JPH04128321A - Production of galvanized high-strength steel sheet having excellent bending workability - Google Patents
Production of galvanized high-strength steel sheet having excellent bending workabilityInfo
- Publication number
- JPH04128321A JPH04128321A JP24954390A JP24954390A JPH04128321A JP H04128321 A JPH04128321 A JP H04128321A JP 24954390 A JP24954390 A JP 24954390A JP 24954390 A JP24954390 A JP 24954390A JP H04128321 A JPH04128321 A JP H04128321A
- Authority
- JP
- Japan
- Prior art keywords
- steel sheet
- hot
- cooling
- temperature
- strength
- 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.)
- Granted
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 41
- 239000010959 steel Substances 0.000 title claims abstract description 41
- 238000005452 bending Methods 0.000 title claims abstract description 17
- 238000004519 manufacturing process Methods 0.000 title claims description 12
- 238000001816 cooling Methods 0.000 claims abstract description 43
- 238000005246 galvanizing Methods 0.000 claims abstract description 18
- 238000007747 plating Methods 0.000 claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 13
- 230000009466 transformation Effects 0.000 claims abstract description 10
- 238000000034 method Methods 0.000 claims description 20
- 238000005275 alloying Methods 0.000 claims description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 6
- 238000005098 hot rolling Methods 0.000 claims description 4
- 238000005097 cold rolling Methods 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 238000005554 pickling Methods 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 16
- 238000000137 annealing Methods 0.000 abstract description 14
- 229910001335 Galvanized steel Inorganic materials 0.000 abstract description 8
- 239000008397 galvanized steel Substances 0.000 abstract description 8
- 238000001953 recrystallisation Methods 0.000 abstract description 8
- 239000010960 cold rolled steel Substances 0.000 abstract description 6
- 229910052804 chromium Inorganic materials 0.000 abstract description 3
- 229910052748 manganese Inorganic materials 0.000 abstract description 3
- 229910052750 molybdenum Inorganic materials 0.000 abstract description 3
- 229910045601 alloy Inorganic materials 0.000 abstract 1
- 239000000956 alloy Substances 0.000 abstract 1
- 239000010953 base metal Substances 0.000 abstract 1
- 229910001563 bainite Inorganic materials 0.000 description 14
- 229910000734 martensite Inorganic materials 0.000 description 14
- 229910000859 α-Fe Inorganic materials 0.000 description 13
- 239000002131 composite material Substances 0.000 description 10
- 229910001566 austenite Inorganic materials 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 230000001105 regulatory effect Effects 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000010791 quenching Methods 0.000 description 3
- 241000282342 Martes americana Species 0.000 description 2
- 229910001562 pearlite Inorganic materials 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- FFBHFFJDDLITSX-UHFFFAOYSA-N benzyl N-[2-hydroxy-4-(3-oxomorpholin-4-yl)phenyl]carbamate Chemical compound OC1=C(NC(=O)OCC2=CC=CC=C2)C=CC(=C1)N1CCOCC1=O FFBHFFJDDLITSX-UHFFFAOYSA-N 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は曲げ加工性に優れた溶融亜鉛めっき高強度薄鋼
板の製造方法に関し、更に詳しくは、特に引張強さ６０
〜１２０ｋｇｆ／ｍｍ”級の複合組織溶融亜鉛めっき高
強度薄銅板の製造方法に関する。Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing hot-dip galvanized high-strength thin steel sheets with excellent bending workability, and more particularly,
The present invention relates to a method for manufacturing a hot-dip galvanized high-strength thin copper plate with a composite structure of ~120 kgf/mm'' class.
（従来の技術及び解決しようとする課題）近年、自動車
安全性及び軽量化対策として加工性の優れた高強度冷延
鋼板が使用されるに至っている。また、自動車の寿命向
上のために、冷延鋼板に防錆力の向上が強く望まれてい
る。最近においては、バンパー ドアインパクトビーム
等の６０〜１２０ｋｇｆ／＋＊ｍ”級の補強部材につい
ても、スポット溶接性と塗装性に優れた合金化溶融亜鉛
めっき鋼板が要望されている。(Prior Art and Problems to Be Solved) In recent years, high-strength cold-rolled steel sheets with excellent workability have come into use as a measure to improve automobile safety and reduce weight. Furthermore, in order to extend the lifespan of automobiles, it is strongly desired that cold-rolled steel sheets have improved anti-rust properties. Recently, there has been a demand for alloyed hot-dip galvanized steel sheets with excellent spot weldability and paintability for 60 to 120 kgf/+*m'' class reinforcing members such as bumpers and door impact beams.
従来、裸鋼板においては、変態組織強化法を用いること
によって高い強度−穴広げ率（λ）バランスを有する６
０ ｋｇｆ ／ ａｍ”級以上の高強度薄鋼板が得ら
れることが知られている。Conventionally, bare steel sheets have a high strength-hole expansion rate (λ) balance by using a transformation structure strengthening method6.
It is known that high-strength thin steel sheets of 0 kgf/am'' class or higher can be obtained.
