Effect Of Preheat Research Articles

Effect of Wire Preheat and Feed Rate in X80 Steel Laser Root Welds: Part 2 — Mechanical Properties

In Part 1 of this study, the influences of feed rate and preheat of the wire on the fusion zone microstructure of X80 steel laser root welds were investigated. Part 2 of this study reveals the effect of cold versus hot wire feed on mechanical properties. Although strength overmatching with the X80 base metal was maintained, the wire alloying elements reduced the hardness of the upper region of the laser fusion zone but had limited effect on the bottom of the fusion zone due to the incomplete mixing of the filler material with the base metal in the bottom root region of the joint. The addition of ER70S-6 filler wire improved the impact toughness of the weld metal at 0°C, due to the formation of an acicular ferrite microstructure. As the temperature decreased to –20°C (–4°F) and –45°C (–49°F), ductile to brittle transition occurred, leading to lower weld metal toughness.

Effect of preheat in DED-LB/wire of Ni-base, Cu-base and Fe-base alloys

Preheating of welding wire by electric current is an established technique for increasing deposition rate during welding, but is a relatively new contribution to additive manufacturing. The few studies that have been performed for additive methods have focused on a limited selection of materials, typically only one material grade, which limits their relevance to other material grades. This study has investigated the effect of resistive wire preheating, also known as hotwire, in a coaxial directed energy deposition system with laser beam and wire (DED-LB/wire), across a wider range of material grades so that effects of hotwire on different alloy compositions and crystal lattice structures can be determined. Inconel 625, aluminium bronze, nickel-aluminium bronze, carbon steel, austenitic, martensitic and duplex stainless steels were examined to provide a sampling of Ni-, Cu- and Fe-based alloys, as well as a comparison of austenitic, martensitic and duplex stainless steels.

The Effect of Preheat and Post Weld Heat Treatment On Welding ASTM A 516 Grade 60 Material On Destructive Test Values

The Effect of Preheat and Post Weld Heat Treatment On Welding ASTM A 516 Grade 60 Material On Destructive Test Values

Analysis of Effect of Temperature Variation Preheat on SMAW Welding of Microstructures, and ST60 and SS400 Steel Hardness

Welding is a metal joining process by melting some base and filler metals. SMAW welding (Shielded Metal Arc Welding) is one of the industry's most widely used welding methods. SMAW welding requires preheating (preheating) to reduce residual stress, distortion, and cold cracking in the weld metal. Preheat also can affect the microstructure and hardness of the weld metal. This study aims to analyze variations preheating on SS400 and ST60 steel against micro tests by SMAW welding, namely electric arc welding with covered electrodes. Temperature variation preheating used in SS400 steel was 140°C, 170°C, 300°C and 400°C in ST 60 steel. The results showed that the higher the temperature preheat, the larger the grain size of the microstructure in the parent metal region, the heat-affected area, and the weld metal area. The higher temperature preheat also led to a decrease in violence in the three areas. ST60 steel has a larger microstructure grain size and lower hardness than SS400 steel at all temperature variations preheat.

A brief review on pre- and post-weld treatment of various grades of aluminium alloys

In the present paper, different types of pre- and post-weld treatments performed on aluminium alloys have been reviewed. Aluminium is the second most widely produced material after steel. Aluminium alloys can be welded using fusion welding techniques but they distort the weldments’ microstructure and the welds are prone to oxidation, porosity and cracking. Therefore, modern welding techniques like laser beam welding, electron beam welding and friction stir welding are now performed on aluminium alloys. Further, treatments like reinforcement, pre-weld and post-weld heat treatment and cryogenic treatment have also been performed by researchers and discussed in the paper. The application of various treatments has significantly improved the aluminium alloy weldments’ properties especially cryogenic treatment. The effect of preheat and cryogenic treatment on microstructure and mechanical properties of aluminium alloys’ weldments has not been researched properly and they require more attention of researchers.

Is pre-heat necessary for the measurement of 8-oxo-7,8-dihydroguanosine and 8-oxo-7,8-dihydro-2'-deoxyguanosine in urine samples.

