Suppression of Coating Layer Crack by Diffusion Heat Treatment in Al-Si Coated HPF Steels

Yun, Sang-Man; Gwon, Hojun; Oh, Jinkeun; Kim, Sung-Joon

doi:10.1007/s12540-021-01161-w

Cited by 7 publications

(4 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4,45 Other compounds that have been identified as minority components after the hot-dipping process include τ 1 , τ 6 , η, and θ. 8,17,25,46 Previous studies have reported that θ and η form at ca. 650 °C, 14 τ 2 at 830 °C, 8 AlFe at 882 °C, 20 and τ 1 at 900 °C.…”

Section: ■ Discussionmentioning

confidence: 99%

“…15,20 Some EDS and electron back-scattering diffraction measurements suggest that Al-Si-coated steels heated to 900 °C contain mixtures of τ 1 , τ 2 , and ω (FeSi 2 ), 24 while others show τ 1 , τ 5 , AlFe, Al 2 Fe, θ, and η. 15,18,20,25,46 Variations in the composition of the Al-Si-Fe layer may arise due to variations in heating time. The temperatures at which Raman spectra identify new phases here are consistent with these observations, attesting to the accuracy of the Raman spectroscopy-based assignment.…”

Section: ■ Discussionmentioning

confidence: 99%

“…In the case of the as-received steel, for example, the dip-coating process is known to produce a layer of τ 5 at the steel interface. ,,,, This layer acts as a barrier between the Al-Si coating and the Fe in the substrate steel, thereby inhibiting further transformation of the Al-Si coating up to 580 °C. , Other compounds that have been identified as minority components after the hot-dipping process include τ 1 , τ 6 , η, and θ. ,,, Previous studies have reported that θ and η form at ca. 650 °C, τ 2 at 830 °C, AlFe at 882 °C, and τ 1 at 900 °C. , AlFe and Al 2 Fe 2 Si emerge at higher temperatures, around 900 °C. , Some EDS and electron back-scattering diffraction measurements suggest that Al-Si-coated steels heated to 900 °C contain mixtures of τ 1 , τ 2 , and ω (FeSi 2 ), while others show τ 1 , τ 5 , AlFe, Al 2 Fe, θ, and η. ,,,, Variations in the composition of the Al-Si-Fe layer may arise due to variations in heating time. The temperatures at which Raman spectra identify new phases here are consistent with these observations, attesting to the accuracy of the Raman spectroscopy-based assignment.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

2023

View full text Add to dashboard Cite

Hot-stamped ultrahigh strength steel components are pivotal to automotive light-weighting. Steel blanks, often coated with an aluminum-silicon (Al-Si) layer to protect them from oxidation and decarburization, are austenitized within a furnace and then simultaneously quenched and formed into shape. The Al-Si coating melts within the furnace and reacts with iron from the steel to yield an intermetallic phase that provides some long-term corrosion protection. During the intermediate liquid phase, some of the coating may transfer to the furnace components, leading to maintenance costs and operational downtime. A detailed understanding of the coating transformation mechanism is needed to avoid such production issues while ensuring that final intermetallic coatings conform to specifications. We introduce cross-sectional Raman microscopic mapping as a method to rapidly elucidate the coating transformation mechanism. Raman spectroscopic fingerprints for relevant intermetallic compounds were determined using synthesized Al-Fe-Si ternary and Al-Fe binary compounds. These fingerprints were used to map the spatial distribution of intermetallic compounds through cross sections of Al-Si-coated 22MnB5 specimens that were heated at temperatures between 570 and 900 °C. These chemical maps show that the intermetallic fraction of the coating does not grow significantly until formation of η (Al5Fe2) at the steel interface, suggesting that η facilitates extraction of iron from the steel and subsequent diffusion through the coating. Under the heating conditions used here, a series of reactions ultimately lead to a silicon-rich τ2 (Al3FeSi) phase on top of the binary η phase. The technique presented here simplifies structural analysis of intermetallic compounds, which will facilitate prototyping of strategies to optimize hot stamping.

show abstract

Section: ■ Discussionmentioning

confidence: 99%

Section: ■ Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

2023

View full text Add to dashboard Cite

show abstract

“…Although there are several variants of light materials such as Al and Mg alloys that can be used for structural components in automobiles, the characteristics of AHSS such as their high strength and low manufacturing cost make them materials of choice over other materials 3 – 5 . Among several grades of AHSS, hot press forming (HPF) steels, also called press hardening steels, have received a great deal of attention since they offer superior tensile properties along with good dimensional accuracy due to their unique processing route consisting of high temperature forming within austenite region followed by cooling in a die to form low temperature hard phases such as martensite or bainite 6 – 8 . However, such a processing route has a poor production efficiency and moreover these HPF steels generally suffer from liquid metal embrittlement (LME) or microcracking due to an interaction between coating and substrate during high temperature forming 9 – 14 .…”

Section: Introductionmentioning

confidence: 99%

Overcoming the strength–formability trade-off in high strength steels via cryogenic treatment

Park

Zargaran

et al. 2022

Sci Rep

View full text Add to dashboard Cite

High strength steels are becoming more important than ever before for automotive applications to reduce the weight of automobiles and to ensure the safety of passengers. Since increased strength usually results in degraded formability, however, cold forming of high strength steels into final shapes remains a challenge to both automotive manufacturers and suppliers. Here we report novel alloy and processing design concepts that can impart high strength to cold-formable steels, which deviates from the traditional approach of improving the formability of high strength steels. Such designed steel subjected to a designed processing route shows an excellent combination of formability and strength as well as crashworthiness, which is crucial for the safety of passengers in the automobiles. The alloy and processing design concepts used in the present study are based on the utilization of thermally induced austenite to martensite transformation, which imparts high strength to cold-formable austenite by cryogenic treatment.

show abstract

Mechanical and Microstructural Properties of Autogenous Arc Welds of 2 GPa Strength Hot-Press-Forming Steel

Kim

Park

Kang

et al. 2023

J. of Materi Eng and Perform

View full text Add to dashboard Cite

Currently, the strength of hot-press-forming (HPF) steel has been increased to produce lightweight vehicles, and in this study, the rst arc welding investigation on a 2.0 GPa-strength HPF steel was conducted. HPF steel sheets with thicknesses of 1.1 mm were butt-welded by gas tungsten arc welding without a ller metal, with the heat input controlled in the range of 140-260 J/mm. The weld metal, coarse-grained heat-affected zone (HAZ), and ne-grained HAZ had martensitic microstructures and contained small amounts of bainite only under the highest heat input (260 J/mm). The softened zone was composed of an intercritical HAZ (ICHAZ) (with polygonal ferrite and martensite/bainite) and a subcritical HAZ (with tempered martensite). The ICHAZ softened the most during welding and fractured during tensile testing. The strengths of the arc welds were in the range of 1141-1264 MPa, which were 57-63% strength of the base metal. The ICHAZ softening was revealed to originate from carbon diffusion during the martensite to austenite transformation, which is unavoidable in arc welding and should be considered in the design of a welded structure.

show abstract

Suppression of Coating Layer Crack by Diffusion Heat Treatment in Al-Si Coated HPF Steels

Cited by 7 publications

References 29 publications

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

Overcoming the strength–formability trade-off in high strength steels via cryogenic treatment

Mechanical and Microstructural Properties of Autogenous Arc Welds of 2 GPa Strength Hot-Press-Forming Steel

Contact Info

Product

Resources

About