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ML00173 - May.2021

Welding Cracks in an Aged HP Cast Fitting

Welding Cracks in an Aged HP Cast Fitting

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2
M

Material

Heat Resistant Steel
  • UNS N08705
  • ASTM A 297 grade HP
  • Modified
Ds

Description

After six years in service in a condition, in a furnace, this HP cast was submitted to a repair and a layer technique was adopted to join it to a centrifugally cast of similar composition, but the aged cracked during the buttering by process, using of similar composition, due to the low ductility condition of the aged , that showed zero in the .

C

Chemistry (% in weight)

Product Analysis

0.42C; 1.78Si; 1.15Mn; 0.013P; 0.005S; 25.50Cr; 35.46Ni; 0.05Mo; 0.082Ti; 0.93Nb; 0.01Cu; 0.029W; 0.033Al.

Associated Images
Aged microstructure of the HP stainless steel, modified with 1%Nb, cast fitting, tubular, operating for 6 years in a furnace which design temperature is 1100°C. The material presented a network of primary carbides, white and grey, and an austenitic matrix with coalescing secondary precipitation. Some voids. The Vickers identation indicates a hardness value about 260HV 100g in the aged austenitic matrix.
491
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Microhardness identations
Condition of the joint between the centrifugally cast tube (bottom) and the buttered fitting (top). During this welding the cast fitting (buttered) showed several cracks but after removal of the fitting it was clear that the cracks were formed during the buttering and not during the joining.
46
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Aspect Before AnalysisDf - General View
After removal of the cracked part of the fitting, the dye check test indicated the presence of several cracks in the internal diameter (ID), out of the buttered layer, that means, in the fitting base metal.
42
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Aspect by NDTDf - Cracks
Cast fitting microstructure. Network of primary carbides and austenitic matrix with coalescing secondary precipitation.
37
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Base Metal
Cast fitting microstructure. The material presented a network of primary carbided and an austenitic matrix with coalescing secondary precipitation.
37
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Aged Microstructure
Micrographic detail of the network of primary carbided, white and grey, and an austenitic matrix with coalescing secondary precipitation.
30
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Aged Microstructure
Aspect of the broken tensile testpiece, cylindrical, in a longitudinal direction in the tubular casting, showing zero elongation and zero area reduction. The Yield Strenght (348MPa) is very close to the Ultimate Strenght (352MPa) in the tensile test. Yield to Ultimate ratio of 0.98.
27
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Testpiece aspectDf - Broken Testpiece
Fusion line between the aged base metal (in the top) and the weld metal (in the bottom). The adopted filler metal is similar to the base metal.
27
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Fusion Line
Fusion line between the aged base metal (in the top) and the weld metal (in the bottom). There is a region where the primary carbides melted (partially melted zone), that appears dark, and a region of high dilution cloe to the fusion line.
26
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Fusion Line
This macrography shows a longitudinal section of the tubular cast fitting. The external side is to the top and the internal side to the bottom. The buttering layer is evident in the groove that would be welded to the centrifugall cast tube (right side) and part of the ID and OD. During the buttering welding of the casting the cracks were not detected because they were formed in the center of the thickness and some have propagated to the internal diameter, but not to the external diameter. They opened only when the buttered casting was welded to the tube.
20
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched MacroDf - Longitudinal Section
Macrographic detail close to the internal diameter (ID in the bottom), where the cracks were detected by dye check (after removal of the damaged part of the cast fitting). Close to the surface it is possible to see the layers of the weld metal that corresponds to the cast fitting buttering.
21
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched MacroDf - Cracks
As polished micrography of the fusion line presenting several microcracks . The base metal is to the top and the weld metal is to the bottom.
23
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - As polished micrographyDf - Fusion Line
Same region as the previous figure, showing the structure of the base metal and weld metal, at the cracked area. In the base metal, the cracks are associated to the primary carbides network and in the weld metal it is associated to the solidification columnar grains.
110
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Fusion Line
Micrographic detail of the cracks at the fusion line, associated to the partially melted region suggesting a liquation effect in a material that presented low ductility. After opening the cracks they propagate brittle into the base metal and created a solidification cracking in the weld metal, detailed in the next figures.
23
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Multiple cracks
Micrographic detail of the cracks in the weld metal generated from the partially melted region at the fusion line suggesting that a liquation effect propagated a solidification cracking.
18
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Hot cracking
Micrographic detail of the cracks in the base metal created from the partially melted region suggesting that a liquation effect propagated brittle cracks into the low ductility base metal.
30
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Cracks
Welding Cracks in an Aged HP Cast Fitting
2
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched MacroDf - Cracks
Welding Cracks in an Aged HP Cast Fitting
1
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched MacroDf - Microhardness identations
Welding Cracks in an Aged HP Cast Fitting
3
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Testpiece aspectDf - Broken Testpiece