Mechanical Properties Of Steel Research Articles

A mini-review of surface severe plastic deformation methods and their effects on steel and stainless steel

Surface severe plastic deformation is an important technology for the preparation of bulk ultrafine grain or even nanocrystalline materials. Based on the technical achievements made in the field of surface severe plastic deformation at home and abroad, this article presents the basic principles of various kinds of surface severe plastic deformation techniques in detail. In addition, the effects of surface severe plastic deformation on the microstructure and mechanical properties of steel and stainless steel are reported. The current status of research on the effects of surface severe plastic deformation on fatigue properties and the tribological and biological properties of steel and stainless steel are summarized. The problems of the current surface severe plastic deformation technology for steel and stainless steel are pointed out, and the future development trend is foreseen.

Effects of Mo and Controlled Cooling on Microstructure and Properties of Thick‐Wall High‐Strength Pipeline Steel

Herein, the effect of molybdenum (Mo) and postrolling cooling processes on the mechanical properties and microstructure transformation characteristics of an X80 thick‐wall high‐strength pipeline steel are deeply investigated. The results reveal that the yield strength and tensile strength of the steel are enhanced with Mo addition at the equalization temperature of 480 °C at a cooling rate of 25 °C s−1, accompanied by the improvement in the yield ratio. However, when the postrolling cooling temperature is reduced to 380 °C, the mechanical properties of steels with Mo‐free and 0.29 wt% Mo are comparable. The mechanistic study indicates that the Mo addition would inhibit the transformation from deformed austenite to polygonal ferrite, and promote the transformation of acicular ferrite/granular bainite at medium–low temperatures, as well as significant differences in the volume fraction, size, and morphology of martensite/austenite (M/A) in the matrix. Notably, the volume fraction of M/A decreases from 7.2% to less than 1.0% with Mo content increasing, while its average size also reduces from 1.5 to less than 1.0 μm. And the fine, spheroidal, and dispersed M/A is found to play a vital role in the high‐strength and excellent low‐temperature toughness of the steel.

Microstructure evolution and strain hardening behavior of thermomechanically processed low-C high-manganese steels: an effect of deformation temperature

Effects of reduced (– 40 °C), ambient (20 °C), and elevated (200 °C) deformation temperatures on the microstructure evolution and strain hardening behavior of two low-C thermomechanically processed high-manganese steels were studied. The microstructure was characterized by means of scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) techniques. The temperature-dependent tendency of austenite to strain-induced ε/α′-martensitic transformation and mechanical twinning was qualitatively and quantitatively assessed using the EBSD technique. The steel containing 26 wt% of Mn showed the beneficial strength–ductility balance at reduced deformation temperature -40 °C due to the intense Transformation-Induced Plasticity (TRIP) effect which resulted in the formation of significant ε- and α′-martensite fractions during tensile deformation. The mechanical properties of steel containing 27 wt% of Mn were more beneficial at elevated deformation temperature 200 °C due to the occurrence of intense Twinning-Induced Plasticity (TWIP) effect expressed by the presence of significant fraction of mechanical twins. Moreover, at the highest deformation temperature 200 °C, the evidence of thermally activated processes affecting the mechanical behavior of the higher Mn steel was identified and described.

Heating duration effects on post-fire structural steel mechanical properties

Post-fire mechanical assessment of steel structures is challenging due to the changes in mechanical properties from the heating and cooling phases of a fire. While the effects of cooling rate and temperature of exposure have been researched in depth, the effects of heating duration are not comprehensive. This paper investigates the effects of heating duration on post-fire A572 Gr. 50 steel mechanical properties over a temperature range of 500–800 °C for durations of 0.5 and 2.0 h. Specimens are subjected to tensile testing in accordance with ASTM A370, Vickers microhardness testing, and optical microscopy. The findings suggest that heating duration has an influence on the post-fire mechanical properties of steel at elevated temperatures (700, 800 °C). At these temperature exposures, retention of yield stress, retention of ultimate stress, and microhardness all decrease. Members subjected to 700 °C for 0.5 h have more retention in yield stress and microhardness compared to those exposed for 2.0 h, while the 800 °C conditions show little difference in mechanical properties between exposure times. The results of this study show that the duration of fire exposure is an important factor when estimating the mechanical properties of fire-exposed steels, in addition to the temperature and cooling rate.

