ProgramMaster Logo
Conference Tools for 2020 AWS Professional Program
Login
Register as a New User
Help
Submit An Abstract
Propose A Symposium
Presenter/Author Tools
Organizer/Editor Tools
About this Abstract
Meeting 2020 AWS Professional Program
Symposium 2020 AWS Professional Program
Presentation Title Resistance Spot Welding Challenges, Root Causes, and Suggested Welding Practices When Welding 3rd Generation AHSS
Author(s) Elliot Biro
On-Site Speaker (Planned) Elliot Biro
Abstract Scope Increasing environmental and safety challenges have brought with them a need to reduce automotive CO2 emissions while improving occupant safety. Greenhouse gas reduction is partially accomplished by thinning the materials used to make vehicles. However, to increase crash performance, these thinner materials are required to withstand higher loads and absorb more energy during crash than past materials. Steelmakers have responded to this challenge by designing multiphase steels that exhibit much higher strain hardening capabilities than past steels, which have been coined 3rd generation advanced high strength steels (3G AHSS). These 3G AHSS exhibit very high strength and elongation, which are beneficial for forming and crash, however these performance improvements have come at the cost of increased alloying and microstructural complexity. Both factors affect steel weldability and weld performance. Specifically, two phenomena have been seen when welding these steels: Liquid metal embrittlement (LME), and a carbon depleted zone at the fusion boundary. This work seeks to explain the material factors responsible for these phenomena, and how the welding process may be modified to minimize or eliminate them though an examination of these phenomena in various steels and under various spot welding conditions. The chemical compositions of all steels used had high C (>0.20 wt%), Mn (>2.0 wt%) and Si (>1.0 wt%) contents. The steels were examined microstructurally using both optical and scanning electron microscopy to understand the base microstructure, which was a combination of ferrite, martensite, tempered martensite and retained austenite. Then the steels were all welded using an MFDC spot welder, followed by shear and cross-tension strength testing and analysis of the post-welded microstructure. The excellent combination of strength and ductility of these steels derives from the multiphase nature. During loading, the retained austenite within the structure transforms into strain induced martensite, which leads to increased dislocation density at the ferrite/martensite grain boundaries enabling an addition source of strengthening aside from typical dislocation generation that occurs in the ferrite grain bodies. The high levels of retained austenite necessary for this strengthening mechanism requires that the material undergoes a heat treatment where the martensite is formed and then reheated to stabilize the surrounding austenite phase so that it is stable at ambient temperatures. However, this also requires high amounts of Si to prevent carbide formation and Mn to ensure stability of the austenite. When welded using typical welding parameters, modelling results have shown that high tensile thermal stresses build in the shoulder and electrode indent due to thermal contraction associated with electrode collapse and electrode withdrawal. These thermal stresses are very high due to the high yield strength of these materials, which stresses the structure. Although this stress is insufficient to cause cracking, grain boundaries are weakened by two factors: Zn penetration from the melted galvanized coating and the high Si, which decreases grain boundary cohesion. The combination of the high thermal tensile stresses, the liquid Zn and the lower strength grain boundaries leads to LME cracking. However, by pulsing the welding current the hot strength of the material may be maintained preventing electrode collapse. As well, by ramping current at the end of the electrode cycle, the intent area is allowed to slowly cool preventing at thermal shock when the electrodes are withdrawn. Both of these techniques have been used to decrease LME crack severity during welding of 3G AHSS. The high carbon in these steels shown to be affect the local chemistry in the HAZ at the fusion boundary. It is known that the welding lobe of AHSS may be widened by increasing welding time. Increasing welding time slows nugget growth in these highly resistive steels, increasing the current at which expulsion occurs. However, it has been seen that when these high C steels are welded, a white halo may be seen surrounding the nugget on the cross-sectioned and etched weld. This halo has been measured to have reduced hardness and reduced carbon content compared to the surrounding material. When the weld is pulled in tension, fracture preferentially follows this local soft zone, decreasing the fracture energy of the joint. Using thermodynamical modelling, it has been shown that the halo is the result of uphill diffusion of C from the solid HAZ to the molten nugget as the nugget growth slows late in the welding cycle. Therefore, the halo may be reduced in one of two ways. Either welding time can be designed so that the ends before nugget growth ends, eliminating halo growth. Alternatively, a short higher current final pulse may be added to the welding cycle to grow the nugget into the halo before current is terminated. The current study examined how the chemical and mechanical properties of 3G AHSS interact with the welding process to result in two welding defects: LME cracking and the low C halo at the fusion boundary. It was seen that both phenomena are rooted in how the material changes during the welding process and how the chemical composition, unique to 3G AHSS, contributes to these phenomena. However, it was also shown that an understanding of how these defects form may be used to decrease or eliminate them. It was seen that reducing thermal shock by preventing electrode collapse and the large change in cooling rate associated with electrode withdrawal through current pulsing and slow cooling could decrease LME severity. Furthermore, it was seen how designing the welding cycle to terminate before nugget growth finishes by quickly growing the nugget a small amount at the end of the welding cycle could eliminate the halo. Both examples show how a firm understanding the metallurgy of the welded material and the welding process can be used to better design welding parameters, resulting in the best possible weld properties. Keywords: 3G Advanced High Strength Steel, Resistance Spot Welding (RSW), Halo, crack propagation, post-weld properties.
