Journal articles: 'UHSS'

1

Noorsumar, Gulshan, Dmitry Vysochinskiy, Even Englund, Kjell G. Robbersmyr, and Svitlana Rogovchenko. "Effect of welding and heat treatment on the properties of UHSS used in automotive industry." EPJ Web of Conferences 250 (2021): 05015. http://dx.doi.org/10.1051/epjconf/202125005015.

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This paper deals with the undesired effects of the heat treatments on the mechanical properties of (UHSS) Ultra High Strength Steel used nowadays in automotive industry to improve crashworthiness performance of vehicles. The UHSS specimens were extracted from certain parts of the car body and subjected to different heat treatments. Four types of specimens were tested: untreated, welded with metal inert gas welding, heat treated at 800 °C, and heat treated at 1250 °C. All heat-treated specimens showed dramatically reduced values of strength. The results suggest that it is important to follow the official repair manuals avoiding unnecessary welding and improper heat treatments of UHSS. The experiments provide the data necessary for constructing a constitutive model and performing a finite-element analysis of improperly repaired UHSS parts.

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Kah, Paul, Markku Pirinen, Raimo Suoranta, and Jukka Martikainen. "Welding of Ultra High Strength Steels." Advanced Materials Research 849 (November 2013): 357–65. http://dx.doi.org/10.4028/www.scientific.net/amr.849.357.

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The ongoing need to reduce the weight of products while increasing strength has resulted in new generation steel manufacturing using special heat treatments to produce High Strength Steels (HSS) and Ultra High Strength Steels (UHSS) with up to 1700 MPa tensile strength. The high strength level of these steels makes it possible to produce structures with a considerable weight and cost reduction, and such steels have been adopted in the automotive industry and for mobile heavy equipment. Welding of UHSS is, however, not without its complications and welding processes for these steels need careful attention. For instance, their high susceptibility to cracking and Heat Affected Zone (HAZ) softening are risks that need to be borne in mind when choosing welding parameters. This research work discusses the difficulties and challenges of successful welding of UHSS. Common welding methods used in welding of UHSS are briefly reviewed to gain a better understanding of the effects of different welding parameters and methods. The paper finds that UHSS can be satisfactorily welded with laser welding, electron beam welding, resistance welding, and conventional arc welding methods, but the quality of the weld is dependent on appropriate control of several parameters and variables of the welding processes.

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El Ghazouani, Laila, Lahouari Bounoua, Joseph Nigro, Majid Mansour, Hassan Radoine, and Hanane Souidi. "Combining Satellite Data and Spatial Analysis to Assess the UHI Amplitude and Structure within Urban Areas: The Case of Moroccan Cities." Urban Science 5, no. 3 (September 14, 2021): 67. http://dx.doi.org/10.3390/urbansci5030067.

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Landsat-8 surface temperature and the European Space Agency land cover are used to assess the impact of land cover on the Urban Heat Island (UHI) and Urban Heat Sink (UHS). We analyzed five Moroccan cities selected for their different local climate, size, and typology during summer at three different spatial scales. The results show multiple causes defining the different forms and amplitudes of the UHI, namely: the ambient climate, the proximity to the sea, the presence of landscaped areas, and the color of building roofs and walls. Contrary to what was expected, the vegetation was not systematically an island of coolness, either because of its typology or its irrigation status. In the coastal cities of Tangier and Casablanca, UHIs around 20 °C are observed on the seaside, whereas a UHS of up to 11 °C is observed between the city center and the southern periphery of Casablanca. A moderate amplitude UHI of 7 °C is formed in the mountainous city of Ifrane. For cities built in desert-like environments, well-defined UHSs between 9 °C and 12 °C are observed in Smara and Marrakech, respectively. At a finer scale, towns recorded lower temperatures than their immediate surroundings, which are attributed to evaporation from irrigated plants.

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Zhang, Yu, Zi Jian Wang, Yi Lin Wang, Zhi Jian Zhang, and Yi Sheng Zhang. "A Study on the Relationship between Hardness and Magnetic Properties of Ultra-High Strength Steel." Advanced Materials Research 1063 (December 2014): 78–81. http://dx.doi.org/10.4028/www.scientific.net/amr.1063.78.

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Magnetic nondestructive testing methods including eddy current testing, magnetic memory, magnetic Barkhausen noise and so on are widely used in testing mechanical properties of ferromagnetic parts. Experiments were done to study the relationship between hardness and magnetic properties of ultra-high strength steel (UHSS), which plays an important role in automobile industry. The magnetic properties of UHSS specimens with different hardness were studied. The result shows that there is a strong connection between hardness and magnetic properties. Coercive force of UHSS is proportional to the hardness. This can be used to explain certain mechanism of magnetic nondestructive testing method such as connection between hardness and Barkhausen noise.

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Chen, T. C., Wen Hao Chien, Yuan Tsung Wang, Ching Yuan Huang, Hung Wei Yen, and Hsin Chih Lin. "Hydrogen Assisted Tempered Martensite Embrittlement of Ultra High Strength Martensitic Steel." Materials Science Forum 880 (November 2016): 29–32. http://dx.doi.org/10.4028/www.scientific.net/msf.880.29.

