| 摘要 |
A process for treating carbide tool bits used by the electronics industry for printed circuit board ("PCB") fabrication combines a cryogenic cycle with two or more tempering cycles. The tool bits are subjected to a cryogenic cycle having a ramp down phase during which the tool bits are ramped down in a dry cryogenic environment to about -300° F. over between about six (6) and eight (8) hours, followed by a cryogenic hold phase during which the tool bits are held at about -300° F. over between about twenty-four (24) and thirty-six (36) hours, followed by a cryogenic ramp up phase during which the tool bits are ramped up to about -100° F. over between about six (6) and eight (8) hours. That is followed by a first tempering cycle having a ramp up phase during which the tool bits are ramped up in a dry tempering environment to about 350° F. over about one-half (½) hour, followed by a hold phase during which the tool bits are held at about 350° F. over about two (2) hours, followed by a ramp down phase during which the tool bits are ramped down to below about 120° F. but not generally all the way to the ambient temperature over between about two (2) and three-and-half (3½) hours. A second tempering cycle follows that and it has a time-temperature profile fairly comparable to the first tempering cycle.
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