CN111690869A - Hot-rolled steel plate for cold-bending steel sheet pile and manufacturing method thereof - Google Patents
Hot-rolled steel plate for cold-bending steel sheet pile and manufacturing method thereof Download PDFInfo
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- C21D—MODIFYING 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
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- C21D—MODIFYING 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
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- C21D2211/009—Pearlite
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Abstract
The invention discloses a hot rolled steel plate for a cold-bending steel sheet pile and a manufacturing method thereof, and mainly solves the technical problems of poor corrosion resistance and high production cost of the hot rolled steel plate for the cold-bending steel sheet pile with the tensile strength of 450 MPa. The invention provides a hot rolled steel plate for a cold-bending steel sheet pile, which comprises the following chemical components in percentage by weight: c: 0.10 to 0.14%, Si: 0.10 to 0.20%, Mn: 0.5-1.0%, P is less than or equal to 0.02%, S is less than or equal to 0.008%, N is less than or equal to 0.0060%, Alt: 0.020 to 0.060%, Cu: 0.2-0.3%, Ni: 0.1-0.2%, Ti: 0.01-0.03%, and the balance of iron and inevitable impurities. The elongation of the hot rolled steel plate with the thickness of 2.0-16.0 mm after fracture is 30-45%, and the cold-bending steel sheet pile made of the hot rolled steel plate can be used for wharfs, impervious walls and the like.
Description
Technical Field
The invention relates to steel for a building structure, in particular to a hot-rolled steel plate for a cold-bending steel sheet pile and a manufacturing method thereof, and specifically relates to a hot-rolled steel plate for a cold-bending steel sheet pile with tensile strength of 450MPa and a manufacturing method thereof, belonging to the technical field of iron-based alloy.
Background
The steel sheet pile is a protective device, and is mainly used in permanent engineering such as quay walls, breakwaters, docks, wharfs, artificial islands, water/ship locks, underground tunnels, embankments, retaining walls, impervious walls, foundation reinforcement and temporary engineering such as cofferdams, foundation pit enclosures and the like. According to different processing and manufacturing processes, the method can be divided into hot rolled steel sheet piles and cold bent steel sheet piles.
Hot rolled steel sheet piles are mainly from foreign countries, korean modern, japanese new-day iron, japanese sumitomo, JFE, and parts of the european and american enterprises. With the development of roll bending forming technology, the size specification, the wall thickness and the section characteristics of a cold-bending steel sheet pile product are enlarged and improved, so that part of the cold-bending steel sheet pile product with large specification can be equivalent to the section technical characteristics of a hot-rolling steel sheet pile product, and the cold-bending steel sheet pile product is more widely applied.
The cold-bending steel sheet pile is mainly used in China, hot-rolled plate coils are provided by steel works, and the cold-bending steel works are processed into steel sheet piles with various cross-section shapes such as Z-shaped or U-shaped steel sheet piles through rolling. At present, most of cold-bending steel sheet piles are produced by adopting structural steel such as Q235, Q345, S450 and the like, and no special steel for the cold-bending steel sheet piles is available. In addition, the service environments of a shore wall, a breakwater, a dock and the like are severe, certain requirements are provided for the corrosion resistance of the steel sheet pile, the steel sheet pile produced by the existing structural steel needs to utilize an anticorrosive coating, cathodic protection and the like, and the material does not have the corrosion resistance condition.
Chinese patent with application publication No. CN104032212A discloses a steel for railway vehicles and a preparation method thereof, wherein the steel mainly comprises the following components of 255-300 MPa of yield strength, 400-445 MPa of tensile strength and 28-37% of elongation, and the components comprise 0.08-0.15% of C, 0.1-0.25% of Si and 0.60-0.80% of Mn. The steel for railway vehicles of the present invention has well-controlled impurity content, fine crystal grains, high strength and toughness, and high stability, and apparently does not have corrosion resistance as an impurity element although it also contains Cr, Ni, Cu, and the like.
