Die Wear and Coating Galling in Stamping Advanced High Strength Steels

2011 ◽  
Author(s):  
Hua-Chu Shih ◽  
Ming F. Shi
Keyword(s):  
Zinc Coating ◽  
High Strength Steels ◽  
High Strength ◽  
Reactive Diffusion ◽  
Process Variables ◽  
Forming Process ◽  
Typical Application ◽  
Advanced High Strength Steels ◽  
Die Wear ◽  
Bending Under Tension

Advanced high strength steels (AHSS) have been widely used in vehicle structural components due to their high strength nature with balanced formability. In a typical application, a zinc coating is often required and applied to AHSS for the purpose of corrosion protection. Due to the high strength nature of AHSS, higher forming forces and binder pressures are also required in stamping AHSS, which often results in coating galling and die wear. The degree of coating galling and die wear depends upon forming process variables such as contact pressure, forming speed, lubrication and die temperatures. In this study, the Bending Under Tension (BUT) tester was used to evaluate the effects of these process variables on coating galling and die wear. Dual phase (DP) 590 and 780 steels with galvanized (GI) and galvannealed (GA) coatings were investigated in the study. The results indicate that GI coatings tend to have better wear resistance than GA coatings. A better surface treated (Thermo-Reactive Diffusion Vanadium Carbide) die material was also identified to decrease coating galling and die wear in stamping AHSS.

Evaluation of Zinc Coating Adhesion in Stamping Advanced High Strength Steel

2014 ◽  
Author(s):  
Hua-Chu Shih
Keyword(s):  
Zinc Coating ◽  
High Strength Steels ◽  
High Strength ◽  
Strength Properties ◽  
Forming Process ◽  
Coating Adhesion ◽  
Advanced High Strength Steels ◽  
Adhesion Behavior ◽  
Lubrication Condition ◽  
Bending Under Tension

Advanced high strength steels (AHSS) have been widely used in vehicle structural components due to their high strength properties balanced with good formability. In many applications, a zinc coating is often applied to AHSS for the corrosion protection. Due to the high strength properties of AHSS, higher forming forces and binder pressures are also required in stamping AHSS, which often results in coating powdering/flaking or galling around the draw bead and die radius areas. The degree of coating powdering/flaking depends upon forming process variables such as draw bead force, forming speed, lubrication, and die temperatures. This study was designed to develop a lab-based coating adhesion test to quickly characterize the coating adhesion behavior of AHSS. In this study, both the bending under tension test and the modified draw bead test were used. A typical substrate of AHSS is coated with either a hot-dip Galvannealed (GA) or a Galvanized (GI) coating. In this study, dual phase (DP) steels with tensile strength levels of 600, 780 and 980 MPa were investigated at two different thicknesses and with two different coating types, GI and GA. The results reveal that GA tends to have worse coating adhesion than GI coatings under normal forming conditions. However, GI coatings are more sensitive to the lubrication condition and have worse coating adhesion than GA coatings under a larger draw bead penetration and smaller draw bead corner radius condition.

Investigations on the Effect of Coating Material and Method on Die Wear in Stamping of Advanced High Strength Steels

2013 ◽  
Author(s):  
Ömer Necati Cora ◽  
Muammer Koç ◽  
Peter J. Blau ◽  
Kunio Namiki
Keyword(s):  
Wear Behavior ◽  
High Strength Steels ◽  
High Strength ◽  
Test Method ◽  
Coating Materials ◽  
Advanced High Strength Steels ◽  
Die Wear ◽  
Die Life ◽  
Metalworking Industry ◽  
Width Measurements

Despite the advantages of advanced high strength steels (AHSS), their stamping into functional lightweight parts demands prolonged die life, which necessitates the use of alternative substrates, coating materials, and/or surface conditioning to minimize and delay the die wear. In order to avoid frequent die replacement and surface quality problems on the stamped parts, the metalworking industry has been investigating various approaches such as reducing/refining the carbide particles, adding alloying elements, and elevating the hardness and toughness values for both substrate materials and coatings. The objective of this work was to investigate the effects of different coatings on the wear behavior of a some selected tool steel materials (die sample of interest) against two different AHSS sheet blanks through a cylinder-on-flat type reciprocating test method. After wear tests, both die sample and sheet blank surface were microscopically examined. Wear resistance of the slider was quantified from wear scar width measurements. Results showed that TD and CVD coated die samples performed better than the two other PVD coated samples.

