JP4084733B2 - High strength low specific gravity steel plate excellent in ductility and method for producing the same - Google Patents
High strength low specific gravity steel plate excellent in ductility and method for producing the same Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims description 83
- 239000010959 steel Substances 0.000 title claims description 83
- 230000005484 gravity Effects 0.000 title claims description 62
- 238000004519 manufacturing process Methods 0.000 title claims description 41
- 238000001816 cooling Methods 0.000 claims description 21
- 238000005098 hot rolling Methods 0.000 claims description 20
- 238000005096 rolling process Methods 0.000 claims description 20
- 238000000137 annealing Methods 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 9
- 238000005097 cold rolling Methods 0.000 claims description 8
- 238000004804 winding Methods 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 7
- 238000005554 pickling Methods 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 38
- 229910015372 FeAl Inorganic materials 0.000 description 24
- 230000000694 effects Effects 0.000 description 17
- 238000001556 precipitation Methods 0.000 description 15
- 229910000765 intermetallic Inorganic materials 0.000 description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 9
- 229910052761 rare earth metal Inorganic materials 0.000 description 9
- 238000005336 cracking Methods 0.000 description 5
- 229910052742 iron Inorganic materials 0.000 description 5
- 229910052749 magnesium Inorganic materials 0.000 description 5
- 239000000654 additive Substances 0.000 description 4
- 230000000996 additive effect Effects 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 229910052750 molybdenum Inorganic materials 0.000 description 4
- 229910000838 Al alloy Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910052791 calcium Inorganic materials 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 238000001953 recrystallisation Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- 229910052727 yttrium Inorganic materials 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 239000010960 cold rolled steel Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910052735 hafnium Inorganic materials 0.000 description 1
- 229910052747 lanthanoid Inorganic materials 0.000 description 1
- 150000002602 lanthanoids Chemical class 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Description
本発明は、自動車部品などに用いられる延性に優れた高強度低比重鋼板およびその製造方法に関するものである。 The present invention relates to a high-strength low specific gravity steel plate excellent in ductility and used for automobile parts and the like and a method for producing the same.
近年、環境問題への対応のため炭酸ガス排出低減や燃費低減を目的に自動車の軽量化が望まれている。自動車の軽量化のためには、鋼材の高強度化が有効な手段であるが、部材の剛性によって板厚が制限されている場合には、高強度化しても板厚を低減することができず、軽量化が困難であった。 In recent years, in order to cope with environmental problems, it has been desired to reduce the weight of automobiles for the purpose of reducing carbon dioxide emissions and reducing fuel consumption. Increasing the strength of steel is an effective means for reducing the weight of automobiles, but if the plate thickness is limited by the rigidity of the member, the plate thickness can be reduced even if the strength is increased. Therefore, it was difficult to reduce the weight.
上記の場合に軽量化を達成する手段としては、鋼材に比べて比重の低いアルミ合金板の使用が考えられるが、アルミ合金板は高価格であることに加え、鋼材に比べて加工性が劣っていることや、鋼板との溶接が困難である等の欠点があるために、自動車部材への適用は限定されたものとなっている。 As a means to achieve weight reduction in the above case, it is conceivable to use an aluminum alloy plate having a specific gravity lower than that of steel, but in addition to being expensive, aluminum alloy plate is inferior in workability compared to steel. In addition, there are drawbacks such as difficulty in welding with steel plates, and therefore, application to automobile members is limited.
そこで、鋼板とアルミ合金板の長所を兼ね備えたものとして、鉄にアルミを多量に添加した高Ａｌ含有鋼板が考えられる。しかし、このような高Ａｌ含有鋼板は、（ｉ）製造性が劣ること（特に、圧延時に割れが発生すること）、（ii）延性が低いこと、などの理由から、自動車用鋼板として適用することは困難であった。 Therefore, a steel plate having a high Al content in which a large amount of aluminum is added to iron can be considered as a combination of the advantages of a steel plate and an aluminum alloy plate. However, such a high Al-containing steel sheet is applied as a steel sheet for automobiles because of (i) poor manufacturability (particularly cracking during rolling) and (ii) low ductility. It was difficult.
特に、Ａｌ含有量が１０％を超えると、Ｆｅ3ＡｌやＦｅＡｌ等の金属間化合物が析出するため、延性、熱間加工性および冷間加工性が大幅に劣化し、通常の薄鋼板製造プロセスで、Ａｌ含有量が１０％超の高Ａｌ含有鋼板を製造することや、良好な強度および延性レベルを確保することは極めて困難であった。 In particular, when the Al content exceeds 10%, intermetallic compounds such as Fe 3 Al and FeAl are precipitated, so that the ductility, hot workability and cold workability are greatly deteriorated, and the normal thin steel sheet manufacturing process Thus, it was extremely difficult to produce a high Al-containing steel sheet having an Al content of more than 10% and to ensure good strength and ductility level.
高Ａｌ含有鋼板の延性を向上させる技術として、例えば、特許文献１には、Ａｌ：４〜９．５％、Ｔｉ：０．５〜２．０％、Ｍｏ：０．５〜２％、Ｚｒ：０．１〜０．８％、Ｃ：０．０１〜０．５％および残余Ｆｅを含有するアルミニウム含有鉄基合金の技術が提案されているが、Ａｌ含有量が９．５％以下であり、低比重に関する言及はなく、重量元素であるＭｏやＺｒが必須となっており、低比重化に考慮しているとはいえない。 As a technique for improving the ductility of a high Al-containing steel sheet, for example, in Patent Document 1, Al: 4 to 9.5%, Ti: 0.5 to 2.0%, Mo: 0.5 to 2%, Zr : 0.1-0.8%, C: 0.01-0.5%, and the technology of an aluminum-containing iron-based alloy containing the remaining Fe has been proposed, but the Al content is 9.5% or less There is no mention of low specific gravity, and Mo and Zr, which are heavy elements, are essential, and it cannot be said that low specific gravity is taken into consideration.
また、製造性についても、鍛造することや温間圧延を行うこととしており、いわゆる、溶解から熱間圧延、冷間圧延へと至る広く工業的に行われている製造方法、製造設備を用いた製法とは異なる。また、本発明者らの試験では、大幅な延性の改善には至っていない。 In addition, for manufacturability, forging and warm rolling are carried out, so-called so-called widely industrialized manufacturing methods and manufacturing equipment from melting to hot rolling and cold rolling were used. It is different from the manufacturing method. Moreover, in the test of the present inventors, the ductility has not been improved significantly.
