KR20140030577A - Hot rolled steel strip of automobile structural components and producing method thereof - Google Patents
Hot rolled steel strip of automobile structural components and producing method thereof Download PDFInfo
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- KR20140030577A KR20140030577A KR1020120096919A KR20120096919A KR20140030577A KR 20140030577 A KR20140030577 A KR 20140030577A KR 1020120096919 A KR1020120096919 A KR 1020120096919A KR 20120096919 A KR20120096919 A KR 20120096919A KR 20140030577 A KR20140030577 A KR 20140030577A
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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
- 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
- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- 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
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- Mechanical Engineering (AREA)
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Abstract
Description
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot rolled steel sheet for a vehicle body and a method for manufacturing the same, and more particularly, to a hot rolled steel sheet for structural strength of a 1000 MPa class body structure and a method of manufacturing the same in a structural member of a vehicle body and a dump mechanism (DUMP MECHANISM).
Recently, in the automotive industry, demand for hot rolled steel sheets having high strength and large weight reduction effect is increasing to lighten automobiles and satisfy customers' needs. Accordingly, various studies are being conducted to manufacture high strength hot rolled steel sheet according to the weight reduction of automobiles. By the way, in the case of hot-rolled steel sheet used in automobile bodies and structural members, the elongation is generally lowered as the strength is increased, there is a limit to the application to automotive parts that require high workability. In addition, recent research interests in the automotive industry have demanded steels with high strength, processability and formability as automobile designs become more complex and consumers' needs are diversified. In addition, the workability of the hot rolled steel sheet is divided into bendability, elongation property, and elongated flange property, the main properties of the hot rolled steel sheet for the vehicle body structure are strength and bendability. In addition, in order to secure stability as a structure here, it must be easy to weld and the welding quality must also be good.
Korean Patent Publication No. 10-0723205 (registered on May 22, 2007) and Korean Patent Application Publication No. 10-2012-0023129 (published on March 12, 2012) are known as prior patents for satisfying such demands of consumers.
Republic of Korea Patent Publication No. 10-0723205 relates to the ultra-high strength hot rolled steel sheet for automobile structure and its manufacturing method, in weight%, C: 0.06 ~ 0.12%, Si: 0.4 ~ 1.0%, Mn: 1.4 ~ 2.2%, P : 0.015% or less, S: 0.005% or less, Al: 0.010-0.050%, Ti: 0.10-0.20%, Nb: 0.020-0.050%, Mo: 0.1-0.3%, N: 50 ppm or less, B: 40 ppm or less, remainder Fe and other unavoidable impurities; Substantially finely precipitated one or two or more of the composite precipitates composed of TiC, (Ti, Mo) C, (Ti, Nb) C and / or (Ti, Nb, Mo) C. A step of providing a hot-rolled steel sheet for ultra-high strength automobile structural, which is a baitite single phase structure, and a steel slab of the composition; Reheating the steel slab and finishing hot rolling at a temperature above the Ar3 transformation point; And a step of winding the hot rolled steel sheet in a temperature range of 400 to 550 ° C. and then winding the hot rolled steel sheet.
Korean Laid-Open Patent Publication No. 10-2012-0023129 relates to a high strength steel sheet and a manufacturing method thereof, wherein the component composition is mass%, C: 0.08% or more and 0.20% or less, Si: 0.2% or more and 1.0% or less, Mn: 0.5% or more and 2.5% or less, P: 0.04% or less, S: 0.005% or less, Al: 0.05% or less, Ti: 0.07% or more and 0.20% or less, V: 0.20% or more and 0.80% or less, and the balance is Fe and It consists of unavoidable impurities. And the structure is a ferrite phase and a 2nd phase of 80% or more and 98% or less by volume occupancy. In addition, the total amount of Ti and V contained in the precipitate whose size is less than 20 nm is 0.150 mass% or more. The difference (HVα-HVS) between the hardness (HVα) of the ferrite phase and the hardness (HVS) of the bainite phase is disclosed in terms of a high strength steel sheet having a diameter of -300 or more and 300 or less and a manufacturing method thereof.
