The role of damping in steel pan manufacture

Results are presented of systematic studies of vibration damping in steel of a type, and processed by a route, rel-evant to Caribbean steel pans. Damping is likely to be a significant factor in the variation of sound quality be-tween different pans. The main stages in pan manufac-ture are simulated in a controlled manner using sheet steel, cold-rolled to a prescribed level of thickness reduc-tion then annealed at a chosen temperature in a laboratory furnace. Small test strips were cut from the resulting material, and tested in free-free beam bending to deduce the Young’s modulus and its associated loss factor. It is shown that the steel type, the degree of cold working and the annealing temperature all have a significant influence on damping. Furthermore, for each individual specimen damping is found to decrease with rising frequency, ap-proximately following a power law. Comparison with samples cut from a real pan show that there are further influences from the pan’s geometrical details.

Asymmetric rolling of 5182 aluminium alloy and interstitial free steel sheets

This Ph.D. research focuses on asymmetric rolling (ASR), as an alternative method for improving mechanical responses of aluminium-magnesium alloy and interstitial free (IF) steel regarding industrial requirements. Aluminium alloys are attractive materials in various industries due to their appropriate properties such as low density and corrosion resistance; however, their low formability has limited their applications. As formability of aluminium alloys can be improved through texture development, part of this dissertation is dedicated to producing the desired crystallographic texture with the ASR process. Two types of ASR (i.e. reverse and continuous asymmetric rolling) were investigated. The impact of shear deformation imposed by ASR processes on developing the desirable texture and consequently on mechanical behaviours was observed. The developed shear texture increased the normal and also planar anisotropy. Texture evolution during plastic deformation as well as induced mechanical behaviour were simulated using the “self-consistent” and Taylor models. Interstitial free (IF) steel was the second material selected in this dissertation. Since IF steel is one of the most often used materials in automotive industries it was chosen to investigate the effect of shear deformation through ASR on its properties. Two types of reverse and continuous asymmetric rolling were carried out to deform IF steel sheets. The results of optical microscopy and atomic force microscopy observations showed no significant difference between the grains’ morphology of asymmetric and conventionally rolled samples, whereas the obtained results of transmission electron microscopy indicated that fine and equiaxed dislocation cells were formed through the asymmetric rolling process. This structure is due to imposed shear deformation during the ASR process. Furthermore, the mechanical behaviour of deformed and annealed sheets was evaluated through uniaxial tensile tests. Results showed that at low thickness reductions (18%) the asymmetric rolled sample presented higher stress than that of the conventionally rolled sheet; while for higher thickness reductions (60%) the trend was reversed. The texture analyses indicated that intense rolling texture components which developed through 60% thickness reduction of conventional rolling cause a relatively higher stress; on the contrary the fine structure resulting from ASR appears to be the source of higher stress observed after pre-deformation of 18%.

A Cost Model for the Effect of Setup Time Reduction in Stainless Steel Strip Production

Setup time reduction facilitate the flexibility needed for just-in-time production. An integrated steel mill with meltshop, continuous caster and hot rolling mill is often operated as decoupled processes. Setup time reduction provides the flexibility needed to reduce buffering, shorten lead times and create an integrated process flow. The interdependency of setup times, process flexibility and integration were analysed through system dynamics simulation. The results showed significant reductions of energy consumption and tied capital. It was concluded that setup time reduction in the hot strip mill can aid process integration and hence improve production economy while reducing environmental impact.

Preparation of Ni-Ti-Mo and Ni-Ti-Mo-Zr Alloys by High-Energy Ball Milling and Subsequent Hot Pressing

This work discusses on the preparation of Ni-45Ti-5Mo, Ni-40Ti-10Mo and Ni-46Ti-2Mo-2Zr (at-%) alloys by high-energy ball milling and hot pressing, which are potentially attractive for dental and medical applications. The milling process was performed in stainless steel balls (19mm diameter) and vials (225 mL) using a rotary speed of 300rpm and a ball-to-powder weight ratio of 10:1. Hot pressing under vacuum was performed in a BN-coated graphite crucible at 900 degrees C for 1 h using a load of 20 MPa. The milled and hot-pressed materials were characterized by X-ray diffraction, electron scanning microscopy, and electron dispersive spectrometry. Peaks of B2-NiTi and Ni4Ti3 were identified in XRD patterns of Ni-45Ti-5Mo, Ni-40Ti-10Mo and Ni-46Ti-2Mo-2Zr powders milled for 1h. The NiTi compound dissolved small Mo amounts lower than 4 at%, which were measured by EDS analysis. Moreover, it was identified the existence of an unknown Mo-rich phase in microstructures of the hot-pressed Ni-Ti-Mo alloys.

