Drill string component with high corrosion resistance, and method for the production of same

Abstract

A drill string component, in particular a drilling collar component, an MWD component, or an LWD component for use in oilfield technology and particularly in deep drilling, is provided. A method of making a drill string component, and a steel alloy useful in making a drill string component, are also provided.

Claims

1. A drill string component, comprising an alloy including the following elements in percent by weight: TABLE-US-00007 Elements Carbon (C) 0.01-0.10 Silicon (Si) <0.5 Manganese (Mn) 5.0-6.0 Phosphorus (P) <0.05 Sulfur (S) <0.005 Chromium (Cr) 26.0-28.0 Molybdenum (Mo) 2.5-3.5 Nickel (Ni) 13.0-15.0 Vanadium (V) below detection level Tungsten (W) below detection level Copper (Cu) <0.1 Cobalt (Co) below detection level Titanium (Ti) below detection level Aluminum (Al) <0.1 Niobium (Nb) below detection level Boron (B) <0.01 Nitrogen (N) 0.54-0.80 Iron (Fe) and inevitable impurities residual.

2. The drill string component according to claim 1, wherein the alloy comprises the copper in an amount of greater than zero.

3. The drill string component according to claim 1, wherein the drill string component is produced by a method that includes secondary metallurgical processing of the alloy, casting the alloy into blocks immediately followed by hot forging, cold forming the alloy, and optionally subjecting the alloy to further mechanical processing.

4. The drill string component according to claim 3, wherein after the cold forming, the alloy has a magnetic permeability r of less than about 1.01.

5. The drill string component according to claim 3, wherein the method further comprises strain hardening the alloy, wherein after the strain hardening, the alloy has a yield strength R.sub.p0.2 of greater than about 1000 MPA.

6. The drill string component according to claim 5, wherein after the strain hardening, the alloy has a notched bar impact work at 20 C. of greater than about 80 J.

7. The drill string component according to claim 3, wherein after the cold forming, the alloy is fully austenitic.

8. A method for producing a drill string component, comprising the steps of: providing an alloy including the following elements in percent by weight: TABLE-US-00008 Elements Carbon (C) 0.01-0.10 Silicon (Si) <0.5 Manganese (Mn) 5.0-6.0 Phosphorus (P) <0.05 Sulfur (S) <0.005 Chromium (Cr) 26.0-28.0 Molybdenum (Mo) 2.5-3.5 Nickel (Ni) 13.0-15.0 Vanadium (V) below detection level Tungsten (W) below detection level Copper (Cu) <0.1 Cobalt (Co) below detection level Titanium (Ti) below detection level Aluminum (Al) <0.1 Niobium (Nb) below detection level Boron (B) <0.005 Nitrogen (N) 0.54-0.80 Iron (Fe) and inevitable impurities residual; melting the alloy: subjecting the alloy to secondary metallurgical processing: casting the alloy into blocks; solidifying the alloy: heating and immediately hot forming the alloy; cold forming the alloy.

9. The method according to claim 8, wherein the hot forming comprises a plurality of sub-steps.

10. The method according to claim 9, further comprising reheating the alloy in between the hot forming sub-steps and after a last of the hot forming sub-steps and solution annealing the alloy after the last hot forming sub-step.

11. A steel alloy useful in forming a drill string component, comprising the following elements in percent by weight: TABLE-US-00009 Elements Carbon (C) 0.01-0.10 Silicon (Si) <0.5 Manganese (Mn) 5.0-6.0 Phosphorus (P) <0.05 Sulfur (S) <0.005 Chromium (Cr) 26.0-28.0 Molybdenum (Mo) 2.5-3.5 Nickel (Ni) 13.0-15.0 Vanadium (V) below detection level Tungsten (W) below detection level Copper (Cu) <0.1 Cobalt (Co) below detection level Titanium (Ti) below detection level Aluminum (Al) <0.1 Niobium (Nb) below detection level Boron (B) <0.01 Nitrogen (N) 0.54-0.80 Iron (Fe) and inevitable impurities residual.

