Thick Steel Plates Research Articles

Microstructure analysis and hardness prediction based on microstructure evolution theory in multi-pass welded joint

During multi-pass butt welding of high-strength steel (HSS) thick plate, it is difficult to estimate the hardness performance of thick weld since multithermal cycles can drive complex microstructure evolution. In this study, butt-welded joint of 75 mm-thick Q690 HSS was prepared by multi-pass shielded metal arc welding (SMAW) in advance; meanwhile, experiments were carried out to characterize microstructure and measure hardness distribution in butt-welded joint. Then, the welding temperature history of butt-welded joint was numerically examined. Based on the irreversibility of Martensite and Bainite, the microstructure evolution model was modified to predict the complicated microstructure evolution in multi-pass welded joint. Compared with experimental data, the validity of modified microstructure evolution model was verified. With the application of simulated thermal cycles and material chemical compositions as input parameters, volume fraction distribution of each phase was obtained by modified microstructure evolution model and hardness value was calculated by hardenability algorithm. Both experimental and predicted results exhibited that microstructure in weld metal (WM) is mainly composed of granular Bainite with a small amount of Ferrite and Martensite, and heat-affected zone (HAZ) consists of predominantly lath Martensite. Hardness distribution in butt-welded joint obtained by the prediction method is in accordance with the measurement. Average hardness value in WM and BM is 290 VPN and 250 VPN. A sharp decrease in HAZ hardness can be found from the fusion line to base metal (BM). The maximal value in the HAZ close to fusion line and the corresponding prediction deviation is 6%.

A Comparative Investigation of the Effect of Microstructure and Crystallographic Data on Stress-Oriented Hydrogen Induced Cracking Susceptibility of API 5L X70 Pipeline Steel

In this research, stress-oriented hydrogen induced cracking (SOHIC) test was carried out on a 50 mm thickness of a commercial API 5L X70 steel plate. The evolution of microscopic features such as phase, boundary, interface, grain, and crystallographic data was analyzed before and after SOHIC, in order to comprehend the effect of crystallographic orientation on SOHIC propagation. Chemical composition and previous thermomechanical processing even finish rolling temperature and cooling rate determine the ferrite matrix microstructure. A recrystallized ultrafine ferrite grain with about 3–5% degenerated pearlite dispersed in the microstructure was characterized, called as-received specimen. The average lattice strain and dislocation density was calculated first using multiple Gaussian peak-fitting method from XRD pattern. Electrochemically charged combination mixed H2S-CO2 solution, constant hydrogen injection, and external loading were applied to tensile specimen, in order to simulate the H2S and CO2 environment. The results show that local misorientation and Taylor factor analyses predicted the possibility of hydrogen crack nucleation especially at boundaries and interfaces. Moreover, SOHIC crack propagation occurred along the mid-thickness of the cross section of steel plate along the ferritic boundaries, pearlitic colonies, and ferrite-cementite interfaces. Moreover, the crack propagated along distorted {110} and {001} grains, indicating a strong strain gradient towards the boundaries. The analysis of XRD patterns of SOHIC tested specimen by multiple Gaussian peak-fitting method estimated about 68% increment in micro-deformation and approximately 170% increase in dislocation density.

Seismic performance of superimposed RC shear walls with concealed bracings using different horizontal connections

