阅读说明：本技术 一种高强高韧电阻焊石油套管用钢及套管的制造方法 (High-strength high-toughness electric resistance welding petroleum casing steel and casing manufacturing method ) 是由 黄明浩 黄国建 王杨 孔祥磊 张英慧 于 2021-06-28 设计创作，主要内容包括：本发明一种高强高韧电阻焊石油套管用钢及套管的制造方法,钢中化学成分按重量百分比计为：C0.19％-0.22％、Si0.25％-0.40％、Mn1.30％-1.50％、P≤0.015％、S≤0.006％、Nb0.02％-0.04％、V0.03％-0.045％、Ti0.010％-0.030％、Cr0.10％-0.19％、Als0.02％-0.05％、N≤0.008％,其余为Fe和不可避免元素。本发明的有益效果是：采用Nb-V-Cr复合强化设计,具有良好冲击韧性的P110级HFW石油套管钢及其制造方法。(The invention relates to a high-strength high-toughness electric resistance welding petroleum casing steel and a manufacturing method of a casing, wherein the steel comprises the following chemical components in percentage by weight: 0.19 to 0.22 percent of C, 0.25 to 0.40 percent of Si, 1.30 to 1.50 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.006 percent of S, 0.02 to 0.04 percent of Nb0.03 to 0.045 percent of V, 0.010 to 0.030 percent of Ti, 0.10 to 0.19 percent of Cr0.02 to 0.05 percent of Als0.008 percent of N, and the balance of Fe and inevitable elements. The invention has the beneficial effects that: adopts Nb-V-Cr composite reinforcement design, has good impact toughness, and is P110 grade HFW petroleum casing steel and a manufacturing method thereof.)

1. The steel for the high-strength high-toughness electric resistance welding petroleum casing pipe is characterized by comprising the following chemical components in percentage by weight: 0.19 to 0.22 percent of C, 0.25 to 0.40 percent of Si, 1.30 to 1.50 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.006 percent of S, 0.02 to 0.04 percent of Nb, 0.03 to 0.045 percent of V, 0.010 to 0.030 percent of Ti, 0.10 to 0.19 percent of Cr, 0.02 to 0.05 percent of Als, less than or equal to 0.008 percent of N, and the balance of Fe and inevitable elements.

2. A method for manufacturing a high-strength high-toughness electric resistance welded oil casing pipe, wherein the oil casing pipe is manufactured from the steel for a high-strength high-toughness electric resistance welded oil casing pipe according to claim 1, the method comprising:

1) the rolling process comprises the following steps: heating the continuous casting plate blank to 1050-;

2) the steel strip is subjected to high-frequency or medium-frequency resistance welding by an ERW unit to be made into a steel pipe;

3) the whole pipe quenching and tempering heat treatment process comprises the following steps: after ERW pipe making, heating the whole pipe to 850-; then heating the whole tube to 500-550 ℃, preserving the heat for 50-70min, and tempering at the cooling speed of 5-10 ℃/s.

3. The method for manufacturing the high-strength high-toughness electric resistance welded petroleum casing pipe as claimed in claim 2, wherein the yield strength of the hot-rolled steel strip is 460-550MPa, the tensile strength is 590-630MPa, and the microstructure is ferrite-pearlite.

4. The method for manufacturing the high-strength high-toughness resistance-welded petroleum casing pipe as claimed in claim 2, wherein the yield strength of the whole pipe after tempering is 800-880MPa, the tensile strength is 900-960MPa, the elongation is 25% -30%, and the 0 ℃ transverse Charpy impact power Akv is not less than 100J.

Technical Field

The invention relates to the technical field of petroleum casing pipe manufacturing, in particular to high-strength high-toughness electric resistance welding steel for petroleum casing pipes and a manufacturing method of the casing pipes, and particularly relates to high-toughness ERW petroleum casing pipe steel with a steel grade of P110 in API SPEC 5CT and with impact power greater than 86J and a manufacturing method of the high-toughness ERW petroleum casing pipe steel.

