Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2002-04-02
2003-12-16
Koehler, Robert R. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C029S897340, C052S749100, C052S749100, C148S527000, C148S595000, C428S682000
Reexamination Certificate
active
06663984
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to ferrous metallurgy and more specifically to clad steel rolled section used to reinforce concrete and a method for producing the same.
Known in the prior art is a method for producing clad steel sheets comprising a basic metal layer made of steel containing, in percent by weight: ≦1.0 C; from 0.05 to 1.0 Si; from 0.3 to 2.5 Mn, and a clad layer containing Ni+Cr≦10.0; one or two from the elements: ≦2.0 Cu; ≦1.0 Mo; ≦0.1 SD; ≦0.1 V; the balance being Fe and minor impurities. The bimetallic clad pack is connected across the edges by welding or by other means, and hot rolled after pre-heating and heat treatment. The composite sheet is heated before rolling to a temperature above 1150° C. and held at this temperature (JP, 61-294223, 21.06.88, B 23 K 20/04) [1].
Also known in the prior art is a clad steel rolled section comprising a main steel layer, intermediate layer and surface stainless steel layer, and a method for producing the same. The layers contain a group of alloy elements including Si and Cr, in percent by weight: from 1.5 to 7.0 Si, up to 3.0 Cr, Si/Cr ≧0.5 in the basic layer; from 0.5 to 7.0 Si, from 2 to 14 Cr, Si/Cr (8.5/Cr-0.5)±0.2 in the intermediate layer, and up to 6.5 Si, from 6.0 to 25.0 Cr, Si/Cr≦0.4 in the surface layer.
The method for producing the clad steel rolled section comprises the steps of making a bimetallic billet, hot rolling the billet in several passes, and subjecting the billet to thermo-mechanical treatment. (RU, 2155134 Cl, 27.08.2000, B 32 B 15/18) [2].
Most closely approaching the present invention is a method for producing clad steel sheets, wherein a basic strip is made of steel containing, in percent by weight: ≦0.05 C, from 0.05 to 0.8 Si, from 0.8 to 2.2 Mn, from 0.02 to 0.08 Al, the balance iron, and a clad layer is made of highly corrosion-resistant steel. The strips, united in a pack, are rolled to a predetermined thickness and heat treated, being held at a temperature of 900-1150° C. for more than 10 seconds and then cooled with the rate more than 0.5° C. per second (JP, 58-150377, 08.03.85, C 21 D 9/52) [3].
Basic problems with the prior art technical solutions include inadequate strength and impact toughness of the produced clad articles, insufficient corrosion resistance, and inferior bond strength between the layers and with concrete.
The object of the present invention is to overcome the above problems and provide a clad steel rolled section used to reinforce concrete, which would exhibit superior mechanical strength and impact toughness, improved corrosion resistance and high-strength bond between the layers and with concrete.
SUMMARY OF THE INVENTION
The object of the invention is attained by a clad steel rolled section for reinforcing concrete, produced from a bimetallic ingot comprising a basic material, such as steel containing, in percent by weight, from 1.0 to 5.8 Si and from 0.1 to 5.0 Al, with the proviso that 3.0≦(Si+Al)≦6.0, and a surface layer of ferritic or austenitic stainless steel containing a group of alloy elements including Cr and Ni, by hot rolling the ingot to an intermediate billet and then to a rolled section, and subjecting the rolled section to heat treatment.
The basic and surface layers preferably comprise one or more components selected from the group including: manganese, molybdenum, tungsten, vanadium, copper, titanium, niobium, zirconium, yttrium, rare-earth metals (REM), nitrogen and carbon, in percent by weight, in the basic layer: up to 3.0 nickel; up to 3.0 chromium; up to 3.0 manganese; up to 1.0 molybdenum; up to 0.5 tungsten; up to 0.7 vanadium; up to 0.5 copper; up to 0.3 titanium; up to 0.5 niobium; up to 0.5 zirconium; up to 0.2 yttrium; up to 0.2 REM; up to 0.5 nitrogen; up to 0.8 carbon; the balance being iron and impurities, and in the surface layer: up to 34 nickel; up to 25 chromium; up to 6.5 silicon; up to 4.0 aluminium; up to 6.0 manganese; up to 6.1 molybdenum; up to 4.0 tungsten; up to 0.5 vanadium; up to 5.0 copper; up to 1.2 titanium; up to 1.0 niobium; up to 1.0 zirconium; up to 0.5 yttrium; up to 0.5 REM; up to 0.8 nitrogen, up to 0.5 carbon, the balance being iron and impurities.
