JPH09227939A - Mechanical treatment for slender-shaped product made of non-magnetic austenitic steel and particularly drill collar for oil well boring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply mechanical treatment to a slender-shaped product made of non-magnetic austenitic steel and to improve the mechanical properties of the product without deteriorating its corrosion resistance.

SOLUTION: A product 1 is made of non-magnetic austenitic steel. This non-magnetic austenitic steel contains, by weight, <0.08% carbon, 12-20% chromium, 17-22% manganese, and 0.15-0.35% nitrogen. The product 1 is stretched out at a temp. lower than 400°C in order to improve its properties and, as a result, the permanent elongation of the product 1 after this treatment becomes greater than 20%. This treatment is applicable, in particular, to the treatment of solid bar steels or tubular parts at the time of producing a drill collar for boring an oil well.

COPYRIGHT: (C)1997,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mechanically processing elongated shaped products made of non-magnetic austenitic steel. The invention is particularly concerned with mechanical properties for improving the mechanical properties of non-magnetic drill collars for oil drilling or of blanks used for producing non-magnetic drill collars. Regarding processing method.

[0002]

BACKGROUND OF THE INVENTION In the field of petroleum boring it is known to use drill collars, i.e. tubular elements or stems of large drill pipes, such drill collars in particular at the bottom of a borehole. Manufactured in non-magnetic form so as not to interfere with the measured measurements.

Such a non-magnetic drill collar has a diameter of 0.
Less than 08% carbon, 12 to 20% chromium, 17
Manufactured by using a non-magnetic austenitic chromium manganese steel containing .about.22% manganese, 0.15 to 0.35% nitrogen, less than 1.5% nickel and less than 2% molybdenum. It is known that

Such non-magnetic austenitic steels have the satisfactory property of corrosion resistance, in particular of chloride corrosion, which, by virtue of their properties, leads to a very diverse range of properties. As an element consisting of a series of pipes or stems for boring,
This makes it possible to use non-magnetic austenitic steel.

Further, the austenitic chromium manganese steels of the type described above can exhibit high mechanical properties when subjected to some treatment during the manufacture of the drill collar or after subsequent manufacture.

In the conventional method, a non-magnetic austenitic chrome manganese steel is cast and then rolled or forged into a certain shape to obtain a bar having a circular cross section. Such rolled or forged steel bar is subjected to hyperquenching and then machined into the form of a blank of a drill collar with good dimensional properties.

Non-magnetic austenitic chromium manganese steels are usually inadequate in the hyperquenched state and are much inferior to the mechanical properties that steels can obtain by work hardening. Shows the typical properties.

[0008] Therefore, the blank of the drill collar in the hyperquenched state is subjected to a work hardening treatment (semi-heat work hardening) at a moderate temperature, and this treatment results in a machine with high hyperquenched steel. It becomes possible to exert the characteristic. Generally, semi-heat work hardening is 7
It is obtained by forging a blank of a drill collar with a good deformation ratio at a temperature of 50 to 650 ° C.

The above method has the advantage that it can be carried out using conventional forging means (presses and tools),
These means are usually available in large forging equipment.

However, a method for improving the mechanical properties of non-magnetic austenitic steels by work hardening at moderate temperatures is disclosed by the carbides and carbonitrides of metals such as chromium, niobium and titanium at the boundaries of austenite crystals. It has the drawback of promoting precipitation and causing such precipitation, which promotes grain boundary type corrosion when the drill collar is used in a boring operation.

In fact, the forging operation for improving the mechanical properties of steel is carried out in the temperature range (650-750 ° C.) at which chromium, niobium or titanium carbides and carbonitrides are formed.

Further, it is known to improve the mechanical properties of austenitic chromium manganese steel by work hardening the steel at a low temperature such as room temperature.

Such cold work hardening processes have been applied and used in the case of elongated shaped products such as drill collars or blanks for making drill collars.

[0014]

Accordingly, it is an object of the present invention to have less than 0.08 wt% carbon and 12 to 20 wt% carbon.
Chromium, 17 to 22% by weight manganese, 0.1
A method for mechanically treating an elongated product made of a non-magnetic austenitic steel containing 5 to 0.35% by weight of nitrogen and improving the mechanical properties of the product without impairing its corrosion resistance. Is to provide.

[0015]

In order to achieve the above object, the product is stretched at a temperature below 400 ° C. so that the permanent elongation of the product after the above treatment is greater than 20%.