また、特許文献２には、Ａｌ：１０〜１９％、Ｔｉ：２〜８％、Ｍｏ：０．５〜１０％、Ｈｆ：０．１〜１％および残余Ｆｅを含有するアルミニウム含有鉄基合金の技術が提案されているが、重量元素であるＨｆが必須となっており、低比重というよりも耐熱性に重点がおかれている。 Patent Document 2 discloses an aluminum-containing iron-based alloy containing Al: 10 to 19%, Ti: 2 to 8%, Mo: 0.5 to 10%, Hf: 0.1 to 1%, and the remaining Fe. However, Hf, which is a heavy element, is indispensable, and heat resistance is emphasized rather than low specific gravity.
また、製造性についても、粉末からの製造を基本としており、いわゆる、溶解から熱間圧延、冷間圧延へと至る広く工業的に行われている製造方法、製造設備を用いた薄鋼板の製法とは異なる。また、本発明者らの試験では、大幅な延性の改善には至っていない。 In addition, as for manufacturability, production is based on powder, so-called so-called widely industrialized production methods ranging from melting to hot rolling and cold rolling, and methods for producing thin steel sheets using production equipment. Is different. Moreover, in the test of the present inventors, the ductility has not been improved significantly.
以上のように、従来の技術では、延性に優れた高強度低比重鋼板を工業規模で生産することは困難であった。 As described above, it has been difficult to produce a high-strength, low-specific gravity steel plate excellent in ductility on an industrial scale with the conventional technology.
本発明は、上記したような問題点を解決しようとするものであって、延性に優れた高強度低比重鋼板、および、その製造方法を提供することを目的とする。 The present invention is intended to solve the above-described problems, and an object of the present invention is to provide a high-strength low-specific gravity steel plate excellent in ductility and a method for manufacturing the same.
本発明者らは、鉄ベースで多量のＡｌを含有し、成分の異なる種々の素材について、延性、熱間加工性および冷間加工性を改善するための方法について、成分と製造法の両面から研究を重ねた結果、Ａｌ含有量が１０％超の高Ａｌ含有鋼の延性、熱間加工性および冷間加工性の劣化は、Ｆｅ3Ａｌ、ＦｅＡｌ等の金属間化合物の析出による粒界脆化によるものであり、Ａｌ含有量を１０超〜２２．０％としたうえで、ＳおよびＰを極低化し、さらに、微細炭窒化物を活用して細粒化を図り鋼鈑の脆化挙動を抑制するとともに、熱延条件の適性化により、熱延、冷却および巻取り時に、Ｆｅ3Ａｌ、ＦｅＡｌ等の金属間化合物の析出を極力抑制することにより、延性、熱間加工性および冷間加工性を大幅に改善できることを見出した。 The inventors of the present invention have found a method for improving ductility, hot workability, and cold workability for various materials containing a large amount of Al on an iron base and having different components from both the component and production methods. As a result of repeated research, the deterioration of ductility, hot workability and cold workability of high Al content steel with Al content exceeding 10% is due to grain boundary brittleness due to precipitation of intermetallic compounds such as Fe 3 Al and FeAl. In addition to making the Al content more than 10 to 22.0%, S and P are made extremely low, and further, fine carbonitride is used to make the steel finer and the steel plate becomes brittle In addition to suppressing the behavior, by optimizing the hot rolling conditions, the precipitation of intermetallic compounds such as Fe 3 Al and FeAl is suppressed as much as possible during hot rolling, cooling and winding, thereby reducing ductility, hot workability and cooling. It has been found that the workability can be greatly improved.
加えて、Ａｌ添加量が多量の場合には、低比重化の程度は大きいものの、Ｆｅ3Ａｌ、ＦｅＡｌ等の金属間化合物の析出を避けられない場合があるが、この場合においても、これら金属間化合物の析出による脆化を抑制できることを知見した。 In addition, when the amount of Al added is large, although the degree of specific gravity reduction is large, precipitation of intermetallic compounds such as Fe 3 Al and FeAl may be unavoidable. It was found that embrittlement due to precipitation of intermetallic compounds can be suppressed.
本発明は、このような知見に基づいて構成したものであり、その要旨は、以下のとおりである。 The present invention is configured based on such knowledge, and the gist thereof is as follows.
（１） 質量％で、
Ｃ ：０．０１超〜５．０％、
Ｓｉ：３．０％以下、
Ｍｎ：０．０１〜３０．０％、
Ｐ ：０．０２％以下、
Ｓ ：０．０１％以下、
Ａｌ：１０超〜３２．０％、
Ｎ ：０．００１〜０．０５％
を含有し、残部がＦｅおよび不可避的不純物からなり、比重：６．５以下であり、引張り強度：ＴＳ（ＭＰａ）と破断伸び：Ｅｌ（％）の積の値：ＴＳ×Ｅｌが８５００ＭＰａ・％以上であることを特徴とする延性に優れた高強度低比重鋼板。
(1) In mass%,
C: more than 0.01 to 5.0%,
Si: 3.0% or less,
Mn: 0.01 to 30.0%,
P: 0.02% or less,
S: 0.01% or less,
Al: more than 10 to 32.0%,
N: 0.001 to 0.05%
The balance is Fe and inevitable impurities, the specific gravity is 6.5 or less, the product of tensile strength: TS (MPa) and elongation at break: El (%): TS × El is 8500 MPa ·% A high-strength, low-specific gravity steel plate excellent in ductility characterized by the above.
（２） さらに、質量％で、
Ｃｒ：０．０１〜５．０％、
Ｎｉ：０．０１〜１５．０％、
Ｍｏ：０．０１〜５．０％、
Ｃｏ：０．０１〜５．０％、
Ｃｕ：０．０１〜５．０％、
の１種または２種以上を含有することを特徴とする（１）に記載の延性に優れた高強度低比重鋼板。
(2) Furthermore, in mass%,
Cr: 0.01 to 5.0%,
Ni: 0.01 to 15.0%,
Mo: 0.01 to 5.0%,
Co: 0.01-5.0%
Cu: 0.01 to 5.0%,
The high strength low specific gravity steel sheet excellent in ductility according to (1), characterized by containing one or more of the above.
（３） さらに、質量％で、
Ｔｉ：０．００５〜１％、
Ｖ ：０．００５〜１％、
Ｎｂ：０．００５〜０．５％、
の１種または２種以上を含有することを特徴とする（１）または（２）記載の延性に優れた高強度低比重鋼板。
(3) Furthermore, in mass%,
Ti: 0.005 to 1%
V: 0.005 to 1%,
Nb: 0.005 to 0.5%,
The high strength low specific gravity steel sheet having excellent ductility according to (1) or (2), comprising one or more of the following.
（４） さらに、質量％で、
Ｃａ：０．００１〜０．０１％、
Ｍｇ：０．０００５〜０．３％、
ＲＥＭ：０．００１〜０．５％、
Ｙ ：０．００１〜０．１％、
の１種または２種以上を含有することを特徴とする（１）〜（３）のいずれか１項に記載の延性に優れた高強度低比重鋼板。
(4) Furthermore, in mass%,
Ca: 0.001 to 0.01%,
Mg: 0.0005 to 0.3%,
REM: 0.001 to 0.5%,
Y: 0.001 to 0.1%
The high strength low specific gravity steel sheet excellent in ductility according to any one of (1) to (3), characterized by containing one or more of the above.
