阅读说明：本技术 一种基于组织调控的抗hic管道用钢及其制备方法 (HIC (hydrogen induced cracking) resistant pipeline steel based on structure regulation and preparation method thereof ) 是由 聂宝华 赵吉诗 陈东初 赵连玉 王子缘 于 2020-05-15 设计创作，主要内容包括：本发明提供了一种基于组织调控的抗HIC管道用钢及其制备方法,该基于组织调控的抗HIC管道用钢,有较强的抗HIC能力,HIC敏感性指标均为0,通过添加微量的B、N、V、Zr等微量元素,设计了(V,B)N和(Nb,B)<Sub>x</Sub>N高度稳定的高温第二相,在控轧控冷的过程中能有效细化晶粒,将晶粒尺寸降低至1μm左右,并通过调控Mo元素的均匀分布,实现了高抗HIC性能和高强度的综合性能。(The HIC-resistant pipeline steel based on the structure regulation has stronger HIC resistance, the HIC sensitivity indexes are all 0, and trace B, N, V, Zr and other micro-scale additives are addedA measuring element, designs (V, B) N and (Nb, B) x The high-temperature second phase with high stability of N can effectively refine crystal grains in the controlled rolling and controlled cooling process, the size of the crystal grains is reduced to about 1 mu m, and the comprehensive performance of high HIC resistance and high strength is realized by regulating and controlling the uniform distribution of Mo element.)

1. The HIC-resistant pipeline steel based on structure regulation is characterized by comprising the following preparation raw materials in percentage by mass:

C：0.01～0.1％，

Mn：0.50～1.00％，

Nb：0.01～0.10％，

Cr：1.0～1.5％，

Mo：0.5～1.5％，

V：0.05～0.20％，

B：0.05～0.10％，

N：0.01～0.02％，

Zr：0.01～0.2％，

the balance being Fe.

2. The HIC-resistant pipeline steel based on the structure regulation and control as claimed in claim 1, which is characterized by comprising the following preparation raw materials in percentage by mass:

C：0.08％，

Mn：0.8％，

Nb：0.10％，

Cr：1.2％，

Mo：1.5％，

V：0.06％，

B：0.10％，

N：0.02％，

Zr：0.01％，

the balance being Fe.

3. The steel for HIC-resistant pipes according to claim 1 or 2, wherein the steel for HIC-resistant pipes has an S content of less than 0.01%.

4. The steel for HIC-resistant pipes according to claim 1 or 2, wherein the content of P in the steel for HIC-resistant pipes is less than 0.01%.

5. The method for preparing the HIC-resistant pipeline steel based on the structure regulation as claimed in any one of claims 1 to 4, is characterized by comprising the following steps:

s1: weighing the C, Mn, Nb, Cr, Mo, V, B, N, Zr and Fe according to the proportion, melting and continuously casting to obtain a billet;

s2: and (5) performing controlled rolling and controlled cooling treatment on the steel billet obtained in the step (S1) to obtain the HIC-resistant pipeline steel based on structure control.

6. The method for preparing the HIC-resistant pipeline steel based on the structure control as claimed in claim 5, wherein the controlled rolling and the controlled cooling comprise the processes of rough rolling, finish rolling and water cooling which are sequentially performed.

7. The method for preparing the HIC-resistant steel for pipelines according to claim 6, wherein the rough rolling is performed at a rolling start temperature of 1070 ℃ and at a single-pass reduction rate of more than 15%.

8. The method for manufacturing steel for HIC-resistant pipelines according to claim 6, wherein the finish-rolled intermediate slab has a final thickness of 60 mm.

9. The method for manufacturing the steel for HIC-resistant pipelines according to claim 6, wherein the finish rolling has a start rolling temperature of 900 ℃.

10. The method for preparing the steel for HIC-resistant pipelines based on texture manipulation as claimed in claim 6, wherein the water cooling process has an entry temperature of 780 ℃, a cooling rate of 13 ℃/s and a final cooling temperature of 620 ℃.

Technical Field

The invention belongs to the field of steel preparation, and particularly relates to HIC (hydrogen induced cracking) resistant pipeline steel based on structure regulation and a preparation method thereof.

Background

Pipeline network construction is a strategic requirement. The natural gas pipeline transportation has the characteristics of high efficiency, economy, safety and the like, and is a main form for transporting gas in a long distance. With the gradual change of the international energy structure, the proportion of natural gas in energy will increase sharply in the coming decades. The development of natural gas transportation pipelines tends to be large-caliber, high-pressure and thick-walled. The service conditions of pipelines are more and more strict, such as increased conveying pressure and complex conveying media, and a plurality of pipelines need to pass through dense areas or deserts, swamps, severe cold zones and the like, thereby providing higher technical requirements for pipeline steel.

