JPH07100817B2 - Method for manufacturing slow-aging cold-rolled steel sheet - Google Patents
Method for manufacturing slow-aging cold-rolled steel sheetInfo
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- JPH07100817B2 JPH07100817B2 JP63292361A JP29236188A JPH07100817B2 JP H07100817 B2 JPH07100817 B2 JP H07100817B2 JP 63292361 A JP63292361 A JP 63292361A JP 29236188 A JP29236188 A JP 29236188A JP H07100817 B2 JPH07100817 B2 JP H07100817B2
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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、低炭素Alキルド鋼を素材とし、短時間過時効
処理を伴う連続焼鈍法で時効劣化の小さい冷延鋼板を製
造する方法に関するものである。TECHNICAL FIELD The present invention relates to a method for producing a cold-rolled steel sheet with low aging deterioration by a continuous annealing method with a short-time overaging treatment, using a low carbon Al killed steel as a raw material. It is a thing.
＜従来の技術＞ 従来、冷延鋼板の製造における焼鈍工程は、箱焼鈍法に
よって行われていた。この箱焼鈍法は、冷延鋼帯をコイ
ル状態のまま、数日間かけて再結晶焼鈍を行い、焼鈍過
程において材質を劣化させる鋼中の固溶C,Nを析出さ
せ、材質を軟質化させる方法であるが、昇温・冷却に数
日乃至数週間かかるばかりでなく、コイル内・外径の温
度が不均一であり、コイル内の材質がかなり不均一であ
った。<Prior art> Conventionally, the annealing process in manufacture of a cold-rolled steel sheet was performed by the box annealing method. This box annealing method, while keeping the cold rolled steel strip in a coil state, performs recrystallization annealing over several days, precipitating solid solution C, N in the steel that deteriorates the material in the annealing process and softening the material. However, not only it took several days to several weeks to heat up and cool, but the temperature inside and outside the coil was not uniform, and the material inside the coil was quite uneven.
近年、この箱焼鈍法に対してラインスピードが100〜400
mpmで通板され、１コイルを焼鈍するに要する時間が数
分〜数十分間で完了する連続焼鈍法が広く適用されてき
ており、連続焼鈍法は箱焼鈍法にとってかわりつつあ
る。In recent years, the line speed is 100 to 400 with respect to this box annealing method.
The continuous annealing method, which is performed at mpm and completes within a few minutes to several tens of minutes for annealing one coil, has been widely applied, and the continuous annealing method is being replaced by the box annealing method.
しかし、連続焼鈍法は加熱・冷却速度が速く鋼中の固溶
C,Nの析出が起こりにくく、そのため焼鈍後、数日以上
経過すると時効劣化が起こり鋼板の降伏点が上昇すると
ともに降伏伸びが発生しやすくなり材質が軟質化する
他、加工した際にストレッチャー・ストレインといった
表面欠陥が発生してしまう等の問題があった。However, the continuous annealing method has a high heating / cooling rate and forms a solid solution in steel.
Precipitation of C and N is difficult to occur, so that after aging for several days or more, aging deterioration occurs, the yield point of the steel sheet rises and yield elongation easily occurs, the material softens, and the stretcher when processed.・ There were problems such as surface defects such as strain.
この連続焼鈍法のかかえる問題を解決するために、次の
ような方法がとられている。In order to solve the problems associated with this continuous annealing method, the following method is adopted.
（１） 熱延後の巻取を650℃以上の高温巻取とし、熱
延鋼帯の時点で、Fe3C,AlN等の析出物を析出させておい
て軟質材を得る手段。(1) A method for obtaining a soft material by precipitating precipitates such as Fe 3 C and AlN at the time of hot-rolling steel strip by winding the hot-rolled material at a high temperature of 650 ° C or higher.
（２） 連続焼鈍中の加熱・均熱後の冷却過程で急冷・
過時効処理を施し、鋼中のカーバイトを析出させる手
段。すなわち、加熱・均熱後に50〜100℃／秒の冷却速
度で急速冷却し、結晶粒内の固溶Ｃの過飽和度を高め
て、300〜500℃の温度域に３分間以上の保持を行い、固
溶Ｃの析出サイトである結晶粒内のカーバイト及び結晶
粒界に固溶Ｃを拡散させ、Fe3Cの析出を促進させて軟質
材を得る手段。(2) Heating during continuous annealing, rapid cooling in the cooling process after soaking
Means for over-aging treatment to precipitate carbide in steel. That is, after heating and soaking, it is rapidly cooled at a cooling rate of 50 to 100 ° C / sec to increase the supersaturation degree of the solid solution C in the crystal grains and hold it in the temperature range of 300 to 500 ° C for 3 minutes or more. A means for obtaining a soft material by diffusing solid solution C into carbides and crystal grain boundaries, which are precipitation sites of solid solution C, and promoting precipitation of Fe 3 C.
（３） さらに深絞り用冷延鋼板の製造に至っては、製
鋼段階であらかじめＣを50ppm以下まで低減させた極低
炭素鋼を素材とし、さらにTi,Nb等の炭窒化物形成元素
を添加し、鋼中の固溶C,Nを完全に固定して、完全非時
効性の鋼板とし、さらに延性，絞り性に有効な結晶粒の
成長及び集合組織の形成等を促進するために高温加熱を
行う方法等が用いられていた。(3) Further, in the production of cold-rolled steel sheets for deep drawing, ultra-low carbon steel in which C was reduced to 50 ppm or less was used as a raw material in the steelmaking stage, and carbonitride forming elements such as Ti and Nb were added. , The solid solution C and N in the steel are completely fixed to form a completely non-aged steel sheet, and high temperature heating is performed to promote the growth of crystal grains and the formation of texture that are effective for ductility and drawability. The method of doing was used.
