JPH0573803B2 - - Google Patents
Info
- Publication number
- JPH0573803B2 JPH0573803B2 JP60233899A JP23389985A JPH0573803B2 JP H0573803 B2 JPH0573803 B2 JP H0573803B2 JP 60233899 A JP60233899 A JP 60233899A JP 23389985 A JP23389985 A JP 23389985A JP H0573803 B2 JPH0573803 B2 JP H0573803B2
- Authority
- JP
- Japan
- Prior art keywords
- temperature
- hot
- slab
- rolled steel
- strength
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 229910000831 Steel Inorganic materials 0.000 claims description 30
- 239000010959 steel Substances 0.000 claims description 30
- 238000005098 hot rolling Methods 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 7
- 229910000859 α-Fe Inorganic materials 0.000 claims description 6
- 238000009749 continuous casting Methods 0.000 claims description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- 229910001563 bainite Inorganic materials 0.000 claims description 3
- 238000003303 reheating Methods 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 238000010583 slow cooling Methods 0.000 claims 1
- 238000010438 heat treatment Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 9
- 239000002131 composite material Substances 0.000 description 6
- 238000001816 cooling Methods 0.000 description 6
- 229910000734 martensite Inorganic materials 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910001568 polygonal ferrite Inorganic materials 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
- B21B1/466—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a non-continuous process, i.e. the cast being cut before rolling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
- B21B3/02—Rolling special iron alloys, e.g. stainless steel
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Metal Rolling (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Description
［発明の利用分野］
本発明は高強度熱延鋼板の製造法に関する。
［発明の背景］
近年自動車業界においては、車体の軽量化のた
め、設計強度を変更しないで板厚を薄くし得るこ
とが要望されているが、従来の析出硬化型の高張
力鋼板では、プレス成形性が良くないこと、溶接
性にも問題があること等からかかる要望に答える
ことができない。
そこで、従来の析出硬化型高張力鋼板に代わる
鋼板として、フエライト、マルテンサイトの２相
からなる複合組織型高張力鋼板の採用が増加しつ
つある。
しかし、かかる複合組織型鋼板も加工性などの
点において必ずしの好ましいものではない。
そこで、さらに、Mnを基本成分とし、Si、Cr
を多量に添加することにより、熱間圧延工程−巻
取工程を経た後においても低降伏比、良延性とい
う特性をもつ複合組織型鋼板が開発されている。
しかし、かかる複合組織型鋼板はSi、Crを大
量に使用するためコストが高いという問題点があ
る。
ところで、従来方法においては、熱延鋼板は、
普通造塊法による鋼塊を分塊して造られたスラブ
又は連続鋳造法により造られたスラブを、一旦常
温にまで冷却して、その後加熱炉にて1200〜1300
℃の高温で長時間の加熱を行なつてから連続熱間
圧延機に噛込ませて製造している。
しかし、このように従来方法のように1200℃の
高温に１時間以上の長時間加熱をスラブに施こす
ことは加熱量の莫大な損失となる。
そこで高強度熱延鋼板を、低コストで、高能率
で製造する方法を見出すべき、鋼材成分組成及び
圧延処理手段の両面から各種試験・調査を繰り返
しながら研究を重ねた結果本発明をなすにいたつ
た。
［発明の目的］
本発明は、加工性が良く、コストの低い熱延鋼
板を低加熱費で製造することができる高強度熱延
鋼製造法を提供することを目的とする。
［発明の概要］
上記目的は、重量％で、Ｃ：0.03〜0.2％、Si：
0.02〜1.5％、Mn：0.6〜2.5％、Ｓ：0.01％以下、
solAl：0.01〜0.06％、残部鉄及び不可避的不純物
からなるベイナイトを含む変態強化型の高強度熱
延鋼板を製造する方法において、連続鋳造を行な
い高温スラブを得た後、該スラブが550℃の温度
になる前に、該スラブを1050℃〜1150℃の温度に
再加熱した後熱間圧延を開始し、該熱間圧延を
Ar3点以上の温度で終了し、次いでフエライトノ
ーズ付近は10℃／ｓ以下で徐冷し、その後600℃
以下の巻取温度まで20℃／ｓ以上で急冷するとを
特徴とする高強度熱延鋼板の製造法によつて達成
される。
以下に本発明の構成を説明する。
Ｃ：0.03〜0.2％、
Ｃは、必要な強度維持及びベイナイト、マルテ
ンサイトなどの低温変態生成物を形成させるうえ
