A nickel-based alloy hot-rolled thick plate and preparation method thereof

Abstract

The invention discloses a nickel-based alloy hot-rolled thick plate and a preparation method thereof, wherein the nickel-based alloy hot-rolled thick plate comprises the following components in weight percentage: C: 0.05-0.1%, Cr: 15-30%, Al: 0.1-1.5%, Ti: 0.1-1.0%, Si≤0.3%, Mn≤0.5%, Ni: 25-40%, N: 0.02-0.04%, Zr: 0.01-0.15%, P≤0.010%, S≤0.010%, and the balance is Fe and unavoidable impurities. The nickel-based alloy hot-rolled thick plate is produced through composition design, and adopts electric arc furnace, VOD refining, die casting, homogenization annealing, forging blanking, variable thickness rolling, heat treatment, etc., to produce high-temperature resistant, large-unit-weight nickel-based alloy hot-rolled thick plate, which not only improves the yield rate and saves production costs, but also has a positive practical effect on the supply capacity of large-size nickel-based alloy hot-rolled thick plates.

Description

Technical Field

[0001] The invention relates to the field of nickel-based alloy preparation, and more specifically to a nickel-based alloy hot-rolled thick plate suitable for long-term service in a high-temperature use environment and a preparation method thereof. Background Art

[0002] Among the nickel-based alloy product series, they are generally divided into high-temperature alloys and corrosion-resistant alloys. When serving at higher temperatures, age-strengthened nickel-based alloys with alloying elements such as Nb, Al, Ti, and W are usually selected. The principle is that the alloy is strengthened by ageing to form strengthening phases such as γ' to improve the performance of long-term use at high temperatures. When the operating temperature is relatively low, such as when the operating conditions are below 800°C, solid solution-strengthened nickel-based alloys are generally selected. The composition characteristics are that they only contain a certain amount of Al, Ti, Cr and other elements. They can also form strengthening phases such as γ' when used at high temperatures for a long time to improve high-temperature long-term creep performance, but the high-temperature strength is significantly lower than that of age-strengthened nickel-based alloys. No matter what kind of nickel-based alloy is selected, due to the high content of alloying elements, technical difficulties such as component segregation and difficulty in deformation are inevitable during the preparation process, and this trend increases with the increase of ingot shape and unit weight.

[0003] After decades of development, the application of nickel-based alloys in the fields of oil extraction, chemical equipment, new energy, etc. in my country has basically formed a system. In the equipment manufacturing process, the selection of materials for different use environments has also been basically finalized. However, with the rapid development of technology in various fields and the increase in cost pressure, in order to improve production efficiency, reduce production costs, increase service temperature, and large-scale equipment has gradually become a feature of technological renewal in various fields. Especially in the field of new energy, the trend of large-scale equipment in nuclear power and solar power generation is particularly obvious. In large-scale equipment, plates are the material with the highest proportion, generally reaching about 2 / 3 of all materials, and the conditions for the use of materials are becoming increasingly harsh; with the large-scale equipment and the complexity of service conditions, higher requirements are put forward for the development of equipment plates. In the actual application of nickel-based alloy plates, due to the material characteristics of nickel-based alloys, my country has continued to use die casting to smelt them. The diameter of the steel ingots is generally less than 1 meter, and they all have the characteristics of small ingot shape, small unit weight, and small steel plate specifications. When continuous casting can be used for smelting, due to the limitation of the billet shape, the billet specifications are within 200mm, and the steel plate specifications and unit weight are also severely limited. The thickness of the nickel-based alloy thick plate is generally limited to less than 70mm, and the unit weight is also limited to less than 8 tons; according to the conventional composition system and production method, it can no longer fully meet the requirements of existing equipment for large specifications and large unit weights.

