CN111254352B

CN111254352B - X65MS acid-resistant pipeline steel

Info

Publication number: CN111254352B
Application number: CN202010096718.0A
Authority: CN
Inventors: 刘川俊; 邓深; 樊雷; 袁勤攀; 陈利; 杨跃标; 赵忠云; 吴海林; 周从锐; 潘刚; 张广川
Original assignee: Liuzhou Iron and Steel Co Ltd
Current assignee: Liuzhou Iron and Steel Co Ltd
Priority date: 2020-02-17
Filing date: 2020-02-17
Publication date: 2021-05-28
Anticipated expiration: 2040-02-17
Also published as: CN111254352A

Abstract

The invention provides X65MS acid-resistant pipeline steel, which comprises the following chemical components in percentage by weight: 0.03-0.05 Wt%, Si less than or equal to 0.15 Wt%, Mn: 1.25-1.35 Wt%, P is less than or equal to 0.015 Wt%, S is less than or equal to 0.0015 Wt%, Alt: 0.020-0.040 Wt%, Ti: 0.010-0.020 Wt%, Nb: 0.040% -0.050 Wt%, Cr: 0.20-0.25 Wt%, Ni: 0.10-0.20 Wt%, O is less than or equal to 0.0020 Wt%, N is less than or equal to 0.0040 Wt%, and the Ca/S ratio is more than or equal to 1.5; the balance of Fe and inevitable trace elements. The method does not adopt precious alloys such as Mo, V, Cu and the like, has lower production cost, can avoid the occurrence of banded structures and reduce the hardness of a segregation zone by adopting the process, improves the H IC (stress corrosion cracking) resistance and SCC (stress corrosion cracking) resistance of the pipeline steel, improves the impact toughness of the pipeline steel, and completely meets the standard and the use requirements of users.

Description

X65MS acid-resistant pipeline steel

Technical Field

The invention relates to the field of metallurgy, and particularly relates to economical X65MS acid-resistant pipeline steel or X65MS acid-resistant pipeline steel.

Background

The pipeline steel is a hot-rolled coiled plate or a wide and thick plate for a large-opening welded steel pipe for conveying petroleum, natural gas and the like, and the pipeline steel is required to have high pressure resistance, good toughness, good fatigue resistance, good low-temperature toughness and good welding performance in the use process.

The acid-resistant pipeline steel is mainly used for oil and gas pipelines in an acid environment; the corrosion of pipeline steel in an acidic environment is mainly Hydrogen Induced Cracking (HIC) and sulfide stress corrosion cracking (SSC). When pipeline steel is in an unstressed or unstressed state in an H2S-rich oil and gas environment, hydrogen generated by corrosion enters the steel to cause cracking called HIC, which is generally referred to as hydrogen induced bubbling (surface cracking) and hydrogen induced step cracking (internal cracking). SSC means that hydrogen atoms generated from H2S penetrate into the interior of steel and dissolve in the lattice, resulting in increased brittleness of the steel and cracks formed by an applied tensile stress or residual stress. Therefore, on the basis of the performance requirement of the original pipeline steel, the acid-resistant pipeline steel also requires stronger hydrogen induced cracking resistance and sulfide stress corrosion resistance.

At present, the common process for producing X65MS acid-resistant pipeline steel by domestic and foreign steel enterprises is to adopt low-carbon, high-manganese, niobium-vanadium microalloying and add more noble alloys such as Mo, Cu, V and the like, and the production cost is higher.

In summary, the following problems exist in the prior art: the existing X65MS acid-resistant pipeline steel is added with more precious alloys such as Mo, V, Cu and the like, and the production cost is higher.

Disclosure of Invention

The invention provides economical X65MS acid-resistant pipeline steel, namely X65MS acid-resistant pipeline steel, and aims to solve the problem that the existing X65MS acid-resistant pipeline steel is high in production cost.

Therefore, the invention provides X65MS acid-resistant pipeline steel, which comprises the following chemical components in percentage by weight: 0.03-0.05 Wt%, Si less than or equal to 0.15 Wt%, Mn: 1.25-1.35 Wt%, P is less than or equal to 0.015 Wt%, S is less than or equal to 0.0015 Wt%, Alt: 0.020-0.040 Wt%, Ti: 0.010-0.020 Wt%, Nb: 0.040% -0.050 Wt%, Cr: 0.20-0.25 Wt%, Ni: 0.10-0.20 Wt%, O is less than or equal to 0.0020 Wt%, N is less than or equal to 0.0040 Wt%, and the Ca/S ratio is more than or equal to 1.5; the balance of Fe and inevitable trace elements.

