Minimal Heat Input Research Articles

Direct laser active brazing of 316Ti to alumina

AbstractThis work addresses the challenges in brazing thermohydraulic sealings involving dissimilar materials, specifically 316Ti stainless steel and alumina, which have significantly different coefficients of thermal expansion (CTEs) and elastic constants. Traditional brazing methods require complex interlayers or extensive metallization steps, leading to issues such as dimensional changes, braze voids, and inadequate corrosion resistance due to prolonged high‐temperature exposure. A novel laser‐based brazing technique utilizing a diode laser is introduced to create high‐quality, localized joints while preserving the integrity of the parent materials. The study systematically optimizes laser process parameters using finite‐element modeling and the Taguchi method to achieve the desired bead geometry and thermal stress distribution with minimal heat input. Comparative analysis between laser active brazing (LAB) and conventional furnace brazing was conducted through metallography, shear testing, and autoclave testing. Results indicate that LAB parameters significantly affect bead thickness and shear strength, with laser‐brazed joints demonstrating superior quality and stability post‐autoclave testing compared with furnace‐brazed joints. The thermodynamic and kinetic aspects of the brazing process were also analyzed. In conclusion, the LAB method for brazing 316Ti to alumina proves to be a successful and efficient alternative, with joint properties meeting or exceeding those of traditional furnace brazing.

A NOVEL DOUBLE-SIDE LASER WELDED THICK PLATE: MICROSTRUCTURE AND NUMERICAL PREDICTION OF TENSILE TEST

The study aims to provide firsthand knowledge on finite element simulation (FES) of double-side laser welded (LW) stainless steel 304 (SS-304) thick plates used for automobile application. Double-side welding technique is an idea of achieving complete penetration with minimal heat input. The microstructural evaluation revealed the presence of dendritic growth that results in the enhancement of tensile strength (TS) for the welded sample. There is a slight increase in the delta ferrite content in weldment. The change in microstructure is due to thermal history during solidification. The TS of base metal (BM) was [Formula: see text][Formula: see text]MPa whereas the welded sample exhibited strength of [Formula: see text][Formula: see text]MPa. FES was successfully employed to simulate TS with error percentage less than 1.

Microstructural and mechanical characterization of electron beam welded low-nickel nitrogen-strengthened austenitic stainless steel

In this paper, the Electron Beam Welding (EBW) was used to join thin plates of low-nickel nitrogen-strengthened austenitic stainless steel (LNiASS), a material valued for its superior mechanical properties and cost-effectiveness. Traditional welding techniques often lead to issues such as hot cracking, reduced toughness, and undesirable microstructures. The objective was to address these challenges using EB·W., which offers precise control, minimal heat input, and deeper penetration.Methodology included joining LNiASS plates with E.B.W. and analyzing the resulting microstructures and mechanical properties through optical microscopy, tensile testing, microhardness testing, and scanning electron microscopy (SEM). The findings indicated the presence of various ferrite morphologies without significant precipitation of deleterious phases like carbides and sigma phase. The weldment strength was ∼90 % of the base alloy, with fractures occurring near the weld cord due to nitrogen loss and grain coarsening in the (HAZ). Microhardness increased by ∼12.9 %, attributed to microstructural evolution and a fine-grained structure. Impact testing in Charpy V-Notch (CVN) configuration showed the weld absorbed ∼50 % more impact energy than the base material, due to refined Microstructure and enhanced hardness. Longitudinal residual stress analysis indicated compressive nature below mid-thickness, resulting from thermal expansion and contraction during welding. These results demonstrated E.B·W.'s effectiveness in preserving mechanical properties and enhancing the performance of nitrogen-strengthened stainless steel welds.

Effect of process parameters on weld geometry and mechanical properties in friction stir welding of AA2024 and AA7075 alloys

FSW joints are promising because they have a minimal heat input in welding and can limit the amount of intermetallic compound formation in dissimilar metals. Solid-state welding processes, particularly friction stir welding (FSW), are preferred for welding aluminium alloys due to their low heat input and ability to minimize intermetallic compound formation. This study conducted FSW trials on AA7075 and AA2024 alloys, each 4 mm thick. Parameters such as axial force, rotational speed, and traverse feed were adjusted while keeping other factors constant. The study analyzed weld geometry characteristics, including bead width and penetration depth. Angle distortions during FSW of thin plates in a butt joint were investigated. Additionally, the study examined the effects of FSW parameters on mechanical properties such as tensile strength and hardness immediately after welding. Microstructures of the welds were observed using optical microscopy (OM). The optimal mechanical properties are achieved at a rotational speed of 1000 rpm, a traverse feed of 30 mm/min, and an axial force of 10 kN. This optimal condition facilitates material flow around the pin at an ideal speed, ensuring adequate material filling and preventing tunnel formation. The stir zone's microstructure under these parameters exhibits a finely recrystallized structure with a significantly smaller grain size than the base material. Consequently, this enhances the joint's microhardness and tensile strength.