しかしながら、これら（１）〜（３）の方法も完全では
ない。たとえば、（１）のように熱延巻取温度を高温と
した場合、コイル内・外径方向，幅方向に冷却むらを生
じて同一コイル内での材質の均一性が悪くなる他、酸化
膜が厚くなり、酸洗工程での脱スケールが悪くなって完
全に脱スケールを行うためには酸洗ラインのラインスピ
ードを低下させなければならなくなり、生産性を著しく
損なってしまう。また酸洗液の取替頻度が多くなりコス
トアップを招く等の問題があった。However, these methods (1) to (3) are not perfect. For example, when the hot rolling temperature is high as in (1), uneven cooling occurs in the coil, in the outer diameter direction, and in the width direction, and the uniformity of the material in the same coil deteriorates. However, the descaling in the pickling step becomes worse, and the line speed of the pickling line must be reduced in order to perform the descaling completely, and the productivity is significantly impaired. Further, there is a problem that the frequency of replacement of the pickling solution is increased and the cost is increased.
（２）の手段のように焼鈍中に急冷・過時効処理を行っ
て固溶Ｃ量の低減を行うには、前述のようにラインスピ
ードが100〜400mpmで通板されている鋼板に３分間以上
の過時効処理を行うとなると、必然的に長大な過時効帯
を有する連続焼鈍設備が必要となり、設備的な限界及び
制限が生じてくる。しかし短時間の過時効処理では遅時
効性の冷延鋼板とするに十分な鋼中の固溶Ｃ量まで低減
することは不可能であり、軟質材を得ることは困難であ
った。In order to reduce the amount of solute C by performing quenching / overaging treatment during annealing as in the case of (2), as described above, the line speed is 100 to 400 mpm for 3 minutes on a steel plate that has been threaded. When the above-mentioned overaging treatment is carried out, a continuous annealing equipment having a long overaging zone is inevitably required, which causes limitations and restrictions on the equipment. However, it is impossible to reduce the amount of solute C in the steel sufficient to form a cold-rolled steel sheet with slow aging by a short-time overaging treatment, and it is difficult to obtain a soft material.
また、（３）の手段のように極低炭素鋼を素材とした鋼
板は、溶鋼コストが高い高付加価値の鋼板に使用されな
ければ商業的なメリットではない。そのため極低炭素鋼
を素材とした鋼板をありとあらゆる種類の冷延鋼板、と
くに軽加工用途である低価格の冷延鋼板に適用すること
はコスト的に問題があり実用的ではなかった。Further, the steel plate made of ultra-low carbon steel as the material of the means (3) is not a commercial merit unless it is used for a high value-added steel plate with high molten steel cost. Therefore, it is not practical to apply a steel sheet made of ultra-low carbon steel to all kinds of cold-rolled steel sheets, especially low-cost cold-rolled steel sheet for light processing, because of cost problems.
以上のようなことから通常の低炭素Alキルド鋼素材・連
続焼鈍法を用いて軟質な冷延鋼板を製造するのは大変難
しいものであった。しかしながら以下に示すような、低
炭素Alキルド鋼素材・連続焼鈍法を用いて軟質な冷延鋼
板を製造する方法が提案されている。すなわち、鋼中に
Ｂを添加した低炭素Alキルド鋼を用い、連続焼鈍法で軟
質冷延鋼板を製造する方法であるが特開昭55−77910号
公報，特開昭56−136956号公報，特開昭56−146825号公
報，特開昭56−156720号公報，特開昭56−166330号公報
に開示されているように、熱延巻取温度を600℃以上の
高温巻取りとし、C,NをＢの析出物として固定し、かつ
連続焼鈍時に２〜３分以上の過時効処理を施すことを特
徴とするものである。From the above, it was very difficult to manufacture a soft cold-rolled steel sheet by using a normal low carbon Al-killed steel material / continuous annealing method. However, a method for producing a soft cold-rolled steel sheet using a low carbon Al-killed steel material / continuous annealing method as described below has been proposed. That is, a method of manufacturing a soft cold-rolled steel sheet by a continuous annealing method using a low carbon Al killed steel in which B is added to the steel is disclosed in JP-A-55-77910 and JP-A-56-136956. As disclosed in JP-A-56-146825, JP-A-56-156720 and JP-A-56-166330, the hot rolling temperature is set to 600 ° C. or higher, and C , N is fixed as a precipitate of B, and overageing treatment is performed for 2 to 3 minutes or more during continuous annealing.
しかし、これらは、高温巻取りを要することから前述の
如く脱スケール性に問題が生じるばかりでなく、連続焼
鈍工程においても２分以上の長時間過時効処理時間を行
っていることから、依然として前述の（１）〜（２）の
製造技術の域を脱しておらず製造コストの上昇，操業上
の規制を招いてしまう等の欠点を有している。However, since these require high-temperature winding, they not only cause a problem in descaling property as described above, but also perform a long overaging treatment time of 2 minutes or more in the continuous annealing step, and therefore, the above-mentioned problems still remain. It does not go beyond the manufacturing technology of (1) and (2), and has the drawbacks of increased manufacturing cost and regulation of operation.
＜発明が解決しようとする課題＞ 本発明の目的は、溶鋼コストが比較的低廉な低炭素Alキ
ルド鋼を用いて高温巻取を行わず、なおかつ連続焼鈍中
で短時間の過時効処理を施しても耐時効性の良好な冷延
鋼板を製造する方法を提案するものである。<Problems to be Solved by the Invention> An object of the present invention is to carry out high-temperature winding using a low carbon Al killed steel whose molten steel cost is relatively low, and to perform a short-time overaging treatment during continuous annealing. Even so, it proposes a method for producing a cold-rolled steel sheet having good aging resistance.
