CN110983187A

CN110983187A - Novel high-strength weather-resistant pipeline steel X80 steel plate and production method thereof

Info

Publication number: CN110983187A
Application number: CN201911361056.9A
Authority: CN
Inventors: 许少普; 袁永旗; 朱书成; 李忠波; 刘庆波; 张占杰; 张涛; 李亮; 杨东; 朱先兴; 王希彬; 任义
Original assignee: Nanyang Hanye Special Steel Co Ltd
Current assignee: Nanyang Hanye Special Steel Co Ltd
Priority date: 2019-12-25
Filing date: 2019-12-25
Publication date: 2020-04-10

Abstract

The invention discloses a novel high-strength weather-resistant pipeline steel X80 steel plate with the thickness of less than 40mm and a production method thereof, wherein the novel high-strength weather-resistant pipeline steel X80 steel plate comprises the following chemical components: C. si, Mn, N, V, Ti, Ni, Cr, Ce, La, Cu, Mo, Als, P, S, and the balance Fe and residual elements; the steel sheet has an acicular ferrite structure; through the process control of converter smelting, VD + LF + VD smelting, continuous casting, heating, controlled rolling and controlled cooling and the like, the yield strength of the obtained steel plate is 562-680 MPa, the tensile strength is 675-790 MPa, the elongation can be controlled to be 25-30%, the V-shaped-30 ℃ longitudinal impact power is controlled to be 180-315J, the average value of a drop hammer tear test at-15 ℃ is 90%, the welding crack sensitivity coefficient Pcm is less than or equal to 0.25, the weather resistance index is more than or equal to 6.0, and meanwhile, the HIC and SSCC tests are qualified through tests and completely meet the X80 pipeline steel standard requirements.

Description

Novel high-strength weather-resistant pipeline steel X80 steel plate and production method thereof

Technical Field

The invention relates to steel, in particular to a novel high-strength weather-resistant pipeline steel X80 steel plate and a production method thereof.

Background

X80 belongs to American standard API5L medium and high strength pipeline steel, and has the characteristics of high strength, excellent low temperature toughness, good processability and welding performance and the like. With the great increase of the demand of petroleum and natural gas, the conveying capacity has been developed greatly, and higher requirements such as weather resistance, service life and the like are provided for the quality of pipeline steel.

Disclosure of Invention

Therefore, the invention aims to provide a novel high-strength weather-resistant pipeline steel X80 steel plate and a production method thereof.

The technical scheme adopted by the invention is that the high-strength weather-resistant pipeline steel X80 steel plate with the thickness of less than 40mm comprises the following chemical components in percentage by mass (unit, wt%): 0.03 to 0.10 percent of C, 0.10 to 0.55 percent of Si, 0.85 to 1.35 percent of Mn, 0.055 to 0.080 percent of Nb, 0.05 to 0.07 percent of V, less than or equal to 0.017 percent of Ti, 0.35 to 0.55 percent of Ni, 0.35 to 0.75 percent of Cr, 0.25 to 1.50 percent of Ce, 0.25 to 2.80 percent of La, 0.25 to 0.70 percent of Cu, 0.35 to 0.50 percent of Mo, less than or equal to 0.050 percent of Als, less than or equal to 0.008 percent of P, less than or equal to 0.002 percent of S, and the balance of Fe and residual elements.

Designing components:

carbon (C): the strength of the steel is improved by solid solution strengthening and precipitation strengthening, but the range of the C element is 0.03-0.10% in consideration of the welding performance of the steel.

Manganese (Mn): the improvement of the strength of steel by solid solution strengthening is the most important and economical strengthening element in line pipe steel to compensate for the strength loss caused by the decrease in C content. Mn is beneficial to expanding an austenite phase region, reducing austenite phase transition temperature, refining internal crystal grains, improving the toughness of steel and reducing ductile-brittle transition temperature. Manganese is second only to nickel in its ability to stabilize the austenitic structure and is also beneficial to increase the hardenability of steel.

Aluminum (Al): the aluminum is mainly used for deoxidizing and refining grains, and can inhibit the aging of low-carbon steel and improve the toughness of the steel at low temperature. When the content is high, the oxidation resistance of the steel and the corrosion resistance in oxidizing acid and H2S gas can be improved, and the electrical and magnetic properties of the steel can be improved.

Niobium (Nb): in the steel, the method is beneficial to refining crystal grains, improving the impact toughness of the steel and reducing the brittle transition temperature of the steel, and can prevent the intergranular corrosion of the steel caused by an oxidizing medium in the austenitic steel.

Vanadium (V): vanadium has strong affinity with carbon, ammonia and oxygen, and forms corresponding stable compounds with the vanadium. Vanadium is mainly present in steel in the form of carbides. The main function of the steel is to refine the structure and crystal grains of the steel and improve the strength and toughness of the steel;

titanium (Ti): titanium can fix nitrogen in steel to form titanium carbide and carbonitride, thereby improving the strength of the steel, preventing the tendency of grain growth of the steel at high temperature and improving the welding performance of the steel.

