JPH05202421A - Production of cold rolled steel sheet for superdeep drawing - Google Patents

Abstract

PURPOSE:To produce a cold rolled steel sheet for superdeep drawing at a low cost by subjecting a slab of a steel, prepared by adding specific amounts of Mn to an ultralow carbon steel containing Ti, N, etc., to hot rolling under specific temp. conditions, to coiling, to pickling, to cold rolling, and then to annealing. CONSTITUTION:A slab of an ultralow carbon steel having a composition consisting of, by weight, 0.0011-0.0025% C, 0.1-1.0% Mn, <0.01% S, <0.003% N, 0.01-0.1% Al, <0.04% Ti (where Ti is contained by the amount not lower than the atomic equivalent ratio of the total content of C and N), and the balance Fe is heated up to 1100-1300 deg.C and hot-rolled under the temp. conditions where heating temp. X represented by absolute temp. and hot finish rolling inlet temp. T satisfy inequality I and inequality II, respectively, where Ti means [(Ti in the steel)-3.43X(N% in the steel)]. Successively, the resulting hot rolled plate is coiled at 400-700 deg.C and pickled to undergo the removal of small amounts of scale. Then, cold rolling and annealing are done. By this method, the cold rolled steel sheet for superdeep drawing excellent in press workability can be produced at a low cost while minimizing the additive quantity of Ti.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、超深絞り用冷延鋼板の
製造方法に関し、特にランクフォード値(ｒ値)の改善を
可能にしたものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cold-rolled steel sheet for ultra deep drawing, and in particular, enables improvement of Rankford value (r value).

【０００２】[0002]

【従来の技術及び発明が解決しようとする課題】自動車
用部品、特にフェンダー、オイルパン等の部品の成形で
は深絞り性が要求され、従来から、ｒ値が２.０前後の
超深絞り用冷延鋼板が使用されてきた。更に近年、ユー
ザーニーズの多様化、或いはファッション性の追求に伴
い、一層高度のプレス成形性の求められる部品が増加し
つつある。2. Description of the Related Art Deep drawing is required in the molding of automobile parts, especially parts such as fenders and oil pans, and has been conventionally used for ultra deep drawing with an r value of about 2.0. Cold rolled steel sheets have been used. Furthermore, in recent years, with the diversification of user needs or the pursuit of fashionability, the number of parts requiring higher press-formability is increasing.

【０００３】従来、上述のような超深絞り用冷延鋼板と
しては、極低Ｃ鋼にＣ或いはＮを十分固着するに必要な
Ｔi或いはＮbを添加したＩＦ鋼(Ｉnterstitial Ｆree
Ｓteel)がよく知られている。しかしながら、これらの
鋼においては、ＴiはＮ、Ｓ及びＣの総量の原子当量比
以下の添加では固溶Ｃが残存し、十分な特性を得ること
ができないと言われてきた。Conventionally, as a cold-rolled steel sheet for ultra deep drawing as described above, an IF steel (Interstitial Free) obtained by adding Ti or Nb necessary for sufficiently adhering C or N to an extremely low C steel is used.
Steel) is well known. However, in these steels, it has been said that when Ti is added in an amount equal to or less than the atomic equivalent ratio of the total amount of N, S and C, solid solution C remains and sufficient properties cannot be obtained.

【０００４】また、Ｍnは、焼鈍時の粒成長性を劣化さ
せる成分として知られており、高ｒ値を得るには、Ｎ、
Ｓ及びＣの総量の原子当量比以上の十分なＴiの添加、
及びＭnの低減を行うことが必要であると言われてい
る。そのため、Ｔiの多量添加によるコストアップ、Ｍn
Ｓの十分な析出が行われないことによるスラブの熱間脆
性割れ等の問題点があった。Further, Mn is known as a component that deteriorates grain growth during annealing. To obtain a high r value, N,
Sufficient addition of Ti equal to or more than the atomic equivalent ratio of the total amount of S and C,
It is said that it is necessary to reduce Mn and Mn. Therefore, the cost increase due to the large addition of Ti, Mn
There is a problem such as hot brittle cracking of the slab due to insufficient precipitation of S.

