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To understand the difference between localized and global fractures, you must first understand strain gradients (see the article in our blog, AHSS Strain Hardening and Gradients). Gradients can result in highly concentrated strains (peak strain condition) that typically occurs in an embossment or character line where the deformation mode is in plane strain. Peak strains can develop rapidly in a very localized area (Figure 1). Under additional loads, this can result in the onset of localized necking, which means the material has reached its tensile strength and will fail at its weakest point or highest strain. When a slight increase in strain is applied, the material will fracture, sometimes at deformation levels less than predicted. This condition can be found in AHSS products, where multiple phases exist within the steel’s microstructure, each with different properties. A global fracture also typically occurs in plane strain, but more commonly down a sidewall or other area with more moderate geometry complexity.
Figure 1: Peak strain in the localized area or embossment
Peak (concentrated) strains are susceptible to localized fractures when even slight variation exists in the forming process. Examples of variation include lubrication pattern and volume, die recipe including blank position, press conditions, and material characteristics.
A localized neck and/or fracture (Figure 2) reduces the sheet metal’s thickness, reducing part strength, and compromising functional performance such as fatigue life, crash worthiness, and stamping stiffness. There are a number of formability analysis tools that can differentiate localized and global fractures and enable die makers to implement die and process improvements that minimize fracture susceptibility. The result is a more robust stamping process.
Figure 2: Schematic of Localized Necking and Fracture
Process control is critical; die recipe discipline is needed to minimize tinkering with die recipe, press settings, and lubrication settings. Mechanical properties of the sheet metal should be tracked to identify trends or variations in the material, and establish the material forming window. Typical mechanical properties that are available from the steel supplier are yield strength, tensile strength, n-value, total and uniformed elongation, and sheet thickness. Additional properties that should be determined include hole expansion and deep cup draw ratios. Failure to identify strain levels, process variables and variation will lead to a reactionary approach to controlling the output. This will lead to an increase in scrap, die-related downtime, and of course, costs.
Contributions made by Phoenix Group.
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Advanced High Strength Steels are a common approach that autobody engineers use for applications requiring grades with yield strength exceeding 500 MPa. Steelmakers are increasingly offering alternatives based on High Strength Low Alloy Steel production concepts. This article explores how those steels can be beneficial for automotive applications.
Advanced High Strength Low Alloy (AHSLA) steels represent an extension of conventional cold-rolled HSLA technology into yield strength levels above the traditional 500 MPa limit. Historically, cold-rolled HSLA grades were constrained by the preference toward full recrystallization annealing after cold reduction, resulting in commercially available grades typically limited to roughly 460-550 MPa minimum yield strength.
For higher strengths, automotive manufacturers generally rely on advanced high-strength steels (AHSS) such as dual-phase (DP) and complex-phase (CP) steels. While AHSS provide superior global formability as measured by elongation and strain hardening capability (n-value), the single phase microstructure of HSLA steels has advantages in local formability, including bendability and hole expansion performance. AHSLA steels seek to bridge this gap by achieving significantly higher yield strengths while preserving the favorable weldability, edge stretchability, and local formability characteristics associated with HSLA metallurgy.
How Annealing Strategies and Alloying Raise HSLA Strength
The key metallurgical strategy enabling microalloyed AHSLA steels is the use of annealing temperatures below those required for full recrystallization. As annealing temperature decreases, yield and tensile strength increase while elongation naturally declines, allowing the production of grades such as CR550LA, CR600LA, CR700LA, and beyond. In recovery annealing, microstructural dislocation density and internal stresses are reduced while much of the deformed cold-rolled microstructure is retained, producing the highest strength levels of AHSLA grades, with correspondingly lower elongation. Partial recrystallization annealing employs somewhat higher temperatures that convert a portion of the deformed structure into recrystallized grains, leading to a mixed microstructure and an intermediate balance of strength and ductility.
Microalloying additions such as niobium and molybdenum influence final properties in addition to annealing practice, steel chemistry, cold reduction, and annealing time. Industrial studies demonstrate that these grades can be produced by multiple processing routes, including batch annealing, continuous annealing, and continuous hot-dip galvanizing, with differing microstructural strategies used to achieve similar strength targets.