12. The steel alloy of claim 11, wherein the alloy comprises a superaustenite having a PREN.sub.16 of >42, where PREN=% Cr+3.3% Mo+16% N.

13. The steel alloy of claim 11, wherein the alloy has a magnetic permeability r of less than about 1.01.

14. The steel alloy of claim 13, wherein the magnetic permeability r is less than about 1.005.

15. The steel alloy of claim 11, wherein the steel alloy has a yield strength R.sub.p0.2 greater than about 500 MPa.

16. The steel alloy of claim 15, wherein the yield strength R.sub.p0.2 is greater than about 1000 MPa.

17. The steel alloy of claim 11, wherein the steel alloy has a tensile strength Rm of at least about 1100 MPa.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention will be explained by way of example based on the drawing. In the drawing:

(2) FIG. 1 shows a very schematic depiction of the production route.

DETAILED DESCRIPTION OF THE INVENTION

(3) In accordance with the invention, the components shown in Table 1 are melted under atmospheric conditions and then undergo secondary metallurgical processing. Then, blocks are cast, which are hot forged immediately afterward. In the context of the invention, immediately means that no additional remelting process such as electroslag remelting (ESR) or pressure electroslag remelting (PESR) is carried out.

(4) TABLE-US-00004 TABLE 1 Alloy Components Alloying Composition More element range Preferred preferred Carbon (C) 0.01-0.25 0.01-0.2 0.01-0.1 Silicon (Si) <0.5 <0.5 <0.5 Manganese (Mn) 3.0-8.0 4.0-7.0 5.0-6.0 Phosphorus (P) <0.05 <0.05 <0.05 Sulfur (S) <0.005 <0.005 <0.005 Iron (Fe) residual residual residual Chromium (Cr) 23.0-30.0 24.0-28.0 26.0-28.0 Molybdenum (Mo) 2.0-4.0 2.5-3.5 2.5-3.5 Nickel (Ni) 10.0-16.0 12.0-15.5 13.0-15.0 Vanadium (V) <0.5 <0.3 below detection level Tungsten (W) <0.5 <0.1 below detection level Copper (Cu) <0.5 <0.15 <0.1 Cobalt (Co) <5.0 <0.5 below detection level Titanium (Ti) <0.1 <0.05 below detection level Aluminum (Al) <0.2 <0.1 <0.1 Niobium (Nb) <0.1 <0.025 below detection level Boron (B) <0.01 <0.005 <0.005 Nitrogen (N) 0.50-0.90 0.52-0.85 0.54-0.80 All values expressed in % by weight

(5) With the alloy according to the invention, it is advantageous that a homogenization annealing or remelting is not necessary.

(6) FIG. 1 shows an example of the possible processing routes for the production of the alloy composition according to the invention. One possible route will be described below by way of example. In the vacuum induction melting unit (VID), molten metal simultaneously undergoes melting and secondary metallurgical processing. Then the molten metal is poured into ingot molds and in them, solidifies into blocks. These are then hot formed in multiple steps. For example, they are pre-forged in the P52 forging press and are brought into their final dimensions in the rotary forging machine. Depending on the requirements, a solution annealing step and/or water cooling can also be performed.

(7) In order to establish the final properties, the cold forming is performed in a rotary forging machine and the parts produced in this way then undergo further processing.

(8) After the last hot forming sub-step, a rapid cooling to room temperature is carried out. With this special processing step, critical temperature ranges are passed through quickly and the formation of grain boundary precipitations is prevented. In the product according to the invention, it is clear that for example chromium nitride precipitations occur to a significantly lower degree, which influences the corrosion properties in an optimal way. Then the cold forming steps are carried out in which a strain hardening takes place. The degree of deformation in this case is between 10 and 50%.

(9) According to the invention, it is advantageous if the following relation applies:
MARC.sub.opt:40<wt % Cr+3.3wt % Mo+20wt % C+20wt % N0.5wt % Mn

(10) The MARC formula is optimized to such an effect that it has been discovered that the otherwise usual removal of nickel does not apply to the system according to the invention and the limit of 40 is required.