（５） さらに、質量％で、
Ｂ ：０．０００２〜０．１％、
を含有することを特徴とする（１）〜（４）のいずれか１項に記載の延性に優れた高強度低比重鋼板。
(5) Furthermore, in mass%,
B: 0.0002 to 0.1%
The high strength low specific gravity steel plate excellent in ductility according to any one of (1) to (4), comprising:
（６） （１）〜（５）のいずれかに記載の延性に優れた高強度鋼板を製造する方法であって、（１）〜（５）のいずれかに記載の成分組成からなる鋼スラブを１０００℃以上１２００℃以下に加熱し、７５０℃以上の仕上げ圧延温度で熱間圧延し、４００℃未満まで２０℃／秒以上で冷却して、４００℃〜室温で巻き取ることを特徴とする延性に優れた高強度低比重鋼板の製造方法。 (6) A method for producing a high-strength steel sheet having excellent ductility according to any one of (1) to (5), wherein the steel slab has the component composition according to any one of (1) to (5). Is heated to 1000 ° C. or higher and 1200 ° C. or lower, hot-rolled at a finish rolling temperature of 750 ° C. or higher, cooled to less than 400 ° C. at 20 ° C./second or more, and wound at 400 ° C. to room temperature. A method for producing a high-strength, low-specific gravity steel sheet with excellent ductility.
（７） （６）記載の延性に優れた高強度低比重鋼板の製造方法にて製造した熱延鋼板を７００〜１１００℃で２０秒〜１時間の焼鈍を施し、その後、２０℃／秒以上で４００℃未満に冷却することを特徴とする延性に優れた高強度低比重鋼板の製造方法。 (7) The hot-rolled steel sheet produced by the method for producing a high-strength, low-specific gravity steel sheet excellent in ductility described in (6) is annealed at 700-1100 ° C. for 20 seconds to 1 hour, and then 20 ° C./second or more. The manufacturing method of the high strength low specific gravity steel plate excellent in ductility characterized by cooling to less than 400 degreeC.
（８） （６）記載の延性に優れた高強度低比重鋼板の製造方法にて製造した熱延鋼板を酸洗した後、１パス当たりの圧延率を５％以上１５％以下の冷延を２０℃以上で行った後、７００〜１１００℃で２０秒〜１時間の焼鈍を施し、その後、２０℃／秒以上で４００℃未満に冷却することを特徴とする延性に優れた高強度低比重鋼板の製造方法。 (8) After pickling the hot-rolled steel sheet produced by the method for producing a high-strength, low-specific gravity steel sheet having excellent ductility as described in (6), the rolling rate per pass is 5% to 15%. After being carried out at 20 ° C. or higher, annealing is carried out at 700 to 1100 ° C. for 20 seconds to 1 hour, and then cooled to less than 400 ° C. at 20 ° C./second or more and high strength and low specific gravity excellent in ductility A method of manufacturing a steel sheet.
（９） （２）〜（５）のいずれかに記載の延性に優れた高強度鋼板を製造する方法であって、（２）〜（５）のいずれかに記載の成分組成からなる鋼スラブを１０００〜１２００℃に加熱し、８５０℃以上の仕上げ圧延温度で熱間圧延し、７５０〜４００℃で巻き取ることを特徴とする延性に優れた高強度低比重鋼板の製造方法。 (9) A method for producing a high-strength steel sheet having excellent ductility according to any one of (2) to (5), wherein the steel slab has the component composition according to any one of (2) to (5). Is heated to 1000-1200 ° C., hot-rolled at a finish rolling temperature of 850 ° C. or higher, and wound up at 750-400 ° C., and a method for producing a high strength low specific gravity steel sheet excellent in ductility.
（１０） （９）記載の延性に優れた高強度低比重鋼板の製造方法にて製造した熱延鋼板を７００〜１１００℃で２０秒〜１時間の焼鈍を施し、その後、２０℃／秒未満で４００℃未満に冷却することを特徴とする高強度低比重鋼板の製造方法。 (10) The hot-rolled steel sheet produced by the method for producing a high-strength, low-specific gravity steel sheet having excellent ductility described in (9) is annealed at 700-1100 ° C. for 20 seconds to 1 hour, and then less than 20 ° C./second. The method for producing a high strength and low specific gravity steel sheet characterized by cooling to less than 400 ° C.
（１１） （９）記載の延性に優れた高強度低比重鋼板の製造方法にて製造した熱延鋼板を酸洗した後、１パス当たりの圧延率を５％以上１５％以下の冷延を２０℃以上で行った後、７００〜１１００℃で２０秒〜１時間の焼鈍を施し、その後、２０℃／秒未満で４００℃未満に冷却することを特徴とする高強度低比重鋼板の製造方法。 (11) After pickling the hot-rolled steel sheet produced by the method for producing a high-strength, low-specific gravity steel sheet excellent in ductility as described in (9), the rolling rate per pass is 5% to 15%. After carrying out at 20 degreeC or more, annealing is performed at 700-1100 degreeC for 20 second-1 hour, and after that, it cools to less than 400 degreeC at less than 20 degree-C / second, The manufacturing method of the low strength steel sheet characterized by the above-mentioned .
本発明により、延性に優れた高強度低比重鋼板を得ることができる。 According to the present invention, a high strength and low specific gravity steel sheet having excellent ductility can be obtained.
以下に、本発明における各要件の意義および限定理由について、具体的に説明する。 Below, the significance of each requirement in the present invention and the reason for limitation will be specifically described.
まず、前記（１）に係る本発明における延性に優れた高強度低比重鋼板の成分限定理由について説明する。なお、％は、質量％を意味する。 First, the reasons for limiting the components of the high-strength low specific gravity steel sheet having excellent ductility in the present invention according to (1) will be described. In addition,% means the mass%.
Ｃ：Ｃは強度を向上させ比重を下げる重要な添加元素であるので、必須の元素として、０．０１％超の添加とした。一方、過剰の添加は黒鉛の生成による製造製の劣化を伴うため、５．０％以下とした。 C: Since C is an important additive element that improves strength and lowers the specific gravity, it is added in an amount of more than 0.01% as an essential element. On the other hand, excessive addition is accompanied by deterioration of production due to the formation of graphite, so it was made 5.0% or less.
Ｓｉ：Ｓｉは固溶強化により鋼板の強度を増大させ、低比重化にも有用な元素であるが、３．０％を超える過剰の添加は、熱間加工性を低下させるとともに、熱間圧延で生じるスケールの剥離性や化成処理性を著しく劣化させるため、Ｓｉ含有量は３．０％以下とした。 Si: Si is an element that increases the strength of the steel sheet by solid solution strengthening and is useful for lowering the specific gravity. However, excessive addition exceeding 3.0% decreases hot workability and hot rolling. In order to remarkably deteriorate the scale peelability and chemical conversion processability caused by the above, the Si content is set to 3.0% or less.
