Support roll forging method

Abstract

This invention discloses a method for forging support rollers, comprising: ingot casting: casting ingots using a single-vacuum casting method, controlling the chemical composition, gas content, and inclusion content during the process; heating: transporting the steel ingot hot to the forging workshop and directly placing it in a high-temperature furnace for heating; forging: during the first forging, pressing the upper ingot body with clamps, then rounding and cutting the bottom; during the second forging, upsetting and drawing the steel ingot; and finally forging the formed forging in the last forging; heat treatment: sequentially performing normalizing, spheroidizing annealing, and hydrogen diffusion treatment on the formed forging. The use of single-vacuum casting steel ingots results in higher material utilization, reduces material costs, and eliminates the need for a holding stage, saving heating energy. The sequential operations of pressing the upper ingot body with clamps, rounding, cutting the bottom, upsetting, and drawing during forging ensure the quality of the forging.

Description

Technical Field

[0001] This invention relates to the field of forging technology, and more particularly to a method for forging support rolls. Background Technology

[0002] Modern rolling mills are evolving towards higher efficiency and precision to produce products with higher accuracy and lower cost. Support rolls play a supporting role, preventing the work rolls from deflecting and deforming; some support rolls also transmit rolling force. Therefore, support rolls are required to have high strength and toughness, high wear resistance in the working layer, and high contact fatigue strength; furthermore, the more advanced the rolling technology, the higher the performance requirements for support rolls. Modern rolling mills almost entirely use support rolls made of forged steel, with the material gradually upgrading from Cr2 and Cr3 to Cr5 to improve strength, wear resistance, and other indicators. However, currently, double-vacuum steel ingots are commonly used in the production of forged steel support rolls, resulting in low material utilization, high costs, and high energy consumption. Furthermore, after the steel ingots are demolded and hot-transported to the forging workshop, they need to be held at 850℃ for a certain period before being raised to a high-temperature holding stage and then forged. Summary of the Invention

[0003] To address some or all of the technical problems existing in the prior art, the present invention provides a method for forging support rolls.

[0004] A method for forging a support roll is provided, comprising:

[0005] Ingot casting: Ingots are cast using a single vacuum casting method, with process control over chemical composition, gas content, and inclusion content;

[0006] Heating: The steel ingots are transported hot to the forging workshop and placed directly in a high-temperature furnace for heating;

[0007] Forging: During the first forging, the ingot body is pressed with clamps, then rounded and the bottom is cut; during the second forging, the steel ingot is uprooted and drawn out; and during the final forging, the ingot is shaped into a forging.

[0008] Heat treatment: The formed forgings are subjected to normalizing, spheroidizing annealing and hydrogen diffusion treatment in sequence.

[0009] In some alternative implementations, during the heating process, the steel ingot is demolded, its surface is covered with a heat-insulating device, and then transported hot to the forging workshop, where it is directly placed in a high-temperature furnace at a temperature above 1220°C for heating.

[0010] In some alternative implementations, during the forging process, a 100-150mm clamp is used to press the inherent positive segregation region of the steel ingot into the clamp area during the first forging.

[0011] In some alternative implementations, during the forging process, the height-to-diameter ratio of the upsetting is controlled between 0.55 and 0.65 during the second forging.

[0012] In some alternative implementations, during the forging process, during the second forging, a flat anvil and a V-shaped anvil are used for drawing, and the first anvil for drawing is pressed down in the middle of the length direction of the billet, with a pressing amount of 5-15% of the billet height.

[0013] In some alternative implementations, the forging process further includes a third forging process, which is the same as the second forging process.

[0014] In some alternative implementations, the final forging process uses flat anvils and a small reduction.

[0015] In some alternative implementations, during normalizing, the heating rate is controlled to be less than or equal to 60℃ / h, and the temperature is maintained in the range of 900-950℃ for 10-14h, followed by air cooling to 400℃.

[0016] In some alternative implementations, during spheroidizing annealing, the heating rate is controlled to be less than or equal to 60℃ / h, the temperature is maintained in the range of 800-850℃ for 20-28h, and then air-cooled to 400℃.

[0017] In some alternative implementations, during hydrogen diffusion treatment, the heating rate is controlled to be less than or equal to 40℃ / h, the temperature is maintained in the range of 640-660℃ for 40-60h, and then cooled in a rate-limited furnace.

