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透氣鋼磨削之后表面堵塞的恢復

PM40和PM35透氣鋼的加工

PORCERAX II-PM35、PM40透氣鋼的加工可采用常規方法，如銑刀、磨床、研磨拋光、電火花等方法。由于透氣鋼蜂窩狀的氣孔結構，加工過程因避免對堵塞進微觀孔結構的金屬碎屑的去除，因此建議采用冷卻油，并在重型表面加工后對表面進行恢復處理（正反面均需要），這一點非常重要！

如上圖所示，磨削加工堵塞了此透氣鋼的所有等級氣孔毛孔，精銑將導致7微米的孔完全堵塞、20微米的孔徑開口下降到7微米。

恢復PM35/PM40透氣鋼表面孔隙的方法有多重：

• 1）研磨/拋光

采用800~1000號的砂紙，橫向來回+縱向來回研磨，可以清楚被壓碎的氣孔，重新建立透氣鋼氣體滲透性。在研磨和拋光過程中，不時地沖洗表面，防止碎屑填塞孔非常重要。

• 2）放電加工

放電加工是恢復PM35/PM40透氣鋼堵塞面的最佳方式。此方法將燒掉磨削加工中堵塞在孔中的金屬碎片。
需要注意的是，使用金屬線放電加工時，由于PORCERAX II透氣鋼的孔狀結構，空中的微小碎屑可能產生電弧，燒斷加工線，解決的辦法是提高線速度或者使用較粗的銅線（如0.25mm）。而使用電極放電時，峰值燃燒率因高于透氣鋼孔隙率，小于7微米的深度加工7微米的孔徑是可行的。

上圖顯示線切割過程中產生的電弧如何攜帶微粒，增加繞線速度不僅大大降低了斷線的可能性也減少了加工時間。

Machining and Polishing
Porcerax II can be machined by conventional methods using cutoff saws, end mills, grinders, EDM methods, stoning, etc. It is important to remember that this material is honey-combed with thousands of microscopic holes which are affected by metal removal. Oil coolant is recommended.
Grinding closes the pores of all grades of this porous steel. Milling will close the pores of 7 micron and reduce the pore size of the 20-micron material down to about 7 microns
(when done correctly) by partially closing the pore opening at the surface. Stoning, using a back and forth/side to side method, will re-establish permeability by removing the metal that is crushed over the pores. Stoning and polishing, up to about a number 800 - 1000 stone/paper finish, is possible. During the stoning and polishing process, it is important to occasionally flush the pores at the surface to prevent packing the pores with debris.
Electric Discharge Machining is the best way to re-establish permeability. This method will burn away the metal fragments that are crushed over the pores by milling and/or grinding.
Note: When using wire EDM machining methods, Porcerax II is porous and generates
waste particles that can create "arcing" conditions between the wire and the work-piece.
This arcing can cut the wire. As a countermeasure, increase wire winding speed.
Note: When using an electrode for EDM, it is important to program a peak-to-valley burn rate that exceeds the pore size; i.e. < 7 micron depth for 7 micron pore size is desirable.
The illustrations above show how particles created by the wire EDM process carry the
electrical current across to the work-piece, creating the potential for a discharge that can break the wire. Increasing the wire winding speed not only greatly reduces the potential for wire breakage but also increases machining times.
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