Cold and hot rolling of iron powder

Conclusions A BPMF atomized iron powder heated for 20 min at a temperature of 800, 900, 1000, or 1100°C is still characterized by good flowability, readily descends into the region of deformation, and can be rolled into strip. At a temperature above 1100°C this powder sinters into a bar, and can no longer be rolled. The mechanical properties of hot-rolled strips are an order higher than those of cold-rolled ones. Even so, the mechanical properties of strips produced by the hot rolling of the powder under the conditions of the experiments described are inferior to those of P/M parts shaped at room temperature and sintered under optimum conditions. In experiments on the hot rolling of powders between rolls with plain barrels it has proved impossible, because of axial splitting and edge cracking, to obtain nonporous strip of width up to 60 mm. The hot rolling of powders into narrow strips should be performed in closed passes; to reduce the cost of rolls, wide strips should be rolled hot between plain roll barrels, and their edges should then be trimmed.Translated from Poroshkovaya Metallurgiya, No. 10(226), pp. 13–18, October, 1981.     

Static recrystallization after hot deformation of α iron

The dependence of static recrystallization characteristics on deformation and annealing conditions has been examined for vacuum melted and zone-refined iron deformed in torsion at high temperatures in the α range. The kinetics of recrystallization are strongly accelerated by increasing deformation at low strains, but are virtually independent of strain in the “steady-state” region of the high temperature flow curve. In the latter case the kinetics of recrystallization are greatly influenced by the dynamic restoration process operative during hot deformation. In particular, for the same material, static recrystallization is faster in dynamically recovered than in dynamically recrystallized structures due to a decrease in growth rate with tie in the latter. This and other differences in the static recrystallization behavior of these two structures are discussed in terms of the differences in their microstructural features. This paper is based upon a thesis submitted by G. GLOVER in partial fulfillment of the requirements of the degree of Doctor of Philosophy at the University of Sheffield.     

攀钢铁水预处理脱磷剂开发初探

本文通过对脱磷影响因素的分析，通过实验和理论分析，得出铁水脱磷的临界脱磷条件。针对攀钢的铁水条件，提出了脱磷剂的大致配比。     

The acylation of megakaryocyte proteins: glycoprotein IX is primarily myristoylated while glycoprotein Ib is palmitoylated

The acylation of megakaryocyte proteins was studied with special emphasis on the myristoylation and palmitoylation of the glycoprotein (GP) Ib complex. Guinea pig megakaryocytes were purified and separated into subpopulations at different phases of maturation. Cells were incubated with [3H]myristate, [3H]palmitate, or [3H]acetate to study endogenous protein acylation. Cycloheximide was used to distinguish between cotranslational and posttranslational acylation and hydroxylamine to distinguish between thioester and amide linkages. After incubations, delipidated proteins or GPIb complex subunits, immunoprecipitated with PG-1, AN-51 or FMC-25 monoclonal antibody, were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and assessed by fluorography. Radiolabeled fatty acids bound to GPIX and GPIb were also analyzed by high pressure liquid chromatography (HPLC) and scintillation spectrometry. With [3H]myristic acid and [3H]acetate, GPIX was found to be a major myristoylated protein in megakaryocytes and CHRF-288 cells. Myristic acid was linked to GPIX by an amide bond, and this process occurred cotranslationally. With [3H]acetate, GPIb was primarily palmitoylated, but with [3H]myristate, GPIb was acylated with about equal mounts of myristic acid and palmitic acids. Both fatty acids were linked to GPIb by thioester bonds, and acylation was posttranslational. The myristoylation of GPIX while the palmitoylation of GPIb occurred throughout megakaryocyte maturation. Myristoylation and palmitoylation may have different functions relevant to the assembly of the GPIb complex in megakaryocytes.     

Behavior of direct reduced iron and hot briquetted iron in the upper blast furnace shaft: Part II. A model of oxidation

The high-temperature properties of the ferrous burden in the cohesive zone of the blast furnace (BF) are a function of its history in the upper shaft. It is considered that charging direct reduced iron (DRI) and hot briquetted iron (HBI) into the BF increases its efficiency and productivity. However, oxidation of DRI and HBI can occur in the low-temperature zone in the BF, which may affect their softening and melting properties. This work was designed to estimate the oxidation degree of DRI/HBI in the upper BF shaft. In this article, a model of oxidation was developed, which predicted that DRI and HBI can be oxidized up to 10 and 2 pct, respectively. The model was then put forth to a laboratory-simulated test and industrial simulated blast furnace (SBF) test for its verification. The results of SBF tests indicated that the oxidation of DRI/HBI occurs in a temperature range of 700 °C to 950 °C with the gas compositions used for the tests. The morphology of iron in DRI is expected to exhibit Fe-FeO-Fe layers in varying thickness at the beginning of the cohesive zone. The oxidation in HBI briquettes is primarily limited to its external surface. These results indicate that the impact of oxidation of DRI/HBI on the cohesive zone will not be significant.     