[0016]

To illustrate the invention, by way of non-limiting example, one embodiment of carrying out the mechanical processing method of the invention used in the manufacture of drill collars made of non-magnetic steel. Will be described below with reference to the drawings. Embodiments of the method of the invention relate to the manufacture of drill rods made of non-magnetic austenitic steel SMF166. The prepared and cast steel contains less than 0.035% carbon, less than 1% silicon, 20-22% manganese, 12-13%.
Chromium, 0.3 to 0.5% molybdenum, and
25 to 0.45% nickel and 0.28 to 0.3
6% nitrogen, less than 0.05% aluminum, 0.
It contains less than 03% phosphorus and less than 0.003% sulfur.

The cast steel is rolled into a bar having a circular cross section and then hyperquenched. Non-magnetic austenitic steels have a yield strength between 450 MPa and 500 MPa in the hyperquenched state. As shown, the hyperquenched blank is then subjected to the stretching process of the present invention. A hyperquenched austenitic steel blank 1 is mounted on a draw table, generally designated by the reference numeral 2.

The blank 1 made of non-magnetic steel has a cylindrical central portion and two end portions 1a and 1b, the diameters of which are larger than the diameter of the central portion. The end portions 1a and 1b of the blank 1 are used to attach the steel bar 1 to the draw table 2.

The extension table 2 is provided with a frame having two parts having symmetrical shapes, and the steel bar 1 is attached between the two parts. Each of the above parts of the frame (left and right) comprises a longitudinal beam 3 and
It has a first horizontal beam 4a and a second horizontal beam 4b. At least one stretching cylinder or ram 5 is interposed between one of the horizontal beams 4a and one end of the longitudinal beam 3. The other end of the longitudinal beam 3 is in pressure contact with the second horizontal beam 4b. Horizontal beams 4a, 4
b comes into pressure contact with the enlarged diameter end portions 1a, 1b of the rod or steel bar 1 via thrust members as indicated by reference numerals 6a, 6b. A single cylinder or a plurality of cylinders can be inserted between the lower horizontal beam 4a and the longitudinal beam 3.

The frame of the draw platform can be provided with one or more longitudinal beams, such as beam 3, on either side of its longitudinal component. The beam of the frame of the stretcher can be made of concrete or steel.

Thrust members, such as 6a and 6b, are usually formed as two pieces in the form of a semi-ring,
These parts are composed of a steel bar 1 having an enlarged diameter 1a, 1
They are provided in contact with each other while being pressed against b. The horizontal beams 4a and 4b are constructed as annular members which can be engaged around the ends of the steel bar 1 and thrust members 6a and 6b can be provided in the members. It is also possible to use a very large single cylinder or ram having an annular structure in which the steel bar 1 to be drawn is engaged.

As another embodiment, as shown in FIG.
It is possible to stretch a steel bar 1 ′ whose end portion, such as 1′b, does not have a diameter much larger than the diameter of the central portion. In this case, an opening that diverges outward,
A horizontal beam as shown at 4'b having a gripping device for gripping the end of the steel bar 1'such as 6'b can be used, the gripping device gripping the end part of the steel bar 1 '. It has the shape of a wedge with internal teeth to improve its functioning. The force exerted by the cylinder on the steel bar 1 to be stretched is determined using data or curves relating to work hardening or strain hardening of an austenitic chromium manganese steel.

In the case of the steel having the above composition, the yield strength in the hyperquenched state is 450.
It is from MPa to 500 MPa. The yield strength reaches 900 MPa when the steel is stretched to have a permanent set of 25%. If the steel was stretched to have a permanent set of 28%, the yield strength would be 9
It is from 50 MPa to 1,000 MPa. The maximum value of the force (maximum force) to be applied during the stretching operation is determined depending on the yield strength to be reached and the cross section of the austenitic steel bar.

After the steel bar to be stretched is attached to the stretching table 2 as shown in FIG. 1, the stretching force is gradually generated by the cylinder 5 to reach the maximum force determined as described above. Room temperature is 2
It is performed at a temperature around 0 ° C. To carry out the method, stretching operations can be carried out at temperatures above room temperature, but such stretching temperatures must be below 400 ° C. When the permanent strain of the steel bar 1 to be stretched reaches a predetermined value, the stretching force applied by the cylinder 5 is released, and the steel bar 1 is removed and removed from the stretching table.

