Back to Low Alloy Medium Carbon QT
ML00098 - Nov.2017

Brittle Fracture of a Casting Lifting Device

Micrography of the secondary crack, paralel to fracture, starting from the internal diameter of the padeye. The crack propagates in an interdendritic morphology, interconnecting casting defects.

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of the secondary , paralel to , starting from the internal diameter of the padeye. The propagates in an interdendritic morphology, interconnecting defects.
M

Material

Low Alloy Medium Carbon QT
  • ASTM A 732 grade 9Q
  • UNS J23055
Ds

Description

The lifting device was broken in service, in a brittle way. The material presented shrinkage defects close to the region of the highest stress level, and these defects clearly reduced the material capacity for loading (see the properties close and far from the rupture). The metallurgical analysis showed the interconnection of , creating that to the rupture of the padeye. There are several , paralel to the .

C

Chemistry (% in weight)

Product Analysis

0.25C; 0.46Si; 0.66Mn; 0.009P; 0.004S; 0.90Cr; 1.93Ni; 0.29Mo; 0.10Cu.

Associated Images
Micrography of a transverse section of the lifting part, showing interdendritic voids close to the surface at the inner diameter of the padeye. The microstructure is tempered martensite.
450
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Casting defects
Aspect of the broken padeye. The outer diameter is about 10" and the thickness of the casting is about 2".
22
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Aspect Before AnalysisDf - General View
Aspect of the fracture surface, showing a brittle morphology. Flat fracture with chevron marks from regions close to the internal diameter of the padeye, where there are secondary cracks.
22
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Aspect Before AnalysisDf - Fracture
Micrography of the lifting padeye showing a dendritic path of a quenched and tempered martensitic microstructure. The segregated regions (white interdendritic regions) are more clearly identified in low magnification. Voids are located in these segregated regions.
21
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Martensite
Micrography of the lifting padeye showing a quenched and tempered martensitic microstructure. Voids are located in interdendritic segregated regions.
20
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Martensite
Micrography of the lifting padeye showing a quenched and tempered martensitic microstructure. Voids are located in interdendritic segregated regions. At this magnification the segregation is not clear.
16
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Martensite
Micrography of the lifting padeye showing a quenched and tempered martensitic microstructure. The hardness level of the material is about 39 HRc.
14
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Martensite
Macrography of a "longitudinal" section of the padeye showing casting defects close to the internal diamater and a secondary crack, paralel to fracture, starting from the internal diameter. The fracture is not presented in this macro, it is to the top of the photo.
17
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - NItal Etched MacroDf - Cracking
Macrographic detail of the secondary crack, paralel to fracture, starting from the internal diameter of the padeye. The dendritic structure is evident.
13
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - NItal Etched MacroDf - Secondary Cracks
Micrography of the secondary crack, paralel to fracture, starting from the internal diameter of the padeye. The crack propagates in an interdendritic morphology, interconnecting casting defects.
13
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Secondary Cracks
Micrographic detail of the secondary crack, paralel to fracture, at the internal diameter of the padeye. The microstructure is martensitic.
15
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Cracking
Micrography transverse to the fracture surface (in the top of the figure). The fracture is brittle and follows the interdendritic spaces, since these regions where the positions where there were casting defects.
14
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Fracture
Micrographic detail of a transverse section, at the fracture (in the top of the figure). The fracture is brittle and follows the voids at interdendritic spaces, with secondary cracks.
12
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Fracture
Micrographic detail of a transverse section, at the fracture (in the top of the figure). The fracture is brittle and follows the voids at interdendritic spaces, with secondary cracks.
10
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Fracture
Micrography of a region where there is a large amount of casting defects. Shrinkage voids in interdendritic spaces, some interconnected and cracked.
13
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Martensite
Micrography of a region where there is a large amount of casting defects. Shrinkage voids in interdendritic spaces, some interconnected and cracked.
13
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Martensite
Micrographic detail of a region with a large amount of casting defects. Shrinkage voids in interdendritic spaces, some interconnected and cracked.
11
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Casting defects
Micrographic detail of a region with a large amount of casting defects. Shrinkage voids in interdendritic spaces, some interconnected and cracked. The microstructure is tempered martensite.
9
VIEW
ML00098 / Nov.2017
Brittle Fracture of a Casting Lifting Device
M - Low Alloy Medium Carbon QTP - CastingAp - LiftingCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Casting defects