JP2818675B2 - Manufacturing method of surface-conditioned cold-rolled steel sheet - Google Patents
Manufacturing method of surface-conditioned cold-rolled steel sheetInfo
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- JP2818675B2 JP2818675B2 JP33975389A JP33975389A JP2818675B2 JP 2818675 B2 JP2818675 B2 JP 2818675B2 JP 33975389 A JP33975389 A JP 33975389A JP 33975389 A JP33975389 A JP 33975389A JP 2818675 B2 JP2818675 B2 JP 2818675B2
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- steel sheet
- rolled steel
- cold
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- layer
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Description
【発明の詳細な説明】 ＜産業上の利用分野＞ 本発明は、自動車のボディ等に使用される冷延ならび
に表面処理された鋼板であって、とりわけ加工性が良好
であるばかりでなく、同時に塗装の下地処理としての良
好な化成処理性（リン酸亜鉛処理性）さらには優れたス
ポット溶接性なども具備するように表面の所定成分濃度
を調整した冷延鋼板の製造方法に関するものである。DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a cold-rolled and surface-treated steel sheet used for an automobile body and the like. The present invention relates to a method for producing a cold-rolled steel sheet in which the concentration of a predetermined component on the surface is adjusted so as to have good chemical conversion treatment (zinc phosphate treatment) as a base treatment for coating and also excellent spot weldability.
＜従来の技術＞ プレス加工用冷延鋼板は、従来Ｃ≧0.01％以上の低Ｃ
−リムド鋼や低Ｃ−Alキルド鋼を箱焼鈍して製造されて
いたが、最近の省エネルギーならびに製造納期の短縮要
求にかんがみ、連続焼鈍法への変換が積極的に進められ
ている。<Conventional technology> Cold-rolled steel sheet for press working is conventionally low C of 0.01% or more.
-Although rimmed steel and low C-Al killed steel were manufactured by box annealing, in consideration of recent demands for energy saving and shortening of production lead time, conversion to a continuous annealing method is being actively promoted.
連続焼鈍法では、加熱および均熱時間が極めて短い。
そこで、絞り性を箱焼鈍材並にするために、低Ｃ鋼の熱
延巻き取り温度を従来より高温にし、さらに焼鈍温度も
箱焼鈍法より高温にする等の対策がとられている。さら
には、冷却時間も極端に短いため、過時効処理を施すこ
とにより焼鈍中に固溶した炭素を析出させている。しか
るに、かような特殊処理によっても、固溶炭素が依然と
して残留するために、加工性はともかく常温遅時効性を
得ることは困難であった。In the continuous annealing method, the heating and soaking time is extremely short.
Therefore, in order to make the drawability comparable to that of the box annealing material, measures have been taken such as setting the hot-rolling coiling temperature of the low-C steel to be higher than before and the annealing temperature to be higher than that of the box annealing method. Furthermore, since the cooling time is extremely short, carbon dissolved during the annealing is precipitated by performing overaging treatment. However, even with such a special treatment, since the solute carbon still remains, it was difficult to obtain ordinary-temperature delayed aging regardless of workability.
このような実状にかんがみ、さらには箱焼鈍された低
Ｃ−Alキルド鋼と同等の耐時効性と、それ以上の高加工
性を得る手段として、Ｃ≦0.01wt％、Al≦0.20wt％を含
有する極低Ｃ鋼とし、必要に応じてTi、Tb、Ｂ等の炭窒
化物形成元素を添加する技術が製鋼技術の進歩と相まっ
て一般的になりつつある。In view of such a situation, as a means of obtaining the same aging resistance as that of the low C-Al killed steel annealed in a box and the higher workability, C ≦ 0.01 wt% and Al ≦ 0.20 wt% are used. A technique of forming a very low C steel to be contained and adding a carbonitride forming element such as Ti, Tb, B or the like as necessary is becoming common in conjunction with the progress of steelmaking technology.
事実このようにして製造された極低Ｃ冷延鋼板は、焼
鈍中の粒成長性が優れ、非常に良好な加工性をとりわけ
引っ張り試験で評価できる良好な全伸び値（El）、なら
びにランクフォード値（値）を示し、現状では広くプ
レス加工用鋼板として採用されている。In fact, the ultra-low C cold rolled steel sheet produced in this way has excellent grain growth during annealing, has a good overall elongation value (El), which can be evaluated for particularly good workability, especially in a tensile test, and also has a Rank Ford. It shows the value (value), and is currently widely used as a steel plate for press working.
