Nickel-based alloy plates and their microstructure and property control rolling methods

Abstract

This invention belongs to the field of stainless steel rolling technology, specifically relating to a nickel-based alloy sheet and its microstructure and property control rolling method. The microstructure and property control rolling method for nickel-based alloy sheets provided by this invention employs a two-stage rolling process, including: a first-stage rolling process: initial rolling temperature ≥1080℃, final rolling temperature ≥950℃, deformation per pass ≥8%, total deformation ≥60%, and rolling speed ≤2m / s; and a second-stage rolling process: initial rolling temperature ≤920℃, final rolling temperature ≥820℃, rolling speed ≥3m / s, and total deformation ≥50%. This invention optimizes the rolling process to achieve uniform grain size control in nickel-based alloy sheets, significantly improving their mechanical properties and corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel rolling technology, specifically relating to a nickel-based alloy sheet and a rolling method for controlling its microstructure and properties. More specifically, it refers to how to optimize the rolling process to control the uniformity of grain size in nickel-based alloy sheets, thereby improving mechanical properties, corrosion resistance, and other properties. Background Technology

[0002] Nickel-based alloys possess high strength at both room temperature and high temperature, as well as excellent oxidation and corrosion resistance, making them widely used in petrochemical, energy, machinery, and environmental protection industries. They are an indispensable and extremely important material for economic development and national defense. Ni-Cr-Fe nickel-based alloys, due to their superior corrosion resistance, are widely used in petrochemical pipelines and chemical equipment. With the increasing parameter levels of high-end chemical equipment and the emergence of specialized production processes, higher performance requirements have been placed on the nickel-based alloys used. Previously, only room-temperature mechanical properties were required, but now requirements for grain size, high-temperature mechanical properties, and sensitized and non-sensitized corrosion resistance have been introduced. This necessitates achieving significant improvements in these properties through process technology control, while maintaining the same material selection. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a nickel-based alloy sheet and a method for controlling its microstructure and properties during rolling.

[0004] Specifically, the nickel-based alloy sheet microstructure and property control rolling method provided by this invention employs a two-stage rolling process to roll the billet, including:

[0005] First stage rolling: initial rolling temperature ≥1080℃, final rolling temperature ≥950℃, deformation per pass ≥8%, total deformation ≥60%, rolling speed ≤2m / s;

[0006] Second stage rolling: initial rolling temperature ≤ 920℃, final rolling temperature ≥ 820℃, rolling speed ≥ 3m / s, total deformation ≥ 50%.

[0007] The above-mentioned rolling method for controlling the microstructure and properties of nickel-based alloy plates involves an initial rolling temperature of 1100-1150℃, a final rolling temperature of 980-1020℃, a deformation of 8-15% per pass, a total deformation of 60-70%, and a rolling speed of 1.5-2 m / s. The second stage rolling involves an initial rolling temperature of 920-880℃, a final rolling temperature of 820-840℃, a rolling speed of 3-4 m / s, and a total deformation of 50-70%.

[0008] In the above-mentioned method for controlling the microstructure and properties of nickel-based alloy plates, the billet is held at 1150-1200℃ for 1.0-1.5 min / mm before the first stage of rolling.

[0009] The above-mentioned method for controlling the microstructure and properties of nickel-based alloy plates involves preparing the billet using the following method:

[0010] (1) The medium frequency furnace + AOD + LF method is used for smelting, and then the large flat ingots are directly cast.

[0011] (2) Flat ingots are rolled or forged to obtain intermediate billets;

[0012] (3) The intermediate billet is ground, measured and inspected to obtain the billet material.

[0013] The above-mentioned rolling method for controlling the microstructure and properties of nickel-based alloy plates, by weight percentage, comprises the following billets: C≤0.150%, Si≤0.50%, Mn≤1.00%, P≤0.030%, S≤0.015%, Cr14.00%-17.00%, Ni≥72.00%, Cu≤0.50%, Fe6.00%-10.00%.

[0014] On the other hand, the present invention also provides a nickel-based alloy sheet, which is prepared by the above-mentioned nickel-based alloy sheet microstructure and property control rolling method.

