Mechanical Properties Of Steel Research Articles

Variation of microstructure and mechanical properties of medium Mn steels with multiphase microstructure

Specimens of medium manganese steels with different manganese contents were austenised at 850°C for 30 min followed by intercritical annealing and water quenching at three different temperatures with different times. After heat treatments, mechanical properties were measured through tensile test. X-ray diffraction, electron back scattered diffraction and scanning electron microscopy examinations were also performed. Results indicate that annealing time, annealing temperature and manganese content all affect the final microstructure, which may consist of ferrite, retained austenite and fresh lath martensite, and variation of microstructure leads to different mechanical properties of steel.

Tank Structural Fatigue Fracture in Hydrocarbon Transportation

The article touches upon the reasons of cracks formation in a vertical steel tank wall used in oil transportation. Here are given the comparative research results of chemical composition and mechanical properties of steel, used in manufacture of the flat product: tensile strength, yield strength, impact strength and hardness.

Effect of micro-cracks in nonhomogeneous stress field on fracture instability in structural components

The paper analyses the effects of statistical distribution in sizes of micro-cracks on scatter of fracture toughness of steels under brittle conditions. The results are utilized for reliability assessment of selected functional parts. The reliability considered as a complementary probability of brittle fracture initiation is discussed in dependence on the character of statistical distribution of micro-crack sizes, mechanical properties of steel, mechanisms of energy dissipation during cracks propagation, variation of loading, stress state of functional part and its service life. This probability approach is compared with deterministic reliability access originating from computation of safety factor. Its rational evaluation as a function of acceptable probability of fracture instability provides high economical effects saving materials and energy.

Analysis of Mechanical Behavior and Microstructural Characteristics Change of ASTM A-36 Steel Applying Various Heat Treatment

In this study ASTM A-36 (mild steel) is selected as specimen for testing various mechanical properties and microstructure change. The effects of heat treatment on the mechanical properties and microstructure characteristics change of selected specimen are analyzed. Annealing, hardening and tempering are the most important heat treatment processes often used to change mechanical properties of engineering materials. The purpose of heat treating is to analyze the mechanical properties of the steel, usually ductility, hardness, Yield strength, tensile strength and impact resistance. The heat treatment develops hardness, softness, and improves the mechanical properties such as tensile strength, yield strength, ductility, corrosion resistance and creep rupture. These processes also help to improve machining effect, and make them versatile. The mechanical properties can easily be modified by heat treating to suit a particular design purpose. In the present study, selected samples are heat-treated at certain temperature above the austenitic region and quenched in order to investigate the effect on the mechanical properties microstructure of the mild steel. The changes in mechanical behavior and microstructure as compared with unquenched samples are explained in terms of changes in tensile strength. Results showed that the mechanical properties of mild steel can be changed and improved by various heat treatments for a particular application.

Assessment of stainless steel 348 fuel rod performance against literature available data using TRANSURANUS code

Early pressurized water reactors were originally designed to operate using stainless steel as cladding material, but during their lifetime this material was replaced by zirconium-based alloys. However, after the Fukushima Daiichi accident, the problems related to the zirconium-based alloys due to the hydrogen production and explosion under severe accident brought the importance to assess different materials. In this sense, initiatives as ATF (Accident Tolerant Fuel) program are considering different material as fuel cladding and, one candidate is iron-based alloy. In order to assess the fuel performance of fuel rods manufactured using iron-based alloy as cladding material, it was necessary to select a specific stainless steel (type 348) and modify properly conventional fuel performance codes developed in the last decades. Then, 348 stainless steel mechanical and physics properties were introduced in the TRANSURANUS code. The aim of this paper is to present the obtained results concerning the verification of the modified TRANSURANUS code version against data collected from the open literature, related to reactors which operated using stainless steel as cladding. Considering that some data were not available, some assumptions had to be made. Important differences related to the conventional fuel rods were taken into account. Obtained results regarding the cladding behavior are in agreement with available information. This constitutes an evidence of the modified TRANSURANUS code capabilities to perform fuel rod investigation of fuel rods manufactured using 348 stainless steel as cladding material.

Research on Hysteretic Performance of Steel Reinforced Concrete T-shaped Column

Through applying MSC.Marc nonlinear finite element software, this research is to explore the ductility performance of steel reinforced concrete T-shaped columns under reciprocating loading. The result shows that the MSC.Marc calculation results are quite consistent with the experimental data, and can objectively reflect the mechanical properties of steel reinforced concrete special-shaped columns. These mean that the MSC.Marc software can be used for performing simulation analysis on the steel reinforced concrete special-shaped column hysteretic performance. Through changing the axial compression ratio, shear span ratio and load angle to research the ductility performance of steel reinforced concrete T-shaped columns under reciprocating loading, the main conclusions are as follows: The bearing capacity of steel reinforced concrete t-shaped cross section column decreases with the increase of shear span ratio; displacement ductility decreases with the increase of axial compression ratio; mechanical properties of the web load are superior to the ones of the flange load.