Effect of citrate ions on the electrochemical behaviour of low-carbon steel in borate buffer solutions

The electrochemical behaviour of cold-rolled low carbon steel was studied on both active and passive potential regions in borate buffer solutions with and without the addition of sodium citrate (NaCit). In the active region anodic charges increased significantly and RCT values decreased with citrate, due to the formation of soluble complexes. In the passive potential region the film formed at +0.4 V in borate buffer solution with and without 0.010 M NaCit is probably enriched by Fe3O4 oxide, while films formed at +0.8 V are probably enriched by gamma-Fe2O3. The equivalent circuit [R-s(R(CT)Q)] fitted all experimental impedance data. (C) 2003 Elsevier Ltd. All rights reserved.

Selection of desulfurizing agents and optimization of operational variables in hot metal desulfurization

The growing demand for steels with tighter compositional specifications led the Companhia Siderúrgica Nacional (CSN) to develop more efficient processes. To solve this problem this paper aims to identify the operational variables more impacting in the desulfurization process, specifically in torpedo car, as well as its causes and solutions. Then select and test, with laboratorial and industrial tests, desulfurizing agents based of CaC 2, CaO, CaCO3, and Mg to assess the cost per quantity of product desulfurized. The mixture with best results was not that one with highest content of CaC2. It is believed that this mixture showed better efficiency because of the increased agitation of the bath, produced by the releasing of gas from compound CaCO3 present in this mixture. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interaction between recrystallization and strain-induced precipitation in a high Nb- and N-bearing austenitic stainless steel: influence of the interpass time

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

ANNEALING BEHAVIOR OF RAFM ODS-EUROFER STEEL

Oxide-dispersion-strengthened (ODS) ferritic-martensitic steels are candidates for applications in fusion power plants where micro structural long-term stability at temperatures of 650 degrees C to 700 degrees C are required. The microstructural stability of 80% cold-rolled reduced-activation ferritic-martensitic 9% Cr ODS-Eurofer steel was investigated within a wide range of temperatures (300 degrees C to 1350 degrees C). Fine oxide dispersion is very effective to prevent recrystallization in the ferritic phase field. The low recrystallized volume fraction (<0.1) found in samples annealed at 800 degrees C is associated with the nuclei found at prior grain boundaries and around coarse M23C6 particles. The combination of retarding effects such as Zener drag and concurrent recovery decrease the local stored energy and impede further growth of the recrystallization nuclei. Above 90 degrees C, martensitic transformation takes place with consequent coarsening. Significant changes in crystallographic texture are also reported.

Effect of Plastic Deformation on the Excess Loss of Electrical Steel

The interpretation of the effect of plastic deformation on the calculated excess loss component (anomalous-loss) supports the concept of loss separation. Magnetic losses and Barkhausen noise of nonoriented electrical steel sheets were measured on Epstein strips taken from a single coil of 0.8% Si nonoriented electrical steel. Sheets were extracted in the annealed condition, without any skin pass and with a grain size of 18 mu m. This material was cold rolled in order to obtain sets of samples with true strain from 2% up to 29%. X-ray diffraction was used to estimate the dislocation density. The analysis of magnetic properties was performed by Barkhausen noise measurements and also by analyzing the hysteresis loops obtained from Epstein frame measurements for different inductions and different frequencies (including the quasi-static regime for hysteresis loss measurements). These data allowed us to observe that most of the well known total loss increase with plastic deformation is due to an increase in the hysteresis loss component, while excess loss decreases to become negligible. This behavior can be explained if it is assumed that the plastic deformation lead to an increase in the number of domain walls per unit volume, thereby decreasing the excess loss. Barkhausen peak area increases with plastic deformation, reproducing results taken from samples of different silicon content.

Hot-Dip Aluminizing of Low-Carbon Steels

In a relatively short period of sixty-five years, aluminum has grown to the rank of fifth in total weight of met­als produced in the world. Throughout its short life, aluminum has been found to have excellent corrosion-resistant properties; yet only in recent years has aluminum been under consideration as a corrosion-resistant coating for iron and steel.

Useful information for engineers, architects, and constructors, and tables of rolled beams, channels, angles, etc. /

Mode of access: Internet.

