CN114657467B

CN114657467B - Production method of weather-resistant steel plate with yield strength of 415MPa

Info

Publication number: CN114657467B
Application number: CN202210277112.6A
Authority: CN
Inventors: 温利军; 薛越; 李�浩; 王国海; 杨文海; 赵超; 徐建东
Original assignee: Baotou Iron and Steel Group Co Ltd
Current assignee: Baotou Iron and Steel Group Co Ltd
Priority date: 2022-03-21
Filing date: 2022-03-21
Publication date: 2023-02-21
Anticipated expiration: 2042-03-21
Also published as: CN114657467A

Abstract

The invention discloses a production method of a 415 MPa-grade yield strength weather-resistant steel plate, which produces the 415 MPa-grade yield strength weather-resistant structural steel plate with good surface quality and mechanical properties through proper smelting, continuous casting, heating, rolling control, cooling control and descaling processes. The steel plate has good strength, plasticity and toughness, and the structure is fine ferrite plus pearlite. The yield strength of the steel plate is 453 MPa-471 MPa, the tensile strength is 558 MPa-583 MPa, the elongation is 23.5% -29%, and the impact energy at-20 ℃ is 205J-297J. The requirements on rolling force and torque are low, and the requirements on the capability of rolling mill equipment are low. The required descaling pressure is low, the requirement on descaling equipment is not high, and the surface quality of the steel plate is good. The steel plate does not need to be subjected to heat treatment, the production period is short, and the cost is low.

Description

Production method of weather-resistant steel plate with yield strength of 415MPa

Technical Field

The invention relates to a production method of a weather-resistant steel plate with yield strength of 415 MPa.

Background

When the structural member made of the common structural steel is used in the field, the steel plate is exposed in media such as sunlight, atmosphere, water and the like for a long time, the surface of the steel plate is corroded quickly, the service life is short, the loss is large, and the requirements of construction, production and development cannot be met. At present, corrosion-resistant weather-resistant structural steel is increasingly adopted to manufacture structural parts, the weather-resistant structural steel is low alloy steel with good corrosion resistance in the atmosphere, low-carbon component design is adopted, and Cr, ni, cu, P, si, mn and the like are used as main alloy elements. Through a great amount of research at home and abroad, at present, a layer of compact oxidation product with good adhesion is generated on the surface of the weathering steel after long-time exposure to the atmosphere, so that a steel matrix is isolated from external corrosive substances, and the corrosion resistance of the weathering steel is obviously improved. Because a certain amount of Cr, ni, cu and other elements are added into the weather-resistant structural steel for corrosion resistance, the addition of the elements is not easy to control the surface quality of the steel plate, and the surface of the steel plate is easy to have pit defects; especially when the contents of Cr and Ni are high. Ni is a relatively difficult element to oxidize in steel, so iron is preferentially oxidized, ni enrichment is generated in an inner layer of an iron scale, ni-rich metal mesh wires and particles are formed, and the Ni-rich metal mesh wires and particles develop along with the increase of temperature. The Ni-rich metal mesh connects the iron scale with the metal matrix, and is not easy to peel off even under the impact of high-pressure water due to the similar plasticity, thermal expansion coefficient and the like of the Ni-rich metal mesh and the metal matrix. When Cr is present, the thickness of the adhesion layer is significantly increased, and descaling is more difficult. Therefore, after the steel plate blank with the weather-resistant structure is heated by the heating furnace, the surface iron scale is serious and is not easy to remove, in the rolling process, the iron scale is pressed into the steel plate to form pits, the surface quality of the steel plate is influenced, the use requirement cannot be met, and the steel plate is often seriously judged to be waste due to the pits. Secondly, the steel plate has more alloy, high strength, complex structure and unstable impact toughness and plasticity, the phenomenon that the impact energy and the elongation of the steel plate are lower than the lower limit of the standard often occurs, and the matching of the strength, the plasticity and the toughness of the steel plate is not good. The pits on the surface of the steel plate are slightly eliminated by additional polishing, and only judgment waste can be cut off seriously; the performance failure can be saved only by adding a heat treatment process, so that the manufacturing cost is greatly increased due to pockmarks or performance failure on the surface of the steel sheet, and the delivery cycle is prolonged. Therefore, the production of the weather-resistant structural steel plate is difficult, especially on a wide and thick plate rolling mill with low descaling pressure and small rolling mill capacity.