BackgroundIt is currently unclear for the necessary of pre‐heating urine samples for the accurate determination of 8‐oxo‐7,8‐dihydroguanosine (8‐oxoG) and 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine (8‐oxodG). Thus, we conducted this study to evaluate the effect of pre‐heat (i.e., to 37°C) on the accurate measurement of 8‐oxoG and 8‐oxodG in frozen urine samples.MethodsRandom urine samples from six healthy volunteers, six patients with renal dysfunction, and six patients with systematic diseases such as diabetes were collected, split, and stored at −80°C for up to 1 month. The frozen samples were thawed at room temperature (RT) or 37°C for different time, 10‐fold diluted with ddH2O containing 1% formic acid, and determined by self‐established LC–MS/MS method coupled with an ACQUITY™ Primer HSS T3 column.ResultsThawing the samples at RT for 30 or 120 min, or at 37°C for 15 or 90 min did not affect the determination of 8‐oxoG and 8‐oxodG in urine samples. Moreover, no significant difference between thawing the urine samples at RT and 37°C was found after storing at −80°C for 1–3 months.ConclusionIt is not always necessary to pre‐heat the frozen urine samples to release 8‐oxoG and 8‐oxodG from precipitates, which is associated with different pre‐treatment and determination methods.

Effect of laser preheat in magnetized liner inertial fusion at OMEGA

Integrated magnetized liner inertial fusion (MagLIF) experiments on the OMEGA laser system are modeled to investigate the effects of laser preheat on implosion performance. In both simulations and experiments, preheating the fuel with a laser enhances the neutron yield, with the maximum yield occurring at an optimal preheat laser energy. Increasing the preheat energy past the optimal value reduces the neutron yield. In simulations, the rate of the drop in neutron yield depends on the inclusion of the Nernst effect. The Nernst effect advects the magnetic field away from the center of the fuel region during the preheat stage of MagLIF on OMEGA and weakens magnetic-flux compression. If the Nernst effect is not included, the simulated drop in yield past the optimal preheat laser energy is more gradual as opposed to the sharper drop seen in experiments. Simulations are able to model trend in measured ion temperatures seen in experiments. A mix model is used to show that including mix from the wall in the simulated fuel region further degrades the yield and lowers the optimal preheat laser energy. Simulations with mix predict that increasing the initial axial magnetic field may still enhance yield performance in integrated implosions.

Effect of preheat and encapsulation of steel particles on the interaction with Bisphenol A composites

In this study, the mechanical and thermal behavior of the steel particles (SP) fabricated epoxy-based composites were investigated. The purpose of using SP was to find out their suitability and compatibility to be used as low-cost fillers for epoxy-based composites. A special steel-cast metal mold was used to fabricate the composites via self-casting method. The effect of SP concentration (10, 20, 30 and 40 wt%) on various properties of the epoxy/SP composites was explored. Another sample was prepared using the optimum loading with a special treatment using heat and encapsulation of the SP. Mechanical properties of the composites were analyzed through tensile, flexural and impact testing. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to examine the structural and morphological properties. In addition, thermal properties of the composites were analyzed with the thermogravimetric analyzer (TGA). Results indicated that the addition of PS into epoxy improved both tensile and flexural strength up to 98.5% and 147.6%, respectively, compared to the neat epoxy (NE). The decomposition temperature was raised nearly 18 °C for adding 30 wt% SP which was the maximum among all other composites. Results showed that 30 wt% of SP was the optimum loading for the better properties of the composites. In addition, the preheat treatment of the particles and the encapsulation process established a better interaction between the epoxy and the particles which resulted in the superior performance of the composites compared to the other samples. Overall, the improved mechanical and thermal properties of the SP-fabricated epoxy composites indicate that the epoxy/SP composite is a good candidate for structural and high temperature applications.

Effect of preheat and post heat on mechanical properties of 6061 aluminium tungsten inert gas welded joints

Tungsten inert gas (TIG) welded joints of 6061 aluminium are often used in the fuel tanks of large launch vehicles, because of the massive loads these vehicles carry, dealing with weld reinforcement on TIG joints represents an important issue in their preheat and post heat on mechanical properties. Experimental and calculation methods were used to investigate the effect of weld preheat and post heat on the mechanical properties of these joints. The purpose of this study was to determine the effect of preheat and post heat on mechanical properties of 6061 aluminium. The experimental result indicated that mechanical properties of Al 6061 of the welding changed. The hardness of weld metal increase in temperature 130°C = 68,72 BHN, in 160°C = 70,51 BHN, and in 190°C = 76,26 BHN. Tensile strength also increase in temperature 130°C = 158,57 N/mm2, in 160°C = 169,85 N/mm2, in 190°C = 174,50 N/mm2.