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The demand for new materials that provide excellent structural performance while reducing weight and being cost-effectively manufactured is increasing. For applications with high strength requirements, ultra-high strength steels (UHSS) have been widely used. However, with such a high strength level, UHSS are very sensitive to the hydrogen that could be ease by the tempering process. In this research, the correlation of hydrogen and tempering process on commercial UHSS 15B30 has been studied. Results show that the tensile strength (TS) of as-quenched 15B30 is about 1900MPa. After tempering treatment of the quenched 15B30, the TS decreases from 1600MPa to 1200MPa with tempering temperature increased from 200°C to 400°C. The 15B30 specimens, being subjected to hydrogen charge, exhibit the dramatic reduction of mechanical strengths.

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Wagner, L., H. Schauer, H. Pauli, and J. Hinterdorfer. "Improved bendability characterization of UHSS sheets." IOP Conference Series: Materials Science and Engineering 651 (November 25, 2019): 012019. http://dx.doi.org/10.1088/1757-899x/651/1/012019.

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Wang, Chao, Bin Zhu, Liang Wang, Yi Lin Wang, and Yi Sheng Zhang. "GPU Accelerated Finite Element Simulation for Ultra-High Strength Steel Quenching." Advanced Materials Research 842 (November 2013): 337–40. http://dx.doi.org/10.4028/www.scientific.net/amr.842.337.

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During the hot stamping of ultra-high strength steel (UHSS), the quenching effect of the mold on the sheet plays an important role to achieve the transition from austenite to martensite. Thus a finite element model for the quenching process of UHSS is established in this paper. The key points of the model include contact thermal conduction and the latent heat processing of phase transforming. Finite element program has been developed to calculate the temperature field of the UHSS quenching process, and temperature measurement device was used to get the temperature-time curve of the mold and the sheet to validate the calculation results. It can be concluded that the latent heat and thermal contact resistance have a critical influence on the temperature filed of the sheet during the hot stamping process. Finally, the parallel computation technology based on GPU(Graphics processing unit) was adopted to accelerate the calculation.

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Thien, Nguyen Trung. "EFFECT OF ELECTRIC CURRENT PULSE ON MECHANICAL PROPERTIES OF ULTRA-HIGH STRENGTH STEEL 1180CP." Vietnam Journal of Science and Technology 54, no. 5A (March 22, 2018): 82. http://dx.doi.org/10.15625/2525-2518/54/5a/12064.

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Effect of the pulse electric current on mechanical properties of an ultra-high strength steel (UHSS) is experimentally investigated. A single pulse of electric current with a short duration of 0.36 sec is applied to the specimen under tensile plastic loading. The experimental result showed that flow stress of the UHSS nearly instantly drops at moment of electric current, following strain hardening until necking of the specimen. Uniform elongation completely depends on the pulsing strain, while ultimate tensile strength slightly changes after electric current.

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Amraei, Mohsen, Lingjia Zong, Antti Ahola, and Timo Björk. "Bonded CFRP to high strength steels." Rakenteiden Mekaniikka 52, no. 4 (December 31, 2019): 222–35. http://dx.doi.org/10.23998/rm.76267.

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Research on the bond performance of CFRP-strengthened steel have been done for the past years, but it has mainly focused on lower grades of steel. The performance of the bond between ultra-high modulus (UHM) CFRP and high/ultra-high strength steel (HSS/UHSS) is investigated in this paper. A series of experiments have been conducted, with single/double side-strengthened (SSS/DSS) HSS/UHSS with CFRP laminates using Araldite adhesive. It was found that strengthening up to the ultimate strength of the DSS specimens is feasible. However, debonding happens at the ultimate strength of SSS specimens.

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Park, Sungpill, and Yongjai Kwon. "The Study of Roll-forming Technology for UHSS Hydroformed Parts." Transactions of the Korean Society of Automotive Engineers 23, no. 1 (January 1, 2015): 41–48. http://dx.doi.org/10.7467/ksae.2015.23.1.041.

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11

Lei, Cheng Xi, Zhong Wen Xing, and Hong Ya Fu. "Effect of Dies Temperature on Mechanical Properties of Hot Stamping Square-Cup Part for Ultra High Strength Steel." Advanced Materials Research 129-131 (August 2010): 390–94. http://dx.doi.org/10.4028/www.scientific.net/amr.129-131.390.

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The numerical simulation of hot-stamping process was carried out for UHSS square-cup parts, and the influence of dies temperature on the hot-stamping process was anlysised. Besides, through the microstructure analysis and mechanical properties testing of the formed parts, effects of dies temperature on microstructures and mechanical properties of hot-stamping square-cup parts were obtained. The experiment and simulation results showed that the mechanical properties of the UHSS are strongly dependent on the temperature, so the dies temperature is one of the most important parameters that have to be taken into account in designing the hot-forming dies and the hot-forming process.

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Kvackaj, Tibor, Jana Bidulská, and Róbert Bidulský. "Overview of HSS Steel Grades Development and Study of Reheating Condition Effects on Austenite Grain Size Changes." Materials 14, no. 8 (April 15, 2021): 1988. http://dx.doi.org/10.3390/ma14081988.

