Forging Method for Hollow Shaft Forgings with Flanges at Both Ends

Abstract

The present invention relates to a forging method of a hollow shaft forging with flanges at both ends, belonging to the technical field of forging, and includes the following steps: S1, pre-treating the steel ingot; S2, upsetting and punching; S3, primary hole expanding: heating the blank after upsetting and punching to 1150-1250 °C and holding for 4-8 h to expand the inner hole of the heated blank; S4, primary drawing: heating the blank after primary hole expanding to 1000-1200 °C and holding for 4-8 h to draw the heated blank until the outer diameter of the blank is equal to the process requirement outer diameter of the flange; S5, forging the flanges and the concave grooves: heating the blank after primary drawing to 1000-1200 °C and holding for 4-8 h, and then forging the flanges at both ends and the middle concave grooves; S6, drawing-hole expanding forging: heating the blank after primary forging to 1000-1150 °C and holding for 3-6 h, then first drawing the middle concave groove to make the outer diameter of the concave groove the process requirement size, and then expanding the inner diameter of the blank to the process requirement size to obtain the finished product. The present invention can avoid the phenomenon of concave center and improve the product quality.

Description

Technical Field

[0001] The invention relates to the technical field of forging, and in particular to a forging method of a hollow shaft forging with flanges at both ends. Background Art

[0002] With the progress of the free forging industry, shaft forgings are also developing in the direction of complex shapes and fine forging, such as double flange solid shafts, single flange hollow shafts, double flange hollow shafts, etc. When forging a hollow shaft with a flange on one end, the metal flow direction is single, and the production difficulty is relatively low. The production of hollow shafts with flanges on both ends is the most difficult. The existing forging process steps of hollow shafts with flanges on both ends include removing water risers, upsetting and punching, drawing, dividing materials, drawing again, forging flanges, and producing finished products. The existing process will have the following problems during the forging process: 1. The flange surfaces at both ends are concave, which makes it very easy to have smaller sizes after subsequent processing; 2. After drawing, the inner hole of the blank is locked with the core rod, and the forging cannot be removed; 3. Coarse grains often occur during ultrasonic testing of forgings. Summary of the invention

[0003] In order to solve the above problems, the present invention proposes a forging method for a hollow shaft forging with flanges at both ends, by forging to form flanges at both ends and then drawing the concave file, using the principle of minimum flow resistance to solve the concave center problem, and using step-type temperature control to solve the coarse grain problem. The specific technical scheme is as follows:

[0004] A forging method for a hollow shaft forging with flanges at both ends comprises the following steps:

[0005] S1. Take the steel ingot and pre-treat it: remove the water riser of the steel ingot to obtain a blank.

[0006] S2. Upsetting and punching: Heat the blank to 1150~1250℃, keep it warm for 15~20h, then upset and punch the heated blank.

[0007] S3. Initial hole expansion: Heat the blank after upsetting and punching to 1150~1250℃, keep it warm for 4~8h, and then expand the inner hole of the heated blank.

[0008] S4. Initial drawing: Heat the blank after the initial hole expansion to 1000~1200℃, keep it warm for 4~8h, and then draw the heated blank until the outer diameter of the blank is equal to the outer diameter required by the flange process.

[0009] S5. Forging flanges and recessed blocks: Heat the blank after the initial drawing to 1000~1200℃, keep it warm for 4~8h, draw the middle part of the blank after indentation and separation, and form flanges at both ends and preliminary recessed blocks.

[0010] S6. Upsetting - hole expanding forging: Heat the billet after the initial forging to 1000 - 1150 °C and hold for 3 - 6 h. Then, first upset the initial concave groove to make the outer diameter of the concave groove reach the process - required size, and then expand the inner diameter of the billet to the process - required size. The concave center of the flange surface is filled, and at the same time, the length of the concave groove reaches the process - required size to obtain the finished product.

[0011] Specifically, in S2, the diameter of the billet after upsetting is 1.25 - 2 times its length, and the punching diameter accounts for 30% - 40% of the diameter of the billet after upsetting.

[0012] Specifically, in S3, the inner diameter of the billet after the initial hole expansion is 1.5 - 2.5 times the punching size.

[0013] Specifically, in S4, the length of the billet after the initial upsetting is 1.45 - 2.5 times the length of the billet after upsetting.

[0014] Specifically, in S5, the unilateral step difference between the flange and the initial concave groove is not less than 150 mm.

[0015] Specifically, in S6, the upsetting - hole expanding forging includes the following steps:

[0016] S6.1. Insert the mandrel into the billet hole, and cooperate with the upper flat anvil and the lower V - shaped anvil to upset the initial concave groove to make the outer diameter of the concave groove reach the process - required size.

