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Microstructural characterization and tensile behavior of Nd:YAG laser beam welded thin high strength low alloy steel sheets
摘要： Laser beam welding (LBW) has many advantages to join high strength low alloy (HSLA) steels compared with conventional fusion welding processes. The present work is focused on joining HSLA plates of 2 mm thickness efficiently through the application of Nd:YAG laser source. Only one process variable i.e. the welding speed was operated between 70 mm/s to 120 mm/s while the rest of the variables were maintained constant. The microstructure evolution of the fusion zone was recorded through optical, scanning and transmission electron microscopy. The fusion zone was observed to be wider but no major defects were present. Fusion zone experienced a change in morphology of ferrite and pearlite depending upon the rate of cooling and exposure time. Fusion zone showcased various ferrites such as acicular ferrite, widmanstatten ferrite, and grain boundary ferrite. Advancement in the welding speed helped in the formation of acicular ferrite. EBSD results presented a descending tendency of prior austenite grain size against increasing welding speed. TEM micrographs affirmed the ferrite transformation and showed the presence of dense dislocations. The changes in hardness and tensile behavior under the experimental conditions were further reported.
关键词： High strength low alloy steel,Microstructure,Tensile strength,Laser beam welding
更新于2025-09-19 17:13:59
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Microstructure of intercritical heat affected zone and toughness of microalloyed steel laser welds
摘要： Microstructure of laser welds of the X70 low-carbon pipe steel was studied. High cooling rates after laser welding and non-uniform distribution of carbon in the ferrite-pearlite base metal caused formation of regions with increased microhardness (up to 650 НV) in inter-critical heat affected zone (ICHAZ). These regions consisted of finely dispersed degenerate upper bainite and martensite-austenite constituents of a slender shape and small fraction of a massive shape along the boundaries of bainite laths, as well as twinned martensite. High concentration of martensite-austenite constituents (10–16%) and residual stresses in ICHAZ, as well as a dendritic martensitic structure with carbide interlayers along the boundaries of martensite laths in fusion zone were the main reasons of sharp decrease in charpy impact energy of the welded samples. High microhardness of the laser welds was decreased down to 320 HV and their brittleness was improved by annealing. Also, in ICHAZ, degenerate upper bainite and the regions of martensite-austenite constituents decayed forming tempered sorbite and Fe2C and Fe3C carbides, respectively. Charpy impact energy of the welds doubled after annealing compared to the welds without annealing, and ductile-brittle transition temperature decreased down to –60 °С.
关键词： Toughness,Heat affected zone,Structure,Laser welding,Low-carbon steel
更新于2025-09-19 17:13:59
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Combined UTC-PD integrated on-chip THz near field microscopy with coupled planar Goubau lines
摘要： This paper proposes a method capable of reproducing the particular operating conditions of a hot strip mill and predicting the evolution of the main electrical variables from both the characteristics of the steel to be milled and the specific features of the rolling mill. The method analyzes the load torque and the motor-speed evolution in the stands of the roughing and finishing mill drives, according to the steel to be milled. In this study, three types of carbon alloy steel are considered, thus involving dissimilar hardness characteristics. The main stands of the mill, the power network, and the filter banks have been modeled. The relationship between the grade of steel and both the electrical demand and various power quality parameters is discussed. The results can be used as a part of an expert system for the automatic estimation of the electrical demand in a hot rolling mill.
关键词： steel,hot rolling mill,Electrical demand,power system harmonics,finishing mill,roughing mill
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Tunable associative readout in self-associative Fourier holography scheme by means of fine alignment
摘要： This paper proposes a method capable of reproducing the particular operating conditions of a hot strip mill and predicting the evolution of the main electrical variables from both the characteristics of the steel to be milled and the specific features of the rolling mill. The method analyzes the load torque and the motor-speed evolution in the stands of the roughing and finishing mill drives, according to the steel to be milled. In this study, three types of carbon alloy steel are considered, thus involving dissimilar hardness characteristics. The main stands of the mill, the power network, and the filter banks have been modeled. The relationship between the grade of steel and both the electrical demand and various power quality parameters is discussed. The results can be used as a part of an expert system for the automatic estimation of the electrical demand in a hot rolling mill.
关键词： steel,hot rolling mill,Electrical demand,power system harmonics,finishing mill,roughing mill
更新于2025-09-19 17:13:59
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The Increasing of the Operational Stability of Wood-Working tools by the laser cementation
摘要： The paper describes the technology of laser cementation of woodworking tools, which allows to increase the operational stability no less than twice. The tool wear resistance is increased due to carbon saturation of the surface to 1.8-2.0% and the formation of martensite and residual austenite on the surface of the structural composition. The tests results of wear resistance and determination of the period of resistance of the treated tool are given. The modes of laser cementation for the studied grades of tool steels are offered.
关键词： wear resistance,woodworking tools,laser cementation,hardening,tool steel
更新于2025-09-19 17:13:59
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The Analysis of Fiber and CO <sub/>2</sub> Laser Cutting Accuracy
摘要： The aim of the conducted research was to compare the functional properties and the cutting accuracy of items produced using Fiber lasers in comparison with CO2 lasers. The object of 6 mm thick sheet plates made of S235JR steel cut with the two different laser types were analyzed. The tests covered dimensional accuracy (in accordance with the PN EN 22768-fH standard) and the surface after cutting (in accordance with the PN-EN ISO 9013: 2017-04). The results of the analysis have demonstrated that for the same welding linear energy, more accurate cutting surface is obtained using Fiber laser cutting.
