Page 57 - MetalForming May 2012

70 60 50 40 30 20 10
0
0 200
500 800
Tensile Strength (MPa)
2
1
HF
3
1100 1400 1700
Fig. 2—Segments of the Fig. 1 curve can be used to describe hot forming and other steel processes. Courtesy of WorldAutoSteel.
The banana curves also provide a better understanding of processing changes to achieve forming and end-product benefits (Fig. 2). The gray ellipses define the AHSS. The numbered ellipses define the hot forming of boron-based steels. This processing provides exceptional stretchability to generate complex shapes with high final tensile strengths. The typical as-received tensile strength (1) is 400 MPa (58 Ksi). The blank is heated to 850 C (2) and formed with a tensile strength of 100 MPa (15 ksi) and a total elongation of 50 to 60 percent. The formed part is quenched in the die (3) to form marten- site with an approximate 1550-MPa (225 ksi) tensile strength.
Stainless steel has been called the “formable high-strength steel.” This reference applies almost exclusively to the 3xx- series of stainless steels. Properties and other stainless-steel information can be found at www.ssina.com. One important
document, under the category of information handbooks, is Design Guidelines for the Selection and Use of Stainless Steel.
An excellent website for information on automotive steels is that of the Auto/Steel Partnership—www.a-sp.org. This organization brings together the Detroit Big 3 automakers and six major North American steel companies to conduct auto- motive research and provide useful technical information for the automotive industry and its suppliers. The AHSS case studies published in the WorldAutoSteel AHSS Application Guidelines were conducted by the Auto/Steel Partnership, and are downloadable from the website. In all, the website contains more than 100 useful documents, including the Automotive Steel Design Manual and Material Uniformity.
Lastly, seminars continue to provide timely updates on the capabilities of new steels, and seminar papers often can be accessed online free of charge. The seminar most focused on automotive steels is Great Designs in Steel, held each year in mid-May in Detroit by the American Iron and Steel Institute’s Steel Market Development Institute. All of the papers pre- sented during the 2003-2011 seminars are available at www.autosteel.org. MF
On July18-19 in Grand Rapids, MI, Stuart Keeler will pres- ent a double seminar covering Sheetmetal 101—Under- standing the Metal, and Forming Sheetmetal—Understand- ing the Properties. Learn more at www.pma.org.
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Total Elongation (%)