A method of strain-induced precipitation rolling of a nickel-base alloy carbide

Abstract

The present application relates to a kind of nickel-based alloy carbide strain-induced precipitation rolling method, comprising: (1) the homogenization heat treatment of blank;(2) the blank is sequentially carried out first fire rolling and second fire rolling.This application realizes the strengthening of carbide strain-induced precipitation auxiliary by means of control rolling, etc., so that it realizes high strengthening when grain size is greater than or equal to 5.

Description

Technical Field

[0001] This invention relates to a method for rolling nickel-based alloy carbide strain-induced precipitation, specifically how to achieve carbide strain-induced precipitation and improve the strength of the sheet through rolling and other control methods. Background Technology

[0002] Nickel-based alloys are widely used in petrochemical, key equipment and other fields due to their excellent high-temperature mechanical properties and corrosion resistance. They are an indispensable and extremely important type of material for economic construction and national defense.

[0003] The performance requirements for nickel-based alloy plates vary depending on the application. For example, for N06625 nickel-based alloy, Grade 1 (high-strength grade, primarily for high strength and high fatigue performance, requiring a yield strength ≥379MPa, tensile strength ≥758MPa, and elongation ≥30%), some applications place even higher demands on the mechanical properties of medium plates (requiring a yield strength ≥414MPa, tensile strength ≥827MPa, and elongation ≥30%).

[0004] Since N06625 is a solid solution strengthened nickel-based alloy, it is difficult to stably achieve the above-mentioned high strength level using conventional rolling and heat treatment processes. Furthermore, in the process of mass production, due to the variety of finished plate specifications, but the billet heating process parameters are basically the same, some plates cannot achieve high strength, and the grain size after annealing is 5-7, which cannot reach the ideal state of grain size ≥7. Summary of the Invention

[0005] To address the above-mentioned technical challenges in production, this invention relates to a method for strain-induced precipitation rolling of nickel-based alloy carbides.

[0006] Specifically, the nickel-based alloy carbide strain-induced precipitation rolling method provided by the present invention includes:

[0007] (1) Homogenize the billet with heat treatment;

[0008] (2) The billet is subjected to a first rolling and a second rolling in sequence.

[0009] In the above-mentioned nickel-based alloy carbide strain-induced precipitation rolling method, the billet is obtained by smelting the alloy in a vacuum induction furnace or electric furnace, and then by continuous casting or ingot casting.

[0010] In the above-mentioned nickel-based alloy carbide strain-induced precipitation rolling method, the homogenization heat treatment temperature is 1200-1250℃ and the holding time is 48-72h.

[0011] In the above-mentioned nickel-based alloy carbide strain-induced precipitation rolling method, the billet heating temperature of the first rolling is 1180-1220℃, the total heating time is 1-1.5min / mm thickness, the initial rolling temperature of the plate is ≥1080℃, the final rolling temperature is ≥850℃, and the plate is air-cooled after rolling.

[0012] In the above-mentioned nickel-based alloy carbide strain-induced precipitation rolling method, the first rolling pass is 7-15 passes, and the deformation amount per pass is ≤10%.

[0013] The above-mentioned nickel-based alloy carbide strain-induced precipitation rolling method, wherein the second heat rolling process sequentially includes:

[0014] (1) Heating

[0015] The heating temperature is 1180-1200℃, and the total heating time is 1.0-1.5 min / mm thickness;

[0016] (2) First three rolling passes

[0017] The initial rolling temperature is ≥1080℃, the deformation amount in each pass is greater than 10%, and the surface temperature of the sheet is ≥1000℃.

[0018] (3) Normal rolling

[0019] The total deformation should be controlled to be above 70%, and the surface temperature of the plate should be ≥930℃;

[0020] (4) Controlling the rolling of the plate shape

[0021] Final rolling temperature ≥ 850℃.

[0022] On the other hand, the present invention also provides a nickel-based alloy sheet, which is rolled using the above-mentioned nickel-based alloy carbide strain-induced precipitation rolling method.

