Comparison of Material Behavior and Economic Effects of Cold and High Temperature Forming Technologies Applied to High-Strength Steels

2005 ◽  
Vol 6-8 ◽  
pp. 101-108 ◽  
Author(s):  
Reimund Neugebauer ◽  
Angela Göschel ◽  
Andreas Sterzing ◽  
Petr Kurka ◽  
Michael Seifert
Keyword(s):  
Elevated Temperatures ◽  
High Strength Steels ◽  
Dimensional Accuracy ◽  
High Strength ◽  
Economic Effects ◽  
Material Behavior ◽  
Spring Back ◽  
Forming Process ◽  
Cold Forming ◽  
Forming Tools

The focus of forming high-strength steel at elevated temperature is to improve its forming properties like elongation and to reduce the power requirements during the forming process in opposite to cold forming. Because of the undefined and large spring-back effects parts made by cold forming are not able to achieve the demanded dimensional accuracy, which is necessary for laser welding operations in car body assembly. The reduction of the spring-back behavior is another advantage of the temperature controlled forming technology. On the other side the forming at elevated temperatures requires increased costs for forming tools and tempering equipment. For a fundamental evaluation of this technology, expenditures for the complete process chain have to be considered.

Numerical and experimental analysis on cold-forming and spring-back of hull plate

2018 ◽  
Vol 233 (3) ◽  
pp. 561-569 ◽  
Author(s):  
Wei Shen ◽  
Renjun Yan ◽  
Shuangying Li
Keyword(s):  
Three Dimensional ◽  
Dimensional Accuracy ◽  
Ship Hull ◽  
Laser Forming ◽  
Successive Approximation Method ◽  
Spring Back ◽  
Forming Process ◽  
Cold Forming ◽  
Thick Plates ◽  
Forming Mechanism

Ship hull structures are fabricated by curved thick plates before they are welded together. There are traditional methods such as, line heating and laser-forming methods for plate bending. However, it is recognized that the hot-forming technology causes a series of troubles on doubly or multiple curved plates. Multi-point forming mechanism with square press heads is a new forming process for three-dimensional ship hull plate. Cold-forming has a high dimensional accuracy but results in spring-back. The spring-back process of curved thick plates in the finite element method is analyzed and the predicted results are compared with the test results in the present paper. To ensure the forming precision, the successive approximation method is also developed and verified to control the spring-back.

Investigation of EN AW 5754 Aluminum Alloy’s Formability at Elevated Temperatures

2017 ◽  
Vol 885 ◽  
pp. 98-103 ◽  
Author(s):  
Dávid Budai ◽  
Miklós Tisza ◽  
Péter Zoltán Kovács
Keyword(s):  
Elevated Temperatures ◽  
High Strength Steels ◽  
High Strength ◽  
Carbon Composite ◽  
Alloy Sheet ◽  
High Mass ◽  
Mass Reduction ◽  
Forming Process ◽  
Forming Temperature ◽  
Operating Distance

Nowadays, mass reduction is the most often used term in the automotive industry. Car manufacturers are continuously working on getting ever lighter models than the previous ones, because of the global competition and the rigorous emission rules. A light car has many advantages: lower consumption, better handling, longer operating distance, etc. The emission rules forced the car brands to start new researches to find new solutions for mass reduction. The formula is relatively simple, using lighter or less materials or both and the car will be lighter. In the recent solutions there are three different ways: application of high strength steels, aluminum alloys, and carbon-composite elements. Our investigations are focusing mainly on aluminum, because of its high mass reduction potential. The biggest problem with the aluminum is its low formability. The formability of aluminum is lower than the steel, and it causes problems for the manufacturers. To increase the formability of the aluminum is a hot topic in the research and development area. Forming at elevated temperatures is one of the best solutions to increase the formability of aluminum. The relation between the formability and the forming temperature is not linear, furthermore beyond the optimum forming temperature the formability decreases. We need dozens of investigations to describe the perfect relation, but sometimes a good approximation is enough to form sheet products safely. In our work we investigated the EN AW 5754 aluminum alloy sheet at room temperature, 130°C, 200°C and 260°C. From these tests we could obtain FLC curves of the alloy at different temperatures. Using these curves, the process engineers could find the optimum parameters of their forming process.

