JPH04305338A - Method for continuously casting billet for steel sheet - Google Patents
Method for continuously casting billet for steel sheetInfo
- Publication number
- JPH04305338A JPH04305338A JP6858691A JP6858691A JPH04305338A JP H04305338 A JPH04305338 A JP H04305338A JP 6858691 A JP6858691 A JP 6858691A JP 6858691 A JP6858691 A JP 6858691A JP H04305338 A JPH04305338 A JP H04305338A
- Authority
- JP
- Japan
- Prior art keywords
- slab
- water
- cooling
- roll
- cooled
- 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.)
- Pending
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 28
- 239000010959 steel Substances 0.000 title claims abstract description 28
- 238000000034 method Methods 0.000 title claims abstract description 18
- 238000005266 casting Methods 0.000 title abstract description 4
- 238000001816 cooling Methods 0.000 claims abstract description 45
- 238000009749 continuous casting Methods 0.000 claims abstract description 25
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000007921 spray Substances 0.000 claims abstract description 20
- 238000005098 hot rolling Methods 0.000 claims abstract description 8
- 239000002344 surface layer Substances 0.000 claims description 14
- 229910052717 sulfur Inorganic materials 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 229910001566 austenite Inorganic materials 0.000 claims description 3
- 229910001562 pearlite Inorganic materials 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 229910000859 α-Fe Inorganic materials 0.000 claims description 3
- 238000009413 insulation Methods 0.000 claims description 2
- 230000001376 precipitating effect Effects 0.000 claims 1
- 238000005096 rolling process Methods 0.000 abstract description 9
- RQMIWLMVTCKXAQ-UHFFFAOYSA-N [AlH3].[C] Chemical compound [AlH3].[C] RQMIWLMVTCKXAQ-UHFFFAOYSA-N 0.000 abstract 1
- 238000005097 cold rolling Methods 0.000 abstract 1
- 239000003595 mist Substances 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- 239000002244 precipitate Substances 0.000 description 4
- 150000003568 thioethers Chemical class 0.000 description 4
- 238000009434 installation Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910000655 Killed steel Inorganic materials 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 229910001208 Crucible steel Inorganic materials 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000005499 meniscus Effects 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 125000000101 thioether group Chemical group 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Landscapes
- Continuous Casting (AREA)
Abstract
Description
【０００１】0001
【産業上の利用分野】連続鋳造スラブを直接圧延する場
合に発生する表面疵の防止に関する。[Industrial Application Field] This invention relates to the prevention of surface defects that occur when continuous casting slabs are directly rolled.
【０００２】0002
【従来の技術】薄板用連続鋳造鋳片の直接圧延（Ｈｏｔ
Ｄｉｒｅｃｔ Ｒｏｌｌｉｎｇ、以下ＨＤＲという）
は、連続鋳造機で鋳造された鋳片を冷却することなく、
そのまま保温またはオンライン加熱することにより、熱
間圧延機により圧延加工する方法である。このＨＤＲプ
ロセスは工程の大幅な合理化、省エネルギー、歩留り向
上が期待でき、今後さらに開発が進むものと考えられて
いる。[Prior art] Direct rolling of continuously cast slabs for thin plates (Hot
Direct Rolling (hereinafter referred to as HDR)
, without cooling the slab cast by a continuous casting machine,
In this method, the material is kept warm or heated on-line, and then rolled using a hot rolling mill. This HDR process is expected to significantly streamline the process, save energy, and improve yield, and is expected to be further developed in the future.
【０００３】しかし、ＨＤＲで製造された鋳片は、従来
の製造方法すなわち連続鋳造鋳片の冷却後、再加熱して
から圧延加工する製造方法に比較して製品（例えば、冷
延コイル）の表面疵が多く、歩留りが低下するという問
題がある（図５参照、蜂谷ら：鉄と鋼６８（１９８２）
Ｓ２０９、小谷野ら：鉄と鋼６８（１９８２）Ｓ．１５
６ ）。図５は、冷延コイルの表面に見られた疵をカウ
ントし、個数が１０個以上発生した場合のコイルを不可
とし、これを全調査コイルで割った値を表面疵発生率と
して、鋼中のＭｎ／Ｓとの関係を示したグラフ図である
。図中、○、△はそれぞれ従来の製造方法および従来の
ＨＤＲによる製品を示す。なお、図中、ＨＣＲは連続鋳
造鋳片を一度冷却し、再加熱して熱間圧延する方法であ
る。[0003] However, the slab produced by HDR has a lower quality as a product (for example, a cold-rolled coil) than the conventional manufacturing method, in which the continuously cast slab is cooled, reheated, and then rolled. There is a problem that there are many surface defects and the yield is reduced (see Figure 5, Hachiya et al.: Tetsu to Hagane 68 (1982)
S209, Koyano et al.: Tetsu to Hagane 68 (1982) S. 15
6). Figure 5 shows that the number of flaws found on the surface of cold-rolled coils is counted, coils with 10 or more defects are rejected, and the value divided by all investigated coils is defined as the surface flaw occurrence rate. FIG. 2 is a graph diagram showing the relationship between Mn/S and Mn/S. In the figure, ◯ and △ indicate products produced by the conventional manufacturing method and conventional HDR, respectively. In addition, in the figure, HCR is a method in which a continuously cast slab is cooled once, reheated, and then hot rolled.