However, according to the preceding patent, the precipitation strengthening is used as the main reinforcing mechanism, so there is a limit in securing a tensile strength of 780 MPa or more, and since the steel contains molybdenum (Mo), the recent rise in the price of molybdenum (Mo) This causes a significant increase in cost. In addition, the globalization of the automobile industry has progressed, and steel sheets used in automobiles are used in a difficult corrosive environment of foreign countries, and higher post-painting corrosion resistance of steel sheets is required. On the other hand, since the addition of molybdenum (Mo) inhibits the formation or growth of chemical conversion crystals, there is a problem of lowering the corrosion resistance after coating of the steel sheet.
The present invention has been made to solve the above problems of the prior art, the object of the present invention is to provide a structural tensile strength 1000MPa class hot rolled steel sheet and a method of manufacturing the structural member of the vehicle body and dump mechanism (DUMP MECHANISM).
Another object of the present invention is to provide a hot rolled steel sheet for a vehicle body structure having excellent chemical properties such as corrosion resistance and resistant to corrosion, and a method of manufacturing the same.
Still another object of the present invention is to provide a hot rolled steel sheet for a vehicle body structure having high strength and excellent elongation and a method of manufacturing the same.
In order to achieve the above object, a method of manufacturing a hot rolled steel sheet for a vehicle body structure according to the present invention includes the steps of: (a) providing a steel slab; (b) reheating the steel slab provided in step (a); (c) forming a steel sheet by finishing hot rolling the steel slab reheated in the step (b) at a temperature of Ar3 transformation point or more; And (d) cooling and winding the steel sheet formed in step (c); wherein the steel slab of step (a) comprises manganese (Mn): 1.45 to 1.75 wt% and silicon (Si): 0.6 to 0.80 wt%, vanadium (V): 0.2-0.3 wt%, titanium (Ti): 0.13-0.18 wt%, carbon (C): 0.04-0.10 wt%, niobium (Nb): 0.055-0.065 wt%, aluminum ( Al): 0.005 to 0.04 wt%, boron (B): 0.001 to 0.003 wt%, phosphorus (P): 0.02 wt% or less, nitrogen (N): 0.004 wt% or less, sulfur (S): 0.003 wt% or less, It is characterized by containing the balance iron (Fe) and impurities.
In addition, in the method for manufacturing a hot rolled steel sheet for a vehicle body structure according to the present invention, reheating in the step (b) is characterized in that it is carried out at a temperature of 1180 ~ 1220 ℃.
In addition, in the method for manufacturing a hot rolled steel sheet for a vehicle body structure according to the present invention, the hot rolling in the step (c) is characterized in that it is carried out at a temperature of 830 ~ 870 ℃.
In addition, in the method of manufacturing a hot rolled steel sheet for a vehicle body structure according to the present invention, the cooling in the step (d) is characterized in that it is carried out to room temperature at a cooling rate of 35 ~ 70 ℃ / sec.
In addition, in the method of manufacturing a hot rolled steel sheet for a vehicle body structure according to the present invention, the winding in the step (d) is characterized in that it is carried out at a temperature of 370 ~ 460 ℃.
In addition, the hot rolled steel sheet for the vehicle body structure according to the present invention is characterized in that it is manufactured by the hot rolled steel sheet for the vehicle body structure and the manufacturing method as described above.
As described above, according to the hot-rolled steel sheet for a vehicle body structure and a method for manufacturing the same according to the present invention, the high-strength and high elongation of niobium (Nb), titanium (Ti), vanadium (V) and the control of the hot rolling process The hot rolled steel sheet for vehicle body structure can be manufactured.
In addition, according to the present invention, the hot rolled steel sheet for a vehicle body structure and a method for manufacturing the same have excellent chemical properties such as corrosion resistance by removing molybdenum (Mo) that inhibits the formation or growth of chemical crystals and is resistant to corrosion.
