Dynamically recrystallized austenitic grain in a low carbon advanced ultra-high strength steel (A-UHSS) microalloyed with boron under hot deformation conditions

2012 ◽  
Vol 1485 ◽  
pp. 143-148 ◽  
Author(s):  
I. Mejía ◽  
E. García-Mora ◽  
G. Altamirano ◽  
A. Bedolla-Jacuinde ◽  
J. M. Cabrera
Keyword(s):  
Grain Size ◽  
Hot Deformation ◽  
High Strength Steel ◽  
Picric Acid ◽  
True Strain ◽  
Research Work ◽  
High Strength ◽  
Low Carbon ◽  
Ultra High Strength Steel ◽  
Wide Range

ABSTRACTThis research work studies the dynamically recrystallized austenitic grain size (Drec) in a new family of low carbon NiCrCuV advanced ultra-high strength steel (A-UHSS) microalloyed with boron under hot deformation conditions. For this purpose, uniaxial hot-compression tests are carried out in a low carbon A-UHSS microalloyed with different amounts of boron (14, 33, 82, 126 and 214 ppm) over a wide range of temperatures (950, 1000, 1050 and 1100°C) and constant true strain rates (10−3, 10−2and 10−1s−1). Deformed samples are prepared and chemically etched with a saturated aqueous picric acid solution at 80°C in order to reveal theDrecand examined by light optical (LOM) and scanning electron microscopy (SEM). TheDrecis related to the Zener-Hollomon parameter (Z), and thereafter theDrecdivided by Burger's vector (b) is related to the steady state stress (σss) divided by the shear modulus (µ) (Derby model). Results shown that theDrecin the current steels is fine (≈ 23 μm) and almost equiaxed, and the recrystallized grain size-flow stress relationship observed after of plastic deformation is consistent with the general formulation proposed by Derby. It is corroborated that boron additions to the current A-UHSS do not have meaningful influence on theDrec.

Ultra-High Strength Steel Hot Stamping Technology and Devices

2014 ◽  
Vol 1063 ◽  
pp. 237-243
Author(s):  
Zhong De Shan ◽  
Qin Tai Yan ◽  
Chao Jiang ◽  
Wen Juan Rong
Keyword(s):  
Tensile Strength ◽  
High Strength Steel ◽  
Hot Stamping ◽  
Research Work ◽  
High Strength ◽  
Parameters Optimization ◽  
Systematic Research ◽  
China Academy ◽  
Ultra High Strength Steel ◽  
Vehicle Structure

Ultra High Strength Steel (UHSS) hot stamping technology is a special process which can enhance the steel tensile strength to 1500MPa. Appling this technology in producing vehicle structure parts can make car lighter and safer. In China there are more and more automobile enterprises adopt this technology. To master and extend the skill, China Academy of Machinery Science & Technology (CAM) have done systematic research, such as the strengthen mechanism of the steel, hot stamping key devices designing, forming and quenching integrated mould designing, stamping process parameters optimization, etc.. By now, CAM has mastered the mass production technology of vehicle parts, which can guarantee its shape and tensile strength, and produced such typical parts as door-beam, B pillar, etc.. The paper is an introduction of the research work and achievement about UHSS hot stamping developed by CAM.

scholarly journals Hot Deformation Process Analysis and Modelling of X153CrMoV12 Steel

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1125 ◽  
Author(s):  
Michal Krbaťa ◽  
Maroš Eckert ◽  
Daniel Križan ◽  
Igor Barényi ◽  
Ivana Mikušová
Keyword(s):  
Hot Deformation ◽  
Process Analysis ◽  
True Strain ◽  
Peak Stress ◽  
High Strength ◽  
True Stress ◽  
Point Of View ◽  
Plastic Behavior ◽  
Hollomon Parameter ◽  
Wide Range