【０００５】例えば、Ｔi添加極低炭素冷延鋼板にＭnを
添加することにより、ｒ値が向上することが「鉄と
鋼」、７６(１９９０)、ｐ４２２に示されている。しか
し、これは、Ｐ、Ｍnを複合添加した高張力鋼板を得る
技術であって、Ｍnを添加するのは、これによりＭnＳが
形成されるが、その結果、ＦeＴiＰの析出状況を変化さ
せ、ｒ値に好ましい再結晶集合組織を形成させる役割を
果たすためであるとされている。For example, it is shown in "Iron and Steel", 76 (1990), p422 that the r value is improved by adding Mn to a Ti-added ultra-low carbon cold-rolled steel sheet. However, this is a technique for obtaining a high-strength steel sheet in which P and Mn are added in combination, and the addition of Mn causes MnS to be formed. As a result, the precipitation state of FeTiP is changed, and r It is said that this is because it plays a role of forming a recrystallized texture that is preferable for the value.

【０００６】以上のように、従来の超深絞り用冷延鋼板
では、Ｔi添加ＩＦ鋼によってある程度の前進が得られ
たとは言え、各種特性値のより一層の向上、それに伴う
操業条件の緩和、歩留りの向上等、残された問題も多
い。特に、極低炭素冷延鋼板のｒ値をＭnにより改善を
図る技術は未だ確立されていないのが実情である。As described above, in the conventional cold-rolled steel sheet for ultra-deep drawing, although the Ti-added IF steel has made some progress, it is possible to further improve various characteristic values and to reduce the operating conditions. There are many remaining problems such as improvement in yield. In particular, the reality is that the technology for improving the r value of ultra-low carbon cold-rolled steel sheet by Mn has not yet been established.

【０００７】本発明は、かゝる状況のもとで、極低炭素
冷延鋼板のｒ値をＭnにより改善を図ると共にＴi量を低
減して超深絞り用冷延鋼板を低コストにて製造し得る方
法を提供することを目的とするものである。Under such circumstances, the present invention aims to improve the r value of an ultra low carbon cold rolled steel sheet by Mn and reduce the Ti content to produce a cold rolled steel sheet for ultra deep drawing at low cost. It is intended to provide a method that can be manufactured.

【０００８】[0008]

【課題を解決するための手段】前記課題を解決するた
め、本発明者らは、ｒ値の改善を図り、Ｔi量を低減し
た超深絞り用冷延鋼板の製造方法について検討した結
果、まず、極低Ｃ−ＩＦ鋼において、Ｍn量を適量添加
することにより、ＭnＳが析出し、ＴiＳ分のＴiがＴiＣ
の析出に働くため、Ｔi添加量がＣ、Ｎ、Ｓの原子当量
比以下であっても固溶Ｃが残存しないことを知見した。In order to solve the above-mentioned problems, the inventors of the present invention investigated the method for producing a cold-rolled steel sheet for ultra deep drawing in which the r value was improved and the Ti amount was reduced. In ultra-low C-IF steel, by adding an appropriate amount of Mn, MnS is precipitated and the TiS content is TiC.
It has been found that solid solution C does not remain even if the Ti addition amount is not more than the atomic equivalent ratio of C, N, and S because it acts on the precipitation of Ti.

【０００９】そこで、本発明者らは、更に鋭意研究を重
ねた結果、適量のＭnを添加すると共に、スラブ加熱温
度、Ｔi、Ｎ及びＳ量を制御することにより、熱間圧延
前のスラブ再加熱時に鋼中の３０％以上のＳ量をＭnＳ
として析出させることで、熱延時にＴiＳの析出を制御
し、比較的粗大な析出物を得ることができることを知見
した。これに伴い、熱延過程で析出する微細なＴiＳよ
りも冷延焼鈍時の回復、再結晶過程での粒成長性が良く
なり、優れた深絞り性を持つことを見い出した。これに
よって、その製造コストが低減でき、また、熱間加工時
の脆化を抑制できることが判明し、ここに本発明を完成
したものである。Therefore, as a result of further intensive studies, the present inventors added an appropriate amount of Mn and controlled the slab heating temperature, Ti, N, and S amounts to re-produce the slab before hot rolling. 30% or more of S in steel when heated is MnS
It has been found that the precipitation of TiS can be controlled during hot rolling and a relatively coarse precipitate can be obtained. Along with this, it has been found that recovery during cold rolling annealing and grain growth during recrystallization are better than fine TiS that precipitates during hot rolling, and that it has excellent deep drawability. As a result, it was found that the manufacturing cost can be reduced and brittleness during hot working can be suppressed, and the present invention has been completed here.

