Compression Of Steel Research Articles

Shock compression of single-crystal stainless steel

We studied the orientation-dependent dynamic properties and plastic deformation mechanisms in single-crystal austenitic FeCr18Ni12.5 stainless steel shocked to peak stresses ranging 3.8-12.0 GPa. The 〈110〉 and 〈111〉 principal Hugoniots generally match that of polycrystalline 304L stainless steel, but the 〈100〉 Hugoniot exhibits lower shock velocities and comprises two distinct regions. The Hugoniot elastic limits (HELs) and spallation strengths range 0.5-1.2 GPa and 2.2-3.8 GPa, respectively, and exhibit trends previously observed in polycrystalline steels. We generally observed the largest HELs along 〈100〉 and the largest spallation strengths along 〈111〉. Microscopy revealed larger twin and martensite fractions in the 〈100〉 samples, correlations in twinning and martensite prevalence with dynamic response, and orientation-dependent differences in dislocation behavior near the spallation plane.

Non-linear analysis of eccentric compression of steel and steel fiber reinforced high strength concrete column

To improve the ductility of high-strength concrete and enhance the ductility and load-bearing capacity of steel reinforced high-strength concrete (SRHSC) columns, steel fibers were added to SRHSC to prepare steel and steel fiber reinforced high-strength concrete (SSFRHSC) columns. In order to study the eccentric compression of SSFRHSC columns, based on the experimental study of the eccentric compression of SSFRHSC columns, finite element model specimens of SSFRHSC eccentric columns were established using ABAQUS software, and the accuracy of the model was verified by combining the test results. On the basis of the experiments, the parameters such as steel fiber volume rate, concrete strength and eccentricity distance were further changed to extend the study. The results show that: with the increase of the volume rate of steel fiber from 0.5 % to 3 % and the concrete strength from C40 to C90, the ultimate bearing capacity of the specimen increases by 40.81 % and 58.69 % respectively; at the same time, when the eccentric distance increases from 0 mm to 100 mm, the ultimate bearing capacity of the specimen decreases by 66.76 %, and when the eccentric distance When the eccentricity distance was increased from 0 mm-40 mm to 60 mm-100 mm, the structural damage form changed from brittle damage to ductile damage.

Hot Processing Maps and Texture Evolution during Hot Compression of CF170 Maraging Stainless Steel

In this work, the hot processing maps of CF170 maraging stainless steel were generated by using flow stress data obtained from an isothermal compression experiment on the Gleeble-3800 hot compression simulator. The microstructure corresponding to the stable regions in the hot processing map was observed with an optical microscope. The results showed that the steel is susceptible to deformation temperature, strain, and strain rate, and the optimal hot working parameter is a strain rate range of 0.01∼0.1 s−1 and a temperature range of 1350∼1373 K when the strain is 0.6. In addition, the texture evolution of prior austenite during hot compression was investigated based on reconstructing a parent grain by Electron Back-Scattered Diffraction. The results showed that twinning-induced dynamic recrystallization is another mechanism except for strain-induced dynamic recrystallization at a higher strain rate. Further, the deformed microstructure with a Cube texture (1 0 0) 〈0 1 0〉 will preferentially nucleate, and the increase in temperature makes the Cube texture (1 0 0) 〈0 1 0〉 change to the rotated Cube texture (1 0 0) 〈1 1 0〉, and the increase of strain rate inhibits the growth of recrystallized grains and weakens texture.

Compression temperature to activate kinking in pearlitic steel

The preferable condition for kinking in the compression of pearlitic steel is reported in this study. Spring steel (0.53 wt%C-1.48%Si-0.70%Mn-0.76%Cr–Fe) with a pearlitic structure was compressed at different temperatures ranging from ambient to 600 °C. The deformation microstructure clarified that the kinking occurred more oftenwhen the compression temperature was less than 400 °C. Three-dimensional reconstruction of the scanning electron microscopy images with focused-ion-beam serial sectioning revealed that the kinked structure comprised a band-like sheared area surrounded by the bent structures. The shear strain in the kinked structure is greater than the macroscopic strain applied by compression. A series of measurements of compressive flow stress (strain rate: 0.001/sec to 1/sec) elucidated negative strain rate sensitivity (m-value < 0) at ∼ 300 °C. Strain localization by kinking occurs preferentially at relatively lower temperature because a smaller strain rate sensitivity can promote local plastic instability.

