Page 20 - MetalForming April 2009

Forming Higher-Strength
Steels
Higher-strength steels perform differently during forming than other grades. Find out how and why, and how to prepare tooling to meet these forming challenges.
BY STUART KEELER and PETE ULINTZ
Forming higher-strength steel pres- progressive-die stations, and other die The die can only respond to certain
ents the same problems as forming
low-strength steel, except the prob- lems are magnified and too often become disastrous. From the steel per- spective, insufficient information about the higher-strength steels only makes these problems worse.
The following scenario occurs all too commonly in a die-build facility. A purchase order arrives with the part design, the allowed number of dies or
Industry experts Stuart Keeler and Pete Ulintz author monthly columns in Metal- Forming magazine and conduct seminars for the Precision Metalforming Association. Keeler, an expert in steel-forming and material technology, is president of Keeler Technologies LLC, a consulting firm in Grosse Ile, MI; e-mail keeltech@comcast.net. Ulintz is advanced product engineering manager for Anchor Mfg. Group, Cleve- land, OH, and has extensive experience in tool design and build. His e-mail: pete.ulintz@toolingbydesign.com.
specifications. First, the die-build shop completes the process design, which allocates the type and amount of defor- mation for each die. Next comes die design and construction. Finally, the time arrives for die tryout. What about the steel? Oh, the trial coil has arrived from the customer and sits over in the corner. Tryout begins. The first piece splits in multiple locations with the stamping completely out of dimen- sional tolerance. What do you know about the coil of steel? Trade names, ASTM numbers, steel-mill process codes or internal customer identifica- tion systems provide little, if any, useful information.
mechanical properties. For a complete evaluation, these properties include elastic modulus, yield strength, work- hardening exponent (n), anisotropy (r) and total elongation. One does not require all of these properties for every stamping. However, availability of the necessary properties throughout part design to production cycle provides critical information, creating up-front compensation before process and die designs even begin. Acquiring this infor- mation minimizes tryout and produc- tion problems. For dies already in pro- duction, knowing the mechanical properties of the current steel and the proposed higher-strength steel upgrade
Stuart Keeler and Pete Ulintz will be presenting information related to forming higher-strength steel at the Precision Metalforming Association (PMA) Technical Conference, April 26-29, at the Holiday Inn Hotel Cleveland South, Independence, OH.
For more information, visit www.pma.org/annual-tech-conference, or contact PMA’s Deanna Nwosu at 216/901-8800 ext. 162, or dnwosu@pma.org.
18 METALFORMING / APRIL 2009
www.metalformingmagazine.com