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By Anne Kvithydl

Printed circuited boards contain considerable quantities of valuable metal, while also containing many environmental pollutants making them unsuitable for landfill. In this study the decomposition of common plastics used in printed circuit boards were studied. Polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC) and polyethylene (PE) were heated in both CO, and argon atmospheres using a thermo-gravimetric furnace (TG) coupled to a mass spectrometer (MS). Soda ash Na,C03 and baking soda NaHC03 were used as reactants. The degradation temperatures and evolved gases are presented for single plastics and mixtures. Mixed plastics are shown to behave as a sum of the individual plastics. The mass loss temperature is the same in CO, and argon. However, less residue is formed when heated in CO,.

Jan 1, 2008

By S. K. Utimurd, D. C. R. Espinosa, J. A. S. Tenório

"Waste Electrical and Electronic Equipment (WEEE) has become an environmental issue due to technological advance and waste plastic is one of the main polluters. The excessive discard of these plastics result in a difficult to dispose it to landfill and need further separation with technique in order to produce high added value plastics. There are many kinds of plastics in extensive use at the present time and the co=on are the acrylonitrile-butadiene-styrene (ABS) and high impact polystyrene (HIPS) used in the production of electric appliances. These plastics are difficult to separate because they have similar densities. Flotation of plastics is one possible separation technique and using selective wetting agents. The separation may be possible given close control at particle size and the concentration of the reagent. The process was able to produce a concentrate of HIPS with at least of 93% purity and a concentrate of ABS with 99% purity.IntroductionThe current situation of municipal solid waste (MSW) management especially in emerging economies like Brazil, the growing population and economic activity will result in a significant increase in the generation of waste in the coming decades. It is worthwhile to review and update the sources, amounts and recovery technologies of specific materials from waste, particularly from municipal solid waste (MSW).The growing impact of the current waste management practices stresses the need for a change in how waste is handled. The 2012 survey and the Brazilian Association of Public Cleaning and Special Waste Disposal Companies (ABRELPE) reports the generation of 62 Mt urban MSW in that year, which is an increase of 13% compared to 2011. It has been reported that in Brazil about 90.17% of the generated MSW is currently collected, which indicates an increase in the coverage of collection services compared to 2011 [ l]."

Jan 1, 2014

By Edmundo Manilla, Merete Tangstad, Daniel Davila, Eli Ringdalen

FeMn alloys are typically produced with lumpy ore or sinters. Minara Autlan, the Mexican FeMn producer, is however making Mn-nodules as a raw material for Mn-alloy production. The Mn nodules have been characterized by XRF, XRD, by wet chemical methods and by EPMA. The Mn/Fe ratio is somewhat lower compared to commercial Mn ore on the marked. The basicity of the ore is however close to 1, and additional fluxes may not be used. The Mn-nodules will be in a state of manganosite (MnO), tephroite ((Mn, Ca)2SiO4) and galaxite ((Mn,Mg)Al2O4). This leads to a low melting temperature area. A low porosity and low amount of higher Mn-oxides gives a high thermal strength to the nodules.

