CN111378899A

CN111378899A - L450 seamless line pipe resistant to low temperature and hydrogen sulfide corrosion and manufacturing method thereof

Info

Publication number: CN111378899A
Application number: CN202010362938.3A
Authority: CN
Inventors: 赵波; 吴红; 解德刚; 袁琴; 王善宝; 张尧
Original assignee: Angang Steel Co Ltd
Current assignee: Angang Steel Co Ltd
Priority date: 2020-04-30
Filing date: 2020-04-30
Publication date: 2020-07-07
Anticipated expiration: 2040-04-30
Also published as: CN111378899B

Abstract

The invention discloses a low-temperature and hydrogen sulfide corrosion resistant L450 seamless line pipe and a manufacturing method thereof. The steel contains C: 0.10% -0.15%, Si: 0.21-0.35%, Mn: 1.35% -1.55%, Nb: 0.03-0.05%, Al: 0.025 to 0.035 percent, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, and the balance of iron and inevitable impurities. The continuous rolling finishing temperature of the round billet is more than 980 ℃, the temperature of the tube blank is heated to 1250-1280 ℃, the temperature after perforation is 1200-1220 ℃, and the sizing temperature is 855-875 ℃. Quenching and quenchingThe heat temperature is 880-900 ℃, the quenching heat preservation time is 40-60 min, the tempering temperature is 570-590 ℃, the tempering heat preservation time is 70-100 min, and the finished steel pipe can meet the requirements of L450-grade pipeline mechanical property, HIC (hydrogen induced cracking) resistance and SSC (Single side chain) corrosion resistance, and the Kv (Kv) of longitudinal impact at-40 DEG C₈≥180J。

Description

L450 seamless line pipe resistant to low temperature and hydrogen sulfide corrosion and manufacturing method thereof

Technical Field

The invention relates to the field of seamless steel pipes made of low-temperature-resistant and corrosion-resistant materials, in particular to a seamless line pipe with hydrogen sulfide corrosion resistance.

Background

The wet hydrogen sulfide environment is generally referred to as an acidic environment, and corrosion of the pipeline in the acidic environment is a key factor affecting the reliability and service life of the pipeline transportation system. H in natural gas as oil and gas well is produced deeply₂Increased S content, H₂S corrosion is unavoidable. Inside of seamless pipe line H₂S corrosion is one of the main forms of corrosion, and this corrosion failure is mainly caused by Hydrogen Induced Cracking (HIC), Sulfide Stress Cracking (SSC). The hydrogen-induced cracks refer to that the metal material is soaked in a medium containing hydrogen sulfide, hydrogen precipitated in the electrochemical corrosion process enters the metal material to generate step-shaped cracks, and the cracks are formed and expanded to finally crack the metal material (such as a pipeline). Sulfide Stress Cracking (SSC), which is the most destructive and harmful corrosion in an acidic environment, refers to the sudden fracture of a metal material that is prone to low stress and has no sign under the combined action of tensile stress or residual stress and corrosion in an acidic environment. For this reason, it is important to design and study the composition design and manufacturing method of seamless line pipes resistant to acid corrosion reasonably.

"X80 pipeline steel with anti-HIC property and its manufacturing method of hot rolled plate" (CN1715435), this patent discloses a method of adding alloy elements such as Cu, Ni, V, B, etc. with a low C, P, S content to facilitate anti-HIC property, but this patent only tests B solution, the test result of a solution is not indicated, and this invention is used for the production of hot rolled steel plate for pipeline.

"X70 QS seamless line pipe with HIC resistance" (CN101921964A), discloses that by controlling the chemical composition: 0.06-0.14% of C, 0.20-0.45% of Si, 1.0-1.3% of Mn1, less than or equal to 0.003% of S, less than or equal to 0.015% of P, 0.05-0.30% of Cr0.05-0.30% of Mo0.05-0.30%, 0.003-0.010% of N, 0.03-0.05% of Nb, 0.05-0.09% of V and 0.015-0.06% of Al.

The patent adds Ti, V, Cu, Ni and other alloys, has higher cost, and the yield strength of the patent is 360MPa grade, and is lower than that of the invention. The three patents only indicate the HIC resistance of the steel grade, and the SSC resistance and the low-temperature resistance of the steel grade are not expressed.

Disclosure of Invention

In view of the above problems of the prior art, an object of the present invention is to provide a seamless pipe or tube having excellent low-temperature resistance and hydrogen sulfide corrosion resistance, and a method for manufacturing the same. In order to achieve the purpose of the invention, the inventor carries out a great deal of systematic experimental research on aspects of screening and proportioning of alloy elements, steel cleanliness control, process optimization and parameter selection, structure optimization and the like, and finally determines the proportioning of the alloy elements and the manufacturing process which can meet the purpose of the invention.

