CN102465235A - X100 large deformation resistant pipeline steel and manufacturing process thereof - Google Patents

Abstract

The invention discloses an X100 large deformation resistant pipeline steel and a manufacturing process thereof. The chemical composition ratio by weight percentage is: C: 0.01-0.07%, Si: 0.1-0.6%, Mn: 1.5-2.2%, P: ≤0.015%, S: ≤0.004%, Nb: 0.03-0.1%, Ti: 0.005-0.03%, Mo: 0.10-0.40%, Cu: ≤0.50%, Ni: ≤0.50%, and the rest is Fe. The process comprises the following steps: in a slab reheating process, the slab heating temperature is 1100°C-1250°C; in a controlled In the rolling process, controlled rolling in the recrystallization zone is first carried out, and then controlled rolling in the non-recrystallization zone is carried out, wherein the termination temperature of the controlled rolling in the recrystallization zone is controlled at 1000℃～1080℃, the starting rolling temperature of the controlled rolling in the non-recrystallization zone is controlled at 880℃～950℃, and the termination rolling temperature is controlled at 760℃～850℃; in the controlled cooling process, the rolled steel plate is first air-cooled, and when the air-cooling is cooled to 10℃～60℃ below the phase transformation point Ar3, it enters laminar accelerated cooling, the cooling rate of the laminar accelerated cooling is 20～40℃/s, and the termination temperature is 250℃～450℃.

Description

A kind of X100 anti-large deformation pipeline steel and its manufacturing process

technical field

The invention relates to a pipeline steel and a manufacturing process thereof, in particular to an X100 large-deformation-resistant pipeline steel and a manufacturing process thereof, belonging to the technical field of iron and steel metallurgy.

Background technique

At present, as the country increases investment in infrastructure construction, the field of oil and gas pipelines is developing rapidly. Following the second line of the West-East Gas Pipeline, the third and fourth lines of the West-East Gas Pipeline have been included in the plan. According to the plan, in 2014, the West Third Line will run through the whole line, and then it will be interconnected with the main pipeline networks such as the West First Line, West Second Line, Shaanxi-Beijing First and Second Lines, and Sichuan-East Gas Transmission Line, forming a natural gas basic pipeline network that runs from east to west and north to south. ; In 2015, 17 natural gas pipeline projects including West Fourth Line, China-Myanmar Pipeline, and Shaanxi-Beijing Third Line will also be completed and put into operation.

The vigorous development of the oil and gas pipeline industry has brought unprecedented development opportunities to the field of pipeline steel, and at the same time it has also made the field of pipeline steel face formidable challenges. The safety of high-pressure, high-flow gas pipelines has put forward increasingly stringent requirements on the quality and performance of pipeline steel, especially the large-deformation-resistant pipeline steel based on strain design, which is one of the most challenging areas for the development of pipeline steel ; At present, there are few research reports on X100 large-deformation-resistant pipeline steel, and there is no relevant patent literature report in China.

Contents of the invention

The technical problem to be solved by the present invention is to provide an X100 large deformation resistant pipeline steel and its manufacturing process.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A X100 large deformation resistant pipeline steel provided by the present invention has the following chemical composition ratios according to weight percentage: C: 0.01-0.07%, Si: 0.1-0.6%, Mn: 1.5-2.2%, P: ≤0.015%, S: ≤0.004%, Nb: 0.03-0.1%, Ti: 0.005-0.03%, Mo: 0.10-0.40%, Cu: ≤0.50%, Ni: ≤0.50%, and the rest is Fe.

A manufacturing process of X100 large deformation resistant pipeline steel provided by the present invention includes converter or electric furnace smelting, out-of-furnace refining, vacuum treatment, continuous casting, slab reheating, controlled rolling, and controlled cooling processes;

The slab is obtained through smelting, refining outside the furnace, vacuum treatment, and continuous casting according to the chemical composition;

In the slab reheating process, the slab heating temperature is: 1100°C to 1250°C;

In the controlled rolling process, the controlled rolling in the recrystallization zone is carried out first, and then the controlled rolling in the non-recrystallized zone is carried out, wherein, the termination temperature of the controlled rolling in the recrystallized zone is controlled at 1000°C to 1080°C, and the non-recrystallized zone The starting rolling temperature of zone controlled rolling is controlled at 880°C~950°C, and the ending rolling temperature is controlled at 760°C~850°C;

In the controlled rolling process, the control of the rolling pass and the reduction: when rolling in the recrystallization zone, the pass reduction is ≥ 15%, and the cumulative total reduction is ≥ 60%, so as to achieve complete recrystallization. Crystallization to refine grains; when rolling in the non-recrystallized area, the compression ratio is controlled above 3.5 times.

