JP2005350724A5

JP2005350724A5 -

Info

Publication number: JP2005350724A5
Application number: JP2004172422A
Authority: JP
Filing date: 2004-06-10
Publication date: 2006-11-02
Anticipated expiration: 2024-06-10

Description

Ｍ値＝5.5 Ｃ＋0.6Si ＋Mn＋0.5Cu ＋0.7Cr ＋0.4Ni ＋1.5Mo ＋２Ｖ・・・(1)
CP値＝Nb−0.6Si −5S−5（Ti−0.015）＋0.2 Ｖ・・・(2)
超高強度ベンド管の亀裂伝播発生特性を向上させるには、1)組織の微細化と、2)歪み集中により亀裂発生の起点となりうる硬化組織の除去を同時に実施する必要がある。 M value = 5.5 C + 0.6Si + Mn + 0.5Cu + 0.7Cr + 0.4Ni + 1.5Mo + 2V (1)
CP value = Nb-0.6Si-5S-5 (Ti- 0.015 ) + 0.2 V (2)
In order to improve the crack propagation characteristics of an ultra-high strength bend pipe, it is necessary to simultaneously perform 1) refinement of the structure and 2) removal of the hardened structure that can be the starting point of crack generation due to strain concentration.

CP値＝Nb−0.6Si −5S−5（Ti−0.015）＋0.2 Ｖ・・・(2)
次に、本発明にかかるベンド管の製造方法について説明する。
本発明では上記に規定された成分組成の鋼管を820〜1050℃に加熱後、曲げ加工し、400℃以下まで加速冷却後、焼き戻し処理をするか、または加工後、450〜250℃の温度まで加速冷却をし、その後室温まで空冷をすることによって、所定のミクロ組織を得るものである。 CP value = Nb-0.6Si-5S-5 (Ti- 0.015 ) + 0.2 V (2)
Next, the manufacturing method of the bend pipe | tube concerning this invention is demonstrated.
In the present invention, the steel pipe having the above-defined component composition is heated to 820 to 1050 ° C. and then bent, accelerated and cooled to 400 ° C. or less, and then tempered or processed, and the temperature is 450 to 250 ° C. A predetermined microstructure is obtained by performing accelerated cooling to room temperature and then air cooling to room temperature.

Claims

By mass ratio C: 0.03-0.12% Si: 0.01-0.2%
Mn: 0.8% to 2.0% P: 0.009% or less,
S: 0.003% or less Ni: 0.1-1.5%
Nb: 0.003 to 0.05% Mo: 0.05 to 1.2%
Ti: 0.002 to 0.03% N: 0.005% or less
Al: 0.002 to 0.07%
It consists of the remainder Fe and inevitable impurities, and has a component composition in which the M value and CP value represented by the formulas (1) and (2) are in the range of 2.75 to 4.00% and −0.08 to 0.10%, respectively, and the microstructure is An ultra-high-strength bend pipe having a tensile strength of 750 MPa or more, wherein the tempered martensite structure is 3% or more in a tempered bainite structure having an average packet particle size of 20 μm or less.
M value = 5.5 C + 0.6Si + Mn + 0.5Cu + 0.7Cr + 0.4Ni + 1.5Mo + 2V (1)
CP value = Nb-0.6Si-5S-5 (Ti- 0.015 ) + 0.2 V (2)

The ultra-high-strength bend pipe according to claim 1, wherein the component composition further contains V: 0.005 to 0.1% by mass ratio.

The component composition is a mass ratio, and
Cu: 0.1-1.4%, Cr: 0.1-1.2%
Ca: 0.0005 to 0.006% Mg: 0.0001 to 0.003%
The ultra high strength bend pipe according to claim 1 or 2, comprising one or more of the following.

A steel pipe having the component composition according to any one of claims 1 to 3 is heated to 820 to 1050 ° C, subjected to bending, and then cooled to a temperature of 400 ° C or lower at a cooling rate of 5 ° C / second or more. A method for producing an ultra-high strength bend pipe having a tensile strength of 750 MPa or more, characterized by performing accelerated cooling and then performing tempering treatment in a temperature range of 350 to 750 ° C.