JPH0756053B2 - Manufacturing method of galvanized hot rolled steel sheet with excellent workability - Google Patents
Manufacturing method of galvanized hot rolled steel sheet with excellent workabilityInfo
- Publication number
- JPH0756053B2 JPH0756053B2 JP1179692A JP17969289A JPH0756053B2 JP H0756053 B2 JPH0756053 B2 JP H0756053B2 JP 1179692 A JP1179692 A JP 1179692A JP 17969289 A JP17969289 A JP 17969289A JP H0756053 B2 JPH0756053 B2 JP H0756053B2
- Authority
- JP
- Japan
- Prior art keywords
- steel sheet
- hot
- less
- rolled steel
- ferrite
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Description
【発明の詳細な説明】 〈産業上の利用分野〉 この発明は、加工性、中でも穴拡げ特性が特に優れた亜
鉛メッキ鋼板の製造方法に関するものである。DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a method for producing a galvanized steel sheet which is particularly excellent in workability, in particular, hole expanding characteristics.
〈従来技術とその課題〉 現在、連続熱間圧延によって製造されるところの所謂
“熱延鋼板”は、比較的安価な構造材料として自動車を
始めとする各種の産業機械類に広く使用されているが、
最近、例えば自動車足回りに使われる部材を中心に、亜
鉛メッキを施して防錆性を強化した熱延鋼板の需要が増
加する傾向を見せてきた。<Prior art and its problems> At present, so-called "hot rolled steel sheet" manufactured by continuous hot rolling is widely used in various industrial machines including automobiles as a relatively inexpensive structural material. But,
Recently, there has been an increasing trend in demand for hot-rolled steel sheets that have been galvanized to enhance their rust prevention properties, centering on components used in automobile chassis, for example.
ところで、このような“亜鉛メッキ熱延鋼板”は、通
常、冷延鋼板の亜鉛メッキラインである連続焼鈍溶融亜
鉛メッキラインをそのまま利用して生産がなされてい
る。この場合、冷延鋼板を対象とするときとは異なって
焼鈍のための加熱は不要であるが、それでも、溶融メッ
キの密着性確保と言う意味合いから溶融亜鉛浴を通す前
に熱延鋼板を亜鉛の溶融温度（約460℃）以上に予熱す
ることが必要とされていた。By the way, such a "zinc-plated hot-rolled steel sheet" is usually produced by directly using a continuous annealing hot-dip galvanizing line which is a galvanizing line of a cold-rolled steel sheet. In this case, unlike the case where a cold-rolled steel sheet is used, heating for annealing is not necessary, but still, from the meaning of ensuring the adhesion of the hot-dip galvanized steel, the hot-rolled steel sheet is zinced before passing through the hot-dip zinc bath. It was necessary to preheat above the melting temperature (about 460 ° C) of.
しかし、一方で、熱延鋼板を上述のように予熱すると
「鋼板中のセメンタイトが溶けてフェライト中の固溶Ｃ
（炭素）が増加する」と言う現象が起き、その結果とし
て、得られる亜鉛メッキ熱延鋼板の加工性、特にその穴
拡げ性の劣化が目立つようになるとの問題が指摘されて
いた。However, on the other hand, when the hot-rolled steel sheet is preheated as described above, "the cementite in the steel sheet is melted and the solid solution C in the ferrite is dissolved.
It has been pointed out that there is a problem in that the workability of the obtained galvanized hot-rolled steel sheet, in particular, the deterioration of its hole expandability becomes conspicuous as a result.
そこで、上記問題を回避すべく、亜鉛メッキ熱延鋼板を
製造するに際してＣ含有量を極低域にまで低減した熱延
鋼板を素材とする方法が提案された（例えば特公昭63-1
79024号参照）。しかしながら、素材鋼板のＣ量を制限
するこの方法では、亜鉛メッキ熱延鋼板製品に十分な強
度を確保することが難しい上に経済的にも不利であり、
従ってそれほど好ましい手段とは言い難かった。Therefore, in order to avoid the above problems, a method of using a hot-rolled steel sheet having a C content reduced to an extremely low range when manufacturing a galvanized hot-rolled steel sheet has been proposed (for example, JP-B-63-1).
