Tensile Properties Of Steel Research Articles

Influence mechanism of solution temperature on microstructure evolution and tensile properties of Ti microalloyed high strength steel CGLC700

The influence mechanism of solution temperature on the strength and toughness of Ti microalloyed steel CGLC700 was studied. The microstructure changes of Ti microalloyed steel were observed by micro-electron microscopy, and the mechanical properties were evaluated by tensile test. The appropriate solution temperature can promote the solid solution of Ti atoms and the formation of small-sized TiN, TiC and other particles, hinder the movement of dislocations, and improve the tensile properties of steel. When the solution temperature is 1240 °C (2#), the grain size of steel is the lowest, the proportion of high angle grain boundary is the highest, and the tensile properties of steel are the best. Ti microalloyed steels increased tensile strength by 4.12%, yield strength by 2.85% and elongation by 28.4%. Too low or too high solid solution temperatures weaken the strengthening effect of the microalloying elements and led to a reduction in the tensile properties of the steel. This can be attributed to the low solid solution of Ti at low solid solution temperatures and the growth of second phase particles and inclusions at too high solid solution temperatures. This study provides a theoretical basis for optimizing the heat treatment process of Ti microalloyed steel.

Specimen Size Effect on the Tensile Properties of Rolled Steel of Long-Term-Operated Portal Crane.

This paper presents the research results on the mechanical behavior of the low-carbon rolled steel of a sea portal crane after a 33-year operation depending on the operational stresses and rolling direction in order to assess its serviceability. The tensile properties of steels were investigated using rectangular cross-section specimens with different thicknesses and the same width. Strength indicators were slightly dependent on the considered factors (operational conditions, the cutting direction, and thickness of specimens). However, a clear trend of higher ultimate strength for thinner specimens was noticed, especially in the case of more brittle material due to its operational degradation. Plasticity of the tested steel specimens was more sensitive to the influence of the above-mentioned factors than strength but less sensitive than impact toughness. Uniform elongation was slightly less for thinner specimens regardless of the investigated steel state or the orientation of specimens relative to the rolling direction. The post-necking elongation was lower for transversal specimens compared with longitudinal ones, and the effect was more significant when testing steel with the lowest brittle fracture resistance. Among the tensile properties, non-uniform elongation was demonstrated to be the most effective for assessing the operational changes in the state of rolled steels.

The effect of renewed melting process under electrical slag on the fatigue life of the precipitation hardened stainless steel Custom-450

The aim of this study was to investigate the effect of under electro slag re-melting (ESR) process on the fatigue behavior of GTD-450 steel used for manufacturing gas turbin blades. These parts are always at risk of failure due to fatigue. Refining of steel by ESR process is one of the most important modern methods of steelmaking in order to achieve a homogeneous structure, minimal elemental and structural segeregation, as well as reducing non-metallic impurities in terms of their number and size and most importantly their uniform distribution in the steel structure. Due to dependency of fatigue properties of steels on structural factors of steel, the role of ESR process using different slag compositions on this important property of GTD-450 steel was investigated. Microstructural studies by optical and electron microscopes showed that grain size of ESR samples were averagely 10% finer than non-ESR ones. As well as performing various mechanical tests including tensile and fatigue on samples prepared in different conditions, showed that although ESR had a minor effect on tensile properties of steel but impact energy of steel in ESR condition were averagely 16% more than non-ESR condition. Finally, the core finding of this paper is that, fatigue life of GTD-steel turbine blade produced via ESR method can be improved by 30%.

Investigation wavy interface forming and stretching in severe plastic deformed copper/steel bimetallic rod

Bimetallic copper-clad steel rod was prepared via three successive passing the samples through equal-channel angular pressing (ECAP) die with route Bc. The core steel tensile properties and copper/steel interface microstructures were investigated after each passes. It is observed the yield strength of steel core increased from about 200 MPa to 840 MPa and equiaxed grains with the size lower than the one-third of the initial size were formed. Only, during the third passing of ECAP deformation, the copper/steel interface was changed to waveforms in some angular positions. The shear strain and mating surface stretch were modeled to explain this phenomenon.

