Showing papers on "Carbon steel published in 2000"

Synergistic effect of cavitation erosion and corrosion of various engineering alloys in 3.5% NaCl solution

Abstract: The cavitation erosion and corrosion characteristics of various engineering alloys including grey cast iron, steels, copper-based alloys and stainless steels were studied by means of a 20 kHz ultrasonic vibrator at a peak-to-peak amplitude of 30 μm in distilled water and in 3.5% NaCl solution at 23°C. The contributions of pure mechanical erosion, electrochemical corrosion, and the synergism between erosion and corrosion to the overall cavitation erosion–corrosion in 3.5% NaCl solution were determined. It was found that in 3.5% NaCl solution, the effect of corrosion on the overall cavitation erosion–corrosion was most pronounced in mild steel and grey cast iron, and negligible in stainless steels. The stainless steels only suffered pure mechanical erosion in 3.5% NaCl solution in the presence of cavitation owing to the unfavourable local environment for pit growth.

Thermal stability and mechanical properties of ultrafine grained low carbon steel

Abstract: Ultrafine grained low carbon steel manufactured by equal channel angular pressing was annealed at 753 K, where negligible grain growth occurred, up to 72 h and the microstructural change and the mechanical properties were examined. This investigation was aimed at providing the guiding information for the effective use of ultrafine grained low carbon steel manufactured by severe plastic deformation processes. Under the present annealing conditions, the microstructural change was dominated by recovery. The tensile behavior of annealed ultrafine grained steel was characterized by much higher strength and the absence of strain hardening compared with that of large grained steel. In addition, the present ultrafine grained steel became mechanically stable by 24 h annealing treatment although recovery was in progress. The microstructure of the deformed sample of annealed ultrafine grained steel exhibited the elongated grains and dislocations distributed densely in the vicinity of grain boundaries. This finding indicated that dynamic recovery during deformation was associated with the absorption of dislocation by grain boundaries. The mechanical behavior of the present ultrafine grained low carbon steel was discussed in light of the recent development explaining that of nanocrystalline materials, i.e. the dislocation bow-out mechanism for high strength and the spreading kinetics of trapped lattice dislocation into grain boundary for the absence of strain hardening.

Electrochemical Behavior of Rust Formed on Carbon Steel in a Wet/Dry Environment Containing Chloride Ions

Abstract: The iron rust phase was analyzed by using the in-situ x-ray diffraction (XRD) and alternating current (AC) impedance methods after a wet/dry corrosion test using sodium chloride (NaCl) solution, which is the main composition of airborne saline particles. The corrosion content of the carbon steel depended on the concentration of Cl ions in the environment of the test chamber. As the concentration of Cl ions increased, the content of β-FeOOH increased in iron rust phases. The transition of β-FeOOH from the green rust I (GRI) was observed directly by in-situ XRD. The amount of GRI depended on the concentration of Cl ions, and β-FeOOH was transformed from GRI automatically in the dry process of the test. AC impedance showed that the resistance of the rust (Rrust) increased with the number of cycles in the corrosion test, and that the structural factor of the rust became predominant in Rrust. With the increase of the amount of rust, the resistance corresponding to the corrosion rate (Rt decreased, whi...

Localized Electrochemical Methods Applied to Cut Edge Corrosion

Abstract: resin, a commercial electrogalvanized low alloy carbon steel sample typical of that used in the automotive industry. The cut edge was exposed in cross section to form an electroactive area of 10 � 0.81 mm. The steel thickness was approximately 800 � m, and the zinc coating ranged from 5 to 10 � m. The cut edge surface was polished to a 1 � m finish and particular care was taken during polishing to avoid spreading the zinc onto the steel surface. Single and double sided electrogalvanized steel were used as indicated in the text. Electrogalvanized steel was chosen for this work because of its high level of purity and reproducibility as an industrial product.

Magnetron sputtered SiC coatings as corrosion protection barriers for steels

Abstract: Silicon carbide films between 2.3 and 3.0 μm were deposited on AISI 304 stainless steel (SS), carbon steel (CS) and crystalline silicon from a SiC target in a magnetron sputtering system. Good mechanical properties were obtained for the films by carefully controlling the deposition parameters. Results of scratch tests revealed that adhesion of the films is a function of deposition parameters and substrate type. Additionally, an influence of substrate preparation prior to deposition was also observed. Critical loads of 20 N, 8 N and 5 N were obtained in case of Si, SS and CS substrates, respectively. Vickers micro-hardness values were between 10 and 30 GPa, films on SS being harder than films on CS. The behavior of the films as corrosion protection barriers in aggressive environments was evaluated by immersion tests and electrochemical impedance spectroscopy measurements. Films on SS exhibited a better corrosion resistance than those on CS. Their adhesion to the SS was outstanding, even after a long time of immersion in a HCl 0.8 M solution, showing that they are efficient protection barriers. The corrosion process of the substrates starts at micro-pores present in the films so that corrosion pits all over the surface of the samples can be observed.

