CN118166288A - High-strength weather-resistant steel and production method thereof - Google Patents
High-strength weather-resistant steel and production method thereof Download PDFInfo
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- 239000010959 steel Substances 0.000 title claims abstract description 93
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- 229910000870 Weathering steel Inorganic materials 0.000 claims abstract description 38
- 229910052802 copper Inorganic materials 0.000 claims abstract description 16
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 14
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- 239000012535 impurity Substances 0.000 claims abstract description 10
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 10
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 10
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 9
- 229910052742 iron Inorganic materials 0.000 claims abstract description 7
- 238000005096 rolling process Methods 0.000 claims description 94
- 238000001816 cooling Methods 0.000 claims description 49
- 238000010438 heat treatment Methods 0.000 claims description 21
- 238000000034 method Methods 0.000 claims description 18
- 229910000859 α-Fe Inorganic materials 0.000 claims description 17
- 230000009467 reduction Effects 0.000 claims description 13
- 238000005098 hot rolling Methods 0.000 claims description 12
- 229910001563 bainite Inorganic materials 0.000 claims description 11
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- 238000004804 winding Methods 0.000 claims 1
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 11
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- 238000013461 design Methods 0.000 description 8
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- 238000003723 Smelting Methods 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
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- UFGZSIPAQKLCGR-UHFFFAOYSA-N chromium carbide Chemical compound [Cr]#C[Cr]C#[Cr] UFGZSIPAQKLCGR-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The application discloses high-strength weather-resistant steel and a production method thereof, wherein the high-strength weather-resistant steel comprises ：C：0.03％～0.09％,Si：0.05％～0.30％,Mn：0.4％～1.8％,P：0.04％～0.07％,S：≤0.0050％,Cr：1.0％-4.0％,Cu：0.20％-0.50％,Al：0.01％-0.05％,Ti：0.05％-0.09％,N：≤0.0060％, mass percent of Fe and other unavoidable impurity elements; the weather resistance index I of the high-strength weather-resistant steel is more than or equal to 8.0. The production method provided by the application has the beneficial effects that the high-strength weathering steel product has good corrosion resistance on the basis of good processability.
Description
Technical Field
The application belongs to the technical field of steel smelting, and particularly relates to high-strength weather-resistant steel and a production method thereof.
Background
Compared with Q235B, Q B, the weather-resistant steel has good atmospheric corrosion resistance, and the weather-resistant steel is widely applied to the fields of containers, railway freight vehicles, bridges and buildings, but the traditional weather-resistant steel still has the problems of insufficient corrosion resistance and short service life.
Photovoltaic power generation is a green environment-friendly industry which is developing at a high speed, in order to ensure the corrosion resistance of a photovoltaic bracket in a life cycle of 25 years, a galvanized bracket made of Q235 and Q355 materials is basically adopted at present, but the atmospheric corrosion resistance of Q235B, Q B is poorer, and a large amount of energy consumption, solid waste and waste acid pollution are generated in the galvanizing processing process on products such as Q235B, Q B, and a zinc layer is separated or new carbon emission and pollution are increased in the service process and maintenance work of the service process is increased. Therefore, research on high-performance atmospheric corrosion resistant steel used without coating is an important direction of research.
Disclosure of Invention
In view of the above, the application provides the high-strength weathering steel and the production method thereof, so that the high-strength weathering steel product has good corrosion resistance on the basis of good processability.
In a first aspect, an embodiment of the present application provides a high strength weathering steel, including, in mass percent:
C：0.03％～0.09％,Si：0.05％～0.30％,Mn：0.4％～1.8％,P：0.04％～0.07％,S：≤0.0050％,Cr：1.0％-4.0％,Cu：0.20％-0.50％,Al：0.01％-0.05％,Ti：0.05％-0.09％,N：≤0.0060％, The balance of Fe and other unavoidable impurity elements; the weather resistance index I of the high-strength weather-resistant steel is more than or equal to 8.0.
According to an embodiment of one aspect of the application, the microstructure of the high-strength weathering steel is 50% -80% ferrite and 50% -80% bainite in terms of volume fraction, and the grain size of the high-strength weathering steel is above 11 grades.
According to an embodiment of one aspect of the application, the mechanical properties of the high strength weathering steel include: the yield strength is more than or equal to 550MPa, the tensile strength is more than or equal to 650MPa, the elongation is more than or equal to 16 percent, and the low-temperature impact energy at minus 40 ℃ is more than or equal to 60J.
