N10276 profiled bar and forming method thereof

Abstract

The invention relates to the technical field of high-temperature alloy materials, and provides an N10276 profiled bar and a forming method thereof.The surface of a blank is coated with a three-layer composite sheath, the blank is heated in a partitioned and gradient mode, the temperature of a side wing plate area is 50-100 DEG C higher than that of a web plate area, the metal fluidity of a side wing plate is improved, cogging rolling, four-roller reciprocating finish rolling, partitioned and gradient cooling and secondary solution treatment are conducted, and the N10276 profiled bar is obtained. A nitric acid and hydrofluoric acid mixed solution is used for pickling and stripping the composite sheath, an oxide layer is removed, intergranular corrosion is avoided, a triple sheath synergistic protection mechanism is adopted, oxygen is physically isolated by outer stainless steel, and heat loss is inhibited by a middle yttria-stabilized zirconia ceramic fiber layer.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy materials technology, specifically to an N10276 profile and its forming method. Background Technology

[0002] Nickel-based superalloy N10276 (Hastelloy C276) is widely used in irregularly shaped structural parts in aerospace, chemical equipment, and other fields due to its excellent corrosion resistance, high-temperature strength, and resistance to stress corrosion. However, it faces the following technical bottlenecks in the hot forming process of complex cross-sections: First, N10276 alloy has high resistance to high-temperature deformation and a narrow hot working window, and is extremely prone to oxidation at high temperatures. Traditional single-layer steel cladding cannot simultaneously meet the contradictory requirements of physically isolating oxygen and suppressing heat loss. Excessive cladding leads to a significant decrease in heat conduction efficiency, affecting forming accuracy; excessive thin cladding easily causes the oxide layer on the billet surface to thicken, which can easily induce intergranular corrosion defects during subsequent pickling. Second, this alloy exhibits significant uneven deformation during the forming of irregular cross-sections, especially in the side flange and web regions of convex cross-sections, where differences in geometric characteristics lead to inconsistent metal flow, easily resulting in defects such as folding and cracking. To address these issues, we propose an N10276 irregular profile and its forming method. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the present invention provides an N10276 profile and its forming method, which overcomes the shortcomings of the prior art, has a reasonable design and compact structure, and solves the problems in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for forming N10276 profiles, characterized by comprising the following steps in sequence:

[0006] (a) The surface of the billet is covered with a three-layer composite cladding: the outer layer is stainless steel, the middle layer is yttrium oxide stabilized zirconia ceramic fiber layer, and the inner layer is hexagonal boron nitride lubricating layer;

[0007] (b) The billet is heated in a zoned gradient so that the temperature of the side flange area is 50–100°C higher than that of the web area;

[0008] (c) Pre-formed convex cross section by rolling blank;

[0009] (d) Four-roll reciprocating finishing mill: including a pair of horizontal rolls and a pair of vertical rolls. The horizontal rolls are equipped with stepped grooves to control the thickness of the web and flanges. The vertical rolls are coated with tungsten carbide-cobalt coating and have rectangular grooves engraved to form double-sided flanges. The ratio of the upper roll speed to the lower roll speed is 1.2–1.5:1.

[0010] (e) After finishing rolling, the material is directly subjected to warm rolling deformation at a temperature of 600–700℃;

[0011] (f) Zoned gradient cooling: side wing plate cooling rate ≤10℃ / s, web plate cooling rate ≥50℃ / s;

[0012] (g) Secondary solution treatment at 1100–1120℃;

[0013] (h) The composite sheath was peeled off by acid washing with a mixture of nitric acid and hydrofluoric acid, with a hydrofluoric acid concentration ≤5 vol%.

[0014] Preferably, in step (a), the thickness of the ceramic fiber layer is 0.2±0.03 mm, and the thickness of the hexagonal boron nitride layer is 0.05±0.01 mm.

[0015] Preferably, in step (d), the vertical roller rectangular groove is embedded with an optical fiber temperature sensor, which is linked to the hydraulic servo system to dynamically adjust the roller gap within 10ms.

[0016] Preferably, in step (f), the cooling rate of the web plate is ≥50℃ / s, and the cooling rate of the side wing plate is ≤5℃ / s.

[0017] Preferably, after step (g), sandblasting is performed to make the surface roughness Ra ≤ 1.6 μm.

[0018] Preferred, including:

[0019] Horizontal roller: The working surface is provided with stepped grooves, and the shoulder angle of the grooves is 30°–45°;

[0020] Vertical roller: The working surface is laser-coated with a tungsten carbide-cobalt coating and has a rectangular groove with a depth of 1.1–1.3 times the height of the side wing plate.

