CN111041366A

CN111041366A - Quenched and tempered high-strength steel plate 12MnNiVR for large-scale oil storage tank pressure vessel and production method thereof

Info

Publication number: CN111041366A
Application number: CN201911359331.3A
Authority: CN
Inventors: 许少普; 陈熙; 朱书成; 李忠波; 康文举; 张占杰; 杨阳; 刘庆波; 李亮; 杨东; 张涛; 陈良; 曹强; 董真真; 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: 2020-04-21

Abstract

The invention discloses a quenched and tempered high-strength steel plate 12MnNiVR for a large-scale oil storage tank pressure vessel and a production method thereof, wherein the steel plate comprises the following chemical components: C. si, Mn, P, S, Nb, V, Mo, Ni, Cr, and the balance Fe and residual elements; the steel plate has a tempered bainite structure; the production method comprises the process control of clean steel smelting, water-cooling die casting, steel ingot heating, steel ingot cogging, intermediate billet cleaning, intermediate billet heating, intermediate billet rolling, steel plate heaping cooling, tempering and the like; the steel grade is based on C-Mn elements, alloy elements such as Ni and V are added, and through quenching and tempering heat treatment, the alloy elements are fully dissolved and separated, the performances of the steel plate in the thickness direction, the rolling direction and the width direction are uniform, the surplus of impact energy is large, the steel plate has high strength not lower than 610Mpa and good longitudinal and transverse impact performances, the flaw detection of the steel plate stably reaches the I-level flaw detection standard requirement, and the standard and the quality requirement of a user on the steel plate are completely met.

Description

Quenched and tempered high-strength steel plate 12MnNiVR for large-scale oil storage tank pressure vessel and production method thereof

Technical Field

The invention relates to the technical field of production of quenched and tempered high-strength steel plates for pressure vessels, in particular to a quenched and tempered high-strength steel plate 12MnNiVR for a large-scale oil storage tank pressure vessel and a production method thereof.

Background

With the development of petrochemical industry and the need of national strategic reserves, the demand and consumption of petroleum are increasing, and the petroleum storage tank is developing towards large-scale and large-scale. The construction of large storage tanks is rapidly developed, and the steel plates for large storage tanks have a non-negligible status as important components. In recent years, the tolerance construction projects of the national crude oil storage are more and more, and the construction of a 10-ten-thousand cubic meter floating roof oil tank becomes the mainstream of large-scale petrochemical projects and the construction of the national storage. The steel 12MnNiVR for the large-scale oil storage tank has good welding performance, high strength and high impact, and is mainly used for manufacturing the large-scale oil storage tank of 10 ten thousand cubic meters.

Disclosure of Invention

Therefore, the invention aims to provide a quenched and tempered high-strength steel plate 12MnNiVR for a large-scale oil storage tank pressure vessel and a production method thereof.

In order to achieve the aim, the invention adopts the technical scheme that the quenched and tempered high-strength steel plate 12MnNiVR for the large-scale oil storage tank pressure container comprises the following chemical components in percentage by mass (unit, wt%): c: 0.09-0.11, Si: 0.20-0.30, Mn: 1.30-1.50, P: less than or equal to 0.010 percent and S: less than or equal to 0.002, Nb: 0.025-0.035, V0.045-0.055, Mo 0.15-0.29, Ni: 0.20-0.40, Cr: 0.18-0.28, and the balance Fe and residual elements.

The thickness of the steel plate is less than or equal to 65 mm; the steel sheet has a tempered bainite structure.

In order to obtain the product, the production method further comprises the steps of clean steel smelting, die casting and casting, steel ingot heating, steel ingot cogging, large billet cutting and cleaning, small billet heating, small billet rolling, steel plate stacking and cooling, and hardening and tempering.