＜課題を解決するための手段＞ 本発明は、重量％で、C:0.02〜0.08％,Mn:0.5％以下,S:
0.005〜0.05％,Al:0.01〜0.20％,N:0.0010〜0.0050％，
必要に応じてB:0.0001〜0.0030％を含有し、残部Fe及び
不可避的不純物からなるスラブを1200℃以下で加熱し熱
間圧延を施した後、600℃以下で巻取り、次いで冷間圧
延を施した後、連続焼鈍法により再結晶温度以上Ac3変
態点以下の温度域に加熱し10秒以下の均熱を行った後、
20〜100℃／秒の冷却速度で350〜500℃の温度域まで冷
却し、その温度域に20〜120秒間保持した後、圧下率1.5
〜5.0％の調質圧延を施すことを特徴とする遅時効性冷
延鋼板の製造方法である。<Means for Solving the Problems> In the present invention, in% by weight, C: 0.02 to 0.08%, Mn: 0.5% or less, S:
0.005 to 0.05%, Al: 0.01 to 0.20%, N: 0.0010 to 0.0050%,
A slab containing B: 0.0001 to 0.0030% if necessary and the balance Fe and unavoidable impurities is heated at 1200 ° C or less and hot-rolled, and then wound at 600 ° C or less, and then cold-rolled. after applying, after the heating of 10 seconds or less soaking in a temperature range of recrystallization temperature or higher Ac 3 less transformation was performed by continuous annealing process,
After cooling to a temperature range of 350 to 500 ° C at a cooling rate of 20 to 100 ° C / sec and holding in that temperature range for 20 to 120 seconds, a reduction rate of 1.5
It is a method for producing a slow-aging cold-rolled steel sheet, characterized by performing a temper rolling of up to 5.0%.
＜作 用＞ 本発明者らは、Al,Nをやや高めにした低炭素Alキルド
鋼、あるいはそれにＢを添加した鋼板に、スラブ加熱温
度を含む適切な熱延条件を付与することで鋼中の固溶Ｎ
を完全にAlN、あるいはBNとして固定し、かつ連続焼鈍
の加熱均熱時間を短くしてカーバイトの再溶解をできる
だけ抑制しておき、さらに過時効処理によりAlN,BNの析
出物を析出核にして固溶Ｃを析出させ、さらに高圧下率
の調質圧延を施して高密度の転位を付与することで耐時
効性の良好な遅時効性冷延鋼板が製造できることを知見
したのである。<Operation> The inventors of the present invention provide a low carbon Al killed steel with slightly higher Al and N, or a steel sheet with B added thereto with appropriate hot rolling conditions including a slab heating temperature. Solid solution of N
Is completely fixed as AlN or BN, and the reheating of the carbide is suppressed as much as possible by shortening the heating and soaking time of continuous annealing, and the precipitates of AlN and BN are made into precipitation nuclei by overaging treatment. It was found that a slow-aging cold-rolled steel sheet having good aging resistance can be manufactured by precipitating solid solution C and further subjecting it to temper rolling at a high-pressure reduction rate to impart high-density dislocations.
以下に本発明のもととなった実験及びその結果について
説明をする。The experiment and the result of the present invention will be described below.
〔実験１〕 重量％で、C:0.042％,Si:0.011％,Mn:0.27％,P:0.013
％,S:0.021％,Al:0.078％,N:0.0032％を含み、残部Fe及
び不可避的不純物から成る鋼を実験室で出鋼し、板厚:3
0mmのシートバーに分塊圧延した後、スラブ加熱温度（S
RT）に模して1250℃,1050℃で１時間加熱し、板厚:3.5m
m,仕上温度:850℃になるように熱延した。引き続き、コ
イル巻取温度（CT）に模してシートバー加熱温度が1050
℃のものには550℃、及びシートバー加熱温度が1250℃
のものには550℃,640℃の保熱炉に２時間挿入し、その
後空冷（冷却速度：約３℃／分）で室温まで冷却した。[Experiment 1] C: 0.042%, Si: 0.011%, Mn: 0.27%, P: 0.013 by weight%
%, S: 0.021%, Al: 0.078%, N: 0.0032%, with the balance Fe and unavoidable impurities produced in the laboratory.
After slab rolling to 0 mm sheet bar, slab heating temperature (S
RT), heating at 1250 ℃, 1050 ℃ for 1 hour, plate thickness: 3.5m
m, finishing temperature: hot-rolled to 850 ℃. Subsequently, the sheet bar heating temperature is 1050, imitating the coil winding temperature (CT).
550 ℃ for those with a temperature of ℃
It was inserted into a heat-retaining furnace at 550 ° C and 640 ° C for 2 hours, and then cooled to room temperature by air cooling (cooling rate: about 3 ° C / min).
酸洗後、圧下率:77％の冷間圧延を施し、板厚:0.8mmの
冷延板とした。脱脂後、加熱速度:15℃／秒で750℃に加
熱し、４〜36秒均熱後、冷却速度:70℃／秒で400℃まで
急速冷却した後、45秒保持し、その後、冷却速度:10℃
／秒で室温まで冷却するヒートサイクルで再結晶焼鈍を
行った。次いで、圧下率:1.8％の調質圧延を施した後、
材料試験を行い機械的特性、とくに降伏点伸び（YE
l），時効指数｛Aging Index:（100℃×30分時効処理後
の降伏点応力）−（7.5％予歪み時の応力）の絶対値｝
を調査した。その結果を第１図に示す。After pickling, cold rolling with a rolling reduction of 77% was performed to obtain a cold rolled sheet with a sheet thickness of 0.8 mm. After degreasing, heating speed: 15 ℃ / sec to 750 ℃, soaking for 4 to 36 seconds, cooling rate: 70 ℃ / sec, rapid cooling to 400 ℃, then holding for 45 seconds, then cooling rate : 10 ℃
Recrystallization annealing was performed by a heat cycle of cooling to room temperature at 1 / sec. Then, after subjecting to temper rolling with a reduction rate of 1.8%,
Material tests were performed to determine mechanical properties, especially yield point elongation (YE
l), aging index {Aging Index: (100 ° C x 30 min yield point stress after aging treatment)-(absolute value of stress at 7.5% pre-strain)}
investigated. The results are shown in FIG.
その結果、スラブ加熱温度・巻取温度の低い鋼は均熱時
間が10秒以下の所で急激に降伏点伸びが小さくなり時効
指数は低下した。それに対してスラブ加熱温度・巻取温
度の高い鋼板は硬化し、降伏点伸び，時効指数は大きく
なり材質は劣化した。また、スラブ加熱温度が高く、巻
取温度が低い鋼板は降伏点伸び，時効指数は共に大きく
耐時効性は良くなかった。As a result, for steels with low slab heating temperature and coiling temperature, the yield point elongation decreased rapidly and the aging index decreased when the soaking time was 10 seconds or less. On the other hand, steel sheets with high slab heating temperature and coiling temperature hardened, yield point elongation and aging index increased, and the material deteriorated. Further, the steel sheet with a high slab heating temperature and a low coiling temperature had large yield point elongation and aging index, and the aging resistance was not good.
