Chemical Composition Of Steel Research Articles

Analytical model of stress field in submerged arc welding butt joint with thorough penetration

Analytical model of temporary and residual stresses for butt welding with thorough penetration was described assuming planar section hypothesis and using integral equations of stress equilibrium of the bar and simple Hooke’s law. In solution the effect of phase transformations (structure changes and structural strains) has been taken into account. Phase transformations during heating are limited by temperature values at the beginning and at the end of austenitic transformation, depending on chemical composition of steel while the progress of phase transformations during cooling is determined on the basis of TTT-welding diagram. Temperature values at the beginning and at the end of transformation are conditioned by the speed of heating. Kinetics of diffusional transformation is described basing on Johnson-Mehl-Avrami-Kolmogorov equation, while martensitic transformation, basing on Koistinen-Marburger equation. Stresses in elasto-plastic state are determined by iteration, using elastic solutions method with changeable longitudinal modulus of elasticity, conditioned by stress-strain curve. Computations of stress field have been conducted for one-side butt welded of two steel flats made from S235 steel. It has enabled a clear interpretation of influence of temperature field and phase transformation on stresses caused by welding using Submerged Arc Welding (SAW) method.

Novi alati za model zavarljivosti čelika zasnovan na oceni rizika

In this paper a new weldability model is presented, which can be applied to different steels grades based on a risk analysis, parent and filler materials properties, welding process and welding technology. The previous weldability models based on carbon equivalent formula or on other indirect methods available in the literature have limited applications. This is because it consider only the steel chemical composition, ignoring others process factors over the weldability. The weldability should consider all material and process factors of influence, even for the very same steel grade, which can be welded in different conditions, thus obtaining different weldability results.

Scientific and Technological Principles of Development of New Cold-Resistant Arc-Steels (Steels for Arctic Applications)

The paper presents the results of quantitative analysis of C, Mn, Ni and Cu content on strength and cold-resistance of rolled plates. Relations between the ferritic-bainitic structure morphology and anisotropy and steel performance characteristics have been established. Influence of thermal and deformation rolling patterns on steel structure has been studied. The steel chemical composition has been improved and precision thermomechanical processing conditions for production of cold-resistant Arc-steel plates have been developed.

Prediction of electrical resistivity of steel using artificial neural network

ABSTRACTElectrical resistivity of commercially produced plain carbon manganese steel has been experimentally measured at room temperature (28–30°C) using four-probe method. Resulting data were used to generate both regression based and artificial neural network-based models for prediction of electrical resistivity from the chemical composition of steel. It was found that both models were capable of predicting the resistivity within ±5% error band. Analysis of data also indicated carbon to be the most influential element to increase resistivity followed by manganese and silicon. A comprehensive literature review indicates no such advanced resistivity prediction model is available in the public literature for commercially produced steel with wide variation in carbon content (0.03 0.85 wt-%), manganese content (0.35–1.50 wt-%) and silicon content (0.015–0.90 wt-%).

Integranular corrosion susceptibility analysis in austeno‐ferritic (duplex) stainless steels

AbstractDuplex stainless steels (DSSs) are characterized by a really good generalized corrosion resistance in many environments and by really interesting mechanical properties, considering both static or quasi‐static and cyclic loading conditions. DSSs are characterized by secondary phases, nitrides, and carbides precipitation phenomena, with consequent age hardening and embrittlement. These mainly occur inside ferritic grains and next to ferrite‐austenite grain boundaries, with a consequent DSS susceptibility to intergranular and/or localized corrosion phenomena and the initiation and propagation of intergranular cracks. In this work, the influence of the secondary phases, nitrides, and carbides precipitation phenomena on intergranular and localized DSS corrosion resistance was investigated, considering both the lower and higher critical temperature ranges and steel chemical composition.

