Advanced High Strength Steels V: Session II
Sponsored by: TMS Structural Materials Division, TMS: Steels Committee
Program Organizers: Ana Araujo, Vesuvius USA; Louis Hector, General Motors Global Technical Center; Igor Vieira, Nucor Steel; Lijia Zhao, ArcelorMittal USA; Krista Limmer, Devcom Army Research Laboratory; Jonah Klemm-Toole, Colorado School of Mines; Sebastien Allain, Institut Jean Lamour; MingXin Huang, University of Hong Kong
Monday 2:00 PM
March 15, 2021
Room: RM 6
Location: TMS2021 Virtual
2:00 PM
Cryogenic Tensile and Microstructural Behaviors of High Manganese Steel Welds: Myeonghwan Choi1; Junghoon Lee1; Hyunbin Nam1; Namhyun Kang1; Myunghyun Kim1; Daewon Cho2; 1Pusan National University; 2Korea Institute of Machinery and Materials
We investigated the weldability and relationship between microstructure and tensile properties in 24 wt% Mn steel welds and, specifically, submerged arc welds (SAWs) were produced using these welds for cryogenic applications. The base metal (BM) and weld metal (WM) exhibited a stacking fault energy (SFE) that maintained a stable austenite phase for 27.1 and 17.0 mJ/m2, respectively. Deformation twins were observed after tensile testing of the BM and WM at 298 K. Weld metals using undermatched fillers showed a lower SFE and coarser grain size compared to that of the BM. Therefore, the tensile testing at 110 K produced deformation twins and ε-martensite. The formation of ε-martensite with deformation twins antedated necking during tensile testing and elongation decreased at 110 K. However, the SAWs of high Mn steels maintained excellent low-temperature mechanical properties such as elongation, tensile strength, and yield strength with values of 20%, 1150 MPa, and 617 MPa.
2:20 PM
Effects of V and Mo Additions on the Suppression of HAZ Softening of Friction Stir Welded Si-Mn Martensitic Steel: Zexi Wu1; Kohsaku Ushioda1; Hidetoshi Fujii1; 1Joining and Welding Research Institute, Osaka University
In recent years, the demand for Advanced High Strength Steels (AHSS) has significantly increased. However, cracking at the fusion welded joints of these steels tends to occur due to the formation of brittle martensite accompanied with the HAZ softening. In our previous study, the FSW joint of 0.2%C-2%Si-3%Mn (wt.%) martensitic steel was investigated, and a good balance of strength and ductility was obtained in the stir zone due to the grain refinement of the prior austenite induced by the dynamic recrystallization of the austenite during FSW. However, the HAZ softening occurred because the martensite structure of the base material was tempered during FSW. In this study, to suppress the HAZ softening and to further improve the properties of the stir zone, V or Mo was added to 0.2%C-2%Si-3%Mn steel and the effects of alloying element addition on the microstructure and mechanical properties of the FSW joints were investigated.
2:40 PM
Microstructural Characterization of Fracture in Fe-10 pct Ni Gas Metal Arc Welds: Richard Baumer1; Daniel Bechetti2; Matthew Sinfield2; 1LeTourneau University; 2Naval Surface Warfare Center, Carderock Division
While ship light weighting and performance enhancements can be achieved through use of advanced high-strength steel alloys with yield strengths exceeding 100 ksi, successful fabrication requires welding filler materials that produce weldments of matching base metal strength and adequate toughness for the intended application, economically. Recent work has demonstrated that a Fe-10 pct nickel welding consumable can produce low distortion weldments with exceptional strength and low temperature toughness when deposited using low deposition rate gas tungsten arc welding. However, toughness is reduced in weldments produced by high deposition rate spray transfer gas metal arc (GMA) welding, the welding process most commonly used in modern shipbuilding. This work reports the relationship of GMA welding heat input of a Fe-10 pct nickel weld metal consumable to weld metal toughness through dynamic tear (DT) test energy experiments. The fusion zone microstructure is investigated, correlated to cleavage fracture, and compared DT test energy results.
