A rolling method of inconel 625 / x65 clad plate

Abstract

The application discloses a rolling method of Inconel 625 / X65 composite plate. The rolling composite plate blank comprises Inconel 625 nickel-based alloy, two pieces of X65 low alloy steel base materials after being opened and reduced, and pure Ni sheet; after the composite material and the surface to be compounded are mechanically processed, the base material, the Inconel 625 composite layer, the Ni sheet and the base material are sequentially stacked and assembled into an asymmetric composite blank in sequence, and the compression ratio of the effective steel and iron base material is 8.75-9.77, which is 25%-39.5% larger than the compression ratio of the conventional symmetric assembly rolling, so that the base material of the composite plate has excellent low-temperature toughness. At the same time, the Inconel 625 composite layer is always located in the inside of the composite blank during the rolling process, so that the temperature of the Inconel 625 composite layer falls in the sensitization temperature range during the rolling process.

Description

Technical Field

[0001] This invention belongs to the field of metal composite plate production technology, and relates to a high compression ratio rolling method for Inconel 625 / X65 composite plates. Background Technology

[0002] In recent years, as oil and gas development has deepened, large amounts of H2S and Cl have been found. - With the frequent occurrence of corrosive oil and gas media and the complex and demanding conditions for oil and gas transportation, the demand for highly corrosion-resistant composite pipeline steel is constantly increasing, indicating a promising market prospect.

[0003] Inconel 625 nickel-based alloy is resistant to H2S and Cl. - It exhibits resistance to alkali metal corrosion and exhibits strong resistance to erosion corrosion and stress corrosion. However, its relatively high price limits the large-scale use of nickel-based alloys. To address this, researchers designed a bimetallic composite material using nickel-based alloys as the cladding material and pipeline steel as the base material. This design ensures both high corrosion resistance of the composite material and a good balance of strength and toughness in the base material, effectively reducing the application cost of nickel-based alloy corrosion-resistant steel.

[0004] Currently, casting composite, explosive composite, and hot rolling composite processes are widely used in the preparation of composite plates. Casting composite has low production efficiency, poor operability, and poor process stability and continuity; explosive composite has a sawtooth-shaped inlaid interface, poor stability of interface bonding effect, and the explosive process poses safety hazards and serious pollution; hot rolling composite uses atomic diffusion welding to achieve complete metallurgical bonding of bimetallic steel plates, with the characteristics of strong bonding rate, high composite rate, and large plate size, and is widely used in composite plate production.

[0005] Chinese patent CN 109694989B, "An Inconel 825 / X70 nickel-based alloy composite plate and its production method", discloses a method for producing Inconel 825 / X70 composite plates using symmetrical billet assembly and vacuum electron beam sealing welding, achieving excellent corrosion resistance in 5-32mm composite plates.

[0006] Chinese patent CN 109693072B, "An 825 / X70 / 825 Double-Sided Composite Plate and Its Production Method," discloses a method for producing Inconel 825 / X70 / Inconel 825 double-sided composite plates using a symmetrical billet assembly and vacuum electron beam sealing welding process. This method achieves a composite interface shear strength ≥454MPa and an X70 substrate impact energy at -20℃ far exceeding 190J. However, in this billet assembly method, the Inconel 825 alloy is directly exposed on the surface of the composite billet. Oxidation of the nickel-based material is unavoidable during heating, and there is a risk that the high shear stress experienced by the billet surface in the first few rolling passes could cause the nickel base layer to be ejected. Furthermore, with the Inconel 825 alloy directly exposed outside the composite billet, the relatively low finishing rolling temperature can easily cause the Inconel 825 alloy temperature to fall within the sensitization temperature range, leading to carbide precipitation and deteriorating the corrosion resistance of the nickel-based material.

[0007] Chinese patent CN 104525611A, “A nickel-chromium alloy and carbon steel composite plate and its production method”, discloses a composite plate involving Incoloy 825 nickel-chromium alloy and carbon steel X60MS and its production method, which achieves an impact energy of 300~400J at -20℃ and a DWTT shear area of ​​≥85% at -10℃ for the steel plate substrate.

