Ferritic stainless steel for automotive exhaust system with improved heat resistance and condensate corrosion resistance, and method for manufacturing the same
Provided are a ferritic stainless steel for automotive exhaust systems with improved heat resistance and condensate corrosion resistance and a method for manufacturing the same. The ferritic stainless steel according to an exemplary embodiment of the present invention includes a stainless steel base material comprising, in % by weight, C: 0.01% or less, Si: 0.5 to 1.0%, Mn: 0.5% or less, P: 0.035% or less, S: 0.01% or less, Cr: 11 to 18%, N: 0.013% or less, Ti: 0.15 to 0.5%, Sn: 0.03 to 0.5%, and the remainder of Fe and other inevitable impurities, and an Al-plated layer formed on the stainless steel base material, wherein the ferritic stainless steel comprises a plating compound comprising (Al 19 FeMnSi 2 ) 5.31 (Aluminum Iron Manganese Silicide) at an interface between the stainless steel base material and the Al-plated layer.
1. A ferritic stainless steel for automotive exhaust systems, comprising: a stainless steel base material comprising, in % by weight, C: 0.01% or less, Si: 0.5 to 1.0%, Mn: 0.5% or less, P: 0.035% or less, S: 0.01% or less, Cr: 11 to 18%, N: 0.013% or less, Ti: 0.15 to 0.5%, Sn: 0.03 to 0.5%, and the remainder of Fe and other inevitable impurities, and an Al-plated layer formed on the stainless steel base material, wherein the ferritic stainless steel comprises a plating compound comprising Aluminum Iron Manganese Silicide at an interface between the stainless steel base material and the Al-plated layer, wherein a chrominance (ΔE) of a surface of the stainless steel before and after a heat treatment is 10 or less, wherein a content of the Sn is concentrated on a surface of the stainless steel base material adjacent to the Al-plated layer by 4.5 to 6.1 times as compared to the stainless steel base material.
2. The ferritic stainless steel according to claim 1 , wherein the plating compound further comprises at least one selected from a group consisting of Al 9 FeSi 2 (Aluminum Iron Silicon), Al 3 FeSi 2 (Aluminum Iron Silicon), and Al (Aluminum).
3. The ferritic stainless steel according to claim 1 , comprising Sn: 0.05 to 0.5%.
4. The ferritic stainless steel according to claim 1 , having a maximum pitting corrosion depth of less than 0.4 mm in the evaluation of condensate corrosion characteristics (JASO-B M611-92).
5. A method for manufacturing a ferritic stainless steel for automotive exhaust systems with improved heat resistance and condensate corrosion resistance according to claim 1 , comprising:
hot-rolling a ferritic stainless steel slab comprising, in % by weight, C: 0.01% or less, Si: 0.5 to 1.0%, Mn: 0.5% or less, P: 0.035% or less, S: 0.01% or less, Cr: 11 to 18%, N: 0.013% or less, Ti: 0.15 to 0.5%, Sn: 0.03 to 0.5%, and the remainder of Fe and other inevitable impurities;
cold-rolling the hot-rolled steel plate; and
aluminum-plating the cold-rolled steel plate.
6. The method according to claim 5 , wherein the ferritic stainless steel is manufactured by a conventional STS 409L manufacturing process.
7. The method according to claim 5 , further comprising heat-treating the aluminum-plated ferritic stainless steel at a temperature of 300 to 500° C. within 48 hours,
wherein a chrominance (ΔE) of a surface of the stainless steel before and after the heat treatment is 10 or less.