Garnets: Structure, compressibility, dynamics, and disorder

The structure and properties of anhydrous end members of the garnet family were investigated by quantum mechanical calculations as a function of applied pressure. The results were used to analyze the compression mechanism of the garnet structure. Hydrogrossular and hydropyrope were also studied at ambient and high pressure; the experimentally observed difference in the stability of the hydrogarnet substitution in grossular and pyrope is explained here. In addition, the potential energy surface for magnesium in the pyrope structure is discussed in relation to vibrational properties and to possible cation disorder in pyrope. For more information, contact V. Milman, Molecular Simulations, the Quorum, Barnwell Road, Cambridge CB5 8RE, United Kingdom; telephone 44-1223-413300; fax 44-1223-413301; e-mail vmilman@msi-eu.com     

Experimental Investigations of Bend Force in Air Bending of Electrogalvanized Steel Sheets

This article deals with bend force behavior of electro-galvanized (EG) steel sheets in air bending process. A detailed experimental study was carried out on EG steel sheets of various coating thicknesses to investigate the influence of parameters such as coating thickness, orientation of the sheet, punch radius, die opening, die radius, and punch velocity on bend force behavior. From the results, it is found that zinc coating reduces the bend force and the increase in coating thickness reduces the bend force significantly. It is observed that the bend force is larger for larger punch radius, smaller die opening, and smaller die radius. It is also observed that the bend force is larger for 0° orientation than for 90° orientation. The bend force decreases with increase in punch velocity, and this influence is more prevailing in EG sheets than in plain sheets.     

The high-speed identification and sorting of nonferrous scrap

There are various approaches to sorting alloys. Perhaps the most simple method and one which is in greatest use today is hand sortation, which is normally a rather inaccurate process. An opportunity exists to recover low-grade nonferrous scrap by sorting it into various alloys with high accuracy by applying spectrographic analysis techniques. This article presents an alternative method for scrap identification and sortation in which optoelectronics are utilized to make a rapid and accurate identification of the scrap item. The scrap is then sorted automatically without operator intervention. Editor’s Note: A hypertext-enhanced version of this article is available on-line at www.tms.org/pubs/journals/JOM/0504/Spencer-0504.html For more information, contact David B. Spencer, Spectramet, LLC, 7 Alfred Circle, Bedford, MA 01730; (781) 275-6400; fax (781) 275-8612; e-mail ccfwte@aol.com.     

Hydrometallurgically recovering zinc from electric arc furnace dusts

The increasing use of zinc-containing scrap for steel production has lead to a high zinc content in the electric arc furnace and converter flue dusts. The cost of disposing of this residue is high due to environmental restrictions. Various recycling processes have been developed for these dusts, but most never reached the pilot plant stage and many investigations were stopped because of metallurgical and economical inefficiencies. While pyrometallurgical methods have to deal with high energy consumption, low zinc yield, and valueless residues, hydrometallurgical processes could offer an economical recycling alternative. This paper describes hydrometallurgical methods for recovering zinc from steel industry dust. These methods can be integrated in the primary zinc-winning process or in galvanization. Investigations of sulfuric-acid leaching show high zinc solubility but also a high iron content in the final liquor. As a result, steps for purification are required that cannot be conducted economically. Alternatively, a NaOH leaching gives a satisfying zinc yield and a very low solubility for the iron that remains in the residue. For more information, contact J. Antrekowitsch, University of Leoben, Nonferrous Metallurgy Department, Franz-Josef-Str. 18, Leoben, Styria A-8700, Austria; +43-3842-402322; fax +43-3842-402627; e-mail antreko@unileoben.ac.at.     