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This review paper concerns the development of the chemical compositions and controlled processes of rolling and cooling steels to increase their mechanical properties and reduce weight and production costs. The paper analyzes the basic differences among high-strength steel (HSS), advanced high-strength steel (AHSS) and ultra-high-strength steel (UHSS) depending on differences in their final microstructural components, chemical composition, alloying elements and strengthening contributions to determine strength and mechanical properties. HSS is characterized by a final single-phase structure with reduced perlite content, while AHSS has a final structure of two-phase to multiphase. UHSS is characterized by a single-phase or multiphase structure. The yield strength of the steels have the following value intervals: HSS, 180–550 MPa; AHSS, 260–900 MPa; UHSS, 600–960 MPa. In addition to strength properties, the ductility of these steel grades is also an important parameter. AHSS steel has the best ductility, followed by HSS and UHSS. Within the HSS steel group, high-strength low-alloy (HSLA) steel represents a special subgroup characterized by the use of microalloying elements for special strength and plastic properties. An important parameter determining the strength properties of these steels is the grain-size diameter of the final structure, which depends on the processing conditions of the previous austenitic structure. The influence of reheating temperatures (TReh) and the holding time at the reheating temperature (tReh) of C–Mn–Nb–V HSLA steel was investigated in detail. Mathematical equations describing changes in the diameter of austenite grain size (dγ), depending on reheating temperature and holding time, were derived by the authors. The coordinates of the point where normal grain growth turned abnormal was determined. These coordinates for testing steel are the reheating conditions TReh = 1060 °C, tReh = 1800 s at the diameter of austenite grain size dγ = 100 μm.

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Li, Ping, Yu Sheng Liu, Tian Zong Gongzi, and Ke Min Xue. "Effect of Pre-Heating Temperature on Microstructure and Properties of 22MnB5 Steel Hot Stamping." Advanced Materials Research 1063 (December 2014): 108–11. http://dx.doi.org/10.4028/www.scientific.net/amr.1063.108.

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The hot stamping process of ultra high strength steel(UHSS) sheet is an innovative way to manufacture the components with a ultra high tensile strength. The sufficiency of martensitic transformation in formed component is affected by pre-heating temperature of blank directly. In this paper, experiments of heating UHSS blanks to 700°C, 800°C, 900°C and 1000°C were implemented to investigate the effect of pre-heating temperature on the formed component’s microstructure and mechanical properties. The results indicate that 900°C is the best pre-heating temperature for hot stamping process. The microstructure of formed component is all fine and uniform martensite. Meanwhile, tensile strength and vickers hardness raise up to 1580MPa and 450HV, respectively.

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14

Choi, Hyun Sung, Jeong Whan Yoon, Jong Sup Lee, and Geun Ho Kim. "A Springback Prediction of 1.5 GPa Grade Steel in Roll Forming Process for Automotive Sill-Side Inner Component." Key Engineering Materials 794 (February 2019): 267–74. http://dx.doi.org/10.4028/www.scientific.net/kem.794.267.

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Roll forming has been widely used to produce steel sheet with low formability such as Ultra High Strength Steel (UHSS). It allows the steel sheet to be formed through successive bending process into a desired shape which even cannot be formed by press brake forming. Although the process effectively improves the formability of UHSS, there still the remains accuracy issue such as springback, flair, bow and so on. Especially, springback of UHSS is one of the major challenges in roll forming process as much as press forming process. In this paper, the springback of 1.5 GPa grade steel in roll forming process was numerically investigated for automotive sill-side inner component. The material behavior was described by using the selected hardening models: isotropic hardening (Piecewise linear model), linear kinematic hardening (Prager model [6]), nonlinear kinematic hardening model (Yoshida-Uemori model [7]). A commercial software LS-DYNA was utilized for the analysis. Eighteen successive roll stages were modelled for the simulation. From the results, it was found that the springback prediction during roll forming process could be successfully achieved when the complicated material behaviors including Bauschinger effect, nonlinear transient hardening, and changeable unloading modulus are taken into account for the Finite Element (FE) simulation.

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Mejía, I., E. García-Mora, G. Altamirano, A. Bedolla-Jacuinde, and J. M. Cabrera. "Dynamically recrystallized austenitic grain in a low carbon advanced ultra-high strength steel (A-UHSS) microalloyed with boron under hot deformation conditions." MRS Proceedings 1485 (2012): 143–48. http://dx.doi.org/10.1557/opl.2013.283.

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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.

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Cai, Wan Hua, Zhong De Shan, Yong Sheng Ye, and Bai Liang Zhuang. "A Force Model for UHSS Hot-Formed Automobile Parts." Advanced Materials Research 1063 (December 2014): 322–29. http://dx.doi.org/10.4028/www.scientific.net/amr.1063.322.

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Combined numerical simulations and experimentally measured data, the relationship between the initial temperature of the workpiece was described, the stamping speed, and the required forming force. Air cooling was included to determine the temperature of the part within the mold, and the required stamping force was optimized by studying the impact of the cooling time on the temperature of the part. The optimized model was verified and validated by comparing simulated data for an anti-collision beam with the experimental results of the hot-forming process. The results showed that the model provides a useful description of the hot-forming process; however, an empirical factor of 0.95 was required to achieve agreement between the simulated and experimentally measured data.

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Gyasi, Emmaniel Afrane, Paul Kah, Heikki Handroos, Pavel Layus, and Sanbao Lin. "Adaptive Welding of S960QC UHSS for Arctic Structural Applications." International Review of Mechanical Engineering (IREME) 12, no. 4 (April 30, 2018): 371. http://dx.doi.org/10.15866/ireme.v12i4.14991.

