A multi-directional composite reaming forming process method for a stepped flange type forging

Abstract

This invention provides a multi-directional composite reaming forming process for stepped flange forgings, relating to the field of forging technology. The process includes the following steps: pre-drawing and blanking, upsetting, punching, integral reaming with a mandrel, mandrel-mounted lengthening, segmented alternating reaming with the mandrel, composite spinning reaming, and mandrel finishing. The composite spinning reaming includes tangential spinning and radial spinning reaming. By adopting a multi-directional, staged composite reaming forming scheme, the reaming objectives of each stage of forging are decomposed, and control dimensions for each stage are proposed. The reaming efficiency of the forged upper shaft forging is high, without problems such as "flared mouth" or "waist-pinching" at the root, and the dimensions are reasonably controlled.

Description

Technical Field

[0001] This invention belongs to the field of forging technology, specifically a multi-directional composite hole expansion forming process for stepped flange forgings. Background Technology

[0002] Stepped flange forgings are part of the hollow shaft of the mill, the cylinder of the autoclave, and the main shaft of the turbine. Their forming process is the key to the entire component.

[0003] Taking the main shaft of a water turbine as an example, the main shaft of a large water turbine usually adopts a segmented, hollow structure design, which is mainly composed of three parts: the upper shaft, the lower shaft, and the middle section. This is also the most typical and common structural design scheme.

[0004] Traditional forgings for upper shafts (stepped flange forgings) used in turbine main shafts typically employ a forging process involving ingot blanking, mandrel clamping and lengthening, and segmented reaming. However, as the specifications of upper shaft flanges increase, their flange diameter gradually increases, and the step difference between the flange and the journal in the surrounding area gradually widens (step difference ≥ 500 mm). When forgings with large step differences are reamed in segments, various defects such as "waist pinching" and root folding are easily caused. Moreover, the larger the step difference, the more obvious this phenomenon becomes when reaming in segments. In addition, when reaming flanges, due to the short flange length and thick wall, according to the law of least resistance, the length dimension increases rapidly while the diameter increases only slightly. This requires reciprocating end face flattening, resulting in extremely low forging efficiency.

[0005] In recent years, with the trend towards larger forging press equipment, the specifications of tooling and auxiliary equipment have also gradually increased. For some specifications, the upper shaft adopts a solution of steel ingot blanking - overall hole expansion - large-specification mandrel directly clamping the step - drawing out the finished product. However, this solution is mainly suitable for medium-sized segmented spindles, but it has great limitations for large segmented spindles. Due to the non-uniformity of spindle specifications and the huge inner diameter, a series of large-diameter mandrels are required, which greatly increases the manufacturing cost and does not meet the needs of green development in the manufacturing industry. In addition, with the increase in the specifications of auxiliary equipment, the operation is extremely difficult when clamping and drawing out the spindle, the safety operation risk is extremely high, and it is easier to produce uneven material distribution.

[0006] The turbine main shaft being constructed has a large step difference between the upper end flange and the journal (510mm), and the flange's outer diameter and inner diameter are large (outer diameter φ4400mm, inner diameter φ2850mm). If the steel ingot blanking-mandrel clamping and elongation-segmented reaming scheme is adopted, the segmented reaming amount will be too large, resulting in more forging cycles, lower forging efficiency, and extremely difficult dimensional control. If the steel ingot blanking-overall reaming-large-size mandrel directly clamping the step and elongating to produce the finished product is adopted, the mandrel size will be huge, doubling the investment cost. Moreover, when the upper end mandrel of this size is directly clamped to the step, the large diameter will easily lead to uneven clamping and uneven material distribution, which is not conducive to precise dimensional control and also increases the difficulty of production organization and operation. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the present invention provides a multi-directional composite cavitation forming process for stepped flange forgings, which adopts a multi-directional, staged composite cavitation forming scheme to achieve refined dimensional control.

[0008] To achieve the above technical objectives, the adopted technical solution is: a multi-directional composite reaming forming process for stepped flange forgings, comprising the following steps: pre-drawing and blanking, upsetting, punching, integral reaming with a mandrel, drawing with a mandrel clamp, segmental alternating reaming with a mandrel, composite spinning reaming, and precision finishing with a mandrel.

