JP2007131899A - Manufacturing method of galvanized steel sheet, and manufacturing method of hot-dip zincing steel sheet - Google Patents
Manufacturing method of galvanized steel sheet, and manufacturing method of hot-dip zincing steel sheet Download PDFInfo
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本発明は、自動車、家電、建材等の分野で好適な、溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板の製造方法に係り、とくにSi含有鋼板を下地鋼板とする溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板について、その表面外観およびめっき密着性の改善に関する。 The present invention relates to a method for producing a hot-dip galvanized steel sheet and an alloyed hot-dip galvanized steel sheet, which is suitable in the fields of automobiles, home appliances, building materials, and the like. About galvanized steel sheet, it relates to the improvement of surface appearance and plating adhesion.
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が、なかでも安価に製造でき防錆性に優れた溶融亜鉛めっき鋼板や、合金化溶融亜鉛めっき鋼板が使用される場合が多くなっている。
一般に、溶融亜鉛めっき鋼板は、スラブを熱間圧延した後に冷間圧延あるいは熱処理を施された薄鋼板を下地鋼板として用い、この下地鋼板の表面を前処理工程にて脱脂および／または酸洗して洗浄するか、あるいは前処理工程を省略して加熱炉内で下地鋼板表面の油分を燃焼除去したのち、非酸化性雰囲気中または還元性雰囲気中で再結晶焼鈍を施し、ついで、非酸化性雰囲気中あるいは還元性雰囲気中で鋼板をめっきに適した温度まで冷却して大気に触れることなく微量Al（0.1〜0.2mass％程度）を添加した溶融亜鉛浴中に浸漬することによって製造されている。また、合金化溶融亜鉛めっき鋼板は、溶融亜鉛めっき後の鋼板を引続いて合金化処理炉で熱処理することによって製造されている。
In recent years, in the fields of automobiles, home appliances, building materials, etc., surface-treated steel sheets with rust-preventing properties have been manufactured at low cost, especially hot-dip galvanized steel sheets and alloyed hot-dip galvanized steel sheets. Is increasingly used.
In general, a hot-dip galvanized steel sheet is a thin steel sheet that has been cold-rolled or heat-treated after hot rolling a slab, and the surface of the base steel sheet is degreased and / or pickled in a pretreatment step. Or by removing the oil on the surface of the underlying steel plate in the heating furnace by omitting the pretreatment process, and then performing recrystallization annealing in a non-oxidizing atmosphere or reducing atmosphere, and then non-oxidizing Manufactured by cooling the steel sheet to a temperature suitable for plating in an atmosphere or reducing atmosphere and immersing it in a molten zinc bath to which a small amount of Al (about 0.1 to 0.2 mass%) is added without touching the atmosphere. . Moreover, the alloyed hot-dip galvanized steel sheet is manufactured by heat-treating the hot-dip galvanized steel sheet in an alloying furnace.
そして最近では、地球環境の保全という観点から、例えば自動車車体の軽量化を推進するために、部品に使用される鋼板の高強度化が要求されている。溶融亜鉛めっき処理を施し防錆性を付与した溶融亜鉛めっき鋼板においても例外ではなく、下地鋼板として高強度鋼板を使用した高強度溶融亜鉛めっき鋼板が要望されている。
鋼板の高強度化の手段としては、Si、Mn、Ｐ等の固溶強化元素の添加が考えられる。なかでも、Siは、鋼の延性を損なうことなく高強度化できる利点があり、高強度鋼板としてSi含有鋼板が有望視されている。
Recently, from the viewpoint of global environmental conservation, for example, in order to promote weight reduction of automobile bodies, it is required to increase the strength of steel plates used for parts. The hot dip galvanized steel sheet that has been hot dip galvanized and imparted with rust prevention is no exception, and a high strength hot dip galvanized steel sheet using a high strength steel sheet as a base steel sheet is desired.
As a means for increasing the strength of the steel sheet, the addition of a solid solution strengthening element such as Si, Mn, or P can be considered. Among these, Si has an advantage that the strength can be increased without impairing the ductility of the steel, and a Si-containing steel plate is considered promising as a high-strength steel plate.
しかし、Si含有鋼板を下地鋼板とする溶融亜鉛めっき鋼板および合金化溶融亜鉛めっき鋼板には、次のような問題がある。
溶融亜鉛めっき鋼板は、上記したように下地鋼板に還元性雰囲気中で焼鈍を施したのち、溶融亜鉛めっき処理を施して製造される。鋼中のSiは、易酸化性元素であり、溶融亜鉛めっき処理前の焼鈍において一般的に用いられる還元性雰囲気中でも選択的に酸化されて表面に濃化し、酸化物を形成する。これらSiの酸化物は溶融亜鉛めっき処理時に鋼板と溶融亜鉛との濡れ性を低下させて不めっきを生じさせる。このため、下地鋼板のSi濃度が増加すると、下地鋼板と溶融亜鉛との濡れ性が急激に低下して不めっきが多発するようになるか、あるいは不めっきに至らない場合でも、さざなみ状の表面欠陥が発生したり、めっき密着性が低下するという問題がある。
However, hot-dip galvanized steel sheets and alloyed hot-dip galvanized steel sheets that use Si-containing steel sheets as base steel sheets have the following problems.
The hot dip galvanized steel sheet is manufactured by subjecting the base steel sheet to annealing in a reducing atmosphere and then subjecting the base steel sheet to a hot dip galvanizing treatment. Si in steel is an easily oxidizable element, and is selectively oxidized and concentrated on the surface in a reducing atmosphere generally used in annealing before hot dip galvanizing to form an oxide. These oxides of Si lower the wettability between the steel sheet and hot dip zinc during hot dip galvanizing and cause non-plating. For this reason, when the Si concentration of the base steel plate increases, the wettability between the base steel plate and molten zinc decreases rapidly, and non-plating occurs frequently, or even if non-plating does not occur, a rippled surface There are problems that defects occur and plating adhesion decreases.
さらに、鋼中のSiが選択的に酸化して表面に濃化し酸化物を形成すると、Siの酸化物がZn−Fe合金化反応を阻害するため、溶融亜鉛めっき後の合金化過程において著しい合金化遅延が生じる。その結果、生産性が著しく低下するという問題がある。生産性を確保するために、過剰に高温で合金化処理を行うと、耐パウダリング性の低下を招くという問題があり、良好な耐パウダリング性と高い生産性とを両立させることは困難であった。 Furthermore, when Si in the steel is selectively oxidized and concentrated on the surface to form oxides, the oxides of Si inhibit the Zn-Fe alloying reaction. Delay occurs. As a result, there is a problem that productivity is significantly reduced. In order to ensure productivity, alloying at an excessively high temperature has the problem of reducing powdering resistance, and it is difficult to achieve both good powdering resistance and high productivity. there were.
このような問題に対し、例えば特許文献１には、予め酸化性雰囲気中で鋼板を加熱して表面に酸化鉄を形成したのち、還元焼鈍を行い、鋼板と溶融亜鉛との濡れ性を改善する技術が提案されている。特許文献１に記載された技術によれば、予め酸化性雰囲気中で加熱して酸化鉄を形成することにより、還元焼鈍時におけるSiの表面濃化を抑制できるとしている。 For such a problem, for example, in Patent Document 1, after the steel plate is heated in an oxidizing atmosphere in advance to form iron oxide on the surface, reduction annealing is performed to improve the wettability between the steel plate and molten zinc. Technology has been proposed. According to the technique described in Patent Document 1, the surface concentration of Si during reduction annealing can be suppressed by previously forming iron oxide by heating in an oxidizing atmosphere.
また、例えば特許文献２には、溶融亜鉛めっき処理に先立ち、硫黄または硫黄化合物をＳ量として0.1〜1000mg/m２付着させたのち、予熱工程を弱酸化性雰囲気で行い、その後水素を含む非酸化性雰囲気中で焼鈍する方法が提案されている。特許文献２に記載された技術によれば、鋼板表面に形成した硫化物層により鋼板と溶融亜鉛との濡れ性が改善されるとしている。
しかしながら、鋼中のSi濃度の増加に伴い、鋼板表面における酸化速度が大きく低下するため、特許文献１に記載された技術によっても、鋼中Si濃度の高い鋼板においては酸化が進まず、Siの表面濃化を抑制するために必要な量の酸化鉄を得ることが困難である。そのため、溶融亜鉛めっき時に不めっきが多発したり、合金化過程で生じる著しい合金化遅延を防止できず、生産性の低下が生じるという問題があった。 However, as the Si concentration in the steel increases, the oxidation rate on the steel sheet surface decreases greatly. Therefore, even with the technique described in Patent Document 1, oxidation does not proceed in a steel sheet with a high Si concentration in the steel, It is difficult to obtain an amount of iron oxide necessary for suppressing surface concentration. For this reason, there has been a problem that unplating frequently occurs during hot dip galvanization, or a significant delay in alloying that occurs during the alloying process cannot be prevented, resulting in a decrease in productivity.