Corrosion is a key factor affecting the reliability and service life of a pipeline delivery system. It not only can cause perforation, cause the leakage of transported substance such as oil, gas, water, etc., but also can bring the loss caused by the waste of materials and manpower produced by maintenance, shutdown and production stoppage, even cause fire, especially the explosion caused by the corrosion of the natural gas pipeline, threaten the personal safety, pollute the environment, and have serious consequences.

Hydrogen Induced Cracking (HIC for short) refers to a stepped crack generated when Hydrogen atoms generated by electrochemical corrosion enter the interior of a metal material in an acidic environment. Acidic environment generally refers to the environment of wet hydrogen sulfide. The hydrogen bubbles are a corrosion form of HIC, and are formed by the fact that after the electrochemical corrosion of metal and sulfur-containing natural gas, cavitation bubbles with the diameter of several to dozens of millimeters are generated in the metal, and the metal on the surface of the bubbles cracks or delaminates. The HIC can cause the steel for the pipeline to crack suddenly without obvious warning, and has great destructiveness and harmfulness.

For microalloyed pipeline steel, non-metallic inclusions and hard phase interfaces are the major hydrogen traps in the steel. The chemical composition is a key factor for determining the HIC resistance of the steel plate. Wherein, the segregation of C, Mn and P elements easily forms a microstructure sensitive to HIC in the center of the steel plate, for example, bainite and even martensite hard phases appear in ferrite plus pearlite steel, and the hard microstructure can become a HIC crack initiation source. High content of carbides forming high pressure CH₄Gas, promoting hydrogen induced cracking. In addition, the rhombohedral MnS elongated by rolling is included in the steel sheet and causes voids around the steel sheet after cooling, and the inclusions become hydrogen-concentrated sites and are likely to be sources of HIC initiation. By reducing the content of elements such as C, S, the HIC sensitivity can be significantly reduced. CN102839326B provides a low-carbon alloy, a fine ferrite structure is obtained through a controlled rolling air cooling process, the HIC resistance is improved, but the alloy strength is low, the resistance strength is 437MPa, and the comprehensive properties such as high strength, good toughness, hydrogen induced cracking resistance and the like are difficult to meet. The increasing size and high pressure of the hydrogen pipeline leads the wall thickness of the steel pipeline to be increased continuously, and the manufacturing difficulty of the hydrogen pipeline is further increased.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides HIC-resistant pipeline steel based on structure regulation and a preparation method thereof.

According to the embodiment of the first aspect of the invention, the HIC-resistant pipeline steel based on structure regulation comprises the following preparation raw materials in percentage by mass:

C：0.01～0.1％，

Mn：0.50～1.00％，

Nb：0.01～0.10％，

Cr：1.0～1.5％，

Mo：0.5～1.5％，

V：0.05～0.20％，

B：0.05～0.10％，

N：0.01～0.02％，

Zr：0.01～0.2％，

the balance being Fe.

C is an element for improving the strength of the steel, and the hydrogen induced cracking sensitivity of the alloy can be increased by improving the carbon content. The invention adopts the alloy design with low carbon content, and can obviously reduce the hydrogen induced cracking sensitivity of the alloy. The reduction of the C content generally results in a reduction of the strength of the alloy steel. In the steel-making process, Mn is a good deoxidizer and desulfurizer, and the Mn content is increased, so that the corrosion resistance of steel can be weakened, and the welding performance can be reduced.

Nb can refine grains, reduce the overheating sensitivity and the temper brittleness of steel and improve the strength, but the plasticity and the toughness are reduced. The addition of Nb to ordinary low-alloy steel can improve the resistance to atmospheric corrosion and hydrogen, nitrogen and ammonia corrosion at high temperature. Nb can improve the weldability. Niobium is added into austenitic stainless steel to prevent intergranular corrosion.

The addition of Cr into steel can significantly improve the oxidation resistance of steel and increase the corrosion resistance of steel. Cr can remarkably increase the hardenability of steel and also can increase the temper brittleness tendency of the steel. The steel with high Cr content can also generate secondary hardening phenomenon when being tempered at 400-500 ℃ after being quenched. In the quenched and tempered structural steel, Cr mainly has the function of improving the hardenability of the steel, so that the steel has better comprehensive mechanical properties after quenching and tempering treatment, namely better plasticity and toughness under the condition of a certain strength level. In the bearing steel, because the special carbide of Cr is relatively wear-resistant, and the Cr-containing steel is quenched and then is ground, a better surface finish can be easily obtained. Therefore, Cr-containing steel is often used as the bearing steel. In tool steels and high speed steels, Cr improves the wear resistance of the steel, so Cr has generally been included in alloy tool steels in the past.

