JPH07118792A - High-strength hot rolled steel plate and its production - Google Patents
High-strength hot rolled steel plate and its productionInfo
- Publication number
- JPH07118792A JPH07118792A JP28564093A JP28564093A JPH07118792A JP H07118792 A JPH07118792 A JP H07118792A JP 28564093 A JP28564093 A JP 28564093A JP 28564093 A JP28564093 A JP 28564093A JP H07118792 A JPH07118792 A JP H07118792A
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Abstract
Description
【0001】[0001]
【産業上の利用分野】この発明は、引張強度65kg/mm2
以上の高強度を有すると共にD.C.バット溶接性,溶接後
加工性並びに化成処理性に優れ、例えば自動車のホイ−
ルリム製造用として好適な熱延鋼板、及びその製造方法
に関するものである。This invention has a tensile strength of 65 kg / mm 2
It has the above high strength and is excellent in DC butt weldability, post-weld workability, and chemical conversion processability.
The present invention relates to a hot-rolled steel sheet suitable for manufacturing rulim, and a manufacturing method thereof.
【0002】[0002]
【従来技術とその課題】近年、省エネルギ−化思想は産
業界の隅々にまで浸透してきているが、これを背景とし
て、例えば自動車業界においても車体重量を軽減して燃
料消費量を低減すべく乗用車を始めとした各種の自動車
類に高強度鋼板を使用することが一般化してきた。そし
て、これに伴い、より一層強度が高く、しかもより優れ
た加工性を示す鋼板への要求が益々高まりつつある。ま
た、自動車類の場合は、ボディ等に比べてホイ−ルの軽
量化が燃料消費量節減に対する効果が大きいことから、
最近では“ホイ−ル材に対する高強度熱延鋼板の適用”
に関しても研究の目が向けられるようになっている。2. Description of the Related Art In recent years, the concept of energy saving has spread to every corner of the industrial world. Against this background, for example, in the automobile industry, the weight of the vehicle body is reduced to reduce the fuel consumption. Therefore, it has become common to use high strength steel sheets for various automobiles including passenger cars. Along with this, there is an increasing demand for steel sheets having higher strength and more excellent workability. Also, in the case of automobiles, the weight saving of the wheel is more effective than the body etc. in reducing the fuel consumption,
Recently, "Application of high strength hot rolled steel sheet to wheel material"
Also, the focus of research is on.
【0003】ところで、通常、上記自動車類のホイ−ル
は“ディスク”と“リム”より構成されている。このう
ちのリムに適用される材料は、従来、所定の幅及び長さ
に切断された鋼板をリング状に成形し、端部を溶接した
上で数工程のロ−ルフォ−ミングを経て加工成形され製
造されている。このように、他の部材とは異なってリム
用材は溶接された後に大きな加工を受けるので、成形性
もさることながら“溶接性”及び“溶接後の加工性”が
良好であることが重要な要件となる。By the way, the wheels of the above-mentioned automobiles are usually composed of a "disk" and a "rim". Conventionally, the material applied to the rim is formed by forming a steel plate cut into a predetermined width and length into a ring shape, welding the ends, and performing roll forming in several steps. Are manufactured. Thus, unlike other members, the rim material undergoes great processing after being welded, so it is important that the "weldability" and "workability after welding" are good as well as the formability. It becomes a requirement.
【0005】なお、上記リム用材の溶接には、従来から
の“フラッシュバット溶接法”に加えて、近年では比較
的新しい方法である“D.C.バット溶接法”も適用される
ようになっている。しかも、ここ数年前からの傾向とし
て、 a) フラッシュが飛ばないので粉塵による作業環境の劣
化がない, b) 騒音が少ない, 3) フラッシュによる材料消耗がないので1%程度の歩
留り向上を図れる, 4) 溶接端面の割れの原因の1つである酸化物を形成し
にくいので、添加量を抑える必要があったSi,Al,Ti等
の成分元素に対してフラッシュバット溶接法の場合ほど
注意を払う必要がない, 等の利点があることから、徐々にD.C.バット溶接法が主
流になりつつある。In addition to the conventional "flash butt welding method", a relatively new method "DC butt welding method" has recently been applied to the welding of the rim material. Moreover, the tendency from the past few years is that a) the flash does not fly, so there is no deterioration of the working environment due to dust, b) there is less noise, and 3) there is no material consumption due to the flash, so the yield can be improved by about 1%. , 4) Since it is difficult to form an oxide, which is one of the causes of cracks on the weld end surface, it is necessary to reduce the amount added, so be careful with the composition elements such as Si, Al, and Ti as in the flash butt welding method. The DC butt welding method is gradually becoming the mainstream because it has advantages such as no need to pay.
【0006】しかしながら、最近の要望を満たすべく、
このD.C.バット溶接法を用いてより強度の高い高強度熱
延鋼板製ホイ−ルリムを製造しようとすると、次のよう
な問題があった。However, in order to meet the recent demands,
Attempts to manufacture a wheel rim made of a high-strength hot-rolled steel sheet having higher strength using this DC butt welding method have the following problems.
【0007】即ち、ホイ−ルリムを製造する際にフラッ
シュバット溶接法を適用していた時代にはそれを念頭に
おいた各種の材料や技術が開発されてきたが、そのた
め、これらの材料や技術ではD.C.バット溶接法を用いた
場合には溶接不良が生じることがあった。そこで、D.C.
バット溶接法が広まるにつれて新しい材料や技術が開発
されてきた。That is, various materials and techniques have been developed with the flash butt welding method applied in manufacturing wheel rims in consideration of it. Therefore, in these materials and techniques, When the DC butt welding method was used, welding defects sometimes occurred. So DC
New materials and techniques have been developed as the butt welding process has become widespread.
【0008】ところが、フラッシュバット溶接法よりD.
C.バット溶接法への転換期から数年後に今度は材料の高
強度化(材料強度の50〜60キロ化)が叫ばれるよう
になり、素材鋼板のC,Si,Mnの含有量を増やして強度
を上げようとしたが、この場合には溶接部の硬度上昇が
問題となった。つまり、強化元素の増量により溶接部の
硬度が非常に高くなって、その後の加工途中で溶接端面
から割れが生じるといった問題や、溶接端面から少し離
れた部分では溶接熱影響のために逆に軟化が生じ、加工
を行うとこの軟化部分に応力の集中が起こって軟化部か
らネッキングによる割れが発生して不良率が増加すると
いう問題が指摘された。ただ、当時の材料強度レベルに
おける“溶接部の硬度上昇問題”は、C当量の制限やTi
添加等の方法でどうにか解決することができた(例えば
特開昭61−170541号公報,特開昭61−264159号公報,特
開昭61−264160号公報等を参照)。However, D.
C. A few years after the transition to the butt welding method, the strengthening of materials (50-60 kg of material strength) came to be called for, and the content of C, Si, and Mn in the material steel sheets increased. However, in this case, the hardness increase of the welded portion became a problem. In other words, the hardness of the weld becomes extremely high due to the increase in the amount of strengthening elements, and cracks may occur from the weld end face during the subsequent processing. It has been pointed out that stress causes concentration of stress in this softened portion when processing is performed, cracking occurs from the softened portion due to necking, and the defect rate increases. However, the "hardness increase problem at the welded part" at the material strength level at that time was limited by the C equivalent and Ti.
The problem could be solved by a method such as addition (see, for example, JP-A-61-170541, JP-A-61-264159, JP-A-61-264160).
【0009】しかるに、最近の高強度化要求レベル(材
料強度の65〜80キロ化)に対応しようとすると、上
述した問題よりも一層複雑で解決困難な問題が発生した
のである。つまり、このような高い強度を要求される熱
延鋼板においては、C当量を余りに制限することは強度
確保の面から困難であり、また多少のTi添加では溶接部
の硬度上昇抑制効果が十分ではない。しかも、単純にTi
の添加量を増しただけではその効果が飽和してくる上
に、TiNの粗大化等による延性の劣化が生じて成形性の
低下が起こりやすい。更に、これら析出強化型の高強度
鋼板では、溶接端面から少し離れた溶接熱影響部におい
てTiCの固溶再析出による粗大化により軟化が生じ、そ
の軟化量は高強度であるほど大きくなるので、かえって
硬度分布が不均一となる。このような現象は、CrやNbを
添加して強化を図った鋼板の場合でも同様である。However, in order to meet the recent demand for higher strength (material strength of 65 to 80 kg), a problem that is more complicated and difficult to solve than the above problem has occurred. That is, in such a hot-rolled steel sheet that requires high strength, it is difficult to limit the C equivalent too much from the viewpoint of ensuring strength, and addition of a little Ti does not sufficiently suppress the increase in hardness of the welded portion. Absent. Moreover, simply Ti
If the addition amount of is increased, the effect is saturated, and the ductility is deteriorated due to coarsening of TiN and the moldability is likely to be deteriorated. Further, in these precipitation-strengthened high-strength steel sheets, softening occurs due to coarsening due to solid solution reprecipitation of TiC in the weld heat-affected zone slightly away from the weld end surface, and the softening amount increases as the strength increases, On the contrary, the hardness distribution becomes non-uniform. Such a phenomenon is the same as in the case of a steel plate strengthened by adding Cr or Nb.