Mechanical properties and constitutive model of Q460 steel during the fire-cooling stage

The mechanical properties of steel under fire-induced elevated temperatures is fundamental and crucial for structural fire-resistance design and analysis. Mechanical properties of high-strength steel (HSS) during the fire-heating and post-fire stages have been extensively investigated, while those during the fire-cooling stage were rarely studied. This study investigated the mechanical properties of HSS Q460 during the fire-cooling stage by steady-state tensile experiments Results show that the mechanical performance of HSS Q460 at the fire-cooling stage is not only related to the test temperature (Tt) but also the peak heating temperature (Tp) before cooling for tests. The strength of HSS Q460 at identical Tt shows an overall download trend with the increase of Tp. The mechanical properties of HSS Q460 at the fire-cooling are similar to those at the fire-heating stage when Tp is not greater than a certain value. This value is 600 °C for Young’s modulus and yield strength f0.2, and 400 °C for yield strength f1.0, f2.0 and ultimate strength. When Tp exceeds certain values, the Young’s modulus and strengths at the fire-cooling stage are less than those at the fire-heating stage. Moreover, the mechanical properties of HSS Q460 were compared with those of HSS Q690, indicating that the degradation rules of mechanical properties of HSSs Q460 and Q690 differ during the fire-cooling stage. Besides, formulas were proposed to calculate the mechanical properties and stress–strain relationship of the HSS Q460 during the fire-cooling stage.

Mechanical properties of carbon steel under uniaxial static tension

With the continuous development of science and technology, carbon steel is widely used in production and life. Especially at the practical application level, in the engineering application, the analysis of the mechanical properties of carbon steel materials has become increasingly prominent. The tensile test is a mechanical property test in which a standard tensile specimen is pulled to fracture at a specified tensile speed under the continuous action of static axial tensile force. The force and elongation are continuously recorded during the tensile process so as to obtain its strength criterion and plasticity criterion. In this paper, the characteristics of mechanical properties of the high, medium, and low carbon steels under uniaxial static tension are discussed. The reasons for the different mechanical properties of steels with different carbon content are explained from a microscopic perspective. The study provides some basic assistance to those who need relevant information.

Roles of Al in enhancing the thermal stability of reverted austenite and mechanical properties of a medium-Mn TRIP steel containing 2.7 Mn

Often, the addition of more than 4 wt.% Mn to medium-Mn steels is necessary to enhance the thermal stability of intercritical austenite for achieving sufficient amounts of retained austenite (RA) at room temperature. In this paper, a medium-Mn steel with Mn content as low as 2.7 wt.% was designed via alloying with a small amount of Al, and the microstructure and mechanical properties of the steel, subjected to intercritical annealing (IA) at 745 °C for different times followed by oil quenching, were investigated. Results show that the volume fraction of RA increases first and then decreases with IA time, with the maximum of 0.36 obtained at IA time of 50 min. It is demonstrated that Al addition slows down the interface migration and growth kinetics of reverted austenite via retarding C diffusion in ferrite during IA, which, hence, decreases the amount and size of the reverted austenite and partitions more C and Mn into it. This suggests that Al plays a favorable role in enhancing the thermal stability of reverted austenite and increasing the amount of austenite retained at room temperature. Due to the presence of large amounts of RA and the strong transformation-induced plasticity effect generated during plastic deformation, the steel exhibits persistent high strain hardening and superior mechanical properties, comparable to those of reported medium-Mn steels containing higher Mn content. The present result offers a new insight into the role of Al in adjusting microstructure-property relationships and opens a promising way for designing low-cost, high performance medium-Mn steels with low Mn content for industrial applications.