In a second aspect, an embodiment of the present application provides a method for producing a high strength weathering steel, including:
Heating the slab to obtain a heated slab, wherein the slab comprises ：C：0.03％～0.09％,Si：0.05％～0.30％,Mn：0.4％～1.8％,P：0.04％～0.07％,S：≤0.0050％,Cr：1.0％-4.0％,Cu：0.20％-0.50％,Al：0.01％-0.05％,Ti：0.05％-0.09％,N：≤0.0060％, mass percent of Fe and other unavoidable impurity elements as the rest; the weather resistance index I of the high-strength weather-resistant steel is more than or equal to 8.0;
hot rolling the heated plate blank to obtain a hot rolled plate;
And cooling and coiling the hot rolled plate to obtain the high-strength weathering steel, wherein the cooling sequentially comprises the steps of performing first cooling at the speed of 80-200 ℃ per second to the temperature of 620-700 ℃, performing air cooling and performing second cooling at the speed of 80-200 ℃ per second to the temperature of 520-580 ℃ and performing air cooling for 7-14s.
According to an embodiment of one aspect of the application, the slab is charged into the furnace at a temperature of 20 ℃ to 550 ℃ or 760 ℃ to 1000 ℃ and the temperature rising speed of the slab is 500 ℃/h to-700 ℃/h; the heat preservation temperature of the slab is 1220-1280 ℃, the heat preservation time is 20-60min, and the total furnace time of the slab is 150-350min; the tapping temperature of the slab is 1200-1260 ℃.
According to an embodiment of one aspect of the present application, the slab is heated by a heating furnace, and the air excess ratio of the furnace interior heating atmosphere of the heating furnace is 1.1-1.5.
According to an embodiment of one aspect of the application, the hot rolling comprises rough rolling, the total reduction rate of the rough rolling is more than or equal to 80%, the reduction rate of the last pass rolling of the rough rolling is more than or equal to 30%, the thickness of the final pass rolling of the rough rolling is 30-40mm, the rolling speed of the rough rolling is less than or equal to 5.0m/s, the final cooling temperature of the rough rolling is 1040-1120 ℃, and the bulk descaling pressure of the rough rolling is more than or equal to 18MPa.
According to an embodiment of one aspect of the present application, the hot rolling includes finish rolling, the finish rolling employs 7 stands of continuous rolling, an inlet descaling pressure of the finish rolling is equal to or more than 18MPa, an initial rolling inlet temperature of the finish rolling is 980-1100 ℃, a final stand reduction rate of the finish rolling is equal to or more than 8%, and a final cooling temperature of the finish rolling is 800-900 ℃.
According to an embodiment of one aspect of the present application, the thickness of the hot rolled sheet and the finishing temperature of the finish rolling satisfy the following relationship:
1) The thickness of the hot rolled plate is less than 2.0mm, and the final rolling temperature of the finish rolling is 880-900 ℃;
2) The thickness of the hot rolled plate is 2.0-3.0 mm, and the finish rolling temperature of the finish rolling is 850-870 ℃;
3) The thickness of the hot rolled plate is more than 3mm and less than or equal to 4.0mm, and the finish rolling temperature of the finish rolling is 810-840 ℃;
4) The thickness of the hot rolled plate is more than 4.0mm, and the finish rolling temperature of the finish rolling is 790-810 ℃.
According to an embodiment of an aspect of the application, the temperature of the coiling is 520-580 ℃; coiling the head and the tail of the hot rolled plate in a U-shaped temperature mode respectively; the coiling temperature at 20m of the two ends of the hot rolled plate is 580-640 ℃.
The application has at least the following beneficial effects:
The high-strength weathering steel provided by the embodiment of the application has high weather resistance, the relative corrosion rate of the high-strength weathering steel relative to Q355B low alloy structural steel is less than or equal to 35%, the uniform corrosion depth of the high-strength weathering steel in a life cycle of 25 years of a common atmospheric environment C1-C3 coating-free service is less than or equal to 0.1mm, the high-strength weathering steel has high strength and good formability, and can be applied to replace galvanized products, such as photovoltaic brackets, highway guardrails and other scenes.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a micrograph showing a high strength weathering steel according to example 1 of the present application.