AHSLA vs. DP and CP Steels: Local and Global Formability
A major advantage of AHSLA steels is their balance of local and global formability. Reported hole expansion ratios (HER) are comparable to, and in some cases exceed, those of dual-phase and complex-phase steels at similar strength levels. Commercial AHSLA products spanning approximately 500 to 1000 MPa yield strength maintain relatively high edge formability despite increasing strength, making them attractive where trimmed edges, pierced holes, or tight bend radii are critical. Direct comparisons between CR550LA and CR590DP show the expected tradeoff: DP steel exhibits greater elongation and strain hardening, while HSLA steel delivers markedly higher yield strength with comparable hole expansion performance. This suggests that AHSLA grades can serve as alternatives to certain AHSS grades when exceptional global formability is unnecessary.
Traditional formability diagrams, which emphasize tensile strength versus elongation, tend to favor AHSS (Figure 1). However, when yield strength is used as the primary design variable, AHSLA steels appear considerably more competitive because they provide high as-delivered strength with acceptable ductility and superior local formability (Figure 2). Expanded formability maps comparing uniform elongation and true fracture strain indicate that AHSLA grades occupy a region of balanced performance, outperforming many DP and CP steels in fracture-limited forming operations.
Figure 1: Traditional Global Formability Diagram based on the VDA 239-100 standard (minimum requirements), with the circle diameter proportional to the minimum yield strength of each grade. Also included are proposed “Super HSLA” grades. [1]
Figure 2: Alternative Global Formability Diagram comparing minimum elongation and minimum yield strength. Here, the circle diameter reflects the minimum tensile strength for each grade. Note that the same data are represented in Figure 1 in the more traditional way (elongation vs tensile strength).
Thin-Slab and EAF Production: Expanding the Supply Base
Beyond performance, AHSLA steels may also broaden the automotive supply base. Low carbon levels, often below about 0.08%, and lower overall alloy content improve castability and make them compatible with both integrated and thin-slab EAF (electric arc furnace) production routes.
Automotive Applications: Roll-Formed Parts, Seating, Bumpers and EV Battery Protection
Minimum yield strength levels above 500 MPa are typically achieved through cold rolling followed by partial recrystallization or recovery annealing. AHSLA steels often exhibit a high yield-to-tensile strength ratio, frequently exceeding 0.9, indicating that high yield strength is already present before forming.
For automotive applications, the combination of high yield strength, low carbon equivalent, good weldability, and limited dependence on work hardening make these grades particularly attractive for roll-formed components, e.g. roof bows or side intrusion protection beams.
Other components that could benefit include those not subjected to the body-in-white (BIW) paint-baking process and therefore do not benefit from bake hardening. These include various automotive seating components (seat tracks, structural members), bumper beams, and electric vehicle battery protection systems. Their high yield-to-tensile strength ratio of AHSLA grades allows strength to remain relatively uniform throughout the component, including low-strain regions that do not benefit from work hardening or bake hardening. Although their suitability for crash-energy-management body-in-white applications relative to established AHSS grades remains under evaluation, AHSLA steels offer a compelling alternative where high yield strength, excellent local formability, manufacturing robustness, and weldability are primary design considerations.
More information about conventional and advanced high-strength low-alloy steels is available here. Thanks to Dr. Brandon Hance and Dr. Daniel Schaeffler for providing this article.
References:
[1] B.M. Hance and H. Mohrbacher, “Optimization of global and local formability properties through Nb microalloying,” Presented at 3rd Automotive Steel International Conference AISTech, 9–12 March 2025, Orlando, Fla., USA, 47-53.
Dr. Brandon Hance has dedicated more than 30 years to the automotive industry focused on the mechanical and physical metallurgy of high-strength steels. In his most recent role at CBMM North America, he supported customers from material grade development through industrial implementation. Before that he served as Vice President & Head of the Applications Engineering Group at Hyundai Steel Company in South Korea, as well as in prior R&D roles at United States Steel Corporation, AK Steel Corporation, The Timken Company and Novelis. Brandon has a PhD degree in Materials Science from the University of Pittsburgh, an MS degree from the Colorado School of Mines, and a BS degree from the Illinois institute of Technology. He currently volunteers as Secretary of the North American Deep Drawing Research Group (NADDRG) and is the USA Representative to the International Deep Drawing Research Group (IDDRG).
Danny Schaeffler is the Metallurgy and Forming Technical Editor of the AHSS Applications Guidelines available from WorldAutoSteel. He is founder and President of Engineering Quality Solutions (EQS). Danny wrote the monthly “Science of Forming” and “Metal Matters” column for Metalforming Magazine, and provides seminars on sheet metal formability for Auto/Steel Partnership and the Precision Metalforming Association. He has written for Stamping Journal and The Fabricator, and has lectured at FabTech. Danny is passionate about training new and experienced employees at manufacturing companies about how sheet metal properties impact their forming success.