[0023] The aforementioned nickel-based alloy sheet is N06625.

[0024] The aforementioned nickel-based alloy sheet, when the grain size is ≥5, has a yield strength Rp0.2 > 480 MPa, a tensile strength Rm > 890 MPa, and an elongation greater than 47%.

[0025] The technical solution of the present invention has the following beneficial effects:

[0026] This invention achieves carbide strain-induced precipitation-assisted strengthening by controlling rolling and other means, enabling high strengthening when the grain size is ≥5. Detailed Implementation

[0027] 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 phrases used below have the meanings commonly understood by those skilled in the art.

[0028] The terms “first,” “second,” etc., used herein do not indicate any order or importance, but are used to distinguish one element from another. The terms “the,” “the,” “an,” and “a” do not indicate a limitation of quantity, but rather indicate the presence of at least one of the mentioned objects. The terms “preferred,” “more preferred,” etc., refer to embodiments of the invention that, in certain circumstances, provide certain beneficial effects. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of the invention.

[0029] Specifically, the nickel-based alloy carbide strain-induced precipitation rolling method provided by the present invention includes:

[0030] Preparation of slabs

[0031] The alloy is smelted in a vacuum induction furnace or electric furnace, and then slabs are obtained by continuous casting or ingot casting.

[0032] Optionally, the slab material is N06625, and the standard composition control range is (wt%):

[0033]

[0034] The ingredient control standards refer to ASME SB-443 or ASME SB-446.

[0035] Homogenization heat treatment

[0036] By homogenizing the slab material through heat treatment, defects such as element segregation can be effectively eliminated.

[0037] Preferably, the homogenization heat treatment is performed at a temperature of 1200-1250℃ for a holding time of 48-72 hours.

[0038] Preferably, the homogenization heat treatment is performed using a gas-fired furnace or an electric furnace.

[0039] First rolling

[0040] The billet heating temperature is 1180-1220℃, and the total heating time is considered based on the billet thickness of 1-1.5 min / mm. The initial rolling temperature of the plate is ≥1080℃, the final rolling temperature is ≥850℃, and it is air-cooled after rolling.

[0041] The first rolling process consists of 7-15 rolling passes, with each pass having a deformation amount of ≤10%.

[0042] The first rolling process transforms the coarse cast structure in the slab into a rolled structure, significantly improving the plasticity of the billet.

[0043] After the first rolling, the surface of the billet is ground to ensure that there are no cracks or defects before the second rolling of the finished plate can be carried out.

[0044] Second rolling

[0045] Because cast nickel-based alloy billets have a coarse microstructure and low thermoplasticity, they cannot be rolled into sheets in a single operation. Therefore, a two-stage rolling process is required to produce the finished product.

[0046] Preferably, the second rolling process requires three-stage control:

[0047] (1) First stage

[0048] The billet is heated to 1180-1200℃ for a total heating time of 1.0-1.5 min / mm thickness. The initial rolling temperature is ≥1080℃. In the first three rolling passes, the deformation in each pass is greater than 10%, ensuring that the surface temperature of the sheet is ≥1000℃ after the first three rolling passes.

[0049] In the first stage, through high temperature and large deformation, the microstructure undergoes dynamic recrystallization, and the grain structure is refined, thus providing a large number of nucleation sites for subsequent strain-induced precipitation of carbides.

[0050] (2) Second stage

[0051] The second stage is strain-induced precipitation rolling, which requires that more than 70% of the total deformation be completed under the condition that the plate surface temperature is ≥930℃ (preferably 930-1000℃).

[0052] In some embodiments, the strain-induced precipitation rolling process involves a deformation amount of ≥8% per pass.

[0053] In the second stage, nanoscale carbides in the slab undergo full strain-induced precipitation and are uniformly distributed within the grains and at the grain boundaries.

[0054] (3) Third stage

[0055] Finally, the rolling process is controlled, with a final rolling temperature ≥850℃.

[0056] In some embodiments, the controlled plate rolling process involves a deformation of ≤5% per pass.

