JPH0147530B2 - - Google Patents
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- Publication number
- JPH0147530B2 JPH0147530B2 JP56196305A JP19630581A JPH0147530B2 JP H0147530 B2 JPH0147530 B2 JP H0147530B2 JP 56196305 A JP56196305 A JP 56196305A JP 19630581 A JP19630581 A JP 19630581A JP H0147530 B2 JPH0147530 B2 JP H0147530B2
- Authority
- JP
- Japan
- Prior art keywords
- steel
- chemical conversion
- conversion treatment
- annealing
- phosphate
- 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
Links
- 229910000831 Steel Inorganic materials 0.000 claims description 51
- 239000010959 steel Substances 0.000 claims description 51
- 239000011572 manganese Substances 0.000 claims description 25
- 238000000137 annealing Methods 0.000 claims description 13
- 229910052710 silicon Inorganic materials 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
- PYLLWONICXJARP-UHFFFAOYSA-N manganese silicon Chemical compound [Si].[Mn] PYLLWONICXJARP-UHFFFAOYSA-N 0.000 claims description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims 2
- 229910000617 Mangalloy Inorganic materials 0.000 claims 1
- 239000012535 impurity Substances 0.000 claims 1
- 229910052742 iron Inorganic materials 0.000 claims 1
- 239000000126 substance Substances 0.000 description 21
- 238000006243 chemical reaction Methods 0.000 description 20
- 239000013078 crystal Substances 0.000 description 16
- 229910052719 titanium Inorganic materials 0.000 description 15
- 239000010936 titanium Substances 0.000 description 15
- 229910019142 PO4 Inorganic materials 0.000 description 14
- 230000000694 effects Effects 0.000 description 14
- 239000010452 phosphate Substances 0.000 description 14
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 14
- 238000001556 precipitation Methods 0.000 description 11
- 239000007789 gas Substances 0.000 description 10
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 9
- 229910052748 manganese Inorganic materials 0.000 description 9
- 229910006639 Si—Mn Inorganic materials 0.000 description 7
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 6
- 229910052758 niobium Inorganic materials 0.000 description 6
- 230000000087 stabilizing effect Effects 0.000 description 6
- 229910052720 vanadium Inorganic materials 0.000 description 6
- 230000003750 conditioning effect Effects 0.000 description 4
- 238000001179 sorption measurement Methods 0.000 description 4