Background

The petroleum casing pipe is one of the most common special petroleum pipes in oil fields, has large consumption and much cost, and is an essential construction material in drilling and production operations of oil and gas fields. Compared with a seamless pipe, the HFW casing has the remarkable advantages of uniform wall thickness, high size precision, good perforation performance, strong collapse resistance, low cost and the like, and gradually replaces the traditional seamless steel pipe.

At present, many oil fields in China are developed in the middle and later stages, the development difficulty is more and more high, and especially, the deep well has higher requirements on the mechanical property of the casing pipe on higher strength and higher toughness. Therefore, it is urgent to develop a high-strength and high-toughness straight-seam electric resistance welding sleeve. The traditional theory holds that the strength and the toughness of steel usually show a mutual negative relationship, and the steel with high strength often has low toughness, and conversely, the strength of the steel must be sacrificed in pursuit of high toughness. The high-strength casing pipe needs to be matched with extremely high toughness, and is always a hot point of research. According to the technical document published by the british department of energy, the transverse notch impact energy of the steel pipe should be higher than 1/10 for the tensile strength.

Disclosure of Invention

The invention aims to provide high-strength high-toughness electric resistance welding steel for petroleum casing pipes and a manufacturing method of the casing pipes, in particular to P110-grade HFW petroleum casing pipe steel which adopts Nb-V-Cr composite reinforcement design and has good impact toughness and the manufacturing method of the steel.

In order to achieve the purpose, the invention adopts the following technical scheme:

the steel for high-strength high-toughness electric resistance welding petroleum casing pipe comprises the following chemical components in percentage by weight: 0.19 to 0.22 percent of C, 0.25 to 0.40 percent of Si, 1.30 to 1.50 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.006 percent of S, 0.02 to 0.04 percent of Nb0.03 to 0.045 percent of V, 0.010 to 0.030 percent of Ti, 0.10 to 0.19 percent of Cr, 0.02 to 0.05 percent of Als, less than or equal to 0.008 percent of N, and the balance of Fe and inevitable elements.

C: is a carbide forming element, is the most effective element for ensuring the strength, can improve the hardenability and ensure the material strength during high-temperature tempering. The carbon content has a significant influence on the carbon content and the volume fraction of the final austenite, martensite. Only if sufficient carbon is ensured will sufficient carbon-rich retained austenite be formed and be able to stabilize to room temperature. If the carbon content is low, in order to achieve a P110 grade after hardening and tempering, a large amount of alloy elements need to be added to improve hardenability and increase alloy cost. Therefore, the carbon content should not be too low, but too high will affect the weldability and impact toughness of the product, and the optimum range is 0.19% -0.22%.

Si: can play a role of solid solution strengthening, can improve hardenability in heat treatment, but the plasticity and the toughness of the steel are reduced when the content is too high, and the optimal range is 0.25-0.40%.

Mn: manganese has a solid solution strengthening effect, can also increase the stability of austenite, is also favorable for improving the hardenability, and effectively ensures the strength of steel. Manganese can lower the martensite transformation temperature Ms and increase the content of retained austenite. Manganese has a significant effect on improving the strength of low-carbon and medium-carbon pearlite steels. Meanwhile, the manganese can also improve the hardness and the wear resistance of the steel. However, if the manganese content is too high, the center segregation tendency of the continuous casting slab can be increased, the band-shaped structure of the steel plate can be increased, and the steel plate can be stored after heat treatment, and finally, a certain amount of band-shaped structure can be contained in the steel plate, and hard phases such as bainite and martensite are aggregated in the band-shaped structure, so that the brittleness of the steel plate is increased, the plasticity is reduced, and the mechanical property is reduced. The optimal range is 1.30% -1.50%.

P: phosphorus is a harmful element in steel, increases the cold brittleness of the steel, deteriorates the welding performance, reduces the plasticity, deteriorates the cold bending performance, and the content of the phosphorus is controlled to be less than or equal to 0.015 percent.

S: sulfur is a harmful element in steel, causes hot brittleness of steel, reduces ductility and toughness of steel, deteriorates welding performance, and is controlled to be less than or equal to 0.006% in order to ensure high purity of molten steel.

