To provide an exhaust gas heat-exchanger made of ferritic stainless-steel in which the texture is prevented from becoming coarse, and the strength and toughness are adequately ensured.
The exhaust gas heat-exchanger N includes outer-case-forming members 11, 12, and a heat-exchanger-tube group DG. The outer-case-forming members 11, 12 and the heat-exchange-tube group DG are made of the ferritic stainless-steel containing molybdenum (Mo) and niobium (Nb) in the weight ratio of 2.3-4.0 wt.% in total of molybdenum (Mo) and niobium (Nb). Thus, grain-growth in high-temperature atmosphere can be hindered to prevent the texture from becoming coarse, and decrease in strength and toughness of the ferritic stainless-steel itself can be prevented. Even when the heat-exchanger N is assembled and used in the engine of a vehicle, decrease in the strength of the heat-exchanger N is properly prevented, and the performance of the heat-exchanger can be maintained favorably over a long term.
SAKAKIBARA YASUFUMI
OTA AKIHIRO
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