[0018] The main advantages of the technical solution of this invention are as follows:

[0019] The support roller forging method of the present invention uses a single vacuum steel ingot, which has a high material utilization rate and reduces material costs. It also eliminates the direct heating during the heat preservation stage, saving heating energy. During forging, the ingot body is pressed with clamps, rounded, cut at the bottom, upsetting, and drawn in sequence to ensure the quality of the forging. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and constitute a part of this invention, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0021] Figure 1 This is a flowchart of a support roll forging method provided in an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of a steel ingot in a support roll forging method provided in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the billet before the first upsetting in the support roll forging method provided in an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the billet after the first upsetting in a support roll forging method provided in an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the billet after the first drawing in the support roll forging method provided in an embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of the billet after the second upsetting in a support roll forging method provided in an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of the billet after the second drawing in the support roll forging method provided in an embodiment of the present invention;

[0028] Figure 8 This is a schematic diagram of a forging formed in a support roll forging method according to an embodiment of the present invention;

[0029] Figure 9 The diagram shows the heat treatment curve after forging in a support roll forging method provided in an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] The technical solutions provided by the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] This invention provides a method for forging support rolls, suitable for support rolls made of 50Cr5NiMoV material with a roll body cross-sectional diameter of φ1100mm-φ1200mm, and forged using 25t-40t steel ingots, as shown in the attached figure. Figure 1 As shown, it includes:

[0033] Ingot casting: Ingots are cast using a single-vacuum casting method, with process control over chemical composition, gas content, and inclusion content. Gas content includes hydrogen content. When controlling the chemical composition, the carbon (C) content is reduced and the chromium (Cr) content is increased to ensure high wear resistance of the forged support rollers during subsequent use. In this embodiment of the invention, a single-vacuum casting steel ingot is selected, resulting in higher material utilization and reduced material costs.

[0034] Heating: The steel ingot is transported hot to the forging workshop and directly placed in a high-temperature furnace for heating. Based on the research of Cr5 material properties, this application involves transporting the steel ingot hot after demolding to the forging workshop and directly placing it in a high-temperature furnace for heating. After holding at that temperature, the ingot is removed from the furnace for forging. Direct heating in a high-temperature furnace after demolding, compared to the existing technology of holding at 850℃ before high-temperature furnace heating, eliminates the holding step, significantly saving initial heating energy consumption.

[0035] Forging: During the first forging, the ingot body is pressed with clamps, then rounded and the bottom is cut; during the second forging, the ingot is uprooted and drawn, and the final forging is to form the forging. By pressing the ingot body with clamps, the inherent positive segregation area of ​​the ingot is pressed outside the ingot body, preventing the product from being unqualified due to excessive carbon content.

[0036] Heat treatment: The formed forgings are subjected to normalizing, spheroidizing annealing and hydrogen diffusion treatment in sequence.

[0037] As can be seen, the support roller forging method provided in this embodiment of the invention uses a single vacuum steel ingot, which has a high material utilization rate and reduces material costs. It also eliminates the need for direct heating during the heat preservation stage, saving heating energy. During forging, operations such as pressing the upper ingot body with clamps, rounding, cutting the bottom, upsetting, and drawing are performed in sequence to ensure the quality of the forging.

[0038] The following provides a detailed explanation of each step:

[0039] Ingot casting: Ingots are cast using a single-vacuum pouring method, with process control over chemical composition, gas content, and inclusion content. Gas content includes hydrogen content.

[0040] Heating: After the steel ingot is demolded, its surface is covered with a heat preservation device to prevent the temperature from dropping too quickly and generating excessive stress. Then it is transported hot to the forging workshop and placed directly in a high-temperature furnace above 1220°C for heating. After the heat preservation is completed, it can be taken out of the furnace for forging production.

[0041] Forging: Cr5 support rollers require high uniformity of hardness during later use. Therefore, during the first forging, a 100mm-150mm clamping handle is required on the upper ingot body to directly press the inherent positive segregation area of ​​the ingot into the clamping handle area. This prevents product defects due to excessive C content. Afterward, the ingot is rounded (to the same diameter as the ingot) and the bottom cone is cut. A schematic diagram of the ingot after clamping can be found in [reference needed]. Figure 2 During this process, it is necessary to control the amount of material removed from the riser and the bottom. The amount of material removed should be such that positive and negative segregation areas are avoided from entering the main body, thereby ensuring the uniformity of the roll neck hardness in the later stage.

