CN115074639A - Hot-rolled steel plate for automobile beam with tensile strength of 600MPa - Google Patents
Hot-rolled steel plate for automobile beam with tensile strength of 600MPa Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 125
- 239000010959 steel Substances 0.000 title claims abstract description 125
- 238000005096 rolling process Methods 0.000 claims abstract description 55
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 33
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 33
- 238000004519 manufacturing process Methods 0.000 claims abstract description 23
- 239000000126 substance Substances 0.000 claims abstract description 15
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 11
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 11
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims description 38
- 238000001816 cooling Methods 0.000 claims description 30
- 230000008569 process Effects 0.000 claims description 26
- 229910001566 austenite Inorganic materials 0.000 claims description 19
- 238000009749 continuous casting Methods 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 13
- 238000005098 hot rolling Methods 0.000 claims description 12
- 238000001953 recrystallisation Methods 0.000 claims description 11
- 229910000859 α-Fe Inorganic materials 0.000 claims description 11
- 238000005452 bending Methods 0.000 claims description 9
- 229910001562 pearlite Inorganic materials 0.000 claims description 8
- 238000012360 testing method Methods 0.000 claims description 8
- 229910001568 polygonal ferrite Inorganic materials 0.000 claims description 6
- 238000012545 processing Methods 0.000 claims description 5
- 238000005266 casting Methods 0.000 claims description 4
- 239000010936 titanium Substances 0.000 description 35
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 14
- 238000001556 precipitation Methods 0.000 description 12
- 239000002245 particle Substances 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 8
- 230000007547 defect Effects 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 150000004767 nitrides Chemical class 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- 238000005728 strengthening Methods 0.000 description 7
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 229910001275 Niobium-titanium Inorganic materials 0.000 description 5
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- RJSRQTFBFAJJIL-UHFFFAOYSA-N niobium titanium Chemical compound [Ti].[Nb] RJSRQTFBFAJJIL-UHFFFAOYSA-N 0.000 description 5
- 238000009864 tensile test Methods 0.000 description 5
- 239000002131 composite material Substances 0.000 description 4
- 238000005336 cracking Methods 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 239000007769 metal material Substances 0.000 description 4
- 238000007670 refining Methods 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 238000004080 punching Methods 0.000 description 3
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- 229910052720 vanadium Inorganic materials 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention discloses a hot rolled steel plate for an automobile beam with 600 MPa-level tensile strength, which solves the technical problems of low tensile strength, high manufacturing cost and poor stamping and forming performance of the existing hot rolled steel plate for the automobile beam. The technical scheme is that the hot rolled steel plate for the automobile beam with the tensile strength of 600MPa comprises the following chemical components in percentage by weight: c: 0.04-0.12%, Si: 0-0.08%, Mn: 1.25-1.50%, P is less than or equal to 0.011%, S is less than or equal to 0.002%, Al: 0.010-0.040%, N is less than or equal to 0.0060%, Nb: 0.03-0.05%, Ti: 0.06 to 0.11 percent, and the balance of Fe and inevitable impurities; hot rolled steelElongation after fracture of the plate A 50mm 23 to 35 percent. The hot rolled steel plate is used for manufacturing a truck beam, and meets the requirements of stamping forming and rolling forming.
Description
Technical Field
The invention relates to a hot-rolled automobile beam steel plate, in particular to a hot-rolled steel plate for an automobile beam with 600 MPa-level tensile strength and a manufacturing method thereof, belonging to the technical field of materials.
Background
With the development of the automobile industry, in order to improve the bearing capacity of automobiles, prolong the service life of automobiles and meet the requirements of energy conservation, material conservation, safe driving and the like, the production of automobile beams by using high-strength steel plates has become a development trend. The girder steel is mainly used for manufacturing the cross beam and the longitudinal beam of the truck, and the quality requirement is strict. The automobile beam is mostly formed by cold stamping and rolling, and mainly bears large static load and certain impact and vibration load, so that the steel plate has good obdurability and formability.