Jan 1, 2016

By Lichao Ding, Jingbiao Fan, Yunnen Chen

"With the development of industrial production, more and more wastewater containing high concentration ammonia nitrogen was discharge into the environmemt, which caused serious harm to the environmemt. Treating the wastewater has great significance to protect water resources. Using air-stripping combined with oxidation to uptake high concentration of ammonia nitrogen wastewater. The influence of operating parameters was investigated. Experimental results revealed that pH of solution, aeration time and aeration strength showed heavy influence on ammonia nitrogen removal. Air-stripping combined with oxidation can be considered as an alternative approach for the removal of high concentration of ammonia nitrogen from practical metallurgical wastewater. When pH was 11, aeration time 20 min, aeration strength 1040 Lh-1, and oxidation with 10 % NaClO solution 10 min, the initial ammonia nitrogen 2130 mgr1 could reduce to 12 mgr1. Other items could also be removed to meet the ""Integrated wastewater discharge standard (GB8978-88)"".1. IntroductionThe rapid development of human activities has caused a worldwide increase of nitrogen in rivers, lakes and coastal waters. It leads to considerable eutrophication and an increase in the frequency of toxic algae blooms [1,2]. The concentrations of nitrogen in the water of China are pervading high [3]. The discharge of wastewater containing high concentration of ammonia nitrogen is one of the most important factors. Great efforts have been devoted to the removal of ammonia nitrogen from wastewater. Traditional methods include biological denitrication [ 4 ], chemical precipitation with magnesium ammonium phosphate [5], electrochemical conversion [6], air-stripping [7] and so on. Biological denitrication is the most common process in the treatment of ammonia nitrogen wastewater. But the process is only suitable for the removal of relatively low ammonia concentration due to the requirement of appropriate C/N ratio [8]. Chemical precipitation needs additional reagents, which may introduce new pollutants to water body. Electrochemical method often uses expensive metal or metal oxide as electrodes, and also consumes large quantity of energy [6].Although air-stripping makes use of stripping tower and consumes energy, it is very suitable for the removal of relatively high ammonia concentration. Different air-stripping conditions would appear different removal efficiency. And only air-stripping the effluent can not be attained the ""Integrated wastewater discharge standard (GB8978-88)"". In this study, we use air-stripping and oxidation to removal high concentration of ammonia nitrogen from simulated and real ammonia nitrogen wastewater."

Jan 1, 2011

By Yuanbo Zhang, Guihong Han, Guanghui Li, Tao Jiang, Zengqing Sun, Yanfang Huang

"Because of small specific surface area and poor ballability, vanadium/titanium-bearing magnetite is difficult for production of oxidized pellet. A novel organic copolymer binder, modified humic acid (MHA), has been authorized recently in China. Effects of the novel MHA binder on the quality of V/Ti-bearing magnetite pellets are studied in this paper. Experimental results show the MHA binder can obviously improve the strength of green pellet. Because of better heat endurance, the MHA binder pellet has a higher strength than Peridur pellet under the same preheating conditions. Moreover, TFe grade of pellet with the MHA binder is much higher than that of the bentonite pellet. The strength of preheated pellet containing MHA binder of 0.25%~1.0% meets the requirements of oxidized pellet production by grate-kiln process. Comparatively, MHA is a promising orgainc binder for iron ore pellets. Its price is only one tenth of Peridur price and about 3 times of bentonite price.IntroductionThe iron-making practices show that the use of pellet is beneficial to blast furnace life, productivity and fuel savings. Therefore, many iron-making plants have expanded the production of oxidized pellets in order to meet the needs of modern large-scale blast furnaces [1]. Presently, bentonite is widely used to improve the quality of iron ore pellets. The negative effects of using bentonite include decreasing total iron (TFe) grade and degrading the metallurgical properties of the final products [2, 3]. Many studies, therefore, have been conducted on the application of organic binders to overcome the weakness of the inorganic bentonite. In comparison with inorganic binders, one of the biggest strengths of organic binders is low residual silica content [4]. However, those studies showed that the economics of foreign organic binder addition into pellets was not attractive. For example, the compression strength of preheated pellets and roasted pellets are both too low, resulting in powder generation and ring formation in the industrial rotary kiln [3, 4]."

Jan 1, 2011

By S. P. Mathew

The ISASMELT Lead Process is a continuous two stage process for the production of crude lead from concentrate. It is based on the use of a top entry submerged Sirosmelt lance to produce turbulent baths in which high intensity smelting or reduction reactions can occur. The process involves oxidizing the concentrates in the first stage to produce a high lead slag. This slag is tapped continuously and transferred down a launder to a second furnace where it is reduced with coal. Crude lead and discard slag are tapped continuously from this furnace through a single taphole and separated in a conventional forehearth. Process and engineering design work for a commercial scale Lead ISASKELT plant designed to produce 60000 tpa crude lead has been completed. This plant is planned to be operational in 1991.