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Shan, Zhong De, Qin Tai Yan, Chao Jiang, and Wen Juan Rong. "Ultra-High Strength Steel Hot Stamping Technology and Devices." Advanced Materials Research 1063 (December 2014): 237–43. http://dx.doi.org/10.4028/www.scientific.net/amr.1063.237.

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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.

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Song, Jung Han, J. Lee, I. Hwang, Y. B. Kim, S. Choi, G. A. Lee, and M. J. Kang. "Effect of Pulsed Electric Current on the Tensile Properties of DP Type Ultra-High Strength Steel Sheets." Applied Mechanics and Materials 389 (August 2013): 284–88. http://dx.doi.org/10.4028/www.scientific.net/amm.389.284.

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Although ultra-high strength steel (UHSS) sheets with tensile stress above 1.0 GPa have a great attention in the automotive industries for reducing the weight and improving fuel efficiency of auto-body, the poor formability of UHSS sheets is one of the main factors hindering their industrial application. Enhancing the formability is a very important and challenging problem to both automotive and manufacturing engineers. In this study, the electro-plastic effect, which is first discovered in 1960s, of ultra-high strength steel sheets is investigated to improve the formability. To begin with, a test system is built up to carry out the tensile test with heavy electric current flowing through the specimen. The evolutions of the flow stress and the electric resistivity are obtained using this test system. The significant decrease in the flow stress caused by the heavy flowing through current is observed.

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Han, Daxin, Réjane Hörhold, Martin Müller, Sebastian Wiesenmayer, Marion Merklein, and Gerson Meschut. "Shear-Clinching of Multi-Element Specimens of Aluminium Alloy and Ultra-High-Strength Steel." Key Engineering Materials 767 (April 2018): 389–96. http://dx.doi.org/10.4028/www.scientific.net/kem.767.389.

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The newly developed joining-by-forming technology “shear-clinching”, features a potentially single-stage process for joining UHSS without requiring any additional elements. Foundational studies have focused on the functionality of shear-clinching at a one-element sample. To ensure the safety of the industrial application of the shear-clinching technology, an investigation with component-like samples with several joints is required. This paper presents a detailed analysis of the material behaviour during the shear-clinching process with multi-element specimens to evaluate the influence of the neighbouring joints. In order to describe the influence of the neighbouring joints, the deformations resulting from the bending and material displacement are recorded without contact after the joining process: locally around the joining point and globally over the entire sample size. To minimize such bending effects, a tool-sided adaptation is provided. The results show the high potential of shear-clinching joining by UHSS and give further recommendations for future multi-material application.

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García-Mora, E., I. Mejía, and J. M. Cabrera. "Boron Effect on the Softening Parameter (Ω) of Advanced Ultra-High Strength Steels (A-UHSS) under Uniaxial Hot-Compression Conditions." MRS Proceedings 1765 (2015): 97–102. http://dx.doi.org/10.1557/opl.2015.813.

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ABSTRACTAdvanced ultra-high strength steels (A-UHSS) are revolutionizing both the steel and automotive industries, therefore it is imperative to study their hot plastic deformation behavior and modeling. The flow characteristics of all hot forming processes consist basically of two competitive phenomena: strain hardening and softening due to dynamic mechanisms (recovery and/or recrystallization). In this research work, the softening parameter was determined in a low carbon A-UHSS microalloyed steel with different amounts of boron (0, 14 and 214 ppm). Experimental stress–strain data of uniaxial hot-compression tests at different temperatures (950, 1000, 1050 and 1100 °C) and strain rates (10–3, 10–2 and 10–1 s–1) were used. The stress–strain relationships as a function of temperature and strain rate were described on the basis of the Estrin, Mecking, and Bergström model. The experimental values of the softening parameter Ω were adjusted using the least-squares method. In general, the results reveal that the softening parameter increases with increasing boron content.

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Cho, Lawrence, Yuran Kong, John G. Speer, and Kip O. Findley. "Hydrogen Embrittlement of Medium Mn Steels." Metals 11, no. 2 (February 20, 2021): 358. http://dx.doi.org/10.3390/met11020358.

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Recent research efforts to develop advanced–/ultrahigh–strength medium-Mn steels have led to the development of a variety of alloying concepts, thermo-mechanical processing routes, and microstructural variants for these steel grades. However, certain grades of advanced–/ultrahigh–strength steels (A/UHSS) are known to be highly susceptible to hydrogen embrittlement, due to their high strength levels. Hydrogen embrittlement characteristics of medium–Mn steels are less understood compared to other classes of A/UHSS, such as high Mn twinning–induced plasticity steel, because of the relatively short history of the development of this steel class and the complex nature of multiphase, fine-grained microstructures that are present in medium–Mn steels. The motivation of this paper is to review the current understanding of the hydrogen embrittlement characteristics of medium or intermediate Mn (4 to 15 wt pct) multiphase steels and to address various alloying and processing strategies that are available to enhance the hydrogen-resistance of these steel grades.

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Tsang, Kwun Sing, William Ion, Paul Blackwell, and Martin English. "Industrial validation of strain in cold roll forming of UHSS." Procedia Manufacturing 15 (2018): 788–95. http://dx.doi.org/10.1016/j.promfg.2018.07.322.

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Tahir, A. F. M., A. R. Rashid, N. E. Sariff, and E. A. Rahim. "CO2 Laser Cutting Performance on Ultra High Strength Steel (UHSS)." Lasers in Manufacturing and Materials Processing 7, no. 1 (December 12, 2019): 15–37. http://dx.doi.org/10.1007/s40516-019-00104-z.

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Park, Dong Hwan, Jae Jung Yun, Hyun Duk Moon, and Tae Gil Lee. "The Development of Seat Track Parts Using Shape Freeze in UHSS." Journal of The Korean Society of Manufacturing Technology Engineers 26, no. 1 (February 15, 2017): 59–65. http://dx.doi.org/10.7735/ksmte.2017.26.1.59.

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Amraei, Mohsen, Tuomas Skriko, Timo Björk, and Xiao-Ling Zhao. "Plastic strain characteristics of butt-welded ultra-high strength steel (UHSS)." Thin-Walled Structures 109 (December 2016): 227–41. http://dx.doi.org/10.1016/j.tws.2016.09.024.

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Ying, Xu, and Shan Zhong-de. "Design parameter investigation of cooling systems for UHSS hot stamping dies." International Journal of Advanced Manufacturing Technology 70, no. 1-4 (September 5, 2013): 257–62. http://dx.doi.org/10.1007/s00170-013-5272-7.

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Arola, Anna Maija, Antti J. Kaijalainen, and Vili Kesti. "Evaluation of Bendability of Hot-Rolled S960 Grade Steel Using Optical Strain Measurements and FE-Modelling." Key Engineering Materials 651-653 (July 2015): 610–16. http://dx.doi.org/10.4028/www.scientific.net/kem.651-653.610.

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Bending is an important forming process for ultra-high strength steel (UHSS) because it is cost-effective, fast and in many cases it can be used to replace welding in a part manufacturing processes. One major challenge in air bending of UHSS is to predict the limits for bendability since the traditional methods for failure prediction, such as forming limit diagram (FLD), cannot generally be applied to bending process. In this paper, 3D FE-modelling coupled with a CDM-damage model is used to simulate the air bending process and to determine the bendability limits for a hot-rolled 960MPa grade. Damage parameters for the CDM-model are determined by using optical strain measurements and inverse modelling of the tensile test. Three point bending tests with optical strain measuring were carried out to determine the deformation field of the outer bend in different bending angles and the results of the bending simulation are compared with the strain measurements of the bending tests. The damage model is then calibrated using the experimental results of the bending tests to adjust the crack occurrence in the simulation. A good agreement was found between simulations and experimental measurements.

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Kim, Ki-Young, Eun-Ho Lee, Soo-Hyun Park, Youn-Hee Kang, Jong-Youn Park, Hyoun-Young Lee, Chang Ho Moon, and Kisoo Kim. "An Infrared Local-Heat-Assisted Cold Stamping Process for Martensitic Steel and Application to an Auto Part." Metals 10, no. 11 (November 20, 2020): 1543. http://dx.doi.org/10.3390/met10111543.

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The automotive industry has tried to employ ultra-high-strength steel (UHSS), which has a higher strength with a thinner thickness. However, because of its low formability, there is a limit to the use of UHSS in industrial applications. Even though the hot-press-forming method can resolve the formability problem, elevated-temperature conditions lead to side effects—heat transfer and productivity issues. This work presents the concept of an infrared local-heat-assisted cold stamping process. Before the forming process, local areas, where the formability problem occurs, are locally heated by the gathering of infrared rays and cooled to room temperature before delivery. Since the heat treatment is completed by the material supplier, the stamping companies can conduct cold stamping without new investments or the productivity issue. In this work, a heat-assisted cold V-bending test was conducted with a martensitic (MS) 1.5 GPa steel, the CR1470M steel provided by POSCO. The heating effects on the microstructure, hardness, and local ductility were also observed. Finally, a commercial door impact beam was successfully manufactured with the present method. In this application, only a targeted small area was heated. The results show that the present method can improve the formability and springback problems of MS steel in the stamping process.

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Ji, Min Ki, Hyunsung Son, Jinkeun Oh, Seongwoo Kim, Kyungmok Kim, and Tea-Sung Jun. "Effects of Al-Si Coating Thickness on 22MnB5 in Hot Stamping Wear." Korean Journal of Metals and Materials 58, no. 8 (August 5, 2020): 573–82. http://dx.doi.org/10.3365/kjmm.2020.58.8.573.

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Al-Si coated ultra-high strength steels (UHSS) are widely used in automotive applications because of their high strength-to-weight ratio, corrosion protection and good weldability. The hot stamping (also called hot press forming) process is an effective and suitable technique for producing automotive parts from Al-Si coated UHSS. However, critical issues, such as the transfer of the coating materials and the build-up of these materials on the tool surface, have been encountered. These defects affect tool life and product quality. The wear behaviour of Al-Si coated 22MnB5 and Cr coated SKD11 tool was investigated using a high temperature friction test which mimicked the actual hot stamping environment. Two kinds of Al-Si coated 22MnB5 with ~19.6 (AlSi-A) and ~29.3 (AlSi-B) µm coating thicknesses were used in this study. After the friction test the coated layer of AlSi-A was found to be worn up to the diffusion layer, while for AlSi-B, the coating layer mostly remained after the friction test. Adhesive wear predominantly occurred on the tool surface in both cases, but the wear increased significantly in case of AlSi-B. This suggests that the coating thickness and the associated surface roughness are critical factors affecting wear behaviour.

