JPS648048B2 - - Google Patents
Info
- Publication number
- JPS648048B2 JPS648048B2 JP16920984A JP16920984A JPS648048B2 JP S648048 B2 JPS648048 B2 JP S648048B2 JP 16920984 A JP16920984 A JP 16920984A JP 16920984 A JP16920984 A JP 16920984A JP S648048 B2 JPS648048 B2 JP S648048B2
- Authority
- JP
- Japan
- Prior art keywords
- rolling
- less
- temperature
- hot
- rolled steel
- 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
Links
- 229910000831 Steel Inorganic materials 0.000 claims description 24
- 239000010959 steel Substances 0.000 claims description 24
- 238000005096 rolling process Methods 0.000 claims description 21
- 238000001816 cooling Methods 0.000 claims description 16
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 238000005098 hot rolling Methods 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 5
- 230000009467 reduction Effects 0.000 claims description 4
- 238000009749 continuous casting Methods 0.000 claims description 2
- 239000000463 material Substances 0.000 description 12
- 229910001562 pearlite Inorganic materials 0.000 description 7
- 238000004804 winding Methods 0.000 description 6
- 229910001563 bainite Inorganic materials 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229910000677 High-carbon steel Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Description
（産業上の利用分野）
本発明は石油、油井管又は天然ガス用油井管、
あるいは長距離輸送用（ラインパイプ）電縫鋼管
に用いる熱間圧延鋼板の製造方法に関するもので
ある。
（従来の技術）
前記電縫鋼管用熱間圧延鋼板に必要な機械的性
質は各規格毎に強度（TS）、降伏点強度（YS）、
靭性等を定めている。
問題はこれ等が成品スペツクであるため、素材
である熱延鋼板の強度設計が極めて重大となる。
なぜなら最終工程である造管工程で変形に起因す
る機械的性質の変化をうけても使用上に支障を生
じないことが望まれるからである。
通常高強度電縫管、例えばAPI 5LX−X60、
X70などは析出強化型の成分系で製造するが、造
管によりTSも上昇するがYSも上昇する。
これがAPI規格のAPI 5A−K55などの場合、
TSは95000lb／in2以上、YSは55000〜80000lb／
in2と規定されているものを析出強化型で熱延鋼
板を製造すると、TSは規格値を満足するがYSは
上限を外れる場合が多いと云う問題が生ずる。特
にK55は規格値が低降伏比型であるため、熱延鋼
板でも特に低降伏比型にする必要があり高炭素系
鋼板が用いられている。
従来この規格値を満足させるための技術として
は特開昭57−145928号公報、特公昭56−44133号
公報などで開示された製造法がある。これらの製
造法には、熱延仕上温度を750〜850℃にして、前
者は降伏点上昇を抑制し、後者はベーナイト、パ
ーライトの生成を促して強度の向上を計ることが
開示されているが、パーライト、フエライトの結
晶粒微細化の考えが無いため、熱間圧延の仕上げ
出側から捲取りまでの冷却速度及び捲取後のコイ
ル内外周の冷却速度の差の影響を受けやすく、長
手方向に材質が不均一となること及び厚物の製造
が実施されにくいという問題がある。
（発明が解決しようとする問題点）
前記した特開昭57−145928号公報、特公昭56−
44133号公報記載の方法は、圧延後捲取りまでの
間に前記したように多量の水を用いて所定の冷却
速度を確保するので鋼板に局部的焼きが入りやす
く、材質が不均一になりやすく、更に次記する問
題点が内在している。
ａ 高炭素系のため靭性が悪い。
ｂ 高炭素系のため製造段階のうち熱間圧延後の
冷却段階で冷却速度の影響を受けやすく熱延鋼
板の長手方向、幅方向で材質の不均一が生じや
すく又コイル全長に亘つて均一な材質を得にく
い。
ｃ 造管による材質変化も大きいため、電縫鋼管
のサイズ毎に熱延鋼板の材質設計を変える必要
がある。
（問題点を解決するための手段）
本発明は上記した問題点を解決し、しかも前記
要求を満すための電縫鋼管用熱延鋼板を容易に製
造する方法を提供することを目的とするものでそ
