Clean tubes which are stainless steel tubes usedfor semiconductor manukicturing apparatus are required ultra-smooth inner-surface to decrease particle and vapor 'turn inner-surice of tube.For smoothing surface of material, it's well known that it'snecessary for material to give high contact pressure and largeplastic strain. We called this 'the principle of smoothing inmetal working process". We apply this principle to the newdrawing process. The new drawing process is characteristic byusing a plug having a protrusive ring on finishing part. Theprotrusive ring makes large plastic strain to inner-surface layer.The amount of plastic strain given by protrusive plug is 4-5times as large as the conventional plug. The new drawingprocess enables the roughness of inner-surface to finish in 0.4-0.6 #mu#m Rmax without electrical polishing.The new drawing process 'ultra-smoothing drawing,' issuccessfully applied to the manufacture of clean tube. Theclean tube of new process is excellent in the performance andthe same as the electrical polishing type.
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