JPH03219015A - Production of square tube having yield point elongation, reduced in yield ratio, and excellent in toughness at low temperature - Google Patents
Production of square tube having yield point elongation, reduced in yield ratio, and excellent in toughness at low temperatureInfo
- Publication number
- JPH03219015A JPH03219015A JP28878690A JP28878690A JPH03219015A JP H03219015 A JPH03219015 A JP H03219015A JP 28878690 A JP28878690 A JP 28878690A JP 28878690 A JP28878690 A JP 28878690A JP H03219015 A JPH03219015 A JP H03219015A
- Authority
- JP
- Japan
- Prior art keywords
- low
- square tube
- yield ratio
- yield
- toughness
- 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
- 238000004519 manufacturing process Methods 0.000 title claims description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 27
- 238000001816 cooling Methods 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 18
- 238000005496 tempering Methods 0.000 claims abstract description 15
- 229910001209 Low-carbon steel Inorganic materials 0.000 claims abstract description 5
- 229910000831 Steel Inorganic materials 0.000 abstract description 31
- 239000010959 steel Substances 0.000 abstract description 31
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 4
- 229910052799 carbon Inorganic materials 0.000 abstract description 4
- 229910000851 Alloy steel Inorganic materials 0.000 abstract description 2
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 229910000859 α-Fe Inorganic materials 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000005482 strain hardening Methods 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 238000013459 approach Methods 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 239000003129 oil well Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は、降伏比の低い角管の製造方法に関するもので
ある。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a rectangular tube with a low yield ratio.
（従来の技術）
近年鉄鋼材料を扱う各分野にわたって、競争力向上のた
めの使用特性の向上、製造コストの低減なと各種の要求
が高まっている。(Prior Art) In recent years, various demands have been increasing across various fields that handle steel materials, such as improving usage characteristics and reducing manufacturing costs in order to improve competitiveness.
このうち建築分野では、構造物の安全性向上のため、特
に耐震性向上のために降伏比の低下が望まれている。こ
れまでは主に厚板分野でこの要求が強かったが、最近で
は鋼管分野でこの要求かたかまっている。低降伏比を有
する厚鋼板の製造方法に関しては、種々の方法が検討さ
れているが、残念ながら鋼管の分野では、少なくとも建
築用として検討された例はほとんどないのが現状である
。例えば電縫鋼管は、ホットコイルを成形して製造する
が、成形の際の加工硬化により降伏比が上昇するため、
降伏比の低い鋼管の製造には、不利な製造方法とされて
いる。例えば、低降伏比油井用電縫鋼管の製造方法とし
て、特開昭５７−１８１１８号があるが、この方法では
低降伏比化のためにＣ量をかなり添加しているため（Ｃ
量： ０．２６〜０．４８％）、溶接性の観点からＣｅ
ｑ上限の規定される建築構造用には適用できない。また
同様に、低降伏比高張力電縫鋼管の製造方法として、特
開昭５７−１６１１９号があるか、これはホットコイル
の段階で極低ＹＲ鋼を製造し、電縫鋼管を製造する際の
加工硬化を押えるために、歪量をかなり制限しているが
、実操業ではかなり困難が伴う。Among these, in the field of construction, it is desired to reduce the yield ratio in order to improve the safety of structures, especially in order to improve their seismic resistance. Until now, this requirement has been strong mainly in the thick plate field, but recently this requirement has become stronger in the steel pipe field. Various methods have been studied for manufacturing thick steel plates with a low yield ratio, but unfortunately, in the field of steel pipes, there are currently almost no examples of such methods being studied, at least for construction purposes. For example, ERW steel pipes are manufactured by forming hot coils, but the yield ratio increases due to work hardening during forming.
