Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Process-microstructure-corrosion interrelations for stainless steel
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Swerea Kimab AB, Sweden.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Stainless steels were first developed in the early 20th century and have since then emerged as a very diverse class of engineering materials. Along with steels having new combinations of properties, there is a continuous development of new technologies allowing the material to be produced in a faster and more energy effcient manner. A prerequisite for new technologies to be adapted quicklyis a fundamental understanding of the microstructure evolution throughout theprocess chain. The first part of this thesis has been dedicated to the annealing and pickling processes from a process-microstructure perspective. In the second part the concept of utilising crystallographic texture as a way to attain microstructures with new combinations of properties has been evaluated.

In the first part, annealing can be regarded as a high temperature oxidation process, resulting in chromium depletion that necessitate subsequent chemical pickling. Chemical pickling, on the other hand, is basically a wet-corrosion process and hence more difficult for highly corrosion-resistant grades. The chromium depleted layer was found to be enriched in austenite in case of duplex stainless steel UNS S32205 (Paper I) and this may inuence the pickling process. Proper pretreatment like shot-blasting dramatically increases the pickling rate because it provides the pickling acid with access to the chromium depleted layer (Paper II). Oxidation kinetics for S30400 in conditions relevant to strip annealing do not seem to be affected by the choice of air/oxygen as oxidiser even though the latter results in substantially higher water content (Paper III). This gives new possibilities regarding both cost savings and increased throughput.

In the second part, the effect of crystallographic texture on resistance towards corrosion of S31603 in a solution of FeCl3 and AlCl3 in ethanol/glycerol and in 30 vol% H2SO4 is investigated. In the former, high density surfaces {1111} and {100} are less prone for pit nucleation, however the effect is relativelysmall. In H2SO4 pronounced crystallographic anisotropy is observed inwhich the corrosion rate increase in the order {111} < {110} ≤ {100} (Paper IV).For corrosion at high temperatures, chromium diffusion is governed by randomhigh angle boundaries with ~20—55° misorientation. The possibilities to alter the texture in austenitic stainless steels by means of warm-rolling and annealing has been evaluated for S30403 and S31603. During warm-rolling, both steels develop the copper-type texture in contrast to the brass-type texture observedat room temperature. However only S30403 is prone to recrytallise cube texture during subsequent annealing (Paper V).

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , xii, 75 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:3
Keyword [en]
stainless steel, processing, annealing, pickling, microstructure, corrosion, anisotropy, oxyfuel
National Category
Metallurgy and Metallic Materials
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-159072ISBN: 978-91-7595-425-7 (print)OAI: oai:DiVA.org:kth-159072DiVA: diva2:782360
Public defence
2015-02-16, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150121

Available from: 2015-01-21 Created: 2015-01-20 Last updated: 2015-01-21Bibliographically approved
List of papers
1. Oxide formation and pickling performance of duplex stainless steel 2205
Open this publication in new window or tab >>Oxide formation and pickling performance of duplex stainless steel 2205
2009 (English)In: Proceeding of the International Stainless Steel Word Conference, 10-12th Nov 2009, Maastricht, Netherlands, 2009Conference paper, Published paper (Refereed)
Abstract [en]

Duplex stainless steels have gained popularity due to their high corrosion resistance and higher strength for a lower/more stable raw material cost compared to the austenitic grades. However, processing of the duplex grades may be more difficult, partly because of their relatively high corrosion resistance. The materials used for this study were cold and hot rolled variants of the duplex stainless steel grade 2205. Annealing was done in industrial production lines using either induction or conventional gas-fired furnaces. The specimens were laboratory pickled in mixed acid (HNO3 + HF) and analyzed after different pickling times. The techniques employed were scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), glow discharge optical emission spectroscopy (GDOES), X-ray diffraction (XRD) and wet-chemical techniques. The aim was to understand the oxidation behaviour during production annealing and to elucidate the pickling mechanism in mixed acid. Comparison was made to the pickling behaviour of the standard austenitic grades 304L and 309L.

The oxide formed on cold and hot rolled 2205 comprised an inner á-Cr2O3 and outer mixture of iron rich M3O4 spinel (M = Fe, Cr, Mn) and á-Fe2O3. The oxide thickness was 0.5-1 and 2-10 μm for the cold and hot rolled materials respectively. Manganese enrichment in the spinel was primary observed for the cold rolled variants.

Chromium enrichment in the oxide alters the phase balance of the material under the oxide towards a higher austenite/ferrite ratio. Pickling duplex stainless steels has many similarities with pickling of austenitic grades in that electrochemical dissolution of this chromium depleted and austenitic enriched layer is the most important process. The oxides formed affect the pickling kinetics to a large extent. Thick oxides formed in scratches or pores require up to three times longer pickling time until clean.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-27729 (URN)
Conference
International Stainless Steel Word Conference, 10-12th Nov 2009, Maastricht, Netherlands
Note

QC 20101220

Available from: 2010-12-21 Created: 2010-12-21 Last updated: 2015-01-21Bibliographically approved
2. Pickling of Process-Oxidised Austenitic Stainless Steels in HNO3-HF Mixed Acid
Open this publication in new window or tab >>Pickling of Process-Oxidised Austenitic Stainless Steels in HNO3-HF Mixed Acid
2010 (English)In: STEEL RES INT, ISSN 1611-3683, Vol. 81, no 7, 542-551 p.Article in journal (Refereed) Published
Abstract [en]