[0009] Composite spinning expansion includes tangential spinning expansion and radial spinning expansion;

[0010] Tangential spinning is used to expand the flange by applying pressure to the upper end face of the flange through a wide hammer. The wide hammer is fully anvil-shaped along the tangential direction of the blank, and the bottom force-bearing surface of the flange is supported by an arc. Under the action of the wide hammer and the arc support, the flange height is gradually reduced.

[0011] Radial spinning enlargement involves applying pressure to the upper face of the flange using a narrow hammer, with the narrow hammer making small infeeds along the radial direction of the blank. An arc-shaped support is placed on the bottom force-bearing surface of the flange, gradually reducing the flange height under the action of the narrow hammer and the arc support.

[0012] The specific implementation steps of the alternating segmented expansion hole using a lever are as follows: After the mandrel is lengthened, the blank is expanded in segments by applying radial pressure with a lever. The amount of pressure applied in each pass is ≤100mm. The inner diameter after expansion is equal to the inner diameter of the designed stepped flange forging.

[0013] The specific implementation steps of tangential spinning expansion are as follows: After the blank flange of the billet is expanded in sections by the lever, the upper wide hammer head applies pressure to the upper end face of the flange, the arc-shaped support pads the lower end face of the flange, and the upper wide hammer head is fully inserted into the anvil along the tangential direction of the blank. As the height of the pressure part decreases, the metal flows radially and the wall thickness gradually increases. The insertion amount is ≥ the flange wall thickness, and the pressing amount is ≤ 50mm. After each hammer press, rotate 30° and spin in turn. After spinning, the wall thickness of the blank is equal to the flange wall thickness of the designed stepped flange forging.

[0014] The specific implementation steps of radial spinning expansion are as follows: After tangential spinning expansion, the blank flange faces upward, the upper narrow hammer head applies pressure to the upper end face of the flange, the arc-shaped support pads the lower end face of the flange, and the upper narrow hammer head is placed along the radial direction of the blank with a small anvil advance. As the height of the pressure part decreases, the metal flows tangentially, causing the inner and outer diameters to increase. The anvil advance is ≤600mm, the reduction is ≤50mm, and the hammer head rotates 15° for each press. The spinning is carried out in turn. After spinning, the inner and outer diameters are equal to the inner and outer diameters of the flange of the designed stepped flange forging.

[0015] The beneficial effects of this invention are:

[0016] The process method of the present invention adopts a multi-directional, staged composite hole expansion forming scheme, decomposes the hole expansion purpose of each stage of forging, and proposes control dimensions for each stage.

[0017] During the overall hole enlargement stage of the mast, the flange diameter is reduced in a targeted manner after hole enlargement, resulting in a smaller outer diameter than that achieved by traditional hole enlargement control methods.

[0018] During the mandrel stage, because the previous hole-expanding process reduced the outer diameter after hole expansion, this process increases the length of the flange step (longer than the flange length in the forging process drawing) while ensuring the overall weight of the flange. After the mandrel is extended, the step difference between the flange and the journal is smaller, which is more conducive to subsequent segmented hole expansion and significantly reduces the waist-pinching phenomenon at the root of segmented hole expansion.

[0019] During the alternating segmented expansion stage, the increased flange length and reduced wall thickness, combined with the law of minimum resistance in metals, result in a faster radial flow rate of metal, which in turn causes the flange diameter to increase rapidly. This significantly reduces the tendency of metal to flow along the length direction, thus improving expansion efficiency. In addition, the reduced step difference allows for more reliable control of the root "pinching" phenomenon after segmented expansion.

