KR101560896B1 - Lightweight hot rolled steel sheet having excellent hot rolling and corrosion resistance properties and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a lightweight hot-rolled steel sheet having excellent hot-rolling and high corrosion resistance, and a method of manufacturing the same. An embodiment of the present invention is a steel sheet comprising, by weight%, C: 0.5% or less, Al: 12 to 18%, Ti: 0.1 to 2.0%, Cu: 0.3 to 1.0% (Ti / C) of 0.5 to 3.0%, Mn: 0.5 to 3.0%, S: not more than 0.01%, P: not more than 0.02%, N: not more than 0.01%, and the balance Fe and other unavoidable impurities. (Ni / Cu) of not less than 0.3 and an Anti-phase Boundary Energy of not more than 70 mJ / m ^2, and a light-weight hot-rolled steel sheet having excellent corrosion resistance ≪ / RTI >
According to the present invention, it is possible to improve the consistency between the ordered phase such as B2 and DO3 and the BCC phase, and suppress the generation of carbide precipitates. Therefore, even when Al as the low melting point element is added by 12% or more, cracks are not generated during hot rolling, A steel sheet having high ductility and low specific gravity and having excellent corrosion resistance in a sulfuric acid atmosphere can be provided.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a lightweight hot-rolled steel sheet having excellent hot-rolling and corrosion resistance, and a method of manufacturing the same. BACKGROUND ART [0002]

The present invention relates to a lightweight hot-rolled steel sheet having excellent hot-rolling and high corrosion resistance, and a method of manufacturing the same.

In general, when Al is added to automotive steel for light weight, fine segregation occurs during solidification due to the difference in melting point between Fe and Al during the cooling process. As a result, the content of the additive element varies depending on the position of the casting structure, and the hot rolling property is deteriorated. As a result, plate rupture is caused in the plate material production, which makes the production of the plate material very difficult.

In addition, when the content of Al in the steel is increased, the BCC and the regular phase (B2, DO3) are stabilized at room temperature, and the ductility is lowered due to low phase compatibility at room temperature. Therefore, although it is necessary to increase the Al content in the steel in order to reduce the weight of automotive steel, there is a limit to the weight reduction by increasing the content of Al owing to the hot rolling property and the room temperature moldability problem. FIG. 1 is a phase diagram of an Fe-Al system. FIG. 1 shows the crystal structure of Al added. BCC is stabilized even when a trace amount of Al is added, and when the Al content is 10 wt% or more at a low temperature close to room temperature, a B2, DO3 ordered phase is formed. That is, when Al is added, the brittleness becomes very high due to the formation of the BCC, B2, and DO3 rules. Further, as the conformity is lowered at the anti-phase boundary between BCC and B2 and DO3, So that plastic deformation becomes difficult.

In recent years, due to the severe environmental conditions such as environmental pollution, automotive materials have been increasingly demanded for corrosion resistance, and development of low-cost materials such as STS409L is under development. However, consideration for lightening is not included and cost is lower than other STS materials There is still a cost burden for the use of expensive Cr.

On the other hand, Patent Literature 1 is a representative example of a conventional technique for solving the problem of lowering ductility at room temperature, which occurs when the content of Al in the steel increases. The above-mentioned technique is to improve the stability of the austenite single phase by increasing the stacking defect energy by adding 10-20 wt% of Mn as an FCC stabilizing element, 0.5-1.0 wt% of C and controlling the addition amount of Al to 2.5-5 wt% The present invention relates to a method for producing a steel sheet having a specific gravity of 7.6 g / cm ³ or less and a uniform elongation of 70% or more. The steel sheet is subjected to hot rolling at 900 캜 or higher and then homogenized at 1000 캜 or higher, As described above, not only a complicated process of quenching after solution treatment but also a drawback that the effect of weight reduction by Al addition is 7.5% or less and the effect of weight reduction is low.

Another technique is the patent document 2. This technology can be applied to the production of Fe-Al light weight steels by controlling addition components and manufacturing methods without using FCC and other phases, The present invention relates to a method for improving the softness, hot workability and cold workability of a steel sheet by suppressing precipitation of intermetallic compounds of Fe-Al. However, the above technology intends to positively suppress B2 and DO3 through cooling and manufacturing conditions, rather than improving the conformity at the anti-phase boundary between BCC and B2 and DO3 phases. Especially, at the room temperature, Is not considered.

