Forging method of M2 high-speed steel square forge piece

Abstract

The invention relates to a forging method of an M2 high-speed steel square forge piece, which comprises the following steps: 1) heating a blank, heating to 500 DEG C at a speed of less than or equal to 200 DEG C / h, heating to 850 DEG C at a speed of less than or equal to 60 DEG C / h, heating to 1070 DEG C at a speed of less than or equal to 80 DEG C / h, heating to 1150-1170 DEG C at a speed of less than or equal to 100 DEG C / h, cooling to 1125-1145 DEG C, and carrying out heat preservation forging; (2) a circle is forged on a 1800-ton radial forging machine, the diameter of the circle is 20-30 mm larger than that of the side of the square forge piece, the hammering amount of the first pass and the hammering amount of the last pass are 20-30 mm, and the hammering amount of the rest passes is 35-45 mm; (3) before forging, an axial feeding clamping jaw for clamping the blank does not rotate and only can do axial reciprocating motion, one-pass lower hammer forging is carried out to form a square piece, and a square forge piece with arc edges and corners is obtained; (4) after forging and forming, feeding to an annealing furnace, heating to 740-780 DEG C at the speed of less than or equal to 80 DEG C / h, preserving heat, cooling to 700-740 DEG C at the speed of less than or equal to 7 DEG C / h, cooling to 530-570 DEG C at the speed of less than or equal to 50 DEG C / h, opening a furnace door, cooling to 280-320 DEG C, and discharging; and (5) straightening is conducted after discharging, the materials are tiled, air-cooled and aired to the room temperature after being straightened, and the problems that uniformity and consistency are poor, the heating number is large, the outturn percentage is low, efficiency is low, and square forgings with arc-shaped edges and corners are not prone to being forged are solved.

Description

Technical Field

[0001] This invention belongs to the field of special steel forging technology, specifically relating to a forging method for M2 high-speed steel square forgings that can improve yield, reduce production costs, and is easy to implement on square forgings with rounded corners, without the corners cracking due to temperature drop. Background Technology

[0002] M2 high-speed steel is the most widely used molybdenum-based high-speed steel, known for its excellent red hardness, wear resistance, and strength. Its performance is greatly improved by refining the carbides through forging, making it one of the preferred materials for manufacturing high-end cutting tools and wear-resistant parts, such as drill bits, milling cutters, gear cutters, broaches, taps, punching and piercing dies, cold extrusion dies, and key components of industrial machine tools.

[0003] M2 high-speed steel square forgings are an important type of raw material for manufacturing high-end cutting tools and wear-resistant parts. Traditional forging methods include: one is forging with a forging hammer, where the impact force of the hammer is beneficial for breaking carbides, but the uniformity along the length is poor and the forging efficiency is affected by the frequency of impacts and the length direction; the other is forging with a press, which has a slow deformation speed and a narrow forging temperature window, resulting in a high tendency to crack, which seriously affects the yield and production cost. At the same time, these two methods are not easy to implement when forging square forgings with rounded corners, resulting in irregular and non-smooth corners, and the corners are prone to cracking due to temperature drop, which increases the forging difficulty. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a forging method for M2 high-speed steel square forgings. This method solves a series of problems such as poor uniformity, multiple forging cycles, low yield, low production efficiency, and difficulty in forging square forgings with curved edges.

[0005] The technical solution of this invention is implemented as follows: a forging method for an M2 high-speed steel square forging, the forging method comprising the following steps: Step 1) Place the billet in the furnace and heat it at a uniform rate of ≤200℃ / h to 500℃. After reaching 500℃, adjust the heating rate to ≤60℃ / h and heat it uniformly to 850℃. Hold it at 850℃ for 1.0-1.5 hours per 100mm cross-sectional diameter. After holding, heat it uniformly at a rate of ≤80℃ / h to 1070℃ and hold it for 0.5-1.0 hours per 100mm cross-sectional diameter. After holding, heat it uniformly at a rate of ≤100℃ / h to 1150-1170℃ and hold it for 2.5-3.0 hours per 100mm cross-sectional diameter. After holding, cool the furnace to 1125-1145℃ and hold it again for 1.0-1.5 hours per 100mm cross-sectional diameter. Then remove the billet from the furnace and forge it. Step 2) After the billet from Step 1) is heated and removed from the furnace, it is sent to an 1800-ton radial forging machine for forging and forged into a circle according to the intermediate dimensions. The diameter of the forged circle is 20-30mm longer than the side length of the final square forging. During the forging process, the hammer drop is 20-30mm in the first and last passes, and 35-45mm in the remaining passes. The forging speed is 1.7-2.5m / min in the first pass and 4.5-5.5m / min in the remaining passes. Step 3) The forged round piece from Step 2) is not reheated in the furnace and is forged again on an 1800-ton precision forging machine into a square part with rounded corners. Before forging, the axial feed jaws holding the billet are set to a non-rotating, axial reciprocating motion mode, which realizes the formation of a square forging from a round shape. After successful setting, the square part is forged to the required side length size by a single hammer blow at a speed of 8.0-12.0 m / min. The square forging with R30-50mm rounded corners is obtained.

