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ML00071 - Jan.2019

Reheating Cracking of a CrMo Vessel Weld

Micrographic aspect of thin cracks.

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Micrographic aspect of thin .
M

Material

CrMo Steel
  • ASTM A 234 WPB12 CL2
  • ASTM A 335 grade P12
Ds

Description

The high presented in the of a circumferential , after less than 2 years in service. The joint was welded in field and the hardness of the weld metal was a little higher than the expected after a (PWHT). Intergranular cracks resulted from a relief during REHEATING of the weld metal in a mechanism similar to .

C

Chemistry (% in weight)

Wled Metal Analysis

0.085C; 0.33Si; 0.91Mn; 0.028P; 0.013S; 1.07Cr; 0.08Ni; 0.53Mo; 0.02Cu; 0.023V.

Associated Images
Image of the magnetic particle test, using a white contrast, presenting the cracks at the surface of the weld metal. The cracks are transverse to the weld and do not propagate into the base metals. A forged T in the right side of the figure and a thick wall tube in the left side of the figure, both in P12 CrMo steel.
1044
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Aspect by NDTDf - Cracks
Aspect of the butt welded joint surface, after grinding to remove the reinforcement, polishing and macro etching. There are multiple cracks, transverse to the weld and restricted to the weld metal. The surface hardness are 167HB for the tube (left side), 180 HB for the Forged T (right side) and 272 HB for the weld metal, suggesting lack of a suitable PWHT.
181
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Surface AspectDf - Cracks
The morphology of the cracking in the weld metal is intergranular (in the previous austenite grain boundaries), and branched. The replication technique was adopted to define the nature of the cracks.
148
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Nital etched, OMDf - Cracks
Detail of the weld metal intergranular and branched cracking (in the previous austenite grain boundaries). The replication technique was adopted to define the nature of the cracks.
125
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Nital etched, OMDf - Cracks
The forged T presented a ferritic perlitic/bainitic structure at the surface, where the replica was conducted. The base material material hardness is 180 HB.
121
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Nital etched, OMDf - Ferrite and Bainite
The thick wall tube presented a bainitic structure at the surface, where the replica was conducted. The base material material hardness is 167 HB.
109
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Nital etched, OMDf - Bainite
The weld metal presented a ferritic/bainitic structure at the surface, where the replica was conducted. The weld metal hardness is 272 HB, too high for this material, suggesting lack of a suitable PWHT.
102
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Nital etched, OMDf - Weld Metal
A small sample containing cracks was removed from the cracked weld metal, by mechanical means.
81
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Transverse Section AspectDf - Weld Metal
Macrographic aspect of a transverse section of the sample with multiple cracks that were deep in the weld metal.
71
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - NItal Etched MacroDf - Weld Metal
After opening a crack it was possible to see the fracture appearance.
70
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Fractography by SEMDf - Fracture
Intergranular morphology of the fracture in a scanning electron microscopy image.
65
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Fractography by SEMDf - Intergranular Cracking
The micrographic aspect of the cracks in a section transverse to the weld (the removed sample), shows that there are cracks with different sizes, the larger are filled with products that indicate they were opened for longer times.
67
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Nital Etched Micrography by OMDf - Intergranular Cracking
Micrographic aspect of opened cracks, filled with oxides.
63
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Nital Etched Micrography by OMDf - Cracks
Micrographic details of opened cracks, filled with oxides.
56
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Nital Etched Micrography by OMDf - Cracks
Micrographic aspect of thin cracks.
59
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Nital Etched Micrography by OMDf - Cracks
Micrographic details of thin cracks.
63
VIEW
ML00071 / Jan.2019
Reheating Cracking of a CrMo Vessel Weld
M - CrMo SteelP - In Field WeldAp - EnergyCd - Welding Defect
Cm - Nital Etched Micrography by OMDf - Cracks