Another technique is disclosed in Non-Patent Document 1, which is a method of constructing a duplex or triplex phase, comprising 0.5 to 2 wt% of C, 18 to 35 wt% of Mn, and 8 To 12% by weight of Al. In the case of the above-mentioned technique, the Al content is as high as 10% or more, but after the heat treatment at 1150 ° C for 25 minutes, the cold rolling is performed at 60% or more and then recrystallization is performed at 1050 ° C for 25 minutes. Quenched and aged at 800 to 1100 占 폚 and then water-cooled. As a result, even if the tensile strength is at least 1500 MPa and the ductility is at least 48%, commercialization is very difficult.

In addition to the above-mentioned techniques, in the development of Fe-Al low specific gravity steel, it is possible to improve the ductility by improving the consistency of the anti-phase boundary by adding the element without using the FCC stabilizing element such as Mn, Document 2, however, the above-mentioned technique does not take into consideration the lowering of casting occurring during Cr addition and the problem of steelmaking and hot rolling.

All of the above-mentioned technologies are very difficult to commercialize because of a very complicated manufacturing process. In some technologies, the cost is increased due to the use of Mn, which is a high-priced element, and corrosion resistance is not considered.

On the other hand, there is a patent document 3 in consideration of corrosion resistance in automotive materials. This technique attempts to achieve a low cost while improving the corrosion resistance of a 400 series STS, which has been attracting attention as a low cost automotive corrosion resistant material. However, And therefore, the use of such materials is not particularly considered.

Korean Patent Publication No. 2011-0115651 Japanese Patent Application Laid-Open No. 2003-354060 Korean Patent Laid-Open Publication No. 2013-0074219

 [G. Frommeyer and U. Brux: "Microstructures and mechanical properties of high-strength Fe-Mn-Al-C light-weight TRIPLEX steels" Int., 77 (2006), No. 9-10, pp. 627-633]  [K. &Quot; Effect of APB type on tensile properties of Cr added Fe3Al with DO3 structure ", Materials Science and Engineering A194 (1995) 53-61], Yoshimi, H. Terashima,

The present invention provides a low specific gravity steel sheet having an ultra light weight by adding a large amount of Al and at the same time improving the hot rolling property and the low ductility at room temperature due to the addition of the high Al and improving the corrosion resistance to a superior hot rolled steel And a method of manufacturing the same.

An embodiment of the present invention is a steel sheet comprising, by weight%, 0.02 to 0.5% of C, 12 to 18% of Al, 0.33 to 2.0% of Ti, 0.3 to 1.0% of Cu, 0.1 to 0.5% of Mn, 0.5 to 3.0% of Mn, 0.01% or less of S, 0.02% or less of P and 0.01% or less of N and the balance Fe and other unavoidable impurities. ) Is not less than 3, the ratio of Ni to Cu (Ni / Cu) is not less than 0.3, and the anti-phase boundary energy is not more than 70 mJ / m ² . to provide.

In another embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising, by weight%, 0.02 to 0.5% of C, 12 to 18% of Al, 0.33 to 2.0% of Ti, 0.3 to 1.0% of Cu, 0.1 to 0.5% of Mn, 0.5 to 3.0% of Mn, 0.01% or less of S, 0.02% or less of P and 0.01% or less of N and the balance Fe and other unavoidable impurities. ) Is 3 or more, the molten steel having a Ni / Cu ratio (Ni / Cu) of 0.3 or more is cast to obtain a steel ingot, and then the steel ingot is heated to 1100 to 1250 캜; Hot-rolling the heated ingot at 800 to 1250 占 폚 to obtain a hot-rolled steel sheet; And a step of air-cooling the hot-rolled steel sheet, wherein a temperature range in which a solid phase and a liquid phase are coexisted during casting is 150 ° C or less, and a method for manufacturing a light-weight hot-rolled steel sheet having excellent hot-

According to the present invention, it is possible to improve the consistency between the ordered phase such as B2 and DO3 and the BCC phase, and suppress the generation of carbide precipitates. Therefore, even when Al as the low melting point element is added by 12% or more, cracks are not generated during hot rolling, A steel sheet having high ductility and low specific gravity and having excellent corrosion resistance in a sulfuric acid atmosphere can be provided.

1 is a state diagram of an Fe-Al system.
2 is a photograph of a hot-rolled steel sheet of Inventive Example 1 according to an embodiment of the present invention.
3 is a photograph of microstructure of Inventive Example 1 according to an embodiment of the present invention.
4 is a photograph of the hot-rolled steel sheet of Comparative Example 1 according to an embodiment of the present invention.
5 is a photograph of microstructure of Comparative Example 1 according to an embodiment of the present invention.

