Page 30 - MetalForming May 2011

Advanced High Strength Steels
resulting in additional energy and heat. This increase in heat can reduce lubricant viscosity and even cause lubricant breakdown.
Press Tonnage and Energy
An obvious concern when stamping AHSS is the force capacity of the stamping press. Less obvious, but of pri- mary concern, is the available press energy to carry out the stamping operation and keep the press running continuously. Press tonnage and press energy are not the same.
The tonnage rating of a press represents the largest load that the press can apply without causing structural damage to its frame, slide-adjusting mechanisms, connection rods or main gear bushings. Calculate the tonnage required to carry out the necessary work (W) by multiplying applied force (f) and its working distance (d): W = f x d.
The energy rating of a press depends on the applied press load and the distance through which the load is applied. Con- sider deep drawing an HSLA steel, pushing 200 tons through 3 in. This application requires 600 in.-tons of energy. Form- ing AHSS could require 500 tons of force working through the same 3 in., expending 1500 in.-tons of energy.
Because energy is expended with each stroke of the press, and this energy must be replaced, critical attention must focus on the size of the main drive motor (horsepower) and the rotational speed of the flywheel, especially for AHSS applications. The amount of energy stored in the flywheel depends on its mass and rotational speed—stored energy varies by the square of the speed. Thus, a large amount of ener- gy can be stored in the flywheel when the press runs at full speed; the available energy of a press diminishes as its speed drops. This is important to realize, because many stampers will reduce the operating speed of a press to reduce the amount of additional heat generated when forming AHSS. However, at these slower speeds, flywheel size becomes the limiting factor for delivering the required press energy. We rec- ommend use of computer-based forming simulations to eval- uate force and energy requirements when stamping AHSS.
Lastly, consider the attributes of a servo-drive press when determining press force and energy requirements—that’s the subject of this month’s Tooling By Design column begin- ning on page 42. MF
Additional Resources on AHSS
A key reference for AHSS and their relationship to HSLA steels is AHSS Application Guidelines–Version 4.1, June 2009. It’s available as a free download at www.worldautosteel.org.
Also, PMA will host two consecutive one-day seminars with Stuart Keeler and Peter Ulintz on June 22-23, 2011, in Detroit, MI. The seminars will address Working with Higher Strength Steels and Designing and Building Dies for Higher Strength Steel Stampings. Learn more at www.pma.org.
Invite You to Participate
in The National Survey of Auto Suppliers
We invite you to participate in the National Survey of Auto Suppliers. Investing only 10 minutes to answer a confidential survey will yield returns to you, your firm, and the industry. Companies that supply goods or services, including tooling, used in making cars and light trucks are eligible.
Free Personalized Benchmarking Report
• BE COUNTED: Findings will be disseminated to policymakers in government and decision-makers at OEMs. To participate, go to https://www.datastat.com/cws
• FREE PERSONALIZED BENCHMARKING REPORT will include a wide array of benchmarks for comparing your firm’s practices to those of similar firms.
• Responses are ABSOLUTELY CONFIDENTIAL.
• Professor Susan Helper, the lead researcher, has studied the auto industry for over two
decades. She frequently appears as an industry expert in media outlets such as the Wall Street Journal, and the New York Times. She is also a judge for the Automotive News PACE Award for supplier innovation.
Questions? Contact Brian Peshek, the study coordinator, at brian.peshek@case.edu or 216.368.5791.
This study is funded by the US Department of Labor and is endorsed by:
PMA – Precision Metalforming Association; IFI – Industrial Fasteners Institute; NTMA – National Tooling and Machining Association; OESA – Original Equipment Suppliers Association; CAR – Center for Automotive Research;
MAGENT – Manufacturing Advocacy and Growth Network; MMTC – Michigan Manufacturing Technology Center Polymer Ohio; NIST MEP – The National Institute of Standards and Technology’s Manufacturing Extension Program
28 MetalForming/May 2011
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