次に降伏点伸び，時効指数におよぼす過時効処理時間の
影響について調査した実験及びその結果について説明す
る。Next, we will explain the experiments and the results of an investigation of the effect of overaging treatment time on yield point elongation and aging index.
〔実験２〕 重量％で、C:0.040％,Si:0.008％,Mn:0.23％,P:0.006
％,S:0.015％,Al:0.074％,N:0.0036％を含み、残部Fe及
び不可避的不純物から成る鋼を実験室で出鋼し、板厚:3
0mmのシートバーに分塊圧延した後、1050℃で１時間加
熱し、板厚:3.5mm,仕上温度:850℃になるように熱延し
た。引き続き、550℃の保熱炉に２時間挿入し、その後
空冷（冷却速度：約３℃／分）で室温まで冷却した。[Experiment 2] C: 0.040%, Si: 0.008%, Mn: 0.23%, P: 0.006 by weight%
%, S: 0.015%, Al: 0.074%, N: 0.0036%, with the balance Fe and unavoidable impurities produced in the laboratory.
After slabbing rolling into a 0 mm sheet bar, it was heated at 1050 ° C. for 1 hour and hot rolled to a plate thickness of 3.5 mm and a finishing temperature of 850 ° C. Then, it was inserted into a heat-retaining furnace at 550 ° C. for 2 hours and then cooled to room temperature by air cooling (cooling rate: about 3 ° C./min).
酸洗後、圧下率:77％の冷間圧延を施し、板厚:0.8mmの
冷延板とした。脱脂後、加熱速度:15℃／秒で720℃に加
熱し、２秒間又は30秒間均熱し、冷却速度:60℃／秒で4
20℃まで急速冷却した後、４〜160秒保持し、その後、
冷却速度:8℃／秒で室温まで冷却するヒートサイクルで
再結晶焼鈍を行った。次いで、圧下率:25％の調質圧延
を施した後、材料試験を行い、降伏点伸び（YEl），時
効指数｛Aging Index:（100℃×30分時効処理後の降伏
点応力）−（7.5％予歪み時の応力）の絶対値｝を調査
した。その結果を第２図に示す。After pickling, cold rolling with a rolling reduction of 77% was performed to obtain a cold rolled sheet with a sheet thickness of 0.8 mm. After degreasing, heating rate: 15 ℃ / sec to 720 ℃, soaking for 2 seconds or 30 seconds, cooling rate: 60 ℃ / sec 4
After rapid cooling to 20 ° C, hold for 4 to 160 seconds, then
Cooling rate: Recrystallization annealing was performed by a heat cycle of cooling to room temperature at 8 ° C / sec. Then, after subjecting to temper rolling with a rolling reduction of 25%, a material test is performed, yield point elongation (YEl), aging index {Aging Index: (100 ° C x 30 minutes yield point stress after aging treatment)-( Absolute value} of 7.5% prestrain). The results are shown in FIG.
その結果、均熱時間が２秒の鋼は過時効時間が20秒以上
であれば短時間の過時効処理でも降伏点伸びが小さく、
Alは低めであった。しかし均熱時間が30秒の鋼はこれに
対して過時効時間が120秒以上にならない限り降伏点伸
びは大きく、A.I.は高めであった。As a result, for steels with a soaking time of 2 seconds, if the overaging time is 20 seconds or more, the yield point elongation is small even with a short overaging treatment,
Al was low. However, the steel with a soaking time of 30 seconds had a large yield point elongation and a high AI unless the overaging time was 120 seconds or more.
次に、材質におよぼすＢ添加量の調査を行った実験及び
その結果について説明する。Next, the experiment and the result of the investigation of the amount of B added to the material will be described.
〔実験３〕 重量％で、C:0.043％,Si:0.010％,Mn:0.31％,P:0.006
％,S:0.023％,Al:0.069％,N:0.0041％を基本成分とし、
Ｂを0.0006,0.0015,0.0025,0.0040％添加した鋼を実験
室で出鋼し、〔実験２〕と同じ工程条件で板厚:3.5mmの
熱圧延とした。酸洗後、圧下率:77％の冷間圧延を施
し、板厚:0.8mmの冷延板とした。脱脂後、加熱速度:15
℃／秒で720℃に加熱し、１秒間均熱し、冷却速度:50℃
／秒で380℃まで急速冷却した後、40秒保持して、その
後冷却速度:8℃／秒で室温まで冷却するヒートサイクル
で再結晶焼鈍を行った。[Experiment 3] C: 0.043%, Si: 0.010%, Mn: 0.31%, P: 0.006% by weight
%, S: 0.023%, Al: 0.069%, N: 0.0041% as basic components,
Steel containing 0.0006, 0.0015, 0.0025, 0.0040% of B was tapped in the laboratory, and hot rolled with a plate thickness of 3.5 mm under the same process conditions as in [Experiment 2]. After pickling, cold rolling with a rolling reduction of 77% was performed to obtain a cold rolled sheet with a sheet thickness of 0.8 mm. After degreasing, heating rate: 15
Heating to 720 ℃ at ℃ / second, soaking for 1 second, cooling rate: 50 ℃
After rapid cooling to 380 ° C./sec, the temperature was maintained for 40 seconds, and then recrystallization annealing was performed by a heat cycle of cooling to room temperature at a cooling rate of 8 ° C./sec.