【０００４】一般に連続鋳造鋳片に発生する表面疵は縦
割れ、横割れまたは表層下介在物に起因する割れが良く
知られている。縦割れについてはモールド内で割れの起
点が形成され、その後の冷却過程で割れが発展すること
が明らかになっている。この防止対策としては、モール
ドパウダーの選択、モールドテーパーの適正化、湯面変
動の適正範囲内へのコントロールまたは二次冷却帯での
均一冷却などが重要な対策として実施されている（河野
ら：鉄と鋼 ６８（１９８２），Ｐ．１７６４）。[0004] In general, surface defects that occur in continuously cast slabs are well known to include vertical cracks, transverse cracks, and cracks caused by subsurface inclusions. Regarding vertical cracks, it has been revealed that the starting point of the crack is formed within the mold, and the crack develops during the subsequent cooling process. Important countermeasures to prevent this include selecting mold powder, optimizing mold taper, controlling mold level fluctuations within an appropriate range, and uniform cooling in the secondary cooling zone (Kono et al.: Tetsu to Hagane 68 (1982), P. 1764).
【０００５】また、表層下の介在物に起因する割れは、
鋳型内の初期凝固シェルに介在物が捕捉されるかどうか
に関係があり、この対策として溶鋼の清浄化をはかり、
溶鋼中のアルミナ介在物を少なくすること、および鋳型
内湯面変動を適正にしてパウダ−の巻き込みを防ぐこと
が行われている（手嶋ら：鉄と鋼，７２（１９８６），
Ｓ．１０１２）。[0005] Furthermore, cracks caused by inclusions below the surface layer are
This is related to whether inclusions are trapped in the initial solidified shell in the mold, and as a countermeasure to this, cleaning of the molten steel is carried out.
Efforts are being made to reduce the amount of alumina inclusions in molten steel and to adjust the level fluctuations in the mold to prevent powder from being entrained (Teshima et al.: Tetsu-to-Hagane, 72 (1986),
S. 1012).
【０００６】横割れは、鋼中の不純物元素（Ｓ，Ｐ）や
添加元素（例えば、Ｖ，Ｎｂ，Ｂ）が凝固、冷却中に析
出物を形成し、これが粒界に析出して鋼の高温粒界脆化
を引き起こして割れを形成する。横割れ防止の基本対策
は連続鋳造機内で曲げ変形（矯正）を加えた時、鋳片の
表面温度を高温脆化温度範囲を回避して矯正することで
ある。更に、析出物の成因であるＳ，Ｐ，Ｎなどの不純
物元素の低減を図り、高温脆化を極力少なくすることも
その対策のひとつとなっている（河野ら：鉄と鋼６８（
１９８２）， Ｐ ．１７９２）。[0006] Transverse cracking occurs when impurity elements (S, P) and additive elements (for example, V, Nb, B) in the steel form precipitates during solidification and cooling, which precipitate at the grain boundaries and cause damage to the steel. It causes high-temperature grain boundary embrittlement and forms cracks. The basic measure to prevent transverse cracking is to correct the surface temperature of the slab by avoiding the high temperature embrittlement temperature range when bending deformation (straightening) is applied in the continuous casting machine. Furthermore, one of the countermeasures is to reduce impurity elements such as S, P, and N, which are the causes of precipitates, and to minimize high-temperature embrittlement (Kono et al.: Tetsu to Hagane 68).
1982), P. 1792).
【０００７】[0007]
【発明が解決しようとする課題】しかしながら、従来の
表面疵低減対策を実施しても、なおＨＤＲプロセスで製
造した製品には表面疵の発生が多く、歩留りの低下が著
しいという問題がある。However, even if conventional surface flaw reduction measures are implemented, products manufactured by the HDR process still have many surface flaws, resulting in a significant decrease in yield.
【０００８】本発明はかかる事情に鑑みてされたもので
、ＨＤＲプロセスにより発生する特有の製品（冷延コイ
ル、熱延コイル）の高温脆化による表面疵発生を低減す
る方法を提供しようとするものである。The present invention has been made in view of the above circumstances, and aims to provide a method for reducing the occurrence of surface flaws due to high temperature embrittlement of specific products (cold rolled coils, hot rolled coils) caused by the HDR process. It is something.