また、特許文献２に記載された技術によっても、鋼中Si濃度の高い鋼板においては、硫化物層の形成のみでは、Siの表面濃化を十分に抑制できないため、鋼板と溶融亜鉛との濡れ性の改善が不十分となり、溶融亜鉛めっき時に不めっきが多発したり、合金化過程で著しい合金化遅延が生じるという問題があった。また、鋼中Si濃度の高い鋼板においては、予熱工程を弱酸化性雰囲気で行ったとしても、鋼板と溶融亜鉛との濡れ性を十分に改善することができず、不めっきや合金化遅延を完全に解決するまでには至っていない。 Further, even with the technique described in Patent Document 2, in a steel sheet having a high Si concentration in steel, the surface concentration of Si cannot be sufficiently suppressed only by the formation of a sulfide layer. The improvement of the property was insufficient, and there was a problem that non-plating occurred frequently during hot dip galvanizing, and a remarkable alloying delay occurred in the alloying process. Also, in steel sheets with a high Si concentration in steel, even if the preheating process is performed in a weakly oxidizing atmosphere, the wettability between the steel sheet and molten zinc cannot be improved sufficiently, and non-plating and alloying delays are prevented. It has not yet been fully resolved.
さらに、特許文献２に記載された技術は、熱処理に先立って硫黄または硫黄化合物を鋼板表面に付着させるものであるため、続く熱処理工程において、硫黄成分が加熱炉内で二酸化硫黄、硫化水素等の腐食性ガスとして多量に排出され、加熱炉炉体や炉内設備を腐食損傷し、煩繁な補修や劣化更新が必要となったり、また炉内ガスを大気中に放出する場合には大気汚染を防止するため脱硫装置の設置が必要になるなど、特許文献２に記載された技術では、製造設備コストが高騰するという問題がある。また、特許文献２に記載された技術では、ピックアップ欠陥や筋状欠陥が発生しめっき表面外観が低下するという問題もあった。 Furthermore, since the technique described in Patent Document 2 is to attach sulfur or a sulfur compound to the steel sheet surface prior to the heat treatment, in the subsequent heat treatment step, sulfur components such as sulfur dioxide, hydrogen sulfide, etc. in the heating furnace. A large amount of corrosive gas is discharged, corroding the furnace body and furnace equipment, requiring complicated repairs and deterioration updates, and if the furnace gas is released into the atmosphere, air pollution. In the technique described in Patent Document 2, for example, it is necessary to install a desulfurization apparatus in order to prevent the production equipment cost. Further, the technique described in Patent Document 2 has a problem in that pick-up defects and streak defects are generated and the plating surface appearance is deteriorated.
本発明は、かかる従来技術の状況に鑑み、高Si含有鋼板を下地鋼板として使用しても、不めっき等の表面欠陥の発生がなく、美麗な表面外観を有し、かつめっき密着性に優れた溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板を安定して生産性高く製造できる、溶融亜鉛めっき鋼板の製造方法および合金化溶融亜鉛めっき鋼板の製造方法を提供することを目的とする。また、本発明が目的とする溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板の製造方法では、溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板を、加熱炉炉体や炉内設備の損傷や外部環境の汚染を防止して製造することをも目的とする。 In view of the state of the prior art, the present invention has no surface defects such as non-plating even when a high Si content steel plate is used as a base steel plate, has a beautiful surface appearance, and has excellent plating adhesion. Another object of the present invention is to provide a method for producing a hot-dip galvanized steel sheet and a method for producing an alloyed hot-dip galvanized steel sheet, which can stably produce the hot-dip galvanized steel sheet and alloyed hot-dip galvanized steel sheet with high productivity. Moreover, in the manufacturing method of the hot dip galvanized steel sheet and the alloyed hot dip galvanized steel sheet, which is the object of the present invention, the hot dip galvanized steel sheet and the alloyed hot dip galvanized steel sheet Another object is to prevent the contamination of the product.
本発明者らは、上記した課題を達成するために、Siの表面濃化を防止する方策について鋭意研究を行った。その結果、鋼板表面に特定元素の化合物を付着させて、所定の鋼板昇温速度でかつ所定の鋼板最高到達温度で、酸化処理を行うことにより、高Si含有鋼板の酸化が飛躍的に促進され、Siの表面濃化を抑制できるとともに、特定元素のガス発生を抑制することが可能であり、加熱炉炉体や炉内設備を損傷することなしに、また外部環境を汚染することなしに、溶融亜鉛めっき鋼板を製造できることを見出した。 In order to achieve the above-described problems, the present inventors have conducted intensive research on measures for preventing the surface concentration of Si. As a result, the oxidation of the high Si steel sheet is dramatically accelerated by attaching a compound of a specific element to the steel sheet surface and performing the oxidation treatment at a predetermined steel sheet heating rate and at a predetermined maximum steel sheet temperature. In addition to suppressing the surface concentration of Si, it is possible to suppress gas generation of specific elements, without damaging the furnace body and furnace equipment, and without polluting the external environment. It has been found that a hot dip galvanized steel sheet can be produced.
本発明は、上記した知見に基づき、さらに検討を加えて完成されたものである。本発明の要旨は次のとおりである。
（１）Si：0.1〜3.0mass％を含有する鋼板を下地鋼板として、該鋼板の表面に、Cl、C、Ｓ、Ｐ、ＦおよびＢからなる特定元素群から選ばれた少なくとも１種の特定元素を含む化合物を付着させたのち、該鋼板に、前記特定元素の付着量に対し50mass％以上が溶融亜鉛めっき鋼板中に残存するように、酸化性雰囲気中で加熱する酸化処理を施して前記鋼板の表面に酸化鉄層を形成し、引続いて還元性雰囲気中で前記酸化鉄層の還元処理を行い、ついで溶融亜鉛めっき処理を施すことを特徴とする溶融亜鉛めっき鋼板の製造方法。
The present invention has been completed based on the above findings and further studies. The gist of the present invention is as follows.
(1) Si: A steel plate containing 0.1 to 3.0 mass% is used as a base steel plate, and at least one type selected from a specific element group consisting of Cl, C, S, P, F and B is provided on the surface of the steel plate. After adhering a compound containing an element, the steel sheet is subjected to an oxidation treatment that is heated in an oxidizing atmosphere so that 50 mass% or more of the adhesion amount of the specific element remains in the hot-dip galvanized steel sheet. A method for producing a hot dip galvanized steel sheet, comprising forming an iron oxide layer on the surface of the steel sheet, subsequently performing a reduction treatment of the iron oxide layer in a reducing atmosphere, and then performing a hot dip galvanizing treatment.
（２）（１）において、前記酸化処理が、酸化性雰囲気中で鋼板昇温速度を5℃／ｓ以上でかつ鋼板最高到達温度を500℃超の温度として加熱する処理であることを特徴とする溶融亜鉛めっき鋼板の製造方法。
（３）（１）または（２）において、前記化合物の付着量が、各特定元素換算で合計0.1〜1000mg／ｍ２であることを特徴とする溶融亜鉛めっき鋼板の製造方法。
(2) In (1), the oxidation treatment is a treatment for heating in an oxidizing atmosphere at a temperature rise rate of 5 ° C./s or more and a maximum temperature of the steel plate exceeding 500 ° C. A method for producing a hot-dip galvanized steel sheet.
(3) The method for producing a hot-dip galvanized steel sheet according to (1) or (2), wherein the adhesion amount of the compound is 0.1 to 1000 mg / m 2 in total in terms of each specific element.