To enrich the horizontal connection method and to further study the seismic performance of superimposed RC shear walls with concealed bracings (SRCBSWs) using different horizontal connections, three specimens including SRCBSW with horizontal connection by steel plate bolt kit (SPBK), SRCBSW with horizontal connection by U-ring buckle insert (URBI) and cast-in-place shear wall with concealed bracings were tested under quasi-static loading test. Test results indicated that SRCBSWs exhibited the seismic performance close to that of cast-in-place specimen. The horizontal connection of URBI not only enabled achieve the goal of equivalent cast-in-place connection, but had a beneficial effect on the energy consumption. Due to the fact that the steel plates of SPBKs slipped relative to the contact concrete, the horizontal connection by SPBK was not conducive to energy dissipation and stiffness degradation of the wall, while the load-bearing capacity and deformation characteristic could be enhanced due to the cooperative work of steel plates and concrete in later loading. Finite element analysis of SRCBSWs by Abaqus was conducted based on the proposed modelling techniques, and the reasonable accuracy of the numerical method was verified. The parametric analysis results showed that the axial load ratio, volumetric ratio of the X-shaped steel plate bracings and longitudinal reinforcement ratio in hidden column had obvious effect on the load-bearing capacity and elastic stiffness of SRCBSWs. Taking displacement ductility into account, the axial load ratio of SRCBSWs should be reasonably restricted in practice. Moreover, appropriate thickness of steel plates in SPBKs should be determined according to actual demand, but at least one set of SPBK needed to be arranged in the middle of the wall along the height direction when conducting the layout of SPBK. Besides, the inserted reinforcement ratio in URBI could be reinforced in accordance with the constructional requirements.

Indentation Plastometry of Welds

This investigation concerns the application of the profilometry‐based indentation plastometry (PIP) methodology to obtain stress–strain relationships for material in the vicinity of fusion welds. These are produced by The Welding Institute (TWI), using submerged arc welding to join pairs of thick steel plates. The width of the welds varies from about 5 mm at the bottom to about 40–50 mm at the top. For one weld, the properties of parent and weld metal are similar, while for the other, the weld metal is significantly harder than the parent. Both weldments are shown to be approximately isotropic in terms of mechanical response, while there is a small degree of anisotropy in the parent metal (with the through‐thickness direction being slightly softer than the in‐plane directions). The PIP procedure has a high sensitivity for detecting such anisotropy. It is also shown that there is excellent agreement between stress–strain curves obtained using PIP and via conventional uniaxial testing (tensile and compressive). Finally, the PIP methodology is used to explore properties in the transition regime between weld and parent, with a lateral resolution of the order of 1–2 mm. This reveals variations on a scale that would be very difficult to examine using conventional testing.

Influence of laser power on microstructure and mechanical properties of laser welded TWIP steel butted joint

The twinning-induced plasticity (TWIP) steel is a newly developed which possesses fantastic mechanical properties and high potential for anti-crash weight-optimized structural applications. In this study, the weldability of 2 mm thick TWIP steel plate by laser welding method was investigated. The welded joint exhibited fully austenitic structure, and the weld seam consisted three types of solidification structures: columnar dendrite, cellular crystal and equiaxed dendrite. The microsegregation of C and Mn elements occurred in the interdendritic regions during the solidification of the weld seam. The toughness of the heat-affected zone (HAZ) was higher than that of the weld seam. The microhardness diagram of cross-section of welded joints presented V-shaped under different laser power. The microhardness of equiaxed dendrite zone was higher than that of the weld seam and coarse grain heat affected zone (CGHAZ). The average strain and tensile strength increased first and then decreased with the rising of laser power. Further study demonstrated that the fracture of the laser welding TWIP steel joints during tensile test presented ductile mode characteristics. The results show that the appearance and performance of the welded joint are optimal with laser power of 1800 W in present study, and the tensile strength and total elongation are 915 MPa and 48%, respectively.

Investigating the Microstructural Properties and Phase Distributions of TIG Welded AISI/SAE 304L Stainless Steel Runners in TNT Filled Ammunutions

