CN116162866A - Double-structure high-strain marine pipeline steel, pipeline pipe and manufacturing method thereof - Google Patents

Abstract

The invention discloses a dual-peak structure high-strain marine pipeline steel, a pipeline pipe and a manufacturing method thereof, and belongs to the technical field of steel. The shape of the inclusion is controlled by Ca treatment, and the harmful elements such as P, S and the harmful gases such as oxygen, hydrogen and nitrogen in steel are strictly controlled; the control rolling of the austenite-ferrite dual-phase region and the medium temperature relaxation treatment of the critical region are adopted, and the accelerated cooling is carried out when the relaxation temperature is lower than the bainite transformation starting temperature, so that a fine-grain/superfine-grain polygonal ferrite-granular bainite dual-phase structure is obtained, a typical dual-peak structure is formed, and the plasticity is improved strongly. Finally, a small amount of MA tissue which is dispersed and distributed is obtained by low-temperature tempering treatment, and the strength of the pipeline tube is further improved, so that the high-strength, high-plasticity and high-toughness comprehensive mechanical property is obtained. The prepared pipeline pipe has excellent performance, particularly has good plastic deformation capacity and good weldability, and can meet the use requirements of deep sea areas on the pipeline steel and the pipeline pipe.

Description

A kind of bimodal structure high-strain marine pipeline steel, pipeline pipe and manufacturing method thereof

technical field

The invention belongs to the technical field of steel materials, and in particular relates to a bimodal high-strain marine pipeline steel, a pipeline pipe and a manufacturing method thereof.

Background technique

With the completion of the development of inshore and offshore oil and gas fields, the development of newly built oil and gas fields gradually develops in remote areas such as the ocean. In recent years, the focus of oil exploration in the world has shifted from land to sea, and from shallow sea to deep sea. The exploration and development of oil and gas resources in deep water and ultra-deep water has become the key field of oil and gas exploitation in the world.

During the construction process of laying submarine pipelines (J-Lay, S-Lay, coiling, dragging, etc.), the pipeline will inevitably undergo deformation, and the deformation often exceeds 0.5%. Therefore, high strength and high plasticity of linepipe are necessary guarantees for deepwater oil and gas development. At the same time, the harsh deep-sea service environment promotes the development of deep-sea pipeline steels in the direction of high steel grade and high toughness (low temperature). Generally speaking, the uniform plastic deformation capacity is larger when the strength of the pipeline steel is low, but it is difficult to obtain a large plastic deformation capacity for high-grade pipeline steel. In addition, during the subsequent anti-corrosion process of high-grade pipeline steel and line pipe, due to the effect of temperature, the strength and hardness will increase, and the plasticity and toughness will decrease, that is, the phenomenon of strain aging. The line pipe will also produce strain aging phenomenon during long-term use.

In recent years, with the development of controlled rolling and controlled cooling technology, the yield ratio of pipeline steel has increased from 0.80 to 0.85 in the past to 0.90 to 0.95. Too high yield ratio limits the deformation capacity of pipeline steel and line pipe, thus affect the safety of use. Although the high-grade marine pipeline steel with high strain performance has been developed internationally and has been applied in engineering, it cannot take into account the matching of high strength, high plasticity and high toughness.

Contents of the invention

In order to overcome the above-mentioned defects in the prior art, the present invention discloses a bimodal high-strain marine pipeline steel, a linepipe and a manufacturing method thereof, which can obtain high-strength, high-plasticity, high-toughness and good weldability. .