例えば、本発明者らが先に提案した特開昭６３−２４１
１１５号公報では、水焼入れタイプ連続焼鈍法を用いて
、再結晶加熱温度をＡｃ１変態点以上とし、強制空冷後
所定の温度から２００〜５００℃の温度で過時効処理し
て、フェライトと焼戻しマルテンサイトからなる複合組
織とし、高い強度−λバランスの高強度薄鋼板が得られ
ることを開示した。しかし、溶融亜鉛めっき鋼板の場合
には、再結晶加熱後、水焼入れすることが困難であるば
かりでなく、Ｍｓ点よりも高い温度でめっき処理又は合
金化処理されるため、焼戻しマルテンサイトを用いた高
い強度−λバランスの高強度薄鋼板が得られない。For example, JP-A No. 63-241 proposed by the present inventors
In Publication No. 115, a water quenching type continuous annealing method is used, the recrystallization heating temperature is set to the Ac1 transformation point or higher, and after forced air cooling, an overaging treatment is performed at a temperature of 200 to 500°C from a predetermined temperature to form ferrite and tempered marten. It has been disclosed that a high-strength thin steel sheet with a high strength-λ balance can be obtained with a composite structure consisting of sites. However, in the case of hot-dip galvanized steel sheets, not only is it difficult to water-quench them after recrystallization heating, but also the plating or alloying treatment is performed at a temperature higher than the Ms point, so tempered martensite cannot be used. A high-strength thin steel plate with a high strength-λ balance cannot be obtained.
かＮる問題を解決するために、例えば、特開平１−１９
８４５９号公報では、Ｍｎ、Ｍｏ、■を添加し、連続式
溶融亜鉛めっきラインにて再結晶温度以上で焼鈍した後
、４６０〜５６０℃の間で保持することによって１００
〜１２０キロクラスの高強度溶融亜鉛めっき鋼板を得て
いる。しかし。In order to solve the problem of
In Publication No. 8459, Mn, Mo, and
We have obtained high-strength hot-dip galvanized steel sheets of ~120 kg class. but.
この方法では、焼鈍後からの冷却速度が規制されていな
い。したがって、ライン速度及び板厚が変化すると容易
に冷却速度は変化する。このため、フェライト、ベイナ
イト及びマルテンサイトの体積率は容易に変化し、安定
した組織が得られず。In this method, the cooling rate after annealing is not regulated. Therefore, when the line speed and plate thickness change, the cooling rate changes easily. Therefore, the volume fraction of ferrite, bainite, and martensite changes easily, making it impossible to obtain a stable structure.
強度や伸びのバラツキが大きい。There are large variations in strength and elongation.
以上のように、曲げ加工性の優れた溶融亜鉛めっき高強
度薄鋼板を製造するに際しては、高強度を得る点で有利
な複合組織強化が必要となるが、単に、化学成分、冷却
速度等に着目した方法で曲げ加工性の優れた溶融亜鉛め
っき高強度薄鋼板を製造することは困難であるのが現状
である。As mentioned above, when manufacturing hot-dip galvanized high-strength thin steel sheets with excellent bending workability, it is necessary to strengthen the composite structure, which is advantageous in terms of obtaining high strength. At present, it is difficult to produce hot-dip galvanized high-strength thin steel sheets with excellent bending workability using the focused method.
本発明は、上記従来技術の欠点を解決し、曲げ加工性の
優れた溶融亜鉛めっき高強度薄鋼板を容易に製造し得る
方法を提供することを目的とするものである。An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a method for easily manufacturing a hot-dip galvanized high-strength thin steel sheet with excellent bending workability.
（課題を解決するための手段）
本発明者らは、前記課題を解決するために鋭意研究を重
ねた結果、連続溶融亜鉛めっきラインの加熱（均熱）温
度、均熱温度から溶融亜鉛めっき浴までの冷却速度及び
合金化処理温度を適正に制御することによって、マルテ
ンサイトよりも硬さの低いベイナイトを利用した微細均
一なフェライト・ベイナイト、或いはＣ濃度の低いマル
テンサイトを含むフェライト・ベイナイト・マルテンサ
イトの複合組織にし、曲げ加工性の優れた溶融亜鉛めっ
き高強度薄鋼板が得られることを見い出して、本発明に
至ったものである。(Means for Solving the Problems) As a result of intensive research to solve the above problems, the present inventors have determined that the heating (soaking) temperature of the continuous hot-dip galvanizing line and the soaking temperature can be By appropriately controlling the cooling rate and alloying temperature, we can produce fine and uniform ferrite/bainite using bainite, which has a lower hardness than martensite, or ferrite/bainite/marten containing martensite with a low C concentration. The present invention was developed based on the discovery that a hot-dip galvanized high-strength thin steel sheet with excellent bending workability can be obtained by forming a composite structure of sites.