【００１０】すなわち、本発明は、Ｃ:０.００１１〜
０.００２５％、Ｍn:０.１〜１.０％、Ｓ:０.０１％以
下、Ｎ:０.００３％以下、Ａl:０.０１〜０.１％、Ｔi:
０.０４％以下で、かつ、ＴiをＮとＣの総量の原子当量
比以上に含み、残部がＦe及び不可避的不純物元素より
なる鋼について、１１００〜１３００℃の範囲に加熱
し、かつ、該加熱温度及び熱間仕上げ圧延入側温度が下
記式(１)、(２)を満足する条件で熱間圧延を行い、４０
０〜７５０℃の温度範囲で巻取り、これを酸洗し、冷間
圧延、焼鈍を行うことを特徴とする超深絞り用冷延鋼板
の製造方法を要旨とするものである。That is, according to the present invention, C: 0.0011-
0.0025%, Mn: 0.1 to 1.0%, S: 0.01% or less, N: 0.003% or less, Al: 0.01 to 0.1%, Ti:
For steel containing 0.04% or less and Ti in an atomic equivalent ratio of the total amount of N and C or more, with the balance being Fe and unavoidable impurity elements, heated to a range of 1100 to 1300 ° C., and Hot rolling is performed under the conditions that the heating temperature and the hot finish rolling inlet temperature satisfy the following equations (1) and (2).
The gist is a method for producing a cold-rolled steel sheet for ultra-deep drawing, which comprises winding in a temperature range of 0 to 750 ° C., pickling it, cold rolling and annealing.

【００１１】記Note

【化３】 [Chemical 3]

【化４】 ここで、Ｓ：鋼中Ｓ量(％) Ｔi：鋼中Ｔi量(％)−３.４３×鋼中Ｎ量(％) Ｍn：鋼中Ｍn量(％) Ｘ：加熱温度(℃＋２７３) Ｔ：熱間仕上げ圧延入側温度(℃＋２７３)[Chemical 4] Here, S: S content in steel (%) Ti: Ti content in steel (%)-3.43 x N content in steel (%) Mn: Mn content in steel (%) X: Heating temperature (° C + 273) T: Hot finish rolling inlet temperature (° C + 273)

【００１２】以下に本発明を更に詳細に説明する。The present invention will be described in more detail below.

【００１３】[0013]

【作用】[Action]

【００１４】まず、本発明における化学成分の限定理由
について説明する。First, the reasons for limiting the chemical components in the present invention will be explained.

【００１５】Ｃ：従来のＩＦ鋼は０.００３０％程度の
Ｃを含み、それを固定するに十分なＴiを添加して初め
て高ｒ値が得られた。これは、固溶Ｃが冷延若しくは回
復再結晶過程で転位の移動に影響を及ぼし、(１１１）
集合組織の発達を抑制することが原因と知られている。
しかし、本発明者らの研究により、Ｃ量を０.００１１
〜０.００２５％にすることにより、その析出及び固定
のために添加する炭化物形成元素の絶対量を少なくする
ことができ、析出物の量も低減できることがわかった。
したがって、Ｃ量は０.００１１〜０.００２５％の範囲
とする。C: Conventional IF steel contains about 0.0030% C, and a high r value was obtained only by adding Ti sufficient to fix it. This is because solid solution C affects the movement of dislocations during cold rolling or recovery recrystallization.
It is known that the suppression of the development of the texture is the cause.
However, according to the studies by the present inventors, the amount of C was 0.0011.
It was found that by setting the content to be 0.0025%, the absolute amount of the carbide-forming element added for the precipitation and fixation can be reduced, and the amount of the precipitate can be reduced.
Therefore, the amount of C is set in the range of 0.0011 to 0.0025%.