Among the stainless steels, the most widely used group is austenitic stainless steels. The prominent reason why austenitic stainless steels are preferred in welded stainless steel fabrications is their good weldability. AISI/SAE 304L austenitic stainless steels exhibit adequate corrosion resistance in oxidizing environments. AISI/SAE 304L austenitic stainless steels are also used in filling interfaces of runners between the Tri-Nitro-Toluen filling vessel and ammunitions in defense industry. For the manufacture of the runners, the stainless steel plates and the stainless steel pipes are mainly joined by fusion welding. These runners are cleaned with hot tapping water at 70°C after each filling of ammunitions by TNT so that cleaning operation can deteriorate the corrosion properties of runners especially weld zones. Austenitic stainless steel weldments include basically delta-ferrite and austenite phases on weld regions. Delta ferrite phase exhibits resistance to chloride bearing medias while austenite phase is more resistive to high temperature oxidizing ambients In this study; 3 mm thick 304L austenitic stainless steel plates and rings are welded to each other with two different filler weld wires of ER316L and ER2209 by Tungsten Inert Gas welding method under pure argon shielding gas. Weld metals and heat-affected zones of welded joints were examined using optical metallurgical microscope. It has been determined that the additional filler weld wires have changed the weld metal and the heat affected zone microstructures and phase distributions dominantly. Microstructures of all welded joints have been compared. Besides, phase distributions of weld metals and heat effected zones are made by image analysis software and Schaefflers diagram. ER2209 welding filler metal increased the phase fraction of delta-ferrite in weld metals while it decreased the austenite phase fraction as compared to ER316L filler metal.

Performance of large-span arched soil–steel structures under soil loading

This paper investigates the structural behavior and soil–structure interaction mechanism of very large-span arched soil–steel structures constructed using steel plates with deep corrugation profile, 500 mm X 237 mm, during and after construction. Field measurements were employed to validate three-dimensional (3D) finite element model (FEM), which was then employed to evaluate the performance characteristics of very large span soil–steel structures. In addition, the FEM was used to evaluate the effectiveness of various strengthening techniques employed for buried steel structures to withstand very large spans, including lateral reinforced steel mesh and circumferential steel stiffeners. The world’s largest-span arched soil–steel bridge constructed using 12 mm thick steel plates with the deepest corrugation profile, of 237 mm total depth and 500 mm pitch was instrumented extensively to monitor the displacements and straining actions of the steel structure. The steel structure has a span of 32.40 m and vertical height of 9.57 m. Lateral reinforced steel mesh was attached to the steel structure and cement-stabilized soil was added to a certain level to enhance the performance of the structure during and after construction. The calculated deformations and straining actions captured the same trend of the field measurements. The numerical results indicated that two main critical zones of the steel structure, the crown and at the change of arc radii (40 degrees from the top arc on each side), were observed to experience high axial stresses, which could cause buckling and should be considered carefully in the structural design. Finally, the numerical results revealed that the deployed steel mesh reinforcement in the current study reduced the induced straining actions in buried structures with up to 50%, while the investigated circumferential steel stiffeners could control the crown vertical deformations down to 0.5% of the structure rise during and after construction.

Experimental study on the buckling behavior of double steel plate concrete composite slabs with stiffening ribs and tie plates

Double steel plate concrete (DSC) composite slabs consist of two outside steel plates and a concrete core that are connected by welded studs or cross tie bars. If weak restraints are designed for the interface between the steel plates and concrete core, the surface steel plate of the DSC slabs may suffer local buckling when subjected to a compressive load. In this paper, a new type of DSC slab with stiffening ribs and tie plates (SDSC slab) is proposed to improve the stability of surface steel plates. Two groups of bending tests are carried out to investigate the buckling behavior of both SDSC slabs and ordinary DSC slabs (ODSC slabs). Furthermore, the influence of the B/t ratio, that is, the ratio between the stud spacing and the steel plate thickness, is intensively analyzed. The experimental results reveal that compared with that of the ODSC slabs, the buckling behavior of steel plates in the SDSC slabs is delayed or even prevented owing to the additional stiffening ribs and tie plates. Thus, the bending capacity and ductility of SDSC slabs are both enhanced. According to the test results, calculation formulas are derived to predict the bending capacity of the ODSC slabs and SDSC slabs, respectively. In addition, design models for buckling analysis are proposed to determine the buckling stress and critical B/t ratio for different types of DSC slabs. The accuracy of the theoretical methods is validated against the test data, and two examples are provided in detail to illustrate the design process of the steel plate in SDSC slabs.