The present invention is achieved through the following technical solutions:

The invention discloses a high-strain marine pipeline steel with bimodal structure, which has a bimodal polygonal ferrite + granular bainite dual-phase structure supplemented by a multi-phase structure formed by an M/A structure. In terms of mass percentage, its The composition is as follows: C: 0.04%～0.06%, Mn: 1.50%～1.90%, Si: 0.15%～0.25%, P≤0.005%, S≤0.003%, Al: 0.005%～0.03%, N≤0.005%, The first strengthening component and the second strengthening component, the balance is Fe; the first strengthening component is one or more of Nb: 0.004%-0.008%, V: 0.01-0.03% and Ti: 0.001%-0.025%, And 0.05%≤Nb+V+Ti≤0.10%; the second strengthening component is Cr: 0.10%～0.30%, Mo: 0.08%～0.30%, Ni: 0.10%～0.30%, Cu: 0.10%～0.30% and B: one or more of 0.0001% to 0.0005%; carbon equivalent ≤ 0.17.

The invention discloses a method for manufacturing pipeline steel with bimodal structure and high strain for marine use, comprising the following steps:

S1: The raw materials containing the above ingredients are smelted in the oxygen-blown converter, treated with Ca, refined outside the furnace and vacuum degassed, and continuously cast into thick slabs;

S2: Heating the thick slab to 1180-1200°C and keeping it warm; performing relaxation treatment after rough rolling and finish rolling;

S3: Perform low-temperature tempering at 450-550° C., and obtain pipeline steel after cooling.

Preferably, in S2, the time for keeping warm is 8-15 minutes.

Preferably, in S2, the rough rolling temperature is 1050-1120° C., and multi-pass rolling is adopted.

Preferably, in S2, the start temperature of finish rolling is 810°C-850°C, the end temperature of finish rolling is 700°C-750°C, and multi-pass rolling is adopted.

Preferably, in S2, the relaxation start temperature is 700-750°C, the relaxation time is 80-150s, and then water-cooled to 150-250°C at a cooling rate of 20-35°C/s.

Preferably, in S3, the time for low-temperature tempering is 15-30 minutes.

Preferably, in S3, the cooling method is air cooling.

The method for preparing a line pipe by adopting the above-mentioned high-strain marine pipeline steel with bimodal structure includes: forming the steel plate through J-C-O or U-O-E, performing straight seam submerged arc welding, and using fine-grained acicular ferrite containing Ti-B as the welding material The bulk material with low oxygen content is expanded by 0.6% to 1.2% to obtain the line pipe.

The line pipe produced by the above-mentioned method of preparing line pipe with high-strain marine pipeline steel with bimodal structure has a transverse yield strength of 529-598 MPa, a tensile strength of 666-694 MPa, a total elongation of 26-38%, and a temperature of -20 °C. The Charpy impact toughness reaches 219~295J, the DWTT shear area at -10℃ is 85~93%, the hardness is 202~236HV10, the longitudinal yield strength of the pipe body is 536~553MPa, the tensile strength is 663~680MPa, and the total elongation is 29~43%. , The uniform elongation rate is 7.2~11.3%, and the work hardening rate n value is 0.101~0.126.

Compared with the prior art, the present invention has the following beneficial technical effects:

The high-strain marine pipeline steel with bimodal structure disclosed by the present invention adopts low-carbon or ultra-low-carbon components, adds Mn to increase the stability of austenite, and adds the first strengthening components Nb, V, Ti for microalloying, At the same time, add a small amount of second strengthening components Mo, Ni, Cu, Cr, B to promote the formation of MA island structure, strictly control harmful elements such as P and S in the steel, and improve the C, S and other elements in the steel by strictly controlling the content of N elements. Strain aging phenomenon caused by the interaction of N elements and dislocations in steel.

The manufacturing method of the bimodal high-strain marine pipeline steel disclosed by the present invention adopts Al and Si fully deoxidized killed steel, Ca treatment controls the shape of inclusions, and strictly controls harmful elements such as P and S in the steel, as well as oxygen, hydrogen and nitrogen. and other harmful gases; through controlled rolling in the austenite + ferrite dual-phase region and moderate temperature relaxation treatment in the critical region, accelerated cooling when the relaxation temperature is lower than the bainite transformation start temperature, in order to obtain fine-grained /Ultrafine-grained polygonal ferrite + granular bainite dual-phase structure, and forms a typical double-peak structure, which effectively improves the plasticity of the line pipe. Finally, low-temperature tempering is used to obtain a small amount of diffusely distributed MA structure, which further improves the strength of the line pipe, thereby obtaining comprehensive mechanical properties of high strength, high plasticity, and high toughness.