Micro structure and wear analysis of multi-layer nitride coating deposited on the austenitic steel

Utilizing the appropriate technology, the surface property must be improved to offset wear loss caused by friction. Hard ceramic coating compounds include titanium nitride (TiN) and titanium aluminium nitride (TiAlN). The cathodic arc deposition method's effects on the stainless steel (SS304) mechanical and wear properties (CAD) Measurements and comparisons are made for the coated samples of the wear rate microstructural study. In the ball-on-disc wear test, the tribological parameters are altered. Compared to different kinds of coatings, The TiN coating offers remarkable mechanical and tribological qualities on the SS316L surface. the microstructure of the wear areas of materials coated with titanium nitrate and aluminium titanium nitride under various loads. Compared to non-coated material, the titanium nitride and aluminium titanium nitride coated materials have high wear resistance.

Effects of titanium addition on austenite grain size and mechanical properties of high manganese steel

Manganese steels have been widely used in industries due to their good wear resistance, high work hardening ability, and high toughness and ductility. This research investigated the effect of modification, i.e., FeTi and Mischmetal, on the grain size and mechanical properties of the high manganese steel (13–15 wt.%). The alloys are modified at different temperatures of 1500, 1550, and 1600 o. The modified alloys were heat-treated after solidification by a two-step process. The grain size, chemical composition, and phase formation of the heat-treated steel were characterized by Optical Microscopy, X-ray Diffractometry, and Energy-Dispersive X-ray Spectroscopy. The mechanical properties of the steel, such as Brinell hardness, tensile strength, and toughness, were measured. As a result, the grain size of the heat-treated alloys is smaller compared to that of un-modified alloys and decreases with the increase in modification amount. The addition of Ti reduced C in the austenite phase by forming very stable carbides, TiC. Maximum tensile strength of 780 MPa was achieved with the addition of 0.1 wt.% Ti, while maximum fracture toughness was 140 J/cm2 at 0.05 wt.% Ti.

Inclusion Metallurgy

Non-metallic inclusions have a great influence on the cleanliness and mechanical properties of steel [...]

Characteristics of ASTM A36 steel mechanical properties in pack carburizing with carburizing agent coconut shell charcoal and goat bone powder mixed

In the study the specimens were ASTM A36 low carbon steel pack carburizing at 950℃, soaking time variations of 1, 2 and 3 hours. The carburizing agent is a mixture of coconut shell charcoal and goat bone powder (Capra aegagrus hircus). The size of the powder is 100 mesh, with variations in weight percentage between goat bone powder and coconut shell charcoal: 10%:90%, 20% : 80%, and 30% : 70%. Furthermore, the impact test, hardness, microstructure test and composition test were carried out, to determine the mechanical properties of the specimens. The results of the study show, soaking time and the composition of the carburizing agent affect the mechanical properties of the specimen The lowest impact toughness of 0,0576 joules/mm2 was obtained by the specimen at a soaking time of 1 hour, the composition of the carburizing agent (% wt goat bone powder: coconut shell charcoal) 20% : 80%. The highest surface hardness value was 854.734 Kg/mm2 at 3 hours soaking time with 10%:90% carburizing media composition. The results of microstructure observations showed that in specimens treated with pack carburizing ferrite structure, pearlite turned into martensite.