Numerical-based analytical model of double-layer steel-LHDCC sandwich composites under punching loads

This study conducts numerical analyses on a newly developed double-layer steel-lightweight high ductility cement composite (LHDCC)-steel sandwich panel under concentrated punching load. Energy absorption ability serves as an important criterion in evaluating the performance of the protective sandwich structures. One critical factor related to energy absorption ability is the stiffness or the deformation capacity of the structure. The present study first develops a procedure to establish a FE model of the double-layer SCS panel. The Concrete Damage Plasticity (CDP) model is adopted to simulate the behavior of LHDCC, with a compressive stress–strain relation represented by a statistically stochastic damage constitutive model. The FE model is validated through comparisons with the test results of 2 single-layer SCS panels and 8 double-layer SCS panels. A series of parametric studies are then performed to check the influences of concrete height, shear span, steel plate thickness, shear connector spacing, loading patch size, concrete strength and steel plate strength on the stiffness and load resistance of the panel. Finally, the paper develops a simplified analytical model to predict the stiffnesses at both elastic and plastic stages, and proposes an idealized load–displacement model to reproduce the load-deformation relation for the double-layer SCS panels. The comparisons with the test and FE results validate the accuracy of the analytical model.

Friction stir processing of thick tempered martensitic steels: Correlation between microstructure and mechanical properties

Thick tempered martensitic steel plates were friction stir processed at different tool traverse and rotational speeds. Friction stir processing led to formation of finer martensite phase, ferrite, and higher angle grain boundaries, which resulted in higher hardness of the processed samples. However, the macro mechanical results indicated that the tensile strength and elongation were reduced after friction stir processing, was due to the formation of ferritic bands and WC debris in the processed zones. The brittle fractured surfaces of processed samples confirmed the negative effect of friction stir processing on tensile behavior, which contained more cleavage than dimples compared to base material. The outcome of this study can be used for surface modification of thick martensitic materials for industrial applications.

Prediction on the Distributions of the Strength and Toughness of Thick Steel Plates Based on Bayesian Neural Network

In the past decades, several artificial intelligence techniques have been applied on regression tasks during the steelmaking process, achieving accurate point estimations. However, models for predicting targets with their uncertainties have been rarely applied to the steelmaking domain due to a computational and a technical limit of Bayesian neural networks (BNN) in the past. Recently, many tractable BNN models have been proposed for predicting the uncertainties in steelmaking, thanks to advances in neural networks. The most convenient and computationally efficient one is a Monte‐Carlo dropout (MC dropout), which interprets the distribution of the neural networks created by a dropout from a Bayesian perspective. In this article, we propose to apply MC dropout on a steelmaking process data of Pohang Iron and Steel Co. and predict two targets and their uncertainties: the strength and the toughness of thick steel plates. This article is widely applicable to other process data, and it is expected to reduce costs for defective products in the future through an uncertainty estimation.

Thickness demand for concrete panel in design of C-PSW/CE under cyclic loading

In composite plate shear walls-concrete encased (C-PSW/CE), the concrete panels provide out-of-plane restraint to the steel plate for preventing premature buckling. This paper investigates the shear resistance of C-PSW/CE under cyclic loading by experimental study and numerical method. The shear resisting mechanism of the postbuckling steel plate, in which the lateral load is resisted by the incomplete tension field action, is analyzed. The effects of the concrete panel thickness, steel plate thickness, headed stud spacing, concrete strength, and reinforcement ratio of the concrete panel on the hysteretic behavior of C-PSW/CE are studied. A larger thickness of concrete panels and a smaller stud spacing lead to less strength degradation of the walls. Based on the numerical results of 450 C-PSW/CE specimens, the formula is proposed to calculate the thickness demand of the concrete panel in the high-seismic design of C-PSW/CE, which meets the ductile requirement that the shearing strength deterioration of C-PSW/CE is no more than 15% at the drift ratio of 2%.