すなわち、本発明は、
Ｃ：０．０６〜０．３％
Ｓｉ：０．６％以下
Ｍｎ：０．６−３．０％
Ｐ：Ｏ，１％以下
ＡＱ：０．１％以下
を含有し、必要に応じて更に、
Ｍｏ：０．１〜１．０％
Ｃｒ：０．１〜１．５％
のうちの少なくとも１種を含有し、残部が鉄及び不可避
的不純物からなる鋼を通常の方法で熱間圧延、酸洗、冷
間圧延した後、連続亜鉛めっきラインにて再結晶焼鈍す
るに際し、加熱温度をＡｃ、変態点−５０以上〜９００
℃以下にし、めっき浴の温度までの冷却条件として、６
５０”Ｃ以上の温度域からめっき浴の温度まで１次式
％式％
で示される下部臨界冷却速度ＣＲ（’Ｃ／ｓ）以上の冷
却速度にて冷却した後、溶融亜鉛めっきを施し。That is, the present invention contains: C: 0.06-0.3% Si: 0.6% or less Mn: 0.6-3.0% P: O, 1% or less AQ: 0.1% or less , if necessary, further contains at least one of Mo: 0.1 to 1.0% Cr: 0.1 to 1.5%, and the balance is iron and unavoidable impurities. After hot rolling, pickling, and cold rolling by the method, when recrystallizing annealing on a continuous galvanizing line, the heating temperature is set to Ac, the transformation point is -50 or higher to 900.
℃ or less, and as a cooling condition to the temperature of the plating bath, 6
After cooling from a temperature range of 50"C or higher to the temperature of the plating bath at a cooling rate higher than the lower critical cooling rate CR ('C/s) expressed by the linear formula %, hot-dip galvanizing is applied.
或いは更に５００＝Ａｃ工の温度にて合金化処理を施す
ことを特徴とする曲げ加工性に優れた溶融亜鉛めっき高
強度薄鋼板の製造方法を要旨とするものである。Another gist of the present invention is a method for producing a hot-dip galvanized high-strength thin steel sheet with excellent bending workability, which is characterized by performing alloying treatment at a temperature of 500=Ac.
以下に本発明を更に詳細に説明する。The present invention will be explained in more detail below.
（作用）
まず、本発明における鋼の化学成分の限定理由について
述べる。(Function) First, the reason for limiting the chemical composition of steel in the present invention will be described.
Ｃ：
Ｃは鋼板の強化に不可欠な元素であって、５０ｋｇｆ／
ｍｍ”以上の高強度複合組織鋼板を得るためには、少な
くとも０．０６％を添加する必要がある。C: C is an essential element for strengthening steel plates, and has a content of 50 kgf/
In order to obtain a high-strength composite steel sheet with a strength of 2 mm or more, it is necessary to add at least 0.06%.
しかし、０．３％を超えるとマルテンサイト等の硬質相
の体積率が高くなり、延性が劣化するだけでなく、スポ
ット溶接性も低下する。したがって、Ｃ量は０．０６〜
０．３％の範囲とする。However, if it exceeds 0.3%, the volume fraction of hard phases such as martensite increases, which not only deteriorates ductility but also reduces spot weldability. Therefore, the amount of C is 0.06~
The range is 0.3%.
Ｓｉ：
Ｓｉはフェライト中の固溶Ｃをオーステナイト中へ排出
する効果を有するため、フェライトの延性を向上させる
作用がある。しかし、過多に添加すると、めっき不良を
生じるので、Ｓｉ量は０．６％以下とする。Si: Since Si has the effect of discharging solid solution C in ferrite into austenite, it has the effect of improving the ductility of ferrite. However, if too much Si is added, plating defects will occur, so the amount of Si is set to 0.6% or less.
Ｍｎ：
Ｍｎはオーステナイト相を安定化し、冷却過程において
硬質相の生成を容易にして高強度にするために添加され
る。しかし、添加量が少ないと、高強度を達成するため
の硬質相を得ることができないので、その下限値を０．
６％とする。一方。Mn: Mn is added to stabilize the austenite phase, facilitate the formation of a hard phase during the cooling process, and increase strength. However, if the amount added is small, it is not possible to obtain a hard phase to achieve high strength, so the lower limit value is set to 0.
6%. on the other hand.
過多に添加すると、バンド組織が発達し、延性などが低
下するだけでなく、コスト高になるため、添加量の上限
を３．０％とする。If added in excess, a band structure develops, which not only reduces ductility but also increases costs, so the upper limit of the amount added is set at 3.0%.
Ｐ：
ＰはＳＬと同様の作用を有し、強度と伸びとのバランス
を確保するために有効である。そのためには０．０２％
以上が好ましい、しかし、０．１％を超えて添加すると
めつき不良等が発生するので、Ｐ量は０．１％以下とす
る。P: P has the same effect as SL and is effective for ensuring a balance between strength and elongation. For that purpose, 0.02%
The above is preferable; however, if more than 0.1% is added, poor plating etc. will occur, so the amount of P should be 0.1% or less.
ＡＱ：
ＡＱは鋼の脱酸のために添加されるが、過多に添加して
も、効果が飽和するのみならず、めっき不良を招くので
、添加量は０．１％以下とする。AQ: AQ is added to deoxidize steel, but adding too much will not only saturate the effect but also cause poor plating, so the amount added should be 0.1% or less.
なお、本発明において用いる鋼は、上記の成分に加えて
、Ｍｏ：０，１〜１．０％及びＣｒ：０．１〜１．５％
よりなる群から選ばれる少なくとも１種を含有させても
よい。In addition to the above-mentioned components, the steel used in the present invention contains Mo: 0.1 to 1.0% and Cr: 0.1 to 1.5%.