The bimodal high-strain marine linepipe prepared by the present invention has excellent properties, especially good plastic deformation capacity and good weldability, and can meet the requirements for the use of such pipeline steel and linepipe in deep sea areas .

Description of drawings

Fig. 1 is the metallographic diagram of the bimodal structure high-strain ocean line pipe of the present invention;

Fig. 2 is the MA island transmission diagram of the bimodal structure high-strain marine line pipe of the present invention;

Fig. 3 is a metallographic diagram of the tensile stress-strain curve of the bimodal high-strain marine line pipe of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, which are explanations of the present invention rather than limitations.

Example 1

Alloy composition: C: 0.05%; Mn: 1.69%; Si: 0.21%; P: 0.0059%; S: 0.0026%; Al: 0.023%; N: 0.0038%; Nb: 0.065%; 0.17%; Ni: 0.23%; Cu: 0.014%; the balance is Fe and unavoidable impurities; carbon equivalent 0.17%.

Manufacturing process: the above-mentioned materials are smelted in an oxygen-blown converter, treated with Ca, refined outside the furnace and vacuum degassed, continuously cast into slabs, heated to about 1200°C, kept for 8 minutes, rough rolled at 1050°C, rolled in two passes, pressed The reduction ratio is 51%, and then cooled to 830°C for rolling, two-pass rolling, the reduction ratio is 72%, the rolling end temperature is 750°C, the relaxation time is 80s, the water cooling temperature is 650°C, and cooled to 250°C, The cooling rate is 20°C-30°C/s, and then tempered at a medium and low temperature at 520°C for 20 minutes to make a hot-rolled steel plate with a thickness of about 29.6mm. The steel plate is formed by J-C-O-E, and multi-pass straight seam submerged arc welding is adopted. The welding material is made of Ti-B-containing fine-grained acicular ferrite material with low oxygen content, and then expanded by 0.6-0.8% to make a straight seam Submerged arc welded line pipe.

Performance characteristics: The high-strain linepipe produced in this example has a thickness of about 29.6mm and a pipe diameter of 1016mm. High strength, high plasticity, high toughness and good weldability, with good plastic deformation capacity. The transverse yield strength of the pipe body is 555-598MPa, the tensile strength is 684-690MPa, the total elongation is 27-35%, the Charpy impact toughness at -20°C reaches 285-293J, and the DWTT shear area at -10°C is 85-92%. The hardness is 215-236HV ₁₀ , the longitudinal yield strength of the pipe body is 536-550MPa, the tensile strength is 663-674MPa, the total elongation is 29-42%, the uniform elongation is 7.2-9.3%, and the work hardening rate n value is 0.101-0.113.

Example 2

Alloy composition: C: 0.06%; Mn: 1.62%; Si: 0.22%; P: 0.009%; S: 0.002%; Al: 0.028; N: 0.003%; V: 0.04%; %; Ni: 0.11%; Cr: 0.022%; the balance is Fe and unavoidable impurities; carbon equivalent 0.17%.

Manufacturing process: the above-mentioned materials are smelted in an oxygen-blown converter, treated with Ca, refined outside the furnace and vacuum degassed, continuously cast into slabs, heated to about 1200 ° C, kept for 10 minutes, rough rolled at 1100 ° C, rolled in two passes, pressed The reduction ratio is 60%, then cooled to 810°C for rolling, two passes rolling, the reduction ratio is 65%, the rolling end temperature is 730°C, the relaxation time is 100s, the water cooling temperature is 620°C, and cooled to 150°C, The cooling rate is 20°C to 30°C/s, and then tempered at a medium and low temperature at 550°C for 15 minutes to make a hot-rolled steel plate with a thickness of about 31.8mm. The steel plate is formed by J-C-O-E, and multi-pass straight seam submerged arc welding is adopted. The welding material is made of Ti-B-containing fine-grained acicular ferrite material with low oxygen content, and then expanded by 0.6-0.9% to make a straight seam. Submerged arc welded line pipe.