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In automotive pre-production, building physical prototypes to test weld distortion is both costly and time-consuming. These distortions can create major challenges during production ramp-up, including poor part tolerances and visible warpage in outer panels. Welding distortion simulation helps address these risks early by predicting distortion before the prototype is built and by enabling countermeasures before manufacturing issues occur.
Why Welding Distortion Matters in Automotive Design
In automotive manufacturing, key decisions about welding equipment, fixtures, and process design are often made before physical testing of weld distortion and part tolerances can take place. This can result in delays, rework, and additional costs during start of production (SOP). Simulation of welded structures and subsequent distortion management enable proof of concept at an early stage, saving cost and time during design and development of both components and production lines for new vehicles.
Advanced high-strength steels (AHSS), deployed throughout the vehicle body structure in applications such as longitudinal beams, sills, upper and lower crossmembers, passenger safety cage, and other components are particularly sensitive to welding-related shape deviations because of their high strength and stiffness. This makes welding distortion analysis an important part of the design process. Modern welding simulation software can predict distortion effects based on component geometry, material properties, clamping conditions, and welding process parameters.
Building and Calibrating the Simulation Model
As with any numerical simulation, reliable welding distortion prediction depends on the quality of the input data. For both AHSS and mild steels, material datasets are available in the literatureP-9 and provide good predictive accuracy for standard material classes. Accuracy can be improved further by measuring the properties of the specific material being used and modifying existing datasets.
Additional inputs are process-related: geometry, clamping locations, and welding sequences must be defined for each weld and included in the model. To keep computation times practical, the welding process itself is simplified by neglecting arc or laser interaction with the material by applying an equivalent heat input to the component.
Because this simplified heat input does not directly correspond to a single physical parameter, it must be calibrated using experimental data. Figure 1 illustrates a calibration approach that compares metallographic cross-sections from experiments with simulated molten zones for two different laser-welded joints.
Figure 1: Calibration of numerical simulation heat input by comparing the molten zone between experiment and simulation.
Validating Results and Optimizing Distortion Control
Once the model inputs are defined, the simulation can be run to calculate temperature evolution, material response, and distortion during and after welding. Figure 2 shows a comparison between simulated and measured distortion in an automotive door structure. The strong alignment demonstrates that the model can reliably capture the main distortion mechanisms and can be used to assess distortion-related risks before SOP. The illustrated inner panel is the main part of the door assembly, to which several reinforcements and door components are joined. Therefore, different material-thickness combinations must be considered.
Figure 2: Comparison of measured and calculated distortion of an automotive door structure. A good agreement between the numerical prediction and experimental tests can be achieved with welding simulations.T-49
The real value of simulation becomes even clearer after the initial model has been validated. Based on the calibrated model, design and process variants can be evaluated with relatively little additional effort. This shifts part of the optimization process from costly physical trials to welding distortion simulation.
Figure 3 shows one such example: a variant with increased clamping time after welding. Allowing the component to cool longer in the fixture can reduce overall distortion, although it may also increase production cycle time. Other potential variants include modified welding sequences, adjusted clamping locations, or geometric changes to the component itself.
Figure 3: Calculated distortion reduction through longer clamping times after welding.
Where Welding Simulation Is Headed
Welding distortions remain a risk that is hard to quantify during the automotive design process. Especially when using high-strength AHSS, deteriorating dimensional accuracy can cause downstream issues during assembly. By integrating welding simulations in the automotive design and SOP process, these risks can be mitigated and decisions for processing variants can be made before committing capital to fixtures, welding equipment, or tooling.
Figure 4: Temperature distribution during welding of a steel battery enclosure.
Several automotive OEMs already use welding simulation in their development processes, but there is still significant untapped potential across the industry. Battery enclosures are among the latest component groups with especially demanding distortion tolerances due to crash and sealing requirements. During the design of steel battery enclosures, welding simulation can help identify robust processing strategies that support compliance with these tight dimensional requirements. In light of current developments aimed at maximizing the available space for battery cells as well as different ways to integrate the battery pack into the vehicle body, advanced welding distortion simulation processes are key to saving costs and minimizing risk at the start of production.