The patent of application No. CN 106435406A "a thick low-alloy weathering steel plate and its manufacturing method" provides a production method of weathering steel with thickness of 10-19 mm, and the weathering steel produced by the method can meet the requirements, but the method is suitable for production on a hot continuous rolling mill set and is not suitable for production of wide and thick steel plates.

The patent of '400 MPa grade high chromium weathering steel and preparation method thereof' of application number CN 111850411A provides a production method of high chromium weathering steel with yield strength of 400MPa grade, the weathering steel produced by the method has the performance meeting the requirements, but the weathering steel produced by the method has higher carbon equivalent and poor welding performance, and meanwhile, the method is suitable for production on a hot continuous rolling mill set and is not suitable for production of wide and thick steel plates.

The patent of '480 MPa grade high-silicon high-chromium weathering steel and preparation method thereof' of application No. CN 111690878A provides a production method of weathering steel, the weathering steel produced by the method has the advantages of meeting the requirements on performance and better corrosion resistance, but the weathering steel produced by the method has high carbon equivalent and poor welding performance, is suitable for production on a hot continuous rolling mill set and is not suitable for production of wide and thick steel plates.

Disclosure of Invention

The invention aims to provide a production method of a 415 MPa-grade weather-resistant steel plate with yield strength, which has the advantages of simple production process, low production cost, short production period, good surface quality and good impact toughness.

In order to solve the technical problems, the invention adopts the following technical scheme:

the invention relates to a production method of a weather-resistant steel plate with 415 MPa-grade yield strength, which comprises the following chemical components in percentage by weight: c: 0.075-0.095%; si:0.25 to 0.35 percent; mn:0.85 to 0.95 percent; 0.5 to 0.6 percent of Cr; 0.25 to 0.35 percent of Ni; 0.32 to 0.42 percent of Cu; 0.035 to 0.045 percent of Nb; ti:0.018 to 0.028 percent; p is less than or equal to 0.014%; s is less than or equal to 0.005 percent; ca:0.0013 to 0.0028 percent; and Als:0.018 to 0.032 percent; h is less than or equal to 1.7ppm; o is less than or equal to 0.0036 percent; n: less than or equal to 0.0044 percent; the balance of iron and inevitable impurities; the preparation process comprises the following steps:

1) The tapping temperature of the converter is less than or equal to 1650 ℃, a single slag process is adopted for smelting, low-carbon ferromanganese and ferro-silico-aluminum alloy are adopted for deoxidation alloying, and the thickness of the slag layer of the converter is 50mm;

2) Carrying out RH furnace treatment on the molten steel, wherein the RH vacuum treatment time is not less than 19 minutes, the pure degassing time is not less than 14 minutes, the minimum vacuum degree is not more than 125Pa, and the ex-situ hydrogen content is not more than 1.5ppm;

3) The thickness of the continuous casting billet is 250mm, the superheat degree is controlled to be 16-29 ℃ during molten steel casting, and the tundish liquid level is not less than 27 tons during ladle changing; adopting light pressing during continuous casting, wherein the lower part of the light pressing is the front three sections of the solidification terminal, and the total pressing amount is 8.5mm; electromagnetic stirring is adopted during continuous casting, the electromagnetic stirring positions are 4 sections and 5 sections, the electromagnetic stirring frequency is 5Hz, and the current is 375A; controlling the temperature of the inlet water of the crystallizer to be 34-36 ℃ and the temperature of secondary cooling water to be 23-26 ℃; protective pouring is adopted, the pressure of the sealing argon gas at the long nozzle is controlled to be more than or equal to 0.3MPa, and the flow is controlled to be 130-160L/min; the pressure of the argon gas for sealing the immersion water inlet of the tundish is 0.2Mpa, and the flow is 15-20L/min; the casting speed is 1.05-1.15 m/min;

