JP2013119643A - High-strength hot-rolled steel sheet having excellent corrosion resistance of coating and bending fatigue characteristic, and method for producing the same - Google Patents
High-strength hot-rolled steel sheet having excellent corrosion resistance of coating and bending fatigue characteristic, and method for producing the same Download PDFInfo
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本発明は、最大引張強度が５４０ＭＰａ以上を有する、電着塗装後の耐食性と曲げ疲労特性に優れた熱延鋼板およびその製造方法に関するものであり、特に、自動車やトラックのフレームやメンバー、シャシーなどの素材として好適である。 The present invention relates to a hot-rolled steel sheet having a maximum tensile strength of 540 MPa or more and excellent in corrosion resistance and bending fatigue characteristics after electrodeposition coating, and a method for producing the same. It is suitable as a material.
自動車やトラックの部材では、通常、防食を目的として鋼板表面に電着塗装が行われる。その際、（ａ）スケール付きの鋼板に電着塗装を行う場合と、（ｂ）酸洗あるいはショットブラスト処理等でスケールを取り除いた鋼板に電着塗装を行う、２つの場合がある。しかしながら、前者（ａ）の場合、高いＳｉやＡｌを含有する熱延鋼板においては、いわゆる赤スケールが発生し、熱延鋼板と塗装皮膜間の密着性が低下する結果、所望の塗装後耐食性が得られない問題が有った。また、後者（ｂ）の場合も、高いＳｉやＡｌを含有する熱延鋼板においては、十分な塗装皮膜の密着性が得られず、所望の塗装後耐食性が得られない問題が有った。 In automobile and truck members, electrodeposition coating is usually performed on the steel plate surface for the purpose of corrosion protection. At that time, there are two cases: (a) electrodeposition coating is performed on a steel plate with a scale; and (b) electrodeposition coating is performed on a steel plate from which the scale has been removed by pickling or shot blasting. However, in the case of the former (a), in a hot rolled steel sheet containing high Si or Al, a so-called red scale is generated, resulting in a decrease in adhesion between the hot rolled steel sheet and the coating film, resulting in desired post-coating corrosion resistance. There was a problem that could not be obtained. In the case of the latter (b), the hot rolled steel sheet containing high Si or Al has a problem that sufficient adhesion of the coating film cannot be obtained and the desired post-painting corrosion resistance cannot be obtained.
一般的に、スケール付きの鋼板に塗装処理を行った場合、その塗装後の耐食性はスケールと地鉄との密着性に大きく左右されると考えられる。スケールの密着性を改善する技術としては、例えば、スケール層の構造をマグネタイト（Ｆｅ3Ｏ4）主体にする方法（例えば、特許文献１〜３を参照）、薄スケール化する方法（例えば、特許文献２〜６を参照）、スケール層中のＭｎＦｅ2Ｏ4の比率を低下させる方法（例えば、特許文献７を参照）が開示されている。しかしながら、上記した従来の技術においては、高いＳｉやＡｌを含有する場合には、安定的に優れた密着性を得ることが難しく、また、酸洗等でスケールを取り除いた熱延鋼板の塗装後耐食性を改善することはできなかった。また、高圧水デスケーリング装置（例えば、特許文献８、９を参照）等により仕上げ圧延前のデスケーリングを完全に行い、薄スケール化を図る方法が開示されているが、この場合も安定的に優れた密着性を得ることが難しく、また、酸洗等でスケールを取り除いた熱延鋼板の塗装後耐食性を改善することはできなかった。
Generally, when a coating treatment is performed on a steel plate with a scale, it is considered that the corrosion resistance after the coating is greatly influenced by the adhesion between the scale and the ground iron. Examples of techniques for improving the adhesion of the scale include, for example, a method in which the structure of the scale layer is mainly magnetite (Fe 3 O 4 ) (see, for example, Patent Documents 1 to 3), and a method for reducing the scale (for example, patents).
一方、自動車やトラックのフレームやシャシー等に用いられる熱延鋼板には、疲労特性が併せて求められる。一般に、疲労特性は鋼板表面の粗さの影響を強く受けることが良く知られており、例えば、特許文献９に記載されたような、仕上げ圧延前のデスケーリングを十分に行うことによって表面を平滑化し、疲労特性を向上させる方法が知られている。しかしながら、ＳｉやＡｌを多量に含有する鋼においては、デスケーリング性が劣るため表面を平滑化しにくい問題が有り、さらに熱延中に地鉄表面が脱炭するために、期待するような曲げ疲労特性が得られないという問題点が有った。 On the other hand, fatigue properties are also required for hot-rolled steel sheets used for automobiles, truck frames, chassis, and the like. In general, it is well known that the fatigue characteristics are strongly influenced by the roughness of the steel sheet surface. For example, as described in Patent Document 9, the surface is smoothed by sufficiently performing descaling before finish rolling. There is known a method for improving fatigue characteristics. However, steel containing a large amount of Si or Al has a problem that it is difficult to smooth the surface due to inferior descaling property, and further, since the base metal surface is decarburized during hot rolling, bending fatigue as expected. There was a problem that characteristics could not be obtained.
本発明は上記問題に鑑みてなされたものであり、高いＳｉやＡｌを含有する鋼において、黒皮まま（スケール付き）表面あるいはスケールを除去した表面の何れの表面上に塗装をしても、優れた塗装後耐食性を有し、更に、曲げ疲労特性不良の原因である地鉄表面の脱炭層の生成を抑制可能な、塗装耐食性と曲げ疲労特性に優れた高強度熱延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 has been made in view of the above problems, and in steel containing high Si and Al, even if the paint is applied on any surface of the surface with the black skin (with scale) or the scale removed, High-strength hot-rolled steel sheet with excellent coating corrosion resistance and bending fatigue properties, which has excellent post-painting corrosion resistance, and can suppress the formation of a decarburized layer on the surface of the steel that causes poor bending fatigue properties, and a method for producing the same The purpose is to provide.
はじめに本発明者らは、諸々の条件で作製したスケール付き熱延鋼板および、酸洗によりスケールを取り除いた熱延鋼板について塗装後耐食性及び疲労を評価した。その結果、図１のデスケーリング後の平均相対湿度（％）と地鉄の脱炭層深さ（μｍ）との関係に示すように、脱炭層の厚さが小さいほど塗装後耐食性及び曲げ疲労特性（曲げ疲労限度比）が優れていることを見出した。 First, the present inventors evaluated post-coating corrosion resistance and fatigue of hot-rolled steel sheets with scales produced under various conditions and hot-rolled steel sheets with scales removed by pickling. As a result, as shown in the relationship between the average relative humidity (%) after descaling in FIG. 1 and the depth (μm) of the decarburized layer of the base iron, the smaller the thickness of the decarburized layer, the more the corrosion resistance after coating and the bending fatigue characteristics. It was found that (bending fatigue limit ratio) was excellent.
そこで本発明者らは、ＳｉおよびＡｌ含有鋼の地鉄表面に形成される脱炭層の形成原因について調査を行った。その結果、この脱炭層が仕上げ圧延前のデスケーリングを行った後、仕上げ圧延を行っている間に主に形成していることを知見した。次いで、発明者らは、この地鉄表面の脱炭を抑制する方法について鋭意検討した。その結果、図１に示すようにデスケーリングを行った後、仕上げ圧延を行うまでの間、および仕上げ圧延中において、鋼板が晒される雰囲気の相対湿度（水蒸気濃度）を増加させることにより表面の鉄炭化物直下に形成される脱炭層の形成が抑制されることを見出した。この原因は定かではないが、地鉄への酸素の供給が抑制され、その結果、地鉄内部での一酸化炭素の形成が抑制される結果、地鉄表面の脱炭が抑制されたものと推測される。相対湿度を増加させる方法としては、鋼板表面に水蒸気あるいはミストを強制的に送気する方法や、高温鋼板表面に直接水を噴射し、鋼板表面での水の蒸発を利用して相対湿度を上げる方法が有るが、工業的には水を噴射する方法が最も容易である。 Therefore, the present inventors investigated the cause of formation of a decarburized layer formed on the surface of the ground iron of Si and Al-containing steel. As a result, it was found that the decarburized layer was mainly formed during the finish rolling after the descaling before the finish rolling. Next, the inventors diligently studied a method for suppressing the decarburization on the surface of the ground iron. As a result, the surface iron is increased by increasing the relative humidity (water vapor concentration) of the atmosphere to which the steel sheet is exposed after performing descaling and performing finish rolling as shown in FIG. 1 and during finish rolling. It has been found that the formation of a decarburized layer formed directly under the carbide is suppressed. The cause of this is not clear, but the supply of oxygen to the steel is suppressed, and as a result, the formation of carbon monoxide inside the steel is suppressed, resulting in the suppression of decarburization on the steel surface. Guessed. As a method of increasing the relative humidity, water vapor or mist is forcibly supplied to the surface of the steel sheet, or water is directly sprayed on the surface of the high temperature steel sheet, and the relative humidity is increased by utilizing evaporation of water on the surface of the steel sheet. There is a method, but industrially, the method of spraying water is the easiest.
また、発明者らは地鉄表面の脱炭に及ぼす添加元素の影響について調査を行った。その結果、ＴｉあるいはＮｂを含有する鋼においては、地鉄表層域の脱炭が抑制される傾向を見出した。 In addition, the inventors investigated the effect of additive elements on the decarburization of the surface of the steel. As a result, the steel containing Ti or Nb was found to have a tendency to suppress decarburization in the surface area of the ground iron.