The specific technical scheme is as follows:

the pipeline pipe with the acid corrosion resistance comprises the following components in percentage by mass: 0.10% -0.15%, Si: 0.21-0.35%, Mn: 1.35% -1.55%, Nb: 0.03-0.05%, Al: 0.025 to 0.035 percent, less than or equal to 0.015 percent of P and less than or equal to 0.005 percent of S; when C: 0.10% -0.12% of carbon equivalent CE_PcmLess than or equal to 0.25, wherein, CE_Pcm(C + Si/30+ Mn/20+ Cu/20+ Ni/60+ Cr/20+ Mo/15+ V/10+5B), when C: when the content is more than 0.12 to 0.15 percent, CE_IIWLess than or equal to 0.42, wherein, CE_IIW＝(C+Mn/6+Cr/5+Mo/5+V/5+Ni/15+Cu/15)。

The main chemical components and effects are as follows:

c is a carbide forming element, can improve the strength of the steel, and is positioned by 0.10% in order to ensure the lower limit of the necessary strength, but the band-shaped generation is aggravated by too high carbon content, and the HIC resistance is influenced, and meanwhile, the carbon is also an element which has the largest influence on the welding cold crack sensitivity, so that the lower carbon content is selected, and the upper limit is 0.15%, namely the C content is controlled to be 0.10% -0.15%.

Si is an effective deoxidizing element, the deoxidizing effect is lacked when the content is too low, and the toughness of the steel is reduced when the content is too high, so that 0.21-0.35 percent of Si is selected as the alloy content range of the invention.

Mn is an austenite forming element and is used for improving the strength of steel and making up for the yield strength lost due to the reduction of carbon content, and can improve the toughness of the steel and reduce the ductile-brittle transition temperature while improving the strength. The invention controls the Mn content to be 1.35-1.55%.

Nb has the function of refining grains, because a carbonitride formed by undissolved niobium is precipitated at an austenite grain boundary in the austenitizing process, the movement of the grain boundary and the growth of the grains are hindered, the grains of austenite are refined, a tempered sorbite structure is more uniformly refined after quenching and tempering, the area of the grain boundary is increased, when plastic deformation and microcrack penetrate through the grain boundary, the resistance of the grain boundary is larger than that of other areas, the grains of the material are finer, the area of the grain boundary is larger, and the low-temperature toughness and the corrosion resistance of the material are higher. The carbide of Nb can pin the grain boundary in the rolling process, can obtain the beneficial effect of higher yield strength, and improves the yield ratio of steel, but the excessively high addition of Nb not only influences the surface quality of the steel pipe, but also reduces the strength and the elongation, so that the Nb content is controlled to be 0.03-0.05 percent.

Al has great affinity with oxygen and nitrogen in steel, and AlN formed by combining with nitrogen can refine crystal grains, inhibit the aging of low-carbon steel and improve the toughness of the steel at low temperature. On the other hand, Al also has oxidation resistance and corrosion resistance, and can improve the corrosion resistance to hydrogen sulfide. The invention controls the Al content to be 0.025-0.035%.

P is an impurity element, promotes center segregation, remarkably reduces the low-temperature impact toughness of steel, improves the ductile-brittle transition temperature of the steel, also deteriorates the welding performance of the steel, and reduces the content of the P as much as possible, and the content of the P is required to be not more than 0.015% in consideration of the cost.

S is an impurity element, sulfide is easily formed, the effect on the HIC resistance is large, when S is less than or equal to 0.012%, HIC is obviously reduced, and the S content is required to be less than or equal to 0.005%.

When the carbon equivalent is high during line pipe welding, the heat crack sensitivity of the weld and the crack sensitivity of the weld heat affected zone increase, and therefore C: 0.10% -0.12% of carbon equivalent CE_PcmLess than or equal to 0.25; when C: 0.12% -0.15% (not including 0.12%), CE_IIW≤0.42。

The invention also provides a method for manufacturing the L450 seamless line pipe with low temperature resistance and hydrogen sulfide corrosion resistance, which comprises the following steps: smelting a square billet, continuously rolling a round billet, continuously rolling a steel pipe (perforating and sizing), performing heat treatment, straightening and flaw detection, wherein the method comprises the following steps of:

the round billet adopts a continuous rolling method, namely, the round billet is obtained by continuous rolling after smelting in a converter, refining outside the furnace (LF + VD), continuously casting a square billet, cooling to room temperature and then entering a heating furnace, and the deformation of the product is greatly increased through the continuous rolling process of the round billet, so that the effect of refining crystal grains is achieved, and the low-temperature impact property of the product is favorably improved. The continuous rolling finishing temperature of the round billet is higher than 980 ℃, so that the generation of cracks on the surface of the round billet can be effectively controlled, and the hydrogen sulfide corrosion resistance of the round billet is improved. The obtained tube blank is heated to 1250-1280 ℃ by a ring furnace, a continuous rolling process is adopted, the temperature after perforation is 1200-1220 ℃, and the sizing temperature is controlled to 855-875 ℃.