Effect of particle composition on consolidation of hot briquetted iron

Abstract

The influence of the carbon concentration of directly reduced iron (DRI) powders on the compressibility and fracture strength of hot briquetted iron (HBI) has been studied. Industrially produced DRI, pure iron powder and Fe–C alloy powders (synthetic DRI) were used in the study. It was found that the mechanism of compaction could be attributed to pure yielding. The pressure required to attain a given density increased proportionally with the carbon content. The morphology and phases present in DRI powder had a significant influence on the compressibility. The fracture strength of the compacts increased with increasing carbon content of the DRI powder. These observations are discussed with reference to the current understanding of the mechanisms of compaction and fracture of compacted particulate materials.     

Kinetics and mechanism of corrosion of laboratory hot briquetted iron

While considerable work has been reported in the literature on the corrosion behavior and products of direct reduced iron and sponge iron, very little has been published on hot briquetted iron (HBI). The present article reports the kinetics and mechanism of HBI corrosion. As corrosion is an electrochemical process, measurements using electrochemical techniques have been made and these are compared to data gained by measuring mass changes in the briquettes over time. Similar trends were seen in data from both techniques, and the corrosion extent predicted by electrochemical measurements in saline solution was very close to the mass gain result obtained. Kinetic analysis of the data from mass gain over time trials was conducted. The activation energy for corrosion at temperatures between 25 °C and 80 °C has been calculated. The values of activation energy obtained indicate that corrosion was predominantly controlled by diffusion of oxygen in the liquid state. The internal structure of the briquettes was observed by microscopy both before and after corrosion in distilled water.     

Why is word recognition impaired by disorientation while the identification of single letters is not?

Past research has shown that speed of identifying single letters or digits is largely indifferent to orientation, whereas the recognition of single words or connected text is markedly disrupted by disorientation. In a series of four experiments, we attempted to reconcile these findings. The results suggest that disorientation does not impair the identification of the characters but disrupts the perception of their spatial arrangement. When spatial order information is critical for distinguishing between different stimuli, disorientation is disruptive because some rectification process is required to restore order information. Utilizing the similarity between the letter B and the number 13, we found strong effects of orientation when a stimulus was interpreted as the two-digit number 13 but not when interpreted as the single letter B. This, however, occurred only when the set of numbers to be classified included permutations of the same digits. Odd–even decisions on single-digit and two-digit numbers (Experiment 3) yielded strong effects of stimulus orientation for order-dependent numbers (e.g., 32), weaker effects for order-independent numbers (e.g., 24), and none for repeated-digit (e.g., 22) or single-digit numbers. Classification time for two-letter Hebrew words evidenced strong effects of orientation for words that differed only in letter order but much weaker effects for words that had no letters in common, even when these were embedded within some words that did (Experiment 4). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

影响铁水罐内衬寿命的因素及措施

通过对攀钢炼铁厂铁水罐内衬耐火材料的损毁方式的分析，认为影响炼铁厂铁水罐寿命的原因主要是铁水冲刷和侵蚀、砖缝过大导致粘铁、清渣铁时掉砖，并针对性提出了改进措施。     

Behavior of direct reduced iron and hot briquetted iron in the upper blast furnace shaft: Part I. Fundamentals of kinetics and mechanism of oxidation

It is considered that the use of prereduced ferrous materials and sources of metallic iron such as direct reduced iron (DRI) or hot briquetted iron (HBI) improves the productivity of the blast furnace (BF). However, oxidation of DRI/HBI can occur in the upper zone of the BF, which may increase the content of the reducing gases but may not decrease the coke rate substantially. The behavior of DRI and HBI was investigated by measuring the rate of oxidation of the materials in CO₂ gas in a temperature range of 400 °C to 900 °C. In addition, the microstructure of “as-received” and oxidized materials was examined. The iron oxide phases formed due to oxidation were determined using X-ray diffraction (XRD) and a vibrating sample magnetometer. The results of isothermal experiments indicated that the kinetics of oxidation of metallic iron is slow at 400 °C. In DRI samples, the initial rate is controlled by the limited mixed control of chemical kinetics at the iron/iron oxide interface and pore mass transfer, whereas gas diffusion in pores is the rate governing step during the final stages of oxidation. The oxidation of wustite from iron is found to be faster than the oxidation of the former to magnetite. The structure of DRI after oxidation resembled a “reverse topochemical-oxide on the surface metal in the center” structure at 600 °C to 700 °C. The final iron oxide phase formed in DRI after oxidation was magnetite and not hematite. The oxidation of HBI was limited to the surface of the samples at lower temperatures; at 900 °C, moderate oxidation was observed and a topochemical iron oxide layer was formed.