Page 69 - MetalForming April 2013

and multiple forming operations. Both can be difficult to remove and should not be left on the stamped parts for extended periods of time. Exposure to the sun can make them impossible to remove.
Higher Pressure, Slower Speed
Blankholder-pressure requirements will be much higher with stainless steel than for low-carbon drawing steel. The fer- ritic grades (430) require about 50-percent more pressure, while austenitic grades (304, 316 etc.) may require as much as three times the force of low-carbon steel. Also, drawing speed will be much lower than that for low-carbon steel. A unique feature when cold-forming stainless steel is that more severe deformation is possible when using slower forming speeds. This differs from mild steels, which form vir- tually the same regardless of forming speed. In general, when forming stainless steel into difficult shapes, slow down.
The required clearances between the draw punch and die- cavity wall will be greater for stainless steels compared to mild steels. For austenitic grades, set clearance equal to workpiece- material thickness plus an additional 35 to 40 percent; most ferritic alloys require a clearance 10 to 15 percent greater than material thickness.
Keep it Clean
The appearance of rust streaks on stainless steel some- times leads to the belief that the material is rusting. Howev- er, the source of the rust will be some other iron or steel com- ponents. Contamination can easily occur when pressroom equipment that has been in contact with mild steel is not thoroughly cleaned prior to processing stainless steel.
Other sources of iron contamination include:
• Producing stainless-steel parts in tooling also used to stamp mild steel;
• Cleaning parts in solutions used to clean mild steel;
• Handling stainless-steel coils with steel chains; and
• Sharing material-handling equipment between mild
and stainless-steel parts.
Be sure to clean all handling and processing equipment
prior to use with stainless steel. Shops would be wise to carefully plan and schedule the handling of stainless steel, to help ensure proper cleaning and preparation. Best practice dictates using dedicated handling equipment for stainless steel whenever possible.
For more information on forming, punching and drawing stainless steel, visit the Specialty Steel Industry of North America at www.SSINA.com. MF
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20th Annual
20 Years...
Look How Far We’ve Come!
April 30–May 1, 2013 | Novi, MI
2013 – NOW
1993 –THEN
Join your fellow automotive suppliers April 30-May 1 at the Sheraton Detroit Novi in Novi, MI for the 20th annual Automotive Parts Suppliers Council (APSC) meeting.
This is an ideal forum for chief executive officers, presidents, chief financial officers and other senior executives of companies serving the automotive market. Benefits of attending include cutting-edge and timely automotive industry trend analysis, production forecasts that can be used to develop marketing plans, the opportunity to network with fellow automotive suppliers, benchmarking, and discussion on strategic trends and changing conditions in the automotive market.
Visit www.pma.org/apsc for more information about the APSC meeting and to register, or contact Allison Grealis at 216/901-8800 or agrealis@pma.org with questions.
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