CN111057812A - High-toughness fire-resistant corrosion-resistant steel with 600MPa tensile strength and manufacturing method thereof - Google Patents

Abstract

A high-toughness fire-resistant corrosion-resistant steel with 600MPa of tensile strength and a manufacturing method thereof, belonging to the technical field of steel materials. Through reasonable and economic component design and strict process control, the steel for the building structure with high strength, high toughness, low yield ratio and low welding crack sensitivity can be stably produced, the fluctuation of the yield strength and the tensile strength is small, the fluctuation is within 60MPa, and the dispersion of the material strength is small. The steel grade has excellent high-temperature fire resistance under harsh high-temperature test conditions, the fire resistance can meet the requirement of 500 MPa-grade fire-resistant steel, and the steel grade has certain engineering application value and prospect. Through strict corrosion resistance test, compared with common structural steel, the corrosion resistance is excellent, and the steel can be widely applied to severe atmospheric environment. The steel integrates low yield ratio, corrosion resistance and fire resistance, has the characteristics of high-toughness building steel, corrosion-resistant steel and fire-resistant steel, and can provide reference for development of future multi-purpose multifunctional composite high-strength building steel.

Description

High-toughness fire-resistant corrosion-resistant steel with 600MPa tensile strength and manufacturing method thereof

Technical Field

The invention belongs to the technical field of steel materials, and particularly relates to high-toughness, fire-resistant and corrosion-resistant steel with the tensile strength of 600MPa and a manufacturing method thereof. The steel for building structures has low yield ratio, excellent corrosion resistance and fire resistance.

Steel structure construction has become the mainstream of urban construction development since the 70 s of the 20 th century. The steel plate for the building structure is widely applied to building engineering of high-rise buildings, super high-rise buildings, stadiums, exhibition centers, airport terminal buildings, hub stations, large power stations, factory buildings and the like. According to statistics of relevant data, the steel amount of foreign steel structure buildings accounts for 10% -30% of the steel yield; in China with popular steel structure buildings such as Japan and America, the proportion of the steel structure buildings reaches more than 30 percent, and the steel amount for the steel structure buildings in China accounts for less than 7 percent of the steel yield every year. In the beginning of the century, the popularization and construction strength of the steel for the building structure is increased in China, and with the arrival of 2004 + 2009 Beijing Olympic engineering, Shanghai world exposition engineering and a new round of city construction climax in various places, the development of the steel for the building structure is driven.

With the development of building structures, higher and higher requirements are put on the construction steel, and particularly, the development of the high-strength, high-performance and functional construction steel is emphasized. In order to ensure the safety of the building structure and enhance the capability of resisting disasters, earthquake resistance, fire resistance and corrosion resistance are important problems to be solved by the building steel. Compared with the steel for common building structures, the steel for high-performance building structures not only satisfies high strength, excellent low-temperature toughness, low yield ratio and narrow yield point, but also has the performances of fire resistance, corrosion resistance, easy welding and the like.

Generally, as the temperature increases, the metal material loading capacity decreases. Under the high temperature action of fire, the strength of the steel structure is a function of temperature; when the temperature reaches about 600-700 ℃, the steel structure loses the bearing capacity completely, and the building collapses. In order to avoid this danger, fire resistance is required in various countries in the world for the beam, column, etc. of various steel structure buildings, and it is required to coat a fire-resistant paint with a certain thickness on the surface of a prescribed steel material, and the temperature of the surface of the steel material must not exceed a prescribed temperature. However, the use of fire-resistant coatings not only increases construction costs and causes environmental pollution, but also reduces the available space for buildings. Therefore, the development of high-performance refractory steel products is imperative.

In addition, the primary mode of failure of metallic materials is atmospheric corrosion. According to foreign statistics, the loss caused by corrosion accounts for about 4% of the total value of national production every year (atmospheric corrosion accounts for about half). China has broad members, various climates, rapid industrial development and serious atmospheric corrosion, and the amount of iron and steel lost due to atmospheric corrosion is about more than 500 million tons every year. Therefore, the use of corrosion-resistant structural steel having atmospheric corrosion resistance is an effective way to improve this situation.