Processing of steel for ultrafine ferrite grain structures

Abstract: The attainment of ultrafine ferrite grain structures in low carbon, low alloy steels is of interest because of the improvement in yield strength and Charpy impact transition temperature predicted by extrapolation of known data to very fine grain sizes. This paper presents a summary of research aimed at producing ultrafine ferrite in a niobium microalloyed, low carbon steel by three processing routes. Transformational grain refinement (TGR), in which extrafine austenite is hot rolled and cooled rapidly, has been shown to be capable of producing grain sizes of <1 µm in a surface layer, and 1.5 µm in the centre of 3 mm thick plate. Dynamic recrystallisation of ferrite during multipass warm rolling was shown to be neither complete nor uniform within the cross-section of the plate. Nevertheless, a partly recrystallised, partly recovered grain structure with an average grain size of 1.5 µm was obtained in the centre of 3 mm thick plate. Cold rolling and recrystallisation of ferrite that had been previou...

Minimisation of calcium additions to low carbon steel grades

Abstract: This investigation aimed to determine the in plant feasibility of decreasing, to an amount close to the minimum literature value, the calcium addition to liquid steel for prevention of alumina buildup during continuous casting. Six plant trials were carried out at calcium additions of 0·14 kg/t of steel (reduced from the original 0·19 kg/t), added to the second ladle of a two or three ladle sequence. Total oxygen samples were taken at the ladle furnace and tundish to determine total oxygen and nitrogen contents of the steel. The total oxygen content at the ladle furnace varied between 19 and 26 ppm, with a slight degree of reoxidation between the ladle furnace and the caster. Alumina clogging was successfully prevented by the addition of 0·14 kg calcium/t of steel during the first five trials. During the sixth trial the submerged entry nozzle (SEN) failed and, although the stopper behaved as if clogging occurred, this behaviour was caused by the poor perfomance of the SEN rather than actual cloggi...

Aqueous Corrosion Behavior of Weathering Steel and Carbon Steel in Acid-Chloride Environments

Abstract: Aqueous corrosion characteristics of carbon steel and weathering steel in aerated acid-chloride solutions were studied by using immersion weight loss tests, crevice corrosion tests, electr...

An overview of mechanisms by which sulphate-reducing bacteria influence corrosion of steel in marine environments.

Abstract: This communication provides an overview of the literature on the biocorrosion of steel in marine media, influenced by the presence of sulphate-reducing bacteria (SRB). Electrochemical aspects, microbial interactions within biofilms, the significance of medium composition and the role of iron sulphides, and hydrogen effects are discussed. A brief description of recent experiments involving the use of electrochemical techniques for corrosion assessment, surface studies employing energy dispersive X-ray analysis (EDAX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and electron microprobe complemented with electron microscopy observations, as well as the application of novel techniques, such as micro sensors and atomic force microscopy, is given. The growth of SRB in marine environments causes significant modifications of many physicochemical parameters at the steel/seawater interface, including local changes in pH and redox potential values, variations in anion and cation concentrations and alteration of the composition and structure of corrosion products. Complex chemical and biological reactions and equilibria are also markedly altered during bacterial proliferation. These effects, which are absent in abiotic media, often lead to significant changes in the corrosion behaviour of steel. The complicated nature of the local environment at the steel/seawater interface is enhanced in the presence of microorganisms and their extracellular polymeric substances (EPS). As a consequence of biofilm heterogeneity, areas with different ion concentrations are formed and the development of corrosion product layers of dissimilar protective characteristics occurs.

Role of corrosion products in biofilms in microbiologically induced corrosion of carbon steel

Abstract: The effects on microbiologically induced corrosion (MIC) of carbon steel resulting from the presence of corrosion products in the biofilm of sulphate reducing bacteria (SRB) have been investigated. The SRB were isolated from the Changqing oilfield in China. Electrochemical impedance spectrometry and a hydrogen monitoring device were used to study the accumulation of the biofilms. The corrosion products were analysed by both electron probe microanalysis and X-ray diffraction, and the metabolites of the SRB in the biofilm were detected by gas chromatrography and mass spectrometry techniques. The results have shown that the first corrosion product to form in the biofilm is mackinawite, followed by the appearance of troilite and greigite. Only the mackinawite layer has protective properties; the others accelerate the corrosion of carbon steel. Both the activity of the SRB and the structure of the SRB biofilm influence the initiation and development of corrosion. The process of MIC involves first the d...

