A method for forging sickle-shaped die forgings

Abstract

This invention belongs to the field of structural component forging, specifically relating to a method for forging sickle-shaped die forgings. By designing forging steps for the "sickle-shaped" blank and die, and using specialized tooling and molds, the manufacturing difficulty of the sickle blank is effectively reduced, the quality stability of the die is improved, and the conformity between the blank and the die forging is enhanced. This ensures that the blank can be completely placed into the die cavity, and that the die and final forging mold match well. It reduces the number of forging passes and defects such as clamping and folding during forging, improving the process from multi-pass forging to single-pass forging. This effectively solves problems such as multiple forging passes, small deformation, coarse grains in forgings, and substandard performance. Simultaneously, it significantly improves material utilization, forging qualification rate, and production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of structural component forging, specifically relating to a method for forging sickle-shaped die forgings. Background Technology

[0002] Among the structural forgings used in Chinese aircraft, rocker arms, cranks, and piston rods are often shaped like a sickle. These forgings have complex structures, often including high bosses, branches, thin webs, and other difficult-to-form structures. They also have large abrupt changes in cross-section and significant height differences. Due to these structural characteristics, the forging process for these forgings is complex, difficult to operate, and results in large dimensional deviations in the rough mold. Furthermore, the rough mold cannot be accurately placed into the cavity during the forging process, making forging difficult, resulting in low yield and low material utilization.

[0003] In actual production, for "sickle-shaped" die forgings with a head-to-bar cross-section ratio ≥3, the cross-section of the sickle part is much larger than that of the bar, and the height difference between the two parts is large, making it difficult to manufacture the rough shape of such die forgings. To meet the cross-section requirements of the sickle part, larger-sized bars are often used. During the bar lengthening process, the material needs to be divided first. When the required bar length dimension for the bar is <1 / 3 of the bar height dimension, the end of the bar is prone to concave during lengthening, resulting in folding and scrapping of the rough shape. To ensure the sickle section of the forging is fully filled, the allowance in the sickle section of the rough die is often increased, and the rough die is used to cover the entire cavity of the sickle section of the forging. This method results in extremely low material utilization, often less than 60%. Furthermore, the portion of the rough die that extends beyond the cavity is placed at the bridge section of the die. During die forging, the rough die at the bridge section is split open, forming burrs that cannot be used to fill the forging. The burrs are thin and cool quickly, leading to increased deformation resistance and making it impossible to continue forging. It is necessary to perform 2-3 more die forgings to ensure that the forging is fully filled.

[0004] In actual production, for titanium alloy forgings such as TC21 and TC18 that require β forging or near-β forging, sufficient deformation and appropriate forging temperature must be ensured. One-time die forging yields the best microstructure and properties. For ultra-high strength steels such as A-100 and 300M alloy steel, multi-stage forging with small deformation can easily lead to problems such as coarse grains and substandard performance. Summary of the Invention

[0005] Purpose of the invention: To provide a forging method for sickle-shaped die forgings, thereby improving the quality stability of the "sickle-shaped" rough mold and the pass rate of the die forgings.

[0006] Technical solution:

[0007] A method for forging a sickle-shaped die forging, wherein the cross-section of the sickle head is larger than the cross-section of the shank, the method comprising:

[0008] Step 1: Using a free forging hammer or free forging press, the bar stock is upset and shaped into a rectangular billet, wherein the cross-section of the rectangular billet is smaller than the cross-section of the sickle head and larger than the cross-section of the bar.

[0009] Step 2: Using a free forging hammer or free forging press, press the rectangular blank at a right angle to form an inclined surface to obtain the first blank; then, according to the required blank volume of the head and shaft of the sickle blank, divide the first blank along the length direction, and then lengthen the shaft position while ensuring that the transition is an inclined surface to obtain the second blank.

[0010] Step 3: Insert the second blank rod into the lower die of the mold and forge it using a free forging hammer or a free forging press. For blanks with a simple upper surface shape of the sickle head, use a pressure plate and hammer anvil to upset and unfold it to the final size of the head. For blanks with a complex upper surface shape of the sickle head, first use a pressure plate and hammer anvil to upset and unfold the second blank, and then use the upper die of the mold to press it to the final size of the head to obtain the third blank.