Carbon mapping in steel using 12C(d,pγ)13C in external beam

Carbon concentration and distribution has a dramatic impact on mechanical properties of steel. The manufacture technology of ancient steel is an important question in archaeometallurgy, especially during medieval times when the production process evolves between indirect and direct modes. Steel is an iron alloy incorporating up to a few % of carbon in weight, heterogeneously clustered in various carbide phases that are usually imaged by metallographic microscopy after acid etching. We have investigated the capability to obtain in a direct, non-destructive way and quantitative maps of carbon in steel samples using the 12C(d,pγ)13C reaction with the simultaneous detection of the emission of the 3089 keV γ-ray (d-PIGE) and of the p0 proton group (d-NRA). Carbon spot measurements and mappings were carried out using an external deuteron microbeam of 1.5 MeV at the New AGLAE facility of the Centre de Recherche et de Restauration des Musées de France. The beam diameter on the target was around 50 µm and its mean intensity 4nA, monitored by using the PIXE signal (Fe Kα line) emitted by the sample. Spectra were fitted using the SIMNRA program and the calculated composition checked against standard reference steel targets. Carbon distribution maps were extracted from the collected γ-ray and proton spectra datacubes. Spot measurements acquired in 2 min yielded a limit of detection of 200 ppm carbon weight for d-PIGE and 10 ppm for d-NRA. Proton detection appeared more effective than γ-ray detection owing to better statistics, mainly due to higher detection efficiency and better S/N ratio while γ-rays detection is affected by the spurious emission from nitrogen contained in the exit foil. Carbon concentration was mapped on a medieval archaeological iron alloy sample (140 × 32 points, 7 mm × 1.6 mm area) using a 1.6 sec dwell time, yielding a carbon content of 0.395 % with an uncertainty of 10 %. Heterogeneities could be evidenced in the maps, and incidentally the presence of oxygen. A simple methodology was developed to derive the depth distribution maps of carbon in the first microns of the sample.

Hydrogen blending in existing natural gas transmission pipelines: a review of hydrogen embrittlement, governing codes, and life prediction methods

Abstract Existing natural gas pipelines provide an economic alternative for the transport of hydrogen (H2) in an envisioned hydrogen economy. Hydrogen can dissolve in the steel and cause hydrogen embrittlement (HE), compromising pipeline structural integrity. HE causes subcritical cracking, decreases ductility and fracture toughness, and increases the fatigue crack growth rate (FCGR). This work analyzes the testing standards in gaseous hydrogen used to quantify those effects. Design code ASME B31.12 applicable to hydrogen pipelines has more stringent requirements than ASME B31.8 code commonly used for constructing natural gas pipelines. Differences in materials requirements specified by those codes are summarized. ASME B31.12 pipeline code applies for H2 at a concentration greater than 10% molar. However, recent testing programs acknowledge that H2 degrades steel mechanical properties regardless of its percentage in the blend. This paper discusses how the hydrogen degraded mechanical properties affect pipeline integrity. Decreased mechanical properties cause a drop in the failure pressure of a flawed pipeline, calculated following a fitness for service methodology. There is an increasing risk of subcritical crack growth in H2 as the hardness of base metal and welds increases. This paper analyzes where zones with high hardness and susceptible microstructures are expected in existing pipelines.

Degradation Mechanisms and Residual Mechanical Properties of Reinforcing Steel Bars Exposed to Natural and Artificial Corrosion – Review & Analysis

Reinforcement corrosion is the most problematic phenomenon and one of the main sources for the degradation of structures and infrastructures all across the world, that leads to their premature deterioration before design life has been attained. Therefore, the structural effects of rebar corrosion are crucial in determining the structural performance and residual strength of impaired structures. In the present work, the corrosion initiation mechanisms, corrosion products, corrosion types, corrosion consequences on structural performance and detrimental factors related to corrosion were presented in brief. Moreover, the propagation period and the main consequences on mechanical properties of steel and concrete are analyzed. Analyses of the available statistical data collected from literature were performed for 443 specimens. The findings are further interpreted from structural point of view, and deterioration equations for the mechanical properties of the corroded reinforcements are developed. The relations are well analyzed, leading to the definition of decay equation for yielding and ultimate stresses, and ultimate strain. It was found that the mass loss of 1% due to the rebar corrosion can cause the strength loss of 1.34%, 1.30%, and 3.54% respectively for yield strength, ultimate strength, and elongation. The suggested formulas can be applied in analytical and numerical structural applications.

