Incremental Bending of Ultra-High-Strength Steels

2011 ◽  
Vol 473 ◽  
pp. 53-60 ◽  
Author(s):  
Antti Määttä ◽  
Kari Mäntyjärvi ◽  
Jussi A. Karjalainen
Keyword(s):  
Automotive Industry ◽  
Rolling Direction ◽  
High Strength Steels ◽  
High Strength ◽  
Roll Forming ◽  
Complex Phase ◽  
Bending Angle ◽  
Bending Radius ◽  
Ultra High Strength Steels ◽  
Traditional Manner

Utilisation of ultra-high-strength steels (UHS) has increased, particularly in the automotive industry. By using these materials vehicle structures can be lightened. However, one of the problems of UHS is weak formability. Materials fracture easily with small bending radii and the minimum bending radii are rather large. In this study, the tested materials were complex phase (CP) bainitic-martensitic UHS steels (YS/TS 960/1000 and 1100/1250). The steels were incrementally bent with a press brake in the rolling direction and perpendicular to it, and the final bending angle was 90 degrees. The incremental bending angles were 150°, 130°, 110° and 90°. The punch was unloaded after every incremental bending step. The test materials were bent with different bending radii. The aim was to find the minimum bending radius which produces an acceptable bend. Every incremental bend was compared with a bending performed in the traditional manner. The aim of this study was to examine how well the results of incremental bending compare to roll forming. In addition, clarification studies of when the bend started to fracture were made. It is well known that steels are more efficiently bent by roll forming compared with traditional bending. The results presented in this study demonstrate that incremental bending does not produce better results than traditional bending. Nevertheless, it has been shown that the examined steels can be bent incrementally against manufacturer’s recommendations.

Texture analysis and joint performance of laser-welded similar and dissimilar dual-phase and complex-phase ultra-high-strength steels

2021 ◽  
Vol 174 ◽  
pp. 111035
Author(s):  
Ajit Kumar Pramanick ◽  
Hrishikesh Das ◽  
Ji-Woo Lee ◽  
Yeyoung Jung ◽  
Hoon-Hwe Cho ◽  
...  
Keyword(s):  
Texture Analysis ◽  
High Strength Steels ◽  
High Strength ◽  
Dual Phase ◽  
Complex Phase ◽  
Joint Performance ◽  
Ultra High Strength Steels

Influence of Predetermined Surface Defect to the Bendability of Ultra-High-Strength Steel

2012 ◽  
Vol 504-506 ◽  
pp. 901-906 ◽  
Author(s):  
Antti Määttä ◽  
Antti Järvenpää ◽  
Matias Jaskari ◽  
Kari Mäntyjärvi ◽  
Jussi A. Karjalainen
Keyword(s):  
Surface Defects ◽  
High Strength Steels ◽  
Steel Structures ◽  
High Strength ◽  
Crack Size ◽  
Critical Crack ◽  
Bending Radius ◽  
Ultra High Strength Steels ◽  
Materials Used ◽  
Critical Crack Size

The use of ultra-high-strength steels (UHS) has become more and more popular within last decade. Higher strength levels provide lighter and more robust steel structures, but UHS-steels are also more sensitive to surface defects (e.g. scratches). Practically this means that the critical crack size decreases when the strength increases. The aim of the study was to study if the formula of critical crack size is valid on forming processes of UHS-steels. Surface cracks with different depths were created by scratching the surface of the sheet by machining center. Effect of the scratch depth was determined by bending the specimens to 90 degrees. Bents were then visually compared and classified by the minimum achieved bending radius. Test materials used were direct quenched (DQ) bainitic-martensitic UHS steels (YS/TS 960/1000 and 1100/1250). Results from the bending tests were compared to the calculated values given by the formula of critical crack size.

Electrically assisted bake hardening of complex phase ultra-high strength steels

2016 ◽  
Vol 17 (2) ◽  
pp. 225-231 ◽  
Author(s):  
Nguyen Trung Thien ◽  
Sung-Tae Hong ◽  
Moon-Jo Kim ◽  
Heung Nam Han ◽  
Dae-Ho Yang ◽  
...  
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Bake Hardening ◽  
Complex Phase ◽  
Electrically Assisted ◽  
Ultra High Strength Steels

scholarly journals EFFECT OF SPRINGBACK IN DP980 ADVANCED HIGH STRENGTH STEEL ON PRODUCT PRECISION IN BENDING PROCESS

2019 ◽  
Vol 25 (3) ◽  
pp. 150
Author(s):  
Hung Thai Le ◽  
Dinh Thi Vu ◽  
Phuong Thi Doan ◽  
Kien Trung Le
Keyword(s):  
Elastic Recovery ◽  
Rolling Direction ◽  
Experimental Studies ◽  
High Strength Steels ◽  
High Strength ◽  
Bending Angle ◽  
Advanced High Strength Steels ◽  
Fem Method ◽  
Bending Process ◽  
The Hill

Springback is a common phenomenon in sheet metal forming, in which the material undergoes an elastic recovery as applied loads are removed. Springback causes the forming shape to deviate from the intended design geometry. This phenomenon, which can be influenced by several factors, effects on both bending angle and bending curvature. The aim of this study is to determine the influence of different tool radius and the gap between punch and die on springback in bending of DP980 Advanced High-Strength Steels (AHSS) sheet. Experimental studies are combined with FEM method in commercial ABAQUS software to determine the bending angle after springback. To predict springback in bending process, the material properties are defined by Ludwik - Hollomon law, combined with the Hill’48 criterion. Experimental results are in good agreement with numerical simulations in case of bending in the rolling direction.

State of the Art: Prototyping of the Roll Bending Machine

2013 ◽  
Vol 549 ◽  
pp. 76-83
Author(s):  
Jarmo Mäkikangas ◽  
Kari Kutuniva ◽  
Kari Mäntyjärvi
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Roll Forming ◽  
Modular Construction ◽  
Forming Process ◽  
Roll Bending ◽  
Short Run ◽  
New Type ◽  
Ultra High Strength Steels ◽  
Functional Components

This paper focuses on the development of a new type of roll bending machine. Our primary aim was to build a machine that could form ultra-high-strength steels (UHS) with smaller inner radii than those achieved by traditional bending methods. One of the main planning principles was modular construction, so a length of a bending line could be easily selected or changed later by the user without major changes to the basic construction of the machine. In contrast, in traditional roll forming, the blank does not move during the forming process, so the accuracy of the profile can be better controlled. Different kinds of cut to size-open profiles can be produced by this machine, which utilizes and combines bending and rolling techniques. In the initial stages of the project, the needs of smaller companies that do short-run productions are taken into account. First, the prototype is designed mainly for research use; moreover, it is important that the properties of the machine are multifunctional. In addition, forming can be done in several ways by this machine. In this paper, there is shown creation of a machine, designing of construction and manufacturing steps of the whole machine including assembling. Also detailed description of the various functional components and the operating principle is presented. The results of the forming tests are also presented.

Bendability and Microstructure of Direct Quenched Optim® 960QC

2014 ◽  
Vol 783-786 ◽  
pp. 818-824 ◽  
Author(s):  
Vili Kesti ◽  
A. Kaijalainen ◽  
A. Väisänen ◽  
A. Järvenpää ◽  
A. Määttä ◽  
...  
Keyword(s):  
Material Handling ◽  
High Strength Steels ◽  
High Strength ◽  
Total Elongation ◽  
Roll Forming ◽  
Direct Quenching ◽  
Thermomechanical Rolling ◽  
Ultra High Strength Steels ◽  
End Use ◽  
Save Energy

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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