の特徴とするところはＣ：0.30〜0.50％、Si：
0.35％以下、Mn：0.70〜1.20％、Al：0.030％以
下、Ｎ：50ppm以下を含み、残部Fe及び不可避
元素からなり、かつCeqが0.45〜0.68（但しCeq＝
Ｃ＋Mn／６）を満足する連続鋳造スラブを、1180
℃以下に加熱した後、仕上圧延温度680〜750℃未
満、仕上圧延の総圧下率50％以上の条件で熱間圧
延し、仕上圧延出側直後から５〜30℃／secの冷
却速度で冷却を開始し、400〜650℃で捲取ること
を特徴とする熱延鋼板の製造方法にある。
本発明の上記した構成要件の限定理由について
以下に詳述する。
まずこの熱延鋼板の成分としては、YSとTSの
バランスを保つ上でＣは重要な元素であり、必要
量としては0.30％以上が必要である。これ未満の
場合規格上必要な強度が得られない。0.50％を超
えてしまうと強度がですぎること、又組織的に炭
化物が大きくなり靭性が劣化してしまう。
Siは本発明の効果を助長する元素ではないが一
般に知られているように製鋼段階で脱酸剤として
用いられるものであり、その含有量は通常の量、
即ち0.35％以下であればよい。
またAlも前記Siと同様に一般的に脱酸剤とし
て用いられるものであつて、通常の量は0.030％
以下である。
Mn及びＣ当量についても同様のことが云え
る。すなわち下限値は強度保証上必要で、その値
はMn0.70％、Ceqは0.45となる。上限は焼入れ性
防止のためであり、Mn、Ceqとも各々1.20％、
0.68以上となると問題となる。
加熱温度（加熱炉抽出温度）は、析出強化元素
を添加しない鋼におけるγ粒の粗大化防止という
意味から1180℃以下とした。加熱温度の下限は圧
延機の能力によつて異なるが、本発明の思想から
は熱間圧延ができる温度、つまりAr3変態点が確
保されればよい。
本発明のもつとも重要な仕上圧延温度（仕上出
側温度）についてはAr3点以上と云う意味で680
℃以上とし、γ粒の微細化を図ると云う意味で上
限を750℃未満とした。この温度以上であるとγ
粒が微細とならずパーライトが得られないこと、
又Ar3変態点未満になると展伸状のフエライトが
生じて材質のの方向性が大きくなり好ましくな
い。
捲取り温度（CT）が低すぎると、過冷却とな
り大量のベイナイト又はマルテンサイトが発生す
る危険があるため、又高すぎると層状パーライト
となり靭性が劣化し、又捲き取り後コイル内外周
で冷速の違いが大きくなりその影響を受けやすく
なるため500〜700℃とした。
圧延後の冷却パターンとしては微細パーライト
を得るためできるだけ冷却速度を早くする必要が
ある。目的とする捲き取り温度までできるだけ早
く圧延直後に冷却を開始し冷却速度を早くする。
冷却速度は５℃／sec以上とする。但し30℃／sec
以上と過冷却となりやすい為上限を設定した。
更に靭性を向上させるため、Ar3変態点直上で
圧延する時、一定の圧下率を確保し細粒化を図る
必要がある。このため仕上圧延前のバー厚を製品
板厚から逆算して50％以上確保できるようにす
る。
又成分的にこのような高〔Ｃ〕材を鋳造する場
合、連続鋳造では表面疵が問題となる場合がある
ためＮは50ppm以下とした。
（作用）
本発明は、上記の如く構成したので、生成する
特有の作用は次の通りである。γ領域でしかも
Ar3変態点直上で圧延することによつてγ粒を微
細化する。この時析出元素がないため加熱炉温度
を低くすることができ圧延前のγ粒粗大化を防止
することができる。
このことが仕上圧延と捲取りの間で圧延直後か
ら急冷して目的温度（捲取り温度）に達するよう
急冷しても局部的にマルテンサイトや多量のベイ
ナイトが生ずることを防止して、微細なパーライ
トとフエライト、一部ベイナイトを含む組織と
し、これによつて靭性を向上させる。
又結晶粒が微細であることより、より低いＣ、
Mn量で強度を確保し、その結果捲取り後のコイ
ル外周と内周に生じている温度差の影響による熱
延鋼板のトツプ部とエンド部の強度上昇が防止さ
れる。
本発明による製品の組織は主に微細なパーライ
トとフエライトより構成されている為造管時の変
形による加工硬化の影響が少く、材質の変化が従
来の高炭素系熱延鋼板より少くなる。
(Industrial Application Field) The present invention relates to oil country tubular goods, oil country tubular goods for oil country or natural gas,
Alternatively, the present invention relates to a method of manufacturing a hot rolled steel plate used for electric resistance welded steel pipes for long-distance transportation (line pipes). (Prior art) The mechanical properties required for the hot-rolled steel sheet for ERW steel pipes are determined by each standard: strength (TS), yield point strength (YS),
It specifies toughness, etc. The problem is that these are specs for finished products, so the strength design of the hot-rolled steel sheet material is extremely important.
