JP5552861B2

JP5552861B2 - High-strength hot-dip galvanized steel sheet and manufacturing method thereof

Info

Publication number: JP5552861B2
Application number: JP2010072872A
Authority: JP
Inventors: 祐介伏脇; 昌浩吉田; 芳春杉本; 善継鈴木
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2009-03-31
Filing date: 2010-03-26
Publication date: 2014-07-16
Anticipated expiration: 2030-03-26
Also published as: JP2010255108A

Description

本発明は、ＳｉおよびＭｎを含有する高強度鋼板を母材とする加工性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法に関するものである。 The present invention relates to a high-strength hot-dip galvanized steel sheet excellent in workability using a high-strength steel sheet containing Si and Mn as a base material and a method for producing the same.

近年、自動車、家電、建材等の分野において、素材鋼板に防錆性を付与した表面処理鋼板、中でも溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板が広範に使用されている。また、自動車の燃費向上および自動車の衝突安全性向上の観点から、車体材料の高強度化によって薄肉化を図り、車体そのものを軽量化しかつ高強度化する要望が高まっている。そのために高強度鋼板の自動車への適用が促進されている。 In recent years, in the fields of automobiles, home appliances, building materials and the like, surface-treated steel sheets imparted with rust resistance to raw steel sheets, particularly hot-dip galvanized steel sheets and galvannealed steel sheets have been widely used. In addition, from the viewpoint of improving the fuel efficiency of automobiles and improving the collision safety of automobiles, there is an increasing demand for reducing the thickness of the vehicle body by increasing the strength of the vehicle body material and reducing the weight of the vehicle body. Therefore, application of high-strength steel sheets to automobiles is being promoted.

一般的に、溶融亜鉛めっき鋼板は、スラブを熱間圧延や冷間圧延した薄鋼板を母材として用い、母材鋼板を連続式溶融亜鉛めっきライン（以下、ＣＧＬと称す）の焼鈍炉にて再結晶焼鈍および溶融亜鉛めっき処理を行い製造される。合金化溶融亜鉛めっき鋼板の場合は、溶融亜鉛めっき処理の後、さらに合金化処理を行い製造される。 In general, a hot dip galvanized steel sheet uses a thin steel sheet obtained by hot rolling or cold rolling a slab as a base material, and the base steel sheet is used in an annealing furnace of a continuous hot dip galvanizing line (hereinafter referred to as CGL). Manufactured by recrystallization annealing and hot dip galvanizing. In the case of an alloyed hot-dip galvanized steel sheet, it is manufactured after further hot-dip galvanizing treatment.

ここで、ＣＧＬの焼鈍炉の加熱炉タイプとしては、ＤＦＦ型（直火型）、ＮＯＦ型（無酸化型）、オールラジアントチューブ型等があるが、近年では、操業のし易さやピックアップが発生しにくい等により低コストで高品質なめっき鋼板を製造できるなどの理由からオールラジアントチューブ型の加熱炉を備えるＣＧＬの建設が増加している。しかしながら、ＤＦＦ型（直火型）、ＮＯＦ型（無酸化型）と異なり、オールラジアントチューブ型の加熱炉は焼鈍直前に酸化工程がないため、Ｓｉ、Ｍｎ等の易酸化性元素を含有する鋼板についてはめっき性確保の点で不利である。 Here, there are DFF type (direct flame type), NOF type (non-oxidation type), all radiant tube type, etc. as the heating furnace type of CGL annealing furnace. The construction of CGLs equipped with an all-radiant tube type heating furnace is increasing for the reason that it is possible to produce high-quality plated steel sheets at low cost due to difficulty in carrying out the process. However, unlike the DFF type (direct flame type) and NOF type (non-oxidation type), the all-radiant tube type heating furnace does not have an oxidation step immediately before annealing, so a steel plate containing an easily oxidizable element such as Si or Mn. Is disadvantageous in terms of securing plating properties.

Ｓｉ、Ｍｎを多量に含む高強度鋼板を母材とした溶融めっき鋼板の製造方法として、特許文献１および特許文献２には、還元炉における加熱温度を水蒸気分圧で表される式で規定し露点を上げることで、地鉄表層を内部酸化させる技術が開示されている。しかしながら、露点を制御するエリアが炉内全体を前提としたものであるため、露点の制御が困難であり安定操業が困難である。また、不安定な露点制御のもとでの合金化溶融亜鉛めっき鋼板の製造は、下地鋼板に形成される内部酸化物の分布状態にバラツキが認められ、鋼板の長手方向や幅方向でめっき濡れ性ムラや合金化ムラなどの欠陥が発生する懸念がある。 As a method for producing a hot-dip galvanized steel sheet using a high-strength steel sheet containing a large amount of Si and Mn as a base material, Patent Document 1 and Patent Document 2 define a heating temperature in a reduction furnace by an expression expressed by a partial pressure of water vapor. A technique for internally oxidizing the surface layer of the railway by increasing the dew point is disclosed. However, since the area for controlling the dew point is premised on the entire inside of the furnace, it is difficult to control the dew point, and stable operation is difficult. In addition, in the manufacture of galvannealed steel sheets under unstable dew point control, variations in the distribution of internal oxides formed on the base steel sheet were observed, and wetting in the longitudinal and width directions of the steel sheet was observed. There is a concern that defects such as unevenness in properties and unevenness in alloying may occur.

また、特許文献３には、酸化性ガスであるＨ_２ＯやＯ_２だけでなく、ＣＯ_２濃度も同時に規定することで、めっき直前の地鉄表層を内部酸化させ外部酸化を抑制してめっき外観を改善する技術が開示されている。しかしながら、特許文献１および２と同様に、特許文献３においても、内部酸化物の存在により加工時に割れが発生しやすくなり、耐めっき剥離性が劣化する。また、耐食性の劣化も認められる。さらにＣＯ_２は炉内汚染や鋼板表面への浸炭などが起こり機械特性が変化するなどの問題が懸念される。 In Patent Document 3, not only the oxidizing gases H ₂ O and O ₂ but also the CO ₂ concentration are simultaneously defined, so that the surface layer immediately before plating is internally oxidized to suppress external oxidation. A technique for improving the appearance is disclosed. However, similarly to Patent Documents 1 and 2, also in Patent Document 3, cracks are likely to occur during processing due to the presence of the internal oxide, and the plating peel resistance deteriorates. Moreover, deterioration of corrosion resistance is also recognized. Further, there is a concern that CO ₂ may cause problems such as in-furnace contamination, carburizing on the steel sheet surface, and mechanical characteristics changing.

さらに、最近では、加工の厳しい箇所への高強度溶融亜鉛めっき鋼板、高強度合金化溶融亜鉛めっき鋼板の適用が進んでおり、高加工時の耐めっき剥離特性が重要視されるようになっている。具体的にはめっき鋼板に９０°超えの曲げ加工を行いより鋭角に曲げたときや衝撃が加わり鋼板が加工を受けた場合の、加工部のめっき剥離の抑制が要求される。 Furthermore, recently, the application of high-strength hot-dip galvanized steel sheets and high-strength alloyed hot-dip galvanized steel sheets to places where machining is severe has progressed, and the anti-plating resistance characteristics at the time of high processing have become important. Yes. Specifically, it is required to suppress plating peeling at the processed part when the plated steel sheet is bent at an angle of more than 90 ° and bent at an acute angle or when the steel sheet is processed by impact.

このような特性を満たすためには、鋼中に多量にＳｉを添加し所望の鋼板組織を確保するだけでなく、高加工時の割れなどの起点になる可能性があるめっき層直下の地鉄表層の組織、構造のより高度な制御が求められる。しかしながら従来技術ではそのような制御は困難であり、焼鈍炉にオールラジアントチューブ型の加熱炉を備えるＣＧＬでＳｉ含有高強度鋼板を母材として高加工時の耐めっき剥離特性に優れた溶融亜鉛めっき鋼板を製造することができなかった。 In order to satisfy such characteristics, not only does a large amount of Si be added to the steel to ensure the desired steel sheet structure, but also the iron core directly under the plating layer, which may be the starting point of cracking during high processing. More advanced control of the structure and structure of the surface layer is required. However, such control is difficult with the prior art, and hot dip galvanization with excellent anti-plating properties at high processing using CGL with Si-containing high-strength steel plate as a base material with an all-radiant tube type heating furnace in the annealing furnace. A steel plate could not be produced.

