Department of Mechanical Engineering

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The welded joint of martensitic P92 steel is associated with heterogeneous microstructure arising due to the thermal history of the welding thermal cycle. The complex microstructure of the welded joint results in degradation of mechanical strength of the joint in-service condition. The present work showed experimental investigation where an improvement in mechanical properties and homogeneous microstructure formation for P92 welded joint has been achieved through grain refinement of virgin P92 steel plate. The grain refinement of virgin P92 steel has been achieved using the double austenitization based normalizing and tempering treatment. The as-received P92 steel having ‘normalized and tempered’ (1040 °C/40 min/air cool+760 °C/2 h/air cool) condition had an average grain size of 9.54±2.50 μm, while after ‘double austenitization based normalizing and tempering’ P92 steel (1040 °C/60 min/water quench+950 °C/40 min/air cool+760 °C/2 h/air cool), average grain size of 15.75 ± 3.75 μm had been obtained. The welded joint has been prepared for both the condition (normalized and tempered; double austenitization based normalized and tempered) of the plates. The paper discusses the effect of grain refinement of virgin base metal on tensile properties, impact toughness and microhardness of the P92 welded joint, and results obtained for the ‘double austenitization based normalized and tempered’ welded plate have been compared with the conventional ‘normalized and tempered’ welded plate. The welded joint was also characterized for heat treatment conditions. The welded joint did not qualify the ultra-supercritical boiler requirements in as-welded condition due to poor impact energy. The fairly good impact energy and tensile properties were obtained after the double austenitization based normalizing and tempering post-weld heat treatment (DHT). After the direct post-weld heat treatment, a superior weld strength was obtained, but impact energy just qualified the minimum required value and also inhomogeneity in microstructure was obtained along welded joint. The DHT showed a significant improvement in tensile strength of welded joint without any loss in ductility. © 2021, ASM International.

World University root node

Journal of Materials Engineering and Performance

Study on the Effect of the Grain Refinement on Mechanical Properties of the P92 Welded Joint

The effects of orientations have been studied for excessive heat dissipation as the vapor and liquid dispersion varies due to drastic variation in density. The heat transfer coefficient and pressure fluctuations are investigated with water as a working fluid at atmospheric pressure in flow boiling for horizontal, vertical up, and vertical down orientations for different mass flux and heat flux. A test-section made up of stainless steel (SS304) of 11.7 mm inner diameter and 0.5 mm thickness having 1.5 m length is used. The Froude number at the test-section outlet is varied from 0.078 to 0.6. The thermal imaging technique is used to visualize and plot the contours of the distribution of wall temperature. The centreline local and average heat transfer coefficient is comparatively higher for horizontal flow than vertical downflow and vertical upflow for the same mass flux and heat flux in flow boiling. However, the heat transfer is asymmetric for horizontal flow while symmetric for vertical up and downflow. For horizontal flow, the wall temperature is asymmetric for the Froude number less than 0.22 and vapor quality greater than 0.03. The pressure fluctuates more in horizontal orientation than the vertical orientation for two-phase flow. © 2021 Elsevier Ltd

Applied Thermal Engineering

Heat transfer distribution and pressure fluctuations during flow boiling in a pipe with different orientations

Biomedical application of ZnO nanoscale materials

Introduction to metal oxide-based biosensing

Applied Nanoscience

Superhydrophobic ZnO-Au nanocomposite over polydimethylsiloxane tubes for efficient photocatalytic dye degradation

Robotics and Computer-Integrated Manufacturing

Identification of elasto-static parameters of an industrial robot using monocular camera

Vision System and Calibration

Heat transfer over a heated plate positioned normal to the horizontal circular impinging jet is investigated experimentally. The area average and local heat transfer characteristics over a large plate impinged by jet of air are investigated for Reynolds numbers ranging from 10,000 to 45,000, with jet-to-plate distances of 3–20 d for a maximum range of 0 ≤ r/d ≤ 44. The experiment is carried out for two jet diameters of 5.88 mm and 11.5 mm on a plate of 600 × 300 mm2 impinged by a jet. The infrared (IR) thermal imaging method is used to find the temperature distribution over the heated plate. The combined heat transfer investigation of both local and area average gives a proper insight of the cooling phenomenon of the jet at any location over the plate. The investigation is effective in identifying areas with a greater rate of heat transfer. At various locations, the Nusselt number growth with increasing mass flow rate is studied. The area average heat transfer is discovered to be the highest at z/d = 3 for all Reynolds numbers in the A1 (0 &lt; r/d &lt; 2.17) region. However, for z/d = 6 and r/d = 0, the local Nusselt number is reported to be the highest. Reduction in area average heat transfer is reported in area A3, i.e., r/d = 6.5, and beyond this area, the profile of Nusselt number practically converges. © 2022 Taylor &amp; Francis.