Impact of barium and strontium on calcium recovery level in ladle treatment of steel by complex modifiers with alkaline-earth metals

Increasingly rigid requirements in terms of the steel products quality are forcing the technical experts of metallurgical production to look for new solutions to stabilize the steel quality. Much attention is paid to ladle treatment technologies and selection well-minded composition of modifiers, which makes it possible to reduce steel contamination by non-metallic inclusions. To solve this problem, complex modifiers containing both calcium and other alkaline-earth metals (barium and strontium) are used. The paper presents the results of the pilot scale tests of steel ladle treatment by complex modifiers with alkaline-earth metals (Si, Ca, Ba) in steel production with increased requirements to non-metallic inclusions in conditions of electric furnace steelmaking shop of JSC “Ural Steel”. During experimental work it was possible to reduce the maximum contamination score profile rolled steel from pipe steel grades for brittle silicates (GOST 1778) from 4.0 to 1.5 – 2.5, for non-deforming silicates from 4.0 to 3.0 – 3.5. The substitution of SK40 grade silicocalcium for experimental modifiers led to an improvement in the strength properties of rolled products, both in tensile tests and in impact bending tests at low temperatures. The indicated impact was observed in all variants of consumption the experimental master alloys. It is noted that with an increasing in the consumption of master alloys, the positive effect on the steel mechanical properties enhanced. It was established that the replacement of silicocalcium with experimental variants of master alloys made it possible to increase the calcium recovery by an average of 1.6 times when using Si – Ca – Ba, and by an average of 2.4 times when using Si – Ca – Ba – Sr. The use of complex modifiers made it possible to obtain the target value of residual calcium in the sample at significantly lower calcium consumption.

Production of a Non-Stoichiometric Nb-Ti HSLA Steel by Thermomechanical Processing on a Steckel Mill

Obtaining high levels of mechanical properties in steels is directly linked to the use of special mechanical forming processes and the addition of alloying elements during their manufacture. This work presents a study of a hot-rolled steel strip produced to achieve a yield strength above 600 MPa, using a niobium microalloyed HSLA steel with non-stoichiometric titanium (titanium/nitrogen ratio above 3.42), and rolled on a Steckel mill. A major challenge imposed by rolling on a Steckel mill is that the process is reversible, resulting in long interpass times, which facilitates recrystallization and grain growth kinetics. Rolling parameters whose aim was to obtain the maximum degree of microstructural refinement were determined by considering microstructural evolution simulations performed in MicroSim-SM® software and studying the alloy through physical simulations to obtain critical temperatures and determine the CCT diagram. Four ranges of coiling temperatures (525–550 °C/550–600 °C/600–650 ° C/650–700 °C) were applied to evaluate their impact on microstructure, precipitation hardening, and mechanical properties, with the results showing a very refined microstructure, with the highest yield strength observed at coiling temperatures of 600–650 °C. This scenario is explained by the maximum precipitation of titanium carbide observed at this temperature, leading to a greater contribution of precipitation hardening provided by the presence of a large volume of small-sized precipitates. This paper shows that the combination of optimized industrial parameters based on metallurgical mechanisms and advanced modeling techniques opens up new possibilities for a robust production of high-strength steels using a Steckel mill. The microstructural base for a stable production of high-strength hot-rolled products relies on a consistent grain size refinement provided mainly by the effect of Nb together with appropriate rolling parameters, and the fine precipitation of TiC during cooling provides the additional increase to reach the requested yield strength values.

Review of Fire-Related Damage of Steel Offshore Structures

Fixed offshore structures are continuously exposed to risk of hydrocarbon fire or cellulosic fire. Hydrocarbon fire generally causes more detrimental effect than cellulosic fire because the rapid increment of temperature gives little response time for people to evacuate the location or to put off the fire. Metallography tests have demonstrated that steel structures continuously exposed to temperature escalation from fires will lose their mechanical properties such as yield strength, tensile strength, toughness, hardenability and elastic modulus. Thus, to understand the structural response during fire, structural integrity assessment with revised steel mechanical properties is advised to be performed. The outcome of the analysis helps to identify the hotspots of the steel structures due to the fire and allow the investigation team to further perform detailed inspection and proposed structural repair to reinstate the integrity of the steel structures.