According to a preferred embodiment of the manufacturing process of the X100 large deformation resistant pipeline steel, in the controlled cooling process, a two-stage controlled cooling process is used to cool the rolled steel plate:

The first stage of cooling is air cooling, the cooling rate is 1°C/s-3°C/s, the cooling termination temperature is 10-60°C below the phase transition point Ar3, and there are 10%-30% proeutectoid ferrite in the structure of the steel plate body generation;

The second stage of cooling is laminar accelerated cooling, the cooling rate is 20-40°C/s, and the cooling termination temperature is 250-450°C. The steel plate after controlled cooling is air-cooled to room temperature; Transform supercooled austenite into lath bainite and M/A, and finally obtain a multiphase structure of ferrite + bainite + M/A.

The X100 large-deformation-resistant pipeline steel provided by the present invention adopts the composition design concept of low C and high Mn and Si in terms of composition control, which improves the stability of austenite, thereby effectively reducing the production process of large-deformation-resistant pipeline steel. The strict requirements on the process in the air-cooling stage ensure that an appropriate amount (10% to 30%) of pro-eutectoid ferrite is produced within a wide cooling range in the air-cooling stage.

The specific role of C, Mn, Si in steel:

C is the most economical and basic strengthening element in steel. It has a significant effect on improving the strength of steel through solid solution strengthening and precipitation strengthening, but the increase of C content has a negative impact on the plasticity, toughness and welding performance of steel, especially Especially in X100 pipeline steel, due to the high content of various alloy elements, the carbon equivalent and weld sensitivity index are high; in this case, reducing the C content will help to improve the toughness and plasticity of the steel on the one hand , On the other hand, it is beneficial to improve the welding performance of steel. Therefore, the low-C design idea is adopted in the X100 large-deformation-resistant pipeline steel, and the C content is controlled at 0.01-0.07%.

Mn improves the strength of steel through solid solution strengthening, and is the most important element in pipeline steel to compensate for the loss of strength caused by the reduction of C content. Mn is also an element that expands the γ phase region, which helps to obtain fine phase transition products, which can improve the toughness of steel and reduce the ductile-brittle transition temperature. Therefore, the design idea of high Mn is adopted in the X100 large-deformation-resistant pipeline steel, and the Mn content is controlled at 1.5-2.2%.

Si increases the chemical potential of C and promotes the uphill diffusion of C. At the same temperature, the Si content in ferrite is much higher than that in austenite, which promotes the transfer of C in ferrite to austenite. Diffusion increases the carbon content in austenite. Therefore, although Si is an element that expands the ferrite phase region, after it is added to the steel, it can kinetically delay the precipitation of carbides in austenite and promote the stabilization of austenite. The stable austenite During the continuous cooling process, when the temperature drops below the Ms point, it transforms into martensite, thereby increasing the content of M/A as a hard phase in the pipeline steel and improving the tensile strength; in addition, the hard phase structure can also be passed through static The strengthening effect increases the yield strength of the material, thereby greatly improving the yield strength of the pipeline steel, which meets the performance requirements of the X100 pipeline steel in the API standard. Therefore, the present invention adopts the design idea of high Si, and the Si content is controlled at: 0.1-0.60%.

The invention provides an X100 large-deformation-resistant pipeline steel manufacturing process, through controlled rolling and controlled cooling, to obtain a pipeline steel with a ferrite+bainite+M/A multiphase structure. The content of ferrite in its structure is 10% to 30%, the content of M/A is 2% to 5%, and the rest is bainite; its transverse tensile and impact mechanical properties meet: yield strength ≥ 690MPa, tensile strength ≥780MPa, yield ratio ≤0.88; Charpy V-notch impact performance: when the test temperature is -20°C, CVN≥150J; drop weight performance: when the test temperature is -15°C, the average shear area SA% ≥85%; longitudinal tensile mechanical properties meet: yield strength ≥650MPa, tensile strength ≥810MPa, yield ratio ≤0.85, uniform elongation ≥7%.

The present invention has following characteristics:

(1) The present invention adopts the composition design concept of low C and high Mn. Reduce the C content, improve the plasticity and toughness of X100 large deformation pipeline steel, improve the welding performance; increase the Mn content to make up for the loss of strength caused by the reduction of carbon content, help to obtain fine phase transformation products, improve the steel toughness, reduce the ductile-brittle transition temperature; in addition, the increase of Mn content stabilizes austenite, and in the subsequent air cooling process, the precipitation of ferrite in a wide temperature range will not be too much, that is, to ensure the formation of an appropriate amount of prior eutectoid ferrite.

