Nippondenso Co., Ltd.

Kouji Hiragami

Shoei Teshima

Tatsuhiko Nonoyama

Haruhiko Otsuka

Yasuyuki Tanaka

A brazing sheet for vacuum brazing is provided wherein the sheet is cladded with an aluminum alloy brazing filler metal having a content of Mg sufficient for vacuum brazing but less than 1.2 wt. % and wherein the Mg.sub.2 Si particle size among Mg contained in the metal is not more than 5 .mu.m as a typical value.

Brazing sheet for vacuum brazing

A vacuum pump is first driven to start evacuation from the interior of a furnace. At the time when the furnace pressure reaches 8.times.10.sup.-5 Torr, a heater is driven to start elevating the furnace temperature. Then, at the time when the furnace temperature reaches 565.degree. C. that corresponds to the solidus line temperature for a brazing filler metal of Al - 10% Si alloy containing Mg of 0.6 wt. %, a motor is driven to close a shutter, thereby vacuum brazing aluminum with evacuation control under a high-vacuum level. By controlling the evacuation after reaching a high-vacuum level, the amount of water vapor in the furnace becomes sufficiently small and Mg vapor is highly densified, which permits brazing of satisfactory quality even with a brazing filler metal containing Mg of 1.2 wt. % or less, in combination with use of such a brazing filler metal as having the Mg.sub.2 Si particle size fined to be 5 .mu.m as a typical value through soaking and the thickness of a surface oxide film thinned to be 80 .ANG. through etching. Thus, Mg's specific functions such as breakage of an oxide film, gettering and reducing can be sufficiently developed even if the Mg content in the brazing filler metal is lowered, with the result of saving resources.

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Okazaki, Japan

Kouji Hiragami