（４）Si：0.1〜3.0mass％を含有する鋼板を下地鋼板として、該鋼板の表面に、Cl、C、Ｓ、Ｐ、ＦおよびＢからなる特定元素群から選ばれた少なくとも１種の特定元素を含む化合物を付着させたのち、該鋼板に、前記特定元素の付着量に対し50mass％以上が合金化溶融亜鉛めっき鋼板中に残存するように、酸化性雰囲気中で加熱する酸化処理を施して前記鋼板の表面に酸化鉄層を形成し、引続いて還元性雰囲気中で前記酸化鉄層の還元処理を行い、ついで溶融亜鉛めっき処理を施し溶融亜鉛めっき層を形成し、さらに該溶融亜鉛めっき層の合金化処理を施すことを特徴とする合金化溶融亜鉛めっき鋼板の製造方法。 (4) Si: 0.1 to 3.0 mass% steel plate as a base steel plate, and at least one type selected from a specific element group consisting of Cl, C, S, P, F and B on the surface of the steel plate After the compound containing the element is adhered, the steel sheet is subjected to an oxidation treatment in which it is heated in an oxidizing atmosphere so that 50 mass% or more of the adhesion amount of the specific element remains in the galvannealed steel sheet. Forming an iron oxide layer on the surface of the steel sheet, subsequently reducing the iron oxide layer in a reducing atmosphere, then performing a hot dip galvanizing treatment to form a hot dip galvanized layer, A method for producing an alloyed hot-dip galvanized steel sheet, characterized by subjecting a plating layer to alloying treatment.
（５）（４）において、前記酸化処理が、酸化性雰囲気中で鋼板昇温速度が5℃／ｓ以上でかつ鋼板最高到達温度が500℃超の温度として加熱する処理であることを特徴とする合金化溶融亜鉛めっき鋼板の製造方法。
（６）（４）または（５）において、前記化合物の付着量が、各特定元素換算で合計0.1〜1000mg／ｍ２であることを特徴とする合金化溶融亜鉛めっき鋼板の製造方法。
(5) In (4), the oxidation treatment is a treatment in which the heating rate of the steel sheet is 5 ° C./s or more and the maximum temperature of the steel sheet is higher than 500 ° C. in an oxidizing atmosphere. A method for producing a galvannealed steel sheet.
(6) The method for producing an galvannealed steel sheet according to (4) or (5), wherein the adhesion amount of the compound is 0.1 to 1000 mg / m 2 in total in terms of each specific element.
本発明によれば、高Si含有鋼板を下地鋼板としても、不めっき等の表面欠陥の発生がなく、美麗な表面外観を有し、かつめっき密着性に優れた溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板を長期間安定して、かつ高い生産性で製造でき、産業上格段の効果を奏する。また、本発明によれば、加熱炉炉体や炉内設備を損傷することもなく、また外部環境を汚染することもなく、溶融亜鉛めっき鋼板を製造できるという効果もある。 According to the present invention, even when a high Si content steel sheet is used as a base steel sheet, there is no occurrence of surface defects such as non-plating, the surface appearance is beautiful, and the hot dip galvanized steel sheet is excellent in plating adhesion. Galvanized steel sheet can be manufactured stably for a long period of time with high productivity, and has a remarkable industrial effect. Moreover, according to this invention, there exists an effect that a hot-dip galvanized steel plate can be manufactured, without damaging a heating furnace furnace body or an in-furnace installation, and polluting an external environment.
本発明で使用する下地鋼板（めっき原板）は、Si：0.1〜3.0mass％を含有する鋼板とする。Si含有量が0.1mass％未満では、還元処理時のSiの表面濃化はそれほど顕著ではなく、したがって不めっきが多発したり、著しい合金化遅延の発生も生じない。一方、Si含有量が3mass％を超えて多くなると、鋼板の強度が高くなりすぎて延性が低下し、延性を確保しつつ高強度化することが困難となる。このため、本発明では下地鋼板のSi含有量は0.1〜3.0mass％の範囲に限定した。なお、Si以外の元素については、本発明の効果を妨げるものではなく、とくにその種類、含有量を限定する必要はないが、用途により必要とされる特性を確保するために、Ｃ、Mn、Ｐ、Al等、従来から公知の元素を含有することができる。代表組成について説明すると、次のとおりである。 The base steel plate (plating base plate) used in the present invention is a steel plate containing Si: 0.1 to 3.0 mass%. If the Si content is less than 0.1 mass%, the surface concentration of Si during the reduction treatment is not so remarkable, and therefore, non-plating does not occur frequently and no significant delay in alloying occurs. On the other hand, when the Si content exceeds 3 mass%, the strength of the steel sheet becomes too high, the ductility is lowered, and it is difficult to increase the strength while ensuring the ductility. For this reason, in this invention, Si content of the base steel plate was limited to the range of 0.1-3.0 mass%. In addition, about elements other than Si, the effect of this invention is not disturbed and it is not necessary to limit the kind and content especially, but in order to ensure the characteristic required by a use, C, Mn, Conventionally known elements such as P and Al can be contained. The representative composition will be described as follows.
Ｃ：0.5mass％以下
Ｃは、一般的に、0.0001〜0.5mass％の範囲で鋼中に含有される元素であり、本発明で下地鋼板として使用する鋼板も上記した範囲でＣが含有されていてもよい。Ｃは、鋼の強度を増加させ高強度化に有効に寄与する元素であるとともに、強度−延性バランスを向上させる残留オーステナイトを生成させる等、組織制御を行う際に有用な元素である。このような作用を発現するためには、0.05mass％以上含有させることが好ましい。しかし、0.25mass％を超えて含有すると溶接性が低下するため、0.25mass％以下とすることが好ましい。
C: 0.5 mass% or less C is an element generally contained in steel in the range of 0.0001 to 0.5 mass%, and the steel plate used as the base steel plate in the present invention also contains C in the above-described range. May be. C is an element that increases the strength of steel and contributes effectively to increase the strength, and is also an element useful for controlling the structure such as generating retained austenite that improves the strength-ductility balance. In order to express such an action, it is preferable to contain 0.05 mass% or more. However, if the content exceeds 0.25 mass%, the weldability deteriorates, so the content is preferably 0.25 mass% or less.
Mn：5mass％以下
Mnは、高強度化に有用な元素であり、一般的に、5mass％以下の範囲で鋼中に含有される元素であり、本発明で下地鋼板として使用する鋼板も上記した範囲でMnが含有されていてもよい。Mnは、鋼の強度を増加させ高強度化に有効に寄与する元素であり、このような作用を発現するためには、0.1mass％以上、好ましくは0.5mass％以上含有させることが好ましい。しかし、MnもSiと同様に、焼鈍時に酸化膜を形成する元素である。このため、５mass％を超えて多量に含有すると、めっき密着性が低下する傾向になる。また、溶接性や強度−延性バランスの確保にも悪影響を及ぼすようになる。このため、Mnは５mass％以下、好ましくは5.0mass％以下とすることが好ましい。なお、より好ましくは1.0〜3.0mass％である。
Mn: 5 mass% or less
Mn is an element useful for increasing strength, and is generally an element contained in steel in a range of 5 mass% or less, and a steel plate used as a base steel plate in the present invention also contains Mn in the above range. May be. Mn is an element that increases the strength of the steel and contributes effectively to increasing the strength. In order to exhibit such an action, it is preferably contained in an amount of 0.1 mass% or more, preferably 0.5 mass% or more. However, Mn, like Si, is an element that forms an oxide film during annealing. For this reason, when it contains exceeding 5 mass% and it contains abundantly, it will become the tendency for plating adhesion to fall. It also has an adverse effect on securing weldability and strength-ductility balance. For this reason, Mn is 5 mass% or less, preferably 5.0 mass% or less. In addition, More preferably, it is 1.0-3.0 mass%.
Ｐ：0.2mass％以下
Ｐは、通常、0.2mass％以下の範囲で鋼中に含有される。本発明で下地鋼板として使用する鋼板も上記した範囲でＰが含有されていてもよい。なお、Ｐは、鋼の強度を増加させる元素であり、このような作用を発現するためには、0.005mass％以上含有させることが好ましい。一方、0.2mass％を超えて含有すると、高強度となり延性が低下する。このため、Ｐは0.005〜0.2mass％とすることが好ましい。なお、より好ましくは0.01〜0.1mass％である。
P: 0.2 mass% or less P is usually contained in steel in a range of 0.2 mass% or less. The steel plate used as the base steel plate in the present invention may also contain P in the above-described range. Note that P is an element that increases the strength of the steel, and in order to exhibit such an action, it is preferable to contain 0.005 mass% or more. On the other hand, when it contains exceeding 0.2 mass%, it will become high intensity | strength and ductility will fall. For this reason, it is preferable to make P into 0.005-0.2 mass%. In addition, More preferably, it is 0.01-0.1 mass%.