Predicting the risk of pitting corrosion initiation of stainless steels using a Markov chain model

A probabilistic approach based on Markov chains for the assessment of pitting and crevice corrosion initiation is proposed. A Markov chain is a stochastic process that undergoes transitions from one state to another through a finite number of possible states, until a so‐called “absorbing state” from which the system has no tendency to evolve is attained. The proposed model calculates the probability to have pitting or to maintain a stable passive condition involving a large number of operating parameters related to both metal and environment: steel chemical composition (namely, the PREN index), chlorides content ([Cl−]), chloride critical threshold ([Cl−]cr), temperature, pH, fluid velocity, electrochemical steel potential, E, presence of crevices. Model and algorithms are mainly based on corrosion data collected from literature. Although the proposed model needs experimental confirmation, the simulations here presented seem acceptable, considering the engineering application of stainless steels.

Analysis of features of stainless steels in dissimilar welded joints in chloride inducted corrosion

Stainless steels of femtic-austenitic microstructure that means the duplex Cr-Ni-Mo steels, in comparison with austenitic steel includes less expensive nickel and has much better mechanical properties with good formability and corrosion resistance, even in environments containing chloride ions. Similar share of high chromium ferrite and austenite, which is characterized by high ductility, determines that the duplex steels have good crack resistance at temperatures up to approximately -40°C. The steels containing approximately 22% Cr, 5% Ni, 3% Mo and 0.2% N crystallizes as a solid solution δ, partially transforming from the temperature of about 1200°C to 850°C into the phase α. The stable structure of considered steels, at temperatures above 850°C, is ferrite, and at lower temperatures the mixture of phase γ+α +σ. The two-phase structure α+γ the duplex steel obtains after hyperquenching at the temperature of stability of the mixture of α+γ phases, and the share of the phases depends on the hyper quenching attributes. Hyperquenching in water, with a temperature close to 1200°C, ensures the instance in the microstructure of the steel a large share of ferrite and a small share of the high chromium austenite. This causes the increase of strength properties and reducing the plasticity of the steel and its resistance ability to cracking and corrosion. Slower cooling from the mentioned temperature, for example in the air, enables the partial transformation of the a phase into the γ one (α → γ) and increasing the share of austenite in the steel structure. It leads to improvement of plasticity properties. In the paper are presented the results of investigations of heteronymous welded joints of duplex steel and austenitic one. The results include the relation between the chemical composition of steels and their weldability.

Three-dimensional numerical modeling of the friction stir welding of dissimilar steels

Steady- and transient-state solutions are developed to predict temperature, streamlines, stress, and viscosity distributions during the friction stir welding of dissimilar carbon steels AISI/SAE 1008 and 1078. The mass, momentum, and energy transport equations are solved using a Eulerian formulation within the computational fluid dynamics package FLUENT in the plates of dissimilar steels being joined. Viscoplastic behavior in the stir zone is supposed. Both Medina and Hernandez flow stress and Perzyna viscoplastic models are used to model this behavior. The Medina and Hernandez model calculates the flow stress based on the Zener–Hollomon parameter, which is valid for large deformations and high strain rates and takes into account the steel chemical composition of any structural steels having low or medium carbon contents. The present work couples this flow stress model to the continuity, momentum, and energy transport equations. Temperature-dependent thermal properties are taken from the literature. A comparison of temperature cycles taken from published experimental data and those obtained by simulation is presented. Results indicate that the steady-state simulation can provide solutions more quickly than simulation using the transient model. However, the latter simulation provides temperature, stress, viscosity, and volume fraction distributions that are more detailed than those that the former simulation provides, with the distributions being asymmetric at welding times longer than 30 s. Volume fraction distributions are more symmetric for a rotational speed ? = 450 rpm and a welding velocity U = 0.31 mm s -1. The shape of the stir region is strongly related to the temperatures on the advancing side (AISI 1008 steel) and retreating side (AISI 1078 steel) and the thermo-mechanical properties of the steels; the lobular shapes correspond to those found experimentally.

