CN107686943B - 370 MPa-yield-strength rare earth weather-resistant bridge steel plate and preparation method thereof - Google Patents

370 MPa-yield-strength rare earth weather-resistant bridge steel plate and preparation method thereof Download PDF

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CN107686943B
CN107686943B CN201710762952.0A CN201710762952A CN107686943B CN 107686943 B CN107686943 B CN 107686943B CN 201710762952 A CN201710762952 A CN 201710762952A CN 107686943 B CN107686943 B CN 107686943B
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rare earth
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CN107686943A (en
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杨雄
高军
吴章忠
王雪莲
黄利
姜秉坤
卢晓禹
王海明
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Baotou Iron and Steel Group Co Ltd
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226Hot rolling
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/005Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/06Ferrous alloys, e.g. steel alloys containing aluminium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/005Ferrite
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/009Pearlite

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Abstract

The invention relates to a rare earth weather-proof bridge steel plate with yield strength of 370MPa and a preparation method thereof. The preparation method comprises the following steps: smelting and casting; heating and rolling: the heating temperature is 1200-1220 ℃, and the total in-furnace time is more than or equal to 240 min; in rolling, rolling in an austenite recrystallization region in the first stage, wherein the initial rolling temperature is 1130-1180 ℃, the 1 st-2 nd pass reduction is more than 10%, and the rest at least 1-2 passes reduction rate is controlled to be more than 25%; rolling in an austenite non-recrystallization region at the second stage, wherein the initial rolling temperature is less than or equal to 930 ℃, and the thickness of an intermediate blank is as follows: 2.0-3.5 times of thickness of a finished product, and finishing temperature: 830-850 ℃; and (6) cooling. The steel plate has yield strength of more than 370MPa, has the advantages of low yield ratio, good corrosion resistance, low-temperature toughness, cold formability and welding performance, can be used without coating, and has the advantages of simple production process flow, short production period and low cost.