Investigating Instabilities in a Rotating Detonation Combustor Operating With Natural Gas–Hydrogen Fuel Blend—Effect of Air Preheat and Annulus Width

Abstract Propagation characteristics of a detonation wave in an air-breathing rotating detonation combustor (RDC) using natural gas (NG)–hydrogen fuel blends is presented in this paper. Short-duration (∼up to 6 s) experiments were performed on a 152.4 mm OD uncooled RDC with two different annulus gap widths (5.08 mm and 7.62 mm) over a range of equivalence ratios (0.6–1.0) at varying inlet air temperatures (∼65–204 °C) and NG content (up to 15%) with precombustion operating pressure slightly above ambient. It was observed that the RDC, with an annulus gap width of 5.08 mm, was inherently unstable when NG was added to the hydrogen fuel while operating at precombustion pressures near ambient and at an inlet air temperature of 65 °C. Increasing the annulus gap width to 7.62 mm improved the stability of the detonation wave at similar temperatures and pressure permitting operation with as much as 5% NG by volume. While observed speeds of the detonation waves were still below theoretical values, an increase in inlet air temperature reduced the variability in wave speed. The frequency analysis thus explored in this study is an effort to quantify detonation instability in an RDC under varying operational envelope. The data presented are relevant toward developing strategies to sustain a stable detonation wave in an RDC using NG for land-based power generation.

English

English

Effects of preheat and mix on the fuel adiabat of an imploding capsule

We demonstrate the effect of preheat, hydrodynamic mix and vorticity on the adiabat of the deuterium-tritium (DT) fuel in fusion capsule experiments. We show that the adiabat of the DT fuel increases resulting from hydrodynamic mixing due to the phenomenon of entropy of mixture. An upper limit of mix, Mclean/MDT ≥ 0.98, is found necessary to keep the DT fuel on a low adiabat. We demonstrate in this study that the use of a high adiabat for the DT fuel in theoretical analysis and with the aid of 1D code simulations could explain some aspects of 3D effects and mix in capsule implosion. Furthermore, we can infer from our physics model and the observed neutron images the adiabat of the DT fuel in the capsule and the amount of mix produced on the hot spot.

Effect of preheat and layer thickness on selective laser melting (SLM) of magnesium

Purpose– The purpose of this paper is to investigate the effect of preheat and layer thickness in selective laser melting (SLM) of magnesium using pulse mode. Magnesium has been considered as a new generation of implant materials which are bioactive and biodegradable for orthopaedic applications.Design/methodology/approach– To produce optimal single magnesium tracks to compare the effect of layer thickness and preheat, different laser parameters were investigated. The analysis was made based on digital and electronic microscope images and mechanical measurements.Findings– Improvements in the magnesium tracks due to preheating were successfully achieved. The analysis shows better bonding to the surface. The preheated tracks present an improvement in quality surface: smoother and flatter surfaces are discovered for the low layer thicknesses. When the thickness increases, the surface was disrupted and presented high surface roughness values. These were attributed to the Marangoni convection.Originality/value– This study continues valuing the fabrication of magnesium with SLM. It shows the improvements of preheat and effect of different layer thicknesses on the part properties.

Numerical Investigation on Interruption in the Welding Process Used in Shipbuilding

Interruptions in the welding process in shipbuilding are unavoidable because of complex geometry and human fatigue. This article presents an uncoupled three dimensional finite element (FE) modeling technique for bead-on-plate welding and an interruption in the welding process for low carbon and high notch toughness steel plate typically used in shipbuilding. The goal of the FE model was to successfully predict the effect of various time delays in the welding interruption on the residual stress distributions. The FE results are compared with the experimental results for the validation of the model. The experimental work was completed using the neutron diffraction method. The element birth-and-death algorithm was used in ANSYSW to simulate the filler metal deposition. A double ellipsoid heat source was used to simulate the heat source of the weld pool. The FE model considers the temperature dependent nonlinear material properties and uses the temperature-dependent combined coefficient of heat loss. The study found that weld interruptions in the welding process change the residual stress patterns and cause an increase in the maximum longitudinal tensile residual stresses. However, the maximum longitudinal compressive stress reduces as a result of interruptions in the weld process. This study found that a weld interruption duration of approximately 2 minutes is optimum for both fatigue and buckling strength. This study also analyzed the effect of preheat on longitudinal residual stress distribution and concluded that a suitable short time lag without any preheat is equivalent to preheat after a long welding interval.