Analysis of the high temperature plastic behavior of high-strength steel X153CrMoV12 was developed in the temperature range of 800–1200 °C and the deformation rate in the range of 0.001–10 s−1 to the maximum value of the true strain 0.9%. Microstructural changes were observed using light optical microscopy (LOM) as well as atomic force microscopy (AFM). The effect of hot deformation temperature on true stress, peak stress and true strain was evaluated from the respective flow curves. Based on these results, steel transformation was discussed from the dynamic recovery and recrystallization point of view. Furthermore, a present model, taking into account the Zener–Hollomon parameter, was developed to predict the true stress and strain over a wide range of temperatures and strain rates. Using constitutive equations, material parameters and activation energy were derived, which can be subsequently applied to other models related to hot deformation behavior of selected tool steels. The experimental data were compassed to the ones obtained by the predictive model with the correlation coefficient R = 0.98267. These results demonstrate an appropriate applicability of the model for experimental materials in hot deformation applications.

Mechanical Joining of Various Materials by Clinching Method

2015 ◽  
Vol 662 ◽  
pp. 205-208 ◽  
Author(s):  
Ľuboš Kaščák ◽  
Emil Spišák ◽  
Jacek Mucha
Keyword(s):  
High Strength Steel ◽  
Steel Sheet ◽  
Low Carbon Steel ◽  
Surface Preparation ◽  
High Strength ◽  
Low Carbon ◽  
Steel Sheets ◽  
Joint Properties ◽  
Wide Range ◽  
Grade Steel

Clinching is a simple, cheap and efficient method of joining that enables to join two or more sheets without any additional elements such as rivets, bolts or nuts. In addition, clinching does not require a surface preparation e.g. drilling (riveting), cleaning and roughening of the surface (adhesive boding) and other types of surface preparations (arc welding). Clinching is utilized in a wide range of applications and can be applied to different materials such as low carbon steel sheets, high-strength steel sheets, aluminium alloys, magnesium alloys. The paper presents the results of evaluation of clinched joint properties. The advanced high-strength steel sheet DP600 in combination with the drawing grade steel sheets DC06, DX51D+Z and high-strength low alloy steel sheet H220PD were used for experiments. The influence of position of the sheets relative to the punch and die of the tool on the carrying capacities of the clinched joints was observed as well. The tension test and microhardness test were used for the evaluation of clinched joint properties.

Thermo-Mechanically Controlled Processed Ultrahigh Strength Steels

2014 ◽  
Vol 783-786 ◽  
pp. 685-691
Author(s):  
Subrata Chatterjee ◽  
S.K. Ghosh ◽  
P.S. Bandyopadhyay
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Yield Strength ◽  
High Strength Steel ◽  
Bainitic Ferrite ◽  
High Strength ◽  
Bearing Steel ◽  
Pressure Vessels ◽  
Low Carbon ◽  
Ultra High Strength Steel

A low-carbon, titanium and niobium (Ti-Nb) bearing and a low-carbon titanium, niobium and copper (Ti-Nb-Cu) bearing ultra high strength steel have been thermo-mechanically processed on a laboratory scale unit. Evolution of microstructure and mechanical properties of the above air cooled steels have been studied at different finish rolling temperatures (FRTs). Microstructural characterization reveals largely a mixture of granular bainite and bainitic ferrite along with the precipitation of microalloying carbide/carbonitride particles and/or Cu-rich precipitates. (Ti-Nb) bearing steel yields higher yield strength (1114-1143 MPa) along with higher tensile strength (1591-1688 MPa) and moderate ductility (12-13%) as compared to (Ti-Nb-Cu) bearing steel having yield strength (934-996 MPa) combined with tensile strength (1434-1464 MPa) and similar ductility (13%) for the selected range of 850-750°C FRT. Due to higher strength-ductility combinations, these present investigated steels can be regarded as the replacement material for ballistic applications as well as other sectors like defense, pipeline, cars, pressure vessels, ships, offshore platforms, aircraft undercarriages and rocket motor casings etc. Key words: Thermo-mechanical controlled processing, ultra high strength steel, microstructure, mechanical properties.

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