4) After the slab is cast, the slab is required to be off-line stacked and slowly cooled, the slow cooling time is not less than 24 hours, and the stacking height is not less than 1.5 m;

5) And a heating process: when the plate blank is heated, a three-section heating stepping heating furnace is adopted, the heating temperature of the first heating section is 1195 to 1215 ℃, and the heating time is 40 to 55 minutes; the heating temperature of the second heating section is 1225-1263 ℃, and the heating time is 45-65 minutes; the total heating time is not less than 235 minutes; the discharging temperature of the plate blank is 1215-1235 ℃;

6) And rolling and cooling process: the two-stage controlled rolling is carried out after the plate blank is heated, the first-stage rolling is finished on a roughing mill, the initial rolling thickness of the first stage is the plate blank thickness, the initial rolling temperature of the first stage is not less than 1170 ℃, the torque is set to be 2100kNm during the first-stage rolling, the rolling reduction is set to be 38mm, the steel throwing distance is 3.8 m, the rolling speed is 2.1-3.4 m/s, the single-pass reduction rate of the high-temperature extension stage is not less than 10%, the final rolling temperature of the first stage is not less than 1050 ℃, and the first-stage rolling is carried out until the initial rolling thickness of the second stage; the second stage rolling is finished on a finishing mill, the initial rolling temperature of the second stage is 895-910 ℃, the initial rolling thickness of the second stage is 57-125 mm, the final rolling temperature of the second stage is 795-815 ℃, the set torque is 2000kNm, the set rolling force is 75MN, the set rolling reduction is 20mm, and the final pass reduction rate is more than or equal to 7 percent during the second stage rolling; carrying out laminar cooling after the steel plate is rolled, wherein the water temperature of ACC is 19-21 ℃, the cooling speed is 15-22 ℃/s, the final cooling temperature is 670-690 ℃, a head is used for shielding during cooling, the shielding length of the head is 0.5m, and the shielding coefficient of the head is 0.6;

7) And the descaling process during steel plate rolling: the pressure of an energy accumulator of the descaling tank is not less than 19.8MPa, and when the slab is descaled by the initial descaler after being discharged from the furnace, the roller speed of the descaler is 0.9m/s; and in the first stage of rolling, the first three times and the last two times of descaling are carried out in each time, the first three times adopt a positive descaling mode, and the last two times adopt a reverse descaling mode. During the second stage of rolling, the first two passes of descaling are carried out, and the descaling mode is positive descaling;

8) And the thickness of the steel plate finished product is 15-33 mm, and the steel plate is produced on a wide and thick plate rolling mill.

Further, the chemical components of the steel plate comprise the following components in percentage by weight: c:0.075%; si:0.35 percent; mn:0.85 percent; 0.5 percent of Cr; 0.35 percent of Ni; 0.32 percent of Cu; 0.045% of Nb; 0.028 percent of Ti; 0.014% of P; 0.005 percent of S; 0.0013 percent of Ca; 0.032% of Als; 1.7ppm of H; 0.0036 percent of O; 0.0044 percent of N; the balance of iron and unavoidable impurities.

Further, the chemical components of the steel plate comprise the following components in percentage by weight: c:0.095%; si:0.25 percent; mn:0.95 percent; 0.6 percent of Cr; 0.25 percent of Ni; 0.42 percent of Cu; 0.035% of Nb; 0.018% of Ti; 0.012 percent of P; 0.003 percent of S; 0.0028% of Ca; 0.018% of Als; 1.5ppm of H; 0.0032 percent of O; 0.0041 percent of N; the balance of iron and unavoidable impurities.