Jan 1, 1990

By Wenjun Duan, Kun Wang, Qingbo Yu, Qin Qin

"A novel oxygen production technology noted chemical looping air separation (CLAS) was introduced and properties of Cu-based oxygen carriers used were investigated. The oxygen carriers were prepared by mechanical mixing. Al2O3, Fe2O3, ZrO2, TiO2 and SiO2 were used as binders during the preparation. XRD patterns show that spine! oxides are formed using Al2O3 and Fe2O3 as binders. Phases of CuO and binders keep stable using ZrO2, TiO2 and SiO2 as binders. BET values of oxygen carriers increase in the order of ZrO2>TiO2>SiO2>Fe2O3>Al2O3. The effects of temperatures, binders, particle sizes and flow rates on reduction/oxidation reaction rates were studied in TG experiments. The reduction reaction rate increases in the order of ZrO2>TiO2>SiO2. The effect of binders on the reactivity of oxidation is not obvious. The reduction and oxidation reaction rates both have the tendencies of increasing with the temperature increasing and with gas flow decreasing. However, the effects of gas flow and particle size are little.IntroductionChemical looping air separation (CLAS) is a novel oxygen production technology. The oxygen carriers used in CLAS release oxygen in reduction reactor and regenerate in the oxidation reactor. Selecting suitable oxygen carriers is the key for CLAS. Oxides of CuO, Mn2O3, Co3O4, Pb3O4, CrO2, SrO2, PdO2 and CeO2 have the property of releasing oxygen at suitable temperature and oxygen partial pressure [1]. Among these oxides, CuO, Mn2O3, Co3O4 are the most common compositions used to prepared oxygen carriers for chemical looping combustion (CLC) or chemical looping with oxygen uncoupling (CLOU) [2-5]. Moreover, thermodynamic calculations and preliminary experiments were carried out on oxides of Cu (CuO/Cu2O), Mn (Mn2O3/Mn3O4) and Co (Co3OJCoO) by Moghtaderi to ascertain their feasibility for CLAS process [6]. CuO has the highest oxygen transport capacity (0.1 g 02/g CuO compared to 0.03 g 02/g Mn2O3 and 0.06 g 02/g Co3O4). However, agglomeration is the biggest issue for copper oxides used at high temperature because of its low melting point (l 450°C for CuO, 1235°C for Cu2O and 1075°C for the mixture of CuO and Cu2O) [7]. In order to improve the capability of anti-sintering and stability ofCuO, binders (ZrO2, MgAl2O4, TiO2, SiO2, Fe2O3, Al2O3, cement) are added during the preparation of Cu-based oxygen carriers [8]. In this paper, the Cu-based oxygen carriers were prepared by mechanical mixing method. TiO2, Al2O3, Fe2O3, ZrO2 and SiO2 were selected as binder. XRD, BET and SEM were used to analyze the phase, surface area and surface morphology of oxygen carrier prepared. The reactivity of oxygen reduction and oxidation of oxygen carriers prepared were investigated in STA409PC thermal analyzer."

Jan 1, 2014

By Bo Jiang, Jiusan Xiao, Hongmin Zhu, Kai Huang, Shuqiang Jiao

Carbothermal selective reduction of simulative titanium slag and various titanium raw materials were presented and SiO2 was found to be partially reduced, forming a series of Fe-Si alloys during the process. Thermodynamic analysis of the selective reduction between TiO2 and SiO2 was performed using HSC 6.0 software, then a series of equilibrium experiments were designed and presented. The activity of Si reduced from SiO2 was affected by the presence of Fe reduced from FeOx and the generation of Fe-Si alloys, promoting the reduction of SiO2 in the whole process. The results of experiment are in great accordance with the calculated data obtained from thermodynamic analysis.

Jan 1, 2016

By Zhihao Yue, Honglie Shen, Yahui Teng, Ye Jiang

"In this paper, manganous nitrate [Mn(NO3)z] was used to assist the etching of silicon wafer in hydrofluoric acid (HF) for the antireflective application, and alumina (Al2O3) layer was deposited on the surface of the etched sample by atomic layer deposition method for further antireflection. The surface morphological and compositional studies of these samples were performed by scanning electron microscopy attached with an energy-dispersive X-ray spectrometer. The surface reflectance measurements were carried out using UV-Vis-NIR spectrophotometer. Binary structures of pyramids and nanopores were obtained by etching the alkaline textured monocrystalline silicon wafer in HF and Mn(NO3)z mixed solution for not more than 15 min. But excessive increase of etching time of up to 30 min resulted in the whole destruction of pyramids. The average reflectances of the 5-min-etched sample before and after being coated with 75-nm-thick Al2O3 layer are 4.62% and 3.47% in the range of 200-1000 nm, respectively.1. IntroductionAs we know, the reflectance of silicon wafer after being sliced is so high that the maximal photoelectric conversion efficiency of silicon based solar cells is limited. Therefore, alkaline texturization process was used for silicon solar cell in industrial production. But the reflectance of this alkaline textured wafer is still greater than 10% and this process can only be used for monocrystalline silicon solar cell."