【0010】しかも、相応の高強度が得られるように
C,Si,Mnを多くしたこの種の高強度鋼板では、従来の
引張強度50〜60kg/mm2以下の熱延鋼板の場合にはそ
れほど問題とならなかった“鋼板の電気抵抗値”や“鋼
板の焼入れ性”が非常に大きな問題となってくる。Moreover, in this type of high-strength steel sheet containing a large amount of C, Si and Mn so as to obtain a correspondingly high strength, it is not so much in the case of the conventional hot-rolled steel sheet having a tensile strength of 50 to 60 kg / mm 2. "Electrical resistance of steel sheet" and "hardenability of steel sheet", which did not pose a problem, become very serious problems.
【0011】なぜなら、C,Si,Mnの含有量が多いと鋼
板の電気抵抗値が大きくなるが、電気抵抗値が大きくな
ると溶接の際に大電流を流さなければならない。その結
果、部分的に発熱量が大きい面が溶け落ちて溶接でき
ず、また電流の量を減少させると十分に端面を加熱でき
ないために冷接と呼ばれる溶接不良を生じるという具合
に、最適溶接条件の範囲が狭くなって溶接条件の設定が
難しくなる。また、鋼板の焼入れ性が高くなると、溶接
してビ−ドリムをした後の冷却過程での冷却速度が早い
ために溶接部の硬度が非常に高くなってしまい、先程述
べたのと同様、加工途中で溶接端面から割れが生じた
り、また溶接端面から少し離れた溶接熱影響部では逆に
軟化が生じ、加工に際し軟化部分に応力の集中が起きて
ネッキングによる割れを発生する。This is because when the content of C, Si and Mn is large, the electric resistance value of the steel sheet becomes large, but when the electric resistance value becomes large, a large current must be passed during welding. As a result, the surface with a large amount of heat generation partially melts down and cannot be welded, and if the amount of current is reduced, the end face cannot be heated sufficiently, resulting in a welding defect called cold welding. The range becomes narrower and it becomes difficult to set the welding conditions. Further, when the hardenability of the steel sheet becomes high, the hardness of the welded portion becomes very high because the cooling rate in the cooling process after welding and forming the bead rim is fast, so that the workability is the same as described above. Cracks may occur from the weld end face on the way, or softening may occur in the weld heat affected zone, which is slightly away from the weld end face, and stress may concentrate in the softened portion during processing, causing cracking due to necking.
【0012】このうち、鋼板の最適溶接条件範囲につい
ては、“2段加圧”等の溶接条件の改善によりある程度
までカバ−できることが判明しており、このような溶接
条件の改善策について更なる研究も進められてはいる。
しかし、作業や製品性能の安定性,生産性等の面から最
適溶接条件範囲の広いことが望ましいことは言うまでも
ない。Among these, it has been found that the optimum welding condition range of the steel sheet can be covered to some extent by improving the welding condition such as "two-stage pressurization". Research is also underway.
However, it goes without saying that it is desirable to have a wide range of optimum welding conditions in terms of workability, stability of product performance, productivity, and the like.
【0013】溶接部の硬度分布については、“溶接端面
の硬度上昇量”と“溶接部近傍の溶接熱影響部での軟化
量”の両方が小さく、最高硬度と最低硬度の差がなるべ
く小さくてフラットな分布であることが必要なことは前
述した通りである。そして、本発明者等の調査によれ
ば、この“最高硬度と最低硬度との差”はビッカ−ス硬
さ(Hv)にて40以下であることが必要で、この条件
を満たしていないとその後の加工中に“軟化部でのネッ
キング割れ”や“軟化部と母材の境界で割れる二番割
れ”等が生じやすく、不良率が無視できなくなる。Regarding the hardness distribution of the welded portion, both "the amount of hardness increase at the weld end surface" and "the amount of softening in the weld heat affected zone near the welded portion" are small, and the difference between the maximum hardness and the minimum hardness is as small as possible. As described above, the flat distribution is required. According to a study by the present inventors, this “difference between the maximum hardness and the minimum hardness” needs to be 40 or less in Vickers hardness (Hv), and this condition is not satisfied. During subsequent processing, "necking cracks in the softened portion" and "second cracks that split at the boundary between the softened portion and the base material" tend to occur, and the defect rate cannot be ignored.
【0014】なお、パイプ用の厚鋼板等において溶接熱
影響部の軟化を抑えるためにMo,V等の添加が有効であ
るということは公知であるが、これらの変態強化元素は
添加するとC当量が上昇するので溶接部の硬度上昇が極
めて大きくなり、溶接部の硬度分布の不均一性を助長す
る。従って、D.C.バット溶接用鋼板への添加は不適切と
されている。It is known that the addition of Mo, V, etc. is effective for suppressing the softening of the weld heat affected zone in thick steel plates for pipes, etc. However, when these transformation strengthening elements are added, the C equivalent Is increased, the hardness of the welded part is extremely increased, which promotes non-uniformity in the hardness distribution of the welded part. Therefore, it is considered inappropriate to add it to the steel plate for DC butt welding.
【0015】また、鋼板を高強度化するためのその他の
手段として“制御冷却によって組織制御を行う方法”が
あるが、この種の鋼板は特に溶接熱影響部の軟化を生じ
やすく、しかも高強度であるほど軟化量が大きくなる傾
向があるため、自動車のホイ−ルリム用鋼板等の高強度
化法として採用するのは不適切である。Further, as another means for increasing the strength of the steel sheet, there is a "method of controlling the structure by controlled cooling". However, this type of steel sheet is particularly liable to cause softening in the weld heat affected zone and has a high strength. Since there is a tendency that the softening amount becomes larger as it is, it is inappropriate to adopt it as a method for strengthening steel plates for wheel rims of automobiles.
【0016】上述のように、現在の一般的な“65キロ
級以上の高強度を有する熱延鋼板”は最適溶接条件範囲
が極めて狭く、硬度分布も非常に不均一となる傾向が高
い等のため、自動車のホイ−ルリム用等としては適用に
問題があった。As described above, the current general "hot-rolled steel sheet having a high strength of 65 kg or more" has a very narrow range of optimum welding conditions, and the hardness distribution tends to be very uneven. Therefore, there is a problem in application as a wheel rim for automobiles.
【0017】その上、自動車のホイ−ルリム等では、成
形の後に化成処理(りん酸塩処理)が施こされ、その後
に塗装されるのが一般的であるため、それに供する材料
は化成処理性が良いことも要求される。ただ、この化成
処理性は熱延鋼板であると冷延鋼板に比べて多少劣りは
するものの、それほど問題になることはないとされてい
た。しかし、本発明者等の調査によると、鋼板の組成に
よっては化成処理性が極端に悪化し、ホイ−ルリム用等
としての適用が難しくなる場合のあることが判明した。In addition, in automobile wheel rims and the like, it is general that after the molding, a chemical conversion treatment (phosphate treatment) is applied and then a coating is applied. Is also required to be good. However, although this chemical conversion treatability is slightly inferior to that of cold-rolled steel sheets for hot-rolled steel sheets, it has been said that it does not pose such a problem. However, according to the investigation by the present inventors, it has been found that the chemical conversion treatment property is extremely deteriorated depending on the composition of the steel sheet, and it may be difficult to apply the composition for a wheel rim.
【0018】このようなことから、本発明が目的とした
のは、今後に望まれる自動車のホイ−ルリム用等として
も十分に満足できるところの、優れたD.C.バット溶接性
と溶接後加工性を示すと共に化成処理性も良好で、かつ
引張強度65kg/mm2以上の高強度熱延鋼板を安定提供で
きる手段を確立することであった。In view of the above, the object of the present invention is to provide excellent DC butt weldability and post-weld workability, which can be sufficiently satisfied for the wheel rims of automobiles which are desired in the future. It was to establish means for stably providing high-strength hot-rolled steel sheet having a tensile strength of 65 kg / mm 2 or more as well as good chemical conversion treatability.