3:00 PM
Use of Physical Simulations for Accelerated Welding Procedure Development in Supermartensitic Stainless Steels: Reed Phillips1; Ezequiel Pessoa1; Richard Baumer1; 1LeTourneau University
The weldability of high strength steels is often limited by control of the microstructure in the heat affected zone (HAZ), the region adjacent to the fusion zone, which experiences rapid heating and cooling rates, resulting is significant microstructural modification and commensurate property changes. To accelerate welding procedure development and qualification, simulative methods are needed to quantify microstructure evolution and identify desired welding and post weld heat treatment conditions. This work presents a framework for using a combination of thermo-mechanical physical simulations, autogenous gas tungsten arc welding experiments, and post weld heat treatment experiments to identify optimal welding process conditions. Using an example from a high strength supermartensitic stainless steel, the physical simulative methods are used to quantify the alloy phase transformation behavior, welding-induced property changes in the HAZ, thereby accelerating design of a welding procedure.
3:20 PM
Use of Thermo-mechanical Simulation to Assess Liquid Metal Embrittlement (LME) in Zinc Coated Advanced High Strength Steels: Kaleb Ponder1; Dean Sage1; Carolin Fink1; Hassan Ghassemi-Armaki2; Michael Karagoulis3; Antonio Ramirez; 1Ohio State University; 2ArcelorMittal Global R&D - East Chicago, East Chicago, IN, USA; 3Retired - General Motors
This work investigates Advanced High Strength Steels (AHSS) resistance to liquid metal embrittlement (LME) using thermo-mechanical simulation. As ‘next-generation’ steels become available, it is important to understand how processing conditions such as resistance spot welding (RSW) affect material performance. In this study, zinc-coated and uncoated coupons compared the effects of zinc on various Gen3 steels strength and ductility during RSW. The experiment composed of a hot tensile test with variable temperature and head rate to simulate regions throughout the RSW heat affected zone. Upon testing each sample was assessed using qualitative and quantitative test criteria to determine LME sensitivity. This study provides a straightforward testing approach to determine a variety of steels susceptibility to LME.
3:40 PM
Revisit the Slow Strain Rate Test for Hydrogen Embrittlement of Press-hardened Steel: Zuoheng Cao1; MingXin Huang1; 1University of Hong Kong
Hydrogen embrittlement (HE) is a prevailing issue in advanced high strength steel (AHSS). The slow strain rate test (SSRT) method after electrochemically hydrogen charging is widely acknowledged to investigate the HE susceptibility. However, the present work shows that SSRT may not be an ideal method to characterize the investigated press-hardened steel (PHS). The inclusions in this material deteriorates the HE performance extensively, whereas their existence is inevitable due to manufacture limitations. The conventional strain rate test (CSRT) method is applied to circumvent the uncertainty and scattering caused by inclusions. The strength degradation first increases with hydrogen content and holds constant after hydrogen saturation, which implies the critical hydrogen concentration where HE initially takes place and its prevalence afterwards. The current results show that, for inclusion-containing high-strength steels, CSRT serves as a more accurate method than traditional SSRT to characterize the HE related properties.
4:00 PM
Methods for Improving the Hydrogen Embrittlement Resistance in Press-hardened Steel: Zuoheng Cao1; Xiaochuan Xiong2; MingXin Huang1; 1University of Hong Kong; 2Ironovation (Suzhou) Materials Technology
Hydrogen embrittlement in high strength pressed-hardened steel (PHS) is a serious issue in the automotive industry. In particular, PHS with a tensile strength of 2 GPa is very sensitive to the defects in the microstructure. The present work shows that non-metallic inclusions such as oxides are the origin of hydrogen embrittlement during the slow strain rate test (SSRT) after electrochemically hydrogen charging. The typical fracture surface shows a fish-eye feature, similar to the fatigue failure in high strength steel. It indicates that the size and volume fraction of the non-metallic inclusions play a crucial role in determining the hydrogen embrittlement of PHS. It is recommended that ultra-clean steel manufacturing practice, similar to the one used for high-performance bearing steel, should be adopted for 2 GPa PHS for improvement of the hydrogen embrittlement resistance.