Chinese patent application publication No. CN103509996A discloses a preparation method of high-strength carbon manganese structural steel with 400MPa of tensile strength, the main chemical components are C (0.10-0.20%), Si (less than or equal to 0.30%) and Mn (less than or equal to 0.40%), high-strength carbon manganese structural steel with the tensile strength of more than or equal to 400MPa is obtained by cold rolling, although the alloy cost is lower, the procedures of cold rolling, annealing, leveling and the like are added, the production cost is higher, and the steel does not have corrosion resistance.
The application publication number CN103469058A discloses ferrite bainite steel with tensile strength of 450MPa and high hole expanding performance and a production method thereof, wherein the ferrite bainite steel comprises the chemical components of C (0.10-0.15%), Si (0.1-0.50%), Mn (0.5-0.40%), Al (0.01-0.06%), and is excellent in hole expanding and flanging performance, stamping forming performance and welding performance, and can be suitable for structural members such as automobile wheels, chassis and the like. Although the process flow is simple, the cost is low, and the corrosion resistance is not achieved.
The application publication No. CN104694820A discloses a low alloy steel hot-rolled steel strip with tensile strength of more than 500MPa and a preparation method thereof, wherein the low alloy steel hot-rolled steel strip comprises the chemical components of C (0.14-0.22%), Si (0.05-0.40%), Mn (0.90-1.30%) and V (0.020-0.040%) and is subjected to microalloying by adopting vanadium-nitrogen alloy, and the tensile strength is improved by about 60MPa compared with Q345. The formed vanadium nitride can refine crystal grains, improve low-temperature impact toughness, obviously prolong the service life of the tool steel, improve creep deformation and endurance strength, and has no corrosion resistance.
The application publication No. CN101736202A discloses a high-strength atmospheric corrosion resistant hot-rolled steel strip and a manufacturing method thereof, wherein the components of the high-strength atmospheric corrosion resistant hot-rolled steel strip are C (0.063-0.10%), Si (0.36-0.45%), Mn (1.29-1.40%), and Cr (0.73-1.0%), Ni (0.23-0.55%), Cu (0.41-0.55%), and Nb + V + Ti (0.09-0.22%). The produced strip steel has the thickness of 4.0-14.0 mm, the yield strength of 485-525 MPa, the tensile strength of 595-645 MPa and the elongation of 26-32.5 percent, and has higher comprehensive mechanical property, atmospheric corrosion resistance and excellent forming property. As a large amount of corrosion-resistant elements such as Cr, Ni and Cu and microalloy elements such as Nb, V and Ti are added into the components, the alloy cost is obviously extremely high.
The application publication number CN106756540A discloses an atmospheric corrosion resistant steel strip for a railway carriage and a preparation method thereof, wherein the atmospheric corrosion resistant steel strip is prepared by adding microalloy elements such as Nb (0.025-0.035%), Ti (0.008-0.018%) and the like in addition to low C (0.05-0.07%), Si (0.15-0.25%), Mn (1.2-1.4%), Cr (0.4-0.5%), Ni (0.2-0.3%) and Cu (0.22-0.32%), and the produced strip steel has the thickness of 5-10 mm, the yield strength of 490-530 MPa, the tensile strength of 570-590 MPa and the elongation of 26-30%. Besides good corrosion resistance, the composite material also has good comprehensive mechanical property and welding property. And a large amount of alloy elements are added, so that the production cost is high.
Therefore, in the prior art, the hot rolled steel plate for the structure with the tensile strength of 450MPa does not have certain corrosion resistance, and cannot meet the requirement of the corrosion resistance of the cold-bending steel sheet pile, while in the prior art, the atmosphere corrosion resistant steel plate is formed by adding a large amount of corrosion resistant elements such as Cu, Cr, Ni and the like on the basis of C-Mn components, and adding one or more of alloy elements such as Nb, V, Ti and the like, so that the alloy addition is more in variety, the resource consumption is large, and the production cost is higher.