＜発明が解決しようとする課題＞ しかしながら、この種の鋼板の使用の増大にともな
い、以下に示す種々の問題点をも有していることが明ら
かにされ、完全無欠の材料としては今一歩の段階であっ
た。<Problems to be Solved by the Invention> However, with the increase in the use of this type of steel sheet, it has been clarified that the steel sheet also has the following various problems. It was a stage.
先ず、極低Ｃ鋼は元来が鈍鉄に近いため、表面の清浄
度が極めて優れている。そのため、プレス後の塗装の下
地処理としての化成処理（リン酸亜鉛処理）において
は、反応性が従来の低Ｃ−Alキルド鋼より幾分劣り、生
成したリン酸亜鉛鉄結晶の細かさ、化成処理条件変動時
の安定性に対して、低Ｃ−Alキルド鋼より若干不利であ
った。First, the ultra-low C steel is originally close to dull iron, and therefore has extremely excellent surface cleanliness. Therefore, in the chemical conversion treatment (zinc phosphate treatment) as a base treatment of the coating after pressing, the reactivity is somewhat inferior to the conventional low C-Al killed steel, and the fineness of the generated zinc iron phosphate crystal and the chemical conversion It was slightly disadvantageous to the low C-Al killed steel in terms of stability when the processing conditions were changed.
次に、溶接性に対しては、極低Ｃ鋼の場合熱影響部
（HAZ）の組成が一般に粗大化し、溶着部や母材よりも
強度が低下しやすい傾向があった。そのため、溶接部の
強度および疲労特性の点で低Ｃ−Alキルド鋼よりも有利
とは言えなかった。このような理由により、溶接に比較
的長時間を要する電縫鋼管等への極低Ｃ鋼の適用は未だ
なされていないのが現状である。Next, in terms of weldability, the composition of the heat-affected zone (HAZ) in the case of ultra-low C steel generally tends to be coarse, and the strength tends to be lower than that of the welded portion or the base metal. Therefore, it could not be said that it was more advantageous than the low C-Al killed steel in terms of strength and fatigue properties of the weld. For these reasons, at present, the application of ultra-low C steel to electric resistance welded steel pipes and the like, which require a relatively long time for welding, has not yet been achieved.
さらに、極低Ｃ鋼は延性に富むので、非常に粘り強
く、低Ｃ−Al−キルド鋼と同一の条件で打ち抜きや剪断
を行った場合に、その端面に生成する笹くれ部いわゆる
バリが低Ｃ−Alキルド鋼に比べより多く生成する。この
バリは、後のプレス工程で剥がれると、いわゆる星目欠
陥を誘発する。極低Ｃ鋼は、このような危険性を有して
おり、バリ高さ低減のためにも極低Ｃ鋼の打ち抜き性改
善が強く望まれていた。Further, since ultra-low C steel is rich in ductility, it is very tenacious, and when punching or shearing is performed under the same conditions as low C-Al-killed steel, the so-called burrs formed on the end face of the steel have low C. -Generates more than Al-killed steel. These burrs, when peeled off in a later pressing step, induce so-called star defects. Ultra-low C steel has such a danger, and it has been strongly desired to improve the punchability of ultra-low C steel in order to reduce the burr height.
また、加工性のさらなる向上のためには、必然的に不
純物元素の低減を伴うため、焼鈍中の鋼中元素の表面濃
化量が抑制される。このことは、結果として鋼板の表面
硬度の低下を引き起こす。そのため、プレス成形を施し
た場合に、潤滑が十分でないと鋼板表面とプレス型とが
接触時に噛りあい、鋼板の表面キズ欠陥が誘発されるば
かりでなく、極端な場合にはプレス割れさえ伴う。この
ような、いわゆる摺動性の低下は、不純物元素が少ない
極低Ｃ鋼と、表面に濃化させるのに十分な時間が確保で
きない連続焼鈍法との組合わせにより最も顕著になる。Further, to further improve the workability, the amount of impurity elements is inevitably reduced, so that the surface concentration of the elements in the steel during annealing is suppressed. This results in a reduction in the surface hardness of the steel sheet. Therefore, when press forming is performed, if lubrication is not sufficient, the steel sheet surface and the press die mesh at the time of contact, not only the surface scratch defect of the steel sheet is induced, but in extreme cases even press cracking is accompanied . Such a decrease in so-called slidability is most remarkable when a combination of an extremely low carbon steel with a small amount of impurity elements and a continuous annealing method that cannot secure a sufficient time for enrichment on the surface is used.