Jan 1, 2013

By R. Hurman Eric

The dew-point technique of activity measurements take advantage of the volatility of a component in solution. The pressure of the volatile component over a sample is determined from observations of the temperature at which condensation of the vapor occurs. The method is applicable best when the vapor pressure of the components would differ by about two to three orders of magnitude. Experimentally, this is a closed system involving the use of evacuated and sealed transparent quartz sample probes. Furthermore reliable vapor pressure data of the volatile component is essential along with a specialized high temperature furnace capable of giving reproducible results. In this context, the vertical Dew-Point Furnace (DPF) was designed and built after elaborate trails until enough proficiency was gained for reprodueible results. Over the years the DPF was modified and improved. The DPF developed was versatile and could easily be used for activity measurements in the isopiestic mode (another method of measuring activities of a volatile component in a solution). The necessary ancillary systems; namely evacuation-flushing-evacuation followed by sealing of quartz sample probes under vacuum were also perfected over the years. As and when necessary the dew-point technique was supplemented by classical equilibration-quenching method employed on the sealed quartz sample probes to reveal necessary phase equilibrium information. The following were studied utilizing the above technique: (i) Activities in CuzS-PbS and FeS-PbS binaries and CU2S-FeS- PbS ternary at 1200°C; (ii) Activities in CuzS-SnS and FeS-SnS binaries and Cu2S-FeS-SnS ternary at 1200°C; (iii) Phase equilibria and thennodynamic in Cu-Pb-S, Fe-Pb-S, Fe-Sn-S, Cu-Sn-S and Ag-Sn-S systems. Most recently the following systems have been tackled: (i) Phase equilibria and thennodynamics in the Ag-Pb-S and Sn-Pb-S systems; and (ii) Activities in Ag2S-FeS-CuzS-PbS quaternary at 1200°C.

Jan 1, 2003

By Donald R. Sadoway

Molten salt electrolysis is a proven technology for the extraction of metals -- all the world's primary aluminum is produced in this manner. The unique properties of molten salts, also make them excellent media in which to treat a variety of forms of waste. Of special .note in this regard is electrolysis in molten oxides, a .concept put forward by. the author, initially as a ."clean technology" for producing primary metal. However, in the context of waste treatment, electroly-sis in molten oxides is a process offering the prospect of changing the. valence of dissolved heavy metals while making pure oxygen gas as the main by-product .Laboratory tests conducted at a temperature of 1550°C on chromate sludge dissolved in an melt composed of Al2O3 and MgO have confirmed electrochemical production of oxygen on a carbon-free anode.

Jan 1, 1996

By R. E. Johnson

The No. 3 reverberatory furnace at Phelps Dodge. Corporation's Morenci, Arizona copper smelter first received oxygen from a new oxygen plant during October 1982 and began operation with oxygen-fuel and oxygen sprinkle smelting burners which burn concentrate with oxygen. The furnace was completely converted to roof-mounted oxygen-fuel firing in October 1982. All conventional air-fuel bridge wall burners were extinguished at that time. The novel arch-mounted oxygen sprinkle smelting system began continuous operation April 1983. Since startup, unit fuel requirements decreased and furnace throughput significantly increased. Furnace off gas SO2 strength increased from an average of 1.5% SO2 to an average of 20% using only oxy-fuel burners. Oxygen sprinkle burner operation also has given excellent results, with the furnace off gas strength increasing to 35%-60% S02. There has been a reduction in overall arch temperatures, an increase in matte and slag temperatures, and a lowering of furnace bottom buildup with oxygen smelting. Furnace off gas is blended with converter off gas and treated in a sulfuric acid plant.

Jan 1, 1983

By R. D. Pehlke

The history and present status of continuous casting of steel are reviewed, including a genera 1 description of current processes. Plant layout, process development and elements of machine component design are outlined, and key steps in integration into a stee-1 production system are detailed. Recent productivity advances and improvements in quality are described. Process developments are reviewed, and some future avenues for this technology are considered.