Further, the steel plate comprises the following chemical components in percentage by weight: c:0.095%; si:0.25 percent; mn:0.95 percent; 0.6 percent of Cr; 0.25 percent of Ni; 0.42 percent of Cu; 0.035% of Nb; 0.018% of Ti; 0.012% of P; 0.003 percent of S; 0.0028 percent of Ca; 0.018% of Als; 1.5ppm of H; 0.0032 percent of O; 0.0041 percent of N; the balance of iron and unavoidable impurities.

Furthermore, the yield strength of the steel plate is 453 MPa-471 MPa, the tensile strength is 558 MPa-583 MPa, the elongation is 23.5% -29%, and the impact energy at minus 20 ℃ is 205J-297J.

Compared with the prior art, the invention has the beneficial technical effects that:

as the 415 MPa-grade yield strength weather-resistant steel plate requires higher performance, the molten steel requires purity, the inclusions in the finished steel plate are few and are distributed dispersedly, and the gas content is low, so that strict requirements are made on relevant process parameters of steelmaking and continuous casting. The 415 MPa-grade yield strength weather-resistant steel plate contains more Cr, ni, cu, mn and other elements, and the residual stress formed in the casting blank is larger in the solidification process, so that the blank is subjected to stacking slow cooling for a certain time while being off line, the residual stress in the blank is reduced, and the quality of the blank is improved. The longer total heating time is adopted when the plate blank is heated, so that the heating quality of the plate blank is improved, and the deformation and the structure are uniform when the steel plate is rolled. The reason for adopting higher furnace-out temperature is to make the alloy melt into austenite during heating, and the deformation resistance is smaller during rough rolling, so that the single-pass large reduction is easy to realize.

Since this steel grade contains a certain amount of Nb, controlled rolling is performed on the above-described heated slab in the austenite recrystallization region and the non-recrystallization region. The steel grade adopts two-stage controlled rolling, the first stage controlled rolling belongs to austenite recrystallization controlled rolling in a high temperature region, and the first stage adopts a rolling strategy under high pressure. The larger single-pass reduction rate can enable rolling deformation to fully permeate to the center of the steel plate, fully refine austenite grains and homogenize austenite tissues, and simultaneously, the defects of looseness, microcracks and the like in casting blanks are eliminated to a great extent by high-temperature welding action generated by rolling, so that the density of the steel plate is improved, and the comprehensive performance of materials is improved. In the first stage of rolling, the first three times of descaling are carried out, the descaling mode is positive descaling, the descaling effect is enhanced, and the descaling is facilitated, the steel plate is thicker and has small temperature drop in the first three times of rolling, and pits are left after the residual iron plate on the surface of the steel plate is removed; and finally, secondary descaling is carried out, namely secondary iron scales generated on the surface of the steel plate in the rolling process are removed, so that the surface quality of the steel plate is good. The first two times of descaling in the second stage are to remove secondary iron scale generated in the process of swinging and cooling the intermediate billet, and the later rolling passes do not need descaling because the steel plate is already thin and has lower temperature and the requirement of plate shape control is considered. After the first-stage rolling is finished, the intermediate billet swings on a roller way to be cooled, the intermediate billet starts to be rolled when the temperature is reduced to the second-stage initial rolling temperature, the second-stage rolling belongs to low-temperature non-recrystallization controlled rolling, the initial rolling temperature and the final rolling temperature are low, the dislocation is pinned through the precipitation of carbonitride of Nb and the like, the strain is generated in the crystal grains under the rolling deformation, and a large amount of deformation energy and phase transformation nucleation positions are accumulated in the crystal grains through multi-pass rolling and large accumulated reduction. The pass reduction rate of finish rolling is required to improve the effect of controlled rolling, the steel plate is rapidly cooled by ACC after rolling, and the steel plate is rapidly cooled to a lower temperature after rolling, so that the transformation of gamma phase → alpha phase of the steel plate is completed at the lower temperature, and an alpha phase structure with fine grains is obtained, thereby the steel plate has good toughness.