Steel–concrete–steel sandwich system in Arctic offshore structure: Materials, experiments, and design

The gravity based structure (GBS) with external Steel–Concrete–Steel (SCS) sandwich ice-resistant wall has been developed for the Arctic oil and gas drilling. This paper firstly reported the experimental studies on the mechanical properties of steel and concretes under Arctic low temperature. With the test data, design equations were developed to incorporate the influences of the low temperature on these mechanical properties. Two types of Arctic GBS structure with flower-conical SCS sandwich shell type and plate type of ice-resistant wall have been developed for the Arctic offshore structure. Besides the studies on the materials, two SCS sandwich prototype shells and plates were, respectively, prepared and tested under patch loading that simulated the localized ice-contact pressure. The structural behaviors of the SCS sandwich structure under patch loading were reported and discussions were made on the influences of different parameters on the structural behavior of the structure. Analytical models were developed to predict the punching shear resistances of the SCS sandwich structure through modifying the code provisions. The accuracies of the developed analytical models were checked through validations against 27 tests in the literature. Corresponding design procedures on resistances of SCS sandwich structure were recommended based on these discussions and validations.

CARBON, NITROGEN AND HYDROGEN IN STEELS: PLASTICITY AND BRITTLENESS

Interstitial elements in steel, carbon, nitrogen and hydrogen, are analyzed in terms of their effect on the electron structure, properties of dislocations, strengthening, plasticity and fracture. It is shown that similarities and differences in the mechanical properties of corresponding solid solutions are controlled by the effect of the above mentioned elements on the density of electron states at the iron Fermi level and, as a result, on the concentration of free electrons. The latter is decreased by the carbon and increased due to nitrogen and hydrogen in the iron, which changes the character of interatomic bonds: carbon enhances their covalent component, whereas nitrogen and hydrogen strengthen the metallic one. The velocity of dislocations in the course of plastic deformation is discussed using the approach of mobile and immobile interstitial atoms. In the fi rst case, they are obstacles for dislocation slip, and mobility of dislocations is determined by the enthalpy of binding between interstitial atoms and dislocations. If interstitial atoms are suffi ciently mobile to accompany dislocations, the character of interatomic bonds within the interstitial clouds around the dislocations is locally changed. As a result, the specifi c energy of dislocations (line tension) and the distance between them in the pile-ups are changed in accordance with the local change of the shear modulus around the dislocations. Based on the performed studies, the effect of interstitial elements on the mechanical properties of steels is discussed. Particularly, the essential similarity between the hydrogen-caused brittleness and the nitrogen-induced ductile-to-brittle transition in the austenitic steels is interpreted.

Corrosion effects on the mechanical properties of reinforcing steel bars. Fatigue and σ–ε behavior

Corrosion of steel reinforcement is one of the most severe problems of durability in reinforced concrete structures. A good understanding of the corrosion effects on the reinforcing steel mechanical properties is necessary to adequately assess impaired structures. A study of the mechanical response of corroded reinforcement subjected to monotonic and cyclic loads by means of an experimental study is presented in this work. More than 180 corroded specimens, 40 monotonic and 140 fatigue tests were performed. Relationships between corrosion penetration and the mechanical properties of reinforcing steel bars were identified. In addition, a study of the influence of the pit geometry on the fatigue life was carried out. A severe non-linear reduction in the mechanical properties studied, related to the corrosion degree was observed. These phenomena can provide relevant information for the assessment of existing structures and for life cycle evaluation.

REINFORCED CONCRETE BEAMS USING LOCALLY MANUFACTURED STEEL BARS: INVESTIGATION OF FLEXURAL BEHAVIOR

While much attention has been and continue deservedly to be given to the effect of the variability of concrete strength and properties on the response of reinforced concrete structures, there is little, if any, information on the effects of variability of steel strength. Steel mechanical properties, including its yield strength, can significantly exceed the minimum nominal strength values for a specific grade of steel depending on the steel manufacturing processes. Such an increase in yield strength can have negative effects on the flexural behavior of beams designed as tension controlled, and reduce their ductility, an essential property in seismic resisting structures. An experimental and analytical study of the flexural behavior of RC beams was conducted through the investigation of the Moment-Curvature relationships and the ultimate steel strains. The main variable was the level of the actual steel yield stress as compared to the nominal value. It was found that unexpectedly high values of steel yield stress reduce the beam ductility and violate the tension-control condition, which was enforced in the design stage. Appropriate design corrections are proposed to account for high yield stress values in order to achieve the desired ductility of beams while maintaining the moment capacities.