Jan 1, 1985

By Fumio Hashiuchi, Yushiro Hirai, Masatoshi Maeda, Toshihiro Nagata

"Increase in the copper smelting capacity at Saganoseki Smelter & Refinery was attained through various improvements in the PSconverters and the flash furnace. Two of the major innovations in the converting process were: a new operational technology which avoids increase in the copper content in the converter slag even when higher copper grade matte (65%) are treated in the slag making stage and a technology which shortens the operational interruption time which is caused by coolant charging. The latter was realized by introducing a new automated coolant charging system with which it was made possible to charge the coolant without stopping the blowing into the converter. These improvements brought about a remarkable increase in · the production capacity per converter and an annual production of 450,000 tons of copper without adding new furnaces was made possible. In addition, good results have been obtained of the tests with modified tuyeres to further increase the production.IntroductionIn a bid to renovate its Saganoseki Smelter & Refinery and to establish a leading production unit in terms of global competitiveness, Nippon Mining & Metals undertook major restructuring efforts since 1994. One of its themes was the shift from· a two-flash furnaces operation to a single-flash furnace operation. The shift was successfully completed in 1996 while maintaining the production at the same level (330,000 tons per annum of copper). Then, the productivity was enhanced to 450,000 mtpy without adding new furnaces through technological and operational improvements. It is now planned to increase the smelting capacity further to 470,000 mtpy this year.Some technological and operational improvements in the matte converting process and the new plan resulted from the tests with modified tuyeres are presented in this paper."

Jan 1, 2000

By Lin Yang, Minjun Tang, Shuishi Liu, Jianfeng Zhou, Linjiang Qing, Xiaolei Song, Yufeng Guo, Tao Jiang

"The dynamics of oolitic hematite magnetic roasting was studied. The results show that oolitic hematite magnetic roasting was controlled by the internal diffusion, and the diffusion coefficient was 9.018x10-7 m2·s-1when the oolitic hematite was roasted at 650°C. Magnetic susceptibility improves when temperature increases and roasted time prolonges under the condition of roasting at 650°Cfor 50min, with the magnetic susceptibility is 39.88%. CaF2 and Na2C03 can significantly improve the magnetic susceptibility at the same roasting condition, and the magnetic susceptibility was 63.35% and 57.99% respectively, thus the reduction of oolimic hematite was promoted.IntroductionWith the continual depletion of free-milling iron ores and its rising price, developing the abundant resources of oolitic hematite has become one of the main research areas. The oolitic hematite accounts for 10% of China's iron ore reserve, and it also accounts for 30% of red ore reserve in China [1]. In order to exploit the oolitic hematite, there are many beneficiation research methods, including fine grinding/selective flocculation/high intensity magnetic separation or flotation, high-gradient magnetic separation, low intensity magnetic separation/high intensity magnetic separation/reverse flotation, chloridizing roasting/acid pickling, magnetic roasting/leaching process etc [2]. However, the oolitic hematite is easy to slim and the valuable mineral is covered by the slim, because of the tiny granule of value mineral, then the ooides are formed due to the state of layer morphology formed by iron ore and ganaue minerals [3, 4]. Fairly good separation indexes were hard to be obtained by traditional separation due to its structural features, so the magnetic property of the iron minerals will be changed with the use of the magnetic roasting [5, 6], which result in hematite variably altered to magnetite and simplified technological process so that a good separation indexes will be obtained by using the low intensity magnetic separation. Therefore, in order to provide theoretical direction of how to use the oolitic hematite effectively through the magnetic roasting, the oolitic hematite of GuiZhou province was studied, which emphasized on researching the dynamics of oolitic hematite magnetic roasting."