Analysis of Factors Influencing Mechanical Properties of Corrugated Steel Based on Entropy Method

In recent years, corrugated steel has been used in some domestic tunnel construction for its large section and high strength, and has become a new type of tunnel support structure. Corrugated steel mechanical properties will directly affect the stability of support structure. Therefore, the important thing is to choose the appropriate parameter to improve the mechanical performance of ripples. Parameters that affecting the mechanical properties of corrugated steel include wave height, corrugation thickness and wave distance. This massage will rely on the Qipan Mountain tunnel project, studying its fabricated corrugated steel supporting structure, and selects corrugated steel with different thicknesses, wave heights and corrugated spans for transient analysis. The largest deformation of corrugated steel under blasting shock is calculated by numerical simulation to react the corrugated steel mechanical properties, and then use the method of Entropy to determine the influence of different parameter values on mechanical performance of corrugated steel. The weight coefficient of wave thickness is 92.38%, the influence weight coefficient of wave height is 7.54%, and the influence weight coefficient of wave short is 0.07%. It is shows that the thickness has the greatest influence on the mechanical properties of the supporting structure, and the wave distance has no influence. Through the above analysis, the parameter design and stability design of corrugated steel support structure can be given some reference and help.

High-performance grout-reinforced shear connectors for hybrid steel-cross-laminated timber building systems: Experimental study

Wood-based construction advancements have been observed recently with the adoption of hybrid assembly and offsite construction methods, relying on prefabricated components, such as volumetric cross-laminated timber (CLT) modules or composite panel-type wall and floor elements. Within the high-rise timber building framework, mass timber structural assembly requires connections designed to accommodate innovative technologies to limit damage under seismic loads and mitigate lateral vibration of the building under serviceability loads. As part of the performance-based capacity and constructability enhancements, current research efforts have been on the development of high-performance and reliable mass timber connections. This paper presents a new connection design method for hybrid steel-CLT composites and assemblies. Shear connectors are fabricated by encasing steel rods into CLT panels using an epoxy-based grout, with geometry specified to provide stiffness and shear capacity target levels. An insight into their behaviour and performance is given based on an experimental dataset comprising 240 full-scale push-out shear tests and an array of rod diameter, grout thickness, and mechanical properties of steel and CLT. Maximum shear strength of 289.6 kN and elastic stiffness of 243.2 kN/mm were attained for the tested specimens, showing that strong and stiff behaviour were attainable. Elastic mechanical properties of connectors were shown to be governed by the rod diameter, whereas strength resistance and failure mode from the grout thickness, allowing for decoupling of design parameters and fine-tuned design. The yield point was shown clearly identifiable, supporting optimum capacity design strategies. Observed failure modes were mostly ductile and with a maximum slip ductility of 6.4, and on average comparable with common wood bolted connections. A resistance factor of 0.8 was shown adequate to design the shear connectors using the calculated 5th percentile values of the yield shear resistance and maximum shear resistance, relatively, for elastic and plastic design strategies. Large-scale building applications were shown attainable by intrinsic individual mechanical properties of the connector, supporting deconstruction and reuse of the hybrid steel-timber structural system components when the connector is capacity-protected and behaves elastically; thus, designed using its 5th percentile yield shear strength.

Permeating hydrogen generated from the elemental sulfur corrosion of low carbon steel

Permeating hydrogen generated from the elemental sulfur corrosion of low carbon steel was investigated using a double cell system and its effect on the mechanical properties of steel was also discussed. Results show that elemental sulfur corrosion of low carbon steel is accompanied by significant hydrogen permeation, e.g., permeating hydrogen current reaches 12.3 μA/cm2 in CO2-containing environment at 80 °C. The hydrogen permeation process are greatly affected by the structure and composition of the corrosion product, the environmental temperature and gas composition. This permeating hydrogen enhances the brittleness of the low carbon steel and tends to cause hydrogen-induced cracking.