Alternating grain orientation and weld solidification cracking

Kou, Sindo; Le, Yi

doi:10.1007/bf02670376

Cited by 76 publications

(45 citation statements)

References 4 publications

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“…Free or forced convection in the weld pool can result in dendrite fragmentation in the mushy zone near the trailing edge of the weld pool and detachment of partially melted grains from the weld pool boundary at the sides. [10] The dendrite debris and partially melted grains are then swept into the bulk weld pool, which can act as nuclei for the formation of new grains. Physical disturbance can be induced into the weld pool by different techniques, e.g., pulsed current and magnetic arc oscillation in GTA welding and beam oscillation in EB welding.…”

Section: Introductionmentioning

confidence: 99%

Influence of Weld Cooling Rate on Microstructure and Mechanical Properties of Alloy 718 Weldments

Sivaprasad

Raman

2008

Metall Mater Trans A

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Even though alloy 718 is the best for welding among all nickel-base superalloys, the formation of the Laves phase in welds is a major concern. The presence of this phase drastically degrades mechanical properties of the welds. To study the influence of weld cooling rate on microstructure and mechanical properties of alloy 718 weldments, two distinct welding processes were adopted-gas tungsten arc (GTA) and electron beam (EB) welding. The EB welding resulted in finer and relatively discrete Laves phase in lower quantity due to higher cooling rates prevailing in this process. On the other hand, due to lower cooling rates, GTA weld fusion zones exhibited coarse Laves with higher niobium. Depletion of the primary strengthening element niobium in the surrounding regions of Laves promoted crack propagation. Because EB welds had finer and lower amount of Laves, EB weldments exhibited superior mechanical properties compared with GTA weldments.

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Section: Introductionmentioning

confidence: 99%

Influence of Weld Cooling Rate on Microstructure and Mechanical Properties of Alloy 718 Weldments

Sivaprasad

Raman

2008

Metall Mater Trans A

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“…This method also adopted by many previously reported experimental investigations for the grain structure evolution in the weld. [21][22][23][24] To obtain the full penetrated weld, the welding current is 110 A, the voltage is 12 V, and the speed is 1.5 mm/s in the simulation. The material properties of the carbon steel are obtained from the reference.…”

Section: The Model Descriptionmentioning

confidence: 99%

Multi-scale Simulation for the Columnar to Equiaxed Transition in the Weld Pool

Han

Dong

et al. 2016

ISIJ Int.

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The heat and mass transfer behavior and the morphological evolution of the solidification structures in the weld pool were simulated by the multi-scale model which combines the finite element (FE) and the cellular automata (CA) methods to investigate the columnar to equiaxed transition (CET) process during welding. The grain structure evolution within the entire weld and the competitive dendrite growth at different locations were studied to better understand the CET process. The results indicate that with the decrease of the distance to weld center, the undercooled zone width and the maximum undercooling increase. In this case, more equiaxed dendrites form in the undercooled melt, and the distance between the equiaxed dendrites and the columnar front also becomes lager. There is more space for the equiaxed dendrites to grow up and block the columnar dendrites. Therefore, the equiaxed dendrites become more competitive, and the CET tendency increases.

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“…Propagation of weld solidification cracks from weld pass to weld pass is described in (Kou and Le 1985). Solidification cracking is intergranular and propagates due to the thermal stresses and contamination acting behind the solidifying pool.…”

Section: 2mentioning

confidence: 99%

Fabrication Flaw Density and Distribution In Repairs to Reactor Pressure Vessel and Piping Welds

Schuster¹,

Simonen²,

Doctor³

2008

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The Pacific Northwest National Laboratory is developing a generalized fabrication flaw distribution for the population of nuclear reactor pressure vessels and for piping welds in U.S. operating reactors. The purpose of the generalized flaw distribution is to predict component-specific flaw densities. The estimates of fabrication flaws are intended for use in fracture mechanics structural integrity assessments. Structural integrity assessments, such as estimating the frequency of loss-of-coolant accidents, are performed by computer codes that require, as input, accurate estimates of flaw densities. Welds from four different reactor pressure vessels and a collection of archived pipes have been studied to develop empirical estimates of fabrication flaw densities.This report describes the fabrication flaw distribution and characterization in the repair weld metal of vessels and piping. This work indicates that large flaws occur in these repairs. These results show that repair flaws are complex in composition and sometimes include cracks on the ends of the repair cavities. Parametric analysis using an exponential fit is performed on the data.The relevance of construction records is established for describing fabrication processes and product forms. An analysis of these records shows there was a significant change in repair frequency over the years when these components were fabricated. A description of repair flaw morphology is provided with a discussion of fracture mechanics significance. Fabrication flaws in repairs are characterized using optimized-access, high-sensitivity nondestructive ultrasonic testing. Flaw characterizations are then validated by other nondestructive evaluation techniques and complemented by destructive testing.iii

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Alternating grain orientation and weld solidification cracking

Cited by 76 publications

References 4 publications

Influence of Weld Cooling Rate on Microstructure and Mechanical Properties of Alloy 718 Weldments

Influence of Weld Cooling Rate on Microstructure and Mechanical Properties of Alloy 718 Weldments

Multi-scale Simulation for the Columnar to Equiaxed Transition in the Weld Pool

Fabrication Flaw Density and Distribution In Repairs to Reactor Pressure Vessel and Piping Welds

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