Non-metallic Inclusions In Steel Research Articles

Mastering the Production of Rolled Products and Tubes of Steel 20-KSKh Guaranteed to Be Free of Corrosion-Active Nonmetallic Inclusions

Results obtained from comprehensive corrosion tests have established that in addition to limiting the content of corrosion-active nonmetallic inclusions in steel to make it resistant to corrosion, it is also desirable to restrict the steel's contents of sulfur, manganese, and silicon. The new specifications for steels 20-KS (corrosion-resistant) and 20-KSKh (corrosion- and cold-resistant) were therefore developed based on steel 20sp, which is distinguished by its relatively low contents of manganese and silicon. These steels also have a limited sulfur content, and they are microalloyed with niobium or vanadium to obtain a fine-grained structure. All the other indices of the steels meet the requirements of SNiP. Mastering the production of welded tubes made of steel 20-KSKh is an important step toward the goal of improving the durability of oil-field tubing in Western Siberia. Such tubes are the first type of tubular metal product that has been guaranteed to be clean with respect to corrosion-active nonmetallic inclusions, and guarantees of this kind are a prerequisite to ensuring that pipelines have satisfactory corrosion resistance and last for their normal service life.

Design and Application of a Set of Vitreous Standards for EDS-SEM Microanalysis of Melting Shop Slags

Non-metallic inclusions in steel are formed due to interactions between liquid steel and its environment in the melting shop (refractories and slags). Particles not trapped in the slag remain in the cast steel, impairing steel properties in service. Inclusion composition varies and certified standards covering the whole compositional range are unavailable.

鋼中介在物評価技術の最近の動向

鋼中介在物評価技術の最近の動向

A HRAES study of the morphology of non-metallic inclusions in non-oriented electrical steel containing Cu and Se

Electrical steel sheets are mainly produced from Fe–Si–C alloys. Non-oriented electrical steels contain, in addition to the important alloying elements Si, Al and Mn, other elements that determine the characteristics of the electrical steel. Al and Mn form the non-metallic inclusions AlN and MnS, which inhibit secondary recrystallization in the steel sheets. This influences both the texture development and the magnetic properties. The aim of this study was to analyze the morphology of the non-metallic inclusions in the non-oriented electrical steel sheet containing copper and selenium additions. The Fe–Si–Al alloy was produced in a laboratory vacuum-induction furnace, hot formed and then finally cold formed into a steel sheet. To achieve the optimum magnetic properties the steel sheet was decarburized in a H 2/H 2O gas mixture. The morphology of the non-metallic inclusions in the steel sheet prior to, and after, decarburization annealing at 840°C and their modification by the addition of the alloying elements Cu and Se were investigated using HRAES.

Fast Scanning Laser-OES. I. Characterization of Non-metallic Inclusions in Steel

Pulsed laser sources with high repetition rates, high beam quality and pulse-to-pulse stability are available since few years. These sources can be applied to micro-analytical scanning techniques requiring high number of laser pulses in a short time, low signal deviation and good focusability. A scanning laser-induced optical emission spectrometer (Laser-OES) using such a laser source was built up and applied to steel cleanness analysis. This novel analytical technique enables to distinguish between different inclusion types based on their chemical compositions. Coincidences of high intensity peaks for single elements at the same co-ordinates can be connected to specific inclusion types.

REDUCING THE CONTENT OF NONMETALLIC INCLUSIONS IN STEEL FOR PLATES

The content of nonmetallic inclusions in steel is one of the primary indicators of the quality of the finished product. Customers’ requirements on the overally quality of steel and on its nonmetallic inclusion content in particular have become more stringent. For example, products must conform to class 2‐3 under standard SEL072, class 0‐1 under standard GOST 22727, and class A under standard EN 160-85. To improve the quality of its flat-rolled products and retain its market reputation for high-quality steel alloyed with niobium, vanadium, chromium, nickel, molybdenum, and boron in different combinations, as well as for products destined for the domestic market (skelp for high-pressure gas-line pipe, plates and slabs for deep-sea drilling platforms, structural and bridge steel, ship plate, and high-strength boiler steel), the combine has had its specialists devise an integrated technology for obtaining continuous-cast semifinished products that keeps nonmetallic inclusions to a minimum. Stabilizing the carbon content of the steel within certain limits is the main way to lower the state of oxidation of the steel and prevent its contamination by nonmetallic inclusions. To this end, we modified the operating and design parameters of the nozzle block in the oxygen lances. This improved the blowing and slag-formation regimes in the converter process and stabilized carbon content at the sampling point (the carbon content now goes no lower than 0.05%), which in turn has allowed better control over the steelmaking operation as a whole. The quality of the deoxidizers used for the steel in large part determines the extent to which the steel will be contaminated by nonmetallic inclusions. The replacement of recycled aluminum of grade AV87 by primary aluminum reduced the amount of nonferrous-metal impurities that entered the steel. Those impurities tend to form low-melting eutectics along the boundaries of the dendrites during crystallization. The presence of these eutectics significantly weakens the boundaries in the cast steel and in the rolled product and ultimately increases the number of products rejected for defects during ultrasonic inspection. Blowing the entire melt with argon in the ladle with the use of a submersible lance creates the conditions necessary for the nonmetallic inclusions to be transferrd from the liquid metal to the slag and subsequently assimilated by the slag phase. When aluminum wire rod was added to the ladle instead of pig aluminum to correct the steel’s aluminum content, the degree of assimilation of this element increased from 45‐50% to 70‐75% and the total amount of aluminum used on the finishing unit decreased while the aluminum content of the finished steel remained stable (0.027‐0.035% Al). This ensured adequate deoxidation of the steel and attainment of the required set of mechanical properties. The reduction in aluminum consumption also decreases the degree of contamination of the steel by inclusions of alumina. The treatment of steel with calcium-silicon is known to improve the ductility properties of the rolled product. We increased the consumption of calcium-silicon of grade SK-25 or SK-30 to 1.5‐2.5 kg/ton steel by injecting it in a carrier gas (argon). In a variant, we also increased the consumption of calcium-silicon to 1.1‐1.6 kg/ton by introducing cored wire which