【０００９】[0009]
【課題を解決するための手段、作用】本発明の薄鋼板用
鋼片の連続鋳造方法は、重量比で、Ｃ；０．０８％以下
、Ｓｉ；０．０５％以下、Ｍｎ；０．１０〜０．４０％
、Ｐ；０．０２％以下、Ｓ；０．０１〜０．０３％、ｓ
ｏｌＡｌ；０．０１〜０．０５％の鋼を連続鋳造後、直
ちに熱間圧延して製造する薄鋼板用鋼片の製造方法にお
いて、連続鋳造鋳型から引き出された鋳片を鋳型下端か
ら１５ｍ以内の２次冷却帯にロール径４００〜５００ｍ
ｍの水冷ロールを一対以上配置し、この水冷ロールの直
前までの鋳片冷却は水スプレーを用いて行った後、上記
水冷ロールと鋳片の接触を利用するロール冷却を行って
、鋳片温度をＡ１ 点直下まで冷却して鋳片表層部分で
フェライト（α相）とパーライトを析出させた後、鋳片
の顕熱および未凝固部分の潜熱を利用し、鋳片の冷却と
断熱を調整して鋼片の表面温度を１０００°Ｃ以上の温
度（オーステナイトγ相）とした薄鋼板用鋳片を熱間圧
延することを特徴とする。[Means and effects for solving the problems] The continuous casting method of steel slabs for thin steel sheets of the present invention has a weight ratio of C: 0.08% or less, Si: 0.05% or less, Mn: 0.10. ~0.40%
, P; 0.02% or less, S; 0.01-0.03%, s
olAl; In a method for producing steel slabs for thin steel plates, which involves continuous casting of 0.01 to 0.05% steel and immediately hot rolling, the slab pulled out of the continuous casting mold is placed within 15 m from the bottom end of the mold. Roll diameter 400-500m in the secondary cooling zone of
At least one pair of water-cooled rolls with a diameter of 50 m are arranged, and the slab is cooled by using water spray up to just before the water-cooled rolls, and then the slab is cooled by utilizing the contact between the water-cooled roll and the slab, and the temperature of the slab is adjusted. After cooling the slab to just below the A1 point to precipitate ferrite (α phase) and pearlite on the surface layer of the slab, the cooling and insulation of the slab are adjusted using the sensible heat of the slab and the latent heat of the unsolidified part. The method is characterized in that a slab for thin steel plate is hot-rolled so that the surface temperature of the steel slab is 1000°C or higher (austenite γ phase).
【００１０】0010
【実施例】鋼を凝固、冷却させるとオーステナイト相（
以下、γ相）中のＳはγ粒界に偏析する。そのため鋼中
のＳとＭｎまたはＦｅとが反応して、硫化物が形成また
は析出してくる。連続鋳造で上述した成分の鋼を凝固さ
せた後、鋳片を連続的に冷却すると、微細な硫化物がγ
粒界に沿って析出してくる。また、連続的にゆっくり冷
却してくると粒成長が起こりγ粒界も大きくなるため、
γ粒界へのＳ偏析もより顕著になる。従って、γ粒界に
沿って析出した硫化物の組成は、Ｆｅリッチな硫化物と
なるため、硫化物自体の融点が非常に低く、１１００℃
〜１２００℃程度まで低下する。[Example] When steel is solidified and cooled, the austenite phase (
S in the γ phase (hereinafter referred to as γ phase) segregates at the γ grain boundaries. Therefore, S in the steel reacts with Mn or Fe, and sulfides are formed or precipitated. After solidifying steel with the above-mentioned components by continuous casting, when the slab is continuously cooled, fine sulfides are
It precipitates along grain boundaries. In addition, continuous slow cooling causes grain growth and the γ grain boundaries also become larger.
S segregation to the γ grain boundaries also becomes more pronounced. Therefore, the composition of the sulfide precipitated along the γ grain boundaries is Fe-rich sulfide, so the melting point of the sulfide itself is very low, at 1100°C.
The temperature decreases to about 1200°C.
【００１１】この状態の鋼の熱間強度は非常に脆く、熱
間圧延すると割れが発生し易い。そこで、次のようなこ
とが考えられる。鋳片の表面層を完全にフェライト＋パ
ーライト相（以下、α＋Ｐ相）にした後、鋳片内部の顕
熱や未凝固部分の潜熱を利用して表面層を復熱させて、
表層部分の温度を上げてＡｃ３点以上（γ相）に戻すこ
とによって、新たなγ粒を析出させ、すでに析出してい
た硫化物を新たに析出したγ粒内に取りこまれるように
する。このような鋳片を１０００ ℃以上の高温に保持
すると、硫化物周囲のＭｎの拡散の進行によって、Ｆｅ
リッチな硫化物はＭｎリッチな硫化物に変化していくと
同時に硫化物同士の凝集が起こり、粗大化する。このよ
うな硫化物析出形態をとる場合には鋼の高温脆化が著し
く改善できる。[0011] The hot strength of the steel in this state is extremely brittle, and cracks are likely to occur when hot rolled. Therefore, the following can be considered. After the surface layer of the slab is completely made into a ferrite + pearlite phase (hereinafter referred to as α + P phase), the surface layer is reheated using the sensible heat inside the slab and the latent heat of the unsolidified part.
By raising the temperature of the surface layer to return it to Ac3 point or higher (γ phase), new γ grains are precipitated, and the sulfides that have already precipitated are incorporated into the newly precipitated γ grains. When such a slab is kept at a high temperature of 1000°C or higher, Fe is dissolved due to the progress of diffusion of Mn around the sulfide.
As the rich sulfide changes to Mn-rich sulfide, agglomeration of sulfides occurs and becomes coarse. When such a sulfide precipitation form is adopted, high-temperature embrittlement of steel can be significantly improved.