[0011] Step 4: Remove the third blank from the mold and use a free forging hammer or free forging press to lengthen the rod part to obtain the final desired "sickle-shaped" blank;

[0012] Step 5: Place the "sickle-shaped" blank into the heating furnace and heat and hold it at that temperature for a certain period of time. After taking it out of the furnace, quickly transfer it to the final forging die. During forging, use a hammer or press to slowly press down to position the blank, so that it moves down along the die exit slope. Then hammer or press down to obtain the final forging.

[0013] Preferably, in step two, the angle θ2 between the inclined surface pressed into the first blank and the upper end face is 135° to 180°.

[0014] Preferably, in step two, the relationship between the width b1 reserved on the upper end face of the first blank and the width b of the rectangular blank is: b1 = 1 / 3b.

[0015] Preferably, in step two, the included angle between the head and the rod of the second blank satisfies γ2: γ2=γ1±10°, where γ1 is the included angle between the head and the rod of the final desired "sickle-shaped" blank.

[0016] Preferably, in step two, the single pressing amount during the elongation process is 20-30 mm.

[0017] Preferably, in step three, the single-sided gap between the thickness δ of the second blank and the thickness δ2 of the mold opening is 10-30mm.

[0018] Preferably, in step four, the height difference Δh between the head and the rod of the final "sickle-shaped" rough shape satisfies: 2 / 3ΔH≤Δh<ΔH, γ1=γ±10°, θ1=θ±10°, where γ is the angle between the head and the rod of the forging, and γ1 is the angle between the head and the rod of the final "sickle-shaped" rough shape.

[0019] Preferably, in step four, when the billet is drawn out, the amount fed per hammer is 30-50mm, and the amount pressed down per hammer is 20-30mm.

[0020] Preferably, in step five, when forging with a press, the pressing speed is ≤5mm / s for TC18 and TC21 titanium alloys; and ≤10mm / s for A-100 ultra-high strength steel and 300M alloy steel.

[0021] Beneficial effects:

[0022] This invention, through a rationally designed "sickle-shaped" blank and die forging process, employs specialized tooling and molds to effectively reduce the manufacturing difficulty of the sickle blank, improve the quality stability of the die, and enhance the conformity between the blank and the forging. It ensures the blank can be fully placed into the mold cavity, and that the die and final forging mold match well. This reduces the number of forging passes and defects such as clamping and folding during forging, improving the process from multi-pass forging to single-pass forging. This effectively solves problems such as numerous forging passes, small deformation, coarse grains in forgings, and substandard performance. Simultaneously, it significantly improves material utilization, forging yield, and production efficiency. The method of this invention is applicable to forgings with a sickle head-to-shaft cross-section ratio ≥3. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the forging of the first blank;

[0024] Figure 2 This is a schematic diagram of the forging process for the second blank.

[0025] Figure 3 Schematic diagram of the forging process for the third blank die;

[0026] Figure 4 This is a schematic diagram of the final wasteland.

[0027] Figure 5 This is a schematic diagram of the final rough shape layout;

[0028] Figure 6 This is a schematic diagram of a rocker arm forging for a certain type of machine in the embodiment. Detailed Implementation

[0029] This invention discloses a forging method for sickle-shaped forgings, primarily applicable to forgings with a sickle head-to-shaft cross-section ratio ≥3. This method, through innovative design of the blank preparation process and the effective coordination of specialized tooling and molds, reduces the difficulty of blank preparation in existing free forging techniques, improves blank dimensional consistency and quality stability, effectively solves various quality problems arising during die forging, and increases product qualification rate and production efficiency.

[0030] like Figure 1-6 A method for forging a sickle-shaped die forging, comprising:

[0031] A rectangular billet is obtained by upsetting and shaping the bar stock using a free forging hammer or a free forging press. The cross-section of the rectangular billet is smaller than that of the sickle head and larger than that of the bar.

[0032] Using a free forging hammer or free forging press, a rectangular blank is pressed at a right angle to form a slope using special tooling to obtain the first blank; then, according to the required blank volume for the head and shaft of the sickle blank, the blank is divided along its length, and the shaft is elongated using special tooling while ensuring the slope at the transition point to obtain the second blank.