特開２００４−３２３９７０号公報JP 2004-323970 A 特開２００４−３１５９６０号公報JP 2004-315960 A 特開２００６−２３３３３３号公報JP 2006-233333 A

本発明は、かかる事情に鑑みてなされたものであって、Ｓｉ、Ｍｎを含有する鋼板を母材とし、めっき外観、耐食性および高加工時の耐めっき剥離性に優れる高強度溶融亜鉛めっき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 such circumstances, and uses a steel sheet containing Si and Mn as a base material, and has a high-strength hot-dip galvanized steel sheet excellent in plating appearance, corrosion resistance, and plating peeling resistance during high processing, and It aims at providing the manufacturing method.

従来は、めっき性を改善する目的で積極的に鋼板の内部を酸化させていた。しかし、同時に、耐食性や加工性が劣化する。そこで、本発明者らは、従来の考えにとらわれない新たな方法で課題を解決する方法を検討した。その結果、焼鈍工程の雰囲気と温度を適切に制御することで、めっき層直下の鋼板表層部において内部酸化の形成を抑制し、優れためっき外観と、より高い耐食性と高加工時の良好な耐めっき剥離性が得られることを知見した。具体的には、均熱過程では焼鈍炉内温度：８２０℃以上１０００℃以下の温度域を水素濃度：２５ｖｏｌ％以上とし、さらに、冷却過程では７５０℃以上の温度域を水素濃度：２５ｖｏｌ％以上となるように制御して焼鈍、溶融亜鉛めっき処理を行う。このような処理を行うことによって、雰囲気中の還元能力が増し、鋼板表面に選択的表面酸化（以後、表面濃化と呼ぶ）したＳｉ、Ｍｎなどの易酸化性元素の酸化物を還元することができる。なお、雰囲気中の酸素ポテンシャルは非常に低いため、内部酸化は殆ど起こらない。そして、このように雰囲気中の水素濃度を制御することにより、内部酸化を形成させずに表面濃化を還元し、不めっきのない、めっき外観、耐食性および高加工時の耐めっき剥離性に優れる高強度溶融亜鉛めっき鋼板が得られることになる。なお、めっき外観に優れるとは、不めっきや合金化ムラが認められない外観を有することを言う。
そして、以上の方法により得られる高強度溶融亜鉛めっき鋼板は、亜鉛めっき層の直下の、下地鋼板表面から１００μm以内の鋼板表層部において、Ｆｅ、Ｓｉ、Ｍｎ、Ａｌ、Ｐ、さらには、Ｂ、Ｎｂ、Ｔｉ、Ｃｒ、Ｍｏ、Ｃｕ、Ｎｉの中から選ばれる１種以上（Ｆｅのみを除く）の酸化物の形成が抑制され、その形成量は合計で片面あたり０.０６０ｇ/m^２以下に抑制される。これにより、めっき外観に優れ、耐食性が著しく向上し、地鉄表層における曲げ加工時の割れ防止を実現させ、高加工時の耐めっき剥離性に優れることになる。 Conventionally, the inside of a steel plate has been actively oxidized for the purpose of improving the plating property. However, at the same time, corrosion resistance and workability deteriorate. Therefore, the present inventors have studied a method for solving the problem by a new method not confined to the conventional idea. As a result, by appropriately controlling the atmosphere and temperature of the annealing process, the formation of internal oxidation is suppressed in the surface layer of the steel sheet directly under the plating layer, and the excellent plating appearance, higher corrosion resistance and good resistance to high processing. It has been found that plating peelability can be obtained. Specifically, in the soaking process, the temperature range in the annealing furnace: 820 ° C. or more and 1000 ° C. or less is set to hydrogen concentration: 25 vol% or more. In the cooling process, the temperature range of 750 ° C. or more is set to hydrogen concentration: 25 vol% or more. Annealing and hot dip galvanizing treatment are performed under control. By performing such treatment, the reducing ability in the atmosphere is increased, and oxides of oxidizable elements such as Si and Mn that are selectively surface oxidized (hereinafter referred to as surface concentration) on the steel sheet surface are reduced. Can do. Since the oxygen potential in the atmosphere is very low, little internal oxidation occurs. And by controlling the hydrogen concentration in the atmosphere in this way, the surface concentration is reduced without forming internal oxidation, and there is no plating, excellent plating appearance, corrosion resistance, and excellent plating peeling resistance during high processing. A high-strength hot-dip galvanized steel sheet will be obtained. In addition, having excellent plating appearance means having an appearance in which non-plating and alloying unevenness are not recognized.
And, the high-strength hot-dip galvanized steel sheet obtained by the above method is Fe, Si, Mn, Al, P, and B, in the steel sheet surface layer portion within 100 μm from the surface of the underlying steel sheet, directly under the galvanized layer. The formation of one or more oxides selected from Nb, Ti, Cr, Mo, Cu, and Ni (excluding only Fe) is suppressed, and the total amount formed is 0.060 g / m ² or less per side. It is suppressed. Thereby, the plating appearance is excellent, the corrosion resistance is remarkably improved, the crack prevention at the bending process in the surface layer of the base metal is realized, and the plating peeling resistance at the high processing is excellent.

本発明は上記知見に基づくものであり、特徴は以下の通りである。
［１］質量％で、Ｃ：０．０１〜０．１８％、Ｓｉ：０．０２〜２．０％、Ｍｎ：１．０〜３．０％、Ａｌ：０．００１〜１．０％、Ｐ：０．００５〜０．０６０％、Ｓ≦０．０１％を含有し、残部がＦｅおよび不可避的不純物からなる鋼板の表面に、片面あたりのめっき付着量が２０〜１２０ｇ／ｍ^２の亜鉛めっき層を有する高強度溶融亜鉛めっき鋼板を製造する方法であって、鋼板に連続式溶融亜鉛めっき設備において焼鈍および溶融亜鉛めっき処理を施すに際し、均熱過程では焼鈍炉内温度：８２０℃以上１０００℃以下の温度域を水素濃度：２５ｖｏｌ％以上とし、さらに、冷却過程では７５０℃以上の温度域を水素濃度：２５ｖｏｌ％以上とすることを特徴とする高強度溶融亜鉛めっき鋼板の製造方法。
［２］前記［１］において、前記鋼板は、成分組成として、質量％で、さらに、Ｂ：０．００１〜０．００５％、Ｎｂ：０．００５〜０．０５％、Ｔｉ：０．００５〜０．０５％、Ｃｒ：０．００１〜１．０％、Ｍｏ：０．０５〜１．０％、Ｃｕ：０．０５〜１．０％、Ｎｉ：０．０５〜１．０％の中から選ばれる１種以上の元素を含有することを特徴とする高強度溶融亜鉛めっき鋼板の製造方法。
［３］前記［１］または［２］において、溶融亜鉛めっき処理後、さらに、４５０℃以上６００℃以下の温度に鋼板を加熱して合金化処理を施し、亜鉛めっき層のＦｅ含有量を７〜１５質量％の範囲にすることを特徴とする高強度溶融亜鉛めっき鋼板の製造方法。
［４］前記［１］〜［３］に記載のいずれかの製造方法により製造され、亜鉛めっき層直下の、下地鋼板表面から１００μｍ以内の鋼板表層部に生成したＦｅ、Ｓｉ、Ｍｎ、Ａｌ、Ｐ、Ｂ、Ｎｂ、Ｔｉ、Ｃｒ、Ｍｏ、Ｃｕ、Ｎｉの中から選ばれる1種以上の酸化物が、片面あたり０．０６０ｇ／ｍ^２以下であることを特徴とする高強度溶融亜鉛めっき鋼板。 The present invention is based on the above findings, and features are as follows.
[1] By mass%, C: 0.01 to 0.18%, Si: 0.02 to 2.0%, Mn: 1.0 to 3.0%, Al: 0.001 to 1.0% , P: 0.005 to 0.060%, S ≦ 0.01%, with the balance being Fe and unavoidable impurities on the surface of the steel sheet, the plating adhesion amount per side is 20 to 120 g / m ² A method for producing a high-strength hot-dip galvanized steel sheet having a galvanized layer, and when the steel sheet is subjected to annealing and hot-dip galvanizing treatment in a continuous hot-dip galvanizing facility, the temperature in the annealing furnace: 820 ° C. or higher in the soaking process A method for producing a high-strength hot-dip galvanized steel sheet, characterized in that a temperature range of 1000 ° C. or lower is a hydrogen concentration: 25 vol% or higher, and further, a temperature range of 750 ° C. or higher is a hydrogen concentration: 25 vol% or higher in the cooling process.
[2] In the above [1], the steel sheet is in mass% as a component composition, and further B: 0.001 to 0.005%, Nb: 0.005 to 0.05%, Ti: 0.005. -0.05%, Cr: 0.001-1.0%, Mo: 0.05-1.0%, Cu: 0.05-1.0%, Ni: 0.05-1.0% A method for producing a high-strength hot-dip galvanized steel sheet, comprising one or more elements selected from the inside.
[3] In the above [1] or [2], after the hot dip galvanizing treatment, the steel plate is further heated to a temperature of 450 ° C. or higher and 600 ° C. or lower to perform alloying treatment, and the Fe content of the galvanized layer is set to 7 A method for producing a high-strength hot-dip galvanized steel sheet, characterized by being in the range of ˜15 mass%.
[4] Fe, Si, Mn, Al produced by the production method according to any one of [1] to [3], and formed directly on the surface of the steel plate within 100 μm from the surface of the underlying steel plate immediately below the galvanized layer. One or more oxides selected from P, B, Nb, Ti, Cr, Mo, Cu, and Ni are 0.060 g / m ² or less per side, and a high-strength hot-dip galvanized steel sheet .