Further, the X65MS acid-resistant pipeline steel comprises the following chemical components in percentage by weight: 0.038% Wt%, Si: 0.12 Wt%, Mn: 1.30 Wt%, P: 0.007 Wt%, S:0.0009 Wt%, Alt: 0.025 Wt%, Nb: 0.049 Wt%, Ti: 0.013% Wt%, Cr: 0.22 Wt%, Ca: 0.0023 Wt%, N: 0.0031 Wt%, Ni: 0.18 Wt%, O: 0.0019% Wt.%; the balance of Fe and inevitable trace elements.

Further, the X65MS acid-resistant pipeline steel comprises the following chemical components in percentage by weight: 0.036% Wt%, Si: 0.13 Wt%, Mn: 1.28 Wt%, P: 0.008 Wt%, S:0.0008 Wt%, Alt: 0.032 Wt%, Nb: 0.047 Wt%, Ti: 0.015% Wt%, Cr: 0.21 Wt%, Ca: 0.0019 Wt%, N: 0.0036 Wt%, Ni: 0.19 Wt%, O: 0.0012% Wt.%; the balance of Fe and inevitable trace elements.

Further, the X65MS acid-resistant pipeline steel comprises the following chemical components in percentage by weight: 0.035% Wt%, Si: 0.13 Wt%, Mn: 1.30 Wt%, P: 0.007 Wt%, S:0.0010 Wt%, Alt: 0.027 Wt%, Nb: 0.046 Wt%, Ti: 0.013% Wt%, Cr: 0.22 Wt%, Ca: 0.0027 Wt%, N: 0.0035 Wt%, Ni: 0.176 Wt%, O: 0.0011% Wt.%; the balance of Fe and inevitable trace elements.

Further, the X65MS acid-resistant pipeline steel comprises the following chemical components in percentage by weight: 0.038% Wt%, Si: 0.13 Wt%, Mn: 1.29 Wt%, P: 0.007 Wt%, S:0.0009 Wt%, Alt: 0.031 Wt%, Nb: 0.047 Wt%, Ti: 0.017% Wt%, Cr: 0.23 Wt%, Ca: 0.0033 Wt%, N: 0.0033 Wt%, Ni: 0.175 Wt%, O: 0.0013% Wt.%; the balance of Fe and inevitable trace elements.

Further, the X65MS acid-resistant pipeline steel comprises the following chemical components in percentage by weight: 0.041% Wt%, Si: 0.13 Wt%, Mn: 1.26 Wt%, P: 0.005 Wt%, S:0.0010 Wt%, Alt: 0.029 Wt%, Nb: 0.045 Wt%, Ti: 0.017% Wt%, Cr: 0.23 Wt%, Ca: 0.0036 Wt%, N: 0.0030 Wt%, Ni: 0.169 Wt%, O: 0.0011% Wt.%; the balance of Fe and inevitable trace elements.

Further, the X65MS acid-resistant pipeline steel is manufactured through a converter steelmaking process and a hot continuous rolling process, wherein in the converter steelmaking process: LF ladle top slag control target, CaO/Al2O 3: 1.4-2.5; CaO/SiO 2: 7-15; al2O3 is less than or equal to 35 percent; tfe + MnO is less than or equal to 1.0 percent.

Further, in the hot continuous rolling process: controlling the heating temperature of the casting blank to 1150 +/-20 ℃; the heating in-furnace time is 150-180 min; the grain size at the outlet of rough rolling is less than 25 microns.

Further, in the hot continuous rolling process: the finishing temperature is controlled to be 810 +/-20 ℃; the coiling temperature is 460 +/-20 ℃.

The method does not adopt precious alloys such as Mo, V, Cu and the like, has lower production cost, can avoid the occurrence of banded structures and reduce the hardness of a segregation zone by adopting the process, improves the H IC (stress corrosion cracking) resistance and SCC (stress corrosion cracking) resistance of the pipeline steel, improves the impact toughness of the pipeline steel, and completely meets the standard and the use requirements of users.

Detailed Description

The present invention will now be described in order to more clearly understand the technical features, objects, and effects of the present invention.

The steel adopted by the invention comprises the following chemical components in percentage by weight: 0.03-0.05 Wt%, Si less than or equal to 0.15 Wt%, Mn: 1.25-1.35 Wt%, P is less than or equal to 0.015 Wt%, S is less than or equal to 0.0015 Wt%, Alt: 0.020-0.040 Wt%, Ti: 0.010-0.020 Wt%, Nb: 0.040% -0.050 Wt%, Cr: 0.20-0.25 Wt%, Ni: 0.10-0.20 Wt%, O not more than 0.0020 Wt%, N not more than 0.0040 Wt%, and Ca/S ratio not less than 1.5.