1) The smelting process of clean steel has the key points that the cleanliness of molten steel can reach that S is less than or equal to 30ppm, P is less than or equal to 100ppm, N is less than or equal to 40ppm, H is less than or equal to 1.2ppm, O is less than or equal to 30ppm, and the sum of four series inclusions of A (sulfides), B (aluminum oxides), C (silicates) and D (spherical oxides) is less than or equal to 2.0 grade;

a. smelting in a converter: the method comprises the following steps of (1) pre-removing S in the converter molten iron by KR pretreatment, wherein the S content is below 0.010% after S removal, the temperature of the converter molten iron is about 1250 ℃, the scrap steel is high-quality scrap steel, the converter smelting is finished, the tapping P is controlled within 0.008% and the tapping C is controlled within 0.05%, and aluminum blocks are added for deoxidation in the tapping process;

b. LF refining: the refining process mainly uses aluminum wires or aluminum particles as deoxidizers, the temperature is controlled to be 1590 +/-10 ℃ after the first heating is finished, the first heating mainly takes slagging as a main component, medium carbon is added to prepare a primary Mn component in the process, the second heating is started after the first heating and sampling, low carbon ferrochrome is added to prepare Cr, ferrocolumbium, ferrovanadium is added to prepare V, ferromolybdenum is added to prepare Mo, nickel plates are added to prepare Ni in the second heating process, the third heating is conducted to fine adjustment components, the temperature is increased to 1630 +/-10 ℃, the lime consumption in the whole refining process is controlled to be 14.5-15.5kg/t steel, the time is controlled to be within 150min, and the final slag is ensured to be white foam slag with good fluidity;

c. VD vacuum smelting: controlling the VD vacuum degree below 60Pa, controlling argon blowing time according to 15-18min, controlling argon blowing intensity at 150-250Nl/min, ensuring the vacuum degassing effect, ensuring that the H content is less than or equal to 1.4ppm after VD is finished, adding an aluminum wire for preparing Als after VD is broken, and blowing argon for 5-8min to ensure that impurities are fully floated;

2) the key points of the water-cooling die casting process are as follows: the casting temperature is 1550-;

3) the main points of the steel ingot heating process are as follows: demoulding the steel ingot, slowly cooling the steel ingot in a slow cooling pit to remove stress, slowly cooling the steel ingot to 200-250 ℃, charging the steel ingot, wherein the temperature of the charging furnace is less than 650 ℃, heating the steel ingot to 880-plus-material temperature 920 ℃ at a temperature of less than 55 ℃/h, preserving the heat for 5-7h, then quickly heating the steel ingot to 1230-plus-material temperature 1250 ℃, preserving the heat for 14-16h, and controlling the temperature and heating to prevent the large temperature difference between the inside and the outside of the steel ingot from generating stress and ensure;

4) the main points of the steel ingot cogging process are as follows: rolling at high temperature, low speed and high pressure is adopted, the deformation coefficient of the rough rolling stage is improved, the rolling effect is enabled to permeate into the core, the initial rolling temperature is 1000-1030 ℃, the single-pass reduction amount is controlled to be 50-55mm, the thickness of an intermediate blank is 200-250mm, the initial rolling temperature is above 850 ℃, the temperature of the initial rolling and the final rolling is above 820 ℃, ACC water cooling is carried out, the temperature of red returning is controlled to be above 750 ℃, the temperature of air cooling is 400 ℃, the intermediate blank is hoisted to a slow cooling pit for slow cooling, and H stress removal is facilitated;

5) the big blank cutting and cleaning process has the following key points: dividing a large billet into small billets according to the requirements of finished products, cleaning cracks, surface pits and peripheral hot cutting slag on the surfaces of the small billets, wherein the division into the small billets is beneficial to the subsequent controlled rolling process and the control of plates, and the hot cutting slag cleaning can prevent the small billets from generating heavy skin during rolling;

6) the key points of the billet heating process are as follows: preheating the small billets to 200-250 ℃, heating the small billets to 450 ℃, performing steel sealing for 2h, heating the small billets to 750 ℃ at a temperature of less than 55 ℃/h, heating the small billets to 1210-1230 ℃ at a temperature of less than or equal to 75 ℃/h, and tapping after heat preservation for 2 h;

7) the key points of the small billet rolling process are as follows: rolling in two stages, wherein the initial rolling temperature in the rough rolling stage is 980-1020 ℃, uniform reduction is performed, steel is dried after rolling to the thickness of 80-120mm, the second stage rolling is started, small pressure is adopted in the second stage, multi-pass slow rolling is performed, the pass reduction is 8-10 mm, crystal grains are fully crushed, the crystal grains are prevented from growing, the final rolling temperature is 800-870 ℃, ACC (aluminum chloride) is added for water cooling after air cooling is performed for 40-60S after the final rolling is finished, and the temperature of red returning is controlled to be 680-720 ℃;