[0004] Through searching, it is found that the research on ultra-thick steel plates is concentrated in the field of carbon steel, while there is currently less research on technical problems such as smelting and processing of nickel-based alloy large unit weight ultra-thick steel plates; a large number of technologies are concentrated on nickel-based alloy composite plates, such as in patents such as CN200610054330, CN1213009, etc., whose composition characteristics are all added with a relatively high content of Al 1.5~7.5wt%, and at the same time, a certain content of W is partially added to improve high temperature strength and oxidation performance, but this type of alloy has a complex composition and high alloy content, which is easy to cause element segregation and cannot be prepared into large ingots. If it is made into steel plates, the unit weight is generally small, not exceeding 8 tons. At the same time, this type of alloy has a large deformation resistance and cannot produce wide and large-size steel plates.

[0005] It can be seen that at present, high-temperature resistant alloy materials have small ingots, whether produced by vacuum smelting or electric arc furnace, due to the characteristics of composition design. It is unable to meet the requirements of large-scale equipment for large-scale batch production of plates. Even some steels produced by continuous casting are limited by the specifications of continuous casting billets and cannot produce ultra-thick plates. Therefore, at present, nickel-based alloys generally have the problem of ingot shape and specifications not matching. At the same time, the gradually deteriorating use conditions also make the commonly used heat-resistant nickel-based alloys have the problem that the high temperature resistance of the material cannot meet the use temperature and other conditions. Summary of the invention

[0006] In view of the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a nickel-based alloy hot-rolled thick plate and a preparation method thereof, which is achieved through composition design and smelting by an electric arc furnace + refining method, followed by homogenization annealing, forging, rolling strategy with alternating small deformation and large deformation, and heat treatment, thereby finally obtaining a nickel-based alloy hot-rolled thick plate with high temperature resistance and large unit weight. While improving the yield rate and saving production costs, it also has a positive practical effect on the supply capacity of large-size nickel-based alloy hot-rolled thick plates.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] The first aspect of the present invention provides a nickel-based alloy hot-rolled thick plate, which includes the following components in weight percentage: C: 0.05-0.1%, Cr: 15%-30%, Al: 0.1-1.5%, Ti: 0.1-1.0%, Si≤0.3%, Mn≤0.5%, Ni: 25-40%, N: 0.02-0.04%, Zr: 0.01-0.15%, P≤0.010%, S≤0.010%, and the balance is Fe and unavoidable impurities.

[0009] Preferably, in the nickel-based alloy hot-rolled thick plate, P+S≤0.015wt%.

[0010] Preferably, the nickel-based alloy hot-rolled thick plate has a yield strength Rp at 300°C. 0.2 ≥240MPa, tensile strength Rm≥560MPa, elongation A50%>50%; and / or

[0011] The nickel-based alloy hot-rolled thick plate has a yield strength Rp at 500°C. 0.2 ≥180MPa, tensile strength Rm ≥465MPa; and / or

[0012] The nickel-based alloy hot-rolled thick plate has a yield strength Rp0.2≥120MPa and a tensile strength Rm≥230MPa at 800°C.

[0013] The second aspect of the present invention provides a method for preparing the nickel-based alloy hot-rolled thick plate as described in the first aspect of the present invention, comprising the following steps:

[0014] S1, using electric arc furnace melting, AOD refining, and die casting to obtain large ingots;

[0015] S2, subjecting the large steel ingot to homogenization annealing treatment to obtain an annealed ingot; and then forging the annealed ingot to obtain a forged ingot having a thickness exceeding 300 mm;

[0016] S3, rolling the forging blank into a thick plate by adopting the rolling principle of alternating small deformation and large deformation, and then subjecting the forging blank to heat treatment and finishing to obtain the nickel-based alloy hot-rolled thick plate.

[0017] Preferably, in step S1, the weight of the large steel ingot is above 20 tons.

[0018] Preferably, in the step S2, during the homogenization annealing process, the annealing temperature is 1220-1280° C., and the annealing time is ≥48 h.

[0019] Preferably, in step S2, the forging blanking is performed by upsetting and drawing.

[0020] Preferably, in step S3, during the thick plate rolling process, the deformation amount of the first pass is 3-5%, the deformation amount of the second and third passes is 15-25%, the deformation amount of the intermediate passes is 10-15%, and the deformation amount of the final pass is 15-20%.

