scholarly journals Alloy Optimization for Reducing Delayed Fracture Sensitivity of 2000 MPa Press Hardening Steel

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 853 ◽  
Author(s):  
Hardy Mohrbacher ◽  
Takehide Senuma
Keyword(s):  
Tensile Strength ◽  
Hydrogen Embrittlement ◽  
Alloying Elements ◽  
Steel Alloy ◽  
Delayed Fracture ◽  
Press Hardening ◽  
Automotive Body ◽  
Body Design ◽  
Delayed Cracking ◽  
Press Hardening Steel

Press hardening steel (PHS) is widely applied in current automotive body design. The trend of using PHS grades with strengths above 1500 MPa raises concerns about sensitivity to hydrogen embrittlement. This study investigates the hydrogen delayed fracture sensitivity of steel alloy 32MnB5 with a 2000 MPa tensile strength and that of several alloy variants involving molybdenum and niobium. It is shown that the delayed cracking resistance can be largely enhanced by using a combination of these alloying elements. The observed improvement appears to mainly originate from the obstruction of hydrogen-induced damage incubation mechanisms by the solutes as well as the precipitates of these alloying elements.

Influence of vanadium on the hydrogen embrittlement of aluminized ultra-high strength press hardening steel

2018 ◽  
Vol 735 ◽  
pp. 448-455 ◽  
Author(s):  
Lawrence Cho ◽  
Eun Jung Seo ◽  
Dimas H. Sulistiyo ◽  
Kyoung Rae Jo ◽  
Seong Woo Kim ◽  
...  
Keyword(s):  
Hydrogen Embrittlement ◽  
High Strength ◽  
Press Hardening ◽  
Press Hardening Steel

scholarly journals A Super-Ductile Alloy for the Diecasting of Aluminium Automotive Body Structural Components

2014 ◽  
Vol 794-796 ◽  
pp. 526-531 ◽  
Author(s):  
Douglas Watson ◽  
Shou Xun Ji ◽  
Zhong Yun Fan
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Aluminium Alloy ◽  
Aluminium Alloys ◽  
Alloying Elements ◽  
Structural Components ◽  
Automotive Body ◽  
Structural Parts

Super-ductile diecast aluminium alloys are critical to future lightweighting of automotive body structures. This paper introduces a diecast aluminium alloy that can satisfy the requirements of these applications. After a review of currently available alloys, the requirement of a diecast aluminium alloy for automotive body structural parts is proposed and an Al-Mg-Si system is suggested. The effect of the alloying elements, in the composition, has been investigated on the microstructure and mechanical properties, in particular the yield strength, the ultimate tensile strength and elongation.

New Generation Press Hardening Steels with Tensile Strength of 1.7-2.0 GPa and Enhanced Bendability

2021 ◽  
Author(s):  
Sarah Tedesco ◽  
Ming Shi ◽  
Jason Coryell ◽  
Qi Lu ◽  
Jianfeng Wang
Keyword(s):  
Tensile Strength ◽  
Automotive Industry ◽  
The Novel ◽  
Component Level ◽  
Press Hardening ◽  
Crash Protection ◽  
Oxidation Resistant ◽  
Light Weighting ◽  
New Generation ◽  
Press Hardening Steel

Abstract Press hardening steel (PHS) applications predominately use 22MnB5 AlSi coated in the automotive industry. This material has a limited supply chain. Increasing the tensile strength and bendability of the PHS material will enable light-weighting while maintaining crash protection. In this paper, a novel PHS is introduced, and properties are compared to 22MnB5. The new Coating Free PHS (CFPHS) steel, 25MnCr, has increased carbon, with chromium and silicon additions for oxidation resistance. Its ultimate tensile strength (UTS) of 1.7 GPa with bending angle above 55° at 1.4mm thickness improves upon the 22MnB5 grade. This steel is not pre-coated, is oxidation resistant at high temperature, thus eliminating the need for AlSi or shot blasting post processing to maintain surface quality. Microstructural mechanisms used to enhance bendability and energy absorption are discussed for the novel steel. Performance evaluations such as: weldability, component level crush and intrusion testing and e-coat adhesion, are conducted on samples from industrial coils.

scholarly journals Effect of Relative Humidity on Mechanical Degradation of Medium Mn Steels

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1304 ◽  
Author(s):  
Qingyang Liu ◽  
Juanping Xu ◽  
Liancheng Shen ◽  
Qingjun Zhou ◽  
Yanjing Su ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Relative Humidity ◽  
Hydrogen Embrittlement ◽  
Hydrogen Concentration ◽  
High Strength Steels ◽  
Threshold Value ◽  
Tensile Tests ◽  
Constant Load ◽  
Mechanical Degradation ◽  
Delayed Cracking

Medium Mn steels have been considered as the next-generation materials for use in the automotive industry due to their excellent strength and ductility balance. To reduce the total weight and improve the safety of vehicles, medium Mn steels look forward to a highly promising future. However, hydrogen-induced delayed cracking is a concern for the use of high strength steels. This work is focused on the service characteristics of two kinds of medium Mn steels under different relative humidity conditions (40%, 60%, 80% and 100%). Under normal relative humidity (about 40%) at 25 °C, the hydrogen concentration in steel is 0.4 ppm. When exposed to higher relative humidity, the hydrogen concentration in steel increases slowly and reaches a stable value, about 0.8 ppm. In slow strain rate tensile tests under different relative humidity conditions, the tensile strength changed, the hydrogen concentration increased and the elongation decreased as well, thereby increasing the hydrogen embrittlement sensitivity. In other words, the smaller the tensile rate applied, the greater the hydrogen embrittlement sensitivity. In constant load tests under different relative humidity conditions, the threshold value of the delayed cracking of M7B (‘M’ referring to Mn, ‘7’ meaning the content of Mn, ‘B’ denoting batch annealing) steel maintains a steady value of 0.82 σb (tensile strength). The threshold value of the delayed cracking of M10B significantly changed along with relative humidity. When relative humidity increased from 60% to 80%, the threshold dropped sharply from 0.63 σb to 0.52 σb. We define 80% relative humidity as the ‘threshold humidity’ for M10B.