Mathematical modeling of steel chemical composition and modes of thermomechanical treatment influence on hot-rolled plate mechanical properties

Methods of economical alloying of high pipe steels were considered in the paper. Due to the large environmental, energy, and economic issues in the destruction of the pipeline, the quality of steel pipes is very important. The method described in this article is considered to be relevant not only for pipe steels but also for high-strength steels used in shipbuilding, bridge construction, etc. Review mechanisms of strengthening microalloyed steels were carried out in this work. Schema evolution of the microstructure of microalloyed steels was discussed. The influence of alloying elements in steel by means of optimal process parameters of thermomechanical rolling was analyzed. There are two methods of mathematical modeling used in the study: artificial neural networks (ANNs) which are based on the multilayered perceptron to select the optimal chemical composition and finite element analysis to optimize the process parameters. An experimental dataset was used to train multilayer perceptron (MLP) networks to allow for prediction of the yield strength, tensile strength, and elongation of steel. Due to large availability, low cost, and high accuracy of the results, these methods are considered to be the most promising ones. The mathematical model for calculating mechanical properties of a rolling pipe has been developed. Two ways to reduce the cost of a hot-rolled plate made of microalloyed steels were developed. There has been developed the complex of replacement technological impact which can make it possible to replace or reduce the amount of expensive chemical elements (vanadium, nickel, copper, manganese, chromium, and niobium) without loss of quality.

Stress corrosion cracking in the context of deep geological nuclear disposal – investigations on P235 and P265 steels

ABSTRACTStress corrosion cracking of P235 and P265 steels is investigated through slow strain rate and constant deformation tests on samples exposed in a cell reproducing the underground conditions of the French deep geological nuclear disposal, at 25 and 90°C. The samples were taken from the base metal, the heat affected zone and the fusion zone of a P265 steel weld joint. Tests were performed at the free corrosion potential and under polarisation in the cathodic or anodic domains. Long-term constant deformation tests were also carried out to evaluate the behaviour of the material under static loading in hydrated clay environment. The results show a significant sensitivity of the tested materials to environmental cracking in the experimental conditions, with an enhancement of the effect of the environment for the weld metal. A mechanism of hydrogen embrittlement is proposed to be responsible for the cracking phenomenon. Susceptibility to environmental assisted cracking observed during these tests indicates the need to optimise welding parameters and steel chemical composition and metallurgy, particularly regarding the presence of inclusions in the base metal and stress relief of the weld metal.This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

Dependence of strength and fracture behaviour on chemical compositions in spot-welded L-type joints

In order to achieve lighter and stronger car bodies by applying high strength steel sheets, one of the key technologies is enhancement of joint strength. In this study, we investigated dependence of strength and fracture behaviour on chemical compositions of steels in spot-welded L-type joints in detail. Consequently, the following experimental results were obtained. (1) Maximum load of the joint decreased with increase of carbon (C) and phosphorous (P). The maximum load was decreased by 0.4–0.7 kN with increase of 0.1% in C, with C content ranging from 0.03 to 0.5%, and 0.5 kN with increase of 0.01% in P, with P content ranging from 0 to 0.03%. (2) Fracture portion changed from the outside to the inside of weld metal with increase of C and P. (3) The fracture path was estimated to accord with the solidification segregation site in the weld metal in the case of a steel of 0.2% C, 0.03% P. (4) By implementation of an appropriate post heat during spot welding process for the steel of 0.2% C, 0.03% P, the degree of solidification segregation was clearly reduced and the maximum load of the joints was improved by 70%.

METALLURGICAL ASPECTS RELATED TO CONTACT FATIGUE PHENOMENA IN STEELS FOR BACK-UP ROLLS

The need of even longer rolling sessions is driving the improvement of back up rolls in terms of wear resistance. This is also aimed to reduce costs. In this paper the effect of steel chemical composition on contact fatigue phenomena, bringing to the macroscopic damage named spalling is reported. Results show that the removal by grinding operations of damaged portion of rolls surface should be not sufficient to restore the initial performances of material. Experimental tests showed that a portion of material below the damaged one keeps memory of the last fatigue cycle, and has to be removed.