以上の状況を打開するために、本発明者らは種々の検
討を行った。良好な機械的性質（El、値等）を維持し
た上で上述の問題を解決するためには、極低Ｃ鋼の使用
は必須と考えられる。一方上述の極低Ｃ鋼にかかわる問
題点は、多かれ少なかれ表面近傍の元素の存在状態と、
密接に影響を及ぼしあっていることは明瞭である。そこ
で本発明者らは数多くの調査および実験室的な確認を行
った結果、表面に炭素あるいは窒素の濃化層が適当な厚
さおよび濃度で存在するように連続焼鈍炉において適切
な条件で浸炭または浸室雰囲気にさらした後適切な条件
で冷却し再拡散を防止してやれば、極低Ｃ鋼の抱えてい
る欠点が一気に解決されることを見出したのである。In order to overcome the above situation, the present inventors have conducted various studies. In order to solve the above-mentioned problems while maintaining good mechanical properties (El, value, etc.), it is considered necessary to use an ultra-low C steel. On the other hand, the problems with the ultra-low C steel mentioned above are more or less the existence of elements near the surface,
It is clear that they have a close effect. Accordingly, the present inventors have conducted a number of investigations and laboratory confirmations, and as a result, carburized under appropriate conditions in a continuous annealing furnace so that a concentrated layer of carbon or nitrogen was present at an appropriate thickness and concentration on the surface. Alternatively, it has been found that if exposed to an immersion atmosphere and then cooled under appropriate conditions to prevent re-diffusion, the drawbacks of ultra-low C steel can be solved at once.
よって、本発明は連続焼鈍炉において浸炭または浸窒
雰囲気にさらした鋼板を適切な条件で冷却することによ
り、耐型かじり性、化成処理性、およびスポット溶接性
などの特性を向上させることができるよう表面の所定成
分の濃度を調整した冷延鋼板の製造方法を提供すること
を目的とする。Therefore, by cooling the steel sheet exposed to the carburizing or nitriding atmosphere in a continuous annealing furnace under appropriate conditions, it is possible to improve properties such as mold resistance, chemical conversion treatment, and spot weldability. It is an object of the present invention to provide a method for producing a cold-rolled steel sheet in which the concentration of a predetermined component on the surface is adjusted.
＜課題を解決するための手段＞ すなわち、原板である冷延鋼板を、加熱、均熱および
冷却ゾーンを有する焼鈍炉を用いて連続焼鈍するに際
し、 原板の冷延鋼板としてはC:0.01wt％以下のものを用
い、前記焼鈍炉における均熱後期あるいは冷却初期に、
所定の成分を濃化させる雰囲気を用いて前記冷延鋼板の
表面に前記所定の成分が濃化した層（以下、表面濃化層
という）を形成し、直ちに500℃までの平均冷却速度が2
0℃／秒超となるように冷却することを特徴とする表面
調整冷延鋼板の製造方法を提供するものである。<Means for Solving the Problems> That is, in continuously annealing a cold-rolled steel sheet as an original sheet using an annealing furnace having heating, soaking, and cooling zones, C: 0.01 wt% is used as the cold-rolled steel sheet of the original sheet. Using the following, in the late soaking or early cooling in the annealing furnace,
A layer in which the predetermined component is concentrated (hereinafter, referred to as a surface-concentrated layer) is formed on the surface of the cold-rolled steel sheet by using an atmosphere for concentrating the predetermined component, and the average cooling rate to 500 ° C. is 2 immediately.
An object of the present invention is to provide a method for producing a surface-conditioned cold-rolled steel sheet, which is cooled to a temperature exceeding 0 ° C./sec.
表面濃化層として浸炭層を形成する場合にはＣが0.01
wt％以下の原板を用い、表面濃化層として浸窒層を形成
する場合にはＣおよびＮが0.01wt％以下の原板を用いる
のがよい。When a carburized layer is formed as a surface-concentrated layer, C is 0.01%.
When an original plate of not more than wt% is used and a nitriding layer is formed as a surface-concentrated layer, it is preferable to use an original plate having C and N of 0.01 wt% or less.
上記原板としての鋼板は、さらに、Si:1.0wt％以下、
Mn:1.0wt％以下、P:0.2wt％以下、S:0.05wt％以下、Al:
0.01〜0.1wt％およびN:0.01wt％以下を含有し、残部はF
eおよび不可避的不純物よりなるものが好ましく、さら
に原板は、Ti:0.001〜0.15wt％および／またはNb:0.001
〜0.10wt％を含有するのがより好ましい。The steel sheet as the original sheet further contains Si: 1.0 wt% or less,
Mn: 1.0 wt% or less, P: 0.2 wt% or less, S: 0.05 wt% or less, Al:
0.01 to 0.1 wt% and N: 0.01 wt% or less, with the balance being F
e and unavoidable impurities are preferable, and the original plate is composed of 0.001 to 0.15 wt% of Ti and / or 0.001% of Nb.
