Elements In Low Alloy Steel Research Articles

Role of segregation behavior of Cu and Sb in the region of inclusions on initial corrosion

The distribution characteristics of corrosion-resistant elements in low-alloy steel affected the initial corrosion behavior of the matrix. In this article, the segregation behaviors of elements at grain boundaries and pearlite defects in low-alloy steel Q500 and the precipitation behavior of Cu in inclusions were studied. Cu, Ni and Sb had segregation behavior at the boundary of the inclusions, which was beneficial for reducing grain boundary segregation. Cu had the ability to capture Sb and Ni. Cu and Sb involvement in local corrosion process of inclusions were observised by multi-cycle 3.5% NaCl immersion test, during which Cu and Sb were oxidized to corresponding Cu2O and Sb2O3. Under the influences of the segregation of elements at the grain boundaries, the internal part of the crystal was preferentially corroded. Cr was enriched in the pearlite cementite, formed (Cr,Fe)7C3 and contributed to the corrosion process, forming Cr2O3 and CrO3.

The austenitic peak stress model of low alloy steel at elevated temperature based on the valence electron theory

The traditional method of calculating the high-temperature austenite peak stress empirical model proposed by Sellars and McTegart has been used for 50 years. A new method based on the valence electron theory is presented in three steps. The first step is to calculate the austenitic valence electron parameters and their statistical values at high temperature. The second one is to calculate the binding energy and total binding energy based on the valence electron statistic parameters. The total binding energy is defined as the sum of the mole fractions of the constituent elements in low alloy steel and the corresponding binding energy. The last step is to establish the model of austenitic peak stress at elevated-temperature based on the combination of Hall-Petch formula and Misaka formula as well as the total binding energy. The prediction results show that the austenitic peak stress model presented in this paper has good precision.

Effect of the detector dead-time uncertainty on the analytical result of minor elements in low-alloy steel by isotope dilution/ICP sector field mass spectrometry.

In the present study the effects of the detector dead-time and its uncertainties on the accuracy and uncertainty of isotope dilution mass spectrometry (IDMS) were considered through an interlaboratory study on the analysis of low-alloy steel by using an ICP-sector field mass spectrometer. Also, an optimized mixing ratio of the sample and the spike to obtain highly precise results was theoretically and experimentally investigated. The detector dead-time used in the interlaboratory study showed a negative value. However, it less affected the trueness of the analytical result if the dead-time correction for the measured isotope ratio was done properly. As many researchers have pointed out, the detector dead-time showed a clear mass dependence. Therefore, it is desirable to check the dead-time in every target element by using assay standards or isotopic standards, which would lead to an accurate result even if the detector dead-time is a negative value. On the other hand, the effect of the uncertainty of the detector dead-time can be minimized when both isotope ratios and ICP-MS signals of the [sample + spike] blend in IDMS are equal to those of [spike + assay standard] in reverse IDMS. From standpoints of error magnification theory and the precision of the isotope ratio measurement, an optimized isotope ratio of the sample-spike blend would be 1.0 for an element with a large difference in ten times and more between the atomic fractions of two isotopes used for IDMS. In the case of an element with no significant difference between the atomic fractions of two isotopes, an optimized isotope ratio can be calculated by a formula expressed as a function of the atomic fractions of the sample and the spike as well as the signal of ICP-MS.

Alloying Effect of Chromium on the Corrosion Behavior of Low-Alloy Steels

Alloying effect of Cr in the interaction with other elements in low alloy steel for corrosion resistance was designed and prepared. The corrosion behavior of the alloy immersed in mild acid­chloride solution (200 atomic ppm Cl and pH 4) at room temperature in an ambient condition has been studied by electrochemical laboratory tests (potentiodynamic polarization test, potentiostatic test, electrochemical impedance spectroscopy) and surface analyses (SEM, XPS). The results reveal that Cr addition improved the localized corrosion resistance by promoting the formation of beneficial Fe and Cu compounds on the protective films of 0.1 and 0.3mass% Cr steels. However, the over-alloying circumstance in 0.5mass% Cr steel caused the negative effect of Cr addition due to metal chloride-induced hydrolysis which accelerated the propagation of the localized corrosion. To summarize, 0.3mass% Cr addition was determined to be the optimum value for alloying to blank steel. [doi:10.2320/matertrans.M2013087]

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS): comparison of different internal standardization methods using laser-induced plasma (LIP) emission and LA-ICP-MS signals.