At least one member selected from the group consisting of:
Ｍｏ：
Ｍｏはオーステナイト相を著しく安定化し、冷却過程に
おいて硬質相の生成を容易にして高強度化するために、
必要に応じて添加される。しかし、添加量が少ないと高
強度を達成するための硬質相を得ることができないので
、その下限値を０．１％とする。一方、１．０％を超え
て添加すると、ベイナイトが抑制され、マルテンサイト
がバンド状で多量に生成するため、曲げ加工性が劣化す
るので、１．０％を上限値とする。Mo: Mo significantly stabilizes the austenite phase, facilitates the formation of a hard phase during the cooling process, and increases strength.
Added as needed. However, if the amount added is small, it is not possible to obtain a hard phase for achieving high strength, so the lower limit is set at 0.1%. On the other hand, if it is added in excess of 1.0%, bainite is suppressed and a large amount of martensite is generated in the form of a band, resulting in deterioration in bending workability, so the upper limit is set at 1.0%.
Ｃｒ：
ＣｒはＭｎ及びＭｏと同様な効果を有し、オーステナイ
ト相を安定化し、硬質相の生成を容易にして高強度を得
るために、必要に応じて添加される。Cr: Cr has the same effect as Mn and Mo, and is added as necessary to stabilize the austenite phase, facilitate the formation of a hard phase, and obtain high strength.
その効果を得るには、少なくとも０．１％が必要である
が、過多に添加すると伸びを低下させるので、添加量の
上限を１．５％とする。To obtain this effect, at least 0.1% is required, but since adding too much will reduce elongation, the upper limit of the amount added is set at 1.5%.
次に本発明の方法における製造条件について説明する。Next, manufacturing conditions in the method of the present invention will be explained.
まず、上記化学成分を有する鋼は１通常工程により製鋼
分塊又は連続鋳造を経てスラブとした後、熱間圧延を経
てホットコイルする。熱間圧延に際しては、特にその条
件を限定する必要はないが、均一微細なフェライトとベ
イナイト等の複合組織の溶融亜鉛めっき高強度薄鋼板を
得るには、熱間圧延の巻取温度を低くし、均一なフェラ
イトとベイナイトの組織にした方が好ましい。First, steel having the above-mentioned chemical composition is made into a slab through steel-making ingots or continuous casting in one normal process, and then hot-rolled and hot-coiled. There is no need to particularly limit the conditions for hot rolling, but in order to obtain a hot-dip galvanized high-strength thin steel sheet with a uniform fine composite structure of ferrite and bainite, it is necessary to lower the coiling temperature during hot rolling. , it is preferable to have a uniform structure of ferrite and bainite.
その後、常法に従って、酸洗し、冷間圧延を施して薄鋼
板を得る。通常、冷間圧延率は３０％以上である。Thereafter, according to a conventional method, the steel plate is pickled and cold rolled to obtain a thin steel plate. Usually, the cold rolling rate is 30% or more.
次いで、この薄鋼板を連続溶融亜鉛めっきラインに導い
て、再結晶焼鈍、亜鉛亜鉛めっき、或いは更に合金化処
理を施す。This thin steel sheet is then led to a continuous hot-dip galvanizing line where it is subjected to recrystallization annealing, galvanizing, or further alloying treatment.
第１図は本発明で規制する連続亜鉛めっきラインの熱履
歴を示している。FIG. 1 shows the thermal history of a continuous galvanizing line regulated by the present invention.
再結晶焼鈍は、Ａｃ、変態点−５０以上、９００℃以下
の温度にて施すことが必要である。加熱時間は１０秒以
上が好ましい。焼鈍加熱温度がＡｃ。Recrystallization annealing needs to be performed at a temperature of Ac, transformation point -50 or higher and 900°C or lower. The heating time is preferably 10 seconds or more. The annealing heating temperature is Ac.
変態点−５０’Ｃよりも低いときは、オーステナイトの
体積率が少なく、Ｃ濃度が高まり安定化するため、ベイ
ナイトの生成が抑制され、粗いフェライトとＣ濃度が高
く粗いマルテンサイトの組織となるので、曲げ加工性が
低くなる。一方、焼鈍加熱温度が９００℃よりも高いと
きは、オーステナイト粒が粗大化し、組織が粗くなるた
めに、曲げ加工性が劣化する。When the transformation point is lower than -50'C, the volume fraction of austenite is small and the C concentration increases and stabilizes, suppressing the formation of bainite and forming a structure of coarse ferrite and coarse martensite with a high C concentration. , the bending workability becomes low. On the other hand, when the annealing heating temperature is higher than 900° C., the austenite grains become coarse and the structure becomes coarse, resulting in poor bending workability.
