Method for forming a large diameter disc from a cast slab by multi-roll calendering

Abstract

The present application relates to a kind of forming method of casting billet multi-roller swing roller integral forming super-large diameter disc piece, comprising the following steps: S1, obtaining casting billet;S2, casting billet is transferred to heating furnace, and heated in the forging temperature interval interval, so that the temperature of casting billet is homogenized;S3, casting billet is transferred to multi-roller swing roller equipment, casting billet is revolved with lower mould under the action of rotating lower mould, and lower mould is driven along the axial direction under the action of sliding beam, and revolves around its own axis under the action of workpiece friction force, so that casting billet generates continuous local plastic deformation, and then height is reduced, diameter is expanded, and disc piece is obtained;S4, disc piece after axial rolling forming is heat treated and modulated.The present application has the characteristics of small equipment tonnage, short process flow, material and energy saving and the like, and the super-large diameter metal disc piece integrally formed using the method has complete metal streamline, uniform structure and good mechanical properties, and can meet the needs of large nuclear power, deep sea exploration, petrochemical and other pressure vessels with high safety grade.

Description

Technical Field

[0001] This invention relates to the field of manufacturing ultra-large diameter disks integrally formed from cast billets, and more specifically, to a forming method for integrally forming ultra-large diameter disk parts from cast billets using multi-roll rolling. Background Technology

[0002] Ultra-large diameter (greater than 8m) metal disks are critical structural components in major fields such as large-scale nuclear power plants and deep-sea exploration. High-quality ultra-large diameter metal disks can ensure the long-term stable operation of heavy and large equipment under harsh conditions such as heavy loads, impacts, high and low temperatures, corrosion, and radiation, thereby improving the safety and reliability of the equipment. Currently, metal disks with diameters greater than 8m are manufactured by welding and assembly; there is no method for integrally forming ultra-large diameter metal disks, which cannot meet the high safety requirements. For example, the ultra-large diameter stainless steel disks required for large-scale nuclear power equipment weigh approximately 63 tons. Considering manufacturing losses, steel ingots weighing over 90 tons are needed, requiring extremely large forging machines and multiple heating of the blanks, resulting in significant material and energy losses.

[0003] In the process of forming large-diameter disc parts using a single-roll oscillating mill, eccentric loading occurs, and the larger the disc part, the more pronounced the eccentric loading. The cone roller angle of the upper die in a single-roll oscillating mill is relatively small (3°–5°). When the formed disc part is thin, warping occurs at the anti-symmetrical area of ​​the rolling zone, making it difficult to form axially thin-walled disc parts. For these two reasons, single-roll oscillating mills are unsuitable for / unable to form large-diameter disc parts. Summary of the Invention

[0004] The technical problem to be solved by this invention is to propose a method for integral forming of ultra-large diameter disks using multi-roller oscillating casting. The ultra-large diameter metal disks integrally formed by this method have complete metal flow lines, uniform structure, and good mechanical properties, which can meet the high safety level requirements of pressure vessels in large nuclear power plants, deep-sea exploration, petrochemical plants, and other applications.

[0005] The technical solution adopted by this invention to solve its technical problem is: a forming method for integrally forming ultra-large diameter disc parts by multi-roll rolling of cast billets, comprising the following steps:

[0006] S1. Obtain the casting billet;

[0007] S2. Transfer the billet to the heating furnace and heat and hold it within the forging temperature range to make the overall temperature of the billet uniform.

[0008] S3. Transfer the billet to the multi-roller rolling equipment. Under the action of the rotating lower mold, the billet revolves around the central axis of the main shaft together with the lower mold. The upper mold moves downward along the axis under the drive of the sliding crossbeam and rotates around its own axis under the action of the workpiece friction force, so that the billet produces continuous local plastic deformation, thereby reducing the height and increasing the diameter to obtain a disc part.

[0009] S4. The axially rolled disc part is heat-treated and tempered.

[0010] According to the above scheme, the billet material is carbon steel, stainless steel, aluminum alloy or titanium alloy.

[0011] According to the above scheme, in step S1, vacuum induction and vacuum arc melting are used to obtain the casting billet.