Nb: niobium is a fine crystal and precipitation strengthening element, and can make up for the reduction of strength caused by the reduction of carbon and improve the impact property; plays a certain role in preventing the crystal grains from growing during quenching, thereby refining the quenched crystal grains and ensuring the impact toughness; however, too high increases the cost of the alloy, and a suitable range is 0.02% to 0.04%.

V: vanadium carbonitride is uniformly precipitated in ferrite in a fine dispersion mode, has a fine-grain strengthening effect, can obviously improve the yield strength and the tensile strength of the material, and simultaneously improves the low-temperature impact toughness; when the steel is melted into austenite at high temperature, the hardenability of the steel can be increased; the solid solution has strong solid solution strengthening effect when dissolved in ferrite. In the quenching and tempering heat treatment processes, the growth of crystal grains can be hindered, and the strength and the toughness of the steel can be improved. However, too high increases the cost of the alloy, and a suitable range is 0.03% to 0.045%.

Ti: titanium is a strong carbide forming element, and when about 0.015 percent of Ti is added, a high-temperature stable fine TiN precipitated phase can be formed during slab continuous casting, the fine TiN precipitated phase can effectively prevent austenite grains of a continuous casting billet from growing in the heating process, and meanwhile, the fine TiN precipitated phase has an obvious effect of improving the toughness of a heat affected zone during steel welding. More Ti content can obtain more TiC particles, and the strength of the steel is improved through strain-induced precipitation and phase-change precipitation. Meanwhile, the precipitated TiC has a strong precipitation strengthening effect and can ensure that crystal grains are not obviously grown in the subsequent heat treatment of the steel pipe, so that the requirements of the strength and the high impact toughness of the whole pipe after the heat treatment are met. However, when the Ti content is too high, the strength is not increased any more, the impact energy is sharply reduced, and the alloy cost is high. The optimal range is 0.01-0.03%.

Cr: chromium can improve strength by solid solution strengthening and fine grain strengthening. Cr may be dissolved in solid solution like Mn to improve strength. After Cr element is dissolved into austenite, the stability of super-cooled austenite is increased, the C curve is shifted to the right, and the hardenability of steel is improved. The steel material has high strength and hardness. Meanwhile, Cr is a medium carbide forming element, and among all carbides, chromium carbide is the finest one, can be uniformly distributed in the steel volume, and blocks the movement of austenite grain boundaries and the growth of austenite grains, and plays a role in refining the grains, thereby improving the temper brittleness of the steel; chromium also has the effect of reducing the corrosion speed of steel in a high-temperature carbon dioxide environment, the corrosion rate of the sleeve in an oil well is reduced, and the service life is prolonged; however, too high chromium content significantly increases the brittle transition temperature of steel, lowers the elongation, and tends to form coarse carbides, resulting in deterioration of toughness. A suitable range is 0.10% to 0.19%.

And Als: aluminum is a common deoxidizer, and a small amount of aluminum is added into steel, so that grains can be refined, the impact toughness is improved, and the proper range is 0.02-0.05%.

N: the solid-dissolved nitrogen has strong pinning dislocation effect and adverse effect on toughness, and the content of the solid-dissolved nitrogen is controlled to be less than or equal to 0.008 percent

A manufacturing method of a high-strength high-toughness electric resistance welding petroleum casing comprises molten iron pretreatment, molten steel smelting, external refining and slab continuous casting, continuous casting billet reheating, rolling, cooling, coiling, ERW pipe manufacturing and whole pipe heat treatment, and specifically comprises the following steps:

1) smelting and continuous casting process: the method comprises the following steps of molten iron pretreatment, converter smelting, top blowing or top-bottom combined blowing, external refining, LF furnace light desulfurization treatment and calcium treatment to control the shape of impurities and improve the ductility, toughness and cold bending performance of steel, continuous casting of a plate blank into a continuous casting plate blank, and continuous casting of the plate blank adopts electromagnetic stirring or dynamic light pressing to improve the quality of the continuous casting plate blank;

2) the rolling process comprises the following steps: heating the continuous casting plate blank to 1050-;

3) the steel strip is subjected to high-frequency or medium-frequency resistance welding by an ERW unit to be made into a steel pipe;

4) the whole pipe quenching and tempering heat treatment process comprises the following steps: after ERW pipe making, heating the whole pipe to 850-; heating the whole tube to 500-550 ℃, preserving heat for 50-70min, and performing water cooling tempering, wherein the high-temperature tempering brittleness can be effectively inhibited by performing rapid tempering at a cooling speed of 5-10 ℃/s;

the yield strength of the hot-rolled steel strip is 460-550MPa, the tensile strength is 590-630MPa, and the microstructure is ferrite-pearlite.