Physical constitutive relational model and structure evolution during dynamic recovery of 23Co14Ni12Cr3MoE (A-100) high-strength steel

ABSTRACT The hot compression of A-100 steel at 850–1150°C and strain rate of 0.01–10 s−1 was tested on a Gleeble-3800 thermal simulation machine to determine the corresponding true stress–strain curve. Based on theoretical calculation, the dislocation density factor was introduced into the Avrami equation and thereby a dynamic recovery physical constitutive relational model based on dislocation density theory was established. Then the hot deformation behaviour of A-100 steel was predicted (correlation coefficient R = 0.9964 with an average absolute relative error AARE = 4.0923%). The structures after hot compression were observed by electron backscattered diffraction and found to be lath-shaped martensite and austenite. With an increase of temperature and deceleration of strain rate, the proportions of large-angle boundaries and substructures increased and the softening mechanism became dominated by dynamic recovery.

ИССЛЕДОВАНИЕ ВЛИЯНИЯ СКОРОСТИ ДЕФОРМАЦИИ НА СКЛОННОСТЬ УГЛЕРОДИСТОЙ СТАЛИ У8 К ДЕФОРМАЦИОННОМУ СТАРЕНИЮ

The effects of the strain rate and degree on the scale of the strain aging effect in carbon steel U8 with lamellar pearlite microstructure, which is a eutectoid mixture of ferrite plates and brittle plates of secondary cementite Fe3C have been investigated. The microstructure and properties of Russian steel U8 after quasistatic compression, dynamic compression (shock processing), and explosion processing have been investigated. A low-temperature annealing (150–500 °C) of the non-deformed steel U8 has been shown to result in a monotonous reduction of hardness. The quasistatic compression and shock processing of the carbon steel were found to result in the strain aging manifested as an increasing hardness at annealing of the deformed steel U8. The increasing of the deformation degree and strain rate was accompanied by the increasing of hardness of the annealed steel. The explosion treatment was shown not to result in a notable improvement of the mechanical properties of carbon steel as well as in a change of the morphology of cementite plates. The deformation aging effect in steel U8 after the explosion loading was absent. The strain aging effect in U8 steel after quasistatic compression and dynamic loading was suggested to originate from an increasing of the lattice dislocation density, the long-range internal stress fields from which lead to the dissociation of the cementite Fe3C plates and to increasing of the concentration of carbon atoms in the ferrite crystal lattice. The absence of the strain aging effect in the carbon steel after the explosion loading is due to a small degree of the explosion deformation that doesn't allow providing an essential increasing of the lattice dislocation density in ferrite.

Orientation-dependent dynamic recrystallization of super austenitic stainless steels

Herein, the hot compression of a super austenitic stainless steel (SASS) containing 7Mo–0.46N–0.02Ce is conducted at different temperatures (900–1200 °C) under a strain rate of 10 s−1. The effect of angle between solidification direction of columnar crystals and loading direction (0°, 30°, 60° and 90°) on microstructural evolution of SASS is studied using OM and EBSD. The results reveal that, at low temperatures of 900 °C and 1000 °C, the dynamic recrystallization (DRX) degree of the 30° and 60° samples is higher than that of the 0° and 90° samples, however, the complete DRX has not occurred. At high temperatures of 1100 °C and 1200 °C, the DRX degree of SASS increases with the decrease of angle between solidification direction of columnar crystals and loading direction. Three kinds of DRX mechanisms for samples with different columnar crystal characteristics are observed, i.e., discontinuous dynamic recrystallization (DDRX), continuous dynamic recrystallization (CDRX) and a combination of DDRX + CDRX mechanism. However, under the same deformation conditions, preferentially triggered and dominant DRX mechanisms of samples with different columnar crystal characteristics are different. In the 0° and 90° samples, a large number of high angle grain boundaries (15° ≤ HAGB ≤65°) are developed, and new DRX grains are formed on them. While in the 30° and 60° samples, preferential expansion nucleation and growth of DRX grains take place on original GBs. At 1200 °C, the DRX degree of SASS reaches a maximum of ∼0.97 when the angle between solidification direction of columnar crystals and loading direction is 0°.

United Approach to Modelling of the Hot Deformation Behavior, Fracture, and Microstructure Evolution of Austenitic Stainless AISI 316Ti Steel

Hot deformation is one of the main technological stages of products made from metallic materials. It is strictly required to decrease the costs of developing optimized technologies at this stage without a significant decrease in the products’ quality. The present investigation offers an algorithm to unite three different models to predict the hot deformation behavior, fracture, and microstructure evolution. The hot compression and tension tests of the AISI 316Ti steel were conducted using the thermomechanical simulator Gleeble 3800 for the models’ construction. The strain-compensated constitutive model and the Johnson–Mehl–Avrami–Kolmogorov (JMAK)-type model of the grain structure evolution show a satisfactory accuracy of 4.38% and 6.9%, respectively. The critical values of the modified Rice and Tracy fracture criteria were determined using the experimental values of the relative cross-section reduction and finite element calculation of the stress triaxiality. The developed models were approved for the stainless AISI 316Ti steel by the hot torsion with tension test.

