Stainless steel castings are known for their rust and corrosion resistance and are used in a wide variety of applications. The variety of stainless steel casting grades makes it suitable for a variety of applications in many different industries. So, how to choose stainless steel castings? We can consider the following points:
1. When castings need to have good formability.
If the application of stainless steel castings requires good formability, the use of martensitic group stainless steels should be avoided. Try an austenitic grade like 304 or a ferritic grade like 430. Martensitic stainless steel castings such as 410 tend to be brittle and difficult to form. Austenitic stainless steel castings are often the best choice for formable stainless steel castings.
2. When stainless steel castings need to be welded.
Welding stainless steel castings is very different from welding other steel castings and can lead to problems such as intergranular corrosion, hot cracking and stress corrosion cracking. The easiest-to-weld stainless steels generally belong to the austenitic group. When welding austenitic stainless steel castings, 304L or 347 should be used. 304L stainless steel castings have a lower carbon content, while 347 has niobium stabilizers added to help prevent intergranular corrosion. Ferritic stainless steel castings such as 430 or 439 are also easy to weld, as are duplex stainless steel castings. Martensitic stainless steel castings are generally not suitable for welding, but some martensitic stainless steel castings with lower carbon content can be welded. For precipitation hardened stainless steel, care should be taken to ensure that the original mechanical properties are not compromised during welding.
3. When post-processing is required for stainless steel castings.
If machining of stainless steel castings is required, special consideration must be given when using stainless steel castings. Most grades of stainless steel castings can be post-worked, but stainless steel castings are prone to work hardening. The machining process must be optimized to help alleviate the speed of this problem, and the tools used for machining must also be kept in good working order. Similar to carbon steel castings, sulfur can be added to increase machinability; grade 303 is an example. It is very similar to grade 304 except that sulfur has been added for processing purposes.
4. When corrosion resistance is required.
Stainless steel castings are often chosen for their corrosion resistance properties, but it is important to know that different grades offer different corrosion resistance. Austenitic stainless steel castings generally have the highest corrosion resistance because of their high chromium content. This makes 304 an excellent choice when corrosion resistance of stainless steel castings is important. Grade 316 stainless steel castings are similar to Grade 304, but contain molybdenum in their chemical composition to further improve their corrosion resistance. Ferritic stainless steel castings and martensitic stainless steel castings are generally more affordable than austenitic stainless steel castings because they have a lower nickel content than austenitic stainless steel castings and sometimes less chromium than austenitic stainless steel castings, which can lead to resistance. Corrosiveness decreased.
5. When stainless steel castings need heat treatment.
If heat treating stainless steel castings, it is important to understand how different grades of stainless steel castings are affected. In most cases, austenitic stainless steel castings and ferritic stainless steel castings are not hardenable when heat treated. Heat treatable stainless steel castings are usually martensitic or precipitation hardened. These examples are grades 440C and 17-4 PH, respectively.
6. When the strength of stainless steel castings is required.
Very high strengths can be obtained using martensitic stainless steel castings such as grade 440C; and precipitation hardening stainless steel castings such as grades 17-4 PH and 15-5 PH. Austenitic stainless steel castings, such as grade 316, can also provide high strength, but not as high as martensitic grades. Austenitic stainless steel castings also contain more nickel than other stainless steel castings, so grades like 316 will have greater toughness and ductility than ferritic and martensitic stainless steel castings. Duplex stainless steel castings can provide the performance of ferritic stainless steel castings while still maintaining ductility and toughness close to that of austenitic stainless steel castings.
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