[0008] In summary, current technologies for producing nickel-based composite plates suffer from a series of problems: 1) The symmetrical billet assembly method results in a smaller rolling compression ratio, thinner steel substrate, and generally lower low-temperature toughness; 2) It mainly involves Incoloy 825 nickel-based alloy, with limited research on Inconel 625 nickel-based alloy; 3) The widespread use of vacuum electron beam welding complicates the production process and increases costs. Therefore, changing the billet assembly method and increasing the rolling compression ratio of the composite billet are essential to improve the low-temperature toughness and increase the thickness of the steel substrate. Summary of the Invention

[0009] The purpose of this invention is to provide a high compression ratio rolling method for Inconel 625 / X65 composite plates. The resulting X65 steel substrate has an impact absorption energy of ≥94J at -60℃ and a composite interface shear strength of ≥386MPa.

[0010] The present invention adopts the following technical solution:

[0011] A rolling method for Inconel 625 / X65 composite plate, wherein the X65 base material has the following composition by mass ratio: C = 0.05%~0.07%, Si = 0.15%~0.25%, Mn = 1.35%~1.45%, P ≤ 0.020%, S ≤ 0.015%, Alt ≤ 0.050%, Cr = 0.10%~0.20%, Cu = 0.15%~0.25%, Ti = 0.007%~0.015%, Nb = 0.030%~0.050%, Mo = 0.10%~0.20%, balance being Fe and unavoidable impurity elements; the mass ratio of the multilayer Inconel 625 nickel-chromium alloy composition is: Cr=20%~23%, Mo=8%~10%, Nb=3.15%~4.15%, Fe≤5%, Mn≤0.5%, Si≤0.5%, P≤0.015%, S:≤0.015%, C:≤0.10%, Al:≤0.40%, Ti:≤0.40%, balance being Ni and unavoidable impurity elements; process steps:

[0012] 1) Billet assembly: After the X65 continuous casting billet is cut to the target thickness, it is asymmetrically assembled with Inconel 625 nickel-based alloy. The upper and lower layers are steel billets of different thicknesses, and the middle layer is Inconel 625 nickel-based alloy. After the steel billets and nickel-based alloy are polished, a welding resist is added between the thin steel billet and the Inconel 625 nickel-based alloy, and a 0.05~0.10mm thick nickel foil is added between the thick steel billet and the Inconel 625 nickel-based alloy. Finally, the four sides of the steel billet are welded and sealed, and a vacuum is drawn to 0.01Pa using a mechanical pump.

[0013] 2) Heating: After heating the composite billet to 1150~1250℃ and holding it at that temperature, two-stage controlled rolling is carried out in the austenite recrystallization zone and the austenite non-recrystallization zone, with rolling temperatures ranging from 1050~1250℃ and 850~900℃, respectively.

[0014] 3) Rolling: The total compression ratio during rolling is 8.23. The total reduction in the austenite recrystallization zone is controlled at 50%~60%, and the total reduction in the austenite non-recrystallization zone is controlled at 60%~80%. The thickness of the intermediate billet to be heated is 2~5 times the thickness of the finished product. The compression ratio of the effective steel substrate of the composite billet is 8.75~9.77.

[0015] 4) Cooling: After rolling, the composite plate is cooled by ultra-fast cooling, and the surface of the steel plate is water-cooled to the red-hot temperature of 450±50℃.

[0016] 5) Disassembly: After the water-cooled composite plate is cut off on all four sides, the useless X65 steel substrate on the upper surface is removed. The remaining Inconel 625 alloy layer and the X65 steel substrate on the lower surface are tightly metallurgically bonded together to form an Inconel 625 / X65 composite plate. The resulting X65 steel substrate has an impact absorption energy of ≥94J at -60℃ and a composite interface shear strength of ≥386MPa.

[0017] The beneficial effects of this invention are as follows: Considering the main approaches to improving the low-temperature toughness of TMCP steel plates, during the TMCP process, as the thickness of the rolled steel plate increases, the deformation penetration from the surface to the core decreases, the effective compression ratio of the steel plate decreases, and the phase transformation products exhibit coarsening. To solve this problem, this invention increases the thickness of the original billet and uses a sufficiently large rolling compression ratio. Simultaneously, the Inconel 625 alloy layer remains inside the billet throughout the rolling process, preventing the surface temperature of the composite billet from being too low, which would cause the Inconel 625 alloy to fall into the sensitization temperature range of carbides, thus ensuring the corrosion resistance of the Inconel 625 alloy. Attached Figure Description

[0018] Figure 1 This describes the billet assembly method for the steel of this invention.