Effect of porosities on brazed martensitic steel tensile properties: 2D and 3D pre-mortem vs post-mortem characterizations

A quantitative investigation of the porosity and its effects on mechanical properties was conducted on brazed materials presenting macroscopically brittle behavior with various defect levels. Three different techniques for evaluating the porosity and the fracture mechanisms were compared: (i) pre-mortem X-ray computed tomography (XCT), (ii) post-mortem laser scanning confocal microscopy (LSCM), and (iii) post-mortem scanning electron microscopy (SEM). The apparent surface area of the pores was evaluated by segmenting the height maps produced by LSCM and the electron backscattered images produced by SEM. The results show good agreement for different porosity levels. The LSCM height maps for opposite fracture faces were virtually stitched together in order to reconstruct three-dimensional (3D) images of the whole brazed joints. These proved to be similar to the XCT 3D segmented images, yet with some discrepancies due to local plastic deformation. Quantitative volume fraction and spatial distribution of pores were assessed as well as the identification of fracture mechanisms. Interestingly, it was noted that two specimens with different ultimate tensile strengths presented the same porosity amount, but different distributions. Two distinctive features were identified in the broken specimens: plastically teared pillars and walls that were separating the pores before fracture, and plateaus of approximately constant height with micro-sized dimples showing interfacial fracture. Although the specimens exhibited a macroscopic brittle behavior, these features are characteristic of ductile fracture. The most probable scenario for fracture was conjectured as follows: (i) Final fracture occurs in the near-surface region of the samples and conversely early damage develops in the volume, (ii) Interfacial fracture within plateaus is responsible of the rupture/strength of the brazed specimen but detrimental effect is induced by the tearing if highly voided regions are present in the joint.

Estimation of the Strength Coefficient and Strain Hardening Exponent from Monotonic Tensile Properties of Steels

In order to derive a method for estimating the strength coefficient and strain hardening exponent of steel, the performance parameters of 86 kinds of steel taken from American Iron and Steel Institute (AISI) Bar Steel Fatigue Database were examined and equations that related the strength coefficient and strain hardening exponent to the ultimate tensile strength and yield strength were developed. Correlations from the literature among the strength coefficient, strain hardening exponent and other monotonic tensile properties were also examined and compared to the relationships proposed in this study using the data of 86 kinds of steel. The proposed method was shown to be better used to estimate the strength coefficient and strain hardening exponent.

Microstructure and Tensile Properties of Ferritic Lightweight Steel Produced by Twin-Roll Casting

Ferritic Fe–8Al–5Mn–0.1Nb–0.1C lightweight steel has been produced by twin-roll casting (TRC) process. The microstructures, in as-cast condition and during subsequent thermomechanical treatments, and tensile properties of the steel have been investigated and compared to those of the similar steel produced with conventional ingot casting (IC). TRC significantly refines the microstructure of the steel in as-cast condition, with a formation of NbC and κ-carbide particles within matrix and along grain boundaries. NbC particles inhibit the grain coarsening during subsequent homogenization treatment, while κ-carbide particles promote recrystallization during final annealing by particle-stimulated nucleation mechanism. Tensile properties of the TRC steel are comparable to those of the IC steel; however, such properties of the TRC steel have been achieved under a much smaller number of processing steps, making TRC as an ideal alternative for the production of ferritic lightweight steels.