- 238000007792 addition Methods 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 239000000084 colloidal system Substances 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000002667 nucleating agent Substances 0.000 description 3
- 229910052718 tin Inorganic materials 0.000 description 3
- 229910052726 zirconium Inorganic materials 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 229910052787 antimony Inorganic materials 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000005238 degreasing Methods 0.000 description 2
- 238000004070 electrodeposition Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000005087 graphitization Methods 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000003973 paint Substances 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- -1 In addition Inorganic materials 0.000 description 1
- 229910000840 Capped steel Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 239000002480 mineral oil Substances 0.000 description 1
- 235000010446 mineral oil Nutrition 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000010731 rolling oil Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000001488 sodium phosphate Substances 0.000 description 1
- 229910000162 sodium phosphate Inorganic materials 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 238000005211 surface analysis Methods 0.000 description 1
- 238000003887 surface segregation Methods 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical group [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
- C21D1/76—Adjusting the composition of the atmosphere
- C21D1/763—Adjusting the composition of the atmosphere using a catalyst
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Description
本発明は化成処理性（リン酸塩塗装下地処理
性）のすぐれたシリコン−マンガン系（以下Si−
Mn系と記述する）の高強度鋼板の製造方法に係
わるものであつて、その骨子はSi0.7〜2.0％、
Mn0.5〜2.0％、C0.1％以下の含有量を有する鋼
に、Cr，Ti，Ｖ，NbおよびZr等の炭化物安定化
元素ならびにSe，Sb，BiおよびSn等のグラフア
イト化抑制元素のいずれか一種または二種以上を
添加することによつて焼鈍時の表面Ｃの析出を抑
制し、同時に焼鈍ガス成分を規定することによつ
て、鋼表面の着色（ブルーイング）を抑制すると
いう両方の効果によつて、化成処理性のすぐれた
Si−Mn系高強度鋼板の製造方法を得ることにあ
る。本発明の契機となつたのはSi−Mn系鋼板の
化成処理性が焼鈍時に内部から拡散してきた表面
Ｃによつて支配されるという新事実を発見したこ
とに基づくものである。
最近自動車用鋼板を中心として、軽量化を目的
に、より高い強度を有する鋼板の開発が要望さ
れ、すでに種々のタイプの高強度鋼板（以下ハイ
テンと称する）が開発、実用化されているが、こ
れらを大別するとSi，Mn，Ｐなどの含有量を高
くする固溶強化型とNb，Ti，Ｖなどを添加する
析出強化型とがある。後者のタイプのハイテン並
びにｐ添加ハイテンは通常所要元素の添加量が少
ない（＜0.2％）ため、化成処理性は一般の軟鋼
板と大差ないが、Si，Mn系では強度アツプのた
めかなり高い添加量を必要とすることから、化成
処理性が劣化（リン酸塩結晶が粗大化）し、した
がつて塗装耐食性が通常の軟鋼板に比べて劣るこ
とが知られている。この理由の一つはSi，Mnが
高いと、焼鈍時（還元ガス中で700〜800℃で加熱
