Hot-rolled Steel Plates Research Articles

Effects of TRIP and TWIP mechanisms on improved Charpy impact energy of thick hot-rolled duplex lightweight steel plates

Charpy V-notch impact testing serves as a fundamental method for assessing the toughness of conventional steels, but its applicability becomes challenging for duplex (δ-ferrite + γ-austenite) lightweight steels due to their complex microstructures and varied deformation mechanisms. In this study, Charpy absorbed energies of hot-rolled duplex lightweight steel plates, incorporating both transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) mechanisms, were investigated to understand their fracture behavior comprehensively. The microstructural analysis revealed that the D4 (0.4C-15Mn-6Al (wt.%)) steel exhibited lower δ-ferrite volume fraction and superior Charpy absorbed energy than the D2 (0.2C-15Mn-6Al) steel, attributed to its dominance of TWIP mechanism. Conversely, the D2 steel, with many ferrite/austenite interfaces, showed lower strain hardening and absorbed energy. At lower temperatures, both TWIP and TRIP mechanisms operated, but dominant TRIP mechanism along with higher δ-ferrite volume fraction in the D2 steel accelerated crack propagation, further reducing absorbed energy. The superior toughness of the D4 steel, driven by the dominant TWIP mechanism at lower temperature, highlighted its potential for practical utilization of thick hot-rolled lightweight steel plates in automotive, shipbuilding, military, and construction industries.

Surface defect identification method for hot-rolled steel plates based on random data balancing and lightweight convolutional neural network

Surface defect identification method for hot-rolled steel plates based on random data balancing and lightweight convolutional neural network

Adjust operating conditions of an in-made house horizontal hydraulic press for a 90° cold bending process

During the cold-bending process, the tooling suffers considerable damage due to excess pressure. This also causes the machines to break down, causing problems in the precision and quality of the metal parts formed. The precision depends on the operating conditions of the press, the tooling employed, and the elastic recovery effect of the material. This study determines the working conditions for a made-in-house horizontal hydraulic press through an experimental design (DOE). This research carried out the V-forming to 90° (ISO 2768-1) of a hot-rolled carbon steel plate, considering pressure, piston permanence time, and recovery factor (Kr). The experimental and statistical analysis ensures accurate forming while the work pressure decreases by 17% and 33%, respectively, regarding the maximum. This reduction will delay the appearance of fatigue damage and have the operating parameters well established; in turn, it will be possible to design tools according to commercial standards.

Pengaruh Metode Quenching dan Tempering Terhadap Kekerasan Material Hot rolled Plate (HRP) Steel

Hot rolled plate steel as a material to be used for steel armor needs to have the characteristics of a high hardness value. Medium carbon steel as the basic material is quenched at a temperature of 900 oC and tempering is carried out at a temperature of 125 oC and 175 oC with a holding time of 30 minutes. The Ms value is a benchmark for changes in martensite which is influenced by the constituent elements of the material. The use of water as a quench medium changes the structure of austenite to martensite. The martensite structure that occurs increases the optimum hardness value in HRP Steel material. The tempering process carried out above the Ms value causes a decrease in the hardness value. The highest hardness value was obtained in the quenching process with 542 HV which was influenced by the distribution of martensite. The decrease in hardness value occurs due to the tempering process, the average hardness value at temper 125 oC is 524.4 HV and 175 oC is 524 HV.

Corrosion behaviour of hot-rolled 316L stainless steel-A6 carbon steel composite steel plate for marine environment

In this study, a composite steel plate for marine construction was fabricated using 316L stainless steel and A6 carbon steel through hot rolling. Neutral salt spray tests and electrochemical experiments were performed to analyse the corrosion behaviours of the cladding material, the carbon steel substrate, and the interface between stainless steel and carbon steel in a marine atmosphere and seawater. The results showed that an evident elemental overlap region was observed at the composite interface of the composite steel plate. After long salt spray test, the A6 carbon steel part showed significant accelerated corrosion along the interface, resulting in the interface specimens corroding at a faster rate than the carbon steel substrate. However, the composite interface showed better corrosion resistance than the carbon steel substrate in the electrochemical tests. A corrosion resistant layer with a width of 15 μm was found on the stainless-steel side of the composite interface.

