A manufacturing process for Monel 400 seamless tubes

Abstract

The application provides a preparation process of Monel 400 seamless pipe and relates to the technical field of seamless pipe.The Monel 400 seamless pipe prepared by the process of specific cold rolling, solid solution heat treatment, argon arc welding and drawing-heat treatment overcomes the difficulties of Monel material in the welding and forming processes, such as weld solidification crack and dendritic segregation, so that the Monel 400 seamless pipe without crack and obvious segregation is prepared.The seamless pipe has excellent mechanical properties and corrosion resistance, and is suitable for harsh oil and gas well environment.The pipe body has a tensile strength greater than 480 MPa, a yield strength greater than 195 MPa, an elongation greater than 35%, and shows extremely high corrosion resistance in the HIC and SSC cracking tests, so that the pipe material use problem in the high temperature and high pressure and corrosive environment in the exploration and development of deep and unconventional oil and gas resources is solved.

Description

Technical Field

[0001] This invention relates to the field of seamless tube technology, and more particularly to a manufacturing process for Monel 400 seamless tube. Background Technology

[0002] The exploration and development of deep and unconventional oil and gas resources is a key development direction of the current national energy strategy. The number of oil and gas wells in harsh environments such as high temperature and high pressure, high H2S / CO2 content, acid fracturing, and gas injection, as well as oil and gas wells in complex formations such as deep, deep sea, and shale oil and gas, is increasing, which in turn makes the formation conditions and media environment for oil and gas pipelines more harsh and complex.

[0003] Seamless steel pipes are made from a single piece of metal through piercing, drawing, or rolling, thus eliminating the need for steel strip welds and avoiding defects and weaknesses that can be introduced by steel strip welding. This makes seamless steel pipes more reliable under high pressure and high temperature environments. Currently, the main materials for seamless steel pipes are Ncoloy 825 alloy and 316L stainless steel. However, seamless steel pipes made from these materials do not perform well in downhole environments containing oxygen, hydrogen sulfide, many strong alkalis, strong acids, brine, and high temperatures containing various corrosive media, and may even be unusable, thus limiting the resource recovery rate in the oil and gas sector.

[0004] Monel is a nickel-based alloy material with excellent corrosion resistance in seawater, chemical solvents, ammonia, sulfur, chlorine, hydrogen chloride, various acidic media such as sulfuric acid, hydrofluoric acid, hydrochloric acid, phosphoric acid, organic acids, alkaline media, salts, and molten salts. Monel 400 also boasts good mechanical properties, weldability, and a wide operating temperature range. However, due to the face-centered cubic lattice structure of the single-phase solid solution Ni-Cu alloy, Monel material exhibits poor thermal stability and porosity resistance. Under conditions of localized heating and cooling during welding, significant tensile stress can form at the joint, leading to weld solidification cracks and making welding difficult. Furthermore, the resulting seamless tubes cannot meet the requirements of harsh operating environments. Additionally, dendrite segregation is prone to occur during the forming process of Monel seamless tube blanks, affecting subsequent rolling and drawing processes. Therefore, the actual production of Monel seamless tubes faces certain difficulties, limiting its use in the exploration and development of deep and unconventional oil and gas resources.

[0005] Therefore, it is necessary to develop a manufacturing process for Monel seamless tubes to overcome the problems in welding and forming in existing processes. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a manufacturing process for Monel 400 seamless tubes. By limiting the element content in the raw billet and combining cold rolling, solution heat treatment, argon arc welding, and drawing-heat treatment processes, the problems existing in the welding and forming process of Monel material are overcome, ultimately resulting in a Monel seamless tube with no joint cracks and no obvious segregation during the forming process.

[0007] The manufacturing process of the Monel 400 seamless tube described in this invention includes the following steps:

[0008] S1 and Monel 400 billets are cold-rolled and then subjected to solution heat treatment;

[0009] This invention uses cold rolling to avoid high-temperature processing, which can reduce oxidation and other surface defects, while providing higher dimensional and geometric accuracy.

[0010] Solution heat treatment after cold rolling can eliminate work hardening.

[0011] S2. After cold rolling to the target pipe diameter and wall thickness, butt welding is performed between individual billets.