See No. 79024). However, with this method of limiting the C content of the raw steel sheet, it is difficult to secure sufficient strength in the galvanized hot-rolled steel sheet product, and it is economically disadvantageous,
Therefore, it was hard to say that it was such a preferable means.
このようなことから、本発明の目的は、母材の熱延鋼板
以上の加工性（特に穴拡げ性）を有する溶融亜鉛メッキ
鋼板を、経済的な不利を伴うことなく安定して量産し得
る手段を提供することに置かれた。Therefore, the object of the present invention is to enable stable mass production of hot-dip galvanized steel sheets having workability (particularly hole expandability) higher than that of hot-rolled steel sheets of the base metal without economic disadvantage. Placed in providing the means.
〈課題を解決するための手段〉 本発明者等は、上記目的を達成すべく、特に溶融亜鉛メ
ッキラインを或る種の熱処理ラインと見立てて数多くの
亜鉛メッキ熱延鋼板製造実験を繰り返しながら研究を重
ねた結果、「成分組成を適切に調整すると共に、熱間圧
延後の冷却・巻取り条件を規制した熱延鋼板を素材と
し、更に亜鉛浴に通す前の再加熱温度を特定の値に制御
した上で溶融亜鉛メッキを施すと、十分な強度とメッキ
密着性の確保は勿論、母材の穴拡げ特性が著しく改善さ
れた亜鉛メッキ熱延鋼板が安定して実現されるようにな
る」ことを見出すに至った。<Means for Solving the Problems> In order to achieve the above object, the present inventors have studied a number of galvanized hot-rolled steel sheet manufacturing experiments by repeating the hot dip galvanizing line as a heat treatment line of a certain type. As a result, "The composition of the components was adjusted appropriately, and the hot-rolled steel sheet that regulated the cooling and winding conditions after hot rolling was used as the material, and the reheating temperature before passing through the zinc bath was set to a specific value. When hot-dip galvanizing is performed under controlled conditions, sufficient strength and plating adhesion can be ensured, and galvanized hot-rolled steel sheet with significantly improved base material hole expansion characteristics can be stably realized. " I came to find a thing.
即ち、亜鉛メッキラインではマルテンサイトが生じ難い
ようにMn含有量を規制した低Mn鋼を熱間圧延し、続いて
特定温度以下の領域にまで急冷してフェライトとセメン
タイトの微細化を図った熱延鋼板を用いると共に、亜鉛
メッキラインでの溶融亜鉛メッキに先立って該熱延鋼板
を（α＋γ）二相域まで加熱処理すると、粒界に存在し
ていたセメンタイトがマトリックス中に溶けて粒内に細
かく分散すると共に、この状態で再加熱時に生成したオ
ーステナイトからフェライトが生成するため、結果とし
て非常に細粒化されたフェライトとパーライト又はセメ
ンタイトの組織が形成される。そして、これによって十
分な加工性（穴拡げ性）改善効果が得られると同時に、
良好なメッキ密着性や強度も確保できるとの知見が得ら
れたのである。That is, in a galvanizing line, low-Mn steel whose Mn content is regulated so that martensite is hard to occur is hot-rolled, and then rapidly cooled to a region of a specific temperature or lower to refine ferrite and cementite. When a hot-rolled steel sheet is used to heat the hot-rolled steel sheet to the (α + γ) two-phase region prior to hot-dip galvanizing in a galvanizing line, the cementite existing at the grain boundaries is melted in the matrix and formed in the grains. In addition to being finely dispersed, ferrite is generated from austenite generated during reheating in this state, and as a result, a very fine-grained ferrite and pearlite or cementite structure is formed. And by this, sufficient workability (hole expandability) improvement effect can be obtained, and at the same time,
It was found that good plating adhesion and strength can be secured.
