Mechanical Properties Of Steel Research Articles

Material Testing and Evaluation of Steel Mechanical Properties for Classification of Steel Grade of Existing Civil Engineering Structure

The paper is generally focused on the determination and evaluation of yield and ultimate strengths of structural steels, not only current materials but also materials of existing steel structures when the properties are unknown and no material certificates exist. The attention is paid i.a. to the testing and evaluation of steel strengths, especially from the viewpoint of the statistical elaboration of material test results aimed to obtain strength values leading to the reliable structural design [3], in the meaning of general rules according to the European Standards for structural design of civil engineering constructions. The paper deals with actual yield and ultimate strengths obtained using material tests and with characteristic and design strengths based on the test results evaluation versus nominal and design strengths given by European Standards which are used for the structural design in the usual cases when steel grade is known. But in the case of existing structures, very often no information about the material exist that actual values of steel properties shall be determined using material tests and their statistical elaboration to obtain such values of steel properties which lead to the reliable structural design [3], [6], [7]. However, approaches of the derivation of characteristic and design steel strengths using actual test results are principally different from the consideration of nominal and design steel strengths covered by the rules of the European Standards. This paper illustrates the evaluation of the results of material tests performed on the test specimens taken from the steel roof structure of the sport stadium almost 50 years aged, within the diagnostics of load-carrying steel structures of this building [1] aimed to the evaluation of the existing construction [2].

On Problems of Mechanical Properties of Structural Steel in Load-Carrying Structure of Historical Building Construction

The paper is focused on the problems of the mechanical properties of steel used for load-carrying structures of civil engineering constructions, especially from the viewpoint of properties of old steels used in historical constructions in comparison with current steels. Chemical composition and physical-mechanical properties of historical steels can be important, for example, in the case of reconstructions, when for the static assessment and evaluation of existing constructions subjected to new (higher) loading actions, material properties of load-carrying structure must be known. In the case of constructions aged about 100 years, usually no project documentation and no information about used material and its properties exist. Then, the properties must be determined using material tests carried-out on the test specimens taken from the real existing structure. But here the sampling of test specimens is limited by the possibilities of existing structural system and by the dimension of particular members from which the specimens are taken, so that the test specimen dimensions and number are limited. Thus, the evaluation of material properties for obtaining representative design values can be more difficult and less reliable than in the case of the large test number. But the main problem is to determine the usable design values of material properties (design yield and ultimate strength) to utilize them for the reliable static re-design of existing structure under actual loading actions. Some problems indicated above have been shown on the example of the material analysis of steel load-carrying structure of slaughterhouse aged more than 100 years. This analysis has been performed recently within the framework of the construction exploration in connection with the intended revitalization of historical “industrial zone” in the city of Brno, Czech Republic.

Changes of Mechanical Properties of Steel 12Cr18Ni10Тi after Electrolytic-Plasma Cementation

In the present work the results of electrolytic-plasma treatment influence on the mechanical properties and structural-phase condition of steel’s 12Cr18Ni10Ti surface layers. In the work, the mechanical characteristics of steel’s surface layers are investigated, cemented in electrolytic plasma with the composition of 10 % Nа2CO3 and 10 % С3Н8О3. The operational parameters for the processing are determined. The optimal content of components in saturating mixtures of plasma by cementation is defined. According to the study it is found that, after electrolyte plasma processing, high wear resistance and hardness increased in 2-2.5 times more than in the original condition. The hardened layer with thickness 30-65 µm is formed. It is shown that after the electrolyte-plasma processing of steel 12Cr18Ni10Ti, microstructure contains particles of carbides and has a fine-grained martensitic structure.

Magnetic and eddy-current testing of hardened constructional steel subjected to combined strain-thermal treatment

The potentialities of magnetic and eddy-current methods for testing a structural state, wear resistance, and mechanical properties of steel 50 (0.51 wt. % C) subjected to quenching from 850°C, nanostructurizing frictional treatment with a hard alloy indenter, and tempering at the temperatures of 100–600°C are studied. It is shown that the structural state of constructional steel 50 that is subjected to combined strain-thermal treatment can be tested using the eddy-current method upon low temperature (to 250°C) tempering and in the tempering temperature range of 250–450°C, the coercitimetric method and based on the maximum permeability in the temperature range of 100–350°C, based on the residual magnetic induction for major and minor magnetic hysteresis loops in the temperature ranges of 100–400°C and 250–600°C, respectively, and based on the specific resistivity in the temperature range of 100–300°C. Correlations between electromagnetic parameters and hardness, mechanical properties, wear intensity under the conditions of dry frictional that point to the possibility of using eddy-current and magnetic testing of the quality of optimized strain-thermal treatment, which provides a good complex of wear resistance and mechanical characteristics of constructional steel, were established.