More preferably, it contains 0.10 wt%.
以下に本発明をさらに詳細に説明する。 Hereinafter, the present invention will be described in more detail.
本発明は、所要の特性を得るために下記組成の冷延鋼
板（原板）の表面に連続焼鈍法により浸炭層または浸窒
層を形成する方法に関する。The present invention relates to a method for forming a carburized layer or a nitriding layer on a surface of a cold-rolled steel sheet (original sheet) having the following composition by a continuous annealing method in order to obtain required characteristics.
本発明は、Ｃ≦0.01wt％を含有する極低炭素鋼板を原
板とし、加熱、均熱および冷却ゾーンを有する連続焼鈍
炉を用いて、後述するように浸炭用雰囲気および浸炭条
件を設定することにより、耐型かじり性、化成処理およ
びスポット溶接性などの特性に優れた表面調整冷延鋼板
を製造する方法を提供する。According to the present invention, an ultra-low carbon steel sheet containing C ≦ 0.01 wt% is used as a base plate, and a carburizing atmosphere and carburizing conditions are set as described below using a continuous annealing furnace having heating, soaking, and cooling zones. Accordingly, the present invention provides a method for producing a surface-conditioned cold-rolled steel sheet having excellent properties such as mold resistance, chemical conversion treatment, and spot weldability.
本発明が適用される鋼板は、基本的には、浸炭により
表面のＣ濃度を本発明が目的とする特性を満足するよう
に調整するものであり、連続焼鈍法を適用してもプレス
成形性などの良好な機械的性質を得るために、Ｃは0.01
wt％以下の極低Ｃ域にすることが必須である。これ以上
では、低Ｃ鋼並またはそれ以上の材質を得ることは不可
能である。The steel sheet to which the present invention is applied basically adjusts the C concentration of the surface by carburization so as to satisfy the characteristics aimed at by the present invention. In order to obtain good mechanical properties such as
It is indispensable to set the extremely low C region of wt% or less. Above this, it is not possible to obtain a material that is as low or better than low C steel.
本発明はまた、Ｃ≦0.01wt％、Ｎ≦0.01wt％を含有す
る極低炭素鋼板を原板とし、加熱、均熱および冷却ゾー
ンを有する連続焼鈍炉を用いて、後述するように浸窒用
雰囲気および浸窒条件を設定することにより、耐型かじ
り性、化成処理性およびスポット溶接性などの特性に優
れた表面調整冷延鋼板を製造する方法を提供する。The present invention also provides a method for nitriding as described later using a very low carbon steel sheet containing C ≦ 0.01 wt% and N ≦ 0.01 wt% as a base plate and using a continuous annealing furnace having heating, soaking and cooling zones. Provided is a method for producing a surface-conditioned cold-rolled steel sheet having excellent characteristics such as mold galling resistance, chemical conversion treatment properties, and spot weldability by setting an atmosphere and nitriding conditions.
本発明が適用される鋼板は、基本的には、浸窒により
表面のＮ濃度を本発明が目的とする特性を満足するよう
に調整するものであり、連続焼鈍法を適用してもプレス
成形状などのプレス成形性などの良好な機械的性質を得
るために、Ｃは0.01wt％以下、Ｎは0.01wt％以下の極低
Ｃ、Ｎ域にすることが必須である。これ以上では、低
Ｃ、Ｎ鋼並またはそれ以上の材質を得ることは不可能で
ある。The steel sheet to which the present invention is applied basically adjusts the N concentration on the surface by nitriding so as to satisfy the characteristics intended by the present invention. In order to obtain good mechanical properties such as press formability such as the shape, it is essential that C is 0.01 wt% or less and N is an extremely low C and N range of 0.01 wt% or less. Above this, it is not possible to obtain materials of low C, N steel or better.
さらに、鋼板原板は、Si、Mn、Ｐ、Ｓ、Alを以下に述
べる範囲内で含有しているが、本発明の目的上好ましく
ない。Furthermore, although the original steel sheet contains Si, Mn, P, S, and Al within the range described below, it is not preferable for the purpose of the present invention.
Siは鋼を強化する作用があり、所望の強度に応じて必
要量添加されるが、添加量が1.0wt％を超えると深絞り
性に悪影響を及ぼすので1.0wt％以下とするのがよい。Si has the effect of strengthening the steel and is added in a required amount according to the desired strength. However, if the added amount exceeds 1.0 wt%, the deep drawability is adversely affected.
