Alloys or metallic compositions – Containing over 50 per cent metal but no base metal – Iron containing
Reexamination Certificate
2002-08-12
2004-07-20
Yee, Deborah (Department: 1742)
Alloys or metallic compositions
Containing over 50 per cent metal but no base metal
Iron containing
C148S650000, C148S651000, C420S045000, C420S049000
Reexamination Certificate
active
06764647
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a material with a high corrosion resistance in media with a high chloride concentration, suitable for equipment in oilfield technology, in particular for drilling line components, comprising the elements carbon (C), silicon (Si), manganese (Mn), chromium (Cr), molybdenum (Mo), nickel (Ni), copper (Cu), nitrogen (N), iron (Fe) and contaminants due to manufacture, which material is hot formed and, after cooling, is cold formed.
2. Discussion of Background Information
Corrosion resistant materials which show paramagnetic behavior and feature a high degree of strength, can be used for equipment in oil field technology, particularly for drilling line components. However, higher demands are always being made on the parts and stricter standards are always being set for the materials.
In order to be able to conduct directional measurements during the sinking or boring of a drill-hole with the necessary precision, the material must have a permeability of less than 1.005.
A high mechanical strength, in particular a high 0.2% elongation value, is necessary in view of an advantageous design in terms of industrial engineering and of high operational safety of the parts, because it is intended to stress same up to the limiting values of the respective material load capacity, and because increasingly large drilling depths are required. Furthermore, a notched impact strength of the material is important, because the parts often have to withstand high stresses in the form of impacts or shocks.
A high fatigue strength under reversed stresses is important in many cases, in particular for drilling line parts and drill stems, because increasing or changing stresses can be present during a rotation of the parts or of the drill stems, respectively.
The parts are often installed or used at low temperatures so that the fracture appearance transition temperature (FATT) of the material also plays an important role.
The corrosion behavior for parts used in oilfield technology is of crucial importance, that is, on the one hand stress corrosion cracking (SCC) and on the other pitting corrosion (pitting, CPT).
As shown by the above statements, materials which have a high degree of corrosion resistance in media with a high chloride concentration and are suitable for equipment in oilfield technology are simultaneously exposed to a plurality of high stresses.
SUMMARY OF THE INVENTION
The object of the invention is to provide a paramagnetic material with a high yield strength, high notched impact strength and high fatigue strength under reversed stresses as well as a low fracture appearance transition temperature, which at the same time is corrosion-resistant, in particular resistant to pitting, in chloride-containing media.
This object is attained with a material of the type mentioned at the outset by this consisting essentially of the elements in percent by weight
Carbon (C)
less than/equal to 0.03
Silicon (Si)
less than/equal to 0.89
Manganese (Mn)
0.51 to 4.49
Chromium (Cr)
25.1 to 38.9
Molybdenum (Mo)
2.1 to 5.9
Nickel (Ni)
22.9 to 38.9
Copper (Cu)
0.51 to 1.49
Nitrogen (N)
0.17 to 0.29
Iron (Fe)
balance
and contaminants due to manufacture, which material is hot formed in a condition free of nitride precipitates and without precipitated associated phases and, after a cooling, cold formed in a condition free of ferrites, and having
a permeability of less than 1.0048
a yield strength (R
p0 2
) of more than 710 N/mm
2
a notched impact strength of over 60 J
a fatigue strength under reversed stresses of more than ±310 N/mm
2
at N=10
7
load reversal and
a fracture appearance transition temperature of less than −28° C. (FATT).
Accordingly, the present invention provides a material which is suitable for equipment in oilfield technology. This material consists essentially of the following elements, in percent by weight, ≦0.03 C; ≦0.89 Si; 0.51 to 4.49 Mn; 25.1 to 38.9 Cr; 2.1 to 5.9 Mo; 22.9 to 38.9 Ni; 0.51 to 1.49 Cu; and 0.17 to 0.29 N, with the balance iron and contaminants due to manufacture. The material is hot formed in a condition free of nitride precipitates and without precipitated associated phases. Moreover, after a cooling, the material is cold formed in a condition free of ferrites. The material has a relative magnetic permeability of less than 1.0048 &mgr;r, a yield strength (R
p0.2
) of higher than 710 N/mm
2
, a notched impact strength of higher than 60 J, a fatigue strength under reversed stresses of at least ±310 N/mm
2
at N=10
7
load reversal, and a fracture appearance transition temperature (FATT) of below −28° C.