The invention adopts a wide and thick plate rolling mill for production, has small requirements on rolling force and torque, has lower requirements on the capability of rolling mill equipment and is easy to realize; the required descaling pressure is low, the requirement on descaling equipment is not high, and the surface quality of the steel plate is good.

The steel plate has good strength, plasticity and toughness, and the structure is fine ferrite plus pearlite. The yield strength of the steel plate is 453 MPa-472 MPa, the tensile strength is 558 MPa-583 MPa, the elongation is 23.5% -29%, and the impact energy at-20 ℃ is 205J-297J.

Drawings

The invention is further illustrated in the following description with reference to the drawings.

FIG. 1 is a metallographic structure diagram of example 1;

FIG. 2 is a metallographic structure drawing of a steel plate according to example 2;

FIG. 3 is a metallographic structure drawing of example 3.

Detailed Description

Example 1

The steel plate is produced by a wide and thick plate mill, a continuous casting blank with the thickness of 252mm is selected, the center segregation of the casting blank is C2.5, the center porosity is grade 2.5, the middle crack is grade 1.0, and the steel plate is rolled into a steel plate with the thickness of 15 mm. The tapping temperature of the converter is 1650 ℃, the converter is smelted by adopting a single slag process, low-carbon ferromanganese and ferro-silico-aluminum alloy are deoxidized and alloyed, and the thickness of the slag layer of the converter is 50mm. And carrying out RH furnace treatment on the molten steel, wherein the RH vacuum treatment time is 19 minutes, the pure degassing time is 14 minutes, the minimum vacuum degree is 125Pa, and the ex-situ hydrogen content is 1.5ppm. The superheat degree of the molten steel during casting is 29 ℃, and the liquid level of the tundish during ladle change is 27 tons; adopting soft reduction during continuous casting, wherein the lower soft reduction position is the front three sections of the solidification terminal, and the total reduction is 8.5mm; electromagnetic stirring is adopted during continuous casting, the electromagnetic stirring positions are 4 sections and 5 sections, the electromagnetic stirring frequency is 5Hz, and the current is 375A; the temperature of the inlet water of the crystallizer is 34 ℃, and the temperature of secondary cooling water is controlled to be 23 ℃; protective pouring is adopted, the pressure of the sealing argon gas of the long nozzle is 0.3MPa, and the flow is 130L/min; the pressure of the argon gas at the immersion inlet of the tundish is 0.2Mpa, and the flow is 20L/min; the casting speed is 1.05m/min. After the slab is cast, the slab needs to be off-line, stacked and slowly cooled, the slow cooling time is 24 hours, and the stacking height is 1.5 meters. When the plate blank is heated, a three-section heating stepping heating furnace is adopted, the heating temperature of the first heating section is 1195 ℃, and the heating time is 40 minutes; the heating temperature of the second heating section is 1225 ℃, and the heating time is 45 minutes; total heating time was 235 minutes; the tapping temperature of the slab is 1215 ℃. The slab comprises the following chemical components in percentage by weight: c:0.075%; si:0.35 percent; mn:0.85 percent; 0.5 percent of Cr; 0.35 percent of Ni; 0.32 percent of Cu; 0.045% of Nb; 0.028 percent of Ti; 0.014% of P; 0.005 percent of S; 0.0013 percent of Ca; 0.032% of Als; 1.7ppm of H; 0.0036 percent of O; 0.0044 percent of N; the balance of iron and unavoidable impurities. The first stage rolling is completed on a roughing mill, and the second stage rolling is completed on a finishing mill. The pressure of the energy accumulator of the descaling tank is 19.8MPa, and the roller speed of the descaling machine is 0.9m/s when the slab is descaled by the initial descaling machine after being discharged from the furnace. And in the first stage of rolling, the first three times and the last two times of descaling are carried out in each time, the first three times adopt a positive descaling mode, and the last two times adopt a reverse descaling mode. And during the second stage of rolling, the first two passes of descaling are carried out, and the descaling mode is positive descaling. The first stage is rolled to the initial rolling thickness of the second stage. And carrying out laminar cooling after the steel plate is rolled, wherein the water temperature of ACC is 19 ℃, the cooling speed is 22 ℃/s, the final cooling temperature is 690 ℃, a head is used for shielding during cooling, the head shielding length is 0.5m, and the head shielding coefficient is 0.6.