Study on the Deterioration Properties of Corroded Steel Based on Weibull Distribution

The change of steel mechanical properties is because of steel corrosion seriously. An important factor of evaluating the performance of active steel structure is the degradation of steel mechanics performance. Corroded steel mechanics performance degradation accords with four parameters Weibull distribution through analysis the rapid steel corrosion experiment data. The each Weibull distribution parameters of the degradation of the steel corrosion rate, yield strength and ultimate strength are solved through Matlab programming. Weibull distribution simulation results and experimental data agree well. These models can predict the degradation of steel mechanics performance and can help people to evaluate the corrosion steel structure bearing performance to reinforce the steel structure.

Impact of corrosion on mechanical properties of steel embedded in 27-year-old corroded reinforced concrete beams

This paper deals with the impact of corrosion on the mechanical properties of steel in reinforced concrete. Steel bars were extracted from a 27-year-old corroded reinforced concrete beam that had been exposed to a chloride environment. Bars with different degrees of corrosion and with different corrosion pit depths were tested in tension. A comparison was made between nominal and true stress for corroded and control steel specimens. It was noted that the degree of corrosion strongly affected the mechanical properties of the steel, particularly the ultimate stress and strain. Interestingly, the true yield strength of all the corroded steel bars remained almost constant while their true ultimate strength was considerably increased. A reduction of the ultimate elongation appeared to be the major effect of corrosion and affected the compliance with standards.

Effect of Strain Rate on Mechanical Properties of Fe-30Mn-3Si-4Al TWIP Steel

Influence of strain rate on mechanical properties of Fe-30Mn-3Si-4Al TWIP steel was studied by compression experiments, indicating that TWIP steel has strain rate softening effect, strain rate insensitivity, and also strain rate hardening effect. According to strain rate sensitivity m changing with strain rate, effect of strain rate on TWIP steel mechanical properties can be divided into three stages: quasi-static stage with strain rate ranging from 0.001 to 100 1/s; high-strain rate stage with strain rate ranging from 701 to 5108 1/s; super-high-strain rate stage with strain rate ranging from 10335 to 30147 1/s. Adiabatic temperature rise tends to increase with strain rate. Strain hardening exponent is divided into three parts: dislocation strengthening stage, twinning strengthening stage and thermal softening stage.

Concepts and implementation of strain-based criteria in design codes for steel structures

A uniaxial tension test is commonly used to determine the mechanical properties of steel, but it has no meaning for the response of the material in a structure. The test was developed as a consensus solution by producers, fabricators, designers and code writers, to have a standard by which similar materials could be compared to a common base. It does not represent the actual behavior of the steel in a structure, and was never intended to do so. To study the true behavior of the structure and how the material responds it would be better to determine the strains and deformations that will take place during actual service condition. Such characteristics reflect the real behavior, whether in the elastic or inelastic range. If stresses or forces are needed, these are easily determined by the value of the strain and the relevant material modulus, along with the type of cross section, whether elastic or inelastic. The paper addresses the properties of a range of structural steels, how these are incorporated into design standards and how the standards define deformation characteristics and demands for bolted and welded connections.

Mechanical properties of high-strength bolts after fire

The effects of heating and cooling of steel in fire are similar to tempering and annealing. The mechanical properties of steel after exposure to fire will, therefore, be different from the initial properties. High-strength bolts, which are widely used in steel structural connections, are more temperature-sensitive than hot-finished steel because the manufacturing process of high-strength bolts consists of cold drawing, annealing, cold forging and heat treatment. A number of experiments have been carried out on the mechanical properties of high-strength bolts at elevated temperatures, but very few studies have focused on the mechanical properties of high-strength bolts after fire. To obtain the mechanical properties of high-strength bolts after fire, including stress–strain curves, strength and elastic modulus, a series of experiments on 10·9S bolts and 8·8S bolts was carried out. In order to simulate real situations in the event of fire, both natural cooling and water cooling were employed in the experimental study. The results show that heating and cooling has a great effect on the mechanical properties of high-strength bolts after fire and that the effects of natural cooling are very different from those of water cooling.

Development of Residual Stress during Manufacturing of Spiral Welded Pipes

Spiral welded pipes (SWPs) are produced from forming and welding of plate or strip material with seam running its entire length in a spiral form. The relative structural weakness of these pipes is due to high residual stress developed during welding, which depends on various parameters and their interaction. Finite element method (FEM) was used to predict the temperature and stress fields in a 56-inch spirally welded steel pipe. Temperature-dependent thermal and mechanical properties of steel were incorporated in the model. Arc welding was modelled as a three-dimensional (3D) volumetric moving heat source. The residual stresses produced after the completion of the welding process were investigated. For validation, the numerically predicted residual stress was compared with measured values using split-ring and hole-drilling methods. It was found that von Mises stress attained high values in the cooling cycle after the solidification of the molten zones. Moreover, the effect of welding speed on the level of residual stress was studied. Increasing the welding speed with constant power resulted in reduction of the width of the high stress zone.