The tensile strength of the existing automobile girder steel is generally 510MPa or below, and in recent years, the girder steel of automobile factories needs to be used with high strength and light weight; the girder steel with the tensile strength of more than 510MPa is required to be developed; however, as the strength is increased, the beam steel is manufactured by adopting a roll forming process, and the roll forming process is simple and is not easy to crack in the production process, but the roll-formed automobile beam needs subsequent further processing and has high subsequent processing cost; when the automobile beam is prepared by adopting the punch forming process, due to the complex forming process, after the tensile strength is improved, the steel is difficult to smelt or the plasticity of the material is poor, and when the requirement is not met, the cracking quality problem is easy to generate.
Chinese patent application publication No. CN101565794A discloses a high-strength hot-rolled automobile frame steel sheet and a manufacturing method thereof, and the chemical compositions of the disclosed hot-rolled steel sheet include: c: 0.05-0.10 wt%, Si is less than or equal to 0.10 wt%, Mn: 1.1-1.85 wt%, P is less than or equal to 0.025 wt%, S is less than or equal to 0.003 wt%, Al: 015-0.060 wt%, N is not more than 0.0060 wt%, Nb: 0.015 to 0.05 wt%, Ti: 0.015-0.15 wt%, Ca less than or equal to 0.0050 wt%, and the balance of Fe and inevitable impurities. The manufacturing method of the steel plate comprises a controlled rolling and controlled cooling process and the like. By adopting the chemical component proportion and the reasonable production process, the yield strength of the hot-rolled automobile frame steel plate can reach 550-700 MPa, and the hot-rolled automobile frame steel plate has excellent cold forming performance and higher fatigue strength and is suitable for manufacturing members such as automobile frame longitudinal beams, automobile frame transverse beams and the like. The invention mainly adds more alloy elements of Mn, Ti and Nb to carry out Ca treatment on spheroidized inclusions to increase the cost, and V is also added in the preferred scheme to improve the strength of the finished product strip steel, so that the manufacturing cost is higher.
The Chinese patent application with the application publication number of CN101914728A discloses niobium-titanium composite light truck automobile girder steel and a preparation method thereof, and the niobium-titanium composite light truck automobile girder steel comprises the following chemical components in percentage by mass: c: 0.09-0.15 wt%, Si: 0.30-0.60 wt%, Mn: 1.25-1.50 wt%, Ti: 0.010-0.030 wt%, Nb: 0.015-0.045 wt%, S less than or equal to 0.030 wt%, P less than or equal to 0.030 wt%, and the balance of Fe and inevitable impurities. The steel strip is prepared by the steps of heating, rough rolling, finish rolling, cooling and coiling, Nb and Ti elements in the steel can be fully dissolved in austenite in the heating process, and then NbC and NbN are separated out in the rolling process and the rolling interval, so that the dynamic recrystallization and static recrystallization processes are inhibited, the grain size and shape of the austenite before phase transformation are controlled, ferrite grains are refined, the strength of the steel strip is obviously improved, and precipitation strengthening is generated by separating out TiN, so that better plastic toughness is kept. The load capacity is large, and the method is suitable for manufacturing the girder of the heavy truck. The method mainly produces the automobile girder steel with the tensile strength of 510MPa, the strength is low, the cost is high due to the Nb content of 0.015-0.045 wt%, the Si content of 0.30-0.60 wt%, a silicon red iron sheet defect is easily formed on the surface, the pickling and the coating of a user are not facilitated, and large-particle impurities are easily generated in a steel plate substrate with the high S, P content, and the stamping cracking is easily caused.
Chinese patent application publication No. CN101914729A discloses a niobium-titanium composite heavy truck automobile beam steel and a preparation method thereof, wherein the niobium-titanium composite heavy truck automobile beam steel has the following chemical components by mass: c: 0.06-0.12 wt%, Si: 0.10-0.30 wt%, Mn: 1.45-1.65 wt%, Nb: 0.030 to 0.060 wt%, Ti: 0.025-0.045 wt%, less than or equal to 0.015 wt% of S, less than or equal to 0.020 wt% of P, and the balance of Fe and inevitable impurities. The steel strip is prepared by the steps of heating, rough rolling, finish rolling, cooling and coiling, Nb and Ti elements in the steel can be fully dissolved in austenite in a solid solution mode in the heating process, and then in the rolling process and the rolling interval, through the precipitation of NbC and NbN, the dynamic recrystallization and static recrystallization processes are inhibited, so that the grain size and the shape of the austenite before phase transformation are controlled, ferrite grains are refined, the strength of the steel strip is obviously improved, and precipitation strengthening is generated through the precipitation of TiN, and better plastic toughness is kept. The load capacity is large, and the method is suitable for manufacturing the girder of the heavy truck. The method mainly produces automobile girder steel with tensile strength of 610MPa, has high comprehensive cost of Mn, Nb and Ti, has Si content of 0.30-0.60 wt%, is easy to form silicon red iron sheet defects on the surface, is not beneficial to acid cleaning and coating of users, and can be suitable for rolling girder steel production with S less than or equal to 0.015 wt%; however, the punching crack is easy to occur in the punching large beam steel due to the inclusion of large particles such as MnS and the like in the punching large beam steel.