Effect of simulated pitting corrosion on the tensile properties of steel

The buildings including steel-structured bridges, plants and ocean platforms which take steel as the main material are prone to fall into pitting corrosion. Mechanical properties are greatly affected by pitting corrosion and hence the security of buildings can hardly be guaranteed. The mechanical drilling and milling method is employed to form conical blind holes and then to simulate corrosion pits in present work, after which the effects of the shape, depth and distribution of corrosion pits on the tensile properties of steel have been systematically investigated. The results indicate that the fracture location of steels with corrosion pits occurred at the cross section with larger pitting corrosion factor. The load-displacement curves of the steels were changed due to the existence of corrosion pits, the yield platform got shorter and even disappeared, accompanied with poorer ductility and brittle fracture. Pit shape, depth and distribution impacted little on the ultimate load of tensile samples, the ultimate strength almost correlated only with the maximum cross-sectional area. However, the yield load of steels was affected by both pit shape and distribution. The elongation was mainly affected by pit denseness and depth, denser and deeper pits per unit area would give rise to smaller elongation. Finally, multivariate regression analysis was performed to acquire the prediction model of elongation.

Microstructural evolution during bainite transformation in a vanadium microalloyed TRIP-assisted steel

The microstructural evolution and subsequent properties of a cold rolled 0.12wt% V microalloyed transformation induced plasticity assisted steel were studied after intercritical annealing, focusing on isothermal bainite transformation at 460°C. The heat treated steel was examined by optical microscopy, scanning-transmission electron microscopy and microanalysis, X-ray diffraction analysis and tensile testing. The tensile testing showed considerable improvements in yield strength and total elongation with longer isothermal bainite holding times (i.e. 180s). According to microscopy observations, these effects were attributed to the increase in the population of film-type retained austenite and newly formed dislocations as a result of bainite transformation. No significant V(C,N) precipitation and growth-coarsening were observed during isothermal bainite transformation, which is consistent with conventional vanadium microalloyed steels. However, the V(C,N) precipitates in dislocation tangles suggested the possible contribution of precipitates on the tensile properties of steel.

Integrated analysis of WWER-440 RPV weld re-embrittlement after annealing

The analysis of WWER-440 RPV welds mechanical properties and behaviour of nanoscale structural features under primary irradiation, thermal annealing and re-irradiation has been performed in the framework of the international research project PRIMAVERA. The weld material of WWER-440 with three different levels of phosphorus contents, specifically 0.025, 0.03 and 0.04wt.% were investigated in the framework of the project.It has been demonstrated that the copper atoms create under irradiation small clusters (d∼1–2nm) surrounded by P, Si or Mn atoms. The phosphorus atoms segregate on Cu-clusters, dislocations and form P-clusters and atmospheres. These mechanisms lead to the embrittlement of RPV steel, which is revealed by the increasing of yield stress and transition temperature shift after irradiation.Due to thermal annealing a substantial part of irradiation induced copper and phosphorus clusters has been dissolved. Moreover, dissolution of Cu clusters occurs simultaneously with the growth of the Cu precipitates. Both steel tensile properties and transition temperature recover due to thermal annealing.A substantial phosphorus effect on ductile-to-brittle transition temperature shift occurs under re-irradiation. Because in the annealed steel a substantial part of the Cu atoms is in the precipitates, the material embrittlement under re-irradiation does not depend so much on Cu, and the Tk shift under re-irradiation is less as compared with primary irradiation.Considering the vacancy type defects, the PAS experiments show that basically three different processes play a role in the microstructure evolution: irradiation induced creation of point defects, thermal induced annealing of these defects and thermal/irradiation induced coarsening of defects. Although, the influence of the vacancy type defects on the mechanical properties was found to be little in comparison to the effect of the Cu–P clusters, the presence of these defects in the irradiated and annealed materials were observed in large number-significantly more than in an equilibrium state.

