Page 47 - MetalForming June 2009

More on Docol 800
Swedish supplier SSAB Tunnplat manufactures Docol cold-rolled dual-phase (DP) alloys from 0.5 to 1.6 mm thick. Docol 800 DP comprises 1.5 Mn, 0.2 Si, 0.12 C, 0.04 Al, 0.015 Mn, 0.015 Nb, and 0.0002 S. Mechanical properties: 116-131- ksi tensile strength, 72.5-94.3-ksi yield strength, and an n-value of 0.11.
Dual-phase steels have a microstructure that blends ferrite and martensite, giving them their relatively low yield point and high ultimate tensile strength. DP steels also boast a relatively high strain-hardening rate, bene- ficial in terms of formability and energy-absorption capacity. SSAB recommends a minimum internal bending radius of one times material thickness and a limited drawing ratio of about 2.0.
CTS to try carbide for the troubling tool insert, rather than have to keep a spare insert in hand and have the inserts coated every 7500 hits, at a cost of $600 to $700. However, machining a carbide insert proved disastrous, as it shattered before it even made one hit. “We tried three times, to no avail,” says Runyon.
Instead, CTS went with a copper alloy for the insert, DieAce SO390 from Sankyo Oilless, Sterling Heights, MI. DieAce, a special hardened copper- alloy casting, is designed to eliminate galling and scoring in harsh drawing and forming applications. SO390, one of three DieAce alloys, has a hardness of HB 270-290 and 0.5 percent minimum elongation. Sankyo says that the alloys can be cast to size, leaving only a min- imal amount of stock for finish machining.
“We were able to mill the insert in 6 hr.,” says Runyon, “and overnight ship the new insert to JCI. “So far, after more than 100,000 hits, the material’s lubri- cation properties and wear resistance have kept the die in the press without requiring any maintenance.” MF
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