RU2552796C2 - High-strength drilling pipe - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, particularly, to structural steels for drilling pipes production. The pipe is made out of steel containing carbon, silicon, manganese, chromium, nickel, molybdenum, copper, titanium, boron, aluminium, sulphur, nitrogen, iron and inevitable admixtures at the following ratio of components, wt %: carbon 0.28-0.34, silicone 0.15-0.45, manganese 0.65-0.95, chrome 0.80-1.30, molybdenum 0.10-0.20, nickel max. 0.50, copper max. 0.30, titanium 0.015-0.045, boron 0.001-0.004, aluminium 0.015-0.050, sulphur max. 0.010, phosphorus max. 0.015, nitrogen max. 0.012, iron and inevitable admixtures are the rest.

EFFECT: pipe has ultimate strength at least 724 MPa, yield strength 655-1138 MPa, impact energy at 21°C at least 54 J, and at -20°C - at least 100 J.

3 tbl

Description

The invention relates to the field of metallurgy, namely to structural steels used in the manufacture of pipes, in particular drill.

Known steel grade 32XMA-3, used for the production of drill pipes with the following content (wt.%): Carbon 0.34; 0.95 manganese; silicon 0.45; chrome 1.00; molybdenum 0.60; nickel 0.50; copper 0.20; sulfur 0.007; phosphorus 0.015; aluminum 0,040 [Proceedings of the XIII international scientific-practical conference "Pipes-2005", 1 part. OJSC "RosNITI". 2005.S. 230-234].

The disadvantage of using this steel composition is that hardenability with a content of at least 90% martensite in the microstructure is achieved only up to a wall thickness of 24 mm, as well as an increase in the cost of a drill pipe made from this composition due to the additional expensive alloying of steel with molybdenum.

For the production of drill pipes, Sinarsky Pipe Plant OJSC uses 32KhGMA grade steel with the following content (wt.%): Carbon 0.31-0.34; silicon 0.30-0.45; chromium 0.95-1.10; molybdenum 0.30-0.40; nickel no more than 0.25; copper no more than 0.20; sulfur not more than 0.010; phosphorus no more than 0.015; aluminum 0.015-0.045 [Technical conditions No. 0913-180-00186269-2012 "Billet pipe made of carbon, low alloy and alloy steel"].

The main disadvantage of this composition is the increase in the cost of the drill pipe due to unreasonable alloying with molybdenum, the introduction of which in this amount does not provide hardenability on thick-walled pipes.

Closest to the claimed invention is steel, having the following ratio of components (wt.%):

carbon 0.31-0.34,

silicon 0.30-0.45,

manganese 0.75-0.95,

niobium 0.045-0.100,

vanadium 0.001-0.080,

boron 0.002-0.004,

aluminum 0.005-0.006,

titanium 0.010-0.045,

chrome 1.10-1.50,

sulfur 0.001-0.045,

phosphorus 0.001-0.045,

nitrogen not more than 0.012,

nickel no more than 0.50,

copper no more than 0.20;

the rest is iron;

when the content of the sum [chromium] + [vanadium] + [niobium] equal to 1.15-1.70%, (US Pat. RF No. 2352647, publ. 04/20/2009).

The disadvantage of this composition is the possibility of using the composition only for pipes with a wall thickness of not more than 27 mm. In addition, boron in an amount of 0.002-0.004% has a negative effect on hardenability with an increase in austenitization temperature due to an increase in its solubility and the release of an excess boron-containing phase along austenite grain boundaries, which leads to a decrease in the visco-plastic properties in high strength due to embrittlement the effects of a boron-containing phase at grain boundaries. And the introduction of strong carbide-forming elements, such as vanadium 0.001-0.080%, niobium 0.045-0.100%, requires elevated heating temperatures during austenitization.

The technical problem to which the claimed invention is directed is to increase hardenability, equal strength of metal over the cross section and the entire length of the finished product, increase the visco-plastic properties of the metal, produce drill pipes with a wall thickness of more than 27 mm (for example, 35 mm) with achievement of the level of strength properties (tensile strength of at least 724 MPa and yield strength of 655 to 1138 MPa) and impact work (at a temperature of 21 ° C of at least 54 J, at a temperature of minus 20 ° C of at least 100 J), corresponding to the strength groups E, L, M , P (E, X, G, S API Spec 5DP / ISO 11961).