Description

370 MPa-yield-strength rare earth weather-resistant bridge steel plate and preparation method thereof
Technical Field
The invention relates to the technical field of ferrous metallurgy, in particular to a rare earth weather-proof bridge steel plate with yield strength of 370MPa and a preparation method thereof.
Background
The steel for bridges in China is developed from the first grade A3 to the current grade Q500Q, and the traditional steel for bridges is not ideal in impact toughness, weldability, fatigue property and the like, and is poorer in performances such as atmospheric corrosion resistance and marine corrosion resistance. With the modern bridge span becoming larger and larger, the safety and reliability of the bridge structure become stricter and stricter. The method is a great challenge for bridge designers, also puts higher requirements on the performance of the steel for the bridge, and has the characteristics of high strength to meet the requirement of structural lightweight, excellent low-temperature toughness, weldability, corrosion resistance and fatigue performance, low maintenance cost, energy conservation, environmental protection and the like, so that the development and application of the high-performance weather-resistant steel for the bridge, which integrates the performances, becomes the development trend of the steel for the bridge in the future.
Patent CN102534384A discloses a Cr-free high-performance weather-resistant bridge steel and a preparation method thereof, and the bridge steel with high strength, excellent low-temperature toughness, excellent welding performance and excellent weather resistance is obtained by TMCP process. However, the Nb and Ni alloy content in the chemical components is high, the strength of the steel plate is high, the final cooling control temperature is low, the requirement on cooling equipment in industrial production is high, and the low final cooling temperature can cause poor plate shape.
Patent CN102534417A discloses a high-performance bridge weathering steel containing Mo and a preparation method thereof, and the bridge weathering steel with high strength, excellent low-temperature toughness, excellent welding performance and excellent weather resistance is obtained by TMCP process. But the chemical components have high Nb content and 0.1-0.3% of Mo, so that the alloy cost is increased, the steel plate has high strength and low final cooling control temperature, the requirement on cooling equipment in industrial production is high, and the control difficulty is increased.
Patent CN102021495A discloses a preparation method of 420MPa high-toughness weather-resistant bridge steel and a hot rolled plate coil thereof, and the high-toughness weather-resistant bridge steel is obtained through smelting, continuous casting, heating, 2-frame rough rolling, 7-frame finish rolling, laminar cooling and coiling. However, the chemical composition contains B element, so that crack defects are easy to generate, and the method is only suitable for producing the rolled plate.
Disclosure of Invention
In view of the above, the invention provides a rare earth weather-resistant bridge steel plate with yield strength of 370MPa and a preparation method thereof.
The invention provides a rare earth weather-proof bridge steel plate with yield strength of 370MPa, which comprises the following chemical components in percentage by weight:
c: 0.04-0.06%, Si: 0.20 to 0.30%, Mn: 1.2-1.4%, P: less than or equal to 0.015%, S: less than or equal to 0.008 percent, Nb: 0.01-0.02%, Cu: 0.25 to 0.35%, Ni: 0.3-0.4%, Cr: 0.4-0.5%, Als: 0.024-0.034%, rare earth Ce: 0.0005-0.0030%, and the balance Fe and inevitable impurities.
The invention also provides a preparation method of the weather-resistant bridge steel plate, which comprises the following steps:
step 1), smelting according to the chemical components of claim 1, and casting into a rectangular steel ingot;
step 2), heating and rolling the steel ingot, wherein:
in the heating process, the heating temperature is 1200-1220 ℃, and the total in-furnace time is more than or equal to 240 min;
the rolling is divided into a first stage rolling and a second stage rolling:
rolling in an austenite recrystallization region in the first stage, wherein the initial rolling temperature is 1130-1180 ℃, the 1 st to 2 nd pass reduction is more than 10%, and the rest at least 1 to 2 passes reduction rate is controlled to be more than 25% in the rolling process;
rolling in an austenite non-recrystallization region at the second stage, wherein the initial rolling temperature is less than or equal to 930 ℃, and the thickness of an intermediate blank is as follows: 2.0-3.5 times of thickness of a finished product, and finishing temperature: 830-850 ℃;
step 3), cooling:
and after the rolling is controlled to be finished, the steel plate enters a laminar flow cooling area, is cooled to 610-630 ℃ at a cooling speed of 10-15 ℃/s, and then enters a cooling bed for cooling.
Compared with the prior art, the weather-resistant bridge steel plate provided by the invention has the advantages that through reasonable chemical component design and the controlled rolling and cooling process, a metallographic structure mainly comprising fine ferrite and pearlite is obtained, so that the weather-resistant bridge steel plate with the yield strength of more than 370MPa, low yield ratio, good corrosion resistance, low-temperature toughness, cold forming performance and welding performance and free of coating is obtained, and meanwhile, the production method has the characteristics of simple preparation process flow, short production period, low production cost and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below.