[0021] Preferably, in step S3, the thickness of the nickel-based alloy hot-rolled thick plate exceeds 80 mm, and the unit weight is greater than 10 tons.

[0022] The principle of composition design of the nickel-based alloy hot-rolled thick plate of the present invention is:

[0023] Cr: The alloy of the present invention is an iron-nickel based alloy. Ni is a basic element for austenitization and is very stable in an oxidizing environment. By adding a certain amount of Cr, on the one hand, Cr in the Ni-Cr austenite solid solution can greatly improve the material's oxidation resistance and gas corrosion resistance. Secondly, considering that the users of the alloy of the present invention are in a high temperature environment for a long time, the high temperature passivation film formed by Cr is very stable and can improve the oxidation resistance of the alloy surface. However, the Cr content should not be too high. If it is too high, it will affect the processing performance of the material and will cause difficulties in the production of the alloy such as rolling. Therefore, the Cr content is controlled between 15% and 30wt%.

[0024] Al: A certain amount of Al is added to the nickel-based alloy. While playing a deoxidation role, a dense Al oxide layer can be formed on the surface of the alloy under high temperature conditions. This oxide layer can prevent oxygen from diffusing into the matrix, thereby improving the stability of the Cr and Al oxide structures and further improving the oxidation resistance of the alloy. However, the amount of Al added should not be too high. When Al increases to a certain level, the processing performance of the material will be reduced, and the risk of increasing the inclusion content in the alloy will be increased. Therefore, the content of Al is controlled at 0.1-1.5wt%.

[0025] C: C in nickel-based alloys plays a vital role in improving material strength, but too high C will affect the plasticity and processing difficulty of the material, and also affect the corrosion resistance of the material, so its content is controlled within the range of 0.05 to 0.1 wt%.

[0026] Ti: A proper amount of Ti is added in the present invention. Ti is a stabilizing element. Adding a proper amount of Ti can improve the weld performance after welding through appropriate heat treatment. However, too much Ti addition will affect the material's oxidation resistance and weldability. At the same time, since a certain amount of N is added in the present invention, too much Ti will increase the content of TiN inclusions in the steel. Therefore, the Ti content is controlled at a relatively low level, and the content is between 0.01 and 1.0 wt%.

[0027] N: A certain amount of N is added in the present invention, the main purpose of which is to improve the strength of the alloy. N in austenite has a good solid solution strengthening effect and is low in price. It can play a certain role in replacing Ni and other alloy strengthening. However, the addition of N should not be too high, as it will affect the plasticity of the alloy and increase the risk of other defects in the steel. Therefore, in the present invention, its content is controlled at 0.02-0.04wt%.

[0028] Si: The content of Si element is controlled in the present invention. Although Si can also form a high-temperature oxidation layer similar to Al, its effect is much smaller than that of Al. However, excessive addition of Si will cause a sharp decline in the thermal processing and oxidation resistance of the material. At the same time, it may also form a high-temperature precipitation phase in the alloy, affecting the comprehensive performance of the material. In the present invention, it is only controlled as a trace element.

[0029] Zr: The present invention also adds a trace amount of Zr element, the addition of Zr can improve the high temperature strength of the alloy. This type of element is generally concentrated at the grain boundaries and between dendrites in the alloy. The appropriate amount of combined addition can significantly improve the high temperature strength of the material. At the same time, the addition of this type of element can improve the morphology of inclusions in the alloy, improve the overall high temperature oxidation resistance of the material, and at the same time improve the stability of the surface oxide layer, and improve the oxidation ability of the material in a dynamic oxidation environment. However, if this type of element is added in excessive amounts, the plastic toughness of the material will drop rapidly, affecting the processing performance of the material. Therefore, in the present invention, Zr is controlled within the range of 0.01 to 0.15wt%.

[0030] Other elements: The content of impurity elements such as P and S is controlled in the nickel-based alloy hot-rolled thick plate of the present invention. A higher P will greatly reduce the welding performance of the material.