で必須な元素であるが、0.02％を越えると加工性
と溶接性を劣化することに加え、本発明の鋼板の
特徴の一つである低降伏比特性を損なうこととな
る。その下限は強化及び焼入性向上効果を発揮さ
せるために0.03％とする。
Si：0.2〜1.5％
Siは溶鋼の脱酸に必要な元素であり、また高強
度かつ高延性をうるうえでもつとも有効な置換型
固溶元素である。さらに正常なポリゴナルフエラ
イト形成を有利にする働きをもつている。このよ
うな特性を発揮させるためには0.2％を下限とし
た。また、溶接部の脆化（遷移温度の上昇）を防
止し、表面酸化スケール状態の悪化を防ぐために
1.5％を上限とした。
Mn：0.6〜2.5％
Mnは焼入性を増し、所望の組織をうるうえで
必須の元素である。その効果を発揮させるために
は0.6％以上を必要とし、2.5％を越えると、溶接
上困難になると同時に延性を劣化し、鋼板の価格
が高価格となるため上限を2.5％とする。
Cr：0.3〜1.5％
Crは他の元素と異なり、それ自体には固溶強
化能はないが、焼入性を向上させ所望の組織を得
るうえで必要な元素である。その下限はその効果
を発揮させうる量から、その上限はその効果が飽
和に達し、経済的でなくなる量から0.1〜1.0％と
する。
Ｓ：0.01％以下
Ｓは硫化物を生成し、加工性を劣化させるので
可及的に少ない方が望ましいが、その含有量が
0.01％以下であれが所望の加工性が確保できるこ
とからＳ含有量の上限を0.01％と定めた。
solAl：0.01〜0.06％
solAlは鋼の脱酸剤として有効なものであるが、
その含有量が0.01未満では打算の効果が期待でき
なくなり、他方0.06％を越えて含有させても脱酸
の効果が飽和してそれ以上の効果が期待できない
ことからsolAl含有量を0.01〜0.06％と限定した。
スラブの溶製後、該スラブを550℃以上に保持
するのは、未変態オーステナイト量が50％以上確
保されている状態より再加熱するためである。こ
の状態より再加熱−熱延後、制御冷却を行なう
と、フエライト変態が高温域で確保されるため、
急冷時生成されるマルテンサイト粒が微細に、か
つ均一に分散され、従来材に比べてきわめて良延
性の複合組織型高強度鋼板となる。
なお、550℃以上の温度への保温は例えば断熱
材により行なえばよい。
1050〜1150℃の温度での熱間圧延
熱間圧延は、1050〜1150℃の温度で開始する。
このように1050℃以上としたのは、加熱費の低
減がその理由であり、一方、1150℃以下としたの
は、加熱費の低減であり、さらに、マルテンサイ
ト粒が微細に均一に分散し、高延性の複合組織型
高強度熱延鋼板が得られるためである。
熱間圧延終了後は所定の制御冷却を行なう。
［実施例］
第１表に示す鋼を溶製した。A1、A2、B1、
B2.C1.C2は実施例であり、他は比較例である。
A1、A2、A3、B1、B2、B3、C1、C2につい
てはスラブ厚230mmｔで連続鋳造機で凝固させた。
さらにA1、A2、B1、B2、C1については連続鋳
造機から出てきた高温スラブに断熱材等で保熱、
さらには軽加熱によつて第２表に示すような条件
のもとで熱間圧延し、板厚2.8mmの熱延コイルと
した。
なお、本実施例においては制御冷却として次の
冷却を行なつた。すなわち、強度・延性のバラン
スからフエライト体積率を50％以上確保するた
め、フエライトノーズ付近は10℃／ｓ以下で徐冷
し、その後600℃以下の巻取温度まで20℃／ｓ以
上で急冷した。
第３表に示すように、本実施例に係る熱延鋼板
はいずれも加工性、特に強度−延性バランス
（TS×El）が飛躍的に向上している上、加熱炉原
単位の低減がはかられているのが明らかである。
従つて、本実施例によれば、加工性の良好な複合
組織鋼強度熱延鋼板を安価に製造することができ
る。
［発明の効果］
本発明によれば次のもろもろの効果が得られ
る。
高価な元素を使用することなく加工性の良好
な熱延鋼板を製造することができ、自動車の車
体用の鋼板として適用するのに好適な高強度熱
延鋼板が得られる。
加熱費の節約が可能である。
[Field of Application of the Invention] The present invention relates to a method for producing high-strength hot rolled steel sheets. [Background of the Invention] In recent years, in the automobile industry, in order to reduce the weight of car bodies, there has been a desire to reduce the plate thickness without changing the design strength. Such requests cannot be met because of poor formability and problems with weldability. Therefore, as a steel plate to replace the conventional precipitation hardening type high-strength steel plate, a composite structure type high-strength steel plate consisting of two phases of ferrite and martensite is increasingly being adopted. However, such a composite structure steel sheet is not necessarily preferable in terms of workability and the like. Therefore, we further added Mn as a basic component, Si, Cr
By adding a large amount of , a composite structure steel sheet has been developed that has the characteristics of a low yield ratio and good ductility even after the hot rolling process and the winding process. However, such a composite structure steel sheet uses a large amount of Si and Cr, so there is a problem that the cost is high. By the way, in the conventional method, hot rolled steel sheets are