关键词： CO2 lasers,Fiber lasers,S235JR steel,surface quality,cutting accuracy,dimensional accuracy
更新于2025-09-19 17:13:59
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Effect of laser shock peening on high cycle fatigue characteristics of 316LN stainless steel
摘要： The influence of ‘laser shock peening’ (LSP) on fatigue behavior of 316LN stainless steel has been studied at 298 K by conducting fully reversed stress controlled fatigue tests in the range 200–300 MPa. A triangular wave form with a constant frequency of 5 Hz was employed for all the tests conducted below 107 cycles on the virgin and laser shock peened samples. The run out tests at 107 cycles were performed at a frequency of 60 Hz. The studies have clearly revealed that the fatigue life is dependent on surface condition of the material and stress amplitude employed. A comparison is made of cyclic stress-strain hysteresis loops and fatigue lives between virgin and peened material. The peened material showed better fatigue strength and life at low stress amplitudes pertaining to high cycle fatigue regime, and exhibited lower density of surface microcracks. The improved fatigue resistance of peened material is attributed to the presence of residual compressive stresses to a depth of ~100 μm from the surface. The beneficial effect of compressive stresses is perceived both in the reduction in number density of Stage-I microcracks and retarded stage-II crack growth in the initial stages (that revealed striations with lesser spacing compared to un-peened samples).
关键词： Laser shock peening,Stainless steel,High cycle fatigue,Compressive residual stresses
更新于2025-09-19 17:13:59
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Experimental and Numerical Study of AISI 4130 Steel Surface Hardening by Pulsed Nd:YAG Laser
摘要： Laser surface transformation hardening (LSTH) of AISI 4130 was investigated by a Nd:YAG pulsed laser. Laser focal height (LFH), pulse width (LPW), scanning speed (LSS), and power (LP) varied during the experiments. The microstructure of the treated zone was characterized by optical (OM) and field emission scanning electron microscopy (FESEM). Micro-hardness was measured in the width and depth directions. Results showed that the hardness and depth of hardened layer increased by decreasing the LSS and the laser focal position (LFP), and by increasing the LPW. The results were compared with those obtained by furnace heat treatment of the same steel. Eventually, a finite element model was employed for the simulation of the LSTH of AISI 4130 steel and calculation of the heat-treated zone. The results showed that the model can predict with accuracy the temperature profile and the size and the shape of the laser hardened region.
关键词： Nd:YAG pulsed laser,laser surface transformation hardening,FEM model,AISI 4130 steel
更新于2025-09-19 17:13:59
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Comparison between Shot Peening, Cavitation Peening, and Laser Peening by Observation of Crack Initiation and Crack Growth in Stainless Steel
摘要： The traditional technique used to modify the surface of a metallic material is shot peening; however, cavitation peening, a more recent technique in which shot is not used, was developed, and improvements in the fatigue strength of metallic materials were demonstrated. In order to compare the fatigue properties introduced by shot peening with those introduced by cavitation peening, crack initiation and crack growth in specimens of austenitic stainless steel (Japanese Industrial Standards JIS SUS316L) treated using these techniques were investigated. With conventional cavitation peening, cavitation is produced by injecting a high speed water jet into water. In the case of submerged laser peening, bubbles are generated using a pulsed laser after laser ablation, and the impact produced when the bubbles collapse is larger than that due to laser ablation. Thus, in this study, cavitation peening using a water jet and submerged laser peening were investigated. To clarify the mechanisms whereby the fatigue strength is improved by these peening techniques, crack initiation and crack growth in specimens with and without treatment were examined by means of a K-decreasing test, where K is the stress intensity factor, and using a constant applied stress test using a load controlled plane bending fatigue tester. It was found that the improvement in crack initiation and the reduction in crack growth were roughly in a linear relationship, even though the specimens were treated using di?erent peening methods. The results presented here show that the fatigue strength of SUS316L treated by these peening techniques is closely related to the reduction in crack growth, rather than crack initiation.
关键词： crack,stainless steel,fatigue,shot peening,cavitation peening
更新于2025-09-19 17:13:59
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KEYHOLE DYNAMICS AND MORPHOLOGY VISUALIZED BY IN-SITU X-RAY IMAGING IN LASER MELTING OF AUSTENITIC STAINLESS STEEL
摘要： In-situ X-ray observation was used to investigate the effect of process conditions on keyhole behavior in laser melting with austenitic stainless steel. It was confirmed that the keyhole depth and width increased, and the fluctuation in the keyhole depth decreased as laser power increased. With no shielding gas, there was a large fluctuation in keyhole depth. This is presumed due to the attenuation of laser power and change in laser beam quality by the interaction between laser and metal vapor. We found that when the laser traverse speed increased relative to the keyhole-forming speed, the inclination of the keyhole decreased, and the width and opening of the keyhole expanded. As the defocus distance increased, the inclination of the keyhole decreased and the fluctuation in the keyhole depth increased. As a result of decreasing the laser power for a predetermined time, the penetration depth of the laser melting portion did not change and the keyhole depth was maintained at a laser power reduction time of 1 ms. These results will contribute to the improvement in quality and efficiency of the laser-melting process regarding keyhole formation such as additive manufacturing and laser welding and cutting.
关键词： X-ray observation,Keyhole,Laser melting,Stainless steel
更新于2025-09-19 17:13:59