[0015] The aforementioned nickel-based alloy plates have a grain size of 3-7; room temperature yield strength of 245-290 MPa, tensile strength of 590-670 MPa, and elongation of 45-55%; and a high-temperature tensile yield strength of 195-215 MPa at 450℃.

[0016] The intergranular corrosion rates of the aforementioned nickel-based alloy plates are 0.8-1.9 mm / a for unsensitized and 1.8-7.7 mm / a for sensitized.

[0017] The technical solution of the present invention has the following beneficial effects:

[0018] This invention optimizes the rolling process to control the uniformity of grain size in nickel-based alloy sheets, thereby significantly improving the mechanical and corrosion properties of the nickel-based alloy sheets. Detailed Implementation

[0019] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms and expressions used below have the meanings commonly understood by those skilled in the art.

[0020] When a range of values ​​is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0021] The nickel-based alloy sheet microstructure and property control rolling method of the present invention employs a two-stage rolling process to roll the billet, including:

[0022] First stage: initial rolling temperature ≥1080℃, final rolling temperature ≥950℃. In this stage, the deformation amount per pass is guaranteed to be ≥8%, the total deformation amount is ≥60%, low-speed rolling, and the rolling line speed is ≤2m / s. Through the high-temperature zone, low-speed large deformation allows the alloy structure to undergo full dynamic recrystallization and grain refinement.

[0023] The second stage: After the billet has been warmed in the intermediate stage of the first stage rolling, the second stage rolling temperature is ≤920℃ and the final rolling temperature is ≥820℃. Finished product rolling is carried out within this temperature range, using a high-speed rolling principle with a rolling speed ≥3m / s and a total deformation ≥50%. Under low-temperature, high-speed deformation conditions, dynamic recrystallization is less likely to occur in the microstructure, and a large amount of deformation energy is introduced into the microstructure, providing favorable microstructural conditions for static recrystallization during the subsequent heat treatment of the finished product. Furthermore, this results in a finer, more dispersed, and more uniform distribution of carbides.

[0024] In some preferred embodiments, the first stage of rolling is characterized by an initial rolling temperature of 1100-1150℃, a final rolling temperature of 980-1020℃, a deformation of 8-15% per pass, a total deformation of 60-70%, and a rolling speed of 1.5-2 m / s; the second stage of rolling is characterized by an initial rolling temperature of 920-880℃, a final rolling temperature of 820-840℃, a rolling speed of 3-4 m / s, and a total deformation of 50-70%.

[0025] In some preferred embodiments, to obtain a fine-grained structure in the alloy sheet, providing a good microstructure for subsequent heat treatment, the billet is held at 1150-1200°C for 1.0-1.5 min / mm before the first stage of rolling.

[0026] In some preferred embodiments, to ensure the metallurgical purity, overall quality, low-cost control, and high-efficiency production of the alloy, the alloy is smelted using a medium-frequency furnace + AOD + LF method, and then directly cast into large flat ingots. The flat ingots are then rolled or forged to transform the original cast structure into a rolled / forged structure, significantly improving plasticity. After grinding, length setting, and inspection, the intermediate billets are rolled into finished plates.

[0027] In this invention, the nickel-based alloy sheet is a typical Ni-Cr-Fe alloy with a standard composition control range (wt%):

[0028]

[0029] The ingredient control standards refer to ASME SB168.

[0030] On the other hand, the present invention provides a nickel-based alloy sheet, which is prepared by the above-mentioned nickel-based alloy sheet microstructure and property control rolling method.

[0031] The nickel-based alloy sheet of the present invention has the following properties: grain size of 6-9; room temperature yield strength of 280-350 MPa, tensile strength of 650-750 MPa, and elongation of 50-65%; high temperature tensile yield strength of 220-280 MPa at 450℃; and intergranular corrosion rates of 0.20-0.50 mm / a for unsensitized and 0.60-2.20 mm / a for sensitized.