Ultra-Narrow Gap Fiber Laser Conduction Welding Technology for 304 Stainless Steel Thick Plates and the Mechanical Properties of Welding Joints

The application of thick metal plates is increasing, and the welding problem is becoming more and more prominent. Narrow gap laser welding is one of the important methods, and it is also a research hotspot. The stainless steel thick plates were welded using the ultra-narrow gap fiber laser conduction welding with filler wire. Results show that the ranges of technological parameters for the achievement of the weld seam with no defects are smaller when the gap width is comparatively larger. Using the optimized technological parameters, the butt welding with no defects on the 3 mm gap between two 304 stainless steel plates with 60 mm thickness was achieved through the filling 20 times. This welding method of 304 metal with large thickness is rare in the literature. The tensile strength of the welding joint can be up to 87% of that of the base metal, and the micro-hardness and yield strength of the joint are comparable with those of the base metal.

Analytical Model Formulation of Steel Plate Reinforced Concrete Walls against Hard Projectile Impact

Steel plate reinforced concrete (SC) walls can effectively resist projectile impact by preventing the rear concrete fragments flying away, thus attracting much attention in defence technology. This work numerically and analytically investigated the hard projectile perforation of steel plate reinforced concrete walls. Impact resistance theories, including cavity expansion analysis as well as the petaling theory of thin steel plates were used to describe the cratering, tunneling and plugging phases of SC walls perforation. Numerical modeling of SC walls perforation was performed to estimate projectile residual velocity and target destructive form, which were validated against the test results. An analytical model for SC wall perforation was established to describe the penetration resistance featuring five stages, i.e., cratering, tunneling and plugging, petaling with plugging and solely petaling. Analytical model predictions matched numerical results well with respect to projectile deceleration evolution as well as residual velocity. From a structural absorbed energy perspective, the effect of front concrete panel and rear steel plate thickness combinations was also studied and analyzed. Finally, equivalent concrete slab thickness was derived with respect to the ballistic limit of SC walls, which may be helpful in the design of a protective strategy.

Multifrequency AC Magnetic Flux Leakage Testing for the Detection of Surface and Backside Defects in Thick Steel Plates

The detection of surface and backside defects in steel plates is essential for safety maintenance. Current ac magnetic flux leakage (ACMFL) testing systems generally operate at a high frequency but cannot detect backside defects owing to the skin effect. Low-frequency ACMFL is limited by low sensitivity and low efficiency in detecting deep defects. This letter presents a multifrequency ACMFL testing method combined with the merits of low- and high-frequency excitation to detect surface and backside defects. In early work, the optimal frequency for detecting the surface defect with a depth of 4 mm or less was 400 Hz. Through simulation analysis, the optimal low frequency for detecting backside defects is determined. Additionally, the influence of the excitation intensity on the response signal is investigated. Relatively small excitation power should be used to obtain a reliable detection waveform. Finally, the experimental results of surface and backside defects detection validated the practicality of the method.

Lateral Load Carrying Capacity of Concrete-filled Cold-formed Steel Shear Wall

A new type of innovative composite shear wall (concrete-filled cold-formed steel shear wall or CFCSW) is proposed, composed of cold-formed channel sections arc-welded together by 20 mm length of welds and filled with concrete. The main study of the CFCSW focuses on the overall behavior, ultimate load capacity, stiffness and ductility. Three specimens of CFCSW with an aspect ratio of 1.0 are tested under lateral monotonic load. Three-dimensional finite element models are developed and benchmarked with the experimental results. The validated models are used to carry out parametric studies to determine the influence of the parameters on the performance of the CFCSW. The parameters are the height, steel plate thickness, weld spacing and concrete thickness of the CFCSW. The experimental and finite element modeling results indicate that increasing the weld spacing from 105 mm to 211 mm improves the stiffness, ductility and load carrying capacity, and similarly, providing holes inside the wall increases the stiffness, ductility and peak strength of the CFCSW. The ultimate capacity of the CFCSW is most influenced by changing the height of the wall and least influenced by varying the concrete thickness of the wall.