MnもSiと同様、Ｓの残留による熱間割れを避けるとい
う鋼を強化する作用があり、所望の強度に応じて必要量
添加されるが、添加量が1.0wt％を超えるとやはり加工
性に悪影響を及ぼすので1.0wt％以下が好ましい。Like Mn, Mn also has the effect of strengthening the steel to avoid hot cracking due to the residual S, and is added in a required amount depending on the desired strength. However, if the added amount exceeds 1.0 wt%, the workability also deteriorates. 1.0 wt% or less is preferable because it has an adverse effect.
ＰもSiもMnと同様、鋼を強化する作用があり、所望の
強度に応じて必要量添加されるが、添加量が0.2wt％を
越えると加工性に悪影響を及ぼすので0.2wt％以下にす
るのがよい。Both P and Si, like Mn, have the effect of strengthening steel and are added in the required amount according to the desired strength. However, if the added amount exceeds 0.2 wt%, the workability is adversely affected. Good to do.
Ｓは、少なければ少ないほど深絞り性が向上するので
極力低減することが好ましいが、その含有量が0.05wt％
以下ではさほど悪影響おを及ぼさないので0.05wt％以下
にするのがよい。The smaller the content of S, the better the deep drawability is. Therefore, it is preferable to reduce the content of S as much as possible.
In the following, it does not adversely affect so much, so it is preferable to set the content to 0.05 wt% or less.
Alは脱酸剤として、また後述する炭窒化物形成元素の
歩留まり向上すなわち鋼中Ｎの固定による耐時効性の向
上のために添加されるが、含有量が0.01wt％に満たない
とその添加効果に乏しく、一方0.1wt％を越えて添加し
てもその効果は飽和に達するので、0.01〜0.1wt％の範
囲にするのがよい。Al is added as a deoxidizing agent and for improving the yield of carbonitride forming elements described later, that is, for improving the aging resistance by fixing N in steel, but if the content is less than 0.01 wt%, the addition of Al is added. The effect is poor. On the other hand, even if it is added in excess of 0.1% by weight, the effect reaches saturation, so it is preferable to be in the range of 0.01 to 0.1% by weight.
ＮはＣについて述べたと同様の理由で0.01wt％以下に
するのが好ましい。N is preferably set to 0.01% by weight or less for the same reason as described for C.
さらに、本発明で原板として用いる冷延鋼板には、Ti
および／またはNbを下記の通り添加してもよい。Further, the cold-rolled steel sheet used as the original sheet in the present invention includes Ti
And / or Nb may be added as described below.
これらの元素の添加は、鋼中に固溶して耐時効性を劣
化させるＣやＮを固定するのに有効である。さらには、
形成された析出物のサイズが適度に粗大であるため、連
続焼鈍時の粒成長を促進されるので、加工性特にElや
値の向上には有利となる。The addition of these elements is effective for fixing C and N which form a solid solution in steel and deteriorate aging resistance. Moreover,
Since the size of the formed precipitate is appropriately coarse, the growth of grains during continuous annealing is promoted, which is advantageous for improving workability, particularly El and the value.
Tiは炭窒化物形成元素であり、鋼中の固溶（Ｃ、Ｎ）
を低させ、深絞り性に有利な｛111｝方位を優先的に形
成されるために添加される。しかしながら添加量が0.00
1wt％未満ではその添加効果に乏しく、一方0.15wt％を
越えて添加してもそれ以上の効果は得られず、むしろ鋼
板表面性状および延性の劣化につながるので、0.001〜
0.15wt％の範囲に限定する。Ti is a carbonitride forming element and solid solution in steel (C, N)
In order to preferentially form a {111} orientation that is advantageous for deep drawability. However, the addition amount is 0.00
If it is less than 1 wt%, the effect of the addition is poor. On the other hand, if it exceeds 0.15 wt%, no further effect can be obtained, but rather the deterioration of the surface properties and ductility of the steel sheet.
Limited to the range of 0.15 wt%.
Nbは炭化物形成元素であり、鋼中の固溶Ｃを低減させ
るとともに、熱延鋼板組織の微細化をそくして、深絞り
性に有利な｛111｝方位を優先的に形成させるために添
加される。しかしながら添加量が0.001wt％未満ではそ
の添加の効果が乏しく、一方0.10wt％を越えて添加して
もそれ以上の効果は得られず、むしろ延性の劣化につな
がるので0.001〜0.10wt％の範囲に限定する。Nb is a carbide forming element, and is added to reduce the solid solution C in steel and to preferentially form the {111} orientation that is advantageous for deep drawability by minimizing the microstructure of the hot-rolled steel sheet. You. However, if the addition amount is less than 0.001 wt%, the effect of the addition is poor. On the other hand, if it exceeds 0.10 wt%, no further effect can be obtained, and rather it leads to deterioration of ductility. Limited to.