The source of signal variations that governs the analytical performance of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was investigated in this study. In order to specify the source of signal variations of LA-ICP-MS, laser-induced plasma (LIP) Fe emission, LA-ICP-MS Fe+ and LA-ICP-MS Ni+ signals were used as internal standards for the determination of trace elements in low-alloy steel certified reference materials (BS 50D and JSS 1005-1008). Fe 1373.5 nm emission signals from LIP were measured, while trace element LA-ICP-MS signals were collected. After that, the LIP emission signals, LA-ICP-MS Fe+ and LA-ICP-MS Ni+ signals were used as internal standards, and the analytical performance was evaluated by the RSDs and the correlation coefficients (r) of the calibration curves. The improvement factors were dependent on the internal standardization methods. Analytical precisions (RSDs) of trace element LA-ICP-MS signals were improved by factors of 1.5-3.3 using LIP Fe emission signals as an internal standard. The improvement factors of 2.5 - 5.9 and 4.1 - 17 were obtained by using LA-ICP-MS Fe+ and LA-ICP-MS Ni+ signals as internal standards, respectively. Better correlation coefficients (r) were also obtained using the LA-ICP-MS signal compensation (0.9985 by LA-ICP-MS Fe+ and 0.9996 by LA-ICP-MS Ni+) rather than the LIP Fe emission compensation (0.9932). In this paper we compare and discuss the analytical performance achieved by LA-ICP-MS using LIP Fe emission, LA-ICP-MS Fe+ and LA-ICP-MS Ni+ signals as internal standards.

Effect of magnetic field on the gas-jet boosted radio frequency glow discharge atomic emission spectrometry

The effect of a magnetic field on the radio frequency (rf) powered gas-jet boosted glow discharge (GD) source was investigated. The fundamental characteristic study includes the effects of discharge power of 10–50 W, and pressures range from 2 to 7 torr, on dc bias potential, sample weight loss rate and emission intensity with and without magnetic field. The bias potential and sample weight loss do not change with pressure above approximately 4 torr; however, as the pressure is dropped below approximately 4 torr there is a significant decrease in the bias potential and sample weight loss with addition of the magnetic field, while significant enhancement in signal intensity was observed with the addition of magnetic fields using Cu samples at 40 W, 200 ml/min gas flow rate and 5 torr pressure. The Cu(I) 324.7-nm and Cu(I) 327.4-nm wavelengths were enhanced as much as three times, while one order of magnitude enhancement was observed at the Cu(II) 224.7-nm wavelength. These results show that a magnetic field in this system only enhanced the excitation of sputtered atoms, and not on the sputtering. Both magnetic and non-magnetic boosted rf-GD shows a short-term precision of <1% RSD and long-term stability of <5% RSD for both major and trace element lines. Calibration curves are linear over 3–4 orders of magnitude with a general improvement of linearity by ratioing the signal to an internal standard of the matrix in both systems. Limits of detection for magnetic boosted GD are tens part per billion from many trace elements in low alloy steel which is an order of improvement over conventional rf-GD system.

Investigation of Stable Coatings forin SituTrapping of Se and Te in Flow-Injection Hydride Generation and Graphite Furnace Atomic Absorption Spectrometry for Automated Determination

Flow-injection hydride generation andin situconcentration of Se and Te hydrides in graphite furnace atomic absorption spectrometry (AAS) can be automated using a highly stable trapping reagent replacing the Pd modifier. In a systematic study, carbide-forming elements (Zr, Nb, Ta, W) and noble metals (Ir, Ir/Mg, Pd/Ir) were investigated as stable adsorbers which require only a single application. Effective trapping of the Se and Te hydrides is achieved on Ir- and Ir/Mg-coated graphite tubes at 550–800°C. Selenium-75 radiotracer was used to measure the trapping efficiency and about 61% was obtained on an Ir-coated tube. Signal stability and reproducibility were tested over 400 trapping and atomization cycles. The adsorptive “carryover effect,” which can lead to errors in absorbance values, was observed with Te, not with Se, at trapping temperatures above 600°C (the “critical temperature”). The characteristic mass is about 11 pg for Se and 12 pg for Te, and the detection limits (3σ) are about 0.011 and 0.007 ng, respectively, on Ir-coated tubes using a 1-ml sample loop. The method was tested by determination of the elements in low-alloy steel certified reference materials.

The influence of chemical composition on peak strain of deformed austenite in low alloy and microalloyed steels

Using hot torsional tests, the influence of the most common elements in low alloy steels (C, Mn, Si, Mo) and in microalloyed steels (Ti, V, Nb) on peak strain has been studied. At the temperatures (900, 1000 and 1100°C) and strain rates (0.544, 1.451, 3.628 and 5.224 s−1) at which the tests were carried out all the elements remained in solution during deformation with the exception of titanium which was in part previously precipitated. In these conditions, the results indicate that C, Si and Mn have hardly any influence on the value of peak strain (ϵp) while Mo, V, Ti and particularly Nb considerably increase its value. The study has been completed with the modelling of ϵp as a function of the Zener-Hollomon parameter and the austenite grain size for all the steels studied, showing the quantitative influence of the different alloying elements.