Slabs made by blooming steel ingots by ordinary ingot making method or slabs made by continuous casting method are once cooled to room temperature and then heated to 1200~1300 in a heating furnace.
It is manufactured by heating at a high temperature of °C for a long time and then rolling it into a continuous hot rolling mill. However, subjecting the slab to heating at a high temperature of 1,200° C. for a long time of one hour or more as in the conventional method results in a huge loss in the amount of heating. Therefore, in order to find a method for manufacturing high-strength hot-rolled steel sheets at low cost and with high efficiency, we have repeatedly conducted various tests and investigations on both the steel material composition and rolling processing methods, and as a result, we have achieved the present invention. Ivy. [Object of the Invention] An object of the present invention is to provide a high-strength hot-rolled steel manufacturing method that can produce a hot-rolled steel sheet with good workability and low cost at low heating costs. [Summary of the invention] The above object is to reduce C: 0.03 to 0.2%, Si:
0.02-1.5%, Mn: 0.6-2.5%, S: 0.01% or less,
solAl: 0.01 to 0.06%, the balance is iron, and a method for manufacturing high-strength hot-rolled steel sheets containing bainite consisting of unavoidable impurities involves continuous casting to obtain a high-temperature slab. Before reaching the temperature, start hot rolling after reheating the slab to a temperature of 1050℃~1150℃, and the hot rolling
Finished at a temperature of Ar 3 points or higher, then slowly cooled the area around the ferrite nose at a rate of 10℃/s or less, then 600℃
This is achieved by a method for manufacturing a high-strength hot-rolled steel sheet characterized by rapid cooling at a rate of 20° C./s or more to the following coiling temperature. The configuration of the present invention will be explained below. C: 0.03-0.2%, C is an essential element for maintaining the necessary strength and forming low-temperature transformation products such as bainite and martensite, but if it exceeds 0.02%, workability and weldability deteriorate. In addition, the low yield ratio characteristic, which is one of the characteristics of the steel sheet of the present invention, will be impaired. The lower limit is set at 0.03% in order to exhibit the effect of strengthening and improving hardenability. Si: 0.2 to 1.5% Si is an element necessary for deoxidizing molten steel, and is also an effective substitutional solid solution element for obtaining high strength and high ductility. Furthermore, it has the function of favoring normal polygonal ferrite formation. In order to exhibit such characteristics, the lower limit was set at 0.2%. In addition, to prevent embrittlement (increase in transition temperature) of the weld and to prevent deterioration of the surface oxide scale condition.