[0006] Step 4) Send the square forging formed in Step 3) to an annealing furnace for heat treatment. Place it in a furnace at 400-450℃ and wait for the material to be processed. After the material is processed, heat it at a rate of ≤80℃ / h to 740-780℃ and hold it at that temperature for 3.5-6.5 min / mm. After the holding time is completed, cool it at a rate of ≤7℃ / h to 700-740℃, and then cool it at a rate of ≤50℃ / h to 530-570℃. After that, open the furnace door and cool it down to 280-320℃ before taking it out of the furnace. Step 5) After annealing and removing from the furnace, straighten the material while it is still hot. After straightening, spread it out to air cool to room temperature. Do not pile it up.

[0007] The method of the present invention has the following positive effects: 1. This invention overcomes the problems of poor microstructure uniformity, multiple forging passes, and low material yield in existing forging technologies. Traditional methods mostly use hammer forging, which is affected by the forging force of the equipment, the deformation method, and the forging efficiency of the hammer. It requires reheating in the furnace and cannot achieve single-pass forging. Repeated reheating causes inconsistent and uneven deformation in the length direction, ultimately resulting in poor microstructure uniformity in the length direction of the forged billet. Furthermore, hammer forging generally uses upper and lower hammers, which are subjected to bidirectional forces during the deformation process. The side is prone to cracking due to tension, requiring additional forging passes or leaving sufficient forging allowance to process the cracks, thus affecting the material yield and reducing production efficiency.

[0008] 2. This invention combines the characteristics of M2 high-speed steel material, and ensures that the material is in the optimal forging temperature window through low-temperature preheating and controlled-speed heating. It adopts a 1800-ton radial forging press for radial forging, and the entire circumferential surface of the billet is subjected to uniform compressive stress. In addition, it involves high-frequency forging and rapid reciprocating motion in the length direction. The billet temperature drop is small and the stress state is good. It can achieve one-time forging, uniform deformation in the length direction of the billet and excellent surface quality.

[0009] 3. By utilizing the rotating and reciprocating motion function of the jaws of the 1800-ton radial forging press, as well as the non-rotating reciprocating motion function, the two are cleverly combined with reasonable size control and high-frequency forging of the hammer head, round to square and square forgings with certain rounded corners can be achieved.

[0010] In summary, the forging method used in this invention solves a series of problems of traditional forging methods, such as poor uniformity, multiple forging cycles, low yield, low production efficiency, and difficulty in forging square forgings with curved edges. Moreover, it eliminates the need for tooling investment, thus reducing manufacturing costs. Detailed Implementation