Numerical and experimental investigation on NbTi superconducting liquid helium level sensor based on a resistance heating

A resistance-heated NbTi superconducting liquid helium level sensor based on the principle of thermal conduction is proposed. A heat transfer model for the sensor was established, and its mathematical model was characterized. The effects of temperature, current, heating resistance value, and superconducting wire diameter on the sensor performance were investigated. It indicates that the temperature of the sensor in the vapor phase is decreased linearly from high to low, and the voltage is decreased with the increase of the liquid level. And the 45 μm diameter superconducting wire has a minimum propagation current, a minimal heat input to the system, and a small measurement error. The variation of the sensor output voltage with a level height was studied experimentally. The linear correlation coefficients R2 of the 1 Ω, 5.1 Ω, and 10 Ω sensors are all greater than 0.999, which are almost identical to the simulation results. The sensor’s response time is all less than 1 s, the sensitivity is 8.7070 mV/mm, 8.0110 mV/mm, and 6.9660 mV/mm, respectively, and the accuracy is 0.8226%, 0.8611%, and 0.9030%.

A new method for refinement of Ti-6Al-4 V prior-β grain structure in the alternating magnetic field assisted narrow gap gas tungsten arc welding (AMF-GTAW) via filler wire oscillation

This study presents a new method for refining Ti-6Al-4 V prior-β grain in the alternating magnetic field assisted narrow gap gas tungsten arc welding (AMF-GTAW) process by stirring the molten pool, which is accomplished directly through the use of an oscillating filler wire. The wire feed rate can be increased from 1.8 m/min to 2.2 m/min by filler wire oscillation in the traditional AMF-GTAW process with minimal heat input. This method greatly increases welding efficiency by efficiently utilizing the energy of the arc and molten pool. Using a high-speed camera, the flow behavior of the molten pool was investigated under different filler wire oscillating amplitudes. The results showed that the oscillation of the filler wire can cause a violent stir in the molten pool. By increasing the oscillating amplitude of filler wire, one can refine the columnar prior-β grain structure and attain a morphology of the upper layer of the welded joint that is nearly equiaxed with crystallographic texture, all while maintaining a fixed heat input. This is because the wire's insertion into the molten pool also creates a negative thermal gradient and the filler wire's high-frequency and high-amplitude oscillation creates an intense convection that prevents randomly oriented nuclei and/or dendrite fragments from remelting and promotes nucleation activation. The oscillating amplitude of 6 mm and the oscillating frequency of 100 Hz are the ideal values for this effect.

Effects of Ultrashort Pulsed Direct Laser Writing on Ni/Al Reactive Multilayer Foils

Reactive multilayer foils (RMFs) for joining processes have attracted a great deal of attention over the last few years. They are capable of exothermic self-propagating reactions and can serve as localized heat sources for joining applications when ignited by suitable means. Using short and ultrashort pulsed lasers with carefully selected parameters, cutting and shaping of RMFs makes it possible to tailor heat release characteristics without triggering the reaction. The present study is an investigation of microstructural changes induced by femtosecond laser machining of a commercially available Ni/Al-based RMF. The effects of the specific laser parameters pulse duration and repetition rate on the heat-affected zone (HAZ) are investigated by scanning and transmission electron microscopy. Debris consisting of oxide deposits can be found at a distance of several tens of microns from the cut edge. A negligible HAZ extending to less than 100 nm was observed for all parameters tested and no signs of ignition of a self-propagating reaction were observed. These results underline the suitability of femtosecond lasers for metal machining with minimal heat input.

Effect on Various Parameter of Stainless Steel 316L Weld Bead Geometry using Cold Metal Transfer (CMT) Process

This study influences the effect of various process parameters on Cold Metal Transfer (CMT) of stainless steel 316L using mild steel as substrate. CMT has a benefit of a minimal heat input, a high deposition rate, and increased efficiency. Typically, single pass weld beads are utilized for repair and remanufacturing. The geometry of the beads determines the cladding performance of additively produced components. Therefore, optimal range of bead characteristics is necessary to ensure superior mechanical qualities. The parameters includes as: welding current, travel speed and feed speed, were tuned to produce joints with complete penetration depth and zero defects. The weld bead with lower wire travel speed of (2.9 m/min) and higher wire feed speed of (4.9 m/min) at current value of (141A) shows the optimum value of (bead width: 3.56 mm, bead height: 1.72mm, weld penetration: 3.83mm and dilution: 1.5%). This was attributed to the decreases of wire travel speed and increases of wire feed speed ensuring better penetration and larger molten metal. While a higher current value causes the convexity area of the bead to rise, it displays a stronger penetration and minimal dilution.

