scholarly journals Hydrogen-related challenges for the steelmaker: the search for proper testing

2017 ◽  
Vol 375 (2098) ◽  
pp. 20160408 ◽  
Author(s):  
R. G. Thiessen
Keyword(s):  
Standardized Test ◽  
High Strength Steels ◽  
High Strength ◽  
Advanced High Strength Steels ◽  
Passenger Safety ◽  
Transportation Sector ◽  
Wide Range ◽  
Increased Sensitivity ◽  
Stress States ◽  
Increased Strength

The modern steelmaker of advanced high-strength steels has always been challenged with the conflicting targets of increased strength while maintaining or improving ductility. These new steels help the transportation sector, including the automotive sector, to achieve the goals of increased passenger safety and reduced emissions. With increasing tensile strengths, certain steels exhibit an increased sensitivity towards hydrogen embrittlement (HE). The ability to characterize the material's sensitivity in an as-delivered condition has been developed and accepted (SEP1970), but the complexity of the stress states that can induce an embrittlement together with the wide range of applications for high-strength steels make the development of a standardized test for HE under in-service conditions extremely challenging. Some proposals for evaluating the material's sensitivity give an advantage to materials with a low starting ductility. Despite this, newly developed materials can have a higher original elongation with only a moderate reduction in elongation due to hydrogen. This work presents a characterization of new materials and their sensitivity towards HE. This article is part of the themed issue ‘The challenges of hydrogen and metals’.

scholarly journals Modeling of Forming Limit Bands for Strain-Based Failure-Analysis of Ultra-High-Strength Steels

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 631 ◽  
Author(s):  
Hamid Bayat ◽  
Sayantan Sarkar ◽  
Bharath Anantharamaiah ◽  
Francesco Italiano ◽  
Aleksandar Bach ◽  
...  
Keyword(s):  
Material Properties ◽  
Driving Forces ◽  
Weight Ratio ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Limit ◽  
Boron Steel ◽  
Passenger Safety ◽  
Ultra High Strength Steels ◽  
Increased Strength

Increased passenger safety and emission control are two of the main driving forces in the automotive industry for the development of light weight constructions. For increased strength to weight ratio, ultra-high-strength steels (UHSSs) are used in car body structures. Prediction of failure in such sheet metals is of high significance in the simulation of car crashes to avoid additional costs and fatalities. However, a disadvantage of this class of metals is a pronounced scatter in their material properties due to e.g., the manufacturing processes. In this work, a robust numerical model is developed in order to take the scatter into account in the prediction of the failure in manganese boron steel (22MnB5). To this end, the underlying material properties which determine the shapes of forming limit curves (FLCs) are obtained from experiments. A modified Marciniak–Kuczynski model is applied to determine the failure limits. By using a statistical approach, the material scatter is quantified in terms of two limiting hardening relations. Finally, the numerical solution obtained from simulations is verified experimentally. By generation of the so called forming limit bands (FLBs), the dispersion of limit strains is captured within the bounds of forming limits instead of a single FLC. In this way, the FLBs separate the whole region into safe, necking and failed zones.

Relationship between Microstructure and Mechanical Properties in Q&P-Steels

2016 ◽  
Vol 879 ◽  
pp. 1933-1938 ◽  
Author(s):  
Richard G. Thiessen ◽  
Georg Paul ◽  
Roland Sebald
Keyword(s):  
Mechanical Properties ◽  
Dual Phase Steel ◽  
High Strength Steels ◽  
High Strength ◽  
The Body ◽  
Advanced High Strength Steels ◽  
Passenger Safety ◽  
Back Scattering ◽  
Body In White ◽  
Expected Increase

Third-Generation advanced high strength steels are being developed with the goal of reducing the body-in-white weight while simultaneously increasing passenger safety. This requires not only the expected increase in strength and elongation, but also improved local formability. Optimizing elongation and formability were often contradictory goals in dual-phase steel developments. Recent results have shown that so-called "quench and partitioning" (Q&P) concepts can satisfy both requirements [1]. Many Q&P-concepts have been studied at thyssenkrupp Steel Europe. Thorough investigation of the microstructure has revealed relationships between features such as the amount, morphology and chemical stability of the retained austenite and the obtained mechanical properties. An evaluation of the lattice strain by means of electron-back-scattering-diffraction has also yielded a correlation to the obtained formability. The aim of this work is to present the interconnection between these microstructural features and propose hypotheses for the explanation of how these features influence the macroscopically observed properties.