PENGARUH HARDENING PADA BAJA JIS G 4051 GRADE S45C TERHADAP SIFAT MEKANIS DAN STRUKTUR MIKRO

Steel represents a metallic material which is still dominantly used in the engineering industry and mechanical construction. In order to fulfil the industrial demand, the high quality and mechanical properties of steel has to be always available.It is necessary to conduct a heat-treatment process to identify the improvement of mechanical properties and microstructure of steel JIS G 4051 grade S 45 C .Results of the heat-treatment process indicate that the maximum tensile strength of the investigated steel is 1074 MPa , it is earning from the warm-up temperature 860 °C and the highest hardness of the investigated steel is 579 HV it is earning from the warm-up temperature 920 °C . These results meet to AISI – SAE 1045 or JIS G 4051 grade S 45 C standard.

저온환경이 선박 및 해양플랜트용 탄소강재의 재료강도특성 및 상선의 최종 종강도 거동에 미치는 영향

저온환경이 선박 및 해양플랜트용 탄소강재의 재료강도특성 및 상선의 최종 종강도 거동에 미치는 영향

Stepping-quenching-partitioning treatment of 20SiMn2MoVA steel and effects of carbon and carbide forming elements

A novel heat treatment process, stepping quenching and partitioning (S-Q-P), has been developed to manipulate microstructure and mechanical properties of steels. Based on incomplete partitioning of carbon from martensite to austenite, volume fraction and distribution of the retained austenite resulting from the following quenching of the steels could be effectively controlled, and then the synthesized mechanical properties of the steels would be improved. In this paper, 20SiMn2MoVA steel was treated with conventional quenching-tempering (Q-T), currently prevailing quenching-partitioning (Q-P) and S-Q-P processes, respectively. The results indicated that the volume fraction of the retained austenite of the steel treated by Q-P and S-Q-P processes increased significantly that resulted in the increase of ductility and decrease of strength. The product of strength and ductility of the steel treated by S-Q-P process reached 23.7GPa%, that was increased by about 13% and 7% compared with that after Q-T and Q-P processes, respectively. Compared with the great improvement of the synthesized mechanical property obtained by S-Q-P process with another steel 35SiMn, there would be some factors that deteriorated the effect of S-Q-P process on 20SiMn2MoVA steel. It was found by microstructural testing that the carbide forming elements V and Mo in the steel led to precipitation of carbides during partitioning period and lack of carbon in austenite. As a result, less austenite would remain after final quenching and mechanical properties of the steel would be influenced. The results would be beneficial for understanding the principle of S-Q-P process and improving the design of the S-Q-P steel compositions.

Effect of semifinished rolled product cooling rate during controlled rolling on the condition of microalloyed steel hot-worked austenite, final microstructure, and mechanical properties. Part 2. Study of the effect of semifinished rolled product cooling rate on ferrite-bainite structure formation*

The effect of cooling rate is studied under laboratory conditions for semifinished rolled product in a temperature range of the order of 1000–850°C using controlled rolling technology on the condition of hotworked austenite, grain refinement in the final microstructure, and set of mechanical properties for lowcarbon microalloyed steel.

Predicting the ferrite grain size in low-alloy steel

Mathematical models are proposed for calculating the onset temperature of ferrite transformation and the ferrite grain size as a function of the cooling conditions and the initial austenite grain size. The models are calibrated on the basis of experimental data for steels with ferrite-pearlite microstructure. The models are integrated in HSMM software, with considerable gain in computational power when considering the mechanical properties of steel rolled on the 2000 mill at OAO Severstal’.

Assessment of the Low Alloy Cast Steel Inoculation Effects with Chosen Additives

Assessment of the Low Alloy Cast Steel Inoculation Effects with Chosen Additives Structure, and thus the mechanical properties of steel are primarily a function of chemical composition and the solidification process which can be influenced by the application of the inoculation treatment. This effect depends on the modifier used. The article presents the results of studies designed to assess the effects of structural low alloy steel inoculation by selected modifying additives. The study was performed on nine casts modeled with different inoculants, assessment of the procedure impact was based on the macrostructure of made castings. The ratio of surface area equivalent to the axial zone of the crystals and columnar crystals zone was adopted as a measure of the inoculation effect.