Chinese patent application publication No. CN102978511A discloses a method for producing a hot-rolled steel sheet for automobile girder steel at low cost. Through the innovation of steel-making and steel-rolling processes, the problems that the Nb and V microalloy cost of casting blanks for producing high-strength hot rolled plates in the steel-making process is high and the transverse cracks of the casting blanks are difficult to control are solved, and in the process of rolling the high-strength steel, the recovery and recrystallization of the steel are obvious, the controlled rolling and controlled cooling process is difficult to give full play, the temperature difference in the length direction of strip steel is large, the mechanical property fluctuation is large, the investment of controlled rolling and controlled cooling process equipment is large, and the like, so that the produced product has high strength, ductility and toughness, good welding performance and the like, the yield strength is 510-580 MPa, the tensile strength is 610-700 MPa, and the elongation is: 26-34%, the yield ratio is less than or equal to 0.85, and the low-temperature impact is more than or equal to 60J at the temperature of-20 ℃, so that the material is very suitable for being used as a material with high requirements on the strength, the toughness and the welding performance of steel, such as automobile girders, bridges and the like. According to the invention, the strength of the hot rolled plate is improved mainly by adding more alloy elements Mn and Ti and utilizing a controlled rolling and controlled cooling process, but because the Si content is controlled to be higher, the defect of silicon red iron sheet is still easily formed on the surface, the requirement that the S content is less than or equal to 0.01 wt% is lower, large-particle MnS inclusion is still easily formed in the steel plate, and when the automobile girder is prepared by stamping, the stamping cracking is easily caused.
Disclosure of Invention
The invention aims to provide a hot rolled steel plate for an automobile beam with 600 MPa-level tensile strength and a manufacturing method thereof, and solves the technical problems of low tensile strength, high manufacturing cost and poor stamping forming performance of the existing hot rolled steel plate for the automobile beam.
The invention adopts the technical scheme that a hot rolled steel plate for an automobile beam with 600 MPa-level tensile strength comprises the following chemical components in percentage by weight: c: 0.04-0.12%, Si: 0-0.08%, Mn: 1.25-1.50%, P is less than or equal to 0.011%, S is less than or equal to 0.002%, Al: 0.010-0.040%, N is less than or equal to 0.0060%, Nb: 0.03-0.05%, Ti: 0.06 to 0.11 percent, and the balance of Fe and inevitable impurities.
The metallographic structure of the hot-rolled steel plate is polygonal ferrite and fine pearlite, the grain size of the ferrite in the metallographic structure is 11-12 grades, and the upper yield strength R of the hot-rolled steel plate with the thickness of 4.0-10.0 mm eH 500 to 670MPa, tensile strength R m 600 to 760MPa, elongation after break A 50mm 23-35%, the product of strength and elongation is 17500-21000 MPa%, the impact power value Akv at-20 ℃ is 50-70J, and d ═ a is qualified in a 180-degree bending test.
The hot rolled steel plate is used for manufacturing girders of medium-sized trucks and heavy trucks, and the girders of trucks manufactured by a stamping forming process or a rolling forming process are not cracked.
The reason why the chemical composition of the hot rolled steel sheet for automobile frame having a tensile strength of 600MPa according to the present invention is limited to the above range is as follows:
c: c is the most important element that determines the carbon equivalent and is an important index that affects the strength and weldability of steel. When the content of C is low, sufficient strength cannot be ensured, and more alloy elements are required to be added to improve the strength; when the content of C is high, the ductility and toughness are reduced, and the welding performance is also obviously reduced; comprehensively considered, the set C content in the steel is 0.04-0.12%.