[0032] The properties of nickel-based alloy sheets rolled under traditional process conditions are as follows: grain size of finished sheets 3-7; room temperature yield strength 245-290MPa, tensile strength 590-670MPa, elongation 45-55%; high temperature tensile yield strength at 450℃ 195-215MPa; intergranular corrosion test by ASTM G28 A method, the intergranular corrosion rates after sensitization and after sensitization are 0.8-1.9mm / a and 1.8-7.7mm / a, respectively.

[0033] Compared with traditional processes, this invention optimizes the rolling process to achieve uniform grain size control of nickel-based alloy plates, thereby significantly improving the mechanical properties and corrosion resistance of nickel-based alloy plates.

[0034] Example

[0035] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments, unless otherwise specified, are performed according to conventional methods and conditions.

[0036] Table 1. Summary of the composition (wt%) of the nickel-based alloy plates prepared in Examples 1-3 and Comparative Example 1

[0037]

[0038] Example 1

[0039] The material was smelted using a medium-frequency furnace + AOD + LF method, and then directly cast into large flat ingots (composition shown in Table 1). The ingots were then rolled into billets with an intermediate billet thickness of 180 mm. The intermediate billet was heated to 1160℃ and held for 1.2 min / mm. A two-stage controlled rolling process was employed. Stage 1: Initial rolling temperature 1100℃, final rolling temperature 960℃, deformation per pass ≥8%, total deformation ≥60%, rolling speed 2 m / s, finished thickness 68 mm. Stage 2: Initial rolling temperature 900℃, final rolling temperature 820℃, rolling speed 3.5 m / s, total deformation ≥50%, finished thickness 20 mm. The finished product underwent heat treatment at 1000℃, held for 3 min / mm, and was water-cooled.

[0040] Tests showed that the finished board had a grain size of 7-8; a room temperature yield strength of 316 MPa, a tensile strength of 691 MPa, and an elongation of 61%; a high-temperature tensile yield strength of 254 MPa at 450℃; and intergranular corrosion tests using the ASTM G28 A method showed intergranular corrosion rates of 0.31 mm / a for unsensitized and 1.22 mm / a for sensitized materials, indicating a significant improvement in performance.

[0041] Example 2

[0042] The material was smelted using a medium-frequency furnace + AOD + LF method, and then directly cast into large flat ingots (composition shown in Table 1). The ingots underwent forging to create intermediate billets with a thickness of 220 mm. The intermediate billet was heated to 1160℃ and held for 1.3 min / mm. A two-stage controlled rolling process was employed. Stage 1: Initial rolling temperature 1110℃, final rolling temperature 980℃, deformation per pass ≥8%, total deformation ≥60%, rolling speed 2 m / s, finished thickness 80 mm. Stage 2: Initial rolling temperature 910℃, final rolling temperature 820℃, rolling speed 3.5 m / s, total deformation ≥50%, finished thickness 22 mm. The finished product underwent heat treatment at 1000℃, held for 2 min / mm, and water cooling.

[0043] Tests showed that the finished board had a grain size of 7-8; a room temperature yield strength of 326 MPa, a tensile strength of 718 MPa, and an elongation of 58%; a high-temperature tensile yield strength of 248 MPa at 450℃; and intergranular corrosion tests using the ASTM G28 A method showed intergranular corrosion rates of 0.41 mm / a for unsensitized and 0.89 mm / a for sensitized materials, indicating a significant improvement in performance.

[0044] Example 3

[0045] The material was smelted using a medium-frequency furnace + AOD + LF method, and then directly cast into large flat ingots (composition shown in Table 1). The ingots were then rolled to form intermediate billets with a thickness of 200 mm. The intermediate billet heating temperature was 1170℃, and the holding time was 1.2 min / mm. A two-stage controlled rolling process was adopted. Stage 1: Initial rolling temperature 1110℃, final rolling temperature 980℃, deformation per pass ≥8%, total deformation ≥60%, rolling speed 2 m / s, finished thickness 70 mm. Stage 2: Initial rolling temperature 900℃, final rolling temperature 830℃, rolling speed 3.5 m / s, total deformation ≥50%, finished thickness 18 mm. The finished product underwent heat treatment at 1030℃, holding time 2 min / mm, and water cooling.

