Page 22 - MetalForming-Jul-2018-issue

Hot-Forming
bottom of stroke during quenching;
• Automated part-handling system
to handle hot parts;
• Process monitoring to ensure
proper heattreatment of the material; and
• Safety features to protect operators from hazards associated with the heat- treatment process.
Comparing Costs
Considering the equipment and process, it should come as no surprise that the cost of a hot-stamping line significantly exceeds that of a cold- stamping operation. “The production cost of processing the sheetmetal is generally higher for hot-formed because of slower process rates, and energy and related costs to heat the sheetmetal, and the higher costs of laser cutting versus secondary cold-stamping oper- ations,” Austin explains, adding that a hot-stamping line will, on average, cost 20 to 40 percent more than a cold- stamping transfer-press operation.
However, Austin also points out that with hot forming, tooling costs can be reduced by as much as 30 to 40 percent. Why? “With cold stamping of AHSS, you have a line of presses or a transfer press, and you’re building three to five dies that may have to be machined multiple times to make the part due to springback variation,” he says. “Fur- thermore, the stamper may still need to re-machine the dies several times over their life-cycle. With hot forming, you build one die—a more expensive die—but because of the material’s near- zero springback, the die doesn’t have to be remachined. It’s a very efficient process in terms of tooling.
“Take for example,” continues Austin, “a transfer press producing medium- sized parts. Every set of tools could cost as much as $1 million, and you might buy 40 sets of tools over the life of that press. If by hot forming you can cut the cost of tooling by nearly half for every set of tools, then guess what? You’ve just bought a couple of presses.”
With more than 40 years of experi- ence in metalforming and fabrication, Austin has witnessed his share of new technologies, including those affecting hot forming. While there are many clas- sifications of AHSS, the PHS hot-form- ing process involves heating a boron- alloyed steel prior to forming to achieve a fully austenitic state and greatly improved formability. The heated blank remains in the press with the water- cooled die kept closed under high pres- sure until the blank’s temperature drops to 150 C, yielding a fully marten- sitic steel with tensile strength to 2000 MPa.
“Presses and furnaces have grown from initial 800-ton presses with beds large enough for two B-pillars, to 1200- ton presses with larger beds capable of four B-pillars, and more recently, 1600-ton presses with beds capable of large door rings,” says Austin.
He continues: “For low-volume pro- duction, a pair of single-cavity RH/LH tools often is used, sometimes in the
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WELD MOLD. A LEGACY OF ACCOMPLISHMENT
Matt Kiilunen founded Weld Mold in 1945, growing our company by flood welding innovation, an accomplishment that has taken forge die repair to the next level– increasing die life while reducing customer costs. Since then, we’ve added to that legacy by developing over 3,000 performance-matched high-quality custom solutions for tool and die welding, as well as welding in the forge. We also recently introduced the RC-17TM, providing totally remote-controlled flood welding, making the process even safer for operators in hazardous environments.
In November 2017, Christina Miller was recognized in MetalForming & Fabricating as one of its Women of Excellence. And in May 2018, Weld Mold was recognized by ASM International and presented with its prestigious Historical Landmark Award,
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Fred Schmidt ASM International President
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designating sites and events that have played a prominent role in the growth and development of metals and metalworking.
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