Jan 1, 2013

By Yongqi Sun, Zuotai Zhang

Hot slags, at the temperatures of 1450-1650 oC, carry a substantial amount of high quality thermal energy, which represents the largest undeveloped energy source in the steel industry. However, the waste heat recovery rate in China is less than 2%; thus there is a great potential of waste heat recovery. In this study, we investigated a chemical method to extract the waste heat from high temperature blast furnace slags, i.e., sludge gasification. Sewage sludge, another substantial waste produced in the municipal system, need to be timely disposed, the organics of which could be gasified using the waste heat in the slags for the purpose of syngas production. Both the kinetics and thermodynamics of the sludge gasification process were clarified here. Most importantly, an integrated system composed of multiple systems such as the steel industry, the cement industry, the municipal system and the chemical engineering industry, was analyzed in this study.

Jan 1, 2016

By Yuanbo Zhang, Qian Li, Helei Zhang, Heng Yu, Guanghui Li, Tao Jiang

"Large reserves of specularite iron ores have been found all over the world, which is characterized by high total iron grade, low gangues content, as well as low commercial price. However, it has not been widely used in sinter or pellet production due to its inferior sintering and roasting behaviors. It has shown that the proportion of specularite ores was increased as high as 40%~50% and good results was achieveed by using Composite Agglomeration Process (CAP), an innovative agglomeration process invented by Central South University. But the mineralization of specularite is still unknown during composite agglomeration processing. In this paper, the induration characteristic of specularite ore is studied by simulating CAP in laboratory, as well as microstructure analysis of CAP product. The results show that specularite pellet is mainly indurated through recrystallization of Fe2O3, calcium ferrite within high basicity sinters matrix interweaves with the recrystallized Fe2O3 on the surface of the pellet, which forms an integral microstructure, and ensures high strength of CAP product for ironmaking.IntroductionLarge reserves of specularite iron ores have been found all over the world, especially in Minas Gerais of Brazil, Xuanhua city and Anshan city of China, Elba island of Italy, St.Gotthard of Switzerland, Cumberland of Britannic, and so on. The specularite ores have a smooth surface, as well as a good crystallization and dense texture. When specularite is used to produce pellets, the specularite ore grains are difficult to adhere onto green ball due to its poor ballability. Moreover, specularite pellet requires high roasting temperature over 1300°C [1]. When specularite ore is used in sintering, the permeability of sintering bed gets bad and the quality of sinter is diminished. The practice in a few sintering plants finds that the output and strength of sinter decrease with the increase of specularite proportion, and the consumption of coke increases [2-4]. Therefore, the utilization of specularite has been limited. Composite Agglomeration Process (CAP) is an innovative technology invented by Central South University [5-7]. The process has the following merits: making reasonable utilization of different iron ore resources; improving the quality and output of sinters; manufacturing sinters with low basicity; significantly reducing energy consumption, etc[8-9]. It has been shown that large proportion specularite ores, as high as 40%~50% can be used well by CAP [10], but the mineralization of specularite pellet is still unknown during composite agglomeration processing. In this investigation, the induration characteristics of specularite ore pellets is studied by simulating CAP in laboratory, and the phase composition and microstructure of CAP product are also characterized by using microscope and Leica image analyzer (Germany, Leica DM RXp)."

Jan 1, 2011

By V. Baltazar

The behaviour of arsenic and antimony during copper electrorefining was studied in order to identify the conditions under which good quality copper cathodes could be produced from anodes with high levels of these impurities. Examination of the effect of current density over the range 21 to 37 mA/cm2 indicated that the relative amounts of As and Sb entering the electrolyte affected the onset of passivation. When the ratio of As/Sb entering the electrolyte was greater than 2, the anodes showed no sign of passivation even at the highest current density; when the ratio was less than 2, the anodes passivated at 37 mA/cm2. Cathode analyses showed that anodes with an As/Sb dissolution ratio less than 2.0 tend to produce cathodes of inferior quality even at normal current densities (25.7 mA/cm2). The criterion of a minimum As/Sb dissolution ratio of 2.0, and mathematical correlations for the distribution of As and Sb between the electrolyte and slime developed in a previous study, allow the calculation of the maximum allowable Sb level in en anode for a given As concentration. Analyses of plant data at the CCR Division of Noranda Inc. for the last four years of operation have demonstrated that the use of this as a quality control tool has allowed the quality of copper cathodes to be maintained despite a significant increase in the average Sb levels in anode receipts.