Proceedings Inclusion? Definite: Other (describe below)

OTHER PAPERS PLANNED FOR THIS SYMPOSIUM

101st Year of the American Welding Society: Changes in Welding & Outlook
Additive Manufacture of the First Concentric Reduction Sleeve Used in the Brazilian Oil and Gas Industry
Additive Manufacturing Using Semi-Solids
Advances in Robotic Arc DED AM for Shipbuilding
An Efficient Part-Scale Model to Predict Distortion on Overhang Structure in Laser Powder Bed Fusion Additive Manufacturing
An Overview of LME Cracking in Advanced High Strength Automotive Steels
Analysis and Control of Humping Defect in Laser Wire Direct Deposition Process
Analysis of Dynamic Evolution of Weld Pool for the Real-Time Monitoring of Penetration Using Deep Learning
Avoiding Tool Failure and Defects in Friction Stir Welding Using Machine Learning
Bondline Properties in High Frequency Welding of Steels
Building a Digital Twin for Welding Process Monitoring, Visualization and Control Based on Deep Learning
Characterization of the Fourth Generation of Nickel-Chromium Welding Products for Nuclear Service
Chipping Study of Friction Element Welding
Computational Modeling on Defect Formation during Self-Reacting Friction Stir Welding
Copper Foil Welding for Battery Manufacturing
Correlating Laser Power and Microstructural Properties of Additively Manufactured Ti-6Al-4V Fabricated by Directed Energy Deposition
Creep Strength Variation in Simulated ICHAZs of Grade 91 Steel
Design of an Austenitic Steel Weldment System Using ICME
Development of Industry 4.0 Software for Arc-Welding Energy Monitoring and Traceability
Development of Interlayer Technology to Join Advanced Materials for the Transportation Industry
Development, Optimization, and Mechanical Testing of ER80S-G Girth Welds on Internally Clad API 5L Grade X65 Pipes
Dissimilar Joining of Carbon Fiber Reinforced Composite to Magnesium Alloy by Friction Self-Piercing Riveting Process
Effect of Aluminum on Primary Carbides in Chromium Carbide Overlays
Effect of Chemical Composition of Welding Consumable on Slag Formation and Weld Corrosion Resistance
Effect of Heating Rate on Austenite Formation in a Low Carbon Microalloyed Steel
Effect of Phase Transformations on Mechanical Properties of Ti Free Grade 300 Maraging Steel Manufactured by Laser Powder Bed Fusion (LPBF)
Electron Beam Brazing of Stainless Steel using NIORO Filler Metal
Evaluation of Braze Joints for Hydrogen Purification Diffuser
Experimental Studies of Wire Feeding Electron Beam Welding-Brazing of Aluminum to Stainless Steel and Titanium
Failure Analysis: Evaluating a Low Strength Solder Joint
Fundamentals and Techniques for High-Speed Imaging of Welding
GMA Weldability Between AISI 316L Pipes Manufactured by Conventional and Additive Manufacturing Processes
High Deposition Gas Metal Arc Variants for Directed Energy Deposition Additive Manufacturing
High Efficient Modification of Arc Welding Processes via Modeling and Sensing Weld Pool Behaviors
High Penetration Buried Arc Gas Metal Arc Welding for Shipyard Steel Plate Fabrication
Hybrid Laser Welding on API 5L Pipeline Steels
Hyper-Duplex Stainless Steel Intermetallic Precipitation Behavior during Cladding
Improper Weld Field Fabrication Caused Premature Failure
In-situ Measurement and Numerical Simulation for Linear Friction Welding of Complex Titanium Structures
In-situ Synchrotron Diffraction Measurement of Solidification Behavior during Laser Welding of Multi-Principal-Component Alloy
Induction Heating-Assisted Friction Stir Welding in Low Carbon Steel Plates
Influence of Composition on the Solidification and Mechanical Properties of HP-Modified Heat-Resistant Austenitic Stainless Steels
Influence of Cooling Rate on Microstructure Formation in Rapid Solidification of Ni2MnGa Alloy
Influence of Hydrogen on the Softened HAZ in Various Carbon Steel Welds
Integrated Computational Materials Engineering (ICME) Techniques to Enable a Material-Informed Digital Twin Prototype for Marine Structures
Integrated Modeling of Multi-Process Automotive Lap Joining – Part 3: Microstructure and Mechanical Properties
Investigation of a Curly Toolpath in Friction Stir Welding
Investigation of Laves Phase Formation in Inconel 718 Fabricated by Laser Powder Bed Fusion
Investigation of Thermally Assisted Friction Element Welding
Joining Dissimilar Metals of DP590 Steel and AZ31B Magnesium Sheets by Ultrasonic Spot Welding
Low-cycle Fatigue Evaluations of Ni-Steel Dissimilar Joints for Coke Drum Welding Repairs
Machine Learning for Automatic Recognition of Microstructures
Material Characteristics of Wire Arc Additive Manufactured Inconel 718
