Showing papers on "Carbon steel published in 1996"

An Electrochemical Model for Prediction of Corrosion of Mild Steel in Aqueous Carbon Dioxide Solutions

Abstract: A predictive model was developed for uniform carbon dioxide (CO2) corrosion, based on modeling of individual electrochemical reactions in a water-CO2 system. The model takes into account the electrochemical reactions of hydrogen ion (H+) reduction, carbonic acid (H2CO3) reduction, direct water reduction, oxygen reduction, and anodic dissolution of iron. The required electrochemical parameters (e.g., exchange current densities and Tafel slopes) for different reactions were determined from experiments conducted in glass cells. The corrosion process was monitored using polarization resistance, potentiodynamic sweep, electrochemical impedance, and weight-loss measurements. The model was calibrated for two mild steels over a range of parameters: temperature (t) = 20°C to 80°C, pH = 3 to 6, partial pressure of CO2 (PCO2) = 0 bar to 1 bar (0 kPa to 100 kPa), and ω = 0 rpm to 5,000 rpm (vp = 0 m/s to 2.5 m/s). The model was applicable for uniform corrosion with no protective films present. Performance of...

Effect of Metallic Cations on Corrosion Inhibition of an Anionic Surfactant for Mild Steel

Abstract: The effect of metallic cations such as Cu2+, Ni2+, and La3+ on corrosion inhibition of the anionic surfactant of cold-rolled mild steel (MS) in hydrochloric acid (HCl) by sodium dodecyl su...

Wear performance and mechanism of electroless NiP coating

Abstract: An electroless NiP coating has been deposited onto an AISI 1020 plain carbon steel by using an acid bath based on NiCl 2 , as source of nickel cations. The tribological behavior under dry non-lubricated conditions has been evaluated by employing the pin-on-disc test, where the pin was made of AISI 52100 steel. The effects of the heat treatment carried out at 400 and 260°C for 1 and 25 h, respectively on the hardness, friction and wear behavior of the coatings were investigated and compared against the properties of the unplated and as-deposited samples. Both optical and electron microscopic techniques were used to study the wear surface. It was shown that the wear resistance was greatly increased with both heat treatments, the treatment performed at 400°C being a little more effective, although no influence was observed on the frictional coefficient.

The effect of stress triaxiality and strain-rate on the fracture characteristics of ductile metals

Abstract: Notched tensile tests have been carried out on three common metals (pure iron, mild steel and aluminium alloy BS1474) over a wide range of strain-rates (10−3 to 104 s−1) and the strain-to-failure measured. The ductility of all three materials was found to be strongly dependent on the level of stress triaxiality in the specimen, this dependency being greatest for the ferrous materials and least for the aluminium alloy. No significant effect of strain-rate could be ascertained from the experimental results provided fracture remained fully ductile. However, for mild steel, a transition to a brittle fracture mode was observed for a given level of stress triaxiality as the strain-rate was increased. Numerical simulations of the experiments have been used to derive constants of a semi-empirical fracture model from the measured results. This model was found to give reasonable predictions of fracture over the range of conditions investigated.

Prediction of dendrite arm spacing for low alloy steel casting processes

Abstract: Simple mathematical expressions to predict the primary dendrite arm spacing (PDAS) and secondary dendrite arm spacing (SDAS) suitable for steel casting processes are presented. The equations of the PDAS and SDAS were based on previously published experimental data for low alloy steels. Good agreement was obtained between previous measurements of dendrite arm spacing (DAS) and the model predications in the range of cooling rate occurring in steel casting processes. The results indicated that the cooling rate and carbon content basically govern the calculation of PDAS, especially for low carbon steel. However, the carbon content governs the selection of mathematical expression to predict SDAS for low alloy steels. Dendritic growth is the most common crystallization mechanism in industrial steels. Many empirical expressions have been employed to correlate the PDAS and SDAS with growth rate, temperature gradient, cooling rate, and local solidification time. However, the comparative advantages of the various expressions with respect to the accuracy with different types of steels remain unclear. Thus, the aim of the present study is to develop simple expressions to predict DAS as a function of carbon content and thermal conditions of low alloy steels.

Pearlite in ultrahigh carbon steels: Heat treatments and mechanical properties

Abstract: Two ultrahigh carbon steel (UHCS) alloys containing 1.5 and 1.8 wt pct carbon, respectively, were studied. These materials were processed into fully spheroidized microstructures and were then given heat treatments to form pearlite. The mechanical properties of the heat-treated materials were evaluated by tension tests at room temperature. Use of the hypereutectoid austenite-cementite to pearlite transformation enabled achievement of pearlitic microstructures with various interlamellar spacings. The yield strengths of the pearlitic steels are found to correlate with a predictive relation based on interlamellar spacing and pearlite colony size. Decreasing the pearlite interlamellar spacing increases the yield strength and the ultimate strength and decreases the tensile ductility. It is shown that solid solution alloying strongly influences the strength of pearlitic steels.