The inventors of the present invention conducted research to solve the problem of cracking and plate fracture during hot rolling in manufacturing a light weight hot rolled steel sheet, and found that not only the high temperature precipitation phase is a main factor for lowering the hot rolling property, The temperature range of the coexistence zone between the solid phase and the liquid phase during the casting is greatly influenced by the main factors of the hot rolling property, To be one of them.

Accordingly, the inventors of the present invention found that, in the course of examining a component system capable of reducing micro-segregation by using a thermodynamic database to reduce the coexistence zone between solid phase and liquid phase during casting to 150 degrees or less, It is possible to improve the hot rolling property by narrowing the coexistence temperature range between the solid phase and the liquid phase during casting, and it is confirmed that when the Ti / C is controlled to 3 or more, it can inhibit the capa carbide phase which precipitates at high temperature and lowers the rolling property Respectively.

Further, the inventors of the present invention have conducted studies to solve the problem that the ductility is lowered due to the lowering of the phase-to-phase consistency and the formation of the precipitates due to the regular stabilization that occurs when a large amount of Al is added, It is recognized that not only the phase-to-phase consistency between the Rule phase and the BCC is improved but also the formation of capa carbide is also suppressed and the ductility of the steel is improved, and applied to the present invention.

In addition, it has been recognized that the corrosion resistance is improved when Al and Al added for weight reduction and Cr and Cu added for securing ductility at room temperature are controlled to appropriate amounts, respectively.

Hereinafter, the present invention will be described.

C: 0.02-0.5 wt%

C is an indispensable element to be added in an amount of 0.02 wt% or more in order to secure the strength of steel in the carbon steel component system, but excessively forms a carbide precipitate when it exceeds 0.5 wt%, thereby lowering the consistency between the precipitate and the phase, And the strength in the mouth is rapidly increased to decrease the ductility. Therefore, the content of C is preferably in the range of 0.02 to 0.5 wt%. The content of C is more preferably 0.45% by weight or less, and still more preferably 0.4% by weight or less.

Al: 12 to 18 wt%

Al is added for the purpose of weight reduction and strength enhancement, but Al is bonded to Fe, Mn and C to form kappa (虜) carbide precipitates ([Fe, Mn] ₃ AlC) B2 / DO3 phase. The solubility of Al in Fe is much higher than that of Mg or Ti in lightweight elements, so that Al can be efficiently utilized as a lightweight element. In order to utilize it effectively, Al is preferably added in an amount of 12 wt% or more. In addition, when the steel is exposed to air in the steel, Al forms a passive film of Al ₂ O _{3 in} combination with oxygen to show a useful property of increasing the corrosion resistance in a sulfuric acid atmosphere. However, when it exceeds 18% by weight, the problem of reduction in ductility due to the rule becomes serious, and therefore it is preferable that the content of Al is in the range of 12 to 18% by weight.

Ti: 0.33 to 2.0 wt%

Ti is added for the purpose of improving the hot rolling property and improving the ductility at room temperature. The above-mentioned Ti prevents the occurrence of cracks in the hot rolling by reducing the zone where the solid phase and the liquid phase coexist in the cooling process after dissolution to an appropriate temperature (150 ° C or less), and also prevents the occurrence of cracks in the hot rolled steel . For this effect, Ti is preferably added in an amount of 0.33% by weight or more. However, when the content of Ti is more than 2.0% by weight, another rule phase called a Laves Phase is formed to lower the ductility at room temperature and the hot rolling property, so that the Ti content is in the range of 0.33 to 2.0% by weight desirable. The Ti content is more preferably in the range of 0.5 to 2.0 wt%, and still more preferably in the range of 1.0 to 2.0 wt%.

Cu: 0.3 to 1.0 wt%

Cu is added for the purpose of improving ductility at room temperature and improving corrosion resistance. The Cu improves the ductility at room temperature by increasing the conformity at the anti-phase boundary between the BCC and the regular phase (B2, DO3) at room temperature, and significantly improves the corrosion resistance in the sulfuric acid atmosphere. For this effect, % Or more. However, if it exceeds 1.0% by weight, it is crystallized to cause a crack at the corner of the slab or the like, which is left as surface defects after hot rolling, causing problems such as plate breakage during processing, It is preferably in the range of 0.3 to 1.0% by weight.