[0019] Figure 2 This is an optical microstructure diagram of the steel matrix of the rolled composite plate in Example 1. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0021] A high-compression-ratio rolling method for Inconel 625 / X65 composite plates is disclosed. The composition mass ratio of the base material X65 and the composition mass ratio of the cladding Inconel 625 nickel-chromium alloy are shown in Tables 1 and 2, respectively. Table 3 shows the assembly method and dimensional information of the composite plates of the embodiments and comparative examples of the present invention; Table 4 shows the heating and rolling process parameters of the composite plates of the embodiments and comparative examples of the present invention; Table 5 shows the mechanical properties of the finished composite plates of the embodiments and comparative examples of the present invention.

[0022] Assembly of blanks in Example 1

[0023] After the X65 continuous casting billets were cut to 56 and 70 mm respectively, they were asymmetrically assembled with Inconel 625 nickel-based alloy. Figure 1Asymmetric billet assembly 1): The upper X65 substrate is 56mm thick, the middle Inconel 625 nickel-based alloy is 14mm thick, and the lower X65 substrate is 70mm thick. After the steel billet and nickel-based alloy are surface polished, a solder resist is added between the thin X65 steel billet and the Inconel 625 nickel-based alloy, and a 0.05mm thick nickel foil is added between the thick X65 steel billet and the Inconel 625 nickel-based alloy. Finally, the four sides of the steel billet are welded and sealed, and a vacuum is drawn to 0.01Pa using a mechanical pump.

[0024] Assembly of blanks in Example 2

[0025] After the X65 continuous casting billets were cut to 49 and 77 mm respectively, they were asymmetrically assembled with Inconel 625 nickel-based alloy. Figure 1 (2) Asymmetric billet assembly: The upper X65 substrate is 49mm thick, the middle Inconel 625 nickel-based alloy is 14mm thick, and the lower X65 substrate is 77mm thick. After the steel billet and nickel-based alloy are surface polished, a solder resist is added between the thin X65 steel billet and the Inconel 625 nickel-based alloy, and a 0.05mm thick nickel foil is added between the thick X65 steel billet and the Inconel 625 nickel-based alloy. Finally, the four sides of the steel billet are welded and sealed, and a vacuum is drawn to 0.01Pa using a mechanical pump.

[0026] Assembly of blanks in Example 3

[0027] After the X65 continuous casting billets were cut to 42 and 84 mm respectively, they were asymmetrically assembled with Inconel 625 nickel-based alloy. Figure 1 (3) Asymmetric billet assembly: The upper X65 substrate is 42mm thick, the middle Inconel 625 nickel-based alloy is 14mm thick, and the lower X65 substrate is 84mm thick. After the steel billet and nickel-based alloy are surface polished, a solder resist is added between the thin X65 steel billet and the Inconel 625 nickel-based alloy, and a 0.05mm thick nickel foil is added between the thick X65 steel billet and the Inconel 625 nickel-based alloy. Finally, the four sides of the steel billet are welded and sealed, and a vacuum is drawn to 0.01Pa using a mechanical pump.

[0028] Comparative model billet assembly

[0029] After the X65 continuous casting billet is cut to 56mm, it is symmetrically assembled with Inconel 625 nickel-based alloy: the upper and lower X65 base materials are both 56mm thick, and the middle is two 14mm thick Inconel 625 nickel-based alloy layers; after the billet and nickel-based alloy are surface polished, a 0.05mm thick nickel foil is added between the X65 billet and the Inconel 625 nickel-based alloy, and a solder resist is added between the two Inconel 625 nickel-based alloy layers; finally, the four sides of the billet are welded and sealed, and a vacuum is drawn to 0.01Pa using a mechanical pump.

[0030] Heating and rolling of comparative examples and embodiments

[0031] After the composite billet is heated to 1200℃ and held for 4 hours, it is subjected to two-stage controlled rolling in the austenite recrystallization zone and the austenite non-recrystallization zone, with specific rolling temperature ranges of 1100~1200℃ and 860~880℃, respectively.

[0032] During the rolling process, the total compression ratio is 8.23, the intermediate billet thickness is 60mm, and the specific rolling procedure is 140-121-100-79-60-54-47-40-33-27-21-17mm.

[0033] After rolling, the composite plate is immediately subjected to ultra-rapid cooling, and the surface of the steel plate is water-cooled to a red-hot temperature of 400~500℃.

[0034] Split of Comparison and Examples

[0035] After the four sides of the rolled composite plate are cut off, a composite plate with an Inconel 625 alloy layer and an X65 steel substrate metallurgically bonded together is obtained.