【００１２】しかし、現実的な問題としては引き抜き速
度が２．０ ｍ ／ｍｉｎを超える高速鋳造において、
連続鋳造鋳型直下から１５ｍの範囲で鋳片表層部をＡ１
点まで低下させることは極めて困難なことである。その
理由は、スプレーノズル（水滴を噴出させるノズル）や
ミストノズル（水と空気等のガスを混合して噴出させる
ノズル）の冷却特性によるものであり、スプレー水量や
ミスト量を上げても、表層部分の温度低下は困難でああ
る。また、さらに冷却能をあげるためには、スプレー水
量やミスト量を供給する配管やポンプ能力、圧縮空気の
ためのコンプレッサーの能力などの設備上の問題もある
。その上、鋳造−直接圧延を前提とした連続鋳造方法に
おいては、鋳片表面温度をできるだけ高温に保持するこ
とが熱間圧延上有利であることから、連続鋳造機内の二
次冷却は出来るだけ緩冷却法を採用しているのが一般的
である （例えば、特公昭５８−３０３６６号）。However, as a practical problem, in high-speed casting where the drawing speed exceeds 2.0 m/min,
The surface layer of the slab is A1 within 15m from directly below the continuous casting mold.
It is extremely difficult to reduce this to a certain point. The reason for this is due to the cooling characteristics of spray nozzles (nozzles that eject water droplets) and mist nozzles (nozzles that eject a mixture of water and gas such as air), and even if the amount of spray water or mist is increased, the surface layer It is difficult to reduce the temperature of the part. Additionally, in order to further increase the cooling capacity, there are equipment issues such as piping and pump capacity for supplying the amount of spray water and mist, and the capacity of the compressor for compressed air. Furthermore, in continuous casting methods based on casting and direct rolling, it is advantageous for hot rolling to maintain the surface temperature of the slab as high as possible, so the secondary cooling in the continuous casting machine is as slow as possible. Generally, a cooling method is used (for example, Japanese Patent Publication No. 58-30366).
【００１３】本発明の方法はスプレー水とロールによる
冷却を組み合わせた方法をとっている。すなわち、ロー
ル冷却に用いる水冷ロールは内部に冷却水を通してロー
ル表面を冷却する構造のものである。The method of the present invention employs a combination of spray water and cooling using rolls. That is, the water-cooled roll used for roll cooling has a structure in which cooling water is passed inside to cool the roll surface.
【００１４】水膜を鋳片と水冷ロ−ルとの間に挟み込ん
で鋳片を冷却すると、鋳片が水冷ロ−ルに挟まれている
間、鋳片表層の温度は急激に低下して、一時的にＡ１点
以下に冷却され、ロ−ルから鋳片が離れると表層部の温
度は直ちに回復する。ロール冷却の前後の表層部の温度
差について検討した結果を図１に示す。[0014] When the slab is cooled by sandwiching a water film between the slab and the water-cooled rolls, the temperature of the surface layer of the slab decreases rapidly while the slab is sandwiched between the water-cooled rolls. , the slab is temporarily cooled to below the A1 point, and when the slab is separated from the roll, the temperature of the surface layer immediately recovers. Figure 1 shows the results of a study on the temperature difference in the surface layer before and after the roll was cooled.
【００１５】図２（Ａ）はスプレー水、図２（Ｂ）はエ
アーミストにより、鋳片を冷却したときの、鋳片表層部
の温度を示すグラフ図で、横軸は鋳型下からの鋳片長さ
である。いずれも、熱電対を鋳片表面に溶着させて測定
した結果である。図中、下方に向かうピ−クはロ−ル直
下の抜熱を示す。スプレー水を使った時には、水冷ロー
ル直下と水冷ロールから離れた位置とでは温度差が約２
００ ℃となって、Ａ１点以下になる。Ａ１点は前記炭
素鋼成分においては約７３０ ℃である。本発明の目的
に対して、この温度差が大きい程有利である。本発明で
は、このスプレー水による冷却とロール冷却を組合わせ
た冷却方法を採用して、ＨＤＲの時の二次冷却法を採用
する。FIG. 2(A) is a graph showing the temperature of the surface layer of the slab when the slab is cooled by spray water and FIG. 2(B) is by air mist, and the horizontal axis is the temperature of the slab from below the mold. It is one length. Both results were measured by welding a thermocouple to the surface of the slab. In the figure, the downward peak indicates heat removal directly below the roll. When using spray water, there is a temperature difference of approximately 2 between directly below the water cooling roll and at a location away from the water cooling roll.
00°C, which is below the A1 point. Point A1 is approximately 730°C in the carbon steel composition. For the purposes of the present invention, the larger this temperature difference is, the more advantageous it is. In the present invention, a cooling method that combines cooling using spray water and roll cooling is employed, and a secondary cooling method during HDR is employed.
【００１６】ロール冷却の条件について種々検討した結
果、冷却をより強化するには水冷ロールと鋳片の接触時
間が極めて重要であることを知見するに至った。一般に
、鋳片とロールとの接触時間ｔＣ は次式で表すことが
できる。As a result of various studies on roll cooling conditions, it has been found that the contact time between the water-cooled roll and the slab is extremely important in order to further strengthen the cooling. Generally, the contact time tC between the slab and the roll can be expressed by the following equation.