[0017] S6.2. Move the working platform of the press, expand the inner diameter of the billet to the process - required size, fill the concave center of the flange surface, and make the length of the billet reach the process - required size to obtain the finished product.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. First, forge the flange. At this time, the billet temperature is high, and the temperature of each part is uniform. The deformation resistance is small, the difference in deformation resistance in each direction of the material is small, and the consistency of each part of the deformation is good. In the upsetting - hole expanding forging, when upsetting the middle concave groove, the change in the shape of the billet causes a greater decrease in the temperature of the two - end flanges, and the deformation resistance is greater. According to the principle of the minimum resistance of metal flow, with constraints at both ends, the material will not flow towards the two - end flanges. Forging at this time can avoid the inner - concave phenomenon of the concave - groove part to the greatest extent, which is beneficial to improving the product quality. When expanding the hole, the surplus material generated by the expansion of the inner diameter will fill the concave center of the flange surface, thus eliminating the concave - center phenomenon of the flange surface.

[0020] 2. In the stage of obtaining the finished product, the combined forging of upsetting + hole expanding is adopted, which avoids the problem that the forging cannot be separated from the mandrel after being locked, and is beneficial to improving production efficiency.

[0021] 3. In each forging process, stepped temperature control is adopted, which can effectively avoid the problem of coarse grains in the forging. Brief Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 It is a schematic drawing of drawing in the drawing - out and expanding - hole forging of the present invention;

[0024] Figure 2 It is a schematic drawing of expanding hole in the drawing - out and expanding - hole forging of the present invention.

[0025] In the figure: 1. upper flat anvil; 2. lower V - shaped anvil; 3. billet; 4. mandrel; 5. mandrel support. Specific embodiments

[0026] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0027] Taking a hollow shaft with flanges at both ends with a forging flange outer diameter φ 外法 = 2300mm, a single - side flange length L1 = 600mm, an outer diameter φ of the concave part between the two flanges 凹 = 1600mm, a length L2 = 6100mm of the concave part between the two flanges, an inner diameter φ of the hollow shaft 内 = 1400mm, and a hollow shaft length L3 = 7300mm as an example, the present invention provides the following specific implementation schemes:

[0028] The forging method includes the following steps:

[0029] S1. Take an ingot and perform pre-treatment on the ingot: Select a 90T ingot made of 21CrMo10, and use a sawing machine to remove the nozzle and riser along the nozzle-riser line of the ingot to obtain a billet with dimensions of φ2000mm×3200mm.

[0030] S2. Upsetting and punching: Place the billet obtained in S1 in a gas-fired heating furnace, heat it to 1150 - 1250°C, and hold for 15 - 20h. In this embodiment, the heating temperature is 1250°C and the holding time is 18h. After the billet is taken out of the furnace, use an upsetting cover plate to upset it so that the diameter of the upset billet is 1.25 - 2 times its length. In this embodiment, the diameter of the upset billet is 2500mm and the length is 2000mm. Then perform punching, and the punching diameter accounts for 30% - 40% of the diameter of the upset billet. In this embodiment, the punching diameter is 800mm.

[0031] S3. Primary reaming: Heat the billet after upsetting and punching to 1150 - 1250°C and hold for 4 - 8h. In this embodiment, the heating temperature is 1200°C and the holding time is 8h. After the billet is taken out of the furnace, perform reaming so that the inner diameter of the billet after primary reaming is 1.5 - 2.5 times the punching size. Specifically, in this embodiment, insert a mandrel with a diameter of 750mm into the inner hole of the billet, and cooperate with a 1500mm upper flat anvil and a horse shoe to ream the inner hole diameter to 1200mm. At this time, the length of the billet is 2100mm and the outer diameter is 2600mm.

[0032] S4. Primary drawing out: Heat the billet after primary reaming to 1000 - 1200°C and hold for 4 - 8h. In this implementation, the heating temperature is 1150°C and the holding time is 7h. After the billet is taken out of the furnace, draw out the heated billet so that the outer diameter of the billet after primary drawing out is equal to the outer diameter required by the flange process. The length of the billet after primary drawing out is 1.45 - 2.5 times the length of the upset billet. Specifically, in this embodiment, insert a mandrel with a diameter of 1200mm into the inner hole of the billet, and cooperate with a 1500mm upper flat anvil and a 1500mm lower V-shaped anvil to draw out the billet length to 2900mm. At this time, the outer diameter is 2300mm.

[0033] S5. Forge the flange and the concave groove: Heat the billet after primary drawing out to 1000 - 1200°C and hold for 4 - 8h. In this embodiment, the heating temperature is 1100°C and the holding time is 5h. Form the two-end flanges and a preliminary concave groove through the following steps:

[0034] S5.1. Insert a mandrel with a diameter of 1200mm into the hole of the billet, and then perform indentation and material division according to the flange length dimension.