【００１６】Ｍn、Ｔi：Ｍn量を０.１〜１.０％、Ｔi量
を０.０４％以下で、かつ、ＮとＣをＴiで固定すること
により、冷延板の焼鈍時の粒成長性が良好になり、ｒ値
が向上する。しかし、Ｍn量が０.１％未満では必要とす
るＭnＳが十分得られず、また、１.０％を超えると延性
の低下が大きくなり、成形性が低下する。一方、Ｔi量
はＮとＣの総量の原子当量比より少ないと固溶Ｃ及び固
溶Ｎが存在し、ｒ値が低下する。またＴi量が０.０４％
を超えると焼鈍時の粒成長性を劣化させるだけでなく、
コストアップの要因ともなる。Mn, Ti: Mn content is 0.1 to 1.0%, Ti content is 0.04% or less, and N and C are fixed at Ti, so that grains during annealing of a cold rolled sheet can be obtained. The growth property is improved and the r value is improved. However, if the amount of Mn is less than 0.1%, the required MnS cannot be obtained sufficiently, and if it exceeds 1.0%, the ductility is greatly reduced and the formability is reduced. On the other hand, when the amount of Ti is less than the atomic equivalent ratio of the total amount of N and C, solid solution C and solid solution N exist and the r value decreases. Also, the Ti content is 0.04%
If it exceeds, not only does the grain growth during annealing deteriorate, but
It also causes a cost increase.

【００１７】Ｓ：Ｓ量が増加すると析出するＭnＳ量の
絶対量も増加し、伸びフランジ性に代表される局部延性
を劣化させるため、Ｓ量は０.０１％以下に制限しなけ
ればならない。S: As the amount of Sn increases, the absolute amount of MnS that precipitates also increases, and local ductility represented by stretch flangeability deteriorates. Therefore, the amount of S must be limited to 0.01% or less.

【００１８】Ａl：Ａlは脱酸に必要な元素であり、十分
に脱酸を行うには最低０.０１％のＡl量が必要である。
しかし、逆に０.１％を超えると脱酸が飽和に達するだ
けでなく、アルミナ系介在物が発生し、成形性を劣化さ
せるので好ましくない。Al: Al is an element necessary for deoxidation, and at least 0.01% of Al is necessary for sufficient deoxidation.
However, on the contrary, if it exceeds 0.1%, not only the deoxidation reaches saturation but also alumina-based inclusions are generated to deteriorate the formability, which is not preferable.

【００１９】Ｎ：Ｎ量の増加に伴い、それを固定するの
に必要なＴiの添加量が多くなり、コストアップを招く
他、析出物量も増加し、粒成長性が劣化し、ｒ値の向上
が得にくくなるので、Ｎ量はできるだけ低レベル、好ま
しくは０.００２％以下が望ましいが、所望の材質を得
るのに必要な最低限の値が０.００３％であることか
ら、Ｎ量は０.００３％以下とする。N: As the amount of N increases, the amount of addition of Ti necessary to fix it increases, which leads to an increase in cost, the amount of precipitates also increases, the grain growth property deteriorates, and the r value Since it is difficult to obtain the improvement, it is desirable that the N content is as low as possible, preferably 0.002% or less, but the minimum value necessary to obtain the desired material is 0.003%, so the N content is Is 0.003% or less.

【００２０】次に本発明の製造条件について説明する。Next, the manufacturing conditions of the present invention will be described.

【００２１】上記成分組成の鋼は通常行われる転炉等で
溶製される。溶製された溶鋼は鋼片とされるが、その方
法としては特に制限はなく、造塊法でもかまわない。鋼
片は室温まで冷却された後、熱延加熱炉に装入される
が、その際、一旦室温まで冷却せず、加熱炉に装入する
ＨＣＲ法でもかまわない。また、鋼片を再加熱すること
なくそのまま圧延することはもとより、短時間の保熱及
び／又は部分的な加熱の後に熱延しても本発明の効果は
何ら損なわれるものではない。The steel having the above-mentioned composition is melted in a converter which is usually used. The melted molten steel is used as a billet, but the method is not particularly limited, and an ingot method may be used. The steel slab is charged to the hot rolling heating furnace after being cooled to room temperature. At that time, the HCR method may be used in which the steel slab is not once cooled to room temperature but is charged to the heating furnace. Further, the effect of the present invention is not impaired at all not only by rolling the steel slab as it is without reheating but also by heat rolling for a short time and / or hot rolling after partial heating.

【００２２】鋼片の加熱温度については、通常の１１０
０〜１３００℃の範囲でよいが、仕上げ温度がＡr₃点以
上に確保できるのであれば、できるだけ低い方が望まし
い。Regarding the heating temperature of the steel slab, the usual 110
The temperature may be in the range of 0 to 1300 ° C., but if the finishing temperature can be secured at the Ar ₃ point or higher, it is desirable that it is as low as possible.

【００２３】但し、加熱温度は次式(１)を満たさなけれ
ばならない。However, the heating temperature must satisfy the following equation (1).