Experimental Study on Galling Behavior of Advanced High Strength Steel in Sheet Metal Forming

2012 ◽  
Vol 502 ◽  
pp. 36-40
Author(s):  
Ying Ke Hou ◽  
Shu Hui Li ◽  
Yi Xi Zhao ◽  
Zhong Qi Yu
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Sheet Material ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Process ◽  
Advanced High Strength Steels ◽  
Sheet Materials ◽  
Materials Used

Galling is a known failure mechanism in many sheet metal forming processes. It limits the lifetime of tools and the quality of the products is affected. In this study, U-channel stamping experiments are performed to investigate the galling behavior of the advanced high strength steels in sheet metal forming . The sheet materials used in the tests are DP590 and DP780. In addition to the DP steels, the mild steel B170P1 is tested as a reference material in this study. Experimental results indicate that galling problem becomes severe in the forming process and the galling tendency can be divided into three different stages. The results also show that sheet material and tool hardness have crucial effects on galling performance in the forming of advanced high strength steels. In this study, DP780 results in the most heaviest galling among the three types of sheet materials. Galling performance are improved with increased hardness of the forming tool.

An Innovative Shearing Process for AHSS Edge Stretchability Improvements

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Hua-Chu Shih ◽  
Ming F. Shi
Keyword(s):  
High Strength Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Straight Edge ◽  
Forming Process ◽  
Expansion Test ◽  
Advanced High Strength Steels ◽  
Sheared Edge ◽  
Shear Edge

A beveled shear hole piercing process has recently been developed for advanced high strength steel (AHSS). The preliminary results have shown the new process is able to improve the quality of the sheared edge and the edge stretchability of AHSS. The goal of the current study is to optimize the beveled shearing process and identify the optimal shearing conditions for AHSS. Four different advanced high strength steels, including DP600, DP780, TRIP780, and DP980 with various thicknesses together with a conventional high strength steel, HSLA50, are selected in this study. The hole expansion test is used to evaluate the effect of shear edge conditions on the edge stretchability. The results show that an optimal selection of the die clearance and the shearing angle results in a less damaged edge, which significantly delays edge fracture in the forming process and increases the edge stretchability for AHSS. To further validate the advantages of the beveled shearing process in improving the shear edge quality of AHSS, a straight edge shearing device with the capability of adjusting the shearing variables (rake angles and die clearance) with respect to different sheet thicknesses was also developed and built. The edge stretchability of the straight edge sheared specimen was then evaluated using the sheared edge tension test. A similar trend to the beveled shear hole piercing process of AHSS is observed, and a significant improvement in the edge stretchability is also obtained with optimal shearing conditions.

Springback Investigation in Roll Forming of a V-Section

2014 ◽  
Vol 553 ◽  
pp. 643-648 ◽  
Author(s):  
Akbar Abvabi ◽  
Joseba Mendiguren ◽  
Bernard F. Rolfe ◽  
Matthias Weiss
Keyword(s):  
Elastic Modulus ◽  
Continuous Process ◽  
High Strength Steels ◽  
Shell Element ◽  
High Strength ◽  
Material Model ◽  
The Body ◽  
Roll Forming ◽  
Forming Process ◽  
Advanced High Strength Steels

To have fuel efficient vehicles with a lightweight structure, the use of High Strength Steels (HSS) and Advanced High Strength Steels (AHSS) in the body of automobiles is increasing. Roll forming is used widely to form AHSS materials. Roll forming is a continuous process in which a flat strip is shaped to the desired profile by passing through numerous sets of rolls. Formability and springback are two major concerns in the roll forming of AHSS materials. Previous studies have shown that the elastic modulus (Young’s modulus) of AHSS materials can change when the material undergoes plastic deformation and the main goal of this study is to numerically investigate the effect of a change in elastic modulus during forming on springback in roll forming. Experimental loading-unloading tests have been performed to obtain the material properties of TRIP 700 steel and incorporate those in the material model used in the numerical simulation of the roll forming process. The finite element simulations were carried out using MSC-Marc and two different element types, a shell element and a solid-shell element, were investigated. The results show that the elastic modulus diminution due to plastic strain increases the springback angle by about 60% in the simple V-section roll forming analyzed in this study.