Detailed Description
In order to make the application object, technical scheme and beneficial technical effects of the application clearer, the application is further described in detail with reference to the following embodiments. It should be understood that the examples described in this specification are for the purpose of illustrating the application only and are not intended to limit the application.
For simplicity, only a few numerical ranges are explicitly disclosed. However, any lower limit may be combined with any upper limit to form a range not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and any upper limit may be combined with any other upper limit to form a range not explicitly recited. Furthermore, each point or individual value between the endpoints of the range is included within the range, although not explicitly recited. Thus, each point or individual value may be combined as a lower or upper limit on itself with any other point or individual value or with other lower or upper limit to form a range that is not explicitly recited.
In the description of the present application, unless otherwise indicated, "above" and "below" are intended to include the present number, and the meaning of "multiple" in "one or more" means two or more.
The above summary of the present application is not intended to describe each disclosed embodiment or every implementation of the present application. The following description more particularly exemplifies illustrative embodiments. Guidance is provided throughout this application by a series of embodiments, which may be used in various combinations. In the various examples, the list is merely a representative group and should not be construed as exhaustive.
In a first aspect, an embodiment of the present application provides a high strength weathering steel, including, in mass percent:
C：0.03％～0.09％,Si：0.05％～0.30％,Mn：0.4％～1.8％,P：0.04％～0.07％,S：≤0.0050％,Cr：1.0％-4.0％,Cu：0.20％-0.50％,Al：0.01％-0.05％,Ti：0.05％-0.09％,N：≤0.0060％, The balance of Fe and other unavoidable impurity elements; the weather resistance index I of the high-strength weather-resistant steel is more than or equal to 8.0.
According to the embodiment of the application, the high-strength weathering steel has high post-resistance performance, the relative corrosion rate of the high-strength weathering steel relative to Q355B low alloy structural steel is less than or equal to 35%, the uniform corrosion depth is less than or equal to 0.1mm in the life cycle of 25 years of coating-free service in a general atmospheric environment C1-C3, the high-strength weathering steel has higher strength and good forming performance, and the high-strength weathering steel can replace galvanized products to be applied, such as being applied to the scenes of photovoltaic brackets, highway guardrails and the like.
The selection principle and the content of each element in the implementation of the application are as follows:
the composition design avoids adding a large amount of Nb, V, ni, mo, W noble elements, and reduces the alloy cost.
C: c is an effective strengthening element in steel, but the Cr content in weather-resistant steel is higher, when the carbon content is higher, martensite structure is extremely easy to form in the steel to lead to rapid reduction of the plasticity and toughness of the steel, and martensite leads to high tensile strength of the steel and easy formation cracking. C can form nano-scale precipitation phase with micro-alloy elements such as Nb, ti and the like in steel, and plays a role in precipitation strengthening. Therefore, in order to fully utilize the strengthening effect of C and avoid the structure from greatly forming martensite to influence the structure, the component C of the invention is controlled to be 0.03-0.09%;
Si: the common deoxidizing element, si is dissolved in ferrite and austenite in a solid manner to improve the strength of the steel, so that the corrosion rate of the whole steel can be reduced, but in the hot rolling process, the higher Si element easily generates obvious red iron scale defects on the surface of the strip steel and is difficult to eliminate through descaling, and the surface quality of the strip steel is influenced, so that the design Si content of the invention is 0.05-0.30%;
Mn: mn is an important strengthening element and is an austenite stabilizing element, which can enlarge an austenite region in an iron-carbon phase diagram, promote transformation of a medium-temperature structure, facilitate refining of the structure and improve the strength and low-temperature toughness of steel, but serious segregation is generated in the steel when Mn is too high, and the low-temperature toughness of the steel is deteriorated; therefore, the design scheme has Mn content of 0.4-1.8%;
p: the corrosion resistant element which is often used as an added corrosion resistant element in the traditional atmospheric corrosion resistant steel can promote the formation of a surface protective rust layer, effectively improve the atmospheric corrosion resistant performance of the steel, but P is also a harmful impurity element in the steel and is easy to segregate in the thickness center during billet continuous casting. Meanwhile, P is easy to generate segregation at the grain boundary, so that the bonding energy of the grain boundary is reduced, and the toughness and the plasticity of the steel are reduced. In order to fully utilize the corrosion resistance of P and inhibit adverse effects caused by P element segregation, the invention designs the P content to be 0.04-0.07%;