本発明は、上記知見等に基づいてなされたものであり、 「C:0.003〜0.018％（以降、成分割合を表わす％は重量
％とする）， Si:1.2％以下,Mn:2.0％以下， sol.Al:0.10％以下,S:0.005％以下 を含有するか、或いは更に Nb:0.01〜0.10％,V:0.01〜0.10％， Ti:0.01〜0.10％,REM:0.002〜0.10％， Ca:0.002〜0.01％,Zr:0.01〜0.10％ の１種以上をも含み、残部が実質的にFe及び不可避不純
物から成る鋼片を熱間圧延してAr3点以上の温度域で仕
上圧延を終了し、続いて冷却速度:10℃/sec以上で急冷
し500℃以下の温度域にて巻取った熱延鋼板を、溶融亜
鉛浴に通す前に（α＋γ）二相域に再加熱してから溶融
亜鉛メッキすることにより、母材鋼板がフェライト・パ
ーライト又はフェライト・セメンタイト組織である加工
性に優れた亜鉛メッキ鋼板を安定して製造し得るように
した点」 を特徴としている。The present invention has been made based on the above findings and the like, "C: 0.003 to 0.018% (hereinafter,% representing a component ratio is% by weight), Si: 1.2% or less, Mn: 2.0% or less, sol.Al:0.10% or less, S: 0.005% or less, or Nb: 0.01 to 0.10%, V: 0.01 to 0.10%, Ti: 0.01 to 0.10%, REM: 0.002 to 0.10%, Ca: A steel slab containing at least one of 0.002 to 0.01% and Zr: 0.01 to 0.10% and the balance consisting essentially of Fe and unavoidable impurities is hot-rolled and finish rolling is performed in a temperature range of Ar 3 points or more. Then, after cooling the hot-rolled steel sheet rapidly cooled at a cooling rate of 10 ° C / sec or more and wound at a temperature range of 500 ° C or less to the (α + γ) two-phase region before passing it through the molten zinc bath, By hot-dip galvanizing, the base steel sheet has a ferrite-pearlite or ferrite-cementite structure, which enables stable production of galvanized steel sheets with excellent workability. " It is.
なお、特公昭57-9831号公報には、強度特性の改善のた
めに熱延鋼板を（α＋γ）二相域まで再加熱した後急冷
してフェライト・マルテンサイトの組織とする方法が記
載されているが、このような方法で製造された熱延鋼板
はマルテンサイトが混入するため穴拡げ性が著しく劣化
し、本発明が目的とするような穴拡げ性の優れた亜鉛メ
ッキ熱延鋼板の製造に適用できるものではない。In addition, Japanese Patent Publication No. 57-9831 describes a method of reheating a hot rolled steel sheet to the (α + γ) two-phase region and then rapidly cooling it to form a ferrite-martensite structure in order to improve strength properties. However, the hot-rolled steel sheet produced by such a method has significantly deteriorated hole expansibility due to the inclusion of martensite, and the production of a galvanized hot-rolled steel sheet having excellent hole expansibility as intended by the present invention. Not applicable to.
また、特公昭56-108830号公報には、高Mn熱延鋼板をフ
ェライトとマルテンサイトを含む複合組織とするために
二相温度域で箱焼鈍し、その後溶融亜鉛メッキを施すこ
とから成る亜鉛メッキ鋼板の製造方法が開示されている
が、この場合も製品亜鉛メッキ鋼板の母材組織にマルテ
ンサイトを混入させており、このように母材組織にマル
テンサイトが混入すると低降伏比が実現されはしても鋼
板の穴拡げ性が著しく劣化するため、やはり本発明が目
的とする穴拡げ性の優れた亜鉛メッキ熱延鋼板は実現で
きない。Further, Japanese Patent Publication No. 56-108830 discloses a galvanizing method in which a high-Mn hot-rolled steel sheet is subjected to box annealing in a two-phase temperature range to form a composite structure containing ferrite and martensite, and then hot-dip galvanized. Although a method for manufacturing a steel sheet is disclosed, in this case also, martensite is mixed in the base material structure of the product galvanized steel sheet, and when martensite is mixed in the base material structure in this way, a low yield ratio is not realized. However, since the hole expandability of the steel sheet is significantly deteriorated, the galvanized hot rolled steel sheet excellent in hole expandability, which is the object of the present invention, cannot be realized.
