Research

21 pages, 10063 KiB

Open AccessArticle

An Improved Method for Deriving the Heat Source Model for FCAW of 9% Nickel Steel for Cryogenic Tanks

by Younghyun Kim, Jaewoong Kim, Hyeongsam Park, Sungbin Hong, Changmin Pyo and Gyuhae Park

Materials 2023, 16(20), 6647; https://doi.org/10.3390/ma16206647 - 11 Oct 2023

Viewed by 726

The International Maritime Organization (IMO) is tightening regulations on air pollutants. Consequently, more LNG-powered ships are being used to adhere to the sulfur oxide regulations. Among the tank materials for storing LNG, 9% nickel steel is widely used for cryogenic tanks and containers [...] Read more.

The International Maritime Organization (IMO) is tightening regulations on air pollutants. Consequently, more LNG-powered ships are being used to adhere to the sulfur oxide regulations. Among the tank materials for storing LNG, 9% nickel steel is widely used for cryogenic tanks and containers due to its high cryogenic impact toughness and high yield strength. Hence, numerous studies have sought to predict 9% nickel steel welding distortion. Previously, a methodology to derive the optimal parameters constituting the Goldak welding heat source for arc welding was developed. This was achieved by integrating heat transfer finite element analysis and optimization algorithms. However, this process is time-consuming, and the resulting shape of the weld differs by ~15% from its actual size. Therefore, this study proposes a simplified model to reduce the analysis time required for the arc welding process. Moreover, a new objective function and temperature constraints are presented to derive a more sophisticated heat source model for arc welding. As a result, the analysis time was reduced by ~70% compared to that previously reported, and the error rates of the weld geometry and HAZ size were within 10% and 15% of the actual weld, respectively. The findings of this study provide a strategy to rapidly predict welding distortion in the field, which can inform the revision of welding guidelines and overall welded structure designs. Full article

(This article belongs to the Special Issue Welding, Joining and Additive Manufacturing: Experiments, Materials and Modelling)

► Show Figures

Figure 1

11 pages, 3116 KiB

Open AccessArticle

Microstructural and Performance Analysis of TP304H/T22 Dissimilar Steel Welded Joints

by Jian Sun, Tong Wang, Fuguang Liu, Zhoubo Zhang, Yunhui Chen, He Lin, Hui Liu, Xiaohui Zhao and Xiaole Cheng

Materials 2023, 16(12), 4474; https://doi.org/10.3390/ma16124474 - 20 Jun 2023

Viewed by 1036

Abstract

In the power plant boiler industry, dissimilar steel welding is widely used in the connection of thermal power generation units. As an important component of the unit, research on the organizational properties of dissimilar steel welded joints has significant guidance for the life [...] Read more.

In the power plant boiler industry, dissimilar steel welding is widely used in the connection of thermal power generation units. As an important component of the unit, research on the organizational properties of dissimilar steel welded joints has significant guidance for the life design of the joint. For the long-term service state of TP304H/T22 dissimilar steel welded joints, the microstructure’s morphological evolution, the microhardness, and the tensile properties of tube samples were analyzed using tests and numerical simulations. The results show that the microstructure of each part of the welded joint was free of damaged features, such as a creep cavity and intergranular cracks. The microhardness of the weld was higher than that of the base metal. In the tensile test, the welded joints broke at the weld metal at room temperature and at the side of the TP304H base metal at a temperature of 550 °C. The tensile fracture morphology demonstrated a change from a ductile fracture to a hybrid fracture when the temperature rose. The fusion zone and base metal on the TP304H side were the stress concentration areas of the welded joint, which easily sprouted cracks. This study holds significant reference value in assessing the safety and reliability of dissimilar steel welded joints in superheater units. Full article

(This article belongs to the Special Issue Welding, Joining and Additive Manufacturing: Experiments, Materials and Modelling)

► Show Figures

Figure 1

21 pages, 11294 KiB

Open AccessArticle

Measuring the Cooling Behavior of Melt Pools in L-PBF by Pyrometry

by Aron Pfaff, Sebastian Schäffer, Martin Jäcklein and Frank Balle

Materials 2023, 16(10), 3647; https://doi.org/10.3390/ma16103647 - 10 May 2023

Cited by 2 | Viewed by 1139

Abstract

This study aims to measure the cooling rates or, more precisely, the cooling durations of single laser tracks by pyrometry within the laser powder bed fusion (L-PBF) process. Two-color, as well as one-color pyrometers are tested within this work. Regarding the second, the [...] Read more.