Ｍｎ：ＭｎはＭｎＳを形成して、固溶Ｓによる粒界脆化を抑制するために有効な元素である。０．０１％未満ではその効果が発現しない。また、複合組織強化を活用する場合には、硬質第２相（例えば、マルテンサイト）を生成させ、強度・延性バランスを向上させるために重要な添加元素となる。一方、３０．０％を超える過剰の添加は、逆に、硬質第２相の生成量が過剰になり延性・靭性を劣化させる。したがって、Ｍｎ含有量は０．０１〜３０．０％とした。 Mn: Mn is an element effective for forming MnS and suppressing grain boundary embrittlement due to S. If it is less than 0.01%, the effect does not appear. Moreover, when utilizing composite structure | strengthening, it becomes an important additive element in order to produce | generate a hard 2nd phase (for example, martensite) and to improve a strength and ductility balance. On the other hand, an excessive addition exceeding 30.0%, on the contrary, produces an excessive amount of hard second phase and deteriorates ductility and toughness. Therefore, the Mn content is set to 0.01 to 30.0%.
Ｐ：Ｐは粒界に偏析して粒界強度を低下させ、靱性を劣化させる不純物元素であり、可及的低レベルが望ましいが、現状の精錬技術の到達可能レベルとコストを考慮して、上限を０．０２％とした。ただし、炭素量やＡｌ添加量が多量な場合には、０．００３０％以下が望ましい。 P: P is an impurity element that segregates at the grain boundary to lower the grain boundary strength and deteriorates toughness, and is preferably as low as possible, but considering the reachable level and cost of the current refining technology, The upper limit was made 0.02%. However, when the amount of carbon and the amount of Al added are large, 0.0030% or less is desirable.
Ｓ：Ｓは熱間加工性および靭性を劣化させる不純物元素であり、可及的低レベルが望ましいが、現状の精錬技術の到達可能レベルとコストを考慮して、上限を０．０１％とした。ただし、炭素量やＡｌ添加量が多量な場合には、０．００３０％以下が望ましい。 S: S is an impurity element that degrades hot workability and toughness, and is preferably as low as possible, but the upper limit was set to 0.01% in consideration of the reachable level and cost of the current refining technology . However, when the amount of carbon and the amount of Al added are large, 0.0030% or less is desirable.
Ａｌ：Ａｌは低比重化を達成するための必須の元素である。１０％以下では低比重化の効果が少ないので、下限を１０％超とした。３２．０％を超えると、熱延条件を適性化しても金属間化合物の析出を抑制することが困難となり、延性、熱間加工性および冷間加工性が大幅に劣化するので、Ａｌの含有量を１０超〜３２．０％とした。 Al: Al is an essential element for achieving a low specific gravity. Since the effect of lowering the specific gravity is small at 10% or less, the lower limit was made over 10%. If it exceeds 32.0%, it becomes difficult to suppress precipitation of intermetallic compounds even if the hot rolling conditions are optimized, and ductility, hot workability and cold workability are greatly deteriorated. The amount was more than 10 to 32.0%.
Ｎ：Ｎは窒化物を形成し結晶粒粗大化を抑制する効果があるが、０．００１％未満ではその効果が発現せず、０．０５％を超えて添加すると靭性が劣化するため、Ｎ含有量を０．００１〜０．０５％とした。 N: N forms nitrides and has the effect of suppressing crystal grain coarsening. However, if less than 0.001%, the effect is not manifested, and if added over 0.05%, the toughness deteriorates. The content was 0.001 to 0.05%.
以上が本発明の基本成分であり、通常は、上記以外はＦｅおよび不可避的不純物からなるが、前記（２）〜（５）に係る発明において、所望の強度レベルやその他の必要特性に応じて、Ｃｒ、Ｎｉ、Ｍｏ、Ｃｏ、Ｃｕ、Ｔｉ、Ｖ、Ｎｂ、Ｃａ、Ｍｇ、ＲＥＭ、Ｙ、Ｂの１種または２種以上を添加してもよい。 The above is the basic component of the present invention, and usually consists of Fe and unavoidable impurities other than the above, but in the inventions according to (2) to (5), depending on the desired strength level and other necessary characteristics , Cr, Ni, Mo, Co, Cu, Ti, V, Nb, Ca, Mg, REM, Y, or B may be added.
Ｃｒ：Ｃｒは強度・延性バランスを向上させるための添加元素であるため、０．０１％以上の添加とした。一方、過剰添加は、延性・靭性を劣化させるため５．０％を上限とした。また、Ｆｅ3Ａｌ、ＦｅＡｌ等の金属間化合物の析出する場合には、その製造性向上に寄与するため、添加することが望ましい。 Cr: Since Cr is an additive element for improving the balance between strength and ductility, it was added in an amount of 0.01% or more. On the other hand, excessive addition degrades ductility and toughness, so 5.0% was made the upper limit. Further, when an intermetallic compound such as Fe 3 Al or FeAl is precipitated, it is desirable to add it because it contributes to improving the manufacturability.
Ｎｉ：Ｎｉは延性および靭性を向上させる有効な元素である。また、Ｍｎ同様、硬質第２相の生成を促進する。これらの効果は０．０１％未満では発現せず、１５．０％を超える過剰添加は、延性を劣化させる。したがって、Ｎｉの含有量を０．０１〜１５．０％とした。 Ni: Ni is an effective element that improves ductility and toughness. Moreover, like Mn, the formation of a hard second phase is promoted. These effects are not manifested at less than 0.01%, and excessive addition exceeding 15.0% degrades ductility. Therefore, the content of Ni is set to 0.01 to 15.0%.
Ｍｏ：Ｍｏは延性および靭性を向上させる有効な元素である。この効果は０．０１％未満では発現せず、５．０％を超える過剰添加は、靭性を劣化させるうえ、低比重化を阻害する。したがって、Ｍｏの含有量を０．０１〜５．０％とした。 Mo: Mo is an effective element that improves ductility and toughness. This effect does not appear at less than 0.01%, and excessive addition exceeding 5.0% deteriorates toughness and inhibits the reduction in specific gravity. Therefore, the Mo content is set to 0.01 to 5.0%.
Ｃｏ：Ｃｏは延性および靭性を向上させる有効な元素である。この効果は０．０１％未満では発現せず、５．０％を超える過剰添加は、靭性を劣化させるうえ、低比重化を阻害する。したがって、Ｍｏの含有量を０．０１〜５．０％とした。 Co: Co is an effective element for improving ductility and toughness. This effect does not appear at less than 0.01%, and excessive addition exceeding 5.0% deteriorates toughness and inhibits the reduction in specific gravity. Therefore, the Mo content is set to 0.01 to 5.0%.