[0012] S3. After the butt joint is completed, multiple drawing and heat treatment processes are performed. After the final drawing and heat treatment process, the tube is cooled to obtain Monel 400 seamless tube.

[0013] Compared to rolling, drawing is faster, has fewer steps, and allows for better dimensional control. Heat treatment eliminates residual stress and work hardening from the drawing process. Nitrogen is used as the protective gas in the heat treatment furnace and tubes. This process aims to eliminate dendrite segregation and produce a uniform γ-grain structure.

[0014] Furthermore, the content of each element in the Monel 400 raw material is as follows: C: ≤0.3, Si: ≤0.5, Mn: ≤2, S: ≤0.024, Fe: ≤2.50, Cu: 28.0~34.0, with the balance being Ni and unavoidable impurities.

[0015] Furthermore, the rolling feed rate during the cold rolling process is 1-4 mm / time, and the speed is 60-120 times / min.

[0016] Furthermore, the solution heat treatment temperature is 800℃, the holding time is 4.5min, the cooling method is rapid cooling (air cooling in an externally covered water atmosphere), the cooling speed is 18m in cooling section, and the cooling time is 4.5min.

[0017] Furthermore, the butt welding is performed using argon arc welding, with a peak welding current of 60A±10A and a base current of 25A±3A.

[0018] Furthermore, the argon arc welding is performed in a pure argon atmosphere to strictly control harmful gases such as hydrogen, oxygen, and nitrogen in the molten pool, and to avoid porosity caused by the poor porosity resistance of Monel 400.

[0019] Furthermore, the number of cycles for the drawing-heat treatment process is 7.

[0020] Furthermore, the pull-out deformation is 69.94%.

[0021] Furthermore, the heat treatment temperature is 800℃, the holding time is 4.5min, the cooling method is rapid cooling (air cooling in an externally covered water atmosphere), the cooling speed is 18m in cooling section, and the cooling time is 4.5min.

[0022] Furthermore, the heat treatment is carried out under a nitrogen atmosphere to prevent sulfidation or oxidation problems.

[0023] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0024] This invention overcomes the problems of Monel weld cracking and dendrite segregation during the forming process, and obtains a Monel 400 seamless tube that can be used in the exploration and development of deep and unconventional oil and gas resources.

[0025] The Monel 400 seamless tube of this invention has a tensile strength > 480 MPa, a yield strength > 195 MPa, and an elongation > 35%.

[0026] The Monel 400 seamless tube of this invention has excellent corrosion resistance. Comparative tests on its resistance to HIC cracking, SSC cracking, and corrosion rate under 95% N2 + 5% O2 showed no HIC or SSC cracking, demonstrating extremely high corrosion resistance. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings.

[0028] Figure 1 a is a sample diagram of Embodiment 1 of the present invention;

[0029] Figure 1 b is the segmented sample tube of Embodiment 1 of the present invention;

[0030] Figure 1 c represents the finished pipe of Embodiment 1 of the present invention;

[0031] Figure 2 This is a sample diagram of Comparative Example 1 of the present invention;

[0032] Figure 3 This is a sample diagram of Comparative Example 2 of the present invention;

[0033] Figure 4 This is a sample diagram of Comparative Example 3 of the present invention;

[0034] Figure 5 This is a sample image of Comparative Example 4 of the present invention. Detailed Implementation

[0035] The technical solution provided by the present invention will be further described below with reference to the embodiments.

[0036] Example 1

[0037] A manufacturing process for Monel 400 seamless tube, comprising the following steps:

[0038] S1 and Monel 400 billets are cold rolled at a feed rate of 1 mm / time and a speed of 120 times / min, and then subjected to solution heat treatment.

[0039] The content of each element in the Monel 400 billet is as follows: C: ≤0.3, Si: ≤0.5, Mn: ≤2, S: ≤0.024, Fe: ≤2.50, Cu: 28.0~34.0, with the balance being Ni and unavoidable impurities;

[0040] The solution heat treatment temperature is 800℃, the holding time is 4.5min, the cooling method is rapid cooling (air cooling in an externally covered water atmosphere), the cooling speed is 18m in the cooling section, and the cooling time is 4.5min.

[0041] S2. After cold rolling to a pipe diameter of 22mm and a wall thickness of 1mm, butt argon arc welding is performed between single billets under a pure argon atmosphere.