上記のような成分を有する鋼板は連続焼鈍を施され
る。The steel sheet having the above components is subjected to continuous annealing.
本発明において好適に用いられるCAL（Continuous An
nealing Line）は加熱、均熱および冷却ゾーンを有す
る。浸炭は均熱ゾーン後期から冷却ゾーンにかけて浸炭
用雰囲気として、浸炭に適する条件にして行なう。CAL (Continuous An) that is preferably used in the present invention
nealing Line) has heating, soaking and cooling zones. Carburizing is performed in a condition suitable for carburizing in an atmosphere for carburizing from the latter stage of the soaking zone to the cooling zone.
浸炭用雰囲気としては、N2＋H2を主体とするガス中に
COを適量添加したものを用いる。そして、浸炭条件は適
切に選定する。As a carburizing atmosphere, in a gas mainly composed of N 2 + H 2
Use what added an appropriate amount of CO. And carburizing conditions are selected appropriately.
また、浸窒は均熱ゾーン後期から冷却ゾーンにかけて
浸窒用雰囲気として、浸窒に適する条件にして行なう。In addition, the nitriding is performed from the latter part of the soaking zone to the cooling zone under an atmosphere suitable for nitriding under conditions suitable for nitriding.
浸窒用雰囲気としては、N2＋H2を主体とするガス中に
NH3などのＮ源を適量添加したものを用いる。そして、
浸窒条件は適切に選定する。As a nitriding atmosphere, in a gas mainly composed of N 2 + H 2
An N source such as NH 3 to which an appropriate amount is added is used. And
Nitriding conditions should be appropriately selected.
本発明においては、上記焼鈍炉における均熱後期ある
いは冷却初期に、浸炭または浸窒用雰囲気に、上記原板
を所要時間さらして原板の表面にＣまたはＮを拡散させ
てＣまたはＮの濃化層を形成する。In the present invention, in the latter stage of soaking in the annealing furnace or in the early stage of cooling, the original plate is exposed to a carburizing or nitriding atmosphere for a required time to diffuse C or N on the surface of the original plate, thereby forming a concentrated layer of C or N. To form
上述したようにして原板の表面に浸炭層または浸窒層
という表面濃化層を形成したら、これらの濃化層が再拡
散により消滅しないように、焼鈍温度から500℃に至ま
では20℃／秒超の平均冷却速度で冷却する。After forming a carburized layer or a carburized layer on the surface of the original sheet as described above, the carburized layer or the carbonitrided layer is formed at a temperature of 20 ° C./50° C. from the annealing temperature to 500 ° C. so as not to disappear by re-diffusion. Cool at an average cooling rate of more than a second.
500℃に至まではと限定するのは、これ以上の温度で
は、濃化させたＣまたはＮの再拡散速度が速いためであ
り、この間は20℃／秒超の平均冷却速度で冷却する。20
℃／秒以下冷却速度では、一旦形成したＣまたはＮの表
面濃化層中の濃化元素が鋼板の内部に向けて拡散してし
まい、表面濃化層を保持できなくなる。The reason why the temperature is limited to 500 ° C. is that at a temperature higher than this, the re-diffusion rate of the concentrated C or N is high, and during this time, cooling is performed at an average cooling rate of more than 20 ° C./sec. 20
At a cooling rate of not more than ° C./sec, the condensed element in the once formed C or N surface concentrated layer diffuses toward the inside of the steel sheet, and the surface concentrated layer cannot be maintained.
以上述べたようにして連続焼鈍法により浸炭処理が施
されて表面層のＣまたはＮ濃度が適切に、すなわち、耐
型かじり性、化成処理性およびスポット溶接性などの諸
特性が優れた表面調整冷延鋼板の製造することができ
る。As described above, the C or N concentration in the surface layer is appropriately adjusted by the carburizing treatment by the continuous annealing method, that is, the surface conditioning is excellent in various properties such as mold galling resistance, chemical conversion treatment properties, and spot weldability. Cold rolled steel sheet can be manufactured.