Determination of transition and rare earth elements in low-alloy steels as chelates with 4-(2-Thiazolylazo)resorcinol by reversed-phase high performance liquid chromatography

4-(2-Thiazolylazo)resorcinol (TAR) is used as a chelating reagent in the reversed-phase HPLC separation and determination of transition and rare earth elements in low-alloy steels. A precolumn derivatization method is used, followed by separation on an octadecyl-bonded silica stationary phase with a sodium octane-1-sulphonate-tartaric acid mobile phase. The eluted metal chelates are detected by uv-visible spectrophotometry. The requirements for sample preparation, characterization of precolumn derivatization and the optimum conditions for the sensitive detection of metal ions after liquid chromatography (LC) separation are discussed. The influence of the pH of the chelating medium and the eluent, the concentration of TAR and the eluent were investigated. The results are compared with those of other methods such as atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES).

Distribution analysis of trace elements in low alloy steel by means of EPMA, SIMS, and TEM

A combination of chemical analysis, EPMA, SIMS, and TEM was applied to gain information on the bulk values, the microstructure and the microdistribution of contaminants. The limitations of classical chemical analysis were overcome by the application of highly sophisticated analytical techniques. Optimized measurement conditions were worked out for SIMS analysis and basic data such as relative sensitivity factors were gained for further investigations. A correlation between the microdistribution of contaminants and mechanical data could not be established so far, since only two samples were investigated.

Simultanbestimmung von Si, Mn, P, Cu, Al, Ni, Cr, Mo, V, Ti, Co und As in Stählen mit ICP-AES

A universal method for quantitative analysis of twelve elements in low-alloy steels is described. The samples are digested in a mixture of sulfuric-/nitric acid/ammonium peroxodisulfate. Si, Mn, P, Cu, Al, Ni, Cr, Mo, V, Ti, Co, As are determined in solution by ICP-AES. The procedure was tested with NBS and BCS reference samples. The analytical results are in good agreement with the certified values. With slight modifications, the method is applicable to the analysis of high-alloy steel samples.

Determination of antimony, arsenic, bismuth, selenium, tellurium, and tin in metallurgical samples using the hydride AA technique—I: Analysis of low-alloy steels

Interferences in the gas phase are very unlikely and have not yet been observed with the hydride AA technique. Gas/liquid interferences between the volatile hydride forming elements and the major and minor components of low-alloy steels can be eliminated by working in the presence of higher acid concentrations and/or in acid mixtures containing nitric acid. Conditions could be found that allow the interference-free determination of the hydride forming elements in low-alloy steels directly against acid standards with detection limits around or below 0.0002%. The influence of the valence state on the determination of antimony and arsenic was investigated.

Study on Trace Analysis of Iron and Steel by Solid Mass Spectrography(II).On Precision, Relative Sensitivities and Analytical Results by Spark Source Mass Spectrograph

Reproducibility of ion intensities, relative senisitivities of various elements by a spark source mass spectrograph were invesigated, and iron and steel were analyzed. Reproducibilities in repeated measurements with constant source parameters were5-35% in coefficients of variation, and in separate measurements6-70%. It seemed that inhomogeneity of emulsion and samples did not attribute to the fluctuation. Relative sensitivities(platinum was unity)of various elements in low alloy steel, nickel base temperature alloy, copper alloy, aluminum alloy, zinc base die casting alloy and stainless steel were 0.17-24.6. They were not related with sample materials, but with heat of sublimation of each element, however, some problems in reproducibility and measuring condition remain to be resolved. More accurate determination was performed by calibrating with relative sensitivities in analysis of standard samples stainless steel. Commercial pure iron was analyzed, and comparison with results in wet chemical methods was tried. The limit of detection was0.005 Reproducibility of ion intensities, relative senisitivities of various elements by a spark source mass spectrograph were invesigated, and iron and steel were analyzed.Reproducibilities in repeated meas urements with constant source parameters were5-35%in coefficients of variation, and in separate measurements6-70%. It seemed that inhomogeneity of emulsion and samples did not attribute to the fluctuation.Relative sensitivities(platinum was unity)of various elements in low alloy steel, nickel base temperature alloy, copper alloy, aluminum alloy, zinc base die casting alloy and stainless steel were0.17-24.6.They were not related with sample materials, but with heat of sublimation of each element, however, some problems in reproducibility and measuring condition remain to be resolved. More accurate determination was performed by calibrating with relative sensitivities in analysis of standard samples stainless steel. Commercial pure iron was analyzed, and comparison with results in wet chemical methods was tried. The limit of detection was0.005-1ppm.

Atmospheric Corrosion of Steels

The effect of additional elements in low-alloy steel on the protective rust layer has been discussed from the view point of atmospheric corrosion.The rust layer of corrosion resistant low-alloy steel is made up of two layers, the outer one which is α or γ FeOOH and the inner one which is amorphous or very fine spinel type oxide (Fe3O4).The inner layer is supposed to play an important role in the corrosion resistance of low-alloy steels in atmosphere.The method of detecting the above-mentioned dense amorphous oxide layer is presented, and the mechanism of its formation is also discussed.