軟化する過程）に鋼表面にSi，Mnを含む厚い複
合酸化膜が形成して鋼板が着色し（ブルーイン
グ）、これがリン酸塩反応を阻害するためとされ、
この観点から特にSiの量を制限する技術が公知で
ある（特公昭53−7371号、特開昭51−107218号）。
一方、鋼板表面の着色は鋼の成分にのみよるも
のでなく、焼鈍時の雰囲気ガスによることもまた
よく知られており、この点から雰囲気露点（D.
P.）を制限することも知られている（特開昭53−
119708号）。すなわち焼鈍は通常H2とN2との混
合ガス中で加熱されるが、混合ガスは微量の水分
を含んでおり、このH2OとH2との比率によつて、
鋼中成分の酸化が起るかどうかが決まる。したが
つて適当な雰囲気ガスを選ぶことによつて、Si，
Mnの高い鋼板でもブルーイングを起すことなく
製造することが可能である。特にハイテンの場合
は、一般に焼鈍時間の短い（＜10分）連続焼鈍で
製造されるため、Si，Mnの量がかなり高くても
ブルーイングのない光輝焼鈍板を得ることがバツ
チ焼鈍に比べて有利である。
而して、本発明者らは、ブルーイングのないSi
−Mn系ハイテンでもまた化成処理不良を起すこ
とを見い出し、Si−Mn系ハイテンの化成処理不
良が、これまでいわれているようなSi，Mnを含
む複合酸緩膜の存在にのみよるものでないことを
知見した。そこでその原因を種々調査した結果、
鋼中Siが表面カーボンの析出を著しく促進する事
実を発見し、この表面Ｃが化成処理不良の原因に
なつていることをつきとめた。一方Mnは表面Ｃ
の析出を抑制するので、同一Si量であれば、リン
酸塩結晶を緻密化し、化成処理性を改善すること
も明らかとなつた。一方、本来化成処理性のよい
軟鋼板の場合でも、表面Ｃ汚れが化成処理に悪影
響をすることは広く知られており、この表面Ｃの
起源は圧延油の残査、焼鈍ガス（Co）からの付
着、鋼中からの拡散などが推定されている。
本発明者らはSi−Mn系ハイテンの化成処理不
良の原因も、究極のところ、この表面Ｃにあり、
この表面Ｃを抑制すれば、Si−Mn系ハイテンの
化成処理不良も改善できるとの着想のもとに種々
の実験を行なつた。その結果、Si−Mn鋼にCr，
Nb，Ti，Ｖなどの炭化物安定化元素、もしくは
優先的に表面に拡散吸着してＣの析出に対して負
触媒的作用をするSe，Bi，Sb，ＢおよびSnを添
加することによつて、表面のＣの析出が抑制され
ると同時に、緻密なリン酸塩結晶が形成され、通
常の軟鋼と同等以上のものが得られることが明ら
かとなり、ここに本発明を構成するに至つたので
ある。以下に本発明の詳細を図面を用いて説明す
る。
第１図は本発明の契機となつた発見で、表面Ｃ
の析出が、鋼中Si濃度に比例して増大することを
示す図面である。図の縦軸はイオンマイクロアナ
ライザー（IMA）によつて測定された表面Ｃの
カウント数（厚さ150Åまでの積分量）である。
表面Ｃは鋼中Si濃度に比例し、Mnはこれを抑制
すること、また表面Ｃに対しては鋼中Ｃ濃度より
も、SiやMnの影響がより大きいことがわかる。
第２図は市販のリン酸塩処理を行なつた場合の
鋼中Si量とリン酸塩処理結晶サイズ（径の大きい
ものほど結晶が粗く、皮膜性能が劣る）との関係
を示したもので、鋼中Siが高いと結晶が粗大化
し、一方Mnが高いと、結晶粗大化に対するSiの
悪影響が緩和されることがわかる。第１図と第２
図の現象的類似性から鋼中Siによるリン酸塩結晶
の粗大化の原因をただちに表面Ｃに結びつけるこ
とはできないが、これを証明するのが、第３図
（写真）と第４図とである。リン酸塩化成処理を
行なう場合は、脱脂後表面調整という前処理が必
須であるが、この表面調整剤はチタンコロイドの
リン酸ソーダ分散液であり、鋼板表面に吸着した
チタンがその後のリン酸塩結晶析出の核となり、
結晶を緻密化させるものといわれている。第３図
はこの効果を示したもので、一般に化成処理性が
すぐれているといわれる軟鋼板（バツチ焼鈍のキ
ヤプド鋼板）でも、ａは表面調整を行つたもので
表面調整をしないｂと、全く粗い結晶しか形成し
ないことが一目りよう然である。
一方第４図は、第１図のサンプルから選ばれた
Si−Mn系ハイテンの表面Ｃ量と、吸着チタン
（表面調整剤）との関係を図示したもので、核形
成剤のチタンは表面Ｃと反比例し、表面Ｃの高い
ものほど、チタンが吸着しにくいことがわかる。
すなわちこの一連の結果は、リン酸塩結晶が鋼表
面に緻密に形成するかどうかは、核形成剤のチタ
ンの吸着性によつて支配きれており、このチタン
の吸着は表面Ｃの存在によつて阻害されること、
並びにSiはこの表面Ｃの析出を助長するがゆえに
リン酸塩結晶を粗大化することを明瞭に示してい
る。
本発明者らは以上の基礎実験に基づき、Si−
Mn系のハイテンに炭化物安定化元素であるCr，
Ti，Ｖ，NbおよびZnを添加することによつて、
またＣ析出の負触媒となるSb，Bi，ＢおよびSn
を添加することにより、Si−Mnハイテンの表面
Ｃの析出を効果的に抑制し、よつて化成処理性の
劣化を防止できることを見い出した。これらの元
素は単独添加によつてもそれなりに効果を示す
が、二種以上を複合添加することによつて、著し
く優れた表面Ｃ抑制効果、従つて化成処理性の改
善が行なわれる。特に作用機構の異なるグループ
（炭化物安定化グループと負触媒グループ）の元
素同志を組合せると、より少ない添加量で、すぐ
れた効果が期待できる。
また本発明ではあくまでもブルーイングのない
光輝焼鈍板の得られる条件でその効果が期待でき
るものであるから、この点から主要成分のSi＋
Mn≦3.0％に制限すると同時に、焼鈍雰囲気も水