Cr: more than 5 to 12%

Cr is added for the purpose of improving ductility at room temperature and improving corrosion resistance similar to Cu. The Cr is a passive film such as increasing the consistency from the reverse phase (Anti-phase) the interface between the BCC and the Regulations phase (B2, DO3) at room temperature improves the room temperature ductility, combine with oxygen and Cr ₂ O ₃ when exposed to air Which is useful for increasing the corrosion resistance in a sulfuric acid atmosphere. For the above effect, it is preferable that the Cr has a range exceeding 5%. However, when it exceeds 12%, the hot rolling property is lowered and the elongation and impact toughness are lowered. Therefore, it is preferable that the Cr content is in the range of more than 5% to 12% by weight. More preferably, the Cr has a range of more than 6% to 12%, more preferably, more than 6% and less than 11%.

Ni: 0.1 to 0.5 wt%

Ni is added for the purpose of improving the hot rolling property, and it is preferable that the Ni is added by 0.1 wt% or more for the above effect. However, when it exceeds 0.5% by weight, the possibility of forming a regular phase such as Ni ₃ Al is increased, and the hot rolling property and the room temperature ductility can be inhibited. Therefore, the content of Ni is in the range of 0.1 to 0.5% by weight desirable.

Mn: 0.5 to 3.0 wt%

Mn is usually added to precipitate solid sulfur in steel as manganese sulfide to prevent embrittlement due to sulfur. Therefore, it is preferable that the Mn is added in an amount of 0.5 wt% or more in consideration of the content of S contained as an impurity. However, when it exceeds 3.0% by weight, the strength is too high and the workability is lowered. Therefore, the content of Mn is preferably in the range of 0.5 to 3.0% by weight.

S: not more than 0.01% by weight

S is an impurity inevitably contained in the production process and is preferably contained as low as possible. If it exceeds 0.01% by weight, the possibility of occurrence of defects due to hot stiffness is very high. Therefore, the content of S is preferably 0.01% Lt; / RTI >

P: not more than 0.02% by weight

P is an impurity inevitably contained in the production process and is preferably contained as low as possible. When it exceeds 0.02% by weight, the hot rolling and the sulfuric acid corrosion resistance are greatly deteriorated. Therefore, the content of P is 0.02% by weight or less .

N: not more than 0.01% by weight

N is an impurity inevitably contained in the production process, and is preferably contained as low as possible. If it exceeds 0.01% by weight, the number of precipitates may increase, resulting in a problem of lowering the ductility. The hot rolling property can be lowered. Therefore, the content of N is preferably 0.01 wt% or less.

The light-weight hot-rolled steel sheet of the present invention preferably has a Ti / C ratio of 3 or more. As described above, by controlling the ratio of Ti and C to 3 or more, hot rolled property can be ensured by suppressing the formation of high temperature precipitates such as capa carbide. In addition, it is preferable that Ni / Cu is 0.3 or more, which can solve the problem of lowering the hot rolling property which may occur when Cu, which is a low melting point element, is added. If Ti / C and Ni / Cu are less than 3 and less than 0.3, respectively, the hot rolling property may be lowered and it may be difficult to perform the hot rolling process. On the other hand, in the present invention, the effect obtained by the present invention can be obtained only when the Ti / C and Ni / Cu satisfy 3 and 0.3 or more, respectively.

In addition, the light-weight hot-rolled steel sheet proposed by the present invention preferably satisfies the condition that the anti-phase boundary energy is 70 mJ / m ² or less. By this, it is possible to ensure excellent hot rolling property and room temperature ductility by increasing the consistency between BCC and regular phase (B2 / DO3), and if the reverse phase boundary energy exceeds 70 mJ / m ² , It is difficult to secure ductility.

Furthermore, it is preferable that the lightweight hot-rolled steel sheet of the present invention does not have cracks or if the cracks have a size of less than 0.5 mm. If the crack is not formed or the crack size is less than 0.5 mm, rolling to the final target thickness is possible. However, if the crack size is 0.5 mm or more, plate fracture may occur and the hot rolling process may not be possible.

Light-weight hot-rolled steel sheet of the present invention are provided of the general carbon steel through control of the alloy composition as described above as described above: for 6.4g / cm ³ or less has a (specific gravity: 7.83g / cm ³⁾ or more than about 18% weight ratio A low specific gravity, a tensile strength of not less than 500 MPa and an elongation of not less than 10%, it can be suitably used for automobile materials which require not only excellent strength and ductility but also lightness. In addition, the corrosion amount in the sulfuric acid aqueous solution of 50 vol% is not more than 20 mg / cm ² / hr, and it is possible to secure very good corrosion resistance, so that it can be safely used even in harsh environments.

