Hot upsetting method for blank with large height-diameter ratio

Abstract

The invention discloses a large height-diameter ratio blank hot upsetting method which comprises the following steps: S1, preparing before forging; s2, a first heating step; S3, a two-end pre-cooling step; S4, a first upsetting step; S5, a second heating step; and S6, a second upsetting step is carried out. The two ends of the blank are pre-cooled before first-time upsetting, in the first-time upsetting process, due to the fact that deformation resistance is inconsistent due to the pre-cooling temperature difference, the center of a forged material deforms firstly, in the second-time upsetting process, deformation of other parts is increased, reasonable deformation of the whole blank is finally achieved, only a common flat die is needed, and a special die is not needed; and generally, only two times of firing are needed, so that the production efficiency can be improved, and the cost can be reduced.

Description

Technical Field

[0001] The invention relates to the field of metallurgy, in particular to a hot processing technology, and more particularly to a hot upsetting method for a large aspect ratio billet. Background Art

[0002] Metal upsetting is the process of increasing the cross-sectional area of ​​the metal from small to large while decreasing its height under the action of an external force, in a direction perpendicular to the force. The die can be a flat die or a profile die. The purpose of upsetting is to prepare for the next stretching step and to achieve the desired shape and / or size.

[0003] In practice, when the aspect ratio (ratio of height to effective diameter) of the forged metal is greater than 2.5 or 3, the metal is prone to instability or double bulging. For forging metals with aspect ratios greater than 2.5 or 3, the traditional method involves simultaneous upsetting and trimming, often requiring multiple heating cycles. This wastes energy, reduces production efficiency, and requires high worker skill, making it particularly difficult to forge large-sized metals. A high aspect ratio in this invention refers to a ratio of 3 or greater.

[0004] In the existing technology, the invention patent application with publication number CN101972830A uses a combination of a mold and a flat die for upsetting. The disadvantage of this method is that it is difficult to "center" (the tip of the upper punch is aligned with the center of the "crown" of the forging blank), and there will be instability problems when the height-to-diameter ratio is close to 4. Frequent die changes (especially replacement of the upper die) affect production efficiency.

[0005] Invention patents with publication numbers CN106623718B and CN113579144B ​​respectively use dies with a convex upper portion and a concave lower portion, and dies with both upper and lower concave portions, both with ejection mechanisms. Although demolding is easy, for taller billets, placing the forged metal into the die requires a very large height clearance for the forging equipment. For longer billets (e.g., longer than 2 meters), the working height of general forging equipment is insufficient.

[0006] In the invention patent applications with publication numbers CN119407082A and CN109500334A, both the upper and lower dies adopt a concave structure. Although the required working space height is relatively low, there is no ejection structure. Once the forged metal is bonded to the die, the forging blank cannot be removed by the operating machine. At this time, the die and the blank must be reversed, padded, and then ejected, which is very troublesome to operate. Summary of the Invention

[0007] The object of the present invention is to provide a method for hot upsetting a billet with a large aspect ratio, which aims to solve the technical problem in the prior art that the forged metal is prone to instability or double drumming.

[0008] The method for hot upsetting a large aspect ratio blank of the present invention is characterized by comprising the following steps: S1, a pre-forging preparation step: first prepare the flat die, the flat die includes an upper flat die and a lower flat die, Then prepare a blank with a height of h0 and a diameter of d0, wherein the diameter d0 is 200 to 1000 mm and the height-to-diameter ratio h0 / d0 is (3 to 6):1; S2, a first heating step: heating the prepared blank to a first temperature, (blank recrystallization temperature + 200°C) ≤ the first temperature ≤ (blank melting point - 50°C), with a temperature difference between the core and the surface of the blank being less than 5°C; S3, a step of pre-cooling at both ends: immersing one end of the first heated billet into a cooling tank filled with a quenching medium for pre-cooling, then turning it 180 degrees and immersing the other end for pre-cooling, with the immersion time of each end being 2 to 20 seconds and the immersion depth of each end being (0.15 to 0.35)h0 respectively; S4, a first upsetting step: Place the pre-cooled billet on the lower flat die, then move the upper flat die downward at a speed of 3 to 10 mm / s, and press the billet down to a height of ; S5, a second heating step: heating the blank after the first upsetting to a second temperature, (the recrystallization temperature of the blank + 200°C) ≤ the second temperature ≤ (the melting point of the blank - 50°C), and the temperature difference between the core and the surface of the blank is less than 5°C; S6. A second upsetting step: placing the second heated blank on the lower flat die, moving the upper flat die, and pressing the upper flat die downward at a rate of 4 to 25 mm / s until it is pressed to the required height.