このようにして製造された表面調整冷延鋼板にはさら
に表面処理を施すことができる。表面処理としては、亜
鉛めっきのほか、Zn−FeあるいはZn−Niめっき鋼板など
の亜鉛系合金めっき、下層樹脂皮膜、上層Zn−Ni鋼板な
どの亜鉛系複合めっきを挙げることができる。The surface-conditioned cold-rolled steel sheet manufactured as described above can be further subjected to a surface treatment. Examples of the surface treatment include zinc-based alloy plating such as Zn-Fe or Zn-Ni-plated steel sheet, and zinc-based composite plating such as lower resin film and upper Zn-Ni steel sheet, in addition to zinc plating.
＜実施例＞ 次に本発明の実施例に基づいて具体的に説明する。<Example> Next, a specific description will be given based on an example of the present invention.
（実施例１） 表１に示す５種類の低Ｃ鋼を、転炉溶製後RH脱ガスと
引き続く連続鋳造法で作成した。(Example 1) Five types of low C steels shown in Table 1 were produced by RH degassing after converter melting and continuous casting.
該スラブを加熱炉に操入し1230℃に加熱した後、熱間
圧延で880℃で仕上げ、535℃で巻き取り3.2mm厚の熱延
コイルとした。次いで、酸洗後冷間圧延で0.8mm厚の冷
延鋼板とした。該冷延コイルを、連続焼鈍ライン（CA
L）で下記の条件で急速加熱、均熱保持、急速冷却し
た。このとき均熱・冷却ゾーンで下記の雰囲気を用いて
浸炭した。The slab was placed in a heating furnace, heated to 1230 ° C., finished at 880 ° C. by hot rolling, and wound at 535 ° C. to form a 3.2 mm thick hot rolled coil. Next, a cold-rolled steel sheet having a thickness of 0.8 mm was formed by cold rolling after pickling. The cold-rolled coil is connected to a continuous annealing line (CA
In L), rapid heating, soaking, and rapid cooling were performed under the following conditions. At this time, carburizing was performed in the soaking / cooling zone using the following atmosphere.
この結果を表２に示す。Table 2 shows the results.
（１）焼鈍条件 昇温速度 20℃／秒 均熱保持温度 750℃ 均熱保持時間 30秒 冷却速度 ２℃／秒以上 （２）浸炭雰囲気 H2 ３％ Co 0.5％ N2 残り （実施例２） 実施例１で用いた表１に示す鋼板について実施例１と
同様にして浸窒した。その結果を表３に示す。(1) annealing conditions Atsushi Nobori rate 20 ° C. / sec soaking temperature 750 ° C. soaking time of 30 seconds cooling rate 2 ° C. / sec or more (2) a carburizing atmosphere H 2 3% Co 0.5% N 2 remaining (Example 2) The steel sheets shown in Table 1 used in Example 1 were nitrided in the same manner as in Example 1. Table 3 shows the results.
（１）焼鈍条件 昇温速度 20℃／秒 均熱保持温度 600℃ 均熱保持時間 30秒 冷却速度 ２℃／秒以上 （２）浸窒雰囲気 H2 ３％ NH3 ５％ N2 残り ＜発明の効果＞ 本発明によれば、連続焼鈍法において、その浸炭およ
び浸窒雰囲気および浸炭または浸窒条件を適切に選定
し、その後の冷却速度を適切に選定することにより、耐
型かじり性、化成処理性、スポット溶接性などの諸特性
の優れた表面調整冷延鋼板を製造することができる。(1) annealing conditions Atsushi Nobori rate 20 ° C. / sec soaking temperature 600 ° C. soaking time of 30 seconds cooling rate 2 ° C. / sec or more (2) nitriding atmosphere H 2 3% NH 3 5% N 2 remaining <Effect of the Invention> According to the present invention, in the continuous annealing method, the carburizing and nitriding atmosphere and the carburizing or nitriding conditions are appropriately selected, and the subsequent cooling rate is appropriately selected, so that the mold resistance to galling is improved. It is possible to manufacture a surface-conditioned cold-rolled steel sheet having excellent properties such as chemical conversion property and spot weldability.