Disclosure of Invention
The invention aims to provide a hot rolled steel plate for a cold-bending steel sheet pile and a manufacturing method thereof, which mainly solve the technical problems of poor corrosion resistance and high production cost of the hot rolled steel plate for the cold-bending steel sheet pile with the tensile strength of 450 MPa.
The technical idea of the invention is that on the basis of C-Mn components, a proper amount of Cu, Ni and Ti alloy is scientifically added and matched with a corresponding hot rolling process, so that the product has good technological properties such as bending and welding on the basis of ensuring the strength and corrosion resistance of the product, and the requirements for processing cold-bending steel sheet piles are met.
The invention adopts the technical scheme that a hot rolled steel plate for a cold-bending steel sheet pile comprises the following chemical components in percentage by weight: c: 0.10 to 0.14%, Si: 0.10 to 0.20%, Mn: 0.5-1.0%, P is less than or equal to 0.02%, S is less than or equal to 0.008%, N is less than or equal to 0.0060%, Alt: 0.020 to 0.060%, Cu: 0.2-0.3%, Ni: 0.1-0.2%, Ti: 0.01-0.03%, C + Mn/6+ (Cr + Mo + V)/5+ (Cu + Ni)/15 is less than or equal to 0.34%, and the balance is iron and inevitable impurities.
The carbon equivalent Ceq in the steel is less than or equal to 0.34 percent, and Ceq is C + Mn/6+ (Cr + Mo + V)/5+ (Cu + Ni)/15; the hot rolled steel plate has good welding performance; usually, the carbon equivalent is below 0.41 percent, namely the steel belongs to the easily-welded steel grade, so the steel grade can be welded without preheating, and the postweld heat treatment is avoided.
The metallographic structure of the hot-rolled steel plate is ferrite and a small amount of pearlite structure, the grain size grade of the ferrite in the metallographic structure is 7-9 grade, and the upper yield strength R of the hot-rolled steel plate with the thickness of 2.0-16.0 mmeH300 to 360MPa, tensile strength Rm450 to 500MPa, elongation A after fracture of 30 to 45 percent, and qualified d-a in a 180-degree bending test.
The hot rolled steel plate is subjected to a week immersion test according to TB/T2375-93 periodic immersion corrosion test method of weather-resistant steel for railways, the test temperature is 45 +/-2 ℃, and 0.01mol/L NaHSO is used in an environment with the humidity of 70 +/-5 percent RH3The solution is used for carrying out a circumferential immersion test for 72 hours on the hot-rolled steel plate with the mark Q345 and the hot-rolled steel plate with the mark Q345 respectively, and the test result shows that the corrosion rate of the hot-rolled steel plate is 56.7 percent of that of the hot-rolled steel plate with the mark Q345, and the corrosion resistance of the hot-rolled steel plate is improved by more than 40 percent compared with that of the hot-rolled steel plate with the mark Q345.
The cold-bending steel sheet pile made of the hot-rolled steel sheet through cold-bending forming can be used for wharfs, harbors, docks, embankments, retaining walls, impervious walls and the like.
The reason why the chemical composition of the hot-rolled steel sheet for a cold-rolled steel sheet pile according to the present invention is limited to the above range is as follows:
carbon: carbon is a main element of the component system, is beneficial to improving the strength of the steel plate, and makes full use of the strengthening effect of C. However, the carbon content can form more coarse and coarse brittle carbide particles in steel, the steel is unfavorable for plasticity and toughness, and welding is not facilitated, the strengthening effect of C and Mn is comprehensively considered, and the set C content is 0.10-0.14%.
Manganese: manganese is also a main element of the composition system, can play a role in solid solution strengthening, and is also one of important elements for improving the strength. Mn can simultaneously enlarge the austenite region, reduce the ferrite transformation temperature and enlarge the rolling process window. However, the high Mn content lowers the toughness of the material, deteriorates the performance, and is not favorable for welding. In consideration of the range of C in the component system of the present invention and the strength grade of the steel sheet, the Mn content is further limited to 0.5 to 1.0%.