【化５】 [Chemical 5]

【００２４】この(１)式の条件を満たすことは、加熱温
度時において鋼中に含まれるＳの少なくとも３０％以上
がＭnＳとして存在していることを表わしている。Satisfying the condition of the equation (1) means that at least 30% or more of S contained in steel exists as MnS at the heating temperature.

【００２５】熱延条件はオーステナイト域での熱延終了
が好ましい。仕上げ温度がＡr₃点未満になると、冷延、
焼鈍後の特性を害する集合組織が形成される。また、こ
の際に熱間仕上げ圧延入側温度(Ｔ)は次式(２)を満たさ
なければならない。The hot rolling condition is preferably the end of hot rolling in the austenite region. When the finishing temperature is less than Ar ₃ points, cold rolling,
A texture is formed that impairs the properties after annealing. At this time, the hot finish rolling entry temperature (T) must satisfy the following equation (2).

【化６】 [Chemical 6]

【００２６】この(２)式の条件を満たすことは、仕上げ
圧延前の鋼中にＴiＳが殆ど存在していないことを表わ
している。Satisfaction of the condition of the equation (2) means that TiS is hardly present in the steel before finish rolling.

【００２７】巻取り温度は、固溶Ｃの固定のために規制
することが必要であるが、Ｃ量が極めて低い本鋼におい
ては、低温巻取りでも残存固溶Ｃ量は少なく、ｒ値の低
下は殆どないので、その下限は４００℃とする。しか
し、巻取り温度が７５０℃を超えると高温巻取り温度に
おける諸問題、例えば、スケール、表面欠陥等の問題が
発生するので、７５０℃を上限とする。The coiling temperature needs to be regulated for fixing the solid solution C. However, in the present steel having an extremely low C content, the residual solid solution C content is small even at low temperature winding, and the r value Since there is almost no decrease, the lower limit is 400 ° C. However, if the coiling temperature exceeds 750 ° C., various problems at high coiling temperature, such as scale and surface defects, occur, so 750 ° C. is set as the upper limit.

【００２８】次に、これを酸洗し、冷間圧延、焼鈍を行
うが、これらの条件は特に制限されない。なお、冷延条
件は冷延率が６５〜９０％であれば高いほどｒ値の向上
が得られるが、最低限６５％の冷延を加えれば所望の特
性が得られ、一方、９０％以上の冷延は通常のタンデム
ミルで１回の圧延で完了することは不可能である。焼鈍
条件は、均熱温度が再結晶温度以上、Ａc₃点未満の範囲
であれば加熱、冷却条件は特に規制されない。しかし、
Ａc₃点を超えてオーステナイト域まで加熱するとγ−α
変態時にランダム核生成をもたらし、極端にｒ値が劣化
するので留意する。Next, this is pickled, cold rolled and annealed, but these conditions are not particularly limited. As for the cold rolling conditions, if the cold rolling rate is 65 to 90%, the higher the r value is, the more the r value is improved. However, if cold rolling of at least 65% is added, desired characteristics can be obtained, while 90% or more. It is impossible to complete the cold-rolling with a single tandem mill in one rolling. Regarding the annealing conditions, if the soaking temperature is in the range of the recrystallization temperature or higher and less than the Ac ₃ point, heating and cooling conditions are not particularly limited. But,
When heating to the austenite range above the Ac ₃ point, γ-α
It should be noted that random nucleation occurs during transformation and the r value deteriorates extremely.

【００２９】本発明により得られる超深絞り用冷延鋼板
は、冷延前にＣ、ＮがＴiによって殆ど固定され、冷
延、焼鈍後も殆ど分解することがないため、過時効処理
は必要でないが、現状の連続焼鈍ラインに設置されてい
る過時効帯を通板し、通常のアルミキルド鋼に採用され
ているような過時効処理を加えても、何ら材質を劣化さ
せるものではない。The cold-rolled steel sheet for ultra-deep drawing obtained by the present invention requires overaging treatment because C and N are almost fixed by Ti before cold rolling and hardly decomposed even after cold rolling and annealing. However, even if the overaging zone installed in the current continuous annealing line is passed through and the overaging treatment as used in ordinary aluminum killed steel is added, the material is not deteriorated at all.

【００３０】次に本発明の実施例を示す。Next, examples of the present invention will be shown.