In addition, according to the hot-rolled steel sheet for a vehicle body structure and the method for manufacturing the same according to the present invention, it is possible to reduce the material cost while using vanadium (V) as a replacement effect of molybdenum (Mo) generated during the production can be lowered in price.
1 is a process chart for explaining a method for manufacturing a hot rolled steel sheet for a vehicle body structure according to the present invention;
Figure 2 is a view showing the microstructure of the hot rolled steel sheet for the structural body according to the present invention.
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the accompanying drawings, but the present invention is not limited to the illustrated embodiments.
These and other objects and novel features of the present invention will become more apparent from the description of the present specification and the accompanying drawings.
Hereinafter, the steel composition component of the present invention and the reason for limitation thereof will be described.
The steel composition of the present invention is carbon (C), manganese (Mn), silicon (Si), boron (B), niobium (Nb), titanium (Ti), vanadium (V), sulfur (S), aluminum (Al) ), Phosphorus (P), nitrogen (N) or iron (Fe).
The carbon (C) is an essential element for increasing the strength of the hot rolled steel sheet, and it is preferable to add 0.04 wt% to 0.10 wt%. If the carbon content is less than 0.04wt%, the required strength cannot be obtained, and if it is added more than 0.10wt%, the TiC, (Ti, V) C, (Ti, Nb) C or (Ti, Nb, V) C It is not preferable because the precipitation of the composite precipitate is suppressed. When 0.04 wt% to 0.10 wt% is added, TiC, (Ti, V) C, (Ti, Nb) C or (Ti, with Ti), Niobium (Nb), and vanadium (V) Nb, V) C complex precipitates are formed to increase the strength of bainite single phase structure.
The manganese (Mn) is an effective element for solid solution transformation and transformation strengthening. When the content is less than 1.45 wt%, the expected strength is not obtained. When the content exceeds 1.75 wt%, the stretching property is deteriorated due to coarsening of precipitates. The strength is 950 MPa or more, but the weldability is drastically reduced. In other words, when the content of manganese is increased, the hardenability of steel is increased, so that it is easy to obtain bainite or phase, but when the content exceeds 1.75 wt%, TiC, (Ti, V) C, (Ti, Nb) C or (Ti Precipitation of, Nb, V) C is suppressed, so the strength increase compared to the added amount does not appear, it is preferable to include 1.45 ~ 1.75wt%.
The silicon (Si, silicon) serves to improve the hardenability of the steel sheet by solid solution strengthening. However, the addition of more than 0.6wt% does not have a large effect and increases the generation of red scale on the surface, so it is preferable to limit it to less than 0.8wt%.
The boron (B) together with manganese (Mn) is an element that increases the hardenability of the steel and lowers the energy of the austenite grain boundary to delay ferrite transformation and to form a low temperature phase. If boron is added less than 0.001wt% (10ppm), the desired effect is not obtained. If it is added more than 0.003wt% (30ppm), it is grain boundary segregation, which tends to drastically reduce the strength, toughness and ductility, so 0.001 to 0.003wt It is preferable to contain% (10-30 ppm).
The niobium (Nb) is preferably included at 0.055 ~ 0.065wt% so as to precipitate at the grain boundaries as Nb (C, N) and NbC precipitates during hot rolling to prevent grain boundary growth and to increase the strength through the refinement of grain (grain). . It is difficult to obtain the desired strength when added below 0.055wt%, and when added above 0.065wt%, the ductility is reduced and the solid solution is harder than the grain refinement effect of austenite. I can't show it.
The titanium (Ti) forms a precipitate in the form of titanium nitride (TiN), and increases the strength of the steel sheet by forming TiN, TiC, NbC, NbN precipitates when added simultaneously with niobium (Nb). The titanium nitride (TiN) precipitate remains undissolved even in the weld heat affected zone due to the high temperature stability, and effectively controls grain growth of the weld heat affected zone by the grain growth inhibiting effect. When the titanium (Ti) is added less than 0.13wt%, the amount of finely dispersed composite carbide cannot be sufficiently exhibited, and when it is added more than 0.18wt%, the composite carbide becomes coarse and the precipitation hardening effect is saturated, thereby decreasing the strength. Not desirable Therefore, 0.13 ~ 0.18wt% should be added.