Zinc coating (hot galvanizing); a bibliography

"United States patents": numb. leaves 74-90. "British patents": numb. leaves 91-110.

Nonmetallic inclusion modification and its effect on the final properties of a linepipe steel

Five linepipe type steels were produced in order to study the effect of calcium and magnesium injection on their final properties. Two of these steels were at the extremes of the sulphide range i.e. 0.003 and 0.017% sulphur with no injection attempted; thereby, providing standards to compare with the injected steels. The oxygen level varied from 21 to 63 p.p.m. The cast ingots were controlled-rolled and isothermally rolled in order to study the deformation characteristics of the residual non-metallic inclusions. The structure and cleanliness of these steels was evaluated metallographically using the light microscope, SEM, and image analysis and the results related to their Charpy toughness and HIC resistance. Increasing sulphur levels decreased final properties of the steel. In the untreated state, with as little as 0.003% sulphur, test orientation was highly influential. Modification of sulphur bearing steels was achieved with low modifying element to sulphur ratios provided that the oxygen content was very low. Injection of calcium into steel caused interaction with oxide and sulphide inclusions which was biased toward oxide reduction relative to sulphur removal. Magnesium again reduced oxides and appeared to be linked with aluminia containing inclusions in the final product. It produced improved toughness values relative to a similar sulphur containing calcium treated steel. The results of this work could be extended to establish the mechanism of inclusion modification with magnesium additions to sulphur bearing steels.

Mechanics of longitudinal rolling of tube through three-grooved rolls

This investigation examined the process of the longitudinal rolling of tubes through a set of three driven grooved rolls. Tubes were rolled with or without internal support i.e. under mandrel rolling or sinking conditions. Knowledge was required of the way in which the roll separating force and rolling torque vary for different conditions of rolling. The objective of this work being to obtain a better understanding and optimization of the mechanics of the process. The design and instrumentation of a complete experimental three-roll mill for the rolling of lead tube as an analogue material for hot steel, with the measurement of the individual roll force and torque is described. A novel type of roll load cell was incorporated and its design and testing discussed. Employing three roll sizes of 170 mm, 255 mm and 340 mm shroud diameter, precise tube specimens of various tube diameter to thickness ratios were rolled under sinking and mandrel rolling conditions. To obtain an indication of the tube-roll contact areas some of the specimens were partially rolled. For comparative purposes the remaining tubes were completely rolled as a single pass. The roll forces, torques and tube parameters e.g. reduction of area, D/t ratio, were collated and compared for each of the three roll diameters considered. The influence of friction, particularly in the mandrel rolling process, was commented upon. Theoretical studies utilising the equilibrium and energy methods were applied to both the sinking and mandrel rolling processes. In general, the energy approach gave better comparison with experiment, especially for mandrel rolling. The influence of the tube deformation zones on the two processes was observed and on the subsequent modification of the tube-roll arc contact length. A rudimentary attempt was made in the theoretical sinking analysis to allow for the deformation zone prior to roll contact; some success was noted. A general survey of the available tube rolling literature, for both the sinking and mandrel processes has been carried out.

Effect of poor curing conditions and remedies on the durability of steel in concrete

An investigation was undertaken to study the effect of poor curing simulating hot climatic conditions and remedies on the durability of steel in concrete. Three different curing environments were used i.e. (1) Saturated Ca(OH)2 solution at 20°C, (2) Saturated Ca(OH)2 solution at 50°C and (3) Air at 50°C at 30% relative humidity. The third curing condition corresponding to the temperature and relative humidity typical of Middle Eastern Countries. The nature of the hardened cement paste matrix, cured under the above conditions was studied by means of Mercury Intrusion Porosimetry for measuring pore size distribution. The results were represented as total pore volume and initial pore entry diameter. The Scanning Electron Microscope was used to look at morphological changes during hydration, which were compared to the Mercury Intrusion Porosimetry results. X-ray defraction and Differential Thermal Analysis techniques were also employed for looking at any phase transformations. Polymer impregnation was used to reduce the porosity of the hardened cement pastes, especially in the case of the poorly cured samples. Carbonation rates of unimpregnated and impregnated cements were determined. Chloride diffusion studies were also undertaken to establish the effect of polymer impregnation and blending of the cements. Finally the corrosion behaviour of embedded steel bars was determined by the technique of Linear Polarisation. The steel was embedded in both untreated and polymer impregnated hardened cement pastes placed in either a solution containing NaCl or an environmental cabinet which provided carbonation at 40°C and 50% relative humidity.