次いで、焼鈍温度からめっき処理までの冷却は、まず、
６５０℃以上の温度域まで冷却するが、その冷却速度は
特に規制されない。次いで、この６５０℃以上の温度域
からめっき浴の温度まで、ｆｉｏｇＣＲ＝１．１８Ｍｅ
ｑ＋３．３７ここで、
Ｍｅｑ＝Ｍｎ＋１．５２Ｍｏ＋１．１０Ｃｒ＋０．１０
８ｉ＋２．ＩＰ
で示される冷却速度ＣＲ（’Ｃ／ｓ）以上の冷却速度に
て冷却する。冷却速度がＣＲより小さいときは、パーラ
イト変態し、所定の強度が得られないのみならず、曲げ
加工性が低下する。Next, cooling from the annealing temperature to the plating process is performed first by
Although it is cooled to a temperature range of 650° C. or higher, the cooling rate is not particularly regulated. Next, from this temperature range of 650°C or higher to the temperature of the plating bath, fiogCR = 1.18Me
q+3.37 where, Meq=Mn+1.52Mo+1.10Cr+0.10
8i+2. Cooling is performed at a cooling rate equal to or higher than the cooling rate CR ('C/s) indicated by IP. When the cooling rate is lower than CR, pearlite transformation occurs, and not only the desired strength cannot be obtained, but also the bending workability deteriorates.
めっき処理後、冷却することにより、フェライト・ベイ
ナイト、或いは、フェライト・ベイナイト・マルテンサ
イト組織を得ることができる。なお、この冷却は空冷、
ミスト冷却などで良い。By cooling after the plating process, a ferrite-bainite or ferrite-bainite-martensitic structure can be obtained. Note that this cooling is air cooling,
Mist cooling is good.
また、溶融亜鉛めっきを施した後、５５０℃〜Ａ ｃ
１の温度にて合金化処理しても、その組織は変化せず、
同等の曲げ加工性が得られる。In addition, after hot-dip galvanizing, 550℃~A c
Even when alloyed at a temperature of 1, the structure does not change,
Equivalent bending workability can be obtained.
次に本発明の実施例を示す。Next, examples of the present invention will be shown.
（実施例） 第１表に示す化学成分を有する供試鋼を溶製し。(Example) A test steel having the chemical composition shown in Table 1 was melted.
２０＋ｓｍ厚のスラブにした。これを仕上温度８５０℃
、巻取温度５６０℃で熱間圧延し、３．２ｍ＋ａ厚の熱
延鋼板とした。得られた鋼板を酸洗し、冷間圧延して、
１．２ｍｍ厚（圧下率６２．５％）の冷延鋼板を得た。It was made into a slab with a thickness of 20+sm. Finishing temperature is 850℃
, and hot rolled at a coiling temperature of 560° C. to obtain a hot rolled steel sheet with a thickness of 3.2 m+a. The obtained steel plate is pickled, cold rolled,
A cold rolled steel plate with a thickness of 1.2 mm (rolling reduction ratio of 62.5%) was obtained.
これらの冷延鋼板について、第２表に示す連続亜鉛めっ
き条件にて合金化溶融亜鉛めっき鋼板或いは溶融亜鉛め
っき鋼板を得て、引張特性及び曲げ特性並びにめっき密
着性について調査した。その結果を第２表に示す。For these cold-rolled steel sheets, alloyed hot-dip galvanized steel sheets or hot-dip galvanized steel sheets were obtained under the continuous galvanizing conditions shown in Table 2, and the tensile properties, bending properties, and plating adhesion were investigated. The results are shown in Table 2.
第２表より以下の如く考察される。The following considerations can be made from Table 2.
本発明材＆１〜ＮＬ１２は、 ８０ｋｇｆ／ｌｌｌｍ２
前後の高強度で、６０％以上の高い打抜き穴広げ率を示
している。また、めっき密着性も優れている。The present invention materials &1 to NL12 are 80kgf/llm2
It has high strength at the front and rear, and exhibits a high punching hole expansion rate of over 60%. Furthermore, plating adhesion is also excellent.
一方、比較材Ｎｎ３は、焼鈍加熱温度が２相域でＡｃ、
変態点−５０℃よりも低いため、オーステナイトのＣ濃
度が高く、硬質かつ粗大なマルテンサイト組織を生成す
るために強度は高いが、穴広げ率は１２％と低い。On the other hand, the comparative material Nn3 has an annealing heating temperature in the two-phase region of Ac,
Since the transformation point is lower than -50°C, the C concentration of austenite is high and a hard and coarse martensite structure is generated, so the strength is high, but the hole expansion rate is as low as 12%.
比較材＆４は、急冷開始温度が５００℃と低いため、そ
の冷却過程で、フェライトが析出し、オーステナイトの
Ｃ濃度が高くなり、硬質なマルテンサイトを生成する。Comparative material &4 has a low quenching start temperature of 500° C., so during the cooling process, ferrite precipitates, the C concentration of austenite increases, and hard martensite is generated.
このため、フェライトとの硬度差が大きくなり、結果と
して穴広げ率が低く、本発明材よりも劣っＣいる。For this reason, the difference in hardness from ferrite becomes large, resulting in a low hole expansion rate, which is inferior to the material of the present invention.
比較材ＮＱ７は、合金化処理の温度がＡｃｍ温度以上の
ため、合金化処理後の冷却時に多量で粗大なマルテンサ
イトが生成するので、高強度ではあるが、穴広げ率は低
い。Comparative material NQ7 has a high strength but a low hole expansion rate because the alloying temperature is higher than the Acm temperature, so a large amount of coarse martensite is generated during cooling after the alloying treatment.