FIG. 1 is a metallographic structure diagram of a steel sheet prepared in example 2 of the present invention.
Detailed Description
The invention discloses a rare earth weather-proof bridge steel plate with yield strength of 370MPa and a preparation method thereof, and a person skilled in the art can use the contents for reference and appropriately improve process parameters to realize the weather-proof bridge steel plate. It is expressly intended that all such similar substitutes and modifications which would be obvious to one skilled in the art are deemed to be included in the invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations and modifications in the methods and applications described herein, as well as other suitable variations and combinations, may be made to implement and use the techniques of this invention without departing from the spirit and scope of the invention.
The invention provides a rare earth weather-proof bridge steel plate with yield strength of 370MPa, which comprises the following chemical components in percentage by weight:
c: 0.04-0.06%, Si: 0.20 to 0.30%, Mn: 1.2-1.4%, P: less than or equal to 0.015%, S: less than or equal to 0.008 percent, Nb: 0.01-0.02%, Cu: 0.25 to 0.35%, Ni: 0.3-0.4%, Cr: 0.4-0.5%, Als: 0.024-0.034%, rare earth Ce: 0.0005-0.0030%, and the balance Fe and inevitable impurities.
According to the weather-resistant bridge steel plate, the design of ultra-low carbon components is adopted, so that the carbon equivalent is reduced, the welding performance of the steel is ensured, the content of harmful elements such as P, S is controlled, and the low-temperature toughness is improved; the trace alloy element Nb is added, so that the growth of austenite grains is effectively inhibited, the austenite grains are refined at high temperature and high pressure, a fine grain structure is finally obtained, and the strength and the low-temperature toughness of the steel are improved through the fine grain strengthening and toughening effects; corrosion-resistant alloys Cu, Cr and Ni are added and a certain proportion is controlled, so that the weather-resistant characteristic is achieved, and the strength of the steel can be improved; through Ni/Cu control, not only can reduce the surface cracks of the casting blank, but also can improve the impact toughness of the steel; by adding trace rare earth Ce, the low-temperature impact toughness of the steel is improved through the purification effect of the rare earth, and the corrosion resistance of the steel can be obviously improved.
The invention also provides a preparation method of the weather-resistant bridge steel plate, which comprises the following steps:
step 1), smelting according to the chemical components, and casting into a rectangular steel ingot;
step 2), heating and rolling the steel ingot, wherein:
in the heating process, the heating temperature is 1200-1220 ℃, and the total in-furnace time is more than or equal to 240 min;
the rolling is divided into a first stage rolling and a second stage rolling:
rolling in an austenite recrystallization region in the first stage, wherein the initial rolling temperature is 1130-1180 ℃, the 1 st to 2 nd pass reduction is more than 10%, and the rest at least 1 to 2 passes reduction rate is controlled to be more than 25% in the rolling process;
rolling in an austenite non-recrystallization region at the second stage, wherein the initial rolling temperature is less than or equal to 930 ℃, and the thickness of an intermediate blank is as follows: 2.0-3.5 times of thickness of a finished product, and finishing temperature: 830-850 ℃;
step 3), cooling:
and after the rolling is controlled to be finished, the steel plate enters a laminar flow cooling area, is cooled to 610-630 ℃ at a cooling speed of 10-15 ℃/s, and then enters a cooling bed for cooling.
In the production process, the step 1) is a smelting and casting process, and the smelting and casting process specifically comprises the following steps:
adding prepared low-phosphorus (less than or equal to 0.010 percent), low-sulfur (less than or equal to 0.005 percent), low-oxygen (less than or equal to 0.0040 percent), low-nitrogen (less than or equal to 0.0060 percent) high-quality scrap steel and other calculated and prepared alloys into a laboratory 100kg vacuum smelting furnace, starting to melt and smelt after vacuumizing, casting into a rectangular steel die after melting, and casting into a rectangular billet with the size of 220 multiplied by 250 multiplied by 300 mm.
Steps 2) and 3) are processes for manufacturing the steel ingot into a steel plate, wherein the heating and rolling processes can be specifically as follows:
