"EN 1.4509 / AISI 441*
Grade 1.4509 is a Ti and Nb dual-stabilized ferritic grade with improved weldability. Corrosion resistance is often comparable to that of general austenitic grade 1.4301. It is used in a wide range of applications, such as elevator and indoor claddings, door frames, catering and appliance, tubes and heat exchangers.
Grade 1.4509 has good oxidation resistance up to 950°C and is therefore used in exhaust system applications, where it also offers a better general corrosion resistance than grade 1.4512." ( ref outokumpu)

Chemical composition (typical)EN 1.4509
C 0.02%, Cr 18%, Ti+Nb 0.6%, Bal Fe Cr Mn
For castings a suitable grade will be ASTM A 743 Gr CB30. The heat treatment recommended is heat to 790C and the furnace or air cool.
As a foundry, it will be difficult to have low Carbon , unless you have refining facilities. Also, remember that a casting will have coarse grains, chemical inhomogeneity, porosity etc. Thus, it is not adequate to maintain the chemistry of a wrought product and achieve similar mechanical properties in a casting. Caution must be exercised.
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Mahatma Gandhi.