It is considered to be a disadvantageous manufacturing method for manufacturing steel pipes with a low yield ratio. For example, there is a method for manufacturing ERW steel pipes for oil wells with a low yield ratio in JP-A-57-18118, but in this method a considerable amount of C is added to achieve a low yield ratio (C
amount: 0.26-0.48%), from the viewpoint of weldability
It cannot be applied to architectural structures where the upper limit of q is specified. Similarly, there is Japanese Patent Application Laid-Open No. 57-16119 as a method for manufacturing low yield ratio, high tensile resistance welded steel pipes. In order to suppress work hardening, the amount of strain is considerably limited, but this is quite difficult in actual operation.
（発明が解決しようとする課題）
建築用低降伏比角管として、引張り強さ４０キロ以上で
降伏比７５％以下という要求があるが、現状の製造方法
では製造が不可能である。(Problems to be Solved by the Invention) As a low yield ratio angle pipe for construction, there is a requirement for a tensile strength of 40 kg or more and a yield ratio of 75% or less, but it is impossible to manufacture with the current manufacturing method.
つまり、ホットコイルを丸く成形しただけで製造する非
調質型、いわゆるアズロール型では、その成形時の加工
硬化のために、また調質型いわゆるＱＴ型では、その組
織が焼戻しマルテンサイトとなるため、降伏比７５％以
下は達成されていない。In other words, in the non-tempered type, the so-called azurol type, which is manufactured by simply forming a hot coil into a round shape, the structure is due to work hardening during forming, and in the tempered type, so-called QT type, the structure becomes tempered martensite. , a yield ratio of 75% or less has not been achieved.
さらに最近耐震構造用として、低降伏比のみならず応力
−歪曲線の形状が規定されるようになってきている。つ
まり、第１図、第２図で示すＡＣの面積の大きい方が、
より塑性伸び能力が大きく、破壊に到達しにくいという
わけである。この時、第２図の方がより耐震構造用とし
て優れていることは明らかであるが、その際ＡＣは降伏
比と降伏点伸びでほぼ決定されるといえる。つまり、耐
震構造用として、低降伏比でかつ降伏伸びを有した鋼材
が要求されはじめている。Furthermore, recently, not only low yield ratios but also the shape of stress-strain curves have been specified for use in earthquake-resistant structures. In other words, the AC shown in Figures 1 and 2 has a larger area,
It has a greater plastic elongation ability and is less likely to break. At this time, it is clear that the one shown in Fig. 2 is better for use in earthquake-resistant structures, but in this case, it can be said that AC is almost determined by the yield ratio and the elongation at yield point. In other words, steel materials with a low yield ratio and yield elongation are beginning to be required for earthquake-resistant structures.
（課題を解決するための手段）
そこで本発明者らは、降伏比を低下させるために、多数
の実験と詳細な検討を加えた結果、降伏比を低下させる
ためには、鋼のミクロ組織をフェライトと第２相の炭化
物の２相組織にする必要性を確認した。さらに、降伏比
を下げるためには、降伏点を下げ、引張り強さを高める
ことが重要であることも確認した。(Means for Solving the Problems) Therefore, the present inventors conducted numerous experiments and detailed studies in order to reduce the yield ratio. The necessity of creating a two-phase structure consisting of ferrite and a second phase of carbide was confirmed. Furthermore, it was confirmed that in order to lower the yield ratio, it is important to lower the yield point and increase the tensile strength.
本発明は、このような知見に基き、低降伏比を有する角
管の製造を可能にしたもので、その要旨とするところは
、低炭素鋼または低炭素低合金鋼管を、Ａ Ｃ５−２５
０〜ＡＣ３−２０℃に加熱し、引き続き１５℃／ｓｅｃ
以上の冷却速度で急冷し、その後冷間で角管に成形し、
さらにその後２００〜６００℃の温度範囲で焼戻しする
ことを特徴とする、降伏点伸びを有し、降伏比が低く、
かつ低温靭性に優れた角管の製造方法である。Based on this knowledge, the present invention has made it possible to manufacture square tubes with a low yield ratio.