Localized forming limit analysis of substrate-supported metals: Influence of yield-dependent necking bound angle

2021 ◽  
pp. 095440542110573
Author(s):  
Ali Bandizaki ◽  
Asghar Zajkani ◽  
Saeed Moulood
Keyword(s):  
Anisotropy Parameter ◽  
High Strength Steels ◽  
High Strength ◽  
Theoretical Models ◽  
Plastic Instability ◽  
Forming Limit ◽  
Yield Criteria ◽  
Advanced High Strength Steels ◽  
Theory Application ◽  
Stress States

In this paper, the influence of functional elastomeric substrate-supported layers for enhancing potential resistance capability against localized plastic failure of advanced high strength steels is considered based on a localized necking model of vertex theory. Application of this structure leads to postponing the plastic instability of the metallic part. By defining diffuse and localized modes of deformation in a general framework, the theoretical models are developed to predict necking limits at several stress states. In addition, the results of the Hookean and neo-Hookean elastomers are compared in terms of strain hardening with the anisotropy parameter of Hill’s yield criteria. Since necking band angle (NBA) is a principal factor for the necking prediction, its effect on bifurcation events is evaluated specifically for different ratios of stress rate, and quadratic and non-quadratic yield criteria. This analysis is performed by proposing a supported and yield-dependent necking bound angle (YD-NBA). All considerations are done by providing equilibrium conditions governed over the NBA. Finally, obtained results indicate good agreements between several theoretical considerations and experimental data.

Manufacturing of Innovative Car Seat Components by Forming of Advanced High Strength Steels – Fundamental Research and Application

2009 ◽  
Vol 410-411 ◽  
pp. 3-11 ◽  
Author(s):  
Marion Merklein ◽  
Markus Kaupper
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Absorption Capacity ◽  
Car Seat ◽  
Advanced High Strength Steels ◽  
Steel Sheets ◽  
Transportation Sector ◽  
Steel Grades ◽  
Fundamental Research ◽  
Part Complexity

Nowadays advanced high strength steel sheets and related forming technologies play an important role in lightweight construction in the transportation sector. Since especially car seat components are subject to very strict safety demands, the application of these modern steel grades, which provide enhanced strength levels, seems to be a promising strategy to meet the challenge of reducing the sheet metal thickness while maintaining the crash energy absorption capacity. Concerning the high required level of part complexity and accuracy both the reduced formability and the increased springback tendency of advanced high strength steels are challenges for forming technologies compared to conventional steel grades. Against this background the forming potentials of advanced high strength steels are investigated and are made accessible for an application in structural car seat components. The analysis is to be done both experimentally and numerically, focusing on the finite element method (FEM) regarding a reliable process design.

scholarly journals Temperature Dependence of the Static and Dynamic Behaviour in a Quenching and Partitioning Processed Low-Si Steel

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 509 ◽  
Author(s):  
Florian Vercruysse ◽  
Carola Celada-Casero ◽  
Bernd M. Linke ◽  
Patricia Verleysen ◽  
Roumen H. Petrov
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
High Strength Steels ◽  
High Strength ◽  
Dynamic Strain ◽  
Strain Rates ◽  
Trip Effect ◽  
Quenching And Partitioning ◽  
Advanced High Strength Steels ◽  
Wide Range

Because of their excellent combination of strength and ductility, quenching and partitioning (Q & P) steels have a great chance of being added to the third generation of advanced high strength steels. The large ductility of Q & P steels arises from the presence of 10% to 15% of retained austenite which postpones necking due to the transformation induced plasticity (TRIP) effect. Moreover, Q & P steels show promising forming properties with favourable Lankford coefficients, while their planar anisotropy is low due to a weak texture. The stability of the metastable austenite is the key to obtain tailored properties for these steels. To become part of the newest generation of advanced high strength steels, Q & P steels have to preserve their mechanical properties at dynamic strain rates and over a wide range of temperatures. Therefore, in the present study, a low-Si Q & P steel was tested at temperatures from −40 °C to 80 °C and strain rates from 0.001 s−1 to 500 s−1. Results show that the mechanical properties are well-preserved at the lowest temperatures. Indeed, at −40 °C and room temperature, no significant loss of the deformation capacity is observed even at dynamic strain rates. This is attributed to the presence of a large fraction of austenite that is so (thermally) stable that it does not transform in the absence of deformation. In addition, the high stability of the austenite decreases the elongation at high test temperatures (80 °C). The additional adiabatic heating in the dynamic tests causes the largest reduction of the uniform strain for the samples tested at 80 °C. Quantification of the retained austenite fraction in the samples after testing confirmed that, at the highest temperature and strain rate, the TRIP effect is suppressed.