Oxide formation during production annealing and the subsequent pickling response in mixed acid have been studied. The aims were to characterise the oxides formed and to understand how the pickling mechanism and kinetics are affected by the nature of the oxide. Totally, eight different versions of the austenitic stainless steel grades AISI 301, 304L and 309L were studied, all annealed in production lines. Cold rolled oxides (formed during annealing) are thin (< 1 mu m), dense and formed in a multilayered manner. Hot rolled oxides (formed during reheating, hot rolling and annealing) are thicker (>1 mu m) and more heterogeneous in thickness and composition. The dissolution rate of the chromium depleted layer (CDL) under the oxide is the most important factor for the overall pickling rate. The permeability of acid through the oxide and the tendency of the oxide to spall are also important factors affecting the pickling kinetics. The dense oxide formed on cold rolled materials can to some extent hinder the acid to reach the CDL. The oxides on hot rolled materials are porous and do not provide such a barrier but they are thicker and thereby more difficult to remove. Shot-blasting prior to pickling of the hot rolled materials improves the pickling performance because it thins the oxide, improves the permeability and increases the tendency of the oxide to spall during the pickling step.

Keyword
pickling, oxidation, stainless steel
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-27718 (URN)10.1002/srin.201000011 (DOI)000280782000006 ()2-s2.0-77956584717 (Scopus ID)
Note

QC 20101220

Available from: 2010-12-20 Created: 2010-12-20 Last updated: 2015-01-21Bibliographically approved
3. Fast and Efficient Annealing of Stainless Steel Strip Using Oxyfuel Burners
Open this publication in new window or tab >>Fast and Efficient Annealing of Stainless Steel Strip Using Oxyfuel Burners
2015 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 86, no 5, 557-566 p.Article in journal (Refereed) Published
Abstract [en]

Pilot plant and annealing experiments have been conducted to study the effect of the higher water content in oxyfuel annealing on oxidation and pickling of cold rolled stainless steel. The experiments were conducted on the austenitic grade AISI 304 in a propane-fired furnace using air and pure oxygen as oxidizers. The experiments were conducted at 1050-1200 degrees C for typically less than 60 s, in order to simulate industrial annealing of thin strip. Supplementary laboratory annealing trials were made to study the evolution of the microstructure during fast heating rates and short hold times. Increasing the water content from 15 to 50 mol% did not alter the oxidation kinetics or the chemistry of the oxide. Since the oxidation is not altered significantly, the pickling performance of the material remains unchanged. The presence of spalled areas increased the pickling efficiency significantly but this was only seen for material annealed at higher temperature compared to industrial practice. Oxyfuel combustion allows higher heat input and therefore faster heating. The 304 grade recrystallizes readily even at moderate cold rolling reductions so the total annealing time can be reduced substantially if the heating rate can be increased. The present work suggests that this can be done without any downstream effects.

Keyword
oxyfuel, cold rolled stainless steel, annealing, oxide formation, mixed acid pickling
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-159022 (URN)10.1002/srin.201400168 (DOI)000354202500012 ()2-s2.0-84928882243 (Scopus ID)
Note

QC 20150120. Updated from e-pub ahead of print to published.

Available from: 2015-01-20 Created: 2015-01-20 Last updated: 2017-12-05Bibliographically approved
4. Crystallographic effects in corrosion of austenitic stainless steel 316L
Open this publication in new window or tab >>Crystallographic effects in corrosion of austenitic stainless steel 316L
2014 (English)Article in journal (Refereed) Epub ahead of print
Abstract [en]

Electron backscatter diffraction and confocal laser microscopy have been used to quantify the degree of crystallographic anisotropy during corrosion of AISI 316L in two test solutions. Corrosion in 30 vol% H2SO4 sulphuric acid shows pronounced crystallographic anisotropy in which the corrosion rate increases in the order {111} < {110} ≲ {100}. The ratio between the slowest corroding {111} and the fasting corroding {100} surfaces is about 3. Pitting corrosion in a solution of FeCl3 and AlCl3 in ethanol/glycerol agrees with other reported observations that high-atomic density surfaces {111} and {100} are less prone to pit nucleation, however the effect was relative small.

Keyword
anisotropy, corrosion, sulphuric acid, pitting
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-159025 (URN)10.1002/maco.201408002 (DOI)
Note

QC 20150120

Available from: 2015-01-20 Created: 2015-01-20 Last updated: 2015-01-21Bibliographically approved
5. Texture evolution of warm-rolled and annealed 304L and 316L austenitic stainless steels
Open this publication in new window or tab >>Texture evolution of warm-rolled and annealed 304L and 316L austenitic stainless steels
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-159066 (URN)
Note

QS 2015

Available from: 2015-01-20 Created: 2015-01-20 Last updated: 2015-01-21Bibliographically approved

Open Access in DiVA

Thesis(11731 kB)640 downloads
File information
File name FULLTEXT01.pdfFile size 11731 kBChecksum SHA-512
46817571923c19b14cb58742969ca9b18275323a9e06469999ebe1ed26240df909f944112b19ddf6b245056a3babaf98e32fefcc1389e5bbd6851d50c768efa9
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Lindell, David
By organisation
Surface and Corrosion Science
Metallurgy and Metallic Materials

Search outside of DiVA

GoogleGoogle Scholar
Total: 640 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 4290 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf