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Yonemura S.,Kimitsu R and D Laboratory | Uenishi A.,Steel Research Laboratories | Kosugi S.,Mathematical Science and Technology Research Laboratory | Yoshida T.,A-D Technologies | And 2 more authors.
Nippon Steel Technical Report | Year: 2013

Bake-hardenable steel sheets are often used in exterior automotive body panels, such as doors, hoods, and fenders, because these applications require high strength for dent resistance as well as low yield strength for surface deflection. The dent resistance depends on the yield strength of materials after work hardening by forming and strain ageing by paint baking. In this study, the anisotropy of yield strength has been investigated in a uniaxially prestrained and baked bakehardenable steel. On the other hand, surface deflection is investigated by press forming experiments and their numerical simulations of the exterior door panel model. Emphasis is placed on the effects of mechanical properties and press forming condition on surface deflection are discussed. Furthermore, a new system for evaluation and visualization of surface deflection using Gaussian curvature is presented.


Hirose S.,A-D Technologies | Yonemura S.,Kimitsu R and D Laboratory | Uenishi A.,Steel Research Laboratories | Hiwatashi S.,Nagoya R and D Laboratory
Nippon Steel Technical Report | Year: 2013

The accuracy of crash analysis is important for design of car body with crashworthiness and depends on some properties of applied material. Strain rate dependency of flow stress and bake hardenability caused by painting process of car body are of particular significance to crash analysis. Here, developed technologies for evaluation of their properties were introduced.


Fujita N.,Quality Management Div. | Matsumura K.-I.,Hirohata R and D Laboratory | Tomokiyo T.,Yawata Steel Works | Kusumi K.,Steel Research Laboratories | Nonaka T.,Nagoya R and D Laboratory
Nippon Steel Technical Report | Year: 2013

Application of ultra-high strength steel sheets is one of the most important methods to satisfy weight reduction and crash safety of a vehicle. Recently, there is a trend to apply ultra-high strength steel sheets widely to auto-body parts. In this report, present situation of ultra-high strength steel sheets, especially with tensile strength more than 980MPa and 1,470MPa by hot-stamping, have been introduced.


Uenishi A.,Steel Research Laboratories | Hirose S.,A-D Technologies | Hiwatashi S.,Nagoya R and D Laboratory | Ito Y.,Quality Management Div. | And 4 more authors.
Nippon Steel Technical Report | Year: 2013

The application of high strength steels to car body structure has been accelerated for improved crashworthiness and light weight body. In order to use effectively diversified materials, the importance of numerical simulation and experimental techniques for crash properties of parts and structures has been increased. Here, an overview of a comprehensive approach for materials and structure optimization is presented, by introducing developed technologies for energy absorbing property evaluation and failure behaviour prediction.


Kusumi K.,Steel Research Laboratories | Maki J.,Yawata Steel Works | Nomura N.,A-D Technologies
Nippon Steel Technical Report | Year: 2013

Production of parts by means of hot stamping process has increased. Applications of hot stamping contribute to the weight reduction of automobiles by the production of parts with both high strength and excellent shape fixability. In this report, basic formability and FEM analysis of hot stamping were presented. In addition, the corrosion resistance of hot stamped aluminized steels was discussed.


Suwa Y.,Steel Research Laboratories
Nippon Steel Technical Report | Year: 2013

Grain growth occurring in the steel manufacturing process is one of the most important phenomena in order to control the polycrystalline microstructure. Due to its heavy computational cost, phase-field(PF) simulations were limited to 2D systems. Recently, 3D PF simulation of grain growth is becoming practical owing to the development of efficient simulation algorithms and the application of parallel computation techniques. In this manuscript, we will report simulation results for the normal grain growth and the system containing finely dispersed second-phase particles. Especially, this manuscript highlights the difference between the 2D and 3D simulation results.


Azuma M.,Steel Research Laboratories | Takahashi M.,Steel Research Laboratories | Fujita N.,Steel Research Laboratories
Nippon Steel Technical Report | Year: 2013

Microstructure development of advanced high strength steels is quiet complicated and, thereby, it takes much time to develop advanced high strength steels. This paper presents a complete model which can simulate microstructure development of high strength steels during a heat treatment and the mechanical properties after the treatment. The model consisting of ferrite, bainite, martensite and predicting stressstrain curve of the steels is successively built based on metallurgical phenomena.


Wakisaka T.,Steel Research Laboratories | Kurosaki Y.,Steel Research Laboratories | Arai S.,Steel Research Laboratories
Nippon Steel Technical Report | Year: 2013

15 years have passed since the first commercial hybrid electric vehicle (HEV) was sold. Meanwhile, the market has been expanding and the type of HEV/EV has been increasing, and then demands to electrical steel sheet for traction motor cores of HEV/EV has become diversified. In this paper, the demands to electrical steel sheet for traction motor cores of HEV/EV are reconfirmed, and then newly developed electrical steel sheet and the application techniques of electrical steel sheet are informed.


Takata K.,Steel Research Laboratories
Nippon Steel Technical Report | Year: 2013

This study examines the application of warm forming of aluminum alloys for automotive panels. Warm forming improved not only the deep-drawing formability of aluminum alloys but also their shape fixability in hat-shaped bending. With increasing BHF, the shape fixability improved further and was comparable to that of steel. Although Molybdenum disulfide have been used in warm forming so far, oil for the exclusive use of this forming is developed. The amount of dynamic recovery reduces with increasing forming rate. A coupled thermo-mechanical finite-element analysis is an efficient method that can be used for forming simulation.


Fujii H.,Steel Research Laboratories | Saga M.,Steel Research Laboratories
Nippon Steel Technical Report | Year: 2012

Capitalizing on its technological assets in the field of iron and steel, Nippon Steel Corporation has also been contributing to progress in nonferrous structural materials technology. Today the company is among the leading manufacturers of various titanium products, mainly pure titanium sheet for industrial use. Needless to say, the titanium refining and re-melting processes are markedly different from those for steel. Therefore, the company purchases ingots or slabs of titanium from outside and makes them into final titanium products mainly employing its steelmaking facilities, but partly using equipment exclusive to titanium production, in the hot rolling process and succeeding processes. In the field of automobiles, the use of rolled or extruded aluminum materials for car bodies and undercarriages is especially noticeable. The application of aluminum in this particular field has been steadily increasing.

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