| 摘要 |
<p>PURPOSE: An austenite system heat-resistant cast steel and an exhaust manifold manufactured by using the same are provided to have an improved fatigue lifetime and improved creep resistance minimal addition of high-priced Ni, thereby stably applying the same with high efficiency and a highly fuel-efficient engine at a low price. CONSTITUTION: An austenite system heat-resistant cast steel includes Fe as a main component, 0.4 to 0.6 wt% of C, 0.5 to 1.0 wt% of Si, 2.1 to 2.9 wt% of Mn, 2.1 to 2.9 wt% of Ni, 1.0 to 2.0 wt% of Nb, 2.0 to 3.0 wt% of W, 0.25 to 0.35 wt% of N, and other inevitable impurities. In the austenite system heat-resistant cast steel, an equivalent ratio of Cr-to-Ni(Cr equivalent/Ni equivalent) is 0.8 to 0.9. The austenite system heat-resistant cast steel is a structure which is formed with microcarbides on a substrate which comprises only austenite. The maximum surface service temperature of a product manufactured with the austenite system heat-resistant cast steel is 800 to 900 Celsius degrees. The maximum service temperature of exhaust gas is 950 to 1050 Celsius degrees. The substrate, which comprises austenite, has an excellent high temperature fatigue strength compared with a ferrite substrate so that the substrate is very advantageous to materials used at high temperatures, and expansion due to phase transformation is prevented by restraining the generation of pearlite during temperature rising and cooling. [Reference numerals] (A) Embodiment_0.6%; (BB) Comparative embodiment 1_0.6%; (CC) Comparative embodiment 2_0.6%; (DD) Embodiment 1_1.0%; (EE) Comparative embodiment 1_1.0%; (FF) Comparative embodiment 2_1.0%</p> |