さらに発明者らは、塗装後耐食性不良の主因であるスケール破砕の原因について調査を行った。その結果、このスケール破砕は仕上げ圧延中に起こっており、ある一定のスケール厚さでありかつ相対湿度を増加させた状態で形成される加熱スケールを圧延した際にはこの破砕が強く抑制される傾向が有ることを初めて知見した。また、スケール破砕が起こる場合、スケール／地鉄界面の粗さが増大し、疲労特性が低下することを併せて知見した。 Furthermore, the inventors investigated the cause of scale crushing, which is the main cause of poor corrosion resistance after painting. As a result, this crushing occurs during finish rolling, and this crushing is strongly suppressed when a heated scale formed with a certain scale thickness and an increased relative humidity is rolled. I found out for the first time that there was a tendency. It was also found that when scale crushing occurs, the roughness of the scale / base metal interface increases and the fatigue characteristics decrease.
また、発明者らは、電着塗装皮膜の密着性に及ぼすスケール構造の影響について詳細に調査した。その結果、スケール内の酸化物結晶粒径が微細であるほど、電着塗装後の耐食性が良好となることを発見した。 In addition, the inventors investigated in detail the influence of the scale structure on the adhesion of the electrodeposition coating film. As a result, it was discovered that the smaller the oxide crystal grain size in the scale, the better the corrosion resistance after electrodeposition coating.
次いで、発明者らは、スケール層内の結晶粒を微細化する条件について鋭意検討を行った。その結果、所定範囲内の厚さのスケールが存在する状態で仕上げ圧延を開始し、さらに、所定の温度範囲内でスケールに適正量の歪を付加した場合には、鋼板の冷却後に形成されるスケール内の酸化物結晶が微細化することを見出した。なお、結晶が微細化する原因は定かではないが、仕上げ圧延中の歪付加によって導入される微細な欠陥が、微細化に関与する可能性があるものと考えられる。 Next, the inventors diligently studied conditions for refining crystal grains in the scale layer. As a result, finish rolling is started in a state where a scale having a thickness within a predetermined range exists, and further, when an appropriate amount of strain is applied to the scale within a predetermined temperature range, the steel sheet is formed after cooling. It has been found that oxide crystals in the scale are refined. In addition, although the cause which crystal | crystallization refines | miniaturizes is not certain, it is thought that the fine defect introduce | transduced by the distortion addition during finish rolling may be concerned in refinement | miniaturization.
上記各実験の結果、発明者らは、成分、仕上げ圧延時の鋼板表面の相対湿度および熱延条件を適正化することで、地鉄脱炭層の厚さ、スケールの結晶粒径、並びに、スケールの破砕度を最適化させ、その結果、ＳｉやＡｌを多量に含有する鋼板においても良好な電着塗装後の塗装耐食性を確保でき、さらに良好な曲げ疲労特性も具備することを明らかにし、本発明を完成させた。 As a result of each of the above experiments, the inventors have optimized the components, the relative humidity of the steel sheet surface during finish rolling, and the hot rolling conditions, so that the thickness of the base metal decarburized layer, the crystal grain size of the scale, and the scale As a result, it was clarified that the steel sheet containing a large amount of Si and Al can secure good coating corrosion resistance after electrodeposition coating and also has good bending fatigue properties. Completed the invention.
即ち、本発明の要旨は以下のとおりである。 That is, the gist of the present invention is as follows.
（１） 質量％で、
Ｃ：０．０５〜０．２５％、
ＳｉとＡｌの合計含有量：０．８％〜２．０％
Ｍｎ：１．０〜４．０％
ＴｉとＮｂの１種又は２種の合計含有量：０．０５〜０．２％
Ｎ：０．０００３〜０．０１％、
Ｐ：０．００１〜０．２％、
Ｓ：０．０１％以下
を含有し、残部がＦｅおよび不可避的不純物からなる成分組成を有し、地鉄表面の脱炭層の厚さが５μｍ以下であり、地鉄表面の平均粗さＲａが２．０μｍ以下であり、最大引張強度が５４０ＭＰａ以上であることを特徴とする塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板。
(1) In mass%,
C: 0.05 to 0.25%
Total content of Si and Al: 0.8% to 2.0%
Mn: 1.0-4.0%
Total content of one or two of Ti and Nb: 0.05 to 0.2%
N: 0.0003 to 0.01%,
P: 0.001 to 0.2%,
S: containing 0.01% or less, the balance is composed of Fe and unavoidable impurities, the thickness of the decarburized layer on the surface of the base iron is 5 μm or less, and the average roughness Ra of the surface of the base iron is A high-strength hot-rolled steel sheet excellent in coating corrosion resistance and bending fatigue characteristics, characterized by being 2.0 μm or less and having a maximum tensile strength of 540 MPa or more.
（２） スケール表面の平均粗さＲａが２．５μｍ以下であり、スケール層中の酸化物の平均結晶粒径が３μｍ以下であることを特徴とする上記（１）記載の塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板。 (2) Coating surface corrosion resistance and bending fatigue according to (1) above, wherein the average roughness Ra of the scale surface is 2.5 μm or less, and the average crystal grain size of the oxide in the scale layer is 3 μm or less. High-strength hot-rolled steel sheet with excellent characteristics.
（３） 質量％で、
Ｖ：０．２％以下、
Ｍｏ：１．５％以下
のうち、１種または２種以上を含有することを特徴とする上記（１）又は（２）に記載の塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板。
(3) In mass%,
V: 0.2% or less,
Mo: High strength hot-rolled steel sheet excellent in coating corrosion resistance and bending fatigue properties as described in (1) or (2) above, comprising one or more of 1.5% or less.
（４） 曲げ疲労限度比が０．４５以上であることを特徴とする上記（１）〜（３）の何れか１項に記載の塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板。 (4) The high-strength hot-rolled steel sheet having excellent coating corrosion resistance and bending fatigue characteristics according to any one of (1) to (3) above, wherein the bending fatigue limit ratio is 0.45 or more.
（５） 上記（１）〜（４）の何れか１項に記載の塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板を製造する方法であって、仕上げ圧延前のデスケーリングを行った後、仕上げ圧延開始までの間に鋼板表面の平均相対湿度が８０％以上になるように保持し、平均スケール厚が２〜３０μｍで仕上げ圧延を開始し、仕上げ圧延終了温度：８５０℃以上である仕上げ圧延を行うことを特徴とする塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板の製造方法。 (5) A method for producing a high-strength hot-rolled steel sheet having excellent coating corrosion resistance and bending fatigue properties according to any one of (1) to (4) above, wherein descaling is performed before finish rolling. After that, until the start of finish rolling, the average relative humidity of the steel sheet surface is maintained to be 80% or more, finish rolling is started at an average scale thickness of 2 to 30 μm, and finish rolling finish temperature is 850 ° C. or more. A method for producing a high-strength hot-rolled steel sheet excellent in coating corrosion resistance and bending fatigue characteristics, characterized by performing finish rolling.
（６） 上記（２）に記載の塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板を製造する方法であって、仕上げ圧延前のデスケーリングを行った後、仕上げ圧延開始までの間に鋼板表面の平均相対湿度が８０％以上になるように保持し、平均スケール厚が２〜３０μｍで仕上げ圧延を開始し、鋼板表面温度：８５０〜９８０℃の範囲内での累積圧下率が３０％以上であり、仕上げ圧延終了温度：８５０℃以上である仕上げ圧延を行うことを特徴とする塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板の製造方法。 (6) A method for producing a high-strength hot-rolled steel sheet having excellent coating corrosion resistance and bending fatigue properties as described in (2) above, after descaling before finish rolling and before the start of finish rolling. The steel sheet is maintained so that the average relative humidity on the surface of the steel sheet is 80% or more, finish rolling is started at an average scale thickness of 2 to 30 μm, and the cumulative rolling reduction within the range of the steel sheet surface temperature: 850 to 980 ° C. is 30%. A method for producing a high-strength hot-rolled steel sheet excellent in coating corrosion resistance and bending fatigue characteristics, characterized by performing finish rolling at a finish rolling finish temperature of 850 ° C. or higher.
（７） 上記（５）又は（６）に記載の塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板を製造する方法であって、仕上げ圧延スタンド間における鋼板表面の平均相対湿度を８０％以上とすることを特徴とする塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板の製造方法。 (7) A method for producing a high-strength hot-rolled steel sheet having excellent coating corrosion resistance and bending fatigue characteristics as described in (5) or (6) above, wherein the average relative humidity on the steel sheet surface between finish rolling stands is 80% A method for producing a high-strength hot-rolled steel sheet excellent in coating corrosion resistance and bending fatigue characteristics characterized by the above.