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31

Chtourou, Rim, Fahmi Chaari, Gregory Haugou, Nicolas Leconte, Eric Markiewicz, and Bassem Zouari. "Experimental study of the mechanical strength and the failure of multi-sheet, multi-material spot-welded assemblies under pure and combined loading conditions." EPJ Web of Conferences 183 (2018): 02009. http://dx.doi.org/10.1051/epjconf/201818302009.

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Resistance Spot Welding (RSW) is widely used in the automotive industry thanks to its production convenience and cost effectiveness. Around four thousands spot welds are indeed employed to assemble the body-in-white. RSW of multiple sheets and combining multiple materials are increasingly realized. The Ultra-High-Strength Steels (UHSS) are particularly well suited for the entire range of structural parts requiring good crash resistance. However, the mechanical strength and the rupture of such new generation of RSW under multi-axial loadings is not yet well studied. The present work investigates the mechanical strength and the failure of a three-sheet spot welded assembly composed of two sheets of UHSS 22MnB5 and a third sheet of mild steel DX54D. An advanced experimental procedure is proposed for testing this assembly in pure and combined (tensile shear modes) modes I/II. Two types of specimen with different sheet thicknesses have been studied. The obtained results are analyzed to investigate the loading angle effect and the assembly configuration effect on the mechanical strength. Failure modes are also studied in relation with the increasing of the loading angle. Finally, the parameters of a macroscopic force-based failure criterion dedicated for FE crash modeling are identified.

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32

Lee, J. H., and S. H. Kim. "Automatic Tool Compensation for an UHSS Automotive Component Using a Compensation Module." Transactions of Materials Processing 25, no. 2 (April 1, 2016): 109–15. http://dx.doi.org/10.5228/kstp.25.2.109.

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33

Cheng, Pengzhi, Yulong Ge, Yong Xia, and Qing Zhou. "Numerical and Experimental Investigation on Tube Hot Gas Forming Process for UHSS." Journal of Physics: Conference Series 1063 (July 2018): 012172. http://dx.doi.org/10.1088/1742-6596/1063/1/012172.

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34

Ferrara, Joseph D., Yasukazu Nakaye, Yasutaka Sakuma, Satoshi Mikusu, and Takuto Sakumura. "UHSS – a hybrid photon-counting detector with a 50 kfps sustained data rate." Acta Crystallographica Section A Foundations and Advances 75, a1 (July 20, 2019): a74. http://dx.doi.org/10.1107/s0108767319099252.

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35

Abeyrathna, B., B. Rolfe, and M. Weiss. "A first step towards an in-line shape compensation for UHSS roll forming." IOP Conference Series: Materials Science and Engineering 651 (November 25, 2019): 012063. http://dx.doi.org/10.1088/1757-899x/651/1/012063.

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36

Choi, Hong-Seok, Sung-Gwi Kim, Pan-Ki Seo, Byung-Min Kim, Byung-Chul Cha, and Dae-Cheol Ko. "Experimental investigation on galling performance of tool steel in stamping of UHSS sheets." International Journal of Precision Engineering and Manufacturing 15, no. 6 (June 2014): 1101–7. http://dx.doi.org/10.1007/s12541-014-0443-5.

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37

Xu, Ya, Zi Jian Wang, and Yi Sheng Zhang. "Experimental Analysis of Hardness Distribution of the Transition Region in Tailored Tempering Stamping of Ultra-High Strength Steel." Advanced Materials Research 774-776 (September 2013): 1200–1203. http://dx.doi.org/10.4028/www.scientific.net/amr.774-776.1200.

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With hot forming parts of ultra-high strength steel (UHSS) widely used, requirements on matching the mechanical properties of parts with the performance on active service are attracting attention. Research shows that the preheat temperature of the molds set to 400°C or above can effectively reduce the hardness of the sheet and get a better region. The width of the air gap between tools is important influencing factor. Too large air gap will increase the difficulty of controlling the region of variable intensity and the position of ultimate strength.

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38

Dorożyński, J., J. Nowacki, and A. Sajek. "Impact Tests of UHSS Steel Welded Joints Using the Drop - Tower Impact Drop Method." Advances in Materials Science 19, no. 3 (September 1, 2019): 19–31. http://dx.doi.org/10.2478/adms-2019-0014.

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AbstractThe article characterizes the impact test method using Drop-Tower Impact Test with the registration of the value of force and energy of breaking. Based on sources, the possibilities and scope of the current application of this method were determined and the current state of knowledge on the results of these tests was reviewed. In order to determine the possibility of using the method in impact tests of high strength steel joints, investigations of hybrid PTA - GMA welding conditions on impact strength of joints of MART S1300QL steel were carried out. In particular, the influence of t8/5 cooling time on the impact strength of welded joints by the Drop - Tower Impact Test method was determined. It has been shown that the use of dropping machine with computer-based registration of breaking force and energy values was possible in the case of impact strength testing of UHSS welded joints and enabled precise analysis of the energy distribution dynamics absorbed by the tested.

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39

Liu, Hui Qiang, Yi Sheng Zhang, and Pei Xing Liu. "Process Optimization of 3D Optical Fiber Laser Cutting Robot for Press Hardening of UHSS." Advanced Materials Research 753-755 (August 2013): 2033–36. http://dx.doi.org/10.4028/www.scientific.net/amr.753-755.2033.