Effect of Pre-heat and Inert Gas Species on Cryogenic Aerosol Cleaning Performance in Semiconductor Manufacturing

Cryogenic aerosol cleaning is a dry cleaning method used in the back end of line (BEOL) semiconductor manufacturing to remove defects from planar hydrophobic surfaces such as SiCOH and SiCxNyHz. Cryogenic aerosol cleaning is preferred over conventional wet cleaning methods as it is a non-contact cleaning method, which uses inert gases to generate sub-micrometer-sized solid aerosol particles that physically remove nanometer-sized contaminants on wafer surfaces. Particle removal mechanism involves detachment of the particles upon impact with aerosol, diffusion, and finally entrainment away from the wafer. In BEOL metal line patterning, particles on the dielectric isolation surfaces translate through the subsequent lithography and copper fill steps in to single or multiple metal line open defects that are yield killers. In this study, we show that the particle removal performance of the standard aerosol cleaning can be enhanced by pre-heating the wafer and use of a higher molecular weight inert gas, namely Ar, for aerosol generation. Both the addition of a Pre-heat step and the use of Ar as the aerosol source showed 47–52% reduction in single and multiple line opens detected through wafer electrical tests during high volume semiconductor manufacturing process.

Thermomechanical Analysis of Preheat Effect on Grade P91 Steel During GTA Welding

Effect of preheat on the thermal cycles, residual stress, and distortion during autogenous GTA welding of Grade P91 steel has been analyzed using FEM. Phase transformation effect on the residual stresses is also analyzed. Thermomechanical analysis has shown that preheat reduced the peak temperatures, cooling rate, and the distortion values. The phase transformation involving martensite during cooling resulted in typical “M” shaped residual stress profile with a reduction in peak tensile residual stress value and a wider distribution of residual stress. There is good agreement between the predicted and measured thermal cycles, residual stresses, and distortion of the P91 steel weld joint.

Numerical Analysis of Effect of Preheat and Swirl of Inlet Air on Temperature Profile in Canister Burner

The main purpose of this paper is to study the Computational Fluid Dynamics (CFD) prediction on temperature distribution inside the canister burner with inlet air pre-heating of 100K and 250K while varying the swirl angle of the radial swirler. Air swirler adds sufficient swirling to the inlet flow to generate central recirculation region (CRZ) which is necessary for flame stability and fuel air mixing enhancement. Therefore, designing an appropriate air swirler is a challenge to produce stable, efficient and low emission combustion with low pressure losses. A liquid fuel burner system with different radial air swirler with 280 mm inside diameter combustor of 1000 mm length has been investigated. Analysis were carried out using four different radial air swirlers having 30°, 40°, 50° and 60° vane angles. The flow behavior was investigated numerically using CFD solver Ansys Fluent. This study has provided characteristic insight into the distribution of temperature inside the combustion chamber. Results show that with the inlet air preheat before the combustion, the temperature distribution inside the canister would stabilize early into the chamber with higher swirl number (SN) compared without inlet air preheat. As for the inlet air preheat, the main effects are the resulting temperatures in the canister are higher, but there is a smaller hot-spot in the flame. This means that the temperature profile in the chamber is well distributed.

辐射驱动实验中预热对冲击波速度诊断的影响

辐射驱动实验中预热对冲击波速度诊断的影响

Effect of preheat on TIG welding of AZ61 magnesium alloy

The effects of preheat treatments on the microstructures and mechanical properties of tungsten inert gas (TIG)-welded AZ61 magnesium alloy joints were studied by microstructural observations, microhardness tests and tensile tests. The results showed that the volume fraction of the lamellar β-Mg17(Al,Zn)12 intermetallic compound of in fusion zone (FZ) increased from 15% to 66% with an increase in preheat temperature. Moreover, the microhardness of the FZ and the ultimate tensile strength of the welded joints reached their maximum values when the preheat temperature was 300°C because more lamellar β-Mg17(Al,Zn)12 intermetallic compounds were distributed at the α-Mg grain boundaries and no cracks and pores formed in the FZ of the welded joint.

Using optically stimulated electrons from quartz for the estimation of natural doses

A flow-through Geiger-Müller pancake electron detector attachment has been fitted to a standard Risø TL/OSL reader enabling optically stimulated electrons (OSE) to be measured simultaneously with optically stimulated luminescence (OSL). Using this detector, OSE and OSL measurements from natural quartz samples are studied to examine the possible use of OSE as a chronometer. First the relative variability in OSE and OSL growth curve shapes and the effect of preheat on these are presented, and from these curves, conclusions are drawn concerning the charge movement in natural quartz. Secondly, a dose recovery test shows that OSE can successfully recover a laboratory dose of 300 Gy given before any laboratory thermal treatment, for preheating temperatures between 160 and 260 °C. Furthermore, for the first time natural OSE decay curves are detected and these signals are used to estimate a burial dose using the single-aliquot regenerative-dose (SAR) procedure. Finally, a comparative study of the equivalent doses estimated using both OSE and OSL from 10 quartz samples are presented, and it is shown that OSE has a significant potential in retrospective dosimetry.