本発明の塗装耐食性と曲げ疲労特性に優れた熱延鋼板によれば、上記構成により、スケール層を有する熱延鋼板に電着焼付塗装を施した場合であっても、またスケールを取り除いた鋼板であっても、優れた塗装耐食性と疲労耐久性が得られる。これにより、従来の鋼板において腐食による減肉量を見込んだ部品板厚が設定されていたのに対し、本発明の高強度熱延鋼板は、優れた塗装耐食性が得られることから、部品の板厚を薄くすることが可能となり、自動車あるいはトラック等の軽量化が可能となる。また、鋼板の板厚が薄い場合、材料には高い疲労強度が求められるが、本発明の熱延鋼板は優れた疲労特性を具備することから、部材の軽量化に極めて好適である。 According to the hot-rolled steel sheet having excellent coating corrosion resistance and bending fatigue characteristics according to the present invention, the steel sheet with the scale removed from the hot-rolled steel sheet having the scale layer even when the electrodeposition baking coating is applied. Even so, excellent paint corrosion resistance and fatigue durability can be obtained. As a result, the thickness of the component plate was set in anticipation of the thickness reduction due to corrosion in the conventional steel plate, whereas the high-strength hot-rolled steel plate of the present invention provides excellent coating corrosion resistance. The thickness can be reduced, and the weight of an automobile or a truck can be reduced. Further, when the steel plate is thin, the material is required to have high fatigue strength. However, the hot-rolled steel plate of the present invention has excellent fatigue characteristics, and thus is extremely suitable for reducing the weight of the member.
また、本発明の塗装耐食性と疲労特性に優れた熱延鋼板の製造方法によれば、上記手順並びに条件を採用することにより、優れた塗装耐食性並びに曲げ疲労特性を備える熱延鋼板を製造することが可能となる。 Moreover, according to the method for producing a hot-rolled steel sheet having excellent coating corrosion resistance and fatigue characteristics according to the present invention, by adopting the above procedure and conditions, producing a hot-rolled steel sheet having excellent paint corrosion resistance and bending fatigue characteristics. Is possible.
以下、本発明の塗装耐食性と曲げ疲労特性に優れた熱延鋼板およびその製造方法の一実施形態について、詳細に説明する。なお、本実施形態は、本発明の塗装耐食性と曲げ疲労特性に優れた熱延鋼板およびその製造方法の趣旨をより良く理解させるために詳細に説明するものであるから、特に指定の無い限り本発明を限定するものではない。 Hereinafter, an embodiment of a hot-rolled steel sheet having excellent coating corrosion resistance and bending fatigue characteristics and a method for producing the same according to the present invention will be described in detail. The present embodiment will be described in detail in order to better understand the purpose of the hot rolled steel sheet and the manufacturing method thereof excellent in coating corrosion resistance and bending fatigue characteristics of the present invention. The invention is not limited.
［熱延鋼板］
質量％で、
Ｃ：０．０５〜０．２５％、
ＳｉとＡｌの合計含有量：０．８％〜２．０％、
Ｍｎ：１．０〜４．０％、
ＴｉとＮｂの１種または２種の合計含有量：０．０５〜０．２％、
Ｎ：０．０００３〜０．０１％、
Ｐ：０．００１〜０．２％、
Ｓ：０．０１％以下
を含有し、残部がＦｅおよび不可避的不純物からなる成分組成を有し、スケール／地鉄界面下の地鉄の脱炭層の厚さが５μｍ以下であり、地鉄表面の平均粗さＲａが２．０μｍ以下であり、最大引張強度が５４０ＭＰａ以上として構成されている。また、スケール付きの鋼板の場合には、前記に加えて、スケール表面の平均粗さＲａが２．５μｍ以下であり、スケール層中の酸化物の平均結晶粒径が３μｍ以下として構成されている。
[Hot rolled steel sheet]
% By mass
C: 0.05 to 0.25%
Total content of Si and Al: 0.8% to 2.0%,
Mn: 1.0-4.0%,
Total content of one or two of Ti and Nb: 0.05 to 0.2%,
N: 0.0003 to 0.01%,
P: 0.001 to 0.2%,
S: containing 0.01% or less, the balance is composed of Fe and inevitable impurities, the thickness of the decarburized layer of the base iron below the scale / base iron interface is 5 μm or less, and the surface of the base iron The average roughness Ra is 2.0 μm or less, and the maximum tensile strength is 540 MPa or more. In addition, in the case of a steel plate with a scale, in addition to the above, the average roughness Ra of the scale surface is 2.5 μm or less, and the average crystal grain size of the oxide in the scale layer is 3 μm or less. .
「地鉄の脱炭層厚さ：５μｍ以下」
スケール／地鉄界面下の地鉄の脱炭層は、曲げ疲労特性およびスケール無し表面材の塗装耐食性と関係する指標であり、本発明において重要な因子である。脱炭層の厚さが５μｍを超えると曲げ疲労特性が低下する。このため、その適正範囲を５μｍ以下に制限した。塗装耐食性確保の観点から３μｍ以下がより好ましい範囲である。下限は特に限定しないが、塗装耐食性と疲労特性の両方の観点からは少ない方がより好ましい。
“Decarburized layer thickness of the steel: 5 μm or less”
The decarburized layer of the base iron below the scale / base iron interface is an index related to the bending fatigue characteristics and the coating corrosion resistance of the unscaled surface material, and is an important factor in the present invention. When the thickness of the decarburized layer exceeds 5 μm, the bending fatigue characteristics are deteriorated. For this reason, the appropriate range was limited to 5 μm or less. From the viewpoint of securing the coating corrosion resistance, 3 μm or less is a more preferable range. The lower limit is not particularly limited, but a lower limit is more preferable from the viewpoints of both coating corrosion resistance and fatigue characteristics.
「地鉄表面の平均粗さＲａ：２．０μｍ以下」
スケール／地鉄界面の粗さ、すなわち地鉄表面の粗さは、曲げ疲労特性に関係する指標である。平均算術粗さＲａが２．０μｍを超えると曲げ疲労特性が低下することから、その上限を２．０μｍに限定した。１．５μｍ以下がより好ましい範囲である。下限は特に限定しないが、一般的に用いられる熱延ロールで得られうる粗度として０．１を実質的な下限とする。
“Average roughness Ra of the surface of the iron core: 2.0 μm or less”
The roughness of the scale / base iron interface, that is, the roughness of the surface of the base iron is an index related to the bending fatigue characteristics. When the average arithmetic roughness Ra exceeds 2.0 μm, the bending fatigue characteristics deteriorate, so the upper limit was limited to 2.0 μm. 1.5 μm or less is a more preferable range. Although a minimum is not specifically limited, 0.1 is made into a substantial minimum as roughness which can be obtained with the hot-rolling roll generally used.
「最大引張強度：５４０ＭＰａ以上」
最大引張強度が５４０ＭＰａ未満であると、塗装耐食性や疲労特性が良好であったとしても、自動車やトラック部材の軽量化効果が期待できない。このため、本発明において、その範囲を５４０ＭＰａ以上に限定した。上限は特に限定しないが、最大引張強度が１２００ＭＰａを超えると打ち抜き部の疲労特性が低下するため、１２００ＭＰａが実質的な上限である。
“Maximum tensile strength: 540 MPa or more”
If the maximum tensile strength is less than 540 MPa, the weight reduction effect of automobiles and truck members cannot be expected even if the coating corrosion resistance and fatigue characteristics are good. For this reason, in the present invention, the range is limited to 540 MPa or more. The upper limit is not particularly limited, but if the maximum tensile strength exceeds 1200 MPa, the fatigue characteristics of the punched portion are deteriorated, so 1200 MPa is a substantial upper limit.
「スケール表面の平均粗さＲａ：２．５μｍ以下」
スケール表面の平均粗さは、スケールの破砕度と正に相関する指標であり、塗装耐食性と関係する重要な因子である。平均粗さＲａで２．５μｍを超えると、スケール破砕が顕著になり塗装耐食性が劣化するので、その適正範囲を２．５μｍ以下とした。１．５μｍ以下がより好ましい。一般的な圧延ロールで得られうる粗度として、０．１μｍが実質的な下限である。
“Average surface roughness Ra: 2.5 μm or less”
The average roughness of the scale surface is an index that correlates positively with the degree of crushing of the scale, and is an important factor related to coating corrosion resistance. If the average roughness Ra exceeds 2.5 μm, scale crushing becomes prominent and the coating corrosion resistance deteriorates. Therefore, the appropriate range is set to 2.5 μm or less. More preferably, it is 1.5 μm or less. As a roughness that can be obtained with a general rolling roll, 0.1 μm is a practical lower limit.
「スケール層中の酸化物の平均結晶粒径：３μｍ以下」
スケール層中の酸化物の平均結晶粒径は、スケールと地鉄の密着性と関係する指標であり、スケール付き鋼板の場合の塗装耐食性と関係する。酸化物の平均結晶粒径が３μｍを超えると、塗装耐食性が劣化するので、その適正範囲を３μｍ以下にした。下限は特に限定しないが、粒径が小さすぎるとスケールの破砕程度が大きくなる傾向が有ることから、０．２μｍ以上であることが好ましい。なお、ここで、酸化物とは、鉄の酸化物であるマグネタイト、ヘマタイト、ウスタイトであり、これら酸化物の結晶構造において、Ｆｅの原子位置にＭｎ、Ａｌ、Ｔｉ等の原子が一部置換した場合でも塗装耐食性に及ぼす効果は変わらない。
“Average crystal grain size of oxide in the scale layer: 3 μm or less”
The average crystal grain size of the oxide in the scale layer is an index related to the adhesion between the scale and the base iron, and is related to the coating corrosion resistance in the case of a steel plate with a scale. When the average crystal grain size of the oxide exceeds 3 μm, the coating corrosion resistance deteriorates, so the appropriate range was made 3 μm or less. The lower limit is not particularly limited. However, if the particle size is too small, the degree of crushing of the scale tends to increase, and therefore it is preferably 0.2 μm or more. Here, the oxides are magnetite, hematite, and wustite, which are iron oxides. In the crystal structure of these oxides, atoms such as Mn, Al, Ti, and the like are partially substituted at the atomic positions of Fe. Even in this case, the effect on the corrosion resistance of the coating remains the same.