S: sulfur, corrosion resistance, cold formability, low temperature toughness, welding performance, etc. of the steel; therefore, the value range of S in the invention is set to be less than or equal to 0.005 percent;
Cr: cr forms a compact oxide film on the surface of the steel, thereby improving the passivation capability of the steel. The effect is particularly remarkable when Cr and Cu are added to the steel at the same time. The increased Cr content is beneficial to refining the alpha-FeOOH, but in areas with higher Cl-content, the addition of Cr element is considered detrimental. In addition, the higher Cr content can also lead the steel to form bainite or martensite at a lower cooling speed, the tensile strength is obviously improved, but the processing and molding properties of the steel are reduced by the bainite or martensite with an excessively high proportion, so the Cr content is 1.0-4.0 percent;
Cu: copper plays a role of an active cathode, and can promote the steel to generate anode passivation under certain conditions, so that the corrosion speed of the steel is reduced; the composite action of Cu and P promotes the formation of extremely compact amorphous Fe 3O4 in the rust layer, so that tissue oxygen and water infiltrate into a steel substrate, cu can also react with S to form insoluble compounds so as to block cracks of the rust layer, and the corrosion resistance of the steel can be improved by 2-3 times by adding 0.25% of Cu, so that the Cu content is 0.20-0.50%;
al: al is a deoxidizing element commonly used in steel, refines grains, and improves the strong performance of the steel. Meanwhile, al promotes ferrite to generate, suppresses pearlite transformation and is beneficial to transformation of ferrite-bainite bidirectional structures, so that the design of the invention has the Al content of 0.01-0.05%;
Ti: the invention relates to a strong carbonitride forming element, which improves the intergranular corrosion resistance of a material, can also form nano TiC or Ti (C, N) second phase particles to be precipitated, obviously improves the strength of the material through precipitation strengthening, and designs 0.05-0.09% of Ti according to the low strength grade;
n is a harmful element in steel, consumes Ti element and forms inclusion, and N component needs to be controlled at a lower level, wherein the N is less than or equal to 0.0060 percent.
Weather resistance index: the weather resistance index can evaluate the weather resistance of the steel, the coating-free use can be carried out by the general weather resistance index being more than or equal to 6.0, the high-strength weather-resistant steel of the embodiment of the application is in coating-free service for 25 years in a C1-C3 environment, and the component design weather resistance index is more than or equal to 8.0.
The weather resistance index I is calculated as follows:
I=26.01×cu mass content in steel+3.88×ni mass content in steel+1.2×cr mass content in steel+1.49×si mass content in steel+17.28×p mass content in steel-7.29×cu mass content in steel-9.1×ni mass content in steel×p mass content in steel-33.39 × (Cu mass content in steel) 2
In the embodiment of the application, molten iron with certain chemical components is smelted into molten steel and cast into a plate blank, and the thickness of the plate blank can be 230-240mm.
In some alternative embodiments, the microstructure of the high strength weathering steel comprises, in volume fraction, 50% to 80% ferrite and 50% to 80% bainite, with the grain size of the high strength weathering steel being above grade 11.
In the embodiment of the application, the microstructure of the high-strength weathering steel has no pearlite structure, a high proportion of fine ferrite structure in the steel and very high low-temperature toughness.
In some alternative embodiments, the mechanical properties of the high strength weathering steel include: the yield strength is more than or equal to 550MPa, the tensile strength is more than or equal to 650MPa, the elongation is more than or equal to 16 percent, and the low-temperature impact energy at minus 40 ℃ is more than or equal to 60J.
In a second aspect, an embodiment of the present application provides a method for producing a high strength weathering steel, including:
Heating the slab to obtain a heated slab, wherein the slab comprises ：C：0.03％～0.09％,Si：0.05％～0.30％,Mn：0.4％～1.8％,P：0.04％～0.07％,S：≤0.0050％,Cr：1.0％-4.0％,Cu：0.20％-0.50％,Al：0.01％-0.05％,Ti：0.05％-0.09％,N：≤0.0060％, mass percent of Fe and other unavoidable impurity elements as the rest; the weather resistance index I of the high-strength weather-resistant steel is more than or equal to 8.0;
hot rolling the heated plate blank to obtain a hot rolled plate;
And cooling and coiling the hot rolled plate to obtain the high-strength weathering steel, wherein the cooling sequentially comprises the steps of performing first cooling at a speed of 80-200 ℃ per second to a temperature of 620-700 ℃, performing air cooling and performing second cooling at a speed of 15-45 ℃ per second to a temperature of 520-580 ℃ and performing air cooling for 7-14s.