Comparison of spark OES methods for analysis of inclusions in iron base matters.

A statistical model for the evaluation of the emission intensities of single spark discharge spectra on three different spark OES instruments (ARL 4460, OBLF-QSN 750, SpectroLab) was developed for the analysis of non-metallic inclusions in steel. In total, the raw measurement data consists of several thousand data points (intensities), about 2000 per element channel. A histogram (frequency distribution of pulse height intensities) of inclusion-forming elements like Al, Ti and Mn performed in intensity classes and the related frequencies contain the information of the measurement. Measurement of a pure iron sample with slag powder rubbed into the surface by single spark emission spectrometry changes the originally (nearly) symmetrical histogram for inclusion related element signals to higher intensities. Thus, the known asymmetry of the histograms for steel samples is explained by the presence of inclusions.A sum of Gaussian fits representing the histogram was expected to express the different elemental species and inclusion sizes by using the variables mean, standard deviation and area of the peak containing the information of the measurement. Even a less complex approximation using a sum of two Gaussian fits is not practicable for the Al, Ti and Mn channel and the three spectrometers due to too many variables in the fitting function resulting in a large scattering. Coincidences of high signals in different element channels could be seen only in terms of MnS.A further attempt was to form the second differential of the logarithmic normal distribution and to compare the resulting partial areas below the functional graph to get information about the asymmetry of the fitting function of the original histogram. Two different procedures to evaluate the effect of the inclusion concentration on the size of the partial areas were applied to measurements on a set of synthetic samples with different concentrations of aluminium oxide in micro alloy steel. The results of both evaluation procedures correlate significantly with the inclusion concentrations. Electronic Supplementary Material is available if you access this article at http://dx.doi.org/10.1007/s00216-002-1595-1. On that page (frame on the left side), a link takes you directly to the supplementary material.

Improvement in the surface quality of ball bearing steel rounds at Bar Mill

The rejection of ball bearing steel rounds had increased at Bar Mill due to surface defects following an increase in the demand for a better surface quality. The genesis of surface defects in ball bearing steel rounds is attributed to steel-making and rolling processes. The steel-making defects are exogenous in nature with the presence of non-metallic inclusions in steel. The rolling defects are generated due to poor quality of the input billets, improper thermal regime of reheating, incorrect setting of entry and exit guides, misaligned roll pass line and inappropriate rolling schedule. This paper discusses the generation of surface defects and the formulation of a strategy to reduce these defects at Bar Mill. The improvement in the surface condition of the input billets, correct entry/exit guide setting and modification in roll pass design have reduced the rejection rate by 34.6%.

鋼中複合介在物の形態解析

鋼中複合介在物の形態解析

Activities of the Constituents in Spinel Solid Solution and Free Energies of Formation of MgO, MgO Al2O3.

Spinel (MgO·Al2O3) is known as one of the most harmful non-metallic inclusions in steel. However, the technology to avoid spinel formation has not yet been established due to lack of thermodynamic information on the spinel itself. In the present work, the free energies of formation of MgO and MgO·Al2O3, and the activities of the constituents in spinel solid solution have been directly measured by the chemical equilibrium technique. The free energies of formation of MgO and MgO·Al2O3 determined in the present work are expressed by the following equation:Mg(l) + 1/2O2(g) = MgO(s) ΔG°f, MgO = -669350 + 135.0T (J/mol)Al2O3(s) + MgO(s) = MgO·Al2O3(s) ΔG°f, MgO· Al2O3 = -20790 - 15.7T (J/mol)The activity of stoichiometric MgO·Al2O3 exhibits negative deviation from ideality in the spinel solid solution. Phase stability diagram of spinel formation in liquid steel was assessed as a function of aluminum, magnesium and oxygen contents in iron at 1 873 K. The predicted phase boundaries of MgO·Al2O3, MgO and Al2O3 agreed well with previous observations by one of the present authors.