Hereinafter, a method of manufacturing a lightweight hot-rolled steel sheet of the present invention will be described.

First, a molten steel having the above-described alloy composition is prepared, and then the molten steel is cast to obtain a steel ingot. If the heating temperature is less than 1100 ° C, the rolling finish temperature is too low to form a regular phase or a bad rolling property. If the heating temperature is 1250 ° C There is a disadvantage that not only the operating cost is increased but also the probability of occurrence of liquid metal embrittlement due to partial melting of Al is increased. Therefore, the heating temperature is preferably in the range of 1100 to 1250 ° C.

At this time, it is preferable that the size of the temperature section in which the solid phase and the liquid phase coexist during casting satisfies a range of 150 DEG C or less. By controlling the size of the temperature zone in which the solid phase and the liquid phase coexist as narrow as possible, it is possible to improve the hot rolling property by suppressing the formation of microcrystalline segregation due to the formation of capasilicate and the difference in melting point between elements, have.

Thereafter, the heated ingot is hot-rolled at 800 to 1250 ° C to obtain a hot-rolled steel sheet. If the hot rolling temperature is less than 800 ° C., the hot rolling property is deteriorated. If the hot rolling temperature is more than 1250 ° C., the melting point of Al is low, so that grain segregation may occur. Therefore, the hot rolling temperature is preferably in the range of 800 to 1250 ° C.

Then, the hot-rolled steel sheet is air-cooled to produce a light-weight hot-rolled steel sheet having excellent hot-rolling and corrosion resistance.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only illustrative of the present invention in more detail and do not limit the scope of the present invention.

(Example)

Molten steel having the alloy composition shown in the following Table 1 was prepared through vacuum induction melting and then the molten steel was cast to obtain a steel ingot having a thickness of 60 mm and a width of 175 mm. Subsequently, the steel ingot was reheated at 1,250 占 폚 for 1 hour, hot rolled at 1100 占 폚, and air-cooled to produce a hot-rolled steel sheet having a thickness of 5 mm. The anti-phase boundary energy and the formation of kappa carbide and the size of the temperature range in which the liquid phase and the solid phase coexist during casting were measured for the thus-prepared hot-rolled steel sheet, and the results are shown in Table 2 below . In addition, the rolling properties in the hot rolling were evaluated and the results are shown in Table 2 below. After rolling, the steel sheet subjected to hot rolling to the target thickness was processed into a tensile specimen, and tensile strength and elongation were measured by a tensile test. The results are shown in Table 2 below. The specific gravity of the specimens was measured and the weight reduction ratio was calculated in comparison with the ordinary carbon steel having a specific gravity of 7.83 g / cm < ³ >. The results are shown in Table 2 below. American Society for Testing and Materials) -The specimens were prepared in accordance with G31 and then immersed in an aqueous 50 vol% sulfuric acid solution for 1 hour to measure the corrosion amount. The results are shown in Table 2 below. On the other hand, the rolling property evaluation was made based on the following criteria.

≪ Evaluation of rolling property &

○: No nutrients or quartz were generated during hot rolling, and there was no cracks on the surface and edge of the plate, and the final rolled thickness specimen could be secured

Δ: Cracks were generated in the surface and edge of the plate due to internal shrinkage due to internal shrinkage during the hot rolling, but cracks having a size of less than 0.5 mm, which is one tenth of the final target thickness of the plate If rolling to the final target thickness is possible (tensile specimen can be manufactured)

X: Nitrogen or quadruple occurred during hot rolling and the cracks on the surface and edge of the plate became 0.5 mm or more, which was one-tenth of the final target thickness of the plate, and the hot rolling could not proceed (impossible to manufacture the tensile specimen)