「Ｃ量：０．０５〜０．２５％」
本発明においては、Ｃ量が０．０５％未満であると、最大引張強度：５４０ＭＰａ以上を得ることが出来ない。また、脱炭層が形成されないため、そもそも曲げ疲労特性の劣化が問題にならない。従って、本発明においては、０．０５％以上の範囲に限定した。Ｃ量が多くなるとパーライト組織の割合やセメンタイトの体積分率が増加し、スケール／地鉄界面粗さを平滑にしても、良好な疲労特性が得られない可能性があるため、Ｃの上限は０．２５％以下が好ましい。
“C amount: 0.05 to 0.25%”
In the present invention, when the C content is less than 0.05%, the maximum tensile strength: 540 MPa or more cannot be obtained. Moreover, since no decarburized layer is formed, degradation of bending fatigue characteristics is not a problem in the first place. Therefore, in this invention, it limited to 0.05% or more of range. If the amount of C increases, the ratio of the pearlite structure and the volume fraction of cementite increase, and even if the scale / base metal interface roughness is smooth, good fatigue characteristics may not be obtained. 0.25% or less is preferable.
「ＳｉとＡｌの合計含有量：０．８％〜２．０％」
ＳｉとＡｌは鋼の強化に用いられる。また、ＳｉとＡｌの量比によらず、その合計量が多いほど地鉄表層の脱炭層厚さが増大し、疲労特性が低下すると共に、デスケーリング性が低下するために塗装耐食性が低下する。ＳｉとＡｌの合計含有量が０．８％未満であると、最大引張強度：５４０ＭＰａ以上を得ることが出来ないだけではなく、脱炭層形成やデスケーリング性への影響もほとんどないことから、本発明の課題が顕在化しない。このため、本発明において、ＳｉとＡｌの合計含有量は０．８％以上に限定した。ＳｉとＡｌの合計含有量が２．０％を超えると、地鉄の脱炭層形成速度が急激に増加し、鋼板表面上の相対湿度を増加させても脱炭層の形成を適正範囲内に抑制できない。このため、その適正範囲を０．８％〜２．０％の範囲に制限した。
“Total content of Si and Al: 0.8% to 2.0%”
Si and Al are used for strengthening steel. Regardless of the amount ratio of Si and Al, as the total amount increases, the thickness of the decarburized layer of the surface iron layer increases, the fatigue characteristics decrease, and the descaling property decreases, so the coating corrosion resistance decreases. . When the total content of Si and Al is less than 0.8%, not only can the maximum tensile strength: 540 MPa or more be obtained, but also there is almost no effect on decarburization layer formation and descaling properties. The problem of the invention does not become apparent. For this reason, in the present invention, the total content of Si and Al is limited to 0.8% or more. When the total content of Si and Al exceeds 2.0%, the rate of formation of the decarburized layer of the base iron increases rapidly, and the formation of the decarburized layer is suppressed within the proper range even if the relative humidity on the steel sheet surface is increased. Can not. For this reason, the appropriate range was limited to a range of 0.8% to 2.0%.
「Ｍｎ量：１．０〜４．０％」
Ｍｎは、鋼の強度確保のために用いられる元素であるが、１．０％未満であると、最大引張強度：５４０ＭＰａを確保することが困難になる。上限は、塗装後耐食性の観点から４．０％以下が好ましい。
“Mn amount: 1.0 to 4.0%”
Mn is an element used for ensuring the strength of steel, but if it is less than 1.0%, it is difficult to ensure the maximum tensile strength: 540 MPa. The upper limit is preferably 4.0% or less from the viewpoint of post-coating corrosion resistance.
「ＴｉとＮｂの１種または２種の合計含有量：０．０５〜０．２％」
ＴｉとＮｂは析出強化元素として鋼の強度調整に用いられる他、高温スケール形成時の地鉄表面の脱炭層形成を抑制する効果が有り、本発明において重要な因子である。合計含有量が０．０５％未満であると、脱炭層形成の抑制効果が小さいことから、その適正範囲を０．０５％以上とした。一方、０．２％を超えると加工性が低下することから、０．２％以下であることが好ましい。
“Total content of one or two of Ti and Nb: 0.05 to 0.2%”
Ti and Nb are not only used for adjusting the strength of steel as precipitation strengthening elements, but also have an effect of suppressing the formation of a decarburized layer on the surface of the steel at the time of high-temperature scale formation, and are important factors in the present invention. When the total content is less than 0.05%, the effect of suppressing the formation of the decarburized layer is small, so the appropriate range is set to 0.05% or more. On the other hand, if it exceeds 0.2%, the workability deteriorates, so that it is preferably 0.2% or less.
「Ｎ量：０．０００３〜０．０１％以下」
ＮはＴｉあるいはＮｂと化合物を形成し、鋼の組織制御に用いられる。Ｎ含有量が０．０１％を超えると、仕上げ前のデスケーリングを開始するまでに、ＴｉとＮｂを含有する窒化物が多量に形成され、固溶状態のＮｂやＴｉ量が減少する結果、仕上げ圧延前後の脱炭層形成の抑制効果が小さくなる。下限は特に限定しないが、０．０００３％未満とするとコスト高となる。このため、その適正範囲を０．０００３〜０．０１％とした。
本発明の熱延鋼板においては、さらに以下の元素を含むことができる。
“N amount: 0.0003 to 0.01% or less”
N forms a compound with Ti or Nb and is used for controlling the structure of steel. When the N content exceeds 0.01%, a large amount of nitride containing Ti and Nb is formed before the descaling before finishing is started, and the amount of Nb and Ti in the solid solution state is reduced. The effect of suppressing the formation of the decarburized layer before and after finish rolling is reduced. The lower limit is not particularly limited, but if it is less than 0.0003%, the cost becomes high. For this reason, the appropriate range was made 0.0003 to 0.01%.
The hot-rolled steel sheet of the present invention can further contain the following elements.
「Ｖ量：０．２％以下」
Ｖは、析出強化元素として鋼の強度調整に用いられる他、高温スケール形成時の脱炭層形成を抑制する効果が有る。しかしながら、０．２％を超えてＶを含有すると、加工性が低下するので、その適正範囲を０．２％以下とする。下限は特に限定しないが、０．０００１％未満であると、製造コストが増大するため、０．０００１％が実質的な下限である。
"V amount: 0.2% or less"
V is used for adjusting the strength of steel as a precipitation strengthening element and has an effect of suppressing the formation of a decarburized layer during the formation of a high-temperature scale. However, if the V content exceeds 0.2%, the workability deteriorates, so the appropriate range is made 0.2% or less. The lower limit is not particularly limited, but if it is less than 0.0001%, the production cost increases, so 0.0001% is a substantial lower limit.
「Ｍｏ量：１．５％以下」
Ｍｏは鋼板のミクロ組織制御に用いられる他、析出強化元素として鋼の強度調整に用いられる。しかしながら、１．５％を超えてＭｏを含有すると、加工性が低下し、またコスト高になるので、その適正範囲を１．５％以下とする。Ｍｏ量の下限は特に限定しないが、０．０００３％未満であると、製造コストが増大するため、０．０００３％が実質的な下限である。
"Mo amount: 1.5% or less"
In addition to being used for controlling the microstructure of the steel sheet, Mo is used for adjusting the strength of the steel as a precipitation strengthening element. However, if the Mo content exceeds 1.5%, the workability is lowered and the cost is increased, so the appropriate range is made 1.5% or less. The lower limit of the amount of Mo is not particularly limited, but if it is less than 0.0003%, the manufacturing cost increases, so 0.0003% is a substantial lower limit.
「Ｐ量：０．００１〜０．２％」
Ｐは、鋼の強度確保のために用いられる。しかしながら、０．２％を超えてＰを含有すると塗装耐食性が低下するので、その適正範囲を０．２％以下とする。また、Ｐ量の下限は、０．００１％未満であると製造コストが増大するため、０．００１％が実質的な下限である。
“P amount: 0.001 to 0.2%”
P is used for securing the strength of the steel. However, if the P content exceeds 0.2%, the coating corrosion resistance decreases, so the appropriate range is made 0.2% or less. Moreover, since the manufacturing cost will increase if the lower limit of the P content is less than 0.001%, 0.001% is the practical lower limit.
「Ｓ量：０．０１％以下」
Ｓは、不可避不純物として含有され母材の疲労特性に影響する元素である。しかしながら、０．０１％を超えてＳを含有すると、地鉄の脱炭層形成を抑制しても、曲げ疲労限度比：０．４５以上を得ることが困難になるため、その適正範囲を０．０１％以下とする。また、Ｓ量の下限は特に限定しないが、０．０００２％未満であると製造コストが増大するため、０．０００２％が実質的な下限である。
"S amount: 0.01% or less"
S is an element contained as an inevitable impurity and affecting the fatigue characteristics of the base material. However, if S is contained in excess of 0.01%, it becomes difficult to obtain a bending fatigue limit ratio of 0.45 or more even if formation of a decarburized layer of the base iron is suppressed. 01% or less. Further, the lower limit of the amount of S is not particularly limited, but if it is less than 0.0002%, the production cost increases, so 0.0002% is a substantial lower limit.