Online Prediction of Mechanical Properties of the Hot Rolled Steel Plate Using Time-series Deep Neural Network

The prediction of steel’s properties by the process parameters has been of great interest because they can effectively reduce production costs and improve product quality. At present, the extensively used artificial neural network (ANN) can only reveal the correlation between parameters and mechanical properties from the perspective of statistics but loses the critical information on time-series correlation in the steel production process. In this work, time-series neural networks based on long short-term memory (LSTM) were established to predict the steel plate’s yield strength (YS), ultimate tensile strength (UTS), and elongation (EL). The results verified that the proposed LSTM model exhibited sufficient accuracy and outperformed the classical algorithms (SVM, random forest, ANN), with mean squared error reduced by 30% when compared with ANN. Also, the sensitivity analysis proved that LSTM was more capable to make full use of the information contained in input parameters and achieved better generalization performance. Notably, the interpretation of the results was more consistent with the real physical metallurgical process of a hot-rolled steel plate and can provide a better understanding of the physical metallurgical process.

Mechanical behavior of additively and conventionally manufactured 316L stainless steel plates joined by gas metal arc welding

Combining several additive manufactured (AM) parts to larger parts by welding may be required due the limited building volume of powder bed AM methods. Laser powder bed fusion (LPBF) has a great potential because it enables the production of nearly full-density components through AM processes; however, additional residual stresses and production defects are induced by LPBF. These residual stresses affect the residual stress state of welded AM parts. In combination with the production related defects, both alter the mechanical and—in particular—the fatigue behavior of these welded joints. In this study, various tests are performed to characterize the butt joints of 316L AM steel plates made by gas metal arc welding. To this goal, joints are produced with weld seams parallel and vertical to the layer orientation of AM plates. The results are compared to joints of conventionally rolled steel plates produced with the same welding parameter. The residual stress states in initial (unloaded) condition and after cyclic loading were determined by X-ray diffraction techniques for AM and rolled plates. Complex residual stress states were determined at the welds made of AM steel plates compared to the welds made of rolled steel plates; however, the residual stress level in the heat affected zone of the butt-welded AM steel plates was similar to the welds made of hot-rolled steel plates. After cyclic loading with a high load level, high residual stress relaxations were observed in the parent materials. The fatigue design curve for butt joints from international standards is exceeded by all three test series, but the fatigue strength of the butt joints made by LBPF and hot rolling vary significantly. This is thought to be related to differences between the AM and conventional joints in microstructure, static strength, residual stress level, and small crack-like defects that partially interact with stress concentrations at the weld transition.

Experimental and numerical studies of screwed connections with hot-rolled steel plate and cold-formed steel sheet

This paper presents a test and numerical program on screwed connections of cold-formed steel (CFS) sheets and hot-rolled steel (HRS) plates. The shear strength, load–deformation relationship, and failure mode of the specimens were obtained. The test results were compared with the results predicted by the North American Specification (AISI S 100–16), European Standard (EN1993-1–3), and finite element (FE) models. The influence of the fastener diameter and thickness of the CFS sheet and HRS plate on the specimens was discussed. In addition, a new method of calculating the bearing capacity of the connections with thicker plates was proposed. The results showed that bearing failure, shear failure, and combined bearing/shear failure were observed in the specimens. The nominal strengths predicted by AISI S 100 and EN 1993–1–3 for specimens are generally conservative. The numerical models can predict the failure modes and load–deformation relationships of the specimens with good agreement. In addition, the proposed method for the bearing capacity has better accuracy when the connections have thicker HRS plates.