Ｃｕ：Ｃｕは延性および靭性を向上させる有効な元素である。この効果は０．０１％未満では発現せず、５．０％を超える過剰添加は、靭性を劣化させる。したがって、Ｃｕの含有量を０．０１〜５．０％とした。 Cu: Cu is an effective element that improves ductility and toughness. This effect is not manifested at less than 0.01%, and excessive addition exceeding 5.0% degrades toughness. Therefore, the Cu content is set to 0.01 to 5.0%.
Ｔｉ：ＴｉはＴｉＮまたはＴｉＣを形成し結晶粒粗大化を抑制する効果があるが、０．００５％未満ではそれらの効果が発現せず、１％を超えて過剰添加すると、靭性が劣化するため、Ｔｉの含有量を０．００５〜１％とした。また、Ｆｅ3Ａｌ、ＦｅＡｌ等の金属間化合物の析出する場合には、その製造性向上に寄与するため添加することが望ましい。 Ti: Ti forms TiN or TiC and has the effect of suppressing coarsening of crystal grains. However, if it is less than 0.005%, those effects are not manifested, and if over 1% is added, toughness deteriorates. The Ti content is set to 0.005 to 1%. Also, Fe 3 Al, in the case of precipitation of intermetallic compounds such as FeAl, it is desirable to add to contribute to its manufacturability improved.
Ｖ：Ｖは微細な炭窒化物を形成し結晶粒粗大化を抑制する効果があるが、０．００５％未満ではその効果が発現せず、１％を超えて過剰添加すると靭性が劣化するので、Ｖの含有量を０．００５〜１％とした。 V: V has the effect of forming fine carbonitrides and suppressing crystal grain coarsening, but if less than 0.005%, the effect does not appear, and if over 1% is added, toughness deteriorates. , V content was 0.005 to 1%.
Ｎｂ：Ｎｂは微細な炭窒化物を形成し結晶粒粗大化を抑制する効果があるが、０．００５％未満ではその効果が発現せず、０．５％を超えて添加すると、低比重化を阻害するうえ、靭性が劣化も懸念されるため、Ｎｂの含有量を０．００５〜０．５％とした。 Nb: Nb has the effect of forming fine carbonitrides and suppressing grain coarsening, but the effect is not manifested if it is less than 0.005%, and if added over 0.5%, the specific gravity is lowered. In addition, the Nb content is set to 0.005 to 0.5%.
Ｃａ、Ｍｇ、ＲＥＭ（Rare Earth Metalの略称でランタノイド系元素を指す）、Ｙ：いずれもＳ等の偏析元素による熱間加工性や靭性の劣化を抑制する有効な元素である。この効果は、Ｃａは０．００１％未満、Ｍｇは０．０００５％未満、ＲＥＭは０．００１％未満、Ｙは０．００１％未満では発現せず、Ｃａは０．０１％、Ｍｇは０．３％、ＲＥＭは０．５、Ｙは０．１％を超える過剰添加は、靭性を劣化させる。また、ＲＥＭおよびＹは、低比重化も阻害する添加元素である。 Ca, Mg, REM (abbreviation of Rare Earth Metal, indicating a lanthanoid element), Y: all are effective elements that suppress deterioration of hot workability and toughness due to segregation elements such as S. This effect is not manifested when Ca is less than 0.001%, Mg is less than 0.0005%, REM is less than 0.001%, Y is less than 0.001%, Ca is 0.01%, and Mg is 0. .3%, REM is 0.5, and Y is excessive addition exceeding 0.1% deteriorates toughness. Moreover, REM and Y are additive elements that inhibit the reduction in specific gravity.
したがって、Ｃａ：０．００１〜０．０１％、Ｍｇ：０．０００５〜０．３％、ＲＥＭ：０．００１〜０．５％、Ｙ：０．００１〜０．１％とした。また、Ｆｅ3Ａｌ、ＦｅＡｌ等の金属間化合物が析出する場合には、その製造性向上に大きく寄与するため添加することが望ましい。特に、ＲＥＭに含まれるＣｅは効果的で、Ｆｅ3Ａｌ、ＦｅＡｌ等の金属間化合物が析出する場合には、添加することが望ましい。 Therefore, Ca: 0.001 to 0.01%, Mg: 0.0005 to 0.3%, REM: 0.001 to 0.5%, and Y: 0.001 to 0.1%. Further, when an intermetallic compound such as Fe 3 Al or FeAl is precipitated, it is desirable to add it because it greatly contributes to the improvement of its manufacturability. In particular, Ce contained in REM is effective, and it is desirable to add it when an intermetallic compound such as Fe 3 Al or FeAl is precipitated.
Ｂ：Ｂは微量添加で靭性向上や硬質第２相の生成を促進する。したがって、０．０００２％以上の添加とした。一方、過剰添加は、熱間加工性や延性および靭性を劣化させるので、０．１％を上限とした。また、Ｆｅ3Ａｌ、ＦｅＡｌ等の金属間化合物が析出する場合には、その製造性向上に寄与するため添加することが望ましい。 B: B is added in a small amount to promote toughness improvement and formation of a hard second phase. Therefore, the addition amount is 0.0002% or more. On the other hand, excessive addition degrades hot workability, ductility and toughness, so 0.1% was made the upper limit. Also, Fe 3 Al, if the intermetallic compound such as FeAl are precipitated is preferably added to contribute to the production improvement.
次に、特性値の限定理由について述べる。 Next, the reason for limiting the characteristic value will be described.
比重は、６．５超では、自動車用鋼板として通常使用されている鋼板の比重（鉄の比重７．８６と同程度）と比較して軽量化効果が小さいので、６．５以下とする。 When the specific gravity exceeds 6.5, the effect of reducing the weight is small compared to the specific gravity of steel plates normally used as automotive steel plates (same as the specific gravity of iron of 7.86).
強度および延性については、加工用自動車用鋼板として必要な特性を考慮して、引張り強度：ＴＳ（ＭＰａ）と破断伸び：Ｅｌ（％）の積の値：ＴＳ×Ｅｌを８５００ＭＰａ・％以上とする。 For strength and ductility, considering the characteristics required for automotive steel sheets for processing, the product of tensile strength: TS (MPa) and elongation at break: El (%): TS × El is 8500 MPa ·% or more. .
次に、製造条件の限定理由について述べる。 Next, the reasons for limiting the manufacturing conditions will be described.