Next, the yield strength, strength and hardness of the steel bar 1 reach values sufficiently higher than the values reached after the hyper-quenching treatment. At elongations near 30%, the yield strength of the steel is effectively doubled.

The steel bar 1 constituting the blank is then machined, in particular drilled, into the form of a drill collar of standard dimensions. The mechanical properties of the drill collar, which are very significantly improved, are obtained by pure mechanical treatment at room temperature or very mild temperature, during which mechanical treatment of carbides or carbonitrides occurs in the steel. No material is formed and thus the corrosion resistance of the austenitic steel is not impaired during processing. That is, since no carbides or carbonitrides are precipitated at the crystal grain boundaries, the obtained austenitic steel has high mechanical strength and hardly causes grain boundary type corrosion.

Further, the work of stretching an elongated product such as a steel bar is performed over the entire cross-sectional area and length of the product.
It is carried out with a very homogeneous distribution of stress and strain. Thus, the mechanical property improvement achieved is substantially constant over the portion of the product that has undergone the stretching operation.

Furthermore, the method of the present invention is considerably faster than the methods which require forging the product at temperatures on the order of 700 ° C. There is no intention to limit the scope of the invention to the embodiments described above. Thus, the elongated product made of austenitic steel can be stretched by a device different from the stretching table shown in FIG.

The permanent set of the product after the stretching operation can be varied depending on the mechanical properties required for the steel to be treated. However, in order to sufficiently improve the mechanical properties of the steel, the stretching operation must be carried out such that the stretched product has a permanent set of at least 20%. Usually, the permanent elongation of the product during the above-mentioned treatment will be limited to a value of 30%, as an elongation of 25% to 28% can be considered particularly effective.

The method applies not only to solid steel bars having a circular cross section which constitutes a blank for producing a drill collar, but also to solid steel bars having any cross section or shape. be able to. The method also
It can also be applied to the treatment of tubular parts, for example drills obtained for the treatment of hollow blanks for producing drill collars or by machining solid steel bars or tubular blanks. It can be applied to the color itself.

In general, the method is used for petroleum boring,
It can be employed to manufacture any tubular element used for mine boring or water exploration.

[Brief description of drawings]

1 is an elevational view in partial section showing a stretching device used to carry out the treatment method of the invention on a drill rod blank for petroleum boring.

FIG. 2 is a partial elevational view showing a partial cross-section of another structure of one end of the stretching device.

[Explanation of symbols]

 1, 1'Blank (bar steel) 1a, 1b Blank end portion 1'b Blank end portion 2 Extending table 3 Longitudinal beam 4a, 4b Horizontal beam 4'b Horizontal beam 6a, 6b Thrust member 6 'b gripping device

Claims (8)

[Claims] 1. A method of mechanically treating an elongated shaped product made of non-magnetic austenitic steel, comprising less than 0.08% by weight carbon, 12 to 20% by weight chromium.
A method for improving the mechanical properties of a product, the method comprising the steps of: containing about 22% by weight to 22% by weight of manganese and 0.15 to 0.35% by weight of nitrogen. A method of mechanical treatment, characterized by stretching, whereby the permanent elongation of the treated product is greater than 20%. 2. The mechanical processing method according to claim 1, wherein the product is stretched at room temperature of about 20 ° C. 3. The mechanical treatment method according to claim 1, wherein the permanent elongation of the product after the treatment is 20% and 3%.
The mechanical treatment method is characterized in that it is between 0%. 4. The mechanical treatment method according to claim 3, wherein the permanent elongation of the product after the treatment is between 25% and 28%. 5. The mechanical treatment method according to claim 1, wherein the non-magnetic austenitic steel is 0.03.
Less than 5% by weight carbon, less than 1% by weight silicon, 20
To 22% by weight manganese, 12 to 13% by weight chromium, 0.3 to 0.5% by weight molybdenum,
25 to 0.45 wt% nickel, 0.28 to 0.35 wt% nitrogen, less than 0.05 wt% aluminum, less than 0.03 wt% phosphorus and less than 0.003 wt% A mechanical treatment method characterized by containing sulfur. 6. The mechanical processing method according to claim 1, wherein the elongated product is a solid steel bar having a circular cross section that constitutes a blank for producing a drill collar. Characteristic mechanical processing method. 7. The mechanical treatment method according to claim 1, wherein the elongated product is a drill collar blank for boring or a tubular drill collar blank. Mechanical processing method. 8. The mechanical treatment method according to claim 1, wherein the elongated product is stretched in a hyperquenched state.