[0021] Preferably, the inclination angle of the groove wall of the rectangular groove of the vertical roller is 5°–8°.

[0022] Preferred, including:

[0023] One-piece central web, upper web and double-sided extended wing plates;

[0024] M6C type carbide particles are diffusely distributed at the root of the flank plate;

[0025] The web region contains high-density nanotwins;

[0026] The matrix is ​​a fully austenitic structure with a grain size ≥ 7.

[0027] The difference in yield strength between the side flanges and the web is ≤15%.

[0028] Preferably, the ends of the side wing plates are chamfered.

[0029] This invention provides an N10276 profile and its forming method. It has the following beneficial effects:

[0030] 1. A triple-layer protective mechanism: the outer stainless steel layer physically isolates oxygen, the middle yttrium oxide stabilized zirconia ceramic fiber layer inhibits heat loss, and the inner hexagonal boron nitride layer generates a liquid B2O3 lubricating film at high temperature, which completely solves the contradiction between high-temperature oxidation and heat conduction efficiency, avoids intergranular corrosion during acid pickling, and improves the surface quality of the finished product.

[0031] 2. Gradient heating: the side plates are 50–100°C hotter than the web plates to optimize metal flow and eliminate folding cracks.

[0032] 3. Four-roll synergistic rolling: The stepped grooves of the horizontal rolls precisely distribute the web / flange thickness, and the rectangular grooves of the vertical rolls with tungsten carbide-cobalt coating suppress steel sticking. The upper roll speed is higher than the lower roll speed, and shear strain is introduced to refine the grains.

[0033] 4. Zoned gradient cooling: The web plate is cooled at ≥50℃ / s to form high-density nanotwins, while the side plates are cooled at ≤5℃ / s to promote the dispersion and precipitation of M6C carbides, thus achieving "strengthening and toughening of the web plate + wear resistance of the side plates". Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0035] Figure 2 This is a schematic diagram of the profile of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, what is described is only a part of this invention, not all of it. All other works obtained by those skilled in the art based on this invention without inventive effort are within the scope of protection of this invention.

[0037] See attached document Figures 1-2 A method for forming N10276 profiles, characterized by comprising the following steps in sequence:

[0038] (a) The billet surface is coated with a three-layer composite cladding: the outer layer is stainless steel to physically isolate oxygen, the middle layer is a yttrium oxide-stabilized zirconia ceramic fiber layer to reduce heat loss, and the inner layer is a hexagonal boron nitride lubricating layer. A liquid B2O3 lubricating film is generated at high temperature;

[0039] (b) The billet is heated in a zoned gradient so that the temperature of the side flange area is 50–100°C higher than that of the web area, thereby improving the metal fluidity of the side flange.

[0040] (c) Roll out the blank to form a pre-shaped convex cross section and establish the basic outline;

[0041] (d) Four-roll reciprocating finishing mill: includes a pair of horizontal rolls and a pair of vertical rolls. The horizontal rolls are equipped with stepped grooves to control the thickness of the web and flanges and to accurately distribute the deformation. The vertical rolls are coated with tungsten carbide-cobalt coating and have rectangular grooves engraved to form double-sided flanges to suppress high-temperature steel adhesion. The ratio of the upper roll speed to the lower roll speed is 1.2–1.5:1, which applies shear strain to the side flanges.

[0042] (e) After precision rolling, warm rolling deformation is performed directly at a temperature of 600–700℃ to induce nano-precipitates;

[0043] (f) Zoned gradient cooling: The cooling rate of the side plate is ≤10℃ / s to promote the precipitation of M6C carbides, and the cooling rate of the web plate is ≥50℃ / s to form nanotwins.

[0044] (g) Secondary solution treatment at 1100–1120℃ to eliminate residual stress and suppress σ phase;

[0045] (h) Use a mixture of nitric acid and hydrofluoric acid to pickle and peel off the composite coating. The concentration of hydrofluoric acid is ≤5 vol%. Remove the oxide layer and avoid intergranular corrosion.

[0046] Furthermore, in step (a), the thickness of the ceramic fiber layer is 0.2±0.03mm, and the thickness of the hexagonal boron nitride layer is 0.05±0.01mm, thereby optimizing the heat insulation and lubrication effects.

[0047] Furthermore, in step (d), an optical fiber temperature sensor is embedded in the rectangular groove of the vertical roller to monitor the temperature rise during deformation in real time, and the hydraulic servo system is linked to dynamically adjust the roller gap within 10ms to control dimensional accuracy.

[0048] Furthermore, in step (f), the cooling rate of the web is ≥50℃ / s to maximize the twin density, and the cooling rate of the side wing is ≤5℃ / s to increase the M6C particle size to 50nm.