【００１７】[0017]
【数１】[Math 1]
【００１８】ここで、ＷＯ；鋳片未凝固巾、Ｗ；鋳片と
ロールの接触巾、ν；鋳片のポアソン比、ＥＳ、ＥＲ；
それぞれ鋳片、ロールのヤング率、Ｐ；溶鋼静圧、Ｌ；
ロールピッチ、ＶＣ；引き抜き速度、ｋ；定数である。Here, WO: unsolidified width of slab, W: contact width between slab and roll, ν: Poisson's ratio of slab, ES, ER;
Young's modulus of slab and roll, P; Static pressure of molten steel, L;
Roll pitch, VC; drawing speed, k: constant.
【００１９】数１からわかる通り、ロール径が大きい程
，接触時間は長くなり，水冷ロールによる鋳片からの抜
熱を大きくできる。また、水冷ロール径を大きくすると
必然的に水冷ロールピッチが大きくなるため、接触時間
はより長くなる。しかし、水冷ロールピッチを大きくす
るとロール間での鋳片バルジングが大きくなり、鋳片内
部割れが発生する虞がある。As can be seen from Equation 1, the larger the roll diameter, the longer the contact time, and the greater the heat removal from the slab by the water-cooled roll. Furthermore, when the diameter of the water-cooled roll is increased, the pitch of the water-cooled roll is inevitably increased, so the contact time becomes longer. However, when the pitch of the water-cooled rolls is increased, bulging of the slab between the rolls becomes large, and there is a possibility that internal cracks in the slab may occur.
【００２０】試験は後述するように、鋳型直下数ｍの位
置に種々の径のロ−ルを設置して、水冷ロールによる鋳
片冷却について行った。その結果、鋳型直下を水冷ロー
ルで強冷却し、その後復熱させてＨＤＲを可能とする条
件は次の通りであることが知見された。
■水冷ロール径は４００ｍｍ乃至５００ｍｍである。
■水冷ロールの設置位置は、鋳型直下１５ｍまでである
。
■鋳片冷却としては、水スプレ−冷却が望ましい。As will be described later, the test was conducted by installing rolls of various diameters several meters directly below the mold, and cooling the slab with water-cooled rolls. As a result, it was found that the conditions for enabling HDR by strongly cooling the area immediately below the mold with a water-cooled roll and then regenerating it were as follows. ■The diameter of the water-cooled roll is 400 mm to 500 mm. ■The installation position of the water-cooled roll is up to 15m directly below the mold. ■Water spray cooling is preferable for cooling slabs.
【００２１】次に、上記の条件が必要な理由について、
試験例に基づいて詳細に述べる。図１に本実施例の試験
に用いた連続鋳造機、圧延機を示す。図中、２１は溶鋼
２３を保持するタンディッシュ、２２は浸漬ノズル、１
３は鋳片を保持するガイドロールで、簡明のためとくに
図示しないが、ガイドロール１３の間にスプレーノズル
が設けられている。１２は水冷ロール、１４は湾曲して
いる鋳片を真線状にする矯正ロールである。１５、１６
は直接、連続鋳造機１０から搬送されてきた鋳片１８を
圧延するタンデム式熱間圧延機の圧延ロールで、それぞ
れ初段、最終段の圧延ロールを示す。１９は上記熱間圧
延機によって圧延された薄板用鋼片である。鋳型１１の
断面サイズは、例えば２２０ｍｍｘ１８００ｍｍである
。Next, the reason why the above conditions are necessary is as follows.
This will be described in detail based on test examples. FIG. 1 shows the continuous casting machine and rolling mill used in the test of this example. In the figure, 21 is a tundish that holds molten steel 23, 22 is an immersion nozzle, 1
Reference numeral 3 denotes guide rolls that hold the slab, and a spray nozzle is provided between the guide rolls 13, although not particularly shown for the sake of clarity. 12 is a water-cooled roll, and 14 is a straightening roll that straightens the curved slab. 15, 16
1 and 2 are rolls of a tandem hot rolling mill that directly rolls the slab 18 conveyed from the continuous casting machine 10, and indicate the first and last rolls, respectively. 19 is a steel piece for a thin plate rolled by the above-mentioned hot rolling mill. The cross-sectional size of the mold 11 is, for example, 220 mm x 1800 mm.