[0031] The present invention has the following beneficial effects:

[0032] 1. The nickel-based alloy hot-rolled thick plate and the preparation method thereof of the present invention balance the composition ratio of the nickel-based alloy, reduce the content of high-alloy elements of conventional high-temperature resistant nickel-based alloys, improve the manufacturability of the material, and improve the oxidation resistance of the alloy matrix and the long-term use under high-temperature conditions by adding appropriate amounts of elements such as Al and Cr, so as to meet the requirements of long-term use at a temperature of 800°C; add a certain content of C and N elements to improve the material strength under high-temperature service conditions, while improving the alloy strength, avoiding the problems of difficult deformation and poor plasticity of the material caused by excessive addition, and improving the processability of the material; add trace amounts of Zr and other elements to improve the high-temperature strength and high-temperature long-lasting creep performance of the material, which can greatly improve the cyclic use performance of the material under long-term high-temperature service conditions;

[0033] 2. The preparation method of the nickel-based alloy hot-rolled thick plate of the present invention proposes a large ingot (≥1m) composition homogenization process and a large unit weight ultra-thick steel plate hot deformation process matching the large ingot, which can improve the segregation caused by the expansion of the ingot, improve the intrinsic quality and reduce the quality risk of the material in the actual use process;

[0034] 3. The preparation method of the nickel-based alloy hot-rolled thick plate of the present invention is to design the composition and adopt an electric arc furnace + refining method for smelting, and then undergo homogenization annealing, forging, thickening rolling with alternating small deformation and large deformation, and heat treatment, etc., to finally obtain a nickel-based alloy hot-rolled thick plate with high temperature resistance and large unit weight. While improving the yield rate and saving production costs, it also has positive practical significance for the supply capacity of large-size nickel-based alloy materials. DETAILED DESCRIPTION

[0035] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with embodiments.

[0036] The invention provides a nickel-based alloy hot-rolled thick plate, comprising the following components by weight percentage: C: 0.05-0.1%, Cr: 15-30%, Al: 0.1-1.5%, Ti: 0.1-1.0%, Si≤0.3%, Mn≤0.5%, Ni: 25-40%, N: 0.02-0.04%, Zr: 0.01-0.15%, P≤0.010%, S≤0.010%, and the balance is Fe and inevitable impurities. The components of the nickel-based alloy hot-rolled thick plate also meet P+S≤0.015wt%.

[0037] The yield strength Rp of the hot-rolled thick nickel-based alloy plate at 300°C is 0.2 ≥240MPa, tensile strength Rm ≥560MPa, elongation A50%>50%; the nickel-based alloy hot-rolled thick plate has a yield strength Rp at 500°C 0.2 ≥180MPa, tensile strength Rm≥465MPa; the nickel-based alloy hot-rolled thick plate has a yield strength Rp0.2≥120MPa and a tensile strength Rm≥230MPa at 800°C.

[0038] The above nickel-based alloy hot-rolled thick plate is prepared by the following method:

[0039] S1, using electric arc furnace melting, AOD refining, and die casting to obtain large ingots;

[0040] The specific process is as follows: the composition of the nickel-based alloy hot-rolled thick plate is proportioned, then smelted in an electric arc furnace, refined by AOD, and then mold-cast to obtain an ingot weighing more than 20 tons;

[0041] S2, subjecting the large steel ingot to homogenization annealing treatment to obtain an annealed ingot; and then forging the annealed ingot to obtain a forged ingot having a thickness exceeding 300 mm;

[0042] The specific process is as follows: in order to reduce the segregation of elements in the alloy, the large steel ingot needs to be homogenized annealed, wherein the annealing temperature is 1220-1280°C, the annealing time is ≥48h, and air cooling is performed to obtain an annealed ingot; then the annealed ingot is forged and blanked to obtain a forging blank with a thickness of more than 300mm, wherein the forging blank is carried out by upsetting + drawing.

[0043] S3, rolling the forging blank into a thick plate by adopting the principle of alternating small deformation and large deformation, and then subjecting the forging blank to heat treatment and finishing to obtain the nickel-based alloy hot-rolled thick plate.