Deepening Design Technology of Super High-rise steel Structure

In view of the difficulties in deepening design of super-high-rise steel structures, we try to use Tekla Structures 3D intelligent steel structure simulation design software to carry out the corresponding deepening design, and verify the implementation effect of the deepening design with engineering practice, providing reference and reference for similar projects. The research shows that Tekla Structures is a very efficient and convenient software for steel structure deepening design; The connection nodes between giant columns and trusses should be divided in sections according to the principle of dividing along the section and along the column height, and reasonable lifting lug plates and studs for site use should be set; For hot-rolled steel plate composite floor slab, full-length reinforcing plates with the same thickness as the steel plate shall be set longitudinally on both sides of the splice weld of the adjacent unit steel plate; The thick plate welding shall be subject to process review in advance.

Formation mechanism of surface upwarping and black line defects on low carbon hot rolled plate

To improve the surface quality of low-carbon hot-rolled steel plates, the upwarping and black line defects were investigated by means of XRF (X-ray diffractometer), OM (optical microscopy), SEM (scanning electron microscopy) and EBSD (electron back scatter diffraction). The results showed that the micro area compositions under surface upwarping and black line defects were mainly made of secondary oxide particles, steelmaking slag and mould flux respectively. According to the metallographic structure, inclusion compositions and grains texture analysis, it could be concluded that surface defects on hot rolled plates were attributed to the entrapment of ladle slag or mould flux, gas bubbles, micro-cracks of casting slab in the steelmaking process, rolled-in scale and unreasonable sizing press rolling parameters during the rolling process, and the position and formation process of typical surface defects on hot rolled plates were discussed in detail. Finally, it concluded that the slag entrapment and solidification hook should be controlled during continuous casting.

Process Study and Application of Hot-rolled Aluminum-Zinc Plating Steel Plate Unit

In accordance with the requirements of hot-rolled aluminum-zinc plating and cold-rolled aluminum-zinc plating mixed line for producing construction steel and the production process characteristics of hot-dip aluminum-zinc products, the critical process control points are put forward by combining theoretical analysis with experimental verification. We should select proper raw materials, ensure the cleanliness of strip steel surface, strictly control the annealing temperature, the temperature of the strip steel entering the zinc pan, the temperature and composition of the plating bath, and explore reasonable and feasible process parameters such as air knife and cooling after plating, so as to produce qualified products. This study is of great significance for the improvement and process control of hot-rolled aluminum-zinc plating plates in steel plate production enterprises.

"Initiation mechanism on transverse microstructure and properties inhomogeneity of hot-rolled low-carbon steel plate "

"Initiation mechanism on transverse microstructure and properties inhomogeneity of hot-rolled low-carbon steel plate "

Controlled Cooling Temperature Prediction of Hot-Rolled Steel Plate Based on Multi-Scale Convolutional Neural Network

Controlled cooling technology is widely used in hot-rolled steel plate production lines. The final cooling temperature directly affects the microstructure and properties of steel plates, but cooling and heat transfer constitutes a nonlinear process, which is difficult to be accurately described using a mathematical model. In order to improve the accuracy of the controlled cooling temperature, a multi-scale convolutional neural network is used to predict the final cooling temperature. Convolution kernels with different sizes are introduced in the layer of a multi-scale convolutional neural network. This structure can simultaneously extract the feature information of different sizes and improve the perceptual power of the network model. The measured steel plate thickness, speed, header flow, and other variables are taken as input. The final cooling temperature is taken as the output and predicted using a multi-scale convolutional neural network. The results show that the multi-scale convolution neural network prediction model has strong generalization and nonlinear fitting ability. Compared with the traditionally structured BP neural network and convolution neural network (CNN), the mean square error (MSE) of the multi-scale convolutional neural network decreased by 24.7% and 12.2%, the mean absolute error (MAE) decreased by 19.6% and 7.97%, and the coefficient of determination (R2) improved by 4.26% and 2.65%, respectively. The final cooling temperature traditional structure by the multi-scale CNN agreed with the actual temperature within ±10% error bands. As the prediction accuracy improved, the multi-scale CNN can be effectively applied to hot-rolled steel plate production.