【0019】[0019]
【課題を解決するための手段】本発明者は、上記目的を
達成すべく鋭意研究を行ったところ、「適量のTi,Nb及
びCrを複合添加し、 更にMo,V,Bを適量添加して高強
度熱延鋼板を構成すると、 高強度を確保しつつ溶接部の
硬度上昇と溶接熱影響部の軟化を同時に抑制することが
可能であり、 かつ溶接可能条件も現状の50〜60kg/m
m2級熱延鋼板に比べて実用上問題が生じるほどは狭くな
らない」との知見が得られた。Means for Solving the Problems The present inventor has conducted extensive studies to achieve the above-mentioned object and found that "adding appropriate amounts of Ti, Nb and Cr in combination, and further adding appropriate amounts of Mo, V and B. By constructing a high strength hot rolled steel sheet with high strength, it is possible to suppress the hardness increase of the weld zone and the softening of the heat affected zone at the same time while ensuring the high strength, and the welding possible condition is the current 50-60kg / m.
It is not narrow enough to cause practical problems compared to m 2 grade hot rolled steel sheets ”.
【0020】その上、これを基にした更なる検討によ
り、「上記熱延鋼板を製造するに際して熱延後の冷却に
簡単な制御冷却を適用すると得られる鋼板の性能が若干
向上する」ことや、「熱延鋼板の化成処理性が極端に悪
化するのは鋼板中に含まれる特定の元素(特にSi)の含
有量がある範囲に入った時であり、 優れた化成処理性を
確保するにはその成分範囲を避ける必要があるが、 実際
上は、 Si以外の他の元素の添加範囲を変更しなくてもSi
含有量さえ“0.2 ±0.04%”の範囲を除外するようにす
れば、 溶接性を阻害せずに所要化成処理性を維持するこ
とができる」ことを見出すことができた。Further, based on further studies based on this, it can be said that "when a simple controlled cooling is applied to the cooling after hot rolling in producing the hot rolled steel sheet, the performance of the obtained steel sheet is slightly improved". , "The chemical conversion treatability of hot-rolled steel sheets is extremely deteriorated when the content of a specific element (especially Si) contained in the steel sheet falls within a certain range, and in order to secure excellent chemical conversion treatability. Is necessary to avoid the range of its components, but in practice Si does not need to be changed without changing the range of addition of elements other than Si.
It was found that even if the content is excluded from the range of "0.2 ± 0.04%", the required chemical conversion treatability can be maintained without impairing the weldability.
【0021】本発明は、上記知見事項等に基づいて完成
されたものであり、「熱延鋼板の成分組成を、C:0.06
〜0.12%(以降、 成分割合を表す%は重量%とする),S
i:0.15%以下あるいは0.25〜0.45%, Mn:1.0 〜
2.0%,P:0.05%以下, S:0.005 %以下, C
r:0.10〜0.70%,Al:0.01〜0.05%, Ti:0.02〜0.0
8%, Nb:0.01〜0.06%,N:0.0015〜0.0080%を含
有すると共に、 更にMo:0.03〜 0.5%, V:0.03〜
0.5%, B:0.0002〜0.0050%の1種以上を含むか、
或いは更にCu:0.1 〜 0.5%, Ni:0.1 〜 0.5%の
2種を組合わせた成分、 並びにCa:0.0005〜 0.005%,
希土類元素:0.005 〜 0.015%の3者のうちの1種又
は2種以上をも含み、 残部がFe及び不可避的不純物から
成る如くに調整することによって、 引張強度65kg/mm2
以上の高強度を有し、 しかも優れたD.C.バット溶接性と
溶接後加工性並びに良好な化成処理性を備えしめた点」
に大きな特徴を有し、更には「上記成分組成の鋼片を仕
上温度850℃以上で熱間圧延し、 400〜550℃で
巻取った後、 脱スケ−ルすることによって、 引張強度6
5kg/mm2以上の高強度を有し、 しかも優れたD.C.バット
溶接性,溶接後加工性並びに良好な化成処理性を備えた
高強度熱延鋼板を安定に製造し得るようにした点」をも
特徴とするものである。The present invention has been completed based on the above-mentioned findings and the like. "The composition of components of a hot rolled steel sheet is C: 0.06
~ 0.12% (Hereafter,% representing the component ratio shall be% by weight), S
i: 0.15% or less or 0.25 to 0.45%, Mn: 1.0 to
2.0%, P: 0.05% or less, S: 0.005% or less, C
r: 0.10 to 0.70%, Al: 0.01 to 0.05%, Ti: 0.02 to 0.0
8%, Nb: 0.01 to 0.06%, N: 0.0015 to 0.0080%, Mo: 0.03 to 0.5%, V: 0.03 to
0.5%, B: 0.0002 to 0.0050%, or more,
Or, in addition, Cu: 0.1-0.5%, Ni: 0.1-0.5%, a combination of two components, and Ca: 0.0005-0.005%,
Rare earth element: 0.005 to 0.015% One or two or more of the three are included, and the balance is adjusted to consist of Fe and inevitable impurities. Tensile strength 65kg / mm 2
It has the above high strength, and has excellent DC butt weldability, post-weld workability, and good chemical conversion treatment. "
In addition, "a steel slab having the above composition is hot-rolled at a finishing temperature of 850 ° C or higher, wound at 400 to 550 ° C, and then descaled to obtain a tensile strength of 6
It has a high strength of 5 kg / mm 2 or more, and is capable of stably producing high-strength hot-rolled steel sheets with excellent DC butt weldability, post-weld workability, and good chemical conversion treatment ”. Is also a feature.
【0022】[0022]
【作用】このように、本発明は、高強度熱延鋼板の製造
に当り、微細に析出するTiNの作用によって溶接部の硬
度上昇を抑制すべく適量のTiの添加を行い、また溶接熱
影響部の軟化を抑えるためにMo,V,Bのうちの1種又
は2種以上を適量添加すると共に、更にNb及びCrをTiと
複合添加することによって、TiNの溶接部の硬度上昇抑
制作用をTi高添加範囲まで強化維持しつつ、しかも軟化
防止のために添加されたMo,V,Bの溶接部硬度上昇作
用を相殺することで溶接部付近の硬度分布の均一化・平
坦化を図り、これによってD.C.バット溶接性及びD.C.バ
ット溶接後の加工性を改善すると共に、Si含有量の適切
な規制によって良好な化成処理性をも兼備した高強度熱
延鋼板を得ようというものであるが、以下、本発明にお
いて熱延鋼板の成分組成、更には製造条件を前記の如く
に限定した理由をより詳細に説明する。As described above, according to the present invention, in producing a high-strength hot-rolled steel sheet, an appropriate amount of Ti is added to suppress an increase in hardness of the welded portion by the action of finely precipitated TiN, and the effect of welding heat is also exerted. In order to suppress the softening of the welded portion, one or more of Mo, V, and B are added in an appropriate amount, and Nb and Cr are added in combination with Ti to suppress the increase in hardness of the welded portion of TiN. While strengthening and maintaining up to the high Ti addition range, by offsetting the weld hardness increasing action of Mo, V, and B added to prevent softening, the hardness distribution near the weld is made uniform and flat, While improving DC butt weldability and workability after DC butt welding by this, it is intended to obtain a high-strength hot-rolled steel sheet that also has good chemical conversion treatability by appropriate regulation of the Si content, Hereinafter, in the present invention, the composition of the hot rolled steel sheet, further The reason for limiting the production conditions as of the will be described in more detail.
【0023】A) 成分割合 〈C〉Cは、必要とする強度を鋼板に確保するのに不可
欠な成分であって、しかも安価な元素である。そして、
C含有量が0.06%未満であると強度確保を他の強化元素
の多量添加により補わなければならず極めて不経済であ
る。一方、鋼板の強度確保をCに頼り過ぎて0.12%を超
える量のCを含有させると、パ−ライト部分が増加して
延性の劣化が顕著になると共に靱性の低下を招き、更に
は溶接部の硬度上昇が抑制できなくなる。従って、C含
有量は0.06〜0.12%と定めたが、出来ればC含有量は0.
10%を超えないように調整するのが望ましい。A) Component ratio <C> C is an essential component for ensuring the required strength of the steel sheet and is an inexpensive element. And
If the C content is less than 0.06%, securing the strength must be supplemented by adding a large amount of other strengthening elements, which is extremely uneconomical. On the other hand, if too much C is used to secure the strength of the steel sheet and C is contained in an amount exceeding 0.12%, the pearlite portion increases, the ductility deteriorates significantly, and the toughness decreases, and further the welded portion The increase in hardness cannot be suppressed. Therefore, the C content was set to 0.06 to 0.12%, but if possible, the C content should be 0.
