CN111519095A

CN111519095A - Multiphase microstructure anti-seismic weather-proof fire-resistant H-shaped steel and preparation method thereof

Info

Publication number: CN111519095A
Application number: CN202010395804.1A
Authority: CN
Inventors: 宋振东; 涛雅; 赵晓敏; 白月琴; 周彦
Original assignee: Baotou Iron and Steel Group Co Ltd
Current assignee: Baotou Iron and Steel Group Co Ltd
Priority date: 2020-05-12
Filing date: 2020-05-12
Publication date: 2020-08-11

Abstract

The invention discloses a multiphase microstructure shock-resistant weather-resistant fire-resistant H-shaped steel and a preparation method thereof, belonging to the technical field of smelting and rolling. The multiphase microstructure anti-seismic weather-resistant fire-resistant H-shaped steel comprises the following chemical components: 0.06-0.08% of C, 0.18-0.20% of Si, 1.2-1.4% of Mn, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 0.40-0.44% of Cu, 0.28-0.31% of Cr, 0.28-0.31% of Ni, 0.02-0.05% of Nb, 0.04-0.07% of V, 0.07-0.10% of Ti, 0.24-0.28% of Mo, 0.0013-0.0015% of B, and the balance of Fe and inevitable impurities. The multiphase microstructure anti-seismic weather-proof fire-resistant hot-rolled H-shaped steel produced by low-carbon microalloying has low cost, low yield ratio and better low-temperature toughness.

Description

Multiphase microstructure anti-seismic weather-proof fire-resistant H-shaped steel and preparation method thereof

Technical Field

The invention belongs to the technical field of smelting and rolling, and particularly relates to multiphase microstructure shock-resistant weather-resistant fire-resistant H-shaped steel and a preparation method thereof.

Background

As a novel green building structure, the steel structure has the advantages of large steel consumption, high steel recovery rate, energy conservation and environmental protection, and is a leading building structure abroad. For example, the steel structure proportion in the construction area of Japan exceeds 50%, especially the steel structure adopted by low-rise buildings is quite common, and the steel structure proportion of low-rise buildings with less than 5 floors even reaches more than 90%. Steel structure houses also become mainstream buildings in developed countries of Europe and America, and the steel structure houses in developed countries of British, Sweden and the like reach more than 40 percent and the steel structure houses in the United states reach 52 percent. Finland, sweden, denmark and france have all formed a considerable scale of industrial steel structure residential systems. Compared with developed countries, the steel structure building occupation ratio in China is still low (less than 10%).

Although the GB/T19879 steel plate for building structures standard expands the steel types from Q235GJ and Q345GJ series to Q235GJ, Q345GJ, Q390GJ, Q420GJ and Q460GJ series, the domestic steel for building structures still takes Q345GJ series as the main part, and the current situation that the strength grade of the steel for building is imperfect and the steel waste amount is large needs to be changed in the process of establishing two types of society is urgent. In recent years, Q390GJ series steel has been used to a certain extent, and Q390GJ series steel is widely used in projects such as guangzhou new television tower and Tianjingtta, and although Q420GJ and Q460GJ steel are still rarely used in practical projects, the strength grade of steel used in steel structure projects will be higher and higher with the rapid development of national economy. At present, the building structure develops towards high-rise and large span, and the building structure must use high-strength steel so as to reduce the weight of the structure, reduce the construction cost, reduce the thickness of the steel structure material and improve the safety and reliability of the steel structure material. Therefore, the development of the steel material with comprehensive properties of high strength, weather resistance, earthquake resistance, fire resistance and the like has wide application prospect.

Disclosure of Invention

In view of one or more of the problems in the prior art, one aspect of the present invention provides a multiphase microstructure earthquake resistant, weather resistant and fire resistant H-section steel, which comprises the following chemical components: 0.06-0.08% of C, 0.18-0.20% of Si, 1.2-1.4% of Mn, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 0.40-0.44% of Cu, 0.28-0.31% of Cr0.28, 0.28-0.31% of Ni, 0.02-0.05% of Nb, 0.04-0.07% of V, 0.07-0.10% of Ti, 0.24-0.28% of Mo, 0.0013-0.0015% of B, and the balance of Fe and inevitable impurities;

the mechanical properties of the multiphase microstructure anti-seismic weather-resistant fire-resistant H-shaped steel are as follows: the yield strength is more than or equal to 495MPa, the tensile strength is more than or equal to 709MPa, the elongation is more than or equal to 20 percent, and the Charpy impact energy A at the temperature of minus 20 DEG C_k160J or more, the yield ratio is 0.70 or less, and the high-temperature tensile yield strength is 325MPa or more.