[0033] The second blank rod is inserted into the lower die of a special die and forged using a free forging hammer or a free forging press. For blanks with a simple upper surface shape of the sickle part, a pressure plate and a hammer and anvil can be used to upset and expand it to the final head size. For blanks with a complex upper surface shape of the sickle head, a pressure plate and a hammer and anvil can be used to upset and expand it to near the final head size first, and then the upper die of the die can be used to press it to the final head size. The sickle head part of the blank is upset and deformed, and the cross-section is increased. The head obtains a third blank with a shape and size that conforms to the die forging.

[0034] The third blank is removed from the mold, and the rod is lengthened using a free forging hammer or free forging press to obtain the final desired "sickle-shaped" blank.

[0035] The final blank is placed in a heating furnace and heated and held at that temperature for a certain period of time. After being taken out of the furnace, it is quickly transferred to the mold. According to the correspondence between the mold and the head and rod of the blank, the outer contour of the blank is completely placed into the lower mold cavity. The height difference between the rod and the sickle part of the blank is determined according to the depth of the sickle placed in the cavity, so that the blank is placed stably and does not tilt. During forging, the blank is first slowly pressed down by a hammer or press for positioning, so that the blank moves down along the mold exit slope. Then, it is hammered or pressed down again to obtain the final die forging.

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be further described below with reference to the accompanying drawings of the embodiments of the present invention.

[0037] For "sickle-shaped" die forgings with a ratio of ≥3 between the head and shaft sections, on the one hand, a reasonable roughing process is designed based on the required blank size and shape.

[0038] Step 1:

[0039] The round bar is flattened radially as a whole, and after forging, it becomes a rectangular blank.

[0040] Step 2:

[0041] The rectangular blank from step 1 is held by a robotic arm and placed at an angle on a special tooling 1. It is then slowly pressed down to flatten one right angle of the rectangle, ensuring the size of the upper end face b1 of the rectangular blank, thus obtaining the first blank.

[0042] The relationship between angle θ3 in special tooling 1 and angle θ2 in the first blank is θ2+θ3=180°. θ2 is generally taken between 135° and 180°. The relationship between the reserved b1 dimension on the upper end face and the width b of the rectangular blank is: b1≈1 / 3b.

[0043] Step 3:

[0044] Based on the required billet volume of the head and rod of the blank, the material is divided using a material dividing tool, and then a special tool 2 is used to slowly press down and elongate it in multiple times to ensure the slope angle γ2, so as to obtain a second blank with a blank thickness of δ2. The second blank includes two parts: the head and the rod.

[0045] The single compression amount is 20-30 mm, and γ2 = γ1 ± 10°

[0046] Step 4:

[0047] Insert the rod of the second blank into the mold cavity. First, use the pressure plate to unfold the head blank along the trend of the θ2 slope so that the lower mold of the mold is basically filled and the shape of the blank head is similar to the trend of the upper mold. Then, use the upper mold to slowly press down and shape it so that the shape of the blank head is completely consistent with the mold. Remove the blank from the mold to obtain the third blank.

[0048] The thickness of the lower mold opening is δ = δ2 + 2*(10-30) mm, and the single-sided gap between the second blank thickness δ and the mold opening thickness δ2 is 10-30 mm.

[0049] Step 5:

[0050] The final blank rod is elongated and shaped using a free forging machine with a hammer and anvil, resulting in a "sickle-shaped" final blank.

[0051] The final height difference Δh between the head and the rod of the billet satisfies 2 / 3ΔH≤Δh<ΔH.