フロントページの続き (72)発明者 加藤 俊之 千葉県千葉市川崎町１番地 川崎製鉄株 式会社技術研究本部内 (72)発明者 阿部 英夫 千葉県千葉市川崎町１番地 川崎製鉄株 式会社技術研究本部内 (56)参考文献 特開 昭60−149729（ＪＰ，Ａ) (58)調査した分野(Int.Cl.6，ＤＢ名) C23C 8/20,8/26Continuing from the front page (72) Inventor Toshiyuki Kato 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Corporation Research and Development Headquarters (72) Inventor Hideo Abe 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Technical Research (56) References JP-A-60-149729 (JP, A) (58) Fields investigated (Int. Cl. 6 , DB name) C23C 8/20, 8/26
Claims (6)
冷却ゾーンを有する焼鈍炉を用いて連続焼鈍するに際
し、 原板の冷延鋼板としてはC:0.01wt％以下ものを用い、前
記焼鈍炉における均熱後期あるいは冷却初期に、所定の
成分を濃化させる雰囲気を用いて前記冷延鋼板の表面に
前記所定の成分が濃化した層（以下、表面濃化層とい
う）を形成し、直ちに500℃までの平均冷却速度が20℃
／秒超となるように冷却することを特徴とする表面調整
冷延鋼板の製造方法。(1) When continuously annealing a cold-rolled steel sheet as an original sheet using an annealing furnace having heating, soaking and cooling zones, the cold-rolled steel sheet of the original sheet is C: 0.01 wt% or less. A layer in which the predetermined component is concentrated (hereinafter referred to as a surface-concentrated layer) is formed on the surface of the cold-rolled steel sheet using an atmosphere for concentrating the predetermined component at a later stage of soaking in the annealing furnace or at an early stage of cooling. Immediately, the average cooling rate to 500 ℃ is 20 ℃
A method for producing a surface-conditioned cold-rolled steel sheet, wherein the steel sheet is cooled so as to be more than 1 / sec.
の表面調整冷延鋼板の製造方法。2. The method according to claim 1, wherein the surface-concentrated layer is a carburized layer.
N:0.01wt％以下のものを用い、表面濃化層が浸窒層であ
る請求項１の表面調整冷延鋼板の製造方法。3. The cold rolled steel sheet of the original sheet is C: 0.01 wt% or less,
The method for producing a surface-conditioned cold-rolled steel sheet according to claim 1, wherein N: 0.01 wt% or less is used, and the surface-concentrated layer is a nitriding layer.
下、Mn:1.0wt％以下、P:0.2wt％以下、S:0.05wt％以
下、Al:0.01〜0.1wt％およびN:0.01wt％以下を含有し、
残部はFeおよび不可避的不純物よりなる請求項１〜３の
いずれかに記載の表面調整冷延鋼板の製造方法。4. The cold-rolled steel sheet as an original sheet further comprises: Si: 1.0% by weight or less, Mn: 1.0% by weight or less, P: 0.2% by weight or less, S: 0.05% by weight or less, Al: 0.01 to 0.1% by weight and N: contains 0.01wt% or less,
The method for producing a surface-conditioned cold-rolled steel sheet according to any one of claims 1 to 3, wherein the balance comprises Fe and unavoidable impurities.
15wt％および／またはNb:0.01〜0.10wt％を含有する請
求項１〜４のいずれかに記載の表面調整冷延鋼板の製造
方法。5. The cold-rolled steel sheet as an original sheet further has a Ti: 0.001-0.
The method for producing a surface-conditioned cold-rolled steel sheet according to any one of claims 1 to 4, comprising 15 wt% and / or Nb: 0.01 to 0.10 wt%.
秒超になるように冷却した後の表層部と中心部のＣまた
はＮ濃度の比が、2.9倍以上の表面濃化層である請求項
１〜５のいずれかに記載の表面調整冷延鋼板の製造方
法。6. The method according to claim 1, wherein the surface-concentrated layer has an average cooling rate of 20 ° C. /
The surface-adjusted cold-rolled steel sheet according to any one of claims 1 to 5, wherein the ratio of the C or N concentration of the surface layer portion and the central portion after cooling to more than seconds is a surface concentrated layer of 2.9 times or more. Manufacturing method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP33975389A JP2818675B2 (en) | 1989-12-28 | 1989-12-28 | Manufacturing method of surface-conditioned cold-rolled steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP33975389A JP2818675B2 (en) | 1989-12-28 | 1989-12-28 | Manufacturing method of surface-conditioned cold-rolled steel sheet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH03199368A JPH03199368A (en) | 1991-08-30 |
| JP2818675B2 true JP2818675B2 (en) | 1998-10-30 |
Family
ID=18330483
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP33975389A Expired - Lifetime JP2818675B2 (en) | 1989-12-28 | 1989-12-28 | Manufacturing method of surface-conditioned cold-rolled steel sheet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2818675B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5810948A (en) * | 1995-07-12 | 1998-09-22 | Nippon Steel Corporation | Nitriding steel excellent in formability and susceptibility to nitriding and press formed article thereof |
-
1989
- 1989-12-28 JP JP33975389A patent/JP2818675B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH03199368A (en) | 1991-08-30 |
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