Metal treatment – Stock – Ferrous
Reexamination Certificate
1999-08-31
2001-09-11
Yee, Deborah (Department: 1742)
Metal treatment
Stock
Ferrous
C148S579000, C148S654000, C420S087000
Reexamination Certificate
active
06287397
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high strength phosphorus-containing steel and a method for producing the same. In further detail, it relates to a carbon steel improved in strength by finely reducing ferritic grains, and to a method for producing the same.
2. Description of the Related Art
Conventionally, much effort has been made to remove P (phosphorus) in a smelting process for low carbon steel because P is known to have negative effects in the low temperature toughness of the product. However, the fact that the presence of P is not allowed had made it difficult to simplify the conventional smelting process, and the presence of P has been an obstacle in the reuse of steel materials.
Practically, for instance, in case P is contained at an amount of 0.1% by mass, the ductile/brittle transition point is increased by 40 K. Thus, carbon steel had been suffering the problem of embrittlement due to the presence of P, and in conventional smelting processes, great effort was necessary for the removal of P.
Apart from the problems above, the present inventors have been studying finely reducing the size of ferritic grains with an aim to develop high strength steel materials. In due course, it has been found that the transition temperature is considerably lowered by finely reducing the size of ferritic grains. Accordingly, it has been presumed that the problem of the embrittlement due to the presence of P can be overcome by finely reducing the size of crystal grains.
However, it was still a problem how to finely reduce the size of ferritic grains while controlling the presence of P.
The invention of the present application has been made in the light of the aforementioned circumstances, and it provides a high strength steel by overcoming the limits of the related art technology, and yet, by positively using the presence of P.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a high strength phosphorus-containing steel having fine texture, which is a carbon steel having an average ferritic grain diameter of 3 &mgr;m or less and containing from 0.04 to 0.1% by mass of P, wherein the volume fraction of P segregated in the grain boundary accounts for 0.3 or less in case the grain boundary is 1 nm in thickness.
Further, in accordance with a second aspect of the present invention, there is provided a high strength phosphorus-containing steel as above, wherein, the basic components thereof as expressed by chemical composition in % by mass are 0.3% or less of C, 0.5% or less of Si, 3.0% or less of Mn, 0.02% or less of S, 0.04 to 0.1% of P and Fe.
Further according to a third aspect of the present invention, there is provided a method for producing the steel above, comprising heating the steel to a temperature of Ac3 point or higher for austenization, applying an anvil compression processing for a draught of 50% or higher at a temperature of Ar3 point or higher, and cooling it thereafter.
REFERENCES:
patent: 409111396 (1997-04-01), None
patent: 411100641 (1999-04-01), None
Hanamura Toshihiro
Nagai Kotobu
Nakajima Hiroshi
Torizuka Shiro
Tsuzaki Kaneaki
Japan as represented by Director General of National Research In
Wenderoth , Lind & Ponack, L.L.P.
Yee Deborah
LandOfFree
High strength phosphorus-containing steel and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High strength phosphorus-containing steel and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High strength phosphorus-containing steel and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2464719