Ferritic Stainless steel material for automobile exhaust gas passage components

Abstract

To provide a ferritic stainless steel material for automobile exhaust gas passage components usable in a high-temperature range over 900° C. and even over 950° C. The ferritic stainless steel material has excellent heat resistance and low-temperature toughness and has a composition comprising, in terms of % by mass, at most 0.03% of C, at most 1% of Si, from 0.6 to 2% of Mn, at most 3% of Ni, from 10 to 25% of Cr, from 0.3 to 0.7% of Nb, from more than 1 to 2% of Cu, from 1 to 2.5% of Mo, from 1 to 2.5% of W, at most 0.15% of Al, from 0.03 to 0.2% of V, and at most 0.03% of N, and optionally containing any of B, Co, W, Ti, Zr, REM and Ca with a balance of Fe and inevitable impurities, and the composition satisfies restrictive formulae 1.2Nb+5Mo+6Cu≧11.5 and 15Nb+2Mo+0.5Cu≧10.5. The steel material has a texture where the total amount of Nb and Mo existing as a precipitation phase is at most 0.2% by mass.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a ferritic stainless steel material for use as automobile exhaust gas passage components, in particular to a ferritic stainless steel material for use as automobile exhaust gas passage components, which has excellent heat resistance and low-temperature toughness favorable for exhaust gas upstream passage components where the material temperature may be over 900° C. or further over 950° C., for example, exhaust manifolds, catalyst converters, front pipes and the like.[0002]Heretofore, two typical ferritic steel species are used properly for automobile exhaust gas passage components, depending on the service temperature range of the components. One is a steel species such as typically SUS429 steel mainly applied to the components of which the maximum ultimate temperature of the material may be on a level of 750° C.; and the other is a steel species such as typically SUS444 steel mainly applied to the components of which...

AI Technical Summary

Benefits of technology

[0024]According to the invention, there is provided a ferritic stainless steel material for automobile exhaust gas passage components, which satisfies all the requirements of high-temperature strength durable to exposure to high temperature of 1000° C., good th

Problems solved by technology

With the increase in various devices to be fitted in an engine room, the limitation to the housing space for exhaust gas components is increasing more than before.

However, this has no description relating to 0.2% yield strength, and in this, the measures for sufficiently securing the durability in a case where the material temperature has actually risen up to 1000° C. or so