【００２２】（試験例１）鋳型下端からから１０ｍの位
置に冷却用の一対の水冷ロ−ル１２を設置した。水冷ロ
−ル１２は直径３００、４００、５００、５５０ｍｍの
４種類を用いた。水冷ロールの直前に、スプレ−水量密
度、４５０ｌ／ｍ２・ｍｉｎのスプレー冷却ノズルを取
り付けた。また、軽圧下を行うためこの水冷ロ−ル１２
を含むロ−ルギャップは０．５０ｍｍ／ｍとして、ロー
ルアライメントにテーパーをつけた。そして、鋳型下端
から６ｍの位置で熱電対を鋳片１８の表面に溶着させて
、鋳片１８の移動とともに流して温度測定を行った。
この方法によって、ロ−ル１２、１３の直下またはロ−
ル１２、１３から離れたときの鋳片表層温度を測定する
ことができる。また、連続鋳造機１０出口（メニスカス
から４３ｍ）での鋳片表面温度を輻射温度計を用いて測
定してＨＤＲ可否の判定を行った。この温度が１０００
℃以上であればＨＤＲが可能である。鋳造鋼種は、低Ｍ
ｎ／Ｓ比（Ｍｎ／Ｓ＝８〜１６）の低炭素Ａｌキルド鋼
である。引抜速度は、２．４ｍ／ｍｉｎであった。(Test Example 1) A pair of water-cooled rolls 12 for cooling were installed at a position 10 m from the lower end of the mold. Four types of water-cooled rolls 12 with diameters of 300, 400, 500, and 550 mm were used. A spray cooling nozzle with a spray water density of 450 l/m 2 ·min was installed just before the water cooling roll. In addition, this water-cooled roll 12 is used to perform light reduction.
The roll gap including the roll gap was 0.50 mm/m, and the roll alignment was tapered. Then, a thermocouple was welded to the surface of the slab 18 at a position 6 m from the lower end of the mold, and the temperature was measured by flowing it as the slab 18 moved. By this method, the
It is possible to measure the surface temperature of the cast slab when it is separated from the bars 12 and 13. Further, the surface temperature of the slab at the exit of the continuous casting machine 10 (43 m from the meniscus) was measured using a radiation thermometer to determine whether HDR was possible. This temperature is 1000
HDR is possible if the temperature is above ℃. Cast steel type is low M
It is a low carbon Al-killed steel with an n/S ratio (Mn/S=8 to 16). The drawing speed was 2.4 m/min.
【００２３】図３に水冷ロール径と水冷ロ−ル直下の最
低温度との関係を○で示した。また同図には水冷ロール
に入る直前の鋳片表面温度も●で示してある。この結果
、水冷ロール径が４００ｍｍ以上の場合に鋳片表層部の
温度がＡ１点以下に下がることが分かる。表１に、各水
冷ロール１２を用いて、水冷ロール１２に入る直前の鋳
片表面温度、水冷ロール１２直下の鋳片表層温度、連続
鋳造機１０出口の表面温度、および内部割れの有無を示
した。いづれのロ−ルを用いてもＨＤＲ可能な温度は確
保できる。しかし、ロ−ル径が３００ｍｍの場合には、
鋳片表層温度が７８０℃であり、Ａ１点まで低下しない
。また、水冷ロ−ル径が５５０ｍｍの場合には内部割れ
の発生が多く問題があった。この結果、水冷ロ−ル径と
しては４００〜５００ｍｍが適当である。In FIG. 3, the relationship between the diameter of the water-cooled roll and the lowest temperature directly below the water-cooled roll is indicated by a circle. The figure also shows the surface temperature of the slab immediately before entering the water-cooled roll. As a result, it can be seen that when the water-cooled roll diameter is 400 mm or more, the temperature of the surface layer of the slab falls below the A1 point. Table 1 shows the surface temperature of the slab immediately before entering the water-cooled roll 12, the surface temperature of the slab immediately below the water-cooled roll 12, the surface temperature at the exit of the continuous casting machine 10, and the presence or absence of internal cracks using each water-cooled roll 12. Ta. Regardless of which roll is used, a temperature that allows HDR can be ensured. However, when the roll diameter is 300mm,
The slab surface temperature is 780°C and does not drop to the A1 point. Further, when the diameter of the water-cooled roll was 550 mm, there was a problem in that many internal cracks occurred. As a result, a suitable water-cooled roll diameter is 400 to 500 mm.
【００２４】[0024]
【表１】[Table 1]
【００２５】（試験例２）ロ−ル冷却のための水冷ロ−
ル１２径を４００ｍｍに選んで、水冷ロ−ル１２の設置
位置を変えて、水冷ロ−ル直下でＡ１ 点以下になるか
どうか、または連続鋳造機１０出口での鋳片１８表面温
度を輻射温度計で測定してＨＤＲ可能な温度かどうかを
判定した。その他の試験条件は試験例１に示した条件と
同じである。(Test Example 2) Water-cooled roll for cooling the roll
Select the diameter of the roll 12 to be 400 mm, change the installation position of the water-cooled roll 12, and check whether the surface temperature of the slab 18 at the outlet of the continuous casting machine 10 is radiated or not. It was determined whether the temperature was high enough for HDR by measuring with a thermometer. Other test conditions were the same as those shown in Test Example 1.
【００２６】表２に水冷ロール１２直前の鋳片表面温度
、水冷ロール直下温度の最低値および連続鋳造機出口の
表面温度の測定結果を示した。表中、水冷ロール１２設
置位置は鋳型１１下端からの長さである。鋳型下端から
１５ｍ以上離れた位置で冷却を強化すると連続鋳造機出
口での表面温度が１０００℃以下となりＨＤＲが困難と
なる。Table 2 shows the measurement results of the slab surface temperature immediately before the water-cooled roll 12, the lowest temperature immediately below the water-cooled roll, and the surface temperature at the outlet of the continuous casting machine. In the table, the installation position of the water-cooled roll 12 is the length from the lower end of the mold 11. If cooling is strengthened at a position 15 m or more away from the lower end of the mold, the surface temperature at the outlet of the continuous casting machine will be 1000°C or less, making HDR difficult.
