Advances in Zinc-coated Sheet Steel Processing and Properties: Advances in Zinc-coated Sheet Steel Processing and Properties
Sponsored by: AIST Metallurgy — Processing, Products & Applications Technology Committee
Program Organizers: Joseph McDermid, McMaster University; Daniel Baker, LIFT
Monday 2:00 PM
October 10, 2022
Room: 406
Location: David L. Lawrence Convention Center
Session Chair: Joseph McDermid, McMaster University; Daniel S. Baker, General Motors Corp.
2:00 PM
Alleviation of Zn-assisted Liquid Metal Embrittlement in Austenitic-TWIP/martensitic-HSLA Steel Multi-layered Sheet Additively Manufactured by Directed Energy Deposition: Seok-Hyun Hong1; Du-Rim Eo2; Sunghak Lee1; Jung-Wook Cho1; Sung-Joon Kim1; 1POSTECH/GIFT; 2KITECH
In resistance spot welding, Zn-coated steel sheets are exposed to high temperature and stress, which may cause the liquid metal embrittlement (LME). TWIP steel has been reported to be susceptible to LME, and austenitic microstructure was often considered to be the cause of vulnerability. However, the explanation for the role of microstructure is still unclear.In this study, the austenitic-TWIP/martensitic-HSLA steel multi-layered sheets (MLSs) were manufactured. Compositionally graded multi-layers from TWIP to HSLA were deposited on the surface of a TWIP slab (140T) by a powder feed additive manufacturing. This slab was homogenized, hot-rolled, and cold-rolled to fabricate a 1.6 mm-thick MLS with a 30 to 50 μm-thick clad layer depending on the number of depositions. After spot welding, the LME cracks were effectively alleviated in MLSs compared to monolithic TWIP steel sheets. Thus, the effect of the clad layer, or subsurface microstructure, on the severity of LME was investigated.
2:20 PM
Microstructure Evolution during Early Stages of Liquid Metal Embrittlement in an Advanced High-strength-steel: Yuki Ikeda1; Renliang Yuan2; Hassan Ghassemi-Armaki3; Anirban Chakraborty4; Jim Zuo2; Robert Maass1; 1Federal Institute for Materials Research and Testing (BAM); 2University of Illinois at Urbana-Champaign; 3General Motors R&D; 4Arcelor Mittal Global R&D
Despite the high strength and ductility of advanced high-strength steels (AHSS), Zn coatings typically applied to increase the corrosion resistance can be the origin of mechanical property degradation after joining. This property degradation is a manifestation of the well-known Liquid Metal Embrittlement (LME) phenomena, during which liquified Zn infiltrates into the substrate along grain boundaries (GBs). Previously, we have revealed the nucleation and growth of nano-scale intermetallic phases inside uncracked GBs (Materials Today Advances 13, 100196, 2022), which highlights the multi-phase microstructure developing before cracking occurs. To shed further light on the early stages of LME in AHSS, we report here on the microstructural evolution of interrupted welds by using analytical scanning transmission electron microscopy. We discuss these findings in the context of the time-resolved substructure evolution right beneath the interface between the AHSS and the Zn-based coating and track how Zn progressively infiltrates the substrate along phase and GBs.
2:40 PM
The Interaction between Mn and Sn and Its Effects on the Selective Oxidation of Advanced High Strength Steels: Jonas Wagner1; Joseph McDermid1; 1Steel Research Centre, McMaster University
Sn microalloying has been found to improve the continuous galvanizing performance of Advanced High Strength Steels (AHSS) with Mn contents between 2 and 6 wt. % by reducing selective oxidation prior to dipping. However, its benefits for steels with higher Mn levels remain uncertain. In this study, the effects of increasing Mn content on the Sn segregation and in turn the effect of the segregated Sn on the selective oxidation of Fe-Mn-Sn model alloys are evaluated. Sn is found to decrease internal and external oxidation, while the surface segregation of Sn is not adversely affected by higher Mn levels. Sn is present at the surface directly after ramping and does not systematically change for holding temperatures between 675 and 825 °C and holding times between 60 and 480 s, indicating Sn microalloying to be a robust strategy for improving galvanizing performance of a wider range of AHSS.
3:00 PM
Leaching Zinc Ions from Industrial Waste Ashes a Kinetic Study and Development of a Semi-empirical Model.: Hilary Rutto1; Tumisang Seodigeng1; 1Vaal University of Technology
The investigation aimed to determine how the zinc will be extracted from secondary sources generated from the galvanising process using dilute sulphuric acid under controlled laboratory conditions of temperature, solid, liquid ratio, and agitation rate. The leaching experiment was conducted for 2 hours. The total zinc extracted was calculated with the amount of zinc dissolved at a unit time compared to the initial zinc content of the zinc ash. Sulphuric acid was an effective leaching agent with overall extraction of 91.1% when concentration is at 2M, and solid/liquid ratio kept at 1g/200mL leaching solution and temperature set at 65oC while slurry agitation is at 450rpm. The leaching mechanism of zinc ash with sulphuric acid conformed well to the shrinking core model. A semi-empirical model was developed to determine the zinc ions leached from industrial zinc ash waste.
3:20 PM Break
3:40 PM
An Exploration of a Neural Network Approach for the On-line Prediction of Steel Strip Radiative Properties: Nishant Narayanan1; Fatima Suleiman1; Kyle Daun1; 1University of Waterloo
Spectral emissivity variations across Advanced High Strength Steel (AHSS) coils may cause non-uniform temperature evolutions and pyrometric temperature errors on continuous galvanising lines (CGL), producing non-homogeneous mechanical properties. This study explores spectral emissivity variations across AHSS coils in their pre-annealed state and finds these variations to be strongly influenced by the presence of surface cavities. The radiative properties are theoretically modelled with the Geometric Optics Approximation (GOA) ray-tracing algorithm, using surface height profiles obtained through 3D depth mapping of optical images. The GOA algorithm provides accurate spectral emissivity predictions within its validity regime, encompassing the typical pyrometric wavelengths; however, it excludes wavelengths important for predicting strip temperature evolutions. For improved spectral emissivity predictions, the paper explores the use of a data-driven regression neural net for correlating the number of cavities and global roughness with spectral emissivity, to possibly serve as a useful tool for on-line spectral emissivity predictions.
4:00 PM
Zinc Coatings and Their Control Using the New Integrated Indicator ECP-Zn: Borys Sereda1; Iryna Kruhliak1; Dmytro Sereda1; 1Dneprovsky State Technical University
To protect parts and structures operating in corrosive environments, zinc coatings obtained under SHS conditions are widely used. Topics of special interest include the effects of these processes on the development of steel microstructures and consequent effects on properties, internal and external oxidation phenomena occuring during processing including effects on development of the zinc coating, advances in zinc coating control.In this paper a new method of zinc coating control - effective reference (ECP-Zn), ECP-Zn was defined for zinc coatings obtained under SHS conditions, which were compared to hot-dip galvanized, electroplated and thermodiffusion zinc coatings. Zinc coatings including G-phase with continuous cubic lattice, δ-phase (FeZn7) with hexagonal lattice, zinc oxides, and ξ-phase (FeZn13) were compared.