Drawing Steel Research Articles

Effect of Blank Holding Force of The Formability and Limiting Drawing Ratio for Steel - Plastic Laminated Sheets.(Dept.M)

In a steel / plastic laminated sheet with a core resin as an intermediate layer. shear deformation is concentrated on the resin layer during the forming in which a shearing force appears due to a considerable difference in strength between the skin steel sheets and the core resin, leading to forming problems such as shear between the two skin steel sheets and stinkhing. It was found that these forming problems are greatly affected by the bonding strength, tensile strength and ductility of che core resin and that good formability is obtained with a bonding strength of 23 8 MPa. Comparing the variable blank holding force with the constant blank holding force, the drawability of steel / plastic laminated sheet of 1.05 mm thick - is improved when using the variable BHF. Three kinds of room temperature laminated steel sheets with polyester, polypropylene, und nylon as corc resin were chosen as investigated materials.

Modelling of the anisotropy of Young's modulus in polycrystals

The crystallographic orientation distribution of cold rolled and recrystallized low‐carbon deep drawing steel is quantitatively investigated by means of the series expansion method and the technique of model component fit. The results of both methods are utilized to describe the elastic properties of the inspected sheets. The application of the model components allows a very good approximation of the course of Young's modulus and corresponds to experimental results as well as to the predictions stemming from the series expansion method. In addition to the influence of peak‐type texture components also the impact of complete and incomplete fibre‐type texture components on the course of Young's modulus is inspected.

Importance of Process Parameters for Texture and Properties of Microalloyed Deep Drawing Steels

Importance of Process Parameters for Texture and Properties of Microalloyed Deep Drawing Steels

Problems and feasibilities of testing the cyclic behaviour of thin sheet steels

This report deals with the testing problems of thin sheet steels subjected to cyclic load and introduces at the same time the appropriate techniques to procure the reliable and significant testing results. Practically, a proper judgement of cyclic fatigue behaviours of such conventional deep drawing steels is only possible, if the specimens were to be tested either under strain control mode in elastic-plastic range with sufficient plastic deformations or load controlled in elastic range by using the notched specimens with adequate local strain concentration. Besides the study of specific material properties, as absolutely determined by using the unnotched specimens, the influence of notch geometry can also be investigated by means of the notched specimens. For a promising performance of elastic-plastic cyclic tests on thin sheets the use of a particular specimen shape with uncritical length of high buckling resistance is most essential. Moreover, a special grip with great precision is necessary to ensure an axial and rigid alignment of specimens. In the course of a development an optimal specimen shape and its gripping device has been designed. The cyclic properties of some thin sheet steels, obtained in this way, are also illustrated. Im nachfolgenden Beitrag wird die Problematik der Prüfung an dünnen Feinblechen unter schwingender Beanspruchung behandelt und dabei geeignete Prüftechniken vorgestellt, mit denen sich aussagefähige Ergebnisse erzielen lassen. In der Regel sind zutreffende Beurteilungen des Ermüdungsverhaltens herkömmlicher Tiefziehbleche nur möglich, wenn die zu prüfenden Proben dehngesteuert elasto-plastisch oder kraftgeregelt bei entsprechender lokaler Spannungskonzentration (gekerbte Proben) elastisch beansprucht werden. Neben reinen werkstoffspezifischen Aussagen an ungekerbten Proben kann bei gekerbten Proben auch das Werkstoffverhalten im Zusammenhang mit der Kerbgeometrie untersucht werden. Vorausetzungen für einen erfolgreichen Versuchsablauf bei elasto-plastischer Schwingprüfung der dünnen Feinbleche ist die Verwendung geeigneter Probenformen mit unkritischer bzw. knickfreier Versuchslänge in Verbindung mit einer mechanischen Klemmvorrichtung, die die Proben zentriert und biegefrei spannt. Probenformen und Spannvorrichtungen wurden im Laufe einer Entwicklungsphase erprobt und optimiert. Die damit ermittelten Versuchsergebnisse einiger Stähle werden als Beispiel aufgeführt.