前記（６）に係る本発明においては、前記（１）〜（５）のいずれかに記載の成分組成を有する鋼スラブを１０００℃以上１２００℃以下に加熱し、７５０℃以上の仕上げ圧延温度で熱間圧延し、４００℃未満まで２０℃／秒以上で冷却して、４００℃〜室温で巻き取ることより、熱間圧延を行う。 In this invention which concerns on said (6), the steel slab which has the component composition in any one of said (1)-(5) is heated at 1000 degreeC or more and 1200 degrees C or less, and by 750 degreeC or more finish rolling temperature. Hot rolling is performed by hot rolling, cooling to less than 400 ° C. at 20 ° C./second or more, and winding at 400 ° C. to room temperature.
スラブ加熱温度が１０００℃未満であると、炭窒化物が十分に固溶せずに、必要な強度や延性が得られず、熱間の靭性が不足して熱間割れなどを引き起こすので、スラブ加熱温度の下限は１０００℃とした。加熱温度の上限は、特に、高炭素系の成分の場合には重要で、熱間加工性の確保の点から１２００℃以下とする。 If the slab heating temperature is less than 1000 ° C, the carbonitride will not dissolve sufficiently, the required strength and ductility will not be obtained, and the hot toughness will be insufficient, causing hot cracking, etc. The lower limit of the heating temperature was 1000 ° C. The upper limit of the heating temperature is particularly important in the case of a high carbon component, and is set to 1200 ° C. or less from the viewpoint of ensuring hot workability.
熱延中のＦｅＡｌやＦｅ3Ａｌ相の脆化相析出を防止するために、熱間圧延は７５０℃以上で行う。仕上圧延温度の上限は、特に定めないが、熱延板組織の粗大化や加熱温度の高温化を避ける目的で９６０℃以下とすることが好ましい。 In order to prevent embrittlement phase precipitation of FeAl and Fe 3 Al phases during hot rolling, hot rolling is performed at 750 ° C. or higher. The upper limit of the finish rolling temperature is not particularly defined, but is preferably 960 ° C. or lower for the purpose of avoiding coarsening of the hot-rolled sheet structure and increasing the heating temperature.
熱間圧延後の冷却速度が２０℃／秒未満であると、冷却中にＦｅＡｌまたはＦｅ3Ａｌが析出して延性が劣化するので、冷却速度は２０℃／秒以上とした。冷却速度の上限は、特に定めないが、１０００℃／秒を超えると設備上特殊な冷却装置が必要になる場合が多く、経済的には好ましくないため、１０００℃／秒以下とすることが望ましい。 If the cooling rate after hot rolling is less than 20 ° C./second, FeAl or Fe 3 Al precipitates during cooling and the ductility deteriorates, so the cooling rate was set to 20 ° C./second or more. The upper limit of the cooling rate is not particularly defined, but if it exceeds 1000 ° C./second, a special cooling device is often required on the equipment, which is not economically preferable, and is preferably 1000 ° C./second or less. .
また、熱間圧延後の冷却停止温度および巻取り温度が４００℃超であると、巻取り中または巻取り後にＦｅＡｌまたはＦｅ3Ａｌが析出して延性が劣化するので、冷却停止温度および巻取り温度は４００℃以下とした。冷却停止温度および巻取り温度の下限は、特に定めないが、生産性の観点から、室温以上とする。 Further, if the cooling stop temperature and the coiling temperature after hot rolling are over 400 ° C., FeAl or Fe 3 Al precipitates during or after the coiling and the ductility deteriorates. The temperature was 400 ° C. or lower. The lower limits of the cooling stop temperature and the coiling temperature are not particularly defined, but are set to room temperature or higher from the viewpoint of productivity.
前記（７）に係る本発明において、熱延板の延性を向上させるために、再結晶や炭素や炭化物析出制御の観点から、熱延板を巻き取った後、７００〜１１００℃で２０秒〜１時間の焼鈍を施し、その後、２０℃／秒以上で４００℃未満に冷却してもよい。 In this invention which concerns on said (7), in order to improve the ductility of a hot-rolled sheet, from a viewpoint of recrystallization, carbon, or carbide precipitation control, after winding a hot-rolled sheet, it is 20 seconds at 700-1100 degreeC. It may be annealed for 1 hour and then cooled to less than 400 ° C. at 20 ° C./second or more.
焼鈍温度は、焼鈍中にＦｅＡｌやＦｅ3Ａｌ相が多量に析出するのを防止するため、７００℃以上とし、また、粒の粗大化を防止するため１１００℃以下とした。焼鈍後２０℃／秒以上で４００℃未満まで冷却する。冷却途中でのＦｅＡｌまたはＦｅ3Ａｌの析出を防止するために、冷却速度の下限を２０℃／秒とし、急冷停止温度の上限を４００℃未満とした。 The annealing temperature was set to 700 ° C. or higher in order to prevent a large amount of FeAl or Fe 3 Al phases from being precipitated during annealing, and was set to 1100 ° C. or lower in order to prevent grain coarsening. After annealing, it is cooled to less than 400 ° C. at 20 ° C./second or more. In order to prevent precipitation of FeAl or Fe 3 Al during cooling, the lower limit of the cooling rate was 20 ° C./second, and the upper limit of the quenching stop temperature was less than 400 ° C.
前記（８）に係る発明において冷延鋼板を製造する場合には、鋼板を巻き取った後、酸洗し、１パス当たりの圧延率を５％以上１５％以下の冷延を２０℃以上で行った後、７００〜１１００℃で２０秒〜１時間の焼鈍を施し、その後、２０℃／秒以上で４００℃未満に冷却する。 When manufacturing a cold-rolled steel sheet in the invention according to the above (8), after winding the steel sheet, pickling and cold rolling with a rolling rate per pass of 5% or more and 15% or less at 20 ° C or more. After performing, it anneals at 700-1100 degreeC for 20 second-1 hour, and cools to less than 400 degreeC after that at 20 degreeC / second or more.
冷延での割れを防止するため、１パスあたりの圧下率と圧延温度を上記のように規定した。また、焼鈍条件は、再結晶させるために、７００℃以上で２０秒以上の条件とし、粒の粗大化を防止する観点から、１１００℃以下１時間以下の条件とした。また、焼鈍後の冷却を、２０℃／秒以上で４００℃未満まで冷却することで、ＦｅＡｌやＦｅ3Ａｌの多量析出を防止した。 In order to prevent cracking during cold rolling, the rolling reduction per pass and the rolling temperature were defined as described above. The annealing conditions were set to 700 ° C. or higher and 20 seconds or longer for recrystallization, and from the viewpoint of preventing grain coarsening, 1100 ° C. or lower and 1 hour or shorter. Further, cooling after annealing was performed at a rate of 20 ° C./second or more and less than 400 ° C., thereby preventing a large amount of FeAl or Fe 3 Al from being precipitated.