比較材ｈ９は、めっき浴への冷却時の冷却速度が本発明
範囲の冷却速度（２９℃／ｓ）よりも小さいため、多量
のフェライト及びパーライトが生成したので、本発明材
Ｎα８に比べて強度及び穴広げ率が低い。Comparative material h9 had a lower cooling rate during cooling to the plating bath than the cooling rate in the range of the present invention (29°C/s), so a large amount of ferrite and pearlite was generated, so the strength was lower than that of the present invention material Nα8. and low hole expansion rate.
比較材Ｎｎ１３は、Ｃ量が低く、めっき浴への冷却時の
冷却速度が本発明範囲の冷却速度（８３℃／ｓ）よりも
小さいため、ベイナイト及びマルテンサイトが得られず
、目的とした高強度が得られていない。また、比較材Ｎ
Ｇ１４〜Ｎ０１６では、化学成分が本発明範囲外である
ため、本発明範囲内の製造条件であっても、焼入性が非
常に高いためにベイナイトを生成せず、フェライトと硬
質なマルテンサイトの複合組織となるので、高強度では
あるが低い穴広げ率を示している。比較材Ｎｎ１７は高
強度で高い穴広げ率を示しているものの、めっき密着性
が劣っている。Comparative material Nn13 has a low C content and the cooling rate during cooling into the plating bath is lower than the cooling rate in the range of the present invention (83°C/s), so bainite and martensite cannot be obtained and the desired high temperature cannot be obtained. strength is not achieved. Also, comparative material N
G14 to N016 have chemical components outside the scope of the present invention, so even under manufacturing conditions within the scope of the present invention, they have very high hardenability and do not produce bainite, but are composed of ferrite and hard martensite. Since it is a composite structure, it has high strength but a low hole expansion rate. Comparative material Nn17 exhibits high strength and high hole expansion rate, but has poor plating adhesion.
これらに対し、他の本発明材＆５〜Ｎα６．＆８、４１
０−４１２は、高い強度−穴広げ率バランスを有すると
共に、めっき密着性も優れている。In contrast, other present invention materials &5 to Nα6. &8,41
0-412 has a high strength-hole expansion rate balance and also has excellent plating adhesion.
また、合金化処理を施さない溶融亜鉛めっき鋼板の本発
明例翫１８も、同様である。The same applies to Example 18 of the present invention, which is a hot-dip galvanized steel sheet that is not subjected to alloying treatment.
なお、第２図は引張強さ（ＴＳ）と１０ｍｍφ打抜き穴
広げ率（λ）との関係を整理したものであり、本発明材
が優れた強度−穴広げ率（λ）バランスを示しているこ
とがわかる。Furthermore, Figure 2 summarizes the relationship between tensile strength (TS) and 10 mmφ punched hole expansion rate (λ), and shows that the material of the present invention has an excellent strength-hole expansion rate (λ) balance. I understand that.
［以下余白１
（発明の効果）
以上詳述したように、本発明の方法によれば、化学成分
を規制すると共に、特に再結晶焼鈍加熱温度から亜鉛め
っき温度までの冷却速度を上述したように制御するので
、冷却過程１合金化処理及びその後の室温までの冷却過
程でＣ濃度の低いオーステナイトをベイナイトを主体と
した微細均一なフェライト・ベイナイトの複合組織又は
フェライト・ベイナイト・マルテンサイトの複合組織に
することができる。また、通常の溶融亜鉛めっき鋼板の
場合も、合金化処理鋼板と同様であり、再結晶焼鈍加熱
温度から亜鉛めっき温度までの冷却過程でベイナイトを
主体とする微細均一な複合組織を得ることができる。[Blank 1 (Effects of the Invention) As detailed above, according to the method of the present invention, the chemical composition is regulated and, in particular, the cooling rate from the recrystallization annealing heating temperature to the galvanizing temperature is controlled as described above. Therefore, during the cooling process 1 alloying treatment and the subsequent cooling process to room temperature, austenite with a low C concentration is transformed into a fine and uniform ferrite-bainite composite structure mainly composed of bainite or a ferrite-bainite-martensite composite structure. can do. In addition, in the case of ordinary hot-dip galvanized steel sheets, it is similar to that of alloyed steel sheets, and a fine and uniform composite structure consisting mainly of bainite can be obtained during the cooling process from the recrystallization annealing heating temperature to the galvanizing temperature. .
したがって、５０ ｋｇｆ ／ ａｍ”以上で、特に６
０〜１２０ｋｇｆ／ａｍ”まで、曲げ加工性の優れた溶
融亜鉛めっき高強度薄鋼板の製造が可能である。Therefore, above 50 kgf/am”, especially 6
It is possible to manufacture hot-dip galvanized high-strength thin steel sheets with excellent bending workability up to 0 to 120 kgf/am''.
しかも、本発明によれば、低温にて合金化処理を行うこ
とができるので、メツキむら、パウダリング性等の表面
性状の向上に加えて、エネルギーコストの低減も可能で
ある。Moreover, according to the present invention, since the alloying treatment can be performed at a low temperature, it is possible to reduce energy costs in addition to improving surface properties such as plating unevenness and powdering properties.
