CN-117305719-B - X80-grade high-toughness high-hydrogen-induced crack-resistance seamless steel tube steel for thick-wall LNG receiving station and heat treatment process thereof

CN117305719BCN 117305719 BCN117305719 BCN 117305719BCN-117305719-B

Abstract

The invention provides an X80-grade high-toughness high-hydrogen-induced crack-resistance steel for a seamless steel tube for a thick-wall LNG receiving station and a heat treatment process thereof, wherein the steel comprises the following components: 0.03 to 0.06 percent of C, 1.30 to 1.50 percent of Mn, 0.20 to 0.50 percent of Cr, 0.40 to 0.60 percent of Mo, 0.20 to 0.40 percent of Ni, 0.080 to 0.150 percent of V, 0.010 to 0.030 percent of Nb, 0.015 to 0.025 percent of Al, less than or equal to 0.012 percent of P, less than or equal to 0.008 percent of S, 0.0060 to 0.0100 percent of N, less than or equal to 0.0020 percent of T.O, and the balance of Fe and other unavoidable impurities, and has good toughness and hydrogen induced cracking resistance when produced by matching with a heat treatment process.

Inventors

YANG ZHIQIANG
WU LIN
HU FANGZHONG
WANG KAIZHONG
ZHUANG ZHEN
CHEN ENXIN
WANG ZIMIN
YANG SHAOPENG
JIN GUOZHONG
CHEN SHIJIE

Assignees

马鞍山钢铁股份有限公司

Dates

Publication Date: 20260508
Application Date: 20230925

Claims (7)

1. The steel for the X80-grade high-toughness high-hydrogen-induced cracking-resistance thick-wall seamless steel tube for the LNG receiving station is characterized by comprising the following components in percentage by mass: C 0.03%～0.06%、Mn 1.30%～1.50%、Cr 0.20%～0.50%、Mo 0.40%～0.60%、Ni 0.20%～0.40%、V 0.080%～0.150%、Nb 0.010%～0.030%、Al 0.015%～0.025%、P≤0.012%、S≤0.008%、N 0.0060%～0.0100%、T.O≤0.0020%, The balance of Fe and other unavoidable impurities; the components of the X80-grade high-toughness high-hydrogen-induced cracking-resistance seamless steel tube steel for the thick-wall LNG receiving station also meet the following conditions: 90.0≤A≤105.0, A=467×(%C+%N)+35×%Mn+30×(%Cr+%Ni)+10×%Mo+3×%V+25×%Nb+60×%Al; the components of the X80-grade high-toughness high-hydrogen-induced cracking-resistance seamless steel tube steel for the thick-wall LNG receiving station also meet the following conditions: Y≥0.6%,Y=10×%Ni+6×(%V+%Nb)+5×%Mo+15×%N-20×%C-3×%Mn。
2. A heat treatment process of the X80 grade high toughness high hydrogen induced cracking resistant steel for seamless steel pipe for thick wall LNG receiving stations of claim 1, wherein the heat treatment process comprises quenching and tempering.
3. The heat treatment process according to claim 2, wherein the quenching is performed at a furnace-in temperature of 400 ℃ or less and a heating temperature T Quenching and heating -900 ℃, a heat-preserving time T Quenching heat preservation is determined by a steel pipe wall thickness S and a heating temperature T Quenching and heating , 150+ (S/2) - (T Quenching and heating /8) ≤t Quenching heat preservation ≤180+(S/2)-(T Quenching and heating /8), water cooling is performed, wherein the steel pipe wall thickness S is in mm, the heating temperature T Quenching and heating is in ℃ and the heat-preserving time T Quenching heat preservation is in min.
4. A heat treatment process according to claim 2 or 3, wherein the tempering temperature T Tempering and heating -700 ℃ is the tempering temperature T Tempering and heating , the heat preservation time T tempering and heat preserving is determined by the steel pipe wall thickness S and the tempering temperature T Tempering and heating , 460+ (S/2) - (T Tempering and heating /2)≤t tempering and heat preserving ≤480+(S/2)-(T Tempering and heating /2), the steel pipe wall thickness S is in mm, the heating temperature T Tempering and heating is in DEG C, and the heat preservation time T tempering and heat preserving is in min.
5. The heat treatment process according to any one of claims 2 to 4, wherein the heat treatment produces a seamless steel pipe for a thick-wall LNG receiving station having a thickness of 60 to 70mm and having a high toughness and a high hydrogen induced cracking resistance.
6. The heat treatment process according to any one of claims 2 to 5, wherein the high hydrogen induced cracking resistance wall thickness produced by the heat treatment process is greater than 50mmLNG, the inner wall, 1/2 wall thickness and outer wall of the seamless steel pipe for receiving station are all 100% tempered sorbite, the grain size is 20 to 27 μm, and the difference between the structure grain sizes of the inner wall, 1/2 wall thickness and outer wall is less than or equal to 1.5 μm.
7. The heat treatment process according to any one of claims 2 to 6, wherein the X80-level high-toughness high-hydrogen-induced cracking resistance thick-wall LNG receiving station seamless steel pipe has a tensile strength of not less than 620MPa, a yield strength of not less than 560MPa, a CKV 2 of not less than 280J, A of not less than 21%, Z of not less than 52%, a section hardness difference of not more than 20HBW, and a hydrogen-induced cracking test according to GB/T8650, and meets CSR of not more than 1.4% and CLR of not more than 11% under A solution.