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WorldAutoSteel periodically invites outside experts to contribute their knowledge on pertinent topics. Here, Danny Schaeffler, President of Engineering Quality Solutions and our Technical Editor for Metallurgy and Forming, worked with Trey Leonard, Ph.D. Founder and CEO, Standard Mechanics, LLC to bring you this overview of several aspects of High Strain Rate testing. You’ll find portions of this content as part of our page on High Strain Rate Testing, but this month, we want to highlight it in our AHSS Insights blog.
High strain rate testing is not an abstract materials exercise in the automotive industry—it is a targeted characterization tool used to ensure that advanced high-strength steels (AHSS) perform as expected during forming and crash events. In the context of automotive body structures, the relevant question is not simply “what is the strength of this steel,” but rather “how does this steel behave when deformed at rates representative of an actual event?”
Why Strain Rate Sensitivity Matters for AHSS Crash Performance
Modern vehicle structures rely heavily on AHSS grades to meet increasingly stringent requirements for crashworthiness and mass reduction. Components such as B-pillars, rocker reinforcements, crash rails, and door intrusion beams are designed to absorb energy through controlled deformation. During a crash, these components experience strain rates on the order of 10² to 10³ s⁻¹ —several orders of magnitude higher than the ~10⁻⁴ s⁻¹ strain rates in conventional tensile testing (Figure 1). As a result, properties like yield strength and ultimate tensile strength derived from these quasi-static tests are insufficient descriptors of in-service behavior.
Figure 1 Strain Rates of Various Events Including Testing, Forming, and Crash
For steels used in these applications, strain rate sensitivity becomes a primary material characteristic. Most automotive steels exhibit positive strain rate sensitivity, meaning their flow stress increases with increasing strain rate. From a design standpoint, this could be advantageous: higher dynamic strength translates to improved energy absorption and greater resistance to intrusion during a crash. However, the magnitude of this effect varies across steel families. Dual-phase (DP) steels, for example, can show a more pronounced increase in flow stress compared to transformation-induced plasticity (TRIP) steels, while martensitic grades may exhibit relatively lower sensitivity. These differences must be quantified experimentally to ensure that simulation models accurately capture the structural response.
Modeling Strain Rate Sensitivity — Cowper-Symonds vs. Johnson-Cook
This is where high strain rate testing becomes directly integrated into the material characterization workflow. Automotive OEMs and suppliers generate stress-strain curves across a range of strain rates, typically spanning quasi-static (~10⁻⁴ s⁻¹), intermediate (~1 to 10² s⁻¹), and high-rate (~10² to 10³ s⁻¹) regimes. These datasets are then used to calibrate constitutive models implemented in crash simulation software such as LS-DYNA or Abaqus. Models like Cowper–Symonds or Johnson–Cook incorporate strain rate terms that scale the flow stress, but their predictive capability depends entirely on the quality and range of the underlying experimental data (Figure 2, Figure 3, Figure 4).
Figure 2 Cowper-Symonds and Johnson-Cook Strain Rate Sensitivity Model fit to Low-Rate Experimental Data
Figure 3 Cowper-Symonds and Johnson-Cook Strain Rate Sensitivity Model fit to All Experimental Data
Figure 4 Cowper-Symonds and Johnson-Cook Strain Rate Sensitivity Model fit to Low-Rate and All Experimental Data
Testing Methods — From Servo-Hydraulic Systems to Split Hopkinson Bar
The testing approach itself is tailored to the strain rate regime of interest. For intermediate rates relevant to forming-to-crash transitions, servo-hydraulic test systems are commonly used. These systems are modified with high-flow servo valves and low-compliance load trains to achieve rapid loading. For higher strain rates typical of crash events, split Hopkinson bar techniques are employed.
Specimen Design and Digital Image Correlation (DIC) Strain Measurement
Specimen geometry and preparation are also influenced by the intended application. Sheet steels used in automotive structures are typically tested in configurations that preserve their rolling direction and thickness, as anisotropy can influence both strength and failure behavior. In addition, special specimen geometries that induce non-uniaxial stress conditions (notched-tensile and tensile-shear specimens) are critical to understand failure modes such as fracture strain and localization, both of which directly impact crash performance.
As a result, full-field strain measurement techniques like digital image correlation (DIC) are widely adopted (Figure 5). DIC enables accurate capture of strain localization and strain rate distribution across various specimen geometries, which is particularly important for calibrating damage and failure models such as Hosford-Coulomb and General Incremental Stress-State dependent Damage Model (GISSMO).