In the past century, steel companies such as JFE developed fire-resistant steel aseismic steels (Q345 grade) such as SM400B-FR/400C-FR (Q235 grade) and SM490B-FR/490C-FR (Q345 grade). In China, Wu steel develops a steel plate for a fire-resistant and corrosion-resistant high-rise building in 2001; wherein, WGJ510C2 (Q345 level) atmospheric corrosion resistance is more than 2 times of that of the ordinary steel, the yield strength at 600 ℃ is not lower than 2/3 at room temperature, the steel integrates fire resistance, corrosion resistance and earthquake resistance, fills the domestic blank, and is successfully applied to the disabled people sports and art center stadium and the martial steel science and technology building in China. Bao steel has developed fire-resistant and corrosion-resistant construction steels such as B400RNQ and B490RNQ (Q345 grade) in the same year, and has also been successfully applied to Zhongfu second-stage engineering.

The comparison document 1, the chinese patent application No. 201410699500.9, "a Q460-grade refractory corrosion-resistant steel and a preparation method thereof", provides a Q460-grade refractory corrosion-resistant steel, which comprises the following chemical components in percentage by weight: 0.01-0.20% of C, 0.1-0.4% of Si, 0.5-1.5% of Mn, 0.1-1.0% of Cr, less than or equal to 1.0% of Ni, less than or equal to 1.0% of Cu, 0.01-0.05% of Nb, 0.01-0.05% of Ti, less than or equal to 0.015% of P, less than or equal to 0.0020% of S, and the balance of Fe and inevitable impurities, wherein the total amount of impurity elements is not more than 0.05%. The patent has the advantages that the precious metal Mo is eliminated; however, the patent has wide composition design, and although the high temperature tempering softening resistant element Mo is not added, other noble elements such as Ni, Cu and Cr are added, and the content is high. For the steel grade with the yield strength of 460MPa, the design of the high composition system inevitably causes the waste of alloy elements. In addition, the logic relation of the patent on the aspect of matching the components with the process is unclear, and the component difference of the steel plates among different thickness specifications is extremely large, which is not in line with the actual production situation. In the aspect of rolling process, the patent requires that the finish rolling starting temperature is between 900 ℃ and 1000 ℃, for Nb-containing steel, the temperature interval is in a recrystallization and non-recrystallization region transition interval, and mixed crystals are easy to appear when the Nb-containing steel is rolled in the temperature interval, so that the impact toughness is greatly influenced. In summary, the patent has certain disadvantages from component design, to control of process parameters and test data listed in the examples.

The invention relates to a comparison document 2, Chinese invention patent with application number '200910045146.7', a high-strength high-toughness low-yield-ratio refractory steel and a manufacturing method thereof, the invention provides a high-strength refractory steel which has room-temperature yield strength of more than 460MPa, yield ratio of less than 0.80, high-temperature yield strength of more than 307MPa at 600 ℃ and good impact toughness, and the high-strength refractory steel comprises the following components in percentage by weight: 0.05 to 0.14 percent of C, 0.15 to 0.50 percent of Si, 0.50 to 1.20 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.015 percent of S, Cu: 0.10 to 0.40%, 0.10 to 0.50% of Ni, 0.015 to 0.050% of Nb, 0.005 to 0.040% of Ti, V: 0.010-0.050%, 0.10-0.50% of Cr, 0.20-0.50% of Mo, 0.015-0.05% of Al, and the balance of Fe and inevitable impurities. The invention also provides a manufacturing method of the refractory steel, which comprises the steps of obtaining molten steel by vacuum smelting, casting the molten steel into a steel billet, heating the steel billet to 1150-. On the whole, the patent has no obvious advantages in the aspects of components and process design, all commonly used noble metals of Ni, Cr, Mo and Cu and micro-alloy elements of Nb, V and Ti are basically added, and the alloy cost is higher; in addition, the patent only relates to the impact toughness at 0 ℃, and does not have the characteristic of high impact toughness.