On the mechanism of bake-hardening

The bake-hardening behaviour of a deep drawing steel sheet was investigated. Aging experiments after different prestrains were carried out in the temperature range from 50 to 180°C. The change of mechanical properties, especially the increase in yield stress, was measured by tensile tests. It was found that the increase in the yield stress by simulated baking treatment occurs in two successive steps. It is assumed that the first rise is based on the Cottrell-effect and the further strengthening in the second step is caused by the precipitation of coherent carbides. A kinetic interpolation-model of the bake-hardening effect is introduced and this allows a description of the experimental data and a calculation of the bake-hardening behaviour. Das Bake-Hardening Verhalten der Tiefzieh-Stahlsorte ZStE 180 BH ist untersucht worden. Es sind Alterungsversuche nach unterschiedlichen plastischen Vordehnungen im Temperaturbereich von 50 bis 180°C durchgeführt worden. In Zugversuchen wurde die Änderungen der mechanischen Eigenschaften, insbesondere der Anstieg der Streckgrenze, untersucht. Durch eine Auslagerung, welche die Wärmeeinwirkung des Einbrennlackierens simuliert, steigt die Streckgrenze in zwei aufeinander folgenden Stufen an. Es wird angenommen, daß der erste Anstieg auf dem Cottrell-Effekt beruht, während der zweite Anstieg auf die Ausscheidung von kohärenten Carbiden zurück zu führen ist. Es wurde ein Interpolationsmodell entwickelt, das die Kinetik des Bake-Hardening Effektes beschreibt, mit dem die Meßwerte gut beschrieben und das Bake-Hardening Verhalten berechnet werden können.

Ultrasonic prediction ofR-value in deep drawing steels

The textures of five types of deep drawing steels were measured and analyzed using the series expansion method. Electromagnetic acoustic (EMAT) techniques were employed to determine the elastic anisotropy in terms of the angular variation of the ultrasonic velocities. The series expansion formalism was employed for predicting the elastic and plastic anisotropies from texture data. Comparison with the experimental measurements of Young's modulus indicates that the elastic energy method can accurately reproduce the elastic anisotropy if the single crystal elastic constants are appropriately chosen. The angular variation of ther-value in the rolling plane was calculated from the ODF coefficients by means of the pancake relaxed constraint model using an appropriate CRSS ratio for glide on the {112} 〈111〉 and {110} 〈111〉 slip systems. The fourth order and first sixth order ODF coefficients were calculatednondestructively from the anisotropy of the ultrasonic velocities. The calculated pole figures based on the ODF coefficients obtained in this way are similar to those derived from complete X-ray data. It is shown that the plastic properties of commercial deep drawing steels are predicted more accurately when the 4th-and 6th-order ODF coefficients are employed than when only the 4th-order ones are used.

Determining stock-sheet-sizes to minimise trim loss

This paper discusses the methods developed by an automobile press shop to determine stock-sheet-sizes to minimise total-trim-loss. The shop stocks sheets in a few sizes and manufactures a number of parts using them. When a part is to be produced, the most economic stock-sheet-size is selected and cut into blanks of required size. From one sheet, blanks of only one size are cut. Cutting blanks of more than one size from a sheet is not done to avoid coordination problems. However, the same sheet size may be used for another part at another time. The stock-sheet-sizes are determined by: (a) suggesting sheet sizes which are likely to give low trim loss for major parts, (b) generating a trim-loss matrix giving trim loss for every combination of suggested sheet sizes and parts, and (c) using a heuristic method to select a given number of sheet sizes. This method was used to determine stock-sheet-sizes for Extra Deep Drawing (EDD) steel sheets. The shop used 8364 tons of sheets in a year and generated 625 tons of trim loss. This could be reduced to 332 tons by selecting the best existing size for every part, without changing the sheet sizes. It could be further reduced to 74 tons by determining stock-sheet-sizes using the method described in this paper.