一方、Ａｌ添加量が多量な場合などには、Ｆｅ3Ａｌ、ＦｅＡｌ等の金属間化合物の析出を避けることは、現状の製造設備では困難な場合が多く、この場合には、Ｃｒ、Ｃｅ、Ｂの１種または２種以上の添加がその製造性向上に寄与する。この様な場合には、以下の製造条件にて製造する（前記（９）に係る本発明）。 On the other hand, when the amount of Al added is large, it is often difficult to avoid precipitation of intermetallic compounds such as Fe 3 Al and FeAl with current production equipment. In this case, Cr, Ce, The addition of one or more of B contributes to the improvement of the manufacturability. In such a case, it manufactures on the following manufacturing conditions (this invention which concerns on said (9)).
前記（２）〜（５）のいずれかに記載の成分組成を有する鋼スラブを１０００℃以上１２００℃以下に加熱し、８５０℃以上の仕上げ圧延温度で熱間圧延し、７５０〜４００℃で巻き取ることより、熱間圧延を行う。 The steel slab having the composition according to any one of (2) to (5) is heated to 1000 ° C. or higher and 1200 ° C. or lower, hot-rolled at a finish rolling temperature of 850 ° C. or higher, and wound at 750 to 400 ° C. Hot rolling is performed.
スラブ加熱温度が１０００℃未満であると、炭窒化物が十分に固溶せずに、必要な強度や延性が得られず、熱間の靭性が不足して熱間割れなどを引き起こすので、スラブ加熱温度の下限は１０００℃とした。 If the slab heating temperature is less than 1000 ° C, the carbonitride will not dissolve sufficiently, the required strength and ductility will not be obtained, and the hot toughness will be insufficient, causing hot cracking, etc. The lower limit of the heating temperature was 1000 ° C.
加熱温度の上限は、特に高炭素系の成分の場合には重要で、熱間加工性確保の点から１２００℃以下とする。一方、高炭素系成分（概ね１．５％以上の炭素を含有する場合）では、融点が低いため１１５０℃以下の加熱が必要となる。 The upper limit of the heating temperature is particularly important in the case of a high carbon component, and is set to 1200 ° C. or less from the viewpoint of ensuring hot workability. On the other hand, a high carbon component (in the case of containing approximately 1.5% or more of carbon) needs to be heated to 1150 ° C. or lower because of its low melting point.
熱延中のＦｅＡｌやＦｅ3Ａｌ相の熱間脆化を防止するために熱間圧延は８５０℃以上で行う。熱間圧延後の巻取り温度が７５０℃超であると、巻き取り時のコイル長手方向の材質ばらつきが懸念されるので、巻取り温度を７５０℃以下とした。また、４００℃未満では、粒界に、Ｃｒ、Ｃｅ、Ｂにより脆化抑制されたＦｅＡｌやＦｅ3Ａｌ相が生成せず、硬質相が多量析出してしまうので、巻取り温度を、４００℃以上とした。 In order to prevent hot embrittlement of FeAl and Fe 3 Al phases during hot rolling, hot rolling is performed at 850 ° C. or higher. If the coiling temperature after hot rolling is higher than 750 ° C., there is a concern about material variations in the coil longitudinal direction during coiling, so the coiling temperature is set to 750 ° C. or less. Further, if the temperature is lower than 400 ° C., FeAl and Fe 3 Al phases which are suppressed in embrittlement by Cr, Ce and B are not generated at the grain boundaries, and a large amount of hard phase is precipitated. That is all.
前記（１０）に係る発明において熱延板の延性をより向上させるために、再結晶や炭素や炭化物析出制御の観点から、熱延板を巻き取った後、７００〜１１００℃で２０秒〜１時間の焼鈍を施し、その後、２０℃／秒未満で４００℃未満に冷却してもよい。 In order to further improve the ductility of the hot-rolled sheet in the invention according to (10), from the viewpoint of recrystallization, carbon and carbide precipitation control, after winding the hot-rolled sheet, 700 to 1100 ° C. for 20 seconds to 1 It may be annealed for a period of time and then cooled to less than 400 ° C. at less than 20 ° C./second.
焼鈍中にＦｅＡｌやＦｅ3Ａｌ相が多量に析出しても、それらの粒界脆化を防止するため、７００℃以上として、所定の冷速で冷却することとした。一方、１１００℃超の焼鈍は粒の粗大化を助長するため、１１００℃以下とした。 Even if a large amount of FeAl or Fe 3 Al phase precipitates during annealing, in order to prevent the grain boundary embrittlement, the temperature is set to 700 ° C. or higher and is cooled at a predetermined cooling rate. On the other hand, annealing above 1100 ° C. promotes grain coarsening, and is set to 1100 ° C. or lower.
前記（１１）に係る発明において冷延鋼板を製造する場合には、鋼板を巻き取った後、酸洗し、１パス当たりの圧延率を５％以上１５％以下の冷延を２０℃以上で行った後、７００〜１１００℃で２０秒〜１時間の焼鈍を施し、その後、２０℃／秒未満で４００℃未満に冷却する。 When manufacturing a cold-rolled steel sheet in the invention according to (11), after winding the steel sheet, pickling, and rolling at a rolling rate per pass of 5% to 15% at 20 ° C or higher. After performing, it anneals at 700-1100 degreeC for 20 second-1 hour, Then, it cools to less than 400 degreeC at less than 20 degree-C / sec.
冷延での割れを防止するため、１パスあたりの圧下率と圧延温度を上記のように規定した。また、焼鈍温度は再結晶させるために、７００℃以上で２０秒以上の条件とし、粒の粗大化を防止する観点から、１１００℃以下１時間以下の条件とした。また、焼鈍後の冷却を、２０℃／秒未満で４００℃未満まで冷却ことで、ＦｅＡｌやＦｅ3Ａｌが析出してもそれらの粒界脆化を防止した。 In order to prevent cracking in cold rolling, the rolling reduction per pass and the rolling temperature were defined as described above. In order to recrystallize, the annealing temperature was set to 700 ° C. or more and 20 seconds or more, and from the viewpoint of preventing grain coarsening, the annealing temperature was set to 1100 ° C. or less and 1 hour or less. Moreover, even after FeAl and Fe 3 Al were precipitated, the cooling after annealing was cooled to less than 400 ° C. at less than 20 ° C./second to prevent grain boundary embrittlement.
以下、実施例により本発明の効果をさらに具体的に説明する。 Hereinafter, the effects of the present invention will be described more specifically with reference to examples.
表１（ＦｅＡｌやＦｅ3Ａｌの析出を抑制した場合）および表２（ＦｅＡｌやＦｅ3Ａｌの析出を許容した場合）に示す組成を有する鋼を、それぞれ、表３と表４（表３の続き）（ＦｅＡｌやＦｅ3Ａｌの析出を抑制した場合）、および、表５と表６（表５の続き）（ＦｅＡｌやＦｅ3Ａｌの析出を許容した場合）に示す条件で、熱間圧延および／または冷間圧延した。 Steels having compositions shown in Table 1 (when the precipitation of FeAl and Fe 3 Al is suppressed) and Table 2 (when the precipitation of FeAl and Fe 3 Al is allowed) are shown in Tables 3 and 4 (Table 3). (Continued) Hot rolling under conditions shown in Table 5 and Table 6 (Continuation of Table 5) (when precipitation of FeAl and Fe 3 Al is allowed) (when precipitation of FeAl and Fe 3 Al is suppressed) And / or cold rolled.