なお、本実施形態における鋼成分は、その他の元素については特に限定はなく、強度調整や脱酸のために各種元素を適宜含有しても良い。 In addition, the steel component in this embodiment does not specifically limit about another element, You may contain various elements suitably for intensity | strength adjustment and deoxidation.
「曲げ疲労限度比：０．４５以上」
本発明の熱延鋼板においては、スケール表面の平均粗さ、スケール層中の酸化物の平均結晶粒径、スケール／地鉄界面下の地鉄の脱炭層厚さ、最大引張強度の平均粗さ、並びに、鋼成分を上記範囲に規定したうえで、さらに、曲げ疲労限度比を０．４５以上とすることがより好ましい。
“Bending fatigue limit ratio: 0.45 or more”
In the hot rolled steel sheet of the present invention, the average roughness of the scale surface, the average crystal grain size of the oxide in the scale layer, the thickness of the decarburized layer of the base iron under the scale / base iron interface, and the average roughness of the maximum tensile strength Moreover, it is more preferable that the bending fatigue limit ratio is 0.45 or more after the steel components are defined within the above range.
ここで、本発明において説明する曲げ疲労限度比とは、疲労限をＴＳで除した値であり、熱延鋼板の有する疲労特性を示す値である。この曲げ疲労限度比が０．４５以上であれば、実用上、疲労破壊が起きないことから、疲労限度比の範囲を０．４５以上に限定した。上限は特に限定しないが、１．０（ＴＳ＝疲労限の時）が実質的な上限である。 Here, the bending fatigue limit ratio described in the present invention is a value obtained by dividing the fatigue limit by TS, and is a value indicating the fatigue characteristics of the hot-rolled steel sheet. If this bending fatigue limit ratio is 0.45 or more, fatigue fracture does not occur practically, so the range of the fatigue limit ratio is limited to 0.45 or more. The upper limit is not particularly limited, but 1.0 (when TS = fatigue limit) is a practical upper limit.
［熱延鋼板の製造方法］
次に、上記構成を備えた本発明の塗装耐食性と曲げ疲労特性に優れた熱延鋼板を製造する方法について説明する。
[Method for producing hot-rolled steel sheet]
Next, a method for producing a hot-rolled steel sheet having the above-described structure and excellent in coating corrosion resistance and bending fatigue characteristics will be described.
本発明の塗装耐食性と曲げ疲労特性に優れた熱延鋼板の製造方法は、仕上げ圧延前のデスケーリングを行った後、仕上げ圧延開始までの間に鋼板表面の平均相対湿度が８０％以上になるように保持し、平均スケール厚が２〜３０μｍで仕上げ圧延を開始し、仕上げ圧延終了温度を８５０℃以上にする方法である。また、スケール付き熱延鋼板上での塗装耐食性を確保するためには、前記に加えて、鋼板表面温度：８５０〜９８０℃の範囲内での累積圧下率が３０％以上である仕上げ圧延を行う方法である。 The method for producing a hot-rolled steel sheet having excellent paint corrosion resistance and bending fatigue characteristics according to the present invention has an average relative humidity of 80% or more on the surface of the steel sheet after descaling before finish rolling and before the start of finish rolling. The finish rolling is started at an average scale thickness of 2 to 30 μm, and the finish rolling finish temperature is set to 850 ° C. or higher. Moreover, in order to ensure the coating corrosion resistance on the hot-rolled steel sheet with scale, in addition to the above, finish rolling is performed in which the cumulative rolling reduction within the range of the steel sheet surface temperature: 850 to 980 ° C. is 30% or more. Is the method.
以下、本発明の熱延鋼板の製造方法で規定する各手順並びに条件について説明する。 Hereinafter, each procedure and conditions prescribed | regulated with the manufacturing method of the hot rolled sheet steel of this invention are demonstrated.
まず、上記成分からなるスラブを加熱し、その後、粗圧延、仕上げ圧延を順次行う。この際、スラブ加熱条件、並びに、粗圧延の条件は特に限定されるものではなく、従来から用いられている各条件を採用することができる。 First, a slab composed of the above components is heated, and then rough rolling and finish rolling are sequentially performed. At this time, the slab heating condition and the rough rolling condition are not particularly limited, and each conventionally used condition can be adopted.
デスケーリング後から仕上げ圧延開始までの鋼板表面直上の雰囲気は、スケールの形成挙動および脱炭挙動に影響を与える重要な因子である。デスケーリング後から仕上げ圧延開始までの空気中の相対湿度が８０％未満であると、最表面に形成される鉄酸化物直下の地鉄の脱炭が進行し、疲労特性が低下するとともに、仕上げ圧延時にスケール破砕が起き、塗装耐食性が低下する。このため、相対湿度の適正範囲を８０％以上とした。９０％以上がより好ましい範囲である。上限は特に限定しないが、１００％である。 The atmosphere immediately above the steel sheet surface from descaling to the start of finish rolling is an important factor affecting the scale formation behavior and decarburization behavior. If the relative humidity in the air from descaling to the start of finish rolling is less than 80%, the decarburization of the iron core directly under the iron oxide formed on the outermost surface proceeds, fatigue characteristics decrease, and finishing Scale crushing occurs during rolling, and the corrosion resistance of the coating decreases. For this reason, the appropriate range of relative humidity was 80% or more. 90% or more is a more preferable range. The upper limit is not particularly limited, but is 100%.
相対湿度を制御する方法としては、水蒸気ミストを鋼板表面に導入する方法、水を鋼板表面に噴射させ、蒸発した水蒸気により鋼板表面の水蒸気密度を増加させる方法のいずれでも構わない。 As a method for controlling the relative humidity, either a method of introducing water vapor mist to the steel plate surface or a method of injecting water onto the steel plate surface and increasing the water vapor density on the steel plate surface by the evaporated water vapor may be used.
なお、本発明においては、仕上げ圧延開始から終了までの鋼板表面直上の相対湿度についても、上記と同様に制御することが好ましい。 In the present invention, it is preferable to control the relative humidity immediately above the steel sheet surface from the start to the end of finish rolling in the same manner as described above.
また、本発明において、仕上げ圧延開始時の平均スケール厚は、疲労特性およびスケール付き材の塗装後耐食性に影響する重要な因子である。ここで、従来の製造方法では、通常、仕上げ圧延前にデスケーリングを完全に行うことが一般的である。しかしながら、デスケーリングを完全に行い、仕上げ圧延開始時の平均スケール厚さが２μｍ未満であると、逆に地鉄の脱炭が進行して疲労特性が劣位になる傾向が有り、さらに熱延後においてスケール内に微細な酸化物結晶が得られないために、電着塗装後の耐食性が劣化する。一方、仕上げ圧延開始時の平均スケール厚さが３０μｍを超えると、仕上げ圧延後にスケールが破砕して塗装耐食性の劣化を引き起こし、さらには地鉄表面の粗さが増大して疲労特性も低下する。このため、本発明の製造方法においては、仕上げ圧延開始時の平均スケール厚の適正範囲を２〜３０μｍに限定した。 In the present invention, the average scale thickness at the start of finish rolling is an important factor affecting the fatigue characteristics and the post-coating corrosion resistance of the scaled material. Here, in the conventional manufacturing method, it is general to perform descaling completely before finish rolling. However, if the descaling is performed completely and the average scale thickness at the start of finish rolling is less than 2 μm, the decarburization of the base metal tends to progress and the fatigue properties tend to be inferior. In this case, since fine oxide crystals cannot be obtained in the scale, the corrosion resistance after electrodeposition coating deteriorates. On the other hand, when the average scale thickness at the start of finish rolling exceeds 30 μm, the scale is crushed after finish rolling to cause deterioration of the coating corrosion resistance, and further, the roughness of the surface iron surface is increased and the fatigue characteristics are also lowered. For this reason, in the manufacturing method of the present invention, the appropriate range of the average scale thickness at the start of finish rolling is limited to 2 to 30 μm.
なお、仕上げ圧延前に行うデスケーリングの方法は特に限定するものではない。但し、デスケーリングの処理の程度は、鋼成分やデスケーリング時の鋼板温度に応じて変化するので、これら鋼成分や鋼板温度に応じて吐出水の水圧・水量や噴射角度を変化させることにより、デスケーリング後のスケール厚さを調整する。 In addition, the descaling method performed before finish rolling is not particularly limited. However, the degree of descaling treatment changes according to the steel composition and the steel plate temperature at the time of descaling, so by changing the water pressure, the amount of water and the injection angle according to these steel components and the steel plate temperature, Adjust the scale thickness after descaling.
仕上げ圧延終了温度は、スケールの破砕とそれに伴う地鉄表面の粗さに影響する重要な因子である。鋼板表面温度が８５０℃未満の条件で仕上げ圧延を行うと、スケールは破砕されて、スケール付き材の塗装後耐食性が低下し、さらにスケール／地鉄界面の粗さが大きくなるため、疲労限度比が低下する。このため、本発明の製造方法においては、仕上げ圧延終了温度の適正範囲を８５０℃以上に限定した。 The finish rolling finish temperature is an important factor that affects the crushing of the scale and the accompanying surface roughness of the steel. If finish rolling is performed under conditions where the steel sheet surface temperature is less than 850 ° C., the scale is crushed, the corrosion resistance after painting of the scaled material is reduced, and the roughness of the scale / base metal interface is increased, so the fatigue limit ratio Decreases. For this reason, in the manufacturing method of this invention, the appropriate range of finish rolling completion temperature was limited to 850 degreeC or more.