Recent Results on Recrystallization Mechanism in Deep Drawing Steels Achieved by Single Orientation Measurements in SEM

Recent Results on Recrystallization Mechanism in Deep Drawing Steels Achieved by Single Orientation Measurements in SEM

The Elastic Strain Ratio, the Lüders Strain Ratio and the Evolution of r-Value During Tensile Deformation

The elastic counterpart of the plastic strain ratio is derived from ultrasonic data measured on twenty commercial deep drawing steels. It is shown that the observed variations in plastic r are related to the evolution of texture, and are not affected either by the elastic range of deformation or by the propagation of Lüders bands. Further quantitative analysis suggests that the elastic strain ratio, determined non-destructively, can be used to predict plastic r-values by means of an empirical relationship.

Rolling and recrystallization textures of bcc steels

The rolling and recrystallization texture development of bcc steels is discussed for three examples belonging to three different types of steels, namely deep drawing steels (e.g. low carbon steel), ferritic stainless steels (e.g. Fe16%Cr) and electrical steels (e.g. Fe3%Si).

Texture and Anisotropy of Plastic Properties in Deep Drawing Steels

The textures of different types of deep drawing steels were measured and analyzed using the series expansion method. The angular variation of r-value in the rolling plane was calculated from the ODF coefficients by means of different models. Comparison with experimental data shows that, in the case of sharp textures, an intermediate relaxed constraint model (pancake version) is a better predictor of the plastic strain ratio than the extreme Taylor or Sachs-Kochendorfer type calculation. This is justified as being more favorable energetically for the texture components present in deep drawing steels. The best quantitative agreement is obtained when the CRSS ratio for glide on the {112} and {110} slip systems is 0.95 (except for the AKDQ and IF2 grades, for which values of 0.90 and 1.0, respectively, are preferred).

Development of Recrystallization Texture in Deep Drawing Steels, Measured by X-Ray and Single Orientation in SEM

Development of Recrystallization Texture in Deep Drawing Steels, Measured by X-Ray and Single Orientation in SEM

Textural Through-Thickness Inhomogeneity and its Influence on the Prediction of Plastic Anisotropy

Work done for this paper centres around two themes: 1) the characterization of the through-thickness inhomogeneity of texture observed in certain deep drawing steels, and 2) attempting to understand to what extent the presence of this inhomogeneity affects the correlation between the texture and the bulk plastic anisotropy of the specimens. For this, the textural inhomogeneities in three deep drawing steels, two interstitial free and one aluminum killed, were measured and described using the orientation distribution function (ODF). The bulk plastic anisotropies of these specimens were obtained through the measurement of the r-value. The impact of the measured inhomogeneities on the bulk properties was analyzed by comparing the r-value anisotropies calculated using a series expansion method from the various texture measurements made through the sheet thicknesses to the experimental r-values. It was observed that the textural inhomogeneities in the specimens were slight and consisted mainly of small Goss components at the surface and sub-surface of the sheets, which were not observed at the sheet centres. The impact of these inhomogeneities was small, but generally the r-value predictions made from the textures measured at the sheet centres were better correlated with the experimental r-value anisotropies.

Ultrasonic Prediction of r-value in Deep Drawing Steels.

The textures of five types of deep drawing steels were measured and analyzed using the series expansion method. Electromagnetic acoustic (EMAT) techniques were employed to determine the elastic anisotropy in terms of the angular variation of the ultrasonic velocities. The series expansion formalism was employed for predicting the elastic and plastic anisotropies from texture data. Comparison with the experimental measurements of Young's modulus indicates that the elastic energy method can accurately reproduce the elastic anisotropy if the single crystal elastic constants are appropriately chosen. The angular variation of ther-value in the rolling plane was calculated from the ODF coefficients by means of the pancake relaxed constraint model using an appropriate CRSS ratio for glide on the {112} 〈111〉 and {110} 〈111〉 slip systems. The fourth order and first sixth order ODF coefficients were calculatednondestructively from the anisotropy of the ultrasonic velocities. The calculated pole figures based on the ODF coefficients obtained in this way are similar to those derived from complete X-ray data. It is shown that the plastic properties of commercial deep drawing steels are predicted more accurately when the 4th-and 6th-order ODF coefficients are employed than when only the 4th-order ones are used.

