High Strength Construction Steel Research Articles

The optimum use of high-strength steel in the construction of gas transmission pipeline

PurposeThe aim of this study is to assess the opportunity for the development of hydrocarbon transportation using high-strength steel (HSS) in pipeline construction in terms of cost savings and reliability.Design/methodology/approachSeveral optimizations of pipeline design and operations were performed to estimate the total life-cycle cost variation associated with different grades of high-strength steel. The generalized reduced gradient (GRG) method was used in an Excel table to determine optimal total life cycle each pipeline. Variables used in this optimization with respect to each steel grade were as follows: pipeline external diameter, wall thickness, number of compression stations and installed power in each compression station. The reliability of a pipeline with optimal cost was assessed to highlight the impact of steel grade on pipeline reliability.FindingsThe study showed that the cost reduction is strongly dependent on the adopted gas pipeline configuration. The number of compression stations and external diameter are the main factors influencing the pipeline total life cycle cost, while the steel price seems to have a minor effect, the reduction of the gas pipeline total life cycle does not exceed 5% even with a 50% difference in pipe steel prices between X70 and X100 steels. On the other side, for the same external diameter, X100 steel presents better pipeline reliability against carbonic corrosion compared to X70 steel.Practical implicationsThe main contribution of this study is to provide a decision-support tool to help pipeline constructors enhance the profitability of natural gas transmission pipelines. The optimization method used is simple to use for design engineers during a feasibility study.Originality/valueThe present study presents one step to fill the gap concerning the question of balancing the trade-off between cost savings and structural reliability in high-strength steel pipelines during the early stages of feasibility studies. The optimal design and operations parameters ensuring cost savings on total life cycle costs are identified via an optimization method. The impact of selected optimal parameters on the long-term pipeline service life was estimated via a structural reliability analysis.

Fire Resistance and Seismic Performance Study of a High-Strength Construction Steel Using Creep and Internal Friction Analysis

Fire resistance and seismic performance are the two of the most important considerations for the design of construction steel. The fire resistance of the high-strength construction steel, Q460FRE, which contains low Mo, was investigated by means of creep test under different experiment conditions. Then, the seismic performance of the Q460FRE steel, after being subjected to various fire temperatures, was characterized by internal friction analysis. The Q460FRE steel exhibited excellent fire resistance, and the yield strength at 600 °C was 67.4% of the yield strength at room temperature. The constitutive equation of creep stress and fracture time at 600 °C was established. The bearing tensile stress of the Q460FRE steel should be lower than 337 MPa to ensure at least 1 h to evacuate from the fire. The creep stress and alternating temperature significantly affected the serration behavior of the creep strain. The internal friction analysis indicated that the seismic performance of the Q460FRE steel decreased with the increase in fire temperature, being consistent with the analysis results of the seismic performance characterized by the yield ratio.

Three-dimensional fatigue crack propagation simulation using extended finite element methods for steel grades S355 and S690 considering mean stress effects

The assessment of fatigue crack propagation of steel structures is essential and important especially to improve the application of high strength steel in construction. The load ratio R, reflecting mean stress effects, will be changed with crack extension in the steel structures with complicated geometry. In this paper, the Walker equation is employed to fit the fatigue crack propagation rate of steel grades S355 and S690 based on experimental data in the literature to incorporate the mean stress effects. The material fatigue crack propagation parameters with 95%, 97.7%, and 99% guarantee of Walker equation were obtained by a stochastic analysis using the Monte Carlo method. The fatigue life was firstly predicted by the analytical method and was used as a baseline for numerical fatigue crack propagation simulation. A user-defined fatigue crack propagation subroutine based on the Walker equation was developed using phantom nodes-based extended finite element method (PN-XFEM) and Virtual Crack Closure Technique (VCCT) to consider the mean stress effects. The proposed three-dimensional fatigue crack propagation simulation subroutine is successfully validated of both steel grades, S355 and S690.