The vanadium (V) is an element that contributes to the improvement of strength as precipitation strengthening or solid solution strengthening, and is an important requirement in obtaining the effect of the present invention together with the titanium (Ti) and niobium (Nb). By containing a composite precipitate of 0.20 to 0.30 wt% of vanadium (V) together with titanium (Ti) and niobium (Nb), when the vanadium (V) is less than 0.20 wt%, the effect of containing finely dispersed complex carbides is insufficient. If vanadium (V) is included in excess of 0.30wt%, the composite carbide is coarse, which not only lowers the precipitation strengthening effect but also increases the cost, which is not preferable.
The aluminum (Al) is an element effective in removing oxygen from steel by having excellent deoxidation ability compared to silicon (Si) or manganese (Mn). When the aluminum content is less than 0.005wt%, sufficient oxygen removal is not achieved, and when the aluminum content is more than 0.04wt%, there is a problem in that the cutting property and impact toughness of the hot-rolled steel sheet for body structure are manufactured. Therefore, it is preferable to contain 0.005-0.04 wt% of the aluminum (Al).
When sulfur (S) is contained in an amount of more than 0.003wt% as an impurity element, fine manganese sulfide (MnS) is precipitated in the course of finishing rolling, and an sulfide-based inclusion is formed to cause cracks and the like. Adversely affects the intellect However, if the content of sulfur (S) is limited to 0.003wt% or less, and the manganese sulfide (MnS) precipitate is fine and uniformly distributed, it is effective in increasing the strength. Therefore, it is preferable to contain the sulfur (S) at less than 0.003wt%.
The phosphorus (P) is preferably included as an impurity element in the total weight of the hot rolled steel sheet for vehicle body structure of the present invention in an amount of 0.02 wt% or less to prevent a decrease in weldability and brittleness.
The nitrogen (N) serves to refine the crystal grains by combining with niobium (Nb), vanadium (V), etc. as an impurity element to form carbonitrides. However, when the nitrogen (N) is added more than 0.004wt% (40ppm), the dissolved nitrogen (N) increases to reduce the elongation and formability of the steel and greatly inhibit the weld toughness. Therefore, it is good to limit the upper limit to 0.004 wt% or less.
Since sulfur (S), nitrogen (N) and phosphorus (P) are impurity elements, the lower limit thereof will not be described.
In addition, except for the above-described composition components, the remainder is substantially made of iron (Fe).
The above-mentioned remainder is substantially made of iron (Fe) means that even containing other trace elements, including inevitable impurities, can be included in the scope of the present invention, so long as it does not interfere with the effect of the present invention.
Hereinafter, the manufacturing method of the hot-rolled steel sheet for vehicle body structure using the above-mentioned steel composition component is demonstrated.
1 is a process chart for explaining a method for manufacturing a hot rolled steel sheet for a vehicle body structure according to the present invention.
As shown in Figure 1, first, to prepare a steel slab (S10).
Manganese (Mn), Silicon (Si), Vanadium (V), Titanium (Ti), Carbon (C), Niobium (Nb), Aluminum (Al), Boron (B), Phosphorus (P), Nitrogen (N), Sulfur (S), balance iron (Fe) and other unavoidable impurities, preferably manganese (Mn): 1.45 to 1.75 wt%, silicon (Si): 0.6 to 0.80 wt%, vanadium (V): 0.2 to 0.3 wt% , Titanium (Ti): 0.13 to 0.18 wt%, carbon (C): 0.04 to 0.10 wt%, niobium (Nb): 0.055 to 0.065 wt%, aluminum (Al): 0.005 to 0.04 wt%, boron (B): A steel slab consisting of 0.001 to 0.003 wt%, phosphorus (P): 0.02 wt% or less, nitrogen (N): 0.004 wt% or less, sulfur (S): 0.003 wt% or less, residual iron (Fe) and other unavoidable impurities Prepare.
Next, the steel slab is reheated (S20).