The detailed first-stage and second-stage rolling processes are shown in tables 1 and 2, and the mechanical properties are shown in table 3.

TABLE 1 first stage Rolling Process

TABLE 2 second stage Rolling Process

TABLE 3 mechanical Properties of the Steel sheets

Example 2

The steel plate is produced by a wide and thick plate mill, a continuous casting blank with the thickness of 252mm is selected, the center segregation of the casting blank is C1.5, the center porosity is grade 2.0, the middle crack is grade 0.5, and the steel plate is rolled into a steel plate with the thickness of 33 mm. The tapping temperature of the converter is 1642 ℃, the single slag process is adopted for smelting, the low-carbon ferromanganese and silicon-aluminum-iron alloy are adopted for deoxidation alloying, and the thickness of the converter slag layer is 50mm. And carrying out RH furnace treatment on the molten steel, wherein the RH vacuum treatment time is 21 minutes, the pure degassing time is 15 minutes, the minimum vacuum degree is 112Pa, and the ex-situ hydrogen content is 1.2ppm. The superheat degree of the molten steel during casting is 16 ℃, and the liquid level of the tundish during ladle change is 28.5 tons; adopting light pressing during continuous casting, wherein the lower part of the light pressing is the front three sections of the solidification terminal, and the total pressing amount is 8.5mm; electromagnetic stirring is adopted during continuous casting, the electromagnetic stirring positions are 4 sections and 5 sections, the electromagnetic stirring frequency is 5Hz, and the current is 375A; the temperature of the inlet water of the crystallizer is 36 ℃, and the temperature of secondary cooling water is controlled to be 26 ℃; protective pouring is adopted, the pressure of the sealing argon gas of the long nozzle is 0.35MPa, and the flow is 160L/min; the pressure of the argon gas at the immersion water inlet of the tundish is 0.2Mpa, and the flow is 18L/min; the casting speed is 1.15m/min. After the slab is cast, the slab needs to be off-line, stacked and slowly cooled, the slow cooling time is 25 hours, and the stacking height is 1.75 meters. When the plate blank is heated, a three-section heating stepping heating furnace is adopted, the heating temperature of the first heating section is 1215 ℃, and the heating time is 55 minutes; the heating temperature of the second heating section is 1263 ℃, and the heating time is 65 minutes; total heating time is 289 minutes; the discharging temperature of the plate blank is 1235 ℃. The slab comprises the following chemical components in percentage by weight: c:0.095%; si:0.25 percent; mn:0.95 percent; 0.6 percent of Cr; 0.25 percent of Ni; 0.42 percent of Cu; 0.035% of Nb; 0.018% of Ti; 0.012% of P; 0.003 percent of S; 0.0028% of Ca; 0.018% of Als; 1.5ppm of H; 0.0032 percent of O; 0.0041 percent of N; the balance of iron and unavoidable impurities. The first stage rolling is completed on a roughing mill, and the second stage rolling is completed on a finishing mill. The pressure of the energy accumulator of the descaling tank is 20.1MPa, and the roller speed of the descaling machine is 0.9m/s when the slab is descaled by the initial descaling machine after being discharged from the furnace. And in the first stage of rolling, the first three times and the last two times of descaling are carried out in each time, the first three times adopt a positive descaling mode, and the last two times adopt a reverse descaling mode. And during the second stage of rolling, the first two passes of descaling are carried out, and the descaling mode is positive descaling. The first stage is rolled to the initial rolling thickness of the second stage. And carrying out laminar cooling after the steel plate is rolled, wherein the water temperature of ACC is 21 ℃, the cooling speed is 15 ℃/s, the final cooling temperature is 670 ℃, a head is used for shielding during cooling, the head shielding length is 0.5m, and the head shielding coefficient is 0.6.