以下、本発明において素材鋼の化学成分組成並びに処理
条件を前記の如くに限定した理由を、その作用と共に詳
細に説明する。Hereinafter, the reason why the chemical composition of the raw material steel and the processing conditions are limited as described above in the present invention will be described in detail together with its action.
〈作用〉 Ａ） 化学成分組成 Ｃ Ｃは鋼板の強度を確保する作用を有しているが、その含
有量が0.003％未満では、前記作用による所望の効果が
得られず、一方、0.18％を超えて含有させると溶接性の
劣化を招くことから、Ｃ含有量は0.003〜0.18％と定め
た。<Action> A) Chemical composition C has the action of ensuring the strength of the steel sheet, but if its content is less than 0.003%, the desired effect due to the above action cannot be obtained, while 0.18% If it is contained in excess, it causes deterioration of weldability, so the C content was set to 0.003 to 0.18%.
Si Siは固溶強化を通して鋼板の強度と延性を向上させる好
ましい成分である。しかし、1.2％を超えて含有させる
と溶接性の劣化を招くことから、Si含有量は1.2％以下
と定めた。Si Si is a preferred component that improves the strength and ductility of steel sheets through solid solution strengthening. However, if the content exceeds 1.2%, the weldability deteriorates, so the Si content was set to 1.2% or less.
Mn Mnは固溶強化を通して鋼板の強度と延性を向上させる好
ましい元素である。しかし、2.0％を超えて含有させる
と溶接性の劣化を招く上、二相域加熱によって生成した
オーステナイトが亜鉛浴を通した後も変態せず、最終製
品中にマルテンサイトが存在することとなって穴拡げ性
劣化の原因になる。従って、Mn含有量は2.0％以下と定
めた。Mn Mn is a preferable element that improves the strength and ductility of steel sheet through solid solution strengthening. However, if the content exceeds 2.0%, the weldability is deteriorated, and the austenite produced by heating in the two-phase region does not transform even after passing through the zinc bath, which means that martensite is present in the final product. Cause deterioration of hole expandability. Therefore, the Mn content is set to 2.0% or less.
sol.Al Alは鋼の脱酸剤として添加されるが、sol.Alとして0.10
％を超えて含有させるとアルミナ系介在物の量が多くな
って加工性を劣化させる。従ってAlの添加量はsol.Al含
有量で0.10％以下と定めた。sol.Al Al is added as a deoxidizer for steel, but as sol.Al 0.10
If it is contained in excess of%, the amount of alumina-based inclusions increases and the workability deteriorates. Therefore, the addition amount of Al was set to 0.10% or less in terms of sol.Al content.
Ｓ ＳはMnS系介在物を形成して加工性を低下させる不純物
元素である。従って、前記弊害を極力回避するため、Ｓ
含有量は0.005以下と定めた。S S is an impurity element that forms MnS inclusions and deteriorates workability. Therefore, in order to avoid the above-mentioned harmful effects as much as possible, S
The content was set to 0.005 or less.
Nb,V,Ti,REM（希土類元素）,Ca及びZr これらの元素には、鋼板の強度又は加工性を改善する作
用があるので必要に応じて１種又は２種以上含有せしめ
られるが、各々の元素の含有量を限定した理由は次の通
りである。Nb, V, Ti, REM (rare earth elements), Ca, and Zr These elements have the effect of improving the strength or workability of the steel sheet, so one or more elements may be included as necessary. The reason for limiting the content of the element is as follows.