A comparison document 3, a chinese patent of invention with application number "201210048691.3" with excellent low-temperature toughness, refractory and corrosion-resistant steel and a preparation process thereof ", discloses a refractory and corrosion-resistant steel with excellent low-temperature toughness, which comprises the following chemical components by weight percent: 0.01 to 0.04 percent of C, 0.15 to 0.25 percent of Si, 1.00 to 1.50 percent of Mn, 0.42 to 0.50 percent of Mo, 0.40 to 0.60 percent of Cr, 0.10 to 0.20 percent of Cu, 0.02 to 0.04 percent of Nb, 0.01 to 0.02 percent of Ti, less than or equal to 0.03 percent of Al, less than or equal to 0.006 percent of N, less than or equal to 0.01 percent of P, less than or equal to 0.006 percent of S, and the balance of Fe and inevitable impurities; the alloy has excellent fire resistance, corrosion resistance and low-temperature toughness after smelting and two-stage rolling, the clothing strength is more than or equal to 325MPa, and the room-temperature tensile strength is more than or equal to 520 MPa. The strength index of the steel related to the patent is low and does not reach the Q345 level. In the rolling procedure, the total reduction rate is more than or equal to 50 percent and the single-pass reduction rate is more than or equal to 15 percent within the recrystallization temperature range; the total reduction rate is more than or equal to 60 percent in the temperature range of the non-recrystallization zone, the single-pass reduction rate is more than or equal to 15 percent, which is not in accordance with the actual production process, especially in the rolling process of the non-recrystallization zone, the single-pass reduction rate of all the passes is more than or equal to 15 percent, which is impractical and unrealizable in the large-scale production process. In addition, in the alloy design process, excessive precious alloy element Mo is added, so that the alloy cost is increased.

The patent document 4, chinese invention patent with application number "201511019355.6", relates to a high-strength anti-seismic fire-resistant corrosion-resistant steel plate and a manufacturing method thereof, and the steel plate comprises: 0.02 to 0.06 percent of C, 3.0 to 6.0 percent of Cr, 0.15 to 0.60 percent of Mo, 0.10 to 1.00 percent of Mn, 0.80 percent of Si, 0.015 percent of P, 0.01 percent of S, 0.08 to 0.16 percent of Nb, 0.01 to 0.03 percent of Ti and 0.01 to 0.05 percent of Al; less than 1.00 percent of Ni, less than 0.10 percent of V, and the balance of Fe and inevitable impurities; the patent obtains low-temperature tempered bainite and martensite structures through smelting, continuous casting, rolling and heat treatment. Rolling: heating the casting blank in a heating furnace to 1200-1280 ℃, and preserving heat for 0.5-3 h; then rolling the cast slab in a rolling mill into a steel plate: firstly carrying out 2-5 times of rough rolling, then carrying out 3-10 times of finish rolling, and then cooling to room temperature, wherein the rough rolling initial rolling temperature is 1100-. And (3) heat treatment: quenching the rolled steel plate: quenching temperature is 900-950 ℃, heat preservation time is 20 min-1 h, water cooling is carried out to below 250 ℃, and then cooling is carried out to room temperature; tempering the steel plate after quenching: tempering at 200-250 ℃, keeping the temperature for 0.5-2 h, and cooling to room temperature. In the patent, the alloy is added extremely high, particularly Cr and Mo, so that the alloy cost is increased; the steel grade is produced by adopting the working procedures of off-line high-temperature quenching and low-temperature tempering, and compared with the normal controlled rolling and controlled cooling or TMCP process, the method increases the heat treatment working procedures, has complex production process and increases the working procedure cost. The data in the patent embodiment is only the result of a laboratory, and has a large gap from industrial production, and the patent embodiment does not necessarily have the value of popularization and application.

The comparison document 5, the Chinese invention patent with the application number of '201310665894.1', the steel and the production method thereof for the fire-resistant, corrosion-resistant and earthquake-resistant building with the yield strength of 550MPa grade, comprises the following chemical components: 0.041 to 0.125 percent of C, 0.31 to 0.62 percent of Si, 1.81 to 2.40 percent of Mn, less than or equal to 0.008 percent of P, less than or equal to 0.002 percent of S, 0.041 to 0.065 percent of Nb, 0.007 to 0.020 percent of Ti, 0.41 to 0.63 percent of Mo, and 0.07 to 0.62 percent of W