Study on Forging Permeability of 06Cr19Ni9NbN Steel during Hot Deformation

The hot compression tests of 06Cr19Ni9NbN steel were conducted at strains rate of 0.005-5s-1 and temperature of 900-1200 °C on Gleeble1500 thermal mechanical simulation tester. Based on stress-strain data, processing maps of the steel were established. According to the results of processing maps, the optimal process parameters of hot compression were obtained, which lies in the temperature range of 1000-1200°C and strain rate of 0.005-0.1s-1. And then, the process of plane strain compression of 06Cr19Ni9NbN steel was investigated and carried out at the temperature of 1000-1200 °C and reduction ratio of 10%-50%. After the hot compression tests, the room temperature tensile tests were carried out. The results indicated that the grain size and the mechanical properties gradually become stable when the reduction ratio increases to 30%, 34% and 40% at 1200 °C, 1100 °C and 1000 °C, respectively. Finally, a new model was presented to describe critical forging penetration efficiency, which is significant to optimize the steel forging process. Furthermore, the calculated results based on this new model were consistent with experimental results, indicating that the model is suitable to predict the critical FPE for the steel.

Embossment effect analysis on compression of mild steel using finite element methods

In the world of construction the use of mild steel is increasing due to the relatively light material and has great strength. This makes the producers start to innovate with the addition of reinforcement to get greater strength. Mild steel is formed from the grinding process on steel plate sheets. Because its thin thickness makes mild steel susceptible to buckling. The use of mild steel as a structural component requires great strength with the addition reinforcement. This research will discuss the effect of embossment width and dimensions on the compressive strength values of mild steel by the finite element method. This thesis uses MIDAS FEA finite element method program. The channel profile used is 75 mm x 34 mm x 5 mm x 0,65 mm with length 2000 mm. Model used is with and without stiffener and embossment distance variation from 15 - 150 mm. Boundary condition used hinge-roller, loading use axial load. The results of the analysis found that the greater the embossment distance, the greater the compressive strength produced. failure that occurs in a stiffener model that has embossment is lateral buckling

Surface Crack Detection in Compression of Pre Heat-Treated Steel (ESW90) Using an Acoustic Emission Sensor

Surface Crack Detection in Compression of Pre Heat-Treated Steel (ESW90) Using an Acoustic Emission Sensor

The Effect of Retained Work Hardening on the Driving Force for Dynamic Transformation

The driving force for dynamic transformation during double-hit hot compression of an as-cast medium-carbon low-alloy steel assessed done at 1473 K at strain rates of 0.25 and 0.50 s−1. Dynamically transformed ferrite was detected using the Kernel Average Misorientation (KAM) technique. The time interval between deformations affects the retained driving force, which decreases at a rate of 65 to 75 J/mol per second. This rate decreases with decreasing temperature due to a lower rate of recovery.

Understanding Hot Workability and Flow Stress Prediction through Processing Map with Microstructural Correlation for HY85 Steel

Abstract In this study, the hot compression tests of HY85 steel have been experimented by using thermomechanical simulator Gleeble 3800 in hot compression temperature range of 750°C–1,100°C under strain rates between 0.001–10 s−1 up to true strain 0.7. It is worth noticing from the results that the flow stresses are dependent on the combination of temperature and strain rate. Adiabatic heating corrections of experimental flow stress data were carried out and were used to model stress-strain curves. The predictability of these stress-strain curves was confirmed from experimental results. True stress-true strain curves show the peak stresses followed by softening probability because of the existence of dynamic recrystallization (DRX). The apparent activation energy is calculated to be 360 KJ/mol using the sinh type constitutive equation, and it is observed that its value decreases with increasing strain. Hot compression of HY85 steel is controlled by dislocation climb and glide (n = 6.3). The processing maps are plotted based on different dynamic materials modeled with strain rate versus temperatures. The flow localization is one of the primary factors with resulting instability, which is revealed from the microstructure. Moreover, the partial DRX was noticed besides the grain boundaries and compression bands. Workability regions were identified using processing maps in the domain of strain rate and temperature and verified with microstructures.