Microstructural Evolution during Laser Cladding of M2 High-Speed Steel

Abstract: Laser cladding of gas-atomized M2 high-speed steel on the mild steel substrate was performed using scan rates of 1 to 10 mm/s, scan line spacings of 0.1 to 0.5 mm, and powder feed rates of 1 to 10 g/min, for a given laser power of 400 W. This article presents a detailed study of the microstructural evolution during laser cladding. The effect of scan rate, scan line spacing, and powder feed rate on cooling rate can be described in terms of the cladding-layer thickness, i.e., the thinner the layer, the higher the cooling rate. The degree of metastability in the laser-clad microstructure can be understood in terms of the lattice parameter of the bcc phase. The lattice parameter of the bcc phase increased with increasing layer thickness and reached a maximum value at a thickness of 0.3 mm. Correspondingly, the microstructure varied from a cellular or dendritic structure of δ ferrite and austenite to a mixture of martensite and retained austenite. However, further increasing the layer thickness led to a decrease of both the lattice parameters of the bcc phase and the proportion of retained austenite in the martensite. This was accompanied by an increase of the amount of carbide at the prior austenitic grain boundaries and a decrease of the carbon content in the martensite and retained austenite.

Technical Note: CAHMT—A New and Eco-Friendly Acidizing Corrosion Inhibitor

Abstract: A new N- and S-containing heterocyclic compound, CAHMT, was synthesized and evaluated as a corrosion inhibitor for oil-well tubular steel (N-80) and mild steel (MS) at 105°C ± 2°C by the weight loss method. Potentiodynamic polarization measurements were carried out at room temperature for both steels in the presence of propargyl alcohol (PA) and CAHMT. Results indicate that the CAHMT is a mixed-type inhibitor while PA is predominantly cathodic. The adsorption of the inhibitors on N-80 steel and MS surface from 15% hydrochloric acid (HCl) has been found to obey Temkin's adsorption isotherm. The efficiency of CAHMT has been found to be comparable with that of PA, a standard corrosion inhibitor for MS in boiling HCl.

Effect of initial grain size on microstructure and toughness of intercritical heat-affected zone of a low carbon steel

Abstract: In this study, the effects of initial grain size with the varying heat inputs on the microstructure and toughness of intercritical heat-affected zone (HAZ) of a low-carbon steel were investigated. In the welding experiments, SAE 1020 steel specimens in hot-rolled (original), in grain-refined and in grain-coarsened conditions were welded by a submerged arc welding machine with the heat inputs of 0.5, 1 and 2 kJ mm −1 . Following the welding, microstructure, hardness and toughness of the intercritical HAZs of the specimens were investigated. The determination of microstructure and measurement of hardness in the intercritical HAZs were performed on the samples taken from the welded specimens, while toughness values were obtained using the weld thermal simulation technique. From the results, we tried to establish a relationship between the heat input, initial grain size, microstructure, hardness and toughness of the intercritical HAZ. From the results of the toughness tests and microstructural observation, it was seen that the fine initial grain size was effective on the formation of ductile phases and on the higher toughness, whereas the coarse initial grain was effective on the formation of brittle phases and on the lower toughness at the same heat input. As a result, considering the microstructure, hardness and toughness of the intercritical HAZ, a higher heat input for both the coarse initial grain size and fine initial grain size gave good results. However, it was also seen that a lower heat input can be used in the welding of low carbon steel with fine initial grain size with respect to the toughness of the intercritical HAZ.

A new lightweight metal-composite-metal panel for applications in the automotive and other industries

Abstract: A new lightweight metal-composite-metal (MCM) panel is developed. This panel consists of two layers of 0.2-mm thick stainless steel sheet with a layer of woven fabric (semi-flexible composite) in between. The stiffness and the dent resistance of this MCM-panel are compared to those of corresponding panels pressed in 1-mm thick aluminium, 0.8-mm thick carbon steel and 0.8-mm thick stainless steel sheets. Compared to the aluminium panel, the MCM-panel exhibits a slightly smaller stiffness. However, the MCM-panel displays a larger dent resistance than the aluminium and the carbon steel panels. The new panel is 46% heavier than the aluminium panel. However, it is 60% lighter than the carbon and stainless steel panels. This new panel is expected to have many applications in manufacturing of parts for car, train and bus bodies, appliances and household machines. Machine chassis and air cargo containers are other examples of products, in which the new panel can be used. Production of the new panel requires that the tools be heated. The cycle time is short, since a newly developed and patented method for ultra-rapid heating of tools has been used in this study. The production is economical, since the cycle times is short and recycled fibres can be used. The production process is not completely optimized yet. However, the conducted experiments show that the panel stiffness and dent resistance are benefited, if the tool pressure applied during the heating is low.