[0035] S5.2. The mandrel is combined with a 1500 mm upper flat anvil and a 1500 mm lower V-shaped anvil. The billet in the middle part after drawing and indentation separation is elongated to form a preliminary concave groove. At this time, the flange surfaces at both ends will show a concave center phenomenon. The unilateral step difference between the flange and the preliminary concave groove, that is, the radius difference, is not less than 150 mm. In this embodiment, the unilateral step difference between the flange and the preliminary concave groove is 250 mm. At this time, the inner hole of the forging is 1200 mm, the outer diameter of the flange is 2300 mm, the unilateral flange length is 600 mm, the outer diameter of the preliminary concave groove is 1800 mm, and the length of the preliminary concave groove is 3650 mm.

[0036] S6. Stretch-expansion forging: Heat the billet after the first forging to 1000 - 1150 °C and hold for 3 - 6 h. In this embodiment, the heating temperature is 1050 °C and the holding time is 4 h. After the billet is taken out of the furnace, stretch-expansion combined forging is carried out to obtain the finished product. As Figure 1-2 shown, the stretch-expansion forging includes the following steps:

[0037] S6.1. As Figure 1 shown, use a 1500 mm upper flat anvil 1, a mandrel 4 with a diameter of 1200 mm, and a 1400 mm lower V-shaped anvil 2. The mandrel 4 passes through the billet 3, and the upper flat anvil 1 and the lower V-shaped anvil 2 cooperate to stretch and forge the preliminary concave groove so that the outer diameter of the concave groove reaches the process requirement size. At this time, the outer diameter of the concave groove is 1600 mm and the length of the concave groove is 5900 mm.

[0038] S6.2. As Figure 2 shown, move the working platform of the press, place the mandrel 4 with the billet on the lower V-shaped anvil 2 and the mandrel support 5. The mandrel support 5 is used to balance the mandrel 4 to make it horizontal. The upper flat anvil 1 expands the whole billet so that the inner diameter of the billet reaches 1400 mm. At this time, for the concave groove part, the inner diameter expansion makes its length increase, and finally the length of the billet reaches the process requirement size; for the flange part, the inner diameter expands, and the material flows to the concave center part of the flange surface to fill the concave center. Finally, the outer diameter of the flange φ 外法 = 2300 mm, the unilateral flange length L1 = 600 mm, the outer diameter of the concave groove part between the two ends of the flange φ 凹 = 1600 mm, the inner diameter of the hollow shaft φ 内 = 1400 mm, the length of the concave groove part between the two ends of the flange L2 = 6100 mm, the length of the hollow shaft L3 = 7300 mm, and the finished product is obtained.

[0039] During the forging process of this example, the two ends of the flange are relatively flat and no concave center phenomenon occurs; and during the last forging, the problem that the inner hole would lock the mandrel and it could not be taken out, which always occurred in the past, did not happen; after forging, the waveform of the ultrasonic detection result is clear and no coarse grain problem appears.

[0040] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. Forging method of a hollow shaft forging with flanges at both ends, characterized in that: Including the following steps, S1. Take an ingot and perform pre-treatment on the ingot: remove the riser of the ingot to obtain a billet; S2. Upsetting and punching: Heat the billet to 1150 - 1250 °C and keep it warm for 15 - 20 h, then first upset the heated billet and then punch it; S3. Primary hole expansion: Heat the billet after upsetting and punching to 1150 - 1250 °C and keep it warm for 4 - 8 h, then expand the inner hole of the heated billet; S4. Primary drawing out: Heat the billet after primary hole expansion to 1000 - 1200 °C and keep it warm for 4 - 8 h, then draw out the heated billet until the outer diameter of the billet is equal to the process required outer diameter of the flange; S5. Forging the flange and the concave groove: Heat the billet after primary drawing out to 1000 - 1200 °C and keep it warm for 4 - 8 h, draw out the middle part of the billet after indentation and dividing the material to form two end flanges and a preliminary concave groove, and the unilateral step difference between the flange and the preliminary concave groove is not less than 150 mm; S6. Drawing out - hole expansion forging: Heat the billet after primary forging to 1000 - 1150 °C and keep it warm for 3 - 6 h, then insert a mandrel into the hole of the billet, and cooperate with the upper flat anvil and the lower V-shaped anvil to draw out the preliminary concave groove so that the outer diameter of the concave groove reaches the process required size; then place the mandrel with the billet on the lower V-shaped anvil and the mandrel support, and cooperate with the upper flat anvil to expand the whole billet, expand the inner diameter of the billet to the process required size, the concave center of the flange surface is filled, and at the same time make the length of the billet reach the process required size to obtain the finished product.

2. The forging method of the hollow shaft forging with flanges at both ends according to claim 1, characterized in that: In S2, the diameter of the billet after upsetting is 1.25 - 2 times its length, and the punching diameter accounts for 30% - 40% of the diameter of the billet after upsetting.

3. The forging method of the hollow shaft forging with flanges at both ends according to claim 2, characterized in that: In S3, the inner diameter of the billet after primary hole expansion is 1.5 - 2.5 times the punching size.

4. The forging method of the hollow shaft forging with flanges at both ends according to claim 3, characterized in that: In S4, the length of the billet after primary drawing out is 1.45 - 2.5 times the length of the billet after upsetting.

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