It is desirable to adjust it so that it does not exceed 10%.
【0024】〈Si〉Siは、溶接過程で酸化し溶接端面に
おいてペネトレ−タ−となって溶接不良を起こしやすく
する元素であり、フラッシュバット溶接を行う場合には
添加を控える必要のある元素であったが、D.C.バット溶
接ではそこまでの影響はない。むしろ、他の元素に比べ
て延性を低下させずに強度を上昇させる効果が大きいこ
とから、むしろ積極的に添加を図りたい元素である。し
かし、Siには電気抵抗値を上昇させて“溶接電流の適切
範囲”の上限を下げる作用があり、またフラッシュバッ
ト溶接ほどではないものの、多量に含有されるとやはり
ペネトレ−タ−の原因となって溶接不良率が上昇する。
そこで、このような問題を避けるためにはSi含有量を0.
45%以下、好ましくは0.05〜 0.2%程度に調整するのが
良いと言える。しかしながら、前述したように、化成処
理性を考慮すると 0.2±0.04%の範囲は避ける必要があ
る。ここで、Siが 0.2%前後で化成処理性が極端に悪く
なる理由は、Si単独での特定範囲での特異現象か、ある
いは他の元素との相互作用によるものかは明らかではな
いが、この範囲を除外すれば他の元素の添加範囲を変更
しなくても、溶接性等の特性を阻害することなく化成処
理性を問題のないレベルに保つことが可能となる。従っ
て、Si含有量については「0.15%以下」又は「0.25〜0.
45%」と定めた。<Si> Si is an element that oxidizes during the welding process and becomes a penetrator at the weld end face to easily cause defective welding. It is an element that should be refrained from addition when performing flash butt welding. However, DC butt welding has no such effect. Rather, it is an element to be positively added because it has a greater effect of increasing the strength without lowering the ductility as compared with other elements. However, Si has the effect of raising the electric resistance value and lowering the upper limit of the “appropriate range of welding current”, and although not as much as flash butt welding, if it is contained in a large amount, it still causes the penetrator. As a result, the defective welding rate increases.
Therefore, in order to avoid such problems, the Si content should be 0.
It can be said that it should be adjusted to 45% or less, preferably about 0.05 to 0.2%. However, as mentioned above, it is necessary to avoid the range of 0.2 ± 0.04% considering the chemical conversion treatability. Here, it is not clear whether the reason why the chemical conversion treatability becomes extremely poor when Si is around 0.2% is due to the peculiar phenomenon in the specific range of Si alone or the interaction with other elements. If the range is excluded, it becomes possible to maintain the chemical conversion treatability at a level without any problem without hindering the characteristics such as weldability without changing the range of addition of other elements. Therefore, the Si content is `` 0.15% or less '' or `` 0.25 to 0.
45% ”.
【0025】〈Mn〉Mnは、溶鋼中に不可避的不純物とし
て含まれるSを固定してその有害作用を低減させると共
に、Cと同様に鋼板の強度を確保するために必要な成分
であり、他の強化元素の添加量にもよるが、60kg/mm2
以上の引張強度を得るためには 1.0%以上含有させる必
要がある。しかし、Mnに頼り過ぎて 2.0%を超える量の
Mnを含有させると溶接性や加工性の劣化が無視できなく
なる上、コストアップにもつながる。従って、Mn含有量
は 1.0〜 2.0%と定めたが、出来ればMn含有量は 1.8%
を超えないように調整するのが望ましい。<Mn> Mn is a component necessary for fixing S contained in molten steel as an unavoidable impurity to reduce its harmful effect and to secure the strength of the steel sheet as with C. 60kg / mm 2 depending on the amount of the strengthening element added
To obtain the above tensile strength, it is necessary to contain 1.0% or more. However, if you rely on Mn too much,
When Mn is contained, deterioration of weldability and workability cannot be ignored, and also leads to cost increase. Therefore, the Mn content was set to 1.0-2.0%, but if possible, the Mn content should be 1.8%.
It is desirable to adjust so that it does not exceed.
【0026】〈P〉Pは、一般的な高張力鋼板を製造す
る場合には延性をそれほど低下させずに強度を上昇でき
る重要な成分となるが、溶接性を考慮した鋼板において
は、溶接時の溶融凝固の際に粒界偏析を生じて脆化を引
き起し溶接部不良の原因となる有害な元素である。その
ため、本発明鋼板ではP含有量は低いほど望ましい。た
だ、本発明では鋼の製造コスト面をも考慮して“不可避
的不純物としてのP”の許容上限を0.05%と定めたが、
より良好な溶接性を確保するにはP含有量を0.03%以下
に抑えるのが望ましい。<P> P is an important component that can increase the strength without significantly lowering the ductility in the case of producing a general high-strength steel plate. Is a harmful element which causes segregation at the grain boundaries during melting and solidification to cause embrittlement and cause defective welds. Therefore, in the steel sheet of the present invention, the lower the P content, the more desirable. However, in the present invention, the allowable upper limit of "P as an unavoidable impurity" is set to 0.05% in consideration of the manufacturing cost of steel.
In order to secure better weldability, it is desirable to keep the P content at 0.03% or less.
【0027】〈S〉Sは鋼板中へ不可避的に混入する不
純物元素であり、“製造工程でのヘゲ疵”や“母材もし
くは溶接材を成形する際の割れ”の原因となる介在物
(MnS)を増大させるので、鋼板の用途にもよるがS含
有量はなるべく低くしなければならない。そして、特
に、優れた溶接後加工性を示し、例えば自動車のホイ−
ルリム用に適用した場合でも不良率を低く抑え得るよう
にするには、鋼板中のS含有量は0.005 %以下に規制す
る必要がある。<S> S is an impurity element that is inevitably mixed in the steel sheet, and it is an inclusion that causes "heavy flaws in the manufacturing process" and "cracking during the forming of the base material or the welding material". Since (MnS) is increased, the S content should be as low as possible depending on the application of the steel sheet. And, in particular, it shows excellent workability after welding, for example, the wheel of an automobile.
Even if it is applied to rulim, it is necessary to regulate the S content in the steel sheet to 0.005% or less in order to keep the defect rate low.
【0028】〈Cr〉Crは、CやMnと同様に鋼板の強度を
確保するのに必要な元素であり、またTi及びNbとの複合
添加によって溶接後の硬度分布均一化に寄与する成分で
ある。そして、本発明が狙いとするような優れた溶接性
と加工性を備え、しかも65kg/mm2以上の引張強度を得
るためには0.10%以上のCr含有量を確保する必要があ
る。しかし、CrはMnと同様に溶接部の硬度上昇作用が大
きな元素であり、多量に添加すると前述した複合添加の
効果が薄れてくる上、添加量が増大してくると強度の上
昇効果が飽和してくると共に延性の劣化比率が増大して
くる。従って、Cr含有量の上限を0.70%と定めた。な
お、Cr含有量の特に好ましい範囲は0.30〜0.60%であ
る。<Cr> Cr is an element necessary to secure the strength of the steel sheet like C and Mn, and is a component that contributes to the uniform hardness distribution after welding by the combined addition of Ti and Nb. is there. Then, in order to have excellent weldability and workability as aimed at by the present invention and to obtain a tensile strength of 65 kg / mm 2 or more, it is necessary to secure a Cr content of 0.10% or more. However, like Mn, Cr is an element that has a large effect of increasing the hardness of the welded part, and adding a large amount diminishes the effect of the above-described composite addition, and when the addition amount increases, the strength increasing effect saturates. As the temperature rises, the deterioration rate of ductility increases. Therefore, the upper limit of the Cr content is set to 0.70%. A particularly preferable range of Cr content is 0.30 to 0.60%.
【0029】〈Al〉Alは鋼の脱酸のために添加され、酸
化によって失われがちなTiの歩留低下を抑えたり、延性
を悪化させる鋼中非金属介在物(酸化物)の生成を抑制
する働きを行う。また、常温時効を起こす原因となって
延性に悪影響を及ぼすNを、AlNとして固定する作用も
ある。しかし、Al含有量が0.01%未満であると上記作用
による所望の効果が得られず、一方、0.05%を超えて含
有させると材料コストが上昇することに加え、 Al2O3
等の介在物が増加して延性の劣化やヘゲと呼ばれる表面
欠陥の原因となることから、Al含有量は0.01〜0.05%と
定めた。<Al> Al is added for deoxidizing the steel and suppresses the reduction in the yield of Ti, which tends to be lost by oxidation, and the formation of non-metallic inclusions (oxides) in the steel which deteriorates the ductility. It works to suppress. It also has a function of fixing N as AlN, which causes aging at room temperature and adversely affects ductility. However, if the Al content is less than 0.01%, the desired effect due to the above-mentioned action cannot be obtained, while if it exceeds 0.05%, the material cost is increased, and Al 2 O 3 is added.