Al：5mass％以下
Alは、脱酸剤としてSiと同様の作用を有する元素であり、0.01mass％以上含有することが好ましい。Alが5mass％を超えて多量に含有されると、めっき密着性が低下する傾向となる。また、溶接性や強度−延性バランスの確保にも悪影響を及ぼすようになる。このため、Alは5mass％以下とすることが好ましい。なお、より好ましくは0.01〜3.0mass％である。
Al: 5 mass% or less
Al is an element having the same action as Si as a deoxidizer, and is preferably contained in an amount of 0.01 mass% or more. When Al is contained in a large amount exceeding 5 mass%, the plating adhesion tends to be lowered. It also has an adverse effect on securing weldability and strength-ductility balance. For this reason, Al is preferably 5 mass% or less. In addition, More preferably, it is 0.01-3.0 mass%.
上記した成分以外の元素としては、Ｎ、Ti、Nb、Cr、Mo、Cu、Ni、Ｂ、Ca、Sb等が例示できる。これらの元素の含有量としては、Ｎ：0.1mass％以下、Ti：１mass％以下、Nb：１mass％以下、Cr：３mass％以下、Mo：１mass％以下、Cu：３mass％以下、Ni：３mass％以下、Ｂ：0.1mass％以下、Ca：0.1mass％以下、Sb：0.5mass％以下、あるいはこれら元素のうちから選ばれた１種または２種以上を合計で５mass％以下であれば、本発明の効果が得られることを確認している。上記した成分以外の残部はFeおよび不可避的不純物である。 Examples of elements other than the above components include N, Ti, Nb, Cr, Mo, Cu, Ni, B, Ca, and Sb. As content of these elements, N: 0.1 mass% or less, Ti: 1 mass% or less, Nb: 1 mass% or less, Cr: 3 mass% or less, Mo: 1 mass% or less, Cu: 3 mass% or less, Ni: 3 mass% Hereinafter, if B: 0.1 mass% or less, Ca: 0.1 mass% or less, Sb: 0.5 mass% or less, or one or more selected from these elements is 5 mass% or less in total, the present invention It has been confirmed that the effect of. The balance other than the above components is Fe and inevitable impurities.
本発明では、まず、上記した組成の下地鋼板の表面に、特定元素を含む化合物を付着させる。特定元素としては、Cl、C、Ｓ、Ｐ、ＦおよびＢからなる特定元素群から選ばれた少なくとも１種の特定元素とする。使用可能な化合物としては、つぎのような化合物が例示できる。
Cl含有化合物：塩酸（HCl）、塩化アンモニウム（NH４Cl）、塩化アンチモン（SbCl３）、塩化鉄（FeCl２、FeCl３）、塩化チタン（TiCl４）、塩化銅（CuCl）、塩化バリウム（BaCl２）、塩化モリブデン（MoCl５）等。
In the present invention, first, a compound containing a specific element is attached to the surface of the base steel plate having the above composition. The specific element is at least one specific element selected from the specific element group consisting of Cl, C, S, P, F and B. The following compounds can be exemplified as usable compounds.
Cl-containing compounds: hydrochloric acid (HCl), ammonium chloride (NH 4 Cl), antimony chloride (SbCl 3 ), iron chloride (FeCl 2 , FeCl 3 ), titanium chloride (TiCl 4 ), copper chloride (CuCl), barium chloride ( BaCl 2 ), molybdenum chloride (MoCl 5 ) and the like.
Ｃ含有化合物：タンニン酸、アジピン酸等のカルボン酸含有化合物；糖類、フマル酸、フタル酸、フェノール、アニリン、安息香酸等の芳香族環含有化合物；グリシン、アラニン等のアミノ酸；エチレングリコール、アセチレングリコール等の多価アルコール類；アクリル酸、ポリエステル、エポキシ、およびそれらの変性化合物等の樹脂類等。
Ｓ含有化合物：硫酸（H２SO４）、硫酸アンモニウム（（NH４）２SO４）、硫化アンモニウム（（NH４）２S）、硫酸水素アンモニウム（NH４HSO４）、硫酸鉄（FeSO４、Fe２(SO４)３
）、硫酸アンモニウム鉄（Fe(NH４)２（SO４）２、FeNH４（SO４）２）、硫酸バリウム（Ba SO４）、硫化アンチモン（Sb２S３）、硫化鉄（FeS）、チオ尿素（H２NCSNH２）、二酸化チオ尿素（（NH２）２CSO２）、ＳＣＨ基のチオフェン酸塩類、ＳＣＮ基を有するチオシアン酸塩類等。
C-containing compounds: carboxylic acid-containing compounds such as tannic acid and adipic acid; aromatic ring-containing compounds such as saccharides, fumaric acid, phthalic acid, phenol, aniline, benzoic acid; amino acids such as glycine and alanine; ethylene glycol, acetylene glycol Polyhydric alcohols such as; resins such as acrylic acid, polyester, epoxy, and modified compounds thereof;
S-containing compounds: sulfuric acid (H 2 SO 4 ), ammonium sulfate ((NH 4 ) 2 SO 4 ), ammonium sulfide ((NH 4 ) 2 S), ammonium hydrogen sulfate (NH 4 HSO 4 ), iron sulfate (FeSO 4 , Fe 2 (SO 4 ) 3
), Ammonium iron sulfate (Fe (NH 4 ) 2 (SO 4 ) 2 , FeNH 4 (SO 4 ) 2 ), barium sulfate (Ba SO 4 ), antimony sulfide (Sb 2 S 3 ), iron sulfide (FeS), thiol Urea (H 2 NCSNH 2 ), thiourea dioxide ((NH 2 ) 2 CSO 2 ), thiophenate of SCH group, thiocyanate having SCN group, and the like.
Ｐ含有化合物：リン酸（H３PO４）、リン酸アンモニウム（(NH４)３PO４）、リン酸鉄（Fe PO４）、ホスホン酸（H３PO３）、ホスフィン酸（H３PO２）等。
Ｆ含有化合物：フッ化アンチモン(SbF３)、フッ化アンモニウム(NH４Ｆ)、フッ化水素アンモニウム(NH４HF)、フッ化水素酸(HF)、フッ化バリウム(BaF)、フッ化コバルト(CoF３)等。
P-containing compounds: phosphoric acid (H 3 PO 4 ), ammonium phosphate ((NH 4 ) 3 PO 4 ), iron phosphate (Fe PO 4 ), phosphonic acid (H 3 PO 3 ), phosphinic acid (H 3 PO 2 ) etc.
F-containing compounds: antimony fluoride (SbF 3 ), ammonium fluoride (NH 4 F), ammonium hydrogen fluoride (NH 4 HF), hydrofluoric acid (HF), barium fluoride (BaF), cobalt fluoride ( CoF 3 ) etc.
Ｂ含有化合物：ほう酸（H３BO３）、ほう酸鉛（Pb(BO２)２）、ほう酸マンガン（MnH４BO３）２）等。
なお、本発明では上記、例示した化合物に限定されるものではないことは言うまでもない。
本発明では、これら化合物を鋼板表面に付着させる方法はとくに限定されないが、これら化合物を物理的に鋼板に付着させればよく、例えば上記した化合物を水または有機溶剤等に溶解またはこれらを混合した溶液を用い、この溶液中に鋼板を浸漬する方法、これら溶液をスプレー等で噴霧する方法、これら溶液をロールコータ等で塗布する方法、これら溶液中に浸漬あるいはこれら溶液をスプレー等で噴霧したのちリンガーロールで付着量を調整する方法を用いることが好ましい。浸漬、噴霧等により鋼板に付着させられた化合物はその後乾燥させても、あるいはさらに化合物を直接塗布してもその効果は変わらない。
B-containing compounds: boric acid (H 3 BO 3 ), lead borate (Pb (BO 2 ) 2 ), manganese borate (MnH 4 BO 3 ) 2 ) and the like.
Needless to say, the present invention is not limited to the exemplified compounds.
In the present invention, the method for adhering these compounds to the surface of the steel sheet is not particularly limited, but these compounds may be physically adhered to the steel sheet. For example, the above-mentioned compounds are dissolved in water or an organic solvent or mixed. After using a solution, immersing the steel plate in this solution, spraying these solutions with a spray, etc., applying these solutions with a roll coater, etc., immersing in these solutions or spraying these solutions with a spray etc. It is preferable to use a method of adjusting the adhesion amount with a ringer roll. The effect of the compound adhered to the steel sheet by dipping, spraying or the like does not change even if it is subsequently dried or further directly applied with the compound.