なお、本発明において、高強度とは、引張強度ＴＳが３４０ＭＰa以上である。また、本発明の高強度溶融亜鉛めっき鋼板は、溶融亜鉛めっき処理後合金化処理を施さないめっき鋼板（以下、ＧＩと称することもある）、合金化処理を施すめっき鋼板（以下、ＧＡと称することもある）のいずれも含むものである。 In the present invention, the high strength means that the tensile strength TS is 340 MPa or more. The high-strength hot-dip galvanized steel sheet of the present invention includes a plated steel sheet (hereinafter sometimes referred to as GI) that is not subjected to alloying after the hot-dip galvanizing process, and a plated steel sheet (hereinafter referred to as GA) that is subjected to the alloying process. In some cases).

本発明によれば、めっき外観、耐食性および高加工時の耐めっき剥離性に優れる高強度溶融亜鉛めっき鋼板が得られる。 ADVANTAGE OF THE INVENTION According to this invention, the high intensity | strength hot-dip galvanized steel plate excellent in plating external appearance, corrosion resistance, and the plating peeling resistance at the time of high processing is obtained.

以下、本発明について具体的に説明する。なお、以下の説明において、鋼成分組成の各元素の含有量、めっき層成分組成の各元素の含有量の単位はいずれも「質量％」であり、以下、特に断らない限り単に「％」で示す。 Hereinafter, the present invention will be specifically described. In the following description, the content of each element of the steel component composition and the unit of the content of each element of the plating layer component composition are all “mass%”, and hereinafter, simply “%” unless otherwise specified. Show.

先ず、本発明で最も重要な要件である、めっき層直下の下地鋼板表面の構造を決定する焼鈍雰囲気条件について説明する。
鋼中に多量のＳｉおよびＭｎが添加された高強度溶融亜鉛めっき鋼板において、耐食性及び高加工時の耐めっき剥離性を満足させるためには、腐食や高加工時の割れなどの起点となる可能性があるめっき層直下の地鉄表層の内部酸化を極力少なくすることが求められる。 First, an annealing atmosphere condition that determines the structure of the surface of the underlying steel sheet immediately below the plating layer, which is the most important requirement in the present invention, will be described.
In high-strength hot-dip galvanized steel sheets with a large amount of Si and Mn added to the steel, in order to satisfy corrosion resistance and anti-plating resistance during high processing, it may be the starting point for corrosion and cracking during high processing. Therefore, it is required to minimize internal oxidation of the surface layer of the railway just below the plating layer.

ＳｉやＭｎの内部酸化を促進させることによりめっき性を向上させることは可能ではあるが、これは逆に耐食性や加工性の劣化をもたらすことになってしまう。このため、ＳｉやＭｎの内部酸化を促進させる方法以外で、良好なめっき性を維持しつつ、内部酸化を抑制して耐食性、加工性を向上させる必要がある。検討した結果、本発明では、まず、めっき性を確保するために、焼鈍加熱過程において形成されたＳｉ、Ｍｎなどの表面濃化物を比較的高温の均熱過程の酸素ポテンシャルを低下させることで還元し、鋼板表面の酸化物を減少させ、めっき性を改善する。そして、地鉄表層部に内部酸化も殆ど形成されないため、耐食性及び高加工性が改善することになる。 Although it is possible to improve the plateability by promoting the internal oxidation of Si and Mn, this leads to deterioration of corrosion resistance and workability. For this reason, it is necessary to improve corrosion resistance and workability by suppressing internal oxidation while maintaining good plating properties, other than a method of promoting internal oxidation of Si or Mn. As a result of the examination, in the present invention, first, in order to ensure the plating property, the surface concentrate such as Si and Mn formed in the annealing heating process is reduced by reducing the oxygen potential in the soaking process at a relatively high temperature. And reducing the oxide on the surface of the steel sheet to improve the plateability. And since almost no internal oxidation is formed in the surface layer portion of the iron base, the corrosion resistance and the high workability are improved.

このような効果は、連続式溶融亜鉛めっき設備において焼鈍および溶融亜鉛めっき処理を施すに際し、均熱過程では焼鈍炉内温度：８２０℃以上１０００℃以下の温度域を水素濃度：２５ｖｏｌ％以上とし、さらに、冷却過程では７５０℃以上の温度域を水素濃度：２５ｖｏｌ％以上となるように制御することにより得られる。このように制御することにより、加熱過程において形成された表面濃化物を還元し、鋼板表層の酸化物を減少させる。また、焼鈍雰囲気は低酸素ポテンシャルであるため、内部酸化を殆ど形成させることなく、不めっきのない、より高い耐食性と高加工時の良好な耐めっき剥離性が得られることになる。水素濃度を２５ｖｏｌ%以上とした理由は以下の通りである。表面濃化の抑制効果が認められるのが水素濃度が２５ｖｏｌ%以上である。水素濃度の上限は特に設けないが、７５ｖｏｌ％超えは効果が飽和し、コスト的に不利となるため、７５ｖｏｌ%以下が望ましい。
均熱過程での焼鈍炉内温度の温度域を８２０℃以上１０００℃以下とした理由は以下の通りである。８２０℃を下回る温度域では、水素濃度を２５ｖｏｌ%以上にまで上昇させ還元能力を増加させたとしても、Ｓｉ、Ｍｎなどの表面濃化物を十分に還元することができない。また、１０００℃以下とした理由は、１０００℃超えの場合、焼鈍炉内設備（ロールなど）の酸化による劣化、及びコスト増大の観点から、不利となる。
冷却過程での焼鈍炉内温度の温度域を７５０℃以上とした理由は以下の通りである。７５０℃以上の温度域では、水素濃度を２５ｖｏｌ％以上に制御しない場合、鋼中成分の表面濃化が起こってしまう。また、冷却帯以降では水素濃度を再び上昇させても温度が低いと、表面濃化物を還元することができない。したがって、冷却過程での焼鈍炉内温度の温度域（露点制御領域）を７５０℃以上とする。なお、焼鈍炉内の気体成分は、水素ガス以外は窒素ガスと不可避不純物気体からなる。本発明効果を損するものでなければ他の気体成分を含有してもよい。 Such an effect, when performing annealing and hot dip galvanizing treatment in a continuous hot dip galvanizing facility, in the soaking process, the temperature range of annealing furnace temperature: 820 ° C or more and 1000 ° C or less is hydrogen concentration: 25 vol% or more, Further, in the cooling process, the temperature range of 750 ° C. or higher is obtained by controlling the hydrogen concentration to be 25 vol% or higher. By controlling in this way, the surface concentrate formed in the heating process is reduced, and the oxide on the surface layer of the steel sheet is reduced. In addition, since the annealing atmosphere has a low oxygen potential, it is possible to obtain higher corrosion resistance without plating and good plating peeling resistance during high processing without almost forming internal oxidation. The reason for setting the hydrogen concentration to 25 vol% or more is as follows. The hydrogen concentration is 25 vol% or more, which shows the effect of suppressing surface concentration. The upper limit of the hydrogen concentration is not particularly set, but if it exceeds 75 vol%, the effect is saturated and disadvantageous in terms of cost, so 75 vol% or less is desirable.
The reason why the temperature range of the annealing furnace temperature in the soaking process is 820 ° C. or more and 1000 ° C. or less is as follows. In the temperature range below 820 ° C., even if the hydrogen concentration is increased to 25 vol% or more and the reducing ability is increased, the surface concentrate such as Si and Mn cannot be sufficiently reduced. Moreover, the reason for setting it as 1000 degrees C or less becomes disadvantageous from a viewpoint of deterioration by the oxidation of the equipment (roll etc.) in an annealing furnace, and a cost increase when it exceeds 1000 degreeC.
The reason why the temperature range of the annealing furnace temperature in the cooling process is set to 750 ° C. or more is as follows. In the temperature range of 750 ° C. or higher, if the hydrogen concentration is not controlled to 25 vol% or higher, the surface concentration of components in the steel occurs. Further, after the cooling zone, even if the hydrogen concentration is increased again, if the temperature is low, the surface concentrate cannot be reduced. Therefore, the temperature range (dew point control region) of the annealing furnace temperature in the cooling process is set to 750 ° C. or higher. The gas components in the annealing furnace are composed of nitrogen gas and inevitable impurity gas other than hydrogen gas. Other gas components may be included as long as the effects of the present invention are not impaired.