[0044] The specific process is as follows: since the forged billet in step S2 is a heavy single-weight forging with a thickness of more than 300 mm, its organizational control is a difficult point in the preparation process. In order to improve the uniformity of the material, the thick plate is rolled using the rolling principle of alternating small deformation + large deformation. The requirements for deformation in the thick plate rolling process are as follows: the deformation of the first pass is 3-5%, the deformation of the second and third passes is 15-25%, the deformation of the middle pass is 10-15%, and the deformation of the last pass is 15-20%. After rolling and forming, it undergoes heat treatment, finishing and other processes to finally obtain a heavy single-weight nickel-based alloy hot-rolled thick plate with a thickness of more than 80 mm and a single weight of more than 10 tons.

[0045] The nickel-based alloy hot-rolled thick plate and the preparation method thereof of the present invention are further introduced below with reference to specific examples.

[0046] Example

[0047] Examples 1 to 4 are prepared by the preparation method of the nickel-based alloy hot-rolled thick plate of the present invention, wherein the chemical composition of the nickel-based alloy hot-rolled thick plate is shown in Table 1, the parameters in the preparation process are shown in Table 2, the mechanical properties of the nickel-based alloy hot-rolled thick plate tested by experiments are shown in Table 3; the oxidation resistance of the nickel-based alloy hot-rolled thick plate is shown in Table 4; after heat treatment, the grain size of the nickel-based alloy hot-rolled thick plate of different thicknesses is shown in Table 5.

[0048] Comparative Example

[0049] Comparative Examples 1 and 2 are high-temperature resistant nickel-based alloys of two commonly used component systems, which are equivalent to 800 series heat-resistant alloys. Their chemical compositions are shown in Table 1. The comparative examples are prepared using conventional processes, and the process parameters are shown in Table 2. The mechanical properties are shown in Table 3, and the oxidation resistance is shown in Table 4. The same heat treatment process as in Examples 1-4 is used for treatment, and the grain size of the high-temperature resistant nickel-based alloys of different thicknesses is shown in Table 5.

[0050] Table 1 Chemical composition of materials in Examples and Comparative Examples (wt%)

[0051] C Si Mn Cr Al Ti Ni Zr P S N Fe Example 1 0.05 0.1 0.2 20 0.3 0.3 28 0.10 0.010 0.002 0.03 Remain Example 2 0.06 0.2 0.2 15 0.6 1.0 38 0.10 0.008 0.01 0.02 Remain Example 3 0.05 0.3 0.5 18 1.5 0.2 40 0.03 0.008 0.005 0.025 Remain Example 4 0.10 0.3 0.4 25 1.0 0.1 25 0.02 0.005 0.002 0.04 Remain Comparative Example 1 0.06 0.5 0.5 22 0.3 0.3 32 — 0.018 0.002 — — Comparative Example 2 0.09 0.3 0.4 23 0.5 0.6 34 — 0.015 0.003 — —

[0052] Table 2 Preparation parameters in Examples and Comparative Examples

[0053]

[0054] Table 3 High temperature mechanical properties parameters of the embodiments and comparative examples

[0055]

[0056] Table 4 Antioxidation properties of alloys of Examples and Comparative Examples

[0057]

[0058] Table 5 Grain sizes of different thicknesses of the embodiments and comparative examples

[0059]

[0060] In summary, it can be seen from Tables 3-5 that although the nickel-based alloy hot-rolled thick plate prepared by the present invention is significantly thicker than the comparative steel, it still obtains comprehensive performance equivalent to the comparative steel, and has no significant difference in high-temperature tensile strength and high-temperature oxidation resistance at 800°C from the comparative steel, and is slightly higher in high-temperature strength at 300°C and 500°C than the comparative steel. At the same time, the problem of uniformity of grain size of ultra-thick hot-rolled steel plates is solved, and the grain size of the nickel-based alloy hot-rolled thick plate of the present invention at different thickness positions is equivalent to that of the comparative example.