[0052] γ1=γ±10°, θ1=θ±10°

[0053] When drawing the billet, the feed per hammer is 30-50mm, and the reduction per hammer is 20-30mm. Secondly:

[0054] The final rough shape is placed in a heating furnace and heated and held at that temperature for a certain period of time. After being taken out of the furnace, it is quickly transferred to the mold-lower mold cavity. According to the correspondence between the mold and the head and rod of the rough shape, the outer contour of the rough shape is completely placed into the lower mold cavity. The height difference Δh between the head and rod of the rough shape corresponds to the height difference ΔH between the head and rod of the forging. Among them, 2 / 3ΔH≤Δh<ΔH. There is a height difference Δh1 between the rod of the rough shape and the lower mold cavity in the height direction. In the design and actual production process, Δh1≤40mm is ensured. If Δh1 is too large, it will cause the rough shape to be too skewed when it is placed, which will affect the forming and deformation of the forging.

[0055] The forging hammer or press is slowly pressed down, so that the blank is slowly pressed into the cavity along the die's draft angle. Subsequent light blows and slow pressing can effectively ensure that the blank flows into the cavity instead of forming a lot of flash, thus obtaining the final forging.

[0056] For β-forged or near-β-forged die forgings of titanium alloys such as TC18 and TC21, ensure that the deformation of each part of the die forging is 30%-60%.

[0057] For die forgings such as A-100 ultra-high strength steel and 300M alloy steel, ensure that the deformation of each part during die forging is ≥25%, and at the same time ensure that there are no obvious defects such as clamping or folding in each part of the forging during the die forging deformation process.

[0058] The preheating temperature of the hammer, anvil, tools, and fixtures is 200-300℃.

[0059] The mold preheating temperature is 250-350℃, and the mold lubricant is water-based graphite emulsion.

[0060] When forging with a press, the pressing speed should be ≤5mm / s for titanium alloys such as TC18 and TC21, and ≤10mm / s for ultra-high strength steel such as A-100 and 300M alloy steel.

[0061] The special tooling, jigs and molds used above are all made of 5CrNiMo.

[0062] Example:

[0063] A forging for a large rocker arm of a certain type of aircraft, made of A-100 material, is characterized by a sickle-shaped die forging. The head is large, and its cross-section is much larger than that of the rod. The difference in cross-section between the head and the rod is as high as 6. A schematic diagram of the forging is shown below. Figure 6The forging head has a thickness of 194 mm, the rod thickness is 50 mm, and there is a large height difference, ΔH = 144 mm. The angle θ between the outer bevel of the head and the rod is 108°. The angle γ between the inner bevel of the head and the rod is 148°.

[0064] The design of the blank and blank forging process was carried out, and various parameters during the forging process were determined. The selected bar stock was φ200×385mm.

[0065] The billet is forged on a forging press at a temperature of 1130℃ and held at that temperature. After exiting the press, it is quickly transferred to a hammer and anvil to forge the bar stock into a rectangular billet with a thickness of 200mm.

[0066] The rectangular blank, measuring 230mm (width) and 265mm (length), is held by a robotic arm and placed at an angle on a special fixture 1. It is then slowly pressed down to flatten one right angle. The upper end face of the rectangular blank has a thickness of b1 = 80mm. The angles in the special fixture 1 are θ3 = 25° and θ2 = 165°. Based on the required volume of the blank head and rod, a material divider is used to divide the blank along its length. Then, using special fixture 2, the rod is slowly pressed down multiple times, with a single press of 20-30mm, ensuring an angle γ2 = 137°. This yields a blank with a thickness of δ2 = 200mm.

[0067] The obtained blank is reheated in the furnace at 1130℃ for a certain period of time. After being taken out of the furnace, the blank is quickly transferred and the rod part is inserted into the mold cavity. First, the head blank is spread out along the slope θ2 using a pressure plate. During the upsetting process, the lower mold of the mold is basically filled, and the shape of the blank head is similar to that of the upper mold. Then, the upper mold is used to slowly press down and shape it so that the shape of the blank head is completely consistent with the mold. The blank is taken out of the mold. The head size has met the final size requirements of the blank. The rod part of the blank is lengthened and shaped to obtain the final blank in the shape of "sickle". The thickness of the lower die opening is δ = 225 mm, and the single-sided gap between the blank thickness and the die opening thickness is 12.5 mm. The final height difference between the blank head and the rod is Δh = 115 mm, γ1 = 140°, θ1 = 109°. During drawing, the feed per hammer is 30-50 mm, and the reduction per hammer is 20-30 mm.