关于钢铁工业废钢资源的基础研究

强调了钢铁工业多用废钢,少用铁矿石的重要意义,构思了一张有时间概念的钢铁产品生命周期铁流图,提出了衡量钢铁工业废钢资源充足程度的指标－废钢指数（Ｓ）,并研究了它与钢铁产品产量变化等因素裼 关系,利用本语文提出的思路和方法,可以具体地分析各国各地区的钢铁工业废钢资源问题。     

Analysis of ductile iron production on steel scrap base

The cast iron production (melting) process is commonly based on pig iron. However, economic and ecological factors necessitate that the melting process is more often based on steel scrap (with no pig iron at all). This kind of cast iron is called synthetic cast iron. This approach may, however, cause a decrease in the quality of the alloys obtained, particularly when ductile iron (DI) is produced. The following article presents an analysis of the product and some aspects of ductile iron produced exclusively on a base of steel scrap. The experiments and the charging materials are described. The results of the chemical analysis of the produced DI, the carburisation efficiency and microstructure of the obtained material are presented as well. The results of cast iron melted on a pig iron base are presented for comparison. A quantitative microstructure analysis is also presented.     

Recycling used automotive oil filters

Over 400 million used automotive oil filters are discarded in the United States each year, most of which are disposed of in landfills wasting valuable resources and risking contamination of ground- and surface-water supplies. This article summarizes U.S. bureau of Mines research evaluating scrap prepared from used automotive oil filters. Experimental results show that crushed and drained oil filters have a bulk density that is higher than many typical scrap grades, a chemical analysis low in residual elements (except tin due to use of tin plate in filters), and an overall yield, oil-filter scrap to cast steel, of 76% to 85%, depending on the method used to prepare the scrap.     

Effect of cations on corrosion of zinc and carbon steel covered with chloride deposits under atmospheric conditions

The effect of sodium, calcium, and magnesium chlorides deposited on zinc and carbon steel surfaces was studied under atmospheric conditions. The cations strongly affected the corrosion rate of zinc, whereas they had a significantly lower impact on the corrosion of carbon steel. The corrosivity of cations of chloride salts for zinc increased in order of Mg²⁺ < Ca²⁺ < Na⁺. The higher corrosion resistance of zinc treated with calcium and magnesium chlorides was connected to prevention of formation of hydrozincite during zinc exposure in wet air. It was observed that zinc weight loss and the carbonate to simonkolleite ratio in corrosion products were correlating. The principal protective effect of bivalent cations can be seen in the decrease of pH of the surface electrolyte, which was caused by hydrolysis of such cations and subsequent formation of simonkolleite that blocked the cathodic sites.     

酒钢CSP工艺薄板坯增氮分析

对酒钢CSP工艺采用的转炉+精炼+连铸+热轧生产线薄板坯的增氮原因进行了调查研究。结果表明,原板坯平均氮含量56×10^-4%,超出了控制范围。从转炉终点到精炼出站过程是钢液增氮较大的环节,这期间由于使用的废钢和合金的氮含量较高造成了精炼增氮。连铸过程中间包钢液并未出现与空气接触的现象,浇注过程的增氮主要来自大包下水口与长水口结合处密封不严密而吸入空气造成增氮。通过对废钢用量进行控制,使用氮含量较低的合金,控制精炼工艺及改进大包下水口与长水口结合处的密封能,使板坯的平均氮含量降至46×10^-4%。     

Zinc runoff from galvanised steel materials exposed in industrial/marine environment