Experimental Heat Transfer

Experimental analysis of local and average heat transfer between circular impinging jet and flat plate

In India, during mining and ore processing, ore fine generation is a common phenomenon, in which more than 60% of process ore becomes discarded material. To explore the alternative of high-grade ores, mutual replacement with the utility of dump ore fines is the best way. With this perspective, Kiruburu iron ore mine (Iron Ore No.1) and Meghataburu iron ore mine (Iron Ore No.2) dumped fines were chosen for a Blaine no. investigation, in the connection of firing temperatures, to get optimum desirable physical properties, Cold Compression Strength (C.C.S.),and Apparent Porosity (A.P.), with physico-chemical properties, Reducibility Degradation Index (R.D.I.), and Reducibility Index (R.I.). To characterize pellet properties with input variables, a microstructure phase study has been conducted using a scanning electron microscope (S.E.M.), energy dispersive spectroscopy (EDS), and X-ray diffraction analysis (XRD). The Iron Ore No.1 and 2 fine pellets survey showed good, desirable properties, at the Blaine no., of 1678 cm2/g and 2311 cm2/g (corresponding to 200 mesh size), and the best results are attained at a firing temperature of 1300 °C. Thermal kinetic analysis of the heating of pellets has been done to knowthe activation energy of different ore characteristics. The results showed that Iron Ore No.2 pellets have high activation energy. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Fulltext

Materials

Experimental Investigation of Different Fineness and Firing Temperatures on Pellets Properties of Different Iron Ore fines from Indian Mines

This research article reports the correlation between microstructure, mechanical properties, and residual stresses of dissimilar weld joints (DWJs) between P92 martensitic steel and 304L austenitic stainless steel (ASS). The groove geometry plays a vital role in DWJs. Thus the effect of groove geometry on mechanical and microstructural properties was also investigated. The V-shape and narrow shape groove profile were implemented for P92/304L SS DWJs. The microstructural characteristic, tensile strength, micro-hardness, Charpy impact toughness and residual stresses were evaluated for both the groove geometry in as-weld (AW) and post-weld heat treatment (PWHT) (760 °C, 2 h) state. Microstructural observations performed using an optical microscope (OM), and scanning electron microscope (SEM) showed that high temperature during the weld thermal cycle leads to the formation of the coarse grain heat-affected zone (CGHAZ), fine grain HAZ (FGHAZ), and inter-critical HAZ (ICHAZ) across the P92 HAZ. The ERNiFeCr-2 (Inconel 718) welding consumable wire (filler rod) of diameter 2.4 mm was used for this investigation. The ERNiFeCr-2 weld fusion zone showed a fully austenitic microstructure with the formation of the secondary phases due to the solidification segregation. The EDS and SEM area mapping results indicated that the secondary phases in the inter-dendritic region contain a higher amount of the Mo and Nb than the matrix region. The ultimate tensile strength (UTS) of the as-weld and PWHT tensile specimen of the P92/304L SS DWJs was 630 and 621 MPa, respectively, for V-groove geometry specimens and 620 and 629 MPa, respectively, for narrow groove geometry specimens. The tensile fracture was experienced at the interface between weld metal and 304L base metal, and the UTS value of DWJs was very close to the UTS of the 304L SS. The abrupt variation in the micro-hardness value of the CGHAZ (456HV0.5), FGHAZ (375HV0.5), and ICHAZ (221HV0.5) was noticed in the as-weld state due to their distinguish microstructure characteristics. After PWHT, the micro-hardness value of the CGHAZ (255HV0.5), FGHAZ (236HV0.5), and ICHAZ (207HV0.5) was below the maximum allowable value of 265HV0.5 for P92 material because of the tempering of the martensite. The Charpy impact test indicated that the ERNiFeCr-2 weld fusion zone has a low toughness value of 33 J (AW) and 25 J (PWHT) for V-groove design and 35 J (AW) and 28 J (PWHT) for narrow groove design than that of the P92 and 304L parent metal. The impact toughness of the ERNiFeCr-2 filler weld was below the minimum requirement of 47 J (EN ISO 3580:2017). The tensile residual stresses were generated in the weld fusion zone due to the volumetric contraction during the solidification. The residual stresses developed in the case of the narrow groove design were less than that for the V-groove design due to the less quantity of weld metal available for volumetric contraction in the case of the narrow groove geometry. From comparing mechanical and microstructural properties obtained for V-groove and narrow groove geometry DWJs, it was found that narrow groove design reduces the overall heat affected zone span, and it requires less welding time and less heat input. © 2022, Wroclaw University of Science and Technology.