This is because it is desired that even if the mechanical properties change due to deformation in the final pipe forming process, there will be no problem in use. Usually high-strength ERW pipe, such as API 5LX-X60,
Products such as X70 are manufactured using a precipitation-strengthened component system, but the TS and YS increase due to pipe making. If this is an API standard such as API 5A-K55,
TS is 95000lb/in 2 or more, YS is 55000~80000lb/
When producing hot-rolled steel sheets using a precipitation-strengthened steel sheet that is specified as in 2 , a problem arises in that although TS satisfies the standard value, YS often falls outside the upper limit. In particular, K55 has a standard value of a low yield ratio type, so even hot rolled steel sheets must be made of a particularly low yield ratio type, so high carbon steel sheets are used. Conventionally, as a technique for satisfying this standard value, there are manufacturing methods disclosed in Japanese Patent Application Laid-open No. 145928/1982, Japanese Patent Publication No. 44133/1983, and the like. These manufacturing methods disclose that the hot rolling finishing temperature is set at 750 to 850°C, and the former suppresses the rise in yield point, while the latter promotes the formation of bainite and pearlite to improve strength. Since there is no consideration of crystal grain refinement of pearlite and ferrite, it is easily affected by the cooling rate from the finishing exit side of hot rolling to winding, and the cooling rate of the inner and outer circumferences of the coil after winding. However, there are problems in that the material is non-uniform and it is difficult to manufacture thick products. (Problems to be solved by the invention) The above-mentioned Japanese Unexamined Patent Publication No. 145928/1983
The method described in Publication No. 44133 uses a large amount of water to ensure a predetermined cooling rate between rolling and rolling, as described above, which tends to cause localized hardening of the steel plate and cause the material to become non-uniform. Furthermore, the following problems are inherent. a) Poor toughness due to high carbon content. b Due to its high carbon content, it is easily affected by the cooling rate during the cooling stage after hot rolling during the manufacturing process, which tends to cause non-uniformity of the material in the longitudinal and width directions of the hot-rolled steel sheet, as well as uniformity over the entire coil length. Difficult to obtain materials. c. Because the material quality changes significantly during pipe manufacturing, it is necessary to change the material design of hot rolled steel sheets for each size of ERW steel pipe. (Means for Solving the Problems) An object of the present invention is to solve the above-mentioned problems and to provide a method for easily producing a hot-rolled steel plate for ERW steel pipes that satisfies the above-mentioned requirements. Its characteristics are C: 0.30-0.50%, Si:
Contains 0.35% or less, Mn: 0.70 to 1.20%, Al: 0.030% or less, N: 50ppm or less, and the balance consists of Fe and unavoidable elements, and Ceq is 0.45 to 0.68 (however, Ceq =
A continuous cast slab satisfying C+Mn/6) is heated to 1180°C or less, and then hot rolled at a finish rolling temperature of 680 to less than 750°C and a total reduction rate of 50% or more on the finish rolling exit side. Immediately thereafter, cooling is started at a cooling rate of 5 to 30°C/sec, and rolling is performed at 400 to 650°C. The reason for limiting the above-mentioned constituent elements of the present invention will be explained in detail below. First, as a component of this hot rolled steel sheet, C is an important element in maintaining the balance between YS and TS, and the required amount is 0.30% or more. If it is less than this, the strength required by the standard cannot be obtained. If it exceeds 0.50%, the strength will be too high, and the carbides will become larger in structure and the toughness will deteriorate. Si is not an element that promotes the effects of the present invention, but as is generally known, it is used as a deoxidizing agent in the steel manufacturing stage, and its content is in a normal amount,
That is, it is sufficient if it is 0.35% or less. Also, like the above-mentioned Si, Al is generally used as a deoxidizing agent, and the usual amount is 0.030%.
It is as follows. The same can be said about Mn and C equivalents. In other words, the lower limit value is necessary to guarantee strength, and the value is Mn 0.70% and Ceq 0.45. The upper limit is to prevent hardenability, and Mn and Ceq are each 1.20%.
