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ML00103 - Nov.2017

Brittle Fracture of a Free-Cutting Connector

Details of the intergranular fracture, probably associated to cementite at grain boundaries.

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Details of the , probably associated to at grain boundaries.
M

Material

Low Carbon Steel
  • ASTM A 29 grade 1211
  • UNS G12110
Ds

Description

The hydraulic hose connector has broken in a brittle way. The material was probably overloaded during assembling/disassembling and although the is fully of a low hardness, the presence of a large amount of inclusions and at ferritic grain boundaries created a condition for easy propagation.

C

Chemistry (% in weight)

Product Analysis

0.083C; 0.045Si; 0.90Mn; 0.070P; 0.127S; 0.13Cr; 0.10Ni; 0.01Mo.

Associated Images
The hose connector fracture surface presented different fracture micromechanisms associated to the microstructure: inclusion decohesion, small regions of intergranular fractures (probably due to cementite at grain boundaries), and cleavage of the ferritic structure. All these mechanisms are brittle.
560
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Fractography by SEMDf - Brittle Fracture
Aspect of the external side of the connector, with a longitudinally crack of a brittle aspect. It is a 5/8" connector (15.8 mm).
134
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Aspect Before AnalysisDf - General View
Aspect of the internal side of the connector. The fracture, in the longitudinal direction, presents a brittle aspect. The thickness of the connector is about 2 mm.
126
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Aspect Before AnalysisDf - Brittle Fracture
Macroscopic detail of the brittle fracture, in the longitudinal direction.
105
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Aspect Before AnalysisDf - Brittle Fracture
Micrography of the longitudinal section of the fitiing, in a free-cutting steel. The microstructure is predominantly ferritic and there is a large amount of sulfide inclusions, aligned perpendicular to the forming direction.
98
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Longitudinal Section
Micrographic detail of the longitudinal section of the fitiing, in a free-cutting steel. The microstructure is predominantly ferritic, with small perlitic areas and some free cementite at ferritic grain boundaries. There is a large amount of sulfide inclusions, aligned perpendicular to the forming direction.
107
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Non Metallic Inclusions
Micrography of the transerse section of the fitiing, in a free-cutting steel. The microstructure is predominantly ferritic and the inclusions appear as dots.
97
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Transverse Section
Micrographic detail of the transverse section of the fitiing, in a free-cutting steel. The microstructure is predominantly ferritic, some perlitic areas and free cementite at ferritic grain boundaries. There is a large amount of inclusions, that appear as spots.
82
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Predominantly Ferritic
Details of the inclusion decohesion and cleavage.
89
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Fractography by SEMDf - Cleavage Facets
Details of the cleavage fracture in the ferritic structure.
86
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Fractography by SEMDf - Brittle Fracture
Details of the intergranular fracture, probably associated to cementite at grain boundaries.
68
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Fractography by SEMDf - Intergranular Fracture
The longitudinal section of the fitting at the thread shows plastic deformation of the fillets, and a crack at the bottom of the thread.
56
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Crack
Micrographic detail of the longitudinal section of the fitting at the thread, showing a crack at the bottom of the thread.
53
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Crack
Micrographic detail of a cracking with inclusions decohesion at the bottom of the thread.
51
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Transgranular Cracking
Micrography of a transverse section, perpendicular to the fracture surface, showing lack of plastic deformation during rupture.
50
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Fracture
Micrography of a transverse section, perpendicular to the fracture surface, showing lack of plastic deformation during rupture.
45
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Fracture
Micrography of a transverse section, perpendicular to the fracture surface, showing lack of plastic deformation during rupture. Cleavage factes are evident in the ferritic structure close to the fracture surface.
47
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Fracture