また、上記した化合物を付着させる前に、必要に応じて電解脱脂や酸洗等の前処理を施してもよい。また、上記した化合物を付着させ後に、必要に応じて電解脱脂や酸洗等の前処理を施しても、上記した化合物が鋼板上に付着していれば本発明の効果を得ることができる。さらに、上記した化合物を含む圧延油を用いて圧延時に付着させる方法を用いてもよい。 Moreover, you may give pretreatments, such as electrolytic degreasing and pickling, as needed before making an above-mentioned compound adhere. Moreover, even if it preprocesses electrolytic degreasing, pickling, etc. as needed after making an above-mentioned compound adhere, the effect of this invention can be acquired if the above-mentioned compound has adhered on the steel plate. Furthermore, you may use the method of making it adhere at the time of rolling using the rolling oil containing an above-described compound.
いずれにしても、鋼板を酸化させる際に上記した化合物が鋼板表面に付着していることが肝要となる。
本発明では、特定元素を含む化合物の付着量は、各特定元素換算で合計0.1〜1000mg／ｍ２とすることが好ましい。特定元素の付着量が合計で0.1 mg／ｍ２未満では、所望の効果が得られない。一方、1000mg／ｍ２を超えると、効果が飽和し経済的に不利となる。
In any case, it is important that the above-mentioned compound adheres to the steel plate surface when oxidizing the steel plate.
In this invention, it is preferable that the adhesion amount of the compound containing a specific element shall be 0.1-1000 mg / m < 2 > in total in conversion of each specific element. If the adhesion amount of the specific element is less than 0.1 mg / m 2 in total, the desired effect cannot be obtained. On the other hand, if it exceeds 1000 mg / m 2 , the effect is saturated and economically disadvantageous.
鋼板に付着させた特定元素量は、一般的な鋼中の元素分析法により測定することができる。すなわち、特定元素を含む化合物を付着させた鋼板について、下地鋼板を含んで特定元素量を分析し、得られた特定元素量から、下地鋼板中の特定元素量を差し引くことにより定量できる。なお、下地鋼板中の特定元素量は、鋼板表層50μm以上を研削除去したのち、該特定元素の分析を行うことにより求めるものとする。 The amount of the specific element adhered to the steel plate can be measured by a general element analysis method in steel. That is, about the steel plate to which the compound containing a specific element was made to adhere, it can be quantified by analyzing the amount of the specific element including the base steel plate and subtracting the specific element amount in the base steel plate from the obtained specific element amount. The amount of the specific element in the base steel plate is determined by analyzing the specific element after grinding and removing the steel plate surface layer of 50 μm or more.
なお、特定元素を含む化合物を付着させた鋼板を採取できない場合には、特定元素を含む化合物を付着させた鋼板についてオンラインで蛍光Ｘ線法を用いて特定元素の強度を測定し、予め作製した検量線から特定元素量を求めてもよい。また、特定元素を水溶液で付着させる場合には、水膜厚をオンラインで測定し水溶液の濃度から特定元素量を求めてもよい。 In addition, when the steel plate which adhered the compound containing a specific element cannot be extract | collected, the intensity | strength of a specific element was measured online using the fluorescent X-ray method about the steel plate which adhered the compound containing a specific element, and produced beforehand. A specific element amount may be obtained from a calibration curve. Moreover, when attaching a specific element with aqueous solution, a water film thickness may be measured online and the amount of specific elements may be calculated | required from the density | concentration of aqueous solution.
表面に特定元素を含む化合物を付着させた下地鋼板に、ついで、酸化性雰囲気中で加熱する酸化処理を施し、鋼板の表面に酸化鉄層を形成する。下地鋼板に付着させた特定元素は、酸化処理により酸化鉄／鋼板の界面近傍に濃化し、溶融亜鉛めっき処理後あるいは合金化処理後も鋼板上に残存するものと、酸化処理時あるいは還元処理時に鋼板から脱落し加熱炉のロール等に付着したり、ガス化して加熱炉内に放出されるものとがある。 Next, the base steel plate with a compound containing a specific element attached to the surface is subjected to an oxidation treatment that is heated in an oxidizing atmosphere to form an iron oxide layer on the surface of the steel plate. The specific elements attached to the base steel plate are concentrated near the iron oxide / steel plate interface by oxidation treatment and remain on the steel plate after hot dip galvanizing or alloying treatment, and during oxidation treatment or reduction treatment. Some may fall off the steel plate and adhere to a roll of a heating furnace, or may be gasified and discharged into the heating furnace.
本発明では、下地鋼板に付着させた特定元素のうち、50mass％以上を、溶融亜鉛めっき処理後あるいは合金化処理後も鋼板上に残存させることを必要とする。とくに、特定元素が強腐食性ガスとなる、Cl、Ｓの場合には、残存する量は付着させた量に対し70mass％以上とすることが好ましい。さらに好ましくは100mass％である。これにより、付着させた特定元素が、ロール等へ付着することを抑制できロールメンテナンス費の削減を可能とするとともに、鋼板へピックアップされて発生するピックアップ欠陥をも防止できる。さらに、これにより、ガスの放出が抑制され、炉体や炉内設備の劣化、損傷を防止できるとともに、放出されるガスによる大気汚染を防止するための脱ガス装置を備える必要がなくなるなどの効果がある。 In the present invention, it is necessary that 50 mass% or more of the specific elements attached to the base steel sheet remain on the steel sheet after the hot dip galvanizing process or after the alloying process. In particular, in the case of Cl and S in which the specific element is a strong corrosive gas, the remaining amount is preferably set to 70 mass% or more with respect to the deposited amount. More preferably, it is 100 mass%. Thereby, it is possible to suppress the attached specific element from adhering to the roll or the like, and to reduce the roll maintenance cost, and it is possible to prevent pick-up defects caused by being picked up by the steel plate. Furthermore, this suppresses the release of gas, prevents deterioration and damage of the furnace body and furnace equipment, and eliminates the need to provide a degassing device for preventing air pollution caused by the released gas. There is.
下地鋼板に付着させた特定元素のうち、50mass％以上を、溶融亜鉛めっき処理後あるいは合金化処理後も鋼板上に残存させるためには、酸化性雰囲気中で加熱する酸化処理を、鋼板昇温速度が5℃／ｓ以上でかつ鋼板最高到達温度が500℃超の温度となるように加熱する処理とすることが好ましい。
酸化処理における鋼板最高到達温度が500℃以下では、酸化鉄の生成量が不足し、特定元素を酸化鉄／鋼板の界面近傍に十分に濃化させることができない。このため、特定元素が、鋼板から脱落しロール等へ付着したり、ガス化して炉内に放出されたりする。酸化処理における鋼板最高到達温度を500℃超えの温度とすることにより、特定元素を酸化鉄／鋼板の界面近傍に十分に濃化させることができ、下地鋼板に付着させた特定元素のうち、50mass％以上を、溶融亜鉛めっき処理後あるいは合金化処理後も鋼板上に残存させることができる。また、酸化処理における鋼板最高到達温度を500℃超えの温度とすることにより、Siの表面濃化を抑制するに足る十分な量の酸化鉄を形成することができる。これにより、不めっきの防止や、Siの表面濃化に起因した筋状の表面欠陥の発生を防止することができる。なお、本発明では、鋼板最高到達温度の上限はとくに限定されないが、酸化処理に続く還元処理で必要とされる鋼板温度以下とすることが経済的であり、実操業上も好ましい。
In order to leave 50 mass% or more of the specific elements attached to the base steel sheet on the steel sheet after hot dip galvanizing or alloying, an oxidation treatment that is heated in an oxidizing atmosphere is performed by heating the steel plate. The heating is preferably performed so that the speed is 5 ° C./s or more and the maximum temperature reached by the steel sheet exceeds 500 ° C.