A METHOD FOR OPTIMIZING CHEMICAL COMPOSITION OF STEELS TO REDUCE RADICALLY THEIR ALLOY ELEMENTS AND INCREASE SERVICE LIFE OF MACHINE COMPONENTS

A method for optimizing chemical composition of steel is proposed and a correlation is established to reduce cardinally alloy elements in existing steel grades that results in high compressive residual stresses at the surface of intensively quenched steel parts and increasing strength and ductility of material due to super- strengthening phenomenon. The algorithm of optimization consists in reducing alloy elements in existing alloy steel in 1.5 – 2 times and then lowering step-by-step content of steel, beginning from the most costly alloy element and ending the most cheaper one, until established correlation is satisfied. The range of reduction is minimal and during computer calculations can be chosen as 0,001wt%. The proposed approach can save alloy elements, energy, increase service life of machine components and improve environmental condition. The method is a basis for development of the new low hardenability (LH) and optimal hardenability (OH) steels.

NEURAL NETWORK MODEL OF IRON DIFFUSION IN AUSTENITIC STEELS

Speed of iron diffusion in austenitic steels is one of the major factors determining swelling of a constructional material of units and details of an active zone of a fast nuclear reactor. The factor of iron diffusion essentially depends on a chemical composition of steels and alloys on the basis of iron. Therefore the problem of its modeling is rather actual. The file of experimental data on diffusion in steels and alloys containing various combinations of C, Si, Cr, Ni, Mn, Mo, Nb, Ti, V, W, Al, Pb, Bi, Sn and Sb in a range of temperatures of 1023 ÷ 1666 K has been generated on the basis of literary data. For correct approximation of iron diffusion the artificial neural network was used in the form of 4-layer-perceptron with number of units on layers as 49:10:17:1. Developed neural network model was tested on independent experimental data and has shown satisfactory statistical characteristics that shows its adequacy. Calculations of coefficient of iron diffusion in pure iron and both steels of grades ChS68 and EK164 show higher factor of diffusion in steels, than in pure iron. On the basis of the developed model the diffusion coefficients of shells of two fuel elements of EK164-ID c.d. steel have been calculated. Fuel elements were irradiated in a reactor on fast neutrons BN-600 at various temperatures and damaging dozes at their maximal and minimal alloying. Calculations have shown that in the steel containing a minimum quantity of alloying elements, speed of diffusion is below, than in steel with maximal contents of alloying elements, and swelling in inverse proportion to coefficient of iron diffusion in EK164-ID c.d. steel. On the basis of these data it has been received linear (in logarithms) regression equation of steel swelling S depending on temperature T, damaging doze D and coefficient of iron diffusion DFe : lnS = –340,511 + 0,036 lnD + 42,64lnT – 1,558lnDFe , where D is measured in dpa; Т – in degrees of Celsius; DFe – in m2 /s; S – in %. A range of change of temperature was 435 – 515 °С, damaging doze was 57 ÷ 76 dpa.

基于成本控制的转炉冷却工艺优化

以物料平衡和热平衡为基础建立了转炉原料成本计算模型，并考察了冷却剂结构变化对转炉物料平衡和原料成本的影响作用规律。结果表明，降低废钢比、提高矿石比和石灰石比均可有效降低转炉原料成本，且矿石替代废钢的降本效果更为显著。综合考虑转炉冷却效果和吹炼过程的稳定性，确定了“先降低废钢比，依次用矿石和石灰石平衡转炉热量”的冷却工艺优化设计原则，并设定了废钢比下限和矿石比上限。工业试验和原料成本核算表明，冷却工艺优化后，转炉吹炼过程平稳，冶炼终点钢水温度和成分及终渣成分控制准确、稳定，且脱磷效果有所改善，转炉原料成本显著降低。 A cost calculation model of converter raw materials was established based on converter material balance and heat balance, and the effect of the cooling agents on the cost of raw materials was in-vestigated. The results showed that it is beneficial to reduce the cost of raw materials through re-ducing scrap ratio, increasing ore ratio and limestone ratio, and the substitution of scrap with ore is more remarkable for cost reducing. Considering the cooling effect and the stability during blowing synthetically, the optimization principle of converter cooling was established, and it is that reducing scrap ratio firstly, then using ore and limestone to balance converter heat in sequence, and the inferior limit of the scrap ratio and the superior limit of the ore ratio were set. The results of industrial experiments and the cost accounting showed that the blowing process was stable, and the steel temperature of the blowing endpoint can be controlled accurately, and the chemical compositions of steel and slag of the blowing endpoint were stable. Furthermore, the dephosphorization effect was improved, and the raw materials cost of converter was reduced sig-nificantly.