Since the inclusions such as lead to deterioration of ductility and surface defects called hegging, the Al content was set to 0.01 to 0.05%.
【0030】〈Ti〉Tiは、微細なTiNを析出させること
により鋼板強度を上昇させると共に、溶接時におけるフ
ェライト粒の発生核となって硬質相の生成を抑制し、ま
た粒成長による軟化を抑える作用を発揮する成分であ
る。しかし、その含有量が0.02%未満であると上記作用
による所望の効果が得られず、一方、Ti含有量が多くな
り過ぎるとTiNが粗大化し、析出数が減少して逆に上記
効果が不十分となる。そして、このような理由からTiの
単独添加の場合にはその含有量を0.04%以下に抑えなけ
ればならないが、NbやCrが複合添加されている本発明鋼
板の場合にはその上限値が拡張し、0.08%までは前記効
果が持続する。この原因については明らかではないが、
複合添加されるこれらの元素とN,Cの析出物間に何ら
かの相互作用が働くことによるものか、或いはこれらの
元素間で複合析出物が生成するためではないかと考えら
れる。従って、Ti含有量は0.02〜0.08%と定めたが、よ
り好ましい範囲は0.03〜0.07%である。<Ti> Ti increases the strength of the steel sheet by precipitating fine TiN, serves as a nucleus for the generation of ferrite grains during welding, suppresses the generation of hard phase, and suppresses softening due to grain growth. It is a component that exerts its action. However, if the content is less than 0.02%, the desired effect due to the above-mentioned action cannot be obtained, while if the Ti content becomes too large, TiN becomes coarse and the number of precipitations decreases, and conversely the above-mentioned effect is not obtained. Will be enough. And, for such a reason, in the case of adding Ti alone, its content must be suppressed to 0.04% or less, but in the case of the steel sheet of the present invention in which Nb and Cr are added in combination, its upper limit value is expanded. However, the effect continues until 0.08%. The reason for this is not clear,
It is considered that this is due to some interaction between these elements to be added in complex and the precipitates of N and C, or because of the formation of complex precipitates between these elements. Therefore, the Ti content is set to 0.02 to 0.08%, but a more preferable range is 0.03 to 0.07%.
【0031】〈Nb〉Nbは、通常の高強度鋼板の場合には
NbC等の析出強化を期待して添加される元素であるが、
本発明においては、Cr及びTiと複合添加されることによ
り溶接部の硬度上昇を抑制しつつ溶接熱影響部の軟化を
抑える効果を奏せしめるために添加される。しかしなが
ら、Nb含有量が0.01%未満であると前記効果が得られ
ず、一方、0.06%を超えて含有させるとその効果が飽和
し始め、材料コスト上昇の割りには性能向上が低くなる
ことから、Nb含有量は0.01〜0.06%と定めたが、より好
ましい範囲は0.02〜0.05%である。<Nb> Nb is an ordinary high strength steel plate
It is an element added with the expectation of precipitation strengthening such as NbC.
In the present invention, Cr and Ti are added in combination in order to exert the effect of suppressing the softening of the heat-affected zone of the weld while suppressing the increase in the hardness of the weld. However, if the Nb content is less than 0.01%, the above effect cannot be obtained, while if the Nb content exceeds 0.06%, the effect begins to saturate, and the performance improvement becomes low despite the increase in material cost. , Nb content was set to 0.01 to 0.06%, but a more preferable range is 0.02 to 0.05%.
【0032】〈N〉Nは、TiN,NbNとして微細析出す
ることで鋼板強度を上昇させると共に、溶接時における
フェライト粒の発生核となるので硬質相の生成を抑制
し、また粒成長による軟化を抑える作用を発揮する成分
である。しかし、その含有量が0.0015%未満であると前
記作用に所望の効果が得られず、一方、0.0080%を超え
て含有らせるとTi,Al,Nbで固定できなくなって鋼板の
時効性が劣化するようになることから、N含有量は0.00
15〜0.0080%と定めた。<N> N finely precipitates as TiN and NbN to increase the strength of the steel sheet, and serves as a nucleus for the generation of ferrite grains during welding, thus suppressing the formation of a hard phase and softening due to grain growth. It is a component that exerts a suppressing effect. However, if its content is less than 0.0015%, the desired effect cannot be obtained, while if it exceeds 0.0080%, it cannot be fixed with Ti, Al, Nb and the aging property of the steel sheet deteriorates. Therefore, the N content is 0.00
It was set at 15 to 0.0080%.
【0033】〈Mo,V,B〉通常、これらの元素は鋼の
強度向上や焼入れ性を高めて溶接部の軟化を防止するた
めに添加されるが、溶接部の硬度上昇作用が大きな元素
でもあり、例えばホイ−ルリム用高強度鋼板への多量添
加は硬度分布の不均一を引き起こす恐れが大きいので、
特にD.C.バット溶接法を用いる鋼板への添加は殆ど行わ
れていない。しかし、本発明に係る組成の鋼板では、こ
れらの添加を行っても溶接部の硬度上昇がそれほど大き
くなく、溶接熱影響部が軟化するのを抑制する効果と強
度向上効果を支障なく得ることができる。この理由は明
らかではないが、前述したようなCr,Ti,Nbの複合添加
によって生じる析出物が関連した相乗作用によるものと
考えられる。そして、上記効果はMo,V,Bの単独添加
又は2種以上の複合添加の何れによっても得られるが、
Mo,Vでは0.03%未満、またBでは0.0002%未満の含有
量であると効果が顕著ではなく、一方、Mo,Vでは 0.5
%、Bでは0.0050%を超えて含有させても効果が飽和し
てコストが増すばかりとなる。従って、Mo含有量につい
ては0.03〜 0.5%(好適範囲0.03〜 0.2%)、V含有量
についても0.03〜 0.5%(好適範囲0.03〜 0.2%)、B
含有量については0.0002〜0.0050%(好適範囲0.0005〜
0.001%)と定めた。<Mo, V, B> Usually, these elements are added in order to improve the strength and hardenability of steel and prevent softening of the welded portion, but even elements having a large effect of increasing the hardness of the welded portion. Yes, for example, since a large amount of addition to a high-strength steel sheet for wheel rims may cause uneven hardness distribution,
In particular, it has hardly been added to steel plates using the DC butt welding method. However, in the steel sheet having the composition according to the present invention, the hardness increase of the welded portion is not so large even if these additions are performed, and the effect of suppressing the softening of the weld heat affected zone and the strength improving effect can be obtained without any trouble. it can. The reason for this is not clear, but it is considered to be due to the synergistic action related to the precipitates generated by the combined addition of Cr, Ti, and Nb as described above. The above effect can be obtained by adding Mo, V, or B alone or by adding two or more kinds in combination.
If the content of Mo and V is less than 0.03% and the content of B is less than 0.0002%, the effect is not remarkable, while the content of Mo and V is 0.5.
%, B, even if the content exceeds 0.0050%, the effect is saturated and the cost only increases. Therefore, the Mo content is 0.03 to 0.5% (preferable range 0.03 to 0.2%), and the V content is 0.03 to 0.5% (preferable range 0.03 to 0.2%).
About content 0.0002-0.0050% (suitable range 0.0005-
0.001%).
【0034】〈Cu,Ni〉Cu,Niは鋼板の耐食性を向上さ
せる作用を有しているため必要により添加される成分で
ある。このうちCuは安価であることからNiに優先して使
用したい成分であるが、Cuを単独添加した場合には“Cu
チェッキング疵”を発生するので、Cuは必ずNiと複合で
添加する必要がある。そして、Cu,Niの含有量が何れも
0.1%未満では効果が十分でなく、一方、何れの場合も
0.5%を超えて含有させる必要はないことから、Cu,Ni
含有量は何れも 0.1〜 0.5%と定めた。<Cu, Ni> Cu and Ni have a function of improving the corrosion resistance of the steel sheet, and are added as necessary. Of these, Cu is a component that we want to use in preference to Ni because it is cheap, but when Cu is added alone,
Since it causes "checking flaws", it is necessary to add Cu in combination with Ni.
If it is less than 0.1%, the effect is not sufficient, while in any case
Since it is not necessary to contain more than 0.5%, Cu, Ni
The content was set to 0.1 to 0.5% in all cases.