[0009] Specifically, the present invention is suitable for upsetting a billet with a diameter d0 between 200 and 1000 mm and an aspect ratio h0 / d0 between (3 and 6):1. During the first heating, the billet is heated to a recrystallization temperature of more than +200°C and a melting point of less than -50°C. The billet is heated evenly so that the temperature difference between the core and the surface of the billet is less than 5°C. Then, both ends of the billet are successively immersed in a cooling tank for pre-cooling. During the first upsetting, the temperature in the middle of the billet is higher, so the middle of the billet has a larger deformation. Then, the billet is heated again, and the second upsetting increases the deformation of the remaining parts. The billet can be pressed to a height below the large aspect ratio range, and the billet with a large aspect ratio is upset into a cake-shaped billet.

[0010] Furthermore, the material of the blank is titanium alloy, high-temperature alloy, steel or aluminum alloy.

[0011] Furthermore, in step S1, after the flat die is installed on the forging equipment, the parallelism of the upper flat die and the lower flat die is made less than or equal to 1 mm by machining; the blank is machined so that the parallelism of the upper end face and the lower end face of the blank is less than or equal to 1 mm, and the perpendicularity of the upper and lower end faces of the blank to the axis of the blank is less than or equal to 1.2 mm, and the two ends of the blank are chamfered, and the chamfer size is 10 mm × 10 mm to 40 mm × 40 mm.

[0012] Specifically, the parallelism of the upper and lower flat dies is adjusted through machining to ensure that the contact surfaces of the upper and lower flat dies and the blank are parallel, and the parallelism of the two ends of the blank and the perpendicularity of the end face of the blank to the axis are adjusted through machining, so that the blank can be pressed more accurately along the axis direction, which can further improve the stability during upsetting. The chamfering is to prevent folding or cracking at the corners of the blank during upsetting.

[0013] Furthermore, in step S2, before the blank is heated, a glass protective coating is applied on the surface of the blank with a thickness of 0.25 to 0.4 mm.

[0014] Specifically, applying glass protective paint can play a protective role, isolate the air, and prevent metal materials from oxidizing, absorbing hydrogen, and absorbing nitrogen at high temperatures; and when the blank is heated to a high temperature and transferred out of the furnace for forging, the glass protective lubricant can reduce the temperature drop of the blank, play a thermal insulation role, and the paint has a lubricating effect.

[0015] Furthermore, in step S3, the middle part of the blank is clamped from the heating furnace by the clamp of the operating machine, the jaws of the clamp are wrapped with insulation material, and then both ends of the blank are immersed in a cooling tank for pre-cooling, and the quenching medium is water or quenching oil.

[0016] Specifically, the clamps grip the middle portion of the blank to facilitate cooling of both ends, and wrapping the jaws of the clamps with insulation cotton can prevent heat loss when the blank is gripped.

[0017] Furthermore, the cooling trough is provided with a fixed-height drain pipe, the cross-sectional area of ​​the cooling trough is greater than or equal to 4 times the cross-sectional area of ​​the blank, and the quenching medium is contained in the cooling trough.

[0018] Alternatively, the cooling tank includes a quenching tank and an overflow tank opening upward, the overflow tank surrounds the quenching tank, the cross-sectional area of ​​the quenching tank is greater than or equal to 4 times the cross-sectional area of ​​the blank, and the quenching medium is contained in the quenching tank.

[0019] Specifically, one end of the blank is immersed in the bottom of a cooling tank filled with quenching medium. The overflow of the quenching medium from the cooling tank can ensure that the immersion depth of the blank is equal. The cooling tank can be provided with a fixed-height drain pipe to discharge the overflowed quenching medium; or the cooling tank is divided into a quenching tank and an overflow tank. One end of the blank is immersed in the quenching tank filled with quenching medium. The quenching medium in the quenching tank overflows into the overflow tank. The purpose of setting the overflow tank is to collect the liquid overflowing from the quenching tank; the cross-sectional area of ​​the quenching tank is greater than or equal to 4 times the cross-sectional area of ​​the blank, so that the cooling tank has sufficient quenching medium to cool both ends of the blank.