The steel pipe is further subjected to quenching and tempering heat treatment, wherein the quenching heating temperature is 880-900 ℃, the quenching medium is water, the quenching heat preservation time is 40-60 min, the tempering temperature is 570-590 ℃, and the tempering heat preservation time is 70-100 min. And then straightening with temperature not lower than 400 ℃ and carrying out flaw detection, wherein the final structure of the finished steel pipe is a tempered sorbite. The quenching and tempering heat treatment mode can improve the strength and the low-temperature impact toughness of the steel, and simultaneously the tempered sorbite of the metallographic structure after quenching and tempering is also the metallographic structure beneficial to resisting the corrosion of the hydrogen sulfide. The proper quenching temperature and quenching time are beneficial to the uniformity, stability and hardenability of austenite, and are beneficial to Nb precipitation and Nb strengthening, and the martensite laths are increased due to overhigh temperature or overlong quenching time to influence the elongation and impact toughness after tempering, so the quenching heating temperature is selected to be 880-900 ℃, and the quenching heat preservation time is 40-60 min. The proper tempering temperature and tempering time are favorable for the uniform dispersion of the carbide in the granular state and the improvement of the impact toughness and the elongation, so the tempering temperature is selected to be 570-590 ℃, and the tempering heat preservation time is 70-100 min.

Has the advantages that:

(1) the invention improves the low temperature resistance and hydrogen sulfide corrosion resistance of the steel pipe by reducing the C content, adding proper Nb and Al alloys, controlling the sulfur and phosphorus content and adopting a heat treatment method of round billet continuous rolling, seamless pipe continuous rolling, quenching and tempering, and can meet the requirements of the mechanical property, HIC resistance and SSC resistance of the L450-grade pipeline pipe.

(2) The steel pipe has tempered sorbite structure, uniform grain structure, excellent low-temperature impact toughness at-40 ℃, and longitudinal impact Kv at-40 DEG C₈Not less than 180J (impact specimen size 7.5 × 10 × 55mm), and yield ratio R_t0.5/R_mLess than 0.9, elongation A_50mm≥28％。

(3) The manufacturing process of the product is easy to realize, the uniformity and stability of the product performance are good, the cost is low, the HIC and SSC resistance is good, and the low-temperature impact and tensile properties are good. The yield strength of the finished steel pipe is more than or equal to 450MPa, the hardness is less than or equal to 250HV10, and the HIC resistance completely meets the requirements that CLR is less than or equal to 15%, CTR is less than or equal to 5%, and CSR is less than or equal to 2% (the actual CLR value, CTR value and CSR value of the crack length rate, the crack thickness rate and the crack sensitivity rate are all 0). According to an SSC corrosion test, a test sample is not broken after 720 hours, and no obvious crack is observed through a magnifying glass of 10 times, so that the SSC corrosion test has good economical efficiency and corrosion resistance, and can be widely applied to oil-gas well pipeline pipes in an acidic corrosion environment.

Drawings

FIG. 1 is a metallographic structure photograph of a steel sheet according to example 1.

Detailed Description

The following examples are intended to illustrate the invention in detail, and are intended to be a general description of the invention, and not to limit the invention.

The chemical compositions of the steels of the examples of the invention are shown in Table 1, the rolling and heat treatment methods of the steels of the examples of the invention are shown in Table 2, the tensile properties of the steels of the examples of the invention are shown in Table 3, the low-temperature impact properties of the steels of the examples of the invention are shown in Table 4, and the transverse Vickers HV10 hardness of the steel pipes of the examples of the invention is shown in Table 5, wherein 4 points are measured at the inner, middle and outer hardness positions. The test result of the HIC performance is shown in Table 6, the corrosion test is according to the API 5L standard, the HIC is tested by NACE-0284-. SSC corrosion test according to ASTM G39-99 standard four-point bending test, in solution A, the loading stress is 0.72 times the minimum yield strength, after 720 hours of test, the test piece is macroscopically checked for breakage, the test piece is not cracked, and the test piece is checked for cracking by a 10 times magnifier and no cracks appear. The pipeline pipe has stable mechanical property, and excellent HIC resistance and SSC resistance.

