Thermal Aspects of the Split-Beam Laser Welding Concept

1991 ◽  
Vol 113 (2) ◽  
pp. 215-221 ◽  
Author(s):  
Elijah Kannatey-Asibu
Keyword(s):  
Heat Source ◽  
Laser Welding ◽  
Cooling Rate ◽  
Weld Pool ◽  
Heat Input ◽  
Total Heat ◽  
Source Process ◽  
Heat Sources ◽  
Single Source ◽  
Beam Laser

The high cooling rates normally encountered in the application of high intensity welding processes such as laser beam welding is often detrimental to the weldment, especially for high hardenability steels. To minimize this effect, the split-beam laser welding concept is proposed and analyzed. The analysis shows that even when the intensity of the single heat source is the same as the intensity of each of the dual heat sources, the resulting cooling rate at any specific temperature is lower for the dual source process than the single source process. For example, for mild steel, the cooling rate at a point 25 mm behind the heat source (where the temperature is 1364°C) was determined to be 382°C/s for the single source system, while that for a point 40 mm behind the major source (where the temperature is 1377°C) was determined to be 206°C/s for the dual heat source system. When the heat inputs for the dual system are reduced such that the total heat input is equal to that of the single source system, the resulting temperature rise is lower at all points of the weldment for the dual system. That also means a smaller weld pool size and heat affected zone. To maintain the same weld pool size and penetration as for the single heat source system then requires an increased total heat input for the dual heat source system, with the additional input depending on the spacing between the two heat sources.

Comparison on welding mode characteristics of arc heat source for heat input control in hybrid welding of aluminum alloy

2015 ◽  
Vol 29 (06n07) ◽  
pp. 1540016
Author(s):  
Moo-Keun Song ◽  
Jong-Do Kim ◽  
Jae-Hwan Oh
Keyword(s):  
Experimental Study ◽  
Aluminum Alloy ◽  
Heat Source ◽  
Laser Welding ◽  
Heat Input ◽  
Heat Sources ◽  
Hybrid Welding ◽  
Input Control ◽  
Mode Characteristics ◽  
Pulsed Arc

Presently in shipbuilding, transportation and aerospace industries, the potential to apply welding using laser and laser-arc hybrid heat sources is widely under research. This study has the purpose of comparing the weldability depending on the arc mode by varying the welding modes of arc heat sources in applying laser-arc hybrid welding to aluminum alloy and of implementing efficient hybrid welding while controlling heat input. In the experimental study, we found that hybrid welding using CMT mode produced deeper penetration and sounder bead surface than those characteristics produced during only laser welding, with less heat input compared to that required in pulsed arc mode.

A NEW HEAT SOURCE MODEL FOR KEYHOLE MODE LASER WELDING

2021 ◽  
pp. 1-14
Author(s):  
Samuel Lorin ◽  
Julia Madrid ◽  
Rikard Söderberg ◽  
Kristina Wärmefjord
Keyword(s):  
Heat Source ◽  
Laser Welding ◽  
Heat Input ◽  
Source Model ◽  
Fluid Simulation ◽  
Heat Sources ◽  
Heat Source Model ◽  
Mode Laser ◽  
Standard Heat

Abstract Laser welding is a common technique for joining metals in many manufacturing industries. Due to the heat input and the resulting melting and solidification, the parts deform causing residual distortion and residual stresses. To assure the geometrical and functional quality of the product, Computational Welding Mechanics (CWM) is often employed in the design phase to predict the outcome of different design proposals. Furthermore, CWM can be used to design the welding process with the objective of assuring the quality of the weld. However, welding is a complex multi-physical process and in a design process it is typically not feasible, for example, to employ fluid simulation of the weld pool in order to predict deformation, especially if a set of design proposals is under investigation. Instead, what is used is a heat source that emulates the heat input from the melt pool. However, standard heat sources are typically not flexible enough to capture the fusion zone for deep keyhole mode laser welding. In this paper, a new heat source model for keyhole mode laser welding is presented. In an industrial case study, a number of bead on plate welds have been employed to compare standard weld heat sources and develop the new heat source model. The proposed heat source is based on a combination of standard heat sources. From the study, it was concluded that the standard heat sources could not predict the observed melted zone for certain industrial application while the new heat source was able to do so.