次いで、圧下率:2.0％の調質圧延を施した後、これらの
鋼板の降伏点伸び、降伏点について調査し、その結果を
第３図に示した。これによればＢ量が増大するにしたが
い降伏点が低下し、降伏点伸びが小さくなる傾向にあ
る。しかし30ppm超になると降伏点が高くなる傾向にあ
る。従って最適Ｂ量は0.0001〜0.0030％で、これらの範
囲で耐時効性は良好であることが判明した。Then, after subjecting to temper rolling with a rolling reduction of 2.0%, the yield point elongation and yield point of these steel sheets were investigated, and the results are shown in FIG. According to this, the yield point tends to decrease as the B content increases, and the yield point elongation tends to decrease. However, if it exceeds 30 ppm, the yield point tends to increase. Therefore, the optimum B amount was 0.0001 to 0.0030%, and it was found that the aging resistance was good in these ranges.
本実験において、Ｂを添加し、短時間の過時効処理を行
った鋼板の降伏点伸びが小さく、時効指数が顕著に低く
なった理由としては、Ｂが添加されることにより結晶粒
径が微細化され固溶Ｃが結晶粒界へ析出しやすくなった
こと、及びBNが析出していることで鋼中の固溶Ｎが固定
されていること、ならびにBNとFe23（C,B）と考えられ
る析出物が固溶Ｃの析出サイトとなりカーバイトの析出
（固溶Ｃが減少）を促進し耐時効性が改善されたためと
考えられる。またさらに、調質圧延圧下率を2.0％と通
常に比べてやや高めの圧下率としたため転位密度が高く
なり、固溶元素がトラップされ時効性がさらに改善され
たためと考えられる。In the present experiment, the reason why the yield point elongation of the steel sheet to which B was added and which was overaged for a short time was small and the aging index was remarkably low was that the addition of B caused the grain size to be fine. That solid solution C is likely to precipitate at the crystal grain boundaries, and that solid solution N in the steel is fixed due to the precipitation of BN, and that BN and Fe 23 (C, B) It is considered that the conceivable precipitate became a precipitation site of solid solution C and promoted precipitation of carbide (reduction of solid solution C), and the aging resistance was improved. Further, it is considered that the temper rolling reduction rate was 2.0%, which was slightly higher than the usual reduction rate, so that the dislocation density was increased, the solid solution element was trapped, and the aging was further improved.
次に、材質とくに耐時効性に及ぼす調質圧延の圧下率の
影響について調査した実験及びその結果について説明す
る。Next, the experiment and the result of the investigation on the influence of the reduction ratio of the temper rolling on the material, especially the aging resistance will be described.
〔実験４〕 重量％で、C:0.034％,Si:0.011％,Mn:0.20％,P:0.007
％,S:0.006％,Al:0.083％,N:0.0034％,B:0.0013％を基
本組成とした鋼を実験室で出鋼し、〔実験３〕と同じ工
程条件で冷延焼鈍板とした。圧下率:0.4,0.8,1.5,3.0,
5.0,7.0％の調質圧延を施した後、これらの鋼板の降伏
点，降伏点伸び，全伸び（El），時効指数について調査
し、その結果を第４図に示した。この結果によればＢを
添加した鋼でも圧下率:1.5％未満では時効性の改善効果
がなかった。また圧下率:5.0％超では降伏点が上昇し材
質（El）は硬化してしまった。[Experiment 4] C: 0.034%, Si: 0.011%, Mn: 0.20%, P: 0.007% by weight
%, S: 0.006%, Al: 0.083%, N: 0.0034%, B: 0.0013% steel with the basic composition was tapped in the laboratory, and cold rolled annealed sheet was made under the same process conditions as [Experiment 3]. . Reduction ratio: 0.4, 0.8, 1.5, 3.0,
After temper rolling of 5.0 and 7.0%, the yield point, yield point elongation, total elongation (El) and aging index of these steel sheets were investigated, and the results are shown in FIG. According to this result, even with the steel containing B, there was no aging improving effect at a rolling reduction of less than 1.5%. If the rolling reduction ratio exceeds 5.0%, the yield point rises and the material (El) hardens.
以上の実験結果から本発明は構成されたものであり、必
要に応じて適量のＢを添加した鋼を用い、熱延条件，連
続焼鈍条件，調質圧延条件を規制することで本発明のよ
うな耐時効性の良好な冷延鋼板が製造することができ
る。The present invention has been constructed from the above experimental results, and by using a steel to which an appropriate amount of B is added as necessary, hot rolling conditions, continuous annealing conditions, and temper rolling conditions are regulated so that the present invention can be realized. A cold-rolled steel sheet having excellent aging resistance can be manufactured.
次に、本発明における成分及び製造条件を限定した理由
について以下に説明する。Next, the reasons for limiting the components and production conditions in the present invention will be described below.
C:Cは、侵入型固溶元素であり、0.08％超の含有は結晶
粒を微細化し、材質を硬化させてしまうので上限を0.08
％とした。しかし、0.02％未満の含有量の場合、結晶粒
が比較的大きくなり、連続焼鈍の急冷・過時効処理で固
溶Ｃの析出が起こりにくくなるため下限を0.02％とし
た。C: C is an interstitial solid solution element, and the content of more than 0.08% makes the crystal grains fine and hardens the material, so the upper limit is 0.08.
%. However, when the content is less than 0.02%, the crystal grains become relatively large and precipitation of solid solution C hardly occurs in the rapid cooling / overaging treatment of continuous annealing, so the lower limit was made 0.02%.
Mn:Mnは、赤熱脆性の原因となるＳをMnSとして固定する
のに必要な元素であるが、0.5％超の含有は、材質を硬
化させ、延性を低下させてしまうことから、本発明の上
限を0.5％とした。Mn: Mn is an element necessary for fixing S that causes red heat embrittlement as MnS, but if it exceeds 0.5%, it hardens the material and reduces the ductility. The upper limit was 0.5%.
S:Sは、通常材質を劣化させることから少ないほうが好
ましいが、本発明では連続焼鈍中のカーバイトの析出を
促進させるサイトを形成するため、積極的にMnSを析出
させることから、少なくても0.005％は必要である。し
かし、0.05％超の含有は、必然的にMn量を増大させてし
まい、コストの上昇，材質の劣化を招いてしまう。よっ
て本発明では0.005〜0.050％に限定した。S: S is usually preferably less because it deteriorates the material, but in the present invention to form a site that promotes the precipitation of carbide during continuous annealing, because it actively precipitates MnS, at least 0.005% is required. However, the content of more than 0.05% inevitably increases the amount of Mn, resulting in an increase in cost and deterioration of material. Therefore, in the present invention, it is limited to 0.005 to 0.050%.