次いで、本発明の対象とする高強度溶融亜鉛めっき鋼板の鋼成分組成について説明する。
Ｃ：０．０１〜０．１８％
Ｃは、鋼組織としてマルテンサイトなどを形成させることで加工性を向上させる。そのためには０．０１％以上必要である。一方、０．１８％を超えると溶接性が劣化する。したがって、Ｃ量は０．０１％以上０．１８％以下とする。 Next, the steel component composition of the high-strength hot-dip galvanized steel sheet that is the subject of the present invention will be described.
C: 0.01 to 0.18%
C improves workability by forming martensite or the like as a steel structure. For that purpose, 0.01% or more is necessary. On the other hand, if it exceeds 0.18%, the weldability deteriorates. Therefore, the C content is 0.01% or more and 0.18% or less.

Ｓｉ：０．０２〜２．０％
Ｓｉは鋼を強化して良好な材質を得るのに有効な元素であり、本発明の目的とする強度を得るためには０．０２％以上が必要である。Ｓｉが０．０２％未満では本発明の適用範囲とする強度が得られず、高加工時の耐めっき剥離性についても特に問題とならない。一方、２．０％を超えると高加工時の耐めっき剥離性の改善が困難となってくる。したがって、Ｓｉ量は０．０２％以上２．０％以下とする。 Si: 0.02 to 2.0%
Si is an element effective for strengthening steel to obtain a good material, and 0.02% or more is necessary to obtain the intended strength of the present invention. If Si is less than 0.02%, the strength within the scope of application of the present invention cannot be obtained, and there is no particular problem with respect to resistance to plating peeling during high processing. On the other hand, if it exceeds 2.0%, it becomes difficult to improve the plating peel resistance at the time of high processing. Therefore, the Si content is 0.02% or more and 2.0% or less.

Ｍｎ：１．０〜３．０％
Ｍｎは鋼の高強度化に有効な元素である。機械特性や強度を確保するためは１．０％以上含有させることが必要である。一方、３．０％を超えると溶接性やめっき密着性の確保、強度と延性のバランスの確保が困難になる。したがって、Ｍｎ量は１．０％以上３．０％以下とする。 Mn: 1.0-3.0%
Mn is an element effective for increasing the strength of steel. In order to ensure mechanical properties and strength, it is necessary to contain 1.0% or more. On the other hand, if it exceeds 3.0%, it becomes difficult to ensure weldability and plating adhesion, and to ensure a balance between strength and ductility. Therefore, the Mn content is 1.0% or more and 3.0% or less.

Ａｌ：０．００１〜１．０％
Ａｌは溶鋼の脱酸を目的に添加されるが、その含有量が０．００１％未満の場合、その目的が達成されない。溶鋼の脱酸の効果は０．００１％以上で得られる。一方、１．０％を超えるとコストアップになる。したがって、Ａｌ量は０．００１％以上１．０％以下とする。 Al: 0.001 to 1.0%
Al is added for the purpose of deoxidizing molten steel, but if the content is less than 0.001%, the purpose is not achieved. The effect of deoxidation of molten steel is obtained at 0.001% or more. On the other hand, if it exceeds 1.0%, the cost increases. Therefore, the Al content is 0.001% or more and 1.0% or less.

Ｐ：０．００５〜０．０６０％以下
Ｐは不可避的に含有される元素のひとつであり、０．００５％未満にするためには、コストの増大が懸念されるため、０．００５％以上とする。一方、Ｐが０．０６０％を超えて含有されると溶接性が劣化する。さらに、表面品質が劣化する。また、合金化処理を施さない時にはめっき密着性が劣化し、合金化処理時には合金化処理温度を上昇しないと所望の合金化度とすることができない。また所望の合金化度とするために合金化処理温度を上昇させると延性が劣化すると同時に合金化めっき皮膜の密着性が劣化するため、所望の合金化度と、良好な延性、合金化めっき皮膜を両立させることができない。したがって、Ｐ量は０．００５％以上０．０６０％以下とする。 P: 0.005 to 0.060% or less P is one of the elements inevitably contained, and in order to make it less than 0.005%, there is a concern about an increase in cost, so 0.005% or more And On the other hand, if P exceeds 0.060%, weldability deteriorates. Furthermore, the surface quality deteriorates. Further, when the alloying treatment is not performed, the plating adhesion is deteriorated, and when the alloying treatment is performed, the alloying treatment temperature cannot be increased unless the alloying treatment temperature is increased. Also, if the alloying temperature is raised to achieve the desired degree of alloying, the ductility deteriorates and at the same time the adhesion of the alloyed plating film deteriorates, so the desired degree of alloying, good ductility, and alloyed plating film Cannot be achieved. Therefore, the P content is 0.005% or more and 0.060% or less.

Ｓ≦０．０１％
Ｓは不可避的に含有される元素のひとつである。下限は規定しないが、多量に含有されると溶接性が劣化するため０．０１％以下とする。 S ≦ 0.01%
S is one of the elements inevitably contained. The lower limit is not specified, but if it is contained in a large amount, the weldability deteriorates, so the content is made 0.01% or less.

なお、強度と延性のバランスを制御するため、Ｂ：０．００１〜０．００５％、Ｎｂ：０．００５〜０．０５％、Ｔｉ：０．００５〜０．０５％、Ｃｒ：０．００１〜１．０％、Ｍｏ：０．０５〜１．０％、Ｃｕ：０．０５〜１．０％、Ｎｉ：０．０５〜１．０％の中から選ばれる１種以上の元素を必要に応じて添加してもよい。
これらの元素を添加する場合における適正添加量の限定理由は以下の通りである。 In order to control the balance between strength and ductility, B: 0.001 to 0.005%, Nb: 0.005 to 0.05%, Ti: 0.005 to 0.05%, Cr: 0.001 One or more elements selected from -1.0%, Mo: 0.05-1.0%, Cu: 0.05-1.0%, Ni: 0.05-1.0% are required. It may be added depending on.
The reason for limiting the appropriate addition amount in the case of adding these elements is as follows.

Ｂ：０．００１〜０．００５％
Ｂは０．００１％未満では焼き入れ促進効果が得られにくい。一方、０．００５％超えではめっき密着性が劣化する。よって、含有する場合、Ｂ量は０．００１％以上０．００５％以下とする。 B: 0.001 to 0.005%
When B is less than 0.001%, it is difficult to obtain an effect of promoting quenching. On the other hand, if it exceeds 0.005%, the plating adhesion deteriorates. Therefore, when it contains, B amount shall be 0.001% or more and 0.005% or less.

Ｎｂ：０．００５〜０．０５％
Ｎｂは０．００５％未満では強度調整の効果やＭｏとの複合添加時におけるめっき密着性改善効果が得られにくい。一方、０．０５％超えではコストアップを招く。よって、含有する場合、Ｎｂ量は０．００５％以上０．０５％以下とする。 Nb: 0.005 to 0.05%
If Nb is less than 0.005%, it is difficult to obtain the effect of adjusting the strength and the effect of improving the plating adhesion at the time of composite addition with Mo. On the other hand, if it exceeds 0.05%, the cost increases. Therefore, when it contains, Nb amount shall be 0.005% or more and 0.05% or less.

Ｔｉ：０．００５〜０．０５％
Ｔｉは０．００５％未満では強度調整の効果が得られにくい。一方、０．０５％超えではめっき密着性の劣化を招く。よって、含有する場合、Ｔｉ量は０．００５％以上０．０５％以下とする。 Ti: 0.005 to 0.05%
If Ti is less than 0.005%, the effect of adjusting the strength is difficult to obtain. On the other hand, if it exceeds 0.05%, the plating adhesion deteriorates. Therefore, when it contains, Ti amount shall be 0.005% or more and 0.05% or less.