Numerical Analysis of Solidification Behavior during Laser Welding Nickel-Based Single-Crystal Superalloy Part: II Crystallography-Dependent Supersaturation of Liquid Aluminum

2021 ◽  
Vol 1018 ◽  
pp. 13-22
Author(s):  
Zhi Guo Gao
Keyword(s):  
Laser Welding ◽  
Single Crystal ◽  
Weld Pool ◽  
Welding Speed ◽  
Heat Input ◽  
Laser Power ◽  
Liquid Aluminum ◽  
Dendrite Growth ◽  
Solidification Cracking ◽  
Solid Liquid Interface

The thermal metallurgical modeling of liquid aluminum supersaturation was further developed through couple of heat transfer model, dendrite selection model, multicomponent dendrite growth model and nonequilibrium solidification model during three-dimensional nickel-based single-crystal superalloy weld pool solidification. The welding configuration plays more important role in supersaturation of liquid aluminum, morphology instability and nonequilibrium partition behavior. The bimodal distribution of liquid aluminum supersaturation along the solid/liquid interface is crystallographically symmetrical about the weld pool centerline in (001) and [100] welding configuration. The distribution of liquid aluminum supersaturation along the solid/liquid interface is crystallographically asymmetrical throughout the weld pool in (001) and [110] welding configuration. Optimum low heat input (low laser power and high welding speed) with (001) and [100] welding configuration is more favored to predominantly promote epitaxial [001] dendrite growth to reduce the metallurgical factors for solidification cracking than that of high heat input (high laser power and slow welding speed) with (001) and [110] welding configuration. The lower the heat input is used, the lower supersaturation of liquid aluminum is imposed, and the smaller size of vulnerable [100] dendrite growth region is incurred to ameliorate solidification cracking susceptibility and vice versa. The overall supersaturation of liquid aluminum in (001) and [100] welding configuration is beneficially smaller than that of (001) and [110] welding configuration regardless of heat input, and is not thermodynamically relieved by gamma prime γˊ phase. (001) and [110] welding configuration is detrimental to weldability and deteriorates the solidification cracking susceptibility because of unfavorable crystallographic orientations and alloying aluminum enrichment. The mechanism of asymmetrical solidification cracking because of crystallography-dependent supersaturation of liquid aluminum is proposed. The eligible solidification cracking location is particularly confined in [100] dendrite growth region. Moreover, the theoretical predictions agree well with the experiment results. The useful modeling is also applicable to other single-crystal superalloys with similar metallurgical properties for laser welding or laser cladding. The thorough numerical analyses facilitate the understanding of weld pool solidification behavior, microstructure development and solidification cracking phenomena in the primary γ phase, and thereby optimize the welding conditions (laser power, welding speed and welding configuration) for successful crack-free laser welding.

The New Heat Source Model of AZ31B Magnesium Alloy Laser-TIG Hybrid Welding

2019 ◽  
Vol 815 ◽  
pp. 120-124 ◽  
Author(s):  
Zhong Lin Hou ◽  
Tan Zhao ◽  
Zhen Xu ◽  
Long Hao Zhu ◽  
Jian Hua Sun ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Heat Source ◽  
Weld Pool ◽  
Inflection Point ◽  
Source Model ◽  
Hybrid Welding ◽  
Single Source ◽  
Heat Source Model ◽  
Keyhole Effect ◽  
Body Heat

A new heat source model consisted of inverted conical heat source and rotary Gauss body heat source is established using the CAE software for the keyhole effect of laser-TIG hybrid welding. The inverted conical heat source is used for analyzing the wide upper part of weld pool due to the rapid heat up by the laser and arc. The rotary Gauss body heat source model is used for analyzing the long and narrow lower part of weld pool formed by the laser. The result showed that, compared with other single source mode, this new heat source model may get a better simulation of the weld pool morphology, especially the inflection point near the keyhole. It provides a new method to predict the morphology and size of the weld pool of magnesium alloy laser-TIG welding.

scholarly journals Numerical simulation of the weld pool dynamics during pulsed laser welding using adapted heat source models