Al:Alは、製鋼段階で脱酸剤として使用される他、鋼中
のＮをAlNとして固定する元素であることから、少なく
ても0.01％の含有は必要である。しかしながら、Alは高
価な元素であり、0.20％超の含有はコスト高となること
から本発明では0.01〜0.20％に限定した。Al: Al is used as a deoxidizing agent in the steelmaking stage and is an element that fixes N in the steel as AlN. Therefore, at least 0.01% is necessary. However, Al is an expensive element, and the content of more than 0.20% increases the cost, so in the present invention, it is limited to 0.01 to 0.20%.
N:Nは、Ｃと同様に侵入型固溶元素であり材質を劣化さ
せるので、通常は極力少ない方が好ましい。本発明で
は、Alを添加して熱延条件を制御することでAlNを析出
させ、これをカーバイトの析出サイトとすることから、
少なくとも0.0010％の含有は必要である。しかし、0.00
50％超の含有は材質を著しく劣化させてしまうことから
本発明ではＮの含有量を0.0010〜0.0050％に限定した。Since N: N is an interstitial solid solution element like C and deteriorates the material, it is usually preferable that the amount is as small as possible. In the present invention, AlN is precipitated by controlling the hot rolling conditions by adding Al, and since this is the precipitation site of the carbide,
A content of at least 0.0010% is necessary. But 0.00
In the present invention, the content of N is limited to 0.0010 to 0.0050% because the content of more than 50% deteriorates the material remarkably.
B:Bは、本発明にとっては必要に応じて添加でき、BNと
してＮを固定する他にカーバイトの析出サイトを形成す
ることから有効な元素である。その効果を引き出すに
は、少なくとも0.0001％の含有が好ましい。しかしなが
ら、多量の含有とくに0.0030％超の含有は材質を劣化さ
せてしまうことからＢの含有量を0.0001〜0.0030％とし
た。B: B is an effective element for the present invention because it can be added as required and fixes N as BN and forms a carbide precipitation site. To bring out the effect, at least 0.0001% is preferable. However, since a large amount of content, particularly more than 0.0030%, deteriorates the material, the content of B is set to 0.0001 to 0.0030%.
その他、不可避的不純物として含有される元素について
は、とくに規定はしないが、その含有は極力低く抑える
のが好ましい。Other elements that are contained as unavoidable impurities are not particularly specified, but the content thereof is preferably suppressed as low as possible.
スラブ加熱温度：スラブ加熱温度を1200℃以下とした理
由は、スラブ鋳込み後の冷却過程で粗大に析出したMnS,
BN,AlN等の析出物を再溶解させないようにするためであ
る。これらの粗大な析出物は冷延・連続焼鈍時の過時効
処理でカーバイトの析出を促進し材質を軟質化すること
ができるからである。Slab heating temperature: The reason for setting the slab heating temperature to 1200 ° C or less is that MnS coarsely precipitated during the cooling process after casting the slab,
This is to prevent redissolution of precipitates such as BN and AlN. This is because these coarse precipitates can promote the precipitation of carbide and soften the material by overaging treatment during cold rolling and continuous annealing.
熱延仕上温度：通常、プレス成形性の良好な冷延鋼板を
製造する場合には、Ar3変態点以上とする必要がある
が、単に軽加工用の軟質な冷延鋼板を製造する目的であ
ればAr3変態点以下の温度で熱延を終了してもなんら問
題はない。よって本発明においてはとくに熱延仕上温度
に関して規制はしない。Hot-rolling finishing temperature: Normally, when manufacturing cold-rolled steel sheets with good press formability, it is necessary to have an Ar 3 transformation point or higher, but for the purpose of simply manufacturing soft cold-rolled steel sheets for light processing. If so, there is no problem even if hot rolling is completed at a temperature below the Ar 3 transformation point. Therefore, in the present invention, the hot rolling finish temperature is not particularly limited.
巻取温度：本発明では高温にするほど材質が良好となる
が、600℃超にした場合、材質の良好な鋼板を製造する
には有利であるが酸化膜が厚くなり、脱スケール性が悪
くなる他、熱延コイルの幅方向・内径方向での均熱むら
が生じ、コイル内での材質の均質性が悪くなる等の問題
がある。よって本発明での上限を600℃とした。Winding temperature: In the present invention, the higher the temperature, the better the material becomes, but if it exceeds 600 ° C, it is advantageous for producing a steel sheet with good material, but the oxide film becomes thick and the descaling property is poor. In addition to this, there is a problem that uneven heat distribution occurs in the width direction and the inner diameter direction of the hot rolled coil, and the homogeneity of the material in the coil deteriorates. Therefore, the upper limit in the present invention is set to 600 ° C.
連続焼鈍法：本発明で再結晶焼鈍に連続焼鈍法を適用し
た理由は、従来の箱焼鈍法では製造日数が非常にかかる
上、なおかつコイル内の材質が均質なものを製造するの
が困難である。しかしながら連続焼鈍を適用することで
これらの問題を解決することが可能であるからである。
また加熱温度を再結晶温度以上、Ac3変態点以下の温度
域にした理由は、再結晶温度未満の温度では加工性が著
しく劣り加工が困難であるからであり、またAc3変態点
超の高温に加熱した場合、AlNが分解し固溶Ｎ量が増大
し材質が劣化するからである。また、均熱時間が10秒以
下の場合は冷延前に析出したカーバイトの再固溶が抑制
され、固溶Ｃ量をできるだけ減少させておくことが可能
である。そのため均熱時間は10秒以内とする必要があ
る。もちろん０秒でもよい。その後の冷却速度を20〜10
0℃／秒とした理由は、20℃／秒未満の冷却速度では結
晶粒内に固溶Ｃを過飽和にすることができないためであ
り、また、100℃／秒超の冷却速度にするには設備的に
困難であるからである。さらに、350〜500℃の温度域ま
で冷却し20〜120秒保持するのは、この温度域で最もＣ
が析出サイトである結晶粒界まで拡散しやすいことから
である。また、それに要する時間は最低限20秒必要であ
る。しかし、120秒超の保持はラインスピードを規制
し、生産性を低下させるか、もしくは長大な過時効処理
設備を必要とすることからこの温度域での滞留時間を20
〜120秒とした。Continuous annealing method: The reason why the continuous annealing method is applied to the recrystallization annealing in the present invention is that the conventional box annealing method takes a lot of manufacturing days, and it is difficult to manufacture the one in which the coil material is homogeneous. is there. However, it is possible to solve these problems by applying continuous annealing.