[0042] The welding peak current is 60A and the base current is 25A;

[0043] S3. After the butt joint is completed, 7 drawing-heat treatments are performed, with a drawing deformation of 69.94%, a heat treatment temperature of 800℃, and a holding time of 4.5min. After the last drawing-heat treatment process, the tube is cooled by rapid cooling (air cooling in an external water atmosphere) at a cooling rate of 18 meters for 4.5min, resulting in a Monel 400 seamless tube.

[0044] Tests showed that the Monel 400 seamless tube prepared in this embodiment had a tensile strength of 578 MPa, a yield strength of 318 MPa, and an elongation of 35%. Comparative tests on its resistance to HIC cracking, SSC cracking, and corrosion rate under 95% N2 + 5% O2 showed no HIC or SSC cracking, demonstrating extremely high corrosion resistance.

[0045] Comparative Example 1

[0046] Same as Example 1, except that the cold rolling speed is 150 times / min.

[0047] Depend on Figure 2 It can be seen that increasing the cold rolling speed causes breakage of seamless tube blanks during the rolling process.

[0048] Comparative Example 2

[0049] Same as Example 1, except that the rolling speed in the cold rolling process is 30 times / min and the feed rate is 6mm / time.

[0050] Depend on Figure 3 It can be seen that after reducing the rolling speed and increasing the feed rate, large-area fractures occurred during the billet rolling process.

[0051] Comparative Example 3

[0052] Same as Example 1, except that: 8 drawing-heat treatments are performed, with a drawing deformation of 69.94%.

[0053] Depend on Figure 4 It is known that when the number of drawing passes is too low, although the total drawing deformation is still 69.94%, the drawing deformation per pass increases due to the low number of drawing passes, and obvious cracks appear on the surface of the pipe when observed under magnification. Therefore, this invention strictly limits the number of drawing-heat treatment cycles to 7.

[0054] Comparative Example 4

[0055] Same as Example 1, except that the solution heat treatment holding time is 4 minutes.

[0056] Depend on Figure 5 It can be seen that when the heat treatment holding time is 4 minutes, due to insufficient holding time, obvious cracks appear on the surface of the pipe when magnified.

[0057] Comparative Example 5

[0058] Same as Examples 1 and 4, except that the solution heat treatment holding time is 5.5 min.

[0059] When the solution heat treatment holding time is 5.5 min, the yield strength tested during mechanical property testing is 174 MPa due to the excessive holding time, which does not meet the acceptance standard ASTM B165 requirement of ≥195 MPa.

[0060] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A manufacturing process for Monel 400 seamless tubes, characterized in that, Includes the following steps: S1 and Monel 400 billets are cold-rolled and then subjected to solution heat treatment; The content of each element in the Monel 400 billet is as follows: C: ≤0.3, Si: ≤0.5, Mn: ≤2, S: ≤0.024, Fe: ≤2.50, Cu: 28.0~34.0, with the balance being Ni and unavoidable impurities; The solution heat treatment temperature is 800℃, the holding time is 4.5 min, the cooling method is rapid cooling, the cooling speed is 18 m in the cooling section, and the cooling time is 4.5 min. S2. After cold rolling to the target pipe diameter and wall thickness, butt welding is performed between individual billets. The rolling feed rate during the cold rolling process is 1~4 mm / time, and the speed is 60~120 times / min; The butt welding is performed using argon arc welding, with a peak welding current of 60 A ± 10 A and a base current of 25 A ± 3 A. S3. After the butt joint is completed, multiple drawing and heat treatment processes are performed. After the final drawing and heat treatment process, the tube is cooled to obtain Monel 400 seamless tube. The drawing-heat treatment process is repeated 7 times, and the total drawing deformation is 69.94%.

2. The manufacturing process of a Monel 400 seamless tube according to claim 1, characterized in that, The argon arc welding is performed under a pure argon atmosphere.

3. The manufacturing process of a Monel 400 seamless tube according to claim 1, characterized in that, The heat treatment temperature is 800℃, the holding time is 4.5 min, the cooling method is rapid cooling, the cooling speed is 18 m in the cooling section, and the cooling time is 4.5 min.

4. The manufacturing process of a Monel 400 seamless tube according to claim 1, characterized in that, The heat treatment was carried out under a nitrogen atmosphere.

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