Solutions for Hydrogen-Induced Delayed Fracture in Hot Stamping

2014 ◽  
Vol 1063 ◽  
pp. 32-36 ◽  
Author(s):  
Hong Zhou Lu ◽  
Shi Qi Zhang ◽  
Bian Jian ◽  
Hardy Mohrbacher ◽  
Ai Min Guo
Keyword(s):  
Automotive Industry ◽  
Fracture Resistance ◽  
Hot Stamping ◽  
Passive Safety ◽  
Effective Solution ◽  
Delayed Fracture ◽  
Press Hardening ◽  
Car Body ◽  
Hot Stamping Steel ◽  
Press Hardening Steel

One of the main targets in automotive industry is to reduce the weight of vehicle as well as increase the safety. To accomplish this goal, press-hardening steel and hot stamping parts have been used in car body. However, the possibility of hydrogen-induced delayed fracture (HDF) of hot stamping parts exits, which will decrease the car’s passive safety. A solution has been presented to reduce the sensitivity of HDF and improve hydrogen-induced delayed fracture resistance (HDFR) by Niobium micro-alloying technology. Traditional press-hardening steel 22MnB5 and new steel 22MnBNb2, 22MnBNb5 and 22MnBNb7 were studied, and it is shown that the appropriate addition of Nb is beneficial to the improvement of the delayed fracture resistance of the hot stamping steel, which indicates that Niobium micro-alloying technology is an effective solution to the HDF in hot stamping steels.

Development of Niobium Alloyed Press Hardening Steel with Improved Properties for Crash Performance

2014 ◽  
Vol 1063 ◽  
pp. 7-20 ◽  
Author(s):  
Bian Jian ◽  
Li Wang ◽  
Hardy Mohrbacher ◽  
Hong Zhou Lu ◽  
Wen Jun Wang
Keyword(s):  
Transition Temperature ◽  
High Strength ◽  
Press Hardening ◽  
Brittle Transition ◽  
Delayed Cracking ◽  
Nb Microalloying ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
Conventional Press ◽  
Press Hardening Steel

Press hardening steel has become a much used material in car body manufacturing due to its excellent safety and lightweight potential. In some recent car models press hardening steel has reached already a weight share of more than 20% in the body structure while it is estimated that it could reach even around 40% in the future. However conventional press hardening steel based on the alloying concept 22MnB5 was designed originally not for automotive application. In spite of the high strength level, press hardening steel has generally low toughness due to the relatively high carbon content and its martensitic microstructure. Particularly important is the ductile-to-brittle transition temperature at low temperature, which might lead to unexpected failure in cold climate regions. Furthermore, hydrogen embrittlement is a major concern in press hardening steel as previous results indicated that only a few ppm of hydrogen could induce delayed cracking. Generally it is important that impact energy should be absorbed by the material to avoid unexpected disintegration of the structure. This material capability is usually characterized by the toughness. All these characteristics have not yet been systematically investigated in press hardening steel. Consequently, no attempts have been made to optimize conventional press hardening steel for obtaining better toughness, lower ductile-to-brittle transition temperature and reduced sensitivity to hydrogen induced cracking.A generally proven approach of improving the resistance against brittle failure in high strength steel is the refinement of microstructure, which can be efficiently achieved by Nb microalloying. This paper will introduce modified alloy designs for press hardening steel and explain fundamentally the metallurgical effects of Nb microalloying on the improvement of crack propagation resistance, bendability and delayed cracking behavior induced by hydrogen penetration in press hardening steel. The results reveal better toughness, improved bending behavior and increased resistance against hydrogen embrittlement.

Effect of Small Iron, Chromium and Boron Additions as Alloying Elements on Microstructure and Mechanical Properties of Ni3Al

2007 ◽  
Vol 23 ◽  
pp. 123-126
Author(s):  
Radu L. Orban ◽  
Mariana Lucaci
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Room Temperature ◽  
Alloying Elements ◽  
Alloyed Powder ◽  
Mechanically Alloyed ◽  
Powder Mixtures ◽  
B Additions ◽  
Strength And Ductility ◽  
Iron Chromium

This paper investigates the effect of Fe, Cr and B additions, in small proportions, as alloying elements in Ni3Al with the purpose to reduce its intrinsic fragility and extrinsic embrittlement and to enhance, in the same time, its mechanical properties. It represents a development of some previous research works of the authors, proving that Ni3Al-Fe-Cr-B alloys obtained by reactive synthesis (SHS) starting from Mechanically Alloyed powder mixtures have superior both room temperature tensile strength and ductility, and compression ones at temperatures up to 800 °C, than pure Ni3Al. These create premises for their using as superalloys substitutes.

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