Silicon: silicon is an element added for deoxidizing steel, although it is also a corrosion resistant element, and has a significant strengthening effect by being dissolved in a steel sheet matrix, and too high a silicon content is disadvantageous to steel sheet plasticity and toughness, and also causes deterioration in steel sheet weldability and toughness of a weld heat affected zone, and also causes formation of a severe red scale difficult to remove on the surface of a hot-rolled sheet, which affects post-process pickling, galvanization, and the like. Therefore, the Si content is limited to 0.10-0.20%.
Sulfur and phosphorus: too high sulfur and phosphorus elements adversely affect the toughness and plasticity of the material, P is detrimental to impact toughness, weldability and formability, and FeP is easily precipitated and formed in steel, increasing the brittleness of the steel, especially drastically reducing the low temperature impact toughness of the steel. The defect of hot brittleness is generated when the content of S is higher, S is unfavorable for the corrosion resistance of steel, and sulfide impurities in the steel can become a starting place of corrosion, so that the weather resistance of the steel is obviously reduced. Too low a sulfur and Lin will increase the cost of desulfurization and dephosphorization in steel making. The invention limits S to be less than or equal to 0.008 percent and P to be less than or equal to 0.02 percent.
Nitrogen: the plasticity and toughness of the material are seriously deteriorated if the nitrogen content is too high, and N is limited to be less than or equal to 0.0060 percent.
Aluminum: the aluminum plays a role in deoxidation in the present invention, and is a strong oxidizing forming element, and forms Al with oxygen in steel2O3Is removed during steel making. Too high an aluminum content can lead to excessive Al formation2O3And the pouring nozzle is easy to block during continuous casting. The invention limits the Al content to be 0.020-0.060%.
Copper: copper can play a certain degree of solid solution and precipitation strengthening roles in steel, and is also a corrosion resistant element. The electrochemical potential of Cu is higher than that of Fe, so that the compact rust layer on the surface of the steel can be promoted to appear, and the hot-rolled strip steel has good corrosion resistance. The atmospheric corrosion resistance of the steel can be obviously improved by adding more than 0.20 percent of Cu, if the Cu content is higher than 0.55 percent, the toughness of a welding heat affected zone is damaged, and the net crack is easy to occur during hot rolling, so that the surface performance of a steel plate is deteriorated, the production is difficult, and the Cu content is set to be 0.2-0.3 percent by comprehensively considering the invention.
Nickel: nickel can improve hardenability, remarkably improve low-temperature toughness of steel, is an advantageous element for improving weather resistance and toughness, and cannot cause adverse effects on weldability of steel and heat property of a welding heat affected zone. Ni can also effectively prevent the net cracking caused by the hot brittleness of Cu, the effect is not good when the Ni content is less than 0.1 percent, and the effect is not good when the Ni content is more than 0.4 percent, the cost of steel is increased, and the scale of the steel plate is easy to fall off. Therefore, the content of the description is limited to 0.1 to 0.2%.
Titanium: titanium is a strong carbide former, mainly present in the form of TiC or Ti (C, N) in steel. TiN can still keep stable at high temperature and has the function of inhibiting austenite growth, in addition, a proper amount of Ti carbonitride particles can prevent the grain coarsening of a welding heat affected zone and improve the welding performance, particularly Ti can inhibit the formation of sulfide, and Ti-containing steel has very good cold forming capability. Based on this, the present invention limits the Ti content to 0.01 to 0.03%.