仕上げ圧延において、圧延時の表面温度と歪付加量は、スケール内酸化物の結晶粒径に影響を及ぼす重要な因子である。８５０〜９８０℃範囲内での累積圧下率が３０％未満であると、スケール内酸化物の細粒化効果が得られない。このため、上記適正温度範囲内での累積圧下率の適正範囲を３０％以上に制限した。また、本発明において、上記適正温度範囲内での累積圧下率は、６０％以上がより好ましい範囲である。 In finish rolling, the surface temperature and the amount of strain applied during rolling are important factors that affect the crystal grain size of the oxide in the scale. When the cumulative rolling reduction within the range of 850 to 980 ° C. is less than 30%, the effect of refining the oxide within the scale cannot be obtained. For this reason, the appropriate range of the cumulative rolling reduction within the above appropriate temperature range is limited to 30% or more. In the present invention, the cumulative rolling reduction within the appropriate temperature range is more preferably 60% or more.
なお、本発明で説明する累積圧下率とは、上記温度範囲内で行った圧延に関して、初期板厚をｔ0、圧延後の板厚をｔfとした場合に、次式｛（ｔ0−ｔf）／ｔ０×１００｝によって求められる量である。 The cumulative rolling reduction described in the present invention is the following expression {(t 0 − when the initial plate thickness is t 0 and the post-rolling plate thickness is t f for rolling performed within the above temperature range. t f ) / t 0 × 100}.
なお、仕上げ圧延においては、通常は複数回のロール圧延を行うので、上記温度範囲内での累積圧下率３０％以上の圧延を含む条件であれば、それ以外の条件の圧延処理を行っても構わない。 In finish rolling, roll rolling is usually performed a plurality of times. Therefore, as long as the conditions include rolling with a cumulative rolling reduction of 30% or more within the above temperature range, rolling under other conditions may be performed. I do not care.
なお、スケール内の酸化物の平均結晶粒径は、鋼板断面において、ＥＢＳＤ法によって１００個以上の結晶粒を測定し、その公称粒径として求めることができる。 The average crystal grain size of the oxide in the scale can be obtained as a nominal grain size by measuring 100 or more crystal grains by the EBSD method in the cross section of the steel sheet.
脱炭層の厚さは、スケールを酸洗で除去した後、グロー放電発光分光分析法により地鉄表面からの深さ方向の炭素濃度分析を行うことにより評価できる。 The thickness of the decarburized layer can be evaluated by performing carbon concentration analysis in the depth direction from the surface of the iron core by glow discharge optical emission spectrometry after removing the scale by pickling.
以上説明したような本発明に係る塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板によれば、上記構成により、スケール有り、スケール無しのいずれの熱延鋼板に電着焼付塗装を施した場合であっても、優れた塗装耐食性と疲労耐久性が得られる。これにより、従来の鋼板において腐食による減肉量を見込んだ部品板厚が設定されていたのに対し、本発明の高強度熱延鋼板は、優れた塗装耐食性が得られることから、部品の板厚を薄くすることが可能となり、自動車あるいはトラック等の軽量化が可能となる。また、鋼板の板厚が薄い場合、鋼材料には高い疲労強度が求められるが、本発明の熱延鋼板は優れた疲労特性を具備することから、部材の軽量化に極めて好適である。 According to the high-strength hot-rolled steel sheet having excellent coating corrosion resistance and bending fatigue properties according to the present invention as described above, the above-described configuration is applied to the hot-rolled steel sheet with or without scale by electrodeposition baking coating. Even in this case, excellent coating corrosion resistance and fatigue durability can be obtained. As a result, the thickness of the component plate was set in anticipation of the thickness reduction due to corrosion in the conventional steel plate, whereas the high-strength hot-rolled steel plate of the present invention provides excellent coating corrosion resistance. The thickness can be reduced, and the weight of an automobile or a truck can be reduced. Moreover, when the steel plate is thin, the steel material is required to have high fatigue strength. However, the hot-rolled steel plate of the present invention has excellent fatigue characteristics, and is therefore extremely suitable for reducing the weight of the member.
また、本発明の塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板の製造方法によれば、上記手順並びに条件を採用することにより、優れた塗装耐食性並びに疲労特性を備える熱延鋼板を製造することが可能となる。 In addition, according to the method for producing a high-strength hot-rolled steel sheet having excellent coating corrosion resistance and bending fatigue characteristics according to the present invention, a hot-rolled steel sheet having excellent paint corrosion resistance and fatigue characteristics is produced by adopting the above procedure and conditions. It becomes possible to do.
以下、本発明に係る塗装耐食性と疲労特性に優れた熱延鋼板の実施例を挙げ、本発明をより具体的に説明するが、本発明は、もとより下記実施例に限定されるものではなく、前、後記の趣旨に適合し得る範囲で適当に変更を加えて実施することも可能であり、それらはいずれも本発明の技術的範囲に含まれるものである。 Hereinafter, examples of the hot-rolled steel sheet excellent in coating corrosion resistance and fatigue characteristics according to the present invention will be given and the present invention will be described more specifically, but the present invention is not limited to the following examples from the beginning, The present invention can be implemented with appropriate modifications within a range that can be adapted to the gist of the following, and these are all included in the technical scope of the present invention.
本実施例においては、まず、下記表１に質量％で示す化学成分（残部はＦｅ及び不可避不純物）を有するＡ〜Ｎの鋼を鋳造した後、このスラブを１０５０〜１２５０℃の範囲内で再加熱し、粗圧延を行った。
次いで、デスケーリング装置を用いて、スケールの残存厚さを変化させ、さらに、デスケーリング後の相対湿度を変化させた上で、下記表２に示す条件で仕上げ圧延を行なった。その後、６５０℃〜室温間で巻き取り処理を行った。
In this example, first, after casting steels A to N having chemical components (the balance is Fe and unavoidable impurities) shown in Table 1 below in mass%, the slab is re-used within a range of 1050 to 1250 ° C. Heating and rough rolling were performed.
Next, the remaining thickness of the scale was changed using a descaling apparatus, and the relative humidity after descaling was changed, and then finish rolling was performed under the conditions shown in Table 2 below. Then, the winding process was performed between 650 degreeC and room temperature.
そして、上記手順で得られた本発明例及び比較例の熱延鋼板について、以下に説明するような評価試験を行った。 And the evaluation test which is demonstrated below was done about the hot-rolled steel sheet of the example of the present invention obtained by the above-mentioned procedure, and a comparative example.
まず、スケール層中の酸化物の結晶粒径はＥＢＳＤ法にて測定した。 First, the crystal grain size of the oxide in the scale layer was measured by the EBSD method.
また、地鉄表面の脱炭層深さは、スケールを酸洗で除去した後、グロー放電発光分光分析法にてＣの濃度分布を測定し、脱炭していない部分のＣ濃度に対して、２／３のＣ濃度になる位置を脱炭層深さとした。 The depth of the decarburized layer on the surface of the ground iron is determined by measuring the C concentration distribution by glow discharge optical emission spectrometry after removing the scale by pickling. The position where the C concentration was 2/3 was defined as the decarburized layer depth.
また、スケール表面の粗さは、ＪＩＳ ０６０１Ｂに記載の方法で測定し、算術平均粗さＲａによって評価した。 Moreover, the roughness of the scale surface was measured by the method described in JIS 0601B and evaluated by the arithmetic average roughness Ra.
また、地鉄表面の粗さは、スケール付き鋼板のスケールを酸洗で除去した後、その後、ＪＩＳ ０６０１Ｂに記載の方法で測定し、算術平均粗さＲａによって評価した。
また、鋼板の引張特性は、各々の鋼板からＪＩＳ５号試験片を採取し、引張方向が圧延方向垂直方向（Ｃ方向）になるような条件で行った。
Moreover, after removing the scale of the steel plate with a scale by pickling, the roughness of the surface iron surface was measured by the method described in JIS 0601B, and evaluated by the arithmetic average roughness Ra.
In addition, the tensile properties of the steel plates were measured under the condition that a JIS No. 5 test piece was taken from each steel plate and the tensile direction was perpendicular to the rolling direction (C direction).
また、鋼板の疲労特性は、ＪＩＳ Ｚ２２７５に記載の方法に従い、応力比＝−１の条件下で平面曲げ疲労試験を行い、２００万回疲労限で評価した後、次式｛疲労限／ＴＳ（引張強度）｝から疲労限度比を算出した。 In addition, the fatigue properties of the steel sheet were evaluated by the plane bending fatigue test under the condition of stress ratio = −1 according to the method described in JIS Z2275, and evaluated at the fatigue limit of 2 million times. Fatigue limit ratio was calculated from (tensile strength)}.