and loading the billet into a high-temperature resistance furnace by using a manipulator. The heating temperature is 1200-1220 ℃, the total in-furnace time is more than or equal to 240min, the temperature of the steel billet is ensured to be uniform, and when the steel billet meets the heating requirement, the steel billet is sent to a phi 750 x 550mm experimental rolling mill by a mechanical arm. The two-stage controlled rolling process, namely austenite recrystallization zone rolling and austenite non-recrystallization zone rolling is adopted. When rolling is carried out in an austenite recrystallization zone, the initial rolling temperature is 1130-1180 ℃, the reduction of 1-2 passes is more than 10%, and the reduction of at least 1-2 passes is controlled to be more than 25% so as to fully refine original austenite grains; in the case of rolling in the austenite non-recrystallization region, the rolling at this stage elongates austenite to increase the grain boundary area, and at the same time, deformation causes a large amount of deformation bands to be introduced into the inside of the grains, and the nucleation density and the nucleation point increase during the subsequent phase transformation, thereby further refining the grains. Setting the initial rolling temperature to be less than or equal to 930 ℃, and the thickness of the intermediate billet: 2.0-3.5 times of thickness of a finished product, and finishing temperature: 830-850 ℃.
Compared with the prior art, the weather-resistant bridge steel plate provided by the invention has the advantages that through reasonable chemical component design and the controlled rolling and cooling process, a metallographic structure mainly comprising fine ferrite and pearlite is obtained, so that the weather-resistant bridge steel plate with the yield strength of more than 370MPa, low yield ratio, good corrosion resistance, low-temperature toughness, cold forming performance and welding performance and free of coating is obtained, and meanwhile, the production method has the characteristics of simple preparation process flow, short production period, low production cost and the like.
The invention is further illustrated by the following examples:
the present invention is described in more detail below with reference to examples. These examples are merely illustrative of the best mode of carrying out the invention and do not limit the scope of the invention in any way.
Example 1
Smelting according to chemical components shown in Table 1, casting into a steel ingot, heating the steel ingot to 1210 ℃, keeping the furnace time for 252 minutes, carrying out first-stage rolling on an experimental rolling mill, namely rolling in an austenite recrystallization region, wherein the starting rolling temperature is 1176 ℃, the reduction of the 1 st to 2 nd pass is more than 10%, the reduction of at least 1 to 2 passes is controlled to be more than 25%, when the thickness of a rolled piece is 45mm, heating to 930 ℃ on a roller way, and then carrying out second-stage rolling, namely rolling in an austenite non-recrystallization region. The final rolling temperature is 830 ℃, and the thickness of the finished steel plate is 14 mm. And after rolling, the steel plate enters a laminar flow cooling device, and is cooled to 630 ℃ at the speed of 10 ℃/s, and finally the steel plate can be obtained.
Example 2
The implementation mode is the same as that of example 1, wherein the heating temperature is 1220 ℃, the total in-furnace time is kept for 256 minutes, the initial rolling temperature of the first stage rolling is 1175 ℃, the thickness of the intermediate blank is 60mm, the initial rolling temperature of the second stage rolling is 925 ℃, the final rolling temperature is 836 ℃, and the thickness of the finished steel plate is 20 mm. And after rolling, the steel plate enters a laminar flow cooling device, and is cooled to 620 ℃ at the speed of 12 ℃/s, and finally the steel plate can be obtained. The metallographic structure of the steel sheet is shown in FIG. 1.
Example 3
The procedure is as in example 1, wherein the heating temperature is 1226 ℃ and the total in-furnace time is 260 minutes; the initial rolling temperature of the first stage rolling is 1180 ℃, and the thickness of the intermediate billet is 80 mm; the initial rolling temperature of the second stage of rolling is 930 ℃, the final rolling temperature is 850 ℃, and the thickness of the finished steel plate is 40 mm; and after rolling, the steel plate enters a laminar flow cooling device, and is cooled to 610 ℃ at the speed of 15 ℃/s, and finally the steel plate can be obtained.
TABLE 1 chemical composition (wt%) of inventive examples 1 to 3
Figure BDA0001393544300000051
Figure BDA0001393544300000061
The mechanical properties of the steel sheets of examples 1 to 3 of the present invention were examined, and the results are shown in Table 2.
TABLE 2 mechanical Properties of Steel sheets according to examples 1 to 3 of the present invention
Figure BDA0001393544300000062
As can be seen from Table 2, the bridge steel according to the embodiment of the invention has yield strength of more than or equal to 370MPa, tensile strength of more than or equal to 510MPa, elongation of more than or equal to 20%, yield ratio of less than or equal to 0.85 and longitudinal impact energy KV at-40 ℃ of2≥120J。
Table 3 shows the weld crack sensitivity Pcm and the corrosion resistance index I of the steels according to the examples of the present invention.
TABLE 3 weld crack susceptibility Pcm and Corrosion resistance index I for inventive examples
Figure BDA0001393544300000063
The smaller the value of the welding crack sensitivity coefficient Pcm is, the better the welding performance of the steel is, the welding cold crack is not easy to generate during welding, when the corrosion resistance index I is more than or equal to 6.0, the good corrosion resistance is shown, the steel plate has the coating-free use condition, and the larger the value I is, the better the corrosion resistance is shown. As can be seen from Table 3, the steel plate prepared by the embodiment of the invention has the coating-free use condition and good corrosion resistance.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (1)