Fatigue crack initiation prediction using phantom nodes-based extended finite element method for S355 and S690 steel grades

The assessment of fatigue crack initiation behavior of steel structures is essential and important especially to improve the application of high strength steel in construction. For a complete understanding of fatigue endurance, it is necessary to combine the phenomenological damage model with finite element numerical approach. In this paper, phantom nodes-based extended finite element method is used to predict the fatigue crack initiation of steel material, considering a prediction by XFEM of coupon tests made of steel grades S355 and S690. A user-defined fatigue damage initiation subroutine based on Smith, Watson, and Topper (SWT) damage model combined with non-linear isotropic/kinematic cyclic hardening model is implemented to predict fatigue crack initiation. The proposed method is successfully validated based on fatigue coupon test results of both steel grades, S355 and S690.

Study on Hot Deformation Behavior of High Strength Construction Steel 34CrNiMo6

The hot pressure deformation tests were carried out by using Gleeble-2000 simulator at the temperature of 950°C ~ 1150 °C and strain rate of 0.001s-1 ~ 1s-1 for a kind of high strength construction steel 34CrNiMo6 for Crankshafts and the curve of its flow stress were obtained. By studied the data, the flow stress constitutive equation, hot deforming active energy and the Z parameter were obtained. The curve of flow stress of 34CrNiMo6 steel indicated that the flow stress was increased with the decrease of temperature or increase of the strain rate. During the deformation, temperature and strain rate take important effect on dynamic recrystallization and dynamic recovery. It was propitious to dynamic recrystallization with raising temperature or reducing strain rate, and also made for the refinement of grain.

Study on Hot Deformation Behavior of High Strength Construction Steel 34CrNiMo6

Study on Hot Deformation Behavior of High Strength Construction Steel 34CrNiMo6

Effects of Processing Variables on Microstructure and Yield Ratio of High Strength Constructional Steels

The process of “controlled rolling+relaxation+ultra fast cooling (UFO)” for high strength constructional steel with low yield ratio was presented. Microstructure and corresponding relationship with low yield ratio were investigated. The results showed that the constructional steels with multiphase microstructure of bainitie ferrite, martensite-austenite (M-A) and lath bainite were obtained through the creative process. The grain size decreased with the decrease in finish rolling temperature, which enhanced the strength by the grain refinement strengthening. The proper relaxation treatment promoted the bainitie ferrite lath width and the formation of blocky M-A constituent. In addition, both the tensile and yield strength increased with the decrease in finish rolling temperature and UFC final temperature, but the yield strength increased more significantly than tensile strength, which caused the increase in yield ratio. By using the process of “controlled rollingh+relaxation+ultra fast cooling”, the excellent comprehensive mechanical properties of 780 MPa grade constructional steels of 12 — 40 mm in thickness were achieved.

Key Issues of Using High Strength Steels in Seismic Structures and some Recent Progress

Since recent advances of technology in material science and increasing demand for high strength steel, Q460 high strength steel has been applied to several landmark buildings and major projects. However, the application of high strength steel in seismic structures is limited by the relative worse ductility, which is usually decreasing with the increasing on yield strength. For this purpose, key issues of using high strength steels in seismic structures are discussed and two design methodologies are proposed. Recent research progress on application of high strength constructional steel achieved at Tongji University is introduced. Finally, future work related to the application of high strength steels are recommended.

Study on Microstructure and Properties of High Strength Construction Steel Bars

In this paper, the microstructure and properties construction steel bars under various quenching and tempering temperature are investigated. Tensile tests show that the maximum tensile strength is1489MPa, elongation 11%, quenching temperature and tempering temperature have effects on the strength and plasticity of the samples, but the latter effect is more pronounced than the former. Steel bars have superior delayed fracture resistance between 390 ~420°C. The microstructure of steel bar is mainly composed of fine tempered sorbite (troostite) with carbide distributed along the lath martensite boundaries. Thus, we draw the conclusion thermal refining is an effective way to improve mechanical properties and delayed fracture resistance of high strength construction steel bars.