Effect of tensile properties on the abrasive wear of steel saw wires used for silicon ingot slicing

The abrasive wear patterns and the tensile properties of steel saw wires (120μm in diameter) were investigated in order to develop highly reliable saw wires for the application to silicon (Si) ingot slicing. Saw wires that underwent heat treatment at different linear velocities during the patenting process were subjected to 2-body abrasive wear (2-BAW) and 3-body abrasive wear (3-BAW) tests. The 2-BAW and 3-BAW tests of the saw wires showed opposite trends in abrasive wear resistance. The wear loss resulting from the 2-BAW test was mainly determined by the tensile strength and microhardness of the steel saw wire samples, while the wear loss from the 3-BAW test was primarily determined by the elongation, or ductility, of the samples.

Effect of Temper Rolling on Tensile Properties of Low-Si Al-Killed Sheet Steel

The tensile properties of steel after temper rolling are affected by the reduction; low-Si Al-killed sheet steel was taken to study the effect of temper rolling on the tensile properties. The results indicate that the yield strength first decreases with the increase of reduction, and then increases. The relationship between the yield strength and the reduction can be expressed using quadratic function. The tensile strength increases with the increase of the reduction, while the total elongation decreases with the increase of the reduction, and the relationship between them and the reduction can be expressed using power function. Under the same condition, the results also indicate that the yield strength and tensile strength of steels across the rolling direction are all larger than those along the rolling direction; there is no obvious distinction between the total elongation along the rolling direction and that across the rolling direction.

Dynamic Tensile Properties of Steels and Aluminum Alloys for a Wide Range of Strain Rates and Strain

Through intensive analysis of the tensile stress-strain curves of a variety of steel sheets over a wide range of strain rates on the order of 10-2 ∼103 s-1 obtained by using the Sensing Block Type High Speed Material Testing System, it was confirmed that the newly-partially extended constitutive model (Tanimura-Mimura Model) is useful to simulate the dynamic stress-strain curves for the entire range of deformation reaching as far as fracture over the wide strain rate range, as long as the quasi-static stress-strain curve of the material concerned is only known in advance. Dynamic tensile properties, over the wide strain rate range and the entire strain region reaching the true fracture strain, of ten kinds of aluminum alloys, which compose of a wide strength level from a commercial pure aluminum to the extra super duralumin are systematically studied. It was cleared that the aluminum alloys belonging to the one group exhibit the positive strain rate sensitivity and the aluminum alloys belonging to another group exhibit the negative sensitivity or almost non sensitivity. It was found that the values of the true fracture strain ef are substantially not affected by the strain rates, for all the tested aluminum alloys, and are closely related to the values of the tensile strength σB whose values are obtained by the quasi-static nominal tensile stress-strain curves.

The Role of Retained Austenite on Tensile Properties of Steels with Bainitic Microstructures

In high-carbon, silicon-rich steels it is possible to obtain a very fine bainitic microstructure by transformation at low temperatures (200– 300 � C). This microstructure consists of slender ferrite plates, with thicknesses of several tens of nm, in a matrix of retained austenite. Whereas strength is mainly provided by to the fine scale of the ferrite plates (stronger phase), ductility is mostly controlled by the retained austenite (softer phase). Further improvement in ductility is achieved by strain induced transformation of austenite to martensite, the so called TRIP effect. In order to take full advantage of this effect, the mechanical stability of the austenite, i.e., its capability to transform to martensite under strain, must not be too low nor excessively high. Two main aspects of the mechanical stability of the retained austenite, morphology and chemical composition, have been studied to determine the role that these play on the ductility behaviour of the bainitic steels studied. It is suggested that the chemical composition has the strongest effect on the ductility of these new high strength alloys.

Evaluation of the mechanical properties of T91 steel exposed to Pb and Pb–Bi at high temperature in controlled environment

It is known that liquid metal embrittlement (LME) is strongly dependent on a so-called `intimate contact' between the solid and liquid metal (LM) phases. This point is emphasised in this paper aimed at determining suitable contact conditions to favour LME of T91 steel after short exposure to stagnant molten Pb or Pb–55%Bi. The temperature range ( T∼540°C) is high with respect to the expected operating conditions of spallation targets. We determine three temperature cycles, in pure lead or lead–bismuth under flowing He–4%H 2 for LME testing. Good contact is obtained between T91 and Pb–Bi, but poor contact between T91 and Pb. Accordingly, the T91 steel tensile properties are not degraded by Pb, but modified after exposure to Pb–Bi. In such case, rupture of the test bar occurs in regions where Pb–Bi is `adherent' onto the steel. The rupture facies is not fully ductile as for T91 in Pb.