素ガス濃度１％以上、露点（D.P.）−60℃〜０℃
の範囲に、望ましくは水素ガス濃度３％以上、露
点−10℃以下に制御されなければならない。ガス
雰囲気の限定範囲が広いのは、Si＋Mnの合計量
によつてブルーイングしやすさが変わり得るから
で、この合計量が少ないほど、より高い露点を採
用することが可能である。例えばSi＋Mn＝2.0％
であれば、H25％，D.P−20℃であれば充分であ
る。
本発明方法によつて製造された鋼板は通常の薄
板製造方法で容易に製造される。すなわち、溶鋼
を連続鋳造または造塊法でスラブ（鋼片）とな
し、加熱炉で1100〜1200℃に加熱後熱間で圧延
し、スケールを酸洗して除去したのち、冷間圧延
によつて所望の板厚に圧延する。ついで焼鈍を行
なうが、複合組織鋼を目的とする場合は、α＋γ
温度域で加熱後急冷する。冷却速度は公知の方法
に従い、Mn量によつて決まる適当な条件（たと
えば1.5Mnでは50℃／sec以上）が選ばれる。必
要に応じて300℃前後の過時効処理を施し、１％
前後の圧延率で調質圧延を行なうことによつて製
品を得る。
本発明において表面Ｃ抑制のために添加される
成分の添加水準は単独添加の場合、幾分でも表面
Ｃの抑制に効果が認められた下限を示し、たとえ
ば抑制効果の大きいＳやＢではその下限は0.008
％と低い水準になつている。一方その効果が目立
つて大きくないCrでは0.1％であり、その他の炭
化物安定化元素ではＣの水準にも依存するため厳
密に決められないが、たとえばC0.005％ではTi，
Ｖ，NbおよびZrなどの炭化物安定化元素は0.03
％程度でも効果が認められる。ただし通常のハイ
テンとして適当な水準のC0.05〜0.07％の範囲で
は前記元素の添加量は0.1〜0.2％が望ましい。こ
れらの添加成分を複合添加する場合は、各々の成
分の添加水準は低くてもよいことになる。一方こ
れらの成分の上限値は、原則的にその効果（リン
酸塩処理性の改善効果）が飽和する濃度である
が、Ti，Ｖ，Nb，Zrなどでは、材料の強度が高
くなり過ぎること、並びに値段が高くなりすぎる
という点も加味してその上限を定めた。またSiは
0.7％以上になるとＣの表面偏析が多くなる。従
つて、このようにＣの析出の多くなる場合にグラ
フアイト化抑制元素が効果をあらわし、化学処理
性を改善することができるのでSiを0.7％以上と
した。Mnは、主として高強度を得るという材質
的見地、並びに表面Ｃの抑制効果の二つの理由か
らその下限0.5％を定めた。Ｃの上限は、0.1％以
上では、たとえＣの抑制元素を添加しても、表面
Ｃの濃化が押えにくくなることから、その上限を
0.1％とした。
以下に本発明の実施例を述べる。
実施例
第１表に示す成分系の鋼種を20Kgの真空溶解に
より溶製し、1250℃で加熱して熱間圧延で約2.3
mmの板厚の熱延鋼板を得た。熱延鋼板表面のスケ
ールはグラインダー研削によつて除去した後、鉱
油系エマルジヨンを潤滑油として、板厚0.7mmま
で冷間圧延した。ついで溶剤脱脂によつて清浄化
した後、第１表に示すガス雰囲気中で770℃１分
間の加熱を行ない、鋼板の両面に雰囲気ガスジエ
ツトを吹きつける方法によつて50℃／secの冷却
速度で300℃まで急冷した。その後150℃まで炉冷
した後大気中に取り出した。このようにして得ら
れたサンプルは一方において表面分析に供し、一
方において化成処理にひきつづき電着塗装を行な
つた。化成処理は日本パーカーライジング社製
Bt3004（デイツプタイプ）で、電着塗装は日本ペ
イント社製パワートツプＵ−30を厚さ20μになる
よう陰極電着した。化成処理性の評価はリン酸塩
結晶の大きさを、１〜５段階で分類（５：good，
1poor）、また塗装耐食性は塩水噴霧試験（SST）
480hr後のスクラツチ部のふくれ巾を１〜５段階
（５：good，1poor）で評価した。
第１表の結果から、Si−Mn系鋼板に炭化物安
定化元素、優先吸着元素（負触媒）を添加したも
の
The present invention is based on silicon-manganese (hereinafter referred to as Si-
It is related to the manufacturing method of high-strength steel sheets (described as Mn-based), and its gist is 0.7 to 2.0% Si,
Carbide stabilizing elements such as Cr, Ti, V, Nb and Zr and graphitization suppressing elements such as Se, Sb, Bi and Sn are added to steel with a content of Mn 0.5 to 2.0% and C 0.1% or less. By adding one or more of these, precipitation on the surface C during annealing is suppressed, and at the same time, by specifying the annealing gas components, coloring (blueing) on the steel surface is suppressed. Both effects result in excellent chemical conversion treatment properties.