Stress-assisted (γ→α′) and strain-induced (γ→ε→α′) phase transformation kinetics laws implemented in a crystal plasticity model for predicting strain path sensitive deformation of austenitic steels

This paper formulates stress-assisted and strain-induced austenite to martensite transformation kinetics laws within a crystal plasticity framework to enable modeling of strain path sensitive elasto-plastic deformation of austenitic steels taking into account the evolution of crystallographic texture and the directionality of deformation mechanisms in the constituent phases. Consistent with experimental observations for mechanically induced martensitic transformation, the stress-assisted transformation is modeled as direct from γ-austenite to α' -martensite, while the strain-induced transformation is modeled as indirect through an intermediate ε-martensite phase, which subsequently transforms to α' -martensite. While the stress-assisted transformation law is conceived based on an energy criterion, the strain-induced transformation law relies on the local stress state sensitive motion of partial dislocations forming shear bands of ε-martensite phase, which after intersecting with other shear bands give rise to α' -martensite. The kinetic models are implemented in the elasto-plastic self-consistent polycrystal plasticity model to facilitate modeling of strain path and crystallographic texture dependence of martensitic transformation, while predicting deformation behavior of metastable austenitic steels. Due to its morphology, the ε-martensite is modeled using a flat ellipsoid approximation, which is a new numerical feature in the model. Simple tension, simple compression, and simple shear data of an austenitic steel have been used to calibrate and to illustrate predictive characteristics of the overall implementation. In doing so, stress-strain response, texture, and phase fractions of γ-austenite, intermediate ε-martensite, and α′-martensite are all calculated, while fully accounting for the crystallography of the transformation mechanisms. It is demonstrated that the appropriate modeling of phase fractions and crystallography facilitates predicting the experimentally measured data. The implementation and insights from these predictions are presented and discussed in this paper.

FORMATION OF CARBON STEEL STRUCTURE DURING HOT PLASTIC DEFORMATION

Purpose. The main purpose of the work is to determine the peculiarities of the development of recrystallization processes of carbon steel austenite depending on the degree of hot plastic deformation and to develop proposals for improving the structural state of the metal of the railway solid-rolled wheel. Methodology. Two carbon steels of a railway wheel with a minimum and maximum carbon content of 0.55 and 0.65 % and other chemical elements within the grade composition of the steel 60 were used as research material. Samples in the form of cylinders with a diameter of 20 mm and a height of 40 mm were heated in a muffle furnace, exposed for a certain time to equalize the temperature across the cross section of the sample. After that, the samples were subjected to hot compression on Instron type test machine. The temperature interval of hot compression of the samples was 950–1100 ºС, with deformation degrees in height in the range of 10–40%. The strain rate was 10-3–10-2sec-1. A standard etching was used to detect the boundaries of the austenite grains. Structural studies were performed using Epikvant type light microscope at magnifications sufficient to determine the structure of austenite grains. The grain size of austenite was determined by the methods of quantitative metallography. Findings. In the case of hot compression of the railway wheel blank, increasing the concentration of carbon atoms only within the grade composition of the steel is sufficient to increase the average austenite grain size, which confirms the proposals to limit the carbon content in the metal of railway wheels. The formation of a certain degree of austenite structural heterogeneity at the cross section of the rim or hub of the railway wheel is due to a change in the development mechanism of recrystallization processes depending on the deformation value. Under conditions of the same degree of hot plastic deformation, the replacement of one-time compression by fractional one is accompanied by a violation of the conditions of formation of the recrystallization nucleus. As a result of the specified replacement of the scheme of hot plastic deformation we obtain reduction in the austenite grain size. Originality. Based on a study of the development of collective recrystallization processes during the hot compression of carbon steel of the railway wheel, it was determined that the increase in carbon content contributes to the austenite grain increase. After hot compression of the wheel blank, the structural inhomogeneity of austenite that occurs is determined by a change in the mechanism of recrystallization processes development. During deformations above the critical degree, the recrystallization nuclei are formed and successively grow, which leads to the structure refinement. In the case of deformations below the critical value, the growth of austenite grains occurs according to the coalescence mechanism, according to which fragments of boundaries with large disorientation angles consistently disappear. Practical value. For austenite grain refining in massive elements of solid-rolled railway wheel we offer to replace one-time hot compression by fractional one.