Abstract

An investigation has been carried out to assess the zinc runoff from a variety of galvanised materials over 16 months at the industrial/marine Port Talbot weathering site. Over 16 months of exposure, bare zinc, and Electrozinc have the highest levels of zinc runoff (4·38 and 4·20 g m^-2) followed by general galvanised steel substrates, i.e. hot dip galvanised (HDG) steel (0·15 wt-%Al) (2·87 g m^-2) and iron zinc intermetallic galvanised steel (galvanneal, 2·36 g m^-2). Galvanneal (IZ) has a higher initial runoff rate than HDG due to the presence of iron/zinc intermetallic in the coating that promotes anodic zinc dissolution. The HDG has a more constant runoff rate that exceeds IZ after 7-8 months due to build up of corrosion products on the IZ surface. Aluminium/zinc alloy coated steels have a much lower runoff rate than general galvanised materials as the aluminium present in the structure provides a strongly protective oxide barrier coating improving corrosion resistance (Galfan 5 wt-%Al, 2·04 g m^-2, and Z alutite 55 wt-%Al, 0·67 g m^-2). Organically coated steels show relatively little zinc runoff (< 0·25 g m^-2) indicating their effectiveness in preventing surface corrosion. Runoff levels measured do not exceed permissible levels of zinc for drinking water and the measured zinc runoff levels pose little threat to organisms if leached into soil. Using an accelerated laboratory test in which distilled water is sprayed onto specimen panels in a recirculatory system for 100 h a good correlation can be obtained with external exposure for up to 6 months exposure. For 12 months exposure iron zinc intermetallic galvanising (galvanneal) begins to become covered in a protective oxide layer, which cannot form under the conditions of the accelerated test. Despite this, the fit for most specimen types is excellent. Where the predictive test fails is when the galvanising layer is breached revealing an efficient iron cathode site. This occurs first for electrocoated zinc after 16 months exposure. Similar predictive results can be obtained using a scanning vibrating electrode technique (SVET) in a semiquantitative manner and an immersion electrolyte of 0·1 wt-%NaCl. Again the predictions are initially very accurate but following 12 months exposure the fit for specimens of electrozinc is poor due to the breaching of the galvanising layer.     

水钢预应力钢绞线SWRH82B钢的冶炼工艺

水城钢铁集团公司根据GB/T24238- 2009质量标准和用户使用要求,确立了预应力钢绞线SWRH82B钢的内控成分（质量分数）：w(C)=0.79%～0.84%、w(Si)=0.15%～0.30%、w(Mn)=0.60%～0.90%、w(P)≤0.025%、w(S)≤0.015%、w(Cr)=0.25%～0.27%。采用高炉铁水→100 t顶底复吹转炉冶炼→LF炉精炼→150 mm×150 mm方坯连铸的工艺流程生产SWRH82B方坯,用于轧制SWRH82B盘条。采用的质量控制方法有：（1）采用含铝量低的合金脱氧,减少钢中的Al2O3夹杂物含量;（2）采用低氮增碳剂、低氮铁合金对钢水进行脱氧合金化,LF炉采用微正压操作,造好泡沫渣,埋弧精炼,连铸采用全封闭保护钢水浇注,使成品钢中的氮质量分数降到40×10-6以内;（3）将中间包钢水过热度控制在15～30 ℃,结晶器电磁搅拌频率5 Hz、电流320 A,铸坯拉速（1.73±0.02） m/min,二冷段气雾冷却比水量0.62 L/kg,将铸坯中心各种缺陷级别之和控制在3级以内。     

Impurity characterization of zinc-recycled WC-6 wt.% Co cemented carbides

The impurity levels of three WC-6 wt.% Co grades produced using new and zinc recycled powders, were characterized using several analytical techniques. One of the grades was produced from 70% mining scrap material which was subjected to the zinc reclamation process, while a second grade was produced from 100% zinc recycled powder of a new, un-used alloy. The spray dried granules and the sintered alloys were characterized using ICP–OES (inductively coupled plasma/optical emission spectrometry), XRD (X-ray diffraction), SEM/EDS (scanning electron microscopy/energy dispersive X-ray spectrometry), and micro-PIXE (proton induced X-ray emission). All grades had high purity levels of approximately 99%. Iron was found to be the main impurity in all the grades and was predominantly concentrated in the Co binder phase. The main source of the impurities was found to be the production processes and not the zinc reclamation process. The 70% mining scrap zinc recycled grade had the most homogeneous Co binder distribution, while the grade produced from new powders had the least homogeneous Co distribution. This difference is due to the additional levels of crushing and milling which the mining scrap grade underwent. The micro-PIXE analysis clearly demonstrated that powder production conditions, powder homogeneity, and recycling directly impact the microstructures of the sintered materials, and that production process contamination can be detected, quantified, and mapped within the microstructures to a depth approaching 30 μm.     