Si: si is a solid solution strengthening element, can expand the range of a critical zone, purify ferrite, improve hardenability and the like, has high Si content, is not favorable for weldability and surface quality of strip steel, is easy to generate the defect of rusty red iron sheet, and is not favorable for acid cleaning and coating; comprehensively considered, the set Si content in the steel is 0-0.08%.
Mn: mn can improve the strength of the quenched steel plate. Mn is an element for stabilizing austenite, can reduce the transformation temperature of austenite, promote the dissolution of C in austenite, increase the enrichment of C and delay the formation of pearlite, thereby expanding the application range of the cooling rate of forming a martensite structure by quenching. However, too high Mn should be avoided because Mn also reduces the activity of C, too high Mn also tends to segregate, deteriorating the formability of the steel; comprehensively considered, the Mn content in the steel is set to be 1.25-1.50%.
Ti, Nb: ti and Nb are strong carbonitride forming elements, a proper amount of Ti and N can fix N in steel and form fine TiN and NbN particles, the low content of Ti and Nb cannot play a role in refining grains, the Ti and Nb not only can obviously refine the grains and improve the strength, but also can be separated out in a TiC or NbC form after the steel coil is coiled, and the strength is further improved; to meet performance requirements and reduce alloy cost; comprehensively considered, the steel has the set Ti content of 0.06-0.11% and the set Nb content of 0.03-0.05%.
Al: al is a main deoxidizing element in steel, and contributes to grain refinement, but too much Al increases the number of inclusions in steel, and deteriorates the workability thereof. The Al added in the invention is mainly used for deoxidizing and refining grains; comprehensively considered, the Al content in the steel is set to be 0.010-0.040%.
N: n in steel is combined with Ti to form TiN, a second phase is precipitated at high temperature to strengthen a matrix, but when the content of N is too high, coarse TiN is formed in the steel or N is dissolved in the steel, the plastic toughness is damaged, and the formability is influenced; comprehensively considered, N is set to be less than or equal to 0.0060 percent.
P and S: p is a harmful element of steel grade, and seriously damages the plasticity and toughness of the steel plate; s is combined with Mn and the like in the steel to form a plastic inclusion MnS which is unfavorable for the transverse plasticity and the toughness of the steel, so the content of S is as low as possible; comprehensively considered, P is less than or equal to 0.011 percent and S is less than or equal to 0.002 percent in the steel.
A manufacturing method of a hot rolled steel plate for an automobile beam with 600 MPa-level tensile strength comprises 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: 0.04-0.12%, Si: 0-0.08%, Mn: 1.25-1.50%, P is less than or equal to 0.011%, S is less than or equal to 0.002%, Al: 0.010-0.040%, N is less than or equal to 0.0060%, Nb: 0.03-0.05%, Ti: 0.06 to 0.11 percent, and the balance of Fe and inevitable impurities;
heating the continuous casting plate blank at 1250-1270 ℃ for 180-260 min, and then carrying out hot rolling, wherein the hot rolling is a two-stage rolling process, the rough rolling is 6-pass continuous rolling, the rolling is carried out at the temperature above the austenite recrystallization temperature, and the finish temperature of the rough rolling is 1060-1100 ℃; the finish rolling is 7-pass continuous rolling, rolling is carried out in an austenite non-recrystallization temperature region, and the finish rolling temperature is 820-870 ℃; after finish rolling, the thickness of the steel plate is controlled to be 4.0-10.0 mm, front-end cooling is adopted for laminar cooling, the laminar cooling speed is not less than 30 ℃/s, and the hot rolled steel coil is coiled when the coiling temperature is 540-580 ℃.