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The hot forming parts of high strength steel are difficult to cut with the presses and the traditional high-energy beam due to its high tensile strength which can be up to 1500Mpa and its complex structure. And the 3D laser cutting is an effective way to solve the problem. However some problems in the laser process affect the efficiency and quality seriously, including interference between the robot arms and the cutting head with the untrimmed parts, difficulty in determining the entry point and over burning etc. In this research three measures are taken to cut the anti-collision beam, including using photogrammetric technology to get its uncutted 3D model for offline programming to avoid interference, selecting appropriate entry point to trim without interrupt, amending normals and adjusting the process parameters at corners to prevent over burning. The results show that the efficiency and quality are improved and a creative new offline programming method is put forward.

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40

Xie, Hui, Wei Cheng, Hangyan Wang, Shan Fu, Wende Li, and Wei Xiong. "Multi-objective reliability-based optimization for cooling channel of a UHSS hot-stamping die." International Journal of Advanced Manufacturing Technology 97, no. 9-12 (May 24, 2018): 3237–49. http://dx.doi.org/10.1007/s00170-018-2065-z.

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41

Mimer, M., L. E. Svensson, and R. Johansson. "Process Adjustments to Improve Fracture Behaviour in Resistance Spot Welds of EHSS and UHSS." Welding in the World 48, no. 3-4 (March 2004): 14–18. http://dx.doi.org/10.1007/bf03266421.

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42

Kesti, Vili, A. Kaijalainen, A. Väisänen, A. Järvenpää, A. Määttä, A. M. Arola, K. Mäntyjärvi, and R. Ruoppa. "Bendability and Microstructure of Direct Quenched Optim^® 960QC." Materials Science Forum 783-786 (May 2014): 818–24. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.818.

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Use of ultra-high-strength steels (UHSS) in weight critical constructions is an effective way to save energy and minimize carbon footprint in the end use. On the other hand, the demands for reducing manufacturing costs and energy consumption of the steelmaker are increasing. This has led to development of energy efficient direct quenching (DQ) steelmaking process as an alternative to the conventional quenched and tempered or thermomechanical rolling and accelerate cooled processes. Ruukki has employed thermomechanical rolling and direct quenching process (TM + DQ) for a novel type of ultra-high-strength strip and plate steels since 2001. Advantages of the ultra-high-strength level (>900MPa) can be fully utilized only if fabricated properties are on a sufficient level. Bending is one of the most important workshop processes and a good bendability is essential for a structural steel. Hence, the metallurgy and bendability of Ruukki ́s TM + DQ strip steel Optim® 960QC have been investigated closely. It was found that by optimizing process parameters and chemical composition, a good combination of strength and ductility can be achieved by a modification of martensitic-bainitic microstructure. Despite of smaller total elongation, the bendability of Optim® 960QC is at least on the same level as on conventionally manufactured 960MPa steels. However, it is important to pay special attention to bending process (tool parameters, springback, bending force, material handling) when bending UHSS. It was also found that the bendability of Optim® 960QC can be significantly enhanced by local laser heat treatments or roll forming.

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43

Yu, Zhi Shui, Wan Peng Dong, Chun Wei Ma, Jiang Wei Ren, Bi Hao Li, and Yu Rong Ji. "Resistance Spot Weldability of Hot-Formed Ultra High Strength Steel Based on Virtual and Physical Experiment." Applied Mechanics and Materials 750 (April 2015): 244–50. http://dx.doi.org/10.4028/www.scientific.net/amm.750.244.

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In this study, virtual and physical experimental investigations were performed on the resistance spot weldability of hot-formed ultra high strength steels (UHSS). The sheets were joined by the resistance spot welding as lap or cross joint. The mechanical properties were assessed in terms of cross tension strength (CTS) and tensile shear strength (TSS). The micro structural profile and weld nugget diameter were also investigated. Both virtual and physical methods yielding results are in good agreement. The results are discussed in the light of earlier work published in the literature and contribute to a better understanding on the evaluation of resistance spot weldability.

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44

Schaffner, Tobias, Alexander Hartmaier, Michael Pohl, and Valentin Kokotin. "Prediction of the Hydrogen-Induced Damage to Ultra-High Strength Steel Concepts." Materials Science Forum 941 (December 2018): 124–29. http://dx.doi.org/10.4028/www.scientific.net/msf.941.124.

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The hydrogen-induced damage behavior of ultra-high strength steels (UHSS) has been predicted by a combination of experimental and numerical investigations. Firstly, the resistance against hydrogen-induced failure was examined by slow strain rate tests (SSRT) using various sample geometries and hydrogen contents. Secondly, the hydrogen distribution and loading conditions during the tensile test were calculated by means of the finite element method (FEM). Finally, a combination of various damage models was applied and validated by further SSRT. The main result of this study is a failure prediction model, which considers local stress and strain conditions, as well as hydrogen content.

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45

Kawata, Hiroyuki, Kunio Hayashi, Natsuko Sugiura, Naoki Yoshinaga, and Manabu Takahashi. "Effect of Martensite in Initial Structure on Bainite Transformation." Materials Science Forum 638-642 (January 2010): 3307–12. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.3307.