[0061] The nickel-based alloy hot-rolled thick plate of the present invention has been successfully used in high-temperature treatment furnace components with a domestic use temperature below 800°C. Because it has excellent high-temperature oxidation resistance and long-lasting creep performance compared to existing heat-resistant nickel-based alloys, the equipment still has good service capacity after actual use. At the same time, the nickel-based alloy hot-rolled thick plate of the present invention is made into ingots through electric arc furnace + refining, which greatly improves the production yield rate compared to existing high-performance heat-resistant nickel-based alloys. At the same time, it can reduce production costs and improve production efficiency, and can provide large-size materials, which can greatly reduce the number of welds in the equipment manufacturing process and reduce manufacturing and use risks. Its successful design and development will bring huge social and economic benefits to the application of domestic high-performance special alloys.

[0062] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A nickel-based alloy hot-rolled thick plate, characterized in that: The nickel-based alloy hot-rolled thick plate comprises the following components by weight percentage: C: 0.05-0.1%, Cr: 15%-30%, Al: 0.1-1.5%, Ti: 0.1-1.0%, Si≤0.3%, Mn≤0.5%, Ni: 25-40%, N: 0.02-0.04%, Zr: 0.01-0.15%, P≤0.010%, S≤0.010%, and the balance is Fe and unavoidable impurities. In the nickel-based alloy hot-rolled thick plate, P+S≤0.015wt%, The nickel-based alloy hot-rolled thick plate is prepared by the following preparation method, comprising the steps of: S1, using electric arc furnace melting, AOD refining, and die casting to obtain large ingots; S2, subjecting the large steel ingot to homogenization annealing treatment to obtain an annealed ingot; and then forging the annealed ingot to obtain a forged ingot having a thickness exceeding 300 mm; S3, rolling the forged billet into a thick plate by adopting the rolling principle of alternating small deformation and large deformation, and then performing heat treatment and finishing to obtain the nickel-based alloy hot-rolled thick plate, wherein the nickel-based alloy hot-rolled thick plate has a yield strength Rp of 1000 g at 300°C. 0.2 ≥240MPa, tensile strength Rm≥560MPa, elongation A50%>50%; The nickel-based alloy hot-rolled thick plate has a yield strength Rp at 500°C. 0.2 ≥180MPa, tensile strength Rm≥465MPa; The nickel-based alloy hot-rolled thick plate has a yield strength Rp0.2≥120MPa and a tensile strength Rm≥230MPa at 800°C.

2. A method for preparing a nickel-based alloy hot-rolled thick plate as claimed in claim 1, characterized in that: The following steps are involved: S1, using electric arc furnace melting, AOD refining, and die casting to obtain large ingots; S2, subjecting the large steel ingot to homogenization annealing treatment to obtain an annealed ingot; and then forging the annealed ingot to obtain a forged ingot having a thickness exceeding 300 mm; S3, rolling the forging blank into a thick plate by adopting the rolling principle of alternating small deformation and large deformation, and then performing heat treatment and finishing to obtain the nickel-based alloy hot-rolled thick plate.

3. The method for preparing a nickel-based alloy hot-rolled thick plate according to claim 2, characterized in that: In the step S1, the weight of the large steel ingot is more than 20 tons.

4. The method for preparing a nickel-based alloy hot-rolled thick plate according to claim 2, characterized in that: In the step S2, during the homogenization annealing process, the annealing temperature is 1220-1280° C., and the annealing time is ≥48 hours.

5. The method for preparing a nickel-based alloy hot-rolled thick plate according to claim 2, characterized in that: In the step S2, the forging blank is performed by upsetting and drawing.

6. The method for preparing a nickel-based alloy hot-rolled thick plate according to claim 2, characterized in that: In step S3, during the thick plate rolling process, the deformation amount of the first pass is 3-5%, the deformation amount of the second and third passes is 15-25%, the deformation amount of the middle pass is 10-15%, and the deformation amount of the last pass is 15-20%.

7. The method for preparing a nickel-based alloy hot-rolled thick plate according to claim 2, characterized in that: In S3, the thickness of the nickel-based alloy hot-rolled thick plate exceeds 80 mm, and the unit weight is greater than 10 tons.

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