Table 1 chemical composition of the example steels, wt.%

Examples	C	Si	Mn	P	S	Nb	Al	CE_Pcm	CE_IIw
										1	0.10	0.21	1.55	0.012	0.0020	0.041	0.025	0.18	/
2	0.11	0.33	1.50	0.011	0.0031	0.030	0.034	0.20	/
										3	0.12	0.29	1.49	0.0063	0.0041	0.050	0.027	0.20	/
4	0.13	0.30	1.40	0.0092	0.0032	0.030	0.035	/	0.36
										5	0.14	0.34	1.36	0.0054	0.0050	0.031	0.030	/	0.37
6	0.15	0.35	1.35	0.006	0.0044	0.043	0.029	/	0.38

Note: the balance of iron and unavoidable impurities.

TABLE 2 Rolling and Heat treatment parameters of steels according to examples of the invention

TABLE 3 tensile Properties of steels of examples of the invention

Examples	Rt_0.5/MPa	Rm/MPa	A_50mm/％	Rt_0.5/Rm
					1	510	594	30.5	0.86
2	596	674	28.0	0.88
					3	515	609	33.5	0.85
4	536	620	32.5	0.86
					5	482	576	33.5	0.84
6	499	590	37.0	0.85

TABLE 4 impact properties of steels of examples of the invention

TABLE 5 HV10 hardness of steels of examples of the invention

Note: the hardness positions of the inner, middle and outer parts are respectively measured at 4 points.

TABLE 6 HIC test results for inventive steels

As can be seen from the above examples, the component design and the process of the invention are adopted to prepare the HIC performance test of the seamless pipe with the yield strength of 480-596 MPa, the tensile strength of 590-674 MPa, the elongation of more than or equal to 28 percent, the-40 impact mean value of more than 180J, NACE-0284 and 2003 standard A solution and the test result of the four-point bending test according to ASTM G39-99 standard prove that the HIC and SSC corrosion resistance of the steel pipe are excellent, and the CLR value, the CTR value and the CSR value of the crack sensitivity rate are all 0, and the HIC and SSC corrosion resistance test is used in an acidic environment.

Claims

1. The L450 seamless line pipe resistant to low temperature and hydrogen sulfide corrosion is characterized in that the steel comprises the following chemical components in percentage by mass: c: 0.10% -0.15%, Si: 0.21-0.35%, Mn: 1.35% -1.55%, Nb: 0.03-0.05%, Al: 0.025 to 0.035 percent, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, and the balance of iron and inevitable impurities; and when C: 0.10% -0.12% of carbon equivalent CE_PcmLess than or equal to 0.25, wherein, CE_Pcm(C + Si/30+ Mn/20+ Cu/20+ Ni/60+ Cr/20+ Mo/15+ V/10+5B), when C: when the content is more than 0.12 to 0.15 percent, CE_IIWLess than or equal to 0.42, wherein, CE_IIW＝(C+Mn/6+Cr/5+Mo/5+V/5+Ni/15+Cu/15)。

2. The L450 seamless line pipe with low temperature resistance and hydrogen sulfide corrosion resistance as claimed in claim 1, wherein the yield strength is more than or equal to 450MPa, the hardness is less than or equal to 250HV10, and the longitudinal impact Kv is at-40 ℃₈≥180J。

3. A method of manufacturing the low temperature and hydrogen sulfide corrosion resistant L450 seamless line pipe of claim 1 or 2, comprising: smelting a square billet, continuously rolling a round billet, continuously rolling a steel pipe, performing heat treatment, and straightening, which is characterized in that:

the round billet is continuously rolled by adopting a converter smelting method, refining outside a furnace, continuously casting a square billet, cooling to room temperature, feeding into a heating furnace, continuously rolling to obtain the round billet, wherein the continuous rolling finishing temperature of the round billet is higher than 980 ℃, the obtained round billet is heated to 1250-1280 ℃ by adopting an annular furnace, the continuous rolling process is adopted, the temperature after perforation is 1200-1220 ℃, and the sizing temperature is controlled to 855-875 ℃.

The heat treatment adopts a quenching and tempering process, the quenching heating temperature is 880-900 ℃, the quenching medium is water, the quenching heat preservation time is 40-60 min, the tempering temperature is 570-590 ℃, the tempering heat preservation time is 70-100 min, and then the straightening with the temperature not lower than 400 ℃ is carried out.