A method of manufacturing a hot rolled steel sheet for a cold-bent steel sheet pile, the method comprising:
continuously casting molten steel to obtain a continuous casting slab, wherein the molten steel comprises the following chemical components in percentage by weight: c: 0.10 to 0.14%, Si: 0.10 to 0.20%, Mn: 0.5-1.0%, P is less than or equal to 0.02%, S is less than or equal to 0.008%, N is less than or equal to 0.0060%, Alt: 0.020 to 0.060%, Cu: 0.2-0.3%, Ni: 0.1-0.2%, Ti: 0.01-0.03%, C + Mn/6+ (Cr + Mo + V)/5+ (Cu + Ni)/15 is less than or equal to 0.34%, and the balance is iron and inevitable impurities;
heating the continuously cast plate blank at 1180-1220 ℃ for 180-240 min, and then carrying out hot rolling, wherein the hot rolling adopts a two-stage controlled rolling process, the rough rolling is 6-pass rolling, the rolling is carried out at a temperature above the austenite recrystallization temperature, and the finish temperature of the rough rolling is 1000-1050 ℃; the finish rolling is 7-pass continuous rolling, rolling is carried out in an austenite non-recrystallization temperature region, the inlet temperature of the finish rolling is 1000-1050 ℃, and the finish rolling finishing temperature is 820-860 ℃; after finish rolling, the thickness of the finished steel plate is 2.0-16.0 mm, front-section cooling is adopted for laminar cooling, the cooling speed is 10-40 ℃/s, and the hot rolled steel coil is coiled when the coiling temperature is 550-620 ℃.
The hot rolling process is the key technology for realizing the invention, and the component system A of the invention is calculated3At 838 ℃ A1The temperature was 711 ℃. The hot rolling process adopted by the invention is based on the component system and the calculated phase change point, and the specific reason of the hot rolling process system adopted by the invention is as follows:
1. setting of heating temperature and heating time of continuous casting slab
The heating temperature and time of the continuous casting slab are set to ensure that the composition segregation and the porosity formed in the solidification process of the continuous casting slab and the defects of the surface of part of the slab are eliminated, and the homogenization of the composition and the structure is ensured. But the heating temperature is too high, or the time is too long, the original structure of the plate blank is coarse, the surface oxidation and decarburization are serious, the final performance of the steel plate is not facilitated, and the total heating time is 180-240 min except the heating temperature which is required to be 1180-1220 ℃.
2. Setting of roughing finishing temperature
The rough rolling process is controlled to be rolled above the austenite recrystallization temperature, so that uniform and fine austenite grains are ensured to be obtained. Therefore, the rough rolling finishing temperature is set to be 1000-1050 ℃.
3. Setting of finish Rolling finishing temperature
The finish rolling temperature setting of the invention has two functions, on one hand, flat austenite grains with deformation zones inside are obtained by rolling in an austenite non-recrystallization zone and are converted into relatively fine ferrite and pearlite grains in the subsequent laminar cooling process, thereby improving the strength of the steel plate. On the other hand, the finish rolling temperature setting is also to prevent the steel sheet from forming significant band defects. According to the theoretical calculation result, the finish rolling finishing temperature is set to be 820-860 ℃.
4. Method of laminar cooling after finish rolling and setting of cooling rate
The set laminar cooling speed after finish rolling is also very critical, and the proper laminar cooling speed can be adopted to inhibit the abnormal growth of ferrite and pearlite structures. The cooling speed is too slow, ferrite and pearlite are obviously coarsened, the strength of the steel plate is reduced, and the subsequent working procedure processing and welding are further influenced; the cooling speed is too fast, which can bring great influence to the plate shape. Therefore, the laminar cooling of the invention adopts a front-stage cooling mode, and the cooling speed is 10-40 ℃/s.
5. Setting of coiling temperature in Hot Rolling
The coiling temperature mainly affects the structure and performance of the strip steel. The ferrite and pearlite structures grow rapidly at an excessively high coiling temperature, and the strength of the steel plate is reduced; if the coiling temperature is too low, a bainite and other hard phases appear in the structure, which is not beneficial to the post-process processing such as cold bending. The hot rolling coiling temperature is set to be 550-620 ℃ by combining the component system of the invention.
The metallographic structure of the hot-rolled steel plate produced by the method is ferrite and a small amount of pearlite structure, the grain size grade of the ferrite in the metallographic structure is 7-9 grade, and the upper yield strength R of the hot-rolled steel plate with the thickness of 2.0-16.0 mmeH300 to 360MPa, tensile strength Rm450 to 500MPa, elongation A after fracture of 30 to 45 percent, and qualified d-a in a 180-degree bending test.