Jan 1, 1987

By Masao Miyake, Eiichiro Matsubara, Tetsuji Hirato, Yasuhiro Awakura

"Zn-Cr alloy coating with around 15 wt% Cr has been found to have much higher chemical corrosion-resistance to steel than conventional zinc plating, while· its structure has not been clarified. The Zn-Cr alloy plating is performed at high current densities around 1 A cm-2 and for 10 to 20 sec using acidic aqueous sulfate solutions with some additives in the iron-steel industry. Due to the high current densities, it seems reasonable to consider that the Zn-Cr alloy plating proceeds under an unsteady-state condition and that the resulting coatings have a non-equilibrium phase and have a structure change in the .direction of thickness. In this research, the crystal structure of the Zn-Cr alloy coating electrodeposited at high current densities and change of the structure in the direction of thickness were examined by X-ray diffraction. The coatings containing under 20 and 35-40 wt% Cr had hcp and bee structure, respectively, while the coatings containing 20-35 wt% Cr comprised two phases with the hcp and the bee structure. The structure of the coating varied in the direction of thickness; both the hcp and bcc phases coexisted in the vicinity of the substrate, while the hcp phase became predominant with increasing distance from the substrate.IntroductionRecently it has been reported that Zn-Cr alloy coating containing around 15 wt% Cr has much higher corrosion-resistance to steel than conventional zinc plating.1-3) The corrosion-resistanc·e of Zn-Cr alloy plated steel sheet with a plating amount of 20 g m·2 is, for example, superior to that of Zn plated steel with a plating amount in the range 60 to 90 g m·2 , which is widely used for automotive bodies today.4l The Zn-Cr alloy plating is obtained by electrodeposition at current densities over 0.5 A cm·2 from a sulfate solution containing zinc and trivalent chromium ions and some additives.5•6) The deposition current densities mentioned above are much higher than those for usual electroplating processes, e.g., Zn, Cu and Ni plating, carried out about 0.05 A cm·2 • Therefore, the time required for plating is very short; around 10-20 sec. Due to the high current densities, it seems reasonable to consider that the· Zn-Cr alloy plating proceeds under an unsteady-state condition and that the resulting coatings do not have a phase expected from equilibrium diagrams; no phase diagram of the Zn-Cr system with a full composition range has been available. 7). In other words, the alloy phase plated would be a non-equilibrium phase with unknown structures."

Jan 1, 2000

By E. A. Werner, A. Pichler, A. Spalek, G. Reisner, P. Stiaszny

"Interstitial free (IF) sheet steels are used for complex shaped parts because of their excellent formability. If a deep drawn part is subjected· to a impact deformation at low temperature brittle fracture of the part may occur. This phenomenon\ is called secondary work embrittlement (SWE). One possibility to characterize this material/structural behavior is the drop-weight test. The result of .this .test is a temperature at and below which a crack can initiated in a deep drawn part under the investigated set of parameters. This paper addresses the influence of the preforming process on the sus- . . ceptibili.ty of IF steels to SWE.IntroductionInterstiiial:free (IF-) steels are frequently used in the automotive industry for complex· shaped p·arts because of their excellent deep drawability. The microstructure of the steel consists of a highly ductile ferritic matrix with embedded precipitates of nitrides and/or carbides. Brittle fracture can occur in deep drawn parts, if they are subjected to a high speed deformation at lo""w temperature. This phenomenon is called ~econdary Work gmbrittlement (SWE) [1-11]. Up to now there are no standardized testing procedures available to quantify the sensibility of IF-sheet steel to SWE. Neveitheless, a reasonable testing procedure which allows to quantify the tendency of a predeformed part to SWE is necessary for further material development. A commonly used test method is the drop-weight test performed at low temperatures. In such ·tests a cone-like drop weight expands a deep drawn cylindrical cup [l-3, 6, 8, 9, 11]. From this expansion experiment the temperature is determined at and below which a brittle crack can be initiated in the deep drawn cup under the investigated impact test parameters. The highest measured temperature at which a deep drawn cup fails by brittle fracture is called frack appearances !emperature (CAPT). The lower the value of the CAPT the lower is the sensibility of a deep drawn part of IF-sheet steel to SWE. This paper aims to clarify the role of the preforming process on the impact behavior of an IF steel. For this purpose a numerical analysis of the deep drawing process and cup expansion tests are conducted."

Jan 1, 2000