The Cold Bending Cracking Analysis of Hot Stamping Door Bumper

T., M.; Zhao, Yanjing; Lu, Hailong; Bian, Jiang; Guo, A. M.; Sun, Zejun

doi:10.1142/9789813140622_0113

Cited by 1 publication

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“…From the macro point of view, the parts are cracking continuously, and even the sound of fracture can be heard. From the micro point of view, the microstructure of the crack fracture is stepped [8], which also shows that the cracking is segmented. Passivation involves microcracks here (Fig.…”

Section: The Hydrogen Embrittlement Mechanismmentioning

confidence: 97%

“…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%

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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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Section: The Hydrogen Embrittlement Mechanismmentioning

confidence: 97%