The object of the present invention is to obtain a method for manufacturing Si-Mn-based high-strength steel sheets. The present invention was based on the discovery of a new fact that the chemical conversion treatability of Si--Mn steel sheets is controlled by surface C that diffuses from inside during annealing. Recently, there has been a demand for the development of steel plates with higher strength for the purpose of reducing weight, mainly for automobile steel plates, and various types of high-strength steel plates (hereinafter referred to as high-strength steel plates) have already been developed and put into practical use. Broadly speaking, these are divided into solid solution strengthened types, which increase the content of Si, Mn, P, etc., and precipitation strengthened types, which add Nb, Ti, V, etc. The latter type of high-tensile steel and p-added high-tensile steel usually have a small amount of required elements added (<0.2%), so their chemical conversion properties are not much different from general mild steel sheets, but Si and Mn-based steel sheets require considerably higher additions to increase strength. It is known that the chemical conversion properties deteriorate (phosphate crystals become coarser) due to the large amount of paint required, and therefore the coating corrosion resistance is inferior to that of ordinary mild steel sheets. One of the reasons for this is that when Si and Mn are high, a thick composite oxide film containing Si and Mn forms on the steel surface during annealing (the process of heating and softening at 700 to 800°C in reducing gas), causing the steel plate to become discolored. bluing, which is thought to inhibit the phosphate reaction.
From this point of view, techniques for particularly limiting the amount of Si are known (Japanese Patent Publication No. 7371/1983, Japanese Patent Application Laid-open No. 107218/1983). On the other hand, it is well known that the coloration of the steel sheet surface is not only caused by the steel components, but also by the atmospheric gas during annealing, and from this point of view, the atmospheric dew point (D.
It is also known to limit P.
No. 119708). That is, annealing is usually heated in a mixed gas of H 2 and N 2 , but the mixed gas contains a small amount of moisture, and depending on the ratio of H 2 O and H 2 ,
It determines whether oxidation of the components in the steel occurs. Therefore, by selecting an appropriate atmospheric gas, Si,
Even steel sheets with high Mn content can be manufactured without causing bluing. In particular, in the case of high tensile strength steel, it is generally produced by continuous annealing with a short annealing time (<10 minutes), so it is easier to obtain bright annealed sheets without bluing even if the amounts of Si and Mn are quite high compared to batch annealing. It's advantageous. Therefore, the present inventors have developed Si without bluing.
- It was discovered that chemical conversion treatment defects also occur in Mn-based high tensile strength steel, and that the chemical conversion treatment defects in Si-Mn-based high tensile strength steel are not solely due to the presence of a composite acid-relaxing film containing Si and Mn, as has been said so far. I found out. As a result of various investigations into the causes,
We discovered that Si in steel significantly promotes the precipitation of surface carbon, and found that this surface C was the cause of poor chemical conversion treatment. On the other hand, Mn has surface C
It has also become clear that the same amount of Si can densify phosphate crystals and improve chemical conversion treatment properties. On the other hand, it is widely known that surface C contamination has a negative effect on chemical conversion treatment, even in the case of mild steel sheets that originally have good chemical conversion properties.The origin of this surface C is from residual rolling oil and annealing gas (Co). It is assumed that this occurs due to adhesion of carbon dioxide, diffusion from within the steel, etc. The present inventors believe that the cause of poor chemical conversion treatment of Si-Mn-based high tensile strength steel lies ultimately in this surface C.
We conducted various experiments based on the idea that by suppressing this surface C, defects in chemical conversion treatment of Si--Mn-based high tensile strength steel could be improved. As a result, we found that Cr,
By adding carbide stabilizing elements such as Nb, Ti, and V, or Se, Bi, Sb, B, and Sn, which are preferentially diffused and adsorbed onto the surface and have a negative catalytic effect on C precipitation. It became clear that the precipitation of C on the surface was suppressed and at the same time dense phosphate crystals were formed, and that a product equivalent to or better than ordinary mild steel could be obtained, which led to the formation of the present invention. be. The details of the present invention will be explained below using the drawings. Figure 1 shows the discovery that led to the present invention.
2 is a drawing showing that the precipitation of Si increases in proportion to the Si concentration in steel. The vertical axis of the figure is the count number (integrated amount up to a thickness of 150 Å) of surface C measured by an ion microanalyzer (IMA).