(2) The present invention adopts the composition design concept of high Si. Due to increasing the content of Si, the uphill diffusion of carbon is promoted, the diffusion of C in ferrite to austenite is promoted, and the carbon content in austenite is increased. It promotes the stabilization of austenite. During the cooling process, the stable austenite transforms into martensite when the temperature drops below the Ms point, thereby improving the hard phase M/ The content of A increases the tensile strength; in addition, the hard phase structure can also increase the yield strength of the material through static strengthening, so that the yield strength of the pipeline steel has been greatly improved.

(3) The present invention adopts a two-stage controlled cooling process of air cooling and laminar accelerated cooling to obtain a multiphase structure of ferrite+bainite+M/A. Compared with the X100 large-deformation-resistant pipeline steel produced by Japan's JFE using the on-line heat treatment (HOP) process, the X100 large-deformation-resistant pipeline steel of the present invention contains a certain amount of pro-eutectoid Ferrite bears part of the plastic deformation, so that the uniform elongation is relatively high; while the laminar flow accelerated cooling process adopts a higher cooling rate, which refines the effective grain size of the structure and makes up for the iron in the air cooling stage. The strength loss caused by the precipitation of the element body. In addition, the present invention takes into account the specific conditions of production equipment in domestic steel mills and does not use an on-line heat treatment (HOP) process, but a controlled rolling and controlled cooling process, thereby simplifying the production process and greatly improving the applicability of process control.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is an optical microstructure photograph obtained in Example 1 of the manufacturing process of X100 large-deformation-resistant pipeline steel of the present invention;

Fig. 2 is the SEM structure photo obtained in the manufacturing process embodiment 1 of the X100 large deformation resistant pipeline steel of the present invention;

Fig. 3 is the distribution picture of M/A obtained in the manufacturing process embodiment 1 of the X100 large deformation resistant pipeline steel of the present invention;

Fig. 4 is the effective grain size distribution diagram obtained in the manufacturing process embodiment 1 of the X100 large deformation resistant pipeline steel of the present invention;

Fig. 5 is an optical microstructure photograph obtained in Example 2 of the manufacturing process of X100 large-deformation-resistant pipeline steel of the present invention;

Fig. 6 is the SEM structure photo obtained in the manufacturing process embodiment 2 of the X100 large deformation resistant pipeline steel of the present invention;

Fig. 7 is the distribution picture of M/A obtained in Example 2 of the manufacturing process of X100 large-deformation-resistant pipeline steel of the present invention;

Fig. 8 is the effective grain size distribution diagram obtained in Example 2 of the manufacturing process of the X100 large deformation resistant pipeline steel of the present invention.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

A X100 large deformation resistant pipeline steel provided by the present invention has the following chemical composition ratios according to weight percentage: C: 0.01-0.07%, Si: 0.1-0.6%, Mn: 1.5-2.2%, P: ≤0.015%, S: ≤0.004%, Nb: 0.03-0.1%, Ti: 0.005-0.03%, Mo: 0.10-0.40%, Cu: ≤0.50%, Ni: ≤0.50%, and the rest is Fe.

A manufacturing process of X100 large deformation resistant pipeline steel provided by the present invention includes converter or electric furnace smelting, out-of-furnace refining, vacuum treatment, continuous casting, slab reheating, controlled rolling, and controlled cooling processes;

(1) According to the chemical composition, the continuous casting slab is obtained through smelting, refining outside the furnace, vacuum treatment and continuous casting process;

(2) In the slab reheating process, the continuous casting slab is sent into a soaking furnace for soaking treatment, the heating temperature is 1100°C to 1250°C, and the heating time is 150min to 240min, so that Ti, Nb, etc. The alloying elements are fully dissolved, and the specific soaking time is determined according to the thickness of the slab;

(3) After the continuous casting slab is released from the furnace through soaking treatment, it is descaled by high-pressure water to remove the oxide scale produced on the surface of the continuous casting slab during the heating process; the temperature of the continuous casting slab after descaling by high-pressure water About 1150°C;

(4) In the controlled rolling process, the descaled continuous casting slab is first subjected to controlled rolling in the recrystallization zone, and then controlled rolling in the non-recrystallized zone,

Among them, the termination temperature of controlled rolling in the recrystallization zone is controlled at 1000-1080°C, and the control of rolling passes and reductions: pass reductions ≥ 15%, cumulative total reductions ≥ 60%, in order to achieve Complete recrystallization to refine grains; since the reduction in the last pass of rolling in the recrystallization zone is related to the impact toughness of the pipeline steel, the reduction in the last pass of rolling in the recrystallization zone is controlled at ≥ 20%.