C of the present invention: 0.03% -0.05%, and the low carbon content is adopted, so that the toughness and ductility of the product are improved, and meanwhile, the welding performance is good, and the HIC resistance of the pipeline steel is improved.

Mn of the present invention: 1.25 to 1.35 percent, properly reduces the manganese content, prevents segregation, avoids the occurrence of banded structures and reduces the hardness of a segregation zone. Improve the HIC resistance of the pipeline steel.

The invention adopts a pure steel smelting continuous casting process, reduces S, P, H, O content, carries out inclusion modified calcium treatment, can greatly improve the HIC (high impact strength) and SCC (stress corrosion cracking) resistance of the pipeline steel, and improves the impact toughness of the pipeline steel.

The invention adopts the micro-titanium treatment technology to improve the toughness of the welding heat affected zone of the pipeline steel.

The invention adopts the combination of niobium microalloying and a thermal mechanical rolling process (TMCP), fully applies the mechanisms of fine grain strengthening, solid solution strengthening, precipitation strengthening, phase change strengthening and the like of the pipeline steel, and improves the strength and the toughness of the product.

The invention can form passive film and prevent hydrogen from invading while improving strength and toughness by adding Cr and Ni elements properly. The present invention does not add Cu because it is considered that Cu has an influence on the ductility.

The manufacturing method of the invention comprises the following process routes: blast furnace molten iron smelting → molten iron desulphurization pretreatment → converter molten steel smelting → LF molten steel refining treatment → RH molten steel refining treatment → whole-process protective casting (+ electric stirring + soft reduction) → hot rolling production → casting blank heating → rough rolling → finish rolling → coiling → steel coil inspection packaging → steel tube factory welding and tube making;

smelting molten steel in a converter: controlling S to be less than or equal to 0.005 Wt% in molten iron fed into the furnace; in order to control the S content, a special steel scrap is used; argon is blown from bottom in the whole smelting process; setting value of final slag alkalinity R: 4.0 to 4.5; endpoint control sets the target reference: c is less than or equal to 0.035%, P is less than or equal to 0.013%; in order to control the content of C, the alloy uses manganese metal (Mn is more than or equal to 98%) and low-carbon ferrochrome (C is less than or equal to 0.25%).

LF molten steel refining treatment and RH molten steel refining treatment: the control target of the LF ladle top slag is CaO/Al2O 3: 1.4-2.5; CaO/SiO 2: 7-15; al (Al)₂O₃Less than or equal to 35 percent; tfe (total iron) + MnO less than or equal to 1.0%.

Accurately controlling chemical components, reducing S, P, H, N, O content, performing inclusion modified calcium treatment, and when S is more than 0.0015%, Ca/S is more than or equal to 1.5. The molten steel sedation time is more than or equal to 18 minutes after refining.

Slab continuous casting: the automatic slag-off detection control of the ladle is required; a whole-process protective casting process is adopted; the superheat degree of pouring of the tundish is 10-30 ℃, an alkaline covering agent is used in the tundish, low-carbon steel covering slag is used, the casting blank drawing speed is 1.20-1.45 m/min, the liquid level fluctuation of the crystallizer is automatically controlled, and the liquid level fluctuation range of molten steel of the crystallizer is controlled to be +/-3 mm.

Hot continuous rolling: the rolling process adopts a controlled rolling and controlled cooling process. In order to fully exert the function of Nb, the heating temperature is not too high so as to exert the function of niobium for inhibiting the growth of crystal grains, and the heating time is not too long. According to 1150 +/-20 ℃; heating in-furnace time: controlling for 150-180 min; and (3) rolling in an austenite recrystallization region and a non-recrystallization region respectively by adopting a two-stage controlled rolling process. Rolling in an austenite recrystallization region in the rough rolling stage, wherein the flatter the crystal grains are, the better the crystal grains are; the grain size at the outlet of rough rolling is controlled to a target of less than 25 microns. The reduction rate of the rough rolling in two passes is more than or equal to 25 percent, the accumulated reduction rate is more than or equal to 70 percent, austenite grains are fully refined through repeated static recrystallization, and the rough rolling temperature is controlled according to 990 ℃. In the finish rolling stage, rolling is carried out in an austenite non-recrystallization region, the initial rolling temperature is not more than 950 ℃, the cumulative reduction rate is not less than 60%, austenite grains are sufficiently flattened through rolling in the non-recrystallization region and are elongated along the rolling direction, meanwhile, a large number of deformation bands are introduced into the austenite grains due to deformation, the nucleation points of austenite phase transformation to ferrite are greatly increased under the action of the deformation bands, and the ferrite grains after phase transformation are sufficiently refined. The final rolling temperature is controlled to be 810 +/-20 ℃, and the phenomenon that the strength and the toughness are reduced due to mixed crystals caused by too low temperature is prevented. And after rolling, laminar cooling is adopted, the lower coiling temperature of 460 +/-20 ℃ is controlled, the cooling speed is ensured to be 10-20 ℃/s, and the uniformity and stability of the final rolling temperature and the coiling temperature of the through coil are ensured to the greatest extent. Through accelerated cooling, the phase transition temperature is reduced, ferrite crystal inner nucleation is promoted, ferrite crystal grains after phase transition are prevented from growing up, and the ferrite crystal grains are further refined. Finally, the uniform structure and fine crystal grains are ensured, and the 0-level control of the banded structure is realized.