division Alloy composition (% by weight) C Al Ti Cu Cr Ni Mn S P N Ti / C Ni / Cu Inventory 1 0.12 15.1 0.7 0.71 8.2 0.32 1.2 0.0076 0.0055 0.0068 5.83 0.45 Inventory 2 0.08 12.3 0.33 0.72 9 0.33 2.1 0.0049 0.0037 0.0072 4.13 0.46 Inventory 3 0.09 17.8 0.7 0.74 10 0.42 1.8 0.0053 0.0029 0.0086 7.78 0.57 Inventory 5 0.07 14.3 1.89 0.74 8.4 0.43 One 0.0075 0.0058 0.0037 27 0.58 Inventory 6 0.11 14.3 0.35 0.32 9.2 0.13 0.8 0.0052 0.0054 0.0067 3.18 0.41 Honorable 7 0.09 13.8 0.68 0.98 8.9 0.32 1.2 0.0038 0.0051 0.0043 7.56 0.33 Honors 8 0.02 16.2 0.73 0.7 5.1 0.32 1.4 0.0043 0.0062 0.0029 36.5 0.46 Proposition 9 0.08 16.4 0.71 0.92 11.8 0.44 1.3 0.0047 0.0052 0.0062 8.88 0.48 Inventory 10 0.12 14.9 0.68 0.35 8.9 0.11 1.1 0.0063 0.0052 0.0039 5.67 0.31 Exhibit 11 0.11 14.2 0.72 0.53 9.1 0.48 1.5 0.0075 0.0048 0.0054 6.55 0.91 Inventory 12 0.13 15.1 0.83 0.69 8.1 0.29 0.52 0.0066 0.0072 0.0058 6.38 0.42 Comparative Example 1 0.52 14.3 1.51 0.74 8.4 0.43 One 0.0075 0.0058 0.0037 2.9 0.58 Comparative Example 2 0.08 11.5 0.33 0.74 9.1 0.35 1.8 0.0072 0.0051 0.0068 4.13 0.47 Comparative Example 3 0.09 19.2 0.56 0.71 8.5 0.45 2 0.0056 0.0084 0.0067 6.22 0.63 Comparative Example 4 0.07 15.3 0.09 0.35 7.6 0.11 1.1 0.0065 0.0054 0.0041 1.29 0.31 Comparative Example 5 0.11 15.7 2.1 0.32 8.5 0.12 0.8 0.0054 0.0056 0.0065 19.09 0.38 Comparative Example 6 0.32 14.3 0.6 0.74 8.4 0.43 One 0.0075 0.0058 0.0037 1.88 0.58 Comparative Example 7 0.09 14.2 0.68 0.28 8.1 0.31 1.8 0.0056 0.0054 0.0065 7.56 1.11 Comparative Example 8 0.12 14.2 0.83 1.2 9.1 0.33 1.1 0.0054 0.0058 0.0062 6.92 0.28 Comparative Example 9 0.09 15.1 0.72 0.72 4.5 0.32 1.3 0.0063 0.0048 0.0058 8 0.44 Comparative Example 10 0.12 15.2 0.69 0.35 12.3 0.42 1.6 0.0063 0.0052 0.0039 5.75 1.2 Comparative Example 11 0.13 14.6 0.83 0.69 8.5 0.08 1.5 0.0066 0.0072 0.0058 6.38 0.12 Comparative Example 12 0.07 15.3 0.85 0.74 8.9 0.63 1.3 0.0075 0.0056 0.0042 12.14 0.85 Comparative Example 13 0.13 15.2 0.73 0.82 8.4 0.13 1.2 0.0065 0.0048 0.0058 5.62 0.16 Comparative Example 14 0.12 14.9 0.72 0.41 8.1 0.32 0.45 0.0092 0.0047 0.0068 6 0.78 Comparative Example 15 0.14 15.3 0.82 0.73 9.1 0.42 3.3 0.0047 0.0058 0.0054 5.86 0.58 Comparative Example 16 0.12 14.9 0.72 0.68 8.9 0.35 1.4 0.0142 0.0063 0.0068 6 0.51 Comparative Example 17 0.08 16.2 0.71 0.88 9.3 0.45 1.7 0.0047 0.0246 0.0062 8.88 0.51 Comparative Example 18 0.12 15.4 0.82 0.55 8.7 0.37 1.6 0.0063 0.0052 0.0152 6.83 0.67 Inventory 13 0.11 14.5 1.56 0.65 9.1 0.33 2.2 0.0074 0.0059 0.0045 14.18 0.51 Inventory 14 0.09 15.5 1.87 0.67 11.3 0.29 1.4 0.0068 0.0051 0.0065 20.78 0.43 Honorable Mention 15 0.12 13.9 0.89 0.68 9.5 0.35 0.9 0.0054 0.0049 0.0041 7.42 0.51 Inventory 16 0.08 15.8 1.79 0.73 10.2 0.4 1.3 0.005 0.0046 0.0062 22.38 0.55 Comparative Example 19 0.14 16.2 0.002 0.76 3.3 0.39 1.5 0.0054 0.0048 0.0073 0.01 0.51 Comparative Example 20 0.12 14.8 0.004 0.59 7.8 0.29 1.1 0.0063 0.0037 0.0058 0.03 0.49 Comparative Example 21 0.09 14.9 1.79 0.88 2.9 0.27 One 0.0061 0.0055 0.0064 19.89 0.31 Comparative Example 22 0.15 15.3 1.92 0.72 15.4 0.32 1.9 0.0056 0.0045 0.0068 12.80 0.44