It can be seen that the surface C is proportional to the Si concentration in the steel, and that Mn suppresses this, and that the influence of Si and Mn on the surface C is greater than that of the C concentration in the steel. Figure 2 shows the relationship between the amount of Si in steel and the phosphate treatment crystal size (the larger the diameter, the rougher the crystals and the poorer the film performance) when commercially available phosphate treatment is applied. , it can be seen that when the Si content in the steel is high, the crystals become coarser, while when the Mn content is high, the negative influence of Si on crystal coarsening is alleviated. Figures 1 and 2
Although the cause of the coarsening of phosphate crystals due to Si in steel cannot be immediately linked to surface C due to the phenomenological similarity in the figures, this is proven by the use of Figures 3 (photo) and 4. be. When performing phosphate chemical conversion treatment, a pretreatment called surface conditioning after degreasing is essential, but this surface conditioning agent is a sodium phosphate dispersion of titanium colloid, and the titanium adsorbed on the steel plate surface is used for subsequent phosphoric acid treatment. It becomes the nucleus of salt crystal precipitation,
It is said to make crystals more dense. Figure 3 shows this effect.Even for mild steel sheets (batch annealed capped steel sheets) which are generally said to have excellent chemical conversion treatment properties, a shows a surface-conditioned one, and a shows no surface-conditioned b, and a shows no surface conditioning at all. It is obvious at first glance that only coarse crystals are formed. On the other hand, Figure 4 is a sample selected from the samples in Figure 1.
This diagram shows the relationship between the surface C content of Si-Mn-based high tensile strength steel and adsorbed titanium (surface conditioning agent).Titanium, a nucleating agent, is inversely proportional to surface C, and the higher the surface C, the more titanium is adsorbed. I know it's difficult.
In other words, this series of results shows that whether or not phosphate crystals are densely formed on the steel surface is determined by the adsorption of titanium as a nucleating agent, and the adsorption of titanium is due to the presence of surface C. to be hindered by
Furthermore, it is clearly shown that Si promotes the precipitation of C on the surface, thereby coarsening the phosphate crystals. The present inventors based on the above basic experiments,
Cr, which is a carbide stabilizing element, is added to Mn-based high tensile strength.
By adding Ti, V, Nb and Zn,
In addition, Sb, Bi, B, and Sn, which serve as negative catalysts for C precipitation,
It has been discovered that by adding , it is possible to effectively suppress the precipitation of C on the surface of Si-Mn high tensile strength steel, thereby preventing deterioration of chemical conversion treatment properties. Although these elements exhibit certain effects when added alone, by adding two or more of them in combination, a significantly superior effect of suppressing surface C and, therefore, an improvement in chemical conversion treatment properties can be achieved. In particular, when elements from groups with different action mechanisms (carbide stabilization group and negative catalyst group) are combined, excellent effects can be expected with a smaller amount added. In addition, in the present invention, the effect can be expected only under the conditions where a bright annealed plate without bluing can be obtained, so from this point of view, the main component Si +
While limiting Mn≦3.0%, the annealing atmosphere also has a hydrogen gas concentration of 1% or more, and a dew point (DP) of -60°C to 0°C.
The hydrogen gas concentration should preferably be controlled to 3% or more and the dew point to -10°C or less. The reason why the limited range of the gas atmosphere is wide is because the ease of bluing can change depending on the total amount of Si + Mn, and the smaller this total amount is, the higher the dew point can be adopted. For example, Si+Mn=2.0%
If so, 5% H 2 and DP -20°C are sufficient. The steel sheet manufactured by the method of the present invention can be easily manufactured by a normal thin sheet manufacturing method. That is, molten steel is made into slabs (steel slabs) by continuous casting or ingot-forming, heated to 1100-1200℃ in a heating furnace, hot rolled, scale removed by pickling, and then cold rolled. and then rolled to the desired thickness. Next, annealing is performed, but if the objective is to obtain composite structure steel, α + γ
After heating in the temperature range, rapidly cool. The cooling rate is determined by a known method and is determined by the amount of Mn (for example, 50°C/sec or more for 1.5Mn). If necessary, overaging treatment at around 300℃ is applied to reduce the temperature to 1%.