第１図は本発明で規制する連続亜鉛めっきラインの熱履
歴を示す図、
第２図は合金化溶融亜鉛めっき鋼板及び溶融亜鉛めっき
鋼板の引張強さ（ＴＳ）と１０ｍ＋ａφ打抜き穴広げ率
（λ）との関係を示す図である。
特許出願人 株式会社神戸製鋼所
代理人弁理士 中 村 尚
第
図
第
図
１５ （ｋ５ｆ／ｆｉ＄つ
手続補正書
平成２年１１月２６日
平成２年特許願第２４９５４３号
２、発明の名称
曲げ加工性の優れた溶融亜鉛めっき高強度薄鋼板の製造
方法
３、補正をする者
事件との関係 特許出願人
住所 神戸市中央区脇浜町１丁目３番１８号名称 （１
１９）株式会社神戸製鋼所
４、代理人
住所 〒１１６東京都荒川区西日暮里５丁目３５番５号
７、補正の対象
８、補正の内容
（１）明細書第１頁第５行〜第２頁第１２行目の記載（
特許請求の範８）を別紙のとおりに訂正する。
（２）同第６頁第１５行目、及び第１１頁第１６行目の
ｒＱｏｇＣＲＪの記載をそれぞれ「ＱｎｃＲ」に訂正す
る。
（別紙）
２、特許請求の範囲
（１）重量％で（以下、同じ）、
Ｃ：０．０６〜０．３％
Ｓｉ：０．６％以下
Ｍｎ：０．６〜３．０％
Ｐ：０．１％以下
ＡＱ：０．１％以下
を含有し、残部が鉄及び不可避的不純物からなる鋼を通
常の方法で熱間圧延、酸洗、冷間圧延した後、連続亜鉛
めっきラインにて再結晶焼鈍するに際し、加熱温度をＡ
ｃ、変態点−５０以上〜９００℃以下にし、めっき浴の
温度までの冷却条件として、６５０℃以上の温度域から
めっき浴の温度まで、次式
％式％
で示される下部臨界冷却速度ＣＲ（℃／ｓ）以上の冷却
速度にて冷却した後、溶融亜鉛めっきを施すことを特徴
とする曲げ加工性に優れた溶融亜鉛めっき高強度薄鋼板
の製造方法。
（２）前記溶融亜鉛めっきを施した後、５００〜Ａｃ１
の温度にて合金化処理を施す請求項１に記載の方法。
（３）前記鋼が、更に、Ｍｏ：０．１〜１．０％及びＣ
ｒ：０．１〜１．５％のうちの少なくとも１種を含有す
るものである請求項１又は２に記載の方法。Figure 1 shows the thermal history of the continuous galvanizing line regulated by the present invention. Figure 2 shows the tensile strength (TS) and 10m+aφ punched hole expansion rate (λ ) is a diagram showing the relationship between Patent Applicant Kobe Steel Co., Ltd. Patent Attorney Takashi Nakamura Figure 15 (k5f/fi$2 Procedural Amendment November 26, 1990 1990 Patent Application No. 249543 2, Distortion of the name of the invention Manufacturing method for hot-dip galvanized high-strength thin steel sheets with excellent workability 3 and its relationship to the amended case Patent applicant address 1-3-18 Wakihama-cho, Chuo-ku, Kobe Name (1)
19) Kobe Steel, Ltd. 4, Agent Address: 5-35-5-7, Nishi-Nippori, Arakawa-ku, Tokyo 116, Subject of Amendment 8, Contents of Amendment (1) Page 1, Lines 5 to 2 of the Specification The statement on the 12th line of the page (
Claim 8) is amended as shown in the attached sheet. (2) The descriptions of rQogCRJ on page 6, line 15 and page 11, line 16 are corrected to "QncR". (Attachment) 2. Claims (1) In weight% (the same applies hereinafter): C: 0.06 to 0.3% Si: 0.6% or less Mn: 0.6 to 3.0% P: Steel containing 0.1% or less AQ: 0.1% or less, with the remainder consisting of iron and unavoidable impurities, is hot rolled, pickled, and cold rolled in the usual manner, and then processed on a continuous galvanizing line. When recrystallizing annealing, the heating temperature is set to A
c. Lower critical cooling rate CR ( 1. A method for producing a hot-dip galvanized high-strength thin steel sheet with excellent bending workability, which comprises performing hot-dip galvanizing after cooling at a cooling rate of 0.degree. C./s or higher. (2) After applying the hot dip galvanizing, 500 to Ac1
2. The method according to claim 1, wherein the alloying treatment is performed at a temperature of . (3) The steel further comprises Mo: 0.1 to 1.0% and C.
The method according to claim 1 or 2, which contains at least one of r: 0.1 to 1.5%.