The invention provides a preparation method of the multiphase microstructure anti-seismic weather-resistant fire-resistant H-shaped steel, which comprises the following steps of carrying out smelting process and rolling process on molten steel to obtain the multiphase microstructure anti-seismic weather-resistant fire-resistant H-shaped steel; wherein the smelting process comprises the following steps: molten iron pretreatment → converter smelting → LF refining → VD vacuum refining → continuous casting billet; the rolling process includes: the method comprises the following steps of profile blank → heating of a stepping heating furnace → high-pressure water dephosphorization → BD1 rolling → BD2 rolling → CCS continuous rolling → sawing → sampling → cold bed prebending → head and tail cutting → straightening → inspection → bundling → warehousing.

In the smelting process of the converter, the w [ S ] in molten iron fed into the converter is controlled to be less than or equal to 0.015 percent, the tapping temperature of the converter is increased to 1570 ℃, and the slag discharging amount of the converter is controlled. The method of the slag blocking cap and the slag blocking ball is adopted to control the slag discharging amount of the converter, the slag blocking cap is blocked at the steel outlet for one-time slag blocking before steel discharging, when the molten steel is in the residual 4/5 state, the slag blocking ball is thrown above the molten steel in the converter, the slag blocking ball is positioned between the molten steel and the liquid level of the steel slag, the secondary slag is blocked at the end of steel discharging, and the slag discharging amount ranges from 3% to 5%.

In the LF refining process and the VD vacuum refining process, the LF heating time and the refining time are respectively 20min and 45min, and the argon blowing time of the VD furnace is not less than 20 min.

In the continuous casting billet process, the drawing speed range of the continuous casting machine is 0.85-0.9 m/min, the superheat degree of the steel grade is less than 30 ℃, and the specific water amount is 0.25L/mg.

In the rolling procedure, the heating temperature of the billet is 1100-1150 ℃; the initial rolling temperature is less than or equal to 1100 ℃, and the final rolling temperature is 860-880 ℃.

Based on the technical scheme, the multiphase microstructure anti-seismic weather-resistant fire-resistant H-shaped steel and the preparation method thereof adopt low-carbon microalloying to produce steel with high strength, anti-seismic, weather-resistant and fire-resistant comprehensive properties, and the mechanical properties are that the yield strength is more than or equal to 495MPa, the tensile strength is more than or equal to 709MPa, the elongation is more than or equal to 20 percent, and the Charpy impact power A at the temperature of minus 20 ℃ is_k160J or more, the yield ratio is 0.70 or less, and the high-temperature tensile yield strength is 325MPa or more. Compared with the traditional method, the multiphase microstructure anti-seismic weather-proof fire-resistant hot-rolled H-shaped steel produced by adopting the low-carbon microalloying method has the advantages of low cost, low yield ratio, better low-temperature toughness and good high-temperature resistance.

Drawings

FIG. 1 is metallographic structure photographs of the multiphase microstructure earthquake resistant, weather resistant and fire resistant H-shaped steel of the present invention at 500 times and 1000 times, in which A represents the metallographic structure photograph at 500 times and B represents the metallographic structure photograph at 1000 times.

Detailed Description

The invention aims to solve the technical problem of providing multiphase microstructure shock-resistant weather-resistant fire-resistant H-shaped steel and a preparation method thereof.

The molten steel for preparing the multiphase microstructure earthquake-resistant weather-resistant fire-resistant H-shaped steel comprises the following chemical components: 0.06-0.08% of C, 0.18-0.20% of Si, 1.2-1.4% of Mn, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 0.40-0.44% of Cu, 0.28-0.31% of Cr0.28, 0.28-0.31% of Ni, 0.02-0.05% of Nb, 0.04-0.07% of V, 0.07-0.10% of Ti, 0.24-0.28% of Mo, 0.0013-0.0015% of B, and the balance of Fe and inevitable impurities.

