JPS6117301A - Prevention of surface cracking of billet during hot rolling - Google Patents

Prevention of surface cracking of billet during hot rolling

Info

Publication number
JPS6117301A
JPS6117301A JP13522884A JP13522884A JPS6117301A JP S6117301 A JPS6117301 A JP S6117301A JP 13522884 A JP13522884 A JP 13522884A JP 13522884 A JP13522884 A JP 13522884A JP S6117301 A JPS6117301 A JP S6117301A
Authority
JP
Japan
Prior art keywords
rolling
steel
billet
surface cracking
hot
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
Application number
JP13522884A
Other languages
Japanese (ja)
Inventor
Kakuji Yoshihara
吉原 佳久次
Noburu Nakano
中野 宣
Yutaka Ogawa
裕 小川
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
Original Assignee
Sumitomo Metal Industries Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Sumitomo Metal Industries Ltd filed Critical Sumitomo Metal Industries Ltd
Priority to JP13522884A priority Critical patent/JPS6117301A/en
Publication of JPS6117301A publication Critical patent/JPS6117301A/en
Pending legal-status Critical Current

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21BROLLING OF METAL
    • B21B1/00Metal-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
    • B21B1/02Metal-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 heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
    • B21B1/026Rolling

Abstract

PURPOSE:To prevent the surface cracking of a billet during hot rolling without an increase in energy cost in direct rolling, etc. to be executed under prescribed conditions by limiting the chemical components S, N and Ti of the billet to prescribed ratios. CONSTITUTION:The chemical components of the billet are adjusted to, by wt%, to 0.003-0.02% S, 0.0015-0.009% N and 0.003-0.04% Ti and >=1.5 Ti/N. Such billet is subjected to direct rolling or hot charge rolling at 600-900 deg.C surface temp. and >=1.3 total reduction ratio.

Description

【発明の詳細な説明】 (産業上の利用分野) 本発明は、連続鋳造後の鋼片を直ちに熱間圧延する(以
下、直送圧延という)か、または連続鋳造後の鋼片をそ
の表面温度が500℃以上の状態で加熱炉に装入し、再
加熱後に熱間圧延を行う(以下、ホットチャージ圧延と
いう)圧延法において、熱間圧延時の鋼片の表面割れを
防止する方法に関する。
Detailed Description of the Invention (Field of Industrial Application) The present invention provides a method for immediately hot rolling a steel billet after continuous casting (hereinafter referred to as direct rolling), or for reducing the surface temperature of a steel billet after continuous casting. The present invention relates to a method for preventing surface cracking of a steel billet during hot rolling in a rolling method in which the billet is charged into a heating furnace at a temperature of 500° C. or higher and hot rolled after reheating (hereinafter referred to as hot charge rolling).

(従来の技術) 連vt鋳造機により鋳造された鋳片は、品質改善のため
もしくは下工場での寸法制約により、下工場での圧延以
前に圧延を行うことが必要となることが多い。この圧延
方法としては、従来は、圧延過程で生ずる鋼片の表面割
れを防止する目的で、連続鋳造した鋼片の表面温度を、
一旦常温付近まで下げ、再加熱を行った後に圧延を施し
ていた。すなわち、転炉または電気炉で溶製した溶湯を
次に示す工程を経由して熱間圧延していた。
(Prior Art) Slabs cast by a continuous VT casting machine often need to be rolled before being rolled in a lower factory in order to improve quality or due to dimensional constraints at the lower factory. Conventionally, in this rolling method, the surface temperature of the continuously cast steel billet was controlled to
Rolling was performed after the temperature was lowered to around room temperature and reheated. That is, molten metal produced in a converter or electric furnace was hot rolled through the following steps.

〔連続鋳造〕−〔冷却(常温)〕− 〔再加熱〕−〔熱間圧延〕 この方法では、圧延前に冷却と再加熱を経ることにより
、オーステナイト粒度が微細化すると同時に、熱間加工
性に悪影響を及ぼすS、P、0(酸素)、N、AC!な
どの元素が硫化物、リン化物、酸化物および窒化物とし
て粒内に固定されるために、熱間加工性の劣化が防止さ
れ、・圧延時の鋼片表面割れが回避できる。
[Continuous casting] - [Cooling (room temperature)] - [Reheating] - [Hot rolling] In this method, by cooling and reheating before rolling, the austenite grain size becomes finer and at the same time hot workability is improved. S, P, 0 (oxygen), N, AC! Since elements such as sulfides, phosphides, oxides, and nitrides are fixed in the grains, deterioration of hot workability is prevented, and surface cracking of the steel billet during rolling can be avoided.

しかし、この方法は再加熱に多大のエネルギーを必要と
する。そこで、熱エネルギー原単位の低減による省エネ
ルギーを目的として、冷却工程において常温まで冷却せ
ずに鋼片表面温度が500℃以上の状態で再加熱して熱
間圧延するホットチャージ圧延法、さらに工程数の低減
も図った直送圧延法が近年提案されている。しかし、直
送圧延法またはホットチャージ圧延法においては、第1
(a)図に模式的に示すように、熔融−凝固−冷却過程
においてP、S、O,N、AQなどの元素がリン化物、
硫化物、酸化物、窒化物としてオーステナイト粒界に沿
ってほぼ連続的に微細に析出し、そのため、熱間加工に
よる引張応力が加わると、この微細析出物が割れの起点
となって鋼片の表面割れが起こる。
However, this method requires a large amount of energy for reheating. Therefore, with the aim of saving energy by reducing the thermal energy consumption rate, we developed a hot charge rolling method in which hot rolling is performed by reheating the steel piece at a surface temperature of 500°C or higher without cooling it to room temperature in the cooling process. A direct rolling method has been proposed in recent years that also aims to reduce the amount of steel. However, in the direct rolling method or hot charge rolling method, the first
(a) As schematically shown in the figure, elements such as P, S, O, N, and AQ are converted into phosphides during the melting-solidification-cooling process.
Fine precipitates as sulfides, oxides, and nitrides occur almost continuously along the austenite grain boundaries. Therefore, when tensile stress due to hot working is applied, these fine precipitates become the starting point of cracks in the steel billet. Surface cracking occurs.

この鋼片の表面割れを防止するには、P、S、0、Nな
どの元素を予め除去しておけばよいが、これは工程数の
増大を意味し、工業的に必ずしも得策とはいえない。
In order to prevent this surface cracking of the steel slab, elements such as P, S, 0, and N can be removed in advance, but this means an increase in the number of steps and is not necessarily an industrially advantageous solution. do not have.

直送圧延またはホントチャージ圧延法における表面割れ
の別の対策として、上記微細析出物はほぼ1150〜9
00℃の温度域で析出するとの知見から、この析出を起
こさないように上記温度域より高い1300〜1150
.’cの温度域において圧延を2回以上行い、その後こ
の温度域より低温でさらに圧延する方法が提案されてい
る(特公昭5B−52441号公報)。
As another countermeasure against surface cracks in direct rolling or real charge rolling, the fine precipitates are approximately 1150-9
Based on the knowledge that precipitation occurs in the temperature range of 00°C, in order to prevent this precipitation, the temperature range of 1300 to 1150
.. A method has been proposed in which rolling is performed two or more times in a temperature range of 'c' and then further rolling is carried out at a temperature lower than this temperature range (Japanese Patent Publication No. 5B-52441).

(発明が解決しようとする問題点) しかし、直送圧延における熱間圧延開始時の鋼片の表面
温度は普通900℃以下に下がっていることが多く、前
述の特公昭58−52441号に記載のように圧延開始
時の表面温度を1150℃以上とするには、直送圧延前
に鋳片を加p1炉か保熱炉に装入しておくことが必要と
なり、コストおよび設備面で不利である。ボットチャー
ジ圧延の場合も、かかる高温まで再加熱するには多大な
エネルギーを要し、省エネルギーという本来の利点が失
われる。
(Problems to be Solved by the Invention) However, the surface temperature of the steel billet at the start of hot rolling in direct rolling is often lower than 900°C, and the In order to achieve a surface temperature of 1150°C or higher at the start of rolling, it is necessary to charge the slab into a P1 furnace or a heat retention furnace before direct rolling, which is disadvantageous in terms of cost and equipment. . In the case of bot charge rolling, too, a large amount of energy is required to reheat to such a high temperature, and the original advantage of energy saving is lost.

また、一般に圧延時の表面割れは、圧下比または圧下率
を非常に低下させれば防止できるが、これは必要な加工
量が大きい場合には現実的な方法ではない。
Additionally, surface cracking during rolling can generally be prevented by significantly lowering the rolling reduction ratio or reduction ratio, but this is not a practical method when the required amount of processing is large.

よって、本発明の目的は、大きな加工量での直送圧延ま
たはホットチャージ圧延において、エネルギーコストの
増大を伴わずに鋼片の表面割れを防止する方法を提供す
ることである。
Therefore, an object of the present invention is to provide a method for preventing surface cracking of a steel billet during direct rolling or hot charge rolling with a large processing amount without increasing energy costs.

(問題点を解決するための手段) 本発明者らは、直送圧延またはボットチャージ圧延を行
う場合、TiをNの含有量に対して重量比で1.5倍以
上、すなわちTi/N≧1.5となるように添加した鋼
種を使用すると、Tiが析出核となって析出物が粒内に
粗大に析出し、固定されるため第1(a)図に示したよ
うな粒界割れの原因となる微細析出物の生成が防止され
、その結果、圧延時の鋼片表面温度が900〜600℃
の比較的低温で全圧下比1.3以上の大きな加工を施し
ても、熱間圧延時の鋼片表面割れが防止され、語呂の品
質および歩留り向上につながることを見出した。
(Means for Solving the Problems) The present inventors have determined that when performing direct rolling or bot charge rolling, the weight ratio of Ti is at least 1.5 times the N content, that is, Ti/N≧1. When using a steel type with an additive content of .5, Ti becomes a precipitation nucleus and the precipitates coarsely precipitate and become fixed within the grains, resulting in intergranular cracking as shown in Figure 1(a). The formation of fine precipitates that cause this is prevented, and as a result, the steel billet surface temperature during rolling is reduced to 900-600℃.
It has been found that even if the steel is subjected to large processing at a total reduction ratio of 1.3 or more at a relatively low temperature, cracking on the surface of the steel billet during hot rolling can be prevented, leading to improvement in the quality of rolling stock and yield.

ここに、本発明は、鋼片の表面温度600〜900℃お
よび全圧下比1.3以上の条件で行う直送圧延またはホ
ントチャージ圧延において、鋼片の化学成分をチタンと
窒素の重量比でTi/N≧1.5とすることを特徴とす
る、熱間圧延時の鋼片表面割れ防止方法である。
Here, the present invention is directed to direct rolling or real charge rolling performed under the conditions of a surface temperature of 600 to 900°C and a total reduction ratio of 1.3 or more. /N≧1.5, which is a method for preventing surface cracking of a steel billet during hot rolling.

本発明において「全圧下比」とは、圧延前の鋼片(鋳片
)厚みの圧延終了後の鋼片厚みに対する比を意味する。
In the present invention, the "total reduction ratio" means the ratio of the thickness of a steel billet (cast slab) before rolling to the thickness of a steel billet after completion of rolling.

圧下率(圧延前後の鋼片厚めの差の圧延前厚みに対する
百分率)に換算すると、圧下比1.3はほぼ圧下率23
%に相当する。
When converted to a rolling reduction ratio (the percentage of the difference in the thickness of a steel slab before and after rolling to the thickness before rolling), a rolling ratio of 1.3 is approximately a rolling ratio of 23.
Corresponds to %.

川−組成 本発明の適用鋼種は特に問わないが、本発明の方法ば特
にアルミキルド鋼、アルミセミキルド鋼およびアルミシ
リコンキルド鋼といった、自動車用鋼板、一般建築用鋼
板、造船用鋼板、機械構造用鋼板などに使用する、Si
およびMnを主成分とする炭素鋼、またはNb、■を含
有するラインパイプ用もしくは油井管用合金鋼に有効で
ある。具体的には、たとえばSS旧、5M41.5M5
0および5M53、ならびにAPIX60級の鋼種であ
る。
- Composition The steel type to which the present invention is applied is not particularly limited, but the method of the present invention is particularly applicable to steel plates for automobiles, general construction steel plates, shipbuilding steel plates, and machine structural steel plates such as aluminum killed steel, aluminum semi-killed steel, and aluminum silicon killed steel. Si used for steel plates etc.
It is effective for carbon steel containing Mn as a main component, or alloy steel for line pipes or oil country tubular goods containing Nb and ■. Specifically, for example, SS old, 5M41.5M5
0 and 5M53, and APIX60 grade steel.

本発明においては、鋼の化学成分は、重量比でTi/N
≧1.5となるようにTiを添加する以外は従来と同一
であってかまわない。添付図面の第1図は、′/g湯の
冷却過程で生ずるP、S、○、N、AQなどの元素によ
る析出物の析出形態を示す模式図であり、第1(a)図
は既に説明したように従来のTi無添加の鋼の場合を示
し、第1(b)図は本発明によりTi/N≧1.5とな
るようにTiを添加した鋼の場合である。第1(b)図
に示すように、Ti/N≧1.5となるようにTiを添
加した鋼では、冷却中に生ずる析出物がTiを核として
容易に成長するため、析出物はオーステナイト粒内にと
どまり、しかも粒内に粗大かつ不連続的に析出し、固定
される。そのた砂、第1(a)図に示したようなオース
テナイト粒界に沿った微細析出物が起点となって起こる
熱間圧延時の鋼片の表面割れが回避される。換言すると
、前記の特公昭58−52441号に記載の高温側で析
出を回避する方法とは異なって、本発明の方法では、P
、S、0、N、AQなどの元素による析出物を粒内に粗
大な状態で積極的に析出させることにより、粒界割れに
よる熱間圧延時の表面割れを防止する。このような表面
割れ防止の効果を十分に発揮させるには、TiをNに対
して重量比で1.5倍以上添加することが必要である。
In the present invention, the chemical composition of the steel is Ti/N in weight ratio.
It may be the same as the conventional method except that Ti is added so that ≧1.5. Figure 1 of the attached drawings is a schematic diagram showing the precipitation form of precipitates due to elements such as P, S, ○, N, and AQ that occur during the cooling process of '/g hot water. As explained above, the case of the conventional steel without the addition of Ti is shown, and FIG. 1(b) shows the case of the steel to which Ti is added according to the present invention so that Ti/N≧1.5. As shown in Figure 1(b), in steel to which Ti is added so that Ti/N≧1.5, the precipitates formed during cooling easily grow with Ti as the nucleus, so the precipitates become austenite. It remains within the grain, and is precipitated coarsely and discontinuously within the grain and becomes fixed. In addition, surface cracking of the steel billet during hot rolling, which is caused by sand and fine precipitates along austenite grain boundaries as shown in FIG. 1(a), is avoided. In other words, unlike the method described in Japanese Patent Publication No. 58-52441 which avoids precipitation on the high temperature side, the method of the present invention
, S, 0, N, AQ, and other elements are actively precipitated in a coarse state within the grains, thereby preventing surface cracks during hot rolling due to intergranular cracks. In order to fully exhibit such an effect of preventing surface cracking, it is necessary to add Ti at least 1.5 times as much as N by weight.

本発明の好適態様では、鋼組成を、 S :  0.003 〜0.020%、N :  0
.0015〜0.0090%、Ti :  0.003
 〜0.040%となるようにする。これは次の理由に
よる。
In a preferred embodiment of the present invention, the steel composition is S: 0.003 to 0.020%, N: 0
.. 0015-0.0090%, Ti: 0.003
0.040%. This is due to the following reason.

S : 0.003%より少ないと製造上メリットが少
ない。一方、0.020%より多いと、#7vi製品の
機械特性が悪化する。この理由は硫化物の析出量が増加
するためである。
S: If it is less than 0.003%, there will be little advantage in manufacturing. On the other hand, if it exceeds 0.020%, the mechanical properties of the #7vi product will deteriorate. The reason for this is that the amount of sulfide precipitated increases.

N : 0.0015%より少ないとS同様に製造上メ
リットが少なく、安定した製造ができない。また、0.
0090%より多いと鋼の機械的特性が悪化する。この
理由は窒化物の析出が多くなるためである。
N: If it is less than 0.0015%, like S, there will be little advantage in manufacturing, and stable manufacturing will not be possible. Also, 0.
If it exceeds 0.090%, the mechanical properties of the steel will deteriorate. The reason for this is that nitride precipitation increases.

Ti : 0.003%より少ないとP、S、OlN、
A(2などの元素の析出物をTiを析出核として粒内に
粗大析出させる機能を失う。一方、0.040%より多
いと、Ti添加による鋼の特性劣化を招く。
Ti: If less than 0.003%, P, S, OlN,
The function of coarsely precipitating the precipitates of elements such as A(2) using Ti as precipitation nuclei is lost. On the other hand, if the amount exceeds 0.040%, the properties of the steel will deteriorate due to the addition of Ti.

圧延条件 本発明においては、直送圧延またはホットチャージ圧延
における圧延温度(鋼片の表面温度)を600〜900
℃の温度範囲とする。600℃未満では−・般に熱間圧
延が困難となる。上限を900℃としたのは、直送圧延
では加熱炉か保熱炉を使用しなければ圧延時に表面温度
が900℃以下に下がっていることが多く、ホントチャ
ージ圧延でも900℃を越える高温メするのはエネルギ
ーコストの面で不利であるためである。また、900℃
より高温では、上記析出物がまだ十分に粗大化しておら
ず、表面割れの防止に有効でないこともある。
Rolling conditions In the present invention, the rolling temperature (surface temperature of the steel billet) in direct rolling or hot charge rolling is set to 600 to 900.
The temperature range is ℃. If the temperature is less than 600°C, hot rolling will generally become difficult. The reason for setting the upper limit at 900°C is that in direct rolling, unless a heating furnace or heat retention furnace is used, the surface temperature during rolling often drops below 900°C, and even in true charge rolling, the surface temperature can exceed 900°C. This is because it is disadvantageous in terms of energy costs. Also, 900℃
At higher temperatures, the precipitates may not yet be sufficiently coarsened and may not be effective in preventing surface cracking.

なお、熱間圧延中に鋼片表面温度は概ね低下していく方
向に変動するので、上記温度範囲は、圧延開始時が90
0℃以下、圧延仕上げ温度が600℃以上であることを
意味する。
Note that during hot rolling, the surface temperature of the steel billet generally changes in the direction of decreasing, so the above temperature range is 90°C at the start of rolling.
It means that the rolling finishing temperature is 600°C or higher.

圧下条件については、全圧下比を1.3以上としたのは
、実施例の結果を示す第2図のグラフからもわかるよう
に、全圧下比が1.2より小さい加工では表面割れは起
こらないからである。
As for the reduction conditions, the total reduction ratio was set to 1.3 or more because, as can be seen from the graph in Figure 2 showing the results of the examples, surface cracking does not occur in machining where the total reduction ratio is less than 1.2. That's because there isn't.

1パス当たりの圧下量は通當の範囲内でよいが、圧下量
が過大になると表面割れが起こりやすくなる。この点か
ら、1パス当たりの圧下量を5〜40耀■の範囲とする
のが好ましい。
The amount of reduction per pass may be within a normal range, but if the amount of reduction is excessive, surface cracks are likely to occur. From this point of view, it is preferable that the rolling reduction amount per pass be in the range of 5 to 40 mm.

熱間圧延時の圧延パススケジュールの・1例を次に示す
:厚さ270 +uの鋼片−20龍/パスの圧下を4回
−115N/パスの圧下を4回→10龍/バスの圧下を
2回−51言/パスの圧下を2同一厚さ100顛の鋼片
、全圧下比= 2.7 (全圧下率=63%)。
An example of the rolling pass schedule during hot rolling is shown below: 270 + U steel billet - 4 times of 20 dragons/pass reduction - 4 times of 115N/pass reduction → 10 dragons/pass reduction 2 times - 51 strokes/pass of 2 steel slabs of 100 pieces of the same thickness, total reduction ratio = 2.7 (total reduction ratio = 63%).

次に実施例により本発明を具体的に説明する。Next, the present invention will be specifically explained with reference to Examples.

夫l拠 Ti添加量をTi/Nの重量比がθ〜10となる範囲内
で変化させた第1表に示す化学成分の鋼の溶湯を、連続
鋳造により270龍(厚) X1350mm (幅)の
鋳片とし、表面温度750℃で直送圧延を開始して、第
2表に示す圧延パススケジュールで全圧下比1,2.1
.3および2.7の圧延を行った。得られた各鋼片につ
いて表面割れの発生をスカーフィング後目視検査し、表
面割れ発生率(表面割れ発生鋼片枚数/圧延された鋼片
枚数)を求めた。結果を第2図にグラフで示す。
A molten steel having the chemical composition shown in Table 1, in which the amount of Ti added was varied within the range where the weight ratio of Ti/N was θ to 10, was continuously cast to 270 mm (thickness) x 1350 mm (width). Direct rolling was started at a surface temperature of 750°C, and the total reduction ratio was 1.2.1 according to the rolling pass schedule shown in Table 2.
.. 3 and 2.7 rollings were performed. The occurrence of surface cracks on each of the obtained steel slabs was visually inspected after scarfing, and the surface crack occurrence rate (number of steel slabs with surface cracks/number of rolled steel slabs) was determined. The results are shown graphically in FIG.

第2図かられかるように、全圧下比が1.2の直送圧延
ではT】を添加しなくても表面割れは起こらない。しか
し、全圧下比が1.3以」二になると、Ti無添加の場
合、加工量の増大とともに表面割れ発生率が高くなる。
As can be seen from FIG. 2, surface cracking does not occur in direct rolling with a total reduction ratio of 1.2 even without the addition of T. However, when the total reduction ratio becomes 1.3 or more, the incidence of surface cracking increases as the amount of processing increases in the case of no Ti addition.

T1の添加により表面割れは抑制されるが、Ti/N比
が1.5未満ではその効果が十分でない。これに対して
、Ti/N比が1.5以」二では、2.7という高い全
圧下比でも表面割れが完全に防止される。ただし、全圧
下比が4.0より大きいと、Tiを添加しても表面割筋
、が発生ずる1頃向があり、経済的にも効果がなくなる
ので、全圧下比は4.0以下とするのが好ましい。
Although surface cracking is suppressed by adding T1, the effect is not sufficient when the Ti/N ratio is less than 1.5. On the other hand, when the Ti/N ratio is 1.5 or more, surface cracking is completely prevented even at a high total reduction ratio of 2.7. However, if the total reduction ratio is greater than 4.0, even if Ti is added, surface splitting will occur at about 1, which is economically ineffective, so the total reduction ratio should be 4.0 or less. It is preferable to do so.

(発明の効果) 以上の説明および実施例から明らかなように、本発明に
よれば、直送圧延およびボ・7トヂヤージ。
(Effects of the Invention) As is clear from the above description and examples, according to the present invention, direct rolling and body 7 shipping are possible.

圧延法において問題となっていた大きな加工での鋼片の
表面割れを、エネルギーコストの増大を伴わずに防止す
ることができ、実用価値が非常に高い。
It is possible to prevent surface cracking of steel slabs during large processing, which has been a problem in the rolling method, without increasing energy costs, and has extremely high practical value.

【図面の簡単な説明】[Brief explanation of the drawing]

第1図は、冷却時に生ずるP、S、O,N、AQなどに
よる析出物の析出形態を示す模式図であり、+a+はT
i無添加の場合、(blは本発明によりTi/N≧1.
5となるようにTiを添加した場合をそれぞれ示し、 第2図ば、鋼中のTi/N重量比に対する各種全圧下比
での熱間圧延による表面割れ発生率の変化を示すグラフ
である。 出願人  住友金属工業株式会社 代理人  弁理士 広 瀬 章 −(tth” ’IL
)第2図 手彰′εネiff正書 昭和60年 7月72日 1、事件の表示 昭和59年特許H第135228号 2、発明の名称 熱間圧延時の鋼片表面割れ防止方法 3、ネ市正をする者 事件との関係  特許出願人 住所 大阪市東区北浜5丁目15番地 名称 (211)住友金属工業株式会社4、代 庁 人 明細書の発明の詳細な説明欄 6、補正の内容 明細書第4頁末行目に段落のうえ以下の記載を加入才ろ
。 「 なお、ここに、熱間加工による鋼片の[表面割れ1
とは鋼片表面直下的10mm1¥の範囲の領域に発生す
る長さ]〜5mm程度のへアクラックのことであって、
まれに鋼片表面に見られろこともある。j以上
FIG. 1 is a schematic diagram showing the precipitation form of precipitates due to P, S, O, N, AQ, etc. that occur during cooling, and +a+ is T
In the case of no addition of i, (bl is Ti/N≧1.
Fig. 2 is a graph showing changes in surface crack incidence due to hot rolling at various total reduction ratios with respect to the Ti/N weight ratio in steel. Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent Attorney Akira Hirose −(tth” 'IL
) Figure 2 Tesho'ε Neiff Official Book July 72, 1985 1, Indication of the incident 1982 Patent H No. 135228 2, Name of the invention Method for preventing surface cracking of steel billet during hot rolling 3, Relationship with the case of the person acting as the city attorney Patent applicant address: 5-15 Kitahama, Higashi-ku, Osaka Name (211) Sumitomo Metal Industries, Ltd. 4, Representative Column 6 of the detailed explanation of the invention in the official specification, Contents of the amendment Add the following statement in a paragraph on the last line of page 4 of the specification. ``In addition, here, [surface crack 1] of the steel billet due to hot working
refers to a hair crack with a length of ~5 mm that occurs in an area of 10 mm 1 yen directly below the surface of a steel piece,
In rare cases, it may be seen on the surface of a steel piece. j or more

Claims (2)

【特許請求の範囲】[Claims] (1)鋼片の表面温度600〜900℃および全圧下比
1.3以上の条件で行う直送圧延またはホットチャージ
圧延において、鋼片の化学成分をチタンと窒素の重量比
でTi/N≧1.5とすることを特徴とする、熱間圧延
時の鋼片表面割れ防止方法。
(1) In direct rolling or hot charge rolling performed at a surface temperature of 600 to 900°C and a total reduction ratio of 1.3 or more, the chemical composition of the steel billet is determined by the weight ratio of titanium and nitrogen: Ti/N≧1. .5 A method for preventing surface cracking of a steel billet during hot rolling.
(2)鋼片の化学成分が、重量比で、 S:0.003〜0.020%、 N:0.0015〜0.0090%、 Ti:0.003〜0.040% であることをさらに特徴とする特許請求の範囲第1項記
載の方法。
(2) The chemical components of the steel slab are as follows in weight ratio: S: 0.003-0.020%, N: 0.0015-0.0090%, Ti: 0.003-0.040%. The method of claim 1, further characterized.
JP13522884A 1984-07-02 1984-07-02 Prevention of surface cracking of billet during hot rolling Pending JPS6117301A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP13522884A JPS6117301A (en) 1984-07-02 1984-07-02 Prevention of surface cracking of billet during hot rolling

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP13522884A JPS6117301A (en) 1984-07-02 1984-07-02 Prevention of surface cracking of billet during hot rolling

Publications (1)

Publication Number Publication Date
JPS6117301A true JPS6117301A (en) 1986-01-25

Family

ID=15146807

Family Applications (1)

Application Number Title Priority Date Filing Date
JP13522884A Pending JPS6117301A (en) 1984-07-02 1984-07-02 Prevention of surface cracking of billet during hot rolling

Country Status (1)

Country Link
JP (1) JPS6117301A (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS55109503A (en) * 1979-02-16 1980-08-23 Nippon Steel Corp Direct rolling method for hot cast billet
JPS58221603A (en) * 1982-06-19 1983-12-23 Kawasaki Steel Corp Method for preventing cracking in hot rolling of extra- low carbon steel

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS55109503A (en) * 1979-02-16 1980-08-23 Nippon Steel Corp Direct rolling method for hot cast billet
JPS58221603A (en) * 1982-06-19 1983-12-23 Kawasaki Steel Corp Method for preventing cracking in hot rolling of extra- low carbon steel

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