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ML00097 - Nov.2017

Cast SS Tube Removed From High Temperature Service

Micrography close to the external surface of the tube removed from service, damaged by high temperature oxidation.

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close to the of the , damaged by oxidation.
M

Material

Heat Resistant Steel
  • ASTM A 297 grade HP
Ds

Description

During maintenance of the blast furnace air heater, after 6 month in service at temperatures about 800°C, the cast was removed and compared with a new tube of the same manufacturer. The microstructural evolution was not advanced but (oxidation) was identified for both internal and external tube surfaces, more pronounced at the of the tube, where there are defects.

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Chemistry (% in weight)

New Tube

0.40C; 1.14Si; 1.37Mn; 0.025P; 0.035S; 24.47Cr; 33.98Ni; 0.04Mo; 0.02Ti; 1.29Nb.

Removed From Service

0.52C; 1.58Si; 1.34Mn; 0.027P; 0.023S; 24.00Cr; 33.17Ni; 0.04Mo; 0.02Ti; 1.62Nb.

Associated Images
Micrography of the new tube close to a region of a casting defect (shrinkage), presenting only austenitic structure with a network of primary precipitates.
351
VIEW
ML00097 / Nov.2017
Cast SS Tube Removed From High Temperature Service
M - Heat Resistant SteelP - Centrifugally Cast PipeAp - SiderurgyCd - High Temperature
Cm - Glyceregia Etched Micrography by OMDf - Austenitic with Primary Carbides
The macrography of a transverse section of the new tube shows that there are shrinkage voids close to the internal surface, that is exposed to high temperature air. The tube is a 4" diameter and 1/4" thick.
62
VIEW
ML00097 / Nov.2017
Cast SS Tube Removed From High Temperature Service
M - Heat Resistant SteelP - Centrifugally Cast PipeAp - SiderurgyCd - High Temperature
Cm - Transverse Section AspectDf - Casting Structure
Micrography close to the external surface of a new tube, sound.
48
VIEW
ML00097 / Nov.2017
Cast SS Tube Removed From High Temperature Service
M - Heat Resistant SteelP - Centrifugally Cast PipeAp - SiderurgyCd - High Temperature
Cm - As polished micrographyDf - Close to the External Surface
Micrography close to the internal surface of a new tube, presenting casting defects.
47
VIEW
ML00097 / Nov.2017
Cast SS Tube Removed From High Temperature Service
M - Heat Resistant SteelP - Centrifugally Cast PipeAp - SiderurgyCd - High Temperature
Cm - As polished micrographyDf - Close to the Internal Surface
Micrography of the tube removed from service after 6 month, close to a region of a casting defect (shrinkage), presenting austenitic structure with a network of primary precipitates (initial stage of coarsening) and intragranular secondary precipitation.
48
VIEW
ML00097 / Nov.2017
Cast SS Tube Removed From High Temperature Service
M - Heat Resistant SteelP - Centrifugally Cast PipeAp - SiderurgyCd - High Temperature
Cm - Glyceregia Etched Micrography by OMDf - Intragranular Secondary Precipitation
The macrography of a transverse section of the tube removed from service after 6 months, with damage close to the internal tube surface. The tube is a 4" diameter and 1/4" thick.
41
VIEW
ML00097 / Nov.2017
Cast SS Tube Removed From High Temperature Service
M - Heat Resistant SteelP - Centrifugally Cast PipeAp - SiderurgyCd - High Temperature
Cm - Transverse Section AspectDf - Casting Structure
Micrography close to the internal surface of the tube removed from service after 6 month, presenting high temperature oxidation and shrinkage voids (casting defects).
32
VIEW
ML00097 / Nov.2017
Cast SS Tube Removed From High Temperature Service
M - Heat Resistant SteelP - Centrifugally Cast PipeAp - SiderurgyCd - High Temperature
Cm - As polished micrographyDf - Close to the Internal Surface
Micrography close to the external surface of the tube removed from service, damaged by high temperature oxidation.
25
VIEW
ML00097 / Nov.2017
Cast SS Tube Removed From High Temperature Service
M - Heat Resistant SteelP - Centrifugally Cast PipeAp - SiderurgyCd - High Temperature
Cm - As polished micrographyDf - Close to the External Surface