Investigations on the lateral-torsional buckling of an innovative U-shaped steel beam

An innovative solution of a steel-concrete composite beam was developed for buildings with beam spans between 6 and 12 m, taking into consideration the fire situation and the construction stage. The beam is composed of an U-shaped steel part, connected to a reinforced concrete part. In the construction phase, the beam is supporting the slab and constitutes a formwork for the reinforced concrete part. When casting concrete, the steel beam is filled at the same time as the slab, this allows considerable time savings on site. In the exploitation stage, the beam behaves as a steel-concrete composite beam.The developed U-shaped section is composed of three steel parts; a hot rolled steel plate (180x8x6300 mm, and two cold-formed steel plates (470x4x6300 mm) before folding. The section was assembled together with four self-drilling screws longitudinally spaced of 150 mm.In the construction stage, the U-shaped steel beam without restraints is prone to lateral torsional buckling instability. In this paper, the mechanical behaviour of the steel beam at the construction stage, in particular its lateral-torsional buckling stability, was studied. In order to characterize this instability without lateral support, a four-point bending test was carried out on a life-size specimen. The load introduction system was developed especially for the test to allow for all displacements due to LTB. The test clearly showed the lateral torsional buckling behaviour of the steel beam. The test results are compared with numerical simulations and analytical studies. A parametrical study, covering 200 geometrical configurations of the U-shaped beam, is carried out to validate the use of the curve “b” for the design of the steel beam for lateral torsional buckling according to Eurocodes 3.

Microstructure and properties of Nb, V and N alloyed low magnetic hot rolled stainless steel plate

Microstructure and properties of Nb, V and N alloyed low magnetic hot rolled stainless steel plate

Seismic behaviour of anchored prefabricated wall–beam joints of bundled lipped channel-concrete composite wall structures

The existing wall–beam joints of bundled lipped channel-concrete composite wall structures (BLC–CCWSs) are mainly fabricated by welding thin-walled steel tubes and hot-rolled steel plates; however, the application of this technology requires further improvement. In this paper, an innovative anchored prefabricated wall–beam joint was presented. The seismic behaviour of joints was studied by cyclic loading tests of four groups of full-scale specimens, and a hysteretic model of joints was established. The main conclusions are as follows: (1) standard joints fail in the ideal beam plastic hinge damage mode, resulting in a good hysteretic characteristics, energy dissipation capacity, stable bearing capacity and stiffness degradation performance. (2) The anchorage length of the embedment, circumferential weld around end plate and the anchor plate have significant influences on the seismic behaviour of the joints. Sufficient anchorage length and the inclusion of the anchor plate and circumferential weld around end plate can delay the pulling out of the embedment and improve the bearing capacity and the hysteretic performance of a joint before failure. (3) The main contributor to the nonlinear deformation of the joints is the plastic hinge rotation or the rotation caused by sliding of the embedment. (4) The beam end strain can be reduced when the flange is widened. The strain distribution of the embedments is not uniform, and the shear strain in the panel zone is small. (5) The established hysteretic model can take the degradation of stiffness and strength into consideration, and thus produces accurate results that are still conservative and that can be applied in engineering practice.