0.10 percent of Mg, 0.0071-0.0098 percent of Mg, and less than or equal to 0.0012 percent of O. The production steps comprise: desulfurizing molten iron; smelting in a converter; vacuum treatment, adding Mg element; carrying out conventional continuous casting and heating a casting blank; rolling in sections; and cooling after finishing rolling. The patent is designed by using abnormal components with high Mn and high Cr, and adding W and Mg, and simultaneously adding 0.09-0.12% of Sn or 0.08-0.12% of Zn or a mixture of the two in any proportion, and the design of the components is questionable on whether the refractory, corrosion resistant and anti-seismic properties are favorable. Although the patent does not add noble elements such as Cu, Cr, Ni and the like which are used for improving the corrosion resistance conventionally, the patent does not add excessive elements such as Mg, Sn, Zn and the like, and the influence of the addition of the elements on the quality of molten steel and the quality of steel plates needs to be evaluated, so that the alloy does not necessarily have actual industrial production and application values.

Disclosure of Invention

The invention aims to develop a steel for building structures with 600 MPa-level tensile strength, high toughness, low yield ratio, fire resistance, corrosion resistance and easy welding by combining self equipment capability and process technical level, reasonably designing a component system of the steel for fire resistance and corrosion resistance, utilizing the alloy carbide of Mo to hinder the deformation of crystal grains at high temperature and the function of Nb-Ti precipitates to increase the grain boundary strength and improve the fire resistance and weather resistance performance, and controlling rolling and cooling processes in two stages on the premise of adding necessary alloy elements of Ni, Cr, Mo and Cu and micro alloy elements of Nb and Ti.

The invention relates to high-toughness fire-resistant corrosion-resistant steel with 600MPa of tensile strength and a manufacturing method thereof.

The technical scheme of the invention is that the high-toughness fire-resistant corrosion-resistant steel with the tensile strength of 600MPa comprises the following chemical components in percentage by weight: 0.035 to 0.055 percent; si: 0.25 to 0.40 percent; mn: 0.90% -1.00%; ni: 0.25 to 0.35 percent; cr: 0.45 to 0.55 percent; mo: 0.10 to 0.20 percent; cu: 0.25 to 0.35 percent; nb: 0.020% -0.040%; ti: 0.010% -0.020%; and (3) Alt: 0.015% -0.035%; p: less than or equal to 0.015 percent; s: less than or equal to 0.005 percent; n: less than or equal to 0.0030 percent; h: less than or equal to 0.0002 percent; ca: 0.0015 to 0.0025 percent; carbon equivalent Ceq (%) = C + Mn/6+ (Cr + Mo + V)/5+ (Ni/+ Cu)/15, and Ceq (%) range is required: 0.35 to 0.40; weld crack sensitivity Pcm (%) = C + Si/30+ Mn/20+ Cu/20+ Cr/20+ Ni/60+ Mo/15+ V/10+5B, and Pcm (%) range is required: 0.14 to 0.18; the balance of Fe and inevitable impurities; weather resistance index I =26.01Cu +3.88Ni +1.2Cr +1.49Si +17.28P-7.29Cu × Ni-9.11Ni × P-33.39Cu2, and requires an I% range: 6.1-6.9; in order to ensure the synergistic effect of Mo and Nb in the phase change strengthening and reduce the dispersion of yield strength, the mass percentage ratio of Mo to Nb is required to be controlled within the range of 5.0-10.0%; the beneficial effects of Nb and Ti precipitates in increasing the crystal boundary strength and improving the fire resistance, weather resistance and comprehensive mechanical properties of steel are utilized, and the mass percentage ratio of Nb to Ti is required to be controlled between 2.0-4.0.

A manufacturing method of high-toughness fire-resistant corrosion-resistant steel with 600MPa of tensile strength comprises the following steps:

(1) the temperature control parameter requirements in the molten steel smelting process are as follows: tapping the steel from the converter 1650 + -20 ℃, ending LF 1635 + -10 ℃, ending RH 1585 + -5 ℃, ending soft blowing temperature 1565 + -5 ℃ and tundish temperature 1538 + -5 ℃;

(2) smelting: the bottom blowing argon mode is adopted, and the flow of the bottom blowing argon is set to be 400 +/-10 m at the initial stage of converter blowing³The flow rate of bottom-blown argon gas at the final stage of converting was set to 500. + -. 10m³/h；