The heating temperature recrystallization temperature or higher, the reason for the range of temperatures lower than or equal to Ac 3 transformation point is because at temperatures below the recrystallization temperature which is difficult to process inferior considerably workability and Ac greater than 3 transformation point This is because when heated to a high temperature, AlN decomposes, the amount of solid solution N increases, and the material deteriorates. Further, when the soaking time is 10 seconds or less, re-dissolution of the carbide precipitated before cold rolling is suppressed, and the amount of solute C can be reduced as much as possible. Therefore, the soaking time must be within 10 seconds. Of course, it may be 0 seconds. The cooling rate after that is 20 to 10
The reason for setting 0 ° C./sec is that solid solution C cannot be supersaturated in the crystal grains at a cooling rate of less than 20 ° C./sec. This is because it is difficult in terms of equipment. Furthermore, cooling to the temperature range of 350 to 500 ° C and holding for 20 to 120 seconds is the most C in this temperature range.
Is easily diffused to the crystal grain boundary which is the precipitation site. The minimum time required for this is 20 seconds. However, holding for more than 120 seconds regulates the line speed and reduces productivity, or requires a long overaging treatment facility, so the residence time in this temperature range is 20
~ 120 seconds.
調質圧延圧下率：圧下率を1.5〜5.0％とした理由は、鋼
中の固溶C,Nを固定するに必要な転位を導入し、降伏伸
びを抑制するには最低限1.5％の圧下率の調質圧延を施
す必要があり、これ以下の圧下率での転位の導入では時
効しやすくなってしまうからである。しかし、5.0％超
の圧下率では、材質が硬化し過ぎ、とくに降伏点が高
く、全伸びが低下してしまうからである。Temper rolling reduction: The reason for setting the reduction ratio to 1.5 to 5.0% is to introduce dislocations necessary to fix the solid solution C and N in steel and to reduce the yield elongation to a minimum of 1.5%. It is necessary to carry out temper rolling of the rolling rate, and if dislocations are introduced at a rolling reduction below this, aging tends to occur. However, if the rolling reduction exceeds 5.0%, the material is excessively hardened, especially the yield point is high, and the total elongation is reduced.
次に実施例について説明をする。Next, examples will be described.
＜実施例＞ 第１表に示したような化学組成の連続鋳造スラブを1000
〜1270℃で１時間加熱し、熱間圧延で板厚:3.5mm,仕上
げ温度:740〜870℃になるように圧延した。引き続き、5
20〜630℃の巻取温度で巻取り熱延コイルとした。<Example> 1000 continuously cast slabs having the chemical composition shown in Table 1 were used.
It was heated at ˜1270 ° C. for 1 hour and hot-rolled to a plate thickness of 3.5 mm and a finishing temperature of 740-870 ° C. Continue to 5
A coiled hot rolled coil was prepared at a coiling temperature of 20 to 630 ° C.
酸洗後、冷間圧延で板厚:0.8mmの冷延板とした。その
後、加熱速度:10℃／秒で第２表に示したように再結晶
温度以上Ac3変態点以下の焼鈍温度×時間，冷却速度，
過時効温度×時間を行った後、冷却速度:8℃／秒で室温
まで冷却するヒートサイクルで再結晶焼鈍を行った。次
いで、圧下率:1.5〜4.0％の調質圧延を施した後、材料
試験を行い機械的特性，時効指数〔Aging Index:（100
℃×30分時効処理後の降伏点応力）−（7.5％予歪み時
の応力）の絶対値〕を調査した。その結果を第３表に示
した。After pickling, cold rolling was performed to obtain a cold rolled sheet having a thickness of 0.8 mm. Then, at a heating rate of 10 ° C / sec, as shown in Table 2, the annealing temperature above the recrystallization temperature and below the Ac 3 transformation point x time, cooling rate,
After performing the overaging temperature × time, recrystallization annealing was performed by a heat cycle of cooling to room temperature at a cooling rate of 8 ° C./sec. Next, after subjecting to temper rolling with a rolling reduction of 1.5 to 4.0%, a material test is conducted to determine the mechanical properties and aging index [Aging Index: (100
The absolute value of (yield point stress after aging treatment at 30 ° C. for 30 minutes) − (stress at 7.5% prestrain)] was investigated. The results are shown in Table 3.
その結果、本発明の化学組成，製造方法で製造された鋼
板は低炭素Alキルド鋼で過時効処理時間が短くても十分
に降伏伸びが小さく、耐時効性は良好であった。それに
対して本発明外の比較鋼は、時効性が悪かった。As a result, the steel sheet produced by the chemical composition and production method of the present invention was a low carbon Al-killed steel, and the yield elongation was sufficiently small even if the overaging treatment time was short, and the aging resistance was good. On the other hand, the comparative steels outside the present invention had poor aging properties.
＜発明の効果＞ 本発明により、低炭素Alキルド鋼に短時間過時効処理の
連続焼鈍を施すことにより、遅時効性の冷延鋼板を製造
することができるようになった。またこの技術を適用す
れば連続焼鈍のラインスピードを高速とすることが可能
であり、生産性を一層向上させることができる。 <Effects of the Invention> According to the present invention, a slow-aging cold rolled steel sheet can be manufactured by subjecting a low-carbon Al-killed steel to continuous annealing in a short-time overaging treatment. Further, if this technique is applied, the line speed of continuous annealing can be increased, and the productivity can be further improved.