8) the steel plate pile cooling process has the key points that: the temperature of the steel plate entering the slow cooling pit is more than or equal to 350 ℃, and the slow cooling time is 48 hours, which is beneficial to removing H and removing stress;

9) the key points of the quenching and tempering process are as follows: adopting a quenching and tempering process, controlling the quenching temperature at 920 +/-10 ℃, keeping the temperature T at 2.2min/mm, discharging the steel plate from the furnace, cooling the steel plate to the normal temperature by water, and controlling the cooling speed to be more than or equal to 15 ℃/s; tempering temperature is 620-640 ℃, the heat preservation time T is 4.0-4.2 min/mm, and the steel plate is slowly cooled to normal temperature at the speed of less than 20 ℃/h after being taken out of the furnace; high-temperature tempering is adopted, so that carbide is precipitated, and a tempered bainite structure is obtained.

Compared with the prior art, the invention has the following advantages:

the method adopts a low-carbon route and controls the carbon equivalent, thereby being beneficial to the control of the yield ratio and the welding performance of the steel plate, C is a main factor influencing the welding crack sensitivity of the steel, and the hardness and the hardening tendency of a welding heat affected zone can be reduced by adopting low carbon under the same Pcm;

the cleanliness, the uniformity and the stability of the quality of the steel plate are ensured by adopting a plurality of measures. The cleanliness of the steel billet is ensured by adopting a clean steel smelting technology; the steel ingot cast by the water-cooled ingot mould is beneficial to reducing the segregation problem inside the steel ingot relative to a continuous casting billet; fully refining the original austenite structure of the steel plate by adopting a rolling process with large rolling reduction and equal control; the roller bottom type non-oxidation radiation heating mode is adopted to ensure that the surface of the steel plate is not oxidized and ensure the surface quality of the steel plate;

the national standard of a quenched and tempered high-strength steel plate 12MnNiVR for the large-scale oil storage tank pressure vessel requires 10-60mm, and the thickness of an experimental steel plate can reach 65mm through the component and process control of the invention;

the steel grade is based on C-Mn elements, alloy elements such as Ni and V are added, and through quenching and tempering heat treatment, the alloy elements are fully dissolved and separated, the performances of the steel plate in the thickness direction, the rolling direction and the width direction are uniform, the surplus of impact energy is large, the steel plate has high strength not lower than 610Mpa and good longitudinal and transverse impact performances, the flaw detection of the steel plate stably reaches the I-level flaw detection standard requirement, and the standard and the quality requirement of a user on the steel plate are completely met.

Drawings

The structure and features of the present invention will be further described with reference to the accompanying drawings and examples.

FIG. 1 is a metallographic schematic diagram of a 10mm 12MnNiVR steel plate in the embodiment of the invention.

FIG. 2 is a metallographic schematic diagram of a 20mm 12MnNiVR steel plate in the embodiment of the invention.

FIG. 3 is a schematic metallographic diagram of a 50mm 12MnNiVR steel plate in the example of the invention.

FIG. 4 is a metallographic schematic diagram of a 65mm12MnNiVR steel plate in the embodiment of the invention.

FIG. 5 is a schematic structural view of a 10mm 12MnNiVR scanning electron microscope after tempering according to the embodiment of the invention.

Fig. 6 is a partially enlarged schematic view of fig. 5.

FIG. 7 is a schematic structural view of 20mm 12MnNiVR in the example of the invention under a scanning electron microscope after tempering.

Fig. 8 is a partially enlarged schematic view of fig. 7.

FIG. 9 is a schematic structural view of a 50mm 12MnNiVR scanning electron microscope after tempering according to the embodiment of the invention.

Fig. 10 is a partially enlarged schematic view of fig. 9.

FIG. 11 is a schematic structural view of a 65mm12MnNiVR scanning electron microscope after tempering according to the embodiment of the invention.

Fig. 12 is a partially enlarged schematic view of fig. 11.