Figure 5. Example of Full Field Digital Image Correlation Strain Mapping of High Strain Rate Tensile Test
Inertia, Stress Wave Propagation, and Load Ringing
Perhaps the most important factor in high strain rate testing is inertia and stress wave propagation. Automotive steels are typically tested in sheet geometries that are relatively thin. Thin specimens gripped with bulky grips often create non-uniform stress states during rapid loading. Non-uniform stress states produce oscillations (often called “load ringing”) in the resulting stress data (Figure 6). Ensuring stress equilibrium within the specimen is essential for obtaining valid data. This often requires careful design of the test setup, including grip size and specimen length.
Figure 6 Example of Growth of Load Ringing in High-Strain-Rate Test Data
From Material Data to Crash Performance Prediction
From an application standpoint, the ultimate goal of high strain rate characterization is to enable accurate prediction of component-level and system-level crash behavior. For example, in a frontal collision, the progressive folding of a front rail or crash box depends on the dynamic flow stress of the steel, as well as its strain hardening and failure characteristics. Similarly, side-impact performance is heavily influenced by the behavior of B-pillar reinforcements under high-rate loading. Without accurate high strain rate data, simulations may underpredict or overpredict intrusion, energy absorption, and failure, leading to suboptimal designs or costly physical test iterations.
Standardization Challenges — ISO 26203 and Lab-to-Lab Variability
Standardization efforts, such as ISO 26203, have helped bring consistency to high strain rate tensile testing, but variability still exists across laboratories. Many factors contribute to these variances: unstandardized specimen geometries and gripping methods, variances in specimen loading conditions, lower quality strain measurement techniques, and non-optimized fixturing for wave transmission and measuring. For automotive applications, this variance places a premium on internal validation—correlating material test data with component-level crash tests to ensure that the material model behaves correctly within the simulation environment.
Key Takeaways
High strain rate testing is a foundational tool in the characterization of automotive steels, directly linking material behavior to vehicle safety performance. It provides the data necessary to describe how steels respond under crash-relevant loading conditions, informs the calibration of constitutive and failure models, and ultimately enables engineers to design lighter, safer vehicle structures with confidence in their predictive simulations.
For additional information, please visit our page on High Strain Rate Testing.
Many thanks to our authors, Trey Leonard and Dr. Danny Schaeffler.
Trey Leonard is the founder and CEO of Standard Mechanics, LLC, where he delivers advanced mechanical testing services and solutions across a wide range of applications, with expertise spanning static and dynamic formability, fatigue, and strain rate sensitivity testing.
Danny Schaeffler is the Metallurgy and Forming Technical Editor of the AHSS Applications Guidelines available from WorldAutoSteel. He is founder and President of Engineering Quality Solutions (EQS). Danny is passionate about training new and experienced employees at manufacturing companies about how sheet metal properties impact their forming success.
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Introduction: Welding with Micro-Alloyed Wire
In automotive vehicle assembly, gas metal arc welding (GMAW) plays an important role: Unlike the dominant resistance spot welding, it is not used as a bulk joining process, but rather specifically to meet the unique requirements of selected components in modern vehicle structures. GMAW of AHSS causes grain coarsening and a brittle weld zone mechanical behaviour.
To reduce this effect, GMAW filler wires are typically alloyed with Nickel (Ni), enabling a more ductile weld structure. To strengthen the welds even further, new alloying concepts have been developed that utilizie micro-alloying of Silicon (Si), as well as Niobium (Nb) and Chromium (Cr) to create finer, more interlocked weld microstructures with an increased fraction of retained austenite (e.g. Posco PosZET® and PosZET® GIGA process).
Fig. 1. Improved corrosion and fatigue achieved with micro-alloyed welding wire
Fig. 1 illustrates an application of micro-alloyed welding wire to a lightweight cradle chassis part. A significant improvement in corrosion behaviour is observed even though the extra cleaning (acid de-scaling) step is not applied to the sample using the new wire. When manufactured parts can withstand corrosion, this acid descaling process can be removed, helping to reduce production cost and rendering the production process more eco-friendly.M-71
Due to the relatively stronger arc (thermal pinch) force when using GMAW filler wires, which improves the efficiency of weld penetration, the input current during welding can be lowered. The width of the weld heat-affected zone (HAZ) is therefore reduced, improving weld fatigue (see left graph of Fig. 1).