The hot rolled steel plate produced by the method is subjected to a weekly immersion test according to TB/T2375-93 periodic immersion corrosion test method of weather-resistant steel for railways, the test temperature is 45 +/-2 ℃, and 0.01mol/L NaHSO is used in an environment with the humidity of 70 +/-5 percent RH3The solution is used for carrying out a week soaking test for 72 hours on the hot rolled steel plate and the hot rolled steel plate with the mark Q345 respectively, and the test result shows that the corrosion rate of the hot rolled steel plate is brand56.7 percent of the corrosion rate of the hot rolled steel plate with the mark Q345, the corrosion resistance of the hot rolled steel plate is improved by more than 40 percent compared with the corrosion resistance of the hot rolled steel plate with the mark Q345
Compared with the prior art, the invention has the following positive effects: 1. the hot rolled steel plate provided by the invention has the advantages that the chemical components are scientifically designed, the reinforcing effect and the easy processing characteristic of C, Mn are fully utilized, the corrosion resistance of Cu and Ni are matched with the corresponding hot rolling process, and the obtained hot rolled steel plate with the tensile strength of 450MPa is easy to cold roll and form and stable in mechanical property compared with a hot rolled structural steel plate with the same strength level. 2. The carbon equivalent is less than 0.41%, and the steel belongs to the easily-welded steel type, the carbon equivalent in the steel is less than or equal to 0.34%, the hot-rolled steel plate has good welding performance, can be welded without preheating, and avoids post-welding heat treatment. 3. The upper yield strength of the hot-rolled steel plate is 300-360 MPa, the tensile strength is 450-500 MPa, and the elongation A after fracture is 30-45%. 4. The hot-rolled steel plate has good corrosion resistance, under the same condition, the corrosion rate of the hot-rolled steel plate is 56.7% of that of the hot-rolled steel plate with the mark of Q345, and the corrosion resistance of the hot-rolled steel plate is improved by more than 40% compared with that of the hot-rolled steel plate with the mark of Q345.
Drawings
FIG. 1 is a metallographic structure photograph of a hot-rolled steel sheet according to example 1 of the invention.
Detailed Description
The present invention is further described with reference to examples 1 to 4, which are shown in tables 1 to 3.
Table 1 shows the chemical composition (in weight%) of the steels of the examples of the invention, the balance being Fe and unavoidable impurities.
Table 1 chemical composition of the steels of the examples of the invention, in units: and (4) weight percentage.
Molten steel meeting the requirements of chemical components is obtained by smelting in a converter, and Ar blowing treatment is carried out on the molten steel in the refining process of an LF ladle refining furnace. And the continuous casting adopts the whole-process Ar blowing protection casting, and the molten steel is cast into a continuous casting slab.
And after the continuous casting plate blank is heated by a heating furnace, rolling the continuous casting plate blank on a hot continuous rolling mill, controlling the rolling by a rough rolling mill and a finish rolling continuous rolling mill unit, cooling the front section by laminar cooling, and then coiling to obtain a hot rolled steel coil. The thickness of the finished hot rolled steel plate is 2.0-16.0 mm, and the control parameters of the hot rolling process are shown in table 2.
TABLE 2 Hot Rolling Process control parameters of the inventive examples
Referring to fig. 1, the hot rolled steel plate produced by the method has a metallographic structure of ferrite and a small amount of pearlite, the grain size of the ferrite in the metallographic structure is 9-10 grade, and the upper yield strength R of the hot rolled steel plate with the thickness of 2.0-16.0 mmeH300 to 360MPa, tensile strength Rm450 to 500MPa, elongation A after fracture of 30 to 45 percent, and qualified d-a in a 180-degree bending test.
The hot rolled steel plate obtained by the invention is subjected to a GB/T228.1-2010 metal material tensile test part 1: room temperature test method "was used for tensile test, and the mechanical properties are shown in Table 3.