Improved design and comparative evaluation of controlled water jet impingement cooling system for hot-rolled steel plates

This work focuses on improved design modification and development of Controlled Water Jet Impingement Cooling System for improving mechanical and metallurgical properties of steel using locally sourced materials. The modification comprised introduction of water pump, adjustable impingement gap mechanism and replacement of complicated hydraulic/chain conveyor mechanism with screw conveyor mechanism. The plant was designed, fabricated and instrumented with temperature and flow probes to simulate the actual operating conditions of steel mill industry. Comparative performance results revealed 8% increase in cooling rate of the improved system over the existing technology. Moreover, with a test-plate initial temperature at 550 °C, a controlled cooling temperature of 160 °C was achieved which produced film and nucleate boiling heat extraction effect. This influenced microstructural properties of the test plates. The plates post treatment exanimations of the grain microstructure and mechanical properties revealed good martensite-phase transformation and enhanced “advanced-steel” hardness of Rockwell 59.9, respectively. In addition, impact energy test showed good value range of 56 to 63 J which compared favorably with AISI standard of 44.3 J. This therefore, gave 53% hardness and 26% to 42.2% impact of improved mechanical and desirable hardened martensite needle-like structure of metallurgical properties thereby saving the high cost of alloying.

Non-Uniform Deformation of Slab during Heavy Reduction Process

The bulge deformation of slab narrow face can cause surface defects of hot rolled steel plate. A three-dimensional bulging model, was proposed to simulate the evolution of deformation behavior of the continuous casting slab during heavy reduction (HR). The model was taken to investigate the non-uniform deformation of slab during HR process. The bulging deformation behavior of the slab was then calculated in one segment included seven pairs of rollers. To improve the edge defect on hot-rolled steel plates, the relationship between the reduction amount and bulge deformation of slab narrow face has been investigated.

Classification of Hot-Rolled Plates Using the Mahalanobis Distance of NMIs in Ti-Stabilized Austenitic Stainless-Steel Produced by Secondary Metallurgy.

Three charges of scrap-based, Ti-stabilized, Cr-Ni-Mo austenitic stainless steel in the form of hot-rolled steel plates were characterized. Based on automated metallographic analyses of representative microstructures, a quality characterization in terms of cleanliness of the hot-rolled steel plates was performed. Elevated contents of impurities, especially Pb, Bi, and oxygen, which affect the hot workability of stainless steels, were detected. The recycled FeTi-cored wire was the main source of the elevated levels of impurities detected in the hot-rolled, Ti-stabilized, stainless-steel plates. Related to this, elevated levels of nonmetallic inclusions (NMIs) and segregations were formed. The three charges were classified based on calculations of the Mahalanobis distance (MD) between the inclusions. The charge with the smallest number of nonmetallic inclusions was set as the reference class. The selection of outlier inclusions based on their MDs and their back-representation into ternary diagrams gave relevant metallurgical information about the abnormalities. The advantage of this technique is that the calculations of the MD and the threshold can be fully automated.

Block shear performance of double-line bolted S690 steel angles under uniaxial tension

We investigated the block shear performance of 16 steel angle specimens connected by double-line bolts. Among these specimens, 10 were made of S690 high-strength steel and 6 were made of normal-strength steel. The angle specimens were fabricated using two hot-rolled steel plates through groove welding. Two angle sections, i.e., 125 × 65 × 6 and 125 × 85 × 6 mm (long leg length × short leg length × thickness), were considered in the test. All angles were connected to the long leg. Apart from steel grade, the test parameters included bolt rows, parallel pitch, transverse pitch, edge distance, and unconnected leg length. Typical block shear of specimens were observed, and different fracture patterns were characterised. The test results confirmed that the block shear strength of the tension angles could be improved by increasing the tension plane area with the increase of the transverse pitch and edge distance and increasing the shear plane area with the increase of the bolt row number and parallel pitch. However, the test results showed that the block shear strength of the angles was not affected by the length of the unconnected leg. Subsequently, numerical models were built to further investigate the block shear behaviour of the double-line bolted angles, and the analysis parameters were the end distance, unconnected leg length, and connected leg length. According to the experimental and numerical results, the accuracy and adequacy of design specifications in the United States, Europe, Canada, and Japan and design equations documented in the literature for evaluating the block shear performance of double-line bolted steel angles were evaluated.