Performance characteristics: The high-strain linepipe produced in this example has a thickness of about 31.8mm and a pipe diameter of 559mm. Strength, high plasticity, high ductility and good weldability, with good plastic deformation capacity and low strain aging sensitivity. The transverse yield strength of the pipe body is 549-580MPa, the tensile strength is 685-692MPa, the total elongation is 28-37%, the Charpy impact toughness at -20°C reaches 219-248J, and the DWTT shear area at -10°C is 87-93%. The hardness is 206-233HV ₁₀ , the longitudinal yield strength of the pipe body is 538-553MPa, the tensile strength is 671-680MPa, the total elongation is 30-41%, the uniform elongation is 9.8-11.3%, and the work hardening rate n value is 0.103-1.126.

Example 3:

Alloy composition: C: 0.05%; Mn: 1.67%; Si: 0.20%; P: 0.008%; S: 0.0024%; Al: 0.019%; N: 0.003%; Nb: 0.055%; 0.14%; Ni: 0.15%; Cu: 0.022%; Cr: 0.2%; B: 0.0002%, the balance is Fe and unavoidable impurities; carbon equivalent 0.17%.

Manufacturing process: the above-mentioned materials are smelted in an oxygen-blown converter, treated with Ca, refined outside the furnace and vacuum degassed, continuously cast into slabs, heated to about 1180 ° C, kept for 15 minutes, rough rolled at 1120 ° C, rolled in two passes, pressed The reduction rate is 60%, then cooled to 850°C for rolling, three passes rolling, the reduction rate is 75%, the rolling end temperature is 700°C, the relaxation time is 150s, the water cooling temperature is 640°C, and cooled to 200°C, The cooling rate is 35°C/s, and then tempered at a low temperature of 450°C for 30 minutes to make a hot-rolled steel plate with a thickness of about 24.1mm. The steel plate is formed by U-O-E, and multi-pass straight seam submerged arc welding is adopted. The welding material is made of Ti-B-containing fine-grained acicular ferrite material with low oxygen content, and then expanded by 0.8-1.2% to make a straight seam Submerged arc welded line pipe.

Performance characteristics: The X70 large-strain linepipe produced in this example with a thickness of about 24.1mm and a pipe diameter of 610mm has a multiphase structure of polygonal ferrite + granular bainite + M/A, and has high strength, high plasticity, High toughness and good weldability, with good plastic deformation capacity and low strain aging sensitivity. The transverse yield strength of the pipe body is 529-541MPa, the tensile strength is 666-671MPa, the total elongation is 26-38%, the Charpy impact toughness at -20°C reaches 243-295J, and the DWTT shear area at -20°C is 85-92%. The hardness is 202-229HV ₁₀ , the longitudinal yield strength of the pipe body is 536-546MPa, the tensile strength is 663-668MPa, the total elongation is 31-43%, the uniform elongation is 8.3-9.8%, and the work hardening rate n value is 0.106-0.123.

As shown in Fig. 1, it is the metallographic diagram of the high-strain marine pipeline pipe with bimodal structure of the present invention, as can be seen from the figure, the structure is composed of ultrafine-grained ferrite and fine-grained ferrite bimodal structure and granular Bainian body tissue composition.

As shown in Figure 2, it is the MA island transmission diagram of the bimodal structure high-strain marine line pipe of the present invention, as can be seen from the figure, there is a typical MA island structure between the ferrite grains and the bainite grains .