(11) Then the required cold forming steps are carried out in which a strain hardening takes place, followed by the mechanical processing, which in particular can be a turning or peeling.

(12) A superaustenitic material according to the invention can be produced not only by means of the production routes described (and in particular shown in FIG. 2), the advantageous properties of the alloy according to the invention can also be achieved by means of a production route using powder metallurgy.

(13) Table 2 shows three different variants within the alloy compositions according to the invention, with the respectively measured nitrogen values, which have been produced with the method according to the invention in connection with the alloys according to the invention. The resulting actual values of the nitrogen content are compared to the theoretical nitrogen solubility of such an alloy according to the prevailing school of thought. These very high nitrogen concentrations contrast with the nitrogen solubility indicated in the columns on the right according to Stein, Satir, Kowandar, and Medovar from On restricting aspects in the production of non-magnetic CrMnN-alloy steels, Saller, 2005. In Medovar, different temperatures are indicated. It is clear, however, that the high nitrogen values far exceed the theoretically expected values.

(14) TABLE-US-00005 TABLE 2 Examples of Alloy Compositions Chemical composition (percentage by weight)/residual Fe Ex. C Si Mn Cr Mo Ni V W* Cu Co* Ti* Al* Nb* N** A 0.01 0.4 5.0 23.01 3.1 15.98 0.05 0 0.15 0 0 0 0 0.51 B 0.01 0.4 5.0 27 3.1 14 0.05 0 0.10 0 0 0 0 0.7 C 0.01 0.4 5.0 24 3.1 14 0.05 0 0.10 0 0 0 0 0.55 N solubility [% N]*** Pressure Medovar at temperature: [atm] Stein Satir Kowanda 1550 C. 1525 C. 1500 C. 1450 C. A 1.00 0.36 030 0.34 0.34 0.35 0.36 0.39 B 1.00 0.61 0.41 0.65 0.47 0.49 0.51 0.56 C 1.00 0.44 0.34 0.45 0.38 0.40 0.41 0.45 *Values are below the detectable level **Actual Value N ***Calculated values for N according to different methods (Source: On Restricting Aspects in the Production of Nomagnetic CrMnNi-Alloyed Steels, Saller, 2005)

(15) This is even more astonishing since with the alloy according to the invention, a route was taken that does not justify the expectation of such a high nitrogen solubility, particularly because the manganese content, which has a very positive influence on the nitrogen solubility, is sharply reduced compared to known corresponding alloys.

(16) In Table 3, the three alloys from Table 2 were produced using a method according to the invention and have undergone a strain hardening.

(17) TABLE-US-00006 TABLE 3 Mechanical Properties of the alloys produced from Table 2 after strain hardening Charpy V notch impact Rp 0.2 Rm A4 strength Rm * KV Alloy [MPa] [MPa] [%] [Joule] [MPa J] A 969 1111 30 271 301303 B 1171 1231 27 290 357236 C 1124 1207 26 329 370588

(18) After this strain hardening, in all three materials, R.sub.p0.2 was approximately 1000 MPa and the tensile strength Rm of each was between 1100 MPa and 1250 MPa. In addition, the notched bar impact work was in the outstanding range from 270 J to even greater than 300 J (alloy C-329.5 J).

(19) It was thus possible to achieve an outstanding combination of strength and toughness; in all three examples, the product of Rm*KV was greater than 300000 MPa J.

(20) The invention therefore has the advantage that a drilling collar alloy with an increased corrosion resistance and low nickel content has been produced, which simultaneously exhibits high strength and paramagnetic behavior. Even after the cold forming, a fully austenitic structure is present, with a magnetic permeability .sub.r<1.005 so that it has been possible to successfully combine the positive properties of an inexpensive chromium-manganese-nickel steel with the technically outstanding properties of a chromium-nickel-molybdenum steel.