Validation of Kinematic Hardening Parameters from Different Stress States and Levels of Plastic Strain with the Use of the Cyclic Bending Test

2015 ◽  
Vol 639 ◽  
pp. 385-392 ◽  
Author(s):  
Martin Rosenschon ◽  
Sebastian Suttner ◽  
Marion Merklein
Keyword(s):  
Kinematic Hardening ◽  
High Strength Steels ◽  
High Strength ◽  
Bending Test ◽  
Compression Tests ◽  
Cyclic Shear ◽  
Cyclic Bending ◽  
Advanced High Strength Steels ◽  
Hardening Law ◽  
Stress States

The recent development of new lightweight sheet metal materials, like advanced high-strength steels or aluminium alloys, in combination with an increasing component complexity provides new challenges to the numerical material modelling in the FEM based process design. An auspicious approach to improve the quality of the numerical results – most notably in springback analysis – is the modelling of the so called Bauschinger effect achieved through implementation of kinematic hardening models. Within this paper the influence of the stress state and the level of pre-strain on the numerical simulation result of the advanced high strength steel DP-K45/78+Z will be analysed. For this purpose, a parameter identification of the kinematic hardening law according to Chaboche and Rousselier is performed at different pre-strains on the basis of experimental data from tension-compression tests as well as cyclic shear tests. Finally, the identified parameters are validated in a comparison between numerical and experimental results of a cyclic bending test.

scholarly journals Integration of Press-Hardening Technology into Processing of Advanced High Strength Steels

2018 ◽  
Vol 941 ◽  
pp. 317-322 ◽  
Author(s):  
Hana Jirková ◽  
Kateřina Opatová ◽  
Josef Káňa ◽  
Dagmar Bublíková ◽  
Martin Bystrianský
Keyword(s):  
Isothermal Holding ◽  
High Strength Steels ◽  
Dimensional Accuracy ◽  
High Strength ◽  
Total Elongation ◽  
Press Hardening ◽  
Advanced High Strength Steels ◽  
Passenger Safety ◽  
Ultra High Strength Steels ◽  
New Processing

Development of high strength or even ultra-high strength steels is mainly driven by the automotive industry which strives to reduce the weight of individual parts, fuel consumption, and CO2 emissions. Another important factor is the passenger safety which will improve by the use of these materials. In order to achieve the required mechanical properties, it is necessary to use suitable heat treatment in addition to an appropriate alloying strategy. The main problem of these treatments is the isothermal holding time. These holding times are technologically demanding which is why industry seeks new possibilities to integrate new processing methods directly into the production process. One option for making high-strength sheet metals is press-hardening which delivers high dimensional accuracy and a small spring-back effect. In order to test the use of AHSS steels for this technology, a material-technological modelling was chosen. Material-technological models based on data obtained directly from a real press-hardening process were examined on two experimental steels, CMnSi TRIP and 42SiCr. Variants with isothermal holding and continuous cooling profiles were tested. It was found that by integrating the Q&P process (quenching and partitioning) into press hardening, the 42SiCr steel can develop strengths of over 1800 MPa with a total elongation of about 10%. The CMnSi TRIP steel with lower carbon content and without chromium achieved a tensile strength of 1160 MPa with a total elongation of 10%.

scholarly journals In Situ Determination of Phase Stress States in an Unstable Medium Manganese Duplex Steel Studied by High-Energy X-ray Diffraction

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1335
Author(s):  
Mathias Lamari ◽  
Sébastien Y. P. Allain ◽  
Guillaume Geandier ◽  
Jean-Christophe Hell ◽  
Astrid Perlade ◽  
...  
Keyword(s):  
Retained Austenite ◽  
High Strength Steels ◽  
High Strength ◽  
High Energy ◽  
Internal Stresses ◽  
X Ray Diffraction ◽  
X Ray ◽  
Advanced High Strength Steels ◽  
Stress States

Duplex medium Mn steels are high-potential advanced high-strength steels (AHSS) for automotive construction. Their excellent forming properties stem from the specific stress partitioning between their constituting phases during deformation, namely the ferritic matrix, unstable retained austenite, and strain-induced fresh martensite. The stability of the retained austenite and the 3D stress tensors of each phase are determined simultaneously in this work by in situ high energy X-ray diffraction on synchrotron beamline during a tensile test. The role of internal stresses inherited from the manufacturing stage are highlighted for the first time as well as new insights to understand the origin of the serrations shown by these alloys.

Modeling and Simulation of Q&P Steels

2016 ◽  
Vol 879 ◽  
pp. 1454-1458
Author(s):  
Georg Paul ◽  
Richard G. Thiessen
Keyword(s):  
Automotive Industry ◽  
High Strength Steels ◽  
High Strength ◽  
The Body ◽  
Special Focus ◽  
High Tensile Strength ◽  
Advanced High Strength Steels ◽  
Passenger Safety ◽  
Steel Grades ◽  
Body In White

Two important objectives of the automotive industry are the decrease of the body-in-white weight and the improvement of the passenger safety. High strength steels (HSS) are widely used to achieve these objectives. Quenching and partitioning (Q&P) has recently been proposed to achieve high strength steel grades for the third generation of advanced high strength steels (AHSS), which contain a considerable amount of retained austenite. Due to their microstructure these new steel grades combine a high tensile strength with good elongation values, as long as cementite precipitation is avoided. A model describing the involved phase transformations is presented. Special focus is put on the cementite precipitation and how it is influenced by silicon and aluminum additions.

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