Solutions for Hydrogen-Induced Delayed Fracture in Hot Stamping

Lu, Hongzhou; Zhang, Shi Qi; Bian, Jian; Mohrbacher, Hardy; Guo, Ai Min

doi:10.4028/www.scientific.net/amr.1063.32

Cited by 13 publications

(6 citation statements)

References 6 publications

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“…Moreover, the curve presents an inflection point which denotes the material's transition from ductile to brittle, in consequence of hydrogen embrittlement phenomenon. Parameters m 5 and m 6 define the geometry of this transition . In the present study, this model with double plateau gave a good approximation of test results, but the first horizontal asymptote is not clearly visible because of an early decay of mechanical properties of the material for a very low diffusible hydrogen concentration.…”

Section: Discussionsupporting

confidence: 49%

“…At the present, many studies have been carried out about deleterious effect of hydrogen on martensitic microstructure . From literature is well known that a very small hydrogen concentration can induce a significant reduction in mechanical properties of martensitic steels, and higher is the ultimate tensile strength (UTS), worse is the effect …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Delayed Fracture in Automotive Advanced High Strength Steel: A New Investigation Approach

Valentini

Tedesco

Corsinovi³

et al. 2019

steel research int.

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Nowadays Al-Si coated boron steels (that are Advanced High Strength Steels, AHSS) are largely used in vehicle bodies. If on one hand they offer great mechanical performances, on the other hand they are susceptible to hydrogen delayed fracture. As this phenomenon brings to the reject of the component during production or even worse the failure during operation, diffusible hydrogen absorbed in the component needs to be monitored during plant process. A simple procedure, by means of a solid-state innovative sensor, is developed to check diffusible hydrogen concentration during laboratory experiments and manufacturing process. The behavior of an Al-Si coated boron steel after hydrogen absorption is investigated by means of slow strain rate mechanical tests (SSRT) and correlated to the diffusible hydrogen content. Finally, in manufacturing process an extensive plant test campaign is performed on semi-manufactured vehicle parts in order to verify the laboratory's results. These tests confirmed the possibility to approach the evaluation of diffusible hydrogen content in semi-products during car manufacturing by means of an easy procedure based on a robust sensor.

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Section: Discussionsupporting

confidence: 49%

Section: Introductionmentioning

confidence: 99%

Delayed Fracture in Automotive Advanced High Strength Steel: A New Investigation Approach

Valentini

Tedesco

Corsinovi³

et al. 2019

steel research int.

View full text Add to dashboard Cite

show abstract

“…1.5 GPa-grade tensile strength PHS (e.g. 22MnB5 or 22MnB5-base) has been used for B pillars, A pillars, Bumpers, and Sills etc., by OEMs [1][2][3], and experienced a rapid growth in the automotive industry [4]. Recently, 1.8-2.0 GPa PHS have also be developed by increasing the carbon content accordingly (0.27-0.37 wt.%C) and controlling various precipitates, thereby attracting great attention as a promising candidate for next-generation reinforcing and lightweight structural components [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

“…New requirements were presented for such ultra-high strength steel and components, e.g. impact toughness [5], bendability [8], and hydrogen-induced delayed fracture properties [1][2][3][4] etc., and hydrogen embrittlement is a severe obstacle and challenge for application of Al-Si coated PHS [9] and 1.8-2.0 GPa PHS [10]. The dew point in the austenitizing furnace can produce hydrogen consequently to the high temperature reaction between water and aluminum/silicon/iron [11], and the high temperature also promotes hydrogen diffusion through the metal lattice under the aluminum-silicon coating, thus increasing the diffusible hydrogen content, after cooling, the coating acts as a strong barrier preventing the hydrogen from going out of the microstructure, this increases the probability of delayed fracture [12].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Dew Point Control on Hydrogen Embrittlement of Al-Si Coated Hot-Stamping Components

Lu¹,

Guo²,

Feng³

et al. 2023

Atlantis Highlights in Materials Science and Technology

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The press hardening steel (PHS) and hot-stamping components were utilized widely on the reinforcement and lightweight structure of car body due to its ultra-high strength. There existed an obstacle of hydrogen embrittlement (HE) for coated 1.5-2.0 GPa PHS, and uncoated 1.8-2.0 GPa PHS. The typical hot-stamping components were industry-tried by slim Al-Si coated 22MnB5Nb PHS, under -20 °C dew points and without dew point control, and the U-shaped constant bending load test in 0.1 mol/L HCL solution of samples from components were performed based on automotive industry standard T/CSAE155-2020, to compare the hydrogen embrittlement resistance. The results were attained that, under same testing fracture stress, the fracture time is higher obviously for samples at -20 °C dew points comparing to the one without dew point control, and the atmosphere in austenitizing furnace affects prominently the diffusible hydrogen produced by reduction reaction in austenitizing process. A hydrogen embrittlement mechanism deduction is that the original diffusible hydrogen in steel and the diffusible hydrogen produced by reduction reaction in austenitizing process leads to initial micro cracking under higher bending stress according to HELP effect, after that microcrack passivates, and restart of microcrack by the effect of dislocation, grain boundary and applied stress, then hydrogen embrittlement fracture occurs by repeated microcrack passivation and restart.

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“…3), thus press hardening process becomes much more robust due to Nb addition. Another important functionality of nano-sized NbC precipitates in the final microstructure is to serve as hydrogen traps and to reduce the sensitivity to hydrogen embrittlement [4] . …”

Section: Precipitation Of Nano-sized Nbc and Impact On High Performanmentioning

confidence: 99%

Development of High Performance Press Hardening Steel Through Microstructure Engineering

Bian¹,

Lu²,

Wang³

et al. 2017

Advanced High Strength Steel and Press Hardening

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Microstructure engineering determines predominantly the properties and applications of steel. Martensite provides the highest strength compared to any other microstructural constitutes, thus press hardening steel with martensite microstructure has been widely used in vehicles' body structure to enhance the passive safety in the event of a crash. However, for such applications there are also potential problems related to martensite microstructure, such as limited ductility (bendability), low impact toughness (low energy absorption and low fracture resistance) and low resistance to hydrogen induced cracking. Usually these properties dominate the fracture behaviour of martensitic microstructure and consequently the crash-resistance performance of press hardened components. Therefore, in order to achieve high performance, it is necessary to optimize the steel microstructure during entire metallurgical processes. This paper introduces metallurgical solutions of microstructure engineering based on niobium metallurgy. The key point of microstructure engineering is to tailor and to fine-tune the microstructure details towards targeted applications with aims for high performance. The paper describes how to implement microstructure engineering in the press hardening steel by refining and homogenising the martensite matrix, strengthening and facilitating high angle grain boundaries in the martensite substructure, integrating a high density of homogenously distributed nano-sized NbC precipitates in the martensite matrix and finally creating a layer of soft microstructure near the surface area through controlled decarburization process during press hardening. The results and benefits of microstructure engineering to press hardening steel (22MnB5) are explained in detail.

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Solutions for Hydrogen-Induced Delayed Fracture in Hot Stamping

Cited by 13 publications

References 6 publications

Delayed Fracture in Automotive Advanced High Strength Steel: A New Investigation Approach

Delayed Fracture in Automotive Advanced High Strength Steel: A New Investigation Approach

The Effect of Dew Point Control on Hydrogen Embrittlement of Al-Si Coated Hot-Stamping Components

Development of High Performance Press Hardening Steel Through Microstructure Engineering

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