Ferritic Stainless Steel (400 Series) - Properties & Applications

Q1: What are the core properties of ferritic stainless steel (400 series)? A1: Ferritic stainless steel has good oxidation resistance at high temperatures, excellent thermal conductivity, and no phase transformation during heating and cooling. Its mechanical properties are moderate, with tensile strength around 400-550 MPa, and it has good formability and weldability. However, its corrosion resistance in chloride environments is weaker than austenitic stainless steel (300 series).

Q2: What is the most common grade of ferritic stainless steel, and what is its typical application? A2: The most common grade is 430. It is widely used in household appliances (such as refrigerator door liners, oven inner walls), decorative materials (such as stainless steel strips for furniture), kitchen utensils (non-food contact parts), and automotive trim. It is also used in heat exchangers due to its good thermal conductivity.

Q3: How does ferritic stainless steel (430) compare with austenitic stainless steel (304) in terms of cost and performance? A3: In terms of cost, 430 is about 30-40% cheaper than 304 because it does not contain nickel. In terms of performance, 304 is superior in corrosion resistance (especially in humid and salt-containing environments) and toughness, while 430 has advantages in thermal conductivity and high-temperature oxidation resistance. 430 is more suitable for dry indoor environments, and 304 for harsh environments.

Q4: Can ferritic stainless steel be used in food contact scenarios? A4: Yes, but with limitations. Food-grade 430 stainless steel that meets national or international standards (such as FDA, GB 4806) can be used in food contact parts that are not in long-term contact with acidic or salt-containing foods (such as the outer shell of food processors). For parts in direct contact with acidic foods (such as tomato sauce), 304 or 316 is recommended for better corrosion resistance.

Q5: What are the precautions for welding ferritic stainless steel? A5: When welding ferritic stainless steel, it is necessary to control the welding temperature (avoid overheating above 900°C) to prevent grain coarsening, which will reduce the toughness and corrosion resistance of the weld. It is recommended to use low-heat input welding methods (such as TIG welding) and perform post-weld annealing if necessary to restore performance. In addition, the weld area should be cleaned in time to avoid contamination.