Parametric Optimisation of Micro Plasma Welding for Wire Arc Additive Manufacturing by Response Surface Methodology

High deposition rate with minimal heat input is one of the primary emphases in wire arc additive manufacturing. This study aims to determine the optimal input parameters of micro plasma welding for single-layer deposition. The stability of a single layer is crucial as it serves as the foundation relative to the deposition of layers to avoid a discontinuous multi-layer material. The study focuses on wire feeding speed, welding speed, and pulse and their interaction between the input and response variables. Based on the study, the regression equation between the three key parameters and the response using the Box-Behnken Design response surface methodology was proposed. The outcome demonstrates that the op-timized sample deposition produces a smooth surface appearance with no apparent defects.

Process response of Inconel 718 to wire + arc additive manufacturing with cold metal transfer

Wire + arc additive manufacturing (WAAM) with cold metal transfer (CMT) process can reduce cost and lead time during the production of large-scale Ni-based components used in the transportation and energy sector. This paper investigates the effects of processing parameters and heat treatments employed on CMT-WAAM of a precipitation hardenable Ni-based alloy – Inconel 718. The process stability was analysed by electrical transients and melt pool imaging, showing an opposite trend to the measured heat inputs. A 1.2 mm diameter wire permitted deposition widths of 5.92–13.15 mm, but widths larger than ~10 mm decreased the arc stability considerably. Laves length and carbide diameter decreased with travel speed, while the as-deposited hardness increased. These observations permitted a linear wall to be fabricated with a minimal heat input per layer of 181–185 J/mm. An increase in the solution treatment temperature from 980 to 1040 °C reduced microsegregation, Laves and δ phase precipitation. Localised regions with high microhardness were found near interlayer regions due to a local dissolution of Nb-rich eutectic phases. Compared to powder-based additive manufacturing, CMT-WAAM IN718 exhibits a larger melt pool size and lower as-deposited hardness, but has been found to show satisfactory ageing response and similar Laves phase area fraction.

Experimental Study on Laser Welding of AISI 304 Steel with Design of Experiments Approach

Austenitic stainless steels find extensive applications in engineering and structural parts requiring inherent corrosion resistance. The main objective of this study is to achieve good quality butt joint in 2.5-mm thick 304 grade Stainless Steel. The joint quality is quantified in terms of weld-bead dimensions. The main issue that manufacturers face is controlling the input process parameters, to get a good quality joint, with required weld bead geometry under controlled thermal distortion. The objective of this work is to select proper input process parameters that would result in desirable weld-bead profiles with minimal heat input. The critical process parameters influencing laser-welding were found using response surface methodology technique. The results proved that the developed model could efficiently predict the responses. The criteria demonstrated a possible reduction in top width of weld bead with enhanced depth of penetration, which automatically envisaged an increase in aspect ratio. A two-factor five-level criteria design was used for predicting the optimized parameters by performing multi-response optimization. Among them, the third criterion has shown a significant decrease in heat input and it was chosen as the best-optimized parameter.

Effects of high pressure, microwave and ultrasound processing on proteins and enzyme activity in dairy systems — A review

Abstract High-pressure processing (HPP), microwaves (MW) and ultrasound (US) are used for pasteurization with minimum heat input. They also alter physico-chemical properties of milk proteins and enzymes. This article aims at identifying the important changes in milk proteins imparted by these three processing technologies. HPP dissociates casein micelles at low pH ( 400 MPa). MW treatment denatures whey proteins rapidly, even below their thermal denaturation temperatures. High-power MW treatment (e.g. 60 kW) deactivates enzymes by denaturing them. However, low-power controlled MW irradiation (e.g. 30 W) improves enzyme activity. Ultrasound can homogenize protein aggregates in dairy systems and cause whey protein denaturation. Sonication under applied pressure and heat (e.g. 3.5 kg/cm2, 126.5 °C) causes enzyme inhibition while mild sonication conditions can improve enzyme activity. Industrial relevance HPP, MW and US are gaining popularity in the dairy industry due to their ability to pasteurize and functionalize dairy streams with minimal heat input. This review offers insights into how these technologies can be used in isolation or in combination to alter milk proteins and enzyme activity for different academic and industrial applications. However, to fully understand the potential of HPP, MW and US treatment on dairy systems, further research is required in several areas including health related nutritional changes in milk and milk products caused by these technologies.