[0057] Rolling nickel-based alloy billets according to the rolling method of the present invention can effectively induce carbide precipitation by strain, thereby improving the strength of the sheet and achieving high strength even when the grain size is ≥5 after annealing.

[0058] The annealing temperature is 950-990℃, and the holding time is based on a plate thickness of 3 min / mm.

[0059] On the other hand, the present invention also provides a nickel-based alloy sheet, which is rolled using the above-mentioned nickel-based alloy carbide strain-induced precipitation rolling method.

[0060] The nickel-based alloy plate is N06625.

[0061] In practice, when the grain size of the nickel-based alloy sheet obtained according to the method of this invention is ≥5, the yield strength Rp0.2 > 480MPa; the tensile strength Rm > 890MPa; and the elongation is greater than 47%.

[0062] Example

[0063] 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.

[0064] The alloy used in Examples 1-3 and Comparative Examples 1-5 was N06625, and the controlled composition content was as follows (wt%).

[0065]

[0066] Example 1

[0067] N06625 alloy was smelted using a vacuum induction furnace with a homogenization temperature of 1230℃ and a holding time of 50h. The composition is shown in the table above. Slabs with a thickness of 250mm and a finished plate thickness of 10mm were obtained. The first rolling process involved heating at 1200℃ for 250min, followed by further rolling at 1100℃ and 890℃. The intermediate slab thickness was 68mm, and the rolling process consisted of 11 passes with a deformation of ≤10% per pass. The second rolling process involved the following stages: First stage: slab heating temperature 1200℃ for 102min, initial rolling temperature 1110℃, and deformations of 12%, 11%, and 12% for the first three passes, respectively. After three passes, the plate surface temperature reached 1020℃. Second stage: Normal rolling, with a plate thickness of 12mm and a surface temperature of 930℃. The total deformation of the first and second stages is 82%. Third stage: Controlled rolling, with a final rolling temperature of 860℃ and a plate thickness of 10mm. Annealing temperature of 980℃, holding time of 30min, and water cooling.

[0068] The measured grain size of the sheet is grade 6, the yield strength Rp0.2 = 515 MPa, the tensile strength Rm = 890 MPa, and the elongation is 51%.

[0069] Example 2

[0070] N06625 alloy was smelted using an electric furnace, with a homogenization temperature of 1230℃ and a holding time of 58 hours. The composition is shown in the table above. This yielded slabs with a thickness of 180mm and finished slab thickness of 15mm. The first rolling process involved heating at 1200℃ for 180 minutes, followed by further rolling at 1090℃ and 880℃. The intermediate slab thickness was 120mm, and the rolling process consisted of 13 passes with a deformation of ≤10% per pass. The second rolling process involved the following stages: First stage: slab heating temperature 1200℃ for 180 minutes, initial rolling temperature 1120℃, and deformations of 12%, 14%, and 13% for the first three passes. After three passes, the slab surface temperature reached 1020℃. Second stage: Normal rolling, with a plate thickness of 18mm and a surface temperature of 940℃. The total deformation of the first and second stages is 85%. Third stage: Controlled rolling, with a final rolling temperature of 870℃ and a plate thickness of 15mm. Annealing temperature of 980℃, holding time of 45min, and water cooling.

[0071] The measured grain size of the sheet is 6.5 grade, the yield strength Rp0.2 = 505 MPa, the tensile strength Rm = 924 MPa, and the elongation is 47%.

[0072] Example 3

[0073] N06625 alloy was smelted using an electric furnace. The homogenization temperature was 1210℃, and the holding time was 72 hours. The composition is shown in the table above. This yielded a slab with a thickness of 180mm and a finished slab thickness of 20mm. The first rolling process involved heating at 1200℃ for 180 minutes, followed by further rolling at 1090℃ and 890℃. The intermediate slab thickness was 120mm, and the rolling process consisted of 11 passes with a deformation of ≤10% per pass. The second rolling process involved: In the first stage, the slab was heated to 1200℃ for 180 minutes, with an initial rolling temperature of 1120℃. The deformation amounts for the first three passes were 11%, 11%, and 13%, respectively. After three passes, the slab surface temperature was 1010℃. Second stage: Normal rolling, with a plate thickness of 22mm and a surface temperature of 940℃. The total deformation of the first and second stages is 85%. Third stage: Controlled rolling, with a final rolling temperature of 870℃ and a plate thickness of 20mm. Annealing temperature of 980℃, holding time of 60min, and water cooling.