The 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 temperature and the time of the continuous casting slab discharging furnace are set to ensure the dissolution of coarse Nb and Ti microalloy carbon and nitride particles in the continuous casting slab, and the Nb and Ti microalloy carbon and nitride particles can be separated out in the cooling process of the continuous casting slab according to the content of Nb and Ti in the technical scheme of the invention, and the separated Nb and Ti microalloy carbon and nitride particles are coarse and have no strengthening effect; when a plate blank before hot rolling is heated, coarse Nb and Ti microalloy carbon and nitride are fully dissolved, so that the combined Nb and Ti elements can be dissolved into austenite in a solid solution mode, interphase precipitation is formed during phase change in the subsequent hot rolling and cooling processes, and ferrite is strengthened, which is very important for the technical scheme of the invention; the temperature is too low and the heating time is too short, original coarse Nb and Ti microalloy carbon and nitride particles in the continuous casting slab cannot be fully dissolved, the temperature is too high, the heating time is too long, the surface of the slab is seriously oxidized and decarburized, the final performance and the surface quality of a steel plate are not facilitated, and energy is also consumed. The method is mainly characterized in that Ti strengthening is adopted, and the dissolution temperature of the alloy carbonitride of Ti is higher than that of the carbonitride of Nb; comprehensively considered, the heating temperature of the continuous casting slab is set to be 1250-1270 ℃, and the heating time is set to be 180-260 min.
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 obtained; comprehensively considering, the rough rolling finishing temperature is set to be 1060-1100 ℃.
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 finishing temperature setting is also to prevent the steel sheet from forming significant band defects. Combining the theoretical calculation result, Ar of the steel grade of the invention 3 The temperature is 803 ℃; comprehensively considered, the finish rolling finishing temperature is set to be 820-870 ℃.
4. Method of laminar cooling after finish rolling and setting of cooling rate
In the hot-rolled steel sheet of the present invention, the cooling after the finish rolling is performed in order to suppress the growth of crystal grains and the precipitation of Nb and Ti microalloy carbonitride in a high temperature zone by a high laminar cooling rate, and therefore, the cooling method is a front-stage cooling. The precipitation of Nb and Ti microalloy carbonitride particles in austenite is inhibited through rapid cooling, and solid-solution Nb and Ti elements are retained in deformed austenite, so that the precipitation of fine and dispersed Nb and Ti microalloy carbonitride in a ferrite region at a lower temperature becomes possible; the cooling speed is too slow, so that the advance precipitation of Nb and Ti microalloy carbonitride in high-temperature deformation austenite cannot be inhibited; by comprehensive consideration, the laminar cooling adopts a front-section cooling mode, and the cooling speed is more than or equal to 30 ℃/S.
5. Setting of coiling temperature in Hot Rolling
The hot rolling coiling temperature mainly influences the structure and the performance of the material. In the invention, Nb and Ti are used, and the coiling temperature is set to 540-580 ℃ according to the optimal precipitation temperature of the niobium-titanium microalloy element. If the coiling temperature is lower than 540 ℃, the precipitation of Nb and Ti microalloy carbon and nitride is inhibited, and the strength is insufficient; if the coiling temperature is higher than 580 ℃, precipitates of carbon and nitride of the Nb and Ti microalloy are coarsened, so that the toughness is insufficient, and the problem that the hot rolled steel plate is cracked in the processes of bending, stamping and the like is caused.
The hot-rolled steel plate produced by the method has a metallographic structure of polygonal ferrite and fine pearlite, the grain size of the ferrite in the metallographic structure is 11-12 grades, and the upper yield strength R of the hot-rolled steel plate eH 500 to 670MPa, tensile strength R m 600 to 760MPa, elongation after break A 50mm 23-35%, the product of strength and elongation is 17500-21000 MPa%, the impact power value Akv at-20 ℃ is 50-70J, and d ═ a is qualified in a 180-degree bending test.
The girder of the medium-sized truck or the heavy truck manufactured by processing the hot rolled steel plate produced by the method by adopting a stamping forming process or a rolling forming process can not crack.
Compared with a hot-rolled steel plate for an automobile frame with the tensile strength of 510MPa, the automobile frame processed by the hot-rolled steel plate disclosed by the invention has the advantages that the thickness is reduced by 0.5-2.0 mm under the same bearing load, and the light weight effect of a vehicle is obvious.