division APB
energy
(mJ / m ² ) kappa
carbide
Presence or absence of formation Solid / liquid
Coexistence zone
Size (℃) Rolling property importance
(g / cm ³⁾ Lightweight
Rate
(%) Bad food
(mg / cm ² / hr) Seal
burglar
(MPa) Elongation
(%) Inventory 1 35 × 49 ○ 6.05 22.7 15.60 595 13.0 Inventory 2 29 × 65 ○ 6.38 18.5 19.87 564 14.0 Inventory 3 30 × 71 △ 5.74 16.7 6.30 573 11.9 Inventory 5 36 × 39 ○ 6.15 21.5 15.31 568 15.4 Inventory 6 29 × 47 △ 6.15 21.5 19.45 575 13.1 Honorable 7 25 × 43 ○ 6.21 20.7 14.12 569 15.2 Honors 8 55 × 41 △ 5.93 24.3 19.67 541 12.9 Proposition 9 42 × 42 ○ 5.90 24.6 3.69 563 14.2 Inventory 10 41 × 44 △ 6.08 22.4 18.22 587 12.6 Exhibit 11 39 × 49 △ 6.16 21.3 17.38 575 13.1 Inventory 12 33 × 53 ○ 6.05 22.7 15.87 609 13.5 Comparative Example 1 45 ○ 53 × - - - - - Comparative Example 2 41 × 130 ○ 6.48 17.3 21.07 566 14.7 Comparative Example 3 38 ○ 64 × - - - - - Comparative Example 4 39 × 191 × - - - - - Comparative Example 5 46 ○ 202 × - - - - - Comparative Example 6 47 ○ 52 × - - - - - Comparative Example 7 36 × 48 △ 6.16 21.3 21.92 571 12.1 Comparative Example 8 40 ○ 55 × - - - - - Comparative Example 9 63 ○ 48 △ 6.05 22.7 22.88 578 12.6 Comparative Example 10 27 × 56 × - - - - - Comparative Example 11 38 ○ 45 × - - - - - Comparative Example 12 44 × 44 × - - - - - Comparative Example 13 41 × 51 × - - - - - Comparative Example 14 46 × 35 × - - - - - Comparative Example 15 39 ○ 29 × - - - - - Comparative Example 16 41 ○ 38 × - - - - - Comparative Example 17 44 × 39 × - - - - - Comparative Example 18 35 ○ 37 × - - - - - Inventory 13 29 × 39 △ 6.08 22 17.47 567 11.9 Inventory 14 19 × 47 △ 6.01 23 18.12 574 12.1 Honorable Mention 15 28 × 45 △ 6.12 21 16.87 556 10.8 Inventory 16 23 × 43 ○ 5.97 24 18.76 579 11.2 Comparative Example 19 73 ○ 183 × - - - - - Comparative Example 20 32 ○ 211 × - - - - - Comparative Example 21 71 × 32 × - - - - - Comparative Example 22 12 ○ 43 × - - - - -

As can be seen from Tables 1 and 2, the alloy composition and the APB energy range proposed by the present invention and the ranges of the temperature ranges in which the solid phase and the liquid phase coexist during casting are satisfied, It can be confirmed that not only capasilicate is precipitated but also the rolling property is excellent. In addition, it has a low specific gravity of less than 6.4 g / cm ³ , which not only has a lighter weight ratio of about 18% or more as compared with a general carbon steel, but also has an excellent tensile strength of 500 MPa or more and an excellent elongation of 10% or more. Further, it can be confirmed that the corrosion amount in an aqueous sulfuric acid solution of 50 vol% is 20 mg / cm ² / hr or less and has very excellent corrosion resistance.

On the other hand, in the case of Comparative Example 1, which exceeds the content of C proposed by the present invention, it is confirmed that the strength is excessively increased and capacarbide is formed coarsely and the rolling property is lowered, It was impossible.

In the case of Comparative Example 2, the Al content was low and the specific gravity and the corrosion amount targeted by the present invention could not be secured. In the case of Comparative Example 3 which exceeded the Al content proposed by the present invention, kappa carbide was formed, And it was impossible to manufacture a tensile specimen.

In the case of Comparative Examples 4 and 5, it can be seen that the rolling property deteriorates as the temperature range in which the solid phase and the liquid phase coexist at the time of casting deviates from the Ti content proposed by the present invention. In Comparative Example 6, It can be confirmed that the composition of the present invention is satisfied but the Ti / C ratio is not satisfied, so that capa carbide is formed and the rolling property is lowered.