即ち、Nb,V及びTiにはC,Nと結合して炭窒化物として析
出することにより鋼板を強化する作用がある。しかし、
Nb,V及びTiの含有量が各々0.01％未満では前記作用によ
る所望の効果が得られず、一方、各々0.10％を超えて含
有させても強度上昇効果が飽和してしまい経済的に不利
となる。従って、これら各成分の含有量は各々0.01〜0.
10％と定めた。That is, Nb, V and Ti have the action of strengthening the steel sheet by combining with C and N and precipitating as carbonitride. But,
If the contents of Nb, V and Ti are each less than 0.01%, the desired effect due to the above-mentioned action cannot be obtained.On the other hand, if each of them exceeds 0.10%, the strength increasing effect is saturated and it is economically disadvantageous. Become. Therefore, the content of each of these components is 0.01 to 0.
It was set at 10%.
また、Ca,Zr,及びREM（希土類元素） これらの成分には、何れも介在物の形状を調整して鋼板
の冷間加工性を改善する作用がある。しかし、その含有
量がCaでは0.002％未満,Zrでは0.01％未満そしてREMで
は0.002％未満であると前記作用による所望の効果が得
られず、一方、Caで0.01％,ZRで0.10％そしてREMで0.10
％を超えてそれぞれ含有させた場合には、逆に鋼中の介
在物が多くなり過ぎて冷間加工性の劣化を招くようにな
ることから、Ca含有量は0.002〜0.01％,Zr含有量は0.01
〜0.10％，そしてREM含有量は0.002〜0.10％とそれぞれ
定めた。Further, Ca, Zr, and REM (rare earth elements) These components all have the effect of adjusting the shape of inclusions to improve the cold workability of the steel sheet. However, if the content is less than 0.002% for Ca, less than 0.01% for Zr and less than 0.002% for REM, the desired effect due to the above action cannot be obtained, while 0.01% for Ca, 0.10% for ZR and REM At 0.10
%, The amount of inclusions in the steel becomes too large, which causes deterioration of cold workability. Therefore, Ca content is 0.002 to 0.01%, Zr content Is 0.01
〜0.10%, and REM content 0.002〜0.10%.
なお、鋼中へ不可避的に混入する元素として知られるＰ
は、固溶強化を通して鋼板の強度と延性を向上する作用
を有しているが、他方で溶接性に悪影響を及ぼすことか
ら、所望の溶接性を確保するためにはＰの含有量を0.07
％以下に抑えるのが好ましい。Note that P, which is known as an element that is inevitably mixed into steel
Has the effect of improving the strength and ductility of the steel sheet through solid solution strengthening, but on the other hand adversely affects the weldability. Therefore, in order to secure the desired weldability, the P content is 0.07
% Or less is preferable.
Ｂ） 熱延鋼板の製造条件 熱間圧延に際しては、直送スラブを用いるかスラブを再
加熱して用いるかは格別問題はないが、仕上圧延温度が
Ar3点未満であると変態して生成したフェライト粒に加
工組織が混入してしまい、これは亜鉛メッキ前の再加熱
処理によっても回復しないことから加工性の劣化につな
がる。従って、仕上圧延温度はAr3点以上と定めた。B) Manufacturing conditions for hot-rolled steel sheet In hot rolling, there is no particular problem whether a direct feed slab or a reheated slab is used, but the finish rolling temperature is
If it is less than the Ar 3 point, the work structure will be mixed into the ferrite grains formed by transformation, and this will not be recovered even by the reheating treatment before galvanization, leading to deterioration of workability. Therefore, the finish rolling temperature was set at 3 Ar or higher.