If it exceeds 0.68, it becomes a problem. The heating temperature (heating furnace extraction temperature) was set to 1180°C or less to prevent coarsening of γ grains in steel without addition of precipitation-strengthening elements. The lower limit of the heating temperature varies depending on the capacity of the rolling mill, but from the idea of the present invention, it is sufficient to ensure a temperature that allows hot rolling, that is, the Ar 3 transformation point. Regarding the finishing rolling temperature (finishing exit temperature), which is the most important aspect of the present invention, it is 680 in the sense of Ar 3 points or higher.
℃ or more, and the upper limit was set to less than 750°C in order to make the γ grains finer. Above this temperature, γ
The grains are not fine and pearlite cannot be obtained.
Further, if the temperature is lower than the Ar 3 transformation point, expanded ferrite is produced and the directionality of the material becomes large, which is not preferable. If the winding temperature (CT) is too low, there is a risk of overcooling and the generation of a large amount of bainite or martensite, and if it is too high, layered pearlite will form and the toughness will deteriorate. The temperature was set at 500 to 700℃ because the difference in temperature becomes large and the temperature is easily affected. As for the cooling pattern after rolling, it is necessary to make the cooling rate as fast as possible in order to obtain fine pearlite. Cooling is started immediately after rolling to increase the cooling rate to the desired rolling temperature as soon as possible.
The cooling rate shall be 5°C/sec or more. However, 30℃/sec
An upper limit was set because overcooling is likely to occur. In order to further improve toughness, when rolling just above the Ar 3 transformation point, it is necessary to ensure a constant rolling reduction and to achieve finer grain size. For this reason, the bar thickness before finish rolling is calculated backwards from the product plate thickness to ensure that it is at least 50%. In addition, when casting such a material with a high [C] composition, surface flaws may become a problem in continuous casting, so the N content was set to 50 ppm or less. (Actions) Since the present invention is constructed as described above, the unique effects produced are as follows. Even in the γ region
The γ grains are refined by rolling just above the Ar 3 transformation point. At this time, since there are no precipitated elements, the heating furnace temperature can be lowered and coarsening of the γ grains before rolling can be prevented. This prevents the local formation of martensite and large amounts of bainite even if the cooling is performed immediately after rolling to reach the target temperature (rolling temperature) between finish rolling and winding. The structure includes pearlite, ferrite, and some bainite, which improves toughness. Also, because the crystal grains are fine, lower C,
Strength is ensured by the amount of Mn, and as a result, an increase in strength at the top and end portions of the hot rolled steel sheet due to the influence of the temperature difference between the outer and inner circumferences of the coil after winding is prevented. Since the structure of the product according to the present invention is mainly composed of fine pearlite and ferrite, it is less affected by work hardening due to deformation during tube manufacturing, and changes in material quality are less than that of conventional high-carbon hot-rolled steel sheets.
【表】
表１及び第１図に示すように本発明例の長手方
向均一性をTSでみると、従来例のσが3.9であつ
たものが0.9〜1.2の範囲に改善され、特に比較例
がフロント・テイルでスペツク保証が困難であつ
たようなことは、本発明例では全くなくなつた。
又、靭性についても、表１及び第２図に示すよ
うに改善は著しく、従来例が−20℃で1.27Kg−
ｍであるのに比して本発明例は−20℃で5.1〜
5.3Kg−ｍであり、温度において100℃程度低温側
においても同等の靭性が得られ、更には材質に起
因する造管トラブルも全くなくなつた。
（発明の効果）
本発明による効果は以下のとおりである。
(1) 造管歩留の向上がはかれる。すなわち、本発
明によれば、主に長手材質の均一化により長手
全長（オープン部を除いて）に亘つて規格値を
満足する鋼板が得られる。
(2) 熱延における捲き取り後冷却速度の影響によ
る熱延テイル部、フロント部のカツト（強度ア
ツプ部）が必要でなくなる。
(3) 低温靭性の優れた鋼管を安価に製造できる。[Table] As shown in Table 1 and Fig. 1, when looking at the longitudinal uniformity of the present invention example in terms of TS, the σ of the conventional example, which was 3.9, was improved to a range of 0.9 to 1.2, and in particular, the comparative example However, the difficulty in guaranteeing specs for the front tail is completely eliminated with the present invention. In addition, the improvement in toughness was remarkable as shown in Table 1 and Figure 2, with the conventional example achieving a reduction of 1.27 kg at -20°C.
m, whereas the example of the present invention has a temperature of 5.1 to -20°C.