Compared with the prior art, the invention has the following positive effects: 1. the chemical composition design of the steel adopts the composition design of medium C, medium Mn, high Ti and medium Nb, the fine grain strengthening effect of the alloy and the precipitation strengthening effect of the Ti and Nb are fully utilized to obtain the high-strength automobile girder steel, and the elongation after fracture of the steel plate is good. 2. The invention adopts the design of medium Mn and low S, can effectively control the strip segregation of the steel plate, has fine and uniform inclusions, and can effectively avoid the cracking defect in the rolling and stamping processes. 3. On the basis of chemical component design, the method is matched with a corresponding hot rolling process to obtain the beam steel with uniform polygonal ferrite and fine pearlite in metallographic structure, the product has good formability, and the beam steel can be used as a rolling beam and a stamping beam and meets the requirements of two processing processes. 4. The hot rolling coiling temperature is controlled to be 540-580 ℃, the wave-shaped defects caused by large residual stress after the strip steel is cooled by laminar flow can be effectively controlled, the automobile girder steel with high plate shape quality is provided for users, and the requirement of automatic production is met.
Drawings
FIG. 1 is a photograph showing a metallographic structure of a hot rolled steel sheet according to example 1 of the present invention.
Detailed Description
The present invention is further described below with reference to examples 1 to 5, 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.
Smelting in a converter to obtain molten steel meeting the requirements of chemical components, blowing Ar to the molten steel in an LF ladle refining furnace refining process, carrying out vacuum cyclic degassing treatment and component fine adjustment in an RH furnace, and then carrying out slab continuous casting to obtain a continuous casting slab; the thickness of the continuous casting slab is 210-230 mm, the width is 900-1600 mm, and the length is 8500-11000 mm.
And (3) sending the fixed-length plate blank produced in the steel-making process to a heating furnace for reheating, taking out the plate blank from the furnace for descaling, and sending the plate blank to a hot continuous rolling mill for rolling. Controlling rolling by a rough rolling and finish rolling continuous rolling unit, carrying out coiling after laminar cooling, and carrying out front-section cooling by the laminar cooling to produce a qualified hot-rolled steel coil; the thickness of the hot rolled steel plate is 4.0-10.0 mm. The hot rolling process control parameters are shown in Table 2.
TABLE 2 Hot Rolling Process control parameters of the inventive examples
Referring to fig. 1, the metallographic structure of the hot-rolled steel plate obtained by the method is polygonal ferrite + fine pearlite, the grain size of the ferrite in the metallographic structure is 11-12 grades, and the upper yield strength R of the hot-rolled steel plate eH 500 to 670MPa, tensile strength R m 600 to 760MPa, elongation after break A 50mm 23 to 35 percent of the total weight of the composition,the product of strength and elongation is 17500-21000 MPa%, the impact power value Akv at-20 ℃ is 50-70J, and the product d is qualified after 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 hot rolled steel plate obtained by the invention is sampled, a transverse sample is obtained by tensile and bending tests, a longitudinal sample is obtained by impact tests, and the tensile test is carried out according to the part 1 of the GB/T228.1-2010 metal material tensile test: room temperature test method for tensile test; performing a bending test according to GB/T232-2010 bending test method for metal materials; the impact test is carried out according to GB/T229-2007 method for testing charpy pendulum impact of metal materials, and the mechanical properties are shown in Table 3.
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 (6)
1. A hot rolled steel plate for an automobile beam with 600 MPa-level tensile strength comprises the following chemical components in percentage by weight: c: 0.04-0.12%, Si: 0-0.08%, Mn: 1.25-1.50%, P is less than or equal to 0.011%, S is less than or equal to 0.002%, Al: 0.010-0.040%, N is less than or equal to 0.0060%, Nb: 0.03-0.05%, Ti: 0.06 to 0.11 percent, and the balance of Fe and inevitable impurities; upper yield strength R of hot rolled steel plate with thickness of 4.0-10.0 mm eH 500 to 670MPa, tensile strength R m 600 to 760MPa, elongation after break A 50mm 23-35%, the product of strength and elongation is 17500-21000 MPa%, the impact power value Akv at-20 ℃ is 50-70J, and d ═ a is qualified in a 180-degree bending test.
2. The hot-rolled steel sheet for an automobile frame having a tensile strength of 600MPa according to claim 1, wherein the metallographic structure of the hot-rolled steel sheet is polygonal ferrite + fine pearlite, and the grain size of ferrite in the structure is in the range of 11 to 12.
