Welding-Induced Microstructure Evolution of a Cu-Bearing High-Strength Blast-Resistant Steel

Abstract

A new high strength, high toughness steel containing Cu for precipitation strengthening was recently developed for naval, blast-resistant structural applications. This steel, known as BlastAlloy160 (BA-160), is of nominal composition Fe-0.05C-3.65Cu-6.5Ni-1.84Cr-0.6Mo-0.1V (wt pct). The evident solidification substructure of an autogenous gas tungsten arc (GTA) weld suggested fcc austenite as the primary solidification phase. The heat-affected zone (HAZ) hardness ranged from a minimum of 353 HV in the coarse-grained HAZ (CGHAZ) to a maximum of 448 HV in the intercritical HAZ (ICHAZ). After postweld heat treatment (PWHT) of the spot weld, hardness increases were observed in the fusion zone (FZ), CGHAZ, and fine-grained HAZ (FGHAZ) regions. Phase transformation and metallographic analyses of simulated single-pass HAZ regions revealed lath martensite to be the only austenitic transformation product in the HAZ. Single-pass HAZ simulations revealed a similar hardness profile for low heat-input (LHI) and high heat-input (HHI) conditions, with higher hardness values being measured for the LHI samples. The measured hardness values were in good agreement with those from the GTA weld. Single-pass HAZ regions exhibited higher Charpy V-notch impact toughness than the BM at both test temperatures of 293 K and 223 K (20°C and -50°C). Hardness increases were observed for multipass HAZ simulations employing an initial CGHAZ simulation.

Weldability Evaluation of a Cu-Bearing High-Strength Blast-Resistant Steel

“…The SSGBs were observed to connect via an epitaxial link with the prior austenite grain boundaries of the PMZ, consistent with observations from autogenous weld microstructures. [3] Overall, the microstructure suggested that good wetting and penetration of liquid occurred along the prior austenite grain boundaries.…”

“…The microstructure evolution during welding has been established from autogenous welding experiments and heat-affected zone (HAZ) simulations. [3] Advanced characterization of simulated HAZ microstructures was completed to understand the observed HAZ hardness profile. [4] Atom-probe tomography (APT) results revealing Cu segregation in the single-pass HAZ regions of BA-160 led to concerns of this alloy being susceptible to HAZ liquation cracking.…”

“…[3,9] The increase in hardness was attributed to the reprecipitation of Cu precipitates and carbides. Because steels strengthened through Cu precipitates and carbides are susceptible to reheat cracking, [10][11][12][13] BA-160 could exhibit susceptibility as well.…”

Effect of Mg–Ti Deoxidation on the Formation Behavior of Equiaxed Crystals During Rapid Solidification of Iron Alloys

“…Grain refinement is a way to improve the mechanical properties as well as to avoid segregation of elements during solidification of iron alloys. Therefore, some researchers investigated the heterogeneous nucleation of primary crystals on the surface of non‐metallic inclusions, while the others have tried to apply the heterogeneous nucleation theory to practical operations such as welding and casting . The catalytic potential of various inclusions for the heterogeneous nucleation of primary delta ferrite during solidification of steel has been reported for several decades.…”

Microstructure and Its Formation Mechanism in the Interface of Ti/NiCr Explosive Cladding Bar

“…The intermetallic compounds exhaust the ductility and increase the risk of brittle fracture of the deformed metal. Bamboo-shaped cracks can also be found in the melting zones (Ref [13][14][15][16]. They have a negative impact on formability during the next materials processing such as rolling and extruding.…”