Nickel (Ni): the nickel strengthens ferrite and refines pearlite in the steel, improves the strength without reducing the ductility, toughness and other process properties of the steel, and can reduce the low-temperature brittle transition temperature of the steel.

Chromium (Cr): chromium is an element for enlarging an austenite phase region, can improve the hardenability of steel, and can improve the hardness and the wear resistance of carbon steel without making the steel brittle;

molybdenum (Mo): mo delays the transformation of proeutectoid ferrite, promotes the formation of acicular ferrite and bainite, improves the obdurability of low alloy steel, and can also improve the solid solubility of microalloy elements (Nb, V and Ti) in austenite, delay the precipitation and precipitation of microalloy carbonitride, so that more microalloy elements can be reserved to be precipitated from the ferrite at a lower temperature, and a larger precipitation strengthening effect can be generated;

copper (Cu): the prominent effect of copper in steel is to improve the atmospheric corrosion resistance of common low alloy steel, and particularly when the copper is used in combination with phosphorus, the strength and yield ratio of the steel can be improved by adding the copper, and the welding performance is not influenced;

cerium (Ce) and lanthanum (la): the fluidity of the steel is improved, non-metallic inclusions are reduced, the steel structure is compact and pure, the plasticity and the impact toughness of the forged and rolled steel are improved, and meanwhile, the oxidation resistance and the corrosion resistance of the steel are greatly improved.

In order to obtain the product, the production method adopted by the invention comprises the process controls of converter smelting, VD + LF + VD smelting, continuous casting, heating, controlled rolling and controlled cooling, slow cooling and the like, and specifically comprises the following steps:

① smelting in a converter, namely adopting high-quality scrap steel, controlling the slag alkalinity R to be 2.5-4.0 in the smelting process, controlling the tapping P to be less than or equal to 0.010 percent and the tapping S to be less than or equal to 0.010 percent after the smelting is finished, and requiring soft argon blowing in the whole process in the tapping process;

② VD + LF + VD smelting, wherein, one VD decarburization is carried out, after the molten steel is hung to a VD furnace from a converter, the pressure is maintained for 15-35 min under the vacuum degree of < 67Pa, the C content in the molten steel is controlled within 0.10 percent, after one VD is finished, the molten steel is hung to the LF furnace for refining treatment, argon is closed and a calcium wire is added before leaving the station after the molten steel is stirred by blowing argon in the whole LF refining process, the slag alkalinity is controlled to be 2.5-4.0, the addition of deoxidizer and slag is timely adjusted according to the oxygen content and white slag condition of the molten steel, the molten steel is hung to the VD furnace for the second VD refining degassing treatment, the vacuum degree of the VD process is < 67Pa, the pressure maintaining time is more than or equal to 20min, after vacuum breaking, soft argon is blown, after the covering agent is kept warm, the leaving station temperature is 1525 ℃, and the cleanliness target is controlled, namely the sum of four series of inclusions A (sulfides), B (aluminum oxides), C (silicates) and D (spherical oxides) is;

③ continuous casting, wherein good equipment condition of the casting machine is ensured before steel casting, the superheat degree of a tundish is 15 +/-15 ℃, the pulling speed is constant, electromagnetic stirring is adopted, and the continuous casting steel casting requires whole-process protection casting;

④ heating, wherein the temperature of the preheating section is less than or equal to 1000 ℃, the temperature of the heating section is 1200-;

⑤ controlled rolling and controlled cooling, namely three-stage rolling, wherein the rolling is performed at one stage by adopting high temperature, low speed and high reduction, the initial rolling temperature is 1050-.

⑥ slow cooling, namely, the steel plate is straightened and then is timely taken off line and piled for cooling, the temperature of the piled cooling is more than or equal to 300 ℃, the time of the piled cooling is more than or equal to 24h, and the slow cooling is adopted to avoid the internal stress from being released too soon and generate internal cracking, and simultaneously, the harmful gas in the steel plate is further promoted to overflow.

Through the component design and the process control, the high-strength weather-resistant pipeline steel X80 steel plate with the thickness of less than 40mm is successfully developed, the yield strength is controlled to be 562-680 MPa, the tensile strength is controlled to be 675-790 MPa, and the elongation is controlled to be 25% -30%; the V-type longitudinal impact energy at minus 30 ℃ is controlled to be 180-315J, the average value of a drop hammer tear test at minus 15 ℃ is 90%, the weld crack sensitivity coefficient Pcm is less than or equal to 0.25, the weather resistance index is greater than or equal to 6.0, and the HIC test and the SSCC test are qualified through tests and completely meet the X80 pipeline steel standard requirement.