3. The hot rolled steel sheet for an automobile frame having a tensile strength of 600MPa according to claim 1, wherein the truck frame is not cracked by processing the hot rolled steel sheet into a frame of a medium-sized truck or a heavy-duty truck by a press forming process or a roll forming process.
4. A manufacturing method of a hot rolled steel plate for an automobile beam with 600 MPa-level tensile strength 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: 0.04-0.12%, Si: 0-0.08%, Mn: 1.25-1.50%, P is less than or equal to 0.011%, S is less than or equal to 0.002%, Al: 0.010-0.040%, N is less than or equal to 0.0060%, Nb: 0.03-0.05%, Ti: 0.06 to 0.11 percent, and the balance of Fe and inevitable impurities;
heating the continuous casting plate blank at 1250-1270 ℃ for 180-260 min, and then carrying out hot rolling, wherein the hot rolling is a two-stage rolling process, the rough rolling is 6-pass continuous rolling, the rolling is carried out at the temperature above the austenite recrystallization temperature, and the finish temperature of the rough rolling is 1060-1100 ℃; the finish rolling is 7-pass continuous rolling, rolling is carried out in an austenite non-recrystallization temperature region, and the finish rolling temperature is 820-870 ℃; after finish rolling, the thickness of the steel plate is controlled to be 4.0-10.0 mm, front-end cooling is adopted for laminar cooling, the laminar cooling speed is not less than 30 ℃/s, and the hot rolled steel coil is coiled when the coiling temperature is 540-580 ℃.
5. The method for manufacturing a hot-rolled steel sheet for an automobile frame having a tensile strength of 600MPa according to claim 4, wherein the hot-rolled steel sheet has a metallographic structure of polygonal ferrite + fine pearlite, the ferrite grain size in the metallographic structure is in the range of 11 to 12, and the hot-rolled steel sheet has an upper yield strength R eH 500 to 670MPa, tensile strength R m 600 to 760MPa, elongation after break A 50mm Is 23 to 35 percentThe product of strength and elongation is 17500-21000 MPa%, the impact power Akv at-20 ℃ is 50-70J, and the product d is qualified after 180-degree bending test.
6. The method of manufacturing a hot rolled steel sheet having a tensile strength of 600MPa for an automobile frame according to claim 4, wherein the hot rolled steel sheet is processed into a frame of a medium-sized truck or a heavy truck by a press forming process or a roll forming process, and the truck frame is not cracked.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116288000A (en) * | 2023-03-02 | 2023-06-23 | 宝武集团鄂城钢铁有限公司 | Impact-welded axle housing steel plate with excellent ductility and welding performance and tensile strength of 630MPa and preparation method thereof |
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| JP2002088447A (en) * | 1999-10-22 | 2002-03-27 | Kawasaki Steel Corp | High strength galvanized steel sheet having excellent workability and plating property and its production method |
| CN104694822A (en) * | 2013-12-06 | 2015-06-10 | 上海梅山钢铁股份有限公司 | High-strength hot rolled steel plate with 700 MPa grade yield strength and manufacturing method thereof |
| CN107868911A (en) * | 2016-09-26 | 2018-04-03 | 上海梅山钢铁股份有限公司 | A kind of yield strength 600MPa level hot rolled steel plates and its manufacture method |
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| JP2002088447A (en) * | 1999-10-22 | 2002-03-27 | Kawasaki Steel Corp | High strength galvanized steel sheet having excellent workability and plating property and its production method |
| CN104694822A (en) * | 2013-12-06 | 2015-06-10 | 上海梅山钢铁股份有限公司 | High-strength hot rolled steel plate with 700 MPa grade yield strength and manufacturing method thereof |
| CN107868911A (en) * | 2016-09-26 | 2018-04-03 | 上海梅山钢铁股份有限公司 | A kind of yield strength 600MPa level hot rolled steel plates and its manufacture method |
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| CN116288000A (en) * | 2023-03-02 | 2023-06-23 | 宝武集团鄂城钢铁有限公司 | Impact-welded axle housing steel plate with excellent ductility and welding performance and tensile strength of 630MPa and preparation method thereof |
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