Implementation of hill orthotropic criterion in finite strain elastoplasticity for sheet metal forming

In order to develop a three dimensional finite element computer program related to the sheet metal forming process modeling for car industry, we are currently implementing an adapted finite elastoplastic strain module. Our aim is then to progress in representing the deep drawing steel behaviour, especially to describe a wide range of complex strain paths. This module is based on a large strain membrane formulation using a set of curvilinear coordinates and the classical Hill orthotropic criterion with non-associated (or associated) plastic flow rule and mixed (isotropic and/or kinematics) hardening. Experimental/numerical comparisons on testing cups have been carried out and discussed to select the suitable hypotheses.

Implementation of hill orthotropic criterion in finite strain elastoplasticity for sheet metal forming

In order to develop a three dimensional finite element computer program related to the sheet metal forming process modeling for car industry, we are currently implementing an adapted finite elastoplastic strain module. Our aim is then to progress in representing the deep drawing steel behaviour, especially to describe a wide range of complex strain paths. This module is based on a large strain membrane formulation using a set of curvilinear coordinates and the classical Hill orthotropic criterion with non-associated (or associated) plastic flow rule and mixed (isotropic and/or kinematics) hardening. Experimental/numerical comparisons on testing cups have been carried out and discussed to select the suitable hypotheses.

Physico-mathematical description of quenching stage of steel sheets for continuous annealing

AbstractIn this paper a study on water cooling of drawing steel produced by continuous annealing is reported. The experimental cooling curves obtained in various cooling conditions are interpreted using a model based on fluctuation theory. The influence of some physical parameters on the cooling rate is also discussed.MST/1084

Development of textures during rapid intercritical annealing of deep drawing steels

Development of textures during rapid intercritical annealing of deep drawing steels

Development of textures during rapid intercritical annealing of deep drawing steels

Abstract It is still possible to optimise the newly developed continuous annealing process for sheet steel production with respect to the properties of the product. In the present contribution, the development of the texture under continuous annealing conditions (very rapid heating, short annealing time, and high annealing temperatures of intercritical range) has been investigated. The orientation distribution function method has been applied to study the detailed effect of the parameters and the underlying mechanisms. It is found that the important {111} recrystallisation components are strengthened on further annealing at higher subcritical or at intercritical temperatures. This is a result of the successive or simultaneous occurrence of oriented grain growth and partial α → γ → α orientation selective transformation. After complete austenitisation, the strong {111} fibre is weakened, which can be attributed to the operation of several crystallographic variants during the course of phase transformations...

α域熱延した低炭素薄鋼板の集合組織形成に及ぼす成分の影響

From a viewpoint of deep drawability, the influence of chemical compositions on the texture formation of steel sheets hot rolled below Ar3 temperature (warm rolled) has been investigated using steels consisting of various combinations of carbon and titanium contents. The formation of texture was greatly influenced by carbon in solution. A steel sheet warm rolled in the absence of carbon in solution revealed strong formation of near ND//<111> orientations in the recrystallization texture. On the other hand, ND//<111> orientations hardly developed and near{113}<110> was recognized as the main orientation of the recrystallization texture when carbon in solution were present. Microscopic studies using transmission electron microscopy and selected area electron diffraction showed that, in the presence of carbon in solution, {114}<110> - {112}<110> orientations were formed in the vicinity of grain boundaries by some unique crystal rotation different from that occurring in the matrix. The occurrence of the unique crystal rotation was explained by the variation of active slip systems caused by work hardening due to the interaction between dislocations and the interstitial atoms. Besides, the influence of grain size before warm rolling and recrystallization temperature on the texture formation, both of which were affected by chemical compositions was also discussed. Finally, proper chemical compositions for producing deep drawing steel sheets by warm rolling were suggested.