372596196

197

RIKEN Accel. Próg. Rep. 24 (1990)

V-2-33. Problems for lmprovement of Existing Aluminum-Alloy Flange

T. Nishidono, S. Yokouchi, H. Daibo, N. Takagi,* and S.H. Be

An aluminum-alloy flange, which is planned to be used in the SPring-8 storage ring, is required to be leakJess even after many cycles of baking at 150°C. To pursue the origin of leakage, we inspected

the surfaces of flange edges in detail of two types of conflat flanges which have been using for particie accelerators so far. Table 1 shows the specifica-tions of two types of the flanges. The surface was

Table 1. Specifications of aluminum-alloy flanges.

		TYPE A	TYPE B	Notes
	Seal	Knife edge seal (Conflat scal)	Knife edge seal (Conflat seal)
	Materiał	Al-Si alloy	Al-Cu alloy
	Tensile Strength	43 kff /na²31 kiT /™²	44 kff /W 36 kg /m,²	Representative value At rooa temp. At 150 *C
Flange	Yield Strength	35 k* /an,²31 kff / B3D ²	33 kg /na²32 kg /ca²	Representative value At rooo teflip. At 150 °C
	Coefficient of thenal expansion		22.3 X10"‘	Reprcsentative value
	Surface treatnent	TiN	CrN.CrC	łon piat i ng
	Surface Roughness	R..« 1.9 u m	R.a> 0.2 /im	Heasured value
Gasket 1 '	Materiał	Pure Al	Pure Al
Gasket 1 '	Hardness	Hv 38 -39		Heasured value

* ULYAC Corporation.

Fig. 2. Fabrication process of the cut sample of fastened flange.

investigated with a scanning electron spectroscope (SEM) and optical microscope. Figurę 1 shows

)

expanded sectional views of flange edges photo-graphed with the optical microscope with a magnify-ing power of 12.5. We observed.: 1, Si segregation on the surface.; 2, Existence of lines of a pitch of 4-16/Ltm drawn by machining.; 3, Non-uniformity of the sealing surface, i.e., average roughness of 0.24-3/xm; 4, Non-uniformity of TiN and CrN film of l-2/xm thick. 5, Existence of pits of 8-16/xm, of cracks of 8-80/xm width and spherical projec-tions. To improve the reliability of leakage, these items are problems to be improved. According to our experience of using them, type A seems to be morę leakless than type B.^1}

(a) (x 12.5)

Assembly



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Fllling of epoxy resin

(b) (x 12.5)

Fig. 1. Photographs of knife edge of aluminum-alloy flanges. (a) at type A flange (x 12.5); (b) at type B flange (x 25).

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