The ingredients of the examples of the invention are shown in Table 1

TABLE 1 product chemistry (wt%)

The converter smelting process parameters of the examples of the invention are shown in Table 2

TABLE 2 converter smelting Process parameters of the examples

The parameters of the hot continuous rolling process of each example of the invention are shown in Table 3

TABLE 3 Hot continuous Rolling Process parameters for each example

The performance parameters of the examples of the invention are shown in Table 4

TABLE 4 examples Performance parameters

The metallographic structure of each example of the invention is shown in Table 5

Table 5 metallographic structure of the examples of the invention, note: a-sulfide inclusion; b-alumina inclusions; c-silicate inclusions; d-spherical oxide inclusions; DS-single-particle inclusion; f is ferrite; p-pearlite; b is bainite.

HIC crack measurement analysis results for each example of the invention are shown in Table 6

TABLE 6 HIC crack measurement analysis results for inventive examples

The casting blank quality control method is good. Corner crack: 0; internal cracking: 0; triangular region cracking: 0; corner cracking: 0; center segregation: c0.5 grade; center loosening: grade 0.5; inclusion: 0; air bubbles: 0. from the low magnification result and the condition that the surface quality of the corner part of the casting blank is inspected, the X65MS casting blank quality control is normal. And hot rolling and trial rolling a steel coil with the thickness of 16mm and 15.45 mm. The X65MS acid-resistant steel coil has high strength allowance, the yield strength is 510-540 Mpa, and the tensile strength is 580-600 Mpa. The yield ratio is less than or equal to 0.90, and the requirement is met. The impact value is higher, the average impact work at 20 ℃ is 390J, and the average impact work at 40 ℃ is 360J. The drop weight performance is good, and the drop weight is more than 95 percent on average at the temperature of-15 ℃. The microstructure of the steel coil: the structure is mainly ferrite and bainite, the crystal grain is uniform overall, the average grain size of the ferrite is 12.5-13.5 grades, the banded structure is 0, and the whole steel quality is pure.

Third-party acid-fast detection is carried out by Pabo detection technology service company, and a test sample HIC test report is entrusted. According to a standard NACE TM0284-2011(HIC) test, after a 96-hour H2S saturated solution soaking test, no hydrogen bubbles appear on the surfaces of all samples; all samples had a cross section without cracks under a microscope of 100 x. And (5) reporting the SSC test. After 720h of testing according to ASTM G39-99(2011) standard 4-point bend method and NACE TM0177-2005 standard Sulfide Stress Cracking (SSC) test, the tensile surface of the test was examined at 10 times magnification under a low power microscope, and all samples were free of cracks or crazes and were acceptable.

The above description is only an exemplary embodiment of the present invention, and is not intended to limit the scope of the present invention. In order that the components of the present invention may be combined without conflict, it is intended that all equivalent changes and modifications made by those skilled in the art without departing from the spirit and principles of the present invention shall fall within the protection scope of the present invention.