また、熱間圧延が終了した後は冷却速度:10℃/sec以上
で急冷し500℃以下で巻取るが、これは次の理由によ
る。即ち、熱間圧延終了後の冷却速度が10℃/sec未満で
あるとフェライトの細粒化が不十分となり、また巻取り
温度が500℃を超えると非常に粗大なセメンタイトが生
成して何れも熱延板での穴拡げ性の劣化につながる。そ
して、これはメッキ後も受け継がれてしまうからであ
る。Further, after the hot rolling is completed, the cooling rate is rapidly cooled at 10 ° C./sec or more and wound at 500 ° C. or less, for the following reason. That is, if the cooling rate after completion of hot rolling is less than 10 ° C./sec, grain refining of the ferrite becomes insufficient, and if the winding temperature exceeds 500 ° C., very coarse cementite is formed, whichever is the case. This leads to deterioration of the hole expandability of the hot rolled sheet. And this is because it is inherited even after plating.
Ｃ） 溶融亜鉛メッキ時の熱延板の処理条件 本発明においては、上記条件で製造された熱延鋼板は冷
間圧延されることなしに溶融亜鉛メッキされる。その
際、熱延鋼板は溶融亜鉛浴に通す前に（α＋γ）二相域
まで際加熱される。そして、この再加熱によりフェライ
トの細粒化とセメンタイトの微細分散により強度−穴拡
げバランスが向上し、またメッキ密着性も改善される。C) Treatment Condition of Hot Rolled Sheet during Hot Dip Galvanizing In the present invention, the hot rolled steel sheet produced under the above conditions is hot dip galvanized without cold rolling. At that time, the hot-rolled steel sheet is reheated to the (α + γ) two-phase region before being passed through the molten zinc bath. This reheating improves the strength-hole expansion balance and also improves the plating adhesion by refining the ferrite and finely dispersing the cementite.
続いて、本発明の効果を実施例によって更に具体的に説
明する。Next, the effects of the present invention will be described more specifically by way of examples.
〈実施例〉 第１表に示す化学成分組成の鋼を50kg真空溶解炉で溶製
し、鋳型に鋳込んで直接的に又は熱間鍛造にて60mm厚の
スラブとした。<Example> A steel having a chemical composition shown in Table 1 was melted in a 50 kg vacuum melting furnace, cast into a mold and directly or hot forged into a slab having a thickness of 60 mm.
次に、この各スラブを第２表に示す条件で熱間圧延して
2mm厚の熱延鋼板となし、更に溶融亜鉛浴を通す前に第
２表に示す温度に再加熱してから溶融亜鉛メッキ処理す
ることによって亜鉛メッキ熱延鋼板を製造した。Next, each slab was hot-rolled under the conditions shown in Table 2.
A hot-rolled steel sheet having a thickness of 2 mm was prepared, and further hot-rolled to a temperature shown in Table 2 before being passed through a hot-dip galvanizing bath and then hot-dip galvanized to produce a hot-dip galvanized steel sheet.
第２表に、このときのメッキ処理前の熱延鋼板とメッキ
処理後の亜鉛メッキ熱延鋼板との機械的特性を併せて示
した。Table 2 also shows the mechanical properties of the hot-rolled steel sheet before the plating treatment and the galvanized hot-rolled steel sheet after the plating treatment at this time.
第２表に示される結果からも明らかなように、本発明で
規定する条件通りに製造された亜鉛メッキ熱延鋼板は優
れた強度−穴拡げバランスを有しているのに対して、熱
延仕上温度が本発明で規定する下限値から外れている試
験番号６の条件では、鋼板の強度が高くなり、熱延のま
ま並びにメッキ後の鋼板の強度−穴拡げバランス（引張
強さ×穴拡げ率）が悪くなっていることが分かる。As is clear from the results shown in Table 2, the galvanized hot-rolled steel sheet produced under the conditions specified in the present invention has an excellent strength-hole expansion balance, whereas Under the condition of the test number 6 in which the finishing temperature is out of the lower limit defined by the present invention, the strength of the steel sheet becomes high, and the strength of the hot rolled sheet and the strength of the plated steel sheet-hole expansion balance (tensile strength x hole expansion) You can see that the rate is getting worse.