【００３１】[0031]

【実施例】【Example】

【表１】 に示す化学成分の供試鋼について常法により製造した鋼
片を[Table 1] About the sample steel with the chemical composition shown in

【表２】 に示す条件で加熱し、熱間圧延を行った後、巻取り、酸
洗後、８０％の圧下率で冷間圧延を施し、板厚０.８mm
の冷延板を得た。この冷延板に８５０℃×１分の焼鈍を
施し、引張試験を行った。[Table 2] After heating under the conditions shown in (1), hot rolling, winding, pickling, and cold rolling at a reduction rate of 80%, the plate thickness is 0.8 mm.
A cold rolled sheet of This cold-rolled sheet was annealed at 850 ° C. for 1 minute and a tensile test was conducted.

【００３２】試験結果は、表２に示すように、本発明の
製造条件により得られた本発明材１、３及び５は、いず
れもｒ値が２.４〜２.５程度の高い深絞り性を示してい
る。これに対し、単に、Ｍn添加量を増加した比較材６
(鋼Ｄ)、７(鋼Ｅ)及び９(鋼Ｇ)では、製造条件を本発明
範囲内の条件にしても、目的とする高い深絞り性を得る
ことができない。As shown in Table 2, the test results show that the invention materials 1, 3 and 5 obtained under the manufacturing conditions of the present invention have a high deep drawing with an r value of about 2.4 to 2.5. Showing sex. On the other hand, the comparative material 6 in which the amount of Mn added was simply increased
With (Steel D), 7 (Steel E) and 9 (Steel G), even if the manufacturing conditions are within the scope of the present invention, the desired high deep drawability cannot be obtained.

【００３３】[0033]

【発明の効果】以上詳述したように、本発明によれば、
自動車ボディ、オイルパン等に用いるプレス加工用鋼板
のプレス加工性を改善することができる。また、Ｔi添
加量を低減することができ、低温巻取り法によっても従
来の高温巻取り材と同等のｒ値を持つ冷延鋼板を製造す
ることができる。As described in detail above, according to the present invention,
It is possible to improve the press workability of the steel plate for press work used for automobile bodies, oil pans and the like. Further, the amount of addition of Ti can be reduced, and a cold rolled steel sheet having an r value equivalent to that of the conventional high temperature coiled material can be manufactured by the low temperature coiling method.

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】 重量％で(以下、同じ)、Ｃ:０.００１１
〜０.００２５％、Ｍn:０.１〜１.０％、Ｓ:０.０１％
以下、Ｎ:０.００３％以下、Ａl:０.０１〜０.１％、Ｔ
i:０.０４％以下で、かつ、ＴiをＮとＣの総量の原子当
量比以上に含み、残部がＦe及び不可避的不純物元素よ
りなる鋼について、１１００〜１３００℃の範囲に加熱
し、かつ、該加熱温度及び熱間仕上げ圧延入側温度が下
記式(１)、(２)を満足する条件で熱間圧延を行い、４０
０〜７５０℃の温度範囲で巻取り、これを酸洗し、冷間
圧延、焼鈍を行うことを特徴とする超深絞り用冷延鋼板
の製造方法。 記 【化１】 【化２】 ここで、Ｓ：鋼中Ｓ量(％) Ｔi：鋼中Ｔi量(％)−３.４３×鋼中Ｎ量(％) Ｍn：鋼中Ｍn量(％) Ｘ：加熱温度(℃＋２７３) Ｔ：熱間仕上げ圧延入側温度(℃＋２７３)1. In weight% (hereinafter the same), C: 0.0011
~ 0.0025%, Mn: 0.1-1.0%, S: 0.01%
Below, N: 0.003% or less, Al: 0.01 to 0.1%, T
i: 0.04% or less, Ti containing at least the atomic equivalent ratio of the total amount of N and C, and the balance being Fe and inevitable impurity elements, heated to a range of 1100 to 1300 ° C., and , Hot rolling is performed under the conditions that the heating temperature and the hot-finish rolling inlet temperature satisfy the following formulas (1) and (2).
A method for producing a cold-rolled steel sheet for ultra-deep drawing, which comprises winding in a temperature range of 0 to 750 ° C., pickling this, cold rolling and annealing. Note: [Chemical 2] Here, S: S content in steel (%) Ti: Ti content in steel (%)-3.43 x N content in steel (%) Mn: Mn content in steel (%) X: Heating temperature (° C + 273) T: Hot finish rolling inlet temperature (° C + 273)