A product is obtained by performing temper rolling at different rolling rates. In the present invention, the addition level of the component added to suppress surface C, when added alone, indicates the lower limit at which some effect on suppressing surface C has been recognized. For example, for S and B, which have a large suppressing effect, the lower limit is 0.008
%, which is at a low level. On the other hand, for Cr, where the effect is not noticeable and large, it is 0.1%, and for other carbide stabilizing elements, it cannot be determined strictly because it depends on the level of C, but for example, for 0.005% C, Ti,
Carbide stabilizing elements such as V, Nb and Zr are 0.03
The effect is recognized even at about %. However, within the range of C 0.05 to 0.07%, which is an appropriate level for ordinary high tensile steel, the amount of the above element added is preferably 0.1 to 0.2%. When these additional components are added in combination, the addition level of each component may be low. On the other hand, the upper limit of these components is, in principle, the concentration at which their effect (improving effect on phosphate treatment) is saturated, but with Ti, V, Nb, Zr, etc., the strength of the material becomes too high. , as well as the fact that the price would become too high, and set an upper limit. Also, Si is
When the content exceeds 0.7%, surface segregation of C increases. Therefore, in the case where a large amount of C is precipitated, the graphitization suppressing element becomes effective and the chemical processability can be improved, so the Si content was set to 0.7% or more. The lower limit of Mn was determined to be 0.5% mainly from the material standpoint of obtaining high strength and the effect of suppressing surface C. The upper limit for C is set at 0.1% or more, because even if a C suppressing element is added, it becomes difficult to suppress the concentration of surface C.
It was set at 0.1%. Examples of the present invention will be described below. Example 20 kg of steel with the composition shown in Table 1 was melted by vacuum melting, heated at 1250°C, and hot rolled to approximately 2.3 kg.
A hot rolled steel plate with a thickness of mm was obtained. The scale on the surface of the hot-rolled steel sheet was removed by grinding, and then cold-rolled to a thickness of 0.7 mm using mineral oil emulsion as a lubricant. After cleaning by solvent degreasing, the steel plate was heated at 770°C for 1 minute in the gas atmosphere shown in Table 1, and cooled at a cooling rate of 50°C/sec by blowing an atmospheric gas jet onto both sides of the steel plate. It was rapidly cooled to 300℃. After that, it was cooled in the furnace to 150°C and then taken out into the atmosphere. The samples thus obtained were on the one hand subjected to surface analysis and on the other hand subjected to chemical conversion treatment followed by electrodeposition coating. Chemical treatment is made by Nihon Parkerizing Co., Ltd.
Bt3004 (deep type) was used for electrodeposition, and Power Top U-30 manufactured by Nippon Paint Co., Ltd. was cathode electrodeposited to a thickness of 20 μm. Chemical conversion treatment properties are evaluated by classifying the size of phosphate crystals on a scale of 1 to 5 (5: good,
1poor), and paint corrosion resistance is tested by salt spray test (SST)
The swelling width of the scratched portion after 480 hours was evaluated on a scale of 1 to 5 (5: good, 1 poor). From the results in Table 1, Si-Mn steel sheets with carbide stabilizing elements and preferential adsorption elements (negative catalysts) added.
【表】
＊ ブルーイング発生
は、いずれも化成処理性が向上し、塗装耐食性が
普通鋼並に改善されていることが明らかである。[Table] *It is clear that the chemical conversion treatment property has improved in all cases where bluing has occurred, and the coating corrosion resistance has been improved to the same level as ordinary steel.
第１図は鋼中Si，Mn量と表面濃化Ｃとの関係
を示す図面、第２図は鋼中Si，Mn量とリン酸塩
処理性（結晶のサイズ）との関係図である。第３
図は表面調整剤（チタンコロイド）処理を行なつ
た場合と省略した場合の軟鋼板のリン酸塩結晶の
析出状態の顕微鏡写真（倍率1000倍）である。ａ
表面調整あり、ｂ表面調整省略したもの、第４図
はチタンコロイド（核形成剤）の吸着に対する表
面Ｃの影響（Si−Mnハイテン鋼）を示す図であ
る。
FIG. 1 is a diagram showing the relationship between the amount of Si and Mn in steel and the surface concentration of C, and FIG. 2 is a diagram showing the relationship between the amount of Si and Mn in steel and phosphate treatability (crystal size). Third
The figures are micrographs (1000x magnification) of the precipitation of phosphate crystals on mild steel plates with and without surface conditioner (titanium colloid) treatment. a
Figure 4 shows the influence of surface C on the adsorption of titanium colloid (nucleating agent) (Si-Mn high-tensile steel), with surface adjustment and b without surface adjustment.