(3) Tapping by a converter: when 1/3 steel is tapped, 2.4 kg-2.6 kg of lime and 0.045 kg-0.055 kg of fluorite are added per ton of molten steel along with steel flow for slag washing; after tapping, 0.025 kg-0.035 kg of aluminum grate is added on the slag surface per ton of molten steel;

(4) refining in an LF furnace: the refining process uses a mixture containing C: 0.20 to 0.70 percent; mn: 80.0% -90.0%; the balance of low-carbon ferromanganese with the impurity of S, P for regulating Mn; aluminum particles are used for adjusting aluminum in the treatment process, the aluminum at the end of LF is controlled according to 0.020-0.050%, the total aluminum adjusting amount of an LF furnace is not more than 5 kg/ton molten steel, ferrotitanium is added before the LF furnace is discharged to adjust Ti, and the reference absorption rate is 80-85%;

(5) RH vacuum treatment: increasing the argon flow to 800-1200 NL/min, and carrying out molten steel dehydrogenation to ensure that the deep vacuum treatment time is 12-16 min; vacuum treatment time is required to be 5-8 min; after the vacuum is finished, hydrogen determination is carried out; feeding 350m of Si-Ca wire and 200 m of Ca wire into molten steel in each furnace to ensure that the content of Ca in the molten steel is between 15ppm and 25 ppm; soft blowing is carried out on the molten steel before the ladle is hung, the flow of soft argon blowing is controlled to be less than or equal to 100L/min, the slag surface cannot be turned over, and the soft blowing time of the molten steel is ensured to be 12-16 min; the molten steel calming time after soft blowing is more than or equal to 5-8 min;

(6) and (3) continuous casting process: adopting a continuous casting billet with the specification of 300 mm; the pulling speed range is as follows: 0.75 m/min-0.85 m/min, ensuring that the low-power center segregation of the casting blank is less than or equal to C class 1.0 level;

(7) heating a steel billet: a walking beam type heating furnace is adopted, the billet is heated to the set soaking temperature of 1150-1200 ℃, and the furnace time is 300-330 min;

(8) rolling a steel plate: the rolling finishing temperature range of the recrystallization zone is 980-1030 ℃, the thickness of the steel plate to be heated is 2.5-4.5 times of the thickness of the finished steel plate, the rolling starting temperature range of the non-recrystallization zone is 860-920 ℃, and the rolling finishing temperature range of the non-recrystallization zone is 800-840 ℃; after rolling, the steel plate quickly enters a cooling device for cooling; the temperature of the entering water is controlled according to 810-780 ℃, the final cooling temperature is controlled according to 450-550 ℃, and the cooling speed is controlled according to 15-35 ℃/S. After the steel plate is rolled, rapidly performing off-line stack cooling, wherein the stack cooling temperature range is 350-450 ℃, and the stack cooling time range is 24-48 h;

(9) and (3) testing the fire resistance: on the basis that the 'steel plate and steel strip for refractory structure' meet the national standard GB/T28415-.

(10) And (3) corrosion resistance test: the accelerated corrosion test period is 72 hours, the test medium is 0.01mol/L NaHSO3, the test environment temperature is 25 ℃, the solution temperature is 45 ℃, the humidity is 70 +/-5% RH, and the supplementary liquid is 0.02mol/L NaHSO 3; each dry-wet cycle period is 60min, the immersion time is 12min, and the drying time is 48 min; the average value of each group of 5 samples is taken, and the sample size is 4mm multiplied by 40mm multiplied by 60 mm; and (5) derusting the test piece after the test is carried out for 72h, and calculating the corrosion weight loss rate.