[0020] Furthermore, both step S2 and step S5 further include preheating the flat mold, and the preheating temperature of the flat mold is 250-950°C.

[0021] Specifically, preheating the flat die while heating the blank can prevent the temperature difference between the flat die and the blank from being too large during upsetting, thereby affecting the temperature of the blank.

[0022] Furthermore, in both step S4 and step S6, thermal insulation materials are used to isolate the blank and the flat mold.

[0023] Specifically, during upsetting, insulation cotton can be used to wrap the upper and lower end surfaces of the blank to reduce the impact of the flat die on the blank temperature when the temperature difference between the flat die and the blank is too large, thereby preventing the blank from cooling too quickly.

[0024] Furthermore, in the step S4, during the first upsetting, the upper flat die first presses the blank down by 50 to 200 mm at a speed of 3 to 4 mm / s, and then presses the blank down to a height of .

[0025] Furthermore, in step S6, during the second upsetting, the upper flat die first presses the blank down 50 to 150 mm at a rate of 4 to 6 mm / s, and then presses the blank down to the target height at a speed of 8 to 25 mm / s.

[0026] Specifically, at the beginning of the first upsetting and the second upsetting, the height of the blank is high and the stability is poor. The upper flat die is first pressed down for a distance at a slower rate, which is conducive to maintaining the stability of the blank. Then it is forged to the target height at a faster rate, which can improve production efficiency and prevent the blank temperature from dropping too much.

[0027] Compared with the existing technology, the present invention has a positive and significant effect. The present invention pre-cools both ends of the blank before the first upsetting. During the first upsetting, the center of the forged material deforms first due to the inconsistent deformation resistance caused by the pre-cooling temperature difference. During the second upsetting, the deformation of the remaining parts is increased, ultimately achieving reasonable deformation of the entire blank. Only common flat dies are required, no special dies are required, no die changes are required, and there are no demolding difficulties. Generally, only two upsettings are required, which can improve production efficiency and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the upsetting process of the present invention.

[0029] Markings in the figure: 1, blank; 2, cooling tank; 201, quenching tank; 202, overflow tank; 3, flat die; 301, upper flat die; 302, lower flat die. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and examples, but the present invention is not limited thereto. Example 1

[0031] A method for hot upsetting TC14 bars with a large aspect ratio comprises the following steps: S1. A pre-forging preparation step: machining the blank 1 to a height h0 = 1300 mm and a diameter d0 = 320 mm (height-to-diameter ratio 4.06), with the parallelism of both ends of the blank 1 less than 0.7 mm, the perpendicularity of the end face of the blank 1 to the axis of the blank 1 less than 0.8 mm, and chamfering the ends of the blank 1 to 15 mm × 15 mm; S2, a first heating step: applying a glass protective coating to a thickness of 0.3 mm on the surface of the blank 1, then heating the blank 1 to 870°C, with the temperature difference between the core and the surface of the blank 1 being less than 5°C, and preheating the flat mold 3 to 300°C; S3, a pre-cooling step: Use the clamp of the operating machine to clamp the middle of the billet in the heating furnace, wrap the jaws of the clamp with insulation cotton, and immerse one end of the billet 1 into a cooling tank 2 filled with water with a fixed depth of 425mm. After immersion for 3 seconds, lift it up, refill the cooling tank 2 with water, and then immerse the other end. After immersion for 3 seconds, lift it up to complete the pre-cooling; S4, a first upsetting step: insulating cotton is laid on the lower flat die 302, the pre-cooled blank 1 is placed in the center of the lower flat die 302, and insulating cotton is laid on the upper end of the blank 1. The upper flat die 301 is lowered. After the upper flat die 301 is in contact with the upper end of the blank 1, the descending speed of the upper flat die 301 is adjusted to 3 mm / s. After the blank 1 is pressed down 100 mm, the descending speed of the upper flat die 301 is adjusted to 5 mm / s until the blank 1 is pressed down to a height of 925 mm, completing the first upsetting. At this time, the effective height-to-diameter ratio is 2.44; S5, a second heating step: heating the blank 1 after the first upsetting to 880°C, with the temperature difference between the core and the surface of the blank 1 being less than 5°C, and heating the flat die 3 to 300°C; S6. A second upsetting step: laying insulation cotton on the lower flat die 302, placing the blank 1 after the second heating in the center of the lower flat die 302, placing insulation cotton on the upper end of the blank 1, and lowering the upper flat die 301. After the upper flat die 301 is attached to the upper end of the blank 1, the descending speed of the upper flat die 301 is adjusted to 4 mm / s. After pressing the blank 1 down 100 mm, the descending rate of the upper flat die 301 is adjusted to 8 mm / s until the blank 1 is 320 mm high, thereby completing the entire upsetting process and obtaining a blank with a height-to-diameter ratio of approximately 0.5. Example 2