The steel slab prepared in step S10 is reheated at a temperature of 1180 ~ 1220 ℃. This is because when the slab reheating temperature is less than 1180 ° C., the precipitates may not be sufficiently reusable, which may make it difficult to dissolve the precipitates in the process after hot rolling. When the slab reheating temperature is higher than 1220 ° C., the manufacturing cost may increase due to the excessive heating process and abnormal growth of grains may occur. There is a problem that occurs. Preferably, when the temperature is 1180 to 1220 ° C., the stock strength of the precipitate may be controlled to improve the strength of the material, and the uniform longitudinal microstructure of the material may be secured.
Thereafter, the reheated steel slab is hot rolled to form a steel sheet (S30).
The steel slab reheated in the step S20 is hot rolled to a temperature equal to or higher than the Ar3 transformation point to form a steel sheet. That is, hot rolling forms steel slab reheated through rough rolling, finishing rolling, etc. as a steel plate, Preferably finish hot rolling is performed at the temperature of 830-870 degreeC. If the temperature is less than 830 ° C, problems such as deterioration of the hardenability of the steel due to excessive unrecrystallized rolling amount may occur, and thus, the steel sheet may be difficult to secure the strength standard value. If the temperature exceeds 870 ° C, the austenite grains may coarsen and the yield strength may be reduced. There exists a problem that it lowers below and the impact toughness of a steel plate falls. Therefore, it is preferable to limit the hot rolling temperature to 830 to 870 ° C.
Next, the steel sheet is cooled and wound up (S40).
Accelerated cooling using water cooling to the winding temperature set in order to coil and coil the hot rolled steel sheet in the step S30, a method of repeatedly performing water cooling and water cooling and air cooling, water cooling method by spraying the cooling water, cooling fan, etc. Select one of the forced air cooling method used to cool to room temperature at a cooling rate of 35 ~ 70 ℃ / sec. Preferably, it winds up by cooling to the temperature of 370-460 degreeC. When the coiling temperature is less than 370 ℃ when the martensite structure is formed in addition to the bainite phase, the tensile strength is not less than 1000MPa or elongation does not meet the tensile properties of the present invention, when the ferrite and the pearlite is over 460 ℃ There is a problem that the tensile strength is reduced while transforming into a coexisting tissue. Therefore, it is desirable to simultaneously secure the tensile strength and elongation by winding at a temperature of 370 ~ 460 ℃ through the bainite organization and precipitation of fine precipitates.
In addition, the wound hot rolled coil may be pickled. The pickling process is conventional and is not limited to a specific method. In addition, an oil may be applied to the surface of the steel sheet for rust prevention after the pickling treatment.
2 is a view showing the microstructure of the hot rolled steel sheet for the vehicle body structure according to the present invention.
When the above-described cooling and winding processes are completed, as shown in FIG. 2, a hot rolled steel sheet for a vehicle body structure is obtained. The final microstructure of the hot rolled steel sheet for the vehicle body structure manufactured by the above production method is one or two of the composite precipitate consisting of TiC, (Ti, V) C, (Ti, Nb) C or (Ti, Nb, V) C. It is a bainite single phase structure that has been strengthened by more than one species, and has mechanical properties of tensile strength of 970 MPa or more, yield strength of 850 MPa or more and elongation of 10% or more.
Experimental Example 1. Chemical Composition Analysis of Hot Rolled Steel Sheet
The chemical composition of the hot-rolled steel sheet for the vehicle body structure produced by the manufacturing method of the embodiment and Comparative Examples 1 and 2 were analyzed the chemical composition of the hot-rolled steel sheet for the vehicle body structure produced by the conventional manufacturing method.