Wherein C is a gap strengthening element, can improve the strength of the matrix, and simultaneously can form dispersed carbide with alloy elements in steel to perform dispersion strengthening on the matrix and improve the strength of the material. Si is a non-carbide-forming element, is present in an atomic state between austenite and ferrite, and solution-strengthens ferrite. But the content of Si is too high, which affects the welding performance and deteriorates the welding structure performance, and the content is controlled to be 0.18-0.20. Mn element can be dissolved in ferrite, and the addition of Mn reduces the phase transition temperature of austenite, increases the nucleation speed of ferrite crystals and reduces the growth speed of ferrite grains, thereby refining the grains. The microalloy element V is added into the steel, and mainly plays roles in grain refinement and precipitation strengthening. V combines with carbon and nitrogen to form carbonitride particles. The carbon and nitrogen compound particles can prevent the original austenite from growing in the heating process, can inhibit recrystallization and the growth of the recrystallized grains in the rolling process, and can precipitate in the cooling process to play a role in dispersion strengthening, thereby improving the comprehensive performance of the material. Mo is an element for narrowing the austenite phase region, and also suppresses the decomposition of austenite, delays the transformation of grain boundary ferrite, and contributes to the formation of a bainite structure. Mo forms Mo with C₂C. MoC and gem Fe form complex carbides. Ti shifts the C curve to the right and is a strong carbide and nitride forming element. Ti can obviously improve the room temperature strength and the high temperature strength of the steel, and the toughness of the steel can also be improved because the Ti can play a role in refining grains. In addition, the steel grade adopts a narrow-component design, so that the stable yield ratio and the small fluctuation range of the anti-seismic H-shaped steel can be ensured.

The steps of preparing the multiphase microstructure shock-resistant weather-resistant fire-resistant H-shaped steel comprise a smelting process and a rolling process, wherein the smelting process comprises the following steps: molten iron pretreatment → converter smelting → LF refining → VD vacuum refining → continuous casting billet. Wherein, corresponding process measures are adopted in the production processes of converter steelmaking, external refining and continuous casting, and the process comprises the following steps: controlling the W [ S ] in the molten iron fed into the converter to be less than or equal to 0.015 percent, improving the tapping temperature of the converter to about 1570 ℃, controlling the slag discharge amount of the converter, prolonging the refining time of the LF furnace, casting at low casting speed of continuous casting and the like, and producing the continuous casting billet with qualified quality. The LF heating time and the refining time are 20min and 45min, the argon blowing time of the VD furnace is not less than 20min, the drawing speed range of the continuous casting machine is 0.85 m/min-0.9 m/min, the superheat degree of the steel grade is less than 30 ℃, and the specific water amount is 0.25L/mg. The rolling process comprises the following steps: the method comprises the following steps of profile blank → heating of a stepping heating furnace → high-pressure water dephosphorization → BD1 rolling → BD2 rolling → CCS continuous rolling → sawing → sampling → cold bed prebending → head and tail cutting → straightening → inspection → bundling → warehousing. Wherein the heating temperature of the steel billet is 1100-1150 ℃; the initial rolling temperature is less than or equal to 1100 ℃, and the final rolling temperature is 860-880 ℃. Finally preparing the multiphase microstructure shock-resistant weather-resistant fire-resistant H-shaped steel.

The present invention will be described in further detail with reference to examples.

In the embodiment, the inventor uses the deformed continuous casting billet smelted by the ladle steel to roll into the H-shaped steel with the specification of 350 multiplied by 12 multiplied by 19 by a ladle rail beam mill, so that the H-shaped steel can be applied to the steel structure of a building. The following table 1 lists the chemical compositions of the molten steels of the examples.

TABLE 1 chemical composition of each example (mass%/%)

The molten steels of the examples listed in table 1 above were respectively smelted and rolled according to the following procedures: molten iron pretreatment → converter smelting → LF refining → VD vacuum refining → continuous casting slab → beam blank → heating of step-by-step furnace → high-pressure water dephosphorization → BD1 rolling → BD2 rolling → CCS continuous rolling → sawing → sampling → cold bed prebending → head and tail cutting → straightening → inspection → bundling → warehousing. Wherein in the smelting process, corresponding process measures are adopted in the production processes of converter steelmaking, external refining and continuous casting, and the process comprises the following steps: controlling the W [ S ] in molten iron entering a converter to be less than or equal to 0.015%, raising the tapping temperature of the converter to about 1570 ℃, controlling the slag discharging amount of the converter, adopting a method of a slag blocking cap and a slag blocking ball to control the slag discharging amount of the converter, blocking the slag blocking cap at a tapping hole for one-time slag blocking before tapping, and when the molten steel is left 4/5, putting the slag blocking ball above the molten steel in the converter, wherein the slag blocking ball is positioned between the molten steel and the liquid level of the steel slag, blocking secondary slag at the end of tapping, and controlling the slag discharging amount to be 3-5%.