[0012] According to the above scheme, in step S2, after the edge temperature of the billet is cooled to the forging temperature range of the billet material, it is transferred to a heating furnace for heating and heat preservation, and the heating and heat preservation time is 1 to 5 hours.

[0013] According to the above scheme, in step S3, the friction conditions between the mold and the workpiece, the feed speed of the tapered roller, the rotation speed of the lower mold, and the initial dimensions of the disc workpiece need to meet the following matching conditions:

[0014]

[0015] In the formula, μ1 is the friction coefficient between the upper mold and the workpiece, μ2 is the friction coefficient between the lower mold and the workpiece, v is the feed speed of the upper mold, n is the rotation speed of the lower mold, and R0 is the initial diameter of the workpiece.

[0016] According to the above scheme, the following forging conditions must be met for the billet to achieve full forging penetration:

[0017]

[0018] In the formula, H0 is the initial height of the workpiece.

[0019] According to the above scheme, the heat treatment and tempering processes for different materials are all within the optimal heat treatment process range. For example, the quenching temperature for SA508Gr.3N stainless steel disc parts used in nuclear power is selected to be 850~925℃, and the tempering temperature is 635~665℃.

[0020] The forming method for integrally forming ultra-large diameter disc parts by multi-roll rolling of cast billets according to the present invention has the following beneficial effects:

[0021] 1. This invention can realize the integrated forming of multi-roll rolling and heat treatment of ultra-large cast billets in a short process. During the axial rolling process of multi-roll rolling, the initial defects of the cast billet can be forged together, the metal density of the cast billet can be improved, the grain size of the cast billet can be refined, and the microstructure and properties of the disc parts formed by multi-roll rolling can be improved.

[0022] 2. This invention saves labor and solves the problem that nearly 90 tons of cast billets cannot be integrally forged into disc-shaped parts. During the axial rolling and forming process of the cast billet using multi-roller oscillating milling, the initial defects of the cast billet can be forged together, improving the metal density of the cast billet and refining the grain size of the cast billet.

[0023] 3. The method of this invention involves cooling the billet to the forging zone temperature and then transferring it to a heating furnace for heat preservation. The diameter of the disc part, after being axially expanded by a multi-roller mill, is then subjected to heat treatment and tempering. This shortens the workpiece cooling and heating process, saving materials and energy. The ultra-large diameter disc part formed by this method has complete metal flow lines, uniform structure, and good overall mechanical properties.

[0024] 4. This invention features small equipment tonnage, short process flow, and saving of materials and energy. The ultra-large diameter metal disc parts integrally formed using this method have complete metal flow lines, uniform structure, and good mechanical properties, which can meet the high safety level requirements of pressure vessels in large nuclear power plants, deep-sea exploration, petrochemical plants, and other applications. Attached Figure Description

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0026] Figure 1 This is a schematic diagram of the target workpiece dimensions of the present invention;

[0027] Figure 2 This is a schematic diagram of the billet dimensions of the present invention;

[0028] Figure 3 This is a schematic diagram of the casting mold of the present invention being opened;

[0029] Figure 4 This is a schematic diagram of the movement of the upper and lower dies during the workpiece forming process of the present invention;

[0030] Figure 5 This is a schematic diagram of the workpiece after forming according to the present invention;

[0031] Wherein: 1 is the sliding crossbeam, 2 is the casting billet, 3 is the lower mold, 4 is the conical roller 1, 5 is the conical roller 2, 6 is the conical roller 3, 7 is the conical roller 4, 8 is the conical roller 5, and 9 is the finished product. Detailed Implementation

[0032] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] Example 1

[0034] A method for integrally forming an ultra-large diameter disk from a multi-roller oscillating casting billet includes the following steps:

[0035] S1. Billet Preparation: Melting is carried out using vacuum induction and vacuum arc melting technologies, resulting in billet dimensions as shown in the figure. Figure 2 As shown.

[0036] S2. Heating and holding the billet: Transfer the billet 2 to the heating furnace and heat and hold it within the forging temperature range to make the overall temperature of the billet uniform.