Through the process flow, the produced steel for the building structure, which has the tensile strength of 600MPa, high toughness, low yield ratio, fire resistance, corrosion resistance and easy welding, has stable comprehensive mechanical properties, better strength, plasticity and toughness and excellent welding performance, and can completely meet the design requirements of structural steel with low crack sensitivity while meeting the mechanical property requirements of the corrosion-resistant and fire-resistant steel. Meanwhile, the steel grade related by the invention has small fluctuation of strength range, lower yield ratio and high use safety factor. The mechanical performance indexes are as follows: yield strength of more than or equal to 500MPa and less than or equal to 560MPa, tensile strength of more than or equal to 600MPa and less than or equal to 660MPa, elongation after fracture of more than or equal to 22.0 percent and less than or equal to 30.0 percent, longitudinal impact of more than or equal to 300J and less than or equal to-40 ℃ and longitudinal impact of more than or equal to 200J and less than or equal to 60 ℃ and less than or equal to 300J; the yield ratio is less than or equal to 0.83; the high-temperature tensile yield strength (600 ℃ and the heat preservation time are more than or equal to 3.5 hours) is less than or equal to 350 MPa; average corrosion rate: less than or equal to 1.2 g/m2 & h.

The invention has the advantages that:

(1) through reasonable and economic component design and strict process control, the steel for the building structure with high strength, high toughness, low yield ratio and low welding crack sensitivity can be stably produced, the fluctuation of the yield strength and the tensile strength is small, the fluctuation is within 60MPa, and the dispersion of the material strength is small.

(2) The steel grade has excellent high-temperature fire resistance under harsh high-temperature test conditions, the fire resistance can meet the requirement of 500 MPa-grade fire-resistant steel, and the steel grade has certain engineering application value and prospect.

(3) The steel grade of the invention is subjected to strict corrosion resistance test; compared with common structural steel, the corrosion resistance is excellent, and the steel can be widely applied to severe atmospheric environment.

(4) The steel grade provided by the invention integrates low yield ratio, corrosion resistance and fire resistance, has the characteristics of high-toughness building steel, corrosion-resistant steel and fire-resistant steel, and can provide reference for development of future multi-purpose multifunctional composite high-strength building steel.

Drawings

FIG. 1 is a typical microstructure (OM) of a 28mm gauge steel plate of an example;

FIG. 2 shows a typical microstructure (SEM) of a 28mm gauge steel plate of example.

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Detailed Description

Example 1

According to the requirements of the chemical component range of the corrosion-resistant and fire-resistant steel with 600 MPa-grade tensile strength and low yield ratio, billet steel smelting, slab casting and steel plate rolling are completed on a 5000mm wide and thick plate production line. Billet type: 300mm 2000mm 3000 mm; specification of rolled steel plate: 28mm 2600mm 12000mm, 2-point scale.

The specific process parameters are controlled as follows:

the actual parameters of temperature control in the molten steel smelting process are as follows: the converter tapping temperature is 1651 ℃, the LF finishing temperature is 1640 ℃, the RH finishing temperature is 1582 ℃, the soft blowing finishing temperature is 1563 ℃, and the tundish finishing temperature is 1540 ℃.

Smelting: bottom blowing argon flow 395-³The flow rate of bottom-blown argon at the end of blowing is 490-498 m³/h。

Tapping by a converter: when 1/3 steel was tapped, 2.45kg of lime and 0.052kg of fluorite were added to the steel stream for slag washing. After tapping, 0.031kg of aluminum grate is added on the slag surface. Actual compositions of molten steel discharged from the converter and then fed to the LF furnace are shown in Table 4.

TABLE 4 LF actual composition (wt%)

Refining in an LF furnace: during the refining process, low-carbon ferromanganese is used for regulating manganese (C: 0.50%, Mn: 85.0%, and the balance of impurities S, P), the aluminum is controlled according to 0.025% -0.045% at the end of LF, the total aluminum regulating amount of an LF furnace is not more than 5 kg/ton molten steel, ferrotitanium is added before the LF furnace is taken out, and the absorption rate is 83%. The actual composition after the completion of the LF furnace is shown in Table 5.

TABLE 5 LF furnace end actual composition (wt%)

RH vacuum treatment: increasing the argon flow to 900-1000 NL/min, carrying out molten steel dehydrogenation, and carrying out deep vacuum treatment for 16 min; after the final batch of alloy is adjusted, the vacuum treatment time is 7 min; feeding the molten steel into a 350m Si-Ca wire and a 200 m Ca wire, wherein the Ca content is 21 ppm; the flow of the soft argon blowing is suspended for 80L/min, and the soft blowing time is 14 min; and (4) after soft blowing, the molten steel is calmed for 7 min. The actual composition after the completion of the RH furnace is shown in Table 6.