Cluster adsorption on oxide inclusions in liquid steel

We refine the determination of forms of the existence of disperse oxide inclusions in liquid steel by taking into account the phenomenon of cluster adsorption near interfaces in structurally microinhomogeneous liquids. We show that every nonmetallic inclusion in steel is surrounded by a shell consisting of many layers of adsorbed metal clusters with thicknesses of a few tens of micrometers. From new positions, we quantitatively evaluate certain specific features of the behavior of oxide inclusions in liquid steel, namely, the effect on its viscosity, the buoyancy of inclusions, and their ability to float up depending on their nature (MgO, ZrO2, Al2O3, and SiO3) and size.

Calculation of the Critical Velocity for the Pushing/Engulfment Transition of Nonmetallic Inclusions in Steel.

Calculation of the Critical Velocity for the Pushing/Engulfment Transition of Nonmetallic Inclusions in Steel.

Nonmetallic inclusions in steel and acoustic properties of piano wire

Piano wire is a specific elastic element, which in most musical instruments is a source of sound vibrations of a specific frequency. In the production of such wire much attention is paid to an analysis of technological methods providing high functional properties for it. The present work concerns the effect of steel purity with respect to nonmetallic inclusions on the parameters of the acoustic properties of wire used for the production of strings of musical instruments.

Effect of Nonmetallic Inclusions in Steels on Stability of their Passive State

Effect of Nonmetallic Inclusions in Steels on Stability of their Passive State

Method for evaluating the content of nonmetallic inclusions in steels

Methods for evaluating the content of nonmetallic inclusions in ShKh 15, ShKH5SG, and ShKh20SG steels used for rolling bearings are considered. These methods can be applied to other steels used for various parts that fail in operation due to fatigue spalling.

サブミクロン二次イオン質量分析装置を用いた鋼中非金属介在物粒子の粒別分析

Nonmetallic inclusions frequently exert a lot of unfavorable influences on the quality of steel. The size of nonmetallic inclusions in current steel products is less than a few μm in diameter. It is desirable to make clear the origin and generation process of such small particles of nonmetallic inclusion. In order to measure the shape, size, composition and inner elemental distribution, development of characterization methods for each inclusion particle is required.By employing a gallium focused ion beam (FIB) as a primary ion beam of secondary ion mass spectrometry (SIMS), the particle analysis with high spatial resolution is easily achieved. In this paper, we present the novel individual analysis of nonmetallic inclusions in steel by gallium FIB SIMS.We analyzed in two ways the nonmetallic inclusion particles segregated by electron beam melting. (1) By crosssectioning of the particle using a gallium FIB, elemental maps of cross-section were obtained. The elements were distributed inhomogeneously on the cross-section. (2) We carried out the compositional analysis for several particles individually. Ten particles were analyzed by the shave-off analysis and the multivariate cluster analysis. Based on the composition of each particle, the inclusions were classified into six types.

介在物はどこからくるのか

介在物はどこからくるのか

Filtration Mechamism of Non-metallic Inclusions in Steel by Ceramic Loop Filter.

For the reduction of non-metallic inclusions in steel, a ceramic loop filter has been developed. Void size of the filter can be adjusted widely by varying the string and loop diameters respectively. Characteristics of the loop filter, such as an inclusion removal efficiency and filter medium resistance were investigated in laboratory. From the experimental results, the mechanism of the filtration was discussed, and it was concluded that firstly the inclusion particle is entrapped onto the filter surface by the interception, secondly glued there by the attraction force based on the molten steel surface tention, and finally bonded by sintering.

Effect of specimen geometry on fatigue crack growth in plane strain. II. Overload response: Shercliff, H.R. and Fleck, N.A. Fatigue Fract. Eng. Mater. Struct. 1990 13, (3), 297–310

The safety assessment of railway axles is based on a two-stage approach: fatigue strength design and regular inspections which, in terms of a general safety philosophy refer to safe-life and damage tolerance concepts. Starting with a recent failure case, a broken axle of a German high speed train, a discussion is presented on issues of both safety levels. These include ideas for finite life design, the treatment of in-service effects on the fatigue strength due to flying ballast damage and corrosion pits, the effect of corrosion on fatigue crack initiation and propagation, potential effects of non-metallic inclusions in steels, the way to detect them by quality control measures and reliability aspects of non-destructive testing with respect to the detection of fatigue cracks. Proposals are made how the safety level could be further improved.

Effect of very rapid explosive deformation on the structure and composition of nonmetallic inclusions in steels

Most nonmetallic inclusions are brittley ruptured in very rapid deformation, or brittle laminations form on their interface with the matrix. Ductile sulfides are nonuniformly deformed. In the matrix deformation is localized around the inclusions. Besides, zones adjacent to inclusions are characterized by the development of deformation by the rotational mechanism.