第１図は、降伏点伸び（YEl）、時効指数（A.I.:Aging
Index）に及ぼすスラブ加熱温度，巻取温度，均熱時間
の影響を示す図、第２図は、降伏点伸び（YEl）、時効
指数（A.I.:Aging Index）に及ぼす均熱時間，過時効時
間の影響を示す図、第３図は、降伏点伸び（YEl）、降
伏点（YP）に及ぼすＢ量の影響を示す図、第４図は、降
伏点（YP）、降伏点伸び（YEl）、全伸び（El）、時効
指数（A.I.:Aging Index）に及ぼす調質圧延圧下率の影
響を示す図である。Figure 1 shows the yield point elongation (YEl) and aging index (AI: Aging).
Fig. 2 shows the effects of slab heating temperature, coiling temperature, and soaking time on Index), and Fig. 2 shows soaking time and overaging time on yield point elongation (YEl) and aging index (AI: Aging Index). Figure 3 shows the influence of B content on yield point elongation (YEl) and yield point (YP). Figure 4 shows yield point elongation (YP) and yield point elongation (YEl). It is a figure which shows the influence of the temper rolling reduction rate which affects on a total elongation (El), and an aging index (AI: Aging Index).
フロントページの続き (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Front page continuation (72) Inventor Hideo Abe 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division
Claims (2)
S:0.005〜0.05％,Al:0.01〜0.20％,N:0.0010〜0.0050％
を含有し、残部Fe及び不可避的不純物からなるスラブを
1200℃以下で加熱し熱間圧延を施した後、600℃以下で
巻取り、次いで冷間圧延を施した後、連続焼鈍法により
再結晶温度以上Ac3変態点以下の温度域に加熱し10秒以
下の均熱を行った後、20〜100℃／秒の冷却速度で350〜
500℃の温度域まで冷却し、その温度域に20〜120秒間保
持した後、圧下率1.5〜5.0％の調質圧延を施すことを特
徴とする遅時効性冷延鋼板の製造方法。1. In weight%, C: 0.02 to 0.08%, Mn: 0.5% or less,
S: 0.005-0.05%, Al: 0.01-0.20%, N: 0.0010-0.0050%
A slab containing Fe and the balance Fe and unavoidable impurities
After heating at 1200 ° C or less and hot rolling, winding at 600 ° C or less, then cold rolling, and heating to a temperature range not lower than the recrystallization temperature and not higher than the Ac 3 transformation point by the continuous annealing method 10 After soaking for no more than 10 seconds, 350 ~ at a cooling rate of 20 ~ 100 ℃ / second
A method for producing a delayed-aging cold-rolled steel sheet, which comprises cooling to a temperature range of 500 ° C, maintaining the temperature range for 20 to 120 seconds, and then subjecting it to temper rolling with a rolling reduction of 1.5 to 5.0%.
S:0.005〜0.05％,Al:0.01〜0.20％,N:0.0010〜0.0050
％,B:0.0001〜0.0030％を含有し、残部Fe及び不可避的
不純物からなるスラブを1200℃以下で加熱し熱間圧延を
施した後、600℃以下で巻取り、次いで冷間圧延を施し
た後、連続焼鈍法により再結晶温度以上Ac3変態点以下
の温度域に加熱し10秒以下の均熱を行った後、20〜100
℃／秒の冷却速度で350〜500℃の温度域まで冷却し、そ
の温度域に20〜120秒間保持した後、圧下率1.5〜5.0％
の調質圧延を施すことを特徴とする遅時効性冷延鋼板の
製造方法。2. In% by weight, C: 0.02 to 0.08%, Mn: 0.5% or less,
S: 0.005 to 0.05%, Al: 0.01 to 0.20%, N: 0.0010 to 0.0050
%, B: 0.0001 to 0.0030%, and a slab consisting of the balance Fe and unavoidable impurities was heated at 1200 ° C or lower and hot rolled, then wound at 600 ° C or lower, and then cold rolled. After that, it is heated to a temperature range not lower than the recrystallization temperature and not higher than the Ac 3 transformation point by a continuous annealing method and subjected to soaking for 10 seconds or less, and then 20 to 100.
After cooling to a temperature range of 350 to 500 ° C at a cooling rate of ℃ / sec and holding in that temperature range for 20 to 120 seconds, a reduction rate of 1.5 to 5.0%
A method for producing a slow-aging cold-rolled steel sheet, which comprises subjecting the steel to temper rolling.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63292361A JPH07100817B2 (en) | 1988-11-21 | 1988-11-21 | Method for manufacturing slow-aging cold-rolled steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63292361A JPH07100817B2 (en) | 1988-11-21 | 1988-11-21 | Method for manufacturing slow-aging cold-rolled steel sheet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02141534A JPH02141534A (en) | 1990-05-30 |
| JPH07100817B2 true JPH07100817B2 (en) | 1995-11-01 |
Family
ID=17780809
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63292361A Expired - Fee Related JPH07100817B2 (en) | 1988-11-21 | 1988-11-21 | Method for manufacturing slow-aging cold-rolled steel sheet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH07100817B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4630250B2 (en) * | 2006-09-07 | 2011-02-09 | 新日本製鐵株式会社 | Steel plate for side seamless cans and method for producing the same |
| CN114107623B (en) * | 2021-12-01 | 2023-09-15 | 安徽工业大学 | Heat treatment method for reducing timeliness of SPHC hot rolled plate coil by online isothermal aging removal annealing |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS48100314A (en) * | 1972-04-03 | 1973-12-18 | ||
| JPS6389625A (en) * | 1986-10-01 | 1988-04-20 | Kawasaki Steel Corp | Production of extremely thin steel sheet having good flange workability |
-
1988
- 1988-11-21 JP JP63292361A patent/JPH07100817B2/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS48100314A (en) * | 1972-04-03 | 1973-12-18 | ||
| JPS6389625A (en) * | 1986-10-01 | 1988-04-20 | Kawasaki Steel Corp | Production of extremely thin steel sheet having good flange workability |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02141534A (en) | 1990-05-30 |
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