The advantages of micro-alloying also apply to the highest strength levels in AHSS welding. Achieving strength of the welded part is of paramount concern, particularly because the use of ultra-high-strength steels enables significant weight reduction through material thickness reduction while maintaining structural performance. This is especially critical in electric vehicles (EVs), where battery weight increases overall vehicle mass and creates strong pressure for lightweight design in other structural components. To this end, some high-strength welding wires that were previously cost-prohibitive for application in the automotive market have recently been mass-produced to meet electrical vehicle (EV) weight reduction pressures.
Metallurgical effects of micro-alloying
During the welding process, mechanical properties deteriorate; the degradation is caused by grain coarsening or the formation of brittle phases that compromise product longevity. Fig. 2 illustrates the concept of utilizing the micro-alloying elements (e.g. Cr + Nb), in lieu of Ni. During the transition from austenite to acicular ferrite and bainite, the specific alloying design lowers the phase transformation temperature by increasing hardenability and segregating specific element atoms along the prior austenite grain boundaries, rendering finer interlocking microstructures in welds.
Fig. 2. Grain refinement through the addition of Niobium and Chromium
(PAGB: Prior Austenite Grain Boundaries)
In addition, the reduced phase transformation temperature impedes the formation of cementite during bainite transformation; therefore, retained austenite fraction increases. The addition of micro–alloying elements also discourages the activity of carbon atoms, suppressing the precipitation of cementite. The outcome is shown in schematically Fig. 2. By forming the finer interlocking microstructure and the higher fraction of film-like retained austenite, the new alloying design creates ultra-strong and ductile steel welds with enhanced tensile properties, impact toughness, and fatigue strength aiming to improve GMAW weldability of 980 MPa or higher strength steels.
These enhancements are achieved at 45% lower material cost and reduced environmental impact because Ni, a costly metal, is removed. The retained austenite absorbs initial strain during tensile deformation; hence, through the transformation-induced plasticity (TRIP) effect during austenite transformation to martensite, ductility is improved. These remarkable improvements in the impact and fatigue properties of the welds are associated with the refinement of the interlocking microstructure with high fraction film-like retained austenite. In other words, refined hierarchical interlocking microstructure and the interruption of crack propagation supported by ductile retained austenite films (as shown in Fig. 3) contribute to greater impact toughness and fatigue resistance properties.
Fig. 3. Hierarchical architecture of the ultrastrong and ductile steel welds
Market solution and application to wheel hub welding
Nb and Cr micro-alloyed welding wires are commercially available from POSCO under the PosZET® GIGA brand for strength levels of 980 MPa and higher. These welding wires are currently in the final stages of approval for serial production by global OEMs for application in their new vehicle line-ups.
For strength levels up to 780 MPa, a micro-alloyed wire with low Si is available under the PosZET® AHSS brand from POSCO. Fig. 4 illustrates an application study of the welding wire used for the weld of a lightweight wheel hub. In hot-rolled (HR) steel plates for wheels, thermal decomposition and gasification of the surface scale can cause porous defects in the welded part, requiring occasional repair welding.
Using micro-alloyed wire removes the need for such repairs. Secondly, spatter adhesion inhibitors are often applied due to welding spatter; with the newly developed wire, spatter generation declines by 80%, removing the need for inhibitors, thereby cutting cost. In addition, the arc force is enhanced, improving weld penetration efficiency; therefore less welding power (i.e., lower welding current/voltage) is required for greater welding productivity (i.e., faster welding speed). An approximate 10 % productivity gain is observed with 15% power reduction, resulting in lower CO2 emissions.
Fig. 4. Crack- and slag-free welds demonstrated on a commercial wheel hub weld
Welding an EV lightweight cradle with micro-alloyed wire
Fig. 5 depicts an application of low Si micro-alloyed wire to the lightweight cradle parts of mass-produced vehicle models, revealing the result after a 15-year corrosion test. The samples exhibit significant corrosion in the weld using conventional welding wire and no corrosion when utilizing the micro-alloyed wire.
Fig. 5. Corrosion test result for lightweight cradle part of an EV
Outlook
GMAW of AHSS using micro-alloyed filler wires offers significant potential for automotive manufacturing. Targeted microalloying allows for the optimization of strength, toughness, and the heat-affected zone of the welds, which is crucial for crash performance and corrosion resistance. This technology opens new possibilities for lightweight construction and series production, particularly for electric vehicles, modular body structures, and safety-critical components.
A special thank you to our author, Dr. Gyuyeol Bae. Bae is the Team Lead of the Automotive Materials Solution Research Group Solution R&D Center in the Technical Research Laboratories of POSCO in South Korea.