The surface layer having a relative thickness of up to 20% in the cross-section of the billet is preferably made of a stainless steel with ferritic structure containing, in percent by weight: ≦3.0 Ni and from 10 to 25 Cr, the basic layer contains Si and Al in the ratio Si/Al≧(1+Ni/Cr), and a diffusion layer between said layers contains the main alloy components in the ratio:
{(Fe)
1-x-y
(Si,Al)
x
Cr
y
}, where x+y≦18.
The surface layer having a relative thickness of up to 20% in the cross-section of the billet is preferably made of a stainless steel with austenitic structure containing, in percent by weight: from 4 to 34 Ni and from 6 to 25 Cr, the basic layer contains Si and Al in the ratio Si/Al≧(2−Ni/Cr), and a diffusion layer between said layers contains the main alloy components in the ratio:
{(Fe,Ni)
1-x-y
(Si,Al)
x
Cr
y
}, where x+y≦18.
The object of the invention is also attained in a method for producing a clad steel rolled section for reinforcing concrete, in accordance with the invention comprising the steps of: making a bimetallic bar with a surface layer of a stainless steel having austenitic or ferritic structure; hot rolling in several passes through calibrated rolls, the final rolling being carried out by calibrated rolls with a corrugated surface observing the following relationship:
H
0
ψ
·
d
≤
1
where H
o
is the maximum depth (height) of corrugations on the roll surface,
d is the bar diameter,
&psgr; is the relative thickness of the surface layer.
The above object is also attained in a method for producing a clad steel rolled section for reinforcing concrete, comprising the steps of: making a bimetallic strip with a surface layer of a stainless steel having austenitic or ferritic structure; hot rolling in several passes by rolls with a plain body, the final rolling being carried out by rolls with a corrugated surface observing the relationship:
0.2
≤
h
1
ψ
·
h
0
≤
1
where h
1
is the maximum depth (height) of corrugations on the roll surface,
h
o
is the thickness of the bimetallic strip,
&psgr; is the relative thickness of the surface layer.
The bimetallic strip is preferably rolled or press formed at a temperature no greater than 1150° K to a half-tube section with surface curvature 1/D and wall thickness h
o
within the relationship:
5
·
h
0
D
≤
1.
DETAILED DESCRIPTION OF THE INVENTION
It is well known that mechanical properties of clad steel rolled products substantially depend on the strength of the basic material. Under optimal conditions, where the content of Si and Al in the basic layer is within the range defined in claim
1
, specifically, in percent by weight: from 1.0 to 5.8 Si and from 0.1 to 5.0 Al, with the proviso that 3.0≦(Si+Al)≦6.0), mechanical strength is from 550 to 1300 MPa, and impact toughness is from 1.1 to 3.1 MJ/m
2
. The clad-to-basic layer bond strength can be considerably improved by disintegration of solid solution Fe—Si—Al—Cr—Ni and formation of new phase {(Fe, Ni)
1-x-y
(Si,Al)
x
Cr
y
} with coherent inter-phase boundaries in the diffusion region. In this case the bond strength can be equal to the basic layer strength or even exceed it, this permitting the production of a bimetallic rolled section with entire corrosion-proof surface, e.g. in the shape of a round or square billet with stainless cladding closed over the entire perimeter. The bimetallic billet may be further deformed to a round or square section or to a strip without cladding discontinuities over the entire perimeter, including the end faces of the rolled strip (with edge uncut), and retain corrosion prevention over the entire surface (FIGS.
1
and
2
).
If in the produced clad steel rolled products Si and Al
Chernyshev Vyacheslav Nikolaevich
Gramotnev Konstantin Igorevich
Sadovsky Aleksei Valerievich
Vostrikov Petr Vasilievich
Vostrikov Vasily Petrovich
Ladas & Parry
Zakrytoe Aktsionerone Obschestvo “Transkom”
LandOfFree
Clad steel rolled section for reinforcing concrete and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Clad steel rolled section for reinforcing concrete and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Clad steel rolled section for reinforcing concrete and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3131275