This study aims to measure the cooling rates or, more precisely, the cooling durations of single laser tracks by pyrometry within the laser powder bed fusion (L-PBF) process. Two-color, as well as one-color pyrometers are tested within this work. Regarding the second, the emissivity of the investigated 30CrMoNb5-2 alloy is determined in-situ within the L-PBF system in order to measure temperature instead of arbitrary units. This is done by heating up printed samples and verifying the measured pyrometer signal by comparing it to values obtained by thermocouples attached to the samples. In addition, the precision of two-color pyrometry is verified for the given setup. Following the verification experiments, single laser track experiments are conducted. The obtained signals prove to be partially distorted mainly due to by-products such as smoke and weld beads arising from the melt pool. To encounter this problem, a new fitting method is presented and experimentally validated. Melt pools resulting from different cooling durations are analyzed by EBSD. These measurements show areas of extreme deformation or potential amorphization correlating with the cooling durations. The obtained cooling duration can be used for the validation of simulations as well as for the correlation of corresponding microstructure and process parameters. Full article

(This article belongs to the Special Issue Welding, Joining and Additive Manufacturing: Experiments, Materials and Modelling)

► Show Figures

Figure 1

19 pages, 9673 KiB

Open AccessArticle

Optimization of CMT Characteristic Parameters for Swing Arc Additive Manufacturing of AZ91 Magnesium Alloy Based on Process Stability Analysis

by Zhongrui Zhang, Junqi Shen, Shengsun Hu, Yang Chen, Chengxuan Yin and Xianzheng Bu

Materials 2023, 16(8), 3236; https://doi.org/10.3390/ma16083236 - 19 Apr 2023

Cited by 4 | Viewed by 1256

Abstract

The droplet transfer behavior and stability of the swing arc additive manufacturing process of AZ91 magnesium alloy based on the cold metal transfer (CMT) technique were studied by analyzing the electrical waveforms and high-speed droplet images as well as the forces on the [...] Read more.

The droplet transfer behavior and stability of the swing arc additive manufacturing process of AZ91 magnesium alloy based on the cold metal transfer (CMT) technique were studied by analyzing the electrical waveforms and high-speed droplet images as well as the forces on the droplet, and the Vilarinho regularity index for short-circuit transfer (IV_SC) based on variation coefficients was used to characterize the stability of the swing arc deposition process. The effect of the CMT characteristic parameters on the process stability was investigated; then, the optimization of the CMT characteristic parameters was realized based on the process stability analysis. The results show that the arc shape changed during the swing arc deposition process; thus, a horizontal component of the arc force was generated, which significantly affected the stability of the droplet transition. The burn phase current I_sc_wait presented a linear function relation with IV_SC, while the other three characteristic parameters, i.e., boost phase current I_boost, boost phase duration t_I_boost and short-circuiting current I_sc2, all had a quadratic correlation with IV_SC. A relation model of the CMT characteristic parameters and IV_SC was established based on the rotatable 3D central composite design; then, the optimization of the CMT characteristic parameters was realized using a multiple-response desirability function approach. Full article

(This article belongs to the Special Issue Welding, Joining and Additive Manufacturing: Experiments, Materials and Modelling)

► Show Figures

Figure 1

21 pages, 8066 KiB

Open AccessArticle

New Partially Water-Soluble Feedstocks for Additive Manufacturing of Ti6Al4V Parts by Material Extrusion

by Ralf Eickhoff, Steffen Antusch, Dorit Nötzel and Thomas Hanemann

Materials 2023, 16(8), 3162; https://doi.org/10.3390/ma16083162 - 17 Apr 2023

Cited by 3 | Viewed by 1087

Abstract

In this work, a process chain for the realization of dense Ti6Al4V parts via different material extrusion methods will be introduced applying eco-friendly partially water-soluble binder systems. In continuation of earlier research, polyethylene glycol (PEG) as a low molecular weight binder component was [...] Read more.