TABLE 6 RH furnace end target composition (wt%)

And (3) continuous casting process: 300mm of continuous casting billet; the pulling speed range is as follows: 0.81m/min, low power center segregation C class 0.5 grade.

Heating a steel billet: the soaking temperature of the billet steel is 1165 to 1190 ℃, and the furnace time is 315 min.

Rolling a steel plate: for a 28mm specification steel plate, the actual temperature of finishing rolling in a recrystallization zone is 1026 ℃, the thickness to be cooled is 84mm (3 times the thickness of a finished steel plate), the rolling starting temperature in a non-recrystallization zone is 882 ℃, and the rolling finishing temperature in the non-recrystallization zone is 806 ℃; the water inlet temperature is 798 ℃, the final cooling temperature is 505 ℃, and the actual cooling speed is 23 ℃/S. The temperature range of the heap cooling is 410 ℃, and the time range of the heap cooling is 30 h.

And (3) finishing rolling of the steel plate, sampling and inspecting component components, comprehensive mechanical properties, fire resistance and corrosion resistance.

The composition of the finished steel sheet of this example is shown in Table 7:

TABLE 7 Final product composition

The comprehensive mechanical properties and yield ratio of the steel plate of the example are shown in table 8:

TABLE 8 mechanical properties and yield ratio of steel plate

Fire resistance: according to the requirement of the high-temperature tensile test method, under the condition of '600 ℃ and 3.5h of heat preservation', the fire resistance indexes of the steel grades related to the embodiment are shown in the table 9, and the fire resistance of the steel grades of the embodiment can meet the requirement of Q500 FR.

TABLE 9 index of fire resistance

Corrosion resistance: by comparison with the ordinary carbon structural steel Q235B, the atmospheric corrosion resistance of the steel grade related to the embodiment is 3.96 times that of the ordinary carbon steel. The specific cycle immersion corrosion test results are shown in table 10.

TABLE 10 periodic immersion corrosion test results

The present embodiment is only a simple description of the present invention, and does not limit the present invention in any way.

Claims (2)

1. A high-toughness fire-resistant corrosion-resistant steel with 600MPa of tensile strength is characterized by comprising the following chemical components in percentage by weight: 0.035 to 0.055 percent; si: 0.25 to 0.40 percent; mn: 0.90% -1.00%; ni: 0.25 to 0.35 percent; cr: 0.45 to 0.55 percent; mo: 0.10 to 0.20 percent; cu: 0.25 to 0.35 percent; nb: 0.020% -0.040%; ti: 0.010% -0.020%; and (3) Alt: 0.015% -0.035%; p: less than or equal to 0.015 percent; s: less than or equal to 0.005 percent; n: less than or equal to 0.0030 percent; h: less than or equal to 0.0002 percent; ca: 0.0015 to 0.0025 percent; carbon equivalent Ceq (%) = C + Mn/6+ (Cr + Mo + V)/5+ (Ni/+ Cu)/15, and Ceq (%) range is required: 0.35 to 0.40; weld crack sensitivity Pcm (%) = C + Si/30+ Mn/20+ Cu/20+ Cr/20+ Ni/60+ Mo/15+ V/10+5B, and Pcm (%) range is required: 0.14 to 0.18; the balance of Fe and inevitable impurities; weather resistance index I =26.01Cu +3.88Ni +1.2Cr +1.49Si +17.28P-7.29Cu × Ni-9.11Ni × P-33.39Cu2, and requires an I% range: 6.1-6.9; in order to ensure the synergistic effect of Mo and Nb in the phase change strengthening and reduce the dispersion of yield strength, the mass percentage ratio of Mo to Nb is required to be controlled within the range of 5.0-10.0%; the beneficial effects of Nb and Ti precipitates in increasing the crystal boundary strength and improving the fire resistance, weather resistance and comprehensive mechanical properties of steel are utilized, and the mass percentage ratio of Nb to Ti is required to be controlled between 2.0-4.0.