Analyse the effect of clad ratio on the stress-strain curve of titanium-clad bimetallic steel for different strain rates and temperatures using Johnson-Cook model

Titanium–clad bimetallic steel plate finds its application in the construction of large pressure vessels which are used for storage and processing of petrochemicals. Mechanical properties can be imparted to any material according to its application by a technique known as cladding. To improve material, two main functions are performed by cladding. The finite element analysis (FEA) technique is an efficacious numerical method for solving several engineering problems. This technique not only provides reliable test results but also reduces the cost of the experiment. The aim of this report is to analyze the effect of clad ratio on stress–strain curves of titanium-clad bimetallic steels for different strain rates and different temperatures using the Johnson-Cook flow stress model. The ratio of the cladding layer thickness (tc) to the total thickness of Titanium-Clad bimetallic steel plate (t) is known as Clad ratio (α). In this report, Titanium Grade 5 is used as a cladding material and AISI 1006 is a parent metal. Furthermore, model constants were estimated from the analyzed result by using material constant for both cladding material and parent material from the research papers. The dimensions of the specimens were taken from GB/T228.1–2010 testing standard. The three-dimensional design of the specimens was created in Solidworks 20 and analyzed in Ansys Explicit Dynamics. A tension test was performed using Ansys for three different temperatures (293 K, 673 K, and 973 K) and for three different strain rates (1/sec, 10/sec, and 100/sec). In this paper, the reference strain rate was taken as 1/sec and the reference temperature as 293 K.

Thermal analysis of Friction Stir welded Steel and Aluminum materials with varying Pre-heat temperature

The objective of this work is to carry out a thermal heat transfer study to acquire the time dependent temperature field in welding process of FS-Welded dissimilar materials with vary in preheat temperature. Joints were made with four mm thick Aluminum and Steel plates. Parameters selected for current study was temperature (100 °C, 150 °C and 200 °C), rotational speed (1000, 1400, and 1800) rpm and traverse speed (16, 20, and 24) mm/min. In numerical model, welded plate was modeled as the weld line is the symmetric line. The work-piece has dimensions of 100x100x4 mm. The obtained result was compared with experimental result, which shows good agreement and within the acceptable limit. The peak temperature at the weld zone increases significantly with respect to increase in process time.

Experimental and numerical investigation of laser-FSW hybrid welding technique for high strength materials

Friction stir welding (FSW) of high-strength materials and thicker plates has a number of challenges that are preventing widespread industry application such as (i) premature tool failure, (ii) selection of tool material and design, and (iii) weld productivity. A finite element (FE) based analysis for Laser-FSW hybrid welding technology is carried out in ABAQUS, commercially accessible FE software, to solve these typical difficulties. The thermal analysis of Laser-FSW hybrid technique is done using two moving heat sources for the case of 3.2 mm thick S45C steel plate. A negative moving heat source is placed as a replacement of the backing plate material in the high contact pressure region under the FSW tool. It was shown that the laser heat source needs to be 10 mm ahead of the FSW tool for achieving the duplex phase (Ferrite + Bainite/Martensite) microstructure.

Calibration and validation of extended back-face strain compliance for a wide range of crack lengths in SENB-4P specimens

Compliance equations based on back-face strain or crack mouth opening displacement, and potential drop techniques are widely used to calculate fatigue crack growth rate. Standard ASTM E647 for fatigue crack growth rate testing does not include compliance based equations for single edge notched four-point bending (SENB-4P) specimens. Equations developed based on finite element (FE) analysis have been reported in literature; however, they are limited to the long crack propagation regime (i.e., relative crack length ratios a/W > 0.15). No compliance relations for crack growth in the physically short crack regime were found in literature. This work reports on a complementary numerical-experimental study towards the development of compliance equations with an extended application range in terms of relative crack length. FE simulations have been used to calibrate a back-face strain compliance equation for calculation of relative crack length in the range 0.05 ≤ a/W ≤ 0.5 for SENB-4P specimens. Four point bending fatigue tests were performed on SENB specimens extracted from 50 mm thick welded steel plates. Direct current potential drop (DCPD) for crack monitoring was used as benchmark and validation of the crack lengths determined from a back-face strain gage.