| 摘要 |
In a gas sensor, a casing which accommodates a sensing element includes an inner cylindrical member and an outer cylindrical member which are caulked together by means of a caulked portion. The Vickers hardness H1 of the inner cylindrical member is Hv 250 to 430; the Vickers hardness H2 of the outer cylindrical member is Hv 160 to 330; and the hardness difference "H1-H2" is not less than 30. Through employment of the above ranges of H1 and H2, the caulked portion can maintain good airtightness even in a working environment involving, for example, thermal shocks.
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