The detailed first-stage and second-stage rolling processes are shown in tables 4 and 5, and the mechanical properties are shown in table 6.

TABLE 4 first stage Rolling Process

TABLE 5 second stage Rolling Process

TABLE 6 mechanical Properties of the Steel sheets

Example 3

The steel plate is produced by a wide and thick plate mill, a continuous casting blank with the thickness of 252mm is selected, the center segregation of the casting blank is C1.0, the center porosity is 1.5 grade, the middle crack is 0.5 grade, and the steel plate is rolled into a steel plate with the thickness of 20 mm. The tapping temperature of the converter is 1638 ℃, the single slag process is adopted for smelting, the low-carbon ferromanganese and silicon-aluminum-iron alloy are adopted for deoxidation alloying, and the thickness of the converter slag layer is 50mm. And carrying out RH furnace treatment on the molten steel, wherein the RH vacuum treatment time is 22 minutes, the pure degassing time is 16 minutes, the minimum vacuum degree is 110Pa, and the ex-situ hydrogen content is 1.3ppm. The superheat degree is 23 ℃ during the casting of the molten steel, and the liquid level of the tundish is 29 tons during ladle changing; adopting light pressing during continuous casting, wherein the lower part of the light pressing is the front three sections of the solidification terminal, and the total pressing amount is 8.5mm; electromagnetic stirring is adopted during continuous casting, the electromagnetic stirring positions are 4 sections and 5 sections, the electromagnetic stirring frequency is 5Hz, and the current is 375A; the temperature of the inlet water of the crystallizer is 35 ℃, and the temperature of secondary cooling water is controlled to be 24 ℃; protective pouring is adopted, the pressure of the sealing argon gas of the long nozzle is 0.32MPa, and the flow is 156L/min; the pressure of the argon gas at the immersion water inlet of the tundish is 0.2Mpa, and the flow is 18L/min; the casting speed is 1.1m/min. After the slab is cast out, the slab needs to be off-line stacked and slowly cooled, the slow cooling time is 26 hours, and the stacking height is 2 meters. When the plate blank is heated, a three-section type heating stepping heating furnace is adopted, the heating temperature of the first heating section is 1206 ℃, and the heating time is 52 minutes; the heating temperature of the second heating section is 1251 ℃, and the heating time is 51 minutes; total heating time was 252 minutes; the tapping temperature of the slab is 1228 ℃. The slab comprises the following chemical components in percentage by weight: c:0.084%; si:0.29 percent; mn:0.91 percent; 0.54 percent of Cr; 0.29 percent of Ni; 0.38 percent of Cu; 0.039 percent of Nb; 0.023 percent of Ti; 0.013 percent of P; 0.002% of S; 0.0022 percent of Ca; 0.025 percent of Als; h is 1.6ppm; 0.0031 percent of O; 0.0039 percent of N; the balance of iron and unavoidable impurities. The first stage rolling is completed on a roughing mill, and the second stage rolling is completed on a finishing mill. The pressure of the energy accumulator of the descaling tank is 20.4MPa, and the roller speed of the descaling machine is 0.9m/s when the slab is descaled by the initial descaling machine after being discharged from the furnace. And in the first stage of rolling, the first three times and the last two times of descaling are carried out, the first three times adopt a forward descaling mode, and the last two times adopt a reverse descaling mode. And during the second stage of rolling, the first two passes of descaling are carried out, and the descaling mode is positive descaling. The first stage is rolled to the initial rolling thickness of the second stage. And carrying out laminar cooling after the steel plate is rolled, wherein the water temperature of ACC is 20 ℃, the cooling speed is 19 ℃/s, the final cooling temperature is 683 ℃, and a head shielding is used during cooling, the head shielding length is 0.5m, and the head shielding coefficient is 0.6.

The detailed first-stage and second-stage rolling processes are shown in tables 7 and 8, and the mechanical properties are shown in table 9.