Procedia CIRP ◽  
2018 ◽  
Vol 74 ◽  
pp. 679-682
Author(s):  
Fritz Lange ◽  
Antoni Artinov ◽  
Marcel Bachmann ◽  
Michael Rethmeier ◽  
Kai Hilgenberg
Keyword(s):  
Numerical Simulation ◽  
Heat Source ◽  
Laser Welding ◽  
Weld Pool ◽  
Pulsed Laser ◽  
Pulsed Laser Welding ◽  
Source Models

Angular Distortion Reduction by In-Process Control Welding Using Back Heating Source

2008 ◽  
Vol 580-582 ◽  
pp. 585-588 ◽  
Author(s):  
Shigetaka Okano ◽  
Masahito Mochizuki ◽  
Masao Toyoda
Keyword(s):  
Process Control ◽  
Heat Source ◽  
Heat Input ◽  
Angular Distortion ◽  
Welding Distortion ◽  
Manufacturing Cost ◽  
Heat Sources ◽  
Heating Method ◽  
Heating Source ◽  
Proper Condition

In order to reduce the number of fabricating processes, it is preferable to control welding distortion during welding; instead of using restraints before the process, or correcting the distortion after the process. The benefits of eliminating extra processes include the reduction of the time and manufacturing cost. This paper presents a method of back heating and welding in tandem, with the back heating occurring at a constant distance from the welding torch during welding. Traditionally, the back heating method has reduced angular distortion in two different ways; One is to bend the welded material in the opposite direction, and the other is homogenization of temperature distribution along the thickness. But, it has recently become known that the angular distortion produced by multiple heat sources, in tandem placement, is not always predicted by the total heat input to the welded joint; and it is possible for the distortion to differ greatly due to factors such as the distance between two heat sources, heat input parameters, and the heat input ratio. Based on these findings, angular distortion is expected to be reduced more effectively by choosing the proper condition for the heat source arrangement in back heating. In this paper, reduction of angular distortion by in-process control welding, using a back heating source, is numerically analyzed by the three-dimensional thermal elastic-plastic analysis, considering moving heat source with weld metal deposition. It was confirmed that the back heating method is effective in reducing angular distortion without restraint or correction. Proper condition concerning the heat source arrangement can be chosen and angular distortion can be perfectly controlled by back heating with ten percent of the welding heat input.

Modeling the Transport Phenomena in Moving 3-D Dual-Beam Laser Keyhole Welding

2005 ◽  
Author(s):  
J. Zhou ◽  
H. L. Tsai ◽  
P. C. Wang
Keyword(s):  
Laser Beam ◽  
Laser Welding ◽  
Weld Pool ◽  
Transport Phenomena ◽  
Pool Shape ◽  
Beam Laser ◽  
Dual Beam ◽  
Laser Keyhole Welding ◽  
Weld Pool Shape ◽  
Welding Technique

In recent years, laser-beam welding using two laser beams, or dual-beam laser welding, has become an emerging welding technique. Previous studies have demonstrated that it can provide benefits over conventional single-beam laser welding, such as increasing keyhole stability, slowing down cooling rate and delaying the humping onset to a higher welding speed. It is reported that the dual beam laser welding can significantly improve weld quality. However, so far the development of the dual-beam laser welding technique has been limited to the trial-and-error procedure. In this study, the objective is to develop mathematical models and the associated numerical techniques to investigate the transport phenomena, such as heat transfer, metal flow, keyhole formation and weld pool shape evolutions during the moving three-dimensional dual-beam laser keyhole welding. Detailed studies have been conducted to determine the effects of key parameters, such as laser-beam configuration on weld pool fluid flow, weld shape, and keyhole dynamics. Some experimentally observed phenomena, such as the changes of the weld pool shape from oval to circle and from circle to oval during the welding process are predicted and can be well explained by the present model.