Heat to 0~AC3-20℃, then 15℃/sec
Rapidly cool at a cooling rate above, then cold form into a square tube,
Furthermore, it is characterized by being tempered at a temperature range of 200 to 600°C, and has a yield point elongation and a low yield ratio.
It is also a method for manufacturing a square tube with excellent low-temperature toughness.
（作 用）
本発明は、熱処理条件を特定するとともに、２相域加熱
後急冷とテンパーという２種の熱処理の間に角管成形を
行うことを特徴とするものである。先ず熱処理条件につ
いて述べると、加熱温度をＡ Ｃ５−２５０〜Ａｃ３−
２０℃とし、その後急冷することによって、パイプ成形
での加工硬化の影響を除去しつつ、２相鋼化を達成する
ことに成功している。(Function) The present invention is characterized in that the heat treatment conditions are specified and square tube forming is performed between two types of heat treatment: quenching after heating in a two-phase region and tempering. First, let's talk about the heat treatment conditions.The heating temperature ranges from AC5-250 to Ac3-
By cooling the steel to 20°C and then rapidly cooling it, they succeeded in achieving duplex steel while eliminating the effects of work hardening during pipe forming.
さらに、その後冷間で角管成形することによって、組織
（フェライト）内に転位を導入し、その後焼戻しを行う
ことにより固溶窒素、固溶炭素で転位を固着して、降伏
点伸びを持たせることに成功している。Furthermore, by cold forming a square tube, dislocations are introduced into the structure (ferrite), and then tempering is performed to fix the dislocations with solid solution nitrogen and solid solution carbon, giving it yield point elongation. It has been extremely successful.
さらに焼戻しにより、第２相部分を軟化させることによ
り、低温靭性を充分回復させることに成功しているが、
この焼戻温度を低くすることによって、第２相の部分を
必要以上に軟化させないことの相乗的効果により、降伏
点伸びを有し、降伏比が低く、かつ低温靭性に優れた角
管の製造を可能にしたものである。Furthermore, by softening the second phase part through tempering, we succeeded in sufficiently recovering the low-temperature toughness.
By lowering this tempering temperature, the synergistic effect of not softening the second phase part more than necessary produces square tubes with yield point elongation, low yield ratio, and excellent low-temperature toughness. This is what made it possible.
続いて、２相域加熱後急冷とテンパーという２種の熱処
理の間に角管成形を行うと有利な点について述べる。ま
ず第１に、２種の熱処理の間に角管成形をすることによ
フて、降伏点伸びを持たせることができる。角管成形後
にこれら２種の熱処理を行う方法もあるが、その方法だ
と降伏比は低下するが、降伏点伸びを持たせることがで
きない。第２に、冷間で角管成形を行う点が有利である
。２相域で角管成形後に急冷することによって、低降伏
比と降伏点伸びを両立させる方法があるが、この方法だ
と温間で角管成形するため、温度制御が非常に困難であ
り、この方法だと熱処理と角管成形を区別することがで
きるので、工業的には適用が容易である。Next, we will discuss the advantages of forming square tubes between two types of heat treatment: rapid cooling after heating in the two-phase region and tempering. First of all, by forming a rectangular tube between the two types of heat treatments, elongation at yield point can be imparted. There is also a method of performing these two types of heat treatment after forming a square tube, but this method lowers the yield ratio, but does not allow it to have elongation at yield point. Secondly, it is advantageous that the square tube is formed cold. There is a method of achieving both a low yield ratio and yield point elongation by rapidly cooling after forming a square tube in the two-phase region, but this method involves forming a square tube at a warm temperature, making temperature control extremely difficult. This method is easy to apply industrially because heat treatment and square tube forming can be distinguished.
次に本発明の鋼管製造・加熱・冷却・角管成形・テンパ
ーの条件について述べる。Next, the conditions for manufacturing, heating, cooling, square tube forming, and tempering the steel pipe of the present invention will be described.