5.3Kg-m, equivalent toughness was obtained even at temperatures as low as 100°C, and furthermore, there were no problems in pipe manufacturing caused by the material. (Effects of the invention) The effects of the invention are as follows. (1) Improved pipe production yield. That is, according to the present invention, a steel plate that satisfies standard values over the entire longitudinal length (excluding the open portion) can be obtained mainly by making the longitudinal material uniform. (2) There is no need to cut the hot-roll tail and front parts (strength-increased parts) due to the influence of the cooling rate after winding in hot rolling. (3) Steel pipes with excellent low-temperature toughness can be manufactured at low cost.
第１図は本発明実施例と従来例から得られた各
鋼板の長手方向強度均一特性を示す図、第２図は
本発明実施例と従来例から得られた各鋼板の靭
性、特性を示す図である。
Fig. 1 shows the longitudinal strength uniformity characteristics of each steel plate obtained from the present invention example and the conventional example, and Fig. 2 shows the toughness and characteristics of each steel plate obtained from the present invention example and the conventional example. It is a diagram.
Claims (1)
0.70〜1.20％、Al：0.030％以下、Ｎ：50ppm以下
を含み、残部Fe及び不可避元素からなり、かつ
Ceqが0.45〜0.68（但しCeq＝Ｃ＋Mn／６）を満足す る連続鋳造スラブを、1180℃以下に加熱した後、
仕上圧延温度680〜750℃未満、仕上圧延の総圧下
率50％以上の条件で熱間圧延し、仕上圧延出側直
後から５〜30℃／secの冷却速度で冷却を開始し、
400〜650℃で捲取ることを特徴とする熱延鋼板の
製造方法。[Claims] 1 C: 0.30 to 0.50%, Si: 0.35% or less, Mn:
Contains 0.70 to 1.20%, Al: 0.030% or less, N: 50ppm or less, and the balance consists of Fe and inevitable elements, and
After heating a continuous casting slab whose Ceq satisfies 0.45 to 0.68 (Ceq=C+Mn/6) to 1180℃ or less,
Hot rolling is performed at a finish rolling temperature of 680 to less than 750 °C and a total reduction rate of 50% or more, and cooling is started immediately after the finish rolling exit at a cooling rate of 5 to 30 °C/sec,
A method for producing hot-rolled steel sheets characterized by rolling at a temperature of 400 to 650°C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16920984A JPS6148518A (en) | 1984-08-15 | 1984-08-15 | Manufacture of hot rolled steel plate |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16920984A JPS6148518A (en) | 1984-08-15 | 1984-08-15 | Manufacture of hot rolled steel plate |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6148518A JPS6148518A (en) | 1986-03-10 |
| JPS648048B2 true JPS648048B2 (en) | 1989-02-13 |
Family
ID=15882222
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16920984A Granted JPS6148518A (en) | 1984-08-15 | 1984-08-15 | Manufacture of hot rolled steel plate |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6148518A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5011773B2 (en) * | 2005-03-24 | 2012-08-29 | Ｊｆｅスチール株式会社 | Manufacturing method of low yield ratio ERW steel pipe with excellent low temperature toughness |
| JP5742207B2 (en) * | 2010-12-21 | 2015-07-01 | Ｊｆｅスチール株式会社 | Low yield ratio high strength ERW steel pipe and method for producing the same |
| CN103255337B (en) * | 2013-04-24 | 2014-12-10 | 河北钢铁股份有限公司邯郸分公司 | Production method of low-cost easily-welded steel |
| EP3395973A4 (en) | 2015-12-21 | 2019-06-12 | Nippon Steel & Sumitomo Metal Corporation | As-rolled type k55 electric-resistance-welded oil well pipe, and hot-rolled steel plate |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5644133A (en) * | 1979-09-14 | 1981-04-23 | Toshiba Corp | Auto reverse unit with program searching mechanism |
| JPS57145928A (en) * | 1981-03-04 | 1982-09-09 | Sumitomo Metal Ind Ltd | Production of steel plate for producing electric welded steel pipe |
-
1984
- 1984-08-15 JP JP16920984A patent/JPS6148518A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6148518A (en) | 1986-03-10 |
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