As shown in Figure 3, it is a longitudinal tensile stress-strain curve diagram of the bimodal high-strain marine line pipe of the present invention, as can be seen from the figure, the longitudinal yield strength of the high-strain marine line pipe is 536MPa, and the tensile strength is 668MPa , The uniform elongation is 9.8%.

Claims (10)

1. A pipeline steel for high-strain ocean with bimodal structure, characterized in that it has a bimodal polygonal ferrite+granular bainite dual-phase structure supplemented by a multi-phase structure formed by M/A organization, in terms of mass percentage, Its composition is as follows: C: 0.04%～0.06%, Mn: 1.50%～1.90%, Si: 0.15%～0.25%, P≤0.005%, S≤0.003%, Al: 0.005%～0.03%, N≤0.005% , the first strengthening component and the second strengthening component, the balance being Fe; the first strengthening component is one or more of Nb: 0.004%-0.008%, V: 0.01-0.03% and Ti: 0.001%-0.025% , and 0.05%≤Nb+V+Ti≤0.10%; the second strengthening component is Cr: 0.10%～0.30%, Mo: 0.08%～0.30%, Ni: 0.10%～0.30%, Cu: 0.10%～0.30% and B: one or more of 0.0001% to 0.0005%; carbon equivalent ≤ 0.17. 2. A method for manufacturing pipeline steel with bimodal structure and high strain ocean, characterized in that it comprises the following steps: S1: The raw material containing the composition as claimed in claim 1 is smelted in an oxygen-blown converter, treated with Ca, refined outside the furnace and vacuum degassed, and continuously cast into a thick slab; S2: Heating the thick slab to 1180-1200°C and keeping it warm; performing relaxation treatment after rough rolling and finish rolling; S3: Perform low-temperature tempering at 450-550° C., and obtain pipeline steel after cooling. 3. The method for manufacturing bimodal high-strain marine pipeline steel according to claim 2, characterized in that in S2, the holding time is 8-15 minutes. 4. The method for manufacturing bimodal high-strain marine pipeline steel according to claim 2, characterized in that, in S2, the rough rolling temperature is 1050-1120°C, and multi-pass rolling is adopted. 5. The method for manufacturing bimodal high-strain marine pipeline steel according to claim 2, characterized in that in S2, the finish rolling start temperature is 810°C-850°C, and the finish rolling finish temperature is 700°C-750°C , using multi-pass rolling. 6. The manufacturing method of bimodal high-strain marine pipeline steel according to claim 2, characterized in that in S2, the relaxation start temperature is 700-750°C, the relaxation time is 80-150s, and then the relaxation time is 20 The cooling rate of ~35°C/s is water-cooled to 150-250°C. 7. The method for manufacturing bimodal high-strain marine pipeline steel according to claim 2, characterized in that in S3, the time for low-temperature tempering is 15-30 minutes. 8. The method for manufacturing bimodal high-strain marine pipeline steel according to claim 2, characterized in that in S3, the cooling method is air cooling. 9. The method for preparing a linepipe by using the bimodal high-strain marine pipeline steel as claimed in claim 1, characterized in that it comprises: J-C-O or U-O-E forming of the steel plate containing the composition of claim 1, and straight seam For submerged arc welding, the welding material is Ti-B-containing fine-grained acicular ferrite material with low oxygen content, and the diameter is expanded by 0.6% to 1.2% to obtain the line pipe. 10. The linepipe produced by the method of preparing linepipes from high-strain marine pipeline steel with bimodal structure as claimed in claim 9, characterized in that the transverse yield strength of the pipe body is 529-598MPa, and the tensile strength is 666-694MPa. The total elongation is 26-38%, the Charpy impact toughness at -20°C reaches 219-295J, the DWTT shear area at -10°C is 85-93%, the hardness is 202-236HV10, the longitudinal yield strength of the pipe body is 536-553MPa, and the tensile strength The strength is 663~680MPa, the total elongation is 29~43%, the uniform elongation is 7.2~11.3%, and the work hardening rate n value is 0.101~0.126.

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