2. A manufacturing method of high-toughness fire-resistant corrosion-resistant steel with 600MPa of tensile strength is characterized by comprising the following steps:

(1) the temperature control parameter requirements in the molten steel smelting process are as follows: tapping the steel from the converter 1650 + -20 ℃, ending LF 1635 + -10 ℃, ending RH 1585 + -5 ℃, ending soft blowing temperature 1565 + -5 ℃ and tundish temperature 1538 + -5 ℃;

(2) smelting: the bottom blowing argon mode is adopted, and the flow of the bottom blowing argon is set to be 400 +/-10 m at the initial stage of converter blowing³The flow rate of bottom-blown argon gas at the final stage of converting was set to 500. + -. 10m³/h；

(3) Tapping by a converter: when 1/3 steel is tapped, 2.4 kg-2.6 kg of lime and 0.045 kg-0.055 kg of fluorite are added per ton of molten steel along with steel flow for slag washing; after tapping, 0.025 kg-0.035 kg of aluminum grate is added on the slag surface per ton of molten steel;

(4) refining in an LF furnace: the refining process uses a mixture containing C: 0.20 to 0.70 percent; mn: 80.0% -90.0%; the balance of low-carbon ferromanganese with the impurity of S, P for regulating Mn; aluminum particles are used for adjusting aluminum in the treatment process, the aluminum at the end of LF is controlled according to 0.020-0.050%, the total aluminum adjusting amount of an LF furnace is not more than 5 kg/ton molten steel, ferrotitanium is added before the LF furnace is discharged to adjust Ti, and the reference absorption rate is 80-85%;

(5) RH vacuum treatment: increasing the argon flow to 800-1200 NL/min, and carrying out molten steel dehydrogenation to ensure that the deep vacuum treatment time is 12-16 min; vacuum treatment time is required to be 5-8 min; after the vacuum is finished, hydrogen determination is carried out; feeding 350m of Si-Ca wire and 200 m of Ca wire into molten steel in each furnace to ensure that the content of Ca in the molten steel is between 15ppm and 25 ppm; soft blowing is carried out on the molten steel before the ladle is hung, the flow of soft argon blowing is controlled to be less than or equal to 100L/min, the slag surface cannot be turned over, and the soft blowing time of the molten steel is ensured to be 12-16 min; the molten steel calming time after soft blowing is more than or equal to 5-8 min;

(6) and (3) continuous casting process: adopting a continuous casting billet with the specification of 300 mm; the pulling speed range is as follows: 0.75 m/min-0.85 m/min, ensuring that the low-power center segregation of the casting blank is less than or equal to C class 1.0 level;

(7) heating a steel billet: a walking beam type heating furnace is adopted, the billet is heated to the set soaking temperature of 1150-1200 ℃, and the furnace time is 300-330 min;

(8) rolling a steel plate: the rolling finishing temperature range of the recrystallization zone is 980-1030 ℃, the thickness of the steel plate to be heated is 2.5-4.5 times of the thickness of the finished steel plate, the rolling starting temperature range of the non-recrystallization zone is 860-920 ℃, and the rolling finishing temperature range of the non-recrystallization zone is 800-840 ℃; after rolling, the steel plate quickly enters a cooling device for cooling; the temperature of the entering water is controlled according to 810-780 ℃, the final cooling temperature is controlled according to 450-550 ℃, and the cooling speed is controlled according to 15 ℃/S-35 ℃/S;

after the steel plate is rolled, rapidly performing off-line stack cooling, wherein the stack cooling temperature range is 350-450 ℃, and the stack cooling time range is 24-48 h;

(9) and (3) testing the fire resistance: on the basis that the 'steel plate and steel strip for refractory structure' meet the national standard GB/T28415-;

(10) and (3) corrosion resistance test: the accelerated corrosion test period is 72 hours, the test medium is 0.01mol/L NaHSO3, the test environment temperature is 25 ℃, the solution temperature is 45 ℃, the humidity is 70 +/-5% RH, and the supplementary liquid is 0.02mol/L NaHSO 3; each dry-wet cycle period is 60min, the immersion time is 12min, and the drying time is 48 min; the average value of each group of 5 samples is taken, and the sample size is 4mm multiplied by 40mm multiplied by 60 mm; and (5) derusting the test piece after the test is carried out for 72h, and calculating the corrosion weight loss rate.

Images