Statistical Modelling of Mechanical Tensile Properties of Steels by Using Neural Networks and Multivariate Data Analysis.

Both Neural networks NN and Multivariate Data Analysis MDA techniques were used to determine mechanical tensile properties of steels. NN apparently proved better in dealing with non-linearity effects and complex interactions between the predictors. However, MDA was found essential in improving the quality of the prediction and providing interpretation to the results from NN modelling.

Effects of Pb-17Li on the tensile properties of steels

Experiments were carried out to study the effect of Pb-17Li on the tensile properties of steels considered as candidate structural materials in fusion reactor conceptual designs. In order to investigate a possible LME effect tensile tests, in Pb-17Li at various strain rates and temperatures, were carried out on AISI 316 L, DIN 1.4914 and AMCR. Data on plastic strain at break and the results of fractographic and metallographic analysis are reported. Stress corrosion tests, in Pb-17Li at 723 K for periods of 2500 h were performed on AISI 316 L specimens. After the tests the samples were longitudinally sectioned and different cross sections microscopically examined. The stressed samples are compared to plain specimens heat treated in the liquid alloy in the same experimental conditions.

Basic study on strength evaluation and life prediction of degraded materials (1st report, An example of .SIGMA.-phase degradation of a stainless steel)

It has been said that σ phase degrades materials ; nevertheless, it is not clear how σ phase degrades materials. In order to clarify the meaning of σ phase degradation in a strength-of-materials sence, this paper evaluates the tensile, impact and fatigue properties of a cast stainless steel which contains approximately 10 wt% of σ phase. The results obtained are as follows : (1) The Charpy absorbed energy of the σ-phase-degraded stainless steel was greatly reduced even at room temperature. (2) The tensile properties of the steel such as 0.2% proof stess, tensile stress and elongation were not affected by σ phase. (3) The S-N diagram was not changed by the existence of σ phase in steel. The distribution of the maximum surface lengths of multiple small cracks in the degraded steel, however, was different from that in non-degraded steel.

Effect of intercritical quenching on microstructure and tensile properties of steels 15 and 15Mn2Nb

The microstructure and tensile properties of steels 15 and 15Mn2Nb after quenching from intercritical (γ + α) temperatures were studied. It was shown that steel 15 has an “island-type” dual-phase structure (ferrite plus martensite) after intercritical quenching, while the steel 15Mn2Nb has the “lamellar” structure with alternatively arranged ferrite and martensite needles. Such a lamellar dual-phase structure obviously has improved strength and ductility and is suggested as one of the effective methods in developing high strength dual-phase steels.

Influence of recrystallization behavior on the mechanical properties of XM-19 stainless steel (22Cr-13Ni-5Mn-2Mo-0.3N)

A study was conducted to evaluate the variation of cold drawn XM-19 stainless steel tensile properties with solution heat treatment, test temperature, and strain rate. An evaluation of fatigue behavior was conducted. Recrystallization behavior resulting from the solution heat treatment was studied. It was found that yield strength increases as: 1) solution heat treatment temperature decreased, 2) strain rate increased, and 3) test temperature decreased. Ductility properties varied in an opposite manner. The thermally activated deformation approach was used to analyze this behavior. The most likely mechanism for the thermally dependent portion of the yield strength was determined to be point defect interaction with dislocations. The athermal portion depends on the degree of recrystallization. The fatigue strength was found to be greater than that of more conventional stainless steels and this was related to lowered stacking fault energy due to nitrogen addition.