Detailed Description

The quenched and tempered high-strength steel plate 12MnNiVR for the large-scale oil storage tank pressure container comprises the following chemical components in percentage by mass (unit, wt%): c: 0.09-0.11, Si: 0.20-0.30, Mn: 1.30-1.50, P: less than or equal to 0.010 percent and S: less than or equal to 0.002, Nb: 0.025-0.035, V0.045-0.055, Mo 0.15-0.29, Ni: 0.20-0.40, Cr: 0.18-0.28, and the balance Fe and residual elements.

(1) Clean steel smelting process key points

through the process, the cleanliness of the molten steel can reach that S is less than or equal to 30ppm, P is less than or equal to 100ppm, N is less than or equal to 40ppm, H is less than or equal to 1.2ppm, O is less than or equal to 30ppm, and the sum of four series inclusions of A (sulfides), B (aluminum oxides), C (silicates) and D (spherical oxides) is less than or equal to 2.0 grade;

(2) the key points of the water-cooling die casting process are as follows: the casting temperature is 1550-;

(3) the main points of the steel ingot heating process are as follows: demoulding the steel ingot, slowly cooling the steel ingot in a slow cooling pit to remove stress, slowly cooling the steel ingot to 200-250 ℃, charging the steel ingot, wherein the temperature of the charging furnace is less than 650 ℃, heating the steel ingot to 880-plus-material temperature 920 ℃ at a temperature of less than 55 ℃/h, preserving the heat for 5-7h, then quickly heating the steel ingot to 1230-plus-material temperature 1250 ℃, preserving the heat for 14-16h, and controlling the temperature and heating to prevent the large temperature difference between the inside and the outside of the steel ingot from generating stress and ensure;

(4) the main points of the steel ingot cogging process are as follows: rolling at high temperature, low speed and high pressure is adopted, the deformation coefficient of the rough rolling stage is improved, the rolling effect is enabled to permeate into the core, the initial rolling temperature is 1000-1030 ℃, the single-pass reduction amount is controlled to be 50-55mm, the thickness of an intermediate blank is 200-250mm, the initial rolling temperature is above 850 ℃, the temperature of the initial rolling and the final rolling is above 820 ℃, ACC water cooling is carried out, the temperature of red returning is controlled to be above 750 ℃, the temperature of air cooling is 400 ℃, the intermediate blank is hoisted to a slow cooling pit for slow cooling, and H stress removal is facilitated;

(5) the big blank cutting and cleaning process has the following key points: dividing a large billet into small billets according to the requirements of finished products, cleaning cracks, surface pits and peripheral hot cutting slag on the surfaces of the small billets, wherein the division into the small billets is beneficial to the subsequent controlled rolling process and the control of plates, and the hot cutting slag cleaning can prevent the small billets from generating heavy skin during rolling;

(6) the key points of the billet heating process are as follows: preheating the small billets to 200-250 ℃, heating the small billets to 450 ℃, performing steel sealing for 2h, heating the small billets to 750 ℃ at a temperature of less than 55 ℃/h, heating the small billets to 1210-1230 ℃ at a temperature of less than or equal to 75 ℃/h, and tapping after heat preservation for 2 h;

(7) the key points of the small billet rolling process are as follows: rolling in two stages, wherein the initial rolling temperature in the rough rolling stage is 980-1020 ℃, uniform reduction is performed, steel is dried after rolling to the thickness of 80-120mm, the second stage rolling is started, small pressure is adopted in the second stage, multi-pass slow rolling is performed, the pass reduction is 8-10 mm, crystal grains are fully crushed, the crystal grains are prevented from growing, the final rolling temperature is 800-870 ℃, ACC (aluminum chloride) is added for water cooling after air cooling is performed for 40-60S after the final rolling is finished, and the temperature of red returning is controlled to be 680-720 ℃;

(8) the steel plate pile cooling process has the key points that: the temperature of the steel plate entering the slow cooling pit is more than or equal to 350 ℃, and the slow cooling time is 48 hours, which is beneficial to removing H and removing stress;

(9) the key points of the quenching and tempering process are as follows: adopting a quenching and tempering process, controlling the quenching temperature at 920 +/-10 ℃, keeping the temperature T at 2.2min/mm, discharging the steel plate from the furnace, cooling the steel plate to the normal temperature by water, and controlling the cooling speed to be more than or equal to 15 ℃/s; tempering temperature is 620-640 ℃, the heat preservation time T is 4.0-4.2 min/mm, and the steel plate is slowly cooled to normal temperature at the speed of less than 20 ℃/h after being taken out of the furnace; high-temperature tempering is adopted, so that carbide is precipitated, and a tempered bainite structure is obtained.