The upper limit was set at 1.5%. Mn: 0.6-2.5% Mn is an essential element for increasing hardenability and obtaining a desired structure. In order to exhibit this effect, a content of 0.6% or more is required, and if it exceeds 2.5%, it becomes difficult to weld and at the same time deteriorates ductility, making the steel plate expensive, so the upper limit is set at 2.5%. Cr: 0.3 to 1.5% Unlike other elements, Cr itself does not have solid solution strengthening ability, but it is a necessary element to improve hardenability and obtain a desired structure. The lower limit is set at an amount that can produce the effect, and the upper limit is set at 0.1 to 1.0%, at which the effect reaches saturation and becomes uneconomical. S: 0.01% or less S produces sulfides and deteriorates workability, so it is desirable to have as little as possible, but if the content is
The upper limit of the S content was set at 0.01% because the desired processability can be ensured at 0.01% or less. solAl: 0.01~0.06% solAl is effective as a deoxidizer for steel, but
If the solAl content is less than 0.01%, no effect can be expected in the calculation, and on the other hand, if the content exceeds 0.06%, the deoxidizing effect will be saturated and no further effect can be expected. limited to. The reason why the slab is held at 550° C. or higher after melting the slab is to reheat it in a state where the amount of untransformed austenite is secured to be 50% or more. If controlled cooling is performed after reheating and hot rolling from this state, ferrite transformation will be ensured in the high temperature range.
Martensite grains produced during rapid cooling are finely and uniformly dispersed, resulting in a composite structure type high-strength steel sheet with extremely good ductility compared to conventional materials. Note that heat retention to a temperature of 550° C. or higher may be carried out, for example, by using a heat insulating material. Hot rolling at a temperature of 1050-1150°C Hot rolling begins at a temperature of 1050-1150°C. The reason for setting the temperature above 1050°C is to reduce heating costs, and on the other hand, setting the temperature below 1150°C is to reduce heating costs. This is because a high-strength hot-rolled steel sheet with a complex structure and high ductility can be obtained. After hot rolling is completed, predetermined controlled cooling is performed. [Example] Steels shown in Table 1 were melted. A1, A2, B1,
B2.C1.C2 are examples, and the others are comparative examples. A1, A2, A3, B1, B2, B3, C1, and C2 were solidified using a continuous casting machine with a slab thickness of 230 mm.
Furthermore, for A1, A2, B1, B2, and C1, the high-temperature slabs that come out of the continuous casting machine are heat-retained with insulation materials, etc.
Furthermore, it was hot-rolled by light heating under the conditions shown in Table 2 to obtain a hot-rolled coil with a thickness of 2.8 mm. In this example, the following cooling was performed as controlled cooling. In other words, in order to maintain a ferrite volume fraction of 50% or more from the balance of strength and ductility, the area around the ferrite nose was slowly cooled at a rate of 10°C/s or less, and then rapidly cooled at a rate of 20°C/s or more to a coiling temperature of 600°C or less. . As shown in Table 3, all of the hot rolled steel sheets according to the present example have dramatically improved workability, especially the strength-ductility balance (TS x El), and have significantly reduced the heating furnace unit consumption. It's obvious that he's being confused.
Therefore, according to this example, a composite structure steel strength hot-rolled steel sheet with good workability can be manufactured at low cost. [Effects of the Invention] According to the present invention, the following various effects can be obtained. A hot-rolled steel sheet with good workability can be produced without using expensive elements, and a high-strength hot-rolled steel sheet suitable for use as a steel sheet for automobile bodies can be obtained. It is possible to save on heating costs.