Comparative studies of bacterial biofilms on steel surfaces using atomic force microscopy and environmental scanning electron microscopy.

Abstract: Environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM) were compared as tools for the observation of bacterial biofilms developed on carbon steel and AISI 316 stainless steel surfaces under stagnant conditions. Biofilms were generated in batch cultures of two different isolates of marine sulphate reducing bacteria (SRB) and in cultures consisting of mixed populations of acidophilic bacteria, known as “acid streamers”;. Imaging of single SRB cells on mica was also carried out to reveal the surface topography of individual bacterial cells at nanometre resolution. Following the removal of biofilms, the stainless steel surfaces were profiled using AFM to determine the degree of steel deterioration. ESEM and AFM studies of bacterial biofilms in‐situ, gave both qualitative and quantitative information on biofilm structure at high resolution. The use of AFM image analysis software allowed estimation of the width and height of bacterial cells, the thickness and width of exopolymeric (...

Influence of substituted benzothiazoles on corrosion in acid solution

Abstract: Compounds such as 2-aminobenzothiazole (ABT), 2-amino-6-chlorobenzothiazole (ACLBT), 2-amino-6-methyl benzothiazole (AMEBT) and 2-amino-6-methoxy benzothiazole (AMEOBT) have been synthesized and their inhibitive action on the corrosion of mild steel in 1 m HCl has been evaluated using weight loss, potentiodynamic polarization studies and hydrogen permeation measurements. Determination of inhibition efficiency in the presence of these compounds at different temperatures clearly indicates that ACLBT shows the best performance, even at a temperature as high as 60°C. Potentiodynamic polarization studies reveal the fact that ABT and its derivatives act as cathodic inhibitors. All these compounds are found to reduce the permeation of hydrogen through mild steel in HCl solution. The adsorption of these compounds on mild steel from HCl solutions obeys Temkin's adsorption isotherm. The adsorption of 2-amino benzothiazole on the mild steel has been substantiated by Auger electron spectroscopy.

Corrosive effects of supercritical carbon dioxide and cosolvents on metals

Abstract: With the eventual phase-out of chlorofluorocarbons and hydrochlorofluorocarbons, and restrictive regulations concerning the use of other volatile organic compounds as cleaning solvents, it is essential to seek new, environmentally acceptable cleaning processes. We are investigating supercritical carbon dioxide (C02) as an alternative solvent for precision cleaning of machined metal parts in governmental and industrial cleaning processes. The compatibility of metals in supercritical-fluid cleaning media with respect to corrosion must be addressed. In this work, a screening study of the corrosive effects of supercritical CO 2 and several supercritical cosolvents on selected metals was conducted. Sample coupons of stainless steel (grades 304LSS, 316SS), aluminum (grades 2024, 6061, 7075), carbon steel (1018), and copper (CDA 101) were statically exposed to pure supercritical C0 2 , water-saturated supercritical C02, 10 wt % methanol/CO 2 cosolvent, and 4 wt % tetrahydrofurfuryl alcohol (THFA)/C0 2 at 24,138 kPa (3500 psig) and 323 K (50 °C) for 24 h. Gravimetric analysis and magnified visual inspection of the coupons were performed before and after the exposure tests. Surface analyses including electron microprobe analysis (EMPA), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) were done where visual and gravimetric changes were indicative of corrosive attack. The metal alloys were found to be compatible with the supercritical test media barring a few exceptions. Corrosive attack was observed on 1018 carbon steel in the water-saturated CO 2 environment, and also on 2024 aluminum and CDA 101 copper, both in the 10 wt % methanol-CO 2 cosolvent. The results of all compatibility testing are reported, and hypotheses are formed in an attempt to explain possible corrosion mechanisms.

Precipitation behavior in a medium carbon, ti-v-n microalloyed steel

Abstract: The precipitation behavior of a medium carbon steel microalloyed with Ti, V, and N has been studied by analytical transmission electron microscopy in the as-cast and isothermally heat-treated states, as well as at different stages in the thermomechanical processing of the steel. Mixed (Ti,V) nitrides were found in all the structures, but there was no evidence for mixed carbonitride formation. The Hillert-Staffansson model was used to predict the composition of the nitrides as a function of tem-perature. Upon prolonged aging many of the precipitates became “fragmented” and were no longer single crystals. At the same time, the volume fraction of precipitates dropped, while their average Ti content increased. Possible explanations for this unexpected behavior are discussed in this article.