Deformation Behavior and Evolution of Austenite Microstructure and Texture During Hot Compression of 5CrNiMoV Steel

Deformation behaviour of 5CrNiMoV steel was investigated at temperature 830–1230 °C and strain rate 0.001–10 s−1. The flow curves were analyzed to illuminate the deformation characteristics. Comprehensive austenite microstructural investigation was carried out using optical microscope for deformed samples. It was found that discontinuous dynamic recrystallization mechanism played a leading part in the nucleation of dynamic recrystallization (DRX) nuclei and growth of DRX grains, and that the austenite grain size increased with deformation temperature, while a larger strain rate was conducive to grain refinement for the quickly generated strain storage-energy favorable for higher DRX nucleation rate. The parent austenite texture evolution and typical martensitic transformation texture for some deformed samples were characterized using electron backscattering diffraction technique and the software of the reconstruction of parent austenite. It was found that increasing temperature contributed to the increase of its maximum of random distribution (MRD) and the strength of rotated Cube texture component, which was probably for the behavior DRX and growth of DRX grains during the hot deformation. The rotated Cube was weakened with the strain rate rising, while the main texture component did not change significantly, which was due to the increase in number of active slip systems and grain fragmentation. Besides, the martensitic transformation texture was related to the parent texture for the variant selection.

Axial compression of steel–timber composite column consisting of H-shaped steel and glulam

A steel–timber composite (STC) column made of H-shaped steel and glulam is proposed in this paper. This STC column is constructed by wrapping the H-shaped steel with the adhesive-applied glulam, which provides confinement to reduce the buckling behaviour of the inner steel. Six STC specimens with lengths of 1100 mm, 1700 mm and 2300 mm were studied using an axial compression test in comparison to three steel and three timber specimens. The distinctive behaviours of the specimens were identified, including the failure mode, load–axial displacement relationship, load–lateral deflection relationship and load–axial strain response. The results demonstrated that the mechanical properties of the STC column are significantly affected by column length. The interaction mechanism between the steel and timber materials was evaluated by analysing the yield strain and the ductility coefficient. The composite effect of the STC column was also discussed by comparing the average strengths. Furthermore, the load-carrying capacity calculation formula including parameter selection of the STC column when yielding was proposed.

Different Evolutions of the Microstructure, Texture, and Mechanical Performance During Tension and Compression of 316L Stainless Steel

The tensile and compressive behaviors of 316L stainless steel at room temperature were compared. The differences between the stress–strain responses during tension and compression were explained by the different evolutions of the texture, defect structure, and phase composition. It was found that up to true strain of ~ 25 pct the flow stress during tension was only slightly higher (by ~ 40 MPa) than that during compression, which can be explained by the different textures of the two types of specimens. On the other hand, between the strains of 25 and 50 pct, the strain hardening for tension was much higher, which resulted in a ~ 200 MPa larger flow stress in the tensile-tested specimen at 50 pct strain. It was revealed that the higher flow stress in tension was caused by the harder texture, the higher dislocation density, and the larger fraction of martensite phase.

Confined uniaxial compression of granular stainless steel 316

The quasi-static compaction response of granular stainless steel 316 was studied under triaxial loading conditions using a confined crucible experiment apparatus, specifically looking at effects of the particle size (127 ± 34μm, 309 ± 88μm, 487 ± 98μm) on mechanical behavior. The material response was captured using a load washer and strain gauges to relate: the porosity effects as a function of hydro-static pressure, particle size dependency on wall friction effects, and particle size-dependent failure mechanism. Our observations revealed that the path of crushing out porosity varied based on the particle size and the frictional effects. Scanning Electron Microscope images were taken to observe the surface features of the compacted material and comment on failure mechanisms. Using these techniques it was observed that the smaller particles exhibited significant plastic deformation and flow, while the larger fragments appeared to show micro-cracking which lead to inelastic deformation and particle fracture. Altogether, these results are important because granular behavior is critical in powder flow applications such as additive manufacturing.

Mathematical model of coupled thermo-mechanical behavior during plane strain compression of 06Cr19Ni9NbN steel

The process of plane strain compression of 06Cr19Ni9NbN steel was carried out in the temperature range of 1000–1200 °C and the reduction ratio range of 10–50%. Combining the finite element numerical simulation, a new constitutive model of thermal deformation was established, which provides the theoretical basis to optimize the plane strain compression process of the steel. The temperature and grain size at different regions were achieved by experiment and simulation, respectively. According to the results, the mathematical models of stress and temperature during the plane strain compression were established by mathematical analysis method. The new temperature models were established in three regions, respectively, and the stress models took account of the variation of temperature and strain rate. Finally, by comparing the results of calculation, numerical simulation and experiment, the accuracy and validity of these mathematical models were verified.