Claims (3)
常の方法で熱間圧延、酸洗、冷間圧延した後、連続亜鉛
めっきラインにて再結晶焼鈍するに際し、加熱温度をＡ
ｃ＿３変態点−５０以上〜９００℃以下にし、めっき浴
の温度までの冷却条件として、６５０℃以上の温度域か
らめっき浴の温度まで、次式 ｌｏｇＣＲ＝１．１８Ｍｅｑ＋３．３７ ここで、 Ｍｅｑ＝Ｍｎ＋１．５２Ｍｏ＋１．１０Ｃｒ＋０．１０
Ｓｉ＋２．１Ｐ で示される下部臨界冷却速度ＣＲ（℃／ｓ）以上の冷却
速度にて冷却した後、溶融亜鉛めっきを施すことを特徴
とする曲げ加工性に優れた溶融亜鉛めっき高強度薄鋼板
の製造方法。(1) In weight% (the same applies hereinafter): C: 0.06-0.3% Si: 0.6% or less Mn: 0.6-3.0% P: 0.1% or less Al: 0. After hot-rolling, pickling, and cold-rolling steel containing 1% or less and the remainder consisting of iron and unavoidable impurities, the heating temperature is A
c_3 Transformation point -50 or higher to 900°C or lower, cooling conditions from a temperature range of 650°C or higher to the temperature of the plating bath, the following formula logCR = 1.18 Meq + 3.37 where, Meq = Mn + 1 .52Mo+1.10Cr+0.10
A hot-dip galvanized high-strength thin steel sheet with excellent bending workability, characterized by applying hot-dip galvanizing after cooling at a cooling rate equal to or higher than the lower critical cooling rate CR (℃/s) indicated by Si+2.1P. Production method.
１の温度にて合金化処理を施す請求項１に記載の方法。(2) After applying the hot-dip galvanizing, 500~Ac_
2. The method according to claim 1, wherein the alloying treatment is performed at a temperature of 1.
ｒ：０．１〜１．５％のうちの少なくとも１種を含有す
るものである請求項１又は２に記載の方法。(3) The steel further comprises Mo: 0.1 to 1.0% and C.
The method according to claim 1 or 2, which contains at least one of r: 0.1 to 1.5%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24954390A JP2862187B2 (en) | 1990-09-19 | 1990-09-19 | Manufacturing method of hot-dip galvanized high-strength thin steel sheet with excellent hole expansion properties |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24954390A JP2862187B2 (en) | 1990-09-19 | 1990-09-19 | Manufacturing method of hot-dip galvanized high-strength thin steel sheet with excellent hole expansion properties |
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| Publication Number | Publication Date |
|---|---|
| JPH04128321A true JPH04128321A (en) | 1992-04-28 |
| JP2862187B2 JP2862187B2 (en) | 1999-02-24 |
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ID=17194556
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|---|---|---|---|
| JP24954390A Expired - Fee Related JP2862187B2 (en) | 1990-09-19 | 1990-09-19 | Manufacturing method of hot-dip galvanized high-strength thin steel sheet with excellent hole expansion properties |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2794133A1 (en) * | 1999-05-28 | 2000-12-01 | Kobe Steel Ltd | Hot dip galvanized steel sheet for car structural parts production has ferrite and martensite microstructure and contains manganese, chromium, molybdenum and aluminum |
| US6306527B1 (en) | 1999-11-19 | 2001-10-23 | Kabushiki Kaisha Kobe Seiko Sho | Hot-dip galvanized steel sheet and process for production thereof |
| US6709535B2 (en) | 2002-05-30 | 2004-03-23 | Kobe Steel, Ltd. | Superhigh-strength dual-phase steel sheet of excellent fatigue characteristic in a spot welded joint |
| US6811624B2 (en) | 2002-11-26 | 2004-11-02 | United States Steel Corporation | Method for production of dual phase sheet steel |
| JP2006265620A (en) * | 2005-03-23 | 2006-10-05 | Nisshin Steel Co Ltd | Method for producing low yield ratio high tensile strength hot dip galvanized steel sheet |
| US7311789B2 (en) | 2002-11-26 | 2007-12-25 | United States Steel Corporation | Dual phase steel strip suitable for galvanizing |
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| JP5194811B2 (en) | 2007-03-30 | 2013-05-08 | Ｊｆｅスチール株式会社 | High strength hot dip galvanized steel sheet |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2794133A1 (en) * | 1999-05-28 | 2000-12-01 | Kobe Steel Ltd | Hot dip galvanized steel sheet for car structural parts production has ferrite and martensite microstructure and contains manganese, chromium, molybdenum and aluminum |
| US6312536B1 (en) | 1999-05-28 | 2001-11-06 | Kabushiki Kaisha Kobe Seiko Sho | Hot-dip galvanized steel sheet and production thereof |
| US6306527B1 (en) | 1999-11-19 | 2001-10-23 | Kabushiki Kaisha Kobe Seiko Sho | Hot-dip galvanized steel sheet and process for production thereof |
| US6709535B2 (en) | 2002-05-30 | 2004-03-23 | Kobe Steel, Ltd. | Superhigh-strength dual-phase steel sheet of excellent fatigue characteristic in a spot welded joint |
| US6811624B2 (en) | 2002-11-26 | 2004-11-02 | United States Steel Corporation | Method for production of dual phase sheet steel |
| US7311789B2 (en) | 2002-11-26 | 2007-12-25 | United States Steel Corporation | Dual phase steel strip suitable for galvanizing |
| JP2006265620A (en) * | 2005-03-23 | 2006-10-05 | Nisshin Steel Co Ltd | Method for producing low yield ratio high tensile strength hot dip galvanized steel sheet |
| JP4679195B2 (en) * | 2005-03-23 | 2011-04-27 | 日新製鋼株式会社 | Low yield ratio high tension hot dip galvanized steel sheet manufacturing method |
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| Publication number | Publication date |
|---|---|
| JP2862187B2 (en) | 1999-02-24 |
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