Influence of copper, cadmium and tin additions in the galvanizing bath on the structure, thickness and cracking behaviour of the galvanized coatings

Abstract: The influence of copper, cadmium and tin additions in the galvanizing bath on the morphology and thickness of galvanized coatings has been studied using X-ray diffraction and optical and scanning electron microscopy associated with energy-dispersive spectroscopy microanalysis. Copper promotes the δ1 phase and hinders the ζ phase growth. In the opposite, cadmium promotes the ζ and Γ phase formation and hinders the growth of the δ1 phase. No change in the morphology of galvanized coatings has been observed with the addition of tin. Mechanisms have been proposed in order to explain the effect of the above elements on the formation of intermetallics. The cracking of the coatings after tensile testing in the plastic region of the specimens has been examined. The δ1 phase is responsible for the nucleation and propagation of transverse cracks parallel to the steel substrate. Cadmium hinders the nucleation and propagation of the transverse cracks during loading up to the yield point of the steel; however, the columnar growth of the ζ phase results in the complete flaking of the coating during loading up to the ultimate tensile strength of steel. The Γ phase remains always adhered to the steel substrate.

Microstructures relevant to brittle fracture initiation at the heat-affected zone of weldment of a low carbon steel

Abstract: Charpy toughness of the heat-affected zone (HAZ) of weldment of a low carbon steel has been investigated by means of an instrumented Charpy test and fractographic analysis. Microstructures were varied with thermal cycles simulating double-pass welding. The ductile-brittle transition temperature is the most deteriorated at an intermediate second-cycle heating temperature. The origin of the difference in the transition temperatures has been analyzed to exist in the brittle fracture initiation stage. Fractographic examination correlating with microstructural features has revealed that the brittle fracture initiation site is associated with the intersection of bainitic ferrite areas with different orientations rather than the martensite-austenite constituents. The role of the constraint of plastic deformation on the brittle fracture initiation is discussed.

Erosion-Corrosion of a Carbon Steel Elbow in a Carbon Dioxide Environment

Abstract: For many conditions, erosion-corrosion can produce higher wall penetration rates than erosion or corrosion alone. While flow velocity generally is believed to be an important factor, more ...

Squeeze cast aluminium reinforced with mild steel inserts

Abstract: The bonding of a mild steel insert to an Al-7Si alloy during squeeze casting has been studied for a range of processing conditions. Assessment of the mild steel/Al-7Si alloy interface shear strength has been made with a push-out test, and the results have been correlated with microstructural observations and residual stress calculations. Uncoated inserts do not exhibit any significant reaction with Al-7Si because of rapid cooling of the melt during squeeze casting, giving a low interface shear strength of ∼ 30 MPa. Preheating the inserts to 900°C slightly improves the interface shear strength to ∼ 45 MPa, but reaction between the steel and Al-7Si is prevented by the formation of an Fe3O4 magnetite layer on the steel surface. Inserts hot-dipped in molten Al-10Fe before squeeze casting have a much greater interface shear strength of ∼ 110 MPa, with failure in the Al-7Si matrix rather than at the steel/Al-7Si interface. Inserts vacuum plasma spray coated with titanium have the greatest interface shear strength of ∼ 130 MPa, without any interface reaction, because of mechanical keying of the rough splat-quenched titanium surface combined with high residual stresses in the Al-7Si matrix.

Response and cyclic strain accumulation of pressurized piping elbows under dynamic in-plane bending

Abstract: Eight pairs of carbon and stainless steel, long and short radius welding elbows were tested under conditions of steady internal pressure and in-plane, resonant dynamic moments that simulated seismic excitations. The elbows had an outside diameter of 60.3 mm and thicknesses of 3.91 and 5.54 mm. The material properties are reported, and the testing procedure and experimental programme fully described. The dynamic response of the comonents indicates that the stainless steel elbows behave differently from the carbon steel elbows.The cyclic strain accumulation for each component is assessed and ratios of applied to limit moments of the elbows at onset of ratcheting are given for each material. While the gross deformation range increased with level of input in testing, no permanent overall swelling or ovalization was recorded; this is contrasted with similar results reported in the general literature.

Effect of Solution Composition and Electrochemical Potential on Stress Corrosion Cracking of X-52 Pipeline Steel

Abstract: Electrochemical measurements and constant extension rate tests (CERT) of cold-worked X-52 carbon steel showed stress corrosion cracking (SCC) can be induced in aqueous sulfate (SO42−), bic...

Effect of Ni content on cracking susceptibility and microstructure of laser-clad FeCrNiBSi alloy

Abstract: An investigation is reported of the laser surface cladding of self-fluxing FeCrNiBSi alloys on a medium carbon steel substrate using the preplaced powder method The cracking susceptibility and microstructure of the laser-cladding layer have been studied in terms of its Ni content, thermal expansion coefficient and wettability on the substrate With increasing Ni content the cracking susceptibility of the cladding layer decreases and its microstructure changes from a “bamboo leaf” structure to a typical dendritic one

Modeling of Atmospheric Corrosion Behavior of Weathering Steel in Sulfur Dioxide-Polluted Atmospheres

Abstract: Atmospheric corrosion resistance of carbon steel (CS) and high-phosphorus weathering steel (WS, Acr-Ten A) was compared after exposure for up to 6 years in Taiwan. In an industrial atmosph...