ます、鋼管の製造については、特に規定はなくどのよう
な方法でも許容される。例えは鋼管はその製造方法から
、シームレス鋼管、電縫鋼管、ＵＯ鋼管、スパイラル鋼
管、鍛接管等に分類できるが、本発明はこれらどの製造
方法でも許容される。これは、その後の熱処理での加熱
温度を加工歪か除去される温度に規定するためである。There are no particular regulations regarding the manufacture of steel pipes, and any method is acceptable. For example, steel pipes can be classified into seamless steel pipes, electric resistance welded steel pipes, UO steel pipes, spiral steel pipes, forge-welded pipes, etc. according to their manufacturing methods, and the present invention is acceptable with any of these manufacturing methods. This is to set the heating temperature in the subsequent heat treatment to the temperature at which processing strain is removed.
次に加熱温度をＡＣ３−２５０〜ＡＣ３−２０℃にした
のは、この温度範囲に加熱することによって、冷却後の
２相鋼化を達成しつつ成形歪の除去を同時に狙ったため
である。すなわち、Ａｃｔ直上に加熱後急冷すると、２
相鋼化するものの、フェライトに加工歪が残存するため
にフェライトの強度か高く、結果的に低降伏比を達成す
ることかてきない。ＡＣ１〜Ａｃ３の中間よりも高温、
つまりＡ ｃ３−２５０℃より高温に加熱することによ
って、この２相鋼化と歪除去を両立できるため、この温
度を下限とした。加熱温度を高くしていくと、降伏比最
下限を通過して今度は逆に降伏比か増加していく。これ
はフェライトの面積率か減少してゆくためて、ＡＣ３に
近づくと降伏比か急激に増加する。これはフェライトの
面積率がゼロに近づくためである。このことから、加熱
温度の上限として、ＡＣ３−２０℃を設定した。ＡＣ３
−２５０〜ＡＣ，−２０に加熱後の急冷は、再加熱時に
オーステナイト化してＣの濃化した部分を焼入組織とす
ることで充分硬化させ、引張り強さを高め低降伏比を得
るためである。急冷が不十分だと、焼入組織が充分に硬
化せず、結果として低降伏比が得られないため、冷却速
度を１５℃／ｓｅｃ以上に規定した。また冷却について
は通常は水冷であるが、冷却速度が確保できれば方法に
はこだわらない。Next, the reason why the heating temperature was set to AC3-250 to AC3-20°C was that by heating to this temperature range, it was possible to achieve duplex steel after cooling and simultaneously remove forming distortion. That is, when heated immediately above Act and then rapidly cooled, 2
Although it becomes a phase steel, the strength of the ferrite is high because of residual processing strain in the ferrite, and as a result, it is impossible to achieve a low yield ratio. higher temperature than the middle between AC1 and Ac3,
That is, by heating the steel to a temperature higher than AC3-250°C, it is possible to achieve both duplex steel formation and strain removal, so this temperature was set as the lower limit. As the heating temperature is increased, the yield ratio passes the lowest limit and the yield ratio increases. This is because the area ratio of ferrite decreases, and as AC3 approaches, the yield ratio increases rapidly. This is because the area ratio of ferrite approaches zero. From this, AC3-20°C was set as the upper limit of the heating temperature. AC3
-250 to AC, rapid cooling after heating to -20 is to austenitize during reheating and harden the C-enriched part into a quenched structure to increase tensile strength and obtain a low yield ratio. be. If the rapid cooling is insufficient, the quenched structure will not be sufficiently hardened and, as a result, a low yield ratio will not be obtained. Therefore, the cooling rate was specified to be 15° C./sec or more. As for cooling, water cooling is usually used, but the method does not matter as long as the cooling rate can be secured.