[0020] The combination of tangential and radial spinning methods avoids a series of problems such as root "pinching", low reaming efficiency and uneven reciprocating end face when reaming due to excessive step difference. Spinning reaming can also more accurately control the dimensions of various parts of the flange, reduce the phenomenon of frequent rework in traditional forming methods, and improve the first-pass dimensional qualification rate. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the implementation process of an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the upper shaft forging of the present invention;

[0023] Figure 3 This is a schematic diagram of the mandrel clamping stage being elongated according to an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of tangential spinning according to an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of radial spinning according to an embodiment of the present invention. Detailed Implementation

[0026] A multi-directional composite reaming forming process for stepped flange forgings, taking the upper end shaft of a turbine main shaft as an example, employs the following steps: heating, pre-drawing and blanking, heating, upsetting, punching, heating, integral reaming with a mandrel, heating, mandrel clamping and drawing, heating, first-stage alternating segmented reaming with a mandrel, heating, second-stage alternating segmented reaming with a mandrel, heating, tangential spinning reaming, radial spinning reaming, finishing, and final product. The specific process is as follows: Figure 1 As shown, it includes the following steps:

[0027] Step 1, Pre-drawing and cutting: According to Figure 2 Select a 95T top-injection ingot type and pre-draw the length to Ф3500×1850mm.

[0028] Step 2, Upsetting: Upset the entire cross-section of the billet to H=1340~Ф2980mm.

[0029] Step 3, punching: Place the upset billet on the stencil and perform the punching process. The punching diameter is Ф900mm.

[0030] Step 4: Expanding the hole of the lever: After punching, the blank is rotated 90° along the axial direction and a Ф880mm lever is inserted to expand the hole. After expansion, the inner diameter is Ф1740mm and the outer diameter is Ф3380mm. The end face is flattened to H1340mm.

[0031] Step 5, mandrel clamping and elongation: according to Figure 3 After the blank is enlarged, it is inserted into a Ф1700mm water-passing mandrel. The mandrel is then used to mark the steps, with the flange section having a step length of 810mm. The mandrel then elongates the journal section to 1140mm.

[0032] Step 6, First stage of alternating expansion using levers: The lengthened billet is expanded in the first stage using alternating levers to increase the inner diameter to Ф2300mm, and then the entire end face is flattened to H1340mm.

[0033] Step 7, Second Stage Alternating Hole Expansion with Lever: The blank after the first stage alternating hole expansion with lever is expanded in the second stage alternating hole expansion with lever to expand the inner diameter to Ф2800mm, and then the overall end face is flattened to H1340mm.

[0034] Step 8, Tangential spinning to expand the hole: According to Figure 4 The blank obtained in step seven is rotated 90° axially with the flange facing upward. The upper wide hammer head is used to press the upper end face of the flange. The upper wide hammer head is inserted into the anvil along the tangential direction of the blank. Under the action of the upper wide hammer head and the lower arc support (axial pressure), as the height of the pressure part decreases, the wall thickness gradually increases. The insertion amount is ≥ the flange wall thickness, and the pressing amount is ≤ 50mm. After each hammer blow, the blank is rotated 30°. This process is repeated step by step. After the blank is pressed, the wall thickness is equal to the wall thickness of the upper end shaft flange.

[0035] Step 9, Radial Spinning Enlargement: According to Figure 5Take the billet from step eight and place it in the same direction as described above (bill flange facing upwards). Apply pressure to the upper end face of the flange with the upper narrow hammer and support the lower end face of the flange with the lower special arc-shaped support. Place the upper narrow hammer along the radial direction of the billet with a small anvil depth. Under the action of the upper narrow hammer and the lower arc support (axial pressure), as the height of the pressure area decreases, the metal flows along the tangential direction, causing the inner and outer diameters to increase. The anvil depth is ≤600mm and the pressing depth is ≤50mm. Rotate 15° for each hammer press and repeat the process step by step. After spinning, the inner and outer diameters are equal to the inner and outer diameters of the upper end shaft flange.

[0036] Step 10: Take the blank from Step 9, rotate it 90° along the axial direction, insert it into the mast, refine all parts, and produce the finished product.

[0037] Furthermore, a multi-directional composite reaming method is adopted, which includes radial segmented reaming, tangential spinning reaming, and radial spinning reaming, to achieve precise shape control in each stage of the process, improve reaming efficiency, and reduce rework rate.