Laboratory studies of atmospheric corrosion—I. Weight loss and electrochemical measurements

Electrochemical studies have been performed with the atmospheric corrosion monitor (ACM) under thin layers of electrolyte which were drying out at R.H. < 100%. Galvanic couples (Cu/steel, Cu/zinc) and one-metal (steel, zinc) ACMs were used. Measurements were carried out as a function of R.H. and Na₂SO₄ concentration. In addition, weight loss data were collected under identical conditions in thin layer experiments for steel and zinc in 0.01N solutions of NaCl, Na₂SO₄, HCl, H₂SO₄ and distilled H₂O in air, air + 1 ppm SO₂, argon and argon + 1 ppm SO₂. The data obtained in air and air + SO₂ were compared to weight loss results in bulk solutions.The electrochemical technique makes it possible to follow the changes of corrosion rates with time. As observed in outdoor exposure, a large increase of corrosion rates occurs when the electrolyte layers become very thin, shortly before the surface dries out. These findings explain the results of the weight loss data which show for most environments a much larger corrosion rate than in the bulk electrolyte. An accelerating effect of SO₂ was observed for steel at higher R.H. values, while for zinc, no effect occurred in NaCl, Na₂SO₄ and H₂SO₄, but an inhibiting effect was measured in HCl and in distilled H₂O.Since weight loss and electrochemical data were recorded under identical conditions, it is possible to determine how accurately the ACM data reflect the true corrosion rate. It was found for Cu/steel ACMs that the electrochemical data follow the same trends as the weight loss data, but account for only about 20% of the corrosion rate. Due to larger scatter in the weight loss data, a similar efficiency factor could not be determined for Cu/zinc. For steel and zinc ACMs, the true Tafel slopes are not known, which makes a calculation of corrosion rates doubtful. The low cell efficiency is considered to be due to local corrosion of single cell plates and to i.r.-drop effects.Despite the fact that exact corrosion rates cannot, at present, be obtained from ACM data, the technique appears very valuable for following the changes of atmospheric corrosion behaviour and for time-of-wetness measurements.     

Lubrication using porous surface layer for cold drawing of steel wire

As a lubricant for steel cold working, metal soap on zinc phosphate coating is widely used. However the lubrication causes hazardous wastes, and hence an alternative system is demanded. The authors proposed to utilize porous layer on workpiece surface as a reservoir of liquid lubricant. In this study, 0.64%C steel wires were oxidized at 923 K under air and chemically reduced by pure hydrogen to form porous surface layer with pores 1–2 μm in diameter. In cold drawing with machine oil, the friction coefficient on the porous surface was 0.06, while that on normal surface was 0.11. The lubrication mechanism with porous surface is discussed.     

Cathodic electrolytic deposition of ZnO on mild steel

Abstract

The present paper deals with the deposition and characterisation of zinc oxide coatings on mild steel substrates by cathodic electrolytic deposition via a 0·1M zinc nitrate aqueous solution. The influence of the deposition parameters, such as applied cathodic potential and deposition time, on the growth of oxide coatings was also investigated. The protection efficiency of these coatings on the mild steel was examined by a potentiodynamic polarisation technique in 0·3M NaCl solution (pH?=?5·5, T?=?25°C). The obtained results showed that the ZnO coatings improve the anticorrosion performance of mild steel.     

Corrosion of superheater steel materials under alkali salt deposits Part 1: The effect of salt deposit composition and temperature

This paper is the first in a series of two reporting on results from an extensive laboratory-scale corrosion study where tailor-made well-characterized synthetic alkali salt deposits were used for corrosion testing of several steel materials used in or aimed for recovery boiler superheater tubing.

The corrosion testing was done in temperatures ranging from 450 to 600 °C. The synthetic alkali salt deposits, containing sodium, potassium sulfates and chlorides, were composed in such a way that their first melting temperature, T₀, and the amount of melt formed at this temperature, varied for each salt mixture.

The results showed on one hand that an increased amount of melt in the salt deposit increased the corrosion of the steel material markedly. The results showed, however also, that corrosion could take place at temperatures clearly below any melting of the salt deposits if the composition was suitable. This took place with salts that contained chlorine. Already a very low amount of chlorine in the salt caused corrosion at temperatures typical for superheaters in the recovery boiler. These effects are qualitatively well-known from earlier but it was surprising that already a very small amount of chlorine caused significant increase in corrosion.