急冷後の冷間での角管成形については特に規定はないが
、角管成形時に同時に長平方向に歪か加わると導入する
転位が多すぎて、降伏比が高くなる。そこで、角管成形
時の長手力向伸びは、±３０％に規定する。There are no particular regulations regarding cold square tube forming after quenching, but if strain is applied in the longitudinal direction at the same time as square tube forming, too many dislocations will be introduced, resulting in a high yield ratio. Therefore, the elongation in the longitudinal direction during square tube forming is specified to be ±30%.
焼戻しは、冷間の角管成形で導入した転位を固溶窒素、
固溶炭素て固着して、降伏点伸びを持たせるのと、靭性
改善のために行う。その際焼戻し温度としては、フェラ
イトと第２相の炭化物の２相組織について、その前の急
冷で充分硬化した第２相部分をあまり高温で焼戻すと軟
化しすき、これが引張り強さの低下つまり降伏比の上昇
の原因となるため、上限を６００℃とした。しかし焼戻
し温度が低くで、 ２００℃未満になるとほとんど焼戻
しの効果がなくなり、靭性か改善されない場合かあるた
め、その下限を２００℃とした。Tempering is the process of replacing dislocations introduced during cold square tube forming with solid solution nitrogen,
This is done to fix solute carbon and give elongation at yield point and to improve toughness. At that time, the tempering temperature should be determined as follows: Regarding the two-phase structure of ferrite and second phase carbide, if the second phase part, which has been sufficiently hardened by the previous quenching, is tempered at too high a temperature, it will soften, resulting in a decrease in tensile strength. Since this causes an increase in yield ratio, the upper limit was set at 600°C. However, if the tempering temperature is low, below 200°C, the effect of tempering will be almost gone and the toughness may not be improved, so the lower limit was set at 200°C.
本発明法は低炭素鋼またはこれに特殊元素を添加した低
炭素低合金鋼に適用して好結果を得ることかできる。好
ましい成分組成としては、Ｃ： ０．０３〜０．３０
％
Ｓｉ ・ ０．０２〜０５０％
Ｍｎ ： ０．２０〜２．００％
Ａ文 ０００１〜０１００％
Ｎ ： ０．０００５〜０．０１００％を基本成分
とする低炭素鋼、または前記基本成分の他に強度鋼の要
求特性によって、
Ｃｕ：２．０％以下
Ｎｉ・９．５％以下
Ｃｒ：５．５％以下
Ｍｏ：２．０％以下
Ｎｂ ： ０．１５％以下
■・０．３％以下
Ｔｉ ： ０．１５％以下
Ｂ ： ０．０００３〜０．００３０％Ｃａ ：
０．００８０％以下
の１種または２ｆ！以上添加してもよい。The method of the present invention can be applied to low carbon steel or low carbon low alloy steel to which special elements are added with good results. A preferred component composition is C: 0.03 to 0.30.
%Si・0.02~050% Mn: 0.20~2.00% A 0001~0100% N: Low carbon steel having 0.0005~0.0100% as a basic component, or other than the above basic components Depending on the required characteristics of the strength steel, Cu: 2.0% or less Ni, 9.5% or less Cr: 5.5% or less Mo: 2.0% or less Nb: 0.15% or less - 0.3% or less Ti: 0.15% or less B: 0.0003-0.0030% Ca:
Type 1 or 2f below 0.0080%! You may add more than that.
Ｃｕは強度上昇、耐食性向上に有用で添加されるか、２
０％を越えて添加しても強度の上昇代かほとんどなくな
るので、含有量の上限は２０％とする。Is Cu useful for increasing strength and improving corrosion resistance?
Even if it is added in excess of 0%, there is almost no increase in strength, so the upper limit of the content is set at 20%.
Ｎｉは低温靭性の改善に有用で添加されるが、高価な元
素であるため含有量は９．５％を上限とする。Ni is added because it is useful for improving low-temperature toughness, but since it is an expensive element, the upper limit of the content is 9.5%.
Ｃｒは強度上昇や耐食性向上に有用で添加されるか、多
くなると低温靭性、溶接性を阻害するため含有量は５５
％を上限とする。Cr is added because it is useful for increasing strength and improving corrosion resistance, or the content is 55 because it inhibits low-temperature toughness and weldability when it increases.