The starting rolling temperature of the controlled rolling in the non-recrystallization zone is controlled at 880-950°C, and the ending rolling temperature is controlled at 760-850°C; the compression ratio of the rolling in the non-recrystallization zone is controlled at more than 3.5 times;

In the controlled cooling process, a two-stage controlled cooling process is adopted to cool the rolled steel plate:

The first stage of cooling is air cooling, the cooling rate is 1°C/s-3°C/s, the cooling termination temperature is 10-60°C below the phase transition point Ar3, and there are 10%-30% proeutectoid ferrite in the structure of the steel plate body generation;

The second stage of cooling is laminar accelerated cooling, the cooling rate is 20-40°C/s, and the cooling termination temperature is 250-450°C. The steel plate after controlled cooling is air-cooled to room temperature; Transform supercooled austenite into lath bainite and M/A, and finally obtain a multiphase structure of ferrite + bainite + M/A.

Through the technological process provided by the present invention, X100 grade anti-large deformation pipeline steel with ferrite + bainite + M/A multiphase structure is obtained; the content of ferrite in the structure is 10% to 30%, M/A The content is 2% to 5%, and the rest is bainite; its transverse tensile and impact mechanical properties meet: yield strength ≥ 690MPa, tensile strength ≥ 780MPa, yield ratio ≤ 0.88, Charpy V-notch impact performance : When the test temperature is -20°C, CVN≥150J, drop weight performance: when the test temperature is -15°C, the average shear area SA%≥85%; longitudinal tensile mechanical properties meet: yield strength ≥650MPa, resistance Tensile strength ≥ 810MPa, yield ratio ≤ 0.85, uniform elongation ≥ 7%.

Example 1

The chemical composition (wt%) of the developed X100 grade anti-large deformation pipeline steel is: C accounts for 0.046, Si accounts for 0.34, Mn accounts for 1.94, Nb accounts for 0.06, Ti accounts for 0.008, Mo accounts for 0.25, Ni accounts for 0.27, Cu accounts for 0.26 , P≤50ppm, S≤50ppm.

Send the cast slab that meets the composition requirements to a soaking furnace at 1200°C. After holding the heat for 150 minutes, descale the cast slab by high-pressure water to remove the oxide scale on the cast slab, and then enter into two-stage rolling; Zone rolling, the rolling start temperature is 1100°C, and the final rolling temperature is 1050°C; after multi-pass rolling, the billet is rolled to 81mm, and the reductions of each pass are 18%, 20%, 22 %, 22%, 24%, and the cumulative total reduction is 70%.

The intermediate billet is warmed to 900°C before the finish rolling mill, and starts the second stage of rolling, that is, the rolling in the non-recrystallized area. The rolling start temperature is 900°C, the final rolling temperature is 830°C, and the compression ratio is 3.7.

After the second stage of rolling, the steel plate is air-cooled to 700°C for 60s, and then enters laminar accelerated cooling at a cooling rate of 25°C/s, and the end temperature of laminar accelerated cooling is 450°C. Through the two-stage cooling system of air cooling + laminar accelerated cooling, the multiphase structure of ferrite + bainite + M/A is finally obtained, as shown in Figure 1, Figure 2, and Figure 3, where the ferrite content is 15%. , the M/A content is 2.1%, and the rest is lath bainite; the effective grain size of the structure is shown in Figure 4, and the average effective grain size is 2.87 μm.

The transverse and longitudinal mechanical properties of the X100 large-deformation-resistant pipeline steel prepared in Example 1 were tested.

The test results of its transverse tensile and impact properties are as follows: yield strength R _t0.5 : 690MPa, tensile strength _Rm : 820MPa, yield ratio: 0.84, elongation after fracture: 28%, Charpy impact energy CVN _{(-20 ℃)} : 185J, drop weight tearing average shear area SA% _{(-15 ℃)} : 90%.

The test results of its longitudinal tensile properties are as follows: yield strength R _t05 : 655MPa, tensile strength R _m : 815MPa, yield ratio: 0.80, uniform elongation uEl: 7.8%.

Example 2

The chemical composition (wt%) of the developed X100 grade anti-large deformation pipeline steel is: C accounts for 0.045, Si accounts for 0.44, Mn accounts for 1.92, Nb accounts for 0.061, Ti accounts for 0.02, Mo accounts for 0.25, Ni accounts for 0.27, Cu accounts for 0.25 , P≤50ppm, S≤50ppm.