Mechanical Properties Assessment of Carbon and Low-Alloy Steel Parts Built by GMA-DED
Mechanics of the Solid-State Bonding and Prediction of Thermomechanical Responses in Friction Stir Welding
Mechanistic Models and Machine Learning to Mitigate Common Defects in Metal Printing
Metallic Powder Core Tubular Wire Development for Additive Manufacturing
Microstructural and Mechanical Property Characterization of Reaction Synthesis Aluminum Metal Matrix Composites Produced by Additive Manufacturing
Microstructural Characterization and Mechanical Property Evaluation of Fusion Zones in a 10 wt% Ni Steel Weld Metal
Microstructure and Mechanical Properties of 410 Stainless Steel Using Different Shielding Gases in the Wire-Arc Additive Process
Microstructure and Mechanical Properties of Intercritical-Treated Grade 91 Steel
Microstructures and Microhardness of LENS DED Deposits of Ti/TiC MMCs
Mitigation of Liquid Metal Embrittlement in Galvannealed AHSS Welds Using High Entropy Alloy Filler
Modal Analysis of Ultrasonic Welding to Enable Multi-Spot Dissimilar Material Joining
Modeling and Comparing Human Welder’s Operation Between Stereo Camera and Virtual Reality
Modeling of In-Situ Tempering of a Creep Resistant Ferritic Martensitic Steel during Multi-Layer Additive Manufacturing
Modeling of Mash Seam Welding Using Improved Electro-Thermo-Mechanical Simulation
Modelling of Laser Cladding Using Gaussian Heat Source Profile and Verification with Experimental Results
Multi-Scale and Multi-Physics Modeling of Process-Microstructure-Property Relationship in Metal Additive Manufacturing
New Approaches in Friction Welding Advanced PM Nickel Base Superalloys
Numerical Study on Heat Transfer Mechanisms in Electric Arc Columns
Optimization of Tool Path and Microstructure in Large Scale Metal Additive Manufacturing with Multi-Heat Sources
Phase Transformation Analysis and Microstructural Characterization of the Heat Affected Zone in Grade 92 Steel Welds
Procedure Qualification Schemes and Build Results for Directed Energy Deposition Additive Manufacturing
Process Control Using Predictive Equations for Zero Programming Laser Cladding Facility
Process, Microstructure and Fracture Mode of Magnesium to Steel Dissimilar Metal Spot Joints
Pulsed-Arc Welding of Battery Tabs for Vehicle Electrification
PWHT of 347SS Weldments for Thermal Energy Storage Concentrating Solar Power Applications
Real-Time Prediction of Weld Penetration from Dynamic Weld Pool-Arc Images Deep Learning Based
Recent Developments in Metal Additive Manufacturing
Research and Development of a Novel TIG Welding Technology for Joining Thin Sheets Applying in Metal Forming Field
Residual Stress Measurement on High-Strength Steel Panels for Shipbuilding Application
Resistance Spot Welding Challenges, Root Causes, and Suggested Welding Practices When Welding 3rd Generation AHSS
Role of Retained Austenite in Mechanical Response of Additively Manufactured 17-4 PH Stainless Steel
SMART Camera in the Welding Torch for Manual Welding Quality and Productivity
State-of-the-Art of Underwater Wet Welding Practice
Strain Ageing of Inconel 740H and 347H
Suitability of Using Thin Wire in Wire Arc Additive Manufacturing (GMA-DED)
Sulfur Implantation in Alloy 690 for the Study of Ductility-Dip Cracking
Surface Modification via Metal Deposition and Selective Alteration
Surface Treatment of 3-D Printing Parts
Temper Bead Welding
The Correlation of Hardness to Toughness and the Superior Low Temperature Impact Properties of Martensite in RPV Steels Applied to Temper Bead Qualification
The Role of Inclusions in Duplex Stainless Steels Produced Using Laser-Based Directed Energy Deposition Additive Manufacturing
Ultrasonic Vibration Assisted Electron Beam Additive Manufacturing
Unit Block-Based Process Planning Strategy of WAAM for Complex Shell-Shaped Component
Universal Representation of Arc Shape and Arc Column Characteristics for DC Electric Arcs Burning in Argon and Helium
Variation in Microstructure and Properties in the Heat Affected and Fusion Zones of Low-Density Fe-Mn-Al-C Steel Welds
Variations in Microstructure and Mechanical Properties with Solidification Mode in L-PBF 316L
Weld Metal Cooling Rate-Mechanical Property Response of Fe-10Ni Steel Gas Metal Arc Weld Deposits and Other Experimental Observations
Weldability and Microstructural Evolution of Fusion Welds in a γ’ Strengthened TRIP Steel
Welding and Joining Challenges in the Astrospace Industry
Welding of FeMnAl High-Manganese Lightweight Steel
Wetting and Low Temperature Bonding of Zirconia Metallized with Ti-Containing Active Solders

Questions about ProgramMaster? Contact programming@programmaster.org