The steel plate is subjected to a week immersion test according to TB/T2375-93 periodic immersion corrosion test method for weathering steel for railways, the test temperature is 45 +/-2 ℃, and 0.01mol/L NaHSO is used in an environment with the humidity of 70 +/-5% RH3The solution is used for respectively carrying out a circumferential immersion test for 72 hours on the hot-rolled steel plate with the mark Q345, and the test result shows that the corrosion rate of the hot-rolled steel plate is 56.7 percent of that of the hot-rolled steel plate with the mark Q345, and the corrosion resistance of the hot-rolled steel plate is improved by more than 40 percent compared with that of the hot-rolled steel plate with the mark Q345。
TABLE 3 mechanical Properties of Hot rolled Steel sheets according to examples of the present invention
In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.
Claims (5)
1. A hot rolled steel plate for a cold-bending steel sheet pile comprises the following chemical components in percentage by weight: c: 0.10 to 0.14%, Si: 0.10 to 0.20%, Mn: 0.5-1.0%, P is less than or equal to 0.02%, S is less than or equal to 0.008%, N is less than or equal to 0.0060%, Alt: 0.020 to 0.060%, Cu: 0.2-0.3%, Ni: 0.1-0.2%, Ti: 0.01-0.03%, C + Mn/6+ (Cr + Mo + V)/5+ (Cu + Ni)/15 is less than or equal to 0.34%, and the balance is iron and inevitable impurities; the metallographic structure of the hot-rolled steel plate is ferrite and a small amount of pearlite, and the grain size grade of the ferrite in the metallographic structure is 7-9 grades.
2. The hot-rolled steel sheet for a cold-formed steel sheet pile according to claim 1, wherein the hot-rolled steel sheet has an upper yield strength R of 2.0 to 16.0mmeH300 to 360MPa, tensile strength Rm450 to 500MPa, elongation A after fracture of 30 to 45 percent, and qualified d-a in a 180-degree bending test.
3. The hot-rolled steel sheet for a cold-bent steel sheet pile according to claim 1, wherein the corrosion resistance of the hot-rolled steel sheet is improved by 40% or more than that of a hot-rolled steel sheet having a mark Q345.
4. A manufacturing method of a hot rolled steel plate for a cold-bending steel sheet pile is characterized by comprising the following steps:
continuously casting molten steel to obtain a continuous casting slab, wherein the molten steel comprises the following chemical components in percentage by weight: c: 0.10 to 0.14%, Si: 0.10 to 0.20%, Mn: 0.5-1.0%, P is less than or equal to 0.02%, S is less than or equal to 0.008%, N is less than or equal to 0.0060%, Alt: 0.020 to 0.060%, Cu: 0.2-0.3%, Ni: 0.1-0.2%, Ti: 0.01-0.03%, C + Mn/6+ (Cr + Mo + V)/5+ (Cu + Ni)/15 is less than or equal to 0.34%, and the balance is iron and inevitable impurities;
heating the continuously cast plate blank at 1180-1220 ℃ for 180-240 min, and then carrying out hot rolling, wherein the hot rolling adopts a two-stage controlled rolling process, the rough rolling is 6-pass rolling, the rolling is carried out at a temperature above the austenite recrystallization temperature, and the finish temperature of the rough rolling is 1000-1050 ℃; the finish rolling is 7-pass continuous rolling, rolling is carried out in an austenite non-recrystallization temperature region, the inlet temperature of the finish rolling is 1000-1050 ℃, and the finish rolling finishing temperature is 820-860 ℃; after finish rolling, the hot rolled steel coil is coiled by adopting front-section cooling at the cooling speed of 10-40 ℃/s and the coiling temperature of 550-620 ℃.
5. The method of manufacturing a hot-rolled steel sheet for a cold-rolled steel sheet pile according to claim 4, wherein the thickness of the steel sheet is controlled to 2.0 to 16.0mm after the hot rolling and finish rolling.
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Application publication date: 20200922 |