Effect of semifinished rolled product cooling rate during controlled rolling on the condition of microalloyed steel hot-worked austenite, final microstructure, and mechanical properties. Part 1. Study of the Effect of Semifinished Rolled Product Cooling Rate on Ferrite-Pearlite Microstructure Formation

Effect of semifinished rolled product cooling rate during controlled rolling on the condition of microalloyed steel hot-worked austenite, final microstructure, and mechanical properties. Part 1. Study of the Effect of Semifinished Rolled Product Cooling Rate on Ferrite-Pearlite Microstructure Formation

Effect of Aging Temperature on the Microstructure and Mechanical Properties of 1000MPa Grade Low Carbon Bainitic Steel

A kind of 1000MPa low carbon bainitic steel belonged to the Fe-Cu-Nb series was hot rolled and aged, the influence of aging temperatures on the microstructure and mechanical properties of the steel were investigated by using Scanning electron microscopy (SEM) and transmission electron microscopy(TEM). The results show that the microstructure of the low carbon bainitic steel consisted of lath-shaped bainite(LB), granular bainite(GB) and quasi-polygonal ferrite(QF), and the proportion of each kind of microstructure changed with the aging temperatures. The strength of steel with the increase of aging temperature first increased, then decreased, Aging temperatures had distinct effect on yield strength of the tested steel, and less effect on the ultimate tensile strength, we can get the best comprehensive properties yield strength 1011.87 MPa and elongation rate 16.38% of good tough match aged at 450°C. Through analysis it is concluded that the strength of the tested steels aged at 450°C reaches the maximum value, which is attributed to the precipitation of a large amount of fine ε-Cu particles(5~10nm) and a small number of(Nb,Ti)(C,N) precipitates.

Change in Mechanical Properties by Titanium Addition in Aged Martensitic 18Ni–9Co–5Mo Alloy

Maraging steels are a group of materials with high strength and toughness. Titanium is the most widely used element in the above group, which helps to improve the mechanical properties by the formation of coherent Ni3Ti precipitates during the aging process. However, due to the high affinity of Ti to elements such as C, N, S and O, harmful inclusions of these elements may form in the steels if due care is not exercised during the processing. The present research explores the effects of titanium, within the range of 1–2 weight percent, on the mechanical properties of C300-grade maraging steels produced by vacuum arc remelting (VAR) technique. Then there is a discussion of the formation of deleterious titanium-rich inclusions and their effect on the mechanical properties of steel.

Numerical simulation of welding distortion in thin plates

A three-dimensional model based on the finite-element method is developed to simulate the temperature field and stress distribution in the welding and heat-affected zones during fusion welding of thin plates. The governing equations are solved using the SYSWELD program commercial code. The model's predic- tions are tested and verified against the experiments. Angular distortion and longitudinal bending are meas- ured, the results are compared with those obtained from the mathematical model, and a relatively good agreement between them is found. The verified model is used to evaluate the effects of various parameters on the temperature and stress distributions in the welding and heat-affected zones of a thin austenitic stain- less steel plate. Introduction. Welding distortion and residual stress have remained major challenges in manufacturing. In the automotive industry, parts involving thin plates are commonly employed, and a lot of such parts are assembled by the arc welding process because of its high productivity. Due to the relatively small stiffness of the plates, significant welding distortion often occurs. To comprehensively understand the characteristics of welding deformation in a struc- ture composed of welded thin plates, it is necessary to carry out further fundamental investigations by means of both experimentation and numerical simulation. Extensive experimental efforts have been made to understand and control the welding distortions and residual stresses. In the last two decades, numerous results on using analytical and computational methods have also been re- ported to predict and quantify the effect of the distortion and residual stresses during the welding process. However, there is a very limited literature concerning the prediction and measurement of welding deformation in structures in- volving welded thin plates, especially for welded structures with plate or wall thickness below 3 mm. For a given con- figuration, the magnitude of those effects depends primarily on the specific thermal energy input of the welding process, that is, on the energy per unit length of weld. Therefore, significant reductions in distortion cannot be achieved without using the welding process with a smaller heat input, which is not always practicable. An accurate prediction of distortion is difficult even for simple welded structures, and all the more for fabrications where several such processes are applied consecutively. In previous works (1, 2), simulation of the welding process for a plate from CT3 steel with a thickness of 3 mm and a plate from austenitic stainless steel with a thickness of 1 mm was carried out. In (2), due to the restriction of the Ls-Dyna program in the removal of material history at high temperatures, the behavior of steel during welding was assumed to be fully plastic. However, many authors suggest that the behavior of metals during welding obeys the model of isotropic or kinematic hardening. Because of this, in the present work the isotropic hardening model is con- sidered. The simulation is accomplished by the SYSWELD program, which is a famous software in simulation of welding, and all the physical and mechanical properties of steel are taken from its library. As a first step towards simplification, the sequential computations for thermal-transient and thermo-elastic-plas- tic stages may be uncoupled without penalty, as suggested by various authors (3-7). In (8), a coupled transient thermal and structural analysis of the temperature distribution and deformation was carried out. The transient temperature field calculated at the first stage provides the input for the thermo-elastic-plastic stage. The outputs of the latter stage, in the form of the transverse angular deformation and contraction forces, provide, in turn, the input for the elastic finite-