Stainless steel grade 430 is a non-hardenable steel containing straight chromium, and belongs to the ferritic group of steels. This steel is known for its good corrosion resistance and formability, coupled with practical mechanical properties. It can be used in certain chemical applications due to its resistance to nitric acid.
Grade 430F stainless steel is usually provided in bar form to be used in automatic screw machines.
Grade 434 has similar properties as grade 430, although it is a molybdenum-bearing version. The molybdenum content enhances its corrosion resistance.
The following sections will provide the key properties of grade 430 stainless steels coil, sheet and plate - covered under ASTM A240/A240M.
All ferritic grades, such as stainless steel grade 430, have excellent stress corrosion cracking resistance. Grade 430 has good corrosion resistance to numerous substances, such as certain organic acids and nitric acid. The corrosion resistance is maximized in well-polished or buffed condition. Its pitting and crevice corrosion resistance is quite similar to that of grade 304. 430F is a high-sulfur free machining grade, and therefore the resistance to pitting and crevice corrosion is comparatively lesser than those grades that are non-free machining.
Stainless steel grade 430 is capable of resisting oxidation up to 870°C (1598°F) in intermittent usage, and up to 815°C (1499°F) in continuous usage. At room temperature, it has the tendency to become brittle, especially when it has been heated for a long time in the 400-600°C (752-1112°F) range. This issue can be overcome with annealing.
Solution annealing can be performed by heating stainless steel grade 430 to 815 - 845°C (1499-1553°F). Then it has to be slow furnace cooled to 600°C (1112°F) and followed by air-cooling in a quick manner - as slow cooling between 540 and 400°C (1004 and 752°F) tends to cause embrittlement.
For sub-critical annealing, heating should be performed to 760-815°C (1400-1499°F), followed by air-cooling or water quenching.
This stainless steel cannot be hardened by thermal treatment.
To perform any welding, stainless steel grade 430 has to be pre-heated at 150-200°C (302-392°F). In case of embrittlement in the welded metal, the particular area can be post-weld annealed at 790-815°C (1454-1499°F); however grain refinement will not happen.
It is recommended that grade 430, 308L, 309 or 310 filler rod should be used based on the application.
The machinability of stainless steel grade 430 is a lot easier than standard austenitic steels such as grade 304 - but there is a chance for galling. Lightly drawn bars are easier to machine than bars in the annealed condition. Grade 430F is easy to machine.
Stainless steel grade 430 has a low work hardening rate which enables easy bending and forming. The low ductility rate, however, makes it difficult to perform very rigorous operations. It is possible for grade 430 wire to handle rigorous cold heading. Sub-critical intermediate annealing may be required for extreme cold working.
The following are the applications for stainless steel grade 430:
Dish washer linings
Refrigerator cabinet panels
Element supports and fasteners
Stove trim rings and chimney liners
Automotive trim and lashing wires