When the maximum steel plate temperature in the oxidation treatment is 500 ° C. or less, the amount of iron oxide produced is insufficient, and the specific element cannot be sufficiently concentrated in the vicinity of the iron oxide / steel plate interface. For this reason, the specific element falls off the steel plate and adheres to a roll or the like, or is gasified and released into the furnace. By setting the maximum temperature of the steel sheet in the oxidation treatment to a temperature exceeding 500 ° C., the specific element can be sufficiently concentrated near the iron oxide / steel interface, and 50 mass among the specific elements attached to the base steel sheet. % Or more can remain on the steel plate after the hot dip galvanizing treatment or after the alloying treatment. Further, by setting the maximum steel sheet temperature in the oxidation treatment to a temperature exceeding 500 ° C., a sufficient amount of iron oxide sufficient to suppress Si surface concentration can be formed. As a result, non-plating can be prevented and the occurrence of streak-like surface defects due to the surface concentration of Si can be prevented. In the present invention, the upper limit of the maximum steel sheet temperature is not particularly limited, but it is economical and preferable for practical operation to be equal to or lower than the steel sheet temperature required for the reduction treatment following the oxidation treatment.
なお、めっき鋼板上に残存する特定元素量は、一般的な鋼中の元素分析方法により、容易に測定することができる。すなわち、めっき層および下地鋼板を含んで、めっき鋼板中の特定元素量を分析し、得られた特定元素量から、下地鋼板に含まれる特定元素量を差し引くことにより、定量することができる。
さらに、本発明では、酸化処理における鋼板昇温速度を5℃／ｓ以上とすることが好ましい。鋼板昇温速度が5℃／ｓ未満では、酸化鉄の生成速度が遅く、特定元素が酸化鉄／鋼板の界面近傍に十分に濃化しない。このため、特定元素が、鋼板から脱落しロール等へ付着したり、ガス化して炉内に放出されたりする。鋼板昇温速度を5℃／ｓ以上とすることにより、特定元素が酸化鉄／鋼板の界面近傍に十分に濃化し、下地鋼板に付着させた特定元素のうち、50mass％以上を、溶融亜鉛めっき処理後あるいは合金化処理後も鋼板上に残存させることができるようになる。なお、鋼板昇温速度の上限はとくに規定する必要はないが、必要以上に鋼板昇温速度を増加させても、効果が飽和し経済的に不利となるため、製造コストとの兼ね合いで適宜決定することが好ましい。なお、ここでいう鋼板昇温速度とは、鋼板を酸化することができる領域での平均を言うものとする。
The specific element amount remaining on the plated steel sheet can be easily measured by a general elemental analysis method in steel. That is, it can be quantified by analyzing the specific element amount in the plated steel plate including the plating layer and the base steel plate, and subtracting the specific element amount contained in the base steel plate from the obtained specific element amount.
Furthermore, in this invention, it is preferable that the steel plate temperature increase rate in an oxidation process shall be 5 degrees C / s or more. When the steel plate heating rate is less than 5 ° C./s, the production rate of iron oxide is slow, and the specific element is not sufficiently concentrated in the vicinity of the iron oxide / steel plate interface. For this reason, the specific element falls off the steel plate and adheres to a roll or the like, or is gasified and released into the furnace. By setting the steel sheet heating rate to 5 ° C / s or more, the specified element is sufficiently concentrated near the iron oxide / steel interface, and 50mass% or more of the specified element attached to the base steel sheet is hot dip galvanized. It becomes possible to remain on the steel plate after the treatment or the alloying treatment. The upper limit of the steel plate heating rate does not need to be specified, but even if the steel plate heating rate is increased more than necessary, the effect is saturated and disadvantageous economically. It is preferable to do. In addition, the steel plate temperature rising rate here shall mean the average in the area | region which can oxidize a steel plate.
本発明における酸化処理は、酸化性雰囲気中で鋼板を加熱することができれば、とくにその方法を限定する必要はない。加熱手段としては、バーナー加熱、誘導加熱、放射加熱、通電加熱等の、従来から知られている加熱手段がいずれも適用できる。
バーナー加熱方式では、酸化炉、無酸化炉等の加熱炉を使用することができる。無酸化炉の場合、例えば直火バーナーの空燃比を1.0超とすることにより容易に酸化性雰囲気とすることができ、鋼板を酸化できる。また、誘導加熱方式、放射加熱方式、通電加熱方式では、被加熱鋼板の近傍を酸化性雰囲気とすることで容易に、鋼板を酸化できる。酸化性雰囲気としては、鋼板を酸化できる雰囲気であればとくに限定されるものではないが、酸素、水蒸気、二酸化炭素等の酸化性ガスを１種または２種以上を含有する雰囲気とすることが好ましい。
The oxidation treatment in the present invention is not particularly limited as long as the steel sheet can be heated in an oxidizing atmosphere. As the heating means, any conventionally known heating means such as burner heating, induction heating, radiant heating, and electric heating can be applied.
In the burner heating method, a heating furnace such as an oxidation furnace or a non-oxidation furnace can be used. In the case of a non-oxidizing furnace, for example, by setting the air-fuel ratio of the direct-fired burner to more than 1.0, an oxidizing atmosphere can be easily obtained and the steel sheet can be oxidized. In addition, in the induction heating method, the radiant heating method, and the energization heating method, the steel plate can be easily oxidized by making the vicinity of the heated steel plate an oxidizing atmosphere. The oxidizing atmosphere is not particularly limited as long as it is an atmosphere that can oxidize a steel sheet, but an oxidizing gas such as oxygen, water vapor, and carbon dioxide is preferably used in an atmosphere containing one or more kinds. .
また、本発明の酸化処理で鋼板表面に形成される酸化鉄層は、酸素量換算で0.01〜5 g／ｍ２とすることが好ましい。形成される酸化鉄層が、酸素量換算で0.01 g／ｍ２未満では、酸化鉄量が不足してSiの表面濃化を十分に抑制することができないため、鋼板と溶融亜鉛との濡れ性を改善することが困難となる。一方、形成される酸化鉄層が、酸素量換算で５g／ｍ２を超えて多くなるとSiの表面濃化を抑制する効果が飽和するとともに、酸化処理後に行う還元処理で形成された酸化鉄を十分に還元することができなくなり、未還元酸化被膜として残存することになる。そのため、めっき後の合金化処理において合金化遅延が生じることになる。 Moreover, it is preferable that the iron oxide layer formed in the steel plate surface by the oxidation process of this invention shall be 0.01-5 g / m < 2 > in conversion of oxygen amount. If the formed iron oxide layer is less than 0.01 g / m 2 in terms of oxygen amount, the iron oxide amount is insufficient and the surface concentration of Si cannot be sufficiently suppressed. It becomes difficult to improve. On the other hand, when the formed iron oxide layer exceeds 5 g / m 2 in terms of oxygen amount, the effect of suppressing the surface concentration of Si is saturated, and the iron oxide formed by the reduction treatment performed after the oxidation treatment is saturated. It cannot be sufficiently reduced and remains as an unreduced oxide film. Therefore, an alloying delay occurs in the alloying process after plating.
なお、酸化鉄層の形成量は、酸化鉄層中の酸素量を、一般的な鋼中の酸素分析法により定量分析することにより求めることができる。すなわち、下地鋼板を含んで全酸素量を分析し、該全酸素量から下地鋼板中の酸素量を差し引くことにより、容易に酸化鉄層の酸素量を求めることができる。また、予め検量線を作成しておけば、蛍光Ｘ線法、ＧＤＳ（グロー放電分光）法等の簡易定量方法を利用することもできる。 The amount of iron oxide layer formed can be determined by quantitatively analyzing the amount of oxygen in the iron oxide layer by a general oxygen analysis method in steel. That is, by analyzing the total oxygen amount including the base steel plate and subtracting the oxygen amount in the base steel plate from the total oxygen amount, the oxygen amount of the iron oxide layer can be easily obtained. In addition, if a calibration curve is prepared in advance, a simple quantitative method such as a fluorescent X-ray method or a GDS (glow discharge spectroscopy) method can be used.
本発明では、ついで、形成された酸化鉄層を還元性雰囲気で加熱し還元する還元処理を行う。還元処理の方法は、鋼板表面に形成された酸化鉄を還元できる方法であればよく、常用の方法がいずれも適用でき、とくに限定されない。例えば、放射加熱方式の焼鈍炉で水素を含む還元性雰囲気中で600〜900℃程度の温度で加熱する処理とするのが一般的である。 In the present invention, a reduction treatment is then performed in which the formed iron oxide layer is heated and reduced in a reducing atmosphere. The method for the reduction treatment is not particularly limited as long as it is a method capable of reducing iron oxide formed on the surface of the steel sheet, and any conventional method can be applied. For example, it is common to use a radiant heating type annealing furnace that is heated at a temperature of about 600 to 900 ° C. in a reducing atmosphere containing hydrogen.