【表】【table】
【表】
○印は実施例
[Table] ○ marks are examples
【表】
○印は実施例
[Table] ○ marks are examples
【表】【table】
Claims (1)
％、Mn：0.6〜2.5％、Ｓ：0.01％以下、solAl：
0.01〜0.06％、残部鉄及び不可避的不純物からな
るベイナイトを含む変態強化型の高強度熱延鋼板
を製造する方法において、連続鋳造を行ない高温
スラブを得た後、該スラブが550℃の温度になる
前に、該スラブを1050℃〜1150℃の温度に再加熱
した後熱間圧延を開始し、該熱間圧延をAr3点以
上の温度で終了し、次いでフエライトノーズ付近
は10℃／ｓ以下で徐冷し、その後600℃以下の巻
取温度まで20℃／ｓ以上で急冷することを特徴と
する高強度熱延鋼板の製造法。1% by weight, C: 0.03-0.2%, Si: 0.02-1.5
%, Mn: 0.6-2.5%, S: 0.01% or less, solAl:
In a method for producing transformation-strengthened high-strength hot-rolled steel sheets containing 0.01 to 0.06% bainite, the balance consisting of iron and unavoidable impurities, after continuous casting is performed to obtain a high-temperature slab, the slab is heated to a temperature of 550°C. After reheating the slab to a temperature of 1050°C to 1150°C, hot rolling is started, and the hot rolling is finished at a temperature of Ar 3 or higher, and then the ferrite nose area is heated at 10°C/s. A method for manufacturing a high-strength hot-rolled steel sheet, characterized by slow cooling at a temperature of 20°C/s or more to a coiling temperature of 600°C or lower.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23389985A JPS6293006A (en) | 1985-10-18 | 1985-10-18 | Production of high strength hot rolled steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23389985A JPS6293006A (en) | 1985-10-18 | 1985-10-18 | Production of high strength hot rolled steel sheet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6293006A JPS6293006A (en) | 1987-04-28 |
| JPH0573803B2 true JPH0573803B2 (en) | 1993-10-15 |
Family
ID=16962319
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23389985A Granted JPS6293006A (en) | 1985-10-18 | 1985-10-18 | Production of high strength hot rolled steel sheet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6293006A (en) |
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|---|---|---|---|---|
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| US10948534B2 (en) | 2017-08-28 | 2021-03-16 | Teradyne, Inc. | Automated test system employing robotics |
| US10983145B2 (en) | 2018-04-24 | 2021-04-20 | Teradyne, Inc. | System for testing devices inside of carriers |
| US11226390B2 (en) | 2017-08-28 | 2022-01-18 | Teradyne, Inc. | Calibration process for an automated test system |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2640065B2 (en) * | 1992-08-11 | 1997-08-13 | 株式会社神戸製鋼所 | High-strength hot-rolled steel sheet having good workability and a strength of 730 N / mm2 or more and method for producing the same |
| JP3352938B2 (en) * | 1998-03-19 | 2002-12-03 | 株式会社神戸製鋼所 | High-strength hot-rolled steel sheet excellent in impact resistance and method for producing the same |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6075518A (en) * | 1983-09-29 | 1985-04-27 | Nippon Steel Corp | Hot rolling method which is effective in improving toughness at low temperature |
-
1985
- 1985-10-18 JP JP23389985A patent/JPS6293006A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6075518A (en) * | 1983-09-29 | 1985-04-27 | Nippon Steel Corp | Hot rolling method which is effective in improving toughness at low temperature |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002521562A (en) * | 1998-07-24 | 2002-07-16 | エス・エム・エス・デマーク・アクチエンゲゼルシャフト | Manufacturing method and manufacturing equipment for duplex stainless steel |
| US9001456B2 (en) | 2010-08-31 | 2015-04-07 | Teradyne, Inc. | Engaging test slots |
| US9459312B2 (en) | 2013-04-10 | 2016-10-04 | Teradyne, Inc. | Electronic assembly test system |
| US10845410B2 (en) | 2017-08-28 | 2020-11-24 | Teradyne, Inc. | Automated test system having orthogonal robots |
| US10948534B2 (en) | 2017-08-28 | 2021-03-16 | Teradyne, Inc. | Automated test system employing robotics |
| US11226390B2 (en) | 2017-08-28 | 2022-01-18 | Teradyne, Inc. | Calibration process for an automated test system |
| US10983145B2 (en) | 2018-04-24 | 2021-04-20 | Teradyne, Inc. | System for testing devices inside of carriers |
| US10775408B2 (en) | 2018-08-20 | 2020-09-15 | Teradyne, Inc. | System for testing devices inside of carriers |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6293006A (en) | 1987-04-28 |
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