Claims

1. The X65MS acid-resistant pipeline steel is characterized by comprising the following chemical components in percentage by weight: 0.03-0.05 Wt%, Si less than or equal to 0.15 Wt%, Mn: 1.25-1.35 Wt%, P is less than or equal to 0.015 Wt%, S is less than or equal to 0.0015 Wt%, Alt: 0.020-0.040 Wt%, Ti: 0.010-0.020 Wt%, Nb: 0.040% -0.050 Wt%, Cr: 0.20-0.25 Wt%, Ni: 0.10-0.20 Wt%, O is less than or equal to 0.0020 Wt%, N is less than or equal to 0.0040 Wt%, and the Ca/S ratio is more than or equal to 1.5; the balance of Fe and inevitable trace elements;

the X65MS acid-resistant pipeline steel is manufactured through a converter steelmaking process and a hot continuous rolling process, wherein in the converter steelmaking process: LF ladle top slag control target, CaO/Al₂O₃：1.4～2.5；CaO/SiO₂：7～15；Al₂O₃≤35％；TFe +MnO≤1.0％；

The X65MS acid-resistant pipeline steel has an average impact work of 390J at-20 ℃ and an average impact work of 360J at-40 ℃;

the average grain size of ferrite is 12.5-13.5 grades;

the hot continuous rolling process comprises the following steps: controlling the heating temperature of the casting blank to 1150 +/-20 ℃; the heating in-furnace time is 150-180 min; the grain size at the outlet of rough rolling is less than 25 microns.

2. The X65MS acid-fast pipeline steel of claim 1, wherein the X65MS acid-fast pipeline steel comprises the following chemical components in percentage by weight: 0.038% Wt%, Si: 0.12 Wt%, Mn: 1.30 Wt%, P: 0.007 Wt%, S:0.0009 Wt%, Alt: 0.025 Wt%, Nb: 0.049 Wt%, Ti: 0.013% Wt%, Cr: 0.22 Wt%, Ca: 0.0023 Wt%, N: 0.0031 Wt%, Ni: 0.18 Wt%, O: 0.0019% Wt%; the balance of Fe and inevitable trace elements.

3. The X65MS acid-fast pipeline steel of claim 1, wherein the X65MS acid-fast pipeline steel comprises the following chemical components in percentage by weight: 0.036% Wt%, Si: 0.13 Wt%, Mn: 1.28 Wt%, P: 0.008 Wt%, S:0.0008 Wt%, Alt: 0.032 Wt%, Nb: 0.047 Wt%, Ti: 0.015% Wt%, Cr: 0.21 Wt%, Ca: 0.0019 Wt%, N: 0.0036 Wt%, Ni: 0.19 Wt%, O: 0.0012% Wt%; the balance of Fe and inevitable trace elements.

4. The X65MS acid-fast pipeline steel of claim 1, wherein the X65MS acid-fast pipeline steel comprises the following chemical components in percentage by weight: 0.035% Wt%, Si: 0.13 Wt%, Mn: 1.30 Wt%, P: 0.007 Wt%, S:0.0010 Wt%, Alt: 0.027 Wt%, Nb: 0.046 Wt%, Ti: 0.013% Wt%, Cr: 0.22 Wt%, Ca: 0.0027 Wt%, N: 0.0035 Wt%, Ni: 0.176 Wt%, O: 0.0011% Wt%; the balance of Fe and inevitable trace elements.

5. The X65MS acid-fast pipeline steel of claim 1, wherein the X65MS acid-fast pipeline steel comprises the following chemical components in percentage by weight: 0.038% Wt%, Si: 0.13 Wt%, Mn: 1.29 Wt%, P: 0.007 Wt%, S:0.0009 Wt%, Alt: 0.031 Wt%, Nb: 0.047 Wt%, Ti: 0.017% Wt%, Cr: 0.23 Wt%, Ca: 0.0033 Wt%, N: 0.0033 Wt%, Ni: 0.175 Wt%, O: 0.0013% Wt%; the balance of Fe and inevitable trace elements.

6. The X65MS acid-fast pipeline steel of claim 1, wherein the X65MS acid-fast pipeline steel comprises the following chemical components in percentage by weight: 0.041% Wt%, Si: 0.13 Wt%, Mn: 1.26 Wt%, P: 0.005 Wt%, S:0.0010 Wt%, Alt: 0.029 Wt%, Nb: 0.045 Wt%, Ti: 0.017% Wt%, Cr: 0.23 Wt%, Ca: 0.0036 Wt%, N: 0.0030 Wt%, Ni: 0.169 Wt%, O: 0.0011% Wt%; the balance of Fe and inevitable trace elements.

7. The X65MS acid-fast pipeline steel according to claim 1, wherein the hot continuous rolling process comprises: the finishing temperature is controlled to be 810 +/-20 ℃; the coiling temperature is 460 +/-20 ℃.

8. The X65MS acid-fast pipeline steel according to claim 1, wherein the hot continuous rolling process comprises: niobium microalloying and a thermal mechanical rolling process are combined to perform fine grain strengthening, solid solution strengthening, precipitation strengthening and phase change strengthening.