[0074] The measured grain size of the sheet is 5.5, the yield strength Rp0.2 = 489 MPa, the tensile strength Rm = 891 MPa, and the elongation is 50%.

[0075] Comparative Example 1

[0076] N06625 alloy was smelted in a vacuum induction furnace at a homogenization temperature of 1220℃ and a holding time of 55 hours. The composition is shown in the table above. Slabs with a thickness of 250 mm and a finished plate thickness of 10 mm were obtained. The first rolling pass was conducted at a heating temperature of 1200℃ for 250 minutes, followed by further rolling at an initial rolling temperature of 1100℃ and a final rolling temperature of 890℃. The intermediate slab thickness was 68 mm, and 13 rolling passes were used, with a deformation of 5-15% per pass. The second rolling pass was conducted at a heating temperature of 1200℃ for 102 minutes, with an initial rolling temperature of 1110℃ and a final rolling temperature of 880℃, for a total of 18 rolling passes. The deformation per pass was between 5-10%, resulting in a plate thickness of 10 mm. The plate was then annealed at 980℃ for 30 minutes and water-cooled.

[0077] The measured grain size of the sheet is grade 6, the yield strength Rp0.2 = 399 MPa, the tensile strength Rm = 798 MPa, and the elongation = 48%.

[0078] Comparative Example 2

[0079] N06625 alloy was smelted using an electric furnace. The homogenization temperature was 1230℃, and the holding time was 58 hours. The composition is shown in the table above. This yielded slabs with a thickness of 180 mm and a finished plate thickness of 15 mm. The first rolling process involved heating at 1200℃ for 180 minutes, followed by further rolling at 1090℃ and 880℃. The intermediate slab thickness was 120 mm, and the rolling process consisted of 13 passes with a deformation of ≤10% per pass. The second rolling process involved heating the slab at 1200℃ for 180 minutes, with an initial rolling temperature of 1120℃ and a final rolling temperature of 860℃. A total of 25 passes were performed, with a deformation of 5-10% per pass, resulting in a plate thickness of 15 mm. The plate was then annealed at 980℃ for 45 minutes and water-cooled.

[0080] The measured grain size of the sheet is 6.5 grade, the yield strength Rp0.2 = 412 MPa, the tensile strength Rm = 815 MPa, and the elongation = 44%.

[0081] Comparative Example 3

[0082] N06625 alloy was smelted using an electric furnace. The homogenization temperature was 1210℃, and the holding time was 72 hours. The composition is shown in the table above. This yielded slabs with a thickness of 180 mm and a finished plate thickness of 20 mm. The first rolling process involved heating at 1200℃ for 180 minutes, followed by further rolling at 1090℃ and 890℃. The intermediate slab thickness was 120 mm, and the rolling process consisted of 11 passes with a deformation of ≤10% per pass. The second rolling process involved heating the slab at 1200℃ for 180 minutes, starting at 1120℃ and ending at 870℃, for a total of 22 passes. The deformation per pass ranged from 5% to 10%, resulting in a plate thickness of 20 mm. The plate was then annealed at 980℃ for 60 minutes and water-cooled.

[0083] The measured grain size of the sheet is 5.5, the yield strength Rp0.2 = 408 MPa, the tensile strength Rm = 809 MPa, and the elongation = 49%.