According to the embodiment of the application, the first cooling is ultra-fast cooling and is used for inhibiting the transformation of the austenite structure of the strip steel into bainite; after the strip steel is ultra-rapidly cooled, the strip steel enters a ferrite transformation temperature zone, austenite is transformed into ferrite through air cooling for 7-14s, the proportion of ferrite generated by transformation is higher as the air cooling time is longer, but the rolling speed is required to be reduced when the air cooling time is too long, and the rolling stability of the thin strip steel is seriously affected; and cooling the strip steel in the air, and then cooling the strip steel in the second stage, wherein the cooling speed of the second stage is more than or equal to 15 ℃/s, coiling the strip steel after cooling the strip steel to 520-580 ℃, and converting unconverted austenite into a bainitic structure, so that the strip steel finally forms a ferrite-bainitic two-phase structure.
According to the embodiment of the application, elements such as P, cu, cr and the like are adopted for designing the composite weather-resistant component, laminar cooling is adopted for cooling, a specific cooling temperature design enables a weather-resistant finished product structure to form a ferrite structure with a higher proportion and obtain a fine structure, the low-temperature impact performance of steel is improved, the weather-resistant performance of the steel is improved by effectively utilizing the low-cost weather-resistant element through proper addition of the P element and good low-temperature toughness, and meanwhile, the addition of a high P component is avoided to deteriorate the toughness of the steel; the method is characterized in that higher Ti element is added, the strength of the weathering steel is improved by precipitation strengthening, meanwhile, the carbide precipitation of chromium formed between Cr element and C is restrained by medium-temperature coiling, the process and the components are adopted to match, the weather resistance and the low-temperature toughness of the steel are further improved, the high-strength weathering steel with the yield strength of more than or equal to 550MPa, the tensile strength of more than or equal to 650MPa, the elongation of more than or equal to 16 percent and the low-temperature impact energy of more than or equal to 60J at minus 40 ℃ is obtained, the microstructure is a ferrite and bainite two-phase structure, the grain size is above 11 grades, the ferrite content is 50-80%, the bainite content is 20-50%, the pearlite structure does not exist in the microstructure, the high-proportion fine ferrite structure and the very high low-temperature toughness of the steel are effectively restrained from adverse effects caused by P segregation, and the weather resistance of the P element is fully utilized.
In some alternative embodiments, the slab is charged to a furnace temperature of 20 ℃ to 550 ℃ or 760 ℃ to 1000 ℃ at a slab heating rate of 500 ℃/h to-700 ℃/h; the heat preservation temperature of the slab is 1220-1280 ℃, the heat preservation time is 20-60min, and the total furnace time of the slab is 150-350min; the tapping temperature of the slab is 1200-1260 ℃.
According to the embodiment of the application, in order to avoid slab cracking caused by slab two-phase region charging, the slab charging temperature is less than or equal to 550 ℃ or more than or equal to 760 ℃; in order to avoid surface defects caused by precipitation of a liquid crystal boundary in the heating process of Cu, the slab is quickly heated, the heating speed of the slab is not less than 500 ℃/h, and the total furnace time of the slab is required to be 150-350min; in order to make Ti fully solid-dissolved, the heat preservation temperature of the heating furnace is 1220-1280 ℃ and the heat preservation time is 20-60min.
According to the embodiment of the application, the heating temperature rising speed is more than or equal to 500 ℃/h, so that the temperature of the slab is quickly increased, the slab is prevented from staying at the temperature of 1085 ℃ near the melting point temperature of Cu element for a long time, the temperature of the slab is quickly increased to a higher temperature, the solid solubility of Cu in steel is improved, the liquefaction and precipitation of Cu in a grain boundary is inhibited, and the surface quality of the steel is improved.
In some alternative embodiments, the slab is heated by a furnace having an air excess factor of 1.1 to 1.5 for the furnace atmosphere.
According to the embodiment of the application, the surface burning loss of the slab is increased and the defects of the slab are removed through the high-temperature environment of the heating furnace. The overheat coefficient of the heating air is controlled to be 1.1-1.5, the burning loss of the plate blank in a heating furnace is improved, and the surface quality of steel is improved.