また、圧延後の冷却速度が本発明で規定する下限値から
外れた試験番号７、及び巻取り温度が本発明で規定する
上限値から外れた試験番号８では、粗大なセメンタイト
が生じ、やはり熱延のまま及 びメッキ後の鋼板の強度−穴拡げバランスが悪くなって
いる。Further, in the test number 7 in which the cooling rate after rolling deviates from the lower limit value specified in the present invention, and in the test number 8 in which the winding temperature deviates from the upper limit value specified in the present invention, coarse cementite occurs, and the heat Extended The balance between strength and hole expansion of the steel plate after plating is poor.
更に、溶融亜鉛浴に通す前の再加熱温度が本発明で規定
する上限値から外れた試験番号９ではフェライトの粗大
化により鋼板の穴拡げ性が低下しており、また溶融亜鉛
浴に通す前の再加熱温度が本発明で規定する下限値から
外れた試験番号10では鋼板の組織変化が小さく、固溶Ｃ
の増加に伴う穴拡げ性の劣化のみ生じていることが分か
る。Furthermore, in Test No. 9 in which the reheating temperature before passing through the molten zinc bath deviates from the upper limit defined by the present invention, the hole expandability of the steel sheet decreases due to the coarsening of ferrite, and before passing through the molten zinc bath. In the test number 10 in which the reheating temperature of the steel sheet deviated from the lower limit value defined in the present invention, the structural change of the steel sheet was small and the solid solution
It is understood that only the hole expandability is deteriorated with the increase of
一方、鋼板のC,Si含有量が本発明で規定する上限値を超
えている試験番号21,22で得られた亜鉛メッキ熱延鋼板
はアーク溶接不良を生じることが確認された。また、鋼
板のMn含有量が本発明の規定値を超えている試験番号23
では、最終製品中（亜鉛メッキ熱延鋼板中）にマルテン
サイトが存在し、フェライト・マルテンサイトの二相組
織鋼板になっているために降伏比（YR）は低いものの強
度−穴拡げバランスが悪くなることが分かる。On the other hand, it was confirmed that the galvanized hot-rolled steel sheets obtained in Test Nos. 21 and 22 in which the C and Si contents of the steel sheets exceeded the upper limits specified in the present invention caused arc welding defects. Further, the test number 23 in which the Mn content of the steel sheet exceeds the specified value of the present invention
Since the final product (in the galvanized hot rolled steel sheet) contains martensite and is a ferrite / martensite dual-phase steel sheet, the yield ratio (YR) is low, but the strength-hole expansion balance is poor. I see.
〈効果の総括〉 以上に説明した如く、この発明によれば、十分な強度，
メッキ密着性を有すると共に、穴拡げ性を始めとする加
工性に優れた亜鉛メッキ熱延鋼板を安定して生産するこ
とが可能となるなど、産業上極めて有用な効果がもたら
される。<Summary of Effects> As described above, according to the present invention, sufficient strength,
It is possible to stably produce a galvanized hot-rolled steel sheet which has plating adhesion and is excellent in workability such as hole expandability.
Claims (2)
熱間圧延してAr3点以上の温度域で仕上圧延を終了し、
続いて冷却速度:10℃/sec以上で急冷し500℃以下の温度
域にて巻取った熱延鋼板を、溶融亜鉛浴に通す前に（α
＋γ）二相域に再加熱してから溶融亜鉛メッキすること
を特徴とする、母材鋼板がフェライト・パーライト又は
フェライト・セメンタイト組織である加工性に優れた亜
鉛メッキ鋼板の製造方法。1. A weight ratio of C: 0.003 to 0.18%, Si: 1.2% or less, Mn: 2.0% or less, sol.Al: 0.10% or less, S: 0.005% or less, with the balance being substantially Fe and Hot rolling a slab of unavoidable impurities and finishing rolling in the temperature range of Ar 3 points or more,
Next, before passing the hot-rolled steel sheet rapidly cooled at a cooling rate of 10 ° C / sec or more and wound in a temperature range of 500 ° C or less into a molten zinc bath (α
+ Γ) A method for producing a galvanized steel sheet having excellent workability in which the base steel sheet has a ferrite / pearlite or ferrite / cementite structure, which is characterized by reheating to a two-phase region and then hot dip galvanizing.