The upper limit is %.
ＭＯは強度上昇に有用であるが、多くなると溶損性を阻
害するため含有量は２．０％を上限とする。Although MO is useful for increasing strength, the upper limit of the content is set at 2.0%, since an excessive amount inhibits the erosion property.
Ｎｂはオーステナイト粒の細粒化や強度上昇に有用で添
加されるが、多くなると溶接性を阻害するので含有量の
上限は０．１５％とする。Nb is added because it is useful for refining austenite grains and increasing strength, but if too much, it impedes weldability, so the upper limit of the content is set to 0.15%.
■は析出強化に有用であるが、多くなると溶接性を阻害
するため、含有量は０．３％を上限とする。(2) is useful for precipitation strengthening, but if too large, it impedes weldability, so the upper limit of content is 0.3%.
Ｔｉはオーステナイト粒の細粒化に有用で添加されるが
、多くなると溶接性を阻害するため、含有量は０．１５
％を上限とする。Ti is added because it is useful for refining austenite grains, but if it increases, it inhibits weldability, so the content is 0.15
The upper limit is %.
Ｂは微量の添加によって、鋼の焼入性を著しく高める効
果を有する。この効果を有効に得るためには、少なくと
も０．０００３％を添加することが必要である。しかし
過多に添加するとＢ化合物を生成して、靭性を劣化させ
るので、上限は０．００３０％とする。B has the effect of significantly increasing the hardenability of steel when added in a small amount. In order to effectively obtain this effect, it is necessary to add at least 0.0003%. However, if added in excess, B compounds are generated and the toughness is deteriorated, so the upper limit is set to 0.0030%.
Ｃａは硫化物系介在物の形態制御に有用で添加されるが
、多くなると鋼中介在物を形成し鋼の性質を悪化させる
ため、含有量はｏ、ｏｏａ、ｏ％を上限とする。Ca is useful for controlling the form of sulfide-based inclusions and is added, but if it increases, it forms inclusions in the steel and deteriorates the properties of the steel, so the upper limit of the content is o, ooa, o%.
（実 施 例）
第１表に供試材の化学成分を示し、第２表に角管のサイ
ズ、熱処理条件と、得られた鋼管の機械的性質を示す。(Example) Table 1 shows the chemical composition of the test materials, and Table 2 shows the size of the square tube, heat treatment conditions, and mechanical properties of the obtained steel tube.
第２表で示した鋼管ＮＯ，ＡＩ、Ｂｌ、に１．Ｄｌ、Ｅ
ｌ、Ｆｌ。1 for the steel pipes No., AI, Bl shown in Table 2. Dl,E
l, Fl.
Ｇ１．）１１．ＩＩ、Ｊｌ、Ｋｌ、Ｌｌ、Ｍｌ、Ｎｌ、
０１．Ｐｉ、Ｑｌ、Ｒ１，Ｓｌ、ＴＩ。G1. )11. II, Jl, Kl, Ll, Ml, Nl,
01. Pi, Ql, R1, Sl, TI.
０１、Ｖｌはそれぞれ本発明実施鋼であり、本発明の狙
いとする低降伏比（降伏比７０％以下）を達成している
。01 and Vl are steels according to the present invention, which have achieved the low yield ratio (yield ratio of 70% or less) targeted by the present invention.
これに対し、Ａ２は角管成形を熱処理の前に実施したた
め、降伏比は低いが降伏点伸びがまったく出ていない。On the other hand, since A2 was formed into a square tube before heat treatment, the yield ratio was low, but no elongation at the yield point was observed at all.
Ａ３は加熱温度が高すぎるため降伏比が高くなっている
。Ａ４は加熱温度が低すぎるため降伏比が高くなってい
る。A3 has a high yield ratio because the heating temperature is too high. A4 has a high yield ratio because the heating temperature is too low.