In some alternative embodiments, the hot rolling includes rough rolling, the total reduction of the rough rolling is greater than or equal to 80%, the reduction of the last pass of the rough rolling is greater than or equal to 30%, the thickness of the rough rolling after the last pass of the rough rolling is 30-40mm, the rolling speed of the rough rolling is less than or equal to 5.0m/s, the final cooling temperature of the rough rolling is 1040-1120 ℃, and the bulk descaling pressure of the rough rolling is greater than or equal to 18MPa.
In the implementation of the application, in order to refine rough rolling grains, the total reduction rate of rough rolling is more than or equal to 80 percent, the reduction rate of rough rolling final pass is more than or equal to 30 percent, the thickness of the rough rolling final pass is 30-40mm, and the final cooling temperature of rough rolling is 1040-1120 ℃; in order to ensure that the rough rolling process is fully recrystallized, the rough rolling speed is less than or equal to 5.0m/s; the descaling pressure of the rough rolling body is more than or equal to 18MPa, and the surface quality of the rough rolled intermediate billet is improved.
In some alternative embodiments, to increase the rolling deformability, the strip steel is promoted to enter into ferrite transformation after layer cooling; the hot rolling comprises finish rolling, wherein 7 frames are adopted for continuous rolling, the descaling pressure at the inlet of the finish rolling is more than or equal to 18MPa, the initial rolling inlet temperature of the finish rolling is 980-1100 ℃, the rolling reduction rate of the final frame of the finish rolling is more than or equal to 8%, and the final cooling temperature of the finish rolling is 800-900 ℃.
In the implementation of the application, the rolling reduction of the finish rolling end frame is more than or equal to 8 percent for refining the strip steel structure.
In some alternative embodiments, the thickness of the hot rolled sheet is < 2.0mm and the finishing temperature of the finish rolling is 880-900 ℃.
In some alternative embodiments, the thickness of the hot rolled sheet is 2.0 to 3.0mm and the finish rolling temperature of the finish rolling is 850 to 870 ℃.
In some alternative embodiments, the thickness of the hot rolled sheet is greater than 3mm and less than or equal to 4.0mm, and the finish rolling temperature of the finish rolling is 810-840 ℃.
In some alternative embodiments, the hot rolled sheet has a thickness of > 4.0mm and a finish rolling temperature of 790-810 ℃.
According to the embodiment of the application, the rolling deformation capacity can be increased by controlling the thickness of the hot rolled plate and the finish rolling temperature of the finish rolling, and the ferrite transformation of the strip steel after entering the layer cooling is promoted.
In some alternative embodiments, the temperature of the coiling is 520-580 ℃; coiling the head and the tail of the hot rolled plate in a U-shaped temperature mode respectively; the coiling temperature at 20m of the two ends of the hot rolled plate is 580-640 ℃.
In the embodiment of the application, the head and the tail of the hot rolled plate are coiled in a U-shaped temperature mode, and the coiling temperature of the hot rolled plate is 520-580 ℃, the cooling speed of the head and the tail of the hot rolled plate is high, and the second phase precipitation strengthening of TiC is not facilitated, so the coiling temperature of the parts which are 0-20m away from the head and the tail of the hot rolled plate is 580-640 ℃, and the hot rolled coil is cooled to below 250 ℃ in an off-line incubator slowly, thereby promoting the precipitation strengthening of TiC and improving the performance stability of the steel strip.
According to the embodiment of the application, the low-temperature finish rolling, the two-stage cooling and the lower coiling temperature are matched with each other, so that a high-proportion fine ferrite structure, namely a proper proportion bainite structure, is obtained, the low-temperature toughness and strength of the steel are improved, the precipitation of chromium carbide formed between Cr element and C is inhibited by the lower coiling temperature, and the weather resistance of the steel is further improved.
In some embodiments, the coiling is followed by slow cooling. Can be slowly cooled in the air, promote the precipitation strengthening of TiC and improve the tensile strength of steel.
Examples
The present disclosure is more particularly described in the following examples that are intended as illustrations only, since various modifications and changes within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the examples below are by weight, and all reagents used in the examples are commercially available or were obtained synthetically according to conventional methods and can be used directly without further treatment, as well as the instruments used in the examples.