In one aspect, the material contains any of the elements in the following weight percentages: C≦0.02, e.g., 0.01 to 0.02; Si≦0.75, e.g., 0.20 to 0.70; Mn 1.1 to 2.9, e.g., 2.01 to 2.6; Cr 26.1 to 27.9, e.g., 26.5 to 27.5 ;Mo 2.9 to 5.9, e.g., 3.2 to 3.8; Ni 27.9 to 32.5, e.g., 30.9 to 32.1; Cu 0.98 to 1.45, e.g., 1.0 to 1.4; and N 0.175 to 0.29, e.g., 0.18 to 0.22.
In another aspect, the material is hot formed at least 3.6-fold and/or cold formed with a degree of forming of less than 38%, e.g., 6 to 19%. In the case of cold forming, the forming temperature may be from 100 to 590° C., e.g., from 360 to 490° C. For example, the material may be hot formed at least 3.6-fold and cold formed with a degree of forming of 6 to 19% at a temperature ranging from 360 to 490° C.
In another aspect, the material has a pitting potential in a neutral solution at room temperature of more than 1,100 mVH/1,000 ppm chlorides and/or more than 1,000
The present invention also provides a drilling line component and a drill stem comprising the above material.
A further aspect of the present invention is represented by a process for making a material suitable for equipment in oilfield technology and having a relative magnetic permeability of less than 1.0048 &mgr;r, a yield strength (R
p0.2
) of higher than 710 N/mm
2
, a notched impact strength of higher than 60 J, a fatigue strength under reversed stresses of at least ±310 N/mm
2
at N=10
7
load reversal and a fracture appearance transition temperature (FATT) of below −28° C. The process comprises hot forming a material which consists essentially of, in percent by weight, ≦0.03 C; ≦0.89 Si; 0.51 to 4.49 Mn; 25.1 to 38.9 Cr; 2.1 to 5.9 Mo; 22.9 to 38.9 Ni; 0.51 to 1.49 Cu; and 0.17 to 0.29 N, with the balance iron and contaminants due to manufacture, in a condition free of nitride precipitates and without precipitated associated phases and, after a cooling, cold forming the material in a condition free of ferrites.
In one aspect, the material contains any of the elements in the following weight percentages: C≦0.02, e.g., 0.01 to 0.02; Si≦0.75, e.g., 0.20 to 0.70; Mn 1.1 to 2.9, e.g., 2.01 to 2.6; Cr26.1 to 27.9, e.g., 26.5 to 27.5;Mo 2.9 to 5.9, e.g., 3.2 to 3.8; Ni 27.9 to 32.5, e.g., 30.9 to 32.1; Cu 0.98 to 1.45, e.g., 1.0 to 1.4; and N 0.175 to 0.29, e.g., 0.18 to 0.22.
In another aspect, the process comprises hot forming the material at least 3.6-fold and/or cold forming it with a degree of forming of less than 38%, e.g., 6 to 19%. In the case of cold forming, the forming temperature may be from 100 to 590° C., e.g., from 360 to 490° C. For example, the material may be hot formed at least 3.6-fold and cold formed with a degree of forming of 6 to 19% at a temperature ranging from 360 to 490° C.
The advantages achieved by the invention lie in particular in the alloying technology effect of a balanced nitrogen concentration. Surprisingly, it was found that a particularly high output can be achieved in the manufacture of parts. Although there cannot be any nitride precipitates with a hot forming, the forming property of the material at a varying forging temperature is abruptly impaired at contents of over 0.29 percent by weight nitrogen. In the narrow concentration range of 0.17 to 0.29 percent by weight N a precipitation of associated phases can also be easily prevented if the other alloyin
Aigner Herbert
Bernauer Josef
Saller Gabriele
Choeller-Bleckmann Oilfield Technology GmbH & Co. KG
Greenblum & Bernstein P.L.C.
Yee Deborah
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