Mo can refine the crystal grains of steel, improve hardenability and heat strength, and maintain sufficient strength and creep resistance at high temperature. Mo is added into the structural steel, so that the mechanical property can be improved, and the brittleness of the alloy steel can be inhibited.

V is an excellent deoxidizer for steel. The addition of 0.5% of V in the steel can refine the structure grains and improve the strength and toughness. The carbide formed by V and C can improve the hydrogen corrosion resistance under high temperature and high pressure.

The addition of trace amount of B can improve the compactness and hot rolling performance of steel and raise strength.

N can improve the strength, low-temperature toughness and weldability of steel and increase aging sensitivity.

Zr is a rare metal with high melting point, is a carbide forming element, is the most powerful deoxidizing and denitrifying element in the steel-making process, and has the functions of dehydrogenation and desulfurization. Zr can refine austenite grains of steel, and zirconium dissolved in austenite can improve hardenability of steel, but if it exists in a form of ZrC in a large amount, hardenability is rather reduced.

According to some embodiments of the present invention, the HIC resistant steel for pipes comprises the following raw materials:

C：0.08％，

Mn：0.8％，

Nb：0.10％，

Cr：1.2％，

Mo：1.5％，

V：0.06％，

B：0.10％，

N：0.02％，

Zr：0.01％，

the balance being Fe.

According to some embodiments of the present invention, the steel for HIC-resistant pipes based on texture control has an S content of less than 0.01%.

During hot rolling, S generates MnS extending in the rolling direction, and reduces low-temperature toughness. Therefore, in the steel for HIC-resistant pipes according to the examples of the present invention, the S content needs to be reduced, and the upper limit is limited to 0.01% or less, and the smaller the S content, the better.

According to some embodiments of the present invention, the content of P in the steel for HIC resistant pipes according to texture modulation is less than 0.01%.

P is an impurity element, and when the content exceeds 0.01%, HIC resistance is impaired, and toughness of the HAZ is lowered. Therefore, the upper limit of the content of P is limited to 0.01% or less.

The HIC-resistant pipeline steel based on structure regulation and control provided by the embodiment of the invention at least has the following technical effects:

the HIC-resistant pipeline steel provided by the embodiment of the invention has strong HIC resistance, and the HIC sensitivity indexes are all 0.

The HIC-resistant pipeline steel provided by the embodiment of the invention is added with trace elements such as B, N, V, Zr and designs (V, B) N and (Nb, B)_xThe high-temperature second phase with high stability of N can effectively refine crystal grains in the controlled rolling and controlled cooling process, the size of the crystal grains is reduced to about 1 mu m, and the comprehensive performance of high HIC resistance and high strength is realized by regulating and controlling the uniform distribution of Mo element.

The method for preparing the HIC-resistant pipe steel according to the embodiment of the second aspect of the invention comprises the following steps:

s1: weighing the C, Mn, Nb, Cr, Mo, V, B, N, Zr and Fe according to the proportion, melting and continuously casting to obtain a billet;

s2: and (5) performing controlled rolling and controlled cooling treatment on the steel billet obtained in the step (S1) to obtain the HIC-resistant pipeline steel based on structure control.

According to some embodiments of the invention, the controlled rolling and controlled cooling comprises a sequence of rough rolling, finish rolling and water cooling.

According to some embodiments of the invention, the rough rolling has a start rolling temperature of 1070 ℃ and a single reduction of more than 15%.

According to some embodiments of the invention, the finish-rolled intermediate slab has a final thickness of 60 mm.

According to some embodiments of the invention, the finishing rolling has a start rolling temperature of 900 ℃.

According to some embodiments of the invention, the water cooling process has an inlet temperature of 780 ℃, a cooling rate of 13 ℃/s and a final cooling temperature of 620 ℃.

Drawings

FIG. 1 shows (V, B) N and (Nb, B) in the steel sample of example 3_xA schematic diagram of a high-temperature second phase morphology with high N stability.

Detailed Description

The following are specific examples of the present invention, and the technical solutions of the present invention will be further described with reference to the examples, but the present invention is not limited to the examples.