[0068] The final blank is placed in a heating furnace and heated to 1120℃ for a certain period of time. After being taken out of the furnace, it is quickly transferred to the mold-lower mold cavity. The outer contour of the blank is completely placed into the lower mold cavity. There is a height difference Δh1 = 20mm between the blank rod and the lower mold cavity in the height direction. The forging hammer or press is slowly pressed down so that the blank is slowly pressed into the cavity along the mold exit slope. The pressing speed is then controlled to be 8mm / s to ensure that the blank flows into the cavity instead of forming a large amount of flash, thus obtaining the final forging. During the forging process, there are no obvious defects such as clamping or folding in any part of the forging.

[0069] Forgings produced using the above methods are formed in one-fire die forging, with good filling and a 100% pass rate. The material utilization rate is high, and the final physical and chemical tests show that the forgings have a uniform structure, meet the standard requirements for performance data, and have good stability.

[0070] The preheating temperature of the hammer, anvil, tools, and fixtures is 200-300℃.

[0071] The mold preheating temperature is 250-350℃, and the mold lubricant is water-based graphite emulsion.

[0072] The special tooling, jigs and molds used above are all made of 5CrNiMo.

Claims

1. A method for forging a sickle-shaped die forging, used for die forgings with a sickle head to shank cross-section ratio ≥ 3, characterized in that, include: Step 1: Using a free forging hammer or free forging press, the bar stock is upset and shaped into a rectangular billet, wherein the cross-section of the rectangular billet is smaller than the cross-section of the sickle head and larger than the cross-section of the bar. Step 2: Using a free forging hammer or free forging press, press the rectangular blank at a right angle to form an inclined surface to obtain the first blank; then, according to the required blank volume for the head and shaft of the sickle-shaped blank, divide the first blank along the length direction, and then elongate the shaft position while ensuring that the transition is an inclined surface to obtain the second blank. The angle θ2 between the inclined surface pressed in the first blank and the upper end face is 135°~180°. The relationship between the width b1 reserved on the upper end face of the first blank and the width b of the rectangular blank is: b1=1 / 3b. The angle between the head and shaft of the second blank satisfies γ2: γ2=γ1±10°, where γ1 is the angle between the head and shaft of the final "sickle-shaped" blank. Step 3: Insert the second blank rod into the lower die of the mold and forge it using a free forging hammer or a free forging press. For blanks with a simple upper surface shape of the sickle head, use a pressure plate and hammer anvil to upset and unfold it to the final size of the head. For blanks with a complex upper surface shape of the sickle head, first use a pressure plate and hammer anvil to upset and unfold the second blank, and then use the upper die of the mold to press it to the final size of the head to obtain the third blank. Step 4: Remove the third blank from the mold and use a free forging hammer or free forging press to lengthen the rod to obtain the final "sickle-shaped" blank. The height difference Δh between the head and the rod of the final "sickle-shaped" blank satisfies: 2 / 3ΔH≤Δh<ΔH, γ1=γ±10°, where γ is the angle between the head and the rod of the forging, γ1 is the angle between the head and the rod of the final "sickle-shaped" blank, and ΔH is the height difference between the head and the rod of the corresponding forging. Step 5: Place the "sickle-shaped" rough mold into the heating furnace and heat it for a certain period of time. After taking it out of the furnace, quickly transfer it to the final forging die. During forging, use a hammer or press to slowly press down to position the rough mold, so that it moves down along the mold's draft angle. Then, hammer or press down to obtain the final forging.

2. The method according to claim 1, characterized in that, In step two, the single pressing amount during the elongation process is 20-30mm.

3. The method according to claim 2, characterized in that, In step three, the single-sided gap between the second blank thickness δ and the mold opening thickness δ2 is 10-30mm.

4. The method according to claim 3, characterized in that, In step four, when the billet is drawn out, the amount fed by each hammer is 30-50mm, and the amount pressed down by each hammer is 20-30mm.

5. The method according to claim 4, characterized in that, In step five, when forging with a press, the pressing speed should be ≤5mm / s for TC18 and TC21 titanium alloys, and ≤10mm / s for A-100 ultra-high strength steel and 300M alloy steel.

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