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发表于 2016-6-12 16:44:06
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本帖最后由 leomet 于 2016-6-12 17:51 编辑
This tooling is called "core rod" for making holes in PM parts.
Its material is CPM 15V. Very fine iron powders "cold welded" onto its surface during powder compacting, forming a Galvanic couple in which the CPM 15V is positive while iron powder is negative in polarity. Therefore corrosion pits created on the CPM 15V rod surface. Under tensile stress, microcrack iniitated, propagated and finally, the rod fractured. |
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