Ｃｒ：０．００１〜１．０％
Ｃｒは０．００１％未満では焼き入れ性効果が得られにくい。一方、１．０％超えではＣｒが表面濃化するため、めっき密着性や溶接性が劣化する。よって、含有する場合、Ｃｒ量は０．００１％以上１．０％以下とする。 Cr: 0.001 to 1.0%
When Cr is less than 0.001%, it is difficult to obtain a hardenability effect. On the other hand, if it exceeds 1.0%, the surface of Cr is concentrated, so that the plating adhesion and weldability deteriorate. Therefore, when it contains, Cr amount shall be 0.001% or more and 1.0% or less.

Ｍｏ：０．０５〜１．０％
Ｍｏは０．０５％未満では強度調整の効果やＮｂ、またはＮｉやＣｕとの複合添加時におけるめっき密着性改善効果が得られにくい。一方、１．０％超えではコストアップを招く。よって、含有する場合、Ｍｏ量は０．０５％以上１．０％以下とする。 Mo: 0.05-1.0%
If Mo is less than 0.05%, it is difficult to obtain the effect of adjusting the strength and the effect of improving the plating adhesion at the time of composite addition with Nb, Ni or Cu. On the other hand, if it exceeds 1.0%, cost increases. Therefore, when contained, the Mo content is 0.05% or more and 1.0% or less.

Ｃｕ：０．０５〜１．０％
Ｃｕは０．０５％未満では残留γ相形成促進効果やＮｉやＭｏとの複合添加時におけるめっき密着性改善効果が得られにくい。一方、１．０％超えではコストアップを招く。よって、含有する場合、Ｃｕ量は０．０５％以上１．０％以下とする。 Cu: 0.05 to 1.0%
If Cu is less than 0.05%, it is difficult to obtain the effect of promoting the formation of the residual γ phase and the effect of improving the plating adhesion when combined with Ni or Mo. On the other hand, if it exceeds 1.0%, cost increases. Therefore, when contained, the Cu content is 0.05% or more and 1.0% or less.

Ｎｉ：０．０５〜１．０％
Ｎｉは０．０５％未満では残留γ相形成促進効果やＣｕとＭｏとの複合添加時におけるめっき密着性改善効果が得られにくい。一方、１．０％超えではコストアップを招く。よって、含有する場合、Ｎｉ量は０．０５％以上１．０％以下とする。 Ni: 0.05-1.0%
When Ni is less than 0.05%, it is difficult to obtain the effect of promoting the formation of the residual γ phase and the effect of improving the plating adhesion when Cu and Mo are added together. On the other hand, if it exceeds 1.0%, cost increases. Therefore, when it contains, Ni amount shall be 0.05% or more and 1.0% or less.

上記以外の残部はＦｅおよび不可避的不純物である。 The balance other than the above is Fe and inevitable impurities.

次に、本発明の高強度溶融亜鉛めっき鋼板の製造方法とその限定理由について説明する。 Next, the manufacturing method of the high-strength hot-dip galvanized steel sheet of the present invention and the reason for limitation will be described.

上記化学成分を有する鋼を熱間圧延した後、冷間圧延し鋼板とし、次いで、連続式溶融亜鉛めっき設備において焼鈍および溶融亜鉛めっき処理を行う。なお、この時、本発明においては、均熱過程では焼鈍炉内温度：８２０℃以上１０００℃以下の温度域を水素濃度：２５ｖｏｌ％以上とし、さらに、冷却過程では７５０℃以上の温度域を水素濃度：２５ｖｏｌ％以上で行うこととする。これは本発明において、最も重要な要件である。 The steel having the above chemical components is hot-rolled and then cold-rolled to obtain a steel plate, and then subjected to annealing and hot-dip galvanizing treatment in a continuous hot-dip galvanizing facility. At this time, in the present invention, in the soaking process, the temperature range in the annealing furnace: 820 ° C. or more and 1000 ° C. or less is set to hydrogen concentration: 25 vol% or more, and in the cooling process, the temperature range of 750 ° C. or more is set to hydrogen. Concentration: 25 vol% or higher. This is the most important requirement in the present invention.

熱間圧延
通常、行われる条件にて行うことができる。 Hot rolling Usually, it can be performed on the conditions performed.

酸洗
熱間圧延後は酸洗処理を行うのが好ましい。酸洗工程で表面に生成した黒皮スケールを除去し、しかる後冷間圧延する。なお、酸洗条件は特に限定しない。 It is preferable to perform a pickling treatment after hot pickling. The black scale formed on the surface in the pickling process is removed, and then cold-rolled. The pickling conditions are not particularly limited.

冷間圧延
４０％以上８０％以下の圧下率で行うことが好ましい。圧下率が４０％未満では再結晶温度が低温化するため、機械特性が劣化しやすい。一方、圧下率が８０％超えでは高強度鋼板であるため、圧延コストがアップするだけでなく、焼鈍時の表面濃化が増加するため、めっき特性が劣化する。 Cold rolling is preferably performed at a rolling reduction of 40% to 80%. If the rolling reduction is less than 40%, the recrystallization temperature is lowered, and the mechanical characteristics are likely to deteriorate. On the other hand, when the rolling reduction exceeds 80%, the steel sheet is a high-strength steel plate, so that not only the rolling cost is increased, but also the surface concentration during annealing is increased, so that the plating characteristics are deteriorated.

冷間圧延した鋼板に対して、焼鈍した後溶融亜鉛めっき処理を施す。
焼鈍炉では、前段の加熱帯で鋼板を所定温度まで加熱する加熱工程を行い、後段の均熱帯で所定温度に所定時間保持する均熱工程を行い、次いで、冷却工程を行う。
そして、上述したように、均熱過程では焼鈍炉内温度：８２０℃以上１０００℃以下の温度域を水素濃度：２５ｖｏｌ％以上とし、さらに、冷却過程では７５０℃以上の温度域を水素濃度：２５ｖｏｌ％以上となるように制御して焼鈍、溶融亜鉛めっき処理を行う。 The cold-rolled steel sheet is annealed and then hot dip galvanized.
In the annealing furnace, a heating step of heating the steel sheet to a predetermined temperature is performed in the heating zone in the previous stage, a soaking step in which the steel plate is maintained at a predetermined temperature for a predetermined time in a soaking zone in the subsequent stage, and then a cooling step is performed.
As described above, in the soaking process, the temperature range in the annealing furnace: 820 ° C. or more and 1000 ° C. or less is set to the hydrogen concentration: 25 vol% or more. In the cooling process, the temperature range of 750 ° C. or more is set to the hydrogen concentration: 25 vol. % Annealing or hot dip galvanizing treatment.

なお、冷却過程を除く焼鈍炉内の温度が８２０℃未満の温度域における水素濃度が１ｖｏｌ％未満では還元による活性化効果が得られず耐めっき剥離性が劣化する。上限は特に規定しないが、２５ｖｏｌ％未満で十分に効果が得られるため、２５ｖｏｌ％未満とする。
溶融亜鉛めっき処理は、常法で行うことができる。 In addition, when the hydrogen concentration in the temperature range where the temperature in the annealing furnace excluding the cooling process is less than 820 ° C. is less than 1 vol%, the activation effect due to reduction cannot be obtained, and the plating peel resistance deteriorates. Although the upper limit is not particularly specified, the effect is sufficiently obtained when it is less than 25 vol%, so it is less than 25 vol%.
The hot dip galvanizing treatment can be performed by a conventional method.

次いで、必要に応じて合金化処理を行う。
溶融亜鉛めっき処理に引き続き合金化処理を行うときは、溶融亜鉛めっき処理をしたのち、４５０℃以上６００℃以下に鋼板を加熱して合金化処理を施し、めっき層のＦｅ含有量が７〜１５％になるように行うのが好ましい。７％未満では合金化ムラが発生したりやフレーキング性が劣化する。一方、１５％超えは耐めっき剥離性が劣化する。 Next, an alloying treatment is performed as necessary.
When the alloying treatment is performed subsequent to the hot dip galvanizing treatment, the hot dip galvanizing treatment is performed, and then the steel plate is heated to 450 ° C. or more and 600 ° C. or less to perform the alloying treatment, and the Fe content of the plating layer is 7 to 15 % Is preferable. If it is less than 7%, unevenness in alloying occurs and flaking properties deteriorate. On the other hand, if it exceeds 15%, the plating peel resistance deteriorates.