Numerical study of steel plate girders under shear loading at elevated temperatures

The ultimate shear capacity of steel plate girders may be influenced by shear buckling, an important and common instability phenomenon occurring in plate girders with slender webs. The transverse loads and consequent shear effort applied on such beams have a large impact on the webs, leading to the possible collapse by shear buckling. In a fire situation, the buckling phenomena in these structural elements are amplified due to the reduction of the steel mechanical properties caused by the elevated temperatures. Recently, there has been an increase in the use of those plate girders, arising from the search for more economical and competitive solutions. However, no specific rules for shear buckling verification in case of fire are given in Eurocode 3 (EC3).After the validation of the numerical models against experimental tests from the literature, an extended number of geometrically and materially nonlinear numerical analyses including imperfections (GMNIA) have been performed dealing with the evaluation of the effect of rigid and non-rigid end posts on the ultimate shear capacity of steel plate girders under fire. The obtained numerical results are compared with the specifications of EC3 for the design at normal temperature adapted to elevated temperatures. These specifications are non-conservative and, for this reason, a new design proposal harmonized with the EC3 principles is presented in order to evaluate the ultimate shear capacity of steel plate girders in fire situation.

Characterization of the fracture behaviour of X42 microalloyed pipeline steel

Purpose – The purpose of this paper is to investigate the fracture of grade X42 microalloyed steel used as pipe material after tensile test at room temperature and impact tests at 0, −20 and −40°C, respectively. Design/methodology/approach – In the first stage of the study, X42 steels in the form of sheet and pipe materials were selected and etched samples were characterized using light microscope. In the second stage, mechanical properties of steels were obtained by microhardness measurements, static tensile and impact tests and all the broken surfaces were examined by scanning electron microscope to determine the fracture type as a function of both microstructure and loading. Findings – The examinations revealed that: first, the sheet material had a typical ferritic-pearlitic matrix, second, the transverse section of the sheet steel exhibited a matrix consisting of polygonal ferrite-aligned pearlite colonies and the longitudinal one had elongated ferrite phase and pearlite colonies in the direction of rolling, third, ferrite and pearlite distribution was different from the sheet material due to multiaxial deformation in the pipe material, fourth, tensile fracture surfaces of the steels had typical dimple fracture induced by microvoid coalescence, fifth, impact fracture surfaces of the steels changed as a function of the test temperature and cleavage fracture mode of ferritic-pearlitic matrix became more dominant as the temperature decreased, and sixth, grain morphology had an effect on the fracture behavior of the steels. Originality/value – The paper explains the fracture behaviour of X42 microalloyed pipeline steel and its fractographical analysis.

Mechanical properties of steel 20 at small deformations

The elastic hysteresis and residual deflections of samples made of steel 20, which correspond to the model of a thin rigid round plate pinched over the contour, have been investigated. It has been shown that annealing of the samples at 470 and 670 K weakly affects these characteristics, while after complete annealing (1170 K), the aging of steel 20 for three days is accompanied by a decrease in amplitude ωh of the elastic hysteresis by ∼20%. A postulate that there is no elasticity limit of metals, below which residual deformation would be absent, has been confirmed experimentally. It has been shown that, based on the values of ωh, the ultimate strength of metals can be estimated acting on the samples by stresses smaller than the yield stress by an order of magnitude. A giant increase (by a factor of ∼2.5) in ωh has been found after a prolonged (for 2 months) aging of steel 20 after the diffusion of hydrogen from it, which indicates the corresponding decrease in its cyclic longevity.

The Influence of Austenisation Temperature and Holding Time on Mechanical Properties, Scale Thickness, and Microstructure in Alloy Steel

The application of steel products have been widely used and various research have been developed to find a good and appropriate quality of steel and can be produced in the country without have to be imported, for example alloy steels. One of the alloy steels that have been constantly developed is Ni-Cr-Mo alloy steel with additional nickel, chromium and molybdenum which can increase hardness, tensile strength, ductility and toughness. The effect during the production process is at the heating process that causes the formation of iron oxide layer (scale) and the loss of steel weight. Therefore, the selection of heat treatment methods and techniques are required to increase the mechanical properties of steel, such as hardness, tensile strength, and toughness, with the scale is about <5% of steel weight. In this research, the heat treatment was carried out at austenisation temperature of 800°, 850°, 900°C and at holding time of 20, 40, 60 minutes, then followed by a rapid cooling (quenching) to improve the mechanical properties of hardness. This research also tested the mechanical properties of steel that consist of hardness test and impact test, and metallographic observation that consist of micro structure observation and scale thickness observation. The micro structure from heat treatment process is martensite, it is due to a rapid cooling (quenching) that rapidly change the austenite phase into martensite. The data showed the highest hardness is 588.35 HVN at 850°C of temperature and 60 minutes of holding time, 8.5 Joules of impact energy, and 91.5 μm of scale thickness. While the lowest hardness is 539.34 HVN at 800°C of temperature, 5 Joules of impact energy, and 47.81 μm of scale thickness.