Examples 1 to 4 and comparative examples 1 to 2
The embodiment of the application provides high-strength weathering steel, which comprises the following components in percentage by mass:
C：0.03％～0.09％,Si：0.05％～0.30％,Mn：0.4％～1.8％,P：0.04％～0.07％,S：≤0.0050％,Cr：1.0％-4.0％,Cu：0.20％-0.50％,Al：0.01％-0.05％,Ti：0.05％-0.09％,N：≤0.0060％, The balance of Fe and other unavoidable impurity elements; the weather resistance index I of the high-strength weather-resistant steel is more than or equal to 8.0. Specifically, the results are shown in Table 1.
TABLE 1
The weather resistance index I in the above table is calculated as follows:
I＝26.01(％Cu)+3.88(％Ni)+1.2(％Cr)+1.49(％Si)+17.28(％P)-7.29(％Cu)(％Ni)-9.1(％Ni)(％P)-33.39(％Cu)2
wherein: the contents of the elements include, (% Cu), (% Ni), (% Cr), (% Si), (% P).
Comparative examples were prepared according to conventional procedures.
The embodiment of the application provides a production method of high-strength weather-resistant steel, which comprises the following steps:
Heating the slab to obtain a heated slab, wherein the slab comprises ：C：0.03％～0.09％,Si：0.05％～0.30％,Mn：0.4％～1.8％,P：0.04％～0.07％,S：≤0.0050％,Cr：1.0％-4.0％,Cu：0.20％-0.50％,Al：0.01％-0.05％,Ti：0.05％-0.09％,N：≤0.0060％, mass percent of Fe and other unavoidable impurity elements as the rest; the weather resistance index I of the high-strength weather-resistant steel is more than or equal to 8.0;
hot rolling the heated plate blank to obtain a hot rolled plate;
And cooling and coiling the hot rolled plate to obtain the high-strength weathering steel, wherein the cooling sequentially comprises the steps of performing first cooling at the speed of 80-200 ℃ per second to the temperature of 620-700 ℃, performing air cooling and performing second cooling at the speed of 80-200 ℃ per second to the temperature of 520-580 ℃ and performing air cooling for 7-14s.
The specific process parameters for the heating of the examples are shown in table 1.
TABLE 1
The hot rolling process parameters of the examples are shown in Table 2.
TABLE 2
The cooling process parameters are shown in table 3.
Table 3.
Test part
The steel plate of the embodiment is measured by using GB/T13298-2015 metal microscopic structure inspection method, the microstructure of the high-strength weathering steel is measured to be 50% -80% ferrite and 50% -80% bainite according to volume fraction, and the grain size of the high-strength weathering steel is found to be above 11 grade according to the classification of the grain size GB/T6394-2017 metal average grain size measuring method. The micrograph of example 1 is shown in figure 1.
The high-strength weathering steels according to the comparative examples and comparative examples were prepared using GB/T228.1-2010 section 1 of tensile test for metallic materials: room temperature test method, the mechanical property test is carried out. The test results are shown in the following table.
The high strength weathering steels of the examples and comparative examples performed corrosion performance on the steel plates of the examples and comparative examples according to TB/T2375-93 and were compared with the relative corrosion rates of the plain carbon steel Q355B for 72h immersion corrosion. The test results are shown in the following table.
TABLE 4 Table 4
Examples 1 to 4 the steel sheet of example 5 was subjected to impact test because the steel sheet was thin, and no impact test was performed.
As can be seen from Table 4, the mechanical properties of the high strength weathering steel of the examples include: the yield strength is more than or equal to 550MPa, the tensile strength is more than or equal to 650MPa, the elongation is more than or equal to 16 percent, and the low-temperature impact energy at minus 40 ℃ is more than or equal to 60J. The corrosion rate of the steel of the example is between 30% and 35% compared with plain carbon steel Q355B. The high-strength weathering steel of the embodiment is predicted by a national material corrosion and protection science data center data resource library and a corrosion dynamics model, the single-sided uniform corrosion depth is less than or equal to 0.1mm in a life cycle of 25 years of a general atmospheric environment C1-C3 coating-free service, and the corrosion depth of the steel of the comparative example is about 0.15-0.25.
The present application is not limited to the above embodiments, and various equivalent modifications and substitutions can be easily made by those skilled in the art within the technical scope of the present application, and these modifications and substitutions are intended to be included in the scope of the present application. Therefore, the protection scope of the application is subject to the protection scope of the claims.