[0049] Further, after step (g), sandblasting is performed to make the surface roughness Ra ≤ 1.6 μm.

[0050] Furthermore, including:

[0051] Horizontal roller: The working surface is provided with stepped grooves, and the shoulder angle of the grooves is 30°–45° to match the transition requirements of the flange;

[0052] Vertical roller: The working surface is laser-coated with tungsten carbide-cobalt coating to improve wear resistance and life, and rectangular grooves are opened with a groove depth of 1.1–1.3 times the height of the side wing plate to ensure complete metal filling.

[0053] Furthermore, the inclination angle of the rectangular groove wall of the vertical roller is 5°–8°, which facilitates demolding.

[0054] Furthermore, the central web, upper web, and double-sided extended wing plates are integrally formed;

[0055] M6C type carbide particles with a size ≤50nm are dispersed at the root of the side wing plate to improve wear resistance;

[0056] The web region contains high-density nanotwins, with a twin boundary density ≥ 5 × 10⁻⁶. 4 m -1 Increase strength;

[0057] The matrix is ​​a fully austenitic structure with a grain size ≥ 7 according to ASTM standards;

[0058] The difference in yield strength between the side flanges and the web is ≤15%, ensuring uniform performance.

[0059] Furthermore, the ends of the side wing plates are chamfered to avoid stress concentration during assembly.

[0060] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0061] The above description is only used to illustrate the technical solutions of the present invention, and is not intended to limit them. Although the present invention has been described in detail with reference to the foregoing, those skilled in the art should understand that modifications can still be made to the foregoing technical solutions, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for forming N10276 profiles, characterized in that... The steps are as follows: (a) The surface of the billet is covered with a three-layer composite cladding: the outer layer is stainless steel, the middle layer is yttrium oxide stabilized zirconia ceramic fiber layer, and the inner layer is hexagonal boron nitride lubricating layer; (b) The billet is heated in a zoned gradient so that the temperature of the side flange area is 50–100°C higher than that of the web area; (c) Pre-formed convex cross section by rolling blank; (d) Four-roll reciprocating finishing mill: including a pair of horizontal rolls and a pair of vertical rolls. The horizontal rolls are equipped with stepped grooves to control the thickness of the web and flanges. The vertical rolls are coated with tungsten carbide-cobalt coating and have rectangular grooves engraved to form double-sided flanges. The ratio of the upper roll speed to the lower roll speed is 1.2–1.5:

1. (e) After finishing rolling, the material is directly subjected to warm rolling deformation at a temperature of 600–700℃; (f) Zoned gradient cooling: side wing plate cooling rate ≤10℃ / s, web plate cooling rate ≥50℃ / s; (g) Secondary solution treatment at 1100–1120℃; (h) The composite sheath was peeled off by acid washing with a mixture of nitric acid and hydrofluoric acid, with a hydrofluoric acid concentration ≤5 vol%.

2. The method according to claim 1, characterized in that: In step (a), the thickness of the ceramic fiber layer is 0.2±0.03 mm, and the thickness of the hexagonal boron nitride layer is 0.05±0.01 mm.

3. The method according to claim 1, characterized in that: In step (d), an optical fiber temperature sensor is embedded in the rectangular groove of the vertical roller, and the hydraulic servo system is linked to dynamically adjust the roller gap within 10ms.

4. The method according to claim 1, characterized in that: In step (f), the cooling rate of the web plate is ≥50℃ / s, and the cooling rate of the side wing plate is ≤5℃ / s.

5. The method according to claim 1, characterized in that: After step (g), sandblasting is performed to make the surface roughness Ra ≤ 1.6 μm.

6. A roll assembly for implementing the method of any one of claims 1–5, characterized in that… include: Horizontal roller: The working surface is provided with stepped grooves, and the shoulder angle of the grooves is 30°–45°; Vertical roller: The working surface is laser-coated with a tungsten carbide-cobalt coating and has a rectangular groove with a depth of 1.1–1.3 times the height of the side wing plate.

7. The roll assembly according to claim 6, characterized in that: The inclination angle of the rectangular groove wall of the vertical roller is 5°–8°.

8. An N10276 irregular material, prepared by any one of claims 1-5, characterized in that... Include: One-piece central web, upper web and double-sided extended wing plates; M6C type carbide particles are diffusely distributed at the root of the flank plate; The web region contains high-density nanotwins; The matrix is ​​a fully austenitic structure with a grain size ≥ 7. The difference in yield strength between the side flanges and the web is ≤15%.

9. The profile according to claim 8, characterized in that: The ends of the side wing plates are chamfered.

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