[0032] A method for hot upsetting a TC4 bar with a large aspect ratio comprises the following steps: S1. A pre-forging preparation step: machining the blank 1 to a height h0 = 2400 mm and a diameter d0 = 500 mm (height-to-diameter ratio 4.8), with the parallelism of the two ends of the blank less than 0.9 mm, the perpendicularity of the end face of the blank 1 to the axis of the blank 1 less than 1 mm, and chamfering the two ends of the blank 1 to 30 mm × 30 mm; S2, a first heating step: applying a glass protective coating to a thickness of 0.4 mm on the surface of the blank 1, then heating the blank 1 to 980°C, with the temperature difference between the core and the surface of the blank 1 being less than 5°C, and preheating the flat mold 3 to 800°C; S3, a pre-cooling step: Use the clamp of the operating machine to clamp the middle of the blank 1 in the heating furnace, wrap the jaws of the clamp with insulation cotton, and immerse one end of the blank 1 in a cooling tank 2 filled with water with a fixed depth of 600mm. After immersion for 5 seconds, lift it up, refill the cooling tank 2 with water, and then immerse the other end. After immersion for 5 seconds, lift it up to complete the pre-cooling; S4, a first upsetting step: insulating cotton is laid on the lower flat die 302, the pre-cooled blank 1 is placed in the center of the lower flat die 302, and insulating cotton is laid on the upper end of the blank 1. The upper flat die 301 is lowered. After the upper flat die 302 is in contact with the upper end of the blank 1, the descending speed of the upper flat die 301 is adjusted to 5 mm / s. After the blank 1 is pressed down 200 mm, the descending speed of the upper flat die 301 is adjusted to 8 mm / s until the blank 1 is pressed down to a height of 1510 mm, completing the first upsetting. The effective height-to-diameter ratio at this time is 2.4; S5, a second heating step: heating the blank 1 after the first upsetting to 980°C, with the temperature difference between the core and the surface of the blank 1 being less than 5°C, and heating the flat die 3 to 800°C; S6. A second upsetting step: laying insulation cotton on the lower flat die 302, placing the blank 1 after the second heating in the center of the lower flat die 302, placing insulation cotton on the upper end of the blank 1, and lowering the upper flat die 301. After the upper flat die 301 is attached to the upper end of the blank 1, the descending speed of the upper flat die 301 is adjusted to 5 mm / s. After pressing the blank 1 down 150 mm, the descending rate of the upper flat die 301 is adjusted to 10 mm / s. When the height of the blank 1 is 500 mm, the descending rate of the upper flat die 301 is adjusted to 5 mm / s again until the height of the blank 1 is 290 mm, thereby completing the entire upsetting process and obtaining a blank with a height-to-diameter ratio of approximately 0.2.

[0033] In the above two embodiments, there is no problem of upsetting failure caused by upsetting instability, double drumming, etc.

