| 摘要 |
<p>The present invention relates to a steel part securing temper softening resistance at 300°C characterized by (a) the content of Si in the steel being made 0.7% or more, (b) the content of C in the carburized layer being made 0.9 to 1.1% for a hyper eutectic content of C by carburization, (c) the carbides with an outside diameter of 0.1 µm or more (proeutectoid cementite or spherical carbides) not being allowed to be present after carburization, and (d) the amount of residual austenite after carburization, quenching, and tempering being made less than 30%. The gist lies in a steel part excellent in temper softening resistance which is comprised of steel containing predetermined ingredients, has a total content of Mn and Cr of 2.5% or less, and is carburized, quenched, and tempered on its surface, which has a content of C at a part at a 50 µm depth from the surface of 0.9 to 1.1%, does not contain proeutectoid cementite or spherical carbides of an average diameter of 0.1 µm or more or even if containing it, has an area ratio of it of less than 1%, and, further, does not containing residual austenite or even if containing it, has an area ratio of it of less than 30%.</p> |