【0035】〈Ca,希土類元素〉Ca,希土類元素(RE
M)には何れも硫化物系介在物を球状化して無害化し、
加工性、特に伸びフランジ性を向上させる作用があるた
め、必要により単独又は複合で添加される成分である
が、Caが0.0005%未満、そして希土類元素の場合には
0.005%未満の含有量では上記効果が十分でなく、一
方、Caの場合には 0.005%を、そして希土類元素では
0.015%を超えて含有させてもその効果が飽和してしま
うばかりか、かえって酸化物系介在物が増加して鋼の清
浄度が悪くなり延性や加工性が劣化する。従って、Ca含
有量は0.0005〜 0.005%、また希土類元素含有量につい
ては 0.005〜 0.015%とそれぞれ定めた。<Ca, rare earth element> Ca, rare earth element (RE
In M), the sulfide-based inclusions are made spherical to make them harmless,
Since it has the effect of improving workability, especially stretch flangeability, it is a component added alone or in combination as necessary, but in the case of Ca less than 0.0005% and rare earth element
If the content is less than 0.005%, the above effect is not sufficient, while for Ca, 0.005% and for rare earth elements
Even if the content exceeds 0.015%, not only the effect is saturated, but also the oxide inclusions increase and the cleanliness of the steel deteriorates and the ductility and workability deteriorate. Therefore, the Ca content was set to 0.0005 to 0.005%, and the rare earth element content was set to 0.005 to 0.015%.
【0036】B) 製造条件 本発明に係る鋼板は、通常の熱延条件に従って製造され
た場合でも実用上問題のない性能が付与されるが、熱間
圧延の仕上温度については、TiCの析出強化をより有効
に活用できることから850℃以上とするのが良い。な
お、仕上温度の上限については特に制限する理由はない
が、930℃程度で十分である。B) Manufacturing conditions The steel sheet according to the present invention is given practically no problem even when manufactured according to ordinary hot rolling conditions. However, regarding the finishing temperature of hot rolling, precipitation strengthening of TiC It is preferable to set the temperature to 850 ° C. or higher because it can be used more effectively. The upper limit of the finishing temperature is not particularly limited, but about 930 ° C is sufficient.
【0037】また、巻取温度は低目に設定し、若干の制
御冷却を行った方が硬度分布が均一になる傾向がある。
これは、巻取温度を低目とすることにより“巻取りまで
の冷却により生じた硬質組織が溶接の熱影響によって軟
化する反応",“巻取りまでの冷却によって析出せずに固
溶していたMo,V等の析出によって生じる2次硬化作
用”及び“前述した硬度均一化作用”とが相乗され、溶
接部の硬度上昇と溶接熱影響部の軟化をより抑制する方
向に働くためと考えられる。The hardness distribution tends to be more uniform when the winding temperature is set low and a little controlled cooling is performed.
This is because when the coiling temperature is set low, the reaction that the hard structure generated by cooling up to coiling softens due to the heat effect of welding, and "the solid structure does not precipitate due to cooling up to coiling and does not precipitate. It is considered that the "secondary hardening effect caused by the precipitation of Mo, V, etc." and the "hardness homogenizing effect described above" are synergistically exerted in the direction of further suppressing the hardness increase of the weld zone and the softening of the weld heat affected zone. To be
【0038】この場合、巻取温度が550℃を上回ると
上記効果を十分に享受することができず、一方、400
℃を下回る温度で巻取ったとしても効果のより一層の向
上は見られない。なお、熱間圧延が終了してから巻取る
までの間の冷却速度は、平均冷却速度で15℃/s以上と
するのが良い。In this case, if the winding temperature exceeds 550 ° C., the above effect cannot be fully enjoyed, while 400
Even when wound at a temperature below 0 ° C, the effect is not further improved. The cooling rate from the end of hot rolling to the winding is preferably 15 ° C./s or more in average cooling rate.
【0039】勿論、素材鋼の組成に関する条件を除く熱
延鋼板の製造条件が必ずしも前記範囲に入っていなくて
も、余程かけ離れた条件で製造を行わない限りは実用上
それ程問題となるような特性不良は生じず、上述した製
造条件は、これを満たすと特性の若干の向上,均一化,
安定化が達成できる好適範囲を示すものと言えなくもな
い。Of course, even if the manufacturing conditions of the hot-rolled steel sheet excluding the conditions relating to the composition of the raw steel do not always fall within the above-mentioned range, it will be a serious problem in practice as long as the manufacturing conditions are not so far apart. Characteristic defects do not occur, and if the above manufacturing conditions are satisfied, the characteristics will be slightly improved, uniformed,
It cannot be said that it shows a preferable range in which stabilization can be achieved.
【0040】次いで、本発明を実施例により説明する。Next, the present invention will be described with reference to examples.
【実施例】まず、常法に従って表1及び表2に示す成分
組成の鋼片を溶製した。Example First, steel pieces having the composition shown in Tables 1 and 2 were melted according to a conventional method.
【0041】[0041]
【表1】 [Table 1]
【0042】[0042]
【表2】 [Table 2]
【0043】続いて、これら鋼片を加熱後、仕上温度が
850〜950℃の間となる熱間圧延を施し、熱間圧延
終了後は表3に示す巻取り温度にまで水冷してから巻取
りを行った。次に、上記巻取り後の各鋼板に 0.5〜1%
の調質圧延を施し、通常の塩酸による酸洗(脱スケ−
ル)を行って製品鋼板(2.6mm厚) とした。Subsequently, after heating these steel slabs, hot rolling was performed so that the finishing temperature was between 850 and 950 ° C., and after the hot rolling was completed, the steel was cooled to the winding temperature shown in Table 3 and then wound. I took it. Next, 0.5 to 1% on each steel plate after winding
Tempered and then pickled with normal hydrochloric acid (descaling
) To obtain a product steel plate (2.6 mm thick).
【0044】[0044]
【表3】 [Table 3]
【0045】そして、このようにして製造された各熱延
鋼板からJIS5号引張試験片を採取して引張強度の測
定を行い、また、これらの熱延鋼板を小型溶接機により
ラボD.C.バット溶接したサンプルについて、ロ−ラ−曲
げ試験(試験片幅160mm)と硬度分布測定(Hv 5k
g)を実施した。更に、各熱延鋼板について化成処理性
の評価も行った。Then, JIS No. 5 tensile test pieces were sampled from each of the hot-rolled steel sheets thus produced to measure the tensile strength, and these hot-rolled steel sheets were lab DC butt welded by a small welding machine. Roller bending test (test piece width 160 mm) and hardness distribution measurement (Hv 5k)
g) was carried out. Further, the chemical conversion treatability of each hot rolled steel sheet was also evaluated.
【0046】これらの結果を表3に併せて示す。なお、
化成処理性の評価は、各熱延鋼板から切り出した試験片
をりん酸亜鉛処理液(PBL-3080:日本パ−カライジング
社商品名)に120秒間浸漬し、その時のりん酸亜鉛皮
膜の形成状態を観察して行ったが、その評価結果は ◎: 全く問題なし, ○: 一部に微小スケ部分があるが問題なし, △: スケ部あり, ×: かなり大きなスケ部分あり で表示した。The results are also shown in Table 3. In addition,
The evaluation of the chemical conversion treatability was carried out by immersing the test pieces cut from each hot-rolled steel sheet in a zinc phosphate treatment solution (PBL-3080: a product name of Nippon Parkerizing Co., Ltd.) for 120 seconds to form a zinc phosphate film at that time. The condition was observed, and the evaluation results were as follows: ⊚: No problem at all, ∘: No problem although there was a small scale part, △: Scaling part, ×: Significantly large part.
【0047】表3に示される結果からも、本発明に係る
熱延鋼板は65kg/mm2以上の高い引張強度を有し、しか
も溶接部の曲げ割れ長さ率が低く、ΔHv の値が小さい
ことが明らかである。また、化成処理性にも問題のない
ことが分かる。従って、本発明に係る熱延鋼板は、例え
ば要求性能がより厳しくなってきた自動車のホイ−ルリ
ム材としても十分に満足できる強度,D.C.バット溶接
性,溶接後の加工性並びに化成処理性を兼備するもので
あることが確認できる。これに対して、成分組成が本発
明で規定する条件を満たしていない比較鋼板では、強度
的には高い値が得られるが、D.C.バット溶接性,溶接後
の加工性あるいは化成処理性面での特性が十分でない。The results shown in Table 3 also show that the hot-rolled steel sheet according to the present invention has a high tensile strength of 65 kg / mm 2 or more, a low bending crack length ratio in the welded portion, and a small ΔHv value. It is clear. Further, it can be seen that there is no problem in chemical conversion processability. Therefore, the hot-rolled steel sheet according to the present invention has sufficient strength, DC butt weldability, workability after welding, and chemical conversion treatability, which can be sufficiently satisfied, for example, as a wheel rim material for automobiles whose performance has become more severe. It can be confirmed that it does. On the other hand, in the comparative steel sheet whose composition does not satisfy the conditions specified in the present invention, a high value is obtained in terms of strength, but in terms of DC butt weldability, workability after welding or chemical conversion treatability. The characteristics are not sufficient.
