| 摘要 |
PURPOSE:To prevent any cracks from occurring on a wall part, by making up the wall surface part of an exhaust gas bypass passage with such special steel as carring the same coefficient of thermal expansion substantially as a metallic material forming other parts of a turbine housing and based on austenite in material. CONSTITUTION:A turbine housing 1 is connected to both of an exhaust manifold and an exhaust pipe in an internal-combustion engine via each of flange parts 2 and 3, while inside the housing 1, there is provided with a swirl passage ex- tending from an inlet port 4 to an outlet port 5 of exhaust gas. In addition, in order to cope with the case that when pressure in the exhaust gas against a partition wall 6 separating the inlet port 4 from the outlet port 5 goes up beyond the specified value, there is provided with a bypass passage 7 leading a part of the exceeded pressure into the outlet port 5. In this case, a swirl surface part of the bypass passage 7 is to be made up of special steel based on austenite excellent in heat resistance and mechanical properties at a high temperature. With this constitution, any cracks on the said wall surface part due to heat fatigue and/or thermal shock are prevented from occurring. |