ついで、還元処理を施された鋼板は、非酸化性あるいは還元性雰囲気中でめっき処理に適した温度まで冷却されたのち、めっき浴中に浸漬し鋼板表面に溶融亜鉛めっき層を形成する溶融亜鉛めっき処理を施される。本発明における溶融亜鉛めっき処理は、従来から行われている方法がいずれも適用でき、とくに限定する必要はない。例えば、溶融亜鉛めっき処理条件としては、Al濃度を0.1〜0.2％とする溶融亜鉛めっき浴を用い、めっき浴温度を440〜520℃、鋼板のめっき浴侵入温度をめっき浴温度にほぼ等しい温度とするのが一般的である。なお、製品の使途によってめっき処理条件を変更することがある。例えば、めっき浴中にAl以外に、Pb、Sb、Fe、Mg、Mn、Ni、Ca、Ti、Ｖ、Cr、Co、Sn等の元素を添加あるいは混入させる場合がある。しかし、これらめっき処理条件の変更は、本発明の効果にはなんら影響を及ぼさないことは言うまでもない。 Next, the steel sheet subjected to reduction treatment is cooled to a temperature suitable for plating treatment in a non-oxidizing or reducing atmosphere, and then immersed in a plating bath to form a hot dip galvanized layer on the steel sheet surface. Plated. Any conventional method can be applied to the hot dip galvanizing treatment in the present invention, and there is no particular need to limit it. For example, as the hot dip galvanizing treatment conditions, a hot dip galvanizing bath having an Al concentration of 0.1 to 0.2% is used, the plating bath temperature is 440 to 520 ° C., and the plating bath intrusion temperature of the steel sheet is substantially equal to the plating bath temperature. It is common to do. The plating conditions may be changed depending on the use of the product. For example, elements such as Pb, Sb, Fe, Mg, Mn, Ni, Ca, Ti, V, Cr, Co, and Sn may be added or mixed in the plating bath in addition to Al. However, it goes without saying that these changes in the plating conditions do not affect the effects of the present invention.
溶融亜鉛めっき処理により鋼板表面に形成される溶融亜鉛めっき層の厚さは、とくに限定する必要はないが、３〜15μmとすることが好ましい。めっき層の厚さが３μm未満では、防錆性が不足し、一方15μmを超えて厚くしても防錆性が飽和するとともに、加工性、経済性が低下する。めっき層厚さの調整方法は本発明ではとくに限定する必要はないが、一般的な、例えばガスワイピングとすることが好ましい。ガスワイピングでは、ガス圧、ワイピングノズルや鋼板との距離等の調整によりめっき層厚さを調整することができる。 The thickness of the hot dip galvanized layer formed on the surface of the steel sheet by hot dip galvanizing is not particularly limited, but is preferably 3 to 15 μm. When the thickness of the plating layer is less than 3 μm, the rust prevention property is insufficient. On the other hand, when the thickness exceeds 15 μm, the rust prevention property is saturated, and the workability and economy are lowered. The method for adjusting the thickness of the plating layer is not particularly limited in the present invention, but a general method such as gas wiping is preferable. In gas wiping, the plating layer thickness can be adjusted by adjusting the gas pressure, the distance from the wiping nozzle and the steel plate, and the like.
溶融亜鉛めっき処理後に、必要に応じて溶融亜鉛めっき層の合金化処理を行い、合金化溶融亜鉛めっき層とすることもできる。合金化処理は、ガス加熱、誘導加熱、通電加熱等、通常の方法がいずれも適用でき、とくに限定する必要はない。また、合金化処理の条件は、とくに限定する必要はなく、溶融亜鉛めっき層を合金化できる条件であればよく、通常の条件がいずれも適用できる。例えば、合金化処理温度を板温で460〜600℃程度、合金化処理時間を5〜60ｓ程度とすることが一般的である。なお、合金化処理条件の変更は、本発明の効果にはなんら影響を及ぼさないことは言うまでもない。 After the hot dip galvanizing treatment, an alloying treatment of the hot dip galvanized layer may be performed as necessary to obtain an alloyed hot dip galvanized layer. For the alloying treatment, any of ordinary methods such as gas heating, induction heating, electric heating, etc. can be applied, and there is no particular limitation. The conditions for the alloying treatment are not particularly limited as long as the hot galvanized layer can be alloyed, and any normal conditions can be applied. For example, the alloying treatment temperature is generally about 460 to 600 ° C. as the plate temperature, and the alloying treatment time is generally about 5 to 60 s. Needless to say, the change in the alloying treatment conditions does not affect the effects of the present invention.
表１に示す組成の鋼板（板厚：1.4mm、板幅：1100mm）を下地鋼板として、連続溶融亜鉛めっきライン（ＣＧＬ）で合金化溶融亜鉛めっき鋼板を製造した。
まず、下地鋼板に、前処理として、電解脱脂処理を施し、鋼板表面の脱脂を行ったのち、鋼板表面に、表２に示す種類の特定元素を含む化合物を、特定元素換算で合計、表２に示す付着量となるように付着させた。化合物の鋼板表面への付着は、表２に示す化合物濃度の水溶液を、表２に示す特定元素付着量となるように、スプレー噴霧装置で鋼板表面に吹き付け、ついでリンガーロールで均一厚さとしたのち、ドライヤで乾燥させて行った。乾燥後、オンラインで蛍光Ｘ線法により特定元素の強度測定を行い、予め作成した検量線を用いて、特定元素の付着量を算出した。
An alloyed hot-dip galvanized steel sheet was produced by a continuous hot-dip galvanizing line (CGL) using a steel sheet having a composition shown in Table 1 (thickness: 1.4 mm, width: 1100 mm) as a base steel sheet.
First, as a pretreatment, the base steel sheet is subjected to electrolytic degreasing treatment and the steel sheet surface is degreased, and then the steel sheet surface is summed with compounds containing specific elements of the type shown in Table 2 in terms of specific elements. It was made to adhere so that it might become the adhesion amount shown in. The adhesion of the compound to the surface of the steel sheet is carried out by spraying an aqueous solution having the compound concentration shown in Table 2 on the surface of the steel sheet with a spray spray device so that the specific element adhesion amount shown in Table 2 is obtained, and then setting the uniform thickness with a ringer roll. And drying with a dryer. After drying, the intensity of the specific element was measured online by the fluorescent X-ray method, and the adhesion amount of the specific element was calculated using a calibration curve prepared in advance.
表面に特定元素を含む化合物を付着させた鋼板に、ついで酸化処理を施した。酸化処理は直火バーナー式の酸化炉を使用し、空燃比：1.15として、表２に示す鋼板到達温度および鋼板昇温速度の条件で加熱した。
ついで、生成した酸化鉄層を還元する還元処理を施した。還元処理は、ラジアントチューブ式の加熱炉で、（５vol.％水素＋窒素）雰囲気（露点：約−35℃）中で板温：850℃の条件で行った。
The steel sheet having a compound containing a specific element attached to the surface was then subjected to an oxidation treatment. For the oxidation treatment, a direct-fired burner type oxidation furnace was used, and the air-fuel ratio was 1.15, and the steel sheet was heated under the conditions of the steel sheet arrival temperature and the steel sheet heating rate shown in Table 2.
Subsequently, the reduction process which reduces the produced | generated iron oxide layer was performed. The reduction treatment was performed in a radiant tube type heating furnace in a (5 vol.% Hydrogen + nitrogen) atmosphere (dew point: about −35 ° C.) under a plate temperature of 850 ° C.
還元処理を施された鋼板は、ついで、非酸化性雰囲気中で溶融亜鉛めっき浴の温度に略等しい温度となるまで冷却されたのち、溶融亜鉛めっき浴に浸漬され、鋼板表面に溶融亜鉛めっき層が付着され、溶融亜鉛めっき鋼板とされた。溶融亜鉛めっき層の付着量は、ガスワイピング装置で片面：50g/m２に調整した。なお、溶融亜鉛めっき浴は、Al：0.13mass％を含む溶融亜鉛めっき浴（Fe飽和）とし、浴温を460℃、侵入板温を460℃とした。 The steel sheet subjected to the reduction treatment is then cooled to a temperature substantially equal to the temperature of the hot dip galvanizing bath in a non-oxidizing atmosphere, and then immersed in the hot dip galvanizing bath, and a hot dip galvanized layer is formed on the surface of the steel plate. Was attached to obtain a hot dip galvanized steel sheet. The adhesion amount of the hot dip galvanized layer was adjusted to 50 g / m 2 on one side with a gas wiping device. The hot dip galvanizing bath was a hot dip galvanizing bath (Fe saturated) containing Al: 0.13 mass%, the bath temperature was 460 ° C, and the penetration plate temperature was 460 ° C.