【0042】[0042]
【効果の総括】以上に説明した如く、本発明によれば、
引張強度65kg/mm2以上の高強度と優れたD.C.バット溶
接性,溶接後加工性及び化成処理性とを兼備した高強度
熱延鋼板を安定提供することが可能となり、自動車用ホ
イ−ルリムを始めとする各種部材の性能向上に大きく寄
与できるなど、産業上有用な効果がもたらされる。[Summary of Effects] As described above, according to the present invention,
It is possible to stably provide high-strength hot-rolled steel sheets with high strength of 65 kg / mm 2 or more and excellent DC butt weldability, post-weld workability, and chemical conversion treatability. Industrially useful effects are brought about, such as being able to greatly contribute to improving the performance of various members including the beginning.
Claims (9)
0.15%以下, Mn:1.0 〜2.0 %,P:0.05%以
下, S:0.005 %以下, Cr:0.10〜0.70%,A
l:0.01〜0.05%, Ti:0.02〜0.08%, Nb:0.01
〜0.06%,N:0.0015〜0.0080%を含有すると共に、更
にMo:0.03〜 0.5%, V:0.03〜 0.5%, B:0.
0002〜0.0050%の1種以上をも含み、残部がFe及び不可
避的不純物からなることを特徴とする、D.C.バット溶接
性及び溶接後の加工性に優れると共に化成処理性の良好
な高強度熱延鋼板。1. A weight ratio of C: 0.06 to 0.12%, Si:
0.15% or less, Mn: 1.0 to 2.0%, P: 0.05% or less, S: 0.005% or less, Cr: 0.10 to 0.70%, A
l: 0.01 to 0.05%, Ti: 0.02 to 0.08%, Nb: 0.01
.About.0.06%, N: 0.0015 to 0.0080%, Mo: 0.03 to 0.5%, V: 0.03 to 0.5%, B: 0.
002 to 0.0050% of one or more, the balance consisting of Fe and inevitable impurities, DC butt weldability and workability after welding are excellent, and high strength hot rolling with good chemical conversion treatability. steel sheet.
0.25〜0.45%, Mn:1.0 〜2.0 %,P:0.05%以
下, S:0.005 %以下, Cr:0.10〜0.70%,A
l:0.01〜0.05%, Ti:0.02〜0.08%, Nb:0.01
〜0.06%,N:0.0015〜0.0080%を含有すると共に、更
にMo:0.03〜 0.5%, V:0.03〜 0.5%, B:0.
0002〜0.0050%の1種以上をも含み、残部がFe及び不可
避的不純物からなることを特徴とする、D.C.バット溶接
性及び溶接後の加工性に優れると共に化成処理性の良好
な高強度熱延鋼板。2. A weight ratio of C: 0.06 to 0.12%, Si:
0.25 to 0.45%, Mn: 1.0 to 2.0%, P: 0.05% or less, S: 0.005% or less, Cr: 0.10 to 0.70%, A
l: 0.01 to 0.05%, Ti: 0.02 to 0.08%, Nb: 0.01
.About.0.06%, N: 0.0015 to 0.0080%, Mo: 0.03 to 0.5%, V: 0.03 to 0.5%, B: 0.
002 to 0.0050% of one or more, the balance consisting of Fe and inevitable impurities, DC butt weldability and workability after welding are excellent, and high strength hot rolling with good chemical conversion treatability. steel sheet.
0.15%以下, Mn:1.0 〜2.0 %,P:0.05%以
下, S:0.005 %以下, Cr:0.10〜0.70%,A
l:0.01〜0.05%, Ti:0.02〜0.08%, Nb:0.01
〜0.06%,N:0.0015〜0.0080%, Cu:0.1 〜 0.5
%, Ni:0.1 〜 0.5%を含有すると共に、更にMo:0.
03〜 0.5%, V:0.03〜 0.5%, B:0.0002〜0.
0050%の1種以上をも含み、残部がFe及び不可避的不純
物からなることを特徴とする、D.C.バット溶接性及び溶
接後の加工性に優れると共に化成処理性の良好な高強度
熱延鋼板。3. A weight ratio of C: 0.06 to 0.12%, Si:
0.15% or less, Mn: 1.0 to 2.0%, P: 0.05% or less, S: 0.005% or less, Cr: 0.10 to 0.70%, A
l: 0.01 to 0.05%, Ti: 0.02 to 0.08%, Nb: 0.01
~ 0.06%, N: 0.0015 ~ 0.0080%, Cu: 0.1 ~ 0.5
%, Ni: 0.1-0.5%, and further Mo: 0.
03-0.5%, V: 0.03-0.5%, B: 0.0002-0.
A high-strength hot-rolled steel sheet excellent in DC butt weldability and workability after welding, and having good chemical conversion treatability, characterized in that it also contains at least one of 50% and the balance is Fe and inevitable impurities.
0.25〜0.45%, Mn:1.0 〜2.0 %,P:0.05%以
下, S:0.005 %以下, Cr:0.10〜0.70%,A
l:0.01〜0.05%, Ti:0.02〜0.08%, Nb:0.01
〜0.06%,N:0.0015〜0.0080%, Cu:0.1 〜 0.5
%, Ni:0.1 〜 0.5%を含有すると共に、更にMo:0.
03〜 0.5%, V:0.03〜 0.5%, B:0.0002〜0.
0050%の1種以上をも含み、残部がFe及び不可避的不純
物からなることを特徴とする、D.C.バット溶接性及び溶
接後の加工性に優れると共に化成処理性の良好な高強度
熱延鋼板。4. A weight ratio of C: 0.06 to 0.12%, Si:
0.25 to 0.45%, Mn: 1.0 to 2.0%, P: 0.05% or less, S: 0.005% or less, Cr: 0.10 to 0.70%, A
l: 0.01 to 0.05%, Ti: 0.02 to 0.08%, Nb: 0.01
~ 0.06%, N: 0.0015 ~ 0.0080%, Cu: 0.1 ~ 0.5
%, Ni: 0.1-0.5%, and further Mo: 0.
03-0.5%, V: 0.03-0.5%, B: 0.0002-0.
A high-strength hot-rolled steel sheet excellent in DC butt weldability and workability after welding, and having good chemical conversion treatability, characterized in that it also contains at least one of 50% and the balance is Fe and inevitable impurities.
0.15%以下, Mn:1.0 〜2.0 %,P:0.05%以
下, S:0.005 %以下, Cr:0.10〜0.70%,A
l:0.01〜0.05%, Ti:0.02〜0.08%, Nb:0.01
〜0.06%,N:0.0015〜0.0080%を含有すると共に、更
にMo:0.03〜 0.5%, V:0.03〜 0.5%, B:0.
0002〜0.0050%の1種以上、並びにCa:0.0005〜 0.005
%, 希土類元素:0.005 〜 0.015%の1種以上をも含
み、残部がFe及び不可避的不純物からなることを特徴と
する、D.C.バット溶接性及び溶接後の加工性に優れると
共に化成処理性の良好な高強度熱延鋼板。5. A weight ratio of C: 0.06 to 0.12%, Si:
0.15% or less, Mn: 1.0 to 2.0%, P: 0.05% or less, S: 0.005% or less, Cr: 0.10 to 0.70%, A
l: 0.01 to 0.05%, Ti: 0.02 to 0.08%, Nb: 0.01
.About.0.06%, N: 0.0015 to 0.0080%, Mo: 0.03 to 0.5%, V: 0.03 to 0.5%, B: 0.
0002 to 0.0050% of 1 or more, and Ca: 0.0005 to 0.005
%, Rare earth elements: 0.005 to 0.015%, including at least one, the balance consisting of Fe and inevitable impurities, excellent in DC butt weldability and workability after welding, and good chemical conversion treatability High strength hot rolled steel sheet.
0.25〜0.45%, Mn:1.0 〜2.0 %,P:0.05%以
下, S:0.005 %以下, Cr:0.10〜0.70%,A
l:0.01〜0.05%, Ti:0.02〜0.08%, Nb:0.01
〜0.06%,N:0.0015〜0.0080%を含有すると共に、更
にMo:0.03〜 0.5%, V:0.03〜 0.5%, B:0.
