Heat Resisting Austenitics - Applications

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The U-309S types have a lower nickel content compared to the U-310S types and this improves their resistance to hydrogen sulphide (H2S) attack at high temperatures.

The U-309S types are low carbon grades and are recommended for applications where sensitisation and subsequent corrosion by high temperature gasses or condensates during shutdown may pose a problem.

The U-309S types are used, for example, in applications such as furnace parts, fire box sheets, high temperature containers, catalytic converters, exhaust systems, etc.

The U-310S types have higher chromium and nickel contents to enable them to resist oxidation in continuous service at temperatures up to 1 200°C provided reducing sulphur gases are not present. The higher silicon content in U-310S Si-1.4841 improves this oxidiation resistance even further.

In intermittent high temperature service, the U-310S types can be used at temperatures up to 1 030°C as they resist scaling and have a relatively low coefficient of expansion differential between the metal and the scale. These stainless steels have superior resistance to both the U-304 types and the U-309S types in carburising and reducing environments.

The U-310S types are used in applications such as furnace parts, muffles, radiant tubes, ammonia converters, etc.