Steel for use in exhaust manifolds of automobiles
AssigneesSumitomo Metal Industries, Ltd., Toyota Jidosha Kabushiki Kaisha
InventorsMasao Koike, Mitsuo Miyahara, Kenji Higuchi, Tomoyuki Sugino, Shinji Shibata, Katsuhiko Maruyama
Life of this patent
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Abstract
A ferritic stainless steel which exhibits improved formability and which is especially useful for making 950.degree. C. or 1000.degree. C. exhaust manifolds is disclosed, the steel composition thereof consisting essentially of, on the basis of weight: C: 0.02% or less, Si: 1.0% or less, Mn: 1.0% or less, P: 0.04% or less, S: 0.005% or less, Cu: 0.1-1.0%, Cr: 18.0-25.0%, Mo: 1.0 (exclusive)-3.0%, Nb: 0.1-1.0%, Al: 0.20% or less, N: 0.02% or less, B: 0-0.01%, C+N.ltoreq.0.03%, preferably, 21%.ltoreq.Cr+Mo+Nb.ltoreq.25%, Fe and incidental impurities: balance.
Claims21
An exhaust manifold which is made of a steel which exhibits improved formability as well as thermal fatigue resistance properties, the steel composition thereof consisting essentially of, on the basis of weight:
- C:
- 0.02% or less, Si:
- 1.0% or less,
- Mn:
- 0.5% or less, P:
- 0.04% or less,
- S:
- 0.005% or less, Cu:
- 0.1-1.0%,
- Cr:
- 18.0-25.0%, Mo:
- 1.0 (exclusive)-3.0%,
- Nb:
- 0.1-1.0%, Al:
- 0.20% or less,
- N:
- 0.02% or less, B:
- 0-0.01%,
- Fe and incidental impurities:
- balance
- wherein the content of C and N satisfies the following equation (i) and the content of Cr, Mo and Nb satisfies the following equation (ii):
- C+N.ltoreq.0.03% - - - (i)
- 21%.ltoreq.Cr+Mo+Nb.ltoreq.25% - - - (ii), and
- the steel having thermal fatigue resistance enabling the steel to withstand 700 cycles or more before rupturing at 1000.degree. C., high temperature strength of at least 1.3 kgf/mm.sup.2 at 1000.degree. C., and elongation of at least 30%.
An exhaust manifold which is made of a steel which exhibits improved formability as well as thermal fatigue resistance properties, the steel composition thereof consisting essentially of, on the basis of weight:
- C:
- 0.02% or less, Si:
- 1.0% or less,
- Mn:
- 0.5% or less, P:
- 0.04% or less,
- S:
- 0.005% or less, Cu:
- 0.1-1.0%,
- Cr:
- 18.0-22.0%, Mo:
- 1.0 (exclusive)-2.0%,
- Nb:
- 0.1-1.0%, Al:
- 0.20% or less,
- N:
- 0.02% or less, B:0.001 (exclusive)-0.01%,
- Fe and incidental impurities:
- balance
- wherein the content of C and N satisfies the following equation (i) and the content of Cr, Mo and Nb satisfies the following equation (ii):
- C+N.ltoreq.0.03% - - - (i)
- 21%.ltoreq.Cr+Mo+Nb.ltoreq.25% - - - (ii), and
- the steel having thermal fatigue resistance enabling the steel to withstand 700 cycles or more before rupturing at 1000.degree. C., high temperature strength of at least 1.3 kgf/mm.sup.2 at 1000.degree. C., and elongation of at least 30%.
An exhaust manifold which is made of a steel which exhibits improved formability as well as thermal fatigue resistance properties, the steel composition thereof consisting essentially of, on the basis of weight:
- C:
- 0.02% or less, Si:
- 1.0% or less,
- Mn:
- 0.5% or less, P:
- 0.04% or less,
- S:
- 0.005% or less, Cu:
- 0.1-1.0%,
- Cr:
- 19.0-25.0%, Mo:
- 1.0 (exclusive)-3.0%,
- Nb:
- 0.1-1.0%, Al:
- 0.20% or less,
- N:
- 0.02% or less,
- Fe and incidental impurities:
- balance
- wherein the content of C and N satisfies the following equation (i) and the content of Cr, Mo and Nb satisfies the following equation (ii):
- C+N.ltoreq.0.03% - - - (i)
- 21%.ltoreq.Cr+Mo+Nb.ltoreq.25% - - - (ii), and
- the steel having thermal fatigue resistance enabling the steel to withstand 700 cycles or more before rupturing at 1000.degree. C., high temperature strength of at least 1.3 kgf/mm.sup.2 at 1000.degree. C., and elongation of at least 30%.
Dependencies are inferred from the claim text.