熱間圧延後および冷間圧延後に、それぞれ、熱延板および冷延板の割れ発生状況を観察した。熱延板および熱延焼鈍板は、厚さ２．３〜２．５ｍｍとし、冷延焼鈍板は厚さ１．４〜１．６ｍｍの鋼板からＪＩＳ５号試験片を採取して試験に供した。結果を、表３と表４（表３の続き）、および、表５と表６（表５の続き）に併せて示す。得られた鋼板または鋼塊から比重測定用試料を採取して比重を測定した。 After hot rolling and after cold rolling, the occurrence of cracks in the hot rolled sheet and the cold rolled sheet was observed, respectively. The hot-rolled sheet and hot-rolled annealed sheet had a thickness of 2.3 to 2.5 mm, and the cold-rolled annealed sheet was subjected to a test by collecting a JIS No. 5 specimen from a steel sheet having a thickness of 1.4 to 1.6 mm. . The results are shown in Tables 3 and 4 (continuation of Table 3) and Tables 5 and 6 (continuation of Table 5). A specific gravity measurement sample was collected from the obtained steel plate or steel ingot, and the specific gravity was measured.
また、得られた鋼板の機械的特性を評価した。比重の測定はピクノメータを用いて行った。比重、降伏応力、引張強度および伸びを、表３と表４（表３の続き）、および、表５と表６（表５の続き）に併せて示す。 Further, the mechanical properties of the obtained steel sheet were evaluated. The specific gravity was measured using a pycnometer. Specific gravity, yield stress, tensile strength and elongation are shown in Tables 3 and 4 (continuation of Table 3) and Tables 5 and 6 (continuation of Table 5).
本発明例では、比重：６．５以下でＴＳ＊ＥＬ＞８５００ＭＰａ・％を満たしている。また、比較例では、熱延および冷延板の割れも発生しており、熱間加工性や冷間加工性にも劣ることがわかる。また、製造条件が本発明の限定範囲から逸脱している比較例では、いずれも比重が大きことがわかる。 In the example of the present invention, the specific gravity is 6.5 or less, and TS * EL> 8500 MPa ·% is satisfied. Moreover, in a comparative example, the crack of a hot-rolled and cold-rolled board has also generate | occur | produced, and it turns out that it is inferior to hot workability and cold workability. Moreover, it turns out that specific gravity is all large in the comparative example from which manufacturing conditions deviate from the limited range of this invention.
以上より、鋼成分を本発明で示した範囲に特定し、本発明で示した条件で製造することにより、延性に優れた高強度低比重鋼板が得られることが明らかである。 From the above, it is clear that a high strength low specific gravity steel plate excellent in ductility can be obtained by specifying the steel components in the range shown in the present invention and producing them under the conditions shown in the present invention.
本発明によれば、延性に優れた高強度低比重鋼板を工業的規模で生産し提供することができるので、本発明は、環境保護技術としての利用価値が高いものである。
According to the present invention, it is possible to produce and provide a high-strength low-specific gravity steel plate having excellent ductility on an industrial scale, and thus the present invention has high utility value as an environmental protection technique.
Claims (11)
Ｃ ：０．０１超〜５．０％、
Ｓｉ：３．０％以下、
Ｍｎ：０．０１〜３０．０％、
Ｐ ：０．０２％以下、
Ｓ ：０．０１％以下、
Ａｌ：１０超〜３２．０％、
Ｎ ：０．００１〜０．０５％
を含有し、残部がＦｅおよび不可避的不純物からなり、比重：６．５以下であり、引張り強度：ＴＳ（ＭＰａ）と破断伸び：Ｅｌ（％）の積の値：ＴＳ×Ｅｌが８５００ＭＰａ・％以上であることを特徴とする延性に優れた高強度低比重鋼板。 % By mass
C: more than 0.01 to 5.0%,
Si: 3.0% or less,
Mn: 0.01 to 30.0%,
P: 0.02% or less,
S: 0.01% or less,
Al: more than 10 to 32.0%,
N: 0.001 to 0.05%
The balance is Fe and inevitable impurities, the specific gravity is 6.5 or less, the product of tensile strength: TS (MPa) and elongation at break: El (%): TS × El is 8500 MPa ·% A high-strength, low-specific gravity steel plate excellent in ductility characterized by the above.
Ｃｒ：０．０１〜５．０％、
Ｎｉ：０．０１〜１５．０％、
Ｍｏ：０．０１〜５．０％、
Ｃｏ：０．０１〜５．０％、
Ｃｕ：０．０１〜５．０％、
の１種または２種以上を含有することを特徴とする請求項１に記載の延性に優れた高強度低比重鋼板。 Furthermore, in mass%,
Cr: 0.01 to 5.0%,
Ni: 0.01 to 15.0%,
Mo: 0.01 to 5.0%,
Co: 0.01-5.0%
Cu: 0.01 to 5.0%,
The high strength low specific gravity steel sheet excellent in ductility according to claim 1, comprising one or more of the following.
Ｔｉ：０．００５〜１％、
Ｖ ：０．００５〜１％、
Ｎｂ：０．００５〜０．５％、
の１種または２種以上を含有することを特徴とする請求項１または２記載の延性に優れた高強度低比重鋼板。 Furthermore, in mass%,
Ti: 0.005 to 1%
V: 0.005 to 1%,
Nb: 0.005 to 0.5%,
The high strength low specific gravity steel sheet excellent in ductility according to claim 1 or 2, characterized by containing one or more of the following.
Ｃａ：０．００１〜０．０１％、
Ｍｇ：０．０００５〜０．３％、
ＲＥＭ：０．００１〜０．５％、
Ｙ ：０．００１〜０．１％、
の１種または２種以上を含有することを特徴とする請求項１〜３のいずれか１項に記載の延性に優れた高強度低比重鋼板。 Furthermore, in mass%,
Ca: 0.001 to 0.01%,
Mg: 0.0005 to 0.3%,
REM: 0.001 to 0.5%,
Y: 0.001 to 0.1%
The high strength low specific gravity steel plate excellent in ductility according to any one of claims 1 to 3, wherein one or more of the above are contained.
Ｂ ：０．０００２〜０．１％、
を含有することを特徴とする請求項１〜４のいずれか１項に記載の延性に優れた高強度低比重鋼板。 Furthermore, in mass%,
B: 0.0002 to 0.1%
The high strength low specific gravity steel plate excellent in ductility according to any one of claims 1 to 4.
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