[0036] from Figure 2 It can be seen that the microstructure of the composite plate substrate of the present invention is refined bainite and polygonal ferrite, the microstructure is fine and uniform, and the composite interface is flat.

[0037] Effects of the embodiment: The effective steel substrate compression ratio of the Inconel 625 / X65 composite plate is 8.75~9.77, which is 25%~39.5% higher than the compression ratio of conventional symmetrical billet rolling, solving the problem of poor low-temperature toughness of the steel substrate caused by the limitation of rolling compression ratio in composite plates; the shear strength of the interface is ≥386MPa; the impact energy of X65 steel substrate at -60℃ is ≥94J.

[0038] It should be noted that due to the limitations of the pilot mill opening, the maximum thickness of the composite billet in both the example and comparative examples is 140 mm, resulting in a relatively small thickness of the finished composite plate. In industrial production, the thickness of the composite billet can be increased to achieve the production of thicker composite plates. Furthermore, this invention does not consider the thickness of the Inconel 625 base layer and X65 steel substrate in the finished composite plate, nor the corrosion resistance of the Inconel 625 base layer.

[0039] Table 1. Composition mass ratio of substrate X65 in the Examples and Comparative Examples

[0040] .

[0041] Table 2. Mass ratio of Inconel 625 nickel-chromium alloy components in the Examples and Comparative Examples

[0042] .

[0043] Table 3. Assembly methods and dimensional information of the embodiments and comparative examples

[0044] .

[0045] Table 4 Heating and rolling processes of the examples and comparative examples

[0046] .

[0047] Table 5 Mechanical properties of the finished products from the examples and comparative examples

[0048] .

Claims

1. A rolling method for Inconel 625 / X65 composite plates, characterized in that: The X65 substrate has the following composition by mass ratio: C = 0.05%~0.07%, Si = 0.15%~0.25%, Mn = 1.35%~1.45%, P ≤ 0.020%, S ≤ 0.015%, Alt ≤ 0.050%, Cr = 0.10%~0.20%, Cu = 0.15%~0.25%, Ti = 0.007%~0.015%, Nb = 0.030%~0.050%, and Mo = 0.10%~0.20%. The percentage of the total content is Fe and unavoidable impurity elements; the mass ratio of the multilayer Inconel 625 nickel-chromium alloy composition is: Cr=20%~23%, Mo=8%~10%, Nb=3.15%~4.15%, Fe≤5%, Mn≤0.5%, Si≤0.5%, P≤0.015%, S:≤0.015%, C:≤0.10%, Al:≤0.40%, Ti:≤0.40%, with the balance being Ni and unavoidable impurity elements; The process includes the following steps: 1) Billet Assembly: After the X65 continuous casting billet is cut to the target thickness, it is asymmetrically assembled with Inconel 625 nickel-based alloy. The upper and lower layers are steel billets of different thicknesses, and the middle layer is Inconel 625 nickel-based alloy. After the steel billets and nickel-based alloy are polished, a welding resist is added between the thin steel billet and the Inconel 625 nickel-based alloy, and a 0.05~0.10mm thick nickel foil is added between the thick steel billet and the Inconel 625 nickel-based alloy. Finally, the four sides of the steel billet are welded and sealed, and a vacuum is drawn to 0.01Pa using a mechanical pump. 2) Heating: After heating the composite billet to 1150~1250℃ and holding it at that temperature, two-stage controlled rolling is carried out in the austenite recrystallization zone and the austenite non-recrystallization zone, with rolling temperature ranges of 1050~1250℃ and 850~900℃, respectively. 3) Rolling: The total reduction ratio during rolling is 8.

23. The total reduction in the austenite recrystallization zone is controlled at 50%~60%, and the total reduction in the austenite non-recrystallization zone is controlled at 60%~80%. The thickness of the intermediate billet at the heating temperature is 2~5 times the thickness of the finished product. The effective steel base material of the composite billet is 8.75~9.

77. 4) Cooling: After rolling, the composite plate is subjected to ultra-rapid cooling, and the surface of the steel plate is water-cooled to the red-hot temperature of 450±50℃; 5) Disassembly: After the water-cooled composite plate is cut off on all four sides, the useless X65 steel substrate on the upper surface is removed. The remaining Inconel 625 alloy layer and the X65 steel substrate on the lower surface are tightly metallurgically bonded together to form an Inconel 625 / X65 composite plate. The resulting X65 steel substrate has an impact absorption energy of ≥94J at -60℃ and a composite interface shear strength of ≥386MPa.

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