[0038] Furthermore, the intermediate deformation process reduces the step difference by increasing the flange length and decreasing the flange diameter. Due to the increase in flange length and the decrease in wall thickness, combined with the law of least resistance, it can be seen that the metal flow rate along the diameter direction is fast when forming a flange by radial strut expansion, which promotes the rapid increase of flange diameter, weakens the tendency of metal to flow along the length direction, and improves the expansion efficiency. The reduction of the step difference can more effectively control the "waist pinching" phenomenon at the root of the segmented expansion.

[0039] Furthermore, employing a multi-stage spinning scheme with different anvil directions and feed rates allows for more precise control of flange dimensions. Tangential spinning expansion uses a wide upper hammer to fully distribute the anvil along the tangential direction of the blank and applies axial pressure, prioritizing ensuring the flange wall thickness meets requirements. Radial spinning expansion uses a narrow upper hammer to distribute the anvil with a small radial feed along the blank and applies axial pressure, prioritizing ensuring the flange's inner and outer diameters meet requirements. During deformation, the flange wall thickness remains essentially constant, while the inner and outer diameters increase rapidly.

Claims

1. A multi-directional composite reaming forming process for stepped flange forgings, characterized in that: The process includes the following steps: pre-drawing and blanking, upsetting, punching, overall hole enlargement by the mandrel, lengthening by the mandrel clamp, segmental alternating hole enlargement by the mandrel, compound spinning hole enlargement, and fine finishing of the mandrel. Composite spinning expansion includes tangential spinning expansion and radial spinning expansion; Tangential spinning is used to expand the flange by applying pressure to the upper end face of the flange through a wide hammer. The wide hammer is fully anvil-shaped along the tangential direction of the blank, and the bottom force-bearing surface of the flange is supported by an arc. Under the action of the wide hammer and the arc support, the flange height is gradually reduced. Radial spinning enlargement involves applying pressure to the upper face of the flange using a narrow hammer, with the narrow hammer making small infeeds along the radial direction of the blank. An arc-shaped support is placed on the bottom force-bearing surface of the flange, gradually reducing the flange height under the action of the narrow hammer and the arc support.

2. The multi-directional composite hole expansion forming process for stepped flange forgings as described in claim 1, characterized in that, The specific implementation steps of the alternating segmented expansion hole using a lever are as follows: After the mandrel is lengthened, the blank is expanded in segments by applying radial pressure with a lever. The amount of pressure applied in each pass is ≤100mm. The inner diameter after expansion is equal to the inner diameter of the designed stepped flange forging.

3. The multi-directional composite reaming forming process for stepped flange forgings as described in claim 1, characterized in that, The specific implementation steps of tangential spinning expansion are as follows: After the blank flange of the billet is expanded in sections by the lever, the upper wide hammer head applies pressure to the upper end face of the flange, the arc-shaped support pads the lower end face of the flange, and the upper wide hammer head is fully inserted into the anvil along the tangential direction of the blank. As the height of the pressure part decreases, the wall thickness gradually increases. The insertion amount is ≥ the flange wall thickness, and the pressing amount is ≤ 50mm. After each hammer blow, rotate 30° and spin in turn. After spinning, the wall thickness of the blank is equal to the flange wall thickness of the designed stepped flange forging.

4. The multi-directional composite reaming forming process for stepped flange forgings as described in claim 1, characterized in that, The specific implementation steps of radial spinning expansion are as follows: After tangential spinning expansion, the blank flange faces upward, the upper narrow hammer head applies pressure to the upper end face of the flange, the arc-shaped support pads the lower end face of the flange, and the upper narrow hammer head is placed along the radial direction of the blank with a small anvil advance. As the height of the pressure part decreases, the metal flows along the diameter direction, causing the inner and outer diameters to increase. The anvil advance is ≤600mm, the reduction is ≤50mm, and the hammer head rotates 15° for each press. The spinning is carried out in turn. After spinning, the inner and outer diameters are equal to the inner and outer diameters of the flange of the designed stepped flange forging.

Images