In Comparative Example 7, although the rolling property was secured, it was found that the corrosion resistance was low due to the low Cu content. In Comparative Example 8, the hot rolling property was deteriorated due to the high Cu content, .

Comparative Examples 9 and 10 It was also found that the corrosion resistance was not ensured or the rolling property was not ensured beyond the Cr content proposed by the present invention. In Comparative Examples 11 and 12, as the Ni content was out of the range, In the case of Comparative Example 13, the alloy composition of the present invention was satisfied but the Ni / Cu ratio was not satisfied, indicating that the rolling property was degraded.

In Comparative Examples 14 and 15, 16, 17 and 18, the rolling properties were deteriorated beyond the content ranges of Cr, S, P and N proposed by the present invention, so that tensile specimens could not be produced.

In the case of Comparative Examples 19 and 20, the temperature range in which the solid phase and the liquid phase coexist at the time of casting was over 180 ° C due to the excessively low Ti content. In particular, in Comparative Example 19, the reverse phase boundary energy was 70 mJ / m < ^{2 &} gt ;, but also the rolling property was deteriorated, so that it was impossible to prepare a tensile specimen.

In the case of Comparative Example 21, the reverse phase boundary energy was out of the range of the present invention due to the low Cr content and the rolling property was not secured. In Comparative Example 22, the reverse phase boundary energy range of the present invention was satisfied, It can be confirmed that the content of cappuccide is formed due to the reduction of the rolling property.

Figs. 2 and 3 are photographs showing hot-rolled steel sheet and microstructure of Inventive Example 1, respectively, and Figs. 4 and 5 are photographs of hot-rolled steel sheet and microstructure of Comparative Example 1, respectively. As can be seen from FIGS. 2 and 3, in the case of Inventive Example 1, cracking and plate breakage do not occur in the hot-rolled steel sheet, and it can be confirmed that tensile specimens can be processed. Examination of the microstructure shows that hot- It can be seen that the cause of the formation of kappa carbide is not formed. On the other hand, in the case of Comparative Example 1, cracks and plate fractures occurred in the steel sheet during hot rolling, and a large amount of capacarbide was generated in the microstructure.

Claims (4)

The steel sheet according to any one of claims 1 to 3, wherein the steel sheet contains 0.02 to 0.5% of C, 12 to 18% of Al, 0.33 to 2.0% of Ti, 0.3 to 1.0% of Cu, 0.5 to 3.0%, S: 0.01% or less, P: 0.02% or less, N: 0.01% or less, the balance Fe and other unavoidable impurities,
The ratio (Ti / C) of the weight% values of Ti and C is 3 or more,
The ratio (Ni / Cu) of the weight% value of Ni to Cu is 0.3 or more,
A light-weight hot-rolled steel sheet with excellent hot-rolling and anti-corrosion properties with an anti-phase boundary energy of 70 mJ / m ² or less. The method according to claim 1,
The light-weight hot-rolled steel sheet has cracks having a length of less than 0.5 mm (including 0), and has excellent hot-rolling and corrosion resistance. The method according to claim 1,
The light-weight hot-rolled steel sheet has an excellent hot-rolled steel sheet having a specific gravity of 6.4 g / cm ³ or less, a tensile strength of 500 MPa or more, an elongation of 10% or more and a corrosion amount of 20 mg / cm ² / hr or less in an aqueous sulfuric acid solution of 50% Light weight hot rolled steel with corrosion resistance. The steel sheet according to any one of claims 1 to 3, wherein the steel sheet contains 0.02 to 0.5% of C, 12 to 18% of Al, 0.33 to 2.0% of Ti, 0.3 to 1.0% of Cu, (Ti / C) of 0.5 to 3.0%, S: not more than 0.01%, P: not more than 0.02%, N: not more than 0.01%, and the balance Fe and other unavoidable impurities. (Ni / Cu) of the Ni / Cu is 0.3 or more, and heating the steel ingot to a temperature of 1100 to 1250 占 폚;
Hot-rolling the heated ingot at 800 to 1250 占 폚 to obtain a hot-rolled steel sheet; And
And air cooling the hot rolled steel sheet,
A method for manufacturing a lightweight hot-rolled steel sheet having excellent hot rolling and corrosion resistance, wherein the size of a temperature zone in which a solid phase and a liquid phase coexist during casting is 150 DEG C or less.

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