Relationship between Microstructure, Residual Stress and Thermal Aspect in Friction Stir Welding of Aluminum AA1050

Abstract Residual stresses (RS) are present in many fabricated structures due to local plastic deformation from thermal and mechanical operations during manufacturing such as Friction Stir Welding. The among the objectives of FSW is used to obtain high quality of joining which means eliminate defects, minimize heat input and/or high mechanical properties. The case of FSW process is more complicate since it leads to the development of residual stress in welded zone and, also, in TMAZ, caused by tool rotation. In the present paper, the effects of the thermal actions on the residual stress field occurring in FSW of AA1050 were investigated. Residual stress are measured in center of welded zone and in different distances from the joint for both retreating and advancing sides by XRD. Experimental results showed that residual stress in welded zone in FSW are higher when stirring rate increased. Also, the central zone of the joint is affected by large deformations resulting from a chaotic movement behind the tool. In this region, the grains of the base metal are fragmented by the tool and undergo dynamic recrystallization.

UV-fs-LA-ICP-MS Analysis of CO2-Rich Fluid Inclusions in a Frozen State: Example from the Dahu Au-Mo Deposit, Xiaoqinling Region, Central China

The recently developed technique of ultraviolet femtosecond laser ablation inductively coupled plasma mass spectrometry (UV-fs-LA-ICP-MS) combined with a freezing cell is expected to improve the analysis of CO2-rich fluid inclusions by decreasing their internal pressure and avoiding the common problem of uncontrolled explosive fluid release on ablation. Here, we report the application of this technique through the case study of CO2-rich fluid inclusions from the quartz vein-style Au-Mo deposit of Dahu in the Xiaoqinling region of central China. The concentrations of Li, B, Na, Al, K, Ca, Mn, Fe, Cu, Zn, Rb, Sr, Mo, Ag, Te, Cs, Ba, Au, Pb, and Bi were analyzed in 124 (not all for Al and Ca) fluid inclusions, which have low to moderate salinity and multiphase composition (liquid H2O + liquid CO2 ± vapor CO2 ± solids). The Dahu fluids are dominated by Na and K. The concentrations of Mo are always below the detection limit from 0.005 to 2 ppm (excluding values obtained from fluid inclusions with accidentally trapped solids). The Dahu ore fluids differ from metamorphic fluids in compositions and most likely represent two separate pulses of spent fluids evolved from an unexposed and oxidized magmatic system. The UV-fs-LA-ICP-MS analysis of fluid inclusions in a frozen state improves the overpressure problem of CO2-rich fluid inclusions during laser ablation. The transformation of gaseous and liquid CO2 into the solid state leads to a significant decline in the internal pressure of the fluid inclusions, while femtosecond laser pulses generate a minimal heat input in the sample and thus maintain the frozen state during ablation. Transient signals of CO2-rich fluid inclusions obtained in this study typically had one or multiple peaks lasting for more than 15 seconds, without an initial short signal spike as obtained by ns-LA-ICP-MS analysis of CO2-rich fluid inclusions at room temperature.

Dissimilar Electron Beam Welds of Nickel Base Alloy A625 with a 9% Cr-Steel for High Temperature Applications

Welding of thick walled components with an electron beam has great potential due to the minimal heat input, high reproducibility and cost-efficiency. In the present work electron beam welding was used to weld 50mm thick plates of cast Ni-base alloy A625 to ferritic/martensitic 9% Cr steel plates. The welds were creep exposed at 625°C with stress levels ranging between 156 - 100MPa. Microstructure analysis of the weld-seam and the heat affected zone was carried out using metallography and scanning electron microscopy employing the EBSD technique to determine the location of the creep rupture. Creep fracture is located in the heat affected zone of the 9% Cr steel. Electron beam welded samples were compared to shield metal arc welded samples regarding welding and creep resistance. The performance and related microstructure properties of the electron beam welded specimen are more than competitive to conventional metal-arc-welding procedures.