The yield strength of the whole quenched and tempered tube is 800-880MPa, the tensile strength is 900-960MPa, the elongation is 25-30%, and the transverse Charpy impact energy (average value of 3 samples) Akv at 0 ℃ is more than or equal to 100J.

API Spec 5CT specifies: the yield strength of the P110 grade steel pipe is 758 & 965MPa, the tensile strength is more than or equal to 862MPa, and the elongation is more than or equal to 14 percent; the transverse Charpy impact energy at 0 ℃ is more than or equal to 32J, but the impact energy is more than 86J for achieving high toughness. In order to successfully realize the production of the high-strength high-toughness P110 casing, hot continuous rolling is adopted to roll a hot rolled steel strip with slightly low strength, then ERW welding is carried out to prepare a pipe, and then the whole pipe is subjected to heat treatment, so that the final performance of the steel pipe meets the requirements of the high-strength high-toughness P110. And the welding seam and the pipe body are subjected to the same heat treatment process, the obtained final structure is the same, the structure and performance difference between the welding seam and the pipe body is effectively reduced, the residual stress is eliminated, and the integral quality of the steel pipe is improved.

Compared with the prior art, the invention has the beneficial effects that:

1) c, Mn, the content is moderate, and the steel strip has high impact toughness;

2) the Nb-V-Cr composite strengthening design can fully refine crystal grains and improve the strength and toughness;

3) cr and Ti are adopted to reduce the tempering brittleness, so that the steel pipe is ensured to have better impact toughness, the brittle failure of the oil well pipe can be prevented, and the safety is higher;

4) the hot-rolled plate coil has low performance, and subsequent pipe making and forming are easy; the whole pipe is subjected to quenching and tempering heat treatment, the performance is P110 grade, and the consistency of the pipe body and the welding seam performance is ensured;

5) the heat treatment mode adopts quenching-tempering, the implementation mode is simpler, and the operation is easy.

Detailed Description

The present invention is described in more detail by way of examples, which are merely illustrative of the best mode of carrying out the invention and are not intended to limit the scope of the invention in any way.

The chemical components of the embodiments 1-6 are shown in table 1, the heating, rolling and cooling process parameters are shown in table 2, the mechanical property detection results are shown in table 3, and table 4 shows the mechanical properties of the sleeve in a heat treatment state.

Table 1 examples chemical composition wt%

Examples	C	Si	Mn	P	S	Nb	V	Ti	Cr	Als	N
												1	0.20	0.28	1.37	0.011	0.003	0.03	0.044	0.02	0.13	0.03	0.0041
2	0.21	0.30	1.40	0.013	0.004	0.02	0.030	0.02	0.11	0.04	0.0042
												3	0.19	0.38	1.48	0.012	0.002	0.04	0.040	0.04	0.16	0.03	0.0043
4	0.22	0.32	1.36	0.010	0.001	0.03	0.038	0.03	0.14	0.03	0.0042
												5	0.21	0.29	1.42	0.008	0.003	0.03	0.032	0.02	0.19	0.04	0.0046
6	0.22	0.25	1.30	0.009	0.002	0.04	0.035	0.03	0.12	0.03	0.0048

TABLE 2 heating, Rolling Process and Hot rolled State mechanical Properties

TABLE 3 Heat treatment Process

TABLE 4 mechanical properties in the heat-treated state

As can be seen from Table 4, the quenching-tempering-state straight seam electric resistance welding petroleum casing produced by adopting the component design, rolling and whole pipe heat treatment process meets the requirements of API SPEC 5CT standard high-toughness P110-grade steel pipes.