7461Alloys 600 601 690 and 602CA

Alloy 600, due to its high nickel content, has excellent resistance to halogens at elevated temperatures and has been used in processes involving chlorination. It has good oxidation and chloride stress corrosion cracking resistance. In production of titanium dioxide by chloride routes natural titanium oxide (illmenite or rutile) and hot chlorine gases reacted to produce titanium tetrachloride. Alloy 600 has been successfully used in this process due to its excellent resistance to corrosion by hot chlorine gas. This alloy has found wide usage in the furnace and heat-treating field due to its excellent resistance to oxidation and scaling at 980°C. The alloy also has found considerable use in handling water environments, where stainless steels have failed by cracking. It has been used in a number of nuclear reactors including steam generator boiling and primary water piping systems. Alloy 690 in recent years has substituted alloy 600 in nuclear applications due to its superior stress corrosion cracking resistance. Alloy 600 has also been used in preheaters and turbine condensers with maximum service temperatures around 450°C. However, the low chromium content of alloy 600 prevented its use in applications that required extended exposure to high temperatures and requiring superior creep properties. This limitation was addressed by increasing the chromium content in alloy 601. Even with this modification, alloy 601 had some limitations. The need to extend the temperature range to 1200°C and still maintain good strength with improved resistance to environmental degradation led to the development of a new alloy, and alloy 602CA, which is described in the high-temperature section.

0 0

Post a comment