TABLE 7 first stage Rolling Process

TABLE 8 second stage Rolling Process

TABLE 9 mechanical Properties of the Steel sheets

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims

1. A production method of a weather-resistant steel plate with 415 MPa-grade yield strength is characterized by comprising the following steps: the steel plate comprises the following chemical components in percentage by weight: c: 0.075-0.095%; si:0.25 to 0.35 percent; mn:0.85 to 0.95 percent; 0.5 to 0.6 percent of Cr; 0.25 to 0.35 percent of Ni; 0.32 to 0.42 percent of Cu; 0.035 to 0.045 percent of Nb; ti:0.018 to 0.028 percent; p is less than or equal to 0.014%; s is less than or equal to 0.005 percent; ca:0.0013 to 0.0028 percent; and Als:0.018 to 0.032 percent; h is less than or equal to 1.7ppm; o is less than or equal to 0.0036 percent; n: less than or equal to 0.0044 percent; the balance of iron and inevitable impurities;

the preparation process comprises the following steps:

3) The thickness of the continuous casting billet is 250mm, the superheat degree is controlled to be 16-29 ℃ during molten steel casting, and the tundish liquid level is not less than 27 tons during ladle changing; adopting soft reduction during continuous casting, wherein the lower soft reduction position is the front three sections of the solidification terminal, and the total reduction is 8.5mm; electromagnetic stirring is adopted during continuous casting, the electromagnetic stirring positions are 4 sections and 5 sections, the electromagnetic stirring frequency is 5Hz, and the current is 375A; controlling the temperature of the inlet water of the crystallizer to be 34-36 ℃ and the temperature of secondary cooling water to be 23-26 ℃; protective pouring is adopted, the pressure of the sealing argon gas at the long nozzle is controlled to be more than or equal to 0.3MPa, and the flow is controlled to be 130-160L/min; the pressure of the argon gas for sealing the immersion water inlet of the tundish is 0.2Mpa, and the flow is 15-20L/min; the casting speed is 1.05-1.15 m/min;

7) And the descaling process during steel plate rolling: the pressure of an energy accumulator of the descaling tank is not less than 19.8MPa, and when the slab is descaled by the initial descaler after being discharged from the furnace, the roller speed of the descaler is 0.9m/s; during the first stage of rolling, the first three passes and the last two passes of descaling each time, wherein the first three passes adopt a positive descaling mode, the last two passes adopt a reverse descaling mode, and during the second stage of rolling, the first two passes of descaling are conducted, and the descaling mode is positive descaling;

2. The method for producing the weather-resistant steel plate with the yield strength of 415MPa according to claim 1, is characterized in that: the steel plate comprises the following chemical components in percentage by weight: c:0.075%; si:0.35 percent; mn:0.85 percent; 0.5 percent of Cr; 0.35 percent of Ni; 0.32 percent of Cu; 0.045% of Nb; 0.028 percent of Ti; 0.014% of P; 0.005 percent of S; 0.0013 percent of Ca; 0.032% of Als; 1.7ppm of H; 0.0036 percent of O; 0.0044 percent of N; the balance of iron and unavoidable impurities.

3. The method for producing the weather-resistant steel plate with the yield strength of 415MPa according to claim 1, is characterized in that: the steel plate comprises the following chemical components in percentage by weight: c:0.095%; si:0.25 percent; mn:0.95 percent; 0.6 percent of Cr; 0.25 percent of Ni; 0.42 percent of Cu; 0.035% of Nb; 0.018% of Ti; 0.012 percent of P; 0.003 percent of S; 0.0028% of Ca; 0.018% of Als; 1.5ppm of H; 0.0032 percent of O; 0.0041 percent of N; the balance of iron and unavoidable impurities.

4. The method for producing the weather-resistant steel plate with the yield strength of 415MPa according to claim 1, is characterized in that: the yield strength of the steel plate is 453MPa to 471MPa, the tensile strength is 558MPa to 583MPa, the elongation is 23.5 to 29 percent, and the impact energy at the temperature of minus 20 ℃ is 205J to 297J.