In this work, a process chain for the realization of dense Ti6Al4V parts via different material extrusion methods will be introduced applying eco-friendly partially water-soluble binder systems. In continuation of earlier research, polyethylene glycol (PEG) as a low molecular weight binder component was combined either with poly(vinylbutyral) (PVB) or with poly(methylmethacrylat) (PMMA) as a high molecular weight polymer and investigated with respect to their usability in FFF and FFD. The additional investigation of different surfactants’ impact on the rheological behaviour applying shear and oscillation rheology allowed for a final solid Ti6Al4V content of 60 vol%, which is sufficient to achieve after printing, debinding and thermal densification parts with densities better than 99% of the theoretical value. The requirements for usage in medical applications according to ASTM F2885-17 can be fulfilled depending on the processing conditions. Full article

(This article belongs to the Special Issue Welding, Joining and Additive Manufacturing: Experiments, Materials and Modelling)

► Show Figures

Graphical abstract

17 pages, 8461 KiB

Open AccessArticle

Processing of Haynes^® 282^® Alloy by Direct Energy Deposition with Arc and Wire

by Manuela Zinke, Stefan Burger and Sven Jüttner

Materials 2023, 16(4), 1715; https://doi.org/10.3390/ma16041715 - 18 Feb 2023

Cited by 2 | Viewed by 1326

Abstract

Direct energy deposition with arc and wire (DED-AW) is a versatile, low-cost, and energy-efficient technology for additive manufacturing of medium- and large-sized metallic components. In this study, the effects of arc energy and shielding gas in cold metal transfer (CMT) welding of walls [...] Read more.

Direct energy deposition with arc and wire (DED-AW) is a versatile, low-cost, and energy-efficient technology for additive manufacturing of medium- and large-sized metallic components. In this study, the effects of arc energy and shielding gas in cold metal transfer (CMT) welding of walls and blocks on cooling time, mechanical properties, and macro- and microstructure have been studied using precipitation-hardenable Ni-based superalloy Haynes^® 282^®. The arc energy and consequently the cooling rate were varied by changing the wire feed rate and the travel speed. As expected, increasing the arc energy leads to higher cooling times for the walls. Due to the 2D thermal conduction, the thin walls cool down much slower than multi-layer welded blocks, but this reduces the strength values only very slightly. While the walls have no sensitivity to the occurrence of unacceptable seam irregularities, the multi-layer blocks show isolated seam defects, such as hot cracks or lack of fusion. Despite shielding gas variation, the as-welded blocks show acceptable strength properties at room temperatures (RT) and impact values at RT and −196 °C. However, the use of an N-containing shielding gas results in lower elongation and notched bar impact energy. Precipitation-hardened specimens tested at 871 °C exhibit a similar strength level to transverse tensile specimens of gas metal arc welding (GMAW) welded joints on 12.7 mm thick plates with fracture in the weld metal. Full article

(This article belongs to the Special Issue Welding, Joining and Additive Manufacturing: Experiments, Materials and Modelling)

► Show Figures

Figure 1

10 pages, 2363 KiB

Open AccessArticle

Analytical Simulation of the Microbubble Collapsing in a Welding Fusion Pool

by Ahmed Teyeb, Mohamad Salimi, Evelyne El Masri, Wamadeva Balachandran and Tat-Hean Gan

Materials 2023, 16(1), 410; https://doi.org/10.3390/ma16010410 - 01 Jan 2023

Cited by 1 | Viewed by 1467

Abstract

This paper explains the use of remote ultrasound vibration at the optimum position and frequencies to vibrate plates under welding, with the aim of initiating cavitation in the molten pool area. It has been shown in the literature that ultrasound cavitation changes microstructure [...] Read more.

This paper explains the use of remote ultrasound vibration at the optimum position and frequencies to vibrate plates under welding, with the aim of initiating cavitation in the molten pool area. It has been shown in the literature that ultrasound cavitation changes microstructure morphology and refines the grain of the weld. In practice, the plates are excited through narrow-band high-power ultrasound transducers (HPUTs). Therefore, a theoretical investigation is carried out to identify the plate-mode shapes due to the ultrasound vibration aligned with the frequency bandwidth of HPUTs available in the marketplace. The effect of exciting the plate at different locations and frequencies is studied to find the optimum position and frequencies to achieve the maximum pressure at the area of the fusion zone. It was shown that applying the excitation from the side of the plate produces an order of