[0037] S3. Multi-roller rolling and forming: The billet 2 is transferred to the lower mold 3. Under the action of the rotating lower mold 3, the billet 2 revolves around the central axis of the main shaft along with the lower mold. The upper mold moves downward along the axis under the drive of the sliding beam 1. At the initial moment, the conical rollers 5, 6, and 7 are in contact with the billet 2. Under the action of the friction force of the billet 2, these three conical rollers rotate around their own axis, causing the billet to undergo continuous local plastic deformation. As the diameter of the billet gradually increases, the conical rollers 4 and 8 also participate in the rolling of the billet, thereby reducing the height of the billet and increasing its diameter, thus obtaining the finished product 9.

[0038] S4. Heat treatment and conditioning: The finished product 9 is subjected to heat treatment and conditioning to obtain a disc part with good comprehensive mechanical properties.

[0039] After the above steps, the large-diameter disc part is formed by multi-roll rolling of the cast billet.

[0040] Furthermore, depending on the requirements of ultra-large diameter disc components, different alloy compositions can be configured. For example, casting stainless steel billets can be used to form ultra-large diameter stainless steel discs integrally using multi-roll rolling, which are applied to the end plates and heads of nuclear power pressure vessels—core components of large-scale nuclear power nanocooled fast reactors. Casting aluminum alloy billets can be used to form ultra-large diameter aluminum alloy discs integrally using multi-roll rolling, which are applied to fuel tanks of medium and large rockets. Casting titanium alloy billets can be used to form ultra-large diameter titanium alloy discs integrally using multi-roll rolling, which are applied to gas turbine disks in ships.

[0041] Furthermore, the friction conditions between the multi-roller oscillating die and the workpiece, the feed speed of the tapered roller, the rotation speed of the lower die, and the initial dimensions of the disc workpiece need to meet the matching condition (1):

[0042]

[0043] In the formula, μ1 is the friction force between the upper mold and the workpiece, μ2 is the friction force between the lower mold and the workpiece, v is the feed speed of the upper mold, n is the rotation speed of the lower mold, and R0 is the initial diameter of the workpiece.

[0044] Furthermore, the forging penetration condition needs to be met:

[0045]

[0046] In the formula, H0 is the initial height of the workpiece.

[0047] Furthermore, in order to produce ultra-large diameter disc parts with good overall mechanical properties, the heat treatment and tempering process needs to select appropriate and reasonable heat treatment process parameters according to different metal materials.

[0048] Example 2

[0049] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0050] This invention provides a method for integrally forming an ultra-large diameter disk from a multi-roller oscillating casting billet. Using the latest generation of SA508Gr.3N steel for nuclear power pressure vessels as the material, and taking an ultra-large diameter stainless steel disk with a diameter of 10 mm and a thickness of 100 mm as the research object, the method is illustrated using a scaled-down test (reduction ratio 1:20, i.e., disk diameter 500 mm, thickness 5 mm, diameter / thickness equal to 100). The method includes the following steps:

[0051] S1. Slab: A stainless steel slab with a diameter of 250mm and a thickness of 40mm is cast according to the chemical composition of SA508Gr.3N steel.

[0052] S2. Heating and holding the billet: After the casting is shaped, it is transferred to a heating furnace for heating and holding. The heating and holding temperature is set at 1150℃ and held for 1 hour to make the overall temperature of the billet uniform.

[0053] S3. Multi-roller oscillating rolling forming: The billet is transferred to a multi-roller oscillating rolling machine. Under the action of the rotating lower die, the billet revolves around the central axis of the main shaft along with the lower die. The rotation speed of the lower die is 100 r / min. The upper die moves downward along the axis under the drive of the sliding crossbeam, with a feed speed of 1 mm / s. The conical roller rotates around its own axis under the action of the workpiece friction, causing continuous local plastic deformation of the billet, thereby reducing its height and increasing its diameter to obtain a disc part with a diameter of 500 mm and a thickness of 5 mm.

[0054] S4. Heat treatment modulation: The quenching temperature of the formed disc part is controlled at 850-925℃ and the tempering temperature is 635-665℃ to obtain a better strength and toughness match.

[0055] After the above steps, the integral forming of the stainless steel disc part by multi-roll rolling of the billet was completed, and a stainless steel disc part with good comprehensive mechanical properties was obtained.