【００２７】[0027]
【表２】[Table 2]
【００２８】（試験例３）径４００ｍｍの水冷ロール１
２を鋳型１１下端から１０ｍの位置に設置して、この水
冷ロール１２の直前の鋳片冷却方法を水スプレ−の場合
とエァーミストの場合とで水冷ロ−ル１２直下の鋳片表
層温度の最低値を測定した。その他の試験条件は試験例
１に示した条件と同じである。得られた結果を図４に示
す。縦軸は鋳片１８の表面温度、横軸は熱伝達係数であ
る。図中、〇、△は水冷ロール１２直下の最低温度、●
、▲は水冷ロール直前の温度を示す。また、〇、●は水
スプレー、△、▲はエアーミストによる冷却を示す。(Test Example 3) Water-cooled roll 1 with a diameter of 400 mm
2 is installed at a position 10 m from the bottom end of the mold 11, and the method of cooling the slab immediately before the water-cooled roll 12 is determined to determine the lowest temperature of the surface layer of the slab immediately below the water-cooled roll 12, depending on whether water spray or air mist is used. The value was measured. Other test conditions were the same as those shown in Test Example 1. The results obtained are shown in FIG. The vertical axis represents the surface temperature of the slab 18, and the horizontal axis represents the heat transfer coefficient. In the figure, 〇 and △ are the lowest temperatures directly below the water-cooled roll 12, ●
, ▲ indicates the temperature immediately before the water-cooled roll. In addition, 〇 and ● indicate cooling by water spray, and △ and ▲ indicate cooling by air mist.
【００２９】冷却強度を上げると鋳片表面温度は低下す
る。水スプレ−の場合には、水冷ロ−ル直下での鋳片温
度低下が大きいが、エァ−ミストの場合には水冷ロール
直下の最低温度の低下率が水スプレーに比べて小さい。
したがって、水冷ロ−ル直前の冷却には，水スプレ−の
方が望ましい。[0029] When the cooling intensity is increased, the slab surface temperature decreases. In the case of water spray, the drop in temperature of the slab directly under the water-cooled roll is large, but in the case of air mist, the rate of decrease in the lowest temperature directly under the water-cooled roll is smaller than that in water spray. Therefore, water spray is preferable for cooling immediately before the water-cooled roll.
【００３０】次に、この方法で鋳片１８表層温度をＡ１
点以下に調整した後、復熱させて、鋳片表面温度を１
０００℃以上としてＨＤＲを行い、得られた製品（冷延
コイル）の表面疵の発生率は、通常のロールを用いた従
来例と比較すると１／３になる。Next, using this method, the surface temperature of the slab 18 is adjusted to A1.
After adjusting the temperature to below the temperature, reheating is performed to bring the surface temperature of the slab to 1.
HDR is performed at a temperature of 000° C. or higher, and the incidence of surface flaws on the obtained product (cold rolled coil) is 1/3 compared to a conventional example using a normal roll.
【００３１】[0031]
【発明の効果】本発明は、連続鋳造による鋳片を、鋳型
直下１５ｍの範囲で水スプレー冷却の直後にロール冷却
を行い、鋳片の表面温度を１０００°Ｃ以上に復熱させ
てから直接圧延を行うので、低炭素Ａｌキルド鋼の直接
圧延による製品の表面欠陥が低減され、歩留まりが向上
される。Effects of the Invention The present invention cools slabs produced by continuous casting immediately after water spray cooling in a range of 15 m directly below the mold, reheats the surface temperature of the slabs to 1000°C or higher, and then directly casts the slabs. Since rolling is performed, surface defects of the product due to direct rolling of the low carbon Al-killed steel are reduced and the yield is improved.
【図１】本実施例の連続鋳造機、圧延機を示す説明図で
ある。FIG. 1 is an explanatory diagram showing a continuous casting machine and a rolling mill of this embodiment.
【図２】スラブ表面温度の引抜き方向の変化を示したグ
ラフ図である。FIG. 2 is a graph showing changes in slab surface temperature in the drawing direction.
【図３】水冷ロール径と水冷ロ−ル直下の最低温度との
関係を示を示すグラフ図である。FIG. 3 is a graph showing the relationship between the diameter of the water-cooled roll and the lowest temperature directly below the water-cooled roll.
【図４】鋳片の表面温度と熱伝達係数との関係を示すグ
ラフ図である。FIG. 4 is a graph showing the relationship between the surface temperature of a slab and the heat transfer coefficient.
【図５】製品の表面疵発生率と鋼中Ｍｎ／Ｓとの関係を
示すグラフ図である。FIG. 5 is a graph showing the relationship between the surface flaw occurrence rate of a product and Mn/S in steel.