The 12MnNiVR finished steel with the chemical components as shown in the following table 1 is obtained by the processes of clean steel smelting, water-cooling die casting, steel ingot heating, steel ingot cogging, large billet segmentation and cleaning, small billet heating, small billet rolling, steel plate heaping cooling, tempering and the like, wherein a die casting ingot type adopts a 40t steel ingot, the thickness of the upper opening of the steel ingot is 800mm, the thickness of the lower opening of the steel ingot is 740mm, and the process parameters are as shown in the following tables 1 and 2.

TABLE 1 12MnNiVR Final product composition with different thicknesses

Thickness/mm	C	Si	Mn	P	S	Als	Cr	Nb	Ni	Mo	V
													10	0.10	0.25	1.41	0.007	0.001	0.025	0.22	0.028	0.28	0.26	0.046
20	0.10	0.26	1.36	0.008	0.002	0.018	0.188	0.026	0.313	0.276	0.046
												50	0.09	0.23	1.43	0.008	0.001	0.030	0.230	0.032	0.26	0.26	0.048
65	0.09	0.20	1.48	0.009	0.001	0.040	0.25	0.033	0.35	0.28	0.052

TABLE 2 Steel plate cleanliness

FIGS. 1 to 4 show metallographic diagrams of 12MnNiVR steel plates of 10mm, 20mm, 50mm and 65mm in examples, respectively, and the results of microscopic examination on the metallographic phase of the steel plates of the above sizes show that the sum of inclusions in four systems of A (sulfide), B (alumina), C (silicate) and D (spherical oxide) in the structure is less than or equal to 2.0. The reasonable rolling and tempering process controls the average grain size between 9.0 and 10.0, the grains are fine, the level of the banded structure is low, and the structure is a bainite tempered structure and a tempered sorbite.

FIGS. 5 to 12 show the structural schematic diagrams of 12MnNiVR steel plates of 10mm, 20mm, 50mm and 65mm in the examples under the scanning electron microscope after tempering respectively, through analyzing the structure of the steel plates under the scanning electron microscope, after the 12MnNiVR steel plates are tempered at high temperature, through the analysis of the structure of the scanning electron microscope, the tempered structure of the steel plates can be seen with the precipitation of carbides which are densely distributed and have the forms of fine spherical particles, and simultaneously the tempered structure can also be seen with the forms of tempered bainite structures.

Tensile samples are prepared according to the GB/T228 metal standard material room temperature tensile test method, and are subjected to room temperature longitudinal tensile test and transverse impact test respectively, and the test results are shown in Table 3.

Tensile and impact properties of MnNiVR steel plate shown in Table 312

The normal-temperature tensile property of the 12MnNiVR steel plate is higher than the technical requirement, and the data is stable; the absorption work of the 12MnNiVR steel plate at minus 20 ℃ of KV2 is far higher than the requirement of technical conditions, and the distribution dispersion is small, which indicates that the steel is in an upper platform area at minus 20 ℃, and the steel is stable when series of impacts are applied to minus 40 ℃, and indicates that the steel plate has very good impact toughness.

Claims

1. The utility model provides a quenching and tempering high strength steel sheet 12MnNiVR for large-scale oil storage tank pressure vessel which characterized in that: the steel plate comprises the following chemical components in percentage by mass (unit, wt%): c: 0.09-0.11, Si: 0.20-0.30, Mn: 1.30-1.50, P: less than or equal to 0.010 percent and S: less than or equal to 0.002, Nb: 0.025-0.035, V0.045-0.055, Mo 0.15-0.29, Ni: 0.20-0.40, Cr: 0.18-0.28, and the balance Fe and residual elements.