The refining time of the LF furnace is prolonged, the continuous casting is performed at a low pulling speed, and the like, and the continuous casting with qualified quality is produced. The LF heating time and the refining time are 20min and 45min, the argon blowing time of the VD furnace is not less than 20min, the drawing speed range of the continuous casting machine is 0.85 m/min-0.9 m/min, the superheat degree of the steel grade is less than 30 ℃, and the specific water amount is 0.25L/mg. In the rolling process, the heating temperature of a steel billet is 1100-1150 ℃; the initial rolling temperature is less than or equal to 1100 ℃, and the final rolling temperature is 860-880 ℃.

The H-sections prepared in examples 1 to 4 above were sampled with tensile test specimens of gauge length L₀The impact test was carried out using a 10mm × l0mm × 55mm charpy V-notch specimen at-20 c and 5 c, the diameter D being 10mm, the test temperature being as shown in table 2 below.

TABLE 2 mechanical Property results of the examples

As can be seen from the above Table 2, the H-shaped steel of each example has the characteristics of high strength, good low-temperature toughness, excellent earthquake resistance and excellent high-temperature fire resistance. As shown in fig. 1, the metallographic structure photographs of 500 times and 1000 times of the multiphase microstructure earthquake resistant, weather resistant and fire resistant H-shaped steel prepared in example 1 are shown, and it can be seen that the structure of the prepared H-shaped steel is mainly: ferrite, bainite and martensite, wherein the ferrite of a soft phase structure ensures that steel has good extensibility, the bainite of a hard phase structure and the martensite structure ensure that the material has high strength, and the soft phase structure ensures that the material has good low-temperature toughness.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The multiphase microstructure anti-seismic weather-resistant fire-resistant H-shaped steel is characterized by comprising the following chemical components: 0.06-0.08% of C, 0.18-0.20% of Si, 1.2-1.4% of Mn, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 0.40-0.44% of Cu, 0.28-0.31% of Cr, 0.28-0.31% of Ni, 0.02-0.05% of Nb, 0.04-0.07% of V, 0.07-0.10% of Ti, 0.24-0.28% of Mo, 0.0013-0.0015% of B, and the balance of Fe and inevitable impurities.

2. The multiphase microstructure earthquake-resistant weather-resistant fire-resistant H-shaped steel according to claim 1, wherein mechanical properties of the multiphase microstructure earthquake-resistant weather-resistant fire-resistant H-shaped steel are as follows: the yield strength is more than or equal to 495MPa, the tensile strength is more than or equal to 709MPa, the elongation is more than or equal to 20 percent, and the Charpy impact energy A at the temperature of minus 20 DEG C_k160J or more, the yield ratio is 0.70 or less, and the high-temperature tensile yield strength is 325MPa or more.

3. The method for preparing the multiphase microstructure earthquake-resistant weather-resistant fire-resistant H-shaped steel as claimed in claim 1 or 2, characterized in that molten steel is subjected to a smelting process and a rolling process to obtain the multiphase microstructure earthquake-resistant weather-resistant fire-resistant H-shaped steel; wherein the smelting process comprises the following steps: molten iron pretreatment → converter smelting → LF refining → VD vacuum refining → continuous casting billet; the rolling process includes: the method comprises the following steps of profile blank → heating of a stepping heating furnace → high-pressure water dephosphorization → BD1 rolling → BD2 rolling → CCS continuous rolling → sawing → sampling → cold bed prebending → head and tail cutting → straightening → inspection → bundling → warehousing.

4. The preparation method of claim 3, wherein in the converter smelting process, the w [ S ] in molten iron fed into the converter is controlled to be less than or equal to 0.015%, the tapping temperature of the converter is increased to 1570 ℃, and the slag discharging amount of the converter is controlled.

5. The preparation method of claim 3, wherein in the LF refining process and the VD vacuum refining process, the LF heating time and the refining time are respectively 20min and 45min, and the VD furnace argon blowing time is not less than 20 min.

6. The production method according to claim 3, wherein in the continuous casting billet process, the drawing speed range of the continuous casting machine is 0.85 m/min-0.9 m/min, the superheat degree of the steel grade is less than 30 ℃, and the specific water amount is 0.25L/mg.

7. The method according to claim 3, wherein the billet heating temperature in the rolling step is 1100 to 1150 ℃; the initial rolling temperature is less than or equal to 1100 ℃, and the final rolling temperature is 860-880 ℃.