以上により、本発明の高強度溶融亜鉛めっき鋼板が得られる。本発明の高強度溶融亜鉛めっき鋼板は、鋼板の表面に、片面あたりのめっき付着量が２０〜１２０ｇ／ｍ^２の亜鉛めっき層を有する。２０ｇ／ｍ^２未満では耐食性の確保が困難になる。一方、１２０ｇ／ｍ^２を超えると耐めっき剥離性が劣化する。
そして、以下のように、めっき層直下の下地鋼板表面の構造に特徴を有することになる。
亜鉛めっき層の直下の、下地鋼板表面から１００μｍ以内の鋼板表層部では、Ｆｅ、Ｓｉ、Ｍｎ、Ａｌ、Ｐ、さらには、Ｂ、Ｎｂ、Ｔｉ、Ｃr、Ｍｏ、Ｃu、Ｎｉの中から選ばれる１種以上の酸化物の形成が合計で片面あたり０．０６０ｇ/m^２以下に抑制される。
鋼中にＳｉ及び多量のＭｎが添加された溶融亜鉛めっき鋼板において、耐食性および高加工時の耐めっき剥離性を満足させるためには、腐食や高加工時の割れなどの起点になる可能性があるめっき層直下の地鉄表層の内部酸化を極力少なくすることが求められる。そこで、本発明では、まず、めっき性を確保するために焼鈍工程において酸素ポテンシャルを低下させることで易酸化性元素であるＳｉやＭｎ等の地鉄表層部における活量を低下させる。そして、これらの元素の外部酸化を抑制し、結果的にめっき性を改善する。さらに、地鉄表層部に形成する内部酸化も抑制され、耐食性及び高加工性が改善することになる。このような効果は、下地鋼板表面から１００μm以内の鋼板表層部に、Ｆｅ、Ｓｉ、Ｍｎ、Ａｌ、Ｐ、さらには、Ｂ、Ｎｂ、Ｔｉ、Ｃｒ、Ｍｏ、Ｃｕ、Ｎｉの中から選ばれる少なくとも１種以上の酸化物の形成量を合計で０．０６０ｇ／ｍ^２以下に抑制することで認められる。酸化物形成量の合計（以下、内部酸化量と称す）が０．０６０ｇ／ｍ^２を超えると、耐食性及び高加工性が劣化する。また、内部酸化量を０．０００１ｇ／ｍ^２未満に抑制しても、耐食性及び高加工性向上効果は飽和するため、内部酸化量の下限は０．０００１ｇ／ｍ^２が好ましい。 As described above, the high-strength hot-dip galvanized steel sheet of the present invention is obtained. The high-strength hot-dip galvanized steel sheet of the present invention has a galvanized layer having a plating adhesion amount of 20 to 120 g / m ^{2 on} one surface of the steel sheet. If it is less than 20 g / m ² , it becomes difficult to ensure corrosion resistance. On the other hand, when it exceeds 120 g / m ² , the plating peel resistance deteriorates.
And it has the characteristic in the structure of the base steel plate surface just under a plating layer as follows.
In the steel plate surface layer portion within 100 μm from the surface of the underlying steel plate immediately below the galvanized layer, it is selected from Fe, Si, Mn, Al, P, and further B, Nb, Ti, Cr, Mo, Cu, and Ni. The formation of one or more oxides is suppressed to 0.060 g / m ² or less per side in total.
In hot-dip galvanized steel sheets with Si and a large amount of Mn added to the steel, in order to satisfy the corrosion resistance and anti-plating resistance during high processing, there is a possibility of starting from corrosion and cracking during high processing. It is required to minimize the internal oxidation of the surface layer of the ground metal directly below a certain plating layer. Therefore, in the present invention, first, the activity in the surface layer portion of the iron base such as Si or Mn, which is an easily oxidizable element, is reduced by lowering the oxygen potential in the annealing process in order to ensure the plating property. And the external oxidation of these elements is suppressed and, as a result, the platability is improved. Furthermore, internal oxidation formed in the surface layer portion of the ground iron is also suppressed, and corrosion resistance and high workability are improved. Such effects are at least selected from Fe, Si, Mn, Al, P, and further B, Nb, Ti, Cr, Mo, Cu, Ni on the steel sheet surface layer portion within 100 μm from the surface of the base steel plate. It is recognized by suppressing the formation amount of one or more oxides to 0.060 g / m ² or less in total. When the total oxide formation amount (hereinafter referred to as internal oxidation amount) exceeds 0.060 g / m ² , the corrosion resistance and the high workability deteriorate. Even if the internal oxidation amount is suppressed to less than 0.0001 g / m ² , the corrosion resistance and the high workability improvement effect are saturated, so the lower limit of the internal oxidation amount is preferably 0.0001 g / m ² .

さらに、上記に加え、本発明では、耐めっき剥離性を向上させるために、Ｓｉ、Ｍｎ系複合酸化物が成長する地鉄組織は軟質で加工性に富むフェライト相が好ましい。 Furthermore, in addition to the above, in the present invention, in order to improve the plating peel resistance, the base iron structure on which the Si and Mn-based composite oxide grows is preferably a soft and rich workability ferrite phase.

以下、本発明を、実施例に基いて具体的に説明する。 Hereinafter, the present invention will be specifically described based on examples.

表１に示す鋼組成からなる熱延鋼板を酸洗し、黒皮スケール除去した後、表２に示す条件にて冷間圧延し、厚さ１．０ｍｍの冷延鋼板を得た。 The hot-rolled steel sheet having the steel composition shown in Table 1 was pickled and the black scale removed, and then cold-rolled under the conditions shown in Table 2 to obtain a cold-rolled steel sheet having a thickness of 1.0 mm.

次いで、上記で得た冷延鋼板を、焼鈍炉にオールラジアントチューブ型の加熱炉を備えるＣＧＬに装入した。ＣＧＬでは、表２に示す通り、均熱過程における焼鈍炉内の８２０℃以上１０００℃以下の温度域の鋼板および冷却過程における７５０℃以上の温度域の鋼板を制御して通板して焼鈍したのち、４６０℃のＡｌ含有Ｚｎ浴にて溶融亜鉛めっき処理を施した。上記鋼板を制御した領域以外の焼鈍炉内の水素濃度は１０ｖｏｌ％を基本とした。
なお、雰囲気の気体成分は窒素と水素および不可避不純物気体からなり、水素濃度の制御は、窒素ガス中へ導入する水素ガス量をガスバルブで調整することで行った。露点は−３５℃を基本とした。
また、ＧＡは０．１４％Ａｌ含有Ｚｎ浴を、ＧＩは０．１８％Ａｌ含有Ｚｎ浴を用いた。付着量はガスワイピングにより調節し、ＧＡは合金化処理した。 Next, the cold-rolled steel sheet obtained above was charged into a CGL equipped with an all-radiant tube type heating furnace in an annealing furnace. In CGL, as shown in Table 2, the steel sheet in the temperature range of 820 ° C. or more and 1000 ° C. or less in the annealing furnace in the soaking process and the steel plate in the temperature range of 750 ° C. or more in the cooling process were controlled to pass and annealed. Thereafter, hot dip galvanizing treatment was performed in an Al-containing Zn bath at 460 ° C. The hydrogen concentration in the annealing furnace other than the region where the steel plate was controlled was basically 10 vol%.
The gas components in the atmosphere consisted of nitrogen, hydrogen, and unavoidable impurity gases, and the hydrogen concentration was controlled by adjusting the amount of hydrogen gas introduced into the nitrogen gas with a gas valve. The dew point was basically -35 ° C.
In addition, GA used a 0.14% Al-containing Zn bath, and GI used a 0.18% Al-containing Zn bath. The adhesion amount was adjusted by gas wiping, and GA was alloyed.

以上により得られた溶融亜鉛めっき鋼板（ＧＡおよびＧＩ）に対して、外観性（めっき外観）、耐食性、高加工時の耐めっき剥離性、加工性を調査した。また、めっき層直下の１００μｍまでの地鉄鋼板表層部に存在する酸化物の量（内部酸化量）を測定した。測定方法および評価基準を下記に示す。 The hot-dip galvanized steel sheets (GA and GI) obtained as described above were examined for appearance (plating appearance), corrosion resistance, plating peeling resistance during high processing, and workability. Moreover, the quantity (internal oxidation amount) of the oxide which exists in the surface steel plate surface layer part to 100 micrometers directly under a plating layer was measured. The measurement method and evaluation criteria are shown below.

＜外観性＞
外観性は、不めっきや合金化ムラなどの外観不良が無い場合は外観良好（記号○）、ある場合は外観不良（記号×）と判定した。 <Appearance>
Appearance was judged as good appearance (symbol ◯) when there was no appearance defect such as non-plating or alloying unevenness, and when it was present, it was judged as poor appearance (symbol x).