Claims (1)
シリコン−マンガン鋼を基本とし、これにCr0.1
〜1.0％、Ti0.03〜0.20％、V0.03〜0.20％、
Nb0.03〜0.20％、Zr0.03〜0.20％、Se0.008〜
0.025％、B0.008〜0.020％、Sb0.01〜0.20％、
Bi0.01〜0.20％およびSn0.02〜0.10％のいずれか
一種または二種以上を含有し、かつSi＋Mn≦3.0
％であつて、残部鉄および不可避的不純物からな
る鋼板を、水素ガス濃度1vol％以上、露点−60℃
〜０℃に制御された雰囲気内で焼鈍することを特
徴とするシリコン−マンガン系高強度鋼板の製造
方法。1 Based on silicon-manganese steel with Si0.7~2.0%, Mn0.5~2.0%, C0.1% or less, and Cr0.1
~1.0%, Ti0.03~0.20%, V0.03~0.20%,
Nb0.03~0.20%, Zr0.03~0.20%, Se0.008~
0.025%, B0.008~0.020%, Sb0.01~0.20%,
Contains one or more of Bi0.01~0.20% and Sn0.02~0.10%, and Si+Mn≦3.0
%, and the balance consists of iron and unavoidable impurities, at a hydrogen gas concentration of 1 vol% or more and a dew point of -60°C.
A method for manufacturing a silicon-manganese-based high-strength steel sheet, characterized by annealing in an atmosphere controlled at ~0°C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19630581A JPS58100622A (en) | 1981-12-08 | 1981-12-08 | Production of silicon-manganese high strength steel plate having excellent suitability to chemical conversion |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19630581A JPS58100622A (en) | 1981-12-08 | 1981-12-08 | Production of silicon-manganese high strength steel plate having excellent suitability to chemical conversion |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS58100622A JPS58100622A (en) | 1983-06-15 |
| JPH0147530B2 true JPH0147530B2 (en) | 1989-10-16 |
Family
ID=16355592
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP19630581A Granted JPS58100622A (en) | 1981-12-08 | 1981-12-08 | Production of silicon-manganese high strength steel plate having excellent suitability to chemical conversion |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS58100622A (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0611919B2 (en) * | 1983-12-26 | 1994-02-16 | 日本鋼管株式会社 | Cold rolled steel sheet with excellent corrosion resistance after painting |
| JPS6237349A (en) * | 1985-08-12 | 1987-02-18 | Kobe Steel Ltd | Wire for steel cord excellent in phosphate chemical conversion treatment |
| JPH07103422B2 (en) * | 1988-01-14 | 1995-11-08 | 新日本製鐵株式会社 | Good workability High strength cold rolled steel sheet manufacturing method |
| JPH07122091B2 (en) * | 1992-02-10 | 1995-12-25 | 株式会社神戸製鋼所 | Method for producing hot-rolled steel sheet excellent in press formability and affinity with resin |
| JP5834388B2 (en) * | 2010-09-29 | 2015-12-24 | Ｊｆｅスチール株式会社 | Manufacturing method of high-strength steel sheet |
| JP5834869B2 (en) * | 2011-12-14 | 2015-12-24 | Ｊｆｅスチール株式会社 | High-strength steel sheet with excellent chemical conversion and process for producing the same |
| WO2013129295A1 (en) * | 2012-02-28 | 2013-09-06 | Ｊｆｅスチール株式会社 | Si-containing high strength cold rolled steel sheet, production method therefor, and vehicle member |
| JP6136876B2 (en) * | 2013-11-18 | 2017-05-31 | 新日鐵住金株式会社 | Automotive steel plate with excellent chemical conversion and corrosion resistance |
| JP6222040B2 (en) * | 2014-10-29 | 2017-11-01 | Ｊｆｅスチール株式会社 | High formability and high strength cold-rolled steel sheet excellent in chemical conversion treatment and production method thereof |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4843401A (en) * | 1971-09-30 | 1973-06-23 | ||
| JPS5113105A (en) * | 1974-06-14 | 1976-02-02 | Getsutsuen Hainritsuhi | Ekiatsushikihoriipu gurabu baketsuto |
| JPS537371A (en) * | 1976-07-09 | 1978-01-23 | Seikosha Kk | Repeat mechanism for clock |
-
1981
- 1981-12-08 JP JP19630581A patent/JPS58100622A/en active Granted
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4843401A (en) * | 1971-09-30 | 1973-06-23 | ||
| JPS5113105A (en) * | 1974-06-14 | 1976-02-02 | Getsutsuen Hainritsuhi | Ekiatsushikihoriipu gurabu baketsuto |
| JPS537371A (en) * | 1976-07-09 | 1978-01-23 | Seikosha Kk | Repeat mechanism for clock |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58100622A (en) | 1983-06-15 |
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