ついで、形成された溶融亜鉛めっき層を、合金化し、合金化溶融亜鉛めっき層とする合金化処理を施した。合金化処理は、誘導加熱方式の合金化炉を使用して、めっき層中の鉄含有量が9〜11mass％となるように調整した。
得られた合金化溶融亜鉛めっき鋼板（めっき鋼板）について、めっき鋼板中の特定元素残存率、めっき外観および耐パウダリング性を調査した。調査方法は次のとおりである。
Next, the formed hot dip galvanized layer was alloyed and subjected to an alloying treatment to form an alloyed hot dip galvanized layer. The alloying treatment was adjusted using an induction heating type alloying furnace so that the iron content in the plating layer was 9 to 11 mass%.
The obtained alloyed hot-dip galvanized steel sheet (plated steel sheet) was examined for the residual ratio of specific elements in the plated steel sheet, the plating appearance and the powdering resistance. The survey method is as follows.
（１）特定元素残存率
得られためっき鋼板について、めっき層および下地鋼板を含んで、めっき鋼板中の特定元素量を鋼中元素分析法で分析し、得られた特定元素量から、下地鋼板に含まれる特定元素量を差し引くことにより、めっき鋼板中に残存する特定元素量を求め、特定元素の付着量に対する残存率を求めた。
(1) Specific element remaining rate About the obtained plated steel sheet, including the plating layer and the base steel sheet, the specific element amount in the plated steel sheet is analyzed by elemental analysis in steel, and from the obtained specific element quantity, the base steel sheet The amount of the specific element remaining in the plated steel sheet was determined by subtracting the amount of the specific element contained in the steel sheet, and the residual ratio relative to the amount of the specific element deposited was determined.
（２）めっき外観
得られためっき鋼板の表面外観を目視で観察し、不めっき、さざなみ状欠陥の有無を調査した。目視で不めっきあるいはさざなみ状欠陥が観察できる場合を×、不めっきおよびさざなみ状欠陥が全く観察されない場合を○としてめっき外観を評価した。
また、得られた鋼板の表面外観を目視で観察し、筋状欠陥およびピックアップ起因の表面欠陥の有無を調査した。目視で観察して、筋状欠陥およびピックアップ起因の表面欠陥が全くない場合を○とし、目視で容易に識別可能な筋状欠陥およびピックアップ起因の表面欠陥がある場合を×としてめっき外観を評価した。
(2) Plating appearance The surface appearance of the obtained plated steel sheet was visually observed to investigate the presence of non-plating and ripple defects. The appearance of the plating was evaluated as x when no plating or a ripple-like defect could be observed visually, and when no plating or a ripple-like defect was observed at all.
Further, the surface appearance of the obtained steel sheet was visually observed to investigate the presence of streak defects and surface defects caused by the pickup. The appearance of the plating was evaluated by visually observing the case where there were no streak defects and pickup-related surface defects at all, and x when there were streak defects and pickup-derived surface defects that could be easily identified visually. .
（３）耐パウダリング性
得られためっき鋼板から試験片（ｔ×幅25mm×長さ40mm）を採取し、試験片の長さ方向中央の位置にセロハンテープ（ニチバン製：幅24mm）を貼り、テープ面を90°内側に曲げた後、曲げ戻しを行った。曲げ−曲げ戻し後、セロハンテープを剥がし、付着したZn量を蛍光Ｘ線によりカウント数として測定した。測定したZnカウント数を試験片幅：単位長さ（１m）当りのカウント数に補正して、カウント数が0〜5000の場合を○（良好）とし、5000以上の場合を×（不良）として耐パウダリング性を評価した。
(3) Powdering resistance A test piece (t x width 25 mm x length 40 mm) is taken from the obtained plated steel sheet, and cellophane tape (Nichiban: width 24 mm) is attached to the center of the test piece in the length direction. The tape surface was bent 90 ° inward and then bent back. After bending and returning, the cellophane tape was peeled off, and the amount of adhered Zn was measured as a count number with fluorescent X-rays. Measured Zn count number is corrected to the test piece width: count number per unit length (1m). When the count number is 0 to 5000, ○ (good), and when it is 5000 or more, × (defect) The powdering resistance was evaluated.
得られた結果を表２に示す。 The obtained results are shown in Table 2.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007332415A (en) * | 2006-06-14 | 2007-12-27 | Jfe Steel Kk | Method for manufacturing hot-dip galvanized steel sheet |
| JP2010043308A (en) * | 2008-08-11 | 2010-02-25 | Jfe Steel Corp | Manufacturing method of cold-rolled steel plate, and cold-rolled steel plate |
| JP2015175040A (en) * | 2014-03-17 | 2015-10-05 | Ｊｆｅスチール株式会社 | Method of manufacturing galvanized steel plate and alloyed galvanized steel plate, and galvanized steel plate and alloyed galvanized steel plate |
| JP2019031721A (en) * | 2017-08-09 | 2019-02-28 | Ｊｆｅスチール株式会社 | Method for manufacturing high strength hot-dip galvanized steel sheet |
Citations (6)
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| JPH05163558A (en) * | 1991-12-12 | 1993-06-29 | Nippon Steel Corp | Manufacture of si-containing high strength hot-dip galvanizing carbon steel sheets and alloy hot-dip galyannealed steel sheets |
| JPH05247614A (en) * | 1992-03-06 | 1993-09-24 | Sumitomo Metal Ind Ltd | Galvanizing method for silicon-containing steel sheet |
| JPH08170160A (en) * | 1994-12-19 | 1996-07-02 | Sumitomo Metal Ind Ltd | Production of silicon-containing high tensile strength hot dip galvanized or galvannealed steel sheet |
| JP2000248346A (en) * | 1999-03-03 | 2000-09-12 | Nkk Corp | Production of silicon-containing high strength hot dip galvanized steel sheet and high strength galvannealed steel sheet |
| JP2001279411A (en) * | 2000-03-29 | 2001-10-10 | Kawasaki Steel Corp | Manufacturing method for galvanized steel sheet |
| JP2003328099A (en) * | 2002-05-02 | 2003-11-19 | Nippon Steel Corp | Production method for high-strength hot-dip galvanized steel sheet |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH05163558A (en) * | 1991-12-12 | 1993-06-29 | Nippon Steel Corp | Manufacture of si-containing high strength hot-dip galvanizing carbon steel sheets and alloy hot-dip galyannealed steel sheets |
| JPH05247614A (en) * | 1992-03-06 | 1993-09-24 | Sumitomo Metal Ind Ltd | Galvanizing method for silicon-containing steel sheet |
| JPH08170160A (en) * | 1994-12-19 | 1996-07-02 | Sumitomo Metal Ind Ltd | Production of silicon-containing high tensile strength hot dip galvanized or galvannealed steel sheet |
| JP2000248346A (en) * | 1999-03-03 | 2000-09-12 | Nkk Corp | Production of silicon-containing high strength hot dip galvanized steel sheet and high strength galvannealed steel sheet |
| JP2001279411A (en) * | 2000-03-29 | 2001-10-10 | Kawasaki Steel Corp | Manufacturing method for galvanized steel sheet |
| JP2003328099A (en) * | 2002-05-02 | 2003-11-19 | Nippon Steel Corp | Production method for high-strength hot-dip galvanized steel sheet |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007332415A (en) * | 2006-06-14 | 2007-12-27 | Jfe Steel Kk | Method for manufacturing hot-dip galvanized steel sheet |
| JP2010043308A (en) * | 2008-08-11 | 2010-02-25 | Jfe Steel Corp | Manufacturing method of cold-rolled steel plate, and cold-rolled steel plate |
| JP2015175040A (en) * | 2014-03-17 | 2015-10-05 | Ｊｆｅスチール株式会社 | Method of manufacturing galvanized steel plate and alloyed galvanized steel plate, and galvanized steel plate and alloyed galvanized steel plate |
| JP2019031721A (en) * | 2017-08-09 | 2019-02-28 | Ｊｆｅスチール株式会社 | Method for manufacturing high strength hot-dip galvanized steel sheet |
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|---|---|
| JP4810980B2 (en) | 2011-11-09 |
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