Consideration of Elastic Tool Deformation in Numerical Simulation of Hydroforming with Granular Material Used as a Medium

2011 ◽  
Vol 473 ◽  
pp. 707-714 ◽  
Author(s):  
Martin Grüner ◽  
Marion Merklein
Keyword(s):  
Numerical Simulation ◽  
Granular Material ◽  
Elevated Temperatures ◽  
High Strength Steels ◽  
High Strength ◽  
Appropriate Technology ◽  
The Body ◽  
Warm Forming ◽  
Forming Process ◽  
Blank Holder

The use of high and ultra high strength steels in modern bodies in white raises steadily since the 1980’s. This trend is caused by the consumers’ wish of low fuel consuming cars with an increased passenger’s safety. The processing of these steels brings new challenges e.g. high flow stresses and a low formability at room temperature or high tool loads. These challenges can be resolved by warm forming at temperatures up to 600 °C reducing the flow stresses and increasing formability. For the production of complex parts that can not be produced by deep drawing hydroforming is an appropriate technology which can also help to reduce the number of parts and thus the weight of the body in white. Nowadays typical fluids used for hydroforming are only temperature stable up to about 330 °C so that it is not possible to combine the benefits of warm forming and hydroforming. Media like gases and fluids tend to leakage during the process which can only be avoided by a sealing or high blank holder forces. A new approach is the use of ceramic beads as medium for hydroforming at elevated temperatures. Building up a heatable tool for hydroforming with granular material used as medium makes it necessary to consider thermal conductivity so that there is a need of thick insulation plates. These insulation plates show high elastic deformations affecting the blank holder forces during the forming process. Measurements of the compressibility of these plates and implementation in numerical simulation allow a significant increase of the prediction accuracy of the model. A comparison of real part geometry and numerical results from models with and without consideration of elastic deformation will be given.

Effect of Heating Parameters on the Part’s Properties in Hot Stamping Process

2012 ◽  
Vol 557-559 ◽  
pp. 2417-2422
Author(s):  
Rui Ge ◽  
An Long ◽  
Yin Chen
Keyword(s):  
Hot Stamping ◽  
High Strength Steels ◽  
Dimensional Accuracy ◽  
High Strength ◽  
Hardness Measurement ◽  
Material Behavior ◽  
Hot Forming ◽  
Accuracy Test ◽  
Stamping Process ◽  
Proper Design

In the automotive industry, the hot forming of high strength steels offers the possibility to obtain significant reduction of weight without affecting the structural performances of final products. Compared with conventional sheet metal forming, the proper design of hot stamping process chain requires the deep knowledge of both interface phenomena and material behavior at high temperatures in order to obtain the desired properties of final products in terms of microstructure and strength characteristics. The work presented in this paper aims at accurately evaluate the effect of heating parameters on the properties of final sheet components produced in hot forming operations. Different from that in the lab, all the samples and parts used for the experimental test were produced in the production line, which can objectively show the manufacturing properties and microstructure character of products in mass. Microstructure evaluation, hardness measurement and dimensional accuracy test after hot stamping were performed and considered. The best heating parameters for the researched hot stamping B-Pillar’s production were obtained through the above research.

scholarly journals Punch Stretch Test for TRIP690 and DP780 Steel at Elevated Temperatures

2016 ◽  
Vol 854 ◽  
pp. 118-123
Author(s):  
Robert Krupa
Keyword(s):  
Elevated Temperatures ◽  
New Technology ◽  
Temper Embrittlement ◽  
High Strength Steels ◽  
High Strength ◽  
Phase Changes ◽  
Warm Forming ◽  
Forming Process ◽  
Contact Heat ◽  
Sheet Formability

The forming at elevated temperatures for Advanced High Strength Steels (AHSS) opens up a new technology. The phase changes during warm deformation are the key to understanding the warm forming process. The desired microstructure and mechanical properties before and after warm forming have to be known in order to find optimal conditions for achieving good sheet formability and preferred material properties in service. In this work, the TRIP690 and DP780 steels are investigated under punch stretch test conditions in order to evaluate the temperature influence on neck formation and fracture occurrence at ambient and elevated temperatures 200oC, 400oC. Contact heat treatment was used for heating up the circular specimens. It was found that formability of the investigated steels was drastically reduced at a temperature of 400oC and brittle fracture occurred because of temper embrittlement. It is recommended to avoid steel tempering at this critical temperature.

