Formation Of Soft Zone Research Articles

Characterization of the soft zone in dissimilar welds joint of 2.25Cr-1Mo and lean duplex LDX2101 steel

• Study on the effect of the post-weld heat treatment on formation of soft proeutectoid ferrite zone near the fusion line. • Effect of the Ni-based filler on microstructure evolution along the weldments of 2.25Cr-1Mo and lean duplex LDX2101 steel. • Role of the filler composition on hardness and Charpy impact toughness variation along the weldments. • Role of the PWHT on mechanical behavior of the soft proeutectoid ferrite zone. The dissimilar welds joint of 2.25Cr-1Mo steel and lean duplex LDX2101 steel was prepared using the Gas Tungsten Arc Welding (GTAW) process and employing the Inconel 617 filler. The microstructural stability of the dissimilar welds joint (DWJ) was studied using the optical microscope and field emission scanning electron microscope (FESEM) for as-welded (AW) and post-weld heat treatment (PWHT) condition. The PWHT was employed at 760 °C (PW 1) and 810 °C (PW 2) for 2 h of duration. The application of the heat-treatment resulted in the formation of the soft zone at the interface of weld metal and HAZ in 2.25 Cr-1Mo side, i.e., low Cr side. The mechanical behavior of the DWJs was also studied for AW and PWHT condition. A measurable change in the width and hardness of the soft and hard zones was measured with an increase in PWHT temperature. For weld metal, the minimum average hardness was measured 237 HV in AW and a maximum of 248 HV for PW 2. In the AW condition, the average CIT of the weld metal was measured 46.5 ± 3.5 J, which meets the minimum recommended value as per EN 1557:1999 standards. The PWHT showed a drastic reduction in CIT and a minimum of 34 ± 3 J was measured for PW 2. The CIT of the 2.25Cr-1Mo HAZ (notch adjacent to fusion boundary includes the soft ferrite region) was measured 45 ± 5 J in AW and get increased drastically after the PWHT and maximum was measured for PW 2 (86 ± 5 J).

Optimization of Fiber Laser Welding of DP980 Steels Using RSM to Improve Weld Properties for Formability

The effect of laser parameters on weld quality is a critical laboratory study before implementation of newly developed high-strength dual-phase steels in fabrication of auto-bodies. In present work, dual-phase steels having tensile strength of 980 MPa (DP980) were welded using different welding speeds by Yb-fiber laser source to fabricate similar material combinations laser-welded blanks (LWBs). The weld zone microhardness, microstructure, and formability of DP980 LWBs were compared with those of the DP600 and micro-alloyed interstitial free high-strength steel (IFHS) LWBs. It was found that the formation of soft zone at the outer side of the HAZ was responsible for significant reduction in formability of DP980 LWBs due to strain localization and premature failure. Hence, response surface methodology based on Box-Behnken design was implemented to establish a mathematical model which could correlate the influence of laser process parameters such as power, welding speed, and focal position on weld quality in terms of aspect ratio of fusion zone, width of the soft zone, and surface roughness of weld to improve formability. The model was successfully implemented to optimize the laser parameters, and approximately 13.58% improvement in Erichsen cup height was achieved due to complete weld penetration with simultaneous 67% reduction in soft zone width and 55% reduction in softening. However, the failure was still observed to occur in the soft zone propagating parallel to weld in radial direction.

Systematic study of formation of soft and hard zones in the dissimilar weldments of Cr–Mo steels

The microstructural stability and elemental redistribution in dissimilar weldments between 9Cr–1Mo and 2.25Cr–1Mo ferritic steels during various postweld heat treatments (PWHTs) have been studied using microscopy techniques ranging from optical to transmission electron microscopy and electron probe microanalyser. Application of PWHT at 1023 K for various times resulted in the formation of a soft zone in the low Cr side and a carbide rich hard zone adjoining the soft zone in the high Cr side of the weldment. The width of these zones and their hardness are influenced by the time of exposure at elevated temperature. A measurable increase in the width and a decrease in the hardness of the soft and hard zones with aging times are observed. Correlation between these observed effects and the elemental redistribution responsible for the formation of these zones is being attempted. Micromechanisms responsible for the formation of these zones are proposed. Migration of carbon from low Cr side to high Cr side driven by the gradient in the carbon activity has been found to be responsible for the formation of these zones.

Glacial sedimentary processes and environmental reconstruction based on lithofacies

ABSTRACTGlacigenic sediments exposed in pits around Villeneuve, near Edmonton, Alberta, are subdivided into facies based on grain size, sedimentary structure, glacially‐induced deformation and faulting, and groove marks. Two diamicton facies are recognised, one of which is interpreted as a primary till, deposited directly from glacier ice, and the other as a product of mass‐movement. The diamicton facies are closely associated with current bedded facies interpreted as fluvioglacial deposits. The stratigraphic sedimentological and tectonic aspects of these fluvial deposits suggest subglacial deposition in channels and cavities. At any one place the glacier appears to have alternated between being attached to the bed, causing thrusting and sole marking, and being separated from the bed by a cavity in which fluvial and mass‐movement sediments accumulated. The net result is a highly complex and laterally variable stratigraphy produced by a single glacial advance. The correct interpretation of such sequences is essential if lithostratigraphy is to be used to establish glacial history. In addition, the interpretations presented here have implications regarding the formation of soft zones in ‘till’. They indicate that the soft zones are beds of sorted sediment redeposited by mass‐movement.