Friction Coefficient Identification in Roll Forming Processes

2014 ◽  
Vol 611-612 ◽  
pp. 425-435 ◽  
Author(s):  
Lander Galdos ◽  
Unai Ulibarri ◽  
Imanol Gil ◽  
Rafael Ortubay ◽  
Eneko Sáenz de Argandoña
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Roll Forming ◽  
High Yield ◽  
High Yield Strength ◽  
Forming Process ◽  
Advanced High Strength Steels ◽  
High Production Rate ◽  
High Production ◽  
Roll Forming Process

Roll forming process is an interesting process for the production of complex profiles because of its high production rate, low investment and efficient use of material. Furthermore, and due to their high yield strength, this technology is suitable for the forming of Advanced High Strength Steels which are being increasingly introduced in the automobile sector.

Galling and Die Build-Up in Forming Uncoated, Cold-Rolled Advanced High-Strength Steels (AHSS)

2015 ◽  
Author(s):  
Hua-Chu Shih
Keyword(s):  
Surface Texture ◽  
Steel Surface ◽  
Sheet Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Roll Surface ◽  
Friction Forces ◽  
Advanced High Strength Steels ◽  
Cold Rolled ◽  
Bending Under Tension

Uncoated advanced high strength steels (AHSS) are being used for non-exposed automotive applications where high strength is required. Due to higher contact pressures and friction forces between the tooling and sheet steel, increased die wear, die build-up and sheet steel surface galling have been observed. Although various countermeasures have been adopted in production to address these issues, the stamping die tryout process has not been revised accordingly. Proper heat treatment of uncoated tryout dies is required to prevent wear in stamping uncoated, cold-rolled AHSS. Whether die build-up and sheet steel surface galling occur depends on the steel surface condition. The intent of this study is to investigate the effects of steel surface topography on die build-up, sheet steel surface galling and friction in forming uncoated cold-rolled AHSS. DP590 and DP980 with different thickness and different finish rolled textures were tested with the bending under tension (BUT) tester to study these effects. A reciprocal cyclic bend test system (CBTS) of modifying bending under tension test was used to investigate wear and build-up between different surface texture steels in a production condition. Results indicate that the finish roll surface texture is found to be the root cause for the die build-up and steel surface galling that occurs during forming with uncoated dies. The ground-roll surface is the worst in terms of galling and build-up while the Electro-Discharge Textured (EDT) surface is the best. The surface parameters Skewness (Rsk) and Kurtosis (Rku) are found to be able to assess steel galling and die build-up behaviors for uncoated cold rolled AHSS using the uncoated D2 die. A surface with Rsk larger than −0.5 and Rku less than 3 can prevent galling and die build-up in the die tryout process, which is recommended to finish roll the uncoated cold rolled AHSS.

Advances in Constitutive Modeling of Plasticity for Forming Applications

2016 ◽  
Vol 725 ◽  
pp. 3-14 ◽  
Author(s):  
Frédéric Barlat ◽  
Youngung Jeong ◽  
Jin Jin Ha ◽  
Carlos Tomé ◽  
Myoung Gyu Lee ◽  
...  
Keyword(s):  
Constitutive Models ◽  
High Strength Steels ◽  
Computation Time ◽  
High Strength ◽  
Industrial Applications ◽  
Dislocation Dynamics ◽  
Forming Process ◽  
Advanced High Strength Steels ◽  
Process Simulations ◽  
Multi Phase

A succinct description of advanced constitutive models for applications to forming process simulations is provided. These models are continuum-based because they are more efficient in terms of computation time than microstructure–based models. However, they are so–called advanced because they are considered in many scientific studies but rather scarcely used in industrial applications. In addition, the relationship between these continuum constitutive models and multi-scale approaches based on crystal plasticity, dislocation dynamics and mechanics of multi-phase materials, such as advanced high strength steels, is substantiated.

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