また、塗装耐食性については、まず、スケール層付き鋼板を脱脂し、次いで、前処理としてリン酸亜鉛処理（化成処理）を行った後、カチオン電着塗装を２５μｍの厚さで行った。そして、電着塗装表面に線状の疵を付与した後、ＪＩＳ Ｚ２３７１に記載の方法に従って２００ｈの塩水噴霧試験（ＳＳＴ試験）を行い、この試験後に、テープ剥離試験を行った際の塗膜剥離幅を測定した。そして、塗膜剥離幅が２ｍｍ以下のものを「○（耐食性ＯＫ）」、２ｍｍを超えるものを「×（耐食性ＮＧ）」として二段階評価した。
次いで、酸洗によりスケールを除去した鋼板についても、上記と同様の方法で、塗装後耐食性を評価した。
As for the coating corrosion resistance, first, a steel sheet with a scale layer was degreased, and after a zinc phosphate treatment (chemical conversion treatment) as a pretreatment, a cationic electrodeposition coating was performed at a thickness of 25 μm. And after giving a linear wrinkle to the electrodeposition coating surface, according to the method of JISZ2371, the 200h salt spray test (SST test) is performed, and the coating film peeling at the time of performing a tape peeling test after this test The width was measured. Then, the film peeling width of 2 mm or less was evaluated in two stages as “◯ (corrosion resistance OK)” and the film exceeding 2 mm as “× (corrosion resistance NG)”.
Subsequently, also about the steel plate from which the scale was removed by pickling, the corrosion resistance after coating was evaluated by the same method as described above.
下記表１に鋼成分の一覧を示すとともに、下記表２に、作製した熱延鋼板に存在するスケール層の解析結果、スケール／地鉄界面粗さ、引張強さ（ＴＳ）、疲労特性、塗装耐食性の評価結果の一覧を示す。なお、下記表２中において、各見出しは以下の項目を示す。
ｔscale ：仕上げ圧延開始時のスケール厚さ（ｍｍ）
ＲＨ ：デスケーリング〜仕上げ圧延開始間の平均相対湿度(%)
Ｒｅｄ ：８５０〜９８０℃間の累積圧下率（％）
ＦＴ ：最終仕上げ圧延温度（℃）
Ｒａ１ ：地鉄表面の算術平均粗さ (μｍ)
Ｒａ２ ：スケール表面の算術平均粗さ（μｍ）
ｄox ：スケール内の酸化物の平均結晶粒径（μｍ）
ｄdec ：地鉄の脱炭層深さ(μｍ)
Table 1 below shows a list of steel components, and Table 2 below shows the analysis results of the scale layer present in the produced hot-rolled steel sheet, scale / base metal interface roughness, tensile strength (TS), fatigue characteristics, and coating. A list of evaluation results of corrosion resistance is shown. In Table 2 below, each heading indicates the following item.
t scale : Scale thickness at the start of finish rolling (mm)
RH: Average relative humidity (%) between descaling and start of finish rolling
Red: Cumulative rolling reduction between 850 and 980 ° C. (%)
FT: Final finish rolling temperature (° C)
Ra1: Arithmetic mean roughness of the surface of the steel (μm)
Ra2: Arithmetic mean roughness (μm) of the scale surface
d ox : Average crystal grain size of oxide in the scale (μm)
d dec : Decarburized layer depth of the railway (μm)
表２に示すように、本発明で規定する各条件で作製され、本発明で規定する範囲の地鉄表面の粗さ、並びに地鉄の脱炭層深さが本発明範囲内に制御された本発明例の熱延鋼板は、何れも、疲労限度比が０．４５以上であり、また、塗装耐食性の評価が「○」であった。また、スケール付き鋼板については、上記に加え、スケール層中の酸化物の平均結晶粒径、並びにスケール表面の平均粗さが本発明範囲内に制御された本発明例の熱延鋼板は、何れも、疲労限度比が０．４５以上であり、また、塗装耐食性の評価が「○」であった。これにより、本発明の熱延鋼板が、塗装耐食性と曲げ疲労特性に優れていることが明らかとなった。 As shown in Table 2, the present invention was manufactured under the conditions specified in the present invention, and the roughness of the surface of the base iron within the range specified by the present invention and the depth of the decarburized layer of the base iron were controlled within the scope of the present invention. All of the hot-rolled steel sheets of the inventive examples had a fatigue limit ratio of 0.45 or more, and the evaluation of coating corrosion resistance was “◯”. As for the steel sheet with scale, in addition to the above, the hot rolled steel sheet of the present invention example in which the average crystal grain size of the oxide in the scale layer and the average roughness of the scale surface are controlled within the scope of the present invention, The fatigue limit ratio was 0.45 or more, and the coating corrosion resistance was evaluated as “◯”. Thereby, it became clear that the hot-rolled steel sheet of the present invention is excellent in coating corrosion resistance and bending fatigue characteristics.
これに対して、表２に示す比較例の熱延鋼板は、地鉄表面の粗さ、地鉄表面の脱炭層の深さ、スケール層中の酸化物の平均結晶粒径、並びに、スケール表面の平均粗さの何れかが本発明の規定範囲を満たしていないことから、塗装耐食性か疲労特性の少なくとも何れかが劣る結果となった。 On the other hand, the hot-rolled steel sheet of the comparative example shown in Table 2 has the roughness of the base iron surface, the depth of the decarburized layer on the base iron surface, the average crystal grain size of the oxide in the scale layer, and the scale surface. Since any one of the average roughnesses did not satisfy the specified range of the present invention, at least one of the coating corrosion resistance and the fatigue characteristics was inferior.
試験番号Ａ−２、Ｂ−４は、仕上げ圧延前のスケール厚が本発明の規定範囲に比べて過大であったため、地鉄表面粗さが大きくなって疲労特性が低下するとともに、スケールが破砕されてスケール表面粗さが大きくなったために、スケール表面材の塗装耐食性がＮＧの評価となった例である。 In test numbers A-2 and B-4, the scale thickness before finish rolling was excessive as compared with the specified range of the present invention. This is an example in which the coating surface corrosion resistance of the scale surface material was evaluated as NG because the scale surface roughness was increased.
試験番号Ｂ−１は、相対湿度は適正だったものの、仕上げ圧延前のスケール厚が本発明の規定範囲に比べて過小であったため、地鉄の脱炭が進行するとともに、スケール内の酸化物粒径が粗大化し、塗装耐食性も疲労特性もＮＧの評価となった例である。 Although test number B-1 had an appropriate relative humidity, the scale thickness before finish rolling was too small as compared with the specified range of the present invention. This is an example in which the particle size becomes coarse and the coating corrosion resistance and fatigue characteristics are evaluated as NG.
また、試験番号Ａ−３、Ａ−４、Ｄ−１は、デスケーリング後から仕上げ圧延開始までの相対湿度が低かったために地鉄の脱炭が進行し、疲労特性がＮＧの評価となり、さらに塗装後耐食性もＮＧの評価となった例である。 In addition, in test numbers A-3, A-4, and D-1, since the relative humidity from the descaling to the start of finish rolling was low, the decarburization of the ground iron progressed, and the fatigue characteristics were evaluated as NG. This is an example in which the corrosion resistance after painting was evaluated as NG.
また、試験番号Ａ−７、Ａ−８は、仕上げ圧延前のスケール厚は適正だったものの、圧延中にスケールに歪が付与されなかったため、スケール内の酸化物結晶粒が微細化せず、塗装耐食性がＮＧとなった例である。ただし、試験番号Ａ−７、Ａ−８は地鉄表面の脱炭層が小さいため、スケール除去後の鋼板については、疲労特性および塗装後耐食性共にＯＫの評価である。 In addition, although test numbers A-7 and A-8 had an appropriate scale thickness before finish rolling, no strain was imparted to the scale during rolling, so the oxide crystal grains in the scale were not refined, This is an example in which the coating corrosion resistance is NG. However, since test numbers A-7 and A-8 have a small decarburized layer on the surface of the base metal, both the fatigue characteristics and the corrosion resistance after coating are evaluated as OK for the steel plates after the scale removal.
また、試験番号Ａ−１０は、デスケーリング後から仕上げ圧延終了まで、相対湿度を規定の範囲内に保持した例であり、脱炭層の形成が強く抑制されると共に、スケール破砕も抑制され、塗装耐食性と曲げ疲労特性の何れも非常に優れていることが明らかとなった。 Test number A-10 is an example in which the relative humidity is maintained within a specified range from the descaling to the end of finish rolling, and the formation of the decarburized layer is strongly suppressed and scale crushing is also suppressed, and the coating is performed. It was revealed that both the corrosion resistance and the bending fatigue properties are very excellent.
また、試験番号Ａ−１１は、仕上げ圧延温度が適正範囲以下であったために、スケール破砕が起こると共にスケール／地鉄界面の粗さが増加し、疲労特性と塗装後耐食性がＮＧとなった例である。なお、試験番号Ａ−１１は脱炭層はないため、酸洗後の板の塗装耐食性はＯＫの評価であった。 In Test No. A-11, since the finish rolling temperature was below the proper range, scale crushing occurred, the roughness of the scale / base metal interface increased, and the fatigue characteristics and corrosion resistance after coating became NG. It is. Since test number A-11 has no decarburized layer, the coating corrosion resistance of the plate after pickling was evaluated as OK.
また、試験番号Ｈ−１、Ｉ−１、Ｋ−１は、Ｃ量、Ｓｉ＋Ａｌ量、Ｍｎ量が適正量以下であっため、最大引張強度が５４０ＭＰａに満たなかった例である。 Test numbers H-1, I-1, and K-1 are examples in which the maximum tensile strength was less than 540 MPa because the C amount, Si + Al amount, and Mn amount were not more than appropriate amounts.