＜耐食性＞
寸法７０ｍｍ×１５０ｍｍの合金化溶融亜鉛めっき鋼板について、JIS Z 2371（2000年）に基づく塩水噴霧試験を３日間行い、腐食生成物をクロム酸（濃度２００g/L、８０℃）を用いて１分間洗浄除去し、片面あたりの試験前後のめっき腐食減量（g/m²・日）を重量法にて測定し、下記基準で評価した。
○（良好）：20g/m²・日未満
×（不良）：20g/m²・日以上 <Corrosion resistance>
An alloyed hot-dip galvanized steel sheet with dimensions of 70 mm x 150 mm was subjected to a salt spray test based on JIS Z 2371 (2000) for 3 days, and the corrosion product was treated with chromic acid (concentration 200 g / L, 80 ° C) for 1 minute. After washing and removing, the plating corrosion weight loss (g / m ² · day) before and after the test per one side was measured by a weight method and evaluated according to the following criteria.
○ (Good): Less than 20g / m ² · day × (Poor): 20g / m ² · Day or more

＜耐めっき剥離性＞
高加工時の耐めっき剥離性は、ＧＡでは、９０°を超えて鋭角に曲げたときの曲げ加工部のめっき剥離の抑制が要求される。本実施例では１２０°曲げした加工部にセロハンテープを押し付けて剥離物をセロハンテープに転移させ、セロハンテープ上の剥離物量をＺｎカウント数として蛍光Ｘ線法で求めた。なお、この時のマスク径は３０mm、蛍光Ｘ線の加速電圧は５０ｋＶ、加速電流は５０mA、測定時間は２０秒である。下記の基準に照らして、ランク１、２のものを耐めっき剥離性が良好（記号○）、３以上のものを耐めっき剥離性が不良（記号×）と評価した。
蛍光Ｘ線Ｚｎカウント数ランク
０−５００未満：１（良）
５００以上−１０００未満：２
１０００以上−２０００未満：３
２０００以上−３０００未満：４
３０００以上：５（劣）
ＧＩでは、衝撃試験時の耐めっき剥離性が要求される。ボールインパクト試験を行い、加工部をテープ剥離し、めっき層の剥離有無を目視判定した。ボールインパクト条件は、ボール重量１０００ｇ、落下高さ１００ｃｍである。
○：めっき層の剥離無し
×：めっき層が剥離 <Plating resistance>
With regard to the resistance to plating peeling at the time of high processing, in GA, it is required to suppress plating peeling at the bent portion when bent at an acute angle exceeding 90 °. In this example, the cellophane tape was pressed against the processed portion bent by 120 ° to transfer the peeled material to the cellophane tape, and the amount of the peeled material on the cellophane tape was determined by the fluorescent X-ray method as the Zn count number. At this time, the mask diameter is 30 mm, the fluorescent X-ray acceleration voltage is 50 kV, the acceleration current is 50 mA, and the measurement time is 20 seconds. In light of the following criteria, those with ranks 1 and 2 were evaluated to have good plating peel resistance (symbol ◯), and those with three or more were evaluated to have poor plating peel resistance (symbol x).
Fluorescent X-ray Zn count number Rank 0 to less than 500: 1 (good)
500 or more and less than 1000: 2
1000 or more and less than −2000: 3
2000 or more and less than −3000: 4
3000 or more: 5 (poor)
In GI, resistance to plating peeling during an impact test is required. A ball impact test was performed, the processed part was peeled off with tape, and the presence or absence of peeling of the plating layer was visually determined. Ball impact conditions are a ball weight of 1000 g and a drop height of 100 cm.
○: Plating layer is not peeled ×: Plating layer is peeled

＜加工性＞
加工性は、試料から圧延方向に対して90°方向にJIS５号引張試験片を採取し、JIS Z 2241の規定に準拠してクロスヘッド速度10mm/min一定で引張試験を行い、引張り強度（ＴＳ／ＭＰａ）と伸び（Ｅｌ％）を測定し、ＴＳが６５０ＭＰａ未満の場合は、ＴＳ×Ｅｌ≧２２０００のものを良好、ＴＳ×Ｅｌ＜２２０００のものを不良とした。ＴＳが６５０ＭＰａ以上９００ＭＰａの場合は、ＴＳ×Ｅｌ≧２００００のものを良好、ＴＳ×Ｅｌ＜２００００のものを不良とした。ＴＳが９００ＭＰａ以上の場合は、ＴＳ×Ｅｌ≧１８０００のものを良好、ＴＳ×Ｅｌ＜１８０００のものを不良とした。 <Processability>
For workability, JIS No. 5 tensile test specimens were taken from the sample in the 90 ° direction with respect to the rolling direction, and subjected to a tensile test at a constant crosshead speed of 10 mm / min in accordance with the provisions of JIS Z 2241. / MPa) and elongation (El%) were measured, and when TS was less than 650 MPa, TS × El ≧ 22000 was judged good, and TS × El <22000 was judged poor. When TS was 650 MPa or more and 900 MPa, TS × El ≧ 20000 was judged good, and TS × El <20000 was judged poor. When TS was 900 MPa or more, TS × El ≧ 18000 was judged good, and TS × El <18000 was judged poor.

＜めっき層直下１００μmまでの領域における内部酸化量＞
内部酸化量は、「インパルス炉溶融−赤外線吸収法」により測定した。ただし、素材（すなわち焼鈍を施す前の高強度鋼板）に含まれる酸素量を差し引く必要があるので、本発明では、連続焼鈍後の高強度鋼板の両面の表層部を１００μｍ以上研磨して鋼中酸素濃度を測定し、その測定値を素材に含まれる酸素量ＯＨとし、また、連続焼鈍後の高強度鋼板の板厚方向全体での鋼中酸素濃度を測定して、その測定値を内部酸化後の酸素量ＯＩとした。このようにして得られた高強度鋼板の内部酸化後の酸素量ＯＩと、素材に含まれる酸素量ＯＨとを用いて、ＯＩとＯＨの差（＝ＯＩ−ＯＨ）を算出し、さらに片面単位面積（すなわち１m^２）当たりの量に換算した値（ｇ／ｍ^２）を内部酸化量とした。 <Internal oxidation amount in the region of 100 μm directly under the plating layer>
The amount of internal oxidation was measured by “impulse furnace melting-infrared absorption method”. However, since it is necessary to subtract the amount of oxygen contained in the material (that is, the high-strength steel plate before annealing), in the present invention, the surface layer portions on both surfaces of the high-strength steel plate after continuous annealing are polished by 100 μm or more in the steel. Measure the oxygen concentration, set the measured value as the amount of oxygen OH contained in the material, measure the oxygen concentration in the steel in the entire thickness direction of the high-strength steel sheet after continuous annealing, and measure the measured value internally. The subsequent oxygen amount OI was used. The difference between OI and OH (= OI-OH) is calculated using the oxygen amount OI after internal oxidation of the high-strength steel plate thus obtained and the oxygen amount OH contained in the material, and further, single-sided unit area (i.e. 1 m ²⁾ value converted into the amount per (g / m ²⁾ as an internal oxide amount.

以上により得られた結果を製造条件と併せて表２に示す。 The results obtained as described above are shown in Table 2 together with the production conditions.

表２から明らかなように、本発明法で製造されたＧＩ、ＧＡ（本発明例）は、Ｓｉ、Ｍｎ等の易酸化性元素を多量に含有する高強度鋼板であるにもかかわらず、耐食性、加工性および高加工時の耐めっき剥離性に優れ、めっき外観も良好である。
一方、比較例では、めっき外観、耐食性、加工性、高加工時の耐めっき剥離性のいずれか一つ以上が劣る。 As is apparent from Table 2, GI and GA (examples of the present invention) produced by the method of the present invention are high-strength steel sheets containing a large amount of oxidizable elements such as Si and Mn. Excellent in workability and anti-plating resistance during high processing, and good plating appearance.
On the other hand, in the comparative example, any one or more of plating appearance, corrosion resistance, workability, and plating peeling resistance during high processing is inferior.

表３に示す鋼組成からなる熱延鋼板を酸洗し、黒皮スケール除去した後、表４に示す条件にて冷間圧延し、厚さ１．０ｍｍの冷延鋼板を得た。 The hot-rolled steel sheet having the steel composition shown in Table 3 was pickled and the black scale was removed, and then cold-rolled under the conditions shown in Table 4 to obtain a cold-rolled steel sheet having a thickness of 1.0 mm.