1. The yield strength 370MPa grade rare earth weather-proof bridge steel plate is characterized by comprising the following chemical components in percentage by weight:
c: 0.06%, Si: 0.28%, Mn: 1.26%, P: 0.010%, S: 0.002%, Nb: 0.012%, Cu: 0.32%, Ni: 0.33%, Cr: 0.46%, Als: 0.028%, rare earth Ce: 0.0019%, the balance being Fe and unavoidable impurities;
the preparation method comprises the following steps:
step 1), smelting according to the chemical components, and casting into a rectangular steel ingot;
step 2), heating and rolling the steel ingot, wherein:
in the heating process, the heating temperature is 1226 ℃, and the total in-furnace time is 260 min;
the rolling is divided into a first stage rolling and a second stage rolling:
rolling in an austenite recrystallization region in the first stage, wherein in the rolling process, the initial rolling temperature is 1180 ℃, the 1 st to 2 nd pass reduction is more than 10%, and the rest at least 1 to 2 passes reduction rate is controlled to be more than 25%;
rolling in an austenite non-recrystallization region at the second stage, wherein the initial rolling temperature is 930 ℃, the thickness of an intermediate blank is 80mm, the thickness of a finished product is 40mm, and the final rolling temperature is as follows: 850 ℃;
step 3), cooling:
after the rolling is controlled to be finished, the steel plate enters a laminar cooling area, is cooled to 610 ℃ at a cooling speed of 15 ℃/s, and then enters a cooling bed for cooling;
the metallographic structure of the rare earth weather-resistant bridge steel plate with the yield strength of 370MPa is mainly fine ferrite and pearlite, and the yield ratio is 0.72.
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CN109468531A (en) * 2018-11-05 2019-03-15 包头钢铁(集团)有限责任公司 A kind of low yield strength ratio Q345qNH steel plate and preparation method thereof
CN109487156A (en) * 2018-11-05 2019-03-19 包头钢铁(集团)有限责任公司 A kind of low yield strength ratio Q370qNH steel plate and preparation method thereof
CN111020397A (en) * 2020-01-16 2020-04-17 五矿营口中板有限责任公司 High-strength high-toughness normalizing Q370 bridge steel plate with good welding performance and production method thereof
CN114032460B (en) * 2021-10-27 2023-02-21 包头钢铁(集团)有限责任公司 Low-yield-ratio bridge steel and production method thereof
CN114774777A (en) * 2022-03-28 2022-07-22 包头钢铁(集团)有限责任公司 Preparation method of rare earth treated weathering structural steel Q355NH
CN117604223B (en) * 2023-12-21 2024-08-16 河北普阳钢铁有限公司 Production method of low-cost 370 MPa-level weather-resistant bridge steel plate

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CN100523265C (en) * 2006-01-11 2009-08-05 株式会社神户制钢所 Toughness superior weather-resistant steel plate for welding heat affected zone
CN103639198A (en) * 2013-11-28 2014-03-19 莱芜钢铁集团有限公司 Method for producing pipeline steel plate by continuous casting billet under condition of small reduction ratio

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Publication number Priority date Publication date Assignee Title
CN100523265C (en) * 2006-01-11 2009-08-05 株式会社神户制钢所 Toughness superior weather-resistant steel plate for welding heat affected zone
CN103639198A (en) * 2013-11-28 2014-03-19 莱芜钢铁集团有限公司 Method for producing pipeline steel plate by continuous casting billet under condition of small reduction ratio

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