appearance, but out-of-doors with periodic cleaning, nickel/chromium sometimes looked the better of the two for a short time after cleaning. For both coatings, thicknesses of 0·0016 in. on steel or 0·0012 in. on brass were inadequate to ensure a sufficiently low level of pore corrosion in severe outdoor exposure.     

有效利用合金废钢,大幅降低冶炼成本

我们对铬、镍、钼合金废钢进行细化分类,并根据P含量的不同采用返回法或氧化法进行冶炼.在保证炼钢投料正常进行的前提下,降低炼钢成本,提高铬、镍、钼合金废钢利用率.     

Three-body Impact Corrosion-Abrasion: Studying for Low Carbon High Alloy Liner in Ore Grinder

The impact-corrosion-abrasion resistance of the low carbon high alloy steel, which can be used for mill lining under impact-corrosion-abrasion condition, are tested in laboratory by means of a new kind of experimental facility. The industrial trial run in the same condition has also been completed. The results show that the new alloy containing 0.2 wt.% carbon, 9 wt.% chromium, and 2 wt.% nickel is consisted of lath martensite entirely, and is more than two times superior to Mn13 cast steel in impact-corrosion-abrasion resistance. Spelling is the leading wear mechanism in impact-corrosion-abrasion condition for this alloy, which is lighter than that of high manganese steels because of its better hardness-toughness match.     

小方坯9SiCr铸坯渣沟成因分析及改进措施

宣钢在生产高碳合金工具钢9SiCr过程中铸坯表面出现严重的渣沟缺陷,严重的还会导致渣沟漏钢问题。针对这些问题通过现场调研和数据分析,研究了钢种特性、钢水成分和连铸保护渣性能,得知钢中氢的质量分数高、连铸保护渣性能不匹配、连铸工艺匹配性存在问题是导致渣沟及渣沟漏钢产生的主要原因。通过将钢中氢的质量分数控制为0.000 17%~0.000 23%,将保护渣的碱度从0.83降低到0.71,并添加质量分数为0.8%的Li₂O,调整连铸工艺参数将浇铸温度控制为1 480~1 495 ℃、水口插入深度为100~120 mm和结晶器锥度为1.2%~1.5%/m,最终解决了9SiCr铸坯出现渣沟及渣沟漏钢的问题。     

水钢100 t转炉出钢过程回磷分析与实践

转炉出钢过程常伴有钢水回磷现象,导致钢水磷含量上升甚至出格,影响钢材成品质量和经济技术指标。为有效控制转炉出钢过程回磷,通过现场取样、数据采集、模拟试验及FactSage软件分析了出钢过程钢水回磷机理,研究探讨了渣中FeO、SiO₂、出钢温度、钢包渣碱度对回磷的影响。研究结果表明,出钢过程下渣,渣中FeO含量与出钢温度过高,钢包渣SiO₂含量与碱度不在合适范围均会增大钢水回磷率,最高达41%。结合水钢生产实践,出钢温度控制为1 625~1 640 ℃、转炉终渣FeO质量分数为15%、钢包渣碱度为3.6~4.1、控制含硅合金加入、控制出钢过程下渣量的条件下,可高效调节出钢过程回磷,将回磷率降低至15%以下。通过控制出钢温度、终渣FeO、碱度等,可有效降低因下渣导致的回磷。     

Sub-Scale Depletion and Enrichment Processes During High Temperature Oxidation of the Nickel Base Alloy 625 in the Temperature Range 900�C1000?��C

Numerous chromia-forming austenitic steels and nickel-base alloys contain chromium-rich strengthening precipitates, e.g. chromium-base carbides. During high temperature exposure the formation of the chromia base oxide scale results in chromium depletion in the alloy matrix and consequently in dissolution of the strengthening phase in the sub-surface zone. The present study describes the oxidation induced phase changes in the chromium depletion layer in case of alloy 625, a nickel base alloy in which the strengthening precipitates contain hardly any or only minor amounts of chromium. Specimens of alloy 625 were subjected to oxidation up to 1000 h at 900 and 1000 °C and analyzed in respect to oxide formation and microstructural changes using light optical microscopy, scanning electron microscopy, energy and wavelength dispersive analysis, glow discharge optical emission spectroscopy, and X-ray diffraction. In spite of the fact that the alloy precipitates ??-Ni₃Nb and/or (Ni, Mo)₆C contain only minor amounts of chromium, the oxidation induced chromium depletion results in formation of a wide sub-surface zone in which the precipitate phases are depleted. However, in parallel, substantial niobium diffusion occurs towards the alloy surface resulting in formation of a thin layer of ??-Ni₃Nb phase adjacent to the alloy/oxide interface. By modeling phase equilibria and diffusion processes using Thermo-Calc and DICTRA it could be shown that the phase changes in the sub-scale zone are governed by the influence of alloy matrix chromium concentration on the thermodynamic activities of the other alloying elements, mainly niobium and carbon. The ??-phase depletion/enrichment process is caused by a decreasing niobium activity with decreasing chromium concentration whereas the (Ni,Mo)₆C dissolution finds its cause in the increasing carbon activity with decreasing chromium content.     

不锈钢冶炼渣铁浴熔融还原动力学实验研究

通过10 kg级小型不锈钢冶炼渣熔融还原试验,研究了不锈钢废渣在1 500～1 650℃温度范围内的熔融还原动力学行为,认为还原反应体现在两个阶段:反应初期不锈钢废渣熔解为反应的控速环节;而反应后期界面处的化学反应演变为反应的控速环节.从整体熔融还原试验上看,不同阶段对炉渣组成有着不同的要求:反应初期需要降低熔渣熔点,能有效促进形成液态渣,以提高不锈钢渣的熔解速度;反应后期需合理调节炉渣流动性以加速熔融还原反应.故可以通过炉渣参数优化以求在保证终渣的残铬达到较高回收的前提下尽可能提高熔融还原的速率.     

变质钨合金铸铁衬板的研究和应用

以钨渣铁合金为主要合金原料制造钨合金铸铁衬板,研究了稀土变质处理提高其使用寿命的可能性。结果表明,钨合金铸铁经适量稀土变质处理后,共晶碳化物由网状分布变成断网状分布,冲击韧性和耐磨性显著提高,变质钨合金铸铁用于制作混凝土搅拌机衬扳,使用安全、可靠,使用寿命与高铬铸铁和镍硬铸铁相当,成本降低50％～60％。     

High temperature oxidation of a commercial Cr-Mn austenitic steel in air

The oxidation of an austenitic steel containing 18% chromium and 12.3% manganese at 800-1000°C in air occurs at a slower rate than that of a steel containing 9.5% chromium and 17.5% manganese. However, the rate of corrosion of this 18% chromium alloy is still large in comparison with the case of formation of a continuous chromia scale at the base of the scale layer. This result is attributed to the negative effect of the manganese on the thermodynamic stability of Cr₂O₃.