This result is achieved in that the drill pipe made of steel containing carbon, silicon, manganese, chromium, molybdenum, nickel, copper, titanium, boron, aluminum, sulfur, phosphorus, nitrogen, iron and inevitable impurities, characterized in that it made of steel containing components in the following ratio, wt. %:

carbon 0.28-0.34 silicon 0.15-0.45 manganese 0.65-0.95 chromium 0.80-1.30 molybdenum 0.10-0.20 nickel no more than 0.50 copper no more than 0.30 titanium 0.015-0.045 boron 0.001-0.004 aluminum 0.015-0.050 sulfur no more than 0,010 phosphorus no more than 0.015 nitrogen no more than 0,012

iron and the inevitable impurities are the rest, while it has a tensile strength of at least 724 MPa, a yield strength of 655-1138 MPa, a shock at 21 ° C of at least 54 J and a shock at -20 ° C of at least 100 J.

The technical result provided by the selected ratio of individual chemical elements in steel is determined by the following factors.

Carbon (0.28-0.34) is introduced to achieve high hardenability and, consequently, equal strength in the cross section of the product, since with additional alloying with manganese, chromium, molybdenum, boron and under conditions of quenching in water, the carbon content should be regulated to avoid occurrence quenching cracks.

Manganese (0.65-0.95) provides high strength in addition to the deoxidizing effect of steel. With the introduction of manganese more than 1.0%, the visco-plastic properties of steel deteriorate.

Chromium (0.80-1.30) has a positive effect on increasing hardenability, which is manifested with a certain minimum content in steel, usually in the range from 1.10% to 1.50%. Chromium has even greater influence in the presence of strong carbide-forming elements, such as molybdenum, titanium, due to an increase in its content in solid solution during austenitization.

Boron (0.001-0.004) has a positive effect on the hardenability of steel. When the boron content is more than 0.005%, the visco-plastic properties of the steel deteriorate due to the release of an excess boron-containing phase along the austenite grain boundaries. Thus, the optimal doping range for boron is 0.001-0.004%.

Molybdenum (0.10-0.20) is introduced in the specified amount, based on the fact that when complexed with boron additives, the amount of molybdenum is required significantly less than is usually required to ensure the strength and visco-plastic properties of products during quenching and low temperature tempering (in the case of medium-carbon chromium-manganese steel, the molybdenum content should be at least 0.30%, and the upper content is limited to 0.80%, in order to exclude the formation of coarse carbides along the boundaries of austenite grains, leading to the opposite mu effect - a decrease in visco-plastic properties).

The transition temperature of molybdenum into a solid solution during austenitization is significantly lower than for niobium and vanadium, which eliminates the need to heat the product to high temperatures during quenching to achieve a positive effect on the hardenability of steel.

Titanium (0.015-0.045) fixes nitrogen in steel in the form of nitrides and ensures the presence of boron in the active form, that is, in the solid solution during quenching, which is required to achieve high hardenability. To obtain these effects, the introduction of titanium, at least at the level of 0.005%. An upper titanium limit is necessary to prevent the formation of large nitrides in the structure.

In the conditions of the Sinarsky Pipe Plant, pipes were made from the known and proposed in the invention steel. Pipes with a wall thickness of more than 27 mm were manufactured at the plant, in particular with a wall of 35 mm.

The results of industrial production of the proposed pipe in comparison with known pipes (including the prototype) are shown in table 1 - chemical composition options, table 2 - study of the stability of supercooled austenite and hardenability, table 3 - mechanical properties.

As can be seen from the results of the study, the achieved hardenability level and mechanical properties of the drill pipe made of the proposed steel make it effective to use them in high strength after heat hardening by means of quenching and tempering in accordance with domestic regulatory documents and the international standard API Spec 5DP / ISO 11961.

The proposed solution of complex alloying with boron and molybdenum in small amounts of 0.10-0.20% steel allows to reduce the cost of pipes to 20% in comparison with the known solution for the use of steel pipes with molybdenum to 0.65%.

Claims (1)

A drill pipe made of steel containing carbon, silicon, manganese, chromium, molybdenum, nickel, copper, titanium, boron, aluminum, sulfur, phosphorus, nitrogen, iron and inevitable impurities, characterized in that it is made of steel containing components in the following ratio, wt.%:
carbon 0.28-0.34 silicon 0.15-0.45 manganese 0.65-0.95 chromium 0.80-1.30 molybdenum 0.10-0.20 nickel no more than 0.50 copper no more than 0.30 titanium 0.015-0.045 boron 0.001-0.004 aluminum 0.015-0.050 sulfur no more than 0,010 phosphorus no more than 0.015 nitrogen no more than 0,012 iron and inevitable impurities rest,
however, it has a tensile strength of at least 724 MPa, a yield strength of 655-1138 MPa, impact at 21 ° C of at least 54 J and impact at -20 ° C of at least 100 J.