A Microkelvin Magnetic Flux Noise Thermometer

Due to its non-driven nature, noise thermometry intrinsically is the method of choice when minimal heat input during the temperature measurement is required. Our noise thermometer, experimentally characterized for temperatures between 42 \({{\upmu }}\)K and 0.8 K, is a magnetic Johnson noise thermometer. The noise source is a cold-worked high purity copper cylinder, 5 mm in diameter and 20 mm long. The magnetic flux fluctuations generated by the electrons’ Brownian motion is measured inductively by two dc-SQUID magnetometers simultaneously. Cross-correlation of the two channels leads to reduction of parasitic noise by more than one order of magnitude which allows for measuring the tiny noise powers at microkelvin temperatures.

자동차 변속기용 정밀 부품의 용접변형 감소화에 관한 연구

In recent years, a demand for precision-welding is increasing in wide industrial fields for getting a high quality welded structures. Although laser welding is commonly used for precision-welding, gas tungsten arc (GTA) welding is also attempted as a precision-welding due to the cost benefit. However, welding heat causes an uneven temperature distribution leading to welding deformation. Since it causes geometric errors and degrades product quality, welding distortion recently rises as an important issue in the field of automobile parts. To control welding deformation, it is needed to design in shapes that can maximize stiffness against deformation during welding; control the welding sequence; minimize heat input; and weld allowing reverse deformation; etc. Thus it is necessary to find the one, among such approaches, that can minimize the deformation range by mathematical analysis and understand how effective it would be when it is actually used in industrial fields. This study performs analyses by numerical calculations and experiments for the De-Tent Lever, one of transmission part that requires precision the most among automobile parts, as the subject of experiment. Decrease in welding deformation is required for this part, since there is currently a trouble in guaranteeing precision due to angular deformation by welding between boss and plate. Finally the ways to minimize welding deformation has been suggested in this study through analyses on it.

Welding of Ti-6Al-4V alloy using dynamically controlled plasma arc welding process

A novel dynamically controlled plasma arc welding process was introduced, which is able to minimize heat input into the workpiece materials while maintaining desired full penetration, and it was used to weld Ti-6Al-4V alloy sheets. The microstructures, facture surfaces and microhardness of the welded joints were characterized by using optical microscope, scanning electron microscope (SEM) and Vickers microhardness tester. Comparing with welds such as gas tungsten arc and conventional plasma arc processes, the experimental results revealed the improvements when using the present process including: 1) reducing prior-beta ( β) grain size and prohibiting formation of hard martensite phases in the fusion zone due to the decreased heat input; and 2) better toughness and higher hardness.

Seawater desalination with memstill technology - a sustainable solution for the industry

Membrane Distillation may be applied over several different configurations to carry out seawater desalination. Using a microporous non-selective hydrophobic membrane, a finite air gap, and a cool surface in a particular arrangement, heat transfer may be employed to drive the transport of only water vapour across the membrane. Several limitations in conventional Membrane Distillation platforms dramatically reduce the viability of this water purification technology, namely low transmembrane fluxes, high thermal energy requirements, and low freshwater recovery rates. Keppel Seghers, through the logical application of system integration expertise, has succeeded in systematically removing these limitations during the development of Memstill technology. Memstill technology is a proprietary application of Membrane Distillation in an ideal counter-current flow configuration which allows for highly efficient recovery of heat within the desalination process. The recovery of heat within the Memstill process allows desalination to be driven with a minimal heat input. As such, Memstill desalination may be conducted using waste heat sources that would otherwise be rejected to the atmosphere. In addition, the efficient recovery of heat from the outlet stream of Memstill implies that it may be discharged at significantly lower temperatures than conventional thermal Membrane Distillation platforms. Keppel Seghers has conducted three previous pilot trials of Memstill technology, and is prepared to design, build, own and operate a Memstill demonstration plant with a freshwater production capacity of about 100 m3/day on a petroleum refinery in Singapore. This work will be carried out with the support of PUB.

Numerical model of CO 2 laser welding of thermoplastic polymers

Nowadays laser welding of plastics can offer flexible seam contouring, minimal heat input, mechanical stress and consistent weld quality. Therefore the laser welding represents an alternative to conventional joining techniques for plastics. The availability of reliable numerical models can help researchers and engineers to give a better place in industrial scale situations to plastics laser welding. In this paper thermo-morphologic and mechanical behaviour of moulded thermoplastic polymers during the laser welding were simulated by means of the finite element method (FEM). Keyhole and conduction welding for butt and overlap configurations were analysed. Recrystallized zones and penetration depth were calculated for different laser welding speeds and powers. The undesired phenomenon of the polymer decomposition associated with recrystallization and thermal heating were predicted and made controllable by varying the laser power and run speed. This investigation showed that laser welding of thermoplastic polymers can be reasonable modelled by FEM both for keyhole and conduction welding conditions.