Ａ５は加熱後の冷却速度が不足のため降伏比が高くなっ
ている。Ａ６は焼戻し温度が高すぎるため降伏比が高く
なっている。A5 has a high yield ratio due to insufficient cooling rate after heating. A6 has a high yield ratio because the tempering temperature is too high.
また、Ｂ２は焼戻し温度が低すぎるため低温靭性が改善
されていない。Ｃ２は冷却速度が不足のため降伏比が高
くなフている。Ｄ２は加熱温度が低すぎるため降伏比が
高くなっている。In addition, B2 has a too low tempering temperature, so low-temperature toughness is not improved. C2 has a high yield ratio due to insufficient cooling rate. D2 has a high yield ratio because the heating temperature is too low.
（発明の効果）
以上詳細に説明した通り、本発明は特別に高価な合金元
素を使用することなく、４０ｋｇｆ７ｍｍ２以上の高強
度を有する低降伏比角管を安価に製造可能としたもので
、産業上その効果は犬である。(Effects of the Invention) As explained in detail above, the present invention makes it possible to manufacture a low yield angle tube having a high strength of 40 kgf7 mm2 or more at a low cost without using any particularly expensive alloying elements. Above that effect is a dog.
第１図は低ＹＲであるが降伏点伸びがないためにＡＣの
面積の小さい場合のＳＳカーブの例を示す。第２図は、
低ＹＲでかつ降伏点伸びを有するためにＡＣの面積の大
きくなった場合のＳＳカーブの例を示す。
化４名
ストレンFIG. 1 shows an example of the SS curve when the AC area is small due to low YR but no yield point elongation. Figure 2 shows
An example of the SS curve is shown when the area of AC is increased due to low YR and elongation at yield point. 4 people stren
Claims (1)
−２０℃に加熱し、引き続き１５℃／ｓｅｃ以上の冷却
速度で急冷した後、冷間で角管に成形し、さらに ２００〜６００℃の温度範囲で焼戻しすることを特徴と
する、降伏点伸びを有し、降伏比が低く、かつ低温靭性
に優れた角管の製造方法。[Claims] 1. Low carbon steel pipes A_c_3-250 to A_c_3
Elongation at yield point characterized by heating to -20°C, followed by rapid cooling at a cooling rate of 15°C/sec or more, cold forming into a square tube, and further tempering at a temperature range of 200 to 600°C. A method for manufacturing a square tube that has a low yield ratio and excellent low-temperature toughness.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1-303708 | 1989-11-22 | ||
| JP30370889 | 1989-11-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH03219015A true JPH03219015A (en) | 1991-09-26 |
Family
ID=17924294
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP28878690A Pending JPH03219015A (en) | 1989-11-22 | 1990-10-26 | Production of square tube having yield point elongation, reduced in yield ratio, and excellent in toughness at low temperature |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH03219015A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013153679A1 (en) | 2012-04-12 | 2013-10-17 | Ｊｆｅスチール株式会社 | Hot-rolled steel plate for square steel tube for use as builiding structural member and process for producing same |
-
1990
- 1990-10-26 JP JP28878690A patent/JPH03219015A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013153679A1 (en) | 2012-04-12 | 2013-10-17 | Ｊｆｅスチール株式会社 | Hot-rolled steel plate for square steel tube for use as builiding structural member and process for producing same |
| KR20140138854A (en) | 2012-04-12 | 2014-12-04 | 제이에프이 스틸 가부시키가이샤 | Hot-rolled steel plate for square steel tube for use as builiding structural member and process for producing same |
| US9708680B2 (en) | 2012-04-12 | 2017-07-18 | Jfe Steel Corporation | Hot rolled steel sheet for square column for building structural members |
| US10876180B2 (en) | 2012-04-12 | 2020-12-29 | Jfe Steel Corporation | Method of manufacturing hot rolled steel sheet for square column for building structural members |
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