Send the slab that meets the composition requirements to a soaking furnace at 1200°C. After holding the heat for 150 minutes, descale the slab with high-pressure water to remove the iron oxide scale on the slab, and then enter into two-stage rolling. The first stage of rolling is rolled in the recrystallization zone, the rolling start temperature is 1130°C, and the final rolling temperature is 1070°C; after multiple passes of rolling, the billet is rolled to 81mm, and the reductions of each pass are respectively 18%, 20%, 22%, 22%, 24%, and the cumulative total reduction is 70%.

The intermediate billet is warmed to 900°C before the finish rolling mill, and starts the second stage of rolling, that is, rolling in the non-recrystallized area. The starting rolling temperature is 900°C, the final rolling temperature is 780°C, and the compression ratio is 3.7.

After the second stage of rolling, the steel plate is air-cooled to 690°C for 61s, and then enters laminar accelerated cooling at a cooling rate of 32°C/s, and the end temperature of laminar accelerated cooling is 420°C. Through the two-stage cooling system of air cooling + laminar accelerated cooling, the multiphase structure of ferrite + bainite + M/A is finally obtained, as shown in Figure 5, Figure 6, and Figure 7, where the ferrite content is 12%. , the M/A content is 3.5%, and the rest is lath bainite; the effective grain size of the structure is shown in Figure 8, and the average effective grain size is 2.04 μm.

The transverse and longitudinal mechanical properties of the X100 large-deformation-resistant pipeline steel prepared in Example 2 were tested.

The test results of its transverse tensile and impact properties are as follows: yield strength R _t0.5 : 700MPa, tensile strength _Rm : 835MPa, yield ratio: 0.84, elongation after fracture: 31%, Charpy impact energy CVN _{(-20 ℃)} : 184J, drop weight tearing average shear area SA% _{(-15 ℃)} : 90%.

The test results of its longitudinal tensile properties are as follows: yield strength R _t0.5 : 665MPa, tensile strength R _m : 825MPa, yield ratio: 0.81, uniform elongation uEl: 7.5%.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present invention. Should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (3)

1. An X100 large-deformation-resistant pipeline steel, characterized in that, according to the weight percentage, its chemical composition ratio is: C: 0.01-0.07%, Si: 0.1-0.6%, Mn: 1.5-2.2%, P: ≤0.015 %, S: ≤0.004%, Nb: 0.03-0.1%, Ti: 0.005-0.03%, Mo: 0.10-0.40%, Cu: ≤0.50%, Ni: ≤0.50%, and the rest is Fe. 2. A manufacturing process of X100 large-deformation-resistant pipeline steel, including converter or electric furnace smelting, refining outside the furnace, vacuum treatment, continuous casting, slab reheating, controlled rolling, and controlled cooling processes; it is characterized in that, According to the chemical composition described in claim 1, the slab is obtained through smelting, refining outside the furnace, vacuum treatment and continuous casting; In the slab reheating process, the slab heating temperature is: 1100°C to 1250°C; In the controlled rolling process, the controlled rolling in the recrystallization zone is carried out first, and then the controlled rolling in the non-recrystallized zone is carried out, wherein, the termination temperature of the controlled rolling in the recrystallized zone is controlled at 1000°C to 1080°C, and the non-recrystallized zone The starting rolling temperature of zone controlled rolling is controlled at 880°C~950°C, and the ending rolling temperature is controlled at 760°C~850°C; In the controlled rolling process, the control of the rolling pass and the reduction: when rolling in the recrystallization zone, the pass reduction is ≥ 15%, and the cumulative total reduction is ≥ 60%, so as to achieve complete recrystallization. Crystallization to refine grains; when rolling in the non-recrystallized area, the compression ratio is controlled above 3.5 times. 3. The manufacturing process of X100 large-deformation-resistant pipeline steel according to claim 2, characterized in that, in the controlled cooling process, a two-stage controlled cooling process is used to cool the rolled steel plate: The first stage of cooling is air cooling, the cooling rate is 1°C/s-3°C/s, the cooling termination temperature is 10-60°C below the phase transition point Ar3, and there are 10%-30% proeutectoid ferrite in the structure of the steel plate body generation; The second stage of cooling is laminar accelerated cooling, the cooling rate is 20-40°C/s, and the cooling termination temperature is 250-450°C. The steel plate after controlled cooling is air-cooled to room temperature; Transform supercooled austenite into lath bainite and M/A, and finally obtain a multiphase structure of ferrite + bainite + M/A.

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