[0042] During the second forging process, the billet is upset and drawn, with the upsetting height-to-diameter ratio controlled at H / D = 0.55-0.65. See the attached diagram for schematic diagrams of the billet before and after upsetting. Figure 3 and attached Figure 4When drawing, use a flat-top, V-shaped anvil. The ratio of the anvil width to the upsetting height should be controlled at approximately 0.5. The first anvil cut should be pressed down in the middle of the billet's length to avoid a concave center. The pressing amount is 5%-15% of the billet height. A schematic diagram of the drawn billet can be found in the appendix. Figure 5 .

[0043] The requirements for the third forging process are the same as for the second. A schematic diagram of the third forging process can be found in the appendix. Figure 6 and attached Figure 7 .

[0044] During the final forming process, use a flat anvil with both top and bottom edges. When the temperature is below 1000℃, use a reduction of ≤10% to ensure the forging is concentric and does not crack. A schematic diagram of the formed forging can be found in the appendix. Figure 8 .

[0045] Heat treatment: First, normalizing treatment, as shown in the attached document. Figure 9 As shown, the heating rate is controlled to be less than or equal to 60℃ / h, and the temperature is maintained in the range of 900-950℃ for 10-14h. Then, it is hoisted off the trolley for air cooling, and after being cooled to 400℃, it is returned to the trolley furnace.

[0046] Then spheroidizing annealing, as shown in the attached figure. Figure 9 As shown, the heating rate is controlled to be less than or equal to 60℃ / h, and the temperature is maintained in the range of 800-850℃ for 20-28h. After cooling to 400℃, the furnace is returned to the trolley.

[0047] Finally, hydrogen expansion treatment is performed, as shown in the attached document. Figure 9 As shown, the heating rate is controlled to be less than or equal to 40℃ / h, and the temperature is maintained in the range of 640-660℃ for 40-60h, and then cooled in the furnace at ≤20℃ / h.

[0048] In summary, the support roller forging method provided by the embodiments of the present invention can reduce material costs, save heating energy consumption, and achieve high production efficiency. It also has good surface quality, ensuring uniform hardness and good wear resistance of the support roller product in the later stage.

[0049] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Additionally, the terms "front," "back," "left," "right," "upper," and "lower" in this document refer to the placement shown in the accompanying drawings.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for forging a support roll, characterized in that, Suitable for support rolls made of 50Cr5NiMoV material, with a roll body cross-section diameter of φ1100mm-φ1200mm, and forged from 25t-40t steel ingots, including: Ingot casting: Ingots are cast using a single vacuum casting method. The process controls the chemical composition, gas content, and inclusion content. The gas content includes hydrogen content. When controlling the chemical composition, the C content is reduced and the Cr content is increased. Heating: The steel ingots are transported hot to the forging workshop and placed directly in a high-temperature furnace for heating; Forging: During the first forging, the ingot body is pressed with clamps, then rounded and the bottom is cut; during the second forging, the steel ingot is uprooted and drawn out; and during the final forging, the ingot is shaped into a forging. Heat treatment: The formed forgings are subjected to normalizing, spheroidizing annealing and hydrogen diffusion treatment in sequence; During the heating process, the steel ingot is demolded and its surface is covered with a heat preservation device. Then it is transported hot to the forging workshop and placed directly into a high-temperature furnace with a temperature higher than 1220°C for heating. During the forging process, a 100-150mm clamping handle is used during the first forging to press the inherent positive segregation region of the steel ingot into the clamping handle area. During the forging process, in the second forging, the height-to-diameter ratio of the upsetting is controlled between 0.55 and 0.

65. During the forging process, during the second forging, a flat anvil on top and a V-width anvil on the bottom are used for drawing. The first anvil is pressed down in the middle of the length of the billet, and the amount of pressing down is 5-15% of the height of the billet. During the final forging process, use flat anvils and small reduction; when the temperature is below 1000℃, use a reduction of ≤10%. During normalizing, the heating rate should be controlled to be less than or equal to 60℃ / h, and the temperature should be maintained in the range of 900-950℃ for 10-14h, and then air-cooled to 400℃. During spheroidizing annealing, the heating rate should be controlled to be less than or equal to 60℃ / h, and the temperature should be maintained in the range of 800-850℃ for 20-28h, and then air-cooled to 400℃. During hydrogen expansion treatment, the heating rate is controlled to be less than or equal to 40℃ / h, and the temperature is maintained in the range of 640-660℃ for 40-60h, and then cooled in a rate-limited furnace.

2. The support roll forging method according to claim 1, characterized in that, The forging process also includes a third forging process, which is the same as the second forging process.

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