[0056] In this embodiment, the several conical rollers of the multi-roller oscillating roller are symmetrically distributed on both sides of the center line of the main shaft of the equipment, which greatly reduces the eccentric load phenomenon during the forming process. This makes it possible to significantly reduce the eccentric load phenomenon during the forming process when forming large-diameter disc workpieces, and therefore it can be used to form ultra-large diameter disc workpieces.

[0057] The multi-roller conical rollers have a relatively large inclination angle, which is 45° in this embodiment. During the forming process of the disc workpiece, the multiple conical rollers of the upper die will rotate under the friction force of the disc workpiece, making it less likely for warping to occur in the anti-symmetrical region of the rolling zone, i.e., the active deformation zone, even when the workpiece is thin. When forming a large-diameter disc workpiece, due to its large size, the heat dissipation rate after heating to the forging temperature range is relatively slower compared to small workpieces, allowing sufficient time for hot working.

[0058] In this embodiment, the intermediate tapered roller needs to be located at the center of the main shaft's central axis. This is to ensure that the entire area of ​​the disc is rolled, so that defects in the central area of ​​the casting are also forged. If it is not located at the center, the central area will not be rolled by any of the tapered rollers, and the defects in the central area will not be healed during the forging process.

[0059] In summary, the method of this invention involves transferring the cast billet after casting and shaping to a heating furnace for heating and heat preservation, then transferring the billet to a multi-roller rolling mill for axial rolling and shaping, and finally heat-treating and tempering the formed disc part. This method can forge and eliminate initial defects in the billet during the multi-roller rolling process, improve the density of the billet metal, refine the grain size of the billet, and improve the microstructure and properties of the disc part after multi-roller rolling, resulting in ultra-large diameter disc parts with good comprehensive mechanical properties. At the same time, this method has the advantages of small equipment tonnage, short process flow, and saving materials and energy.

[0060] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for integrally forming an ultra-large diameter disk from a multi-roller oscillating casting billet, characterized in that, Includes the following steps: S1. Obtain the casting billet; S2. Transfer the billet to the heating furnace and heat and hold it within the forging temperature range to make the overall temperature of the billet uniform. S3. Transfer the billet to the multi-roller rolling equipment. Under the action of the rotating lower mold, the billet revolves around the central axis of the main shaft together with the lower mold. The upper mold moves downward along the axis under the drive of the sliding crossbeam and rotates around its own axis under the action of the workpiece friction force, so that the billet produces continuous local plastic deformation, thereby reducing the height and increasing the diameter to obtain a disc part. S4. Heat treatment and conditioning of the axially rolled disc parts. In step S3, the friction conditions between the mold and the workpiece, the feed speed of the tapered roller, the rotation speed of the lower mold, and the initial dimensions of the disc workpiece need to meet the following matching conditions: （1） In the formula, μ1 is the friction coefficient between the upper mold and the workpiece, and μ2 is the friction coefficient between the lower mold and the workpiece. v This represents the feed rate of the upper die, expressed in mm / s. n R0 is the rotational speed of the lower mold, in r / min; R0 is the initial radius of the workpiece, in mm.

2. The method for integral forming of ultra-large diameter disks from multi-roller oscillating casting billets according to claim 1, characterized in that, The billet material is carbon steel, stainless steel, aluminum alloy, or titanium alloy.

3. The method for integrally forming an ultra-large diameter disk from a multi-roller oscillating casting billet according to claim 1, characterized in that, In step S1, a casting billet is obtained by vacuum induction and vacuum arc melting.

4. The method for integrally forming an ultra-large diameter disk from a multi-roller oscillating casting billet according to claim 1, characterized in that, In step S2, after the edge temperature of the billet is cooled to the forging temperature range of the billet material, it is transferred to a heating furnace for heating and holding for 1 to 5 hours.

5. The method for integrally forming an ultra-large diameter disk from a multi-roller oscillating casting billet according to claim 1, characterized in that, The following forging conditions must be met for the billet to achieve full forging penetration: （2） In the formula, H0 is the initial height of the workpiece, in mm.

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