[0034] The above describes the specific embodiments of the present invention, but the present invention is not limited to the above embodiments. Any alternative modifications based on the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for hot upsetting a billet with a large aspect ratio, characterized in that: The following steps are involved: S1, a pre-forging preparation step: first prepare the flat die, the flat die includes an upper flat die and a lower flat die, Then prepare a blank with a height of h0 and a diameter of d0, wherein the diameter d0 is 200 to 1000 mm and the height-to-diameter ratio h0 / d0 is (3 to 6):1; S2, a first heating step: heating the prepared blank to a first temperature, (blank recrystallization temperature + 200°C) ≤ the first temperature ≤ (blank melting point - 50°C), with a temperature difference between the core and the surface of the blank being less than 5°C; S3, a step of pre-cooling at both ends: immersing one end of the first heated billet into a cooling tank filled with a quenching medium for pre-cooling, then turning it 180 degrees and immersing the other end for pre-cooling, with the immersion time of each end being 2 to 20 seconds and the immersion depth of each end being (0.15 to 0.35)h0 respectively; S4, a first upsetting step: Place the pre-cooled billet on the lower flat die, then move the upper flat die downward at a speed of 3 to 10 mm / s, and press the billet down to a height of ; S5, a second heating step: heating the blank after the first upsetting to a second temperature, (the recrystallization temperature of the blank + 200°C) ≤ the second temperature ≤ (the melting point of the blank - 50°C), and the temperature difference between the core and the surface of the blank is less than 5°C; S6. A second upsetting step: placing the second heated blank on the lower flat die, moving the upper flat die, and pressing the upper flat die downward at a rate of 4 to 25 mm / s until it is pressed to the required height.

2. The method for hot upsetting a billet with a large aspect ratio according to claim 1, wherein: The material of the blank is titanium alloy, high temperature alloy, steel or aluminum alloy.

3. The method for hot upsetting a billet with a large aspect ratio according to claim 1, wherein: In step S1, after the flat die is installed on the forging equipment, the parallelism of the upper flat die and the lower flat die is made less than or equal to 1 mm by machining; the blank is machined so that the parallelism of the upper end face and the lower end face of the blank is less than or equal to 1 mm, and the perpendicularity of the upper and lower end faces of the blank to the axis of the blank is less than or equal to 1.2 mm, and the two ends of the blank are chamfered, and the chamfer size is 10 mm × 10 mm to 40 mm × 40 mm.

4. The method for hot upsetting a billet with a large aspect ratio according to claim 1, wherein: In the step S2, before the blank is heated, a glass protective coating is applied on the surface of the blank to a thickness of 0.25 to 0.4 mm.

5. The method for hot upsetting a billet with a large aspect ratio according to claim 1, wherein: In step S3, the middle part of the blank is clamped from the heating furnace by the clamp of the operating machine, the jaws of the clamp are wrapped with insulation material, and then both ends of the blank are immersed in a cooling tank for pre-cooling, and the quenching medium is water or quenching oil.

6. The method for hot upsetting a billet with a large aspect ratio according to claim 5, wherein: The cooling trough is provided with a fixed height drainage pipe, and the cross-sectional area of ​​the cooling trough is greater than or equal to 4 times the cross-sectional area of ​​the blank.

7. The method for hot upsetting a billet with a large aspect ratio according to claim 5, wherein: The cooling tank includes a quenching tank and an overflow tank with an upward opening. The overflow tank surrounds the quenching tank. The cross-sectional area of ​​the quenching tank is greater than or equal to 4 times the cross-sectional area of ​​the blank. The quenching medium is contained in the quenching tank.

8. The method for hot upsetting a billet with a large aspect ratio according to claim 1, wherein: Both step S2 and step S5 further include preheating the flat mold, and the preheating temperature of the flat mold is 250-950°C.

9. The method for hot upsetting a billet with a large aspect ratio according to claim 1, wherein: In both step S4 and step S6, thermal insulation materials are used to isolate the blank and the flat mold.

10. The method for hot upsetting a billet with a large aspect ratio according to claim 1, wherein: In the step S4, during the first upsetting, the upper flat die first presses the blank down 50 to 200 mm at a speed of 3 to 4 mm / s, and then presses the blank down to a height of 5 to 10 mm / s at a speed of 5 to 10 mm / s. .

11. The method for hot upsetting a billet with a large aspect ratio according to claim 1, wherein: In step S6, during the second upsetting, the upper flat die first presses the blank down 50 to 150 mm at a rate of 4 to 6 mm / s, and then presses the blank down to the target height at a speed of 8 to 25 mm / s.

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