Dimensional Deviation of Roll Formed Components Made of High Strength Steel

2007 ◽  
Vol 344 ◽  
pp. 285-292 ◽  
Author(s):  
Peter Groche ◽  
Michael Henkelmann
Keyword(s):  
Quality Control ◽  
Wide Spectrum ◽  
Control Process ◽  
High Strength Steels ◽  
Dimensional Accuracy ◽  
High Strength ◽  
Roll Forming ◽  
Forming Process ◽  
Forming Technology ◽  
Quality Control Process

During the last half century roll forming has become a highly productive metal forming technology, well-established in the industry for the manufacturing of mass products. About 8 % of the annual world production of steel is processed by roll forming mills. Roll forming technology enables the manufacturing of profile-shaped products with an extremely wide spectrum of geometrical shapes. In lightweight construction, the utilization of roll-formed structures of high and ultra-high-strength steels has increased remarkably in the recent years. However, the application of those types of steel entails some disadvantages resulting in a decreasing forming capacity and enormous efforts to reach the required dimensional accuracy. Until a profile leaves the roll forming machine with the target quality, it is mostly necessary to align the forming rolls several times. Sometimes even design changes are required. This is the result of unreliable process planning. Furthermore, typical profile failures such as twist, flare and spring-back occur even stronger compared to mild steels. Nowadays, it is usual to control the dimensional accuracy of the profiles after the last forming stand. This kind of quality control has the following disadvantage: manufacturing errors are detected very late. Therefore, a continuous quality control process and an active manipulation during the forming process promise a large potential for an improvement of the dimensional accuracy and an increase of roll forming productivity.

scholarly journals EXPERIMENTAL INVESTIGATION OF SPRINGBACK OF LOCALLY HEATED ADVANCED-HIGH STRENGTH STEELS

2021 ◽  
Vol 9 (3) ◽  
pp. 269-277
Author(s):  
Omer Eyercioglu ◽  
Sevket Alacaci ◽  
Mehmet Aladag
Keyword(s):  
Heating Temperature ◽  
Local Heating ◽  
High Strength Steels ◽  
High Strength ◽  
Hot Forming ◽  
Spring Back ◽  
Cold Forming ◽  
Advanced High Strength Steels ◽  
Forming Temperature ◽  
Bending Loads

Sheet metal bending is one of the important metals forming processes at ambient temperature. The usage of high-strength steel is one of the stronger materials for the construction of components in the automotive industries. However, for complex shapes, cold forming is not always sufficient, and heating the workpiece plays a major role in manufacturing these shapes. Bendability may increase with increasing forming temperature and currently, hot forming of advanced high strength steels (AHSS) is becoming more attractive. While hot forming of AHSS is beneficial for high formability, subsequent quenching is required to maintain final strength. This procedure extends the production time. In this study, temperature gradients, bending loads, and springback after V-bending were investigated. The experimental study was carried out on a 2 mm thick Docol 1500M steel at various temperatures by using a speed-controlled servo press machine. The bending regions of the specimens were locally heated to 200, 300, 400, 500, and 600oC by using a high-frequency induction heating device. The results show that; punch loads were significantly lowered with increasing the local heating temperature during bending. There were no cracks observed on the specimens. The amount of spring back is decreasing with the bending temperature and around 500oC almost no springback was measured. Negative spring back was observed for the bending temperatures higher than 500oC

Methods to Decrease Cut Edge Sensitivity of High Strength Steels

2014 ◽  
Vol 611-612 ◽  
pp. 1294-1307 ◽  
Author(s):  
Thorsten Gläsner ◽  
Christina Sunderkötter ◽  
Armin Plath ◽  
Wolfram Volk ◽  
Hartmut Hoffmann ◽  
...  
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Cutting Process ◽  
Forming Process ◽  
Cold Forming ◽  
Cut Edge ◽  
Cutting Surface ◽  
Edge Sensitivity ◽  
Two Stages ◽  
Edge Cracking

The edge cracking sensitivity of AHSS and UHSS is quite challenging in the cold forming process. Expanding cut holes during flanging operations is rather common in automotive components. During these flanging operations the pierced hole is stretched that its diameter is increased. These flanging operations stretch material that has already been subjected to large amounts of plastic deformation, therefore forming problems may occur. An innovative cutting process decreases micro cracks in the cutting surface and facilitates the subsequent cold forming process. That cutting process consists of two stages, which produces close dimensional tolerance and smooth edges. As a result the hole expanding ratio was increased by nearly 100% when using thick high strength steels for suspension components

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