Description

X80-grade high-toughness high-hydrogen-induced crack-resistance seamless steel tube steel for thick-wall LNG receiving station and heat treatment process thereof Technical Field The invention belongs to the field of alloy steel, and particularly relates to steel for an X80-grade high-toughness high-hydrogen-induced crack-resistance thick-wall LNG receiving station and a heat treatment process thereof. Background In order to improve LNG conveying efficiency, pipelines are developed to the directions of high pressure, large caliber and long service life, so that the strength of the pipelines in LNG stations is increased, and the wall thickness is increased. Because the welding pipeline has limitation on the thickness of the pipe wall, too thick welding has poor economy, and the welding seam is easy to fail after the pressure is increased, the pipeline produced by welding cannot meet the production requirement. For the above reasons, there is an increasing demand for high-strength thick-walled seamless steel pipes for LNG receiving stations. After the strength of the steel pipe is improved, the risk of hydrogen induced cracking is increased, and particularly, the crack threshold value of hydrogen induced cracking in a low-temperature LNG conveying environment is obviously reduced, so that cracking failure is more likely to occur. In addition, the uniformity of the wall thickness of the thick-wall pipe is poorer than that of the thin-wall pipe, and weak points are easy to generate due to uneven performance and tissues, so that cracking is easier to generate. The patent with publication number CN 110331333A published in 10 and 15 in 2019 discloses a tube blank of a large-diameter seamless steel tube for an X80 pipeline and a production method thereof, and discloses that converter molten iron and scrap steel are mixed and smelted in an electric furnace to obtain crude molten steel, a silicon-titanium alloy cored wire is added into the molten steel to perform silicon-titanium oxide reaction, the molten steel is subjected to slag formation and desulfurization, the content of C, S is regulated, the content of Si and Ti is regulated to obtain refined molten steel, and the refined molten steel is poured and stretched to form a continuous casting round tube blank. The continuous casting round tube blank can be used for producing large-diameter seamless steel tubes for natural gas transmission pipelines, and has good welding performance and excellent low-temperature toughness and corrosion resistance. But its properties to the product are not mentioned. The performance of the steel pipe with the wall thickness of 38.5mm is only listed in examples, the welding is needed, the hydrogen induced cracking resistance of the steel pipe is not checked, and the use requirement of the high-toughness high-hydrogen induced cracking resistance thick-wall LNG receiving station cannot be met. The patent with publication number CN 112570487A published in 3 month 30 of 2021 discloses a forming process for producing an X80 pipeline steel seamless steel tube by adopting a large round billet with the specification of phi 800mm, which comprises the steps of first step, heating forging stock, second step, perforating, third step, vacuum annealing, fourth step, straightening, fifth step, acid washing, sixth step, cold rolling, seventh step, secondary treatment, filling lubricant into a blank centering hole during perforation by controlling heating temperature, solving the problems caused by the phenomena of difficult perforation at low temperature, easy adhesion with a guide disc and the like of the steel tube in the prior art, and enabling the X80 pipeline steel seamless steel tube to have excellent mechanical properties through vacuum annealing and acid washing. However, this patent does not relate to the composition or the method of producing steel, and only describes the pipe making process. The feasibility of the patent is not enough. Therefore, it is necessary to develop a steel for a seamless steel pipe with high strength, high toughness, large diameter and large wall thickness and hydrogen induced cracking resistance, which meets the use requirements of an X80-level high-toughness high-hydrogen induced cracking resistance thick-wall LNG receiving station. Disclosure of Invention The invention aims to provide a X80-grade high-toughness high-hydrogen-induced cracking-resistance thick-wall steel for a seamless steel tube for an LNG receiving station, which is obtained by designing components. According to the heat treatment process of the steel for the seamless steel tube for the X80-grade high-toughness high-hydrogen-induced cracking-resistance thick-wall LNG receiving station, provided by the invention, the matched heat treatment process is designed according to the components, so that the use requirement of the X80-grade high-toughness high-hydrogen-induced cracking-resistance thick-wall LNG receiving station with excellent performance