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ML00016 - Apr.2017

SCC in Free Cutting 303SS

Regions of the pin thread presenting pitting corrosion.

1

635
Regions of the thread presenting .
M

Material

Austenitic Stainless Steel
  • UNS S30300
Ds

Description

The safety 3/8" diameter, manufactured in a free machinning , was adopted for a marine coupling and its function is to break when external loads are exceeded, activating the mechanism, closing the flow and avoiding product spillage. Some pins broke without external loads in a non expected behavior. It occurred because the created a crevice condition that to Stress . Free cuting are not suitable for corrosive conditions.

C

Chemistry (% in weight)

Product Analysis

0.06C; 0.38Si; 1.90Mn; 0.029P; 0.220S; 17.4Cr; 8.18Ni; 0.55Mo.

Associated Images
Regions of the pin thread presenting pitting corrosion.
635
VIEW
ML00016 / Apr.2017
SCC in Free Cutting 303SS
M - Austenitic Stainless SteelP - Machined PartAp - OffshoreCd - Stress Corrosion
Cm - Surface Aspect by SEMDf - Localized Corrosion
Regions of the localized corrosion spots associated to non metallic inclusions.
123
VIEW
ML00016 / Apr.2017
SCC in Free Cutting 303SS
M - Austenitic Stainless SteelP - Machined PartAp - OffshoreCd - Stress Corrosion
Cm - Surface Aspect by SEMDf - Non Metallic Inclusions
The macrography of the longitudinal section of the pin (9.5 mm nominal diameter) shows the localized corrosion associated to the non metallic inclusions.
107
VIEW
ML00016 / Apr.2017
SCC in Free Cutting 303SS
M - Austenitic Stainless SteelP - Machined PartAp - OffshoreCd - Stress Corrosion
Cm - Macro Oxalic Acid Electrolytic EtchedDf - Localized Corrosion
The low magnification micrography of the longitudinal section of the pin shows the localized corrosion associated to the non metallic inclusions.
89
VIEW
ML00016 / Apr.2017
SCC in Free Cutting 303SS
M - Austenitic Stainless SteelP - Machined PartAp - OffshoreCd - Stress Corrosion
Cm - Micrography by OM using A262 Method ADf - Localized Corrosion
The pin microstructure in the longitudinal section shows austenitic structure, free from carbides, and sulfide inclusions that characterize the free cutting condition of this stainless steel.
77
VIEW
ML00016 / Apr.2017
SCC in Free Cutting 303SS
M - Austenitic Stainless SteelP - Machined PartAp - OffshoreCd - Stress Corrosion
Cm - Micrography by OM using A262 Method ADf - Non Metallic Inclusions
The micrographic detail of the longitudinal section of the pin shows the localized corrosion associated to the non metallic inclusions.
67
VIEW
ML00016 / Apr.2017
SCC in Free Cutting 303SS
M - Austenitic Stainless SteelP - Machined PartAp - OffshoreCd - Stress Corrosion
Cm - Micrography by OM using A262 Method ADf - Localized Corrosion
The micrographic detail of the longitudinal section of the pin shows the stress corrosion cracks propagating from crevice corrosion regions.
52
VIEW
ML00016 / Apr.2017
SCC in Free Cutting 303SS
M - Austenitic Stainless SteelP - Machined PartAp - OffshoreCd - Stress Corrosion
Cm - Micrography by OM using A262 Method ADf - Branched Cracks
Visual aspect of the 3/8" diameter pin surface, presenting several lozalized corrosion spots.
53
VIEW
ML00016 / Apr.2017
SCC in Free Cutting 303SS
M - Austenitic Stainless SteelP - Machined PartAp - OffshoreCd - Stress Corrosion
Cm - Aspect Before AnalysisDf - At the Surface
Detail of the pin surface showing that the material easily cracks because it presents regions of localized corrosion.
45
VIEW
ML00016 / Apr.2017
SCC in Free Cutting 303SS
M - Austenitic Stainless SteelP - Machined PartAp - OffshoreCd - Stress Corrosion
Cm - Surface Aspect by SEMDf - Fracture