から成る鋼片を熱間圧延してAr3点以上の温度域で仕上
圧延を終了し、続いて冷却速度:10℃/sec以上で急冷し5
00℃以下の温度域にて巻取った熱延鋼板を、溶融亜鉛浴
に通す前に（α＋γ）二相域に再加熱してから溶融亜鉛
メッキすることを特徴とする、母材鋼板がフェライト・
パーライト又はフェライト・セメンタイト組織である加
工性に優れた亜鉛メッキ鋼板の製造方法。2. By weight ratio, C: 0.003 to 0.18%, Si: 1.2% or less, Mn: 2.0% or less, sol.Al: 0.10% or less, S: 0.005% or less, and Nb: 0.01 to 0.10%. , V: 0.01 to 0.10%, Ti: 0.01 to 0.10%, REM: 0.002 to 0.10%, Ca: 0.002 to 0.01%, Zr: 0.01 to 0.10%, and the balance is essentially Fe and unavoidable. Hot rolling a steel slab containing impurities and finishing rolling in a temperature range of Ar 3 points or more, followed by quenching at a cooling rate of 10 ° C / sec or more.
The base material steel sheet is ferrite, which is characterized in that hot-rolled steel sheet wound in a temperature range of 00 ° C or less is reheated to the (α + γ) two-phase area before being passed through the hot-dip zinc bath and then hot-dip galvanized.・
A method for producing a galvanized steel sheet having a pearlite or ferrite / cementite structure and excellent workability.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1179692A JPH0756053B2 (en) | 1989-07-12 | 1989-07-12 | Manufacturing method of galvanized hot rolled steel sheet with excellent workability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1179692A JPH0756053B2 (en) | 1989-07-12 | 1989-07-12 | Manufacturing method of galvanized hot rolled steel sheet with excellent workability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0344423A JPH0344423A (en) | 1991-02-26 |
| JPH0756053B2 true JPH0756053B2 (en) | 1995-06-14 |
Family
ID=16070207
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1179692A Expired - Lifetime JPH0756053B2 (en) | 1989-07-12 | 1989-07-12 | Manufacturing method of galvanized hot rolled steel sheet with excellent workability |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0756053B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001020051A1 (en) * | 1999-09-16 | 2001-03-22 | Nkk Corporation | Steel thin plate having high strength and method for production thereof |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2563021B2 (en) * | 1991-10-25 | 1996-12-11 | 株式会社神戸製鋼所 | Method for producing high-strength hot-rolled hot-dip galvannealed steel sheet with excellent stretch flangeability |
| JP5338873B2 (en) * | 2011-08-05 | 2013-11-13 | Ｊｆｅスチール株式会社 | High-strength hot-dip galvanized steel sheet excellent in workability with a tensile strength of 440 MPa or more and its production method |
| JP6497437B2 (en) | 2015-04-22 | 2019-04-10 | 新日鐵住金株式会社 | Hot-rolled steel sheet, steel material and method for producing hot-rolled steel sheet |
| WO2017169871A1 (en) | 2016-03-31 | 2017-10-05 | Ｊｆｅスチール株式会社 | Thin steel plate and plated steel plate, hot rolled steel plate manufacturing method, cold rolled full hard steel plate manufacturing method, thin steel plate manufacturing method and plated steel plate manufacturing method |
-
1989
- 1989-07-12 JP JP1179692A patent/JPH0756053B2/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001020051A1 (en) * | 1999-09-16 | 2001-03-22 | Nkk Corporation | Steel thin plate having high strength and method for production thereof |
| EP2166122A1 (en) | 1999-09-16 | 2010-03-24 | JFE Steel Corporation | Method of manufacturing high strength steel |
| EP2166121A1 (en) | 1999-09-16 | 2010-03-24 | JFE Steel Corporation | High strength steel sheet and method for manufacturing the same |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0344423A (en) | 1991-02-26 |
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