0002〜0.0050%の1種以上、並びにCa:0.0005〜 0.005
%, 希土類元素:0.005 〜 0.015%の1種以上をも含
み、残部がFe及び不可避的不純物からなることを特徴と
する、D.C.バット溶接性及び溶接後の加工性に優れると
共に化成処理性の良好な高強度熱延鋼板。6. A weight ratio of C: 0.06 to 0.12%, Si:
0.25 to 0.45%, Mn: 1.0 to 2.0%, P: 0.05% or less, S: 0.005% or less, Cr: 0.10 to 0.70%, A
l: 0.01 to 0.05%, Ti: 0.02 to 0.08%, Nb: 0.01
.About.0.06%, N: 0.0015 to 0.0080%, Mo: 0.03 to 0.5%, V: 0.03 to 0.5%, B: 0.
0002 to 0.0050% of 1 or more, and Ca: 0.0005 to 0.005
%, Rare earth elements: 0.005 to 0.015%, including at least one, the balance consisting of Fe and inevitable impurities, excellent in DC butt weldability and workability after welding, and good chemical conversion treatability High strength hot rolled steel sheet.
0.15%以下, Mn:1.0 〜2.0 %,P:0.05%以
下, S:0.005 %以下, Cr:0.10〜0.70%,A
l:0.01〜0.05%, Ti:0.02〜0.08%, Nb:0.01
〜0.06%,N:0.0015〜0.0080%, Cu:0.1 〜 0.5
%, Ni:0.1 〜 0.5%を含有すると共に、更にMo:0.
03〜 0.5%, V:0.03〜 0.5%, B:0.0002〜0.
0050%の1種以上、並びにCa:0.0005〜 0.005%, 希
土類元素:0.005 〜 0.015%の1種以上をも含み、残部
がFe及び不可避的不純物からなることを特徴とする、D.
C.バット溶接性及び溶接後の加工性に優れると共に化成
処理性の良好な高強度熱延鋼板。7. A weight ratio of C: 0.06 to 0.12%, Si:
0.15% or less, Mn: 1.0 to 2.0%, P: 0.05% or less, S: 0.005% or less, Cr: 0.10 to 0.70%, A
l: 0.01 to 0.05%, Ti: 0.02 to 0.08%, Nb: 0.01
~ 0.06%, N: 0.0015 ~ 0.0080%, Cu: 0.1 ~ 0.5
%, Ni: 0.1-0.5%, and further Mo: 0.
03-0.5%, V: 0.03-0.5%, B: 0.0002-0.
0050%, one or more of Ca, 0.0005 to 0.005% of Ca, and one or more of 0.005 to 0.015% of rare earth elements, the balance being Fe and unavoidable impurities.
C. High-strength hot-rolled steel sheet with excellent butt weldability and workability after welding, and good chemical conversion treatability.
0.25〜0.45%, Mn:1.0 〜2.0 %,P:0.05%以
下, S:0.005 %以下, Cr:0.10〜0.70%,A
l:0.01〜0.05%, Ti:0.02〜0.08%, Nb:0.01
〜0.06%,N:0.0015〜0.0080%, Cu:0.1 〜 0.5
%, Ni:0.1 〜 0.5%を含有すると共に、更にMo:0.
03〜 0.5%, V:0.03〜 0.5%, B:0.0002〜0.
0050%の1種以上、並びにCa:0.0005〜 0.005%, 希
土類元素:0.005 〜 0.015%の1種以上をも含み、残部
がFe及び不可避的不純物からなることを特徴とする、D.
C.バット溶接性及び溶接後の加工性に優れると共に化成
処理性の良好な高強度熱延鋼板。8. A weight ratio of C: 0.06 to 0.12%, Si:
0.25 to 0.45%, Mn: 1.0 to 2.0%, P: 0.05% or less, S: 0.005% or less, Cr: 0.10 to 0.70%, A
l: 0.01 to 0.05%, Ti: 0.02 to 0.08%, Nb: 0.01
~ 0.06%, N: 0.0015 ~ 0.0080%, Cu: 0.1 ~ 0.5
%, Ni: 0.1-0.5%, and further Mo: 0.
03-0.5%, V: 0.03-0.5%, B: 0.0002-0.
0050%, one or more of Ca, 0.0005 to 0.005% of Ca, and one or more of 0.005 to 0.015% of rare earth elements, the balance being Fe and unavoidable impurities.
C. High-strength hot-rolled steel sheet with excellent butt weldability and workability after welding, and good chemical conversion treatability.
分組成の鋼片を、仕上温度850℃以上で熱間圧延し、
400〜550℃で巻取った後、脱スケ−ルすることを
特徴とする、D.C.バット溶接性及び溶接後の加工性に優
れると共に化成処理性の良好な高強度熱延鋼板の製造方
法。9. A steel slab having the chemical composition according to any one of claims 1 to 8 is hot-rolled at a finishing temperature of 850 ° C. or higher,
A method for producing a high-strength hot-rolled steel sheet, which is excellent in DC butt weldability and workability after welding and has good chemical conversion treatability, which is characterized by performing descaling after winding at 400 to 550 ° C.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP28564093A JPH07118792A (en) | 1993-10-21 | 1993-10-21 | High-strength hot rolled steel plate and its production |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP28564093A JPH07118792A (en) | 1993-10-21 | 1993-10-21 | High-strength hot rolled steel plate and its production |
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JPH07118792A true JPH07118792A (en) | 1995-05-09 |
Family
ID=17694151
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Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR20020040213A (en) * | 2000-11-24 | 2002-05-30 | 이구택 | A METHOD FOR MANUFACTURING HOT ROLLED STEEL SHEET OF TENSILE STRENGTH 80kg/㎟ GRADE WITH EXCELLENT WEATHER RESISTANCE AND WORKABILITY |
KR100371960B1 (en) * | 2000-09-29 | 2003-02-14 | 주식회사 포스코 | High atmosphere corrosion resting and workability hot rolled strip having tensile strength of 60 kg/㎟ and method for manufacturing it |
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WO2013108861A1 (en) * | 2012-01-18 | 2013-07-25 | Jfeスチール株式会社 | Steel strip for coiled tubing and method for producing same |
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1993
- 1993-10-21 JP JP28564093A patent/JPH07118792A/en active Pending
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KR100371960B1 (en) * | 2000-09-29 | 2003-02-14 | 주식회사 포스코 | High atmosphere corrosion resting and workability hot rolled strip having tensile strength of 60 kg/㎟ and method for manufacturing it |
KR20020040213A (en) * | 2000-11-24 | 2002-05-30 | 이구택 | A METHOD FOR MANUFACTURING HOT ROLLED STEEL SHEET OF TENSILE STRENGTH 80kg/㎟ GRADE WITH EXCELLENT WEATHER RESISTANCE AND WORKABILITY |
EP1288322A1 (en) * | 2001-08-29 | 2003-03-05 | Sidmar N.V. | An ultra high strength steel composition, the process of production of an ultra high strength steel product and the product obtained |
WO2003018858A1 (en) * | 2001-08-29 | 2003-03-06 | Sidmar N.V. | An ultra high strength steel composition, the process of production of an ultra high strength steel product and the product obtained |
CN100339500C (en) * | 2001-08-29 | 2007-09-26 | 西德玛有限公司 | Ultra high strength steel composition, the process of production of an ultra high strength steel product and the product obtained |
US8715427B2 (en) | 2001-08-29 | 2014-05-06 | Arcelormittal France Sa | Ultra high strength steel composition, the process of production of an ultra high strength steel product and the product obtained |
US6872264B2 (en) * | 2002-08-31 | 2005-03-29 | Hyundai Motor Company | Road wheel composition and method for manufacturing road wheel using the same |
KR100643361B1 (en) * | 2005-06-23 | 2006-11-10 | 주식회사 포스코 | A method for manufacturing precipitation hardening type steel for line pipe with low yeild ratio and a precipitation hardening type steel for line pipe manufactured by the method |
WO2013108861A1 (en) * | 2012-01-18 | 2013-07-25 | Jfeスチール株式会社 | Steel strip for coiled tubing and method for producing same |
JP5494895B2 (en) * | 2012-01-18 | 2014-05-21 | Jfeスチール株式会社 | Steel strip for coiled tubing and manufacturing method thereof |
KR20170105565A (en) | 2015-03-27 | 2017-09-19 | 신닛테츠스미킨 카부시키카이샤 | Steel plate |
US10435772B2 (en) | 2015-03-27 | 2019-10-08 | Nippon Steel Corporation | Steel sheet |
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