| 摘要 |
<p>Careful control of chemistry, and in particular niobium, and of annealing temperatures provides a ferritic stainless steel of improved creep strength. Annealing is performed at a temperature of at least 1038°C (1900°F), and in certain embodiments, at a temperature no higher than 1088°C (1990°F). The steel comprises, by weight, up to 0.1 % carbon, up to 0.05% nitrogen, from 11 to 20%chromium, up to 5%aluminium, up to 5% molybdenum, up to 1.5% manganese, up to 1.5% silicon, up to 0.5% nickel, up to 0.5% copper, up to 0.6 % titanium, and nrobium and tantalum in accordance with the following:
<UnorderedLists id="ula01" listStyle="none"><ListItem>(a) 0.63 to 1.15% effective niobium, in the absence of tantalum, or</ListItem><ListItem>(b) effective niobium and tantalum in accordance <Sup>1</Sup> with the equation<MathDetails id="matha01"><MathText><![CDATA[ <img id="ia01" file="imga0001.tif" wi="73" he="8" img-content="math" img-format="tif" inline="no" /> ]]></MathText></MathDetails></ListItem></UnorderedLists></p><p>When both niobium and tantalum are present, balance essentially iron; said effective niobium and tantalum being computed in accordance with the following:<MathDetails id="matha02"><MathText><![CDATA[ <img id="ia02" file="imga0002.tif" wi="71" he="13" img-content="math" img-format="tif" inline="no" /> ]]></MathText></MathDetails></p><p>If A is positive or zero:
<UnorderedLists id="ula02" listStyle="none"><ListItem>Then Effective Nb content = weight %Nb</ListItem><ListItem>Effective Ta content = weight %Ta</ListItem></UnorderedLists></p><p>If A is negative:
<UnorderedLists id="ula03" listStyle="none"><ListItem>Then When Ta is absent</ListItem><ListItem>Effective Nb content<MathDetails id="matha03"><MathText><![CDATA[ <img id="ia03" file="imga0003.tif" wi="58" he="7" img-content="math" img-format="tif" inline="no" /> ]]></MathText></MathDetails>When Nb and Ta are present together<MathDetails id="matha04"><MathText><![CDATA[ <img id="ia04" file="imga0004.tif" wi="59" he="7" img-content="math" img-format="tif" inline="no" /> ]]></MathText></MathDetails></ListItem><ListItem>Then if B is positive:<MathDetails id="matha05"><MathText><![CDATA[ <img id="ia05" file="imga0005.tif" wi="57" he="7" img-content="math" img-format="tif" inline="no" /> ]]></MathText></MathDetails></ListItem></UnorderedLists></p><p>If B is negative:
<UnorderedLists id="ula04" listStyle="none"><ListItem>Effective Nb content = 0</ListItem><ListItem>Effective Ta content =<MathDetails id="matha06"><MathText><![CDATA[ <img id="ia06" file="imga0006.tif" wi="59" he="8" img-content="math" img-format="tif" inline="no" /> ]]></MathText></MathDetails>said steel having a creep life to one percent elongation at 871 °C (1600°F) under a load of 84.48kg. per sq. cm. (1200 pounds per square inch), of at least 160 hours.</ListItem></UnorderedLists></p> |