2. The quenched and tempered high-strength steel plate 12MnNiVR as claimed in claim 1, wherein the quenched and tempered high-strength steel plate comprises: the thickness of the steel plate is less than or equal to 65mm, and the steel plate has a tempered bainite structure.

3. The production method of the quenched and tempered high-strength steel plate 12MnNiVR for the large-sized oil storage tank pressure vessel according to claim 1, which comprises the steps of clean steel smelting, water-cooling die casting, steel ingot heating, steel ingot cogging, large billet segmentation and cleaning, small billet heating, small billet rolling, steel plate cooling by piling and quenching and tempering, and is characterized in that:

1) clean steel smelting: the cleanliness of molten steel can reach S less than or equal to 30ppm, P less than or equal to 100ppm, N less than or equal to 40ppm, H less than or equal to 1.2ppm, O less than or equal to 30ppm and A, B, C, D quaternary inclusions with the total content less than or equal to 2.0 grade, and the method is realized by the following steps:

a. smelting in a converter: the method comprises the following steps of (1) pre-removing S in molten iron fed into a converter by KR, wherein the S content is below 0.010% after S removal, finishing converter smelting, ensuring that the tapping P is controlled within 0.008% and the tapping C is controlled within 0.05%, and adding aluminum blocks for deoxidation in the tapping process;

b. LF refining: the temperature of the first heating is controlled to be 1590 +/-10 ℃, the first heating mainly takes slag formation as a main component, the medium carbon is added to prepare a Mn primary component in the process, the second heating is started after the first heating and sampling, the low carbon ferrochrome is added to prepare Cr, ferrocolumbium is added to prepare Nb, ferrovanadium is added to prepare V, ferromolybdenum is added to prepare Mo and a nickel plate is added to prepare Ni in the second heating process, the third heating is finely adjusted, the third heating temperature is increased to 1630 +/-10 ℃, the lime consumption in the whole refining process is controlled to be 14.5-15.5kg/t steel, the time is controlled to be within 150min, and the final slag is ensured to be white foam slag with good;

2) water-cooling die casting: the casting temperature is 1550-;

3) heating a steel ingot: demoulding the steel ingot, slowly cooling to 200-250 ℃, charging, heating to 880-1250 ℃ at a temperature of less than 55 ℃/h and keeping the temperature for 5-7h when the temperature of the charging furnace is less than 650 ℃, and then quickly heating to 1230-1250 ℃ and keeping the temperature for 14-16 h;

4) steel ingot cogging: rolling at high temperature, low speed and high pressure, wherein the initial rolling temperature is 1000-;

5) cutting and cleaning a large blank: dividing the large blank into small blanks according to the requirements of finished products, and cleaning cracks, pits on the surface and fire-cut slag on the periphery of the small blanks;

6) heating the small blank: preheating the small billets to 200-250 ℃, heating the small billets to 450 ℃, performing steel sealing for 2h, heating the small billets to 750 ℃ at a temperature of less than 55 ℃/h, heating the small billets to 1210-1230 ℃ at a temperature of less than or equal to 75 ℃/h, and tapping after heat preservation for 2 h;

7) rolling small billets: rolling in two stages, wherein the initial rolling temperature in the rough rolling stage is 980-1020 ℃, uniform reduction is performed, steel is dried after rolling to the thickness of 80-120mm, rolling in the second stage is started, the reduction of pass in the second stage is 8-10 mm, the final rolling temperature is 800-870 ℃, air cooling is performed for 40-60 seconds after the final rolling is finished, ACC water cooling is performed, and the temperature of red returning is controlled to be 680-720 ℃;

8) and (3) steel plate stacking and cooling: the temperature of the steel plate entering the slow cooling pit is more than or equal to 350 ℃, and the slow cooling time is 48 hours;

9) tempering: adopting a quenching and tempering process, controlling the quenching temperature at 920 +/-10 ℃, keeping the temperature T at 2.2min/mm, discharging the steel plate from the furnace, cooling the steel plate to the normal temperature by water, and controlling the cooling speed to be more than or equal to 15 ℃/s; the tempering temperature is 620-640 ℃, the heat preservation time T is 4.0-4.2 min/mm, and the steel plate is slowly cooled to the normal temperature at the speed of less than 20 ℃/h after being taken out of the furnace.