Claims (10)
1. The high-strength weather-resistant steel is characterized by comprising the following components in percentage by mass:
C：0.03％～0.09％,Si：0.05％～0.30％,Mn：0.4％～1.8％,P：0.04％～0.07％,S：≤0.0050％,Cr：1.0％-4.0％,Cu：0.20％-0.50％,Al：0.01％-0.05％,Ti：0.05％-0.09％,N：≤0.0060％, The balance of Fe and other unavoidable impurity elements; the weather resistance index I of the high-strength weather-resistant steel is more than or equal to 8.0.
2. The high-strength weathering steel according to claim 1, characterized in that the microstructure of the high-strength weathering steel is 50% -80% ferrite and 50% -80% bainite in terms of volume fraction, and the grain size of the high-strength weathering steel is 11 or more.
3. The high strength weathering steel according to claim 1, characterized in that the mechanical properties of the high strength weathering steel comprise: the yield strength is more than or equal to 550MPa, the tensile strength is more than or equal to 650MPa, the elongation is more than or equal to 16 percent, and the low-temperature impact energy at minus 40 ℃ is more than or equal to 60J.
4. The production method of the high-strength weather-resistant steel is characterized by comprising the following steps of:
Heating the slab to obtain a heated slab, wherein the slab comprises ：C：0.03％～0.09％,Si：0.05％～0.30％,Mn：0.4％～1.8％,P：0.04％～0.07％,S：≤0.0050％,Cr：1.0％-4.0％,Cu：0.20％-0.50％,Al：0.01％-0.05％,Ti：0.05％-0.09％,N：≤0.0060％, mass percent of Fe and other unavoidable impurity elements in balance; the weather resistance index I of the high-strength weather-resistant steel is more than or equal to 8.0;
Carrying out hot rolling on the heating plate blank to obtain a hot rolled plate;
and cooling and coiling the hot rolled plate to obtain the high-strength weather-resistant steel, wherein the cooling sequentially comprises a first cooling process at a speed of 80-200 ℃/s to a temperature of 620-700 ℃, an air cooling process at a speed of 15-45 ℃/s and a second cooling process at a temperature of 520-580 ℃, and the air cooling process is carried out for 7-14s.
5. The production method according to claim 4, wherein the slab charging temperature is 20-550 ℃ or 760-1000 ℃, and the slab heating rate is 500 ℃/h to 700 ℃/h; the heat preservation temperature of the slab is 1220-1280 ℃, the heat preservation time is 20-60min, and the total furnace time of the slab is 150-350min; the tapping temperature of the slab is 1200-1260 ℃.
6. The method according to claim 4, wherein the slab is heated by a heating furnace, and the air excess ratio of the heating atmosphere in the heating furnace is 1.1 to 1.5.
7. The method according to claim 4, wherein the hot rolling comprises rough rolling, the total reduction of the rough rolling is not less than 80%, the reduction of the last pass of the rough rolling is not less than 30%, the thickness of the rough rolling after the last pass of the rough rolling is 30-40mm, the rolling speed of the rough rolling is not more than 5.0m/s, the final cooling temperature of the rough rolling is 1040-1120 ℃, and the bulk descaling pressure of the rough rolling is not less than 18MPa.
8. The method according to claim 4, wherein the hot rolling comprises a finish rolling, the finish rolling is performed by 7-frame continuous rolling, the inlet descaling pressure of the finish rolling is equal to or higher than 18MPa, the initial rolling inlet temperature of the finish rolling is 980-1100 ℃, the final frame rolling reduction of the finish rolling is equal to or higher than 8%, and the final cooling temperature of the finish rolling is 800-900 ℃.
9. The method according to claim 4, wherein the thickness of the hot rolled sheet and the finish rolling temperature of the finish rolling satisfy the following relationship:
1) The thickness of the hot rolled plate is less than 2.0mm, and the finishing temperature of the finish rolling is 880-900 ℃;
2) The thickness of the hot rolled plate is 2.0-3.0 mm, and the finish rolling temperature of the finish rolling is 850-870 ℃;
3) The thickness of the hot rolled plate is more than 3mm and less than or equal to 4.0mm, and the finish rolling temperature of the finish rolling is 810-840 ℃;
4) The thickness of the hot rolled plate is more than 4.0mm, and the finish rolling temperature of the finish rolling is 790-810 ℃.
10. The production method according to claim 4, wherein the temperature of the winding is 520-580 ℃; the head and the tail of the hot rolled plate are coiled in a U-shaped temperature mode respectively, and the coiling temperature at 20m positions at two ends of the hot rolled plate is 580-640 ℃.
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