[0011] The specific embodiments of the present invention will be further described and illustrated below with reference to specific examples. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0012] Example 1: A forging method for an M2 high-speed steel square forging. Taking the forging of a φ360mm billet into a square forging with a side length of 170mm and an R40mm arc as an example, the specific forging method is as follows: Step 1) Place the billet in the furnace and heat it at a constant rate of 140℃ / h to 500℃. After reaching 500℃, adjust the heating rate and heat it at a constant rate of 50℃ / h to 850℃. Hold it at 850℃ for 4.5h. After holding, heat it at a constant rate of 65℃ / h to 1070℃ and hold it at 1070℃ for 4.5h. After holding, heat it at a constant rate of 90℃ / h to 1155℃ and hold it for 9.5h. After holding, cool the furnace temperature to 1140℃ and hold it for another 4.0h. Then remove the billet from the furnace and forge it. Step 2) After heating, the billet is sent to an 1800-ton radial forging machine and forged to a diameter of φ192mm using an R100 hammer. The forging deformation process is: φ360-φ340-φ300-φ255-φ215-φ192, where the forging speed for φ360-φ340 is 2m / min, and the forging speed for the remaining passes is 5m / min. Step 3) The round billet with a diameter of φ192mm is forged into a square part with rounded corners on an 1800-ton precision forging machine without being reheated in the furnace. Before forging, the axial feed jaws holding the billet are set to a non-rotating mode that can only move axially back and forth. After the setting is successful, the square part is forged to a side length of 170mm with a hammer depth of 22mm in one pass and a forging speed of 10.0m / min. This will give you the square forging with a side length of 170mm and rounded corners of R40mm. Step 4) The formed square forging is sent to an annealing furnace for heat treatment. It is placed in a furnace at 400°C to wait for the material. After the material is waited for, the temperature is raised to 760°C at a uniform rate of 60°C / h and held for 13.0h. After the holding time is completed, the temperature is lowered to 720°C at a uniform rate of 5.0°C / h and then lowered to 550°C at a uniform rate of 45.0°C / h. After that, the furnace door is opened and the temperature is lowered to 300°C before the part is taken out of the furnace. Step 5) After annealing and removing from the furnace, straighten the material while it is still hot. After straightening, spread it out to air cool to room temperature. Do not pile it up.

[0013] Compared with traditional methods, the M2 high-speed steel square forgings produced by implementing this invention have a series of problems such as uniformity, low yield, low production efficiency, and inability to forge square forgings with curved edges. However, the invention eliminates the need for tooling investment and reduces manufacturing costs.

Claims

1. A forging method for an M2 high-speed steel square forging, characterized in that, The specific forging steps are as follows: Step 1) Place the billet in the furnace and heat it at a uniform rate of ≤200℃ / h to 500℃. After reaching 500℃, adjust the heating rate to ≤60℃ / h and heat it uniformly to 850℃. Hold it at 850℃ for 1.0-1.5 hours per 100mm cross-sectional diameter. After holding, heat it uniformly at a rate of ≤80℃ / h to 1070℃ and hold it for 0.5-1.0 hours per 100mm cross-sectional diameter. After holding, heat it uniformly at a rate of ≤100℃ / h to 1150-1170℃ and hold it for 2.5-3.0 hours per 100mm cross-sectional diameter. After holding, cool the furnace to 1125-1145℃ and hold it again for 1.0-1.5 hours per 100mm cross-sectional diameter. Then remove the billet from the furnace and forge it. Step 2) After the billet from Step 1) is heated and removed from the furnace, it is sent to an 1800-ton radial forging machine for forging and forged into a circle according to the intermediate dimensions. The diameter of the forged circle is 20-30mm longer than the side length of the final square forging. During the forging process, the hammer drop is 20-30mm in the first and last passes, and 35-45mm in the remaining passes. The forging speed is 1.7-2.5m / min in the first pass and 4.5-5.5m / min in the remaining passes. Step 3) The forged round piece from Step 2) is not reheated in the furnace and is forged again on an 1800-ton precision forging machine into a square part with rounded corners. Before forging, the axial feed jaws holding the billet are set to a non-rotating mode that can only move axially back and forth, so as to form a square forging from a round shape. After the setting is successful, the square part is forged to the required side length size by a single hammer blow at a speed of 8.0-12.0 m / min. The square forging with R30-50mm rounded corners is obtained. Step 4) Send the square forging formed in Step 3) to an annealing furnace for heat treatment. Place it in a furnace at 400-450℃ and wait for the material to be processed. After the material is processed, heat it at a rate of ≤80℃ / h to 740-780℃ and hold it at that temperature for 3.5-6.5 min / mm. After the holding time is completed, cool it at a rate of ≤7℃ / h to 700-740℃, and then cool it at a rate of ≤50℃ / h to 530-570℃. After that, open the furnace door and cool it down to 280-320℃ before taking it out of the furnace. Step 5) After annealing and removing from the furnace, straighten the material while it is still hot. After straightening, spread it out to air cool to room temperature. Do not pile it up.