As a result, as shown in Table 1, molybdenum (Mo) analyzed in the hot-rolled steel sheet for the vehicle body structure of the comparative example was not analyzed in the hot-rolled steel sheet for the vehicle body structure of the embodiment, vanadium (V) is analyzed, molybdenum (Mo) substitutes As vanadium (V) was confirmed that it was produced. In addition, Comparative Examples 1 and 2 are conventional steels, which control carbon (C) content and boron (B) to add strengths and ductility by adding carbide forming elements of titanium (Ti), niobium (Nb), and molybdenum (Mo). You can see the improvement. Therefore, the steel to be achieved in the present invention is compared to the addition of carbide forming elements of titanium (Ti), niobium (Nb), vanadium (V) by controlling the carbon (C) content and boron (B) in Examples 1 and 2 , 2 and strength and ductility were improved.
Table 1 shows the present invention and the conventional alloy design schemes are divided into Examples and Comparative Examples.
Experimental Example 2. Mechanical Properties Analysis of Hot Rolled Steel Sheet
The mechanical properties such as yield strength, tensile strength, and elongation of the hot rolled steel sheet for a structural body manufactured by the manufacturing method of the embodiment were analyzed.
As a result, as shown in Table 2, Comparative Example 1 showed a yield strength of 976 Mpa, a tensile strength of 1063 Mpa, an elongation of 12%, and Comparative Example 2 showed a yield strength of 937 Mpa, a tensile strength of 985 Mpa, and an elongation of 13.2%, respectively. Example 1 shows a yield strength of 958Mpa, tensile strength of 1008Mpa, elongation of 14.6%, Example 2 of yield strength of 800Mpa, tensile strength of 980Mpa, elongation of 14%, respectively, compared to the body structural hot-rolled steel sheet of Comparative Example It was confirmed that the elongation of the structural hot rolled steel sheet is excellent.
Table 2 shows the results of the mechanical properties according to the alloy design of Table 1 above.
(MPa)
(MPa)
(%)
Although the present invention has been described in detail with reference to the above embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.
Claims (6)
(b) reheating the steel slab provided in step (a);
(c) forming a steel sheet by finishing hot rolling the steel slab reheated in the step (b) at a temperature of Ar3 transformation point or more; And
(d) cooling and winding the steel sheet formed in step (c);
Steel slab of step (a) is manganese (Mn): 1.45 ~ 1.75wt%, silicon (Si): 0.6 ~ 0.80wt%, vanadium (V): 0.2 ~ 0.3wt%, titanium (Ti): 0.13 ~ 0.18 wt%, carbon (C): 0.04 to 0.10 wt%, niobium (Nb): 0.055 to 0.065 wt%, aluminum (Al): 0.005 to 0.04 wt%, boron (B): 0.001 to 0.003 wt%, phosphorus (P) ): 0.02wt% or less, nitrogen (N): 0.004wt% or less, sulfur (S): 0.003wt% or less, residual iron (Fe) and impurity manufacturing method of a hot rolled steel sheet for a structural body.
Reheating in the step (b) is a method for manufacturing a hot rolled steel sheet for a vehicle body structure, characterized in that carried out at a temperature of 1180 ~ 1220 ℃.
Hot rolling in the step (c) is a method for manufacturing a hot rolled steel sheet for a vehicle body structure, characterized in that carried out at a temperature of 830 ~ 870 ℃.
In the step (d), the cooling is a manufacturing method of a hot rolled steel sheet for a vehicle body structure, characterized in that carried out to room temperature at a cooling rate of 35 ~ 70 ℃ / sec.
Winding in the step (d) is a method for manufacturing a hot rolled steel sheet for a vehicle body structure, characterized in that carried out at a temperature of 370 ~ 460 ℃.
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| KR1020120096919A KR20140030577A (en) | 2012-09-03 | 2012-09-03 | Hot rolled steel strip of automobile structural components and producing method thereof |
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| KR1020120096919A KR20140030577A (en) | 2012-09-03 | 2012-09-03 | Hot rolled steel strip of automobile structural components and producing method thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| USD792439S1 (en) | 2015-12-23 | 2017-07-18 | Samsung Electronics Co., Ltd. | Display screen or portion thereof with graphical user interface |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| USD792439S1 (en) | 2015-12-23 | 2017-07-18 | Samsung Electronics Co., Ltd. | Display screen or portion thereof with graphical user interface |
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