Detailed Description

The high-strength weather-resistant pipeline steel X80 steel plate with the thickness of less than 40mm comprises the following chemical components in percentage by mass (unit, wt%): 0.03 to 0.10 percent of C, 0.10 to 0.55 percent of Si, 0.85 to 1.35 percent of Mn, 0.055 to 0.080 percent of Nb, 0.05 to 0.07 percent of V, less than or equal to 0.017 percent of Ti, 0.35 to 0.55 percent of Ni, 0.35 to 0.75 percent of Cr, 0.25 to 1.50 percent of Ce, 0.25 to 2.80 percent of La, 0.25 to 0.70 percent of Cu, 0.35 to 0.50 percent of Mo, less than or equal to 0.050 percent of Als, less than or equal to 0.008 percent of P, less than or equal to 0.002 percent of S, and the balance of Fe and residual elements.

The high-strength weather-resistant pipeline steel X80 steel plate with the chemical components of less than 40mm is obtained through the process control of KR molten iron pretreatment, converter smelting, VD + LF + VD smelting, continuous casting, heating, controlled rolling and controlled cooling, slow cooling and the like, wherein the process parameters and the mechanical properties are shown in the following tables 1 and 2.

TABLE 1 chemical composition of high-strength weathering line steel X80 steel plate (Wt,%)

TABLE 2 mechanical Properties of high-strength weathering-resistant pipeline steel X80 steel plate

50 batches of high-strength weather-resistant pipeline steel X80 steel plates with the thickness of less than 40mm are produced in a trial mode, all performance indexes meet standard requirements and the allowance is large, wherein the yield strength is controlled to be 562-680 MPa, the tensile strength is controlled to be 675-790 MPa, the elongation is controlled to be 25-30%, the V-type longitudinal impact energy at the temperature of 30 ℃ below zero is controlled to be 180-315J, the welding crack sensitivity coefficient Pcm is less than or equal to 0.25, and the weather resistance index is more than or equal to 6.0;

the average value of drop-weight tear tests at 15 ℃ below zero is 90 percent, and the standard requirement of X80 is completely met.

The HIC and the SSCC both meet the requirements of relevant standards and are qualified through the detection of the national petroleum pipe quality supervision and inspection center.

And (3) external inspection and flaw detection, wherein the developed steel plate is subjected to flaw detection according to EN10160 strictly according to the standard of quality product rate of 100%, wherein the proportion reaching the S2/E3 standard is 90%, and the proportion reaching the S1/E1 standard is 100%, so that the expected effect is achieved.

Claims

1. The utility model provides a novel high strength resistant weathering pipeline steel X80 steel sheet which characterized in that: the thickness of the steel plate is less than or equal to 40mm, and the steel plate comprises the following chemical components in percentage by mass (unit, wt%): 0.03 to 0.10 percent of C, 0.10 to 0.55 percent of Si, 0.85 to 1.35 percent of Mn, 0.055 to 0.080 percent of Nb, 0.05 to 0.07 percent of V, less than or equal to 0.017 percent of Ti, 0.35 to 0.55 percent of Ni, 0.35 to 0.75 percent of Cr, 0.25 to 1.50 percent of Ce, 0.25 to 2.80 percent of La, 0.25 to 0.70 percent of Cu, 0.35 to 0.50 percent of Mo, less than or equal to 0.050 percent of Als, less than or equal to 0.008 percent of P, less than or equal to 0.002 percent of S, and the balance of Fe and residual elements; the steel sheet has an acicular ferrite structure.

2. The production method of the novel high-strength weather-resistant pipeline steel X80 steel plate according to claim 1, which comprises converter smelting, VD + LF + VD smelting, continuous casting, heating, controlled rolling and controlled cooling, and is characterized in that:

② VD + LF + VD smelting, wherein, primary VD decarburization is carried out, after molten steel is hung from a converter to a VD furnace, pressure is maintained for 15-35 min under the vacuum degree of < 67Pa, the C content in the molten steel is controlled within 0.10%, after primary VD is finished, the molten steel is hung to the LF furnace for refining treatment, argon is closed and a calcium wire is added before leaving the station after argon stirring is carried out in the whole LF refining process, slag making materials are added, the slag alkalinity is controlled to be 2.5-4.0, the addition of deoxidizing agents, slag materials and the like is timely adjusted according to the oxygen content and white slag condition of the molten steel, the molten steel is hung to the VD furnace for secondary VD refining degassing treatment, the vacuum degree of the VD process is < 67Pa, the pressure maintaining time is more than or equal to 20min, after vacuum breaking, soft argon is blown, after finishing, the covering agent is kept warm, the leaving station temperature is 1525 ℃, and the cleanliness target is controlled, namely, wherein, the;

③ continuous casting, wherein the condition of the casting machine is ensured to be good before steel casting, the superheat degree of a tundish is 15 +/-15 ℃, the pulling speed is constant, electromagnetic stirring is adopted, and the continuous casting steel casting requires whole-process protection casting;

⑤, rolling and cooling control, namely rolling in three stages, wherein rolling is performed in one stage at high temperature, low speed and high reduction, the initial rolling temperature is 1050-.