Use of Nitrocarburizing for Strengthening Threaded Joints of Drill Pipes from Medium-Carbon Alloy Steels

Nitrocarburizing is tested at the Drill Equipment Plant for reinforcing threaded joints of drill pipes for units with retrievable core receiver (RCR). The effect of the nitrocarburizing on the mechanical properties of steels of different alloying systems is considered. Steels for the production of threaded joints of drill pipes are recommended.

Effect of Temperature Reversion on Hot Ductility and Flow Stress–Strain Curves of C-Mn Continuously Cast Steels

The influence of temperature reversion in secondary cooling and its reversion rate on hot ductility and flow stress–strain curve of C-Mn steel has been investigated. Tensile specimens were cooled at various regimes. One cooling regime involved cooling at a constant rate of 100 °C min−1 to the test temperature, while the others involved temperature reversion processes at three different reversion rates before deformation. After hot tensile test, the evolution of mechanical properties of steel was analyzed at various scales by means of microstructure observation, ab initio prediction, and thermodynamic calculation. Results indicated that the temperature reversion in secondary cooling led to hot ductility trough occurring at higher temperature with greater depth. With increasing temperature reversion rate, the low temperature end of ductility trough extended toward lower temperature, leading to wider hot ductility trough with slightly reducing depth. Microstructure examinations indicated that the intergranular fracture related to the thin film-like ferrite and (Fe,Mn)S particles did not changed with varying cooling regimes; however, the Widmanstatten ferrite surrounding austenite grains resulted from the temperature reversion process seriously deteriorated the ductility. In addition, after the temperature reversion in secondary cooling, the peak stress on the flow curve slightly declined and the peak of strain to peak stress occurred at higher temperature. With increasing temperature reversion rate, the strain to peak stress slightly increased, while the peak stress showed little variation. The evolution of plastic modulus and strain to peak stress of austenite with varying temperature was in line with the theoretical prediction on Fe.

Cavitation-resistant high-alloyed chromium steels

The structure and properties of high-alloy chromium steels, used in the manufacture of equipment, working in the conditions of erosion caused by cavitation, are analysed. The compositions and the mechanical properties of steels in the equipment for hydraulic turbines and circulation pumps of reactor systems are determined. The weldability is evaluated and the welding methods and welding materials are outlined

Welding of elements of cryogenic equipment produced from 03Kh16N9M2 steel

Investigations were carried out into the properties of sheets and forged 03Kh16N9M2 austenitic steel and the properties of welded joints in equipment working in a wide temperature range from –196 to 600°C. The determination of the mechanical properties of steel and of welded joints and also of cyclic strength characteristics shows that the properties of these steels are higher in a wide temperature range than the properties of 12Cr18Ni10Ti steel. A method was developed for welding bodies of cryogenic equipment with large thicknesses of welded joints with no need for heat treatment.

Cold Rolling Effect on Microstructure and Mechanical Properties of Low Carbon Al-Killed Steels

It have been studied the cold rolling effects on the microstructure of samples prepared from Al-killed low carbon steel sheets with high coiling temperatures. The microstructure of the hot rolled steels sheet is formed from ferrite and large carbides when the coiling temperature is high. The cold rolling affects the steel mechanical and electrochemical properties due to microstructural changes. We have studied the microstructure by optical microscope and scanning electron microscope. Low angles grain boundaries and the texture of samples were studied by EBSD method.

Effect of volume fraction of phases and precipitates on the mechanical behavior of UNS S31803 duplex stainless steel

Mechanical properties of a grade UNS S31803 duplex stainless steel were studied. Samples were annealed at three different temperatures, 1060°C, 1200°C, and 1300°C, to change the α/γ proportion, to precipitate undesirable phases (for example, α′, σ and chromium nitrides), and to study the effect of the microstructure on the mechanical behavior. Specimens with a thickness of 1.8mm were prepared according to ASTM standards and tested at room temperature. Tensile tests were conducted using displacement control at a rate of 5mm/min. Force-controlled constant amplitude axial fatigue tests were conducted at a frequency of 30Hz and an R stress ratio of 0.1. Microstructural analyses, performed by optical microscopy and scanning electron microscopy, showed the following modifications to the microstructure: changes in the phase volume fractions, the phase grain growths, and the morphology of the γ-phase and the precipitation of chromium nitrides in the α-phase. The mechanical properties of the steel were significantly changed due to the changed microstructure. The results demonstrate the sensitivity of the steel to the annealing temperature.