また、試験番号Ｌ−１は、Ｎ量が適正量以上であっため、Ｔｉの効果が発揮されず、地鉄表面の脱炭層の形成が抑制できず、疲労特性とスケール除去後の板の塗装後耐食性がＮＧであった例である。 Further, test number L-1 is that the amount of N is equal to or more than the appropriate amount, the effect of Ti is not exhibited, the formation of a decarburized layer on the surface of the ground iron cannot be suppressed, and fatigue characteristics and coating of the plate after scale removal This is an example in which the post-corrosion resistance was NG.
また、試験番号Ｊ−１、Ｎ−１は、ＴｉとＮｂの合計添加量が適正量以下であったため、地鉄の脱炭が抑制できず、疲労特性とスケール除去後の板の塗装後耐食性がＮＧであった例である。 Moreover, since the total addition amount of Ti and Nb was below an appropriate amount for the test numbers J-1 and N-1, the decarburization of the base iron could not be suppressed, and the fatigue characteristics and corrosion resistance after painting of the plate after scale removal This is an example in which NG.
また、試験番号Ｍ−１は、製造条件は適正であるものの、ＳｉとＡｌの合計添加量が適正範囲以上であったため、地鉄表面の脱炭層の形成を抑制できず、疲労特性とスケール除去後の板の塗装後耐食性がＮＧであった例である。
以上説明した実施例の結果より、本発明の熱延鋼板およびその製造方法が、塗装耐食性と疲労特性に優れていることが明らかである。
Moreover, although test number M-1 was suitable for manufacturing conditions, since the total addition amount of Si and Al was more than the appropriate range, formation of a decarburized layer on the surface of the iron base could not be suppressed, and fatigue characteristics and scale removal were achieved. This is an example in which the corrosion resistance after painting of the later plate was NG.
From the results of the examples described above, it is clear that the hot-rolled steel sheet and the manufacturing method thereof of the present invention are excellent in coating corrosion resistance and fatigue characteristics.
本発明によれば、例えば、自動車やトラックのフレームやメンバー、シャシー等の素材として好適な、塗装耐食性と疲労特性に優れた熱延鋼板を提供することが可能となる。このように、自動車やトラックのフレームやメンバー、シャシー等の部材に本発明を適用することにより、塗装後の耐食性や疲労強度の向上、さらに、軽量化等のメリットを十分に享受することができ、産業上の効果は極めて高い。 ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the hot-rolled steel plate excellent in coating corrosion resistance and a fatigue characteristic suitable as raw materials, such as a frame, a member, and a chassis of a motor vehicle or a truck, for example. In this way, by applying the present invention to members such as automobiles and truck frames, members, chassis, etc., it is possible to fully enjoy the benefits such as improved corrosion resistance and fatigue strength after painting, and weight reduction. Industrial effect is extremely high.
Claims (7)
Ｃ：０．０５〜０．２５％、
ＳｉとＡｌの合計含有量：０．８％〜２．０％、
Ｍｎ：１．０〜４．０％、
ＴｉとＮｂの１種または２種の合計含有量：０．０５〜０．２％、
Ｎ：０．０００３〜０．０１％、
Ｐ：０．００１〜０．２％、
Ｓ：０．０１％以下
を含有し、残部がＦｅおよび不可避的不純物からなる成分組成を有し、地鉄表面の脱炭層の厚さが５μｍ以下であり、地鉄表面の平均粗さＲａが２．０μｍ以下であり、最大引張強度が５４０ＭＰａ以上であることを特徴とする塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板。 % By mass
C: 0.05 to 0.25%
Total content of Si and Al: 0.8% to 2.0%,
Mn: 1.0-4.0%,
Total content of one or two of Ti and Nb: 0.05 to 0.2%,
N: 0.0003 to 0.01%,
P: 0.001 to 0.2%,
S: It contains 0.01% or less, the remainder has a component composition consisting of Fe and inevitable impurities, the thickness of the decarburized layer on the surface of the base iron is 5 μm or less, and the average roughness Ra of the surface of the base iron is A high-strength hot-rolled steel sheet excellent in coating corrosion resistance and bending fatigue characteristics, characterized by being 2.0 μm or less and having a maximum tensile strength of 540 MPa or more.
Ｖ：０．２％以下、
Ｍｏ：１．５％以下
の１種または２種を含有することを特徴とする請求項１又は請求項２に記載の塗装耐食性と曲げ疲労特性に優れた高強度熱延鋼板。 Furthermore, in mass%,
V: 0.2% or less,
The high-strength hot-rolled steel sheet having excellent coating corrosion resistance and bending fatigue characteristics according to claim 1 or 2, wherein Mo: 1.5% or less is contained.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016163906A (en) * | 2015-02-27 | 2016-09-08 | Ｊｆｅスチール株式会社 | Silicon-containing hot-rolled pickled steel sheet and method for production thereof |
Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1192859A (en) * | 1997-09-18 | 1999-04-06 | Kawasaki Steel Corp | High tensile strength hot rolled steel plate having ultrafine structure and its production |
| JPH11269539A (en) * | 1998-03-23 | 1999-10-05 | Kawasaki Steel Corp | Manufacture of austenitic stainless steel sheet excellent in descaling property |
| JP2001040451A (en) * | 1999-07-29 | 2001-02-13 | Kawasaki Steel Corp | Hot rolled steel plate for press forming |
| JP2001303186A (en) * | 2000-04-21 | 2001-10-31 | Nippon Steel Corp | Dual-phase steel sheet excellent in burring property, and its manufacturing method |
| JP2002226944A (en) * | 2001-02-02 | 2002-08-14 | Kawasaki Steel Corp | Hot-rolled, high-tensile steel plate having excellent chemical convertibility and corrosion resistance, and its manufacturing method |
| JP2005029883A (en) * | 2002-09-27 | 2005-02-03 | Nippon Steel Corp | Cu-CONTAINING STEEL MATERIAL HAVING SUPERIOR SURFACE QUALITY, AND MANUFACTURING METHOD THEREFOR |
| JP2008214650A (en) * | 2007-02-28 | 2008-09-18 | Jfe Steel Kk | Hot-rolled steel plate for die quench and manufacturing method therefor |
| JP2009068079A (en) * | 2007-09-14 | 2009-04-02 | Sumitomo Metal Ind Ltd | Steel tube with excellent steam oxidation resistance |
| JP2009161836A (en) * | 2008-01-09 | 2009-07-23 | Nisshin Steel Co Ltd | Ferritic stainless steel sheet excellent in corrosion resistance in welding crevice part |
| JP2010065298A (en) * | 2008-09-12 | 2010-03-25 | Jfe Steel Corp | Method for producing ferritic stainless steel sheet having excellent surface quality |
| JP2012021192A (en) * | 2010-07-14 | 2012-02-02 | Nippon Steel Corp | High strength hot rolled steel sheet superior in coating corrosion resistance and punched part fatigue characteristic, and method for manufacturing the same |
-
2011
- 2011-12-06 JP JP2011267124A patent/JP5857694B2/en active Active
Patent Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1192859A (en) * | 1997-09-18 | 1999-04-06 | Kawasaki Steel Corp | High tensile strength hot rolled steel plate having ultrafine structure and its production |
| JPH11269539A (en) * | 1998-03-23 | 1999-10-05 | Kawasaki Steel Corp | Manufacture of austenitic stainless steel sheet excellent in descaling property |
| JP2001040451A (en) * | 1999-07-29 | 2001-02-13 | Kawasaki Steel Corp | Hot rolled steel plate for press forming |
| JP2001303186A (en) * | 2000-04-21 | 2001-10-31 | Nippon Steel Corp | Dual-phase steel sheet excellent in burring property, and its manufacturing method |
| JP2002226944A (en) * | 2001-02-02 | 2002-08-14 | Kawasaki Steel Corp | Hot-rolled, high-tensile steel plate having excellent chemical convertibility and corrosion resistance, and its manufacturing method |
| JP2005029883A (en) * | 2002-09-27 | 2005-02-03 | Nippon Steel Corp | Cu-CONTAINING STEEL MATERIAL HAVING SUPERIOR SURFACE QUALITY, AND MANUFACTURING METHOD THEREFOR |
| JP2008214650A (en) * | 2007-02-28 | 2008-09-18 | Jfe Steel Kk | Hot-rolled steel plate for die quench and manufacturing method therefor |
| JP2009068079A (en) * | 2007-09-14 | 2009-04-02 | Sumitomo Metal Ind Ltd | Steel tube with excellent steam oxidation resistance |
| JP2009161836A (en) * | 2008-01-09 | 2009-07-23 | Nisshin Steel Co Ltd | Ferritic stainless steel sheet excellent in corrosion resistance in welding crevice part |
| JP2010065298A (en) * | 2008-09-12 | 2010-03-25 | Jfe Steel Corp | Method for producing ferritic stainless steel sheet having excellent surface quality |
| JP2012021192A (en) * | 2010-07-14 | 2012-02-02 | Nippon Steel Corp | High strength hot rolled steel sheet superior in coating corrosion resistance and punched part fatigue characteristic, and method for manufacturing the same |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016163906A (en) * | 2015-02-27 | 2016-09-08 | Ｊｆｅスチール株式会社 | Silicon-containing hot-rolled pickled steel sheet and method for production thereof |
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