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Lath-shaped upper bainite structures play a very important role in many high-strength steels (HSSs) and ultra high-strength steels (UHSSs). Although bainite transformation is strongly affected by the initial structure, the effect of the second phase in a multi-phase structure is yet to be clearly understood. It is significant for the advancement of UHSS to study this effect. The aim of this study is to clarify the effect of martensite, which forms before bainite, in Fe-0.2C-8Ni alloy. The bainite transformation from an austenite and martensite dual-phase structure is faster than that from single-phase austenite and the nucleation of bainitic ferrite laths are accelerated around martensite. This effect of martensite on bainite kinetics is equivalent to that of polygonal ferrite when their volume fractions are almost the same. This suggests that the boundary between martensite and austenite is a prior nucleation site of bainitic ferrite. Martensite also affects the crystallographic features of bainite. The orientations of bainitic ferrite laths tend to belong to the same block with martensite adjacent. This tendency intensifies with an increase of the transformation temperature of bainite, resulting in the formation of huge blocks consisting of bainitic ferrite and martensite laths at high temperatures (693K and 723K). In contrast, at a low temperature (643K), bainitic ferrite laths belong to same packet as martensite and have several orientations. This change of crystallographic features with transformation temperature can explain with the driving force of the nucleation of bainitic ferrite.

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46

Bang, Junho, Namsu Park, Junghan Song, Hong-Gee Kim, Gihyun Bae, and Myoung-Gyu Lee. "Tool Wear Prediction in the Forming of Automotive DP980 Steel Sheet Using Statistical Sensitivity Analysis and Accelerated U-Bending Based Wear Test." Metals 11, no. 2 (February 10, 2021): 306. http://dx.doi.org/10.3390/met11020306.

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The forming process of ultra-high-strength steel (UHSS) may cause premature damage to the tool surface due to the high forming pressure. The damage to and wear of the tool surface increase maintenance costs and deteriorate the surface quality of the sheet products. Hence, a reliable prediction model for tool wear can help in the efficient management of the quality and productivity of formed sheet products of UHSS. In this study, a methodology is proposed for predicting the wear behavior of stamping tools that are used in the forming process of DP980 steel sheet. Pin-on-disk tests were conducted based on the Taguchi method to develop the tool wear prediction model. Using statistical analysis based on the signal-to-noise (S/N) ratio and ANOVA result, the contact pressure and the sliding distance were selected as the major contact parameters for tool wear. The Archard wear model has a limitation in predicting the nonlinear behavior of tool wear. Therefore, the power-law nonlinear regression model as a function of the contact pressure and the sliding distance was constructed. To verify the reliability of the constructed tool wear prediction model, the U-draw bending tests were designed. The modified U-draw bending test, which accelerates tool wear, is newly designed to evaluate the tool wear for different contact pressures and sliding distances. The modified die generated a contact pressure four times higher than that of the conventional die from the finite element (FE) simulation results. The tool wear prediction model was validated by comparing the predicted results with the experimental results of DP980 sheets formed using the physical vapor deposition (PVD) CrN-coated STD11 tool steel.

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47

Zhang, Jing Guo, Guang Min Luo, Xiao Jun Li, Jun Wang, Biao Yan, Yi Jian Lin, Hai Sheng Shi, and Hao Zhang. "Recent New Development of Spray Formed Ultrahigh-Carbon Steels." Materials Science Forum 475-479 (January 2005): 2779–84. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.2779.

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The recent investigations on spray formed ultrahigh-carbon steels (UHCSs) are reviewed. A satisfactory combination of strength and ductility in spray formed UHCSs can be obtained by hot rolling and annealing. The composition and hot rolling have a marked effect on the formation of graphite in UHCSs. The possibility of achieving high strain rate superplasticity in the spray formed UHCS was first revealed by very recent investigations in Shanghai Baosteel Research Institute. The UHCS processed by a combination of spray forming and hot rolling exhibited high strain rate superplasticity.

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48

Gui, Zhong Xiang, Yi Sheng Zhang, Hong Qing Li, and Ming Tu Ma. "Hot Stamping and Blank Designing for a Vehicle Bumper Using Ultra High Strength Steel (UHSS)." Advanced Materials Research 690-693 (May 2013): 2240–44. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.2240.

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Full-scaled hot stamping dies were designed for a vehicle bumper, based on evaluation of cooling system by FE simulation and the temperature variation assessment by analytical model. The blank shape was gained using inverse algorithm and well-designed according to production practice. Experiments were conducted to verify the reliability of both the die and blank design, as well as tests for microstructure and mechanical properties of the hot-stamped part. Results show that, CAE analysis provides a robust support for hot stamping die and blank design; Position stability of hot blank is greatly improved during robotic transport process after shape designing; Metallographic analysis demonstrates the hot-stamped bumper obtained a fully martensitic microstructure, its tensile strength is about 1550 MPa, microhardness is 47.5 HRC, and the elongation is up to 6%.

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49

Pelcastre, Leonardo, Jens Hardell, and Braham Prakash. "Tribological behaviour of Zn coated UHSS sliding against hot-work tool steel at high temperatures." Wear 376-377 (April 2017): 423–32. http://dx.doi.org/10.1016/j.wear.2016.10.029.

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50

Liu, Xiao-li, Jian-guo Cao, Su-xia Huang, Bin Yan, Yan-lin Li, and Rong-guo Zhao. "Experimental and numerical prediction and comprehensive compensation of springback in cold roll forming of UHSS." International Journal of Advanced Manufacturing Technology 111, no. 3-4 (October 2, 2020): 657–71. http://dx.doi.org/10.1007/s00170-020-06133-9.

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Journal articles on the topic 'UHSS'

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