１０ 連続鋳造機 １１ 鋳型 １２ 水冷ロール １３ ガイドロール １５、１６ 熱間圧延機のロール 10 Continuous casting machine 11 Mold 12 Water cooling roll 13 Guide roll 15, 16 Hot rolling mill rolls
Claims (1)
；０．０５％以下、Ｍｎ；０．１０〜０．４０％、Ｐ；
０．０２％以下、Ｓ；０．０１〜０．０３％、ｓｏｌＡ
ｌ；０．０１〜０．０５％の鋼を連続鋳造後、直ちに熱
間圧延して製造する薄鋼板用鋼片の製造方法において、
連続鋳造鋳型から引き出された鋳片を鋳型下端から１５
ｍ以内の２次冷却帯にロール径４００〜５００ｍｍの水
冷ロールを一対以上配置し、この水冷ロールの直前まで
の鋳片冷却を水スプレーを用いて行った後、上記水冷ロ
ールと鋳片の接触を利用するロール冷却を行って、鋳片
温度をＡ１ 点直下まで冷却して鋳片表層部分でフェラ
イト（α相）とパーライトを析出させた後、鋳片の顕熱
および未凝固部分の潜熱を利用し、鋳片の冷却と断熱を
調整して鋼片の表面温度を１０００°Ｃ以上の温度（オ
ーステナイトγ相）とした鋳片を熱間圧延することを特
徴とする薄鋼板用鋼片の連続鋳造方法。Claim 1: In terms of weight ratio, C: 0.08% or less, Si
; 0.05% or less, Mn; 0.10 to 0.40%, P;
0.02% or less, S; 0.01-0.03%, solA
l; In a method for producing a steel billet for thin steel plate, which is produced by continuous casting of 0.01 to 0.05% steel and immediately hot rolling,
The slab pulled out from the continuous casting mold is 15 mm from the bottom of the mold.
A pair or more of water-cooled rolls with a roll diameter of 400 to 500 mm are placed in a secondary cooling zone within 300 m, and after cooling the slab immediately before the water-cooling roll using water spray, the water-cooled roll and the slab are brought into contact with each other. After cooling the slab to just below the A1 point and precipitating ferrite (α phase) and pearlite on the surface layer of the slab, the sensible heat of the slab and the latent heat of the unsolidified part are A steel billet for thin steel plate, characterized in that the billet is hot-rolled to have a surface temperature of 1000°C or more (austenite γ phase) by adjusting the cooling and insulation of the billet. Continuous casting method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6858691A JPH04305338A (en) | 1991-04-01 | 1991-04-01 | Method for continuously casting billet for steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6858691A JPH04305338A (en) | 1991-04-01 | 1991-04-01 | Method for continuously casting billet for steel sheet |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH04305338A true JPH04305338A (en) | 1992-10-28 |
Family
ID=13378049
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6858691A Pending JPH04305338A (en) | 1991-04-01 | 1991-04-01 | Method for continuously casting billet for steel sheet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH04305338A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102764869A (en) * | 2012-07-16 | 2012-11-07 | 莱芜钢铁集团有限公司 | Continuous casting billet strengthening device and strengthening method in continuous casting process |
| JP2017100180A (en) * | 2015-12-04 | 2017-06-08 | 株式会社神戸製鋼所 | Continuous casting method |
| CN109093084A (en) * | 2018-09-29 | 2018-12-28 | 东北大学 | A kind of production method of continuous-casting sheet billet |
| JP2019022911A (en) * | 2018-09-03 | 2019-02-14 | 株式会社神戸製鋼所 | Method for steel continuous casting |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5852443A (en) * | 1981-09-19 | 1983-03-28 | Chugai Ro Kogyo Kaisha Ltd | Method and installation for continuous bright annealing of steel wire rod |
| JPS6167549A (en) * | 1984-09-11 | 1986-04-07 | Nippon Kokan Kk <Nkk> | Direct hot rolling method in continuous casting |
-
1991
- 1991-04-01 JP JP6858691A patent/JPH04305338A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5852443A (en) * | 1981-09-19 | 1983-03-28 | Chugai Ro Kogyo Kaisha Ltd | Method and installation for continuous bright annealing of steel wire rod |
| JPS6167549A (en) * | 1984-09-11 | 1986-04-07 | Nippon Kokan Kk <Nkk> | Direct hot rolling method in continuous casting |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102764869A (en) * | 2012-07-16 | 2012-11-07 | 莱芜钢铁集团有限公司 | Continuous casting billet strengthening device and strengthening method in continuous casting process |
| CN102764869B (en) * | 2012-07-16 | 2014-12-10 | 莱芜钢铁集团有限公司 | Continuous casting billet strengthening device and strengthening method in continuous casting process |
| JP2017100180A (en) * | 2015-12-04 | 2017-06-08 | 株式会社神戸製鋼所 | Continuous casting method |
| JP2019022911A (en) * | 2018-09-03 | 2019-02-14 | 株式会社神戸製鋼所 | Method for steel continuous casting |
| CN109093084A (en) * | 2018-09-29 | 2018-12-28 | 东北大学 | A kind of production method of continuous-casting sheet billet |
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