次いで、上記で得た冷延鋼板を、焼鈍炉にオールラジアントチューブ型の加熱炉を備えるＣＧＬに装入した。ＣＧＬでは、表４に示す通り、均熱温度が８００℃以上で、均熱過程における焼鈍炉内の８００℃以上１０００℃以下の温度域の水素濃度および冷却過程における６５０℃以上の温度域の水素濃度を制御して通板して焼鈍したのち、４６０℃のＡｌ含有Ｚｎ浴にて溶融亜鉛めっき処理を施した。上記水素濃度を制御した領域以外の焼鈍炉内の水素濃度は１０ｖｏｌ％を基本とした。
なお、雰囲気の気体成分は窒素と水素および不可避不純物気体からなり、水素濃度の制御は、窒素ガス中へ導入する水素ガス量をガスバルブで調整することで行った。露点は−３５℃を標準とした。
また、ＧＡは０．１４％Ａｌ含有Ｚｎ浴を、ＧＩは０．１８％Ａｌ含有Ｚｎ浴を用いた。付着量はガスワイピングにより調節し、ＧＡは合金化処理した。 Next, the cold-rolled steel sheet obtained above was charged into a CGL equipped with an all-radiant tube type heating furnace in an annealing furnace. In CGL, as shown in Table 4, the soaking temperature is 800 ° C or higher, the hydrogen concentration in the temperature range of 800 ° C to 1000 ° C in the annealing furnace in the soaking process, and the hydrogen concentration in the temperature range of 650 ° C or higher in the cooling process. After controlling the concentration and passing through and annealing, hot dip galvanizing treatment was performed in an Al-containing Zn bath at 460 ° C. The hydrogen concentration in the annealing furnace other than the region where the hydrogen concentration was controlled was basically 10 vol%.
The gas components in the atmosphere consisted of nitrogen, hydrogen, and unavoidable impurity gases, and the hydrogen concentration was controlled by adjusting the amount of hydrogen gas introduced into the nitrogen gas with a gas valve. The standard dew point was -35 ° C.
In addition, GA used a 0.14% Al-containing Zn bath, and GI used a 0.18% Al-containing Zn bath. The adhesion amount was adjusted by gas wiping, and GA was alloyed.

＜耐食性＞
寸法７０ｍｍ×１５０ｍｍの合金化溶融亜鉛めっき鋼板について、JIS Z ２３７１（２０００年）に基づく塩水噴霧試験を３日間行い、腐食生成物をクロム酸（濃度２００g/L、８０℃）を用いて１分間洗浄除去し、片面あたりの試験前後のめっき腐食減量（g/m^２・日）を重量法にて測定し、下記基準で評価した。
○（良好）：２０g/m^２・日未満
×（不良）：２０g/m^２・日以上 <Corrosion resistance>
A salt spray test based on JIS Z 2371 (2000) is performed on an alloyed hot-dip galvanized steel sheet having a size of 70 mm × 150 mm for 3 days, and the corrosion product is used for 1 minute using chromic acid (concentration 200 g / L, 80 ° C.). After washing and removing, the plating corrosion weight loss (g / m ² · day) before and after the test per one side was measured by a weight method, and evaluated according to the following criteria.
○ (Good): Less than 20 g / m ² · day × (Bad): 20 g / m ² · day or more

＜加工性＞
加工性は、試料から圧延方向に対して９０°方向にJIS５号引張試験片を採取し、JIS Z ２２４１の規定に準拠してクロスヘッド速度１０mm/min一定で引張試験を行い、引張り強度（ＴＳ／ＭＰａ）と伸び（Ｅｌ％）を測定し、ＴＳが６５０ＭＰａ未満の場合は、ＴＳ×Ｅｌ≧２２０００のものを良好、ＴＳ×Ｅｌ＜２２０００のものを不良とした。ＴＳが６５０ＭＰａ以上９００ＭＰａの場合は、ＴＳ×Ｅｌ≧２００００のものを良好、ＴＳ×Ｅｌ＜２００００のものを不良とした。ＴＳが９００ＭＰａ以上の場合は、ＴＳ×Ｅｌ≧１８０００のものを良好、ＴＳ×Ｅｌ＜１８０００のものを不良とした。 <Processability>
For workability, a JIS No. 5 tensile test piece was taken from the sample at a 90 ° direction with respect to the rolling direction, a tensile test was conducted at a constant crosshead speed of 10 mm / min in accordance with the provisions of JIS Z 2241, and tensile strength (TS / MPa) and elongation (El%) were measured, and when TS was less than 650 MPa, TS × El ≧ 22000 was judged good, and TS × El <22000 was judged poor. When TS was 650 MPa or more and 900 MPa, TS × El ≧ 20000 was judged good, and TS × El <20000 was judged poor. When TS was 900 MPa or more, TS × El ≧ 18000 was judged good, and TS × El <18000 was judged poor.

以上により得られた結果を製造条件と併せて表４に示す。 The results obtained above are shown in Table 4 together with the production conditions.

表４から明らかなように、本発明法で製造されたＧＩ、ＧＡ（本発明例）は、Ｓｉ、Ｍｎ等の易酸化性元素を多量に含有する高強度鋼板であるにもかかわらず、耐食性、加工性および高加工時の耐めっき剥離性に優れ、めっき外観も良好である。
一方、比較例では、めっき外観、耐食性、加工性、高加工時の耐めっき剥離性のいずれか一つ以上が劣る。 As is apparent from Table 4, GI and GA (examples of the present invention) produced by the method of the present invention are high-strength steel sheets containing a large amount of oxidizable elements such as Si and Mn. Excellent in workability and anti-plating resistance during high processing, and good plating appearance.
On the other hand, in the comparative example, any one or more of plating appearance, corrosion resistance, workability, and plating peeling resistance during high processing is inferior.

本発明の高強度溶融亜鉛めっき鋼板は、めっき外観、耐食性、加工性および高加工時の耐めっき剥離性に優れ、自動車の車体そのものを軽量化かつ高強度化するための表面処理鋼板として利用することができる。また、自動車以外にも、素材鋼板に防錆性を付与した表面処理鋼板として、家電、建材の分野等、広範な分野で適用できる。 The high-strength hot-dip galvanized steel sheet according to the present invention is excellent in plating appearance, corrosion resistance, workability, and anti-plating resistance during high processing, and is used as a surface-treated steel sheet for reducing the weight and strength of an automobile body. be able to. In addition to automobiles, the steel sheet can be applied in a wide range of fields such as home appliances and building materials as a surface-treated steel sheet provided with rust prevention properties.

Claims

In mass%, C: 0.01 to 0.18%, Si: 0.02 to 2.0%, Mn: 1.0 to 3.0%, Al: 0.001 to 1.0%, P: A galvanized layer containing 0.005 to 0.060%, S ≦ 0.01%, the balance being Fe and unavoidable impurities on the surface of the steel sheet, and the coating amount per one side being 20 to 120 g / m ² Is a method of manufacturing a high-strength hot-dip galvanized steel sheet having an annealing furnace temperature of 820 ° C. or higher and 1000 ° C. or lower in a soaking process when the steel sheet is subjected to annealing and hot-dip galvanizing treatment in a continuous hot-dip galvanizing facility. temperature range only the hydrogen concentration: a 25 vol% or more, further, hydrogen concentration only temperature range of not lower than 750 ° C. in the cooling process: high-strength method for manufacturing a galvanized steel sheet and to control more than 25 vol%.

The steel sheet is in mass% as a component composition, and B: 0.001 to 0.005%, Nb: 0.005 to 0.05%, Ti: 0.005 to 0.05%, Cr: 0 One or more elements selected from 0.001 to 1.0%, Mo: 0.05 to 1.0%, Cu: 0.05 to 1.0%, Ni: 0.05 to 1.0% The manufacturing method of the high intensity | strength hot-dip galvanized steel plate of Claim 1 characterized by the above-mentioned.

After the hot dip galvanizing treatment, the steel plate is further heated to a temperature of 450 ° C. or higher and 600 ° C. or lower to perform alloying treatment, and the Fe content of the galvanized layer is set in the range of 7 to 15% by mass. The manufacturing method of the high intensity | strength hot-dip galvanized steel plate of Claim 1 or 2.

Fe, Si, Mn, Al, P, B, Nb, produced by the production method according to any one of claims 1 to 3 and formed on a steel sheet surface layer portion within 100 μm from the surface of the underlying steel sheet immediately below the galvanized layer. A high-strength hot-dip galvanized steel sheet, wherein one or more oxides selected from Ti, Cr, Mo, Cu, and Ni are 0.060 g / m ² or less per side.