A Dual-Source Organic Rankine Cycle (DORC) for Improved Efficiency in Conversion of Dual Low- and Mid-Grade Heat Sources

2009 ◽  
Author(s):  
F. David Doty ◽  
Siddarth Shevgoor
Keyword(s):  
Heat Source ◽  
Heat Input ◽  
Temperature Limit ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Low Grade ◽  
Heat Sources ◽  
Reaction Products ◽  
Pinch Point ◽  
Low Grade Heat

Detailed thermodynamic and systems analyses show that a novel hybrid cycle, in which a low-grade (and low-cost) heat source (340 K to 460 K) provides the boiling enthalpy and some of the preheating while a mid-grade source (500 K to 800 K) provides the enthalpy for the final superheating, can achieve dramatic efficiency and cost advantages. Four of the more significant differences from prior bi-level cycles are that (1) only a single expander turbine (the most expensive component) is required, (2) condenser pressures are much higher, (3) the turbine inlet temperature (even with a low-grade geothermal source providing much of the energy) may be over 750 K, and (4) turbine size is reduced. The latent heat of vaporization of the working fluid and the differences in specific heats between the liquid and vapor phases make full optimization (approaching second-law limits) impossible with a single heat source. When two heat sources are utilized, this problem may be effectively solved — by essentially eliminating the pinch point. The final superheater temperature must also be increased, and novel methods have been investigated for increasing the allowable temperature limit of the working fluid by 200 to 350 K. The usable temperature limit of light alkanes may be dramatically increased by (1) accommodating hydrogen evolution from significant dehydrogenation; (2) periodically or continually removing undesired reaction products from the fluid; (3) minimizing the fraction of time the fluid spends at high temperatures. Detailed simulation results are presented for the case where (1) the low-grade heat source (such as geothermal) is 400 K and (2) the mid-grade Concentrated Solar Power (CSP) heat source is assumed to be 720 K. For an assumed condensing temperature of 305 K and working fluid flow rate of 100 kg/s, preliminary simulations give the following: (1) low-grade heat input is 25 MWT; (2) mid-grade heat input is 24 MWT; (3) the electrical output power is 13.5 MWE; and (4) the condenser rejection is only 35 MWT. For comparison, with a typical bi-level ORC generating similar power from this geothermal source alone, the low-grade heat requirement would be ∼100 MWT.

Fluid Flow and Weld Pool Dynamics in Dual-Beam Laser Keyhole Welding

2003 ◽  
Author(s):  
J. Hu ◽  
H. L. Tsai
Keyword(s):  
Fluid Flow ◽  
Laser Welding ◽  
Weld Pool ◽  
Welding Process ◽  
Laser Beams ◽  
Pool Shape ◽  
Beam Laser ◽  
Dual Beam ◽  
Oval Shape ◽  
Weld Pool Shape

The use of dual or multiple laser beams is necessary for welding thick-section metals, especially for Nd:Yag lasers which are limited to relatively low power as compared to CO2 lasers. It was also reported that the use of dual laser beams for welding can increase keyhole stability leading to a better weld quality. So far, the development of dual-beam laser welding technologies has been in the experimental stage. The objective of this paper is to develop mathematical models and the associated numerical techniques to calculate the transient heat transfer and fluid flow in the weld pool and to study weld pool dynamics during the dual-beam laser welding process. The simulation was conducted for a three-dimensional stationary dual-beam laser welding. A very interesting change of the top-surface view of the weld pool was predicted. During the welding process, the top-view shape of the weld pool changes, starting from an oval-shape with the long-axis connecting the centers of the two laser beams, to a circle, and finally to an oval-shape with the short-axis connecting the centers of the two laser beams. Although a direct comparison with published experimental observation is impossible (due to the lack of detailed experimental data), the predicted weld pool shape is similar to that observed from experiments. The dynamical change of the weld pool shape can be well explained by the predicted fluid flow field.

Edge Weld Cooling Rates

1983 ◽  
Vol 7 (1) ◽  
pp. 25-32 ◽  
Author(s):  
A.S. Oddy ◽  
M.J. Bibby
Keyword(s):  
Numerical Modelling ◽  
Heat Source ◽  
Cooling Rate ◽  
Heat Sources ◽  
Cooling Rates ◽  
Volume Heat ◽  
Modelling Techniques ◽  
Experimental Values ◽  
Point Line ◽  
Infinite Temperature

Numerical modelling techniques are used to investigate the effect of heat source shape on the cooling rate (at 700 C) of edge welds. Cooling rates are determined for point, line, planar and volume heat sources. These, in turn, are compared to experimental values and to cooling rates calculated by the traditional Adams[1] relationship where the heal source is approximated by a line of no volume and infinite temperature. The experience presented in this investigation provides a basis for rationalizing the effect of heat source approximations on the 700 C cooling rate calculated by traditional methods.

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