10^{3}

higher vibration displacement amplitude, compared with excitation from the corner. The forced vibration of cavitation and bursting time are studied to identify vibration amplitude and the time required to generate and implode cavities, hence specifying the vibration-assisted welding time. Thus, the proposed computational platform enables efficient multiparametric analysis of cavitation, initiated by remote ultrasound excitation, in the molten pool under welding. Full article

(This article belongs to the Special Issue Welding, Joining and Additive Manufacturing: Experiments, Materials and Modelling)

► Show Figures

Figure 1

18 pages, 5538 KiB

Open AccessArticle

Comparative Study on the Behavior of Keyhole in Analogy Welding and Real Deep Penetration Laser Welding

by Zhongjia Hao, Huiyang Chen, Xiangzhong Jin and Zuguo Liu

Materials 2022, 15(24), 9001; https://doi.org/10.3390/ma15249001 - 16 Dec 2022

Cited by 2 | Viewed by 1058

Abstract

In deep penetration laser welding, the behavior of the keyhole has an important influence on the welding quality. As it is difficult to directly observe the keyhole and detect the pressure inside the keyhole during metal laser welding, theoretical analysis and numerical simulation [...] Read more.

In deep penetration laser welding, the behavior of the keyhole has an important influence on the welding quality. As it is difficult to directly observe the keyhole and detect the pressure inside the keyhole during metal laser welding, theoretical analysis and numerical simulation methods are commonly used methods in studying keyhole behavior. However, these methods cannot provide direct real information on keyhole behavior. In this paper, a method of analogy welding is proposed, in which high speed gas is used to blow the liquid to generate the keyhole. Relevant process experiments were conducted to explore keyhole behavior in analogy welding and real deep penetration laser welding. The pressure balance of the keyhole, both in analogy welding and real deep penetration laser welding, were analyzed. The laws obtained in analogy welding and real deep penetration laser welding are similar, which indicates that studying keyhole formation and the maintenance principle using the analogy welding method proposed in this paper may be helpful for deep understanding of the keyhole formation and maintenance mechanisms in real deep penetration laser welding. Full article

(This article belongs to the Special Issue Welding, Joining and Additive Manufacturing: Experiments, Materials and Modelling)

► Show Figures

Figure 1

18 pages, 20081 KiB

Open AccessArticle

Microstructure and Mechanical Properties of Steel and Ni-Based Superalloy Joints for Rotors of High-Speed Electric Motors

by Eero Scherman, Eerik Sikanen, Hemantha Kumar Yeddu, Mohsen Amraei and Jussi Sopanen

Materials 2022, 15(19), 6906; https://doi.org/10.3390/ma15196906 - 05 Oct 2022

Cited by 3 | Viewed by 1630

Abstract

High-speed electric motors, e.g., axially laminated anisotropic synchronous reluctance motors (ALA-SynRM), use a solid rotor manufactured by joining alternating layers of magnetic and non-magnetic metallic sheets. The strength of the dissimilar metallic joints is critical for the rotor’s ability to withstand the operating [...] Read more.

High-speed electric motors, e.g., axially laminated anisotropic synchronous reluctance motors (ALA-SynRM), use a solid rotor manufactured by joining alternating layers of magnetic and non-magnetic metallic sheets. The strength of the dissimilar metallic joints is critical for the rotor’s ability to withstand the operating conditions of the high-speed electrical machine. In this work, various dissimilar metallic joint configurations that can be used in high-speed ALA-SynRM rotors are studied by analyzing the shear strength, microstructure, hardness, and composition of the joints. Metallic joints of structural steels and Inconel^® alloys fabricated by vacuum brazing and hot isostatic pressing (HIP) are studied. Finite element analysis (FEA) was performed to calculate the maximum shear stress of the joints that were subjected to various high speed operating conditions. The shear strength of the test specimens was measured and compared with FEA results. The microstructure and chemical composition of the joints were studied by using optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) on SEM. The results show that the hot isostatic pressed S1100MC-IN718 joint achieved the highest ultimate shear strength (233.3 MPa) followed by vacuum brazed S355MC-IN600 joint (230.1 MPa) and HIP S355-IN718 (203.5 MPa), thereby showing that vacuum brazing and HIP can be viable manufacturing methods to fabricate a high-speed ALA-SynRM rotor. Full article

(This article belongs to the Special Issue Welding, Joining and Additive Manufacturing: Experiments, Materials and Modelling)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Welding, Joining and Additive Manufacturing: Experiments, Materials and Modelling

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (9 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI