JPS6216802A - Hot rolling method for preventing surface crack of ingot - Google Patents
Hot rolling method for preventing surface crack of ingotInfo
- Publication number
- JPS6216802A JPS6216802A JP15624885A JP15624885A JPS6216802A JP S6216802 A JPS6216802 A JP S6216802A JP 15624885 A JP15624885 A JP 15624885A JP 15624885 A JP15624885 A JP 15624885A JP S6216802 A JPS6216802 A JP S6216802A
- Authority
- JP
- Japan
- Prior art keywords
- rolling
- steel
- roll
- direct
- edge
- 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
- 238000000034 method Methods 0.000 title claims description 25
- 238000005098 hot rolling Methods 0.000 title claims description 16
- 238000005096 rolling process Methods 0.000 claims abstract description 63
- 230000009467 reduction Effects 0.000 claims abstract description 29
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 26
- 239000010959 steel Substances 0.000 claims abstract description 26
- 239000000463 material Substances 0.000 claims abstract description 14
- 238000005336 cracking Methods 0.000 claims description 26
- 238000009749 continuous casting Methods 0.000 claims description 5
- 229910052705 radium Inorganic materials 0.000 abstract 1
- HCWPIIXVSYCSAN-UHFFFAOYSA-N radium atom Chemical compound [Ra] HCWPIIXVSYCSAN-UHFFFAOYSA-N 0.000 abstract 1
- 238000001556 precipitation Methods 0.000 description 8
- 238000007796 conventional method Methods 0.000 description 7
- 238000001953 recrystallisation Methods 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 6
- 239000002436 steel type Substances 0.000 description 5
- 229910000655 Killed steel Inorganic materials 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 150000003568 thioethers Chemical class 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 229910000851 Alloy steel Inorganic materials 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 229910001336 Semi-killed steel Inorganic materials 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 2
- 239000010962 carbon steel Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910021652 non-ferrous alloy Inorganic materials 0.000 description 1
- 238000009497 press forging Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 229910000859 α-Fe Inorganic materials 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
- B21B1/02—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 heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Metal Rolling (AREA)
Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は、アルミキルド鋼、アルミセミキルド鋼または
アルミシリコンキルド鋼等自動車用鋼板、一般建築用鋼
板、造船用鋼板、機械構造用鋼板等に供される炭素鋼な
らびにＮｂ、■等を含有する低合金鋼の熱間圧延時の表
面割れを防止した熱間圧延法に関するものであり、特に
それら鋼の造塊もしくは連続鋳造直後の鋼塊もしくは鋳
片をただちに熱間圧延するか、または造塊、もしくは連
続鋳造後そのまま鋼塊もしくは鋳片を保温炉あるいは加
熱炉等に装入してから熱間圧延を行うプロセスにおいて
、熱間圧延時に鋼片の表面に割れの発生するのを防止す
る方法に関する。Detailed Description of the Invention (Field of Industrial Application) The present invention is applicable to steel plates for automobiles such as aluminum killed steel, aluminum semi-killed steel, or aluminum silicon killed steel, steel plates for general construction, steel plates for shipbuilding, steel plates for machine structures, etc. It relates to a hot rolling method that prevents surface cracking during hot rolling of carbon steel and low alloy steel containing Nb, In the process of immediately hot-rolling a slab, or placing the steel ingot or slab after continuous casting into an insulating furnace or heating furnace, and then hot rolling, the steel This invention relates to a method for preventing cracks from forming on the surface of a piece.
（従来の技術）
すでに当業界において良く知られるように凝固のままの
鋳片または鋼塊を途中加熱することなく、その保存熱を
利用してそのまま直接熱間圧延すること（以下、単に“
直接圧延”という）あるいは未だＡｒ＋変態点以上の表
面温度を有する鋳片または鋼塊を一旦加熱炉、保温炉等
に装入してから熱間圧延すること（以下、単に 直送圧
延”という）は省エネルギーの観点から最も望ましい操
業形態であるが、その実現に当たっては鋳片等表面性状
あるいは設備レイアウトなどに関する問題が種々存在し
ていた。しかし近年に至り、それらに対する技術改善が
進むにつれ、直接圧延あるいは直送圧延に関する検討が
活発となってきた。(Prior art) As is already well known in the industry, hot rolling is a method of directly hot rolling a solidified slab or steel ingot using its stored heat without heating it midway (hereinafter simply referred to as "
(hereinafter simply referred to as "direct rolling"), or hot rolling after charging a slab or steel ingot whose surface temperature is still above the Ar + transformation point into a heating furnace, insulating furnace, etc. (hereinafter simply referred to as "direct rolling") Although this is the most desirable mode of operation from the perspective of energy conservation, there were various problems in realizing it, such as the surface properties of slabs and equipment layout. However, in recent years, as improvements in these technologies have progressed, studies on direct rolling or direct delivery rolling have become active.
その結果、直接圧延あるいは直送圧延においては、従来
法、すなわち、造塊あるいは連続鋳造後、一旦Ａｒ＋変
態点以下、室温近くまで冷却後再加熱して圧延する方法
にみられる冶金学的現象とは異なった現象が多く見出さ
れた。中でも材料の熱間加工性が著しく低下すること、
つまり従来法においては何ら問題とならなかったような
鋼種においても直接圧延あるいは直送圧延においては熱
間圧延時に鋼片表面に割れの発生することが判明した。As a result, in direct rolling or direct rolling, the metallurgical phenomena observed in the conventional method, that is, after ingot formation or continuous casting, are cooled to below the Ar+ transformation point and close to room temperature, and then reheated and rolled. Many different phenomena were found. Among these, the hot workability of the material decreases significantly;
In other words, it has been found that even in steel types that did not cause any problems in the conventional method, cracks occur on the surface of the steel piece during hot rolling in direct rolling or direct rolling.
一般に、鋼の熱間加工性はオーステナイト粒径（以下、
“γ粒径”という）と硫化物、炭窒化物などの析出状態
の影響を強く受け、一般にγ粒径が微細なほど、また１
粒界への硫化物、炭窒化物などの析出が少ないほど、熱
間加工性は向上する。Generally, the hot workability of steel is determined by the austenite grain size (hereinafter referred to as
In general, the finer the γ grain size, the more 1
The less precipitation of sulfides, carbonitrides, etc. at grain boundaries, the better the hot workability.
そして従来法においては、材料に冷却再加熱を繰り返す
ことでＴ（オーステナイト）−α（フェライト）変態を
経験させて、γ粒を微細化し、かつ析出物の多くを粒内
に固定して１粒界への析出量を少なくすることにより熱
間加工性を向上させていた。In the conventional method, the material is repeatedly cooled and reheated to undergo T (austenite)-α (ferrite) transformation, thereby refining the γ grains and fixing most of the precipitates within the grains. Hot workability was improved by reducing the amount of precipitation in the interface.
これに対し、直接圧延法あるいは直送圧延法の場合には
、鋼塊もしくは鋳片のもつ保有熱を最大限に利用するこ
とがらγ−α変態を経ずに圧延するのでγ粒径は非常に
大きく、かつγ粒界への析出も多く、したがって、熱間
加工性は低下することとなる。このような熱履歴が、熱
間圧延時の割れの原因とされるのである。On the other hand, in the case of the direct rolling method or the direct rolling method, the heat retained in the steel ingot or slab is utilized to the maximum and rolling is performed without going through the γ-α transformation, so the γ grain size is extremely small. It is large and there is a lot of precipitation at the γ grain boundaries, and therefore hot workability is reduced. Such thermal history is considered to be the cause of cracks during hot rolling.
このような直接圧延あるいは直送圧延にみられる熱間圧
延時の割れの発生防止に関しては、既にいくつかの提案
がなされているが、これらに共通する考え方は特開昭５
５−８４２０１号あるいは特開昭５５−８４２０３号に
代表されるように、凝固後の鋳片の冷却速度を遅くする
か、冷却途中で所定温度に一定時間以上保持して、析出
物を凝集・粗大化させ、γ粒界における析出物の数を減
らすことにより割れを防止しようとするものである。す
なわち、従来技術にあってはいずれも前述の割れ原因の
一つである硫化物、炭窒化物などの析出形態の制御を狙
ったもので、一応相当の効果が認められた。Several proposals have already been made regarding the prevention of cracks during hot rolling that occur in direct rolling or direct rolling, but the common idea among these is the
As typified by No. 5-84201 or JP-A No. 55-84203, the cooling rate of the slab after solidification is slowed down, or the cooling rate is maintained at a predetermined temperature for more than a certain period of time to cause the precipitates to coagulate. This attempts to prevent cracking by coarsening the grains and reducing the number of precipitates at the γ grain boundaries. That is, all of the conventional techniques aim at controlling the precipitation form of sulfides, carbonitrides, etc., which are one of the causes of cracking, and have been found to be reasonably effective.
しかし、その一方でこれら従来技術がかかえる問題点も
浮き彫りになってきた。すなわち、割れ防止に必要な冷
却速度あるいは温度保持条件を満足させることは実際の
操業において著しい生産性の低下を招き、そのような条
件にしたがう限り殊に現在開発中の連続鋳造圧延法の適
用は至難なことである。However, on the other hand, problems with these conventional techniques have also come to light. In other words, satisfying the cooling rate or temperature maintenance conditions necessary to prevent cracking will lead to a significant drop in productivity in actual operations, and as long as such conditions are followed, it will be difficult to apply the continuous casting and rolling method currently under development. This is extremely difficult.
（発明が解決しようとする問題点）
ここに、本発明の第１の目的とするところは、圧延法の
改善により熱間圧延時の割れを防止する方法を提供する
ことである。(Problems to be Solved by the Invention) The first object of the present invention is to provide a method for preventing cracking during hot rolling by improving the rolling method.
本発明の第２の目的とするところは、直接圧延法もしく
は直送圧延法において圧延法の改善により熱間圧延時の
割れを防止する方法を提供することである。A second object of the present invention is to provide a method for preventing cracking during hot rolling by improving the rolling method in direct rolling or direct rolling.
（問題点を解決するための手段）
従来より、熱間圧延時の割れに関しては合金元素、温度
等のいわゆる冶金学的観点からの検討は非常に多い。本
発明者らは新規な割れ防止技術を開発すべくこれまでほ
とんど行われていない圧延条件の影響に関し基礎検討を
行った。(Means for Solving Problems) Conventionally, cracks during hot rolling have been studied from a so-called metallurgical viewpoint, such as alloying elements, temperature, etc. In order to develop a new crack prevention technology, the present inventors conducted a basic study on the influence of rolling conditions, which has rarely been done so far.
そこでまず圧延条件と割れの関係について検討を行った
結果、圧延条件の変化に伴い割れ発生形態が異なること
が明らかとなった。なお、ここにいう割れ発生形態の違
いとは、割れの発生位置すなわち割れが材料の圧下面に
発生するか（面割れ）、板端面近傍に発生するか（耳割
れ）をいう、そして割れ発生形態におよぼす要因として
は、ロール径、板厚そして圧下量の影響が大きい。すな
わち、ロール径および板厚の影響に関しては、ロール径
／板厚の値が大きい場合、割れは耳割れとして発生する
。そしてこの値が小さくなるに伴い耳割れは軽微となり
、圧下面での横ヒビ状の面割れが増加する。また圧下量
に関しては全体の圧下量を一定とした場合、１パス当た
りの圧下量を大きくしたいわゆる強圧下スケジュールの
場合、耳割れが主体であるが、１パス当たりの圧下量を
小さくした軽圧下スケジュールとなるに従い耳割れは減
少し、面割れが増大する。さらにこれら要因を総合的に
検討した結果第１図に示すように、割れ発生形態は下記
（１）式で示される形状比（ｍ）で整理できることを知
見した。すなわち、ｍが１未満の場合、割れは面割れ傾
向となり、一方、ｍが１以上では逆に耳割れ傾向となる
。Therefore, we first investigated the relationship between rolling conditions and cracking, and as a result, it became clear that the form of cracking differs as the rolling conditions change. The difference in the form of crack occurrence here refers to the location of crack occurrence, that is, whether the crack occurs on the rolled surface of the material (face crack) or near the edge surface of the plate (edge crack), and The factors that affect the shape are the roll diameter, plate thickness, and reduction amount. That is, regarding the influence of roll diameter and plate thickness, when the value of roll diameter/plate thickness is large, cracks occur as edge cracks. As this value decreases, edge cracks become slighter and horizontal crack-like surface cracks on the rolled surface increase. Regarding the amount of reduction, when the overall amount of reduction is constant, in the case of a so-called strong reduction schedule in which the amount of reduction per pass is large, edge cracking is the main cause, but in the case of a light reduction schedule with a smaller amount of reduction per pass. As the schedule progresses, the number of edge cracks decreases and the number of surface cracks increases. Furthermore, as a result of comprehensively examining these factors, as shown in FIG. 1, it was found that the form of crack occurrence can be summarized by the shape ratio (m) expressed by the following equation (1). That is, when m is less than 1, the cracks tend to be surface cracks, whereas when m is 1 or more, the cracks tend to be edge cracks.
ｈ、＋ｈ。h, +h.
ただし、Ｒ；圧延ロール半径
ｈｌ＋ロール入側の材料厚さ
ｈｌ：ロール出側の材料厚さ
さらにその原因について調査を行った結果、材料板幅方
向での圧延方向応力の分布状態が圧延条件により変化す
ることを明らかにした。すなわち、ｍが大きい場合、板
端部において圧延方向応力は引張側に大きく、機中央部
では圧縮側に大きいため、板端部において耳割れが発生
するが、ｍが小さい場合、全く逆の傾向となり、従って
耳割れは発生しにくいが、面割れが生ずる。However, R: Roll radius hl + Material thickness on the roll entry side hl: Material thickness on the roll exit side.As a result of further investigation into the cause, we found that the distribution state of stress in the rolling direction in the width direction of the material plate depends on the rolling conditions. revealed that it would change. In other words, when m is large, the stress in the rolling direction is large in tension at the edge of the plate and large in compression at the center of the machine, resulting in edge cracking at the edge of the plate, but when m is small, the opposite trend occurs. Therefore, edge cracks are less likely to occur, but surface cracks do occur.
以上のように割れ発生形態は圧延条件、特に、（１）式
で示される形状比（ｍ）により大きく変化することが明
らかとなったが、このことはまた、圧延条件のコントロ
ールだけでは耳割れ、面割れの両者を同時に防止できな
いことを示している。As mentioned above, it has become clear that the form of crack occurrence changes greatly depending on the rolling conditions, especially the shape ratio (m) shown by equation (1). , indicating that both surface cracks cannot be prevented at the same time.
そこで、本発明者らは両者の割れを各々別な対策により
防止すべく検討を行った。まず、面割れに対しては前述
の検討結果をもとに形状比（ｍ）が１以上となる圧延条
件で対処した。そしてその結果生ずる耳割れに対しては
以下のような幅圧下による耳割れ対策について検討を行
った。これは水平ロールによる厚み圧下に先立ち、耳割
胱発生湯所となる板端部に圧下を加えることにより、厚
み圧下時の耳割れを防止せんとするものであり、その原
理は耳割れ発生場所となる板端部にひずみを加えること
により、再結晶を生しさせ、γ粒の微細化を図るか、再
結晶が生じないまでも１粒内に転位を発生させ、割れの
原因となるγ粒界への硫化物、炭窒化物等の析出を転位
を核とした粒内析出に改善することにより割れを防止せ
んとするものである。Therefore, the inventors of the present invention conducted studies to prevent cracking in both cases by taking different measures. First, surface cracking was dealt with under rolling conditions such that the shape ratio (m) was 1 or more based on the above-mentioned study results. In order to deal with the resulting edge cracks, we investigated measures against the edge cracks by width reduction as described below. This is to prevent edge cracking during thickness reduction by applying pressure to the edge of the plate, where the edge cracks occur, prior to the thickness reduction using horizontal rolls. By applying strain to the edge of the plate, recrystallization will occur and the γ grains will become finer, or even if recrystallization does not occur, dislocations will occur within each grain, causing cracks. The purpose is to prevent cracking by improving the precipitation of sulfides, carbonitrides, etc. at grain boundaries to intragranular precipitation with dislocations as nuclei.
そこで幅圧下による耳割れ防止効果を調査すべく以下の
如き実験的検討を行った。Therefore, the following experimental study was conducted to investigate the effect of width reduction on preventing edge cracking.
■鋼塊形状： ４０ｍｍｔｘ１６０ｍｍ ′、４０ｍｍ
ＬＸ１２０ｍｍ ’■鋼種：普通鋼、低合金鋼
■圧延ロール直径： ８５０ｍｍ
■パススケジュール：４０−”２０−２０−１Ｏｔ（，
０７，４，３５）
■圧延形式：直送圧延および直接圧延
■幅圧下方式：ミル方式、プレス方式および鍛造方式
以上の条件を組合せ、合計８０枚の圧延実験を行った。■Steel ingot shape: 40mmtx160mm', 40mm
LX120mm ■Steel type: Ordinary steel, low alloy steel ■Roll roll diameter: 850mm ■Pass schedule: 40-"20-20-1Ot(,
07, 4, 35) ■Rolling type: Direct rolling and direct rolling ■Width reduction method: Mill method, press method, and forging method A total of 80 sheets were subjected to rolling experiments by combining the above conditions.
第２図は本実験結果をまとめたものであるが片側で５１
以上（全幅で１０ｍｍ以上）の圧下を加えることにより
、その後の厚み圧下において耳割れを防止できることが
明らかとなった。しかも、耳割れ防止に必要な幅圧下量
は素材板幅によらないことも確認された。Figure 2 summarizes the results of this experiment, with 51% on one side.
It has become clear that by applying a reduction of at least 10 mm in total width, it is possible to prevent edge cracking in the subsequent thickness reduction. Furthermore, it was confirmed that the amount of width reduction required to prevent edge cracking does not depend on the width of the material plate.
本発明は以上の知見をもとに完成されたもので、その要
旨とするところは造塊もしくは連続鋳造した直後の鋼塊
もしくは鋼片を直送圧延もしくは直接圧延する方法にお
いて、該鋼片にまず片側５ｍｍ以上の幅圧下を施した後
、下記式で定義される形状比（ｍ）が１以上となる圧延
条件下で圧延することを特徴とする鋼片の表面割れを防
止した熱間圧延法。The present invention has been completed based on the above knowledge, and its gist is that in a method of direct rolling or direct rolling of a steel ingot or steel billet immediately after ingot making or continuous casting, the steel billet is first rolled. A hot rolling method that prevents surface cracking of a steel billet, which is characterized by rolling under rolling conditions such that the shape ratio (m) defined by the following formula is 1 or more after applying a width reduction of 5 mm or more on one side. .
ｈ、 ＋ｈ。h, +h.
ただし、Ｒ：圧延ロール半径 ｈｌ：ロール入側の材料厚さ ｈｌ：ロール出側の材料厚さ である。なお、望ましくはｍが１．２以上である。However, R: rolling roll radius hl: Material thickness at roll entry side hl: Material thickness at roll exit side It is. Note that m is desirably 1.2 or more.
ここに、本発明の好適態様にあっては、本発明が適用さ
れる鋼種はアルミキルド鋼、アルミセミキルド鋼または
アルミシリコンキルド鋼などの炭素鋼であり、またＮｂ
、 Ｖ等の合金元素を有する低合金鋼である。In a preferred embodiment of the present invention, the steel type to which the present invention is applied is carbon steel such as aluminum killed steel, aluminum semi-killed steel, or aluminum silicon killed steel, and Nb
, V, and other alloying elements.
（作用）
ところで、幅圧下による耳割れ対策としては特開昭５２
−７７８５８号がすでに知られている。これは高速高圧
下圧延において鋳片をエツジヤ−により幅圧延後、再結
晶化カロ熱を行うことにより、鋳片端部の鋳造組織を破
壊、再結晶させ耳割れを防止せんとするものである。(Function) By the way, as a countermeasure against edge cracking due to width reduction, Japanese Patent Application Laid-Open No. 52
-77858 is already known. This is intended to prevent edge cracking by destroying and recrystallizing the cast structure at the end of the slab by performing recrystallization Calocytherm after width-rolling the slab using an edger during high-speed, high-reduction rolling.
しかしながら、以下の点において本発明とこの従来技術
とは異質なものであって、その相違は明確である。However, the present invention is different from this prior art in the following points, and the differences are clear.
（１）圧延条件の規定方法
従来法においては高圧下圧延における耳割れを問題とし
ているが、前述の如く耳割れが問題となるのは単に高圧
下圧延時だけでなく、ロール径／板厚の値が大きい場合
にも問題となるものモある。(1) Method for specifying rolling conditions In conventional methods, edge cracking occurs during high pressure rolling, but as mentioned above, edge cracking is a problem not only during high pressure rolling but also due to roll diameter/plate thickness. There are also problems when the value is large.
本発明はこれら要因を形状比（ｍ）で整理したものであ
るが、このような知見は本発明者らの検討において初め
て明らかとなったものである。In the present invention, these factors are organized in terms of shape ratio (m), but this knowledge was first revealed in the studies conducted by the present inventors.
（２）対称とする鋼種および熱履歴
特開昭５２−７７８５８号の明細書中には対称とする鋼
種は特殊鋼、非鉄合金であり、普通鋼はとくに問題ない
ものとされており、このことは従来の再加熱圧延を対象
としていることを示している。これに対し本発明は直送
圧延あるいは直接圧延のような熱履歴においては従来の
再加熱圧延において何ら問題とならなかったような普通
鋼、低合金鋼においても割れが問題となることからなさ
れたものである。(2) Steel types and thermal history to be symmetrical In the specification of JP-A No. 52-77858, the symmetrical steel types are special steels and non-ferrous alloys, and ordinary steel is said to pose no particular problem. indicates that the target is conventional reheat rolling. On the other hand, the present invention was developed because the thermal history of direct rolling or direct rolling causes cracking to become a problem even in ordinary steel and low alloy steel, which did not pose any problem in conventional reheat rolling. It is.
（３）再結晶化加熱装置の必要性
従来法では幅圧下稜再結晶化のための加熱装置を必要と
しているが、本発明者らの検討によれば第２図に示す調
査結果から明らかなように、とくに再結晶化加熱装置が
なくても幅圧下だけで耳割れを防止できることが明らか
である。これは前述の如く幅圧下により再結晶にいたら
ないまでも、その結果生ずる転位を核として、問題とな
る硫化物、炭窒化物等が粒界析出から粒内析出へと改善
されるためである。(3) Necessity of recrystallization heating device The conventional method requires a heating device for width reduction edge recrystallization. It is clear that edge cracking can be prevented by width reduction alone, even without a recrystallization heating device. This is because, as mentioned above, although width reduction does not lead to recrystallization, the problem sulfides, carbonitrides, etc. are improved from grain boundary precipitation to intragranular precipitation, using the resulting dislocations as nuclei. .
以上のように両者では多くの相違点があり、これらは本
発明者らの検討においてはじめて明らかとなったもので
ある。As mentioned above, there are many differences between the two, and these were only revealed through the studies conducted by the present inventors.
次に、実施例によって本発明をさらに具体的に説明する
。Next, the present invention will be explained in more detail with reference to Examples.
（実施例）
ＪＩＳ ５ＰＨＣ相当の４０ｍｍ’ Ｘ６００ｍｍ ’
の鋳片を直径５００＋ｕ＋のワークロール径を有する４
段圧延機で４０＝２０→１ＯＩＩＩｌｔのバススケジュ
ールで直接圧延を行った。この場合ｍは２，３６および
３．３３であった０本例では上記水平圧延に際し、あら
かじめ孔型を有する竪型ロールにより事前に最大、片側
で３０＋ｗ−まで（板幅全体で６０ｍｍ）の幅圧下を行
った０幅圧下量は片側で２１１１１１程度の場合、ｍは
１以上のため面割れは発生しないものの耳割れが残存し
た。しかし、幅圧下量を片側で５ｍｍ以上（板幅全体で
１０問以上）とすることにより耳割れも皆無となった。(Example) 40mm' x 600mm' equivalent to JIS 5PHC
4 with a work roll diameter of 500+u+
Direct rolling was performed using a high-pressure rolling mill with a bus schedule of 40=20→1OIIIlt. In this case, m was 2,36 and 3.33.0 In this example, during the above-mentioned horizontal rolling, a vertical roll with grooves was used to roll the sheet to a maximum width of 30+w- on one side (total width of 60mm). When the zero-width reduction was approximately 211,111 on one side, m was 1 or more, so no surface cracks occurred, but edge cracks remained. However, by setting the width reduction amount to 5 mm or more on one side (10 questions or more over the entire board width), there were no edge cracks.
なお、幅圧下方式としては、前述の如くミル方式の他に
、プレス鍛造等公知の方法でよく、また幅圧下とその後
の水平圧延は単独でも、あるいは連続でもよい。In addition to the mill method as described above, the width reduction method may be a known method such as press forging, and the width reduction and subsequent horizontal rolling may be performed alone or consecutively.
（発明の効果）
以上のように、本発明は省エネ、歩留向上にとって有効
なプロセスである直送圧延あるいは直接圧延の実施にあ
たって問題となる鋼片の表面割れを確実に防止できると
いう点で、その効果は非常に大である。(Effects of the Invention) As described above, the present invention has advantages in that it can reliably prevent surface cracking of steel slabs, which is a problem when performing direct rolling or direct rolling, which is an effective process for energy saving and yield improvement. The effect is very large.
第１図は、形状比（ｍ）と割れ発生形態の関係を示すグ
ラフ；および
第２図は、幅圧下量と耳割れ評点の関係を示すグラフで
ある。FIG. 1 is a graph showing the relationship between the shape ratio (m) and the form of crack occurrence; and FIG. 2 is a graph showing the relationship between the width reduction amount and the edge crack score.
Claims (1)
送圧延もしくは直接圧延する方法において、該鋼塊もし
くは鋼片にまず片側５ｍｍ以上の幅圧下を施した後、下
記式で定義される形状比（ｍ）が１以上となる圧延条件
下で圧延することを特徴とする鋼片の表面割れを防止し
た熱間圧延法。 ｍ＝｛２√［Ｒ（ｈ＿１−ｈ＿２）］｝／（ｈ＿１＋ｈ
＿２）ただし、Ｒ：圧延ロール半径 ｈ＿１：ロール入側の材料厚さ ｈ＿２：ロール出側の材料厚さ[Claims] In a method of direct rolling or direct rolling of a steel ingot or slab immediately after ingot making or continuous casting, the steel ingot or slab is first subjected to a width reduction of 5 mm or more on one side, and then the following formula is applied. A hot rolling method that prevents surface cracking of a steel billet, characterized by rolling under rolling conditions such that the shape ratio (m) defined by: is 1 or more. m={2√[R(h_1-h_2)]}/(h_1+h
_2) However, R: Roll radius h_1: Material thickness on roll entry side h_2: Material thickness on roll exit side
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15624885A JPS6216802A (en) | 1985-07-16 | 1985-07-16 | Hot rolling method for preventing surface crack of ingot |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15624885A JPS6216802A (en) | 1985-07-16 | 1985-07-16 | Hot rolling method for preventing surface crack of ingot |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS6216802A true JPS6216802A (en) | 1987-01-26 |
Family
ID=15623620
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15624885A Pending JPS6216802A (en) | 1985-07-16 | 1985-07-16 | Hot rolling method for preventing surface crack of ingot |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6216802A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4917962A (en) * | 1986-07-28 | 1990-04-17 | Centre De Recherches Metallurgiques-Centrum Voor Research In De Metallurgie | Metal product having improved luster after painting |
| JPH04372477A (en) * | 1991-06-24 | 1992-12-25 | Toyota Autom Loom Works Ltd | Side cover of fork lift |
-
1985
- 1985-07-16 JP JP15624885A patent/JPS6216802A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4917962A (en) * | 1986-07-28 | 1990-04-17 | Centre De Recherches Metallurgiques-Centrum Voor Research In De Metallurgie | Metal product having improved luster after painting |
| JPH04372477A (en) * | 1991-06-24 | 1992-12-25 | Toyota Autom Loom Works Ltd | Side cover of fork lift |
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