[0084] Comparative Example 4

[0085] N06625 alloy was smelted using an electric furnace. The homogenization temperature was 1230℃, and the holding time was 56 hours. The composition is shown in the table above. This yielded slabs with a thickness of 180 mm and a finished plate thickness of 20 mm. The first rolling process involved heating at 1200℃ for 180 minutes, followed by further rolling at 1090℃ and 890℃. The intermediate slab thickness was 120 mm, and the rolling process consisted of 11 passes with a deformation of ≤10% per pass. The second rolling process involved heating the slab at 1200℃ for 180 minutes, starting at 1120℃ and ending at 870℃, for a total of 20 passes. The deformation per pass was between 5-10%, resulting in a plate thickness of 20 mm. The plate was then annealed at 980℃ for 60 minutes and water-cooled.

[0086] The measured grain size of the sheet is 5.5, the yield strength Rp0.2 = 396 MPa, the tensile strength Rm = 811 MPa, and the elongation = 51%.

[0087] Comparative Example 5

[0088] N06625 alloy was smelted using an electric furnace, with a homogenization temperature of 1230℃ and a holding time of 56 hours. The composition is shown in the table above. This yielded slabs with a thickness of 180mm and finished slab thickness of 20mm. The first rolling process involved heating at 1200℃ for 180 minutes, followed by further rolling at 1090℃ and 890℃. The intermediate slab thickness was 120mm, and the rolling process consisted of 11 passes, with a deformation of ≤10% per pass. The second rolling process involved: Stage 1: The slab was heated to 1200℃ for 180 minutes, with an initial rolling temperature of 1120℃. The deformations in the first three passes were 5%, 7%, and 7%, respectively. After three passes, the surface temperature of the slab was 1040℃. Stage 2: Normal rolling was performed, but the deformation per pass was ≤8%. When the slab thickness was 22mm, the surface temperature was 900℃. Third stage: Controlled rolling, final rolling temperature 850℃, plate thickness 20mm. Plate annealing temperature 980℃, holding time 60min, water cooling.

[0089] The measured grain size of the sheet is grade 5.5, the yield strength Rp0.2 = 377 MPa, the tensile strength Rm = 811 MPa, and the elongation is 46%. Although the sheet is also rolled, there is no carbide strain-induced precipitation, resulting in low sheet strength.

[0090] 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 strain-induced precipitation rolling of nickel-based alloy carbides, characterized in that, include: (1) Homogenize the billet with heat treatment; The homogenization heat treatment temperature is 1200-1250℃, and the holding time is 48-72h; (2) The billet is subjected to a first rolling process and a second rolling process in sequence; The billet being rolled in the first heat is heated to 1180-1220℃, with a total heating time of 1-1.5 min / mm thickness. The initial rolling temperature of the plate is ≥1080℃, the final rolling temperature is ≥850℃, and it is air-cooled after rolling. The second rolling process includes, in sequence: (1) Heating The heating temperature is 1180-1200℃, and the total heating time is 1.0-1.5 min / mm thickness; (2) The first three rolling passes The initial rolling temperature is ≥1080℃, the deformation amount in each pass is greater than 10%, and the surface temperature of the sheet is ≥1000℃. (3) Normal rolling The total deformation should be controlled to be above 70%, and the surface temperature of the sheet should be ≥930℃; (4) Controlling the rolling of the plate shape Final rolling temperature ≥ 850℃; The nickel-based alloy is designated as N06625.

2. The method for strain-induced precipitation rolling of nickel-based alloy carbides according to claim 1, characterized in that, The billet is obtained by smelting the alloy in a vacuum induction furnace or electric furnace, followed by continuous casting or ingot casting.

3. The method for strain-induced precipitation rolling of nickel-based alloy carbides according to claim 1, characterized in that, The first rolling process consists of 7-15 rolling passes, with each pass having a deformation amount of ≤10%.

4. A nickel-based alloy sheet, characterized in that, The rolling process is carried out using the strain-induced precipitation rolling method for nickel-based alloy carbides as described in any one of claims 1-3.

5. The nickel-based alloy sheet according to claim 4, characterized in that, When the grain size of the nickel-based alloy plate is ≥5, the yield strength Rp0.2 > 480MPa; the tensile strength Rm > 890MPa; and the elongation is greater than 47%.

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