Industrial Testing of Group IV Hardness Grinding Balls Produced by Donetsk Metal Rolling Plant

Results are given for a complete processing scheme for manufacturing small diameter grinding balls of hardness groups III and IV produced from small cross-section continuously-cast carbon steel billet. The steel chemical composition and rolling and heat treatment regimes proposed have made it possible to produce balls of grinding hardness groups III and IV since the beginning of mastering ball rolling mill 30–80. Industrial tests of grinding balls 40 mm in diameter of hardness group IV performed under Southern Mining and Processing Plant conditions demonstrate that grinding efficiency of finished class size –0.074 mm is better by 3.1% higher and specific consumption of grinding balls is 8.83% lower than in the case of using grinding balls of hardness group III produced by DMKD or Azovstal Metallurgical Combine.

Analysis of the intergranular corrosion susceptibility in stainless steel by means of potentiostatic reactivation tests

Abstract: Intergranular corrosion cracking in stainless steels is a selective corrosion attack due to a local (grain boundary) Cr depletion. An undesired Cr carbides (Cr 23 C 6 ) precipitation after heat treatment in the sensitization temperature range (usually between 550 and 850°C, depending on the steel chemical composition) is obtained with a kinetics that is mainly influenced by the C content. In this work, the sensitization susceptibility of four sensitized stainless steels was investigated by means of potentiostatic reactivations tests. In addition, chronoamperometric tests and scanning electron microscope (SEM) observations of the specimens surfaces were performed in order to analyze the evolution of the corrosion morphologies.

Transformation of 20Х13 steel structure during intensive friction interactions

The results of an investigation of the influence of intensive friction interactions upon the transformation of a 20Х13 steel structure using optic metallography, scanning electron microscopy, and X-ray microanalysis have been described. It has been stated that, at a depth of 3 mm, structural changes connected with heating and intensive plastic deformation processes take place. Diagrams of chemical elements distribution show changes in the steel chemical composition in the surface layer up to 20 μm depth. An increase in microhardness to 5000 MPa has been observed at certain sections.

Quality assessment of structural steel in mining equipment manufacture

The relevance of this work is to form a methodical, scientific-based approach and the application of this experience in solving problems of quality control and improvement, as well as to identify ways of eliminating defects and small lifetime of the materials, used in critical parts and units of mining equipment. The aim of scientific research of the article is the study of discrepancy of structural steels quality problem, used for the manufacture of parts and components of mining equipment, established by standards. The goals are also, development and practical application of quality control methods in delivery condition and at all main stages of parts manufacture in accordance with the current state standards. As a result of steel quality complex control in delivery condition, it was possible to identify: the deviation of the chemical composition of steels and alloys, macrodefects, microdefects, deviation in hardness. Practical recommendations to eliminate and reduce and prevent the defects in parts and units used in mining engineering were developed. The paper presents practical experience in evaluation the quality of construction materials, which may be useful in design, manufacture and operation of mining industry and related manufacture industries.

Computer Simulation of Microsegregation of Sulphur and Manganese and Formation of MnS Inclusions while Casting Rail Steel

Abstract The quality of rail steel is conditioned by its high mechanic qualities, which greatly depend on the presence of undesired nonmetallic inclusions. The paper is devoted to the segregation of components, mainly sulphur, and the formation of manganese sulphide in the process of steel solidification, at the casting rate of 100 and 500 K/min. Sulphur is a steel component which disadvantageously influences its numerous parameters. The oxide-sulphide and sulphide precipitations cause cracks and lower the strength of the material. This phenomenon was modeled with the use of author’s computer program based on Matsumiya interdendritic microsegregation model. The main assumptions of this model and thermodynamic conditions of inclusion formation during casting of steel are discussed in this paper. Two cases were analyzed: in the first one the MnS was assumed to form a pure and constant compound, whereas in the other one the manganese sulfide was precipitated as a component of a liquid oxide solution, and its activity was lower than unity. The final conclusion is that chemical composition of steel is the major parameter deciding about the formation of MnS inclusions.