Experimental Study on Fracture Toughness of Q460C the High-Strength Construction Steel at Low Temperature

Three point bending tests were carried out on 14mm-thick Q460C the high-strength structural steel at low temperature, and scanning electronic microscope of the fracture appearance was analyzed. The results showed that the obvious feature of brittle mechanism was shown on the three point bending specimen fracture whose testing took place at -40°C. And the crack tip opening displacement value of Q460C steel, which was less than that of Q235 steel, Q345 steel and Q390 steel at low temperature, tended to decrease with respect to the temperature reduction. Moreover, a Boltzmann function fitting analysis was applied to the experimental data, and the ductile-brittle transition temperature and the changing regularity were obtained.

Structure of duplex CrN/NbN coatings and their performance against corrosion and wear

In tribological applications the coating-substrate combination can be considered as a system, since both greatly influence the properties of that affect the tribological performance. Further, it is often desirable that both high wear resistance and corrosion resistance can be achieved even when low cost and easily machineable substrate materials are considered. Duplex surface treatment combining pulse plasma nitriding and PVD coating can provide solution for excellent wear and corrosion resistance for low alloy and constructional steels. In this work three different pulse plasma nitriding processes were carried out prior to the CrN/NbN PVD coating to attain high surface hardness and enhanced load bearing behaviour for S154 high strength construction steel. The phase composition of the compound layer, formed in the nitriding process, was found to greatly affect the tribological properties of the duplex system. The compound layer with high amount of ɛ-phase contributed to superior corrosion and wear resistance, whereas the ductile γ'-phase compound layer provided better impact resistance and enhanced. The best duplex treated S154 samples had wear resistance comparable to that of similarly coated HSS. The corrosion resistance was also improved by duplex process. If anodic current at + 500 mV vs. SCE is considered as criteria, the best system has almost 3 orders of magnitude lower corrosion current than with the PVD coating alone.

Experimental behaviour of high strength steel end-plate connections

The use of high strength steel in construction has recently provided some challenges to structural engineers. One such challenge is to minimise the cross-section dimensions as the material provides higher strength, which brings great economic benefits. However, high strength steels exhibit high yield ratios and limited deformation capacity when compared to mild steel grades. This behaviour can be particularly important when structures are designed for abnormal loading conditions that produce inelastic deformations. In this situation, both members and connections have to develop sufficient ductility. The connections between members, in particular, are the regions where the material is exposed to higher deformation demands. To address these topics, an experimental investigation was undertaken of moment connections with end-plates made up of the high strength steel S690. The major contributions of this study are (i) the characterisation of the nonlinear behaviour, (ii) the validation of current Eurocode 3 specifications and (iii) the ductility analysis of high strength steel moment connections. The test results show that the tested connections satisfy the current design provisions for stiffness and resistance and achieve reasonable rotation demands.

Magnetic and metallurgical properties of high-tensile steels

An investigation into the relation between magnetic and metallurgical properties of 26 types of high-strength constructional steel is reported. Correlation between chemical composition and coercive field was found. An independent correlation between coercivity, grain size and relative pearlite and ferrite fractions was also found. The coercivity and initial permeability varied with ultimate tensile strength but Vickers hardness measurements were not found to be a reliable method of predicting coercivity over the hardness range found in the sample set. For a larger hardness range, produced by heat treating one steel type, an excellent linear relationship was found between hardness and coercivity.

N-A-X HIGH-TENSILE

Abstract N-A-X HIGH-TENSILE is a low-alloy high-strength construction steel combining good ductility, workability and weldability. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and compressive and shear strength as well as fracture toughness and fatigue. It also includes information on low and high temperature performance, and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SA-94. Producer or source: Great Lakes Steel Corporation.