To stress the importance of the deposit layer on the corrosion we introduce two new terms: (1) sub-T₀ corrosion, indicating corrosion taking place below any melting of the deposit and (2) super-T₀ corrosion, indicating corrosion taking place when the deposit contains melt.     

Zinc corrosion runoff process induced by humid tropical climate

Zinc and hot dip galvanized steel are frecuently used metals in building application. They have relatively good atmospheric resistance to corrosion, due to its oxidation in air and formation of protective rust on its surface, which acts as barrier between the metal and environment. However, some part of the rust can be dissolved by pluvial precipitations and water condensed on the metal surface. This process, called metal runoff, contributes for zinc dispersion in soils and waters. In order to make accurate estimation of zinc runoff induced by atmosphere in humid tropical climate, samples of pure Zn and hot dip galvanized steel have been exposed in the Gulf of Mexico. The data reveal that this process is strongly influenced by factors which determine the aggressivity of the environment (pluvial precipitations, cycles of dry and rainy periods, atmospheric pollutants, air humidity). High annual rates of zinc runoff (6.5 – 8.5 ± 0.30 g Zn m^?2yr^?1) were released, being the runoff 63 – 87% of the zinc corrosion rust. The zinc mass loss has been related to several independent parameters, presenting linear equation, which indicates the air contaminant SO₂ as the major factor controlling the runoff of zinc. The reported results show higher runoff of zinc samples, compared to that of hot dip galvanized steel     

Zum Elektrodenverhalten des Zinks und des Eisens in Calciumhydroxidlösung und in Mörtel

The electrode behaviour of zinc and iron in calcium hydroxide solutions and in mortar The behaviour of zinc (fine zinc and metallurgical zinc) and of unalloyed steel in a saturated calcium hydroxide solution and in mortar has been the subject of electrode-kinetic investigations. The observations showed that the behaviour of fine zinc, metallurgical zinc and galvanized steel is more or less identical, and that even the mortar coating has little effect on the electrode behaviour. It is found that

• (a) zinc is passivated by a zinc oxide layer;
• (b) the potential of a short-circuit cell consisting passive zinc and iron becomes so negative that hydrogen is developed at the iron at an appreciable rate;
• (c) the passivity Of the zinc in a solution containing chloride is removed at a much higher chloride concentration than that of steel.

In the case of a galvanized electrode with an electrolytically dissolved layer of pure zinc, the current/potential characteristic was similar to that of the passive iron.     

Atmospheric Exposure Trials of Electrodeposited Iron-Zinc Alloy Coatings

Abstract

Iron-zinc alloy coatings applied by electrodeposition have been tested for their protective quality on steel exposed to an industrial atmosphere. A coating consisting of iron 40% and zinc 60% was twice as corrosion-resistant as a zinc e1ectrodeposit of the same thickness. The improvement was more noticeable for the thicker coatings (1 or 2 mils) than for the thinner ones (0·1 or 0·5 mils). Coatings containlng from 50 to 80 % of zinc and the remainder iron were almost as good. The coatings developed a rather unattractive uniform dark grey-brown colour which was, however, clearly distinguishable from rusting of the steel. Resistance to damage, proteciion at scratches, the effect of superimposed paint films and the performance of the coatings in other atmospheres will need checking before they can be used commercially.     

热力参数对0Cr11Ni2MoV钢高温流变应力的影响

在Gleeble1500热模拟试验机上进行等温热模拟压缩试验,研究了热力参数(变形温度、变形速度和变形程度)对0Cr11Ni2MoVNb钢在变形温度950℃~1100℃、应变速率0.01~10s-1时的高温变形行为的影响。基于数理统计原理,科学分析并回归确定了合金在该温度范围下的变形激活能Q为429.48kJ/mol,应变速率敏感指数m为0.11059,得出了能综合反映热力参数对材料性能影响的本构方程。通过计算相关系数(R)和绝对误差的平均值(AARE)表明该本构有较好的精度,可对0Cr11Ni2MoVNb钢的流变应力进行很好的预测。