[0046] Tests showed that the finished board had a grain size of 7-8; a room temperature yield strength of 309 MPa, a tensile strength of 698 MPa, and an elongation of 65%; a high-temperature tensile yield strength of 255 MPa at 450℃; and intergranular corrosion tests using the ASTM G28 A method showed intergranular corrosion rates of 0.38 mm / a for unsensitized and 1.33 mm / a for sensitized materials, indicating a significant improvement in performance.

[0047] Comparative Example 1

[0048] Nickel-based alloy slabs were prepared according to traditional process conditions, the composition of which is shown in Table 1. The process conditions are as follows:

[0049] The material was smelted using a medium-frequency furnace + AOD + LF method, and then directly cast into large flat ingots (composition shown in Table 1). The flat ingots were then rolled into billets, with an intermediate billet thickness of 200 mm. The intermediate billet was heated to 1180℃ and held for 1.2 min / mm. The initial rolling temperature was 1110℃, and the final rolling temperature was 880℃, using uncontrolled rolling, resulting in a finished product thickness of 18 mm. The finished product underwent heat treatment at 1030℃, held for 2 min / mm, and was water-cooled.

[0050] The finished board was tested and found to have a grain size of grade 5; a room temperature yield strength of 246 MPa, a tensile strength of 613 MPa, and an elongation of 49%; a high temperature tensile yield strength of 201 MPa at 450℃; and intergranular corrosion tests conducted using the ASTM G28 A method showed intergranular corrosion rates of 0.79 mm / a for unsensitized and 3.67 mm / a for sensitized materials.

[0051] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art should understand that these embodiments are merely illustrative of the invention and should not be construed as limiting its scope. It should be noted that any variations and substitutions equivalent to these embodiments should be considered to be covered within the scope of the claims. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for controlling the microstructure and properties of nickel-base alloy plate by rolling, characterized by, The billet is rolled using a two-stage rolling process, including: First stage rolling: initial rolling temperature 1100-1150℃, final rolling temperature 980-1020℃, deformation per pass 8-15%, total deformation 60-70%, rolling speed 1.5-2m / s; Second stage rolling: initial rolling temperature 920-880℃, final rolling temperature 820-840℃, rolling speed 3-4m / s, total deformation 50-70%.

2. The process for controlling the microstructure and properties of nickel-based alloy plate according to claim 1, characterized in that, Before the first stage of rolling, the billet is held at 1150-1200℃ for 1.0-1.5 min / mm.

3. The process for controlling the microstructure and properties of nickel-based alloy plate according to claim 1, characterized in that, The blank is prepared by the following method: (1) The medium frequency furnace + AOD + LF method is used for smelting, and then the large flat ingots are directly cast. (2) Flat ingots are rolled or forged to obtain intermediate billets; (3) The intermediate billet is obtained after grinding, length setting and inspection.

4. The method for controlling the microstructure and properties of nickel-based alloy plates according to claim 1, characterized in that, The billet comprises, by weight percentage: C ≤0.150%, Si ≤0.50%, Mn ≤1.00%, P ≤0.030%, S ≤0.015%, Cr 14.00%-17.00%, Ni ≥72.00%, Cu ≤0.50%, and Fe 6.00%-10.00%.

5. A nickel-based alloy sheet, characterized in that, The nickel-based alloy sheet was prepared using the microstructure and property control rolling method described in any one of claims 1-4.

6. The nickel-based alloy sheet according to claim 5, characterized in that, The finished board has a grain size of 3-7; room temperature yield strength of 245-290MPa, tensile strength of 590-670MPa, and elongation of 45-55%; and a high temperature tensile yield strength of 195-215MPa at 450℃.

7. The nickel-based alloy sheet according to claim 5, characterized in that, The intergranular corrosion rates after sensitization and after sensitization were 0.8-1.9 mm / a and 1.8-7.7 mm / a, respectively.

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